Three new multidimensional organic-inorganic hybrids based on polyoxometalates and copper coordination polymers with 4,4′-bipyridine ligands

Three new organic-inorganic hybrid materials with 4,4′-bipy ligands and copper cations as linkers, [Cu^II(H₂O)(4,4′-bipy)₂][Cu^II(H₂O)(4,4′-bpy)₂]₂H[Cu^IIP₈Mo₁₂O₆₂H₁₂] · 5H₂O (1), [Cu^I(4,4′-bipy)][Cu^II(4,4′-bipy)]₂ (BW₁₂O₄₀) · (4,4′-bipy) · 2H₂O (2) and [Cu^I (4,4′-bipy)]₃ (PMo₁₂O₄₀) · (pip) · 2H₂O (3) (pip = piperazine; 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. The single X-ray structural analysis reveals that the structure of 1 is constructed from [Cu(H₂O)(4,4′-bipy)₂] complexes into a novel, three-dimensional supermolecular network with 1-D channels in which Cu[P₄Mo₆]₂ dimer clusters reside. To the best of our knowledge, compound 1 is the first complex in which the [P₄Mo₆] clusters have been used as a non-coordinating anionic template for the construction of a novel, three-dimensional supermolecular network. Compound 2 is constructed from the six-supported [BW₁₂O₄₀]⁵⁻ polyoxoanions and [Cu^I(4,4′-bipy)] and [Cu^II(4,4′-bipy)] groups into a novel, 3-D network. Compound 3 exhibits unusual 3-D supramolecular frameworks, which are constructed from tetrasupporting [PMo₁₂O₄₀]³⁻ clusters and [Cu^I (4,4′-bipy)_n] coordination polymer chains. The electrochemical properties of 2 and 3 have been investigated in detail.     

Hydrothermal synthesis, crystal structures and photoluminescent properties of four cadmium(II) coordination polymers derived from diphenic acid and auxiliary ligands

Four novel metal coordination polymers, [Cd(dpa)(H₂O)]_n (1), [Cd(dpa)(2,2′-bipy)]_n (2), {[Cd₂(dpa)₂(4,4′-bipy)₃](4,4′-bipy)(H₂O)₂}_n (3) and [Cd(dpa)(bim)₂(H₂O)]}_n (4) (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, bim = benzimidazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that the 2,4′-diphenic acids acts as bridging ligands, exhibiting rich coordination modes to link metal ions: bis-monodentate, bidentate chelating, chelating/bridging, monoatomic bridging and monodentate modes. In addition, the luminescent properties for compound 1-4 are also investigated in this work.     

Syntheses, structures, and magnetic properties of 3d-4f heterometallic complexes constructed from pyrazole-bridged CuLn dinuclear units

A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)₂(H₂O)₄] · (2H₂O)(H₃O⁺) (1) and [CuLn(pdc)(ipdc)(H₂O)₄] · H₃O⁺ (Ln = Ho (2), Er (3), Yb (4); H₃ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H₃pdc = 3,5-pyrazoledicarboxylic acid), {[Cu₃Ln₄(ipdc)₆(H₂O)₁₆] · xH₂O}_n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H₃ipdc was in situ obtained by iodination of ligand H₃pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K.     

A series of d transition metal coordination complexes: Structures and comparative study of surface electron behaviors (n = 9, 8, 7, 6, 5)

