Syntheses and crystal structures of the metal complexes based on pyrazolecarboxylic acid ligands

Abstract

This paper aims at introducing five new metal complexes, Co(HL 1) 2(H 2O) 2 ( 1), {[Cu(HL 1) 2] · (H 2O)} n ( 2), {[Zn(HL 2)(H 2O) 3] · 2H 2O} n ( 3), {[Co(HL 2)(H 2O) 3] · 2H 2O} n ( 4) and [K(H 2L 2)] n ( 5), (in which H 2L 1 is 3-methyl-5-pyrazolecarboxylic acid and H 3L 2 is 3,5-pyrazoledicarboxylic acid, respectively), which have been synthesized under hydrothermal conditions or by using diffusion methods. Their molecular structures have been characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction analyses. The X-ray analyses reveal that complex 1 has a mononuclear structure, which is further assembled to a three-dimensional (3-D) framework through intermolecular hydrogen bonds; complex 2 is a 1-D coordinated polymer, which is further assembled to a 2-D layer through intermolecular hydrogen bonds and π–π interactions; both complexes 3 and 4 possess similar 1-D chain structures, and the adjacent chains are further linked by hydrogen bonds to form 2-D supramolecular networks; complex 5 exhibits a 3-D structure, in which, the metal–metal weak interaction, K–K, plays an important role.