Two- and three-dimensional lanthanide complexes: synthesis, crystal structures, and properties

3,5-pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1-9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal-organic framework structures. The complexes {[Ln2(HL)3(H2O)4].2H2O}n (Ln=Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3].3H2O}n (Ln=Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln=Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoledicarboxylic acid were observed, which proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers. The photophysical and magnetic properties have also been investigated.     

Cyanide-bridged polynuclear heterobimetallic complexes: synthesis,crystal structures,and magnetic properties

Transition Metal Chemistry - The reactions of [MnIII(3-EtOSalen)(H2O)2]ClO4 (Salen=N,N-ethylenebis(salicylideneaminato)dianion) with K3[M(CN)8] (M=Mo, W) have been investigated, from which...     

Pyrrole azocrown ethers—synthesis, crystal structures, and fluorescence properties

Pyrrole containing macrocycles with chromophoric and fluorescent residues were prepared. X-ray structures for compounds 1 and 4 were determined. The presented pyrrole azocrowns are lead(II) chemosensors, which can be used both in UV-vis and fluorescence spectroscopy.     

New lead inorganic-organic hybrid microporous and layered materials: synthesis,properties, and crystal structures

Two new lead(II) phosphonates, namely, Pb2[PMIDA]*1.5H2O (1) (H4PMIDA = H2O3PCH2N(CH2CO2H)2) and Pb(H2L) (2) (H4L = CH3N(CH2PO3H2)2), have been synthesized by hydrothermal reactions at 150 degrees C. Complex 1 crystallized in tetragonal P42/n with cell dimensions of a = 17.317(7) and c = 7.507(5) A and Z = 8. In complex 1, Pb(1) is 6-coordinated by chelation in a tetradentate fashion by a PMIDA ligand (3 O, 1 N) and two phosphonate oxygen atoms from neighboring Pb(PMIDA) units in a severely distorted octahedral geometry, whereas Pb(2) is 6-coordinated by 4 carboxylate and 2 phosphonate oxygen atoms also with a severely distorted octahedral environment. These two different types of Pb(II) ions are interconnected through bridging carboxylate and phosphonate groups, resulting in a 3D network with micropores, whose cavity is filled by lattice water molecules interlinked via hydrogen bonds. Each PMIDA ligand bridges with 8 Pb(II) ions (3 Pb(1) and 5 Pb(2)). Complex 2 is orthorhombic, P2(1)2(1)2(1), with a = 7.382(5), b = 7.440(6), and c = 30.75(2) A and Z = 8. The structure of 2 features a 2D double lead(II) phosphonate layer along the ab plane. Each lead(II) ion is 5-coordinated by five phosphonate oxygen atoms from four ligands in a distorted trigonal bipyramid geometry. These double layers are further interconnected via hydrogen bonds between the protonated and uncoordinated phosphonate oxygens along the c-axis.     

Two nickel(II) carboxyphosphonates with different supramolecular structures: synthesis,crystal structures and magnetic properties

Transition Metal Chemistry - Two Ni(II) carboxyphosphonates, namely [Ni(H4L)2] (1) and [Ni(H3L)(H2O)]·2H2O (2) (H5L=HOOCC6H4CH2N(CH2PO3H2)2), have been hydrothermally synthesized. Structural...     

One dense and two open chiral metal-organic frameworks: crystal structures and physical properties

Three 3D robust homochiral helical coordination polymers, [Cu(2,2',3,3'-H2odpa)(bpy)] (1), {[Ni4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)16} (2), and {[Co4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)14} (3), have been hydrothermally synthesized from a flexible ligand of 2,2',3,3'-odpda (2,2',3,3'-oxydiphthalic dianhydride). Compound 1 crystallized in space group P3(1)21 and has a rare chiral dense qzd 7.(5)9 topology that incorporates single helical substructures with the same accessibility, whereas compounds 2 and 3 crystallized in the space group C2 and possessed isostructural 3D chiral open frameworks based on the homochiral 2D sheets and 4,4'-bpy pillars. TGA and PXRD analyses show that the porous framework of 2 is stable after the removal of solvent water molecules. In contrast, 3 changed its structure to an amorphous one because of the simultaneous loss of solvent and coordination water molecules. 1 is nearly paramagnetic, whereas weak ferromagnetic interactions between M(II) (M = Ni, Co) ions have been found in 2 and 3.     

