Nido -boranes constitute a versatile class of electron-deficient polyhedral clusters whose noncovalent recognition behaviour can be finely modulated through heteroatom substitution. In this work, we investigate how halogen (Br, Cl, F) and hydroxyl substituents influence the interaction energies and binding orientations of nido -heteroboranes toward aromatic (benzene) and aliphatic (trimethylamine, TMA) ligands under vacuum, polar (water), and non-polar (heptane) environments. Density functional theory calculations (B3LYP-D3/def2-TZVPP) using an IEFPCM solvation model show that solvent polarity strongly reduces interaction strength due to dielectric stabilization and electrostatic screening. Hydroxyl substitution produces the strongest and most directional interactions due to enhanced dipolar and hydrogen-bonding contributions, whereas halogen substitution yields substituent-specific behaviour governed by differences in σ-hole magnitude and polarizability. Bromine shows strong, well-defined halogen-directed binding, whereas chloride exhibits solvent-dependent switching between binding orientations, and fluoride, lacking a σ-hole, drives binding toward the positively charged open boron face. These results elucidate how substituent identity, carbon distribution, and solvent polarity collectively modulate the electrostatic landscape of nido -boranes, offering transferable design principles for their application in supramolecular recognition, catalysis, and boron-based functional materials.
Sankar et al. (Wed,) studied this question.