Complexation of 2,6-helic[6]arene and its derivatives with 1,1'-dimethyl-4,4'-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid-base controllable complexation.

ABSTRACT: 2,6-Helic[6]arene and its derivatives were synthesized, and their complexation with 1,1'-dimethyl-4,4'-bipyridinium and protonated 4,4'-bipyridinium salts were investigated in detail. It was found that the helic[6]arene and its derivatives could all form 1:1 complexes with both 1,1'-dimethyl-4,4'-bipyridinium salts and protonated 4,4'-bipyridinium salts in solution and in the solid state. Especially, the helic[6]arene and its derivatives containing 2-hydroxyethoxy or 2-methoxyethoxy groups exhibited stronger complexation with the guests than the other helic[6]arene derivatives for the additional multiple hydrogen bonding interactions between the hosts and the guests, which were evidenced by ¹H NMR titrations, X-ray crystal structures and DFT calculations. Moreover, it was also found that the association constants (K _a) of the complexes could be significantly enhanced with larger counteranions of the guests and in less polar solvents. Furthermore, the switchable complexation between the helic[6]arene and protonated 4,4'-bipyridinium salt could be efficiently controlled by acids and bases.

SUBMITTER: Li J 

PROVIDER: S-EPMC6664404 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature