Electronic states of polyanionic high-spin C 60 fullerene and their clusters: anomalous spin relaxation and Jahn-Teller effects

Abstract

Tri- and dianionic C 60 fullerenes and polyanionic C 60 clusters were prepared by the successive chemical reduction of C 60 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=1, 3/2, 2, 3). Their clustering structures were proposed in terms of tensorial analyses of the fine structure parameters.