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R E V I E W A R T I C L E
Interplay of thermochemistry and Structural Chemistry,the journal (volume 21, 2010) and the discipline
Maja Ponikvar-Svet Joel F. Liebman
Received: 24 January 2011 / Accepted: 16 February 2011 / Published online: 5 March 2011
Springer Science+Business Media, LLC 2011
Abstract In the current review the content of the journal
Structural Chemistry for the calendar year 2010 is relatedto thermochemistry. To a short summary of each article in
this volume of the journal a thermochemical comment is
added.
Keywords Structural Chemistry Thermodynamics Physical Chemistry Thermochemistry Enthalpy of
formation Chemical reactions Phase transitions
Introduction
The current review ofStructural Chemistry for the calendar
year 2010 has become tradition as this is already the 10th
review and as such, constitutes a jubilee review. Let us
add that we have been told that these reviews in which an
attempt is made to link experiments and theory of all of the
articles in a given chemistry/physics/material science
periodical, represents a unique and appreciated approach.
This adds to our enthusiasm to continue with this annual
project.
This review is conceptually and organizationally very
much the same as the reviews of previous volumes of this
journal [110] in which each article has been reviewed and
summarized by us from our personal perspectives as well
as knowledge, facilitated wherever possible by the originalauthors choice of key words. Of course, our perspectives
are often very much different as is also our basic scientific
educationit is interesting to observe how scientists
working in different areas consider the same subject.
Therefore, it is perhaps also educational how we handle the
same area of investigation from our perspectives of theo-
retical and analytical chemistry and then combine the
comments into a logical unit. The review is supplemented
by adding thermochemical comments. Occasionally, it is
found that the investigations presented in the articles doc-
ument inadequacy of current knowledge by the scientific
community and that additional studies enlightening the
investigated area would be highly desirable. As such, hints,
suggestions, and encouragement for possible future
research are often given.
Thermochemical data are occasionally given as part of
our added material as well. All data for inorganic com-
pounds with otherwise unreferenced enthalpies of forma-
tion will be assumed to be taken from the Wagman
compendium [11], while corresponding unreferenced
enthalpies of formation of organic compounds will be
assumed to be taken from the Pedley compendium [12].
Issue 1
Volume 21 begins with the editorial by Hargittai [13] on
Linus Pauling and his work on the structure of proteins and
eventual discovery of the alpha-helix. Pauling postulated
that the amino acid units are linked to each other in the
folded protein molecule not only by the normal peptide
bond but also by hydrogen bonding that is facilitated by
this folding of the protein. His quantum chemical theory of
M. Ponikvar-Svet (&)
Department of Inorganic Chemistry and Technology, Jozef
Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
e-mail: [email protected]
J. F. Liebman (&)
Department of Chemistry and Biochemistry, University of
Maryland, Baltimore County, Baltimore, MD 21250, USA
e-mail: [email protected]
123
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DOI 10.1007/s11224-011-9769-0
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resonance contributed to his understanding of other scien-
tific phenomena, although at the same time, this theory was
attacked in Soviet Union as an ideological aberration.
In the first of the theoretical papers that follow Xu and
Chen [14] described use of density functional theory (DFT)
to predict the structural parameters, IR spectra, and ther-
modynamic properties of tetrazole derivatives. The total
energies, heats of formation, and enthalpies of combustionindicate the following order of stability: 5-(2,4,6-trinitro-
phenyl)-2H-tetrazole[ [5-(2,4,6-trinitrophenyl)-1H-tetra-
zole[ [5-(2,4,6-trinitrophenyl)-5H-tetrazole. A similar
result is found for the corresponding three isomers of
5-(2,4,6-trinitrobenzyl)-tetrazole. While there is a consid-
erable body of experimental data that allow for the com-
parison of the stability of 1Hand2H-tetrazoles, we know of
no corresponding study for 5H-tetrazoles. Indeed, we know
of but few thermochemically relevant studies of species
with a N=NN=N substructure. One was the study of
species [15] of the type ArN=NN=NAr as part of the
comparison of the dimerization of, and N2 loss by, tran-siently formed ArN2 radicals. Another is the suggestion that
5-nickelatetrazoles may enjoy significant stability [16].
Liu et al. [17] then used DFT to study the correlation
between regioselectivity and site charge in propene poly-
merization by single-site metallocene catalysts such as
[Cp2ZrMe]?. The activation energy for 1,2-insertion was
shown to be lower than that for 2,1-insertion in agreement
with the experimental data. Let us ask now if there is any
steric repulsion between the methyl group of the propene
and the cyclopentadienyl rings that contributes to the reg-
ioselective addition? How different are the activation
energies for Z- and E-2-butene from that of propene
wherein this methyl/cyclopentadienyl repulsion in these
4-carbon olefins is unavoidable?
Chapkanov [18] studied 2-aminopyridinium tetrachlo-
rocuprate (II) salt both in solution and in the solid-state
using IR and UVVis spectroscopy 1H-NMR, TGV, and
DSC methods. A change of aromatic character was
explained by the Npy protonation that leads to weak charge
redistribution in the pyridinium ring and thereby changes in
geometrical parameters. Thermodynamically, the stability
of the aminopyridines decreases in the order 2-[ 4-[
3- and span a 25 kJ mol-1 range. The proton affinities [19]
of the aminopyridines decrease in the order 4-[ 3-[ 2-
and span a 33 kJ mol-1 range. From these data we find that
the stability of the aminopyridinium ions decreases in the
order 2-[4-[ 3-. Is this change in enthalpy of formation,
and presumably aromaticity, reflected in the properties of
the corresponding aminopyridinium salts such as the above
cuprates?
For typical concentrations found in solutions the number
the solvent molecules outnumber the solute molecules
which makes the analysis of solute molecular structure
difficult. Lee and Ihee [20] used time-resolved X-ray
solution scattering for determining structures of small
molecules and proteins in solution. The difference scat-
tering curves generally exhibit much higher structural
sensitivity to the solute structure than the original scatter-
ing curves. The authors discuss solutions of iodine in
methanol and dissociation to form atomic iodine. We note
that the enthalpy of solution of gaseous I2 in methanol is54 kJ mol-1; we know of no corresponding data for the
atomic iodine as solute.
Stem and Ellzey [21] studied organotin(IV) molecules
using computational optimization modeling (COM) which
enables the prediction of molecular properties and struc-
tures. The data were compared to the experimental data as
obtained by X-ray crystallography and solid-state NMR.
Hyperconjugation-derived stabilization is suggested to be
an important force in these molecules. The lack of vali-
dation of computational optimization treatments for many
organotin(IV) molecules remains a limiting factor against
generating accurate COMs. These authors explicitlyinvestigated species with SnS bonds. The enthalpy of
formation of the simplest condensed phase species of
tin(IV) with sulfur, namely the binary sulfide and inorganic
material, SnS2 has been reported [22] but comparison with
organotin sulfides remains unexplored.
Suleymanoglu et al. [23] describe synthesis and char-
acterization, including crystal structure analysis, of 2-pro-
pylamino-5-[4-(2-hydroxy-3,5-dichlorobenzylideneamino)
phenyl]-1,3,4-thiadiazole. The experimentally determined
molecular geometry was compared to the geometry
obtained by DFT calculations. The results showed that the
Schiff base, which contains a thiadiazole ring, prefers the
E-configuration. A thermochemical comparison of 1,2,3-,
1,2,4-, and 1,3,4-thiadiazole, their amino analogs and
derived Schiff bases is welcomed.
Six new salicylic acid derivatives were prepared by
Djurendic et al. using conventional heating or microwave-
assisted synthesis [24]. Comparison of structures obtained
from X-ray analysis and molecular mechanics calculations
for three of these synthesized compounds, N-(2-hydrox-
ybenzoyl)-2,20-bis(2-hydroxybenzoyloxy)diethylamine,
2,20,200-tris(2-hydroxybenzoyloxy)triethylamine and N-phenyl-
2,20-bis(2-hydroxybenzoyloxy)diethylamine revealed that
the intramolecular hydrogen bonds play an important role in
stabilizing the conformation of the molecules. The antioxi-
dant activity and cytotoxicity tests showed strong activity
against hydroxyl radical, as well as exhibiting promising
lipid peroxidation inhibition. Comparison with the 3- and
4-hydroxybenzoic acid isomers is welcomed: it is to be
noted that the enthalpies of formation of the three isomeric
hydroxybenzoic acids spans but 6 kJ mol-1 in the solid
state. Does this mean the effect of the OH groups on stability
and conformation is rather negligible?
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In the experimental paper by Zhang et al. [25] the syn-
thesis and characterization of complex [Co(Imazameth)3]
0.5DMF4H2O (Imazameth = ()-2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-5-methyl-3-
pyridinecarboxylic acid) by IR spectroscopy, elemental
analysis, thermal gravimetric analysis, fluorescence prop-
erties, and single crystal X-ray structure analysis is reported.
Octameric water clusters were observed. We know of nodirect measurement as to the enthalpy of formation differ-
ence of the tautomeric 4,5-dihydro-4(5)-oxo-imidazole and
imidazole-4(5)-ol or even between their methylated deriva-
tives [26]: synthetic chemists [27, 28] have provided useful
information.
In the following experimental study by Kruszynski [29],
2,20-bipyridine complexation properties of the dichloroac-
etates of zinc and cadmium is reported. [Zn(C10H8N2)
(CHCl2COO)(H2O)3][Zn(C10H8N2)(CHCl2COO)3]
? and
[Cd(C10H8N2)2(CHCl2COO)2] were synthesized and char-
acterized by elemental and thermal analyses, IR and
UVVIS spectroscopy, and crystal X-ray structure analysis.The zinc compound is a rare example of a salt containing
complex anions and complex cations in which the same
organic ligands and anions are in the inner coordination
spheres. Consider now Zn(C10H8N2)(CHCl2COO)2(H2O)2[30]. Forgetting now the differences of Zn and Cd, do the
three compounds in this paragraph compose a homologous
series of hydrates with regards to nearly constant enthalpy
of formation differences, cf. [31]?
