π-Olefin—iridium -komplexe : III. Über (η4-cyclodien)(η5-cyclodienyl)iridium-verbindungen,einen neuartigen hydridoiridium-komplex und das (η4-cyclooctadien)(η6-cyclooctatrien)iridium-kation

The complexes [Ir(COD)(η⁵-C₇H₉)] and [Ir(COD)(η⁵-C₈H₁₁)] are obtained by the isoprophyl Grignard synthesis of [Ir(COD)Cl]₂ (COD = η⁴-1,5-cyclooctadiene) in the presence of cycloheptatriene, and cyclooctatriene, respectively. The later reaction yields [IrH(COD)(δ⁴-1,3,6-C₈H₁₀)] as a by-product which, in contrast to other [IrH(η⁴-cyclodiene)₂] complexes, does not show H-addition-elimination equilibria. Reduction of [Ir(1,3-C₇H₁₀)₂Cl] with C₂H₅OH/Na₂CO₃ yields [Ir(η⁴-1,3-C₇H₁₀)](η⁵-C₇H₉)] which was characterized by X-ray analysis. [Ir(COD)Cl]₂ reacts with Na₂C₈H₈, and after hydrolysis unstable [Ir(COD)(η⁵-C₈H₉)] is formed which by protonation with HPF₆ is converted into the [Ir(COD)(η⁶-1,3,5-C₈H₁₀)]⁺ cation. All these compounds are fluxional in solution.     

Self-assembly, optical behavior, and permeability of a novel capsule based on an azo dye and polyelectrolytes

A novel capsule composed of an azo dye, Congo red (CR), and different polymers, including poly(styrenesulfonate, sodium salt) (PSS), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA), have been successfully fabricated by the layer-by-layer self-assembly technique. The stepwise linear deposition process was monitored by means of UV-visible absorption measurements. The formation of hollow capsules was verified by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). The resulting hollow PSS/PAH/CR/PDDA capsules displayed a sensitive response to visible light. Optical changes of the hollow capsules prior to and after the photoreaction were investigated in detail by means of UV-visible spectroscopy, CLSM, and SFM. It was found that the photochemical reaction of the assembled hollow capsules depends strongly on the matrix. Qualitative results on the permeability of the hollow capsule walls with CR as one component indicate that the permeability of the walls can be easily photo-controlled at varying irradiation time intervals without addition of external chemicals.     

Mössbauer and molecular orbital study of the myoglobin-CO complex

Experimental Mössbauer spectra of the Fe⁵⁷-enriched CO complex of sperm whale myoglobin (MbCO) at T= 4.2 K with and without applied magnetic field (H⊥γ) were measured to derive the sign of the electric field gradient (EFG), the quadrupole splitting ΔE _Q, and the isomer shift δ of the heme iron. We find a positive EFG, δE _Q = 0.363 mm/sec, and δ + 0.266 mm/sec. Molecular orbital calculations were carried out to obtain theoretical estimates of EFG and ΔE _Q for several steric arrangements of the CO ligand relative to the heme group. Our results are most consistent with the conclusion that the iron is situated in the heme plane, and that a bent geometry with a Fe-C-O angle of about 135 ° is more favorable than a more symmetric structure with a linear Fe-C-O geometry.     

Fabrication of superhydrophobic surfaces from binary colloidal assembly

In this work, superhydrophobic surfaces were derived from binary colloidal assemblies. CaCO(3)-loaded hydrogel spheres and silica or polystyrene ones were consecutively dip-coated on silicon wafers. The former assemblies were recruited as templates for the latter self-assembly. Due to the hydrophilicity difference between silicon wafers and CaCO(3)-loaded hydrogel spheres, the region selective localization of silica or polystyrene spheres leads to irregular binary structures with a hierarchical roughness. The subsequent modification with low surface energy molecules yields a superhydrophobic surface. The heating treatment may largely enhance the mechanical stability of the resulting binary structures, which allows regeneration of the surface superhydrophobicity, providing a good durability in practice.     

π-Olefin-iridium-komplexe : IV. Umsetzungen von chloro-dien-iridium-verbindungen mit lithiumorganylen

The complexes [(1,3-C₆H₈)₂IrR] and [(1,3-C₇H₁₀)₂IrR] (R = CH₃, C₆H₅) are obtained by reaction of the corresponding chloro compounds with RLi. Interaction of [Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) with CH₃Li in the presence of 1,3-cyclohexadiene or isoprene yields [(COD)(1,3-C₆H₈IrCH₃] and [(COD)(C₅H₈IrCH₃], respectively. The products of the reaction of chlorodicyclodieneiridium with n-C₄H₉Li depend on the ring size of the cyclodiene ligands; with 1,3-cyclohexadiene [(1,3-C₆H₈)₂IrH] is formed while with 1,3-cycloheptadiene [(1,3-C₇H₁₀)(C₇H₉)Ir] is obtained together with [(1,3-C₇H₁₀)₃Ir₂(μ-H)₂]. Chemical and spectroscopic properties of the new compounds are discussed.     

