5‐n‐Butylpyridine‐2‐carboxylate–copper(II) and –iron(III) complexes

In trans‐bis(5‐n‐butyl­pyridine‐2‐carboxyl­ato‐κ²N,O)­bis­(methanol‐κO)copper(II), [Cu(C₁₀H₁₂NO₂)₂(CH₄O)₂], the Cu atom lies on a centre of symmetry and has a distorted octahedral coordination. The Cu—O(methanol) bond length in the axial direction is 2.596 (3) Å, which is much longer than the Cu—­O(carboxylate) and Cu—N distances in the equatorial plane [1.952 (2) and 1.977 (2) Å, respectively]. In mer‐tris(5‐n‐bu­tyl­pyridine‐2‐carboxyl­ato‐κ²N,O)­iron(III), [Fe(C₁₀H₁₂NO₂)₃], the Fe atom also has a distorted octahedral geometry, with Fe—O and Fe—N bond‐length ranges of 1.949 (4)–1.970 (4) and 2.116 (5)–2.161 (5) Å, respectively. Both crystals are stabilized by stacking interactions of the 5‐n‐butyl­pyridine‐2‐carboxyl­ate ligand, although hydrogen bonds also contribute to the stabilization of the copper(II) complex.     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A mixed‐valence chloride‐bridged (pincer)IrIII–(diene)IrI complex

The title compound, [2,6‐bis(di‐tert‐butylphosphino)phenyl‐1κ³P,C¹,P′]di‐μ‐chlorido‐1:2κ⁴Cl:Cl‐(2η⁴‐cycloocta‐2,5‐diene)hydrido‐1κH‐diiridium(I,III) hexane hemisolvate, [Ir₂(C₈H₁₂)(C₂₄H₄₃P₂)Cl₂H]·0.5C₆H₁₄ or [(^tBuPCP)IrH(μ₂‐Cl)₂Ir(COD)][^tBuPCP is κ³‐2,6‐(^tBu₂PCH₂)₂C₆H₃ and COD is η⁴‐2,5‐cyclooctadiene], is an Ir^III/Ir^I dimer bridged by two chloride ions. The Ir₂Cl₂ framework is nearly planar, with a dihedral angle of 13.04 (4)° between the two Ir centers. The compound was isolated as a hexane hemisolvate. A list of distances found in Ir(PCP) compounds is given.     

Synthesis and characterization of (cryptand‐222)potassium (2‐methylimidazolato)(meso‐tetraphenylporphinato)ferrate(II)–2‐methylimidazole–tetrahydrofuran (1/1/2)

Metalloporphyrin complexes containing an additional imidazole ligand can provide information about the effect of deprotonation or hydrogen bonding on the axial histidine unit in heme proteins. The title high‐spin five‐coordinate imidazolate‐ligated iron(II) porphyrinate, [K(C₁₈H₃₆N₂O₆)][Fe(C₄H₅N₂)(C₄₄H₂₈N₄)]·C₄H₆N₂·2C₄H₈O, has been synthesized and investigated. The solvated salt crystallizes with one 2‐methylimidazole molecule, two tetrahydrofuran solvent molecules and a potassium cation chelated inside a cryptand‐222 (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) molecule. The imidazolate ligand is ordered. The average Fe—Np (Np is a porphyrin N atom) bond length is 2.113 (11) Å and the axial Fe—N_Im (N_Im is an imidazolate N atom) is 2.0739 (13) Å. The out‐of‐plane displacement of the Fe^II atom from the 24‐atom mean plane is 0.6098 (5) Å, indicating an apparent doming of the porphyrin core.     

Poly(N‐phenylmaleimide‐co‐acrylic acid)–copper(II) and poly(N‐phenylmaleimide‐co‐acrylic acid)–cobalt(II) complexes: Synthesis,characterization, and thermal behavior

The free‐radical copolymerization of N‐phenylmaleimide (N‐PhMI) with acrylic acid was studied in the range of 25–75 mol % in the feed. The interactions of these copolymers with Cu(II) and Co(II) ions were investigated as a function of the pH and copolymer composition by the use of the ultrafiltration technique. The maximum retention capacity of the copolymers for Co(II) and Cu(II) ions varied from 200 to 250 mg/g and from 210 to 300 mg/g, respectively. The copolymers and polymer–metal complexes of divalent transition‐metal ions were characterized by elemental analysis, Fourier transform infrared, ¹H NMR spectroscopy, and cyclic voltammetry. The thermal behavior was investigated with differential scanning calorimetry (DSC) and thermogravimetry (TG). The TG and DSC measurements showed an increase in the glass‐transition temperature (T_g) and the thermal stability with an increase in the N‐PhMI concentration in the copolymers. T_g of poly(N‐PhMI‐co‐AA) with copolymer composition 46.5:53.5 mol % was found at 251 °C, and it decreased when the complexes of Co(II) and Cu(II) at pHs 3–7 were formed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4933–4941, 2005     

A Charge‐Stabilizing,Multimodular, Ferrocene–Bis(triphenylamine)–Zinc‐porphyrin–Fullerene Polyad