Using the MP2 method Qiu et al. [32] studied hydrogen
bonding patterns of the base pairs between 4-thiouracil,
analogue of uracil and four RNA bases, adenine, uracil,
guanine, and cytosine. The order of stability is s4U : guan-
ine[ s4U : adenine[ s4U : uracil * s4U : cytosine and
the calculated interaction energies for the complexes vary
from -7.4 to-13.3 kcal mol-1. What about the difference
of their interaction energies with other nucleobases? What is
the enthalpy of formation difference of 4-thiouracil and the
isomeric 2-thiouracil?
Tomura and Yamashita [33] successfully synthesized the
2:1 co-crystal of 1,2,5-thiadiazole-3,4-dicarboxylic acid and
4,40-bipyridine, which has been widely used as a ligand in
supramolecular architecture in crystal engineering. A unique
two-dimensional ladder-type molecular network in the
co-crystal is built using intermolecular OHN hydrogenbonds and SO heteroatom interactions. The 1,2,5-thiadia-
zole ring is expected to be aromatic by the criterion of having
6 p electrons. Comparison of the aromaticity of its ring
annelated qunoxaline and dihydroquinoxaline derivatives
has recently been reported [34]. How do these species
compare with the parent 1-ring heterocycle?
Gossypol is a polyphenolic terpene that is found in the
cotton plant. Four new solid-state forms, two polymorphic
and two solvated, of the likewise naturally occurring
derivative, 6,60-dimethoxygossypol were synthesized and
their structures determined by X-ray diffraction by Zelaya
et al. [35]. We note that gossypol and its dimethoxy
derivative may be recognized as 2,8-dihydroxy-1-napthal-
dehydes. What is the enthalpy of formation difference
between the aldehyde hydrogen-bonded species involving
the 2-hydroxy group and the ring closed lactol isomer
formed with the 8-hydroxy?In the following study, Qi et al. [36] studied the silyle-
noid 2-NH2CH2C6H4(CH3)SiLiF using DFT to get more
insight into the structures, and properties and solution
phase reactions of pentacoordinate silylenoids. 2-NH2CH2C6H4(CH3)SiLiF is more stable than corresponding silyl-
ene NH2CH2C6H4(CH3)Si. The insertion of 2-NH2CH2C6H4(CH3)SiLiF into CF bonds is similar to that of
NH2CH2C6H4(CH3)Si. The activation barrier for the for-
mer is 62.9 kJ mol-1 higher than that for the latter. What
are the corresponding values for the 3- and 4-isomers of
NH2CH2C6H4(CH3)SiLiF and the corresponding silylene,
and what are the differences of enthalpies of formationwithin sets of isomers?
Trzesowska-Kruszynska [37] synthesized, characterized
by spectroscopic and thermogravimetric analyses, and
determined the crystal and molecular structures of
N-(2-carboxyphenyl)-4-dimethylaminebenzylideneimine penta-
hydrate, which is an example of Schiff base compound
existing as the zwitterion, stabilized by the intramolecular
N?HO- hydrogen bond. As shown by NBO analysis this
form is energetically unfavorable for the free molecule but in
the solid and solution states the intermolecular interactions
support the presence of the zwitterionic form. How many
waters are needed to stabilize the zwitterionis it neces-
sarily at least five?
In the theoretical study by Macaveiu et al. [38] the
effects of NO2 groups on intramolecular interactions were
studied using chloromethane, ClCH3. NO2 groups were
successively introduced to form chloronitromethanes.
Corresponding CN and F derivatives were also checked.
Shortening of the carbonchlorine bond in chloronitrome-
thanes was explained by the changes in the attractive ClOelectrostatic interactions. Following up on this investiga-
tion of chlorotrinitromethane, Klapotke and Liebman [39]
studied the energetics of chlorotrinitromethane and other
trinitromethyl derivatives.
Ghosh et al. [40] synthesized mononuclear nickel(II)
and copper(II) complexes with the tetradentate Schiff base
biacetyl bis(benzoylhydrazone) (H2babh) with the general
formula [M(babh)] and characterized them by microanal-
ysis, magnetic susceptibility, spectroscopically, and X-ray
crystal structure analysis. Both compounds form one-
dimensional self-assemblies via pp interaction and
hydrogen bonding. Considering the partial double bond
character of amides, the above species are seen to have four
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contiguous p bonds not counting the terminal benzene
rings. What is their conjugation energy?
In the next article, Khalaji et al. [41] report the synthesis
of the Schiff base 6-[(5-bromopyridin-2-yl)iminometh-
yl]phenol, and additionally characterized this species by
elemental analysis and spectroscopic methods. X-ray
crystal structure analysis showed a monoclinic structure.
DFT analysis showed that conformer in which the hydroxylgroup and imine nitrogen participate in an intermolecular
hydrogen bonding and pyridine nitrogen is in the other side
of the N1C7 bond is the most stable of four isomers. How
are the relative isomer stabilities modulated by 5-substit-
uents, such as bromine in the current species?
An et al. [42] in their study describe thermal synthesis,
characterization, and crystal structures of 3-D supramo-
lecular compounds [Co(phen)(tdc)(H2O)3]5H2O and [Co(phen)(Htdc)(H2O)3](Htdc)2H2O (phen = 1,10-phenan-
throline, H2tdc = thiophene-2,5-dicarboxylate). While in
the former compound water layers were found to enable
overall 3-D supramolecular architecture by H-bond inter-actions, they were not observed in the latter compound.
What is the equilibrium constant of the reaction
Co phen tdc H2O 3
5H2O H2tdc, Co phen Htdc H2O 3
Htdc 2H2O 3H2O
1
In the following paper, Ye et al. [43] report on the syn-
thesis of four new lanthanide complexes (Ln(3,4-DMBA)3phen)2 (Ln(III) = Nd, Sm, Tb, Dy, 3,4-DMBA = 3,4-
dimethylbenzoate, phen= 1,10-phenanthroline). Compounds
were characterized by elemental and thermal analyses, IR
spectroscopy and X-ray crystal structure analysis. Kinetic
and thermodynamic parameters were calculated which
reveal that the decomposition of the complexes is not
spontaneous. Four of fourteen lanthanides are discussed
above. What periodic trends would be exhibited for these
kinetic and thermodynamic parameters had all these
lanthanide species were to be studied?
Using DFT and Baders theory of Atoms in molecules
(AIM) theory Maecka [44] investigated the nature of
resonance-assisted NHO hydrogen bonds for 3-amino-
methylene-2-methoxy-5,6-dimethyl-2-oxo-2,3-dihydro-
2k5-[1,2]oxaphosphinin-4-one and its derivatives at the
bond critical points. Analysis of the ellipticity parameters
indicated p-delocalization over all six ring atoms. How is
this delocalization manifest in terms of resonance stabil-
ization? We note that there are no thermochemical data for
any [1, 2]phosphinin derivative.
Obtaining single crystals suitable for single crystal
X-ray crystallography of bile acid derivatives is difficult.
Ahonen et al. [45] studied solid state structures of litho-
cholyl-N-(2-aminoethyl) amide. One pure polymorph along
with four solvates were isolated. 13C and 15N CP/MAS
NMR and powder X-ray diffraction (PXRD) was a useful
structural determination strategy. We note few determina-
tions of the enthalpy of few steroids have been made. Does
this mean that samples for calorimetry are likewise hard to
find? More precisely, the thermochemical review by Do-
malski [46] gives a collection of results but the later
compendium, our organic archive by Pedley, inexplicablyfails to include most of these data.
As part of the study toward extraction of heavy metals
and the inclusion of diorganodithiophosphates in activated
composite membranes (ACM) as carriers in the selective
transport of mercury, Perez-Garca et al. [47] synthesized
and characterized five Sn-alkyl (O,O0)-diorganodithio-
phosphates RS2P(OC6H4)2. Structure elucidation showed
that the crystal packing of these compounds is stabilized by
cation-p, weak hydrogen bonding CHO, as well as aro-
matic non-bonded interactions. What is found for the iso-
meric RO2P(SC6H4)2 derivatives and both of the mixed
O- and S-alkylated RO(S)P(OC6H4C6H4S) and RS(O)-P(OC6H4C6H4S) species. Indeed, what are the relative
stabilities of the various isomers?
Theoretical work by Liu et al. [48] is aimed toward
investigation of bonding character of noble-gas com-
pounds of the type CH3NgF (Ng = He, Ar, Kr, or Xe) at
the MP2 level of theory. NgF bond lengths of the
CH3NgF species are all longer than those of the corre-
sponding HNgF species and infrared intensity of the CNg
and NgF stretching vibrations are larger than that of the
other vibrations. The AIM analysis indicated that the
NgF bond (Ng = He, Ar, or Kr) bonds are dominated by
electrostatic interaction and the two CNg (Ng= Ar or
Kr) bonds by covalent interaction. The bond length anal-
ysis seems to indicate that both the NgF and the CNg
bonds are dominated by covalent interaction. No CH3NgF
have yet been observed. However, except for Ng = He,
all the related CH3Ng? are known from experiment and
indeed, their CNg bond energies have been determined
[49, 50].
The following paper by Wang et al. [51] deals with the
synthesis and characterization of new silver coordination
polymers with high packing coefficients. Reactions of sil-
ver squarate, including a new polymorph, and silver tar-
trates with pyrazine resulted in three products which have
been structurally characterized. The crystal structures and
the space-filling properties with respect to the information
retrieved from the Cambridge Structural Database (CSD)
are discussed. The enthalpy of formation of silver squarate
has been determined [52]; now, how we appraise the aro-
maticity of this species with its 2 p-electron anion [53]
especially confounded because of the presence of the Ag?
counterion?
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Avc et al. [54] compared results of HartreeFock (HF)
and DFT for computed and experimental IR vibrational
frequencies and chemical shifts of 3-[(1E)-N-ethylethanim-
idoyl]-4-hydroxy-6-methyl-2H-pyran-2-one. The B3LYP
DFT studies, which include the effects of electron correla-
tion, show a better fit to the experimental vibrational fre-
quencies and 13C NMR chemical shifts than those using HF.
We recognize this species as the N-ethylamide of dehydra-cetic acid, a highly substituted pyrone. No enthalpies of
formation of either 2- or 4-pyrone, or any simple derivatives,
have been determined experimentally to compare with
recent high level theoretical predictions [55]. We note the
enthalpy of dimerization of diketene to dehydracetic acid has
been measured [56], but as we said the latter species is highly
substituted and therefore, comparisons are problematic [57].
In the theoretical work by Oliveira et al. [58] DFT was
used to study trimolecular properties of bifurcated
BeH22HX and linear HXBeH2HX dihydrogen-bon-ded complexes with X = CN and NC. The geometries of
these systems are well-defined wherein the linear com-plexes present shorter dihydrogen bond distances and the
bifurcated complexes present the larger ones. Vibrational
effects were interpreted by the quantum theory of atoms in
molecules (QTAIM) parameters. We may ask what is the
difference of the enthalpies of formation of the ligating
HCN and HNC; only once answered should we ask about
the above beryllium complexes later. Ionmolecule reac-
tions result in ca. 75 kJ mol-1 [59, 60], to be compared
with the calorimetrically determined 90 kJ mol-1 for
CH3CN and CH3NC, and 63 kJ mol-1 for 2,4,6-(CH3)3C6
H2CN and its corresponding isonitrile [61].
A series of experimental papers then follows. As little is
known about multiple bonds linking two reactive centers
Kassaee et al. [62] continued their related investigations
using DFT on unstable and experimentally difficult to
obtain the (nitrenoethynyl)halomethylenes, NC:CCX
(X = H, F, Cl, Br). Triplet minima are 5456 kcal mol-1
more stable than their corresponding quintets. No reac-
tive intermediate is observed through connecting singlet
states of carbene and nitrene subunits and show about
70 kcal mol-1 greater stability than the corresponding
triplet states. We recognize these species as excited states
of cyanoacetylene and its substituted derivatives. An
enthalpy of formation of ca. 85 kJ mol-1 has been reported
in the ion molecule literature [63] for cyanoacetylene itself,
very discrepant from a value by interpolating those calo-
rimetrically determined for acetylene and dicyanoacety-
lene. So, is this value for cyanoacetylene correct? Not
enough is known about the thermochemistry of cyano-
acetylenes and the isomeric polyacetylenes to appraise this.
Lu et al. [64] studied rarely investigated complexes that
contain an asymmetrically 3,5-disubstituted 1,2,4-triazole.
Syntheses, characterization, and single crystal structures of
trans-[CuL2(ClO4)2] and cis-[CoL2(H2O)2](ClO4)2H2OCH3OH (L = 3-methyl-4-(p-bromophenyl)-5-(2-pyri-
dyl)-1,2,4-triazole) which have a similar pseudo-octahedral
[MN4O2] core, two ClO4 ions in the trans position in the
former and two H2O molecules in the cis arrangement of
the latter compound. What are the respective cistrans
isomerization enthalpies and why are they of opposite
sign?In the next paper, Eimann et al. [65] report syntheses
and X-ray crystal structure analyses of 5-iodocytosine and
of three different derivatives of bromo substituted nucleo-
sides. The packing structures reveal aggregations created
via networks of hydrogen bonds involving NHN,NHO, and OHO interactions between the nucleobase
and ribose units. A further support stems from weak
CHO contacts. These species all contain C, H, N, O, andeither I or Br. We know of comparatively few species with
C, H, N, O, and Br for which the enthalpy of formation is
known, e.g., bromotrinitromethane [66] and 5,7-dibromo-
8-hydroxyquinoline [67], and with C, H, N, O, and I,the iodo analog of these species, respectively [66, 67].
Other species are the parent and n-butanoate of the two
3,5-dihalo-4-cyanophenols [68].
Then Jiet al. [69] describe the synthesis, characterization,
and crystal structures of [Cu2(HL)2](ClO4)26H2O and[Zn2(HL)2](ClO4)22H2O (H2L = di(2-pyridylcarbalde-
hyde)-6,60-dicarboxylic acid hydrazone-2,20-bipyridine)
which revealed to be bimetallic molecular squares. We know
of no enthalpy of formation data for any bipyridine carbox-
ylic acid derivative; by contrast this quantity has been
determined for several biphenyl carboxylic acid derivatives
[70] including the 2,20-dicarboxylic acid anhydride [71].
Lah and Leban [72] show in their study on the syntheses
and crystal structures of three new Cu(II) complexes
comprising three simple pyridine alcohol ligands, 3-pyri-
dinepropanol, 2-pyridineethanol, and 2-pyridinemethanol
in their neutral forms. This study documented considerable
structural diversity within the system limited to simple
pyridine alcohols and Cu(II) halides. The solution phase
complexation enthalpy of Cu(II) with the latter two alco-
hols has been directly determined [73]; we know of no such
measurement for the first species. The sole enthalpy mea-
surement we know of for this species is that involving its
intra- and intermolecular hydrogen bonding, a study that
involves the other two pyridine alcohols as well [74].
Styczen et al. [75] describe the syntheses, characteriza-
tion, and crystal structures of manganese and cobalt tetrab-
romometallates(II), [(C2H5)4N]2[CoBr4] and [(C4H9)4N]2[MnBr4]. Magnetic measurements suggest weak anti-
ferromagnetic intermolecular interactions between the
divalent metal ions in the crystal lattice. Consider tetrae-
thylammonium and tetrabutylammonium halides. There is a
nearly constant 200 kJ mol-1difference for the enthalpies of
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formation of these chlorides, bromides, and iodides. Is the
difference (per cation) found for the above tetrabromomet-
allates affected by this antiferromagnetic coupling?
The issue closes with the paper by Szekely et al. [76]
who studied crown ethers containing an alkyl diary-
lphosphinate or diarylphosphinic acid unit. Crystals for
X-ray analysis of the achiral and chiral methyl phosphi-
nates as well as the achiral phosphinic acid which wasfound to form hydrogen bonded dimers in the crystal were
successfully prepared. The calculated electronic circular
dichroism spectrum shows a reasonable agreement with the
spectra obtained in solution which shows that the structure
observed in the crystal is predominant in solution as well.
The thermochemistry of organophosphorus compounds has
been largely ignored when compared to that of sulfur-
containing species; indeed, the Pedley archive includes
none of the former data, Domalskis compendium [46] but
a few. We note that the enthalpies of formation of phe-
nylphosphinic, diphenylphosphinic, and phenylphosphonic
acids have been measured [77].
Issue 2
This issue is devoted to the Polish chemist Adam Bartecki
on the occasion of his 90th birthday. The first paper is an
editorial by Cieslak-Golonka [78] who gives a short
introduction on the work of Adam Bartecki whose interests
range from coordination chemistry to practical applica-
tions, where especially worth mentioning is his expertise in
electronic spectroscopy and his successful work on color.
Following is a paper by Warnke et al. [79], who report onthe synthesis and crystal structure of the new Fe(III) com-
plex [(C2H5)4N][FeCl4] crystallizing in the hexagonal sys-
tem. The magnetic susceptibility measurements revealed
suggests weak antiferromagnetic coupling. Results of
electron paramagnetic resonance spectroscopy indicate
symmetric arrangement of the chloride ligands in the
coordination sphere of Fe(III). The enthalpies of formation
of (C2H5)4NCl, KFeCl4 and KCl are well-established; that
of [(C2H5)4N][FeCl4] remains unknown. We wonder how
close to thermoneutral is the following solid state exchange
reaction
C2H5 4NCl KFeCl4 ! KCl C2H5 4N
FeCl4
2
The related halogen exchange reactions (X = Br, I)
C2H5 4NCl KX ! KCl C2H5 4NX 3
are exothermic by ca. 20 and 40 kJ mol-1, respectively.
In the next paper, Griffiths et al. [80] describe catalyst-
enhanced molten salt oxidation, which is an extension of
molten salt oxidation originally employed in the 1960s. As
revealed, by addition of nitrate catalyst the concentration of
the oxidizing species, superoxide, and peroxide ions that
are produced from the oxygen entering the carbonate melt
could be increased and maintained. Further characteriza-
tion of possible adducts between nitrate and nitrite with
oxygen and peroxide has been done by employing DFT.
While the enthalpy of formation of peroxynitrate and its
covalent hydrogen and alkyl derivatives has only now beenunderstood [81], the enthalpy of formation of peroxynitrite
ion is solidly established [82].
Radecka-Paryzek et al. [83] synthesized, characterized,
and determined the X-ray crystal structure of 2,6-diace-
tylpyridinediphenylhydrazone perchlorate. Spectroscopic
and analytical data of its chelating behavior toward lan-
thanum(III), praseodymium(III), and neodymium(III)
showed 1:2 metal to ligand stoichiometry. What are the
relative stabilities of the isomeric diacetylpyridines? Is it
the same order as recently found for the related pyridine-
dicarboxylic acids [84] wherein COOH replaces COCH3?
The enthalpies of formation of the three monoacetylatedpyridines have all been reported [85].
