Silole Moiety Research Articles

Silole Amino Acids with Aggregation‐Induced Emission Features Synthesized by Hydrosilylation

The synthesis of silole amino acids was achieved through hydrosilylation of alkene or alkyne‐containing amino acids with 1‐methyl‐2,3,4,5‐tetraphenyl‐1H‐silole, using Karstedt's catalyst with yield up to 95 % and without epimerization. After selective deprotection of carboxylic acid or amine functions respectively, C‐ or N‐peptide coupling with an alanine moiety proved their possible incorporation into peptides. A model tripeptide was synthesized by solid phase synthesis with the N‐Fmoc protected silole amino acid version. The silole moiety can be also grafted on a precursor peptide directly on the solid support. These amino acids and peptides exhibit AIE properties with λem ca. 500 nm and Δλ ca. 100 nm. This approach constitutes an alternative and promising strategy for incorporation of such AIE fluorogens to peptides.

Synthesis of reactively functionalized 2,5-siloles using kumada-type nickel-mediated intramolecular cyclization and their utilization in polymer synthesis

The syntheses of reactively functionalized 2,5-siloles by the Kumada-type nickel-catalyzed intramolecular cyclization of alkynes and disilane, and their subsequent polymerization with diketopyrrolopyrrole (DPP) are described. The prefunctionalization of the 2,5-positions of the silole ring, which avoids the problem of silole susceptibility to nucleophiles during post-modification highlights this synthesis. Suzuki, Stille, and direct arylation silole precursors were prepared by this reaction and were subsequently subjected to polymerization with DPP by the various polymerization methods. The polymers all had reduced bandgaps (Eg < 2 eV). A lower Eg was observed for the 2,5-dithienylsilole polymers (P2 and P3) compared to the 2,5-diphenylsilole polymers (P1 and P4) highlighting the effect of thiophene - silole orbital overlap on the Eg. While the direct arylation reaction resulted in the desilylation of the silole moiety of P5 causing a hypsochromic shift in the absorption wavelength compared to P1P4, a similar Eg to the 2,5-diphenylsilole polymers was observed.

Photoluminescence Enhancement of Silole-Capped Silicon Quantum Dots Based on Förster Resonance Energy Transfer.

Photoluminescent porous silicon were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 650 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon quantum dots in porous silicon. HO-terminated red luminescent PS was obtained by an electrochemical treatment of fresh PS with the current of 150 mA for 60 seconds in water and sodium chloride. As-prepared PS was sonicated, fractured, and centrifuged in toluene solution to obtain photoluminescence silicon quantum dots. Dichlorotetraphenylsilole exhibiting an emission band at 520 nm was reacted with HO-terminated silicon quantum dots to give a silole-capped silicon quantum dots. The optical characterization of silole-derivatized silicon quantum dots was investigated by UV-vis and fluorescence spectrometer. The fluorescence emission efficiency of silole-capped silicon quantum dots was increased by about 2.5 times due to F6rster resonance energy transfer from silole moiety to silicon quantum dots.

Synthesis and Characterization of New Poly(silole-fluorene) Copolymers.

New poly(silole-fluorene) copolymers were designed and synthesized. Copolymers were obtained by Suzuki coupling reaction with different ratio of fluorene and silole. The obtained copolymers were characterized by the spectroscopic methods such as FT-IR and 1H-NMR spectroscopies. The resulting copolymers were soluble in common organic solvents such as toluene, tetrahydrofurane, chloroform, chlorobenzene, etc. The obtained copolymers showed thermal stabilities, which were characterized by TGA and DSC. PLEDs with device configurations of ITO/PEDOT:PSS/Copolymer I~VI/LiF/AI. The best device performances, with maximum brightness of 231.5 cd/m2 at a current density (J) of 408.3 mA/cm2, and a maximum luminance efficiency of 0.115 cd/A, were achieved in the composition of fluorene and silole moiety (0.9:0.1).

New AIEgens containing tetraphenylethene and silole moieties: tunable intramolecular conjugation, aggregation-induced emission characteristics and good device performance

Three AIE luminogens were successfully synthesized by the covalent incorporation of tetraphenylethene into the dibenzosilole core, and their emission colours were tuned through simple structural modifications.

