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

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

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

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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

Fe(III), Co(II, Ni(II), Cu(II) complexes of 1,2-bis-(2-1H-benzimidazolyl)-1,2-ethanediol and 1,4-bis-(2-1H-benzimidazolyl)-1,2,3,4-butanetetraol

The complexes of 1,2-bis(2-benzimidazolyl)-1,2-ethanediol (L1) and 1,4-bis-(2-benzimidazolyl)-1,2,3,4-butanetetraol (L2) with FeCl3, CoCl2, NiCl2, CuCl2 were isolated and characterized by elemental analysis, IR and UV-vis, spectra, magnetic susceptibility and molar conductivity. The ionic and paramagnetic complexes have a 1:1 M:L ratio in general. Fe(L1)Cl-3 shows high spin property due to the nitrogen atom coordination, while Fe(L2)Cl-3 is low-spin because of the OH oxygen coordination. The magnetic moments of Ni(L1)Cl-2 and the L2 complexes are below the expected values because of M-M interaction

1,2-Bis-[(5-methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and their PdCl2 complexes

1,2-Bis-[(5-methyl)-2-1H-benzimidazolyl]- (L-1), 1,2-bis-[(5-chloro)-2-1H-benzimidazolyl]- (L-2), 1,2-bis-[(5-nitro)-2-1H-benzimidazolyl]-1,2-ethanediol (L-3) and their PdCl2 complexes were synthesized and characterized by elemental analysis, molar conductivity, i.r. and H-1-n.m.r. spectra. The benzene ring substituents lead to a decrease in melting point. The methyl group reduces the solubility and the acidity of L-1 and Pd(L-1)Cl-2, whereas the Cl and NO2 groups increase the solubility and the acidity of L-2, L-3, Pd(L-2)Cl-2 and Pd(L-3)Cl-2. In Pd(L-1)Cl-2 and Pd(L-2)Cl-2 complexes, the ligands act as a bidentate through two nitrogen atoms. In Pd(L-3)Cl-2, ligand coordination occurs through one OH group oxygen atom and one of the benzimidazole nitrogen atoms

A new cloud-point preconcentration approach for the spectrophotometric determination of p-aminophenol in the presence of paracetamol with 2-(2-hydroxyphenyl)-1H-benzimidazole as a coupling reagent

A preconcentration and determination method for trace p-aminophenol (PAP) in paracetamol was developed. Cloud-point extraction (CPE) was employed for the preconcentration of p-aminophenol prior to spectrophotometric determination using Triton X-100 (TX-100) as an extractant. The determination is based on the reaction of p-aminophenol with 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) at room temperature in the presence of an oxidant to produce indophenol blue dye. The dye formed is subsequently entrapped in micelles of the surfactant TX-100. The surfactant-rich phase shows maximum absorbance at 650 nm and the proposed method is linear in the 0.1 to 5.0 mg mL(-1) concentration range. By preconcentrating 10 mL of the sample solution, a detection limit as low as 55 ng/mL was obtained after a single-step extraction and the experimental concentration factor achieved for this method was found to be 10. The stoichiometric composition of the dye is 1: 1 (PAP: HPBI). Some parameters such as HPBI, KIO4, Na2CO3, and TX-100 concentration, extraction temperature, incubation, and centrifugation time, and the sample volume were investigated in detail. The established procedure was successfully adopted for the determination of p-aminophenol in the presence of paracetamol in various pharmaceutical preparations

Experimental study on thermal conductivity and viscosity of water-based nanofluids

Thermal conductivity and viscosity of deionized water-based TiO 2, SiO2, and Al2O3 nanofluids were investigated for various volume fractions of nanoparticles content and at different temperatures. A 3? technique was developed for measuring thermal conductivity of nanofluids. The theory and the experimental setup of the 3? measuring system is explained; a conductive wire is used as both heater and sensor in this system. At first, the system is calibrated using water with known thermophysical properties. Measured results showed that the effective thermal conductivity of nanofluids increases as the concentration of the particles increases but not anomalously as indicated in the majority of the literature and this enhancement is very close to the Hamilton-Crosser model; also this increase is independent of the temperature. The effective viscosities of these nanofluids increase by the increasing particle concentration and decrease with an increase in temperature, and cannot be predicted by the Einstein model. © 2010 Begell House, Inc