Effects of secondary ligand and excitation on the thermally induced and photoinduced valence tautomerism semiquinonate – catecholate

Twelve mixed cobalt dioxolene complexes with various amines or pyridyl secondary ligands were prepared and characterized, two of which exhibit thermal valence tautomeric phase transitions. When these two complexes are excited in situ with a nanosecond Nd:YAG source (532 nm) at 10 K, the magnetization of their low temperature phases exhibits a combination of heating and photoexcitation effects. Time-dependence on the applied temperature and laser intensity of the thermal decay, concentration saturation and equilibration effects was observed for the photoinduced phase. It is concluded that laser heating effects should be explicitly accounted for when studying the low-temperature photoinduced valence tautomerism.

The occurrence of valence tautomeric transition in cobalt(II) dioxolene complexes is not determined only by the structure of the secondary ligand, but also probably by the ligand field of the metal. The laser heating effects should be accounted for in the studies of low-temperature photoinduced valence tautomerism.Figure optionsDownload as PowerPoint slide