The Zn2+ and Cd2+ complexing properties of four ligands containing a 4,4'-substituted biphenyl moiety are described. Ligands I and 3. containing only one 1-aza-18-crown-6 cavity, lead to selective complexation of Cd2+ versus Zn2+. Ligand 4, with two crown cavities linked to a tetramethylbenzidine unit, is able to form 1:1 complexes with Zn2+ and Cd2+, showing a higher complexing constant with Zn2+ than with Cd2+ probably due to enthalpic factors. Several complementary experiments suggest that the 1:1 complexes formed by ligand 4 involve both crown cavities acting together to give rise to clamp structures. The formation of this type of zinc complex gives rise to red shifted emission bands and distinct quenching of the fluorescence. A similar situation is observed with cadmium but the change is then less pronounced. When mixtures of both salts are used, ligand 4 selectively responds to zinc. Finally, ligand 2, which also has two crown cavities but contains nitro rather than amino groups in the biphenyl moiety, shows no propensity to form clamp complexes and, for this reason, it complexes cadmium much more strongly than zinc and binds the former selectively when mixtures of both salts are used in complexing experiments. (C) 2004 Elsevier Ltd. All rights reserved.
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Univ Salerno, Dept Chem & Biol, Via Giovanni Paolo II 132, I-84084 Fisciano, SA, ItalyUniv Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, Italy
Voccia, Maria
Formica, Mauro
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Univ Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, ItalyUniv Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, Italy
Formica, Mauro
Caporaso, Lucia
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Univ Salerno, Dept Chem & Biol, Via Giovanni Paolo II 132, I-84084 Fisciano, SA, ItalyUniv Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, Italy
Caporaso, Lucia
Macedi, Eleonora
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Univ Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, ItalyUniv Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, Italy
Macedi, Eleonora
Fusi, Vieri
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Univ Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, ItalyUniv Urbino, Dept Pure & Appl Sci, Via Stn 4, I-61029 Urbino, Italy
机构:
National Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering andNational Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering and
刘丽艳
李鑫钢
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National Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering andNational Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering and
李鑫钢
唐国武
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机构:National Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering and
唐国武
孙津生
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National Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering andNational Engineering Research Center for Distillation Technology School of Chemical Engineering and Technology,Tianjin University,Tianjin 300072,China
2. College of Chemistry Chemical Engineering and
National Engineering Research Center for Distillation Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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National Engineering Research Center for Distillation Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China