Tunable Photochromism of Spirooxazines via Metal Coordination

Through the incorporation of a phenanthroline ligand into the oxazine moiety of photochromic spirooxazines, a series of photochromic spirooxazine-phenanthroline metal complexes have been synthesized, resulting in tunable and significantly increased photoresponsivities. Such systems are of interest for the investigation of multifunctional photochromic materials. These novel metal complexes retain their photochromic activity in the complexed state, leading to ligand binding in both the spirooxazine and the photomerocyanine forms during the photoconversion. A significant stabilization of the photomerocyanine form results from metal complexation, as indicated by the shift in thermal equilibrium values (KT = 0.06) upon metal complexation (KT = 0.6-1.2). Photoconversion occurs with first-order kinetics, suggesting the absence of an intermediate state. A third photostationary state is observed in these systems induced by visible irradiation of the thermal equilibrium state, leading to a three-state system. This new class of compounds provides the opportunity to investigate the synergy between changes in electronic structure associated with photoisomerization, and metal-centered functionality.