Infrared Absorption Spectra of the 18O-Labeled Acetylacetonates of Cr(III) and Mn(III)

Abstract

The ¹⁸O‐induced isotopic shifts of the Cr(III) and Mn(III) acetylacetonate (of over 90 at % ¹⁸O) infrared absorption bands were measured in the 400–1650‐cm⁻¹ region. The hitherto accepted assignments of these bands are discussed in the light of these measurements. It is found that the band at about 1520 cm⁻¹ is due to C=C stretching while that at about 1570 cm⁻¹ has a C=O stretching character. The ∼1425‐cm⁻¹ band must be due to the asymmetrical CH₃ bending while the one at 661 cm⁻¹ probably belongs to an out‐of‐plane deformation and that at 590 cm⁻¹ to an M—O stretching.