Synthesis, Characterization and Biological Studies of S-1,3-Benzothiazol- 2-ylthiophene-2-carbothioate and Its Ce(IV) and Nd(III) Complexes

Abstract

S-1,3-Benzothiazol-2-ylthiophene-2-carbothioate (SBC) was synthesized by the S-acylation of 2-mercaptobenzothiazole with thiophene-2-carbonylchloride in the presence of pyridine. Its Ce(IV) and Nd(III) complexes were also synthesized. The ligand and its Ce(IV) and Nd(III) complexes were characterized by UV-visible, IR and GC-MS spectroscopy. In addition, the ligand was characterized based on its 1 H and 13 C NMR data and the metal complexes based on conductivity measurement and stoichiometric ratio of combination. The infrared spectral study of S-1,3-benzothiazol-2-ylthiophene-2-carbothioate and its Ce(IV) and Nd(III) complexes gave evidence for coordination through the nitrogen of the benzothiazole ring and carbonyl oxygen. All the complexes were found to contain coordinated water and were assigned octahedral geometry. Antibacterial screening of the compounds were carried out in vitro on Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The compounds showed significant activities against Gram-positive bacteria than Gram-negative bacteria. However, the ligand showed more chemotherapeutic efficacy than the complexes. The compounds were not active against Pseudomonas aeruginosa. Synthesis of S-1,3-benzothiazol-2-ylthiophene-2carbothioate:The ligand was prepared by S-acylation of 2mercaptobenzothiazole with thiophene-2-carbonylchloride in the presence of pyridine which acts as a catalyst 11 . To a solution of 2-mercaptobenzothiazole (2.51 g, 0.015 mole), thiophene-2-carbonylchloride (1.60 mL, 0.015 mole) was added followed by 5 mL of pyridine. The mixture was heated with stirring over a water bath until fumes of hydrogen chloride ceased to appear. About 2 mL of distilled water was added, followed by 2 mL of pyridine to eliminate the excess reagent. The product solidified upon stirring with a glass rod into a white coloured solid. Water (10 mL) was added, the product filtered and recrystallized from dilute ethanoic acid. The yield was 40.38 % and the melting point 162 °C. The spectral results are as follows: UV (λmax nm, cm -1 ) (ethanol): (256, 271, 336); (13, 845,14,657,18,172). IR (KBr, νmax, cm -1 ): 3054 (s), 2985 (m), 1670 (m), 1560 (m), 1497 (m), 1420 (s), 1077 (s), 896 (s), 738 (sh), 706 (w). 1 H NMR (CDCl3) (δ, ppm): 7.15 (1H, d), 7.20 (2H, t), 7.23 (1H, d), 7.25-7.40 (4H, m). 13 C NMR (δ, ppm): 112. 551, 121.412, 124.622, 127.232, 130.365, 141.002, 191.212. Syntheses of Ce(IV) and Nd(III) complexes:The complexes were synthesized by refluxing ethanol solutions of Ce(SO4)2 and Nd(NO3)3·5H2O with the ligand, respectively in amounts equal to metal: ligand molar ratio of 1:2 to ensure complete reaction 6,7 . To ethanolic solution (20 mL) of cerium(IV) sulphate (0.32 g, 0.004 mole) was added a solution of S-1,3benzothiazol-2-ylthiophene-2-carbothioate (2.22 g, 0.008 mole) in ethanol (40 mL). The mixture was refluxed for 1 h under constant stirring at 80 °C. On cooling, milk coloured precipitate formed. They were filtere...

Synthesis, Characterization and Antibacterial Studies of N-(Benzothiazol-2-yl)-4-chlorobenzenesulphonamide and Its Neodymium(III) and Thallium(III) Complexes

“…Peaks assignable to phenyl ring carbon (C7) and (C8) are observed at 130.30 and 130.60 ppm respectively. Similar observations have been made in literature [ 21 , 22 , 29 , 44 ]. The 13 C-NMR of the complexes show none of the peaks except for the solvent peak at 40.0 ppm.…”

“…In [Tl(NBTCS) 2 ]CH 3 COO, the peaks at 7.10 (2H, d) ppm and 7.25 (2H, d) ppm are assigned to the two chemically equivalent phenyl protons while the peaks at 7.28, 7.47, 7.52 and 7.79 ppm (4H, m) are assigned to benzothiazole protons. Similar observation has been made in literature [ 21 , 22 , 29 , 44 , 47 ]. The chemical shift due to the N–H proton is observed at 13.30 ppm for the ligand but disappeared in the metal complexes indicating its replacement by metal ions.…”

“…In the Nd(III) complex, these shifted to 1589 and 1410 cm −1 while in the Tl(III) complex a single peak at 1548 cm −1 was obtained. This suggest that the C=N of benzothiazole was involved in the coordination [ 21 , 29 ]. This was further supported by emergence of M–N bands between 392 and 420 cm −1 .…”

“…Metal complexes of sulpha drugs have been reported with appreciable biological activities [ 23 , 24 , 25 , 26 , 27 , 28 ]. Recently, there have been several reports on neodymium(III) and thallium(III) complexes [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Mimouni et al, 2014 [ 38 ] have synthesized, characterized, and studied the antibacterial, antifungal and antitubercular activities of thallium complexes of monensin and lasalocid.…”

Surface Active Properties of Some Bioactive Azole Series Complexes of Copper in Binary Solvent Mixture

“…Now again in another beaker prepare a saturated solution of CuSO4 (about 3-4 gm in 5 ml H2O) and mix it into the above solution with stirring till the blue coloured soap is farmed. Filtered and washed with warm water and 10% ethyl alcohol then dried and recrystallised with hot benzene22,23 .…”