From Chains to Arrays: Substrate-Mediated Self-Assembly of Diboron Molecules

In this study, we explore the substrate-mediated control of self-assembly behavior in diboron molecules (C₁₂H₈B₂O₄, B₂Cat₂) using scanning tunneling microscopy (STM). The structural transformation of B₂Cat₂ molecules from one-dimensional (1D) molecular chains to two-dimensional (2D) molecular arrays was achieved by changing the substrate from Au(111) to bilayer graphene (BLG), highlighting the key role of substrate interactions in determining the assembly structure. Notably, the B-B bond in the molecular arrays on BLG is distinctly pronounced, reflecting a more refined molecular resolution with distinct electronic states than that on Au(111). Density functional theory (DFT) calculations confirm the weak interaction between B₂Cat₂ molecules and the BLG substrate, which facilitates the formation of 2D molecular arrays on BLG. This work demonstrates how controlling substrate properties enables the formation of 1D chains and 2D arrays, providing valuable insights for the design of next-generation molecular electronics and catalysis systems.