Effect of the π bridge and acceptor on intramolecular charge transfer in push-pull cationic chromophores: An ultrafast spectroscopic and TD-DFT computational study

Benedetta Carlotti, Enrico Benassi, Vincenzo Barone, Giuseppe Consiglio, Fausto Elisei, Alessandra Mazzoli, Anna Spalletti

Research output: Contribution to journalArticle

25 Citations (Scopus)


Three (donor-π-acceptor)+ systems with a methyl pyridinium or quinolinium as the electron-deficient group, a dimethyl amino as the electron-donor group, and an ethylene or butadiene group as the spacer have been investigated in a joint spectroscopic and TD-DFT computational study. A negative solvatochromism has been revealed in the absorption spectra, which implies a solution color change, and interpreted by considering the variation in the permanent dipole moment modulus and orientation upon photoexcitation. The fluorescence efficiency decreases upon increasing solvent polarity, in agreement with the excited-state optimized geometries (planar in low-polarity media and twisted in high-polarity media). Femtosecond transient absorption has revealed the occurrence of a fast photoinduced intramolecular charge transfer (ICT) and the molecular factors that determine an efficient ICT. Considering the crucial role of the ICT in tuning the nonlinear optical (NLO) properties, these compounds can be considered promising NLO materials.

Original languageEnglish
Pages (from-to)1440-1450
Number of pages11
Issue number7
Publication statusPublished - 18 May 2015
Externally publishedYes



  • charge transfer
  • density functional calculations
  • femtosecond transient absorption
  • nitrogen heterocycles
  • solvent effects

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry

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