Polarized light-induced orientation of chiral schiff base Ni(II) and Zn(II) complexes having substituted azobenzene moiety

In this chapter, new chiral Schiff base metal Ni(II) and Zn(II) complexes containing azobenzene moiety in ligands were synthesized, in which substituents (H and Cl) at the ortho position of azobenzene were introduced for wavelength selective molecular orientation by light irradiation. By irradiation of linearly and circularly polarized UV light, a direct effect to the molecular orientation changes in polymethyl methacrylate (PMMA) films is expected by the isomerization behavior of the azobenzene moiety. The anisortropic orientation induced by linearly polarized UV light was investigated with polarized spectroscopic method as well as wide angle X-ray scattering (WAXS). Furthermore, we also detected the molecular orientation changes by circularly polarized UV light with CD spectra measured from various orientation. Similar to many previous studies, the introduction of electron withdrawing groups at the ortho position of azobenzene affects the isomerization wavelength and the stability of trans-form of azobenzene relatively. Molerular alignment in crystals of the complexes and chiral crystallization was discussed by comparison with polarized light-induced one in a softmater (PMMA) matrix.