THE SYNTHESIS, CHARACTERIZATION, DFT-OPTIMIZATION, BIOLOGICAL ASSAYS, AND HEAVY METAL STUDIES OF A NEW TETRA DENTATE DERIVATIVE LIGAND AND ITS COMPLEXES

 

Kwestan Namiq Aziz ^{1, *}, Eman Ibrahim Alsalihi ¹

 

¹Department of Chemistry, Faculty of Science and Health, Koya University, Koya, KOY45, Iraq

 

^* Corresponding author email: kwestan.200062336248@gmail.com

 

ABSTRACT:

A new tetra dentate derivative ligand [(E)-N-((E)-(2-(((Z)-1-hydroxybutylidene) amino) phenyl) (isopropylimino) methyl) butyrohydrazonic acid] [N₃O] type has been prepared from the condensation process of equimolar 2-aminobenzohydrazide, isopropyl amine and followed by another addition of butyric acid. Spectroscopic techniques as FT-IR, UV-visible, Mass spectrum, ¹H,¹³C-NMR, T.L.C., Melting point, Conductivity measurements, Magnetic moment, DFT-optimization studies and other methods have been used to characterize the ligand and its new complexes with the general formula [L(M₂)Cl₃.H₂O] (where M= Ni^II, Co^II, Cu^II, Mn^II, Cd^II, and Zn^II). Studying biological activity for the ligand and its complexes against two gram-positive and two gram-negative bacteria . The formed compounds were evaluated for antibacterial activity against two gram-positive and two gram-negative bacteria which are Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. The developed ligand and its metal complexes performed well versus both kinds of bacteria Scheme 1.

GRAPHICAL ABSTRACT:

Scheme 1: Graphical Abstract [ where M= Ni^II, Co^II, Cu^II, Cd^II, Zn^II, Mn^II]

 

1.       INTRODUCTION

        A Schiff base is the reaction of condensation between the carbonyl part of an aldehyde or ketone and a primary amine (Abu-Dief & Mohamed, 2015). Imine, anil, and azomethine are various nomenclature for Schiff base, characterized by the  functional group (Ghosh, et al., 2019). Since Schiff bases have basic properties due to the presence of an electron pair on the nitrogen atom (Hamad et al., 2024), Coordination chemistry science, analytical chemistry, colors and dyes, the polymer industry, vitamins, and enzymes for model biomolecules are just a few of the various diverse sectors in which they find use. It is commonly recognized that Schiff bases have herbicidal, antifungal medication, and anticancer properties (Nawaz, et al., 2020). In addition to their significant roles in catalysis and organic synthesis (Abd El‐Halim, 2018). Schiff bases can be from to poly dentate ligands that form extremely stable complexes with metals. Hydrazides of carboxylic acids are important chemical molecules that have garnered a lot of interest from scientists. As intermediates in the synthesis of several chemical derivatives, these substances are essential. Hydrazides have the typical chemical formula RCONHNH₂, where R stands for an aromatic or aliphatic group that has been substituted or left unsubstituted (Wang, et al., 2016). Isopropyl amine is an organic compound that is colourless liquid with an ammonia-like odour, hygroscopic, flammable, miscible with water. Isopropyl amine a basic substance that exhibits the protonation process, acylation, alkylation, and condensing reaction with carbonyls characteristic of other simple alkyl amines, similar to other simple aliphatic amines. Besides being a hair remover, it is also added to petroleum-based materials, used to create insecticides, and regulated in plastics. Isopropyl amine is a building block for the production of many different herbicides and also serves as an intermediate in the organic synthesis of coating materials, dyes, rubber compounds, pharmaceuticals, polymers, textiles, dyes, plastics, insecticides, adhesives, solvents, and other items (Kumar & Anthony, 2015). Butyric acid has the chemical formula CH₃CH₂CH₂CO₂H, and it is anaerobic bacteria naturally create butyric acid, a short-chain volatile fatty acid. Butyrate, or butanoates, are butyric acid salts and esters. It is a colourless, oily liquid with an acidic taste and a foul odour, followed by a sweet aftertaste that is comparable to ether. Although the acid is not found in large quantities in nature, its esters are. Butyric acid boils at 164.85°C (Baroi, Gavala, Westermann, & Skiadas, 2017). Butyric acid can be used in various ways such as food, cosmetic, the chemical, and pharmaceutical sectors all make substantial use of butyric acid (Xiao, 2018).

