title: Photoinduced processes within compact dyads based on triphenylpyridinium-functionalized bipyridyl complexes of ruthenium(II).
abstract: As an alternative to conventional charge-separation functional molecular models based on long-range ET within redox cascades, a "compact approach" has been examined. To this end, spacer elements usually inserted between main redox-active units within polyad systems have been removed, allowing extended rigidity but at the expense of enhanced intercomponent electronic communication. The molecular assemblies investigated here are of the P-(theta (1))-A type, where the theta (1) twist angle is related to the degree of conjugation between the photosensitizer (P, of {Ru(bpy)(3)}(2+) type) and the electron-acceptor (A). 4-N- and 4-N-,4'-N-(2,4,6-triphenylpyridinio)-2,2'-bipyridine ligands (A(1)-bpy and A(2)-bpy, respectively) have been synthesized to give complexes with Ru(II), 1-bpy and 2-bpy, respectively. Combined solid-state analysis (X-ray crystallography), solution studies ((1)H NMR, cyclic voltammetry) and computational structural optimization allowed verifying that theta (1) angle approaches 90 degrees within 1-bpy and 2-bpy in solution. Also, anticipated existence of strong intercomponent electronic coupling has been confirmed by investigating electronic absorption properties and electrochemical behavior of the compounds. The capability of 1-bpy and 2-bpy to undergo PET process was evaluated by carrying out their photophysical study (steady state emission and time-resolved spectroscopy at both 293 and 77 K). The conformational dependence of photoinduced processes within P-(theta (1))-A systems has been established by comparing the photophysical properties of 1-bpy (and 2-bpy) with those of an affiliated species reported in the literature, 1-phen. A complementary theoretical analysis (DFT) of the change of spin density distribution within model [1-bpy(theta (1))](-) mono-reduced species as a function of theta (1) has been undertaken and the possibility of conformationally switching emission properties of P was derived.
authors.affiliation: Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques (CNRS UMR 8601), Université René Descartes, Paris, France. philippe.laine@univ-paris5.fr
authors.forename: Philippe P
authors.initials: PP
authors.lastname: Lainé
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ciofini
authors.forename: Philippe
authors.initials: P
authors.lastname: Ochsenbein
authors.forename: Edmond
authors.initials: E
authors.lastname: Amouyal
authors.forename: Carlo
authors.initials: C
authors.lastname: Adamo
authors.forename: Fethi
authors.initials: F
authors.lastname: Bedioui
mesh_terms: D015082:2,2'-Dipyridyl / Q000138:chemical synthesis / Q000737:chemistry / Q000528:radiation effects*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000528:radiation effects*; D010777:Photochemistry; D011726:Pyridinium Compounds / Q000737:chemistry / Q000528:radiation effects*; D012428:Ruthenium / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011726:Pyridinium Compounds; D015082:2,2'-Dipyridyl; D012428:Ruthenium