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Journals / Journal of the Turkish Chemical Society Section A: Chemistry / 2026 / Volume: 2026 Issue: 2

Novel Mixed-Ligand Co(II), Ni(II), and Cu(II) Complexes of Azo-Schiff Bases with 1,10-Phenanthroline and Metformin: Synthesis, Characterization, Molecular Docking, and Antibacterial Evaluation

Zainab Abbas(University of Mosul)0009-0001-0584-8751
Alyaa Al-Barwari(University of Mosul)0000-0003-0167-8027
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Publication Date
2026-10-03
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AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

The combined experimental and molecular docking results highlight the potential of these mixed-ligand complexes as promising bioactive coordination compounds.

📌 3 Key Takeaways

🎯
Objective & Hypothesis:In this study, two azo-Schiff base ligands were synthesized via condensation of vanillin and 4-(dimethylamino)benzaldehyde with 4-aminoazobenzene.
📊
Key Findings & Data:Mixed-ligand complexes of Co(II), Ni(II), and Cu(II) were synthesized using 1,10-phenanthroline (Phen) and metformin (Met), affording twelve complexes with a metal-to-ligand ratio of 1:2.
💡
Conclusion & Impact:The combined experimental and molecular docking results highlight the potential of these mixed-ligand complexes as promising bioactive coordination compounds.
🔬Design:Research Article
📍Scope:Comprehensive Sample
⚙️Variables:Coordination compounds · Transition metal complexes · Octahedral geometry

Abstract

In this study, two azo-Schiff base ligands were synthesized via condensation of vanillin and 4-(dimethylamino)benzaldehyde with 4-aminoazobenzene. Mixed-ligand complexes of Co(II), Ni(II), and Cu(II) were synthesized using 1,10-phenanthroline (Phen) and metformin (Met), affording twelve complexes with a metal-to-ligand ratio of 1:2. The synthesized ligands and their complexes were characterized using FT-IR, 1H-NMR, UV-Vis spectroscopy, atomic absorption spectroscopy (AAS), elemental analysis (C, H, N), molar conductivity, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD analysis revealed an average crystallite size of 56 nm using Scherrer's equation. Spectral data confirmed coordination through the azomethine and azo nitrogen atoms, while electronic spectra and magnetic measurements supported octahedral geometry around the metal ion. The effective magnetic moments were 3.91-4.25 B.M. for Co(II), 2.654-2.899 B.M. for Ni(II), and 1.65-1.721 B.M. for Cu(II) complexes. Molar conductivity values (135-170 Ω-1cm2mol-1) indicated that complexes behave as 1:2 electrolytes. TGA confirmed the presence of water of crystallization, whereas SEM revealed aggregated nanostructures with particle sizes of 130-270 nm. Molecular docking studies against the bacterial protein (1JIK) and acetylcholinesterase (1B41) showed favorable binding affinities, with ligand L2 exhibiting the highest affinity toward the acetylcholinesterase target (-9.494 kcal/mol). Antibacterial evaluation against Escherichia coli and Staphylococcus aureus demonstrated enhanced activity of the complexes compared with the free ligand, with complex 5 showing the highest inhibition zones (22 and 20 mm, respectively). The combined experimental and molecular docking results highlight the potential of these mixed-ligand complexes as promising bioactive coordination compounds.

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Cite This Article

Abbas, Z., Al-Barwari, A. (2026). Novel Mixed-Ligand Co(II), Ni(II), and Cu(II) Complexes of Azo-Schiff Bases with 1,10-Phenanthroline and Metformin: Synthesis, Characterization, Molecular Docking, and Antibacterial Evaluation. Journal of the Turkish Chemical Society Section A: Chemistry, Volume: 2026 Issue: 2. https://doi.org/10.18596/jotcsa.1960619

