Binding Interactions between a Ferrocenylguanidinium Guest and Cucurbit[n]uril Hosts

作者：Iglesias Vivian; Avei Mehdi Rashvand; Bruna Sonia; Cuadrado Isabel; Kaifer Angel E^*

来源：Journal of Organic Chemistry, 2017, 82(1): 415-419.

DOI：10.1021/acs.joc.6b02508

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. H-1 NMR spectroscopic experinients 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 center dot PcG(+) 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 x 10(9) and 2.5 x 10(8) M-1 for CB7 and CB8, respectiely, in 50 mM sodium acetate-d(3) D2O solution (pD 4.7). DFT computational studies confirmed the 1:1 stoichiornetry 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.

• 出版日期2017-1-6