Coordination Chemistry of Mixed-Donor Pyridine-Containing Macrocyclic Ligands: From Optical to Redox Chemosensors for Heavy Metal Ions
2,8-Dithia-5-aza-2,6-pyridinophane (<b>L1</b>) has been used as a receptor unit in the construction of the conjugated redox chemosensor 5-ferrocenylmethyl-2,8-dithia-5-aza-2,6-pyridinophane (<b>L3</b>). In order to further explore the coordination chemistry of <b>L1<...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/1/130 |
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| Summary: | 2,8-Dithia-5-aza-2,6-pyridinophane (<b>L1</b>) has been used as a receptor unit in the construction of the conjugated redox chemosensor 5-ferrocenylmethyl-2,8-dithia-5-aza-2,6-pyridinophane (<b>L3</b>). In order to further explore the coordination chemistry of <b>L1</b>, and comparatively, that of its structural analogue 2,11-dithia-5,8-diaza-2,6-pyridinophane (<b>L2</b>), featuring two secondary nitrogen atoms in the macrocyclic unit, the crystal structures of the new synthesised complexes [Pb(<b>L1</b>)(ClO<sub>4</sub>)<sub>2</sub>]·½CH<sub>3</sub>CN, [Cu(<b>L2</b>)](ClO<sub>4</sub>)<sub>2</sub>·CH<sub>3</sub>CN and [Cd(<b>L2</b>)(NO<sub>3</sub>)]NO<sub>3</sub> were determined by X-ray diffraction analysis. The electrochemical response of <b>L3</b> towards the metal ions Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>, Hg<sup>2+</sup>, and Pb<sup>2+</sup> was investigated by cyclic voltammetry (CV) in CH<sub>2</sub>Cl<sub>2</sub>/CH<sub>3</sub>CN 0.25:1 (<i>v</i>/<i>v</i>) mixture. Upon addition to <b>L3</b> of increasing amounts of the aforementioned metal cations, the wave corresponding to the Fc<sup>+</sup>/Fc redox couple of the un-complexed <b>L3</b> was gradually replaced by a new reversible wave at more positive potentials and corresponding to the Fc<sup>+</sup>/Fc redox couple of the complexed ligand. The maximum anodic shift of the ferrocene oxidation wave is observed in the presence of Pb<sup>2+</sup> (230 mV), to which corresponds a reaction coupling efficiency (RCE) value as large as 7.9 × 10<sup>3</sup>. The response selectivity of <b>L3</b> is discussed in reference to the optical selectivity observed for conjugated chemosensors featuring <b>L1</b> as receptor unit and different fluorogenic fragments as signalling units. |
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| ISSN: | 1420-3049 |