| Abstract
| - The magnetic and photomagnetic properties of two cyano-bridged, [Mn(bpy)2]4[Mo(CN)8]2·14H2O (1)and [Mn(bpy)2]4[W(CN)8]2·9H2O (2) (bpy = 2,2‘-bipyridyl), hexanuclear clusters (hereafter namedMnII4MIV2) have been investigated. Before irradiation both compounds behave as paramagnets in almostthe whole temperature range due to the presence of magnetic MnII centers separated by the diamagneticMIV spacers in the molecules. After several hours of irradiation (337−356, 406−415, and 480 nm) in asuperconducting quantum interference device at 10 K, the magnetic signal at 10 K has increased by afactor of almost 30% compared to that of the initial magnetic state. The magnetic characterization of theirradiated samples indicates the formation of a photoproduct exhibiting antiferromagnetic interactions.The X-ray photoelectron spectroscopy (XPS) data of the irradiated samples show the presence of MnII,MnI, MIV, and MV centers. The formation of MnI and MV centers is interpreted in terms of the reductivequenching of the excited state through an intramolecular electron-transfer mechanism in the MnII4MIV2clusters. After irradiation at room temperature in the presence of air, both compounds behave as aparamagnet, but with a lower magnetic response than that of the initial state. The XPS data show thepresence of MIV, MVI, and only MnII centers. The photochemical pathway in the presence of O2 is discussedin relation to the ligand-field photochemistry of octacyanometalates(IV), leading ultimately to the formationof [MVI(CN)4(O2)] and low-spin [MnII(bpy)2(CN)2] species in the solid state.
- MnII4MIV2 clusters exhibit photomagnetic properties dependent on the experimental conditions. Irradiation at 10 K leads to the formation of MV and MnI due to the intramolecular reductive electron-transfer process. Irradiation in ambient conditions leads to the formation of [MVI(CN)4(O2)] and low-spin [MnII(bipy)2(CN)2] associated with the photodissociation of Mo−CN bonds in Mo−CN−Mn linkages.
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