Charge transfer and complex formation of transition metal and lanthanide fullerides prepared by metal vapor synthesis

Transition metal and lanthanide fullerides MxC60 films (M=Ag, Au, Al, In, Sn, Pb and Sm) were prepared by metal vapor synthesis. The UV-NIR absorption spectra and infrared transmission spectra of MxC60 suggested that charge transfer occurred and bonds formed between metals and C-60. The IR spectra of these fullerides showed two new major features located at 1369-1401 and 1441-1451 cm(-1), respectively. The former could be the softing mode of F-1u(4) induced by charge transfer, which suggested that the C-60 cage was between 1- and 3-(+/-1) charged in these fullerides at present synthesis conditions. The latter could be A(g)(2) mode activated in the IR by disorder. The metal atoms may be as a bridge connecting C-60 molecules like a linear polymer or bridged binuclear complexes for M=Ag, Au, Al, In, Sn and Pb). For lanthanide fulleride SmxC60, the Sm atoms may be bounded to the five-membered ring of the C-60 cage and ferrocene-like SmxC60 complexes may be formed.