Published July 28, 2021 | Version v1
Preprint Open

Design of High-Performance Pyridine/Quinoline Hydrazone Photoswitches

  • 1. Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 84215, Bratislava, Slovakia
  • 2. Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, 97400 Banská Bystrica, Slovakia
  • 3. Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, 97400 Banská Bystrica, Slovakia; Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University Olomouc, Krížkovského 8, 77900 Olomouc, Czech Republic
  • 4. Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovicova 6, 84215, Bratislava, Slovakia
  • 5. Institute of Physical and Theoretical Chemistry, Faculty of Biochemistry, Chemistry, Pharmacy, Goethe University, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
  • 6. Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237 Bratislava, Slovakia

Description

Design of P-type photoswitches with thermal stability of the metastable form of hundreds of years that would efficiently transform using excitation wavelengths above 350 nm remains a challenge in the field of photochromism. In this regard, we designedand synthesized an extended set of 13 pyridine/quinoline hydrazones and systematically investigated the structure–property relationships defining their kinetic and photoswitching parameters. We show that the operational wavelengths of pyridine hydrazone structural motif can be effectively shifted towards the visible region without simultaneous loss of their high thermal stability. Furthermore, we characterized the ground state and excited state potential energy surfaces with quantum-chemical calculations and ultrafast transient absorption spectroscopy which allowed us to rationalize both the thermal and photochemical reaction mechanisms of the designed hydrazones. Whereas introducing an electron-withdrawing pyridyl moiety in benzoylpyridine hydrazones leads to thermal stabilities exceeding 200 years, extended -conjugation in naphthoylquinoline hydrazones pushes the absorption maxima towards the visible spectral region. In either case, the compounds retain highly efficient photoswitching characteristics. Our findings open a route to rational design of a new family of hydrazone-based P-type photoswitches with high application potential in photonics or  photopharmacology.

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Additional details

Funding

European Commission
LAMatCU – Establishing Laboratory of Advanced Materials at the Comenius University 810701