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Chlorophylls (Chls) are natural pigments essential to photosynthesis that have been shown to act as photosensitizers for Photodynamic Therapy (PDT). Many studies have used Chls A and its colloidal formulations in the PDT field but little is known about the potential of Chls B for this application. Here we have detailed the interaction, spectroscopic, and photophysical properties of Chlorophyll b (Mg-Chl b), Pheophytin b (Pheo b), and its formulations with nonionic surfactants aiming photodynamic applications. Both pigments were formulated in some suitably nanostructured drug delivery systems based on aqueous solutions of Pluronics triblock copolymers and Tweens surfactants. High binding constants have evidenced that Chls B interact strongly with these micelles, and the results are correlated with logP, zeta potential, and hydrodynamic diameter. Spectroscopic studies showed high molar absorption coefficients in the therapeutic window (600–800 nm), significant fluorescence quantum yields, and solubilization of Chls B as monomers, especially for Pluronics systems. Pheo b is completely photostable in all investigated micellar systems, whereas Mg-Chl b is photobleached with a rate constant correlated with the interaction and relative location in these micelles. High singlet oxygen quantum yields identify these chlorophylls B as possible Type II photosensitizers for PDT. Mg-Chl b in particular is almost twice as effective as Mg-Chl a, which makes it one of the most potent generators of singlet oxygen in nature.

Zwitterionic surfactants have unique properties for applications in separation methods and catalysis. Their properties and efficiencies depend on two main factors: surfactant structure and preferential interactions of zwitterionic surfactant interfaces with anions. Structural changes are related to hydrocarbon chain length, distance between charges, and type and order of functional groups in the polar head. Interactions of anions with zwitterionic micelles follow the Hofmeister series and change the surface charge. The interactions between surfactants and molecules/ions allow the rational control of separation by chromatography and micellar capillary electrophoresis; cloud point extraction; and stabilization and catalytic activity of biomolecules and nanoparticles.

We report a study of the P–O bond cleavage of the anion of 2,4-dinitrophenyl ethyl phosphate (2,4-DNPEP), promoted by methylamine. The aminolysis reaction was investigated in the gas phase and an aqueous environment using the hybrid quantum mechanical/effective fragment potential (QM/EFP) approach. According to the B3LYP/6-31++G(d,p) results, in the gas phase the cleavage of the P–O bond of 2,4-DNPEP proceeds in one step through a concerted mechanism, with an activation free energy of 39 kcal/mol. Including solvent effects at the B3LYP/6-31++G(d,p)/EFP level changes the reaction to a two-step associative mechanism. The first step corresponds to the formation of the P–NHMe bond and the second step to concerted proton transfer and P–O(2,4-dinitrophenolate) cleavage. In the absence of any assistance of water molecules to promote the proton transfer, the second step is rate determining with an activation free energy for the breakdown of the intermediate of 21.8 kcal/mol at the MP2/cc-pVTZ level and a free energy of activation of 32.3 kcal/mol for the overall reaction. However, the proton transfer with the assistance of a water molecule may occur without significant energy barrier. The results show how solvent can play an important role in favoring an associative mechanism for the aminolysis of phosphate diesters, through the formation and stabilization of a pentacoordinate phosphorane intermediate.

Zwitterionic surfactants are relatively overlooked and some of their properties resemble those of ionic and non-ionic surfactants, but others are unique. There is unimpeachable evidence that aqueous solutions of zwitterionic micelles interact specifically with anions, forming “anionoid” micelles, which concentrate cations in the surfaces. Thus, unlike ionic micelles, both the cation and anion of the electrolyte solution can be concentrated at zwitterionic interfaces. This unique effect, known as the “Chameleon Effect”, can be used to catalyze a variety of simple reactions, as the attraction of ions to the micelle brings the reactants together. Furthermore, zwitterionic surfactants stabilize metallic nanoparticles and the magnetically stirred two-phase system could be reused 3 more times in the hydrogenation of cyclohexene (Pd:cyclohexene ratio of 1:18300), with very little loss in activity, and an average turn-over frequency of 1000 h − 1 .

