Molecularly excited processes play a crucial role in many disciplines, ranging from fundamental steps in biology to modern applications in advanced materials science. Most molecular excited-state processes — especially photochemical reactions — are governed by radiationless electronic transitions between two or more electronic states. Among these processes, we focus our research on the photochemistry of two molecular photoswitches, the 1,3-cyclohexadiene (CHD) molecule and an asymmetric dithienylethene (DTE). In addition to photochromatic properties, the molecules with CHD as backbone exhibit properties such as high fatigue resistance, high thermal irreversibility and high photoisomerization quantum yield (QY). These properties make these molecules excellent candidates for the development of new technologies such as molecular electronic devices. The aim of this thesis is, on the one hand, to shed light on the photochemical interconversion of CHD and a non-symmetric DTE for nanotechnology applications using electronic structure calculations using the spin-flip time-dependent density functional theory (SF-TDDFT) method. On the other hand, to contribute to the discussion on the ability of the fewest switching surface hopping (FSSH) and the Landau-Zener surface hopping (LZSH) methods at the SF-TDDFT level to capture the key features of the non-adiabatic dynamics associated with the photoisomerization process of the CHD molecule. The aim of this thesis is, on the one hand, to shed light on the photochemical interconversion of CHD and a non-symmetric DTE for nanotechnology applications using electronic structure calculations using the spin-flip time-dependent density functional theory (SF-TDDFT) method. On the other hand, to contribute to the discussion on the ability of the fewest switching surface hopping (FSSH) and the Landau-Zener surface hopping (LZSH) methods at the SF-TDDFT level to capture the key features of the non-adiabatic dynamics associated with the photoisomerization process of the CHD molecule. The aim of this thesis is, on the one hand, to shed light on the photochemical interconversion of CHD and a non-symmetric DTE for nanotechnology applications using electronic structure calculations using the spin-flip time-dependent density functional theory (SF-TDDFT) method. On the other hand, to contribute to the discussion on the ability of the fewest switching surface hopping (FSSH) and the Landau-Zener surface hopping (LZSH) methods at the SF-TDDFT level to capture the key features of the non-adiabatic dynamics associated with the photoisomerization process of the CHD molecule.