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91.
Olson C Heth CL Lapidus SH Stephens PW Halder GJ Pokhodnya K 《The Journal of chemical physics》2011,135(2):024503
The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of M(II)(TCNE) (NCMe)(2)[SbF(6)] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly reso-lved crystal structures. The vibrational properties of the isolated TCNE(●-) anion in the paramagnetic Bu(4)N [TCNE(●-)] salt and recently characterized 2D layered magnet Fe(II)(TCNE)(NCMe)(2)[FeCl(4)] are also reported for comparison. Additionally, a linear correlation between ν(C=C) (a(g)) frequency of the TCNE ligand and its formal charge Z (the spin density on the π* orbital), Z = [1571 - ν(C=C) (a(g))]/154.5 [e], is presented. It is shown that monitoring Z by Raman spectroscopy is of great use in providing information that allows understanding the peculiarity of the superexchange interaction in M-[TCNE] magnets and establishing the structure-magnetic properties correlations in this class of magnetic material. 相似文献
92.
2,3-Naphthalenediol on superelectrophilic activation with aluminium halides smoothly reacts with benzene to give 4-((3-phenyl-1H-inden-1-yl)methyl)benzene-1,2-diol, which in turn undergoes intramolecular cyclization to form 5,10-methano-5-phenyldibenzo[a,d]cycloheptane-2,3-diol. The mechanistic aspects of these unusual transformations are discussed. 相似文献
93.
T. V. Rodionova Yu. A. Dyadin K. A. Udachin Ya. Lipkowski K. Suwinska 《Journal of Structural Chemistry》1995,36(3):458-464
Phase diagrams of some binary aqueous systems with tetraalkylammonium fluorides are examined. The size of the hydrophobic
moiety of the guest is consecutively varied in the series (i-C5H11)4−k(C4H9)kNF (k=0, 1, 2, 3) by replacing bulky isoamyl radicals with n-butyl radicals. Changes in clathrate formation caused by variations
of the sizes and forms of guests are analyzed in the series (i-C5H11)k−4(C4H9)kNF−H2O (k=0, 1, 2, 3, 4). All tetraisoamylammonium fluoride hydrates are more stable than other hydrates of this series. The stability
of the compounds increases due to the fact that the isoamyl radicals use the host cavities more effectively than the butyl
radicals. In all hydrates of the series, tetragonal structures-I (TS-I), which were earlier thought typical only for hydrates
of tetrabutylammonium salts, are formed. Hydrates of the orthorhombic system are formed until three isoamyl radicals have
been replaced by butyl radicals. Hydrates with 26–28 water molecules (mp 27.4–34.6°C) are the most stable hydrates of the
series, except for i-AmBu3NF·25.9 H2O, melting 0.3°C lower than the tetragonal hydrate in the same system. All compounds are defined chemically, and for some
of them crystal data are given.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Physical Chemistry, Polish Academy
of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 501–508, May–June, 1995.
Translated by L. Smolina 相似文献
94.
Vadim A. Dubskikh Anna A. Lysova Denis G. Samsonenko Alexander N. Lavrov Konstantin A. Kovalenko Danil N. Dybtsev Vladimir P. Fedin 《Molecules (Basel, Switzerland)》2021,26(5)
Three new 3D metal-organic porous frameworks based on Co(II) and 2,2′-bithiophen-5,5′-dicarboxylate (btdc2−) [Co3(btdc)3(bpy)2]·4DMF, 1; [Co3(btdc)3(pz)(dmf)2]·4DMF·1.5H2O, 2; [Co3(btdc)3(dmf)4]∙2DMF∙2H2O, 3 (bpy = 2,2′-bipyridyl, pz = pyrazine, dmf = N,N-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co3(RCOO)6}, connected either by btdc2– ligands (1, 3) or by both btdc2– and pz bridging ligands (2). The permanent porosity of 1 was confirmed by N2, O2, CO, CO2, CH4 adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m2⋅g−1 and promising gas separation performance with selectivity factors up to 35.7 for CO2/N2, 45.4 for CO2/O2, 20.8 for CO2/CO, and 4.8 for CO2/CH4. The molar magnetic susceptibilities χp(T) were measured for 1 and 2 in the temperature range 1.77–330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds 1 and 2 are μeff (300 K) ≈ 4.93 μB. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures T < 20 K in 2 between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of 1 and 2. 相似文献
95.
96.
Pavel V. Avramov Konstantin N. Kudin Gustavo E. Scuseria 《Chemical physics letters》2003,370(5-6):597-601
We study the electronic structure of a variety of single wall carbon nanotubes and report density of states obtained with the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation and hybrid PBE0 approximation of density functional theory using Gaussian orbitals and periodic boundary conditions. PBE gives very good results for metallic tubes but the addition of a portion of exact exchange in the hybrid PBE0 functional worsens the agreement between experiment and theory. On the other hand, the PBE0 hybrid significantly improves the theoretical predictions (compared to PBE) for semiconducting tubes. 相似文献
97.
