Stable Single‐Molecule Lines of Terrylene in Polycrystalline para‐Dichlorobenzene at 1.5 K

The spectroscopic properties of single terrylene (Tr) molecules are studied in a polycrystalline matrix of para‐dichlorobenzene (p‐DCB) at 1.5 K. Samples grown in a glass capillary show a very strong site at 597 nm, which is redshifted by more than 700 cm^?1 from the observed transition energy for Tr in p‐DCB prepared as a film on a coverslip (572 nm). Each of these two sites is characterized by measuring their single‐molecule spectroscopic parameters at 1.5 K. Lifetime‐limited linewidths of 45±5 MHz are found for both sites. Fluorescence detection rates reach 8×10⁴ count s^?1 at saturation. The spectral trails of the majority of single molecules show no spectral jumps, indicating an absence of interacting two‐level systems; however, the small distribution of linewidths may indicate weak interactions with low‐frequency modes. Frequency jumps are observed for 10 % of the molecules. The complete emission spectra from two different single molecules at the center of each of the two sites is presented. Debye–Waller factors of α_DW=0.33±0.05 for the normal site (572 nm) and α_DW=0.30±0.05 for the red site (597 nm) are reported. This new host–guest system provides a quick and easy way to obtain lifetime‐limited single‐molecule lines.     

Periodic Mesoporous Organosilica with Molecular‐Scale Ordering Self‐Assembled by Hydrogen Bonds

Nanoporous materials with functional frameworks have attracted attention because of their potential for various applications. Silica‐based mesoporous materials generally consist of amorphous frameworks, whereas a molecular‐scale lamellar ordering within the pore wall has been found for periodic mesoporous organosilicas (PMOs) prepared from bridged organosilane precursors. Formation of a “crystal‐like” framework has been expected to significantly change the physical and chemical properties of PMOs. However, until now, there has been no report on other crystal‐like arrangements. Here, we report a new molecular‐scale ordering induced for a PMO. Our strategy is to form pore walls from precursors exhibiting directional H‐bonding interaction. We demonstrate that the H‐bonded organosilica columns are hexagonally packed within the pore walls. We also show that the H‐bonded pore walls can stably accommodate H‐bonding guest molecules, which represents a new method of modifying the PMO framework.     

A Single‐Step Synthesis of Electroactive Mesoporous ProDOT‐Silica Structures

The single‐step preparation of highly ordered mesoporous silica hybrid nanocomposites with conjugated polymers was explored using a novel cationic 3,4‐propylenedioxythiophene (ProDOT) surfactant (PrS). The method does not require high‐temperature calcination or a washing procedure. The combination of self‐assembly of the silica surfactant and in situ polymerization of the ProDOT tail is responsible for creation of the mesoporosity with ultralarge pores, large pore volume, and electroactivity. As this novel material exhibits excellent textural parameters together with electrical conductivity, we believe that this could find potential applications in various fields. This novel concept of creating mesoporosity without a calcination process is a significant breakthrough in the field of mesoporous materials and the method can be further generalized as a rational preparation of various mesoporous hybrid materials having different structures and pore diameters.     

Interplay of Hole Transfer and Host–Guest Interaction in a Molecular Dyad and Triad: Ensemble and Single‐Molecule Spectroscopy and Sensing Applications

A new molecular dyad consisting of a Cy5 chromophore and ferrocene (Fc) and a triad consisting of Cy5, Fc, and β‐cyclodextrin (CD) are synthesized and their photophysical properties investigated at both the ensemble and single‐molecule levels. Hole transfer efficiency from Cy5 to Fc in the dyad is reduced upon addition of CD. This is due to an increase in the Cy5‐Fc separation (r) when the Fc is encapsulated in the macrocyclic host. On the other hand, the triad adopts either a Fc‐CD inclusion complex conformation in which hole transfer quenching of the Cy5 by Fc is minimal or a quasi‐static conformation with short r and rapid charge transfer. Single‐molecule fluorescence measurements reveal that r is lengthened when the triad molecules are deposited on a glass substrate. By combining intramolecular charge transfer and competitive supramolecular interaction, the triad acts as an efficient chemical sensor to detect different bioactive analytes such as amantadine hydrochloride and sodium lithocholate in aqueous solution and synthetic urine.     

Nanoparticle Vesicles Through Self Assembly of Cyclodextrin‐ and Adamantyl‐Modified Silica

Stable nanoparticle vesicles were for the first time prepared from adamantyl‐ and cyclodextrin (CD)‐modified silica nanoparticles forming host–guest interactions in aqueous solution. Adamantyl‐functionalized nanoparticles were obtained from thiol‐isocyanate reaction of thiol‐modified nanoparticles with 1‐adamantyl isocyanate. The CD modified silica particles were isolated from a reaction of mono‐6‐para‐toluenesulfonyl‐β‐cyclodextrin with the thiol functionalized silica under microwave conditions in basic media. The obtained particles were characterized in respect of agglomeration and self‐assembly behavior in aqueous solution by dynamic light scattering and transmission electron microscopy. The found vesicle structures are exceptionally stable even after evaporation of water. Such inorganic hollow spheres formed through self‐assembly processes may be important for chemical storage and transport. The technique of chemically‐driven assembly is an attractive option to form useful complex structures by tunable agglomeration.

     

Influence of Guest Exchange on the Magnetization Dynamics of Dilanthanide Single‐Molecule‐Magnet Nodes within a Metal–Organic Framework

Multitopic organic linkers can provide a means to organize metal cluster nodes in a regular three‐dimensional array. Herein, we show that isonicotinic acid N‐oxide (HINO) serves as the linker in the formation of a metal–organic framework featuring Dy₂ single‐molecule magnets as nodes. Importantly, guest solvent exchange induces a reversible single‐crystal to single‐crystal transformation between the phases Dy₂(INO)₄(NO₃)₂?2 solvent (solvent=DMF (Dy₂‐DMF), CH₃CN (Dy₂‐CH₃CN)), thereby switching the effective magnetic relaxation barrier (determined by ac magnetic susceptibility measurements) between a negligible value for Dy₂‐DMF and 76 cm^?1 for Dy₂‐CH₃CN. Ab initio calculations indicate that this difference arises not from a significant change in the intrinsic relaxation barrier of the Dy₂ nodes, but rather from a slowing of the relaxation rate of incoherent quantum tunneling of the magnetization by two orders of magnitude.     

Orientation‐Controlled Single‐Molecule Junctions

The conductivity of a single aromatic ring, perpendicular to its plane, is determined using a new strategy under ambient conditions and at room temperature by a combination of molecular assembly, scanning tunneling microscopy (STM) imaging, and STM break junction (STM‐BJ) techniques. The construction of such molecular junctions exploits the formation of highly ordered structures of flat‐oriented mesitylene molecules on Au(111) to enable direct tip/π contacts, a result that is not possible by conventional methods. The measured conductance of Au/π/Au junction is about 0.1 G_o , two orders of magnitude higher than the conductance of phenyl rings connected to the electrodes by standard anchoring groups. Our experiments suggest that long‐range ordered structures, which hold the aromatic ring in place and parallel to the surface, are essential to increase probability of the formation of orientation‐controlled molecular junctions.     

Fine‐Tuning Mesochannel Orientation of Organically Functionalized Mesoporous Silica Nanoparticles

Three orientations to choose from : 2D hexagonal organically functionalized mesoporous silica nanoparticles with tunable mesochannel orientation (straight, helical, and radial mesochannels) were synthesized through a simple addition of various amounts of ureidopropyltrimethoxylsilane (UDPTMS) in the condensation of tetraorthosilicate (TEOS) in aqueous solution.

