Novel Thienyl DPP derivatives Functionalized with Terminal Electron-Acceptor Groups: Synthesis,Optical Properties and OFET Performance

Three novel diketopyrrolopyrrole (DPP) based small molecules have been synthesized and characterized in terms of their chemical-physical, electrochemical and electrical properties. All the molecules consist of a central DPP electron acceptor core symmetrically functionalized with donor bi-thienyl moieties and flanked in the terminal positions by three different auxiliary electron-acceptor groups. This kind of molecular structure, characterized by an alternation of electron acceptor and donor groups, was purposely designed to provide a significant absorption at the longer wavelengths of the visible spectrum: when analysed as thin films, in fact, the dyes absorb well over 800 nm and exhibit a narrow optical bandgap down to 1.28 eV. A detailed DFT analysis provides useful information on the electronic structure of the dyes and on the features of the main optical transitions. Organic field-effect transistors (OFETs) have been fabricated by depositing the DPP dyes as active layers from solution: the different end-functionalization of the dyes had an effect on the charge-transport properties with two of the dyes acting as n-type semiconductors (electron mobility up to 4.4 ⋅ 10⁻² cm²/V ⋅ s) and the third one as a p-type semiconductor (hole mobility up to 2.3 ⋅ 10⁻³ cm²/V ⋅ s). Interestingly, well-balanced ambipolar transistors were achieved by blending the most performant n-type and p-type dyes with hole and electron mobility in the order of 10⁻³ cm²/V ⋅ s     

Synthesis and characterization of α,ω-disubstituted quaterthiophenes functionalized with polar groups for solution processed OTFTs

A series of soluble quaterthiophenes (4Ta-g) bearing ester groups in the α,ω-terminal positions separated from the quaterthiophene core by ethylene (4Ta-c), vinylene (4Td-f) or ethynylene (4Tg) spacers was synthesized by means of a Pd-catalyzed homocoupling of bithiophenes proceeding via C-H bond activation. The synthetic approach gave satisfying yields of 4Ta-f but resulted in only 3% yield of 4Tg due to the competitive hydrofluorination of the triple bond. The quaterthiophenes 4Ta-g were characterized by NMR, FTIR, UV-vis, PL spectroscopies, HRMS, TGA and CV. Thin-films of 4Ta-g were deposited either by spin-coating or by thermal evaporation on Si/SiO₂ for the fabrication of top-contact OTFTs. The devices prepared using 4Ta-c bearing the ester functional group separated from the quaterthiophene core by an ethylene spacer showed average hole field-effect mobility up to 2.7×10⁻³ cm² V⁻¹ s⁻¹ and up to 6×10⁻³ cm² V⁻¹ s⁻¹ for solution processed and for thermally evaporated OTFTs, respectively. The remarkably high solubility of 4Ta-c, along with their respectable performances in OTFTs render these molecules promising for practical applications as active layers in chemically-sensitive devices.     

Molecular design of n-type organic semiconductors for high-performance thin film transistors

This digest aims to provide organic chemists with an overview of recent progress on n-type organic semiconductors for application in organic thin film transistors (OTFTs) with an emphasis on molecular design. Herein, we survey n-type organic semiconductors with field effect mobility of 1 cm²/Vs or higher in OTFTs after a brief introduction to the structure and operation of OTFTs and discussion of two key factors (frontier molecular orbitals and molecular packing) of organic semiconductors. On the basis of this survey, we finally reach conclusions on the current status of n-type organic semiconductors for OTFTs and provide an outlook for molecular design.     

Field-induced π-polarization in barrelene derivatives: a computational study based on structural variation

Barrelene, H–C(CH=CH)₃C–H, is an unsaturated polycyclic hydrocarbon containing three isolated double bonds in a non-planar arrangement. We have studied the transmission of field effects through the barrelene framework by analyzing the small structural changes occurring in the phenyl group of many Ph–C(CH=CH)₃C–X molecules, where X is a variable substituent. Molecular geometries have been determined by quantum chemical calculations at the HF/6-31G* and B3LYP/6-311++G** levels of theory. Comparison with the results obtained for the corresponding saturated molecules, the bicyclo[2.2.2]octane derivatives Ph–C(CH₂–CH₂)₃C–X, reveals a small, but significant, field-induced π-polarization of the barrelene cage, especially when the remote substituent is a charged group. Additional evidence of π-polarization is obtained by comparing the electric dipole moments of the two sets of uncharged molecules. The structural variation of the barrelene cage caused by the variable substituent in Ph–C(CH=CH)₃C–X molecules has also been investigated. It is much larger than that of the phenyl group and depends primarily on the electronegativity of the substituent. Particularly pronounced is the concerted variation of the non-bonded distance between the bridgehead carbons of the cage, r(C···C) ₁ ^BARR , and the average of the three C–C–C angles at the cage carbon bonded to the variable substituent, α ₁ ^BARR . A scattergram of r(C···C) ₁ ^BARR versus the corresponding parameter for bicyclo[2.2.2]octane derivatives, r(C···C) ₁ ^BCO , shows that the variation of r(C···C) ₁ ^BARR becomes gradually less pronounced than that of r(C···C) ₁ ^BCO as the electronegativity of the substituent increases.     

