Several novel copper (II) complexes of reduced Schiff bases containing fluoride substituents were prepared and structurally characterized by single-crystal X-ray diffraction. The complexes exhibited diverse structures, with the central atom in distorted tetrahedral geometry. The biological effects of the products were evaluated, specifically their cytotoxicity, antimicrobial, and antiurease activities, as well as affinity for albumin (BSA) and DNA (ct-DNA). The complexes showed marked cytotoxic activities in the HepG2 hepatocellular carcinoma cell line, considerably higher than the standard cisplatin. The cytotoxicity depended significantly on the substitution pattern. The best activity was observed in the complex with a trifluoromethyl group in position 4 of the benzene ring-the dichloro[(±)-trans-N,N'-bis-(4-trifluoromethylbenzyl)-cyclohexane-1,2-diamine]copper (II) complex, whose activity (IC50 28.7 μM) was higher than that of the free ligand and markedly better than the activity of the standard cisplatin (IC50 336.8 μM). The same complex also showed the highest antimicrobial effect in vitro. The affinity of the complexes towards bovine serum albumin (BSA) and calf thymus DNA (ct-DNA) was established as well, indicating only marginal differences between the complexes. In addition, all complexes were shown to be excellent inhibitors of the enzyme urease, with the IC50 values in the lower micromolar region.

Department Chemical Theory of Drugs Faculty of Pharmacy Comenius University in Bratislava Odbojárov 10 832 32 Bratislava Slovakia

Department of Cell and Molecular Biology of Drugs Faculty of Pharmacy Comenius University in Bratislava Odbojárov 10 832 32 Bratislava Slovakia

Department of Materials Chemistry Institute of Inorganic Chemistry of the CAS Husinec Řež č p 1001 250 68 Řež Czech Republic

NMR Laboratory Faculty of Pharmacy Comenius University in Bratislava Odbojárov 10 832 32 Bratislava Slovakia

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Qin W., Long S., Panunzio M., Biondi S. Schiff bases: A short survey on an evergreen chemistry tool. Molecules. 2013;18:12264–12289. doi: 10.3390/molecules181012264. PubMed DOI PMC

Sankar R., Sharmila T.M. Schiff bases-based metallo complexes and their crucial role in the realm of pharmacology. A review. Results Chem. 2023;6:101179. doi: 10.1016/j.rechem.2023.101179. DOI

Nguyen Q.T., Jeong J.H. Syntheses and X-ray structures of Cu(II) and Zn(II) complexes of N,N′-dibenzyl-(R,R)-1,2-diaminocyclohexane and application to nitroaldol reaction. Polyhedron. 2008;27:3227–3230. doi: 10.1016/j.poly.2008.07.011. DOI

Sharma M., Joshi P., Kumar N., Joshi S., Rohilla R.K., Roy N., Rawat D.S. Synthesis, antimicrobial activity and structure-activity relationship study of N,N-dibenzyl-cyclohexane-1,2-diamine derivatives. Eur. J. Med. Chem. 2011;46:480–487. doi: 10.1016/j.ejmech.2010.11.027. PubMed DOI

Rafii E., Dassonneville B., Heumann A. Highly selective R,S-coordination of non racemic (1R,2R)-(1,2-dialkyl)-1,2-diamine cyclohexane derivatives to palladium dichloride. Chem. Commun. 2007;2007:583–585. doi: 10.1039/b613961b. PubMed DOI

Evans D.A., Seidel D. Ni(II)−bis[(R,R)-N,N′-dibenzylcyclohexane-1,2-diamine]Br2 catalyzed enantioselective Michael additions of 1,3-dicarbonyl compounds to conjugated nitroalkenes. J. Am. Chem. Soc. 2005;127:9958–9959. doi: 10.1021/ja052935r. PubMed DOI

Habala L., Varényi S., Bilková A., Herich P., Valentová J., Kožíšek J., Devínsky F. Antimicrobial activity and urease inhibition of Schiff bases derived from isoniazid and fluorinated benzaldehydes and of their copper(II) complexes. Molecules. 2016;21:1742. doi: 10.3390/molecules21121742. PubMed DOI PMC

