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The transition metal complexes of ethylvanillin [Mn(L)2(H2O)2] (1), [Co(L)2(H2O)2] (2), [Ni(L)2(H2O)2] (3), and [Zn(L)2(H2O)2] (4) have been synthesized. The geometric and electronic structure of 1, 2, 3 and 4 has been solved by X-ray diffraction analysis and EPR spectroscopy. They are octahedral complexes with a cis arrangement of the two water molecules. All the structures were calculated by DFT methods at the level of theory B3P86/6-311g. The EPR spectra of 1 are isotropic both at 298 and 77 K with g values at 2.034 ± 0.010 and 2.040 ± 0.010, respectively indicating Mn(II) ion (3d5) with a S = 5/2 spin. 1 shows a hyperfine structure with six strong absorptions, corresponding to the |−1/2, m> → |1/2, m> ‘allowed’ transitions (ΔM = ±1, Δm = 0), and five pairs of ‘forbidden’ absorptions (ΔM = ±1, Δm = ±1), between the Δm = 0 hyperfine transitions in an organic solvent such as DMF, DMSO and CH3CN. EPR spectroscopy and DFT calculations suggest that in the temperature range 77–298 K 2 presents a high-spin S = 3/2 state, whereas the low-spin state S = 1/2 begins to be populated at temperatures higher than 77 K (liquid nitrogen temperature). In 3, the weak signal due to a small amount of an octahedral Ni(III) complex (NiL3), is characterized by a rhombic spectrum. DFT simulations on 4 indicate that the octahedral structure with a cis arrangement of the two water ligands is more stable than the octahedral one with a trans arrangement and the tetrahedral geometry.

A new iron(III) complex, [Et3NH][FeIII(L2−˙)2] (1) with a substituted o-aminophenol based ligand is reported. Complex 1 is an anionic complex with a triethylammonium cation in the lattice. It contains two O,O,N-coordinated o-iminobenzosemiquinonate(2−) radical anions with an Fe(III) centre in a high-spin configuration. The crystal structure of 1 was determined by X-ray diffraction, which revealed a trigonal prismatic coordination environment whose electronic structure was established by various physical methods including EPR, Mossbauer spectroscopy and variable-temperature (2–300 K) magnetic susceptibility measurements. Electrochemical analysis indicated primarily ligand-centred redox processes. Complex 1 retained the high-spin character of Fe(III) throughout the temperature range studied (2–300 K) and exhibited, as expected, strong antiferromagnetic coupling operating between two radicals (SR = 1/2) and the high-spin Fe(III) centre (SFe = 5/2), yielding a St = 3/2 as the ground state. This was confirmed by means of DFT calculations (M06-2X/6-31+G*) and a spin density analysis of the high spin and low spin configurations.

A potentially tetradentate Schiff base ligand containing carboxylic acid group, HL, (E)-2-((pyridin-2-yl)methyleneamino)-5-chlorobenzoic acid is synthesized and characterized. Reaction of HL with hydrated zinc(II) trichloroacetate and zinc(II) trifluoroacetate under similar reaction condition yields two discrete dinuclear complexes, [Zn(L)(Cl)]2 (1) and [Zn(L)(CF3COO)]2 (2) and characterized by different physicochemical methods. Single crystal X-ray structural characterization reveals different ligating properties of the coordinated anionic ligand (L−) in its zinc(II) complexes. The side arm carboxylate of L− shows μ1,3-carboxylato-bridging mode in 1 and connects zinc(II) atoms in syn-anti fashion while it exhibits a μ1,1-carboxylato-bridging mode in 2. The metal ions display distorted square pyramidal geometries in both the structures and associated with different degrees of distortions. The fluorescence spectra of HL and its zinc(II) complexes recorded in methanol at room temperature which reveal the enhancement of emission intensity for the complexes compared to that of the free ligand. Thermogravimetric analyses (TGA) reveal high thermal stabilities of the complexes.

International audience; Two new copper(II) polymeric complexes, {[Cu(HPymat)(H2O)](NO3)}n (1) and [Cu2(Pymat)2(H2O)3]n (2), have been synthesized using the Schiff base ligand H2Pymat [H2Pymat = (E)-2-(1-(pyridin-2-yl)-methyleneamino)terephthalic acid]. Complex 1 is a cationic 1D polymer, whereas complex 2 is a two dimensional polymer. Both complexes were crystallographically, spectroscopically and magnetically characterized. Theoretical studies were performed and the catecholase activity of the complexes was also examined. Complex 1 is a ferromagnetically coupled complex with J = 2.8 cm−1 and 2 shows antiferromagnetic coupling with J = −1.6 cm−1. Both complexes show notable features in the EPR study. They show rhombic spectra at 77 K in the solid state, but by varying the temperature or solvents the nature of the spectra can be changed or inverted. This behaviour indicates a change of the ground state from dx2−y2 to dz2 orbitals. Theoretical calculations of 1 focus on the evaluation and characterization of interesting anion–π–anion assemblies that are formed in the solid state. In 2 we have analysed the unconventional chelate ring⋯chelate ring π-stacking interactions that govern its solid state architecture. Both complexes act as functional models and show catechol oxidase activity with a kcat value of the order of 103 h−1.

