Research progress on chitosan and its derivatives in the fields of corrosion inhibition and antimicrobial activity

Chitosan stands out as the only known polysaccharide of its kind, second only to cellulose. As the second-largest biopolymer globally, chitosan and its derivatives are extensively used in diverse areas such as metal anti-corrosion prevention, food production, and medical fields. Its benefits include environmental friendliness, non-toxicity, cost-effectiveness, and biodegradability. Notably, the use of chitosan and its derivatives has gained substantial attention and has been extensively researched in the fields of metal anti-corrosion prevention and antibacterial applications. By means of chemical modification or synergistic action, the inherent limitations of chitosan can be substantially improved, thereby enhancing its biological and physicochemical properties to meet a wider range of applications and more demanding application requirements. This article offers a comprehensive review of chitosan and its modified composite materials, focusing on the enhancement of their anticorrosion and antibacterial properties, as well as the mechanisms by which they serve as anticorrosion and antibacterial agents. Additionally, it summarizes the synthesis routes of various modification methods of chitosan and their applications in different fields, aiming to contribute to the interdisciplinary development and potential applications of chitosan in various areas.

3,4-Dimethoxy phenyl thiosemicarbazone as an effective corrosion inhibitor of copper under acidic solution: comprehensive experimental, characterization and theoretical investigations

This study investigates the corrosion inhibition potential of 3,4-dimethoxy phenyl thiosemicarbazone (DMPTS) for copper in 1 M hydrochloric acid (HCl) solutions, aiming to disclose the mechanism behind its protective action. Through an integrative methodology encompassing electrochemical analyses-such as weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)-we quantitatively evaluate the corrosion protection efficacy of DMPTS. It was determined that the optimal concentration of DMPTS markedly boosts the corrosion resistance of copper, achieving an impressive inhibition efficiency of up to 89% at 400 ppm. The formation of a protective layer on the copper surface, a critical aspect of DMPTS's inhibitory action, was characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). These techniques provided empirical evidence of surface morphology modifications and roughness changes, affirming the formation of a protective barrier against corrosion. A significant advancement in our study was the application of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, which identified chemical adsorption as the definitive mechanism of corrosion inhibition by DMPTS. The ATR-FTIR results explicitly demonstrated the specific interactions between DMPTS molecules and the copper surface, indicative of a robust protective adsorbed layer formation. This mechanistic insight, crucial to understanding the inhibitory process, aligns with the protective efficacy observed in electrochemical and surface analyses. Theoretical support, provided by the Quantum Theory of Atoms in Molecules (QTAIM) and quantum chemical computations, further validated the strong molecular interaction between DMPTS and copper, corroborating the experimental findings. Collectively, this research not only confirms the superior corrosion inhibition performance of DMPTS in an acidic setting but also elucidates the chemical adsorption mechanism as the foundation of its action, offering valuable insights for the development of effective corrosion inhibitors in industrial applications.

Part-II: an update of Schiff bases synthesis and applications in medicinal chemistry-a patent review (2016-2023)

INTRODUCTION

Schiff bases are compounds with characteristic features of azomethine linkage (-C=N-). Schiff bases are capable of coordinating with metal ions via azomethine nitrogen. Schiff base derivatives and their metal complexes are known for intriguing novel therapeutic properties. In organic synthesis, the Schiff base reaction is prime in creating the C-N bond. Synthetic accessibility and structural diversity are the salient features for facile synthesis of Schiff base hybrids via a condensation reaction between an aldehyde/ketone and primary amines.

AREA COVERED

This review aims to provide a comprehensive overview of the commendable medicinal applications of Schiff base derivatives and their metal complexes patented from 2016 to 2023.

EXPERT OPINION

Schiff base derivatives are exceptional molecules for their assorted applications in medicinal chemistry. Several Schiff base products are marketed as drugs, and plenty of room is available for the purposive synthesis of new compounds in a diverse pool of disciplines. Expansion in the derivatization of Schiff bases in innumerable directions with multitudinous applications makes them 'magical molecules.' These compounds have proved extraordinary, from medicinal chemistry to other fields outside medicine. This review covers the therapeutic importance of Schiff base derivatives and aims to cover the patents published in recent years (2016-2023).

High-performance corrosion resistance of chemically-reinforced chitosan as ecofriendly inhibitor for mild steel

Finding new cost-effective and environmentally friendly anti-corrosion materials is a never-ending task. The present study is to prepare a new formulation based on chitosan derivatives with different degrees of substitution (chitosan-5-HMF) as an efficient green corrosion inhibitor to protect mild steel against corrosion in 1 M HCl. The inhibition performance of chitosan-5-HMF was determined by electrochemical tests coupled with theoretical study like as molecular dynamics (MD) simulations to assess the reactivity and adsorption mechanisms between chitosan-5-HMF and Fe. The obtained results revealed that chitosan-5-HMF3 performs excellently inhibition performance where its inhibition efficiency reached 97.01% at 200 mg/L, and it acted as an anode-based mixed inhibitor. SEM and contact angle analysis showed the formation of compact chitosan-5-HMF film on the steel surface. Molecular dynamic simulations also manifested that chitosan-5-HMF was absorbed more strongly on the metal surface in a parallel mode.

