Design and synthesis of ferrocene-tethered pyrazolines and pyrazoles: Photophysical studies, protein-binding behavior with bovine serum albumin, and antiproliferative activity against MDA-MB-231 triple negative breast cancer cells

We report synthesis and characterization of a series of ferrocene-pyrazoline and pyrazole hybrids and demonstrate their biomedical applications. All new compounds were identified with the help of spectroscopic techniques and single-crystal X-ray analysis. The compounds from both the series show fluorescent activity. The effect of C5 aryl substituent on the luminescent behavior of the parent system was followed by studying their absorption and emission behavior. The binding affinity of a selected ferrocenyl pyrazoline with C5 2-naphthyl substituent (4g) to bovine serum albumin (BSA) was examined through fluorescence quenching experiments using excitation wavelength 290 nm. The ligand 4g quenched the intrinsic fluorescence of BSA. Strong binding between 4g and BSA was observed with equilibrium constant for the complex formation of the order of 105 M-1. In vitro anticancer activity of a series of ferrocenyl-pyrazolines and pyrazoles (4f, 4g, 4h, 5f, 5g, and 5h) was tested against hormone-independent triple negative breast cancer cells MDA-MB-231 in which maximum inhibition potency was noted for 4h with IC₅₀ value of 3.61 mg ml⁻¹.