Confinement Effect of Micro- and Mesoporous Materials on the Spectroscopy and Dynamics of a Stilbene Derivative Dye

Int J Mol Sci. 2019 Mar 15;20(6):1316. doi: 10.3390/ijms20061316.


Micro- and mesoporous silica-based materials are a class of porous supports that can encapsulate different guest molecules. The formation of these hybrid complexes can be associated with significant alteration of the physico-chemical properties of the guests. Here, we report on a photodynamical study of a push⁻pull molecule, trans-4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), entrapped within faujasite-type zeolites (HY, NaX, and NaY) and MCM-41 in dichloromethane suspensions. The complex formation gives rise to caged monomers and H- and J-aggregates. Steady-state experiments show that the nanoconfinement provokes net blue shifts of both the absorption and emission spectra, which arise from preferential formation of H-aggregates concomitant with a distortion and/or protonation of the DCM structure. The photodynamics of the hybrid complexes are investigated by nano- to picosecond time-resolved emission experiments. The obtained fluorescence lifetimes are 65⁻99 ps and 350⁻400 ps for H- and J-aggregates, respectively, while those of monomers are 2.46⁻3.87 ns. Evidences for the presence of a charge-transfer (CT) process in trapped DCM molecules (monomers and/or aggregates) are observed. The obtained results are of interest in the interpretation of electron-transfer processes, twisting motions of analogues push⁻pull systems in confined media and understanding photocatalytic mechanisms using this type of host materials.

Keywords: H- and J-aggregates; confinement effect; host–guest interaction; porous silica-based materials; push–pull molecule.

MeSH terms

  • Coloring Agents / chemistry*
  • Molecular Structure
  • Porosity
  • Silicon Dioxide / chemistry*
  • Spectrometry, Fluorescence / methods
  • Stilbenes / chemistry*
  • Zeolites / chemistry


  • Coloring Agents
  • Stilbenes
  • Zeolites
  • Silicon Dioxide