Details

Autor(en) / Beteiligte

• Lainé, Philippe P.
• Ciofini, Ilaria
• Ochsenbein, Philippe
• Amouyal, Edmond
• Adamo, Carlo
• Bedioui, Fethi

Titel

Photoinduced Processes within Compact Dyads Based on Triphenylpyridinium-Functionalized Bipyridyl Complexes of Ruthenium(II)

Ist Teil von

• Chemistry : a European journal, 2005-06, Vol.11 (12), p.3711-3727

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2005

Quelle

MEDLINE

Beschreibungen/Notizen

• 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‐(θ 1)‐A type, where the θ 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 (A1‐bpy and A2‐bpy, respectively) have been synthesized to give complexes with RuII, 1‐bpy and 2‐bpy, respectively. Combined solid‐state analysis (X‐ray crystallography), solution studies (1H NMR, cyclic voltammetry) and computational structural optimization allowed verifying that θ 1 angle approaches 90° 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‐(θ 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(θ 1)]− mono‐reduced species as a function of θ 1 has been undertaken and the possibility of conformationally switching emission properties of P was derived. The ability of compact dyads, P‐(θ 1)‐A, made of a photosensitizer (P) directly linked to an electron acceptor (A), to undergo intramolecular photoinduced electron transfer processes is investigated (see scheme). Formation of a charge‐separated state is examined as a function of the degree of conjugation of P with A. The derived possibility of a conformational control (θ 1) of the emission properties of P within *[P‐(θ 1)‐A] is discussed.