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Original Article
ARTICLE IN PRESS
doi:
10.25259/AJC_1212_2025

Synthesis, characterization, and corrosion inhibition performance of multifunctional organoselenium schiff base–metal hybrids for Q235 steel in acidic media

, , , , , , , , , ,
aDepartment of Chemistry, College of Science, King Faisal University, Al-Ahsa, Saudi Arabia
bDepartment of Chemistry, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh, Saudi Arabia
cDepartment of Chemistry, College of Science, Taibah University, Madinah, Saudi Arabia
dDepartment of Chemistry, College of Science, Qassim University, Buraidah, Saudi Arabia
eDepartment of Chemistry, Faculty of Women for Art, Science, and Education, Ain Shams University, Heliopolis, Cairo, Egypt
fDepartment of Physical Sciences, Chemistry Division, Jazan University, Jazan, Kingdom of Saudi Arabia.
gDepartment of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
hDepartment of Chemistry, College of Science, Tikrit University, Tikrit, Iraq
iDepartment of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia.
jDepartment of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt

*Corresponding authors: E-mail addresses: sibrahim@kfu.edu.sa (S. Shaaban), k.shalabi@psau.edu.sa (K. Shalabi)

Received: , Accepted: ,
© 2026 Arabian Journal of Chemistry - Published by Scientific Scholar
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Abstract

In this study, we report the synthesis of a novel selenated Schiff base, namely, 2-(((4-(methylselanyl)phenyl)imino)methyl)phenol (MeSeOH), and its [Ni(MeSeO)2(H2O)2] complex. Their corrosion inhibition performance toward Q235 steel in 0.5 M H2SO4 was evaluated using electrochemical techniques, surface characterization, density functional theory (DFT) calculations, and Monte Carlo (MC) simulations. The Ni(II) complex [Ni(MeSeO)2(H2O)2] exhibited a maximum inhibition efficiency of 95.5%, markedly higher than that of the free ligand MeSeOH. DFT analysis and MC simulations indicate strong adsorption of the inhibitors on the steel surface and a favorable planar orientation that maximizes surface coverage. These results demonstrate that the synthesized organoselenium Schiff base and its Ni(II) chelate are promising candidates for anticorrosion applications, particularly as protective coatings in oil and gas, automotive, and construction industries.

Keywords

Corrosion inhibitors
DFT
Monte carlo simulations
Ni(II) complexes
Organic selenides
Schiff bases

1. Introduction

Carbon steel is universally employed in the fabrication of tanks, petroleum refining facilities, and pipeline infrastructure. However, a significant challenge associated with the use of carbon steel is its susceptibility to dissolution in acidic solutions [1]. Acidic solutions are widely used in industrial applications to eliminate unwanted scale and rust deposits [2]. As a result, protecting metal from corrosion is a crucial industrial and scientific issue. Regrettably, most corrosion inhibitors, including benzothiazole, CrO42-, and polyphosphates, are pricey. Some are dangerous and detrimental to the environment [3,4]. The most effective, practical, and cost-efficient method to prevent chloride-ion adsorption and oxidation on mild steel is to incorporate organic inhibitors into the acid solution. Numerous hydrocarbons are widely used to inhibit the corrosion of metals and alloys in acidic environments. The heteroatom-containing compounds, in addition to aromatic rings, are the most potent corrosion inhibitors [5]. Recent investigations have focused on using various classes of organic compounds, including Schiff bases, plant extracts, pyrimidine derivatives, polymeric materials, and surfactants, to inhibit the corrosion of carbon steel in H₂SO₄ solutions [6,7].

Selenium (Se) has attracted much attention in material science owing to its unique physical and chemical properties. The lower electronegativity, larger atomic radius, and greater electron-donating ability of Se relative to its homologs, i.e., oxygen and sulfur, make it particularly useful in applications such as photocatalysis, photovoltaics, and optoelectronic devices. Furthermore, the Se’s higher polarizability, electron-donor ability, and nucleophilicity enabled tailoring more efficient and tunable materials for catalysis, light emission, and energy conversion. In this regard, integrating Se centers into the backbone of organic structures is a versatile approach to developing novel materials with improved properties. The Se centers are incorporated into the framework of organic ligands using different approaches [8,9]. Moreover, Se-containing compounds showed an intrinsic chemisorption efficiency, making them valuable in several applications, including corrosion inhibition, coatings, and catalysis [10,11]. The latter stems from the organoselenium (OSe) agents’ tendencies to bind to the metal surfaces either via direct electron donation, H-bond formation, or participation in chelation via multidentate coordination [10].

Within this context, mount reports showed that OSe agents typically exhibit enhanced corrosion protection efficiency compared with classical candidates, particularly with respect to antimicrobial resistance and stability in abiotic/biotic environments. Despite their unique corrosion protection characteristics, the anticorrosive potential of OSe compounds remains largely unreported in the literature.

Several organoselenium compounds have shown potent corrosion inhibition (Figure 1). For instance, OSe inhibitors I and II were effectively adsorbed on mild steel in 1 M HCl via charge transfer, blocking active sites. Furthermore, isoxazoles bearing a selenadiazole group (III) acted as mixed-type inhibitors for Cu in 3.5 wt% NaCl with ∼90% efficiency. Moreover, diorganyl diselenide tetrazoles (IV and V) exhibit mixed-type inhibition of N80 and J55 steels in acidic media and display antimicrobial activity against sulfate-reducing bacteria.

Some Se-based compounds as potential anticorrosion agents.
Figure 1.
Some Se-based compounds as potential anticorrosion agents.

The strong electron-donating character of Se has enabled the design of numerous Se-based ligands and their metal complexes, which exhibit optimized catalytic activity in organic transformations. These ligands display diverse denticity and coordination modes (e.g., selenoethers, selenopincers, selenocarbonyls, and Se-containing Schiff bases). In this context, peroxyseleninic acid (V) has been used as an efficient catalyst for oxidation reactions, including epoxidation, sulfoxidation, and dihydroxylation (Figure 1). Additionally, we recently presented the Zn(II) chelate IV as a promising catalyst for the oxidation of phenylmethanol and the epoxidation of cyclohex-1-ene [12].

