Hydrolytically active three tetranuclear nickel(ii) complexes of a new symmetrical μ-bis(tetradentate) ligand, H5chdp were prepared and their catalytic activity toward the phosphoester hydrolysis was examined.

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A carboxyamine functionalized tridentate ligand in combination with three different carboxylate bridging groups (RCO 2 À ; R = CH 3 , C 2 H 5 and CF 3 ) has been utilized to prepare tetra-and pentanuclear nickel(II) complexes, [Ni 4 (CC 2 H 5 ) 2 (CH 3 OH) 2 ] (2) and [Ni 5 (L) 4 (μ 3 -OH) 2 (μ 1,3 -O 2 CCF 3 ) 2 ]Br 2 ⋅3H 2 O (3) (HL = 3-[(2-pyridylmethyl)-amino]-propionic acid). The complexes have been characterized using several techniques such as elemental analysis, solution electrical conductivity, FTIR and UV-Vis spectroscopy, and low temperature magnetic measurements. While complex 1 and 3 were further characterized using single crystal X-ray diffraction, molecular structure of complex 2 has been optimized using DFT calculation. Whereas the acetate/propionate groups deliver Ni 4 cluster, the trifluoroacetate group provides Ni 5 assembly. Molecular structures of complexes 1 and 2 comprise a central [Ni 4 O 6 ] core that could be described as a distorted face-shared dicubane with two missing vertices. On the other hand, the [Ni 5 (μ 3 -OH) 2 (μ 1,3 -O 2 CCF 3 ) 2 ] 6 + structural core of complex 3 contains five coplanar nickel(II) ions in a rectangular organization. Variable-temperature magnetic susceptibility studies reveal the interesting magnetic properties of complexes 1 and 3. While complex 1 shows both ferro-and antiferromagnetic interactions with J 1 = À 1.10 cm À 1 , J 2 = + 2.40 cm À 1 and J 3 = À 0.65 cm À 1 , complex 3 exhibits only ferromagnetic interactions with J 1 = + 2.0 cm À 1 and J 2 = + 1.0 cm À 1 .

New water-soluble mononuclear iron(III) and zinc(II) complexes, (Me 4 N) 4 [Fe 2 OCl 6 ][Fe(pbal)Cl 3 ] 2 (1), (Me 4 N)[Fe(pbal)(NO 3 ) 3 ] (2) and (Me 4 N)[Zn(pbal)Cl 2 ] (3)(Hpbal = N-(2-pyridylmethyl)-b-alanine) have been synthesized and fully characterized. The interactions of the complexes with biologically relevant monosaccharides, such as D-glucose, D-xylose and D-mannose have been studied by UV-Vis, 13 C NMR and ESI-MS techniques in alkaline aqueous solution. All the monosaccharides bind to metal complexes in 1:1 molar ratio. Binding-induced gradual increase in the absorption intensities of 1 and 2 has been observed in the UV-Vis spectra, with a significant blue shift of absorption maxima of the complexes upon increasing the concentration of monosaccharides. The binding ability and binding mode of these monosaccharides with 3 are identified by their characteristic coordination-induced shift (CIS) values for carbon atoms C1 and C2 in the 13 C NMR spectra. The ESI-MS for the complexes under the same experimental conditions but in the presence of one mol equiv. of the applied monosaccharides indicate the formation of complex/monosaccharide-bound associations in solution.