Molecular photochromic systems: a theoretical and experimental investigation on zinc(II) dithizonate

Zinc(II)-dithizone based molecular systems [Zn(HDz)2] are intriguing candidates for the development of optical devices thanks to their interesting photochromic and nonlinear optical properties. In the present work, the behavior of Zn(HDz)2 in different solvents was investigated by a combined theoretical and experimental approach. In particular, solutions of both dithizone (H2Dz) and Zn(HDz)2 were analyzed by optical absorption spectroscopy and nuclear magnetic resonance (NMR) techniques, with particular attention to structure-properties relationships. Density functional and time-dependent density functional calculations were performed on the stable and the activated forms of the complex, obtaining information on the energetics of their interconversion, as well as on the nature of their electronic excitations.