Light-induced control of textures and cholesteric pitch in liquid crystals containing chromium complexes, by means of circular and linear polarized light

A nematic liquid crystal doped with a chiral dopant has a cholesteric texture with a regular pitch. The pitch is changed by variation of concentration of the dopant. We observed the appearance of a fingerprint texture on irradiation of a homeotropic mixed liquid crystal doped with a racemic chromium complex, Cr(Buacac)3, and an auxiliary chiral dopant, with right-circular polarized light (r-CPL); the fingerprint texture disappeared on irradiation with left-circular polarized light (l-CPL). We also measured a helical twisting power, βm, of the chromium complex from the cholesteric pitch of the mixed liquid crystal doped with optically resolved Λ -(Cr(Buacac)3; and clarified the relationship between the change in the cholesteric pitch and the quantum yield of the photoinversion reaction.