Analytical derivatives, π bonding and d–s mixing in the ligand field molecular mechanics method

Abstract

Expressions are presented for the analytical energy derivatives of the ligand field stabilisation energy (LFSE) within the angular overlap model formalism. In addition to the σ-bonding contributions already incorporated in the ligand field molecular mechanics (LFMM) code, explicit contributions from π-bonding and d–s mixing have been added. Illustrative LFMM parameters are developed for planar [CuCl₄]²⁻ and tetragonal octahedral [CuCl₆]⁴⁻ to demonstrate that it is now possible to reproduce to high accuracy both the structures and the associated d–d transition energies.