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We have studied electron acceptor and electron donor spiro-conjugated dimers based, respectively, on bis(benzoquinoidal tetracyano carbon-bridged para-phenylene-vinylene) and on bis(benzo-aromatic ...

Donor-acceptor-donor conjugates composed of electron-donating carbon-bridged styrylstilbene (COPV2) and electron-accepting thiadiazole derivatives equipped with carbazolyl (Cz) terminators, Cz-COPV2-A-COPV2-Cz (A = benzothiadiazole (BTz), naphthobis(thiadiazole) (NTz), or benzobis(thiadiazole) (BBTz)), were newly synthesized and found to serve as efficient and stable long-wavelength photoluminescent dyes in organic and aqueous media. In particular, Cz-COPV2-BBTz-COPV2-Cz showed photoluminescence in the near infrared region (895-927 nm) with a photoluminescence quantum yield (PLQY) of up to 0.19 in cyclohexane and of 0.02-0.03 in THF/water mixtures. Its analogues with weaker acceptors, Cz-COPV2-BTz-COPV2-Cz and Cz-COPV2-NTz-COPV2-Cz, showed yellow to deep-red emission in organic solvents, with PLQYs of up to 0.71 in organic solvents and 0.45 in THF/water mixtures.

A naphtho[2,1-b:6,5-b′]difuran derivative was found to serve as an effective violet-emitting laser dye. It showed amplified spontaneous emission at 413 nm with the threshold of 1.1–2.9 mJ cm−2 using 0.1–0.5 wt% in polystyrene film. Lasing was also demonstrated using all-polymeric distributed-feedback lasers emitting at 411–417 nm with the threshold of 2.0–2.9 mJ cm−2. This work was supported by JSPS KAKENHI grant JP19H05716 (to H. T.) and by the “Ministerio de Ciencia, Innovación y Universidades” of Spain, via grants MAT2015-66586-R and PID2020-119124RB-I00 and by the “Generalitat Valenciana” through grant AICO/2021/093.

The efficacy of carbon-bridged oligo(phenylenevinylenes)s (COPVs) as light-harvesting antenna for porphyrins is demonstrated using a series of 5,15-di-COPVn-substituted free-base and zinc porphyrins, COPVn-MP-COPVn (n=1-3, M=H2 , Zn). These molecules were synthesized by Suzuki-Miyaura cross-coupling reactions of COPVn-Bpin and Br-H2 P-Br. The absorption spectra of these compounds in solution show a significant expansion of the Soret band region together with a bathochromic shift of the Q band, suggesting a significant interaction between these chromophores in the ground state. The photoluminescence quantum yield of the porphyrin-COPV conjugates is enhanced up to four times relative to the parent porphyrins. Theoretical calculations also indicated interactions between these chromophores in the HOMO, which suggests that the light-harvesting ability stems from the expansion of the π-electron-conjugation system.

All‐solution processed surface‐emitting organic distributed feedback lasers are attractive devices for low‐cost applications. Here, lasers emitting in the spectral region between 375 and 475 nm, in which both active material and resonator (1D relief gratings) are based on solution‐processable polymer films, are reported. Ten different organic compounds dispersed in polystyrene are used as active layers of the prepared devices. They include various carbon‐bridged oligo(p‐phenylenevinylene) (COPVn, with n = 1,2) derivatives and two terfluorene compounds. The synthesis and complete optical and amplified spontaneous emission properties of one of the COPV1 compounds, COPV1(Me)‐t‐Bu, designed for deep‐blue emission, are also included. The feasibility of the resonator fabrication, performed by holographic lithography with a dichromated gelatine photoresist over the active film, is successfully demonstrated for all devices. Remarkably, no resolution limitations are found even for the lowest grating period (235 nm) required for the fabrication of the laser based on COPV1(Me)‐t‐Bu. It is also demonstrated that the rectangular grating profile with duty cycle 0.75:0.25 (hill:valley) is very convenient to optimize the resonator efficacy. The Spanish team acknowledges support from the Spanish Government (MINECO) and the European Community (FEDER) through Grant No. MAT2015-66586-R. H.T. and E.N. thank the financial support from MEXT (JP19H05716 for H.T. and JP19H0549 for E.N.).

Carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1–6) have demonstrated great success as laser dyes for thin-film organic lasers. The excellent photostability observed in the longer homologues is, however, not present in the blue-emitting shorter compounds COPV1 and COPV2, attributed to the unprotected terminal positions that can degrade by photoreaction in the excited state. Here we report the synthesis of various COPV1 and COPV2 derivatives functionalized at the terminal positions with two types of sterically bulky protecting substituents: Tip (2,4,6-triisopropylphenyl) and tert-butyl (t-Bu) groups. Such molecular designs aim at preventing such photodegradation processes and thus to improve their stability. The efficacy of kinetic isotope effect for stabilization is also examined for COPV2, by the addition at terminal positions of deuterium atoms. Absorption, photoluminescence (PL), including PL quantum yield, and amplified spontaneous emission (ASE) studies have been conducted in polystyrene films doped with each of the derivatives. Significant and slight improvements of the ASE photostability are observed for the compounds with Tip groups and deuterium, respectively. Installation of substituents slightly affects the ASE wavelength within the blue spectral region, that is 385–413 nm and 462–474 nm, for COPV1 and COPV2, respectively. Financial support from Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant MAT2015-66586-R is gratefully acknowledged. This work was partially supported by MEXT and JSPS KAKENHI Grant Numbers JP16H04106 and JP19H05716 to HT and JP19H0549 to EN.

Microcrystallites are promising minute mirrorless laser sources. A variety of luminescent organic compounds have been exploited along this line, but dendrimers have been inapplicable owing to their fragility and extremely poor crystallinity. Now, a dendrimer family that overcomes these difficulties is presented. First-, second-, and third-generation carbazole (Cz) dendrimers with a carbon-bridged oligo(phenylenevinylene) (COPV2) core (GnCOPV2, n=1-3) assemble to form microcrystals. The COPV2 cores align uni/bidirectionally in the crystals while the Cz units in G2- and G3COPV2 align omnidirectionally. The dendrons work as light-harvesting antennas that absorb non-polarized light and transfer it to the COPV2 core, from which a polarized luminescence radiates. Furthermore, these crystals act as laser resonators, where the lasing thresholds are strongly coupled with the crystal morphology and the orientation of COPV2, which is in contrast with the conventional amorphous dendrimers.

Highly efficient emissive conjugated polymers are desired for optoelectronic applications. While efficient blue to green emissive polymers have been successfully developed, efficient red emission is still challenging, mainly because of the increased nonradiative process rates upon decreasing the energy gap by extension of the π-system. Suppression of this nonradiative decay would be the key for efficient red-emitting polymers. We have previously developed carbon-bridged oligo(p-phenylenevinylene)s (COPVs), which could be promising backbones for efficient light-emitting polymers because of the suppression of rotational disorder by the rigidified coplanar structures. In this work, we report that a series of COPV-based homopolymers and copolymers show fluorescence over a wide range of the visible region (437–667 nm) with high to excellent fluorescence quantum yield: 0.60–0.94 for the blue to green emission and 0.50 for red. The polymers also exhibited high thermal and electrochemical stabilities, which could...

Fluorescence-switching dyes serve as important tools for bioimaging and environment sensing. Herein, we report a new type of molecule, tetrakis(benzo[b]furyl)ethene (TBFE), that undergoes two-wavelength ON–OFF–ON three-stage fluorescence switching triggered by aggregation. This compound features a sterically hindered tetrasubstituted ethene, made available by a hafnium-mediated McMurry coupling reaction. A fluorescent band of TBFE at 360 nm in THF disappears upon dilution with water towards 40% water in THF, giving way to a new peak at 510 nm. This switching behaviour is attributed to the combination of THF/H2O ratio-dependent aggregation-caused quenching and aggregation-induced emission, as supported by the change of size distribution measured by dynamic light scattering and scanning electron microscopy.

