Coordination-Induced Cofacial Dimer Formation of a Phenanthroline-Tethered Porphyrin

A zinc porphyrin bearing four 1,10-phenanthroline units, ZnPor(phen)₄, forms cofacial dimers upon coordination with Zn²⁺ or Cu⁺ ions. UV-vis spectroscopy, electrospray ionization mass spectrometry, and 1H NMR ring-current analysis reveal dimers comprising two porphyrins linked by four tetrahedral M(phen)₂ complexes (M = Zn²⁺, Cu⁺). Compared with a bipyridine analogue, the phenanthroline derivative exhibits higher stability, demonstrating that ligand rigidity and stronger metal–ligand binding enhance the robustness of coordination-induced porphyrin assemblies.