title: Conjugated Porphyrin Dimers: Cooperative Effects and Electronic Communication in Supramolecular Ensembles with C60.
abstract: Two new conjugated porphyrin-based systems (dimers 3 and 4) endowed with suitable crown ethers have been synthesized as receptors for a fullerene-ammonium salt derivative (1). Association constants in solution have been determined by UV-vis titration experiments in CH2Cl2at room temperature. The designed hosts are able to associate up to two fullerene-based guest molecules and present association constants as high as ∼5 × 108M-1. Calculation of the allosteric cooperative factor α for supramolecular complexes [3·12] and [4·12] showed a negative cooperative effect in both cases. The interactions accounting for the formation of the associates are based, first, on the complementary ammonium-crown ether interaction and, second, on the π-π interactions between the porphyrin rings and the C60moieties. Theoretical calculations have evidenced a significant decrease of the electron density in the porphyrin dimers 3 and 4 upon complexation of the first C60molecule, in good agreement with the negative cooperativity found in these systems. This negative effect is partially compensated by the stabilizing C60-C60interactions that take place in the more stable syn-disposition of [4·12].
authors.affiliation: Laboratorie de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), ECPM , 67087 Strasbourg, Cedex 2, France.|Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Moreira
authors.affiliation: Instituto de Ciencia Molecular, Universidad de Valencia , 46890 Paterna, Spain.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Calbo
authors.affiliation: Instituto de Ciencia Molecular, Universidad de Valencia , 46890 Paterna, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Aragó
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.
authors.forename: Beatriz M
authors.initials: BM
authors.lastname: Illescas
authors.affiliation: Laboratorie de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), ECPM , 67087 Strasbourg, Cedex 2, France.
authors.forename: Iwona
authors.initials: I
authors.lastname: Nierengarten
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS (UPR 8241), Université de Toulouse (UPS, INPT) , 31077 Toulouse, Cedex 4, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Delavaux-Nicot
authors.affiliation: Instituto de Ciencia Molecular, Universidad de Valencia , 46890 Paterna, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Ortí
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.|Imdea-Nanoscience , Campus Cantoblanco, 28049 Madrid, Spain.
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
authors.affiliation: Laboratorie de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), ECPM , 67087 Strasbourg, Cedex 2, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Nierengarten