[40]Nonaphyrin(1.1.1.1.1.1.1.1.1) and its heterometallic complexes with palladium-carbon bonds

meso-Pentafluorophenyl-substituted [40]nonaphyrin-(1.1.1.1.1.1.1.1.1) 3 has been prepared by using a stepwise ring-size-selective synthesis, and has been reduced with NaBH₄ to [42]nonaphyr-in(1.1.1.1.1.1.1.1.1) 5. Structurally, 3 is characterized by a figure-of-eight shape, consisting of a porphyrin-like tetrapyrrolic segment and a hexaphyr-in-like hexapyrrolic segment, whereas 5 has been found to adopt a distorted nonplanar butterfly-like shape. In the mono-metal complexes 6 and 7, a Zn^II or Cu^II ion is bound by the porphyrin-like tetrapyrrolic segment, maintaining the overall structure of 3. Similarly to 3. complexes 6 and 7 are interconvertible with the corresponding complexes 9 and 10 through two-electron reduction with NaBH₄ and oxidation with DDQ. The metal-free hexaphyrin-like segments of 6 and 7 have been shown to serve as a suitable platform for the complexation of two palladium ions, providing hetero-trinuclear metal complexes 11 (Zn ^II-Pd^II-Pd^II) and 13 (Cu^II-Pd ^II-Pd^II) in high yields, in which the Zn or Cu ion resides at the same porphyrin-like segment, and one Pd ion is bound in an NNCC fashion through double C-H bond activation while the other is bound in an NNC fashion with single C-H bond activation. Multi-metal complexes 11, 12. and 13 exhibit small electrochemical HOMO-LUMO gaps (<0.6eV). despite their nonplanar conformations.