Mixed salts containing croconate violet, lanthanide and potassium ions: Crystal structures and spectroscopic characterization of supramolecular compounds

The vibrational spectra and crystal structures of four lanthanide and potassium salts of 3,5-bis(dicyanomethylene)cyclopentane-1,2,4-trionate (), known as croconate violet (CV), are described in this work. All LnKC₂₂N₈O₆ (Ln = La⁺³, Nd⁺³, Gd⁺³ and Ho⁺³) compounds are isostructural, crystallizing in the triclinic space group. In each compound the lanthanide ion is acting as both monodentate and chelate metal sites, whereas the potassium presents only monodentate coordination. The crystal structure shows the formation of a periodic 2D structure extended by K-N bonds parallel to the crystallographic [0 0 1] direction; these 2D sheets form hydrogen bonds with water molecules giving rise to a 3D extended arrangement. It is not possible to observe any type of π-interaction and the main forces responsible to stabilize the structures are the hydrogen bonds. The vibrational spectra of all the compounds are very similar, and the most important vibrational markers for the croconate violet ion, namely the ν(CN) and ν(CO) modes, behave differently: the ν(CN) modes are not shifted by the presence of the lanthanide ion species, only showing small band intensity differences, whereas the ν(CO) bands are shifted to higher wavenumbers, due to their coordination to the metal sites.     

Octahedral hexanuclear complexes involving light lanthanide ions

Two new hexanuclear complexes involving two of the lightest lanthanide ions have been synthesized and structurally described. Their chemical formula is [Ln₆(μ₆-O)(μ₃-OH)₈(NO₃)₆(H₂O)₁₄] · 2NO₃ · 2H₂O with Ln = Pr or Nd. The structure has been solved for the Pr³⁺-containing compound. It crystallizes in the monoclinic system, space group P21/n (no. 14) with a = 12.4163(2) Å, b = 10.51210(10) Å, c = 16.0389(2) Å, β = 95.7810(6)° and Z = 4. The chemical and thermal stabilities of both the compounds have been studied. These studies reveal that they can be used as molecular chemical precursors for further materials synthesis. To the best of our knowledge, this praseodymium-containing hexanuclear complex is the first ever reported.     

Crystal structures and spectroscopic properties of palladium complexes isolated from Pd-EDTA solutions

Two complexes were isolated from aqueous Pd(NO₃)₂-Na₂H₂EDTA solutions and studied by single crystal X-ray diffraction, IR/Raman spectroscopy, and photoelectron spectroscopy. The first complex, Pd(Hkpda)₂ (kpda = ketopiperazinediacetate dianion, C₈H₁₀N₂O₅), forms yellow parallelepipeds during slow evaporation of Pd(NO₃)₂-Na₂H₂EDTA solution at 25 °C, and is a result of EDTA oxidation. The second one, [Pd(μ-H₂EDTA)]₂ · 2NaNO₃ · 7.5H₂O, with two EDTA molecules acting as bridges between two palladium atoms, forms yellow bipyramides during fast evaporation at 60 °C. In both complexes, the palladium atoms adopt a planar trans-geometry by bonding to two nitrogen and two oxygen atoms of two ligand molecules.     

Syntheses, structures and fluorescence of lanthanide complexes of 4-acyl pyrazolone derivatives

Three lanthanide complexes of 4-acyl pyrazolone derivatives: Ln(PMPP-SHZ)₂(CH₃OH)₂ (Ln = Sm (1), Eu (2), Gd (3); PMPP-SHZ = N-(1-phenyl-3-methyl-4-propionyl-5-pyrazolone)-salicylidene hydrazide) have been synthesized and structurally characterized by X-ray crystallography. And all of them were carefully investigated by elemental analysis, thermal analysis and spectral characterization. The fluorescence of these three complexes 1-3 in solid state was investigated at room temperature. All complexes emit a blue emission band, and there are three characteristic emission peaks of Sm³⁺ evidently and one characteristic emission peak of Eu³⁺.     

