Electrochimica Acta, Vol.296, 102-111, 2019
One-step electrochemically driven production of aza macrocycle-based pseudo-cryptand: An accessible route for creating of diverse cryptand-resembles compounds
Cryptands (CPs) are appeal architectures because they offer better selectivity and binding properties to alkali metals than crown ethers, although their synthesis is harsh and costly. We report here using an accessible and easy to use method for synthesis of a pseudo-cryptand structure by taking advantage of two homologues of "aza-crown ethers" and of in-situ generated "ortho-quinone" (OQ). The procedure relies on the in-situ production of three different 3-R-substituted (R=H, CH3, and OCH3) quinones, playing the role of electrophiles, which are electrochemically produced from their equivalent catechols in the presence of two studied azacrowns (ACs), in the role of the nucleophile, in aqueous buffered solutions. The advancement of electrochemically-triggered process is followed by cyclic voltammetry, controlled potential coulometry and UV-Vis techniques. The corresponding results infer a 1,4-Michael addition of ACs via their amine moieties to the electrochemically derived o-quinones. DFT calculation was employed to evaluate the diverse aspects of the process including the ability of thermodynamic proceeding of the reactions during different steps of processes, the effect of different substituted pendant groups on the Delta G and the HOMO-LUMO energy levels in either of OQs that directly introduce reactivity of them. Two different mechanisms ECE and ECECE were proposed for either of the nucleophiles. The NMR, FTIR, and mass-spectroscopy (MS) were exploited to characterize the possible structures formed. The binding affinities for the prepared compounds were shown by spectrophotometry using the respective solution of metallic cations. (C) 2018 Elsevier Ltd. All rights reserved.