Structures and Ligand Exchange of N-Confused Porphyrin Dimer Complexes with Group 12 Metals

N-confused 5,20-diphenylporphyrin (NCDPP, 1) formed 2:2 dimer complexes with group 12 metals both in the solid
state and in solution. X-ray single-crystal analyses of the Zn(II) and Cd(II) complexes (7, 8) revealed that each
metal ion is coordinated with three inner core nitrogens and a peripheral nitrogen of the other NCDPP in the pair.
In the 1H NMR spectra of 7, 8, and the Hg(II) complex (9), the outer α-H signals of the confused pyrrole ring
appeared in the upfield region at 2.57, 3.44, and 3.60 ppm, respectively, due to the ring current effect by the
coordinated porphyrins. In the case of the Cd(II) and Hg(II) complexes (8, 9), additional magnetic couplings with
the metal nuclei of the partner rings were observed. The equilibrium constants (K) of the monomer exchange
reaction at 25 °C were determined to be 2.5, 1.3, and 0.6 for the (Zn−Cd), (Cd−Hg), and (Zn−Hg) heterodimer
complexes, respectively, from the 1H NMR spectra of a solution containing two different dimers. Furthermore, a
metal-transfer reaction from a Zn(II) NCP dimer complex to the free base porphyrin was demonstrated.