A neutral tridentate nitrogen donor Schiff base ligand L (L = (E)-N-(phenyl(pyridin-2-yl)methylene)-2-(pyridin-2-yl)ethanamine) has been synthesized and characterized by spectroscopic techniques, and employed to synthesize two new μ1,1-azido/cyanato bridged dinuclear copper(II) complexes, [Cu(L)(μ1,1-N3)(ClO4)]2 (1) and [Cu(L)(μ1,1-NCO)(ClO4)]2 (2). Both compounds have been spectroscopically and structurally characterized. Structural investigation reveals centro-symmetric nature of the complexes in which the center of inversion lies at the midpoint of the two copper(II) ions. The metal ions display distorted octahedral geometry. The tridentate neutral ligand L coordinates the metal ion in mer-orientation. Crystal packing reveals that hydrogen bonding and π⋯π stacking interactions play a dominant role on the solid state structure of the complexes. Low temperature susceptibility measurements support EPR studies and reveal antiferromagnetic (J = −7.2 cm–1) and ferromagnetic (J = +0.41 cm–1) behavior for 1 and 2, respectively.

International audience; The hydrazone Schiff base ligands (E )‐N′‐(2‐hydroxybenzylidene)acetohydrazide (HL1 ) and (E )‐N′‐(2,3‐dihydroxybenzylidene)acetohydrazide (H2L2 ) with a functional group variation in the aromatic moiety have been synthesized. The ligands have been used to synthesize the following MnII complexes: the mononuclear complex [Mn(HL1 )2][ClO4]2· 2H2O (1 ), the cocrystallized discrete dinuclear complex {[Mn(HL1 )2]· [Mn(L1 )2]}[ClO4]2 (2 ), and the phenoxido‐bridged dinuclear complex [Mn(μ‐HL2 )(H2O)]2[ClO4]2 (3 ). The ligands and the complexes were characterized by FTIR and UV/Vis spectroscopic techniques, and their crystal structures were determined by single‐crystal X‐ray diffraction analysis. 1H and 13C NMR spectroscopy shows evidence of keto–enol tautomerism of the ligands in solution. All of the compounds develop hydrogen‐bonded assemblies of different dimensionalities and architectures. CH–π and π–π interactions also contribute significantly to the overall binding energies of the supramolecular assemblies. The supramolecular interaction energies have been computed at the BP86‐D3/def2‐TZVPD level of theory.

Department of Chemistry and Environment, Heritage Institute of Technology, Kolkata-700 107, India E-mail : samiranju92@gmail.com, samiran.mitra@heritageit.edu Department of Chemistry, West Bengal State University, Kolkata-700 126, India Instituto de Ciencia Molecular (ICMol), C/ José Beltrán Martinez nº 2, 46980 Paterna, Valencia, Spain Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca (Baleares), Spain Manuscript received 02 November 2016, revised 16 February 2017, accepted 28 February 2017 Doubly phenoxo bridged heterometallic dinuclear Ni(II)-Na(I) complex [NiNaL(ClO4 )(CH3OH)], 1 (H2L = [(OCH3 )C6H3 (OH)CH=N(CH2CH)(CH3 )N=CH(OH)C6H3 (OCH3 )] has been synthesised and characterized by infrared, electronic spectra, electrochemistry and single crystal X-ray diffraction study. In complex 1, Ni(II) centre is distorted square-planar while the sodium(I) centre possesses pentagonal bipyramidal geometry. In the dimeric unit, the nickel and sodium atoms are held together by two distinct µ2 -phenoxo oxygen of the Schiff base ligand. The Ni-Na distance is 3.354(2) Å and the Ni-O-Na angles are found to be 107.4(5)º and 108.2(4)º. Density functional theory (DFT) calculation results for the complex 1 are also reported and compared with the experimental data.

International audience; The Mn(II) complex {[Mn(atpa)(H2O)2]·H2O}n (1),with the dicarboxylate ligand 2-aminoterephthalic acid (H2atpa), has been synthesized and crystallographically, spectroscopically and magnetically characterized. Complex 1 shows a very unusual 1κ2N,O coordination mode of the aminoterephthalate dianion with the Mn(II) ion. One of the carboxylate groups shows a syn-anti-μ2-η1:η1 binding mode to form a 2D square grid. The magnetic properties of this compound can be very well reproduced with a regular S = 5/2 chain model with a very weak antiferromagnetic coupling constant of J = −0.2 cm−1 through the single syn-anti carboxylate bridges. EPR measurement also supports the experimental data obtained from the magnetic study. The influence of the torsion angle between the carboxylate groups on the various interaction energies of 1 is calculated by means of DFT study.

The tetradentate (ONNO) donor Schiff base ligand LH2, derived from the condensation of salicylaldehyde and 1,3-diaminopropane, has been synthesized and reacted with CuBr2 to yield a trinuclear complex with the molecular formula [Cu3L2Br2]. Single crystal X-ray diffraction study reveals that the two terminal copper atoms adopt a square pyramidal geometry, whereas the central copper atom, situated at the inversion centre, is surrounded by four phenoxide oxygen atoms in a square planar fashion. Variable temperature magnetic susceptibility measurement study shows strong antiferromagnetic intra-trimer interactions between the copper centers with a J value of −302 cm−1. EPR study of the complex depicts that, due to the exchange coupling between the copper ions, the EPR spectra were unresolved, having very broad resonances with g = 2.133. A theoretical DFT calculation was also carried out to supplement the experimental results.

The new tetranuclear nickel(II) complex [Ni4(OH)(L)(HL)2(CH3OH)1.5(H2O)1.5]·9H2O (1) has been synthesised by the reaction of NiCl2·6H2O and the Schiff base ligand H3L (H3L = (CH3O)(OH)C6H3CH N–C(CH3)(CH2OH)2), prepared by the 1:1 condensation of 2-amino-2-methyl-1,3-propanediol and o-vanillin, and characterized by different physicochemical methods. Single crystal X-ray structural determination identifies a Ni4O4 cubane moiety as the central part of the complex unit. The presence of a single μ3-hydroxido bridged oxygen occupying only one vertex of the Ni4O4 cubane core is rare in Ni4O4 cubanes (ca. 5% of occurrence). Structural analysis also reveals two similar alkoxido oxygen atoms of the Schiff base coordinating the metals in two different modes; one in the μ3-bridging mode whilst the other binds in a monodentate fashion. The metal centers display distorted octahedral geometries with two different coordination environments. The magnetic properties reveal the presence of ferromagnetic nickel(II)–nickel(II) interactions in the cluster with two different exchange pathways. The magnetic data can be fitted to a Ni4O4 cubane model with g = 2.058, J1 = +17.2 cm−1 and J2 = +6.6 cm−1. Isothermal magnetization measurements confirm the S = 4 spin ground state. Both J values agree with previous magneto-structural correlations in doubly oxido-bridged nickel(II) complexes.