Heteropolysaccharides in sustainable corrosion inhibition: 4E (Energy, Economy, Ecology, and Effectivity) dimensions

Carbohydrate polymers (polysaccharides) and their derivatives are widely utilized in sustainable corrosion inhibition (SCI) because of their various fascinating properties including multiple adsorption sites, high solubility and high efficiency. Contrary to traditional synthetic polymer-based corrosion inhibitors, polysaccharides are related to the 4E dimension, which stands for Energy, Economy, Ecology, and Effectivity. Furthermore, they are relatively more environmentally benign, biodegradable, and non-bioaccumulative. The current review describes the SCI features of various heteropolysaccharides, including gum Arabic (GA), glycosaminoglycans (chondroitin-4-sulfate (CS), hyaluronic acid (HA), heparin, etc.), pectin, alginates, and agar for the first time. They demonstrate impressive anticorrosive activity for different metals and alloys in a variety of corrosive electrolytes. Through their adsorption at the metal/electrolyte interface, heteropolysaccharides function by producing a corrosion-protective film. In general, their adsorption follows the Langmuir isotherm model. In their molecular structures, heteropolysaccharides contain several polar functional groups like -OH, -NH₂, -COCH₃, -CH₂OH, cyclic and bridging O, -CH₂SO₃H, -SO₃OH, -COOH, -NHCOCH₃, -OHOR, etc. that serve as adsorption centers when they bind to metallic surfaces.

Organic Compounds as Corrosion Inhibitors for Carbon Steel in HCl Solution: A Comprehensive Review

Most studies on the corrosion inhibition performance of organic molecules and (nano)materials were conducted within “carbon steel/1.0 M HCl” solution system using similar experimental and theoretical methods. As such, the numerous research findings in this system are sufficient to conduct comparative studies to select the best-suited inhibitor type that generally refers to a type of inhibitor with low concentration/high inhibition efficiency, nontoxic properties, and a simple and cost-economic synthesis process. Before data collection, to help readers have a clear understanding of some crucial elements for the evaluation of corrosion inhibition performance, we introduced the mainstay of corrosion inhibitors studies involved, including the corrosion and inhibition mechanism of carbon steel/HCl solution systems, evaluation methods of corrosion inhibition efficiency, adsorption isotherm models, adsorption thermodynamic parameters QC calculations, MD/MC simulations, and the main characterization techniques used. In the classification and statistical analysis section, organic compounds or (nano)materials as corrosion inhibitors were classified into six types according to their molecular structural characteristics, molecular size, and compound source, including drug molecules, ionic liquids, surfactants, plant extracts, polymers, and polymeric nanoparticles. We outlined the important conclusions obtained from recent literature and listed the evaluation methods, characterization techniques, and contrastable experimental data of these types of inhibitors when used for carbon steel corrosion in 1.0 M HCl solution. Finally, statistical analysis was only performed based on these data from carbon steel/1.0 M HCl solution system, from which some conclusions can contribute to reducing the workload of the acquisition of useful information and provide some reference directions for the development of new corrosion inhibitors.

Corrosion inhibition potential of chitosan based Schiff bases: Design, performance and applications

Chemically, chitosan is a linear polysaccharide constituted of arbitrarily distributed D-glucosamine and N-acetyl-D-glucosamine constituents combined together via β-1,4-glycosidic linkage. Because of increasing ecological awareness and strict environmental regulations, species of natural and biological origin such as chitosan can be identified as ideal environmental sustainable alternative to replace traditional heterocyclic (toxic) corrosion inhibitors. Although, chitosan contains numerous electron rich sites however chitosan itself is not highly effective aqueous phase corrosion inhibitors. Aqueous phase application of chitosan is limited because of its limited solubility. However, chemically modified chitosan derivatives, such as chitosan based Schiff bases (CSBs) exhibit remarkable solubility in such electrolytes. Therefore, recently various reports dealing with the anticorrosion potential of CSBs have been reported. Present review article describes the collections on CSBs as aqueous phase corrosion inhibitors. Nature of CSBs adsorption through chelation (coordination) has also been discussed based on literature outcomes.

Surface functionalization of chitosan with 5-nitroisatin

Several possible configurations (CS/NI1-10) for the surface adsorption of 5-nitroisatin (NI) on the chitosan polymer (CS) were investigated using quantum mechanical methods in the gas and solution phases. The values of the binding energies indicate the energetic stability of these configurations. The solvation energies demonstrate that the solubility of NI and CS increases in the presence of each other. The role of hydrogen bonds in noncovalent surface functionalization was determined by AIM analysis. The mechanism of covalent surface functionalization and the explicit solvent effects (methanol) in this mechanism were investigated and it was determined that the covalent functionalization through Schiff base formation is possible. These findings, in addition to the biological applications of the chitosan Schiff bases and their complexes, led us to synthesize a new Schiff base from condensation reaction of CS and NI (CSB) together with its Ni(II) and Cu(II) complexes. The synthesized compounds were characterized by the elemental analysis, infrared spectroscopy (IR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Also, optimized geometries, assignment of the IR vibrational bands as well as exploring of the frontier orbitals of the synthesized compounds have been calculated using density functional levels of theory.

