Photon-, electron-, and proton-induced isomerization behavior of ferrocenylazobenzenes

3-, 4-, and 2-ferrocenylazobenzenes, 1, 2, and 3, respectively, and several derivatives of 1 were synthesized, and their photoisomerization behaviors were examined. The molecular structures of 1 and its derivatives, 2-chloro-5-ferrocenylazobenzene (5) and 3-ferrocenyl-4'-hydroxylazobenzene (11), were determined by X-ray diffraction analysis. 3-Ferrocenyl compound 1 undergoes reversible trans-to-cis isomerization with a single green light source and the Fe(III)/Fe(II) redox change. 4- and 2-Ferrocenyl compounds, 2 and 3, also respond to green light in addition to UV light, exciting the pi-pi* transition, but the cis molar ratio in the photostationary state (PSS) is lower than that of 1. The response to green light in 2 and 3 is caused by the MLCT (from Fe d orbital to azo pi* orbital) band excitation, while the character of the MLCT band, as estimated by time-dependent density functional theory calculations, differs between 1 and 2. The oxidized form of 2 undergoes facile cis-to-trans thermal isomerization. Both 1 and 2 undergo facile protonation and show proton-catalyzed cis-to-trans isomerization. Among the derivatives of 1, 2-chloro-5-ferrocenylazobenzene (5) exhibits the highest cis molar ratio (47%) in the PSS of green light irradiation.     

Open spaces and molecular motions of acrylic epoxy-based network polymers probed by positron annihilation

Lifetime spectra of positrons have been measured for acrylic epoxy-based network polymers. For the specimens with the different permeability coefficients to water vapor C_p, the lifetime of ortho-positronium (o-Ps) τ₃ increased with increasing C_p. This fact suggests that the permeability increases with an increase in the size of open spaces. From measurements of temperature dependencies of τ₃ and the intensity of o-Ps, three onset temperatures for the change in the temperature gradient of these parameters were determined. The highest onset temperature (T_α = 300–325 K) was identified to be the glass transition temperature, and others (T_γ = 90–180 K and T_β = 160–205 K) were associated with the onset temperatures for limited local motions of molecules; those molecular motions were found to be affected by both the number of crosslinks and the presence of free side chains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2875–2880, 1999     

Ab initio calculations of lower resonant states of two-electron systems

The complex scaling and the stabilization methods are applied to calculating the parameters of the lowest resonance states of He and Li⁺. The results obtained by both methods are in a good agreement with the published data. It is shown that the wave functions constructed using the restricted configuration interaction approximation provide fairly accurate estimates of the resonance parameters. The possibility of using the stabilization method for calculating the phase shift function is also discussed.     

Reactions C<Subscript>2</Subscript>H<Subscript>2</Subscript> + OH and C<Subscript>2</Subscript> + H<Subscript>2</Subscript>O: Ab initio study of the potential energy surfaces

The stationary points of the potential energy surfaces for the reactions C₂H₂ + OH and C₂ + H₂O are calculated using density functional theory and the coupled cluster method. The relative energies and geometric parameters of the stable intermediates and transition states are in good agreement with the results of independent studies. In most cases, the relative energies differ from the earlier published values by no more than 3 kcal/mol, whereas the rotational constants, by 1–2%. The mechanism of the reaction CCOH₂ → C₂ + H₂O is studied in detail. The possible sources of errors in the calculation methods are examined.     

A Nonaromatic Thiophene‐Fused Heptalene and Its Aromatic Dianion

Heptalene, a nonaromatic, bicyclic 12 π‐electron system with a twisted structure, is of great interest with regard to its potential Hückel aromaticity in the two‐electron oxidized or reduced forms. The synthesis of thiophene‐fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4 , and its solid‐state structure, which was confirmed by X‐ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)⁺]₂ 5 ^2?. The X‐ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5 . ¹H NMR spectroscopy exposed the effect of a diamagnetic ring current on dianion 5 ^2?, which was corroborated by nucleus‐independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 π‐electrons, does indeed exhibit pronounced degrees of Hückel aromaticity.     

Preparation of cross-linked poly[(epsilon-caprolactone)-co-lactide] and biocompatibility studies for tissue engineering materials

In this study, cross-linked materials were prepared using the branched macromonomer with different CL/LA molar ratios, and feasibility studies for tissue engineering were carried out. The thermal and mechanical properties of these materials depended on the CL/LA compositions; however, there was no change in the wettability of each material. The HeLa cells adhesion and growth on the CL-LA7030c were equal to that on the commercially available polystyrene dish. The protein absorption experiment using the FBS proteins revealed that the materials with well-grown cells showed better adhesion of the proteins. [photo: see text]     

Correlation‐free reflection diagnostics of graphene‐like surface layers in the infrared region

New diagnostics possibilities for graphene‐like (two‐dimensional absorbing) ultrathin films on dielectric substrates by integrating ellipsometric and reflectance measurements are analyzed. The analysis is based on the analytical theory which has been developed in the framework of a long‐wavelength approximation. Importantly, the new method allows simultaneously (without correlation) to determine the thickness and optical constants of two‐dimensional materials in the infrared region. Another interesting feature of this reflection technique lies in the fact that for data handling the traditional model‐based regression analysis is not in use. The inversion problem is resolved on the basis of an analytical approach which has no need of initial guesses for the desired parameters. The results are also of interest as suitable starting points for non‐approximated numerical iterative methods where the proper choice of the initial data plays a crucial role. The presented method is tested using a numerical simulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Interactions of Tetrakis(4-sulfonatophenyl)porphyrin with γ-Cyclodextrin and Alkyltrimethylammonium Bromides in Aqueous Solutions

Tetrakis(4-sulfonatophenyl)porphyrin (TSPP) forms complexes with octyltrimethylammonium bromide (OTMA) and hexyltrimethylammonium bromide (HTMA) in pH 7.3 buffers. At low concentrations of OTMA (HTMA), a 1:1 TSPP–OTMA complex is formed. As the OTMA (HTMA) concentration is increased, a 1:2 TSPP–OTMA (HTMA) complex is also formed. The equilibrium constants for the formation of the TSPP–OTMA (HTMA) complexes have been evaluated from a simulation of the observed fluorescence intensity data. In the induced circular dichroism spectrum, the signal intensity of TSPP in aqueous solutions containing both γ-CD and OTMA has been similar to that containing only γ-CD, suggesting the formation of the 1:1:1 γ-CD–TSPP–OTMA (HTMA) inclusion complex. Capillary electrophoretic study has exhibited the formation of the 1:1 TSPP–OTMA (HTMA) complex, although the 1:2 TSPP–OTMA (HTMA) complex could not be observed, probably because the OTMA (HTMA) concentration used was low. The equilibrium constants for these 1:1 complexes have been evaluated from the variation in the electrophoretic mobility. The equilibrium constant for the formation of the 1:1:1 γ-CD–TSPP–OTMA or γ-CD–TSPP–HTMA complex has been evaluated from a simulation of the electrophoretic mobility change in TSPP solution containing γ-CD and OTMA or HTMA, although the equilibrium constants for the ternary inclusion complexes could not be evaluated using the fluorescence method due to the small fluorescence intensity change.