title: "Wurster-type" ureas as redox-active receptors for anions.
abstract: Four redox-active receptors, 1-4, based on the incorporation of p-phenylenediamine(s) within a urea framework, were synthesized, and the affinities of two for a series of anions were quantified through UV-vis and NMR spectroscopic studies. The structure of 1 was confirmed by X-ray crystallography. For the oxoanions studied, complex stabilities approached 10(6) M(-1) in acetonitrile and decreased with the decreasing basicity of the anion (CH(3)COO(-) > C(6)H(5)COO(-) > H(2)PO(4)(-) > NO(2)(-) > NO(3)(-)). The presence of the urea functionality caused an increase in the oxidation potential of the p-phenylenediamine subunit compared to that of free p-phenylenediamine. Electrochemical studies of the anion complexes revealed two-wave behavior with the appearance of a second oxidation wave cathodic to that in the free receptors and characteristic of the bound anion. Ab initio DFT studies of a representative acetate complex revealed the consequences of host oxidation state on complex structure.
authors: Department of Chemistry, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors: John P
authors: JP
authors: Clare
authors: Anna
authors: A
authors: Statnikov
authors: Vincent
authors: V
authors: Lynch
authors: Andrew L
authors: AL
authors: Sargent
authors: John W
authors: JW
authors: Sibert