Solvatochromism of 3-[2-(4-diphenylaminophenyl) benzoxazol-5-y]alanine methyl ester - A new fluorescence probe

ArticleinSpectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 61(6):1133-40 · May 2005with6 Reads
DOI: 10.1016/j.saa.2004.06.035 · Source: PubMed
Abstract
The photophysical properties of 3-[2-(4-diphenylaminophenyl)benzoxazol-5-yl]alanine methyl ester (1b) and its Boc derivative (1a) were studied in a series of solvents. Its UV-Vis absorption spectra are less sensitive to the solvent polarity than the corresponding fluorescence spectra which show pronounced solvatochromic effect leading to large Stokes shifts. Using an efficient solvatochromic method, based on the molecular-microscopic empirical solvent polarity parameter E(T)(N), a large change of the dipole moment on excitation has been found. From an analysis of the solvatochromic behaviour of the UV-Vis absorption and fluorescence spectra in terms of bulk solvent polarity functions, f(epsilon(r),n) and g(n), a large excited-state dipole moment (mu(e) = 11D), almost perpendicular to the smaller ground-state dipole moment, was observed. This demonstrates the formation of an intramolecular charge-transfer excited state. Large changes of the fluorescence quantum yields as well as the fluorescence lifetimes with an increase of a solvent polarity cause that the new non-proteinogenic amino acid, 3-[2-(4-diphenylaminophenyl)benzoxazol-5-yl]-alanine methyl ester, is a new useful fluorescence probe for biophysical studies of peptides and proteins.
    • "Solvatochromism, inherently dynamical phenomenon, is universally exploited to probe chemical and biological properties of molecules in various environments. Solvatochromic effects probed by spectroscopic techniques have been a subject of several investigations123456789101112131415. A change in polarity, dielectric constant or polarizability of the solvent differently causes perturbation in the ground and excited states of organic compounds . "
    [Show abstract] [Hide abstract] ABSTRACT: The solvatochromic and spectral properties of oxazolone derivatives in various solvents were reported. Fluorescence spectra clearly showed positive and negative solvatochromism depending on substituents. The solvatochromic plots and quantum chemical computations at DFT-B3LYP/6-31 + G(d,p) level were used to assess dipole moment changes between the ground and the first excited singlet-states. The electron accepting nitro substituent at the para-position increased the π-electron mobility, however, the 3,5-dinitro substituent decreased the π-electron mobility as a result of inverse accumulation of the electronic density as compared with that of its ground state. Experimental and computational studies proved that the photoinduced intramolecular electron transfer (PIET) is responsible for the observed solvatochromic effects. We demonstrate that PIET can be finely tailored by the position of the electron accepting and donating substituents in the phenyl ring of the oxazolone derivatives. We propose that the photoactive CPO derivatives are new molecular class of conjugated push-pull structures using azlactone moiety as the π-conjugated linker and may find applications in photovoltaic cells and light emitting diodes.
    Full-text · Article · Jul 2013
  • Article · · Inorganic Chemistry Communications
  • [Show abstract] [Hide abstract] ABSTRACT: The synthesis of N-Boc-3-[2-(2-quinoxalinyl)benzoxazol-5-yl]alanine methyl ester (1) and 3-[2-(2-quinoxalinyl)benzoxazol-5-yl]alanine (2), useful in peptide chemistry, are described. The influence of metal ions and pH on spectroscopic properties of compounds studied is presented. The compounds studied are very weak bases in the ground state and their basicity increases in the excited state. Among ions studied, in the ground state only Cu(II) and Al(III) and Pb(II) ions form stable complexes with (1), whereas in the excited state – only Ni(II) ion. Contrary to the most fluoroionophores the fluorescence intensity of ligand (1) in acetonitrile increases with the increase of Ni(II) ion concentration, whereas the fluorescence intensity of (2) in water is totally quenched by H3O+ ion.
    Article · Oct 2005
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