Solvent mediated reversible solid state photochromism of {Mo72Fe30} Keplerate

When the yellow rhombohedral crystals of Keplerate [Mo72Fe30O252(CH3COO)(12){Mo2O7(H2O)}(2){H2Mo2O8(H2O)}(H2O)(91)]center dot 150H(2)O (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.

Automated summary

This passage describes the remarkable reversible solid state photochromic behavior of Keplerate compound 1 when wetted with N,N-dimethylformamide (DMF) and irradiated with sunlight, resulting in a color change from yellow to dark green. It also highlights that the photochromic phenomenon can only be activated in the presence of the DMF solvent.