Synthesis of Electron-Deficient Corona[5]arenes and Their Selective Complexation with Dihydrogen Phosphate: Cooperative Effects of Anion-π Interactions.

Reported here are the syntheses, conformational structures, electrochemical properties, and noncovalent anion binding of corona[5]arenes. A (3+2) fragment coupling reaction proceeded efficiently under mild reaction conditions to produce a number of novel heteroatom- and methylene-bridged corona[3]arene[2]tetrazine macrocycles. Selective oxidation of the sulfur atom between two phenylene rings afforded sulfoxide- and sulfone-linked corona[5]arenes in good yields. All corona[5]arenes synthesized adopted similar 1,2,4-alternate conformational structures, forming pentagonal cavities. The cavity sizes and the electronic properties such as redox potentials, were measured with CV and DPV, and were influenced by the different bridging units. As electron-deficient macrocycles, the acquired corona[3]arene[2]tetrazines served as highly selective hosts, forming complexes with the hydrogen-bonded dimer of dihydrogen phosphate through cooperative anion-π interactions.