Ten transition metal coordination complexes [Cu₂(phen)(p-tpha)(μ-O)]_n1, [Cu(m-tpha)(imH)₂]_n2, [Ni(5-Haipa)₂(H₂O)₂]_n3, [Ni(phen)₂(H₂O)₂]·btc·[Ni(H₂O)₆]_0.5·9H₂O 4, [Co(2,5-pdc)(H₂O)₂]_n·nH₂O 5, [Co₂(2,5-pdc)₂(H₂O)₆]_n·2nH₂O 6, [Fe(2,5-Hpdc)₂(H₂O)₂]·H₂O 7, [Co(C₆H₄NO₂)₃]·H₂O 8, [Fe₂(μ₂-btec)(μ₂-H₂btec)(bipy)₂(H₂O)₂]_n9, [Mn(phen)(2,5-pdc)(H₂O)₂]·H₂O 10 (H₄btec = 1,2,4,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline, 2,5-H₂pdc = 2,5-pyridine-dicarboxylic acid, p-tpha = p-phthalic acid, m-tpha = m-phthalic acid, bipy = 2,2′-bipyridine, 5-H₂aipa = 5-aminoisophthalic acid, imH = imidazole, H₃btc = 1,3,5-benzenetricarboxylic acid) were synthesized through hydrothermal method. They were characterized by UV-Vis absorption spectra, single-crystal X-ray diffraction and surface photovoltage spectra (SPS). Structural analysis indicated that the complexes 1, 2, 3, 5, 6 and 9 were linked into infinite structures bridged by organic acid ligands. The other four complexes were molecular complexes and further connected to 2D or 3D structures by the hydrogen bonds. The SPS of complexes 1-10 indicate that there are positive response bands in the range of 300-800 nm showing different levels of photo-electric conversion properties. The intensity, position, shape and the number of the response bands in SPS are obviously different since the structure, species, valence, dⁿ electrons configuration and coordinated environment of the center metals are different. There are good relationships between SPS and UV-Vis spectra.     

Hybrid organic-inorganic assemblies built up from saturated heteropolyoxoanions and copper coordination polymers with mixed 4,4′-bipyridine and 2,2′-bipyridine ligands

Three new organic-inorganic hybrid compounds [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(2,2′-bipy)(4,4′-Hbipy)][Cu^I(4,4′-bipy)]₂[P₂W₁₈O₆₂] · 3H₂O (1), [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(4,4′-bipy)]₂[PW₁₂O₄₀] · 0.25H₂O (2), and[Cu^I(4,4′-bipy)]₃[PMo₁₂O₄₀] · en · 3H₂O (3) (2,2′- bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. Compound 1 represents the first 1D ladderlike structure formed by Dawson-type polyoxoanion [P₂W₁₈O₆₂]⁶⁻ and coordination polymer with mixed 4,4′-bipy and 2,2′-bipy ligands. The novel structure of 2 is composed of 1D hybrid zigzag chains linked by chains into a 3D framework. In compound 3, the [PMo₁₂O₄₀]³⁻ clusters are hung on chains to form a new 1D chain.     

Hydrogen-bonded copper(II) and nickel(II) complexes and coordination polymeric structures containing reduced Schiff base ligands

Complexes [Cu(HSas)(H₂O)] · 2H₂O (H₃Sas = N-(2-hydroxybenzyl)-l-aspartic acid) (1), [Cu(HMeSglu)(H₂O)] · 2H₂O (H₃MeSglu = (N-(2-hydroxy-5-methylbenzyl)-l-glutamic acid) (2), [Cu₂(Smet)₂] (H₂Smet = (N-(2-hydroxybenzyl)-l-methionine) (3), [Ni(HSas)(H₂O)] (4), [Ni₂(Smet)₂(H₂O)₂] (5), and [Ni(HSapg)₂] (H₂Sapg = (N-(2-hydroxybenzyl)-l-aspargine) (6) have been synthesized and characterized by chemical and spectroscopic methods. Structural determination by single crystal X-ray diffraction studies revealed 1D coordination polymeric structures in 2 and 4, and hydrogen-bonded network structure in 5 and 6. In contrast to previously reported coordination compounds with similar ligands, the phenol remains protonated and bonded to the metal ions in 2 and 4, and also probably in 1. However, the phenolic group is non-bonded in 6.     

