Asymmetrical Fluorene[2,3‐b]benzo[d]thiophene Derivatives: Synthesis,Solid‐State Structures,and Application in Solution‐Processable Organic Light‐Emitting Diodes

A series of novel asymmetrical fused compounds containing the backbone of fluorene[2,3‐b]benzo[d]thiophene (FBT) were effectively synthesized and fully characterized. Single‐crystal X‐ray studies demonstrated that the length of the substituent side chains greatly affects the solid‐state packing of the obtained fused compounds. DFT, photophysical, and electrochemical studies all showed that the FBTs have large band gaps, low‐lying HOMO energy levels, and therefore good stability toward oxidation. Moreover, the substituents strongly influence the fluorescence properties of the resulting FBT derivatives. The di‐n‐hexyl compound exhibits intense fluorescence in solution with the highest quantum yield of up to 91 %. Solution‐processed green phosphorescent organic light‐emitting diodes with the di‐n‐butyl derivative as the host material exhibited a maximum brightness of 14 185 cd m^?2 and a luminescence efficiency of 12 cd A^?1.     

Total Synthesis of Ciguatoxin

Something fishy : Ciguatoxin (see structure) is one of the principal toxins involved in ciguatera poisoning and the target of a total synthesis involving the coupling of three segments. The key transformations in this synthesis feature acetylene–dicobalthexacarbonyl complexation.

     

Systematic Control of the Excited‐State Dynamics and Carrier‐Transport Properties of Functionalized Benzo[ghi]perylene and Coronene Derivatives

A series of benzo[ghi]perylene (Bp) and coronene (Cor) derivatives substituted with electron‐withdrawing methoxycarbonyl (COOMe) or electron‐donating methoxyl (MeO) groups was synthesized. The electrochemical, spectroscopic, and photophysical properties of these compounds were investigated by cyclic voltammetry, steady‐state and time‐resolved spectroscopy, and quantum‐yield measurements. Introduction of suitable substituents onto the aromatic rings enabled control of electrochemical and spectroscopic behavior. Examination of excited‐state dynamics revealed that fluorescence quantum yields increased with increasing number of COOMe groups in both Bp and Cor derivatives, consistent with the findings of DFT calculations. Single‐crystal analysis allowed the performance of field‐effect transistors containing single crystals of the derivatives to be rationalized.     

Synthesis and Structural Data of Tetrabenzo[8]circulene

In 1976, the first attempted synthesis of the saddle‐shaped molecule [8]circulene was reported. The next 37 years produced no advancement towards the construction of this complicated molecule. But remarkably, over the last six months, a flurry of progress has been made with two groups reporting independent and strikingly different strategies for the synthesis of [8]circulene derivatives. Herein, we present a third synthetic method, in which we target tetrabenzo[8]circulene. Our approach employs a Diels–Alder reaction and a palladium‐catalyzed arylation reaction as the key steps. Despite calculations describing the instability of [8]circulene, coupled with the reported instability of synthesized derivatives of the parent molecule, the addition of four fused benzenoid rings around the periphery of the molecule provides a highly stable structure. This increased stability over the parent [8]circulene was predicted by using Clar’s theory of aromatic sextets and is a result of the compound becoming fully benzenoid upon incorporation of these additional rings. The synthesized compound exhibits remarkable stability under ambient conditions—even at elevated temperatures—with no signs of decomposition over several months. The solid‐state structure of this compound is significantly twisted compared to the calculated structure primarily as a result of crystal‐packing forces in the solid state. Despite this contortion from the lowest‐energy structure, a range of structural data is presented confirming the presence of localized aromaticity in this large polycyclic aromatic hydrocarbon.     

From pentalene to dicyclopenta[b,g]naphthalene, or the change towards delocalized structures.

Using triples-corrected coupled-cluster methods as well as other high-level theoretical approximations, the optimized parameters and isomerization barriers of the family of compounds cyclopentadiene-(benzene)x-cyclopentadiene (x = 0, 1, 2) are computed. In contrast to previous studies, s-indacene presents a localized C(2h) geometry. Also, the localized structure of pentalene is found to be the most stable, but when two benzene rings are intercalated between the five-member rings of pentalene, the resulting molecule preferably adopts a delocalized D(2h) conformation.     

