ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 11, pp. 2400–2409. © Pleiades Publishing, Ltd., 2018. 2400 Synthesis, Physicochemical, and Biological Studies of New Pyridoxine HCl Mononuclear Drug Complexes of V(III), Ru(III), Pt(II), Se(IV), and Au(III) Metal Ions 1 K. A. Alibrahim a , F. A. Al-Saif a , H. A. Bakhsh a , and M. S. Refat a–c * a College of Science, Princess Nourah bint Abdulrahman University, Department of Chemistry, Saudi Arabia b Chemistry Department, Faculty of Science, Taif University, P.O. Box 888, Al-Hawiah, Taif, 21974 Saudi Arabia *e-mail: msrefat@yahoo.com c Department of Chemistry, Faculty of Science, Port Said, Port Said University, Egypt Received September 3, 2018 Abstract—Pyridoxine HCl (vitamin B 6 ; Pyr-H 3 ) complexes with the formula [M(Pyr-H)(H 2 O) 4 ] . Cl·nH 2 O [M= V(III), Ru(III); n = 0.1], [Pt(Pyr-H)(H 2 O)(Cl)] . Cl, [Se(Pyr-H 3 )(O)(OH) 2 ], and [Au(Pyr-H)(H 2 O) 2 ]·Cl are synthesized by the reactions of Pyr-H 3 with metal chlorides [V(III), Ru(III), Pt(II), Se(IV), and Au(III)] at 60°C in methanol–water 50 : 50 v/v. The accumulated data of the elemental analysis, conductivity measurements, mass, FT-IR, 1 H, and 13 C NMR, UV-Vis spectroscopy and magnetic moments support elucidated stoichiometry, structures and chelation of the complexes. Thermogravimetric analysis of the synthesized solid complexes is carried out for determining their thermal stability, number of crystalline water molecules and decomposition steps. According to the physicochemical analyses Pyr-H 3 reacts with metal ions as a bidentate ligand via both phenolate oxygen and oxygen of the CH 2 OH group. The antimicrobial and anticancer tests reveal that complexes demonstrate higher antibacterial activity than free Pyr-H 3 chelate. According to the cytotoxic results of Pt(IV) and Au(III) complexes in vitro based on human hepato cellular carcinoma (HepG-2) and human breast cancer (MCF-7) tumor cell lines, the former one exhibits promising activity. Keywords: vitamin B 6 , chelation, gold, platinum, physicochemical, anticancer 1 The text was submitted by the authors in English. INTRODUCTION Metallodrug complexes have played a major role in the development of modern methods of chemotherapy [1–5]. Metal-dependent drugs were also used to treat a variety of diseases (diabetes, rheumatoid arthritis, inflammatory and cardiovascular) as well as in dia- gnostics [6, 7]. Vitamin B 6 has some synonyms, 2-methyl-3-hydroxy-4,5-bis(hydroxymethyl) pyridine, pyridoxine, and adermine. Different complexes of vitamin B 6 with La, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Er, and Y(III) were synthesized and its antioxidative activity was determined [8]. Pyridoxine deficiency can cause anemia, nerve damage, seizures, skin problems, and ulcers in the mouth [9]. Vitamin B 6 is stored in muscles and excreted only in urine in cases of excessive intake [10]. Pyridoxine under various pH conditions exhibits four interchangeable ionic forms. At pH < 5 it occurs in the cationic form, its dipolar ion form exists at pH 6.8, at pH 8 it is in the neutral form, and it forms anionic form at pH > 8 [11] (Fig. 1). UV spectra, acid dissociation constants [12], and NMR [13] data of pyridoxine demonstrated that the first loss of proton took place at its 3-hydroxy group. The second ionization resulted in the loss of the pyridinium proton. The crystal structure of pyridoxine hydrochloride showed that both pyridine nitrogen and phenolic oxygen can be protonated, as expected [14]. Complexation of manganese, nickel, and cobalt with pyridoxine/pyridoxal in equilibrium media was associated with the meta-oxy atom in situ [15]. The coordination site of pyridoxine molecule depends on the type of media. According to 13 C NMR pyridoxine molecule acted as a bidentate ligand via the phenolic oxygen and oxygen at the adjacent group in the 4'-position in aqueous media. In H 2 O–DMSO mixture pyridine nitrogen became a more effective donor, and with increased ratio of DMSO some cations were coordinated by it rather than pyridoxine [16]. Single DOI: 10.1134/S1070363218110245