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41.
Dr. Chongwei Zhu Dr. Albert Poater Dr. Carine Duhayon Dr. Brice Kauffmann Dr. Alix Saquet Valérie Maraval Prof. Dr. Remi Chauvin 《Angewandte Chemie (International ed. in English)》2018,57(20):5640-5644
Ring carbo‐mers of oligo(phenylene ethynylene)s (OPEn, n=0–2), made of C2‐catenated C18 carbo‐benzene rings, have been synthesized and characterized by NMR and UV‐vis spectroscopy, crystallography and voltammetry. Analyses of crystal and DFT‐optimized structures show that the C18 rings preserve their individual aromatic character according to structural and magnetic criteria (NICS indices). Carbo‐terphenyls (n=2) are reversibly reduced at ca. ?0.42 V/SCE, i.e. 0.41 V more readily than the corresponding carbo‐benzene (?0.83 V/SCE), thus revealing efficient inter‐ring π‐conjugation. An accurate linear fit of E1/2red1 vs. the DFT LUMO energy suggests a notably higher value (?0.30 V/SCE) for a carbo‐quaterphenyl congener (n=3). Increase with n of the effective π‐conjugation is also evidenced by a red shift of two of the three main visible light absorption bands, all being assigned to TDDFT‐calculated excited states, one of them restricting to a HOMO→LUMO main one‐electron transition. 相似文献
42.
Joel M. Kauffman Peter T. Litak John A. Novinski Charles J. Kelley Alem Ghiorghis Yuanxi Qin 《Journal of fluorescence》1995,5(3):295-305
Absorption and fluorescence emission spectral data, as well as fluorescence quantum yields (f), were determined for 41p-oligophenylene compounds containing 2–6, 8, and 10 benzene rings. Of 29 compounds containing carbon-bridged rings (fluorenes), 28 were dialkylated on each bridge for improved solubility and photostability. Absorption maxima for oligophenylenes were observed at wavelengths as long as 366 nm, emission maxima to 437 nm, and molar extinction coefficients () as large as 153,000 L/mol-cm; all three exceeded predicted maximum values for the corresponding unbridged oligophenylenes. The substitution of furan for benzene or carbazole for a fluorene (two examples each) bathochromically shifted absorption and emission maxima. Dialkylated carbon bridges bathochromically shifted absorption and emission maxima, and lowered f in biphenyl and in one terphenyl analogue, but appeared to cause no diminution of f in higher oligophenylenes. Bis(2-methoxyethyl) substitution on the bridges, incorporated to provide solubility in polar solvents, lowered f in all examples. Tertiary alkyl substituents on terminal rings bathochromically shifted the absorption and emission maxima and generally increased f. The loose bolt effect, which lowers f in mononuclear substituted benzenes, may operate in 9,9-dialkylfluorenes, but not in 2,7-di-t-butylfluorene or in higher oligophenylenes. Cyclic ether and methoxy substituents as auxofluors on terminal rings generally bathochromically shifted absorption and emission maxima and increased and f. Cyano substituents bathochromically shifted absorption and emission maxima, and increased , but lowered f slightly. 相似文献
43.
44.
Jianwei Xu Chaobin He T.‐S. Chung 《Journal of polymer science. Part A, Polymer chemistry》2001,39(17):2998-3007
Two series of polyimides based on laterally attached p‐terphenyl and biphenyl groups were synthesized. The solubility and thermal properties were studied using DSC, thermogravimetric analysis, and the solubility test. These polymers exhibited good thermal stability and excellent solubility. The high solubility for both polymer series was attributed to the non‐coplanarity of diamine monomers and the use of fluorinated dianhydride, whereas the slightly better solubility for polymers based on p‐terphenyl was attributed to further weakening of interchain interaction of the polymers. Both polymer series exhibited glass‐transition temperatures (Tg's) in the range of 244–272 °C. The Tg's of polymers containing laterally attached p‐terphenyls were higher than those of their counterparts containing biphenyls by 5–17 °C. This was attributed to the formation of an interdigitated structure that hinders the segmental movement of polymer chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2998–3007, 2001 相似文献
45.
Trihapto Ligation of a Borirene to a Single Metal Atom: A Heterocyclic Analogue of the η3‐Cyclopropenyl Ligand 下载免费PDF全文
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Dr. Krzysztof Radacki Dr. Christopher W. Tate Dr. Alfredo Vargas 《Angewandte Chemie (International ed. in English)》2014,53(24):6263-6266
The first example of a complex containing an η3‐coordinated borirene ligand bound to a single metal atom was prepared by photolytic transfer of an arylborylene ligand to diphenylacetylene and loss of three CO ligands from the precursor. The η3‐borirene complex possesses a chromium(0) atom which is also bound to one phenyl group in an η6 fashion. The complex was isolated in 15 % yield along with the corresponding metal‐free borirene, which was isolated in 62 % yield. The bonding between the chromium center and the borirene ring was studied computationally by DFT methods. 相似文献
46.
