A 1,3‐Capped Calix[4] Conjugate Possessing an Amine Moiety as an Anion Receptor: Reversible Anion Sensing Detected by Spectroscopy and Characterization of the Supramolecular Features by Microscopy

A phenylenediamine‐capped conjugate of calix[4]arene ( L_amino ) was synthesized by reducing its precursor, L_imino , with sodium borohydride in methanol. The L_amino sample binds to anions due to the more flexible and bent conformation of the capped aminophenolic binding core, compared to the precursor L_imino . The L_amino sample showed selectivity towards H₂PO₄^? by exhibiting a ratiometric increase in emission by about 11‐fold with a detection limit of (1.2±0.2) μm ((116±20) ppb) over 15 anions studied, including other phosphates, such as P₂O₇^4?, adenosine monophosphate (AMP^2?), adenosine diphosphate (ADP^2?), and adenosine triphosphate (ATP^2?). The L_amino sample shows an increase in the absorbance at λ=315 nm in the presence of H₂PO₄^?, CO₃^2?, HCO₃^?, CH₃CO₂^?, and F^?. The ¹H NMR spectroscopic titration of L_amino with H₂PO₄^?, F^?, and CH₃CO₂^? showed major changes in the phenylene‐capped and salicyl moieties, and thereby, confirming the aminophenolic region as the binding core. However, the binding strength of these anions followed the trend H₂PO₄^?>F^??CH₃CO₂^?>HSO₄^?. The heat changes observed by isothermal titration calorimetry support this trend. The L_amino sample showed reversible sensing towards H₂PO₄^? and F^? in the presence of Mg²⁺ and Ca²⁺, respectively. NOESY studies of L_amino , in comparison with its anionic complexes, revealed that major conformational changes occurred in the capping region to facilitate the binding of anion. ESI‐MS and the Job's method revealed 1:1 stoichiometry between L_amino and H₂PO₄^? or F^?. In the SEM micrographs of L_amino , the spherical particles are converted into spherical aggregates and further form large agglomerates and even branched sheets in the presence of anions, depending upon their binding strength.     

On‐Wafer Crystallization of Ultralow‐κ Pure Silica Zeolite Films

A higher goal : An on‐wafer crystallization process to prepare pure silica zeolite (PSZ) MEL‐type films that is superior to the previously used hydrothermal process is reported. These striation‐free MEL‐type films (right, see picture) outperform the traditional spin‐on films (left) in terms of the κ value, mechanical properties, surface roughness, mesopore size, and size distribution.

     

A Simple Quantitative Method to Study Protein–Lipopolysaccharide Interactions by Using Liquid Crystals

The interaction of proteins with endotoxins has divergent effects on lipopolysaccharide (LPS)‐induced responses, which serve as a basis for many clinical and therapeutic applications. It is, therefore, important to understand these interactions from both theoretical and practical points of view. This paper advances the design of liquid crystal (LC)‐based stimuli‐responsive soft materials for quantitative measurements of LPS–protein binding events through interfacial ordering transition. Micrometer‐thick films of LCs undergo easily visualized ordering transitions in response to proteins at LPS–aqueous interfaces of the LCs. The optical response of the LC changes from dark to bright after aqueous solutions of hemoglobin (Hb), bovine serum albumin (BSA), and lysozyme proteins (LZM) are in contact with a LPS‐laden aqueous–LC interface. The effects of interactions of different proteins with LPS are also observed to cause the response of the LC to vary significantly from one to another; this indicates that manipulation of the protein–LPS binding affinity can provide the basis for a general, facile method to tune the LPS‐induced responses of the LCs to interfacial phenomena. By measuring the optical retardation of the 4′‐pentyl‐4‐cyanobiphenyl (5CB) LC, the binding affinity of the proteins (Hb, BSA, and LZM) towards LPS that leads to different orientational behavior at the aqueous interfaces of the LCs can be determined. The interaction of proteins with the LPS‐laden monolayer is highest for LPS–Hb, followed by LPS–BSA, and least for LPS–LZM; this is in correlation with their increasing order of binding constants (LPS‐Hb>LPS‐BSA>LPS‐LZM). The results presented herein pave the way for quantitative and multiplexed measurements of LPS–protein binding events and reveal the potential of the LC system to be used as quantitative LC‐based, stimuli‐responsive soft materials.     

