Structural and electronic effects of cation binding (Li+, Na+, K+, Mg2+ and Ca2+) to the π system of the (η6-benzene)-Cr(Co)3 complex: A theoretical study

Abstract

Cation binding to the π-electrons of benzene is known to show a periodic trend in interaction energies. In the present work, the chemistry of cation–π interaction in a benzene ring bound with tripodal Cr(CO)3 (BC) was considered. In contradiction to the anticipated destabilisation due to competition between two Lewis acids towards a common sandwiched base, cation binding with BC showed a similar trend as that to benzene. Furthermore, it was found to activate the benzene ring by reducing the frontier orbital energy gap substantially. The NICSzz index adds sufficient evidence to the arguments. In addition, TDDFT studies indicate a bathochromic shift upon cation binding as an immediate consequence of the reduction in the energy of the Frontier orbital.

Keywords

• Cation complexed (η6-benzene)-tricarbonylchromium system
• Cation-π interaction energy
• Charge transfer
• nucleus-independent chemical shifts (NICS)
• time-dependent density functional theory (TDDFT)