In this study, peroxidase from alfalfa sprout extract (Medicago sativa) was immobilized on a gold electrode, using a solution of the zwitterionic surfactant 3-(1-tetradecyl-3-imidazolio)propanesulfonate (ImS3-14) containing well-dispersed gold nanoparticles. In the presence of hydrogen peroxide, the peroxidase enzyme catalyzes the oxidation of hydroquinone to o-quinone, which is electrochemically reduced at a potential of +0.09 V vs. Ag/AgCl. The hydroquinone biosensor exhibited excellent electrocatalytic activity under the optimized experimental conditions ([peroxidase] = 97 units mL−1, [H2O2] = 7.4 × 10−5 M, pH 7.0, frequency of 100 Hz, pulse amplitude of 60 mV and scan increment of 4.0 mV). Peak current linearity was observed in the range of 6.96 × 10−7 to 8.54 × 10−6 M, and the detection limit was estimated to be 1.88 × 10−7 M. This biosensor demonstrated good repeatability and reproducibility with relative standard deviations of 3.6% and 6.5%, respectively, and an acceptable stability (at least 100 determinations). The method has been applied to the determination of hydroquinone in skin-brightening creams and the recoveries were 98.3–104.5%.

The low oxidative stability of biodiesel derived from polyunsaturated oils is one of the great challenges to be overcome in biodiesel technology. Here, we use a high activity catalyst Pd/ImS3-12@Al 2 O 3 , prepared by adsorption of water-prepared palladium nanoparticles on aluminum oxide, for partial biodiesel hydrogenation. The catalyst shows higher hydrogenation activity than conventional Pd/C, leading in the absence of ionic liquid (IL) to fully hydrogenated product. In the presence of BMIM·NTf 2 (1-butyl-3-methylimdazolium bis(trifluoromethylsulfonyl)imide) IL the activity of the Pd/ImS3-12@Al 2 O 3 catalyst could be controlled and selective reduction to monoene product, with large preference for formation of the cis isomer, could be achieved at low temperature and pressure, with very low catalyst loading, no detectable metal leaching and good recyclability. The partially hydrogenated biodiesel is far more stable to oxidation than the crude, without compromising its cold-flow properties.

We report a detailed photophysical study of 1-dodecyl-4-[5-(4-dodecyloxyphenyl)-1,3,4-oxadiazole-2-yl]pyridinium bromide ( 454Do ), a cationic amphiphile that behaves as a fluorescent liquid crystal. Excitation and emission spectra of the probe in different environments result in significant changes in quantum yields which are correlated with changes in lifetimes and theoretical calculations.

Hydrolysis of 4-nitrophenyl benzoate (PNPB) in the presence of ionene nanoreactors was studied comparing the ionenes, poly[(dimethyl)-2-hydroxy propanodiyl chloride] (2-OH-33R1), poly[(methylbutyliminium)-2-hydroxy propanodiyl chloride] (2-OH-33R4) and poly[(methyloctyliminium)-2-hydroxy propanodiyl chloride] (2-OH-33R8). Methyl orange incorporation and study of viscosity showed that increase of the side chain length of the ionene enhances the ability to form globular hydrophobic microdomains. Catalytic hydrolysis of PNPB follows the order 2-OH-33R8 ≫ 2-OH-33R4 > 2-OH-33R1, and 2-OH-33R8 has the lowest pKa that may reflect its higher hydrophobicity, which apparently influences the ionene nanoreactor reactivity. A lower pKa indicates easier deprotonation of the alkoxide group, which participates more effectively in the reaction and the 2-OH-33R8 functionalized ionene acts as a specially effective catalytic homogeneous nanoreactor.

Hydrolysis of DNA is of increasing importance in biotechnology and medicine. In this Letter, we present the DNA-cleavage potential of metal-free hydroxylamines and oximes as new members of nucleic acid cleavage agents.

Micelle-mediated catalysis was compared to that of ionene polymers. Hexadecyltrimethylammonium bromide (CTABr) and benzyldimethylhexadecylammonium chloride (BDHA) were the surfactants employed and 2-hydroxy-3-ionene chloride (2-OH-33R) and poly[(dipropyliminium)-1,3-propanediyl bromide], 33R33, the tested ionenes. A modified Michaelis–Menten equation described the kinetics of ionene-mediated hydrolysis. The cationic polymer 2-hydroxy-3-ionene chloride proved to be the most efficient catalyst and a detailed mechanism is proposed for the reaction with benzoic anhydride (Bz 2 O) based on the kinetic evidence obtained. The catalytic efficiency follows the order 2-OH-33R > BDHA > 33R33 > CTABr.

