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861.
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Da-Zhi Li Lin-Yan Feng Ling Pei Ming-Zhi Song Li-Juan Zhang Hui Wang Hua-Jin Zhai 《International journal of quantum chemistry》2019,119(15):e25907
Boron oxide clusters are electron-deficient species with novel structures and bonding, in which the emergence of rhombic and boroxol rings is of interest. We report on computational prediction of the global-minimum structures for two boron oxide clusters: B4O5 and B4O5−. These structures differ distinctly, as established through global machine searches and electronic structure calculations at B3LYP and single-point CCSD(T) levels. While B4O5 neutral cluster has a rhombic B2O2 core, the B4O5− anion features a boroxol B3O3 ring. One electron completely changes the potential landscapes. Bonding analyses show that the 4π electron-counting is crucial for a rhombic B O cluster, in contrast to π sextet for a boroxol ring, which underlies the competition between rhombic and boroxol rings in B4O5/B4O5− clusters. A possible pathway for rhombic-to-hexagonal transformation is proposed based on intrinsic reaction coordinate calculations. Anion B4O5− cluster, a new member of the inorganic benzene family, is among the smallest B O species with a free-standing boroxol ring, governed collectively by composition and electron-counting. 相似文献
863.
Guangwu Li Yi Han Ya Zou Johnathan Joo Cheng Lee Yong Ni Jishan Wu 《Angewandte Chemie (International ed. in English)》2019,58(40):14319-14326
Reported here is the step‐by‐step dearomatization of a highly aromatic polycyclic aromatic hydrocarbon (PAH), the hexa‐peri‐hexabenzocoronene (also called as “superbenzene”), to give a series of superbenzoquinones containing two, four, and six ketone groups. Different from traditional PAH‐based quinones, these superbenzoquinones show open‐shell multiradical character by rearomatization in the open‐shell forms as experimentally validated by X‐ray crystallographic analysis, NMR and ESR spectroscopy, and FT‐IR measurements, as well as theoretically supported by restricted active space spin‐flip calculations. These compounds exhibit structure‐ and molecular‐symmetry‐dependent optical, electrochemical, and magnetic properties. 相似文献
864.
Typical salts are composed of positive and negative ions that appear alternatively, whereas decorated layered materials normally have ions anchored on the polygonal sites. In this way, the ions are spatially fixed and the system is stabilized on electrostatic grounds. Here we report on a unique boron‐lithium cluster, B7Li4?, which contains a disk‐like B7 core, being sandwiched by a Li3 ring and an isolated Li atom. All Li centers are stacked exactly on the B atoms from top or bottom, rather than being anchored on triangular B3 sites. The cluster shows dynamic fluxionality, whose Li3 ring rotates freely on the B7 disk even at below room temperature (200 K), akin to a subnanoscale propeller. The rotation barrier is only 0.37 kcal mol?1 at the single‐point CCSD(T) level. The sandwich shape facilitates intramolecular charge‐transfers, leading to a [Li3]+[B7]3?[Li]+ salt complex. The [Li3]+ layer has 2σ aromaticity, while [B7]3? core is robust with both π and σ sextets. Three‐fold π/σ aromaticity collectively stabilizes the system, as well as underlies its dynamic fluxionality. The interlayer bonding turns out to be strong, dominated by ionic interactions (of the order of 3–4 eV per Li3/Li unit). The work demonstrates a propeller at the subnanoscale, which is dynamically fluxional despite strong covalent and ionic bonding. 相似文献
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Effects of interaction between the chelate rings and π‐conjugated systems in fused salphen complexes on UV‐Vis‐NIR spectra
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Hirohiko Houjou Keisuke Yagi Isao Yoshikawa Toshiki Mutai Koji Araki 《Journal of Physical Organic Chemistry》2017,30(6)
Dinuclear (Zn2, Ni2, and NiZn) complexes of fused salphen with acene‐type annelation were synthesized from 3,7‐diformyl‐2,6‐dihydroxynaphthalene. The spectroscopic properties of these complexes were compared with those of their constitutional isomers with phene‐type annelation. The acene‐type complexes exhibited a characteristic absorption band in the near‐infrared region that showed a noticeable solvent effect. Time‐dependent density functional theory calculations suggested that the absorption arose from a π → π* transition localized at the naphthalene ring, which was perturbed by the adjoining chelate rings. Effects of the connection topology in the fused salphen complexes are discussed by comparison with those of polycyclic aromatic hydrocarbons. 相似文献
867.
本文采用DFT-B3LYP和MP2(full)方法对三聚体Cl–…苯氰…H2O中O/C–H…Cl–阴离子氢键与传统氢键O–H…N和C–H…O之间的协同效应、热力学性质以及芳香性进行了研究.结果表明阴离子氢键O/C–H…Cl–对O–H…N或C–H…O相互作用的影响更显著.在线性结构中发生正协同效应,熵变是促进热力学协同效应的主要因素,而在环状结构中发生反协同效应,焓变成为主要因素.在三聚体形成过程中,苯氰环的芳香性是减弱的,而苯氰中π→π*共轭效应是增强的.结果表明,协同效应能Ecoop.分别与Rc(NICS(1)ternary/NICS(1)binary),ΔΔδ(Δδternary-Δδbinary),Rc'((NICS(1)ternary-NICS(1)binary)/NICS(1)binary)和RBDE(C–CN)(BDE(C–CN)ternary/BDE(C–CN)binary)均具有良好的线性关系.同时,AIM的分析也佐证了协同效应的存在. 相似文献
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