This book provides a detailed description of photofunctionalization of molecular switch based on pyrimidine ring rotational isomerization in copper complexes bearing two bidentate ligands. The most important features of this work focus on the properties associated with the rotational isomerization based on the two possible coordination geometries at the copper center derived from two nitrogen atoms on the unsymmetrically substituted pyrimidine ring. The functions of systems such as dual emission and redox potential switching based on photo-driven rotation will be of particular interest to readers. Both the functions and the procedures for proving these phenomena are beneficial for the development of more functionalized systems based on material science, molecular science, nanoscience, nanotechnology, electrochemistry, photochemistry, coordination chemistry, physical chemistry, and related disciplines. The finding elucidated here holds promise for handling the photoprocesses of metal complexes, valid for both applications and novel properties. This system is expected make it possible to extract an electrochemical potential response from molecular switches, aiming to simulate the five senses of human beings at a single molecular level.