Molecular Modeling of Halogen-Induced Electronic and Spectroscopic Modulation in (λ5-Boraneylidene)Methanone Derivatives

Abstract

This study investigates (lambda 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 omega B97X-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 & boxH;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.