Engineering solid-state porosity of synthetic supercontainers via modification of exo-cavities

Two new coordination supercontainers have been successfully isolated from the self-assembly reactions of the container precursor p-phenylsulfonylcalix [4]arene, Ni(II) or Co(II) ion, and diphenylmethane-4,4'-dicarboxylic acid. Crystal structure analysis revealed that these two coordination supercontainers possess a similar endo cavity and two deeper exo cavities compared to the related supercontainers based on p-tert-butylsulfonylcalix [4]arene. Gas and vapor adsorption studies indicated that the new compounds are permanently porous and show much better CO₂/O₂ and CO₂/N₂ selectivity and higher vapor adsorption than the tert-butyl analogues.     

Monomer sequence of partially hydrolyzed poly(4-tert-butoxystyrene) and morphology of diblock copolymers composing this polymer sequence as one block

The molecular characteristics of poly(4-tert-butoxystyrene) (O) upon hydrolysis reaction were investigated. It is known that O can be converted into poly(4-hydroxystyrene) (H) through hydrolysis reaction using strong acid. In this study, a set of poly(4-tert-butoxystyrene-co-4-hydroxystyrene)s (O/H copolymers) having various conversion rates, f_Hs, were prepared. Hydrolysis reaction is found to occur uniformly by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) where the average f_H obtained was consistent with that from ¹H NMR though a certain distribution in the number of hydrolyzed units was conceived. Monomer sequence of O/H copolymers was determined by ¹³C NMR and the changes in triad concentration were obtained by spectra subtraction method. As a result, ¹³C NMR reveals that O and H are statistically distributed. To evaluate the effect of hydrolysis on microphase-separated structure, we observed the morphology of partially hydrolyzed poly(4-tert-butylstyrene-block-4-tert-butoxystyrene) (BO) by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Samples with f_H from 0.21 to 0.67 form both lamellar (major component) and cylindrical (minor component) structures reflecting both the statistical manner of hydrolysis reaction and the possible localized distribution of H sequence.     

Decomposition of tert-butyl hydroperoxide into tert-butyl alcohol and O2 catalyzed by birnessite-type manganese oxides: Kinetics and activity

Birnessite-type manganese oxides (M-OL-1s, M = K, Mg, Fe, Ni and Cu) are first reported to efficiently catalyze the decomposition of tert-butyl hydroperoxide (TBHP) into tert-butyl alcohol (TBA) and O₂ with a 100% selectivity towards TBA under heterogeneous conditions. The same form of overall second-order kinetic equations is fitted out for the M-OL-1s and explained by the proposed mechanism. Life tests and XRD analyses demonstrate no losses in both the activity and the birnessite-type structure after the reaction.     

Synthesis and electrocatalytic function for hydrogen generation of cobalt and nickel complexes supported by phenylenediamine ligand

To study the effect of different metal centers on catalytic function, two complexes [L-M] (M = Co, 1; Ni, 2) were prepared by the reactions of N,N′-bis(2-amino-3,5-di-tert-butylphenyl)-o-phenylenediamine, H₂L, with Co(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O, respectively. Electrochemical investigations show 1 and 2 can electrocatalyze hydrogen generation both from acetic acid and aqueous buffer. Complexes 1 and 2 afford a turnover frequency (TOF) of 738.23 and 1331.23 mol of hydrogen per mole of catalyst per hour (mol h^− 1) at an overpotential (OP) of 0.838 V from a neutral buffer, respectively, indicating that the nickel center constitutes the better active catalyst.     

