Ethylbenzene (EB) films prepared on cold metal substrates by vapor deposition in vacuum show a curious light scattering in the supercooled liquid (SCL) state when the temperature is raised at a constant rate. To investigate the cause of this phenomenon, we examined the behavior of similarly prepared samples of a series of alkylbenzenes. We found that the vapor-deposited glass of propylbenzene (PB) and isopropylbenzene (IPB) showed a deposition-temperature (T d ) dependence of the initial molar volume (V m ) on deposition similar to EB glass. Interestingly, the samples of the three compounds, which were formed initially as glasses with V m much larger than that of SCL at the same temperature, exhibited the curious light scattering when they transformed to SCL states after the temperature elevation to above their glass-transition temperature, while the corresponding samples with initial V m smaller than that of SCL did not exhibit this light scattering. On the basis of these observations, a hypothesis on the cause of the light scattering in the SCL state is proposed in relation to structural transformation between different SCL states. A microscopic mechanism of the formation of a high-density glass with V m smaller than that of SCL is briefly discussed by referring to the observations of toluene samples which showed a slightly different T d dependence of V m and did not show the curious light scattering in the SCL state.We have studied the structure and relaxation behavior of amorphous molecular systems prepared by vapor deposition on cold metal substrates. 16 The samples were films with a thickness of about 10¯m. Such amorphous samples usually tend to crystallize when they are annealed with temperature elevation. 16 However, vapor-deposited amorphous samples of certain compounds undergo a glass transition and transform into supercooled liquid (SCL) states by temperature elevation without experiencing crystalline states. 710 Similar phenomena have been known for a variety of bulk amorphous materials prepared by liquid quenching.1113 Such special amorphous states are called glasses by analogy with conventional glass. A common structural feature of these glass-forming molecular compounds is their flexibility which permits various intra-and intermolecular conformations and hinders crystallization.We found that glass samples of ethylbenzene (EB) and related alkylbenzenes could be prepared by vapor-deposition with good reproducibility. We studied the properties of these materials using laser light interference in film samples.14,15 One of the remarkable observations during these studies was that the density and relaxation behavior of the glass state systematically depended upon the vapor-deposition temperature (T d ). 15 Glass samples deposited at a T d much lower than the glass-transition temperature (T g ) had a lower density than that estimated for the SCL state at the same temperature. In this paper, we call such a glass "low-density glass" (LDG). In contrast, glass samples deposited at a T d close to T g sometim...

The photo-hydrogen-evolving activity (activity to enhance the photochemical EDTA-reduction of water into molecular hydrogen) was evaluated for three different Ru(II)Pt(II) dimers with a general formula of [(bpy)2Ru(micro-bridge)PtCl2]2+(bpy = 2,2'-bipyridine; bridge = 4,4'-bis(N-(3-aminopropyl)carbamoyl)-2,2'-bipyridine (L1), 2,3-bis(2-pyridyl)pyrazine (L2), and 4,4'-bis(N-(4-pyridyl)methylcarbamoyl)-2,2'-bipyridine (L3); EDTA = ethylenediaminetetraacetic acid disodium salt). A new Ru(II)Pt(II) complex, [(bpy)2Ru(micro-L3)PtCl2]2+, was synthesized and characterized. It was confirmed that all three compounds are ineffective towards photochemical H2 production. In each case, an acetate-buffer solution (pH = 5) containing the Ru(II)Pt(II) dimer and EDTA was photolysed using a 350-W Xe lamp under an Ar atmosphere, during which the amount of H2 evolved was analysed by gas chromatography. Additional photolysis experiments were carried out by adding [Ru(bpy)3]2+ and methylviologen (N,N'-dimethyl-4,4'-bipyridinium) to the photolysis solutions described above to test the H2-evolving activity of the Pt(II) unit involved in these Ru(II)Pt(II) dimers. As a result, the Pt(II) units involved in the L1 and L2 compounds were found to be active as an H2-evolving catalyst, while that of the L3 compound was found to show no activity at all. The extent of intramolecular electron-transfer quenching from the 3MLCT excited state of the [Ru(bpy)3]2+ derivative to the tethering Pt(II) catalyst centre was investigated by comparison of the luminescence spectra of these compounds, together with the related compounds. The results showed that the quenching of the 3MLCT luminescence is not at all enhanced in either the L1 or the L3 compounds. On the other hand, the L2 compound is strongly quenched as previously reported. In addition to the above studies, the H2-evolving activity of some Pt(II) monomers, cis-PtCl2(NH3)2, PtCl2(en)(en = ethylenediamine), cis-PtCl2(4-methylpyridine)2, PtCl2(2,2'-bipyrimidine), PtCl2(4,4'-dicarboxy-2,2'-bipyridine), and [PtCl(terpy)]+(terpy = 2,2':6',2''-terpyridine), were similarly investigated in the presence of EDTA, [Ru(bpy)3]2+ and methylviologen, since they were regarded as structural analogues of the Pt(II) units involved in the L1-L3 compounds. The compounds having a cis-Pt(II)Cl2 unit were generally found to show high H2-evolving activity. This was interpreted in terms of the ligation of negatively charged chloride anions leading to the destabilization of the Pt(II) dz2 orbital responsible for the hydrogenic activation. Importantly, cis-PtCl2(4-methylpyridine)2 exhibited relatively high activity as an H2-evolving catalyst, suggesting the importance of the flexible rotation of the pyridyl ligands for efficient hydrogenic activation at the axial site of the Pt(II) ion. The DFT calculations also showed the validity of the structure-activity relationship discussed above for the L3 compound.

