Synthesis and structural characterization of three zinc coordination complexes based on 3,5-dimethylpyrazole and carboxylate ligands

Abstract

Three new zinc(II) complexes, Zn(Hdmpz)₂(L1)₂ (1) (Hdmpz = 3,5-dimethylpyrazole, HL1 = 1-hydroxy-2-naphthoic acid), Zn₂(Hdmpz)₄(L2)₂ (2) (HL2 = maleic acid), and Zn₃(µ-dmpz)₄(Hdmpz)₂(L3) (3) (HL3 = phthalic acid), were prepared and structurally characterized by elemental analysis, infrared spectra, thermogravimetric analysis, and single-crystal X-ray diffraction analysis. X-ray crystallographic studies show that these complexes display mononuclear to coordination polymer structures with a tetrahedral arrangement around each zinc ion. Pyrazole is coordinated both in terminal and bridging in 3, whereas in 1 and 2 both are coordinated only monodentate. In 1 the carboxylates are monodentate, while in 2 and 3 both function as bridging bis-monodentate ligands. Rich intra- and inter-molecular weak interactions such as classical hydrogen bonds, C–H ··· O, CH₃ ··· O, C–H ··· π, and CH₃–π interactions are analyzed.

Keywords:

• Zinc(II)
• 3,5-Dimethylpyrazole
• Carboxylate ligands
• Crystal structure
• Non-bonding interaction

Acknowledgments

We gratefully acknowledge the financial support of the Education Office Foundation of Zhejiang Province (project No. Y201017321) and the financial support of the Zhejiang A & F University Pre-research Science Foundation (2009FK63).