title: Synthesis of new self-assembled PdII and PtII rectangular metallomacrocycles: a comparative study of their inclusion complexes.
abstract: New palladium and platinum metallocycles have been synthesized by reacting 4,4'-bipyridinium-based ligands with PdII and PtII complexes. Strict thermodynamic self-assembly of 1 and [M(en)(NO3)2] (M=Pd, Pt) 6 a,b afforded metallocycles 7 a,b. However, the synthesis of 8 a,b and 9 a,b required a self-assembly process that used sodium p-phenylenediacetate (12) as a template. Finally, metallocycles 10 a,b were synthesized under high dilution conditions from ligand 4. The formation of inclusion complexes between metallocycles 7-10 and substrates 13 and 14 were studied by low-temperature 1H NMR, and the association constants were determined in nitromethane and water by following the characteristic charge-transfer band that these metallomacrocycles show in their UV-visible absorption spectra. A clear correlation between the affinity for a substrate and the dimensions of the metallocycle was observed. Metallocycles 8 b and 9 b exhibited the highest binding constants in water and nitromethane. This observation is in agreement with the DFT (B3LYP)-optimized geometries obtained for the different metallomacrocycles, which indicate that only macrocycles 8 and 9 possess a cavity with a width larger than 3.5 A. The insertion of hydroquinone or diol 13 into the cavity of metallocycle 11 a was confirmed by single-crystal X-ray crystallography.
authors.affiliation: Departamento de Química Fundamental, Universidade da Coruña, Facultad de Ciencias, A Zapateira, s/n 15071, La Coruña, Spain.
authors.forename: Marcos
authors.initials: M
authors.lastname: Chas
authors.forename: Dolores
authors.initials: D
authors.lastname: Abella
authors.forename: Víctor
authors.initials: V
authors.lastname: Blanco
authors.forename: Elena
authors.initials: E
authors.lastname: Pía
authors.forename: Gerardo
authors.initials: G
authors.lastname: Blanco
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernández
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.forename: Carlos
authors.initials: C
authors.lastname: Peinador
authors.forename: José M
authors.initials: JM
authors.lastname: Quintela