Syntheses,crystal structures,and magnetic properties of three one-dimensional metal–nitroxide complexes linked by 1,4-cyclohexanedicarboxylate ligands

Three one-dimensional metal–nitroxide complexes [Cu(NIT4Py)₂(1,4-chdc)] _n (1), {[Cu(IM4Py)₂(1,4-chdc)(H₂O)]·H₂O} _n (2) and {[Zn(IM4Py)₂(1,4-chdc)(H₂O)₂]·H₂O} _n (3) (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and 1,4-chdc = 1,4-cyclohexanedicarboxylate anion) have been synthesized and characterized structurally as well as magnetically. All three complexes crystallize in neutral one-dimensional chains in which the nitroxide–metal–nitroxide units are linked by linear 1,4-cyclohexanedicarboxylate anions. The 1,4-chdc ligands only present the e,e-trans-configuration in these complexes, although there are both cis- and trans-isomers in the free ligand. Magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the copper atoms and nitroxide radicals.     

Syntheses and crystal structures of transition metal complexes of 1,1′-bisacetylacetoferrocene

Bimetallic complexes 3a–e of 1,1′-bisacetylacetoferrocene (2) were prepared by reactions of transition metal acetates M(OAc)₂ (M?=?Co²⁺, Mn²⁺, Cu²⁺, Ni²⁺, Zn²⁺) with the 2 in refluxing methanol. The X-ray structures of the cobalt and manganese complexes were determined showing very similar centrosymmetric macrocyclic dimeric frameworks constituted by linkage of two Co²⁺ or Mn²⁺ ions and two 1,1′-diacetoacetylferrocene units with two additional methanols as bridges dividing this macrocyclic framework into two small cyclic subunits. The UV-Vis spectra and electronic properties were also studied.     

pH-dependent syntheses and crystal structures, characterizations, and DFT calculations of complexes with 2,2′-biimidazole and terephthalic acid ligands

The divalent transition metal complexes [Zn(L)₂(H₂O)₂](Tere) (I), [Cd(L)₂(H₂O)₂](Tere]) (II) and [Cd(L)₂(HTere)₂] (III) (L = 2,2’-biimidazole, Tere = terephthalate) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectrum, thermal analysis and single-crystal X-ray diffraction analysis. Complexes II and III have the same starting materials but possess different frame-works and are prepared from H₂Biim and H₂Tere under hydrothermal conditions with different pH values. The crystal structures show I and II have the same coordination circumstances and are coordinated by two H₂O molecules and two neutral bidentate 2,2′-biimidazole ligands. The terephthalate acts as the counter anion. In contrast, complex III contains protonated carboxylate groups coordinated to the metal centre to give neutral species. Furthermore, based on the optimized structures, molecular frontier orbitals, Mulliken charges and IR spetra of complex I and III are investigated by density functional theory. Calculated results show that the energy gap (ΔE _L-H) between HOMO and LUMO of complex III is bigger than that of I. It is revealed that complex III is more stable, and this calculated estimation corresponds with experimental analysis of TGA curves.     

Structural and thermal properties of rare earth complexes with 2,2′-biphenyldicarboxylic acid

Rare earth complexes with 2,2′-biphenyldicarboxylic acid (diphenic acid = H₂dpa) were obtained as hydrated precipitates of the general formula Ln₂(C₁₄H₈O₄)₃∙nH₂O, where n = 3 for the of Y(III) and Ce(III)–Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30–210 °C in one step and form anhydrous compounds, which are stable up to 315–370 °C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)–Er(III) complexes) crystal systems.     

