title: New luminescent cyclometalated iridium(III) diimine complexes as biological labeling reagents.
abstract: We report the synthesis, characterization, and photophysical and electrochemical properties of thirty luminescent cyclometalated iridium(III) diimine complexes [Ir(N-C)(2)(N-N)](PF(6)) (HN-C = 2-phenylpyridine, Hppy; 2-(4-methylphenyl)pyridine, Hmppy; 3-methyl-1-phenylpyrazole, Hmppz; 7,8-benzoquinoline, Hbzq; 2-phenylquinoline, Hpq; N-N = 4-amino-2,2'-bipyridine, bpy-NH(2); 4-isothiocyanato-2,2'-bipyridine, bpy-ITC; 4-iodoacetamido-2,2'-bipyridine, bpy-IAA; 5-amino-1,10-phenanthroline, phen-NH(2); 5-isothiocyanato-1,10-phenanthroline, phen-ITC; 5-iodoacetamido-1,10-phenanthroline, phen-IAA). The X-ray crystal structure of [Ir(mppz)(2)(bpy-NH(2))](PF(6)) has also been investigated. Upon irradiation, all the complexes display intense and long-lived luminescence under ambient conditions and in 77-K glass. On the basis of the photophysical and electrochemical data, the emission of most of these complexes is assigned to an excited state of predominantly triplet metal-to-ligand charge-transfer ((3)MLCT) (dpi(Ir) --> pi(N-N)) character. In some cases, triplet intraligand ((3)IL) (pi --> pi)(N-N or N-C(-)) excited states have also been identified. In view of the specific reactivity of the isothiocyanate and iodoacetamide moieties toward the primary amine and sulfhydryl groups, respectively, we have labeled various biological molecules with a selection of these luminescent iridium(III) complexes. The photophysical properties of the luminescent conjugates have been investigated. In addition, a heterogeneous assay for digoxin has also been designed on the basis of the recognition of biotinylated anti-digoxin by avidin labeled with one of the luminescent iridium(III) complexes.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, P. R. China. bhkenlo@cityu.edu.hk
authors.forename: Kenneth Kam-Wing
authors.initials: KK
authors.lastname: Lo
authors.forename: Chi-Keung
authors.initials: CK
authors.lastname: Chung
authors.forename: Terence Kwok-Ming
authors.initials: TK
authors.lastname: Lee
authors.forename: Lok-Hei
authors.initials: LH
authors.lastname: Lui
authors.forename: Keith Hing-Kit
authors.initials: KH
authors.lastname: Tsang
authors.forename: Nianyong
authors.initials: N
authors.lastname: Zhu
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007202:Indicators and Reagents; D007495:Iridium / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D007202:Indicators and Reagents; D007495:Iridium