Two novel benzenedicarboxylate‐metal complexes: synthesis,crystal structures and fluorescent properties

Two novel benzenedicarboxylate–metal complexes, [Sm(nphth)(Hnphth)(H₂O)₃^?H₂O]₂ and [Zn(nphth)(bipy)(H₂O) ?H₂O]₂ (2) (H₂nphth = 3‐nitrophthalic acid, bipy = 2,2′‐bipyridine), have been synthesized under hydrothermal condition and characterized by single‐crystal X‐ray diffraction. Both complex 1 and 2 exhibit a dimeric structure, and nphth ligand shows different coordination mode in the f‐block and d‐block complexes. The fluorescent properties of two complexes are investigated; the results reveal that the two complexes show different kinds of fluorescence. Copyright © 2007 John Wiley & Sons, Ltd.     

Multi-iron silicotungstates: synthesis, characterization, and stability studies of polyoxometalate dimers

The reaction of Fe(III) with Na(+) and K(+) salts of the trivacant [alpha-SiW(9)O(34)](10)(-) ligand have been investigated at pH 6 and pH 1. A new dimer, [(alpha-SiFe(3)W(9)(OH)(3)O(34))(2)(OH)(3)](11-) (1), is synthesized by reacting Na(7)H(3)[alpha-SiW(9)O(34)] or K(10)[alpha-SiW(9)O(34)] with exactly 3 equiv of Fe(III) in a 0.5 M sodium acetate solution (pH 6). The structure of 1, determined by single-crystal X-ray diffraction (a = 22.454(2) A, b = 12.387(2) A, c = 37.421(2), beta = 100.107(8) degrees , monoclinic, C2/c, Z = 4, R(1) = 5.11% based on 12739 independent reflections), consists of two [alpha-SiFe(3)W(9)(OH)(3)O(34)](4-) units linked by three Fe-mu-OH-Fe bonds. Reaction of K(10)[alpha-SiW(9)O(34)] with 3 equiv of Fe(III) in water (pH 1) yields [(alpha-Si(FeOH(2))(2)FeW(9)(OH)(3)O(34))(2)](8)(-2). The structure of 2 was also determined by single-crystal X-ray diffraction (a = 36.903(2) A, b = 13.9868(9) A, c = 21.7839(13) A, beta = 122.709(1) degrees , monoclinic, C2/c, Z = 4, R(1) = 4.57% based on 11787 independent reflections). It consists of two [alpha-Si(FeOH(2))(2)FeW(9)(OH)(3)O(34)](4-) Keggin units linked by a single edge. The terminal ligand on Fe1 in each trisubstituted Keggin unit becomes a mu(2) oxo ligand bridging to a [WO(6)](2-) moiety. The UV-vis spectra of both complexes show the characteristic oxygen-to-metal-charge-transfer bands of polyoxometalates as well as an Fe(III)-centered band at 436 nm (epsilon = 146 M(-1) cm(-1)) and 456 nm (epsilon = 104 M(-1) cm(-1)) for complexes 1 and 2, respectively. Differential scanning calorimetry data show that complex 1 decomposes between 575 and 600 degrees C whereas no decomposition is observed for complex 2 up to temperatures of 600 degrees C.     

Cyanocomplexes with one-dimensional structures: preparations,crystal structures and magnetic properties

The review surveys the preparation methods, crystallochemistry and magnetic properties of one-dimensional cyanocomplexes. Their preparation methods are mainly based on reactions in solutions containing suitable building blocks as precursors of the polymeric structure. The analysis of published data on crystal structures is given, as the knowledge of the crystal structure is essential for the study of magneto-structural correlation. Published data on magnetic properties are discussed along with the methods used for the study of magnetic properties.     

