Singly and Doubly 1,2-Phenylene-Inserted Porphyrin Arch-Tape Dimers: Synthesis and Highly Contorted Structures

Singly and doubly 1,2-phenylene-inserted Ni^II porphyrin arch-tape dimers 3 and 9 were synthesized from the corresponding β-to-β 1,2-phenylene-bridged Ni^II porphyrin dimers 5 and 11 via Ni⁰ -mediated reductive cyclization and DDQ/Sc(OTf)₃ -promoted oxidative cyclization as key steps, respectively. Owing to the fused eight-membered ring(s), 3 showed a more contorted structure than those of previously reported arch-tape dimers 2 a and 2 b possessing a fused seven-membered ring. Furthermore, 9 displayed much larger molecular contortion. As the molecular contortion increases, the Q band of the absorption spectrum becomes more red-shifted and the electrochemcial HOMO-LUMO gap becomes smaller, reaching at 1294 nm and 0.77 eV in 9, respectively. The effect of molecular contortion on the electronic properties was studied by means of DFT calculations.