Femtosecond two-photon-absorption-resonant four-wave mixing for time-resolved studies of photochromism in three dimensions

A generalized vibronic-coupling Hamiltonian for molecules without symmetry: Application to the photoisomerization of benzopyran

We present a model for the lowest two potential energy surfaces (PESs) that describe the photoinduced ring-opening reaction of benzopyran taken as a model compound to study the photochromic ring-opening reaction of indolinobenzospiropyran and its evolution toward its open-chain analog. The PESs are expressed in terms of three effective rectilinear coordinates. One corresponds to the direction between the equilibrium geometry in the electronic ground state, referred to as the Franck-Condon geometry, and the minimum of conical intersection (CI), while the other two span the two-dimensional branching space at the CI. The model correctly reproduces the topography of the PESs. The ab initio calculations are performed with the extended multiconfiguration quasidegenerate perturbation theory at second order method. We demonstrate that accounting for electron dynamic correlation drastically changes the global energy landscape since some zwitterionic states become strongly stabilized. Quantum dynamics calculations using this PES model produce an absorption spectrum that matches the experimental one to a good accuracy.

Research Trends in Photochromism: Control of Photochromism in Rigid Polymer Matrices and other Advances

Photochromism is receiving increasing attention because of its current application in high value-added ophthalmic lenses and potential applications in data storage and molecular switching. The performance of photochromic dyes, such as spirooxazines, chromenes, and diarylethenes, in polymers is important because the above applications require the dyes to be in a host polymer. The dyes can be broadly divided into P (photo) and T (thermal) types depending on the availability of a thermal decolouration route. Current research themes for the two types are presented with an emphasis on a new method of manipulating switching speeds in polymer matrices.