Tuning of the exchange interaction and the Curie temperature by mixed crystal formation of the bridging anionic ligands.

Mixed crystals with the composition [Co(NCS)x(NCSe)2-x(pyridine)2]n were prepared from solution and by annealing of Co(NCS)x(NCSe)2-x(pyridine)4. With increasing selenocyanate content, an increase of the magnetic exchange constant and of the critical temperature (Curie temperature) is observed, which offers a rational route to control these parameters in detail, without changing the metal cations.

Modeling Spin Interactions in a Triangular Cobalt(II) Complex with Triaminoguanidine Ligand Framework: Synthesis, Structure, and Magnetic Properties.

The new tritopic triaminoguanidine-based ligand 1,2,3-tris[(pyridine-2-ylmethylidene)amino]guanidine (Hpytag) was synthesized. The reaction of a mixture of cobalt(II) chloride and cobalt(II) perchlorate with the ligand Hpytag in pyridine solution leads to the formation of the trinuclear cobalt(II) complex [Co(pytag)(py)Cl]ClO. Three octahedrally coordinated high-spin cobalt(II) ions are linked through the bridging triaminoguanidine backbone of the ligand leading to an almost equilateral triangular arrangement.

Static and dynamic magnetic properties of the ferromagnetic coordination polymer [Co(NCS)(py)].

[Co(NCS)(py)] (py = pyridine) is composed of ferromagnetic chains of Co(ii) cations connected by double NCS bridges. The chains are irregular because of two crystallographically inequivalent Co(ii) cations. The coordination polyhedron of the Co(ii) cations is a distorted octahedron built from two N and two S atoms of four equatorial NCS anions and two apical N atoms of the pyridine ligands.

Influence of metal coordination and co-ligands on the magnetic properties of 1D Co(NCS) coordination polymers.

Two new transition metal thiocyanate coordination polymers with the composition [Co(NCS)(4-vinylpyridine)] (1) and [Co(NCS)(4-benzoylpyridine)] (2) were synthesized and their crystal structures were determined. In both compounds the Co cations are octahedrally coordinated by two trans-coordinating 4-vinyl- or 4-benzoylpyridine co-ligands and four μ-1,3-bridging thiocyanato anions and linked into chains by the anionic ligands. While in 1 the N and the S atoms of the thiocyanate anions are also in trans-configuration, in 2 they are in cis-configuration.

A magnetooptical study of (4-(2-dibutylaminoethanolato-N,O,O,O) chlorido copper(II)): a cubane complex with dominant ferromagnetic interactions.

This paper reports the experimental and theoretical study of a tetranuclear (CuClOCH2CH2N(C4H9)2)4 complex. Analysis of the magnetic circular dichroism spectrum was performed based on the Hamiltonian that includes the crystal field of the nearest ligands and the spin-orbit interaction. The crystal field parameters were evaluated in the framework of the exchange charge model that accounts for the exchange and covalence effects.

Synthesis, structure and properties of [Co(NCS)2(4-(4-chlorobenzyl)pyridine)2]n, that shows slow magnetic relaxations and a metamagnetic transition.

The reaction of Co(NCS)2 with 4-(4-chlorobenzyl)pyridine (ClBP) leads to the formation of Co(NCS)2(4-(4-chlorobenzyl)pyridine)4 () and [Co(NCS)2(4-(4-chlorobenzyl)pyridine)2]n (). In the crystal structure of the Co(ii) cations are octahedrally coordinated by two terminal bonded thiocyanato anions and four ClBP ligands, whereas in the Co(ii) cations are linked into chains by pairs of μ-1,3-bridging thiocyanato anions. Magnetic measurements of show an antiferromagnetic phase transition with TN = 3.

Synthesis, characterization, hydrolase and catecholase activity of a dinuclear iron(III) complex: Catalytic promiscuity.

