Bio-macromolecular interaction studies: Synthesis, crystal structure of water-soluble manganese(II) complexes

A new family of mono-chelated water soluble Mn(II) complexes [Mn(Pyimpy)(H2O)Cl-2], 1 and [Mn(Me-Pyimpy)(H2O)Cl-2], 2 were synthesized using designed tridentate ligands. These Mn(II) complexes (1 and 2) were analyzed through a variety of spectroscopic, analytical and theoretical studies. Single crystal X-ray diffraction of [[Mn(Pyimpy)(H2O)Cl-2], 1 confirm distorted octahedral environment with meridionally oriented ligand Pyimpy. Packing illustration of complex 1 shows weak pi-pi interaction along with H-bonding, Cl-O and Cl-H-py connections. The Hirshfeld surface investigation of 1 gave quantitative analysis of different types of intermolecular contact such as Cl center dot center dot center dot H, N center dot center dot center dot H, C center dot center dot center dot H, O center dot center dot center dot H, Cl center dot center dot center dot O, H center dot center dot center dot H and C center dot center dot center dot C and presented by 2D fingerprint plot. Electrochemical studies afforded metal centered reduction [Mn(II)/Mn(I) couple] with E1/2 value of -1.234 and -1.257 V (for 1 and 2, respectively) versus Ag/AgCl. Interactions of water soluble complexes 1 and 2 towards DNA and protein (BSA) have been illustrated. It was establish through UV-visible and fluorescence studies that both metal complexes (1 and 2) interact with ct-DNA and BSA fluorophore using groove and static interactions, respectively. Further, Forster theory of nonradiation energy transfer implimented to obtained the distance, r (arround 4 nm), between BSA (donor) and manganese complexes (acceptor). In Addition, molecular docking studies confirmed adequate interactions of DNA/protein with complex 1, using crystallographic parameters.