Exploring the binding ability of polyammonium hosts for anionic substrates: selective size-dependent recognition of different phosphate anions by bis-macrocyclic receptors.

Binding of mono-, di-, and triphosphate, adenosine diphosphate (ADP), and adenosine triphosphatase (ATP) with receptors L1-L3, composed of two [9]aneN(3) units separated by a 2,9-dimethylene-1,10-phenanthroline (L1), a 2,6-dimethylenepyridine (L2), or a 2,3-dimethylenequinoxaline (L3) spacer, has been studied by means of potentiometric titrations, (1)H and (31)P NMR measurements in aqueous solutions, and molecular modeling calculations. In the case of inorganic phosphates, the binding properties of the receptors appear to be determined by their geometrical features, in particular the distance between the two [9]aneN(3) units imposed by the spacer separating the two macrocyclic units. While L1 is able to selectively bind triphosphate over di- and monophosphate, L3 selectively coordinates the smaller monophosphate anion.

Unusual formation of a [NiSFe(2)(CO)(6)] cluster: a structural model for the inactive form of [NiFe] hydrogenase.

The synthesis and characterisation of the trinuclear Ni-Fe complex [Ni(L(2))SFe(2)(CO)(6)] (1) formed from the reaction of [Ni(L(1))] with Fe(3)(CO)(12) is described. The single-crystal X-ray structure of 1 shows Ni(ii) bound to three thioether R(2)-S donors and bridged by a sulfide (S(2-)) group to two Fe(CO)(3) units. undergoes a reversible one-electron reduction process at E(1/2) = -1.

Encapsulation of metal cations and anions within the cavity of bis(1,4,7-triazacyclononane) receptors.

The synthesis and characterisation of a new bis([9]aneN3) ligand (L4) containing two [9]aneN3 macrocyclic moieties separated by a 2,6-dimethylenepyridine unit is reported. A potentiometric and 1H NMR study in aqueous solution reveals that ligand protonation occurs on the secondary amine groups and does not involve the pyridine nitrogen. The coordination properties toward Cu(II), Zn(II), Cd(II) and Pb(II) were studied by means of potentiometric and UV spectrophotometric measurements.

Electrocatalytic production of hydrogen by a synthetic model of [NiFe] hydrogenases.

The radical cluster anion [Ni(L)Fe2(CO)6]- catalyses the reduction of protons to produce molecular hydrogen.

Co-ordination chemistry of amino pendant arm derivatives of 1,4,7-triazacyclononane.

The binding properties of 1,4,7-triazacyclononane ([9]aneN3) to metal cations can be adapted through sequential functionalisation of the secondary amines with aminoethyl or aminopropyl pendant arms to generate ligands with increasing numbers of donor atoms. The new amino functionalised pendant arm derivative of 1,4,7-triazacyclononane ([9]aneN3), L1, has been synthesised and its salt [H2L1]Cl2 characterised by X-ray diffraction. The protonation constants of the ligands L1-L4 having one, two or three aminoethyl or three aminopropyl pendant arms, respectively, on the [9]aneN3 framework, and the thermodynamic stabilities of their mononuclear complexes with CuII and ZnII have been investigated by potentiometric measurements in aqueous solutions.

Coordination properties of new bis(1,4,7-triazacyclononane) ligands: a highly active dizinc complex in phosphate diester hydrolysis.

The synthesis and characterization of three new bis([9]aneN(3)) ligands, containing respectively 2,2'-bipyridine (L(1)), 1,10-phenanthroline (L(2)), and quinoxaline (L(3)) moieties linking the two macrocyclic units, are reported. Proton binding and Cu(II), Zn(II), Cd(II), and Pb(II) coordination with L(1)-L(3) have been studied by potentiometric titrations and, for L(1) and L(2), by spectrophotometric UV-vis measurements in aqueous solutions. All ligands can give stable mono- and dinuclear complexes.