TP Molecules Research Articles

Two-Dimensional CuMn-Layered Double Hydroxides: A Study of Interlayer Anion Variants on the Electrochemical Sensing of Trichlorophenol.

Despite their diverse application profile, aromatic organochlorides such as 2,4,6-trichlorophenol (TP) are widely renowned for creating a negative toll on the balance of the ecosystem. Strict regulatory regimes are required to limit exposure to such organic pollutants. By deployment of a straightforward detection scheme, electrochemical sensing technology offers a competitive edge over the other techniques and practices available for pollutant monitoring. Here, we present a streamlined hydrothermal approach for synthesizing copper-manganese layered double hydroxide (CuMn-LDH) rods to be employed as electrocatalysts for detecting TP in various media. With a focused intention to leverage the full potential of the prepared CuMn-LDHs, the interlamellar region is configured using a series of intercalants. Further, a thorough comparative analysis of their structures, morphologies, and electrochemical performance is accomplished using various analytical techniques. The electrocatalytic oxidation ability of the CuMn-LDH toward TP molecules is markedly altered by incorporating various anions into the gallery region. The dynamic attributes of the developed sensor, such as a wide linear response (0.02-289.2 μM), a low detection limit (0.0026 μM), and good anti-interfering ability, acclaim its superior viability for real-time detection of TP with exceptional tolerance to the presence of foreign moieties. Hence, this work manifests that the nature of intercalants is a vital aspect to consider while designing LDH-based electrochemical probes to detect priority pollutants.

Design and Investigation of New Water-Soluble Forms of α-Tocopherol with Antioxidant and Antiglycation Activity Using Amphiphilic Copolymers of N-Vinylpyrrolidone.

Water-soluble forms of α-tocopherol (TP) as an effective antioxidant were obtained by encapsulating it into nanoparticles (NPs) of amphiphilic copolymers of N-vinylpyrrolidone with triethylene glycol dimethacrylate (CPL1-TP) and N-vinylpyrrolidone with hexyl methacrylate and triethylene glycol dimethacrylate (CPL2-TP) synthesized by radical copolymerization in toluene. The hydrodynamic radii of NPs loaded with TP (3.7 wt% per copolymers) were typically ca. 50 or 80 nm depending on copolymer composition, media, and temperature. Characterization of NPs was accomplished by transmission electron microscopy (TEM), IR-, and 1H NMR spectroscopy. Quantum chemical modeling showed that TP molecules are capable to form hydrogen bonds with donor groups of the copolymer units. High antioxidant activity of both obtained forms of TP has been found by the thiobarbituric acid reactive species and chemiluminescence assays. CPL1-TP and CPL2-TP effectively inhibited the process of spontaneous lipid peroxidation as well as α-tocopherol itself. The IC50 values of luminol chemiluminescence inhibition were determined. Antiglycation activity against vesperlysine and pentosidine-like AGEs of TP water-soluble forms was shown. The developed NPs of TP are promising as materials with antioxidant and antiglycation activity and can be used in various biomedical applications.

Efficient Hole Transfer from a Twisted Perylenediimide Acceptor to a Conjugated Polymer in Organic Bulk-Heterojunction Solar Cells.

Non-fullerene acceptors have recently attracted tremendous interest due to their potential as alternatives to fullerene derivatives in bulk-heterojunction solar cells. Nevertheless, physical understanding of charge carrier generation and transfer mechanism that occurred at the interface between the non-fullerene molecule and donor polymer is still behind their enhanced photovoltaic performance. Here we report examples of a non-planar perylene dimer (TP) as an electron acceptor and achieve a power conversion efficiency of 6.29% in a fullerene-free solar cell. Photoluminescence (PL) measurements show high quenching efficiency driven by the excitons of both conjugated polymer and TP molecule, respectively, indicating efficient electron and hole transfer, which can support a highly intermixed phase of blends measured by atomic force microscopy (AFM) and grazing incident wide-angle X-ray diffraction (GIWAXS). Femtosecond transient absorption spectroscopy (fs-TAS) reveals that the fast exciton dissociation process from TP molecule to donor polymer contributes to additionally increasing current density, leading to stronger incident photon to current efficiency in the visible region.

Th17/Treg imbalance mediates hepatic intolerance to exogenous lipopolysaccharide and exacerbates liver injury in triptolide induced excessive immune response

Ethnopharmacological relevanceTriptolide (TP) is a major active ingredient and toxic component of Tripterygium wilfordii Hook F (TWHF), which exhibits multiple activities and remarkable hepatotoxicity, the latter of which limits its clinical application due to the risk of liver injury. Previous research has revealed the hepatotoxicity of TP resulting in liver hypersensitivity upon lipopolysaccharide (LPS) stimulation. However, existing research has not elucidated the potential immune mechanism such as Th17/Treg imbalance in TP-induced hepatic excessive immune response to exogenous LPS. Aim of the studyTo investigate the role of Th17/Treg imbalance in TP-induced hepatic excessive immune response to exogenous LPS. Materials and methodsMice were administered with TP, LPS, neutralization antibody and small molecule inhibitor respectively. Serum transaminase level was measured to determine the severity of liver injury. Frequencies of liver Th17 and Treg cells were analyzed by flow cytometry. Serum cytokine levels were performed by ELSIA, and mRNA levels of liver cytokine were performed by qPCR. The status of neutrophil infiltration was performed by myeloperoxidase (MPO) IHC measurement. Morphological observation of liver was performed by hematoxylin and eosin (H&E) staining. ResultsMice given a single intragastric dose of TP (500 μg/kg) developed lethal fulminant hepatitis following intraperitoneal injection of LPS (0.1 mg/kg), characterized by low survival rate, severe liver injury, high levels of inflammation and neutrophil infiltration. Hepatic Th17/Treg imbalance emerged together with liver injury in these mice. Neutralization of IL-17A attenuated the liver injury and ameliorated the neutrophil infiltration. The TP-induced alteration of hepatic Th17/Treg balance was closely related to the outcome of immune-mediated acute liver injury triggered by LPS. Pretreatment with the STAT3 inhibitor AG490 effectively restored Th17/Treg balance, significantly reducing the production of IL-17A and finally attenuating the degree of liver injury. ConclusionHepatic Th17/Treg imbalance not only exacerbates TP- and LPS-induced liver injury, but also serves as an indispensable part in the mechanisms of TP-induced hepatic intolerance to exogenous endotoxin.

Morphological transformation in the supramolecular assembly of discotic liquid crystal molecules using silver nanoparticles and its sensing application

Triphenylene based discotic liquid crystal (TP) molecules are rich in π-electrons which facilitate π-stacking interaction of the molcules leading to formation of one dimensional nanowires. These nanowires can assemble to form nanoribbons due to a lateral cohesive force among the nanowires. The flat nanoribons undergo a morphological transformation due to incorporation of silver nanoparticles (SNP) into the matrix of TP molecules. The presence of SNP induces a chiral twisting to the nanoribbons and therefore the flat nanoribbons transform into a helical nanoribbon structure. The global chiral structure exhibited by the composition of achiral constituents is due to the creation of topological defects like disclination and dislocation. These defects can lead to a geometrical frustration in the nanoribbons which relaxes with the formation of twisted helical nanoribbons. A minor change in morphology of the supramolecular assembly can have a remarkable effect on the physicochemical properties of the nanoribbons. In this article, we demonstrate that even a minor change in the geometry of aliphatic chains on the surface of nanoribbons can be employed for sensing organic solvents such as acetone and ethanol. The sensing was performed at room temperature. Relative humidity has no effect on the sensing response.

Vitamin E-Loaded PLA- and PLGA-Based Core-Shell Nanoparticles: Synthesis, Structure Optimization and Controlled Drug Release.

