Synthesis and aggregation-induced emission properties of tetraphenylethylene derivatives

Two kinds of compounds bearing tetraphenylethylene (TPE) moiety and possessing aggregation-induced emission (AIE) active, 5-(4-(1, 2, 2-triphenylvinyl)phenyl)-2, 2'-bipyridine (Bpy-1TPE) and 5, 5'-bis(4-(1, 2, 2-triphenylvinyl)phenyl)-2, 2'-bipyridine (Bpy-2TPE), were synthesized via Suzuki coupling reaction of 4-(1, 2, 2-triphenylvinyl)phenylboronic acid with 5-bromo-2, 2'-bipyridine and 5, 5'-dibromo-2, 2'-bipyridine, respectively. ¹HNMR and ¹³CNMR spectra and elemental analysis were employed to confirm the structure of the targeted products. Their UV-vis absorption, fluorescence, AIE, piezochromic properties and structure-property correlation were investigated. Compared with Bpy-1TPE, Bpy-2TPE containing two TPE units has a larger conjugation and a symmetrical charge distribution, which exhibits a lower energy gap width. A red-shift of the emission from 483 nm to 490 nm in CH₂Cl₂ was observed. Bpy-2TPE also shows obvious AIE and piezochromic properties. The maximum emission of its solid sample displayed a red-shift from 485 to 500 nm after grinding.