Synthesis, structural characteristics, and optical and electrochemical properties of various meso–meso-linked porphyrin arrays were described. The Ag^I-salt-promoted meso–meso coupling reaction of 5,15-diaryl and 5,10,15-triaryl Zn^II-porphyrins is advantageous in light of its high regioselectivity as well as its easy extension to large porphyrin arrays. A similar coupling reaction is also possible by electrochemical oxidations for Zn^II- and Mg^II-porphyrins, while the electrochemical oxidation of Ni^II-, Pd^II, and Cu^II-porphyrins led to formation of meso-β linked biporphyrins with high regio-selectivity. As an extension of the above Ag^I-promoted coupling reaction, 1,4-phenylene-bridged linear porphyrin arrays were coupled to give orthogonally arranged windmill-like porphyrin arrays, which in turn were further coupled to afford grid-like porphyrin arrays of giant size. In all the Zn^II-metallated windmill arrays, the intramolecular singlet–singlet excitation energy transfer proceeds efficiently from the peripheral porphyrins to the central biporphyrin core. The doubling reaction was repeated up to the synthesis of 128-mer. During these attempts, many meso–meso-linked porphyrin arrays were isolated in a discrete form by repetitive gel-permeation chromatography (GPC)–HPLC, all exhibiting high solubility in common organic solvents in spite of their giant molecular sizes. Finally, the oxidation with strong oxidant tris(4-bromophenyl)aminium hexachloroantimonate allowed the coupling of 5,10,15-triaryl Ni^II- and Pd^II-porphyrins to meso-β doubly-linked fused biporphyrins and the smooth conversion of meso–meso-linked Cu^II-biporphyrin to meso–meso β–β β–β triply-linked biporphyrin. These fused biporphyrins exhibit full π-conjugation over the arrays.

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