Electron-rich salen-type Schiff base complexes of Cu(II) as catalysts for oxidation of cyclooctene and styrene with tert-butylhydroperoxide: A comparison with electron-deficient ones

Two square planar copper(II) complexes of tetradentate Schiff base ligands derived from aromatic aldehydes and 2,2′-dimethylpropandiamine (H₂{salnptn(3-OMe)₂}, H₂{hnaphnptn}) have been prepared and used as catalysts for oxidation of cyclooctene and styrene with tert-butylhydroperoxide (TBHP). Oxidation of cyclooctene with TBHP gave cyclooctene oxide as the sole product, but in the case of styrene a mixture of styrene oxide and benzaldehyde has been obtained in ca. 1:3 molar ratio. It has been shown that the rate and selectivity of reaction depend to the electron-donor ability of substituents at the phenyl groups of the ligand and can be improved by introduction of π-electron-donating groups at the aromatic rings of salen-type Schiff bases. The structure of Cu{salnptn(3-OMe)₂} has been determined by X-ray crystallography at 291 K with results generally in agreement with those previously reported. The results suggest that the symmetrical Schiff base ligands are bivalent anions with tetradentate N₂O₂ donors derived from the phenolic oxygen and azomethine nitrogen atoms.     

A Facile Access to New Polymethylmethacrylate-Anchored Ferrocene Substituted Nickel(II) Unsymmetrical Schiff Base Complexes: Synthesis and Characterization

This paper discloses two new side-chain metallopolymers containing an unsymmetrical organometallic Schiff base complex of Ni(II) linked to a polymethylmethacrylate (PMMA) matrix. The neutral ferrocene substituted Schiff base complex 1, Ni{CpFe(η⁵-C₅H₄)-C(O)CH=C(CH₃)N–o-C₆H₄N=CH-(2-O,5-OH-C₆H₃)} where (Cp = η⁵-C₅H₅), was synthesized via template reaction by condensation of the tridentate half-unit metalloligand Fc-C(O)CH=C(CH₃)-N(H)-o-C₆H₄NH₂ (Fc = ferrocenyl = CpFe(η⁵-C₅H₄)) with 2,5-dihydroxybenzaldehyde in the presence of nickel(II) acetate tetrahydrate. The binuclear Schiff base complex of Ni(II) containing an aromatic free hydroxyl group was reacted under basic conditions with PMMA to afford, upon trans-esterification reaction, metallopolymers 2 (complex 1 monomeric unit/PMMA = 1/5) and 3 (complex 1 monomeric unit/PMMA = 1/3). Elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopies, and cyclic voltammetry were utilized to characterize the newly synthetized compounds. Surface morphology of the metallopolymer film of 2 was studied using atomic force microscopy.     

Molecular switching of nickel(ΙΙ) complexes using a hemilabile N,N′-bis(β-carbamoylethyl)1,2-diaminocyclohexane ligand

The reaction of NiCl₂·6H₂O with one equivalent hemilabile diaminodiamide ligand N,N′-bis(β-carbamoylethyl)1,2-diaminocyclohexane (1) gave a pale blue compound [Ni(C₁₂H₂₄N₄O₂)(H₂O)₂]₂·3H₂O·4Cl (2). With more than one equivalent ligands, 2 was transformed to a yellow species [Ni(C₁₂H₂₂N₄O₂)]·3H₂O (3) by the Ni–O to Ni–N bond rearrangement at two amide sites of the complex. The color change could be described as a pH dependent isomerization of the ligand. The results presented could be useful in the design of new Ni(II)-based switching materials.     

A readily prepared,highly reusable and active polymer-supported molybdenum carbonyl Schiff base complex as epoxidation catalyst

Polymer-bound Schiff base ligand 2 was prepared by oxidation of chloromethylated polystyrene to aldehydic polystyrene 1 and then reaction with ethylene diamine. The functionalized polystyrene 2 was used to immobilize Mo(CO)₆ and polymer-bound molybdenum carbonyl Schiff base catalyst 3 was produced. This supported catalyst shows high activity in epoxidation of various alkenes in the presence of tert-butylhydroperoxide (TBHP). The supported molybdenum catalyst can be recovered and reused for eight times without loss in its activity.     

