Blue Phosphorescence and Hyperluminescence Generated from Imidazo[4,5‐b]pyridin‐2‐ylidene‐Based Iridium(III) Phosphors

Abstract

Four isomeric, homoleptic iridium(III) metal complexes bearing 5-(trifluoromethyl)imidazo[4,5-b]pyridin-2-ylidene and 6-(trifluoromethyl)imidazo[4,5-b]pyridin-2-ylidene-based cyclometalating chelates are successfully synthesized. The meridional isomers can be converted to facial isomers through acid induced isomerization. The m-isomers display a relatively broadened and red-shifted emission, while f-isomers exhibit narrowed blue emission band, together with higher photoluminescent quantum yields and reduced radiative lifetime relative to the mer-counterparts. Maximum external quantum efficiencies of 13.5% and 22.8% are achieved for the electrophosphorescent devices based on f-tpb1 and m-tpb1 as dopant emitter together with CIE coordinates of (0.15, 0.23) and (0.22, 0.45), respectively. By using f-tpb1 as the sensitizing phosphor and t-DABNA as thermally activated delayed fluorescence (TADF) terminal emitter, hyperluminescent OLEDs are successfully fabricated, giving high efficiency of 29.6%, full width at half maximum (FWHM) of 30 nm, and CIE coordinates of (0.13, 0.11), confirming the efficient Förster resonance energy transfer (FRET) process.

Gold Nanocluster Probe-Based Electron-Transfer-Mediated Electrochemiluminescence Sensing Strategy for an Ultrasensitive Copper Ion Detection

“…The highest energy occupied molecular orbital (HOMO)–lowest energy unoccupied molecular orbital (LUMO) energy levels of Met-Cu 2+ were further studied to demonstrate the ET-ECL mechanism using cyclic voltammetry and spectrophotometry. The following equations were applied to calculate the HOMO–LUMO energy levels. , E HOMO = prefix− ( E onset ox − E Fc / Fc + + 4.8 ) eV E LUMO = E HOMO + E normalg where E onset ox is the oxidation onset potential and E Fc/Fc + is related to the onset potential of the oxidation and reducing peak of the ferrocene couple (Fc/Fc + ). E Fc/Fc + was determined to be 0.58 eV (Figure S6), and E onset ox of Met-Cu 2+ was determined to be 0.84 V (Figure S7).…”

The acid-mediated isomerization of iridium(iii) complexes with cyclometalated NHC ligands: kinetic vs. thermodynamic control

“…The results obtained with Ir(tzp) 3 indicate that conformationally restricted carbene ligands are not suited. However, there are numerous publications about Ir(C^C:) 3 complexes with ligands similar to pmb and pbb, 3–20 and we anticipate that some of them are also susceptible to an acid/base-mediated fac → mer isomerization.…”

“…2 Blue emitters are important for organic light-emitting devices (OLEDs), and Ir(C^C:) 3 complexes have been widely investigated in this context. 3,4–18…”

“…The preparation of the ligand precursors can be demanding, and the final metalation step often gives moderate yields. 2–20 In addition, the complexes are typically obtained as a mixture of fac and mer isomers.…”

“…The methodology can be used for other Ir(C^C:) 3 complexes, as reported in a series of recent publications. 4,7,9,10,19 a …”