ic301365y_si_001.pdf (1002.19 kB)
Steady-State and Time-Resolved Investigations on Pyrene-Based Chemosensors
journal contribution
posted on 2013-01-07, 00:00 authored by Javier Fernández-Lodeiro, Cristina Núñez, Catherine S. de
Castro, Emilia Bértolo, J. Sérgio Seixas de
Melo, José Luis Capelo, Carlos LodeiroTwo 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 (Cu2+, Zn2+, and Ag+) to P, a gradual quenching
effect of the monomer emission is observed and found to be more pronounced
with Cu2+. 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.
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metal additiondioxanemonomer emission band increasesmonomer emissionquenching effectpyrene unitsemission spectra392 nmcompound Lpicosecond time scalemetal cationsfluorescence excitationUVgas phaseemission bandsL spectracharge characteremissive bandisoemissive pointmonomer absorption490 nmemission spectroscopyground statespeciesemission maximaintramolecular dimer formation
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