Mapping the supramolecular chemistry of pyrazole-4-sulfonate: layered inorganic–organic networks with Zn²⁺, Cd²⁺, Ag⁺, Na⁺and NH₄⁺, and their use in copper anticorrosion protective films

Abstract

Five compounds based on the versatile pyrazole-4-sulfonate anion (4-SO 3 -pzH ¼ L À ) were synthesized by the reaction of ligand HL with ZnO, CdCO 3 , Ag 2 O, NaOH and NH 3 , respectively. Crystals of Zn(4-SO 3 -pzH) 2 (H 2 O) 2 , Cd(4-SO 3 -pzH) 2 (H 2 O) 2 , Ag(4-SO 3 -pzH), Na(4-SO 3 -pzH)(H 2 O) and NH 4 (4-SO 3 -pzH) were obtained from aqueous solutions upon evaporation, and were characterized by single-crystal X-ray diffraction, IR and NMR spectroscopy, thermogravimetric analysis and copper corrosion inhibition experiments. We found that the non-isomorphous, 3-dimensional inorganic-organic layered solid state structure of these compounds is determined by an intricate interplay between the size, charge and coordination preference of the cation, and an extended lattice of hydrogen bonds and aromatic interactions. Ligand L À incorporates a host of different binding capabilities (metal coordination through the pyrazole N-atom and/or the sulfonate O-atom, hydrogen-bonding both as donor and acceptor, p-p and C-H/p interactions). Thin films formed by these complexes on copper metal surfaces were studied by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. ZnL 2 , CdL 2 , AgL and NH 4 L, in addition to the free ligand HL, were tested as corrosion inhibitors on copper metal surfaces at three different pH values (2, 3 and 4), and the corrosion rates were quantified. Significant corrosion protection was observed with all compounds at pH 4 and 3.

Synthesis and Structural Studies of Three‐Dimensional Supramolecular Motifs Derived from Neutral and Cationic Zinc Alkanesulfonates

“…The cumulative effects of secondary interactions are pivotal to the stability of higher‐dimensional structures, and these interactions provide flexibility to porous frameworks. The synthetic approach often requires the involvement of zero‐, one‐, or two‐dimensional coordination frameworks associated with complementary ligands that offer secondary interactions . Several such reliable synthons that encode well‐defined noncovalent motifs have been reported.…”

Multifunctional metal–organic frameworks: from academia to industrial applications

“…Several anti-corrosion agents have been reported in the literature and MOF compounds emerge as potential candidates. 73,75,[196][197][198][199] This family of materials, typically with high surface areas, wide supramolecular natures and unique topologies, being rich in p-systems and heteroaromatic moieties, should thus attract the interest of industry and society while being employed as corrosion inhibitors. 198 Demadis's research group pioneered the preparation of organic-inorganic hybrid networks with an inhibiting effect on metallic corrosion.…”

“…200 These authors reported multidimensional MOFs from the self-assembly of phosphonate-or sulfonatebased organic linkers and alkaline, alkaline-earth and transition metal centers. 75,196,197,200,201 In 2008, they reported a series of layered or three-dimensional coordination polymers, generally coined M-HPAA [where HPAA = hydroxyphosphonoacetate; and M = Ma, Ca, Sr and Ba], obtained from hydrothermal synthesis from the adjustment of the pH of the reactive mixtures to 2.7 using NaOH. 75 The resulting M-HPAA materials were formulated as {M[(HPAA)(H 2 O) x ](H 2 O) y } n with x and y determining the amount of metal-coordinated and lattice water.…”

“…Fernando et al investigated the capacity of some layered inorganic-organic networks as corrosion inhibitors of copper surfaces. 196…”

Enhancing Anticorrosion Properties of Micro–Nano Zinc Vanadate from Atomic Modulation Supplemented by Light Modification

“…The impedance spectra of the samples obtained by the EIS test was an important indicator to analyze the corrosion resistance of ZVO materials. 61 In the high frequency region, the Nyquist plots of all samples exhibited a semicircular arc (Figure 7). However, in the intermediate frequency region, the semicircular arc of pure epoxy resin disappeared, demonstrating that the films had been damaged and lost the protective effect.…”