Solvent mediated reversible solid state photochromism of {Mo72Fe30} Keplerate

Abstract

When the yellow rhombohedral crystals of Keplerate [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁]·150H₂O (1), on wetting with N,N-dimethylformamide (DMF), are irradiated with sunlight, a remarkable reversible solid state photochromic behaviour is achieved with the formation of green coloured crystals (1_red). The reduction of the {Mo^VI} centres to {Mo^V} is responsible for the observed colour change from yellow to dark green. Importantly, compound 1 can be activated towards photochromism only in the presence of the DMF solvent. The photochromic phenomenon displayed by Keplerate compound 1 is a classic example of sunlight activated solvent driven photoactivity.