1-D calcium, 2-D zinc and 3-D manganese coordination polymers derived from pyrazine-2,3,5,6-tetracarboxylic acid

Three coordination polymers were synthesized from pyrazine-2,3,5,6-tetracarboxylic acid (H(4)pztc) in combination with calcium, zinc and manganese ions under hydrothermal conditions and their structures were determined by single crystal X-ray diffraction, powdered X-ray diffraction, Fourier transformed infrared spectroscopy, thermogravimetric and elemental analyses. Structure 1, {(Ca(H(2)pztc)(H2O)(3)) n, crystallizes as 1-D chains, with the partially deprotonated ligand in -O, N, O-coordination mode and with the Ca atoms in an uncommon nine coordinate environment. Structure 2, {Zn1(pztc)(H2O)(2)Zn-2(H2O)(4)} n, is an infinite, 2-D coordination network that contains two nonequivalent Zn atoms, each with octahedral geometry, and the fully deprotonated pztc(4) in bis-bridging chelating coordination mode. The stacked 2-D layers are stabilized by extensive inter-layer water-carboxylate hydrogen-bonding with an interlayer distance of 4.9 angstrom. Structure 3, {(Mn-2(pztc)(H2O)(2))} n, is a covalently bonded 3-D network containing two nonequivalent Mn atoms, each with octahedral geometry, and the fully deprotonated pztc(4) angstrom units. Structure 3 exhibits paramagnetic behavior at room temperature, and weak antiferromagnetic properties at very low temperature, which is consistent with their nearest Mn... Mn separation distance of 4.9 angstrom. (C) 2017 Elsevier B.V. All rights reserved.