IR Spectroscopic Study of Lanthanide Hydroxo Complexes with Esters of Acetoacetic Acid

Abstract

The IR spectra of hydroxo complexes of lanthanides (Ln) with the β-ketoesters methyl, ethyl, and allyl acetoacetate with the general formula LnL2OH·H2O (Ln = La, Gd, Lu; L = β-ketoesterate anion) were studied in the range of 400–1700 cm–1. In order to interpret the spectra and assign bands to the vibrations of the β-ketoesterate ligands a normal coordinate analysis of the model complexes LnL(OH)2 (Ln = La, Lu) was performed in the PBE0/ECP46(60) MWB + DZP approximation. The experimental data and the theoretical calculations show that the radius of the Ln(III) ion and the structure of the hydrocarbon radical of the alkoxyl substituent have a negligible effect on the value of π-electron delocalization in the [OCCCO] conjugated system of the chelate fragment, whereas the decrease of the Ln(III) ionic radius leads to increase of conjugation in the ester C(O)O group of the ligands.