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Wyniki wyszukiwania dla: DFT calculations
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Coupled cluster and DFT calculations of 14N nuclear quadrupole coupling constants
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Structural studies of methyl brevifolincarboxylate in solid state by means of NMR spectroscopy and DFT calculations
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Syntheses, spectroscopic and structural properties of phenoxysilyl compounds: X-ray structures, FT-IR and DFT calculations
PublikacjaThe reaction of silicon disulfide with alkylphenols leads to tetraphenoxysilane, cyclodisilthiane and silanethiol. The products of the reaction of silicon disulfide with phenols are characterized by FT-IR, NMR, X-ray diffraction and DFT calculations. The intramolecular interactions in the compounds are mainly XH---π (X = C, S) whereas the intermolecular interactions are either very weak CH---π/CH---O contacts found in aryloxysilane...
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Large-scale DFT calculations in implicit solvent-A case study on the T4 lysozyme L99A/M102Q protein
PublikacjaW ostatnich latach zaproponowano szereg modeli typu implicit solvent, ktore bazują na bezpośrednim rozwiązaniu niejednorodnego równania Poissona w przestrzeni rzeczywistej. Modele te charakteryzują się elegancją, ponieważ wnęka, w której umieszczona jest molekuła substancji rozpuszczanej zdefiniowana jest bezpośrednio w funkcji gęstości elektronowej, a rozkład ładunku jest w sposób samouzgodniony polaryzowany dzięki reakcji dielektryka,...
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Weak hydrogen bonding interaction S-H···O=C studied by FT-IR spectroscopy and DFT calculations
PublikacjaInteractions between the thiolate group of tri-tert-butoxysilanethiol (TBST) and carbonyl group of acetone are studied with the use of FT-IR spectroscopy and DFT calculations.
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Singlet oxygen in the removal of organic pollutants: An updated review on the degradation pathways based on mass spectrometry and DFT calculations
PublikacjaThe degradation of pollutants by a non-radical pathway involving singlet oxygen (1O2) is highly relevant in advanced oxidation processes. Photosensitizers, modified photocatalysts, and activated persulfates can generate highly selective 1O2 in the medium. The selective reaction of 1O2 with organic pollutants results in the evolution of different intermediate products. While these products can be identified using mass spectrometry...
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Theoretical estimation of acid–base properties of Lewis and Brønsted centres at the V-W-O catalyst surface: water molecule as the probe in DFT calculations
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Properties of Oxygen Vacancy and Hydrogen Interstitial Defects in Strontium Titanate: DFT + Ud,p Calculations
PublikacjaThis work presents extensive theoretical studies focused on the mixed ion-electron transport in cubic strontium titanate (STO). A new approach to the description of this difficult system was developed within the framework of linear-scaling Kohn–Sham density functional theory, as realized in the ONETEP program. The description we present is free of any empirical parameters and relies on the Hubbard U and Hund’s J corrections applied...
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Minimal parameter implicit solvent model for ab initioelectronic-structure calculations
PublikacjaAbstract - We present an implicit solvent model for ab initio electronic-structure calculations which is fully self-consistent and is based on direct solution of the nonhomogeneous Poisson equation. The solute cavity is naturally defined in terms of an isosurface of the electronic density according to the formula of Fattebert and Gygi (J. Comput. Chem., 23 (2002) 662). While this model depends on only two parameters, we demonstrate...
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Ambiphilic phosphorous compounds
Dane BadawczeResults of theoretical and experimental studies on ambiphilic phosphorous compounds:
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Ambiphilic phosphorous compounds 2
Dane BadawczeResults of theoretical and experimental studies on ambiphilic phosphorous compounds:
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Ligand-Modified Boron-Doped Diamond Surface: DFT Insights into the Electronic Properties of Biofunctionalization
PublikacjaWith the increasing power of computation systems, theoretical calculations provide a means for quick determination of material properties, laying out a research plan, and lowering material development costs. One of the most common is Density Functional Theory (DFT), which allows us to simulate the structure of chemical molecules or crystals and their interaction. In developing a new generation of biosensors, understanding the nature...