A new nickel(II) coordination polymer derived from [Ni(N,N-ethylenebis(1,1,1-trifluoroacetylacetoneiminato)] and 1,4-diazabicyclo[2.2.2]octane

The presence of two electron-withdrawing CF₃ groups in [Ni{N,N-ethylenebis(1,1,1-trifluoroacetylacetoneiminato)}] (NiL) has been demonstrated to promote axial coordination by pyridine (Py) ligands to form the corresponding octahedral base adduct complex in the solid state, while the corresponding solid products do not form in the absence of the CF₃ groups. The change to octahedral geometry is accompanied by a spin-state change of the nickel from low- to high-spin. The structure of the octahedral product, [NiL(Py)₂], has been confirmed by X-ray diffraction. In an extension of this study, [NiL] was reacted with the difunctional (stronger) base 1,4-diazabicyclo[2.2.2]octane (dabco); the X-ray structure of the product confirmed the formation of a one-dimensional coordination polymer in which dabco axially bridges [NiL] units in a highly linear fashion. This product represents an example of a new class of one-dimensional polymeric structures in which a difunctional base (in this case dabco) links square planar [NiL] units of the present type.     

Control of main chain structure and possibility of molecular weight control of polymer on polymerization of vinyl chloride with tert-butyllithium

The controlled polymerization of vinyl chloride (VC) with tert-butyllithium (tert-BuLi) was investigated. The polymerization of VC with tert-BuLi at −30 °C proceeded to give a high molecular weight polymer in good yield. In the polymerization of VC −30 to 0 °C under nearly bulk, the relationship between the M_n of polymers and polymer yields gave a straight line passed through the origin, but the M_w/M_n of PVC was not narrow. When CH₂Cl₂ was used as polymerization solvent, the M_n of PVC increased with the polymer yield, and the M_w/M_n of 1.25 was obtained. Structure analysis of the resulting polymers indicates that the main chain structure could be regulated in the polymerization of VC with tert-BuLi. Accordingly, a control of molecular weight of polymer and main chain structure is possible in the polymerization of VC with tert-BuLi.     

Preparation of Ni/MgxTi1 − xO catalysts and investigation on their stability in tri-reforming of methane

Ni/Mg_xTi_1 − xO catalysts were prepared through a wet impregnation method by dispersing Ni on Mg_xTi_1 − xO composite oxides obtained via a sol–gel technique. The Ni/Mg_xTi_1 − xO catalysts were characterized by various means including ICP–OES, BET, XRD, H₂–TPR, SEM, and TG. No free NiO peak was found in all XRD patterns of the Ni/Mg_xTi_1 − xO catalysts. The H₂–TPR and chemisorption results indicated that adding Ti to the NiO–MgO system obstructed the formation of solid solution, and thus increased the reducibility of the catalysts. The prepared Mg_xTi_1 − xO composite oxides had the same ability to disperse Ni as TiO₂ and MgO. The tri-reforming (simultaneous oxygen reforming, carbon dioxide reforming, and steam reforming) of methane over Ni/Mg_xTi_1 − xO catalysts was carried out in a fixed bed flow reactor. The conversions of CH₄ and CO₂ can respectively be achieved as high as above 95% and 83% over Ni/Mg_0.75Ti_0.25O catalyst under the reaction conditions. The activity of Ni/Mg_0.75Ti_0.25O and Ni/Mg_0.5Ti_0.5O did not decrease for a reaction period of 50 h, indicating their rather high stability. The experimental results showed that the nature of support, the interaction between metal and support, and the ability to be reduced played an important role in improving the stability of catalysts.     

Synthesis of magnetically separable ordered mesoporous carbons from F127/[Ni(H2O)6](NO3)2/resorcinol-formaldehyde composites

An easy method is described for the synthesis of a mesostructured Ni/ordered mesoporous carbon (OMC) composite with a highly ordered cubic structure (space group Im3m). This synthesis was carried out by the carbonization of the F127/[Ni(H₂O)₆](NO₃)₂/RF (resorcinol-formaldehyde) composite self-assembled in an alkaline medium. The effects of nickel loading content and carbonization temperature on the morphologies, pore features, structures and magnetic properties of these Ni/OMC composites were investigated using the thermogravimetric analysis, X-ray diffraction, nitrogen sorption, transmission electron microscopy and vibrating-sample magnetometer measurements. It was found that Ni²⁺ was captured by the network of F127/RF and further reduced into metallic Ni nanoparticles during the carbonization. The nickel nanoparticles were well-dispersed in the ordered mesoporous carbon walls. The Ni/OMC composites exhibit the soft ferromagnetic behavior and the magnetization parameters can be adjusted by the content of nickel and the carbonization temperatures. The excellent acid-resistant property of the magnetic materials makes them useful in magnetic separation.     