Synthesis and crystal structures of di- and tetra-nuclear dicarboxylate-bridged copper(II) complexes

Three new Cu(II) complexes, [Cu₂(C₃H₂O₄)(phen)₂(H₂O)₃](NO₃)₂(H₂O)₂ (1) (C₃H₂O₄ = malonate, phen = 1,10-phenanthroline), [Cu₂(C₄H₄O₄)(phen)₂(H₂O)₂](NO₃)₂ (2) (C₄H₄O₄ = succinate), and {[Cu₂(phen)₂(H₂O)(NO₃)]₂(C₅H₆O₄)₂}(NO₃)₂ (3) (C₅H₆O₄ = glutarate) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The X-ray analysis reveals that the structures of 1 and 2 are of dinuclear copper(II) complexes bridged by malonate and succinate dianions, respectively, and 3 is a tetranuclear species formed by two {[Cu₂(phen)₂(H₂O)(NO₃)](C₅H₆O₄)} fragments. The copper ions in 1 and 3 show square-pyramidal coordination geometry, while the copper ions in 2 exhibit a square planar geometry. In each complex, the dicarboxylate ligand is coordinated to copper ions as a chelate and monodentate (1), bis-monodentate (2), and bis-bridging ligand toward the copper ions with syn-syn coordination mode (3).     

In situ 5-sulfosalicylate decarboxylation or dimethylformamide hydrolysis generating supramolecular assembly architectures

Six transition-metal complexes, {[Co(4,4′-bipy)(H₂O)₄](Hbs)₂ · 3H₂O}_n (1), [Mn(4,4′-bipy)₂(H₂O)₄](Hbs)₂ · 2H₂O (2), {[Mn(HCOO)(H₂O)₂(4,4′-bipy)]₂[Mn(4,4′-bipy)(Hssal)₂(H₂O)₂]}_n (3), [Cd(4,4′-bipy)₂(H₂O)₄](Hbs)₂ · 2H₂O (4), {[Cd₃(CH₃COO)₄(4,4′-bipy)₄](Hbs)₂ · 10H₂O}_n (5), and {[Cd(HCOO)(H₂O)₂(4,4′-bipy)]₂[Cd(4,4′-bipy)(Hssal)₂(H₂O)₂]}_n (6), have been synthesized by hydrothermal or reflux synthetic method and characterized by single-crystal X-ray diffraction, IR, elemental analysis, thermogravimetric analysis and fluorescence analysis, where Hssal²⁻ is doubly deprotonated 5-sulfosalicylate, Hbs⁻ is 4-hydroxybenzenesulfonate and 4,4′-bipy is 4,4′-bipyridine. The structural analyses showed that all of the six complexes are cation-anion species containing in situ synthesized ligands, Hbs⁻ or HCOO⁻, and the former arises from the decarboxylation of 5-sulfosalicylic acid under the hydrothermal conditions. The formate anions derived from the hydrolysis of DMF. A series of supramolecular compounds show that the structural diversity is strongly associated with their properties.     

Analysis of the main structural trends for biscyclometalated dinuclear rhodium compounds of general formula Rh2(O2CR)2(PC)2 · 2H2O

A new series of biscyclometalated dinuclear rhodium (II) compounds with the general formula Rh₂(O₂CR)₂(PC)₂ · 2H₂O, being PC = (C₆H₄)P(C₆H₅)₂, R = CH₃ (1 · 2H₂O), PC = [(p-CH₃ OC₆H₃)P(p-CH₃ OC₆H₄)₂], R = CF₃ (2 · 2H₂O), PC = (C₆H₄)P[CH(CH₃)₂]₂, R = CH₃ (3 · 2H₂O) and PC = (C₆H₄)P(C₆H₅)₂, R = C₆F₅ (4 · 2H₂O) has been obtained. The crystal structures for these compounds have been determined by X-ray diffraction and the main structural trends, bond lengths, bond angles and torsion angles have been analyzed, and have also been compared with the structural parameters for different analogous complexes described previously in the literature.     

