Highly emissive tridentate fluorophores based on bis-imidazo[1,2-α]pyridine for deep-blue photoluminescence with CIE y ≤ 0.08

Abstract

Imidazo[1,2-α]pyridine-based multifunctional derivatives have been widely utilized in pharmaceuticals, chemical sensing, bioimaging, optoelectronics, and other fields. Through incorporation of different substituents at the C4 position of central pyridine ring, nine tridentate imidazo[1,2-α]pyridine derivatives 4a-i have been synthesized and fully characterized. The influence of substituents on the luminescence of 4a-i was systematically investigated by spectroscopic methods, which was in accordance with density functional theory calculations and electrochemical measurement. In CH2Cl2, all compounds exhibited strong near-UV to deep-blue emission and retained CIE y coordinates ≤0.08, with maximum emission band located at 378–450 nm and photoluminescence quantum yields in the range of 15%–94%. Meanwhile, compound 4f exhibited a positive acidochromism in CH2Cl2 upon addition of TFA, accompanied with the dual change of colorimetric and fluorometric determination, indicating its potential application for the development of pH sensor. Moreover, the high decomposition temperatures of 4a-i ranging from 289 °C to 450 °C indicated that these compounds showed good thermal stability. On the basis of their excellent photophysical and thermal properties, the electroluminescence performance of 4f were further evaluated with a maximum EQE of 3.14% and CIE coordinate (0.16, 0.08), which could be utilized as promising novel blue organic light-emitting material.