Electron Transfer and Aggregate Formation Coinduced Emission Enhancement of 9-Cycloheptatrienylidene Fluorenes in the Presence of Cupric Chloride

Abstract

A series of 2,7-diaryl-9-cycloheptatrienylidene fluorenes (9-CHFs) were synthesized, and their structures were confirmed by spectroscopic methods. By cooperation with cupric chloride in tetrahydrofuran, 9-CHFs exhibited emission enhancement at locally excited (LE) band and aggregation induced emission at lower energy band when the solution was excited at two different wavelengths. By kinetically tracking the process via absorption, emission, dynamic light scattering, and TEM photography, it could be concluded that electron transfer from 9-CHFs to cupric cation and the aggregate formation coinduced the turn-on luminescence. Based on the study of the fluorescent structure−property relationship, the investigation of anion effect, and the analysis of X-ray diffraction, it was revealed that electrostatic interactions and intermolecular C−H...π interactions resulted in aggregates formation and thereafter restricted the intramolecular free rotation of σ-bonds, which finally increased the quantum yields at two bands. Thus, emission efficiencies of 9 and cupric chloride in THF solution were determined to be 0.55 and 0.48 for LE band emission and lower energy band emission, respectively.

Fulvenyl-Functionalized Polyisocyanides: Cross-Conjugated Electrochromic Polymers with Variable Optical and Electrochemical Properties

“…Applications of hepta- and triafulvene-derived compounds have been investigated much less comprehensively. Heptafulvalenes can serve as chemical sensors that exhibit turn-on fluorescence. , However, the investigation of hepta- and triafulvenes as electron-donating (p-type) materials seems limited by their lower redox stability. For instance, dibenzo­[ a,d ]­heptafulvenes ( 3 , Figure B) exhibit only irreversible oxidation between +0.1 V (R = NMe 2 ) and +0.85 V (R = H) .…”

New cyano functionalized silanes: aggregation‐induced emission enhancement properties and detection of 2,4,6‐trinitrotoluene

“…In previous reports the crystal structures of fluorophores in the crystalline states have been used to understand the supramolecular stacking and the intermolecular interactions in the aggregation state, which is key to AIEE mechanism. Our attempt to cultivate single crystals of 1 , 2 and CN-1 was unsuccessful.…”

“…Development of highly efficient electroluminescent devices is a hot topic of current interest because of their applications in fluorescence sensing and light‐emitting diode fabrication . However, owing to intermolecular interactions and the corresponding nonradiative decay, the fluorescence efficiency of organic luminescent materials often decreases in the solid state . This aggregation‐caused emission quenching (ACQ) has seriously obstructed the development of efficient organic light‐emitting diodes (OLEDs), chemosensors, biosensors, etc .…”

Multiple Logic Functions Based on Small Molecular Fluorene Derivatives and Their Application in Cell Imaging

“…36,44,45 As described previously, the molecular backbone of polyfluorene has a large number of absorbing units with efficient intrachain and interchain energy-transfer channels to amplify fluorescence sensing signals. In addition, cationic polyfluorene can form a complex with oppositely charged biomolecules through strong electrostatic interactions.…”

“…The optical and electronic properties of fluorene-based materials highly depend on their chemical structures. ,, As described previously, the molecular backbone of polyfluorene has a large number of absorbing units with efficient intrachain and interchain energy-transfer channels to amplify fluorescence sensing signals. In addition, cationic polyfluorene can form a complex with oppositely charged biomolecules through strong electrostatic interactions. , Therefore, these kinds of polyfluorenes can be used as a sensitive optical platform for the construction of multiple DNA logic gates with the ability of simultaneous detection of multiplex targets, which will improve the development of logic gates in computing and the intelligently sensing due to their signal amplification based on FRET.…”