Bonding Trends in Lanthanide Mandelates

Abstract

The lanthanide mandelates have been prepared by reacting the lanthanide hydroxides with mandelic acid (HL). The coordination number in these compounds has been discussed on the basis of analytical, infrared and electronic spectral, and thermal data. The mandelates have the general formula, LnL3.nH2O, where n3 for LnLa, Pr, Nd and Sm, and n=2 for LnGd, Dy, Br, Yb and Y. The infrared spectral data reveal that the mandelate ion is coordinated to the lanthanide ions in a bidentate fashion through the oxygen atoms of the carboxylate and the hydroxyl groups. The antisymmetric COO−, the δ OH, and the Ln‐O frequencies in the mandelates show a linear relationship with the ionic radius of the lanthanide ions. The infrared spectral and thermal data afford evidence of the coordination of all the molecules of water to the lanthanide ions. Hence, coordination numbers nine and eight have been assigned to the two sets of mandelates. This conclusion is supported by a study of the shapes of the hypersensitive transitions in the electronic absorption spectra of Nd and Br mandelates. The electronic spectra also suggest that the bonding in these compounds is predominantly ionic.

Synthesis, characterization and thermal behaviour of solid alkali metal mandelates in pyrolytic and oxidant atmosphere

“…Mandelic acid is an aromatic alpha hydroxyl acid with the molecular formula C 6 H 5 CH(OH)CO 2 H and it has a long history as antibacterial, particularly in treatment of urinary tract infectious [1]. It has been reported in the literature some work about mandelic acid and their compounds, as shown: studies of some bivalent solid complexes of iron [2], infrared spectrum of mandelate complex of nickel II [3], the complexation of mandelates of lanthanide [4], magnesium bis[D(−)mandelate] anhydrous and other alkaline earth, alkali and zinc salts of mandelic acid [5], mixed-ligand complexes of copper (II) with ␣-hydroxycarboxylic acid and 1,10phenanthroline [6], synthesis, structures and magnetic properties of layered bivalent metal mandelates [7] mononuclear, dinuclear and hidroxo-briged tetranuclear complexes from reactions of Cu (II) ions, mandelic acid diimina ligands [8] and synthesis, characterization and thermal study of solid-state alkaline earth mandelates, except beryllium and radium [9]. In this paper, the object of the present research was to prepare solid-state compounds of alkali metal mandelates (i.e.…”