A numerical approach to model chemistry of complex organic molecules in a protoplanetary disk

Multiphase astrochemical modeling presents a numerical challenge especially for the simulation of objects with the wide range of physical parameters such as protoplanetary disks. We demonstrate an implementation of the analytical Jacobian for the numerical integration of the system of differential rate equations that govern chemical evolution in star-forming regions. The analytical Jacobian allowed us to greatly improve the stability of the code in protoplanetary disk conditions. We utilize the MONACO code to study the evolution of abundances of chemical species in protoplanetary disks. The chemical model includes 670 species and 6,015 reactions in the gas phase and on interstellar grains. The specific feature of the utilized chemical model is the inclusion of low-temperature chemical processes leading to the formation of complex organic molecules (COMs), included previously in the models of chemistry of COMs in prestellar clouds. To test the impact of analytical Jacobian on the stability of numerical simulations of chemical evolution in protoplanetary disks, we calculated the chemical composition of the disk using a two-phase model and four variants of the chemical reaction network, three values of the surface diffusion rates, and two types of the initial chemical composition. We also show a preliminary implementation of the analytical Jacobian to a three-phase model. © 2022 Mikhail Yu. Kiskin et al., published by De Gruyter.Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2020-0038; Foundation for the Advancement of Theoretical Physics and Mathematics: 20-1-2-20-1Funding information : MYK and AIV acknowledge the support Ministry of Science and Higher Education of the Russian Federation via the State Assignment contract FEUZ-2020-0038. VVA is grateful to the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS” for financial support (20-1-2-20-1)

Easy-plane to easy-axis anisotropy switching in a Co(ii) single-ion magnet triggered by the diamagnetic lattice

Single ion magnets SIMs with large magnetic anisotropy are promising candidates for realization of single molecule based magnetic memory and qubits. Creation of materials with magnetically uncoupled spatially separated SIMs requires dilution in a diamagnetic matrix. Herein, we report that progressive dilution of paramagnetic Co II by diamagnetic Zn II in the SIM [CoxZn 1 amp; 8722;x piv 2 2 NH2 Py 2], x 1 0 beyond a threshold of 50 reveals an abrupt structural change, where the distorted tetrahedral Zn coordination structure is superimposed on the remaining Co ions, which were initially in a distorted octahedral environment. Dilution induced structure modification switches the magnetic anisotropy from easy plane D 36.7 cm amp; 8722;1 to easy axis type D amp; 8722;23.9 cm amp; 8722;1 , accompanied by a fivefold increase of the magnetic relaxation time at 2 K. Changes of the static and dynamic magnetic properties are monitored by electron paramagnetic resonance spectroscopy and AC susceptibility measurements. Complementary quantum chemical ab initio calculations quantify the influence of structural changes on the electronic structure and the magnetic anisotropy. Thus, magnetic dilution hits two goals at once, the creation of isolated magnetic centres and an improvement of their SIM propertie

Numerical Studies of the Chemical Evolution of Protoplanetary Disks: Event Treatment in the Three-Phase Model

В случае трехфазного (газ — поверхность — мантия) астрохимического моделирования вид системы балансных дифференциальных уравнений зависит от текущего состояния решения этой системы. Таким образом, уравнения оказываются с разрывной правой частью и не интегрируются в классическом понимании. Подобные уравнения также носят название уравнений с «событиями». Игнорирование этого факта может приводить к ошибкам и проблемам в работе численного интегратора. Наше исследование показало, что учет событий является критически важным для астрохимического моделирования в широком диапазоне физических параметров, характерных для протопланетных дисков. Для повышения стабильности и скорости расчетов в численный код MONACO были добавлены отслежевание событий и дальнейшая корректировка хода решения.In the case of three-phase (gas-surface-bulk) astrochemical modeling, the form of the system of differential rate equations depends on the current state of the solution of this system. Thus, the equations turn out to have a discontinuous right-hand side and are not integrated in the classical sense. Similar equations are also called equations with ”events”. Ignoring this fact can lead to errors and problems in the operation of the numerical integrator. Our study showed that accounting for events is critical for astrochemical modeling in a wide range of physical parameters typical of protoplanetary disks. To improve the stability and speed of calculations, event tracking and further correction of the solution progress were added to the MONACO numerical code.Работа выполнена при финансовой поддержке Министерства науки и высшего образования Российской Федерации, тема FEUZ-2020-0038

Expanding 1,2,4-triketone Toolbox for use as Aluorinated Building Blocks in the Synthesis of Pyrazoles, Pyridazinones and β-diketohydrazones

