Time-resolved EPR study of the photoreduction of phthalic anhydride and chlorinated phthalic anhydrides in 2-propanol

The photoreduction of phthalic anhydride (PA), 3,6-dichlorophthalic anhydride (3,6-DCPA), 4,5-dichlorophthalic anhydride (4,5-DCPA) and tetrachlorophthalic anhydride (TCPA) in 2-propanol has been studied with time-resolved electron paramagnetic resonance. The chemically induced dynamic electron polarization spectra show that the reaction takes place through the excited triplet states. From PA, cyclohexadienyl-type hydrogen adduct and ketyl radicals were observed, whereas 3,6-DCPA produced the 3,6-DCPA anion and hydrogen adduct radicals. With 4,5-DCPA only the anion radical appeared, whilst the TCPA system showed no apparent anion and adduct radical formation. These data show that the hydrogen adduct formation occurs at the 4 position in the benzene ring, but that 4,5-DCPA and TCPA do not undergo this reaction. The anion radicals of PAs are formed in subsequent deprotonation reactions of the ketyl radicals. We propose that the hydrogen adduct radical formation in PA and 3,6-DCPA takes place through direct hydrogen abstraction by the excited triplet molecules, in competition with similar abstraction by the carbonyl group to form the ketyls.     

Phase behaviour of the thermotropic cubic mesogen 1,2-bis(4-n-decyloxybenzoyl)hydrazine under pressure

The phase transition behaviour of an optically isotropic, thermotropic cubic mesogen 1,2-bis(4-n-decyloxybenzoyl)hydrazine, BABH(10), was investigated under pressures up to 300 MPa using a high pressure differential thermal analyser, a wide angle X-ray diffractometer and a polarizing optical microscope (POM) equipped with a high pressure optical cell. The reversible change in structure and optical texture between the cubic (Cub) and smectic C (SmC) phases was associated with a change from a spot-like X-ray pattern and dark field for the Cub phase to the Debye-Sherrer ring pattern and sand-like texture for the SmC phase under both isobaric and isothermal conditions. The Cub phase was found to disappear at pressures above about 11 MPa. The phase transition sequence, low temperature crystal (Cr₃)-intermediate temperature crystal (Cr₂)-high temperature crystal (Cr₁)-Cub-SmC-isotropic liquid (I) observed at atmospheric pressure, is maintained in the low pressure region below 10 MPa. The transition sequence changes to Cr₃-Cr₂-(Cr₁)-SmC-I in the high pressure region. Since the Cub-SmC transition line determined by POM has a negative slope (dT/dP) in the T-P phase diagram, a triple point is estimated approximately at 10-11 MPa, and 143-145°C for the SmC, Cub and Cr₁ phases, giving the upper limit of pressure for the observation of the cubic phase.     

In situ observation of the pressure-induced mesophase for 4'-n-hexadecyloxy-3'-nitrobiphenyl-4-carboxylic acid

In situ observation of the optical texture, and X-ray patterns of the pressure-induced mesophase seen for 4'-n-hexadecyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-16) was performed under hydrostatic pressures up to 100MPa using a polarizing optical microscope equipped with a high pressure hot stage and a wide angle X-ray diffractometer equipped with a high pressure vessel respectively. It was found that the pressure-induced mesophase (hereafter refered to as 'X') appeared at pressures above 60 MPa, and exhibits a birefringent broken-fan or a sand-like texture that remain unaltered in the SmC phase. The POM-transmitted light intensity curve measured on heating clearly showed the Cr₄ →Cr₁ →SmC →'X' →SmA →I transition sequence at 80 MPa. The optical texture and the POM-transmitted light intensity measured during a pressure cycle at 185°C showed a reversible change between the cubic and 'X' phases. The WAXD pattern of the 'X' phase showed a spot-like pattern, suggesting no layered structure for this phase, and also revealed a substantial decrease in the d-spacing of the low angle reflection at 80 and 100 MPa, compared with the d-spacings of the (0 0 1) reflection of the SmC phase and also the (2 1 1) reflection of the cubic phase. It is concluded from these data that the 'X' phase is a birefringent hexagonal columnar phase.     