A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

ChemInform Abstract: Highly Enantioselective Synthesis of Silahelicenes Using Ir‐Catalyzed [2 + 2 + 2] Cycloaddition.

AbstractThe first synthesis of silahelicenes (IV), which have helical chirality including silole moieties, is reported.

2,3,4,5‐Tetraphenylsilole‐Based Conjugated Polymers: Synthesis, Optical Properties, and as Sensors for Explosive Compounds

A series of linear 2,5-tetraphenylsilole-vinylene-type polymers were successfully synthesized for the first time. The tetraphenylsilole moieties were linked at their 2,5-positions through a vinylene bridge with p-dialkoxybenzenes to obtain polymer PSVB and with 3,6-carbazole to obtain polymer PSVC. For comparison, 2,5-tetraphenylsilole-ethyne-type polymer PSEB was also synthesized, in which the vinylene bridge of PSVB was replaced with an ethyne bridge. Very interestingly, the bridging group (vinylene or ethyne) had a significant effect on the photophysical properties of the corresponding polymers. The fluorescence peak of PSEB at 504 nm in solution originated from the emission of its silole moieties, whereas PSVB and PSVC emitted yellow light and no blueish-green emission from the silole moieties was observed, thus demonstrating that the emissions of PSVB and PSVC were due to their polymer backbones. More importantly, the 2,5-tetraphenylsilole-ethyne polymer exhibited a pronounced aggregation-enhanced emission (AEE) effect but the 2,5-tetraphenylsilole-vinylene polymer was AEE-inactive. Moreover, both AEE-active 2,5-tetraphenylsilole-ethyne polymer and AEE-inactive 2,5-tetraphenylsilole-vinylene polymers were successfully applied as fluorescent chemosensors for the detection of explosive compounds.

Highly enantioselective synthesis of silahelicenes using Ir-catalyzed [2+2+2] cycloaddition

Silahelicenes, which contain two silole moieties in a helically chiral structure, were synthesized by a chiral Ir-catalyzed intermolecular [2+2+2] cycloaddition of tetraynes with diynes along with a Ni-mediated intramolecular [2+2+2] cycloaddition. The photophysical properties of the obtained highly enantiomerically enriched silahelicenes (up to 93% ee) were also measured.

Electrochemical and Photovoltaic Properties of Electropolymerized Poly(thienylsilole)s

Electrochemical and photoelectrochemical properties were studied of a series of donor-acceptor materials based on polythiophene modified with silole moieties. The materials were prepared by electrochemical anodic polymerization of 2,5-bis([2,2'-bithiophen]-5-yl)-1,1-dimethyl-3,4-diphenylsilole and 2,5-bis([2,2'-terthiophen]-5-yl)-1,1-dimethyl-3,4-diphenylsilole, as well as copolymerization of these monomers with 2,2'-bithiophene. Photocurrent measurements showed that introduction of silole resulted in a considerable enhancement of the photovoltaic properties of silole-containing materials and especially the fill factor. However, as demonstrated by Mott-Schottky measurements, electropolymerized silole-containing materials showed a substantial degree of disorder and high density of states in the midgap, which negatively affected their photovoltaic properties. Atomic force microscopy (AFM) and phase imaging revealed the presence of phase segregation and heterogeneity of the silole-containing materials. Interestingly, introduction of siloles suppressed the cathodic (n-type) doping typical for polythiophenes. This work demonstrates that siloles show great promise as electron-acceptor groups for all-organic solar cells; however, further work is required to optimize the properties and performance of poly(thienylsilole)-based materials.