Reversible Photoinduced Switching of Permeability in a Cast Non‐Porous Film Comprising Azobenzene Liquid Crystalline Polymer

Permeation characteristics of an azobenzene‐containing liquid crystalline (LC) non‐porous film are investigated using a metallic corrosion method. Thin films (300 nm) are fabricated by the solution casting of an azobenzene side‐chain LC polymer on freshly polished carbon steel coupons. Coated coupons are treated under the following conditions: a) gradual annealing at a cooling rate lower than 1 °C · min⁻¹ from 150 °C (above its T_g) to room temperature, and b) irradiation at 465 nm (20 mW · cm⁻²) with either circularly polarized light (CPL) or non‐polarized light (NPL). The morphology of these films is characterized using X‐ray diffraction, polarized optical microscopy, and transmission measurements. The results suggest that the annealing treatment resulted in the formation of a polydomain structure consisting of locally ordered small smectic domains that lack mutual orientation. Ordered micro domains are surrounded by disordered phases. CPL and NPL irradiation generates a monodomain orientated structure and an isotropic liquid crystal glass, respectively. The permeability of these non‐porous films treated by CPL, NPL, and annealing are found to be 6.14 × 10⁻⁴, 1.92 × 10⁻², and 1.56 × 10⁻³ cm³ · m⁻² · d⁻¹. An orientation‐dependent structure model is constructed to explain the permeation phenomenon, considering the ordered phase is impermeable, only the disordered phase is accessible to penetrating molecules. Fast switching of gas permeation is demonstrated by alternative irradiation of the film with CPL and NPL, which results in an approximately 30‐fold difference in the permeability of the non‐porous film.

     

Polydopamine-based molecularly imprinting polymers on magnetic nanoparticles for recognition and enrichment of ochratoxins prior to their determination by HPLC

A polydopamine-based molecularly imprinted polymer was deposited on the surface of magnetite (ferroferric oxide) nanoparticles (Fe₃O₄@PDA MIPs) and is shown to be an efficient and fairly specific sorbent for the extraction of various ochratoxins. The MIPs were characterized by IR spectroscopy and transmission electron microscopy. The adsorption capacities, evaluated through the langmuir adsorption isotherm model, are 1.8, 0.23 and 0.17 mg·g^?1 for ochratoxin A, ochratoxin B and ochratoxin C, respectively. Parameters such as the amount of magnetic MIPs, pH value, time for ultrasonication, elution solvent and volume were optimized. Following desorption from the MIP with acetonitrile, the ochratoxins were quantified by HPLC with fluorometric detection. Under optimal experimental conditions, the calibration plots are linear in the range of 0.01–1.0 ng·mL^?1 of OTA, 0.02–2.0 ng·mL^?1 of OTB, and 0.002–0.2 ng·mL^?1 of OTC. The LODs are between 1.8 and 18 pg·mL^?1, and the recoveries from spiked samples are 71.0% - 88.5%, with RSDs of 2.3–3.8% in case of rice and wine samples. The MIPs can be re-used for at least 7 times.

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Graphical abstract Schematic of the preparation of a magnetic molecularly imprinted polymer based on self-polymerization of dopamine in weakly alkaline solution. Ochratoxins are recognized owing to homologous cavities in the MIPs, and quantified by HPLC after desorption with acetonitrile.

