ja8b02416_si_001.pdf (1.26 MB)
Highly Luminescent Cyclometalated Iridium Complexes Generated by Nucleophilic Addition to Coordinated Isocyanides
journal contribution
posted on 2018-04-27, 00:00 authored by Hanah Na, Thomas S. TeetsIn this work, we
report a new class of blue-emitting cyclometalated
iridium complexes supported by acyclic diaminocarbene (ADC) ancillary
ligands. These neutral, tris-chelated complexes are not obtainable
via traditional synthesis routes and instead are generated through
metal-mediated nucleophilic addition to a metal-bound isocyanide,
which is followed by orthometalation of the ADC under mild conditions.
Importantly, four of the variants exhibit efficient phosphorescence
when immobilized in PMMA matrix, achieving quantum yields of 79% for
blue emitters with a 2-(2,4-difluorophenyl)pyridine (F2ppy) C^N ligand and 30–37% for orange emitters with a 2-phenylbenzothiazole
(bt) C^N ligand. Electrochemical studies demonstrate significantly higher-lying
HOMO levels in the ADC complexes relative to the NHC analogues, a
phenomenon that results in enhanced charge-transfer character in the
excited states of the ADC complexes. This study demonstrates that
ADC ancillary ligands not only give rise to new structures for Ir(III)-based
phosphorescent emitters but also are promising targets for use in
light-emitting devices and other thin-film optical applications.