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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: Four novel trinuclear copper(II)/nickel(II) complexes with four trianionic pentadentate ligands, N-(3-t-butylbenzoyl)-5-nitrosalicylhydrazide (H33-t-bbznshz), N-(3,5-dimethylbenzoyl)salicylhydrazide (H33,5-dmbzshz), N-(phenylacetyl)-5-bromosalicylhydrazide (H3pabshz) and N-(3-t-butylbenzoyl)salicylhydrazide (H33-t-bbzshz) have been synthesized and characterized by X-ray crystallography. These trinuclear compounds all have an M–N–N–M–N–N–M core formed by three metal ions and two ligands. The geometries of three Cu(II) ions in compound Cu3(3-t-bbznshz)2(H2O)(DMF)(py)2 ·DMF (1) alternate between distorted square pyramidal and square planar, while in compound Cu3(3,5-dmbzshz)2(py)2 (2), they are all square planar. Three Ni(II) ions in compound Ni3(pabshz)2(DMF)2(py)2 (3) and Ni3(3-t-bbzshz)2(py)4 ·2H2O (4) follow square-planar/octahedral/square-planar coordination geometry. Compounds 1, 2 and 4 are bent trinuclear, with the bend angles of 156.4°, 141.49° and 127.1°, respectively, while the three nickel ions in compound 3 are strictly linear, with an angle of 180°. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups are easier to yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazides ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data indicate that the trinuclear Cu(II) compound 2 is more active than 1 and mononuclear Cu(II) compound, bent trinuclear Ni(II) compound 4 is more active than linear compound 3 and less active than tetranuclear nickel compound in the previous study. [Copyright &y& Elsevier]

Abstract: A new trinuclear linear Ni(II) compound [Ni3(H2O)2(DMA)2(acshz)2]·2DMF (DMA=dimethylamine) (1) and a new Fe(III) 18-metallacrown-6 [Fe6(acbshz)6(DMF)(H2O)5]·5DMF (2), with two similar pentadentate ligands, N-acryloyl-salicylhydrazide (H3acshz) and N-acryloyl-5-bromosalicylhydrazide (H3acbshz) have been synthesized and characterized by X-ray crystallography. In compound 1, three nickel ions arrange in a strictly linear structure, adjacent molecules are linked by intermolecular H bonds to form a 2D infinite wave-like structure. In compound 2, the ring of the metallacrown is consisted of six interlink [Fe–N–N] repeated units through hydrazide N–N group bridging. It is the first metallacrown that the coordination environments of metal ions in the cycle ring are different, and these differences make the two faces of the disc-shaped hexanuclear ring do not have opposite chiralities. The studies in solution integrity and stability of the metallacrown 2 show it is soluble and stable in DMF. UV–Vis titrations demonstrate the metallacrown 2 is stable in DMF even in the presence of excess metal ions. Antibacterial screening data indicate the two compounds all have antimicrobial activities against the tested microorganisms. The activities of metallacrown 2 are stronger than trinuclear compound 1. [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]