Furthermore, Schiff base ligands have recently attracted our interest owing to their ability to coordinate with d- and f-block elements [13]. Moreover, their chelates showed potential biological properties. The imine (-N=CH-) nitrogen’s ability to coordinate to metal ions and form H-bonding with several enzymes and proteins [14]. In this context, the potential characteristics of Schiff bases and their respective chelates have been extensively studied for the inhibition/modulation of various enzymes [15]. To this end, OSe Schiff bases are of significant interest for stability, multiple coordination sites, chelation modes, and bio- and redox activities [16].

Carrying on our previous work for the synthesis and evaluation of transition metal complexes of OSe-containing Schiff base as corrosion inhibitors [17]. Here, we present the synthesis of the new MeSeOH and its [Ni(MeSeO)2(H2O)2].

Despite the structural similarity of the current MeSeOH ligand to our previously reported O/Se Schiff bases, it constitutes an entirely novel SeMe-functionalized scaffold. It was intentionally designed to explore how para-SeMe substitution and the corresponding Ni(II) chelate [Ni(MeSeO)2(H2O)2] modify the electronic structure and corrosion-inhibition properties, thereby extending our earlier structure–activity framework rather than duplicating it. The usual analytical and spectroscopic tools have been used to clarify the structures of the novel agents. Additionally, various investigative techniques have been employed to assess their corrosion-inhibition properties. The analytical methods employed included Potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, and MC simulations.

2. Materials and Methods

2.1. Materials

Chemicals and reagents used in this study were obtained from commercial suppliers. 4-Aminophenylselenocyanate (2), bis(4-aminophenyl)diselenide (3), and 4-(methylselanyl)aniline (4) [18] were synthesized according to our reported protocols (see Supplementary Information for all experimental details). Q235-steel specimens comprised the following weight percentages: 0.18% carbon, 0.45% manganese, 0.01% phosphorus, 0.02% silicon, and 0.02% sulfur, with iron accounting for the remainder of the composition. H2SO4 (0.5 M) was used as a corrosive medium.

Supplementary Information

2.2. Chemistry

The synthesis of the OSe compounds 2, 3, 4, MeSeOH, and [Ni(MeSeO)2(H2O)2] and Copies of the IR, 1HNMR, 13CNMR, and MS spectral data are presented in Supplementary Information S1, S2, and S3, respectively.

2.3. Electrochemical measurements

The experimental details of electrochemical investigations are listed in Supplementary Information S4.

2.4. XPS Surface morphology analysis

The experimental details of XPS analysis are listed in Supplementary Information S5 (Table S1).

2.5. Theoretical computations

All details of the DFT calculation and MC simulations are listed in the Supplementary Information S6.

3. Results & Discussions

3.1. Chemistry

Recently, Schiff bases have been recognized as versatile building blocks with diverse biological (e.g., anticancer, antiviral, and anti-inflammatory) and industrial (e.g., catalysis, anticorrosion, pigments, and dyes) applications [17,19]. The OSe-based Schiff bases have attracted special attention due to their interesting coordination chemistry and structural features [16]. Typically, synthesizing OSe ligands is associated with challenges, such as using toxic OSe intermediates such as K2Se2 and NaSeH [12,20]. Accordingly, several emerging protocols are being developed to provide more efficient, mild, and simple synthetic procedures for the preparation of innovative OSe Schiff bases and their respective chelates [21,22]. These procedures are well-suited for different functionalities to guarantee their implications in various fields (e.g., corrosion inhibition, catalysis, and materials science) [21-23]. In this regard, diorganyl diselenides are widely used to prepare various OSe ligands owing to their ease of handling and stability.

Our synthetic strategy utilized 4,4’-diselanediyldianiline (3) to synthesize the MeSeOH Schiff base. First, diselenide 3 is obtained in 88% yield via selenocyanation of phenylamine (1), followed by hydrolysis. Next, the treatment of diselenide 3 with sodium borohydride in a solution of NaOH in EtOH to furnish, in situ, the corresponding Na phenylselenolate. The latter was allowed to react with CH3I immediately, affording the corresponding 4-(methylseleno) benzenamine (4) in fair yield (57%) (Scheme 1). Thereafter, the reaction of OSe 4 with 2-hydroxybenzaldehyde afforded the corresponding Schiff base (MeSeOH) in 86% yield (Scheme 1).

The synthesis of MeSeOH. Reagents and conditions: (i) SeO2 (9.6 mmol), CH2(CN)2 (4.8 mmol), DMSO (18 mL); (ii) Compound 2 (18 mmol), NaBH4 (3 mmol), NaOH (18 mmol), ethanol (50 mL); (iii) Compound 3 (10 mmol), MeI (12 mmol), ethanol (50 ml), NaBH4 (30 mmol), NaOH (10 mmol), ethanol (50 mL); (iv) Compound 4 (10 mmol), 2-hydroxybenzaldhye (12 mmol), ethanol (30 ml), acetic acid (two drops).
Scheme 1.
The synthesis of MeSeOH. Reagents and conditions: (i) SeO2 (9.6 mmol), CH2(CN)2 (4.8 mmol), DMSO (18 mL); (ii) Compound 2 (18 mmol), NaBH4 (3 mmol), NaOH (18 mmol), ethanol (50 mL); (iii) Compound 3 (10 mmol), MeI (12 mmol), ethanol (50 ml), NaBH4 (30 mmol), NaOH (10 mmol), ethanol (50 mL); (iv) Compound 4 (10 mmol), 2-hydroxybenzaldhye (12 mmol), ethanol (30 ml), acetic acid (two drops).

Treatment of NiCl2.6H2O with two equivalents of MeSeOH in a basic medium in methanolic and aqueous solution to afford a chelate of the type [Ni(MeSeO)2(H2O)2] in 86% yield (Scheme 2). MeSeOH was coordinated as a bidentate with the Ni2+ ion through the “O” of the phenolic group and the “N” atom of the “-N=CH-” group, with two aqua molecules to provide an octahedral geometry around the nickel ion. It is proposed that the coordination structure be monodentate and bidentate toward the Ni ion. This proposal was confirmed by Electron ionization mass spectrometry (EI-MS), thermal analysis, elemental analysis, molar conductivity, and Fourier Transform Infrared spectroscopy (FTIR) spectroscopy.

