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Titolo:
Co2+ translocation in a terpyridine-cyclam ditopic receptor
Autore:
Padilla-Tosta, ME; Lloris, JM; Martinez-Manez, R; Pardo, T; Sancenon, F; Soto, J; Marcos, MD;
Indirizzi:
Univ Politecn Valencia, Dept Quim, E-46071 Valencia, Spain Univ Politecn Valencia Valencia Spain E-46071 m, E-46071 Valencia, Spain Univ Valencia, Inst Ciencia Mat, Valencia 46071, Spain Univ Valencia Valencia Spain 46071 st Ciencia Mat, Valencia 46071, Spain
Titolo Testata:
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
fascicolo: 5, , anno: 2001,
pagine: 1227 - 1234
SICI:
1434-1948(200105):5<1227:CTIATD>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
THERMAL HYSTERESIS; SPIN TRANSITION; COMPLEXES; SYSTEMS; ELECTRODES; MOLECULES; MEMBRANES; SWITCHES; DOMAINS; IONS;
Keywords:
translocation; ditopic receptors; electrochemistry; cobalt complexes;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Martinez-Manez, R Univ Politecn Valencia, Dept Quim, Camino Vera S-N, E-46071 Valencia, Spain Univ Politecn Valencia Camino Vera S-N Valencia Spain E-46071
Citazione:
M.E. Padilla-Tosta et al., "Co2+ translocation in a terpyridine-cyclam ditopic receptor", EUR J INORG, (5), 2001, pp. 1227-1234

Abstract

The coordination behaviour of the ditopic receptor of 1-[p-(2,2':6',2 "- terpyrid-4'-yl)tolyl]-1,4,8,11-tetraazacyclo-tetradecane (L-1) towards Co2+ in acetonitrile/water (70:30, v/v) has been investigated. At acidic pH values, the L-1-H+-Co2+ system shows an oxidation wave at 150 mV vs. SCE, characteristic of Co2+ in a bis(terpyridine) environment. Upon addition of OH-, a reduction in the intensity of the wave at 150 mV is observed and a new oxidation wave appears at 1.30 V. This new wave is close to that found for [Co(cyclam)](2+) under similar working conditions. The electrochemical data thus suggest that there is a pH-controlled translocation of the Co2+ ion from the bis(terpyridine) to the cyclam environment. A similar inference can be made from the results of UV/Vis studies. A thermodynamic characterizationof the L-1-H+-Co2+ system has also been carried out. Stability constants have been determined in acetonitrile/water (70:30, v/v, containing 0.1 mol dm(-3) nBu(4)NClO(4) at 25 degreesC) using potentiometric techniques. The following species were found: [Co(L-1)(2)H-4](6+), [CO(L-1)(2)H-3](5+), [CO(L-1)H](3+), [Co(L-1)](2+), and [Co(L-1)(OH)](+). The 2:1 ligand-to-metal species [Co(L-1)(2)H-4](6+) and [Co(L-1)(2)H-3](5+) are assigned to complexes where Co2+ is coordinated by two terpyridine units. The [Co(L-1)H](3+), [CO(L-1)](2+), and [Co(L-1)(OH)](+) species are assigned to complexes where the Co2+ cation is in the cyclam binding domain. The pH-induced Co2+ jumping between coordination sites is discussed in terms of the different basicities of cyclam and terpyridine. Co2+ jumping between coordination sites has also been studied by the sequential acidification of basic mixtures of L-1 and Co2+. Under these conditions, the translocation was observed at a different pH value than when an acid-to-basic path was followed. The effect of anions such as phosphate and chloride on the translocation process has also been studied. In the presence of phosphate, translocation occurs at pH = 11 rather than at pH approximate to 8. The phosphate-L-1 and phosphate-L-1-Co2systems have been characterized by potentiometry and a remarkably good agreement has been found between the electrochemical and potentiometric data.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/09/20 alle ore 09:58:55