     

Charge Separation in a Multifunctionalized Framework of Hydrogen‐Bonded Periodic Mesoporous Organosilica

Integration of functional molecular parts into nanoporous materials in a state that allows intermolecular charge or energy transfer is one of the key approaches to the development of photofunctional and electroactive materials. Herein, we report charge separation in a functionalized framework of a periodic mesoporous organosilica (PMO) self‐assembled by hydrogen bonds. Electroactive π‐conjugated organic species with different electron‐donating and electron‐accepting properties were selectively fixed onto the external surface of a nanoparticulate PMO, within the pore wall, and onto the surface of the internal mesopore. UV irradiation of the modified PMO resulted in photoinduced electron transfer and charge separation from the external surface to the pore wall and from the pore wall to the surface of the internal mesopores. These results suggest the high potential of multifunctionalized PMOs in the construction of photocatalytic reaction fields.     

Allyl‐Functionalized Dioxynaphthalene[38]Crown‐10 Macrocycles: Synthesis,Self‐Assembly,and Thiol‐ene Functionalization

Five dioxynaphthalene[38]‐crown‐10 ( DNP38C10 ) macrocycles bearing one, two, three, or four allyl moieties have been synthesized and their ability to spontaneously self‐assemble with methyl viologen to form [2]pseudorotaxanes has been evaluated. Association constants between methyl viologen and several of the allyl‐functionalized DNP38C10 macrocycles are found to be comparable to that of methyl viologen and unfunctionalized DNP38C10 , however, the enthalpic and entropic factors that underlie overall binding free energy vary systematically with increasing allyl substitution. These variations are explained through a combination of solution phase and solid‐state analysis of the macrocycles and their complexes. The utility of endowing DNP38C10 macrocycles with allyl moieties is further demonstrated by the ease with which they can be functionalized through thiol‐ene click chemistry.     

A Porphyrin‐Based Discrete Tetragonal Prismatic Cage: Host–Guest Complexation and Its Application in Tuning Liquid‐Crystalline Behavior

The host–guest complexation between a porphyrin‐based 3D tetragonal prism ( H ) and electron‐rich pyrene is investigated. This host–guest molecular recognition is further utilized to suppress the liquid‐crystalline behavior of a nematic molecule ( G ) containing cyanobiphenyl mesogens functionalized with a pyrenyl unit. Furthermore, coronene, with an increased number of π‐electrons, is used as a competitive guest to recover the liquid‐crystalline behavior of G . This supramolecular approach provides a glimpse of the new possibilities to modulate the structures of the mesophases.

     

Manganese‐Doped Highly Ordered Mesoporous Silicate with High Efficiency for Oxidation Suppression

Herein, we demonstrate a facile approach to manganese‐doped highly ordered mesoporous silicate with oxidation‐suppression function. As biocompatible supports of guest ions, the ordered mesoporous silicate was synthesized by evaporation‐induced self‐assembly. The phase‐transition from disordered to lamellar structures in the highly ordered mesoporous structure of these porosity‐tuned materials was controlled by adjusting the concentration of a lab‐made polystyrene‐b‐polyethylene oxide copolymer. Manganese was successfully incorporated as a guest in the hexagonally packed mesoporous silicate by using an ultrasound‐assisted technique. The incorporation of manganese ions into the pores of a mesoporous silicate support could be induced for host–guest functional applications. Manganese‐doped mesoporous silicate structures have been examined for their use as antioxidizing agents by electron spin resonance (ESR) measurements and radical‐scavenging tests. The manganese atoms in the mesoporous structures could act in a free‐radical‐scavenging capacity, much like manganese nanoparticles. The high efficiency of their oxidation‐suppression function is extended for application to catalytic products.     

The Interactions of Spore‐Coat Morphogenetic Proteins Studied by Single‐Molecule Recognition Force Spectroscopy

Bacillus subtilis can form a spore, which is a dormant type of cell, when its external environment becomes unsuitable for vegetative growth. The spore is surrounded by a multilayered proteinaceous shell called a spore coat, which plays a crucial role in dormancy and germination. Of the over 70 proteins that form the spore coat, only a small subset of them affect its morphogenesis; they are referred to as morphogenetic proteins. How these morphogenetic proteins interact, and furthermore, how they build the ordered, functional coat layers is not well understood. Elucidating the self‐assembly mechanism of individual proteins into such a complex structure may contribute to its potential use in nano‐biotechnology applications for preparing highly organized, robust, and resistant proteinaceous layers. Herein, direct, noncovalent, low‐affinity interactions between the spore‐coat morphogenetic proteins SpoIVA, SpoVID, and SafA were studied by using single‐molecule recognition force spectroscopy in vitro for the first time. Based on the real‐time examination of interactions between these three proteins, a series of dynamic kinetic data were obtained. It was also observed that the SafA–SpoVID interaction was stronger than that of SafA–SpoIVA.     