Synthesis of the [Ni(MeSeO)2(H2O)2].
Scheme 2.
Synthesis of the [Ni(MeSeO)2(H2O)2].

3.2. Characterization

The MeSeOH and [Ni(MeSeO)2(H2O)2] were characterized, and all characteristic data are registered in the experimental section. The [Ni(MeSeO)2(H2O)2] complex is a dark green solid that is insoluble in water. It is slightly soluble in most solvents but highly soluble in dimethyl sulfoxide (DMSO) and nonhygroscopic. The CHN analysis and mass data indicate their monomeric nature. The molar conductance value is 17.21 Ohm−1.cm2.mol−1 designates the non-electrolyte nature.

The 1H NMR spectrum of the selenated Schiff base ligand (MeSeOH) (Figure 2) manifested the proton of the “OH” group and “-CH=N-” group as a singlet peak at δH = 13.12 ppm and 8.96 ppm, respectively. Also, the spectrum displayed the aromatic protons as five divided peaks, three as doublet peaks at δH = 7.64 ppm (JHH = 7.86 Hz), 7.48 ppm (JHH = 8.00 Hz) and 7.36 ppm (JHH = 8.00 Hz), due to the protons in position 5, 9 and 10 respectively, and the protons in position 2 and (3,4) displayed at δH = 7.42ppm (t, JHH = 7.80 Hz) and 6.98 ppm, respectively. The protons of the methyl group appeared as a singlet at 2.38 ppm. The hydroxyl group peak was absent in the 1H-NMR spectrum of the [Ni(MeSeO)2(H2O)2] compound (Figure 3), clearly displaying the deprotonation of the “OH” of the MeSeOH after complexation with the Ni(II) ion, which promotes the deprotonation and bonding with the ions via the “O” atom. Additionally, the spectrum exhibited two singlet peaks at δH = 8.76 ppm and 2.38 ppm, attributable to the protons of the azomethine and methyl groups, respectively. The chemical shifts of the phenyl ring protons are observed as two unresolved multiplets at δH = 7.46 and 6.98 ppm.

1H NMR of MeSeOH.
Figure 2.
1H NMR of MeSeOH.
1H NMR of [Ni(MeSeO)2(H2O)2].
Figure 3.
1H NMR of [Ni(MeSeO)2(H2O)2].

Exhibited two singlet peaks at δH = 8.76 ppm and 2.38 ppm due to the protons of the azomethine group and methyl group, respectively. The chemical shifts of the phenyl ring protons are observed as two unresolved multiplets at δH = 7.46 and 6.98 ppm.

The IR of the MeSeOH and [Ni(MeSeO)2(H2O)2] displayed an absorption band at 3427 cm−1 attributed to the “OH” vibration of the aqua ligands coordinated within the chelate. Additionally, a band at 833 cm−1 further supports the presence of a bonded H2O ligand [24]. A prominent band observed at 1101cm−1 relative to the υ(C-O) stretching vibration, which is lifted to a greater vibration, indicating the bonding of the hydroxylate group with Ni+2. The band 1611 cm−1 (C=N) in [Ni(MeSeO)2(H2O)2], confirms the coordination to the Ni (II) ion to “N” of the imine group [17,18,25]. Novel bands at 456 cm−1 and 514 cm−1 are due to the vibration of the metal bond with the “N” and “O”, respectively [17,18,26]. The µeff value of the complex is 3.12 B.M, suggesting the octahedral environment around the Ni(II) ion [17,18,22]. The electronic spectra are measured in DMSO. The results obtained showed band at 287 nm assigned to the π→π* intra-ligand transition and three bands appeared at 339 nm, 523 and 789 nm are ascribed to 3A2g(F)→3T2g(F), 3A2g(F)→3T1g(F), and 3A2g(F)→3T1g(P) transitions, respectively, comparable to the characteristic features of octahedral Ni(II) complexes [27]. The mass spectrometry (MS) spectrum of the [Ni(MeSeO)2(H2O)2] (Figure 4) exhibited characteristic molecular ion peaks (M+) at an m/z value of 673.1. The measured readings nearly corresponded with the calculated value of 673.97. The observed mass spectra corroborated the expected chemical composition.

MS of [Ni(MeSeO)2(H2O)2].
Figure 4.
MS of [Ni(MeSeO)2(H2O)2].

The scanning electron microscopy (SEM) picture of the [Ni(MeSeO)2(H2O)2] compound (Figure 5a) demonstrated an irregular and fused sheet in addition to other irregular shapes, and the average size of these sheets ranges from 26 to 97 nm. Energy-dispersive X-ray spectroscopy (Figure 5b) is an analytical technique used for elemental analysis or chemical characterization of a sample. The powder X-ray diffraction (PXRD) pattern of the [Ni(MeSeO)2(H2O)2] compound was documented within the range (2θ = 0–80) were shown in Figure 5(c). The XRD pattern exhibits distinct crystalline peaks, particularly indicating their crystalline phase, with a pronounced diffraction peak at specific angles 2θ of (5, 8, 22, 29, and 34).

(a) SEM, (b) EDX, and (c) XRD pictures of [Ni(MeSeO)2(H2O)2].
Figure 5.
(a) SEM, (b) EDX, and (c) XRD pictures of [Ni(MeSeO)2(H2O)2].

