Synthesis, study and structural characterization of a new water soluble hexanuclear silver(I) cluster with the 2-mercapto-nicotinic acid with possible antiviral activity

Abstract

Silver(I) chloride reacts with 2-mercapto-nicotinic acid (H 2mna, C 6H 5NO 2S) in the presence of an excess of triethylamine in DMSO to form a hexanuclear, water soluble, cluster of formula {[Ag 6(μ 3-Hmna) 4(μ 3-mna) 2] 2−·[(Et 3NH) +] 2·(DMSO) 2·(H 2O)} ( 1). The complex 1 was characterized by elemental analyses, and FT-IR, UV–Vis and 1H NMR spectroscopy. Crystal structures of complex 1 and the ligand, 2-mecapto-nicotinic acid ( 2), have been determined by X-ray diffraction. Compound 1, C 52H 68Ag 6N 8O 15S 8, is monoclinic with a space group P2 1/ c (No. 14) and a=11.7080(10), b=16.2920(10), c=18.3010(10) Å, β=91.350(10)°, Z=4. The entire molecule is ionic and consists of a double anionic hexa-nuclear cluster and two protonated triethylamine counter cations while it is solvated by two DMSO and one water molecule. The 2-mercapto-nicotinic acid ( 2), C 6H 5NO 2S, is orthorhombic (space group Pna2 1 (No. 33), a=8.3910(10), b=13.2720(10), c=5.892 Å, Z=4). An extended inter-molecular hydrogen bonding via O⋯HN contacts (O(1)⋯H(5)[N(5)]=1.8998, O(1)⋯N(5)=2.8049 Å) links the molecules forming a supramolecular two-dimensional network. Complex 1, was evaluated for anti-HIV-RT activity. It was found to inhibit the human immunodeficiency viral replication reverse transcriptase (HIV-RT) with calculated inhibiting concentration (IC 50) 0.01275±0.00115 mg ml −1.