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Molecular geometry of phenylboronic acid
Dane BadawczeData presents molecular geometry of the ground singlet state of phenylboronic acid. The geometry was obtained via DFT calculations using Becke–Lee–Yang–Parr density functional (B3LYP) with the balanced polarized triple-zeta def2-TZVP basis set. Geometry is provided in the XYZ file format.
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Density functional theory calculations on entire proteins for free energies of binding: Application to a model polar binding site
PublikacjaIn drug optimization calculations, the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method can be used to compute free energies of binding of ligands to proteins. The method involves the evaluation of the energy of configurations in an implicit solvent model. One source of errors is the force field used, which can potentially lead to large errors due to the restrictions in accuracy imposed by its empirical nature....
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List of initial and final geometries of hybrid organic-inborganic perovskites
Dane BadawczeList of initial and optimized geometries of hybrid organic-inorganic perovskites. Calculations were performed on DFT level of theory. Those results were reported in the Influence of Orientational Disorder on the Optical Absorption Properties of the Hybrid Metal‐Halide Perovskite CH3NH3PbI3 publication. Geometries, HOMO, LUMO, Band gap energies are concatenated...
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New uranium(vi) and isothiouronium complexes: synthesis, crystal structure, spectroscopic characterization and a DFT study
PublikacjaThe crystal structures of S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) diacetate (1_ac), S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (1_Cl), 1_U complex, S,S′-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (2_Cl), and 2_U complex were determined for the first time. The supramolecular structures of the compounds obtained are mainly based on hydrogen bonding and ionic interactions...
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Variable-temperature X-ray diffraction study of structural parameters of NH---S hydrogen bonds in triethylammonium and pyridinium silanethiolates
PublikacjaHydrogen bonds in triethylammonium and pyridinium silanethiolate salts have been characterized by X-ray, FT–IR and NMR spectroscopies. DFT calculations reveal strongly asymmetric double-well minima at the potential energy curves of the studied compounds
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Structural properties of hypothetical CeBa2Cu3O7 compound from LSDA+DMFT calculations
PublikacjaThe hypothetical stoichiometric CeBa2Cu3O7 (Ce123) compound, which has not been synthesized as a single phase yet, was studied by the density functional theory (DFT). We utilized a method which merges the local spin density approximation (LSDA) with the dynamical mean-field theory (DMFT) to account for the electronic correlations. The LSDA+DMFT calculations were performed in the high-temperature range. The particular emphasis was...
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Calculating the Partition Coefficients of Organic Solvents in Octanol/Water and Octanol/Air
PublikacjaPartition coefficients define how a solute is distributed between two immiscible phases at equilibrium. The experimental estimation of partition coefficients in a complex system can be an expensive, difficult, and time-consuming process. Here a computational strategy to predict the distributions of a set of solutes in two relevant phase equilibria is presented. The octanol/water and octanol/air partition coefficients are predicted...
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Electronic structure and magnetism of samarium and neodymium adatoms on free-standing graphene
PublikacjaThe electronic structure of selected rare-earth atoms adsorbed on a free-standing graphene was investigated using methods beyond the conventional density functional theory (DFT+U, DFT +HIA, and DFT+ED). The influence of the electron correlations and the spin-orbit coupling on the magnetic properties has been examined. The DFT+U method predicts both atoms to carry local magnetic moments (spin and orbital) contrary to a nonmagnetic...
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Copper(II) complexes of 7-amino-2-methylchromone and 7-aminoflavone: Magneto-structural, spectroscopic and DFT characterization
PublikacjaFour new complexes of copper(II) consisting of two different chromone derivatives with carbonyl and amine donor atoms: 7-aminoflavone (L1) and 7-amino-2-methylchromone (L2), were synthesized and characterized by X-ray diffraction, UV–Vis, FT-IR, EPR spectroscopy, MS and elemental analysis. In all four compounds, the chromone derivatives were found to act as monodentate O- or N-ligands. The structural characteristics of 1a and...
