排序方式: 共有74条查询结果,搜索用时 31 毫秒
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(34):10222-10226
Single‐crystal X‐ray analysis of the β‐heptakis(trifluoromethyl)‐meso ‐tetrakis(p ‐fluorophenyl)porphyrin, H2[(CF3)7TpFPP], has revealed the first example of a stable cis tautomer of a free‐base porphyrin, the long‐postulated intermediate of porphyrin tautomerism. The stability of the unique molecule appears to reflect a dual origin: a strongly saddled porphyrin skeleton, which alleviates electrostatic repulsion between the two NH protons, and two polarization‐enhanced, transannular N−H⋅⋅⋅O−H⋅⋅⋅N hydrogen bond chains, each involving a molecule of water. DFT calculations suggest that the observed tautomer has a lower energy than the alternative, doubly hydrated trans tautomer by some 8.3 kcal mol−1. A fascinating prospect thus exists that H2[(CF3)7TpFPP]⋅2 H2O and cognate structures may act as supramolecular synthons, which, given their chirality, may even be amenable to resolution into optically pure enantiomers. 相似文献
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Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.Dedicated to Professor Leslie S. Ettre with best wishes for his 70th birthday anniversary. 相似文献
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Aaron Chin Yit Tay Benjamin J. Frogley David C. Ware Jeanet Conradie Abhik Ghosh Penelope J. Brothers 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(10):3089-3093
The first examples of diboron complexes of the tetrapyrroles octaethylporphyrazine (OEPz) and 2,9,16,23‐tetra‐t‐butyl‐phthalocyanine (Pc) are reported, counterpoints to the better known monoboron tripyrroles, subporphyrazine and subphthalocyanine. Two stereochemical possibilities are observed, with cisoid‐B2OF2(OEPz), both cisoid‐B2OPh2(OEPz) and transoid‐B2OPh2(OEPz), transoid‐B2OF2(Pc) and cisoid‐B2OPh2(Pc) having been isolated and characterised, including structure determinations for the OEPz complexes. This variation in stereochemistry, which can be extended to include the previously reported transoid‐B2OF2(porphyrin), cisoid‐[B2OF2(corrole)]?, and both transoid‐ and cisoid‐B2OF2(calixphyrin), prompted a wider DFT study to elucidate the factors influencing the stereochemical preferences. This shows that the cisoid/transoid preference is correlated to the ease with which the macrocycle accommodates a rectangularly distorted N4 cavity. 相似文献
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Songlin Xue Daiki Kuzuhara Naoki Aratani Hiroko Yamada 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12654-12658
Vinylene‐bridged hexaphyrin(2.1.2.1.2.1) was synthesized from dipyrrolyl diphenylethenes by acid‐catalyzed condensation reactions. Freebase hexaphyrin(2.1.2.1.2.1) forms a distorted structure with non‐aromatic characteristics. The aromaticity and molecular configuration of non‐planar hexaphyrin(2.1.2.1.2.1) can be controlled by insertion of metal ions. Freebase and zinc complexes show a distorted structure without macrocyclic aromaticity, whereas copper complexes show a figure‐of‐eight structure with macrocyclic aromaticity. It is the first example of aromaticity conversion of a distorted expanded porphyrin involving vinylene bridges. 相似文献
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Karolis Norvaia Keith J. Flanagan Dire Gibbons Mathias O. Senge 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16705-16709
Die Selektivität und funktionale Variabilität von Porphyrinkofaktoren basiert typischerweise auf der Substratbindung durch Metalloporphyrine, wobei die Pyrrolstickstoffatome nur zur Chelatisierung der Metallionen dienen. In einem ersten Schritt zu Porphyrinzentren mit “enzymähnlicher” Aktivität zeigt eine strukturelle und spektroskopische Untersuchung der Substratbindung im Kern jedoch, dass ein sattelverbogenes Porphyrin mit peripheren Aminorezeptorgruppen ( 1 , 2,3,7,8,12,13,17,18‐Oktaethyl‐5,10,15,20‐tetrakis(2‐aminophenyl)porphyrin), abhängig von der Azidität der Lösung, Analyte in einer schaltbaren Weise koordiniert. Das supramolekulare Ensemble weist eine hohe Affinität und Selektivität für das Pyrophosphatanion (2.26±0.021)×109 m ?1 auf. 1H‐NMR‐Spektroskopie liefert Einblicke in den wahrscheinlichen Bindungsmodus und erlaubt die Charakterisierung der Atropisomere, deren Struktur auch durch Röntgenstrukturanalysen aufgeklärt wurde. 相似文献
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Xuan Gong Yufei Shu Zhuo Jiang Lingxiang Lu Xiaohui Xu Chao Wang Prof. Hexiang Deng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5364-5369
Discoveries of the accurate spatial arrangement of active sites in biological systems and cooperation between them for high catalytic efficiency are two major events in biology. However, precise tuning of these aspects is largely missing in the design of artificial catalysts. Here, a series of metal–organic frameworks (MOFs) were used, not only to overcome the limit of distance between active sites in bio-systems, but also to unveil the critical role of this distance for efficient catalysis. A linear correlation was established between photocatalytic activity and the reciprocal of inter active-site distance; a smaller distance led to higher activity. Vacancies created at selected crystallographic positions of MOFs promoted their photocatalytic efficiency. MOF-525-J33 with 15.6 Å inter active-site distance and 33 % vacancies exhibited unprecedented high turnover frequency of 29.5 h−1 in visible-light-driven acceptorless dehydrogenation of tetrahydroquinoline at room temperature. 相似文献
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Jinseok Kim Dr. Juwon Oh Dr. Takanori Soya Dr. Tomoki Yoneda Dr. Seongchul Park Prof. Dr. Manho Lim Prof. Dr. Atsuhiro Osuka Prof. Dr. Dongho Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5167-5172
Expanded porphyrins with appropriate metalation provide an excellent opportunity to study excited-state aromaticity. The coordinated metal allows the excited-state aromaticity in the triplet state to be detected through the heavy-atom effect, but other metalation effects on the excited-state aromaticity were ambiguous. Herein, the excited-state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via electronic and vibrational spectroscopy. The SQ states of gold [26]- and [28]-hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground-state, indicating aromaticity reversal. Furthermore, while the T1 states of gold [28]-hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand-to-metal charge-transfer state of gold [26]-hexaphyrins contributed by the gold metal showed non-aromatic features arising from the odd-number of π-electrons. 相似文献
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