‘meta-Wurster's crowns’: The synthesis and properties of meta-Phenylenediamine-based macrocycles

“Wurster-Type” Ureas as Redox-Active Receptors for Anions

“…As has been previously shown for cationic receptors, replacement of a donor atom functionality with a redox-active phenylenediamine unit adds redox activity (in some cases, reversible) without compromising the ability of the host to form complexes . For example, it was shown that replacement of a single O atom in 18-crown-6 with an N , N -dimethylamino- p -phenylenediamino group gave a Wurster’s crown ether that not only was selective for the potassium ion, like 18-crown-6, but was electrochemically responsive to cations.…”

“…The basic template of these responsive receptors consists of a recognition site coupled to a subunit that undergoes a measurable change in one or more physical properties, such as color, fluorescence, or shifts in redox potential upon binding. , In particular, redox-active anion and cation receptors based on ferrocene and tetrathiafulvalene have received much attention. Redox-active cation receptors that employ a functional equivalent of Wurster’s reagent, N , N ′-tetramethyl- p -phenylenediamine ( p -TMPD), as a signaling subunit, are also well-studied, but those for anions are unknown . Here we report the synthesis, characterization, anion affinities and electrochemistry of Wurster-type ureas, new anion receptors that incorporate p -phenylenediamine within the urea framework.…”

In situ FTIR spectroelectrochemistry and spectral simulations using DFT: Efficient complementary tools to elucidate complex electrochemical mechanisms

“…The redox-active ''Wurster's Crowns'', phenylenediamine-containing macrocycles that are inspired by the well-known molecule N,N,N 0 ,N 0 -tetramethyl-para-phenylenediamine (p-TMPD) or Wurster's reagent [6][7][8] offer the opportunity for strong mutual interaction between the redox center and guest in redox-switching and sensing applications. Wurster's crowns, like TMPD, undergo two successive, one electron oxidations and, importantly, contain a macrocyclic ''N'' donor atom that is critical to both complex stability and electrochemical activity.…”

On the oxidation of Wurster’s reagent and the Wurster’s crown analog of 15-crown-5 in the presence of alkali metal cations

“…In general, these host molecules are structurally distinguished by the presence of a redox-active subunit near or within a cation binding cavity. To enhance the interaction between the redox center and a bound guest, we have focused our efforts on the synthesis and study of ''Wurster's Crowns'', redox-active, phenylenediamine-containing macrocycles that are inspired by the well-known molecule N,N,N',N'-tetramethyl-para-phenylenediamine (p-TMPD) or Wurster's reagent [8][9][10][11]. Wurster's crowns, like Wurster's reagent, undergo two successive one electron oxidations and, importantly, contain a macrocyclic ''N'' donor atom that is critical to both complex stability and electrochemical activity.…”

“…As such, this class of hosts offers the opportunity for strong mutual interaction between the redox center and guest in redox-switching and sensing applications. While a number of previous studies [1][2][3][4][5][6][9][10][11][12] have monitored the complexation ability of redox-active hosts through electrochemical measurements (primarily cyclic voltammetry), these data either do not or, typically, have not been used to provide detailed structural information. Electrochemical simulations of CV curves can be used to postulate reaction mechanisms but, in the absence of additional data, typically not used to confirm proposed mechanisms.…”