Photophysical characterization of a benzo-fused analogue of Brooker's merocyanine: solvent polarity and pH effects

J Phys Chem A. 2012 Dec 27;116(51):12470-5. doi: 10.1021/jp3106869. Epub 2012 Dec 14.

Abstract

The photophysical properties of 4-[2-(6-hydroxy-2-naphthalenyl)-ethenyl]-1-methyl-pyridinium (HNEP(+)) and its deprotonated form (NEP), a benzofused derivative of Brooker's merocyanine (BM), were investigated through a combined spectroscopic and computational approach. Despite their structural similarities and similar pK(a) values, HNEP(+)/NEP and BMH(+)/BM differ in the extent of charge delocalization in the ground and excited states. NEP exhibits the spectral characteristics of a charge transfer species in solvents in which BM exists in a charge-delocalized quinoid; however, quantum chemical calculations show that the CT absorption of NEP is not necessarily a consequence of the zwitterionic character. HNEP(+) displays larger Stokes shifts than BMH(+), and NEP demonstrates enhanced solvatochromism relative to BM as a consequence of benzofusion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Coloring Agents / chemistry*
  • Hydrogen-Ion Concentration
  • Models, Molecular
  • Molecular Conformation
  • Protons
  • Pyridines / chemistry*
  • Pyrimidinones / chemistry*
  • Quantum Theory
  • Solvents / chemistry*
  • Spectrum Analysis

Substances

  • Coloring Agents
  • Protons
  • Pyridines
  • Pyrimidinones
  • Solvents
  • merocyanine dye