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Luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes were synthesized for practical applications in immunoassays. The polystyrene core particles were synthesized by miniemulsion polymerization of oil-in-water emulsion styrene droplets dissolving 2-(2-chloropropionyl)ethyl methacrylate and the europium complex emulsified with 2-methacryloyloxyethyl-N,N-dimethyl-N–n-dodecylammonium bromide. The red luminescence attributed to europium complexes embedded in the core particles was observed upon UV irradiation. The PSt-g-POEGMAx-NH2 aminated core–shell particles were prepared by surface-initiated atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMAx), followed by Gabriel synthesis. The densities of grafted chains were determined by the composition, the hydrodynamic diameters, and the fluorescence labeling method. POEGMAx-grafted chains were found to affect the dispersion stability of the particles. The nonspecific adsorption of bovine serum albumin was suppressed by the POEGMAx-grafted chains. The enzymatic activity of horseradish peroxidase covalently bound to the terminal amino groups of POEGMAx-grafted chains was evaluated by colorimetric immunosorbent assay.

Electro-optically responsive liquid crystal (LC) nanocapsules were prepared by miniemulsion polymerization of oil-in-water emulsion monomer droplets dissolving LC compounds. As theoretically predic...

Two boron complexes of 1-(o-hydroxyphenyl)imidazo[1,5-a]pyridine, which were named as BOHPIP, have been synthesized. These complexes exhibited blue emission in solution with high quantum yields (ΦFL = up to 0.71). In addition, 1-(o-hydroxyphenyl)imidazo[1,5-a]pyridine-BPh2 complex showed the strong blue emission even in the solid state (ΦFL = 0.58).

Photoresponsive molecular assembly based on diarylethene (DAE) is an interesting class of supramolecular system as it can allow remarkable morphological transition via small structural changes upon photoisomerization. Herein, we report coassemblies of diarylethene and perylene bisimide through complementary multiple hydrogen-bonding. The open isomer of the diarylethene and the perylene bisimide coassemble to afford photoresponsive helical supramolecular polymer nanofibers. The ring-closure photoreaction of the diarylethene unit enables transformation of helical nanofibers to non-helical fibers. The non-helical fibers can only be obtained through the photoisomerization, and are never achievable by thermal coaggregation of the close isomer and the perylene bisimide. This study illustrates that the proper incorporation of photochromic units into a non-equilibrated molecular assembly system achieved by strong intermolecular interaction enables us to design new self-assembled products in terms of morphology and functions, which are not obtainable through the self-assembly of ground state molecules under either kinetic or thermodynamic control.

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.

Liquid crystal nanocapsules (LC-Nanocapsules) were prepared by miniemulsion polymerization of the oil-in-water emulsion monomer droplets dissolving the liquid crystal (LC) compounds. In order to establish the preparation conditions of LC-Nanocapsules exhibiting the liquid crystallinity, the effects of the capsule wall-forming monomers and the crosslinking agent concentration on the capsule structure were investigated in detail. The monodisperse colloidal products covered with the robust polymer shell wall was successfully prepared by the polymerization of the emulsion monomer droplets obtained through the phase inversion temperature emulsification technique using the amphiphilic block copolymer as an emulsifier. The endothermic peak was observed at the nematic-isotropic phase transition temperature (TNI) of the LC in the differential scanning calorimetry diagram of LC-Nanocapsules. The bright- and dark-field images of the dried thin films of LC-Nanocapsules spread on a glass substrate were found to appear repeatedly by the temperature change below and above TNI by polarized optical microscopic analysis. These results revealed that the LC-Nanocapsules with a complete engulfing morphology were successfully formed by the spontaneous coacervation phenomena between the crosslinked polymer and the LC with a progression of the polymerization, as theoretically predicted from the viewpoint of the spreading coefficients.

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 concent...