3.3. Electrochemical measurements

3.3.1. PDP measurements

PDP curves revealed the corrosion performance of Q235 structural steel in acidic medium (0.5 M H2SO4). The Tafel analysis results (Figure 6) demonstrate the corrosion kinetics under varying experimental parameters, encompassing experimental configurations that include the addition of MeSeOH and [Ni(MeSeO)2(H2O)2], as well as a control setting without any additions (i.e., blank). The diagrams present a graphical representation of corrosion kinetics as a function of the applied electrochemical potential, clearly displaying the PDP curves for the anodic and cathodic branches. Tafel analysis permits precise determination of corrosion kinetics parameters, facilitating direct comparison of inhibition performance between MeSeOH (0.1-10 mM) and [Ni(MeSeO)2(H2O)2] through quantitative evaluation of polarization resistance. The graphical representations exhibit that the incorporation of MeSeOH and [Ni(MeSeO)2(H2O)2] into the corrosive solution significantly changes the polarization behavior, as well as a notable decrease in both anodic and cathodic reaction rates. This decline in corrosion rates indicates effective mitigation of Q235-steel dissolution, thereby affirming the efficacy of the employed inhibitors. Additionally, the slight changes in the Tafel slopes imply that MeSeOH and [Ni(MeSeO)2(H2O)2] exerted minimal influence on the processes underlying the corrosion reactions. Table 1 presents the Tafel diagrams incorporating essential corrosion parameters, inhibition efficacy, and surface coverage (θ). The data reveal that the Tafel constants (βa and βc) demonstrate negligible fluctuations with the introduction of MeSeOH and [Ni(MeSeO)2(H2O)2]. These results propose that both MeSeOH and [Ni(MeSeO)2(H2O)2] inhibit corrosion by adsorbing on the metal surface and modulating anodic dissolution and cathodic hydrogen evolution reactions. Their adsorption establishes a shielding interfacial layer, effectively protecting the Q235-steel from aggressive media and mitigating the corrosion [28].

PDP diagrams for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH, (b) [Ni(MeSeO)2(H2O)2], and (c) both MeSeOH and [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Figure 6.
PDP diagrams for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH, (b) [Ni(MeSeO)2(H2O)2], and (c) both MeSeOH and [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Table 1. PDP corrosion parameters for Q235-steel in 0.5 M H2SO4 without and with different concentrations of MeSeOH and [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Inhibitors code Cinh/M icor/µA·cm⁻2 ± SD -Ecor/(mV Ag/AgCl) βa/mV dec -1 -β c/mV dec -1 C.R./mpy Θ ηPDP/%
0.5 M H2SO4 849.94 ± 0.547 408.80 48.47 84.61 392.55 -- --
MeSeOH 1×10-5 329.90 ± 0.316 408.48 51.46 84.69 152.37 0.612 61.2
5×10-5 261.27 ± 0.245 408.52 48.92 80.76 120.67 0.693 69.3
10×10-5 214.09 ± 0.221 406.61 50.53 89.78 98.88 0.748 74.8
15×10-5 121.91 ± 0.208 408.51 48.66 85.91 56.30 0.857 85.7
20×10-5 80.04 ± 0.159 406.73 50.03 95.13 36.97 0.906 90.6
[Ni(MeSeO)2(H2O)2] 1×10-5 300.01 ± 0.289 411.47 55.27 77.75 138.56 0.647 64.7
5×10-5 197.95 ± 0.199 408.96 57.40 85.58 91.43 0.767 76.7
10×10-5 111.94 ± 0.174 407.41 52.83 93.20 51.70 0.868 86.8
15×10-5 73.07 ± 0.122 405.26 48.91 89.24 33.75 0.914 91.4
20×10-5 38.09 ± 0.098 401.51 54.21 96.29 17.59 0.955 95.5

The presence of the MeSeOH and [Ni(MeSeO)2(H2O)2], has been shown to considerably lower the corrosion current density (icor), with observed values of 329.90 µA·cm⁻2 for MeSeOH and 300.01 µA·cm⁻2 for [Ni(MeSeO)2(H2O)2] at a concentration of 1 × 10-5 M, as detailed in Table 1. Furthermore, the corrosion potential (Ecor) exhibited minor shifts toward more positive and more negative values upon introduction of these inhibitors, but no discernible pattern was observed. The difference in Ecor values between the uninhibited and inhibited samples generally remained within ±85 mV in most cases, suggesting that MeSeOH and [Ni(MeSeO)2(H2O)2] exhibit mixed-type inhibition [29]. Moreover, the effectiveness of MeSeOH and [Ni(MeSeO)2(H2O)2] as mixed-type corrosion inhibitors is further supported by slight differences in the anodic and cathodic Tafel slope values (βa and βc) attributable to their presence, indicating that their presence prevents corrosion through surface adsorption on both anodic and cathodic sites rather than through a mechanistic alteration of the charge-transfer process of either the anodic or cathodic reactions [29].

The recorded corrosion current density values (icor) demonstrate that the blank sample of H2SO4 (0.5 M) exhibited a current density of 849.94 µA·cm⁻2. Upon introducing the MeSeOH at a concentration of 20 × 10-5 M, the icor value decreased to 80.04 µA·cm⁻2. Further reductions were observed with the incorporation of the complex [Ni(MeSeO)2(H2O)2], which exhibited a corrosion current density of 38.09 µA·cm⁻2, respectively. These results imply that adding the MeSeOH and [Ni(MeSeO)2(H2O)2] significantly diminishes the corrosion rate of Q235-steel. A consistent reduction in current density was observed with the gradual increase of these compounds. The following equation (1) was applied to determine the protective efficacy (ȠP/%) of the MeSeOH and [Ni(MeSeO)2(H2O)2] based on the icor values [30]:

(1)
ηPDP /%= icor 0 −icori icor 0 ×100=θ×100

Where, icor 0 = corrosion current density of the blank medium, icori = corrosion current density of any required concentration of MeSeOH and [Ni(MeSeO)2(H2O)2].

The corrosion inhibition efficacy of the MeSeOH and [Ni(MeSeO)2(H2O)2] reached the maximum of 90.6% and 95.5%, respectively, at a concentration of 20 × 10-5 M, as indicated in Table 1. The enhanced adsorption of the MeSeOH can explain the marked improvement in the inhibition performance and [Ni(MeSeO)2(H2O)2], which causes an improved surface coverage of the carbon steel substrate. The development of this adsorptive layer mitigates exposure of the metal interface to the corrosive medium, thereby reinforcing the inhibitors’ barrier properties and thereby increasing their overall effectiveness as protectors.

3.3.2. EIS studies

EIS was used to investigate the interfacial interactions of Q235 Steel under different conditions, both before and after the application of anti-corrosion agents. The insights obtained from EIS provided a deeper understanding of the substrates, capacitive, and electro-resistive properties, thereby advancing the knowledge of the mechanisms underlying corrosion inhibition [31]. This study analyzes Nyquist plots for Q235-steel in H2SO4 (0.5 M), as depicted in Figures 7 and 8.