     

Synthesis, crystal structure, and properties of the rhombohedral modification of the thiospinel CuZr1.86(1)S4

The rhombohedral modification of the thiospinel, CuZr_1.86(1)S₄, has been synthesized by the reaction of the constituent elements in an alkali metal halide flux and structurally characterized by single crystal X-ray diffraction techniques. The title compound crystallizes in the rhombohedral space group (#166, a=7.3552(2) Å, c=35.832(2) Å, V=1678.76(13) Å³, Z=12, and R/wR=0.0239/0.0624). The structure is composed of close packed S layers, with a stacking order of ?ABCBCABABCACAB?·along the c axis. The Zr and Cu atoms occupy the octahedral and tetrahedral holes between S layers, respectively. Three different kinds of S-M-S layers exist in the structure: layer I has fully occupied Zr and Cu sites, layer II has fully occupied Zr sites but no Cu, and layer III has partially occupied Zr and fully occupied Cu sites. Transport and optical properties indicate that the title compound is a small band gap (1.26 eV) n-type semiconductor.     

Synthesis and crystal structures of 2,4,6-pyridine-tricarboxylic anions/guanidinium and tetraalkylammonium inclusion compounds

Two different hydrogen-bonded inclusion compounds, [2,4,6-C₅H₂N(COO^?)₃]_0.5·[C(NH₂) ₃ ⁺ ]_0.5·[(C₂H₅)₄N⁺]·2H₂O (1) and [2,4,6-C₅H₂N(COO^?)₃]·[C(NH₂) ₃ ⁺ ]·[(C₂H₅)₄N⁺]·[(C₃H₇)₄N⁺]·6H₂O (2) are reported in this paper, in which 2,4,6-pyridine-tricarboxylic anions, guanidiniums and water molecules jointly construct host lattices while tetraalkylammonium cations are accommodated as guest species. Both two compounds formed sandwich-like hydrogen-bond inclusion compounds. In compound 1, the dimers composed of 2,4,6-pyridine-tricarboxylic anions and guanidiniums form 2D hydrogen-bonded layers by connecting with water molecules. In compound 2, 2,4,6-pyridine-tricarboxylic anions, guanidiniums and water molecules contribute to generate an undulate rosette hydrogen-bonded architecture. Interestingly, in compound 2, there are two species of guest molecules, tetraethylammonium and tetrapropylammonium, which are alternately arranged between the neighboring layers. Mixed guest cations accommodated in hydrogen-bonded inclusion compounds are seldom seen.     

Electronic Properties and Field‐Effect Transistors of Thiophene‐Based Donor–Acceptor Conjugated Copolymers

Summary: The thiophene‐quinoxaline donor–acceptor conjugated copolymer poly[(thiophene‐2,5‐diyl‐alt‐(2,3‐diheptylquinoxaline‐5,8‐diyl)] (PTHQx) was explored as a semiconductor in thin‐film organic field‐effect transistors (OFETs). A hole mobility of 3.6 × 10⁻³ cm² · V⁻¹ · s⁻¹ and an on/off current ratio of 6 × 10⁵ were observed in p‐channel OFETs made from spin‐coated PTHQx thin films. The electronic structures of PTHQx and a related thiophene‐thienopyrazine donor–acceptor copolymer were calculated by density functional theory. Atomic force microscopy of PTHQx thin films showed a polycrystalline grain morphology that varied with the substrate.

Output (left) and transfer (right) characteristics of a PTHQx (structure shown) organic field‐effect transistor.     

High-yield and sustainable synthesis of quinoidal compounds assisted by keto–enol tautomerism

The classical synthesis of quinoids, which involves Takahashi coupling and subsequent oxidation, often gives only low to medium yields. Herein, we disclose the keto–enol-tautomerism-assisted spontaneous air oxidation of the coupling products to quinoids. This allows for the synthesis of various indandione-terminated quinoids in high isolated yields (85–95%). The origin of the high yield and the mechanism of the spontaneous air oxidation were ascertained by experiments and theoretical calculations. All the quinoidal compounds displayed unipolar n-type transport behavior, and single crystal field-effect transistors based on the micro-wires of a representative quinoid delivered an electron mobility of up to 0.53 cm² V⁻¹ s⁻¹, showing the potential of this type of quinoid as an organic semiconductor.

Facilitated by the highly efficient Pd-catalyzed coupling and keto–enol-tautomerism-assisted spontaneous air oxidation, various indandione-terminated quinoidal compounds have been synthesized in isolated yields up to 95%.     

