Existence of weakly bound states for metal–benzene molecules confirmed from a long-range model

A long-range model adding a repulsive term from SCF calculations and an attractive term from dispersion evaluated in an oblate spheroidal formalism is proposed for the interaction energy between a transition metal atom and a benzene molecule. An analytical form is derived for the total energy of MC6H6 complexes versus the distance R between M and the benzene center of mass. Ground state weakly bound (De ∼ 200–600 K) at long range (Re ∼ 4–4.5 Å) are obtained for the three systems ScC6H6, VC6H6 and NiC6H6, confirming the first evidence of these structures previously pointed out from both electric dipole measurements and CASSCF-MRCI calculations.