Co-ordination behaviour of a novel bisthiourea tripodal ligand: structural, spectroscopic and electrochemical properties of a series of transition metal complexes

The synthesis of a thiourea substituted derivative of tris(pyridyl-2-methyl)amine (TPA) is reported. Two of the three pyridine rings are substituted in the 6-position with benzoylthiourea groups. These thiourea groups undergo intramolecular hydrogen bonding to form six-membered rings which leaves one N-H group available to form hydrogen bonds with other molecules. This reports details how the complexation of this new ligand with transition metal ions yields complexes with differing geometries. Seven co-ordinate Mn(II) and Cd(II), six co-ordinate Ni(II) and five co-ordinate Co(II), Cu(II) and Zn(II) complexes have been isolated.     

A thiazole-containing tripodal ligand: synthesis, characterization, and interactions with metal ions and matrix metalloproteinases

A new tripodal ligand, tris[2-(((2-thiazolyl)methylidene)amino)ethyl]amine (Tatren), has been synthesized and characterized by NMR, IR, and UV-visible absorbance spectroscopy and elemental analysis. Tatren forms stable complexes with transition metal ions (Zn(2+), 1; Mn(2+), 2; Co(2+), 3) and the alkaline earth metal ions (Ca(2+), 4; Mg(2+), 5). Single-crystal X-ray structures of 1, 2, and 5 revealed six-coordinate chelate complexes with formula [M(Tatren)](ClO(4))(2) in which the metal centers are coordinated by three thiazolyl N atoms and three acyclic imine N atoms. Crystals of 1, 2, and 5 are monoclinic, P2(1)/c space group. Crystals of 4 are triclinic, P space group. The Ca(2+) complex is eight-coordinate with all N atoms of Tatren and one water molecule coordinated to the metal ion. Spectrophotometric titrations show that formation constants for the chelates of metal ions are >1 in methanol. Free Tatren inhibits the catalytic domain of matrix metalloproteinase-13 (MMP-13, collagenase-3) with K(i) = 3.5 +/- 0.6 microM. Molecular mechanics-based docking calculations suggest that one leg of Tatren coordinates to the catalytic Zn(2+) in MMPs-2, -9, and -13 with significant hydrogen bonding to backbone amide groups. High-level DFT calculations suggest that, in the absence of nonbonded interactions between Tatren and the enzyme, the most stable first coordination sphere of the catalytic Zn(2+) is achieved with three imidazolyl groups from His residues and two imine N atoms from one leg of Tatren. While complexes (1-3) do not inhibit MMP-13 to a significant extent, 4 does (K(i) = 30 +/- 10 microM). Hence, this study shows that tripodal chelating ligands of this class and their Ca(2+) complexes have potential as active-site inhibitors for MMPs.     

Synthesis, crystal structures, luminescent and magnetic properties of homodinuclear lanthanide complexes with a flexible tripodal carboxylate ligand

Six new homodinuclear lanthanide(III) complexes with a flexible tripodal carboxylate ligand (H(3)L), of formulae [Ln(2)L(2)(DMF)(4)]·4DMF (Ln = La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), DMF = N, N-Dimethylformamide) have been synthesized. Among them, 1, 2, 3, 4, 6 were characterized by single-crystal X-ray diffraction, which crystallized in the monoclinic space group P2(1)/n with a = 13.309(2) ?, b = 27.404(4) ?, c = 16.686(3) ?, β = 105.115(2) and V = 5875.2(17) ?(3) for 1, a = 13.3016(5) ?, b = 27.1952(12) ?, c = 16.6339(7) ?, β = 105.030(2) and V = 5811.3(4) ?(3) for 2, a = 13.2797(10) ?, b = 27.072(2) ?, c = 16.6564(13) ?, β = 104.9390(10) and V = 5785.7(8) ?(3) for 3, a = 13.2855(3) ?, b = 27.0074(6) ?, c = 16.6357(3) ?, β = 104.9790(10) and V = 5766.2(2) ?(3) for 4, a = 13.2837(5) ?, b = 26.9105(10) ?, c = 16.6066(6) ?, β = 104.917(2) and V = 5736.3(4) ?(3) for 6. The crystal structures reveal that these complexes are isostructural, and molecules are connected from 0D to 3D supramolecular structures by hydrogen bonds. All of them were characterized by elemental analysis, IR spectroscopy, XRD and TGA. Unusually, non-luminescent Tb(III) complex was obtained. The photophysical property of the Eu(III) complex and the magnetic property of Gd(III) complex are investigated and discussed in detail.     