Lyudmila V Saloutina Aleksandr Ya Zapevalov Konstantin A Lyssenko Victor I Saloutin 《Journal of fluorine chemistry》2003,120(1):41-47
The reaction of oxides of internal trans- and cis-perfluoroolefins with (1S, 4S)- or racemic camphor thiosemicarbazone leads to the formation of trans- and cis-isomers of (1S, 4S)- or racemic camphor 5′-fluoro-4′-hydroxy-4′,5′-di(perfluoroalkyl)-1′,3′-thiazolinyl-2′-hydrazones, respectively. Unsymmetrical dodecafluoro-2,3-epoxyhexane yields a mixture of regioisomeric hydrazones. The molecular structure of the trans-isomer of (1S, 4S)-camphor 5′-fluoro-4′-hydroxy-4′,5′-bis(trifluoromethyl)-1′,3′-thiazolinyl-2′-hydrazone has been established by X-ray crystallography. The quite rare example of cocrystallization of two diastereomers of the latter in homochiral crystal (sp. group P21) has been revealed. 相似文献
98.
Mikhail E. Minyaev Alexandr A. Vinogradov Dmitrii M. Roitershtein Konstantin A. Lyssenko Ivan V. Ananyev Ilya E. Nifant'ev 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):578-584
The significant variety in the crystal structures of rare‐earth carboxylate complexes is due to both the large coordination numbers of the rare‐earth cations and the ability of the carboxylate anions to form several types of bridges between rare‐earth metal atoms. Therefore, these complexes are represented by mono‐, di‐ and polynuclear complexes, and by coordination polymers. The interaction of LnCl3(thf)x (Ln = Eu or Y; thf is tetrahydrofuran) with sodium or diethylammonium diphenylacetate in methanol followed by recrystallization from a DME/THF/hexane solvent mixture (DME is 1,2‐dimethoxyethane) leads to crystals of the non‐isomorphic dinuclear complexes tetrakis(μ‐2,2‐diphenylacetato)‐κ4O:O′;κ3O,O′:O′;κ3O:O,O′‐bis[(1,2‐dimethoxyethane‐κ2O,O′)(2,2‐diphenylacetato‐κ2O,O′)europium(III)], [Eu(C14H11O2)6(C4H10O2)2], (I), and tetrakis(μ‐2,2‐diphenylacetato)‐κ4O:O′;κ3O,O′:O′;κ3O:O,O′‐bis[(1,2‐dimethoxyethane‐κ2O,O′)(2,2‐diphenylacetato‐κ2O,O′)yttrium(III)], [Y(C14H11O2)6(C4H10O2)2], (II), possessing monoclinic (P21/c) symmetry. The [Ln(Ph2CHCOO)3(dme)]2 molecule (Ln = Eu or Y) lies on an inversion centre and exhibits three different coordination modes of the diphenylacetate ligands, namely bidentate κ2O,O′‐terminal, bidentate μ2‐κ1O:κ1O′‐bridging and tridentate μ2‐κ1O:κ2O,O′‐semibridging. The terminal and bridging ligands in (I) are disordered over two positions, with an occupancy ratio of 0.806 (2):0.194 (2). The interaction of EuCl3(thf)2 with Na[Ph3CCOO] in methanol followed by crystallization from hot methanol produces crystals of tetrakis(methanol‐κO)tris(2,2,2‐triphenylacetato)‐κ4O:O′;κO‐europium(III) methanol disolvate, [Eu(C19H15O2)3(CH3OH)4]·2CH3OH, (III)·2MeOH, with triclinic (P) symmetry. The molecule of (III) contains two O,O′‐bidentate and one O‐monodentate terminal triphenylacetate ligand. (III)·2MeOH possesses one intramolecular and four intermolecular hydrogen bonds, forming a [(III)·2MeOH]2 dimer with two bridging methanol molecules. 相似文献
99.
Interrupted Baeyer–Villiger Rearrangement: Building A Stereoelectronic Trap for the Criegee Intermediate 下载免费PDF全文
Dr. Vera A. Vil' Gabriel dos Passos Gomes Oleg V. Bityukov Prof. Konstantin A. Lyssenko Prof. Gennady I. Nikishin Prof. Igor V. Alabugin Prof. Alexander O. Terent'ev 《Angewandte Chemie (International ed. in English)》2018,57(13):3372-3376
The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer–Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2‐alkyl shift. Stable cyclic Criegee intermediates constrained within a five‐membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β‐hydroperoxy‐β‐peroxylactones) which were formed in high yields in reaction of β‐ketoesters with BF3?Et2O/H2O2. 相似文献
100.
High‐Pressure Synthesis of a Nitrogen‐Rich Inclusion Compound ReN8⋅x N2 with Conjugated Polymeric Nitrogen Chains 下载免费PDF全文
Dr. Maxim Bykov Dr. Elena Bykova Egor Koemets Timofey Fedotenko Georgios Aprilis Dr. Konstantin Glazyrin Dr. Hanns‐Peter Liermann Dr. Alena V. Ponomareva Johan Tidholm Dr. Ferenc Tasnádi Prof. Dr. Igor A. Abrikosov Prof. Dr. Natalia Dubrovinskaia Prof. Dr. Leonid Dubrovinsky 《Angewandte Chemie (International ed. in English)》2018,57(29):9048-9053
A nitrogen‐rich compound, ReN8?x N2, was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser‐heated diamond anvil cell. Single‐crystal X‐ray diffraction revealed that the crystal structure, which is based on the ReN8 framework, has rectangular‐shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN8?x N2 is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [?N=N?]∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN8?x N2 provide strong support for the experimental results and conclusions. 相似文献