Photochemical Expulsion of the Neutral Monodentate Ligand L in
Ru(Terpy*)(Diimine)(L)2+: A Dramatic Effect of the Steric Properties of
the Spectator Diimine Ligand
posted on 2004-12-27, 00:00authored bySylvestre Bonnet, Jean-Paul Collin, Jean-Pierre Sauvage, Emma Schofield
A series of photoreactive complexes of the type Ru(terpy*)(N−N)(L)2+, where terpy* is 4‘-(3,5-ditertiobutylphenyl)-2,2‘:6‘,2‘ ‘-terpyridine, N−N is the bidentate chelate phen or dmp (phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline), and L is the monodentate ligand dms, MeBN, or MeOBN (dms = dimethyl sulfide, MeBN =
2,6-dimethyl benzonitrile, MeOBN = 2,6-dimethoxybenzonitrile), has been synthesized and fully characterized by
proton NMR spectroscopy, electrospray mass spectrometry, and UV−vis spectroscopy. The X-ray structures of
four complexes were also obtained. In neat pyridine, the quantum yields for the photosubsitution of L by pyridine
were measured and showed dramatic variations depending on the steric interactions between the spectator bidentate
ligand and the leaving monodentate ligand L. The use of dmp instead of phen multiplied the photosubstitution
efficiency by a factor of 20−50, depending on L. This effect could be qualitatively correlated to the distortions
observed in the X-ray structures of the corresponding complexes. The highly distorted structure of Ru(terpy*)(dmp)(dms)(PF6)2 showed a very high photosubsitution quantum yield φ = 0.36 in neat pyridine. The high
photoreactivity of some of the compounds makes them particularly promising as components of future light-driven
molecular machines.