Synthesis, structures, and properties of unsymmetrical heteroacenes containing both pyrrole and furan rings

Unsymmetrical heteroacenes, 11-phenylbenzofuro[3,2-b]carbazole (Ph-BFC) and its alkoxylated derivatives, were readily synthesized by palladium-catalyzed double N-arylation of arylamines. They characteristically form antiparallel cofacial pi-stacking arrangements, which may result from their unsymmetrical structures. Their physical properties show their potential for application as active layers in organic field-effect transistors.     

Crystal structures and spectroscopic characterization of radical cations and dications of oligothiophenes stabilized by annelation with bicyclo[2.2.2]octene units: sterically segregated cationic oligothiophenes

The remarkably stable SbF(6)(-) salts of the radical cations of bithiophene 1(2T) and terthiophene 1(3T), completely surrounded by bicyclo[2.2.2]octene (BCO) units, were obtained by one-electron oxidation of the neutral precursors with NO(+)SbF(6)(-), and their solid-state structures were determined by X-ray crystallography. In these radical cations, the presence of quinoidal character was apparent, as shown by the increased planarity and by comparison of the bond lengths with those of the neutral precursors. The shortest intermolecular pi-pi distances in the crystal structure of 1(2T)(*)(+)SbF(6)(-) (distance between two sp(2) carbon atoms, 4.89 A) and 1(3T)(*)(+)SbF(6)(-) (distance between an sp(2) carbon and a sulfur atom, 3.58 A) were found to be longer than the sums of the van der Waals radii of the corresponding atoms. In accord with this, no apparent change was observed in ESR and UV-vis-NIR spectra of solutions of 1(2T)(*)(+) and 1(3T)(*)(+) upon lowering the temperature, indicating that the pi- (or sigma-) dimer formation is inhibited in solution as well as in the solid state. The dications 1(2T)(2+) and 1(3T)(2+) were generated with the stronger oxidant SbF(5) in CH(2)Cl(2) at -40 degrees C and characterized by NMR spectroscopy. In the (1)H NMR spectra, two conformers were observed for each dication of both 1(2T)(2+) (transoid (t) and cisoid (c)) and 1(3T)(2+) (t,t and c,t) at room temperature due to the high rotational barrier around the inter-ring bond(s) between thiophene rings, which was caused by the enhanced double bond character of these bonds following two-electron oxidation. This is supported by DFT calculations (B3LYP/6-31G(d)), which predicted the rotational barriers in the dications of unsubstituted bithiophene and terthiophene to be 27.6 and 22.9 kcal mol(-)(1), respectively. In the case of quaterthiophene and sexithiophene surrounded by BCO frameworks 1(4T) and 1(6T), oxidation with even one molar equivalent of NO(+)SbF(6)(-) afforded the dication salts 1(4T)(2+)2SbF(6)(-) and 1(6T)(2+)2SbF(6)(-), which were isolated as stable single crystals and allowed the X-ray crystallography. In their crystal structures, the cationic pi-systems became planar again due to the great contribution of quinoidal resonance structures, and the pi-systems, which were arrayed in a parallel geometry, were also segregated by the steric effect of BCO units. The degree and tendency of changes in the bond lengths of thiophene rings of 1(4T)(2+) and 1(6T)(2+) as compared with neutral precursors were similar to those of 1(2T)(*)(+)SbF(6)(-) and 1(3T)(*)(+)SbF(6)(-), respectively, implying that the contribution of quinoidal character is modulated by the amount of positive charge per thiophene unit.     

1H NMR study on the self-association of quinacridone derivatives in solution

The pi-stacking structures and self-association thermodynamics of N, N'-di(n-alkyl) quinacridone derivatives (n-alkyl QAs) with various substituents on the side aromatic rings and different length of n-alkyl chains are investigated in organic solvents by (1)H NMR spectroscopy. The stacking geometries are built based on both the magnitudes and directions of peak shifts with concentration and solvent polarity. The intermolecular interaction between nitrogen atoms and oxygen atoms dominates the general geometrical preferences of the stacking in which the molecules are face-to-face arranged in a parallel and an antiparallel fashion, respectively. The stacking structures are little affected by the length of the n-alkyl chains but are regulated in an allowed range by the size and properties of the substituents. The association processes of all the n-alkyl QAs are enthalpically favorable at 298 K, while the relative stability of these n-alkyl QAs assemblies is governed mainly by the entropy of the association processes. The introduction of larger substituents and longer n-alkyl chains disfavors the association of the n-alkyl QAs, while the binding of the halogen atoms on the side aromatic rings is favorable to the association. The relative strength of the stacking interaction for the substituted n-alkyl QAs has not obvious correlation with the electron-donating or electron-withdrawing nature of the substituents, while it is well associated to the dispersion energy and repulsive exchange energy. The different entropy-enthalpy compensation of the halogen-substituted n-alkyl QAs from others may suggest different association mechanism for the two types of n-alkyl QAs.     

