Vibrational studies and phase transitions in tetramethylammonium chloride

Volume 92, number 1

VIBRATIONAL

CHEMICAL

STUDIES

8 October 1982

PHYSICS LETTERS

AND PHASE TRANSITIONS

IN TETRAMETHYLAhfMONIUM

CHLORIDE

Mahendra PAL, G.S. RAGHUVANSHI and H.D. BET Dcparzme~rr of P~~JWCS. Indm

Institute

of T?chnolagy.

Kanpur 108016. Itldro

Received 25 hlay 1982

The characteratrc Raman

spcs113oi(CH3),NCI IIIfour m (CHX).N+

knoan phases are repotted along wth their assrgnmcnts The and thcv spbrtmgs have been used to determmc the I~XISI-

CH,

modes o~spec~es E and F:

axe dlswprshed

non

tempcrawrcsThe rransitian III - IV ISfust orderand revsrwblc

1. Introduction Tetramethylammoniurn chlonde (TMAC) undergoes four SUC~~SSI~~ phase rranvtions derected by differential thermal analysis [l-4], nuclear magnetic resonance [5] and proton spin-lattice relaxation [6] studres. The dettis of phases and transitions are compiled in table 1. The space groups of TMAC tn phases I,11 and111 arereportedtobeOi(E4) [4],C$,(Z=I) [-I], and Dih(z=2) [7,8], respectiveIy.The vlbrational assignments of the obsemed bands in aqueous solutions of several compounds containing the TMA Ion are available III lirerature [9-151, including TMAC [9,11,13,15]. However, the asslgnments m CH3 stretching and deformation regions suggested by different authors [9,11,14,15] are stall controvernai.

Table 1 The hnown phaxs and trmmon Phxe

temperatures

ior

At room temperature (RT) the Raman and mfrared spectra of polycrystalline compounds containing TLlA ions have been reported by Kabisch [ 161 and Harmon [ 171, respectively. Until new there are no vibratlonal studies avadable for other phases. Evidently, these phase transitions have not been studied so far by mfrared (IR)or Raman spectroscopic methods. In the present COIIUIIUNCatlOII the characteristrc Raman spectra of TMAC m the four phases (I-IV) along wrth their assignments based on their behaviour with temperature variation are reported. We have characrensed the phase transitions on the basis of the temperature dependence of the CH3 deformation modes. The transItIon temperatures reported by us are close to those reported earher [l-6].

tetramcth~l~mmon~um chlonde

Ttansrt~on temperature

Type

536 Kl3;lj

reveruble 13.41

413 Kl3.41

ureverslble [3,4I

184.9 Kill

h-ttans~uon [ 11

I II III

Spxe Group

Srtucrurr

obcz=~,141

ICC [3,-l]

t&Q

rhombohcdral[3,4J

D:h(z=

IV 75.8 K[ll

first order

[I]

V

0 00%2614/82/0000_0000~.S

02.75 0 1982 North-Holland

= 1) 141 ?) [7.S]

terragonal [ 7,8]

,

terngon3l [JI

9

7 82

Yolumc 92. number 1

8 October 19B2

CHEMICALPHYSICSLE’MERS

trophotometer with a resolution of 2 cm-l. The &best temperature approachable with this HT c&i is = 700 K and the measured temperatures are correct Withillk2K.

2. Experimental For Raman stuck at RT and low temperature (LT), pellets of dned and powdered AR-grade TMAC were prepared ITIa humidity free atmosphere. The pellet was mounted on the cold finger (makmg an angle of IS” with the vertical) of a home-made Iowtemperature cell which was kept under vacuum. The sample holder was cooled by liquid nitrogen. For bightempentuie (HT) studies the sample was filled in a Pyrex glass tube and mounted m a home-made Iugbtemperature cell at the usual 90” geometry. The sample was excited by a 5 14.5 nm laser beam obtamed from a Spectra Phyucs Ar+ laser and the Raman spectra were recorded ma Spex Rsmaiog spec-

3. Factor group analysis The TMA group retams its identity over a wider range of environmental conditions. It is, therefore, appropriate to take only two groups, viz. TMA and Cl for a detailed group theoretical analysis. In phase n (C~y,Z = 1) the total number of modes, 54, for a unit cell could be distrtbuted as six translatory phonons (mclud~g three acoustic phonons), three rotatory

