title: Ru(II) complexes of new tridentate ligands: unexpected high yield of sensitized 1O2.
abstract: Ru(II) complexes possessing new tridentate ligands with extended pi systems, pydppx (3-(pyrid-2'-yl)-11,12-dimethyl-dipyrido[3,2-a:2',3'-c]phenazine) and pydppn (3-(pyrid-2'-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene), were synthesized and characterized. The investigation of the photophysical properties of the series [Ru(tpy)(n)(L)(2-n)](2+) (L = pydppx, pydppn, n = 0-2) reveals markedly different excited state behavior among the complexes. The Ru(II) complexes possessing the pydppx ligand are similar to the pydppz (3-(pyrid-2'-yl)dipyrido[3,2-a:2',3'-c]phenazine) systems, with a lowest energy metal-to-ligand charge transfer excited state with lifetimes of 1-4 ns. In contrast, the lowest energy excited state in the [Ru(tpy)(n)(pydppn)(2-n)](2+) (n = 0, 1) complexes is a ligand-centered (3)pipi* localized on the pydppn ligand with lifetimes of approximately 20 mus. The [Ru(tpy)(n)(pydppn)(2-n)](2+) (n = 0, 1) complexes are able to generate (1)O(2) with approximately 100% efficiency. Both [Ru(tpy)(pydppn)](2+) and [Ru(pydppn)(2)](2+) bind to DNA, however, the former exhibits a approximately 10-fold greater DNA binding constant than the latter. Efficient DNA photocleavage is observed for [Ru(tpy)(pydppn)](2+), owing to its ability to photosensitize the production of (1)O(2), which can mediate the reactivity. Such high quantum yields of (1)O(2) photosensitization of transition metal complexes may be useful in the design of new systems with long-lived excited states for photodynamic therapy.
authors.affiliation: Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Liu
authors.forename: Richard
authors.initials: R
authors.lastname: Hammitt
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Lutterman
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Joyce
authors.forename: Randolph P
authors.initials: RP
authors.lastname: Thummel
authors.forename: Claudia
authors.initials: C
authors.lastname: Turro
mesh_terms: D000042:Absorption; D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry; D053837:DNA Cleavage / Q000187:drug effects / Q000528:radiation effects; D004563:Electrochemistry; D008024:Ligands; D009279:Naphthacenes / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D010619:Phenazines / Q000737:chemistry*; D010778:Photochemotherapy; D010782:Photolysis / Q000187:drug effects / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D012428:Ruthenium / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013997:Time Factors
chemical_list: D008024:Ligands; D009279:Naphthacenes; D009942:Organometallic Compounds; D010619:Phenazines; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; D012428:Ruthenium; D004247:DNA; C487736:naphthacene