Tetraphenyl ethylene derivatives exhibiting aggregation induced emission enhancement for OLEDs and optical sensors of nitroaromatic explosives

Abstract

The design, synthesis, and properties of derivatives of tetraphenyl ethylene (TPE) and donor moieties of tert-butylcarbazole and dimethylacridane are described. The targeted compounds are characterized by single crystal X-ray analysis, mass and NMR spectrocopies. With the temperatures of the onsets of thermal decomposition of ca. 450–520 °C, the compounds exhibit remarkably high thermal stability. Density functional theory calculations are employed to investigate the frontier molecular orbitals and charge transfer dynamics between the distinct moieties of the studied compounds. The dimethylacridine derivative exhibits pronounced charge transfer, as elucidated through the experimental study of the solvatochromic effect. The results of the study of the photophysical properties of the dispersions of the compounds in the mixtures of THF and water demonstrate a pronounced aggregation-induced emission enhancement. The applicability of the synthesized compounds for the detection of nitroaromatic explosives is demonstrated, on the example of quenching of their emission by picric acid. The film of tert-butylcarbazolyl-substituted TPE exhibits almost twice photoluminescence quantum yield than a dimethylacridine-based counterpart. Due to this and a suitable energy level of HOMO of −5.43 eV, the derivative of TPE and tert-butylcarbazole is applied as emitter in a sky-blue organic light emitting diode, reaching external quantum efficiency of 1.7 % without doping into a host material.