Aromatic guest inclusion by a tripodal ligand: Fluorescence and structural studies

The newly synthesized simple tripodal ligand tris-[2-(naphthalen-2-yloxy)-ethyl]-amine (L₁) act as a fluorescence signaling system for aromatic guest. It forms inclusion complexes with several electron deficient aromatic compounds. This inclusion phenomenon has been studied by steady-state fluorescence spectroscopy and solid-state structural analysis. Electron-rich L₁ shows dramatic color change and a concomitant quenching of luminescence in solution as well as solid phase when titrated with several other electron deficient aromatic guest molecules. Rather high selectivity towards the picric acid was observed. L₁ simultaneously forms inclusion complex and organic salt co-crystal with the composition [(L₁H⁺) (Pic⁻)]  PicH (PicH = picric acid) when crystallized in the presence of picric acid. In the solid state, it forms a strong π–π, C–Hπ and C–HO type interactions.     

Three novel lanthanide complexes with imidazole-4,5-dicarboxylate ligand: Hydrothermal syntheses, structural characterization, and properties

Three novel lanthanide complexes, namely, [Ce(Himdc)(H₂imdc)(H₂O)₃]·H₂O (1), {[Dy(Himdc)(Ox)_0.5(H₂O)₂]·H₂O}_n (2), and {[Nd(Himdc)(Ox)_0.5(H₂O)₂]·H₂O}_n (3) (H₃imdc = imidazole-4,5-dicarboxylic acid, Ox = oxalate), have been successfully prepared by the assembly of lanthanide ions and H₃imdc ligand under different synthetic conditions. All of the complexes have been characterized by means of elemental analysis, IR, TG analysis, luminescence spectroscopy as well as single-crystal X-ray diffraction analysis. The 3D supramolecular structure of 1 is constructed from 1D zig-zag chains through the hydrogen bonding interactions. Complex 2 possesses the chair-shaped secondary building units (SBUs) with Dy₆(Himdc)₄(Ox)₂ and meso-helical chains (P + M), resulting in a novel 2D structure based on the linkages of oxalate ligand. Complex 3 also presents 2D layer structure with uninodal 6-connected net topology, but crystallizes in the different space group and owns higher coordination number of the central metal atom than complex 2. The luminescence property of 2 is investigated in the solid state at room temperature.     

Influence of metal ions on the structures of Keggin polyoxometalate-based solids: Hydrothermal syntheses, crystal structures and magnetic properties

Three new Keggin polyoxometalate (POM)-based compounds linked to 3d metal complexes have been synthesized under hydrothermal conditions: [Cu(phen)₂]₂{[Cu(phen)]₂ [SiMo₁₂O₄₀(VO)₂]} (1), {[Zn(phen)₂]₂[GeMo₁₂O₄₀(VO)₂]}{[Zn(phen)₂(H₂O)]₂ [GeMo₁₂O₄₀(VO)₂]}·3H₂O (2) and {[Co(phen)₂]₂[PMo₁₂O₄₀(VO)₂]}{[Co(phen)₂(OH)]₂ [PMo₁₂O₄₀(VO)₂]}·2.5H₂O (3) (phen=1,10-phenanthroline). These three compounds present, as building blocks, the bicapped Keggin anions [XMo₁₂O₄₀(VO)₂] (X=Si, Ge and P). Compound 1 consists of a bicapped Keggin anion [SiMo₁₂O₄₀(VO)₂]²⁻ linked to two [Cu(phen)]⁺ complexes with two [Cu(phen)₂]⁺ countercations. Compound 2 contains two bicapped Keggin anions [GeMo₁₂O₄₀(VO)₂]⁴⁻, one linked to two [Zn(phen)₂(H₂O)]²⁺ cations and the other one linked to two [Zn(phen)₂]²⁺ cations. Compound 3 is a two-dimensional POM-based square network formed by bicapped Keggin anions [PMo₁₂O₄₀(VO)₂]⁴⁻ connected by [Co(phen)₂]²⁺ cations. Discrete bicapped Keggin anions [PMo₁₂O₄₀(VO)₂] linked to two [Co(phen)₂(OH)]⁺ cations are located between the layers. The magnetic properties show the presence of antiferromagnetic interactions among the reduced Mo(V) atoms (in the three compounds) plus a paramagnetic contribution from the V(IV) atoms (in 1 and 2). Compound 3 shows, in addition, an antiferromagnetic interaction between the Co(II) and the V(IV) ions directly linked through an oxygen bridge. The low-temperature ESR spectra of compound 3 confirm the presence of the reduced Mo(V) ions and the antiferromagnetic coupling between the Co(II) and the V(IV) ions.     