As showed in the study by Staszak et al. [86] 3-methyl-
4-nitropyridine-N-oxide (3-mnpn) interacts with copper(II)
acetate to form a solid, crystalline, dinuclear copper(II)
complex with formula [Cu(OAc)2(3-mnpn)]2. New bands
observed at 16000 and 24000 cm-1 in the electronic
spectra were plausibly ascribed to metalmetal interactions
and solid state effects. We wonder how different are the
spectroscopic and thermochemical properties of 3-methyl-
4-nitropyridine-N-oxide and 4-methyl-3-nitropyridine-N-
oxide, and of related complexes; the enthalpy of formation
of only the former N-oxide is available from the literature
[87].
Phenytoin complexes of Co(II) and Ni(II), [Ni(H2O)4(pht)2] and [Co(H2O)4(pht)2]1.5NH3H2O (pht = phenot-oinate anion) were synthesized by Puszynska-Tuszkanow
et al. [88]. The compounds were characterized by spec-
troscopic, thermal, and magnetic measurements. X-ray
structural analysis revealed that the environment around
the nickel and cobalt ions can be described as a distorted
octahedron. Although the first measurement of the com-
bustion enthalpy of a hydantoin (5-ureidoimidazolin-2,4-
dione, the so-called allantoin) was first reported over
100 years ago [89] that of phenotoin (the 5,5-diphenyl-
derivative) remains unmeasured despite its biomedical
importance. The thermochemistry of hydantoins remains
problematic [90] and incompletely studied.
Nowak et al. [91] report the synthesis of several
new compounds of the flavonoid, rutin, with Fe(II) and
Fe(III) ions. This study gains relevance because selective
inhibitory effect of rutin under pathologic conditions
induced by iron overload is thought to be due to the forma-
tion of inactive ironrutin complexes. Complexes having
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formulas FeOH(C27H29O16)5H2O, Fe2OH(C27H27O16)9H2O,Fe(OH)2(C27H29O16)8H2O, [Fe6(OH)2(4H2O)(C15H7O12)-
SO4]10H2O were synthesized. Their composition wasdetermined by elemental analysis and thermogravimetric
measurements. These species were additionally character-
ized by spectroscopic and magnetic properties. A thermo-
dynamic study of metal-flavonoid interactions has been
reported [92].In the next paper, Adach et al. [93] report synthesis,
characterization, and X-ray crystal structure of a novel
cobalt(II) complex [Co(L)Cl]2[CdI4] (L = tris(1-(3,5-
dimethylpyrazolylmethyl)amine) obtained in situ from the
redox system (Co0, CdCl2, NH4I, 1-hydroxymethyl-3,5-
dimethylpyrazole). Diverse isomers exchanging the halo-
gens Cl and I may be suggested: what determines the
formation of the above iodocadmate? We do note that the
solid state reaction
CoI2 CdCl2 ! CoCl2 CdI2 4
is exothermic by ca. 45 kJ mol-1 suggesting [Co(L)Cl]2[CdI4] is plausibly more stable than [Cd(L)Cl]2[CoI4].
However, this ignores all contributions from metal-N
bonding.
Wojciechowska et al. [94] reported the new crystalline
Cu (II) complex Cu(phen)2OCrO3](phen)0.54H2O, derived
from the [Cu(II)-phen-K2CrO4] system (phen = 1,10-phe-
nantroline) system. The compound was characterized by
spectroscopic (NIRVisUV) methods and its structure
determined by X-ray diffraction. The chromate unit was
found to be monodentate. Consider now the simpler, i.e.,
uncomplexed, CuCrO4. Comparison of its enthalpy of
formation with the other mixed copper chromium oxides,Cu2Cr2O4, and CuCr2O4 [95] is welcomed; a study of their
Gibbs energies has been reported [96].
In the study by Kamecka et al. [97] systems Cu(II)L1L2(L1 = ethylenediamine (en), diethylenetriamine (dien) or
N,N,N0,N0,N00-pentamethyldiethylene triamine (Me5dien)
and L2 = (aminomethyl)phosphonic acid (glycinephos-
phonic acid, Gly(P)) were investigated using potentiomet-
ric, spectrophotometric, and EPR methods. The EPR
parameters obtained correspond to a five-coordinate spe-
cies. The enthalpies of formation of ethylenediamine,
diethylenetriamine [98, 99], and triethylenetetramine [98]
have all been determined as well as that of tetraethylene-pentamine [100], the last value should solvation enthalpies
be ignorable.
As part of continuing investigations on interpretation of
the electronic spectra of the copper(II) complexes with
Schiff bases, Kurzak and Kuzniarska-Biernacka [101]
synthesized the bis(salicylidene-2-amino-3-methylpyridine)
copper(II) complex, which was characterized by elemental
analysis, conductivity measurements, and UVVis spec-
troscopy. Coordination properties of donor atoms and their
bonding abilities, as well as solvatochromism were studied
by electronic spectra. The angular overlap model (AOM)
calculations were carried out within the framework of the
simplest model. Colorimetry and calorimetry have occa-
sionally been combined to enhance understanding of sol-
vatochromic systems, e.g. [102].
Further Radtke et al. [103] describe synthesis, spectral
characterization, thermal properties, and X-ray crystalstructures of the novel Zr(IV) b-ketodiester complexes of
general formulas [Zr(dtbacdc))4], [Zr(dmacdc)3(OiPr)]2,
and [Zr(dtbacdc)3(OiPr)]2 (dtbacdc = di-tert-butyl-1,3-ac-
etonedicarboxylato, dmacdc = dimethyl-1,3-acetonedi-
carboxylato ligands). As the synthesized compounds have
potential application in the technique of chemical vapor
deposition, the most often used method in the preparation
the high quality of ceramic materials and thin metal oxide
layers, thermal decomposition pathways were discussed.
The enthalpies of formation of the related homoleptic
8-coordinate zirconium complexes with acetylacetone and
its 1,1,1-trifluoro derivative have been reported [104].With interest in cobalt(II) complexes with tetrahedral or
pseudo-octahedral geometries with Schiff bases derived
from salicylaldehyde and amines in a variety of solvents,
Kurzak et al. [105] prepared [Co(sap)2] (Hsap = salicyli-
dene-2-aminopyridine) and characterized it by elemental
analysis, molar conductivity, cyclic voltammetry, and Vis
NIR spectroscopy. A tetrahedral geometry was suggested
in the solid state and in solution. Electronic spectroscopy
was used to study the ligandfield parameters and solva-
tochromism. The authors describe electrochemical reduc-
tion and the addition of the electron to the metal and
pyridine ring. What does that tell us about the conjugation
of the endo and exocyclic nitrogens? The thermochemistry
of 2-aminopyridine metal complexes has been explored,
e.g., the enthalpy of formation of bis(2-aminopyridine)zinc
chloride has recently been reported [106] .
Zeolites or related materials have been widely used as
catalysts, cation exchangers, and adsorption media. In the
paper by Roth and Dorset [107], it is shown that the
symmetry principles may govern and rationalize formation
of different zeolite frameworks from corresponding layered
zeolite precursors. Despite their seeming complexity as
defined by the large number of atoms per formula unit,
enthalpies of formation of zeolites are encouragingly well-
understood [108].
With the purpose to provide better understanding of the
interactions between explosives and surfaces of selected
porous metalorganic frameworks that possess the catalytic
activity, Petrova et al. [109] theoretically studied the
interactions between the adsorption of 1,3,5-trinitro-s-tri-
azine (RDX) and triacetone triperoxide (TATP) on repre-
sentative fragments of metal organic framework (IRMOF-1).
Comparison of these species with their respective
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oligomers is welcomed: we note the enthalpies of forma-
tion of RDX and the corresponding tetramer (HMX) are
both known. The value for neither TATP nor for the
corresponding dimer, tetramethyl-1,2,4,5-tetroxane, are
known from experiment. However that of several other
tetroxanes such as the parent species [110], and the
3,6-bis(butanal) [111], 3,6-bis(butanoic acid) [112] and
3,6-diphenyl [113] derivatives have been reported.Dro_zd_zewski et al. [114] reexamined the X-ray crystal
structure of bis(4-hydroxybenzhydrazide)copper(II) sulfate
dihydrate complex. The two water molecules are not coordi-
nated to the metal, but rather stabilize the sulfate group ori-
entation and link the layers of complex molecules by strong
hydrogen bonds. DFT calculations were used to interpret IR
and Raman spectra that had been enhanced by deuteration and
copper stable isotope substitutions. Copper (II) sulfate exists
as the anhydrous and the mono-, tri-, and pentahydrateso,
why not also the dihydrate [115] here as well?
New mixedligand lanthanide complexes of Er(III),
Yb(III), and Lu(III) with 4,40-bipyridine and dichloroace-tates were prepared by Czylkowska et al. [116]. X-ray
crystal structures of the complexes were determined as well
as elemental, IR spectroscopic analysis, conductivity
measurements, and thermal studies (TG-DTA-DTG)
were performed. The intermolecular OHO, OHN,CHO, CHCl, and p p interactions link complex
and organic molecules to the three-dimensional network.
The relative acidity of haloacetic acids, e.g., dichloroacetic
acid, or conversely, the relative basicity of haloacetate
anions is an exemplary exercise in the relative importance
of substituent steric and inductive effects and solvation
energies of ions and related neutrals [117, 118]. How are
complexation energies and enthalpies of the diverse halo-
acetates affected by halogens?
Kulesza et al. [119] synthesized the new neodymium(III)
complex NaNd(SP)4 chelate (SP = C6H5S(O)2NP(O)
(OCH3)2) and determined it X-ray crystal structure. Large
intensity of the 4I9/2 ?4G5/2;
2G7/2 transition with a rela-
tively high symmetry has been found. The high-resolution
absorption, emission, and excitation spectra and accompa-
nying crystal-field calculations have been performed and
compared with the earlier reported compound NaNd-
Wo4H2O(Wo = CCl3CONP(O)(OCH3)2)).Weknowofnoenthalpy of formation data for any acylphophoramide;
indeed, the only phosphoramides with known enthalpies of
formation are the parent species P(O)(NH2)3 [120] and the
alkylphosphonic dianilides, CH3P(O)(NHC6H5)2 and
C2H5P(O)(NHC6H5)2 [121]. Likewise, we know of only one
unequivocal example of the enthalpy of formation of an
acylsulfonamide, namely that of saccharin [122].