Oboňová B., Habala L., Litecká M., Herich P., Bilková A., Bilka F., Horváth B. Antimicrobially active Zn(II) complexes of reduced Schiff bases derived from cyclohexane-1,2-diamine and fluorinated benzaldehydes—Synthesis, crystal structure and bioactivity. Life. 2023;13:1516. doi: 10.3390/life13071516. PubMed DOI PMC

Aston N.S., Watt N., Morton I.E., Tanner M.S., Evans G.S. Copper toxicity affects proliferation and viability of human hepatoma cells (HepG2 line) Hum. Exp. Toxicol. 2000;19:367–376. doi: 10.1191/096032700678815963. PubMed DOI

Gaetke L.M., Chow-Johnson H.S., Chow C.K. Copper: Toxicological relevance and mechanisms. Arch. Toxicol. 2014;88:1929–1938. PubMed PMC

Jiménez I., Aracena P., Letelier M.E., Navarro P., Speisky H. Chronic exposure of HepG2 cells to excess copper results in depletion of glutathione and induction of metallothionein. Toxicol. Vitr. 2002;16:167–175. doi: 10.1016/S0887-2333(01)00117-5. PubMed DOI

Shaaban S., Shabana S.M., Al-Faiyz Y.S., Manolikakes G., El-Senduny F.F. Enhancing the chemosensitivity of HepG2 cells towards cisplatin by organoselenium pseudopeptides. Bioorg. Chem. 2021;109:104713. doi: 10.1016/j.bioorg.2021.104713. PubMed DOI

Merlino A. Metallodrug binding to serum albumin: Lessons from biophysical and structural studies. Coord. Chem. Rev. 2023;480:215026. doi: 10.1016/j.ccr.2023.215026. DOI

Topală T., Bodoki A., Oprean L., Oprean R. Bovine serum albumin interactions with metal complexes. Clujul Med. 2014;87:215–219. doi: 10.15386/cjmed-357. PubMed DOI PMC

Andrezálová L., Országhová Z. Covalent and noncovalent interactions of coordination compounds with DNA: An overview. J. Inorg. Biochem. 2021;225:111624. doi: 10.1016/j.jinorgbio.2021.111624. PubMed DOI

Pages B.J., Ang D.L., Wright E.P., Aldrich-Wright J.R. Metal complex interactions with DNA. Dalton Trans. 2015;44:3505–3526. doi: 10.1039/C4DT02700K. PubMed DOI

Komor A.C., Barton J.K. The path for metal complexes to a DNA target. Chem. Commun. 2013;49:3617–3630. doi: 10.1039/c3cc00177f. PubMed DOI PMC

Topală T., Bodoki A., Oprean L., Oprean R. Experimental techniques employed in the study of metal complexes-DNA interactions. Farmacia. 2014;62:1049–1061.

Habala L., Devínsky F., Egger A.E. Metal complexes as urease inhibitors. J. Coord. Chem. 2018;71:907–940. doi: 10.1080/00958972.2018.1458228. DOI

Gharagozlou M., Boghaei D.M. Interaction of water-soluble amino acid Schiff base complexes with bovine serum albumin: Fluorescence and circular dichroism studies. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2008;71:1617–1622. doi: 10.1016/j.saa.2008.06.027. PubMed DOI

Jozefíková F., Perontsis S., Koňáriková K., Švorc Ľ., Mazúr M., Psomas G., Moncol J. In vitro biological activity of copper(II) complexes with NSAIDs and nicotinamide: Characterization, DNA- and BSA-interaction study and anticancer activity. J. Inorg. Biochem. 2022;228:111696. doi: 10.1016/j.jinorgbio.2021.111696. PubMed DOI

Sharma R.P., Kumar S., Venugopalan P., Ferretti V., Tarushi A., Psomas G., Witwick M. New copper(II) complexes of the anti-inflammatory drug mefenamic acid: A concerted study including synthesis, physicochemical characterization and their biological evaluation. RSC Adv. 2016;6:88546–88558. doi: 10.1039/C6RA14706B. DOI

Li L., Guo Q., Dong J., Xu T., Li J. DNA binding, DNA cleavage and BSA interaction of a mixed-ligand copper(II) complex with taurine Schiff base and 1,10-phenanthroline. J. Photochem. Photobiol. B. 2013;125:56–62. doi: 10.1016/j.jphotobiol.2013.05.007. PubMed DOI

Boghaei D.M., Farvid S.S., Gharagozlou M. Interaction of copper (II) complex of compartmental Schiff base ligand N, N′-bis (3-hydroxysalicylidene) ethylenediamine with bovine serum albumin. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2007;66:650–655. doi: 10.1016/j.saa.2006.04.006. PubMed DOI

Rambabu A., Pradeep Kumar M., Tejaswi S., Vamsikrishna N., Shivaraj DNA interaction, antimicrobial studies of newly synthesized copper(II) complexes with 2-amino-6-(trifluoromethoxy)benzothiazole Schiff base ligands. J. Photochem. Photobiol. B. 2016;165:147–156. doi: 10.1016/j.jphotobiol.2016.10.027. PubMed DOI

Ramesh G., Daravath S., Swathi M., Sumalatha V., Shankar D.S., Shivaraj Investigation on Co(II), Ni(II), Cu(II) and Zn(II) complexes derived from quadridentate salen-type Schiff base: Structural characterization, DNA interactions, antioxidant proficiency and biological evaluation. Chem. Data Coll. 2020;28:100434. doi: 10.1016/j.cdc.2020.100434. DOI

Mohapatra D., Patra S.A., Pattanayak P.D., Sahu G., Sasamori T., Dinda R. Monomeric copper(II) complexes with unsymmetrical salen environment: Synthesis, characterization and study of biological activities. J. Inorg. Biochem. 2024;253:112497. doi: 10.1016/j.jinorgbio.2024.112497. PubMed DOI

Mijatović A., Caković A.Z., Lolić A., Klisurić O., Živanović M.N., Šeklić D.S., Sretenović S., Ilić M., Bogojeski J. Structure, interaction with biomolecules, and cytotoxicity of copper (II) complexes chelating some Schiff base ligands. Appl. Organomet. Chem. 2023;37:e7253. doi: 10.1002/aoc.7253. DOI

Banerjee D., Pal S.K. Simultaneous binding of minor groove binder and intercalator to dodecamer DNA: Importance of relative orientation of donor and acceptor in FRET. J. Phys. Chem. B. 2007;111:5047–5052. doi: 10.1021/jp0715427. PubMed DOI

Erxleben A. Interactions of copper complexes with nucleic acids. Coord. Chem. Rev. 2018;360:92–121. doi: 10.1016/j.ccr.2018.01.008. DOI

Nitha L.P., Aswathy R., Mathews N.E., Sindhu kumari B., Mohanan K. Synthesis, spectroscopic characterisation, DNA cleavage, superoxidase dismutase activity and antibacterial properties of some transition metal complexes of a novel bidentate Schiff base derived from isatin and 2-aminopyrimidine. Spectrochim. Acta A. 2014;118:154–161. doi: 10.1016/j.saa.2013.08.075. PubMed DOI

Balamurugan V., Muruganandam L., Chandra Mohan S. Synthesis, characterisation, antioxidant, antimicrobial and DNA cleavage studies of copper(II) complex of Schiff base derived from (2E,2′E)-2,2′-(pyridine-2,3-diylbis(azanylylidene))bis(1,2 diphenylethanol) Results Chem. 2022;4:100523. doi: 10.1016/j.rechem.2022.100523. DOI

Fathalla E.M., Abu-Youssef M.A.M., Sharaf M.M., El-Faham A., Barakat A., Badr A.M.A., Soliman S.M., Slawin A.M.Z., Woollins J.D. Synthesis, characterizations, antitumor and antimicrobial evaluations of novel Mn(II) and Cu(II) complexes with NNN-tridentate s-triazine-Schiff base ligand. Inorg. Chim. Acta. 2023;555:121586. doi: 10.1016/j.ica.2023.121586. DOI

Srivastava A.K., Yadav P., Srivastava K., Prasad J. Synthesis, characterization, biological and electrochemical investigation of copper (II) complexes containing 4-chloro-2-[2,6-diisopropylphenylimino) methyl] phenol Schiff base ligand and aromatic diinines. Chem. Data Coll. 2021;32:100659. doi: 10.1016/j.cdc.2021.100659. DOI

Anjaneyulu Y., Rao R.P. Preparation, characterization and antimicrobial activity studies on some ternary complexes of Cu(II) with acetylacetone and various salicylic acids. Synth. React. Inorg. Met. Org. Chem. 1986;16:257–272. doi: 10.1080/00945718608057530. DOI

Follmer C., Carlini C.R. Effect of chemical modification of histidines on the copper-induced oligomerization of Jack Bean urease (EC 3.5.1.5) Arch. Biochem. Biophys. 2005;435:15–20. doi: 10.1016/j.abb.2004.12.001. PubMed DOI

You Z.-L., Lu Y., Zhang N., Ding B.-W., Sun H., Hou P., Wang C. Preparation and structural characterization of hetero-dinuclear Schiff base copper(II)–zinc(II) complexes and their inhibition studies on Helicobacter pylori urease. Polyhedron. 2011;30:2186–2194. doi: 10.1016/j.poly.2011.05.048. DOI

Taha M., Shah S.A.A., Khan A., Arshad F., Ismail N.H., Afifi M., Imran S., Choudhary M.I. Synthesis of 3,4,5-trihydroxybenzohydrazone and evaluation of their urease inhibition potential. Arab. J. Chem. 2019;12:2973–2982. doi: 10.1016/j.arabjc.2015.06.036. DOI

Rigaku . CrysAlisPRO. Rigaku Oxford Diffraction; Yarnton, UK: 2022. Version 1.0.43.

Dolomanov O.V., Bourhis L.J., Gildea R.J., Howard J.A.K., Puschmann H.J. OLEX2: A complete structure solution, refinement and analysis program. J. Appl. Crystallogr. 2009;42:339–341. doi: 10.1107/S0021889808042726. DOI

Sheldrick G.M. SHELXT-integrated space-group and crystal-structure determination. Acta Cryst. Sect. A. 2015;A71:3–8. doi: 10.1107/S2053273314026370. PubMed DOI PMC

Sheldrick G.M. Crystal Structure Refinement with SHELXL. Acta Cryst. Sect. C. 2015;71:3–8. doi: 10.1107/S2053229614024218. PubMed DOI PMC

The DIAMOND Program (Version 2.1e). Diamond—Crystal and Molecular Structure Visualization, Crystal Impact—Dr. H. Putz & Dr. K. Brandenburg GbR, Kreuzherrenstr. 102, 53227 Bonn, Germany. [(accessed on 10 August 2024)]. Available online: https://www.crystalimpact.de/diamond.

Link L., Niewa R. Polynator: A tool to identify and quantitatively evaluate polyhedra and other shapes in crystal structures. J. Appl. Cryst. 2023;56:1855–1864. doi: 10.1107/S1600576723008476. DOI

Piroš M., Schoeller M., Koňáriková K., Sumbalová Z., Valentová J., Moncoľ J., May N.V., Pap J.S., Švorec J. Synthesis, characterization and biological evaluation of three novel copper(II) clonixinate complexes with methylpyridines: Insights into structure, DNA and BSA binding properties and anticancer activity. Polyhedron. 2023;245:116619. doi: 10.1016/j.poly.2023.116619. DOI

Malis G., Geromichalou E., Geromichalos G.D., Hatzidimitriou A.G., Psomas G. Copper(II) complexes with non–steroidal anti–inflammatory drugs: Structural characterization, in vitro and in silico biological profile. J. Inorg. Biochem. 2021;224:111563. doi: 10.1016/j.jinorgbio.2021.111563. PubMed DOI

Barmpa A., Hatzidimitriou A.G., Psomas G. Copper (II) complexes with meclofenamate ligands: Structure, interaction with DNA and albumins, antioxidant and anticholinergic activity. J. Inorg. Biochem. 2021;217:111357. doi: 10.1016/j.jinorgbio.2021.111357. PubMed DOI

Tanaka T., Kawase M., Tani S. Urease inhibitory activity of simple α,β-unsaturated ketones. Life Sci. 2003;73:2985–2990. doi: 10.1016/S0024-3205(03)00708-2. PubMed DOI

Mosmann T. Rapid colorimetric assay for cellular growth and survival: Application to proliferation and cytotoxicity assays. J. Immunol. Methods. 1983;65:55–63. doi: 10.1016/0022-1759(83)90303-4. PubMed DOI