AIM OF THE PROJECT: The aim of this study is to prepare a new tetra dentate ligand and its complexes that form a crystal around metal ions in a tetrahedral geometrical shape (sp³). And expect that the complexes will find applications in various industries, and medicine.

SYNTHESIS

Experimental - Materials and Methods:

        Every chemical used in this project was of the reagent grade and was used exactly as Scharlau,Merck, and Fluka supplied it. The Infrared (FT-IR) spectra was done by two universities with two different instruments. The first one in the Koya University genetic center was recorded by using an FT-IR in the frequency of (4000-600 cm^-1), other one was at Hawler University, where FT-IR spectra was obtained by using a spectrophotometer range at (4000-400 cm^-1) with KBr discs. In the (800–200 nm) region, the Uv-visible was obtained using an Agilent Technologies UV-visible spectrophotometer. The ligand field and charge transfer were measured using (1.0 cm) quartz cells, with the ligand and complexes having a concentration of (10^-3 M) in ethanol. A Bruker BM6 equipment was used to record magnetic measurements for complexes at room temperature using Faraday's technique. Using a Buchi Melting Point B-540 electrothermal apparatus, it has been measured for all the novel complexes were determined. An AD8000 conductivity meter for measuring how well the compounds conduct electricity at (27 °C) a (10⁻³ M) solution of the samples in methanol. The ¹H and ¹³C NMR were examined with a Bruker Analytik 300 MHz spectrometer, using tetramethyl silane (TMS) as a reference and deuterated DMSO-d₆ as the solvent. An Agilent 5975C Mass spectrophotometer was used to analyse the mass spectrum in DMSO solvent.

Synthesis of Derived Ligand [N3O] Type:

        The first step to prepare the [N₃O] derivative ligand starts with 2-aminobenzohydrazide (5.50 g, 36.40 mmol) in (40 ml) of absolute ethanol alcohol, added 5 drop of glacial acetic acid, heated on a hot plate and then mixed with isopropyl amine (2.15 g, 36.31 mmol). After that, the mixture was refluxed and stirred for 4 hours, in 1:1 molar ratio respectively. Evaporated the solution to remove ethanol by oven and left until dried, red crystals have been formed, recrystallized with hot ethanol, (yield 91.2%, 6.31 g), m.p. (118-119°C).

        The reaction was followed the second step by the condensation reaction between a (40 ml) methanolic solution of synthesized ligand (5.98 g, 31.10 mmol) and butyric acid (5.49 g, 62.30 mmol) in a 1:2 ratio respectively. Refluxed on a hot plate for 4 hours. Upon evaporating the mother liquor, left until dried and a pale red crystal was obtained. The result of reaction gains (9.30 g) of the derived ligand, (Yield 89.9%), m.p. (81-83°C), the scheme of reaction demonstrates in Scheme 1.

Synthesis of [L(Ni2)Cl3.H2O] Complex:

        About (0.60 g, 1.80 mmol) of the new derivative ligand in 20 mL methanol dissolved, and (0.47 g, 3.63 mmol) of  NiCl₂.6H₂O salt dissolved in (20 ml) of hot distilled water was added to it, in the ratio of 2:1 metal: ligand respectively. Refluxed for 2 hours to obtain (0.73 g) grey precipitate. (Yield 70.7%), m.p. (288-290 °C).

        The remaining complexes have been synthesized similarly as the [L(Ni₂)Cl₃.H₂O] complex, and Table 1 shows the ligand and complexes physical characteristics.

 

Table 1: Some physical properties of ligand and its complexes

CHARACTERIZATION

FT-IR

FT-IR spectrum of the derivative ligand: In the spectrum of isopropyl amine Figure 1-B, two absorption bands at (3350 cm-1) that referred to the stretching vibration of υ(NH2) of the primary amine group (Akkuş Taş, 2024), and in the spectrum of 2-aminobnzohydrazide Figure 1-A displayed strong band at (1680 cm-1) assigned to the stretching vibration of υ(C=O) group (Islam & Mohsin, 2007). The two occurrence peaks were removed from the ligand's spectra. Figure 1-C, and switched with another new peak at (1616 cm-1) belongs to υ(C=N), indicating Schiff base reactions.

