Planar and pyramidal conformers of the alkali–ethylene complexes

Two geometric forms of the ethylene complex with an alkali atom are studied by ab initio methods. The lowest bound state of LiC2H4 belongs to the B2 point-group symmetry in the pyramidal conformer lying 0.20 eV higher than the dissociation asymptote into the ground state, while it is A2 in the planar conformer lying 0.20 eV higher than the former state. The 12A2 state is more ionic than the 12B2 state with the effective metal charges of 0.62 and 0.47, respectively. We give here the potential energy surfaces, the electronic structures and spectroscopic properties of LiC2H4, NaC2H4 and KC2H4.