No abstract

6,7-Bis(alkyloxy)-2,3-dihydrophthalazine-1,4-diones self-assemble into lactim-lactam trimeric disks in solution as demonstrated by SEC and NMR. With suitable substituents, as in Phthal8, Phthal12, and Phthal16, these disks self-organize into a thermotropic, columnar, discotic phase. The disubstituted phthalhydrazide unit thus represents a general motif for the recognition-induced generation of supramolecular, discotic liquid crystals by self-assembly.

No abstract

Macrocycles possessing radially oriented π−orbitals have experienced a fantastic development. However, their incorporation in organic electronic devices remains very scarce. In this work, we aim at bridging the gap between organic electronics and nanorings by reporting the first detailed structure-properties-device performance relationship study of organic functional materials based on a nanoring system. Three [4]cyclo-N-alkyl-2,7-carbazoles bearing different alkyl chains on their nitrogen atoms have been synthesized and characterized by combined experimental and theoretical approaches. This study includes electrochemical, photophysical, thermal and structural solid-state measurements and charge transport properties investigations. An optimized protocol of the Pt approach has been developed to synthesize the [4]-cyclocarbazoles in high yield (52-64%), of great interest for further development of nanorings especially in materials science. The charge transport properties of [4]-cyclocarbazoles and a model compound, [8]-cycloparaphenylene ([8]CPP), have been studied. Although no field effect (FE) mobility was recorded for benchmark [8]CPP, FE mobility values of ca 10 -5 cm².V -1 .s -1 were recorded for the [4]-cyclocarbazoles. The characteristics (threshold voltage VTH, subthreshold swing SS, trapping energy ∆E) recorded for the three[4]-cyclocarbazoles appear to be modulated by the alkyl chain length borne by the nitrogen atoms. Remarkably, the space-charge-limited current mobilities measured for the [4]-cyclocarbazoles are about 3 orders of magnitude higher than that of [8]CPP (1.37/ 2.78×10 -4 for the [4]-cyclocarbazoles vs 1.21×10 -7 cm².V -1 .s -1 for [8]CPP) highlighting the strong effect of nitrogen bridges on the charge transport properties. The whole study opens the way to the use of nanorings in electronics, which is now the next step of their developments.

The realization of spin-crossover (SCO)-based applications requires study of the spin-state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface-bound thin molecular film is either quenched or heavily altered due to: (i) molecule-surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self-assembly strategy is proposed to fabricate thin spin-switchable surface-bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H B(pz) ) (bpy)] (pz = pyrazole, bpy = 2,2'-bipyridine) with a dodecyl (C ) alkyl chain yields a classical amphiphile-like functional and vacuum-sublimable charge-neutral Fe complex, [Fe(H B(pz) ) (C -bpy)] (C -bpy = dodecyl[2,2'-bipyridine]-5-carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiO surfaces of the complex show comparable spin-state switching characteristics mediated by similar lamellar bilayer like self-assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO-based applications, especially in molecular spintronics.

In this work, we wish to report the first member of a new family of organic semi-conductors constructed on a meta dihydroindacenodithiophene core, that is 2,2'-(2,8-dihexyl-4,6-dihydro-s-indaceno [1,2-b:7,6-b']dithiophene-4,6-diylidene)dimalononitrile (called meta-IDT(=C(CN) 2 ) 2 ). The properties of this molecule have been studied in detail through a structure properties relationship study with its regioisomer, that is 2,2'-(2,7-dihexyl-4,9-dihydro-s-indaceno [1,2-b:5,6-b']dithiophene-4,9-diylidene)dimalononitrile (para-IDT(=C(CN) 2 ) 2 ) (see isomers structures in blue in Chart 2). The influence of the bridge functionalization has also been investigated by comparison with their diketone analogues meta-IDT(=O) 2 and para-IDT(=O) 2 . This study sheds light on the impact of regioisomerism on the electronic properties at the molecular level (electrochemistry, absorption spectroscopy, molecular modelling) and also on the supramolecular arrangement (SWAXS), and finally on the OFET performances and stabilities. The significant effect of self-assembled monolayers of 4-(dimethylamino) benzenethiol (DABT) grafted on the gold drain and source electrodes or of the use of flexible substrate (polyethylene naphtalate: PEN) instead of glass on the OFET performances and stabilities are also reported. In the light of these results (maximum mobility reaching 7.1×10 -2 cm² V -1 cm -1 , high Id on /Id off of 2.3×10 7 and

F substituents & bulky alkyl side-chains for polymer:fullerene face-on orientation and high PV performances.

Combining side chain engineering and controlled alignment of PBTTT is an effective strategy to produce oriented thin films with improved thermoelectric performance when doped sequentially with the acceptor molecule hexafluoro‐tetracyanonaphthoquinodimethane (F6TCNNQ). The substitution of linear alkyl side‐chains (n‐C12) with a chain of identical length including an ether function (n‐C7OC4) leads to a new class of slightly polar PBTTT polymers, preserving the ease of synthesis and air stability of alkylated PBTTTs. This side‐chain modification improves the structural order of PBTTT backbones and the thermo‐mechanical properties of the polymer. It then can be oriented by high temperature rubbing up to 240 °C to reach very high dichroic ratios up to 20 thanks to enhanced cohesive forces within side‐chain layers. The side chain polarity of n‐C7OC4 helps to tune the polymer‐dopant interactions. A multi‐technique approach demonstrates that F6TCNNQ dopants are randomly oriented in the disordered side chain layers of n‐C7OC4 with some evidence of dopant clustering. The combination of improved alignment and random orientation of intercalated F6TCNNQ dopants helps reach a very high charge conductivity σ = 5 ⋅ 104 S cm−1 and a record power factor of 2.9 mW m−1 K−2 in the polymer chain direction.