A heterodinuclear complex of s-d block containing sodium(I), manganese(II) and the enrofloxacinate anion: Preparation, crystal structure and antibacterial activity Mohammad Hakimi a, * , Mina Alikhani a , Mansour Mashreghi b , Nourollah Feizi a , Heidar Raeisi c , Yahya Mirzai a , Vaclav Eigner d , Michal Dusek d a Chemistry Department, Payame Noor University, 19395-4697, Tehran, Iran b Department of Biology, Ferdowsi University of Mashhad, Mashhad, 9177948974, Iran c Department of Chemistry, Faculty of Science, University of Birjand, Birjand, Iran d Institute of Physic of the Czech Academy of Sciences, Na Slovance 2,182 21, Prague, Czech Republic article info Article history: Received 2 December 2018 Received in revised form 14 March 2019 Accepted 15 March 2019 Available online 16 March 2019 Keywords: Enrofloxacin Manganese(II) Heterodinuclear complex Crystal structure Carboxylate bridge Antimicrobial activity abstract In the present work, the first manganese(II) heterodinuclear complex with enrofloxacin (Henro) has been synthesized and characterized using the following methods: elemental analysis, FT-IR, Raman, ultraviolet evisible (UVeVis) spectroscopy, molar conductivity and single-crystal X-ray diffraction. In the complex structure, the deprotonated bidentate enrofloxacin ligands (Enrofloxacinate, Enro) are coordinated to manganese(II) via the pyridone oxygens and carboxylato oxygens. Sodium(I) is surrounded by carbox- ylate oxygens from three Enro ligands and oxygens from three water molecules. It should also be noted that, manganese(II) and sodium(I) have the distorted octahedral coordination geometry. Binuclear Na(I)/Mn(II) unit is linked by three carboxylate oxygens of Enro ligands. This crystal structure is the first example of a binuclear complex of sodium(I) and manganese(II) with carboxylate bridge. The antimi- crobial activity of the complex was evaluated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains by using broth microdilution, well diffusion, and growth inhibition methods. In all experiments, a higher antimicrobial activity of the complex was observed compared to the free ligand. © 2019 Elsevier B.V. All rights reserved. 1. Introduction Manganese is a significant biometal; manganese is located in the active center of a plethora of enzymes that exhibits a variety of functions [1]. In medicine, compounds containing manganese are used as an anticancer agent SCe52608 and the MRI contrast agent Teslascan [2]. Furthermore, preparation of manganese complexes with different ligands because of their fungicidal [3], anti- proliferative [4], and anti-bacterial activities [5] have been consid- ered in recent years. A number of drugs used as a ligand for the synthesis of the manganese complexes, including monensin A [5], chloramphenicol [6], thiopental sodium [7] and quinolones [8e10]. Quinolones (quinolonecarboxylic acids or 4-quinolones) are structurally related to nalidixic acid. They are used to treat in- fections and diseases, including respiratory infections, soft tissue infections, urinary tract infections, bone-joint infections, typhoid fever, sinusitis and sexually transmitted diseases [11 , 12]. Fluo- roquinolones are the most active class of these compounds, which contain a fluorine atom in their chemical structure and are effective against both Gram-negative and Gram-positive bacteria. Cipro- floxacin, enrofloxacin, ofloxacin, perfloxacin, and norfloxacin are the most important examples of fluoroquinolone which recently, their complexes have been considered [13e15]. Enrofloxacin (Henro, Fig. 1) with systematic name 1- cyclopropyl-7-(4-ethyl piperazin-1-yl)-6-fluor-4-oxo-1,4- dihy- droquinoline -3-carboxylic acid is a typical second-generation quinolone antimicrobial drug [16] and it is widely used in veteri- nary clinical practice [17] because of its wide range of activities against Gram-negative and Gram-positive bacteria. Also, enrofloxacin and related fluoroquinolones have been considered in coordination chemistry because of their potential as multidentate/bridging ligands [18]. However, various metal com- plexes of enrofloxacin have been studied [19e21], but only the complexes of the manganese(II) and enrofloxacin which have been structurally characterized are [Mn(erx) 2 (phen)] [9] and [Mn(C 19 H 22 N 3 FO 3 ) 2 (H 2 O) 2 ]$2(C 8 H 5 O 4 )$8(H 2 O) [22] (where erx and * Corresponding author. E-mail address: mohakimi@yahoo.com (M. Hakimi). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2019.03.051 0022-2860/© 2019 Elsevier B.V. All rights reserved. Journal of Molecular Structure 1186 (2019) 355e361