New Mixed-Ligand Complexes of Cobalt(II), Nickel(II), and Copper(II) with Adenosine 5′-Triphosphate and Amino Acids

In the systems metal [Co(II), Ni(II), Cu(II)]-adenosine 5′-triphosphate-amino acid (glycine, α-alanine, valine, proline) new mixed-ligand complexes with the adenosine 5′-triphosphate coordinated by deprotonated hydroxy groups of the ribose moiety were found; the stability and lability parameters of the compexes were determined, and their structures were assessed

Modeling of Complex Formation Equilibria and Proton and Ligand Exchange Reactions in Aqueous Solutions of Oxovanadium(IV) with L- and DL-Histidine

For the further development of the magnetic relaxation method, the STABLAB program was implemented, which makes it possible to calculate both thermodynamic equilibrium parameters and kinetic characteristics of the proton and ligand exchange reactions from the results of parallel measurements of the spin relaxation times T1 and T2, of solvent nuclei. With this program, the nuclear magnetic relaxation data on water protons were used to calculate the stability constants and proton and ligand exchange rates for the complexes formed in the oxovanadium(IV)-L-histidine (LH) and oxovanadium(IV)-DL-histidine systems at pH 0.5-10: VOLH, VO(LH)2, VOL, VOL2H, VOL2, VOL2H1, and (VO)2L2H-2. The structures of these complexes were determined based on the comparison of isotropic EPR parameters, stability constants, and molar proton relaxation coefficients. LH is coordinated in the equatorial plane of oxovanadium(IV) through the NH2 and COO- groups or through the imidazole nitrogen atom and the carboxy group; both of these coordination modes concurrently occur in the VO(LH)2 structure. The occurrence of two ligands exerts a synergistic effect on stabilization of the VO(LH)2, VOL2H, and VOL2 bis-complexes, which is explained by the effect of d-π bonding in the complexes with the trans arrangement of the imidazole nitrogen atom of one ligand and the COO- group of the other ligand in the equatorial plane. This d-π bonding is the main cause of some other unusual effects - the stereoselectivity in the formation of the VOL2 complex and the fast spontaneous proton exchange for VOL2H-1. In the proton exchange reactions, the enhanced kinetic activity of the LH2 form is attributed to the occurrence of the intraligand microequilibrium of the proton migration from the imidazole moiety to the carboxy group in interaction with VO2+ and to the fast interligand proton transfer in interaction with VOLH. A significant stereoeffect in the ligand exchange reactions was found for the first time: the rate constant of the exchange between VOL2 and L in solutions with L-histidine is 1.5 times the constant in solutions with DL-histidine. This is rationalized by the fact that the imidazole nitrogen atom in the VOL2 meso form efficiently protect the axial position from the attack of the entering ligand. The extremely high kinetic activity of the LH form in the ligand exchange with the oxovanadium(IV) complexes as compared to the complexes of other metal ions is attributed to a special mechanism that implies the formation of the hydrogen bond involving the protonated nitrogen atom of LH and the oxygen atom of V=O, as well as to a rather high nucleophilicity of the imidazole nitrogen atom of LH

Time-resolved EPR study of radicals from 2,2-dimethoxy-2-phenylacetophenone in ethylene glycol after flash photolysis

The dynamic behaviour of transient free radicals generated by laser pulse photolysis (with λ = 351 nm) of 2,2-dimethoxy-2-phenylacetophenone (DMPA) in ethylene glycol solutions have been studied by time-resolved EPR at room temperature. A main result of the study is a suitable evaluation method for radical systems with CIDEP in the case of very close hyperfine lines and hence with a overlap of several signals. The evaluation of single EPR time-profile signals requires in this case to take in account also the influence of the near resonance positions, what successfully has been done. The formation and decay of the two spin polarized radicals, 7,7-dimethoxy-benzyl (R1) and benzoyl radical (R2), has been observed. For R1 the relaxation time T2 was determined with a good accuracy and the rate constants k1 and k2 were estimated by fitting the time evolution of the EPR signal at resonance and near resonance positions of the field using the Bloch equations and direct Fourier transform analysis. Radicals from DMPA in the high viscous solvent ethylene glycol have been proved to be an excellent model system for this study however the treatment is applicable also for other systems. © 2002 Elsevier Science B.V. All rights reserved

RESOURCES OF BIM TECHNOLOGIES AT THE STAGES OF JUSTIFICATION OF CONSTRUCTION AND DESIGN OF COMPLEX THE BUILDINGS FOR VARIOUS PURPOSES