Fluorinated lithium β-diketonates bearing a methyl acetal group behave in the condensation reactions with hydrazines as trielectrophilic building blocks for the preparation of pyrazoles, pyridazinones and β-diketohydrazones. For the first time, solvent-induced regioisomeric and heterocyclic ring size-controlled formation was observed for 1,2,4-triketone analogues. Fluoroalkylated acetyl NH-pyrazoles or substituted 5-RF-pyrazoles were obtained from the acid-catalyzed cyclocondensation of lithium β-diketonates with (aryl)hydrazines in ethanol. In methanol solvent acetyl-containing 3-CF3-pyrazoles were isolated because of inverse nucleophilic attack of arylhydrazines. The use of aprotic acetonitrile in the condensation resulted in regioselective trifluorinated pyridazinones and fluorinated β-diketohydrazones formation via initial acetal fragment interaction with N,N-dinucleophile. © 2021 Elsevier B.V.This work carried out in the framework of the basic theme of the Russian Academy of Sciences (state registration № AAAA-A19-119011790132-7). Single-crystal X-ray diffraction analysis for 3g, 3f and 10a was performed using the equipment of the JRC PMR IGIC RAS. Single-crystal X-ray diffraction analysis for 5d, 7a, 9a and physicochemical studies were carried out using the equipments of the Center for Joint Use "Spectroscopy and Analysis of Organic Compounds" at the Postovsky Institute of Organic Synthesis UB RAS

Betaine–N-Heterocyclic Carbene Interconversions of Quinazolin-4-One Imidazolium Mesomeric Betaines. Sulfur, Selenium, and Borane Adduct Formation

Reaction of N-alkylated imidazoles with 2-chloro-4-quinazolinone gave mesomeric betaines, 2-(1-alkyl-1H-imidazolium-3-yl)quinazolin-4-olates, for which three tautomeric forms of N-heterocyclic carbenes (NHCs) can be formulated, in addition to an anionic NHC after deprotonation. The NHC tautomers were trapped with sulfur, selenium, triethylborane, and triphenylborane as thiones, selenones and borane adducts, respectively. We obtained two isomers of the cyclic borane adducts, diazaboroloquinazolinones with [1,5-a] and [5,1-b]-type fusion between the quinazolinone and the diazaborole rings. They correspond to two different NHC tautomers and to the anionic NHC derived thereof. The third NHC tautomer was trapped as a non-cyclic adduct with tris(pentafluorophenyl)borane by coordination to the quinazoline oxygen atom. 2D 1H-15N HMBC experiments of 15N-labeled quinazolinone fragments, quantitative measurements of long-range 1H-15N coupling constants (JHN), and five X-ray single crystal analyses have been carried out for the structure elucidations and to gain insight into the NMR spectroscopic properties of these compounds. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.Russian Foundation for Basic Research, RFBR: 17-03-01029Deutscher Akademischer Austauschdienst, DAADMinistry of Education and Science of the Russian Federation, Minobrnauka: 4.6351.2017/8.9This work was supported by the Russian Ministry of Education and Science (State contract 4.6351.2017/8.9) and the Russian Foundation for Basic Research (grant 17-03-01029). Single crystal X-ray analysis of 23b was performed at the User Facilities Centers of IGIC RAS within the State Assignment on Fundamental Research to the Kurnakov Institute of General and Inorganic Chemistry. We thank the Deutscher Akademischer Austauschdienst DAAD for the financial support of the internship of S. D. at Clausthal University of Technology, Germany

Easy-plane to easy-axis anisotropy switching in a Co(ii) single-ion magnet triggered by the diamagnetic lattice

Single-ion magnets (SIMs) with large magnetic anisotropy are promising candidates for realization of single-molecule based magnetic memory and qubits. Creation of materials with magnetically uncoupled spatially separated SIMs requires dilution in a diamagnetic matrix. Herein, we report that progressive dilution of paramagnetic Co(ii) by diamagnetic Zn(ii) in the SIM ([CoxZn(1−x)(piv)2(2-NH2-Py)2], x = 1 ÷ 0) beyond a threshold of 50% reveals an abrupt structural change, where the distorted tetrahedral Zn coordination structure is superimposed on the remaining Co ions, which were initially in a distorted octahedral environment. Dilution-induced structure modification switches the magnetic anisotropy from easy-plane (D = 36.7 cm−1) to easy-axis type (D = −23.9 cm−1), accompanied by a fivefold increase of the magnetic relaxation time at 2 K. Changes of the static and dynamic magnetic properties are monitored by electron paramagnetic resonance spectroscopy and AC susceptibility measurements. Complementary quantum chemical ab initio calculations quantify the influence of structural changes on the electronic structure and the magnetic anisotropy. Thus, magnetic dilution hits two goals at once, the creation of isolated magnetic centres and an improvement of their SIM properties

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone, Bearing Pyrazole Moiety and CHF2-Group: Structure, Color Tuning, and Kinetics of Energy Transfer between Lanthanide Ions

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL3(H2O)2], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [EuxTb1-xL3(H2O)2] (EuxTb1-xL3), [EuxGd1-xL3(H2O)2] (EuxGd1-xL3), and [GdxTb1-xL3(H2O)2] (GdxTb1-xL3), were studied. The EuxTb1-xL3 complexes exhibit the simultaneous emission of both Eu3+ and Tb3+ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu3+. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb3+ and Eu3+ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation