X-ray studies of lanthanide(III) complexes with 4-hydroxy-3-methoxybenzoate anion

Polycrystalline complexes of lanthanide(III) with 4-hydroxy-3-methoxybenzoic acid were obtained as hydrated compounds of general formula Ln(C₈H₇O₄)₃?·?nH₂O. After slow recrystallization we obtained single crystals of complexes and determined their structures. Praseodymium(III) and neodymium(III) form isostructural dihydrated complexes [Ln(C₈H₇O₄)₃(H₂O)₂], which crystallize in the triclinic system, space group P 1. Sm(III), Eu(III), Gd(III), Ho(III) and Tb(III) compounds are hexahydrates and also crystallize in the triclinic system, space group P 1. Dihydrated compounds form polymeric chains with metal centres linked by oxygen atoms of bridging carboxylates. Each metal ion is coordinated by chelating carboxylic group and two water molecules. Complexes of the second isostructural group form dinuclear units [Ln₂(C₈H₇O₄)₆(H₂O)₄]?·?8H₂O. Lanthanide(III) ions are linked by oxygen atoms of two chelating–bridging carboxylate groups. In the dimeric structure each metal ion coordinates additionally two chelating carboxylic groups and two water molecules.     

Tetraaqua-bis(3-hydroxy-4-nitrobenzoato) Co(II) and Ni(II) complexes and diaqua-bis(2-hydroxy-4-methoxybenzoato) Zn(II) complex: crystal structure and thorough metal-coordination investigation

Reactions of Co(II) and Ni(II) salts with the monosodium salt of 3-hydroxy-4-nitrobenzoic acid (3) in aqueous solution resulted in isomorphous covalent complexes 3C and 3D, of centrosymmetric geometries. In similar conditions, 2-hydroxy-4-methoxybenzoic acid (5) led to the covalent Zn(II) complex 5A, exhibiting a marked dissymmetric geometry. The present crystallographic data with structural data for a series of closely related metal complexes previously reported allow a tentative rationalization of the solid-state architecture of such complexes. The dissymmetry in 5A was interpreted on the basis of a mixed (monodentate and bidentate) metal-ligation mode and a pyramidal coordination at the metal.     

Self-assembly of three Cd(II) complexes: 0-D, 1-D,and 3-D structures based on 2-(1H-imidazol-1-methyl)-1 H-benzimidazole

Three new complexes, [Cd(L)I₂]₂ (1), {[Cd(L)I₂]?·?DMF} _n (2), and [Cd₂(L)₄(μ ₂-I)I(H₂O)] _n (3), have been obtained through self-assembly of an unsymmetrical ligand 2-(1H-imidazol-1-methyl)-1H-benzimidazole (L) with Cd(II) salts. Single-crystal X-ray diffraction shows that 1 displays a dimeric structure in which two Cd(II) ions are bridged by two bidentate bridging L. Complex 2 exhibits a 1-D chain structure (···Cd–L–Cd–L···) constructed by L bridging Cd(II) ions. In 3, the Cd(II) ions are five-connected nodes and linked by L and iodide leading to the 3-D network. Complexes 2 and 3 are synthesized maintaining the same solvents and stoichiometric ratio of metal and ligand at different reaction temperature. The different structures of the complexes indicate that the temperature plays a significant role in construction of the complexes. Luminescent properties of 1–3 have been investigated in the solid state at room temperature.     

Tetranuclear cobalt(II) complex and trinuclear copper(II) complex with the ligand 2-hydroxy-3-[(2-sulfoethylimino)-methyl]-benzoic acid: synthesis,structure and properties

A cobalt(II) compound, [Co₄(L)₂(OH)₂(phen)₂(H₂O)₄] · 6H₂O (1), and a copper(II) compound, [Cu₂(L)₂(H₂O)₂][Cu(H₂O)₆] · 6H₂O (2) [where H₃L is 2-hydroxy-3-[(2-sulfoethylimino)-methyl]-benzoic acid and phen is O-phenanthroline], were prepared and characterized. The tetranuclear cobalt complex 1, C₄₄H₆₂N₆O₂₈S₂Co₄, crystallizes in the monoclinic space group P2₁/c, with a = 11.847(10) Å, b = 19.061(15) Å, c = 12.635(10) Å, β = 105.483(9)°, and Z = 2; R ₁ for 4821 observed reflections [I > 2σ(I)] was 0.0679. Complex 1 is a centrosymmetric tetranuclear cobalt complex with all cobalts having distorted octahedral geometry. The molecule can be viewed as two planar [Co₂(OH)(L)(Phen)H₂O] units tied together by two terminal water molecules. The framework of 1 has the appearance of two connected face-sharing cubes, each with one vertex missing. The trinuclear copper complex 2, C₂₀H₄₄Cu₃N₂O₂₆S₂, crystallizes in the triclinic space group P1, with a = 7.524(1) Å, b = 7.902(2) Å, c = 16.885(4) Å, α = 88.993(6)°, β = 80.725(7)°, γ = 66.725(4)° and Z = 1; R ₁ for 4298 observed reflections [I > 2σ (I)] was 0.0360. Complex 2 is an ionic compound, in which the three Cu(II) centers have two coordination modes. The molecule has a centrosymmetric dinuclear copper coordinated anion and a hexa-aqua-copper cation. The sulfonic acid group has less coordination ability than carboxylate oxygen.     

One-pot synthesis and crystal structure of diaquabis(hydrazoneglyoxylato)cadmium(II)

The mononuclear complex [Cd(H₂NNCHCOO)₂(H₂O)₂] has been prepared from an aqueous solutions of reactants by one-pot synthesis and is characterized by IR, TG-DTA and single-crystal X-ray diffraction studies. The cadmium ion has distorted octahedral coordination (C ₂ symmetry) with two trans water molecules and oxygen and nitrogen donors forming two five-membered chelate rings. On heating, the anhydrous complex decomposes in two steps yielding CdO.     

Polynuclear Cu(II), Ni(II) and Cd(II) coordination compounds with bis(pyrimidin-2-yl)amine and dicyanamide

In this study the synthesis, crystal structure and characterization of three new transition metal polynuclear compounds with formula [Cu(dipm)(μ-dca)₂]_n(H₂O) (1), [Ni(dipm)(μ-dca)₂]_n(C₂H₆O)_1/2 (2) and [Cd(dipm)(μ-dca)₂]_n (3) (in which dipm = bis(pyrimidin-2-yl)amine and dca = dicyanamide) are reported. The isostructural compounds 1 and 2 contain a double-bridging end-to-end dca unit connecting two metal ions and a single bridging end-to-end dca unit between subsequent metals. Compound 3 exhibits only single bridging end-to-end dca units, oriented in three directions, giving rise to a 3D framework.     

Zinc(II) and cadmium(II) complexes with PDT: study of the effect of weak interactions on crystal packing

Two new zinc(II) and cadmium(II) complexes, [Zn(PDT)₂(NCS)₂] (1) and [Cd((PDT)₂I_1.6(H₂O)_0.4(OH)_0.4] · 0.4H₂O (2) (“PDT” is the abbreviation of 3-(2-pyridyl)-5, 6-diphenyl-1,2,4-triazine), have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectroscopy, and studied by X-ray crystallography. Zinc(II) in 1 is six coordinate ZnN₆. 2 is a co-crystal with cadmium(II) being 60% six-coordinated with a CdN₄I₂ environment and 40% seven-coordinated with a CdN₄O₂I environment. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular S ··· π, C–H ··· π, C–H ··· I, and π ··· π interactions.     

