Synthesis and Single Crystal Structural Characterization of Hexaaquacobalt(II) 1-oxopyridinium-2-thiopropionate

Abstract

Compounds containing N-oxides and sulfur possess important biological activity. N-Hydroxy pyridine-2-thione behaves as a source of the ˙OH radical upon irradiation. Further, compounds containing sulfur, such as 2-mercaptopyridine, 2mercaptopyridine N-oxide, 2,2′-dithiopyridine-1,1′-dioxide and related derivatives, as well as their metal complexes exhibit numerous biochemical applications. 1 Earlier we synthesized 1oxopyridinium-2-thiopropionic acid (OPTPH) and characterized its structure. 2 However, its coordination chemistry remains relatively unexplored. Thus, we wanted to investigate the coordination ability of this N-oxide that contains-COOH, NO , as well as C-S-C as donor entities, which could form stable chelates with various ions. Frequently, more complex macrostructures can be attained by the incorporation of organic components to yield composite inorganic-organic hybrid materials, providing a powerful synthetic approach. 3 Herein, we report on the synthesis and structural characterization of the title complex, Co(H2O)6(OPTP)2(I) [where OPTP = 1-oxopyridinium-2-thiopropionate]. A mixture of 1-oxo-pyridinium-2-thiopropionic acid (0.1 g, 0.5025 mmol), cobalt(II) chloride (0.0598 g, 0.251 mmol), sodium hydroxide (0.020 g, 0.5025 mmol) and methanol (20.0 mL) was mechanically stirred overnight. The solution was filtered and the filtrate kept aside for slow evaporation. After one week, shiny pink colored crystals of the titled complex(I) were formed. They were washed with cold water and dried (0.1103 g, 78%). High-quality single crystals were hand picked under a microscope for an X-ray investigation. X-ray data for (I) was collected by graphite-monochromatized Mo Kα radiation at 298 K. An analytical absorption-correction was applied. The structure was solved by direct methods and refined by full-matrix least-squares with anisotropic temperature factors for the non-hydrogen atoms. All H atoms other than those of water molecules were positioned geometrically (C-H = 0.93-0.97 Å) and refined as riding, with Uiso(H) = 1.2Ueq(C).

Supramolecular network formed through O-H⋯O and π-π stacking interactions: Hydrothermal syntheses and crystal structures of M(H2O)6](optp)2 (M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate)

“…This prompted us to undertake a systematic study of Hoptp complexation reactions with alkaline earth metal and transition metals. 6,7 The ligand Hoptp possesses several features: (i) it is a polydentate ligand of up to four donor atoms; (ii) the N-oxide group has been proved to be more versatile in the coordination mode than pyridine ring because the N-oxide's O atom with more lone electron pairs of different orientations provides more flexibility in its coordination geometry than the pyridine's N-atom, which affords straight coordination geometry only; (iii) the steric hindrance is much smaller for N-oxide, and in addition, it has the capability of hydrogen bonding; (iv) some N-oxides possess important antimicrobial activity; 8 (v) N-oxides are recognized as potential DNA cleaving agents. 9 Also the pyridine-N-oxide derivatives represent a peculiar class of antiviral compounds that qualify as promising novel drugs for exploration as potential anti-HIV agents.…”