Syntheses,structures and catalytic activities of low-coordinated rare-earth metal complexes containing 2,2′-pyridylpyrrolides

Reactions of the ligand precursors 2-(2′-pyridyl)-3,5-Me₂-pyrrole ( L ¹ H) and 2-(2-pyridyl)-3,4,5-Me₃-pyrrole ( L ² H) with [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ in toluene afforded a series of low-coordinated rare-earth metal bis-amido complexes L ¹ RE[N(SiMe₃)₂]₂ [RE = Y ( 1a ), Dy ( 1b ), Er ( 1c ), Yb ( 1d )] and L ² RE[N(SiMe₃)₂]₂ [RE = Y ( 2a ), Dy ( 2b ), Er ( 2c ), Yb ( 2d )]. With the ionic radius of rare-earth metal increasing, the reaction of L ¹ H and [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ gave dinuclear complexes ( L ¹ )₂RE(μ-Cl)(μ-η⁵:η¹:η¹- L ¹ )RE( L ¹ )[N(SiMe₃)₂]₂ [RE = Sm ( 1e ), Pr ( 1f )]; however, the reaction of L ² H and [(Me₃Si)₂N]₃Sm(μ-Cl)Li(THF)₃ afforded ( L ² )₂Sm[N(SiMe₃)₂]₂ ( 2e ). Results indicated that the ionic radius of rare-earth metal and subtle change in the ligands have substantial effects on the structure and bonding mode of complexes. The complexes showed a high catalytic activity for the ring-opening reaction of cyclohexene oxide with amines to afford various β-aminoalcohols under mild solvent-free conditions.     

Synthesis,crystal structures and characterization of iron(III) and cobalt(III) complexes bearing 2,2′-bipyridylcarboxylate ligands

Transition Metal Chemistry - The Fe(III) complex [FeIII(bpdc)(Hbpdc)] (1) (bpdc?=?2,2′-bipyridyl-6,6′-dicarboxylate and...     

Syntheses,crystal structures,and optical properties of a series of transition metal coordination polymers with chelidamic acid and 4,4′-bipyridine

A series of transition metal (Zn, Cu, Mn) complexes with chelidamic acid (2,6-dicarboxy-4-hydroxypyridine, H₃CAM) and 4,4′-bipyridine (bipy), [Zn₂(bipy)Cl₂] _n (1), {[Zn₂(HCAM)(H₂CAM)₂]?·?(bipy)?·?3.5H₂O} _n (2), [Mn₃(HCAM)₃(H₂O)₇]?·?(bipy)?·?3H₂O (3), [Mn₂(HCAM)₂(bipy)?·?(H₂O)₂]?·?4H₂O (4), [Cu₂(HCAM)₂(bipy)?·?(H₂O)₂]?·?4H₂O (5), and Cu₂(HCAM)₂(bipy)?·?(H₂O)₂ (6), have been synthesized by hydrothermal or solution methods and characterized by single-crystal X-ray diffraction. The structural analyses reveal that 1 exhibits a zigzag chain of Zn(II), Cl^?, and 4,4′-bipyridine. In 2, a 1-D polymeric [Zn₂(HCAM)(H₂CAM)₂] _n chain and a discrete 4,4′-bipyridine assemble into a 2-D supramolecular network via H-bonds. Complex 3 consists of asymmetric units of Mn₃(HCAM)₃(H₂O)₇ that are linked by hydrogen bonds to form a 2-D H-bonded network. Complexes 4–6 are isomorphous and possess discrete structures. The photoluminescent properties of 1–6 at room temperature were studied.     

Synthesis,crystal structures,and photoluminescence of two new zinc complexes based on 2,2′-thiodibenzoic acid

{[Zn₂(tdba)₂(phen)₂(H₂O)₂]?·?2H₂O?·?2DMF} _n (1) and [Zn(tdba)(bpy)] _n (2) (H₂tdba?=?2,2′-thiodibenzoic acid, phen?=?1,10-phenanthroline, bpy?=?2,2′-bipyridine, DMF?=?dimethylformamide) were hydrothermally synthesized, and characterized by single-crystal X-ray diffraction analysis, FT-IR, and elemental analysis. The obtained complexes exhibit different structures. Compound 1 is 0-D with tdba connecting two Zn ions in a μ ₁–η ¹/μ ₁–η ¹ coordination forming a dinuclear molecule. Each molecule is further connected with neighbors via hydrogen-bonding and π?···?π interactions. Compound 2 displays a 1-D structure in which Zn²⁺ centers are connected via tdba anions into 1-D chains propagating along the a-axis; these chains are further packed via π?···?π interactions. In addition, photoluminescence for 1 and 2 has been investigated.     