In this paper, experimental and computational investigations are combined to analyze the impact of the diradical character in the photonic and chemical properties of two tetracyano quinodimethane derivatives of phenylene-vinylenes. The photonic properties are evaluated with high-level quantum-chemical calculations and are rationalized in the context of the four-level model typical of diradical molecules, including one triplet and three singlet states, whereas the diradical extent in the ground electronic state is shown to be the driving force for the dimerization reactions. To this end DFT, CASSCF, and CASPT2//CASSCF calculations are carried out and complemented with experimental UV-vis-NIR absorption and emission measurements, as a function of the temperature along with resonance Raman spectroscopy investigations. The study of diradical molecules with enhanced chemical stability in the framework of organic electronics is an important field of research in organic π-conjugated molecules with direct applications in organic electronics.

The fused polycyclic furan structure is a ubiquitous motif in naturally occurring organic compounds. However, they had been rarely seen in the literature of organic electronic research until very recently, probably because of the lack of stability of simple furans under conditions that the compounds experience in the active layer of the device. Nonetheless, from the viewpoint of molecular structure, furans look to have potential merits as organic semiconductors such as thiophenes, which are more popular in the organic electronic area. For example, the small atomic radius and large electronegativity of oxygen will increase intermolecular molecular orbital (MO) overlap and hence facilitate charge transporting ability in the solid state. In this Account, we describe the molecular design and optoelectronic applications of fused polycyclic furans, such as benzodifurans (BDFs), naphthodifurans (NDFs), and anthradifurans (ADFs). The molecular design that was exploited in this study crucially depends on the synthetic flexibility of a "modular" synthetic strategy that we purposely developed and reviewed in a separate report. Our synthetic strategy comprises two steps carried out in situ: cyclization of an o-alkynylphenol into a zincio benzofuran and its electrophilic Negishi-type trapping to obtain a range of multisubstituted fused furan compounds. These compounds are found to possess electronic structures resembling those of fused polyaromatic hydrocarbons, such as acenes or phenacenes, rather than oxygen-bridged phenylenevinylene, along with unique characteristics: a wide HOMO-LUMO gap originating from the weak aromaticity of the furan rings, an intense photoluminescent character, and mechanofluorochromism. Semiconducting properties of fused furans are also excellent among organic materials: some BDF derivatives show high hole mobility on the order of 10-3 cm2/(V s) in the amorphous state using time-of-flight (TOF) technique. The p-type BDFs exhibit high performance as hole-transporting material in heterojunction organic light-emitting diodes (OLEDs), while carbazole-substituted BDFs (CZBDFs) are ambipolar with well-balanced high carrier mobility for both hole and electron and serve as host materials for full-color electroluminescence in both hetero- and homojunction architectures. More π-expanded NDFs showed good crystallinity and are effective active materials for organic field-effect transistors (OFETs) with a high hole mobility of up to 3.6 cm2/(V s) using a solution process. These studies have illustrated the high potential of fused polycyclic furans in organic electronics research, which thus far have attracted much less attention than their thiophene congeners.

Carbon-bridged bis(aminoaryl) oligo(para-phenylenevinylene)s have been prepared and their optical, electrochemical, and structural properties analyzed. Their radical cations are class III and class II mixed-valence systems, depending on the molecular size, and they show electronic couplings which are among the largest for the self-exchange reaction of purely organic molecules. In their dication states, the antiferromagnetic coupling is progressively tuned with size from quinoidal closed-shell to open-shell biradicals. The data prove that the electronic coupling in the radical cations and the singlet–triplet gap in the dications show similar small attenuation factors, thus allowing charge/spin transfer over rather large distances. ·, We thank MINECO of the Spanish Government (CTQ2015- 69391-P, CTQ2013-40480-R and MAT2015-66856-R) for their support. We also thank the Research Central Services (SCAI) of the University of M#laga. This work is partially supported by Grant-in-Aid for Scientific Research (16H04106 to HTand 15H05754 to EN) and the Strategic Promotion of Innovative Research, JST (to EN) from MEXT, Japan. M.H. and C.L. are grateful to the Deutsche Forschungsgemeinschaft for supporting this work (GRK 2112).

