Synthesis and Properties of Symmetric and Unsymmetric Dibenzothienopyrroles

Symmetrical and unsymmetrical heteroacenes containing thiophene and pyrrole rings were synthesized. The unsymmetrical heteroacene was synthesized in two steps involving an unexpected palladium catalyzed amination of alkyl or aryl amines with benzo[b]thiophene followed by a copper catalyzed coupling. The symmetrical heteroacene was obtained by a palladium catalyzed amination reaction and also by a copper catalyzed amidation reaction. The crystal structure, photophysical and electrochemical properties of symmetrical and unsymmetrical heteroacenes are described

Water-Soluble Multifunctional Cross-Conjugated Poly(<i>p</i>-phenylenes) as Stimuli-Responsive Materials: Design, Synthesis, and Characterization

The design, synthesis, and characterization of a series of thermally stable water-soluble polymers with cross-conjugation and multiple functional groups are reported. All copolymers were characterized by means of FT-IR, GPC, 1H and 13C NMR, UV−vis, and fluorescence spectroscopy. Photophysical properties showed collective responses from their respective conjugated segments. Titration studies showed that such polymers have good sensitivity for both cationic and anionic quenchers in fluorescence decay, with an average Stern−Volmer constant of 105 M-1. Besides fluorescence quenching, significant shifts in absorption and emission maxima upon addition of small molecules were also observed. High concentration of small molecular quenchers induced aggregation of the polymers. All polymers were able to form highly fluorescent, flexible, free-standing thin films via evaporation of the solvent. Hence, by attaching cationic and anionic groups on a cross-conjugated water-soluble structure, a multifunctional CP system was developed for potential applications

Synthesis and Properties of Symmetric and Unsymmetric Dibenzothienopyrroles

Symmetrical and unsymmetrical heteroacenes containing thiophene and pyrrole rings were synthesized. The unsymmetrical heteroacene was synthesized in two steps involving an unexpected palladium catalyzed amination of alkyl or aryl amines with benzo[b]thiophene followed by a copper catalyzed coupling. The symmetrical heteroacene was obtained by a palladium catalyzed amination reaction and also by a copper catalyzed amidation reaction. The crystal structure, photophysical and electrochemical properties of symmetrical and unsymmetrical heteroacenes are described

Synthesis and Self-Assembly of Copolymers with Pendant Electroactive Units

The methacrylic copolymers incorporated with electroactive groups such as thiophene, carbazole, and fluorene moieties on the side chain were synthesized. Our approach consists of incorporating multiple electroactive functional groups onto a polymer backbone that can be used to develop functional materials. All copolymers were characterized, and a systematic structure−property relationship study was established. The structure and morphology of supramolecular self-assembly of copolymers were studied using transmission electron microscopy, wide-angle X-ray diffraction, and atomic force microscopy. Polymers can be patterned using an atomic force microscope, and nanosized lines or dots can be drawn on the polymer films. Polymer nanotubes obtained through self-assembly can be further stabilized by electropolymerization of the side chains

Sequential Removal of Oppositely Charged Multiple Compounds from Water Using Surface-Modified Cellulose

Efficient removal of organic and inorganic pollutants is a challenge owing to the involvement of different physicochemical properties. Herein, we discuss a novel approach for successive adsorption of oppositely charged multiple compounds [acid fuchsin (AF), Cu­(II), perylene tetracarboxylate (PTC) anions, and Zn­(II) ions] from water using chemically modified cellulose fibers (PEI/CE). The changes in net surface charges of the adsorbent accompanied by the successive adsorption of oppositely charged compounds from water are utilized as a concept for adsorption of multiple pollutants on the same adsorbent. The PEI/CE adsorbent was separated via simple filtration after each adsorption experiment and used directly for further successive adsorption without any drying or surface treatments. Compared to most of the reported adsorbents, PEI/CE fibers showed excellent adsorption capacities of 562, 552, 216, and 157 mg/g for AF, Cu­(II) ions, PTC dye, and Zn­(II) ions, respectively. Analysis of the data from kinetic and isotherm studies revealed the best fit to the pseudo-second-order and Langmuir isotherm model for all adsorbates. Furthermore, data from the zeta potential measurements and elemental analysis helped to establish the mechanism of the adsorption process. Such concepts are viable for the removal of known pollutants from multiple industrial effluents. A series of such simple, renewable adsorbents and successive adsorption processes could be developed as a new platform for effective removal of several pollutants from wastewater effluents

