Sandwich-type polyoxotungstate hybrids decorated by nickel-aromatic amine complexes

Three new sandwich-type polyoxotungstates (POTs) decorated by nickel-2,2′-bpy complexes [{Ni(2,2′-bpy)₂(H₂O)}₂{Ni(2,2′-bpy)}₂ {Ni₄(H₂O)₂(B-α-XW₉O₃₄)₂}]ⁿ⁻ (X=P^V, n=4 for 1; X=As^V, n=4 for 2; X=Ge^IV, n=4 for 3) (2,2′-bpy=2,2′-bipyridine) were successfully synthesized under hydrothermal conditions and structurally characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, and magnetic properties. Single-crystal structural analyses indicate that 1 and 2 are isostructural and both crystallize in the monoclinic space group C2/c, whereas 3 belongs to the triclinic space group . To our knowledge, 1, 2 and 3 represent rare examples of the organic-inorganic hybrid sandwich-type polyoxometalates functionalized by multiple nickel-aromatic amine complexes. Magnetic measurements of 1 exhibit the presence of ferromagnetic interactions within the rhombic tetranuclear-Ni^II cluster.     

Two 3D networks based on sandwich-type polyoxometalate units linked by Sr-O clusters: Synthesis, structure, and magnetic property

Two 3D hybrid sandwich-type polyoxometalates, [{Sr(H₂O)₅Sr(H₂O)₆Sr_0.5(H₂O)₇}₂Mn₄(H₂O)₂(α-PW₉O₃₄)₂]·6H₂O (1) and [{Sr(H₂O)₆[Sr(H₂O)₈]₂Sr(H₂O)₄}₂Mn₄(H₂O)₂(αββα-P₂W₁₅O₅₆)₂]·5H₂O (2), have been obtained by the routine synthetic reactions in aqueous solution and characterized by IR, elemental analysis, thermal analysis, and X-ray single-crystal diffraction. The 3D hybrid framework of 1 and 2 are built by tetra-Mn^II substituted sandwich-type polyoxotungstates modified by fourteen Sr(H₂O)_x (x=4-8) units acting as bridges, forming centrosymmetric sandwich structures. The magnetic property of compound 1 has been studied by measuring its magnetic susceptibility in the temperature range of 2-300 K, which indicates predominant ferromagnetic interactions between the Mn^II-O-Mn^II bridge unit. Additionally, the electrochemical behaviours have been detected on solid bulk modified carbon paste electrodes of compounds (CPEs) and three redox couples are detected.     

Assemblies based on the directing effect of non-classical W18 anionic clusters and the rod-like trans-1,2-di-(4-pyridyl)-ethylen (bpe)

Two polyoxometalate (POM) supramolecular assemblies based on W₁₈ clusters and the rigid organic trans-1,2-di-(4-pyridyl)-ethylen (bpe) have been synthesized and fully characterized, namely (H₂bpe)3.5H₂[SbW₁₈O₆₀]·5H₂O (1), and (H₂bpe)5[Ni₄(AsW₉O₃₄)₂(H₂O)₂]·3H2O (2). Compounds 1-2 are formed from organic bpe cations and different polytungstate anions: pseudo-Dawson-type [SbW₁₈O₆₀]⁹⁻ in 1 and sandwich-type [Ni₄(H₂O)₂(AsW₉O₃₄)₂]¹⁰⁻ in 2. Both of compounds 1-2 crystallize in a low-symmetrical space group of P-1 and consist of a complicated supramolecular network based on non-covalent intermolecular weak interactions, including hydrogen bonding and π···π stacking. The multipoint hydrogen bonding interactions constitute the structural feature in two supramolecular frameworks. The UV-vis, fluorescence and electrochemistry properties are also studied.     

