Synthesis,Structure, and Air‐stable N‐type Field‐Effect Transistor Behaviors of Functionalized Octaazanonacene‐8,19‐dione

Increasing the length of N‐heteroacenes or their analogues is highly desirable because such materials could have great potential applications in organic electronics. In this report, the large π‐conjugated N‐heteroquinone 6,10,17,21‐tetra‐((triisopropylsilyl)ethynyl)‐5,7,9,11,16,18,20,22‐octaazanonacene‐8,19‐dione (OANQ) has been synthesized and characterized. The as‐prepared OANQ shows high stability under ambient conditions and has a particularly low LUMO level, which leads to it being a promising candidate for air‐stable n‐type field‐effect transistors (FETs). In fact, FET devices based on OANQ single crystals have been fabricated and an electron mobility of up to 0.2 cm² V^?1 s^?1 under ambient conditions is reported. More importantly, no obvious degradation was observed even after one month. Theoretical calculations based on the single crystal are consistent with the measured mobility.     

Dithieno[3,2‐b:2′,3′‐d]pyrrole Cored p‐Type Semiconductors Enabling 20 % Efficiency Dopant‐Free Perovskite Solar Cells

Organic p‐type semiconductors with tunable structures offer great opportunities for hybrid perovskite solar cells (PVSCs). We report herein two dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) cored molecular semiconductors prepared through π‐conjugation extension and an N‐alkylation strategy. The as‐prepared conjugated molecules exhibit a highest occupied molecular orbital (HOMO) level of ?4.82 eV and a hole mobility up to 2.16×10^?4 cm² V^?1 s^?1. Together with excellent film‐forming and over 99 % photoluminescence quenching efficiency on perovskite, the DTP based semiconductors work efficiently as hole‐transporting materials (HTMs) for n‐i‐p structured PVSCs. Their dopant‐free MA_0.7FA_0.3PbI_2.85Br_0.15 devices exhibit a power conversion efficiency over 20 %, representing one of the highest values for un‐doped molecular HTMs based PVSCs. This work demonstrates the great potential of using a DTP core in designing efficient semiconductors for dopant‐free PVSCs.     

Hot π‐Electron Tunneling of Metal–Insulator–COF Nanostructures for Efficient Hydrogen Production

A metal–insulator–semiconductor (MIS) photosystem based on covalent organic framework (COF) semiconductors was designed for robust and efficient hydrogen evolution under visible‐light irradiation. A maximal H₂ evolution rate of 8.42 mmol h^?1 g^?1 and a turnover frequency of 789.5 h^?1 were achieved by using a MIS photosystem prepared by electrostatic self‐assembly of polyvinylpyrrolidone (PVP) insulator‐capped Pt nanoparticles (NPs) with the hydrophilic imine‐linked TP‐COFs having =C=O?H?N= hydrogen‐bonding groups. The hot π‐electrons in the photoexcited n‐type TP‐COF semiconductors can be efficiently extracted and tunneled to Pt NPs across an ultrathin PVP insulating layer to reduce protons to H₂. Compared to the Schottky‐type counterparts, the COF‐based MIS photosystems give a 32‐fold‐enhanced carrier efficiency, attributed to the combined enhancement of photoexcitation rate, charge separation, and oxidation rate of holes accumulated in the valence band of the TP‐COF semiconductor.     

Synthesis,Structure, and Air‐stable N‐type Field‐Effect Transistor Behaviors of Functionalized Octaazanonacene‐8,19‐dione

Increasing the length of N‐heteroacenes or their analogues is highly desirable because such materials could have great potential applications in organic electronics. In this report, the large π‐conjugated N‐heteroquinone 6,10,17,21‐tetra‐((triisopropylsilyl)ethynyl)‐5,7,9,11,16,18,20,22‐octaazanonacene‐8,19‐dione (OANQ) has been synthesized and characterized. The as‐prepared OANQ shows high stability under ambient conditions and has a particularly low LUMO level, which leads to it being a promising candidate for air‐stable n‐type field‐effect transistors (FETs). In fact, FET devices based on OANQ single crystals have been fabricated and an electron mobility of up to 0.2 cm² V⁻¹ s⁻¹ under ambient conditions is reported. More importantly, no obvious degradation was observed even after one month. Theoretical calculations based on the single crystal are consistent with the measured mobility.     