Structurally different cadmium(II) and lead(II) supramolecular polymers with the same benzene-1,2,3,4-tetracarboxylate dianion as bridging ligands from hydrothermal reactions

Two crystalline metal-organic frameworks, [Cd₂(o-BTC)(H₂O)₂] _n (1) and [Pb₂(o-BTC)] _n (2) (o-BTC?=?benzene-1,2,3,4-tetracarboxylic), were synthesized under hydrothermal conditions and characterized by analytical, spectroscopic and single crystal X-ray diffraction studies, which reveal three-dimensional reticular structures via M²⁺ and carboxylate ligands. All carboxyl groups of o-BTC are deprotonated, in agreement with the IR data. The Cd²⁺ centers of 1 have one coordination environment, while Pb²⁺ centers of 2 have two coordination environments. Both 1 and 2 form 3D interpenetrated grid structures along the b and c axes, respectively.     

Syntheses,crystal structures and magnetic study of two binuclear manganese(II) complexes with aromatic N-oxide as bridging ligand

Two new binuclear complexes, [Mn₂(μ-dmpo)₂(SCN)₄(H₂O)₂] (1) (where dmpo?=?3,5-dimethylpyridine N-oxide), [Mn₂(μ-po)₂(H₂O)₆I₂]I₂ (2) (where po?=?pyridine N-oxide), have been synthesized and their crystal structures determined by X-ray crystallography. Complexes 1 and 2 crystallize in monoclinic, space group P2₁/c, with unit cell dimensions a?=?8.8836(18)?Å, b?=?15.450(3)?Å, c?=?15.484(3)?Å, β?=?91.020(3)° for 1, and a?=?8.8352(13)?Å, b?=?17.927(3)?Å, c?=?8.3338(12)?Å, β?=?103.765(2)° for 2. In each binuclear complex two Mn(II) were bridged by two 3,5-dimethylpyridine N-oxides or by two pyridine N-oxides and the distances between the bridged Mn(II) ions are 3.599?Å for 1 and 3.552?Å for 2. Variable temperature (4–300?K) magnetic measurements were performed for 1 and the susceptibility data were fitted by using a binuclear Mn(II) magnetic coupling formula producing the 2J?=??2.17?cm^?1.     

Extended chains via hydrogen bond linkages of dinuclear copper(II) and cadmium(II) complexes with a new flexible disulfoxide ligand

A new flexible disulfoxide ligand 1,6-bis(benzylsulfinyl)hexane (L), which is a mixture of the meso and rac isomers, was treated with Cu^II or Cd^II nitrate and obtained dimeric complex [Cu₂(L)₃(H₂O)₂(NO₃)₄] 2 or [Cd₂(L)₃(H₂O)₂(NO₃)₄] 3. In the reacting system the crystals of meso isomer 1 of L together with 2 or 3 were obtained. 2 and 3 have similar molecular structures. In the neutral dimer, three ligands present two kinds of coordination models: monodentate and bis-monodentate. The neutral dimeric units in 2 and 3 are linked by hydrogen bonds to yield a chain structure. Crystal structures of all three compounds were determined by single-crystal X-ray diffraction methods. Crystal data for 1: monoclinic, space group Cc, a=41.95(2), b=5.132(2), c=8.660(4) Å, β=94.898(9)°, V=1857.7(15) Å³, Z=4, final refinement (I>2σ(I)): R1=0.0659, wR2=0.1415. Crystal data for 2: triclinic, space group P-1, a=9.242(4), b=9.539(4), c=21.042(9) Å, α=83.888(9), β=87.971(8), γ=74.177(9)°, V=1774.6(13) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0577, wR2=0.0954. Crystal data for 3: triclinic, space group P-1, a=9.203(4), b=9.831(3), c=20.860(7) Å, α=84.313(6), β=86.432(7), γ=74.188(6)°, V=1805.9(11) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0548, wR2=0.1192.     

