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Two trinuclear Ni(II) complexes Ni3(L1)2(py)2(DMF)(H2O) (1) and Ni3(L2)2(py)2(DMF)2 (2) with two new trianionic pentadentate ligands N-(3,5-dimethylbenzoyl)-salicylhydrazide (H3L1) and N-(phenylacetyl)-5-nitrosalicylhydrazide (H3L2) have been synthesized and characterized by X-ray crystallography. Nickel ions in the two complexes have square-planar/octahedral/square-planar coordination. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated ligands, forming a trinuclear structural unit with an M-N-N-M-N-N-M core. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazide ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data in a previous study indicates that bent trinuclear Ni(II) compound 1 is more active than linear compound 2 and less active than a tetranuclear nickel compound. [ABSTRACT FROM AUTHOR]

Abstract: Three polynuclear transition metal complexes [Mn8(DMF)8(L1)8]·4DMF (1), [Mn6(DMF)6(L2)6]·[Mn6(DMF)4(H2O)2(L2)6]·2DMF (2), [Cu3(L3)2(py)2] (3) of the pentadentate ligands N-acyl-salicylhydrazides were synthesized and characterized, their crystal structures were investigated. The oxidation state and properties of the central metal ions are important in crystal structure formation, trivalent Mn(III) ion which easily form stable octahedral coordination metallamacrocycle complexes, metallacrowns 1 and 2 were obtained; while bivalent Cu(II) ion is easier to form square planar, trinuclear complexes 3 was obtained. The steric effect of the N-acyl side chains also plays an important role in the structures of these polynuclear complexes. The magnetic property of 1 was also investigated. [Copyright &y& Elsevier]

Abstract: Two new trinuclear complexes, Cu3L2(py)2 (1) and Ni3L2(py)4 (2), have been synthesized and characterized, where L3− is N-2-methyl-acryloyl-salicylhydrazidate. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated L3− ligands, forming a bent trinuclear structure unit with an M–N–N–M–N–N–M core. The bent angles in complexes 1 and 2 are 167.6(1)° and 75.4(1)°, respectively. Three nickel ions in compound 2 exhibit alternating square-planar and octahedral geometries, while three copper ions in compound 1 follow square-planar mode. The studies in solution integrity and stability of compounds 1 and 2 show they are soluble and stable in DMF. UV–Vis titrations demonstrate compound 1 is stable in DMF even in the presence of excess metal ions. Antibacterial screening data indicate the two compounds all have stronger antimicrobial activities against the tested microorganisms than ligand. The trinuclear copper compound 1 is more active than monocopper compounds in the previous study, and the trinuclear nickel compound 2 is less active than tetranuclear nickel compound in the previous study. [Copyright &y& Elsevier]

Abstract: Two new macrocyclic hexanuclear metal(III) 18-metallacrowns-6, [Mn6(acshz)6(H2O)6]·18H2O (1) and [Fe6(acshz)6(CH3OH)6]·6CH3OH·6H2O (2), have been synthesized and characterized, where acshz3− is N-acetyl-5-chlorosalicylhydrazidate. These crystal structures contain neutral 18-membered metallacrown rings consisting of six metal(III) ions and six acshz3− ligands. The ring is formed by the succession of six structural moieties of the type [M(III)–N–N] through hydrazide N–N groups bridging the ring metal ions. The ligand enforces the metal ions to form the stereochemistry of a propeller configuration with alternate Λ/Δ or Δ/Λ forms. The largest diameters of the hexanuclear rings are about 6.97Å at the entrance and 9.53Å at the centre of the cavity for 1; and 7.94 and 10.24Å for 2, respectively. The solution integrity and stability of the metallacrowns were confirmed using electrospray ionization ESI-MS and UV–Vis spectroscopy in methanol. Antibacterial screening data indicate the formation of the metallacrown 1 reduces the antimicrobial activity of the ligand H3acshz hugely, while metallacrown 2 has strong antimicrobial activity against Bacillus subtilis (B. subtilis). [Copyright &y& Elsevier]

Abstract: A novel macrocyclic hexanuclear manganese(III) 18-metallacrown-6 compound, [Mn6(H2O)6 (anshz)6]·10DMF, has been prepared using a trianionic pentadentate ligand N-acetyl-5-nitrosalicylhydrazide (anshz3−) and characterized by X-ray diffraction (DMF= N,N-dimethylformamide). The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Mn(III) and six anshz3− ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Mn(III)h name="sbnd" />N]. Due to the meridional coordination of the ligand to the Mn3+ ion, the ligand enforces the stereochemistry of the Mn3+ ions as a propeller configuration with alternating Δ/Λ forms. The disc-shaped hexanuclear ring shows at its largest diameter about 7.14Å at entrance, about 9.76Å at the center of the cavity, respectively. Antibacterial screening data showed that the manganese metallacrown has strong antimicrobial activity against Bacillus subtilis. [Copyright &y& Elsevier]