J. Phys. Chem. 1996, 100, 6421-6426
6421
Weak Hydrogen Bonding in Ethanol and Water Solutions in Liquid Hydrides of Group IV-VI Elements (SiH4, GeH4, PH3, AsH3, H2S, and H2Se). 2. IR Spectroscopy of Hydrogen Bonding in Solutions Containing Water in Hydrides P. G. Sennikov* and V. E. Shkrunin Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, 49 Tropinin Street, GSP-75, Nizhny NoVgorod 603600, Russia
K. G. Tokhadze Department of Physics, the UniVersity of St. Petersbourg, Petergof, St. Petersbourg 198904, Russia ReceiVed: NoVember 1, 1995X
The results of an IR spectroscoic study of solutions of water in liquid hydrides of the group V and VI elements (PH3, AsH3, H2S, and H2Se) in the temperature range from Tb of hydride up to 290 K are presented. The solubility of water in liquid SiH4 and GeH4 is lower than the detection limit of infrared spectroscopy. The spectral parameters of the stretching and bending vibration bands of water are measured. The formation of weak hydrogen bonds between the molecules of water and hydrides takes place. To account for the shape of the stretching band of water, 1:2 complexes with hydrides are postulated to be present in these solutions. Their binding energy is estimated. Values of the Gutman donor numbers of the hydrides in the liquid phase are given.
Introduction The study of molecular interactions, both nonspecific (van der Waals complexes) and with specific contribution (donoracceptor and hydrogen-bonded complexes), is an important part of modern physical chemistry and chemical physics. A great number of publications deal with rather strong DA and hydrogen-bonded complexes of organic molecules (e.g. refs 1-5). Starting from the 1970s, the number of investigations of van der Waals complexes using the methods of microwave and IR spectroscopy (e.g. refs 6-13) increased substantially. Unfortunately, there is still a relatively limited number of studies of very weak specific interactions with energy less than 3-4 kcal mole-1 in general and under equilibrium conditions in particular.14 Among the species that participate in such interactions, the molecules containing the atoms of the second, third, and, perhaps, the fourth periods are of particular interest. Volatile inorganic hydrides of the group IV-VI elements are the simplest types of such molecules that can show both electron (proton) donor- and acceptor properties. Some aspects of the theoretical and experimental study of the complexes of these hydrides have been considered by one of us in an earlier paper15 in this journal. It was shown that the quantitative notion of the relative strength of the complexes of hydrides of the first through third periods of the group V and VI with constant proton donor HHal (were Hal ) F, Cl, Br) can be obtained only by ab initio calculations. The data on the structure of complexes of some hydrides (mainly NH3 and rarely PH3 and H2S) have been obtained by microwave (MW) spectroscopy in molecular beams and in low-temperature matrices. The common disadvantage of both approaches lies in the nonequilibrium conditions of the study and hence the impossibility to study the thermodynamics of complex formation. It was also shown in ref 15 that, taking into account the weakness of the intermolecular interaction with participation of hydrides, IR spectroscopy of dilute solutions of proton donors (acceptors) in pure liquid hydrides is one of a few methods for the quantitative study of this interaction. The X
Abstract published in AdVance ACS Abstracts, March 1, 1996.
