Electronic Structure Effects on Electron Transfer Controlled Hydrogen Bonding in Substituted Dinitrobenzene Electrogenerated Anions As Receptors for 1,3-Diethylurea

Abstract

In Electron Transfer Controlled Hydrogen Bonding (ETCHB), switching molecules experiment changes in their reduction potential values as hydrogen bond donor species (DH) are added to the solution. ETCHB is the basis of operation of many molecular switches [1-3]; therefore a comprehensive understanding of the mechanistic routes that govern electron transfer in these systems would allow the design of devices with more specific applications. These processes have been extensively studied employing model molecules, such as nitrocompounds as receptor species [1-3]. In the case of complexes formed via ETCHB with electrogenerated anions from dinitrobenzene isomers [3-7], proton transfer reactions were also observed, thus diminishing the stability of these intermediates. Therefore, in this work, a similar electrochemical analysis was performed using 1,3-diethylurea to avoid protonation. The results showed two sequential reversible voltammetric signals, from which Kb (binding constant) values were calculated. The experimental behavior suggest that the mechanistic routes for ETCHB depend on the relative position of the nitro groups within the molecule: For o- and p-dinitrobenzenes radicals, a reduction involving an Erev Erev C mechanism occurs while for with m-dinitrobenzene radicals, the reaction evolves by an Erev C Erev route. By employing m-dinitrobenzenes substituted in 5 position as receptors, results revealed an inductive effect on Kb values in the formation of the anion radical binding complex. Acknowledgments E. M.-G. thanks CONACYT for support his M. Sc. Studies (scholarship no. 270926). C. F. thanks CONACYT for support through project 107037.