The modern history of conducting organic systems started with a fortuitous error in 1967 on acetylene polymerization, followed by a rational discovery in 1976 on the effects of doping that generates a polaron and, hence, dramatically increases conductivity. Not unexpectedly, however, the prototypical polyacetylene suffers many problems, including C-C single bond rotation, short effective conjugation length, radiationless deactivation, and instability of the polarons. Several strategies have been put in place to solve these problems. An early approach relied on partial rigidification of the polyene structure by conversion into polymers with thiophene, pyrrole, and benzene linkages. An oligo(phenylene vinylene) (OPV) is an all-carbon analogue of polyacetylene, where every other diene unit in the polyene chain is converted to a benzene unit, still leaving many C-C single bonds freely rotating in the molecule. We considered adding additional carbon bridges to rigidify the OPV skeleton entirely to create a carbon-bridged OPV (COPV). Making such a compound was an obvious challenge. This Account describes the authors' efforts to design and synthesize a series of COPV molecules, where the benzene rings in OPV are bridged by sp

Stabilization of the radical cationic state of a donor molecule by 3-D homoconjugation was probed using a substituted carbon-bridged oligophenylenevinylene backbone (COPV, or 5,5-diarylindeno[2,1-a]indenes). For molecules bearing electron-donating groups as the 5,5-aryl moieties, a one-electron oxidation of the COPV backbone results in delocalization of the cationic charge over the whole molecule with a small reorganization energy. The compounds forming a stable radical cation by 3-D homoconjugation produce a uniform amorphous film and show high short-circuit current, high fill factor, and hence high power-conversion efficiency when used as a hole-transporting layer of an organic-inorganic hybrid lead perovskite solar cell. This material thus shows a performance and stability in air comparable to those obtained with the benchmark material, spiro-MeOTAD.

The photophysical properties of oligosilanes show unique conformational dependence due to σ-electron delocalization. The excited states of the SAS, AAS, and AEA conformations of peralkylated n-hexasilanes, in which the SiSiSiSi dihedral angles are controlled into a syn (S), anti (A), or eclipsed (E) conformation, were investigated by using UV absorption, magnetic circular dichroism (MCD), and linear dichroism spectroscopy. Simultaneous Gaussian fitting of all three spectra identified a minimal set of transitions and the wavenumbers, oscillator strengths, and MCD B terms in all three compounds. The results compare well with those obtained by using the symmetry-adapted-cluster configuration interaction method and almost as well with those obtained by time-dependent density functional theory with the PBE0 functional. The conformational dependence of the transition energies and other properties of free-chain permethylated n-hexasilane, n-Si6 Me14 , was also examined as a function of dihedral angles, and the striking effects found were attributed to avoided crossings between configurations of σσ* and σπ* character.

π-conjugated organic microcrystals often act as optical resonators in which the generated photons in the crystal are confined by the reflection at the crystalline facets and interfere to gain lasing action. Here, we fabricate microcrystals from a mixture of carbon-bridged oligo- para-phenylenevinylenes (COPVs) with energy-donor (D) and energy-acceptor (A) characters. Upon weak excitation of the single D-A co-crystal, Förster resonance energy transfer (FRET) takes place, exhibiting spontaneous emission from A. In contrast, upon strong pumping, stimulated emission occurs before FRET, generating lasing action from D. Lasing occurs with single- and dual-vibronic levels, and the lasing wavelength can be modulated by the doping amount of A. Time-resolved spectroscopic studies reveal that the rate constant of lasing is more than 20 times greater than that of FRET. Furthermore, microcrystals, vertically grown on a Ag-coated substrate, reduce the lasing threshold by one-fourth. This study proposes possible directions toward organic solid FRET lasers with microcrystalline resonators.

