CHAPTER 1 SYNTHESIS OF SELECTED FUNCTIONALIZED

CALIX[4]PYRROLES AND THEIR NON COVALENT INTERACTIONS

“ Don’t read success stories,u will only get a message. Read failure stories , u will get some ideas to get success”

-Dr. A. P. J. Abdul Kalam

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1.1 INTRODUCTION

Meso-Octamethylcalix[4]pyrrole ( a molecule first synthesized more than 100 years ago 1 along with its many derivatives are a well recognized class of anion receptor but only recently it has been investigated as chemical receptor for small anions.2 ,3 ,4 ,5 ,6 ,7 ,8 This easy to make tetrapyrrolic macrocycle has been known for over a century, yet its anion binding potential has only recently been discovered. This discovery has prompted various structural modifications 9 ,10

,11 , 12 ,13 in hopes of fine-tuning the affinity and selectivity for a variety of anions. Despite the considerable amount of experimental 14 ,15 and theoretical16 ,17 ,18 ,19 work devoted to understanding the anion binding behavior of calixpyrroles, there remain a number of issues that are not fully resolved, including those associated with solute, solvent, and countercation effects. Structural flexibility is a characteristic of the calix[4]pyrroles. A closer look at the structure of calix[4]pyrroles leads to an appreciation that they can adopt four different conformations. The form predicted to be most stable,20and experimentally lowest energetically, is the 1,3 alternate conformation, where the pyrroles are found to alternate in an up-down-up-down setup. In the solid state, the known octamethyl derivative Me8-calix- [4]pyrrole adopts a 1,3-alternate conformation in the absence of substrates as judged from single-crystal X-ray diffraction analysis21, 22, 23 and a cone conformation when bound to F-or Cl- 24. Among the various modifications, introduction of straps on one side of the calix[4]pyrroles are the most effective. Incorporation of aromatic rings other than pyrroles also exhibited interesting binding behaviour. Introduction of signalling units as part of the strapping element enable to detect the anions on chromogenic or fluorogenic fashion. Finding of the anion transport properties across the membrane and cytotoxic effects of the calix[4]pyrroles open new window for calixpyrrole-related research. The polymer-incorporated systems have also been employed as anion complexants in solvent-solvent extraction. These old, yet easy-to-make macrocycles have well advanced more recently with the discovery of the ion-pair complexation properties. 1.1.1 Altering the binding affinity towards anions through substitution and structural means. Anion binding is one of the important phenomena for different medicinal and biological processes. The selective detection of anion is of importance in environmental monitoring,

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medicinal diagnostics, catalysis and in the analysis of biological samples .25, 26 , 27 The use of non-covalent interactions such as hydrogen bonding, electrostatic interactions and coordination with metal complexes have been used in the detection of anions by receptors 28 , 29. The calix[4]pyrroles are macrocyclic compounds formed by condensation of pyrrole and ketones through the pyrrolic 2 and 5 positions by sp2 hybridized carbon atoms analogous to calix[4]arenes 30, 31. The anion binding properties of calix[4]pyrroles have been examined by UV–Visible 32, 33 , fluorescence34 and 1H NMR spectroscopy .35 , 36 , 37

Among the various non-covalent interactions that might prove useful for the assembly of electron-transfer systems, anion binding appears particularly attractive. Recently, anion recognition has emerged as an important sub-discipline within the broader field of supramolecular chemistry. In order to use such supramolecular complexes as models for the photosynthetic reaction centre, the rates of anion binding and the dissociation from the supramolecular complexes must be slower than the electron-transfer processes. The first system found to be suitable for the analysis of anion binding and photoinduced electron-transfer dynamics is based on the use of the cyclo[8]pyrrole. An acetate anion (AcO-) binds to diprotonated form ([C8.2H]2+) to produce a supramolecular complex, [C8.OAc.Cl], wherein strong hydrogen bonds are formed between the AcO- substrate and the pyrrole protons as shown in Scheme 1.1 .

Scheme 1. 1 : Model used to fit the kinetic data obtained upon mixing C8.2HCl with TBAOAc. The kinetics of AcO- binding to [C8.2H]2+ was monitored by following the absorbance change at 425 nm in acetonitrile (MeCN) at 243 K using stopped-flow methods. The binding obeyed first-

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order kinetics and the observed first-order rate constant (kobs) was found to increase with increasing AcO- concentration . The binding constant Ka value was found to be (9.5± 0.9) ×104

M-1 . This concordance, although not a ‘proof’, serves as important check for the kinetic parameters obtained via stopped flow. The off-rate of 200 s-1 corresponds to a lifetime of 5 ms.

1.1.2 Functionalized calixpyrroles and their applications One of the early goals of the research was to synthesize functionalized calix[4]pyrroles that would allow a range of applications to be targeted.38 Some specific structures and applications for which they might be suited is described below .

1.1.2.1 Calix[4]pyrrole-Based Receptor That Displays Anion-Modulated, Cation-Binding Behavior The receptor systems that can bind both anionic and cationic guests, are particularly attractive because of their potential applications in various fields including salt solubilization,39 extraction,40 trans-membrane ion-transport agents41 ,42 and as recognition elements in chemosensors43 , 44 or logic gates.45 , 46 To date, a number of systems containing two different binding sites within a single molecular framework have been reported.47, 48, 49 Such systems are of interest because they might allow for a fine-tuning of the recognition properties by appropriate placement of the ion binding sites within suitably preorganized scaffolds. Recently, a new ion-pair receptor, specifically a calix[4]pyrrole core that is covalently linked to a m-dibenzo-[26]crown-8 subunit through phenyl spacers 50 ( Scheme 1.2 ) has been reported . This system, was found to act as an anion-modulated, cationselective ion-pair receptor in CDCl3 and CD3CN, displaying selectivity for specific cation and anion combinations within a series of closely related salts of alkali and alkaline earth metals. Detailed binding studies served to confirm that this receptor binds fluoride and chloride ions (studied as their tetraalkylammonium salts) and forms stable 1:1 complexes in CDCl3. Treatment of the halide-ion complexes of I with Group I and II metal ions (Li+, Na+, K+, Cs+, Mg2+ and Ca2+ ; studied as their perchlorate salts in CD3CN) revealed unique interactions that were found to depend on both the choice of the added cation and the precomplexed anion. In the case of the fluoride complex [1·F]- (preformed as the tetrabutylammonium (TBA+) complex), little evidence of interaction with the K+ ion was seen.

