Porous molecular crystals are an emerging class of porous materials that is unique in being built from discrete molecules rather than being polymeric in nature. In this study, we examined the effects ...of molecular structure of the precursors on the formation of porous solid-state structures with a series of 16 rigid aromatics. The majority of these precursors possess pyrazole groups capable of hydrogen bonding, as well as electron-rich aromatics and electron-poor tetrafluorobenzene rings. These precursors were prepared using a combination of Pd- and Cu-catalyzed cross-couplings, careful manipulations of protecting groups on the nitrogen atoms, and solvothermal syntheses. Our study varied the geometry and dimensions of precursors, as well as the presence of groups capable of hydrogen bonding and π···π stacking. Thirteen derivatives were crystallographically characterized, and four of them were found to be porous with surface areas between 283 and 1821 m2 g–1. Common to these four porous structures were (a) rigid trigonal geometry, (b) π···π stacking of electron-poor tetrafluorobenzenes with electron-rich pyrazoles or tetrazoles, and (c) hydrogen bonding between the terminal heteroaromatic rings.
The goal of this paper is to study the contribution of taxation reformation to the provision of new quality of economic growth in Russia and China. The methodology is based on determining the ...interdependencies between the indicators of quality of economic growth and the indicators of taxation in Russia and China in 2003-2021 with the help of regression analysis, which allows verifying the offered hypothesis. A set of other econometric methods is also used. Novelty of this research is ensured by formation of a scientific and methodological basis for the complex qualitative treatment of economic growth from the positions of such aspects as conditions for business, digitalization, quality of life, investments, inflation, import, export, and unemployment. Originality of the research is achieved by means of a new - qualitative - view at economic growth and by determining the new quality of economic growth in Russia and China with a comparative research based on thorough analysis of their experience (which has not been sufficiently studied). Uniqueness of the research is due to the systemic view at taxation as a mechanism that ensures - at the same time - the general government structural balance and acceleration of the rate and increase of quality of economic growth.
Endometriosis remains one of the most topical diseases in current gynecology and is a multifactorial condition with an overgrowth of tissue morphologically and functionally similar to the endometrium ...outside the uterine cavity. One of the most frequently diagnosed forms of endometriosis is endometrioid ovarian cysts. An important feature of the clinical course of ovarian endometriosis is its negative impact on reproductive function and the recurrent nature of the disease, which may require repeated surgeries with even greater damage to the ovarian tissue. Therefore, the development of a long-term drug treatment strategy for patients with a history of endometrioid cysts aimed at preventing recurrences is urgently needed. According to domestic and foreign clinical guidelines, progestagen hormone therapy is recommended as first-line therapy for such patients. One of the most clinically studied drugs with a favorable efficacy and safety profile proven in numerous studies is dienogest. The paper presents the experience of foreign and domestic authors in conservative therapy in patients with a history of endometrioid cysts using dienogest in terms of recurrence prophylaxis.
Four new divalent tin benzenedicarboxylates (bdc) have been synthesized by hydrothermal techniques, and their structures have been determined from single crystal X-ray data. A chiral complex layer is ...formed by SnII and 1,2-bdc. In Sn(1,2-bdc)-II (2), such layers are stacked in a AA pattern, leading to a chiral and polar structure with the space group symmetry C2, while in Sn(1,2-bdc)-I (1) the same layer is alternately stacked with the mirror-image layer, leading to a structure with the space group C2/c. The one-sided coordination of SnII combined with the 120° angle of the carboxylate groups in 1,3-bdc results in the tubular structure of Sn(1,3-bdc) (3). The tubes are connected by very weak intertube Sn−O bonds. The compound Sn3O(1,4-bdc)2 (4) has a 3D framework structure based on Sn3O triangular secondary building units that are cross-linked by the 1,4-bdc ligands. Strong π−π interactions occur between the neighboring phenyl rings.
A series of alkali-metal tin benzenedicarboxylates A2Sn2(bdc)3(H2O) x , A = Li, Na, K, Rb, Cs, in single crystal forms have been synthesized by using a hydrothermal technique. The compounds all have ...cubic crystal structures based on a very open anionic Sn2(bdc)32− framework which is 8-fold interpenetrated noncentrosymmetrically (space group I23) in Li2Sn2(bdc)3(H2O)2, 1, K2Sn2(bdc)3, 3, Rb2Sn2(bdc)3, 4, and Cs2Sn2(bdc)3, 5, but centrosymmetrically (space group Pn3̅) in Na2Sn2(bdc)3(H2O), 2. The ion size and coordination requirements of the alkali ions play an important role in the interpenetration of the anionic framework and the symmetry of the structures.
A new copper (II) complex, {Cu(OH)(phen)}4∙(ClO4)4, having a Cu4O4 cubane core was synthesized hydrothermally and characterized by single crystal X-ray diffraction. The best fit to the 2–300 K ...magnetic data was obtained with a previously unreported 1 + 1 + 4 model for the exchange coupling between the copper (II) ions.
