Chapter 7

7.1 Introduction

7.2 Experimental

7.3 Factor Group Analysis

7.4 Results and Discussion

7.4.1 P60~~ vibrations

7.4.2 [(CH2

)2(NH3

)2)2+ vibrations

7.4.3 Te(OH)6 vibrations

7.4.4 Water vibrations

7.5 Conclusions

References

Tables

Ffgures

229

7.1 Introduction

The study of cyclohexaphosphate is of particular importance as

6-the P6018 anion in aqueous solution behaves as a polyelectrolyte,

forming extraspherical complexes with cations by electrostatic

The phosphate6-

(V) ion P60

18is built up by six

corner-sharing P04

tetrahedra. A large number of adducts of telluric

interaction [1}.

acid with various inorganic phosphate, condensed or not, is presently

ethylenediammonium ion,

example of adducts of telluric acid with an organic cation [2}. The

H3N+CH2

CH2

N+H3

(eda2+) is structurally

interesting because of the possibility of its being either in,-the

non-centrosymmetric gauche configuration or in the planar trans

configuration of the C2h symmetry. Infrared and Raman spectra of

powdered samples of ethylenediammonium dihalides [3-8} conform to the

trans configuration of CH2 groups, while both trans and gauche forms

present in aqueous solution [9-11}. In this chapter, FTIR and Raman

more information about the structure of the compound.

7.2 Experimental

2Te(OH)6.(eda)3P6018.2H20 was prepared by slow evaporation at

room temperature (300+3K) from an aqueous solution containing

stoichiometric amounts of telluric acid and ethylenediammonium

230

cyclohexaphosphate [2). The powdered sample was filled in a capillary

tube to record the Raman spectrum. A 1401 Spex Raman Spectrometer

equipped with a Spectra Physics Model 165.08 argon ion laser was used

and the spectrum was recorded using 514.5 urn radiation at a resolution

-1better than 3 cm • Raman spectrum was also recorded on a Cary 82

spectrometer equipped with a Spectra Physics model 165 argon ion

laser. The infrared spectrum was recorded on a Perkin Elmer model 882

spectrophotometer by KBr pellet method. The FTIR spectrum of the

compound was recorded in the region-1

400-4000 cm on a Bruker

IFS-66V-FTIR spectrometer by the KBr pellet method.

7.3 Factor Group Ana1ysis

2Te(OH\. (eda)3P6018.2H20 crystallizes in the tric1inic system

with space group Pi and has one molecular unit per unit cell [2]. The

6- 2+P60

18anion occupies the Ci site in the crystal and eda , Te0

6, H

atoms and H20 molecules occupy the general site C

l. Factor group

analysis of the compound has been carried out using the correlation

method developed by Fateley et ale [12). Excluding acoustic modes, at

k = 0, (Tables 7.1 and 7.2) the 291 fundamental modes are distributed

as,

147A + 144Ag u

Gerade modes are Raman active and ungerade modes are IR active.

231

7.4 Results and Discussion

6-7.4.1 P6018 vibrations

The local symmetry of a PO 4 tetrahedron is not fundamentally

different from those 0 bserved in other condensed phosphates.

Therefore, the assignments of the cyclohexaphosphate modes are carried

2-out on the basis of the characteristic vibrations of P0

2and P"""O-P

groups. As the p-o bond in P02

group is stronger than that in the

P-O-P bridges, the vibrational frequencies of the P02

group are

expected to be higher than those for the P-O-P bridge [131. The

assignment of the bands to various modes of vibration is given in

Table 7.3.

2-The symmetric stretching mode of P0

2exhibits very large

splitting in both the IR and Raman spectra (Figs.7.1 and 7.2) • A very

-1strong band at 1148 em ,three medium intense bands at 1050, 1062 and

1095 cm-1

and a shoulder at 1055 cm-1 are observed for this mode in

-1the Raman spectrum. A very strong band at 1120 em ,a strong band at

1057 cm-1 and a shoulder at 1091 cm-1 appear for this mode in the FTIR

spectrum.

-1The very strong absorption band in the 1200-1260 em region

in the infrared spectrum is assigned to the asymmetric stretching mode

2-of P0

2• In the FTIR, this broad band is resolved to give two very

strong bands at 1246 and 1267 em-I. They appear as weak to medium

intense bands in the 1230-1300 em-1 region in the Raman spectrum.

expected, as weak bands in the

intense band at 662 cm-1 \'1ith a

232

The symmetric P-O-P stretching mode appears in the Raman

spectrum as an intense band at 683 cm-1 and a medium intense band at

663 cm-1 while the asymmetric p-o-p stretching mode appears, as

-1900-990 em region. In FTIR,an

shoulder at 690 cm-1 is obtained for

the symmetric stretching mode while a very intense broad band at

949 cm-1 (with a shoulder at 911 cm-1) is obtained for the asymmetric

stretching mode.

Bands in the 550-430 cm-1 region are due to the bending modes

of p02

group. The bending modes of the p-o-p group are expected

around 330 cm-1• The librational modes of water molecules and V3Teo 6-1

mode also appear in the 550-430 em region. Hence, an unambiguous

assignment of all these modes is very difficult. However, a few of

these modes are assigned on the basis of the IR and Raman activities

and in comparison with the spectra of similar compounds [14-17]. The

3- 1ring breathing frequency for P

30

9is observed at 360 cm- [13]. The

6-breathing vibration of the heavier ring P

60

18is expected at a much

lower frequency. The bands in the region 300-320 cm-1 are assigned to

this mode.

Asymmetric stretching vibrations of p-o-p in octametaphosphate

usually appear in the-1

region 905-930 em This is close to the

-1wavenumber 900 ern observed in chain polyphosphates. In cyclo tri-

-1and tetra- metaphosphnt28 they appear around 1000 em • In the present

case, these vibrations are at 940-980 cm-1. It is an indication that

233

cyclohexaphosphate compounds occupy a position intermediate between

that of chain polyphosphate and cyclic tetra-and tri-metaphosphates

[ 15,18) •

6­Large splitting is observed in all the modes of the P6018

anion. This suggests that the anion is considerably distorted in the

crystal. Therefore, it cannot be established from the observed bands,

6-whether the P6018 anion is centrosymmetric or not.

The ethylenediammonium ion has 36 normal modes of vibration,

which in the trans configuration are distributed as 11A + 8A + 7B +g u g

lOB . lIence, 18 modes are Raman active (A +B) and 18 IR activeu g g

(A +B) [19). Bands observed are assigned on the basis of theu u

characteristic vibrations of CH2

and Wi3

groups.

Bands obtained in the 2965-2760 cm-1

region in the IR and

Raman spectra are assigned to the asymmetric and symmetric stretching

modes of the ion, lJ ClI2

(B ) andas g lJ CH

2(A ). Several overtone and

s g

combination modes are also obtained in the spectra. The scissoring

modes of CH2

are observed in the-1

1480-1420 cm region. Large

splitting is observed for this mode in the Raman spectrum. While CH2

-1wagging mode is obtained only in the Raman spectrum at 1360 cm ,CH2

twisting mode appears in both the IR and Raman spectra as medium

-1intense bands around 1330 cm . Though the CH 2 wagging band has larger

intensity than the CH2

twisting band in ethylenediammonium

234

Therefore, an intense broad band extending from 2636 to 3524 cm-1 is

obtained in the FTIR spectrum. However, the most intense bands in the

Raman spectrum have been somewhat arbitrarily chosen as the

fundamentals. The symmetric stretching vibrations of NH3

which is

expected to provide the most intense band in the Raman spectrum, is

assigned to the intense broad band at 2998 cm-1 and to the medium

-1intense' band at 2970 cm • Also, the asymmetric stretching modes of

NH3

are obtained as weak bands at 3013, 3046 and 3060 cm-1 • X-ray data

[21 show hydrogen bonds of the types N-H •••O having bond lengthsa

ranging from 2.772 to 3.045 A. The presence of such strong hydrogen

bonding may lead to considerable Fermi resonance between NH3

stretching fundamentals and overtones and combinations of the NH3

deformation modes. This can cause a shift in the fundamental

frequencies. In the title compound, the symmetric and asymmetric NH3

stretching modes appear at lower wavenumbers than in (eda)SnC\ and

(eda)PtC16 and Sr(eda)3P4012.14H20 indicating strong hydrogen bonding

as in (eda)CdC14

[20,231.

The multiplicity of bands (Table 7.3) observed for all the

vibrational modes of CH2

and NH3

, apart from the lifting of

degeneracies, suggests the existence of two different types of

ethylenediammonium cations in the crystal which confirms the X-ray

structural data.

