Synthesis and structure of nitrogen bridged calix[5]- and -[10]-pyridines and their complexation with fullerenes

摘要

Azacalix[5]pyridine, a heteroatom bridged calixaromatic with an odd number of arene units, and azacalix[10]pyridine, a giant molecular belt, were selectively synthesized based on a 2 + 3 macrocyclic coupling strategy; both novel macrocyclic hosts formed strong 1 : 1 complexes with fullerenes C_(60) and C_(70) in a size-selective manner with association constants up to 1.3 × 10~5 + 0.03 × 10~5 M~(-1). One of the challenging and thrilling tasks in supramolecular fullerene chemistry is the design and the synthesis of fullerene receptors. The application of the concave-convex π-π interactions based on the complementarity principle has resulted in a few types of macrocyclic host molecules such as crown ethers, γ-cyclodex-trin (γ-CD), cyclotriveratrylenes (CTV), calix[n]arenes, homo-oxacalix[3]arenes, corannulenes and carbon nanorings. Intriguingly, polycyclic aromatic hydrocarbons and porphyrins and metalloporphyrins with planar π-surfaces are also able to complex fullerenes. Unfortunately, the binding of fullerenes to these synthetic receptors is weak or modest. To enhance the power of complexation with fullerenes, a strategy for the construction of molecular tweezers has been explored.