Synthesis, Characterization, Thermal Properties, and Antimicrobial Activities of 5-(Diethylamino)-2-(5-nitro-1H-benzimidazol-2-yl)phenol and Its Transition Metal Complexes
Synthesis and antimicrobial activities of new metal [Co(II), Cu(II), Ni(II), and Fe(II)] complexes from 5-(diethylamino)-2-(5-nitro-1H-benzimidazol-2-yl)phenol are described. The newly synthesized ligands were characterized by IR, 1H NMR, and LC-MS analysis, and metal-ligand complex formations were confirmed by using atomic absorption spectroscopy and elemental analysis. All complexes show significant in vitro antibacterial activities against E. coli and S. aureus strains and in vitro antifungal activity against C. albicans and A. niger strains by using serial dilution method. The antibacterial activities were expressed as the minimum inhibitory concentration (MIC) in μg/mL. Thermal properties and electrochemical behavior of novel transition metal complexes have been studied. 1. Introduction Imidazole/Benzimidazole and their derivatives are important class of organic compounds in coordination chemistry, photophysics, photochemistry, bioinorganic chemistry, and bioorganic chemistry [1–7]. 2-(2′-Hydroxyphenyl) benzimidazole (Hpbm) is an important benzimidazole-derived N, O-donor ligand. It’s Zn(II), Be(II), and Al(III) derivatives are photoluminescent [8]. Hydroxyl benzimidazole shows excited-state intramolecular transfer (ESIPT) properties due to acidic protons of phenol and imidazole nitrogen (tautomerism phenomenon). It has been reported that hydroxyl benzimidazole and benzoxazole behave as a structural mimic of DNA base pair for which tautomerism may be initiated at a definite time and position within duplex DNA [9]. Structurally similar natural product bis(benzoxazole) UK-1 has been reported to posses anticancer activity, and the metal-binding studies of UK-1 indicates that benzoxazole-like compound are capable of binding a variety of biologically important metal ions [10]. Benzimidazole derivatives exhibit significant activity against several viruses such as HIV, human cytomegalovirus (HCMV) [11, 12], herpes (HSV-1) [13], and influenza [14]. Benzimidazole derivatives are unique and broad-spectrum class of antirhino/enteroviral agents such as antihistaminic [15], antipyretic [16], antiulcerative [17], antihypertensive, antiviral [18, 19], antitumor [20–24], antihistaminic [25], and antiallergic [26] and are also efficient selective neuropeptide Y Y1 receptor antagonists [27]. Several derivatives are reported in literature for the synthesis of benzimidazole-metal complexes for fluorescent probes and bioorganic application, but antimicrobial activities of these classes of compounds have received little attention. In the literature, there are no reports
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