SYNTHESIS AND ANALYSIS OF MIXED-LIGAND COMPLEXES OF Cu(II) ION WITH HYDROXYBENZAMIDE ISOMERS AND DIETHANOLAMINE

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 53 SYNTHESIS AND ANALYSIS OF MIXED-LIGAND COMPLEXES OF Cu(II) ION WITH HYDROXYBENZAMIDE ISOMERS AND DIETHANOLAMINE M.M. Yadgarova1, Sh.B. Khasanov2, O.I. Khudoyberganov3 Doctorate Student, Khorezm Ma’mun Academy1 PhD, Deputy Chairman of Khorezm Mamun academy for Scientific Affairs2 PhD., senior researcher of Khorezm Ma’mun Academy3 https://doi.org/10.5281/zenodo.17744461 Abstract. In this study, for the first time, a mixed-ligand complex of Cu(II) ion with 2hydroxybenzamide, 4-hydroxybenzamide, and diethanolamine was synthesized in aqueous solutions. The structure of the synthesized complexes was investigated using FT-IR spectroscopy and SEM-EDS (scanning electron microscopy with energy-dispersive spectroscopy) analysis. The results were recorded and final conclusions were drawn. Keywords: copper(II)acetate dihydrate, 2-hydroxybenzamide, 4-hydroxybenzamide, diethanolamine, FT-IR spectroscopy, SEM-EDS analysis. Introduction. Hydroxybenzamide derivatives — especially 2-hydroxybenzamide and 4hydroxybenzamide — are biologically active compounds. They possess anti-inflammatory, antibacterial, antifungal, antimicrobial, and antioxidant properties, and are widely used in medicine, pharmaceuticals, and therapy [1]. The molecules of these compounds contain functional groups with nitrogen and oxygen atoms capable of forming chelating bonds with metal ions [2]. Therefore, such ligands have attracted great interest in the fields of coordination chemistry, metal complex chemistry, and drug design. Hydroxybenzamides combined with nitrogen-containing ligands often form various coordination geometries (octahedral, square-planar, and tetrahedral). In particular, oand p-hydroxybenzamides play an important role in the formation of hydrogen bonds, π–π interactions, and supramolecular layers when coordinated with metal ions [3, 4]. Diethanolamine (DEA) contains two hydroxyl and one amino group, allowing it to act as a multidentate ligand that forms stable complexes with metal ions. Its combination with hydroxybenzamide derivatives provides a favorable basis for the synthesis of new mixed-ligand complexes [5]. In this study, a mixed-ligand complex of the Cu(II) ion with 2-hydroxybenzamide, 4-hydroxybenzamide, and diethanolamine was synthesized in aqueous solution, and its structure was investigated using FT-IR spectroscopy. The obtained results confirm the efficiency of coordination between these ligands and metal ions, indicating that such compounds are promising for future development of biologically active materials and pharmaceutical applications. Literature Review. Copper, as an essential trace element in the human body or as a component of various externally administered compounds, exerts significant biochemical effects. In the first case, it exists bound to proteins such as ceruloplasmin, albumin, and others; in the second, it forms complexes by binding to various ligands, which then interact with biomolecules— mainly proteins and nucleic acids. The multifaceted role of copper in biological systems has been confirmed by numerous studies. In particular, the involvement of copper in human diseases has been discussed from both medicinal-chemical [6] and biochemical perspectives [7], with emphasis placed on the molecular physiology of copper transport [8]. Most current studies focus on copper SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 54 homeostasis [9], its role in iron metabolism [10], and its significance in biological processes related to human physiology and pathology [11, 12]. Although many functions related to inorganic, noncomplexed copper homeostasis in the human body have been elucidated, only a few review articles address biochemical phenomena directly associated with the medical use of copper complexes. The growing interest in copper complexes arises from their potential as antimicrobial, antiviral, anti-inflammatory, antitumor agents, as well as enzyme inhibitors and chemical nucleases. In particular, the biochemical interactions between copper