Synthesis, characterization, biological evaluation and docking studies of macrocyclic binuclear manganese(II) complexes containing 3,5-dinitrobenzoyl pendant arms

•Three pendant-armed manganese(II) complexes have been synthesized.•Antibacterial activity against Gram (−ve) and Gram (+ve) bacteria have been studied.•DNA binding studies suggest the intercalative mode of binding.•Molecular docking results corroborate the intercalative mode of binding.•The synthesized complexes act as potent metallonucleases.

A series of bis(phenoxo) bridged binuclear manganese(II) complexes of the type [Mn2L1–3](ClO4)2 (1–3) containing 3,5-dinitrobenzoyl pendant-arms have been synthesized by cyclocondensation of 2,6-diformyl-4-R-phenols (where R = CH3, C(CH3)3 or Br) with 2,2′-3,5-dinitrobenzoyliminodi(ethylamine) trihydrochloride in the presence of manganese(II) perchlorate. The IR spectra of complexes indicate the presence of uncoordinated perchlorate anions. The UV–Vis spectra of complexes suggest the distorted octahedral geometry around manganese(II) nuclei. The EPR spectra of Mn(II) complexes show a broad signal with g value 2.03–2.04, which is characteristic for octahedral high spin Mn2+ complex. The observed room temperature magnetic moment values of the Mn(II) complexes (5.60–5.62 B.M.) are less than the normal value (5.92 B.M.), indicating weak antiferromagnetic coupling interaction between the two metal ions. Electrochemical studies of the complexes show two distinct quasi-reversible one electron transfer processes in the cathodic (E1pc = −0.73 to −0.76 V, E2pc = −1.30 to −1.36 V), and anodic (E1pa = 1.02–1.11 V, E2pa = 1.32–1.79 V) potential regions. Antibacterial efficacy of complexes have been screened against four Gram (−ve) and two Gram (+ve) bacterial strains. The DNA interaction studies suggest that these complexes bind with CT-DNA by intercalation, giving the binding affinity in the order 1 > 2 > 3. All the complexes display significant cleavage activity against circular plasmid pBR322 DNA. Docking simulation was performed to insert complexes into the crystal structure of EGFR tyrosine kinase and B-DNA at active site to determine the probable binding mode.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide