Molecular-level investigation of the adsorption mechanisms of thiazolidinediones on Cu2O(111) surface: a first-principles DFT study

Hassane Lgaz; Han-Seung Lee

doi:10.1515/corrrev-2023-0003

Abstract

We have employed first principles DFT calculation with van der Waals (vdW) corrections to investigate the adsorption mechanism of thiazolidine-2,4-dione (TZD) substituted by 4-methylbenzylidene (MTZD) at 5-position and by an additional allyl group (ATZD) at 3-position on copper oxide surface (Cu₂O(111)). Parallel configurations were found the most energetically stable geometries. The adsorption binding energy magnitudes predicted that ATZD outperformed MTZD by −0.11 eV. Our calculations indicated that O and S atoms of thiazolidine-2,4-dione nucleus significantly enhanced the chemical bonding of ATZD and MTZD with Cu₂O(111) surface. Hydrogen bond interactions between Lewis base site at unsaturated O atom above the copper surface and TZD molecules are contributing to the stability of TZD molecules on Cu₂O(111) surface. The adsorption induced-work function of different TZD adsorption configurations decreased from 4.563 eV (Cu₂O(111)) to 4.114–4.373 eV due to electron transport between TZD molecules and Cu₂O(111). The analysis of electronic properties of TZDs adsorption geometries revealed strong charge transfer and redistribution at the interface of TZDs-Cu₂O(111), strengthening the stability of molecules on copper oxide surface. These theoretical insights would pave the way for further in-depth investigations into TZD-Copper interactions and provide valuable information for an optimized design of copper corrosion inhibitors.

Keywords: cuprous oxide; inhibitors; thiazolidine-2,4-dione; density functional theory; interfaces

1 Introduction

Thiazole and its derivatives are widely recognized to be of great value in diverse fields, with boundaryless biological activities (Ali and Sayed 2021). When its non-aromatic analogue thiazolidine is substituted at the 2- and 4-positions, the heterocyclic ring system becomes thiazolidine-2,4-dione (TZD) (Figure 1). TZD and its derivatives (also known as glitazones) have emerged as versatile heterocycles due to their multifaceted pharmacological activities (Jain et al. 2013; Naim et al. 2017). TZDs can be easily substituted with a variety of functional groups at 3 and 5 positions, opening access to various multifunctionalized heterocyclic systems, some of which have reached anticancer clinical studies (Jain et al. 2013). In addition to their proven utility in medicinal chemistry, thiazolidines are known as efficient corrosion inhibitors, considerably slowing down the corrosion rate of metals and alloys (Alink and Outlaw 2001). It is well-proven that azole compounds are effective corrosion inhibitors, particularly for mitigating corrosion of copper and its alloys (Alamiparvin et al. 2017; Fateh et al. 2020). Yet, there are still far too few studies focusing on the corrosion inhibition characteristics of TZDs for different metals and alloys. A survey of literature shows that there have been limited studies on corrosion mitigation performances of thiazolidinediones for steels and copper (Chafiq et al. 2022; Öztürk et al. 2013; Yadav et al. 2015).

Figure 1:

Molecular structure with atomic numbering of (a) thiazole, (b) thiazolidine and (c) thiazolidine-2,4-dione.

Several factors can affect the corrosion inhibition performance of organic compounds; however, there is a general belief among chemists that an organic compound must adsorb on the metallic substrate to act as a corrosion inhibitor (Bockris et al. 1998; Ebenso et al. 2021; Ofoegbu et al. 2017; Saha et al. 2016, 2015; Sukul et al. 2018). Accordingly, there have been numerous computational works addressing the adsorption of organic compounds on different metal surfaces employing density-functional theory (DFT) (Chen et al. 2022; Gao et al. 2022; Gustinčič and Kokalj 2018; Kokalj and Peljhan 2015; Kumar et al. 2020b, 2022; Lgaz and Lee 2022; Obot et al. 2019; Shariatinia and Ahmadi-Ashtiani 2019; Xiong et al. 2019). First-principle-based computational studies are well suited to study in detail the adsorption characteristics of molecules on metal surfaces. In his recent work, Anton Kokalj has demonstrated that first-principle computational modeling studies can be successfully used to understand the corrosion inhibition mechanism of molecules on metal surfaces; highlighting that, compared to some experimental parameters such as the standard free energy of adsorption and the adsorption enthalpy, “much more reliable criteria (…) are readily available in computational studies, such as the molecule–surface bond lengths and the electronic structure analysis of the molecule–surface bonding” (Kokalj 2022).

In our recent work, two thiazolidinedione derivatives substituted at 5-position by (4-fluorobenzylidene) (FTZD) and 4-hydroxy-3-methoxybenzylidene (HMTZD) have been reported as steel corrosion inhibitors in acidic medium (Chafiq et al. 2022). Their ability to inhibit the steel corrosion in acidic medium has been investigated through chemical and electrochemical techniques. We found that upon addition of increasing amount of TZDs to the HCl solution, the capacitive double layer of steel electrode significantly decreased due to a change in the double layer thickness because of inhibitor molecules adsorption on the steel surface. Furthermore, the adsorption characteristics of selected molecules on Fe(110) iron surface have been investigated using first principles DFT computations. In both adsorption systems, i.e., HMTZD@Fe(110) and FTZD@Fe(110), TZD molecules formed two covalent bonds with iron atoms via oxygen and sulfur atoms of the thiazolidine-2,4-dione nucleus; their distances were found within the sum of the covalent radii of iron and O/S atoms. Also, the analysis of the projected density of states of isolated and adsorbed molecules confirmed the strong charge transfer between inhibitor molecules and iron surface. More recently, additional efforts have been made, in our laboratory, to develop novel TZD molecules by introducing 4-methylbenzylidene (MTZD) at 5-position and an additional allyl group (ATZD) at 3-position of the thiazolidinedione nucleus (Figure 2). Their anticorrosion properties have been explored for copper in 3.5 wt % NaCl medium (Lgaz et al. 2021). Electrochemical impedance spectroscopy results showed that ATZD outperformed MTZD by 6 % inhibition efficiency, achieving 96 % and 90 %, respectively. The addition of 300 ppm of ATZD and MTZD to 3.5 wt % NaCl medium decreased the effective double layer capacitance from 33.8 μF cm⁻² in blank to 1.9 and 6.7 μF cm⁻², respectively. It is well-reported that the modification of the double-layer behavior by increasing the thickness of the barrier film formed on the steel surface is a result of inhibitor molecules’ adsorption (Hirschorn et al. 2010). It confirms what we have mentioned before that these organic compounds act by adsorption on the metal surface.