Sodium-assisted self-assembly of two nickel(II) Schiff base complexes under similar reaction conditions yield hetero-metallic compounds [{Ni(salpn)}2Na(ClO4)] (1) and [{Ni(salpr)}3Na][Ni(salpr)]2ClO4·2H2O (2) (where salpn = N,N′-bis-(salicylidene)-1,3-diaminopropane and salpr = N,N′-bis-(salicylidene)-1,2-diaminopropane). Both have been characterized by physico-chemical techniques and single-crystal X-ray diffraction. Crystal structure reveals that in the tri-metallic system of 1 sodium is sandwiched between two [Ni(salpn)] units while the hexametallic system of 2 consists of tetrametallic cluster ion [{Ni(salpr)}3Na]+ with encapsulated sodium by three [Ni(salpr)] units. In both complexes, sodium adopts distorted trigonal prismatic geometry leaving nickel(II) in a distorted square-planar environment. Structural characterization also reveals that 2 : 1 (for 1) and 3 : 1 (for 2) self-assemblies of metallo-ligand and sodium were achieved with slight variation in ligand backbone.

The reaction of Cu 2 (CH 3 COO) 4 ·2H 2 O with the Schiff base ligand, H 4 L [(OH) 2 C 6 H 3 CH N–C(CH 3 )(CH 2 OH) 2 ], yields a novel hexanuclear copper (II) cluster {[Cu 6 (HL) 4 ]·CH 3 OH·0.5CH 3 CN·6.5H 2 O} ( 1 ) with a rare “bicapped cubane” core. Title complex has been characterized by different physico-chemical techniques. Single-crystal X-ray structure reveals that the “bicapped cubane” core was formed by a cubane-like Cu 4 O 4 subcore capped by two copper(II) atoms over opposite faces. The cubane copper(II) atoms are in distorted square pyramidal geometry and connected each other via μ 3 -alkoxo oxygens while two apical copper(II) atoms are in distorted square planar environments and connected to the main cubane subcore by doubly phenoxo bridged oxygen atoms. EPR spectra of the complex reveals overall strong antiferromagnetic behavior, well supported by cryomagnetic susceptibility measurements in the range 2–300 K under the magnetic field of 0.1 T leading different coupling constants: J 1 = +60 cm −1 , J 2 = −45.5 ± 1 cm −1 ; J 3 = −140 ± 1 cm −1 , using the general Hamiltonian H = − J (S i ·S j ). A plausible magneto-structural correlation has also been established.

One ONNO-donor tetradentate Schiff base ligand LH2 was derived from the condensation of salicylaldehyde and 1,3-diaminopropane and reacted with Cu(NO3)2·6H2O and NaNCO to yield one trinuclear complex with molecular formula [Cu3L2(µ1,1-NCO)2]. The synthesized complex was characterized by IR, UV–vis spectroscopy, and electrochemical analysis. Single-crystal X-ray diffraction study explores that the two terminal copper atoms adopt square pyramidal geometry, whereas the central copper atom situated at the inversion center is surrounded by four phenoxo oxygens and two end-on cyanato anions to adopt an octahedral geometry. The ONNO-tetradentate Schiff base ligand coordinates with the copper(II) ion via two oxygen atoms of the phenoxo-group and two nitrogen atoms from the imine moiety. A theoretical density functional theory (DFT) calculation was also carried out to supplement the experimental results. All the DFT calculations were done in gas phase.

A new 1D polymeric copper(II) complex [{Cu(L)(CF3COO)}2]n has been synthesized using a potentially tetradentate Schiff base ligand, HL, ((E)-2-((pyridin-2-yl)methyleneamino)-5-chlorobenzoic acid) and characterized by different spectroscopic methods. Single crystal X-ray structural characterization reveals that the side arm carboxylate group of the coordinated Schiff base exhibits a μ 1,3-bridging mode and connects the neighbouring copper(II) ions leading to a zigzag 1D chain structure where the copper(II) ions display distorted square pyramidal geometries. Variable temperature magnetic susceptibility measurement reveals a weak antiferromagnetic exchange (J = −0.47 ± 0.01 cm−1) prevails between copper(II) ions in the chain mediated by the bridging carboxylate group, is also supported by the room temperature EPR spectral study. Electrochemical property of the complex is also reported.

International audience; Four new dicyanamide (dca) bridged multinuclear ZnII-Schiff-base complexes, {[Zn2L1(μ1,5-dca)dca]·CH3OH}2 (1), [Zn2L2(μ1,5-dca)dca]n (2), [Zn3L32(μ1,5-dca)2]n (3), and [(ZnL4)2Zn(μ1,5-dca)dca]n (4), have been synthesized using four different Schiff bases L1H2 = N,N/-bis(3-methoxysalicylidenimino)-1,3-diaminopentane, L2H2 = N,N′-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane, L3H2 = N,N′-bis(5-bromosalicylidenimino)-1,3-diaminopropane, and L4H2 = N,N′-bis(5-chlorosalicylidenimino)-1,3-diaminopropane and NaN(CN)2 in order to extend the metal–ligand assembly. The directional properties of linear end-to-end bridging dca ligands have resulted in different metal ion connectivities leading to unique variety of templates in each of the complexes. All the ligands and complexes have been characterized by microanalytical and spectroscopic techniques. The structures of the complexes have been conclusively determined by single crystal X-ray diffraction studies. Thermogravimetric analyses have been performed to investigate the thermal stability of the metal–organic frameworks. Finally, the photoluminescence properties of the complexes as well as their respective ligands have been investigated with a comparative approach.

