A novel coordination polymer of Cd(II) based on 2-mercaptopyrimidine: Sonochemical synthesis, characterization, and antibacterial properties

Highlights

• The complex crystallizes in the tetragonal system, space group P4₂/nnm.

• Nanoparticles was also synthetized by sonochemical process.

• Synthesized nanoparticle has stronger antibacterial activity than the complex.

Abstract

A new complex of [Cd(2-mpym)₄(H₂O)₂](NO₃)₂ (1) was obtained from the reaction of Cd(NO₃)₂.4H₂O with 2-mercaptopyrimidine in methanol solution. This complex and its nano form were characterized by elemental analysis, UV–Vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR), luminescence measurements, thermal analysis (TG-DTA), and single X-ray diffraction. X-ray structure determination revealed two types of cadmium metal ions: hexagonally coordinated cadmium with two oxygen atom of a water molecule, and four sulfur atom of 2-mpym ligand; and eight-coordinated cadmium with four sulfur atoms and four nitrogen atoms of the pyrimidine ring of 2-mpym ligand. The antibacterial properties of this compound were investigated in vitro against standard Gram-positive and Gram-negative bacterial strains. The results of antibacterial tests showed that the complex 1 was a stronger antibacterial agent than the free ligand.

In this study, 1 was also synthetized in a form of nanoparticles by sonochemical process. The nanoparticles of the size about 80 nm were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis absorption spectra, and Fourier transform infrared spectroscopy (FT-IR). It was found that preparing the complex 1 as nanoparticles enhanced its antibacterial effect.

Introduction

Chelating ligands containing sulfur and nitrogen are important compounds in structural chemistry of metal complexes with a strong electron-donating property. The presence of nitrogen and sulfur decreases solubility of the complexes and allows the complex to be isolated from the solution [1]. Ambidentate aromatic ligands including sulfur and nitrogen take part in a variety of reactions [[2], [3], [4]]. Many important drugs are related to analogues of pyridine, pyrimidine and their sulfur-containing derivatives [[5], [6], [7]]. Thio derivatives of pyrimidine, mercaptopyrimidines, exhibit remarkable antiviral, antibacterial, antitumor and antithyroidal activities [[8], [9], [10], [11], [12]]. These heterocyclic compounds are involved in a tautomeric equilibrium of the thiol/thione (pym-SH/Pym-NH) kind, which has important biological consequences [[13], [14], [15], [16]].

In this work, we reported the synthesis, characterization and crystal structure of a new cadmium (II) complex with 2-mercaptopyrimidine ligand. As a representative of mercaptopyrimidines, this ligand exhibits a rich coordination chemistry [17], and its tautomerism influences the coordination ability and biological activities of the corresponding coordination compounds [[18], [19], [20]]. We tested antibacterial properties of the complex prepared in a form of single crystals as well as nanoparticles. For preparation of the nanomaterial, we used sonochemistry, which provides the targeted compounds at mild temperatures, without surfactants, and usually yields small particles [[21], [22], [23], [24], [25], [26]]. The ultrasonic irradiation may accelerate or initialize new reactions which cannot occur under normal conditions [[27], [28], [29]].