Regioselective aromatic substitution reactions of cyclometalated Ir(III) complexes: Synthesis and photochemical properties of substituted Ir(III) complexes that exhibit blue, green, and red color luminescence emission

摘要

In this manuscript, the regioselective halogenation, nitration, formylation, and acylation of Ir(tpy)_3 and Ir(ppy)_3 (tpy = 2-(4/-tolyl)pyridine and ppy = 2-phenylpyridine) and the subsequent conversions are described. During attempted bromination of the three methyl groups in fac-Ir(tpy)_3 using N-bromosuccinimide (NBS) and benzoyl peroxide (BPO), three protons at the 5'-position (p-position with respect to the C-Ir bond) of phenyl rings in tpy units were substituted by Br, as confirmed by 1H nMr spectra, mass spectra, and X-ray crystal structure analysis. It is suggested that such substitution reactions of Ir complexes proceed via an ionic mechanism rather than a radical mechanism. UV-vis and luminescence spectra of the substituted Ir(III) complexes are reported. The introduction of electron-withdrawing groups such as CN and CHO groups at the 5'-position of tpy induces a blue shift of luminescence emission to about 480 nm, and the introduction of electron-donating groups such as an amino group results in a red shift to about 600 nm. A reversible change of emission for the 5'-amino derivative of Ir(tpy)_3,Ir(atpy)_3, between red and green occurs upon protonation and deprotonation.