A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)3(NO)(μ-CN)]n·3H2O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis. It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm−1) through long diamagnetic [Fe(CN)5(NO)]2− bridges. Spin state of the iron atom was established by 57Fe Mossbauer spectroscopy.

International audience; Three new complexes of cobalt, manganese, and zinc have been synthesized using a hydrazone Schiff base ligand {(E)-N′-[1-(2-hydroxyphenyl)ethylidene]acetohydrazide} (LH2) produced by the 1:1 condensation of acetic hydrazide and 2-hydroxyacetophenone. The ligand has shown three different coordination modes in the three complexes: a monoanionic tridentate coordination mode with the CoII complex ([Co(LH)2]·CH3OH, 1), a dianionic tridentate coordination mode with the MnIV complex ([Mn(L)2], 2), and monoanionic μ2-phenoxo-bridged tridentate coordination mode with the ZnII complex ([Zn(LH)(OOCCF3)]2, 3). All three complexes show interesting supramolecular architectures, especially for 3 a nanoporous supramolecular (4, 4) grid 2D framework is formed. The ligand and the complexes are well characterized by elemental analysis, IR and UV–vis spectroscopy. The spin states of the CoII and MnIV metal ions and hence the coordination modes of the ligand in these complexes are in good agreement with the EPR spectroscopic data. The fluorescence emission spectra of LH2 and the zinc complex 3 are measured in acetonitrile solution as well as in solid state.

A novel hexanuclear complex [{(CuL)2Cu}2(μ-dca)2](ClO4)2·2L′(1) (where H2L = (OH)C6H4C(CH3) N(CH2)3N C(CH3)C6H4(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)2− and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV–Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ2-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)2Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)2Cu}2(μ-dca)2]2+. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm−1) between the copper(II) centers.

A new tetra-nuclear coordination complex [Cu 4 (HL) 4 ] ( 1 ) containing Cu 4 O 4 cubane core has been synthesized by using Schiff base ligand [(OH)C 6 H 4 CH N C(CH 3 )(CH 2 OH) 2 ] (H 3 L), obtained by the 1:1 condensation of 2-amino-2-methyl-1,3-propanediol with salicylaldehyde and thoroughly characterized by micro-analytical, FT-IR, UV–Vis, thermal and room temperature magnetic susceptibility measurements. Structural characterization of the complex has been done by single crystal X-ray diffraction analysis. Structural elucidation reveals versatile coordination modes for two identical alkoxo oxygen atoms of the Schiff base ligand; one in its deprotonated form exhibits μ 3 -bridging to bind three similar copper(II) centers whilst the protonated one remains as monodentate or non-coordinating. Structural analysis also shows that the Cu 4 O 4 cubane core in 1 consists of four μ 3 -alkoxo oxygen bridged copper(II) atoms giving an approximately cubic array of alternating oxygen atoms and copper(II) atoms where the metal centers display both distorted square pyramidal and distorted octahedral geometries.

A dicyanoamide-bridged 2D polynuclear zinc(II) complex having formula [Zn2(L)(μ-dca-κN1κN5)2]n, 1 has been synthesized using the Schiff base ligand N,N′-bis(salicylidene)-1,3-diaminopentane, (H2L) ...

International audience; By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)Cdouble bond; length as m-dashN(CH2)3Ndouble bond; length as m-dashC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment of the two μ-phenoxo and μ1,1-azido bridged isomorphous tetranuclear CuII complexes are slightly different. Thus, both complexes are formed by very similar building units, although with a significant variation in the bridging Cu–O(phenoxo)–Cu and Cu–N(azido)–Cu bond angles. The consequences of these structural variations on the magnetic properties have been investigated from both the experimental and theoretical points of view by variable temperature magnetic measurements and DFT calculations.

Two terdentate NNO donor Schiff base ligands CH 3 C(OH) CHC(CH 3 ) NCH 2 C 5 H 4 N [ HL 1 ] and C 6 H 5 C(OH) CHC(CH 3 ) NCH 2 C 5 H 4 N [ HL 2 ] were used to synthesize two mononuclear square planar copper(II) complexes, [Cu L 1 (CF 3 COO)] ( 1 ) and [Cu L 2 (CF 3 COO)] ( 2 ). The complexes were characterized by elemental analyses, FT-IR, UV–vis spectral methods and their structures were established by single crystal X-ray diffraction study. The biochemical activity of the complexes towards DNA binding were performed using absorbance and fluorescence titration methods and their mode of binding with calf thymus DNA has been established by viscosity measurement technique.

Two new copper(II) complexes, [Cu3(L1)2(H2O)2](ClO4)2 (1) and [CuL2 ⊂ (H2O)] (2) have been derived from two di-compartmental Schiff base ligands H2L1 and H2L2, respectively. Depending on slight modification of the substituent group of the potentially N2O4 donor ligands, tri- and mononuclear structures are obtained, which have been confirmed by single-crystal X-ray diffraction studies. Both complexes have been characterized by elemental analysis, IR, UV–vis and EPR spectroscopy. Complex 1 consists of an angular trinuclear array of copper ions, while complex 2 consists of a mononuclear copper center. Variable temperature magnetic susceptibility measurements have been performed to investigate the magnetic behaviour of complex 1 and the result indicates a strong antiferromagnetic exchange interaction (J = −120.1(2) cm−1) between the adjacent copper(II) centers through two double μ2-phenoxo bridges. Complex 2 is a mononuclear inclusion compound encapsulating one water molecule in the vacant external compartment of the ligand through hydrogen-bonding interactions.

