A novel trinuclear nickel(II) complex of an unsymmetrical tetradentate ligand involving bridging oxime and acetylacetone functions

A novel trinuclear nickel(II) complex, [Ni₃(L)₂(H₂O)₂](ClO₄)₂, where L is a bridging unsymmetrical tetradentate ligand, involving o-phenylenediamine, diacetyl monoxime and acetylacetone (H₂L = 4-[2-(3-hydroxy-1-methyl-but-2-enylideneamino)-phenylimino]-pentan-2-one oxime) has been synthesized and characterized structurally. In the complex, an octahedral Ni(II) centre is held in the middle by two square planar units with the aid of oxime and ketonic bridges.     

Synthesis and crystal structure of a novel three-dimensional supramolecular network containing one-dimensional honeycomb-like channels

A novel supramolecular assembly containing honeycomb-like channels [Cu(mal)(bpy)] · 3H₂O (mal = malate, bpy = 2,2′-bipy) has been synthesized and characterized by elemental analyses, IR, EPR, TG, UV-Vis and single crystal X-ray diffraction. Compound 1 is constructed from spiral-shaped chains via O-H?O hydrogen bonds and π-π stacking interactions. To our knowledge, compound 1 represents the first supramolecular network constructed from the mixed malate and pyridine ligand.     

Syntheses, structures and magnetic properties of two new metal complexes based on a pyridyl-diphosphonate ligand

Two new first-raw transition metal diphosphonate complexes, namely, {[Ni₃([hpyedpH)₂(H₂O)₄]·(H₂O)₂}_n (1) and [Mn[hpyedpH₂](H₂O)]_n (2), based on a multidentate ligand 1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid (hpyedpH₄) have been synthesized under hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and element analyses. The data reveals that complex 1 is a 2D layer structure, whereas the complex 2 possesses a 1D motif. The powder X-ray diffraction (PXRD) patterns for complexes 1 and 2 were collected as well, which match well with the ones calculated from their single-crystal structure data. Magnetic measurements show that complex 1 is a ferrimagnet with T_c = 5.0 K. Magnetic studies of complex 2 indicate antiferromagnetic behavior.     

A novel three-dimensional hybrid framework based on fishbone-like copper halide inorganic units

A novel inorganic-organic hybrid cuprous chloride, , has been hydrothermally synthesized and structurally characterized by the elemental analyses, IR spectrum, TG analysis and the single crystal X-ray diffraction. The structure of 1 exhibits a three-dimensional network built up from unusual fishbone-like copper(I) chloride ribbons bridged by linear isonicotinato ligands. Its luminescent property was also investigated.     

Construction of a series of mercury(II) complexes based on a bis-pyridyl-bis-amide ligand: Effect of counter anions, interactions on the supermolecular structures

Four new complexes, [Hg(L)Cl₂]₂ (1), [Hg(L)Br₂]₂ (2), [Hg(L)I₂(DMF)₂]_n (3), and [HgLCl(SCN)]_n (4) (L = N,N-bis-(3-pyridyl)isophthalamide) were obtained through the self-assembly of a rigid conjugated clamp-like bis-pyridyl-bis-amide ligand L with HgX₂ (X = Cl for 1, Br for 2, I for 3, and Cl for 4 with the addition of KSCN) and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum, etc. Employments of different anions result in different structures. Complexes 1 and 2 feature bimetallic macrocycle formed by coordinating two Hg(II) metal centers by two ligands which are in syn-syn conformation. The macrocyclic subunits further self-assemble into a porous macrocycle structure via the hydrogen-bonding and π-π stacking interactions. Introduction of I⁻ and SCN⁻ ions bring about stronger steric hindrance effect. Complexes 3 and 4 are polymers with infinite 1D polymeric chain in herringbone fashion and the hydrogen-bonding interactions and π-π stacking interactions between the parallel benzene rings and the pyridyl rings stabilize the supromolecular framework. Furthermore, we measured their fluorescent properties in the solid state at room temperature and XRD properties also have been determined.     

Synthesis and structural characterisation of a novel polynuclear copper ribbon-like network. A study of its magnetic properties between 4 and 300 K

A new route to {Cu₂(κ¹-pyNH₂)₂(μ-OMe)₂Cl₂}_n (pyNH₂ = 2-aminopyridine) (3) is reported. Structural characterisation reveals the presence of methoxide and chloride bridging units within the complex which support close copper-copper bonding interactions resulting in interesting magnetic properties. The variable-temperature (4-300 K) magnetic susceptibility data of the complex were interpreted with the dimer law using the molecular field approximation. The results obtained indicate a weak antiferromagnetic (zJ′ = −15 cm⁻¹) inter-chain interaction through the chloro-bridge. A relatively strong antiferromagnetic interaction, transmitted through the oxygen-bridge, with an exchange coupling of 2J = −305 cm⁻¹, which dominates the magnetic properties of the title complex.     