0022-3654/96/20100-6421$12.00/0
previous report considered the results of an IR spectroscopic study of the solutions of a hydroxyl-containing impurity (ethanol) in the liquid hydrides of the group IV-VI elements. It was shown that ethanol forms weak hydrogen-bonded complexes with PH3, AsH3, H2S, and H2Se, with ethanol acting as a proton donor. The aim of this paper is an IR spectroscopic study of molecular interactions of these hydrides with another hydroxylcontaining impurity (containing two OH groups): water in a two-component solution. The data obtained should us allow to expand our knowledge about the formation of weak H-bonded complexes in solutions. In addition, water is one of the most common impurities in these hydrides. Its interaction with molecules of the main component in the liquid phase during distillation of hydrides can substantially affect the efficiency of this purification method. Finally, it should be pointed out that due to the utmost importance of water for the environment, any additional information on the nature of molecular interactions with its participation is always of current interest. This is demonstrated by numerous studies of water complexes with various molecules by physical, including spectral, methods (see e.g. ref 16). As for the complexes of water with hydrides, the main data are given by ab initio calculations (complexes of NH3, CH4, and rarely those of PH3 and H2S17). The NH3‚‚‚H2O complex was studied in detail by MW spectroscopy in a molecular beam18 as well as by the another “nonequilibrium” method, i.e., IR spectroscopy of low-temperature matrices.19-21 In addition, there are two papers dealing with the formation of complexes of water with H2S in matrices.22,23 In all these cases water acts as a proton donor toward the hydride molecules. We were not aware of a single paper where the interaction of water with these hydrides under equilibrium conditions in the gas phase and in solution has been discussed. On the other hand, a relatively large number of studies are known related to water behavior in liquids. From the point of view of the investigation of the water-hydride interaction directly in the liquid phase of hydride, the results of these studies were of great interest to us. A review of the main results of the IR spectroscopic study of © 1996 American Chemical Society
6422 J. Phys. Chem., Vol. 100, No. 16, 1996
Sennikov et al.
solutions of water in organic solvents (bases of various strength) is given in refs 24-26. These data will be referred to while discussing our results. Experimental Section The main features of the present IR spectroscopic study of the solutions of hydroxyl-containing substances (ethanol, water) in the liquid hydrides, including the errors of determinaion of basic values, were discussed in the same section of the part 1 of this series.27 For convenience, some important relationships are given here. The integral absorption coefficient A (cm2 molecule-1 s-1) of the OH fundamental bands of water in solutions is calculated in general by the relation
A ) CVB/Nalx
(1)
where C is the speed of light (cm s-1), V is the molar volume of the solvent (cm3 mol-1), B is the integral intensity of a band (cm-1), Na is Avogadro’s number (mol-1) l is the length of the optical path (cm), and x is the concentration of the dissolved substance, give as a mole fraction. As has been already mentioned in the previous paper, the main problem in the application of (1) is related to the determination of concentration of the solutions prepared directly in a cell. In most cases the following procedure was used. The integral absorption coefficient of the bending band A(νb) of water in the liquid phase (solution) which is the least perturbed by intermolecular interactions can be found from
A(νb)sol )
(n2 + 2)2 A(νb)gas ) L(n) A(νb)gas 9n
(2)
where n is the refractive index of the liquid hydride and L(n) is the correction factor accounting for local radiation field changes in going from a low-density gas to a condensed medium. (For numerical values of n and L(n) see Table 1 of part 1). In the case of determination of the integral absorption coefficient A(νs) of the stretching band of water which is very sensitive to the intermolecular interaction, the relation of integral intensities B(νs)/B(νb) has been calculated for water solutions in all considered hydrides. At T ) 298 K it was equal to 3.2 ( 0.5 for solution in PH3, 2.0 ( 0.2 for solution in AsH3, 4.3 ( 0.2 for solution in H2S, and 2.8 ( 0.2 for solution in H2Se. Using the A(νb)sol value determined by eqs 2 and 1, the A(νs) was calculated. This procedure was tested on the solution of water in arsine where the value of A(νs) was found directly from relation 1. To this end, mixtures of water of known content with arsine were prepared. The concentration of water was determined electrochemically by blowing out wet arsine evaporated from the liquid phase in a transportation cylinder