Discogens Possessing Aryl Side Groups Synthesized by Suzuki Coupling of Triphenylene Triflates and Their Self-Organization Behavior

Mesomorphism Modulation of Perfluorinated Janus Triphenylenes by Inhomogeneous Chain Substitution Patterns

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, C6 F6 , to yield p-TPFn and m-TPFn, or o-difluorobenzene, C6 H4 F2 , 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.

Induction and Stabilization of Columnar Mesophases in Fluorinated Polycyclic Aromatic Hydrocarbons by Arene-Perfluoroarene Interactions

The straightforward synthesis of several Fluorinated Polycyclic Aromatic Hydrocarbons by the efficient, transition-metal-free, arene fluorine nucleophilic substitution reaction is described, and the full investigation of their liquid crystalline and optical properties reported. The key precursors for this study, i. e. 2,2'-dilithio-4,4',5,5'-tetraalkoxy-1,1'-biphenyl derivatives, were obtained in two steps from the highly selective Scholl oxidative homo-coupling of 3,4-dialkoxy-1-bromobenzene, followed by quantitative double-lithiation. In situ room temperature nucleophilic annulation with either perfluorobenzene or perfluoronaphthalene leads to 1,2,3,4-tetrafluoro-6,7,10,11-tetraalkxoytriphenylenes and 9,10,11,12,13,14-hexafluoro-2,3,6,7-tetraalkoxybenzo[f]tetraphenes, respectively, in good yields. Exploiting the same strategy, subsequent double annulations resulted in the formation of 9,18-difluoro-2,3,6,7,11,12,15,16-octa(alkoxy)tribenzo[f,k,m]tetraphenes and 9,10,19,20-tetrafluoro-2,3,6,7,12,13,16,17-octakis(hexyloxy)tetrabenzo[a,c,j,l]tetracenes, respectively. Despite the presence of only four alkoxy chains, the polar "Janus" mesogens display a columnar hexagonal mesophase over broad temperature ranges, with higher mesophase stability than the archetypical 2,3,6,7,10,11-hexa(alkoxy)triphenylenes and their hydrogenated counterparts. The improvement or induction of mesomorphism is attributed to efficient antiparallel face-to-face π-stacking driven by the establishment of non-covalent perfluoroarene-arene intermolecular interactions. The larger lipophilic discotic π-extended compounds also exhibit columnar mesomorphism, over similar temperature ranges and stability than their hydrogenated homologs. Finally, these fluorinated molecules form stringy gels in various solvents, and show interesting solvatochromic emission properties in solution as well as strong emission in thin films and gels.

Ditriphenylenothiophene butterfly-shape liquid crystals. The influence of polyarene core topology on self-organization, fluorescence and photoconductivity

Two series of regio-isomeric mesomorphous, luminescent and conductive compounds, based on a ditriphenylenothiophene core (α/β-DTPT), were successfully synthesized by the Suzuki–Miyaura cross-coupling/Scholl cyclo-dehydrogenation reactions tandem.

Board-like Fused-Thiophene Liquid Crystals and their Benzene Analogs: Facile Synthesis, Self-Assembly, p-Type Semiconductivity, and Photoluminescence

Fused-thiophene discotic liquid crystals were designed and easily synthesized by Suzuki coupling and FeCl₃ oxidized tandem cyclodehydrogenation reactions, including homo- and cross-coupling reactions. The resulting hexagonal and rectangular columnar mesomorphic supramolecular structures formed were characterized by polarizing optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The charge carrier transport properties in the mesophases of two of the synthesized fused-thiophene discogens were measured by transient photocurrent time-of-flight (TOF) technique, revealing fast hole transport values in the range of 10^-3 to 10^-2  cm²  V^-1  s^-1 , thus demonstrating potential applications in electronic devices. The luminescent sanidic mesogens, with different extended π-conjugated systems, also emit blue, green, or red light, with absolute photoluminescent quantum yields as high as 18 %.

Multiple glassy dynamics in dipole functionalized triphenylene-based discotic liquid crystals revealed by broadband dielectric spectroscopy and advanced calorimetry - assessment of the molecular origin

A selected series of dipole functionalized triphenylene-based discotic liquid crystals (DLCs) was synthesized and investigated in a systematic way to reveal the phase behavior and molecular dynamics. The later point is of particular importance to understand the charge transport in such systems which is the key property for their applications such as organic field-effect transistors, solar cells or as nanowires in molecular electronics, and also to tune the properties of DLCs. The mesomorphic properties were studied by polarizing optical microscopy, X-ray diffraction, and differential scanning calorimetry, which were compared to the corresponding unfunctionalized DLC. The molecular dynamics were investigated by a combination of state-of-the-art broadband dielectric spectroscopy (BDS) and advanced calorimetry such as fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). Besides localized fluctuations, surprisingly multiple glassy dynamics were detected for all materials for the first time. Glassy dynamics were proven for both processes unambiguously due to the extraordinary broad frequency range covered. The α1-process is attributed to fluctuations of the alky chains in the intercolumnar space because a polyethylene-like glassy dynamics is observed. This corresponds to a glass transition in a confined three-dimensional space. The α2-process found at temperatures lower than α1-process, is assigned to small scale rotational and/or translational in plane fluctuations of the triphenylene core inside distorted columns. This can be considered as a glass transition in a one-dimensional fluid. Therefore, obtained results are of general importance to understand the glass transition, which is an unsolved problem of condensed matter science.

Synthesis and investigation on optoelectronic properties of mesogenic triphenylene–perylene dyads linked by ethynylphenyl bridges

Columnar mesogenic dyads consisting of triphenylene and perylene units are a novel kind of single-component photovoltaic materials.

Highly efficient synthesis of C3-symmetric O-alkyl substituted triphenylenes and related Mannich derivatives

C₃-Symmetric tris-benzyl-O-substituted hexahydroxytriphenylene (HHTP) was prepared through selective ring opening with DIBAL-H in 48% yield (38% from HHTP in a two-step synthesis).