Switchable Intermolecular Communication in a Four‐Fold Rotaxane

Firmly tied: A four-fold rotaxane was prepared from a porphyrin unit with four alkylammonium chains and a phthalocyanine unit with four peripheral crown ethers. In a dinuclear Cu2+ complex of the four-fold rotaxane, the Cu2+–porphyrin and the Cu2+–phthalocyanine moieties were stacked efficiently on one another to afford spin–spin communication. The spin states were switched reversibly (see picture).