complexes and non-steroidal antiinflammatory drugs (NSAIDs) have been extensively studied [13]. Numerous Cu(II) complexes formed with NSAIDs have demonstrated higher anti-inflammatory and anti-ulcer activity and lower gastrointestinal toxicity compared to the parent drugs. These complexes are considered potential members of a new class of anti-inflammatory drugs, and their mechanism of action is explained by superoxide dismutase (SOD)-like activity. Other studies have shown that copperbased compounds can be applied as chemotherapeutic agents [14, 15]. Furthermore, several authors have drawn attention to the antiviral and antibacterial activities of Cu(II) complexes. Two new complexes — [Cu(Phen)(o-Hbza)(H₂O)₂][Cu(Phen)(o-Hbza)Cl]₂(o-Hbza) (I) and [Cu(Phen)(H₂O)(p-Hbza)Cl]•H₂O (II) — (where o-Hbza = o-hydroxybenzoic acid, p-Hbza = phydroxybenzoic acid, Phen = 1,10-phenanthroline) — were synthesized and characterized by single-crystal X-ray diffraction (CIF files: CCDC No. 975524 (I) and No. 975525 (II)), elemental analysis, IR spectroscopy, thermal analysis, and magnetic measurements. Complex I forms 1D chains through hydrogen bonding, which are further assembled into 2D supramolecular layers via π–π stacking interactions. Complex II, on the other hand, forms diad motifs through hydrogen bonding between dimeric units; these motifs are linked into 1D chains via π–π interactions and further connected through O–H⋅⋅⋅Cl hydrogen bonds to form 2D supramolecular networks. For [Cu(Phen)(o-Hbza)Cl]₂(o-Hbza) (I), the FT-IR absorption bands (KBr; ν, cm⁻¹) are as follows: 3447 (w), 3065 (w), 2924 (w), 1624 (m), 1583 (s), 1560 (s), 1517 (s), 1485 (s), 1450 (s), 1389 (vs), 1256 (s), 1220 (w), 1140 (s), 1107 (w), 1030 (m), 852 (s), 758 (s), 721 (s), 667 (s). For [Cu(Phen)(H₂O)(p-Hbza)Cl]•H₂O (II), the FT-IR absorption bands (KBr; ν, cm⁻¹) are: 3169 (m), 2673 (w), 1595 (vs), 1541 (vs), 1520 (s), 1506 (vw), 1425 (w), 1389 (vs), 1283 (s), 1242 (s), 1163 (s), 1101 (m), 849 (s), 789 (s), 721 (s), 700 (w), 669 (w), 636 (m), 507 (m) [16]. Research Methodology: Initially, 0.218 g (1 mmol) of copper(II) acetate dihydrate salt (Cu(CH₃COO)₂∙2H₂O) was taken and dissolved in a mixture of 5 mL of water and 5 mL of ethanol. Separately, 0.274 g (2 mmol) of 2-hydroxybenzamide and 4-hydroxybenzamide ligands were each dissolved in 10 mL of ethanol. Their pH values at room temperature (25 °C) were measured to be 6.36 for 2-OHBA and 2.63 for 4-OHBA. A 10 mL ethanolic solution of diethanolamine (0.21 g, 2 mmol) was prepared and added to the copper salt solution. Then, 2-hydroxybenzamide (and in subsequent processes 4-hydroxybenzamide) was gradually added to the reaction mixture, which was stirred magnetically at 60–70 °C for 2 hours. The pH of the medium was maintained within the range of 7.5–8.0 using an ammonium buffer solution. At the end of the process, the reaction mixture was cooled to room temperature and kept in a thermostat at a constant temperature of 40 °C for six days. Slow evaporation of the solvent yielded dark green monocrystals, which were subjected to IR spectral analysis [17]. The synthesis reaction can be represented as follows: Cu(CH3COO)×2H2O+2-OHBA+DEA=[Cu(2-OHBA)2DEA]×H2O+2CH3COOH +H2O Cu(CH3COO)×2H2O+4-OHBA+DEA=[Cu(4-OHBA)2DEA]×H2O+2CH3COOH +H2O SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 55 Based on the results obtained from IR and SEM-EDS spectral analyses, the structures of the newly synthesized complex compounds can be assumed to have the following configuration. Cu OO CH H2NH O CH NH2 H O N H OO Cu CH H2NH O CH NH2 H O N H OO OO [Cu(2-OHBA)DEA]×H2O b) [Cu(4-OBA)DEA]×H2O Analysis and Results: According to the IR spectral analysis, the ligands (L1 – 2hydroxybenzamide and L2 – 4-hydroxybenzamide) and diethanolamine (DEA) are coordinated with Cu(II) ions to form stable mixed-ligand complexes. In the IR spectra, the peaks corresponding to –OH, –NH2, and C=O groups have shifted or decreased in intensity as a result of complex formation. In particular, the downward shift of the carbonyl vibration bands indicates the formation of bonds between the metal ion and the ligands. Furthermore, new peaks observed around 500 cm⁻¹ confirm the presence of Cu–O and Cu–N coordination bonds [18]. a) Cu(CH3COO)2×2H2O+L1+DE A b) Cu(CH3COO)2×2H2O+L2+DE A 400500600700800900100011001200130014001500160017001800190020002200240026002800300032003400360038004000 cm-1 -8 -5 -3 0 3 5 8 10 13 15 18 20 23 25 28 30 33 35 38 %T 3408,22 3363,86 3203,76 3059,10 2791,00 2746,63 2686,84 2640,55 2430,31 2368,59 2202,71 2146,77 2092,77 1988,61 1946,18 1915,31 1888,31 1826,59 1799,59 1693,50 1637,56 1508,33 1454,33 1431,18 1373,32 1305,81 1170,79 1141,86 1122,57 1082,07 1037,70 879,54 856,39 775,38 763,81 740,67 690,52 655,80 617,22 567,07 530,42 518,85 460,99 418,55 Cu(CH3COO)2*2H2O + L1(at) + DEA 2:1 (01.03.2024) a) Description of the initial state of the reaction process. b) Description of the final state of the reaction process. c) Description of the obtained crystal. Figure 1. Images obtained during the synthesis process. 4005006007008009001000120014001600180020002200240026002800300032003400360038004000 cm-1 -3 0 3 5 8 10 13 15 18 20 23 25 28 30 33 35 %T 3423,65 3350,35 3238,48 2812,21 2763,99 2684,91 2617,40 2517,10 2488,17 2299,15 2260,57 2112,05 2027,19 1990,54 1936,53 1907,60 1888,31 1666,50 1620,21 1523,76 1454,33 1427,32 1384,89 1280,73 1255,66 1172,72 1141,86 1118,71 962,48 846,75 788,89 752,24 605,65 536,21 418,55 Cu(CH3COO)2*2H2O L2(sp)+DEA 3:1 (09.04.2024) SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 56 c) 2-hydroxybenzamide (L1) d) 4hydroxybenzamide (L2) Figure 2. IR spectra of the obtained complex compounds and ligands. 1-table Description L1 (2-GBA) L2 (4-GBA) 1-complex (Cu+L1+DEA) 2-complex (L2+DEA+Cu) –OH peak 3350–3400 cm⁻¹ 3350–3420 cm⁻¹ decreased in intensity. broadened peak C=O peak 1670 cm⁻¹ 1665 cm⁻¹ 1645 cm⁻¹( shifted peak) 1637 cm⁻¹ (shifted peak) –NH2 Available Available Elongated Elongated Cu–O/Cu–N not available not available 470–515 cm⁻¹ 475–520 cm⁻¹ To further investigate the morphological and elemental characteristics of the coordination bonding, scanning electron microscopy (SEM) and EDS analyses were performed. The SEM images (Figure 3) revealed an uneven, layered structure of the crystals, while the EDS analysis confirmed the presence of Cu, O, N, and C elements in the complex. This indicates that a stable and homogeneous mixed-ligand complex was formed during the synthesis process. The obtained results demonstrate that such hydroxybenzamides and alkanolamines can jointly Figure 3. Cu(CH3COO)2×2H2O + L2+DEA SEM-EDS spectrum image of the complex synthesized on this basis. 4005006007008009001000120014001600180020002200240026002800300032003400360038004000 cm-1 -3 0 3 5 8 10 13 15 18 20 23 25 28 30 33 35 %T 3408,22 3363,86 3207,62 3059,10 2791,00 2746,63 2686,84 2640,55 2505,53 2428,38 2366,66 2202,71 2144,84 2092,77 1988,61 1946,18 1915,31 1888,31 1799,59 1693,50 1637,56 1598,99 1510,26 1452,40 1433,11 1375,25 1305,81 1269,16 1172,72 1122,57 1083,99 1037,70 883,40 858,32 763,81 655,80 617,22 520,78 460,99 L1+salitsilamid SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 57 form complexes with Cu(II) ions. These complexes are considered promising for future applications as biologically active substances, pharmaceutical agents, or in materials science [19]. Conclusion: In this study, mixed-ligand complexes of Cu(II) ions with 2hydroxybenzamide, 4-hydroxybenzamide, and diethanolamine were successfully synthesized. The structures of the complexes were investigated using FT-IR spectroscopy and SEM-EDS analyses. The shifts in the vibrational bands of –OH, –NH₂, and C=O groups in the IR spectra, as well as the appearance of new peaks in the range of 470–520 cm⁻¹, confirmed the formation of Cu–O and Cu– N coordination bonds. SEM images revealed a layered and uneven morphology of the crystals, while EDS analysis confirmed the presence of Cu, O, N, and C elements in the complexes. The obtained results indicate that hydroxybenzamides and diethanolamine can jointly form stable mixed-ligand complexes with Cu(II) ions. Such complexes are considered promising for potential applications as biologically active compounds, pharmaceutical agents, and in materials science. REFERENCES 1. 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