Theoretical study of photo-physical properties of indolylmaleimide derivatives

Phys Chem Chem Phys. 2012 Mar 7;14(9):3017-24. doi: 10.1039/c2cp22946c. Epub 2012 Jan 31.

Abstract

Photo-physical properties of bromo-indolylmaleimide (IM-Br), indole-succinimide (IS), and their anions were theoretically investigated compared with the previous theoretical result for indolylmaleimide (IM) [Phys. Chem. Chem. Phys., 2010, 12, 9783]. The energies for the electronic excited states as well as the ground states were computed for these molecules using the multi-reference perturbation calculations based on the second order Rayleigh-Schrödinger perturbation theory (CASPT2) at the cc-pVDZ basis set level. The electron-accepting or electron-donating effect caused by bromine-substitution was discussed in the intra-molecular charge transfer (ICT) mechanism. The order of natural orbitals of the bromine-substituted monovalent anion with a deprotonated indole NH group (I((-))M-Br) was found to be rearranged by the effect of electron-donation, which leads to pseudo-crossing of the potential energy cures of the S(1) and S(2) states. The large stokes shift observed for I((-))M-Br was due to pseudo-crossing. Meanwhile, IM and IM-Br show abnormal deprotonation, which is explained by the charge distribution on the indole and maleimide moieties. Finally, the monovalent anions I((-))M-Br and I((-))M by a deprotonation of the indole NH end and the neutral IS were proposed to be the most feasible candidates corresponding to the experimental spectra in solution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Electron Transport
  • Indoles / chemistry*
  • Maleimides / chemistry*
  • Models, Molecular*
  • Molecular Conformation
  • Protons
  • Quantum Theory*
  • Spectrum Analysis

Substances

  • Indoles
  • Maleimides
  • Protons
  • maleimide