A new approach for the synthesis of mono- and A1/A2-dihydroxy-substituted pillar[5]arenes and their complexation with alkyl alcohols in solution and in the solid state

Abstract

A new approach was employed for the synthesis of mono- and A1/A2-dihydroxy-functionalized pillar[5]arenes by the removal of the pillar[5]arene-bearing benzyl group(s) using catalytic hydrogenation. Host–guest complexation between a mono-hydroxy-pillar[5]arene with long-chain alkyl alcohol guests was studied. The encapsulation characteristics of the pillar[5]arene was affected by the presence of a hydroxy group, resulting in the formation of a 1 : 2 complex with long-chain alkyl alcohols in solution and in the solid state. For comparison, analog experiments were conducted with permethylated pillar[5]arene (DMP5) and long-chain alkyl alcohol guests. The complexation experiments revealed that the absence of a hydroxyl group on the pillar[5]arene frame resulted in the formation of a 1 : 1 complex. The formed complexes were confirmed by proton nuclear magnetic resonance spectroscopy and single-crystal X-ray analysis.