The Force Field of Porphycene:  A Theoretical and Experimental Approach

The contribution deals with the theoretical and experimental examination of the force field of porphycene ([18]porphyrin-(2.0.2.0)) a structural isomer of porphyrin. Special care was taken for a possible tautomerism of the hydrogen atoms in the cavity of the molecule. We report IR, Raman, UV, as well as site-selective fluorescence and fluorescence excitation spectra. Most spectra were measured under matrix isolation conditions. Quantum chemical calculations based on density functional theory methods were used to derive force fields and IR intensities for the most probable tautomeric forms.