Conjugated Porphyrin Dimers: Cooperative Effects and Electronic Communication in Supramolecular Ensembles with C60.
J Am Chem Soc
; 138(47): 15359-15367, 2016 11 30.
Article
em En
| MEDLINE
| ID: mdl-27640915
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 CH2Cl2 at room temperature. The designed hosts are able to associate up to two fullerene-based guest molecules and present association constants as high as â¼5 × 108 M-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 C60 moieties. Theoretical calculations have evidenced a significant decrease of the electron density in the porphyrin dimers 3 and 4 upon complexation of the first C60 molecule, in good agreement with the negative cooperativity found in these systems. This negative effect is partially compensated by the stabilizing C60-C60 interactions that take place in the more stable syn-disposition of [4·12].
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Bases de dados:
MEDLINE
Idioma:
En
Revista:
J Am Chem Soc
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
França