查看更多>>摘要：Various strategies for producing lanthanide-containing luminescent sensors, which were used mainly in the studies of 2015-2021, are considered. The review is structured according to the types of sensor response and analyte nature. Particular attention is focused on the mechanisms of sensor response to a certain analyte.
查看更多>>摘要：The primary (ultrafast) photophysical and photochemical processes characteristic of the following halogen-containing complexes of platinum group metals were examined: hexahalide complexes ((PtBr62-)-Br-IV, (PtCl62-)-Cl-IV, (IrCl62-)-Cl-IV, (IrBr62-)-Br-IV, (OsCl62-)-Cl-IV, and (OsBr62-)-Br-IV), pseudohexahalide complex Pt-IV(SCN)(6)(2)(-), and mixed diiodide complexes of Pt-IV. The historical and practical aspects of the photochemistry of platinum metals complexes are presented. The ultrafast (femtosecond) research methods and general features of ultrafast processes that occur in the presence of coordination compounds are outlined. The stages of target product transformation from the absorption of a light quantum to the formation of final products are considered. The levels of completeness of research for each of the systems examined are listed.
Smolobochkin, A., VGazizov, A. S.Garifzyanov, A. R.Burilov, A. R....
7页
查看更多>>摘要：This review covers and summarizes comprehensive data reported within the period from 2017 to 2021 on the synthetic strategies and approaches to 1H-pyrazolo[3,4-b]pyridine derivatives. Methods for the synthesis are systematized according to the method to assemble the pyrazolopyridine system, whereas their advantages and drawbacks are considered.
Kuptsova, A. O.Vinogradova, E. E.Kravchenko, A. N.Gazieva, G. A....
20页
查看更多>>摘要：The review is focused on the desulfurization of imidazolidine-2-thiones to imidazolidin-2-ones, which are widely applied in the synthesis of natural and synthetic practically useful compounds, primarily biologically active substances. The described methods are systematized in accordance to the key transformations, namely, nucleophilic substitution, oxidation, and more complex cascade reactions.
查看更多>>摘要：The formation of products of oxidative and reductive allylation of norbornadiene by allyl formate (AF) in the presence of Pd-0 triphenylphosphine complexes was modeled by the PBE/L11 method in terms of the density functional theory. According to calculations of all most probable routes to the norbornadiene allylation products, the highest energy barriers correspond to the transition state of formation of the first C-C bond. Two complexes, Pd(AF)(PPh3)(2) and Pd(AF)(PPh3), can be treated as catalytically active ones. The PPh3 ligands cause a 7.6-8.2 kcal mol(-1) decrease in the activation barriers to the formation of the second C-C bond necessary to generate the products of oxidative allylation of norbornadiene. The formation of 5-methylene-6-vinylbicyclo[2.2.1]-hept-2-ene proceeds via opening of the cyclobutane ring.
查看更多>>摘要：The enzyme-substrate complexes of penicillin-binding proteins PBP2 from FA19, 35/02, and H041 strains of Nisseria gonorrhoeae with ceftriaxone were simulated by the molecular dynamics method with the combined quantum mechanics/molecular mechanics potentials. The hydrogen bond lengths between the carbonyl oxygen atom of the substrate and amino acid residues of the oxyanion hole, as well as the distances of the nucleophilic attack by the oxygen atom of the catalytic serine of the carbonyl carbon atom of the substrate were considered. The 2D maps of the Laplacian of electron density show a more efficient activation of the substrate by the wild type enzyme rather than mutated species. This is consistent with the geometry features: distributions of the lengths of hydrogen bonds forming oxyanion hole and nucleophilic attack distance that are shifted toward lower values.
Kulakova, A. M.Mulashkina, T., INemukhin, A., VKhrenova, M. G....
6页
查看更多>>摘要：Full-atom molecular models of the phosphotriesterase dimer from the Pseudomonas diminuta bacterium with organophosphorus compounds bearing good and poor leaving groups, dibutyl p-nitrophenyl phosphate and dibutyl phenyl phosphate, respectively, were constructed. Molecular dynamic simulations with combined quantum mechanics/molecular mechanics (QM/MM) potentials depicted differences in the properties of intermediates of the hydrolysis reaction with pentacoordinated phosphorus for these substrates. In the case of a substrate with the good leaving group, the bond between the phosphorus and oxygen atoms of the leaving group is weaker than that between the phosphorus and oxygen atoms of the nucleophilic hydroxide anion, which leads to an almost barrierless formation of the reaction products from the intermediate. For the substrate with the poor leaving group, an opposite pattern is observed, which favors the return of the system from the intermediate to reactants. These conclusions were made on the basis of an analysis of the distributions of bond lengths along the trajectories, as well as from an analysis of the maps of the Laplacian of electron density in the reaction region.
查看更多>>摘要：Decomposition reactions of azoalkanes of different structure were studied by quantum chemistry methods (MP2/6-311++G** calculations) and by the method of three intersecting parabolas (M3IP). The MP2 method was used to obtain the transition-state geometries, the bond lengths in the molecules under study, and the activation energies. Possible mechanisms of decomposition are discussed. Concerted decomposition of branched azoalkanes was shown to be the most probable mechanism of the process. The M3IP method was used to calculate the kinetic and thermodynamic parameters of concerted decomposition of azoalkanes and to determine and evaluate the main factors affecting the activation energy (E). The stabilization energy of the radical being formed in the decomposition reaction is one of the key factors determining the concerted mechanism. The kinetic parameters calculated by the two independent methods are in good agreement.
查看更多>>摘要：The molecular structures and relative energies of stereoisomers of the Co-?? and Ni-?? bis(chelate) complexes composed of hexa-, penta-, or tetracoordinate metal atoms and (N, O, O)-tridentate azomethine ligands and having the MN2O2O2, MN2O2O, and MN2O2 coordination sites, respectively, were obtained from the B3LYP (PBE0, TPSSh)/6-311++G(d,p)) density functional calculations. Simulation of the mechanism of formation of the complexes revealed the energy preferableness of the structures with hexacoordinate central atoms.
Topchiy, M. A.Ageshina, A. A.Rzhevskiy, S. A.Minaeva, L., I...
6页
查看更多>>摘要：The effect of various factors on the activity and selectivity of palladium N-heterocyclic carbene (NHC) complexes in the telomerization of isoprene with alcohols has been studied. The leaving group of the palladium complex does not affect the results of telomerization of isoprene with methanol, which leads to a predominant formation of the head-to-head product. The use of more fatty alcohols as nucleophiles changes the reaction selectivity toward a preferential formation of the head-to-tail isomers.
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Springer Nature