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Gottfried Mrkl Andreas Pll Norbert G. Aschenbrenner Corinna Schmaus Theodor Troll Peter Kreitmeier Heinrich Nth Martin Schmidt 《Helvetica chimica acta》1996,79(5):1497-1517
Extremely Expanded Tetrathiafulvalenes with Polyene Spacers. Carotinoid Tetrathiafulvalenes. Polymethin-Tetracyanotetrathiafulvalene Radical Cations, a New Class of Violenes The synthesis of extended tetrathiafulvalenes 11 with di-, tetra-, hexa-, octa-, deca- and dodecamethine spacers is described by a PPh3-induced Wittig-reaction-like condensation of the corresponding polyenedials 10 with 2-thio-1,3-dithiole-4,5-dicarbonitrile ( 9 ). By the same procedure, the dimethyloctamethine- and the tetramethyl-hexadecamethine-tetrathiafulvalenes 14 and 15 , respectively, were obtained. The extended tetrathiafulvalenes represent multistep vinylogous redox systems of the ‘violene type’. They can be oxidized to give the cyanine-like radical cations, e.g. 11 sem, 14 sem, and 15 sem, and the dications, e.g. 11 ox, 14 ox, and 15 ox; their UV/VIS/NIR spectra are reported. The crystal and molecular structure of (all-E)-2,2′-(octa-2,4,6-trien-1,8-diylidene)bis[1,3-dithiole-4,5-dicarbonitrile] ( 11e ) was determined: it is a rod-like, planar molecule; in the crystal, it forms staples along the longest molecule axis. The CV measurements confirm that the redox potentials of 11, 14 , and 15 decrease asymptotically with the increasing length of the spacer. Because of the close relationship of the extended tetrathiafulvalenes (ETTF's) to the carotinoids, they are named ‘caroviologenes’; they formally belong to the class of molecular wires. 相似文献
23.
Electrocatalytic Carbon Dioxide Reduction by Using Cationic Pentamethylcyclopentadienyl–Iridium Complexes with Unsymmetrically Substituted Bipyridine Ligands
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Fanni D. Sypaseuth Corinna Matlachowski Manuela Weber Dr. Matthias Schwalbe Prof. Dr. C. Christoph Tzschucke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6564-6571
Eight [Ir(bpy)Cp*Cl]+‐type complexes (bpy= bipyridine, Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) containing differently substituted bipyridine ligands were synthesized and characterized. Cyclic voltammetry (CV) of the complexes in Ar‐saturated acetonitrile solutions showed that the redox behavior of the complexes could be fine tuned by the electronic properties of the substituted bipyridine ligands. Further CV in CO2‐saturated MeCN/H2O (9:1, v/v) solutions showed catalytic currents for CO2 reduction. In controlled potential electrolysis experiments (MeCN/MeOH (1:1, v/v), Eapp=?1.80 V vs Ag/AgCl), all of the complexes showed moderate activity in the electrocatalytic reduction of CO2 with good stability over at least 15 hours. This electrocatalytic process was selective toward formic acid, with only traces of dihydrogen or carbon monoxide and occasionally formaldehyde as byproducts. However, the turnover frequencies and current efficiencies were quite low. No direct correlation between the redox potentials of the complexes and their catalytic activity was observed. 相似文献
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25.
A highly enantioselective epoxidation of cyclic enones with hydrogen peroxide has been developed that is catalyzed by chiral primary amine salts. 相似文献
26.
DNA--metal base pairs 总被引:1,自引:0,他引:1
Recent developments show encouraging results for the use of DNA as a construction material for nanometer-sized objects. Today, however, DNA-based molecular nanoarchitectures are constructed with mainly unmodified or at best end-modified oligonucleotides, thus shifting the development of functionalized DNA structures into the limelight. One of most recent developments in this direction is the substitution of the canonical Watson-Crick base pairs by metal complexes. In this way "metal-base pairs" are created, which could potentially impart magnetic or conductive properties to DNA-based nanostructures. This review summarizes research which started almost 45 years ago with the investigation of how metal ions interact with unmodified DNA and which recently culminated in the development of artificial ligand-like nucleobases so far able to coordinate up to ten metal ions inside a single DNA duplex in a programmable fashion. 相似文献
27.
Reisinger CM Nowack RJ Volkmer D Rieger B 《Dalton transactions (Cambridge, England : 2003)》2007,(2):272-278
A route to various substituted phosphine phosphonic acid compounds of the general form Ar(2)PC(6)H(4)PO(OH)(2) (Ar = Ph, o-MeC(6)H(4), o-MeOC(6)H(4)) has been investigated. These compounds were employed as bidentate anionic [P,O] ligands in neutral palladium complexes. The [P,O] chelating coordination was determined by X-ray crystallography of a representative palladium complex. Furthermore, the bifunctional ligand Ph(2)PC(6)H(4)PO(OH)Ph represents the first example of a chelating anionic [P,O] ligand resulting from the combination of a phosphine and a phosphinate moiety. 相似文献
28.