Synthesis, structure, and luminescent properties of three silver(I) complexes with organic carboxylic acid and 4,4′-bipyridine-like ligands

The reactions of AgNO₃ with combinations of 1,2-bis(4-pyridyl)ethane(bpa)/4,4′-bipyridine (bpy), 4,4′-stilbenedicarboxylic acid (H₂sda)/2,2′-diphenylaminedicarboxylic acid (H₂dpadc)/2,6-naphthalenedicarboxylic acid (H₂ndc) in aqueous alcohol/ammonia at room temperature produce block-like crystals of [Ag₂(bpa)_1.5(sda)_0.5](sda)_0.5·7H₂O, [Ag₂(bpa)₂(H₂O)₃](dpadc), [Ag₂(bpy)₂](ndc)·4H₂O. All three complexes consist of 1D infinite silver–ligand cationic chains, interspersed with organic carboxylate anions that provide charge compensation in the crystal structures. The lattice water molecules are situated among the framework of the crystal structure and show rich hydrogen-bonding interactions, which help to orientate the organic carboxylate anions in the crystal packing, and the presence of Ag···N and Ag···Ag contacts contributes to strengthen the frameworks. The luminescent properties and thermogravimetric analyses of the three complexes are also presented.     

Temperature-dependent synthesis, crystal structures, characterizations, and DFT calculations of two new copper(II) complexes with p-fluorobenzoic acid and 2,2′-bipyridine ligands

Two new copper(II) complexes, [Cu(p-FBA)₂(2,2′-bpy)]·(H₂O) (1) and [Cu(p-FBA)(2,2′-bpy)₂]·(p-FBA)₂ (2) {p-FBA = p-fluorobenzoic acid, 2,2′-bpy = 2,2′-bipyridine} have been obtained from an identical starting mixture using temperature as the only independent variable and characterized by X-ray single crystal diffraction as well as with infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The results reveal that 1 has 1D infinite chain structure formed by O–H···O hydrogen bonds, while 2 features a 0D structure. Additionally, there exist C–H···O hydrogen bonds and π–π stacking interactions in 1, forming 2D supramolecular structure. Furthermore, density functional theory (DFT) calculations of the structures, stabilities, orbital energies, composition characteristics of some frontier molecular orbitals and Mulliken charge distributions of the [Cu(p-FBA)₂(2,2′-bpy)] of 1 and [Cu(p-FBA)(2,2′-bpy)₂]⁺ cation of 2 were performed by means of Gaussian 03W package and taking B3LYP/lanl2dz basis set.     

Synthesis,characterization and magnetic properties of supramolecular metal–organic complexes constructed from flexible–rigid mixed ligands

Two new supramolecular metal–organic complexes have been synthesized under hydrothermal conditions. Complex 1 exhibits a three-dimensional supramolecular network, constructed from [Co₂(H₃BPTC)₂(phen)₂] (H₄BPTC = 3,3′4,4′-benzophenone tetracarboxylate acid, phen = 1,10-phenanthroline) discrete units. Complex 2 similarly exhibits discrete [Cu₂(DPA)₂(bipy)₂(H₂O)₂] (DPA = 1,1′-biphenyl-2,2′-dicarboxylate acid, bipy = 2,2′-bipyridine) units, which are linked to form a three-dimensional supramolecular network through π–π interactions. It is interesting that during the synthesis of complex 1, the H₄BPTC ligands undergo partial decomposition to give 1,2,4-benzenetricarboxylate (H₃BTC) ligands, which react with Co to form [Co₃(BTC)₂]_n (3). Complex 3 shows a three-dimensional covalent network. The magnetic properties of complexes 1 and 2 have been studied.     