Sugar interaction with metal ions. The coordination behavior of neutral galactitol to Ca(II) and lanthanide ions

The crystal structures of CaCl(2).galactitol.4 H(2)O and 2EuCl(3).galactitol.14 H(2)O were determined to compare the coordination behavior of Ca and lanthanide ions. The crystal system of the Ca-galactitol complex, CaCl(2).C(6)H(14)O(6).4 H(2)O, is monoclinic, Cc space group. Each Ca ion is coordinated to eight oxygen atoms, four from two galactitol molecules and four from water molecules. Galactitol provides O-2, -3 to coordinate to one Ca(2+), and O-4, -5 with another Ca(2+), to form a chain structure. The crystal system of the Eu-galactitol complex, 2EuCl(3).C(6)H(14)O(6).14 H(2)O, is triclinic, P1; space group. Each Eu ion is coordinated to nine oxygen atoms, three from an alditol molecule and six from water molecules. Each galactitol provides O-1, -2, -3 to coordinate with one Eu(3+) and O-4, -5, -6 with another Eu(3+). The other water molecules are hydrogen-bonded in the structure. The similar IR spectra of Pr-, Nd-, Sm-, Eu-, Dy-, and Er-galactitol complexes show that those lanthanide ions have the same coordination mode to neutral galactitol. The Raman spectra also confirm the formation of metal ion-carbohydrate complexes.     

Syntheses, crystal structures, and luminescence properties of lanthanide complexes with 5-carboxy-1-carboxymethyl-2-oxidopyridinium

Five new lanthanide complexes Ln(HL)₃(H₂O)₅ · 3H₂O (H₂L = 5-carboxy-1-carboxymethyl-2-oxidopyridinium, Ln = La (1), Sm (2), Eu (3),Tb (4), Dy (5)) have been synthesized and characterized by elemental analyses, FT-IR spectra and X-ray single crystal diffraction. All crystals are isostructural and crystallize in the triclinic space group . The metal center is nine-coordinated completely by two phenol O atoms, two chelating carboxylic O atoms from three HL ligands and five water molecules with a distorted tri-capped trigonal prismatic geometry. Photoluminescence studies revealed that complexes 2-4 exhibit strong fluorescent emission bands in the solid state at room temperature. The transition intensity varies in the order of Tb³⁺ > Dy³⁺ > Eu³⁺ > Sm³⁺.     

A series of pyrazolone lanthanide (III) complexes: Synthesis, crystal structures and fluorescence

A series of pyrazolone lanthanide complexes: Ln(PMPP)₃ · 2H₂O · C₂H₅OH (Ln = Nd (1), Sm (2), Gd (3), Dy (4); PMPP = 1-phenyl-3-methyl-4-propionyl-5-pyrazolone) have been synthesized by the hydrothermal method with the starting ligand PMPP-SAH (1-phenyl-3-methyl-4-(salicylidene hydrazone)-propionyl-5-pyrazolone) changed into PMPP during the formation process of complexes. All the complexes were structurally characterized by X-ray crystallography. The fluorescence of these four complexes 1-4 in solid state and DMF solution was investigated via F-4500 spectrophotometer and all of them indicate a fluorescent behavior at room temperature.     

Hydrothermal synthesis and crystal structures of two lanthanide coordination polymers with novel tetradentate-coordinated perchlorates

Two new 3D lanthanide coordination polymers {[Ln(C₂O₄)(ClO₄)(H₂O)] · Cl}_n [Ln = Pr (1) and Nd (2)] have been synthesized by hydrothermal reactions and characterized by elemental analysis, X-ray single-crystal analyses, IR and Raman spectroscopy. X-ray crystal structure analyses reveal that compounds 1 and 2 are isostructural and crystallized in the space group P2₁/c. A 1D zigzag chains formed by oxalate ligands in μ₂-mode to bridge Ln(III) atoms present in the two complexes and the adjacent zigzag chains were further connected by μ₃-η¹:η¹:η¹:η¹ fashion of into a 3D framework with ordered 1D channels, in which uncoordinated Cl⁻ anions are located as counterions. In addition, the IR and Raman spectrum further confirm the presence of tetradentate-coordinated perchlorates.     

Synthesis and characterization of new lanthanide complexes with hexadentate hydrazonic ligands