Hydrothermal syntheses, crystal structures and characterizations of three new copper coordination polymers

Three new copper complexes, [Cu^IICu^I(ip)(ipH)(4,4′-bipy)_3/2]_n (1), [Cu(ip)(4,4′-bipy)]_n · 3nH₂O (2), and [Cu(ipH)₂(4,4′-bipy)]_n (3), have been hydrothermally synthesized by the reaction of Cu(NO₃)₂ · 3H₂O with isophthalic acid (ipH₂) and 4,4′-bipyridine (4,4′-bipy) under different reaction conditions. Complex 1, a mixed-valence copper(I,II) complex, exhibits a 2-D interpenetrating grid framework, in which five-coordinated Cu^II and three-coordinated Cu^I environments are established. The oxidation states of center Cu atoms have been confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR). Complex 2 features a 2-D box-like bilayer architecture, in which Cu^II atoms are linked by ip ligands to form a 1-D double-chain and the resulting chains are further strutted by the 4,4′-bipy ligands. In complex 3, two bridging 4,4′-bipy ligands and two terminal ipH ligands confine the Cu^II center in a square plane coordination geometry. The whole molecule of 3 was arranged into a 1-D linear chain structure. Additionally, the thermogravimetric analyses (TGA) for complexes 1-3 are also discussed in this paper.     

Solvothermal syntheses and structural characterization of a series of metal-hydroxycarboxylate coordination polymers

The combination of transition metal ions with mixed ligands resulted in the formation of three new coordination polymers, {[Co(C₄H₄O₅)(bpe)(H₂O)₂] · (0.5bpe)(H₂O)}_n (1), {[Cu(C₄H₄O₆)(bipy)] · 5H₂O}_n (2) and {[Cu(C₄H₄O₅)(bpa)] · 2.5H₂O}_n (3) (, , bpe = 1,2-bis(4-pyridyl)ethene, bipy = 2,2′-bipyridine, bpa = 1,2-bis(4-pyridyl)ethane), which were prepared under solvothermal conditions and characterized by single-crystal X-ray diffraction. 1 and 2 feature 1D chain structures. Interestingly, each pair of chains recognizes each other through aromatic π-π stacking interactions, generating a zipper-like double-stranded chain in 2. Compound 3 shows 2D 6³ topology framework with a rectangle-like grid.     

Anion-directed supramolecular assembly of cobalt(II)-fluconazole coordination polymers: Structural diversity, fluorescent and magnetic properties

Six fluconazole-bridged cobalt(II) coordination polymers, namely [Co(HFlu)₂(H₂O)₂](ClO₄)₂ (1), [Co(HFlu)₂(H₂O)(AcO)](AcO)·2C₂H₅OH (2), [Co(HFlu)₂Cl₂]·2C₂H₅OH (3), [Co₃(Flu)₂(acac)₄]·C₂H₅OH (4), [Co(HFlu)₂(malo)(H₂O)]·3H₂O (5), and [Co(HFlu)₂(fum)(H₂O)₂]·H₂O (6) (HFlu = 2-(2′,4′-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol, AcOH = acetate acid, Hacac = acetylacetonate, H₂malo = malonate acid, H₂fum = fumaric acid), have been synthesized and structurally characterized, and the thermal, fluorescent and magnetic properties investigated. The crystal structures display the one-dimensional cationic double-bridged chain consisting of 20-membered macrocycles to be parallel in 1 and perpendicular in 2. The structure of 3 consists of two-dimensional neutral rhombic grid in bc plane with (4,4) topology and alternative P/M helices intersecting at the Co sites along b direction. Complex 4 shows one-dimensional polymeric chain, in which binuclear Co₂(Flu)₂(acac)₂ units act as bridging blocks to link Co(acac)₂ nodes through triazolyl nitrogen atoms. The structure of 5 shows dimeric 20-membered macrometallacyclic motif. Complex 6 shows HFlu-bridged one-dimensional chain, which is stabilized by hydrogen-bonding interactions to produce alternative hydrophobic and hydrophilic architecture. Complexes 1-3 and 5-6 exhibit the similar electronic absorption and fluorescent spectra as those of HFlu, while complex 4 shows a fluorescent quenching phenomenon. Fluorescence titration of HFlu suggests that the fluorescent intensities at the maximal emission decrease upon the addition of Co(acac)₂. The variable-temperature magnetic measurement of 4 reveals weak ferromagnetic interaction combined with the spin-orbit coupling effect in the 1-D Co(II) chain.     

