Synthesis, characterization, enzyme assay, DNA binding and antimicrobial activity of a monomeric complex of CuII with tinidazole: significance of the controlled formation of the nitro radical anion.

Reactions of Zn(II) ion with the ligand H 2 L (H 2 L = N,N′-dimethyl-N,N′bis(2-hydroxy-3-methoxy-5-methylbenzyl)ethylenediamine) in the presence of bridging coligands, chloride, thiocyanate/acetate, or azide/acetate yielded three new dinuclear complexes, [Zn 2 LCl 2 (H 2 O)] (1), [Zn 2 L(SCN) 2 (H 2 O)]•H 2 O (2), and [Zn 2 L(N 3 )-(CH 3 CO 2 )] (3), whereas Cd(II) ion formed three new tetranuclear complexes, [Cd 4 L 2 Cl 4 ]•H 2 O (4), [Cd 4 L 2 (SCN) 2 (CH 3 CO 2 ) 2 ]•2H 2 O (5), and [Cd 4 6) with the same ligand and coligands. The Zn(II) ions are pentacoordinated in all of its complexes 1−3 except one zinc center in complex 3, which is distorted tetrahedral. All four Cd(II) centers in each of its complexes 4 and 5 possess hexacoordinated distorted octahedral geometry. In complex 6, two Cd(II) centers are hexacoordinated, and the other two are hepta-coordinated. The deprotonated ligand (L 2− ) is hexa-/hepta-dentate in the Zn(II) complexes, 1−3 but octa-dentate in the Cd II complexes 4−6. The differences in nuclearity and in the coordination modes of the ligands in the resulting complexes have been explained considering the preference for different coordination numbers of these two metal ions. H 2 L exhibited highly specific, sensitive, and selective turn-on fluorescence sensing properties for the Zn 2+ ion. The mechanism of fluorescence enhancement, host guest binding stoichiometry, and binding constant has also been calculated. The detection limit of Zn 2+ ion is 7.69 nM, with the binding constant K = 1.508 × 10 10 M −2 . The produced Zn(II) complexes sense nitroaromatic explosives in solution via a turn-off florescence response. The solution phase sensing mechanism has been studied thoroughly. Remarkably, the limit of detection of picric acid at the ppt level (912, 910, and 896 ppt for complexes 1, 2, and 3 respectively) having a strong quenching constant (K SV ) is 8.063 × 10 4 , 7.987 × 10 4 , and 8.51 × 10 4 M −1 for complex 1, 2, and 3 respectively.

Three Zn(II) complexes, [Zn 2 (HL) 2 (NO 3 ) 2 ]•H 2 O (1), [(Zn 4 L 2 )-(μ 3 -OH) 2 ](NO 3 ) 2 •0.5H 2 O (2), and [(Zn 6 L 2 )(o-van) 2 (μ 3 -OCH 3 ) 2 (μ 3 -OH) 2 ]-(NO 3 ) 2 (3), have been synthesized by exploiting the flexidentate nature of a multidentate Schiff base ligand, H 2 L (N,N′-bis(3-methoxysalicylidene)diethylenetriamine), by changing the reaction conditions and stoichiometry of the reactants. All three complexes are highly fluorescent in solution as well as in solid and have been used as luminescence sensors toward nitrophenol explosives in both the media. In aqueous/methanol medium, these complexes show very high selectivity and sensitivity with detection limit in ppb (2.03) or nM level (8.89 nM) for picric acid. The yellow color of all three Zn(II) complexes changes to red on mixing with small amount (∼5%) of picric acid in solid state, revealing the potential of these complexes for practical use in naked eye detection of 2,4,6trinitrophenol (TNP) or picric acid in ambient light. In order to identify the host− guest interactions between Zn(II) complex and TNP, single crystals of the adduct of TNP with Zn(II) complex, [Zn 2 (HL) 2 (H 2 O) 2 ][C 6 H 2 N 3 O 7 ] 2 (4), were grown. Its X-ray crystal structure reveals that two picrate ions are attached to a dinuclear host with the help of H-bonding and π•••π interactions, throwing light into the quenching mechanism and selectivity of detection.

Four new end-on pseudohalide-bridged dinuclear copper(II) complexes, [Cu2(L(1))2(N3)2]·DMF (1), [Cu2(L(2))2(N3)2] (2), [Cu2(L(3))2(NCS)2] (3), and [Cu2(L(4))2(N3)2] (4) {where HL(1), HL(2), HL(3), and HL(4) are tridentate N2O donor Schiff bases}, are synthesized and characterized. Complexes 1, 2, and 3 possess π···π stacking interactions, while in addition hydrogen-bonding interactions are present in 1 and 3. However, by contrast, complex 4 contains neither type of interaction. Field-induced long-range ferromagnetic ordering beyond 0.9 T is observed in complexes 1 and 2 due to π···π stacking interactions, while ferroelectric ordering is observed in complexes 1 and 3 due to hydrogen-bonding interactions. Most interestingly, complex 1, which contains both π···π stacking and hydrogen-bonding interactions, shows multiferroic behavior as a result of coupling between the dielectric and magnetic fields with 8% change in the magneto-dielectric effect at room temperature. We believe that from this study will emerge a new class of multiferroic materials.

The present paper focuses on the analysis of thermophoretic hydromagnetic slip flow over a permeable flat plate with convective surface heat flux at the boundary and temperature dependent fluid properties in the presence of non-uniform heat source/sink. The transverse magnetic field is assumed to be a function of the distance from the origin. Also it is assumed that the liquid viscosity and the thermal conductivity vary as an inverse function and a linear function of temperature, respectively. The shooting method is employed to yield the numerical solutions for the model. Results show that the thermal boundary layer thickness reduces with increase of surface convection parameter whereas reverse effect occurs for viscosity parameter. It is also observed that the thermophoretic parameter decreases the concentration distribution across the boundary layer. ª 2014 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/3.0/).

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