Ionic complexes simultaneously containing fullerene anions and coordination structures of metal phthalocyanines with I<Superscript>−</Superscript> and EtS<Superscript>−</Superscript> anions

The ionic complexes simultaneously containing negatively charged coordination structures of metal phthalocyanines and fullerene anions, viz., {Mn^IIPc(CH₃CH₂S^?) _x ·(I^?)_1?x }·(C₆₀ ^·?)· ·(PMDAE⁺)₂·C₆H₄Cl₂ (PMDAE is N,N,N′,N′,N′-pentamethyldiaminoethane, x = 0.87, 1) and {Zn^IIPc(CH₃CH₂S^?)_y·(I^?)_1?y }₂·(C₆₀ ^?)₂·(PMDAE⁺)₄·(C₆H₄Cl₂) (y = 0.5, 2) were synthesized. The both compounds were obtained as single crystals, which made it possible to study their crystal structures. In complex 1, the fullerene radical anions form honeycomb-like layers in which each fullerene has three neighbors with center-to-center interfullerene distances of 10.13–10.29 Å. Rather long distances between the C₆₀ ^·? radical anions results in the retention of monomeric C₆₀ ^·? in this complex down to the temperature of 110(2) K. In complex 2, fullerenes form dimers (C₆₀ ^?)₂ bonded by one C-C bond. The dimers are packed in corrugated honeycomb-like layers with interfullerene center-to-center distances of 9.90–10.11 Å. Manganese(II) and zinc(II) phthalocyanines coordinate iodide and ethanethiolate anions to the central metal atom to form unusual negatively charged coordination structures M^IIPc(An^?) (An^? is anion) packed in dimers {M^IIPc(An^?)}₂ with a short distance between the phthalocyanine planes (3.14 Å in 1 and 3.27 Å in 2). The pthalocyanine dimers also form layers with the PMDAE⁺ cations, and these layers alternate with the fullerene layers. The packing of spherical fullerenes with planar phthalocyanine molecules is attained by the insertion of fullerenes between the phenylene groups of phthalocyanines. The π-π-interactions of the porphyrin macrocycle with five- or six-membered fullerene rings are characteristic of the earlier studied ionic porphyrin and fullerene complexes. Such interactions are not observed for ionic complexes 1 and 2.     

Synthesis,Crystal, and Molecular Structure of bis(Thiosemicarbazide)Nickel(II) 1,5-Naphthalene Disulfonate Dihydrate Complex [Ni(Tsc)<Subscript>2</Subscript>](1,5-Nds) · 2H<Subscript>2</Subscript>O

Complex [Ni(Tsc)₂](1.5-Nds) · 2H₂O (I), where Tsc = thiosemicarbazide, NH₂NHC(=S)NH₂; 1,5-Nds^2– is double deprotonated anion of 1,5-naphthalene disulfonic acid \(\rm{CH_{10}H_6(SO_3)_2^{2-}}\) was synthesized, characterized by IR spectroscopy, and studied by thermogravimetry and X-ray diffraction. Crystal I is built of complex cations [Ni(Tsc)₂]²⁺, anions (Nds)^2–, and crystallization water molecules. The Ni atom is coordinated along the vertices of the trans-square by two sulfur atoms and two nitrogen atoms of two bidentate chelating ligands Tsc. The structural units of crystal I are joined by a branched network of N–H···O and O–H···O hydrogen bonds with the participation of donors, namely, the hydrogen atoms of two NH₂ groups and the NH group of complex cation [Cu(Tsc)]²⁺ and the H atoms of water molecules, and acceptors, namely, oxygen atoms of the sulfate group of anion 1,5-Nds^2– and solvate water molecules.     

DFT Study of the Molecular Structure,Conformational Preference,HOMO, LUMO,and Vibrational Analysis of 2-, and 3-Furoyl Chloride

Molecular structure, conformational stability and vibrational wave numbers for the rotational isomers of 2-furoyl chloride and 3-furoyl chloride have been computed using the B3LYP method with the 6-311++G(d,p) basis set. From computations, 2-furoyl chloride was predicated to exist predominantly in cis conformation with cis–trans rotational barrier 40.40 kJ·mol^?1, and 3-furoyl chloride was predicated to exist predominantly in the trans conformation with cis–trans rotational barrier 30.17 kJ·mol^?1. The effects of solvents on the conformational stability of all the molecules in nine different solvents (heptane, chloroform, tetrahydrofuran, dichloroethane, acetone, ethanol, methanol, dimethylsulfoxide and water) were investigated. The integral equation formalism of the polarizable continuum model was used for all solution phase computations. The vibrational wave numbers and the corresponding vibrational assignments of the molecules in C₁ symmetry were examined and the simulated infrared spectra of the molecules are reported. The geometrical parameters, highest occupied and lowest unoccupied molecular orbitals, Infrared intensities, and molecular electrostatic potentials results are reported.     