A review on applications of chitosan-based Schiff bases

Biopolymers have become very attractive as they are degradable, biocompatible, non-toxic and renewable. Due to the intrinsic reactive amino groups, chitosan is vibrant in the midst of other biopolymers. Using the versatility of these amino groups, various structural modifications have been accomplished on chitosan through certain chemical reactions. Chemical modification of chitosan via imine functionalization (RR'CNR″; R: alkyl/aryl, R': H/alkyl/aryl and R″: chitosan ring) is significant as it recommends the resultant chitosan-based Schiff bases (CSBs) for the important applications in the fields like biology, catalysis, sensors, water treatment, etc. CSBs are usually synthesized by the Schiff condensation reaction between chitosan's amino groups and carbonyl compounds with the removal of water molecules. In this review, we first introduce the available synthetic approaches for the preparation of CSBs. Then, we discuss the biological applications of CSBs including antimicrobial activity, anticancer activity, drug carrier ability, antioxidant activity and tissue engineering capacity. Successively, the applications of CSBs in other fields such as catalysis, adsorption and sensors are demonstrated.

Chitosan oligosaccharide derivatives as green corrosion inhibitors for P110 steel in a carbon-dioxide-saturated chloride solution

Two chitosan oligosaccharide derivatives (PHC and BHC) were synthesized for use as corrosion inhibitors. They were characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The inhibition efficiency of PHC and BHC on P110 steel corrosion in a 3.5 wt.% NaCl CO₂-saturated solution at 80℃ was studied using gravimetric measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical analysis, and quantum chemical calculation. The results indicated that inhibition efficiency increased with increasing concentration of inhibitor. Energy dispersive X-ray (EDX), contact angle, and electrochemical impedance spectroscopy (EIS) measurements showed that the inhibitors had been successfully adsorbed to the surface of the P110 steel. The results of potentiodynamic polarization indicated that both compounds were mixed-type inhibitors.

Microwave-Induced Synthesis of Chitosan Schiff Bases and Their Application as Novel and Green Corrosion Inhibitors: Experimental and Theoretical Approach

Environmentally friendly three chitosan Schiff bases (CSBs) were first time synthesized under microwave irradiation by the reaction of chitosan and aldehydes [benzaldehyde (CSB-1), 4-(dimethylamino)benzaldehyde (CSB-2), and 4-hydroxy-3-methoxybenzaldehyde (CSB-3)] and characterized by IR and NMR spectroscopy. The corrosion inhibition performance of the synthesized inhibitors was studied by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). The results show that all the Schiff bases (CSBs) act as effective corrosion inhibitors for mild steel in 1 M HCl solution. Among the synthesized Schiff bases, CSB-3 exhibited the maximum inhibition efficiency of 90.65% at a very low concentration of 50 ppm. The EIS results showed that the CSBs inhibit corrosion by the adsorption mechanism. The PDP results show that all the three Schiff bases are mixed-type inhibitors. The formation of inhibitor films on the mild steel surface was supported by scanning electron microscopy/energy dispersive X-ray analysis and Fourier-transform infrared spectroscopy methods. The adsorption of CSBs on the mild steel surface obeys the Langmuir adsorption isotherm. The theoretical studies via density functional theory and molecular dynamics simulation corroborated the experimental results.

2-Hydroxy-N'-((Thiophene-2-yl)methylene)benzohydrazide: Ultrasound-Assisted Synthesis and Corrosion Inhibition Study

2-Hydroxy-N'-((thiophene-2-yl)methylene)benzohydrazide (HTMBH) was synthesized by conventional method as well as by ultrasonication (US). The ultrasound-assisted synthesis of HTMBH was found to have good yield and be more eco-friendly compared to the conventional method of synthesis. The synthesized compound HTMBH was characterized by Fourier transform infrared, 1H NMR, and CHN analyses. The corrosion inhibition behavior of HTMBH was investigated using gravimetric and electrochemical methods in 0.5 M H2SO4. The thermodynamic adsorption parameters revealed that HTMBH was adsorbed on the mild steel surface in both ways, physically and chemically, although physisorption is predominant. The study of activation parameters revealed that it is the increase in activation energy that is a prominent factor to lower the corrosion rate in acid medium. Atomic force microscopy analysis is also carried out to investigate the effect of HTMBH on the surface of mild steel surface in acid solution. The contact angle measurement showed decreased affinity of mild steel surface for acid solution containing HTMBH. The results obtained from all of these methods showed good consistency.

Gravimetric, electrochemical and surface studies on the anticorrosive properties of 1-(2-pyridyl)-2-thiourea and 2-(imidazol-2-yl)-pyridine for mild steel in hydrochloric acid

1-(2-Pyridyl)-2-thiourea and 2-(imidazol-2-yl)-pyridine are described here for the first time as inhibitors of mild steel corrosion in acidic medium.