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 [Mn^II₂(L)₂(H₂O)][Mo^IV(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[Mo^IV(CN)₈]·2H₂O 1 with the complex [Mn^IIL(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 Mo^IV (diamagnetic) to Mo^V (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.