A Raman and infrared spectroscopic study of compounds characterized by strong hydrogen bonds

Journal of Molecular Structure, 73 (1981) 19-29 Elsevier Scientific Publishing Company, Amsterdam -

Printed in The Netherlands

A RAMAN AND INFRARED SPECTROSCOPIC CHARACTERIZED BY STRONG HYDROGEN

ALESSANDRO BERTOLUZZA, PATRIZIA and MARIA ANGELA BATTAGLIA Istituto Chimico “G. Ciamician di Chimica. Facoitti di Medicina

MONTI,

STUDY BONDS

MARIA

OF COMPOUNDS

ANTONIE’M’A

lMORELL1

Raman, Cattedra “, Centro di Studro per la Spettroscopia e Chirurgia. Universitti di Bologna, Bologna (Italy)

‘Received 18 August 1980)

ABSTRACT Raman and IR spectra of some components of the sodium carbonatesodium hydrogencarbonate system and deuterated analogues are presented and discussed. The behaviour of the asymmetric stretching vibration YOHOshows the presence of strong asymmetric and strong symmetric hydrogen bonds in sodium hydrogencarbonate and sodium sesquicarbonate, respectively, in agreement with X-ray diffraction measurements. In the case of the Wegscheider salt (3NaHCO,.Na,CO,) the spectra show that hydrogen bonds of different “strengths” are present and lead to a hypothesis for the probable structure of this salt. INTRODUCTION

In the present paper the Raman and IR spectra of sodium hydrogencarbonate, sodium sesqujcarbonate (NaHCOS -Naz CO3 -2H20) and the Wegscheider salt (3NaHC03-Na,CO,) are presented and discussed. This study forms part of a programme of spectroscopic vibrational investigations dealing with strong hydrogen bonds (symmetric and asymmetric) [l-9]. The above-mentioned salts are the main components of the sodium carbonate--sodium hydrogencarbonate system and are characterized by strong hydrogen bonds. Moreover they form an interesting class of components of biomaterials (carbonate apatites) where CO:- ions substitute for PO:- ions in the apatite structure [lo]. We believe that the strong hydrogen bonds present in the sodium carbonate-sodium hydrogencarbonate system within a certain range of compositions are responsible for some of the physicochemical-mechanical properties of the carbonate apatites, in a similar way to the strong hydrogen bonds which originate in the CaO-H3P04 system as a function of the Ca/P molar ratio [IO] . The structure of sodium hydrogencarbonate is known from X-ray measurements [ll, 121 and consists of infinite chains of HCOJ ions linked by strong hydrogen bonds. The 0 - - - 0 interatomic distance is 2.595 A, with the hydrogen atom arranged asymmetrically with respect to the oxygen atoms (Fig. 1). 0022-2860/81/0000-0000/$02.50

0 1981 Elsevier Scientific Publishing Company

20

Fig. 1. Structure of NaHCO,

[12].

The structure of sodium sesquicarbonate is also known from X-ray and neutron diffraction measurements [ 13, 141. Two CO’,- ions are linked together by a very short hydrogen bond (0 - - - 0 = 2.50 A), with the hydrogen atom symmetric with respect to the oxygen atoms. The (C03HC03 )3- ions thus formed are linked by two HZ0 molecules (Fig. 2). Consequently the potential function of the hydrogen bond in sodium hydrogencarbonate is considered to be of the double minimum type, while that of sodium sesquicarbonate must be regarded of the single minimum type (or of double minimum type characterized by a very low barrier). The structure of the Wegscheider salt has never been investigated. Only an X-ray crystallographic study on the mineral Wegscheiderite is available in the literature [ 151. As far as vibrational studies are concerned, Novak et al. 1161 have reported the IR spectra of sodium

hydrogencarbonate

and sesquicarbonate,

giving a

vibrational assignment, while for the former salt only, a partial Raman spectrum between 4000 and 1600 cm-’ is reported in the literature 117) . Neither the Raman nor the IR spectrum of the Wegscheider salt are actually known. The purpose of this work is to characterize by Raman and IR means the strength of the hydrogen bond present in the main components of the sodium carbonate-sodium hydrogencarbonate system, and, in the case of the Wegscheider salt, to give the most probable structure. EXPERIMENTAL

Sodium sesquicarbonate and the Wegscheider salt were prepared as described in the literature [ 18, 191, starting from products obtained from Erba RPE. The respective deuterated compounds were obtained in the same way by using D20 and NaDCO, instead of I&O and NaHC03, respectively. NaDCO, was prepared by bubbling COZ into a saturated solution of Na,C03 in DzO. The IR spectra at room temperature were obtained from Nujol and hexachlorobutadiene mulls on CsI disks, while those at low temperature (-180°C) were obtained from thin layers deposited by a n-hexane evaporation on a KBr disk. The IR spectra were recorded with a Jasco DS701G spectrophotometer.

Fig. 2. Structure of NaHCO;Na,CO,-2&O

113,141.

21

The Raman spectra were obtained using a Jasco R300 spectrophotometer with a Lexel Ar+ 4880-A laser source. Some measurements at low temperature were recorded with a Cary 81 Raman Spectrophotometer equipped with a low-temperature Coderg cell. DISCUSSION

It is known, from IR spectra rather than from the much less utilized Raman spectra, that for a strong asymmetric hydrogen bond, characterized by a double minimum potential function with a low barrier [R(O - - - 0) < 2.60 A], three main bands, commonly referred to as the A, B and C bands, are to be expected [20]. These bands cannot be interpreted solely on the basis of the potential function for which two active transitions are expected in the IR and two active in the Raman, and various hypotheses have been advanced to explain their origin [ 21-23]_ According to the most commonly accepted hypothesis, they originate from a Fermi resonance between the fundamental vibration Vou and the second harmonics of the deformation vibrations [ 241. For a strong symmetrical (or nearly symmetrical) hydrogen bond, characterized by a single minimum potential function (or a double minimum with very low barrier), one can expect from the potential curve a single transition, in the IR spectrum only, and therefore the appearance of a broad band, called the D band, whose maximum can be found even below 1000 cm-l 1201. The distinction between these two situations is not clear, since in IR spectra intermediate situations involving a progressive weakening of the band intensity at higher frequencies and a strengthening of those at low frequencies are observed [7, 171. The IR and Raman spectra of NaHC03 and NaDCOs are shown in Figs. 3 and 4, respectively, while the frequencies of the bands are listed in Table 1. Our spectra are in agreement with those of Novak et al. [ 161. In particular the Raman measurements confirm the assignment given by these authors as regards internal vibrations, considering the coupling of the two ions, according to the isomorphic symmetry group CZV. Moreover in both the Raman and IR spectra of NaHC03, two main groupings of bands appear in the range 3000-1800 cm-* centred at ca. 2550 and 1920 cm-l. These bands are connected with proton motion since they shift to lower wavenumbers on deuteration, and are attributable to van and 2You harmonics, reSpeCtiVely [ 163. The absence of the trio of bands A, B and C shows that NaHC03 is an example of transition between intermediate and strong hydrogen bonds according to the R(0 * . * 0) value of 2.595 rS [ll, 121. On the basis of such a distance we expect the yon band to lie 2t ca. 1000 cm-l [25]. Thus, we agree with the assignment of Novak et al. of the Ton vibration at 997 cm-* _ This band is also present in the Raman spectrum at 993 cm-l, where it shifts to 1007 cm-’ at low temperature. The in-plane deformation 6on is more difficult to assign both in the IR and the Raman spectrum for the reason already discussed by Novak et al. [ 161.

22 TABLE

1

IR and Raman spectra (cm-’ ) of NaHCO,

and NaDCOSa

NaHCO,

NaDCO,

IR

Raman

3053

w

2915 2760 2650 2542 2450 2270 2040 1921 1833 1730 1695 1655 1617 1452

m,b vw,sh w,sh s,b m,sh vw,sh w,b s,b w,b w m s s s

Assignment

IR

3060 vw,b 2920 vw,b 2750 vw.b 2530 2450 2660 2270 2060 1914 1844

vw,b vw,b sh > vw,b vw,b vw vw

“OH

“a “2

+ YOH

“4

+

70H

m sh w s s,b w,sh vw,sh sh s,sh vs sh s

“s

I’

2230 2160 2115 2005 1950

VOD

yw vw vw w,b w,b

1597 w

V6

1570 vw 1434 1414 1393 1379 1319 1307

1395 vw,sh 1380 vw,sh 1326 vs,b

and 60H

Assignment

1728 VW 1698 vw 1675 vw

“6

1623 vw 1 1459 w 1437 w 1

1269 m

AOH

+

2rOH

1684 vw

1398 s 1300 vs,b

2230 2160 2120 2005 1940 1726 1695 1665 1620 1598 1560 1444

Raman

w vw vw vw m w,sh

1250 w,sh

as. strong; m, medium; w, weak; v, very; sh, shoulder; b, broad. For the type of vibration “1, IJz. . . see Novak et al. [ IS]_

I 4000

I

I

I

I

I

2000

I

I

I

I1

I1

I

1500

I

I

i

11

1000

I,

I1

I

500

cm-’ Fig. 3. IR spectra of NaHCO,

(-

) and NaDCO,

(---) at room temperature.

