Photoinduced Magnetization on Mo Ion in Copper Octacyanomolybdate: An X-ray Magnetic Circular Dichroism Investigation

Recently synthesized copper octacyanomolybdate molecules present interesting photomagnetic properties. Before irradiation, the molecules behave as noncoupled CuII paramagnetic ions (with central diamagnetic MoIV ion), whereas after irradiation (406 nm) they behave as superparamagnetic molecules with CuII ions coupled to the molybdenum ion. The proposed mechanism to explain these photomagnetic properties is based on the photoinduced charge transfer from MoIV (S = 0) to CuII (S = 1/2) leading to the formation of MoV (S = 1/2) and CuI (S = 0) with strong ferromagnetic coupling between MoV and the other CuII spin carriers. This paper presents X-ray magnetic circular dichroism (XMCD) measurements at the molybdenum L2,3 edges. Two bimetallic molecules have been investigated: [Mo(CN)2(CN-CuL)6]8+, L being tris(2-amino)ethylamine and [Mo(CN)6(CN-CuL′2)2], with L′ being N,N′,dimethyl ethylene diamine (labeled MoCu2-Meen). In both cases, before irradiation the XMCD signal is null as expected for diamagnetic MoIV (S...