| Autor: |
Romano GM; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Simonini Steiner YT; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Bartoli F; Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Via Savi 10, 56126, Pisa, Italy., Conti L; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Macedi E; Department of Industrial Engineering, Università di Firenze, Via S. Marta 3, Firenze, Italy., Bazzicalupi C; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Rossi P; Department of Pure and Applied Sciences, University of Urbino 'Carlo Bo', Via della Stazione 4, 61029 Urbino, Italy., Paoli P; Department of Pure and Applied Sciences, University of Urbino 'Carlo Bo', Via della Stazione 4, 61029 Urbino, Italy., Innocenti M; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Bencini A; Department of Chemistry 'Ugo Schiff', Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Firenze, Italy. andrea.bencini@unifi.it., Savastano M; Department of Human Sciences for the Promotion of Quality of Life, Università San Raffaele Roma, via di Val Cannuta 247, 00166 Roma, Italy. |
| Abstrakt: |
Selective binding and optical sensing of Zn(II) and Cd(II) by L1, HL2, L3, H 2 L4 and H 2 L5 receptors were analysed in aqueous solutions by coupling potentiometric, UV-vis absorption and fluorescence emission measurements, with the aim to determine the effect of complex stability on selective signalling of metals with similar electronic configurations. All receptors share the same cyclic tetra-amine binding unit attached to a single quinoline (Q) or 8-hydroxyquinoline (8-OHQ) unit (L1 and HL2, respectively), two Q or 8-OHQ moieties (L3 and H 2 L4, respectively), and, finally, two Q and two acetate groups (H 2 L5). The crystal structures of the Cd(II) and Zn(II) complexes show that L3 and H 2 L4 feature a cavity in which the larger Cd(II) complex is better fitted than the Zn(II) complex, leading to the formation of more stable Cd(II) complexes. In turn, Zn(II) forms more stable complexes with L1 and HL2, owing to its high tendency to give 5-coordinated complexes. Considering optical selectivity, Zn(II) gives the most emissive complex with L3, while the corresponding Cd(II) complex is basically quenched. The gathered structure of the Zn(II) complex, in which the two Q units are associated with one another-a structural motif not observed in the [CdL3] 2+ complex-leads to poor solvation of the Q units, favouring complex emission. Among 8-OHQ-containing receptors, the most emissive complex is formed by Cd(II) with HL2, containing a single 8-OHQ moiety. H 2 L4 forms non-emissive complexes: the presence of two coordinating 8-OHQ moieties weakens metal interactions with the tetra-amine unit, favouring PET to the excited fluorophore that quench the emission. |
