Freeze-fracture electron microscopic and calorimetric studies on microscopic states of surface-modified liposomes with poly(ethylene glycol) chains

The differential scanning calorimetry (DSC) and the freeze-fracture electron microscopy of dipalmitoyl phosphatidylcholine (DPPC) liposomes containing distearoyl-N-monomethoxy poly(ethylene glycol)-succinyl-phosphatidylethanolamines (PEG-DSPE) were carried out. The DSC peak of DPPC liposomes containing PEG-DSPE had a shoulder. The main phase transition temperature of DPPC bilayer membranes containing PEG-DSPE whose molecular weight of PEG is less than 3000 was slightly shifted to a higher temperature, while that containing PEG-DSPE whose molecular weight of PEG is more than 5000 was slightly shifted to a lower temperature. The electron micrographs of freeze-fracture replicas of DPPC liposomes containing PEG-DSPE quenched from 37±2°C exhibited banded and planar textures, suggesting the lateral phase separation in the bilayer membranes.     

2,3,3a,4,9,9a‐Hexahydro‐9‐phenylbenzo[f]indene derivatives

The title compounds, 3a,9a‐trans‐9,9a‐trans‐4,4‐di­methyl‐9‐phenyl‐2,3,3a,4,9,9a‐hexa­hydro­benzo­[f]­indene, C₂₁H₂₄, (I), and 3a,4‐trans‐3a,9a‐cis‐9,9a‐trans‐4‐methoxy‐9‐phenyl‐2,3,3a,4,9,9a‐hexa­hydro­benzo­[f]­indene, C₂₀H₂₂O, (II), are products of the photoinduced electron‐transfer reaction of 1,1‐di­phenyl‐1,n‐alka­dienes. The molecular structures are in good agreement with those proposed from the reaction mechanisms. The central rings of the fused systems of both compounds take chair and boat conformations in (I) and (II), respectively. There are no remarkable short contacts shorter than the sum of the van der Waals radii in the crystals, but some weak C—H?π interactions are found.     

Simultaneous Measurement of Refractive Index and Thickness by Low Coherence Interferometry Considering Chromatic Dispersion of Index

Low coherence interferometry can provide simultaneous measurement of refractive index n and thickness t of a transparent plate, as reported recently by some research groups. Precise measurement of n and t is impossible unless chromatic dispersion of index is taken into account. We then proposed and demonstrated a unique technique for simultaneous measurement of phase index n_p, group index n_g and thickness t using a special sample holder. This paper describes a novel technique for simultaneous measurement of n_p, n_g and t using an approximate expression of the chromatic dispersion in terms of n_p. The approximate expression of chromatic dispersion does not require use of the special sample holder, and n_p, n_g and t are determined from two measurable quantities with an accuracy of 0.3% or less, for the sample thickness was around 1 mm. In addition, it is possible to shorten the measurement time compared with the above method.     

Near- and Mid-Infrared Spectroscopy of Sol-Gel Derived Ormosil Films for Photonics from Tetramethoxysilane and Trimethoxysilylpropylmethacrylate

Ormosil dipped thin films and cast films were prepared using tetramethoxysilane and trimethoxysilylpropylmethacrylate (TMSPM). Structural changes during thermally induced polymerisation of the organic groups were investigated using near- and mid-infrared (IR) spectroscopy. IR spectra of the ormosil dipped thin films, dried at 60°C, have shown that further heat-treatment of the films at 160°C leads to the free radical polymerisation of C=C bonds in TMSPM. In the mid-infrared spectra, the intensity of the band at around 3500 cm^–1, due to O–H bonds, increased with the progress of polymerisation of vinyl groups. Near-infrared spectra of the cast films showed that this increase in intensity of the O–H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. We suggest that optical loss measurements must be made in a dry atmosphere or, with a cover coating to protect the ormosil from adsorption of water, to reduce this source of optical loss for waveguides based on TMSPM.     

Preparation and characterization of ruthenium(II), rhodium(III) and iridium(III) complexes of isocyanide bearing the azo group

