Resonance Raman excitation profiles of the tetraisothiocyanatocobaltate(II) ion

Abstract

The Raman band intensities of four of the fundamentals of the [Co(NCS)₄]^2– ion have been investigated as a function of excitation frequency in the region of the ⁴T₁(P)â†�⁴A₂ ligand-field transition. All four Raman bands increase their intensities as the excitation frequency approaches the maximum in the ligand-field transition. In particular, the excitation profile of the most resonantly enhanced band, viz. that arising from the ν₁₁(t₂) Co–N stretching fundamental, has been studied in detail. The results suggest that it reaches a maximum ca. 250 cm^–1 to the high-frequency side of the absorption maximum. This is discussed with reference to current theories of Raman scattering. The observed excitation profiles contrast with those recently observed for various centrosymmetric ions in the vicinity of their ligand-field transitions and reasons for this difference are discussed.