Theoretical calculations on structural and electronic properties of BGaAsBi alloys

The structural and electronic properties of cubic B _x Ga_1?x As_1?y Bi _y alloys with bismuth (Bi) concentration of 0.0625, 0.125, 0.1875 and 0.25 are studied with various boron (B) compositions by means of density functional theory (DFT) within the Wu-Cohen (WC) exchange correlation potential based on generalized gradient approximation (GGA). For all studied alloy structures, we have implemented geometric optimization before the volume optimization calculations. The obtained equilibrium lattice constants and band gap of studied quaternary alloys are investigated for the first time in literature. While the lattice constant behavior changes linearly with boron concentration, increasing small amount of bismuth concentration alter the lattice constant nonlinearly. The present calculation shows that the band gap decreases with increasing bismuth concentration and direct band gap semiconductor alloy became an indirect band gap with increasing boron concentration. From the band offset calculation we have shown that increasing B and Bi concentration in host GaAs reduced the valance band offset in a heterostructure formed by GaAs and studied alloys.     

Experimental and Semi-Empirical and DFT Calculational Studies on (<Emphasis Type="Italic">E</Emphasis>)-2-[(2,4-Dichlorophenylimino) methyl]-<Emphasis Type="Italic">p</Emphasis>-cresol

Abstract  

The molecular and crystal structure of the title compound, C₁₄H₁₁Cl₂NO, has been determined by X-ray single crystal diffraction technique. The compound crystallizes in the orthorhombic, space group Pbca with unit cell dimensions a = 7.5537(10) ?, b = 11.5518(13) ?, c = 29.760(4) ?, M _r  = 280.14, V = 2596.8(6) ?³, Z = 8, R ₁ = 0.065 and wR ₂ = 0.191. The title compound exists in the enol–imine tautomeric form with a strong intramolecular O–H···N hydrogen bond. The dihedral angle between the two benzene rings is 37.66(15)°. The asymmetric unit in the crystal structure contains only one neutral molecule. Calculational studies were performed by using AM1, PM3, PM6 semi-empirical and DFT methods. Geometry optimizations of compound have been carried out by using three semi-empirical methods and DFT method and bond lengths, bond and torsion angles of title compound have been determined. Dipole moments (Debye) and the energy parameters of compound (kcal/mol) were calculated by using above mentioned calculation methods. Atomic charge distribution has been obtained from AM1, PM3, PM6 and DFT. In order to determine conformational flexibility on the molecule, molecular energy profile of the title compound was obtained with respect to the selected torsion angle T(N1–C7–C1–C2), which is varied from −180° to +180° in every 10 via PM3 semi-empirical method.     

Self-Assembled Hydrogen-Bonding Chains of Copper(II) 2-Nitrobenzoate with Nicotinamide

Abstract  

The synthesis, spectral characterization and crystal structure of two new nitrobenzoatocopper(II) complexes, namely, [Cu₂(2-O₂Nbz)₄(nia)₂]·ACN (1) and [Cu₂(2-O₂Nbz)₄(ACN)₂] (2) (where 2-O₂Nbz = 2-nitrobenzoate, nia = nicotinamide and ACN = acetonitrile) are reported. The complexes 1 and 2 form dinuclear units of the paddle-wheel type around the crystallographic inversion centers. The copper ions are bridged by four 2-nitrobenzoate anions and the neutral N-donor ligands, viz. nicotinamide in 1 and acetonitrile in 2, are coordinated at apical positions. Selected geometric parameters of both complexes are compared with values for related tetra-2-nitrobenzoate complexes of copper(II) as well as the other dimeric copper(II) carboxylates with apical nicotinamide and acetonitrile ligands. The molecules of 1 are linked with N–H···O and C–H···O hydrogen bonds. The π–π stacking interactions in 1 are observed between benzene rings of 2-nitrobenzoate anions and pyridine rings of nicotinamide and also between acetonitrile molecules and benzene rings of 2-nitrobenzoate anions. The C–H···O hydrogen-bonds and CH/π interactions are observed in crystal structure of 2.     

Calculation of three-center nuclear attraction integral over Slater type orbitals in molecular coordinate system using Löwdin <Emphasis Type="Italic">α</Emphasis>-radial function and Guseinov’s two-center charge density expansion formulae

Using Löwdin α-radial function and the Guseinov’s charge density expansion formulae, the calculation of the three-center nuclear attraction integrals over Slater type orbitals in molecular coordinate system is performed. The proposed algorithm is especially useful for computation of multicenter-multielectron integrals that arise in the Hartree-Fock-Roothaan approximation, which plays a significant role for the study of electronic structure and electron-nuclei interaction properties of atoms, molecules and solids. The algorithm described in the present work is valid for the arbitrary values of quantum numbers, screening constants and internuclear distances. The calculation results are in good agreement with those obtained using the alternative evaluation procedure.     

