A “Molecular Pivot-Hinge” Based on the pH-Regulated Intramolecular Switching of Pt−Pt and π<i>−</i>π Interactions

The binuclear cycloplatinated complex {[Pt(L)]2(μ-dppm)}2+ (1), where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine, is found to behave as a molecular pivot-hinge in which the closing and opening of the hinge is effected by the reversible formation and cleavage of the Pt−Pt d8−d8 interaction and the intramolecular π−π interaction mediated by the protonation/deprotonation of the 1-pyrazolyl-NH on the cyclometalating ligand L.