        From the spectrum of the generated ligand, Figure 1-C, we have been two additional little sharp peaks of (NH₂) amino group at (3441 cm^-1), and the butyric acid Figure 1-D displayed a strong band at (1710 cm^-1) referred to the stretching vibration of υ(C=O) group, twice again these two peaks has been dispersed in the spectrum of derivative ligand Figure 4-E, and substituted with υ(C=N) stretching at (1653 cm^-1) resulting from the Schiff base (Hadi, 2022), interaction for the second time.

FT-IR spectrum of the complexes:  In the spectrum of the derivative ligand Figure 2-E, the sharp peak at (1653 cm-1) that assign to the stretching υ(C=N). This band has been migrated to the range's lower frequencies (1637-1523 cm-1) for the NiII, CoII, CuII, MnII, CdII, and ZnII metal ion complexes respectively, Figure 2-F, G, H, I, J, and K in compression with that of the free ligand, resulting from the interaction between the metal and the ligand. Other peaks in the range of (572-510 cm-1) were assigned to stretching υ(M-O). Peaks within the range of (543-415 cm-1) were assigned to stretching υ(M-N). All the peaks have been summarized in Table 2.

Figure 1: FT-IR spectra of ligand and precursors of it.

 

 

 

Figure 2: FT-IR spectra derivative ligand and its complex’s

Table 2: FT-IR spectral data of the Ligand and its Complex’s

UV-Visible Analysis of the Derivative Ligand and its Complexes:

        The ligand's spectrum Figure 3-A illustrates a major absorption peak at (241 nm) (41493 cm-1) (∈max=900 molar-1cm-1) assigned to (π→ π*), with a shoulder peak at (342 nm) (29239 cm-1) (∈max=280 molar−1. cm−1) were assigned to (n→ π*) transition.

        The same case with the derivative ligand Figure 3-B, that shows a significant absorption peak at (248 nm) (40322 cm^-1) (∈max=880 molar^-1cm^-1) assigned to (π→ π*) (Singh, 2021), with a shoulder peak at (345 nm) (28985 cm^-1) (∈max=330 molar⁻¹. cm⁻¹) were referred to (n→ π*) transition (Kane, et al., 2016).

        While the spectrum of the Ni^II complex Figure 3-C, includes three peaks at (230 nm) (43478 cm^-1) (Îmax= 900 molar^-1. cm^-1), (275 nm) (36363 cm^-1) (Îmax= 380 molar^-1. cm^-1), and (348 nm)(28735 cm^-1) (Îmax= 150 molar^-1.cm^-1), were tasked with (π → π*), (n®p*), and charge transfer (C.T) transition respectively (Senthilkumar, 2021). Theoretically, three d-d transitions exist (³T₁³T₁(p)), (³T₁​→³T₂​), (³T₁³A₂) (Tanabe, 1954), but only peak at (620 nm)(16129 cm^-1)(Îmax=100 molar^-1.cm^-1) represents the high-energy  (³T₁³T₁(p))  band visible region is typically observed due to its intensity and experimental constraints, it is indicating tetrahedral structure around the Ni^II metal ion complexes. The lower-energy transitions require specialized techniques for detection. And Co⁺² complex same as Ni⁺² have three predicted d-d transitions (⁴A₂​→⁴T_1​(p)), (⁴A₂​→⁴T_2​(f)), (⁴A₂​→⁴T_1​(f)), but only one intense band is observed (Tanabe, 1954). All complexes are shown in Figure 3-D, E, F, G, and H. But only the Zn^II and Cd^II metal complexes do not included d-d transitions, because the d-orbitals at that case are filled, and there is no possibility for any electronic promotion in d-levels (Reddy, 2007). This peak is related to charge transfer transitions because the metal ion of compounds is a member of the (d10) system (Alsalihi, 2018). Table 3. provides a summary of all peaks.

Figure 3: The UV-vis Spectra of the ligand and its complex’s

 

Table 3: The UV-vis spectral data for the ligand and its complexes are explained in.

