Effect Of Group Substitution Research Articles

First-Principles Study of Bi-Doping Effects in Hg0.75Cd0.25Te.

First-principles calculations based on density functional theory have been performed for exploring the structural and electronic properties of Bi-doped Hg0.75Cd0.25Te (MCT), using the state-of-the-art computational method with the Heyd–Scuseria–Ernzerhof (HSE) of hybrid functional to correct the band gap. Structural relaxations, charge densities, electron localization functions (ELFs), density of states (DOSs), band structures, and band decomposed charge density were obtained to reveal the amphoteric behavior of Bi in Hg0.75Cd0.25Te. The bonding characteristics between Bi and host atoms were discussed by analyzing charge densities and ELFs. The influence of Bi impurity on the electronic structure of Bi-doped Hg0.75Cd0.25Te was also analyzed by the calculated DOSs, band structures, and the band decomposed charge density of the defect band. It has been demonstrated that Bi can show a typical amphoteric substitution effect of group V elements.

Theoretical study on the change of thermoelectric properties by substitution of group 4 elements in Fe2TiSn

In this study, substitution effects of group 4 elements in Fe2TiSn thermoelectric material are studied by using density functional theory (DFT) and semi-classical Boltzmann transport theory. All of the substitution elements showed the most thermodynamic preference for the Sn site, and these substitutions for Fe2TiSn did not give much influence in the stability and mechanical property of Fe2TiSn. e2TiSn[Formula: see text]Pb[Formula: see text], and thermoelectric calculations showed the prominence of [Formula: see text]-type on [Formula: see text]-type dopingin these materials. The highest Seebeck coefficients of these compounds were −148, −228, −165 and −120 [Formula: see text]V/K for [Formula: see text]-type of Fe2TiSn, Fe2TiSn[Formula: see text]Si[Formula: see text], Fe2TiSn[Formula: see text]Ge[Formula: see text] and Fe2TiSn[Formula: see text]Pb[Formula: see text], respectively. The results showed that Si and Ge partial substitutions for Fe2TiSn could be the effective methods to enhance the thermoelectric property, and the maximum dimensionless figure of merit (ZT) at room temperature reached about 0.7 ([Formula: see text]cm[Formula: see text] [Formula: see text]-type doping concentration) in Fe2TiSn[Formula: see text]Si[Formula: see text] and 0.6 ([Formula: see text]cm[Formula: see text] [Formula: see text]-type doping concentration) in Fe2TiSn[Formula: see text]Ge[Formula: see text].

Glass-Forming Ability of Fe-Ni Alloys Substituted by Group V and VI Transition Metals (V, Nb, Cr, Mo) Studied by Thermodynamic Modeling

The glass-forming ability (GFA) of Fe-Ni-TM alloys, where TM = V, Nb, Cr, Mo, was determined utilizing thermodynamic modeling. Enthalpies of formation of amorphous state were calculated and analyzed along with normalized mismatch entropy and glass-forming ability parameter. All thermodynamic quantities were qualitatively compared with enthalpies of formation of solid solution and experimental results. Due to the fact that FeNi-based amorphous ribbons are used nowadays in magnetoelastic sensors (MES), which can be used in biomedical or chemical applications, discussion is concentrated mainly on the substitution effect of group V and VI transition metals on the improvement of GFA. In this sense, group V elements are preferred, with Nb as the most promising candidate among all analyzed TM elements. This is a consequence of significant differences of potential and density of electrons at the boundary of Wigner–Seitz cell comparing to Fe and Ni, which in turn leads to more negative values of interfacial enthalpy and higher driving force for vitrification.

The effect of group-substitution on the sensitization properties of alkynylrhenium(I) tricarbonyl diimine complexes adsorbed to TiO2(101) film surface: a theoretical study.

A series of dyes are designed by adding the different electron-donating (-CH3, -NH2, -OH) and electron-withdrawing groups (-Br, -Cl, -NO2) to the different ancillary ligands in the alkynylrhenium(I) tricarbonyl diimine complexes [Re(CO)3(N^N){C≡C-C6H4-CH=C(CN)(COOH)}], where N^N = 1,10-phenanthroline (phen)(1) and then investigated the sensitization properties of dyes linked to the TiO2(101) surface. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to study the electronic structure, frontier molecular orbitals, and absorption spectral properties. The effect of group-substitution on sensitization properties is obvious. When the dye molecules are combined with TiO2(101) surface, not only the absorptions of some sensitizers containing -CH3 or -OH groups have red shift but also the electrons can be directly injected into the TiO2 conduction band from the dye molecules compared with the parent molecular 1. The results indicate that the designed dyes containing electron-donating groups have smaller energy gaps, better light-harvesting efficiency, sufficient driving force, and higher charge transfer efficiency as appropriate dye sensitizers. We hope it can provide valuable hints so that we can design more efficient dye sensitizers in DSSCs.

