title: Design of triads for probing the direct through space energy transfers in closely spaced assemblies.
abstract: Using a selective stepwise Suzuki cross-coupling reaction, two trimers built on three different chromophores were prepared. These trimers exhibit a D(^)A1-A2 structure where the donor D (octa-β-alkyl zinc(II)porphyrin either as diethylhexamethyl, 10a, or tetraethyltetramethyl, 10b, derivatives) through space transfers the S1 energy to two different acceptors, di(4-ethylbenzene) zinc(II)porphyrin (A1; acceptor 1) placed cofacial with D, and the corresponding free base (A2; acceptor 2), which is meso-meso-linked with A1. This structure design allows for the possibility of comparing two series of assemblies, 9a,b (D(^)A1) with 10a,b (D(^)Â1-A2), for the evaluation of the S1 energy transfer for the global process D*→A2 in the trimers. From the comparison of the decays of the fluorescence of D, the rates for through space energy transfer, kET for 10a,b (kET ≈ 6.4 × 10(9) (10a), 5.9 × 10(9) s(-1) (10b)), and those for the corresponding cofacial D(^)A1 systems, 9a,b, (kET ≈ 5.0 × 10(9) (9a), 4.7 × 10(9) s(-1) (9b)), provide an estimate for kET for the direct through space D*→A2 process (i.e., kET(D(^)A1-A2) - kET(D(^)A1) = kET(D*→A2) ∼ 1 × 10(9) s(-1)). This channel of relaxation represents ∼15% of kET for D*→A1.
authors.affiliation: Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR 6302), Université de Bourgogne, UFR Sciences et Techniques, 9 Avenue Alain Savary, BP 47870, 21078 Dijon, France.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Camus
authors.forename: Shawkat M
authors.initials: SM
authors.lastname: Aly
authors.forename: Daniel
authors.initials: D
authors.lastname: Fortin
authors.forename: Roger
authors.initials: R
authors.lastname: Guilard
authors.forename: Pierre D
authors.initials: PD
authors.lastname: Harvey
mesh_terms: D015195:Drug Design; D004735:Energy Transfer; D008665:Metalloporphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D008665:Metalloporphyrins