Luminescent cyclometallated iridium(III) bis(quinolylbenzaldehyde) diimine complexes--synthesis, photophysics, electrochemistry, protein cross-linking properties, cytotoxicity and cellular uptake.
Four new luminescent cyclometallated iridium(III) bis(quinolylbenzaldehyde) diimine complexes [Ir(qba)(2)(N⁁N)](PF(6)) (Hqba = 4-(2-quinolyl)benzaldehyde, N⁁N = 2,2'-bipyridine, bpy (1); 1,10-phenanthroline, phen (2); 3,4,7,8-tetramethyl-1,10-phenanthroline, Me(4)-phen (3); 4,7-diphenyl-1,10-phenanthroline, Ph(2)-phen (4)) have been synthesised and characterised, and their electronic absorption, emission and electrochemical properties investigated. The X-ray crystal structures of complexes 1 and 2 have been determined. Upon irradiation, complexes 1-4 exhibited intense and long-lived orange-yellow emission in fluid solutions at 298 K and in alcohol glass at 77 K. The emission has been assigned to a triplet intra-ligand ((3)IL) excited state associated with the qba ligand, probably with mixing of some triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Ir) →π*(qba)) character. Reductive amination reactions of complexes 1-4 with the protein bovine serum albumin (BSA) afforded the bioconjugates 1-BSA-4-BSA, respectively. Upon photoexcitation, these bioconjugates displayed intense and long-lived (3)MLCT (dπ(Ir) →π*(N⁁C)) emission in aqueous buffer at 298 K. The cross-linked nature of the Ir-BSA bioconjugates has been verified by SDS-PAGE. Additionally, the cytotoxicity of the complexes towards human cervix epithelioid carcinoma (HeLa) cells has been examined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assays, and the cellular uptake of complex 4 has been investigated by laser-scanning confocal microscopy and flow cytometry.
Lee
Pui-Kei
PK
Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, People's Republic of China.
Liu
Hua-Wei
HW
Yiu
Shek-Man
SM
Louie
Man-Wai
MW
Lo
Kenneth Kam-Wing
KK
D015082:2,2'-Dipyridyl / Q000737:chemistry; D000818:Animals; D001547:Benzaldehydes / Q000737:chemistry*; D002417:Cattle; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D003432:Cross-Linking Reagents / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D006367:HeLa Cells; D006801:Humans; D007495:Iridium / Q000737:chemistry*; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013696:Temperature
D001547:Benzaldehydes; D056831:Coordination Complexes; D003432:Cross-Linking Reagents; D009942:Organometallic Compounds; D010618:Phenanthrolines; C027290:3,4,7,8-tetramethyl-1,10-phenanthroline; D012710:Serum Albumin, Bovine; D007495:Iridium; D015082:2,2'-Dipyridyl; C032175:benzaldehyde; C025205:1,10-phenanthroline