title: Design and Sensing Properties of a Self-Assembled Supramolecular Oligomer.
abstract: Supramolecular polymers are a class of macromolecules stabilized by weak non-covalent interactions. These self-assembled aggregates typically undergo stimuli-induced reversible assembly and disassembly. They thus hold great promise as so-called functional materials. In this work, we present the design, synthesis, and responsive behavior of a short supramolecular oligomeric system based on two hetero-complementary subunits. These "monomers" consist of a tetrathiafulvalene-functionalized calix[4]pyrrole (TTF-C[4]P) and a glycol diester-linked bis-2,5,7-trinitrodicyanomethylenefluorene-4-carboxylate (TNDCF), respectively. We show that when mixed in organic solvents, such as CHCl3, CH2ClCH2Cl, and methylcyclohexane, supramolecular aggregation takes place to produce short oligomers stabilized by hydrogen bonding and donor-acceptor charge-transfer (CT) interactions. The self-associated materials were characterized by1H NMR and UV/Vis/NIR absorption spectroscopy, as well as by concentration- and temperature-dependent absorption spectroscopy and dynamic light scattering (DLS) analyses of both the monomeric and oligomerized species. The self-associated system produced from TTF-C[4]P and TNDCF exhibits a concentration-dependent aggregation behavior typical of supramolecular polymers. Further support for the proposed self-assembly came from theoretical calculations. The fluorescence emitting properties of TNDCF are quenched under conditions that promote the formation of supramolecular aggregates containing TTF-C[4]P and TNDCF. This quenching effect has been utilized as a probe for the detection of substrates in the form of anions (i.e., chloride) and nitroaromatic explosives (i.e., 1,3,5-trinitrobenzene). Specifically, the addition of these substrates to mixtures of TTF-C[4]P and TNDCF produced a fluorescence "turn-on" response.
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
authors.forename: Steffen
authors.initials: S
authors.lastname: Bähring
authors.affiliation: Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, 03202, Alicante, Spain), Fax.
authors.forename: Luis
authors.initials: L
authors.lastname: Martín-Gomis
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Olsen
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
authors.forename: Kent A
authors.initials: KA
authors.lastname: Nielsen
authors.affiliation: Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street, Stop A5300, Austin, Texas, 78712-1224, USA), Fax.
authors.forename: Dong Sub
authors.initials: DS
authors.lastname: Kim
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Duedal
authors.affiliation: Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Elche, 03202, Alicante, Spain), Fax. asastre@umh.es.
authors.forename: Ángela
authors.initials: Á
authors.lastname: Sastre-Santos
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark. joj@sdu.dk.
authors.forename: Jan O
authors.initials: JO
authors.lastname: Jeppesen
authors.affiliation: Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street, Stop A5300, Austin, Texas, 78712-1224, USA), Fax. Sessler@cm.utexas.edu.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
keywords: calix[4]pyrrole; fluorescence; sensors; supramolecular ensembles; tetrathiafulvalene