Structural and photomagnetic studies of a 1-D bimetallic chain [MnII2(L)2(H2O)][MoIV(CN)8]·5H2O (L = macrocycle): analogy with the photo-oxidation of K4[MoIV(CN)8]·2H2O

Abstract

A one-dimensional chain [MnII2(L)2(H2O)][MoIV(CN)8]·5H2O 2 (L = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, macrocyclic ligand) has been prepared from the reaction of K4[MoIV(CN)8]·2H2O 1 with the complex [MnIIL(H2O)2]Cl2·4H2O and its structure and photomagnetic properties have been studied. The structure of 2 consists of a polymeric zigzag chain of alternating Mn(L) and Mo(CN)8 units with another Mn(L) unit linked to the Mo as a pendant arm. The paramagnetic compound 2 shows important modifications of its magnetic properties under UV-light irradiation, leading to the formation of ferrimagnetic chains. This non-reversible photomagnetic effect is thought to be caused by an internal photo-oxidation of MoIV (diamagnetic) to MoV (paramagnetic) as observed in the precursor 1. The crystallographic data seem to indicate that the formation of hydrogen bonds between water molecules and nitrogen atoms of non-bridging cyano groups is a key factor to observe the molybdenum photo-oxidation.