Tridentate Schiff base and 4,4′‐bipyridine coordinated di/polynuclear Cu (II) complexes: Synthesis, crystal structure, DNA/protein binding and catecholase activity

Abstract

Abstract4,4′‐bipyridine bridged two Cu (II) complexes, [Cu2L12(4,4′‐bipy)(H2O)2](ClO4)2 (1) and [Cu2L22(4,4′‐bipy)]n·(2H2O)n (2) (where, HL1 = 2‐[(3‐methylamino‐propylimino)‐methyl]‐phenol, H2L2 = 3‐[(2‐hydroxy‐3‐methoxy‐benzylidene)‐amino]‐propionic acid, and 4,4′‐bipy = 4,4′‐bipyridine) have been synthesized and characterized by single crystal structure determination, mass spectrometry, FT‐IR, electronic absorption, and emission spectroscopy. Complex 1 is dinuclear cationic compound and counter balanced by perchlorate anion, whereas complex 2 possesses 1D poly‐nuclear structure. Both the complexes crystallize in monoclinic system with P21/c space group and the copper centers possess square pyramidal geometry. H‐bonding, C‐H···π, π···π interactions results the formation of two dimentional supramolecular structure for both the complexes. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by using electronic absorption and emission spectroscopic technique. The calculated values of binding constants (Kb) are (9.22 ± 0.26) × 105 L mol−1 (1‐BSA), (7.19 ± 0.16) × 105 L mol−1 (1‐HSA), (5.05 ± 0.20) × 105 L mol−1 (2‐BSA) and (3.56 ± 0.25) × 105 L mol−1 (2‐HSA). The mechanism of serum albumins‐complex interactions have been investigated by fluorescence lifetime measurement. Fluorescence spectroscopic studies indicate that both the complexes interact with calf thymas‐DNA. Catecholase activity of the complexes has been studied in methanol using 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) as substrate and the result show that both the complexes are active for catalytic oxidation of 3,5‐DTBC to 3,5‐di‐tert‐butylquinone (3,5‐DTBQ) in presence of molecular oxygen. Calculated values of turnover numbers are 71.81 ± 1.04 h−1 and 69.45 ± 0.74 h−1 for 1 and 2, respectively.