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Scheme 1. 2 : Synthesis of the bis(1,3-phenylene)-[26]crown-8-capped calix[4]pyrrole In contrast, when this same complex (i.e., [1·F]- as the TBA+ salt) was treated with the Li+ or Na+ ions, complete decomplexation of the receptor-bound fluoride ion was observed. In sharp contrast to what was seen with Li+, Na+ and K+, treating complex [1·F]- with the Cs+ ion gave rise to a stable, receptor-bound ion-pair complex [Cs·1·F] that contains the Cs+ ion complexed within the cup-like cavity of the calix[4]pyrrole, which in turn was stabilized in its cone conformation. Different complexation behavior was observed in the case of the chloride complex [1·Cl]- . 1.1.2.2 Calixpyrrole−trans-Pt(II) Complex in Drug Delivery A number of novel drug-delivery methods have emerged over recent years that are based on the achievements of supramolecular chemistry and which include the use of dendrimers. Platinum complexes are a group of anticancer drugs with a long history, cis-[PtCl2(NH3)2] being the first of a large number of Pt(II) derivatives studied in this area, a few of which have reached and are still in clinical use.51 ,52 ,53 ,54 ,55 The initial assumption that cis-stereochemistry is an absolute prerequisite for anticancer activity, fostered by the observation that the trans-[PtCl2(NH3)2] is inactive, has been re-examined by the discovery of a number of trans-Pt(II) derivatives that were

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found to be effective and/or even complementary where cis-[PtCl2(NH3)2] resistance was observed.56 ,57 ,58 ,59 ,60 In 1998, Sessler and co-workers 61 reported that SiO2 stationary phase functionalized with calix[4]pyrrole units could be used in the HPLC separation of oligonucleotides and peptides with advantages over sapphyrin-modified silica gels, thus indicating the ability of the calix[4]pyrrole unit to recognize these anionic biomolecules. Inspired by the above-mentioned results on the separation of oligonucleotides, the aminophenyl derivative of calix[4]pyrrole was prepared (Scheme 1.3) to be used as a suitable ligand in Pt(II) coordination. Adenosine monophosphate (AMP) was used as a model compound to evaluate the potential for the assisted delivery of the metal to the DNA nucleobases via the phosphate anion-binding properties of the calix[4]pyrrole unit. An NMR investigation of the kinetics of AMP complexation in the absence of an H-bonding competing solvent (dry CD3CN) was consistent with this hypothesis, but the interaction of the calix[4]pyrrole with phosphate in the presence of water could not be detected . However, in vitro tests of the new trans-calixpyrrole−Pt(II) complex on different cancer cell lines indicate a cytotoxic activity that is unquestionably derived from the coexistence of both the trans-Pt(II) fragment and the calix[4]pyrrole unit.

Scheme 1. 3 : Synthesis of meso-p-nitroaniline-calix[4]pyrrole derivative trans-coordinated to a

Pt(II) center

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Specifically, we have concentrated on altering both, the structural, and electronic properties of these molecules to approach concerns with selectivity, binding strength and application based uses. Early endeavors focused on appending the calix[4]pyrrole core in such ways to exhibit varying behaviors such as cooperative effects and anion extraction through the synthesis of an anion sponge. The synthesis of calixpyrroles bears analogy to that of porphyrins in that they are obtained from the condensation of pyrrole with an electrophile. In the case of calixpyrroles, the electrophile is a ketone, whereas in the case of porphyrins, it is generally an aldehyde. 1.2 RESULTS AND DISCUSSION 1.2.1 Synthesis of meso aryl substituted calix[4]pyrroles and separation of their isomers The synthesis of calixpyrroles bears analogy to that of porphyrins in that they are obtained from the condensation of pyrrole with an electrophile. In the case of calixpyrroles, the electrophile is a ketone, whereas in the case of porphyrins, it is generally an aldehyde. The substituents in the meso-position and the N or C-rim of pyrrole rings play a significant role in the choice of the preferred conformation and tunability of substrate binding strength . In recent years, calixpyrroles with functional group were also reported, including the modification of the molecular skeleton. Aryl extended calix[4]pyrroles are produced by substitution at each of the 4 meso-carbons with aryl group.Tetramethyl tetraaryl calix[4]pyrroles are actually formed as a mixture of configurational isomers as depicted in Figure 1.1 . These can exist in the form of four different configurational isomers, as well as in different conformational forms62. Although there are no detailed studies on the conformational features of aryl extended calixpyrroles, we (63 , 64) and others (65) have observed that their chloride and fluoride complexes adopt the cone conformation in solution and in the solid state.

NH

NH HN

HN

Ar

Ar

Ar

Ar NH

NH HN

HN

Ar

Ar

Ar

NH

NH HN

HN

Ar

Ar

Ar

Ar

NH

NH HN

HN

Ar

Ar

Ar

ArAr

αααα ααββ αααβ αβαβ

Figure 1. 1 : Possible isomers of meso-substituted tetramethyl tetraaryl calix[4]pyrroles

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This conformation has also been routinely observed in the crystal structure of aryl extended calixpyrroles grown from hydrogen bonding solvents (e.g., acetonitrile, acetone and N,Ndimethylformamide) (66) . Four of the configurational isomers, namely the αααα, αααβ, αβαβ and ααββ isomers, where the terms “α” and “β” indicate whether the bulky functionalized phenyl substituent faces “up” or “down” relative to the mean calixpyrrole plane, were isolated by column chromatography. Different isomers have been separated from one another and found to display, interestingly enough, differing relative anion binding affinities67. It is clearly shown in Figure 1.2 that in the cone conformation , the αααα isomers of aryl extended calix[4]pyrroles have a deep aromatic cavity suitable for including molecular guests .

HN HN

HN H

NHN

HN N

HNH

R

R RR

Cl-

αααα - isomer1,3 alternate conformer Cl- complex , cone conformation

Cl-

RR R R

Figure 1. 2 : Molecular structures of aryl extended calix[4]pyrroles. Conformational change of

the αααα - isomer from 1,3-alternate to cone promoted by chloride binding. 1.2.2 Synthesis and isolation of configurational isomers of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetraaryl calix[4]pyrroles The acid-catalyzed condensation of arylmethyl ketone with pyrrole ( Scheme 1.4 ) affords a new type of calix[4]pyrrole derivative that contains deep cavities and fixed walls. These new systems, which can be readily converted into the corresponding 4-methoxyphenyl species, can exist in the form of four different configurational isomers, as well as in different conformational forms. The aromatic cavity present in the cone conformation of aryl extended calix[4]pyrroles is deeper and more sizeable than that of a corresponding calixarene counterpart. Furthermore, and similarly to calixarenes, aryl extended calix[4]pyrroles possess an ‘‘upper rim’’ , surrounding the open end

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of their structure, which can be functionalized and further elaborated. However, in striking contrast with calixarenes, the deeper aromatic cavity of aryl extended calix[4]pyrroles is functionalized in its closed end with 4 converging NHs.

Scheme 1. 4 : Synthesis of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetraaryl calix[4]pyrroles These configurational isomers can be easily distinguished from β-proton peaks of pyrrole in 1H-NMR . For αααα isomer the eight β-protons of the calix[4]pyrrole are equivalent and should theoretically depict a singlet whereas the ααββ should depict a triplet for three type of β-pyrrolic protons in the ratio 1:1:2 . But it is observed that the αααα isomer shows a doublet at 5.95ppm(doublet for coupling with NH-protons ) ( Figure 1.3 ) where coupling constant J = 2.6Hz , whereas the ααββ shows a triplet at 5.82ppm , J= 2.6 Hz ( Figure 1.5 ) . We further took a 2D-COSY spectrum ( Figure 1.4 ) to support the αααα isomer . However there is change in the chemical shift of aryl protons depending upon the type of groups attatched to the benzene ring.

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Figure 1. 3 : 1H-NMR of αααα isomer of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra(-4-

nitrophenyl) calix[4]pyrrole in CDCl3

Figure 1. 4 : 2D-COSY NMR of αααα isomer of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra(- 4-

nitrophenyl) calix[4]pyrrole in CDCl3

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Figure 1. 5 : 1H-NMR of ααββ isomer of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra(4-

nitrophenyl) calix[4]pyrrole in CDCl3

1.2.2.1 Synthesis of αααα-isomer of tetraureacalix[4]pyrrole Calix[4]pyrroles having extended aromatic cavities were functionalized with 4 ureas in the para position of their meso phenyl substituents. Synthesis of tetraurea claix[4]pyrrole was completed in three steps . The tetranitroaryl extended calix[4]pyrrole was synthesized by acid condensation of pyrrole and 1-(4- nitrophenyl)ethanone in dichloromethane 68. Of the 4 possible configurational isomers, the αααα-isomer was isolated after careful purification of the reaction mixture (column chromatography and crystallization) as a yellowish solid in 10% yield. Catalytic hydrogenation of tetranitro calix[4]pyrrole using H2/10% Pd-C as catalyst in ethyl acetate afforded the corresponding tetraamine . Subsequent reaction of tetraamine with p-methylbenzylisocyanate gave the corresponding tetraurea(5) in good yield.

HN HN

HN H

N

NO2 NO2

O2N

NO2

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11

NH

COCH3

NO2

NH HN

HNNH

H3C

CH3

CH3

H3C

NO2

NO2

O2N

O2N

+HCl , ethanol20 hrs , r.t

NH HN

HNNH

H3C

CH3

CH3

H3C

NH2

NH2

H2N

H2N

RNCO

CHCl3 ,rt , 2 hrsNH HN

HNNH

H3C

CH3

CH3

H3C

NHCONHR

NHCONHR

RHNOCHN

RHNOCHN

Pd / C

CH3R =

5 4

Scheme 1. 5 : Synthesis of αααα-isomer of tetraurea calix[4]pyrrole

Urea is a good H-bond donor and an excellent receptor for Y-shaped anions, such as carboxylates, through the formation of two hydrogen bonds.

H3C

O

O N

N

O

H

H

Moreover, selectivity is also related to the energy of the receptor-anion interaction; in this sense, strong H-bond interactions are established with anions containing the most electronegative atoms: F (fluoride) and O (carboxylates, inorganic oxoanions)69. 1 contain eight urea NH groups as hydrogen-bonding donors . Solvent cannot be polar or any other hydrogen bond-forming medium since they would compete successfully with the receptor for the anion. Thus, aprotic

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solvents of varying polarity are currently employed in anion recognition studies based on H-bonds (e.g. CHCl3, MeCN, and DMSO). 1H-NMR of tetraurea calix[4]pyrrole is shown in Figure 1.6 . Characteristic peaks of tetraurea calix[4]pyrrole are the protons in the region 5.7–8.7 ppm . The 4 pyrrole NHs emerge as a broad singlet at δ = 8.71 ppm (proton j). One doublet at 5.78 ppm , J=2.68 Hz depicts only one type of β–pyrrole ( protons i ) conforming αααα conformation for the molecule . Two doublets ( ortho coupled ) at 6.93 , 7.30 ppm depict aryl protons g and f respectively and two doublets ( ortho coupled ) at 7.08 , 7.29 ppm depict aryl protons b and c respectively . Broad singlets at 7.24 and 7.26 ppm represent urea protons e and d respectively .

Figure 1. 6 : 1H-NMR of αααα isomer of tetraurea calix[4]pyrrole in CH3CN

NH

NH HN

HN

H3C

CH3

CH3

H3C

HN

NH

NH

HNHN

HN

NH

NH

O

O

O

O

CH3

CH3

H3C

H3C

abcd

efgh

ij

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1.2.2.1.1 UV – Visible absorption spectrum studies of αααα isomer of tetraurea calix[4]pyrrole with anions (used as tetrabutylammonium salt) in MeCN The interaction of receptor 5 with the anions(used as tetrabutylammonium salt) was investigated in MeCN solution through UV-VIS titration experiments . A standard solution of anions(in form of tetrabutyl ammonium salt) in MeCN was added stepwise to 1× 10-5 M solution of 1 at 25 oC. MeCN was used due to better solubility of the receptor in the solvent. The UV–vis spectra of urea 5 changed dramatically on addition of fluoride (Figure 1.7a) , dihydrogen phosphate (Figure 1.8a) and acetate anions (Figure 1.7b). On addition of fluoride anions in MeCN (1× 10-5 M), the characteristic absorption peak of 1 at 259 nm decreased gradually with a red shift and a new peak at 264 nm was produced. Figure 1.7 shows the family of spectra taken during the course of the titration for fluoride, acetate and dihydrogen phosphate(as tetrabutyl ammonium salts) with receptor 1 in MeCN.

( a )

( b )

Figure 1. 7 : UV-vis titration of receptor 5 (1 x 10-5 M) with (a) F-n-Bu4N+ (b) AcO-n-Bu4N+ in MeCN from 0 equiv. - 20 equiv.

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14

( a )

( b ) ( c ) ( d )

Figure 1. 8 : UV-vis titration of receptor 5 (1 x 10-5 M) with (a) H2PO4-n-Bu4N+ (b) HSO4-n-Bu4N+ (c) Cl-n-Bu4N+ (d) Br-n-Bu4N+ in MeCN from 0 equiv. - 20 equiv.

Figure 1. 9 : Titration profile of 1 x 10-5 M MeCN solution in receptor 5, indicates the formation

of a 2:1 adduct [CH3COO:5]

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At the same time a clear isobestic point at 260 nm for fluoride and 261 nm for acetate and 259 nm for dihydrogenphosphate was observed. But the receptor 5 was found to be insensitive to addition of a large excess of hydrogen sulphate ,chloride and bromide (Figure 1.8) . The titration profile shown in Figure 1.9 , indicates a 2:1 stoichiometry for the process. The binding constant(Kass) values are summarized in Table 1.1.

