矢貝 史樹

<p>We unravel the impact of metal coordination and light irradiation on hierarchical self-assembly processes by combined theoretical and experimental results.</p>

We have developed a new photon upconversion (UC) system utilizing a new amphiphilic sensitizer 1a that comprises a hydrophilic ruthenium complex and a lipophilic bisanthracene appendage. At concentrations higher than 5 μM in toluene, the sensitizer 1a formed a reverse micellar assembly which facilitated the triplet sensitization of 9,10-diphenylanthracene (DPA) more efficiently than homogeneously dispersed solutions to enhance the UC efficiency up to 38.2%. The Stern-Volmer analyses revealed the stepwise triplet-triplet energy transfers (TTET): (1) intramicellar energy transfer from the ruthenium core to the bisanthracene surface and (2) diffusion-dependent energy transfer from the surface to DPA. On these bases, it can be assumed that the reverse micellar assemblies accelerate the former TTET process to enhance the UC efficiency.

Folding one-dimensional polymer chains into well-defined topologies represents an important organization process for proteins, but replicating this process for supramolecular polymers remains a challenging task. We report supramolecular polymers that can fold into protein-like topologies. Our approach is based on curvature-forming supramolecular rosettes, which affords kinetic control over the extent of helical folding in the resulting supramolecular fibers by changing the cooling rate for polymerization. When using a slow cooling rate, we obtained misfolded fibers containing a minor amount of helical domains that folded on a time scale of days into unique topologies reminiscent of the protein tertiary structures. Thermodynamic analysis of fibers with varying degrees of folding revealed that the folding is accompanied by a large enthalpic gain. The self-folding proceeds via ordering of misfolded domains in the main chain using helical domains as templates, as fully misfolded fibers prepared by a fast cooling rate do not self-fold.

<p>Bestowing amphiphilicity to specifically designed perylene bisimide dyads enables diverse self-assembly pathways in aqueous media.</p>

<p>Higher order structures of semiconducting supramolecular polymers have a huge impact on their BHJ-OPV device performance.</p>

Intricately designed π-conjugated molecules containing interactive groups can be used to generate supramolecular polymers with outstanding structural and functional properties. To construct such supramolecular polymers, the non-covalent synthesis of supermacrocyclic monomers from relatively simple molecules represents an attractive strategy, although this has been rarely exploited. Here, we report the supramolecular polymerization of two barbiturate-naphthalene derivatives that circularly hexamerize by hydrogen bonding. The two molecules contain an aliphatic “wedge” unit with either an ether or ester linkage. This subtle difference is amplified into distinct features both in terms of the morphology of the supramolecular polymers and the polymerization process. The degrees of conformational freedom of the wedge unit determine the stacking of the supermacrocycles, as is evident from 2D X-ray diffraction analyses on the aligned fibers. The differences in stacking impart the supramolecular polymer fibers with different morphological features (cylindrical or helical), which are reflected in the properties of concentrated solutions (suspension or gel). The degrees of conformational freedom of the wedge unit also affect the polymerization kinetics, in which the more flexible ether linkage induces pathway complexity by the formation of off-pathway aggregates.

The design of molecular systems with high-fidelity self-assembly pathways that include several levels of hierarchy is of primary importance for the understanding of structure-function relationships, as well as for controlling the functionality of organic materials. Reported herein is a high-fidelity self-assembly system that comprises two hydrogen-bonding molecular semiconductors with regioisomerically attached short alkyl chains. Despite the availability of both discrete cyclic and polymeric linear hydrogen-bonding motifs, the two regioisomers select one of the two motifs in homogeneous solution as well as at the 2D-confined liquid-solid interface. This selectivity arises from the high directionality of the involved hydrogen-bonding interactions, which renders rerouting to other self-assembly pathways difficult. In thin films and in the bulk, the resulting hydrogen-bonded assemblies further organize into the expected columnar and lamellar higher-order architectures via solution processing. The contrasting organized structures of these regioisomers are reflected in their notably different miscibility with soluble fullerene derivatives in the solid state. Thus, electron donor-acceptor blend films deliver a distinctly different photovoltaic performance, despite their virtually identical intrinsic optoelectronic properties. Currently, we attribute this high-fidelity control via self-assembly pathways to the molecular design of these supramolecular semiconductors, which lacks structure-determining long aliphatic chains.

