Mechanically interlocked molecules (MIMs) attract significant attention of scientists over the past few decades due to their unusual architecture. For a long time, architectures of MIMs were represented by catenanes, rotaxanes, molecular knots, and their derivatives. Only several years ago, a new type of MIMs that do not possess interlocked rings or dumbbell shaped molecule threaded through a macroring was introduced. Suitanes – a class of MIMs, which consist of two separate components - contains a body with two or more rigid limbs protruding outwards and a close-fitting, all-in-one suit.

We present the results of computational modelling of the photoinduced processes in the recently reported by F. Stoddart two-component MIM - suit[3]ane, and similar systems with aromatic 3-fold symmetric bodies.^[1] The reported suit[3]ane contains a benzotrithiophene (BTT) derivative with three n-hexyl substituents (BTT-3C₆) as a body and 3-fold symmetric pyridinium-based cage, namely HexaCage⁶⁺ (HC⁶⁺∙6PF₆^-), as a suit.

Analysis of the ground state properties of the suit[3]anes show that low LUMO of HC⁶⁺∙6PF₆^- and its ability to delocalize charge make this cage an efficient electron acceptor. The TDDFT calculations for a series of inclusion complexes (HC⁶⁺∙6PF₆^-⊃XXX, where XXX are aromatic 3-fold symmetric bodies) revealed that the photoinduced electron transfer process is favorable not only for the complexes with strong donors, such as thiatruxene or benzotrithiophenes, but also for poor donors, such as benzotrifuran. The photoinduced charge separation in the studied complexes occurs on a picosecond time scale. The computations predicts very similar electronic properties not only for single unit of suit[3]ane but also for its aggregates.

The high stability of suit[3]anes in combination with their photoinduced electron transfer properties makes this new class of interlocked molecules promising materials for photovoltaic applications.^[2]

References:

[1] J. F. Stoddart et al., J. Am. Chem. Soc. 2020, 142, 20152.

[2] A.J. Stasyuk et al., J. Mater. Chem. C, 2021, 9, 9436.