Chemically Modified Sawdust as Renewable Adsorbent for Arsenic Removal from Water

Environmentally friendly and cost-effective adsorbent materials for arsenic extraction are needed for removing pollutants from groundwater. Here, lanthanum or zirconium oxide nanoparticle-incorporated sawdust was used for the removal of arsenic anions from water. The chemically modified sawdust was fully characterized and used for extraction of arsenic from water. The influences of ionic strength, pH, and interfering ionic pollutants toward the extraction efficiency of arsenic anions were investigated to understand the mechanism. ZrO2-sawdust showed extraction capacities of 29 and 12 mg/g for arsenite and arsenate anions, respectively, while La2O3-sawdust extracted arsenite (22 mg/g) and arsenate (28 mg/g) anions efficiently. Desorption studies were performed on surface-modified sawdust to check the recyclability. La2O3-sawdust can be fully regenerated with no change in arsenic removal efficiency, while ZrO2-sawdust retains ∼50% of its adsorption efficiency. Such modified renewable bioadsorbents are useful for developing environmentally friendly materials for water purification

Eggshell Membrane-Supported Recyclable Catalytic Noble Metal Nanoparticles for Organic Reactions

Heterogeneous catalysts are used in many industrial processes. Here, we report a simple method for a template-assisted synthesis of nanoparticle catalysts and for testing their catalytic efficiency toward two model organic reactions. Eggshell membrane (ESM) reduced metal cations to metal atoms, stabilized the nanoparticles, and was used as a supporting material for the nanoparticles. The gold and silver nanoparticles were characterized using UV–vis spectroscopy, FESEM, XRD, and XPS studies. As a proof of concept, the resultant membrane-supported nanoparticles were used as a heterogeneous catalyst for the reduction of p-nitrophenol and synthesis of propargylamine. High recyclability of the reactions indicates that nanoparticles are strongly attached to the eggshell membrane surface. Easy synthesis, high catalytic activity, and recyclability make these catalysts interesting for further studies

Regioisomers of Perylenediimide: Synthesis, Photophysical, and Electrochemical Properties

A series of conjugation extended donor–acceptor 1,6- and 1,7-regiomers of perylenediimide were synthesized, separated, and characterized. The photophysical, electrochemical, and thermal properties of these compounds were investigated and compared. The absorption spectra of 1,6-substituted PDI showed blue shift as compared to its 1,7-substituted PDI. At the same time, the emission spectrum showed no significant differences among the regiomers. Both 1,6- and 1,7-regiomers were thermally stable up to 450 °C and showed different melting and crystallization transitions. The electrochemical studies did not show significant differences in oxidation and redox potentials owing to similar HOMO/LUMO gap of 1,6- and 1,7-regiomers, which is also supported by theoretical calculations. Comparison of properties of a series of 1,6- or 1,7-substituted PDIs showed significant differences. Such regiomerically pure compounds can offer certain advantages in applications, which are currently being investigated

Self-Assembly of Tetraphenol and Its Complexes with Aromatic Diamines: Novel Interpenetrating and Noninterpenetrating Organic Assemblies

The solid-state self-assembly of tetraphenol 1 and its complexes with 4,4‘-bipyridine (bpy), trans-1,2-bis(4-pyridyl)ethylene (bpy-ethe), and 1,2-bis(4-pyridyl)ethane (bpy-etha) is reported. Forces such as O−H···N, O−H···O and weak interactions prevalent in the structures promote the formation of interpenetrating and noninterpenetrating supramolecular assemblies. The crystal structure of tetraphenol 1 is characterized by the formation of hydrogen-bonded eight-membered cyclic structures. A diamondoid network was observed in the crystal lattice of 1·bpy with tetraphenol as the node and 4,4‘-bipyridine as the spacer. The resulting superadamantane framework is filled via self-clathration to give an 8-fold interpenetrating network. 1·bpy-ethe self-assembled into a stepladder-type arrangement with the bpy-ethe linkers forming the rungs of the ladder. In the lattice of complex 1·bpy-etha, ladder-type and cyclic structures organized adjacent to each other and the water molecules present inside the lattice stabilized the assembly through hydrogen bonding. No interpenetrating networks were observed in the lattices of 1·bpy-ethe and 1·bpy-etha. The C3 symmetry of tetraphenol 1, orientation of the -OH groups, and the rigidity or the flexibility of the linking aza compounds together with the interplay of hydrogen bonds and packing forces facilitate the formation of stable supramolecular architectures