Synthesis, characterisation and catalytic activities of manganese(III) complexes of pyridoxal-based ONNO donor tetradenatate ligands

Reaction of Mn^II(CH₃COO)₂ with dibasic tetradentate ligands, N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-en, I), N,N′-propylenebis(pyridoxylideneiminato) (H₂pydx-1,3-pn, II) and 1-methyl-N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-1,2-pn, III) followed by aerial oxidation in the presence of LiCl gives complexes [Mn^III(pydx-en)Cl(H₂O)] (1) [Mn^III(pydx-1,3-pn)Cl(CH₃OH)] (2) and [Mn^III(pydx-1,2-pn)Cl(H₂O)] (3), respectively. Crystal and molecular structures of [Mn(pydx-en)Cl(H₂O)] (1) and [Mn(pydx-1,3-pn)Cl(CH₃OH)] (2) confirm their octahedral geometry and the coordination of ligands through ONNO(2-) form. Reaction of manganese(II)-exchanged zeolite-Y with these ligands in refluxing methanol followed by aerial oxidation in the presence of NaCl leads to the formation of the corresponding zeolite-Y encapsulated complexes, abbreviated herein as [Mn^III(pydx-en)]-Y (4), [Mn^III(pydx-1,3-pn)]-Y (5) and [Mn^III(pydx-1,2-pn)]-Y (6). These encapsulated complexes are used as catalysts for the oxidation, by H₂O₂, of methyl phenyl sulfide, styrene and benzoin efficiently. Oxidation of methyl phenyl sulfide under the optimized reaction conditions gave ca. 86% conversion with two major products methyl phenyl sulfoxide and methyl phenyl sulfone in the ca. 70% and 30% selectivity, respectively. Oxidation of styrene catalyzed by these complexes gave at least five products namely styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde with a maximum of 76.9% conversion of styrene by 4, 76.3% by 5 and 76.0% by 6 under optimized conditions. The selectivity of the obtained products followed the order: benzaldehyde > benzoic acid > styrene oxide > phenylacetaldehyde > 1-phenylethane-1,2-diol. Similarly, ca. 93% conversion of benzoin was obtained by these catalysts, where the selectivity of the products followed the order benzil > benzoic acid > benzaldehyde-dimethylacetal. Tests for the recyclability and heterogeneity of the reactions have also been carried. Neat complexes are equally active. However, the recycle ability of encapsulated complexes makes them better over neat ones.     

Two New One-Dimensional Chain-Like Compounds Constructed from the Sandwich-Type Polyoxotungstate Clusters

Two new one-dimensional chain-like compounds, K₄Na₄[Mn₂(H₂O)₈Mn₄(H₂O)₂(GeW₉O₃₄)₂] · 20.5H₂O (1) and K₂Na₄Cu₂(H₂O)₁₂[Cu(H₂O)₂Cu₄(H₂O)₂(SiW₉O₃₄)₂] · 15H₂O (2), constructed from the sandwich-type clusters, have been obtained by the routine synthetic reactions in aqueous solutions, and their structures were determined by X-ray single crystal diffraction analysis. The crystal data is following: for 1, space group, monoclinic, P _21/n, a = 16.693(3) Å, b = 14.935(3) Å, c = 20.090(4) Å, β = 92.23(3)°, V = 5004.7(17) ų, Z = 2; For 2, space group, triclinic, P _?1, a = 11.744(2) Å, b = 13.415(3) Å, c = 17.609(4) Å, α = 73.08(3)°, β = 82.68(3)°, γ = 65.18(3)°, V = 2409.1(8) ų, Z = 1. The crystal structure of 1 shows a 1D ladder-like chain, built up of the sandwich anions [Mn₄(H₂O)₂(GeW₉O₃₄)₂]^12? and the Mn²⁺ ions. Compound 2 is a polymeric chain, composed of the Cu-substituted sandwich-type anions [Cu₄(H₂O)₂(SiW₉O₃₄)₂]^12? linked by the Cu(H₂O)₄ clusters. These extended materials based on the sandwich-type polyoxoanions are rarely reported in the POM chemistry.     

