N-Confused Porphyrin-aza-Dipyrrin Chimera: A Versatile Metal Coordination Ligand Using its Unique NH Tautomerism.

A novel N-confused porphyrin (NCP) analogue bearing an external aza-dipyrrin-like coordination site was synthesized by a Schiff-base forming reaction of N-confused oxoporphyrin and 2-aminopyridine derivatives. The chimera molecule enhances the intrinsic NH tautomerism of NCP to enable four possible tautomeric structures, three of which were identified by metal coordination.