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The copper(II), nickel(II), etc. complexes of 5,15-bis(trimethylsilylethynyl)tetrabenzoporphyrin (TMS-H2BP) and 5,15-bis(triisopropylsilylethynyl)tetrabenzoporphyrin (TIPS-H2BP) have been prepared from the corresponding bicycle[2.2.2]octadiene(BCOD)-fused precursors by the retro-Diels-Alder reaction. X-ray diffraction (XRD) analyses show that TMS-H2BP and its metal complexes of zinc(II) (TMS-ZnBP) and copper(II) (TMS-CuBP) adopt flat molecular conformations and form herringbone-type packing structures in the single crystalline state. TIPS-H2BP and the zinc(II) and copper(II) complexes (TIPS-ZnBP and TIPS-CuBP) are similar to the TMS derivatives in molecular conformation, but these TIPS derivatives form one-dimensional slipped-stack structures. The nickel complexes TMS-NiBP and TIPS-NiBP have U-shaped structures because of the small size of nickel(II) ion. Solution processed organic thin-film transistors of the benzoporphyrins were fabricated and TMS-H2BP showed the highest hole mobility of 0.11 cm2.V-1.s-1. Bulk heterojunction organic solar cells based on TMS- or TIPS-H2BP and their metal complexes as p-type and PC71BM as n-type materials were fabricated by solution process. Atomic force microscopy and thin-film XRD measurements indicated that the film crystallinities were increased by raising the annealing temperature over 180°C or by changing the substituents from triisopropylsilyl to trimethylsilyl. The best power-conversion efficiency (PCE) of 1.49% was achieved with TMS-ZnBP by annealing at 180°C with a moderate crystallinity and smooth surface.

The butadiyne- and acetylene-linked 3,3′-porphycene dimers 1 and 2 were synthesized from the common intermediate, 3-ethynyl-2,7,12,17-tetrahexylporphycene 4. The butadiyne-linked dimer 1 was prepared from 4 by copper mediated Glaser-type homo-coupling. The acetylene-linked dimer 2 was synthesized by Sonogashira coupling of 4 and 2,7,12,17-tetrahexyl-3-iodoporphycene 5. These porphycene dimers were characterized by 1H and 13C NMR spectroscopies, mass spectroscopy, X-ray diffraction analysis, UV-vis absorption and fluorescence spectra, cyclic voltammetry and differential pulse voltammetry. Crystal structure of 1showed a coplanar structure of two porphycene units. The absorption spectra in CH2Cl2 indicated the small interaction between the porphycene units through the linkage at 3,3′-positions. The electrochemical measurement showed two one-electron oxidation potentials and four one-electron reduction potentials indicating the electric interaction between the porphycene units.

We have synthesized 13,13'-(3,5-bis(trifluoromethyl)phenyl)-6,6'-bipentacene from a soluble bispentacenequinone precursor. Bispentacene takes orthogonal conformation in the solid state and exhibits four reversible redox potentials. In addition, a tetracyanobipentacenequinodimethane was obtained for the first time from the pure bispentacenequinone.

Preparation of high-performance organic semiconductor devices requires precise control over the active-layer structure. To this end, we are working on the controlled deposition of small-molecule semiconductors through a photoprecursor approach wherein a soluble precursor compound is processed into a thin-film form and then converted to a target semiconductor by light irradiation. This approach can be applied to layer-by-layer solution deposition, enabling the preparation of p–i–n-type photovoltaic active layers by wet processing. However, molecular design principles are yet to be established toward obtaining desirable thin-film morphology via this unconventional method. Herein, we evaluate a new windmill-shaped molecule with anthryl blades, 1,3,5-tris(5-(anthracen-2-yl)thiophen-2-yl)benzene, which is designed to deposit via the photoprecursor approach for use as the p-sublayer in p–i–n-type organic photovoltaic devices (OPVs). The new compound is superior to the corresponding precedent p-sublayer materials in terms of forming smooth and homogeneous films, thereby leading to improved performance of p–i–n OPVs. Overall, this work demonstrates the effectiveness of the windmill-type architecture in preparing high-quality semiconducting thin films through the photoprecursor approach.

