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The corrosion inhibiting performance and mechanism of two dithioamide derivatives, N,N′-di-ethyl-dithiodipropinoamide (ED) and N,N′-di-ethyoxylpropyl-dithiodipropinoamide (EPD), for mild steel in 1.0 M HCl solution were investigated by experiments, DFT calculation and MD simulations. EPD and ED are both mixed-type inhibitors with excellent inhibition efficiency (95.2% and of 92.6%, respectively) by weight loss experiments; SEM images also demonstrate the formation of compact inhibiting monolayer. On molecular level, both molecules can be tightly parallel absorbed on Fe (110) surface through S–Fe and O–Fe coordination bounds by the overlapping of heteroatom p orbitals and Fe 3 d orbitals, with binding energies of 369.56 kJ/mol and 608.55 kJ/mol. Strong multi-intermolecular H-binding network drives ED and EPD molecules orderly self-assemble on iron surface and form protective monolayer. EPD network keeps intact up to 1.0 MPa, guarantees its potential applications in deep-sea environment. EPD could be self-assembled by hydrogen bonding to form monolayer film. Image 1 • The inhibition properties and mechanism of ED and EPD were investigated. • The inhibition efficiency of ED and EPD are 92.6% and 95.2%, respectively. • Monolayer of ED or EPD could be self-assembled by cross-link H-bonding network. • EPD filming kept intact under 1.0 MPa. [ABSTRACT FROM AUTHOR]

The formation of host-guest inclusion complexes by Pillar [5]arene (P [5]) and cationic nitrogen heterocyclic molecules were studied by DFT calculations at B3LYP-D3/6-311 + G** level, together with their equilibrium geometries, binding energies and electronic structures. MESP, NCI-RDG and AIM topography analysis were performed to explore underlying interactions. Geometric structures of inclusion complexes were changed compared with the individual molecules; MESP analysis revealed the driving force for the binding process; QTAIM and NCI-RDG methods were utilized to reveal the underlying non-covalent interactions. The inclusion complexes in 1:1 ratio were stabilized through weak C–H⋯O hydrogen bonds, C–H···π, π+···π and van der Waals interactions. The calculated electrophilic charge transfer indicated that charge flowed from P [5] to guests. Gibbs free energy accompanying the recognition process certified that formation of complexes were spontaneous and thermodynamically favorable. • The cation guests prefer to accommodate in the cavity of pillar [ 5 ]arene. • Pillar [ 5 ]arene undergoes distortion after encapsulation. • Charge distribution is the major driving force for the encapsulation process. • C–H⋯O, C–H···π and π+···π interactions are stabilizing factors. • The recognition processes are spontaneous and thermodynamically favorable. [ABSTRACT FROM AUTHOR]