Synthesis, crystal structure and magnetic properties of a polymeric copper(II) schiff-base complex having binuclear units covalently linked by isonicotinate ligands

The polynuclear copper(II) complex [{Cu2L(O2CC5H4N)}·C2H5OH]x (1), where H3L is a 1:2 Schiff base derived from 1,3-diaminopropan-2-ol and salicylaldehyde, has been prepared and structurally characterized. The structure consists of a one-dimensional zigzag chain in which the binuclear [Cu2L]+ units are covalently linked by isonicotinate ligands to give a syndiotactic arrangement of the copper ions protruding outside the chain. In the basic unit, the copper(II) centres are bridged by an alkoxo and a carboxylato ligand, giving a Cu···Cu distance of 3.492(3) Å and a Cu-O-Cu angle of 130.9(2)° . While one copper centre has a square-planar geometry, the other copper is squarepyramidal with the pyridine nitrogen being the axial ligand. The visible electronic spectrum of 1 shows a broad d-d band at 615 nm. The complex shows a rhombic X-band EPR spectral pattern in the polycrystalline phase at 77 K. Magnetic susceptibility measurements in the temperature range 22 to 295 K demonstrate the antiferromagnetic behaviour of 1. A theoretical fit to the magnetic data is based on a model assuming 1 as an equimolar mixture of copper atoms belonging to an antiferromagnetically coupled one-dimensional Heisenberg chain with the other copper atoms outside the chain behaving like paramagnetic centres

Synthesis, spectral, electrochemical and magnetic properties of new asymmetric dicopper(II) complexes bearing chemically distinct coordination sites

Two new unsymmetrical binucleating ligands, 2-[bis(3- N, N -dimethylaminopropyl)-aminomethyl]-6-[prolin-1-yl)methyl]-4-bromophenol [H 2 L 1 ] and 2-[bis(3- N, N -dimethylaminopropyl)aminomethyl]-6-[prolin-1-yl)methyl]-4-methylphenol [H 2 L 2 ], and their dicopper(II) complexes with different exogenous bridging motifs (OAc, Br and Cl) have been prepared and characterized by spectral, electrochemical, magnetic and e.p.r. studies. Electrochemical studies indicate the presence of two irreversible reduction peaks in the cathodic region. Variable temperature magnetic susceptibility studies of the complexes show that the extent of antiferromagnetic coupling increases in the order: OAc − < Cl − < Br − . Broad isotropic or axial symmetric spectral features are observed in powder e.p.r. spectra of the complexes at 77 K. A comparison of the electrochemical and magnetic behaviour of the complexes derived from the ligands is discussed on the basis of an exogenous bridge as well as the substituent at the para position of the phenolic ring.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43855/1/11243_2004_Article_5272793.pd

SYNTHESIS, CHARACTERISATION AND ANTIMICROBIAL ACTIVITY OF NICKEL(II) COMPLEXES DERIVED FROM PENTADENTATE SCHIFF BASE LIGAND

Two different para substituted dinuclear nickel(II) complexes [ Ni2L(O2CC6H4-p-X)] [ X= NO2, Cl ] were synthesized by the reaction of corresponding precursor withpentadentate Schiff base ligand.The ligand was characterized by UV-Visible,FTIR, NMRstudies.The synthesized complexes were characterized by molar conductance, UV- Visible, FTIR spectral studies.The ligand and its complexes screened for antimicrobial activity

Synthesis, crystal structure and properties of [Cu<SUB>2</SUB>(O<SUB>2</SUB>CC<SUB>6</SUB>H<SUB>4</SUB>Me-p)<SUB>3</SUB>(Me<SUB>2</SUB>NCH<SUB>2</SUB>CH<SUB>2</SUB>NMe<SUB>2</SUB>)<SUB>2</SUB>]PF<SUB>6</SUB>: an unprecedented [Cu<SUB>2</SUB>(μ-O<SUB>2</SUB>CR)<SUB>4</SUB>] into [Cu<SUB>2</SUB>(μ-O<SUB>2</SUB>CR)<SUB>3</SUB>]<SUP>+</SUP> core conversion

