Fluorogenic Detection of Sulfite in Water by Using Copper(II) Azacyclam Complexes.

Copper(II) azacyclam complexes (azacyclam = 1,3,5,8,12-pentaazacyclotetradecane) containing naphthyl or dansyl subunits can be prepared by template synthesis involving proper sulfonamide derivatives as locking fragments. The macrocyclic complexes are very poorly emissive due to the fluorescence-quenching behavior displayed by Cu ions. However, the fluorescence can be recovered as a result of the decomposition of the complexes, which induces the release of free light-emitting subunits to the solution.

Detection of Copper(II) in Water by Methylene Blue Derivatives.

Two novel phenothiazin-5-ium derivatives bearing cyclam moieties (3 a and 3 b ) were synthesized and investigated as Cu sensors. Both ligands show intense spectral changes in the presence of Cu in aqueous solutions. The high molar extinction coefficient of the chromophore allows both naked eye detection and spectrophotometric quantitative determination of the cation at a micromolar-concentration scale.

Oxo-anion recognition by mono- and bisurea pendant-arm macrocyclic complexes.

The novel macrocyclic copper(II) complexes [2](2+) and [3](2+), carrying one or two (nitrophenyl)urea fragments appended to an azacyclam or diazacyclam framework, exploit the hydrogen-bond-forming abilities of the urea subunits, along with the metal-ligand interaction, in the recognition of anionic species. Equilibrium studies in acetonitrile performed on [2](2+) and [3](2+) show that (nitrophenyl)urea pendant arms strongly interact with anionic species such as carboxylates and phosphates, which display both coordinating tendencies toward copper(II) and good affinity toward urea subunits. Stability constants of the adducts are considerably higher than those determined for the interaction of the same anions with a "plain urea" reference compound, confirming the synergistic action of metallomacrocyclic and urea subunits.

Light-emitting charge transfer species promoted by metal ion coordination.

The coordinative interaction between zinc(II) and naphthalene-labeled diiminopyridine ligands induces the formation of light-emitting intracomplex charge transfer species.

A two-channel molecular dosimeter for the optical detection of copper(II).

A cyclam-like macrocycle with an integrated push-pull chromophore selectively detects Cu2+ inclusion through both orange-to-yellow colour change and quenching of the green fluorescence.

Metal-induced assembling/disassembling of fluorescent naphthalenediimide derivatives signalled by excimer emission.

The new quadridentate bischelating ligands 2 and 3 display in solution the typical absorption and emission properties expected for naphthalenediimide derivatives. Spectrophotometric studies show that systems 2 and 3 interact with Zn(II), Cd(II) and Cu(I) in CHCl3 or MeCN according to an apparent 1:1 stoichiometry. Molecular modelling, ESI-MS and 1H NMR experiments indicate that the complex species formed in the presence of stoichiometric amounts of metal ion are nonhelical [2 + 2] adducts.

Light-emitting molecular machines: pH-induced intramolecular motions in a fluorescent nickel(II) scorpionate complex.

A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.

Water soluble molecular switches of fluorescence based on the Ni(III)/Ni(II) redox change.

The water soluble Ni(II) complexes of the cyclam derivatives with 1,3-benzodioxole and 1,2,3-trimethoxybenzene display the fluorescent emission typical of the covalently linked fluorophores, which results from a charge transfer excited state. On oxidation to Ni(III), the fluorescence is completely quenched due to the occurrence of an electron transfer (eT) process from the excited fluorogenic fragment Fl to the oxidized metal. Thus, fluorescence can be switched off/on at will, for several cycles, by consecutively oxidizing and reducing the metal center, in controlled potential electrolysis experiments both in acetonitrile and in aqueous 0.