A new tetradentate N 2 O 2 donor Schiff base ligand [OHC 6 H 4 CH NCH 2 CH 2 CH(CH 2 CH 3 )N CHC 6 H 4 OH = H 2 L ] was obtained by 1:2 condensation of 1,3-diaminopentane with salicylaldehyde and has been used to synthesise an unusual copper(II) complex whose asymmetric unit presents two structurally different almost linear trinuclear units [Cu 3 (μ- L ) 2 (ClO 4 ) 2 ] [Cu 3 (μ- L ) 2 (H 2 O)(ClO 4 ) 2 ] ( 1 ). The ligand and the complex were characterised by elemental analysis, FT-IR, 1 H NMR and UV–Vis spectroscopy in addition electrochemical and single crystal X-ray diffraction studies were performed for the complex. The magnetic properties of 1 reveal the presence of strong intra-trimer ( J 1 = −202(3) cm −1 and J 2 = −233(3) cm −1 ) as well as very weak inter-trimer ( zJ ′ = −0.11(1) cm −1 ) antiferromagnetic interactions.

A new tetranuclear complex, [Cu4L4]·2H2O (1), has been synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligand 4-chloro-2-[(E)-(2-hydroxyethylimino)methyl]phenol (H2L). Single-crystal X-ray diffraction studies reveal that complex 1 consists of a Cu4O4 cubane core where the four copper(II) centers are linked by μ3-alkoxo bridges. Each CuII ion assumes a distorted square-pyramidal geometry with CuNO4 chromophore. Variable-temperature magnetic susceptibility data exhibit distinct ferromagnetic exchange interaction, corroborating with the geometrical parameters of the structural unit. Theoretical calculations based on DFT method have been used to quantify the strength of the Cu···Cu magnetic interactions which help to evaluate the experimental coupling constants: J1 = +64.8, J2 = +24.4 and J3 = +3.0 cm–1. The EPR spectroscopy also gives some insight on the ferromagnetic S = 2 ground state of 1. In addition, detailed investigations have been carried out on the catalytic activity of the complex towards the oxidation of cycloalkanes using H2O2 as terminal oxidant.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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.

Two new dicyanamido-bridged di- and polynuclear complexes of Co(II), [Co(dca)(tptz)(H2O)]2·2(ClO4) (1) and [Co(dca)2(imz)2]n (2) [dca, dicyanamide; tptz, 2,4,6-tris(2-pyridyl)1,3,5-triazine; and imz, imidazole] have been synthesized and characterized structurally, as well as magnetically. The X-ray single crystal structure determination of complex 1 shows that two symmetry related octahedral Co(II) ions are separated by dca ligand and other coordination sites are satisfied by tptz and aquo ligands. Each dinuclear unit is associated with each other by intramolecular hydrogen bonding interactions, giving rise to a 1D chain structure. On the other hand complex 2 is a 1D coordination polymer having [Co(II)(imz)2] units connected by double bridging dca ligands. These 1D chains interact through face-to-face π–π stacking interactions of the imz rings extending the dimensionality to a 2D supramolecular network. The variable temperature (300–2 K) magnetic measurements of both compounds reveal that dicyanamide exhibits a weak antiferromagnetic interaction between the metal centers.

Three new coordination complexes, [Cu(L 1 )(H 2 O)] ( 1 ), [Ni(L 2 ) 2 ]·CH 3 CN ( 2 ) and [Co(HL 3 )(L 3 )] ( 3 ) [where H 2 L 1 , N,N′ -bis(3-methoxysalicylidenimino)-1,3-diamino-propane; HL 2 , 2-(( E )-(1,3-dihydroxy-2-methylpropan-2-ylimino)methyl)phenol; H 2 L 3 , 2-(( E )-(2-hydroxyethylimino)methyl)-4-bromophenol] have been synthesized and systematically characterized by elemental analyses, FT-IR, electronic spectroscopy, cyclic voltammetry and thermogravimetric analyses. Single crystal X-ray diffraction studies confirm that the metal center in complex 1 has distorted square-pyramidal geometry while it is distorted octahedral in the other two complexes. In all the complexes O–H⋯O hydrogen bondings assemble the molecular units leading to ordered supramolecular architectures. While both complexes 1 and 2 form infinite one-dimensional arrays through the self organisation of hydrogen bonded ring motifs, complex 3 is a unique star-shaped cyclic hexamer generated through intermolecular hydrogen bonding.

Three new coordination complexes, 2{[Co(L1)2]ClO4} · 0.5CH3OH (1), [Mn(L2)2] (2), and [Cu(HL2)(L2)]ClO4 · 2H2O (3) have been synthesized from two tridentate N,N,O-donor hydrazone ligands HL1, 2-acetylpyridine-salicyloylhydrazone, and HL2, 2-benzoylpyridine-salicyloylhydrazone, respectively and thoroughly characterized by elemental analysis, FT-IR, UV–Vis, electrochemical, and room temperature magnetic susceptibility measurements. Structures of the complexes have been unequivocally established by single crystal X-ray diffraction technique. Structural analysis reveals that 1 consists of two chemically similar but crystallographically independent cationic [Co(L1)2]+ units and 2 consists of a neutral [Mn(L2)2] molecule while 3 consists of a cationic [Cu(HL2)(L2)]+ unit. Metal ions display distorted octahedral geometry in 1 and 2 while in 3 it shows a distorted square pyramidal geometry. Ligand conformations around the metal ions are stabilized by the presence of intra-ligand hydrogen bonding in all the complexes. Structure of 3 reveals that a perchlorate ion linked to the complex by hydrogen bonding via a water molecule.

