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31.
Stefan Scheerer Dr. Michael Linseis Dr. Evelyn Wuttke Sabrina Weickert Prof. Dr. Malte Drescher Dr. Oliver Tröppner Prof. Dr. Ivana Ivanović‐Burmazović Andreas Irmler Prof. Dr. Fabian Pauly Prof. Dr. Rainer F. Winter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9574-9590
Metallamacrocylic tetraruthenium complexes were generated by treatment of 1,4‐divinylphenylene‐bridged diruthenium complexes with functionalized 1,3‐benzene dicarboxylic acids and characterized by HR ESI‐MS and multinuclear NMR spectroscopy. Every divinylphenylene diruthenium subunit is oxidized in two consecutive one‐electron steps with half‐wave potential splittings in the range of 250 to 330 mV. Additional, smaller redox‐splittings between the +/2+ and 0/+ and the 3+/4+ and 2+/3+ redox processes, corresponding to the first and the second oxidations of every divinylphenylene diruthenium entity, are due to electrostatic effects. The lack of electronic coupling through bond or through space is explained by the nodal properties of the relevant molecular orbitals and the lateral side‐by‐side arrangement of the divinylphenylene linkers. The polyelectrochromic behavior of the divinylphenylene diruthenium precursors is retained and even amplified in these metallamacrocyclic structures. EPR studies down to T=4 K indicate that the dications 1‐H2+ and 1‐OBu2+ are paramagnetic. The dications and the tetracation of macrocycle 3‐H display intense (dications) or weak ( 3‐H4+ ) EPR signals. Quantum chemical calculations indicate that the four most stable conformers of the macrocycles are largely devoid of strain. Bond parameters, energies as well as charge and spin density distributions of model macrocycle 5‐HMe were calculated for the different charge and spin states. 相似文献
32.
Fabian Uhlemann Prof. Dr. Andreas Schnepf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10748-10753
The reaction of a metastable SiCl2 solution with the sterically less‐demanding carbene N,N‐diisopropylimidazo‐2‐ylidene (IPr) yields the salt [(IPr3Si3Cl5)+]Cl? ( 1 ‐Cl), containing a silyl cation with a Si3 backbone. Salt 1 is highly reactive, but it can be used as a reagent in deuterated dichloromethane, whereby dehalogenation with Me3SiOTf (OTf=O3SCF3) gives the dicationic silyl halide [(IPr3Si3Cl4)]2+ 2 . Quantum chemical calculations show that the HOMO is localized at the negatively charged central silicon atom of 1 and 2 , and thus although both compounds are cations they are better described as silanides, which was also corroborated by NMR investigations. 相似文献
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Nikolay Tyutyulkov Ivo Kanev Oskar Polansky Jürgen Fabian 《Theoretical chemistry accounts》1977,46(3):191-203
The analysis of experimental data for singlet transitions (E
n) of even polyenes (I), cations (II) and anions (III) of odd polyenes show that for infinite chains E
(I)/E
(II)=E
(I)/E
(III) = 2:1. It is shown that the energy gap is equal for the three systems. In cases (II) and (III) there is a level (NBMO) in the gap which is vacant in (II) and occupied in (III). That is why the first optical transition in (II) and (III) depends on the semiwidth of the gap. 相似文献
38.
N-Boc-12-aza-epothilone analog (azathilone) 1 is a potent inhibitor of human cancer cell growth and represents a structurally new class of natural product-derived microtubule-stabilizing agents. Compound 1 has been prepared employing a convergent strategy that is based on the consecutive assembly of building blocks 3, 4, and 19 into diene 20 and subsequent RCM-mediated macrocycle formation. The aldol reaction between aldehyde 3 and ketone 4 delivered the required 6R,7S diastereoisomer 5 with good selectivity and provided a reliable entry into the stereoselective synthesis of carboxylic acid 12. RCM with diene 20 was highly E-selective, thus giving efficient access to (E)-9,10-dehydro-1 (2). The latter is a key analog in SAR studies with 1. 相似文献
39.
In the present paper, we describe the first structural characterization of cymantrenyl(dihalo)borane and report on its use for the synthesis of novel cymantrenylboryl complexes. 相似文献
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