Table 1.1 Association constants (Kass)a for receptor 5 (M-1) and anionic substrates both at 1.0 ×10-5 M

in MeCN solution at 25 oCb F- Cl- Br- I- AcO- H2PO4

- HSO4-

3 × 108 n.dc n.dc n.dc 4.4 × 108 6 × 108 n.dc

a Determined from absorption spectroscopic titrations b All errors are ± 15%. c Changes in the UV–vis spectra were insufficient to calculate the binding constants 1.2.2.1.2 Study of interaction of tetraurea calix[4]pyrrole (5) with anions by 1H-NMR spectroscopy in CD3CN To get more insight about the binding of receptor 5 with anions , 1H-NMR titration experiments were carried out in CD3CN .The interaction of receptor 5 with flouride (used as tetrabutylammonium salt) was investigated (Figure 1.10). A 10×10-3 M CD3CN solution of tetraurea was titrated with F-, which was added stepwise up to 5 equiv. Figure 2 shows the NMR spectra obtained in the course of the titration and illustrates the spectral shifts. Dramatic changes were observed for both the urea and the pyrrole NH protons . Deshielding is observed for the pyrrolic protons on addition of fluoride anion(in form of tetrabutylammonium salts) in CD3CN. The pyrrole peak initially at 8.71 ppm is shifted to 13 ppm . A similar pattern is observed for urea NH protons .The urea peaks shift from 7.26 and 7.24 ppm to 10.56 and 10.43 ppm. We thus conclude that the anions are encapsulated within the deep cavity of αααα - isomer of tetra urea calix[4]pyrrole . On careful examination of the titration spectra , it was observed that the β-pyrrolic protons became broadened and experienced a significant upfield shifting (∆δβ-pyrrolic = 0.05 to 0.1), since anion binding to the pyrrole NHs is expected to increase the electron density on the pyrrole ring and engender upfield shifts in the β-pyrrolic CH signals. The observed

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spectral shifts are consistent with the structural changes that cause the respective protons to move away from the Calix[4]pyrrole plane upon anion binding . The experimental observations suggest that tetraurea calix[4]pyrrole attain a preferential cone conformation upon anion binding , which is in agreement with the various theoretical studies reported previously.70 The final results are pictorially depicted in Figure 1.11 .

Figure 1.10 : Titration of a 5 × 10-3 M solution of receptor 5 in CD3CN with F-(as TBA salt)

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Figure 1. 11 : Pictorial depiction of how tetraurea interacts with anions

Fullerenes (originally buckminsterfullerenes) are a new class of carbon molecules; the first example discovered in 1985,71 being composed of sixty carbon atoms arranged in a soccer-ball structure (C60). The condensed aromatic rings present in the compound lead to an extended π-conjugated system of molecular orbitals and therefore to significant absorption of visible light. Along with the characteristic covalent σ-bonding, fullerenes are known to form rather stable conjugates held together by noncovalent forces, i.e. π–π stacking interactions, donor–acceptor bonds, hydrophobic inclusion interactions, and other bonding interactions with different classes of organic compounds. Construction of supramolecular architectures involving electrondeficient fullerenes72 , 73 and various host compound such as calix[n]arene,74, 75 , 76 , 77 crown ether,78 , 79 porphyrin,80 ,81 , 82 , 83 , 84 , 85 , 86, 87 , 88 , 89 and phthalocyanine , 90,91,92,93,94 is not only a topic of current interestsstudies along these lines have led to some significant practical applications 95, 96 ,

97 , 98 , 99 .

Photophysical and electrochemical studies have revealed that C60 and their derivatives are excellent electron acceptors100 , 101 . Recently Debabrata Pal and his coworkers have proved meso-octamethyl calix[4]pyrrole to behave as an efficient macrocyclic receptor in forming productive ground state noncovalent complexes with fullerenes C60 and C70 in solvents with high dielectric constant . All these results provoked us to investigate the complexation pattern

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and binding strength of the αααα isomer of tetraurea with C60 Fullerene in CHCl3 using UV-vis spectroscopic techniques. 1.2.3 Spectrochemical investigation of non covalent interactions of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetraaryl calix[4]pyrroles with Fullerene (C60) The purpose of the present investigations is to examine the nature of the complexation pattern and binding strength of the αααα and ααββ isomers of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(4-nitrophenyl) calix[4]pyrrole with C60 Fullerene in CHCl3 because tetraurea C4P does not show appreciable change in UV-VIS titration for satisfactory determination of binding constant . The 1H-NMR titration depicts that pyrrolic NH-protons do not undergo any appreciable change(7.8735 to 7.8736 ppm ) on addition of C60 to tetraurea in CHCl3 . Whereas the urea NH-protons get shielded and shift from 6.99 ,6.92 ppm to 6.97 , 6.90 ppm . This suggests that the Fullerene does not interact to the inner core NH-protons of calix[4]pyrrole . Fullerene is present on the periphery of the deep cavity tetraurea calix[4]pyrrole , thus causing a minor change in the chemical shift of the urea NH-protons . Moreover these urea NH-protons are shielded due to anisotropic effect of fullerene thus. 1.2.3.1 UV-Vis and 1H-NMR spectroscopic techniques for insight into non covalent interactions of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetraaryl calix[4]pyrroles with (C60) UV-vis spectroscopic techniques were employed for the determination of the binding constant(K) 102 of C60 fullerene- tetraaryl calix[4]pyrrole complex. It is observed that with the gradual addition of αααα tetraurea calix[4]pyrrole to the C60 solution in CHCl3 the intensity of the absorption band of the C60 fullerene does not show any appreciable change . This may be attributed to the deep cavity of αααα tetraurea calix[4]pyrrole which is unfavourable for the convex shaped C60 molecule interaction . However on the other hand the αααα and ααββ isomers of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetrakis(4-nitrophenyl) calix[4]pyrrole show an appreciable change on addition to C60 solution in CHCl3 in UV-Visible spectrum .UV-vis titration plot for the C60-tetranitro calix[4]pyrrole in chloroform medium is shown in Figure 1.12 for both the isomers. It is observed that with the gradual addition of configurational isomers of 3 to the C60 solution , the intensity of the absorption band at 329 nm( resulting from a forbidden singlet-singlet transition in C60) of the

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C60 fullerene increases . The increase in intensity of the band at 329.7 nm is due to molecular complex formation between fullerene and receptor .

Figure 1. 12 : UV-VIS titration plot of 1.36×10-6 M solution of fullerene C60 upon addition of 3.92×10-5 M of (a) receptor 1 and (b) receptor 3 in CHCl3

Titration curves gave a satisfactory fit to a 1:1 binding model as confirmed by the continuous variation method. Figure 1.13 shows the Job’s plot of the data obtained from UV-VIS titration

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20

changes of both receptor 1 and receptor 3 as a function of C60 concentration which was found to exhibit a maximum at 0.5 which is consistent with formation of a 1 : 1 complex.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 0.2 0.4 0.6 0.8 1 1.2[1]/[C60]+[1]

Abso

rban

ce

Figure 1. 13 : Job’s plot showing 1:1 stoichimetry for C60 : receptor 1 complex in CHCl3

Figure 1. 14 : 1H-NMR titration of 3.95 × 10-5 M solution of receptor 5 with C60 in CHCl3

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We have also carried out proton NMR investigations to substantiate the extent of binding between C60 and 1 (Figure 1.14). It is observed that, we get only 0.0001 ppm downfield shift for pyrrolic NH-protons in the case of C60-1 complex .On the other hand both the isomers of receptor 3 are found to show the same stoichiometry but show better binding to fullerene as compared to tetraurea. Table 1.2 represents the binding constant values for the two conformers of 3 compared with the octamethylcalix[4]pyrrole(OMC4P) , tetraphenylporphyrin(TPP)103 and metallated tetraphenyl porphyrin(ZnTPP).