In this paper, we report the synthesis and the characterization of a novel series of lanthanide (III) complexes with two potentially hexadentate ligands.The ligands contain a rigid phenanthroline moiety and two flexible hydrazonic arms with different donor atom sets (NNN′N′OO and NNN′N′N″N″, respectively for H₂L¹ (2,9-diformylphenanthroline)bis(benzoyl)hydrazone and H₂L² (2,9-diformylphenanthroline)bis(2-pyridyl)hydrazone).Both nitrate and acetate complexes of H₂L¹ with La, Eu, Gd, and Tb were prepared and fully characterized, and the X-ray crystal structure of the complex [Eu(HL¹)(CH₃ COO)₂] · 5H₂O is presented.The stability constants of the equilibria Ln³⁺ + H₂L¹ = [Ln(H₂L¹)]³⁺ and Ln³⁺ + (L¹)²⁻ = [Ln(L₁)]⁺ (Ln = La(III), Eu(III), Gd(III), and Tb(III)) are determined by UV spectrophotometric titrations in DMSO at t = 25 °C. The nitrate complexes of H₂L² with La, Eu, Gd and Tb were also synthesized, and the X-ray crystal structures of [La(H₂L²)(NO₃)₂(H₂O)](NO₃), [Eu(H₂L²)(NO₃)₂](NO₃) and [Tb(H₂ L²)(NO₃)₂](NO₃) are discussed.     

Sugar complexes with neodymium nitrate. Spectroscopic and structural studies of two Nd(NO3)3-galactitol complexes

Two different Nd(NO3)3-galactitol complexes, 2Nd(NO3)3.C6H14O6.8 H2O and Nd(NO3)3.C6H14O6 have been obtained and were characterized by FT-IR and X-ray diffraction techniques. The spectral differences of the two complexes were consistent with the crystal-structure data.     

Syntheses, crystal structures, and bond valence sum analyses of lanthanide complexes with a planar pentadentate ligand

The syntheses and X-ray crystal structures of the Eu, Gd, Dy, Ho, and Er nitrate complexes of the pentadentate ligand 2,6-diacetylpyridine bis acetic acid hydrazone, or H₂dapaah, are reported. The complexes can be divided into 3 groups depending on the number of water molecules per metal ion. The Ln · 4H₂O complexes with Eu, Gd and Dy are isomorphous, with the Ln ion being 10 coordinate. The Ln · 6H₂O group includes Ho and Er, where the cation is 9 coordinate. The final complex Gd · 5H₂O is 10 coordinate like the Eu, Gd and Dy complexes, but the additional water molecule has stabilized an ordered crystal. The bond valence sum method has been used to analyze the bonding in the complexes and has suggested that bond valence equalization in three dimensions may be an important concept.     

Synthesis, structures and properties of alkaline earth metal benzene-1,4-dioxylacetates with three-dimensional hybrid networks

Three novel alkaline earth metal benzene-1,4-dioxylacetates M(L)H₂O (M = Ca, Sr or Ba, L = benzene-1,4-dioxylacetate) with three-dimensional (3D) hybrid frameworks were reported. Both Ca(L)H₂O (1) and Sr(L)H₂O (2) crystallize in the monoclinic space group P2₁/c while Ba(L)H₂O (3) in the monoclinic space group P2₁. As determined by X-ray single-crystal analysis, in these compounds each metal ion is coordinated by eight O atoms: four from different carboxylate groups, two from one carboxylate group, one from the ether oxygen and one from one water molecule. Each L²⁻ ligand coordinates to five alkaline earth metal centers through one of its ether oxygen atoms and two carboxylate groups adopting novel μ₃-η²:η²-bridging and μ₂-η¹:η¹-bridging coordination modes to give rise to a 3D network. The luminescence analysis shows that complexes 1 and 2 exhibit fluorescence in the solid state at room temperature.     

Complexation of trivalent lanthanide cations by erythritol in the solid state. The crystal structure and FT-IR study of 2EuCl3.2C4H10O4.7H2O

Erythritol was chosen to study the interactions between metal ions and carbohydrates. FTIR spectroscopy results indicate that a EuCl3-erythritol complex different from a previously reported one was obtained. The crystal structure of EuCl3-erythritol complex, 2EuCl3.2C4H10O4.7H2O, Mr=443.49, a=13.846(3) A , b=7.4983(15) A, c=14.140(3) A, beta=116.39(3) degrees, V=1315.1(5) A(3), Z=4, mu=5.394 mm(-1) and R=0.0395 for 2965 observed reflections and 143 parameters, was determined. Characteristic of this complex is the presence of binuclear europium ions with different coordination structures. One Eu3+ ion is nine-coordinated, with five Eu-O bonds from water molecules, and four from hydroxyl groups of two erythritol molecules and another Eu3+ is eight-coordinated with two water molecules, two chloride ions, and four hydroxyl groups from two erythritol molecules. Erythritol provides two hydroxyl groups to one lanthanide ion and the other two to another rare earth ion. The OH, CO stretching and other vibrations are shifted in the IR spectra of the complexes and the results are consistent with the crystal structure.     