Tabfe 1

Correlationoi molecularsymmrttrgto Pliise faceQr

86

bcror Eroups

through ate s~rmmetnesfor ‘MA ion in phzs~sit and IIf Phase

II site

V=UP

spnetry

5”

c3v

HOl@CUlFX

SF-try Td

s:metrJ Dti

III

fC!ctor

sate

rjJ=e Cla

%h

Volume 92, number 1

CHEMICALPHYSICSLETTERS

modes and forty five internal ~bmtions of the ThiA ion. The forty five internal modes of the TMA ion

under point group T, are distnbuted as 3At + A2 + 4E t 4F, t 7F2 and represented as q-v19 [ 141. In of total number of modes can be obtained from those of phase II (2 = 1) by multipiy~g them with the number of formula units per unit cell (2) in the desired phase (2 = 4 for phase I and2 = 2 for phase III>. Table 2 illustrates the correlations of the species of molecular point group Td for the TMA ion to the species of factor groups Cjv and D,, for phases II and III, respectively, through the species of their respecttve sixes. The internal modes of ThiA ion in phase II (45 m total) and phase iii (90 in total) are distnbuted as follows.

8 October 1982

~~espond~g to Z = 4 is available [ lSl_ Therefore, a group theoretical analysis for these phases has not been carried out.

other phases the distributions

r$,

= lOAl(R,IR)

+ 5AZ + 15E(R, IR) ,

F$, = 7A,&R) t4Az,t

7B,,(R) t5B,,(R)+

f 5A,, t7A~“~IR)~4B,u

llE,(R)

+ 7B2, + 1 IE,(IR).

For phases IV and V no structural data are available. The space group for phase I has been suggested to be 0: (2 = 4) [4], but no possible site symmetry

WAUENUYBER

4. Results and discussion 4.1. ChamcteristirRitmanspectra oft&e four phases above iiquid-ilitroge~~ temperirturead their assrgmrrents

The observed Raman spectra of polycrystallme TMAC taken tn the hi-temperature cell at 300,430 and 540 K correspondmg to its phases III, II and I, respectively, tn the regions 200-1000 cm-t and 2700-3 100 cm-l, are given in fig. I. The spectra taken in the low-temperature cell at 150 and 300 K npresntutg the phases Iv and III, respectively, are given tn fig. 2. The peak positions of the observed Raman bands for the four phases along with thetr assignments (referred to the undistorted Td symmetry of TMA ion and wlthout taking into account the sphttings due to lowering of symmetry) are gtven m table 3.

{emi)

FQ. 1. Raman spectra of tetramethykunmoruum chloride. taken m the hgh-temperature cell. at 300,130 and 540 K cormpondtng to phases 111,Ii and 1. respectively.

87

VoIumc 92. number I

CHEWCAL PHYSICS LETTERS

FG. 1 Rmunanspectra oi trtramerhylammonium chlondc. tkn phses ill and IV. respectMy.

4.1.1. Phase1 For T-MAC, Pinonus

nnd Clbson [4] hnvr suggested the space group for phase I to be O&Z = 4)_

The possible site symmetries for space group 02 and ~~h(l),Td(2), D&j), C.&Q, $(8), 3+(% X,(24) and C I(4S) [i8]. So there IS no possrble site symmetry in this space group that can contain four symmetry points. According to Dufourcq et al. [3], the catrons are at two Td ates. If it IS true, the Raman spectra of ThlAC in phase I must closely resembie the aqueous solution spectra as obsrved by I&bsch 1173 III (~H~)~~~SnC~~_ But in phase 1 the intensities of a!l the bands reduce to nearlyzero. SO it _wem either TMAC does not have space group Oi(Z=4) ur phase I or due to some other effects intensities of bands are suddenly reduced to zero. Besides other reasons it may be due to very low activation energy for CH3 librations [4] and occurrence of ~oruc diffusion in this phase [S]. 4.1.2. Phase II The Raman spectra of TMAC in thrs paper below 1300 cm-l are similar to aqueous solution spectra an assigned identic~y [7- 151. In the Raman spectra 88

