A novel block copolymer with excellent amphiphobicity synthesized via ARGET ATRP

The poly(methyl methacrylate)‐b‐poly(2‐[[[[2‐(perfluorohexyl)]‐sulfonyl]‐amino]ehthyl] methacrylate) (PMMA‐b‐PC₆SMA) copolymers were successfully synthesized for the first time using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) method. Under optimized reaction conditions, the degree of polymerization (DP) of resulting copolymers increased approximately linearly with monomer conversion. Structures of a well‐defined block copolymer were determined by GPC, FT–IR, and ¹H‐NMR spectra. Results from AFM and contact angle measurements of polymer films revealed the presence of block segments derived from PC₆SMA, as indicated by the obvious increase in hydrophobicity and oleophobicity. The relationship between surface composition and surface wetting ability was confirmed by XPS and AFM spectra. Compared with the random copolymer PMMA‐co‐PC₆SMA, C₆SMA dosages in the PMMA‐b‐PC₆SMA copolymers were greatly decreased, which retained its hydrophobic and oleophobic properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2040–2049     

Polymerization and Catalytic Properties of Cluster-Containing Monomers and Polymers

Summary : Cluster-containing monomers were obtained and characterized. Mono- and disubstituted products were obtained under mild conditions via the interaction of Rh₆(CO)₁₆ with 4-vinylpyridine (4-VPy). Substitution of labile acetonitrile ligand in Rh₆(CO)₁₅NCMe by allyldiphenylphosphine (AlPPh₂) yields Rh₆(CO)₁₄(µ,η²-PPh₂CH₂CHCH₂) with formation of π-complex. The copolymerization of cluster-containing monomers synthesized with traditional monomers has been studied. It was found that Rh₆- containing monomers change neither the ligand surroundings nor the structure of cluster monomer framework during polymerization reaction. Polymer-immobilized clusters were found to be active in hydrogenation reactions of cyclohexene.     

Synthesis and properties of Rh6- and Os3-cluster-containing monomers and their copolymers with styrene

Cluster metal-containing monomers were obtained and characterized. Mono- and disubstituted products were obtained under mild conditions via the interaction of Rh₆(CO)₁₆ with 4-vinylpyridine (4-VPy) in the presence of trimethylamin-N-oxide. Substitution of labile acetonitrile ligand in Rh₆(CO)₁₅NCMe by allyldiphenylphosphine (AlPPh₂) yields Rh₆(CO)₁₄(μ,η²-PPh₂CH₂CH=CH₂) with formation of π-complex. The structures of Rh₆(CO)₁₅(4-VPy), Rh₆(CO)₁₄(μ,η²-PPh₂CH₂CH=CH₂) and (μ-H)Os₃(μ-OCNM₂)(CO)₉PPH₂CH₂CH=CH₂ have been determined by single-crystal X-ray diffraction studies, as well as by IR-, ¹H NMR spectroscopies. The Rh - Rh bond lengths are within 2.72÷2.80 Å. The copolymerization of cluster-containing monomers synthesized with traditional monomers has been studied. It was found that Rh₆- and Os₃-containing monomers did not change either the ligand surroundings or the structure of cluster monomer framework during polymerization reaction.     

Ring‐opening polymerization and block copolymerization of L‐lactide with divalent samarocene complex

Divalent samarocene complex [(C₅H₉C₅H₄)₂Sm(tetrahydrofuran)₂] was prepared and characterized and used to catalyze the ring‐opening polymerization of L ‐lactide (L‐LA) and copolymerization of L‐LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L‐LA was retained. The structure of the block copolymer of CL/L‐LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)‐b‐P(L‐LA) copolymer were monitored with real‐time hot‐stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL‐b‐P(L‐LA) copolymer was demonstrated through AFM observation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2667–2675, 2003     

Catalytic asymmetric hydrogenation with the cluster Rh6(CO)10[(-)DIOP]3

Rh₆(CO)₁₀[(-)DIOP]₃ has been isolated after ligand exchange between Rh₆(CO)₁₆ and DIOP. The molecular cluster is an efficient catalyst for asymmetric reduction of various prochiral olefins; optical yields up to 47% have been achieved; the results are compared with those obtained with mononuclear rhodium (I) complexes.     

Elektronenstruktur von Rh4(CO)12, ein Modell für linear und brückenförmig gebundenes CO an Rhodiumkatalysatoren

Electronic Structure of Rh₄(CO)₁₂, a Model for Linear- and Bridge-bonded CO on Rhodium Catalysts The electronic structure of the Rh₄(CO)₁₂ cluster containing both linear- and bridgebonded CO groups has been studied by the EHMO method and compared with that of the Ir₄(CO)₁₂ cluster with only linear-bonded CO ligands. The charge distribution shows a distinctly higher π-back donation for the bridge-bonded CO groups. This result is compared with experimental data such as bond lengths, force constants of the C? O stretching frequencies and XPS data. It allows further an interpretation of results of CO hydrogenation on supported rhodium catalysts and on rhodium model complexes.     

