Photocatalytic CO2 reduction sensitized by a special-pair mimic porphyrin connected with a rhenium(i) tricarbonyl complex

Zn porphyrins with an imidazolyl group at the meso position generate a highly stable porphyrin dimer by complementary coordination from the imidazolyl to the Zn ion in noncoordinating solvents such as chloroform, which mimics the natural special pair in photosynthesis. In this work, we have synthesized an imidazolyl-substituted Zn porphyrin connected with a Re 2,2-bipyridine tricarbonyl complex as a CO₂ reduction catalyst via a p-phenylene linker, affording a homodimer with two Re complexes on both sides (ReDRe). The dimeric structure is easily dissociated into the corresponding monomers in coordinating solvents. Therefore, we prepared a mixture containing a heterodimer with the Re carbonyl complex on one side (ReD) by simple mixing with an imidazolyl Zn porphyrin and evaporating the solvent. Using the Grubbs catalyst, the subsequent olefin metathesis reaction of the mixture gave covalently linked porphyrin dimers through the allyloxy side chains, enabling the isolation of the stable hetero- (ReD′) and homo-dimers (ReD′Re) with gel permeation chromatography. The Zn porphyrin dimers have intense absorption bands in the visible light region and acted as good photosensitizers in photocatalytic CO₂ reduction in a mixture of N,N-dimethylacetamide and triethanolamine (5 : 1 v/v) containing 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as the electron donor, giving CO with high selectivity and durability. Under irradiation with strong light intensity, the reaction rate in ReD′ exceeded that of the previous porphyrin Re complex dyad, ZnP-phen=Re. For instance, after irradiation at 560 nm for 18 h, the turnover number (TON_CO) of ReD′ reached 2800, whereas the TON_CO of ZnP-phen=Re was 170. The high activity in the system using the porphyrin dimer originates from no accumulation of the one-electron reduced species of the porphyrin that inhibit light absorption due to the inner-filter effect.

An artificial special pair was connected with a Re 2,2-bipyridine tricarbonyl complex. The special pair derivative acted as a good photosensitizer in photocatalytic CO₂ reduction, giving CO with high selectivity and durability.     

Improved accuracy of determination of dissolved silicate in seawater using absorption spectrometry

We studied to develop a certified reference material of seawater for nutrient analysis whose relative combined standard uncertainty for dissolved silicate was <0.5 %. In order to precisely measure the content of dissolved silicate in seawater, widely used absorption spectrometry with the so-called molybdenum blue was investigated as one of the highly sensitive determination methods. For the absorption spectrometry, a batch mode and a continuous flow analysis (CFA) mode were used and the characteristics of the calibration curves in the both modes were examined in detail. The calibration curve in the batch mode could be explained by a first-order regression line, whereas that in the CFA mode fitted to a second-order regression line. Therefore, for measuring the silicate content of seawater whose matrix depends on its origin, a standard addition method in a batch mode is preferable, though strict control of the compositions of the solutions for the standard addition calibration curve are greatly important for getting good linearity of the curve. In addition, in the case of the standard addition method, it is important to measure the blank value including the background; in the present study, the origins related to the blank were discussed and evaluated. The relative combined standard uncertainty of 0.48 % could be achieved for the measurement of content of 28 μmol/kg silicate in seawater, providing that the volume ratio between each of the molybdenum blue colorimetric reagents and the seawater was kept constant among all the solutions for the standard addition calibration curve. The procedure was validated using artificial seawater with a known concentration of silicate. Such highly improved precision and trueness which reaches the recent target of the community related to analysis of nutrients in seawater is reported for the first time. The developed procedure will provide a good way of validation for the analysts who need measurement with high precision and trueness on the content of silicate in seawater and other samples.     

W ± boson pair production ine + e − process

I discuss the determination ofW ^± boson mass by the total cross-section ofe ⁺ e ^?→W⁺W^? process and its relation to tests of the electroweak higher order effects. In order to get rid of the confusion in recent theoretical arguments on this subjects, I arrange and clarify how to develop analysis once the corresponding experimental data become available.     

Single molecular observation of penta- and hexagonic assembly of bisporphyrin on a gold surface

Artificial light-harvesting antennae of coordination-organized macrocyclic porphyrin pentamer and hexamer are visualized by high resolution scanning tunneling microscopy (HRSTM) on a gold surface.     

Scalable Electrochemical Decarboxylative Olefination Driven by Alternating Polarity**

A mild, scalable (kg) metal-free electrochemical decarboxylation of alkyl carboxylic acids to olefins is disclosed. Numerous applications are presented wherein this transformation can simplify alkene synthesis and provide alternative synthetic access to valuable olefins from simple carboxylic acid feedstocks. This robust method relies on alternating polarity to maintain the quality of the electrode surface and local pH, providing a deeper understanding of the Hofer-Moest process with unprecedented chemoselectivity.     

Facile palladium(0)-catalyzed ring expansion reactions of hydroxy methoxyallenyl cyclic compounds via hydropalladation

Palladium(0)-catalyzed one-atom ring expansion of various hydroxy methoxyallenyl compounds has been achieved in excellent yields without the use of aryl halides. Hydroxy methoxyallenylisoindolinones, -indanones, and -phthalans have been readily converted to the corresponding isoquinolones, naphthoquinones, and isochromanones in the presence of P(o-tolyl)(3).     

Synthesis of N-substituted cyclic triglycines and their response to metal ions

N,N^′,N^″-Trisubstituted-cyclo-triglycines were synthesized. The major conformation of these compounds has C₃ symmetry, and the carbonyl groups and substituents on the nitrogen are inclined in the same direction. Their response to various metal ions was estimated by constructing ion-selective electrodes. Two of them responded selectively to Ca²⁺ over other cations, demonstrating that N,N^′,N^″-trisubstituted-cyclo-triglycines provide a new scaffold to act as host molecules.