Zhenning Yu Huilin Tu Xinhua Wan Xiaofang Chen Qi‐Feng Zhou 《Journal of polymer science. Part A, Polymer chemistry》2003,41(10):1454-1464
A series of novel mesogen‐jacketed liquid‐crystal polymers, poly[2,5‐bis(4′‐alkoxyphenyl)‐styrene] (P‐n, n = 1–11), were prepared via free‐radical polymerization of newly synthesized monomers, 2,5‐bis(4′‐alkoxyphenyl)styrene (M‐n, n = 1–11). The influence of the alkoxy tail length on the liquid‐crystalline behaviors of the monomers and the polymers was investigated with differential scanning calorimetry (DSC), thermogravimetry, polarized optical microscopy (POM), and wide‐angle X‐ray diffraction (WAXD). The monomers with n = 1–4, 9, and 11 were monotropic nematic liquid crystals. All other monomers exhibited enantiotropic nematic properties. Their melting points (Tm's) decreased first as n increased to 6, after which Tm increased slightly at longer spacer lengths. The isotropic–nematic transition temperatures decreased regularly with increasing n values in an odd–even way. The glass‐transition temperatures (Tg's) of the polymers first decreased as the tail lengths increased and then leveled off when n ≥ 7. All polymers were thermally stable and entered the mesophase at a temperature above Tg. Upon further heating, no mesophase‐to‐isotropic melt transition was observed before the polymers decomposed. WAXD studies indicated that an irreversible order–order transition for the polymers with short tails (n ≤ 5) and a reversible order–order transition for those with elongated tails (n ≥ 6) occurred at a temperature much higher than Tg. However, such a transition could not be identified by POM and could be detected by DSC only on heating scans for the polymers with long tails (n ≥ 7). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1454–1464, 2003 相似文献
47.
Relationships between the structure characteristics of natural p-terphenyl com- pounds isolated from three edible mushrooms (Thelephora ganbajun, Thelephora aeronautical, and Boletopsis grisea) indigenous to China and their mechanism of antioxidant activity were studied. Geometry structures of terphenyl molecule and four corresponding radicals, bond dissociation energy (BDE), frontier orbitals (HOMO and LUMO) and single electron density were calculated using DFT methods (B3LYP/6-311G**). The computational results which are consistent with the experimental data well show that terphenyl molecule scavenges DPPH radical by hydrogen abstract mechanism and the high antioxidant activity depends on the substitution position of hydroxyls. Two active 7-, 8-hydroxyls facilitate the hydrogen abstraction due to the intramolecular hydrogen bond and the resonance effect makes 4-hydroxyl radical more stable. 相似文献
48.
《中国化学快报》1998,(10)
Wehavereportedtheeffectofovercrowdinginthemassspectfaofcondensedpolycyclicaromaticcompounds'-'.Themassdifferencebetweenamolecularionandthemostintensefragmentionintheionfamilyofthehighestvalencecorrespondstothenumberofovercrowdedhydrogenatomsdetachingfromtheparention,andtheirmasspatternsaredifferentwiththetypeofovercrowding,i.e.fjord-orcrab-likeovercrowding.Thehighabundanceofspecificfragmentionsat70Vwascorrelatedwiththeloweringoftheirappearanceenergies.Hereweinvestigatedthemassspectraandthemech… 相似文献
49.
Xi Liu Bo Fu Lin Li Yun-Fei Jian Si Shu 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(3):277-282
The assembly of metal–organic frameworks (MOFs) with metal ions and organic ligands is currently attracting considerable attention in crystal engineering and materials science due to their intriguing architectures and potential applications. A new three‐dimensional MOF, namely poly[[diaqua(μ8‐para‐terphenyl‐3,3′,5,5′‐tetracarboxylato)dizinc(II)] dimethylformamide disolvate monohydrate], {[Zn2(C22H10O8)(H2O)2]·2C3H7NO·H2O}n, was synthesized by the self‐assembly of Zn(NO3)2·6H2O and para‐terphenyl‐3,3′,5,5′‐tetracarboxylic acid (H4TPTC) under solvothermal conditions. The compound was structurally characterized by FT–IR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction analysis. Each ZnII ion is located in a square‐pyramidal geometry and is coordinated by four carboxylate O atoms from four different TPTC4? ligands. Pairs of adjacent equivalent ZnII ions are bridged by four carboxylate groups, forming [Zn2(O2CR)4] (R = terphenyl) paddle‐wheel units. One aqua ligand binds to each ZnII centre along the paddle‐wheel axis. Each [Zn2(O2CR)4] paddle wheel is further linked to four terphenyl connectors to give a three‐dimensional framework with NBO‐type topology. The thermal stability and solid‐state photoluminescence properties of the title compound have also been investigated. 相似文献
50.
The reaction of 4-bromophenylferrocene with butyllithium followed by treatment of the organolithium compound with tributyl borate afforded tris(4-ferrocenylphenyl)boroxine (2). X-ray diffraction study of the solvate 2·2C6H6 revealed an intermolecular stacking interaction between the boroxine ring and the Cp rings in the crystal structure. Cross-coupling of compound 2 with 4-bromo-4-nitro-1,1-biphenyl produced 4-ferrocenyl-4-nitro-1,1:4,1-terphenyl (3). X-ray diffraction study of terphenyl 3 showed that this compound crystallizes in the noncentrosymmetric space group P21. In the crystal, molecules 3 are packed in an antiparallel head-to-tail fashion, which is unfavorable for generation of strong nonlinear optical effects.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2657–2662, December, 2004. 相似文献