Solvent-dependent formation of two different Cd(II) complexes with p-BrC6H4C(S)NHP(O)(OiPr)2 (HL). Crystallographic modification of Cd(HL)2L2

Reaction of the potassium salt of N-(diisopropoxyphosphoryl)-p-bromothiobenzamide p-BrC₆H₄C(S)NHP(O)(OiPr)₂ (HL) with Cd(II) cations in freshly dried and distilled EtOH leads exclusively to the complex [Cd(p-BrC₆H₄C(S)NH₂-S)(L-O,S)₂] ([Cd(L^I)L₂]), while the same reaction in H₂O leads to the complex [Cd(HL-O)₂(L-O,S)₂] ([Cd(HL)₂L₂]). The corresponding reactions with Zn(II) always lead to the complex [Zn(L-O,S)₂] ([ZnL₂]) regardless of the solvent. The crystal structure of [Cd(HL)₂L₂]^.2/3H₂O reveals to be a polymorph to the previously reported anhydrous [Cd(HL)₂L₂].     

Mixed-metal single-molecule magnets: Syntheses, structure, and magnetic properties of [Mn8Fe4O12(O2CR)16(H2O)4] (R = CH2Cl, CH2Br, CHCl2)

Three mixed-metal single-molecule magnets containing [Mn₈Fe₄O₁₂]¹⁶⁺ cores are synthesized and characterized. The reaction of FeCl₂·4H₂O with KMnO₄ and RCOOH (R = CH₂Cl, CH₂Br) in H₂O gives [Mn₈Fe₄O₁₂(O₂CR)₁₆(H₂O)₄] (R = CH₂Cl (1), CH₂Br (2)) in yields of 43% and 40%, respectively. Treatment of complex 1 with an excess of CHCl₂COOH in CH₂Cl₂ gives [Mn₈Fe₄O₁₂(O₂CCHCl₂)₁₆(H₂O)₄]·CH₂Cl₂·10H₂O (3·CH₂Cl₂·10H₂O) in a yield of 83%. The X-ray structure analysis reveals that all three complexes consist of a trapped-valence dodecanuclear core comprising 4Mn^III, 4Fe^III, and 4Mn^IV ions. DC magnetic susceptibility and magnetization measurements indicate that all three complexes exhibit intramolecular antiferromagnetic interaction, resulting in an S = 4 ground state. In addition, frequency-dependent out-of-phase AC magnetic susceptibility signals at low temperature for complexes 1, 2, and 3 are indicative of their single-molecule magnetism behavior.     

Ionothermal syntheses of three transition-metal-containing polyoxotungstate hybrids exhibiting the photocatalytic and electrocatalytic properties

Employing the ionothermal synthesis approach, three new transition-metal-containing polyoxotungstate hybrids: [Dmim]₂Na₃[SiW₁₁O₃₉Fe(H₂O)]·H₂O (Dmim=1,3-Dimethylimidazole) (1), [Emim]₉Na₈[(SiW₉O₃₄)₃{Fe₃(μ₂-OH)₂(μ₃-O)}₃(WO₄)]·0.5H₂O(Emim=1-Ethyl-3-meth-ylimidazole) (2) and [Dmim]2[HMim]Na₆[(AsW₉O₃₃)₂{Mn^III(H₂O)}₃]·3H₂O (Dmim=1,3-Dimethylimidazole; Mim=1-Methylimidazole) (3) have been synthesized in 1-ethyl-3-methyl imidazolium bromide ([Emim]Br) ionic liquids (ILs). Compound 1 possesses a 3-D open framework constructed from the mono-iron^III-substituted α-Keggin-type anion and the organic cations [Dmim]+ through the hydrogen bond interactions. Compound 2 contains a [{Fe^III₃(μ₂-OH)₂(μ₃-O)}₃(μ₄-WO₄)] cluster surrounded by three [SiW₉O₃₄]¹⁰⁻ ligands, eight sodium cations and nine dissociative [Emim]⁺ cations around the polyoxoanion. The polyoxoanion of 3 consists of a high-valent trinuclear-manganese (III)-substituted sandwiching polyoxoanion based on the [α-AsW₉O₃₃]⁹⁻ units. All the compounds are characterized by elemental analyses, IR, UV-vis spectra, TG-DTA and XRD analyses. The XPS and EPR spectra of Mn^III in 3 were studied. The photocatalytic and electrocatalytic properties, as well as the stabilities of 1-3 were also investigated.     

