A natural bond orbital analysis of the bonding in solvated electrons within a localised electron model

Abstract

The bonding between a localised electron and the solvent within the recently introduced localised electron ab initio molecular-orbital model of solvated electrons has been analysed using the natural bond orbital (NBO) procedure for a variety of organic solvents. The dominant interaction between the electron and the solvent is found to be donation into the σ* orbitals of bonds to hydrogen in the solvent, even for C—H bonds. This type of bonding is very reminiscent of the classical hydrogen bonding found in anion solvation or oligomerisation of protic solvents. Spin polarisation of the solvent bonds and other effects do not appear to play a major role in determining the structure of the solvated electron. The optimised structure of e^–(H₂O)₆ is reported, as are model calculations designed to test the effect of the second solvation shell. In these calculations, the angle between the ‘electron’(the centre of the cavity), the closest hydrogen and oxygen is very close to 180°, as suggested by Kevan's experimental work.