The general pattern of solvatochromic behavior for a
variety of iron(II) complexes has been documented by
Burgess and Hubbard [123]. The emphasis of this study was
diimine complexes and their behavior in a variety of ternary
aqueous solvent media. Enthalpy and entropy changes
associated with the redox chemistry of two different types
of iron diimine complexes have been reported [124, 125].
Two contributions by Sobczyk and Dro_zd_zynski then
follow. In the first contribution [126] U(III)-doped LaBr3single crystals were synthesized and their high-resolution
low temperature emission spectra were studied. The emis-sion from the 2K15/2,
2H11/2, and4F9/2 levels to the ground
state, 4I9/2, and from2K15/2 to the first excited state
4I11/2have been investigated and discussed with respect to vib-
ronic transitions. The assignment has been proposed. In the
following contribution [127], synthesis of U(IV)-doped
KPb2Cl5 single crystal and its unpolarized absorption,
excitation, and emission spectra studied. Good agreement
was found between theoretical lifetimes calculated by
JuddOfelt intensity analysis of 5f25f2 transitions calcu-
lated and experimentally measured for this compound. Here
are U(III) and U(IV)can U(II) be likewise studied? U(II)
has been observed in alkaline earth halide matrices [128]and in salt melts [129] for which a redox potential, and
hence a Gibbs energy from the Nernst equation, has been
assigned.
The last paper in this issue is by Godlewska et al. [130],
who studied IR and Raman spectra of Dy, Ho, Er, and Lu
phthalocyanine of the type PcLn(OAc). The changes of the
structure and symmetry of the axially substituted metall-
ophthalocyanine complexes have been checked and dis-
cussed on the basis of group theory. As concluded, this
analysis can assist in gaining information on the molecular
structure of this type of compounds. How strong is the
LnO bond? We wonder about the stability of divalent
PcLn species formed by the formal cleavage of the bond,
and are they better described as PcLn(III). After all,Pc2Ln species have been studied as neutral species and as
radical cations and anions. When do they contain trivalent
lanthanides [131]?
Issue 3
Issue 3 of 2010 review opens with the obituary written by
Hargittai [132] for Lev V. Vilkov (19312010), a premier
scientist interested in the structures of relatively small
organic molecules and the techniques capable of this
determination. Following this essay, Hargittai [133] wrote
an obituary for Torvard C. Laurent (19302009). Laurent
was an expert in X-ray diffraction technique of macro-
molecular structures that led him to do the pioneering
research on the structural chemistry of hyaluronan. He
determined many of the physicochemical properties of
hyaluronan and their relationship to the versatile biological
functions.
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In the next contribution, Notario et al. [134] discuss the
enthalpy of formation of acrylonitrile, which despite the
industrial importance of this species, is still not accurately
known from experiment. Using defining reactions, G2 and
G3 quantum chemical calculations, and using literature
sources, values between 185 and 191 kJ mol-1 were sug-
gested with a recommended average of (188 7) kJ
mol-1. A delocalization stabilization energy of but4 kJ mol-1 has been suggested, a small value in accord
with the value for acrylic acid earlier discussed by these
authors [135].
Using one- and two-dimensional NMR spectroscopy
Silva et al. [136] completed the 1H and 13C NMR signal
assignments for four luminescent 1,2,4-oxadiazole con-
taining light-emitting liquid crystals. Experimental chemi-
cal shift calculations were in rather good agreement with
the signals as calculated by DFT incorporated with GIAO.
The thermochemical literature of 1,2,4-oxadiazoles and
their 1,3,4- and 1,2,5-isomers is surprisingly rich albeit
seemingly only for solid state species. We note that theenthalpies of formation of the diphenyl derivatives of these
three heterocycles span a ca. 160 kJ mol-1 range.
Organophosphorus inhibitors are among the most dan-
gerous compounds developed by man as they inhibit acetyl-
cholinesterase (AChE). Post-treatment regimens involve also
oxime AChE reactivators. Skorska-Stania et al. [137] syn-
thesized (E)-1,4-bis(4-hydroxyiminomethylpyridinium)-
but-2-ene (K075) and 4,40-bis(hydroxyiminomethyl)-1,10-
(1,4-phenylenedimethyl)-bispyridinium (K114) bromides and
determined their structure by X-ray single crystal analysis.
Hydrogen bonds were shown to be of considerable impor-
tance in stabilizing these crystals and in the reactivation of
AChE. Despite their importance, enthalpies of formation
data for oximes is scarce and generally not particularly
reliable [138].
Nicola and Mahe [139] prepared the solvated form of
biclotymolN,N-dimethylacetamide 1:1 solvate and deter-
mined its crystal structure, which was then compared to
the crystal structures of the DMSO and DMF 1:1 solvates
of biclotymol. Two conformers have been observed
experimentally although conformational analysis con-
ducted by employing semiempirical and ab initio tech-
niques of the isolated biclotymol molecule revealed that
there are six possible conformers. Biclotymol is a
p-chlorophenol derivative. The enthalpy of formation of
both m- and p-chlorophenol has been determined; sur-
prisingly, there are no such data for the o-isomer given
there are also measurements for all six dichlorophenols
[140]. We know of no data for the enthalpy of formation
of any of their solvates.
Husak et al. [141] determined crystal structures of two
new polymorphs of simvastatin, a drug for the treatment
hypercholesterolemia, by X-ray powder diffraction and
solid-state NMR spectroscopy. The main differences
among three polymorphs, the two new and the one earlier
described, is only in the O4C20C21C22 and C20C21
C22C23 torsion angles describing the rotation of the side
group. It is interesting to note that the phase changes are
fully reversible. Simvastatin is a hexahydronaphthalene
derivative. The relative enthalpies of formation of the
parent hexahydronaphthalenes have been studied [142,143]; we know of no analogous relative biomedical activ-
ities of their analogous simvastatin isomers.
Due to the interest in the IIVI semiconductors Xu et al.
[144] studied CdTe nanocrystals by DFT. After optimizing
Cd3Te3, (Cd3Te3)2, (Cd3Te3)3, and Cd4Te4 structures
TeCdligand clusters were optimized to further discuss
the bond and optical spectrum qualities of CdTe nano-
crystals. The sublimation enthalpy of CdTe and other group
12 chalcogenides was recently explained in terms of atom-
based thermochemistry [145].
Ponikvar-Svet et al. [6] in the next paper relate ther-
mochemistry to the content of the articles contained inStructural Chemistry for the year 2005 and so this paper
represents a conceptual ancestor of the current study.
The Kuhn segment, varying in polyheteroarylenes from
10 to 15 A to ?, links the geometric structure of a
monomer unit of polyheteroarylenes to its physical prop-
erties. In the paper by Ronova [146], a volume factor that
serves as a good proxy for the geometric structure of a unit
of aliphatic polymers has been suggested. This factor
correlates with those physical properties that depend on the
free volume. The simplest polyarylene is polyphenylene,
(C6H4)n. The enthalpies of formation of the p-isomer
[147] and its monophenylated derivative have been deter-
mined [148].
The family of plants known as Clusiaceae (Guttiferae)
shows a diversity of metabolites, such as oxygenated xant-
hones which have been widely studied due to their potential
biological activities. Correa et al. [149] managed to iso-
late 1-hydroxyxanthone, 1-hydroxy-7-methoxyxanthone,
1,5-dihydroxy-3-methoxyxanthone, and 1,7-dihydroxy-3,8-
dimethoxyxanthone, to determined their X-ray crystal
structures and study molecular interactions. Important
bonding is represented by hydrogen bonds and the crystal
self-assemblies are kept together bypp interactions. While
the enthalpy of formation of the parent species xanthone has
been determined multiple times [150152], we know of no
measurements at all for the above (or for that matter, any)-
substituted derivatives.
Huang et al. [153] studied the nature of hydrogen bonds
through structures, energies, frequencies, and electron
density topological analysis in (CH3OH)n (n = 28) clus-
ters using DFT, natural bond orbital (NBO), and QTAIM
approaches. The strengths of OHO H-bonds in (CH3OH)nclusters increase from n = 2 to 8, along with the increasing
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of DEprep (the amount of energy required to deform the
separate bases from their free monomer structure to the
geometry that they acquire in the pair cluster) due to
the deformations during the formations of clusters. At what
stage does the cluster become effectively indistinguishable
from the bulk liquid? From the bulk solid?
Using DFT approach, Contreras et al. [154] studied
nitrogen-containing exohydrogenated carbon nanotubesformed by covalently arranging 210 and 20 layers of
identical cyclic units having a pyrimidine backbone.
Structural and electronic properties were investigated.
Calculated band gap values were small (around 0.2 eV) for
all the studied structures and were dependent on the
number of layers and the configurations. Recently, the
energetics of carbon nitrides (and carbon oxides) was dis-
cussed [155]: no thermochemical data yet exist for these
nitrogenated carbon nanotubes.
Geometric and electronic changes of a series of
poly(carbosilysilanes) induced by varying the size and
species of the substituting groups was investigated by Dinget al. [156] using DFT combined with AM1 method. While
the bias-trans conformation is preferred if the side chain
contains fewer than three carbons, the all-trans confor-
mation with a loose-helix backbone is a preference with
more than four carbons in side chain. The enthalpy of
formation of solid SiC is well-established. How does this
number relate to enthalpies of formation for these polymers
and discrete organosilicon compounds such as the meth-
ylated silanes?