Lone-pair orbital interactions in polythiaadamantanes

The electronic structures of a series of polythiaadamantanes from thiaadamantane through 2,4,6,8,9,10-hexathiaadamantane (HTA) have been analyzed using density functional theory calculations in conjunction with Hückel and natural bond orbital analysis. The effects of multiple sulfur p-type lone-pair orbital interactions on ionization potentials, hole mobilities, and electronic coupling have been determined. An overall increase in the average energy of the lone-pair orbitals as the number of sulfur atoms increases is predicted, with the exact positioning of the HOMO depending on specific lone-pair interactions. Separation of through-bond (TB) and through-space (TS) interactions between intramolecular sulfur atoms has been performed using localized molecular orbitals and model systems based on interacting hydrogen sulfide molecules. TB interations were found to reduce orbital splitting, while TS interactions were found to increase orbital splitting. TS interactions were more or less constant from one polythiaadamantane to the next, and the contributions of TB effects to individual orbital energies vary depending on the relative orientation of sulfur atoms as determined by the sigma molecular framework. Electronic coupling between intermolecular sulfur lone-pair orbitals was determined by investigating unique dimer pairs observed in the crystal structure of HTA. Electronic coupling is not as strong as expected given the short intermolecular S-S distances observed in the crystal structure. In general, B3LYP/6-31G(d) and B3LYP/6-311+G(d,p) give very similar orbital energies and splittings.     

High performance n- and p-type field-effect transistors based on tetrathiafulvalene derivatives

The first n-type FET based on TTF derivatives was prepared. TTF derivatives with halogeno-substituted quinoxaline rings showed excellent n- or p-type performances with high carrier mobilities. Introduction of halogen groups determined the FET polarity by controlling the HOMO and LUMO levels of the molecules. The pi-stacking structures were observed in the single crystals of tetrahalogeno-TTFs.     

Structural control of the electronic properties of photodynamic azobenzene-derivatized pi-conjugated oligothiophenes

Quaterthiophenes containing a median 3,3'-dimethoxybithiophene (4MTZ) or bis(3,4-ethylenedioxythiophene) (4ETZ) block and an azobenzene group attached at two internal beta-positions of the end thiophene rings have been synthesized. The analysis of the crystal structure of the two compounds by X-ray diffraction shows that, for 4MTZ, the quaterthiophene chain adopts a syn-anti-syn conformation similar to the parent system based on unsubstituted quaterthiophene. In contrast, 4ETZ presents an all-anti conformation stabilized by noncovalent intramolecular interactions between oxygen atoms and thiophenic sulfur atoms. The effect of the photoisomerization of the azobenzene group on the electronic properties of the attached pi-conjugated quaterthiophene chain has been analyzed by UV-vis spectroscopy and cyclic voltammetry. The results obtained for 4MTZ suggest very limited geometrical changes due to the restricted rotation around the central interannular single bond caused by steric interactions between the methoxy groups. In contrast, upon trans to cis photoisomerization of the attached azobenzene group of 4ETZ, the quaterthiophene chain undergoes a reversible conformational switch to a final state with a lower HOMO level and a larger HOMO-LUMO gap than the initial state.     

Intermolecular charge transfer between heterocyclic oligomers. Effects of heteroatom and molecular packing on hopping transport in organic semiconductors

For electron or hole transfer between neighboring conducting polymer strands or oligomers, the intrinsic charge-transfer rate is dictated by the charge-resonance integral and by the reorganization energy due to geometric relaxation. To explain conduction anisotropy and other solid-state effects, a multivariate, systematic analysis of bandwidth as a function of intermolecular orientations is undertaken for a series of oligoheterocycles, using first-principles methods. While cofacial oligomers show the greatest bandwidths at a given intermolecular C-C contact distance, for a fixed center-to-center intermolecular distance, tilted pi-stacking increases pi-overlap (particularly for LUMO orbitals) and decreases electrostatic repulsion, yielding optimum tilt angles for packing of approximately 40-60 degrees at small intermolecular separations. The calculations also reveal that bandwidths and intrinsic mobilities of holes and electrons in conjugated oligoheterocycles can be quite comparable.     

