Stepped light-induced transient measurements of photocurrent and voltage in dye-sensitized solar cells: application for highly viscous electrolyte systems

To measure electron diffusion coefficients (D) and electron lifetimes (tau) of dye-sensitized solar cells (DSC), we introduced stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV), which can simplify the optical setup and reduce measurement time in comparison to conventional time-of-flight and frequency-modulated measurements. The method was applied to investigate the influence of the viscosity of a thermally stable high-boiling-point solvent on the energy conversion efficiency of DSCs. By systematic study of the influence of the viscosity, the species of cations as the counter charge of I(-)/I(3)(-), and the concentrations of electrolytes, we concluded that a lower dye cation reduction rate due to slower iodine diffusion is a limiting factor for a highly viscous electrolyte system. On the other hand, comparable values of D and increased values of tau were observed in a highly viscous electrolyte. By employing 0.5 M TBAI and 0.05 M I(2) in propylene carbonate, the efficiency of the DSC became comparable to that of a DSC using conventional electrolytes consisting of LiI, imidazolium iodide, and 4-tert-butylpyridine in methoxyacetonitrile. The simultaneous evaluation of D and tau through the appropriately simple measurement realizes fast optimization of the efficient and reliable DSC composed of thermally stable but often viscous electrolytes.     

CO2‐Induced Spin‐State Switching at Room Temperature in a Monomeric Cobalt(II) Complex with the Porous Nature

CO₂‐responsive spin‐state conversion between high‐spin (HS) and low‐spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [Co^II(COO‐terpy)₂]?4 H₂O ( 1?4 H₂O ), stably formed cavities generated via π–π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1?4 H₂O transformed to solvent‐free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO₂ adsorption via a gate‐open type of the structural modification. Furthermore, the HS/LS transition temperature (T_1/2) was able to be tuned by the CO₂ pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO₂‐accomodated form 1?CO₂ (P =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO₂ accommodation, which provides reversible spin‐state conversion by introducing/evacuating CO₂ gas into/from 1 .     

Metal ion-promoted hydrolyses of ligand esters in the presence of polycarboxylates

Copper(II), nickel(II), cobalt(II), and zinc(II) accelerated the carboxylate-catalyzed hydrolyses of 2,4-dinitrophenyl isonicotinate (DNPI) and 2,4-dinitrophenyl picolinate (DNPP). The rate enhancement effect of the metal ions in the partially neutralized poly(methacrylic acid)- or poly(acrylic acid)-catalyzed hydrolysis of DNPI was greater than that in the monomeric acetate ion-catalyzed hydrolysis of this ester. This feature of the reactions was explained by the formation of a ternary complex composed of the polymer, the metal ion, and the substrate, in which the metal ion serves as a template for the nucleophilic reaction between the carboxylate groups along the polymer chain and the coordinated substrate. In DNPP the metal ion effect on the polycarboxylate-catalyzed hydrolysis was smaller than that on the acetate ion-catalyzed hydrolysis. This was interpreted as the result of differences in the structure of the complex.     

Analysis of Spatial Transfer Function by Using FDTD for Wireless Communication

Spatial transfer function for wide band wireless communication system is analyzed by using FDTD and DFT method. Ray-based method is not sufficiently accurate, when the size of objects on the propagating path is comparable to the wavelength. In our proposed method, the tranfser function can be obtained exactly by using the FDTD method. For the numerical examples, the transfer functions in an aperture of the waveguide are calculated by proposed procedure. Furthermore, experimental verification is made by using two-dimensional propagation system, which is constructed of copper plates, antennas and vector network analyzer. The proposed algorithm is valid for estimating of the spatial transfer function.     

Selective Ion Exchange in Supramolecular Channels in the Crystalline State

Artificial ion channels are of increasing interest because of potential applications in biomimetics, for example, for realizing selective ion permeability through the transport and/or exchange of selected ions. However, selective ion transport and/or exchange in the crystalline state is rare, and to the best of our knowledge, such a process has not been successfully combined with changes in the physical properties of a material. Herein, by soaking single crystals of Li₂([18]crown‐6)₃[Ni(dmit)₂]₂(H₂O)₄ ( 1 ) in an aqueous solution containing K⁺, we succeeded in complete ion exchange of the Li⁺ ions in 1 with K⁺ ions in the solution, while maintaining the crystalline state of the material. This ion exchange with K⁺ was selectively conducted even in mixed solutions containing K⁺ as well as Na⁺/Li⁺. Furthermore, remarkable changes in the physical properties of 1 resulted from the ion exchange. Our finding enables not only the realization of selective ion permeability but also the development of highly sensitive biosensors and futuristic ion exchange agents, for example.     

Synthesis of Hypervalent Iodine(III) Reagents Containing a Transferable (Diarylmethylene)amino Group and Their Use in the Oxidative Amination of Silyl Ketene Acetals

The preparation of some hypervalent iodine reagents containing a transferable amino group derived from benzophenone imine derivatives is reported. The reagents can be readily prepared and stored as a bench‐stable solid, and were successfully used in the transition‐metal‐free oxidative amination of silyl ketene acetals to afford the corresponding α‐amino esters, the benzophenone imine moieties of which could be easily hydrolyzed, thereby leading to the formation of primary amines.     

Synthesis of trifluoromethyl-group-containing cyclopentadienones by the palladium-catalyzed [2 + 2 + 1] cycloaddition of aryl- and trifluoromethyl-group substituted internal alkynes and carbon monoxide

We investigated the palladium-catalyzed [2?+?2?+?1] cycloaddition of aryl- and trifluoromethyl-group-substituted internal alkynes and carbon monoxide, and revealed that the PdBr₂ effectively catalyzed the intended reaction. The PdBr₂-catalyzed reaction smoothly proceeded and provided aryl- and trifluoromethyl-group-containing cyclopentadienone derivatives in up to 92% yield.     

A new and known cytotoxic aryltetralin-type lignans from stems of Bursera graveolens

A new 4alpha-aryltetralin-type lignan called burseranin (1) and a known analogous lignan picropolygamain (2) were isolated along with known triterpenes, lupeol and epi-lupeol from the methanol extract of stems of Bursera graveolens, which showed a remarkable inhibitory activity against human HT1080 fibrosarcoma cells. The whole structure of 1 was established based on combined spectral studies and the absolute structure for 2 was first confirmed by CD spectral evidence. In addition, cytotoxic activities of the stem (methanol) extract and its components are evaluated in this paper.