A two-dimensional calcium (II) coordination polymer constructed from 2,2'-[terephthaloylbis(azanediyl)]diacetate: synthesis, structure and properties.

A new two-dimensional (2D) coordination polymer, namely, poly[[diaqua-[μ ₄ -2,2'-[terephthaloylbis(azanediyl)]diacetato]calcium(II)] monohydrate], {[Ca(C ₁₂ H ₁₀ N ₂ O ₆ )(H ₂ O) ₂ ]·H ₂ O} _n , (I), has been synthesized by the reaction of CaCl ₂ with 2,2'-[terephthaloylbis(azanediyl)]diacetic acid (H ₂ L). The title compound was structurally characterized by single-crystal X-ray diffraction analysis, elemental analysis and IR spectroscopy. In the crystal structure of (I), each Ca ^II cation binds to six carboxylate groups from four symmetry-related L ^2- dianions. The hexadentate L ^2- ligand links four symmetry-related calcium cations into a 2D layer-like structure, which can be simplified as a uninodal SP 2-periodic (3,6)III net with the point symbol (4 ³ ·6 ³ ). In the lattice, all layers pack in parallel arrays through weak interlayer hydrogen bonding and π-π interactions. The thermal stability and photoluminescence properties of (I) have been investigated. Thermogravimetric analysis reveals the different thermal stabilities of the two coordinated water molecules due to their different hydrogen-bonding interactions. The title coordination polymer exhibits an excitation-wavelength-dependent fluorescence in the solid state.