The in situ formation of an iridium nanoparticles dispersion obtained from the reduction of the organometallic precursor [Ir(cod)Cl]2 in 1-n-butyl-3-methyl imidazolium hexafluorophosphate ionic liquid by molecular hydrogen is an autocatalytic process. These nanoparticles possess a small size and a monomodal size distribution of 2.0 ± 0.4 nm iridium nanoparticles can be confirmed by TEM and XRD analysis before and after the catalytic process. The 1-decene hydrogenation by the Ir(0) nanoparticles in the ionic liquid follows the classical monomolecular surface reaction mechanism v = k c K [ S ] 1 + K [ S ] . The reaction rate is a mass controlled process under hydrogen pressure

The kinetics of the hydrolysis of bis(2,4-dinitrophenyl) phosphate (BDNPP) has been studied in the presence of a dinuclear Fe(III) complex that acts as a catalyst in the hydrolytic reaction. One equivalent of the 2,4-dinitrophenolate ion (DNP) and one equivalent of 2,4-dinitrophenylphosphate (DNPP) were liberated for each equivalent of BDNPP, and the reaction showed first-order kinetics in relation to both BDNPP and the metal ion complex. Potentiometric titrations of the dinuclear complex are consistent with two deprotonation constants of the metal coordinated water molecules, with p K a values of 4.88 and 6.33 and the reactions show a pH dependence which is consistent with a Fe 2 (OH)(OH 2 ) form as the reactive species during the hydrolytic reaction. The kinetics of the reaction show an inverse solvent isotope effect of 0.44, which is consistent with a pre-equilibrium proton transfer before the hydrolysis reaction of the BDNPP.

Potassium 4-nitrophenyl sulfate, C6H4KNO6S, crystallizes in the orthorhombic system, Pbca space group, with cell parameters: a=6.990(1), b=13.130(1), c=19.180(1) A, V=1760.3(3) A3. The asymmetric unit consists of a discrete ionic pair of the salt. The packing shows the K+ ion surrounded by eight oxygen atoms from six different p-nitrophenyl sulfate anions. In addition, the structure–structure and structure–reactivity correlations relevant to sulfate transfer process are discussed.

The equilibrium constants and molar absorptivities for the fast formation of a 1:3 complex between cadmium(II) (Cd(II)) and dithizonate anion, in the presence of cationic and non-ionic surfactants, allowed a simple and fast spectrophotometric determination of total cadmium. Indeed, the molar absorptivities of the Cd(II)–dithizone (Dz) complex formed in the presence of the neutral Triton X-100 and cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost twice the value observed in the standard method and the maxima of absorption are shifted by about 40 nm when compared with the standard method. Clearly, the use of neutral and cationic surfactants promotes a higher value of the molar absorptivities of the complex, resulting in an increase in the sensitivity of the method. Application of the method to the desorption of Cd(II) ions from clays is illustrated.

The thermal degradation of N -( o -carboxybenzoyl)- l -phenylalanine (NCBPh), N -( o -carboxybenzoyl)- l -leucine (NCBL) and N -( o -carboxybenzoyl)- l -valine (NCBV) were studied by thermogravimetry and infrared spectroscopy. The results suggested that the loss of mass occurred by two main events which were defined as the imide formation and sublimation. The values of the activation energy ( E ) for the imide formation, considering both systems, were at the range 170–60 kJ mol −1 and the results indicate that thermal stability obeys the order: NCBPh>NCBV>NCBL. The apparent activation energies obtained for the sublimation process are consistent with the structure of the imides N -Phthaloylphenylalanine (PhtPh), N -phthaloylvaline (PhtV) and N -phthaloylleucine (PhtL). The values of E are in the order PhtPh>PhtV>PhtL. This higher energy for the sublimation of the phenylalanine derivative, may be associated to the presence of the phenyl group, which favours the crystalline packing. In a sealed tube at higher temperature, we detected the degradation of the imide, with the concurrent appearance of CO 2 (2370 and 2340 cm −1 ), CO (2200–2100 cm −1 ).

Polymer-mixed surfactant complex formation among poly(ethylene oxide), sodium dodecyl sulfate, and sodium decyl phosphate was identified using conductivity measurements and following the kinetics of the acid-catalyzed hydrolyses of di-tert-butyl and di-n-butyl benzaldehyde acetals. By conductivity, the onset of the mixed complexation, the critical aggregation concentration, follows an ideal mixing behavior in the same way as takes place in the absence of polymer, previously investigated. The reaction of di-tert-butyl benzaldehyde acetal is generally acid catalyzed, and the first-order rate constant increases linearly up to ca. 0.5 mole fraction of sodium decyl phosphate; however, as the hydrolysis of di-n-butyl benzaldehyde acetal is specifically hydrogen ion catalyzed, the rate constant is independent of the mole fraction of the phosphate surfactant.

