Ruthenium(IV) N-confused porphyrin μ-oxo-bridged dimers: acid-responsive molecular rotors

Ruthenium(IV) N-confused porphyrin μ-oxo-bridged complexes were synthesized via oxidative dimerization of a ruthenium(II) N-confused porphyrin complex using 2,2,6,6-tetramethylpiperidine 1-oxyl. The deformed core planes in the dimers conferred a relatively high ring rotational barrier of ca. 16 kcal mol−1. Rotation of the complexes was controlled by protonating the peripheral nitrogen.