Ionic triads formed by [NiII(bipy)3]2+ (bipy = 2,20-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