Thin-film organic lasers are attractive light sources for a variety of applications. Recently, it is reported that carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1–6) function as unique laser dyes which combine high fluorescence efficiency, wavelength tunability, and both thermal and photostability, making them ideal for use in organic semiconductor lasers. However, in order to obtain such excellent properties, COPVn require blending in a matrix, such as a thermoplastic polymer, thus leading to miscibility issues, limited absorption, and charge transporting properties. Here, high-performance lasers with a novel active polymer poly-COPV1, based on the basic unit of COPV1 and prepared as a high-quality neat film, are reported which overcome the trade-off between the device performance and durability. The prepared lasers show thresholds 30 times lower and operational lifetimes 300 times longer than devices based on COPV1 dispersed in polystyrene. The low threshold operation allows the poly-COPV1 lasers to be pumped by a nitride diode laser., Spanish Government (MINECO). Grant Numbers: MAT2011-28167-C02-01, MAT2015-66586-R European Community (FEDER) MINECO FPI Fellowship. Grant Number: BES-2009-020747 Junta de Castilla y León (JCYL) Postdoctoral Fellowship. Grant Number: SA046U16 MEXT. Grant Numbers: 16H04106, 15H05754 Engineering and Physical Sciences Research Council. Grant Numbers: EP/K503162/1, EP/J009016/1 Royal Society Wolfson Research

We have used Raman spectroscopy to study the molecular and electronic structures of the radical cations and dications of carbon-bridged oligo(para-phenylenevinylene)s (COPVn, n = 1-6) possessing consecutive fused pentagons and hexagons, up to 19, along with COPV derivatives having electron-donating and -withdrawing groups. This study was made possible by the outstanding stability of the charged states of COPVs. We could untangle the effects of π-conjugation in the planar structure on the Raman frequency by distinguishing it from other structural effects, such as strain in the vinylene groups shared by the two pentagons. The analyses showed that the radical cations have benzo-quinoidal structures confined in the center of the molecule, as well as benzo-aromatic rings at the terminal sites. In contrast, dications of COPVn longer than n = 3 exhibit a biradicaloid character because of the recovery of aromaticity in the central rings and quinoidal rings at the terminal positions. These biradicaloids favor a singlet nature in their ground electronic states because of the double spin polarization. The introduction of electron-donating and -withdrawing groups on the termini of a COPV core affords, upon oxidation or reduction, a fully delocalized class III mixed valence system because of the high degree of conjugation of the COPV platform, which favors extensive charge delocalization.

Thin film organic lasers represent attractive light sources for numerous applications. Currently, efforts are devoted to the development of low-cost high-performance and color-tunable devices, whereby both the resonator and the active layer should consist of solution-processable organic materials. Herein, solution-processed distributed-feedback lasers are reported with polymeric resonators on top of active films of perylene orange or carbon-bridged oligo(p-phenylenevinylene) dispersed in polystyrene, which combine these properties. These lasers emit in the 520–595 nm range and show low thresholds (≈1 kW cm−2) and long operational lifetimes (7 × 105 pump pulses), which are comparable to other state-of-the-art lasers that contain the same active materials but resonators made on inorganic substrates. Due to this top-layer resonator configuration, the laser slope efficiencies of the present devices are remarkably superior. A centimeter-size device emitting at different wavelengths within a broad spectral range, based on a perylene-based film of uniform thickness that contributes to preserve a low threshold, is demonstrate, MINECO. Grant Numbers: MAT2011-28167-C02-01, MAT2015-66586-R, BES-2009-020747 Junta de Castilla y León. Grant Number: SA046U16 MEXT. Grant Numbers: 16H04106, 15H05754

Electron transfer (ET) is a fundamental process in a wide range of biological systems, photovoltaics and molecular electronics. Therefore to understand the relationship between molecular structure and ET properties is of prime importance. For this purpose, photoinduced ET has been studied extensively using donor-bridge-acceptor molecules, in which π-conjugated molecular wires are employed as bridges. Here, we demonstrate that carbon-bridged oligo-p-phenylenevinylene (COPV), which is both rigid and flat, shows an 840-fold increase in the ET rate compared with the equivalent flexible molecular bridges. A 120-fold rate enhancement is explained in terms of enhanced electronic coupling between the electron donor and the electron acceptor because of effective conjugation through the COPVs. The remainder of the rate enhancement is explained by inelastic electron tunnelling through COPV caused by electron-vibration coupling, unprecedented for organic molecular wires in solution at room temperature. This type of nonlinear effect demonstrates the versatility and potential practical utility of COPVs in molecular device applications.