through a specially designed hygrometer. This mixture was loaded into a cell also by evaporation from the liquid phase in the cylinder. That provided an adequate comparison of the data obtained by electrochemical and spectral methods. It should be noted that the experimental conditions brought to a minimum the absorption of moisture on the walls of the pipe lines: their length was minimal, the system was carefully evacuated, and the procedure of loading-unloading was repeated many times. For determination of A(νs) of water, two solutions were taken with a content of moisture equal to (3.5 ( 0.2) × 10-5 and (1.3 ( 0.4) × 10-4. The mean value of A(νs), calculated by (1), was equal to (71 ( 4) × 10-8 cm2 molecule-1 s-1. Then using the above relation for solution in arsine, B(νs)/B(νb) ) 2.0 ( 0.2, the value A(νb) ) 35.5 × 10-8 cm2 molecule-1 s-1 was determined. Using (2), the corresponding value of A(νb) equal
to 32 × 10-8 cm2 molecule-1 s-1 was obtained. It should be pointed out that for water solution in AsH3 the direct determination of A(νb) according to (1) using the independently measured concentration of a solution could lead to a considerable error since the conditions of registration of the νb band of water in arsine are noticeably worse than those of the νb band (see Figure 3). Hence, relation 2 can be effectively used for the determination of the integral absorption coefficients of the bands which are perturbed to a lesser degree by the intermolecular interactions. To estimate the energy of molecular interaction ∆H between water and the hydride in a solution, the Iogansen relation from ref 27 was used: 1/2 ∆H ) -2.9[A1/2 bound(νs)/m - Afree(νs)]
(3)
where A1/2bound(νs) and A1/2free(νs) are integral absorption coefficients of the νs stretching band of water molecules participating or not in hydrogen bonding with hydride molecules; m is the number of hydrogen bonds which probably is equal to the maximum value m ) 2 in solution (for ethanol solution in the hydride m ) 1). Results and Discussion It was shown in the part 1 of this series27 that quantitative information on the intermolecular solute-solvent interaction could be obtained based on the IR spectra of dilute solutions of ethanol in the hydrides of group IV-VI elements. It followed from the analysis of spectra that the interaction ethanol-silane and ethanol-germane as well as ethanol-pentane and ethanolcarbon tetrachloride was of the van der Waals type, but the interaction in solutions of ethanol in liquid PH3, AsH3, H2S, and H2Se could be dscribed in terms of weak H bonding. The experimental IR study of water solutions in hydrides of group IV elements was preceded by ab initio calculations of complexes of water with silane and methane (6-31G basis set with electron correlation).28 First, a great difference in the structure of both complexes was clear. Only the CH4‚‚‚H2O complex demonstrated formation of an intermolecular H bond with the CH4 molecule acting as proton donor. The electronic interaction energy ∆E was founded to increase from -1.32 kcal mol-1 in complex CH4‚‚‚H2O to -2.42 kcal mol-1 in complex SiH4‚‚‚H2O. Perhaps, while going down by the group, i.e., from silane to germane, the value ∆E will somewhat increase its absolute value. However, it turned to be impossible to record the stretching band of water in the region 3600-1600 cm-1 in the spectra of water solutions in liquid silane and germane. The reasons for this are as follows. Among all the studied hydrides silane has the lowest critical temperature (Tc ) 269.4 K). This impedes the study of the IR spectra of water solutions at room temperature where the solubility of water is relatively high. Such study is possible for liquid germane where the solubility of water should be higher than in silane due to increase of the solutesolvent van der Waals interaction. However, with this hydride a strong interfering effect on the observation of the νs band of water is produced by the combination ν3 + 2ν4 band of germane itself in the region 3700 cm-1.29 Nevertheless, we tried to observe the spectra of water solution in germane and that of “dry” germane at 292 K in the layer of 0.5 cm that is the maximum path length available. The corresponding spectra are shown in Figure 1a. Figure 1b gives the difference between the mentioned spectra (curve 3). Despite a small value of absorbance, the obtained result can be interpreted at first glance as a spectrum of dissolved water with the most intensive
Water in Liquid Hydrides. 2
Figure 1. IR transmission and absorption spectra of water solution in the liquid germane in the stretching region at T ) 292 K and l ) 5 mm. (a) The transmission spectrum of “dry” germane (1) and of germane saturated with water (2). (b) The absorption spectrum (3) corresponding to the difference between spectra (2) and (1) and the absorption spectrum (4) corresponding to the difference between the spectra of “dry” germane (1) at 292 and 264 K.