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  38. Singh HL, Khaturia S, Solanki VS, Sharma N. Synthesis of coordination compounds of dibutyltin(IV) with schiff bases having nitrogen donor atoms. J Indian Chem Soc. 2023 Mar;100(3):100945. Available from:.
  39. Wang R, Lee CS, Lu Z. Recent development of three-coordinated boron-doped aromatics for optoelectronic applications. J Organomet Chem. 2023 Jan;984:122564. Available from:.
  40. Katouah H, Hameed AM, Alharbi A, Alkhatib F, Shah R, Alzahrani S, et al. Green synthesis strategy for new schiff‐base complexes: Characterization, conductometry, in vitro assay confirmed by in silico approach. ChemistrySelect. 2020 Sep 7;5(33):10256–68. Available from:.
  41. Al-Abbasy O, Alsarraf Z, Mahdi N, Al-Barwari A. Ascorbic acid: Rationale and applications in inhibiting enzymatic browning of fruits and vegetables-A comprehensive review. Iran Food Sci Technol Res J. 21(6):697–715. Available from:.
  42. Pang X, Lv J, Zhu C, Qin L, Yu Y. Photodeformable azobenzene‐containing liquid crystal polymers and soft actuators. Adv Mater. 2019 Dec 9;31(52):1904224. Available from:.
  43. Saleh MY, Al-barwari ASMO, Ayoob AI. Synthesis of some novel 1,8-naphthyridine chalcones as antibacterial agents. J Nanostructures. 2022 Jul 1;12(3):598–606. Available from:.
  44. Derafa W, A.A. Elkanzi N, M. Ali A, Abdou A. Three Co(II), Ni(II) and Cu(II) schiff base complexes incorporating 2-[(4-{[(4-methylphenyl)sulfonothioyl]oxy}phenyl)methylene] amino}benzoic acid: Synthesis, structural, dft, biological and molecular docking investigation. Bull Chem Soc Ethiop. 2024 Jan 23;38(2):325–46. Available from:.
  45. Raj J, Jain A, Sharma N, Kumari A, Fahmi N. Synthesis, spectral characterization, and biological activities of novel palladium(II) and platinum(II) complexes of active Schiff base ligands. Bull Chem Soc Ethiop. 2023 Sep 19;37(6):1383–96. Available from:.
  46. Genchi G, Carocci A, Lauria G, Sinicropi MS, Catalano A. Nickel: Human health and environmental toxicology. Int J Environ Res Public Health. 2020 Jan 21;17(3):679. Available from:.
  47. Ali M. F, S.M.O. Al-barwari A. Divalent transition metal complexes with mixed of β-enaminone and N,O-donor ligands: Synthesis, characterization and biological assessment. Bull Chem Soc Ethiop. 2024 Oct 25;39(1):65–78. Available from:.
  48. Kargar H, Aghaei-Meybodi F, Behjatmanesh-Ardakani R, Elahifard MR, Torabi V, Fallah-Mehrjardi M, et al. Synthesis, crystal structure, theoretical calculation, spectroscopic and antibacterial activity studies of copper(II) complexes bearing bidentate schiff base ligands derived from 4-aminoantipyrine: Influence of substitutions on antibacterial activity. J Mol Struct. 2021 Apr;1230:129908. Available from:.
  49. Saleh MY, Aldulaimi AKO, Saeed SM, Adhab AH. Palladium fabricated on Fe3O4 as an organic-inorganic hybrid nanocatalyst for the Suzuki and Stille coupling reactions. J Mol Struct. 2025 Feb;1321:139597. Available from:.
  50. Othman AY, Saleh MY, Owaid KA. Recyclable bio-functionalized graphene oxide nanocatalyst for sustainable and high-yield synthesis of arylimine-substituted benzo[b]pyridonaphthyridin-7-one derivatives in water. J Nanostructures. 2025 Jul 1;15(3):1463–74. Available from:.
  51. Witwit IN, Mubarak HM, Ibrahim RA, Majeed MM. Synthesis, coordination study, and anti-microbial ability of new mixed-ligand complexes derivatized from azo imidazole, and 1, 10-phenanthroline. Microb Biosyst. 2024 Dec 20;9(2):19–29. Available from:.
  52. Pervaiz M, Sadiq S, Sadiq A, Younas U, Ashraf A, Saeed Z, et al. Azo-Schiff base derivatives of transition metal complexes as antimicrobial agents. Coord Chem Rev. 2021 Nov;447:214128. Available from:.
  53. Al-Adilee KJ, Hasan SR. Synthesis, characterization and biological activity of heterocyclic azo-schiff base ligand derived from 2-Amino-5-methyl thiazol and some transition metal ions. IOP Conf Ser Earth Environ Sci. 2021 Jun 1;790(1):012031. Available from:.
  54. Ali IM, Said MH, AlWazni W. Synthesis, characterization, and studying of new azo-azomethine ligand and its complexes: Analysis of their biological activity. In: The 9th International Conference on Applied Science and Technology (ICAST 2021). 2022. p. 040014. Available from:.