Polyelectrolyte gels comprising fixed ions exhibit swelling behaviors because of external solution conditions. Such behaviors are usually explained by using the Flory–Rehner model that considers the Donnan equilibrium. However, this model assumes a homogeneous distribution for fixed ions; therefore, its applicability to the case of heterogeneous distributions remains unclear. Here, we successfully designed a hydrogel with alternating neutral/highly charged sequences (i.e., tetrapoly­(acrylic acid)–poly­(ethylene glycol) gel). The Flory–Rehner model with the Donnan equilibrium was found to predict the swelling ratio only below pH 5.6. The distance between two neighboring fixed ions is larger than the Bjerrum length. The swelling behaviors above pH 5.6, where the fixed ions are more closely located than the Bjerrum length, can be explained by considering additionally the counterion condensation in the poly­(acrylic acid) units. These results indicate that the ionic interactions within the length scale of the network strand can determine the counterion condensation and that it is vital to estimate accurately the distance between neighboring fixed ions for predicting the swelling behaviors of polyelectrolyte gels.

Rhodium-catalyzed direct coupling of benzothioamides with alkenes proceeds smoothly involving ortho-CH bond cleavage. The thioamides also couple with alkynes under similar conditions accompanied by desulfurization and CN bond cleavage to produce indenone derivatives.The direct coupling of aromatic substrates with alkenes and alkynes involving CH bond cleavage provides atom-and stepeconomical routes for synthesizing π-conjugated molecules.

The Mount Sakurajima volcano in Kyushu, Japan, is proximal to a large residential area, and it emits an enormous amount of volcanic ash during frequent eruptions. In our previous study, we investigated, for the first time, respiratory effects of chronic exposure to volcanic ash. The study demonstrated a low prevalence of respiratory symptoms, even in the area of highest exposure; only a slight excess prevalence of symptoms appeared to be associated with exposure to volcanic ash. To confirm the findings of our previous study, the prevalence study of chronic respiratory symptoms for residents was repeated in Kanoya and Tashiro, which are located 25 and 50 km, respectively, from the crater of Mt. Sakurajima. The concentration of suspended particulate matter in Kanoya frequently exceeded the national environmental quality standards and, during summer and winter, was 2-3 times higher than that found in Tashiro. Women who were 30-59 y of age and who had resided in Kanoya or Tashiro for more than 3 y completed a modified ATS-DLD questionnaire. The prevalence of nonspecific respiratory disease was low, i.e., 6.5% in Kanoya and 6.2% in Tashiro; similar prevalences were found in women who had never smoked. When we restricted the analysis to individuals without a history of occupational exposure to dusts and who had no exposure to passive smoking, there was a slightly higher prevalence of nonspecific respiratory disease in Kanoya than Tashiro, but the difference was not significant. Eye symptoms were equally prevalent in the two areas.(ABSTRACT TRUNCATED AT 250 WORDS)