title: Self-assembled systems of water soluble metal 8-hydroxyquinolates with surfactants and conjugated polyelectrolytes.
abstract: We have studied the interaction of 8-hydroxyquinoline-5-sulfonate (8-HQS) with the metal ions Al(iii) and Zn(ii) in aqueous solution in the presence of tetraalkylammonium surfactants using UV/vis absorption, fluorescence, NMR spectroscopy and electrical conductivity measurements, complemented by DFT calculations and molecular dynamics (MD) simulations. Under appropriate conditions, complexes between 8-HQS and metal ions form rapidly, and have similar electronic, spectroscopic and photophysical properties to the corresponding metal quinolates, such as Alq3. These interact with the cationic surfactants, leading to marked increases in fluorescence intensity. However, significant differences are seen in the behavior of the two metal ions. With aluminium, a stable [Al(8-QS)3](3-) anion is formed, and interacts, predominantly through electrostatic interactions, with the surfactant, without disrupting the metal ion coordination sphere. In contrast, with Zn(ii), there is a competition between the metal ion and surfactants in the interaction with 8-HQS, although the [Zn(8-QS)2(H2O)2](2-) species is stable at appropriate pH and surfactant concentration. The studies are extended to systems with the conjugated polyelectrolyte (CPE) poly-(9,9-bis(6-N,N,N-trimethylammonium)hexyl)-fluorene-phenylene bromide (HTMA-PFP), which has a similar alkylammonium chain to the surfactants. Mixing metal salt, 8-HQS and HTMA-PFP in the presence of a nonionic surfactant leads to the formation of a metal complex/CPE supramolecular assembly between the conjugated polyelectrolyte and the metal/8-HQS complex, as demonstrated by electronic energy transfer. The potential of these systems in sensing, light harvesting, and electron injection/transport layers in organic semiconductor devices is discussed.
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Hugh D
authors.initials: HD
authors.lastname: Burrows
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Telma
authors.initials: T
authors.lastname: Costa
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Ramos
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Artur J M
authors.initials: AJ
authors.lastname: Valente
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Beverly
authors.initials: B
authors.lastname: Stewart
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Licinia L G
authors.initials: LL
authors.lastname: Justino
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Aline I A
authors.initials: AI
authors.lastname: Almeida
authors.affiliation: Centro de Química, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. burrows@ci.uc.pt.
authors.forename: Nathanny Lessa
authors.initials: NL
authors.lastname: Catarina
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernandez de Elche, Avda. de la Universidad s/n, 03202 Elche, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mallavia
authors.affiliation: Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Matti
authors.initials: M
authors.lastname: Knaapila