Inter- and intramolecular pi-stacking interactions in cis-bis[1-(9-anthracene)]phosphirane complexes of platinum(II)

The bis[1-(9-anthracene)phosphirane]dithiolatoplatinum(II) complexes, Pt[1-(9-anthracene)phosphirane](2)(dithiolate), where dithiolate = 1,1-dimethoxycarbonyl-ethylene-2,2-dithiolate (dmdt) (2), 1,1-diethoxycarbonyl-ethylene-2,2-dithiolate (dedt) (3), 1-ethoxycarbonyl-1-cyano-ethylene-2, 2-dithiolate (ecdt) (4), and 1,1-dicyano-ethylene-2,2-dithiolate (dcdt) (5), were prepared from cis-dichlorobis[1-(9-anthracene)phosphirane]platinum(II) (1). Complexes 3 and 5 were characterized by X-ray crystallography and were found to have vastly different crystal and molecular structures. The crystal and molecular structure of 3 is dominated by intramolecular pi-stacking between the anthracene rings of the cis-bis(anthracene)phosphiranes with a ring...ring separation of 3.48(6) A. The molecular structure of 5 does not exhibit an intramolecular interaction between the anthracene rings. Instead, the crystal structure of 5shows significant intermolecular pi-stacking between the anthracene rings of the phosphirane ligands of adjacent molecules packed in the crystal lattice. The intermolecular stacking interaction results in a ring...ring separation of 3.33(4) A. Complexes 2-5 were found to emit at 530 nm at low temperatures in the solid state. Complex 5 emits strongly in fluid THF or benzene solution at 430 nm.     

Nitrogen-rich oligoacenes: candidates for n-channel organic semiconductors

The successive replacement of CH moieties by nitrogen atoms in oligoacenes (benzene to hexacene) has been studied computationally at the B3LYP/6-311+G(d,p)//6-31G(d) level of theory, and the effects of different heteroatomic substitution patterns on structures, electron affinities, excitation, ionization, and reorganization energies are discussed. The calculated tendencies are rationalized on the basis of molecular orbital arguments. To achieve electron affinities of 3 eV, a value required to allow for efficient electron injection from common metal electrodes, at least seven nitrogen atoms have to be incorporated into tetracenes or pentacenes. The latter require rather small reorganization energies for electron transfer (<0.20 eV) making these compounds promising candidates for n-channel semiconducting materials. Particularly interesting are heptaazapentacenes 5 and 6 in which the nitrogen atoms are arranged to form self-complementary systems with a maximum number of intermolecular CH-N contacts in planar oligomers. These interactions are expected to facilitate the formation of graphite-like sheet structures with cofacial arrangements of the pi systems and short interlayer distances due to attractive N-C(H) interlayer interactions. This should not only be ideal for charge transfer but also might contribute to improved air stability of these semiconductors. Self-complementarity is maintained in azaacenes containing two cyano groups in the terminal rings. These compounds require lower reorganization energies than the unsubstituted heterocycles (0.13-0.14 eV), show high electron affinities (3.3 eV), and are thus promising candidates for materials applications.     

Dinitro and quinodimethane derivatives of terthiophene that can be both oxidized and reduced. Crystal structures,spectra, and a method for analyzing quinoid contributions to structure

Two new oligothiophenes, the dinitro compound 3',4'-dibutyl-5,5' '-dinitro-2,2':5',2' '-terthiophene (1) and the quinodimethane 3',4'-dibutyl-5,5' '-bis(dicyanomethylene)-5,5' '-dihydro-2,2':5',2' '-terthiophene (2), have been synthesized and studied with electrochemistry, UV-vis-NIR-IR spectroscopy, ESR, and X-ray crystallography. These compounds, designed to be both electron and hole carriers, show redox properties that are unusual for oligothiophenes. Cyclic voltammetry and spectroelectrochemistry demonstrated that each compound could be oxidized to a cation radical and reduced to an anion radical and dianion. The spectra of 2 and its three redox partners were analyzed in terms of a limiting structure in which the neutral 2 has orbitals corresponding to those of a substituted-terthiophene dication. Compound 1 crystallizes with the thiophene rings held in an unusual nonplanar, cisoid configuration in face-to-face pi-stacks, with a spacing between molecules of 3.65 A. The C-C bond lengths of the outer nitro-substituted rings have quinoid character. Compound 2 crystallizes with the thiophene rings in a planar, transoid configuration. The molecules are held in pi-stacks formed from pi-dimers with a spacing between molecules of 3.47 and 3.63 A. The C-C bond distances of the thiophene rings of 1 and 2 and other oligomers were analyzed by a principal component analysis. The analysis found that 93% of the structural variance resided in one principal component related to the quinoid structure of the oligothiophene moiety. The analysis reliably demonstrated a quinoid contribution to the structure of 1. This method should be applicable to understanding the structure of other conjugated molecules in which quinoid structures contribute.     

