Circular Dichroism and Isotropy – Polarity Reversal of Ellipticity in Molecular Films of 1,1’-Bi-2-Naphtol

Alexander von Weber, David Hooper, Matthias Jakob, Ventsislav Valev, Aras Kartouzian, Ueli Heiz

Research output: Contribution to journalArticle

7 Citations (Scopus)
13 Downloads (Pure)

Abstract

We have studied the circular dichroism (CD), in the ultraviolet and visible regions, of the transparent, chiral molecule 1,1’-Bi-2-naphtol (BINOL) in 1.5 μm thick films. The initial transparent film shows an additional negative cotton effect in the CD compared to solution. With time under room temperature the film undergoes a structural phase transition. This goes hand in hand with a cotton effect at the low energy absorption band which inverts with opposite propagation direction of light through the film which is revealed as a polarity reversal of ellipticity (PRE). After completion of the phase transition the film exhibits circular differential scattering throughout the visible range which also shows PRE. The structure change was studied with Raman, microscopy under cross polarization conditions and nonlinear second-harmonic generation circular dichroism (SHG-CD). The superposition of the optical activity of individual molecules and isotropy effects makes an interpretation challenging. Yet overcoming this challenge by finding a suitable model structural information can be derived from CD measurements.

Original languageEnglish
Pages (from-to)62-69
Number of pages8
JournalChemPhysChem
Volume20
Issue number1
Early online date16 Nov 2018
DOIs
Publication statusPublished - 7 Jan 2019

Keywords

  • circular dichroism
  • ellipticity
  • films
  • isotropy
  • second-harmonic generation

ASJC Scopus subject areas

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

Cite this