Encapsulation of squaraine dyes by a tetralactam macrocycle with anthracene side-walls produces a threaded complex with very favorable fluorescent properties for biological imaging and diagnostics. The kinetics for complex formation and dissociation are known to be very sensitive to the steric size of the substituents at the end of the squaraine structure. This study investigated macrocycle encapsulation of indolenine squaraine dyes. The geminal dimethyl groups at either end of the squaraine structure act as a major kinetic barrier and prevent macrocycle encapsulation. An encapsulated complex can be prepared by a macrocycle clipping reaction and there is no evidence of complex dissociation. An X-ray structure of the interlocked molecule shows the reasons why the geminal dimethyl groups are so effective at blocking complex dissociation.

Stopper group steric effects on macrocycle encapsulation of indolenine squaraine dyes

253rd National Meeting (2017)

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