Figure 2:

The copper oxide surface and molecular structures of compounds under study. (a) Top and side views of the copper oxide surface, Cu₂O(111), and (b) molecular structure and names of thiazolidine-2,4-dione derivatives.

Taking advantage of first-principle-based computational methods and lack of any studies investigating the adsorption behaviors of TZD-based inhibitors on copper surfaces (to the best of authors’ knowledge), we report herein the computational characterization of the adsorption of ATZD and MTZD compounds on cuprous oxide surface Cu₂O(111). Under 3.5 wt % NaCl medium, the copper surface is often oxidized due to the formation of thin Cu₂O oxide film while it is oxide-free under acidic mediums (Gustinčič and Kokalj 2015). This is the reason why the Cu₂O(111) surface was selected in the current study. It should be noted that for purely technical modeling reasons, results represented and discussed herein are for neutral inhibitor molecules and solid/vacuum interface.^[1] In the present work, TZDs–Cu₂O(111) interactions was characterized by first-principles DFT simulations; then energetics and electronic structure analysis of investigated adsorption systems were discussed.

As we delve into the atomic-scale investigation of thiazolidine-2,4-dione (TZD) derivatives as corrosion inhibitors for copper, it is essential to underscore that this computational study, based on density functional theory, seeks to supplement and enhance our understanding of experimental observations. Particularly, comprehending fundamental processes such as bond formation, charge transfer, and associated changes in work function, which serve as potential indicators of an inhibitor’s adsorption on the copper oxide surface, can allow for a more thorough interpretation of experimental results, and provide guidance for future investigations. Through the integration of computational and experimental insights, a comprehensive picture of the corrosion inhibition mechanism of TZD derivatives on copper surfaces can be created.

2 Technical details

2.1 Computational details

All calculations were carried out within the framework of DFT using the Cambridge sequential total energy program (CASTEP) (Clark et al. 2005). The exchange-correlation energy was described within the generalized gradient approximation (GGA) parameterized by Perdew–Burke–Ernzerh (PBE) (Perdew et al. 1996). The empirical Grimme’s DFT-D2 correction was used to accurately describe the effect of van der Waals (vdW) interactions (Grimme 2006; Ramalho et al. 2013). The core electrons were replaced with Vanderbilt type ultrasoft pseudopotentials. An energy cutoff of 30 Ry was used for the plane wave base set to expand the electronic wave function. Monkhorst–Pack Brillouin zone k-point grids of (8 × 8 × 8) and (2 × 2 × 1) were used for the optimization calculation of the bulk lattice parameters and adsorption models, respectively. All systems were geometrically optimized using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm until the displacement, force, and total energy converged to less than 1.0 × 10⁻³ Å, 0.03 eV/Å and 1.0 × 10⁻⁵ eV/atom, respectively. Convergence tests have been rigorously carried out to validate the computational parameters employed. Specifically, the energy cutoff and k-point grid sizes were systematically analyzed to achieve a balance between computational efficiency and numerical accuracy. Detailed results of these convergence tests can be found in the Supplementary Material. The initial lattice parameter of Cu₂O (cuprite structure, Pn3m space group) was 4.27 Å while the optimized one is 4.34 Å, confirming that selected methods and models were reasonable.

The surface Cu₂O(111) was built by constructing a periodic multi-slab model with a (4 × 4) supercell and a vacuum spacing of 20 Å along the z direction to account for spurious interactions between slabs. TZD molecules were placed on the top side of the slab. The two bottom-most atomic layers were fixed to bulk positions whereas all other degrees of freedom were allowed to relax. For our (4 × 4) supercell representing 16 surface sites, a single adsorbate equates to a surface coverage of 0.0625 monolayers (ML). A cubic box of 30 Å in size was created for DFT calculations of standalone molecules.

Figure 2 shows the Cu₂O(111) surface used in this work where each Cu atom is linearly coordinated with two O ions, and latter is tetrahedrally coordinated with four Cu ions. The open source BURAI 1.3 software was used to produce the molecular graphics. Partial density of states plots were plotted using Origin 2016 while Inkscape software was used for post-processing of all figures.

2.2 Energy and electronic properties

The total energies of isolated TZD molecules (noted E_mol), Cu₂O(111) copper surface (noted E_surf), and TZD/Cu₂O(111) adsorption systems (noted E_mol/surf) were used to determine the adsorption binding energy as:

(1)Eads=Emol/surf− (Emol+Esurf)

The charge density difference was determined to intuitively reflect and visualize the charge transfer after contact. It is calculated as follows:

(2)Δρ(r)=ρmol/Cu2O(111)(r)−ρCu2O(111)(r)−ρmol(r)

where Δρ, ρmol/Cu2O(111), ρCu2O(111), and ρ_mol refer to the charge density difference, the charge density of TZD/Cu₂O(111) adsorption system, charge density of isolated Cu₂O(111) copper surface, and charge density of isolated TZD molecule, respectively.

The adsorption-induced work function can be expressed by the standard equation:

(3)φ=Evac−Ef

where E_vac and E_f represent the electrostatic potential in the vacuum and the fermi energy of the slab.