Modulation of Aggregation‐Induced Emission and Electroluminescence of Silole Derivatives by a Covalent Bonding Pattern

The deciphering of structure–property relationships is of high importance to rational design of functional molecules and to explore their potential applications. In this work, a series of silole derivatives substituted with benzo[b]thiophene (BT) at the 2,5‐positions of the silole ring are synthesized and characterized. The experimental investigation reveals that the covalent bonding through the 2‐position of BT (2‐BT) with silole ring allows a better conjugation of the backbone than that achieved though the 5‐position of BT (5‐BT), and results in totally different emission behaviors. The silole derivatives with 5‐BT groups are weakly fluorescent in solutions, but are induced to emit intensely in aggregates, presenting excellent aggregation‐induced emission (AIE) characteristics. Those with 2‐BT groups can fluoresce more strongly in solutions, but no obvious emission enhancements are found in aggregates, suggesting they are not AIE‐active. Theoretical calculations disclose that the good conjugation lowers the rotational motions of BT groups, which enables the molecules to emit more efficiently in solutions. But the well‐conjugated planar backbone is prone to form strong intermoelcular interactions in aggregates, which decreases the emission efficiency. Non‐doped organic light‐emitting diodes (OLEDs) are fabricated by using these siloles as emitters. AIE‐active silole derivatives show much better elecroluminescence properties than those without the AIE characterisic, demonstrating the advantage of AIE‐active emitters in OLED applications.     

Structure–Property Investigations of Substituted Triarylamines and Their Applications as Fluorescent pH Sensors

Fourteen triphenylamine derivatives functionalized with fluorophenyl, methoxyphenyl, and pyridinyl groups as respective donors and acceptors were synthesized and characterized. Their photophysical properties were systematically investigated in various solvents with different polarities. The solvent‐dependent Stokes shifts of these compounds were observed and analyzed by the Lippert–Mataga equation. The synthesized compounds, especially tris(4‐(pyridin‐4‐yl)phenyl) amine, presented pH‐dependent absorptions and emissions, indicating that these compounds might be used as pH sensors.     

Rationally Developed Organic Salts of Tolfenamic Acid and Its β‐Alanine Derivatives for Dual Purposes as an Anti‐Inflammatory Topical Gel and Anticancer Agent

A new series of primary ammonium monocarboxylate (PAM) salts of a nonsteroidal anti‐inflammatory drug (NSAID), namely, tolfenamic acid ( TA ), and its β‐alanine derivatives were generated. Nearly 67 % of the salts in the series showed gelling abilities with various solvents, including water (biogenic solvent) and methyl salicylate (typically used for topical gel formulations). Gels were characterized by rheology, electron microscopy, and so forth. Structure–property correlations based on single‐crystal and powder XRD data of several gelator and nongelator salts revealed intriguing insights. Studies (in vitro) on an aggressive human breast cancer cell line (MDA‐MB‐231) with the l ‐tyrosine methyl ester salt of TA ( S7 ) revealed that the hydrogelator salt was more effective at killing cancer cells than the mother drug TA (3‐(4,5‐ di methyl thiazol ‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay); displayed better anti‐inflammatory activity compared with that of TA (prostaglandin E₂ assay); could be internalized within the cancer cells, as revealed by fluorescence microscopy; and inhibited effectively migration of the cancer cells. Thus, the easily accessible ambidextrous gelator salt S7 can be used for two purposes: as an anti‐inflammatory topical gel and as an anticancer agent.     

Synthesis,Properties, and n‐Type Transistor Characteristics of π‐Conjugated Compounds Having a Carbonyl‐Bridged Thiazole‐Fused Polycyclic System

A series of electron‐deficient π‐conjugated systems with 4,9‐dihydro‐s‐indaceno[2,1‐d:6,5‐d′]dithiazole‐4,9‐dione‐based structures and fluorinated acyl groups as the terminal units have been designed and synthesized for application as organic field‐effect transistor (OFET) materials. The thermal, photophysical, and electrochemical properties and OFET performance of the synthesized compounds were investigated. OFET evaluation revealed that all compounds exhibited typical electron‐transporting characteristics, and electron mobilities up to 0.26 cm² V^?1 s^?1 could be achieved. The air stabilities of OFET operation were dependent on the nature of the compounds and were investigated by X‐ray diffraction and atomic force microscopy. The terminal units had a great influence not only on the molecular properties, but also on the film‐forming properties and OFET performance.     

PEG‐Induced Synthesis of Coordination‐Polymer Isomers with Tunable Architectures and Iodine Capture

Controllable synthesis of coordination polymer (CP) isomers and revealing their structure–property relationships remain enormous challenges. Three new supramolecular isomers have been synthesized by tuning the poly(ethylene glycol) (PEG) content in the feed. These supramolecular isomers have the same framework formula of [Cu₂I₂(tppe)] and different architectures from the classical 2D stacking framework to a 3D entangled system with the coexistence of interpenetration and polycatenation, and a 3D topological framework. Interestingly, these CPs could be utilized for capturing iodine molecules. According to multiple complementary experiments and crystallographic analyses, iodine capture is mainly based on halogen‐bond interactions in the inorganic {Cu₂I₂} building blocks of the framework. The present study describes a structure–property relationship in supramolecular isomerism with distinct topological structures.     