Unlike π-electron chromophores, the peralkylated n-tetrasilane σ-electron chromophore resembles a chameleon in that its electronic spectrum changes dramatically as its silicon backbone is twisted almost effortlessly from the syn to the anti conformation (changing the SiSiSiSi dihedral angle ω from 0 to 180°). A combination of UV absorption, magnetic circular dichroism (MCD), and linear dichroism (LD) spectroscopy on conformationally controlled tetrasilanes 1-9, which cover fairly evenly the full range of angles ω, permitted a construction of an experimental correlation diagram for three to four lowest valence electronic states. The free chain tetrasilane n-Si4 Me10 (10), normally present as a mixture of three enantiomeric conformer pairs of widely different angles ω, has also been included in our study. The spectral trends are interpreted in terms of avoided crossings of 1B with 2B and 2A with 3A states, in agreement with SAC-CI calculations on the excited states of 1-7 and conformers of 10.

In this account, we summarize our recent studies on the synthesis of multisubstituted furan compounds. The synthetic strategy relies on the electrophilic cyclization of o-hydroxy(alkynyl)arenes by using main-group metal reagents. For example, zinc salts have been found to mediate the cyclization of o-alkynylphenols to form thermally stable yet chemically reactive β-zincio intermediates (‘synthetic modules’) that serve as platforms for the syntheses of a series of analogues having the same core structural motif (the ‘molecular library’). This modular approach is applicable to the synthesis of new benzofurans and benzodifurans and their homologues, and allows us to study the photophysical and semiconducting properties of these products systematically. We have similarly developed a synthesis of benzotrifurans by a cesium hydroxide-mediated tandem SNAr/triple-cyclization reaction, as well as a synthesis of trisubstituted furans by indium-catalyzed cyclo­isomerization of α-propargyl β-keto esters. 1 Introduction 2 Modular Approach for the Synthesis of Fused Furan Derivatives Using Zinc Salt 2.1 Zinc-Mediated Cyclization Reaction and Synthesis of Functionalized Benzofurans 2.2 Selective Syntheses of Benzodifurans Based on the Modular Method 2.3 Homologues of BDF: Naphtho- (NDF) and Anthradifurans (ADF) 3. Syntheses of Other Furans 3.1 Cesium Hydroxide-Promoted One-Pot Reaction for the Synthesis of Benzotrifurans 3.2 Indium-Catalyzed Cycloisomerization Reaction for the Synthesis of Multisubstituted Furans 4 Conclusions

Diphosphenes stabilized by the fused-ring bulky 1,1,3,3,5,5,7,7-octa-R-substituted s-hydrindacen-4-yl (Rind) groups have been obtained as orange crystals by the reduction of the corresponding dichlorophosphines, (Rind)PCl2, with lithium naphthalenide (LiNaph). The molecular structures of (Eind)PCl2 and the diphosphenes, (Eind)PP(Eind) and (EMind)PP(EMind), having the bulky Eind and the less bulky EMind groups, have been confirmed by X-ray crystallography. The formation of the PP bond has been fully characterized by spectroscopic methods.

A versatile method for the synthesis of dibenzo[g,p]chrysene (DBC) derivatives based on regio- and stereoselective stannyllithiation to diarylacetylenes is described. This method affords a variety of DBCs possessing both electron-donating and electron-withdrawing functional groups. These twisted molecules take brickwork packing structures in single crystals. Thus, ambipolar carrier transport properties with mobility values of up to 10(-3) cm(2) V(-1) s(-1) in the amorphous state were achieved. Functional groups on DBC frameworks are considered to increase carrier mobility through the enhancement of intermolecular interactions in the brickwork packing structures.

We developed a concise synthetic method for benzotrifurans and benzotripyrroles from 1,3,5-triethynyl-2,4,6-trifluorobenzenes by one-pot reactions in good to excellent yield. By investigating 2-D and 3-D structures of a variety of benzotrifuran and benzotripyrrole derivatives using scanning tunneling microscopy (STM) and single-crystal X-ray diffraction techniques, we found both similarities and dissimilarities. We also found that diverse molecular 3-D orientations were derived in their single crystals according to substituents on the molecules and that the emission properties in the solid state are dependent on their packing manners.

