The dynamic chemistry of molecular borromean rings and Solomon knots.

The dynamic solution equilibria between molecular Borromean rings (BRs) and Solomon knots (SKs), assembled from transition metal-templated macrocycles, consisting of exo-bidentate bipyridyl and endo-tridentate diiminopyridyl ligands, have been examined with respect to the choice of the metal template and reaction conditions employed in the synthesis of the metalated BRs, otherwise known as Borromeates. Three new Borromeates, their syntheses templated by Cu(II), Co(II), and Mn(II), have been characterized extensively (two by X-ray crystallography) to the extent that the metal centers in the assemblies have been shown to be distanced sufficiently from each other not to communicate. The solid-state structure of the Co(II)-Borromeate reveals that six MeOH molecules, arranged in a [O--H.

Supramolecular metal-polypyridyl and Ru(II) porphyrin complexes: photophysical, electron paramagnetic resonance, and electrochemical studies.

A series of mixed-metal supramolecular porphyrin arrays in which the geometry of the central metal-polypyridyl moiety defines the spatial arrangement of two or more Ru(II)-porphyrin units through axial coordination have been prepared by employing self-assembly based protocols, and their photophysical and electrochemical properties have been studied. The electrochemical properties of the constituent parts of these arrays depend only on their own chemical environment, regardless of the nuclearity and the overall charge of the compound; in this way species with predetermined redox patterns can be obtained via the synthetic control of the self-assembly process. Interestingly, several of these arrays are luminescent both at room and at low temperatures, and in many cases core-to-periphery or periphery-to-core intramolecular energy transfer processes take place according to the nature of the central metal template.

Single-walled carbon nanotubes under the influence of dynamic coordination and supramolecular chemistry.

A dynamic coordinative-directed solubilization of single-walled carbon nanotubes (SWNTs) in aqueous solutions has been achieved through a combination of a Zn(II) metalloporphyrin complex and a cis-protected Pd(II) complex, which are believed to form charged acyclic and/or cyclic adducts on or around the side walls of SWNTs. The solubilization of SWNTs in aqueous solution only occurs when these acyclic and/or cyclic complexes are allowed to enter simultaneously into a self-assembly process with SWNTs under mild conditions. The aqueous solubility properties that these dynamic complexes confer upon SWNTs are believed to involve noncovalent bonding interactions between the two entities.

Bioinspired detection of light using a porphyrin-sensitized single-wall nanotube field effect transistor.

Single-wall carbon nanotube (SWNT) field effect transistors (FETs), functionalized noncovalently with a zinc porphyrin derivative, were used to directly detect a photoinduced electron transfer (PET) within a donor/acceptor (D/A) system. We report here that the SWNTs act as the electron donor and the porphyrin molecules as the electron acceptor. The magnitude of the PET was measured to be a function of both the wavelength and intensity of applied light, with a maximum value of 0.

Nanoscale borromeates.

[Structure: See text] In addition to a parent zinc(II) Borromean ring (BR) complex, the preparation and characterization of two hexasubstituted BR complexes with either 4-acetoxymethylphenyl or 4-methylthiophenyl substituents associated in turn with all six pyridyl rings has been achieved convergently in good yields by appealing to the dynamic features of the reactions between primary amino groups in a preformed acyclic ligand and 2,6-diformylpyridine. Two molecules of the acyclic ligands react with two molecules of 2,6-diformylpyridine to form a cyclic [2 + 2] tetraimine in the presence of Zn(II) ions as templates in 2-propanol at 70 degrees C. The successful preparation of the two derivatives by convergent template-directed syntheses opens up opportunities to self-assemble, under equilibrium control, numerous nanoscale metallo-organic particles with potentially useful properties.

Nanoscale Borromean links for real.

Borohydride reduction of a Borromean Ring (BR) complex containing six zinc(II) ions and 12 imine bonds has resulted in its demetallation, producing a neutral BR compound and also its free macrocycle, following cleavage of at least one of the imine bonds in the ethanolic reaction mixture.

Dynamic nanoscale Borromean links.

Employing halogen atom labels on one of the ligand precursors, the lability of at least some of the 30 dative and 12 imine bonds stabilizing and constituting the three rings of a metallo-Borromean linked compound are scrambled in acidic methanolic solution.

Molecular borromean rings.

The realization of the Borromean link in a wholly synthetic molecular form is reported. The self-assembly of this link, which is topologically achiral, from 18 components by the template-directed formation of 12 imine and 30 dative bonds, associated with the coordination of three interlocked macrocycles, each tetranucleating and decadentate overall, to a total of six zinc(II) ions, is near quantitative. Three macrocycles present diagonally in pairs, six exo-bidentate bipyridyl and six endo-diiminopyridyl ligands to the six zinc(II) ions.