• intersystem crossing
• photoisomerization
• qm/mm methods
• quantum chemical methods
• semiemprical methods
• spin-orbit coupling
• surface hopping

Spiropyrans, a class of photochromic molecules known for their reversible isomerization between closed and open forms, have attracted significant attention for their potential applications in material science, molecular electronics, and biological imaging. This thesis investigates the excited-state dynamics and photoisomerization behavior of nitrospiropyran (NSP), a derivative of spiropyrans, using the surface hopping method within a semiempirical framework. A particular focus is placed on understanding NSP’s photophysical and photochemical properties, as well as the role of solvent interactions in influencing the photoisomerization of the simplest spiropyran (SP) in different environments.