Информационное моделирование зданий в настоящее время становится все более востребованным. Применение информационного моделирования позволяет на протяжении всего жизненного цикла объекта сокращать расходы на управление финансами, ресурсами, оборудованием и материалами. В данной статье рассмотрены возможности использования BIM-технологий при энергомоделировании.Building information modeling is now becoming more and more in demand. The use of information modeling allows you to reduce the cost of managing finances, resources, equipment and materials throughout the entire life cycle of an object. This article discusses the possibilities of using BIM-technologies for energy modeling

Time-resolved ESR studies on transient radicals photogenerated in solutions of melamine in ethylene glycol

Chemically Induced Dynamic Electron Polarization (CIDEP) spectra of transient radicals generated by laser pulse with λ = 248 nm in solutions of melamine in ethylene glycol have been studied by means of time-resolved (TR) ESR at room temperature. The main products are radicals of the solvent molecules formed through abstraction of hydrogen from ethylene glycol by excited melamine molecules and a melamine radical with attached hydrogen atom on melamine. Parameters obtained from well resolved TR ESR spectra coincide with parameters of radical of ethylene glycol HOC{radical dot}HCH2OH and methylol {radical dot}CH2OH, and an unresolved ESR spectrum was attributed to the melamine radical. The electron spin polarization results from the radical pair mechanism (RPM) involving S-T0 mixing (ST0M) and additionally from a small part of triplet mechanism (TM). In order to establish the possible structure and nature of melamine radical quantum-chemical calculations by the DFT B3LYP method using several different basis sets have been done. The reaction pathway and mechanisms of alcohol and melamine radicals formation are proposed and supported by DFT calculations within B3LYP and CIS(D) methods. Melamine and ethylene glycol free radicals relaxation time T2 was estimated as 1.5 and 0.5 μs, respectively. © 2005 Elsevier B.V. All rights reserved

The C-H bond activation in 1-ethyl-3-methylimidazolium acetate-copper(ii) acetate-water-air (dioxygen) systems

Ionic liquid (1-ethyl-3-methylimidazolium acetate, [C2C 1im][AcO])-copper(ii) diacetate monohydrate-water-air (O2) systems have been investigated by 13C NMR, EPR, spectrophotometry, HPLC, and synthetic chemistry methods at different temperatures. The C-H bond activation of [C2C1im]+ with the formation of the unusual dication 1,1′-diethyl-3,3′-dimethyl-2,2′- biimidazolium ([(C2C1im)2]2+) at 50°C and 1-ethyl-3-methyl-1H-imidazol-2(3H)-one (C2C 1imO) at 50-85°C was revealed. Two new complexes with the above compounds, [(C2C1im)2][Cu(AcO)4] and Cu2(AcO)4(C2C1imO)2, were isolated from the systems and characterized by X-ray structural analysis. Catalytic cycles with the participation of copper(ii) acetate and dioxygen and the production of [(C2C1im)2]2+ and C2C1imO have been proposed. The catalysis presumably includes the formation of the CuII(O2)CuII active centre with μ-η2:η2-peroxide bridging in analogy with tyrosinase and catechol oxidase activity. © 2014 The Royal Society of Chemistry

New Mixed-Ligand Complexes of Cobalt(II), Nickel(II), and Copper(II) with Adenosine 5′-Triphosphate and Amino Acids

In the systems metal [Co(II), Ni(II), Cu(II)]-adenosine 5′-triphosphate-amino acid (glycine, α-alanine, valine, proline) new mixed-ligand complexes with the adenosine 5′-triphosphate coordinated by deprotonated hydroxy groups of the ribose moiety were found; the stability and lability parameters of the compexes were determined, and their structures were assessed

New Mixed-Ligand Complexes of Cobalt(II), Nickel(II), and Copper(II) with Adenosine 5′-Triphosphate and Amino Acids

In the systems metal [Co(II), Ni(II), Cu(II)]-adenosine 5′-triphosphate-amino acid (glycine, α-alanine, valine, proline) new mixed-ligand complexes with the adenosine 5′-triphosphate coordinated by deprotonated hydroxy groups of the ribose moiety were found; the stability and lability parameters of the compexes were determined, and their structures were assessed

Modeling of Complex Formation Equilibria and Proton and Ligand Exchange Reactions in Aqueous Solutions of Oxovanadium(IV) with L- and DL-Histidine

