Thermochemical stabilities, electronic structures, and optical properties of C 56 X 10 (X = H, F, and Cl) fullerene compounds

Stimulated by the recent isolation and characterization of C 56 Cl 10 chlorofullerene (Tan et al., J Am Chem Soc 2008, 130, 15240), we perform a systematic study on the geometrical structures, thermochemistry, and electronic and optical properties of C 56 X 10 (X = H, F, and Cl) on the basis of density functional theory (DFT). Compared with pristine C 56 , the equatorial carbon atoms in C 56 X 10 are saturated by X atoms and change to sp 3 hybridization to release the large local strains. The addition reactions C 56 + 5X 2 → C 56 X 10 are highly exothermic, and the optimal temperature for synthesizing C 56 X 10 should be ranged between 500 and 1000 K. By combining 10 X atoms at the abutting pentagon vertexes and active sites, C 56 X 10 molecules exhibit large energy gaps between the highest occupied and lowest unoccupied molecular orbitals (from 2.84 to 3.00 eV), showing high chemical stabilities. The C 56 F 10 and C 56 Cl 10 could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states is also calculated, which suggest that the frontier molecular orbitals of C 56 X 10 are mainly from the carbon orbitals of two separate annulene subunits, and the contributions derived from X atoms are secondary. In addition, the ultraviolet–visible spectra and second‐order hyperpolarizabilities of C 56 X 10 are calculated by means of time‐dependent DFT and finite field approach, respectively. Both the average static linear polarizability 〈α〉 and second‐order hyperpolarizability 〈γ〉 of these compounds are larger than those of C 60 due to lower symmetric structures and high delocalization of π electron density on the two separate annulene subunits. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011