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

Inorg Chem. 2013 Jan 7;52(1):121-9. doi: 10.1021/ic301365y. Epub 2012 Dec 11.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dioxanes / chemistry
  • Fluorescent Dyes / chemical synthesis
  • Fluorescent Dyes / chemistry*
  • Molecular Structure
  • Pyrenes / chemistry*
  • Spectrometry, Fluorescence
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Spectrophotometry, Ultraviolet
  • Time Factors

Substances

  • Dioxanes
  • Fluorescent Dyes
  • Pyrenes
  • pyrene
  • 1,4-dioxane