Synthesis, Characterization, Antibacterial and Antifungal study of Novel Co (II) metal complexes of bidentate 3-Formylchromone based Schiff bases
Ram Vishun Prasad1*, Ashutosh Singh2
1Assistant Professor, Department of Chemistry, Kisan PG College Babhnan, Gonda, India.
2Associate Professor, Department of Chemistry, KS Saket PG College Ayodhya, India.
*Corresponding Author E-mail: vishunram72@gmail.com
ABSTRACT:
The present paper is all about the synthesis of complex compounds of already synthesized schiff bases of chromones. The structure conformation of ligand molecule is done by using various spectroscopic techniques such as 1H NMR, IR and elemental analysis. The antibacterial and anti-fungal activities of synthesized complexes were tested according to standard procedure.
INTRODUCTION:
Cobalt is a first-row transition metal with electronic configuration [Ar] 4s23d7. It is found in combined form in the Earth's crust, having +2 (Co+2) and +3 (Co+3) oxidation states. Although the oxidation states of cobalt from -1 to +5 are known, but they are rare. Co[II] ion have electronically configured d7 and, due to presence of single unpaired electrons, is paramagnetic. Its coordination numbers vary between 2 and 8, but in most of the Co (II) complex, it coordinates are 6 or 4 ligands. Generally, its octahedral geometry with high spin Co (II) having the magnetic moments between 4.3–5.2 B.M. Co (II) complexes contribute highest number of tetrahedral complex compounds rather than any transition metal ion1. Due to difference in crystal field stabilization of the octahedral and tetrahedral geometries, the cobalt (II) complex prepared by the use of Schiff base ligands generally results into tetrahedral coordinated complexes.
Schiff base complexes are oxygen carriers2. Due to multi-dental baseline Schiff bases, Majority of Co (II) have square planar geometries3.
Contradictory, bipyramid trigonal Co (II) complex Geometry4 and self-assembled octahedral geometry of the Schiff base complex5 is also reported. The Schiff base of Co (II) ion complexes also show high catalytic activity6 and are also essential in biochemical processes7. Like, Epoxidation8. Pharmacological view, they have a broad array of applications in the bio-medicinal and analytical field9 like, fluorogenic, herbicides, anti-fungal10, anti-viral, anthelmic11, antipaludinal, antituberculosis12, anti-cancers13 and anti-inflammatories.
Chromone ring system is the most heterogeneous naturally occurring compounds and key for potential biological groups of natural products. It appears to contain the 5th and 6th position C-pyrone nucleus condensed with benzene ring. They are actually a fairly and demonstrate a wide variety of biological features of the human diet14. Those other biological characteristics are antimicrobial, antioxidant and antiviral, nematicidal and antiallergenic15. They also demonstrated a comprehensive continuum of biological potentials comprising anti-microbial16 antibacterial17, antitumor18, antifungal19, anti-allergic20, antiviral21, anti-inflammatory22, and anticancer activities23. Structural chromone modification has gained increasing attention by implementing heterocyclic replacements at 3-positions.
EXPERIMENTAL:
1-aminopropen-2-ol, 2-amino-phenylehanol and metal salts (CoCl2·6H2O) are commercially available (Sigma Aldrich) and are used without further purification. The solvents used are purified and dried by standard procedure. The melting points of the ligand and complexes were recorded on open capillaries and are uncorrected. The ligand and complexes were further characterized by using partial elemental analyses, FT-IR, electronic and 1 H NMR spectra. The Schiff base ligands of 3-formyl chromone (L1-L8) were synthesized (as per previous chapter).
Scheme-2: Synthesis of Co (II) metal complexes with 3-formylchromone based Schiff base Ligand L1
1. Preparation of [Co (L1)2Cl2]:
0.01mol, Schiff base (L1) (231mg) in methanol was mixed dropwise and a solution 0.005mol of CoCl2·6H2O (119mg) was added and continued refluxing until the solution became green. The solid separated was filtered and resulting violet red solid compound was separated, washed with water followed by methanol, dried and recrystallized with methanol. Finally, brown color crystals were obtained.
Brown color crystals, yield: 72%, mp: >300°C, IR υmax (KBr) cm-1: 496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC26H26O6N2: Co-11.31, C- 59.89, H- 4.99, N- 5.38; Found: Co-11.28, C- 58.80, H-5.02, N- 5.92.