Photochromic materials have attracted considerable attention for their practical applications in optoelectronic devices. In this study, we developed the photochromic liquid core nanocapsules by polymerization of oil-in-water (O/W) nanoemulsion monomer droplets on the basis of Hansen solubility parameters. The thermoresponsive amphiphilic block copolymers (POEGMAm-b-PStn and POEGMAm-b-PMMAn) were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization of hydrophilic oligo(ethylene glycol) methyl ether methacrylate and hydrophobic styrene or MMA. The O/W nanoemulsion methyl methacrylate (MMA) droplets, dissolving dipropylene glycol methyl-n-propyl ether (DPMNP) and (E)-3-(adamantan-2-ylidene)-4-[1-(2,5-dimethyl-3-furyl) ethylidene]dihydro-2,5furandione (Aberchrome 670) as a core liquid and a photochromic dye, respectively, were obtained through the phase inversion temperature emulsification technique using POEGMAm-b-PStn as a surfactant. As theoretically predicted in terms of the spreading coefficients, the DPMNP solution of Aberchrome 670 was successfully encapsulated by coacervation of the crosslinked PMMA condensed phase. Aberchrome 670 dissolved in a liquid core was found to photoisomerize twice as fast as that dispersed in the solid polymer matrices.

Among the six alkyldiphenylmethanol derivatives assessed in this study, five showed persistent room temperature phosphorescence (pRTP), whereas the original diphenylmethanol (DPhHOH) did not. pRTP is a unique luminescence phenomenon that appears only in the crystalline state and is different from the luminescence produced by dispersed molecules, such as those in a glassy solvent matrix at 77 K or a polymeric matrix. The data also suggest that pRTP appears in conjunction with a specific crystal structure. The present work demonstrates that various crystal structures show pRTP regardless of the presence or absence of weak hydrogen bonds. However, nonradiative deactivation is suppressed by both intermolecular interactions and steric regulation in the crystal, such that the emission quantum yield is dependent on the crystal structure. In addition, although the molecular structure in the crystalline state necessary for the appearance of pRTP was not fully elucidated, intermolecular interactions between face-to-face and face-to-edge benzene rings appear to play a major role. Density functional theory calculations indicate that intersystem crossing is promoted in the crystalline state because the number of paths that allow this intersystem crossing is greater in a structure having weak interactions between molecules as compared to a dispersed state. DPhHOH did not show pRTP and is considered to have a structure based on the column-like stacking of multiple molecules. In contrast, the crystals that exhibited pRTP had pseudo racemic conformation in their crystals even though each molecule was achiral. In these racemic crystals, the interactions between pairs of molecules were important to the generation of pRTP.

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 (C1 → C2) transformation are rare. Single-crystal X-ray diffraction may allow direct analysis of the molecular packing of mechanochromic luminescence materials before and after C1 → C2 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 C1 → C2 transformation mediated by a transient amorphous phase (C1 → [A] → C2). This mechanochromic luminescence material was developed by introducing soft triethylene glycol side chains in a crystalline gold(I) complex that exhibits mechanochromic luminesc...

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.

Diarylethenes (DAEs) have rarely been used in the design of photoresponsive supramolecular assemblies with a well-defined morphology transition owing to rather small structural changes upon photoisomerization. A supramolecular design based on the parallel conformation of DAEs enables the construction of photoresponsive dye assemblies that undergo remarkable nanomorphology transitions. The cooperative stacking of perylene bisimide (PBI) dyes was used to stabilize the parallel conformer of DAE through complementary hydrogen bonds. Atomic force microscopy, UV/Vis spectroscopy, and molecular modeling revealed that our DAE and PBI building blocks coassembled in nonpolar solvent to form well-defined helical nanofibers featuring J-type dimers of PBI dyes. Upon irradiating the coassembly solution with UV and visible light in turn, a reversible morphology change between nanofibers and nanoparticles was observed. This system involves the generation of a new self-assembly pathway by means of photocontrol.

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.

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).