Trinuclear copper complexes with triplesalen ligands: geometric and electronic effects on ferromagnetic coupling via the spin-polarization mechanism

A series of trinuclear Cu(II) complexes with the tris(tetradentate) triplesalen ligands H(6)talen, H(6)talen(tBu(2) ), and H(6)talen(NO(2) ), namely [(talen)Cu(II) (3)] (1), [(talen(tBu(2) ))Cu(II) (3)] (2), and [(talen(NO(2) ))Cu(II) (3)] (3), were synthesized and their molecular and electronic structures determined. These triplesalen ligands provide three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone. The structure of [(talen)Cu(II) (3)] (1) was communicated recently. The structure of the tert-butyl derivative [(talen(tBu(2) ))Cu(II) (3)] (2) was established in three different solvates. The molecular structures of these trinuclear complexes show notable differences, the most important of which is the degree of ligand folding around the central Cu(II)-phenolate bonds. This folding is symmetric with regard to the central phloroglucinol backbone in two structures, where it gives rise to bowl-shaped overall geometries. For one solvate two trinuclear triplesalen complexes form a supramolecular disk-like arrangement, hosting two dichloromethane molecules like two pearls in an oyster. The FTIR spectra of these complexes indicate the higher effective nuclear charge of Cu(II) in comparison to the trinuclear Ni(II) complexes by the lower C--O and higher C=N stretching frequencies. The UV/Vis/NIR spectra of 1-3 reflect the stronger ligand folding in the tert-butyl complex 2 by an intense phenolate-to-Cu(II) LMCT. This absorption is absent in 1 and is obscured by the nitro chromophore in 3. The more planar molecular structures cause orthogonality of the Cu(II) d(x(2)-y(2) ) orbital and the phenolate O p(z) orbital, which leads to small LMCT dipole strengths. Whereas 1 and 3 exhibit only irreversible oxidations, 2 exhibits a reversible one-electron oxidation at +0.26 V, a reversible two-electron oxidation at +0.59 V, and a reversible one-electron oxidation at +0.81 V versus Fc(+)/Fc. The one-electron oxidized form 2(+) is strongly stabilized with respect to reference mononuclear salen-like Cu complexes. Chemical one-electron oxidation of 2 to 2(+) allows the determination of its UV/Vis/NIR spectrum, which indicates a ligand-centered oxidation that can be assigned to the central phloroglucinol unit by analogy with the trinuclear Ni triplesalen series. Delocalization of this oxidation over three Cu(II)-phenolate subunits causes the observed energetic stabilization of 2(+). Temperature-dependent magnetic susceptibility measurements reveal ferromagnetic couplings for all three trinuclear Cu(II) triplesalen complexes. The trend of the coupling constants can be rationalized by two opposing effects: 1) electron-withdrawing terminal substituents stabilize the central Cu(II)-phenolate bond, which results in a stronger coupling, and 2) ligand folding around the central Cu(II)-phenolate bond opens a bonding pathway between the magnetic Cu(II) d(x(2)-y(2) ) orbital and the phenolate O p(z) orbital, which results in a stronger coupling. Density functional calculations indicate that both spin-polarization and spin-delocalization are operative and that slight geometric variations alter their relative magnitudes.     

醌式杂环化合物的设计、合成及应用性能研究进展

醌式杂环(噻吩、吡咯、呋喃等)分子具有结构刚性、最高占据分子轨道(HOMO)/最低未占据分子轨道(LUMO)能级低、能级带隙窄和摩尔消光系数高等特点.醌式分子因其结构平面性特点,分子间作用力较强,因而分子间电荷传输能力强.目前,醌式杂环分子已成为有机半导体材料领域特别是有机场效应晶体管领域的研究热点.根据醌式杂环分子的结构特点,以端基为分类依据,综述了近年来醌式杂环化合物在分子设计、合成及应用性能等方面的研究进展,并展望了醌式杂环分子的发展前景.     

