title: Binding Interactions between a Ferrocenylguanidinium Guest and Cucurbit[n]uril Hosts.
abstract: The binding interactions between a novel ferrocenylguanidinium derivative (FcG+) and the macrocyclic hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solution.1H NMR spectroscopic experiments indicated that both hosts form stable 1:1 inclusion complexes with FcG+, in which the ferrocenyl group is engulfed by the host cavity. The stoichiometry of the CB7·FcG+complex was also confirmed by electrospray mass spectrometric (ESI MS) experiments. The association equilibrium constants (K) were determined from NMR competition experiments. The measured K values were 3.5 × 109and 2.5 × 108M-1for CB7 and CB8, respectively, in 50 mM sodium acetate-d3D2O solution (pD 4.7). DFT computational studies confirmed the 1:1 stoichiometry and the inclusion character of both complexes. Voltammetric experiments were carried out to measure the complexation-induced shifts on the half-wave potentials for the one-electron oxidation of the ferrocenyl moiety. Complexation by CB7 led to a 12 mV anodic shift, while CB8 caused a larger 32 mV shift also in the positive direction. These potential shifts suggest that the delocalization of the positive charge on the side arm over the three nitrogens in the guanidinium unit results in electrochemical behavior similar to that observed with neutral ferrocene derivatives.
authors.affiliation: Department of Chemistry and Center for Supramolecular Science, University of Miami , Coral Gables, Florida 33124, United States.
authors.forename: Vivian
authors.initials: V
authors.lastname: Iglesias
authors.affiliation: Department of Chemistry and Center for Supramolecular Science, University of Miami , Coral Gables, Florida 33124, United States.
authors.forename: Mehdi Rashvand
authors.initials: MR
authors.lastname: Avei
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad Autónoma de Madrid , Cantoblanco, 28049 Madrid, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Bruña
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad Autónoma de Madrid , Cantoblanco, 28049 Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Cuadrado
authors.affiliation: Department of Chemistry and Center for Supramolecular Science, University of Miami , Coral Gables, Florida 33124, United States.
authors.forename: Angel E
authors.identifier: 0000-0001-7155-9889
authors.initials: AE
authors.lastname: Kaifer