Syntheses, crystal structures, and magnetic and fluorescence properties of three complexes of mixed flexible N,N′-bis(3-pyridylmethyl)amine and rigid pyromellitate ligands

Three new complexes, {[Mn(Hbpma)₂(pm)(H₂O)₂]·8H₂O}_n, {[Co(Hbpma)₂(pm)(H₂O)₂]·8H₂O}_n and {[Zn(Hbpma)₂(pm)(H₂O)₂]·8H₂O}_n (bpma = N,N′-bis(3-pyridylmethyl)amine and H₄pm = pyromellitic acid) were synthesized and structurally characterized by single-crystal X-ray diffraction. All three complexes are isomorphous consisting of one-dimensional coordination polymers bridged by rigid pm ligands, while the flexible dipyridyl bpma only acts as a terminal ligand. The bpma ligand adopts the trans–trans conformation in all three complexes. The magnetic properties of the Mn(II) and Co(II) complexes show the occurrence of antiferromagnetic interactions between adjacent metal atoms. The Zn(II) complex exhibits fluorescent emission in the solid state at room temperature.     

Synthesis,characterization and magnetic properties of coordination polymers of manganese with 1,1′-biphenyl-2,2′-dicarboxylic acid ligands

Three new coordination polymers have been synthesized from 1,1′-biphenyl-2,2′-dicarboxylic acid (2,2-dpa), nitrogen-containing coligands and Mn salts under hydrothermal conditions. The X-ray crystal structures of all three complexes are presented. With the change of nitrogen-containing ligand, the structural features of the complexes also change. The complex prepared without a nitrogen coligand exhibits a one-dimensional covalent chain-like structure, composed of the rare pentanuclear Mn building unit. The complex with 4,4′-bipyridine as a secondary ligand shows a two-dimensional layer structure. With the chelating ligand 1,10-phenanthroline, a discrete molecular complex is synthesized. The magnetic properties of the complex with 4,4′-bipyridine in the temperature range 1.99–300 K are reported.     

Crystal structures of two new dinuclear Ag(I) complexes constructed from 4,4′-biphenyldicarboxylic acid and N-containing ligands

The reaction of silver 4,4′-biphenyldicarboxylate with 1,3-diaminopropane (DAP) and 2-amino-5-methylpyridine (AMP) respectively results in the formation of two dinuclear silver(I) complexes: [Ag₂(DAP)₂](BPC)·2H₂O (1) and [Ag₂(BPC)(AMP)₄]·2H₂O (2), where BPC is 4,4′-biphenyldicarboxylate. The complexes are characterized by elemental analysis and X-ray crystallography. Complex 1 crystallizes in the triclinic system, P-1 space group, a = 8.585(2) Å, b = 8.849(2) Å, c = 9.890(3) Å, α = 107.893(3)°, β = 94.139(3)°, γ = 113.202(3)°, V = 640.9(3) ų, Z = 1. Complex 2 crystallizes in the triclinic system, P-1 space group, a = 11.818(3) Å, b = 13.132(4) Å, c = 13.281(4) Å, α = 92.571(4)°, β = 96.425(3)°, γ = 102.142(4)°, V = 1997.5(10) ų, Z = 2. Complex 1 consists of a macrocyclic dinuclear silver(I) dication, a 4,4′-biphenyldicarboxylate anion, and two water molecules of crystallization. Each Ag atom is in a linear coordination. Complex 2 consists of a dinuclear silver(I) complex molecule and two water molecules of crystallization. Each Ag atom is in a T-shaped coordination. The Ag...Ag separations are 5.127(2) Å in 1 and 3.172(2) Å in 2.     

