Biomolecular Affinities and Cytotoxicity of Copper(I) and Silver(I) Phosphine–Pyridinyl Complexes Against CACO‐2 and CASKI Cell Lines

A series of three copper (I) and three silver (I) complexes with the general formula [M L(PPh 3 ) 2 ]NO 3 , (M = Cu for complexes 1–3 and Ag for complexes 4–6 ) are synthesized by reacting copper(I) or silver(I)‐nitrate and triphenylphosphine with the bidentate ligands, ( E )‐1‐(pyridin‐2‐yl)‐ N ‐( o‐ tolyl)methanimine L1 , ( E )‐ N ‐isopropyl‐1‐(pyridine‐2‐yl)methanimine L2 , or ( E )‐ N ‐(2,6‐dimethylphenyl)‐1‐(pyridine‐2‐yl)methanimine L3 . The structures of these complexes are elucidated using a combination of NMR spectroscopy, FTIR, UV–visible, mass spectrometry, elemental analysis, and single‐crystal X‐ray diffraction. Structural analysis revealed that the Schiff bases coordinate to the metal centers in a bidentate fashion, with triphenylphosphine occupying the remaining coordination sites in complexes 1 , 2 , and 5 . In contrast, in complexes 3 , 4 , and 6 , one coordination site is occupied by a nitrate anion instead of triphenylphosphine. All six complexes exhibit a distorted tetrahedral geometry around the metal center, as confirmed by τ 4 values ranging from 0.54 to 0.87. Binding studies with calf‐thymus DNA demonstrated that complexes 1–6 interact via intercalation, with complex 5 exhibiting the highest binding constant. Furthermore, all complexes showed strong binding affinity toward bovine serum albumin. Cytotoxicity studies revealed significant cytotoxicity of complexes 1–6 against human colon adenocarcinoma (Caco‐2) and human cervical epidermoid carcinoma (Caski) cell lines.