Herein, we report the synthesis and characterization of the new di-iron(III) complex [(bbpmp)(H2O)(Cl)Fe(III)(μ-Ophenoxo)Fe(III)(H2O)Cl)]Cl (1), with the symmetrical ligand 2,6-bis{[(2-hydroxybenzyl)(pyridin-2-yl)methylamino]methyl}-4-methylphenol (H3bbpmp). Complexes 2 with the unsymmetrical ligand H2bpbpmp - {2-[[(2-hydroxybenzyl)(2-pyridylmethyl)]aminomethyl]-6-bis(pyridylmethyl) aminomethyl}-4-methylphenol and 3 with the ligand L(1)=4,11-dimethyl-1,8-bis{2-[N-(di-2-pyridylmethyl)amino]ethyl}cyclam were included for comparison purposes. Complex 1 was characterized through elemental analysis, X-ray crystallography, magnetochemistry, electronic spectroscopy, electrochemistry, mass spectrometry and potentiometric titration.

Thermodynamically metastable thiocyanato coordination polymer that shows slow relaxations of the magnetization.

Reaction of cobalt thiocyanate with 4-acetylpyridine leads to the formation of [Co(NCS)2(4-acetylpyridine)2]n (3/I). In its crystal structure the Co cations are connected by pairs of μ-1,3-bridging thiocyanato ligands into dimers that are further connected into layers by single anionic ligands. DTA-TG measurements of Co(NCS)2(4-acetyl-pyridine)4 (1) led to the formation of 3/I.

A Co(II) thiocyanato coordination polymer with 4-(3-phenylpropyl)pyridine: the influence of the co-ligand on the magnetic properties.

Three new coordination compounds with the composition Co(NCS)2(4-(3-phenylpropyl)pyridine)4 (1), Co(NCS)2(4-(3-phenylpropyl)pyridine)4(H2O)2 (2) and [Co(NCS)2(4-(3-phenylpropyl)pyridine)2]n (3) were prepared and investigated. The crystal structures of compounds 1 and 2 consist of discrete complexes, in which the Co(II) cations are coordinated by only terminal N-bonded thiocyanato anions. In the crystal structure 3 of the Co(II) cations are linked into chains by pairs of μ-1,3-bridging thiocyanato anions.

Influence of the co-ligand on the magnetic and relaxation properties of layered cobalt(II) thiocyanato coordination polymers.

Reaction of Co(NCS)2 with 1,2-bis(4-pyridyl)-ethane (bpa) leads to the formation of [Co(NCS)2(bpa)2]n, which, on heating, transforms into the new layered coordination polymer [Co(NCS)2(bpa)]n. This compound can also be prepared in solution, but because no reasonable single crystals are available, its crystal structure was determined from X-ray powder data from scratch. In the crystal structure of [Co(NCS)2(bpa)]n, the cobalt(II) cations are coordinated by two S-bonded and two N-bonded thiocyanato anions and two N atoms of the bpa co-ligands in a distorted octahedral geometry.

Structural and magnetic studies of a new Co(II) thiocyanato coordination polymer showing slow magnetic relaxations and a metamagnetic transition.

Reaction of Co(NCS)2 with 4-ethylpyridine leads to the formation of three new compounds of composition Co(NCS)2(4-ethylpyridine)4 (1), [(Co(NCS)2]2(4-ethylpyridine)6 (2), and [Co(NCS)2(4-ethylpyridine)2]n (3). In all compounds the coordination of the Co(II) ions is distorted octahedral. 1 consists of discrete monomeric complexes and in 2 two Co(II) cations are linked by pairs of μ-1,3-bridging thiocyanato ligands into dimers.

In vitro and in vivo activity of a new unsymmetrical dinuclear copper complex containing a derivative ligand of 1,4,7-triazacyclononane: catalytic promiscuity of [Cu2(L)Cl3].