Table 1.2 Association constants (Kass)a for C60 (1.36 × 10-6 M) and receptors 3 , OMC4P , TPP and ZnTPP

at (3.92 × 10-5M) in CHCl3 solution at 25 oCb

P4OMC ZnTPP TPP 3 Receptor 1 Receptor 5 Receptor

3 × 105 6 ×104 10.5 × 104 4.2 × 105 2 × 105 1.5 × 104 60C a Determined from absorption spectroscopic titrations b All errors are ± 15% Though both the receptor 1 and receptor 3 show same stoichiometry but they have different binding constant values . The αααα isomer has almost half the binding as compared to ααββ . This may be attributed to the steric hindrance caused by the αααα isomer for the bulky C60. The greater flexibility of calix[4]pyrroles helps in achieving a relatively strong non covalent interactions as compared to rigid porphyrins . We thus say the following decreasing order of non covalent interaction is supported by spectroscopic studies .

HN HN

HN H

N

NO2 NO2

O2N

NO2

HN HN

HN H

N

O2N NO2NO2 NO2

HN HN

HN H

N

HN NH HN NH

HN NHNH HN

OO OO

CH3 CH3CH3 CH3

> >

Figure 1.15 : Decreasing order of binding ability of tetraaryl calix[4]pyrroles to fullerene (C60)

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1.2.3.2 Fluorescence spectroscopy studies to study non covalent interactions of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetraaryl calix[4]pyrroles with (C60) Fluorescence spectroscopy studies were also carried out in order to evaluate the ability of the receptors to operate as a fluorescent sensor. A 1.36×10-6 M solution of C60 fullerene in CHCl3 in a quartz cell was titrated with an increasing volume of tetraitroC4P (αααα) (3.92×10-5) ( Figure 1.16 ) . On continuous addition of tetraitroC4P (αααα) to a solution of fullerene C60 the peak was red shifted to 366 nm from 361.07 nm with constant increase in the intensity .

Figure 1. 16 : Fluorescence spectra of 1.36×10-6 M solution of fullerene C60 upon addition of

3.92×10-5M of αααα isomer of 3 in CHCl3 1.2.4 Synthesis of meso-tetra acid and ester functionalized calix[4]pyrroles The synthesis of functional calix[4]pyrrole is very important in order to develop new ion receptors ad selective sensors . We therefore studied the reaction of levuliic acid with pyrrole in acidic and Amberlyst-15 medium (Scheme 1.6) . The expected tetraacid C[4]P was not obtained.

OH

O

O NH

NH HN

HN

H3C CH2CH2COOH

HOOCH2CH2C CH3

HOOCH2CH2C

H3C

CH3

CH2CH2COOH

HCl , DCM

Amberlyst- 15 , DCM

X

X Scheme 1. 6 : Failed attempt to synthesis of tetraacid calix[4]pyrrole

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We then followed another scheme ,where we first converted the acids to the esters and then reacted esters with pyrrole in acidic medium under nitrogen atmosphere at 0 oC for 2-3 hours.

Scheme 1. 7 : Stepwise synthesis of tetraacid functionalized calix[4]pyrroles

The tetraester functionalized calix[4]pyrrole was obtained as a crude product which was subjected to column chromatography on silica gel mesh size 60-120 . These tetraesters (9 and 8) were further subjected to hydrolysis in presence of ethanol and sodium hydroxide to yield tetraacids (10 and 11) in good yields , which were not obtained otherwise by direct condensation of an acidic ketone with pyrrole .The FT-IR spectrum of tetraester C4Ps showed a peak near 1724 cm-1 due to ester group and near 3443 cm-1 due to NH-groups . The 1H-NMR showed a broad singlet near 7.56 ppm for pyrrolic NH-protons and a doublet at 4.5 ppm for β-pyrrolic protons . This data confirms the formation of tetraester funtionalised calix[4]pyyrole .

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Figure 1. 17: 1H-NMR of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl)

calix[4]pyrrole(9) in CDCl3 To examine the anion binding properties of tetraester functionalized calix[4]pyrrole they were then subjected to tetrabutylammoniumfluoride binding . 1H-NMR titration experiments were carried out in CDCl3 .A 5 × 10-3 M solution of tetrabutylmmoium fluoride was added to the solution of tetraester functionalized C4P (5 × 10-4 M) . For 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl) calix[4]pyrrole(9) and 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylethyl) calix[4]pyrrole(8) in CDCl3 the β - pyrrolic peaks did not undergo any appreciable change but downfield shifts of the pyrrolic NH proton signals (7.85

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Figure 1. 18 : Titration of a 5 × 10-4 M solution of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl) calix[4]pyrrole in CDCl3 with F- (as TBA salt)

Figure 1.19 : Titration of a 5 × 10-4 M solution of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(2-

ethoxycarbonylethyl) calix[4]pyrrole in CDCl3 with F-(as TBA salt)

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ppm to 8.23 ppm) for 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl) calix[4]pyrrole (Figure 1.18) and ( 8.65 ppm to 8.83 ppm ) for 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(2-ethoxycarbonylethyl) calix[4]pyrrole (Figure 1.19) were seen upon the addition of these anions (as TBA) salts in CDCl3 . Binding studies made an interesting revelation that tetraester functionlised calix[4]pyrrole did not undergo intramolecular hydrogen binding . This is to say that tetraester functionalized calix[4]pyrroles having esters at meso positions do not interact with pyrrolic NH protons . Anions bind to the pyrrolic protons and depict a visible change in the 1H-NMR titration studies made in CDCl3 . 1.2.4.1 Hydrogen bonded self aggregated assembly of meso tetraacid fuctionalised calix[4]pyrroles However ,the same cannot be said about tetraacid calix[4]pyrroles .The presence of carboxylic groups at the meso positions of the calix[4]pyrrole induced self-assembly due to hydrogen bonding amongst the molecules . The tetraacid functionalized calix[4]pyrroles undergo some kind of self aggregation in less polar solvents . There is an intense broadening of -NHs in CDCl3 , the solvent favouring hydrogen bonding) in 1H-NMR spectrum . Thus the solvent of choice for recording 1H-NMR spectrum of meso tetraacid fuctionalised calix[4]pyrroles was DMSO-d6 . The 1H-NMR spectrum of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl) calix[4]pyrrole(11) in DMSO is shown in Figure 1.21 .The -CH3 protons appear as a singlet at 1.49 ppm , the two types of –CH2 protons appear as triplets at 1.93 and 2.16 ppm . The β–pyrrolic protons appear as a doublet at 6.56 ppm and the pyrrolic protons appear at 10.31 ppm in DMSO , which are too broad to be seen in CDCl3 . Also a broad peak appears at 3.37 ppm which disappears on the addition of D2O . this is clearly depicted in Figure 1.22 . The pyrrolic protons are shifted upfield by 0.26 ppm on addition of D2O .The pyrrolic NH resonances which appeared at 7.78 and 8.53 ppm for tetraester C4P underwent a significant downfield shift of (∆δpyrrole NH ~1.0 ppm) for tetraacid calix[4]pyrroles . This significant downfield shifting was supposed to be as a consequence of H-bonding interactions since the free carboxylate spacer in tetraacid calix[4]pyrroles is capable to form some higher homologues.

