DFT and TD-DFT investigation of metal-decorated borazine as molecular sensors for acetohydrazide: Energetic, electronic, NBO, QTAIM, and NCI-RDG insights.

Abstract

This study relies on density functional theory (DFT) and its time-dependent formulation (TD-DFT) to examine the adsorption of acetohydrazide (ACH) on pristine borazine (BRZ) and on structures decorated with Fe, Ni, Cu, and Zn (M@BRZ). Energetic, electronic, and optical properties were investigated using complementary NBO, NPA, QTAIM, NCI-RDG, and DOS/PDOS analyses. The results indicate that adsorption on BRZ is primarily governed by an N-H•••O hydrogen bond, whereas metal decoration significantly alters these interactions. The calculated interaction energies are -60.49, -31.83, -29.26, and -42.19 kcal•mol-1 for Fe@BRZ, Ni@BRZ, Cu@BRZ, and Zn@BRZ, respectively, compared to -10.34 kcal•mol-1 for BRZ. Based on these findings, Fe@BRZ exhibits the most favorable interaction, while Zn@BRZ shows the largest variation in the HOMO-LUMO gap, shifting from 1.959 to 3.724 eV. NBO analysis reveals N→Fe donor-acceptor interactions characterized by stabilization energies of 30.00 and 14.45 kcal•mol-1. NPA results indicate a net charge transfer of +0.171 e for ACH@Fe@BRZ, while QTAIM analysis identifies an Fe•••N contact with an electron density of 0.03575 a.u. B3LYP-D3(BJ) calculations confirm a favorable contribution from dispersion interactions. TD-DFT results reveal wavelength shifts of +78.89 nm for Fe@BRZ and +24.92 nm for Zn@BRZ between the dominant transitions before and after adsorption. SMD calculations also suggest a differential influence of aqueous solvation, which is particularly pronounced for Zn@BRZ.

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