Rh2[(R)-(+)-MTPA]4 as an NMR auxiliary for the enantiodifferentiation of chiral secondary and tertiary phosphine–borane complexes

The direct chiral recognition of secondary and tertiary phosphine–borane complexes is made possible by applying the dirhodium method (NMR in the presence of Rh₂[(R)-(+)-MTPA]₄, Rh¹). Due to the acid lability of the phosphine–borane complexes, it is advisable to use deuterated benzene as solvent rather than deuterated chloroform. The decomposition of the phosphine–borane complexes and the resulting Rh¹–phosphine adducts are also studied.     

XPS study of the electronic structure of heterometallic complexes Fe2MO(Piv)6(HPiv)3 (M = Ni, Co)

Heterometallic complexes Fe₂MO(Piv)₆(HPiv)₃ (M = Ni, Co) have been studied by XPS. The complexes are identified as high-spin complexes with metal atoms in oxidation states M(II) and M(III). A change in the ligand environment of metal atoms has an effect on both the energetic state of metal atoms and the XPS pattern. The substitution of a Co atom for the nickel atom in the heterometallic complexes changes the XPS pattern of iron and their magnetic state. For the Fe₂MO(Piv)₆(HPiv)₃ complexes, quantum-chemical calculations have been performed at the density functional theory (DFT) level. In combination with XPS and magnetochemistry data, the quantum-chemical calculation demonstrates that the Fe, Ni, and Co atoms in the trinuclear complexes are in the high-spin local state and that the ground state is dominated by antiferromagnetic exchange interaction.     

Hydrosilylation of alkenes catalysed by rhodium complexes immobilized on silica via a pyridine group

2-(2-Trimethoxysilylethyl)pyridine, together with 3-methcryloxypropyltrimethoxysilane, was used to prepare a series of rhodium carbonyl complexes bound to silica via a pyridine group. The rhodium complex Rh₂(CO)₄Cl₂ (Rh₂) was used as the starting compound, and the immobilized complexes were prepared by four different routes which yielded both surface-bonded complexes and complexes bonded within the silicate matrix. These complexes were efficient catalysts of hydrosilylation of octene by triethxysilane. All the immobilized complexes were more than their homogeneous analogues and some could be re-used.     

PEGMA/MMA copolymer graftings: generation, protein resistance, and a hydrophobic domain

We synthesized various graft copolymer films of poly(ethylene glycol) methacrylate (PEGMA) and methyl methacrylate (MMA) on silicon to examine the dependency of protein-surface interactions on grafting composition. We optimized atom transfer radical polymerizations to achieve film thicknesses from 25 to 100 nm depending on the monomer mole fractions, and analyzed the resulting surfaces by X-ray photoelectron spectroscopy (XPS), ellipsometry, contact angle measurements, and atomic force microscopy (AFM). As determined by XPS, the stoichiometric ratios of copolymer graftings correlated with the concentrations of provided monomer solutions. However, we found an unexpected and pronounced hydrophobic domain on copolymer films with a molar amount of 10-40% PEGMA, as indicated by advancing contact angles of up to 90 degrees . Nevertheless, a breakdown of the protein-repelling character was only observed for a fraction of 15% PEGMA and lower, far in the hydrophobic domain. Investigation of the structural basis of this exceptional wettability by high-resolution AFM demonstrated the independence of this property from morphological features.     

First Stabilization of 14‐Electron Rhodium(I) Complexes by Hemichelation

Hemichelation is emerging as a new mode of coordination where non‐covalent interactions crucially contribute to the cohesion of electron‐unsaturated organometallic complexes. This study discloses an unprecedented demonstration of this concept to a Group 9 metal, that is, Rh^I. The syntheses of new 14‐electron Rh^I complexes were achieved by choosing the anti‐[(η⁶:η⁶‐fluorenyl){Cr(CO)₃}₂] anion as the ambiphilic hemichelating ligand, which was treated with [{Rh(nbd)Cl}₂] (nbd=norbornadiene) and [{Rh(CO)₂Cl}₂]. The new T‐shaped Rh^I hemichelates were characterized by analytical and structural methods. Investigations using the methods of the DFT and electron‐density topology analysis (NCI region analysis, QTAIM theory) confirmed the closed‐shell, non‐covalent and attractive characters of the interaction between the Rh^I center and the proximal Cr(CO)₃ moiety. This study shows that, by appropriate tuning of the electronic properties of the ambiphilic ligand, truly coordination‐unsaturated Rh^I complexes can be synthesized in a manageable form.     