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Density functional theory-based simulations of sum frequency generation spectra involving methyl stretching vibrations: effect of the molecular model on the deduced molecular orientation and comparison with an analytical approach
PublikacjaThe knowledge of the first hyperpolarizability tensor elements of molecular groups is crucial for a quantitative interpretation of the sum frequency generation (SFG) activity of thin organic films at interfaces. Here, the SFG response of the terminal methyl group of a dodecanethiol (DDT) monolayer has been interpreted on the basis of calculations performed at the density functional theory (DFT) level of approximation. In particular,...
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The ONETEP linear-scaling density functional theory program
PublikacjaWe present an overview of the ONETEP program for linear-scaling density functional theory (DFT) calculations with large basis set (planewave) accuracy on parallel computers. The DFT energy is computed from the density matrix, which is constructed from spatially localized orbitals we call Non-orthogonal Generalized Wannier Functions (NGWFs), expressed in terms of periodic sinc (psinc) functions. During the calculation, both the...
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Spectroscopic and cytotoxic characteristics of (p-cymene)Ru(II) complexes with bidentate coumarins and density functional theory comparison with selected Pd(II) complexes
PublikacjaThis paper presents the synthesis of two new (p-cymene)-ruthenium(II) complexes with the bidentate coumarin ligands. Both complexes were characterized by FTIR spectroscopy, 1H NMR, 13C NMR, MS, elemental analysis and DFT calculations. The X-ray structure of complex 3a was also solved. The cytotoxic properties of both complexes were examined on human leukemia NALM-6 and HL-60 cells and melanoma WM-115 cells. The complexes possess...
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Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces
PublikacjaDensity functional theory (DFT) is often used for simulating extended materials such as infinite crystals or surfaces, under periodic boundary conditions (PBCs). In such calculations, when the simulation cell has non-zero charge, electrical neutrality has to be imposed, and this is often done via a uniform background charge of opposite sign (“jellium”). This artificial neutralization does not occur in reality, where a different...
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Lead(II) coordination polymers with imidazole-4- and pyrazole-3-carboxylate isomeric linkers: Structural diversity and luminescence properties
PublikacjaUsing 1H-imidazole-4-carboxylic acid (4imCOOH) and 1H-pyrazole-3-carboxylic acid (3pyrCOOH) coordination polymers [Pb(4imCOO)2(H2O)]n (1) and [Pb2(3pyrCOO)4]n (2) were constructed. Obtained polymers were characterized via FT-IR, X-ray, PL and TG methods. The coordination polyhedron around Pb(II) in 1 is described as distorted pentagonal pyramid with hemidirected coordination sphere (based on DFT calculations). Compound 2 consists...
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Electrostatic interactions in finite systems treated with periodic boundary conditions: Application to linear-scaling density functional theory
PublikacjaWe present a comparison of methods for treating the electrostatic interactions of finite, isolated systems within periodic boundary conditions (PBCs), within density functional theory (DFT), with particular emphasis on linear-scaling (LS) DFT. Often, PBCs are not physically realistic but are an unavoidable consequence of the choice of basis set and the efficacy of using Fourier transforms to compute the Hartree potential. In such...
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Atmospheric degradation mechanism of anthracene initiated by OH•: A DFT prediction
PublikacjaDensity functional theory (DFT) calculations at the M06-2X/def2-TZVP level have been employed to investigate the atmospheric oxidation mechanism of anthracene (ANT) initiated by HO•. Direct hydrogen atom abstraction from the ANT using HO• takes place hardly at ambient conditions while the addition of HO• to the C1, C2, and C4 sites are thermodynamically and kinetically more advantageous. The addition reactions are controlled by...