Synthesis,structural and spectroscopic characterization of a new cadmium(II) complex containing imidazole (Im) as ligand, [Cd(Im)6](ClO4)2

Reaction between the 1,1′-carbonyldiimidazole ligand and mixtures of cadmium(II) acetate with sodium perchlorate provided the unusual crystalline material [Cd(Im)₆](ClO₄)_2, (Im?=?imidazole). This new Cd^II complex, has been characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR and ¹¹³Cd NMR spectroscopy. The coordination number in this complex is six, CdN₆ and coordination environment around the Cd(II) may be described as distorted octahedral with a D_2h point group. There are both edge-to-face π–π stacking and C–H(Im)?···?π interactions between aromatic “Im” rings belonging to adjacent chains in this network.     

Nickel(II) compounds of a tri-amine mono-imine macrocycle: Preparations and structures of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II) compounds

Reduction of one imine function of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nickel(II) with 1 molar proportion of NaBH₄ produces as the major product the tri-amine-mono-imine macrocyclic cation (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II), Ni(tm)]²⁺. Pairs of isomeric singlet ground state perchlorate and tetrachlorozincate salts of [Ni(tm)]²⁺ were prepared and the structures determined for the 1RS,8SR,11SR,12RS (labeled as β) and 1RS,8RS,11RS,12SR (labeled as α) tetrachlorozincate salts. Triplet ground state trans-β-[Ni(tm)(NCS)₂] and catena-trans-{β-Ni(tm)-NC-Ni(CN)₂-CN-}_n·2nH₂O have the macrocycle in planar coordination and α-[{Ni(tm)}₂(C₂O₄)](ClO₄)₂ has the macrocycle folded. With pentane-2,4-dione the compounds [β-Ni(tm)]·[α-Ni(tm)(acac)](ClO₄)₃ and [Ni(teta)]·[α-Ni(tm)(acac)](ClO₄)₃ (teta = C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) with both square-planar and octahedral Ni(II) cations were prepared and the latter was structurally characterized. Isomerisation in solution of metastable α-[Ni(tm)]²⁺ to stable β-[Ni(tm)]²⁺ is extremely slow, even in base.     

Synthesis,characterization, and fluorescence properties of dinuclear cadmium(II) complexes

Four dinuclear cadmium(II) complexes, [Cd₂(L¹)(μ₂-Cl)Cl₂] (1), [Cd₂(L²)(μ₂-Cl)Cl₂] (2), [Cd₂(L³)(μ₂-Cl)Cl₂] (3), and [Cd₂(L⁴)₃ClO₄] (4), where HL¹ = 4-methyl-2,6-bis(1-(2-piperidinoethyl)iminomethyl)-phenol, HL² = 4-methyl-2,6-bis(1-(2-pyrrolidinoethyl)iminomethyl)-phenol, HL³ = 4-methyl-2,6-bis(1-(2-morpholinoethyl)iminomethyl)-phenol and HL⁴ = 4-methyl-2,6-bis(cyclohexylmethyl)iminomethyl)-phenol, were synthesized. They were characterized by elemental analysis, FT-IR, UV–Vis, fluorescence and electronspray ionization mass spectroscopy. Complexes 1 and 4 were also characterized by single crystal X-ray analysis. The cadmiums atoms in 1 are linked by μ₂-chloride in a distorted square pyramidal geometry, whereas cadmium atom in 4 is in a distorted octahedral environment. The complexes show emission bands around 500 nm with excitation at 395 nm.     

Syntheses and characterization of mixed-anion cadmium(II) complexes,structural characterization of [Cd(phen)2(NO2)1.65(NO3)0.35], as a new eight-coordinate Cd(II) complex

New mixed-anion cadmium(II) complexes of 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) ligands, [Cd(phen)₂(NO₂)_1.65(NO₃)_0.35] and Cd(bpy)(ClO₄)(CH₃COO) have been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C- NMR and ¹¹³Cd NMR spectroscopy. The single crystal X-ray data of [Cd(phen)₂(NO₂)_1.65(NO₃)_0.35] show the complex to be a monomer and that the Cd atom has an unsymmetrical eight-coordinate geometry, being coordinated by four nitrogen atoms of ‘phen’ ligands and four oxygen atoms of the nitrite and nitrate anions. There is a short π–π stacking interaction between parallel aromatic rings.     