The (±)-α-Tocopherol (TP) with vitamin E activity has been encapsulated into biocompatible poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) carriers, which results in the formation of well-defined nanosized (d ~200–220 nm) core-shell structured particles (NPs) with 15–19% of drug loading (DL%). The optimal ratios of the polymer carriers, the TP active drug as well as the applied Pluronic F127 (PLUR) non-ionic stabilizing surfactant, have been determined to obtain NPs with a TP core and a polymer shell with high encapsulation efficiency (EE%) (69%). The size and the structure of the prepared core-shell NPs as well as the interaction of the carriers and the PLUR with the TP molecules have been determined by transmission electron microscopy (TEM), dynamic light scattering (DLS), infrared spectroscopy (FT-IR) and turbidity studies, respectively. Moreover, the dissolution of the TP from the polymer NPs has been investigated by spectrophotometric measurements. It was clearly confirmed that increase in the EE% from ca. 70% (PLA/TP) to ca. 88% (PLGA65/TP) results in the controlled release of the hydrophobic TP molecules (7 h, PLA/TP: 34%; PLGA75/TP: 25%; PLGA65/TP: 18%). By replacing the PLA carrier to PLGA, ca. 15% more active substance can be encapsulated in the core (PLA/TP: 65%; PLGA65/TP: 80%).

Unidirectional diffusion synthesis of covalent organic frameworks (COFs) on polymeric substrates for dye separation

Covalent organic frameworks (COFs) are regarded as important candidates for the preparation of advanced membranes with remarkable performances on account of their uniform and tailorable channels and good chemical stability. The development of COFs-based membranes is burgeoning, and there remains lacking of facile and mild methods to prepare to these membranes. Herein, we report on the unidirectional diffusion synthesis (UDS) of TpPa (an imine-based COFs) on commercial polyvinylidene fluoride (PVDF) microfiltration substrates for the preparation of composite COFs-based membranes at room temperature. The p-phenylenediamine (Pa) aqueous solution and 1,3,5-triformylphloroglucinol (Tp) n-hexane solution were separately charged into the two sides of a diffusion cell. With the suitable solution pairs and molar ratio of two precursors, only Pa molecules can pass through the macropores of PVDF to react with Tp molecules at the phase interface formed by this solution pairs, leading to the in situ synthesis of TpPa layer on the top side of PVDF substrates. The membrane fabricated with a synthesized duration of 24 h exhibits a superior selectivity for dyes (>90%) and appreciable water permeance (60 L·m−2·h−1·bar−1). The permeance of the resultant membrane is ∼2–20 times higher than other reported membranes with comparable dye rejections. The UDS offers a facile and mild process to directly grow COFs on porous polymeric substrates to construct composite membranes capable of efficient separations of dye molecules.

Enhancement of C-phycocyanin purity using negative chromatography with chitosan-modified nanofiber membrane.

In this work, a chitosan-modified nanofiber membrane was fabricated and used to examine the permeation characteristics of C-phycocyanin (CPC) obtained from Spirulina platensis. The effects of NaCl concentration (0.1-1.0 M), chitosan coupling pH (6-8), chitosan coupling concentration (0.1-3.0%), algal solution pH (6-8), algal mass concentration (0.1-1.0% dw/v), and membrane flux (4.08 × 10-2-2.04 × 10-1 mL/min·cm2) on the penetration performance of the membrane for CPC were investigated. The results show that the order of binding selectivity of the membrane for these proteins is contaminating proteins (TP) > allophycocyanin (APC) > CPC. TP and APC molecules were more easily adsorbed by the chitosan-modified membrane, and the CPC molecules most easily penetrated the membrane without being adsorbed, enhancing CPC purity. The purification factor and total mass flux were 3.3 fold and 66%, respectively, in a single step.