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•A new example of a Cu(II) complex with a Cu4O4 cubane core was synthesized and characterized.•The magnetic interactions are between the four Cu ions connected by μ3-hydroxo groups.•The magnetic susceptibility data indicate a singlet total spin multiplicity.•A 1+1+4 model was used to fit the data with three exchange constants.•The exchange constants (cm−1) are J1 = −28.0, J2 = +72.2, and J3 = −15.3.
The dependence on structure of the magnetic exchange coupling between copper (II) ions in complexes containing Cu4O4 cubane units has been the subject of several previous studies. A new example of a tetranuclear copper (II) complex, {Cu(OH)(phen)}4∙(ClO4)4 (1), having a Cu4O4 cubane core is reported here. 1 was synthesized hydrothermally at 80 °C using 1,10-phenanthroline (phen) as a ligand in a mildly acidic water/ethanol solution (pH = 4.8–5.3) and structurally characterized by single crystal X-ray crystallography. The best fit to the magnetic data in the 2–300 K temperature range was obtained with a previously unreported 1 + 1 + 4 model for the exchange coupling among the copper (II) ions with J1 = − 28.0 cm−1, J2 = +72.2 cm−1, and J3 = − 15.3 cm−1. The model corresponds to one medium, one short, and four long exchange pathways. The overall predominant antiferromagnetic exchange leads to a singlet total spin ground state.
The A-site ordered double-perovskite oxides, LnBaMn2O5+δ (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of ...these materials. The present results are compared with our previous data for YBaMn2O5+δ. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn2O5+δ. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln3+ ions larger than Y3+. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn2O5 and fully-oxidized LnBaMn2O6 during changes of the oxygen partial pressure between air and 1.99% H2/Ar. In addition, the oxygen non-stoichiometries of GdBaMn2O5+δ and PrBaMn2O5+δ were determined as a function of pO2 at 600, 650, 700 and 750°C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching ~6. The stabilities of the LnBaMn2O5+δ phases extend over a wide range of oxygen partial pressures (∼10−25≤pO2 (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln3+ cation the lower pO2 for phase conversion. At some temperatures and pO2 conditions, the LnBaMn2O5+δ compounds are unstable with respect to decomposition to BaMnO3−δ and LnMnO3. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions.
Structure of LnBaMn2O5.5 and the variation of stoichiometry of GdBaMn2O5+x with −log(pO2)
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•Determination of the oxygen non-stoichiometry of GdBaMn2O5+δ and PrBaMn2O5+δ as a function of pO2 and T.•Establishment of pO2 ranges of stability of O5 and O5.5 at 600°C, 650°C, 700°C and 750°C.•Investigation of the kinetic instability of LnBaMn2O5+δ (Ln=Gd, Pr) with respect to decomposition to BaMnO3−x and LnMnO3•Comparison of the thermodynamics of the oxidation of LnBaMnO5 (Ln=Y, Gd, Pr) as a function of the rare earth cation size
The A-site ordered double-perovskite oxides, LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage ...properties of these materials. The present results are compared with our previous data for YBaMn{sub 2}O{sub 5+δ}. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn{sub 2}O{sub 5+δ}. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln{sup 3+} ions larger than Y{sup 3+}. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn{sub 2}O{sub 5} and fully-oxidized LnBaMn{sub 2}O{sub 6} during changes of the oxygen partial pressure between air and 1.99% H{sub 2}/Ar. In addition, the oxygen non-stoichiometries of GdBaMn{sub 2}O{sub 5+δ} and PrBaMn{sub 2}O{sub 5+δ} were determined as a function of pO{sub 2} at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching ~6. The stabilities of the LnBaMn{sub 2}O{sub 5+δ} phases extend over a wide range of oxygen partial pressures (∼10{sup −25}≤pO{sub 2} (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln{sup 3+} cation the lower pO{sub 2} for phase conversion. At some temperatures and pO{sub 2} conditions, the LnBaMn{sub 2}O{sub 5+δ} compounds are unstable with respect to decomposition to BaMnO{sub 3−δ} and LnMnO{sub 3}. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions. - Graphical abstract: Structure of LnBaMn{sub 2}O{sub 5.5} and the variation of stoichiometry of GdBaMn{sub 2}O{sub 5+x} with −log(pO{sub 2}) Display Omitted - Highlights: • Determination of the oxygen non-stoichiometry of GdBaMn{sub 2}O{sub 5+δ} and PrBaMn{sub 2}O{sub 5+δ} as a function of pO{sub 2} and T. • Establishment of pO{sub 2} ranges of stability of O{sub 5} and O{sub 5.5} at 600 °C, 650 °C, 700 °C and 750 °C. • Investigation of the kinetic instability of LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr) with respect to decomposition to BaMnO{sub 3−x} and LnMnO{sub 3} • Comparison of the thermodynamics of the oxidation of LnBaMnO{sub 5} (Ln=Y, Gd, Pr) as a function of the rare earth cation size.
A large spin, magnetically anisotropic, octanuclear vanadium(
iii
) wheel-like cluster has been synthesized. The coupling between adjacent V
III
ions is ferromagnetic giving a ground state of
S
t
= ...8, the largest known for a vanadium-based complex.
A large spin, magnetically anisotropic, ferromagnetically coupled octanuclear vanadium(
iii
) wheel-like cluster has been synthesized.
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