Two regioisomeric barbituric acid compounds possessing (phenylethynyl) anthracene cores and tridodecyloxy phenyl units were synthesized. UV-Vis spectroscopic studies showed that the two compounds self-assemble by a cooperative mechanism in methylcyclohexane (MCH) with different stacking arrangements of the π-conjugated core, which leads to distinct aggregation-induced color changes. Atomic Force Microscopic studies revealed the formation of well-defined fibrous supramolecular polymers with different topological features, that is, cylindrical or helically twisted shapes. For the helically twisted supramolecular polymer, adding small amounts of limonene as a cosolvent induced more pronounced changes in absorption, which indicated an increased π-π stacking interaction in the cosolvent system compared with that in pure MCH. Molecular modeling studies suggested that the two molecules form supramolecular polymers by forming hydrogen-bonded hexameric supermacrocycles (rosettes) and that different twisting angles of the anthracene chromophore with respect to the barbituric acid plane can explain the observed difference in spectroscopic and morphological properties.

Supramolecular polymerization of a naphthalene-azobenzene dyad bearing a barbituric acid hydrogen-bonding unit was studied in nonpolar media. The length of supramolecular polymers could be regulated by changing the assembly conditions in terms of kinetics. Supramolecular polymerization initiated by cis-to-trans photoisomerization afforded shorter supramolecular polymers with narrower polydispersity compared to those generated by thermal polymerization.

<p>Linking two perylene bisimide dyes through an alkylene tether enforces aggregation in aqueous media, affording helical supramolecular polymers that can form gel-like lyotropic mesophases.</p>

<p>One-dimensional nanoassemblies obtained by the columnar stacking of hydrogen-bonded supermacrocycles (rosettes) comprising π-conjugated molecules.</p>

The significant contribution of conventional living polymerization to polymer science assures that living supramolecular polymerization will also lead to a variety of novel phenomena and applications. However, the monomer scope still remains limited in terms of the self-assembly energy landscape; a kinetic trap that retards spontaneous nucleation has to be coupled with a supramolecular polymerization pathway, which is challenging to achieve by molecular design. Herein, we report a rational approach to addressing this issue. We combined the supramolecular polymerization and photoisomerization processes to build the energy landscape, wherein the monomer can be activated/deactivated by light irradiation. In this way, the supramolecular polymerization and kinetic trap can be independently designed in the energy landscape. When the "dormant" monomer was activated by light in the presence of the seed of the supramolecular polymer, the "activated" free monomer was polymerized at the termini of the seed in a chain growth manner. As a result, we achieved supramolecular polymers with controlled lengths and a narrow polydispersity. Although photoisomerization has been extensively employed in supramolecular polymer chemistry, most studies have focused on the stimuli responsiveness. In this respect, the present study would provoke supramolecular chemists to revisit stimuli-responsive supramolecular polymer systems as potential

Photoluminescent materials that exhibit tunable emission properties when subjected to mechanical stimuli have numerous potential applications. Although many organic/inorganic and organometallic compounds display this property, called mechanochromic luminescence, most of these materials undergo a crystalline-to-amorphous (C → A) phase transition; examples of crystalline-to-crystalline (C → C ) transformation are rare. Single-crystal X-ray diffraction may allow direct analysis of the molecular packing of mechanochromic luminescence materials before and after C → C transformation, which may help to understand the underlying mechanism of this transformation. Reported herein is a mechanochromic luminescence material that displays an unprecedented type of C → C transformation mediated by a transient amorphous phase (C → [A] → C ). This mechanochromic luminescence material was developed by introducing soft triethylene glycol side chains in a crystalline gold(I) complex that exhibits mechanochromic luminescence based on a C → A phase transition. When this new gold(I) complex bearing triethylene glycol chains was subjected to a mechanical or thermal stimulus, dynamic phase changes were observed with irreversible luminescence color changes from blue to yellow to green in both the cases. The crystallinity of the mechanically generated C phase was lower than that of the thermally generated C phase. This is because the mechanically induced C → [A] → C process was finished within seconds, whereas the thermal C → [A] → C process occurred over a few minutes. To control the C → [A] → C transformation, we doped the complex with an inactive soft component. This successfully made the transformation reversible (from green to blue) upon thermal annealing of the mechanically obtained C phase. This approach allowed the development of an imaging process involving invisible information storage even under UV illumination. 1 2 1 2 1 2 1 2 2 2 1 2 1 2 1 2 2

<p>In this work we demonstrate the time-evolvable self-sorting of hydrogen-bonding naphthalene regioisomers.</p>

