Vibrational Spectra of C60 Polymers: Experiment and First-Principle Assignment

Infrared, Raman, and DFT Vibrational Spectroscopic Studies of C60F36 and C60F48

“…Nevertheless, until very recently, application of vibrational spectroscopy in the fullerene chemistry was very limited; it suffered from the lack of theoretical background, since the required first-principle vibrational calculations were hardly feasible for molecules of such large size ( n (C) > 60). Reported examples included mainly vibrational analysis of the parent fullerenes C 60 , , C 70 , and C 84 , azafullerene, some endohedral metallofullerenes, − C 60 polymers, − and four exohedral derivatives, C 60 Br 24 , C 60 F 20 , C 60 Cl 6 , and C 60 Cl 30 . The B3LYP/6-31G* approach was successfully used to provide complete assignment of C 60 and C 70 vibrational spectra with reported deviations from experimental data of less than 5 cm -1 . , Computations of the IR spectra of two C 84 isomers at this level of theory have also shown qualitative agreement with experimental data .…”

“…The use of smaller basis sets (such as 3-21G) with Hartree−Fock or density functional theory (DFT) methods, , as well as application of semiempirical methods either of MNDO- 22 or tight-binding types, ,,, resulted in computational data of sufficient accuracy to provide a qualitative understanding of the vibrational structure but did not allow peak-to-peak assignment of the whole set of experimental data. Taking advantage of the density fitting technique, which allows considerable acceleration of pure DFT computations, we have applied the PBE/TZ2P approach to interpret vibrational spectra of polymeric C 60 , , and bromo- 39 and chlorofullerenes. , The method was found to be quite accurate in predictions of the carbon cage vibrations, while the frequencies of C−Hal bending and stretching modes were underestimated. However, due to the systematic character of these errors they could be effectively corrected with the use of the scaling procedure of Pulay et al Recently, we have succeeded in the measurement and DFT-based interpretation of the C 60 F 20 IR and Raman spectra, which in turn provided unambiguous structural assignment for the D 5 d -C 60 F 20 isomer isolated from the metal−fluoride reaction product .…”

“…The use of smaller basis sets (such as 3-21G) with Hartree-Fock or density functional theory (DFT) methods, 25,26 as well as application of semiempirical methods either of MNDO- 22 or tight-binding types, 24,27,31,32 resulted in computational data of sufficient accuracy to provide a qualitative understanding of the vibrational structure but did not allow peak-to-peak assignment of the whole set of experimental data. Taking advantage of the density fitting technique, 37 which allows considerable acceleration of pure DFT computations, we have applied the PBE 38 /TZ2P approach to interpret vibrational spectra of polymeric C 60 , 29,30 and bromo- 39 and chlorofullerenes. 35,36 The method was found to be quite accurate in predictions of the carbon cage vibrations, while the frequencies of C-Hal bending and stretching modes were underestimated.…”