Aggregation-Induced Emission:  Effects of Molecular Structure, Solid-State Conformation, and Morphological Packing Arrangement on Light-Emitting Behaviors of Diphenyldibenzofulvene Derivatives

Abstract

Propeller-shaped molecules diphenyldibenzofulvene (1) and (4-methoxyphenyl)phenyldibenzofulvene (2) were nonemissive when dissolved in good solvents but became luminescent when aggregated in poor solvents or in the solid state, showing a novel phenomenon of aggregation-induced emission (AIE). 8-Phenylbenzo[e]-acephenanthrylene (3), a ring-closed form of 1 with one of its phenyl blades locked, was emissive in the solutions, suggesting that the AIE effects of 1 and 2 are caused by the restrictions of intramolecular rotations of their aromatic blades in the aggregation state. The crystals of 1 and 2 emitted stronger, bluer lights than their amorphous powders, possibly due to the structural rigidification and conformational twisting of the dye molecules in the crystalline phase. The light-emitting diodes with a device configuration of ITO/NPB/dye/ BCP/Alq 3 /LiF/Al were fabricated, which emitted bluish-green and yellow lights with maximum luminance and current efficiency up to 5000 Cd/m 2 and 1.90 Cd/A, respectively.

Fabrication of Fluorescent Silica Nanoparticles Hybridized with AIE Luminogens and Exploration of Their Applications as Nanobiosensors in Intracellular Imaging

“…While 3 was prepared following our previously published experimental procedures, [13,18] the synthetic route to 12 is given in Scheme 2. Compound 6 is first prepared by the etherization of 4-iodophenol (5) with 1,2-dibromoethane.…”

“…1,2-Bis(4-bromomethylphenyl)diphenylethene (3) was prepared using our previously reported procedures. [13,18] Instrumentations: 1 H and 13 C NMR spectra were recorded on a Bruker ARX 400 spectrometer with tetramethylsilane (TMS; d = 0) as internal standard. HRMS spectra were recorded on a Finnigan TSQ 7000 triple quadrupole spectrometer operating in a MALDI-TOF mode.…”

“…Nonemissive luminogens, such as tetraphenylethene (TPE) and hexaphenylsilole, are induced to emit efficiently by aggregate formation. [12][13][14] The AIE effect dramatically boosts fluorescence quantum yields (F F ) of the luminogens, turning them from faint fluorophores to strong emitters. An extreme example of such AIE luminogen is 4,4'-bis(1,2,2-triphenylvinyl)biphenyl: its emission efficiencies in the solution (F F,S ) and aggregate (F F,A ) states are~0 and 100 %, respectively, resulting in an infinitely large AIE effect (a AIE = F F,A /F F,S !…”

“…[27][28][29][30] When the molecules of 1 and 2 are covalently incorporated into, and aggregate in, the silica networks, strong fluorescence spectra peaked at 465 and 485 nm, respectively, are recorded, confirming that 1 and 2, similar to their respective congeners 3 and 12, are AIE active. [13,18] The rigid silica networks largely restrict intramolecular rotations in the luminogens. This blocks the nonradiative relaxation channel and populates the radiative decay, thus making the FSNPs highly luminescent.…”

Aggregation-Induced Emission and Applications of Aryl-Substituted Pyrrole Derivatives

“…The distance between two molecules within one column for PPP is 5.14 A , which is too large to undergo p-p interactions. As shown in Figure 6.25c, no face-to-face p-p stacking exists but rather edge-to-face interactions such as aromatic CHÁ Á Áp hydrogen bonding in the crystal structure [31,34,89]. The delocalized system of sp 2 -hybridized covalent bonds can act as an acceptor group, and hydrogen atoms serve as proton donors for the formation of aromatic CHÁ Á Áp hydrogen bonds.…”