Evaluation of a new procedure for quantum-chemical estimates of constants of isotropic hyperfine coupling with protons in free radicals

A new procedure for quantum-chemical estimates of the constants of isotropi c hyperfine coupling (IHFC) with protons using the orbital spin populations calculated in the basis set of symmetrically orthogonalized (according to Lowdin) atomic orbitals is tested taking 16 well-studied simplest K-electro n and sigma-electron radicals as:examples. The most probable reasons for an d possible ways of correcting large deviations of calculated IHFC constants from experimental values are considered. The efficiency of the semiempiric al MNDORU scheme, which makes it possible to consistently estimate the delo calization and spin-polarization contributions to the constants of IHFC wit h protons in free radicals, is demonstrated.