Another parameter relevant to the adsorption of inhibitor molecules on metallic surface is the electron localization function (ELF), η(r) proposed by Becke and Edgecombe as follow (Becke and Edgecombe 1990):

(4)ELF=11+(D(r)/Dh(r))2

The term D(r)/D_h(r) normalizes the same spin probability by the uniform density electron gas so that ELF is dimensionless.

Adsorption-induced work function of different adsorption systems and electron localization function (ELF) were calculated through post-processing calculations using CASTEP with same computational details mentioned above.

3 Results and discussion

3.1 Geometries and energies of TZDs on Cu₂O(111) surface

To find out the preferential adsorption geometries of TZD molecules on the Cu₂O surface, several configurations were considered for DFT studies. Five configurations, namely ATZD¹, ATZD², MTZD¹, MTZD², and MTZD³ were energetically stable, and their stable geometries are represented in Figure 3a–e, respectively. Adsorption binding energy values of different adsorption geometries are listed in Table 1. As can be seen from Figure 3a, the ATZD molecule adsorbs on the Cu₂O(111) surface in two stable geometries, i.e., ATZD¹, ATZD² while the MTZD has three stable different geometries, i.e., MTZD¹, MTZD², and MTZD³. Inspecting the preferential adsorption geometry is very crucial in understanding the adsorption characteristics of corrosion inhibitors on metal surfaces. The TZD molecules have several potential adsorption sites such as sulfur, oxygen, and nitrogen atoms in addition to π-electrons of aromatic rings. On the other side, the Cu₂O surface has Lewis acid–base site pairs that would facilitate its interaction with TZD molecules (Jiang et al. 2004). Lone pair electrons on TZDs’ heteroatoms could form chemical bonds with surface copper cations, which can be further stabilized through hydrogen bond interactions between molecules’ protons and copper surface oxygen anions. An additional mode of interaction that would contribute to the stability of the inhibitors’ adsorption is the π back-donation from filled Cu(I) d-orbital to π* orbitals of TZD molecules.

Figure 3:

Optimized adsorption geometries of ATZD and MTZD on Cu₂O(111) surface. Grey, white, blue, red, and yellow spheres represent C, H, N, O and S atoms, respectively. All bond distances are in Å. (a–e) Represent ATZD¹, ATZD², and MTZD¹, MTZD², MTZD³ configurations, respectively.

Table 1:

Computed adsorption binding energies and adsorption-induced work function of different configurations of ATZD and MTZD molecules on Cu₂O(111).

Adsorption system	Binding energy (eV)	Work function (eV)
ATZD¹	−2.48	4.114
ATZD²	−1.61	4.373
MTZD¹	−2.37	4.341
MTZD²	−1.37	4.373
MTZD³	−1.35	4.364
Cu₂O(111)	–	4.563

Looking at stable adsorption geometries in Figure 3, one can notice that ATZD molecules tend to adsorb parallelly on the Cu₂O surface. In the initial parallel disposition (ATZD¹, Figure 3a) as well as perpendicular initial configuration (ATZD², Figure 3b), ATZD molecule exhibits a parallel configuration on the copper oxide surface and forms several bonds with copper atoms. In Figure 3a, copper atoms form bonds with carbon and oxygen atoms of ATZD molecule having a binding energy of −2.48 eV. The bond lengths are 2.059–2.123 Å and 1.961 Å for C–Cu and O–Cu, respectively. In the ATZD² configuration, ATZD molecule moved from initial perpendicular configuration to a nearly parallel disposition on copper oxide surface with formation of one bond between sulfur atom and surface copper atom exhibiting 2.199 Å bond length and a binding energy of −1.61 eV. The sums of covalent radii are 1.98 Å for O and Cu atoms, 2.37 Å for sulfur and copper atoms, and 2.1 Å for carbon and sulfur atoms (Cordero et al. 2008). With reference to these covalent radii values, distances of formed bonds between ATZD molecule and copper oxide surface are all within the sum of covalent radii values.

In the case of MTZD molecule, its initial parallel geometry (MTZD¹, Figure 3c) maintains the same disposition with formation of several bonds with copper surface atoms through carbon, oxygen, and sulfur atoms, having a binding energy of −2.37 eV. The bond distances are 2.12 Å for C–Cu, 2.229 Å for S–Cu, and 1.927 Å for O–Cu. The adsorption configuration MTZD² in Figure 3d was initially perpendicular to copper oxide surface then becomes tilted after optimization and stabilized by forming one bond between an oxygen atom of the thiazolidine-2,4-dione moiety and copper surface atom that has a bond distance of 1.876 Å. Its binding energy is −1.37 eV. The third adsorption configuration of MTZD molecule on copper oxide surface, i.e., MTZD³ was initially created that the thiazolidine-2,4-dione group lay vertically near the surface. Its DFT optimized adsorption geometry also stabilized by forming a bond between one of thiazolidine-2,4-dione’s oxygen atom and copper surface atom, having a similar length of 1.874 Å and a binding energy of −1.35 eV. Similar to ATZD molecule, all bonds formed between MTZD molecule and copper surface atoms are within the sums of covalent radii of each pair of atoms. For all configurations of both molecules, bond distances are reasonably within the sums of covalent radii of each pair of atoms and less than the sum of their electrostatic radii (Cordero et al. 2008). Therefore, we can infer that those bonds are covalent in nature. Additionally, all selected adsorption geometries exhibit a negative binding energy value, which suggests that they are energetically stable, and that more than one configuration of same molecule may coexist in real experiments.

Covalent bonds formation between organic corrosion inhibitors and Lewis acid site at unsaturated Cu atoms is highly favorized when involved molecules contain heteroatoms with lone pair of electrons as the case of present thiazolidine-2,4-dione derivatives. The presence of a Lewis base site at unsaturated O atom above the copper surface is an additional factor that would contribute to the stability of TZD molecules on Cu₂O(111) surface through hydrogen bond interactions (Jiang et al. 2004). In the following sections, the electronic properties of stable adsorption geometries will be investigated in detail.