Recent Progress in Synthesis and Application of Thiophene Oligomers Based on Bithiophene Dicarbanions

This focus review summarizes our recent efforts on the synthetic applications of bithiophene dicarbanions generated from three bithiophene isomers: 2,2′‐, 3,3′‐, and 2,3′‐bithiophene. Based on these bithiophene dicarbanions, a series of dithienothiophenes ( DTT s) and cyclooctatetrathiophenes ( COTh s) were synthesized by intra‐ and intermolecular cyclizations, respectively. Moreover, recent applications of DTT and COTh in characteristic compounds such as dendrimers, thio[8]circulenes, double helicenes, and thienoacenes are summarized in this account. Besides the synthetic work, some photoelectric properties of the thiophene‐based oligomers including organic field‐effect transistors and organic photovoltaics are briefly reviewed.

     

Solid Synthesis and Crystal Structure of Compound [（PPh3）3Cu2MoOS3]

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Synthesis of Nature‐Inspired Medium‐Sized Fused Heterocycles from Amino Acids

Herein, we describe the synthesis of molecular scaffolds consisting of medium‐sized fused heterocycles using amino acids, which are some of the most useful building blocks used by nature as well as chemists to create structural diversity. The acyclic precursors were assembled by using traditional Merrifield solid‐phase peptide synthesis, and cyclization was carried out through acid‐mediated tandem endocyclic N‐acyliminium ion formation, followed by nucleophilic addition with internal nucleophiles. The synthesis of molecular scaffolds consisting of seven‐, eight‐, and nine‐membered rings proceeded with full stereocontrol of the newly generated stereogenic center in most cases.     

Sulfonyl Azoles in the Synthesis of 3‐Functionalized Azole Derivatives

Sulfonyl indoles, as well as related azolyl derivatives, have been recently introduced in synthesis as stable precursors of reactive indolenine intermediates. This personal account reports on the discovery of sulfonyl azoles and their practical utilization in many synthetic processes for the preparation of functionalized 3‐substituted indoles, indazoles, and pyrroles. The indolenine intermediates obtained by treatment of sulfonyl azoles with Brønsted bases or Lewis acids can be considered as vinylogous imino derivatives that can be made to react with different nucleophilic reagents. These include organometallic reagents, reducing agents, stabilized carbanions, and heteronucleophiles. The controlled and mild conditions for the generation of indolenines from sulfonyl azoles make these substrates particularly useful in asymmetric synthesis, exploiting organo‐ or metal‐catalyzed processes. Although less exploited, sulfonyl indoles can also be involved in photochemical processes for the preparation of polycyclic derivatives.

     

Comparative study on the structural, optical, and electrochemical properties of bithiophene-fused benzo[c]phospholes

Three types of bithiophene-fused benzo[c]phospholes were successfully prepared by Ti(II)-mediated cyclization of the corresponding dialkynylated bithiophene derivatives as a key step. Each sigma(3)-phosphorus center of the benzo[c]phosphole subunits was readily transformed into sigma(4)-phosphorus center by Au coordination or oxygenation. In addition, the bithiophene subunit was functionalized at the alpha,alpha'-carbon atoms by Pd-catalyzed cross-coupling reactions with heteroarylmetals and by an S(N)Ar reaction with hexafluorobenzene. The experimentally observed results (NMR spectroscopy, X-ray analysis, UV/Vis absorption/fluorescence spectroscopy, and cyclic/differential-pulse voltammetry) have revealed that the structural, optical, and electrochemical properties of the bithiophene-fused benzo[c]phospholes vary considerably depending on the pi-conjugation modes at the bithiophene subunits and the substituents of the heterocyclopentadiene components. The appropriately ring-annulated sigma(3)-P derivatives and sigma(4)-P-AuCl complexes were found to emit fluorescence in the orange-red region, and the sigma(4)-P-oxo derivatives proved to undergo reversible one-electron reduction at -1.4 to -1.8 V (vs ferrocene/ferrocenium). These results indicate that the bithiophene-fused benzo[c]phospholes possess narrow HOMO-LUMO gaps and low-lying LUMOs, which was confirmed by density functional theory calculations of their model compounds. The time-of-flight measurement of an ITO/benzo[c]phosphole/Al device showed that the electron mobility in the P-oxo derivative is one-order higher than that in Alq(3) at low electric fields. The present study demonstrates that the arene-fused benzo[c]phosphole skeleton could be a highly promising platform for the construction of a new class of phosphole-based optoelectrochemical materials.     

Synthesis,Crystal Structure,Magnetic Property,and Electronic Structure of Ba2YbInSe5

A new barium ytterbium indium selenide, Ba₂YbInSe₅, was obtained by conventional high temperature solid state reaction. The compound crystallizes in the noncentrosymmetric space group Cmc2₁ of the orthorhombic system. The structure contains infinite one‐dimensional anionic chains ¹_∞[YbInSe₅]^4–, which are built from YbSe₆ octahedra and InSe₄ tetrahedra and separated by Ba²⁺ cation. The magnetic measurement indicates that the compound is paramagnetic. In addition, the calculated bandgap is 0.29 eV.     

