Regular Article

Merocyanine–spiropyran relaxation processes

¹ Department of General and Theoretical Physics, Sumy State University, 2, Rymsky-Korsakov St., 40007 Sumy, Ukraine
² Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C. Marcel.lí Domingo s/n, Tarragona 43007, Spain
³ Department of Theoretical and Applied Physics, Aerospace Institute, National Aviation University, 1, Kosmonavt Komarov Ave., 03680 Kyiv, Ukraine
⁴ Department of Modeling of Complex Systems and Applied Physics, Sumy State University, 2, Rymsky-Korsakov St., 40007 Sumy, Ukraine

^a e-mail: olha.kovalenko@ssu.edu.ua

Received: 4 May 2017
Received in final form: 3 November 2017
Published online: 25 January 2018

Abstract

In the paper mechanisms of merocyanine–spiropyran transformation were investigated. It was shown that in dark conditions for such transformation it is necessary to overcome the potential barrier with height of ~0.6 eV. A barrierless transformation into the spiropyran molecule is possible due to the rotation of the phenyl moiety of the merocyanine molecule by 90^∘ relative to the plane of the molecule. It was proved that a 90^∘ orientation of moieties in the merocyanine molecule is achievable only in a photochemical way because in S₁ state of the molecule energy of the potential surface is lowered by rotation the phenyl moiety relative to its plane.