Determination of the polarization direction of the UV bands of chromophore molecules by use of cyclodextrins

Abstract

Abstract Cyclodextrins (CDxs) were utilized to determine the polarization direction in the UV bands of aromatic compounds. By choosing CDxs of suitable size for an axial inclusion Axial inclusion is the inclusion in which the long‐axis of arenes is parallel to the axis of the CDxs' cavity. , the induced circular dichroism (ICD) bands of the included chromophore molecules are well resolved. Thus, except for the bands which consist of two or more perpendicularly polarized transitions with quite a different oscillator strength, the polarization direction is simply determined from the sign of ICD spectra: a plus sign is produced by transitions polarized parallel to the long‐axis while a negative sign by those polarized along the short‐axis. Besides being simple, this method is applicable to bands as short as 195 nm, since water is used as solvent. Thus, several UV bands of some compounds were recorded for the first time and even their polarization directions were determined. Merit and limitation of this method are discussed and compared with other methods.