Synthesis and Characterization of Silica@Copper Core–Shell Nanoparticles: Application for Conjugate Addition Reactions

Silica@copper (SiO₂@Cu) core–shell nanoparticles were synthesized and well characterized by XRD, TEM, AFM, XPS, UV/Vis, TGA–MS, and ICP–AES techniques. The synthesized SiO₂@Cu core–shell nanoparticles were employed as catalysts for the conjugate addition of amines to α,β‐unsaturated compounds in water to obtain β‐amino carbonyl compounds in excellent yields in shorter reaction times. Furthermore, the catalyst works well for hetero‐Michael addition reactions of heteroatom nucleophiles such as thiols to α,β‐unsaturated compounds. As the reaction is performed in water, it allows for easy recycling of the catalyst with consistent activity.     

Working group report: Neutrino and astroparticle physics

This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed.     

Ab initio study of the electronic structures and conduction properties of some novel low band-gap donor-acceptor polymers

The results of the electronic structures and conduction properties of four novel donor-acceptor polymers based on polysilole, obtained on the basis of ab initio Hartree-Fock crystal orbital method using their optimized geometries, are reported. The repeat unit of these polymers consists of bicyclopentadisilole unit bridged by an electron-accepting group Y(Y=CCH₂ in PSICH, CO in PSICF, CCF₂ and CC(CN)₂ in PSICN). All the polymers on the basis of their geometries and π-bond order values are found to have benzenoid-type electronic structures. Comparison of the important electronic properties such as ionization potential, electron affinity and band-gap of these polymers indicates PSICN to be the best candidate for intrinsic conductivity and reductive (n-) doping while PSICH is predicted to be the best candidate for oxidative (p-) doping. All these polymers are estimated to have band-gap values ranging between 1 and 2 eV. The low band-gap values of these polymers are rationalised on the basis of the patterns of their frontier orbitals.     

Photochemical C–N bond forming reactions for the synthesis of five-membered fused N-heterocycles

Abstract

Few conversions cannot take place with ground-state reactions even with the help of a catalyst, therefore they are made to occur under photochemical conditions. The transfer of electrons took place even with the photochemical excitement of one molecule where redox reaction cannot occur at the ground state. The ground-state reactions resulted in the formation of side products. The substrates did not require any sort of chemical activation for C–N bond construction in the course of photochemical reactions. The source of energy; light has always been the interest of researchers in order to induce chemical reactions ever since the starting of scientific chemistry. The present review encloses the chemistry of photochemical transformations with a focus on their synthetic uses. The organic photochemical reactions prevent the polluting or harmful reagents thus, provides a possibility for sustainable procedures as well as green chemistry. This review article displays the formation of numerous of five-membered fused nitrogen-heterocyclic compounds.     

Utilization of CS2 as a source of C1 chemistry for the generation of methyldithioformate

Insertion of CS(2) into the Ru-H bond of cis-[(dppe)(2)Ru(H)(2)] takes place to afford the hydride dithioformate complex trans-[(dppe)(2)Ru(H)(SC(S)H)]. The hydride dithioformate complex reacts under very mild conditions with MeX (X = OTf, I) to give the hydride methyldithioformate derivative trans-[(dppe)(2)Ru(H)(SC(SMe)H)][X]. Three different pathways have been found to cleave off the ester moiety from the metal complex. A method to recover the ruthenium starting material upon elimination of the methyldithioformate is presented. This is a novel case of C(1) chemistry using carbon disulfide.     

Novel double insertion of carbon disulfide into two Ru-H bonds of [(dppm)(2)Ru(H)(2)] (dppm = Ph(2)PCH(2)PPh(2)): synthesis and crystal structure of a methanedithiolate complex

Addition of excess carbon disulfide to cis/trans-[(dppm)(2)Ru(H)(2)] results in the methanedithiolate complex [(dppm)(2)Ru(eta(2)-S(2)CH(2))] 4 via the intermediacy of cis-[(dppm)(2)Ru(H)(SC(S)H)] 2. The X-ray crystal structure of this species has been determined.     

Nitrogen isotopomer site preference of N2O produced by Nitrosomonas europaea and Methylococcus capsulatus Bath

The relative importance of individual microbial pathways in nitrous oxide (N(2)O) production is not well known. The intramolecular distribution of (15)N in N(2)O provides a basis for distinguishing biological pathways. Concentrated cell suspensions of Methylococcus capsulatus Bath and Nitrosomonas europaea were used to investigate the site preference of N(2)O by microbial processes during nitrification. The average site preference of N(2)O formed during hydroxylamine oxidation by M. capsulatus Bath (5.5 +/- 3.5 per thousand) and N. europaea (-2.3 +/- 1.9 per thousand) and nitrite reduction by N. europaea (-8.3 +/- 3.6 per thousand) differed significantly (ANOVA, f((2,35)) = 247.9, p = 0). These results demonstrate that the mechanisms for hydroxylamine oxidation are distinct in M. capsulatus Bath and N. europaea. The average delta(18)O-N(2)O values of N(2)O formed during hydroxylamine oxidation for M. capsulatus Bath (53.1 +/- 2.9 per thousand) and N. europaea (-23.4 +/- 7.2 per thousand) and nitrite reduction by N. europaea (4.6 +/- 1.4 per thousand) were significantly different (ANOVA, f((2,35)) = 279.98, p = 0). Although the nitrogen isotope value of the substrate, hydroxylamine, was similar in both cultures, the observed fractionation (delta(15)N) associated with N(2)O production via hydroxylamine oxidation by M. capsulatus Bath and N. europaea (-2.3 and 26.0 per thousand, respectively) provided evidence that differences in isotopic fractionation were associated with these two organisms. The site preferences in this study are the first measured values for isolated microbial processes. The differences in site preference are significant and indicate that isotopomers provide a basis for apportioning biological processes producing N(2)O.