The supramolecular design of photochromic molecules has produced various smart molecular assemblies that can switch their structures and/or functions in response to light stimuli. However, most of these assemblies require large structural changes of the photochromic molecules for an efficient conversion of assembled states, which often suppresses the photoreactivity within the self-assemblies. Here we report molecular assemblies, based on a photo-cross-linkable chromophoric dyad, in which a small amount of ultraviolet-generated photochemical product can guide the entire system into different assembly processes. In apolar solution, the intact dyad self-assembles into right-handed superhelical fibrils. On ultraviolet-irradiation of these fibrils, an effective photoreaction affords a sole photo-cross-linked product. When right-handed helical fibrils, containing a minor amount of the photoproduct, are thermally reconstructed, the intact molecule and the photoproduct undergo a co-assembly process that furnishes superhelical fibrils with different molecular packing structures. This molecular design principle should afford new paradigms for smart molecular assemblies.

We demonstrated that amphiphilic dipolar π-conjugated systems can form several metastable self-assembled phases with distinct molecular packing and emission properties. The designed metastable state was converted to a more stable packing state by the application of both weak and strong mechanical stimuli. The rationale for this behavior involves unfavorable parallel orientation of the molecular dipole moments that become kinetically trapped upon segregation between incompatible molecular segments. The present study provides one of the basic molecular strategies for the design of new mechano-responsive materials with various π-conjugated luminophores.

Supramolecular rosettes of oligothiophenes that do not bear long aliphatic tails have been designed as semiconducting nanomaterials for solution-processable bulk het-erojunction solar cells. The rosettes consist of six barbiturat-ed thienyl[oligo(hexylthiophene)] units (Bar-T-hT ; n = 3,4,5) aggregated by multiple hydrogen bonds, which have been directly visualized by scanning tunneling microscopy (STM) at a solid-liquid interface. H NMR spectroscopy in [D ]toluene showed that Bar-T-hT exists as a mixture of monomers and small hydrogen-bonded aggregates. Hierarchical organization of the hydrogen-bonded aggregates took place through π - π stacking interactions upon casting their toluene solutions, resulting in the growth of highly ordered nanorods whose widths are consistent with the diameters of the rosettes. The nanorods could be generated in the presence of soluble fullerene derivatives via solution casting or the annealing of the resulting thin films. The solar cells fabricated based on these bulk heterojunction films showed power conversion efficiencies of 1-3%, which are far higher than those of the non-hydrogen-bonded reference oligothiophene and the derivative that possesses long aliphatic tails. n 8 n 1

Diarylethenes have rarely been used in the design of photoresponsive molecular assemblies featuring a well-defined morphology transition because of rather small structural changes upon photoisomerization. We demonstrate that a supramolecular design based on the parallel conformation of diarylethenes enables the construction of photoresponsive dye assemblies that undergo a remarkable nanomorphology change. The parallel conformer of diarylethene was stabilized by cooperative stacking of perylene bisimide dyes through complementary hydrogen bonds. UV/Vis spectroscopy, atomic force microscopy, and molecular modeling showed that our diarylethene and perylene building blocks coassembled in nonpolar solvent, affording well-defined helical nanofibers comprising dimeric J-aggregates of perylene dyes. Upon irradiating the coassembly solution with UV and visible light in turn, a reversible morphology transition between nanofibers and nanoparticles took place. Furthemore, our system involves the generation of a new self-assembly pathway by means of photocontrol.

Iridium complexes are one of the most important materials for fabrication of organic light emitting diodes (OLEDs). There are difficulties in the preparation of blue phosphorescent complexes with respect to chromaticity, emission efficiency, and stability of the material, compared with green and red phosphorescent complexes. Control of the frontier orbital energy level (HOMO-LUMO) is the sole method to achieve better blue phosphorescent iridium complexes by appropriate ligand selection and the introduction of adequate substituents. Homoleptic and heteroleptic iridium(III) tris(phenylimidazolinate) complexes were synthesized, and the effect of the substituents on their nature in the excited state was examined. Density functional theory calculation showed that the imidazolinato complexes have the HOMO localized at the iridium d- and phenyl pi-orbitals. The LUMO is also localized on the phenyl moiety with a much higher population than HOMO. This LUMO is quite different from other complexes, such as iridium(III) tris(phenylpyridinate) and tris(phenylpyrazolinate) complexes. Therefore, substitution with pi-electron donating groups and electron withdrawing groups induces blue and red spectral shifts, respectively, which is the reverse shift exhibited by other complexes. The ancillary ligand (acetylacetone) acts as a path for nonradiative deactivation in the blue phosphorescent complexes.