Solid chemistry of the Zn/1,2,4-triazolate/anion system: Separation of 2D isoreticular layers tuned by the terminal counteranions X (X=Cl, Br, I, SCN)

An array of 2D isoreticular layers, viz. [Zn(atrz)X]_∞ (1·X; X=Cl⁻, Br⁻, I⁻; atrz=3-amino-1,2,4-triazole anion), [Zn₄(atrz)₄(SCN)₄·H₂O]_∞ (1·SCN·H₂O) and [Zn(trz)X]_∞ (2·X; X=Cl⁻, Br⁻, I⁻; trz=1,2,4-triazole anion), have been hydrothermally synthesized and structurally characterized. Compounds 1·X and 1·SCN·H₂O are constructed from binuclear planar Zn₂(atrz)₂ subunits and exhibit (4,4) topological network when the subunits are simplified as four-connected nodes. Based on changing the terminal counteranions X (X=Cl⁻, Br⁻, I⁻, SCN⁻), the average interlayer separations of 1·X and 1·SCN·H₂O are enlarged, which equal to 5.851, 6.153, 6.651 and 8.292 Å, respectively. As a result, H₂O molecules reside in the spaces between two adjacent layers of 1·SCN·H₂O. 2 and 1 are the isomorphous structures. In common with 1, the interlayer separations of 2·X are widened with increasing the ion radius. Solid-state luminescence properties and thermogravimetric analyses of 1 and 2 were investigated, respectively.     

Complexes derived from the copper(II)/succinamic acid/N,N′,N″-chelate tertiary reaction systems: Synthesis,structural and spectroscopic studies

The use of succinamic acid (H₂sucm) in Cu^II/N,N′,N″-donor [2,2′:6′,2″-terpyridine (terpy), 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (dmbppy)] reaction mixtures yielded compounds [Cu(Hsucm)(terpy)]_n(ClO₄)_n (1), [Cu(Hsucm)(terpy)(MeOH)](ClO₄) (2), [Cu₂(Hsucm)₂(terpy)₂](ClO₄)₂ (3), [Cu(ClO₄)₂(terpy)(MeOH)] (4), [Cu(Hsucm)(dmbppy)]_n(NO₃)_n·3nH₂O (5^.3nH₂O), and [CuCl₂(dmbppy)]·H₂O (6·H₂O). The succinamate(−1) ligand exists in four different coordination modes in the structures of 1–3 and 5, i.e., the μ₂-κO:κO′:κO″ in 1 and 5 which involves asymmetric chelating coordination of the carboxylato group and ligation of the amide O-atom leading to 1D coordination polymers, the μ₂-κ²O:κO′ in 3 which involves asymmetric chelating and bridging coordination of the carboxylato group, and the asymmetric chelating mode in 2. The primary amide group, either coordinated in 1 and 5, or uncoordinated in 2 and 3, participate in hydrogen bonding interactions, leading to interesting crystal structures. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the Hsucm⁻ ligands. The thermal decomposition of complex 5·3nH₂O was monitored by TG/DTG and DTA measurements.     

Syntheses,structures and electrochemistry of manganese(III) complexes derived from N,N′-o-phenylenebis(3-ethoxysalicylaldimine): Efficient catalyst for styrene epoxidation

Syntheses, characterizations, electrochemistry and catalytic properties for styrene epoxidation of three manganese(III) compounds [Mn^IIIL¹(H₂O)(MeOH)](ClO₄) (1) [Mn^IIIL¹(N₃)(H₂O)]·dmf (2) [Mn^IIIL¹(Cl)(H₂O)] (3) derived from the Schiff base compartmental ligand N,N′-o-phenylenebis(3-ethoxysalicylaldimine) (H₂L¹) are reported. The three compounds are characterized by elemental analyses, IR, mass and UV–Vis spectra and conductance values. Single crystal X-ray structures of 1 and 2 have been determined. The structures of 1 and 2 show that these are mononuclear compounds having a salen type structure. In both structures, a dinuclear species is formed by bifurcated hydrogen bonding involving coordinated water molecule. The coordination of chloride in 3 is shown by conductance measurements. The compounds have also been characterized by UV–Vis and mass spectroscopic studies. Cyclic voltammetric and square wave voltammetric studies of the three compounds reveal that these undergo Mn(III)/Mn(II) reduction reversibly with the order of the ease of reduction as 3 > 2 > 1. This order has been explained proposing the composition of active species in solution. Catalytic properties for epoxidation of styrene by all the three complexes using PhIO and NaOCl as oxidant have been studied. The order of both the styrene conversion and styrene epoxidation using the three title compounds is 3 > 1 > 2. Again, it has been observed that more efficient conversion and epoxidation take place when PhIO is used as oxidant.     

