Facile Synthesis and Photoluminescent Properties of Asymmetric Perylene Diimides Capable of Tuning Emission Colors in Polymeric Matrices.

We report the facile synthesis of asymmetric perylene diimides (asym-PDIs) using readily available reagents, demonstrating their distinct photoluminescent properties. In CHCl3, asym-PDIs exhibit higher solubility compared to traditional perylene dyes, of which solubilities can be varied by substituent selections. Among them, UV-vis absorption spectra of CPE in CHCl3 solution displayed no aggregate peaks in the ground state, maintaining high photoluminescent quantum yields. Also, CPE can be readily dispersed into poly(methyl methacrylate) PMMA (CPE-PMMA), forming thin films without aggregate formation. Importantly, the emission color of CPE-PMMA thin films significantly changes with the addition of polycyclic aromatic hydrocarbons (PAHs). These color changes should be strongly correlated with the HOMO level of the added PAHs.

Stimuli-Responsive Self-Assembly of π-Conjugated Liquids Triggers Circularly Polarized Luminescence.

We developed novel room-temperature stimuli-responsive N-heteroacene-based liquid materials bearing a chiral alkyl chain. When these liquid materials were exposed to HCl vapor as an external stimulus, a disordered-ordered state change occurred immediately to yield self-assembled solid states from fluidic liquids. The self-assembly mechanism during this state change was evaluated by experimental in situ observations and molecular dynamics simulations over various spatiotemporal scales. These self-assembled structures led to supramolecular chirality through the influence of the chiral alkyl chain. As a result, circularly polarized luminescence (CPL) was triggered in the solid state, which was absent in the precursor liquid, thereby rendering this the first report on a stimuli-responsive CPL on/off liquid material. In addition, the initial state was recovered by exposure to air or upon heating. Moreover, the synergy between the experimental and the theoretical studies opens a new avenue to develop a novel class of stimuli-responsive materials and to discover novel phenomena in such materials.

Stimulus-Responsive Supercooled π-Conjugated Liquid and Its Application in Rewritable Media.

Herein, we report a stimulus-responsive supercooled π-conjugated liquid and the possibility of its application in rewritable media. Supercooled liquid 1 showed a dramatic change in its photoluminescent color upon the transformation from liquid 1l (yellow emission) to solid 1s (green emission). These phenomena were revealed by fluorescence spectra as well as lifetime decay profiles.

Gas sorption of nano-porous supramolecules formed by multi-hydrogen bonded coordination capsules.

[{ReI(CO)3(Hbim)}3(tpta)]2 (1, Hbim- = 2,2'-biimidazolate monoanion, tpta = 2,4,6-tripyridyl-1,3,5-triazine) was prepared as a nano-space supramolecule by using a new group of H-bonded coordination capsules. The hamburger bun-shaped half unit [{ReI(CO)3(Hbim)}3(tpta)] contains six intermolecular H-bonds of Hbim- ligands with complementary dual NHN types, and three [ReI(CO)3(Hbim)] are coordinated by bridging tridentate tpta. Interestingly, mechanical grinding easily would convert single crystals of 1 to an amorphous state with minor crystallinity while maintaining the nano-space pores. The ground sample can reversibly uptake and release small molecules such as CO2 and (CH2Cl)2.

Stimuli-responsive Behaviors for Room-temperature Fluorescent Liquid Materials based on N-Heteroacenes and their Mixtures in Response to HCl Vapor and their Facile Synthesis.

In this paper, we report on stimuli-responsive behaviors for room temperature fluorescent liquid materials based on N-heteroacene frameworks in response to HCl vapor. These liquid materials as well as their mixtures prepared by varying the combination can provide various emission colors and stimuli-responsive properties in liquid states. Also, we achieved an improvement in total synthetic yield (>40%) by redesigning the molecular structures of liquid materials as compared to previous liquid materials (<10%).

One-dimensional single-helix coordination polymer self-assembled by a crown-ether appended-N-heteroacene radical anion.

