Potential building blocks for improved porphyrinic molecular magnetic materials: Design, synthesis and characterization.

摘要

Syntheses of three novel nitroxide-substituted porphyrins and four novel biradical-dication bisporphyrins are described. These porphyrins have been characterized by a range of experimental techniques to judge their relative potential as constituents of porphyrinic molecular magnetic materials. In the nitroxide-substituted porphyrins, the conjugated spacer between the nitroxide and the porphyrin was varied. Hyperfine coupling constants (hfcc) in the room temperature Electron Paramagnetic Resonance (EPR) spectra of zinc metallated porphyrins were compared to determine the extent of nitroxide delocalization. The copper derivatives were also produced and studied by EPR. The bisporphyrins contain different cross-conjugated linkers. These were compared by room temperature and frozen solution Electron Paramagnetic Resonance, Variable-Temperature EPR, Electrochemistry, Visible/Near Infrared Spectroscopy and Spectroelectrochemistry. The relative amount of exchange coupling between the radical-cations of the bisporphyrins was accessed. Additionally, during the synthesis of three of the bisporphyrins, an improvement to Sonogashira couplings was discovered.