Water-soluble hollow nanocrystals from self-assembly of AIEE-active Pt(II) metallomesogens

Abstract

Luminescent hollow micro- and nanocrystals have been successfully obtained taking advantage of the self-assembly behavior and the aggregation-induced emission enhancement properties of several bispyrazolate Pt(II) metallomesogens decorated with four terminal alkyl chains. Oil-in-water droplets have been used to confine the Pt(II) compounds and drive them to be self-assembled via intermolecular Pt···Pt interactions into spherical aggregates of about 200 or 50 nm. Evaporation of the oil phase generates highly-stable aqueous dispersions of nanocrystals that emit a bright orange light as a result of the existence of 3MMLCT excited states. Different methods and conditions have been tested for studying the effect of several parameters such as the temperature and the stirring speed in the final particle size and in the polydispersity index. Moreover, the micro- and nanocrystals are able to entrap hydrophobic drugs between the alkyl chains of the compounds, forming stable dispersions of drug-loaded capsules in water. The droplet method is applied in the area of metallomesogens for the first time to synthesize self-assembled Pt(II) nanocapsules, which opens a new field of study that could allow the use of these liquid crystal materials in biomedical applications.