Electronic states of polyanionic high-spin C60 fullerene and their clusters:: anomalous spin relaxation and Jahn-Teller effects

Tri- and dianionic C-60 fullerenes and polyanionic C-60 clusters were prepared by the successive chemical reduction of C60 With potassium metal in solution. Trianionic spin quartet C-60 and polyanionic high-spin C-60 clusters were detected by cw-ESR and pulsed ESR-based 2D Electron Spin Transient Nutation (2D-ESTN) spectroscopy. The high spin states of annealed polyanionic C-60 show a spin relaxation anomaly. A phonon bottleneck phenomenon is responsible for the anomaly and the phenomenon is attributable to the occurrence of Jahn-Teller hot phonon molecular states of polyanionic C-60 fullerenes. Wiggling behaviours of the T-1 relaxation curves were observed for both the annealed tri- and dianionic C-60 The peculiar time profiles were identified to arise from a quantum spin tunnelling between the Jahn-Teller assisted vibronic states. Polyanionic C-60-based molecular clusters have high-spin ground states (S=l, 3/2, 2, 3). Their clustering structures were proposed in terms of tensorial analyses of the fine structure parameters.