title: Tuning photoinduced energy- and electron-transfer events in subphthalocyanine-phthalocyanine dyads.
abstract: A series of subphthalocyanine-phthalocyanine dyads has been prepared by means of palladium-catalyzed cross-coupling reactions between a monoalkynylphthalocyanine and different monoiodosubphthalocyanines. Electronic coupling between the two photoactive units is ensured by a rigid and pi-conjugated alkynyl spacer. In addition, the electronic characteristics of the subphthalocyanine moiety were modulated by the introduction of different peripheral substituents. Cyclic and Osteryoung square-wave voltammetry experiments revealed that the reduction potential of this subunit can be decreased by about 400 mV on going from thioether or no substituents to nitro groups. As a consequence, the energy level of the charge-transfer state could be fine-tuned so as to gain control over the fate of the photoexcitation energy in each subunit. The diverse steady-state and time-resolved photophysical techniques employed demonstrated that, when the charge-transfer state lies high in energy, a quantitative singlet-singlet energy-transfer mechanism from the excited subphthalocyanine to the phthalocyanine takes place. On the contrary, stabilization of the radical pair by lowering the redox gap between electron donor and acceptor results in a highly efficient photoinduced electron-transfer process, even in solvents of low polarity such as toluene (Phi(ET) approximately 0.9). These features, together with the extraordinary absorptive cross section that these molecular ensembles display across the whole UV/Vis spectrum, make them model candidates for application in situations where broadband light sources are needed.
authors.affiliation: Departamento de Química Orgánica (C-I), Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: González-Rodríguez
authors.forename: Christian G
authors.initials: CG
authors.lastname: Claessens
authors.forename: Tomas
authors.initials: T
authors.lastname: Torres
authors.forename: Shenggao
authors.initials: S
authors.lastname: Liu
authors.forename: Luis
authors.initials: L
authors.lastname: Echegoyen
authors.forename: Nuria
authors.initials: N
authors.lastname: Vila
authors.forename: Santi
authors.initials: S
authors.lastname: Nonell
mesh_terms: D004563:Electrochemistry; D004583:Electrons; D007211:Indoles / Q000737:chemistry* / Q000528:radiation effects; D054833:Isoindoles; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry; D013053:Spectrophotometry; D014050:Toluene / Q000737:chemistry
chemical_list: D007211:Indoles; D054833:Isoindoles; D011725:Pyridines; D014050:Toluene; C023666:pyridine; C013647:phthalocyanine