Cyclization of methacrylate–functional silane on particulate clay

Physically absorbed γ-methacryloxypropyltrimethoxysilane (γ-MPS) deposited from aqueous alcohol on particulate clay exists as low-molecular-weight cyclic, caged polysilsesquioxanes. These structures are incapable of forming high-molecular-weight chains or networks because of this internal cyclization tendency. The behavior is extremely different from that found in bulk solutions or when organofunctional silanes are adsorbed on low-surface-area glass or metal substrates. Fourier-transform infrared spectroscopy and gel permeation chromatography were used to characterize the silane species deposited in bulk and on the surface of particulate clay. The cyclization tendency is postulated from analysis of the behavior of hydrolyzed γ-methacryloxypropyltrimethoxysilane upon cocondensation with other organofunctional silanes and under variable cure conditions.     

Self-sorting self-complementary assemblies of π-conjugated acyclic anion receptors

Pyrrole-based π-conjugated anion-responsive molecules bearing an anionic moiety form self-complementary dimers, which exhibit self-sorting behaviours depending on the substituted positions of anionic sites.     

Photocatalytic water splitting using semiconductor particles: History and recent developments

Overall water splitting to produce H₂ and O₂ over a semiconductor photocatalyst using solar energy is a promising process for the large-scale production of clean, recyclable H₂. Numerous attempts have been made to develop photocatalysts that function under visible-light irradiation to efficiently utilize solar energy. In general, overall water splitting over a photocatalyst particle can be achieved by modifying the photocatalyst with a suitable cocatalyst to provide an active redox site. Therefore, the development of active photocatalytic materials has relied on both photocatalysts and cocatalysts. This review article describes the historical development of water-splitting photocatalysts.     

Water-supported organized structures based on wedge-shaped amphiphilic derivatives of dipyrrolyldiketone boron complexes

Wedge-shaped amphiphilic derivatives of 1,3-dipyrrolyl-1,3-propanedione boron complexes, with one or no aliphatic chains attached at one aryl moiety and three hydrophilic chains at the other, exhibited formation of assembled structures in aqueous solutions. UV/vis, fluorescence and DLS analyses suggested that the wedge-shaped amphiphiles exist in assembled modes in the solution state, and TEM measurements revealed that a balance of hydrophobic and hydrophilic moieties in the amphiphiles is crucial for the formation of organized structures in aqueous solutions as evidenced by the formation of spherical and cylindrical micelles.     

AgSbF6-promoted cycloaddition reaction of 2-trifluoromethyl-N-tosylaziridine with aldehydes

2-Trifluoromethyl-N-tosylaziridine reacted with various aldehydes in the presence of a catalytic amount of AgSbF(6) to provide the corresponding cis-4-trifluoromethyl-2-substituted-N-tosyl-1,3-oxazolidines with excellent regio- and stereoselectivity.     

Regioselective cycloaddition of La2@I(h)-C80 with tetracyanoethylene oxide: formation of an endohedral dimetallofullerene adduct featuring enhanced electron-accepting character

We describe the regioselective cycloaddition of La(2)@I(h)-C(80) with tetracyanoethylene oxide (TCNEO), which enabled the formation of the corresponding adduct having a tetracyanotetrahydrofuran moiety. X-ray crystallographic analysis revealed that the cycloaddition took place as a [5,6] addition. Along with dynamic swing motion of the metal atoms, the results of this electrochemical study demonstrate that TCNEO addition enhanced the electron-accepting character of La(2)@I(h)-C(80) and that the first reduction potential of the adduct reached -0.21 V versus the ferrocene/ferrocenium couple, which is the lowest value reported for endohedral metallofullerenes and their derivatives to date.