The use of metallosurfactants to prevent pitting corrosion of aluminum surfacesi sd iscussed based on the behavior of the metallosurfactants [Zn II (L N2O2 )H 2 O] (1)a nd [Ga III (L N2O3 )] (2). These speciesw ere deposited as multilayer Langmuir-Blodgett films and characterized by IR reflection absorption spectroscopy and UV/Vis spectroscopy.S canning electron microscopy images, potentiodynamic polarization experiments,a nd electrochemical impedance spectroscopy were used to assessc orrosion mitigation. Both metallosurfactants demonstrate superior anticorrosiona ctivity due to the presence of redox-inactive3 d 10 metal ions that enhancet he structuralr esistance of the ordered molecular films and limit chloride mobility and electron transfer.Aluminumi salight, malleable, moldable, and nonmagnetic metal that resists atmosphericc orrosion,a nd displays electrical and thermalc onductivity. These attributes enable wideu se in automotive, aerospace, and naval industries. Although the metal is the third most abundant element in the crust (80 700 ppm), isolation from bauxite has ah igh environmental cost and generates an estimated1 3tons of CO 2 per ton of Al, [1] along with at oxic solid waste known as red mud. As such, conservation efforts are necessarya tall levelsa nd include recycling and corrosion mitigation.Unlike iron, in which adventitious oxygen and water leads to the formation of Fe(OH) 3 and Fe 2 O 3 , [2][3][4][5][6] the mechanismso fA l corrosion are more complex and less understood. Nonetheless, the action of pitting corrosionl eads to perniciouss tructural failures in car frames, airplane fuselages, and ship hulls, and demands immediate attention. With an electronic configuration given by [Ne] 3s 2 3p 1 ,t he metal has as tandard potential of À1.7 V SHE associated with the loss of the 3s 2 and3 p 1 electrons during the processg iven by Al (s) ÐAl 3 + + 3e À .P itting is initiated in neutral media by the presence of chloride [7] and other anions [8] that physisorb at the positively charged surface of the Al 2 O 3 passivation layer. [2,9] The Cl À anions penetrate through nanometer-sized cracks or migrate via oxygen vacancies [10][11][12] reaching the Al 2 O 3 j Al 0 interface, quickly converting Al 0 into AlCl 3 ,a nd then the anionic tetrahedral [13] complex [Al III Cl 4 ] À .T his soluble anion reacts with water forming aluminum hydroxide,g iven by [Al III Cl 4 ] À + 3H 2 O![Al III (OH) 3 ] + 3H + + 4Cl À .T he propagationp hase yields localized blisters of acidic pH that eventually erupt and exposet he corrosion pit. [14] The corrosion rate decreases over time, but perforation may occur, and chromium-based coatings have been commonly used. [15,16] However, concerns with the environmental impact of hexavalent chromium generated by these coatings imposes teep restrictionst ot heir use. [16] In searching for potential alternatives, we hypothesize that the presence of an ordered Langmuir-Blodgett (LB) multilayer of molecularm etallosurfactants would act as ah ydrophobic barriert hat decreases access of w...

Targeting the development of stimulus-responsive molecular materials with electronic functionality, we have synthesized and studied the redox and electronic properties of a new bimetallic iron hydrophobe [FeIII2(LN4O6)] (1). The new H6LN4O6 ligand displays bicompartmental topology capable of accomodating two five-coordinate HSFeIII ions bridged by tetraaminobenzene at a close distance of ca. 8 Å. We show that the metal-based reduction processes in (1) proceed sequentially, as observed for electronically coupled metal centers. This species forms a well-defined Pockels-Langmuir film at the air-water interface, with collapse pressure of 32 mN m-1. Langmuir-Blodgett monolayers were deposited on gold substrates and used to investigate current-voltage (I-V) measurements. This unprecedented bimetallic hydrophobe [FeIII2(LN4O6)] (1) shows unquestionable molecular rectification and displays a rectification ratio RR between 2 and 15.

Two new metallosurfactants containing the 3d 1 vanadyl(IV) and 3d 3 chromium(III) ions bound to the phenylenediamine-bridged phenolate-rich ligand L N 2 O 2 were designed, deposited as monolayer films on gold electrodes, and probed for directional electron transfer in Au|LB|Au junctions. Both [V�O IV L N 2 O 2 ] (1) and [Cr III (L N 2 O 2 )(MeOH)(H 2 O)]Cl (2) promote current rectification. Through a concerted experimental and computational effort, we compare the behavior of 1 and 2 with that of our previously studied 3d 5 [Fe III (L N 2 O 2 )Cl] (3). Based on the analysis of comprehensive electrochemical, spectroscopic, and microscopy results allied to DFT calculations, we propose distinct mechanisms by which electronic configurations influence the energy gap between the electrode Fermi levels and the different molecular orbitals responsible for electron transport. While the 3d 5 species 3 shows electron transport through the metal-based SOMO located above the Fermi levels of the electrode, the 3d 1 species 1 uses a metal-based SOMO below Fermi, and the 3d 3 species 2 takes advantage of a ligand-based HOMO, which becomes available when a bias is applied.

We have recently described a new potential use for Langmuir–Blodgett films of surfactants containing redox-inert metal ions in the inhibition of corrosion and have shown good qualitative results for both iron and aluminum surfaces. In this study we proceed to quantify electrochemically the viability of gallium­(III)- and zinc­(II)-containing metallosurfactants [GaIII(LN2O3)] (1) and [ZnII(LN2O2)­H2O] (2) as mitigators for iron corrosion in saline and acidic media. We evaluate their charge transfer suppression and then focus on potentiodynamic polarization and impedance spectroscopy studies, including detailed SEM data to interrogate their metal dissolution/oxygen reduction rate mitigation abilities. Both complexes show some degree of mitigation, with a more pronounced activity in saline than in acidic medium.