Reactions of [(η⁶-arene)RuCl₂]₂ (1) (η⁶-arene=p-cymene (1a), 1,3,5-Me₃C₆H₃ (1b), 1,2,3-Me₃C₆H₃ (1c) 1,2,3,4-Me₄C₆H₂(1d), 1,2,3,5-Me₄C₆H₂ (1e) and C₆Me₆ (1f)) or [Cp*MCl₂]₂ (M=Rh (2), Ir (3); Cp*=C₅Me₅) with 4-isocyanoazobenzene (RNC) and 4,4′-diisocyanoazobenzene (CN–R–NC) gave mononuclear and dinuclear complexes, [(η⁶-arene)Ru(CNC₆H₄N=NC₆H₅)Cl₂] (4a–f), [Cp*M(CNC₆H₄N=NC₆H₅)Cl₂] (5: M=Rh; 6: M=Ir)_, [{(η⁶-arene)RuCl₂}₂{μ-CNC₆H₄N=NC₆H₄NC}] (8a–f) and [(Cp*MCl₂)₂(μ-CNC₆H₄N=NC₆H₄NC)}] (9: M=Rh; 10: M=Ir)_, respectively. It was confirmed by X-ray analyses of 4a and 5 that these complexes have trans-forms for the ---N=N--- moieties. Reaction of [Cp*Rh(dppf)(MeCN)](PF₆)₂ (dppf=1,1′-bis (diphenylphosphino)ferrocene) with 4-isocyanoazobenzene gave [Cp*Rh(dppf)(CNC₆H₄N=NC₆H₅)](PF₆)₂ (7), confirmed by X-ray analysis. Complex 8b reacted with Ag(CF₃SO₃), giving a rectangular tetranuclear complex 11b, [{(η⁶-1,3,5-Me₃C₆H₃)Ru(μ-Cl}₄(μ-CNC₆H₄N=NC₆H₄NC)₂](CF₃SO₃)₄ bridged by four Cl atoms and two μ-diisocyanoazobenzene ligands. Photochemical reactions of the ruthenium complexes (4 and 8) led to the decomposition of the complexes, whereas those of 5, 7, 9 and 10 underwent a trans-to-cis isomerization. In the electrochemical reactions the reductive waves about −1.50 V for 4 and −1.44 V for 8 are due to the reduction of azo group, [---N=N---]→[---N=N---]²⁻. The irreversible oxidative waves at ca. 0.87 V for the 4 and at ca. 0.85 V for 8 came from the oxidation of Ru(II)→Ru(III).     

Electrical properties of perovskite-type La(Cr1−xMnx)O3+δ

Perovskite-type La(Cr_1−xMn_x)O_3+δ (0.0x1.0) was synthesized using a sol–gel process. The crystal structure of La(Cr_1−xMn_x)O_3+δ changes from orthorhombic to rhombohedral at x=0.6. The Mn⁴⁺ ion content increases monotonically in the range 0.2x1.0. The magnetic measurement of La(Cr_1−xMn_x)O_3+δ indicates that a Mn³⁺ ion is a high-spin state with (d)³(dγ)¹. The variation of the average (Cr, Mn)-O distance is explained by ionic radii of the Cr³⁺, the Mn³⁺, the Mn⁴⁺ ions. Since the log σT–1/T curve is linear and the Seebeck coefficient (α) is independent of temperature, it is considered that La(Cr_1−xMn_x)O_3+δ is a p-type semiconductor and exhibits the hopping conductivity.     

The First Conjugated Allene Polymer

A novel conjugated polymer with allene moieties in the polymer main chain, poly(4,4′‐biphenylylene‐1,3‐diphenylpropadien‐1,3‐ylene), was synthesized from 1,3‐bis(4‐bromophenyl)‐1,3‐diphenylpropadiene by dehalogenative polycondensation using Ni(cod)₂. The polymer shows good solubility in common organic solvents, good processability for making thin films, intense blue fluorescence in solution and acid sensitivity resulting in coloration. The conductivity increased by an order of 10⁴ upon exposure to trifluoroacetic acid vapor.     

Characterization and Reactivity of a Tetrahedral Copper(II) Alkylperoxido Complex

A tetrahedral Cu^II alkylperoxido complex [Cu^II(TMG₃tach)(OOCm)]⁺ ( 1^OOCm ) (TMG₃tach={2,2′,2′′-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1^OOCm in acetonitrile (MeCN) indicates that the reaction involves O−O bond homolytic cleavage of the peroxide moiety with concomitant C−H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O−O bond homolysis leads to C−H activation of the substrate. Furthermore, the reaction of 1^OOCm with 2,6-di-tert-butylphenol derivatives produces the corresponding phenoxyl radical species (ArO^.) together with a Cu^I complex through a concerted proton-electron transfer (CPET) mechanism. Details of the reaction mechanisms are explored by DFT calculations.     

A Synthetic Chlorophyll Dimer Appending Fullerene: Effect of Chlorophyll Pairing on (Photo)redox Properties

Accurately mimicking structure and function of natural chlorophyll (Chl) assemblies is very challenging. Herein, we report the synthesis of a fullerene-appended Chl dimer being capable of intramolecular photoinduced charge separation (CS) with a unique structure reminiscent of reaction centers (RCs) in phototrophs. Structural analyses revealed that the Chl dimer adopts a bird-like structure in which two Chl components overlapped partially with one of the four pyrrole rings in a Chl ring similar to in a Chl pair in the natural RC complexes. A comparative study including voltammetry and spectrometric analyses using the Chl dimer and its corresponding monomer with and without a fullerene moiety was performed to gain insight into the effect of Chl pairing on (photo)redox properties. Our results suggest that the present dimer motif that closely resemble the Chl pair in natural RCs lead to more facile oxidation and lower energy of the CS state of the Chl dimer than those of the Chl monomer, resulting in its photoredox behavior different from that of the monomer Chl.