Allosteric regulation of a reactive squaraine rotaxane endoperoxide

Squaraine rotaxane endoperoxides are known to undergo a cycloreversion reaction that is sensitive to the cross-component strain within the interlocked molecules. Two new squaraine rotaxane endoperoxides are described with structures containing metal cation chelation sites that are distal to the reaction centre. Fluorescence and absorption titration studies in CH3CN prove that the metal cations bind to the chelation sites. In one case, the binding of dinuclear metal cations such as Zn(II) increases the rate of cycloreversion by a factor of 4, whereas in the second case, metal cation binding decreases the rate by a factor of 2.