Cation recognition controlled by protonation or chemical reduction: a computational study.

To control biochemical processes, non-covalent interactions involving cations are activated by protons or electrons. In the present study, the bonding situation between: (i) carboxylic acid or (ii) ferrocene-functionalized crown ether derivatives and cations (Li, Na or K) has been elucidated and, mainly, tuned by the substitution of hydrogen atoms by electron donor (-NH) or acceptor (-NO) groups. The deprotonation of the carboxyl groups improves the interaction with the cations through more favorable electrostatic O⋯cation interactions.