In Table 1 the results of our Raman and IR measurements are reported. These agree with the assignment of the above-mentioned authors for both the hydrogen bond vibrational modes and CO’,- internal modes. In Figs. 5 and 6, respectively, are reported the IR and Raman spectra of

23

NaDCO,

NaHCO,

IR

Assignment

1045 1032 997 836 812 694

m s s,b vs sh vs

656 s

993 vw 834 v-w 699 687 660 646

m w w

230 211 206 182 166 152 144 124 113 91

m m m vw w,sh w,sh s vw,sh s s

“I TOH

v2

w

255 m

v,,

vz

. . .

Assignment

IR 1076 1040 990 835

vs vw,sh m s

818 715 686 626 255

sh m, sh vs s m

1068 1036 995 835

w vs vw vw

714 vw 678 s 627 w

60D

“I u2

YOD

Vd u3

225 w 206 w

200 w 164 150 140 122 110 89

w,sh sh s w s s

see Novak et al. [ 163 _

2D,O*. The frequencies of the NaHC03-NazC03*2Hz0 and NaDCO, - Na,C03 bands are listed in Table 2. Our IR and Raman results confirm the assignment given by Novak et al. [16] onIy on the basis of the IR spectra as far as the internal vibrations of CO:- groups are concerned. In particular they are in agreement with the rule of mutual exclusion according to the Ci symmetry group of the (C03HC03 )“- ion. The IR spectrum of sodium sesquicarbonate shows a broad band centred between 1200 and 1100 cm-[ which becomes more intense and narrower at the temperature of liquid nitrogen, shifting between 1100 and 1000 cm-l, and is absent in the Raman spectrum. The presence of such a band assigned by us to the vOH asymmetric stretching vibration (band D) is in agreement with the existence in sodium sesquicarbonate of a strong symmetric hydrogen bond characterized by an 0 - . - 0 interatomic distance of 2.5 A. Moreover this hand is interrupted by a transmission “window” at 1050 cm-l. This phenomenon has been observed by -X [26] in the IR spectrum of sodium hydrogendiacetate and has been A ributed to a resonance between two bands, one of which is broad, with l

*In Fig. 5 and subsequently in Fig. 7 are reported the II2 spectra between 4000 and 400 cm-1 of thin layers obtained as described under Experimental, since they appear more suitable for showing the spectroscopical behaviour of the compounds. In making the tables we have considered also the spectra obtained from the mulls in the range 4000-200 cm-’ _

24 TABLE

2

IR and Raman

spectra(cm-l)

NaHCO,-NalCO,-

of NaHCO;Na,CO,-2H,O

NaDCO,-Na,CO,-2D,O

2H,O Assignment

Raman

IR -180°C

25°C 3470 m,b 3210 sh 3050 m

25%

3470 s 3240 w 3050 s 2495 vw.b

1740 sh

1740 sh

1691 s.b

1696 s.b

1717 w

us and H,O

1562 m _ 1549 m 1465 s,b

1465 s.b

-1170

s.vb

1540 sh

&OH?

1432 m 1

v5

1213 s

1191 m.b

-1070

675 m 653 m

1052= 849 799 718 690 675 670 656

vs,vb

vOH

vs m m s s sh s

) 85Ovw 790 vw.b 701 w

610 vs.b 570 s 485 sh

i 225 vi 216 w 187 m 176 w 156 m 141 m 123 sb 111 sh 100 “5 88sb 71 s

230 s

aTransmksion

--18O”C

2575 vs

2575 vs 2540 s

2370 sh 2290 s

2290 vs

1560 vs.b 1420 vs.b

1560 vs,b 1435 vs.b

1153 m

1170 m 1058 w

w.b

v1 H,O

25°C

2545 s 2372 vw.sh 2305 1820 1730 1700 1567 1433 1250

m VW VW VW VW w VW

1060 vs

DZO

V6 v< “10 VI

1042 w 865 m.sh

850 vs

850 vs

YOD 854vw

v2

800 m.b

“1

LJ, and us 643 w

602 s.b

25°C

1055

Assignment

Raman

IR

YOH 1064 vs

105Oa 849 vs 790 w.sh

and NaDCO,-Na,CO;2D,O

695 w 670 s 660 610 565 485 440 225

sh sh m.b sh s m

675 670 660 610 575 502 455

s sh m m.sh s s vs

vJ and u,

223 213 185 173 159 153 140 110 100 86 69

m w s m m m m sb vs m s

“window”.