7.4.3 Te(Oll)6 vibrations

Vibrations of Te(Oll) 6 group consist of Te0 6 and hydrogenic

1) )) d2)vibrations. The selected stretching modes of Te0 6 are l' 2 an 3

235

tetrachlorocadmate [20], in the title compound CH2

twisting mode has

larger intensity than the CH2

wagging mode.

The CH2

rocking mode is observed in the FTIR at 735 cm-1 and

in Raman at 750 cm-1. The CH2

rocking vibration provides a most

clear-cut diagnosis of the conformation of the eda2+ ion. A single

-1band is observed in the IR around 749 cm for a trans configuration

while t\VO bands (A and B)-1

appear in the IR around 918 cm and

-1845 cm for a gauche configuration [21]. As only one band around

-1735 cm is observed in the IR corresponding to the CH

2rocking mode,

a trans configuration can be assumed for the ethylenediammonium ion in

the present compound.

Symmetric stretching modes of CH2

adjacent to N atoms usually

shift to lower wavenumbers [22]. Therefore, CH2

stretching modes in

the present study are obtained at considerably lower wavenumbers.

The presence of strong hydrogen bonding in salts of this type

may lead to considerable Fermi resonance between NH3

stretching

fundamentals and overtones and combinations of the NH3

deformation

modes [20].

~ (NH3),as

Three groups of combination modes designated ~ I (NH3

) +as

~as(NH3) + ~s(NH3) and ~s/(NH3) + &s(NH3) can occur and

they may gain in intensity by Fermi resonance. In the absence of Fermi

resonance, these modes can be observed

in the region 3180-3150 cm- 1 , ~ (NH3

)as

~~(NH3) + ~s(NH3) around 2940 cm-1

[20] as ~ I (NH3

) + ~ (NH3

)as as

( -1+ds(NH3) around 3060 cm and

In the title compound, these

bands fall in the region of NH1

, CHZ

and OH stretching modes.

236

and bending modes are))4 and US' Out of these,)) 1 and 1)2 are normally

IR inactive. The very strong band at 642 cm-1 in the Raman spectrum is

assigned to the nondegenerate symmetric stretching mode of Te06

[16,17]. A medium intense band at 610 cm-1

and a weak band at 620 cm-1

are observed in Raman for the 1J 2 mode. No bands are obtained in this

region in the IR spectra. The lJ3

mode cannot be identified2­

unambiguously as they appear in the region of the bending modes of P02

and librational modes of water molecules. The 1)4 and})5 modes are

assigned in the region 350-380 cm-1

• The lJ6

mode which is inactive in

-1both IR and Raman in the free ion state appears around 280 em in

both the Raman and IR spectra [16,17,24,25]. Te-OR in-plane bending

modes are obtained around 1219 cm- 1 with medium intensity in the FTIR.

The OR stretching mode of the Te (OH) 6 group cannot be identified as

they fall in the region of the CH2

and NH3

stretching modes. The

vibrational frequencies observed for the Te06

ion are in agreement

with those of a free ion. Therefore, it can be inferred that these

ions exist independently in the compound, confirming X-ray data.

7.4.4 Water vibrations

Stretching modes of water molecules appear along with the CH2

,

NR3

and (Te)O-H stretching modes as explained earlier. A few of these

bands are identified in the Raman spectrum. In the bending mode

region, two clearly distinct bands are observed in both the Raman and

IR spectra. The presence of two clearly distinct bands for the .2)2

mode obtained repeatedly in the ordinary IR and FTIR, the appearance

237

of a broad band in IR spectra upto 3524 cm-1 and four bands in the

Raman spectrum for the stretching modes suggest the presence of two

crystallographically distinct water molecules in the compound. They

form hydrogen bonds of varying strengths.

7.5 Conc1usions

6-p-o-p vibrations indicate that P6°18 ion occupy a position

intermediate between that of chain polyphosphate and cyclic tetra- and

6-trimetaphosphates. The P

60

18ion is distorted in the crystal.

[(CH2

)2(NH3

)2]2+ ion is in a trans configuration. Multiplicity of

bands confirms the existence of two types of ethylenediammonium ions.

Te(OH)6 groups exist independently in the crystal confirming the X-ray

data. Two distinct water molecules are identified in the crystaL

Water molecules and NH3

groups form hydrogen bonds of varying

strengths.

