Cross-couplings in the elaboration of luminescent bis-terpyridyl iridium complexes: the effect of extended or inhibited conjugation on emission

Dalton Trans. 2004 Feb 21:(4):623-31. doi: 10.1039/b313638h. Epub 2004 Jan 26.

Abstract

The utility of Suzuki cross-coupling methodology for the in situ elaboration of bromo-functionalised bis-terpyridyl iridium(III) complexes has been explored. The complex [Ir(tpy)(tpy-phi-Br)]3+ [tpy-phi-Br = 4'-(4-bromophenyl)-2,2':6',2''-terpyridine] undergoes palladium-catalysed cross-coupling with aryl boronic acids to yield biaryl-substituted complexes directly. The biphenyl and 4-cyanobiphenyl-substituted products display relatively intense, long-lived (tau > 100 mus) yellow emission in degassed aqueous solution at room temperature, assigned to a 3pi-pi* state. A 4-aminobiphenyl-substituted analogue displays an additional low energy absorbance band, attributed to an intraligand charge-transfer (ILCT) excited state, and is scarcely emissive under the same conditions. The iridium(III) complex of 4'-mesityl-terpyridine is also reported. Its emission is much shorter-lived, with a spectral profile resembling that of unsubstituted [Ir(tpy)2]3+, confirming the need for the attainment of a roughly coplanar geometry for stabilisation of the 3pi-pi* excited state.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Absorption
  • Crystallography, X-Ray
  • Heterocyclic Compounds, 3-Ring / chemistry
  • Iridium / chemistry*
  • Luminescence
  • Models, Molecular
  • Molecular Conformation
  • Organometallic Compounds / chemical synthesis
  • Organometallic Compounds / chemistry*
  • Pyridines / chemistry*

Substances

  • Heterocyclic Compounds, 3-Ring
  • Organometallic Compounds
  • Pyridines
  • Iridium