Crystal structure, magnetism and photophysics of the lanthanide maleates RE(C4O4H3)3·8H2O (RE=Nd, Sm)

Abstract

This article reports the results of an X-ray study, of the magnetic and spectroscopic characteristics of lanthanide maleates. An X-ray single crystal structure determination was performed for Nd(C4O4H3)3·8H2O. The crystal structure is triclinic (P1, Z=2, a=7.285(1) Å, b=10.394(2) Å, c=16.765(3) Å, α=72.13(2)°, β=87.77(2)°, γ=70.86(2)°, Rall=0.0322) and isotypic with the respective praseodymium compound. Nd3+ is nine-fold coordinated by oxygen atoms in the form of a tricapped trigonal prism. Two carboxyl groups of two crystallographically independent hydrogenmaleate ions are attached to Nd3+ in a monodentate manner. The third hydrogenmaleate anion forms hydrogen bonding with unbound and coordinated water molecules. Thus, the crystal structure of the title complexes points to an unusual carboxyl group coordination with lanthanide ions. Absorption spectra of neodymium and samarium single crystals at 293 and 4.2 K were recorded. Analysis of the f–f transition probabilities were performed and Judd–Ofelt parameters were determined. Strong vibronic coupling was found, mainly promoted by modes which correspond to co-ordinated moieties of ligand molecules. A structural transformation is expected based on the relatively high temperature factors in the X-ray data. This was confirmed by the spectroscopic investigation. Magnetic susceptibility results were correlated with X-ray data and results reported previously.