Here we present the synthesis of the dinuclear complex [Cu(II)2(L)Cl3] (1), where L is the deprotonated form of the 3-[(4,7-diisopropyl-1,4,7-triazacyclononan-1-yl)methyl]-2-hydroxy-5-methylbenzaldehyde ligand. The complex was characterized by single crystal X-ray diffraction, potentiometric titration, mass spectrometry, electrochemical and magnetic measurements, EPR, UV-Vis and IR. Complex 1 is able to increase the hydrolysis rate of the diester bis-(2,4-dinitrophenyl)phosphate (2,4-BDNPP) by a factor of 2700, and also to promote the plasmidial DNA cleavage at pH 6 and to inhibit the formazan chromophore formation in redox processes at pH 7.

Synthesis, crystal structure, and magnetic properties of the coordination polymer [Fe(NCS)2(1,2-bis(4-pyridyl)-ethylene)]n showing a two step metamagnetic transition.

Reaction of iron(II) thiocyanate with an excess of trans-1,2-bis(4-pyridyl)-ethylene (bpe) in acetonitrile at room temperature leads to the formation of [Fe(NCS)(2)(bpe)(2)·(bpe)] (1), which is isotypic to its Co(II) analogue. Using slightly different reaction conditions the literature known compound [Fe(NCS)(2)(bpe)(2)(H(2)O)(2)] (2) was obtained as a phase pure material. Simultaneous differential thermoanalysis and thermogravimetry prove that the hydrate 2 transforms into the anhydrate [Fe(NCS)(2)(bpe)(2)] (3), that decomposes on further heating into the new ligand-deficient 1:1 compound of composition [Fe(NCS)(2)(bpe)](n) (4), which can also be obtained directly by thermal decomposition of 1.

Design of a dinuclear nickel(II) bioinspired hydrolase to bind covalently to silica surfaces: synthesis, magnetism, and reactivity studies.

Presented herein is the design of a dinuclear Ni(II) synthetic hydrolase [Ni(2)(HBPPAMFF)(μ-OAc)(2)(H(2)O)]BPh(4) (1) (H(2)BPPAMFF = 2-[(N-benzyl-N-2-pyridylmethylamine)]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl)])-4-methyl-6-formylphenol) to be covalently attached to silica surfaces, while maintaining its catalytic activity. An aldehyde-containing ligand (H(2)BPPAMFF) provides a reactive functional group that can serve as a cross-linking group to bind the complex to an organoalkoxysilane and later to the silica surfaces or directly to amino-modified surfaces. The dinuclear Ni(II) complex covalently attached to the silica surfaces was fully characterized by different techniques.

Doubly phenoxo-hydroxo-bridged dicopper(II) complexes: individual contributions of the bridges to antiferromagnetic coupling based on two related biomimetic models for catechol oxidases.

This paper describes the synthesis, structure and spectroscopic and magnetic properties of two (μ-phenoxo)(μ-hydroxo)dicopper(II) complexes (1 and 2) which contain similar N,O-donor atoms but with distinct coordination arrangements around the Cu(II) centers. Structural and magnetic studies of 1 and 2 allowed us to evaluate, for the first time, the individual contributions of the {Cu(μ-phenoxo)Cu} and {Cu(μ-hydroxo)Cu} structural units to the antiferromagnetic coupling between the Cu(II) centers in these complexes.

Synthesis, magnetostructural correlation, and catalytic promiscuity of unsymmetric dinuclear copper(II) complexes: models for catechol oxidases and hydrolases.

Herein, we report the synthesis and characterization, through elemental analysis, electronic spectroscopy, electrochemistry, potentiometric titration, electron paramagnetic resonance, and magnetochemistry, of two dinuclear copper(II) complexes, using the unsymmetrical ligands N',N',N-tris(2-pyridylmethyl)-N-(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L1) and N',N'-bis(2-pyridylmethyl)-N,N-(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L2). The structures of the complexes [Cu(2)(L1)(μ-OAc)](ClO(4))(2)·(CH(3))(2)CHOH (1) and [Cu(2)(L2)(μ-OAc)](ClO(4))·H(2)O·(CH(3))(2)CHOH (2) were determined by X-ray crystallography. The complex [Cu(2)(L3)(μ-OAc)](2+) [3; L3 = N-(2-hydroxybenzyl)-N',N',N-tris(2-pyridylmethyl)-1,3-propanediamin-2-ol] was included in this study for comparison purposes only (Neves et al.

