Synthesis and Structural Characterization of Four Zinc Complexes Containing 3,5‐Dimethylpyrazole and Carboxylate Ligands

Abstract

AbstractFour new zinc(II) complexes Zn2(μ‐dmpz)2(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5‐dimethylpyrazole, HL1 = 2‐methyl‐2‐phenoxypropanoic acid), Zn(Hdmpz)2(L2)2 (2) [HL2 = 2‐hydroxy‐5‐(phenyldiazenyl)benzoic acid], Zn2(μ‐dmpz)2(Hdmpz)2(L3)2 (3) [HL3 = 3,4‐(methylenedioxy)benzoic acid], and Zn2(μ‐dmpz)2(Hdmpz)2(L4)2 (4) [HL4 = 3‐(4‐methoxyphenyl)acrylic acid] were prepared and structurally characterized by different techniques including elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction analysis. The X‐ray studies suggested that all these complexes except compound 2 are centrosymmetric dinuclear complexes with a tetrahedral arrangement around each zinc ion, whereas compound 2 is a mononuclear complex. The pyrazole ligand is coordinated in both terminal as well as a bridging fashion in the dinuclear moiety, whereas the pyrazole ligand in compound 2 is coordinated only in monodentate terminal fashion with its neutral nitrogen group. In all four complexes the carboxylate functions behave as monodentate ligands. All complexes show intramolecular hydrogen bonding of N–H···O between N–H of pyrazole and nonbonded oxygen atom of carboxylate. Furthermore, rich intermolecular weak interactions such as classical hydrogen bonds, C–H···O, C–H···N, C–H···π, and CH3–π interactions exist and complexes 1–4 display a set of 3D superamolecular frameworks. In addition, the four compounds are thermally stable below 150 °C.