Calculation of thermochemical properties of conjugated radicals

Heat of formation for 30 conjugated hydrocarbon radicals were calculated within the framework of an unrestricted Hartree–Fock method using the same set of π‐Hamiltonian parameters for systems with closed and open electronic shell. Based on π‐electronic perturbation theory, the model of aromatic annelation and radical CH 2 substitution of neutral molecules was developed. The proposed model makes it possible to obtain thermochemical properties of radicals on the basis of calculated or experimental data for less lengthy analogues. Direct calculation and results based on perturbation theory agree closely with each other and with experiment. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004