In order to find new anti-Pseudomonas agents, we carried out whole-cell based P. aeruginosa growth assay, and identified 1,2,3,4-tetrahydro-1,3,5-triazine (Compound A). This compound showed anti-Pseudomonas activity against wild as well as pumpless strain equally at a same concentration. Also, this compound was structurally very similar to A22, which is known to inhibit the bacterial actin-like protein MreB. By the analysis of resistant strains, the primary target of this compound in P. aeruginosa was definitely confirmed to be MreB. In addition, these compounds showed a bacteriostatic effect, and induced the morphology changes in P. aeruginosa from rod shape to sphere shape, which leads to be clinically favorable in terms of susceptibility to phagocytosis and release of endotoxin. These results display that Compound A is a very attractive compound which shows anti-P. aeruginosa activity based on inhibition of MreB without being affected by efflux pumps, and could provide a new step toward development of new promising anti-Pseudomonas agents, MreB inhibitors.

A heptacyclic carbocycle possessing three p-quinodimethane units conjugated in one plane has been synthesized and shown to exhibit distinct biradical characteristics. The molecule has a HOMO/LUMO band gap of ca. 1 eV and a S(0)-T(1) energy gap of 2.12 kcal/mol, and it absorbs and emits near-IR light at room temperature. It is air-stable under ambient light for several months and thermally stable up to 160 °C under nitrogen, and it undergoes reversible two-electron oxidation and reduction. The synthetic approach is such that a smaller and larger oligo-p-quinodimethane can be synthesized.

We developed a versatile synthesis of tetraaryl-substituted benzo[1,2-b:5,4-b′]difurans (m-BDFs) via a zinc-mediated intramolecular double cyclization reaction of 4,6-bis(phenylethynyl)-1,3-benzenediol, followed by a palladium-catalyzed cross-coupling reaction. In comparison with the corresponding benzo[1,2-b:4,5-b′]difuran (p-BDF) isomers reported previously, the m-BDFs are slightly wider between HOMO and LUMO, as well as a lower energy level of the former. These differences in properties between the structural isomers can be ascribed to the difference in the conjugation type. The compounds had high charge carrier mobility up to 1 × 10−3 cm2/Vs, which makes them attractive materials for organoelectronics applications. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:316–324, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20682

We have synthesized a new homoconjugated donor–acceptor (D–A) system featuring a rigid planar carbon-bridged oligo(p-phenylenevinylene) that shows efficient intramolecular charge separation (CS, 98...

The hydrogen/deuterium primary kinetic isotope effect provides useful information about the degradation mechanism of OLED host materials. Thus, replacement of labile C-H bonds in the host with C-D bonds increases the device lifetime by a factor of five without loss of efficiency, and replacement with C-C bonds by a factor of 22.5.

The manganese-catalyzed dehydrative [2 + 2 + 2] annulation reaction of a 1,3-dicarbonyl compound and a terminal alkyne provides an efficient and regioselective synthesis of a substituted benzene derivative, highlighted by the exclusive formation of a p-terphenyl derivative from an aryl acetylene. The mechanism and the origin of the regioselectivity of the reaction were explored by experiments and density functional theory (DFT) calculations. Experimental data revealed the cis stereochemistry of a cyclohexadienol precursor to the benzene product and suggested that two reaction pathways may operate competitively sequential carbometalation reactions of a manganese enolate and formation of a manganacyclopentadiene intermediate. The DFT study supported the first possibility, namely that the reaction involves three steps: (1) addition of a manganese enolate of a 1,3-dicarbonyl compound to a terminal alkyne to give a vinylmanganese complex, (2) insertion of a second alkyne into the vinyl-Mn bond to give a dienylmanganese complex, and (3) intramolecular nucleophilic addition of the dienylmanganese to the carbonyl group. This mechanism is consistent with the experimental facts such as the perfect regioselectivity of the reaction of an aryl acetylene, the moderate regioselectivity of the reaction of an alkyl acetylene, and the stereochemistry of the annulation product. An alternative mechanism involving a manganacyclopentadiene intermediate failed to account for the experimental regioselectivity, although it may be occurring as a very minor competitive pathway.

