Radical exchange reaction of multi-spin isoindoline nitroxides followed by EPR spectroscopy

The synthesis of a rigid, isoindoline-functionalized tetraphenylmethane multi-spin system is described. The isoindoline nitroxide groups are used in a nitroxide exchange reaction with a TEMPO containing alkoxyamine. Using EPR spectroscopy it is possible to follow the exchange process and thereby find the optimal experimental conditions to have the maximum yield. The presented approach could be used to study the nitroxide exchange process of various systems and to determine the kinetics of the exchange process. The presented molecular components can be used as tectons in the construction of covalently linked organic networks or as model systems for EPR distance measurements

Linear and Nonlinear Optical Spectroscopy of Fluoroalkylated BODIPY Dyes

A series of fluoroalkyl-labeled BODIPY dyes have been synthesized with different substituents on the 2- and 6-positions and investigated in terms of their spectroscopic properties. The dyes were decorated with aryl, alkenyl, and alkynyl substituents, respectively. Those substituents are able to expend the dyes’ delocalized π-electron system to different extents. Detailed linear and nonlinear optical spectroscopy methods as well as quantum-chemical calculations have been employed to verify the influence of those different substituents on the electronic distribution and, ultimately, on the molecules’ optical properties. From the nonlinear optical measurements, we find that the substituents highly influence the excited-state absorption properties, which could be tuned in wavelength by ∼100 nm and in magnitude by over 1 order of magnitude, reaching peak values close to 10^–15 cm² for one of the alkynyl-containing dyes