Synthesis,Photophysical and Electrochemical Properties,and Self‐assembly Behavior of Two Hexaazatriphenylene Derivatives: A Single Bond Makes a Big Difference

A hexaazatriphenylene (HAT) derivative (compound 1 ) that bears four n‐octyl chains and two thienyl groups was designed and synthesized. Further light‐induced oxidation coupling reaction led to thienyl‐fused compound 2 . Their photophysical and electrochemical properties and self‐assembly behavior have been investigated by UV/Vis, fluorescence, and ¹H NMR spectroscopies, cyclic voltammetry (CV), scanning electron microscopy (SEM), and powder X‐ray diffraction (PXRD). Although the difference in compounds 1 and 2 only lie in one single bond that connects the two thienyl segments, they displayed remarkably different properties, revealing an interesting structure–property relationship.     

Polymer‐Induced Surface Modifications of Pd‐based Thin Films Leading to Improved Kinetics in Hydrogen Sensing and Energy Storage Applications

The catalytic properties of Pd alloy thin films are enhanced by a thin sputtered PTFE coating, resulting in profound improvements in hydrogen adsorption and desorption in Pd‐based and Pd‐catalyzed hydrogen sensors and hydrogen storage materials. The remarkably enhanced catalytic performance is attributed to chemical modifications of the catalyst surface by the sputtered PTFE leading to a possible change in the binding strength of the intermediate species involved in the hydrogen sorption process.     

Synchronizing Steric and Electronic Effects in {RuII(NNNN,P)} Complexes: The Catalytic Dehydrative Alkylation of Anilines by Using Alcohols as a Case Study

A series of new hexacoordinated {Ru^II(NNNN,P)} complexes was prepared from [RuCl₂(R₃P)₃]. Their structure was determined by X‐ray crystallography. The catalytic potential of this new class of complexes was tested in the alkylation of aniline with benzyl alcohol. In this test reaction, the influence of the counteranion plus electronic influences at the tetradentate ligand and the phosphine ligand were examined. The electrochemistry of all complexes was studied by cyclic voltammetry. Depending on the substituent at the ligand backbone, the complexes showed a different behavior. For all N‐benzyl substituted complexes, reversible Ru^II/III redox potentials were observed, whereas the N‐methyl substituted complex possessed an irreversible oxidation event at small scan rates. Furthermore, the electronic influence of different substituents at the ligand scaffold and at the phosphine on the Ru^II/III redox potential was investigated. The measured E₀ values were correlated to the theoretically determined HOMO energies of the complexes. In addition, these HOMO energies correlated well with the reactivity of the single complexes in the alkylation of aniline with benzyl alcohol. The exact balance of redox potential and reactivity appears to be crucial for synchronizing the multiple hydrogen‐transfer events. The optimized catalyst structure was applied in a screening on scope and limitation in the catalytic dehydrative alkylation of anilines by using alcohols.     

Turn‐On Luminescence Sensing and Real‐Time Detection of Traces of Water in Organic Solvents by a Flexible Metal–Organic Framework

The development of efficient sensors for the determination of the water content in organic solvents is highly desirable for a number of chemical industries. Presented herein is a Mg²⁺ metal–organic framework (MOF), which exhibits the remarkable capability to rapidly detect traces of water (0.05–5 % v/v) in various organic solvents through an unusual turn‐on luminescence sensing mechanism. The extraordinary sensitivity and fast response of this MOF for water, and its reusability make it one of the most powerful water sensors known.     

Kinetic Effects on Self‐Assembly and Function of Protein–Polymer Bioconjugates in Thin Films Prepared by Flow Coating

The self‐assembly of nanostructured globular protein arrays in thin films is demonstrated using protein–polymer block copolymers based on a model protein mCherry and the polymer poly(oligoethylene glycol acrylate) (POEGA). Conjugates are flow coated into thin films on a poly(ethylene oxide) grafted Si surface, forming self‐assembled cylindrical nanostructures with POEGA domains selectively segregating to the air–film interface. Long‐range order and preferential arrangement of parallel cylinders templated by selective surfaces are demonstrated by controlling relative humidity. Long‐range order increases with coating speed when the film thicknesses are kept constant, due to reduced nucleation per unit area of drying film. Fluorescence emission spectra of mCherry in films prepared at <25% relative humidity shows a small shift suggesting that proteins are more perturbed at low humidity than high humidity or the solution state.

     

Green and Efficient Processing of Cinnamomum cassia Bark by Using Ionic Liquids: Extraction of Essential Oil and Construction of UV‐Resistant Composite Films from Residual Biomass

There is significant interest in the development of a sustainable and integrated process for the extraction of essential oils and separation of biopolymers by using novel and efficient solvent systems. Herein, cassia essential oil enriched in coumarin is extracted from Cinnamomum cassia bark by using a protic ionic liquid (IL), ethylammonium nitrate (EAN), through dissolution and the creation of a biphasic system with the help of diethyl ether. The process has been perfected, in terms of higher biomass dissolution ability and essential oil yield through the addition of aprotic ILs (based on the 1‐butyl‐3‐methylimidazolium (C₄mim) cation and chloride or acetate anions) to EAN. After extraction of oil, cellulose‐rich material and free lignin were regenerated from biomass–IL solutions by using a 1:1 mixture of acetone–water. The purity of the extracted essential oil and biopolymers were ascertained by means of FTIR spectroscopy, NMR spectroscopy, and GC‐MS techniques. Because lignin contains UV‐blocking chromophores, the oil‐free residual lignocellulosic material has been directly utilized to construct UV‐light‐resistant composite materials in conjunction with the biopolymer chitosan. Composite material thus obtained was processed to form biodegradable films, which were characterized for mechanical and optical properties. The films showed excellent UV‐light resistance and mechanical properties, thereby making it a material suitable for packaging and light‐sensitive applications.     

Geometric and Electronic Structures of Boron(III)‐Cored Dyes Tailored by Incorporation of Heteroatoms into Ligands

Complexation of a boron atom with a series of bidentate heterocyclic ligands successfully gives rise to corresponding BF₂‐chelated heteroarenes, which could be considered as novel boron(III)‐cored dyes. These dye molecules exhibit planar structures and expanded π‐conjugated backbones due to the locked conformation with a boron center. The geometric and electronic structures of these BF₂ complexes can be tailored by embedding heteroatoms in the unique modes to form positional isomer and isoelectronic structures. The structure–property relationship is further elucidated by studying the photophysical properties, electrochemical behavior and quantum‐chemical calculations.     

Ru–bis(pyridine)pyrazolate (bpp)‐Based Water‐Oxidation Catalysts Anchored on TiO2: The Importance of the Nature and Position of the Anchoring Group

Three distinct functionalisation strategies have been applied to the in,in‐[{Ru^II(trpy)}₂(μ‐bpp)(H₂O)₂]³⁺ (trpy=2,2′:6′,2′′‐terpyridine, bpp=bis(pyridine)pyrazolate) water‐oxidation catalyst framework to form new derivatives that can adsorb onto titania substrates. Modifications included the addition of sulfonate, carboxylate, and phosphonate anchoring groups to the terpyridine and bis(pyridyl)pyrazolate ligands. The complexes were characterised in solution by using 1D NMR, 2D NMR, and UV/Vis spectroscopic analysis and electrochemical techniques. The complexes were then anchored on TiO₂‐coated fluorinated tin oxide (FTO) films, and the reactivity of these new materials as water‐oxidation catalysts was tested electrochemically through controlled‐potential electrolysis (CPE) with oxygen evolution detected by headspace analysis with a Clark electrode. The results obtained highlight the importance of the catalyst orientation with respect to the titania surface in regard to its capacity to catalytically oxidize water to dioxygen.     

Structural and Electrical Properties of Sol–Gel-processed CdTiO3 Powders and Films

Cadmium titanate, CdTiO₃, was prepared by the sol–gel technique in bulk and in thin film form. The thermal evolution of the gels and the phase changes were studied by thermo- gravimetric analysis (TGA), X-ray diffractometry (XRD) and Raman and energy-dispersive (EDS) spectroscopies. The morphology of the samples was observed using scanning electron microscopy (SEM). Gels heated to 800 °C gave rise to powders with only the ilmenite-like phase. The orthorhombic perovskite phase is the only crystalline phase observed after a 4 h heat-treatment at 1100 °C. With respect to the conventional preparation method by solid-state reaction, by the sol–gel method it is possible to prepare the ilmenite phase at lower temperatures and the perovskite phase in a shorter time. Clear, homogeneous thin films were obtained by the dip-coating method. The refraction index and the thickness of the films were measured using ellipsometry. The humidity-sensitive electrical properties were measured for thin films deposited on alumina substrates with comb-type gold electrodes, heated to 200 °C and 450 °C. The films heated to 200 °C, which still contained organics, showed a variation of the resistance of six orders of magnitude in the relative humidity (RH) range tested (4–87% RH). The films heated to 450 °C, made of ilmenite-type CdTiO₃, were nearly insensitive to RH. © 1997 by John Wiley & Sons, Ltd.