Synthesis of oligo(phenyleneethynylene)-tetrathiafulvalene cruciforms for molecular electronics

[reaction: see text] Novel oligo(phenyleneethynylene) (OPE)-tetrathiafulvalene (TTF) cruciform molecules containing thiol end-groups have been prepared and characterized. These redox-active molecules are interesting for future applications as molecular wires/transistors for molecular electronics.     

Synthesis and characterization of X-shaped oligo(para-phenylene)derivatives functionalized with fluorene ethynylene

<正>A series of linear and X-shaped oligo(para-phenylene) derivatives functionalized with fluorene ethynylenes 1,3 and 4 were synthesized through sequent Sonogashira coupling and Suzuki-Miyaura reaction in high yield.The electron-donating group-OCH_3 and electron-withdrawing counterparts-CF_3 were introduced to tune the spectra properties of compounds 3 and 4.The detail investigation of their photophysical properties in solution and film indicated that the introduction of both -OCH_3 and -CF_3 makes maximum emission distinct red-shift in comparison with parent compound 1,but the latter more prominently.     

Progresses in organic field-effect transistors and molecular electronics

In the past years, organic semiconductors have been extensively investigated as electronic materials for organic field-effect transistors (OFETs). In this review, we briefly summarize the current status of organic field-effect transistors including materials design, device physics, molecular electronics and the applications of carbon nanotubes in molecular electronics. Future prospects and investigations required to improve the OFET performance are also involved. __________ Translated from Huaxue Tongbao (Chemistry), 2006, 69(6) (in Chinese)     

Diamine anchored molecular junctions of oligo(phenylene ethynylene) cruciform

Using diamine as anchoring group, the self-assembled monolayers (SAMs) based on oligo(phenylene ethynylene)s (OPEs) and cruciform OPEs with an extended tetrathiafulvalene (TTF) (OPE3 and OPE3-TTF) were successfully formed on the Au substrate and then utilized in molecular junctions by conductingprobe atomic force microscopy (CP-AFM).     

Synthesis of linear and V-shaped oligo(phenylene ethynylene) derivatives: geometric effects on photophysical properties

<正>A series of linear and V-shaped oligo(phenylene ethynylene) derivatives 1-3 were synthesized through sequent Sonogashira coupling and propargyl alcohol deprotection reaction in high yields.The alkoxy chains(i.e.,n-hexyloxy groups) were introduced to assure good solubility of compounds 1-3 in common solvents.The photophysical properties of 1-3 in solution depend strongly on the geometries of these compounds.     

Synthesis and testing of new end-functionalized oligomers for molecular electronics

Several new classes of oligomers have been synthesized with functionalities designed to aid in the understanding of molecular device behavior, specifically when molecules are interfaced between proximal electronic probes. The compounds synthesized are series of azobenzenes, bipyridines and oligo(phenylene vinylene)s that bear acetyl-protected thiols for ultimate attachment to metallic surfaces. Some initial electrochemical and solid-state test results are also reported.     

Oligo(p‐phenyleneethynylene) (OPE) Molecular Wires: Synthesis and Length Dependence of Photoinduced Charge Transfer in OPEs with Triarylamine and Diaryloxadiazole End Groups

The systematic synthesis and photophysical, electrochemical and computational studies on an extended series of triphenylamine‐[C?C‐1,4‐C₆H₂(OR)₂]_n‐C?C‐diphenyl‐1,3,4‐oxadiazole dyad molecules (the OR groups are at 2,5‐positions of the para‐phenylene ring and R=C₆H₁₃; n=0–5, compounds 1 , 2 , 3 , 4 and 5 , respectively) are reported. Related molecules with identical end groups, triphenylamine‐C?C‐1,4‐C₆H₂(OR)₂‐C?C‐triphenylamine (R=C₆H₁₃; 6 ) and diphenyl‐1,3,4‐oxadiazole‐[C?C‐C₆H₂(OR)₂]₂‐C?C‐diphenyl‐1,3,4‐oxadiazole (R=C₆H₁₃; 7 ) were also studied. These D–B–A 1 – 5 , D–B–D 6 and A–B–A 7 (D=electron donor, B=bridge, A=electron acceptor) systems were synthesized using palladium‐catalysed cross‐coupling reactions of new p‐phenyleneethynylene building blocks. Steady‐state emission studies on the dyads 1 – 5 reveal a complicated behavior of the emission that is strongly medium dependent. In low polarity solvents the emission is characterized by a sharp high‐energy peak attributed to fluorescence from a locally excited (LE) state. In more polar environments the LE state is effectively quenched by transfer into an intramolecular charge‐transfer (ICT) state. The medium dependence is also observed in the quantum yields (QYs) which are high in cyclohexane and low in acetonitrile, thus also indicating charge‐transfer character. Low‐temperature emission spectra for 2 – 5 in dichloromethane and diethyl ether also reveal two distinct excited states, namely the LE state and the conventional ICT state, depending on solvent and temperature. Hybrid DFT calculations for 1 – 7 establish that the OPE bridge is involved in both frontier orbitals where the bridge character increases as the bridge length increases. Computed TD‐DFT data on 1 – 5 assign the emission maxima in cyclohexane as LE transitions. Each time‐resolved emission measurement on 2 – 7 in cyclohexane and diethyl ether reveals a wavelength dependent bi‐exponential decay of the emission with a fast component in the 5–61 ps range on blue detection and a slower approximately 1 ns phase, independent of detection wavelength. The fast component is attributed to LE fluorescence and this emission component is rate limited and quenched by transfer into an ICT state. The fast LE fluorescence component varies systematically with conjugation length for the series of D–B–A dyads 2 – 5 . An attenuation factor β of 0.15 Å^?1 was determined in accordance with an ICT superexchange mechanism.     

