Is the 3MLCT the only photoreactive state of polypyridyl complexes?
By means of Delta-SCF and time-dependent density functional theory (DFT) calculations on [Ru(LL)3]2+ (LL = bpy = 2,2'-bipyridyl or bpz = 2,2' -bipyrazyl) complexes, we have found that emission of these two complexes could originate from two metal-to-ligand charge-transfer triplet states (3MLCT) that are quasi-degenerate and whose symmetries are D3 and C2. These two states are true minima. Calculated absorption and emission energies are in good agreement with experiment; the largest error is 0.14 eV, which is about the expected accuracy of the DFT calculations. For the first time, an optimized geometry for the metal-centered (MC) state is proposed for both of these complexes, and their energies are found to be almost degenerate with their corresponding 3MLCT states. These [RuII(LL)(eta1-LL)2]2+ MC states have two vacant coordination sites on the metal, so they may react readily with their environment. If these MC states are able to de-excite by luminescence, the associated transition (ca. 1 eV) is found to be quite different from those of the 3MLCT states (ca. 2 eV).
Alary
F
F
Laboratoire de chimie et physique quantiques, IRSAMC, Université Paul Sabatier, Toulouse Cedex, France. fabienne.alary@irsamc.ups-tlse.fr
Heully
J-L
JL
Bijeire
L
L
Vicendo
P
P
D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*
D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D012428:Ruthenium