A new fluorescent macrocyclic structure (0) bearing two naphthalene units at both ends of a cyclic polyaminic chain containing two phenanthroline units was investigated with potentiometric and fluorescence (steady-state and time-resolved) techniques. The fluorescence emission spectra show the simultaneous presence of three bands: a short wavelength emission band (naphthalene monomer), a middle emission band (phenanthroline emission), and a long-wavelength band. All three bands were found to be dependent on the protonation state of the macrocyclic unit (including the polyaminic and phenanthroline structures). The existence of the long-wavelength emission band is discussed and is shown to imply that a bending movement involving the two phenanthroline units leads to excimer formation. This is determined by comparison with the excimer emission formed by intermolecular association of 1,10-phenanthroline. With ligand L1, excimer formation occurs only at pH values above 4. At very acidic pH values, the protonation of the polyamine bridges is extensive leading to a rigidity of the system that precludes the bending movement. The interaction with metal cations Zn(II) and Cu(II) was also investigated. Excimer formation is, in these situations, increased with Zn(II) and decreased with Cu(II). The long-emission band is shown to present a different wavelength maximum, depending on the metal, which can be considered as a characteristic to validate the use of ligand L1 as a sensor for a given metal.

Speciation studies in aqueous solution on the interaction Of Cu2+ and Zn2+ with a series of polyaminic ligands N-naphthalen-1-ylmethyl-N'-[2-[(naphthalen-1-ylmethyl)- amino]-ethyl)-ethane-l,2-diamine (LI), N-naphthalen-lylmethyl-iV-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethyl- amino]-ethyl)-ethane-l,2-diamine (L2) and N-naphthalen-1-ylmethyl-N'-[2-(2-{2-[(naphthalen-1-ylmethyl)-amino]- ethylamino)-ethylamino)-ethyl]-ethane-1,2-diamine (L3) containing two naphthylmethyl groups at their termini and N-1-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethyl-amino)-ethyl)-ethane-1,2-diamine (L4) containing just one naphthylmethyl group have been carried out at 298.1 K in 0.15 mol dm (-3) NaCl. In the case of the tetraamines L2 and L4, their coordination capabilities towards Cd2+, Ni2+, Co2+ and Pb2+ have also been considered. The stability constants follow the general Irving-Williams sequence. The steady-state fluorescence emission studies on the interaction with metal ions show that while Cu2+ produces a chelation enhancement of the quenching (CHEQ), the interaction with Zn2+ leads to a chelation enhancement of the fluorescence (CHEF). Finally, ligands L1, L2 and L3 have been successfully covalently attached to silica surfaces and some preliminary results of their emissive properties are given.

The synthesis, protonation behavior, and Cu2+ and Zn2+ coordination chemistry of the novel bibrachial aza lariat ether (naphthalen-1-ylmethyl)[2-(20-{2-[(naphthalen-1-ylmethyl)amino]ethyl}-3,6,9,17,20,23,29,30-octaazatricyclo-[23.3.1.1*11,15*]triaconta-1(29),11(30),12,14,25,27-hexaen-6-yl)ethyl]amine (L) are discussed. The macrocycle, which has two aminoethyl naphthyl moieties symmetrically appended to a 2:2 azapyridinophane structure, displays, in the pH range 2-11, six protonation steps that correspond to the protonation of the secondary amino groups. Steady-state fluorescence measurements show emissions due to the monomer and to the excimer formed between the two naphthalene fragments of the macrocycle. The time-resolved fluorescence data, obtained by the time-correlated single photon counting technique, show that a significant percentage of excimer is preformed as ground-state dimers. The ligand L forms with the metal ions Cu2+ and Zn2+ mono- and dinuclear complexes in aqueous solution. The influence of metal coordination in the fluorescence emission of L is analyzed. The acid-base, coordination capabilities, and emissive behavior of L are compared with those presented by its synthetic precursor L1, which has a tripodal tris(2-aminoethyl)amine structure functionalized at one of its terminal amino groups with a naphthyl moiety.