A thiophene-based blue-fluorescent emitting chemosensor for detecting indium (III) ion

A thiophene-based chemosensor TP, ((Z)-N′-(pyridine-2-ylmethylene)thiophene-2-carbohydrazide), was synthesized and characterized. TP showed a significant fluorescence enhancement only in the presence of In3+. Importantly, the detection limit was calculated to be 0.61 μM, which is the lowest one reported to date. Job plot and ESI-mass analyses indicated that two TP molecules bind to one In3+ ion. In addition, the sensing mechanism of TP towards In3+ was proposed as chelation-enhanced fluorescence (CHEF) effect from the theoretical calculations.

Zn(tp)(RdmB)(H2O)] and [Cd(tp)(RdmB)]: Two Unusual One-Dimensional Rhodamine B Coordination Polymeric Ribbons as Luminescent Sensors for Small Molecules and Metal Cations

Two new complexes, [Zn(tp)(RdmB)(H2O)] (I) and [Cd(tp)(RdmB)] (II) (tp = terephthalate, RdmB = rhodamine B), are obtained by similar hydrothermal synthesis reactions. X-ray crystallography reveals that both compounds are one-dimensional (1D) polymeric solids, in which I (C36H36N2O8Zn) ascribes to monoclinic C2/m space group, Z = 4 (a = 18.834(5) A, b = 16.859(5) A, c = 10.111(3) A, β = 97.638(4)°), while II (C108H102N6O21Cd3) crystallizes in monoclinic P21/n, 4 (a = 12.2309(1) A, b = 61.5661(7) A, c = 12.5852(1) A, β = 93.951(1)°). Owing to the difference in the coordination sphere around the metal center, four-coordinated zinc centers for I bridged by linear tp molecules associated with RdmB ligands result in an interesting 1D infinite zigzag tape-like structure, whereas six-/seven-coordinated cadmium centers for II bridged by the same ligands generate a novel 1D infinite biserrated edge ribbon structure with a 2,3,3-linked {62.10}{63}{6} network or a simplified 2,4-linked {43.62.8}{4} topological networ...

Solvent Effect on Morphology and Optical Properties of Poly(3-hexylthiophene):TIPS-Pentacene Blends

Optical, electrical, and morphological properties of poly(3-hexylthiophene):6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene (P3HT:TP) blend films, in the proportion of 1:1 (w/w), have been investigated using chloroform, toluene, or trichlorobenzene as solvent. The main morphological feature was formation of aggregates that tended to segregate vertically, exhibiting characteristics that were strongly influenced by the type of solvent applied. The phase segregation of TP observed for the P3HT:TP blend film obtained using chloroform, the most volatile of the investigated solvents, can be explained based on the Marangoni effect and the Flory–Huggins model. The TP molecules induce better organization of P3HT, as evidenced by the ultraviolet–visible (UV–Vis) absorption spectra. Photoluminescence (PL) measurements revealed quenching and an increase in the lifetime of the carriers. The PL measurements also showed that the exciton dissociation was dependent on the characteristics of the surface on which the film was deposited. P3HT:TP blend film prepared using trichlorobenzene showed the best morphology with moderate phase segregation and better P3HT ordering. The output current from organic field-effect transistors (OFETs) with blend film prepared using trichlorobenzene was three times (3×) larger than when using the other solvents, with carrier mobility of 5.0 × 10−3 cm2 V−1 s−1.

(Invited) High-Yield and Long-Lived Triplet Excited States of Pentacene Alkanethiolate Monolayer Protected Gold Nanoparticles By Singlet Fission