Structures and magnetism of bimetallic octacyanometallates: honeycomb-like [Mo(CN)8Ni2(pn)4]n·4nH2O and binuclear [Mo(CN)8Ni(en)2(H2O)][Ni(en)3]·2H2O (pn=1,3-diaminopropane,en=1,2-diaminoethane)

Bimetallic octacyanometallates [Mo(CN)₈Ni₂(pn)₄]_n·4nH₂O (1) and [Mo(CN)₈Ni(en)₂(H₂O)][Ni(en)₃]·2H₂O (2) based on [Mo(CN)₈]⁴⁻ were synthesized in aqueous solution, and their crystal and molecular structures have been determined. The complex [Mo(CN)₈Ni₂(pn)₄]_n·4nH₂O (1) consists of novel two-dimensional honeycomb-like layers. The complex [Mo(CN)₈Ni(en)₂(H₂O)][Ni(en)₃]·2H₂O (2) contains a binuclear anion [Mo(CN)₈Ni(en)₂(H₂O)]²⁻,[Ni(en)₃]²⁺ cation and two lattice water molecules. Magnetic studies suggest a possible weak antiferromagnetic interaction between Ni²⁺ ions in 1.     

A Michael-type reaction between acrylato ions and ethylenediamine coordinated to Ni(II). Synthesis,crystal structure and magnetic properties of [Ni2(EDDP)2(H2O)2] · 2H2O (H2EDDP = ethylenediamine-N,N-dipropionic acid)

The reaction between NiCO₃ · Ni(OH)₂, acrylic acid and ethylenediamine in a 2:4:1 molar ratio affords the binuclear complex, [Ni₂(EDDP)₂(H₂O)₂] · 2H₂O 1. The organic ligand, EDDP^2? (the dianion of the ethylenediamine-N,N-dipropionic acid ligand), results from the addition of one amine group to the carbon–carbon double bonds of two acrylato ions. The crystal structure of 1 consists of neutral centrosymmetric entities, with the nickel ions connected by two carboxylato groups, each one acting as a monoatomic bridge. The intramolecular Ni?Ni distance is 3.212 Å. The metal ions exhibit an octahedral geometry. The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the nickel(II) ions (J = ?21.8 cm^?1, H = ?JS_Ni1S_Ni2).     

Synthesis and characterization of the dihydrosalpren ligand (H2L1) and of its trinuclear Ni(II) complex

The synthesis of the new unsymmetrical tetradendate Schiff ligand N-(2-hydroxybenzyl)-N′-(2-hydroxybenzylidene)-1,3-diaminopropane (H₂L¹) is reported. The ligand comprises two different coordination moieties: a rigid salicylaldimmine unit and a more flexible (2-hydroxybenzyl)-amino (hydrogenated salicylaldimmine) unit. The reaction of H₂L¹ with Ni(OAc)₂·4H₂O (1:1 molar ratio) leads to the spontaneous formation of a trinuclear complex with composition {[Ni(L¹)OH₂]₂(OAc)₂Ni}·2H₂O, characterized by X-ray crystallography, where two [Ni(L¹)] units act as O,O-bidentate chelate to a Ni(II) ion.     

