Yoshihiro Matano

Nanostructured artificial photosynthesis

Abstract We have proposed a novel strategy for artificial photosynthesis where porphyrins and fullerenes are assembled as building blocks into nanostructured artificial photosynthetic systems by the help of self-assembled monolayers. Photodynamical studies on porphyrin–fullerene-linked systems revealed that fullerenes accelerate photo-induced electron transfer and charge-shift and slow down charge recombination, which is in sharp contrast with the modalities of conventional two-dimensional aromatic acceptors such as quinones and imides. We proposed and demonstrated, for the first time, that such electron transfer properties are attributable to the small reorganization energies of fullerenes, which make it possible to optimize artificial photosynthetic multistep charge separation. The multistep electron transfer strategy was combined with our finding that fullerenes have small reorganization energies, which are well-suited for the construction of light energy conversion systems as well as artificial photosynthetic models. Highly efficient photosynthetic energy and electron transfers were realized at gold and indium–tin oxide (ITO) electrodes modified with self-assembled monolayers of porphyrin–fullerene-linked systems. Porphyrin-modified gold nanoclusters were found to have potential as artificial photosynthetic materials and photonic molecular devices. These results provide basic principles and concepts for the development of nanostructured artificial photosynthetic materials as well as molecular devices.

Stabilized bismuthonium ylides bearing a highly cross-conjugated ylidic carbon atom: synthesis, structures, and reactions

Abstract The reaction of iminotriaryl-λ 5 -bismuthanes ( 2 ; Ar 3 Biue605NR; R=COR″ or SO 2 R″) with dialkyl acetylenedicarboxylates ( 3 ; R′O 2 CCue606CCO 2 R′) has been found to afford highly stabilized bismuthonium ylides ( 4 ; Ar 3 Biue605C(CO 2 R′)ue5f8C(CO 2 R′)ue605NR) in 50–92% yield. The X-ray crystallographic analyses of two of these ylides demonstrated that their bismuth center possesses a distorted tetrahedral geometry with the highly cross-conjugated ylidic carbon atom. The observed Biue5f8C ylide bond lengths of 2.178(7)–2.199(7) A are close to ordinary Biue5f8C Ar bond lengths, suggesting an appreciable single bond character of the Biue5f8C ylide bond. The action of two equivalents of acetic acid, hydrogen chloride, or 4-nitrophenol on 4 cleaved the Biue5f8C ylide bond to give the corresponding triarylbismuth(V) compounds of the type Ar 3 BiX 2 and olefins ( 5 ; R′O 2 CCHue605C(CO 2 R′)NHR). 4-Nitrobenzenethiol was oxidized by 0.5 equivalents of 4 to give bis(4-nitrophenyl) disulfide with a good recovery of triarylbismuthane 6 and olefin 5 . On thermolysis at 200°C, or when decomposed in the presence of a copper catalyst at room temperature, the ylides 4 bearing an N -aroyl group gave 2,4,5-trisubstituted oxazoles 7 and triarylbismuthanes 6 in moderate to excellent yields.

First synthesis of alkynyltriphenylbismuthonium salts and their dual reaction modes in sulfonylation

Treatment of triphenylbismuth difluoride with nalkynyldiisopropoxyboranes in the presence of nBF3·OEt2 in CH2Cl2 gives nalkynyltriphenylbismuthonium tetrafluoroborates, which react with sodium np-toluenesulfinate in dual reaction modes depending on the nsolvents employed.