8 October 1982

m the low-temperature ceU. at 300 3nd 150 K conespondlng to

of TMAC above 1300 cm-1 we get two strong bands at 1403 and 1462 cm-l in the CH, deformatron region and two strong bands at 2962 and 3016 cm-l m the CH, stretching region. Table 4 is an iktration and extension of table 2 for CH3 modes. For an Mated CH, group having Clv symmetry, group theoretically, the stretching (or deformatron) modes produce two vibrations of species Al and E as shown in column 1 of table 4. The four symmetric stretches (or deformations) of sprcxesA 1 for the four CH, groups in the WA ion

underrnole~i~ sy~et~ T, producethe species At t Fz, the ~o~e~ond~~ modes are denoted = ~1 and u14 for stretches (~2 and 9j for deformations). Lrkewise the asymmetric stretches (or deformations) of species E are datriiuted as E + F, + F,, corresponding modes are denoted as p5, VPand v13 for stretches (p6, vlo and v js for defo~ations) as given in tabte 4. As given in column 5 of table 4, the four symmetric A, and four asymmetric E stretches (or deformations) are further split as bands of species 2A, t E and A, t A2 + 3E under the factor group C,, (through the site C,,). Thus all the CH3 stretches (or defo~atio~) may split into seven 3A, + 4E

Table 3 Raman band ponuons

(III cm-‘)

of letramethylammotuum

chlondc

m alJ the tirst four phases wth their proposed assgnment under

point group Td of (CHs),N+a) Phase

I

Phve II

Phase II 364 VW, b

450 WJ, vb 454 m

738 w. sh 752. w, b

946 w. b

376 w

376 w

388 454 459 730

389 m

m m m w. b 760 vs -

152s 916w.b

930 w. b 948 VS -

944 m

1182 1192 1286 1398 1402

1180w.b 1282 w. b 1403 w

w w s sh 5

1454 5 1462 s 1477 5 1482 s I 2800 w. b

2790 w 2840 2877 2892 2920 295 I

2872

3908 2962

5

w m sh sh “I

ua(E)C4N

456 m 464 m 736 w, b

vt9(F2)

C,N asym def

&J(E) uJ(At)

758 vs 887 w. b 940 w, stl 946 vs 958 w 1183 w 1197 w 1291s 1392m 1397 m 1407 m 1452 5 1474 sh 1479 5 1486 s 2710 w 2792 w 2800 w 2834 w 2872 m 2886 sh 2902 sh

sym. dcf.

C,N sym. str.

3,903

vta(F2)

C4N asym str.

VT(C) CH3 rock vt,(Fz)

CHI rock

utb(F2)

CHJ sym. def

Q(E)

CHJ asjm

vts(Fz)

def.

CH, asym def

hs(F,) “6(E) QSWZ)

x u16(Fz) x yi6(rZ)

2u6W) zqs(F2) v,(A,) CH,

2950 %S

6>m. SU.

3019 vs

3011 vs 3022 m

us(E) CHs z.ym. str

3027 “S

3028 vs 3033 vs

q~(F2)

3016 vs I

Assrgnment

Phase IV

CH, asym str.

a) Y. very; w, weak; m, medtum; s. strong, sh. shoulder; b. broad.

Table 4 The numb.% and types of viirahons rehted Nk denotes o Ramangcttve spenes)

Iwhted

CH3

CC3v) CH viirattons (stretch or

to CHS strcetcbmg (or deformation)

ThlA (T-d) species

deiomwtton)

notations

modes tn phws

II and III md TMA 1011s(an aste-

PhiiseII (2 = I)

Phase 111(2 = 2)

CW

D4h

ior CH modes

stretch

deformstton

Al

At

“I

y2

Ai

Afg

sym.

Ft

“14

“I6

Ai+E’

B;g+E;+Az,+Eu

E

E*

“5

*6

E*

Aig+B;g+A1U+Bzu

=ym

Fl

v9

“IO

Fi

“Ia

“IS

A2 + EA, +E*

A2g+E*+B,,+Eu g B:g+Eg+Az,+E,

total number of bands expected

3A; + A2 + 4E8

+ B2u

‘A&+

Alg + 2B&

f B& + 3E; +

Alu+2A2,+B,u+2BLu+3E,

89

Volume 92, number

I

CHEMICAL PHYSICS LElTERS

Raman actice components in phase 11as given in last row of table 4 (A2 berng rnactrve both in IR and R). E~perrmentally two strong bands tn deformation (or stretchtng) region are observed in the Raman spectra in phase II which are rdentical to the Raman spec. tra of isolated CH, group. So tt ts only appropriate to assignthe bands at 1403 and 1462 cm-’ as CH3 symmetnc deformation and CHj asynunetnc deformaLION,resprctwely. Sunilarly in the CH, stretchmg regron the bands at 2962 and 3016 cm-l are assigned asCH, sy~et~cstretch~dCH~ a~y~etricstretch, respectively.

