Pyrithione metal (Cu, Ni, Ru) complexes as photo-catalysts for styrene oxide production

Selective photochemical oxidation of styrene was performed in an active acetonitrile medium, using H2O2 with or without ultraviolet (UV) light radiation. Pyrithione metal complexes (M–Pth: M = Cu(II), Ni(II), Ru(II); Pth = 2-mercaptopyridine-N-oxide) were used as catalysts. Catalytic testing measurements were done by varying the time, chemical reaction temperature and H2O2 concentration with or without UV energy. Epoxide styrene oxide (SO), benzaldehyde and acetophenone were the major synthesized products. A high batch rate, conversion and selectivity towards SO was shown in the presence of UV. A minor constant formation of CO2 was observed in the stream. Coordinated Ru-based compounds demonstrated the highest process productivity of SO at 60 °C. The effect of the functional alkyl substituent on the ligand Pth, attached to the specific ruthenium(II) centre, decreased the activity of the substance. Ni-Pth selectively yielded benzaldehyde. The stability of the catalysts was examined by applying nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis coupled with mass spectrometry. Tested metal complexes with pyrithione (M–Pth) exhibited excellent reuse recyclability up to 3 cycles.

Pyrithione Metal (Cu, Ni, Ru) Complexes as Photo-Catalysts for Styrene Oxide Production

Selective photochemical oxidation of styrene was performed in an active acetonitrile medium, using H2O2 with or without ultraviolet (UV) light radiation. Pyrithione metal complexes (M–Pth: M = Cu(II), Ni(II), Ru(II); Pth = 2-mercaptopyridine-N-oxide) were used as catalysts. Catalytic testing measurements were done by varying the time, chemical reaction temperature and H2O2 concentration with or without UV energy. Epoxide styrene oxide (SO), benzaldehyde and acetophenone were the major synthesized products. A high batch rate, conversion and selectivity towards SO was shown in the presence of UV. A minor constant formation of CO2 was observed in the stream. Coordinated Ru-based compounds demonstrated the highest process productivity of SO at 60 °C. The effect of the functional alkyl substituent on the ligand Pth, attached to the specific ruthenium(II) centre, decreased the activity of the substance. Ni-Pth selectively yielded benzaldehyde. The stability of the catalysts was examined by applying nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis coupled with mass spectrometry. Tested metal complexes with pyrithione (M–Pth) exhibited excellent reuse recyclability up to 3 cycles.

Aggregation Induced Enhanced Emission (AIEE) Based Colorimetric and Selective Turn-on Fluorescent Sensor for Cyanide

We have prepared and reporting a new cyanide colorimetric and turn-on fluorescent chemo sensor L. Naked-eye colorimetric studies shows the prepared receptor is selectively sensing cyanide ion in acetonitrile medium. The sensor L shows very weak fluorescence in acetonitrile medium. The emission intensity of L gets reduced (quenching of fluorescence) upon addition of one equivalent of cyanide. Meanwhile further gradual addition of more than one equivalents of cyanide onto 1:1 cyanide complex of L shows remarkable fluorescence enhancement. The weakly emissive receptor L show drastic enhancement in fluorescence intensity upon addition of excessive cyanide ion which is mainly attributed due to the restriction of intramolecular rotation of 1:1 L•CN- complex and intermolecular aggregation of host: guest complex. This enhanced fluorescence emission is attributed due to the aggregation induced enhanced emission (AIEE) is subsequently supported with UV-Vis, emission and 1H-NMR spectroscopic studies. The preferential binding of cyanide by electron deficient receptor L through hydrogen bonding and anion···π interaction over benzene analogue of L is also analyzed with help of MEP surface analyses. To the best of our knowledge, this is the first example for selective colorimetric and turn- on cyanide sensor through AIEE mechanism. This type of fluorine rich organic material having such an aggregation enhanced emission properties in response to cyanide addition will be useful to construct the new type of material for various sensory applications.

