Multidimensional Hybrid Metal Phosphonate Coordination Networks as Synergistic Anticorrosion Coatings.

In the technologically important field of anticorrosion coatings, it is imperative to form well-defined and characterized films to protect the metal surface from corrosion. Phosphonate-based corrosion mitigation approaches are currently being exploited. Herein, the synergistic action of alkaline-earth metal ions and two carboxy-diphosphonates, PAIBA [N,N-bis(phosphonomethyl)-2-aminoisobutyric acid] and BPMGLY [N,N-bis(phosphonomethyl)glycine], is explored. Also, a family of four novel hybrid metal phosphonate materials is reported, Mg-PAIBA, Ca-PAIBA, Sr-PAIBA, and Sr-Na-PAIBA, whose topological analysis revealed a variety of underlying networks with the 6,10T9, unc, SP 1-periodic net (4,4)(0,2), and unique topologies. The synergistic metal/carboxy-diphosphonate blends were tested for their anticorrosion performance on carbon steel at preselected concentrations (0.1-1.0 mM) and pH values (4.0-6.0). The results showed an enhanced inhibitory performance in the presence of metal cations at higher concentrations. The inhibition of corrosion at pH 5.0 in the presence of BPMGLY, PAIBA, and their combination with Sr2+ was investigated in detail using electrochemical measurements. Enhanced inhibition was achieved with a 1:1 Sr2+/BPMGLY (or PAIBA) binary system. Polarization curves indicated that the system is a "mixed" inhibitor. This study widens the family of carboxyphosphonate coordination polymers, showing their potential as attractive hybrid coatings with anticorrosion performance.

catena-Poly[oxidanium [tris{µ-[amino(iminio)methyl]phosphonato}zincate(II)]].

The crystal structure of the anionic zinc-[amino-(iminio)meth-yl]phospho-nate one-dimensional coordination polymer, Zn-AIMP, is reported; the negative charge is balanced by an oxidanium cation (H3O+) to give the composition {(H3O)[Zn(CH4N2PO3)3]} n . The building unit of the coordination polymer comprises a divalent Zn2+ cation (site symmetry ..) and three [amino(iminio)meth-yl]phospho-nate mono-anionic ligands (point group symmetry m). The AIMP ligand exists in a zwitterionic form with a total charge -1 as the phospho-nate is fully deprotonated (-PO3 2-), while the amino-(iminio)methyl moiety is protonated (H2N-C-NH2 +).

5-Phenyl-3-(2-phosphono-eth-yl)-1,2,3-triazol-1-ium chloride.

The new triazole-functionalized phospho-nic acid 5-phenyl-3-(2-phosphono-eth-yl)-1,2,3-triazol-1-ium chloride, C10H13N3O3P+·Cl- (PTEPHCl), was synthesized by the 'click' reaction of the alkyl azide diethyl-(2-azido-eth-yl)phospho-nate with phenyl-acetyl-ene to give the dieth-yl[2-(4-phenyl-1H-1,2,3-triazol-1-yl)eth-yl]phospho-nate ester, which was then hydrolyzed under acidic conditions (HCl) to give the 'free' phospho-nic acid. The use of HCl for the hydrolysis caused protonation of the triazole ring, rendering the compound cationic, charged-balanced by a Cl- anion. There are extensive hydrogen-bonding inter-actions in the structure of PTEPHCl, involving the phospho-nic acid (-PO3H2) group, the triazolium ring and the Cl- anion.