3.2 Charge density difference

The differential charge density plots are a useful tool to investigate the electronic nature of the interaction between TZD molecules and copper oxide surface. Through electron density difference (EDD) plots, the charge rearrangement in the molecule-surface direction can be visualized and analyzed (Guo et al. 2017a,b; Kumar et al. 2020b). The EDD plots are determined for the five most energetically stable adsorption geometries of TZD molecules on Cu₂O(111) surface as displayed in Figure 4.

Figure 4:

Charge density difference plots of most energetically favored adsorption geometries of (a)–(e) ATZD¹, ATZD², and MTZD¹, MTZD², MTZD³, respectively. Grey, white, blue, red, and yellow spheres represent C, H, N, O and S atoms, respectively (iso-surface value: ±0.035 e/Å³).

In these plots, light purple globules represent electron-depletion while dark navy-blue globules represent electron-accumulation. For all adsorption geometries, we can notice a strong electron density buildup in the bonding region between TZDs’ atoms and copper surface atoms. After adsorption, TZDs’ molecules transfer their electrons present on their heteroatoms and π-electrons of aromatic rings to the vacant d-orbitals of copper, creating a charge redistribution. This charge redistribution can also be a result of electron retro-donation from filled Cu atoms to π*-electrons of inhibitor molecules, especially where carbon atoms are participating in bonding. For instance, for ATZD molecule, the strong charge accumulation is attributed to C–Cu and O–Cu covalent bonds (Figure 4a), and to the S–Cu bond (Figure 4b). Moreover, although sulfur atoms have a high affinity to metal surfaces, no bonding is formed between sulfur and copper surface in the parallel configuration of ATZD (ATZD¹). In contrast, a remarkable charge accumulation and depletion appears in ATZD² between the sulfur atom and copper surface atoms, confirming a strong interaction when the ATZD molecule adsorbs vertically on the Cu₂O(111) surface. Interestingly, for MTZD³ configuration, although charge accumulation and depletion are evident on the N–Cu direction, the charge redistribution is too little to form a covalent bond. Hence, in this case, the interaction is mainly attributed to the van der Waals and electrostatic interactions along with N–H–Cu hydrogen bonds (Kumar et al. 2022).

3.3 Electron localization function

A more detailed picture of the electronic structure of stable adsorption geometries of TZD molecules can be obtained by analyzing their electron localization function (ELF) (Jiang et al. 2004). The ELF and its topological analysis developed by Silvi and Savin allow to determine areas of chemical interest based on the probability of finding paired electrons with the same spin, thus investigating the bonding situation and its evolution (Fuentealba et al. 2007). The topological analysis of this theoretical tool allows the partition of a molecular space into core and valence attractor basins, where maximum chances of finding electronic pair lies (Li et al. 2021). This could yield a chemical interpretation routed in nonbonding, bonding and core electron pairs concepts, hence serving as an interesting tool to study covalently bonded systems. The ELF range is restricted to [0, 1]; high ELF values indicate a high electron localization, while an ELF value of 0.5 corresponds to perfect delocalization and a uniform electron gas behavior. Areas between high concentrations of electron density are indicated by ELF values lower than 0.5 (Fuentealba et al. 2007; Li et al. 2021).

Figure 5 shows the ELF maps in three-dimensional real space for the five most stable adsorption geometries of TZD molecules on Cu₂O(111) surface. It can be seen that a red area (highly localized) is shown below all molecules’ atoms, especially S and O atoms bonded to the copper surface atoms surrounded by lower concentration regions (blue). It indicates the formation of strong covalent bonds (Breedon et al. 2013). The areas where significant electron localization occurs with non-covalent interactions (red-yellow) are indicative of a strong physisorption, while less localized and spread out areas (yellow-green) are possibly pointing to a weaker bond (Chen et al. 2018; Yan et al. 2020). We note that green areas characterize a very low ELF values and are attributed to copper metallic bonds. The ELF plots confirm the strong chemisorption of TZD molecules on the copper oxide surface through lone pair electrons on S and O atoms and π-electrons of aromatic rings. Not only that, it supports the concept that hydrogen bonds are formed with the Lewis base site at unsaturated O atoms of Cu₂O(111) surface.

Figure 5:

Electron localization function (ELF) distribution maps of (a)–(e) ATZD¹, ATZD², and MTZD¹, MTZD², MTZD³, respectively.

3.4 Adsorption induced-work function

The work function is another important theoretical parameter to characterize the electron transport at metal/inhibitor interface (Dlouhy and Kokalj 2022). The physical meaning of WF is simply defined as the minimum necessary energy to carry an electron to infinity away from the system (Somaiya et al. 2020). The favorable molecular adsorption on a metal surface is expected to decrease its WF value because of strong electron transport (Kumar et al. 2020b). As shown in Table 1, the DFT calculated work function of the Cu₂O(111) surface is 4.563 eV, which is consistent with previous reports (Ma et al. 2020). It can be seen from WF data in Table 1 that the adsorption induced work function of all stable adsorption geometries significantly decreased compared with that of Cu₂O(111) surface. It reaches 4.114 and 4.373 eV for ATZD¹ and ATZD², respectively. For the MTZD configurations, the WF values are 4.341, 4.373, and 4.364 eV for MTZD¹, MTZD², and MTZD³, respectively. The decreased values of adsorption-induced WF is mainly a result of electron transport between TZD molecules and copper oxide surface, however, the chemical adsorption in the present case can be more reasonably attributed to the charge transfer from a more electronegative TZD molecules to the copper oxide substrate, but not necessarily to the change in the adsorption induced work function. The interactions between TZD molecules and Cu₂O(111) surface would lead to a strong charge redistribution, which would greatly influence the work function.