  55. Hadi MA, Kareem IK. Synthesis, characterization and spectral studies of a new azo-schiff base ligand derived from 3,4-diamino benzophenone and its complexes with selected metal ions. Res J Adv Sci. 2020;1(1):54–73. Available from:.
  56. Geary WJ. The use of conductivity measurements in organic solvents for the characterisation of coordination compounds. Coord Chem Rev. 1971 Oct;7(1):81–122. Available from:.
  57. Mohammed LA, Mahdi NI, Aldujaili RAB. Preparation, characterization and the biological activity study of a new heterocyclic (Azo-Schiff base) ligand and their complexation with {Co,Ni,Cu,Zn(II)} ions. Egypt J Chem. 2020 Jan 1;63(1):289–300. Available from:.
  58. Rafeeq NH, Sheat AM, Altayy MAM. Synthesis and spectroscopic studies of some new 4-amino-7-nitro acridin 9 (10H) one Schiff base complexes. In: 2nd International Conference of Mathematics, Applied Sciences, Information and Communication Technology. 2023. p. 030024. Available from:.
  59. El-Lateef HMA, Ali MA, Mai MK, Abdou A. New iron(III), cobalt(II), nickel(II), copper(II), zinc(II) mixed-ligand complexes: Synthesis, structural, DFT, molecular docking and antimicrobial analysis. Bull Chem Soc Ethiop. 2023 Nov 29;38(1):147–66. Available from:.
  60. Vatagude SD, Horitani M, Gurubasavaraj PM. Ligand-field modulation, Jahn–Teller distortion and redox behavior in Cu(II) schiff base complexes. Dalt Trans. 2026; Available from:.
  61. Aziz DM, Hassan SA, Aziz SB. Synthesis and characterization of enhanced azo-azomethine doped PANI/HCl conducting polymers for electrochemical applications. Sci Rep. 2024 Aug 5;14(1):18122. Available from:.
  62. Aziz DM, Hassan SA, Hamad OQ. Azo-azomethine complex activity and sensor potential toward Ca(II) ion in life samples: The spectroscopic and morphological studies. J Mol Struct. 2023 Dec;1293:136204. Available from:.
  63. Mohammed KF, Hasan HA. Synthesis, chemical and biological activity studies of azo-schiff base ligand and its metal complexes. Chem Methodol. 2022 Dec 1;6(12):905–13. Available from:.
  64. Alshdoukhi IF, Al-barwari ASMO, Mohammed Aziz N, Khalil T, Faihan AS, Al-Jibori SA, et al. Pd(II), Pt(II), Zn(II), Cd(II) and Hg(II) complexes of the newly prepared 1,2-benzo- isothiazol-3(2H)-dithiocarbamate (BIT-DTC) ligand. Bull Chem Soc Ethiop. 2024 Apr 30;38(4):889–99. Available from:.
  65. Kurdy RN, Kareem IK. Synthesis, characterization and study of molecular docking of a new azo-schiff base ligand with its metal complexes. J Kufa Chem Sci. 2024 Nov 1;3(3):68–85. Available from:.
  66. Ismail Yousif E, Ibrahim Ahmed A, Al-Jeboori MJ. Synthesis, characterisation, thermal analysis and antimicrobial evaluation of an azo–schiff base derived from 4‑aminoantipyrine and its selected transition metal complexes. Bull Pharm Sci Assiut Univ. 2026 Jan 20;49:237–55. Available from:.
  67. Rezaie MA, Khojastehnezhad A, Shiri A. Post-synthetic modification of Zr-based metal organic framework by schiff base zinc complex for catalytic applications in a click reaction. Sci Rep. 2024 Oct 20;14(1):24644. Available from:.
  68. Rani A, Sharma J, Ramasamy SK, Aman S. Schiff base metal complexes as dual antimicrobial and anticancer agents: Synthesis, characterization, DFT, and molecular docking investigations. ChemistrySelect. 2026 Jan 10;11(2):e05632. Available from:.
  69. Juyal VK, Thakuri SC, Panwar M, Rashmi, Prakash O, Perveen K, et al. Manganese(II) and Zinc(II) metal complexes of novel bidentate formamide-based Schiff base ligand: Aynthesis, structural characterization, antioxidant, antibacterial, and in-silico molecular docking study. Front Chem. 2024 Jul 19;12. Available from:.
  70. Slyvka YI, Pokhodylo NT, Mys’kiv MG. Copper(I) п-complexes with allyl substituted 1-aryl-1H-tetrazole-5-thiols: Synthesis and their structural features. Vopr Khimii i Khimicheskoi Tekhnologii. 2019;(2):30–8. Available from:.
  71. Al-Barwari ASMO, Faihan AS, Ashfaq M, Behjatmanesh-Ardakani R, Al-Shammari RH, Tahir MN, et al. Bis(diphenyl)phosphinomethane platinum(II) complex of 1-(benzo[d]thiazol-2-yl)-3-phenylthiourea: Crystal structure and DFT study. J Mol Struct. 2024 May;1304:137624. Available from:.
  72. Soliman ABM, Abdel-Mawgoud AMM, El‑Raheem WMA, Abu-Dief AM, Abdou A. New octahedral Co(II)/Ni(II) and square-pyramidal VO(II) complexes derived from azo-schiff-base ligand: Synthesis, spectroscopic, DFT, molecular docking, and biological profiling correlation. J Mol Struct. 2026 Aug;1366:146114. Available from:.