Nonclassical Dihydrogen Bond-Directed Assembly of o -Carborane-Based Molecules into Macroscopic Architectures with Circularly Polarized Luminescence

Abstract

Hierarchical architectures are ubiquitous in nature; however, the bottom-up construction of multilevel chiral macroscopic assemblies from small organic molecules remains highly challenging. Herein, we report an unprecedented assembly strategy for constructing hierarchically organized particles (HOPs) through the co-assembly of achiral o-carborane-based molecules (C-1 and C-2) with chiral (R/S)-limonene. Intriguingly, C-1-(S)-limonene forms microscale cocoon-like superstructures, whereas C-1-(R)-limonene undergoes self-assembly into fibrous architectures that ultimately evolve into random aggregates at the micrometer scale. In contrast, C-2-(R/S)-limonene assembles into bowtie-shaped microarchitectures. Graph Theory (GT) analysis reveals structural complexity indices (CIs) of 5.5 and 54 for the C-1-(S)-limonene- and C-2-(S)-limonene-based HOPs, respectively, indicating significantly higher architectural complexity for the latter. These assemblies exhibit distinct circularly polarized luminescence (CPL) properties: C-1-(S)-limonene displays intense CPL emission at 504 nm with a high luminescence dissymmetry factor (glum) of +0.006, whereas C-2-(S)-limonene exhibits CPL emission at 560 nm with a glum value of +0.002. These results demonstrate that chirality signals are transferred across multiple length scales from the molecular level to macroscopic architectures. The observed structural divergence originates from the synergistic effects of nonclassical dihydrogen bonding (Bδ+−Hδ−···Hδ+−Cδ−) between achiral o-carborane derivatives and chiral limonene, together with molecular polarity and elasticity effects. This study establishes a paradigm for fabricating chiral o-carborane-based hierarchical aggregates with programmable architectures and tailored chiroptical properties.