component ν3 at 3700 cm-1. However, as is seen from Figure 1b (curve 4), the same result is obtained from the difference of spectra of “dry” germane at different temperatures. Probably, the band observed (curve 4) is an artifact caused by the subtraction of spectra in the region of strong self-absorption of the hydride. We believe that the solubility of water in germane is lower than the detection limit of the IR spectrometer, i.e., xsolute ∼ 3 × 10-4 at 292 K. As it is seen from Figures 2-5, the water fundamentals can be recorded in the spectra of water solutions in the liquid hydrides of group V and VI elements of the second and third periods despite considerable self-absorption of hydrides between 3600 and 1600 cm-1 (see insertions in the figures) at the given optical thicknesses and despite a relatively low solubility of water, even at T ∼ 290 K. Table 1 gives spectral parameters for the νs and νb bands of water dissolved in the hydrides as compared with the gas phase and with a solution of the inert conventional organic solvent (CCl4). As can be seen from these data, the stretching νs band of water (resolved on high- and low-frequency components corresponding to asymmetric and symmetric vibrations in the gas phase) shifts during transition from the gas phase or CCl4 solution to solution in liquid hydride with simultaneous broadening and increase of the integral absorption coefficient A(νs). It is worth noting that in all cases the A(νs) value in solution exceeds the A(νb) value although the reverse situation is observed in the gas phase. The bending band actually does not change its position compared to the gas phase and from one hydride to another. All these features give an indication of the formation of H bonds O-H‚‚‚B, where B is the central atom of the hydride molecule having a lone electron pair. During dissolving water in solvents of HB type containing proton-donor and proton-acceptor groups, formation of different complexes is possible that in general have distinct absorption
J. Phys. Chem., Vol. 100, No. 16, 1996 6423
Figure 2. IR absorption spectrum of water dissolved in the liquid phosphine in the stretching (a) and bending (b) regions. xsolute ) 1.5 × 10-4, l ) 50 mm, and T ) 292 K. The insertions give the transmission spectra of the pure liquid phosphine in the corresponding spectral region.
spectra. For example,
HOH‚‚‚BH (I)
HB‚‚‚HOH...BH (II)
H2O‚‚‚HB (III)
HB‚‚‚H2O‚‚‚HB (IV)
(HB)2‚‚‚H2O‚‚‚HB (V)
H2O‚‚‚(HB)2 (VI), etc.
Due to the distinctive feature of the problem considered (study of dilute solutions of water in hydrides and not vice versa), it is, perhaps, possible to study experimentally only the species containing the OH‚‚‚B bond. It can be an asymmetric 1:1 (I) or a symmetric 1:2 (II) complex (V is its variant). In addition, the solution may contain free molecules of water HOH and its dimers (HOH)2 , each with distinct spectra. Luck31 and Burneau26 carried out a detailed analysis of the variation of the spectral features of water fundamentals during transition from dilute solutions of water and organic bases of different strength in CCl4 to two-component solutions of water in these bases. The latter solutions can be considered as a model with respect to the present solutions of water in liquid hydrides, at approximately the same temperature (∼290 K). An analysis of the νs band shape in Figures 2-5, as well as of the position and intensity of its high- and low-frequency components using data from refs 26 and 31 as well as ref 32, where the possibility of formation of water dimers in CCl4 solutions has been considered, leads to the conclusion that the bonding of water molecules with the surrounding molecules of the hydrides preferentially involved both OH groups (species II or V). The fact that with a temperature decrease both components of the νs band shifted to low-frequency symmetrically with respect to each other indicates according to refs 26 and 31 the preferential formation of the 1:2 complex at low temperatures as well. The content of 1:1 complexes and of “free” molecules of water as
6424 J. Phys. Chem., Vol. 100, No. 16, 1996
Figure 3. IR absorption spectrum of water dissolved in the liquid arsine in the stretching (a) and bending (b) regions. xsolute ) 2 × 10-4, l ) 10 mm, and T ) 298 K. The insertions give the transmission spectra of the pure liquid arsine in the corresponding spectral region.
Figure 4. Absorption spectrum of water dissolved in the liquid hydrogen sulfide in the stretching (a) and bending (b) regions. xsolute ) 7 × 10-3, l ) 0.87 mm, and T ) 293 K. The insertions give the transmission spectra of the pure liquid hydrogen sulfide in the corresponding spectral region.
well as its dimers is less than 10% and 2%, respectively, according to our estimates. Using relation 3, it is possible to estimate the energy of
Sennikov et al.