Structural changes of the complex formed by the polysaccharide hyaluronic acid, as its salt, partially modified by a covalently bound fluorescence probe, 4-fluoro-7-nitrobenz-2-oxa-1,3-diazole, and dodecyltrimethylammonium bromide, were observed by measuring fluorescence depolarization with 0.175 M NaBr as a function of surfactant concentration. Values of depolarization change significantly between 2.0 and 10.0 mM surfactant. The critical micelle concentrations of the surfactant in 0.175 M NaBr in the absence and presence of the polymer are in the surfactant concentration range at which fluorescence polarization changes. Formation of the surfactant-polymer complex at high salt concentration is consistent with appearance of free micelles, which associate with the anionic polymer.

The partition coefficients, K-values, of adenosine, guanosine, cytidine, uridine, 51-adenylic acid (AMP), 51-guanylic acid (GMP), 51-cytidylic acid (CMP), and 51-uridylic acid (UMP) between water and aqueous sodium dodecanoate has been determined by gel filtration on Sephadex G-25. Below the critical micelle concentration of the surfactant, K-values for all nucleotides and nucleosides are similar. Differential uptake of the four nucleotides and nucleosides is observed, however, by micellar sodium dodecanoate. K-values for adenosine, AMP; guanosine, GMP; cytidine, CMP; and uridine, UMP are 6.16·103, 9.52·103; 12.0·103, 14.6·103; 19.6·103, 19.6·103, 34.2·103 and 40.3·103. Similar K-values for corresponding pairs of nucleotides and nucleosides imply that the predominant interaction is between the pyrimidine or purine rings of the substrates and the charged Stern layer of the surfactant. Prebiotic significance of these results is discussed.

Bromophenol blue and picric acid undergo hydrogen bonded ion pair formation with polyoxyethylene (6) nonylphenol, Igepal CO-530, in dry benzene. Combination of the absorption spectrophotometric data for complex formation between bromophenol blue and Igepal CO-530 with the 1 H NMR chemical shifts of the surfactant protons in the presence of the dye allowed the estimation of the average aggregation number for the association of the surfactant. This value in the presence of bromnphenol blue is 2.6 while in neat Igepal CO-530 it is 1.5. Solubilizates affect, therefore, the aggregation properties of surfactants in nonpolar solvents. Apparent dissociation constants, p K a app values, have been determined for malachite green, bromophenol blue, thymol blue and methyl orange in water pools, solubilized by Igepal CO-530 in benzene, by titration with HC10 4 . The p K a app values in this medium differ from the corresponding p K a values in bulk water by as much as 7.0 units. For malachite green effects on p K a app increased with increasing ratios of [Igepal CO-530]/[H 2 O]. At given HC10 4 concentrations ratios of unprotonated to protonated malachite green increase with increasing concentrations of the surfactant. In no case, however, is the deprotonation complete. The higher the HC10 4 concentration the less complete is the deprotonation. Water pools entrapped by Igepal CO-530 in benzene provides, therefore, a relatively basic medium.

The reaction of vitamin B 12r , generated by photolysis of methylcobalamin under a nitrogen atmosphere, with 1,1,1-trichloro-2,2-bis( p -chlorophenyl)ethane (DDT), results in extensive dechlorination and formation of 1,1-dichloro-2,2-bis( p -chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis( p -chlorophenyl)ethylene (DDE) as the major products. Minor quantities of 1,1-bis( p -chlorophenyl)-2-chloroethane (DDMS), 1,1-bis( p -chlorophenyl)-2-chloroethylene (DDMU), 1,1-bis( p -chlorophenyl)ethane (DDO), and 1,1-bis( p -chlorophenyl)ethylene (DDNU) were also formed. Reaction of vitamin B 12r with DDD results in the production of DDMU and DDMS, the latter of which can react to produce DDNU and DDO. DDE and DDMU do not react with vitamin B 12r . The results obtained are suggestive of a vitamin B 12r -mediated dechlorination pathway for polyhalogenated hydrocarbon pesticides.