Intramolecular Excimer Formation and Delayed Fluorescence in Sterically Constrained Pyrene Dimers

Abstract

The synthesis is described for a series of five molecular dyads comprising pyrene-based terminals covalently linked through a 1,3-disubstituted phenylene spacer. The extent of through-space communication between the pyrene units is modulated by steric interactions imposed by bulky moieties attached at the 6,8-positions of each pyrene unit. For the control compound, only hydrogen atoms occupy the 6,8 positions (DP1), whereas the remaining compounds incorporate ethynylene groups terminated with either triisopropylsilyl (DP2), 1-tert-butylbenzene (DP3), 2,6-di-tert-butylbenzene (DP4) or 1-tert-butyl-3,5-dimethylbenzene (DP5) units. Each compound shows a mixture of monomer and excimer fluorescence in fluid solution at room temperature, but only monomer emission in a glassy matrix at 77 K. The ratio of monomer to excimer fluorescence depends markedly on the molecular structure; DP1 is heavily biased in favour of the excimer and DP4 is enriched with monomer fluorescence. Photophysical properties, including laser induced and delayed fluorescence data, are reported for each compound. Delayed fluorescence occurs by both intramolecular and bimolecular steps, but these events take place on different timescales. The possibility is raised for using intramolecular triplet-triplet annihilation as a means of molecular imaging.

A new pyrene-based aggregation induced ratiometric emission probe for selective detections of trivalent metal ions and its living cell application

“…Specific colorimetric and ratiometric fluorescence responses toward trivalent metals have been exhibited by pyridinyl-functionalized tetraphenylethene [2]. Moreover, only a few reports of AIE behavior were demonstrated by excimer formations of fluorophores containing pyrene rings [32][33][34][35][36][37][38][39][40][41]. Surprisingly, present results of our pyrene-based fluorophore with Schiff-base probes showed another special aggregation induced ratiometric emission (AIRE) processes upon increasing water content.…”

Redox‐Controlled Fluorescence Modulation in a BODIPY‐Quinone Dyad

“…[9] A general problem inherent to all luminescent sensors is background noise created by other endogenous luminophores that are accidentally excited; time-gated methods using long-lived emitters [10] or delayed emission [11] offer potential solutions to this predicament. The next problem is to provide a failsafe means by which the emission intensity can be related to the property under investigation.…”

The Use of Nano Polymeric Self-Assemblies Based on Novel Amphiphilic Polymers for Oral Hydrophobic Drug Delivery

“…We have shown previously that Fmoc modified PAA polymers formed excimers at higher polymer concentrations (18). The flat stereochemistry of aromatic structures allow π-π stacking and hence forming excimers, a known phenomenon supported by others (35). This limits the expansion of the core to accommodate more drugs at higher concentrations (Fig.…”