Spectral and Thermal Characterization and Antimicrobial Effect of 3-(5-H/Me/Cl/NO2-1H-benzimidazol-2-yl)- benzene-1,2-diols and Some Transition Metal Complexes

3-(5-H/Me/Cl/NO2-1H-benzimidazol-2-yl)-benzene-1,2-diols (HLX; X=1–4) ligands and HL3 complexes with Fe(NO3)3, Cu(NO3)2, Co(NO3)2, Zn(NO3)2 have been synthesized and characterized. The structural representations of the compounds are proposed on the basis of elemental analysis, molar conductivity,TGA, mass, FT-IR, 1H- and 13C-NMR spectrometry. All of the complexes are 1:1 electrolyte and have 1:1 M:L ratio except that of Cu(II).All of the complexes present fluorescence, the Co(II) complex showing the highest fluorescence intensity and the highest emission wavelength in comparison to the other complexes. Antibacterial activities of the ligands and the complexes formed by the HL3 ligand were evaluated using the disk diffusion method against six bacteria and Candida albicans. HL1,HL2,HL3 and [Cu(HL3)(L3 )(H2O)2](NO3)·H2O show considerable antimicrobial activity toward S. epidermidis and C. albicans.Keywords: Benzimidazole, benzene-1,2-diol, metal complexes, antimicrobial activity, fluorescence spectroscop

Spectral characterizations and antibacterial effect of 2-(5-R-1H-benzimidazol-2-YL)-4-methyl/bromo-phenols and some metal complexes

2-(5-H/Cl/Me/NO2-1H-benzimidazol-2-yl)-4-Me/Br-phenols (HL1–HL5) were synthesized. HL1 complexes with Cu(NO3)2, AgNO3, Zn(ClO4)2 and; HL4, HL5 complexes with Zn(ClO4)2 were prepared. The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magnetic moment, FT-IR, 1H- and 13C-NMR. Antibacterial activity of the ligands and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against nine bacteria, and the results were compared with penicillin–G and oxytetracycline. While HL1 ligand has considerable antibacterial activity on B. cereus only; it’s Ag(I) complex show antibacterial effect toward almost all the bacteria. It is highly interesting that HL5 and [Zn(HL5)(L5)]ClO4 exhibit considerable high antibacterial activity toward K. pneumoniae, B. cereus, S. epidermidis and B. subtilis. KEY WORDS: Benzimidazole, Phenol, Metal complexes, Antibacterial activity  Bull. Chem. Soc. Ethiop. 2010, 24(3), 391-400

Spectral characterization and antimicrobial activity of some transition metal complexes of 2-(5-nitro-1H-benzimidazol-2-yl)-4-bromophenol

ABSTRACT. MnCl2, FeCl3, Ru(DMSO)4Cl2, CoCl2, NiCl2, PdCl2, CuCl2, AgNO3, CdCl2 and HgCl2 complexes of 2-(5-nitro-1H-benzimidazol-2-yl)-4-bromophenol (HL) were synthesized and characterized. The structures of the complexes were confirmed on the basis of elemental analysis, TGA, molar conductivity and magnetic moment measurements, FT-IR, far-IR, FT-Raman, UV-Visible, NMR and fluorescence spectroscopy. According to the analytical and spectral data, the ligand acted as bidentate, via the imine nitrogen and the phenolate oxygen atoms towards to the metal ions except the Ag(I). The complexes were screened for in vitro antibacterial activities against S. aureus, S. epidermidis, E. coli, K. pneumoniae, P. aeruginosa, P. mirabilis and for antifungal activity against C. albicans. Ciprofloxacin and fluconazole were used as reference for antibacterial and antifungal activities of the complexes, respectively. In most cases, the complexes tested showed considerable activity on S. aureus especially, which is a Gram positive bacterium. In addition, the Hg(II) and Ag(I) complexes were found to have superior activity toward all of the microorganisms whereas the Pd(II) and Cd(II) complexes showed considerably antimicrobial effect on S. aureus and C. albicans selectively.               KEY WORDS: Benzimidazole, Bromophenol, Transition metal complexes, Antibacterial, Antifungal Bull. Chem. Soc. Ethiop. 2019, 33(3), 451-466.   DOI: https://dx.doi.org/10.4314/bcse.v33i3.