The augments of all the fundamental of ThfA IOU for the RT phase Ill below 1300 cm-* are identrcal to those made by Kabisch [ 161. In the CH, deformatton region, 1350-1500 cm-t, group theoretically as already explanted and gtven tn table 4, five bandsva(Al),‘,6(E2),V6(E)r”IO(F1)~dYlj(Fr) are expected under pomt symmetry Td for the free ThiA Ion. The splittings of the bands in phase III under the factor group I),, throu~ the site D,d rs given in the last column of table 4. In the Raman spectraofThlAC we get five bandsat 1398,140’. 1454, 1477 and 1483 cm-l.The doublet with componentsat 1398 and I402 cm-l (which splitsinto a tnplet wrth componentsat 1392,1397 and IJOircm-1 tn phase 1V) are assigned as ut6(F,), consistent WI&Igroup theoretreal analyns. The bands of species F, are expected to spht rnto two Raman actrve (El, anbEg) components for RT phase Iii. It is observed that most of the bands of speciesF2 tn phase IV splrt mto three components. Srmdzrly the bands at 1477 and 1482 cm-i assigned ;LSVtj(Fz) in phase 111also split into three components (l-174,1179 and 1486 cm-l) in phase 1V. The band at l-154 cm-* may be assigned to +(A l) or Q(E) However, it has been observed that in CH, and CJN stretchurg regrons of ThlA in that the intensities of the bands corresponding to symmetric species A, are dtmintshed wtth respect to the corresponding asymmetric bands m gomg from the solution to the poIyc~sr~e state [ 191. Therefore the band at l-l54 cm-1 could be assigned to us(E)_ This band can, however, have some minor contnbution due to vz(Ar) as expected by spectra of deuterated TMA ions f 141. The band of species F i under T, fs Raman inactive, so the band of species E, arismg from vg(F1) 90

8 October 1982

may be very weak to Identify in polycrystalllne MAC in phaseIII.

_ 4.1.4.Phase IV Prstorius and Grbson [4] have suggested that the lattice is tetragonaI m this phase with lattice constants closeto that of the RT phaseIII. No structural data are avattabte for this phase. As mentioned before, it 1sobserved that most of the bands of species F1 splrt into three components in the Raman spectra of ‘MAC in this phase. It can be expected that on lowering the temperature (III + IV) the inversion symmetry in phase 111is lost and therefore the lattice goes to a space group lower than D&. The most probable tetragonal space groups having four fold symmetry without inversion would be anyone from D:, D$ . . Df, D:‘. However D: and Di are the only space groups which do not possess screw sy~et~, thus resembhnk the D&, group as far as screw symmetry is concerned. If one assumes that the prirmtive cell IS preserved on lowering the temperature, the space group for phase IV will be Di (2 = 2). Under this situation the bands of species Fz are expected to spht into three Raman active components, which is actually observed in phase IV.

The phase transition temperatures are determined

uvlththe temperature dependence of t@E) and v~~(F$ for tr~s~tions III + if + I as shown in fig. 3. The transttton III + IV is followed by monitoring the temperature dependence of vm(F7) as shown in fig. 4. It IS observed from fig. 3 that in transition HI + II, the bands at 1454,1477 and 1482 cm-t start to diminish at 412 K and a new baud starts to appear at 1462 cm-i, the latter band gaining intensity with increase in temperature. At = 430 K the bands at 1454, 1477 aud 1482 cm-1 completely disappear and the band at 1462 cm-l becomes fairly strong. So it is seen here that the phase transition III--* II is a secondorder transitton taking place over a temperature range of 2: 18 K. Prstorius and Gibson [4] have suggested that III -+ II transition has a thermal hysteresis of 18-24 K. We have observed that the transltion temperature depends on the tnltral motsture content and the rate of heating. On very slow heating it is found to be * 20 K higher than the reported one. But in

Volume 92, number

I

8 October 1982

CHEMICAL PHYSICS LETTERS

1’11

I&

18

191

f9!

