Stable radicals have demonstrated their usefulness in solving many problems in chemistry, physics, biology and biomedicine. Chapter 1 gives a brief outline of the classes of stable radicals. The synthesis of hybrid fluorophore-nitronyl nitroxide and -imino nitroxide radicals, their characterization by IR, CV, EPR techniques, and X-ray structural analysis are reported in Chapter 2. UV-Vis studies form the basis for the evaluation of nitroxides potential as redox-probes. The results of subsequent PL investigation of the sensing properties of the obtained radicals confirmed preliminary assumptions. Advantages in the area of design and investigation of magnetic materials on the basis of nitroxides are the main subjects of Chapter 3. According to the magnetic characterization, a promising candidate for a purely organic low-dimensional quantum magnet was synthesized. The idea behind this investigation was to show how, by using a set of structural units, the sensitivity of the nitroxide containing probes and the intramolecular exchange interactions in pi-conjugated spin systems could be adjusted to obtain molecules with the desired sensing or magnetic properties.