Iridium(III) Complexes Bearing a Formal Tetradentate Coordination Chelate: Structural Properties and Phosphorescence Fine-Tuned by Ancillaries

摘要

Synthesis of the multidentate coordinated chelate N3C-H-2, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation of Ir(III) metal complexes bearing a N3C chelate in the tridentate (kappa(3)), tetradentate (kappa(4)), and pentadentate (kappa(5)) modes was executed en route from two nonemissive dimer intermediates [Ir(kappa(3)-N3CH)Cl-2](2) (1) and [Ir(kappa(4)-N3C)Cl](2) (2). Next, a series of mononuclear Ir(III) complexes with the formulas [Ir(kappa(4)-N3C)Cl(py)] (3), [Ir(kappa(4)-N3C)Cl(dmap)] (4), [Ir(kappa(4)-N3C)-Cl(mpzH)] (5), and [Ir(kappa(4)-N3C)Cl(dmpzH)] (6), as well as diiridium complexes [Ir-2(kappa(5)-N3C)-(mpz)(2)(CO)(H)(2)] (7) and [Ir-2(kappa(5)-N3C)-(dmpz)(2)(CO)(H)(2)] (8), were obtained upon treatment of dimer 2 with pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3, 5, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations. Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the development of highly efficient iridium complexes for OLED applications.