Discrete giant porphyrin arrays: Challenges to molecular size, length and the extent of electronic pi-conjugation

Our studies on synthesis of directly meso-meso-linked and fused porphyrin a rrays were reviewed. Ag-1-promoted meso-meso coupling reaction of 5,15-diar yl Zn-II-porphyrins is advantageous in light of its high regioselectivity a s well as its easy extension to large porphyrin arrays. Doubling reactions have been repeated to make 128-mer as the longest man-made discrete molecul e. The similar coupling reaction has been applied to 1,4-phenylene-bridged linear porphyrin arrays, providing three dimensionally arranged windmill po rphyrin arrays and grid-like porphyrin arrays. meso-beta Doubly-Linked dipo rphyrins were prepared by oxidations of 5,15-diaryl Cu-II-, Ni-II-, and Pd- II-porphyrins with (p-BrC6H4)(3)NSbCl6 (BAHA). In a similar manner, meso,me so-end capped meso-meso linked Cu-II-, Ni-II-, and Pdl-diporphyrins were co nverted into meso-meso P-P, P-P triply-link-ed fused diporphyrins. We devel oped an alternative, more effective method to convert meso-meso-linked dipo rphyrins to triply-linked diporphyrins by using DDQ as an oxidant in the pr esence of Sc-III-salt, which, when applied to higher meso-end capped meso-m eso linked Zn-II-porphyrin arrays, allowed the synthesis of fully conjugate d triply-linked Zn-II-porphyrin arrays up to 12-mer which exhibited a low-e nergy electronic absorption band reaching the infrared region.