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Figure 1.20 : 1H-NMR of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl)

calix[4]pyrrole in DMSO

Figure 1.21 : 1H-NMR of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl)

calix[4]pyrrole in DMSO+D2O

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In solutions favouring hydrogen bonding , such as chloroform , as the concentration of compound 10 is increased from 0.5 × 10-6 to 1.2 × 10-4 , small changes are observed in UV-Visible absorption spectrum . The peak which appeared at 488 nm in the dilute solution blue shifted to 485 nm at higher concentration .

Figure 1.22 : Concentration dependent UV-Visible spectrum of 5,10,15,20-tetramethyl-

5’,10’,15’,20’-tetra-(3-carboxyethyl) calix[4]pyrrole in CHCl3 We thus recorded the 1H-NMR spectrum of compound 10 in CDCl3 . It was observed that the –CH3 protons appear as a singlet at 1.75 ppm , -CH2 protons at 3.04 ppm , β-pyrrolic protons appeared at 6.62 ppm .Strangely there was another peak at 8.34 ppm for seven protons approximately . But the peak at 8.34 ppm disappeared on the addition of D2O to the CDCl3 solution of acidic calix[4]pyrrole . And a new broad peak appeared at 4.56 ppm ( Figure 1.23). Above observations suggest the formation of hydrogen bonded aggregates in non polar solvents . The addition of D2O leads to the disruption of hydrogen bonded complexes in CDCl3 . This phenomenon was further confirmed by recording the IR spectrum in solid state (KBr) and non polar solvent (CDCl3) . The sharp peak in solid state at 3369 cm-1 (Figure 1.24a) and a broad peak in chloroform at 3355 cm-1 (Figure 1.24b) clearly depicted that tetraacid calix[4]pyrrole undergo intermolecular H-bonding.

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29

Figure 1.23 : 1H-NMR of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxyethyl)

calix[4]pyrrole(10) in a) CDCl3 and b) CDCl3 + D2O

Figure 1.24 : IR-spectrum for 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxyethyl)

calix[4]pyrrole(10) in (a) KBr and (b) CHCl3

a) b)

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30

1.2.4.2 Transmission Electron Microscopy (TEM) Transmission Electron Microscopy is a widely used technique to determine the shape and size of aggregated complexes . Transmission electron micrograph of aqueous dispersion of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl) calix[4]pyrrole showed the formation of spherical aggregates as shown in Figure 1.25 . A 10-6 M solution of sample in H2O was prepared and sonicated before transferring it to the grid. The average diameter of these particles is 500-1000 Å . Presence of spherical aggregates suggests the formation of vesicles . The aqueous dispersion of aggregates was stable for several weeks .

Figure 1.25 : TEM micrograph of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl)

calix[4]pyrrole 1.3 CONCLUSION Calix[4]pyrroles have been synthesized by the reaction of aldehyde and pyrrole catalysed by Amberlyst-15 at room temperature . The configurational isomers were separated carefully by column chromatography .The αααα isomer of tetraurea calix[4]pyrole has been isolated and characterized by 1H-NMR , UV-Visible and ESI-MS spectroscopy techniques .The deep cavity tetraurea calix[4]pyrrole was then subjected to anion binding in acetonitrile . The UV–Vis spectra of 5 changed dramatically on addition of fluoride , dihydrogen phosphate and acetate anions . Anions such as Cl- , Br- , I- and HSO4- were found to hardly induce any change .UV-

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31

Visible and 1H-NMR spectroscopic techniques indicates the formation of a 2:1 adduct [CH3COO:5] . This phenomenon was further confirmed by Job’s plot . Further non covalent interaction of meso aryl substituted calix[4]pyrroles with fullerene (C60) indicate a 1:1 adduct formation .Binding studies reveal that receptor 3 has the maximum binding potential . The meso-tetra acid and ester functionalized calix[4]pyrroles were synthesized and subjected to anion binding .The tetraester functionlised calix[4]pyrroles bind to anions depicting a visible change in the 1H-NMR titration studies . Whereas meso tetraacid fuctionalised calix[4]pyrroles tend to self aggregate in non polar solvents . 1.4 EXPERIMENTAL 1.4.1 Materials and Methods All the melting points are uncorrected and were determined on a Thomas Hoover Unimelt capillary melting point apparatus . The IR spectra were recorded on a Perkin Elmer Spectrum 2000 infrared spectrophotometer and the υmax is expressed in cm-1 . The electronic transition spectra were recorded on a Perkin Elmer Lambda-35 UV/Visible spectrophotometer and the absorption maxima (λmax) is expressed in nanometers(nm) . The 1H-NMR spectra were recorded in CDCl3 using tetramethylsilane (TMS) as an internal standard on JEOL 400 MHz spectrometer and the chemical shifts (δ) are expressed in ppm . The mass spectra (ESI-MS) was recorded on a Micromass LCT KC 455 spectrometer (+ve mode ) . The fluorescence spectra were recorded on Shimadzu RF-5301 spectrophotometer . All the reactions were carried out under nitrogen atmosphere . All the solvents and reagents were used as received. TEM measurements were conducted on a Tecnai G-30 Utwin FTI company at an operating voltage of 300 kV .Column chromatography was carried out using silica gel 60-120 mesh and neutral alumina of Spectrochem . All the reagents and chemicals were of analytical grade and used without further purification . 1.4.2 Synthesis of αααα - 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(4-nitrophenyl) calix[4]pyrrole(1) 4-nitroacetophenone (3.67g , 0.022mol) and pyrrole( 1.49ml , 0.022mol ) were dissolved in absolute ethanol (50 ml) and stirred . Activated Amberlyst-15 was added to stirring solution .

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The solution turned brownish-yellow after a while and yellow solid material began forming after 2-3 hrs. After 20 hrs stirring at room temperature a yellow powder was filtered . This crude product was then subjected to column chromatography on silica gel (60-120) mesh with EtOAc : Hexane ( 1:9 ). Physical state : yellow solid Yield : 2.82 g (15%) M.pt : decomposes above 300oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 2.08 ( s , 24H , CH3 ) , 5.95 ( d , 8H , J = 2.6Hz ) , 7.27 ( d , 8H , J = 8.08Hz ) , 7.86 ( bs , NH , 4H ) , 8.10 ( d , 8H , J = 8.08Hz ) . IR( KBr pellet , cm-1) : 3419 (-NH) , 2925(sp3 –CH) , 1513 (-NO2 ) , 1348 (-NO2) , 1110 HRMS(ESI+ve) for C48H40N8O8 [M+Na]+ : Calcd : 856.8867 , Found : 879.8878. 1.4.3 Synthesis of ααββ - 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(4-nitrophenyl) calix[4]pyrrole(3) Another fraction was separated from above column. 1H-NMR(400MHz , CDCl3 , 25oC ) : 1.99 ( s , 24H , CH3 ) , 5.82 ( t , 8H , J = 2.6Hz ) , 7.22 ( d , 8H , J = 7.8Hz ) , 7.83 ( bs , NH , 4H ) , 8.05 ( d , 8H , J = 7.8Hz ) . Physical state : yellow solid Yield : 2.28 g (12%) 1.4.4 Synthesis of αααα - 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(4-aminophenyl) calix[4]pyrrole(4) Crystallized tetranitro calix[4]pyrrole (50 mg , 0.058 mmol ) was dissolved in 25 mL of ethyl acetate. The solution was filtered to remove any precipitate. The resulting solution was poured on a suspension of Pd/C (30 mg) in 3mL of ethyl acetate. The reaction mixture was connected to a hydrogenation apparatus, purged twice with hydrogen, charged with a hydrogen pressure of 4 bar under constant stirring for 3 h. The Pd/C suspension was filtered over celite and the resulting solution was evaporated to dryness under vacuum. The tetraamine calix[4]pyrrole was obtained . Physical state : yellow solid Yield : 0.395 g (92%)