2. Preparation of [Co (L2)2Cl2]:
0.01mol, Schiff base (L2) (245mg) in methanol was mixed dropwise and a solution 0.005mol of CoCl2·6H2O (119mg) was added and continued refluxing until the solution became brown. The solid separated was filtered and resulting violet red solid compound was separated, washed with water followed by methanol, dried and recrystallized with methanol. Finally, dark brown color crystals were obtained.
Brown color crystals, yield: 72%, mp: >300 °C, IR υmax (KBr) cm-1: 496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC28H30O6N2: Co-10.73, C- 61.21, H- 5.47, N- 5.10; Found: Co-10.65, C- 61.45, H-5.40, N- 5.08.
3. Preparation of [Co (L3)2Cl2]:
0.01mol, Schiff base (L3) (266mg) in methanol was mixed dropwise and a solution 0.005mol of CoCl2·6H2O (119mg) was added and continued refluxing until the completion of reaction. Separated solid was filtered, washed with water followed by methanol, dried and recrystallized with methanol. Finally, light brown color crystals were obtained.
Light-Brown crystals, yield: 70%, mp: >300 °C, IR υmax (KBr) cm-1: 496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC26H24O6N2: Co-9.97, C- 52.80, H- 4.06, N- 4.74; Found: Co-9.98, C-52.76, H-4.04, N- 4.92.
4. Preparation of [Co (L4)2Cl2]:
0.01 mol, Schiff base (L4) (293mg) in alcohol was mixed dropwise and a solution 0.005 mol of CoCl2·6H2O (119 mg) in ethanol was added and continued refluxing until the completion of reaction. Separated solid was filtered, washed with water followed by methanol, dried and recrystallized with methanol. Finally, light brown color crystals were obtained.
Reddish-Brown crystals, yield: 74%, mp: >300 °C, IR υmax (KBr) cm-1: 496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC36H30O6N2: Co-9.13, C- 66.96, H- 4.65, N- 4.34; Found: Co-9.08, C-66.84, H-4.64, N- 4.30.
5. Preparation of [Co (L5)2Cl2]:
0.01mol, Schiff base (L5) (307mg) in methanol was mixed dropwise and a solution 0.005mol of CoCl2·6H2O (119mg) in ethanol was added and continued refluxing until the completion of reaction. Separated solid was filtered, washed with water followed by methanol, dried and recrystallized with methanol. Finally, dark brown color crystals were obtained.
Dark-Brown crystals, yield: 78%, mp: >300°C, IR υmax (KBr) cm-1: 496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC38H34O6N2: Co-8.75, C- 67.76, H- 5.05, N- 4.16; Found: Co-8.62, C-67.84, H-5.02, N- 4.08.
6. Preparation of [Co (L4)2Cl2]:
0.01mol, Schiff base (L4) (330mg) in alcohol was mixed dropwise and a solution 0.005mol of CoCl2·6H2O (119mg) in ethanol was added and continued refluxing until the completion of reaction. Separated solid was filtered, washed with water followed by methanol, dried and recrystallized with methanol. Finally, brown color crystals were obtained.
Brown crystals, yield: 64%, mp: >300°C, IR υmax (KBr) cm-1:496 cm-1, 562 cm-1, 854 cm-1, 1582 cm-1, 1640 cm-1; Analytical Calculations (%) for CoC36H28O6N2Cl: Co-8.67, C- 63.63, H- 4.12, N- 4.12; Found: Co-8.58, C-63.54, H-4.16, N- 4.06.
Antibacterial and Antifungal Activity:
The synthesized compounds were screened for their in vitro antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and antifungal activity against Aspergillus niger, Aspergillus flavus, by measuring the zone of inhibition in mm. The antimicrobial activity was performed by filter paper disc plate method at concentration 100 μg/mL and reported in Table 7.1. Muller Hinton agar & Sabouroud Dextrose agar were employed as culture medium and DMSO was used as solvent control for antimicrobial activity. Streptomycin and Fluconazole were used as standard for antibacterial and antifungal activities respectively.
*Zone of inhibition was measured in mm. Escherichia coli (E.c.), Pseudomonas aeruginosa (P.a), Aspergillus niger (A.n.), Aspergillus flavus (A.f.).
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Received on 08.02.2022 Modified on 07.03.2022
Accepted on 24.03.2022 ©Asian Pharma Press All Right Reserved
Asian J. Pharm. Res. 2022; 12(3):203-206.
DOI: 10.52711/2231-5691.2022.00033