Rearrangements in Model Peptide‐Type Radicals via Intramolecular Hydrogen‐Atom Transfer

Intramolecular H‐atom transfer in model peptide‐type radicals was investigated with high‐level quantum‐chemistry calculations. Examination of 1,2‐, 1,3‐, 1,5‐, and 1,6[C ? N]‐H shifts, 1,4‐ and 1,7[C ? C]‐H shifts, and 1,4[N ? N]‐H shifts (Scheme 1), was carried out with a number of theoretical methods. In the first place, the performance of UB3‐LYP (with the 6‐31G(d), 6‐31G(2df,p), and 6‐311+G(d,p) basis sets) and UMP2 (with the 6‐31G(d) basis set) was assessed for the determination of radical geometries. We found that there is only a small basis‐set dependence for the UB3‐LYP structures, and geometries optimized with UB3‐LYP/6‐31G(d) are generally sufficient for use in conjunction with high‐level composite methods in the determination of improved H‐transfer thermochemistry. Methods assessed in this regard include the high‐level composite methods, G3(MP2)‐RAD, CBS‐QB3, and G3//B3‐LYP, as well as the density‐functional methods B3‐LYP, MPWB1K, and BMK in association with the 6‐31+G(d,p) and 6‐311++G(3df,3pd) basis sets. The high‐level methods give results that are close to one another, while the recently developed functionals MPWB1K and BMK provide cost‐effective alternatives. For the systems considered, the transformation of an N‐centered radical to a C‐centered radical is always exothermic (by 25 kJ ? mol^?1 or more), and this can lead to quite modest barrier heights of less than 60 kJ ? mol^?1 (specifically for 1,5[C ? N]‐H and 1,6[C ? N]‐H shifts). H‐Migration barriers appear to decrease as the ring size in the transition structure (TS) increases, with a lowering of the barrier being found, for example when moving from a rearrangement proceeding via a four‐membered‐ring TS (e.g., the 1,3[C ? N]‐H shift, CH₃? C(O)? NH^. → ^.CH₂? C(O)? NH₂) to a rearrangement proceeding via a six‐membered‐ring TS (e.g., the 1,5[C ? N]‐H shift, ^.NH? CH₂? C(O)? NH? CH₃ → NH₂? CH₂? C(O)? NH? CH₂^.).     

Host–Guest Interactions in ExBox4+

The host–guest interaction between poly aromatic hydrocarbon/azine and the newly synthesized ExBox⁴⁺ complex is studied with the help of density functional theory. The solvent‐phase interaction energy is found to decrease with gradual substitution of methine groups (?CH?) from the six‐membered ring of guest molecules with N atoms in the resultant azine@ExBox⁴⁺ complex. The nature of the binding interaction is studied with the help of newly developed noncovalent interaction (NCI) plot program package along with energy decomposition analysis and charge decomposition analysis. The interactions are mostly π‐type van der Waals interactions.     

Use of the Wilkinson Catalyst for the ortho‐CH Heteroarylation of Aromatic Amines: Facile Access to Highly Extended π‐Conjugated Heteroacenes for Organic Semiconductors

An unprecedented catalytic system composed of the Wilkinson catalyst [Rh(PPh₃)₃Cl] and CF₃COOH enabled the highly regioselective cross‐coupling of aromatic amines with a variety of heteroarenes through dual C? H bond cleavage. This protocol provided a facile and rapid route from readily available substrates to (2‐aminophenyl)heteroaryl compounds, which may be conveniently transformed into highly extended π‐conjugated heteroacenes. The experimental studies and calculations showed that thianaphtheno[3,2‐b]indoles have large HOMO–LUMO energy gaps and low‐lying HOMO levels, and could therefore potentially be high‐performance organic semiconductors. Herein we report the first use of a rhodium(I) catalyst for oxidative C? H/C? H coupling reactions. The current innovative catalyst system is much less expensive than [RhCp*Cl₂]₂/AgSbF₆ and could open the door for the application of this approach to other types of C? H activation processes.     

An A‐D‐A′‐D‐A Conjugated Molecule Entailing Diazapentalene Unit for an n‐Type Organic Semiconductor

Conjugated molecules with low lying LUMO levels are demanding for the development of air stable n‐type organic semiconductors. In this paper, we report a new A‐D‐A′‐D‐A conjugated molecule ( DAPDCV ) entailing diazapentalene (DAP) and dicyanovinylene groups as electron accepting units. Both theoretical and electrochemical studies manifest that the incorporation of DAP unit in the conjugated molecule can effectively lower the LUMO energy level. Accordingly, thin film of DAPDCV shows n‐type semiconducting behavior with electron mobility up to 0.16 cm²?V^?1?s^?1 after thermal annealing under N₂ atmosphere. Moreover, thin film of DAPDCV also shows stable n‐type transporting property in air with mobility reaching 0.078 cm²?V^?1?s^?1.     