3.5 Projected density of states

While the charge density difference and electron localization function analyses have given us valuable insights into the bonding between thiazolidine-2,4-dione molecules and the Cu₂O (111) surface, the projected electronic density of states (PDOS) offers more explicit evidence of the bonding mechanism, especially for chemical adsorption. PDOS can provide insights into the individual contribution of atomic orbitals from both the inhibitors and the substrate to the molecular energy states (Chafiq et al. 2022; Thomas et al. 2014; Zhang et al. 2021).

The PDOS plots of isolated inhibitor molecules, i.e., ATZD and MTZD (6 Å above Cu₂O(111) surface) are represented in Figures 6a and 7a, respectively. The PDOS plots of interacting TZDs atoms and Cu/O atoms of Cu₂O(111) surface are shown in Figure 7b–c and b–d for ATZD and MTZD, respectively. Although, based on several previous reports, the Cu-3d valence states lie in the −5/−1 range, a broader energy range between −10 and 5 is considered for maximum coverage of interacting atoms’ states (Kumar et al. 2020a).

Figure 6:

PDOS of ATZD before and after the adsorption on Cu₂O(111) surface. (a) Before adsorption (6 Å above the upper surface layer), (b) and (c) ATZD¹, ATZD² configurations, respectively.

Figure 7:

PDOS of MTZD before and after the adsorption on Cu₂O(111) surface. (a) Before adsorption (6 Å above the upper surface layer), (b)–(d) MTZD¹, MTZD², MTZD³ configurations, respectively.

In Figures 6a and 7a, the PDOS plots of isolated ATZD and MTZD molecules, respectively, show that their molecular states, including those within the energy range of the Cu-3d-band, are distinct and intense. Upon adsorption (Figure 7b–c and b–d for ATZD and MTZD, respectively), the peaks corresponding to the p orbitals of the interacting atoms from the TZDs broaden significantly where they overlap with the Cu-3d band. This broadening indicates strong hybridization between the Cu-3d and p orbitals of the interacting atoms from the TZDs. This hybridization not only reflects the formation of covalent bonds between the adsorbate and the substrate but also accounts for charge transfer and redistribution at the interface (Kumar et al. 2020a). As the orbitals overlap, electrons from the TZD molecules can easily move into the Cu-3d orbitals, leading to charge transfer from the molecule to the surface. The chemical bonding, as revealed by PDOS, strengthens the inhibition action of the TZDs, which, alongside the physical interactions, contributes to their effective corrosion inhibition performance.

3.6 Corrosion inhibition mechanism and implications

The correlation between the computational findings and the experimental knowledge is crucial for further explorations of thiazolidine-2,4-dione derivatives (TZDs) as corrosion inhibitors for copper. Firstly, the energetically stable configurations of the TZD molecules on the copper oxide surface as deduced from the density functional theory (DFT) calculations suggest a robust adsorption process, which is a key factor in an efficient corrosion inhibition mechanism. The formation of covalent bonds, as confirmed by the electron density difference, electron localization function, and projected density of states, suggest that investigated molecules can serve as effective barrier that prevents corrosive species from reaching the copper surface. The substantial effect of charge transfer and redistribution along the TZDs–Cu₂O(111) interface and the observed decrease in the copper oxide surface’s work function upon TZDs adsorption suggest enhanced ease of electron transport, potentially contributing to a protective film formation on the copper surface, thereby preventing anodic dissolution, a primary step in metal corrosion.

Experimental studies have indicated higher inhibition efficiency of ATZD over MTZD, which aligns with the computational findings showing stronger adsorption energies for ATZD. This highlights the importance of structural modifications in TZD derivatives for improving their efficiency as copper corrosion inhibitors. Moreover, beyond chemical adsorption, this work highlights physical interactions’ significance in corrosion inhibition. While covalent bonding is fundamental, hydrogen bonds and physical interactions contribute significantly to the stability of adsorbed TZD molecules on the copper oxide surface, thereby enhancing the protective layer’s effectiveness. This aspect can be helpful for designing more effective corrosion inhibitors, emphasizing not only the formation of strong inhibitor-metal chemical bonds but also optimizing inhibitor’s molecular structures for physical interactions.

These computational results provide significant insights into the potential of TZDs as copper corrosion inhibitors. These findings can guide future experimental investigations and contribute to the development of efficient corrosion preventive compounds. Future studies could extend this investigation to include the solvent effects, which would bring the analysis closer to real-world corrosion scenarios.

4 Summary and conclusions

In this work, the experimentally observed adsorption of two thiazolidine-2,4-dione derivatives substituted by 4-methylbenzylidene (MTZD) at 5-position and by an additional allyl group (ATZD) at 3-position on copper oxide surface (Cu₂O(111)) was investigated using first-principles calculations based on the density functional theory with Grimme’s DFT-D2 corrections. Results showed that MTZD and ATZD can adopt two and three energetically stable configurations when reaching the copper oxide surface, respectively. The magnitude of binding energy trend confirmed the outperformance of the ATZD molecule, consistent with experimental inhibition efficiency. The optimized adsorption geometries revealed the formation of several covalent bonds between parallelly adsorbed ATZD and MTZD molecules and copper oxide surface. In contrast, adsorption geometries with initial perpendicular configuration were stabilized by S–Cu and O–Cu bonds for ATZD and MTZD, respectively. Electronic properties analysis by electron density difference, electron localization function and projected density of states confirmed the formation of covalent bonds resulted from strong charge transfer and redistribution at the TZDs–Cu₂O(111) interface. Furthermore, electron density difference and electron localization maps suggest that hydrogen bonds and physical interactions had significant contribution to the stability of adsorbed TZD molecules on the copper oxide surface. On the other side, this study has taken a step forward in connecting surface science investigations performed under ultra-high vacuum conditions to practical corrosion scenarios. Our computational findings enrich our understanding of the underlying processes in corrosion inhibition by TZD derivatives on copper surfaces, providing guidance for future experimental and computational research, aiming to stimulate further research in this field, and contribute to more efficient strategies for corrosion inhibition in real-world applications. While the present work is conducted using Cu₂O layer, it would be interesting to extend the investigation by investigating the adsorption characteristics on a surface model closer to experimental state of copper such as the epitaxial Cu(111)‖Cu₂O model, which, along with solvent effect, will be the subject of future works.

