Two novel cadmium(II) complexes with demethylcantharate and polypyridyl: Crystal structure, interactions with DNA and bovine serum albumin

Abstract Two novel mixed-ligand complexes [Cd 2 (DCA) 2 (bipy) 2 (H 2 O) 2 ] ( 1 ) and [Cd 2 (DCA) 2 (phen) 2 ]·4H 2 O ( 2 ) (DCA = demethylcantharate, 7-oxabicyclo[2,2,1]heptane-2,3-dicarboxylate, C 8 H 8 O 5 ; bipy = 2,2′-bipyridine, C 10 H 8 N 2 ; phen = phenanthroline, C 12 H 8 N 2 ) were synthesized and characterized by elemental analysis, infrared spectra, thermogravimetric analysis and X-ray diffraction. The complexes crystallized in the triclinic crystal system with P 1 ¯ space group. The complex was binuclear molecule. In complex 1 , Cd(II) ion was seven-coordinated by two nitrogen atoms from bipy, four oxygen atoms of carboxyl groups from DCA and one water molecule. In complex 2 , each Cd(II) ion was six-coordinated by two nitrogen atoms from phen, one ether oxygen atom and three oxygen atoms of carboxyl groups from DCA. DNA binding properties of the complexes were investigated by electronic absorption spectra, fluorescence spectra and viscosity measurements. Results indicated that the complexes bound to DNA via partial intercalation mode. The values of binding constants K b / (M −1 ) were 1.03 × 10 4 ( 1 ) and 5.26 × 10 4 ( 2 ) at 298 K. Meanwhile, the complexes could quench the fluorescence of bovine serum albumin (BSA) through static quenching with the binding constants K A / (M −1 ) of 2.87 × 10 5 ( 1 ) and 3.87 × 10 5 ( 2 ) and the binding site of 0.98 ( 1 ) and 0.97 ( 2 ). In addition, complex 2 had stronger inhibition ratios than Na 2 (DCA) against human hepatoma cells (SMMC7721) lines and human gastric cancer cells (MGC80-3) lines in vitro . The IC 50 values of complex 2 against the two tested cells were 25.54 ± 6.66 and 19.14 ± 1.05 μM, respectively.