The self-assembly of two regioisomeric hydrogen-bonding naphthalenes was studied in mixed states in different polarity solvents. The regioisomers co-assemble to form heteromeric rosettes in chloroform. Upon injecting this solution into methylcyclohexane the heteromeric rosettes kinetically form amorphous aggregates, which over time differentiate into thermodynamically stable distinct nanostructures through self-sorting.

We report a precise control over the hierarchy levels in the outstanding self-organization process shown by chiral azobenzene dimer 1. This compound forms uniform toroidal nanostructures that can hierarchically organize into chiral nanotubes under the control by temperature, concentration, or light. The nanotubes further organized into supercoiled fibrils, which finally intertwined to form double helices with one-handed helical sense.

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. 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.

Ditopic melamines possessing one (1) or two (2) perylene bisimide (PBI) chromophores were synthesized and their self-aggregation and coaggregation with dodecyl cyanurate (dCA) or barbital (Bar) were investigated. Optically transparent organogels were formed through self-aggregation of 1 and coaggregation of 1 or 2 with dCA or Bar in nonpolar solvents. X-ray diffraction of the xerogels exhibited typical diffraction patterns assignable to lamellar structures, suggesting the formation of tapelike hydrogen-bonded motifs. Remarkably low critical gelation concentrations (cgc) of 8.0 × 10−4 M were revealed for all organogels, thus they can be classified as supergelators. Comparison of the thermal stabilities of the gels revealed that the gels containing 2 have higher melting temperatures (Tm) than those containing 1. Scanning electron microscopy and atomic force microscopy showed that the gels containing 1 are composed of sheetlike microstructures, whereas those containing 2 are composed of fibrous nanostructures, consistent with the difference in their thermal stabilities. The different self-assembled structures of our PBI aggregates can be related to whether extended stacks of PBI dyes along the hydrogen-bonded strands are possible or not. Ditopic hydrogen bonding melamines possessing perylene bisimide chromophores were synthesized and their self-aggregation and coaggregation with complementary guest molecules were investigated. In this system, 2-D lamellar structures of perylene bisimides were constructed through hierarchical organization of hydrogen-bonded tapes, which can gelate aliphatic and aromatic solvents. The resulting gels are highly transparent and exhibit remarkably low critical gelation concentrations of 8.0 × 10−4 M. The thermal stabilities and the mesoscopic morphologies of these organogels could be reasonably explained by the number of perylene bisimide chromophores introduced in the melamine components.

Two soluble phosphorescent host materials, 1,4-bis(3,6-di([1,1′:3′,1″:3″,1‴:3‴,1⁗-quinquephenyl]-5″-yl)-9 H -carbazol-9-yl)benzene (P-mPCCP) and 1,4-bis(3,6-bis(4,4″-di-tert-butyl-[1,1′:3′,1″-terphenyl]-5′-yl)-9 H -carbazol-9-yl) benzene (T-mPCCP) derived form carbazole and m -terphenyl derivatives were designed and synthesized. These two hosts exhibit good solubility in common organic solvents and possess high glass transition temperature ( T g > 160 °C) and thermal stability. P-mPCCP and T-mPCCP as the host materials doped with the guest of fac -Ir(ppy) 3 , we fabricated phosphorescent organic light emitting diodes (PHOLED) by spin coating process. The turn-on voltage of P-mPCCP and T-mPCCP composing device was 4.0 and 7.0 eV and showed a maximum luminance of 21,100 and 3290 cd/m 2 and a maximum luminance efficiency of 15.0 and 7.6 cd/A, respectively.