三爪结构萘乙酰胺衍生物与过渡金属离子的螯合荧光增强

合成了具有三爪结构的化合物三-(1-萘乙酰胺乙基)胺(1),它对具有荧光猝灭能力的过渡金属离子具有荧光增强的效应。比较不同的过渡金属离子存在时上述化合物溶液的荧光光谱和吸收光谱变化,可以发现：在利用荧光光谱进行检测时必须注意过程中引起荧光增强和猝灭的机制,这将对考察配体与金属离子间配位能力大小作出正确估计有着重要的帮助。     

Transition metal coordination complexes based on V-shaped bis-triazole ligand: syntheses,structures, and properties

Hydrothermal reactions of 1,3-bis(1,2,4-triazol-1-yl)benzene (btb) and M(NO₃)₂ (M = Co²⁺ (1), Cu²⁺ (2)) afforded two new coordination polymers, [Co(btb)₂(NO₃)(H₂O)]_n·NO₃·H₂O (1) and [Cu(btb)₂(NO₃)₂]_n (2), respectively. Single-crystal X-ray diffraction reveals that 1 crystallizes in the space group P2₁/m and 2 crystallizes in the space group Pī, both showing a double-stranded chain structure. The 1-D chains are interconnected via π?π interactions to lead to 2-D ladder-like supramolecular architectures. In addition, magnetic behavior and thermal stability of 1 and 2 have been investigated. For 1, weak antiferromagnetic interactions are observed at low temperature, and the data obey the Curie–Weiss law χ_M = C/(T?θ), with C = 3.22 cm³·mol^?1·K and θ = ?10.39 K. For 2, the decrease of the χT vs. T curve at low temperature is the result of intermolecular antiferromagnetic magnetic interactions.     

Mono-, di-, and oligonuclear complexes of Cu(II) ions and p-hydroquinone ligands: syntheses, electrochemical properties, and magnetic behavior

Four highly soluble square-planar Cu(II) and Ni(II) complexes of siloxy-salens (2SiCu, 2SiNi) and hydroxy-salens (2Cu, 2Ni) have been synthesized. An X-ray crystal structure analysis was performed on 2SiCu, 2SiNi, and 2Ni. The compounds have been investigated by cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and EPR spectroscopy. According to these results, the monooxidized species [2SiCu]+ and [2SiNi]+ are to be classified as Robin-Day class II and III systems, respectively. Magnetic measurements on the dinuclear (PMDTA)Cu(II) complex 1Cu2 x (PF6)2 with deprotonated 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)-benzene (1) linker revealed antiferromagnetic coupling between the two Cu(II) ions thereby resulting in an isolated dimer compound. Coordination polymers [1Cu]n(H2O)(2n) of Cu(II) ions and bridging p-hydroquinone linkers were obtained from CuSO4 x 5 H2O and 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)benzene. X-ray crystallography revealed linear chains running along the crystallographic a-direction and stacked along the b-axis. Within these chains, the Cu(II) ions are coordinated by two pyrazolyl nitrogen atoms and two p-hydroquinone oxygen atoms in a square-planar fashion.     

A new lanthanum coordination polymer built from a semi‐rigid tripodal carboxylic acid ligand: synthesis,crystal structure and properties

By employing the semi‐rigid multidentate carboxylic acid ligand 4,4′,4′′‐{[(2,4,6‐trimethylbenzene‐1,3,5‐triyl)tris(methylene)]tris(oxy)}tribenzoic acid (denoted H₃L), a new lanthanum coordination polymer, namely poly[[bis(dimethylformamide)(μ₆‐4,4′,4′′‐{[(2,4,6‐trimethylbenzene‐1,3,5‐triyl)tris(methylene)]tris(oxy)}tribenzoato)lanthanum(III)] dimethylformamide tetrasolvate 0.25‐hydrate], {[La(C₃₃H₂₇O₉)(C₃H₇NO)₂]·4C₃H₇NO·0.25H₂O}_n or {[La(L)(DMF)₂]·4(DMF)·0.25(H₂O)}_n (DMF is dimethylformamide) ( 1 ), was prepared and characterized by single‐crystal X‐ray diffraction, elemental analysis, thermogravimetric analysis, IR spectroscopy and photoluminescence studies. The asymmetric unit contains one La^III cation, one anionic L^3? ligand, two coordinated DMF molecules, four free DMF molecules and one‐quarter of a free water molecule. Compound 1 possesses (3,6)‐connected two‐dimensional kgd topology sheets consisting of secondary building units of La₂ clusters and L^3? ligands, which further stack into three‐dimensional supramolecular networks through π–π interactions. Compound 1 exhibits a photoluminescence emission at room temperature, with a peak at 410 nm, owing to a ligand‐centred excited state.     

