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Two isomeric series of compounds with "inverted" chains' substitution patterns, 7,10‐dialkoxy‐1,2,3,4‐tetrafluoro‐6,11‐dimethoxytriphenylene and 6,11‐dialkoxy‐1,2,3,4‐tetrafluoro‐7,10‐dimethoxytriphenylene, labelled respectively p‐TPFn and m‐TPFn, and two non‐fluorinated homologous isomers, 3,6‐dibutoxy‐2,7‐dimethoxytriphenylene and 2,7‐dibutoxy‐3,6‐dimethoxytriphenylene, p‐TP4 and m‐TP4, respectively, were synthesized in three steps and obtained in good yields by the efficient transition‐metal‐free, fluoroarene nucleophilic substitution via the reaction of appropriate 2,2'‐dilithium biphenylenes with either perfluorobenzene, C6F6, to yield p‐TPFn and m‐TPFn, or o‐difluorobenzene, C6H4F2, for p‐TP4 and m‐TP4, respectively. The single‐crystal structures of p‐TPF4, m‐TPF4 and p‐TP4, unequivocally confirmed that the cyclization reactions occurred at the expected positions, and that the fluorinated molecules stack up into columns with short separation, a propitious situation for the emergence of columnar mesophases. The mesomorphous properties were found to be greatly affected by both chains' length and positional isomerism: a Colhex phase is found for p‐TPF4 and m‐TPF4, but mesomorphism vanishes in p‐TPF6, and changes for the isomeric homologs m‐TPFn, with the induction for n≥6 of a lamello‐columnar phase, LamColrec. As expected, both non‐fluorinated compounds are deprived of mesomorphism. These compounds emit blue‐violet colour in solution, independently of the chains' substitution pattern, and the absolute fluorescence quantum yields can reach up to 46 %. In thin films, fluorescence is slightly redshifted. [ABSTRACT FROM AUTHOR]

Non-covalent arene–fluoroarene interactions have been increasingly exploited to create complex, soft and/or rigid supramolecular assemblies and more recently to design liquid crystals. These interactions stem from the strong electronegativity of the fluorine atoms which modifies the dipole moment of the fluorinated aromatic rings. Here, two new series of fluorine-containing triphenylene derivatives bearing 4 peripheral alkyl chains of various lengths were synthesized by nucleophilic substitution of fluoroarenes (SNFAr). A first monotonous series i.e. 2-phenyl-1,3,4-trifluorotriphenylenes (PHn, R = CnH2n+1, n = 3–12) was obtained in ca. 60–90% yields by reacting lipophilic 2,2′-dilithiobiphenyl derivatives with pentafluorobiphenyl C6F5–C6H5. Following a similar synthetic procedure, a second series of analogous compounds with larger functional aryl pending moieties, i.e. 2-aryl-1,3,4-trifluorotriphenylene derivatives, such as naphthalen-1/2-yl (NAA/NAB), benzothiophen-2-yl (BT), triphenylen-2-yl (TP), pyren-1-yl (PY) and tetraphenylethylenyl (TPE), were also prepared and obtained in moderate to high yields. Quite remarkably, induction and/or stabilization of columnar mesophases were systematically observed for all these new fluorine-containing triphenylene derivatives. PHn show a wide range of Colhex phases including room temperature phases with clearing temperatures that gradually decrease with the lengthening of alkyl chains, in contrast to the analogous non-fluorinated triphenylene derivatives deprived of liquid crystal properties. BT8, NAA8, NAB8, TP8, PY8, and TPE8 consistently display a columnar hexagonal (Colhex) mesophase while their mesophase ranges, though also broad, depend strongly on the size and bulkiness of the side aromatic residue. This study demonstrates the essential role played by aromatic fluorination and the predominance of arene–fluoroarene supramolecular interactions in the effective induction of mesophases by directing face-to-face stacking of aromatic rings of opposite nature. An X-ray single-crystal structure of PH0 indeed reveals the presence of such arene–fluoroarene interactions in the solid state and the antiparallel π–π stacking pattern. All the fluorinated molecules show blue photoluminescence in diluted solution, with the fluorescence absolute quantum yield as high as 57% for the PY-containing triphenylene. PY8 exhibits a high hole transport mobility rate on the order of 10−3 cm2 V−1 s−1, measured using the TOF technique, which is similar to those of other triphenylene-containing homologues. [ABSTRACT FROM AUTHOR]

Hetero-bimetallic liquid crystalline materials, exhibiting a single Colhex mesophase, were obtained by simple chemical blending between two structurally-related Cu(II) and Zn(II) metallomesogens based on 1,10-phenanthroline and two chelating gallate ligands. Mesomorphous and optical properties were modified upon their relative respective proportions. This study highlights the numerous possibilities for the fabrication of new multifunctional polymetallic materials, with the possibility of tuning the properties and controlling supramolecular interactions between metal centres and corresponding synergistic effects. [ABSTRACT FROM AUTHOR]