Synthesis, structures and luminescent properties of novel coordination polymers constructed by lanthanide salts and benzimidazole-5,6-dicarboxylic acid

Two three-dimensional (3D) novel lanthanide complexes with the H₂Lbenzimidazole-5,6-dicarboxylate [Ln₂L₃(H₂O)] [Ln = Eu (1), Tb (2)] and one two-dimensional (2D) novel lanthanide complex [Pr(L)(HL)H₂O]·H₂O (3) were synthesized by hydrothermal reaction at 180 °C and characterized by elemental analysis, infrared spectra and single-crystal X-ray diffraction. The result showed that complexes 1 and 2 are isostructural and build porous 3D networks by L²⁻ groups linking Ln(III) atoms via tetradentate (bridging and bridging) and pentadentate (bridging/chelating and bridging) coordination modes. Complex 3 is a eight-coordinated Pr(III) chain complex, exhibiting a 2D polymeric network with parallel Pr-carboxylate chains along the crystallographic c-axis. In addition, it is found that in these structures, coordination modes of L²⁻ and HL⁻ are versatile and can adopt different conformations according to distinct dimensions of polymeric structures. The photoluminescent properties of 1, 2 and thermogravimetric analyses of the three complexes were discussed in detail.     

Ferrocenesuccinate-bridged lanthanide polymeric complexes: Syntheses, structures and properties

One-dimensional lanthanide-ferrocenesuccinate polymeric complexes [M(η²-FcCOC₂H₄COO)(μ₂-η²-FcCOC₂H₄COO)₂(H₂O)₂]_n (Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₄), M = Pr, 1; Ce, 2; La, 3) have been synthesized and structurally characterized by single-crystal X-ray crystallography. The three polymers are isomorphous, in which each Ln(III) ion is 10-coordinated and connects with two water molecules and eight oxygen atoms from ferrocenesuccinate units in two kinds of coordination modes: bidentate-chelating mode and tridentate-bridging mode. The variable-temperature magnetic susceptibility in the temperature range 5-300 K for 1 and 2 shows that both of them display weak antiferromagnetic interaction. In addition, the redox and fluorescent properties have been investigated. The redox properties are different from the previous results of transition metal compounds containing ferrocenyl systems. Compared with sodium ferrocenesuccinate, polymers 1 and 3, the fluorescent intensities of 2 are markedly enhanced in the solid state.     

Lanthanide complexes with disulfide ligand generated in situ: Syntheses, crystal structures and fluorescent properties

Five new lanthanide complexes [Ln₂(DTDN)₄(phen)₄]·7H₂O·2H₃O⁺ (Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5), H₂DTDN = 2,2′-dithiodinicotinic acid, phen = 1,10-phenanthroline) have been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. By in situ oxidation of 2-mercaptonanicotinic acid (2-H₂MN), the expected ligand H₂DTDN was generated. All crystals are isostructural and crystallize in monoclinic system with space group C2/c. The metal center is eight-coordinated completely by four carboxylic oxygen atoms from four different DTDN²⁻ ligands, and four nitrogen atoms from two phen molecules with a distorted square-antiprismatic geometry. The structures can be considered as two-dimensional (2D) structures and further linked by hydrogen bonds into the final trinodal 4-connected network. Photoluminescence studies revealed that complexes 2-5 exhibit strong fluorescent emission bands in the solid state at room temperature.     

Preparation, crystal structure and luminescent properties of the 3-D netlike supramolecular lanthanide picrate complexes with 2,2′-[1,2-phenylenebis(oxy)]bis(N-benzylacetamide)

Solid complexes of lanthanide picrates with a new podand-type ligand, 2,2′-[(1,2-phenylene)bis(oxy)]bis(N-benzylacetamide) (L) have been prepared and characterized by elemental analysis, conductivity measurements, IR, electronic and ¹H NMR spectroscopies. The crystal and molecular structures of the complex NdL(Pic)₃ have been determined by single-crystal X-ray diffraction. The crystal structure shows that the Nd(III) ion is coordinated with four oxygen atoms of the ligand L and six oxygen atoms of three bidentate picrates. Furthermore, the NdL(Pic)₃ complex units are linked by the intermolecular hydrogen bonds to form a three-dimensional (3-D) netlike supermolecule. Under excitation, Eu complex exhibited characteristic emissions. The lowest triplet state energy level of the ligand indicates that the triplet state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion.     

