Solvent-directed formation of helically twisted stacking constructs via self-assembly of tris(phenylisoxazolyl)benzene dimers

Ureido-pyrimidinone (UPy)-appended tris(phenylisoxazolyl)benzenes were synthesized. The UPy moieties of the tris(phenylisoxazolyl)benzenes stably formed self-complementary dimers in solution. The dimers self-assembled to form helically twisted stacking constructs in a process driven by π-π stacking interactions of UPy dimer moieties and dipole-dipole interactions of isoxazole units. Strong association affinity was seen within the stacking constructs compared with the previously reported isoxazole derivatives owing to the auxiliary π-π stacking interaction. Notably, tris(phenylisoxazolyl)benzenes showed an environmentally responsive nature. The absorption bands, emission intensities, and sizes of ensembles depended significantly on the mixing ratio of CHCl₃ and methylcyclohexane (MCH). Additionally, sharp on-off switching phenomena were seen in their circular dichroism (CD) and circularly polarized luminescence (CPL) spectra in response to the mixing ratio of CHCl₃ and MCH. CD and CPL were activated only at a certain mixing ratio of CHCl₃/MCH, thus showing potential for the creation of molecular sensors.

Impact of a chiral supramolecular nanostructure on the mechanical and electrical performances of triphenylene-based discotic physical gels

Discotic π-conjugated supramolecular assemblies, especially with chiral supramolecular nanostructures, have been attracting growing research interest due to their significant optoelectronic properties and the possibilities of their applications in the new generation of organic semiconductors. However, the impact of supramolecular chirality on their mechanical and electrical performances remains poorly understood. Herein, a series of optically active supramolecular gels were formed from achiral triphenylene derivatives by introducing limonene as the chiral source. Owing to the well-ordered supramolecular packing, the homochiral supramolecular gels exhibited greater mechanical strength and higher conductivity, compared to heterochiral architectures. The impact of supramolecular packing in homochiral or heterochiral assemblies on their resulting mechanical and electrical performances was investigated in detail, which might be of great fundamental value for the rational design of chiral π-conjugated supramolecular nanostructures for applications in chiral optoelectronics.

Supramolecular Assembly of Thiophene-Based Oligomers into Nanostructured Fluorescent Conductive and Chiral Microfibers

The implementation of nano/microelectronic devices requires efficient strategies for the realization of supramolecular structures with desired function and supported on appropriate substrates. This article illustrates a strategy based on the synthesis of thiophene oligomers having the same "sulfur-overrich" quaterthiophene inner core (non bonding interactional algorithm) and different terminal groups. Nano/microfibers are formed on surfaces having a morphology independent of the nature of the deposition substrate and displaying a wide tuning of properties that make the fibers optoelectronically suitable for application in devices.

Supramolecular Nanowires from an Acceptor-Donor-Acceptor Conjugated Chromophore

Oligothiophene derivatives have been extensively studied as p-type semiconducting materials in organic electronics applications. This work reports the synthesis, self-assembly and photophysical properties of acceptor-donor-acceptor (A-D-A)-type oligothiophene derivatives by end-group engineering of quaterthiophene (QT) with naphthalene monoimide (NMI) chromophores that are further connected to a trialkoxy benzamide wedge. Conjugation to the NMI units reduces the HOMO-LUMO gap significantly, and consequently the absorption spectrum exhibits a bathochromic shift of about 50 nm compared with QT. Furthermore, extended H-bonding interactions among the amido groups of the peripheral wedges produce entangled fibrillar nanostructures and gelation in hydrocarbon solvents such as methylcyclohexane, wherein the A-D-A chromophore exhibits typical H-aggregation. On the contrary, the fact that the same chromophore, lacking only the amido units, does not produce gels or H-aggregates indicates strong impact of H-bonding on the self-assembly. Computational studies revealed the electronic properties of the chromophore and predicted the geometry of a dimer in the H-aggregate that reasonably matches with the experimental results. Bulk electrical conductivity measurements determined an excellent conductivity of 2.3×10^-2  S cm^-1 for the H-aggregated system (OT-1), which is two orders of magnitude higher than that of the same chromophore lacking the amido groups (OT-2).