GGA and GGA + U Study of ThMn2Si2 and ThMn2Ge2 Compounds in a Body-Centered Tetragonal Ferromagnetic Phase

Our study used the full-potential linearized augmented plane waves (FP-LAPW) method to conduct a first-principles evaluation of the structural, electronic, and magnetic properties of ThMn₂X₂ (X = Si and Ge) compounds. To establish theoretical dependability with the currently available experimental results, computations for the structural findings of ternary intermetallic thorium (Th)-based compounds were achieved using the generalized gradient approximation in the scheme of Perdew–Burke–Ernzerhof (PBE–GGA) potential, while the generalized gradient approximation plus the Hubbard U (GGA + U) approach was employed to improve the electrical and magnetic properties. In contrast with both the paramagnetic (PM) and antiferromagnetic (AFM) phases, the ThMn₂X₂ compounds were optimized in a stable ferromagnetic (FM) phase, which was more suited for studying and analyzing magnetic properties. The electronic band structures (BS) and the density of state (DOS) were computed using the two PBE–GGA and GGA + U approximations. The thorium (Th)-based ThMn₂X₂ compound has full metallic character, due to the crossing and overlapping of bands across the Fermi level of energy, as well as the absence of a gap through both spin (up and down) channels. There was a significant hybridization between (Mn-d and (X = Si and Ge)-p states of conduction band with Th-f states in the valence band. The total magnetic moment of ThMn₂Si₂ in the ferromagnetic phase was 7.94534 μB, while for ThMn₂Ge₂ it was 8.73824 μB with a major contribution from the Mn atom. In addition, the ThMn₂Ge₂ compound’s total magnetic moment confirmed that it exhibits higher ferromagnetism than does the ThMn₂Si₂ compound.     

Mononuclear vs. binuclear carboxylates of copper(II) with 2,2′‐bipyridine: Synthesis,characterization, structural description,and properties

Two new copper(II) carboxylate complexes with 2,2′‐bipyridine and para‐nitrophenyl acetate (complex 1 ) and phenyl acetate (complex 2 ) have been synthesized; isolated in quantitative yield; and characterized using fourier‐transform infrared spectroscopy (FT‐IR), electron paramagnetic resonance, absorption spectroscopy, electrochemistry, and powder and single crystal X‐ray diffraction (XRD) techniques. Being mononuclear, the geometry around copper in complex 1 is a Jahn–Teller distorted octahedral, while complex 2 is binuclear with slightly distorted square pyramidal geometry around both copper ions. Powder XRD indicated several peaks in spectra of both complexes, which coincided with their theoretical spectra. FT‐IR results of the carboxylate stretching frequency were in accordance with the single crystal structure data. Electron paramagnetic resonance spectra of complexes 1 and 2 yielded g_┴ values of 2.06161 and 2.24623 and 1.94959, respectively, indicating a localized electron in b₁ (d _x²_–y²‐orbital). Ultra‐violet (UV)–visible spectroscopy and electrochemistry helped in characterization, as well as in deoxyribonucleic acid (DNA)‐binding ability of the complexes, yielding DNA‐binding constant values = 1.351 × 10⁴ and 1.361 × 10⁴ and 1.820 × 10⁴ and 2.426 × 10⁴ M^?1, respectively, for complexes 1 and 2 . The complexes demonstrate good biological potential.     

Synthesis, structural elucidation and biological activities of organotin(IV) derivatives of (E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoic acid

A new series of di- and tri-organotin(IV) compounds with the general formula R_4?n SnL _n , where R?=?Me (1,2), Et (3), n-Bu (4,5), n-Oct (6), Ph (7) and L?=?(E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoate, were synthesized by reaction of silver salt of ligand or ligand acid with diorganotin dichloride/oxide and triorganotin chloride in 2:1 and 1:1 molar ratio, respectively. These compounds were characterized by elemental analyses, FT-IR, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and mass spectrometry. The spectroscopic results revealed that all the diorganotin(IV) compounds possess trigonal bipyramidal structures in solution and octahedral geometry in the solid state around the tin atom. A linear polymeric trigonal bipyramidal structure in the solid state and a tetrahedral environment around the tin atom in non-coordinating solvents has been proposed for the triorganotin(IV) compounds. All synthesized compounds were tested in vitro against a number of microorganisms to assess their biocidal activity. These studies revealed that ligand acid and some of its organotin compounds show promising activity against different strains of bacteria and fungi but lowered than reference drugs.     

