Facially Coordinated, Tris-bidentate Purin-8-ylidene Ir(III) Complexes for Blue Electrophosphorescence and Hyperluminescence

Homoleptic fac-substituted Ir(III) carbene complexes exhibit higher emission energy (in purple region) in comparison to their mer-counterparts, prohibiting them to be employed in fabrication of blue emissive organic light-emitting diode (OLED) devices. Now, the design of two distinctive CF₃-functionalized purin-8-ylidene Ir(III) complexes, namely, m- and f-CF₃ and m- and f-PhCF₃, from new carbene motifs, 9-(3-(tert-butyl)phenyl)-7-isopropyl-2-(trifluoromethyl)-7,9-dihydro-8H-purin-8-ylidene (A4) and 9-(3-(tert-butyl)phenyl)-7-methyl-6-phenyl-2-(trifluoromethyl)-7,9-dihydro-8H-purin-8-ylidene (B7), having notably stabilized lowest unoccupied molecular orbital energy levels is reported. Hence, the corresponding f-isomers f-CF₃ and f-PhCF₃ exhibit electroluminescence with peak max. at 478 and 495 nm, max. external quantum efficiencies (EQEs) of 10.4% and 12.8%, respectively. By using f-CF₃ as assistant dopant to convey its energy to terminal emitter t-DABNA and from f-PhCF₃ donor to 2TCzBN acceptor, two hyper-OLED devices are successfully fabricated, giving high max. EQE of 23.8%, full-width at half-maximum (FWHM) of 30 nm, and CIE_x,y coordinate of (0.13, 0.14) for the acceptor t-DABNA, and max. EQE of 24.0%, FWHM of 28 nm, and CIE_x,y of (0.11, 0.36) for the acceptor 2TCzBN, confirming the advantages of these purin-8-ylidene Ir(III) complexes.