侧链间氢键的协同效应对环状多肽自组装的影响

运用密度泛函(DFT)B3LYP方法和半经验分子轨道方法AM1对四种环状多肽[-(L-Asn-Ala)4-], [-(L-Asp-Ala)4-], [-(L-Gln-Ala)4-] 和[-(L-Glu-Ala)4-]的单体、平行和反平行二聚体到十聚体进行了理论研究. 结果表明, 四种环状多肽无论以平行还是以反平行的方式聚集, 聚集体中相邻两个环状多肽的侧链之间都能形成氢键. 侧链间氢键的相互作用使得这些环状多肽在组装过程中的结构和能量变化均表现出一定的协同效应, 这种协同效应加强了多肽纳米管的稳定性, 同时对聚集模式的选取起到了决定性作用.     

Identification of the radical anions of C2N4S2 and P2N4S2 rings by in situ EPR spectroelectrochemistry and DFT calculations

The previously unknown radical anions of unsaturated E2N4S2 ring systems (E=RC, R2NC, R2P) can be generated voltammetrically by the one-electron reduction of the neutral species and, despite half-lives on the order of a few seconds, have been unambiguously characterized by electron paramagnetic resonance (EPR) spectroelectrochemistry using a highly sensitive in situ electrolysis cell. Cyclic voltammetric studies using a glassy-carbon working electrode in CH3CN and CH2Cl2 with [nBu4N][PF6] as the supporting electrolyte gave reversible formal potentials for the [E2N4S2]0/- process in the range of -1.25 to -1.77 V and irreversible peak potentials for oxidation in the range of 0.66 to 1.60 V (vs the Fc+/0 couple; Fc=ferrocene). Reduction of the neutral compound undergoes an electrochemically reversible one-electron transfer, followed by the decay of the anion to an unknown species via a first-order (chemical) reaction pathway. The values of the first-order rate constant, kf, for the decay of all the radical anions in CH2Cl2 have been estimated from the decay of the EPR signals for (X-C6H4CN2S)2*-, where X=4-OCH3 (kf=0.04 s(-1)), 4-CH3 (kf=0.02 s(-1)), 4-H (kf=0.08 s(-1)), 4-Cl (kf=0.05 s(-1)), 4-CF3 (kf=0.05 s(-1)), or 3-CF3 (kf=0.07 s(-1)), and for [(CH3)3CCN2S]2*- (kf=0.02 s(-1)), [(CH3)2NCN2S]2*- (kf=0.05 s(-1)), and [(C6H5)2PN2S]2*- (kf=0.7 s(-1)). Values of kf for X=4-H and for [(CH3)2NCN2S]2*- were also determined from the cyclic voltammetric responses (in CH2Cl2) and were both found to be 0.05 s(-1). Possible pathways for the first-order anion decomposition that are consistent with the experimental observations are discussed. Density functional theory calculations at the UB3LYP/6-31G(d) level of theory predict the structures of the radical anions as either planar (D2h) or folded (C2v) species; the calculated hyperfine coupling constants are in excellent agreement with experimental results. Linear correlations were observed between the voltammetrically determined potentials and both the orbital energies and Hammett coefficients for the neutral aryl-substituted rings.     

Low-bandgap conjugated polymers based on benzodipyrrolidone with reliable unipolar electron mobility exceeding 1 cm~2 V~(-1) s~(-1)

The employment of an intrinsic quinoidal building block, benzodipyrrolidone(BDP), on constructing conjugated polymers(PBDP-2F and PBDP-2CN) with high electron mobility and unipolar transport characteristic in polyethylenimine ethoxylated(PEIE) modified organic field-effect transistors(OFETs) is reported. The intrinsic quinoidal characteristic and excellent coplanarity of BDP can lower the lowest unoccupied molecular orbital(LUMO) levels and improve ordered interchain packing of the resulting polymers in solid states, which are favorable for electron-injection and transport. By using PEIE as the interlayer to block the hole injection, unipolar n-type transport characteristics with high electron mobility of 0.58 and 1.01 cm~2 V~(-1) s~(-1) were achieved by the OFETs based on PBDP-2F and PBDP-2CN, respectively. More importantly, the extracted mobilities are highly reliable with the reliability factor of above 80%. To the best of our knowledge, PBDP-2CN is the very first quinoid-based conjugated polymer with reliable electron mobility exceeding 1 cm~2 V~(-1) s~(-1). This work represents a significant step in exploring intrinsic quinoidal CPs for application in n-channel OFETs and logic complementary circuits.     

