Synthesis and structure of complex nitrates of some Ln(III) and of Am(III) with 1,10-phenanthroline-2,9-dicarboxylic acid anions

Abstract

The structures of Ln(III) and Am(III) complexes with anions of 1,10-phenanthroline-2,9-dicarboxylic acid (H2PDA) of the compositions [Pr(PDA)(NO3)(H2O)3]·H2O (I), [Ln(PDA)(NO3)(H2O)2]·H2O [where Ln = Nd (IIa), Sm (IIb), Gd (IIc)], [Am(PDA)(NO3)(H2O)2]·H2O (III), and [Nd(PDA)(NO3)· (H2O)] (IV), containing in the coordination sphere of the metal atom three different ligands, PDA2−, nitrate ions, and water molecules, were studied. The structures of compounds I–III prepared at room temperature differ essentially from that of compound IV isolated at ∼200°C. Compounds I–III have a chain structure, with compounds II and III being isostructural and differing from compound I. The structure of compounds I–III isolated at room temperature is based on zigzag cationic chains Ln3+,Am3+-PDA2− in which the anions have the coordination capacity of 5 and act as N,O-donor chelating ligands and as bridging monodentate ligands. Analysis of the hydrogen bonds shows that they influence the configuration of the cationic chains Ln3+,Am3+-PDA2− and are responsible for the difference between the cationic chain in I and those in II and III. The coordination polyhedron (CP) of the Pr atom in I is characterized by CN 10. The CP of Ln3+ and Am3+ in II and III can be described as a distorted tricapped trigonal prism (CN 9). Elimination of one water molecule in the high-temperature modification of IV is accompanied by incorporation of the oxygen atom of the PDA2− anion from the adjacent chain. As a result, the cationic chains become combined in cationic layers, and the coordination capacity of the ligand increases to 6. The CP of the Nd atom has nine vertices.