Two iridium(III) complexes displaying for one a high HOMO-LUMO gap and for the other a weaker gap were linked in a controlled and logical manner to closo-p-carborane spacers. The bridging ligand is composed of 5-ethynyl-2,2′-bipyridine units, and the peripherical Ir-ligands are orthometalated 2′,4′-difluoro-2-phenylpyridine (dfppy) (λabs at 400 nm for the "Ir(dfppy)2(bpy′ )") for the energy donor fragment and dibenzo[a,c]phenazine (dbpz) (λabs at 525 nm for "Ir(dbpz)2(bpy′) ") for the energy acceptor fragment.Redox, spectroscopic, and photophysical properties for models and the donor-carborane-acceptor complex were determined. Efficient energy transfer from the "Ir(dfppy)2(bpy′) " moiety to the "Ir(dbpz)2(bpy′)" fragment is occurring with a rate constant of 3.3 × 108 s-1 despite weak electronic coupling through the inert p-carborane spacer. From flash photolysis experiments it is shown that, by excitation of the donor, a low lying triplet state localized on the acceptor bridging ligand side is formed which decays by conversion to the 3MLCT of the acceptor fragment which phosphoresces at 644 nm. © 2013 American Chemical Society.

P-carborane-bridged bipyridine ligands for energy transfer between two iridium centers

INDELLI, Maria Teresa;
2013

Abstract

Two iridium(III) complexes displaying for one a high HOMO-LUMO gap and for the other a weaker gap were linked in a controlled and logical manner to closo-p-carborane spacers. The bridging ligand is composed of 5-ethynyl-2,2′-bipyridine units, and the peripherical Ir-ligands are orthometalated 2′,4′-difluoro-2-phenylpyridine (dfppy) (λabs at 400 nm for the "Ir(dfppy)2(bpy′ )") for the energy donor fragment and dibenzo[a,c]phenazine (dbpz) (λabs at 525 nm for "Ir(dbpz)2(bpy′) ") for the energy acceptor fragment.Redox, spectroscopic, and photophysical properties for models and the donor-carborane-acceptor complex were determined. Efficient energy transfer from the "Ir(dfppy)2(bpy′) " moiety to the "Ir(dbpz)2(bpy′)" fragment is occurring with a rate constant of 3.3 × 108 s-1 despite weak electronic coupling through the inert p-carborane spacer. From flash photolysis experiments it is shown that, by excitation of the donor, a low lying triplet state localized on the acceptor bridging ligand side is formed which decays by conversion to the 3MLCT of the acceptor fragment which phosphoresces at 644 nm. © 2013 American Chemical Society.
Indelli, Maria Teresa; T., Bura; R., Ziessel
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1828101
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