Electrochemically controlled hydrogen bonding. Nitrobenzenes as simple redox-dependent receptors for arylureas

Abstract

Reduction of nitrobenzene derivatives in the presence of arylureas in aprotic solvents results in large positive shifts in potential of the nitrobenzene0/- cyclic voltammetry wave with little change in wave shape. This behavior is indicative of reversible hydrogen bonding between nitrobenzene radical anions and arylureas. Computer fitting of the cyclic voltammetry of 4-nitroaniline, NA, plus 1,3-diphenylurea in DMF shows essentially no binding between urea and NA in the oxidized state (Kox < 1 M-1), but very strong binding in the reduced state (K red = 8 × 104 M-1), along with very rapid rates of hydrogen bond formation (kf′s ≈ 10 8-1010 M-1 s-1), making this system a fast on/off redox switch. © 2005 American Chemical Society.