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33

M.pt : decomposes above 300oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 1.90 ( s , 24H , CH3 ) , 4.04 ( brs , 8H , NH2) , 5.94 ( d , 8H , J = 2.68Hz ) , 6.52 ( d , 8H , J = 7.76Hz ) , 6.73 ( d , 8H , J = 7.76Hz ) , 7.63 ( bs , NH , 4H). IR( KBr pellet , cm-1) : 3398 , 3201 , 3108 , 2966 , 1614 , 1556 , 1510 , 1418 , 1263 HRMS(ESI+ve) for C48H48N8 [M+Na]+ : Calcd : 736.9564, Found : 759.9397 1.4.5 Synthesis of αααα-tetraurea calix[4]pyrrole(5) p-tolylisocyanate( 0.2436ml , 0.0203mmol) was added dropwise to the stirring solution of the tetraamine( 150mg , 0.0203mmol ) in CHCl3( 25 ml ) at room temperature . The product began to separate out within an hour . After 2 hrs , when the reaction was complete , the chloroform was removed in vaccum and the crude product hence obtained was purified by column chromatography on silica gel (60-120) mesh with EtOAc : Hexane ( 1:19 ). Physical state : yellow solid Yield : 0.134 g M.pt : decomposes above 168 oC 1H-NMR(400MHz , CD3CN , 25oC ) : 2.18 ( s , 12H , CH3 ) , 2.27( s , 12H , CH3 ) , 5.79 ( d , 8H , J = 2.68Hz ) , 6.93 ( d , 8H , J = 8.8Hz ) , 7.08 ( d , 8H , J = 8.08Hz ) , 7.24 ( bs , NH , 4H) , 7.26 ( bs , NH , 4H) , 7.29 ( d , 8H , J = 8.08Hz ) , 7.30 ( d , 8H , J = 8.8Hz ) , 8.71 ( bs , NH , 4H) . IR( KBr pellet , cm-1) : 3406 , 3315 , 1649 , 1599 , 1557 , 1512 , 1407 , 1316 , 1233. HRMS(ESI+ve) for C80H76N12O4 [M+Na]+ : Calcd : 1269.5412, Found : 1292.5297 1.4.6 Synthesis of Ethyl acetoacetate (6) Acetoacetic acid ( 1 g , 9.79 mmol ) was added to a 50 ml round bottom flask containing absolute ethanol as solvent. Sulphuric acid was then added and the reaction was left to reflux to 10 – 12 hrs. Reaction mixture was cooled to room temperature and solvent was evaporated in vaccuo . The crude mixture was then washed with water several times and extracted in chloroform .The chloroform was dried over Na2SO4 and solvent was evaporated in vaccuo to give the final product. Physical state : colourless liquid

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34

Yield : 1.14 g (90%) B.pt : boils at 180 oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 1.0 (t , 3H , CH3 ) , 1.90 (s , 3H , CH3 ) , 2.30 ( s , 2H , CH2 ) , 2.47 (t , 2H , CH2 ) IR( KBr pellet , cm-1) : 2984 , 1745 , 1723 , 1655 , 1634 , 1237 , 1154 , 1460 , 1380 , 1123 1.4.7 Synthesis of Ethyllevulinate(7) Levulinic acid( 10ml , 0.0981 mol) was added to a 50ml round bottom flask containing absolute ethanol as solvent. Sulphuric acid was then added and the reaction was left to reflux to 10 – 12 hrs. Reaction mixture was cooled to room temperature and solvent was evaporated in vaccuo . The crude mixture was then washed with water several times and extracted in chloroform .The chloroform was dried over Na2SO4 and solvent was evaporated in vaccuo to give the final product. Physical state : yellowish liquid Yield : 13.6 ml (98%) B.pt : boils at 93-94 oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 0.96 (t , 3H , CH3 ) , 1.90 (s , 3H , CH3 ) , 2.26 ( t , 2H , CH2 ) , 2.46 (t , 2H , CH2 ) , 3.82 (q , 2H , CH2 ) IR( KBr pellet , cm-1) : 2985 , 2900 , 1735 , 1715 , 1460 , 1380 , 1123 1.4.8 Synthesis of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl) calix[4]pyrrole(9) The ethyl levulinate ( 5.50 ml , 38.76 mmol ) and pyrrole ( 2.60 ml , 38.76 mmol ) were dissolved in dry DCM (200 ml ) and cooled to 0 oC . Mixture was bubbled with N2 for 10 min. , HCl( 0.8 ml , 37% ) was then added dropwise over the reaction mixture under N2 atm. for 2 hrs and the at room temperature for 10hrs . After the reaction was completed the solvent was removed and the crude product which was dissolved in EtOAc was washed with water 2- 3 times and dried over Na2SO4 . Physical state : brown sticky solid Yield : 23.9 g (80%)

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35

M.pt : decomposes over 198 oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 1.24 (t , 12H , CH3 ) , 1.53 (s , 12H , CH3 ) , 2.16 ( t , 8H , CH2 ) , 2.28 (t , 8H , CH2 ) , 4.06 (q , 2H , CH2 ) , 6.54 ( d , 8H , β-pyrrolic , J = 1.48Hz ) , 7.78 (brs , 4H , NH) IR( KBr pellet , cm-1) : 3439 , 3108 , 2984 , 1724 , 1570 , 1375 , 1197 1.4.9 Synthesis of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(2-ethoxycarbonylethyl) calix[4]pyrrole(8) Ethylacetoacetate ( 0.9290 ml , 7.21 mmol ) and pyrrole( 0.5 ml , 7.21 mmol ) were used and same procedure was followed as above. Physical state : brown sticky solid Yield : 4.4 g (86%) M.pt : decomposes over 196 oC 1H-NMR(400MHz , CDCl3 , 25oC ) : 1.19 (t , 12H , CH3 ) , 1.76 (s , 12H , CH3 ) , 3.02 ( s , 8H , CH2 ) , 4.07 (q , 8H , CH2 ) , 6.05 ( s , 8H , β-pyrrolic) , 8.53 (brs , 4H , NH) IR( KBr pellet , cm-1) : 3443 , 2970 , 1727 , 1577 , 1420 , 1240 1.4.10 Synthesis of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-carboxypropyl) calix[4]pyrrole(11) 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylpropyl) calix[4]pyrrole ( 0.100 g , 0.129 mmol) was dissolved in 1 ml EtOH and 1 ml NaOH ( 2M ) was then added and left in microwave at 80oC for 20 mins. The solvent was evaporated in vaccum and the crude mixture was dissolved in chloroform and washed with water several times to eradicate any trace of left over base . The compound in chloroform was dried over Na2SO4 . The corresponding acidic calix[4]pyrrole was obtained . Physical state : yellow solid Yield : 0.083 g (97%) M.pt : decomposes over 200 oC 1H-NMR(400MHz , DMSO , 25oC ) : 1.49 (s , 12H , -CH3 ) , 1.93 (t , 8H , CH2 ) , 2.16 ( t , 8H , CH2 ) , 6.56 (d , 8H , β-pyrrolic) , 10.31 (s , 4H , NH)

