Relaxation dynamics of a photoinduced di-cobalt-tetraoxolene valence tautomer

The temperature dependence of the relaxation dynamics of a dinuclear cobalt-tetraoxolene complex undergoing photoinduced valence tautomerism is reported and discussed. Two different regimes were detected, one at low (5-20 K) and a second at higher temperatures (20-35 K). The activation energy for the low temperature regime suggests a tunnelling process assisted by lattice phonons. In the thermally activated region the activation energy is far from that expected for the total-symmetric Co-O breathing mode, thus suggesting an important role for other internal vibrational modes.