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From a mononuclear Cu(II)-hydrazone complex [Cu(PBH)2] (1), one μ1,1-azido bridged dinuclear Cu(II) complex having the formula [{Cu(PBH)(μ1,1-NNN)}2] (2) (where HPBH = 2-pyridinecarboxaldehyde benzoyl hydrazone) has been synthesised. Both the complexes are characterised by elemental analyses, IR and UV–Vis spectroscopic studies. The tridentate hydrazone pro-ligand (HPBH) is obtained by the condensation of benzhydrazide and pyridine-2-carboxaldehyde. The structures of the complexes have conclusively been established by the X-ray single crystal diffraction method. Complex 1 and 2 both display DNA binding ability, which is ascertained by UV–Vis titration and cyclic voltammetric studies using calf thymus DNA (CT-DNA). The apparent binding constants (Kapp) are of moderate values and are 2.048 × 104 M−1 (±0.006) and 1.644 × 104 M−1 (±0.005), respectively. The modes of binding of the complexes with CT-DNA has been investigated using circular dichroism, ethidium bromide displacement assay and viscosity measurements. The cleavage properties of these complexes as well as the free pro-ligand with super coiled (SC) pUC19 are studied using the gel electrophoresis method, where both the complexes displayed chemical nuclease activity in the presence of H2O2 via an oxidative mechanism. The antimicrobial study using the free pro-ligand, 1 and 2 against both Gram positive and Gram negative bacteria are performed, 2 showed antimicrobial activity against both Gram negative and Gram positive bacteria whereas the free ligand and 1 show no antibacterial activity.

International audience; Metal complexes of Schiff bases derived from an aromatic hydrazide are well characterised and have been reported several times. Single crystal structures of metal hydrazone complexes derived from an aliphatic hydrazide are very rare and still remain unexplored. In this paper we report two new end-on azido bridged dinuclear copper(II) and cobalt(III) hydrazone complexes derived from an aliphatic hydrazide. The Schiff base [LH = CH3C(O)NHNCHC5H4N] has resulted from the condensation of acetic hydrazide and pyridine-2-carboxaldehyde. The ligand and the complexes [Cu2(L)2(μ1,1-N3)2] (1) and [Co2(L)2(μ1,1-N3)2(N3)2] (2) are characterised by elemental analysis, IR and UV–Vis spectral studies and in addition mass spectroscopy has been also carried out for LH. The structures of 1 and 2 have been established by X-ray crystallography. Variable temperature magnetic susceptibility measurement studies of 1 indicate the χMT values remain constant in the whole range of temperature 10 to 300 K at a value close of 0.75 cm3 K mol−1, which is in good agreement with the one expected for two uncoupled copper(II) centers.

The effects of pseudohalides on the modes of binding of a hydrazone ligand are investigated and we report here four new hydrazone complexes [Co(L) 2 ] · ClO 4 ( 1 ), [Co(L) 2 ] 2 [Co(SCN) 4 ] ( 2 ), [Mn(L) 2 ] ( 3 ) and [Mn(N 3 ) 2 ( LH ) 2 ] · H 2 O ( 4 ) [where LH = condensation product of pyridine-2-carboxaldehyde and benzhydrazide]. The hydrazone ligand is quite diverse in its chelating ability and can act as a neutral or mononegative ligand and as a bidentate or tridentate unit. In this paper, we report structures showing different denticities of the ligand having different charges. The complexes are characterized by IR, UV–Vis spectroscopy and cyclic voltammetric studies and the structures are conclusively established by single crystal X-ray diffraction study. Of the complexes, 1 and 3 are purely metal hydrazone complexes whereas 2 and 4 incorporate coordinated pseudohalides in their crystal structures, and 4 shows different coordination modes of the hydrazone ligand.

Three new dinuclear Zn(II) complexes [Zn(L)(μ1,1-N3)Zn(L)(N3)] · 1.5H2O (1), [Zn(L)(μ1,1-NCO)Zn(L)(NCO)] · 1.5H2O (2) and [Zn(L)(μ1,1-NCS)Zn(L)(NCS)(OH2)] (3) have been synthesized from a potentially tetradentate N2O2-donor Schiff base ligand LH, [LH = (OCH3)(OH)C6H3CHN(CH2)2N(CH3)2], which is the condensation product of o-vanillin and 2-dimethylaminoethylamine. All the three complexes 1, 2 and 3 have been characterized by elemental analysis, IR and 1H NMR spectroscopy, TGA and fluorescence studies. Finally, their structures have been established by the single crystal X-ray diffraction method. Structural studies reveal that in complexes 1, 2 and 3 the two Zn(II) centers are held together by a μ2-phenolato oxygen atom and also by an end-on pseudohalide nitrogen (azide for 1; cyanate for 2; thiocyanate for 3) atom. Among the two deprotonated Schiff base ligands present in each complex, one acts as a tetradentate ligand (N2O2 donor set) while the other acts as a tridentate ligand (N2O donor set), having a non-coordinated methoxy group. All the synthesized complexes display intraligand 1(π–π∗) fluorescence and can potentially serve as photoactive materials.

