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The inhibition effect of a Schiff base with several functional groups on the corrosion of aluminum in alkaline solution is studied by experimental techniques and density function theory (DFT) calculations. The Schiff base are characterized by 1 HNMR, 13 CNMR, FT-IR, and CHN elemental analysis. In addition, different electrochemical and corrosion techniques such as weight loss, tafel polarization, electrochemical impedance spectroscopy (EIS) and optical microscopy images are performed to analyze the inhibiting performances. In the Tafel measurements the cathodic Tafel slopes values incurred small changes with increasing the inhibitor concentration, which revealed that the inhibitor was adsorbed on the aluminum surface. The inhibition efficiencies are calculated from weight loss measurement and electrochemical tests. The adsorption of the inhibitor onto the aluminum surface follows the Langmuir adsorption isotherm with the free adsorption energy of −8.66 kJ mol −1 . The calculated adsorption energies and the amount of charge transfer obtained by DFT calculation revealed that corrosion inhibition effectively occurs with chemisorption, where new N Al bonds are formed between of N atoms in azo (–N N–) group and Al surface atoms, which is confirmed from ab initio molecular dynamics (AIMD) simulation. [ABSTRACT FROM AUTHOR]

We systematically investigated the tuning of the reduction potentials ( E 0 ) for the first row transition metal (M = Cr, Mn, Fe, Co, Ni) complexes with the functionalized 1,4,7-Triazacyclononane-N,N',N”-triacetate (TCTA) ligands by means of DFT calculations. To predict reliable E 0 , the modified UB3LYP functional and equilibrium concept between high and low spin states were utilized. The functional groups NH 2 , CN, −F, and NO 2 were attached to the carbon atoms carefully selected by considering the LUMO and steric hindrance. Based on firmed accuracy of DFT calculations, finally we obtained the calculated E 0 for a series of complexes. It was found that electron donating group such as NH 2 will cause a negative shift of E 0 while electron withdrawing groups have the opposite effect. The overall trend of the calculated E 0 s according to ligand modifications were predicted to have the order as −NH 2 < Pristine < −F ≈ −CN < −NO 2 . In addition, optimized geometries, LUMO, vertical electron attachment and energy components constituting E 0 were discussed in detail to assist the further understanding for E 0 s. Consequently, we suggested that 16 complexes can play a role as an electrolyte in aqueous redox flow battery. They can be classified into 5 groups having similar E 0 ranges: Group I (- 0.6 V ∼ − 0.7 V), Group II (around 0.0 V), Group III (around 0.3 V), Group IV (0.6 ∼ 0.8 V) and Group V (1.1 ∼ 1.2 V). Especially, it is expected that [MnL F ] , [MnL CN ] and [NiL NH2 ] can be used as promising catholyte candidates possibly possessing high E 0 s which almost reach to the reduction potential limitation 1.25 V in aqueous redox flow battery. Our systematic approach to tune E 0 can be applied to the design of other complexes via rational ligand modification. [ABSTRACT FROM AUTHOR]