very close maxima. In the case of sodium sesquicarbonate this interaction can occur between the large Van band and the V, stretching mode which appears at 1064 cm-l in the Raman spectrum of NaHC03-NazC03- 2&O and at 1060 and 1058 in the Raman and IR spectrum of NaDCOJ-Na2C03-2Dz0, respectively. Finally, in Figs. 7 and 8 the IR and Raman spectra of the Wegscheider salt and of its deuterated analogue, respectively, are reported. The frequencies of the bands are listed in Table 3. For this salt it is possible to suggest three main structures (Fig. 9). The first two are linear, with the carbonate group inside (Fig. 9a) or outside (Fig. 9b) the chain. Both are characterized by the presence of structural units typical of both sodium hydrogencarbonate and

25

--I

4000

3000

C

2000

[

t

I 4000

3000

2000

-8 0

1000

cm-’

Fig. 4. Raman

spectra

of (a) NaHCO,

and (b) NaDCO,

at room temperature.

cm-’ 4000

2000

1500

1000 ““I’

2000

I500

1000

I”“““““”

l111’1’1111111’1

4000

500

Illll~l

cm

500

-I

Fig. 5. IR spectra of (a) NaHCO;Na,CO;2Hz0 and (b) NaDCO;Na,CO;2D,O ) and at the temperature of liquid nitrogen (---). temperature (-

at room

sodium sesquicarbonate, and consequently they must contain different types of hydrogen bond. The third structure is branched (Fig. 9c) and contains only sesquicarbonate units and, therefore, hydrogen bonds of the same type. The IR and Raman spectra of the Wegscheider salt show two main groupings of bands at ca. 2550 and at 1910 cm-l, respectively, which characterize the hydrogen bond present in sodium hydrogencarbonate. These bands shift to

26

3000

4000

2000

1000

0

cm-’

Fig. 6. Raman spectraof (a) NaHCO;Na,CO;2H,O room temperature.

and (b) NaDCO;Na,CO,*2D,O

at

cm-’ 4000

1

”

”

2000 ”

1500 ”

”

”

”

1000 ”

500 ’

’

”

cm-’

Fig. 7. IR spectra of (a) 3NaHCO;Na,CO, and (b) 3NaDCO,*Na,CO, ature () and at the temperature of liquid nitrogen (---).

at room temper-

lower wavenumbers in 3NaDC03-Na,COj and therefore are connected with motion. Moreover the IR spectrum of 3NaHCO,-Na,CO, shows the broad absorption band typical of the strong symmetric hydrogen bond in sodium sesquicarbonate; this band becomes more intense in the spectrum at low temperature and is not present in the Raman spectrum_ Therefore the

proton

27

TABLE

3

IR and Raman 3NaHCOJ-

spectra

of 3NaHCO,-

(cm-l)

Na,CO,

Assignment

RaITlm 2 5%

-180%

3096 sh

2935 m 2580 s.b

2933 m 2520 s.b

2230 w.b -1960 vw.b 1725 sh

VW vw.b m.sh vs

1651 vs 1455 m,sh 1425 m.sh 1370 vs.b

-2000 1945 1725 1690

w w m.sh vs

3930 vw.b 2500 vw,b

“OH

1910 vw.b

2YOH

1700 w 1675vw.sh

ug

1651 vs 1466 1438 1410 1368

m s sh vs.b

1560 1450 1429 1391

VW sh m m

1635 s.b 1620 s.sh 1444 m 1368 vs.b

I

60H

and “5

1047 1034 1019 1000 845 837 835 696 675 669 655 640 250 222

m w m sh “5 vs sh s vs.b s.sh m s.sh s s

1230 s.b 1050 s 1026 1013 e4 839 835 697 686 680 669 655 609

s m vs vs vs vs sh vs vs vs vs

1057 vs 1038 s 1022 s 841 VW

-,

YOH VI

I

YOH “2

699 m 686 m uq and u, 654 m 240 224 186 153 118 105 96 89 72 55

m m m s m vs w m vs m

1144 m 1082 s.b 1045 sb 994 m 845 s,sh 838 vs

1355 w.b 1270 vw,b

J

Raman

IR 25%

3120 vw.b

3096 w.sh

-2000 1910 1725 1686

Na,CO,

3NaDCO,-Na,CO,

Na,CO,

IR 25%

and 3NaDCO;