Two cadmium(II) fluorous coordination compounds tuned by different bipyridines

Fluorine is the most electronegative element and can be used as an excellent hydrogen‐bond acceptor. Fluorous coordination compounds exhibit several advantageous properties, such as enhanced high thermal and oxidative stability, low polarity, weak intermolecular interactions and a small surface tension compared to hydrocarbons. C—H…F—C interactions, although weak, play a significant role in regulating the arrangement of the organic molecules in the crystalline state and stabilizing the secondary structure. Two cadmium(II) fluorous coordination compounds formed from 2,2′‐bipyridine, 4,4′‐bipyridine and pentafluorobenzoate ligands, namely catena‐poly[[aqua(2,2′‐bipyridine‐κ²N ,N ′)(2,3,4,5,6‐pentafluorobenzoato‐κO )cadmium(II)]‐μ‐2,3,4,5,6‐pentafluorobenzoato‐κ²O :O ′], [Cd(C₇F₅O₂)₂(C₁₀H₈N₂)(H₂O)]_n , (1), and catena‐poly[[diaquabis(2,3,4,5,6‐pentafluorobenzoato‐κO )cadmium(II)]‐μ‐4,4′‐bipyridine‐κ²N :N ′], [Cd(C₇F₅O₂)₂(C₁₀H₈N₂)(H₂O)₂]_n , (2), have been synthesized solvothermally and structurally characterized. Compound (1) shows a one‐dimensional chain structure composed of Cd—O coordination bonds and is stabilized by π–π stacking and O—H…O hydrogen‐bond interactions. Compound (2) displays a one‐dimensional linear chain structure formed by Cd—N coordination interactions involving the 4,4′‐bipyridine ligand. Adjacent one‐dimensional chains are extended into two‐dimensional sheets by O—H…O hydrogen bonds between the coordinated water molecules and adjacent carboxylate groups. Moreover, the chains are further linked by C—H…F—C interactions to afford a three‐dimensional network. In both structures, hydrogen bonding involving the coordinated water molecules is a primary driving force in the formation of the supramolecular structures.     

Synthesis and structural characterization of copper(II), cadmium(II) and zinc(II) complexes with 4,5-diazaspirobifluorene and bis-9-biphenyl-4,5-diazafluorenyl peroxide

The synthesis and structural chemistry of four new divalent transition metal complexes of the fluorene ligands 4,5-diazaspirobifluorene (L1) and bis-9-biphenyl-4,5-diazafluorenyl peroxide (L2), [Cu₃(L1)₄(NO₃)₆(H₂O)₂] · 2CH₃CN (1), [Cu(L1)(CH₃CO₂)₂(H₂O)] · 2H₂O (2), [Cd(L1)₂(NO₃)₂] · DMF (3) (DMF = N,N-dimethylformamide) and [Zn₂(L2)(μ-Cl)₂Cl₂]_∞ (4) are described. Single-crystal X-ray diffraction analysis reveal that the four complexes exhibit various frameworks due to diverse coordination modes and different conformations of ligands L1 or L2, as well as nitrate, acetate or chloro counterions. L1 in complexes 1, 2 and 3 present an asymmetric rigid bidentate ligand with two nitrogen atoms as the donor sites. Novel complex 4 was formed through complexation between conformationally bent shaped peroxide ligands and zinc(II) dichlorides that adopt a linear coordination geometry, which can also give rise to extended polymeric chains with a zigzag secondary structure.     