Use of the Wilkinson Catalyst for the ortho‐C?H Heteroarylation of Aromatic Amines: Facile Access to Highly Extended π‐Conjugated Heteroacenes for Organic Semiconductors

An unprecedented catalytic system composed of the Wilkinson catalyst [Rh(PPh₃)₃Cl] and CF₃COOH enabled the highly regioselective cross‐coupling of aromatic amines with a variety of heteroarenes through dual C H bond cleavage. This protocol provided a facile and rapid route from readily available substrates to (2‐aminophenyl)heteroaryl compounds, which may be conveniently transformed into highly extended π‐conjugated heteroacenes. The experimental studies and calculations showed that thianaphtheno[3,2‐b]indoles have large HOMO–LUMO energy gaps and low‐lying HOMO levels, and could therefore potentially be high‐performance organic semiconductors. Herein we report the first use of a rhodium(I) catalyst for oxidative C H/C H coupling reactions. The current innovative catalyst system is much less expensive than [RhCp*Cl₂]₂/AgSbF₆ and could open the door for the application of this approach to other types of C H activation processes.     

3,6‐Bis(dimethylamino)‐10‐(10‐iododecyl)acridinium iodide

In the title compound, C₂₇H₃₉IN₃⁺·I^?, the acridinium system shows the usual approximate mirror symmetry about the central C?N line, and the corresponding bond lengths and angles in the two halves agree within experimental error. The alkyl chain at the ring N atom is initially perpendicular to the ring plane and then bends sharply at the fourth C atom. Pairs of centrosymmetrically related cations overlap two of their rings and the di­methyl­amino groups are also partly involved in the overlap. Each I^? ion is involved in short‐range interactions with two cations. These interactions give rise to a 14‐membered cyclic structure, which involves pairs of cations and anions across an inversion centre.     

Design of a Quinoidal Thieno[3,4‐b]thiophene‐Diketopyrrolopyrrole‐Based Small Molecule as n‐Type Semiconductor

A quinoidal small‐molecule semiconductor QDPPBTT was synthesized. Organic thin‐film transistor (OTFT) devices based on QDPPBTT showed an electron mobility as high as 0.13 cm² V^?1 s^?1 and I_on/I_off ratio of 10⁶ under ambient conditions. We suggested that 2D extended π‐conjugation and quinoid‐enhancing effect had an important role in electron mobility and stability of n‐type FET devices, which might be a good strategy in designing new material systems.     

Facile Synthetic Approach to a Large Variety of Soluble Diarenoperylenes

Fused, extended π‐systems such as larger acenes and heteroacenes are interesting compounds for organic thin‐film transistors (TFTs). The larger the number of linearly cata‐fused rings, the lower the stability of the acenes. By peri‐fusion of additional rings, the stabilities can significantly be increased. Here we present a facile approach to use a diborylated dihydroanthracene as precursor to get diareno‐fused perylenes in just two steps in high yields. The compounds show pronounced packing in the crystalline states by π‐stacking. Promising candidates have been used to fabricate p‐channel TFTs by vacuum sublimation showing field‐effect mobilities up to 0.12 cm² V^?1 s^?1.     

Functional carbo‐Butadienes: Nonaromatic Conjugation Effects through a 14‐Carbon, 24‐π‐Electron Backbone

A systematic study of carbo‐butadiene motifs not embedded in an aromatic carbo‐benzene ring is described. Dibutatrienylacetylene (DBA) targets R¹?C(R)?C?C?C(Ph)?C≡C?C(Ph)?C?C?C(R)?R² are devised, in which R is C≡CSiiPr₃ and R¹ and R² are R, H, or 4‐X‐C₆H₄, with the latter including three known representatives (X: H, NMe₂, or NH₂). The synthesis method is based on the SnCl₂‐mediated reduction of pentaynediols prepared by early or late divergent strategies; the latter allows access to a OMe–NO₂ push–pull diaryl‐DBA. If R¹ and R² are H, an over‐reduced dialkynylbutatriene (DAB) with two allenyl caps was isolated instead of the unsubstituted DBA. If R¹=R²=R, the tetraalkynyl‐DBA target was obtained, along with an over‐reduced DBA product with a 12‐membered 1,2‐alkylidene‐1H₂,2H₂‐carbo‐cyclobutadiene ring. X‐ray crystallography shows that all of the acyclic DBAs adopt a planar trans–transoid–trans configuration. The maximum UV/Vis absorption wavelength is found to vary consistently with the overall π‐conjugation extent and, more intriguingly, with the π‐donor character of the aryl X substituents, which varies consistently with the first (reversible) reduction potential and first (irreversible) oxidation peak, as determined by voltammetry.     

