Macrocycles and cages based on tetraphenylethylene with aggregation-induced emission effect

Abstract

Organic molecules with an aggregation-induced emission (AIE) effect have recently been attracting more and more attention due to their colossal potential in solid emitters and chemo/biosensors. The number and variety of AIEgen compounds are expanding very rapidly to obtain better application performance and a wider area of application. Among AIEgen systems, tetraphenylethylene (TPE) and its derivatives are the class that have received the most extensive study and the most rapid development because of their facile synthesis. Due to its C2 symmetry and at least tetratopic reaction positions, the TPE unit is also an ideal building block for constructing macrocycles and cages. The resultant cyclic TPE compounds have exhibited many exceptional performances that are difficult to access in their open chain counterparts, such as AIE enhancement, improvement in selectivity and sensitivity as sensors, emission tuning by guests, supramolecular catalysis, further disclosure of the AIE mechanism, molecular adsorption, storage and release, the propeller-like conformation exploitation of the TPE unit in chiral materials and so on. Recently, therefore, a large variety of studies about the synthesis, properties and application research of TPE macrocycles and cages have been reported. These TPE macrocycles and cages significantly expand the research area for the AIE phenomenon and its applications, and represent a development of the AIE area. However, up to now, no review of TPE macrocycles and cages has been available. Thus, this review serves as a summary of the designs, synthesis, photophysical properties, self-assembly, applications and prospects of TPE macrocycles and cages.

Selective Fluorescence Turn‐On Sensing of Phosphate Anion in Water by Tetraphenylethylene Dimethylformamidine

“…[1][2][3][4][5][6][7][8] The recently discovered aggregation-inducede mission (AIE) has become one of top research frontiers in chemistry and materials due to great potential in solid emitter andc hemo/biological sensors. [9][10][11][12][13] Up to now,al arge number of sensors based on AIEgens have been developed. [14][15][16][17][18][19][20] Some of them show valuablea pplication prospecti nm onitoring,a nalysis, imaging of ions.…”

“…Meanwhile, the resultant monohydrogen chloride salt possessed a free formamidineu nit, in which one imine double bond was . The absorption spectra of 4 (5 10 À5 m)i nwater with addition of 0, 10,20,30,40,50,60,70,80,90,100,110,120,130,140,150,175,200,250,300,350, 400 mm of phosphate anion, respectively,and the structure transformation of 4 upon addition of phosphate. Inset,c urve of the absorbance at 257 nm vs. the concentrationo fp hosphate anion.…”

Aggregation‐Induced Emission of Highly Planar Enaminone Derivatives: Unexpected Fluorescence Enhancement by Bromine Substitution

“…This aggregation‐caused quenching (ACQ) of fluorescence would dramatically limit their practical applications . In the past decade, the development of aggregation‐induced emission (AIE)‐active molecules with typically twist/rotor structures, which are nonemissive in dilute solution and turn to be highly emissive in the aggregate or solid states, has been a highly active research area . Planar conformation is of critical importance for organic semiconductors to enhance intramolecular charge transport and decrease bandgap because of close π–π stacking and high intermolecular orbital overlap in solid state .…”

“…As shown in Figure , both BrE and HE possess highly planar conformations due to the formation of typical intramolecular hydrogen bonds between the N−H proton and the carbonyl oxygen (BrE: OH distance = 1.939 Å, NHO angle = 130.0° and HE: OH distance = 1.941 (2.004) Å, NHO angle = 131.4 (131.7)°), which is consistent with their low field broad doublet signals (BrE: 12.13 ppm and HE: 12.16 ppm, Figures S11 and S14, Supporting Information) in their 1 H NMR spectra. In fact, the AIE behaviors for these two planar molecules are quite unusual because most AIE luminogens are propeller‐like luminogens . In BrE, which crystallizes in the orthorhombic space group Pbca , neighboring molecules link in corrugated chains via type II Br⋅⋅⋅Br (3.64 Å, θ 1 = 161.6°, θ 2 = 101.6°) halogen bond interactions (Figure d) and these chains are further connected via abundant intermolecular interactions, such as CO⋅⋅⋅HAr (2.415 Å) and CH⋅⋅⋅π (2.724 Å) interactions as well as partial edge‐to‐edge π–π interactions (3.464 Å) (Figure c), forming a firm 3D intermolecular interaction network, which will restrict the molecular rotational or vibrational motions to reduce the nonradiative transitions.…”

Easily Accessible Schiff Base ESIPT Molecules with Tunable Solid State Fluorescence: Mechanofluorochromism and Highly Selective Co2+ Fluorescence Sensing

“…Aggregation caused quenching effect makes strongly solution fluorescent π‐conjugated organic molecules into non‐fluorescence in the solid state . Discovery of aggregation enhanced emissive (AEE) phenomena in non‐planar molecular structure via supramolecular interactions mediated rigidification of intramolecular rotation produced enhanced emissive solids . On the other hand, excited state intramolecular proton transfer (ESIPT) mechanism lead to strong fluorescence in the solid state from planar π‐conjugated molecules .…”