A new family of Er(III) complexes: from chains to nanotubes

The reaction, in a gel medium, of Er(III) chloride with the trisodium salt of benzene-1,3,5-tricarboxylic acid (H3TMA) yielded three different kind of crystals. All three have been structurally characterized. ErTMA(H2O)5·3.5H2O (1) crystallizes in C2/c with a=14.7396(15), b=16.9874(15), c=14.4591(14) Å, β=118.754(9)° and Z=8. Its crystal structure has been reported elsewhere already. It consists of juxtaposed criss–cross chains. ErTMA(H2O)3·1.5H2O (2) has been found to be isostructural to the Gd(III) complex reported already. It crystallizes in C2/c with a=20.452(2), b=9.973(1), c=15.251(1) Å, β=125.68° and Z=8. Its structure consists of parallel double-sheet networks based on honeycomb-like motifs. Er3TMA3(H2O)8·4H2O (3) crystallizes in P1̄ with a=9.988(2), b=15.656(3), c=19.698(3) Å, α=110.77(2), β=100.63(2), γ=100.58(2)° and Z=2. Its structure consists of parallel tube like layers based on the honeycomb-like molecular motifs already observed in 2. The crystal structure is reported herein. A predominant phase diagram has been established versus the concentrations of the gel medium and of the solutions. Heating one of them progressively liberates water molecules, which finally leads to ErTMA (4), which can reversibly bind water reforming 1.