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排序方式: 共有96条查询结果,搜索用时 15 毫秒
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Dirk Schlüter Florian Kleemiss Dr. Malte Fugel Dr. Enno Lork Prof. Dr. Kunihisa Sugimoto PD Dr. Simon Grabowsky Prof. Dr. Jeffrey R. Harmer Dr. Matthias Vogt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1335-1343
Derivatives of 1,2-dithienylethene (DTE) have superb photochromic properties due to an efficient reversible photocyclization reaction of their hexatriene structure and, thus, have application potential in materials for optoelectronics and (multi-responsive) molecular switches. Transition-metal complexes bearing switchable DTE motifs commonly incorporate their coordination site rather distant from the hexatriene system. In this work the redox active ligand 1,2-bis(2,5-dimethylthiophen-3-yl)ethane-1,2-dione is described, which reacts with [V(TMEDA)2Cl2] to give a rare non-oxido vanadium(IV) species 3(M,M/P,P) . This blue complex has two bidentate en-diolato ligands which chelate the VIV center and give rise to two five-membered metallacycles with the adjacent hexatriene DTE backbone bearing axial chirality. Upon irradiation with UVA light or prolonged heating in solution, the blue compound 3(M,M/P,P) converts into the purple atropisomer 4(para,M/para,P) . Both complexes were isolated and structurally characterized by single-crystal X-ray diffraction analysis (using lab source and synchrotron radiation). The antiparallel configuration (M or P helicity) present in both 3(M,M/P,P) and 4(para,M/para,P) is a prerequisite for (reversible) 6π cyclization reactions. A CW EPR spectroscopic study reveals the metalloradical character for 3(M,M/P,P) and 4(para,M/para,P) and indicates dynamic reversible cyclization of the DTE backbone in complex 3(M,M/P,P) at ambient temperature in solution. 相似文献
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We present a combined Monte‐Carlo/molecular dynamics study of a Cu0.327Ni0.673 alloy system. On the basis of nearest‐neighbor coordination number analyses atomic clustering and phase segregation is explored. Along this line, free energy profiles are calculated and separated into entropic and energetic contributions. The competition of both terms was found in accordance to the experimental phase diagrams (phase separation of the solid solution below about 600 Kelvin). Two independent simulation runs were performed. At 1000 Kelvin the observed configurations correspond to solid solutions exhibiting a weak tendency to cluster atoms of identical species. At room temperature the energetic favoring of atomic separation is clearly dominant and leads to the formation of Ni‐rich and Cu‐rich domains. The latter are separated by interfacial regions whose width ranges from 0.5 to 1 nanometers. 相似文献
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Reaction of iron(II) thiocyanate with 4,4‐bipyridine (bipy) in methanol leads to the formation of three new solvates of different composition depending on the reaction conditions: At room temperature two new ligand‐rich 1:2 (1:2 = ratio between metal and N‐donor ligand) polymorphic forms [Fe(NCS)2(bipy)2 · 2MeOH]n ( 1I ) and [Fe(NCS)2(bipy)(MeOH)2 · (bipy)]n ( 1II ) are obtained, whereas solvothermal conditions leads to the formation of the new ligand‐deficient 1:1 compound [{Fe(NCS)2(bipy)(MeOH)}2]n ( 2 ). All crystal structures were determined by X‐ray single crystal structure analysis. In the crystal structure of modification 1I the metal atoms are coordinated by four bridging bipy ligands, which connect them into layers. The methanol molecules occupy voids in the structure. Compared to 1I in modification 1II the crystal structure contains of linear Fe–bipy–Fe chains, which are further connected by hydrogen bonds between coordinating MeOH and noncoordinated bipy ligands into layers. The ligand‐deficient 1:1 compound 2 shows a completely different coordination topology with linear Fe–bipy–Fe chains, which are connected by coordinating methanol molecules into double‐chains. In all compounds the thiocyanato anions are terminal N‐bonded to the metal atoms. Investigation of the thermal behavior of compound 1I shows a two‐step decomposition, in which ligand‐deficient intermediates are formed. Magnetic measurements on 1I reveal Curie–Weiss paramagnetism with increasing antiferromagnetic interactions on cooling. 相似文献