Complexes of divalent metal ions with cinchomeronic and dinicotinic acid thermal properties

The thermal properties of the complexes of cinchomeronic and dinicotinic acid with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA).For the thermal stability of the anhydrous compounds a sequence may be observed for the metal ions with cinchomeronic (3,4-H₂PC) and dinicotinic acid (3,5-H₂PC):

The thermal stability of the pyridine carboxylic acid for each metal of the series is: dinicotinic > cinchomeronicThe activation energy values for each thermal reaction were also calculated, using the Coats and Redfern algorism, by the Univac 1108 computer, by a program properly implemented for the statistical analysis of the data to obtain the reaction order and the activation parameters with the relative confidence limits.     

Synthesis, spectroscopic characterization and magnetic properties of homo- and heterodinuclear complexes of transition and non-transition metal ions with a new Schiff base ligand

Four homodinuclear complexes of Ni(II)-Ni(II), Cu(II)-Cu(II), Co(II)-Co(II) and Co(III)-Co(II) and five heterodinuclear complexes of Co(III)-Zn(II), Co(III)-Cu(II), Co(III)-Ni(II), Cu(II)-Zn(II) and Zn(II)-Cu(II) with the octadentate Schiff base compartmental ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H4fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV-vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes.     

Erbium-formate frameworks templated by diammonium cations: syntheses, structures, structural transition and magnetic properties

Two structurally different Er-formate frameworks, one NaCl-like [dmenH(2)][Er(HCOO)(4)](2) (1) and the other pillared-layer type [tmenH(2)][Er(HCOO)(4)](2) (2), were obtained when templated by the corresponding protonated N,N'-dimethylethylenediamine (dmenH(2)) and N,N,N',N'-tetramethyl- ethylenediamine (tmenH(2)). The shape and size of the template cations dictate the different coordination geometries of erbium and consequently the framework topologies, though erbium adopts eight coordination in the two compounds. In the NaCl-like structure of 1, erbium is coordinated by eight anti-anti bridging formates in a square antiprism, while in the pillared-layer structure of 2, it is coordinated by six anti-anti bridging formates and one chelating formate in a pentagonal bipyramid. 2 exhibits a structural phase transition around -70 °C which is related to the disorder-order transition of the template cation. Both compounds behave as paramagnets between 2 and 300 K. However, they display field-dependent ac-susceptibilities with complicated field-induced magnetic relaxation processes, and the major slow ones probably results from spin-lattice relaxation.     

Four complexes with a bulky carboxylate ligand: syntheses,crystal structures,and luminescent properties

Abstract  

Four complexes of 3,3-diphenylpropanoate (L) and 4,4′-bipyridine as auxiliary bridging ligands were synthesized and characterized, namely [Zn(L)₂(4bpy)(EtOH)₂]_∞ (1), [Co(L)₂(4bpy)(EtOH)₂]_∞ (2), [Ni(L)₂(4bpy)(EtOH)₂]_∞ (3), and [Cu(L)₂(4bpy)(H₂O)]_∞ (4) (4bpy = 4,4′-bipyridine). X-ray single-crystal diffraction analyses show that complexes 1–4 all take one-dimensional (1D) fishbone-like structures incorporating bridging 4bpy ligands. The complexes show different supramolecular frameworks interlinked via intermolecular hydrogen bonds, π···π stacking, and/or C–H···π supramolecular interactions. Complex 3 only has a simple one-dimensional fishbone-like chain, whereas complexes 1 and 2 show two-dimensional supramolecular structures by interchain C–H···O hydrogen bonds. Complex 4 is assembled into two-dimensional layers and then an overall three-dimensional framework by a combination of interchain O–H···O hydrogen bonds and C–H···π supramolecular interactions. The luminescent properties of the ligands and their complexes were investigated.     