Figure 5. IR absorption spectrum of water dissolved in the liquid hydrogen selenide in the stretching (a) and bending (b) regions. xsolute ) 2 × 10-3, l ) 0.87 mm, and T ) 293 K. The insertions give the transmission spectra of the pure liquid hydrogen selenide in the corresponding spectral region.
hydrogen bonding ∆H between water and the hydrides in the liquid phase. As earlier in the case with determination of ∆H for ethanol-water complexes (part 1 of this series27), it is reasonable to use as Afree(νs) the A(νs) value in the gas phase corrected for vibrational transition changes going from a lowdensity gas to a liquid according to (2). The value of Abound(νs) was taken to be equal to the experimental value of A(νs) in the liquid (Table 1). Assuming in this case in (3) that m ) 2, we can estimate the lower limit of the enthalpy of intermolecular interaction (Table 2). Actually, the experimental value of A(νs) represents a sum of A values related to various species I-VI, free H2O molecules, dimers, etc. (i.e., a sum of Afree and Abound). Since an independent estimation of the Abound value was impossible, it was assumed that the estimation of the upper limit of the hydrogen bond energy will be represented by the value obtained according to (3) assuming the formation of only one water-hydrided hydrogen bond, i.e., at m ) 1 (Table 2). It is seen that the strength of the complexes of hydrides of group VI elements with water is somewhat higher than that of the complexes of hydrides of the group V elements. The strength of complexes of hydrides of the elements belonging to the fourth period is slightly less than that of complexes of hydrides of the third period. The data obtained correspond in general with the results of ab initio calculations of the complexes of the hydrides35,36 as well as with their experimental study by microwave spectroscopy in molecular beams (only PH3, H2S)10 and IR spectroscopy in low-temperature Ar matrices33,34 with the strong proton donor HF. The latter data are also given in Table 2. There is a discrepancy between the relative strength of complexes of PH3 and H2S with constant proton-donor obtained by both methods. Our results, which involve equilibrium conditions in solution, as well as the results of MW spectroscopy indicate that H2S is a better proton acceptor toward
Water in Liquid Hydrides. 2
J. Phys. Chem., Vol. 100, No. 16, 1996 6425
TABLE 1: Spectral Parameters of Stretching and Bending Vibrational Bands of Water in the Gas Phase, in the Solutions of CCl4, and in the Liquid Hydrides at 298 K (ν, cm-1; A, cm2 molecule-1 s-1) solvent
ν1
∆ν1/2a
ν3
∆ν1/2
gas30
3657 3616 3606 3610 3560 3555
35 60 ∼75 ∼80 ∼80
3756 3707 3696 3698 3645 3643
45 160 120 110 105
CCl4 PH3 AsH3 H2S H2Se a
∆ν1/2
ν1 - ν3
A(νs) × 108
ν2
22.8 30 84 71 203 168
1596
160 170 ∼150 ∼150
99 92 90 88 85 88
1598 1600 1606 1600
∆ν1/2
A(νb) × 108 25.2
∼55 ∼50 42 45
28 35.5 32 33
Half-width of the corresponding band.