Unexpected assembly of a novel triply bridged diiron(II) core by a bidentate Schiff base ligand

The unusual dinucleating properties of a simple bidentate Schiff base (LH, 1) in the presence of weakly coordinating methanol solvent lead to the self-assembly of (2) (b and t refer to bridging and terminally bound ligands, respectively). Complex 2 is the first diiron(II) species in which the two metal centers are triply bridged by single atoms in an asymmetric fashion, involving both μ-O^Ph and μ-OH^Me bridges. This binding mode produces an Fe?Fe distance of 3.139(1) Å. Dinucleation appears to be driven by a combination of ligand deficiency and solvent-mediated chemistry reminiscent of host-guest interactions. The presence of a μ-MeOH ligand is unprecedented in iron chemistry. Parallel-mode EPR spectra of complex 2 recorded at 4 K show an intense negative signal at g_∥≈16, suggesting the dimeric form exists in solution.     

Synthesis, characterization and structure of a new zinc(II) complex containing the hexadentate N,N′,N,N′-bis[(2-hydroxy-3,5-di-tert-butylbenzyl)(2-pyridylmethyl)]-ethylenediamine ligand: Generation of phenoxyl radical species

This work summarizes the results of our studies on the structural, spectral and redox properties of a mononuclear zinc(II) complex with the new H₂L ligand (H₂L = N,N′,N,N′-bis[(2-hydroxy-3,5-di-tert-butylbenzyl)(2-pyridylmethyl)]-ethylene diamine). The crystal structure of the complex [Zn^II(HL)] · ClO₄ (1) was determined by X-ray crystallographic analysis. The structure of this complex consists of a discrete mononuclear cation [Zn^II(HL)]⁺, in a strongly distorted geometry with a slight tendency toward a distorted square pyramidal geometry, as reflected by the structural index parameter τ of 0.44. The zinc(II) cation is coordinated to one oxygen and four nitrogen atoms: the pyridine nitrogen atoms (N22 and N32), tertiary amine nitrogen atoms (N1 and N4) and phenolate oxygen atom (O10). ¹H and ¹³C NMR spectral data show a rigid solution structure for 1 in agreement with X-ray structure. Potentiometric studies of complex 1 were also performed and revealed three titratable protons which are attributed to the protonation/deprotonation of two phenol groups (p[K]_a1 = 4.04 and p[K]_a3 = 11.34) and dissociation of a metal-bound water molecule (p[K]_a2 = 7.8). The phenolate groups in complex 1 are suitably protected by bulky substituents (tert-butyl) in the ortho- and para-positions, which through electrochemical oxidation generate a one-electron oxidized phenoxyl species in solution. This radical species was characterized by UV-Vis, EPR and electrochemical studies. The Zn(II)-phenoxyl radical species is of bioinorganic relevance, since its spectroscopic, redox and reactivity properties can be used to establish the role of phenoxyl radicals in biological and catalytical systems.     

Synthesis and crystal structures of four pH-dependent Pb(II) and Cd(II) phosphonates based on a novel ligand, 3-phosphono-benzoic acid

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb₃(pbc)₂(H₂O)₂] (2), [Cd(H₂pbc)₂(H₂O)₂] (3) and [Cd_1.5(pbc)(H₂O)_1.5] · 0.5H₂O (4) (H₃pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1-4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd₂O₁₀ dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.     

One trinuclear copper(II) complex derived from a new Schiff base ligand based on the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol: Synthesis, structure, spectroscopic and magnetic properties

A linear trinuclear copper(II) complex (1), prepared from a new Schiff base ligand, namely the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol, was synthesized and characterized in this paper. The X-ray structural study reveals that the geometry of the central Cu2 ion is elongated octahedral and that of the two side Cu(II) ions is distorted square pyramidal. The magnetic susceptibility measurements from 2 to 300 K reveal medium antiferromagnetic interactions between the Cu(II) ions with a J value of −64.6(1) cm⁻¹.     