Corresponding author: Han-Seung Lee, Department of Architectural Engineering, Hanyang University, 1271 Sa 3-dong, Sangrok-gu, Ansan-si, 15588, Republic of Korea, E-mail: ercleehs@hanyang.ac.kr

Funding source: National Research Foundation of Korea

Award Identifier / Grant number: NRF-2018R1A5A1025137

Research ethics: The local Institutional Review Board deemed the study exempt from review.
Author contributions: HL: conceptualization, methodology, software, formal analysis, investigation, data curation, writing-original draft, writing-review & editing. H-SL: project administration, supervision, conceptualization, funding acquisition, software, validation, writing – review & editing.
Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Research funding: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2018R1A5A1025137).
Data availability: Raw data used for this work is part of ongoing works and cannot be shared at this time.

References

Alamiparvin, L., Kalhor, E.G., Nabavi, S.R., Ebrahimi, S., and Farzamnia, A. (2017). Studies on corrosion inhibitor activity of azoles for copper. Adv. Sci. Lett. 23: 11293–11297, https://doi.org/10.1166/asl.2017.10269.Search in Google Scholar

Ali, S.H. and Sayed, A.R. (2021). Review of the synthesis and biological activity of thiazoles. Synth. Commun. 51: 670–700, https://doi.org/10.1080/00397911.2020.1854787.Search in Google Scholar

Alink, B.A.M.O. and Outlaw, B.T. (2001). Thiazolidines and use thereof for corrosion inhibition, WO2001040205A1.Search in Google Scholar

Becke, A.D. and Edgecombe, K.E. (1990). A simple measure of electron localization in atomic and molecular systems. J. Chem. Phys. 92: 5397–5403, https://doi.org/10.1063/1.458517.Search in Google Scholar

Bockris, J.O., Reddy, A.K.N., and Gamboa-Aldeco, M.E. (1998). Modern electrochemistry 2B: electrodics in chemistry, engineering, biology and environmental science. Springer Science & Business Media, New York, NY.Search in Google Scholar

Breedon, M., Spencer, M.J.S., and Miura, N. (2013). Adsorption of NO2 on YSZ(111) and oxygen-enriched YSZ(111) surfaces. J. Phys. Chem. C 117: 12472–12482, https://doi.org/10.1021/jp310016r.Search in Google Scholar

Chafiq, M., Thari, F.Z., Lee, H., Chaouiki, A., Salghi, R., Ko, Y.G., Karrouchi, K., Bougrin, K., Ali, I.H., and Lgaz, H. (2022). Experimental and first-principles DFT insights into the corrosion protection mechanism of carbon steel in an HCl medium by two thiazolidinedione compounds. Mater. Today Commun. 32: 103841, https://doi.org/10.1016/j.mtcomm.2022.103841.Search in Google Scholar

Chen, D., Zhang, X., Tang, J., Fang, J., Li, Y., and Liu, H. (2018). Adsorption and dissociation mechanism of SO2 and H2S on Pt decorated graphene: a DFT-D3 study. Appl. Phys. A 124: 404, https://doi.org/10.1007/s00339-018-1827-7.Search in Google Scholar

Chen, M.-F., Chen, Y., Jia Lim, Z., and Wah Wong, M. (2022). Adsorption of imidazolium-based ionic liquids on the Fe(100) surface for corrosion inhibition: physisorption or chemisorption? J. Mol. Liq. 367: 120489, https://doi.org/10.1016/j.molliq.2022.120489.Search in Google Scholar

Clark, S.J., Segall, M.D., Pickard, C.J., Hasnip, P.J., Probert, M.I., Refson, K., and Payne, M.C. (2005). First principles methods using CASTEP. Z. Kristallogr. – Cryst. Mater. 220: 567–570, https://doi.org/10.1524/zkri.220.5.567.65075.Search in Google Scholar

Cordero, B., Gómez, V., Platero-Prats, A.E., Revés, M., Echeverría, J., Cremades, E., Barragán, F., and Alvarez, S. (2008). Covalent radii revisited. Dalton Trans. 21: 2832–2838, https://doi.org/10.1039/B801115J.Search in Google Scholar PubMed

Dlouhy, M. and Kokalj, A. (2022). How adsorbed H, O, OH, and Cl affect plain adsorption of imidazole on copper. Corros. Sci. 205: 110443, https://doi.org/10.1016/j.corsci.2022.110443.Search in Google Scholar

Ebenso, E.E., Verma, C., Olasunkanmi, L.O., Akpan, E.D., Verma, D.K., Lgaz, H., Guo, L., Kaya, S., and Quraishi, M.A. (2021). Molecular modelling of compounds used for corrosion inhibition studies: a review. Phys. Chem. Chem. Phys. 23: 19987–20027, https://doi.org/10.1039/D1CP00244A.Search in Google Scholar

Fateh, A., Aliofkhazraei, M., and Rezvanian, A.R. (2020). Review of corrosive environments for copper and its corrosion inhibitors. Arab. J. Chem. 13: 481–544, https://doi.org/10.1016/j.arabjc.2017.05.021.Search in Google Scholar

Fuentealba, P., Chamorro, E., and Santos, J.C. (2007). Chapter 5: Understanding and using the electron localization function. In: Toro-Labbé, A. (Ed.). Theoretical and computational chemistry. Theoretical aspects of chemical reactivity. Elsevier, Amsterdam, pp. 57–85.10.1016/S1380-7323(07)80006-9Search in Google Scholar

