The Crystalline Molecular Complex between Cationic Surfactant and Some Additive Systems: II. Complex Formation with Basic Substances as Additives

Solution Behavior of Crystalline Surfactant Molecular Complexes: Electric Conductivity Measurements of Aqueous Solutions of Molecular Complexes between Cationic Surfactant and Aromatic Additive Systems

Wormlike micelles of CTAB with phenols and with the corresponding phenolate derivatives - When hydrophobicity and charge drive the coacervation

The adsolubilization of 2-naphthol by binary mixtures of cationic and nonionic surfactants on silica was investigated. Two cationic surfactants used were hexadecyltrimethylammonium bromide (HTAB) and 1,2-bis(dodecyldimethylammonio)ethane dibromides (2RenQ), and a nonionic surfactant used was hexaoxyethylenedecyl ether (C10E6). In the single surfactant systems, adsolubilization of 2-naphthol for HTAB and 2RenQ was very similar and was greater than that for C10E6. In the HTAB/C10E6 system the adsolubilization of 2-naphthol was enhanced by surfactant mixtures of HTAB and C10E6 compared to those of single systems. However, in the 2RenQ/C10E6 system the adsolubilization of 2-naphthol by surfactant mixtures of 2RenQ and C10E6 was rather smaller than that of 2RenQ alone but still larger than that of C10E6. It is found that the adsorbed layers of surfactant mixtures formed from different surfactant structures exhibit different adsolubilization behaviors of 2-naphthol, and the alkyl chain length of the surfactants is an important factor to correlate with the adsolubilization of 2-naphthol.

Noncovalent interactions and copper(II) coordination in systems containing l-aspartic acid and triamines

Effect of cationic micelles on the fluorescence of the zirconium—morin complex

Trophoblastic p53 is stabilised by a cis– trans isomerisation necessary for the formation of high molecular weight complexes involving the N-terminus of p53

The directing effect of coordinating ligands in the formation of uranium molecular complexes has been well established, but the role of counterions in metal-ligand interactions remains ambiguous and requires further investigation. In this work, we describe the targeted isolation, through the choice of alkali-metal ions, of a family of tetravalent uranium sulfates, showing the influence of the overall topology and, unexpectedly, the UIV nuclearity upon the inclusion of such countercations. Analyses of the structures of uranium(IV) oxo/hydroxosulfate oligomeric species isolated from consistent synthetic conditions reveal that the incorporation of Na+ and Rb+ promotes the crystallization of 0D discrete clusters with a hexanuclear [U6O4(OH)4(H2O)4]12+ core, whereas the larger Cs+ ion allows for the isolation of a 2D-layered oligomer with a less condensed trinuclear [U3(O)]10+ center. This finding expands the prevalent view that counterions play an innocent role in molecular complex synthesis, affecting only the overall packing but not the local oligomerization. Interestingly, trends in nuclearity appear to correlate with the hydration enthalpies of alkali-metal cations, such that the alkali-metal cations with larger hydration enthalpies correspond to more hydrated complexes and cluster cores. These findings afford new insights into the mechanism of nucleation of UIV, and they also open a new path for the rational design and synthesis of targeted molecular complexes.

An equally-charged mixture of an anionic gemini surfactant, O,O'-bis(sodium 2-tetradecylcarboxylate)-p-azodiphendiol (G14-azo), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was dissolved in cyclohexane to form reverse worm-like micelles. Samples with different surfactant concentrations and amounts of added water were studied using rheological measurements. The amount of water, represented as the molar ratio of water to total surfactants W0, was c. 13 (at its minimum) in these equally charged systems of G14-azo (200 mmol L(-1))/CTAB. The low shear viscosity ηL of this system reached 4370 Pa s at W0 = 13 and the dynamic rheological result showed typical surfactant gel behaviour. Under UV-light irradiation, the transparent sample (G14-azo (300 mmol L(-1))/CTAB (600 mmol L(-1))) at W0 = 40 became turbid, during which ηL was rapidly reduced from the original 285 Pa s to 0.3 Pa s, indicating a transition of aggregate morphology from reverse worms into simple reverse micelles. Then the sample was returned to its original homogeneous state with c. 290 Pa s viscosity under visible light irradiation. However, this transition cannot be well achieved at low W0 due to the interior cores being too small. This limit has been attributed to both the Gemini type of surfactant molecule and to the inverted structure of aggregates.

Effect of α-tocopherol on the properties of microemulsions stabilized by the ionic surfactants

Tetramethylene-1,4-bis(N,N-dodecylammonium bromide), cationic gemini surfactant, (12-4-12) was first synthesized with an one-step and shortened procedure and its interfacial and antimicrobial properties were compared with a conventional single-chain cationic surfactant, cetyltrimethylammonium bromide (CTAB). The interfacial and thermodynamic properties of both surfactants reveal that critical micelle concentration (CMC) of this novel synthetic cationic dimeric surfactant is lower than that of cationic monomeric surfactant at almost 15 times of its magnitude, which is due to the increase in hydrophobicity of the surfactant molecules by having dual hydrocarbon chains. In comparison with CTAB, the produced compound 12-4-12 yields much better interfacial and thermodynamic properties. The antimicrobial activities of the synthesized gemini surfactant were tested against eight strains of bacteria, as well as two strains of fungi. The results showed that both 12-4-12 compound and CTAB exhibited higher inhibitory effects on the growth of Gram-positive bacteria and fungi than that of Gram-negative bacteria. The minimum inhibitory concentrations in molar of 12-4-12 against all tested Gram-negative bacteria were lower than those of CTAB, which is hypothetically due to the lower HLB together with smaller CMC values of our gemini surfactant.

The interaction of Indian natural dye, that is, Himalaya (Quercus infectoria) with cationic surfactant (cetyl trimethyl ammonium bromide) and anionic surfactant (sodium lauryl sulphate) has been studied. The spectrophotometric data showed an interaction between the natural dye and surfactants. Critical micelle concentration (CMC) of the surfactants, determined by measurement of specific conductance and surface tension methods, was found to be increase in case of anionic surfactant while that was found to decrease in case of cationic surfactant. Thermodynamic and surface parameters showed domination of micellization of dye in case of cetyl trimethyl ammonium bromide and domination of adsorption of dye in case of sodium lauryl sulphate.

The formation of molecular complexes between riboflavin (RFN) and some β-carboline derivatives (antidepressant drugs that have a pronounced inhibition of monoamine oxidase) has been studied by using electronic absorption and fluorescence spectroscopic methods in aqueous solution. The formation constants for the molecular complexes were determined from data of absorption, using the Foster–Hammick–Wardley method. The quenching phenomenon observed in RFN fluorescence is related to the concentration of the β-carboline derivatives, allowing the calculation of the quenching constants for RFN–β-carboline complexes. Thermodynamic parameters have been determined from the values of associations constants for the molecular complexes at various temperatures. The influence of substituents in the β-carboline molecule on the stability of the complexes formed was also investigated.

Using the spectrophotometric method it was shown that molecular complexes are formed in the diene synthesis reaction of acrolein, acrylic acid, acrylonitrile and methyl acrylate with cyclopentadiene and of SO2 with 2,3-dimethyl-1,3-butadiene.

The formation of molecular complexes in isopropanol-water solutions is studied by means of vibrational spectroscopy techniques. The ATR FTIR spectra of solutions with different mixing ratios are detected. The multivariate curve resolution of the experimental data set shows that the investigated solution could be treated as a four-component mixture, which contains pure isopropanol, pure water, and two molecular complexes.

Charge-transfer and Proton-transfer in the Formation of Molecular Complexes. II. Kofler’s Ternary Molecular Complex