Synthesis, spectroscopic, thermal and antimicrobial studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff base derived from 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine

Abstract

Coordination complexes of Co(II), Ni(II), Cu(II) and Zn(II) with Schiff base derived from syringaldehyde and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine have been synthesized. These complexes have been characterized by elemental analysis, magnetic moment, spectroscopic (IR, Electronic, 1 H NMR, ESR) and thermogravimetric analysis. Magnetic and spectral data suggest octahedral geometry for Co(II), Ni(II) and Zn(II) complexes and square planar for Cu(II) complexes. The presence of coordinated water in metal complexes was confirmed by thermal and IR data. The Schiff base and its metal complexes have been screened for antibacterial (Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, Staphylococcus aureus) and antifungal activities (Aspergillus niger, A. flavus). A comparison is made between activities of complexes with Schiff base and with the standard antibiotics.

Spectroscopic, Thermal, and Antimicrobial Studies of Co(II), Ni(II), Cu(II), and Zn(II) Complexes Derived from Bidentate Ligands Containing N and S Donor Atoms

“…The electronic spectra provided enough information regarding the arrangements of the ligands around the metal ions. Co(II) complexes of HL 1-2 at room temperature show magnetic moments 4.11 and 4.20 BM, respectively [25, 27]. These values are in good agreement with those reported for octahedral Co(II) complexes.…”

“…After complexation, the band due azomethine vibration shifted to lower frequency (10–15 cm −1 ), thus indicating the coordination of the azomethine-N to metal ions [26]. The ligands show a characteristic strong band at 2739–2770 cm −1 , which is attributed to ν (SH), disappeared in the spectra of metal complexes, confirming deprotonation and coordination of thiol group [27]. This is further supported by the lower frequency band appeared at 710–735 cm −1 in the metal complexes due to ν (C–S).…”

“…These values are in good agreement with those reported for octahedral Co(II) complexes. The Co(II) complexes exhibited two distinct absorptions in the regions 10599–10913 cm −1 and 20809–20998 cm −1 assigned to 4 T 1 g (F) →  4 T 2 g (F) ( ν 1 ) and 4 T 1 g (F) →  4 T 1 g (P) ( ν 3 ) transitions, respectively, which suggests octahedral geometry around the Co(II) ion [14, 25, 27]. ν 2 is not observed, but it is calculated by using relation ν 2 = ν 1 + 10 Dq , which is very close to ( ν 3 ) transition [32].…”

Microwave-Assisted Synthesis, Crystal Structures, and In Vitro Antibacterial Studies of Manganese(III) and Iron(III) Complexes Derived From N,N′-1,2-ethylene-bis(3-ethoxysalicylideneimine)

“…The Schiff base ligand and the complexes were screened in vitro for their antibacterial property against two Gram-positive [18] DMSO was used as a negative control, and ciprofloxacin was used as positive control.…”

Eaton’s Reagent Catalyzed Synthesis, Invitro α-Amylase Inhibitory Activity and Molecular Docking Study of some Schiff’s Bases as Diabetic-II Inhibitors

“…Schiff's bases possess imine or azomethine (-C=N-) functional group and constitute a versatile pharmacophore and reaction intermediates for the design, synthesis, and development of various bioactive lead compounds of various biological interest such as 4thiazolidinone, 5 inorganic metal complexes 6 and azetidinones. 7 Furthermore, they are also well known to exhibit numerous biological activities such as antimicrobial, 8 antitubercular, 9 antioxidant, 10 anticonvulsant, 11 anti-inflammatory, 12 and anticancer activity. 13 They are also useful in pigments and dyes, 14 intermediates for organic synthesis, 15 polymer stabilizers 16 and corrosion inhibitors.…”