Novel bioactive vic-dioxime ligand containing piperazine moiety: Synthesis,X-ray crystallographic studies, 2D NMR applications and complexation with Ni(II)

A new vic-dioxime ligand bearing an important pharmacophore substituent, anti-1-(4-benzylpiperazine-1-yl) phenylglyoxime (LH₂) (Scheme 1), has been synthesized and its nickel(II) complex was obtained by the reaction of NiCl₂·6H₂O and the ligand. The characterization of the newly formed compounds was performed by elemental analysis, FT-IR, 1D NMR (¹H, ¹³C, DEPT), 2D NMR (HMBC), ESI mass-spectrometry, TG/DTA, X-ray crystallography. The antibacterial activity was also studied against Staphylococcus aureus ATCC 25923, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Lactobacillus acidophilus RSHM 06029, Escherichia coli ATCC 25922, E. coli ATCC 35218, Pseudomonasaeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have mild antibacterial activity against both Gram negative and Gram positive bacterial species.     

Synthesis,spectroscopic, electrochemical and spectroelectrochemical properties of metal free,manganese, and cobalt phthalocyanines bearing peripherally octakis-[4-(thiophen-3-yl)-phenoxy] substituents

Metal free (2), manganese (3), and cobalt (4) phthalocyanines, which are octa-substituted at the peripheral positions with [4-(thiophen-3-yl)-phenoxy] moieties, were synthesized and electrochemical properties were reported for the first time. The complexes were characterized by elemental analysis, IR, ¹H NMR, mass spectroscopy, and electronic spectroscopies. Electrochemical and spectroelectrochemical measurements exhibit that incorporation of the redox active metal ions, Co^II and Mn^IIIOAc, into the phthalocyanine core extends the redox richness of the Pc ring with the reversible metal-based reduction and oxidation couples in addition to the common Pc ring-based electron transfer processes. Presence of molecular oxygen in the electrolyte system causes to form π-oxo MnPc complexes, which alter the voltammetric and spectroelectrochemical responses of the complex. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications.     

Synthesis and characterization of new air stable primary amido substituted diborane(4) derivatives

Three new diborane(4) derivatives, 1,2-bis(2,4,6-trimethylanilide)-1,2-bis(dimethyamido)diborane(4) (1), 1,2-bis(2,4,6-trimethylanilide)-1,2-bis(duryl)diborane(4) (2) and 1,2-bis(anilide)-1,2-bis(duryl)diborane(4) (3), have been synthesized and characterized by means of elemental analysis, IR, ¹H, ¹³C and ¹¹B NMR spectroscopy. Additionally, the structures of compounds 1 and 2 have been determined by the single crystal X-ray diffraction technique. The compounds 1 and 2 crystallize in the monoclinic P21/c space group. All of the compounds were found to be air stable.     

Synthesis, H- or J-type aggregations,electrochemistry and in situ spectroelectrochemistry of metal ion sensing lead(II) phthalocyanines

We report, in this study, peripherally 3- and 4-substituted functionalized ionophore ligands (1–3) and their α- and β-tetra polyalcohol substituted lead(II) phthalocyanines M{Pc[S–CH(C₃H₇)(C₂H₅OH)]₄} (7, 9 and 11) and M{Pc[S–C₆H₁₂(OH)]₄} (8, 10 and 12) which are a mixture of different isomers. The complexes have been fully characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, MS (MALDI-TOF) and UV–Vis spectral data. These complexes induced H-type (face-to-face fashion) or J-aggregate (edge-to-edge) dimers when titrated with AgNO₃ or Na₂PdCl₄ in a THF–MeOH solution. Cyclic and square wave voltammetry studies showed that the complexes gave three one-electron ligand-based reductions and two one-electron oxidation couples having diffusion controlled mass transfer character. Assignments of these redox couples were confirmed by spectroelectrochemical measurements. The observation of split Q bands, which are characteristic spectral behavior of metal-free phthalocyanines, indicates demetallization of the complexes during the spectroelectrochemical measurement under the applied potentials. The types of the substituents on the ring of the phthalocyanines affect the demetallization process of the complexes.     

Pretreatment of landfill leachate by chemical oxidation processes

Kinetics and efficiency of Fenton’s and ozonation processes for the pretreatment of two landfill leachates (fresh and mature) resulting from municipal waste disposal were studied. Both samples presented high organic load, high toxicity and low biodegradability. These were the reasons why oxidative treatment was proposed. Fresh and mature leachate showed different behaviors in the oxidation experiments. The final extents of removal were attained in comparable time intervals in both oxidation systems. Maximal removal of organics by the Fenton’s oxidation reached more than 50 % according to COD. Zero or first order kinetics were found the best to describe the organic components (in terms of COD and DOC) removal by the Fenton’s oxidation for both landfill leachates. Higher reaction rate values of the Fenton’s oxidation were achieved with fresh leachate samples. The efficiency of initial organics removal with ozone was about 70 % for mature leachate, while in case of the fresh one only 41 % of COD were removed. The best fits of COD and DOC experimental data from oxidation of fresh and mature leachates were obtained by a combined kinetic model. No significant improvement of the biodegradability of landfill leachates was achieved using these treatment procedures. Regarding toxicity, ozonation showed to be more effective than the Fenton’s oxidation. Advanced oxidation experiments confirmed that the Fenton’s oxidation and ozonation are comparable oxidative treatment techniques for the reduction of organic pollution in the investigated municipal landfill leachates. However, neither of them is effective enough to be used as a pretreatment method followed by biological treatment.