Sensing of SO3, SO2, H2S, NO2 and N2O toxic gases through aza-macrocycle via DFT calculations

The toxic gas sensing applications find immense attention in environmental monitoring. In this research, the adsorption of nitrogen and sulfur-containing gaseous molecules i.e., N2O, NO2, H2S, SO2 and SO3 on organic aza-macrocyclic hexaazabipyH(2) (HA) is analyzed through DFT simulations. The interactions of toxin analytes with HA are expressed through the interaction stabilities of optimized geometries, and electronic parameters including highest occupied and lowest unoccupied molecular orbitals energies and NBO charged transfer analysis. Our results indicate that the gaseous molecules are physisorbed onto the HA with the interaction energies of -4.80, -4.86, -7.09, -7.42 and -11.64 kcal/mol for NO2, N2O, H2S, SO2 and SO3, respectively. The trend of interaction stability of complexes is observed as, SO3@HA > SO2@HA > H2S@HA > N2O@HA > NO2@HA. The adsorption of the gaseous molecule on the electronic structure of HA is significant, especially for sulfur containing analytes. The effects of the applied electric field from the range of -0.15 to +0.15 V/angstrom in the direction of adsorbed molecules (Y-axis) on the interaction energies and dipole moment of complexes have been measured. It can be concluded that the HA macrocycle shows greater sensitivity towards the toxic gas molecules and therefore, can be applied for their sensing.