Structure and bonding in M-X-M systems (M=Li, Na and K; X=O, S): Effects of charge-transfer

Structure and bonding for a series of oxo-bridged and sulphur bridged alkali-metal centers (M-X-M: Li, Na and K; X = O, S) are studied for various M-X-M angles. The structures for these charge-transfer systems are compared with H-X-H. These chargetransfer systems show bonding and structures that are distinctively different from the covalent H-X-H molecules. The singlet-triplet gap for all of these molecules are positive suggesting the stabilization of the spin-paired configuration instead of the paramagnetic state. The variation in the exchange-coupling constant (J) with the change in M-X-M angle suggest that the singlettriplet gap for these systems can be reduced through stabilization of geometries with M-X-M angles differing from the ground state geometries. Strategies are proposed for reducing the singlet-triplet gaps in these systems by confining them inside fullerenes.