Synthesis, Photophysical and Electrochemical Properties, and Biological Labeling Studies of Cyclometalated Iridium(III) Bis(pyridylbenzaldehyde) Complexes: Novel Luminescent Cross‐Linkers for Biomolecules
- 16 January 2003
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 9 (2) , 475-483
- https://doi.org/10.1002/chem.200390050
Abstract
We report the synthesis, characterization, photophysical, and electrochemical properties of a series of luminescent cyclometalated iridium(III) complexes containing two aldehyde functional groups [Ir(pba)2(N–N)](PF6) (Hpba=4‐(2‐pyridyl)benzaldehyde; N–N=2,2′‐bipyridine, bpy (1), 1,10‐phenanthroline, phen (2), 3,4,7,8‐tetramethyl‐1,10‐phenanthroline, 3,4,7,8‐Me4‐phen (3), 4,7‐diphenyl‐1,10‐phenanthroline, 4,7‐Ph2‐phen (4)). The X‐ray crystal structure of complex 1 has been investigated. Upon photoexcitation, complexes 1–4 exhibit intense and long‐lived emission in fluid solutions at 298 K and in low‐temperature glass. The luminescence is assigned to a triplet intra‐ligand (3IL) excited state associated with the pba− ligand, probably with mixing of some triplet metal‐to‐ligand charge‐transfer (3MLCT) (dπ(Ir)→π*(pba−)) character. Since each of these complexes possesses two aldehyde groups, which can react with the primary amine groups of biomolecules to form stable secondary amines after reductive amination, we have investigated the possibility of these complexes as novel luminescent cross‐linkers for biological substrates. L‐Alanine has been labeled with complexes 1–4 to give the luminescent bioconjugates 1‐(Ala)2–4‐(Ala)2. These conjugates show strong photoluminescence with long emission lifetimes under ambient conditions. On the basis of the emission energy trend, the excited state of these luminescent bioconjugates is likely to bear a high parentage of 3MLCT (dπ(Ir)→π*(N–N)) character. In addition, the glycoprotein avidin (Av) has also been conjugated with complexes 1–4 to give the bioconjugates 1‐Av–4‐Av. Upon photoexcitation, these bioconjugates also display intense and long‐lived 3MLCT (dπ(Ir)→π*(N–N)) emission in aqueous buffer at 298 K. Furthermore, a heterogeneous competitive assay for biotin has been developed using 2‐Av and biotinylated microspheres. We have shown that complexes 1–4 represent a new class of multicolor luminescent cross‐linkers for biomolecular species.Keywords
This publication has 65 references indexed in Scilit:
- Iridium(III) bis-terpyridine complexes incorporating pendent N-methylpyridinium groups: luminescent sensors for chloride ions †J. Chem. Soc., Dalton Trans., 2000
- SIR97: a new tool for crystal structure determination and refinementJournal of Applied Crystallography, 1999
- Functional Elements in Molecular Chaperone α-Crystallin: Identification of Binding Sites in αB-CrystallinBiochemical and Biophysical Research Communications, 1997
- Spatial Proximity of Cys113, Cys172, and Cys422 in the Metalloactivation Domain of the ArsA ATPasePublished by Elsevier ,1996
- Tetranuclear Bimetallic Complexes of Ruthenium, Osmium, Rhodium, and Iridium. Synthesis, Absorption Spectra, Luminescence, and Electrochemical PropertiesJournal of the American Chemical Society, 1994
- Synthesis and characterizations of cyclometalated iridium(III) solvento complexesInorganic Chemistry, 1994
- Investigation of the photochemical, electrochemical, and spectroelectrochemical properties of an iridium(III)/ruthenium(II) mixed-metal complex bridged by 2,3,5,6-tetrakis(2-pyridyl)pyrazineInorganic Chemistry, 1993
- Conformational changes in the foot protein of the sarcoplasmic reticulum assessed by site-directed fluorescent labelingBiochemistry, 1992
- A new synthetic route to the preparation of a series of strong photoreducing agents: fac-tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridinesInorganic Chemistry, 1991
- A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye bindingAnalytical Biochemistry, 1976