Photochemical conversion to high-yield and log-lived triplet excited states of organic molecules is an interesting research content. For example, three-dimensional self-assembled monolayers (SAMs) of organic dyes on metal nanoparticles (MNP) are highly promising as photofunctional nanomaterials. A major research topic is light energy conversion via photoinduced processes such as electron and energy transfer. The other application is optical molecular rulers (nanoruler) in the biological fields. In these cases, a serious problem of organic dye-modified SAMs on MNP is the significant deactivation pathway of the excited states of dyes caused mainly by the fast nanosurface energy transfer (NSET). Actually, more than 90% of fluorescence is quenched and formation of the excited triplet states is negligible. Therefore, the formation of high-yield and long-lived triplet excited states on MNP is favorable for various applications relaying on photoinduced processes. Generation of efficient singlet fission (SF) on gold nanoparticles (GNP) is a promising method to overcome the above-mentioned problem. SF is described as a spin-allowed process in which one singlet exciton splits into two triplet excitons.1 In our study, TIPS-pentacene-alkanethiolate monolayer-protected gold nanoparticles with different chain lengths and particle sizes were successfully synthesized to efficiently generate excited triplet states by singlet fission (Fig. 1). Time-resolved spectroscopy revealed high-yield excited triplet states by suppressing ET to the gold surface.2 The mean diameters (R CORE) of TP-C11-S-MPC and TP-C11-L-MPC are 1.65 ± 0.30 nm and 2.13 ± 0.33 nm, respectively. The core of TP-C11-S-MPC and TP-C11-L-MPC contains 158 and 338 Au atoms, respectively. Moreover, based on the values of elemental analysis, there are 51 and 75 TP molecules on one GNP. In addition, the coverage ratios of TP units (γ) to surface Au atoms in TP-C11-S-MPC and TP-C11-L-MPC are 63% and 51%, respectively. Steady-state absorption and fluorescence spectra of TP-Cn-X-MPCs and TP-Ref were measured in toluene. In absorption spectra (Fig. 2A), the spectral shape of TP-C11-S-MPC (spectrum a) matches well with that of TP-Ref (spectrum b).The fluorescence of TP-C11-S-MPC was strongly quenched relative to TP-Ref. To compare the emission spectral shapes, the fluorescence spectra of TP-C11-S-MPC (spectrum a) and TP-Ref (spectrum b) were normalized in Fig. 2B. The fluorescence excitation spectrum was observed (spectrum c in Fig. 2A) to carefully check the fluorescence species of TP-C11-S-MPC. Then, Fig. 2C shows the femtosecond transient spectra of TP-C11-S-MPC. After laser pulse excitation, the triplet–triplet absorption of TP units at ca. 520 nm develops, whereas the singlet–singlet absorption at ca. 630 nm decays. The maximum Φ Τ values attained 172 ± 26% and 157 ± 17% in TP-C11-S-MPC and TP-C7-S-MPC, respectively. [1] Hasobe, T. et al, J. Phys. Chem. A 2016, 120, 1867. [2] Hasobe, T. et al, Angew. Chem. Int. Ed. 2016, 55, 5230. Figure 1

Effect of anchoring atom and electrostatic gating on the electronic transport properties in single molecular electronic devices

The effect of anchoring atom and electrostatic gate on the electron transport through gated thiophene single molecular device is studied by utilizing non-equilibrium Green’s function coupled with self-consistent extended Huckel theory. Gated gold–molecule–gold junctions are built using thiophene (Tp) molecule as functional component and sulphur (S) and selenium (Se) as anchoring atoms in field effect transistor (FET) configuration. The electron transport analysis of the gated thiophene single molecular device is investigated through the current–voltage and the electron transmission spectra. The results show that the anchoring atoms modulate the transport nature of these devices in a controlled manner. We find that the S–Tp–S device produces larger current than Se–Tp–Se device. Also we studied the effect of electrostatic gating on S–Tp–S and Se–Tp–Se device. We find that, positive bias or negative bias for Vg, will correspondingly, raise or lower the transmission coefficients T(E) in relation to the Fermi level (EF) for both the devices. Our results show that magnitude of Isd current varies more than one order for same Vsd over different Vg bias for S–Tp–S device, whereas for Se–Tp–Se device Isd current varies more than five times for same Vsd over different Vg bias. Se–Tp–Se device shows gate controlled NDR behavior. Finally, we demonstrated the application of using thiophene based single molecular FET to realize five basic logic gates very low Vsd bias. The key feature of the suggested design is the opportunity of demonstrating various logic gates with just one molecular unit transistor and demonstrated at very low Vsd bias.