238

Ill1ll0fCg. Jl>ht:e:n::. 16" 93 U 9$([))) •

2. lMI. 'I. Awerbtnc1hL-JIlloucbot: and A. ])urif

(eMS ll 38([))42 GrelOOb.l.e" Cedexll France) Private

COIJJIlIDIIlIJJrcat::i01l1l..

3. J. llJe:lJ1.allllato

SpectroChfum. Acta" 16, 1344 (1960).

4. lR...~. .\Berg .am.d IK.']. JRaSllIlllUSsenn.

Spectrosc. Lett" 4" 285 (1911)~

5. D.ijl. JIl'ove..l1

SpectroChfum. ~t:all 16" 241 (1960).

6. 1l.J. lMIurenik and ijl. Robb

Spectrochi..nml. Acta, 24A.." 311 (1968).

1. R..D. Mil: Lachlan

Spectroclrlmm.. Acta, 30&11 985 (914).

8. L.C. Christensen and lK•.J. JRasmussen

SpectrlOC.ll:ni.nm. Acta, 31All 8'915 (915).

9. J."['. JEl.A:lls.a.l

J. AB. Chenm. Soc. 65, 1761 (1943).

Ull. Y. Omura and T. Shi.mman01l1lcl!:ni.

J. MOl. Spectrosc. 45, 20S (1913); 55, 430 (1915).

11. S .A.S. Ghazanfar, .J.Jl). JEdsal and D.V. Hyers

J. Am.. C1uenm. Soc. 86, 559 (964).

12. 'MI.G. Fateley, F.R. IDollish ll N.T. Me Devitt and F.F. Bentley

"Infrared and IRamIDan Selectio1l1l Rules for ~lo1ecu1ar and Lattice

Vibrations - the Correlation Het:hod", \~iley- Interscielllce, Me.w

York 0'9112).

13. P. Tarte. A. R1Ullmonlt. K. SlbaiaJrudl B.A. Simonot.-Grange,

Sp€ctroc1him. Acta, A43, JJl 0.987),

239

14. Sunila Abraham and G. Aruldhas

Indian J. of Pure Appl. Phys. 32, 254 (1994).

15. Sunila Abraham and G. Aruldhas

J. Raman Spectrosc. 22, 423 (1991).

16.· H. Haresh, P. Rajagopal and G. Aruldhas

Spectrochim. Acta, 48A, 1453 (1992).

17. Xavier Mathew and V. u. Nayar

Spectrochim. Acta, 45A, 243 (1989).

18. U. Shulke and N.N. Chudinova

Inorg. Mater. 10, 1459 (1974).

19. Mylrajan and T.K.K. Srinivasan

Phase Trans. 12, 285 (1988).

20. LA. Oxton and Osvald Knop

J. Mol. Struct. 43, 17 (1978).

21. K. Nakamoto

"Infrared Spectra of Inorganic and Coordination Compounds",

Second Edn. Wiley-Interscience, New York, p.225 (1970).

22. N.B. Colthup, L.R. Daly and S.E. Wiberly

"Introduction to Infrared and Raman Spectroscopy", Academic

Press, Inc., London (1964).

23. Mariamma John, N. Santha and V.U. Nayar

Indian J. Phys. 67B, 41 (1993).

24. J. Gaunt

Trans. Faraday Soc. 49, 1122 (1953).

25. G. Sekar, V. Ramakrishnan and G. Aruldhas

Infrared Phys. 26, 293 (1986).

Table 701: Factor group modes of 2Te(OH)6o(C2N2HI0)3P6018o2H20

Space group PI - C., Z = 1, ZB = 11

Factor group modes under Ci

A Ag u

6- 33Pb0

18 33

d 2+ 54 54Internal modes ofe a

Te06

15 15

H2O 3 3

6- 3 0P6018d 2+ 9 0e a

Rotational modes ofTe06 3 3

H2O 3 ~

6- 0 3P6018

d 2+ a 9e a

Translational modes of Te06

3 3

H2O 3 .3

H 18 18

Acoustic modes

147A + 144Ag u

10

147

-3

144

Table 7.2: Correlation for the internal vibrational modes of P60~;

eda2+, Te06 and H20 in ZTe(OH)6· (eda)3p601So2HZO

Free ion symmetryC

i

Site symmetryC.