Polynuclear rhodium complexes of phenothiazines: synthesis and characterization

Polynuclear complexes of RH^II and RH^III with fiveN-alkylphenothiazines as principal ligands have been prepared. The complexes were characterized by their elemental analyses, molar conductivities, and spectral data. The molecular formulae of the new complexes are as follows: [Rh₃(PTZ)₂(OH₂)₂Cl₈]Cl, where PTZ=chlorpromazine or promethazine; [Rh₃(EP)₂(OH₂)₂Cl₈][Rh(OH₂)₂Cl₄], where EP=ethopropazine; [Rh₄(TF)₂(OH₂)₅Cl₉]Cl·H₂O, where TF=trifluoperazine; and [Rh₂(TC)₃(OH₂)Cl₆]. H₂O, where TC=2-chlorophenothiazine. A tentative structure for each of the complexes is proposed. TMC 2627     

Radiolytic synthesis of Rh2(CO)4Cl2 and Rh6(CO)16 from RhCl3 in ethanol under CO atmosphere

Ethanolic solutions of Rh^III chloride exposed to γ-radiation under CO atmosphere are shown to be totally reduced into Rh^I complexes (Rh₂(CO)₄Cl₂ and Rh(CO)₂Cl^-₂) within a few hours with a radiolytic reduction yield of about 6.0 elementary reductions/100 eV (6.2·10^-7 mol·J^-1). The chloride ions freed in the medium inhibit further reduction through Rh(CO)₂Cl^-₂ formation. On addition of copper metal under the same conditions, Rh^III is transformed into Rh₆(CO)₁₆ with a conversion yield 50%. This cluster is formed via Rh₂(CO)₄Cl₂ although Rh(CO)₂Cl^-₂ is also present under these conditions. Rh₆(CO)₁₆ cluster is also formed under radiolysis by direct reduction of Rh₂(CO)₄Cl₂, but metallic rhodium and other reduced products are obtained at the same time.     

A Class of Trinuclear Clusters with Carbonyl Bridging

The impetus for this work was the structure of a trinuclear complex with two carbonyl groups showing incipient triple bridging - Cp₂Rh₃(CO)₄^?. Its structure, barrier to rotation of one Rh(CO)₂^? piece vs. the rest of the molecule, and the nature of the bridging carbonyl interaction are analyzed. Isolobal analogies form an interesting connection between this complex and a bridged isomer of the recently synthesized carbene complexes, Cp₂Rh₂(CO)₂CR₂, one isomer of Cp₂Rh₃(CO)₃, and hypothetical carbyne complexes Cp₂Rh₂(CO)₂CH^+,?. A general bonding model for Cp₂Rh₂(μ-CO)₂X complexes is constructed. The model, rich in geometrical detail, allows minima for the bridging carbonyl groups bending toward and away from the bonded ligand X.     

Dirhodium Complexes as Panchromatic Sensitizers,Electrocatalysts, and Photocatalysts

Dinuclear rhodium complexes are attractive candidates as homogeneous panchromatic photosensitizers and photocatalysts. Modification of the coordination sphere of the Rh₂(II,II) compounds results in photophysical and redox properties that are highly desirable for electro- and photocatalysis. Specifically, Rh₂(II,II) complexes have shown promising catalytic activity towards proton reduction to generate H₂, a clean fuel, and for the selective reduction of CO₂ to HCOOH. In addition, paddlewheel Rh₂(II,II) complexes provide robust platforms for the design of efficient and stable single-component photocatalysts. Optimization of the Rh₂(II,II) catalysts is crucial to realize their future application in devices or systems designed for the production of fuels from sunlight.     

N‐Heterocyclic Carbene–Phosphinidyne Transition Metal Complexes

The N‐heterocyclic carbene–phosphinidene adduct IPr?PSiMe₃ is introduced as a synthon for the preparation of terminal carbene–phosphinidyne transition metal complexes of the type [(IPr?P)ML_n] (ML_n=(η⁶‐p‐cymene)RuCl) and (η⁵‐C₅Me₅)RhCl). Their spectroscopic and structural characteristics, namely low‐field ³¹P NMR chemical shifts and short metal–phosphorus bonds, show their similarity with arylphosphinidene complexes. The formally mononegative IPr?P ligand is also capable of bridging two or three metal atoms as demonstrated by the preparation of bi‐ and trimetallic RuAu, RhAu, Rh₂, and Rh₂Au complexes.     

