Synthesis and Characterization of Novel Mn(II), Fe(II) and Fe(III) complex of 5-ethyl-4-[(E)- (phenylmethylidene) amino]-4H-1,2,4-triazole-3-thiol

Abstract

The synthesis and characterization of metal complexes with Triazole Schiff Base ligand is of great utility as these compounds possesses a wide variety of biological and medicinal properties. 1,2,4-triazole Schiff base ligand, 5-ethyl-4-[(E)- (phenylmethylidene) amino]-4H-1,2,4-triazole-3-thiol and its metal complexes with Mn(II), Fe(II) and Fe(III) were prepared. The ligand was characterized by micro analytical technique and FT-IR, 1H & 13C NMR spectroscopy. The IR spectra of the metal complex revealed that ligand is bidentate and donating to metal ion from deprotonated thiol group (S-) and azomethine N-atom. On the basis of elemental analysis data, octahedral geometry was proposed for the prepared metal complexes. Lattice water is also associated with all the prepared metal complexes.

Introduction

I. INTRODUCTION

1,2,4-triazole based Schiff base and their metal complexes are pharmaceutically important compounds as they possesses a wide array of biological activity such as antibacterial, antifungal, antihelmintic, antiproliferative, antioxidant etc [1], [2], [3]. The derivatives of 1,2,4-triazole containing thiol and amino group have been studied as ligand to prepare Ni(II), Co(II), Cu(II), Zn(II), Pd(II), Cd(II) and Pb(II) complexes [4]. Some of the metal complexes of 1,2,4-triazole Schiff base, 4-[(E)-benzylidine amino]-5-methyl-4H-1,2,4-triazole-3-thiol have been prepared, characterized by spectral techniques and molecular docking studies revealed that they are potentially anti-bacterial [5]. Pb(II) complex of 1,2,4-triazole derivative have been studied by IR, NMR and elemental analysis [6]. In this paper, we are reporting the synthesis and characterization of three novel Mn(II), Fe(II) and Fe(III) complex with 1,2,4-triazole based Schiff base ligand which was prepared by condensation of 4-amino-5-ethyl-1,2,4-triazole-3-thiol and benzaldehyde.

II. MATERIALS AND METHODS

All the chemicals procured were AR/ACS grade. The melting point was determined by open capillary method. The elemental analysis data was obtained by CHNS analyzer : ELEMENTAR Vario ELIII. The FT-IR spectra were recorded by Agilent Cary 360 FTIR Spectrometer in the range 4000-450cm-1 using KBr pellets. The 1H & 13C NMR was taken in CDCl3 solvent using 400 MHz FT NMR : Bruker Advance III. The percentage of metal and chloride was estimated by standard procedure [7].

A. Experimental

1. Synthesis of Ligand ( EPMTH ):

Ligand was prepared by reported method [8]. Equimolar quantity of 4-amino-5-ethyl-4H-1,2,4-triazole-3-thiol and benzaldehyde was taken in RB flask and dissolved in ethanol. It was refluxed on water bath for 3hrs with few drops of acetic acid. Cream coloured crystals separated on cooling, filtered, washed with cold ethanol and dried in dessicator. It was recrystallized by hot ethanol.

White fibrous crystal; mp 170°C; 1H NMR (400 MHz, CDCl3) δ 1.35-1.37 (t,3H,CH3), 2.82-2.87 (q,2H,CH2), 5.27 (s,1H,NH), 7.25-7.80 (m,5H,arH), 10.34 (s,1H,-HC=N-), 11.80 (s,1H,SH); 13C NMR (100MHz, CDCl3) δ 10.4, 18.9, 128.7, 128.9, 132.4, 132.6, 153.8, 161.2, 161.9.

2. Synthesis of [ Mn(EPMT)2(H2O)2 ].2H2O

Methanolic solution of 0.3 mmol MnCl2.4H2O was drop wise added to hot methanolic solution of 06 mmol ligand. Mn(II) complex separated on adjusting the pH to 7.5-8.0, filtered, washed with methanol and dried in dessicator.

3. Synthesis of [ Fe(EPMT)2(H2O)2 ].2H2O

Aqueous solution of 03 mmol Mohr’s salt was prepared and diluted with methanol. It was drop wise added to hot methanolic solution of 06 mmol ligand. Fe(II) complex precipitated on increasing the pH, filtered, washed with methanol and dried in dessicator.

4. Synthesis of [ Fe(EPMT)2(H2O)Cl ].2H2O

Methanolic solution of 03 mmol FeCl3 was drop wise added to hot methanolic solution of 06 mmol ligand. Fe(III) complex separated on increasing the pH, filtered, washed with methanol and dried in dessicator.

III. RESULTS AND DISCUSSION

All the prepared compounds were in solid state at room temperature. They were stable in air and non-hygroscopic. Ligand was soluble in almost all the common organic solvents but metal complexes were soluble in DMF and DMSO. Solubility chart of the compounds is provided in Table-I.

IV. ACKNOWLEDGEMENT

We are thankful to DST-SAIF Cochin and SAIF-CDRI Lucknow for providing elemental analysis and spectral data. One of the author (Vivek Kumar), CSIR-SRF wants to acknowledge CSIR-HRDG, New Delhi for providing financial help in research work under CSIR-NET-JRF/SRF scheme, File No.- 09/138(0078)/2019-EMR-I.

Conclusion

Novel Mn(II), Fe(II) and Fe(III) metal complexes with bidentate 1,2,4-triazole containing Schiff base ligand were prepared. All the compounds were characterized by elemental analysis and spectral techniques such as FT-IR, 1H &13C NMR. Geometry of the metal complexes was proposed to be octahedral. The ligand is found to be bidentate and binding to metal via azomethine N-atom and deprotonated thiol S-. The synthesized compounds could be potentially biologically active and might posses medicinal properties.

References

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Copyright

Copyright © 2023 Abhay Kumar, Vivek Kumar, Piyush Kumar, Pooja Kumari Yadav, L. K. Mishra. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.