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The effect of cosolvent (ethane-1,2-diol and dimethyl sulfoxide) on the self-assembly of three surfactants, N,N,N-trimethyl-1-dodecanaminium bromide (DTAB), sodium [dodecanoyl(methyl)amino]acetate (SDDS), and polyoxyethylene (20) sorbitan monolaurate (Tween-20) in aqueous solution have been investigated by conductometric, tensiometric, and viscometric techniques at 298 K. The main focus was on the effect of solvent on critical micelle concentration (cmc), free energy contribution to micellization (ΔG m 0 ), tail transfer Gibbs free energy (ΔG trans 0 ), Gibbs adsorption energy (ΔG ads 0 ), and some micellar interfacial parameters, for example, Gibbs surface excess (Γ max ), minimum area per surfactant molecule (A min ), surface pressure (Π cmc ), and pC 20 (= −log(C 20 ), where C 20 is the surfactant molar concentration required to reduce the surface tension of mixed solvent by 20 mN m −1 ). With increasing concentration of cosolvent in the binary mixture, the cohesive force decreases, and surfactant molecules are more soluble in mixed solvent. As a result, micellization process becomes less favorable, and an increase in cmc was obtained. Steady state fluorescence spectroscopy was used to determine the aggregation number (N agg ) of the surfactants in organic solvent−water binary mixture and also the micropolarity of the mixed solvent. It was observed that N agg decreased with the increase of organic solvent concentration. The micropolarity of the mixed solvent and packing parameter (P) were also determined.

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A vanadium(V) complex with the formula [Et3NH][V(V)O2(sox-pydx)] with a new tridentate ligand 2-[2-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methylene]hydrazinyl]-2-oxoacetamide (soxH-pydxH), obtained by condensation of oxamohydrazide and pyridoxal (one of the forms of vitamin B6), has been synthesized. The compound was characterized by various analytical and spectroscopic methods, and its structure was determined by single-crystal X-ray diffraction technique. Density functional theory (DFT) and time-dependent DFT calculations were used to understand the electronic structure of the complex and nature of the electronic transitions observed in UV-vis spectra. In the complex, vanadium(V) is found to be pentacoordinated with two oxido ligands and a bianionic tridentate ONO-donor ligand. The vanadium center has square-pyramidal geometry with an axial oxido ligand, and the equatorial positions are occupied by another oxido ligand and a phenolato oxygen, an imine nitrogen, and a deprotonated amide oxygen of the hydrazone ligand. A DFT-optimized structure of the complex shows very similar metrical parameters as determined by X-ray crystallography. The O4N coordination environment of vanadium and the hydrogen-bonding abilities of the pendant amide moiety have a strong resemblance with the vanadium center in bromoperoxidase enzyme. Bromination experiments using H2O2 as the oxidizing agent, with model substrate phenol red, and the vanadium complex as a catalyst show a remarkably high value of kcat equal to 26,340 h(-1). The vanadium compound also efficiently catalyzes bromination of phenol and salicylaldehyde as well as oxidation of benzene to phenol by H2O2.

Interactions of the cationic gemini surfactant, 14-4-14 with anionic polymer, NaCMC.

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The interactions between myoglobin, a monomeric water soluble heme protein, and cationic gemini surfactants 14-3-14, 14-4-14, 14-5-14 have been studied in phosphate buffer at pH 7.4 using different techniques such as surface tension, UV-visible spectroscopy, fluorescence spectroscopy and circular dichroism. Myoglobin is a surface active protein and it is bound with surfactant molecules. The spin states of the heme group of myoglobin change depending on the concentration of surfactant. The unfolding process of protein in the presence of surfactant is observed from fluorescence spectra. With increasing surfactant concentration, a-helicity of myoglobin decreases with the appearance of b-sheet and random coil. The extent of interaction of myoglobin with gemini surfactant increases with increasing spacer length. Fig. 4 a CD spectra of 0.0025 g % myoglobin solution at increasing concentration of 14-5-14 in phosphate buffer at pH 7.4, b CD spectra of 0.0025 g % myoglobin solution in presence of different gemini surfactants at 0.168 mM concentration in phosphate buffer at pH 7.4 J Surfact Deterg (2015) 18:471-476 475

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