Molecular architecture based on manganese triangles: Monomer, dimer, and one-dimensional polymer

The reaction of salicylaldoxime (H₂salox) with MnCl₂·4H₂O and NEt₄OH in MeOH affords the trinuclear manganese complex (NEt₄)[Mn₃O(salox)₃(MeOH)₂(H₂O)₂Cl₂]·MeOH (1·MeOH). A similar reaction of 1·MeOH was carried out using MnBr₂·4H₂O to obtain the hexanuclear manganese complex (NEt₄)₃{NaBr₂[Mn₃O(salox)₃(H₂O)₄Br₂]₂} (2). The reaction of 2-hydroxy-4-methoxybenzaldehyde oxime (4-MeO-H₂salox) and Mn(ClO₄)₂·6H₂O with 1,2-di(4-pyridyl)ethylene (dpe) in MeOH/DMF mixtures yields the one-dimensional complex {[Mn₃O(4-MeOsalox)₃(dpe)_1.5(DMF)₂(H₂O)](ClO₄)}_n (3·DMF·H₂O). Complex 1·MeOH shows a typical structure of a [Mn^III₃O]⁷⁺ core, and complex 2 contains a dimer [Mn^III₃O]⁷⁺ core connected by a Na⁺ ion. Complex 3 has a one-dimensional chain structure constructed from [Mn^III₃O]⁷⁺ units linked by dpe ligands. Magnetic analysis shows that all three complexes exhibit antiferromagnetic interactions between the Mn^III ions.     

Dinuclear double-helical cobalt complexes with two-armed terdentate ligands: Synthesis,structure and physical properties

Three ligands with flexible bis-terdentate coordination sites, di(2-pyridylcarbaldehyde)-6,6′-dicarboxylic acid hydrazone-2,2′-bipyridine (H₂L¹), di(2-acetylpyridyl)-6,6′-dicarboxylic acid hydrazone-2,2′-bipyridine (H₂L²) and di(2-pyridylketone)-6,6′-dicarboxylic acid hydrazone-2,2′-bipyridine (H₂L³) have been easily prepared. Dinuclear double-stranded helicates Co₂(L¹)₂(ClO₄)₂(C₂H₅OH)₂(H₂O)₂ (1), Co₂(HL²)(L²)(ClO₄)₃(C₂H₅OH)₂(H₂O)₂ (2) and Co₂(HL³)(L³)(ClO₄)₃(H₂O)₄ (3) based on the ligands, H₂L^1–3, respectively, have been obtained via self-assembly, their structures were determined by FT-IR, Elemental Analysis, ESI-MS and X-ray diffraction method.     

Two Mn6 single-molecule magnets with sulfur-contained capping ligand

The reactions of Mn(ClO₄)₂·6H₂O, 1-(2-hydroxyphenyl)ethanone oxime (abbr. as MeSao), NEt₃ and thiophene-2-carboxylic acid/thiophene-3-carboxylic acid (2-TCA/3-TCA) lead to [Mn₆O₂(MeSao)₆(2-TCA)₂(EtOH)₄(H₂O)₂](EtOH)₂ (1) and [Mn₆O₂(MeSao)₆(3-TCA)₂(EtOH)₄(H₂O)₂](EtOH)₂ (2), respectively. Their structures can be described as a core of the [Mn^III₆O₂(Mesao)₆(O₂C-thiophene)₂(EtOH)₄] consisting two off-set, stacked [Mn^III₃(μ³-O²⁻)]⁷⁺ triangular subunits linked by two central oximato O-atoms and two O-atoms from phenoxide group. Magnetic investigation revealed that 1 and 2 all have a spin ground state S = 4, and both complexes show single-molecule magnet behaviors with similar energy barriers U_eff ∼45 K.     

