Designing Functional Coordination Motif: Structural and Electronic Insights from a Nicotinamide-Co(II) Complex

Authors : Mücahit Özdemir

Pages : 371-384

Doi:10.7240/jeps.1794749

View : 50 | Download : 181

Publication Date : 2025-12-23

Article Type : Research Paper

Abstract :A new cobalt(II) complex containing nicotinamide has been synthesized and structurally characterized. Single crystal X-ray diffraction revealed that the complex crystallizes in the triclinic P-1 space group, with the Co(II) center surrounded by two nicotinamide ligands and four water molecules, forming a slightly distorted octahedral geometric arrangement. Thiophene-2-carboxylate anions in the unit cell are not ligands but anionic counterions, contributing to the stability of the structure through hydrogen bonds. The complex exhibits a broad absorption band in the 200-350 nm range, while a broad d-d transition band is observed in the 350-650 nm range. The electrochemical HOMO-LUMO gap was measured as 1.82 eV, while the theoretical band gap of 4.40 eV and the optical band gap of 4.32 eV were found to be quite close, and this result is in good agreement with the observed data. Hirshfeld surface analysis highlighted the fundamental role of hydrogen bonds and π–π interactions in crystal structures. The data obtained in this study contribute to the comprehensive understanding of the effects of non-coordinating counterions in cobalt(II)-nicotinamide systems and expand the knowledge base for the design of charged coordination compounds with broad application potential.
Keywords : Kobalt(II) kompleks, nikotinamid, tek-kristal XRD, DFT

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