201

251 3M 1

WAVENUMEE~

60

(c&]

oi

pEiand tits modes of CH, in T&IA ion for determmmg the

FI& 4. Temperature dcpcndcnce (in Ihe range 300-150 K) of 1~16mode of CH3 m TMA ion ior determlmng the phase tran-

phases trimsltfons liI+if-+l.

SllIOfl111-IV.

presence of much moisture and fast heating it is found to be around 390 K. In the transition II + I the band at 1462 em-1 disappears tn an hour when the sample is kept at constant temperature at 540 K just above the reported tram&on temperature. Other bands also disappear in phase I except the bands of C,N skeleton which are found to be very weak. On lowering the temperature in phase transition III + IV the band at 1402 cm-l having slight asymmetry on lower frequency side at 1398 cm-I fast suddenly split into two components near the transltion temperature and fmaIIy into three components at 1392,1397 and 1407 cm-t within a temperature

mterval of * IO K. The sudden splitting of band at 1402 cm-t into three components at 185 K indicates that the traction III + IV is fust order. On heating back we observe the same pattern, mdtcatmg the Cranstton III + IV IS reversible without hysteresis.

r&_ 3 Temperature dependence(III the range 300440

K)

5. c0nc1usi0fE

For dlstingulshmg the bands of different species in ail phases, ~n~e~~sc~ Raman spectra in different orientatrons are required. X-ray data for phase IV and V are not avaiIabIr. With the splitting of bands of species F2 in TMA ion under molecular symmetry Td

Volume 92. number 1

CHEMICAL PHYSICS LETTERS

into three. the space group for phase IV is suggested be D: (Z = 2) which needs v&fication by X-ray data. For phase 1 the earher suggested space group to

O$Z = 4) is questionable

as per our observations

and

hu to be reinvestigated crystallographmlly.

[S]

8 October

R.W.G. Wyckott. Z. Knst. 67 (1928)

1982

91.

[9] J.T. EdsaIl, J. Chem. Phys. 5 (1937) 225. [IO] E.A.V. Ebswortb and N. Sheppard, Spectrochim. Acta

13 (1959) 261.

[ 11J J,\

Stanley and hl C. Tobm, Spectrochun. ACM 28A

(1972) 1141.

[ 121 w. van der

Ohe, J. Chem Phys. 62 (1975) 3933.

[ 131 G L. Bottger and A L. Ceddes. Specrrochim. Acta 21 References

[I]

S S Chang and E F. Weltrum Jr, J. Chum. Phys 36

(1962) 24’0 [I] hl. Stammlcr, J lnorg Nucl. Chem 29 (1967) 2203 [ 3 J J Dufourcq. Y Haget-Boutiud, N B Chanh and B Lemanceau, Acra Cryst 828 (1972) 1305. [-!I C.W F T Plstonus and A.4.V. Clbson, J. Sohd Srate Chem. 8 (1973) 126. [S ] AA-V. Clbson and R.E. Raab, J Chem Phys 57 (1972) 4688 [6] S Albert, H S. Cutowsky and J A. Rlpmczster, J Chrm Phys. 56 (1972) 3672. [7] L. Vegxd and I; Sollesnes, Phil i&g 4 (1937) 985.

92

(1965)

1701.

[ 141 R.W. Berg, Specuoch Acta 34A (1978) 655 [ 151 C. Kablich and M. Klase. J. Raman Specctry. 7 (1978) 311

[ 16) G. Kabisch, J. Raman Spectra. 9 (1980) 279. [ 171 KM. Harmon, 1. Cenmck and S L. Kleman, J Phys. Chem. 78 (1974) 2585. 1181 WC. Fateley, F.R Dolbsh, NJ. hlcDe.vltt and F.F. Bentley, Infrared and Raman selection rules of molecule and lattice nbratlons. the conehtlon method (Wileylnrersciencr, New York, 1972) p. 179. [ 191 hl. Pd, G S Raghuvanshi and H.D. Brst, unpubhshed re-

SIllIS.