meso-Dibenzoporphycene has a Large Bathochromic Shift and a Porphycene Framework with an Unusual cis Tautomeric Form.

meso-Monobenzoporphycene (mMBPc) and meso-dibenzoporphycene (mDBPc), in which one or two benzene moieties are fused at ethylene-bridged positions (meso-positions) of porphycene, were prepared in an effort to further delocalize the π-electrons within the porphycene molecule. mMBPc and mDBPc were fully characterized by mass spectrometry, (1)H and (13)C NMR spectroscopy, and X-ray crystallography. The longest-wavelength Q-bands of mMBPc and mDBPc are red-shifted by 92 nm and 418 nm, respectively, compared to that of the unsubstituted porphycene (Pc). Electrochemical measurements indicate that the HOMO is destabilized and the LUMO is stabilized by the fused benzene moieties at the meso positions. Furthermore, both XPS and theoretical studies support the presence of a cis tautomeric form in the ground state of mDBPc, despite the fact that essentially all known porphycene derivatives adopt the trans tautomeric form.