C_(60)C1_(24) Molecule in Crystalline Toluene Matrix

摘要

The absorption spectra of the molecules C_(60)Cl_(24) embedded in a solid matrix of toluene,C_6H_5(CH_3),consist of three groups of lines,A,B,and C,situated at 1.6-1.8,2.3-2.5,and 2.6-2.8 eV.We assign the groups of lines to purely electronic and electron-vibrational (vibronic) transitions S_0-> S_n in C_(60)Cl_(24) molecules in different positions with respect to the crystalline matrix (Shpol'skii effect).The molecules C_(60)Cl_(24) are known to have three isomers:a T_h-symmetric and two D_(2h)-symmetric (1 and 2).The D_(2h)-symmetric isomer 1 has the most appropriate value of the first electronic transition and is probably responsible for the observed absorption spectra.We report the results of calculations made to find the most appropriate cavities in a toluene crystal and the most advantageous positions of D_(2h)-symmetric isomers 1 of the C_(60)Cl_(24) molecule in these cavities.The most appropriate three cavities in the toluene crystal for the D_(2h)-symmetric isomers 1 of the C_(60)Cl_(24) molecule are found to be centered in the inversion center rc = 0.5 a (a,b,c being primitive translation vectors) and formed by moving away 14 somewhat different toluene molecules.The very fact that there exists a relatively small number of energetically preferred ways to embed the molecule C_(60)Cl_(24) in the crystal matrix of toluene is encouraging and correlates with the small number of Shpol'skii lines in the spectra of pure electronic transitions in the system under consideration.Taking into account toluene molecule relaxation around the embedded molecule C_(60)Cl_(24) will permit a closer comparison of the theoretical and experimental results.