An Investigation into Interactions between 1‐Butyl‐3‐methyl‐imidazolium Tetrafluoroborate Guest and Pillar[5]arene Hosts: An Experimental and Molecular Dynamics Approach

Abstract

AbstractVarious synthesized Pillar[5]arene macrocycles were allowed to form complexes with the ionic liquid; 1‐Butyl‐3‐methyl‐imidazolium tetrafluoroborate (IL). The pillar[5]arenes used in the study were synthesized by the established pioneering method of Ogoshi that involves treatment of 1,4‐disubstituted benzenes with paraformaldehyde in the presence of BF3.OEt2. Selected synthesized pillar[5]arenes; DMpillar[5]arene (4a), DPpillar[5]arene (4b), DPGpillar[5]arene (4c) were allowed to form complexes with the ionic liquid, and complexations were confirmed by MALDI‐TOF, ESI‐MS, 1H NMR, and DOSY spectroscopy. ESI‐MS reveals highly intense ion peaks that correspond to [pillar[5]arene+IL]+ for the complexes of the three pillar[5]arenes with the ionic liquid. Changes in characteristic peaks in hosts and guests, as a result of complexation, were studied by 1H NMR. Results obtained suggest a formation of 1 : 1 complexes between the pillar[5]arene host and the IL guest. Host‐guest interactions in such complexes have also been studied using 1H‐1H 2D ROESY NMR spectroscopy. Obtained through‐space correlations revealed interactions between certain parts of the pillar[5]arene hosts and the ionic liquid. The complexation between the three pillar[5]arenes and the IL was studied by molecular dynamics (MD) simulations. The obtained results suggest the insertion of the IL inside the nanocavities of the hosts.