The magneto-structural correlation of two novel 1D antiferromagnetic chains with different magnetic behaviors

Herein, the magneto-structural correlation concerning two analogous 1D magnetic chains [Fe^IIMn^II(8-quinolinato)₄·(H₂O)_0.25]_n (1) and [Mn^II(8-quinolinato)₂]_n (2) is investigated in detail. Complex 1 exhibits typical antiferromagnetic behaviors owing to the strong anisotropy accompanying with the position of the intrachain inversion centers, while complex 2 undergoes a spin-flop transition due to weak crystal anisotropy. The strengths of different kinds of supramolecular interactions within 1 and 2 are evaluated and compared using the theory of atoms in molecules.     

Hydrothermal Syntheses and Structural Characterization of Two 3-D Supramolecular Networks Constructed from Tetra-CoII Sandwiched Polyoxometalates

Two Co₄-substituted sandwich-type polyoxometalates (H₂en)₉[Co₄(H₂O)₂(PW₉O₃₄)₂]{[Co(H₂O)₄][Co₄(H₂O)₂(PW₉O₃₄)₂]}·18H₂O (1) and (H₂en)₅[Co₄(H₂O)₂(H₃GeW₉O₃₄)₂]{[Co(H₂O)₄]₂[Co₄(H₂O)₂(H₂GeW₉O₃₄)₂]}·16H₂O (2) (en = ethylenediamine) have been hydrothermally synthesized and characterized by IR spectra, elemental analyses, thermogravimetric analyses, powder X-ray diffraction and single-crystal X-ray diffraction. Single-crystal structure analysis reveals that the molecules of 1 and 2 contain two Co₄-substituted sandwich-type polyoxoanions. This type of a molecular unit containing double polyoxoanions is very rare. From the viewpoint of supramolecular chemistry, the sandwich-type polyoxoanions in 1 and 2 can be further extended to 3-D frameworks via extensive hydrogen-bonding interactions.     

Chains,helices, sheets and unusual 3D nets: Diverse structures of the flexible,ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazolyl)ethane

The flexible ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazol-1-yl)ethane (L^4Et) displays remarkable versatility in the complexes that it forms with transition metals with products ranging from 1D chains to interpenetrating 3D networks. The L^4Et ligand itself crystallises in the space group P2₁, adopting a helical twist, although it is found in a variety of other conformations in its complexes. Coordination polymers containing the L^4Et ligand vary from almost straight, parallel 1D chains of [Ag₂(L^4Et)₂(ClO₄)₂(DMF)]·DMF (1), through interdigitating helical complexes containing tetrahedral Zn(II), [Zn(NCS)₂(L^4Et)]·DMF·H₂O (2) to 2D sheets of [Cu(L^4Et)₂(H₂O)₂](PF₆)₂·xH₂O (3) and the three-fold interpenetrating 3D network of [Co(L^4Et)₂(NCS)₂] (4). The 3D network adopts an unusual 3D 4-connected dmp (6⁵.8) topology. Dimensionality can be limited by the use of chelating co-ligands, demonstrated by the formation of the dinuclear complex [{Cu(py-2,6-CO₂)(H₂O)}₂(L^4Et)] (5).     