Four coordination polymers constructed from a multicarboxylate ligand and metal centers various from Ba, Cu, Zn to Gd: Syntheses, crystal structures and properties

Hydrothermal reactions between H₄ODPA (2,2′,3,3′-oxydiphthalic acid) and metal ion salts of Ba²⁺, Cu²⁺, Zn²⁺ and Gd³⁺ afford four novel coordination polymers [Ba(H₂ODPA)(H₂O)₄] · H₂O (1), [Cu₂(ODPA)(H₂O)₃] · H₂O (2), Zn₂(ODPA)(H₂O)₂ (3) and [Gd(HODPA)(H₂O)_3.5] · H₂O (4), accordingly. These polymers show great differences in regard to their structures and properties originated from the variation of size and coordination geometry of the metal ions. Compound 1 presents puckered achiral layer structure with (4.8²) topology with helices, 2 has a 6³ topology with copper tetramer as SBUs, 3 has chiral layer with two kinds of helices built up from Zn-binuclear “paddle-wheel” like SBUs, and 4 features a simple 1D helix with opposite chirality. Compound 3 shows obvious fluorescent emissions upon excitation. Compound 2 shows ferromagnetic interactions between Cu^II centers bridged by carboxylate groups, whereas compound 4 presents weak ferromagnetic interaction between Gd^III ions.     

Construction of crystal structures of metal(II)-benzoates (M = Mn, Ni, Co, Cu, Zn, and Cd) and 1,2-bis(4-pyridyl)ethane: Effects of metal coordination modes and their catalytic activities

Five polymeric metal(II)-benzoate complexes of formula [Mn(O₂CPh)₂(CH₃OH)₂(bpa)]_n (1-Mn), [Co(O₂CPh)₂(H₂O)(bpa)_1.5]_n (2-Co), [Ni(O₂CPh)₂(H₂O)(bpa)_1.5]_n (3-Ni), [Cu(O₂CPh)₂(CH₃OH)₂(bpa)]_n (4-Cu), and [Cd(O₂CPh)₂(bpa)_1.5]_n (6-Cd) have been synthesized and characterized (bpa = 1,2-bis(4-pyridyl)ethane). They showed two kinds of structures: parallelogram-like two-dimensional sheets for Co, Ni, and Cd, and one-dimensional chains for Mn, Cu, and Zn. Since similar structures provide similar coordination geometries, the structures depend on the coordination geometries of metal ions. The compounds 1-Mn, 2-Co, 4-Cu, 5-Zn, and 6-Cd have catalyzed efficiently the transesterification of a variety of esters, while 3-Ni has displayed a very slow conversion. The reactivity of catalyst 6-Cd containing Cd ion, well known as an inert metal ion for the ligand substitution, was found to be comparable to that of 5-Zn. The reactivities of the compounds used in this study are in the order of 5-Zn > 6-Cd > 1-Mn > 4-Cu > 2-Co ? 3-Ni, indicating that the non-redox metal-containing compounds (5-Zn and 6-Cd) show better activity than the redox-active metal-containing compounds (1-Mn, 4-Cu, 2-Co, and 3-Ni).     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