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Gunter Heymann Jan F. Riecken Sudhindra Rayaprol Sandra Christian Rainer Pöttgen Prof. Dr. Hubert Huppertz PD Dr. 《无机化学与普通化学杂志》2007,633(1):77-82
The high‐pressure (HP) modification of CePdSn was synthesized under multianvil high‐pressure (10.5 GPa) high‐temperature (1100 °C) conditions from the normal‐pressure (NP) modification. The structures of both modifications were studied by X‐ray powder and single crystal diffraction: TiNiSi type, Pnma, a = 754.1(2), b = 470.6(1), c = 798.4(3) pm, wR2 = 0.0333, 945 F2 values, 20 variables for NP‐CePdSn and ZrNiAl type, , a = 760.03(5), c = 416.06(3) pm, wR2 = 0.0443, 248 F2 values, 13 variables for HP‐CePdSn. The structural chemistry of both modifications is goverened by platinum centered trigonal prisms. The platinum and tin atoms in NP‐CePdSn and HP‐CePdSn build up a three‐dimensional [PdSn] network in which the cerium atoms fill channels. Susceptibility measurements on HP‐CePdSn reveal an experimental magnetic moment of 2.55(1) μB/Ce atom in the paramagnetic region. At 5 K a paramagnetic‐to‐antiferromagnetic transition is evident from magnetization and specific heat measurements. 相似文献
8.
Matthias Weil PD Dr. 《无机化学与普通化学杂志》2007,633(8):1217-1222
Single crystals of a third modification of Ag2Te2O6 (denoted as Ag2Te2O6–III) and of Ag4TeO5 have been obtained as minor by‐products during hydrothermal phase formation experiments in the system Ag‐Hg‐Te‐O. The crystal structure of Ag2Te2O6–III (P21/c, Z = 4, a = 6.4255(10), b = 6.9852(11), c = 13.204(2) Å, β = 90.090(3)°, 1885 independent reflections, R[F2 > 2σ(F2)] = 0.0334, wR2(F2 all) = 0.0817) comprises tellurium in oxidation states +IV and +VI and is topologically related to the structure of the Ag2Te2O6–I modification, which consists of similar layers and interjacent layers of Ag+ cations. Ag4TeO5 (C2/c, Z = 8, a = 16.271(2), b = 6.0874(10), c = 11.4373(16) Å, β = 106.730(10)°, 2372 independent reflections, R[F2 > 2σ(F2)] = 0.0288, wR2(F2 all) = 0.0737) is made up of a layer‐like arrangement of isolated [TeVI2O10] double octahedra and of Ag+ cations situated both in layers parallel and inside the layers of the anionic moieties. 相似文献
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Prof. Dr. Lena Keller Dr. Emilia Oueis Dr. Amninder Kaur Dr. Nasim Safaei Dr. Susanne H. Kirsch Dr. Antonia P. Gunesch Dr. Sibylle Haid Dr. Ulfert Rand Prof. Dr. Luka Čičin-Šain Dr. Chengzhang Fu PD Dr. Joachim Wink Prof. Dr. Thomas Pietschmann Prof. Dr. Rolf Müller 《Angewandte Chemie (International ed. in English)》2023,62(6):e202214595
A new family of highly unusual sesquarterpenoids (persicamidines A–E) exhibiting significant antiviral activity was isolated from a newly discovered actinobacterial strain, Kibdelosporangium persicum sp. nov., collected from a hot desert in Iran. Extensive NMR analysis unraveled a hexacyclic terpenoid molecule with a modified sugar moiety on one side and a highly unusual isourea moiety fused to the terpenoid structure. The structures of the five analogues differed only in the aminoalkyl side chain attached to the isourea moiety. Persicamidines A–E showed potent activity against hCoV-229E and SARS-CoV-2 viruses in the nanomolar range together with very good selectivity indices, making persicamidines promising as starting points for drug development. 相似文献