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Antibacterial and Antifungal Studies on Some Schiff Base Complexes of Zinc(II).

Joseyphus RS, Nair MS - Mycobiology (2008)

Bottom Line: A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands.Zinc ions are proven to be essential for the growth-inhibitor effect.The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli-627 012, India.

ABSTRACT
Two Schiff base ligands L1and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1: 1electrolytes. The IR data demonstrate the tetradentate binding of L1and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1and L2 have the crystallite sizes of 53 and 61nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium.

No MeSH data available.


Related in: MedlinePlus

Proposed structure of Schiff base ligand (L1).
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Figure 1: Proposed structure of Schiff base ligand (L1).

Mentions: The Schiff base ligands L1 and L2 show ν(C=N) azomethine bands observed at 1631 and 1618 cm-1. On complexation, this band was shifted to 1621 and 1609 cm-1 regions (Nakamoto, 1978) due to the coordination of azomethine nitrogen to the Zn(II) ion. In the Schiff base ligand (L1), the imidazole nitrogen band appeared at 1612 cm-1. This band was shifted to lower frequency at 1602 cm-1, indicating that the imidazole nitrogen is coordinated to Zn(II) ion. In the spectra of Schiff base ligands, the peptide bands are observed at 1532 and 1542 cm-1. On complexation, this band was shifted to 1525 and 1528 cm-1 region, indicating the linkage between metal ion and the peptide nitrogen atoms. The asymmetric carboxyl stretching νasym(COO-) was shifted to higher frequency in the 1585 and 1589 cm-1 range and the symmetric carboxyl stretching νsym(COO-) was shifted to lower frequency in the 1379 and 1384 cm-1 range, indicating the linkage between the metal ion and carboxylato oxygen atom. The asymmetric and symmetric stretching vibration of the carboxylato group in the complexes shows the separation value (Δν) greater than 200 cm-1. This indicates monodentate binding of carboxylato group in Zn(II) complexes. Furthermore, the presence of coordinated and lattice water molecules appeared respectively at 3419 and 3397 cm-1 in ZnL1 and ZnL2 complexes may be attributed to O-H stretching vibration. The IR spectra of the complexes show the bands at 1363 and 1374 cm-1, which can be ascribed to the presence of free NO3 group. The appearance of two bands at 520 and 534 cm-1 corresponds to ν(M-O) and the bands at 444 and 449 cm-1 corresponds to ν(M-N) stretching vibrations respectively. Thus, the IR spectral data indicate that in the ZnL1 complex, L1 is tetradentate binding through azomethine nitrogen, imidazole nitrogen, amide nitrogen and carboxylato oxygen atoms, whereas in ZnL2 complex, L2 is tridentate binding through azomethine nitrogen, amide nitrogen and carboxylato oxygen atoms (Figs. 1 and 2).


Antibacterial and Antifungal Studies on Some Schiff Base Complexes of Zinc(II).

Joseyphus RS, Nair MS - Mycobiology (2008)

Proposed structure of Schiff base ligand (L1).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3755241&req=5

Figure 1: Proposed structure of Schiff base ligand (L1).
Mentions: The Schiff base ligands L1 and L2 show ν(C=N) azomethine bands observed at 1631 and 1618 cm-1. On complexation, this band was shifted to 1621 and 1609 cm-1 regions (Nakamoto, 1978) due to the coordination of azomethine nitrogen to the Zn(II) ion. In the Schiff base ligand (L1), the imidazole nitrogen band appeared at 1612 cm-1. This band was shifted to lower frequency at 1602 cm-1, indicating that the imidazole nitrogen is coordinated to Zn(II) ion. In the spectra of Schiff base ligands, the peptide bands are observed at 1532 and 1542 cm-1. On complexation, this band was shifted to 1525 and 1528 cm-1 region, indicating the linkage between metal ion and the peptide nitrogen atoms. The asymmetric carboxyl stretching νasym(COO-) was shifted to higher frequency in the 1585 and 1589 cm-1 range and the symmetric carboxyl stretching νsym(COO-) was shifted to lower frequency in the 1379 and 1384 cm-1 range, indicating the linkage between the metal ion and carboxylato oxygen atom. The asymmetric and symmetric stretching vibration of the carboxylato group in the complexes shows the separation value (Δν) greater than 200 cm-1. This indicates monodentate binding of carboxylato group in Zn(II) complexes. Furthermore, the presence of coordinated and lattice water molecules appeared respectively at 3419 and 3397 cm-1 in ZnL1 and ZnL2 complexes may be attributed to O-H stretching vibration. The IR spectra of the complexes show the bands at 1363 and 1374 cm-1, which can be ascribed to the presence of free NO3 group. The appearance of two bands at 520 and 534 cm-1 corresponds to ν(M-O) and the bands at 444 and 449 cm-1 corresponds to ν(M-N) stretching vibrations respectively. Thus, the IR spectral data indicate that in the ZnL1 complex, L1 is tetradentate binding through azomethine nitrogen, imidazole nitrogen, amide nitrogen and carboxylato oxygen atoms, whereas in ZnL2 complex, L2 is tridentate binding through azomethine nitrogen, amide nitrogen and carboxylato oxygen atoms (Figs. 1 and 2).

Bottom Line: A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands.Zinc ions are proven to be essential for the growth-inhibitor effect.The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli-627 012, India.

ABSTRACT
Two Schiff base ligands L1and L2 were obtained by the condensation of glycylglycine respectively with imidazole-2-carboxaldehyde and indole-3-carboxaldehyde and their complexes with Zn(II) were prepared and characterized by microanalytical, conductivity measurement, IR, UV-Vis., XRD and SEM. The molar conductance measurement indicates that the Zn(II) complexes are 1: 1electrolytes. The IR data demonstrate the tetradentate binding of L1and tridentate binding of L2. The XRD data show that Zn(II) complexes with L1and L2 have the crystallite sizes of 53 and 61nm respectively. The surface morphology of the complexes was studied using SEM. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method. A comparative study of inhibition values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium.

No MeSH data available.


Related in: MedlinePlus