Research Article

Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin

Volume: 2026 Number: 2 July 31, 2026

Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin

Abstract

This study describes a multi-step synthetic protocol for constructing a coumarin-based scaffold, subsequently functionalized into a versatile Schiff base intermediate. This precursor served as a foundational unit for synthesizing a series of novel heterocyclic derivatives through five distinct cyclization strategies. A specific derivative was coordinated as a bidentate ligand to yield a novel Cobalt (II) complex (Q11). Comprehensive characterization via molar conductivity and magnetic susceptibility confirmed the formation of a non-electrolytic complex, while FE-SEM analysis revealed its nanostructured nature. Spectroscopic data (µeff = 1.95 B.M.) corroborated a rare low-spin, tetragonally distorted octahedral (D4h) geometry with a (t2g6eg1) geometry for the Cobalt complex. The antimicrobial screening of the synthesized heterocyclic derivatives and the Cobalt(II) complex against Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae revealed significant biological potency. Notably, compounds (Q5-Q6) exhibited larger inhibitory zones than the antibiotic control, while the nanostructured complex (Q11) demonstrated superior activity, particularly against the resistant K. pneumoniae strain (22 mm). In addition, molecular docking simulations were performed for these derivatives against bacterial DNA gyrase targets (PDB IDs: 2XCT and 4DX5). The results revealed exceptional binding affinities of -10.6 kcal/mol for Q5 and -10.2 kcal/mol for Q6, significantly outperforming the reference drugs Ciprofloxacin and Ceftriaxone. A high correlation was observed between the in silico binding energies and the in vitro results. These findings, highlighting the superior potency of the nanostructured complex in overcoming diverse membrane barriers of both Gram-positive and Gram-negative bacteria, position this series as a promising candidate for high-surface-area catalysis and advanced biomedical applications.

Keywords

Supporting Institution

None

Ethical Statement

Not applicable. This study is purely chemical synthesis and characterization and does not involve any biological, human, or animal testing.

Thanks

The authors would like to express their sincere gratitude to their home institutions for providing the necessary laboratory facilities and financial support to conduct this research. Special thanks are also extended to the technical staff at the analytical centers for their assistance with FE-SEM and other characterization measurements.

References

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Details

Primary Language

English

Subjects

Transition Metal Chemistry

Journal Section

Research Article

Publication Date

July 31, 2026

Submission Date

March 14, 2026

Acceptance Date

May 18, 2026

Published in Issue

Year 2026 Volume: 2026 Number: 2

APA
Almolah, M. H., Al-Assafe, A., & Al-Jawaherı, Y. (2026). Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin. Journal of the Turkish Chemical Society Section A: Chemistry, 2026(2), 1-14. https://doi.org/10.18596/jotcsa.1909496
AMA
1.Almolah MH, Al-Assafe A, Al-Jawaherı Y. Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin. JOTCSA. 2026;2026(2):1-14. doi:10.18596/jotcsa.1909496
Chicago
Almolah, Mohamed H., Amaal Al-Assafe, and Yassır Al-Jawaherı. 2026. “Synthesis, Nano-Structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin”. Journal of the Turkish Chemical Society Section A: Chemistry 2026 (2): 1-14. https://doi.org/10.18596/jotcsa.1909496.
EndNote
Almolah MH, Al-Assafe A, Al-Jawaherı Y (July 1, 2026) Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin. Journal of the Turkish Chemical Society Section A: Chemistry 2026 2 1–14.
IEEE
[1]M. H. Almolah, A. Al-Assafe, and Y. Al-Jawaherı, “Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin”, JOTCSA, vol. 2026, no. 2, pp. 1–14, July 2026, doi: 10.18596/jotcsa.1909496.
ISNAD
Almolah, Mohamed H. - Al-Assafe, Amaal - Al-Jawaherı, Yassır. “Synthesis, Nano-Structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin”. Journal of the Turkish Chemical Society Section A: Chemistry 2026/2 (July 1, 2026): 1-14. https://doi.org/10.18596/jotcsa.1909496.
JAMA
1.Almolah MH, Al-Assafe A, Al-Jawaherı Y. Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin. JOTCSA. 2026;2026:1–14.
MLA
Almolah, Mohamed H., et al. “Synthesis, Nano-Structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin”. Journal of the Turkish Chemical Society Section A: Chemistry, vol. 2026, no. 2, July 2026, pp. 1-14, doi:10.18596/jotcsa.1909496.
Vancouver
1.Mohamed H. Almolah, Amaal Al-Assafe, Yassır Al-Jawaherı. Synthesis, Nano-structural Characterization, and Spectral Investigation of a Rare Low-Spin Distorted Octahedral (D4h) Cobalt(II) Complex Derived from Coumarin. JOTCSA. 2026 Jul. 1;2026(2):1-14. doi:10.18596/jotcsa.1909496