Optical properties and crystal structure of lanthanide(III) coordination compounds with 2-propenoic acid

Coordination compounds of a new type, Ln(C3H3O2)3·xH2O (where Ln = Nd3+, Dy3+; C3H3O2− = 2-propenoic anion/acrylic anion, x = 3 or 1.5 for Nd and Dy, respectively), were obtained in crystalline state and their structures were determined. Both crystals are composed of polymeric chains and in both crystals there are two symmetry-independent lanthanide ions, each with a different coordination sphere. The Nd crystal (I) is monoclinic, space group P21/c, and the Dy crystal (II) is triclinic, P1¯. The Ln3+ ions occupy low-symmetry sites in the dimeric structure of Ln(H2CCHCOO)3·xH2O. The spectroscopic investigations of the title monocrystals at room and low temperatures down to 4.2 K were performed to explain the electrostatic nature of the Ln3+–ligand bond. Variations in the spectroscopic parameters and their correlations with the nature of the Ln3+–L bond are discussed. Analysis of the low-temperature spectra indicates the presence of ion-pair interactions. The influence of the –CC– double bond in the substituent of the carboxylate ions on the distribution of charge, polarity, strength, and character of the Ln–O(L) coordination bond is analysed. The number of electronic components observed in the absorption spectra measured at 4.2 K is compatible with that expected for these systems. Spectroscopic measurements allowed us to compare the optical properties of Ln(H2CCHCOO)3·xH2O with lanthanide acetates and other carboxylates.

Coordination compounds of a new type, Ln(C3H3O2)3·xH2O (where Ln = Nd3+, Dy3+; C3H3O2− = 2-propenoic anion/acrylic anion, x = 3 or 1.5 for Nd and Dy, respectively), were obtained in crystalline state and their structures were determined. Both crystals are composed of polymeric chains and in both crystals there are two symmetry-independent lanthanide ions, each with a different coordination sphere. The Nd crystal (I) is monoclinic, space group P21/c, and the Dy crystal (II) is triclinic, P1¯. The Ln3+ ions occupy low-symmetry sites in the dimeric structure of Ln(H2CCHCOO)3·xH2O. Variations in the spectroscopic parameters and their correlations with the nature of the Ln3+–L bond are discussed. The influence of the –CC– double bond in the substituent of the carboxylate ions on the distribution of charge, polarity, strength, and character of the Ln–O(L) coordination bond is analysed.Figure optionsDownload as PowerPoint slide