TABLE 2: Energy Characteristics of the Hydride-Water Complexes (∆ν, cm-1; ∆H, kcal mol-1) complex
∆ν3a
-∆H298b
HOH‚‚‚NH3 HOH‚‚‚PH3 HOH‚‚‚AsH3 HOH‚‚‚SH2 HOH‚‚‚SeH2
60 58 111 113
0.4-1.6 0.2-1.2 1.2-2.5 1.0-2.4
-∆Hcalcc
∆νsd
4.7 0.8
913 327 260 302 299
1.3
a ∆ν ) ν gas - ν sol is the difference in frequencies of stretching 3 3 3 vibrations ν3 of water in the gas phase and in the complex in the solution. b The interval of enthalpy of complex formation determined by the Iogansen equation (3) at m ) 1 and m ) 2, respectively. c Calculated values for enthalpy of hydrogen bonds.17 d ∆ν ) ν f(HF) s s - νsb(HF) is the difference between frequencies of stretching vibrations of the molecule HF in the free state and in the complex in Ar matrix.33,34
TABLE 3: Spectral Parameters (cm-1) of the Fundamentals of Water Dissolved in Various Solvents (Ref 25 for Organic Bases) and Gutman Donor Numbers (DN)37 bases
ν1
ν3
ν2
ν3 - ν1
gas trichlorotrifluoro ethane carbon tetrachloride tetrachloroethylene carbon disulfide phosphine arsine chloroform toluene p-xylene mesitylene nitromethane anisole epichlorohydrin benzonitrile hydrogen selenide hydrogen sulfide benzaldehyde acetonitrile cyclohexanone acetophenone diethyl ether dioxan dimethyl sulfoxide pyridine
3657 3628 3613 3613 3610 3606 3610 3607 3595 3592 3590 3579 3548 3542 3545 3555 3560 3544 3543 3530 3535 3518 3517 3444 3405
3756 3721 3705 3705 3701 3696 3698 3690 3681 3680 3677 3663 3662 3653 3650 3693 3645 3639 3636 3610 3612 3590 3584 3494 3450
1595
99 93 92 92 91 90 88 83 86 88 87 84 114 111 105 88 85 95 93 80 77 72 67 50 45
1598 1600
1623 1621 1600 1606 1632 1628 1639 1663
DN
0 2 4 4 5 10 6 9 13.9 11 16 14 18 15 19.2 14.8 29 33
the constant proton donor as compared with PH3. The IR matrix data demonstrate the reverse relationship. Comparing the results of the estimation of the strength of hydride-water and hydride-ethanol complexes according to (3) at m ) 1 (part 1 of this series27), it can be seen that ethanol is a substantially weaker proton donor as compared with water. This should be expected after replacement of one atom of hydrogen by the electron-donating ethyl group. It is also shown by our ab initio calculations of the electron energy ∆E of the complexes HOH‚‚‚SH2 (∆E ) -2.85 kcal mol-1) and CH3OH‚‚‚SH2 (∆E ) -2.0 kcal mol-1). A review article25 summarizes the main spectral parameters of water dissolved in various organic solvents. These data in
part are given in Table 3. It can be seen that with an increase of proton-acceptor ability of the solvent molecules (the basicity) that is characterized by the donor number according to Gutman,37 the low-frequency shift of the symmetric and asymmetric stretching bands of water takes place with simultaneous decrease of the frequency separation between them. The liquid hydrides studied by us do not differ in principle from these nonaqueous solvents in case we do not account for their additional protondonor ability that we do not consider in the present paper. Considering the data given in Tables 1 and 3, phosphine and arsine should be positioned between carbon disulfide and chloroform which corresponds to the interval DN ) 0-4; hydrogen sulfide and hydrogen selenide should occupy the place between benzonitrile and benzaldehyde and be characterized by DN ) 13-16. Conclusions The IR spectroscopic study of water solutions in the liquid hydrides of group V and VI elements at various temperatures and concentrations has permitted an estimate of the nature of intermolecular interaction between the solute (water) and the solvent (hydride). Similar to solutions in conventional organic solvents, 