George R. Newkome

Terpyridine-Based, Flexible Tripods: From a Highly Symmetric Nanosphere to Temperature-Dependent, Irreversible, 3D Isomeric Macromolecular Nanocages

A three-dimensional, highly symmetric sphere-like nanocage was synthesized using a terpyridine (tpy)-based, flexible tris-dentate ligand and characterized by single crystal X-ray analysis. To introduce more rigidity, one of the tpy units of the tris-dentate ligand was preblocked by stable connectivity to form the corresponding Ru2+-dimer. The complexation between Ru2+-dimer and Fe2+ demonstrates an unexpected temperature-dependent assembly between two irreversible isomeric 3D nanocages. Investigation of the coordination process and structural configurations of the metal-ligand framework, affected by the introduction of rigidity and in the presence of external stimuli (temperature), is reported.

Chapter 8 Eight-membered and larger rings

Publisher Summary This chapter provides information on eight-membered and larger rings. The expansion into crystal engineering, has added a focus on the intermolecular interactions within the nanoscale regime. The chapter discusses (1) carbon-oxygen rings, (2) carbon-nitrogen rings, (3) carbon-sulfur rings, and (4) carbon-nitrogen-oxygen rings. 24-Membered macrocycles with chalcone subunits and isobutenyl linkages have been formed through a mixed aldol condensation. Polycondensation of a trifunctional, ketone-activated fluoroarene with bis - or tris -phenoxides under pseudo -high dilution conditions gave rise to a series of very large macropolycyclic aromatic ethereal ketones. The incorporation of diazacrown ethers into a polymeric polyimide backbone has been reported and shown to complex barium(II). Comparative naphtholysis of crown-bearing tetrachlorocyclotriphosphazene, prepared by the treatment of hexachlorocyclotriphosphazatriene with the disodium salt of the tetraethylene glycol, and its acyclic analog revealed a significant macrocyclic effect of the substituent on both the kinetics and regiochemistry of chlorine substitution in the N 3 P 3 ring. 6,11,16,21-Tetraphenylbenziporphyrin, in which one pyrrole is replaced by a benzene ring, is formed in good yields by the condensation of the appropriate precursor with pyrrole and benzaldehyde.

A Long Pathway to the Quantitative Assembly of Metallodendrimers

This overview describes our research progression from the study of heterocycle synthesis to dendritic architecture to simple metallomacrocycles, and finally to complex, fractal-based, suprametallomolecular materials. Construction of the first terpyridine-modified dendritic scaffold was followed by the construction and self-assembly of polyterpyridine monomers. Preparation of tristerpyridine building blocks used in concert with bisterpyridine analogs facilitated access to a Sierpiński gasket, as verified by direct visual observation with UHV-STEM, as well as other techniques. Numerous examples of heteroleptic self-assembly are described that include the quantitative preparation of a Sierpiński triangle. Addition of angled spacer moieties within polyterpyridine building blocks has generated a new family of 3D spherical materials that has facilitated the construction of hybrid fractal-dendritic materials that exhibit the unexpected concentration mediated, architectural transformations.