Poly(3-hexylthiophene): TIPS-pentacene blends aiming transistor applications

Poly(3-hexylthiophene):6,13-bis(triisopropylsilylethynyl)-pentacene (P3HT:TP) blends with a ratio of 1:1 (wt/wt) were deposited via spin coating on anodized oxide (Al2O3). A phase separation of the compounds was observed, resulting in the formation of crystalline aggregates of TP molecules that segregate vertically on the surface. The form of segregation depends on the oxide surface treatment used. Spectroscopy analysis shows a higher molecular order of P3HT in the blend than for neat film and that TP molecules are also distributed in the polymeric matrix. Regarding the OFET characteristics, charge carrier mobilities of 1.2×10−3cm2V−1s−1 and 2.0×10−3cm2V−1s−1 were obtained from devices for untreated and (hexamethyldisilazane) HMDS-treated Al2O3 gate dielectric, respectively. These results confirm that P3HT:TP blends have good potential as an active layer in organic field effect transistors (OFETs).

Interactions of black and green tea polyphenols with whole milk

Interactions of black tea polyphenols (BTP) and green tea polyphenols (GTP) with whole milk were comparatively studied. Upon the ultracentrifugation of BTP– and GTP–milk systems (40% v/v milk), most BTP and GTP partitioned into milk protein fractions: whey proteins and casein micelles, with 35.1% and 73.0% of total catechins bound to the casein micelles accordingly. The affinities of catechins for casein micelles were differentiated by the structures of catechins in the GTP–milk system but the BTP–milk system, being enhanced by a gallate group in catechins and the cis-form and weakened by a pyrogallol group. Fourier transforms infrared spectroscopy (FTIR) analysis showed that TP binding altered the secondary structures of milk proteins by reducing inter β-sheet, random coil and the large loop and increasing α-helix, intra β-sheet and turn structures, and more intense hydrophobic interaction was observed in the BTP–milk system. UV–vis spectra indicated no obvious impacts on TP molecules at a low concentration of milk proteins. With the increasing addition of tea infusion, BTP exhibited a similar fluorescence quenching ability to GTP, but the variance in the ORAC values of BTP–milk system was different from that of the GTP–milk system, suggesting that fluorescence quenching may not fully represent the interactions between polyphenols and proteins.

Molecular Basis for the Inhibition of Anticancer Agents-induced Apoptosis by Thymidine Phosphorylase

An angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-D-ribose, a degradation product of thymidine generated by TP enzymatic activity, partially prevented hypoxia-induced apoptosis. TP was expressed at higher levels in tumor tissues compared to the adjacent non-neoplastic tissues in a variety of human carcinomas. High expression of TP is associated with an unfavorable prognosis. To investigate the effect of TP on cisplatin-induced apoptosis, human leukemia Jurkat cells were transfected with wild-type or mutant (L148R) TP cDNA. Jurkat cells transfected with TP cDNA (Jurkat/TP) and mutant TP cDNA (Jurkat/TPMu) expressed high levels of TP, while Jurkat/CV cells which were transfected with a control vector did not express TP. A high TP enzyme activity was detected in Jurkat/TP cells, but not in Jurkat/CV and Jurkat/TPMu cells. Sensitivities to cisplatin of these cells were determined by MTT assay. IC50 values for cisplatin of Jurkat/CV, Jurkat/TP, and Jurkat/TPMu cells were 4.50, 14.08, 13.40 microM, respectively. Jurkat/TP and Jurkat/TPMu cells were about three times more resistant to cisplatin than Jurkat/CV cells. TP inhibited activation of caspase 3, 9 and mitochondrial cytochrome c release induced by cisplatin. These findings suggest a mechanism by which TP confers the resistance to cisplatin-induced apoptosis. Moreover, mutant TP that has no enzymatic activity also suppressed the cisplatin-induced apoptosis. These suggest that TP molecules have cytoprotective functions against cytotoxic agents.

