Synthesis of the Three Mixed-ligand Metal Complexes and One Organic Salt of 3,5-Dinitrobenzoic Acid for Biopharmaceutica
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ORIGINAL PAPER
Synthesis of the Three Mixed‑ligand Metal Complexes and One Organic Salt of 3,5‑Dinitrobenzoic Acid for Biopharmaceutical Optimization Through Monoethanolamine: Structures and DFT Studies of Complexes Avazbek B. Ibragimov1 · Jamshid M. Ashurov1 · Aziz B. Ibragimov2 · Alisher G. Eshimbetov3 Received: 27 May 2020 / Accepted: 26 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The simplest derivatives of benzoic acid show a wide spectrum of the biological action mostly being poor water soluble. In order to demonstrate on example of 3,5-dinitrobenzoic acid (DNBA) a possibility of the simultaneous enhancement of water solubility and antimicrobial activity the complexation (salt formation and metal coordination) approach has been examined. Monoethanolamine (MEA) is selected as the complexing agent. Three isomorphic mixed-ligand complexes of Cu, Ni, Co with DNBA and MEA as well one organic salt in the polymorphic form have been synthesized and their structures are characterized by the element analysis, FTIR and X-ray crystallography. Measurements of water solubility and determination of the antimicrobial activity attest that a solubility of the copper mixed-ligand complex and organic salt is increased about four and eight times with simultaneous enhancement of the bioactivity. The DFT studies by B3LYP/def2-TZVP and B3LYP/6-311G (d,p) showed that Cu, Ni, and Co complexes with DNBA and MEA have high-spin ground electronic states as a doublet, triplet and quartet, respectively. Calculated bond lengths and bond angles of all metal complexes in higher-spin ground electronic states are in good agreement (about R 2 = 0.97) with X-ray data. Additionally, the energies of the frontier MOs and frontier electron densities and also electrostatic potential of isostructural complexes have been analyzed by the DFT/6-311G(d,p) method. Graphic Abstract The water solubility and bioactivity of poorly soluble 3,5-dinitrobenzoic acid are enhanced by a preparation of three isostructural metal complexes and one polymorphic organic salt with participation of monoethanolamine and DFT study of metal complexes has been carried out.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10870-020-00864-z) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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Vol.:(0123456789)
Journal of Chemical Crystallography
Keywords Metal complex · Organic salt · X-ray structure · H-bond · Polymorphism · Water solubility · Bioactivity · DFT study
Introduction The simplest monoderivative of benzoic acid, 4-nitrobenzoic acid, demonstrates a very low antimicrobial activity against bacteria and yeasts, e.g., against filamentous fungi M. gypseum with minimal inhibitory concentration (MIC) of 2 mmol·l–1 [1, 2]. Biological activity of benzoic acid binitroderivatives, for instance, 3,5- dinitrobenzoic acid (DNBA) is even less and its MIC is equal to 3 mmol·l–1 ag
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