Reevaluating the Solution Photophysics of Tetraphenylethylene at the Origin of their Aggregation-Induced Emission Properties

Although tetraphenylethylene (TPE) and its derivatives have been the most commonly used building blocks in the construction of molecules with aggregation-induced emission (AIE) properties, no absolute consensus exists regarding the mechanisms at the origin of the phenomenon. Restriction of intramolecular rotations (RIR) of peripheral phenyls has historically been a dominant paradigm, which has served as a valuable guideline in the molecular engineering of AIEgens. Yet, an increasing number of recent works have established that photoisomerization or photocyclization may actively participate in the nonradiative dissipation of the excitation energy. In this paper, the first experimental evaluation of the quantum efficiencies of these different processes is reported, and photoisomerization is shown to be by far the dominant photophysical pathway in solution, accounting for virtually all nonradiative decay of the molecule's excited state in degassed solution.

Unusual emission properties of the selected organosilicon compounds containing a styryl-carbazole chromophore: inversion of the singlet excited states

The presence of the silicon atom in a trimethylsilyl-styryl-carbazole derivative induced the inversion of the lowest excited states in polar solvents.

Anticancer phototherapy using activation of E-combretastatins by two-photon-induced isomerization

The photoisomerization of relatively nontoxic E-combretastatins to clinically active Z-isomers is shown to occur in solution through both one- and two-photon excitations at 340 and 625 nm, respectively. The photoisomerization is also demonstrated to induce mammalian cell death by a two-photon absorption process at 625 nm. Unlike conventional photodynamic therapy (PDT), the mechanism of photoisomerization is oxygen-independent and active in hypoxic environments such as in tumors. The use of red or near-infrared (NIR) light for two-photon excitation allows greater tissue penetration than conventional UV one-photon excitation. The results provide a baseline for the development of a novel phototherapy that overcomes nondiscriminative systemic toxicity of Z-combretastatins and the limitations of PDT drugs that require the presence of oxygen to promote their activity, with the added benefits of two-photon red or NIR excitation for deeper tissue penetration.

Synthesis and Photophysical Properties of Novel Fluorescent Quinoline-Based Aryl Substituted Styryl Systems

Synthesis of (E)-2-(4-bromostyryl)quinoline has been easily achieved by an acid catalysed condensation of 2-methylquinoline with 4-bromobenzaldehyde. Various boronic acid derivatives reacted with (E)-2-(4-bromostyryl)quinoline to afford a series of novel quinoline-based aryl substituted styryl derivatives by the catalysis of Pd(PPh3)4 at 85 °C in dimethoxyethane. The UV-Vis absorption and photoluminescent spectra of them in CH2Cl2 were investigated.