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36

IR( KBr pellet , cm-1) : 3363 , 3105 , 2965 , 1702 , 1572 , 1043 IR( CHCl3 solution , cm-1) : 3346 , 3104 , 2965 , 1702 , 1572 , 1403 1.4.11 Synthesis of 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(2-carboxyethyl) calix[4]pyrrole(10) 5,10,15,20-tetramethyl-5’,10’,15’,20’-tetra-(3-ethoxycarbonylethyl) calix[4]pyrrole ( 0.100 g , 0.1395 mmol ) was used and the same procedure was followed as above . Physical state : yellow solid Yield : 0.081 g (96%) M.pt : decomposes over 200 oC 1H-NMR(400MHz , DMSO , 25oC ) : 1.53 (s , 12H , CH3 ) , 2.23 (s , 8H , CH2 ) , 6.62 (s , 8H , β-pyrrolic) , 11.23 (brs , 4H , NH) IR( KBr pellet , cm-1) : 3367 , 3100 , 2924 , 1707 , 1577 , 1035 IR( CHCl3 solution , cm-1) : 3355 , 3101 , 2923 , 1707 , 1577 , 1035

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37

1.5 REFERENCES 1 Baeyer, A. Ber. Dtsch. Chem. Ges. 1886, 19 , 214– 220. 2 Gale, P. A. ; Sessler, J. L. ; Kral, V. ; Lynch, V. Calix[4]pyrroles: Old Yet New Anion-Binding Agents , J. Am. Chem. Soc. 1996, 118, 5140 –5141. 3 Gale, P. A. ; Sessler, J. L. ; Allen, W. E. ; Tvermoes, N. A. ; Lynch, V. Calix[4]pyrroles: C-rim substitution and tunability o f anion binding strength , Chem. Commun. 1997, (7) , 665 - 666. 4 Gale, P. A ; Sessler, J. L ; Kral, V. Calixpyrroles , Chem. Commun. 1998 , (1) , 1–8. 5 Anzenbacher, P. Jr. ; Jursikova, K. ; Sessler, J. L. Second Generation Calixpyrrole Anion Sensors, J. Am. Chem. Soc. 2000 , 122(38) , 9350–9351. 6 Sessler, J. L. ; Anzenbacher, P. Jr. ; Miyaji, H. ; Jursikova, K. ; Bleasdale, E. R. ; Gale, P. A. Modified Calix[4]pyrroles, Ind. Eng. Chem. Res. 2000 , 39(10) , 3471 –3478. 7Turner, B. ; Shterenberg, A. ; Kapon, M. ; Suwinska, K. ; Eichen, Y. Selective anion binding and solid-state host–guest chemistry of an extended cavity calix[6]pyrrole, Chem. Commun. 2001 , (1) , 13–14. 8 Custelcean, R. ; Delmau, L. H. ; Moyer, B. A. ; Sessler, J. L. ; Cho, W. S. ; Gross, D. ; Bates, G. W. ; Brooks, S. J. ; Light, M. E. ; Gale, P. A. Calix[4]pyrrole: An Old yet New Ion-Pair Receptor, Angew. Chem. Int. Ed. 2005 , 44, 2537 –2542. 9 Cafeo, G. ; Kohnke, F. H. ; La Torre, G. L. ; White, A. J. P. ; Williams, D. J. The complexation of halide ions by a calix[6]pyrrole , Chem. Commun. 2000 , (13) , 1207-1208.

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10 Turner, B. ; Botoshansky, M. ; Eichen, Y. Extended Calixpyrroles: meso-Substituted Calix[6]pyrroles, Angew. Chem. Int. Ed. 1998 , 37, 2475-2478. 11 Sato, W. ; Miyaji, H. ; Sessler, J. L. Calix[4]pyrrole dimers bearing rigid spacers: towards the synthesis of cooperative anion binding agents, Tetrahedron Lett. 2000 , 41(35) , 6731-6736. 12 Anzenbacher, P. Jr. ; Try, A. C. ; Miyaji, H. ; Jursıkova, K. ; Lynch, V. M. ; Marquez, M. ; Sessler, J. L. Fluorinated Calix[4]pyrrole and Dipyrrolylquinoxaline:  Neutral Anion Receptors with Augmented Affinities and Enhanced Selectivities , J. Am. Chem. Soc. 2000 , 122, 10268-10272. 13 Gale, P. A. ; Hursthouse, M. B. ; Light, M. E. ; Sessler, J. L. ; Warriner, C. N. ; Zimmerman, R. S. Ferrocene-substituted calix[4]pyrrole: a new electrochemical sensor for anions involving CH⋯anion hydrogen bonds, Tetrahedron Lett. 2001 , 42, 6759- 6762. 14 Schmidtchen, F. P. Surprises in the Energetics of Host−Guest Anion Binding to Calix[4]pyrrole, Org. Lett. 2002 , 4(3) , 431-434. 15 Camiolo, S. ; Gale, P. A. Fluoride recognition in ‘super-extended cavity’ calix[4]pyrroles , Chem. Commun. 2000 , (13) , 1129-1130. 16 Woods, C. J. ; Camiolo, S. ; Light, M. E. ; Coles, S. J. ; Hursthouse, M. B. ; King, M. A. ; Gale, P. A. ; Essex, J. W. Fluoride-Selective Binding in a New Deep Cavity Calix[4]pyrrole: Experiment and Theory, J. Am. Chem. Soc. 2002 , 124 , 8644-8652. 17 Blas, J. R. ; Marquez, M. ; Sessler, J. L. ; Luque, F. J. ; Orozco, M. Theoretical Study of Anion Binding to Calix[4]pyrrole: the Effects of Solvent, Fluorine Substitution, Cosolute, and Water Traces, J. Am. Chem. Soc. 2002 , 124 , 12796-12805.

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18 Pichierri, F. J. Halide anion recognition by calix[4]pyrrole: a quantum chemical study, Journal of Molecular Structure: THEOCHEM , 2002 , 581, 117-127.

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