Unraveling Adsorption and Bonding Behaviors of 2,6-Dithiopurine (Dtp) Inhibitor Molecule on Iron Surface

Abstract

Purine derivatives present a high efficiency for anti-corrosion purposes while the nanoscale mechanisms remain unclear. In this work, the inhibition mechanism of 2,6-dithiopurine (DTP) molecule was investigated using advanced characterizations and atomic simulations. We uncovered that DTP molecule adopts a mode of multi-layer adsorption, governed by both chemisorption and physisorption. An organometallic layer of a thickness of ~3.8 nm was captured using TEM, which is composed of Fe-N and Fe-S bonds firmly anchored to the iron interface based on XPS results. The heteroatoms like N or S in DTP molecule act as the reactive sites to promote its chemisorption on iron surfaces. Our quantum chemical calculations also reflected that these metal-organic bonds (i.e., Fe-N, Fe-S) display both ionic and covalent components due to the unique bonding features at the DFP-iron interfaces. Different chemisorption behaviors can be distinguished concerning the various substrates including pure iron or lepidocrocite surfaces. Meanwhile, the physisorption of DTP is dominated by the vdWs forces among the molecules. Intermolecular interactions such as π-π stacking can lead to the self-assembly of DTP molecules to form a thicker inhibition layer.

Keywords: Corrosion inhibitor, adsorption, Chemical bonding, Atomic simulation, Anti-corrosion mechanism, Interface