Synthesis,crystal structures and fluorescence of cadmium(II) coordination polymers with derivatives of pyrazine-1,4-dioxide and thiocyanate as mixed-bridging ligands

Two Cd(II) coordination polymers have been synthesized with derivatives of pyrazine-1,4-dioxide and thiocyanate anion as bridging ligands and structurally determined by X-ray crystallography. Complex 1, [Cd(μ_1,3-SCN^?)₂(μ_1,6-L1)] _n (L1?=?2,5-dimethylpyrazine-1,4-dioxide), belongs to the triclinic, space group P 1 with a?=?5.7627(18)?Å, b?=?7.182(2)?Å, c?=?7.509(2)?Å, α?=?74.042(3)°, β?=?84.766(4)°, γ?=?88.162(4)°; complex 2, [Cd₂(μ_1,3-SCN^?)₄(μ₄-L2)] _n (L2?=?2,3,5,6-tetramethylpyrazine-1,4-dioxide), crystallizes in a monoclinic system with space group C2/m with a?=?10.194(4)?Å, b?=?13.491(6)?Å, c?=?8.140(3)?Å, β?=?120.372(4)°. Complex 1 shows a two-dimensional sheet structure, and in a direction the Cd(II) ions were coordinated by μ_1,3-SCN^? forming the one-dimensional chain and the L1 bridging ligand made the chains connect in the c direction leading to formation of a two-dimensional sheet on the ac plane. For 2 the one-dimensional chains in the a axis were constructed by coordination of μ_1,3-SCN^? bridging ligands with the Cd(II) ions, and in b and c directions the chains were joined by L2 bridging ligands leading to a three-dimensional structure. In 2 L2 displays a μ₄-bridging coordination mode. Both complexes exhibit strong fluorescence emission.     

Synthesis,crystal structures and spectral characterization of Cu(II) and Mn(II) complexes of 4-hydroxy-3-methoxybenzaldehyde: antioxidant properties and molecular docking studies

[Cu(L)₂(H₂O)₂] (1) and [Mn(L)₂(H₂O)₂] (2) (HL = 4-hydroxy-3-methoxybenzaldehyde) were synthesized and characterized using elemental, spectral (FTIR, ESI-MS, UV–visible, fluorescence and EPR), thermal, cyclic voltammetric, powder, and single crystal X-ray crystallographic studies. Spectral and X-ray data ascertained the structural features, binding modes of ligand and distorted octahedral geometry around the metal ions. Cyclic voltammetric studies confirmed the formation of a quasi reversible redox couple in solution. Crystal structure analysis of 1 and 2 reveal the presence of non-covalent interactions, resulting in a 1-D polymeric chain. Antioxidant properties (using DPPH and hydrogen peroxide assay) and molecular docking studies (using 1BNA) are also examined. The binding free energies (calculated from docked models), ?270 (1) and ?295 kJ mol^?1 (2), suggest that the complexes reasonably bind to DNA, and the DNA-binding affinity of 2 is stronger than that of 1.     

Syntheses,Structures and Luminescent Properties of 2D and 3D Cadmium(II) Coordination Polymers Derived from Two Isomeric Perchlorinated Benzenedicarboxylates

The coordination polymers {[Cd(o‐BDC‐Cl₄)(H₂O)₂]·EtOH}_n ( 1 ) and {[Cd(p‐BDC‐Cl₄)(DMF)]·H₂O}_n ( 2 ) (o‐BDC‐Cl₄ = tetrachlorophthalate and p‐BDC‐Cl₄ = tetrachloroterephthalate) were synthesized in different solvents using two isomeric tetrachlorinated benzenedicarboxylic acids. Complex 1 based on o‐BDC‐Cl₄ features an extremely rare 2D trinodal (3,4,6)‐connected network constructed by the combination of 1D [Cd‐H₂O]_n chains and 1D [Cd₂(o‐BDC‐Cl₄)₂]_n loop‐like motifs. Complex 2 based on p‐BDC‐Cl₄ has a 3D framework and shows a uninodal 4‐connected sra topology. Complexes 1 and 2 were characterized by elemental analyses, IR spectroscopy, single‐crystal X‐ray diffraction and thermogravimetric (TG) analyses. The photoluminescence of 1 and 2 were investigated in the solid state at room temperature.