Nyquist plots for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Figure 7.
Nyquist plots for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Bode plots for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Figure 8.
Bode plots for Q235-steel in 0.5 M H2SO4 without and with different concentrations of (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.

These plots were constructed for conditions featuring differing concentrations of the MeSeOH and [Ni(MeSeO)2(H2O)2]. EIS analysis revealed that the addition of MeSeOH and [Ni(MeSeO)2(H2O)2] significantly enhanced the corrosion resistance of Q235 Steel in acidic media; the Nyquist and Bode diagrams clearly depicted this behavior. The Nyquist plot reveals only a single capacitive loop, whereas the Bode plot shows a single phase-angle maximum. This behavior is attributed to a one-time constant in the corrosion process occurring at the metal-solution interface, which is influenced by the electrical double layer [32]. The presence of a capacitive loop in the Nyquist plots (Figure 7) suggests that a charge transfer process governs the corrosion of Q235 Steel. Additionally, the arc diameter in the Nyquist plot indicates the charge-transfer resistance (Rct), which is a leading indicator of the ease or difficulty of electron transfer at the metal/solution interface [33]. Furthermore, Nyquist plots showed an increase in the capacitive loop diameter with inhibitor concentration, which correlated with inhibitor efficacy. This behavior suggests the formation of a protective barrier that prevents Q235 Steel from dissolving in corrosive environments by hindering ionic and electronic transport, thereby limiting charge transfer at the interface between the N80 steel surface and the solution [34]. The non-ideal semicircular profiles observed in Nyquist diagrams reflect interfacial heterogeneity, likely arising from inhibitor adsorption dynamics or surface structural irregularities [35]. In addition, Bode plots (Figure 8) corroborated these findings, showing a systematic increase in the magnitude of total impedance with increasing inhibitor concentration. Concurrently, the phase angle maxima broadened and shifted toward higher frequencies, indicating increased inhibitor adsorption on the Q235 Steel surface. These trends collectively indicate the formation of a dense protective film that reduces metal dissolution by limiting charge transfer at the electrode-electrolyte interface [36].

To model the electrochemical behavior of Q235 steel under inhibited and uninhibited conditions, an equivalent circuit was designed and fitted to the EIS data (Figure 9). The circuit comprised key elements such as solution resistance (Rs), charge-transfer resistance (Rct), and a constant phase element (CPE), reflecting the interfacial charge transfer and surface heterogeneity observed experimentally. Impedance parameters derived from this model are summarized in Table 2.

Equivalent-circuit models for uninhibited and inhibited systems.
Figure 9.
Equivalent-circuit models for uninhibited and inhibited systems.
Table 2. EIS parameters for Q235-steel in 0.5 M H2SO4 without and with different concentrations of MeSeOH and [Ni(MeSeO)2(H2O)2] at 25 ± 1°C.
Inhibitors code Cinh/mol/l Rs/Ω cm 2 Rct/Ω cm 2 ± SD Y0/Ω -1 s n cm -2 × 10-4 n χ2 / × 10-4 Θ η EIS/%
0.5 M H2SO4 1.54 30.95 ± 0.143 5.96 0.909 3.34 -- --
MeSeOH 1×10-5 2.06 71.53 ± 0.191 3.96 0.897 1.96 0.567 56.73
5×10-5 3.68 87.27 ± 0.189 2.58 0.896 1.38 0.645 64.54
10×10-5 4.21 114.93 ± 0.216 2.11 0.894 1.04 0.731 73.07
15×10-5 4.99 195.49 ± 0.234 1.09 0.892 5.23 0.842 84.17
20×10-5 5.17 296.05 ± 0.389 0.51 0.890 2.38 0.895 89.55
[Ni(MeSeO)2(H2O)2] 1×10-5 2.91 77.42 ± 0.156 1.99 0.915 1.34 0.600 60.03
5×10-5 3.62 123.60 ± 0.208 1.81 0.904 5.98 0.750 74.96
10×10-5 4.96 211.94 ± 0.263 0.99 0.895 5.56 0.854 85.40
15×10-5 5.03 317.80 ± 0.251 0.93 0.879 4.77 0.903 90.26
20×10-5 6.59 542.09 ± 0.326 0.62 0.880 2.87 0.943 94.29

Furthermore, Table 2 confirms the validity of the fitting process, yielding a low Chi-squared (χ2) value of 3.26 × 10-4, indicating strong accord between the theoretical model and empirical data. Integration of a CPE (rather than an ideal capacitor) accounts for surface roughness and non-uniform current distribution, enhancing the accuracy of the interfacial impedance characterization. The admittance behavior of the CPE is quantified using the following equation (2) [37]:

(2)
ZCPE = 1 Y0 (iω)n = 1 Y0 (2iπf)n

The constant phase element (CPE) admittance is indicated by ‘Y0’ in this equation, where ‘i’ is the imaginary unit, ‘ω’ is the angular frequency in radians per second, ‘f’ is the input signal frequency, and ‘n’ is the phase shift. This phase-shift parameter is essential for analyzing surface imperfections and elucidating the characteristics of Y0. To be more precise, Y0 acts as an ideal capacitance when its phase shift value is n equal to 1, and as an ideal resistor when it is equivalent to 0. Values of ‘n’ between 0 and 1 suggest that ‘Y0’ can be interpreted as a composite system. The analogous circuit model is employed to assess and record impedance parameters, which include Rs, Rct, Y0 (admittance), and ‘n,’ as outlined in Table 2. In blank solutions lacking MeSeOH and [Ni(MeSeO)2(H2O)2], the measured ‘n’ value is 0.909, with a noted decrement corresponding to increased inhibitor concentration. Generally, a higher ‘n’ value is a sign of increased surface roughness, while a lower value reflects a smoother surface. Therefore, it can be inferred that adding MeSeOH and [Ni(MeSeO)2(H2O)2] reduces the surface roughness of the Q235 steel interface, thereby improving the compactness and uniformity of the protective layer [38]. The observed low value of ‘Rs’ indicates the presence of a stable and corrosive environment. At the same time, the decrease in ‘Y0’ at higher inhibitor concentrations indicates a substantial reduction in charge accumulation on the surface of Q235 Steel. As presented in Table 2, the addition of the inhibitor to the corrosive medium led to a marked augmentation in charge-transfer resistance (Rct) values, which increased from 30.95 Ω cm2 to 296.05 and 542.09 Ω cm2 with the application of 20×10-5 M concentrations of MeSeOH and [Ni(MeSeO)2(H2O)2]. An obvious trend of rising Rp values was noted in conjunction with the escalating concentrations of both MeSeOH and [Ni(MeSeO)2(H2O)2]. The observed enhancement in charge-transfer resistance (Rct) correlates with an expansion in the diameter of the Nyquist semicircle and a rise in the absolute impedance magnitude. These results suggested MeSeOH and [Ni(MeSeO)2(H2O)2] can significantly improve the corrosion resistance of Q235-steel when subjected to corrosive conditions. The enhanced inhibition efficiency arises from reducing the local dielectric constant at the steel-electrolyte interface and from thickening the electrical double layer. These changes promote greater surface coverage by the adsorbed inhibitor molecules MeSeOH and [Ni(MeSeO)2(H2O)2], forming a protective barrier that impedes corrosive ion penetration. The corrosion inhibition efficiency (ηEIS/%) was computed using charge-transfer resistance (Rct) values via the following equation (3):

