Liquid Crystal — Linear Dichroism Stereochemical Applications of Electronic State Assignments

Abstract

A very introductory and tutorial survey of the liquid crystal — linear dichroism (l.c.—l.d.) technique is presented. Liquid crystalline orienting solvents suitable for l.d. spectra of electronic transitions of guest molecules, i.e. transparent to UV-Visible light, macroscopically orientable and able to dissolve both lipo-and hydro-philic guest molecules can be found. Methods of achieving an oriented solution, of recording the l.d. by a modulated technique and of interpreting the data are outlined. Several emblematic applications to stereochemical problems of electronic state assignments, achieved by the l.c.-l.d. technique, are also presented.

Liquid crystalline solvents provide very effective ways of imparting to an organic or inorganic molecule the partial orientation required to run its l.d. spectrum. The very sensitive modulated l.d. recording technique is most suitable for partially oriented liquid crystalline samples. The label liquid crystal — linear dichroism (I.e. — l.d.) has therefore been associated since the very beginning with the Joint set-up and use of liquid crystalline solvents and l.d. modulated techniques

The purpose of this paper is to introduce our instrumental and interpretative approach to people unfamiliar with the l.d. technique