Synthesis and Crystal Structure of Dimorphic Dibenzo[cde,opq]rubicene

Dibenzo[cde,opq]rubicene has been synthesized by an eight-step reaction sequence including an iron-mediated [2+2+1] cycloaddition and a flash vacuum pyrolysis as key steps. Two crystal modifications of the S-shaped, planar polycyclic aromatic hydrocarbon have been obtained and characterized by X-ray diffractometry.     

Synthesis of a Tetrabenzotetraaza[8]circulene by a “Fold‐In” Oxidative Fusion Reaction

Tetrabenzotetraaza[8]circulene ( 1 ) has been synthesized in good yield by a “fold‐in” oxidative fusion reaction of a 1,2‐phenylene‐bridged cyclic tetrapyrrole. X‐ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic‐like character, such as sharp absorption bands, high fluorescence quantum yields (Φ_F=0.55 in THF), and a single exponential fluorescence decay with τ_F=3.8 ns. These observations indicate a dominant contribution of an [8]radialene‐like π conjugation and hence aromatic character of the local aromatic segments in 1 .     

Diode‐Like I–V Characteristics of a Nonplanar Polyaromatic Compound: a Spectroscopic Study of Isolated and Stacked Dibenzo[g,p]chrysene

In this scanning‐tunneling‐microscopy/spectroscopy study (STM/STS), samples of isolated and close‐packed dibenzo[g,p]chrysene (DBC), a nonplanar polyaromatic compound, are used as model systems to demonstrate the effect of intermolecular interactions on the electronic structures. For dropcast films, DBC molecules adopt an edge‐on orientation in a close‐packed structure on graphite. Isolated DBC molecules are prepared on graphite from a DBC‐coated STM tip by a ca. 7 V/10 μs pulse. STS spectra for both isolated‐ and close‐packed DBC molecules exhibit diode‐like I–V curves in which the latter shows a turn‐on voltage (0.47 V) smaller than that of the former (0.91 V). The diode‐like behaviors are attributed to the more‐facile tunneling of electrons through the HOMO of DBC than through the LUMO. The reduced turn‐on voltage for the films is ascribed to the diminished HOMO–LUMO gap based on the results of DFT (density functional theory) simulations for the energy‐level couplings of π‐stacked DBC molecules.     

Synthesis of dibenzo[g,p]chrysenes from bis(biaryl)acetylenes via sequential ICl-induced cyclization and Mizoroki-Heck coupling

We report a facile synthesis of functionalized dibenzo[g,p]chrysenes via initial ICl-promoted cyclization of bis(biaryl)acetylenes, followed by the Mizoroki-Heck coupling reaction. This new approach works well for various bis(biaryl)acetylenes to afford dibenzo[g,p]chrysenes bearing various functionalities. With substrates of one special type including 4'-methoxy-2-ethynylbiphenyls, we found that the ICl treatment led to ipso cyclization to give bicyclic spirocyclohexadienones. In the presence of MeOH/H2SO4, these spiroketone products undergo rearrangement to give 9-iodophenanthrenes through a selective 1,2-alkenyl migration. We prepared various 4'-methoxy-2-ethynylbiphenyl compounds to show the generalization of such an ipso cyclization and 1,2-alkenyl shift. This ipso-cyclization approach can be extended to the preparation of dibenzo[g,p]chrysenes.     

二苯并[b,f][1,5]二氮杂芳辛四烯衍生物的合成及拆分

以邻氨基二苯甲酮为原料,经自身缩合环化合成了3种二苯并[1,5]二氮杂芳辛四烯衍生物(1a~1c);以邻苯二甲酸酐和溴苯为原料经傅-克反应制得中间体2-(4-溴苯甲酰溴)苯甲酸(M1);M1经叠氮化后自缩合制得6,12-二(4-溴苯基)二苯并[b,f][1,5]二氮杂环辛四烯(1d);以邻氨基苯甲酸甲酯为原料,经自身缩合环化制得中间体二苯并[b,f][1,5]二氮杂环辛四烯-6,12(5H,11H)-二酮(M2);M2经氯化合成6,12-二氯二苯并[b,f][1,5]二氮杂环辛四烯(1e),化合物1a~1e的结构经~1H NMR,~(13)C NMR和ESI-MS表征,其中化合物1c为新化合物。利用超临界色谱(SFC)技术对化合物1a~1e实现了手性拆分,获得5对具有高旋光度的光学活性异构体(ee99%)。