Fast calculation of π-electron charge densities in organic molecules: Non-condensed compounds

A novel approach to fast computation of π-electron charges in non-condensed conjugated systems is described. The conjugated parts of the molecular structure are regarded as formed of simple rings (annulenes) and chains (polyenes) and their molecular orbital (MO) energies and eigenvectors are given with simple analytical expressions. The nature of the different atoms within the structure are further characterized by employing the perturbation MO theory. The reliability of the charges is tested by correlations with 13C nuclear magnetic resonance chemical shifts. Keywords: Phenyls, substituted; Molecular orbitals; Charge densities; Fast calculation; Finite differences theory; Nuclear magnetic resonance; Perturbation theory