Experimental and computational studies of the interaction of gemifloxacin and manganese (II) gemifloxacin complex with DNA

•A novel manganese(II)–gemifloxacin complex was synthesized and characterized.•The interaction of gemifloxacin and its manganese complex with Fish-DNA was investigated.•The complex had higher binding affinity to Fish-DNA than the free ligand.•DFT and docking studies were carried out.•The antibacterial activities of gemifloxacin and its manganese complex were tested against four different microorganisms.•The complex showed higher antibacterial activity than the free gemifloxacin. A novel manganese (II) complex (Mn‑gem) of the quinolone antibacterial agent gemifloxacin (gem) with Mn2+ has been synthesized and characterized. The experimental data suggested that gem is deprotonated and acting as a bidentate ligand bound to manganese(II) ion through the carboxylato oxygen and the pyridone oxygen. The binding affinity of gem and Mn‑gem to Fish-DNA (FS-DNA) monitored by circular dichroism (CD), spectrophotometric, spectrofluorometric, viscometric and cyclic voltammetry (CV) techniques indicated that these two compounds had a moderate interaction with DNA, presumably by partial intercalation and/or groove binding. Density functional theory (DFT) was carried out to optimize the geometry of gem and Mn‑gem. The docking studies were done to explore more binding information of the compounds to DNA. Moreover, the antimicrobial activities of the compounds were tested against four different microorganisms (Eshrishia coli, Staphylococcus aureose, Pseudomonas aeruginosa, Enterococcus faecalis) and the results showed that Mn‑gem complex had more biological efficiency than the parent gem drug.