Journal of Inorganic and General Chemistry Zeitschrift für anorganische und allgemeine Chemie ARTICLE DOI: 10.1002/zaac.201700022 Structure, Physicochemical and Biological Properties of an Aqua (2,2',2''-Nitrilotriacetato)-oxidovanadium(IV) Salt with 4-Methylpyridinium Cation Aleksandra Tesmar, [a] Dariusz Wyrzykowski,* [a] Katarzyna Kazimierczuk, [b] Julia Klak, [c] Szymon Kowalski, [d] Iwona Inkielewicz-Ste ˛pniak, [d] Joanna Drzez ˙dz ˙on, [a] Dagmara Jacewicz, [a] and Lech Chmurzyn ´ski [a] Abstract. The crystal structure of a nitrilotriacetate (nta) oxidovanadi- um(IV) salt with 4-methylpyridinium cation, [4-Me(Py)H] + , of [4- Me(Py)H][VO(nta)(H 2 O)] stoichiometry was determined. The com- plex comprises a discrete mononuclear [VO(nta)(H 2 O)] – coordination entity that can be rarely found among other known compounds con- taining nitrilotriacetate oxidovanadium(IV) moieties. The complex was characterized by spectroscopic (IR and EPR) methods, magnetic mea- surements, and thermogravimetry (TG-FTIR). The stability of the title compound in aqueous solutions was investigated by using the potentio- metric titration method. Furthermore, spectrophotometric (UV/Vis) studies have revealed that the compound is capable to scavenge the Introduction Oxidovanadium(IV) complexes are the subject of interest to many research groups [1–9] since it has been found that they reveal an interesting biological activity. Much attention has been focused on studies of their insulin-mimetic (-enhancing) properties, [10–15] the anticancer properties [16–18] as well as the cytoprotective activity against an oxidative damage. [19–22] However, the main challenge in designing new oxido- vanadium(IV) complexes for the future use in medicine is the selection of the appropriate type of ligands in order to over- come the balance existing between the therapeutic action and adverse effects exerted by vanadium compounds by shifting this balance toward the beneficial side. It has been proven that strong chelating ligands are very important in aqueous systems * Dr. D. Wyrzykowski E-Mail: dariusz.wyrzykowski@ug.edu.pl [a] Faculty of Chemistry University of Gdan ´sk Wita Stwosza 63 80–308 Gdan ´sk, Poland [b] Department of Inorganic Chemistry Gdan ´sk University of Technology Narutowicza 11/12 80–233, Gdan ´sk, Poland [c] Faculty of Chemistry Wroclaw University 14 F. Joliot-Curie St. 50–383, Wroclaw, Poland [d] Department of Medical Chemistry Medical University of Gdan ´sk De ˛binki 1 80–211 Gdan ´sk, Poland Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/zaac.201700022 or from the au- thor. Z. Anorg. Allg. Chem. 0000, ,0–0 © 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 superoxide free radicals (O 2 •– ) as well as stable organic radicals i.e. 2,2'-azinobis(3-ethylbenzothiazoline-6 sulfonic acid) cation radical (ABTS +• ) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH • ). Finally, biological properties of the complex studied were investigated in rela- tion to its cytoprotective activity against the oxidative damage gener- ated exogenously by using hydrogen peroxide in the HT22 hippocam- pal neuronal cell line (the MTT assay). Additionally, the biological action of the compound towards two human osteosarcoma HOS and MG-63 cell lines (the MTT and BrdU tests) as well as the untrans- formed human osteoblast hFOB 1.19 cell line was tested. since they are models for a trapping, transport and storage of different metallic species in living organisms. [23] For this reason we have used nitrilotriacetate ions (nta) as they are known to form fairly stable complexes with oxido- vanadium(IV) ions. [24] Numerous nitrilotriacetate (nta) metal complexes have been isolated and structurally characterized. Owing to the coordina- tion flexibility of the nitrilotriacetate ligand, the nta complexes (including heterometallic systems) exhibit a wide variety of structures (mononuclear, dinuclear, trinuclear: one-, two- and three-dimensional networks). Among these complexes some oxidovanadium(IV) nitrilotriacetate crystal structures have been reported. [25–28] The X-ray studies unveiled that with the inorganic cations (NH 4 + , La 3+ , Eu 3+ , Nd 3+ ) acting as counter- ions the dinuclear oxidovanadium(IV) coordination entities of the [(VO) 2 (μ 2 -O)(nta) 2 ] 4– and [(VO) 2 (μ 2 -O)(nta) 2 M(H 2 O) 4 ] 2– (M = Mn, Zn) types are formed. Recently, we have described the first example of the oxidovanadium(IV) complex contain- ing a discrete mononuclear [VO(nta)(H 2 O)] – coordination unit and the 1,10-phenanthrolinium cation, [phenH][VO(nta) (H 2 O)](H 2 O) 0.5 . [19] Such a coordination of the VO(IV) cation with the nta ligand is rare when compared to other known nitrilotriacetate oxidovanadium(IV) compounds. Therefore, it has been assumed that other protonated N-heterocyclic com- pounds are able to stabilize mononuclear [VO(nta)(H 2 O)] – spe- cies. To confirm this assumption we have used 4-methyl- pyridinium cation, [4-Me(Py)H] + , acting as a counterion for the stabilization of the mononuclear oxidovanadium(IV) ni- trilotriacetate entity. In this paper, the crystal structure as well as physicochemi- cal and biological properties of the oxidovanadium(IV) com- plex, namely [4-Me(Py)H][VO(nta)(H 2 O)], are presented.