A novel strapped porphyrin receptor for molecular recognition

A novel strapped porphyrin receptor , in which two electron-rich bis(p-phenylene)-34-crown ether-10 units are incorporated, has been designed and synthesized from the newly developed intermediate for investigating new chemistry of molecular recognition. 1H NMR and UV–Vis studies revealed that displays relatively weak binding abilities to neutral electron deficient naphthalene-1,8,4,5-tetracarboxydiimide (NDI) derivatives (no simple complexing stoichiometry was observed), (Ka=48(±5) M−1) and (Ka=46(±5) M−1) in chloroform-d, strong binding ability to pyridine derivative , (Ka=1.5(±0.12)×103 M−1) in chloroform, moderately strong binding ability to tetracationic compound (Ka=475(±50) M−1) in acetone-d6, and very strong binding affinity to compound (Ka=6.5(±0.7)×105 M−1), which consists of one pyridine and two NDI units, in chloroform. Remarkable cooperative effect of the intermolecular metal–ligand coordination and donor–acceptor interactions in complex was observed by comparing the complexing behaviors between and the appropriately designed guests. Complex possesses an unique three-dimensional tri-site binding feature. For comparison, the complexing affinity of toward compounds , , and in chloroform-d and in acetone-d6 has also been investigated and the binding patterns in different complexes were explored. The results demonstrate that strapped porphyrin derivatives are ideal precursors for constructing new generation of three-dimensional multi-site artificial receptors for molecular recognition and host–guest chemistry.