In the theoretical paper by Kassaee et al. [157], DFT was
used to investigate the effects of different sized rings
(cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl sub-
stituents) on the stability of spirocyclic (alkyl)(amino)carb-
enes (CAACs). The cyclopropyl-substituted CAAC shows
higher DEs-t and DEHOMO-LUMO than the others (54.2 and
116.7 kcal mol-1, respectively). The ring inversion energy
barriers were assigned which do not show a considerable
difference with those of the bare cyclohexane, cyclopentane,
andcyclobutane;enthalpies of formationare known for these
cycloalkanes but none of these carbenes derivatives.
In the experimental paper by Prathapachandra Kurup
et al. [158] synthesis and characterization including the
X-ray crystal structure determination of oxovanadium(IV/V)
complexes of 2-hydroxyacetophenone-3-hydroxy-2-naph-
thoylhydrazone (H2L) along with the crystal structure of
an oxovanadium(V) complex [VOL(OCH3)] existing in
two polymorphic forms is reported. Consider the related
VOL(OH) complex. What is the gas acidity of this species?
On which oxygen does VOL(OH) protonate and what is the
corresponding gas phase basicity? The enthalpy of forma-
tion of aqueous VO2? and VO2? are well-established.
Using single crystal X-ray analysis and quantum chemi-
cal calculations Fukin et al. [159] analyzed the basic
geometrical, kinetic, and energetic properties features of 4,5-
disubstituted 3,6-di-tert-butyl-o-benzoquinones. Identified
contacts of the C=OH(tBu)-type (2.373.83 kcal mol-1)can be interpreted as intramolecular hydrogen bonds. These
hydrogen bonds were not considered in the analysis of
enthalpies of formation of the parent and t-butylated o-ben-
zoquinones [160]. Should the literature analysis be redone?
Clozapine and haloperidol are two common antipsy-chotic agents. With the purpose to develop compounds
with the clozapine-like profile of high dopamine D4 and
serotonin 5-HT2A receptor affinity for the treatment of
schizophrenia Capuano et al. [161] synthesized, charac-
terized, and determined X-ray crystal structures of three
new prospective antipsychotic agents, one originating from
the structural hybridization of the commercial therapeutics,
clozapine, and haloperidol, while the others possess an
alternative tricyclic nucleus derived from JL13, a cloza-
pine-like atypical antipsychotic. Clozapine is a dibenzo-
1,4-diazepine derivative; haloperidol is a piperidine-4-ol
derivative. No thermochemical data is seemingly availablefor 1,4-diazepines, save from a study of their basicity
[162]. Piperidine-4-ols have been discussed in the context
of enthalpies of formation [163, 164] and of their enzy-
matic interconversion with the related 4-piperidiones [165].
Gholivand et al. [166] synthesized and characterized by
IR, 1H-, 13C-, 31P-NMR spectroscopy and CHN elemental
analysis four new phosphoric triamides derived from iso-
nicotinamide with the general formula 3-NC5H4C(O)NH-
P(O)XY (X = Y = Cl; X = Y = NHC(CH3)3; X =Y =
N(C4H9)2; X = Cl, Y = N(C2H5)2. Two new polymorphs
of the compound with X = Y = NHC(CH3)3 for which
X-ray crystal structure were determined were obtained.
These compounds form centrosymmetric dimers via inter-
molecular hydrogen bonds. Due to different strengths of
hydrogen bonds a three-dimensional polymeric cluster is
formed in the first while two-dimensional polymeric chain
is formed in the case of second compound. The enthalpies
of formation of isonicotinamide and its 2- and 3-pyridin-
ecarboxamide isomers (nicotinamide and picolinamide),
and also of isonicotinamide and nicotinamide Npy-oxides
have been reported [167]. Picolinamide Npy-oxide has
seemingly not been studied by thermochemists. Its photo-
chemistry shows [168] rearrangement to N-formylpyrrole-
2-carboxamide, a likewise thermochemically uncharacterized
species.
A new ruthenium arsine complex with pyrazole ligand
[RuCl3(AsPh3)(C3H4N2)2]0.5CH3OH complex has beenprepared and characterized by X-ray structure analysis and
IR and UVVis spectroscopy by Maecki and Kruszynski
[169]. Next to DFT and time-dependent DFT methods also
natural bond orbital (NBO) analysis were used to calculate
the electronic structure and UVVis spectrum. Good
agreement between experimental and calculated UVVis
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spectra was obtained. There are three isomers
RuCl3(AsPh3)(C3H4N2)2: the isomer with the two pyra-
zoles cis to each other and the arsine trans to one of them is
the one that was studied. What is the relative energy of this
species and the other two isomers in which the arsine and
the two pyrazoles are all cis, and the pyrazole is cis to the
two pyrazoles which are trans to each other?
In the theoretical study by Chermahini et al. [170] DFTand ab initio calculation were employed to study the
hydrogen bond interactions of dimer of difluoroacetic acid.
Eight different conformers were considered. The calcula-
tions predict the order of stability in monomeric difluro-
acetic acid: EHC[EFC[EHT. The interaction energy of
dimer of difluoroacetic acid is enough to overcome the
relative stability of the monomers and dimer formation
proceeds. As well understood as the hydrogen bonding in
the dimer is as well as conformational preferences from
this study, reliable information as to the value of the
enthalpy of formation of difluoroacetic acid itself is still
lacking, cf. [171, 172].In the theoretical study by He et al. [173], periodic DFT
calculation was used to investigate crystalline 2,6-diamino-
3,5-dinitropyridine-1-oxide, an important explosive and
raw materials for preparing high energetic explosive. The
insight into chemical molecular properties was obtained by
analyzing band structures, densities of states and charge
distributions. The theoretical lattice energy of the crystal
was predicted to be -166.03 kJ mol-1. How does this
lattice energy compare with this quantity for the 1,4-
dioxide, the unoxygenated heterocycle and the isomeric
4-oxide?
In the article by Zhu and Xiao [174] recent papers on
first-principles band gap predictions of the impact sensi-
tivity for different classes of energetic crystals were
reviewed. It was shown that the first-principles band gap
criterion is applicable to different series of energetic
crystals with similar structure or with similar thermal
decomposition mechanism and therefore this principle
could be used for molecular design of high-energy den-
sity materials. These authors discuss metal azides. We
note a recent paper that discusses the anomalously high
electron affinity of azido radical [175] and thus the sta-
bility of species with the azide ion such as these metal
azides.
Issue 4
Issue 4 of the 2010 review begins with an editorial written
by Hargittai [176] on the occasion of publishing the new
book by Victor McElheny Drawing the Map of Life
describing the huge importance and background of Human
Genome Project (HGP) completed in 2003 by succeeding
to determine the entire DNA sequence.
In the theoretical study by Wu et al. [177], DFT was
used for the purpose of studying the structures and elec-
tronic properties of endohedral metallofullerenes TM@C24and TM@C24H12 (TM = Cr, Mo, W). The results show
that TM atoms bind over the pentagon ring inside the C24
cage. The analyses of dissociation energy and energy gapindicate that these compounds are not only thermody-
namically, but also considerably kinetically stable. We note
that the simplest species involving Cr, Mo, and W, the
bis-cyclopentadienyl or ocene derivatives Cp2TM, are
all known. The enthalpy of formation of the Cr species is
well-established [178, 179], while that with Mo and W
remain unmeasured except as oxidized (higher metal
valence) form with affixed ligands [180].
In the experimental paper by Petek et al. [181], synthesis
and X-ray crystal structure of o-hydroxy Schiff base deriv-
ative, (E)-2-ethoxy-6-[(2-methoxyphenylimino)methyl]phe-
nol was synthesized and its molecular geometries at thedifferent stages in tautomerism of (E)-2-ethoxy-6-[(2-
methoxyphenylimino)methyl]phenol studied. The Harmonic
Oscillator Model of Aromaticity (HOMA) indices were
calculated for each step of a potential energy surface (PES)
scan. This showed that there is a dynamic equilibrium
between the aromaticity level of the phenol and chelate ring.
How do the alkoxy groups affect the aromaticity? We recall
a study comparing the enthalpies of formation of the iso-
meric methoxy and dimethoxyphenols [182].
In the following theoretical paper, Farmanzadeh and
Ashtiani [183] proposed single molecular wire, 4,40-[eth-
ane-1,2-diylidenedi(nitrilo)] dibenzenethiol and studied
electric field effects on the structural and electronic prop-
erties by employing DFT. The results show that the elec-
tronic structure is more sensitive than geometric structure
to both directions of the applied electric field and that with
increasing the electric field X component of electric dipole
moment and total dipole moment increase continuously.
We note the NC6H4S substructure of the above key
species and that there are but three species containing
this thioaniline functionality with a measured enthalpy of
formation, phenothiazine, 1,3,7,9-tetranitrophenothiazine-
5-oxide and cis-5a,6,11a,12-tetrahydro[1, 4]benzothiazino
[3,2-b][1, 4]-benzothiazine [184]. None of these, however,
have the p-N,S substitution pattern found in the above
benzenethiol derivative.
Aghabozorg et al. [185] report the synthesis and charac-
terization including X-ray crystal structures of three new
metal compounds (H2bda)[Mn(pydc)2]3H2O, (H2bda)[Zn(pydc)2]3H2O, and (H2bda)3[Ce(pydc)3]24H2O (bda =butane-1,4-diamine, pydcH2 = pyridine-2,6-dicarboxylic
acid). In the crystalline network hydrogen bonds, pp
stacking, and ion pairing play important roles in the
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formation of supramolecular structures. The complexation
studies on these compounds in addition to Ni(II), Cu(II), and
Cd(II) compounds including the (H2bda)(pydc) ion pair have
also been performed. What about other diamines? It is
perhaps surprising that there are no thermochemical data for
butane-1,4-diamine. Then again, of all the a,x-diaminoalk-
anes, only the ethane and hexane [186] derivatives have
been so-investigated.A series of theoretical studies then follow. In the first
Wanno and Ruangpornvisuti [187] report use of DFT for
studying electronic properties and structural properties of
helical thiophene carbonsulfur oligomers, H2(C2S)nC2H2(n = 120). It was found that helix of the icosamer
(H2(C2S)20C2H2) makes one full turn for every approxi-
mately 3.493 A along its length and its inner diameter is
approximately 4.04 A. It may be asked how the aromaticity
varies with n. Then again, it must be asked are we using the
thermochemical, magnetic, or geometric criterion for aro-
maticity (see [188] for a study of the n = 2 case).
