DFT-D3 and TD-DFT Studies of the Adsorption and Sensing Behavior of Mn-Phthalocyanine toward NH 3 , PH 3 , and AsH 3 Molecules.

This study employs density functional theory (DFT) calculations at the B3LYP/6-311+g(d,p) level to investigate the interaction of XH 3 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 XH 3 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 XH 3 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 XH 3 adsorption, highlighting MnPc's potential as a naked-eye sensor for XH 3 molecules. Thermodynamic calculations indicate exothermic interactions, with NH 3 /MnPc being the most stable complex. The stability of NH 3 /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 XH 3 /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 XH 3 /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 XH 3 gases.