DFT Study on the Spin States of Polyaniline-3d Transition-Metal (Sc-Zn) Composites and Their Sensing Application to Detect Chemical Warfare Agents

Organic-inorganic composite materials, combining polymers with transition metal (TM) atoms based on PAni and 3d TMs, have been designed and investigated in various spin states by performing density functional calculations. These designed composites were analyzed for their stability in different spin states as well as for their calculated electronic properties, including binding energies, frontier molecular orbitals, and dipole moments. Additionally, 3D isosurfaces and 2D scattered plots of reduced density gradient as a function of (sign lambda(2))-rho provide insights into the noncovalent interactions between the composite units. The most stable Mn@PAni composite has been assessed as a sensing material for chemical warfare blood agents (HCN, NCCl, NCBr, NCCN, and AsH3) using density functional-based calculations. The reduced band gap and significant red/blue shift in the UV-vis spectra obtained through TDDFT calculations underline the selectivity and efficiency of the Mn@PAni composite toward different analytes.