Ab initio studies of adsorption of Haloarenes on Heme group.

In the present investigation, we have employed heme as a material for absorbing haloarenes due to its unique structural property, abundant availability, non-toxic nature and its dynamic nature in absorbing oxygen molecule. Haloarenes are toxic gases that are released into atmosphere as an aftermath of various refrigerants. Using first principle study, the absorption of haloarenes on heme molecule was systematically investigated. Fluorine, Chlorine, Bromine and Iodine substituted Haloarenes were allowed to interact with heme molecule with metal ion at +2, +3 and + 4 oxidation states of both low and high spin states. The TD-DFT analysis shows that the heme is a better absorbent at +3 and + 4 oxidation states of Fe ion at low spin state. Among the haloarenes, the interaction energy between IHA and Fe ion at +4 state is maximum with -1.877 eV. The HOMO-LUMO band gap decreases with increase in oxidation state and the orbital delocalization is maximum for high oxidation state. The delocalization of these electronic orbitals shows the active interaction between the heme molecule and haloarene which was confirmed by the DOS plot and the LP to LP* transition in NBO analysis. The absorbing nature of heme was further extended to hexahaloarenes, where heme still stand as a strong absorbing candidate for these toxic gases. The detailed study of the interaction between heme and haloarenes showed that heme at low spin state and with both +3 and + 4 oxidation states can be employed as an absorbent for Haloarenes. Graphical abstract.