In scientific researches proposed and developed model of small radius impurity centres in dielectric crystals and semiconductors, which includes detailed study of dynamic Jahn-Teller effect and of crystalline fieldsin uncompleted electronic shells of transition ions and rare lands. He developed the theory of non-radiative multi-pho- nic transitions, form of optical electron-vibrational bands and effects of polarization dichroism in Jahn-Teller centres, which allows calculation of key parameters of the doped laser crystals. He proposed a new modality for analysis of exchange interaction in multi-electronic systems, based on the theory of higher symmetries and irreducible tensor operators. He developed the theory of magnetic susceptibility, nuclear magne- cit resonance, inelastic scattering of neutrons in magnetic clusters of transition metals. He developed the theory of exchange interactions in exchange clusters of transition metals with degenerated electronic shells when use of Heisenberg Hamiltonian be- comes inadequate; elucidated anomalous strong magnetic anisotropy, connected with orbital movement of electrons. He proposed a new treatment for analysis of the ener- getic spectrum and thermodynamic characteristics of polynuclear clusters of mixed valence that takes into account double exchange and vibronic interaction, explained diamagnetism offullerenes and composed polyoxometalates as wel as magnetic pro- perties of important metal clusters in biology.