Significance of charge-dipolar moiety interaction: Computational study of cyanospherands

Cyanospherands (CN-spherands) are highly preorganized hosts which bind cations. Density functional theory calculations were used to investigate the complexation between cyanospherands and alkali metal ions (Li ,N a, and K). CN8- spherand undergoes significant shape change upon complexation, i.e., the oval free host becomes spherical when complexed with cations. All cationic guests prefer external binding to encapsulation in spite of spherically well organized charged moieties and the spacious cavity of hosts. The ion-dipolar moiety interaction has been found to be a decisive factor for the preference for external binding. This demonstrates the importance of ion-dipolar moiety orientations as well as the host-guest size complementarity, to design novel ionophores.