Langmuir–Blodgett films of p-terphenyl in different matrices: Evidence of dual excimer

Langmuir–Blodgett (LB) films at different mole fractions of p-terphenyl have been prepared using two different matrices, viz., stearic acid (SA) and polymethyl methacrylate (PMMA). Multilayered LB films have been formed by changing various LB parameters namely, mole fraction of mixing, changing the number of layers as well as also the different surface pressure of lifting. The spectroscopic characteristics of mixed LB films, solution and microcrystal have been compared using UV–vis absorption and steady state fluorescence spectroscopy. Change of planarity of TP molecules are occurred while going from solution to solid states/films. Fluorescence spectra of the mixed LB films reveal intense excimeric emission in the mixed LB films with D 1 excimer peak at 397 nm and D 2 excimer peak at 412 nm. Various LB parameters namely changing the number of layers as well as the different surface pressure of lifting played important roles in the formation of dual excimeric sites in the mixed LB films.

π-electronic charge-transfer interactions in supramolecular complex formation between fullerenes and 5,10,15,20-tetrahexylporphyrin

UV–Vis spectral investigations on fullerenes/5,10,15,20-tetrahexylporphyrin (TP) supramolecular complexes are reported in CCl 4 and CHCl 3. An absorption band due to charge transfer (CT) transition is observed in the visible region. Vertical ionization potential of TP was determined from the CT transition energy. CT is very weak in these complexes as reflected from very low values of oscillator strengths and transition dipole strengths. All of the complexes are found to be stable with 1:1 stoichiometry. Thermodynamic parameters for the supramolecular complexes of TP with [60]- and [70]fullerenes are reported. The high formation constant value for the [60]fullerene/TP complex as compared to [70]fullerene/TP complex indicates selectivity of TP molecule towards [60]fullerene.

Halogen-Substituted Thiophenol Molecules on Cu(111)

Para-halosubstituted thiophenols (X-TPs, where X is Br, Cl, or F) form ordered islands and monolayers on Cu(111) at temperatures as low as 81 K. At incomplete coverages, all X-TPs adsorb with the dehydrogenated thiol group attached to the substrate and the substituted ring inclined toward the surface, as verified experimentally and theoretically. The structure of ordered islands has a pronounced dependence on the nature of the halogen substituent: while unsubstituted TP and pentafluoro-TP molecules do not self-assemble into extended ordered patterns at 81 K, X-TP molecules form a range of different structures which depend both on the size and electronegativity of the substituent, as well as on the coverage.

Evaluation of local polarity of polymer solids by a rigid fluorescent probe of carbazole–terephthalate cyclophane

A novel rigid fluorescent probe, carbazole–terephthalate cyclophane (Cz–TP) was applied to evaluate local dielectric constants (e) of various polymer solids in a wide range of temperatures. For poly(vinylidene fluoride), the e increased above the glass transition temperature (Tg), due to relaxations of the polar segment –(CH2CF2)– of the main chain. For poly(alkyl methacrylate)s, the e increased above the Tg or the melting temperature of the side chain, where motions of the polar ester groups are activated. For cyanoethylated polymers, the e increased owing to motions of the polar cyano groups at the end of the side chain and the e corresponded to the dielectric constant evaluated by dielectric relaxation measurement at a high frequency, because the Cz–TP exciplex has a lifetime of tens of nanoseconds. For a cyanoethylated polymer with a high content of cyano groups, the e was larger at low temperatures than the dielectric constant obtained by the macroscopic dielectric relaxation measurement. These results show that the Cz–TP molecule is a useful probe for evaluation of the local polarity in polymer solids over a wide temperature range and can detect even a small change in e at transition temperatures such as glass transition, side-chain melting, and side-chain relaxation.