A novel copper formate-based framework RbCu(HCO 2 ) 2 Cl: synthesis, crystal structure, thermal, vibrational and magnetic properties and antibacterial activity

Abstract

In this contribution, we report on the synthesis and characterization of a novel biologically active Cu(II)-based paddlewheel (PW) metal–organic framework (MOF), RbCu(HCO2)2Cl (1). Single-crystal X-ray diffraction result confirmed a monoclinic unit cell with space group P21/n and the Rb+ cation as a counter-balanced ion located in the cavities of the framework of the dinuclear copper-copper dimer formed by a PW-arrangement of formate anions in the syn-syn configuration. Each Cu(II) atom has a square pyramidal environment with a Cu⋯Cu intramolecular distance of 2.7070 (7) Å. The IR spectrum confirms the existence of the formate anion (HCO2−). Magnetic susceptibility experiments, performed from 5 to 300 K, revealed a strong antiferromagnetic coupling (J = -531 cm-1) between the two Cu2+ ions linked by four formate groups. The powder EPR spectra show the typical lines of the triplet state (S = 1) with significant zero-field splitting, attributed to Cu2+–Cu2+ dimers. In vitro antibacterial activity was evaluated against two Gram-positive bacteria (Staphylococcus) aureus CECT 86 and Listeria monocytogenes CECT 4031) and two Gram-negative bacteria (Escherichia coli CECT 99 and Klebsiella pneumoniae CECT 143T). The studies revealed that MOF 1 exhibits both bacteriostatic and bactericidal activity against all the microorganisms analyzed, making it a potential candidate for treating bacterial infections. The obtained findings give more insight into the interesting properties of Cu-based frameworks and antibacterial activity. Keywords: Cu formate-based MOF· Dinuclear Cu(II) paddle-wheel· Crystal structure· Vibrational studies· EPR· Magnetic properties· Antibacterial activity.