Thin Layer Chromatography:

        The T.L.C. measuring technique of the derived ligand and its complexes was done using NiII, CoII, CuII, MnII, CdII, ZnII metal ions in a 10 ml of ethyl acetate and 15 ml of n-hexane mixed solution. The results of the experiment revealed the development of new spots with distinct Rf readings in comparison to the Rf of the derived ligand. Table 4, the spot positions at (5.6 cm), (2.0 cm), (1.1 cm), (5.0 cm), (5.2 cm), and (4.9 cm) of NiII, CoII, CuII, MnII, CdII, ZnII metal ion complexes respectively different from the derived ligand spot position at (7.0 cm) accordingly, which suggests the creation of the complexes and the differences between all of themes indicate it, Figure 4.

 

Figure 4: Derivative ligand and its complexes T.L.C. measurement

 

Table 4: The TLC spot positions for ligand and its metal ion complexes

1H-NMR of Derivative Ligand:

        Nuclear magnetic resonance spectroscopy was done using DMSO-d6 solvent. Figure 5. Its assignments are detailed in Table 5. and the discussion concerning these assignments is outlined below: The Mass spectrum of [N3O] derivative ligand, exhibited the triplet signal at the range δ (0.9 ppm) corresponding to the (CH3) methyl group proton signal, the doublet signal at the range δ (1.6 ppm) corresponding to the (CH3) methyl group proton signal, the multiplet signal at the range δ (1.44 ppm) due to the (CH2) methylene group, the triplet signal at the range δ (2.11 ppm) due to the (CH2) methylene group, and a singlet signal at δ (2.4 ppm) assigned to (H) proton of DMSO solvent, and a multiplet signal of (CH) at δ (3.3 ppm) of methine group, A singlet signal of (NH) group at  δ (5.20 ppm) was caused by the proton of hydrazide. The multiplet signal of the proton of (CH) group ranged between δ (6.50-7.42 ppm) attributed to benzene ring. The broad singlet signal of hydroxyl (OH) group at δ (9.9 ppm) due to alcohol. All the mentioned signals indicate the precise structure of the [N3O] derived ligand (Diab, 2019).

Figure 5: ¹H-NMR spectrum of [N₃O] derivative ligand

 

 

Table 5: ¹H-NMR spectral data for [N₃O] derivative ligand

13C HNMR Spectroscopy:

        Based on 13C-NMR spectroscopy for [N3O] derivative ligand was done using the DMSO-d6 solvent. The number of signals detected correlates with the existence of magnetically nonequivalent carbon atoms. The signals of (CH3) at range (14.2-21.9 ppm) are attributed to the aliphatic carbon. The signals of the (CH2) group appear at the range (20-37 ppm) due to aliphatic carbon. While the signal of the DMSO solvent appears at (40 ppm). The signal of (C-H) group at (61.8 ppm) were assigned to methine. Six signals at the range δ (113.7-132.6 ppm) corresponding to (C=C) to aromatic carbon of the benzene ring. The bands appear at range between δ (150-175 ppm) is attributed to the azomethine carbon of the (CH=N) group of ligand. These results correspond with those of substances that have been previously distributed, as illustrated in Figure 6. Details of the remaining chemical changes are outlines in Table 6. (Kumagai, 2024).

 

Figure 6: ¹³C-NMR spectrum of [N₃O] derivative ligand

 

Table 6: ¹³C-NMR spectral data for [N₃O] derivative ligand

 

Mass Spectroscopy:

        The derivative ligand’s mass spectrum Figure 7, illustrates that the parent ion peak corresponds to [M]+ at (m/z=331.2), which aligns closely with the calculated molecular weight of the derivative ligand (332.45 g/mol). This observation further substantiates the superior synthesis and purity of the derivative ligand. All fragment structures are positioned accurately, and the cations and fragments with precise mass are detailed in Table 7 (Lockyer, 2024).

 

 

Figure 7: Mass spectrum of the derivative ligand

 

Table 7: Mass spectral data of the derivative ligand

APPLICATIONS

Conductivity Measurements:

        At room temperature, the molar conductance values of complexes were measured in methanol with a 10⁻³ M solution (Aran, 2025). The conductance values were below (50 Ohm⁻¹.cm².mol⁻¹) of all formed complexes, this indicates that all the complexes are non-electrolytic, Table 8.