A novel multimodular donor–acceptor polyad featuring zinc porphyrin, fullerene, ferrocene, and triphenylamine entities was designed, synthesized, and studied as a charge‐stabilizing, photosynthetic‐antenna/reaction‐center mimic. The ferrocene and fullerene entities, covalently linked to the porphyrin ring, were distantly separated to accomplish the charge‐separation/hole‐migration events leading to the creation of a long‐lived charge‐separated state. The geometry and electronic structures of the newly synthesized compound was deduced by B3LYP/3‐21G(*) optimization, while the energy levels for different photochemical events was established using data from the optical absorption and emission, and electrochemical studies. Excitation of the triphenylamine entities revealed singlet‐singlet energy transfer to the appended zinc porphyrin. As predicted from the energy levels, photoinduced electron transfer from both the singlet and triplet excited states of the zinc porphyrin to fullerene followed by subsequent hole migration involving ferrocene was witnessed from the transient absorption studies. The charge‐separated state persisted for about 8.5 μs and was governed by the distance between the final charge‐transfer product, that is, a species involving a ferrocenium cation and a fullerene radical anion, with additional influence from the charge‐stabilizing triphenylamine entities located on the zinc‐porphyrin macrocycle.     

Piperazine‐1,4‐diium–2,4‐dinitrophenolate–water (1/2/2)

In the title 1/2/2 adduct, C₄H₁₂N₂²⁺·2C₆H₃N₂O₅^?·2H₂O, the dication lies on a crystallographic inversion centre and the asymmetric unit also has one anion and one water mol­ecule in general positions. The 2,4‐di­nitro­phenolate anions and the water mol­ecules are linked by two O—H?O and two C—H?O hydrogen bonds to form molecular ribbons, which extend along the b direction. The piperazine dication acts as a donor for bifurcated N—H?O hydrogen bonds with the phenolate O atom and with the O atom of the o‐nitro group. Six symmetry‐related molecular ribbons are linked to a piperazine dication by N—H?O and C—H?O hydrogen bonds.     

Amphiphilic conetworks. II. Novel two‐step synthesis of poly[2‐(dimethylamino)ethyl methacrylate]–polyisobutylene,poly(N‐isopropylacrylamide)–polyisobutylene,and poly(N,N‐dimethylacrylamide)–polyisobutylene hydrogels

Amphiphilic polymer conetworks consisting of hydrophilic poly[2‐(dimethylamino)ethyl methacrylate], poly(N‐isopropylacrylamide), or poly(N,N‐dimethylacrylamide) and hydrophobic polyisobutylene chains were synthesized with a novel two‐step procedure. In the first step, a methacrylate‐multifunctional polyisobutylene crosslinker was prepared by the cationic copolymerization of isobutylene with 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate. In the second step, the methacrylate‐multifunctional polyisobutylene crosslinker, with a number‐average molecular weight of 8200 and an average functionality of approximately 4 per chain, was copolymerized radically with 2‐(dimethylamino)ethyl methacrylate, N‐isopropylacrylamide, or N,N‐dimethylacrylamide into transparent amphiphilic conetworks containing 42–47 mol % hydrophilic monomer. The synthesized conetworks were characterized with solid‐state ¹³C NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6378–6384, 2006     

f‐Element Half‐Sandwich Complexes: A Tetrasilylcyclobutadienyl–Uranium(IV)–Tris(tetrahydroborate) Anion Pianostool Complex

Despite there being numerous examples of f‐element compounds supported by cyclopentadienyl, arene, cycloheptatrienyl, and cyclooctatetraenyl ligands (C_5–8), cyclobutadienyl (C₄) complexes remain exceedingly rare. Here, we report that reaction of [Li₂{C₄(SiMe₃)₄}(THF)₂] ( 1 ) with [U(BH₄)₃(THF)₂] ( 2 ) gives the pianostool complex [U{C₄(SiMe₃)₄}(BH₄)₃][Li(THF)₄] ( 3 ), where use of a borohydride and preformed C₄‐unit circumvents difficulties in product isolation and closing a C₄‐ring at uranium. Complex 3 is an unprecedented example of an f‐element half‐sandwich cyclobutadienyl complex, and it is only the second example of an actinide‐cyclobutadienyl complex, the other being an inverse‐sandwich. The U?C distances are short (av. 2.513 Å), reflecting the formal 2? charge of the C₄‐unit, and the SiMe₃ groups are displaced from the C₄‐plane, which we propose maximises U?C₄ orbital overlap. DFT calculations identify two quasi‐degenerate U?C₄ π‐bonds utilising the ψ₂ and ψ₃ molecular orbitals of the C₄‐unit, but the potential δ‐bond using the ψ₄ orbital is vacant.     

The peptide (Z)‐Pro–Leuol

The structure of the synthetic protected dipeptide (Z)‐Pro–Leuol [systematic name: benzyl 2‐(1‐hydroxy­methyl‐3‐methyl­butyl­amino­carbonyl)­pyrrolidine‐1‐carboxyl­ate], C₁₉H₂₈N₂O₄, was determined by X‐ray crystallography. The peptide adopts a novel backbone conformation compared with other longer oligopeptides containing Pro–Leuol.