Syntheses, spectroscopies and structures of zinc complexes with malate

Reactions of zinc(II) ion with racemic malic acid (C₄H₆O₅ = H₃mal) result in the isolation of four new zinc(II) malato complexes: (NH₄)[Zn(R-H₂mal)₃] · H₂O (1), trans-[Zn(R-H₂mal)(S-H₂mal)(H₂O)₂] · 2H₂O (2), (NH₄)₂[Zn(R-Hmal)(S-Hmal)] · 2H₂O (3), and [Zn₂(R-Hmal)(S-Hmal)(H₂O)₄]_n · 2nH₂O (4). Three R-malic acids in 1 act as bidentate ligands via their alcoholic and the central carboxy groups with Zn(II) ion, leaving the terminal carboxylic acid groups free. The R- and S-malates of 2 coordinate in a bidentate manner with zinc ion in trans-form. In 3, Zn(II) ion is coordinated by R- and S-malates in a tridentate fashion via their alcoholic and two carboxy groups. Complex 4 forms a two-dimensional layered structure through the links of a new dimeric unit [Zn₂(R-Hmal)(S-Hmal)(H₂O)₄] with one of the oxygen atoms from the terminal carboxy group of malate ligand. The coordination of malates depends on pH variation, on Zn:malate ratio, and also on temperature. Tridentate chelation of malate in 3 is found between pH 4.5-9.0. The soluble monomeric species 1-3 have been investigated using ¹³C NMR spectra by long-time acquisition. The solution NMR spectra indicate that zinc malate complexes dissociate in H₂O (D₂O). Obvious downfield shifts of the central carboxy carbon atoms in 1-3 are observed compared with those of free malate, which indicate that these zinc malate complexes dissociate in aqueous solution.     

Substituent dependent dimensionalities in cobalt isophthalate supramolecular complexes and coordination polymers containing dipyridylamine ligands

Hydrothermal synthesis has afforded cobalt 5-substituted isophthalate complexes with 4,4′-dipyridylamine (dpa) ligands, showing different dimensionalities depending on the steric bulk and hydrogen-bonding facility of the substituent. [Co(tBuip)(dpa)(H₂O)]_n (1, tBuip = 5-tert-butylisophthalate) is a (4,4) grid two-dimensional coordination polymer featuring 2-fold parallel interpenetration. [Co(MeOip)₂(Hdpa)₂] (2, MeOip = 5-methoxyisophthalate) is organized into 3-fold parallel interpenetrated (4,4) grids through strong N-H⁺?O⁻ hydrogen bonding. {([Co(OHip)(dpa)(H₂O)₃])₃·2H₂O}_n (3, OHip = 5-hydroxyisophthalate) possesses 1-D chain motifs. The 5-methyl derivative {[Co(mip)(dpa)]·3H₂O}_n (4, mip = 5-methylisophthalate) has a 3-D 6⁵8 cds topology. {[Co(H₂O)₄(Hdpa)₂](nip)₂·2H₂O} (5, nip = 5-nitroisophthalate) and {[Co(sip)(Hdpa)(H₂O)₄]·2H₂O} (6, sip = 5-sulfoisophthalate) are coordination complexes. Antiferromagnetic superexchange is observed in 1 and 4, with concomitant zero-field splitting. Thermal decomposition behavior of the higher dimensionality complexes is also discussed.     

New chelate complexes of trivalent Y and lanthanides (Eu, Ho, Yb) with a triazene N-oxide: Synthesis, structural characterization and luminescence properties

Deprotonated 3-(4-nitrophenyl)-1-phenyltriazene N-oxide reacts with YCl₃·6H₂O and LnCl₃·6H₂O (Ln = Eu, Ho, Yb) to give the monoclinic chelate complexes [Y{O₂N(C₆H₄)NNN(O)Ph}₄](Et₃NH)·H₂O (1) (Ph = C₆H₅; Et = C₂H₅) and [Ln^III{O₂N(C₆H₄)NNN(O)Ph}₄](Et₃NH)·H₂O·{CH₃OH∗} {Ln^III = Eu (2), Ho (3), Yb∗ (4), in which the metal centers present a square antiprismatic configuration. As already observed for hydrated ammonium complexes of triazene-oxides ligands with (C₆H₄)−NO₂ groups, multiple, effective O···H and N···H interactions hold the species in supramolecular 3D assemblies. The optical and the luminescent properties of the triazene-oxide europium complex 2 are also presented and fully discussed.     