Electronegative oligothiophenes for n-type semiconductors: difluoromethylene-bridged bithiophene and its oligomers

The synthesis of difluoromethylene-bridged bithiophene and its oligothiophenes are reported. The spectroscopic and electrochemical measurement as well as X-ray analyses unambiguously revealed that the difluoromethylene bridge largely contributes to keeping planarity between the thiophene rings and lowering the LUMO level. The perfluorohexyl-substituted quaterthiophene derivatives showed n-type semiconducting behavior with field-effect electron mobilities up to 0.018 cm2 V-1 s-1.     

Polyvinyl‐Locked versus Free Quaterthiophene: Effect of Spatial Constraints on the Electronic Properties of n‐Hexylquaterthiophene

A soluble, low‐weight fraction of poly(α‐vinyl,ω‐n‐hexyl‐quaterthiophene), PT4Hex, having n‐hexylquaterthiophenes as side‐chain groups, is prepared by free‐radical polymerization of α‐vinyl,ω‐n‐hexyl‐quaterthiophene and the corresponding properties compared to those of free di‐n‐hexylquaterthiophene (T4Hex). Optical analysis (absorption and emission) and X‐ray diffraction data indicate that in the polyvinyl‐locked architecture the quaterthiophene pendants adopt a cofacial arrangement with a mutual distance close enough for π–π orbitals to overlap (～4 Å). As a consequence of the close chain packing, a shift of the reduction potential of about 0.5 V toward less negative values with respect to free T4Hex, is found for PT4Hex films. Due to its enhanced electron affinity, PT4Hex displays an electron‐acceptor behavior when blended with alkylated and silylated quaterthiophenes acting as donors.     

General synthesis of extended fused oligothiophenes consisting of an even number of thiophene rings

The intramolecular double cyclization of bis(3-bromo-2-thienyl)acetylenes though a lithium-halogen exchange reaction with tBuLi followed by treatment with elemental sulfur produces two thiophene-fused thieno[3,2-c](1,2-dithiin)s. The subsequent dechalcogenation from the 1,2-dithiins with copper nanopowder affords tetrathienoacenes. On the basis of this two-step procedure, a series of trialkylsilyl-terminated, fused oligothiophenes, including hexathienoacene (a six thiophene-fused system) and octathienoacene (an eight thiophene-fused system), were synthesized. In the UV/Vis absorption and fluorescence spectra of the fused oligothiophenes, the absorption and emission maxima shift to longer wavelengths, as the pi-conjugation length increases. Their maximum wavenumbers have linear relationships with the reciprocal number of thiophene rings consisting of the pi-conjugated frameworks. In the cyclic voltammograms, all the compounds show reversible oxidation waves, the first oxidation potential of which shifts to less positive as the conjugation length increases. Among them, the octathienoacene also shows a reversible second oxidation process. Indeed, its chemical oxidation with an excess amount of NO(+)SbF(6) (-) produces the dication as a golden crystal. The crystal structures of the neutral octathienoacene and its dication were determined by X-ray crystallography. While in the neutral state, the octathienoacene has a benzenoid structure with a large bond alternation of about 0.04 A, its dication has a quinoid structure in which two cationic charges are mainly localized on the terminal rings.     

Theoretical insights into the 1D‐charge transport properties in a series of hexaazatrinaphthylene‐based discotic molecules

Discotic liquid crystal (DLC) materials have attracted considerable attention mainly due to their high charge carrier mobilities in quasi‐one‐dimensional columns. In this article, five hexaazatrinaphthylene‐based DLC molecules were investigated theoretically, and their frontier molecular orbital energy levels, crystal structures, and electron/hole drift mobilities were calculated by combination of density functional theory (DFT) and semiclassical Marcus charge transfer theory. The systems studied in this work include three experimentally reported molecules ( 1 , 2 , and 3 ) and two theoretically designed molecules ( 4 and 5 ). Compared with the 1 – 3 compounds, 4 and 5 have three more extended benzene rings in the π‐conjugated core. The present results show that the orders of the frontier molecular orbital energy levels and electron drift mobilities agree very well with the experiment. For 4 and 5 , the electron/hole reorganization energies are lower than those of compounds 1 – 3 . Furthermore, the calculated electron/hole transfer integral of 5 is the largest among all the five systems, leading to the highest electron and hole mobilities. In addition, the hydrophobicity and solubility were also evaluated by DFT, indicating that compound 5 has good hydrophobicity and good solubility in trichloromethane. As a result, it is expected that compound 5 can be a potential charge transport material in electronic and optoelectronic devices. © 2017 Wiley Periodicals, Inc.