Associate-induced circular dichroism (AICD): A theory of the circular dichroism of associated or bonded chromophores in the dipole approximation

Abstract

A theory is presented for the circular dichroism of an achiral chromophore which is associated or bonded to some other chromophores (which may be chiral or achiral). It is argued that second-order perturbation terms in the dipole approximation are at least of the same order as first-order perturbation terms involving higher multipoles. The latter are a common feature of current models of the natural circular dichroism of magnetic dipole allowed transitions of achiral chromophores in chiral molecules. These second-order terms are derived and the symmetry rules for the mechanisms discussed. The theory is qualitatively applied to some simple cyclic peptides.