First example of photomagnetic effects in ionic pairs [Ni(bipy)3]2[Mo(CN)8] · 12H2O

Ionic triads formed by [NiII(bipy)3]2+ (bipy = 2,2′-bipyridyl) and diamagnetic [MIV(CN)8]4− (M = Mo and W) were prepared and structurally characterized. The two compounds are isostructural and their structure consists of a three-dimensional hydrogen-bonded framework where cation–anion interactions occur through short contacts M–CN⋯H–C(bipy). Before irradiation, the Mo analogue behaves as paramagnet with small intermolecular interactions between the [NiII(bipy)3]2+ cations. Upon irradiation with visible light, it exhibits a reversible photomagnetic effect, which is interpreted in terms of the formation of paramagnetic [MoV(CN)8]3− and [NiII(bipy)2(bipy−)]+ due to the outer-sphere electron transfer.