695 sh 672 s 660 m.sh 615 w.b 247 m 225 w

2230 -1940 1710 1655 1635 1621 1560 1452

w.b w.b m.sh sh vs.b vs w.b m

1365 vs.b 1152 1093 1046 -1038 999 847 838 753 731 695 674 670 655

Asnwment

25°C

-180%

m s.b w sh m vs vs m w sh vs sh vs

2230 vw.b 1925 vw.b

VOD

1680 vw.b v.s

1422 m 1362 w.b 1315 w.b

v5

&OD 1039 vs 1001 1051 s vs 841 vw,b

“1 1 u2 I YOD

610 s 570 sh 237 222 182 155 130 120 106 88 73

w w Ww sh sh s s vs

analysis of the spectra leads to the conclusion that the Wegscheider salt possesses a linear structure of type (a) or (b), but not of type (c). As for the remaining IR and Raman bands, the probable attribution is reported in Table 3, according to the assignment given for sodium sesquicarbonate and hydrogencarbonate, and also on the basis of temperature and isotope effects.

28

cm-’

4(300 I""""""

3000

0

1000

2000 ’

”

”

”

1

b 41000

3000

2000

1000

0

cm-’ Fig. 8. Raman spectra of (a) 3NaHC0, temperature.

- NalCO,

and (b) 3NaDCO;

Na,CO,

at room

Fig. 9. The three possible structures of the Wegscheider salt. These structures are indicative only of the structural centres present (carbonate, hydrogencarbonate, sesquicarbonate). ACKNOWLEDGEMENTS

The authors thank Prof. G. B. Bonino for his useful advice and suggestions. This work was supported, in part, by C.N.R., Rome. REFERENCES I A. Bertoluzza, C. Fagnano, M. A.. Morelli and R. Tosi, Rend. Accad. Naz. Lincei, 58 (1975)919.

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29 5 A. Marinangeli, M. A. More& R. Simoni and A. Bertoluzza, Can. J. Spectrosc., 23 (1978) 173. 6 A. Bertoluzza, C. Fagnano, P. Finelli, M. A. Morelli and R. Tosi, Ital. J. Biochem., 28 (1979) 368. 7 A. Bertoluzza, P. Monti, M. A. Battaglia and S. Bonora, J. Mol. Struct., 64 (1980) 123. 8 A Bertoluzza, M. A. Battaglia, S. Bonora, C. Fagnano, P. Fine& G. Fini, P. Monti, M. A. Morelli and R. Tosi, Int. Conf. Raman Spectrosc. 7th Ottawa, Canada, August, 1980. 9 A Bertoluzza, C. Fagnano, P. Finelli, M. A. Morelli and R. Tosi, Horizons in Hydrogen Bond Research, Uppsela, Sweden, August 1980. 10 F. S. Parker, Application of Infrared Spectroscopy in Biochemistry, Biology and Medicine, Hilger, London, 1971_ 11 W. H. Zachariasen, J. Chem. Phys., 1(1933) 634. 12 R. L. Sass and R. F. Scbeuerman, Acte Crystallogr., 15 (1962) 77. 13 C. J. Brown, H. S. Peiser and A. Turner-Jones, Acta Crystallogr., 2 (1949) 167. 14 G. E. Bacon and N. A. Curry, Acta Crystallogr., 9 (1956) 82. 15 D. E. Appleman, Am. Mineral., 48 (1963) 404. 16 A. Novak, P. Saumagne and L. D. C. Bok, J. Chim. Phys., 60 (1963) 1385. 17 A. Novak, J. Chim. Phys., 72 (1975) 981. 18 J. W. Mellor, Inorganic and Theoretical Chemistry, Vol. II, Longmans, London, 1960. 19 E. M. Barral and L. B. Rogers, J. Inorg. Nucl. Cbem., 28 (1966) 41. 20 D. Had% and S. Bratos, The Hydrogen Bond, Vol. JI, North-Holland, Amsterdam, 1976, p. 563. 21 D. Had%, Pure Appl. Chem., 11 (1965) 435. 22 M. F. Claydon and N. Sheppard, Chem. Commun., (1969) 1431. 23 G. L. Hofacker, Y. Marecbal and M. A. Ratner, The Hydrogen Bond, Vol. I, NorthHolland, Amsterdam, 1976, p. 337. 24 D. HadZi, Horizons in Hydrogen Bond Research, 3rd Workshop on Dynamics of Hydrogen Bonds in Solids and Liquids, Ankaran, 8-11 September, 1979. 25 A. Novak, Struct. Bonding (Berlin), 18 (1974) 177. 26 J. C. Evans, Spectrochim. Acta, 18 (1962) 507.