Remarkably facile heck and suzuki reactions in water using a simple cationic surfactant and ligand-free palladium catalysts

A facile surfactant mediated Heck and Suzuki coupling procedure in water has been developed using ligand-free Pd-catalysts. The procedure which involves nanometric palladium colloids, is operationally simple, environmentally benign and synthetically as efficient as conventional procedures using organic solvents

Synthesis of gold nanoparticles stabilised by metal-chelator and the controlled formation of close-packed aggregates by them

Nanoparticles have properties that can be fine-tuned by their size as well as shape. Hence, there is significant current interest in preparing nano-materials of small size dispersity and to arrange them in close-packed aggregates. This manuscript describes ways of synthesising gold nanoparticles using a metal-chelator derivative 1, as stabiliser. Controlled synthesis conditions lead to formation of nanoparticles thereby indicating the ability of 1 to act as efficient stabiliser. The nanoparticles formed were characterised by transmission electron microscopy and UV-Vis spectroscopy. TEM analysis showed the formation of dense aggregates of nanoparticles. This can be ascribed to the inter-particle hydrogen bonding possible by the carboxylic acid moiety of 1 that leads to aggregation. The aggregation can be controlled by the pH of the solution employed for dispersing the particles

Synthesis and characterization of novel cationic lipid and cholesterol-coated gold nanoparticles and their interactions with dipalmitoylphosphatidylcholine membranes

Novel gold nanoparticles bearing cationic single-chain, double-chain, and cholesterol based amphiphilic units have been synthesized. These nanoparticles represent size-stable entities in which various cationic lipids have been immobilized through their thiol group onto the gold nanoparticle core. The resulting colloids have been characterized by UV-vis, (1)H NMR, FT-IR spectroscopy, and transmission electron microscopy. The average size of the resultant nanoparticles could be controlled by the relative bulkiness of the capping agent. Thus, the average diameters of the nanoparticles formed from the cationic single-chain, double-chain, and cholesterol based thiolate-coated materials were 5.9,2.9, and 2.04 nm, respectively. We also examined the interaction of these cationic gold nanoparticles with vesicular membranes generated from dipalmitoylphosphatidylcholine (DPPC) lipid suspensions. Nanoparticle doped DPPC vesicular suspensions displayed a characteristic surface plasmon band in their UV-vis spectra. Inclusion of nanoparticles in vesicular suspensions led to increases in the aggregate diameters, as evidenced from dynamic light scattering. Differential scanning calorimetric examination indicated that incorporation of single-chain, double-chain, and cholesteryl-linked cationic nanoparticles exert variable effects on the DPPC melting transitions. While increased doping of single-chain nanoparticles in DPPC resulted in the phases that melt at higher temperatures, inclusion of an incremental amount of double-chain nanoparticles caused the lowering of the melting temperature of DPPC. On the other hand, the cationic cholesteryl nanoparticle interacted with DPPC in membranes in a manner somewhat analogous to that of cholesterol itself and caused broadening of the DPPC melting transition

Frontispiece: Anion Binding‐Induced White Light Emission using a Water‐Tolerant Fluorescent Molecular Tweezer

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137318/1/chem201681061.pd

Modulation of viscoelastic properties of physical gels by nanoparticle doping: influence of the nanoparticle capping agent

Cap in hand: The viscoelastic properties of low-molecular-mass organogelator–gold nanoparticle (LMOG–Au NP) composites can be modulated by the capping agent on the nanoparticle. The interactions between the LMOG and Au NP depend on the ability of ligands to interdigitate within the gel aggregate

Role of Capping Ligands on the Nanoparticles in the Modulation of Properties of a Hybrid Matrix of Nanoparticles in a 2D Film and in a Supramolecular Organogel

We incorporate various gold nanoparticles (AuNPs) capped with different ligands in two-dimensional films and three-dimensional aggregates derived from N-stearoyl-L-alanine and N-lauroyl-L-alanine, respectively. The assemblies of N-stearoyl-L-alanine afforded stable films at the air-water interface. More compact assemblies were formed upon incorporation of AuNPs in the air-water interface of N-stearoyl-L-alanine. We then examined the effects of incorporation of various AuNPs functionalized with different capping ligands in three-dimensional assemblies of N-lauroyl-L-alanine, a compound that formed a gel in hydrocarbons. The profound influence of nanoparticle incorporation into physical gels was evident from evaluation of various microscopic and bulk properties. The interaction of AuNPs with the gelator assembly was found to depend critically on the capping ligands protecting the Au surface of the gold nanoparticles. Transmission electron microscopy (TEM) showed a long-range directional assembly of certain AuNPs along the gel fibers. Scanning electron microscopy (SEM) images of the freeze-dried gels and nanocomposites indicate that the morphological transformation in the composite microstructures depends significantly on the capping agent of the nanoparticles. Differential scanning calorimetry (DSC) showed that gel formation from sol occurred at a lower temperature upon incorporation of AuNPs having capping ligands that were able to align and noncovalently interact with the gel fibers. Rheological studies indicate that the gel-nanoparticle composites exhibit significantly greater viscoelasticity compared to the native gel alone when the capping ligands are able to interact through interdigitation into the gelator assembly. Thus, it was possible to define a clear relationship between the materials and the molecular-level properties by means of manipulation of the information inscribed on the NP surface

Remarkably facile Heck and Suzuki reactions in water using a simple cationic surfactant and ligand-free palladium catalysts

A facile surfactant mediated Heck and Suzuki coupling procedure in water has been developed using ligand-free Pd-catalysts. The procedure which involves nanometric palladium colloids, is operationally simple,environmentally benign and synthetically as efficient as conventional procedures using organic solvents

A Tetrameric Sugar-Based Azobenzene That Gels Water at Various pH Values and in the Presence of Salts

A novel low-molecular mass tetrameric sugar derivative containing azobenzene core, 1, showed pronounced hydrogelation at micromolar concentration. Based on this observation, four related azobenzene based tetrameric sugar derivatives, 4-7, and three tetrameric sugar derivatives with a bis-terephthalamide core, 9-11, were also synthesized. However, none of these closely related analogues of the compound 1 showed effective gelation. The gel formed from 1 was characterized extensively using melting temperature analysis, UV-vis, FT-IR, circular dichroism spectroscopy, and scanning electron microscopy. The resultant gel exhibited impressive tolerance to the pH variation of the aqueous phase and gelated water in the pH range of 4-10. While UV-vis and CD spectroscopy indicated that pronounced aggregation of the azobenzene chromophores in 1 was responsible for gelation, FT-IR studies showed that hydrogen bonding is also a contributing factor in the gelation process. The melting of gel was found to depend on the pH of the aqueous medium in which gel was formed. The gel showed considerable photostability to UV irradiation, indicating tight intermolecular packing inside the gelated state that rendered azobenzene groups in the resultant aggregate refractory to photoisomerization. The electron micrographs of the aqueous gels of 1 showed the existence of spongy globular aggregates in such gelated materials. Addition of salts to the aqueous medium led to a delay in the gelation process and also caused remarkable morphological changes in the microstructure of the ge