A series of 1-D to 3-D metal-organic coordination architectures assembled with V-shaped bis(pyridyl)thiadiazole under co-ligand intervention

Six new coordination polymers based on V-shaped linkage 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and transition metal ions, [Co(bpt)(pm)_0.5(H₂O)]_n · 3nH₂O (1), [Cu₂(bpt)(pm)(H₂O)₄]_n (2), [Co(bpt)(pydc)]_n · 2nCHCl₃ · nH₂O (3), [Cu₂(bpt)(pydc)₂(H₂O)₂]_n (4), [Cu₂(bpt)(pydco)₂(H₂O)₂]_n · nH₂O (5) and [Cd(bpt)(pydco)]_n (6) (H₄pm = pyromellitic acid, H₂pydc = pyridine-2,6-dicarboxylic acid, H₂pydco = pyridine-2,6-dicarboxylic acid N-oxide), have been synthesized under the intervention of various polycarboxylate ligands. Complex 1 exhibits a 3-D 4-connected structure with 1-D nanosized open channels encapsulated lots of water molecules. Complex 2 represents a 2-D grid containing two types of rectangular windows. When pydc and pydco instead of pm, complexes 3 and 6 were obtained with highly undulated 2-D layers. The interlayers of 3 are filled with two kinds of solvent molecules, whereas 6 is a double-layered framework without free molecules. Complexes 4 and 5 consist of two distinct 1-D infinite chains held together to form different 2-D supramolecular networks. Importantly, bpt spacer shows changeful conformational geometries and generates complicated crystalline architectures with the introduction of polycarboxylate ligands. Additionally, thermal stability of complexes 1, 3 and 5, fluorescent properties of 6 and X-ray powder diffraction of 1 have also been investigated.     

Iron(III), chromium(III) and cobalt(II) complexes with squarate: Synthesis, crystal structure and magnetic properties

The preparation and variable temperature-magnetic investigation of three squarate-containing complexes of formula [Fe₂(OH)₂(C₄O₄)₂(H₂O)₄]·2H₂O (1) [Cr₂(OH)₂(C₄O₄)₂(H₂O)₄]·2H₂O (2) and [Co(C₄O₄)(H₂O)₄]_n (3) [H₂C₄O₄ = 3.4-dihydroxycyclobutene-1,2-dione (squaric acid)] together with the crystal structures of 1 and 3 are reported. Complex 1 contains discrete centrosymmetric [Fe₂(OH)₂(C₄O₄)₂(H₂O)₄] diiron(II) units where the iron pairs are joined by a di-μ-hydroxo bridge and two squarate ligands acting as bridging groups through adjacent oxygen atoms. Two coordinated water molecules in cis position complete the octahedral environment at each iron atom in 1. The iron-iron distance with the dinuclear unit is 3.0722(6) Å and the angle at the hydroxo bridge is 99.99(7)°, values which compare well with the corresponding ones in the isostructural compound 2 (2.998 Å and 99.47°) whose structure was reported previously. The crystal structure of 3 contains neutral chains of squarato-O¹,O³-bridged cobalt(II) ions where four coordinated water molecules complete the six-coordination at each cobalt atom. The cobalt-cobalt separation across the squarate bridge is 8.0595(4) Å. A relatively important intramolecular antiferromagnetic coupling occurs in 1 whereas it is very weak in 2, the exchange pathway being the same [J = −14.4 (1) and −0.07 cm⁻¹ (2), the spin Hamiltonian being defined as ]. A weak intrachain antiferromagnetic interaction between the high-spin cobalt(II) ions occurs in 3 (J = −0.30 cm⁻¹). The magnitude and nature of these magnetic interactions are discussed in the light of their respective structures and they are compared with those reported for related systems.