Deductive molecular mechanics as applied to develop QM/MM picture of dative and coordination bonds

Abstract

Previously developed method of analysis of electronic structure of organic molecules performed on the basis of the APSLG trial electronic wave function led to deductive molecular mechanical description of molecular potential energy surface (PES). It is based on the observation that the covalent (Heitler–London) configuration is the only one which survives under the infinite bond elongation. In the present paper the APSLG based treatment of ‘organic’ molecules is modified to cover the case of dative (coordination) bonds which can be characterized as ones having one of the ionic configurations as an asymptotic limit under the bond elongation. This analysis allows to establish deductively the QM/MM form of PES for compounds containing dative bonds between donor atoms and metal cations with empty valence shells. A case of ether oxygen donor atom is considered in details. Particular attention is paid to to the shaping effect of the donor–acceptor interaction upon the system of the hybrid orbitals centered on the donor oxygen atom.