title: 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.
abstract: 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 (1)H 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.
authors.affiliation: Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda, Chiba, Japan. shinaoki@rs.noda.tus.ac.jp
authors.forename: Shin
authors.initials: S
authors.lastname: Aoki
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Shiori
authors.initials: S
authors.lastname: Ogura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ohwada
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Hisamatsu
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Moromizato
authors.forename: Motoo
authors.initials: M
authors.lastname: Shiro
authors.forename: Masanori
authors.initials: M
authors.lastname: Kitamura
mesh_terms: D000107:Acetylation; D018360:Crystallography, X-Ray; D003500:Cyclization; D054879:Halogenation; D007495:Iridium / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010777:Photochemistry; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry*; D013053:Spectrophotometry; D013237:Stereoisomerism
chemical_list: D009942:Organometallic Compounds; D011725:Pyridines; D007495:Iridium