- Full-color tunable mechanofluorochromism and excitation-dependent emissions of single-arm extended tetraphenylethylenes
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We propose a new single-arm extension strategy on traditional tetraphenylethylene and successfully develop a new series of full-color (from ~450 nm to ~740 nm) tunable mechanofluorochromic materials. These materials exhibit efficient solid-state emission (quantum yield Φf > 10%) and high mechanofluorochromic contrast (wavelength shift from ~50 nm to ~100 nm). More importantly, we discover an unexpected excitation-dependent emission phenomenon of mechanofluorochromic materials and propose to utilize this new excitation-dependent emission behavior of materials to evaluate their mechanical-responsive performances more comprehensively. Finally, the unique feature of abundant emissions of mechanofluorochromic materials by changing the excitation light has shown application potential in dual channel anti-counterfeiting.
- Wang, Yi,Zhang, Ivan,Yu, Binhong,Fang, Xiaofeng,Su, Xing,Zhang, Yu-Mo,Zhang, Ting,Yang, Bing,Li, Minjie,Zhang, Sean Xiao-An
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supporting information
p. 12328 - 12334
(2015/12/08)
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- Aggregation emission properties of oligomers based on tetraphenylethylene
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A series of eight derivatives based on tetraphenylethylene were prepared, and two of these, i.e., 1,1-bis(4-phenylcarbonyl)-2,2-diphenylethylene (2), 1,1,2,2-tetrakis(4-phenylcarbonyl)phenylethylene (4), were characterized crystallographically. Because the rigidity and steric hindrance in the molecular structure enhanced regularly from sample 5 to 8, UV-visible absorption and PL spectra of 5-8 show the transition from aggregation-induced emission (AIE) to aggregation-induced emission enhancement (AIEE) behavior. Solid fluorescence lifetime characterization shows that samples with less steric hindrance and more interaction in or between molecules will result in a short fluorescence lifetime. All samples 5-8 become more emissive when their chains are induced to aggregate by adding water into their acetonitrile solutions. Cyclic voltammetry measurements taken give the band gap of sample 5-8 as 2.88, 2.70, 2.56, and 2.43 eV, and theoretical calculations also support these bad gap results. Conformational simulations also suggest that the origin of transition from AIE to AIEE behavior is due to the restricted intramolecular rotations of the aromatic rings in samples.
- Wang, Weizhi,Lin, Tingting,Wang, Min,Liu, Tian-Xi,Ren, Lulu,Chen, Dan,Huang, Shu
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experimental part
p. 5983 - 5988
(2010/10/02)
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- Practical synthesis of unsymmetrical tetraarylethylenes and their application for the preparation of [triphenylethylene-spacer-triphenylethylene] triads
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(Chemical Equation Presented) We have demonstrated that reactions of diphenylmethyllithium with a variety of substituted benzophenones produces corresponding tertiary alcohols that are easily dehydrated, without any need for purification, to produce various unsymmetrical and symmetrical tetraarylethylenes in excellent yields. The simplicity of the method allows for the preparation of a variety of ethylenic derivatives in multigram (10-50 g) quantities with great ease. The methodology was successfully employed for the preparation of various triphenylethylene (TPE)-based triads (i.e., TPE-spacer-TPE) containing polyphenylene and fluoranyl-based spacers. The ready availability of various substituted tetraarylethylenes allowed us to shed light on the effect of substituents on the oxidation potentials (Eox) of various tetraarylethylenes. Moreover, the electronic coupling among the triphenylethylene moieties in various TPE-spacer-TPE triads was briefly probed by electrochemical and optical methods.
