Constructing a Nonfluorescent Conformation of AIEgen: A Tetraphenylethene Embedded in the Calix[4]arene's Skeleton

Abstract

Two novel 1,1-diphenylmethylidene decorated calix[4]arenes, (Calix-DPE(OCH ) and Calix-DPE(OH) ), were designed and prepared. The tetraphenylethene (TPE) unit is embedded in the calix[4]arenes skeleton, so the conformation of tetraphenylethene unit is significantly affected by the conformation of calix[4]arene. Unlike the Calix-DPE(OCH ) , the Calix-DPE(OH) does not show the aggregation-induced emission (AIE) phenomena in solution or the crystal state because of the presence of intramolecular hydrogen bonding, which leads to a cone conformation for the calix[4]arene skeleton in which the embedded phenyl rings of the TPE have to take an almost perpendicular configuration to the C=C bond. This result provides direct evidence that the maximal cross-chromophore π-conjugation within the tetraphenylethene is one of the prerequisites of switching on its AIE. This offers the possibility of switching the emission of TPE by conformation changes.

Tetraphenylethylene-Incorporated Macrocycles and Nanocages: Construction and Applications

“…These three macrocycles represent the first examples of employing pillar[6]­arene as the skeleton to construct TPE-based macrocycles. Subsequently, two well-known host molecules, namely, calix[4]­arene and pillar[5]­arene, were employed (Scheme ) to construct TPE-incorporated macrocycles 63 and 64 . The characterization showed that Calix-DPE­(OMe) 4 exhibits the typical AIE property, while Calix-DPE­(OH) 4 has no emission in either solution or the solid state.…”

Straightforward intra/intermolecular cyclization to AIE-active cyclic TPE: selectively distinguishing benzaldehyde and a temperature sensor

“…Among AIEgen systems, TPE 19,20 as a type AIEgens, not only have been studied for MFC behavior by varying substituents to modify its molecular structure, 21–23 but it also has been employed as a fluorescent building block of fluorescent macrocycles 24–28 or cages 29–31 in recent years. These cyclic TPE compounds exhibit outstanding performances, which enable them as selectivity sensors, 32 molecular storage materials, 33 and supramolecular catalysts.…”

“…Furthermore, the AIE luminogens (AIEgens) display variable emitting color in the solid state by external stimuli for the change in molecular packing, namely MFC, [16][17][18] which are promising candidates for stimulus-responsive fluorescent materials. Among AIEgen systems, TPE 19,20 as a type AIEgens, not only have been studied for MFC behavior by varying substituents to modify its molecular structure, [21][22][23] but it also has been employed as a fluorescent building block of fluorescent macrocycles [24][25][26][27][28] or cages [29][30][31] in recent years. These cyclic TPE compounds exhibit outstanding performances, which enable them as selectivity sensors, 32 molecular storage materials, 33 and supramolecular catalysts.…”