Structural and Biological Insights Into Copper(I) Phosphane Complexes With Boron-Phenylated Poly(3-(CF3)Pyrazolyl)- and Poly(6-(CF3)-2-pyridyl)-Borates

Six new copper(I) phosphane complexes supported by B-phenylated poly(3-(CF3)pyrazolyl)- and poly(6-(CF3)-2-pyridyl)borate ligands as [Ph3B(3-(CF3)Pz)]− (1), [Ph2B(3-(CF3)Pz)2]− (2), [PhB(3-(CF3)Pz)3]− (3), [Ph3B(6-(CF3)Py)]− (4), [Ph2B(6-(CF3)Py)2]− (5) and [PhB(6-(CF3)Py)3]− (6) have been synthesized to systematically modulate steric and electronic properties at copper(I), (Pz = pyrazolyl, Py = pyridyl). The complexes [Cu(PPh3){Ph3B(3-(CF3)Pz)}] (7), [Cu(PPh3){Ph2B(3-(CF3)Pz)2}] (8), [Cu(PPh3){PhB(3-(CF3)Pz)3}] (9), [Cu(PPh3){Ph3B(6-(CF3)Py)}] (10), [Cu(PPh3){Ph2B(6-(CF3)Py)2}] (11) and [Cu(PPh3){PhB(6-(CF3)Py)3}] (12) were fully characterized by multinuclear NMR spectroscopy, electrochemistry, and single-crystal X-ray diffraction. All compounds display trigonal-planar copper centers, with mono(pyrazolyl)- and mono(pyridyl)borate complexes 7 and 10 exhibiting an unusual pseudo-κ2 coordination supported by Cu•••C(ipso) interactions. Cyclic voltammetry revealed complex multielectron oxidation behavior, with poly(pyridyl)borate systems undergoing Cu(I)→Cu(II) oxidation at relatively lower potentials than their pyrazolyl analogues, consistent with stronger pyridyl σ-donation. We also conducted efficacy tests on newly synthesized copper(I) complexes and related free ligands against a panel of human cancer cell lines from various solid tumors to explore relevant structure-activity relationships. Studies on molecular target interaction, cellular redox modulation, and cell-death pathways, have also been conducted to elucidate their mode(s) of action. Altogether, these results highlight how fluorinated scorpionate ligand design enable fine tuning of structure and properties of copper(I) complexes and underscore their promise as anticancer candidates.