Structural and photomagnetic studies of two compounds in the system Cu2+/Mo(CN)84-:: From trinuclear molecule to infinite network

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 M-2(II)[Mo-IV(CN)(8)]. xH(2)O (2 with M = Cu, x = 7.5; 3 with M = Mn, x = 9.5) are presented. 1 crystallizes in the triclinic space group P (1) over bar (a = 11.3006(4) Angstrom, b = 12.0886(5) Angstrom, c = 22.9589(9) Angstrom, alpha = 81.799(2)0, beta = 79.787(2)degrees gamma = 62.873(2)degrees, 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 Fe(II)2(H2O)(4)[Mo-IV(CN)(8)]. 4H(2)O whose X-ray structure has been previously solved. 2, 3, and Fe(II)2(H2O)(4)[Mo-IV(CN)(8)]. 4H(2)O 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 Mo-IV (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.