A crown-ether appended N-heteroacene 1 was reduced in the presence of NaBPh4 to the radical anion 2 by accepting one electron transferred from both the cathode and BPh4- as a reductant. The obtained radical anion 2 can function as a radical anion ligand to bridge two sodium ions to self-assemble into one-dimensional helical coordination polymers.

Synthesis and electrochromic behavior of a multi-electron redox-active N-heteroheptacenequinone.

We report a novel N-heteroheptacenequinone derivative (C6OAHCQ) as a large π-conjugated framework. C6OAHCQ shows good electron-accepting behaviour owing to eight electron-deficient imino-N atoms and two carbonyl moieties and excellent solubility in common organic solvents. When a potential between 0 and -2.20 V is applied, C6OAHCQ is able to accept four electrons, which is more than fullerene C60 (three electrons) could accept in this voltage range. Moreover, a solution of C6OAHCQ and nBu4NPF6 in CH2Cl2 exhibits a clearly reversible brown-to-green colour change, suggesting that C6OAHCQ has potential as an electrochromic material.

Stimuli-Responsive Room-Temperature N-Heteroacene Liquid: In Situ Observation of the Self-Assembling Process and Its Multiple Properties.

A novel stimuli-responsive room-temperature photoluminescent liquid 1 based on the N-heteroacene framework is developed and analyzed by several experiments such as differential scanning calorimetry, X-ray diffraction, dynamic viscoelasticity measurement, in situ observation by optical and polarized optical microscopes, UV-vis absorption and fluorescence spectroscopy, and by theoretical methods such as ab initio calculation and molecular dynamics (MD) computer simulation techniques. In contrast to stimuli-responsive solid materials reported previously, liquid 1 in response to HCl vapor as a single stimulus can involve dramatically multiple changes in physical properties such as rheological behavior, morphology, as well as photoluminescence. The present ab initio calculation and microsecond-timescale MD simulations reveal that the complexation of 1 and HCl molecules induces a large dipole moment, leading to the formation of stacking structures because of their dipole-dipole interaction. Upon exposure to HCl vapor, in situ microscopic observation of the stimuli-responsive liquid elucidates a self-assembling process involving the formation of the wrinkle structure in a micrometer scale, indicating disorder-order phase transition. Further exposure of 1 to HCl vapor from seconds to hours has an influence on the macroscopic physical properties such as viscosity, viscoelasticity, and photoluminescent colors. The synergy between the experimental and theoretical investigations opens a new strategy to develop a novel class of stimuli-responsive materials showing multiple changes in physical properties.

Tuning the Electronic Properties and Acid-Response Behavior of N-Heteroacene-Based π-Conjugated Liquids by Changing the Number of π-Conjugated Substituents.

We have designed and synthesized two room-temperature-fluorescent π-conjugated liquids based on the N-heteroacene framework (1 and 2). These two π-conjugated liquids, which contained one and two thiophene rings, respectively, exhibited different electronic properties and rheology behaviors. Single-crystal X-ray analysis of dithiophene-appended compound 4 revealed that two thiophene rings hindered the interactions of the imino N atoms with acids through the formation of interactions between the S atoms of the thiophene rings and the imino N atoms of the pyrazine group. On the other hand, monothiophene-appended molecules 1 and 3 each contained an unhindered imino N atom on the opposite site to the thiophene ring. Upon dissolving various acids with different pKa values in compounds 1 and 2, these slight structural differences gave rise to marked differences in their acid-response behaviors, thereby resulting in the emission of variously colored fluorescence in the liquid state. Furthermore, when acids with lower pKa values was dissolved in compounds 1 and 2, phase transition occurred from an isotropic liquid state to a self-organized liquid-crystalline phase.

Acid-Responsive N-Heteroacene-Based Material Showing Multi-Emission Colors.

An acid-responsive N-heteroacene-based material has been prepared, which shows a blue emission color in a film. The protonation of this material in a thin film gives rise to remarkable changes in luminescent color compared to that in solution states. As the protonation of N-heteroacene molecules in films gradually occurs, their emission color can be tuned by adjusting the exposure time of the thin films to HCl vapor.

Anomalous enhancement of proton conductivity for water molecular clusters stabilized in interstitial spaces of porous molecular crystals.