(3)
Rcti−Rct 0 Rcti ×100=θ×100

In this equation, Rct 0 indicates the unrestricted medium’s charge-transfer resistance while Rcti Represents the charge-transfer resistance recorded at specific concentrations of MeSeOH and [Ni(MeSeO)2(H2O)2]. The data reveal a positive relationship between the ηEIS/% values and inhibitor concentration, with inhibition efficiencies of 89.55% and 94.29% for MeSeOH and [Ni(MeSeO)2(H2O)2], respectively, at an optimal concentration of 20 × 10-5 M.

3.3.3. Adsorption isotherm and mechanism of the corrosion inhibition

The molecular configurations of MeSeOH and [Ni(MeSeO)2(H2O)2] incorporate heteroatoms (e.g., Se, O, N) and aromatic moieties, enabling their adsorption onto Q235-steel surfaces to form corrosion-inhibiting protective films. Adsorption occurs through three possible mechanisms: (i) Physisorption is driven by electrostatic attractions between charged inhibitor species and the charged metal surface; (ii) Chemisorption involves coordinate bonds constructed between heteroatom lone pairs and vacant d-orbitals on the steel substrate; and (iii) synergistic adsorption is A hybrid mechanism combining physisorption and chemisorption. To identify the dominant adsorption behavior, empirical data were fitted to distinctive isotherm models: Langmuir, Freundlich, Temkin, Frumkin, Flory-Huggins, and Henry (Figure S9) [39]. Among these, the Langmuir model exhibited the strongest correlation (R2 > 0.99) for both inhibitors on the Q235-steel surface. This conformity between theoretical predictions and empirical data features the Langmuir model’s suitability for describing the adsorption properties of the MeSeOH and [Ni(MeSeO)2(H2O)2] on the Q235-steel surface as seen in Equation 4 [40]:

(4)
Cinh θ= 1 Kads +Cinh

The molarity of the tested inhibitors, denoted as Cinh, along with the surface coverage (θ) derived from the PDP technique, correlates with the equilibrium constant for the adsorption and desorption processes occurring on the metallic surface, referred to as Kads. The linear fitting reveals a slope and a linear coefficient (R2) that approximates unity, as illustrated in Figure 10, indicating a significant relationship between Cinh and the ratio Cinh/θ. A perfect Langmuir model would yield a slope of 1.00. In our case, the obtained slopes are very close to unity (e.g., 1.06), indicating minor deviations from the Langmuir model, likely arising from slight surface heterogeneity [41]. The standard free energy of adsorption, ΔGads° , forms the foundation for equation (5) utilized to compute Kads [42]:

(5)
ΔGads°=−RTlnKads Cwater

Langmuir adsorption isotherm plots for (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2].
Figure 10.
Langmuir adsorption isotherm plots for (a) MeSeOH and (b) [Ni(MeSeO)2(H2O)2].

In this context, ‘R’ signifies the universal gas constant, ‘T’ represents the temperature in Kelvin, and ‘Cwater’ signifies the molarity of the water content within the solution. Table 3 provides an illustration of the thermodynamic parameters correlated to MeSeOH and [Ni(MeSeO)2(H2O)2].

Table 3. Langmuir adsorption parameters for MeSeOH and [Ni(MeSeO)2(H2O)2].
Inhibitors R 2 S=slope Intercept, × 10-5 Kads/L mol -1, × 10 4 ΔGads° /kJ mol-1
MeSeOH 0.9847 1.06 1.53 6.55 -37.41
[Ni(MeSeO)2(H2O)2] 0.9960 1.01 1.06 9.40 -38.30

The negative values of ΔGads° propose that both MeSeOH and [Ni(MeSeO)2(H2O)2] exhibit spontaneous adsorption on the surface of Q235-steel. Furthermore, the magnitude of the Kads values indicates a direct relationship with the adsorption strength and the overall inhibitory efficacy, as reflected by the high Kads values listed in Table 3. The ΔGads° serves as a critical indicator of the dominant interaction mechanisms between corrosion inhibitors and metal surfaces. Thermodynamic analysis reveals distinct adsorption mechanisms: (i) ΔGads° values are less negative than -20 kJ mol⁻1 suggesting the predominance of electrostatic attractions. In comparison, values varying from -20 kJ mol⁻1 to -40 kJ mol⁻1 indicate the potential for charge sharing and bond establishment, which signifies both physisorption and chemisorption processes. Specifically, ΔGads° values are more negative than -40 kJ mol⁻1 implying a substantial likelihood of chemisorption phenomena [21]. The ΔGads° values listed in Table 3 expose the contributions of both physisorption and chemisorption (i.e., mixed adsorption) mechanisms for MeSeOH and [Ni(MeSeO)2(H2O)2] on Q235-steel, with chemical adsorption demonstrating a distinctly more substantial adsorptive effect [43]. Furthermore, Table 3 exhibits higher Kads values and a more negative ΔGads° value in comparison to MeSeOH, thereby establishing a hierarchy of inhibition efficiency delineated as MeSeOH < [Ni(MeSeO)2(H2O)2].