Azobenzene dimer 1 has been previously shown to form chiral nanorings in nonpolar solvents. In this study, azobenzene chromophores are replaced with oligo(p-phenylenevinylene) (OPV). The resulting OPV dimer 2 was shown to form a small number of nanorings, and other assemblies were extended fibrils due to stronger π-π stacking interaction. © 2013 The Chemical Society of Japan.

A free-standing polymer brush film with tailored thicknesses based on a colorless polydopamine (PDA) thin layer is prepared and characterized. The surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) is performed on a PDA layer with thickness of ca. 6 nm, which generated an optically transparent and colorless free-standing PHEMA brush film (1.5 cm x 1.5 cm). Because the cross-linked PDA layer is used as the base for the polymer brushes, the reported method does not require cross-linking the polymer brushes. The free-standing film thicknesses of approximate to 16-75 nm are controlled by simply changing the ATRP reaction time. The results show that the free-standing PHEMA brush film transferred onto a plate exhibits a relatively smooth surface and is stable in any solvent.

Photochromism: Functionalization of a diarylethene derivative with π-conjugated oligomers resulted in a higher aggregation capability in the open rather than the closed form due to tunable steric hindrance of methyl groups of the diarylethene core (see scheme). Distinct aggregation abilities of the open and the closed isomers in nonpolar solvent and phototunable energy transfer between the two functional units enabled visible-light-triggered formation of fluorescent organogels. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organogels: Dimerization of perylene bisimide dyes through an oligomethylene linker enabled the facile control over columnar and lamellar self-organized architectures by an odd/even effect with respect to the number of methylene groups. The difference in the self-organized architectures was shown to have an impact on their material morphologies, as well as charge-carrier mobilities (see scheme). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Derivatization of fullerene (C-60) with branched aliphatic chains softens C-60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C-60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 degrees C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 + 0.1%) in comparison with another compound, 10 (PCE: 0.5 + 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C-60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.

The intramolecular photochemical processes excimer formation and charge-transfer (CT) complex formation were investigated by comparing the behavior of α,ω-di(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2)n-(1-naphthyl); NS n N, n = 1, 3, and 6) and 1-(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2)n-Me; NS n, n = 1, 3, and 6) by use of stationary and time-resolved fluorescence (TR-FL) measurements. Formation of excimer and CT complexes is highly dependent on the silicon chain length and polarity of the medium. Graphical Abstract: Intramolecular excimer formation between the two naphthyl groups and charge transfer interactions between the naphthyl and silane moieties were investigated by use of a time-correlated single-photon counting method.[Figure not available: see fulltext.] © 2012 Springer Science+Business Media B.V.

Herein, we describe a facile method to prepare a colorless functional polydopamine (PDA) thin layer by the in situ oxidative copolymerization of dopamine (DA) and ATRP initiator-bearing DA (DA-BiBB) onto polystyrene (PSt) core particles: PSt@PDA/BiBB2. Surface-initiated ATRP of 2-hydroxyethyl methacrylate (HEMA) was performed on PSt@PDA/BiBB2 particles, followed by the removal of the template particles, which generated PHEMA capsules that were based on a colorless PDA thin layer and have tailored hollow core sizes and capsule wall thicknesses. The PDA thin layer is used as a basis for polymer brushes. The present method does not require cross-linking the polymer brushes. Furthermore, subsequent preparation of functional PHEMA capsules by post-functionalization of hydroxy groups of PHEMA chains was successful.

Three series of alkyl methacrylate based copolymers having photo-reactive side chains (C=C double bond) were synthesized and examined their performances as photopolymer in the presence of suitable oxime ester or triazine type radical photo-initiators for 365 nm light. Along to our previous report showed that correlation was observed between photochemical reactivity and chain length of the side chain/density of reactive side chain in the cyclohexyl methacrylate main chain. Our proposed mechanism is that sterically stacked nonpolar cyclohexyl groups may push out the polar reactive side chains, and length and density of the side chain controls cross linking between two reactive sites in the single main chain or two different main chains. Now we have examined structural effect of the alkyl groups on the efficiency of photocrosslinking. We have examined 5 series and totally 15 polymers. As a result, cyclohexyl methacrylate based copolymer showed excellent performance for polymerization. © 2013SPST.

A cholesterol-functionalized gold(I)-isocyanide complex exhibiting mechanochromic luminescence properties was self-organized into distinct microscopic structures with different photoluminescence properties through vapor-diffusion of a poor solvent into its dichloromethane solution. The structure-optical property relationship of these microstructures could be related to the mechanically induced phase transition. © 2013 Royal Society of Chemistry.