Aromaticity of heptafulvene charge transfer complexes with lithium and caesium atoms: A computational approach

Geometry optimization of heptafulvene complexes with Li and Cs atoms at B3LYP/6-311++G(d, p) level of theory using Gaussian 03 software allowed us to estimate the magnitude of charge transfer from metal atoms to the heptafulvene moiety (charges equal to +0.938 and +0.994 for Li and Cs, respectively) and energies of dissociation of the complex (−36.65 and −20.44 kcal/mol, respectively). A substantial increase of aromatic character of the ring results from the charge transfer leading to aromaticity index HOMA equal 0.439 and 0.515, for Li and Cs complex respectively, comparing to HOMA = 0.165 for isolated heptafulvene.