To elucidate the corrosion inhibition mechanism of Q235-steel in 0.5 M H₂SO₄, it is essential to first delineate the sequential surface corrosion processes preceding inhibitor adsorption. [44] The corrosion mechanism involves distinct anodic and cathodic reactions, as outlined below in Equations 6-12.

  • (i)

    The anodic dissolution reactions:

(6)
Fe+ SO 4 2− → FeSO 4 2−   ads

(7)
FeSO 4 2−   ads → FeSO 4   ads + 2e −

(8)
FeSO 4   ads → FeSO 4

(9)
FeSO 4 →  Fe 2+  +  SO 4 2−

  • (ii)

    The cathodic hydrogen evolution reactions:

(10)
Fe +  H +  →  FeH + ads

(11)
FeH + ads   +   e −  →  FeH ads

(12)
FeH ads  +  H +  +  e −  → Fe +  H 2

The corrosion mitigation mechanism, inferred from ΔGads° values, operates via two distinct pathways: (i) Physisorption requires a positively charged steel surface and protonated inhibitor molecules in the acidic medium (Scheme S1, see Supporting Information) [45]. Herein, sulfate ions ( SO 4 2− ) act as intermediaries, bridging the protonated inhibitors and the positively charged steel substrate. (ii) Chemisorption: involves direct coordination bonding between MeSeOH or [Ni(MeSeO)2(H2O)2] and the steel surface (Scheme S1, see Supporting Information). Electron-rich sites on the inhibitors, such as N, O, and Se atoms (lone pair donors) and benzene rings (π-electron donors), interact with empty d-orbitals of surface Fe atoms, forming stable coordinate bonds [45].

3.4. Surface morphology analysis using XPS analysis.

XPS analysis was executed to validate the adsorption of the [Ni(MeSeO)2(H2O)2] onto Q235-steel surfaces in a 0.5 M H₂SO₄ solution. Comparative analysis of uninhibited and inhibitor-protected specimens revealed distinct spectral signatures (see Supporting Information Figures S5 and S6).

Both samples exhibited distinctive spectra for C 1s, Fe 2p, O 1s, and S 2p, while the inhibited sample additionally displayed N 1s, Ni 2p, and Se 3d spectra, confirming the adsorption of [Ni(MeSeO)2(H2O)2] on Q235-steel surface in a corrosive environment. The binding energy (BE) values and their corresponding assignments are documented in Supporting Information Table S1 [27] and are elaborately detailed in the Supporting Information.

3.5. DFT studies

Quantum-chemical calculations were performed to explore the electronic structures of MeSeOH and [Ni(MeSeO)2(H₂O)2] complex and to link their molecular properties to the experimentally observed corrosion inhibition behavior on Q235 steel. The results (Table 4) show that, although both molecules contain electron-rich donor atoms (selenium, nitrogen, and oxygen), coordination of the ligand to Ni(II) significantly reorganizes its electronic structure. This transformation enhances the molecule’s capacity to bind effectively to the steel surface, offering a clear molecular explanation for why the [Ni(MeSeO)2(H₂O)2] complex outperforms the free ligand as a corrosion inhibitor.

Table 4. The calculated DFT parameters for MeSeOH and [Ni(MeSeO)2(H2O)2].
Compound MeSeOH [Ni(MeSeO)2(H2O)2]
EHOMO, eV -5.68 -3.24
ELUMO, eV -3.19 -1.69
ΔE, eV 2.49 1.55
I 5.68 3.24
A 3.19 1.69
χ 4.44 2.47
η 1.25 0.78
σ 0.80 1.29
ω 7.90 3.92
ΔN 1.03 2.93
ΔEback-donation -0.31 -0.19

Most notably, the HOMO energy of [Ni(MeSeO)2(H₂O)2] complex (-3.24 eV) is significantly higher than that of the free ligand (-5.68 eV), indicating a much stronger propensity to donate electrons to vacant d-orbitals of surface iron atoms. This aligns with the lower ionization potential (3.24 eV vs. 5.68 eV) and higher fractional electron transfer (ΔN = 2.93 vs. 1.03), both of which confirm that the Ni complex acts as a far more effective electron donor critical for forming stable coordinate bonds with the metal substrate [46,47].

Conversely, the LUMO energy of the [Ni(MeSeO)2(H₂O)2] complex is less negative (-1.69 eV vs. -3.19 eV), suggesting reduced electron-accepting capacity. While this might imply weaker back-donation from the metal surface, it is well established that in acidic corrosion environments, forward donation (inhibitor → metal) dominates the adsorption mechanism [21,22]. Thus, the slightly stronger back-donation observed for MeSeOH (more negative ΔEback) does not translate into better inhibition, consistent with experimental findings.

The narrower HOMO–LUMO gap (ΔE = 1.55 eV vs. 2.49 eV) and higher global softness (σ = 1.29 vs. 0.80) of the Ni complex further support its enhanced reactivity. According to the Hard–Soft Acid-Base (HSAB) principle, soft molecules preferentially bind to soft metals like Fe(0)/Fe(II), a key factor in strong adsorption on carbon steel [48]. This increased polarizability likely promotes dense, multi-point attachment to the surface, as evidenced by SEM and XPS.

Additionally, the [Ni(MeSeO)2(H₂O)2] complex exhibits lower electronegativity (χ) and lower chemical hardness (η), both of which reflect a reduced resistance to charge transfer and a greater tendency to release electrons, traits directly linked to high inhibition efficiency [25,26]. The lower electrophilicity index (ω) further underscores its nucleophilic character.

The spatial distribution of the frontier orbitals further clarifies the preferred adsorption centers. For MeSeOH, the HOMO is mainly localized over the aromatic ring, the azomethine nitrogen, and the selenium atom, revealing these sites as the dominant electron-donating centers that interact with surface Fe atoms. In contrast, the LUMO is delocalized over the π-system and heteroatoms, enabling some degree of back-donation from filled metal orbitals. For [Ni(MeSeO)2(H₂O)2] complex, the HOMO extends not only over the organoselenium ligand (N, O, and benzene rings) but also over the Ni–N/O coordination sphere, generating a highly polarizable donor framework that can simultaneously engage multiple surface Fe sites and stabilize a compact interfacial film. The LUMO of the complex remains localized on the ligand backbone, which allows limited back-donation but, combined with the high HOMO energy and small ΔE, yields a net electronic profile dominated by forward donation, consistent with its superior inhibitory efficiency.