 

Table 8: Molar Conductance data of the complexes

 

 

 

 

 

 

Biological activity:

        This study is focused on determining inhibitory effect against the development of four different kinds of harmful bacteria of the derivative ligand and its complexes two were gram-positive which are Staphylococcus aureus and Staphylococcus epidermidis, and the second two were gram-negative which are Escherichia coli and Pseudomonas aeruginosa  (Mukhtar, et al., 2021). The biological activity of compounds was studied using the inhibition method (Ali, et al., 2022). The derivative ligand and its metal ion complex may serve as bioactive agents for antibacterial action. The disk diffusion technique was employed to perform the experiments. The primary solution was prepared through the mixture of 60 mg of every component in 1 ml of solvent.

        N,N-dimethyl sulfoxide (DMSO), and then it was diluted three times in a row. The synthesized ligand exhibited inhibitory activity against Staphylococcus aureus after 24 hours, but not against other types of bacteria, and this inhibitory effect remained consistent after 48 hours. Table 9 illustrates the inhibition diameters of all substances. Moreover, under same experimental conditions with identical types of bacteria, the complexes demonstrated superior efficacy compared to the derivative ligand, as seen in Figure 8.

 

 

Figure 8: Antibacterial activity of derivative ligand [N₃O] and its complexes

 

Table 9: Inhibition zone (mm) for antibacterial action

                                                                                                

 

 

Magnetic Susceptibility:

        The magnetic moment in solid form has been determined by applying Faraday's theory. This allows the number of unpaired electrons to be counted. This should help with the bonding model and electrical structure predictions (Bain, 2008). Table 10. shows the results of measuring the effective magnetic moment (µ_eff =B.M) after measuring the magnetic susceptibility of a few chosen complexes at room temperature. By Using the formula (µ_eff =2.828) and according to the calculated μ eff it is demonstrated that some complexes are in a high spin state. The d orbital of Ni^II have 2 unpaired electrons and 3 paired electrons, Co^II have 3 unpaired electron and 2 paired electrons, Cu^II have 1 unpaired electron and 4 paired electrons, Mn^II has 5 unpaired electrons, but Cd^II and Zn^II have not unpaired electrons because they have 10 electrons in d orbital, therefore magnetic moment is equal to zero and doesn’t take magnetic susceptibility, Consequently, the hybridization is sp³, expressing the tetrahedral geometry structure for each complex. The magnetic moment value demonstrates that the complexes are paramagnetic and has high spin except Zinc and Cadmium complexes with low spin and diamagnetic and magnetic moment equal to zero.

 

[L(Ni₂)Cl₃·H₂O] (Ni^II, d⁸)

 

Calculated (µ_eff = 2.71) is generally slightly lower than the spin-only value (µ_eff = 2.83). Tetrahedral Ni^II is susceptible to spin-orbit coupling which reduces the magnetic moment.

[L(Co₂)Cl₃·H₂O] (Co^II, d⁷)

 

Calculated (µ_eff = 4.09) is generally slightly higher than the spin-only value (µ_eff= 3.87). Tetrahedral Co^II complexes always exhibit significant orbital angular momentum contribution because the ground state (⁴T₁) has significant orbital degeneracy. due to orbital contribution in tetrahedral Co^II complexes increase the magnetic moment well above the spin-only value.

 

[L(Cu₂)Cl₃·H₂O] (Cu^II, d⁹)

Calculated (µ_eff = 1.99) is generally slightly higher than the spin-only value (µ_eff= 1.73). This is typical for Cu^II complexes and arises from a small orbital angular momentum contribution.

 

[L(Mn₂)Cl₃·H₂O] (Mn^II, d⁵)

Calculated (µ_eff = 5.99)are very close to the spin-only value  (µ_eff= 5.92).  High-spin d⁵ (Mn^II) ion has spherically symmetric, half-filled shells. This results in negligible orbital angular momentum contribution. Any slight deviation from the spin-only value is usually due to weak spin-orbit coupling effects. The observed values are characteristic of high-spin Mn^II in tetrahedral field. The magnetic moments strongly support the suggested tetrahedral geometry for all complexes.

