|Name||Ms. Vivian Iglesias|
|Organization or Institution||University of Miami|
Supramolecular complexation studies between a ferrocenylguanidinium guest and cucurbit[n]uril hosts.
Vivian Iglesias, Mehdi Rashvand Avei, Sonia Bruña, Isabel Cuadrado, Angel E. Kaifer
University of Miami, Universidad Autónoma de Madrid
The binding interactions of supramolecular complexes between a ferrocenylguanidinium derivative (FcG+) and the macrocyclic hosts cucurbituril (CB7) and cucurbit[n]uril (CB8) were studied in aqueous medium. The guest forms a stable 1:1 inclusion complex with both hosts where the ferrocenyl group is encapsulated by the host cavity as illustrated in 1H-NMR spectroscopic experiments and DFT computational studies. NMR competition experiments were used to calculate the association equilibrium constants (K) for the complexes and were found to be 3.5 x 109 and 2.5 x 108 M-1 for CB7 and CB8, respectively, in 50 mM sodium acetate-d3 D2O solution at pD 4.7. Electrospray mass spectrometric (ESI MS) experiments also confirm the stoichiometry of the complex for CB7•FcG+. Voltammetric experiments were performed to measure the half-wave potentials shifts of the one-electron oxidation of the ferrocene due to complexation. There was a 12 mV anodic shift in the positive direction by complexation with CB7 and larger shift of 32 mV caused by CB8, suggesting that the delocalization of the positive charge on over the three nitrogens in the guanidinium moiety causes a similar electrochemical behavior to that detected with neutral ferrocene derivatives.