Optical spectroscopy on monomeric and polymeric 1:1 fulleride salts

Abstract

We compare infrared spectra of the C60 monoanion in different solid-state structures with each other as well with that of the neutral molecule. We relate the shift and splitting of the Tu infrared modes to the strength and anisotropy of electron-phonon coupling in those environments.

Discrete Fulleride Anions and Fullerenium Cations

“…The symmetry-lowering effect of C-C bond formation in dimer and polymer phases of RbC 60 has been studied for the two highest frequency modes. 263,264 The splittings and shifts should be useful for detecting possible dimer formation in discrete fullerides. 265 The first fullerenium ion salt to be characterized by infrared spectroscopy was [C 76 + ][CB 11 H 6 Br 6 -].…”

Far-infrared study of the Jahn-Teller-distortedC60monoanion inC60Long1, Musfeldt2, Schilder3 et al. 1998Phys. Rev. B255391View full textAdd to dashboardCite

“…The slight redshift of F 1u (3) is attributed to increased intermolecular distances, 8 whereas the pronounced red shift and enhanced oscillator strength of F 1u (4) are ascribed to the charged-phonon mechanism. 8,9,12 This mechanism is well known in the alkali-doped fullerides, where extra charge on the C 60 ball causes coupling of the F 1u phonons to the doping-induced electronic transitions, resulting in a downshift and enhancement of the F 1u (2) and F 1u (4) modes. 17,18 The Jahn-Teller effect ͑JTE͒ is another expected manifestation of electron-phonon coupling in the charged C 60 ball.…”

“…9,12 Until now, attention has focused on two of the four IR-active fundamental modes, F 1u (3) and F 1u (4), which resonate in the middle infrared. 8,9,12,16 Whereas in pristine C 60 these modes occur at 1182 and 1428 cm Ϫ1 , in (Ph 4 P) 2 Y C 60 they downshift to 1179 and 1394 cm -1 (1390 cm Ϫ1 in XϭAs), respectively. The slight redshift of F 1u (3) is attributed to increased intermolecular distances, 8 whereas the pronounced red shift and enhanced oscillator strength of F 1u (4) are ascribed to the charged-phonon mechanism.…”

“…8,9,12,16 Whereas in pristine C 60 these modes occur at 1182 and 1428 cm Ϫ1 , in (Ph 4 P) 2 Y C 60 they downshift to 1179 and 1394 cm -1 (1390 cm Ϫ1 in XϭAs), respectively. The slight redshift of F 1u (3) is attributed to increased intermolecular distances, 8 whereas the pronounced red shift and enhanced oscillator strength of F 1u (4) are ascribed to the charged-phonon mechanism. 8,9,12 This mechanism is well known in the alkali-doped fullerides, where extra charge on the C 60 ball causes coupling of the F 1u phonons to the doping-induced electronic transitions, resulting in a downshift and enhancement of the F 1u (2) and F 1u (4) modes.…”

“…4,5 These latter materials have excited interest as prototypical systems of the isolated C 60 monoanion in a crystalline environment. [6][7][8][9][10][11][12] The aforementioned charge-transfer salts, (Ph 4 X) 2 Y C 60 ͑with XϭP or As and YϭI, Br, or Cl͒, are isostructural members of the tetragonal 13 space group I 4/m . 4,5 Singly charged C 60 and halide anions occupy vertices of interpenetrating tetragonally distorted tetrahedra.…”