Three new mono–di–trinuclear cobalt complexes of three different Schiff bases have been synthesised. In all the three complexes psuedohalides (NCO− and N3−) have been incorporated to generate structural variation. Of the three Schiff bases, HL1 and HL2 were obtained by selective condensation of two different 1,3-diamines with 2-hydroxyacetophenone and H2L3 resulted from non-selective condensation of 1,3-diamine with 2-hydroxyacetophenone. Only one –NH2 functionality of 1,3-diaminopropane and 1,3-diaminopentane was selectively condensed with 2-hydroxyacetophenone to generate Schiff bases HL1 and HL2, respectively. H2L3 was obtained by condensing both the amine functionality of 1,3-diaminopropane with 2-hydroxyacetophenone. Therefore HL1 and HL2 behave as a N2O donors, whereas H2L3 provides a N2O2 donor coordination environment for the cobalt ions in the respective complexes. In [Co(L1)2]2 [Co(NCO)4] (1) the asymmetric unit comprises of five mononuclear cobalt centers, [Co2(μ–N3)2(L2)2(N3)2] (2) is a dinuclear and [(H2O)2Co(μ–N3)2(μ–L3)2Co2(N3)1.25(CH3O)0.75] · H2O (3) is a trinuclear cobalt species. The three complexes have been characterised using IR, UV–Vis spectroscopy and cyclic voltammetry. Structural aspects of 1, 2 and 3 have been described by performing single crystal X-ray analysis. EPR analyses of 1 and 3, and DNA binding abilities of all three cobalt complexes have been studied in detail.

Two new square-planar Ni(II) complexes, [NiL1(NCS)] (1) and [NiL2(N3)] (2) have been synthesized with the unsymmetrical tridentate Schiff base ligands [(CH3)2NCH2CH2N=C(CH3)CH=C(OH)(C6H5)], L 1 H, derived from benzoylacetone and 2-dimethylaminoethylamine and [(CH3CH2)2NCH2CH2N=C(CH3)CH=C(OH)(C6H5)], L 2 H, derived from benzoylacetone and 2-diethylaminoethylamine, respectively. The complexes have been characterized by elemental analysis, FT-IR, UV-Vis spectroscopy, electrochemical and thermal methods (where applicable). Structures have been established by the single-crystal X-ray diffraction technique which reveals the discrete nature of the complexes in which the metal centers adopt a distorted square planar geometry. Coordination environments of the metal ions in the complexes are satisfied with two different unsymmetrical Schiff base ligands having similar N2O donor sets and a terminal pseudohalide anion (thiocyanate for 1 and azide for 2).

International audience; A novel centrosymmetric dinuclear Cd(II) complex [CdL (CH3COO)]2 (1) has been synthesized by the reaction of Cd(CH3COO)2·2H2O with a Schiff base ligand HL [HL = (E)-2-((pyridin-2-yl)methyleneamino)benzoic acid]. Title complex has been systematically characterized by elemental analysis, FT-IR, and thermal studies. Single crystal X-ray structural analysis reveals that Cd(II) centers in 1 adopt distorted monocapped octahedral geometry and held together by rare doubly μ-2, 2 carboxylato bridging which is believed to be first relating to anthranilic carboxylate. At room temperature, compound in the solid state exhibits moderate photoluminescence activities indicating its potential as promising photoactive material.

International audience; A new tridentate N2O donor Schiff base ligand [(C6H5C(OH)CHC(CH3)NCH2C5H4N)LH] was obtained by 1:1 condensation of benzoylacetone with 2-picolylamine and has been used to synthesise a mononuclear [CuLCl] (1) and an end-to-end dicyanamide bridged polynuclear {[Cu2(μ-L)2(μ2-1,5-(CN)2N)]ClO4}n (2) copper(II) complexes. The ligand, 1 and 2 were clearly characterised by elemental analysis, FT-IR, 1H NMR, UV–Vis spectral studies, electrochemical studies and in addition single crystal X-ray diffraction studies were performed for 1 and 2. The Schiff base ligand [LH] shows a significant variation in its coordination behaviour with copper(II) ion in absence and in presence of dicyanamide ion in 1 and 2 respectively. In absence of dicyanamide the deprotonated enolato oxygen of the tridentate Schiff base ligand [L]− coordinates the copper(II) ion in a monodentate fashion generating a mononuclear species (1) whereas in presence of the dicyanamide ion, the deprotonated enolato oxygen of [L]− bridges two adjacent [CuL(CN)2N] units through μ-OL bridges, forming dimers. The dimeric units are further linked to adjacent dimeric units through μ2-1,5-dicyanamide bridges to produce 1D polymeric chains in 2. Variable temperature magnetic susceptibility measurements for 2 in the temperature range 2-300 K reveal the presence of weak antiferromagnetic exchange interactions in the polymeric chain.

A novel hydroxo-bridged cyclic tetranuclear copper(II) complex with the guanazole ligand (3,5-diamino-1,2,4-triazole = Hdatrz), [Cu4(datrz)4(μ2-OH)2(NO3) (H2O)6] · (NO3) · 5(H2O) (1) has been synthesised and characterised by X-ray crystallography. In 1, the four copper(II) centres are linked by hydroxo bridges and the N1,N2-coordination of the deprotonated guanazole ligands. The core has considerably short Cu⋯Cu distances in the range of 3.3550(4)–3.3611(4) A. Thermal analysis of 1 reveals that the cyclic framework constructed with hydroxo and guanazole ligands is stable up to 285 °C.

