Photo-orientation and Electron Paramagnetic Resonance Spectra of a Nitroxide and Azobenzene-Containing Hydrogen-Bonded Complex

Alexey V. Bogdanov*, Yoshiaki Uchida, Andrey Kh Vorobiev

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Photochromism and light-induced orientation of a hydrogen-bonded paramagnetic mesogenic complex were investigated. The azopyridine chromophore included in the chemical structure of the complex is capable of reversible trans-to-cis photoisomerization with the lifetime of the cis-isomer being on the order of seconds. The action of polarized light on the solid film of the complex results in its in-plane photo-orientation, wherein the azopyridine chromophores become preferentially aligned perpendicular to the electric vector of the incident light. The photo-orientation kinetics strongly depends on the morphological properties and thermal history of the film and has an unusual S-shaped form due to the topochemical nature of the process (Avrami kinetics). The observed peculiarities of the photoinduced alignment of the complex corroborate the mechanism of photo-orientation by means of microscopic structure rearrangement. The polarized optical absorbance and electron paramagnetic resonance spectra of the photoaligned film of the material prove that the sample is characterized by macroscopic biaxiality due to the presence of two competing orienting forces, namely, the polarized light and the orienting influence of the surface. Electron paramagnetic resonance spectra of the complex in aligned crystalline and nematic samples are interpreted in terms of the macroscopic order of the material and intermolecular spin-spin interactions of the nitroxyl fragments.

Original languageEnglish
Pages (from-to)13332-13340
Number of pages9
JournalJournal of Physical Chemistry C
Volume126
Issue number31
DOIs
Publication statusPublished - 11 Aug 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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