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Ab-initio study of electrical and optical properties of allylamine
PublikacjaThe Density functional theory is one of most promising methodology in fast and accurate calculations of electrical and optical properties from the atomic basis. In this paper, we calculate electrical and optical properties of allylamine (2-propen 1- amine) in terms of accuracy and speed of calculations obtained by selection of DFT-1/2 method with ultrasoft Vanderbilt pseudopotentials. Comparison of density of states between...
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Ab-initio study of electrical and optical properties of allylamine
PublikacjaThe Density functional theory is one of most promising methodology in fast and accurate calculations of electrical and optical properties from the atomic basis. In this paper, we calculate electrical and optical properties of allylamine (2-propen 1- amine) in terms of accuracy and speed of calculations obtained by selection of DFT-1/2 method with ultrasoft Vanderbilt pseudopotentials. Comparison of density of states between molecule...
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Practical Approach to Large-Scale Electronic Structure Calculations in Electrolyte Solutions via Continuum-Embedded Linear-Scaling Density Functional Theory
PublikacjaWe present the implementation of a hybrid continuum-atomistic model for including the effects of a surrounding electrolyte in large-scale density functional theory (DFT) calculations within the Order-N Electronic Total Energy Package (ONETEP) linear-scaling DFT code, which allows the simulation of large complex systems such as electrochemical interfaces. The model represents the electrolyte ions as a scalar field and the solvent...
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Experimental and DFT insights into an eco-friendly photocatalytic system toward environmental remediation and hydrogen generation based on AgInS2 quantum dots embedded on Bi2WO6
PublikacjaBismuth tungstate (Bi2WO6) can work as a photocatalyst but suffers from rapid recombination of photogenerated charge carriers. Herein, density functional theory (DFT) simulations revealed that the formation of a thermodynamically stable AgInS2(112)/Bi2WO6(010) heterojunction could promote charge separation and enhance the photoactivity of Bi2WO6. To confirm these theoretical predictions, a new type of photocatalysts in the form...
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Isostructural zinc and cadmium silanethiolates with bridging biimidazole co-ligands – Enhanced luminescence of zinc complex
PublikacjaTwo dinuclear complexes of zinc and cadmium with silanethiolate and bridging biimidazole ligands are characterized by X-ray diffraction, FT-IR, UV–Vis and emission spectroscopies. The complexes 1 (Zn) and 2 (Cd) are isostructural but exhibit different electronic structures and different character of frontier HOMO orbitals as indicated by DFT calculations. Lluminescence studies prove strong emission properties of zinc complex.
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Diaminophosphinoboranes: effective reagents for phosphinoboration of CO2
PublikacjaThe monomeric diaminophosphinoboranes readily react with CO2 under mild conditions to cleanly form products of the general formula R2P-C(=O)-O-B(NR2)2 in the absence of a catalyst. The isolated products from the CO2-phosphinoboration were fully characterized by NMR spectroscopy, IR spectroscopy, and X-ray diffraction. The mechanism of CO2 phosphinoboration with diaminophosphinoboranes was elucidated by DFT calculations.
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Exploring thiophene-2-acetate and thiophene-3-acetate binding modes towards the molecular and supramolecular structures and photoluminescence properties of Pb(ii) polymers
PublikacjaTo evaluate the impact of the flexible positional isomeric ligands thiophene-2-acetate (2tpacCOO) andthiophene-3-acetate (3tpacCOO) on the construction and self-assembly process of Pb(II) polymers, twonovel compounds, [Pb(2tpacCOO)2(H2O)]n(1) and [Pb(3tpacCOO)2]n(2), were preparedviaanonhydro-thermal method with respect to green chemistry rules. The obtained polymers were fully characterized byelemental analysis, TG/DTG and PXRD,...