Diarylethene 1 equipped with two monotopic melamine hydrogen-bonding sites and oligothiophene-functionalized ditopic cyanurate (OTCA) were mixed in a nonpolar solvent to form AA-BB-type supramolecular co-polymers (SCPs) bearing photoswitchable moieties in their main chains and extended π systems as side chains. UV/Vis, fluorescence, dynamic light scattering (DLS), TEM, and AFM studies revealed that the two functional co-monomers formed flexible quasi-one-dimensional SCPs in solution that hierarchically self-organized into helical nanofibers through H-aggregation of the oligothiophene side chains. Upon irradiating the SCPs with UV light, a transition occurred from the H-aggregated state to non-aggregated monomeric oligothiophene side chains, as shown by spectroscopic studies, which indicates the formation of small oligomeric species held together only by hydrogen-bonding interactions. TEM and AFM visualized unfolded fibrils corresponding to elongated single SCP chains formed upon removal of solvent. The helical nanofibers were regenerated upon irradiating the UV-irradiated solution with visible light. These results demonstrated that the supramolecular polymerisation followed by hierarchical organization can be effectively controlled by proper supramolecular designs using diarylethenes and π-conjugated oligomers.

Three series of cyclohexyl 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. As a result, those polymers gave negative patterns with micrometer resolution. Correlation between photochemical reactivity and chain length of the side chain/density of reactive side chain in the cyclohexyl methacrylate main chain was observed. Sterically stacked nonpolar cyclohexyl groups may push out the polar reactive side chain, 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. The image on a printing plate has enough strength for practical times of run off the print. These polymers were white or transparent powder having enough stability to preserve. Over all, three copolymers have promising features as photopolymer for printing.

Muscle Building The signaling mechanisms involved in actin filament formation for myofibril formation, which is required for growth factor-induced muscle maturation and hypertrophy, remain unclear. Takano et al. (p. 1536 ; see the Perspective by Gautel and Ehler ) now show that the mechanism involves the interaction of nebulin and N-WASP. N-WASP is an activator of the Arp2/3 complex, which induces branched actin filaments in nonmuscle cells. The nebulin–N-WASP complex formed in muscle, however, causes nucleation of unbranched actin filaments within myofibrils without the Arp2/3 complex. Nebulin–N-WASP–mediated myofibrillar actin filament formation is required for muscle hypertrophy and might explain a congenital hereditary neuromuscular disorder caused by nebulin gene mutation: nemaline myopathy.

Substitution effects on the photoluminescence and electrochemical properties and the photochemical stability of tris-(phenylbenzimidazolinato)Ir III complexes were investigated. Facial and meridional isomers of a series of complexes having the general structure of Ir(CC) 3 , where (CC) is (4-R-phenyl)benzimidazolinato (R = H, CF 3 , CN, OCH 3 ), were prepared. They are abbreviated to Ir(pmb) 3 (1), Ir(CF 3 pmb) 3 (2), Ir(CNpmb) 3 (3), and Ir(Opmb) 3 (4), respectively. Electron-donating or -withdrawing groups on the phenyl ring lead to both higher emission quantum yields and longer emission lifetimes compared to those of 1 in each mer and fac series. Particularly, the emission quantum yields were high in the cases of 2a, 3a, 3b, and 4a. No photochemical isomerization was observed in both fac- (a) and mer (b) isomers of Ir(pmb) 3 , Ir(CF3pmb) 3 , and Ir(CNpmb) 3 on irradiation with a 313-nm wavelength light from a 400 W mercury lamp for more than 20 h. All complexes excluding facIr(pmb) 3 (1a) show excellent photochemical stability in degassed anhydrous thf solution. The locations of the HOMO and LUMO and the lowest excitation energy of these complexes were investigated by DFT and TD-DFT calculations on fac- and mer-Ir(Opmb) 3 (4a and 4b). The HOMO is mainly localized over the Ir metal center and the phenyl moiety, and the LUMO mainly localized over the benzimidazole moiety. The calculated lowest excitation energies agree with the experimental values. The X-ray single crystal structures obtained for fac-Ir(CF 3 pmb) 3 (2a) and mer-Ir(Opmb) 3 (4b) are also discussed.

Dianthrylsilanes composed of two 9-anthryl groups and permethyloligosilane (n = 1, 2 or 3) chain units were prepared (A2S1, A2S2, and A2S3). Photochemical intramolecular cyclization reactions of these compounds were studied in solution and in PMMA spin coated film. In cyclohexane solution, the A2Sn molecules gave one of three cycloadducts, depending on the chain length of the A2Sn molecules. We also demonstrate the fabrication of fluorescent images using cycloaddition reactions in PMMA film.

Irradiation of the optically resolved mer-Δ isomer of tris(1-phenylpyrazolato,N,C2′)iridium(III) with 366-nm light in CH3CN purged by argon at 25 °C gave 59 % fac-Δ and 41 % fac-Λ (18 % ee) at the end of geometrical isomerization. Formation of the intermediate mer-Λ species was not observed, which is quite characteristic when compared with the corresponding thermal isomerization reaction. This enantiomeric photoisomerization is rationally explained by a mechanism based on Ir–N bond dissociation at the top or bottom axial ligand. This reaction mechanism is explained by the potential energy surface of the triplet excited state.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

This review article deals with recent studies on photochemistry and photophysics of organosilicon monomer to oligomers (here, chain length of Si is mostly less than 10). Arylmonosilanes have been caught attention as the fluorescent and charge-transporting materials. Increasing in silicon chain length, an importance of conformation for silicon single chain in organooligosilane is significant. The conformation affects the spectroscopic, photochemical, and photophysical characteristics. This review is mainly focused on the properties of arylsilanes and α,ω-diaryloligosilanes in which three types of intramolecular interactions, the σ–σ interaction between silicon atoms in a chain unit, the π–π interaction between two aromatic groups, and the σ–π interaction between an aromatic group and a silicon chain unit are expected. As a result, intramolecular excimer/exciplex formation, charge-transfer (CT) complex formation, excitation energy or photoinduced electron transfers were observed by the steady-state and the time-resolved fluorescence (TR-FL) spectroscopy. For the better understanding, the recent conformational studies of single oligosilane chain are also reviewed.

Bis- and monoureas hybridized with the oligo(p-phenylene vinylene) (OPV) pi-electronic segment and 3,4,5-tridodecyloxyphenyl wedge were synthesized and their supramolecular polymerization in diluted solution, gel formation in concentrated solution, and liquid crystallinity in bulk state were investigated. Bisurea 1a featuring a hexamethylene linker showed the highest supramolecular polymerization ability and formed tapelike nanofibers that can gelate various organic solvents. On the other hand, bisurea 1b featuring a dodecamethylene linker and monourea 2 showed a lower degree of supramolecular polymerization, resulting in gel formations in a smaller variety of solvents. These results clearly reflect a high level of cooperativity between the two urea sites and the two OPV segments of 1a upon hydrogen-bonding and pi-pi stacking interactions, respectively. When the gels of 1a, 1b, and 2 were dried, all the compounds self-organized into multilamellar superstructures. Thermal treatment of these lamellae at high temperatures induces columnar liquid-crystalline mesophases as a result of microsegregation between the rigid OPV parts and the molten aliphatic wedges. These results demonstrate that the present molecular constituent is very useful for fabricating dye-based functional assemblies providing nanoscale pi-electronic fibers, and solvent-incorporated and bulk soft materials.

Nanodonuts: A hydrogen-bonded cyclic assembly (rosette, left) of a melamine featuring π-conjugated oligo(p-phenyleneethynylene) hierarchically self-organizes with a cyanurate in decane under dilute conditions to form toroidal nanostructures (right) with a diameter of 40 nm.

3-R-5-Nitro-1,2-benzisothiazole derivatives (1, R = substituents) in solution, undergo photochemical isomerization to produce 2-R-5-nitro-1,2-benzothiazole derivatives. Here, generalizations and limitations by the substituent, solvent, and excitation wavelength for the photoisomerization reaction of 5-nitro-1,2-benzisothiazoles are reported.