 

Table 10: Magnetic susceptibility (B.M) data of the complexes and suggested structure

Computational Studies- (DFT-Optimized Geometries)

HOMO-LUMO energies of [N3O] ligand: The LUMO, HOMO, and global properties of the indicated molecule present in Table 11. This data was acquired via the (LanL2DZ) basis set and the DFT/B3LYP theoretical framework. The energy gap denotes the disparity between a molecule's kinetic stability and its chemical reactivity, it including both EHOMO and ELUMO. A molecule possessing A molecule with a substantial HOMO-LUMO gap is considered hard. Less soft, indicating a diminutive size and markedly diminished polarizability. Table 11 shows that this is calculated based on the energy values of the (HOMO) and (LUMO). The negative chemical potentials of -4.7310 and -1.1581, respectively, show that these compounds are stable and do not decompose into their basic components. The HOMO-LUMO energy gap  (ΔE = 3.5729 eV) with the LanL2DZ basis set is a crucial parameter that defines the molecule’s stability and reactivity, with a larger gap signifying higher stability and lower chemical reactivity (Becke, 1993), The small energy gap with a LanL2DZ basis set indicates that this more flexible basis set can more effectively account for electron correlation, demonstrating significant electronic diffusion from donor to acceptor orbitals . The literature research indicates that systems exhibiting elevated ionization potential and chemical hardness demonstrate reduced reactivity. Soft molecules have greater reactivity than hard molecules owing to their superior electron transfer capacity. The ionization potential (IP = 4.7310 eV) quantifies the energy necessary to extract an electron from the molecule, reflecting its susceptibility to oxidation. Electron affinity (EA = 1.1581 eV) quantifies the energy produced upon the addition of an electron, indicating the molecule's propensity to acquire electrons. The chemical harshness (η = 1.7864eV) indicates the molecule's resistance to alterations in electron density, with elevated values denoting enhanced stability, whereas chemical softness (S = 0.5598 eV⁻¹), its reciprocal, denotes heightened reactivity.  A high Electronegativity (χ = 2.9445 eV) for the LanL2DZ basis set indicates a molecule's capacity to attract electrons, hence affecting its interactions with adjacent entities.  The electrophilicity index (ω = 2.4267 eV) measures the molecule's propensity for accepting electrons, which is essential for its reactivity (Parr, 1999). The back-donation energy (ΔE = -0.4466 eV) and, the transferred electrons (∆𝑁) exhibit positive values, (ΔN = 3.6224 eV), A positive ∆𝑁 indicates that the molecules are emitting electrons and signify electron transfer between the ligand and metal center, enhancing complex stability (Akbari, 2024). A high dipole moment the existence of a (LanL2DZ) (6.4156) component in a molecule indicates a significant level of electrical charge polarity (Lundgren, 2016).

 

 

Table 11: The quantum chemical parameters for the derivative ligand

Parameters	Values
HOMO (eV)	-4.7310
LUMO (eV)	-1.1581
ΔE (eV)	3.5729
Ionization potential IP"(eV)	4.7310
Electron affinity “EA"(eV)	1.1581
Chemical hardness "η" (eV)	1.7864
Chemical softness "S” (eV−1)	0.5598
Electronegativity "χ" (eV)	2.9445
Chemical potential "μ"(eV)	-2.9445
Electrophilicity "ω" (eV)	2.4267
Nucleophilicity "Nu" (eV-1)	0.4121
ΔE backdonation	-0.4466
Transfer electron fraction ΔN	3.6224
Dipole-moment (Debye)	6.4156

 

MEP: The Molecular Electrostatic Potential (MEP) map of the ligand explains its charge distribution and potential reactive sites. The MEP was calculated via the (DFT/LanL2DZ) basis set (Chérif, 2024). displaying areas with differing electrical potential. Figure 9 displays a representation of the (MESP) surface, according to Figure 9, The primarily green surface signifies a neutral electrostatic potential, indicating a balanced electron density devoid of notable nucleophilic or electrophilic characteristics.

        Small blue portions correspond to electron-deficient areas, potentially serving as electrophilic sites, whereas yellow regions signify electron-rich, nucleophilic sites and red regions indicate high electron density (negative charge concentration). The MEP analysis forecasts ligand-metal interactions and coordination, facilitating comprehension of chemical reactivity and biological activity.

