Synthesis, characterization, and antimicrobial activity of some new 2-diazo-benzimidazole derivatives and their Ni(II),

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Med Chem Res (2013) 22:2266–2272 DOI 10.1007/s00044-012-0220-x

ORIGINAL RESEARCH

Synthesis, characterization, and antimicrobial activity of some new 2-diazo-benzimidazole derivatives and their Ni(II), Cu(II), and Ag(I) complexes Yellajyosula Lakshmi Narasimha Murthy Guduru Durga • Anjali Jha



Received: 4 May 2012 / Accepted: 24 August 2012 / Published online: 18 October 2012 Ó Springer Science+Business Media, LLC 2012

Abstract 2-Aminobenzimidazole was diazotized and made to react with active methylene compounds viz: ethylcyanoacetate and malanonitrile. The ligands [IIIa and IIIb] were isolated, characterized, and then condensed with Ni(II) chloride, Cu(II) chloride, and Ag(I) nitrate. The ligands and complexes were characterized by elemental analysis, IR, 1H NMR, ESR, UV–Visible spectral techniques, and along with thermal studies. The antimicrobial activity of the ligands [IIIa (C12H11N5O2) and IIIb (C10H6N6)] and their metal complexes [IVa–IVf] against bacterial strains and fungal strains were investigated. The antimicrobial activity of the above metals and the ligands were discussed. Keywords 2-Aminobenzimidazole  Dinucleating ligands  Nickel(II), copper(II), silver(I) complexes  Antimicrobial activity

Introduction Benzimidazole is a heterocyclic aromatic organic compound. It is an important pharmacophore and a privileged This article is a part of PhD Thesis work of Guduru Durga. Y. L. N. Murthy (&) Organic Research Labs, Department of Organic Chemistry, Andhra University, Visakhapatnam, India e-mail: [email protected] G. Durga Department of Chemistry, St. Joseph’s College for Women, Visakhapatnam, India A. Jha Department of Chemistry, GITAM University, Visakhapatnam, India

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structure in medicinal chemistry. The most prominent benzimidazole compound in nature is N-ribosyl-dimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12 (Barker et al., 1960). Various types of benzimidazole ligands have been described in the literature for their chemotherapeutic importance (Boruah and Skibo, 1994; Kubo et al., 1993). These compounds have different activities as they can act as bactericides, fungicides, and anticarcinogens (Ku¨c¸u¨kbay et al., 2003; Garuti et al., 1999; Gata et al., 2003). This ring system is present in numerous antiparasitic, antihelmintic, and anti-inflammatory drugs (El-masry et al., 2000). Hunger et al. (1960) reported that 1-(dialkyl amino alkyl)benzimidazole ligands, and particularly the 2-amino ligands (Hunger et al., 1961) showed potent analgesic activity. Earlier work has shown that some drugs exhibit increased activity when administered as metal chelates rather than as organic compounds (Mahindru et al., 1983). Several metal complexes containing b-diketones, b-ketamines, and other related ligands have been reported by different group of workers (Jayakumar and Natarajan, 1992; Prasanna et al., 2001). After the discovery of the chemical nuclease activity of transition metal complexes in the 1980s (Sigman et al., 1979; Downey et al., 1980), many scientists stu