The formation of dimetallocycles from reactions of alkynes with (η-C5Me5)2Rh2(CO)2; X-ray structure of [(η-C5Me5)2Rh2(η-CO) {μ-η2,η2-C(O)C2-(CF3)2}]

The complexes (η-C₅Me₅)₂Rh₂(μ-CO) {μ-η²,η²-C(O)CRCR} are obtained from reactions between (η-C₅Me₅)₂Rh₂(CO)₂ and the alkynes RCCR (R  CF₃, CO₂Me, or Ph) at 25°C. The molecular geometry of the complex with R  CF₃ has been established by X-ray diffraction; the bridging 'ene-one' unit adopts a μ-η²,η² conformation. Other complexes isolated from these reactions include (η-C₅Me₅)Rh(C₆R₆) (R  CF₃, CO₂Me), (η-C₅Me)₂Rh₂(C₄R₄) (R  CO₂Me) and (η-C₅Me₅)₂Rh₂(CO₂C₂R₂) (R  Ph). The reaction between (η-C₅Me₅)₂Rh₂(CO)₂ and C₆F₅CCC₆F₅ gives (η-C₅Me₅)₂Rh₂(CO)₂(C₆F₅C₂C₆F₅). Mononuclear complexes such as (η-C₅Me₅)Co(C₄R₄CO) are the major products isolated from reactions between (η-C₅Me₅)₂CO₂(CO)₂ and alkynes at 25°C.     

Surfactant‐free synthesis of amphiphilic copolymer of poly(styrene‐co‐acrylamide) in aqueous emulsion with the assistance of ultrasound

The hydrophilic monomer acrylamide (AM) and hydrophobic monomer styrene (St) have been directly copolymerized in a surfactant‐free aqueous emulsion with the assistance of powerful ultrasound. Fourier Transform Infrared spectrocopy (FT‐IR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) measurements revealed that copolymers of AM and St were obtained. Elemental analysis was used to calculate the composition of the copolymer. Size exclusion chromatography (SEC) measurement showed that the molecular weight (M_w) of the copolymer is 1.86 × 10⁵ g/mol and the polydispersity index (PDI( = 2.31. The self‐assembly behavior in different solvents was investigated utilizing laser light scattering (LLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM); the copolymer film showed amphiphilicity, as measured by contact angle goniometry. Copyright © 2008 John Wiley & Sons, Ltd.     

Darstellung und Schwingungsspektren von Chloro-Bromo-Dirhodaten(III), [Rh2ClnBr9−n]3−, n = 0–9

Preparation and Vibrational Spectra of Nonahalogenodirhodates(III), [Rh₂Cl_nBr_9-n]^3?, n = 0–9 The pure nonahalogenodirhodates(III), A₃[Rh₂Cl_nBr_9-n], A = K, Cs, (TBA); n = 0–4, 9, have been prepared. They are formed from the monomer chlorobromorhodates(III), [RhCl_nBr_6-n]^3?, n = 0–6, which are bridged to confacial bioctahedral complexes by ligand abstraction in less polar organic solvents. From the mixtures the complexions are separated by ion exchange chromatography on DEAE-cellulose. The solid, air-stable, air-stable, K-, Cs- and (TBA)-salts of [Rh₂Cl_nBr_9-n]^3?, n = 0–4, are green, of [Rh₂Cl₉]^3? are brown. The IR and Raman spectra of [Rh₂Br₉]^3? and [Rh₂Cl₉]^3? are assigned according to the point group D_3h. The chlorobromodirhodates exist as mixtures of geometrical and structural isomers, which belong to different point groups. The vibrational spectra exhibit bands in characteristic regions; at high wavenumbers stretching vibrations with terminal ligands v(Rh—Cl_t): 360–320, v(Rh—Br_t): 280–250; in a middle region with bridging ligands v(Rh—Cl_b): 300–270, v(Rh—Br_b): 210–170 cm^?1; the deformation bands are observed at distinct lower frequencies. The terminal ligands are fixed very strong, and the distance between v(Rh—X_t) and v(Rh—X_b) increases with decreasing size of the cations.     

Structural Chemistry of Chiral Complexes. NMR and X-ray studies on Rh1 compounds of (S)-1-[bis(p-methylphenyl)phosphino]-2-[(p-methoxybenzyl)amino]-3-methylbutane

The Rh¹(diolefin)complexes [Rh(nbd)( 2 )][PF₆] [Rh(1,5-cod)( 2 )][PF₆], and [Rh((Z)-α -acetamidocinnamic acid)( 2 )][PF₆] ( 2 = the chiral P,N-ligand (S)-1-[bis(p-methylphenyl)phospino]-2-[p-methoxybenzyl)amino]-3-methylbutane have been prepared and characterized. These complexes exit as a mixture of isomers arising from different five-membered-ring conformations and diastereoisomers due to both the prochiral nitrogen and olefin ligands. The three-dimensional solutions structures of these complexes have been studied with the specific aim of understanding how the chiral pocket is built. Aspects of the exchange dynamics and their possible relevance to homogeneous hydrogenation are discussed The solid-state structure for the nbd complex, [Rh(nbd)( 2 )][PF₆], as well as detailed one- and two-dimensional ³¹P-, ¹³C-, and ¹H-NMR results are presented.