In the presence of a bidentate chelate containing two
convergent nitrile groups, Ru(phen)2L2+ (L =
sterically hindering aromatic diimine ligand; phen = 1,10-phenanthroline)
undergoes a photochemical reaction leading to quantitative replacement of
the diimine by the bis-nitrile ligand; the reverse reaction takes place
upon heating, also quantitatively.