Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

Synthesis of Dendrimers Based on Tetrakis(thiophene-2-yl)ethene as New Dendron

Two novel dendrimers, <b>16T</b> and <b>20T</b>, based on 1,1,2,2-tetra(thiophen-2-yl)ethene (<b>4T</b>) as a new dendron, were efficiently synthesized via carbonylation, Suzuki, and McMurry reactions. All intermediates and title compounds were fully characterized by ¹H NMR, ¹³C NMR, and HRMS. <b>4T</b> and <b>16T</b> were confirmed by X-ray single crystal analyses. In addition, the absorption behaviors of two titled dendrimers are also described

Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

Selectivity of Br/Li Exchange and Deprotonation of 4,4′-Dibromo-3,3′-bithiophene for Synthesis of Symmetrical and Unsymmetrical Dithienoheteroaromatic Rings

The novel selective synthesis of symmetrical and unsymmetrical dithienoheteroaromatic rings (<b>DTHA</b>s) has been developed via intramolecular cyclization of 4,4′-dibromo-3,3′-bithiophene (<b>3</b>). Four reaction conditions including <i>n</i>-BuLi/Et₂O, <i>n</i>-BuLi/THF, <i>s</i>-BuLi/Et₂O, and <i>t</i>-BuLi/Et₂O were employed to react with <b>3</b> for selective formation of two types of dicarbanions, which generate the symmetrical and unsymmetrical <b>DTHA</b>s after quenching with three electrophilic reagents (<b>4a</b>–<b>c</b>). The possible mechanism of formation of <b>DTHA</b>s was proposed. In addition, two unsymmetrical <b>DTHA</b>s were confirmed by X-ray single-crystal analyses

From Saddle-Shaped to Planar Cyclic Oligothienoacenes: Stepped-Cyclization and Their Applications in OFETs

A series of cyclic oligothienoacenes (<b>1</b>, <b>3</b>, and <b>4</b>) have been successfully synthesized through a stepped-cyclization synthetic strategy from tetra­[3,4-thienylene] (<b>2</b>). Single-crystal X-ray diffraction analysis combined with theoretical calculations elucidated that the molecular configuration transforms from the saddle shape of <b>2</b> to the quasi-saddle shape (<b>3b</b>, <b>3c</b>), then to the quasi-helical shape (<b>4b</b>), and at last to the quasi-plane shape (<b>1</b>, <b>3a</b>, <b>4a</b>). Organic field-effect transistors (OFETs) based on <b>1</b>, <b>3a</b>, and <b>4a</b> were fabricated. The field-effect mobilities of 7.5 × 10^–4, 2.6 × 10^–3, and 6.8 × 10^–4 cm² V^–1 s^–1 were obtained for <b>1</b>, <b>3a</b>, and <b>4a</b>, respectively. Compounds <b>3a</b> and <b>4a</b> can act as air-stable p-type organic semiconductors, while <b>1</b> is sensitive to the air

Synthesis of Dendrimers Based on Tetrakis(thiophene-2-yl)ethene as New Dendron

Two novel dendrimers, <b>16T</b> and <b>20T</b>, based on 1,1,2,2-tetra(thiophen-2-yl)ethene (<b>4T</b>) as a new dendron, were efficiently synthesized via carbonylation, Suzuki, and McMurry reactions. All intermediates and title compounds were fully characterized by ¹H NMR, ¹³C NMR, and HRMS. <b>4T</b> and <b>16T</b> were confirmed by X-ray single crystal analyses. In addition, the absorption behaviors of two titled dendrimers are also described

A Chemically Accurate Implicit-Solvent Coarse-Grained Model for Polystyrenesulfonate Solutions

