DFT-D3 and TD-DFT Studies of the Adsorption and Sensing Behavior of Mn-Phthalocyanine toward NH3, PH3, and AsH3 Molecules

Abstract

This study employs density functional theory (DFT) calculations at the B3LYP/6-311+g(d,p) level to investigate the interaction of XH₃ gases (X = N, P, As) with the Mn-phthalocyanine molecule (MnPc). Grimme's D3 dispersion correction is applied to consider long-range interactions. The adsorption behavior is explored under the influence of an external static electric field (EF) ranging from -0.514 to 0.514 V/Å. Chemical adsorption of XH₃ molecules onto the MnPc molecule is confirmed. The adsorption results in a significant decrease in the energy gap (E_g) of MnPc, indicating the potential alteration of its optical properties. Quantum theory of atoms in molecules (QTAIM) analysis reveals partially covalent bonds between XH₃ and MnPc, and the charge density differenc (Δρ) calculations suggest a charge donation-back donation mechanism. The UV-vis spectrum of MnPc experiences a blue shift upon XH₃ adsorption, highlighting MnPc's potential as a naked-eye sensor for XH₃ molecules. Thermodynamic calculations indicate exothermic interactions, with NH₃/MnPc being the most stable complex. The stability of NH₃/MnPc decreases with increasing temperature. The direction and magnitude of the applied electric field (EF) play a crucial role in determining the adsorption energy (E_ads) for XH₃/MnPc complexes. The E_g values decrease with an increasing negative EF, which suggests that the electrical conductivity (σ) and the electrical sensitivity (ΔE_g) of the XH₃/MnPc complexes are influenced by the magnitude and direction of the applied EF. Overall, this study provides valuable insights into the suggested promising prospects for the utilization of MnPc in sensing applications of XH₃ gases.