Synthesis, Structure, Magnetic and Catalytic Competency of a Tetradentate (NNOO) Schiff Base Mediated Dimeric Copper(II) Complex

One dinuclear copper(II) complex {μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)]}-{μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}- dicopper(II), [Cu2(salen)2] (1) [salen2− = [2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)] has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. X-ray single crystal structure examination revealed that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square planar geometry with a CuN2O2 chromophore, where two asymmetric units are attached through congregation of Salen involving Cu-O bond to form dinuclear molecular unit [Cu2(salen)2]. In crystalline state, these dinuclear entities in 1 are extended through C-H···π interactions and π···π interactions displaying a 3D network structure. The variable-temperature magnetic susceptibility measurement asserted a dominant antiferromagnetic interaction between the copper(II) centers through Cu-O-Cu linkage in 1 with J = -1.46 cm-1. The catalytic efficacy of complex 1 was studied in a series of solvents for the oxidation of styrene and cyclooctene using tert-butyl-hydroperoxide (TBHP) as an active oxidant under mild conditions. The catalytic reaction mixture has been analyzed by gas chromatography and it displayed that the yield of the epoxidation and its selectivity is optimum in acetonitrile medium.

COMPARATIVE STUDY OF OXIDATIVE TRANSFORMATION OF ALIPHATIC ALCOHOLS BY CE(IV) -ONE ELECTRON KINETICS

The comparative study of oxidation of aliphatic alcohols likes methanol, ethanol and propanol was carried out by CAN in the presence of perchloric acid in acetonitrile medium. The reaction is first order with respect to [substract], [oxidant] and [H+] concentration. The kinetics of the reaction was followed spectrophotometrically at λmax = 400 nm. The reactions were studied at different temperature [303 to 323 K]. A possible mechanism is proposed here. The reaction constant involved in the mechanism have been computed. There is good agreement between the observed and calculated rate constant under different experimental conditions. The activation parameters have been evaluated.

Luminescence studies of uranyl-aliphatic dicarboxylic acid complexes in acetonitrile medium

The uranyl (UO22+)-aliphatic dicarboxylic acid complexes are studied by luminescence and UV-Vis spectroscopy in acetonitrile (MeCN) medium. The ligands used are malonic acid (MA), succinic acid (SA), glutaric acid (GA), adipic acid (AA) and pimelic acid (PA). The complexes of UO22+ with the above ligands showed well resolved luminescence spectra at pH 4.0 with M/L = 5. Both luminescence and UV-Vis spectra indicated the formation of 1:2 and 1:3 complexes of UO22+ with MA and GA, AA, PA, respectively. DFT computations indicated the formation of 1:2 chelate complex of UO22+ with MA and two types of 1:3 complexes of UO22+ with SA, GA, AA and PA. Furthermore, the effect of solvent (water and acetonitrile) on the UO22+-ligand complexes has been performed using COSMO model. The present study demonstrates, for the first time, the formation of tris complexes of uranyl with these ligands in acetonitrile medium.

Catalytic Efficacy of 2,2′-Bipyridine Cobalt(II) Complex: Hydrothermal Synthesis, X-Ray Structure and Aerobic Epoxidation of Alkenes

A mononuclear cobalt(II) complex, [Co(bpy)2(NO3)](NO3)·3H2O (1) (bpy = 2,2′-bipyridine) has been synthesized hydrothermally and the crystal structure was characterized by X-ray crystallography. Complex 1 is capable of activating aerobic oxygen at atmospheric pressure. [Co(bpy)2(NO3)](NO3)·3H2O (1) was used as an active catalyst for the aerobic epoxidaion of various alkenes with isobutyraldehyde as co-reductant in acetonitrile medium. Complex 1 catalyzes the epoxidaion reaction efficiently, which reflected in high yield of products with desired selectivity.

Electron Deficient π-hole Assisted Colorimetric Probe for Selective Cyanide Recognition.

Here in, simple and novel electron deficient pi-Hole assisted amide based colorimetric receptor synthesized for cyanide recognition which produce yellow to brownish red color change upon the addition of cyanide in acetonitrile medium. Cyanide has selectively recognized successfully with 1:1 stoichiometric ratio and 1.5523x104 M-1 association constant. Cyanide recognition study was carried out with UV-Vis absorption and FTIR-Analysis and association constant and stoichiometric ratio were calculated by Benasi-Hildebrand plot and job’s continues variation method respectively