Molecular assembly with a figure-of-eight nanohoop as a strategy for the collection and stabilization of cyclo[18]carbon

Abstract

The recently synthesized novel figure-of-eight nanohoop with two strained oligoparaphenylenes (OPPs) was theoretically designed to collect and stabilize new allotropic carbon cyclo[18]carbon (C₁₈) through molecular assembly. The size adaptability and shape complementarity of C₁₈ to OPP make it possible for them to combine into extraordinary ring-in-ring supramolecules. Thermodynamic analysis of 2C₁₈@OPP showed that the host–guest complex should spontaneously form below 404 K. Molecular dynamics (MD) simulations demonstrated that the assembly of C₁₈ and OPP into host–guest complexes of up to 1 : 2 can occur at ambient temperature. Various real-space function analyses revealed that the nature of the non-covalent interaction between C₁₈ and OPP is the van der Waals (vdW) attraction characterized by π–π stacking. Photoexcitation makes the host–guest complexes less stable in their S₁ state by causing the central linker to flatten.