In sum, while MeSeOH shows modest donor capability, Ni(II) coordination creates a highly polarized, electron-rich architecture optimized for interfacial bonding with steel. The combined electronic profile higher HOMO, smaller ΔE, greater softness, and more substantial net electron donation fully explains why [Ni(MeSeO)2(H₂O)2] complex achieves 95.5% inhibition compared to 89.6% for the ligand alone. This synergy between metal center and organic scaffold exemplifies a rational design strategy for next-generation corrosion inhibitors.

3.6. MC simulations

To gain deeper insight into the interaction between our inhibitors and the steel surface, Monte Carlo (MC) simulations were performed to model the adsorption of MeSeOH and [Ni(MeSeO)2(H₂O)2] complex on the Fe(110) surface a representative model of Q235 carbon steel in a simulated 0.5 M H₂SO₄ environment containing water, hydronium, and sulfate ions.

As shown in Figure S8 (Supporting Information), both molecules adopt a near-parallel (planar) orientation on the metal surface. This configuration maximizes contact between the electron-rich aromatic ring, selenium, nitrogen, and oxygen atoms and the Fe surface, thereby enhancing surface coverage and blocking active corrosion sites consistent with the dense protective films observed in our SEM and XPS analyses [25,26].

Computed adsorption energies further support the superior performance of the [Ni(MeSeO)2(H₂O)2] complex, as shown in Table S2 (Supporting Information). In the unrelaxed state (initial adsorption), [Ni(MeSeO)2(H₂O)2] complex exhibits a significantly more negative adsorption energy (-2575.96 kcal mol-1) compared to MeSeOH (-1871.74 kcal mol-1). Following geometry relaxation (allowing molecular and surface rearrangements), the system stabilizes, with relaxed adsorption energies of 357.85 kcal mol-1 and 262.33 kcal mol-1, respectively. Although these absolute values are large (due to the simulation of adsorption over a 108 atom Fe surface), the relative difference clearly indicates stronger binding for the Ni complex, aligning perfectly with its higher experimental inhibition efficiency (95.5% vs. 90.6%) [49,50].

Moreover, the dEads/dNi values which reflect the displacement energy per adsorbed molecule show that [Ni(MeSeO)₂(H₂O)₂] complex (-553.17 kcal mol-1) displaces interfacial species more effectively than MeSeOH (-337.91 kcal mol-1). Critically, both inhibitors bind far more strongly than water (-17.71), H3O+ (-58.29), or SO42- (-99.62) [51]. This thermodynamic preference explains the spontaneous displacement of the solvation layer by inhibitor molecules, a key step in forming a stable protective barrier.

In sum, the MC results confirm that Ni(II) coordination enhances adsorption strength, surface coverage, and film stability, providing a compelling atomic scale rationale for the outstanding corrosion inhibition performance of [Ni(MeSeO)₂(H₂O)₂] complex in acidic media.

4. Conclusions

The OSe ligand MeSeOH and its respective chelate were prepared and characterized. The [Ni(MeSeO)2(H2O)2] complex showed octahedral geometries, with the ligand coordinating to the metal centers via the azomethine N and phenolic O atoms. The findings demonstrate that both MeSeOH and [Ni(MeSeO)2(H2O)2] provide an effective protective barrier for Q235-steel when immersed in H2SO4 (0.5 M). The enhancement in corrosion protection is generally associated with elevated charge-transfer resistance (Rct) and diminished corrosion current density (icorr) values. The shielding ability of these compounds improved in a concentration-dependent manner for both MeSeOH and [Ni(MeSeO)2(H2O)2]. The protective efficiencies of the MeSeOH and [Ni(MeSeO)2(H2O)2] were 90.6% and 95.5% at 20 × 10-5 M. The Gibbs free energy values suggested that interactions between the MeSeOH, [Ni(MeSeO)2(H2O)2], and Q235 steel exhibit a spontaneous nature. Additionally, the XPS analysis demonstrates the adsorption of the [Ni(MeSeO)2(H2O)2] inhibitor on the surface of Q235-steel in H2SO4 (0.5 M), signifying the enhancement of a protective film on the Q235-steel surface against a corrosive environment. The [Ni(MeSeO)2(H2O)2] exhibits outstanding corrosion inhibition properties compared to MeSeOH based on the quantum chemical parameters analyzed. Its higher reactivity, greater electron-donating ability, and lower charge-transfer resistance make it a more effective inhibitor.

Acknowledgements

This work was supported and funded by the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research, King Faisal University, Saudi Arabia [Grant No. KFU254788].

CRediT authorship contribution statement

Saad Shaaban: Supervision and Conceptualization Visualization, Data analysis, Methodology, and Writing–review & editing Tarek A. Yousef: Supervision and Conceptualization Visualization, Data analysis, Methodology, and Writing–review & editing Ahmed M. Abu-Dief: Supervision and Conceptualization Visualization, Data analysis, Methodology, and Writing–review & editing Amal H. T. Haffez: Visualization, Data analysis, Methodology, and Writing–review & editing Khadra B. Alomari: Visualization, Data analysis, Methodology, and Writing–review & editing Hanan A. Althikrallah: Visualization, Data analysis, Methodology, and Writing–review & editing Faisal M. Alkahtani: Visualization, Data analysis, Methodology, and Writing–review & editing Mohamed Alaasar: Visualization, Data analysis, Methodology, and Writing–review & editing Anwar A. Hameed: Visualization, Data analysis, Methodology, and Writing–review & editing Ahmed S. M. Al-Janabi: Supervision and Conceptualization Visualization, Data analysis, Methodology, and Writing–review & editing Kamal Shalabi: Supervision and Conceptualization Visualization, Data analysis, Methodology, and Writing–review & editing.

Declaration of competing interest

There are no conflicts of interest.

Data availability

The data supporting this article have been included as part of the supplementary information.

Declaration of generative AI and AI-assisted technologies in the writing process

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Supplementary data

Supplementary material to this article can be found online at https://dx.doi.org/10.25259/AJC_1212_2025.

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