The effect of heteroatoms on the formation of magnetic ceramic nanocomposites in pyrolysis of organometallic precursors: similar molecular structure, but totally different morphology, composition and properties

Four organometallic compounds were synthesized for solid-state pyrolysis (SSP) to research the structure-property relationship between the precursors and the as-generated magnetic ceramic nanocomposites (MCNs). In which, the only saturated carbon atom in MC was replaced by N or O or S atom, to produce MN, MO and MS, respectively. It was found that, the crystal phase of the cobalt catalyst could be regulated by introducing different heteroatoms during the pyrolysis: fcc-Co for MC/MN, while fcc/hcp-Co hybrid for MO/MS. Metal cobalt with different crystal phases has their special catalytic and magnetic properties. Thus, MCNs with totally different morphology, composition and properties could be prepared by just changing one heteroatom in the precursors upon SSP. Uniform nanotubes were generated from pyrolysis of MC/MN, while nanospheres were generated from MO/MS. The obtained MCNs all show excellent magnetic properties with Ms ranged from 47.6 to 54.2 emu g-1. Analyzing carefully, due to the magnetic difference between fcc-Co and hcp-Co, the Ms of the MCNs obtained from MO/MS were slightly lower than those of MC/MN, but, their Mr and Hc were 2 to 5 times higher than the latter.

A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom

Nucleophilic substitution reaction is an important reaction of haloalkane. By such a reaction, halogen functional group can turn into various other functional groups. Therefore, it is widely used in organic synthesis and there are many researches on its reaction mechanism. Hydrolysis reaction of bromoalkane is especially a nucleophilic substitution reaction that is studied quite fully. This paper mainly discusses the nucleophilic substitution reaction on saturated carbon atom.

ELECTRON TRANSFER INDUCED DISSOCIATION OF CHLORO-CYANO-BENZENE RADICAL ANION: DRIVING CHEMICAL REACTIONS VIA CHARGE RESTRAINTS

We introduce a new quantum mechanics/molecular mechanics based method to drive electron transfer reactions. Our approach uses the dynamically restrained electrostatic potential derived charges of the quantum atoms1 as a reaction coordinate, and allows an estimation of the free energy barrier of the electron transfer process. Moreover, it provides an accurate description of the electronic structure changes and of the nuclear reorganization associated with the reaction. We use the method to describe the electron-transfer induced dissociation of the m-chloro-cyano-benzene radical anion in aqueous solution. The reaction is triggered by solvent reorganization by a change in the coordination water shell around the cyano nitrogen atom. At the onset of the reaction, charge-spin segregation is observed. The negative charge is transferred to the leaving Cl , while the spin density localizes on the non-saturated carbon atom of the benzene ring. The calculated free energy barrier of dissociation is in good quantitative agreement with the experimental data.