Melamine-linked perylene bisimide dyes (MPBIs) bearing an ethylene or trimethylene group as linker moieties were synthesized, and their self-aggregation and coaggregation with cyanurates through complementary triple hydrogen bonds have been investigated. UV/vis studies revealed that both the MPBIs self-assemble in nonpolar organic solvent through pi-pi stacking interaction between perylene cores, giving self-aggregates with nearly identical thermal stabilities. Upon addition of 1 equiv of cyanurate components, however, the stabilities of the resulting aggregates were dramatically changed between the two systems, suggesting the formation of different types of hydrogen-bonded supramolecular species. Dynamic light scattering and atomic force microscopic studies revealed that the system featuring ethylene linker moieties generates a discrete dimer of MPBI supported by two cyanurate molecules, whereas the system featuring trimethylene linker moieties affords extended supramolecular polymers hierarchically organizing into nanoscopic fibers. These results demonstrate that it is possible to obtain distinct supramolecular species by just changing the number of carbon atoms at the linker moieties of MPBI components. The present strategy for the fabrication of discrete or polymeric supramolecular assemblies should be applicable to other functional pi-conjugated molecules.

Upon complexation with bismelamine receptors (BMn) featuring different alkyl linker lengths (number of methylene groups (n) = 5-12), a barbituric acid merocyanine dye (1) can be loaded into diverse self-organized superstructures through multiple hydrogen-bonding interactions. UV/vis, dynamic light scattering, and NMR studies in cyclohexane demonstrate that the diversification of the primarily formed hydrogen-bonded species in solution occurs by varying the linker length of BMn. Hierarchical organization of the hydrogen-bonded species is achieved by slow evaporation of the solvent (forming solvent-free films), and the resulting superstructures are evaluated by polarized optical microscopy, X-ray diffraction, SEM, and AFM techniques. The formation of columnar structures with and without two-dimensional ordering are revealed for shorter (n = 5-7) and longer (n = 11, 12) linker bis(melamines), respectively. On the contrary, in the cases of n = 8-10, the formation of lamellar structures is unveiled. Several assemblies (n = 5, 7, 11) indicate the formation of a liquid crystalline mesophase in POM and DSC analyses. Hierarchical organization is also achieved in solution by prolonged aging, affording phase-separated crystalline nanofibers (n = 5, 7) and soft nanofibrils agglomerating into wormlike objects (n = 8), gel-forming continuous globular networks (n = 10), and nanofibers (n = 11, 12). These superstructural and morphological diversifications are an outcome of the variation in the primarily formed hydrogen-bonded supramolecular architectures. Using this strategy, diverse self-assembled materials will be obtained from a single dye component.

The substitution of the bulky substituents, such as the triphenylsilyl groups, on the 9,10-positions of anthracene produced a remarkable increase in Φ f , and the substituents controlled the intermolecular stacking by diminishing the electroplex formation and inter- and intra-molecular photochemical reactions. Organic light-emitting diode (OLED) devices composed of these anthracene derivatives showed highly pure blue electroluminescence (EL).

A perylene bisimide anchored with melamine hydrogen-bonding units has been prepared, and its supramolecular polymerization upon binding with N-dodecylcyanurate (CA) was examined. The resulting flexible supramolecular polymers self-organized via a pi-pi stacking interaction between perylene chromophores, affording ribbonlike aggregates in cyclic alkanes and ropelike aggregates in acyclic alkanes to form gels. [structure: see text]

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., The ability to switch structure or function in response to an external stimulus is highly desirable for many applications. Here, the authors report the guidable supramolecular assembly of photocross-linkable molecules into different complex superstructures, dependant on their exposure to UV light.

Photophysical properties of meridional (mer) and facial (fac) isomers of eight iridium(III) trischelete complexes composed of combination of two ligands, 2-(p-tolyl)pyridine and 2-phenylpyrazole, were investigated. Characteristics of heteroleptic complexes were compared to the homoleptic complexes. Phosphorescence radiation process is rationally explained by inter-ligand energy transfer, however, mer → fac isomerization showed different behavior indicating participation of another excited state.

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.