Three new complexes, [{Cu(L)I}2]n (1), [Ag(L)]n·nClO4 (2) and [{Ag(L)(CF3COO)}2]n (3), have been synthesised and characterized by different physico-chemical methods with the aim of exploring the ligating properties of pyridine-4-amidoxime (L). Single crystal X-ray structure analysis reveals that 1 is a 2D coordination polymer, while 2 and 3 are wavy 1D chains in spite of the same coordination mode adopted by the ligand. The crystal structures also show that the coordination geometry of the metals is different in each complex, being tetrahedral in 1, but distorted trigonal planar and distorted linear in 2 and 3, respectively. The asymmetric units of 1 and 3 consist of two independent metal centres and each is associated with a counter anion of the metal salt used, while the asymmetric unit of 2 is cationic in nature, the perchlorate anion being non-coordinated. Structural diversities are also evident as the 2D structure of 1 is stabilized by O–H⋯I interactions, while several classical and non-classical hydrogen bonds lead to 3D supra-molecular structures for complexes 2 and 3. The solid state fluorescence of L and of its complexes were studied revealing that both 1 and 2 show a broad emission band with a maxima at 525 and 522 nm, respectively, strongly red shifted when compared to the free ligand band (463 nm), while 3 is found surprisingly to be non-emissive.

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is found to be a simple mono alkoxo-bridged Co(III) dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ(3)-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered Co(II) and Co(III) ions and 4 has both six- and five-coordinate Ni(II) centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, (1)H-NMR and ESI mass study results and is supposed to have one Ni(II) center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions.

Syntheses and crystal structures of four new hydrazone-based Cu(ii) complexes, [{Cu(L(1))(H(2)O)}(2)(mu-pyraz)](ClO(4))(2) (), [{Cu(L(1))(OClO(3))}(2)(mu-4,4'-bipy)] (), [{Cu(L(2)H)}(mu-pyraz){Cu(L(2)H)(OClO(3))}].(ClO(4)) () and [{Cu(L(2))}(2)(mu-bpe)] () [L(1)H = condensation product of benzhydrazide and pyridine-2-carbaldehyde and L(2)H(2) = condensation product of benzoyl acetone and benzhydrazide], bridged by various organic spacers [pyrazine (pyraz), 4,4'-bipyridine (4,4'-bipy) and 1,2-di(4-pyridyl)ethane (bpe)] are reported in this paper. The single-crystal X-ray crystallographic studies reveal that all are dinuclear units where and form strong intermolecular H-bonding to form sheets of interconnected ions, whereas forms sheets of dinuclear chains through pi-pi interactions; in , molecules are linked only through van der Waals interactions. The variable-temperature magnetic moment studies reveal that and show antiferromagnetic coupling between the Cu(ii) centers at lower temperatures. The binding ability of with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of with CT-DNA, as calculated by different methodologies, are of the order of 10(5) M(-1). The mode of interaction between and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that most probably interacts with DNA via intercalation between the base pairs leading to a change in B-DNA conformation. is also able to cleave supercoiled (SC) plasmid DNA pUC19 in a time and dose dependent manner as demonstrated by agarose gel electrophoresis, and also demonstrates its potential to cleave the SC plasmid DNA via both oxidative and hydrolytic mechanisms. Approximately 50% of leukemic cells are found to be dead when two representative leukemic cell lines are exposed to ( approximately 80 muM) even for 24 h as determined by different cell cytotoxicity assays. Preliminary results also showed that, at 20 muM, could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes.

International audience; Two new pseudohalide-bridged copper(II) complexes [{Cu(PBH)(μ1,1-CNO)}2] (1) and {Cu(PBH)(μ1,5-NCNCN)}n (2) (where HPBH = 2-pyridinecarboxaldehyde benzoyl hydrazone) have been synthesised and characterised by elemental analysis, CV, IR and UV–Vis spectral studies. The tridentate hydrazone pro-ligand (HPBH) was obtained by the condensation of benzhydrazide and pyridine-2-carboxaldehyde. Structures of both complexes have been established by X-ray crystallography which shows that 1 is a μ1,1-CNO−-bridged dimer whereas 2 is a μ1,5-dca-bridged (dca = dicyanamide) linear polynuclear structure. Variable temperature magnetic susceptibility studies indicate weak antiferromagnetic interactions with J values −0.50 cm−1 and −0.10 cm−1 for 1 and 2, respectively.

A potentially tetradentate NOOO donor hydrazone ligand, LH2 (condensation product of benzhydrazide with O-vanillin) generates a tetranuclear CuII complex [Cu4(L)4]·4H2O (1), whose void spaces are occupied by water tetramers presenting a ‘butterfly’ conformation with the highest dihedral angle reported to date, as revealed by its X-ray crystal structure. 1 has also been characterized using various spectroscopic techniques, including IR, UV-vis, and elemental analysis. Variable temperature magnetic susceptibility measurements reveal the presence of moderate antiferromagnetic intra-tetramer coupling between the four CuII centres connected through simple oxo groups of the hydrazone ligand with two different coupling constants (J1 = –61.7(3) cm–1 and J2 = –92(1) cm–1) corresponding to the two different CuII tetramers identified in the X-ray structure. We also report a quantum chemical study (MP2(full)/6–311+G(3df,2p)//B3LYP/6–311+G(3df,2p)) to calculate the stability of the water tetramers.