Nuclearity controlled cyanide-bridged bimetallic CrIII-MnII compounds: synthesis, crystal structures, magnetic properties and theoretical calculations

The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)4]- coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between CrIII and MnII through the single cyanide bridge [J=-6.2 cm(-1), the Hamiltonian being defined as H=-J(SCr1.SMn+SCr2.SMn] occurs in 2 leading to a low-lying spin doublet which is fully populated at T <5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field Hc being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic Cr2III MnII chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties.     

Homochiral imidazole-based dicarboxylate metal complexes with SrSi2 topology: synthesis,crystal structures,and properties

Two new complexes with homochiral frameworks, {Co₃(EIDC)₂(H₂O)₅}_n (1) and {Zn₃(EIDC)₂(H₂O)₄}_n (2) (H₃EIDC?=?2-ethyl-1H-imidazole-4,5-dicarboxylic acid), have been synthesized from achiral starting precursors via spontaneous resolution and fully characterized by elemental analyses, IR, circular dichroism, photoluminescence (PL) spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis. X-ray diffraction data revealed that 1 and 2 have SrSi₂ topologies and that both are homochiral metal–organic frameworks. Compound 1 is constructed by left-handed chiral chains; however, right-handed chains constitute the homochiral framework of 2. Variable temperature magnetic susceptibility measurements of 1 indicate strong antiferromagnetic interactions between the magnetic Co centers. Compound 2 exhibited weak blue PL in the solid state at room temperature.     

Cyclic triureas--synthesis, crystal structures and properties

The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been studied by 1H NMR. Complexation constants for chloride, bromide and acetate have been measured for all trimers by UV spectrophotometry. Molecular dynamics simulations have been carried out to determine the conformation of the free receptors in chloroform and acetonitrile. They show that in chloroform, intramolecular hydrogen bonding occasionally facilitated by trans-->cis isomerisation of an amide bond dominates the conformation of the macrocycles while in acetonitrile (the solvent used for complexation measurements), the ligating urea NH protons are properly arranged for the complexation of anions, however, their strong solvation is counteractive to the complexation.     

Heterometallic copper(Ⅱ) vanadates: synthesis,crystal structures and third-order nonlinear optical properties

Three polymeric heterometallic clusters with 1D, 2D, and 3D frameworks, constructed from a cyclic vanadate {V4O12}4-building block and three geometric constraint ligands, were synthesized by a one-pot self-assembly reaction. Z-scan experiments demonstrated that all the three cluster polymers have large hyperpolarizability γ values. TD-DFT calculations afforded insight into the electronic transitions and spectral characterization of these novel NLO molecular materials.     

Rhodium-catalyzed enantioselective synthesis, crystal structures, and photophysical properties of helically chiral 1,1'-bitriphenylenes

The highly enantioselective synthesis of helically chiral 1,1'-bitriphenylenes has been achieved via rhodium-catalyzed double [2 + 2 + 2] cycloaddition of biaryl-linked tetraynes with 1,4-diynes (up to 93% ee). Crystal structures and photophysical properties of these helically chiral 1,1'-bitriphenylenes have also been studied.     

TDDFT studies on the electronic structures and chiroptical properties of mono-tin-substituted Wells-Dawson polyoxotungstates

The UV/CD spectra of tin-bearing acetonyl-substituted Wells-Dawson polyoxotungstates α(1)- and α(2)-[P(2)W(17)O(61){SnCH(2)CH(2)C(═O)}](6-) were systematically investigated using the time-dependent density functional theory (TDDFT) method. The electronic circular dichroism (ECD) spectra were produced over the range of 3.3-5.8 eV. The calculated ECD spectra of the α(1)-R isomer were generally in agreement with the experimental spectra. The CAM-B3LYP hybrid functional was found to predict the excitation energies of tin-containing polyoxotungstates well. The fact that the UV/ECD spectra of α(1)-isomers are different from those of α(2)-isomers demonstrates the effect of the tin substitution site on the chiroptical properties of the studied isomers. The origins of the ECD bands are mainly ascribed to charge-transfer (CT) transitions from oxygen atoms to W atoms, from organic fragments to W atoms, or from the combination of two CT transitions. The results suggest that the organic fragment and polyoxometalate (POM) cage are chiroptical chromophores.     

