Abstract
Two new tetranuclear zinc(II) complexes, [Zn4(L1)2(μ2-η1:η1-CH3COO)4(μ1,1-N3)2] (1) and [Zn4(L2)4(CH3CH2OH)(H2O)] (2), where L1 and L2 are the deprotonated forms of 4-fluoro-2-((pyridin-2-ylmethylimino)methyl)phenol (HL1) and 4-fluoro-2-((2-(hydroxymethyl)phenylimino)methyl)phenol (H2L2), have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy, and single crystal X-ray diffraction. X-ray crystal structural study indicated that the distances between the adjacent Zn atoms are 3.160(1)-3.353(1) Å in 1 and 3.005(1)-3.168(1) Å in 2. All zinc atoms in 1 are pentacoordinated in trigonal bipyramidal geometry, and those in 2 are in square pyramidal and octahedral geometry. The complexes and the Schiff bases were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method.
Highlights
Zinc is an important element for biological processes of human beings.[1]
Complex 1 was prepared by the reaction of 4-fluoro-2-[(pyridin-2-ylmethylimino)methyl]phenol, zinc acetate and sodium azide in methanol, and complex 2 was prepared by the reaction of 4-fluoro-2-((2-(hydroxymethyl)phenylimino)methyl)phenol and zinc acetate in methanol
When compared with the zinc complexes with similar Schiff base ligands but different zinc salts,[14] we found that the acetate and azide ligands are interesting bridging groups, which are readily participate in the construction of polynuclear complexes
Summary
Zinc is an important element for biological processes of human beings.[1] the mechanism of action of zinc in physiology and pathology are poorly understood. Zinc is an essential cofactor in six classes of enzymes as well as in several families of regulatory proteins.[2] Its importance in DNA synthesis, control of gene expression, and induction of cell apoptosis is becoming better understood.[3] Schiff bases derived from substituted salicylaldehyde with various organic amines are important ligands in coordination chemistry,[4] and show various biological properties such as antitumor,[5] antibacterial,[6] anti-fungi,[7] and enzyme inhibition.[8] It was reported that the compounds containing one or more halo-atoms on the aromatic ring have improved biological properties, especially for the antibacterial activities.[9] Rai et al reported a series of fluoro, chloro, bromo and iodo-substituted compounds, and found that they have significant antimicrobial activities.[10] Acetate, azide anions and the phenolate group of Schiff base ligands usually act as flexible bridging ligands, which bind different metal atoms to form interesting polymeric structures.[11] In the present work, two new tetranuclear zinc(II) complexes, [Zn4(L1)2(μ2-η1:η1CH3COO)4(μ1,1-N3)2] (1) and [Zn4(L2)4(CH3CH2OH) (H2O)] (2), where L1 and L2 are the deprotonated forms of 4-fluoro-2-((pyridin-2-ylmethylimino)methyl)phenol (HL1; Scheme 1, left) and 4-fluoro-2-((2-(hydroxymethyl) phenylimino)methyl)phenol (H2L2; Scheme 1, right), is reported.
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