In an investigation into the proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials, we have found that water-stable nanoporous crystals are formed by complementary hydrogen bonding between [Co(III) (H2 bim)3 ](3+) (H2 bim: 2,2'-biimidazole) and TATC(3-) (1,3,5- tricarboxyl-2,4,6-triazinate); the O atoms in the -COO(-) groups of TATC(3-) in the porous outer wall are strongly hydrogen bonded with H2 O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2 O molecules as a novel C2 -type WMC, which are hydrogen bonded with four-, three-, and two-coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two-coordinated H2 O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre-melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10(-5) S cm(-1) at 300 K with an activation energy of 0.30 eV) through a proton-hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10(-5) S cm(-1) at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b-axis. The proton-transfer route can be predicted in WMCs, as O(4) of an H2 O molecule at the center of an SCTC shows a motion that rotates the dipole in the b-axis direction, but not the c-axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X-ray crystallography reflect a structural fluctuation along the b-axis direction induced by [Co(III) (H2 bim)3 ](3+) .

Electron transport of photoconductive n-type liquid crystals based on a redox-active tetraazanaphthacene framework.

The preparation of two liquid crystals composed of a redox-active tetraazanaphthacene (TANC) framework is reported. The materials form smectic A (SmA) thin-film liquid-crystalline (LC) phases over a wide temperature range. Cyclic voltammetry analysis revealed that LC TANCs behave as organic electron acceptors. The electron mobilities of the thin films were determined by time- of-flight (TOF) measurements, which are the order of 10(-4)  cm(2) V(-1) s(-1) in the SmA LC phase. This value is two orders of magnitude larger than those of amorphous organic semiconductors. To the best of our knowledge, very few reports exist on the electron-transporting behaviors of LC N-heteroacene semiconductors.

DNA terminal mismatch-induced stabilization of polymer micelles from RAFT-generated poly(N-isopropylacrylamide)-DNA block copolymers.

Temperature-responsive diblock copolymers made of poly(N-isopropylacrylamide) (PNIPAAm) generated by reversible addition-fragmentation chain transfer (RAFT) polymerization and a single-stranded DNA (ssDNA) self-assembled into polymer micelles. The micelles consisted of the PNIPAAm core surrounded by the ssDNA corona with a hydrodynamic diameter up to 300 nm in an aqueous medium above the lower critical solution temperature. In a medium of high ionic strength, the formation of the fully matched duplex with the complementary ssDNA on the surface of the polymer micelles induced rapid and spontaneous aggregation. By contrast, the micelles remained dispersed under the identical conditions when single-base-substituted ssDNA was added to form the corresponding terminal-mismatched duplex on the micellar surface. This highly sequence-selective process took place irrespective of the size of the PNIPAAm core.

Molecular cable-like 1-D iodic spiral chains covered with triple helices stabilized in guest-included chiral porous framework.

The supramolecular crystal {[Pr(DMFA)](3)[Ni(II)(Hbim)(3)](2)I}(n) with intricate chiral networks of [Ni(II)(Hbim)(3)](-) molecules is reported. It includes a cationic architecture as a guest, constructed from chiral nanotubes that penetrate I(-) chains with spiral channels wrapped by triple helices. The I(-) chains have AC conductivity in crystals like a molecular cable.

Truxene-based columnar liquid crystals: self-assembled structures and electro-active properties.

Columnar liquid-crystalline (LC) truxene derivatives containing branched flexible alkyl chains have been designed and synthesized. The dicyanomethylene and dithiafulvene substituents have been introduced into the pi-conjugated truxene framework to tune their electronic and redox properties as well as the molecular assembled structures. The pi-conjugated cores of dicyanomethylene- and dithiafulvene-appended truxenes adopt bowl-shaped conformations, giving rise to a large intrinsic dipole moment perpendicular to the aromatic framework. These molecules form stable columnar LC structures through intermolecular dipole-dipole interactions. The redox properties of LC truxene derivatives have been examined by cyclic voltammetry. The dicyanomethylene-appended truxene shows the reversible four-step electrochemical reductions, whereas the dithiafulvene-appended truxene undergoes three-step oxidations.