Structure of a novel polynuclear europium compound with N-phosphonomethylglycine: heptaaquaperchloratodi-μ4-N-phosphonomethylglycine-dieuropium(III) triperchlorate monohydrate, [Eu2(HO3PCH2NH2CH2CO2)2(H2O)7(ClO4)]·3ClO4·H2O

Abstract

The solid-state structure of the europium(III) complex with N-phosphonomethylglycine (PMG) has been obtained from aqueous solution, at pH ca. 1.6, where a 1:1 M:L molar ratio has been kept. The crystal structure of the [Eu₂(HO₃PCH₂NH₂CH₂CO₂)₂(H₂O)₇(ClO₄)]·3ClO₄·H₂O compound has been determined by single-crystal X-ray diffraction. In the structure of the title compound a two-dimensional polymer is formed, with an unexpected architecture. The oxygen atom of one of four perchlorate groups is engaged in the coordination besides that of the PMG groups. The glyphosate molecules are present as zwitterions. The polymeric chains are composed of two types of dimeric subunits. The first one is created by simple and chelating carboxyl bridges, and the second by phosphonate groups; in the latter type the dimeric unit coordination of metal ions is completed by two oxygen atoms of two perchlorate groups. In the first subunit four, and in the second subunit three water molecules are coordinated by each europium atom. The eighth water molecule and three of four perchlorate groups are outside the metal coordination. Therefore, two non-equivalent metal sites, eight- and nine-fold coordinated, exist in the structure. The structure is stabilized by an extended network of hydrogen bonds. The conformations of the two PMG molecules are quite different.