Synthesis, characterization and antimicrobial activity of some transition metal complexes of N-(5-chloro-2-hydroxyphenyl)-3-methoxy-salicylaldimine

Cr(III), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) complexes of N-(5-chloro-2-hydroxyphenyl)-3-methoxy-salicylaldimine (H2L), an ONO type tridentate ligand, were synthesized and characterized by elemental analysis, magnetic moment, molar conductivity, TGA, NMR, IR, UV-vis. and ESI-MS spectral techniques. All of the complexes except [Zn(L)(H2O)2] are paramagnetic. The CoCl2 gives a complex with 1:2 M:L ratio while the others form 1:1 non-ionic complexes with H2L. The ligand coordinated to the metal ions through the both OH oxygen and the azomethine nitrogen atoms acting tridentate behaviour. Octahedral geometry has been proposed for the Fe(II), Cr(III), Co(II), Ni(II) complexes considering the magnetic moment values and the electronic spectral data. The Zn(II) and Fe(III) complexes exhibit five coordination geometries and the Cu(II) complex is four-coordinated having acetato bridged dimeric structure. Antimicrobial activities of the compounds were determined against six bacteria and C. albicans as fungi. The Ni(II) and Co(II) complexes exhibit considerable selective activity on S. epidermidis and C. albicans whereas the ligand has no activity on the microorganisms. In addition, the Cr(III) complex shows antibacterial activity toward S. epidermidis and the Zn(II) complex has antifungal activity on C. albicans

Preparation, characterization and antibacterial effect of 2-methoxy-6-(5-H/Me/Cl/NO2-1H-benzimidazol-2-yl)phenols and some transition metal complexes

2-Methoxy-6-(5-H/methyl/chloro/nitro-1H-benzimidazol-2-yl)phenols (HLx; x = 1–4, respectively) ligands and HL1 complexes with Fe(NO3)3, Cu(NO3)2, AgNO3 and Zn(NO3)2 were synthesized and characterized. The structures of the compounds were confirmed based on elemental analysis, molar conductivity, magnetic moment, FT-IR, 1H- and 13C-NMR. The antibacterial activity and minimum inhibitory concentration (MIC) of the free ligands, their hydrochloride salts and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) and the dilution method, respectively, against 9 bacteria. HL1 and HL3, as well as the Cu(II) and Zn(II) complexes, showed antibacterial activity against Gram-positive bacteria

Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review

Nanofluids, i.e., well-dispersed (metallic) nanoparticles at low- volume fractions in liquids, may enhance the mixture's thermal conductivity, knf, over the base-fluid values. Thus, they are potentially useful for advanced cooling of micro-systems. Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed

Review of thermo-physical properties, wetting and heat transfer characteristics of nanofluids and their applicability in industrial quench heat treatment

The success of quenching process during industrial heat treatment mainly depends on the heat transfer characteristics of the quenching medium. In the case of quenching, the scope for redesigning the system or operational parameters for enhancing the heat transfer is very much limited and the emphasis should be on designing quench media with enhanced heat transfer characteristics. Recent studies on nanofluids have shown that these fluids offer improved wetting and heat transfer characteristics. Further water-based nanofluids are environment friendly as compared to mineral oil quench media. These potential advantages have led to the development of nanofluid-based quench media for heat treatment practices. In this article, thermo-physical properties, wetting and boiling heat transfer characteristics of nanofluids are reviewed and discussed. The unique thermal and heat transfer characteristics of nanofluids would be extremely useful for exploiting them as quench media for industrial heat treatment

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

n/

1,2-bis-[(5-H/methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and 1,4-bis[(5-H/methyl/chloro)-2-1H-benzimidazolyl]-1,2,3,4-butanetetraols complexes with AgNO3

The complexes of 1,2-Bis-[(5-H/methyl/chloro/nitro)-2-H-1-benzimidazolyl]-1,2-ethanediols (L1-L4) and 1,4-Bis-[(5-H/methyl/chloro)2-H-1-benzimidazolyl]-1,2,3,4-butanetetraols (L5-L7) with AgNO3 were synthesized and characterized using elemental analysis, molar conductivity, IR, H-1-NMR spectroscopy. All of the complexes have ionic character. Ag(I) complexes of L1-L4 have 1:1 M:L ratio, whereas those of L5-L7 have 2:1 M:L ratio. It was determined that the ligands are coordinated to Ag(1) ion through hydroxy oxygen atoms only