Synthesis and pH-sensitive luminescence of bis-terpyridyl iridium(III) complexes incorporating pendent pyridyl groups.

Arm, K.J.; Leslie, W.; Williams, J.A.G.

Abstract

A series of iridium(III) bis-terpyridine complexes have been prepared which incorporate pendent pyridyl groups at the 4′-positions of one or both of the terpyridine (tpy) ligands. These include: three mutually isomeric homoleptic complexes, in which the nitrogen atom of the pendent pyridyl is para, meta or ortho to the C–C bond to the terpyridine; their heteroleptic analogues in which the second ligand is 4′-tolyl-terpyridine (ttpy); analogous complexes of the new ligand, 4′-(2,6-dimethylpyrid-4-yl)-terpyridine; and related complexes incorporating an additional phenyl ring interposed between the terpyridine and the pendent pyridyl group. All of the complexes are luminescent in air-equilibrated aqueous solution at room temperature. The homoleptic complexes display structured emission resembling that of unsubstituted [Ir(tpy)2]3+, with luminescence lifetimes of around 1 μs under these conditions. The heteroleptic analogues give broader, red-shifted emission spectra, similar to that of [Ir(ttpy)2]3+, indicating that emission in these complexes arises primarily from a lower-energy excited state associated with the 4′-tolyl-terpyridine ligand. A further red-shift for the complexes incorporating the additional phenyl ring suggests that the emissive state involves the more conjugated phenylpyridyl-appended ligand in these cases. The luminescence of all of the heteroleptic complexes investigated, except the meta-substituted system, is sensitive to the protonation state of the pendent pyridyl group, and the structure of the ligand can have a significant influence on both the magnitude of the response and the pH region over which it occurs.

Citation

Arm, K., Leslie, W., & Williams, J. (2006). Synthesis and pH-sensitive luminescence of bis-terpyridyl iridium(III) complexes incorporating pendent pyridyl groups. Inorganica Chimica Acta, 359(4), 1222-1232. https://doi.org/10.1016/j.ica.2005.09.021

• Journal Article Type: Article
• Acceptance Date: Sep 16, 2005
• Online Publication Date: Oct 25, 2005
• Publication Date: 2006-03
• Journal: Inorganica Chimica Acta
• Print ISSN: 0020-1693
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 359
• Issue: 4
• Pages: 1222-1232
• DOI: https://doi.org/10.1016/j.ica.2005.09.021