| Abstract
| - The macrocycles L1−L3 incorporating N2S3-, N2S2O-, and N2S2-donor sets, respectively, and containing the 1,10-phenanthroline unit interact in acetonitrile solution with heavy metal ions such as PbII, CdII, and HgII to give 1:1 ML,1:2 ML2, and 2:1 M2L complex species, which specifically modulate the photochemical properties of the ligands.The stoichiometry of the complex species formed during spectrofluorometric titrations and their formation constantsin MeCN at 25 °C were determined from fluorescence vs MII/L molar ratio data. The complexes [Pb(L1)][ClO4]2·1/2H2O (1), [Pb(L2)][ClO4]2·MeNO2 (1a), [Pb(L3)2][ClO4]2·2MeCN (1b), and [Cd(L3)][NO3]2 (2b) were also characterizedby X-ray diffraction studies. The conformation adopted by L1−L3 in these species reveals the aliphatic portion ofthe rings folded over the plane containing the heteroaromatic moiety with the ligands trying to encapsulate themetal center within their cavity. In 1, 1a, and 2b the metal ion completes the coordination sphere by interactingwith counteranion units and solvent molecules. On the contrary, the 1:2 complex 1b shows PbII sandwiched betweentwo symmetry-related molecules of L3 reaching an overall [4N + 4S] eight-coordination.
- Spectrofluorometric titrations of novel mixed-donor phenanthroline-containing macrocycles with heavy metal ions PbII, CdII, and HgII reveal modulation of the fluorescence emission intensity of the ligands with differentiation for CdII over PbII and HgII. Conductometric and crystallographic studies clarify the nature of the complex species formed during spectrofluorometric titrations.
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