Initial excited-state dynamics of an N-alkylated indanylidene-pyrroline (NAIP) rhodopsin analog

J Phys Chem B. 2014 Oct 23;118(42):12243-50. doi: 10.1021/jp508060z. Epub 2014 Oct 10.

Abstract

N-Alkylated indanylidene-pyrroline-based molecular switches mimic different aspects of the light-induced retinal chromophore isomerization in rhodopsin: the vertebrate dim-light visual pigment. In particular, they display a similar ultrashort excited-state lifetime, subpicosecond photoproduct appearance time, and photoproduct vibrational coherence. To better understand the early light-induced dynamics of such systems, we measured and modeled the resonance Raman spectra of the Z-isomer of the N-methyl-4-(5'-methoxy-2',2'-dimethyl-indan-1'-ylidene)-5-methyl-2,3-dihydro-2H-pyrrolium (NAIP) switch in methanol solution. It is shown that the data, complemented with a <70 fs excited-state trajectory computation, demonstrate initial excited-state structural dynamics dominated by double-bond expansion and single-bond contraction stretches. This mode subsequently couples with the five-membered ring inversion and double-bond torsion. These results are discussed in the context of the mechanism of the excited-state photoisomerization of NAIP switches in solution and the 11-cis retinal in rhodopsin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkylation
  • Indans / chemistry*
  • Models, Molecular
  • Molecular Conformation
  • Pyrroles / chemistry*
  • Rhodopsin / chemistry*
  • Spectrum Analysis, Raman
  • Stereoisomerism

Substances

  • Indans
  • Pyrroles
  • pyrroline
  • Rhodopsin