Synthesis and luminescent properties of spiroacridine-imidazole derivatives

Abstract

Two new spiroacridine-imidazole derivatives (SAF-BI and SAF-PI) with narrow deep-blue emission spectrum were synthesized by incorporating a spiroacridine donor unit with benzimidazole and phenanthroimidazole acceptors via the Buchwald–Hartwig cross coupling reaction, respectively. Their photophysical and electrochemical properties, based on theoretical calculations and experimental measurements, as well as thermal stabilities and organic electroluminescence properties were systematically investigated. These compounds exhibited a strong deep-blue emission (ca. 410 nm) with full-width at half maximum (FWHM) of less than 55 nm in toluene solution and a blue emission (ca. 440 nm) in solid films, and the theoretical singlet–triplet energy splittings (ΔE_ST) were calculated to be 0.05 eV for SAF-BI and 0.38 eV for SAF-PI. The doped devices with a structure of ITO/PEDOT:PSS (30 nm)/mCBP:SAF derivative (x wt%) (30 nm)/BmPyPB (35 nm)/Liq (2 nm)/Al (200 nm) were fabricated using solution-processed emitting layers to investigate their electroluminescence (EL) performances, in which the doped devices of SAF-BI exhibited a deep-blue emission with an EQE_max of 1.81% and an L_max of 352 cd m⁻², and its Commission Internationale de l′Eclairage (CIE) coordinates were (0.17, 0.07).