Vanadiumoxo–aroylhydrazone complexes: Synthesis,structure and DFT calculations

The aroylhydrazone Schiff base ligands (E)-N’-(2-hydroxybenzylidene)benzohydrazide = H₂L¹, (E)-N’-(2-hydroxy-3-methoxybenzylidene)benzohydrazide = H₂L² and = (E)-N’-(5-bromo-2-hydroxybenzylidene)benzohydrazide = H₂L³ gave the vanadium(V)oxo-aroylhydrazone complexes [V^VOL¹(OCH₃)(OHCH₃] (1), [V^VOL²(OCH₃)(OHCH₃]·CH₃OH (2) and [V^VOL³(OCH₃)(OHCH₃] (3) on reaction with vanadium(IV) oxide acetylacetonate. The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV–Vis, ¹H NMR). Single crystal X-ray analysis was performed with 3. In methanol solution six-coordinated V^VOL³(OCH₃)(OHCH₃) was formed. V^IV was oxidized to V^v by aerial oxygen in the synthesis. In the VO₅N coordination sphere the alcohol oxygen lies trans to the oxo oxygen. The general V–O bond length order is oxo < methoxylato < phenoxidic < enolato < alcoholic. The complexes are mononuclear, but intermolecular O–H?N hydrogen bonding affords a zigzag chain. DFT calculations on complex 3 reproduced the geometric parameters, IR and UV–Vis spectroscopic data well in a reasonable range.     

Mixing Behavior of Conventional and Gemini Cationic Surfactants

Micellization behavior of cationic monomeric surfactants, hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), and dimeric (gemini) cationic surfactant pentamethylene‐1, 5‐bis(hexadecyldimethylammonium bromide) with formula C₁₆H₃₃(CH₃)₂N⁺(CH₂)₅N⁺(CH₃)₂C₁₆H₃₃ · 2Br^?, abbreviated as 16‐5‐16, in mixed states (binary) have been studied by conductivity. The micellar compositions, activities of the components, and their mutual interactions have been estimated from Rubingh's theory. The mixtures show nonideal behavior with favorable interactions.     

Role of surfactants in clouding phenomenon of imipramine hydrochloride

The clouding behavior of tricyclic antidepressant drug imipramine hydrochloride (IMP) in aqueous solution has been studied in presence of surfactants. A pH increase in the presence as well as in the absence of surfactants decreased the CP. Drug molecules become neutral at high pH and therefore head–head repulsion decreases which lead to CP decrease. Addition of non-ionic and cationic surfactants increased the CP whereas anionic surfactants showed a peaked profile. Effect of CTAB/TX-100 at different fixed drug concentrations showed that at all surfactant concentrations the CP value was higher for higher drug concentrations. However, variation of pH produced opposite effect: CP at all CTAB/TX-100 concentrations decreased with increasing pH. All results are interpreted in terms of increase in hydrophobicity or hydrophilicity of micelles on addition of surfactants.     

Thermal, structural and solution studies of a new lead(II) coordination polymer with η Pb-C interactions

A new Pb(II) one-dimensional coordination polymer {[Pb(PAA)₂]_n (1), PAA⁻ = phenylacetate} was synthesized by the reaction of Pb(CH₃COO)₂ · 3H₂O and ligand phenyl acetic acid. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The crystal structure of this compound consists of one-dimensional polymeric units of [Pb(PAA)₂] and the coordination number of Pb^II ions is six. The lead atoms have irregular coordination sphere containing stereo-chemically active lone pair and tetra-hapto (η⁴) interactions, thus attaining a total hapticity of 10 with environment C₄O₆Pb. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The results of studies of the stoichiometry and formation of complex 1 in methanol, ethanol and acetonitrile solutions were found to be in support of their solid state stoichiometry.     

TX-114+TBAB体系中非电解质对CP的影响

The effects of nonelectrolytes (ureas, amino acids, sugars) on the cloud point (CP) of nonionic surfactant Triton X-114 (TX-114) and tetra-n-butylammonium bromide (TBAB) system were studied. Ureas as well as thioureas increased the CP. Behaviors of amino acids depended upon their nature. Nonpolar and uncharged polar amino acids were less effective in changing the CP. However, tryptophan and phenylalanine increased the CP sharply. Acidic amino acid (aspartic acid) and sugars decreased the CP. The results were explained in terms of their effect on water structure. Amino acids got solubilized either in the micellar interior or in the bulk phase.     

Conductometric study of antidepressant drug-cationic surfactant mixed micelles in aqueous solution

Conductivity measurements have been carried out on aqueous solutions of two antidepressant drugs (nortriptyline hydrochloride and clomipramine hydrochloride) with four cationic surfactants (monomeric: cetyltrimethylammonium bromide, tetradecylammonium bromide; dimeric: 1,5-pentanediyl-alpha-omega-bis(hexadecyldimethylammonium bromide), 1,4-butanediyl-alpha,omega-bis(hexadecyldimethylammonium bromide) as well as with sodium chloride. Counterions from NaCl adsorb to the charged headgroup of the drug molecules and reduce the repulsion, hence cmc decreases. cmc values decreased with the addition of surfactants indicating mixed micelle formation. Experimental mole fraction of surfactants in micelle (X1) and their ideal values (X1 id) also support this explanation. Interaction parameter, beta, and excess free energy of micellization are negative suggesting synergism in mixed state. Activity coefficients are less than unity which means non-ideal mixing.     

Mixed Micellization and Interfacial Properties of Nonionic Surfactants with the Phenothiazine Drug Promazine Hydrochloride at 30 °C

In the present work, the micellization and adsorption behaviors of mixed systems containing an amphiphilic phenothiazine drug, promazine hydrochloride (PMZ) and nonionic surfactants in aqueous media at different mole fractions of nonionic surfactants (?? ₁) were investigated at 30?°C by surface tension measurements. The critical micelle concentrations of the mixtures fall between the values of the individual components, which indicates nonideal mixing. With Tritons the interactions are repulsive at low mole fractions. At high ?? ₁ the mixing becomes almost ideal. On the basis of regular solution theory, the micellar mole fractions of surfactants ( $X_{1}^{m}$ ) and interaction parameter (?? ^m ) were evaluated, while their interfacial mole fractions ( $X_{1}^{\sigma} $ ) and interaction parameters at the interface (?? ^?? ) were calculated using Rosen??s model. The results indicate that the surfactant??s contribution is greater than that of the drug both at the interface and in micelles. The short and rigid hydrophobic structure of the drug resists its participation in micelle formation more than in the monolayer, leading to $X_{1}^{m}<X_{1}^{\sigma}$ . Values of the surface excess (?? _max) and minimum area per head group (A _min) indicate attractive interactions. ?? _max increases and A _min decreases as the surfactant mole fraction increases.     

Cloud Point Phenomenon in Amphiphilic Drug Promethazine Hydrochloride+Electrolyte Systems

Herein we report clouding phenomenon occurring in amphiphilic drug promethazine hydrochloride (PMT) in the presence of electrolytes. The CP of 50 mM drug solution, prepared in 10 mM sodium phosphate buffer, was found to decrease with increasing pH due to deprotonation of drug molecules at high pH. Addition of inorganic salts (KF, KCl and KBr) to drug solutions at fixed pH (6.7) and drug concentration (50 mM) caused an increase in CP. The results have been discussed on the desorption/adsorption of counterions to the headgroups. Cations also increased the CP by affecting the water structure with their effectiveness being in the order: Li⁺<Na⁺<K⁺<NH₄ ⁺. In the presence of NaCl, increase in drug concentration increased the CP while increase in pH showed an opposite trend.