An application of the advanced high-accuracy universal polarimeter to the chiroptical measurement of an intercalated compound K4Nb6O17 with high anisotropy

Abstract

The advanced high-accuracy universal polarimeter (HAUP) method was applied to observe anisotropic and chiroptical properties of an intercalated azobenzene derivative compound into K4Nb6O17 crystals. Prior to the HAUP measurement of the intercalated compound, we extended the HAUP method employing a conventional light source system composed of Xe or D2 lamps and a monochromator instead of a laser system. The performance of the advanced HAUP system was evaluated and we determined the parasitic ellipticities of the cross polarizers, which are essential for obtaining accurate values. The optical system was applicable to simultaneously measure the linear dichroism (LD), circular dichroism (CD), linear birefringence (LB) and circular birefringence (CB) spectra of an intercalated compound in the ultraviolet and visible regions. We found the Kramers–Kronig relation between CB and CD as well as in the case of LB and LD. Changes in LB and LD signals as obtained from HAUP measurements originated from the molecular orientation of guest molecules by the intercalation. Moreover, CB and CD signals indicated the appearance of induced chirality in the intercalated azobenzene derivative compound. These results demonstrated the usefulness of the HAUP system for evaluating the molecular conformation of chiral anisotropic specimens.