ESR studies of electron irradiated K3IrIII(CN)6 in KCl single crystals. II. Strong quadrupole effects on the hyperfine structure in IrII(CN)5 species

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Abstract
The effects of a large quadrupolar interaction in the IrII(CN)5 molecule in a KCl lattice are analysed using a MAGNSPEC computer program. Some empirical rules are given to help in the interpretation of this kind of spectra. g and A formulas deduced in a ligand field approximation for a d z2 ground state are used to calculate the unpaired electron density on the metal. The hyperfine constant are determined to be positive leading to a positive value for the core polarization constant χ, indicating a contribution of 6s wave function to the unpaired electron molecular orbital. The analysis of the ESR data indicate the presence of two nonequivalent sites for the IrII(CN)5 molecule in KCl, differing only by the orientation of the principal axes of the quadrupolar interaction. A possible influence of the vacancies created by charge compensation on the existence of these two sites is discussed. The ratio between the nuclear quadrupole moments for the iridium isotopes is determined to be 193Q: 191Q = 0.91 ± 0.03.