Coordination Complexes and Polymers of Novel Hybrid Tetrazole‐Triazole‐Pyrazole Ligands: Synthesis, Structural Characterization, and Biological Evaluation

ABSTRACT New series of triazole/pyrazole and tetrazole/triazole/pyrazole ligands were synthesized and coordinated with various transition metals to yield a diverse library of 14 complexes. All compounds were fully characterized by elemental analysis, mass spectrometry, powder X‐ray diffractometry, and a range of spectroscopic techniques ( 1 H NMR, 13 C NMR, FT‐IR, and UV–visible diffuse reflectance). The crystal and molecular structures were elucidated via single‐crystal X‐ray diffraction, and their supramolecular features were explored through Hirshfeld surface analysis. The 57 Fe Mössbauer and magnetic SQUID measurements confirmed the high‐spin nature of the Fe II complex 1 . In the three human cancer cell lines, most metal complexes are somewhat more cytotoxic than the inactive ligands, with Co(II) complexes 2 and 8 being the most potent in two of the cell lines (with IC 50 values in the two‐digit micromolar range). Overall, this study highlights how blending tetrazole/triazole/pyrazole ligands with transition metals can lead to coordination compounds with potential in anticancer research, as a proof of concept. These results add valuable insight to the expanding field of metal‐based therapeutics and could help guide the development of next‐generation, more effective agents.