INTERMOLECULAR INTERACTIONS OF DIMETHYLDICHLOROSILANE WITH DIFFERENT SOLVENTS STUDIED BY IR SPECTROSCOPY

Rodica Grecu1, I. Bratu2, T. Iliescu3, O. Cozar3

1 “Raluca Ripan” Institute for Research in Chemistry, 30 Fantanele Street, RO-400294, Cluj-Napoca;
2 National Institute for Research and Devewlopment of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca:
3 Physics Department, “Babes-Bolyai” University, RO-400084 Cluj-Napoca

	The parameters of a vibrational band (band position, halfbandwidth, intensity) are sensitive to the environment created by solvents. Studies on the solvent dependence of these parameters can provide information on the intermolecular interactions between the solute and solvent molecules.
We paid attention to asymSiCl2 and symSiCl2 vibrational bands of dimethyldichlorosilane observed at 530.3 cm-1 and 464.8 cm-1 in the IR spectrum of neat liquid. Excepting the 1,4-dioxane solvent, the frequency shift of these bands is in a direct relation with the dielectric constant of the solvents. A linear dependence of the frequency shift for both studied bands on the dielectric function f(ε) = (ε – 1)/(2ε + 1) and the empirical solvatochromic parameters W [1] and * [2, 3] was observed, evidencing non-specific long-range dipolar interactions between the molecule of dimethyldichlorosilane and the studied solvents. 
The effect of CCl4/CH3CN solvent mixtures was the decreasing of the frequency of the band maximum in proportion as the acetonitrile mole fraction increases. The difference between the frequency of asymSiCl2 and symSiCl2 vibrational bands also decreases indicating the reduction of the vibrational coupling of these vibrational modes in mixtures of higher polarity. The process of dielectric local enrichment (with a value of the preferential solving index of 0.69-0.80) and the formation of some collision complexes could explain the effect of carbon tetrachloride/acetonitrile mixtures on the SiCl2 vibrational bands parameters.

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