Structural and Photomagnetic Studies of Two Compounds in the System Cu2+/Mo(CN)84-: From Trinuclear Molecule to Infinite Network

Abstract
The syntheses and structural and physical characterization of the compounds [Cu(bipy)2]2[Mo(CN)8]·5H2O· CH3OH (1) with bipy = 2,2‘-bipyridine and MII2[MoIV(CN)8xH2O (2 with M = Cu, x = 7.5; 3 with M = Mn, x = 9.5) are presented. 1 crystallizes in the triclinic space group P1̄ (a = 11.3006(4) Å, b = 12.0886(5) Å, c = 22.9589(9) Å, α = 81.799(2)°, β = 79.787(2)°, γ = 62.873(2)°, Z = 2). The structure of 1 consists of neutral trinuclear molecules in which a central [Mo(CN)8]4- anion is linked to two [Cu(bipy)2]2+ cations through two cyanide bridges. 2 crystallizes poorly, and hence, structural information has been obtained from the wide-angle X-ray scattering (WAXS) technique, by comparison with 3 and FeII2(H2O)4[MoIV(CN)8]·4H2O whose X-ray structure has been previously solved. 2, 3, and FeII2(H2O)4[MoIV(CN)8]·4H2O form extended networks with all the cyano groups acting as bridges. The magnetic properties have shown that 1 and 2 behave as paramagnets. Under irradiation with light, they exhibit important modifications of their magnetic properties, with the appearance at low temperature of magnetic interactions. For 1 the modifications are irreversible, whereas they are reversible for 2 after cycling in temperature. These photomagnetic effects are thought to be caused by the conversion of MoIV (diamagnetic) to MoV(paramagnetic) through a photooxidation mechanism for 1 and a photoinduced electron transfer in 2. These results have been correlated with the structural features.

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