This paper reports a new scorpiand-type fluorescent ligand able to sense Zn(ii) in aqueous solution at physiological pH 7.4.

A series of symmetrical and unsymmetrical alkyl tren based tris-thiourea anion transporters were synthesised and their anion binding and transport properties studied. Overall, increasing the steric bulk of the substituents resulted in improved chloride binding and transport abilities. Including a macrocycle in the scaffold enhanced the selectivity of chloride transport in the presence of fatty acids, by reducing the undesired H+ flux facilitated by fatty acid flip-flop. This study demonstrates the benefit of including enforced steric hindrance and encapsulation in the design of more selective anion receptors.

Rates of cleavage have been measured spectrophotometrically for some PhS-M R, compounds (M = Si, Ge, Sn, and Pb) in neutral and acidic aqueous dioxan. The reactivity sequences are unrelated to the electronegativity of the metals and the ease of cleavage increases in the order Si < Ge -= Sn < Pb. The substituent and solvent isotope effects indicate some differences in the cleavage mechanism of these compounds. This is governed by sulphurmetal bond polarization enhanced in the heavier Sn and Pb derivatives by co-ordination between water and the metal. A dual mechanism which fits the experimental results is proposed.

1993 mercaptans, thioethers mercaptans, thioethers (benzene compounds) Q 0580 41 -159 Fluoride Ion Induced Thiophilic Addition of Allylsilanes to Thioketones. -Addition of the allylsilanes (II) to the thioketones (I) and (IV) in the presence of fluoride ions yields the allyl sulfides (III) and (V) respectively. Different sources of the fluoride ion have been examined: tetrabutylammonium fluoride proves to give the highest yields. -(CAPPERUCCI, A.; FERRARA, M. C.; DEGL'INNOCENTI, A.; BONINI, B. F.; MAZZANTI, G.; ZANI, P.; RICCI, A.; Synlett (1992) 11, 880-882; Centro CNR Chim. Strutt. Comp. Eterocicl., 50121 Firenze, Italy; EN)