Ten Ag + -selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with π-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag + sensors can be maintained in the subnanomolar range for at least one month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3× 10 −11 M (potentiometrically) and 2 × 10 −11 M Ag + (optically) are found with bridged thiacalixarenes.

A simple synthesis of a dendritic hexaferrocenyl electron donor (5) is described in which six ferrocene moieties are connected at the vertices of the propeller of the hexaphenylbenzene core. The molecular structure of 5 is confirmed by X-ray crystallography. An electrochemical analysis along with redox titrations (which are tantamount to coulometry) confirmed that it ejects six electrons at a single potential. [structure: see text]

The one-electron oxidation of tetramethoxydibenzobicyclo[4.4.1]undecane (4) prompts it to undergo a clam-like electromechanical actuation into a cofacially pi-stacked conformer as established by (i) electrochemical analysis, (ii) by the observation of the intense charge-resonance transition in the near IR region in its cation radical spectrum, and (iii) by X-ray crystallographic characterization of the isolated cation radical salt (4(+*) SbCl(6)(-)).

We have designed and synthesized a versatile fluorene-based receptor (1) in a one-pot reaction from readily available precursors, which adapts a deltaphane- or pi-prismand-like conformer via a simple C-C bond rotation. Such a conformational adaptability of 1 allows it to bind a single silver cation with remarkable efficiency (K approximately 15 000 M-1) as monitored by 1H NMR or UV-vis spectroscopy and further confirmed by competition experiments with tris[2.2.2]paracyclophane (or pi-prismand 2) as well as a model compound 3 containing only one fluoranyl ring.

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