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Title: Spectroscopy and Coordination Chemistry of a New Bisnaphthalene−Bisphenanthroline Ligand Displaying a Sensing Ability for Metal Cations
Authors: Pina, João 
Melo, J. Seixas de 
Pina, Fernando 
Lodeiro, Carlos 
Lima, J. C. 
Parola, A. Jorge 
Soriano, Conxa 
Paz Clares, M. 
Albelda, M. Teresa 
Issue Date: 17-Oct-2005
Publisher: American Chemical Society
Citation: Inorganic Chemistry. 44:21 (2005) 7449-7458
Abstract: A new fluorescent macrocyclic structure (L1) bearing two naphthalene units at both ends of a cyclic polyaminic chain containing two phenanthroline units was investigated with potentiometric and fluorescence (steady-state and time-resolved) techniques. The fluorescence emission spectra show the simultaneous presence of three bands: a short wavelength emission band (naphthalene monomer), a middle emission band (phenanthroline emission), and a long-wavelength band. All three bands were found to be dependent on the protonation state of the macrocyclic unit (including the polyaminic and phenanthroline structures). The existence of the long-wavelength emission band is discussed and is shown to imply that a bending movement involving the two phenanthroline units leads to excimer formation. This is determined by comparison with the excimer emission formed by intermolecular association of 1,10-phenanthroline. With ligand L1, excimer formation occurs only at pH values above 4. At very acidic pH values, the protonation of the polyamine bridges is extensive leading to a rigidity of the system that precludes the bending movement. The interaction with metal cations Zn(II) and Cu(II) was also investigated. Excimer formation is, in these situations, increased with Zn(II) and decreased with Cu(II). The long-emission band is shown to present a different wavelength maximum, depending on the metal, which can be considered as a characteristic to validate the use of ligand L1 as a sensor for a given metal.
ISSN: 0020-1669
DOI: 10.1021/ic050733q
Rights: openAccess
Appears in Collections:FCTUC Química - Artigos em Revistas Internacionais

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