Gao, X., Ma, D., Huang, Q., Ren, T., Li, G., and Guo, L. (2022). Pyrazole ionic liquid corrosion inhibitor for magnesium alloy: synthesis, performances and theoretical explore. J. Mol. Liq. 353: 118769, https://doi.org/10.1016/j.molliq.2022.118769.Search in Google Scholar

Grimme, S. (2006). Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27: 1787–1799, https://doi.org/10.1002/jcc.20495.Search in Google Scholar PubMed

Guo, L., Obot, I.B., Zheng, X., Shen, X., Qiang, Y., Kaya, S., and Kaya, C. (2017a). Theoretical insight into an empirical rule about organic corrosion inhibitors containing nitrogen, oxygen, and sulfur atoms. Appl. Surf. Sci. 406: 301–306, https://doi.org/10.1016/j.apsusc.2017.02.134.Search in Google Scholar

Guo, L., Qi, C., Zheng, X., Zhang, R., Shen, X., and Kaya, S. (2017b). Toward understanding the adsorption mechanism of large size organic corrosion inhibitors on an Fe(110) surface using the DFTB method. RSC Adv. 7: 29042–29050, https://doi.org/10.1039/C7RA04120A.Search in Google Scholar

Gustinčič, D. and Kokalj, A. (2015). A DFT study of adsorption of imidazole, triazole, and tetrazole on oxidized copper surfaces: Cu2O(111) and Cu2O(111)-w/o-Cu CUS. Phys. Chem. Chem. Phys. 17: 28602–28615, https://doi.org/10.1039/c5cp03647j.Search in Google Scholar PubMed

Gustinčič, D. and Kokalj, A. (2018). DFT study of azole corrosion inhibitors on Cu2O model of oxidized copper surfaces. I. Molecule–surface and Cl–surface bonding. Metals 8: 310, https://doi.org/10.3390/met8050310.Search in Google Scholar

Hirschorn, B., Orazem, M.E., Tribollet, B., Vivier, V., Frateur, I., and Musiani, M. (2010). Determination of effective capacitance and film thickness from constant-phase-element parameters. Electrochim. Acta 55: 6218–6227, https://doi.org/10.1016/j.electacta.2009.10.065.Search in Google Scholar

Jain, V.S., Vora, D.K., and Ramaa, C.S. (2013). Thiazolidine-2,4-diones: progress towards multifarious applications. Bioorg. Med. Chem. 21: 1599–1620, https://doi.org/10.1016/j.bmc.2013.01.029.Search in Google Scholar PubMed

Jiang, Y., Adams, J.B., and Sun, D. (2004). Benzotriazole adsorption on Cu2O(111) surfaces: a first-principles study. J. Phys. Chem. B 108: 12851–12857, https://doi.org/10.1021/jp049457b.Search in Google Scholar

Kokalj, A. (2022). Corrosion inhibitors: physisorbed or chemisorbed? Corros. Sci. 196: 109939, https://doi.org/10.1016/j.corsci.2021.109939.Search in Google Scholar

Kokalj, A. and Peljhan, S. (2015). Density functional theory study of adsorption of benzotriazole on Cu2O surfaces. J. Phys. Chem. C 119: 11625–11635, https://doi.org/10.1021/acs.jpcc.5b01677.Search in Google Scholar

Kumar, D., Jain, N., Jain, V., and Rai, B. (2020a). Amino acids as copper corrosion inhibitors: a density functional theory approach. Appl. Surf. Sci. 514: 145905, https://doi.org/10.1016/j.apsusc.2020.145905.Search in Google Scholar

Kumar, D., Jain, V., and Rai, B. (2020b). Imidazole derivatives as corrosion inhibitors for copper: a DFT and reactive force field study. Corros. Sci. 171: 108724, https://doi.org/10.1016/j.corsci.2020.108724.Search in Google Scholar

Kumar, D., Jain, V., and Rai, B. (2022). Capturing the synergistic effects between corrosion inhibitor molecules using density functional theory and ReaxFF simulations - a case for benzyl azide and butyn-1-ol on Cu surface. Corros. Sci. 195: 109960, https://doi.org/10.1016/j.corsci.2021.109960.Search in Google Scholar

Lgaz, H. and Lee, H. (2022). First‐principles based theoretical investigation of the adsorption of alkanethiols on the iron surface: a DFT-D3 study. J. Mol. Liq. 348: 118071, https://doi.org/10.1016/j.molliq.2021.118071.Search in Google Scholar

Lgaz, H., Saha, S.K., Lee, H., Kang, N., Thari, F.Z., Karrouchi, K., Salghi, R., Bougrin, K., and Ali, I.H. (2021). Corrosion inhibition properties of thiazolidinedione derivatives for copper in 3.5 wt % NaCl medium. Metals 11: 1861, https://doi.org/10.3390/met11111861.Search in Google Scholar

Li, R., Zhang, Y., Li, M., and Wang, Y. (2021). Adsorption behaviors of NH3 and HCl molecules on Fe-based crystal planes: a DFT study. Chem. Eng. Sci. 246: 116976, https://doi.org/10.1016/j.ces.2021.116976.Search in Google Scholar

Ma, C., Yang, Z., Wang, W., Zhang, M., Hao, X., Zhu, S., and Chen, S. (2020). Fabrication of Ag–Cu2O/PANI nanocomposites for visible-light photocatalysis triggering super antibacterial activity. J. Mater. Chem. C 8: 2888–2898, https://doi.org/10.1039/C9TC05891E.Search in Google Scholar

Naim, Mohd.J., Alam, Md.J., Ahmad, S., Nawaz, F., Shrivastava, N., Sahu, M., and Alam, O. (2017). Therapeutic journey of 2,4-thiazolidinediones as a versatile scaffold: an insight into structure activity relationship. Eur. J. Med. Chem. 129: 218–250, https://doi.org/10.1016/j.ejmech.2017.02.031.Search in Google Scholar PubMed