Mohajeri and Alipour [189] next describe use of con-ceptual DFT with the aim to compare the site selectivity in
the complete series of dichloropyridines as ambiphilic
molecules toward the reactivity and regioselectivity.
Nucleophilic and electrophilic characters were analyzed.
Of the six position isomers only 2,5-dichloropyridine is not
a dually active molecule and is just prone to nucleophilic
attack while remaining five are ambiphilic. The enthalpy of
formation of diverse chloropyridines is discussed in Refs.
[190, 191].
In the following paper, Deng and Zhou [192] used DFT
to study two complexes with significant antitumor activity,
[Ti(g5-C5H4{CMe2CH2CH2CH=CH2})2Cl2] and [Ti{Me2Si(g5-C5Me4)(g
5-C5H3{CMe2CH2CH2CH=CH2})}Cl2],
which have different substituent monofunctional bindings
to the purine bases and phosphate group which are poten-
tial binding targets. Results reveal that the monoaquated
complex binding to guanine shows the smallest activation
free-energy with 15.3 kcal mol-1 for the former and
21.5 kcal mol-1 for the latter complex. In the first dia-
quated compound, the lowest activation-free energy is
16.7 kcal mol-1 for the guanine closely followed by the
phosphate group by 18.3 kcal/mol, while the lowest acti-
vation-free energy is 16.9 kcal mol-1 for the second
complex binding to the phosphate group. Additionally,
major electronic characteristics were investigated. Are we
right to assume there is but a negligible effect of the p
electrons in the dimethylpentenyl substituent?
Then experimental paper by Zhang et al. [193] follows
in which synthesis and characterization by elemental
analysis, spectroscopic methods, and X-ray crystal analysis
of a series of dinuclear and trinuclear half-sand-
wichzirconocene complexes derived from (diphenyl-,
dibenzyl-)phosphate and methylphenylphosphinic acid is
reported. The results reveal the importance of experimental
conditions for the design of molecular structures. The tri-
nuclear species contain a central l3 oxygen. How strong is
the ZrO bond for these triply bridged species as opposed
to the more customary doubly bridging oxygen? There are
but few cases of multiply bridging oxygen for which the
thermochemistry is known. Among them are the so called
basic beryllium salts or beryllium oxy salts of the genericformula Be4OX6 with a l
4-oxygen at its core (X = nitrate
[194], acetate [195], and propionate [193]).
Alkorta and Elguero [196] investigated the absolute 13C
shielding of 13 methane derivatives (CH3X, X = CH3, CN,
NH2, NO2, OH, F, Cl, Br, SH, SeH, PH2) and proposed a
method for correction of chemical shifts obtained by DFT
calculations for carbon atoms directly linked to heavy
atoms that takes into account a quadratic variation with the
atomic number. It is well-established that the CO bond in
CH3OH is different than in (CH3)2O as shown by their
different proton affinities [19].
Machura et al. [197] managed to synthesize and char-acterize by IR, UVVis spectroscopy, magnetic measure-
ments, and X-ray crystallography a novel rhenium(III)
complex [ReBr3(dppt)(OPPh3)] (dppt = 5,6-diphenyl-3-(2-
pyridyl)-1,2,4-triazine). Using DFT approach the electronic
structure was determined. Spectroscopic and magnetic
properties were revealed to be characteristic of mononu-
clear complexes with d4 low-spin octahedral Re(III) com-
plexes (3T1g ground state). How different is the binding of
3-(2-pyridyl)-1,2,4-triazine and the isomeric 3,30-bis(py-
ridazines)? Insufficient is known about the energetics of
substituted pyridazines and triazines to attempt answering
this about metal complexes.
Systematic investigation by X-ray structural and thermal
analysis of solvates of nevirapine used in combination with
other antiretroviral drugs to treat HIV-1 infection and
AIDS, with the homologous series of primary alcohols
CH3(CH2)nOH with n = 27 is then reported by Steiger
et al. [198]. Nevirapine is a tetraaza derivative of diben-
zosuberane. The parent heterocycle is thermochemically
uncharacterized; only recently, the enthalpy of formation
of the corresponding carbocycle was reported [199].
In the paper by Kaczmarek et al. [200] synthesis and
characterization by spectroscopic methods and X-ray
structural analysis of (La(III), Eu(III), Gd(III), Er(III),
Tm(III), and Lu(III) complexes containing N,N0-bis(sali-
cylidene)-4-methyl-1,3-phenylenediamine (H2L) ligand is
presented formed by self-assembly formation of dinuclear
lanthanide salicylaldimines. Crystal structure determina-
tion revealed a rare coordination pattern of salen-type
ligand. There is a 12 kJ mol-1 spread in the enthalpies of
formation of the three isomeric phenylenediamines, as
solids. Now, how different are thus the related isomeric
salen-type ligands or any such complexes.
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Hamza [201] report on the synthesis of 5,6,11,12-tetra-
hydrodibenzo[a,e]cyclooctene (THDC) and its two selec-
tively deuterated isotopomers which were studied by
resonance-enhanced two-photon ionization spectroscopy in
a supersonic jet expansion. The results showed that about
90% of THDC in the gas phase exists in the twist-boat and
the remaining 10% in chair conformation. The enthalpy of
formation of the 5-keto species has been measured [202]but not that of the parent, three-ring compound mentioned
above. We welcome that of this species and note the
comparison of the enthalpies of formation of ben-
zocycloalkanes the corresponding keto compounds is of
continuing interest, e.g. [203] for a study of indane and the
isomeric indanones.
In the study by Kaynak et al. [204] synthesis, character-
ization including X-ray structural characterization and
theoretical investigations of two novel derivatives of 1,2,4-
triazolo[3,4-b]-1,3,4-thiadiazine, 3-[2-(4-methoxyphenyl)
ethyl]-6-phenyl-7H-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazine
and 3-[2-(3,4,5-trimethoxyphenyl)ethyl]-6-phenyl-7H-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazine having analgesic
anti-inflammatory activity is reported. The six-membered
thiadiazine ring adopts the screw boat conformation in both
compounds. Potential energy surface scans were drawn. We
know of no thermochemical studies for thiadazines. For
dithiazines, admittedly 1,3,5- and not 1,3,4-derivatives,
there is none but the over 100-year-old study [205] which is
simultaneously suspect and suggestive.
Campanelli et al. [206] in their contribution describe
advantages and limitations of gas-phase electron diffrac-
tion for determining molecular structure of five different
benzene derivatives, 1,4-difluorobenzene, 1,3,5-trifluoro-
benzene, 1,4-dichlorobenzene, 1,3,5-trichlorobenzene, and
silylbenzene. The report is rather unique, as it is only rarely
possible that the analyses can be repeated independently by
the same technique in two different laboratories. Except for
the last species, the enthalpy of formation of each of these
species is known. As such, we are thwarted from com-
paring the energetics of the phenyl transfer reaction
4C6H5EH3 ! C6H5 4E 3EH4 5
for E = C and Si.
Ethyl 2-methyl-4-(4-methylbenzoyl)-5-(4-methylphenyl)-
7-oxo-3,3a-dihydropyrazolo[1,5-c]pyrimidine-3-carboxylate
and ethyl 2-methyl-4-(4-methylbenzoyl)-5-(4-methylphenyl)-
7-thioxo-3,3a-dihydropyrazolo[1,5-c]pyrimidine-3-carbox-
ylate are interesting because of diverse medical and
biological activities of pyrimidine derivatives. These species
were successfully synthesized and characterized by Onal
et al. [207] by reactions of 1-amino-5-(4-methylbenzoyl)-4-
(4-methylphenyl)pyrimidin-2(1H)-one/-thione with ethyl
acetoacetate. Theoretical calculations (DFT, NBO analysis,
and Fukui function) revealed the former compound is more
stable than the latter. We note the initial synthetic step
involves furan-2,3-diones. To the extent that furan is aro-
matic, are these species at least antiaromatic because of
their nominal 4 p electrons as discussed for the isomerically
related furan-2,5-dione (more commonly known as maleic
anhydride) [208]?
Isomerization of azobenzene derivatives is important
from the perspective of their applications. Using DFT Zhuet al. [209] studied cistrans isomerization mechanisms in
the S0 and T1 states of 3,30-azobenzene disulfonate. In the
S0 state the energy barrier is 22.79 kcal mol-1 and it con-
cerns mainly the rotational pathway around the NN double
bond while the energy barrier of T1 state is 5.02 kcal mol-1
and requires a change in spin-multiplicity. The strength of
NN bonds in azo compounds shows considerable depen-
dence on the affixed groups [210]. How is that reflected in
the rotational barriers of these azo compounds?
Picolinic acid derivatives form a group of bidentate
ligands effectively complex the tricarbonyltechne-
tium(I) and rhenium(I) cations and form promising radio-pharmaceutical precursors. Using DFT, Fuks et al. [211]
proved that in vitro behavior of tricarbonylrhenium(I) and
tricarbonyltechnetium(I) complexed by the N-methyl-2-
pyridinecarboxyamide and chloride, water or tert-butyl-3-
isocyanopropionate is thermodynamically controlled. The
energy of formation of the complexes containing tert-
butyl-3-isocyanopropanoate ligand is more negative by a
few kcal mol-1 than energy of those having a coordinated
water molecules instead. The energetics ofp-complexes of
the valence isoelectronic tricarbonylmanganese(I) cation
has recently been reviewed [212]. Comparison with the
above technetium and rhenium species is welcomed.