Two novel oxomolybdenum complexes derived from the reaction of chlorotrisulfidomolybdate precursor with a pyridine-containing tridentate ligand

Reaction of chlorotrisulfidomolybdate [PPh₄][MoClS₃] (1) with one equivalent of tridentate ligand PyCH₂NHC₂H₄SNa (PyNSNa) in THF generated both a mononuclear and a dinuclear complexes, [PPh₄][(PyNS)MoO(η²-S₂)₂] (2) and [PPh₄][(PyNS)Mo(O)(μ-S)₂Mo(S)(η²-S₂)]·0.5MeCN (3·0.5MeCN). These two complexes were separated mechanically and fully characterized using IR, UV/Vis spectra, ¹H NMR spectra and X-ray single crystal diffraction analysis. In both complexes, one terminal sulfido ligand was substituted by one oxo group. In complex 3, two types of intermolecular hydrogen bonding in its solid state led to a 1-D structure in which each unit was a dimmer formed via hydrogen bonding.     

In situ hydrothermal syntheses, crystal structures and luminescent properties of two novel zinc(II) coordination polymers based on tetrapyridyl ligand

Two novel Zn(II) coordination polymers, [Zn(2-pytpy)(fum)]_n·nH₂O (1) and [Zn₆(4-pytpy)₃(mal)₄]_n·5n(H₂O) (2), (2-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, 4-pytpy = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H₂fum = fumaric acid and H₂mal = malic acid) have been hydrothermally synthesized and structurally characterized. Notably, in situ ligand reactions occur in the formation of complexes 1 and 2, in which maleic acid is converted into fumaric acid and malic acid, respectively. Complex 1 is a 1D infinite chain structure, which is extended into a supramolecular layer by intermolecular π…π stacking interactions. Complex 2 is a 3D network structure, in which the bidentate-bridging 4-pytpy ligands link the layers based on the tetranuclear Zn(II) subunits to form the (4,10)-connected network. The luminescent properties of 1 and 2 have been investigated with emission spectra and UV-Vis diffuse reflectance spectra in the solid state. Additionally, these two complexes possess great thermal stabilities.     

Hydrothermal synthesis and characterizations of a novel 2-D double-layers metal-organic coordination polymer involving in situ ligand synthesis

A novel 2-D metal-organic coordination polymer [Ni_0.5(apddica)(H₂O)] · H₂O 1 (Hapddica=2-(4-Amino-phenyl)-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carboxylic acid) has been hydrothermally synthesized and structurally characterized by element analyses, IR and XPS spectra, TG analyses and single crystal X-ray diffraction. Crystal data: C₁₅H₁₃N₂Ni_0.5O₆, monoclinic, P2(1)/c, a=12.181(2) Å, b=7.9392(6) Å, c=14.835(3) Å, β=94.25(3) °, V=1430(75) ų, Z=4. Compound 1 exhibits a novel 2-D double-layers network based on apddica and Ni center. It is noteworthy that new ligand Hapddica was first prepared with hydrothermal technique involving in situ ligand synthesis and used for constructing coordination polymers. There are unusual parallelogram tunnels along a-axis in which the dissociative water molecules filled in. The magnetic property of compound has been studied.     

Design and synthesis of a novel fluorescence probe for Zn based on the spirolactam ring-opening process of rhodamine derivatives

The spirolactam ring-opening process of rhodamine derivative is one of the most useful mechanisms for controlling fluorescence properties. However, the open/closed equilibrium reaction of rhodamine spirolactam has not been well characterized. Therefore, we examined the relationship between the spirolactam ring-opening process of rhodamine derivatives and the structure of the xanthene moiety. Based on the results of this investigation, we selected a candidate xanthene moiety for a Zn²⁺ sensor, and successfully developed a new fluorescence probe for Zn²⁺.     

Coordination network solids based on Cu(II) coordination compounds with 1,4-bis-(1,2,4-triazol-1-yl)-butane as a flexible alkyl spacer ligand: Synthesis, characterization and X-ray structures

The coordination chemistry of three selected copper(II) salts with the flexible ligand 1,4-bis(1,2,4-triazol-1-yl)butane (abbreviated as btb) is described. This ligand acts as a bidentate ligand, bridging copper(II) ions, thereby generating polymers in 2D and 3D network solids.     

The three-dimensional structures of tick carboxypeptidase inhibitor in complex with A/B carboxypeptidases reveal a novel double-headed binding mode

The tick carboxypeptidase inhibitor (TCI) is a proteinaceous inhibitor of metallo-carboxypeptidases present in the blood-sucking tick Rhipicephalus bursa. The three-dimensional crystal structures of recombinant TCI bound to bovine carboxypeptidase A and to human carboxypeptidase B have been determined and refined at 1.7 A and at 2.0 A resolution, respectively. TCI consists of two domains that are structurally similar despite the low degree of sequence homology. The domains, each consisting of a short alpha-helix followed by a small twisted antiparallel beta-sheet, show a high level of structural homology to proteins of the beta-defensin-fold family. TCI anchors to the surface of mammalian carboxypeptidases in a double-headed manner not previously seen for carboxypeptidase inhibitors: the last three carboxy-terminal amino acid residues interact with the active site of the enzyme in a way that mimics substrate binding, and the N-terminal domain binds to an exosite distinct from the active-site groove. The structures of these complexes should prove valuable in the applications of TCI as a thrombolytic drug and as a basis for the design of novel bivalent carboxypeptidase inhibitors.     