Tris(μ-p-methylbenzoato-O,O')bis(N,N,N',N'-tetramethyl-1,2-diaminoethane)dicopper(II) hexafluorophosphate, [Cu2(O2CC6H4Me-p)3(tmen)2]PF61, was prepared from a reaction of [Cu2(O2CC6H4Me-p)4(H2O)2] with tmen in ethanol at 0°C and characterized by spectral, electrochemical, magnetic and X-ray crystallographic studies. The cationic complex consists of a dicopper(II) unit having three bridging carboxylates and two bidentate chelating tmen ligands. The co-ordination geometry of the copper centres is distorted square pyramidal (CuO3N2). The Cu···Cu distance in the core is unusually long, 3.419(2) Å. The Cu-O-C angles at two copper centres are drastically different. Magnetic studies in the temperature range 20-296 K show the presence of an antiferromagnetically coupled dicopper(II) unit giving -2J = 81.4 cm-1 and g = 2.081. Cyclic voltammetric studies have shown a cathodic peak at -0.92 V with an anodic response at 0.10 V vs. SCE at 100 mV s-1. The visible electronic spectrum of the complex shows a d-d band at 665 nm (ε=263 M-1 cm-1) in MeCN. The magnetostructural data among the syn, syn-carboxylato bridged dicopper(II) systems with a [Cu2(μ-O2CR)m]n+ (m=4−1; n=0−3) core show that while 1 structurally has a tricarboxylato bridged dicopper(II) unit, magnetically it behaves like a dibridged one

An alkoxo-hydroxo-bridged octanuclear copper(II) complex with a hydrophobic exterior and a hydrophilic metallamacrobicyclic core showing selective hydrogen-bonding interactions

Selective binding of a substrate to a molecular receptor system leads to the formation of a supramolecular entity by the process of molecular recognition.1 Organic macrocyclic compounds having binding sites suitable for noncovalent interactions are the key systems in supramolecular chemistry.1,2 It is envisaged that the metallamacrocyclic transition-metal complexes could be potential “inorganic analogues” of the organic macrocyclic receptor systems.3-5 The presence of metal ions in the metallamacrocyclic framework is expected to fine-tune the receptor capabilities of the available binding sites for noncovalent interactions with other molecular species. Recent reports have shown that a new class of complexes, viz. metallacrowns and metallacryptates, show novel physicochemical properties that are distinctly different from those of their organic analogues.

Synthesis, crystal structure and magnetic properties of a polymeric copper(II) Schiff-base complex having binuclear units covalently linked by isonicotinate ligands

The polynuclear copper(II) complex [{Cu2L(O2CC5H4N)}. C2H5OH](x) (1), where H3L is a 1&ratio;2 Schiff base derived from 1,3-diaminopropan-2-ol and salicylaldehyde, has been prepared and structurally characterized. The structure consists of a one-dimensional zigzag chain in which the binuclear [Cu2L](+) units are covalently linked by isonicotinate ligands to give a syndiotactic arrangement of the copper ions protruding outside the chain. In the basic unit, the copper(II) centres are bridged by an alkoxo and a carboxylato ligand, giving a Cu ... Cu distance of 3.492(3) Angstrom and a Cu-O-Cu angle of 130.9(2)degrees. While one copper centre has a square-planar geometry, the other copper is square-pyramidal with the pyridine nitrogen being the axial ligand. The visible electronic spectrum of 1 shows a broad d-d band at 615 nm. The complex shows a rhombic X-band EPR spectral pattern in the polycrystalline phase at 77 K. Magnetic susceptibility measurements in the temperature range 22 to 295 K demonstrate the antiferromagnetic behaviour of 1. A theoretical fit to the magnetic data is based on a model assuming 1 as an equimolar mixture of copper atoms belonging to an antiferromagnetically coupled one-dimensional Heisenberg chain with the other copper atoms outside the chain behaving like paramagnetic centres