Molecular Modeling of Halogen‐Induced Electronic and Spectroscopic Modulation in (λ ⁵ ‐Boraneylidene)Methanone Derivatives

ABSTRACT

This study investigates (λ ⁵ ‐boraneylidene)methanone (BCO) and its F‐, Cl‐, and Br‐substituted derivatives using density functional theory. B3LYP/6‐311G(d,p) calculations were used for the primary electronic, spectroscopic, thermochemical, and real‐space analyses, while ωB97X‐D/def2‐TZVP calculations assessed the robustness of structural and frontier‐orbital trends. Halogen substitution progressively reduced the calculated HOMO‐LUMO gap, and this ordering was retained at both computational levels. The B‐X and C‐B geometries showed the largest substituent‐dependent changes, but the C═O bond was less affected. Calculated FT‐IR and NMR parameters showed nonmonotonic shifts, while the lowest‐energy TD‐DFT transition moved from 211.23 nm for BCO to 371.24 nm for Br‐BCO. MEP, DOS, NCI, and DORI analyses indicated substituent‐dependent electron‐density redistribution, although these results were interpreted qualitatively. Thermal energy, heat capacity, and entropy increased between 300 and 900 K within the ideal‐gas harmonic approximation. Exploratory ADMET predictions also varied across the series but remain model dependent and do not establish biological activity or safety. Halogen substitution provides a systematic means of modulating the calculated properties of this boron‐containing molecular system.