Shigeru Yamaguchi’s research while affiliated with The University of Tokyo and other places

Utilizing tetraethynyl porphyrin derivative (TE-Por) as a small molecule donor material, we fabricated a small molecule solution-processed bulk heterojunction (BHJ) solar cell with inverted structure, which exhibited 1.6% power conversion efficiency (JSC (short-circuit current) = 4.6 mA/cm2, VOC (open-circuit voltage) = 0.90 V, and FF (fill factor) = 0.39) in the device configuration indium tin oxide/TiOx (titanium sub-oxide)/[6,6]-phenyl-C61-butyric acid methyl ester:TE-Por (5:1)/MoOx (molybdenum sub-oxide)/Au under AM1.5 G illumination at 100 mW/cm2. Without encapsulation, the small molecule solution-processed inverted BHJ solar cell also showed remarkable durability to air, where it kept over 73% of its initial power conversion efficiency after storage for 28 days under ambient atmosphere in the dark.

Facile synthesis of meso-aryl-substituted 5,15-dithiaporphyrins and 10-thiacorroles has been achieved by sulfidation of α,α'-dichlorodipyrrin metal complexes with sodium sulfide in DMF. Thiacorrole metal complexes exhibit distinct aromaticity due to 18 π-conjugation including the lone pair on sulfur, whereas dithiaporphyrins are nonaromatic judging from (1) H NMR spectra, X-ray analysis, and absorption spectra. We have found that Ni(II) and Al(III) dithiaporphyrin complexes undergo smooth thermal sulfur extrusion reaction to give the corresponding thiacorrole complexes, whereas free base, Zn(II) , Pd(II) , and Pt(II) dithiaporphyrin complexes did not exhibit the similar reactivity. The DFT calculations have elucidated a reaction pathway involving an episulfide intermediate, which can explain the markedly different reactivity among dithiaporphyrin metal complexes.

Two types of thieno-bridged porphyrins were synthesized by incorporating a thiophene group across their meso and β positions with different directions of the thiophene ring to investigate the aromaticity of these porphyrins with extended π-systems. The 2,3-thieno-bridged porphyrin showed a larger antiaromatic contribution than did the 3,4-thieno-bridged porphyrin. In the former, the antiaromatic contribution is based on a 20-π-electron conjugated circuit. The two thieno-bridged porphyrins were characterized by calculations of nucleus-independent chemical shift and anisotropy of the induced current density as well as by X-ray crystallography, NMR spectroscopy, UV-vis-NIR absorption spectroscopy, electrochemical studies, time-resolved excited-state analysis, and two-photon absorption cross section measurements. Chemical derivatization of the 2,3-thieno-bridged porphyrin was also demonstrated.

This paper describes the rational design of porphyrin donors for application in solution-processed small molecule bulk heterojunction (BHJ) solar cells. The porphyrin donors were designed to possess high solubility and strong intermolecular interactions, via the appropriate selection of peripheral substituents: these molecules bear tetraethynyl porphyrin cores with two aromatic and two aliphatic groups in a trans manner. We have also demonstrated the substitution effect on the aromatic groups: energy levels, solubility and film morphology were significantly modified by the substituents, which consequently influenced the efficiencies of the solar cells as well. After optimization, the device based on [5,15-bis(phenylethynyl)-10,20-bis[(triisopropylsilyl)ethynyl]porphyrinato] magnesium(II) (2):PC60BM showed a PCE of 2.5%.

Synthesis of nickel(II) complexes of meso-aryl-substituted azacorroles was performed by Buchwald-Hartwig amination of a dipyrrin Ni(II) complex with benzylamine through C-N and C-C coupling. The highly planar structure of Ni(II) azacorroles was elucidated by X-ray diffraction analysis. (1)H NMR analysis and nucleus independent chemical shift (NICS) calculation on Ni(II) azacorrole revealed its distinct aromaticity with [17]triaza-annulene 18π conjugation. In addition, acylation of azacorrole selectively afforded N- and C-acylated azacorroles depending on the reaction conditions, showing the dual reactivity of azacorroles.

A biphenyl-fused BODIPY was synthesized through a facile oxidative cyclization of peripheral aryl-substituents at the β-position of the BODIPY unit. The extended π-system of the fused BODIPY induces near-infrared (NIR) absorption and strong π-π interactions in the solid state. These features are beneficial for the application of the dye as a functional material. The biphenyl-fused BODIPY dye was demonstrated to exhibit photocurrent conversion ability on the basis of its n-type semiconducting property.

Treatment of a meso-arylboron dipyrrin (BODIPY) with NBS provides mono- and dibrominated BODIPYs at the 2- and 6-positions in excellent yields with high regioselectivity. Brominated products can be employed as a nice building block for the synthesis of a variety of BODIPY derivatives through Suzuki-Miyaura coupling. Because of a lack of substituents at the 1,3,5,7-positions, a directly β-β-linked BODIPY dimer exhibits a completely coplanar conformation of BODIPY units, offering effective π-conjugation.

Two types of novel iridium pincer complexes bearing a porphyrin backbone were synthesized and characterized from dipyridylporphyrin. One of the complexes has a Lewis acidic site on the iridium center in the mer-coordination mode. The other complex takes the fac-coordination, which is rarely observed in benzene-based pincer complexes.

Die Synthese cyclischer BODIPY-Dimere (siehe Struktur; C weiß, B orange, N blau, F grün) und -Trimere mit Butadiin- Brücken gelingt durch eine Pd-katalysierte Stille-Kupplung mit anschließender Cu-vermittelter Glaser-Kupplung. Die cyclischen BODIPYs sind stabile antiaromatische 24π- bzw. 36π-Porphyrinoide mit planaren Konformationen. Strukturen, elektronische Zustände und Reaktivität der Verbindungen wurden untersucht.

Pt(II) and Pt(IV) porphyrin pincer complexes were synthesized and characterized. Their structures and electronic properties were influenced by the valence state of platinum at the outer coordination site. The considerable distortion in the porphyrin core of the Pt(II) complex was relieved in the Pt(IV) complex, due to the change of the coordination geometry of platinum. Oxidation of the phenylplatinum(II) pincer complex with iodine induced a facile carbon−carbon bond formation reaction at the meso position via reductive elimination.