Hydrothermal synthesis and characterisation of alkaline-earth metal salts of benzene-1,3,5-tricarboxylic acid

Abstract

The reaction of M^II acetate (M = Sr or Ba) with benzene-1,3,5-tricarboxylic acid (H₃btc) yielded crystals of formulae [M(Hbtc)(H₂O)₂]·0.5H₂O. These compounds are isostructural as shown by X-ray single-crystal analysis and by X-ray powder diffraction patterns. The structures consist of alternating layers of parallel Hbtc anions and cations stacked along the c axis. The metal ions are co-ordinated by two bidentate carboxylate groups, three monodentate carboxylate groups and two water molecules giving an overall co-ordination number of nine. Heating liberates 2.5 water molecules per formulae unit to give M(Hbtc) which can reversibly bind water reforming [M(Hbtc)(H₂O)₂]·0.5H₂O.