Explicit spectral response of the geometrical isomers of a bio-active pyrazoline derivative encapsulated in β-cyclodextrin nanocavity: a photophysical and quantum chemical analysis

J Phys Chem A. 2012 Oct 25;116(42):10371-82. doi: 10.1021/jp307964z. Epub 2012 Oct 11.

Abstract

The existence of two geometrical isomers (cis- and trans-) of a biologically significant pyrazoline derivative [5-(-1'-(4-bromo-phenyl)-3a',7a'-hexahydro-1'H-indazol-3'-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile] (PZ) has been established using a combined theoretical and experimental investigation. Solvatochromic analysis of PZ revealed the existence of said cis- and trans- isomers. The unique solvatochromic response of the PZ isomers and their preferential encapsulation within β-cyclodextrin (β-CD) nanocavity clearly shows the difference in the behavioral nature of the isomers of PZ in homogeneous and heterogeneous medium. Solvent polarity, time-resolved study, and anisotropy results also reinforce in favor of the existence of the isomers. To evaluate the actual orientation of cis and trans-PZ, the ground and excited state geometry of these isomers were optimized by the DFT/LanL2DZ and CIS/LanL2DZ methods, respectively. The experimentally observed results and the theoretically calculated results are found to be in close agreement.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Models, Molecular
  • Molecular Structure
  • Nanostructures / chemistry*
  • Photochemical Processes
  • Pyrazoles / chemistry*
  • Quantum Theory*
  • Spectrometry, Fluorescence
  • Spectrophotometry, Ultraviolet
  • Stereoisomerism
  • beta-Cyclodextrins / chemistry*

Substances

  • Pyrazoles
  • beta-Cyclodextrins
  • betadex