VIBRATIONAL SPECTRUM AND THERMOCHROMISM OF $VOCl_{3}$

Abstract

The infrared spectrum of $VOC1_{3}$ has been measured for the first time, covering the range 300-$3000 cm^{-1}$. The Raman spectrum has been obtained with qualitative depolarizations. The interpretation of the spectrum (using $C_{3{v}}$ symmetry) is straightforward. Species $a_{1}$ fundamentals are at 1035 (V=O stretch), 408, and $165 cm^{-1}$; those of species \underline{e} are 504, 249, and $129 cm^{-1}$. $VOCI_{3}$ provides a striking and unique example of thermochromism. At room temperature it is a pale yellow liquid, whereas it becomes cherry red on cooling. This is unique in two respects: a) it occurs in the pure liquid, and b) the color deepens on cooling. To find an explanation, the visible and ultraviolet absorption have been measured at several temperatures. The results will be discussed.