The electrodepositions of copper and nickel from trifluoroacetate-H2O baths

In the present study, the electrodepositions of copper from the Cu(CF₃COO)₂CF₃COOHH₂O bath and nickel from the Ni(CF₃COO)₂NH₄ClH₂O bath, were studied.In the copper electrodeposition from Cu(CF₃COO)₂ (100 g/l)CF₃COOH(0.1 N)H₂O bath, the cathode current efficiency showed about 100% and the anode current efficiency showed over 100% at low cd. In the nickel electrodeposition from Ni(CF₃COO)₂ (200 g/lH₄Cl(15.0 g/l)H₂O bath, the efficiencies of the cathode and anode were about 100%. The range of current density to obtain bright and smooth copper and nickel deposits were 4.0 ～ 24 A/dm², 5.0 ～ 16 A/dm² respectively, and the cross-section of the electrodeposits showed a granular structure.The rates of the electrodeposition of copper and nickel from the above-mentioned baths were controlled by the charge-transfer reaction in the same way as in the reaction in non-aqueous solution[1, 2].     

[Ba(H2O)4(CuL)2]n: a novel coordination polymer constructed from L-bridged 1D chains via inter-chain hydrogen bonds (L=Schiff base derived from 5-bromosalicylaldehyde and glycylglycine)

A novel coordination polymer [Ba(H₂O)₄(CuL)₂]_n (where L=Schiff base derived from 5-bromosalicylaldehyde and glycylglycine) has been synthesized and characterized by X-ray crystallography. The structure reveals the formation of one-dimensional chains, which are assembled further into two-dimensional network by hydrogen bonds between the coordinated water molecules.     

A sandwich-type tungstoantimonate containing trinuclear nickel ions modified with aminopyrazine ligand

A new organic–inorganic hybrid tungstoantimonate, Na₄[Ni₂(apy)(H₂O)₁₀]_1/2[(Ni(Hapy))₃(Na(H₂O)₂)₃(SbW₉O₃₃)₂]·23H₂O (1) (apy = aminopyrazine), has been synthesized and fully characterized. Single crystal X-ray diffraction analysis indicates that the polyanion [(Ni(Hapy))₃(Na(H₂O)₂)₃(SbW₉O₃₃)₂]^6 − displays a sandwich-type dimeric structure in which the Ni^2 + ions in the central belt are modified by aminopyrazine ligands. The contrast experiment analyses show that the existence of organic amine ligand is a key role to the formation of the stable Hervé-type tungstoantimonate containing trinuclear nickel(II) ions, which crystallized with dinuclear nickel complex constructed from an aminopyrazine bridging two [Ni(H₂O)₅]^2 + ions as part of counterions. The variable-temperature magnetic measurements of 1 exhibit the weak antiferromagnetic exchange interactions among Ni(II) clusters in 1.     

In situ synthesis and dielectric properties of copper(II) and nickel(II) chiral Schiff base complexes

Two chiral Schiff base-containing complexes, [Cu(L¹)](ClO₄)₂·H₂O (1, L¹ = (S,S)-N1,N2-bis((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) and [Ni(L²)₂](ClO₄)₂ (2, L² = (S,S)-N1-((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) were synthesized from the reaction mixture of 1H-imidazole-4-carbaldehyde, (S,S)-1,2-diaminocyclohexane and Cu(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O in methanol. Single-crystal X-ray diffraction analyses reveal that the in situ generated chiral Schiff base ligands L¹ and L² are bisubstituted and monosubstituted, respectively, corresponding to the different metal ions Cu^II and Ni^II. Variable-frequency and -temperature dielectric properties of 1 and 2 have been studied.     

A new cyclic binuclear Ni(II) complex as a catalyst towards nitroaldol (Henry) reaction

A new cyclic binuclear Ni(II) complex, [Ni₂(H₂L)₂] · 4MeOH (1), has been synthesized using the Schiff base N′¹,N′³-bis(2-hydroxybenzylidene)malonohydrazide (H₄L). The X-ray crystal structure of 1 shows that the ligand coordinates in the dianionic keto form (H₂L^2 −) via mutual sharing of two Ni(II) ions. Complex 1 acts as a heterogeneous catalyst for the Henry reaction in water. A maximum conversion of ca. 93% was obtained under optimized conditions.