Broad HOMO-LUMO gap tuning through the coordination of a single phosphine, aminophosphine or phosphite onto a Ru(tpy)(bpy)2+ core.
The synthesis of new ruthenium(II) terpyridine bipyridine complexes bearing a phosphorus(III) ligand is presented. The steric and electronic properties of the phosphorus ligand were varied using aminophosphines, alkyl and aryl phosphites and the bulky tri(isopropyl)phosphine. All complexes were characterized by multi-nuclear NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The electronic properties of the complexes were probed by cyclic voltammetry, absorption and luminescence spectroscopy. The complexes do not show luminescence at room temperature, whereas at 77 K in an alcoholic matrix, emission is observed in the range 600-650 nm with lifetimes of 3.5-5.5 micros, originating from 3MLCT states. The MLCT transition spans over 65 nm, which corresponds to a variation of 0.4 eV in the HOMO-LUMO gap. The oxidation potential of the ruthenium varies over a broad range of 290 mV, from +1.32 V vs. SCE with L = PiPr3 to +1.61 V vs. SCE with L = P(OPh)3. This range is unprecedented upon the variation of a single monodentate ligand coordinated by the same heteroatom in the same oxidation and charge states. This work underlines the specific capacity of phosphorus in bringing up a large variety of electronic properties by changing its substituents.
Laboratoire de Chimie de Coordination du CNRS, UPR 8241, 205 route de Narbonne, 31077 Toulouse Cedex 4, France.
Isabelle M
IM
Dixon
Emilie
E
Lebon
Gilles
G
Loustau
Pierre
P
Sutra
Laure
L
Vendier
Alain
A
Igau
Alberto
A
Juris