Synthesis, crystal structures and CT-DNA/BSA binding of Cd(II) and Mn(II) complexes with 5-hydroxypyrazine-2-carboxylic acid as a ligand

Due to the potential applications of bioactive compounds, two isomorphous mononuclear coordination polymers [M(pydc)(H₂O)]_n (M = Cd (1), Mn (2), H₂pydc = 5-hydroxypyrazine-2-carboxylic acid) were synthesized and fully characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy and powder X-ray diffraction analysis. Complexes 1 and 2 are six-coordinated motifs and exhibit slightly deformed octahedral geometry, which extends into three-dimensional frame structures. Complexes 1 and 2 interact with calf thymus DNA (CT-DNA) through intercalation, hydrogen bonding and van der Waals forces. Both complexes had good binding propensity for bovine serum albumin (BSA) with a relatively high binding constant (10⁴ L mol⁻¹) superior to that of H₂pydc (10³ L mol⁻¹). The interactions between H₂pydc, complexes 1 and 2 and BSA were static quenching procedures. Site competition experiments showed that the ligands and complexes interact with BSA at site II.