Structure and relative energies of regioisomers and valence isomers of C-60 adducts. HF and DFT study

摘要

Fullerene C-60 and N-bridged C60NH regioisomeres are investigated by HF and DFT methods with BLYP, B3LYP and PBE functionals at the 6-31G(**), 6-311G(**) and TZ2P levels. Method DFT/PBE/TZ2P, providing the good compliance with experimental results, is chosen. Cross-sections of potential energy surface of adducts. at a variation of 5,6- or 6,6- bonds lengths are investigated. It is shown, that C60C2H4NH and C60H2 are characterized by local minima for [5,6]-closed forms, whereas local minima for [5,6]-open forms are absent. So absence of stable conformations of the [5,6]-closed forms of methanofullerenes and aziridinofullerenes is a consequence of strain energy in three-membered rings. It is shown that relative stability of the regioisomers depends from the lengths of single or double bonds of monoadducts, participating in reactions. The coordinated change of relative energies of the open and closed isomers N-bridged mono-(C60NR 1-7) and bis-adducts (C-60(NR)(2) 8-14) is revealed. The [6,6]-closed form is more stable for compounds C60NR (2,3) and cis-1-C-60 (NR)(2) (9,10) (R= Me, Ph), while [5,6]-open and cis-1 [6,6]-open forms are more stable for compounds C60NR (6,7) and cis-1-C-60(NR)(2) (13,14) (R = COOMe, R-*-the nitropyrimidine), what has been confirmed by experiment. The factors, defining relative isomers stability are investigated. (c) 2007 Wiley Periodicals, lnc.