Electronic g values of Na⁺-NO and Cu⁺-NO complexes in zeolites: Analysis using a relativistic density functional method

Electronic g values of molecular systems are usually difficult to interpret. We propose a new tool for the analysis of g values in terms of contributions of particular atomic orbitals. This tool benefits from a direct relationship between ground-state relativistic Kohn-Sham orbitals and g values in our novel scheme which takes spin-orbit effects into account self-consistently and employs two-component orbital wave functions obtained after a Douglas-Kroll decoupling of the four-component Dirac-Kohn-Sham equation to calculate electronic g values. We rationalize the notable difference in the g tensor anisotropy of adsorption complexes of an NO probe with charge compensating Na⁺ and Cu⁺ cations in zeolites, g components of the Na⁺-NO species, all three of them measured and calculated smaller than the free-electron value g_e, reflect the essentially electrostatic adsorption mechanism. At variance, two g components larger than g_e are obtained for the complex Cu⁺- NO and they are shown to manifest covalent interactions due to Cu 3d orbitals.