Effect Of Electronic Nature Research Articles

Effect of electronic nature of substituents in arylacetylene on the rate of reaction with 2,2,2-trichloroareno-1,3,2-dioxaphosphols

Effect of electronic nature of substituents in arylacetylene on the rate of reaction with 2,2,2-trichloroareno-1,3,2-dioxaphosphols

Core-Tetrasubstituted Naphthalene Diimides: Synthesis, Optical Properties, and Redox Characteristics

2,3,6,7-tetrabromonaphthalene dianhydride has been synthesized by the bromination of naphthalene dianhydride with dibromoisocyanuric acid in excellent yield. The condensation of this dianhydride with 2,6-diisopropylaniline yielded the corresponding tetrabromo-substituted naphthalene diimide (NDI), which is a versatile precursor for the synthesis of core-tetrafunctionalized NDIs. Nucleophilic substitution of tetrabromo NDI with alkoxy, alkylthio, and alkylamino nucleophiles afforded a series of core-tetrasubstituted NDI chromophores that complete the series of previously reported di- and trifunctionalized NDI derivatives. The effects of electronic nature and number of core substituents on the optical and electrochemical properties of NDIs have been investigated by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The absorption maxima (629-642 nm) of tetraamino NDIs are strongly bathochromically shifted compared to those of other core-functionalized NDIs.

Effect of electronic nature and substitution behavior of ternary microadditions on the ductility of polycrystalline nickel aluminides

The value of the density of states at the Fermi level N( E F) as a function of the energy difference E i d − E h F between atoms in the metal-metal bond has been introduced as a criterion in order to estimate the probable microalloying ternary additions capable of improving the grain boundary ductility of Ni 3Al and NiAl compounds, Pd and Cu may be among such additions in the case of substitution for Al sites, forming NiPd (NiCu) bonds. In turn, Cr, Mo and W, entering the Ni sublattice, may form bond pairs with Al, all with close to zero energy difference. This prevents the splitting of the electron density of states and increases its total value at the Fermi level. To analyse more carefully the site preference of selected metals, a thermodynamic formalism accounting for the activities of Ni and Al, as well as the lattice parameter and concentration dependence of atomic interactions, has been applied. It was revealed that in Ni-rich off-stoichiometric Ni 3Al (<25 at.% Al), even Pd microadditions (<1 at.%) are able to substitute preferentially for Al and form NiPd bond pairs. The microalloying of NiAl with Cu may be favorable for ductility enhancement in the Al-poor off-stoichiometric region (<51 at.% Al), where Cu substitution for Al sites becomes more preferable. Cr, Mo or W may substitute for Ni and consequently form pairs with Al in Al-rich off-stoichiometric NiAl (>52 at.% Al), mainly owing to the formation of a Ni-vacancy structure with lower electron density.