Cover Picture (Angew. Chem. Int. Ed. Engl. 3/1986)


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The cover page shows the skeleton (white) of porphycene, a novel aromatic isomer of porphin (gray) with effective D2h symmetry, which is determined by extremely rapid NH-tautomerism. This fascinating pyrrolic macrocycle, which dissolves in organic solvents to give blue solutions showing beautiful red-violet fluorescence, is, despite its—in comparison to porphin—much smaller cavity, capabable of forming metalloporphyrin- and metallophthalocyanine-type complexes. In the light of the intensively studied chemistry and biochemistry of the porphyrins it seems remarkable that porphycene and its derivatives, for which a host of interesting applications can be envisaged, could have remained concealed for such a long time. Further details are reported by E. Vogel et al. on page 257ff.