| Autor: |
Esteves CV; Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. delgado@itqb.unl.pt., Costa J; Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal., Esteban-Gómez D; Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña, Spain., Lamosa P; Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. delgado@itqb.unl.pt., Bernard H; Université de Brest, UMR-CNRS 6521, IBSAM, UFR des Sciences et Techniques, 6 Avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France., Platas-Iglesias C; Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña, Spain., Tripier R; Université de Brest, UMR-CNRS 6521, IBSAM, UFR des Sciences et Techniques, 6 Avenue Victor le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France., Delgado R; Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. delgado@itqb.unl.pt. |
| Abstrakt: |
In the search for receptors suitable for the recognition of phosphate or polyphosphate anions, a new unsymmetrical squaramide-based ligand bearing dipicolylamine (dpa) and ethylpiperazine units (L) was designed and prepared. The acid-base reactions of L, its copper(ii) complexation behaviour and the binding of phosphate and polyphosphate anions by the copper(ii) complexes used as receptors were evaluated. 1 H and 13 C NMR titrations of L performed in D 2 O allowed the determination of its protonation sequence. The ligand L is able to coordinate two copper(ii) cations forming thermodynamically stable dinuclear complexes likely having two water molecules bound to each metal centre, as supported by DFT calculations. Coordinated water molecules can be replaced by the O-donors of the phosphate/polyphosphate anions. The potentiometric studies showed that at 2 : 1 Cu 2+ : L ratio the dinuclear [Cu 2 LH -1 ] 3+ species predominates from pH ∼ 5 to ∼7, and hydroxodinuclear species prevail at pH > 7. 1 H NMR experiments in both H 2 O/D 2 O 9 : 1 v/v and in DMSO proved that copper(ii) coordination provokes deprotonation of the squaramide NH bound to the ethylpiperazine moiety, resulting in [Cu 2 LH -1 ] 3+ species. The dicopper(ii) complexes of L, [Cu 2 LH -i ] 4-i , were used as the receptor for the uptake of some phosphate and polyphosphate anions. The receptor presents very high association constants with HPPi 3- and ATP 4- and the determined K eff showed that at physiological pH ATP 4- is selectively taken from an aqueous solution containing phenylphosphate (PhPO 4 2- ), aminoethylphosphate (Haep - ), AMP 2- and ADP 3- , but HPPi 3- strongly interferes. DFT calculations suggest that the strong interaction with HPPi 3- and ATP 4- is related to the simultaneous coordination of the polyphosphate unit to the two copper(ii) centres. |