Development of C3‐Symmetric Tris‐Urea Low‐Molecular‐Weight Gelators

This article describes recent developments in C₃‐symmetric tris‐urea low‐molecular‐weight gelators and their applications. The C₃‐symmetric tris‐ureas are excellent frameworks to form supramolecular polymers through noncovalent interactions. In organic solvents, hydrophobic tris‐ureas form supramolecular gels. Amphiphilic tris‐ureas form supramolecular gels in aqueous media. Functional supramolecular gels were prepared by introducing appropriate functional groups into the outer sphere of tris‐ureas. Supramolecular hydrogels obtained from amphiphilic tris‐ureas were used in the electrophoresis of proteins. These electrophoreses results showed several unique characteristics compared to typical electrophoreses results obtained using polyacrylamide matrices.

     

Controlled Self‐Assembly by Mono‐p‐sulfonatocalix[n]arenes and Bis‐p‐sulfonatocalix[n]arenes

The complexation‐induced critical aggregation concentrations of 1‐pyrenemethylaminium by mono‐p‐sulfonatocalix[n]arenes and bis‐p‐sulfonatocalix[n]arenes (n=4, 5) were systemically measured by fluorescence spectroscopy. In all cases, the complexation‐induced critical aggregation concentration decreases by about 3 times upon addition of p‐sulfonatocalix[n]arenes. However, the optimal molar ratios for the aggregation of 1‐pyrenemethylaminium by mono‐p‐sulfonatocalix[n]arenes and bis‐p‐sulfonatocalix[n]arenes are distinctly different: For mono‐p‐sulfonatocalix[n]arenes, the optimum mixing ratio for the aggregation of 1‐pyrenemethylaminium is 1:4 mono‐p‐sulfonatocalix[n]arenes/1‐pyrenemethylaminium, whereas only 2.5 molecules of 1‐pyrenemethylaminium can be bound by one cavity of bis‐p‐sulfonatocalix[n]arenes. The intermolecular complexation of mono‐p‐sulfonatocalix[n]arenes and bis‐p‐sulfonatocalix[n]arenes with 1‐pyrenemethylaminium led to the formation of two distinctly different nanoarchitectures, which were shown to be nanoscale vesicle and rod aggregates, respectively, by using dynamic laser scattering, TEM, and SEM. This behavior is also different from the fiber‐like aggregates with lengths of several micrometers that were formed by 1‐pyrenemethylaminium itself above its critical aggregation concentration. Furthermore, the obtained nanoaggregates exhibit benign water solubility, self‐labeled fluorescence, and, more importantly, temperature responsiveness.     

Single‐Molecule Spectroscopy on a Ladder‐Type Conjugated Polymer: Electron–Phonon Coupling and Spectral Diffusion

We employ low‐temperature single‐molecule spectroscopy combined with pattern recognition techniques for data analysis on a methyl‐substituted ladder‐type poly(para‐phenylene) (MeLPPP) to investigate the electron–phonon coupling to low‐energy vibrational modes as well as the origin of the strong spectral diffusion processes observed for this conjugated polymer. The results indicate weak electron–phonon coupling to low‐frequency vibrations of the surrounding matrix of the chromophores, and that low‐energy intrachain vibrations of the conjugated backbone do not couple to the electronic transitions of MeLPPP at low temperatures. Furthermore, these findings suggest that the main line‐broadening mechanism of the zero‐phonon lines of MeLPPP is fast, unresolved spectral diffusion, which arises from conformational fluctuations of the side groups attached to the MeLPPP backbone as well as of the surrounding host material.