A series of 2D lanthanide (III) coordination polymers constructed from 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate

Reactions of 2-(pyridine-3-yl)-1H-4,5-imidazoledicarboxylic acid (H₃PyIDC) with a series of Ln(III) ions affords ten coordination polymers, namely, {[Ln(H₂PyIDC)(HPyIDC)(H₂O)₂]·H₂O}_n [Ln=Nd (1), Sm (2), Eu (3) and Gd (4)], {[Ln(HPyIDC)(H₂O)₃]·(H₂PyIDC)·H₂O}_n [Ln=Gd (5), Tb (6), Dy (7), Ho (8) and Er (9)], and {[Y₂(HPyIDC)₂(H₂O)₅]·(bpy)·(NO₃)₂·3H₂O}_n (10) (bpy=4,4′-bipyridine). They exhibit three types of networks: complexes 1-4 are isomorphous coordination networks containing neutral 2D metal-organic layers, while complexes 5-9 are isomorphous, which consist of cationic metal-organic layers and anionic organic layers, and complex 10 is a 2D network built up from 4-connected HPyIDC²⁻ anion and 4-connected Y(III) ions. In addition, thermogravimetric analyses and solid-state luminescent properties of the selected complexes are investigated. They exhibit intense, characteristic emissions in the visible region at room temperature.     

Synthesis,crystal structures and spectroscopic studies of praseodymium(III) malonate complexes

Reactions of malonic acid (H₂mal) with PrCl₃·6H₂O afforded the known complex [Pr₂(mal)₃(H₂O)₆]_n (1), and compounds [Pr₂(mal)₃(H₂O)₆]_n·2nH₂O (2·2nH₂O), [PrCl(mal)(H₂O)₃]_n·0.5nH₂O (3·0.5nH₂O) and [Pr(mal)(Hmal)(H₂O)₃]_n·nH₂O (4·nH₂O) using various reaction ratios, reaction media (H₂O, MeOH) and pH values. Analogous reactions with CeCl₃·7H₂O afforded compounds [Ce₂(mal)₃(H₂O)₆]_n (5), [CeCl(mal)(H₂O)₃]_n·nH₂O (6·nH₂O) and [Ce(mal)(Hmal)(H₂O)₃]_n·nH₂O (7·nH₂O). Compounds 2·2nH₂O and 3·0.5nH₂O were characterized by X-ray crystallography, and 4–7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1–3, i.e., the μ₂-κO:κO′:κO″ and the μ₄-κ²O:κO′:κ²O″:κO? in 1 and 2 leading to a 3D network structure, and the μ₃-κ²O:κO′:κ²O″:κO? in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5nH₂O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1–3 are discussed in terms of known malonato(-2) Ln^III and Ca^II complexes. The bioinorganic chemistry relevance of our results is discussed.     

Crystal structure, spectroscopy and magnetism of trinuclear nickel(II), cobalt(II) complexes and their solid solution

Four new complexes [Ni₃(μ-L)₆(H₂O)₆](NO₃)₆·6H₂O (1), [Co₃(μ-L)₆(H₂O)₆](NO₃)₆·6H₂O (2), [Ni₃(μ-L)₆(H₂O)₄(CH₃OH)₂](NO₃)₆·4H₂O (3), [Co₃(μ-L)₆(H₂O)₄(CH₃OH)₂](NO₃)₆·4H₂O (4) (L = 4-amino-3,5-dimethanyl-1,2,4-triazole) were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that complex 1 and 2 are isomorphous; complex 3 and 4 are isomorphous. Four complexes all consist of the linear trinuclear cations ([M₃(μ-L)₆(H₂O)₆]⁶⁺ (M = Ni,Co) for 1 and 2; [M₃(μ-L)₆(H₂O)₄(CH₃OH)₂]⁶⁺ (M = Ni,Co) for 3 and 4), NO₃⁻ anions and crystallized water molecules. In the trinuclear cations, the central M(II) ions and two terminal M(II) ions are bridged by three triazole ligands. Other eleven solid solution compounds which are isomorphous with complex 3 and 4 were obtained by using different ratio of Ni(II) and Co(II) ions as reactants and ICP result indicates that ligand L has higher selectivity of Ni(II) ions than that of Co(II) ions. The magnetic analysis was carried out by using the isotropic spin Hamiltonian ? = −2J(?₁?₂ + ?₂?₃) (for complexes 1 and 3) and simultaneously considering the temperature dependent g factor (for complexes 2 and 4). Both the UV-Vis spectra and the magnetic properties of the solid solutions can be altered systematically by adjusting the Co(II)/Ni(II) ratio.