meso-Aryl core-modified fused sapphyrins: syntheses and structural diversity.

Two new, fused core-modified expanded porphyrins, sapphyrins 3 and 4, were synthesized by a simple acid-catalyzed condensation of electron-rich and rigid precursor, dithienothiophene (DTT) diol, and core-modified tripyrrane. These sapphyrins exhibit structural diversity depending upon the heteroatom present in the macrocyclic framework, where the thiophene ring is inverted in 3, while the selenophene ring in 4 exists in normal and inverted form in the free base and addition of two protons shifts the equilibrium to inverted form.