A systematic molecular coarse-graining (CG) approach for aqueous polyelectrolyte solutions is presented with sodium polystyrenesulfonate (NaPSS) with different chain tacticities as example systems. The styrenesulfonate repeat unit is mapped on a three-site CG representation with the counterion being modeled explicitly while the solvent is modeled implicitly. The CG force field discriminates between bonded and nonbonded forces, which have been developed independently. The bonded interactions correspond to the potentials of mean force of CG bond, angle, and torsion degrees of freedom obtained from sampling isolated chains with an atomistic force field that includes only the local interactions along the chain. The nonbonded interactions correspond to bead–bead potentials of mean force, obtained from simulations of small molecule or ion pairs in explicit water. The CG model reproduces the local and global conformations of polyelectrolyte chains in good agreement with the parent atomistic chains in aqueous solution. By using a relative dielectric permittivity based on the local concentration of counterions around the polyelectrolyte chain, the quality of our CG models can be further improved substantially. The effect of added salt (NaCl) on the radius of gyration of PSS chains with different tacticities has also been studied and results show the transferability of the CG NaPSS model to regimes with different electrostatic conditions. We furthermore show that the CG procedure presented here can easily be extended to CG models for partially sulfonated polystyrene systems

Synthesis of Dendrimers Based on Tetrakis(thiophene-2-yl)ethene as New Dendron

Two novel dendrimers, <b>16T</b> and <b>20T</b>, based on 1,1,2,2-tetra(thiophen-2-yl)ethene (<b>4T</b>) as a new dendron, were efficiently synthesized via carbonylation, Suzuki, and McMurry reactions. All intermediates and title compounds were fully characterized by ¹H NMR, ¹³C NMR, and HRMS. <b>4T</b> and <b>16T</b> were confirmed by X-ray single crystal analyses. In addition, the absorption behaviors of two titled dendrimers are also described

Understanding the Control of Mineralization by Polyelectrolyte Additives: Simulation of Preferential Binding to Calcite Surfaces

Understanding the mechanisms that govern the crystallization of natural minerals such as calcium carbonate, calcium oxalate, or hydroxyapatite and its control by biological and synthetic polymers can help to guide the design of new biomimetic materials. In this paper, the adsorption behavior of oligomers of polystyrene sulfonate (PSS) on calcite surfaces was investigated by molecular dynamics simulations. The binding strengths of PSS oligomers to different calcite surfaces were computed via potential of mean force calculations, and the binding modes were analyzed in detail. These results could be set in relation to and serve as a molecular-level explanation of the experimentally observed PSS-stabilized exposure of (001) surfaces during calcite mineralization. The simulations show that oligomers of PSS preferentially bind to the polar calcite (001) surface, much stronger than to the nonpolar (104) surface. While sharing in common a dominant role of solvent-induced forces, the mode of binding to the two surfaces is different. The interaction of the sulfonate group with the (001) surface is dominated by both direct and solvent-mediated binding, while the binding of the styrene sulfonate to the (104) surface is mediated by one or two layers of water molecules. Moreover, local solvent density variations at the interface impact the geometry of binding which vastly differs between the two surfaces. In particular, these last effects have important further implications for the preferential binding of PSS polymers (compared to monomers or oligomers) and specific material recognition by synthetic polymers and peptides in general

From Saddle-Shaped to Planar Cyclic Oligothienoacenes: Stepped-Cyclization and Their Applications in OFETs

A series of cyclic oligothienoacenes (<b>1</b>, <b>3</b>, and <b>4</b>) have been successfully synthesized through a stepped-cyclization synthetic strategy from tetra­[3,4-thienylene] (<b>2</b>). Single-crystal X-ray diffraction analysis combined with theoretical calculations elucidated that the molecular configuration transforms from the saddle shape of <b>2</b> to the quasi-saddle shape (<b>3b</b>, <b>3c</b>), then to the quasi-helical shape (<b>4b</b>), and at last to the quasi-plane shape (<b>1</b>, <b>3a</b>, <b>4a</b>). Organic field-effect transistors (OFETs) based on <b>1</b>, <b>3a</b>, and <b>4a</b> were fabricated. The field-effect mobilities of 7.5 × 10^–4, 2.6 × 10^–3, and 6.8 × 10^–4 cm² V^–1 s^–1 were obtained for <b>1</b>, <b>3a</b>, and <b>4a</b>, respectively. Compounds <b>3a</b> and <b>4a</b> can act as air-stable p-type organic semiconductors, while <b>1</b> is sensitive to the air