Combinatorial synthesis of oligo(phenylene ethynylene)s

The combinatorial synthesis of oligo(phenylene ethynylene) tetramers, both in solution and on solid support, is described. These products are of interest for molecular electronics applications. An iterative sequence, coupling of aryl halides to alkynes under Sonogashira conditions, was used. Five monomers functionalized with electron-donating or electron-withdrawing groups were synthesized, and used to generate a library of 25 trimers in a solution-phase based process. A library of 24 tetramers was prepared by subsequent protodesilylation and coupling with the alligator clip 4-iodo-1-thioacetylbenzene. The solution-phase based sequence was successfully adapted to a higher yielding directed split-and-pool solid-phase process, with average yields of 78–86% for each step over seven steps. A triazene linker group was used to attach the starting monomer to the polymer beads. At the completion of the solid-phase-based process, traceless cleavage of trimers from the resin was achieved by sonication of the resin in 10% HCl/THF solution. The released products were then poised for the final step in the sequence, attachment of the alligator clip.     

Synthesis of oligo(ethylene glycol) methacrylate polymer brushes

Here we report a study into controlling the polymerization of mono-hydroxy and mono-methoxy terminated oligo(ethylene glycol) methacrylates (HOEGMA and MeOEGMA, respectively) from functionalised, planar surfaces via atom transfer radical polymerization (ATRP). The effects of initiator structure, initiator density, temperature, and monomer ratios have been investigated for these polymerizations. The polymer brushes grown in this way were found to convey protein resistance to the underlying inorganic substrates, prone to facile protein adsorption in their native state.     

Synthesis of oligo(phenyleneethynylene)s containing central pyromellitdiimide or naphthalenediimide groups and bearing terminal isocyanide groups: molecular components for single-electron transistors

Oligo(phenyleneethynylene)s that are of variable length, contain a central arenediimide unit, either a pyromellitdiimide or a naphthalenediimide group, and are terminated by isocyanide groups have been prepared. The extended frameworks were assembled from appropriately functionalized arenediimide and areneformamide units whose lengths were adjusted by adding phenyleneethynylene units. Final transformation of the formamide groups into isocyanide groups gave the title compounds. Several isocyanide-terminated oligo(phenyleneethynylene)s without an arenediimide unit have also been prepared.     

Synthesis and polymerization of oligo(oxyethylene) macromonomer bearing sodium sulfonate

Oligo(oxyethylene) macromonomers bearing sodium sulfonate group have been synthesized through four reactions: (1) ring-opening polymerization of oxirane, (2) etherification of monomethoxyl oligo(oxyethylene) and epichlorohydrin, (3) sulfonation of cycloxyl compound, and (4) end-capping of sodium oligo(oxyethylene) sulfonate by methacrylic group. A desired length of oligo(oxyethylene) in the macromonomers can easily be achieved by controlling the ratio of reactants in the ring-opening step. The structures of the products of each reaction were identified by IR, ¹H-NMR, and GPC. Polymers of the monomers were also characterized by GPC and DSC. © 1993 John Wiley & Sons, Inc.     

Aldehyde separation by polymer-supported oligo(ethyleneimines)

Chlorosulfonated styrene (10%) divinylbenzene resin beads reacted with an excess of ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA) to give the corresponding sulfonamides with pendant oligo(ethyleneimines). The resulting modified resins are useful in the separation of aldehydes from hydrocarbon mixtures. Sorption of aldehydes occurs through formation of both Schiff base and five-membered (imidazoline) rings. Sorbed aldehydes can readily be stripped from the resins by treating with dilute acid solutions. Since the sulfamide bond has a reasonable stability toward acid-base hydrolysis, the loaded resins can be regenerated and recycled by simple acid-base washings, without losing their activity. In the present study, sorption and desorption kinetics of acetaldehyde, benzaldehyde, and salicylaldehyde have been investigated under different conditions. The aldehyde sorption obeys second-order kinetics. The method presented is applicable for all aromatic aldehydes. However, in the case of aliphatic aldehydes carrying an α-hydrogen, aldol condensation products form in solution. So aliphatic aldehydes and their aldol products are sorbed together by the resins. This limits the recovery of aliphatic aldehydes. Consequently, the resins described are cost effective sorbents for the removal and recovery of aromatic aldehydes from various mixtures. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2857–2864, 1997     

Synthesis and evaluation of bipendant-armed (oligo)thiophene crown ether derivatives as new chemical sensors

Three new (oligo)thiophene bipendant-armed ligands 2a-c, derived from 2-(aminomethyl)-15-crown-5, have been synthesized and characterized. Compounds 2a-c were prepared by reductive amination of the corresponding macrocycle with formyl thiophene derivatives 1a-c in the presence of NaBH(OAc)₃ in fair to good yields. The photophysical properties of ligands 2a-c were studied and they were also evaluated as chemosensors in the presence of Na(I), Ag(I), Pd(II) and Hg(II) cations in acetonitrile solution.     

