Accurate clarification on assembling and protective mechanisms of β-cyclodextrin/benzothiazole complex for copper in marine environment

Molecular assembly based on cyclodextrins can realize the aqueous utilization of inherently-insoluble corrosion inhibitors for metals; however, the associated protection mechanism is not yet fully understood. Herein, hydrophobic benzothiazole (BT) was assembled with β-cyclodextrin (β-CD) forming the complex (CD-BT) for protecting copper in the simulated seawater (SSW). Supramolecular complexing was optimized through response surface methodology, and the host–guest interaction was confirmed by spectral, thermal and morphological examinations besides the disclosed assembling thermodynamics. Electrochemical and surface analyses indicated that CD-BT effectively suppressed copper dissolution in SSW yielding a maximum inhibition efficiency of 97.0%. Density functional theory (DFT) calculations were deployed to clarify the accurate complexing behavior of BT inward β-CD's cavity. Benefitting from the favorable incorporating configuration of BT and its overwhelming adsorption energy over the assembling counterpart, CD-BT underwent an incubation–guest release–adsorption process at the copper/SSW interface. Adsorption of released BT molecules and its chelation ability towards cuprous/cupric species accounted for the efficient protection of copper in SSW.