Thermo-Optical Properties of Organic Verdazyl Biradicals via UV-VIS Spectroscopy*

Recently, biradicals have attracted attention due to their magnetic properties which could be used in different fields such as electronics, computer technologies, and renewable energy. Unlike most of the other radicals, organic verdazyl biradicals are stable at room temperature which makes them easy to work with. We investigated the photo-physical properties (i.e. singlet-triplet spin gap) of verdazyl biradicals utilizing thermo-optical spectroscopy (UV-VIS) between room temperature and 400 K.The spectra were then analyzed using Beer’s law and Curie population analysis to extract the singlet-triplet spin gap at several wavelengths by evaluating the excitations. The analysis suggests, stronger excitations are representative of π→π* transitions while the weaker excitations are representative of forbidden π→π* transitions. Switching between singlet ground and triplete excited states can lead to an improved understanding of the manipulation via change in temperature and possibly with the magnetic field.