Vinylene-bridged cyclic boron–difluoride complex of dipyrrin (BODIPY) trimers were successfully prepared from expanded dimethyl-vinylene bridged hexaphyrin(2.1.2.1.2.1) Me-Hex that has the structure of alternate dipyrrins and vinylene bridges. The hexaphyrin(2.1.2.1.2.1) Me-Hex can coordinate with boron ions to afford five kinds of cyclic BODIPYs given by step-by-step boron complexations. Crystal structures of all cyclic BODIPYs except for 3BF2-Me-Hex(b) formed non-planar structures. The theoretical calculation predicted that mono-/bis-boron cyclic BODIPYs show the intramolecular charge transfer (ICT) characteristics, whereas tri-boron cyclic BODIPYs have no ICT characteristics. Reflecting these electronic properties, tri-boron cyclic BODIPYs exhibit weak fluorescence in the red region, but mono-/bis-boron cyclic BODIPYs exhibit no emission. Vinylene bridged cyclic dipyrrin trimer Me-Hex is the novel porphyrinoid ligand allowed to control the boron coordination under different reaction conditions to form various boron complexes.

A 2,2′-tert-butyl-5,9-6′,8′-cyclooctameric pyrenylene ([8]CP) was synthesized by a one-pot Suzuki–Miyaura cross-coupling reaction from two kinds of bifunctionalized monomers, as a rare example of a cyclic octamer. The octameric molecular structure of [8]CP was revealed by single-crystal X-ray diffraction analysis.

Bottom-up synthesis of graphene nanoribbons (GNRs) may open new possibilities in future electronic devices owing to their tunable electronic structure, which depends strongly on their well-defined width and edge geometry. For instance, armchair-edged GNRs (AGNRs) exhibit width-dependent bandgaps. However, the bandgaps of AGNRs synthesized experimentally so far are relatively large, well above 1 eV. Such a large bandgap may deteriorate device performance due to large Schottky barriers and carrier effective masses. Here, we describe the bottom-up synthesis of AGNRs with smaller bandgaps, using dibromobenzene-based precursors. Two types of AGNRs with different widths, namely 17 and 13 carbon atoms, were synthesized on Au(111), and their atomic and electronic structures were investigated by scanning probe microscopy and spectroscopy. We reveal that 17-AGNRs have the smallest bandgap, as well as the smallest electron/hole effective mass, among bottom-up AGNRs reported so far. The successful synthesis of 17-AGNRs is a significant step toward the development of GNR-based electronic devices.

As a homoditopic back-to-back host molecule, a cyclic 1,8-pyrenylene tetramer CP4 having two cavities for guest complexation was investigated. The unique two-face structural feature of CP4 allows it to bind spherical pristine fullerenes. The host-guest interactions were characterized by 1H NMR spectroscopy and single-crystal X-ray diffraction analysis.

Boron complexes of [14]triphyrins(2.1.1) were prepared from free-base [14]triphyrins(2.1.1) with phenylboron dichloride. The absorption spectrum of the meso-free [small beta]-alkyl-triphyrin boron complex in CH2Cl2 showed a broad weak band at around 640 nm assigned to transition from B-phenyl to the triphyrin, while that of the meso-aryl benzotriphyrin boron complex showed only Soret and Q bands.

P-n junction solar cells based on anthradithiophene (ADT) as a p-type semiconductor were fabricated by using the photoprecursor method in which an [small alpha]-diketone-type precursor was spin-coated and then transformed to ADT in situ by photoirradiation. Combination with PC71BM as an n-layer material led to 1.54% photoconversion efficiency.

Sterically congested tetraarylpyrenes exhibited emission in both solution and the solid state. The monocationic species of pyrene 1 could be isolated because of the reasonably protected system. The aromaticity of 1 relocates from the biphenyl part to the naphthalene unit upon two-electron oxidation.

Stable 9,9'-anthryl-anthroxyl radicals were synthesized and isolated, and the structures were fully characterized by single crystal X-ray diffraction analysis and ESR measurement. The resonance structure and steric protection of the peripheral positions and the most reactive 9-position of anthracene prolong the half-life of the radical in solution to 11 days.

A p-i-n organic photovoltaic cell with tetrabenzoporphyrin (BP), a BP-C60 dyad and PCBM for the p-, i- and n-layers, respectively, gave a better fill factor and power conversion efficiency than the corresponding p-i-n cell having a 1 : 1 blend film of BP and PCBM as the i-layer.