 

 

Figure 9: The optimized structure, LUMO, HOMO and MEP for the derivative ligand

 

Stability Measurement of Derivative Ligand and its Complexes Using UV-Visible Spectroscopy :

        The stability of the made derivative ligand and its complexes was checked over time using UV-visible spectroscopy, with the absorbed spectra recorded at different times. The absorbed spectra were recorded at various intervals. The results showed that the UV-visible spectra for the ligand and all the made complexes stayed the same in every test, signifying no notable alteration in the maximum absorption values or variations in peak strength. This consistency indicates that the derivative ligand and its complexes maintain structural integrity and exhibit stability over time under experimental conditions. The lack of spectrum changes indicates the stability of the derivative ligand and its complexes, making it suitable for future applications in coordination chemistry and biological research (Ravichandran, 2014). The stability of the derivative ligand and all six complexes was assessed by measuring absorbance at various time intervals (24 hours, 48 hours, and one, two, and three weeks). No substantial changes in absorbance were observed, affirming its stability. The UV-visible spectra of the derivative ligand and all complexes are shown in Figure 10.

 

Figure 10: The stability UV-visible spectra of derivative ligand and all complexes.

 

Wastewater Heavy Metal Removal:

        Wastewater contamination is a significant global problem that affects both developed and developing countries. Contaminants in wastewater, such as heavy metals, chemicals, pharmaceuticals, and pathogens, can severely impact the environment, public health, and biodiversity. The removal of lead (Pb) from 0.1 Molar of Pb (CH3COO)2 in 200 ml of D.W and then divided into two containers the first one included just the lead metal ion solution, while the second solution contained the calculated amount from the derivative ligand, forming a brown precipitate by filtration concentration by a specific method in Baghdad University.

        [N₃O] type Schiff base derivative ligand is a practical approach for mitigating lead contamination. In this process, the lead ions in the wastewater, initially at a concentration of 5000 ppm in 100 mL of solution, interact with the derivative ligand to form a complex. After the reaction, the concentration of lead in the solution decreases to 3600 ppm, indicating a reduction of 1400 ppm. This reduction suggests that the derivative ligand has successfully chelated a portion of the lead ions, thus facilitating their removal from the wastewater. The derivative ligand, which typically features nitrogen and oxygen donor atoms, binds to the lead ions, forming a stable complex and reducing the free lead concentration and capturing it in the water by about 26%. This method is a promising strategy for treating contaminated wastewater, highlighting the potential of derivative ligands in environmental cleanup processes (Zaman Brohi, 2020).

CONCLUSION

        Spectroscopic analyses confirmed complex formation, with FT-IR spectra showing characteristic shifts indicating derivative ligand coordination. Uv-visible spectra showed distinct peaks in the visible region, confirming d-d transitions and metal ion coordination.  Furthermore, the 1H and 13C-NMR analyses corroborated the structure of the derivative ligand. The nature of the fragments in the mass spectrum frequently elucidates the derivative ligand's molecular structure. Measurements of magnetic moments indicate that the geometrical configuration of the complexes is tetrahedral. Conductivity measurements suggest that all complexes are non-electrolytic. Antibacterial studies against two-gram positive bacteria and two-gram negative bacteria revealed enhanced activity of CdII and ZnII complexes over the free derivative ligand. The DFT analysis indicates the HOMO-LUMO and all chemical and physical properties. MEP mapping delineates critical interaction sites for metal coordination and biological function.

Acknowledgement:

        I am grateful to Assist. Prof. Dr. Iman Ibrahim, my supervisor, for her support and direction. Many thanks to the head of the chemistry department for their help, and thanks to the assistant of the head of the chemistry department at Koya University.

Ethical Approval:

        In this research, we did not address any applications on humans or animals and did not seek support from any institution. Therefor have no moral obligations to others, also, this research is to complete the master's degree in inorganic chemistry. The Ethical Committee of the Koya University, Kurdistan region approved the current research.

Author Contributions:

Author Contributions: All authors have reviewed the final version to be published and agreed to be accountable for all aspects of the work.

Concept and design: Iman Ibrahim Abdulkareem Alsalihi and Kwestan Namiq Aziz

Acquisition, analysis, or interpretation of data: Iman Ibrahim Alsalihi and Kwestan Namiq Aziz

Drafting of the manuscript:  Iman Ibrahim Alsalihi and Kwestan Namiq Aziz

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