For the further development of the magnetic relaxation method, the STABLAB program was implemented, which makes it possible to calculate both thermodynamic equilibrium parameters and kinetic characteristics of the proton and ligand exchange reactions from the results of parallel measurements of the spin relaxation times T1 and T2, of solvent nuclei. With this program, the nuclear magnetic relaxation data on water protons were used to calculate the stability constants and proton and ligand exchange rates for the complexes formed in the oxovanadium(IV)-L-histidine (LH) and oxovanadium(IV)-DL-histidine systems at pH 0.5-10: VOLH, VO(LH)2, VOL, VOL2H, VOL2, VOL2H1, and (VO)2L2H-2. The structures of these complexes were determined based on the comparison of isotropic EPR parameters, stability constants, and molar proton relaxation coefficients. LH is coordinated in the equatorial plane of oxovanadium(IV) through the NH2 and COO- groups or through the imidazole nitrogen atom and the carboxy group; both of these coordination modes concurrently occur in the VO(LH)2 structure. The occurrence of two ligands exerts a synergistic effect on stabilization of the VO(LH)2, VOL2H, and VOL2 bis-complexes, which is explained by the effect of d-π bonding in the complexes with the trans arrangement of the imidazole nitrogen atom of one ligand and the COO- group of the other ligand in the equatorial plane. This d-π bonding is the main cause of some other unusual effects - the stereoselectivity in the formation of the VOL2 complex and the fast spontaneous proton exchange for VOL2H-1. In the proton exchange reactions, the enhanced kinetic activity of the LH2 form is attributed to the occurrence of the intraligand microequilibrium of the proton migration from the imidazole moiety to the carboxy group in interaction with VO2+ and to the fast interligand proton transfer in interaction with VOLH. A significant stereoeffect in the ligand exchange reactions was found for the first time: the rate constant of the exchange between VOL2 and L in solutions with L-histidine is 1.5 times the constant in solutions with DL-histidine. This is rationalized by the fact that the imidazole nitrogen atom in the VOL2 meso form efficiently protect the axial position from the attack of the entering ligand. The extremely high kinetic activity of the LH form in the ligand exchange with the oxovanadium(IV) complexes as compared to the complexes of other metal ions is attributed to a special mechanism that implies the formation of the hydrogen bond involving the protonated nitrogen atom of LH and the oxygen atom of V=O, as well as to a rather high nucleophilicity of the imidazole nitrogen atom of LH

Modeling of Complex Formation Equilibria and Proton and Ligand Exchange Reactions in Aqueous Solutions of Oxovanadium(IV) with L- and DL-Histidine

For the further development of the magnetic relaxation method, the STABLAB program was implemented, which makes it possible to calculate both thermodynamic equilibrium parameters and kinetic characteristics of the proton and ligand exchange reactions from the results of parallel measurements of the spin relaxation times T1 and T2, of solvent nuclei. With this program, the nuclear magnetic relaxation data on water protons were used to calculate the stability constants and proton and ligand exchange rates for the complexes formed in the oxovanadium(IV)-L-histidine (LH) and oxovanadium(IV)-DL-histidine systems at pH 0.5-10: VOLH, VO(LH)2, VOL, VOL2H, VOL2, VOL2H1, and (VO)2L2H-2. The structures of these complexes were determined based on the comparison of isotropic EPR parameters, stability constants, and molar proton relaxation coefficients. LH is coordinated in the equatorial plane of oxovanadium(IV) through the NH2 and COO- groups or through the imidazole nitrogen atom and the carboxy group; both of these coordination modes concurrently occur in the VO(LH)2 structure. The occurrence of two ligands exerts a synergistic effect on stabilization of the VO(LH)2, VOL2H, and VOL2 bis-complexes, which is explained by the effect of d-π bonding in the complexes with the trans arrangement of the imidazole nitrogen atom of one ligand and the COO- group of the other ligand in the equatorial plane. This d-π bonding is the main cause of some other unusual effects - the stereoselectivity in the formation of the VOL2 complex and the fast spontaneous proton exchange for VOL2H-1. In the proton exchange reactions, the enhanced kinetic activity of the LH2 form is attributed to the occurrence of the intraligand microequilibrium of the proton migration from the imidazole moiety to the carboxy group in interaction with VO2+ and to the fast interligand proton transfer in interaction with VOLH. A significant stereoeffect in the ligand exchange reactions was found for the first time: the rate constant of the exchange between VOL2 and L in solutions with L-histidine is 1.5 times the constant in solutions with DL-histidine. This is rationalized by the fact that the imidazole nitrogen atom in the VOL2 meso form efficiently protect the axial position from the attack of the entering ligand. The extremely high kinetic activity of the LH form in the ligand exchange with the oxovanadium(IV) complexes as compared to the complexes of other metal ions is attributed to a special mechanism that implies the formation of the hydrogen bond involving the protonated nitrogen atom of LH and the oxygen atom of V=O, as well as to a rather high nucleophilicity of the imidazole nitrogen atom of LH