Expanded-ring N-heterocyclic carbenes efficiently stabilize gold(I) cations, leading to high activity in π-acid-catalyzed cyclizations.

A series of six- and seven-membered expanded-ring N-heterocyclic carbene (er-NHC) gold(I) complexes has been synthesized using different synthetic approaches. Complexes with weakly coordinating anions [(er-NHC)AuX] (X(-) = BF4(-), NTf2(-), OTf(-)) were generated in solution. According to their (13)C NMR spectra, the ionic character of the complexes increases in the order X(-) = Cl(-) < NTf2(-) < OTf(-) < BF4(-). Additional factors for stabilization of the cationic complexes are expansion of the NHC ring and the attachment of bulky substituents at the nitrogen atoms. These er-NHCs are bulkier ligands and stronger electron donors than conventional NHCs as well as phosphines and sulfides and provide more stabilization of [(L)Au(+)] cations. A comparative study has been carried out of the catalytic activities of five-, six-, and seven-membered carbene complexes [(NHC)AuX], [(Ph3 P)AuX], [(Me2S)AuX], and inorganic compounds of gold in model reactions of indole and benzofuran synthesis. It was found that increased ionic character of the complexes was correlated with increased catalytic activity in the cyclization reactions. As a result, we developed an unprecedentedly active monoligand cationic [(THD-Dipp)Au]BF4 (1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydrodiazepin-2-ylidene gold(I) tetrafluoroborate) catalyst bearing seven-membered-ring carbene and bulky Dipp substituents. Quantitative yields of cyclized products were attained in several minutes at room temperature at 1 mol % catalyst loadings. The experimental observations were rationalized and fully supported by DFT calculations.

Effect of Electrode Morphology on Performance of Ionic Actuators Based on Vat Photopolymerized Membranes.

Bucky gel electrodes are composed of morphology-determining polyvinylidene difluoride (PVDF) filled with carbon nanotubes (CNT). The electrodes are commonly fabricated via the casting of a CNT dispersion containing PVDF and ionic liquid. In this study, several pore-forming additives such as polyethylene glycol (PEG), dibutyl phthalate (DBP), and the common ionic liquid BMIMBF4 were used to control the morphology of the bucky gel electrodes. The crystalline phase type and content of PVDF in the electrodes were determined by FT-IR and DSC, respectively. SEM revealed a sponge-like structure in the case of the use of BMIMBF4 and a spherulite structure if PEG and DBP were used as additives. A strong influence of morphology on the anisotropic increase in the volume of electrodes upon impregnation with electrolyte was observed. The PEG-based electrode elongated more than the others, while the BMIMBF4-based electrode thickened to a greater extent. Ionic actuators were fabricated to experimentally reveal the effect of electrode morphology on their electromechanical efficiency. A high-precision vat photopolymerization technique was used to fabricate identical ionic membranes and minimize their influence on the properties of the actuators. The electrodes were characterized by the same porosity and electrical capacitance, while the actuators differ significantly in performance. As a result, a simple method of using pore-forming additives made it possible to increase the maximum deformation of bucky gel ionic actuators by 1.5 times by changing the morphology of the electrodes.

Ionomers Based on Addition and Ring Opening Metathesis Polymerized 5-phenyl-2-norbornene as a Membrane Material for Ionic Actuators.

Two types of poly(5-phenyl-2-norbornene) were synthesized via ring opening metathesis and addition polymerization. The polymers sulfonation reaction under homogeneous conditions resulted in ionomer with high sulfonation degree up to 79% (IEC 3.36 meq/g). The prepared ionomer was characterized by DSC, GPC, 1H NMR and FT-IR. Polymers for electromechanical applications soluble in common polar organic solvents were obtained by replacing proton of sulfonic group with imidazolium and 1-methylimidazlium. Membranes were prepared using the above-mentioned polymers and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), as well as mixtures with polyvinylidene fluoride (PVDF). Mechanical, morphological, and conductive properties of the membranes were examined by tensile testing, SEM, and impedance spectroscopy, respectively. Dry and air-stable actuators with electrodes based on SWCNT were fabricated via hot-pressing. Actuators with membranes based on methylimidazolium containing ionomers outperformed classical bucky gel actuator and demonstrated high strain (up to 1.14%) and generated stress (up to 1.21 MPa) under low voltage of 2 V.

Data on synthesis and characterization of sulfonated poly(phenylnorbornene) and polymer electrolyte membranes based on it.

This article describes data on preparation of sulfonated hydrogenated poly(phenylnorbornene) with different cations synthesized via sequential ring-opening metathesis polymerization, reduction, homogeneous sulfonation and cation exchange reactions. The data of the characterization of new polymers by nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) are presented. The effect of imidazolium and 1-methylimidazolium cations, ionic liquid and Zwitter-type ion liquid on ionic conductivities evaluated by impedance spectroscopy. Preparation procedure of polymer electrolyte membrane based on new polymers and Nafion as a blend with polyvinylidene fluoride (PVDF) is given. Scanning electron microscopy images and ionic conductivities of these membrane are presented.