Syntheses,crystal structures,and properties of two Cd–Fe heterobimetallic compounds with bridging en and dien ligands

From the system Cd(II)–L–[Fe(CN)₆]^4?, complexes [{Cd(en)}₂{Fe(CN)₆}] (1) and [{Cd(H₂O)(dien)}₂{Fe(CN)₆}] ? 4H₂O (2) were prepared and characterized. The same products were also isolated from mother liquors containing [Fe(CN)₆]^3? in which Fe(III) was reduced to Fe(II) upon irradiation. By the combination of IR and Mössbauer spectroscopy, the presence of the low-spin state (S = 0) for Fe(II) was corroborated in both 1 and 2. The Cd(II) and Fe(II) in both complexes are linked by bridging cyano ligands forming a 3-D crystal structure of 1 and a 1-D ribbon-like structural motif in 2. The bidentate en in 1 links two pentacoordinated Cd(II), while in 2 the dien ligand exhibits a rare chelating-bridging bonding mode completing the hexacoordination of Cd(II) and enhancing the dimensionality of the formed structure to 2-D. Fe(II) in both structures exhibits octahedral coordination by cyano bridging in 1 whereas in 2 two cyano ligands are terminal. Water of crystallization and the coordinated water in 2 are involved in hydrogen bonds. Dehydration in 2 is a one-step process with a minimum on the DTA curve at 92°C.     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

Syntheses,crystal structures and photochemistry of two new organic–inorganic hybrid compounds based on copper–glycin complexes and paradodecatungstates

Two organic–inorganic hybrid materials built from copper–glycin complexes and paradodecatungstates, Na₆[{Cu(gly)(H₂O)}]₂[{Cu(H₂O)}(H₂W₁₂O₄₂)] ? 21H₂O (1) and Na{Na(H₂O)₆}{Na(H₂O)₄}₃[{Cu(gly)₂}]₂{H₅(H₂W₁₂O₄₂)} ? 8.5H₂O (gly = glycin) (2), have been synthesized in aqueous solution and characterized by IR, UV, TG, elemental analysis, electrochemistry, and single-crystal X-ray analyses. In 1, [H₂W₁₂O₄₂]^10? building block connects two neighboring clusters with [Cu(H₂O)]²⁺ groups to produce an infinite 1-D chain; then these chains are linked through [Cu(gly)(H₂O)]⁺ groups to form a 2-D layer structure, which is further joined by Na⁺ to form a 3-D network. In 2, [H₂W₁₂O₄₂]^10? decorated by two [Cu(gly)₂] moieties connects four adjacent clusters with six Na⁺ into a 2-D layer. In addition, luminescence and photocatalysis properties of these compounds have been investigated.     

Synthesis and characterization of two new metal–organic frameworks with interpenetrated structures and luminescent properties

Two new metal–organic compounds, [Ag₂(HADC)₂(bimh)] (1) and [Cd(ADC)(bpp)]_n (2) [H₂ADC = 1,3-adamantanedicarboxylic acid, bimh = 1,6-bis(2-methyl-imidazole-1-yl)hexane, bpp = 1,3-bis(4-pyridyl)propane], have been synthesized and characterized. Compound 1 exhibits a discrete symmetric unit with 0D→2D interpenetrating structure. Compound 2 crystallizes in a chiral space group P212121 and presents a threefold interpenetrated 3D diamondoid network containing three helical chains. Thermal stability, X-ray powder diffraction, and luminescence for 1 and 2 are also measured and discussed.     

Synthesis,characterization, and cytotoxicity of complexes of platinum(II) with 2,2′-bipyridine and N-benzoyl-L-amino acid dianion

Four new platinum(II) complexes (1–4) with N-benzoyl-L-amino acid and bipy were synthesized and characterized by elemental analysis, IR, UV, ¹H NMR, and mass spectra. The crystal structure of 1 was determined by X-ray diffraction analysis. Cytotoxicities were measured by MTT and SRB assays. Complexes 1–4 exert cytotoxicity with selectivity against HL-60, Bel-7402, BGC-823, and KB cell lines. This suggests that amino acids and acylated groups have important effects on cytotoxicity; the cytotoxicity is also related to the species of tumor cells, but the IC₅₀ values do not show definite correlation with the variation of amino acids and acylated groups.