Evaluation of the binding ability of a macrobicyclic receptor for anions by potentiometry and molecular dynamics simulations in solution (original) (raw)

The macrobicycle derived from bis-tren and containing diphenoxy groups as spacers, L 1 , was synthesized and used as receptor for anions. The binding ability of the new receptor for some aromatic carboxylates [phthalate (ph 2À), isophthalate (iph 2À), terephthalate (tph 2À), benezenetricarboxylate (btc 3À), and the herbicide 4-amino-3,5,6-trichloro-2-pyridinecarboxylate (ATCP À)], and the aliphatic cyclohexanetricarboxylate (ch 3À) anions was evaluated by potentiometric measurements and molecular dynamic simulation in solution. The association constants were determined by potentiometry in H 2 O/MeOH (1:1 v/v) at 298.2 K and 0.10 mol dm À3 in KCl. The strongest association was found with btc 3À anion and the effective binding constants at pH 5.5 follow the order: btc 3À >tph 2À >ph 2À ziph 2À >ch 3À zATCP À. Molecular dynamics simulations carried out for the associations of (H 6 L 1) 6þ with btc 3À , tph 2À and iph 2À in the same mixture of solvents indicated that these anions interact with the receptor by a combination of electrostatic and multiple NeH/O]C hydrogen bond interactions. It was also verified that in the recognition process the tph 2À remained encapsulated over the entire time of simulation while the btc 3À is partially inserted into the receptor cavity with one carboxylate group largely exposed to water solvent molecules, and iph 2À anion exhibited an intermediate binding behaviour. The free energy difference between btc 3À and iph 2À associations estimated by free energy calculations is in excellent agreement with the difference found from the experimental values for the corresponding association constants, which indicates that the unconstrained molecular dynamics simulations carried out with these two anions are realistic pictures of their molecular recognition processes.

Sign up for access to the world's latest research.

checkGet notified about relevant papers

checkSave papers to use in your research

checkJoin the discussion with peers

checkTrack your impact