Dihydroazulene-Boron Subphthalocyanine Conjugates with Oligo(phenyleneethynylene) Bridging Unit: Photoswitchable Fluorophores

In this work, we have linked the dihydroazulene (DHA)/vinylheptafulvene (VHF) photo-/thermoswitch and the boron subphthalocyanine (BsubPc) fluorophore via an axial oligo(phenyleneethynylene) bridging unit into new DHA-BsubPc conjugates. The objectives were to elucidate the influence of BsubPc on the DHA/VHF switching reactions and the influence of DHA/VHF on the BsubPc fluorescence in these conjugates for which the entire axial substituent connected to boron comprises one large, conjugated scaffold. We present the synthesis and properties of DHA-BsubPc conjugates with varying peripheral substituents on the BsubPc core, being either unsubstituted (H₁₂BsubPc) or partially fluorinated (F₆BsubPc). Fluorination of the BsubPc core provided a remarkable increase in the reversibility of the DHA-VHF interconversions promoted by light and heat, respectively, and accompanied by on/off switching of the BsubPc fluorescence. Synthetically, the units were connected using Sonogashira coupling reactions of suitable acetylenic building blocks.     

Biomaterials for molecular electronics development of optical biosensor for retinol

Molecular electronics involves expertise from several branches of science. Various biomaterials and electronics are involved in the fabrication of such devices. While passive biomaterials are involved in anchoring the active biomolecules, the latter are involved in switching and/or signal transduction. In the present investigation we have used a glass-capillary-based approach to design a biosensor for retinol. The sensing element is retinol-binding protein (RBP). The affinity of retinoic-acid-horseradish peroxidase (conjugate) to RBP is tested using a surface plasmon resonance technique. A simple photomultiplier-tube-based system is exploited to monitor the chemiluminescent signal generated upon reaction of hydrogen peroxide and luminol with the conjugate bound to RBP. The photomultiplier tube is directly coupled to a computer for data logging.     

High density polyethylene/hydrogenated oligo(cyclopentadiene) blends: Tensile stress-strain behavior

The influence of hydrogenated olio(cyclopentadiene) (HOCP) on tensile mechanical properties of its blends with high density polyethylene (HDPE) has been studied at 20, 80, and 100°C. The nominal stress-strain curves performed at 20°C indicate an increase of the modulus and a conspicuous decrease of the ultimate properties increasing the HOCP content in the blend. Blends with HOCP content > 20%-wt are found to be very fragile at 20°C. These behaviors have been related to the presence of the HOCP-rich phase that has the glass transition at about 55°C. At 20°C the HOCP oligomers act as a hardener for the HDPE. The nominal stress-strain curves performed at 80 and 100°C show a strong decrease of the modulus (compared to the value at 20°C), plastic deformation for all the blends tested, and rupture of HDPE and blend samples at the beginning of the cold-drawing. Moreover, the modulus and the ultimate parameters are found to decrease with the composition. The behaviors at 80 and 100°C have been related to several factors: the higher mobility of HDPE molecules at these temperatures compared to that at 20°C; the HOCP-rich phase that is at temperatures higher than its glass transition, and so it acts as a plasticizer for the HDPE; and the decreases of crystallinity and number of entanglements when the HOCP is added to the HDPE component. ©1995 John Wiley & Sons, Inc.     

Photochromism of dihydroindolizines. Part XVI: first attempts toward molecular wires comprising photochromic dihydro 5-azaindolizines and π-extended ethynyl and butadiynyl oxadiazole derivatives

Eight new photochromic dihydro 5-azaindolizines (DHAIs) linked with 2,5-diaryl-1,3,4-oxadiazole (OXD) derivatives containing terminal ethynes and butadiyne substituents on the fluorene part of the DHAI skeleton are synthesized via palladium-mediated coupling reaction pathways. Irradiation of the DHAI-OXD derivatives with polychromatic light affords red- and green-colored betaines.     

Synthetic protocols and building blocks for molecular electronics

Simple and readily accessible aryl bromides are useful building blocks for thiol end-capped molecular wires. Thus, 4-bromophenyl tert-butyl sulfide and 1-bromo-4-(methoxymethyl)benzene serve as precursors for a variety of oligo(phenylenevinylene) and oligo(phenyleneethynylene) wires via efficient synthetic transformations as presented in this paper.