Bioinspired FeIIICdII and FeIIIHgII complexes: synthesis, characterization and promiscuous catalytic activity evaluation.

In this work we report on the synthesis, crystal structure, and physicochemical characterization of the novel dinuclear [Fe(III)Cd(II)(L)(μ-OAc)(2)]ClO(4)·0.5H(2)O (1) complex containing the unsymmetrical ligand H(2)L=2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol. Also, with this ligand, the tetranuclear [Fe(2)(III)Hg(2)(II)(L)(2)(OH)(2)](ClO(4))(2)·2CH(3)OH (2) and [Fe(III)Hg(II)(L)(μ-CO(3))Fe(III)Hg(II)(L)](ClO(4))(2)·H(2)O (3) complexes were synthesized and fully characterized.

Tuning the structure and the magnetic properties of metallo-supramolecular polyelectrolyte-amphiphile complexes.

Self-assembly of Fe(2+) ions and the rigid ditopic ligand 1,4-bis(2,2':6',2''-terpyridin-4'-yl)benzene results in metallo-supramolecular coordination polyelectrolytes (MEPE). Sequential self-assembly of MEPE and dialkyl phosphoric acid esters of varying chain length via electrostatic interactions leads to the corresponding polyelectrolyte-amphiphile complexes (PAC), which have liquid-crystalline properties. The PACs have a stratified architecture where the MEPE is embedded in between the amphiphile layers.

Unsymmetrical Fe(III)Co(II) and Ga(III)Co(II) complexes as chemical hydrolases: biomimetic models for purple acid phosphatases (PAPs).

The design and development of suitable biomimetic catalytic systems capable of mimicking the functional properties of enzymes continues to be a challenge for bioinorganic chemists. In this study, we report on the synthesis, X-ray structures, and physicochemical characterization of the novel isostructural [Fe(III)Co(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (1) and [Ga(III)Co(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (2) complexes with the unsymmetrical dinucleating ligand H(2)BPBPMP (2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol). The previously reported complex [Fe(III)Zn(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (3) was investigated here by electron paramagnetic resonance for comparison with such studies on 1 and 2.

Liquid crystalline phase transition induces spin crossover in a polyelectrolyte amphiphile complex.

Self-assembly of Fe(2+) or Ni(2+) ions and the ditopic ligand 6,6',6''-bis(2-pyridyl)-2,2':4',4'':2'',2'''-quaterpyridine (btpy) through coordinative binding results in rodlike metallosupramolecular coordination polyelectrolytes (Fe-MEPE or Ni-MEPE). Sequential self-assembly with dihexadecyl phosphate (DHP) via electrostatic interactions between MEPE and DHP leads to the corresponding polyelectrolyte amphiphile complex (PAC) with liquid crystalline properties. The MEPE rods are embedded in between the interdigitated DHP layers.

Synthesis, structure, and physicochemical properties of dinuclear NiII complexes as highly efficient functional models of phosphohydrolases.

As metal ions are present in the catalytic sites of several enzymes, attention has been focused on the synthesis and characterization of metal complexes able to act as biomimetic functional and structural models for these systems. In this study, a novel dinuclear NiII complex was synthesized, [Ni2(L2)(OAc)2(CH3CN)]BPh4 (2) (HL2=2-[N-(2-(pyridyl-2-yl)ethyl)(1-methylimidazol-2-yl)amin omethyl]-4-methyl-6-[N-(2-(imidazol-4-yl)ethyl)amino methyl]phenol), employing a new unsymmetrical dinucleating ligand containing N,O-donor groups as a model for hydrolases. Complex 2 was characterized by a variety of techniques including: elemental analysis, infrared and UV-vis spectroscopies, molar conductivity, electrochemistry, potentiometric titration, magnetochemistry, and single-crystal X-ray diffractometry.