Two-dimensional Cu and first Pb coordination polymers based on a flexible 1,4-cyclohexanedicarboxylate ligand displaying different conformations and coordination modes

Two novel metal-organic hybrid coordination polymers {[Cu(bpo)(chdc)(H₂O)](H₂O)_0.5}_n (1) and [Pb(chdc)(H₂O)]_n (2) have been synthesized under different conditions and structurally characterized by single-crystal X-ray diffraction technique, where H₂chdc refers to a flexible 1,4-cyclohexanedicarboxylic acid ligand and bpo is 2,5-bis(4-pyridyl)-1,3,4-oxadiazole. Complex 1 has a two-dimensional (2-D) grid-like [11.28 × 13.63 Å²] framework in which the Cu^II centers are extended via bidentate bridging ligands bpo and e,e-trans-chdc along two directions, exhibiting large porous cavities. Coordination polymer 2 represents the first Pb^II complex of H₂chdc in which the larger Pb^II centers are connected by e,a-cis-chdc anions to afford a 2-D close-knit structure.     

Detecting protein complexes based on a combination of topological and biological properties in protein-protein interaction network

Protein complexes are known to play a major role in controlling cellular activity in a living being. Identifying complexes from raw protein protein interactions (PPIs) is an important area of research. Earlier work has been limited mostly to yeast. Such protein complex identification methods, when applied to large human PPIs often give poor performance. We introduce a novel method called CSC to detect protein complexes. The method is evaluated in terms of positive predictive value, sensitivity and accuracy using the datasets of the model organism, yeast and humans. CSC outperforms several other competing algorithms for both organisms. Further, we present a framework to establish the usefulness of CSC in analyzing the influence of a given disease gene in a complex topologically as well as biologically considering eight major association factors.     

Synthesis, characterization and crystal structure of a novel 2D network structure based on hexacopper(II) substituted tungstoantimonate

The dimeric, hexacopper(II) substituted tungstoantimonate NaK₆[Cu₆Cl(SbW₉O₃₃)₂] · 14H₂O (1a) has been synthesized in good yield using a one-pot procedure by reaction of Cu²⁺ ions with the trilacunary precursor salt Na₉[α-B-SbW₉O₃₃] and characterized by IR spectroscopy, UV electronic spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction. The title polyanion represents the first tungstoantimonate substituted by six copper centers and the polyanion as basic building unit is assembled into a two-dimensional network-like complex by Cu-OW bonds. The electrochemical behavior of 1a was investigated in buffer solution (pH 3.0) by cyclic voltammetry. In the potential range between −0.7 and 0.6 V, the compound exhibits the successive redox processes of the addenda atoms (W) followed by the redox reaction originating from the substituted Cu^II, which revealed the stepwise reduction of Cu²⁺ centers within the polyanion 1 before deposition of Cu⁰ on the glassy carbon electrode surface. The compound 1a is shown to have electrocatalytic properties towards the reductions of nitrate and nitrite.     

3D network structure and spin gap behavior in two new molecular magnets based on bis(maleonitriledithiolato)nickelate monoanion

Two new molecular magnets, based on [Ni(mnt)₂]⁻ monoanion, [DiBrBzPy][Ni(mnt)₂] (1) and [DiBrBzIQl][Ni(mnt)₂] (2) ([DiBrBzPy]⁺ = 1-(3′,5′-dibromobenzyl)pyridinium, [DiBrBzIQl]⁺ = 1-(3′,5′-dibromobenzyl)isoquinolinium and mnt²⁻ = maleonitriledithiolate), were prepared and characterized by elemental analyses, IR, ESI-MS spectra, single crystal X-ray diffraction and magnetic measurements. The [Ni(mnt)₂] anions and the cations of 1 and 2 are alternately stacked and form 1D column via π?π stacking interactions between the [Ni(mnt)₂] anions and the neighboring cations. Some weak Ni?N, C?N interactions and CH?Br, CH?N hydrogen bonds between the adjacent columns further generate a 3D network structure. Magnetic susceptibility measurements show that both 1 and 2 exhibit the typical magnetic behavior of a spin gap system with an energy gap of 1151.9 K for 1 and 73.9 K for 2.