Regioisomeric effect of heteroatoms and functional groups of organic ligands: Impacts on coordination bonding and corrosion protection performance

The regioisomeric effect, which refers to the different positions of heteroatoms and functional groups on a molecule, significantly impacts the stability, physicochemical properties, chemical reactivity, and coordination bonding of organic compounds. These effects are critical for their commercial applications, notably in corrosion inhibition. Regioisomeric ligands, with their unique spatial configurations of functional groups, influence their ability to establish stable coordination interactions with metal surfaces. Certain regioisomers may exhibit enhanced affinity and adsorption capacities based on their structural configurations, thereby facilitating the formation of a more durable protective layer on the metal substrate. This review explores the impact of regioisomerism on the coordination bonding and corrosion inhibition performance of organic compounds. A literature survey reveals that identical substituents (e.g., –OH, –NH₂, –COOH, –NO₂, –OR), multiple bonds (e.g., >C[dbnd]C< and –C[tbnd]C–), or heteroatoms (e.g., N, O, and S) at varying positions exhibit diverse coordination bonding capabilities and corrosion inhibition efficiencies. The detailed analysis indicates that certain regioisomers, due to the strategic placement of functional groups, achieve increased stability and form relatively stronger and more stable metal complexes. This enhances their effectiveness in corrosion inhibition and metal chelation mechanisms. The role of functional group stability and regioisomerism has been seldom observed and documented in previous studies. The current research also underscores the significance of regioisomerism and functional group stability in determining the corrosion inhibition performance of organic ligands. A thorough understanding of regioisomerism and functional group stability will assist corrosion scientists and engineers in developing more effective corrosion inhibitors.