Alkali-earth metal fullerides Ca(C_(60))_2 and Ba(C_(60))_2: a new solution-phase method for the preparation and characterization with ESR, UV-NIR, IR and Raman spectroscopy

摘要

Ca(C_(60))_2 and Ba(C_(60))_2, prepared in a THF/H_2O solution, were characterized by UV-NIR, ESI-MS, IR, ESR and Raman spectroscopy. ESR spectra of Ca(C_(60))_2 and Ba(C_(60))_2 are temperature-dependent: the linewidth increases abruptly at about the melting point of THF and the ESR signal diminishes gradually below 170 K. A possible explanation for this is that THF crystallization results in the exclusion of solute from the lattice and leads to C_(60)~- aggregation, which promotes line broadening and the formation of a diamagnetic dimer of (C_(60))_2~(2-). The oxidation of Ca(C_(60))_2 and Ba(C_(60))_2 in THF was monitored by UV-NIR. The oxidation rate of C_(60)~- was found to depend on the countercation.