Two isomorphous 3-D lanthanide oxalatophosphonate frameworks based on glyphosate: Syntheses, crystal structures, and luminescence properties

Abstract

Two new 3-D isomorphous lanthanide(iii) compounds [Eu2(H 2L)2(C2O4)2]·2. 51H2O (1) and [Tb2(H2L)2(C 2O4)2]·2.46H2O (2, H 3L = glyphosate), based on glyphosate and oxalate have been successfully synthesized under hydrothermal conditions, and structurally characterized. In the two compounds, tetra-connected glyphosate ligands are coordinated to Ln3+, resulting in the formation of 1-D {Ln 2(H2L)2}n double chains along the c direction. Each of the chains is connected to its four neighbors via the O atoms of phosphates of H2L- ligands, resulting in a 3-D (4, 6)-connected framework with 43·58·6 3·7 topology, which possesses 1-D channels with oxalates and lattice water molecules as troglodytes. The oxalates are stabilized via chelating Ln3+ in the form of 1-D Ln-C2O42- zigzag chains along the c direction. To the best of our knowledge, compounds 1 and 2 represent the first single-crystal structures of lanthanide(iii)-glyphosate compounds incorporating second ligands. The luminescent properties of compounds 1 and 2 have been investigated at room temperature. The energy gaps between the triplet excited state of oxalic acid and the lowest excited resonance levels of Eu3+ (5D 0) and Tb3+ (5D4) are 7270 cm -1 and 4070 cm-1, respectively, indicating that oxalate is more suitable for the sensitization of Tb3+ luminescence than Eu3+ luminescence. © 2011 The Royal Society of Chemistry.