溶液法制备氧化锌半导体薄膜及其顶栅极晶体管器件

采用旋涂法用浓度分别为0.05,0.10和0.25 mol·L^-1的氧化锌前躯体溶液制备了氧化锌薄膜,并且制备了基于氧化锌多层膜的顶栅极晶体管器件,其中以利用光刻工艺刻蚀的氧化铟锡为源漏电极。通过原子力显微镜(AFM)和X-射线衍射(XRD)分别表征了薄膜的形貌以及结晶情况,并且讨论了前躯体的浓度顺序对氧化锌多层膜的影响。按照浓度从大到小的顺序依次旋涂前躯体溶液制备的氧化锌薄膜表现出了较高的载流子迁移率(7.1×10^-3 cm²·V^-1·s^-1),而按照浓度从小到大的顺序依次旋涂前躯体溶液制备的氧化锌薄膜的载流子迁移率为5.2×10^-3 cm²·V^-1·s^-1。文中通过对两种多层薄膜的形貌和结晶性能的分析表明影响顶栅极薄膜晶体管性能的主要因素是薄膜的粗糙度。平整的薄膜有利于形成较好的半导体层/绝缘层接触界面,从而有利于提高器件的载流子迁移率。     

Anion-directed organized assemblies of protonated pyrazole-based ionic salts

The reactions of 3(5)-(4-methoxyphenyl)-5(3)-phenyl-1H-pyrazole (L ¹ ) with nitric acid and 5-(4-benzyloxyphenyl)-3-(furan-2-yl)-1H-pyrazole(L ² ) with hydrochloric acid produced [HL ¹ · NO₃] (Salt-1) and [HL ² · Cl] (Salt-2). The structures of Salt-1 and Salt-2 were determined by single crystal X-diffraction. In Salt-1, HL ¹ showed [2 + 2] binding of NO₃ ^? ions in the solid state to form dimer architecture with R ₁ ² (4) and R ₄ ⁴ (14) graph sets. An anion directed one-dimensional anion-assisted helical chain with active participation of the chloride ion and protonated pyrazole via N–H···Cl hydrogen bonding in Salt-2. In addition, the protonated HL ² molecules interacted with each other through weak C–H···π interactions resulting in the formation of another one-dimensional helical chain.     

Guest inclusion in cyclic imides containing flexible tethers

Guest inclusion properties of two cyclic imides which have carboxylic acids connected through flexible tether, namely, 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid (1) and 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-cyclohexanecarboxylic acid (2) are studied. The crystals of host 1 containing one molecule of 1, the crystals of 4,4′-bipyridine (bpy) cocrystal of 1 containing one molecule of 1 and half molecule of bpy (1a), the crystals of 1,4-dioxane solvate of 1 containing two molecule of 1 and one and half molecule of 1,4-dioxane (1b) and the crystals of quinoline solvate of 1 containing one molecule of 1 and one molecule of quinoline (1c) in their crystallographic asymmetric units are investigated. Intermolecular hydrogen bonded two dimensional (2D) sheet structure of 1 and 3D channel network of 1b are comprised of cyclic R ₂ ² (8) hydrogen bond motifs; whereas cleavage of dimeric carboxylic acid R ₂ ² (8) motifs occurs in the structures of 1a and 1c in which 3D host–guest networks are comprised of discrete O–H···N and cyclic R ₂ ² (7) interactions, respectively. Various types of weak interactions between the two symmetry nonequivalent host molecule are found to be responsible for the formation of channels (14 × 11 Å) filled by guest 1,4-dioxane molecules in the crystal lattice of 1b. Two different solvates of 2 containing one molecule of 2 with a water molecule (2a) and one molecule of 2 with a quinoline molecule (2b) in their crystallographic asymmetric units, respectively, are also crystallized in different space groups. The quinoline molecules are held with host molecules by discrete O–H···N and C–H···O interactions and reside inside the voids formed by 3D repeated hexameric assemblies of host molecules in the crystal lattice of 2b.     

