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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(45):14362-14365
The reactions of the phosphaethynolate anion ([PCO]−) with a range of boranes were explored. BPh3 and [PCO]− form a dimeric anion featuring P−B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C6F5)3 yields a less symmetric dimer of [PCO]− with P−B and P−O bonds. Less sterically demanding HB(C6F5)2 and H2B(C6F5) boranes form a third isomer with [PCO]− featuring both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P‐coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(48):15464-15468
This work describes a two‐dimensional polymerization at an air/water interface and provides, for the first time, direct spectroscopic evidence for the kind of crosslinks formed and for the conversion reached in a covalently bonded monolayer sheet. This evidence was obtained through a combination of a variety of monolayer characterization techniques before and after transfer onto solid substrates, in particular by tip‐enhanced Raman spectroscopy (TERS) and TERS mapping after transfer of both the monomer and polymer monolayer onto Au(111). This work is a major advance for the field of 2D polymers synthesized at the air/water interface as it, in principle, allows estimation of the crystallinity by percolation theory and the location of regions with defects. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(33):9974-9978
From DNA base pairs to drug–receptor binding, hydrogen (H‐)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored. H‐bond strength modulation due to enhancement or disruption of aromaticity of heterocycles is experimentally revealed by comparing homodimer H‐bond energies of aromatic heterocycles with analogs that have the same H‐bonding moieties but lack cyclic π‐conjugation. NMR studies of dimerization in C6D6 find aromaticity‐modulated H‐bonding (AMHB) energy effects of approximately ±30 %, depending on whether they enhance or weaken aromatic delocalization. The attendant ring current perturbations expected from such modulation are confirmed by chemical shift changes in both observed ring C−H and calculated nucleus‐independent sites. In silico modeling confirms that AMHB effects outweigh those of hybridization or dipole–dipole interaction. 相似文献
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Avijit Maiti Jessica Stubbe Dr. Nicolás I. Neuman Dr. Pankaj Kalita Prakash Duari Prof. Dr. Carola Schulzke Prof. Dr. Vadapalli Chandrasekhar Prof. Dr. Biprajit Sarkar Dr. Anukul Jana 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6795-6800
Diradicals have been of tremendous interest for over a century ever since the first reports of p- and m-phenylene-bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non-Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head-to-tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox-active organic compounds. 相似文献