Three Er(III) coordination polymers: Synthesis, crystal structures and photophysical properties

Three Er(III) coordination complexes: {[Er-2(btec)(1.5)(H2O)(4)] center dot 2H(2)O}(n) (1), [Er-4(NO2-C6H4COO)(12)(H2O)(10)] center dot 2H(2)O (2), [Er(C9H7O2)(3)](n) (3) have been synthesized with the 1,2,4,5-benzenetetracarboxylic acid, p-nitro benzoic acid and cinnamate as the ligand by the hydrothermal method. The structures were determined by single-crystal X-ray diffraction. Structure analysis indicates that the complex 1 is a 3D structural polymer with the constructed unit of {[Er-2(btec)(1.5)(H2O)(4)] center dot 2H(2)O}, in which four Er3+ belong to two kinds of crystallographic types. There are three different coordination fashions of benzenetetracarboxylic acid radical in the unit of molecule. The complex 2 is a four nuclear molecule. There are four Er3+ ions in the same molecule, which belong to two kinds of crystallographic types. A lot of hydrogen bonds were formed in the crystal of complex 2. The complex 3 is a 1D coordination polymer. The fluorescence spectra, IR, and UV-Vis-NIR of the complexes were measured and analyzed. The NIR luminescence of three coordination polymers were compared. CCDC: 826590, 1; 826591, 2; 826952, 3.