Exploration of Substituent and Isotope Effects on Reaction Rates by a Computational Modeling Experiment

The effects of substitution on reaction rates are at the heart of both physical chemistry and organic chemistry. In this paper, we present a computational laboratory module to explore the effects of group substitution and isotopic substitution on reaction rates by using a readily accessible graphical interface, a computational engine, and spreadsheet software. The module focuses on simple unimolecular isomerization reactions, often used as a classic example for kinetics in first-year, organic, and physical chemistry courses. In the context of a physical or physical organic chemistry course, the module is used to illustrate substituent and/or isotope effects on reaction rates, as well as chemical reaction rate calculations.

The effect of group-substitution on structures and photophysical properties of rhenium(I) tricarbonyl complexes with pyridyltetrazole ligand: A DFT/TDDFT study

A series of rhenium(I) tricarbonyl complexes having a general formula fac-[Re (CO)3(L)(R-NˆN)] (L = Br; N∧N = tert-butylated pyridyltetrazole; R = H, 1; NO2, 2; CN, 3; OCH3, 4; CH3, 5) have been investigated theoretically by density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The calculated results reveal that introductions of different groups on R position of NˆN ligand can induce changes on electronic structures, photophysical properties and emission quantum yield for these complexes. When the electron-withdrawing groups (NO2 and CN) are introduced in complex 2 and 3, the lowest energy absorption and emission bands are red-shifted compared with that of 1. On the contrary, the introduction of electron-donating group (OCH3 and CH3) in complex 4 and 5 cause corresponding blue-shifted. For these complexes, the stronger electron-donating ability of introduced group on NˆN ligand is, the larger blue-shifted of the lowest energy absorption and emission bands is. The solvent effect on absorption and emission spectrum indicates that the lowest-energy absorption and emission bands have both red shifts with the decrease of solvent polarity. The electronic affinity (EA), ionization potential (IP) and reorganization energy (λ) results show that complex 4 may be suitable to be used as an emitter in organic light-emitting diodes OLEDs. Meanwhile the emission quantum yield of complex 4 is possibly higher than other complexes.

Design, Synthesis, and Properties of Phthalocyanine Complexes with Main-Group Elements Showing Main Absorption and Fluorescence beyond 1000 nm

We present a comprehensive description of the unique properties of newly developed phthalocyanines (Pcs) containing main-group elements that absorb and emit in the near-IR region. Group 16 (S, Se, and Te) elements and group 15 (P, As, and Sb) elements were used as peripheral and central (core) substituents. With the introduction of group 16 elements into free-base Pc, a red-shift of the Q-band was observed, as a result of the electron-donating ability of group 16 elements particularly at the α positions. An X-ray crystallographic analysis of α-ArS-, ArSe-, and ArTe-linked free-base Pcs was also successfully performed, and the relationship between structure and optical properties was clarified. When a group 15 element ion was introduced into the center of the Pc ring, the resulting Pcs showed a single Q-band peak beyond 1000 nm (up to 1056 nm in CH2Cl2). In particular, [(ArS)8PcP(OMe)2](+) and [(ArS)8PcAs(OMe)2](+) exhibited a distinct fluorescence in the 960-1400 nm region with moderate quantum yields. The atomic radius of the group 15 element is important for determining the Pc structure, so that this can be controlled by the choice of group 15 elements. Electrochemical data revealed, while MO calculations suggested, that the red-shift of the Q-band is attributable to a decrease of the HOMO-LUMO gap due to significant and moderate stabilization of the LUMO and HOMO, respectively. The effect of peripheral substutuents and a central P(V) ion on the Q-band shift was independently predicted by MO calculations, while the magnitude of the total calculated shift was in good agreement with the experimental observations. The combination of spectral, electrochemical, and theoretical considerations revealed that all of the central group 15 elements, peripheral group 16 elements, and their positions are necessary to shift the Q-band beyond 1000 nm, indicating that the substitution effects of group 15 and 16 elements act synergistically. The Pcs having Q-bands beyond 1000 nm in this study also had stability under aerobic conditions comparative to that of CuPc, which is presently being widely used in consumer products.