1.

Factor group symmetryCi

33 Ag

Ag

Ag

33

33 Au

Au

Au

33

eda2+

Free ion symmetryCZh

Site symmetryC

i

Factor group symmetryCi

33

AA 5424 g

g

21

A A 54u u

30

Table 7.2 continued

Free ion symmetry Site symmetry

C1

Factor group symmetry

Ci

2

4

6

12

6

Eg

_______.....:;::~A

Ag

Au

15·

15

Molecular symmetryC2v

Site symmetryC1

Factor group symmetryC

i

4

2

A

Ag

Au

3

3

Table 1.3 contd .•••

1 2 3 4

132Sw NH3 rocking ( V10

)

88Sw 2J C-N (2,))s 9

90Svw 911s 91Sw2.J930w P-O-P

9S0vs 949vs 96Sw as

98Svw

1000w 1008w 100Svw lJ C-N &',

lU2Sw 1030w 1025w as (JJ )NH 3 rocking 16

1050w 1057s 1050m1090sh 1091sh 1055sh

1) PO1062m10713m s 2

ll1Uvs 112Uvs 1147vs

1210sh 1219m 1195w Te-OH in plane bend1225w

124Uvs 1246vs 123Sw1260sh 1267vs 12S7vw )) PO

1270m as 2128Sw1297vw

1330m 1342m 1330m CH2

twisting (L>1S)

1360w CH2

wagging (J)7)

1455m 1460m 142Sm1470s 1482s 146Um CH

2scissoring (V)

1470w 61480m

1505w 1515s 1S02m 6 NH (2.>S)s 3

1540m 1553s 1550w J NH3

(})4)1570w 1579w 1570w1580w

as

contd•••

Table 7.3 contd

1 2 3 4

1610m 16148 1610m D1650m 1646s 1650w 2 H2O

1700w 2077w 1730vw1980w 2358m 2350vw Combinations and2060w 2520w 2665vw overtones2400m 2770w 2705vw

2810w2885w Te-OH stretch &

Broad band 2920m 1J &.v CH2ex~ending from -1 2930m s as

(V3' V 13 ' ))21' U29 )2636 - 3524 cm

Broad band2970m ~ NH

3(V2,lJ 28 )

extending2998s

from -12500-3500 cm 3013w3046m lJ NH3 (.l)1'»12'~0'~7)3060w

as

3150w3210w lJ

1& ~ H2O

3340w3440w

y - very, s - strong, m - medium, w - weak, sh - shoulder, br - broad

0(\/I

00

(\)0

o· '(I)0II) 0

o...(f)r()-0

"0Q)

........(f)-0 I

0- 000- ........m'\t IE ~u C\I.....,

......0::: 0W tl(J) '-+-~ u:::> Q)

Q.0 0 z II)

0 0 wco tQ > c<! 0S E

00:::

0

0 0 I"-0 0I'- (\J 0'1

IL

----------------t-=--~ ______. 0

8 @

oo 0'------------- -+~lO!_ ___' 0

A1ISN31NI

12850 3000 3125 3200 3325 34001/\

>-f--(J)

zW /1600 A r700 2500 2650 2750 2850f-z

1100 1200 1300 /400 /500WAVENUMBER (cm- I )

Fig .7.1. b. Raman spectra of 2Te(OH)6'(edo)3PSOIS2H20

1600

r-------.---.--- ._----~-~=-------,g-~ q-

ooort)

o.

......0­o IE!e u- '0

0:LaJ Em ::J

~ .:==' 0z 8­lLJ CJ)o

g ~ ~t\I ~ ....

lJ..

.IS)

lfl

"OJ

Ultn

~._-

1TJ£"'1

~---..._--_._~~

01

£~~ 0~ 0

~-__---l l~~ --l --'L---------' 01'1q­m

(%) 3::>NVJ.l.llNSN'VC!1

0(\J

0 I0 C\JCO 'co

O'o..(!)

r0'N,-..,

t()

IZ.........

0 (\J

~~I0.........~

,...." <.D,...."

IE :r:0u .........

......... CDI-

0:: C\I0 W0 .....~ CO 0

~E:::::> ::Jz L--W u

> CD0..« Vl

3 "0CDL-

0L-..-C..0

C\Ir--:.QI.L.

000r0

oo~

8----..L- --l~

r---------r-------- ----. g(\J