Ultramicroporous channel lanthanide coordination polymers of 2,5-pyrazinedicarboxylate

Five lanthanide coordination polymers with composition {[Ln(pzdc)_1.5(H₂O)₃] · 0.5H₂O}_∞, (Ln = Pr, 1; Nd, 2; Sm, 3; Eu, 4; Gd, 5; pzdc = 2,5-pyrazinedicarboxylate), have been synthesized by reacting Ln(NO₃)₃ · 6H₂O with 2,5-pyrazinedicarboxylic acid under hydrothermal condition in the absence of additional base and characterized by elemental analysis, IR spectra and TG analysis, as well as single-crystal X-ray diffraction. They crystallize isostructurally in the triclinic space group P-1 and the cell parameters agree with the ionic radii of the Ln(III) ions. Each trivalent rare earth ion is nine coordinate in an N₂O₇ environment. The ligand 2,5-pyrazinedicarboxylate adopts three coordination modes, through which the lanthanide ions are linked together to form an infinite three dimensional structure. A 1D channel exists along the (1 0 0) direction which accommodates uncoordinated water by hydrogen bonds. Heating of 4 at 120 °C evacuated the uncoordinated water while retaining its single crystallinity with only minor change in cell parameters (crystal 6, [Eu(pzdc)_1.5(H₂O)₃]_∞). This hydrophilic ultramicroporous channel is selective to accommodate water only among common solvents, which has some potential interest for solvent separation.     

Complexes of triphenylphosphine oxide with lanthanide bromides

The reaction between hydrated lanthanide bromides and triphenylphosphine oxide in 1:3 and 1:4 ratios in ethanol gave a series of complexes [LnBr₂(Ph₃PO)₄]Br (Ln = Pr, Nd, Gd, Tb, Er, Yb, Lu) which contain ethanol and water in the lattice, regardless of the ratio of reactants used. The single crystal X-ray structures of [NdBr₂(Ph₃PO)₄]Br, [GdBr₂(Ph₃PO)₄]Br and [YbBr₂(Ph₃PO)₄]Br have been determined and have an octahedral geometry about the metal ion. Analysis of the bond distances shows that the Ln-O and Ln-Br distances change in accord with the lanthanide contraction, but the non-bonded Ln?P distances and the Ln-O-P angles differ significantly for the Yb complex. Conductivity and variable temperature ³¹P NMR measurements in dichloromethane indicate that the complexes dissolve as [LnBr₂(Ph₃PO)₄]⁺ for the lighter lanthanides with further ionisation becoming progressively more important for the heavier metals. In methanol more extensive dissociation is apparent. The electrospray mass spectra obtained from methanol solution show [LnBr₂(Ph₃PO)₄]⁺ is present in high abundance in the gas phase with other species formed due to ligand redistribution, ionisation and solvolysis.     

X-ray structure and spectroscopic characterization of divalent dinuclear cobalt complexes containing carboxylate- and phosphodiester- auxiliary bridges

Two dinuclear spin-coupled divalent cobalt complexes, [Co₂(P1-O)(μ₂-OAc)](ClO₄)₂, (1) and [Co₂(P1-O)(μ₂-BNPP)](ClO₄)₂, (2) containing μ-1,3 acetate (OAc) and bis(4-nitrophenyl)phosphate (BNPP) auxiliary bridges, respectively, were synthesized by the reaction of a classic dinucleating ligand, P1-OH with cobalt(II) perchlorate in presence of acetic acid/bis(4-nitrophenyl)phosphate. They were characterized by single crystal X-ray diffraction, to show a trigonal bipyramidal geometry around each cobalt center and the intervening bridging atoms that are responsible for spin-transfer between the two divalent cobalt centers; the alkoxo oxygen donor occupies an equatorial position, and the auxiliary ligand oxygens (OAc/BNPP) occupy the axial positions. Solution state magnetic moment measurement together with UV-Vis/NIR spectra revealed a high-spin ground state (S = 3/2) for Co(II) in these compounds. Complexes 1 and 2 show interesting ¹H NMR spectral features of resonances with relatively narrower linewidths in conjunction with a sizable chemical shift dispersion of −5 and 265 ppm. Complex 2 containing the bis(4-nitrophenyl)phosphate auxiliary bridge showed narrower spectral window than complex 1 that has the acetate auxiliary bridge.