Probing E/Z Isomerism Using Pillar[4]pyridinium/Gold Nanoparticle Ensembles and Their Photoresponsive Behavior.

Despite the fundamental importance and broad applicability of E/Z dicarboxylic acids, their discrimination remains challenging and greatly unexplored. Herein, we present a general approach for the recognition of E/Z diacids using supramolecular interactions coupled with plasmonic response. The method allows detecting both single isomers and their light-induced interconversion, which ultimately entails multiple reversible nanoparticle aggregations. Such a molecular recognition-coupled responsive nanoscale self-assembly resembles natural mechanisms and can be a versatile means of building artificial complexity.

Carbazole-modified thiazolo[3,2-c][1,3,5,2]oxadiazaborinines exhibiting aggregation-induced emission and mechanofluorochromism.

Two highly emissive carbazole-containing thiazole-fused oxadiazaborinines were designed and synthesized. These N,O-chelated organoboron dyes displayed large Stokes shifts and remarkable solvatofluorochromism in solutions, as well as good thermal stability and comparatively high photoluminescence quantum yields (up to 34%) in the solid state. The presence of a carbazole donor unit, linked with the oxadiazaborinine acceptor via a phenyl linker, restricted intramolecular rotation, leading to enhanced aggregation-induced emission properties of the compounds: in THF/water mixtures with a large water percentage, they demonstrated the formation of emissive nanoaggregates with an average size of 79 and 89 nm for complexes 2 and 3, respectively. The introduction of bulky tert-butyl groups attached to the carbazole moiety induced significant mechanofluorochromic properties of the compounds.

Visual discrimination of aromatic acid substitution patterns by supramolecular nanocooperativity.

Physicochemical and, in particular, visual recognition of positional isomers, due to their similar appearance and properties, is an extremely challenging task. Here we present an easy-to-prepare assay for the naked-eye differentiation of all possible isomers of phthalic acids. The desired optical response is attained through specific non-covalent interactions between the acids and a cationic macrocyclic host. These interactions are then translated to and amplified by gold nanoparticles which subsequently aggregate to various extents producing a color palette.