Fluorescence quenching detection of peanut agglutinin based on photoluminescent silole-core carbosilane dendrimer peripherally functionalized with lactose

A glycocluster peripherally functionalized with a lactose (Lac: Galβ1→4Glcβ1–) derivative possessing a silole moiety as a luminophore was synthesized. The photoluminescence spectrum of the glycocluster showed extremely strong emission at 474 nm and the absolute quantum yield was estimated to be 92% in distilled water. The emission intensity was decreased by increasing the amount of peanut agglutinin (PNA), a lactose-binding lectin, and plots of the relative fluorescence intensity revealed a decline of 95% in emission intensity. Fluorescence quenching of the glycocluster upon mixing with PNA could be easily observed by the naked eye under UV irradiation, whereas no distinct change in fluorescence properties of the glycocluster was observed when wheat germ agglutinin (WGA) was employed.

New electropolymerized poly(thienyl-silole)s for all-polymer solar cells: Incorporation of silole results in remarkable enhancement of photoefficiency compared to polybithiophene

New electropolymerized donor–acceptor materials were prepared containing thiophenes and siloles in the main chain. The introduction of the silole moiety gave rise to more than 5 times improvement in the photoefficiency of the polymer material as compared to the parent polymer, polybithiophene (PBT). The energy conversion efficiency of the poly(thienyl-silole) material measured in electrolytic arrangement under 90 mW cm −2 monochromatic 405 nm light was estimated to be ca. 0.16% with a fill factor of 60%. The efficiency is expected to further increase upon optimization of the thickness and composition of the active layer.

Highly luminescent glycocluster: silole-core carbosilane dendrimer having peripheral globotriaose

A novel glycocluster periphery functionalized by globotriaose (Galα1–4Galβ1–4Glcβ1–) possessing a silole moiety as a luminophor was synthesized. The photoluminescence spectrum of the glycocluster in pure water showed extremely strong emission at 475 nm. Analogous intense emission of the silole dendrimer was also observed in a lower water fraction of water/acetone mixture. The water fraction of the silole dendrimer solution strongly affected the emission intensity; however, these luminescences were constantly detected at around 475 nm.

Silole‐containing poly(diphenylacetylene): Synthesis, characterization, and light emission

AbstractA disubstituted polyacetylene consisting of a poly(diphenylacetylene) backbone and a 1,2,3,4,5‐pentaphenylsilole (SiC4Ph5) pendant, that is, {(C6H5) CC [C6H4O(CH2)3CCSiC4Ph5]}n (PS3DPA), was synthesized, and its light emission from both the backbone and the pendant was evaluated. The polymerization of C6H5CCC6H4O(CH2)3CCSiC4Ph5 with two ethynyl groups was effected with WCl6–Ph4Sn as the catalyst. The structure and properties of PS3DPA were characterized and evaluated by IR, UV, NMR, thermogravimetric analysis, differential scanning calorimetry, photoluminescence, and electroluminescence analyses. The ethynyl group of the diphenylacetylene moiety was polymerized exclusively, giving a soluble PS3DPA. The chloroform solution of PS3DPA showed a backbone emission that peaked at 522 nm, whereas the silole pendant was nonradiative at room temperature. The polymer did not show the aggregation‐induced emission phenomenon, probably because the silole clusters were difficult to form when the polymer chains aggregated because of the very high rigidity of the main chain. Intramolecular rotations of the phenyl groups of the silole moieties were responsible for the nonradiative decay of the silole chromophore. The intramolecular rotations, however, could be largely restricted in a cooling process of the polymer solution, showing cooling‐enhanced emission. The silole emission became dominant at lower temperatures. A multilayer electroluminescence device based on PS3DPA emitted a green light that peaked at 512 nm. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2487–2498, 2006

Crystal Structure of a 2-Biphenyl-2-yl-1,1,3,4-tetraphenyl-1H-silole

Crystals of silole (silole = silacyclopentadiene) analogue, 2-biphenyl-2-yl-1,1,3,4-tetraphenyl-1H-silole, were grown from a dichloromethane/hexane solution and the crystal structure was determined. The crystal belongs to the monoclinic system with space group of P21/c. There is an intramolecular π-π interaction in an asymmetric unit, and the shortest distance between one of the phenyl rings in the biphenyl and the phenyl ring at the 3-position of silole is about 3.643 A. This silole can be used as a potential building block for generating linear polymers containing the silole moiety owing to the labile nature of the proton attached at the 2-position.