A four component coupling strategy for the synthesis of D-phenylglycinamide-derived non-covalent factor Xa inhibitors.

A novel isonitrile derivative was synthesized and used in an Ugi four component coupling reaction to explore aryl group substitution effects on inhibition of the coagulation cascade serine protease factor Xa.

Combined modality treatment with ternary CU(II) complexes and x rays

Ternary Cu(II) complexes with bidentate malonato- and heterocyclic amine ligands were tested with regard to cytotoxicity and potentiation of x-ray induced cell killing in V79 cells. Two lead complexes were also tested in a tumor assay using the MTG-B murine adenocarcinoma model growing in the flanks of female C3H/HeJ mice. One complex, [2,2′-bipyridyl malonatoCu(II)] (RL-5077), produced sensitizer enhancement ratios (SER's) of 1.8 (hypoxic conditions) and 1.0 (oxic conditions) in vitro when irradiation followed 1 hr exposure to the drug at 100 μM. When RL-5077 was administered at doses of 1 2 (11.65 mg/kg) or 1 4 (5.25 mg/kg) the maximum tolerated dose (MTD), 15 min prior to a locally delivered dose of 20 Gy, enhancement ratios (ER's) of 1.6 and 2, respectively, resulted. The second lead complex, [1,10 phenanthroline (malonato)Cu(II)hydrate] (RL-5027), produced SER's of 1.8 and 1.2 under hypoxic and oxic conditions, respectively, at a concentration of 25 μM. Injection of RL-5027 (5 mg/kg) resulted in toxicity without enhancement in combination with radiation. Analogues of these two complexes have been synthesized in an effort to optimize the potentiation of radiation effects while minimizing toxicity to drug alone and increasing water solubility of the drug. Further studies of the structure-activity relationship of Cu(II) ternary complexes using in vitro radiosensitization as the endpoint have identified four classes of ligands with varying biological activity and have supplied information about the effects of group substitution on solubility, toxicity, and radiation potentiation. This group of complexes represents a new class of radiopotentiators that deserves further investigation into its potential for clinical use.

Comparative Disposition Kinetics of Two Diastereomeric Pairs of Cinchona Alkaloids in the Dog

The comparative disposition kinetics of quinidine, quinine, cinchonine, and cinchonidine were investigated in five male, mongrel dogs after intravenous bolus injections of a 9.2-mmol/kg dose of each alkaloid base. Blood and plasma specimens were obtained at various times up to 6h postdose and assayed for quinidine and quinine with a TLC-fluorometric procedure and for cinchonine and cinchonidine by HPLC. The plasma alkaloid concentration-time data were analyzed by weighted, nonlinear least-squares regression analysis to obtain the central compartment volume (Vc), disposition rate constants (α and β), and corresponding half-life values (t1/2). Total body clearance (CL) and apparent volume of distribution (Vd) were estimated by nonparametric analysis. In this study, the highest plasma alkaloid concentrations were reached with quinidine and the lowest concentrations with the quinidine congener, cinchonine. The other congeneric pair, quinine and cinchonidine, exhibited plasma alkaloid concentrations that were comparable and intermediate to those of quinidine and cinchonine. With cinchonine and cinchonidine, the plasma and blood concentration-time curves were virtually superimposable. However, with quinidine and quinine, the plasma alkaloid concentrations of these diastereomers were approximately twice the corresponding blood concentrations. The total body clearance rate of quinidine was significantly slower than quinine and cinchonine clearance. No difference in clearance was observed between cinchonine and cinchonidine. The β andt1/2β for quinidine were significantly smaller and larger, respectively, than the corresponding values obtained with the other alkaloids. No significant differences in α orVc andVd were found between and within the two diastereomeric pairs of alkaloids. The differences in disposition kinetics observed in this study were attributable to an interaction of stereochemical and 6′-methoxy group substitution effects.

Investigation of the Electrochemical Characteristics of Organic Compounds: X . Sulfur Compounds

Anodic half‐cell potential discharge data are presented for various classes of organic sulfur compounds, such as the thiophenols, mercaptans, and thioureas in alkaline electrolyte. The effect of group substitution and aromaticity on the anode potential of the thiophenol compounds is interpreted in terms of the electron density distribution in the molecule. Half‐cell potential discharge data for the reversible thiourea‐formamidine disulfide and dithiobiuret‐thiuret systems in different electrolytes of varying pH are also presented.