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.

One new one-dimensional polymeric complex [Cd(C5H6N2)2(SeCN)2] n (1) has been synthesized and characterized by elemental analyses, spectroscopic studies and single crystal X-ray crystallography. Crystal structure shows the one-dimensional chain is propagated through doubly bridging selenocyanate and 4-aminopyridine acts as terminal ligand. The complex was characterized by fluorescence and NMR spectral studies and the results are consistent with the crystal structure.

Two new Cu(II) linear trinuclear Schiff base complexes, [Cu3(L)2(CH3COO)2] (1) and [Cu3(L)2(CF3COO)2] (2), have been prepared using a symmetrical Schiff base ligand H2L [where H2L = N,N'-bis(2-hydroxyacetophenone)propylenediimine]. Both of the complexes have been characterized by elemental analyses, Fourier transform IR, UV/vis, and electron paramagnetic resonance spectroscopy. Single-crystal X-ray structures show that the adjacent Cu(II) ions are linked by double phenoxo bridges and a mu(2)-eta(1):eta(1) carboxylato bridge. In each complex, the central copper atom is located in an inversion center with distorted octahedral coordination geometry, while the terminal copper atoms have square-pyramidal geometry. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit a distinct antiferromagnetic interaction of J = -36.5 and -72.3 cm(-1) for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) and continuous-shape measurement (CShM) studies have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the antiferromagnetic behavior shown by the complexes.

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.

Two new L–M–L type transition metal coordination polymers [M(C 6 H 12 N 4 )(NCO) 2 (H 2 O) 2 ] n , where M = Co(II) ( 1 ) and Ni(II) ( 2 ), have been synthesised under controlled hydrothermal condition and characterised spectroscopically and by thermal analyses. Here hmt or hexamethylenetetramine has behaved as a neutral organic bidentate spacer molecule. Both the complexes crystallise in the monoclinic system as confirmed from single crystal X-ray diffraction studies. Cryomagnetic susceptibility measurements over a wide range of temperature (2–300 K) under 0.5 T magnetic fields show a weak antiferromagnetic interaction of J = −0.65 cm −1 for 1 and −1.6 cm −1 for 2 . The values have been given a favorable support by weak covalent and H-bonding interactions between octahedral M(II) metal centers as revealed from X-ray structure determination. The high dimensionality of the structures is probably a manifestation of extensively weak covalent interactions and H-bondings.

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL1] · CH3OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N2O2 tetradentate Schiff base ligand H 2 L 1 , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL2)3] · (ClO4)3 · H2O (2) was synthesised using an asymmetric N2O2 tetradentate Schiff base ligand HL 2 on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N2O2 functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.

Two new Cd(II) complexes, having one binuclear structure [Cd2(L)2(Cl)2] (1) and another azido bridged one-dimensional zig-zag polynuclear network [Cd3(μ1,1-N3)4(L)2{H2N(CH2)2N(C2H5)2} · H2O]n (2) have been synthesized from a tridentate N2O donor Schiff base ligand LH, [LH = (OCH3)(OH)C6H3CHN(CH2)2N(C2H5)2], which is the condensation product of 2-hydroxy-4-methoxybenzaldehyde and 2-diethylaminoethylamine. Both the complexes 1 and 2 have been characterized by elemental analyses, IR & 1H NMR spectroscopy, TGA and fluorescence studies. Finally their structures have been established by single crystal X-ray diffraction method. Structural study reveals that in the complex 1, two Cd(II) centers are held together by two μ2-phenolato oxygen atoms and the terminal chlorine atom occupies the apical site of the square pyramidal environment of each metal center. In case of complex 2, the trinuclear asymmetric unit contains octahedral Cd(II) centers which are further held together by doubly end-on azido bridging to form a zig-zag polynuclear structure. It also displays intraligand 1(π–π∗) fluorescence and can potentially serve as photoactive material.

A new ligand LH (where LH = N-(picolinoyl)-biurate) has been prepared and characterized. The presence of three amide linkages make this ligand sufficiently flexible to act as N,N,O donor tridentate blocking ligand in the formation of a one dimensional metal-ligand layer like structure. Reaction of LH and dicyanamide (dca) with Co(NO3)2 · 6H2O gives [CoL(dca)]n (1). In this compound picolinamide modulated ligand L coordinated the central Co(II) ion in a meridonal-fashion. The single crystal X-ray crystallography revealed that in 1, dca acts as μ1,5− singly bridging ligand whereas μ1,5− doubly bridging is the more common type. This gives rise to the 1D undulated waves like structure. The Co(II) centre is surrounded in a distorted square pyramidal coordination geometry. The variable temperature magnetic (VTM) susceptibility measurements show that the global feature of the χMT versus T curve for 1 is characteristic of very weak antiferromagnetic interactions through the dicyanamide ligand and between 300 and 5 K the best fit parameter was determined as J = −3.52 cm−1. The X-ray structure, VTM study and UV–Vis spectrum of the compound show that 1 is a low-spin square-pyramidal compound whereas high-spin compounds are more common for the five coordinated cobalt (II) compounds. The X-band EPR spectrum of 1 at room temperature shows only one isotropic band centred at g = 2.08.