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The synthesis and structure of a potential immunosuppressant: N-mycophenoyl malonic acid dimethyl ester
PublikacjaThe synthesis of a potential immunosuppressant, i.e. dimethyl ester of N-mycophenoyl malonic acid was optimized in the reaction of mycophenolic acid (MPA) with amino malonic dimethyl ester in the presence of propanephosphonic anhydride (T3P) as a coupling reagent. The structural properties of the obtained MPA derivative were investigated by NMR, MS and single crystal X-ray diffraction methods. Theoretical considerations of conformational...
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Linear-scaling calculation of Hartree-Fock exchange energy with Non-orthogonal Generalised Wannier Functions
PublikacjaWe present a method for the calculation of four-centre two-electron repulsion integrals in terms of localised non-orthogonal generalised Wannier functions (NGWFs). Our method has been imple- mented in the ONETEP program and is used to compute the Hartree-Fock exchange energy component of Hartree-Fock and Density Functional Theory (DFT) calculations with hybrid exchange-correlation functionals. As the NGWFs are optimised in situ...
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Unassisted formation of hemiaminal ether from 4-aminopyridine and o-vanillin - experimental and theoretical study
PublikacjaThe reactions between o-vanillin and three isomeric aminopyridines lead to imines of diverse spatial conformation and reactivity. The direct products of these simple reactions carried out in methanol are either imine compounds formed in the reactions of 2- amino- and 3-aminopyridine with o-vanillin or the α-aminoether formed in the reaction of o-vanillin with 4-aminopyridine. The Schiff-type derivative of 4-aminopyridine and o-vanillin,...
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Protein thermal stabilization in aqueous solutions of osmolytes
PublikacjaProteins’ thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared...
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The reactivity of 1,1-dichloro-2,2-di-tert-butyldiphosphane towards lithiated metal carbonyls: a new entry to phosphanylphosphinidene dimers
PublikacjaReactions of [Cp*(OC)3M]Li (Cp* = C5Me5, M = Mo, W) towards t-Bu2P–PCl2 lead to the formation of phosphanylphosphinidene dimers [Cp*(OC)3M(η2-t-Bu2P–P)]2 in fairly good yields. The formation of a tetraphosphorus ligand proceeds via reductive dimerization of t-Bu2P–P units. NMR, X-ray investigations and DFT calculations show that the resulting tetraphosphorus ligand has a structure of dication t-Bu2P+=P–P=P+t-Bu2.
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Theoretical study of the photoelectron spectrum of ethyl formate: Ab initio and density functional theory investigation
PublikacjaThe first ionization energy and associated photoelectron spectrum of ethyl formate are investigated with quantum chemistry calculations. The geometries, harmonic vibrational frequencies and first ionization energy are computed at the Hartree-Fock (HF) and at the second order Moller-Plesset perturbation theory (MP2). Moreover, accurate ionization energies are obtained with the Coupled-Cluster theory including singles and doubles...
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Reactive imines: Addition of 2-aminopyrimidine to the imine bond and isolation of the aminal from the equilibrium mixture aminal/imine
PublikacjaThe reaction between o-vanillin and 2-aminopyrimidine leads to the formation of a single crystalline product: aminal, 1, which results from the reaction of the initially formed imine with 2-aminopyrimidine. The reaction was followed by the NMR spectroscopy. VT NMR studies prove that in solution two major species are observed: aminal and imine and their ratio depends on the time or/and temperature with the imine content increasing...
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Crystal structure and electronic structure of CePt2In7
PublikacjaWe report a corrected crystal structure for the CePt2In7 superconductor, refined from single crystal x-ray diffraction data. The corrected crystal structure shows a different Pt–In stacking along the c-direction in this layered material than was previously reported. In addition, all of the atomic sites are fully occupied with no evidence of atom site mixing, resolving a discrepancy between the observed high resistivity ratio of...