Isostructural M2L4 molecular capsules with anthracene shells: synthesis, crystal structures, and fluorescent properties

An isostructural series of M(2)L(4) molecular capsules quantitatively self-assembled from two M(II) ions (M=Zn, Cu, Pt, Pd, Ni, Co, and Mn) and four bent ligands with embedded anthracene fluorophores. X-ray crystallographic analysis (for M=Zn, Cu, Ni, and Pd) confirmed the formation of closed-shell structures in which the large interior cavities inside the molecular capsules (about 1 nm) were shielded by eight anthracene panels. Analysis of the Zn(II) and Cu(II) structures showed the inclusion of an unusual triad guest cluster; four MeCN molecules, one water molecule, and one CF(3)SO(3)(-) ion were located inside the cavities. Full characterization by NMR spectroscopy and MS (ESI-TOF) demonstrated that the molecular capsules were quite stable and persist in solution. The fluorescence properties of the isostructural capsules were strongly dependent on the identity of the metal species: the Zn(II) capsule emitted strong blue fluorescence with a high quantum yield (Φ=0.8), in sharp contrast to the weakly emissive Ni(II) and Mn(II) capsules and the completely non-emissive Pd(II), Pt(II), and Co(II) capsules. On the other hand, the Cu(II) capsule exhibited solvatochromism and solvent-dependent emission behavior; blue emission of the capsule was "on" in DMSO but "off" in MeCN.     

异金属膦酸铀的合成、晶体结构和荧光性质

构建异金属膦酸铀仍然具有挑战性。在本工作中,从苯磺酰甲基膦酸二乙酯(Et₂L)出发,成功合成了一系列同构的异金属膦酸铀化合物[UO₂Mn (L)₂(H₂O)₄],其中M=Mn (1)、Co (2)、Ni (3)、Zn (4)、Cd (5)。晶体结构研究表明,磺酰基团没有与金属离子配位,而膦酸基团完全去质子化,连接2个铀酰离子和1个过渡金属离子,形成了二维层状晶体结构。荧光研究表明,在Mn (Ⅱ)、Co (Ⅱ)和Ni (Ⅱ)离子存在时,铀酰离子的特征荧光发射被淬灭,而在Zn (Ⅱ)和Cd ((Ⅱ)离子存在时,显示出强的特征荧光发射。     

异金属膦酸铀的合成、晶体结构和荧光性质

构建异金属膦酸铀仍然具有挑战性。在本工作中,从苯磺酰甲基膦酸二乙酯(Et₂L)出发,成功合成了一系列同构的异金属膦酸铀化合物[UO₂M (L)₂(H₂O)₄],其中M=Mn (1)、Co (2)、Ni (3)、Zn (4)、Cd (5)。晶体结构研究表明,磺酰基团没有与金属离子配位,而膦酸基团完全去质子化,连接2个铀酰离子和1个过渡金属离子,形成了二维层状晶体结构。荧光研究表明,在Mn (Ⅱ)、Co (Ⅱ)和Ni (Ⅱ)离子存在时,铀酰离子的特征荧光发射被猝灭,而在Zn (Ⅱ)和Cd (Ⅱ)离子存在时,显示出强的特征荧光发射。     

Two dioxomolybdenum(VI) complexes with hydrazone ligands: synthesis,characterization, crystal structures and catalytic properties

A pair of Mo(VI) complexes, [MoO₂L¹(MeOH)] (1) and [MoO₂L²(MeOH)] (2), where L¹ and L² are the dianions of 2-amino-N’-(3-bromo-5-chloro-2-hydroxybenzylidene)benzohydrazide (H₂L¹) and 2-amino-N’-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (H₂L²), respectively, have been prepared and characterized by physico-chemical methods and single-crystal X-ray diffraction. The Mo atom in each complex is coordinated by the phenolate oxygen, imino nitrogen and enolate oxygen of the hydrazone ligand, together with a methanol ligand and two oxo groups, giving a distorted octahedral geometry. The complexes proved to be effective catalysts for the oxidation of various olefins.