Fluorine-hydrocarbon separation and microdomain formation in N-(2,3,5,6-Tetrafluoropyridin-4-yl)benzene-diamines

Compounds with both aromatic and perfluoro aromatic moieties often assemble in the form of π-stacks with alternating arene perfluoroarene arrangements. The 1,4 and 1,3-diamines of N-(2,3,5,6-tetrafluoropyridin-4-yl)benzene (1) and (2), C₁₁H₇F₄N₃, however, show a behavior more commonly observed for diblock perfluoro alkyl derivatives: the fluorinated and the hydrocarbon moieties of the molecules segregate from each other and form fluoro and hydrocarbon microdomains with parallel layers of π-stacked tetrafluoropyridine rings and diamino-phenyl moieties. The structural features of the two derivatives are, despite the different substitution patterns and cell settings, strikingly similar. The main feature in the non-fluorinated domains of 1 and 2 is a set of N–H···H and N–H···π interactions that connect the amino groups of four molecules with each other, which are augmented by some weaker C–H···π and C–H···F interactions, but no π–π stacking is observed. The fluoro microdomains in both 1 and 2 are characterized by extremely short interplanar distances between the tetrafluoropyridine rings of only about 3 Å. The molecules in the layers are shifted sideways against each other by half a pyridyl ring thus bringing the fluorine atoms to atop of the aromatic carbon atoms and vice versa.     

Solution and solid-state studies of a new supramolecular proton transfer salt and its VO<Subscript>2</Subscript> complex constructed with chelidamic acid and 3,4-diaminopyridine

The proton transfer compound (Hdap)(chelH)·2H₂O (1) and its related anionic complex (Hdap) [VO₂(chel)] (2), where chelH₂ = 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) and dap = 3,4-diaminopyridine, were synthesized and characterized by elemental analysis, spectroscopy (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. Compound 1 resulted from proton transfer between chelH₂ and dap in aqueous solution. In 1, two carboxylic acids of chelH₂ were deprotonated and the protons transferred to the nitrogen atoms of one chelidamate anion and one dap moiety. Compound 2 resulted from complexation of 1 and vanadyl sulfate. In the crystal structure of 2, the metal ion is five coordinated by one tridentate ligand (chel)^2? and two O^2? anions, with (Hdap)⁺ as a counter cation. In both structures, a complicated hydrogen-bonding network accompanied with π–π, C–O···π and C–H···π stacking interactions leads to formation of a 3D supramolecular network. In the following, solution studies have been performed by means of pH potentiometric titrations method as a power technique. This method was used for determination of protonation constants of chelH₂ and dap in their probable protonated forms and for calculation of equilibrium constants for the chelH₂–dap proton transfer system and the stoichiometry and stability constants of binary and ternary complexes of this system with VO²⁺ ion in aqueous solution. The stoichiometries of the most complex species in solution were compared with the corresponding crystalline complexes in the solid state.     

New columnar liquid crystal materials based on luminescent 2-methoxy-3-cyanopyridines

A new series of donor–acceptor–donor (D–A–D) type luminescent mesogens carrying 2-methoxy-3-cyanopyridine as a central core linked with variable alkoxy chain lengths (m = 6 and 8) as terminal substituents was synthesized and characterized using spectral methods. The newly synthesized molecules were subjected to single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetric (DSC), polarizing optical microscopy (POM), and fluorescence emission studies in order to ascertain their mesogenic and photophysical properties. The SCXRD data on 4a and 4b reveal that the presence of short intermolecular contacts, viz. C–H···N, C–H···O, C–H···π, and π···π interactions, is responsible for their crystal packing. The measured torsion angle values indicate that molecules possess distorted non-planar structure. The DSC, POM, and PXRD studies confirm that all the molecules show thermotropic liquid crystalline behaviour and exhibit rectangular columnar phase. Further, their UV–visible and fluorescence spectral studies reveal that the target molecules are luminescent displaying a strong absorption band in the range of 335–340 nm and a blue fluorescence emission band in the range of 395–425 nm (both in solution and film state) with good fluorescence quantum yields (10–49 %).     

n-型有机半导体插入层提高p-型并五苯薄膜晶体管性能(英文)

在金电极和p-型并五苯有源层之间插入n-型有机半导体层显著提高了并五苯薄膜场效应晶体管的性能。在插入2nm厚的N,N-bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl)-1,4,5,8-naphthalenetetracarboxylicdiimide(NTCDI-C8F)和N,N′-dioctyl-3,4,9,10-perylenedicarboximide(PTCDI-C8)层后,器件的阈值电压由-19.4V显著降低到-1.8和-8.7V、迁移率提高了约2倍、电流开关比保持在105~106。这为通过简单地在电极和有机半导体有源层之间引入其他有机半导体薄层的方法来构建具有低阈值电压和高迁移率特征的有机薄膜场效应晶体管器件提供思路。