INFRARED STUDY OF GROUP-V HEXAFLUORIDE FULLERIDES

Compounds of C-60 and hexafluoride ions of group V elements (P,As,Sb) were studied by infrared spectroscopy. C-60(AsF6)(1.9) was formed by r eacting C-60 powder with AsF5 gas dissolved in liquid SO2. The AsF6- i on was identified by a broad nu(3) absorption at 703 cm(-1) a shoulder at 681 cm(-1) and evidence of the sharp nu(4) absorption just below 4 00 cm(-1) in the infrared spectrum. The low-frequency modes of C-60 at 527 and 576 cm(-1) were unshifted in the reacted powder. The T-1u(3) mode of C-60, at 1183 cm(-1), was accompanied by neighbouring absorpti ons at 1194 and 1206 cm(-1), which were assigned to splitting of the t riply degenerate mode. Three strong broad peaks at 1549, 1406 and 1322 cm(-1) observed in the spectra were assigned to splitting of the thre efold degenerate T-1u(4) mode of pristine C-60 at 1428 cm(-1). Heat tr eatments of the sample, with temperatures ranging up to 350 degrees C, were performed to thermally decalate the sample and to aid in identif ying the infrared modes. The PF6- ion, in the sample of C-60 reacted w ith NO2PF6 in SO2, was observed in the IR spectra by the broad nu(3) a bsorption at 830 cm(-1) and the sharp nu(4) absorption at 558 cm(-1). No strong absorption of NO2- at 2360 cm(-1) was observed, indicating t hat the sample was not a simple mixture of the two powders. The C-60 a bsorption lines, at 527, 576, 1183 and 1428 cm(-1), were unshifted. Ho wever, the T-1u(4) mode at 1428 cm(-1) showed asymmetric broadening on the low-frequency side and small absorptions flanking the T-1u(4) mod e. These features, although much less pronounced, may correspond to th e shifting and splitting observed in the T-1u(4) mode of the C-60(AsF6 )(1.9) compound. The octahedral SbF6- ion was identified in the sample of C-60 powder reacted with NO2SbF6 by the strong nu(3) absorption at 660 cm(-1). The C-60 lines were unshifted, but small absorptions flan king the T-1u(4) mode were again similar to the absorptions assigned t o splitting in the C-60(AsF6)(1.9) compound.