Two solvent-dependent Al16 nanorings: design, synthesis and nonlinear optical limiting behavior

Cyclic compounds are of great interest to chemists for their adjustable organic shells and inorganic cores. Although the abundant bridges provide a bottom-up synthesis approach for the diversity and functionalization of ring compounds, the lack of suitable models still limits us in exploring the influence of bridge types on ring structures. Herein, we demonstrate two Al16 molecular nanorings synthesized via 2 × 8 and 4 × 4 strategies based on the “ligand-induced aggregation and solvent regulation” strategy and discuss the influence of surface bridge flexibility on molecular ring distortion and curvature. Rigid phenol endows AlOC-135 with unique intramolecular π⋯π interactions and higher curvature to increase the delocalization and transfer of electrons, resulting in a superior third-order nonlinear optical (NLO) response. This work provides a platform for explaining the relationship between the structure and optical properties of ring compounds at the molecular level.