N Basicity of Substituted Fullero[60]/[70]pyrrolidines According to DFT/TD-DFT Calculations and Chemical Thermodynamics

The basicity thermodynamic parameters of pyridyl/imidazole-substituted fullero[60]/[70]­pyrrolidines with respect to N heteroatoms in dichloromethane, which are necessary both to deepen insight into aromaticity “neque levia” and to create supramolecular chemical structures for application, are obtained and discussed in this work. Because of the presence of a chromophore in the molecules, the acid–base reactions of three C₆₀ derivatives functionalized in different ways and one C₇₀ derivative are studied using spectrophotometric titration with trifluoroacetic acid. The dependence of the pK values determined using the data on Hammett’s acidity functions, H₀, for a binary nonaqueous solvent on the molecule’s chemical structure is shown. Density functional theory (DFT) and time-dependent DFT (TD-DFT) at the B3LYP/6-311G­(d,p) level were used for the optimization of the fullerene derivative structures and modeling of their UV–vis spectra. The pK_BH⁺ values of substituted fullero[60]/[70]­pyrrolidines are predicted by quantum-chemical calculations.