σ‐Aromaticity in an Unsaturated Ring: Osmapentalene Derivatives Containing a Metallacyclopropene Unit

In general, aromaticity can be clarified as π‐ and σ‐aromaticity according to the type of electrons with major contributions. The traditional π‐aromaticity generally describes the π‐conjugation in fully unsaturated rings whereas σ‐aromaticity may stabilize fully saturated rings with delocalization caused by σ‐electron conjugation. Reported herein is an example of σ‐aromaticity in an unsaturated three‐membered ring (3 MR), which is supported by experimental observations and theoretical calculations. Specifically, when the 3 MR in cyclopropaosmapentalene is cleaved by ethane through two isodesmic reactions, both of them are highly endothermic (+29.7 and +35.0 kcal mol^?1). These positive values are in sharp contrast to the expected exothermicity, thus indicating aromaticity in the 3 MR. Further nucleus‐independent chemical shift and anisotropy of the current‐induced density calculations reveal the nature of σ‐aromaticity in the unsaturated 3 MR.     

A Three‐Dimensional Porous Organic Semiconductor Based on Fully sp2‐Hybridized Graphitic Polymer

Dimensionality plays an important role in the charge transport properties of organic semiconductors. Although three‐dimensional semiconductors, such as Si, are common in inorganic materials, imparting electrical conductivity to covalent three‐dimensional organic polymers is challenging. Now, the synthesis of a three‐dimensional π‐conjugated porous organic polymer (3D p‐POP) using catalyst‐free Diels–Alder cycloaddition polymerization followed by acid‐promoted aromatization is presented. With a surface area of 801 m² g^?1, full conjugation throughout the carbon backbone, and an electrical conductivity of 6(2)×10^?4 S cm^?1 upon treatment with I₂ vapor, the 3D p‐POP is the first member of a new class of permanently porous 3D organic semiconductors.     

meso‐N‐Pyrrole as a Versatile Substituent Influencing the Optical Properties of Porphyrin

A meso‐N‐pyrrole porphyrin converts into a π‐extended porphyrin forming an indolizine‐3‐one motif. The indolizine‐3‐one frame opens a lactam subunit preserving a six‐membered, heterocyclic structure fused with the main macrocycle. The optical properties of formed derivatives follow the structural modifications giving the absorbance and emission eventually modulated by the NH‐centered modifications of the fused unit.     

Synthesis and Spectroscopic Study of Some New Phosphoramidates,Crystal Structures of N‐Benzoyl‐N′,N″‐bis(azetidinyl)phosphoric Triamide and N‐Benzoyl‐N′,N″‐bis(hexamethylenyl)phosphoric Triamide

Some new N‐carbonyl, phosphoramidates with formula C₆H₅C(O)N(H)P(O)R₂ (R = NC₃H₆ ( 1 ), NC₆H₁₂ ( 2 ), NHCH₂CH=CH₂ ( 3 ), N(C₃H₇)₂ ( 4 )) and CCl₃C(O)N(H)P(O)R′₂ (R′ = NC₃H₆ ( 5 ), NHCH₂CH=CH₂ ( 6 )) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR and IR spectroscopy and elemental analysis. The structures were determined for compounds 1 and 2 . Compound 1 exists as two crystallographically independent molecules in crystal lattice. Both compounds 1 and 2 produced dimeric aggregates via intermolecular ‐P=O…H‐N‐ hydrogen bonds, which in compound 2 is a centrosymmetric dimer. In compounds with four‐membered ring amine groups, ³J(P,C)>²J(P,C), in agreement with our previous studies about five‐membered ring amine groups. Also, ³J(P,C) values in compounds 1 and 5 are greater than in compounds with five‐, six‐ and seven‐membered ring amine groups.     