Hayvali et al. [213] report the synthesis and character-
ization of the substituted benzyloxybenzaldehyde deriva-
tives by reaction of the appropriate hydroxy benzaldehydes
with p-nitrobenzyl bromide in DMF and NaOH. After 5 h
of reflux with furfuryl amine the corresponding imine
compounds were formed, and the crystal structures were
determined. After longer reflux time, cyclization reaction
with a CO bond occurs and corresponding benzofuran
derivatives are formed. Quoting a recent review [214],
de-benzoannnelation resulting in an aromatic one-ring
species (e.g., benzofuran) is generally more favorable than
processes involving non- or antiaromatic species. This
was discussed in context of heterocyclic analogs of indene
and indane, cyclopentadiene and cyclopentene, with benzo-
annelated 5-membered rings. What about other size rings,
e.g., the 6-membered ring containing analogs of naphtha-
lene and its hydrogenated derivatives?
A series of theoretical papers then follows. Using DFT,
Zhu and Xiao [215] studied substituent effects on the
electronic structure and properties of the 1H-tetrazole
crystal and variously substituted derivatives. The
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calculated thermodynamic properties show that the order
of their thermodynamic stability is 5-amino-1H-tetrazole
\5-methyl-1H-tetrazole\5-azido-1H-tetrazole\1H-tetra-
zole and that their decomposition reactions are favorable at
high temperature. An attempt to correlate the impact sen-
sitivity of the four crystals with their band gaps showed
that the first-principles band gap criterion can be used to
predict impact sensitivity for the substituted 1H-tetrazoles.Do the same substituent trends for stability apply to the
isomeric triazoles, diazoles and parent pyrroles?
In the subsequent paper by Huang et al. [216] use of
DFT, the QTAIM and NBO analyses to study hydrogen
bonds and the interaction characteristics in cysteineprop-
anoic acid complexes are reported. More than 10 kinds of
H-bonds including intra- and intermolecular H-bonds have
been found. The results show that the important factors for
the stability of complexes are strength of H-bonds and the
deformations. What about alanine and serinepropanoic
acid complexes? When can we ignore hydrogen bonding
involving SH groups?Further Huang et al. [217] report use of DFT, QTAIM,
and NBO to study geometries, energies, and IR charac-
teristics of the intermolecular hydrogen bonds in com-
plexes formed between N-protonated adrenaline and
dimethyl sulfoxide. While the H-bonds involving amino or
hydroxyls as H-donor are dominant in complexes and
considered as strong H-bonds, weak H-bonds, such as p
H-bonds and H-bonds involving methyl or methenyls
(C2H6 and C5H7 of AdH?) as H-acceptors were found in
complexes as well. The reader will note we said N-pro-
tonated earlier in this paragraph. Was there a choice? For a
discussion of the alternative N and O protonation sites in
aminoalcohols, the reader is referred to Ref. [218].
Using DFT the structures and properties of the planar
double hydrogen-bonded imidazoleadenineimidazole
trimer were studied by Cui et al. [219]. The H-bond gen-
erated by NH group of adenine decreases significantly in
length upon oxidation to form the radical cation and sig-
nificant IR spectra red-shift occurs upon oxidation for all
NHH bonds. The molecular orbital analysis was effec-tive to reveal the geometry variations and the IR spectral
shifts. We note that while the ionization energy of imid-
azole is greater than that of purine as the authors point out,
the proton affinities are in the reverse order [19].
The theoretical study by Qi et al. [220] follows with a
study of the insertions of the p-complex silylenoid H2SiLiF
into CX bonds of CH3XHn-1 (X = F, Cl, Br, O, N;
n = 1, 1, 1, 2, 3) using DFT is the following. The results
revealed that substituted silanes H2Si(XHn-1)CH3 and LiF
are formed. The reaction barriers for the insertion of the
p-complex into CX bond increase for the same-row ele-
ment X from right to left in the periodic table and do not
change much for the insertion of the same family element
X. All this is sensible except that we also note there are no
reliable measurements of the CF bond strength in CH3F or
equivalently, of the enthalpy of formation of methyl
fluoride.
Alkorta and Elguero [221] report conformational anal-
ysis of medium-sized rings, namely four derivatives of
cyclooctadiene bearing two aromatic or heteroaromatic
rings. Good agreement between experimental results andtheoretical results was reached. We look forward to studies
comparing the findings of Hamza [201] to this article.
In the last paper in this issue Zhan and Feng [222] report
on synthesis of two 3D supramolecular complexes con-
structed from p-thioacetatebenzoic acid (H2L), [Mn(HL)2(bpp)2(H2O)2]n and [NiL(4,4
0bipy)(H2O)3]nnH2O (bpp =
1,3-bi(4-pyridyl)propane, 4,40-bipy = 4,40-bipyridine). The
former compound exhibits intense structure-related fluo-
rescent emission bands. The latter exhibits irreversible
redox processes. The enthalpy of formation of numerous
substituted benzoic acids has been studied. We know of no
examples where the substituent is bonded to the benzenering by a sulfurhowever, enthalpy of hydrolysis studies
discussing CH3C(O)O- and CH3C(O)S-substituted benzoic
acids is recalled [223, 224].
Issue 5
Issue 5 of the present volume opens with the editorial by
Hargittai [225] written in honor of Gyorgy Kepes, designer
and art theorist. Although not a chemist Kepes managed to
influence chemistry and science with his visionary
approach in design and so ultimately accomplishing design
in science.
The next paper is a theoretical study by Beheshtian et al.
[226] in which the DFT approach was used to study the
interaction of water with the outer layer of single-walled
boron nitride nanotubes. The results suggest that water can
be adsorbed on the surface through BO interactions by asignificant charge transfer and NHO hydrogen bond
interactions, and that the water is better adsorbed as the
cluster size increases. As an archetypical study, we ask
what is the interaction energy of borazine with water and is
B or N-bonding to water preferable? What is the hydration
energy of borazine to form the saturated B,B0,B00-tri-
hydroxyborazane? We note that borazine photochemically
reacts with water to form the B-hydroxy derivative and the
corresponding ether [227], the latter being shown to be
more stable. By contrast, for the isoelectronic benzene
derivatives, phenol is rather much more stable than the
corresponding ether (?water).
In multiple types of non-bonded interactions it is intui-
tively expected that they would be formed hierarchically
based on energetic gains. In the paper by Rathore et al.
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[228], synthesis of derivatives of 3-azabicyclo[3.3.1]
nonan-9-one, namely 10,12-bis(2-fluorophenyl)-11-azatri-
cyclo[7.3.1.02,7]trideca-2,4,6-trien-13-one, and its bis(2-
methylphenyl) and bis(2-methoxyphenyl) counterparts, is
reported and the interactions studied. Preferences for
weaker interactions over strong hydrogen bonds were
observed. How strong are the nitrogencarbonyl transan-
nular interactions in these species and how are theseinteractions impacted by the above substitution of the two
phenyl groups?
What follows is a theoretical study by Goodarzi et al.
[229], who investigated energies of the gas phase reaction of
SewithO3 using DFT. As calculationally shown, SeO3(D3h)
and (SeO ? 3O2) products are obtained via transformations
of the linear chain SeO3 isomer. Both reactions are at
atmospheric pressure and temperature of 298.15 K exo-
thermic and exergonic (DH\ 0,DG\ 0).WenoteSeO2 is a
classic oxidizing agent in organic chemistry; presumably
SeO3 would be even more oxidizing. Sulfur dioxide is an
occasional reductant. This is reflected in some 70 kJ mol-1
difference in the enthalpies of formation of selenium diox-
ide, as solid, and sulfur dioxide, as gas (where the solid is
unequivocally even more stable by an unstated enthalpy of
sublimation). The difference is over 200 kJ mol-1 for the
trioxides for the same choice of phases. Why do the dioxides
and trioxides differ by so much?
He et al. [230] in their experimental paper report on
synthesis and characterization including X-ray single crystal
analysis of 3d4f heterometallic coordination polymers
based on 2,5- and 2,6-pyridinedicarboxylic acid, [Cu3Eu2(2,5-pydc)6(H2O)12]4(H2O), [Zn2Eu2(2,5-pydc)5(H2O)2]
3(H2O), and [Co3Ln2(2,6-pydc)6 (H2O)6]4(H2O) (Ln = Eu,3; Dy, 4) (H2pydc = pyridinedicarboxylic acid) under
hydrothermal conditions. The results, which indicate that
compounds generate 3D heterometallic coordination frame-
works containing 1D channels that are occupied by lattice
water guest mole, are important from the perspective of
further construction of novel 3D lanthanidetransition metal
heterometallic coordination frameworks. We note the tran-
sition metal is always divalent while the lanthanide is always
trivalent. Some transition metals are naturally trivalent while
some lanthanides enjoy the divalent oxidation state. Can
related species be prepared with these reversed oxidation
states and how does that effect the structure, and thereby
properties, of these complexes?
With the aim to investigate influence of oxidation
damage on the guanine:cytosine base pairs Qiu et al. [231]
studied structures of their derivatives with MllerPlesset
perturbation theory. Marked differences in the interaction
energy were shown: among the hydrogen bond complexes
ranging from-24.1 to-13.0 kcal mol-1 for derivatives of
the guanine bonded to cytosine derivatives and from-24.5
to -9.7 kcal mol-1 for cytosine bonded to guanine
derivatives. Thermochemical data for the free component
nucleobases and their derivatives are almost totally absent
in the experimental literature (see Domalski [46] but not
Pedley). We note that the unmodified