Absorption Spectrophotometric, NMR and Quantum Chemical Investigations of Ground State Non-Covalent Interactions between Fullerenes and a Designed Trihomocalix[6]arene in Solution

摘要

Ground state non-covalent interactions between a newly designed macrocyclic 1,3,5-trihomo calix[6]arene receptor, designated as 1, and the C_(60) and C_(70) fullerenes have been studied in toluene solutions. It was observed that the absorbances of both C_(60) and C_(70) solutions increased upon the addition of increasing concentrations of compound 1. Job’s method of continuous variation established 1:1 stoichiometry for these fullerene-1 complexes. The binding constant (K) data reveal that compound 1 binds to C_(70) more strongly compared to C_(60), i.e., K_(C60-1) = 230 dm~3·mol~(?1) and K_(C70-1) = 517 dm~3·mol~(?1). Proton NMR analysis provides very good support for strong binding between C70 and 1. Estimations of the solvent reorganization energy (RS) suggest that the C_(70)-1 complex is stabilized more than the corresponding C_(60)-1 complex, with RS_((C60-1)) =?1.970 eV and RS_((C70-1)) =?2.300 eV. Molecular mechanics force field method calculations established that the binding pattern of C_(70) towards 1 occurs in the side-on rather than end-on orientation, and that the C_(70)-1 complex gains 5.23 kJ·mol~(?1) of extra stabilization energy with this side-on geometrical arrangement.