Synthesis,crystal structures and magnetic properties of three porous coordination polymers based on a semirigid tripodal carboxylate ligand

Transition Metal Chemistry - Three new coordination polymers, namely, {[Cu2(bcpmba)(μ4-OH)]·2H2O}n (1), [Mn(Hbcpmba)]n (2), and [Co2(bcpmba)(μ3-OH)·H2O]n (3)...     

Isolation of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand: syntheses, structural descriptions and magnetic studies

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

Zinc and cobalt complexes with (2-carboxyphenoxy) acetic acid ligand: syntheses,structures, fluorescent and magnetic properties

Four binary compounds, [Zn(cpa)(H₂O)₃] (1), [Co(cpa)(H₂O)₃] (2), [Zn(cpa)(H₂O)]_n, (3) and [Co(cpa)(H₂O)]_n (4) (H₂cpa = (2-carboxyphenoxy)acetic acid), have been synthesized and structurally characterized. In mononuclear 1 or 2, the metal ion (Zn^II for 1 and Co^II for 2) is surrounded by three water molecules and one tridentate chelate cpa^2? in a distorted octahedral geometry, while in 3 or 4, the central metal ion (Zn^II for 3 and Co^II for 4) is located in a deformed square–pyramid formed by one water and two cpa^2?. Each cpa^2? is chelate bridging μ₂ coordination and forms a 1-D zigzag chain structure 2 or 3. The different synthesis conditions for 1–4 have been carefully discussed. The solid-state fluorescence measurements for 1 and 3 together with magnetic properties for 4 also have been investigated.     

Three-dimensional metal phosphonodicarboxylates with GIS-zeolite topology: syntheses, structures and magnetic studies

Compounds [M(2)(4-pi)(H(2)O)(4)]·1.5H(2)O [M(II) = Mn(1), Co(2), Ni(3)] and a heterometallic analogue [Co(1.14)Ni(0.86)(4-pi)(H(2)O)(4)]·1.5H(2)O (4) have been synthesized utilizing a rigid 4-phosphonoisophthalic acid (4-piH(4)). Compounds 1-4 are isostructural, confirmed by their powder XRD measurements. Single crystal structural determinations of 1 and 2 reveal that these compounds display a novel pillared layered open framework structure with zeolite gismondine (GIS) topology. Within the layer, edge-sharing {MO(6)} octahedra are found, which are connected by carboxylate and phosphonate groups along the c- and b-axis, respectively. Dominant antiferromagnetic interactions are propagated between the magnetic centers in 1, 2 and 4. While in 3, ferromagnetic exchange couplings are observed.     

Thermodynamics, structure and properties of polynuclear lanthanide complexes with a tripodal ligand: insight into their self-assembly

Self-assembly processes between a tripodal ligand and Ln(III) cations have been investigated by means of supramolecular analytical methods. At an equimolar ratio of components, tetranuclear tetrahedral complexes are readily formed in acetonitrile. The structural analysis of the crystallographic data shows a helical wrapping of binding strands around metallic cations. The properties of this series of highly charged 3D compounds were examined by using NMR spectroscopy and optical methods in solution and in the solid state. In the presence of excess metal, a new trinuclear complex was identified. The X-ray crystal structure elucidated the coordination of metallic cations with two ligands of different conformations. By varying the metal/ligand ratio, a global speciation of this supramolecular system has been evidenced with different spectroscopic methods. In addition, these rather complicated equilibria were successfully characterised with the thermodynamic stability constants. A rational analysis of the self-assembly processes was attempted by using the thermodynamic free energy model and the impact of the ligand structure on the effective concentration is discussed.     

Anion-controlled assembly of four manganese ions: structural, magnetic, and electrochemical properties of tetramanganese complexes stabilized by xanthene-bridged Schiff base ligands

The reaction of manganese(II) acetate with a xanthene-bridged bis[3-(salicylideneamino)-1-propanol] ligand, H(4)L, afforded the tetramanganese(II,II,III,III) complex [Mn(4)(L)(2)(μ-OAc)(2)], which has an incomplete double-cubane structure. The corresponding reaction using manganese(II) chloride in the presence of a base gave the tetramanganese(III,III,III,III) complex [Mn(4)(L)(2)Cl(3)(μ(4)-Cl)(OH(2))], in which four Mn ions are bridged by a Cl(-) ion. A pair of L ligands has a propensity to incorporate four Mn ions, the arrangement and oxidation states of which are dependent on the coexistent anions.