- Banerjee, Moloy,Emond, Susanna J.,Lindeman, Sergey V.,Rathore, Rajendra
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p. 8054 - 8061
(2008/02/13)
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- Organometallic chemistry sans organometallic reagents: Modulated electron-transfer reactions of sub valent early transition metal salts
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The potential of low-valent, early transition-metal reagents as selective reductants in organic chemistry has been foreshadowed by intensive research on the ill-defined and heterogeneous subvalent titanium intermediates generated in the McMurry reaction and its numerous variants. As part of a long-term research effort to develop soluble, well-defined transition-metal reductants of modulated and selective activity toward organic substrates, the THF-soluble reductant, titanium dichloride, has been thoroughly examined, as well as the analogous ZrCl2 and HfCl2 reagents, all of which are readily obtainable by the alkylative reduction of the Group 4 tetrachloride by butyllithium in THF. Noteworthy is that such interactions of MCl4, with butyllithium in hydrocarbon media lead, in contrast, to M(III) or M(IV) halide hydrides. Analogous alkylative reductions in THF applied to VCl4, CrCl3, and MoCl5 have yielded reducing agents similar to those obtained from MCl4 but gradated in their reactivity. Such reductants have proved capable of coupling carbonyl derivatives, benzylic halides, acetylenes and certain olefins in a manner consistent with an oxidative addition involving a two-electron transfer (TET). Such a reaction pathway is consistent with the observed stereochemistry for pinacol formation from ketones and for the reductive dimerization of alkynes. In contrast to the reaction of CrCl3 with two equivalents of butyllithium, which leads to a CrCl intermediate, the interaction of CrCl3 in THF with four equivalents of butyllithium at -78°C yields a reagent of the empirical formulation, LiCrH4 · 2 LiCl · 2 THF, as supported by elemental and gasometric analysis of its protolysis. This hydridic reductant cleaves a wide gamut of o carbon-heteroatom bonds (C-X, C-O, C-S and C-N), towards which the CrCl reductant is unreactive. The type of cleavage and/or coupled products resulting from the action of "LiCrH4" on these substrates is best understood as arising from single-electron transfer (SET). In light of the aforementioned findings, the gradated reducing action noted among TiCl2, ZrCl2, HfCl2 and CrCl, as well as the contrasting reducing behavior between CrCl and LiCrH4, there is no doubt that future research with early transition metals will continue to yield novel reductants of modulated and site-selective reactivity. VCH Verlagsgesellschaft mbH,.
- Eisch, John J.,Shi, Xian,Alila, Joseph R.,Thiele, Sven
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p. 1175 - 1187
(2007/10/03)
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- Influence of Solvent and Cation on the Properties of Oxygen-containing Organic Anions. Part 4. Mechanism and Reactivity of Tetraaryloxirane Cleavage with Alkali Metals
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Six tetraaryloxiranes 1a-f (Scheme 4) were reduced (Schemes 1-3) with alkali metals (M = Li, Na, K, Cs) in eight polar aprotic solvents under an inert atmosphere.The organometallic solutions thus obtained were hydrolysed and the reaction products analysed.Similar experiments were carried out where the same solutions were quenched with D2O or MeI.In some cases the same solutions were studied by NMR and ESR spectroscopy before quenching.A stepwise reduction mechanism was established where the transfer of a first electron produces CO-bond scission in the oxirane ring, yielding a short-lived radical anion 4 or 5 (Scheme 1), i. e., a tetraalkyl-β-oxidoethyl radical.This intermediate can either eliminate oxygen as metal oxide (MO) to produce a tetraarylethylene 24 (Scheme 2) or be further reduced to a dianion 8 or 9 (Scheme 1).This anion yields, upon hydrolysis, low yields,if any, of the corresponding tetraphenylethanol 15 or 16 (Z = H).The larger proportion of the dianion, after the first protonation step, yielding anion 11 or 22, undergoes CC-bond scission which leads eventually to the corresponding ketone and diarylmethane 19 + 20 or 21 + 23 (Z = H) (Scheme 2).Other possible pathways were excluded through experiments where other possible intermediates were generated.These led to different end products.A triparametric linear correlation as a function of solvent parameters ETN and DN, as well as the cationic radius, was established for the influence of the nature of the solvent and counter-ion on the ratio between the rates of formation of products stemming from metal oxide (MO) elimination by the ring-opened radical anion 4 or 5 (Schemes 1 and 2) and rates of formation of products stemming from further reduction of the same radical anion to the dianion 8 or 9, thus confirming the mechanism established.
- Franco, M. Luisa T. M. B.,Herold, Bernardo J.,Maercker, Adalbert
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p. 119 - 129
(2007/10/02)
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- SOME NEWER ASPECTS OF CLEMMENSEN REDUCTION OF AROMATIC KETONES
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9,9'-Bifluorenyl (6), 1,2,2,2-tetraphenylethane (10) and 10,10'-bianthrone (18) have been obtained as a new type of products in Clemmensen reduction of 9H-fluoren-9-one (3), benzophenone (7) and 9,10-anthraquinone (13) respectively.Dibenzochrysene (5) is formed as the major product in the reduction of 3.Plausible mechanistic pathways for the formation of the unconventional products have been delineated.
- Talapatra, Sunil K.,Chakrabarti, Syamal,Mallik, Asok K.,Talapatra, Bani
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p. 6047 - 6052
(2007/10/02)
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