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791.
Arpita Varadwaj Pradeep R. Varadwaj Helder M. Marques Koichi Yamashita 《Molecules (Basel, Switzerland)》2022,27(11)
In chemical systems, the arsenic-centered pnictogen bond, or simply the arsenic bond, occurs when there is evidence of a net attractive interaction between the electrophilic region associated with a covalently or coordinately bound arsenic atom in a molecular entity and a nucleophile in another or the same molecular entity. It is the third member of the family of pnictogen bonds formed by the third atom of the pnictogen family, Group 15 of the periodic table, and is an inter- or intramolecular noncovalent interaction. In this overview, we present several illustrative crystal structures deposited into the Cambridge Structure Database (CSD) and the Inorganic Chemistry Structural Database (ICSD) during the last and current centuries to demonstrate that the arsenic atom in molecular entities has a significant ability to act as an electrophilic agent to make an attractive engagement with nucleophiles when in close vicinity, thereby forming σ-hole or π-hole interactions, and hence driving (in part, at least) the overall stability of the system’s crystalline phase. This overview does not include results from theoretical simulations reported by others as none of them address the signatory details of As-centered pnictogen bonds. Rather, we aimed at highlighting the interaction modes of arsenic-centered σ- and π-holes in the rationale design of crystal lattices to demonstrate that such interactions are abundant in crystalline materials, but care has to be taken to identify them as is usually done with the much more widely known noncovalent interactions in chemical systems, halogen bonding and hydrogen bonding. We also demonstrate that As-centered pnictogen bonds are usually accompanied by other primary and secondary interactions, which reinforce their occurrence and strength in most of the crystal structures illustrated. A statistical analysis of structures deposited into the CSD was performed for each interaction type As···D (D = N, O, S, Se, Te, F, Cl, Br, I, arene’s π system), thus providing insight into the typical nature of As···D interaction distances and ∠R–As···D bond angles of these interactions in crystals, where R is the remainder of the molecular entity. 相似文献
792.
793.
Bimetallic palladium(II) complexes containing classical NHC donor ligands are becoming increasingly popular owing to their various catalytic applications. However, examples of the aforementioned complexes with mixed NHC/PPh3 ligands are still rare. Bimetallic palladium(II) complexes possessing these mixed ligands are described starting from a C2-symmetric bis-imidazolium salt containing 4,4′-substituted central biphenyl ring. All the palladium(II) complexes have been tested as precatalysts in α-arylation of oxindole and Suzuki–Miyaura coupling reactions. The complex composed of mixed NHC/PPh3 donor ligands shows superior catalytic activity compared with the corresponding PEPPSI type complexes when applied in α-arylation of oxindole. The dinuclear complexes display better activity compared with the mononuclear complexes. The preliminary electrochemical measurements show the facile oxidation of PdII in the presence of combined NHC/PPh3 ligands compared with a combination of NHC/Py ligands. 相似文献
794.
《Mendeleev Communications》2023,33(3):393-396
Two novel aromatic compounds containing thieno[2',3':4,5]-thieno[3,2-b]thieno[2' ' , 3' ':4' ,5']thieno[2',3':4,5]-pyrrolo[3,2-g]indole as the electron-donating center and terminal 3-(dicyanomethylene)indan-1-one (or 5,6-difluoro analogue) electron-accepting groups exhibit efficient light absorption in the red and near-infrared spectral regions, have low levels of the highest occupied molecular orbital (up to –5.65 eV) and lowest unoccupied molecular orbital (–3.91 eV) and a relatively low band gap value (up to 1.74 eV). The optical, thermal and structural properties are explored and compared with those of their closest and well known analogues, Y5 and Y6. 相似文献
795.
Dr. Atsushi Kobayashi 《Angewandte Chemie (International ed. in English)》2023,62(46):e202313014
Biomass photoreforming is a promising method to provide both a clean energy resource in the form of hydrogen (H2) and valuable chemicals as the results of water reduction and biomass oxidation. To overcome the poor contact between heterogeneous photocatalysts and biomass substrates, we fabricated a new photoredox cascade catalyst by combining a homogeneous catalyst, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), and a heterogeneous dual-dye sensitized photocatalyst (DDSP) composed of two Ru(II)-polypyridine photosensitizers ( RuP6 and RuCP6 ) and Pt-loaded TiO2 nanoparticles. During blue-light irradiation (λ=460±15 nm; 80 mW), the DDSP photocatalytically reduced aqueous protons to form H2 and simultaneously oxidized TEMPO• radicals to generate catalytically active TEMPO+. It oxidized biomass substrates (water-soluble glycerol and insoluble cellulose) to regenerate TEMPO•. In the presence of N-methyl imidazole as a proton transfer mediator, the photocatalytic H2 production activities for glycerol and cellulose reforming reached 2670 and 1590 μmol H2 (gTiO2)−1 h−1, respectively, which were comparable to those of state-of-the-art heterogeneous photocatalysts. 相似文献
796.
《Journal of Saudi Chemical Society》2023,27(4):101675
Halogenated inhibitors showed robust, reversible, and selective monoamine oxidase-B (MAO-B) inhibitory efficacy in candidates that were derived from them. Our team has previously synthesized and assessed a panel of halogenated chalcones and coumarin for the study on MAO-B inhibition. The aim of this study was to build GA-MLR based QSAR models and predictive 3D Pharmacophore models, as well as to investigate the relationship between halogenated derivatives and MAO-B inhibitory activity. The robust statistical significance in the parameter (R2 = 0.78 and Q2 = 0.69) was demonstrated. Best Hypo1 contains one hydrophobic and two aromatic rings. The lead molecule for quantum mechanics was performed, and it was revealed that it would bind to proteins and provide stability. To determine the stability of the ligand-enzyme complex, a thorough molecular dynamics analysis of the lead compounds was accomplished. 相似文献