Triply phenoxo bridged Eu(III) and Sm(III) complexes with 2,6-diformyl-4-methylphenol-di(benzoylhydrazone): structure, spectra and biological study in human cell lines

Two dinuclear lanthanide(III) complexes, [M2(HL)3] (M = Sm(III) (1), Eu(III) (2); H3L, 2,6-diformyl-4-methylphenol-di(benzoylhydrazone)) were generated with good yield and characterized systematically. The single crystal x-ray structure detn. of [Eu2(HL)3] (2) confirmed the tricapped trigonal prismatic geometry of the N3O6 coordination environment around Eu. Indeed, Eu(1) and Eu(2) are bridged by phenolato-O belonging to the p-cresol ring, by deprotonated 'enol' groups from the benzoyl hydrazide part and by the imine-N centers. A temp. dependent magnetic study suggested that anti-ferromagnetic coupling occurs between the two Eu(III) ions and the magnetic moment was found to vary from 0.48 μB at 5 K to 3.03 μB at 300 K. ESR spectroscopy confirmed that anti-ferromagnetic coupling occurs between the atoms of Eu(III) and Sm(III). Both the complexes show emission in the visible range. The ligand, H3L and the complexes exhibit anti-mycobacterial activity against M. tuberculosis H37Rv (ATCC 27294) and M. tuberculosis H37Ra (ATCC 25177) strains. The mol. docking of H3L with the enoyl acyl carrier protein reductase of M. tuberculosis H37Rv (PDB ID: 4U0K) was examd. and the best docked pose of H3L has one H bond with Thr196 (2.03 Å). [on SciFinder(R)]