title: Sequence, stoichiometry, and dimensionality control in porphyrin/bis-calix[4]arene self-assemblies in aqueous solution.
abstract: The use of a water-soluble octacationic bis-calix[4]arene with divergent cavities (BC(4)) as a templating agent for the assembly of a tetraanionic porphyrin (CuTPPS) has allowed the noncovalent synthesis of 2D or 3D multiporphyrin assemblies. Self-assembly of CuTPPS and BC(4) molecules proceeded under hierarchical control in a stepwise fashion to yield discrete and isolable supramolecular nanostructures containing up to 33 molecular elements (i.e., the CuTPPS/BC(4) 17:16 assembly, obtained in less than three hours). The formation of these species could be conveniently monitored by means of UV/Vis spectroscopy by following the absorbance of the Soret band at 412 nm. In particular, the attainment of the pivotal CuTPPS/BC(4) 5:4 species with a cruciform structure, as the key fork-point intermediate for the subsequent formation of the higher 2D and 3D assemblies, has been demonstrated by light-scattering studies and by an unequivocal synthesis of mixed-porphyrin/calixarene 5:4 species involving the use of two different types of metallated porphyrins, namely CuTPPS and MnTPPS. The remarkable stability of these assemblies permits a stepwise synthesis that makes it possible to choose the desired porphyrin sequence.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: D'Urso
authors.forename: Domenico Andrea
authors.initials: DA
authors.lastname: Cristaldi
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Fragalà
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gattuso
authors.forename: Andrea
authors.initials: A
authors.lastname: Pappalardo
authors.forename: Valentina
authors.initials: V
authors.lastname: Villari
authors.forename: Norberto
authors.initials: N
authors.lastname: Micali
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Pappalardo
authors.forename: Melchiorre F
authors.initials: MF
authors.lastname: Parisi
authors.forename: Roberto
authors.initials: R
authors.lastname: Purrello