Spectral and in vitro antimicrobial properties of 2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid transition metal complexes

doi:10.1016/j.saa.2012.02.096

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Volume 93, July 2012, Pages 348-353

https://doi.org/10.1016/j.saa.2012.02.096 Get rights and content

Abstract

2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid (ADP) was complexed with acetates of Mn(II), Ni(II), Cu(II) and Zn(II). The structures of the ligand and its metal complexes were characterized by microanalysis, IR, NMR, UV–vis spectroscopy, magnetic susceptibility and TGA–DTA analyses. Octahedral and square planar geometries were suggested for the complexes in which the central metal ion coordinated with single bond O donors of ligand and acetate ions. Each ligand binds the metal using carboxylate oxygens. The ligand and complexes were evaluated for their antimicrobial activities against different species of pathogenic bacteria and fungi. The present novel pyrimidine containing complexes could constitute a new group of antibacterial and antifungal agents.

Graphical abstract

Octahedral and square planar geometries suggested for the transition metal complexes which bind the metal using carboxylate oxygens, resulted effective and selective antibacterial activity against bacterial and fungal strains.

Highlights

► We evaluate pyrimidine carboxylic acid based Mn(II), Ni(II), Cu(II), Zn(II) complex formation. ► Mn(II), Ni(II), Cu(II), Zn(II) metal ions coordinate with –O donors of ligand and acetate ions. ► Octahedral, Square planar geometries were suggested for the complexes. ► We investigate in vitro antibacterial and antifungal activities of pyrimidine metal complexes.

Introduction

The design of ligands is an important part of the synthetic repertoire of chemists. It gets via subtle control coordination of ligands on a metal centre [1], [2], [3]. Ligands contain significantly different chemical functionalities, such as hard and soft donors, often called hybrid ligands that find utility in molecular chemistry [4], [5], [6]. The incorporation of pyrimidine moieties in multifunctional ligands of increasing complexity makes for excellent complexation; have rarely been documented in pyrimidine chemistry [7]. The coordination chemistry of pyrimidine derived ligands is of relevance due to their biological implications.

In general, the three dimensional coordination of metal with ligands allows molecule to identify and interact with definite site of the target bio-molecules. Also, deviation in the oxidation state of transition metal is important feature for the bio-redox chemistry. The exchange processes of metal complexes permit the bio-molecule to interact and coordinate with metals centre [8]. The systematic study of metal based bio-active complex are summarized with (i) the active entire inert complex, (ii) the active entire reactive complex, (iii) a active fragment of the complex, (iv) the active metal ion or one of its bio-transformation products, (v) the enhancer metal after radiation, (vi) the radioactive metal, and (vii) responsible for the bio-activity via one or more of the ligands [9].

In recent years, a number of studies have reported on synthesis and structural analysis of metal complexes of pyrimidine containing bi- and tri-dentate ligands (ONO donors) having microbial activity, i.e., from donor ligands and complexes [10], [11]. Pyrimidines are endowed with a wide range of biological activities [12], [13], [14], [15]. The chelation of metal ions with pyrimidine ring enhances their activities due to easy availability of potential sites for binding. The complexed metal ions give information on their coordination properties and insights towards understanding the role of metal ions in the biological systems [17]. Herein, we expand on the scope of pyrimidine ligands, emphasize hybrid ligands, and explain the synergies obtained by combining these two facets of ligand design. The synthesis and physical properties of new Ni(II), Cu(II) and Zn(II) pyrimidine complexes were determined and the ligands investigated for potential microbial activities.

Section snippets

Materials

Benzaldehyde (Qualigen Fine Chemicals, 99.9%), ethylacetoacetate (Qualigen Fine Chemicals, 99%), urea (Qualigen Fine Chemicals, 99.8%), sodium hydroxide (Qualigen Fine Chemicals, 99%) and metal acetates (Qualigen Fine Chemicals, 99.9%) were used without further purification. All supplementary chemicals were of analytical grade and aqueous solutions were prepared with sterilized Milli-Q water (18.2 Ω/cm²).

Synthesis of ligand (E)-2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-caboxylic acid (ADP)

A mixture of 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic ethyl ester

IR spectra

The derivatives of carboxylic acids are characterized by several intense absorptions in infrared Spectrum. The most prominent ones are in carbonyl stretching region (1700–1725 cm⁻¹). Their exact position depends on the type of acid derivative. In addition to carbonyl stretching absorption, the acids themselves exhibit a strong, broad single bond OH stretching at a range from 3500 to 2500 cm⁻¹. Bands at 3231 and 1686 cm⁻¹ are characteristic of OH and C double bond O group at free ligand. The disappearance of 1686 cm⁻¹ band

Conclusion

MPMC, CPMC, NPMC and ZPMC complexes were synthesized and characterized. Analytical data, electronic spectra, magnetic susceptibility, IR and ¹H NMR have been revealed octahedral geometry of MPMC and square planar geometry of CPMC, NPMC and ZPMC, respectively. The low conductance values showed non-electrolytic behaviour of the complexes. Single crystals of the compounds could not be isolated; however, powder XRD data, spectroscopic and magnetic data enabled us to elucidate possible structures.

Acknowledgements

RPD gratefully acknowledges UGC, New Delhi for financial assistance under faculty improvement program of XI plan. The authors wish to express their gratitude to the Department of Pharmacy, Nagpur for IR spectroscopic analysis; the Sophisticated Analytical Instrumentation Facility (SAIF), Chandigarh for ¹H NMR spectroscopic analysis and mass analysis; and the University of Pune, Pune for ¹³C NMR spectroscopic data. We also wish to acknowledge Metallurgical and Materials Engg. Department, VNIT,

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Spectral and in vitro antimicrobial properties of 2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid transition metal complexes

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Materials

Synthesis of ligand (E)-2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-caboxylic acid (ADP)

IR spectra

Conclusion

Acknowledgements

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Spectrochim. Acta A: Mol. Biomol. Spectrosc.

Arch. Pharm.

J. Mol. Struct.

J. Inorg. Biochem.

Dalton Trans.

Dalton Trans.

Aust. J. Chem.

Arch. Pharm.