Negative dipole potentials of uncharged langmuir monolayers due to fluorination of the hydrophilic heads

The dipole potential, affecting the structure, functions, and interactions of biomembranes, lipid bilayers, and Langmuir monolayers, is positive toward the hydrocarbon moieties. We show that uncharged Langmuir monolayers of docosyl trifluoroethyl ether (DFEE) exhibit large negative dipole potentials, while the nonfluorinated docosyl ethyl ether (DEE) forms films with positive dipole potentials. Comparison of the Delta V values for these ethers with those of the previously studied(37-39) monolayers of trifluoroethyl ester (TFEB) and ethyl ester of behenic acid (EB) shows that the reversal of the sign of Delta V causes the same change Delta(Delta V) = -706 +/- 16 mV due to fluorination of heads. The Delta V values of both TFEB and EB films differ by -122 +/- 16 mV from those of DFEE and DEE monolayers, respectively, with the same density. Such quantitative coincidence points to a common mechanism of reversal of the sign of the dipole potential for the ether and ester films despite the different structure of their heads. The mechanical properties and phase behaviors of these monolayers show that both fluorinated heads are less hydrated, suggesting that the change of the sign of Delta V could, at least partially, be related to different hydration water structure. The same negative contribution of the carbonyl bond in both TFEB and EB films contrasts with the generally accepted positive contribution of the C(delta+)=O(delta-) bond in condensed Langmuir monolayers of fatty acids, their alcohol esters, glycerides, and phospholipids but concurs with the theoretical analysis of Delta V of stearic acid monolayers. Both results question the literature values of the molecular dipole moments of these substances calculated via summation of bonds and atomic group contributions. Mixed monolayers of DFEE and DEE show smooth monotonic variation of Delta V from +450 to -235 mV, indicating a way for adjustment of the sign and magnitude of the dipole potential at the membrane-water boundary and regulation of such membrane behaviors as binding and translocation rate of hydrophobic ions and ion-carriers, adsorption and penetration of amphiphilic peptides, polarization of hydration water, and short-range repulsion. The interaction of the hydrophobic ions tetraphenylboron TPhB- and tetraphenylphosphonium TPhP+ with DFEE and DEE monolayers qualitatively follows the theory of binding of such ions to lipid bilayers, but the shifts Delta(Delta V) from the values obtained on water are much smaller than those for DPPC monolayers. This difference seems to be due to the solid (polycrystalline) character of the DFEE and DEE films that hampers the penetration of TPhB- and TPhP+ in the monolayers and reduces the attractive interaction with the hydrophobic moiety. This conclusion orients the future synthesis of amphiphiles with fluorinated heads to those which could form liquid-expanded Langmuir monolayers.     

Formation of polyelectrolyte multilayer architectures with embedded DMPC studied in situ by neutron reflectometry

The coupling of lipid molecules to polymer components in a planar biomimetic model membrane made of a lipid bilayer (dimyristoylphosphatidylcholine) supported by polyelectrolyte multilayers is studied. The polyelectrolyte support was prepared by layer-by-layer deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly(sodium 4-styrenesulfonate) (PSS). Two polymer sample terminations were considered: positively charged (PAH-terminated) and negatively charged (PSS-terminated). Neutron reflectometry studies showed that, whereas positively charged samples did not favor the deposition of lipid, negatively charged samples allowed the deposition of a lipid bilayer with a thickness of approximately 5 nm. In the latter case, formation of polyelectrolyte layers after the deposition of the lipid layer was also possible.     

Amphiphilic dendritic copolymers of tert‐butyl‐glycidylether and glycidol as a nanocontainer for an anticancer ruthenium complex

Dendritic copolymers comprising a hydrophobic core and hydrophilic shell with nearly equal numbers of hydroxyl groups in the shell and different densities in the core were prepared by a multi‐step process based on anionic ring‐opening polymerization. The diversity in the core density was obtained by using copolymer stars with poly(tert‐butyl‐glycidylether)‐block‐polyglycidol arms with nearly equal length of hydrophobic blocks and numbers of hydroxyl groups of polyglycidol but different numbers of arms as macroinitiators. The ability of the dendritic copolymers to serve as a nanocontainer for a ruthenium complex Ru(NH₃)₃Cl₃ with anticancer properties was studied. The possibility of improving the water solubility of this poorly soluble drug by loading it onto dendritic copolymers was investigated. The hydroxyl groups of the dendritic copolymers were used for complexation of the ruthenium compound to the shell. The loading efficiency was analyzed by UV–vis spectroscopy. The dendritic nanoparticles in their hydrated state were visualized using cryo‐TEM. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3488–3497