A ligand field theory analysis of the spectra of the t_2g³ levels of IrF₆

Abstract

Calculations and experimental data are presented for the t _2g ³ molecular levels of IrF₆ which imply that a substantial interaction takes place between these 5d³-configuration states and charge transfer states at ca. 20 000 cm^-1. This t _2g ³-charge transfer state configuration interaction is so extensive that the five t _2g ³ levels can only be fit with physically unreasonable values of the Racah (electrostatic) parameters and a spin orbit coupling parameter that is not consistent with expectations for 5d-series transition metal hexafluorides. Parameter values presented for IrF₆ are thus determined from the lowest three levels only, as these should experience the smallest relative shift due to configuration interaction: B = 297 cm^-1, C = 1167 cm^-1, ζ_5d = 4182 cm^-1, and 10Dq = 35 000 cm^-1. In order to corroborate the assertion that t _2g ³-charge transfer configuration interaction is an important factor for the determination of IrF₆ crystal and molecular properties, a number of t _2g ³ spectroscopic properties, which turn out to be quite sensitive to charge transfer state admixture, were studied theoretically and experimentally. These include gas-to-crystal shifts, site splittings, and Jahn-Teller interactions; comparison of calculated and experimental values clearly substantiate the conclusion that there is a strong influence of charge transfer states on the nature of the 5d³-t _2g ³ manifold. Finally, new data for the Γ_8g (² E_g ) and Γ_6g (² T _1g ) states at 1·2 μm are given, completing the data set for the t _2g ³ transitions of IrF₆.

Supported in part by ARO-D and ONR.

Supported in part by ARO-D and ONR.

Notes

Supported in part by ARO-D and ONR.