Reductive coupling of a 9,10-dibromo-9,10-disilatriptycene derivative followed by treatment with chlorotrimethylsilane (TMSCl) affords a series of TMS-capped 9,10-disilatriptycene oligomers DSiT[n]. Each isomer, up to the pentamer (n = 5), can be separated using recycling gel permeation chromatography. The X-ray structural analysis of DSiT[2] shows that the six silicon atoms are linearly aligned in a rigid array structure. While the ultraviolet (UV) absorption maximum remains constant at 230 nm, irrespective of the chain length, the magnetic circular dichroism (MCD) spectra exhibit a red shift band near 245 nm, and the emission maximum steadily shifts from 319 to 337 nm as the number of silicon atom increases. These spectra indicate the occurrence of electronic delocalization along the one-dimensional arrangement of bridge-head disilane moieties.

Construction of a nonracemic all-carbon quaternary stereocenter at the alpha-position of beta-ketoesters was achieved by way of an indium(III)-catalyzed diastereoselective alpha-alkenylation reaction of chiral enamines with 1-alkynes. The enamine bearing a chiral auxiliary derived from l-isoleucine was added to the alkyne to give an alpha-alkenylated product in excellent yield and with a stereoselectivity better than 90% ee. One can ascribe the high selectivity to a chelate intermediate involving the auxiliary and the metal atom and the high yield to efficient interactions between the indium(III) atom and the alkyne. The selectivity increased as the reaction temperature was raised to 120 degrees C and decreased at higher temperatures.

We have investigated the photophysical properties of the oligosilane-bridged zinc porphyrin-fullerene[60] dyads. Dependence of the rate of the relaxation processes of the singlet-excited state of the ZnP moiety of the dyads on the oligosilane linker was mostly ascribable to the conformational differences of the silicon chain. The charge-separated state with sub-microsecond lifetime was observed in the time-resolved absorption measurements of benzonitrile solution of the dyads. The lifetime of the radical-ion pair scarcely depended on the length and little on the conformation of the oligosilane linkage, which suggests that the super-exchange mechanism disciplines the charge recombination process.

A series of zinc porphyrin–[60]fullerene dyads linked by conformation-constrained tetrasilanes and permethylated tetrasilane have been synthesized for the evaluation of the conformation effect of the tetrasilane linkers on the photoinduced electron transfer. The excited-state dynamics of these dyads have been studied using the time-resolved fluorescence and absorption measurements. The fluorescence of the zinc porphyrin moiety in each dyad was quenched by the electron transfer to the fullerene moiety. The transient absorption measurements revealed that the final state of the excited-state process was a radical ion pair with a radical cation on the zinc porphyrin moiety and a radical anion on the fullerene moiety as a result of the charge separation. The charge separation and charge recombination rates were found to show only slight conformation dependence of the tetrasilane linkers, which is characteristic for the Si-linkages.

Thin film organic lasers represent a new generation of inexpensive, mechanically flexible devices for spectroscopy, optical communications and sensing. For this purpose, it is desired to develop highly efficient, stable, wavelength-tunable and solution-processable organic laser materials. Here we report that carbon-bridged oligo(p-phenylenevinylene)s serve as optimal materials combining all these properties simultaneously at the level required for applications by demonstrating amplified spontaneous emission and distributed feedback laser devices. A series of six compounds, with the repeating unit from 1 to 6, doped into polystyrene films undergo amplified spontaneous emission from 385 to 585 nm with remarkably low threshold and high net gain coefficients, as well as high photostability. The fabricated lasers show narrow linewidth (105 pump pulses for oligomers with three to six repeating units) and wavelength tunability across the visible spectrum (408–591 nm)., Thin film organic solid-state lasers are low-cost flexible devices which require efficient, stable, colour-tunable, solution-processable materials. Here, the authors show that oligo(p-phenylenevinylene)s simultaneously possess all such properties, as demonstrated by their use in laser devices.