"Wurster-type" ureas as redox-active receptors for anions.

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)(-)).

Wurster's crowns: a comparative study of ortho- and para-phenylenediamine-containing macrocyclic receptors.

Two series of isomeric, redox-responsive azacrown ethers based on ortho- and para-phenylenediamine (Wurster's crowns) have been synthesized and their properties explored through 13C NMR spectroscopy, electrospray ionization mass spectrometry, cyclic voltammetry, and X-ray crystallography. These crowns display strong affinity for alkali metal cations while maintaining comparable selectivity profiles to the parent crown ethers from which they are derived. Like Wurster's reagent (N,N,N',N'-tetramethyl-p-phenylenediamine or para-TMPD), the para-Wurster's crowns undergo two reversible one-electron oxidations.

Electron transfer vs coordination chemistry: isomer-specific binding of HgII by an ortho-Wurster's thiacrown ether.

Isomeric p- and o-phenylenediamine-containing macrocyclic hosts (Wurster's thiacrown ethers L1 and L2, respectively) were prepared and studied as Hg(II) ionophores. The distinct electrochemical properties of the two hosts allowed for the formation of a coordination compound with the ortho-Wurster's thiacrown ether but not the para isomer. In the latter case, the Hg(II) ion served as an oxidant in an electron-transfer reaction with the host.

A theoretical investigation on the Wurster's crown analogue of 18-crown-6.

An ab initio, quantum mechanical study of the Wurster's crown analogue of 18-crown-6 and its interactions with the alkali metal cations are presented. This study explores methods for accurately treating large, electron-rich species while providing an understanding of the molecular behavior of a representative member of this class of crowns. The molecular geometries, binding energies, and binding enthalpies are evaluated with methods similar to those reported for the analysis of 18-crown-6 and its alkali metal complexes to facilitate direct comparison.

Wurster's thiacrown ethers: synthesis, properties, and Pt(II)-coordination chemistry.

Two isomeric redox-responsive azathiacrown ethers, based on p-phenylenediamine, have been synthesized in traditional crown (L1) and crownophane (L2) architectures. Each of these "Wurster's crowns" was designed to target the encapsulation of transition or heavy metal ions. The solid-state structures of these ligands show binding cavities defined by three exocyclic sulfur atoms and either a N donor atom (L1) or the electron-rich pi face of the phenylenediamine subunit (L2).

"ortho-Wurster's crowns": synthesis and properties of a novel phenylenediamine-based redox-active macrocyclic ligand.

A hybrid, macrocyclic structure based on o-phenylenediamine and a crown ether promotes an intimate mutual interaction with a bound potassium ion in the form of chelation by the redox-active moiety. A general synthetic method and properties are described for the first member of a new class of redox-active, lariat-type macrocycles called the "o-Wurster's crowns".

Lipophilic derivatives of cyclam as new inhibitors of tumor cell growth.

Two new lipophilic tetraazamacrocycles were prepared and, in contrast to non-lipophilic analogs, found to be potent inhibitors of tumor cell growth in vitro with IC50 values below 10 micromolar.