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Imidazolium silanethiolates relevant to the active site of cysteineproteases. A cooperative effect in a chain of NH(+)...S(-) hydrogenbonds
PublikacjaThree imidazolium silanethiolates relevant to the active site of cysteine proteases have been synthesized and investigated by X-ray diffraction, IR spectroscopy and computational methods. As indicated by crystallographic and FT-IR data in the solid state, the transfer of proton from thiol to imidazole takes place and a thiolato-imidazolium ion pair is formed. The FT-IR spectra of crystalline imidazolium silanethiolates exhibit...
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Syntheses and structures of the first terminal phosphanylphosphido complexes of molybdenum(IV)
PublikacjaThe reactions of R2P-P(SiMe3)Li (R = tBu, iPr2N) with [Cp2MoCl2] yield terminal phosphanylphosphido complexes formally via the insertion of the phosphinidene P-atom into the C - H bond of a cyclopentadienyl ring and the migration of the hydrogen atom or SiMe3 moiety to the molybdenum centre. Solid state structures of [Cp(C5H4P-PtBu2)MoH], [Cp(C5H4P-PtBu2)Mo(SiMe3)] and [Cp{C5H4P-P(NiPr2)2}Mo(SiMe3)] were established by single crystal...
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DMSO and TMAO—Differences in Interactions in Aqueous Solutions of the K-Peptide
PublikacjaInteractions between a solvent and their co-solute molecules in solutions of peptides are crucial for their stability and structure. The K-peptide is a synthetic fragment of a larger hen egg white lysozyme protein that is believed to be able to aggregate into amyloid structures. In this study, a complex experimental and theoretical approach is applied to study systems comprising the peptide, water, and two co-solutes: trimethylamide...
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Sulfurization of phosphanylphosphinidene ligand: Access to phosphinothioyltrithiophosphonato platinum(II) complexes
PublikacjaThe reactivity of phosphanylphosphinidene Pt(0) complexes [DppePt(η2-P–PtBu2)] (1) and [(pTol3P)2Pt(η2-P–PtBu2)] (2) toward sulfur was studied. Reactions of 1 and 2 with an excess of sulfur led to the formation of the first transition metal complexes 3 and 4 with phosphinothioyltrithiophosphonato ligands with the formula [tBu2P(=S)–P(=S)S2]2-. In contrast to previous reports on the phosphanylphosphinidene moiety sulfurization,...
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Emerging oxidized and defective phases in low-dimensional CrCl3
PublikacjaTwo-dimensional (2D) magnets such as chromium trihalides CrX3 (X ¼ I, Br, Cl) represent a frontier for spintronics applications and, in particular, CrCl3 has attracted research interest due its relative stability under ambient conditions without rapid degradation, as opposed to CrI3. Herein, mechanically exfoliated CrCl3 flakes are characterized at the atomic scale and the electronic structures of pristine, oxidized, and defective...
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A comparison of structural and luminescence properties of lead(II) coordination polymers with isomeric thiophenecarboxylate ligands
PublikacjaTwo new lead(II) coordination polymers with isomeric thiophenecarboxylates, namely [Pb(2tpCOO)2]n (1) and [Pb(3tpCOO)2(H2O)]n (2) (2tpCOO− = thiophene-2-carboxylate, 3tpCOO− = thiophene-3-carboxylate), were synthesized and characterized. Single crystal X-ray crystallography revealed a distorted pentagonal pyramidal geometry {PbO6} around Pb in 1 and a distorted dodecahedral geometry {PbO8} in 2. The distortion derived from the...
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In situ transformation boosts the pseudocapacitance of CuNi-MOF via cooperative orientational and electronic governing
PublikacjaThe disordered arrangement and thereof inferior conductivity of 2D MOF sheets seriously hinder their practical application. Herein, we propose in situ transformation strategy to architect vertically oriented bimetallic CuNi-MOF as a self-supporting electrode, leading to a decuple high specific capacitance of 1262 C g-1 in comparison with the pristine Ni-MOF powder of 114 C g-1 at 2 A g-1. DFT calculations reveal that introduction...