Ce3Cl5[SiO4] and Ce3Cl6[PO4]: A Chloride‐Rich Chloride Silicate of Cerium as Compared to the Phosphate By reacting CeCl3 with CeO2, cerium and SiO2, or P2O5, respectively, in molar ratios of 5 : 3 : 1 : 3 or 8 : 3 : 1 : 2, respectively, in sealed evacuated silica tubes (7 d, 850 °C) colorless, rod‐shaped single crystals of Ce3Cl5[SiO4] (orthorhombic, Pnma; a = 1619.7(2), b = 415.26(4), 1423.6(1) pm; Z = 4) and Ce3Cl6[PO4] (hexagonal, P63/m; a = 1246.36(9), c = 406.93(4) pm; Z = 2) are obtained as products insensitive to air and water. Excess cerium trichloride as flux promotes crystal growth and can be rinsed off again with water after the reaction. The crystal structures are determined by discrete [SiO4]4– or [PO4]3– tetrahedra as isolated units. Both, the chloride silicate Ce3Cl5[SiO4] and the chloride phosphate Ce3Cl6[PO4], exhibit structural similarities to CeCl3 (UCl3 type), when four or three Cl– anions are each substituted formally by one [SiO4]4– or [PO4]3– unit, respectively, in the tripled formula (Ce3Cl9). The coordination number for Ce3+ is thus raised from nine in CeCl3 to ten in Ce3Cl5[SiO4] and Ce3Cl6[PO4], along with a drastic reduction of the molar volume with the transition from Ce3Cl9 (Vm = 186.17 cm3/mol) to Ce3Cl5[SiO4] (Vm = 144.15 cm3/mol) and Ce3Cl6[PO4] (Vm = 164.84 cm3/mol). The polyhedra of coordination around Ce3+ can be described as quadruple‐capped trigonal prisms, which in addition to seven Cl– anions each also show another three oxygen atoms of two ortho‐silicate or ortho‐phosphate tetrahedra, respectively. 相似文献
29.
Pr4S3[Si2O7] and Pr3Cl3[Si2O7]: Derivatives of Praseodymium Disilicate Modified by Soft Foreign Anions For synthesizing both the disilicate derivatives Pr4S3[Si2O7] and Pr3Cl3[Si2O7], Pr, Pr6O11 and SiO2 are brought to reaction with S and PrCl3, respectively, in suitable molar ratios (850 °C, 7 d) in evacuated silica tubes. By using NaCl as a flux, Pr4S3[Si2O7] crystallizes as pale green, transparent single crystals (tetragonal, I41/amd, a = 1201.6(1), c = 1412.0(2) pm, Z = 8) with the appearance of slightly compressed octahedra. On the other hand, Pr3Cl3[Si2O7] emerges as pale green, transparent platelets and crystallizes monoclinically (space group: P21, a = 530.96(6), b = 1200.2(1), c = 783.11(8) pm, β = 109.07(1)°, Z = 2). In both crystal structures ecliptically conformed [Si2O7]6– units of two corner‐linked [SiO4] tetrahedra with Si–O–Si bridging angles of 131° in the sulfide and 148° in the chloride disilicate are present. In Pr4S3[Si2O7] both crystallographically independent Pr3+ cations show coordination numbers of 8 + 1 (5 S2– and 3 + 1 O2–) and 9 (3 S2– and 6 O2–). For Pr1, Pr2 and Pr3 in Pr3Cl3[Si2O7] coordination numbers of 10 (5 Cl– and 5 O2–) and 9 (2 ×; 4 Cl– and 5 O2– or 3 Cl– and 6 O2–, respectively) occur. 相似文献
30.
Catherine Pale-Grosdemange Corinna Feil Michel Rohmer Karl Poralla 《Angewandte Chemie (International ed. in English)》1998,37(16):2237-2240
Tetracyclic triterpenes (for example, 3 ) are formed as minor products of the cyclization of squalene ( 1 ) by squalene/hopene cyclase; they have also been found in vivo. The identification of these side products offers new insight into the complex biosynthesis of the hopane skeleton, and proves that the enzyme has no absolute control of the conformation of the acyclic substrate squalene and that tetra- and pentacyclic carbocationic intermediates are involved (for example, 2 ) in the cyclization process. 相似文献