(N‐Maleoylglycinato)trimethyltin(IV)

The Sn atom in the crystal structure of the title compound,catena‐poly­[trimethyl­tin‐μ‐[(2,5‐di­oxo‐2,5‐di­hydro­pyrrol‐1‐yl)­acetato‐O:O′]], [Sn(CH₃)₃(C₆H₄NO₄)], adopts a distorted trigonal bipyramidal coordination geometry with three methyl groups defining the trigonal plane [mean Sn—C 2.117 (11) Å] and the axial positions occupied by O atoms from different carboxylate groups, with significantly different Sn—O bond lengths [2.207 (5) and 2.358 (6) Å]. The structure forms a polymeric chain of complex molecules linked via carboxylate moieties.     

A weak Galerkin method for second order elliptic problems with polynomial reduction

The second order elliptic equation, which is also know as the diffusion-convection equation, is of great interest in many branches of physics and industry. In this paper, we use the weak Galerkin finite element method to study the general second order elliptic equation. A weak Galerkin finite element method is proposed and analyzed. This scheme features piecewise polynomials of degree $k\geq 1$ on each element and piecewise polynomials of degree $k-1\geq 0$ on each edge or face of the element. Error estimates of optimal order of convergence rate are established in both discrete $H^1$ and standard $L^2$ norm. The paper also presents some numerical experiments to verify the efficiency of the method.     

An Unusual Diorganotin Bis-carboxylate Structure: catena-{(μ2-2-methyl-3,5-dinitrobenzoato-O,O′)dibutyltin(IV)}

Abstract  

The structure of n-Bu₂Sn(2-methyl-3,5-dinitrobenzoato)₂ (1) presents a rare structural motif for compounds with the general formula R ₂Sn(O₂CR′)₂ which almost exclusively adopt skew-trapezoidal bipyramidal geometries. By contrast, the structure of (1) is polymeric with the polymer backbone comprising eight-membered {SnOCO}₂ rings linked at the pivotal tin atoms. The coordination geometry is octahedral trans-C₂O₄. The relationship between structural motifs for R ₂Sn(O₂CR′)₂ is discussed. Compound (1) crystallizes in the monoclinic space group P2₁/c with a = 5.0114(2) ?, b = 13.7120(5) ?, c = 19.5956(7) ?, β = 91.385(2)o, and Z = 2.     

"Click"-capture, ring-opening metathesis polymerization (ROMP), release: facile triazolation utilizing ROMP-derived oligomeric phosphates

Soluble, high-load ring-opening metathesis polymerization (ROMP)-derived oligomeric triazole phosphates (OTP) are reported for application as efficient triazolating reagents of nucleophilic species. Utilizing a "Click"-capture, ROMP, release protocol, the efficient and purification-free, direct triazolation of N-, O-, and S-nucleophilic species was successfully achieved. A variety of OTP derivatives were rapidly synthesized as free-flowing solids on a multigram scale from commercially available materials.     

Monomer-on-monomer (MoM) Mitsunobu reaction: facile purification utilizing surface-initiated sequestration

A monomer-on-monomer (MoM) Mitsunobu reaction utilizing norbornenyl-tagged (Nb-tagged) reagents is reported, whereby purification was rapidly achieved by employing ring-opening metathesis polymerization, which was initiated by any of three methods utilizing Grubbs catalyst: (i) free catalyst in solution, (ii) surface-initiated catalyst-armed silica, or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles.     

Synthesis of stannic(IV) complexes: Their structural elucidation in solid and solution state and antimicrobial activity

A series of organotin(IV) thiocarboxylates have been synthesized with the general formula R₂SnL₂ and R₃SnL (R = Ph₂(I), Me₃(II), n‐Bu₃(III), Ph₃(IV), Cy₃(V), Me₂(VI), n‐Bu₂(VII), and L = piperidine‐1‐thiocarboxylic acid) in anhydrous toluene under the reflux conditions. The complexes were characterized by microanalysis, IR, ¹H and ¹³C NMR, mass spectrometry, and XRD. NMR data revealed that thiocarboxylic acid acts as bidentate, and complexes exhibit the four‐coordinated geometry in solution state. In solid state, diorganotin complexes exhibit the hexa‐coordinated geometry whereas the triorganotin(IV) compounds show the five‐coordinated geometry. These complexes were also tested for their antimicrobial activity along with the ligand against different animals, plant pathogens, and Artemia salina. All complexes with few exceptions show high activity as compared to the ligand. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:664–674, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20380