Electronic state and photosensitivity of metal alkoxides chemically modified with β-diketones

Electronic state and optical absorption spectra of metal alkoxides stabilized with β-diketones, which had various substituents, were calculated by the first principle molecular orbital methods. The characteristics of the optical absorption and the mechanism of the photodissociation of alkoxides with irradiation of light were discussed. The position of the first peak observed near UV region in the theoretical optical absorption spectra corresponded to that in the experimental ones with about 25 nm shift toward the shorter wavelength. The first absorption peak observed in the visible range was originated from the electron transitions to molecular orbitals including the antibonding components of the C-O bonding in the chelate ring. The results suggested that the bonding nature of chelate rings should be important to understand the photosensitivity of the chemically modified titanium alkoxides