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Steady-state and time-resolved investigations on pyrene-based chemosensors.

Inorganic chemistry (2012-12-13)
Javier Fernández-Lodeiro, Cristina Núñez, Catherine S de Castro, Emilia Bértolo, J Sérgio Seixas de Melo, José Luis Capelo, Carlos Lodeiro
ABSTRACT

Two novel fluorescent probes bearing a single (P) and two (a podand-like structure, L) pyrene units derived from 1,5-bis(2-aminophenoxy)-3-oxopentane have been synthesized and investigated in dioxane using UV-vis absorption, and steady-state and time-resolved (in a picosecond time scale) emission spectroscopy; in the gas phase, matrix-assisted laser desorption ionization mass spectrometry was employed. In dioxane, the absorption and emission spectra of P present a unique band with maxima at 361 and 392 nm, which have been associated with the monomer absorption and emission bands, respectively. In dioxane, for compound L, an additional band with a maximum at ∼525 nm is observed; upon the addition of water, an emissive band (with maxima varying from 405 to 490 nm) appears in both P and L spectra; this is discussed in terms of the emission of a species with charge character. Upon metal addition (Cu(2+), Zn(2+), and Ag(+)) to P, a gradual quenching effect of the monomer emission is observed and found to be more pronounced with Cu(2+). In the case of L, upon the addition of metal cations, the long emission band (∼550 nm) decreases and the monomer emission band increases (with an isoemissive point at ∼450 nm) and no evidence for the intermediate band (at ∼405-490 nm) now exists. Time-resolved data in dioxane/water mixtures showed that for P and L these two fit double- and triple-exponential decay laws, respectively. With P, this has been attributed to a two-state system, which involves the monomer and a charged species, with its emission maxima varying with the polarity of the media (here mirrored by its dielectric constant), which can potentially be addressed to an exciplex-like species, whereas with L, it has been attributed to a three-state system involving, in addition to these two species, an excimer. From absorption and fluorescence excitation and time-resolved data, evidence is given for the presence of intramolecular dimer formation in the ground state.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1,4-Dioxane, anhydrous, 99.8%
Sigma-Aldrich
1,4-Dioxane, ACS reagent, ≥99.0%
Sigma-Aldrich
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Sigma-Aldrich
1,4-Dioxane, suitable for HPLC, ≥99.5%
Supelco
1,4-Dioxane, analytical standard
Sigma-Aldrich
1,4-Dioxane, ReagentPlus®, ≥99%
Sigma-Aldrich
Pyrene, puriss. p.a., for fluorescence, ≥99.0% (GC)
Supelco
1,4-Dioxane solution, certified reference material, 2000 μg/mL in methanol, ampule of 1 mL
Supelco
Pyrene, certified reference material, TraceCERT®
Sigma-Aldrich
1,4-Dioxane, ACS reagent, ≥99.0%
Sigma-Aldrich
1,4-Dioxane, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.5% (GC)
Supelco
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Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D)
Sigma-Aldrich
Pyrene, sublimed grade, 99%
Pyrene, BCR®, certified reference material
Supelco
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 5 mm × 8 in.
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1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), chromium(III) acetylacetonate 5 mg/mL, NMR tube size 5 mm × 8 in.
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1,4-Dioxane solution, NMR reference standard, 1 mM in D2O ("100", 99.96 atom % D), NMR tube size 5 mm × 7 in.
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1,4-Dioxane solution, NMR reference standard, 10 mM in D2O ("100%", 99.96 atom % D), NMR tube size 5 mm × 7 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 0.1 mM in D2O ("100%", 99.96 atom % D), NMR tube size 5 mm × 7 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), chromium(III) acetylacetonate 5 mg/mL, NMR tube size 6.5 mm × 8 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 10 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 5 mM in chloroform-d (99.8 atom % D), NMR tube size 3 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 5 mM in benzene-d6 (99.6 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), chromium(III) acetylacetonate 5 mg/mL, NMR tube size 3 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 3 mm × 8 in.

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