RhI complexes [Rh(L)4](A) (A− = Cl−, BF4−, [Au(CN)2]−) with conventional arylisocyanides (p-MeC6H4(NC), LA; p-MeOC6H4(NC), LB; 3,5-(OMe)2C6H3(NC), LC) or with the alkoxy-functionalized triphenylene-arylisocyanides TPh(OC12H25)5(O(CH2)6OC6H4(NC)-p) (LD1) and TPh(OC12H25)5(O(CH2)6OC6H2Me2(NC)-p) (LD2), have been prepared and their self-assembly, aggregation, optical, redox, mesogenic and conducting properties investigated. Intermolecular π–π stacking, RhI⋯RhI, and RhI⋯AuI interactions rule the crystal packing and aggregation in solution for the complexes with LA, LB, and LC. For the RhI complexes with the alkoxy-functionalized-triphenylene isocyanides LD1 and LD2 mesogenic behaviour is induced, giving rise to multicolumnar mesophases in broad temperature ranges (ca. 70–160 °C). Detailed analysis (POM, DSC, SAXS/WAXS and GIWAXS) of the columnar mesophases has allowed us to propose precise packing models that explain the diverse supramolecular arrangements found in the nanostructured condensed phases. Columnar alignments predominantly with Rh⋯Rh interactions (or Rh⋯Au, only for LD2 in specific conditions) are observed, depending on the aligning conditions. The hole mobility in the columnar mesophases of the complexes with Rh⋯Rh interactions are ∼1 cm2 V−1 s−1, that is up to four orders of magnitude higher than those reported for columnar mesophases of organic triphenylene derivatives, and increases one order of magnitude further in the mesophases containing the [Au(CN)2]− counteranion. [ABSTRACT FROM AUTHOR]

The synthesis of an exclusive family of liquid-crystalline dimers consisting of two protomesogenic triphenylene moieties connected via a rigid, p-conjugated bridge, and the study of their mesomorphous, gel self-assembly and optical properties as a function of the nature of the bridge are reported. Various triphenylene bridged dimers were successfully prepared by either palladium-catalyzed Suzuki-Miyaura cross-coupling between pentakis(alkoxy)triphenylene nonaflates and various commercially accessible aryldiboronic acids (as bridges) or by FeCl3-promoted Scholl oxidative homo-coupling of thiophene/thienothiophene/furan-containing pentakis(alkoxy)triphenylene derivatives. All linear dimers are mesomorphous, and self-organize into large multi-columnar rectangular superlattices, with columnar pairs arranged according to a chevron-like pattern, as deduced from SWAXS and supported by STM. At high temperature, most compounds also display a nematic columnar mesophase (NCol), easily recognized by characteristic optical textures. The transition temperature and mesophase ranges show a high dependency on the bridge nature and, to a lesser extent, on the chain-lengths around the triphenylene moieties. The sole kinked bridged-dimeric homolog of this series exhibits a single, room-temperature hexagonal mesophase (Colhex), as do the monofunctionalized triphenylene precursors, whereas the dimeric triphenylene with no bridge is not mesomorphous. UV-visible absorption and fluorescence emission spectra were measured in both solvents and thin films. The p-conjugated bridged-dimers exhibit emission spanning from 400-700 nm, thus covering the full visible-light range, whose emission maxima are obviously influenced by the chemical nature of the bridge. Furthermore, fluorescence quantum yields as high as 64% were measured for some of them. DFT theoretical computing calculations fully support the experimental measurements. Most dimers also form gels in cyclohexane and emit blue-to-orange light when irradiated by UV light; the corresponding xerogels revealed that their gelation ability results from the 3D morphology of entangled ultra-long and thin microfibers. The facile synthesis of these unique, multifunctional rigid discotic dimers, their rich mesomorphism, strong gelation ability and fine-tuned photophysical properties make these materials very attractive for the active field of organic electronics. [ABSTRACT FROM AUTHOR]

The ligands L10(super Cn) and L12(super Cn) are suited for exploring the consequences of specific molecular shapes and charge distributions on the intermolecular interactions responsible for the macroscopic organization. The concomitant detection of anomalous luminescence behavior occurring during first order phase transitions is encouraging for implementing new optical functions in liquid crystalline displays.

The present system describes unique examples of organogelators as well as thermotropic phenanthroline-based metallomesogen. The use of a potential hydrogen-bound director allows for the production of mesomorphic materials with both ligands and complexes.

Two series of regio-isomeric butterfly-shaped liquid crystalline systems, based on a ditriphenylenothiophene core (α/β-DTPT) equipped with eight peripheral long alkoxy chains, were synthesized in two steps by the Suzuki-Miyaura cross-coupling/Scholl cyclo-dehydrogenation reactions tandem from appropriate precursors. The influence of the core topology (i.e. positional isomerism) on the mesomorphism, gelling self-assembly, absorption and luminescence, and charge-transport properties of both sets of isomers was investigated and compared. The six fused π-conjugated molecules systematically display columnar hexagonal (Colhex) mesophases with β-fused ditriphenylenothiophene compounds (DTPTBn) showing more extended mesophase ranges and higher phase transition temperatures than their isomeric α-counterparts (DTPTAn). All ditriphenylenothiophenes also show strong aggregation behavior in organic solvents, and, in addition, good organic gelling abilities were found for the β-isomers. Interestingly too, high hole mobility rates greater than 10-3 cm2 V-1 s-1 were measured for the β-isomers, which were about 10 times higher than those of the α-counterparts. Modeling of the molecular structures combined with DFT calculations showed that the β-isomers possess flatter and more extended π-conjugated cores than the slightly distorted α-isomers, and consequently were more prone to optimize π-π intermolecular interactions, in agreement with the high-temperature mesophases and high charge carrier mobilities observed for these isomers. Finally, both sets of compounds emit blue-purple light in solution and the emission is substantially redshifted when organized in films. DFT calculations of the HOMO-LUMO energy levels were also consistent with the optical measurements. This original molecular design and straightforward synthesis combination provides an efficient way to obtain novel π-extended organic, potentially semiconductor materials for further electronic device investigations. [ABSTRACT FROM AUTHOR]