Kopelman, R. A.; Paquette, M. M.; Frank, N. L. Photoprocesses and magnetic behavior of photochromic transition metal indoline[phenanthrolinospirooxazine] complexes: Tunable photochromic materials. Inorg. Chim. Acta 2008 361, (12-13) Special Issue-SI, 3570-3576. Invited Submission in Honor of Dante Gatteschi, (SEP 1 2008). DOI: 10.1016/j.ica.2008.03.079
Metal complexation of photochromic ligands provides a powerful strategy for modulating the electronic structure of both transition metals and their respective photochromic ligands. The effect of transition metal complexation on spirooxazine-phenanthroline ligands is investigated through the preparation and spectroscopic investigation of a series of M(IPSO)(3)(BPh(4))(2) complexes consisting of first row transition metals and IPSO = spiro[indole-phenanthrolinoxazine: (M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), and Cu(II)). The optical properties associated with photochromic behavior were evaluated by determination of the(i) equilibrium constants (K) for the thermal and photostationary states, (ii) rates of photochemical ring-opening and ring-closure, and (iii) rates of thermal ring-closure. The photoresponsivities of bound photochromes associated with conversion from the colorless spirooxazine to the colored photomerocyanine isomer are greatly enhanced upon metal coordination. Variable temperature magnetic susceptibility experiments suggest deviations from cubic symmetry associated with desymmetrization induced by a dependence of ligand field strength on the photochromic state of the photochrome.