Thermochemistry of N‐heterocyclic carbenes with 5‐, 4‐, 3‐, and 2‐membered rings

N‐heterocyclic carbenes (NHCs) based on imidazole‐2‐ylidene ( 1 ) or the saturated imidazolidine‐2‐ylidene ( 2 ) scaffolds are long‐lived singlet carbenes. Both benefit from inductive stabilization of the sigma lone pair on carbon by neighboring N atoms and delocalization of the N pi lone pairs into the nominally vacant p‐pi atomic orbital at the carbene carbon. With thermochemical schemes G4 and CBS‐QB3, we estimate the relative thermodynamic stabilization of smaller ring carbenes and acyclic species which may share the keys to NHC stability. These include four‐membered ring systems incorporating the carbene center, two trivalent N centers, and either a boron or a phosphorus atom to complete the ring. Amino‐substituted cyclopropenylidenes have been reported but three‐membered rings containing the carbene center and two N atoms are not known. Our calculations suggest that amino‐substituted cyclopropenylidenes are comparable in stability to the four‐membered NHCs but that diazacyclopropanylidenes would be substantially less effectively stabilized. Concluding the series are acyclic carbenes with and without neighboring N atoms and a series of “two‐membered ring” azapropadienenylidene cations of form :C?N?W with W = an electron‐withdrawing agent. We have studied W = NO₂, CH₂(+), CF₂(+), and (CN)₂C(+). Although these systems display a degree of stabilization and carbene‐like electronic structure, the stability of the NHCs is unsurpassed. © 2014 Wiley Periodicals, Inc.     

Structural Studies of Bis(cyclopentadienyl)molybdenum‐Amino Acid Complexes

The crystal structures of molybdocene‐amino acid compounds of the type [Cp₂Mo^IV(κN, κO‐AA)]⁺Cl^—·xH₂O with AA = D ‐phenylalaninato (x = 1.5), DL ‐leucinato (x = 2) and DL ‐valinato (x = 1) have been determined (Cp = η⁵‐C₅H₅). The compounds feature an almost planar, five‐membered chelate ring of the aminocarboxylate moiety (deprotonated amino acid) with the molybdenum atom. In the phenylalaninato complex π‐stacking between the phenyl rings is found. The complexes were proven kinetically stable at pH < 1 for at least 24 h.     

Conformational Change from a Twisted Figure‐Eight to an Open‐Extended Structure in Doubly Fused 36π Core‐Modified Octaphyrins Triggered by Protonation: Implication on Photodynamics and Aromaticity

Two examples of core‐modified 36π doubly fused octaphyrins that undergo a conformational change from a twisted figure‐eight to an open‐extended structure induced by protonation are reported. Syntheses of the two octaphyrins (in which Ar=mesityl or tolyl) were achieved by a simple acid‐catalyzed condensation of dipyrrane unit containing an electron‐rich, rigid dithienothiophene (DTT) core with pentafluorobenzaldehyde followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). The single‐crystal X‐ray structure of the octaphyrin (in which Ar=mesityl) shows a figure‐eight twisted conformation of the expanded porphyrin skeleton with two DTT moieties oriented in a staggered conformation with a π‐cloud distance of 3.7 Å. Spectroscopic and quantum mechanical calculations reveal that both octaphyrins conform to a [4n]π nonaromatic electronic structure. Protonation of the pyrrole nitrogen atoms of the octaphyrins results in dramatic structural change, which led to 1) a large redshift and sharpening of absorption bands in electronic absorption spectrum, 2) a large change in chemical shift of pyrrole β‐CH and ? NH protons in the ¹H NMR spectrum, 3) a small increase in singlet lifetimes, and 4) a moderate increase in two‐photon absorption cross‐section values. Furthermore, nucleus‐independent chemical shift (NICS) values calculated at various geometrical positions show positive values and anisotropy‐induced current density (AICD) plots indicate paratropic ring‐currents for the diprotonated form of the octaphyrin (in which Ar=tolyl); the single‐crystal X‐ray structure of the diprotonated form of the octaphyrin shows an extended structure in which one of the pyrrole ring of each dipyrrin subunit undergoes a 180 ° ring‐flip. Four trifluoroacetic acid (TFA) molecules are bound above and below the molecular plane defined by meso‐carbon atoms and are held by N? H ??? O, N? H ??? F, and C? H ??? F intermolecular hydrogen‐bonding interactions. The extended‐open structure upon protonation allows π‐delocalization and the electronic structure conforms to a [4n]π Hückel antiaromatic in the diprotonated state.