Supercooling of functional alkyl-π molecular liquids.

Metastable states of soft matters are extensively used in designing stimuli-responsive materials. However, the non-steady properties may obstruct consistent performance. Here we report an approach to eradicate the indistinguishable metastable supercooled state of functional molecular liquids (FMLs), which remains as a liquid for weeks or months before crystallizing, via rational molecular design. The phases (solid, kinetically stable liquid, and supercooled liquid) of a model FML, branched alkyl chain-substituted 9,10-diphenylanthracene (DPA), are found to be governed by subtle alterations of the molecular structure (alkyl-DPA ratio and bulkiness of the DPA unit). We thus outline molecular design principles to avoid supercooled FML formation. Moreover, we demonstrate a practical technique to rapidly discriminate supercooled FMLs (within 5 h) by accelerating their crystallization in differential scanning calorimetry heating via pre-annealing or relatively slow scanning.

Polyaromatic molecular tubes with a subnanometer pore and the guest-induced emission enhancement behavior.

New polyaromatic molecular tubes with a subnanometer pore (0.8 nm) were prepared. The tube bearing six sulfonate groups on the periphery and twelve methoxy groups at the openings provides a cylindrical hydrophobic cavity with a length of ∼1.3 nm. The aqueous tube can quantitatively bind one molecule of hydrocarbon guests in water with accompanying guest-induced emission enhancement (up to ∼3 times) of the host framework.

An aqueous molecular tube with polyaromatic frameworks capable of binding fluorescent dyes.

An aqueous molecular tube composed of polyaromatic frameworks with peripheral hydrophilic groups was prepared. The new tube has a well-defined hydrophobic cavity with a diameter of ∼1 nm and quantitatively binds two molecules of fluorescent coumarin dyes in aqueous solutions. The bound coumarin dimers in a stacked fashion exhibit unusual excimer-like emissions in the confined space through efficient host-guest energy transfer.

Nonvolatile liquid anthracenes for facile full-colour luminescence tuning at single blue-light excitation.

Nonvolatile room-temperature luminescent molecular liquids are a new generation of organic soft materials. They possess high stability, versatile optical properties, solvent-free fluid behaviour and can effectively accommodate dopant dye molecules. Here we introduce an approach to optimize anthracene-based liquid materials, focussing on enhanced stability, fluorescence quantum yield, colour tunability and processability, with a view to flexible electronic applications. Enveloping the anthracene core in low-viscosity branched aliphatic chains results in stable, nonvolatile, emissive liquid materials. Up to 96% efficient energy-transfer-assisted tunable emission is achieved by doping a minute amount of acceptor dye in the solvent-free state. Furthermore, we use a thermoresponsive dopant to impart thermally controllable luminescence colours. The introduced strategy leading to diverse luminescence colours at a single blue-light excitation can be an innovative replacement for currently used luminescent materials, providing useful continuous emissive layers in developing foldable devices.

A tubular macrocycle from covalently linked anthracenes and meta-phenylene spacers.

A novel tubular macrocycle containing four anthracene panels covalently linked by meta-phenylene spacers was synthesized. The tube is approximately 1 nm long with anthracene panels delimiting a columnar cavity with a diameter of ~1 nm and exhibits strong blue fluorescence.