Synthesis And Structural Study Of Coordination Complexes Of 5-Methyl-1,2,4-Triazole With Co(Ii), Ni(Ii), Cu(Ii)

In this study, coordination compounds of 5-methyl-1H-1,2,4-triazole with Co(II), Ni(II), and Cu(II) acetates were synthesized and characterized. The 5-methyl-1,2,4-triazole ligand (L) was obtained via a cyclization route using acetamidine hydrochloride and formamide, yielding a pale crystalline product (m.p. 46°C) in 78% yield. Reaction of L with cobalt, nickel, and copper (II) acetates in ethanol produced the corresponding metal–ligand complexes in good yields (75–82%). These complexes are insoluble in nonpolar solvents but dissolve readily in water and ethanol. The composition and structures of the complexes were investigated using infrared (IR) spectroscopy, thermogravimetric analysis (TGA/DTG/DTA), and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis. IR spectral data revealed shifts in the triazole ring vibration bands upon complexation, indicating coordination of the ligand to the metal center via a ring nitrogen atom. SEM–EDS elemental analysis provided the C, H, N, O and metal percentages, consistent with empirical formulas of [ML2(CH₃COO)2] for M = Co, Ni, Cu. Thermal analysis showed multi-step decomposition for each complex, ultimately yielding metal oxide residues at high temperatures. Notably, the copper complex [CuL2(CH₃COO)2] displayed a major mass loss (~45%) around 680°C corresponding to the formation of CuO. The synthesized coordination compounds thus feature the triazole ligand coordinated through nitrogen donors, and their structures and stabilities have been confirmed by the combined physicochemical data.