Three new coordination complexes of Zn(II) and Mn(II) have been synthesised using two different tridentate N,N,O donor hydrazone ligands, Hpbh and Hacpbh respectively. The complexes [Zn(pbh)2] (1) and [Zn(acpbh)2] (2) have been synthesized by the treatment of ZnSO4 · 7H2O with Hpbh and Hacpbh hydrazone ligands, respectively. The Mn(II) complex [Mn(acpbh)2] (3) was obtained on reacting Mn(NO3)2 · 4H2O with the ligand Hacpbh. The ligands Hpbh and Hacpbh were prepared by condensing pyridine-2-carboxaldehyde and 2-acetylpyridine with benzhydrazide respectively. Inspite of varying the carbonyl functionality attached to the pyridine moiety present in the hydrazone ligands in both the Schiff bases, we obtained three mononuclear complexes 1, 2, and 3 which were clearly characterized from single crystal X-ray diffraction studies. Spectroscopic investigations like IR and UV/Vis have been carried out for 1, 2, and 3. Fluorescence studies have been performed for 1 and 2. For 3 cyclic voltammetry, room temperature magnetic study and EPR measurements have been recorded.

The reaction of copper(II) chloride dihydrate with 2-hydroxy-3-methoxybenzaldehydethiosemicarbazone (HL) ligand in a 1:1 ratio forms the complex [Cu(L)(Cl)] · H2O. The complex is characterized by spectroscopic, electrochemical, and thermal analysis. X-ray crystallographic analysis reveals that the central copper atom displays the distorted square planar geometry. The water molecule present in the lattice participates in a strong hydrogen bonding network, which leads to a 2D supramolecular arrangement.

Two new square planar Cu(II) and Ni(II) complexes, [CuL1(NCO)] (1) and [NiL2(N3)] (2) have been synthesized with two different tridentate N2O donor Schiff base ligands L 1 H (1:1 condensation product of benzoylacetone and 2-diethylaminoethylamine) and L 2 H (1:1 condensation product of benzoylacetone and 2-dimethylaminoethylamine), respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis spectroscopy, room temperature magnetic susceptibility measurement, electrochemical, thermal, and single crystal X-ray diffraction studies. Structural studies reveal that in both the complexes metal centers have square planar environment with N2O donor set of Schiff base ligands and terminal pseudohalide anions (isocyanate for 1 and azide for 2) at four coordination sites of square plane. Square planar complexes of Cu(II) and Ni(II) with N 2 O donor set of two Schiff base ligands: synthesis and structural aspects Subhra Basak, Soma Sen, Samiran Mitra, C. Marschner, W. S. Sheldrick Two new square planar Cu(II) and Ni(II) complexes, [CuL1(NCO)] (1) and [NiL2(N3)] (2) have been synthesized with two different tridentate N2O donor Schiff base ligands L 1 H and L 2 H respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis spectroscopy, room temperature magnetic susceptibility measurement, electrochemical, thermal and single crystal X-ray diffraction studies.

Three novel Schiff base Cd(II) trimeric complexes, [Cd3(L1)2(SCN)2(CF3COO)2] (1), [Cd3(L1)2(SCN)2(HCONMe2)] (2) and [Cd3(L2)2{N(CN)2}2] (3) have been prepared from two different symmetrical Schiff bases H2L1 and H2L2 (where H2L1 = N1,N3-bis(salicylideneimino)diethylenetriamine, a potentially pentadentate Schiff base with a N3O2 donor set, and H2L2 = N1,N3-bis(3-methoxysalicylideneimino)diethylenetriamine, a potentially heptadentate Schiff base with a N3O4 donor set). All the complexes have been synthesised under similar synthetic procedures and their crystal structures have been established by single crystal X-ray diffraction methods. The ligands and their metal complexes have been characterised by analytical and spectroscopic techniques. Among the three complexes, 1 and 3 are linear whereas 2 is a cyclic trimer. In 1 and 3, all the doubly phenoxo bridged Cd(II) metal centres are in a distorted octahedral environment. In complex 2, two of the three Cd(II) centres reside in a distorted octahedral environment and the remaining one enjoys a monocapped octahedral geometry. Altogether the variety in the bridging mode of two new salen-type ligands has been established through these complexes.

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.

Two new cyano bridged Cu–Co and Cu–Fe trinuclear bimetallic assemblies, [(CuL)[Co(CN)6](CuL)]ClO4 · 3.5H2O (1) and [(CuL)[Fe(CN)6](CuL)] · 13H2O (2) where [L = (3E,5E)-N1,N4-bis((pyridin-2-yl)methylene)butane-1,4-diamine] have been prepared using cyanometallates as anion precursors and characterised by elemental analyses, spectroscopic studies, single crystal X-ray diffraction and cryomagnetic susceptibility measurements. Magneto-structural correlations have been drawn from cryomagnetic susceptibility measurements over a wide temperature range (2–300 K) under 0.5 T magnetic fields. Weak antiferromagnetic interactions with J = −0.81 and −0.73 cm−1 are found for 1 and 2, respectively, showing a very weak coupling, as expected from the diamagnetic long chain –NC–Co–CN–CN– and –NC–Fe–CN–CN– bridges revealed from the single crystal X-ray diffraction studies.

Four new coordination complexes, NiII(L)2 (1), [CoIII(L)2]ClO4 (2), [Zn(HL)(L)]ClO4 · H2O (3) and [Zn(L)2][Zn(L)(HL)]ClO4 · 7H2O (4) (where L is a monoanion of a Schiff base ligand, N′-[(2-pyridyl)methylene]salicyloylhydrazone (HL) with NNO tridentate donor set), have been synthesised and systematically characterised by elemental analysis, spectroscopic studies and room temperature magnetic susceptibility measurements. Single crystal X-ray diffraction analysis reveals that 1 is a neutral complex, while 2–4 are cationic complexes. Among them, 4 is a rare type of cationic complex with two molecules in the asymmetric unit. The ligand chelates the metal centre with two nitrogen atoms from the pyridine and imino moieties and one oxygen atom coming from its enolic counterpart. All the reported complexes show distorted octahedral geometry around the metal centres, with the two metal–N (imino) bonds being significantly shorter than the two metal–N (Py) bonds.