1:2 complexes of water with hydrides have been identified in the liquid phase. The energy of water-hydride intermolecular interaction increases in the series AsH3 < PH3 < H2Se < H2S. Acknowledgment. We are grateful to Prof. V. M. Vorotyntsev and Dr. V. V. Balabanov for supplying the ultrapure hydrides. References and Notes (1) Pimentel, G. C.; McClellan, A. L. The Hydrogen Bond; Freeman: San Francisco, 1960. (2) The Hydrogen Bond. Recent AdVances in Theory and Experiment; Schuster, P., Zundel, G., Sandorfy, C., Eds.; North-Holland: Amsterdam, 1976; Vols. 1-3. (3) Joesten, M. D.; Schaad, L. J. Hydrogen Bonding; Dekker: New York, 1974. (4) Mulliken, R. S.; Person, W. B. Molecular Complexes: a Lecture and Reprint Volume; Wiley: New York, 1969. (5) Foster, R. Organic Charge-Transfer Complexes; Academic Press: New York, 1969. (6) Hobza, P.; Zahradnik, R. Intermolecular Complexes (The Role of Van der Waals Systems in Physical Chemistry and in Biodisciplines); Elsevier: Amsterdam, 1988. (7) Dyke, T. R. Top. Curr. Chem. 1984, 120, 85. (8) Dyke, T. R., Muenter, J. S. In International ReView of Science: Physical Chemistry Series Two; Buckingham, A. D., Ed.; Butterworths: London, 1975; Vol. 2. (9) Peterson, H. J.; Fraser, G. T.; Nelson, D. D.; Klemperer, W. in: Comparison of ab initio Quantum Chemistry with Experiment for Small Molecules. State of the Art; Barlett, R. J., Ed.; Reidel Publishing: Dordrecht, 1985. (10) Legon, A. C.; Millen, D. J. J. Am. Chem. Soc. 1987, 109, 356. (11) Hallam, H. E. In The Hydrogen Bond. Recent AdVances in Theory and Experiment; Schuster, P., Zundel, G., Sandorfy, C., Eds.; NorthHolland: Amsterdam, 1976; Vol. 3. (12) Andrews, L. Annu. ReV. Phys. Chem. 1971, 22, 109. (13) Barnes, A. J. In Molecular Interactions; Ratajczak, H., OrvilleThomas, W. J., Eds.; Wiley: New York, 1980.
6426 J. Phys. Chem., Vol. 100, No. 16, 1996 (14) Tokhadze, K. G., Tkhorzhevskaya, N. A. J. Mol. Struct. 1992, 270, 351. (15) Sennikov, P. G. J. Phys. Chem. 1994, 98, 4973. (16) Devjatykh, G. G.; Sennikov, P. G. High-Purity Subst. 1990, 4, 401. (17) Del Bene, J. E. J. Phys. Chem. 1988, 92, 2874. (18) Herbine, P.; Dyke, T. R. J. Chem. Phys. 1985, 83, 3768. (19) Aboauf-Marguin, L.; Jacox, M. E.; Milligan, D. E. J. Mol. Spectrosc. 1977, 76, 34. (20) Engdahl, A.; Nelander, B. J. Chem. Phys. 1989, 91, 6604. (21) Nelander, B.; Nord, L. J. Phys. Chem. 1982, 86, 4375. (22) Nelander, B. J. Chem. Phys. 1978, 69, 3870. (23) Barnes, A. J.; Bentwood, R. M.; Wright, M. P. J. Mol. Struct. 1984, 118, 97. (24) Luck, W. A. P. Pure Appl. Chem. 1987, 59, 1215. (25) Scherer, J. R. AdV. Infrared Raman Spectrosc. 1978, 5, 149. (26) Burneau, A. J. Mol. Liq. 1990, 46, 99. (27) Sennikov, P. G.; Shkrunin, V. E.; Raldugin, D. A.; Tokhadze, K. G. J. Phys. Chem. 1996, 100, 6415.
Sennikov et al. (28) Sennikov, P. G.; Sharibjanov, R. J.; Khoudoinazarov, K. J. Mol. Struct. 1992, 270, 87. (29) Sennikov, P. G.; Shkrunin, V. E.; Melikova, S. M.; Lebedeva, Ju.A. High-Purity Subst. 1992, 6, 229. (30) Pugh, L. A.; Rao, K. N. In Molecular Spectroscopy. Modern Research.; Rao, K. N., Eds.; Academic Press: New York, 1976; Vol. 2. (31) Luck, W. A. P.; Schioberg, D. AdV. Mol. Relax. Interact. Processes. 1979, 14, 277. (32) Magnusson, L. B. J. Phys. Chem. 1970, 74, 4221. (33) Arlinghaus, R. T,; Andrews, L. J. Chem. Phys. 1984, 81, 4341. (34) Arlinghaus, R. T.; Andrews, L. Inorg. Chem. 1987, 24, 1523. (35) Hinchliffe, A. J. J. Mol. Struct. (THEOCHEM) 1985, 121, 201. (36) Hinchliffe, A. J. J. Mol. Struct. (THEOCHEM) 1984, 107, 361. (37) Marcus, J. J. Solution Chem. 1984, 13, 599.
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