title: Photophysics of pyridylporphyrin Ru(II) adducts: heavy-atom effects and intramolecular decay pathways.
abstract: Eight adducts between different pyridylporphyrins and ruthenium complexes, MPyP[RuCl(2)(DMSO)(2)(CO)], c-DPyP[RuCl(2)(DMSO)(2)(CO)](2), TrPyP[RuCl(2)(DMSO)(2)(CO)](3), TPyP[RuCl(2)(DMSO)(2)(CO)](4), (MPyP)(2)[RuCl(2)(DMSO)(2)], [c-DPyP[RuCl(2)(DMSO)(2)]](2), MPyP[RuCl(2)(CO)(3)], and [c-DPyP[RuCl(2)(CO)(2)]](2), have been investigated. The results show that in all the adducts the porphyrin singlet is quenched, to a greater or lesser extent, relative to the parent-free molecule. This study provides insight into the mechanisms of singlet quenching in the adducts. Two mechanisms for singlet quenching, both related to the "heavy-atom effect" of the ruthenium center and experimentally distinguishable by transient spectroscopy, are examined. Enhanced intersystem crossing within the porphyrin chromophore is demonstrated for the series of adducts MPyP[RuCl(2)(DMSO)(2)(CO)], c-DPyP[RuCl(2)(DMSO)(2)(CO)](2), TrPyP[RuCl(2)(DMSO)(2)(CO)](3), and TPyP[RuCl(2)(DMSO)(2)(CO)](4), where a nice correlation is observed between the magnitude of the effect and the number of ruthenium centers attached to the pyridylporphyrin chromophore. Singlet-triplet energy transfer from the pyridylporphyrin chromophore to the ruthenium center(s) is an additional efficient quenching channel for adducts containing ruthenium centers with weak field ligands and low triplet energies, such as (MPyP)(2)[RuCl(2)(DMSO)(2)] and [c-DPyP[RuCl(2)(DMSO)(2)]](2).
authors: Dipartimento di Scienze Chimiche, Università di Trieste, Trieste 34127, Italy.
authors: A
authors: A
authors: Prodi
authors: C J
authors: CJ
authors: Kleverlaan
authors: M T
authors: MT
authors: Indelli
authors: F
authors: F
authors: Scandola
authors: E
authors: E
authors: Alessio
authors: E
authors: E
authors: Iengo
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008665:Metalloporphyrins / Q000138:chemical synthesis* / Q000737:chemistry*; D010777:Photochemistry; D010782:Photolysis; D012428:Ruthenium / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008024:Ligands; D008665:Metalloporphyrins; D012428:Ruthenium