Obot, I.B., Onyeachu, Ikenna. B., Wazzan, N., and Al-Amri, A.H. (2019). Theoretical and experimental investigation of two alkyl carboxylates as corrosion inhibitors for steel in acidic medium. J. Mol. Liq. 279: 190–207, https://doi.org/10.1016/j.molliq.2019.01.116.Search in Google Scholar

Ofoegbu, S.U., Galvão, T.L.P., Gomes, J.R.B., Tedim, J., Nogueira, H.I.S., Ferreira, M.G.S., and Zheludkevich, M.L. (2017). Corrosion inhibition of copper in aqueous chloride solution by 1H-1,2,3-triazole and 1,2,4-triazole and their combinations: electrochemical, Raman and theoretical studies. Phys. Chem. Chem. Phys. 19: 6113–6129, https://doi.org/10.1039/C7CP00241F.Search in Google Scholar PubMed

Öztürk, S., Yıldırım, A., and Çetin, M. (2013). Some higher N-substituted 1,3-thiazolidine-2,4-diones and 5,5-diphenylhydantoins, their synthesis and corrosion preventive properties in mineral oil medium. Appl. Surf. Sci. 265: 895–903, https://doi.org/10.1016/j.apsusc.2012.11.144.Search in Google Scholar

Perdew, J.P., Burke, K., and Ernzerhof, M. (1996). Generalized gradient approximation made simple. Phys. Rev. Lett. 77: 3865, https://doi.org/10.1103/physrevlett.77.3865.Search in Google Scholar PubMed

Ramalho, J.P.P., Gomes, J.R.B., and Illas, F. (2013). Accounting for van der Waals interactions between adsorbates and surfaces in density functional theory based calculations: selected examples. RSC Adv. 3: 13085–13100, https://doi.org/10.1039/C3RA40713F.Search in Google Scholar

Saha, S.K., Dutta, A., Ghosh, P., Sukul, D., and Banerjee, P. (2015). Adsorption and corrosion inhibition effect of Schiff base molecules on the mild steel surface in 1 M HCl medium: a combined experimental and theoretical approach. Phys. Chem. Chem. Phys. 17: 5679–5690, https://doi.org/10.1039/C4CP05614K.Search in Google Scholar

Saha, S.K., Dutta, A., Ghosh, P., Sukul, D., and Banerjee, P. (2016). Novel Schiff-base molecules as efficient corrosion inhibitors for mild steel surface in 1 M HCl medium: experimental and theoretical approach. Phys. Chem. Chem. Phys. 18: 17898–17911, https://doi.org/10.1039/C6CP01993E.Search in Google Scholar PubMed

Shariatinia, Z. and Ahmadi-Ashtiani, A. (2019). Corrosion inhibition efficiency of some phosphoramide derivatives: DFT computations and MD simulations. J. Mol. Liq. 292: 111409, https://doi.org/10.1016/j.molliq.2019.111409.Search in Google Scholar

Somaiya, R.N., Sonvane, Y., and Gupta, S.K. (2020). Adsorption of toxic gas molecules on the pre-oxidized Cu2Si nanosheet – a DFT study. Comput. Mater. Sci. 173: 109414, https://doi.org/10.1016/j.commatsci.2019.109414.Search in Google Scholar

Sukul, D., Pal, A., Saha, S.K., Satpati, S., Adhikari, U., and Banerjee, P. (2018). Newly synthesized quercetin derivatives as corrosion inhibitors for mild steel in 1 M HCl: combined experimental and theoretical investigation. Phys. Chem. Chem. Phys. 20: 6562–6574, https://doi.org/10.1039/C7CP06848D.Search in Google Scholar PubMed

Thomas, A.G., Jackman, M.J., Wagstaffe, M., Radtke, H., Syres, K., Adell, J., Lévy, A., and Martsinovich, N. (2014). Adsorption studies of p-aminobenzoic acid on the anatase TiO2(101) surface. Langmuir 30: 12306–12314, https://doi.org/10.1021/la5032619.Search in Google Scholar PubMed

Xiong, S., Liang, D., Ba, Z., Zhang, Z., and Luo, S. (2019). Adsorption behavior of thiadiazole derivatives as anticorrosion additives on copper oxide surface: computational and experimental studies. Appl. Surf. Sci. 492: 399–406, https://doi.org/10.1016/j.apsusc.2019.06.253.Search in Google Scholar

Yadav, M., Behera, D., Kumar, S., and Yadav, P. (2015). Experimental and quantum chemical studies on corrosion inhibition performance of thiazolidinedione derivatives for mild steel in hydrochloric acid solution. Chem. Eng. Commun. 202: 303–315, https://doi.org/10.1080/00986445.2013.841148.Search in Google Scholar

Yan, G., Gao, Z., Zhao, M., Yang, W., and Ding, X. (2020). A comprehensive exploration of mercury adsorption sites on the carbonaceous surface: a DFT study. Fuel 282: 118781, https://doi.org/10.1016/j.fuel.2020.118781.Search in Google Scholar

Zhang, Z., Zhou, Q., Yuan, Z., Zhao, L., and Dong, J. (2021). Adsorption of Mg2+ and K+ on the kaolinite (001) surface in aqueous system: a combined DFT and AIMD study with an experimental verification. Appl. Surf. Sci. 538: 148158, https://doi.org/10.1016/j.apsusc.2020.148158.Search in Google Scholar

Supplementary Material

This article contains supplementary material (https://doi.org/10.1515/corrrev-2023-0003).

Received: 2023-01-04

Accepted: 2023-11-14

Published Online: 2024-02-05

Published in Print: 2024-04-25

Supplementary Material

Molecular-level investigation of the adsorption mechanisms of thiazolidinediones on Cu₂O(111) surface: a first-principles DFT study

Abstract

1 Introduction