Anellated N-heterocyclic carbenes: 1,3-Dineopentyl-benzimidazol-2-ylidene,structural aspects of C-protonated precursor salts and an AgCl complex

Access to 1,3-dineopentyl-benzimidazol-2-ylidene (1) by deprotonation of various benzimidazolium salts was studied. [Ag(1)Cl] was prepared from the corresponding benzimidazolium chloride. X-ray crystal structure analyses of benzo-, naphtho- and quinoxalino-anellated imidazolium salts displayed neither significant changes nor systematic trends of bond lengths and angles within the five-membered ring. Consistently downfield shifts of the ¹³C¹H(2) nuclei reflect the influence of electron-withdrawing anellation.     

A Flexible Composite Mechanical Energy Harvester from a Ferroelectric Organoamino Phosphonium Salt

A new binary organic salt diphenyl diisopropylamino phosphonium hexaflurophosphate (DPDP?PF₆) was shown to exhibit a good ferroelectric response and employed for mechanical energy harvesting application. The phosphonium salt crystallizes in the monoclinic noncentrosymmetric space group Cc and exhibits an H‐bonded 1D chain structure due to N?H???F interactions. Ferroelectric measurements on the single crystals of DPDP?PF₆ gave a well‐saturated rectangular hysteresis loop with a remnant (P_r) polarization value of 6 μC cm^?2. Further, composite devices based on polydimethylsiloxane (PDMS) films for various weight percentages (3, 5, 7, 10 and 20 wt %) of DPDP?PF₆ were prepared and examined for power generation by using an impact test setup. A maximum output peak‐to‐peak voltage (V_PP) of 8.5 V and an output peak‐to‐peak current (I_PP) of 0.5 μA was obtained for the non‐poled composite film with 10 wt % of DPDP?PF₆. These results show the efficacy of organic ferroelectric substances as potential micropower generators.     

A rugged lead-ruthenate pyrochlore membrane catalyst for highly selective oxidation of alcohols

A rugged lead-ruthenate pyrochlore (Py, Pb₂Ru₂O₇) Nafion 417 membrane catalyst (|NPy|) has been demonstrated for highly efficient and fully selective oxidation of primary and secondary alcohols to aldehydes and ketones. Under a triphasic condition of CH₂Cl_2(org)//|NPy|_(s)//NaOCl-pH 11_(aq), the |NPy| can be recycled and reused effectively on oxidations of alcohols. Using a same piece of |NPy|, similar reaction yields were obtained by repeating benzyl alcohol oxidation reaction for 20 times. Electrochemical mechanistic investigation indicated that the perruthenate ion (RuO₄⁻) intermediate was responsible for selective mediation of the alcohol oxidation.     

Kinetics of bromine addition to unsaturated sulphones

The effect of varying the structure of the unsaturated sulphones on the rate of bromine addition has been systematically studied and the direction of the effect is such as to be expected on the basis of polar and (or) steric effects of the substituents. All the kinetic data regarding bromine addition to several substituted and unsubstituted α, β- and β, γ-unsaturated sulphones seem to support the view that the addition of bromine to these sulphones follows the electrophilic mechanism.     

Inhibitor screening of pharmacological chaperones for lysosomal β-glucocerebrosidase by capillary electrophoresis

Pharmacological chaperones (PCs) represent a promising therapeutic strategy for treatment of lysosomal storage disorders based on enhanced stabilization and trafficking of mutant protein upon orthosteric and/or allosteric binding. Herein, we introduce a simple yet reliable enzyme assay using capillary electrophoresis (CE) for inhibitor screening of PCs that target the lysosomal enzyme, β-glucocerebrosidase (GCase). The rate of GCase-catalyzed hydrolysis of the synthetic substrate, 4-methylumbelliferyl-β-d-glucopyranoside was performed using different classes of PCs by CE with UV detection under standardized conditions. The pH and surfactant dependence of inhibitor binding on recombinant GCase activity was also examined. Enzyme inhibition studies were investigated for five putative PCs including isofagomine (IFG), ambroxol, bromhexine, diltiazem, and fluphenazine. IFG was confirmed as a potent competitive inhibitor of recombinant GCase with half-maximal inhibitory concentration (IC ₅₀ ) of 47.5 ± 0.1 and 4.6 ± 1.4 nM at pH 5.2 and pH 7.2, respectively. In contrast, the four other non-carbohydrate amines were demonstrated to function as mixed-type inhibitors with high micromolar activity at neutral pH relative to acidic pH conditions reflective of the lysosome. CE offers a convenient platform for characterization of PCs as a way to accelerate the clinical translation of previously approved drugs for oral treatment of rare genetic disorders, such as Gaucher disease.     

Anellated N-heterocyclic carbenes: 1,3-dineopentylnaphtho[2,3-d]imidazol-2-ylidene: synthesis, KOH addition product, transition-metal complexes, and anellation effects

Two novel anellated N-heterocyclic carbenes (NHC), 1,3-dineopentylnaphtho[2,3-d]imidazol-2-ylidene, and 1,3-dineopentyl-2-ylido-imidazolo[4,5-b]pyridine were obtained by reduction of the respective thiones with potassium, the former also by deprotonation of the corresponding naphthimidazolium hexafluorophosphate by using excess KH in THF. The use of equimolar amounts of KH provided an unexpected formal addition product of this NHC with KOH. X-ray crystal structure analysis of the adduct provided evidence for a distorted tetrameric N-heterocyclic alkoxide, stabilized by two THF molecules. In C(6)D(6) the compound undergoes disproportionation. Transition-metal complexes [(NHC)AgCl], [(NHC)Rh(cod)Cl], and (E)-[(NHC)(2)PdCl(2)] of the novel naphthimidazol-2-ylidene were synthesized. X-ray crystal structures and (1)H and (13)C NMR spectroscopic data provided detailed structural information. Comparing characteristic data with those of nonanellated and differently anellated NHCs or their complexes provides information on the influence of the extended anellation.     

A Flexible Energy Harvester from an Organic Ferroelectric Ammonium Salt

Organic ferroelectrics due to their low cost, easy preparation, light weight, high flexibility and phase stability are gaining tremendous attention in the field of portable electronics. In this work, we report the synthesis, structure and ferroelectric behavior of a two-component ammonium salt 2 , containing a bulky [Bn(4-BrBn)NMe₂]⁺ (Bn=benzyl and 4-BrBn=4-bromobenzyl) cation and tetrahedral (BF₄)⁻ anion. The structural analysis revealed the presence of rich non-classical C−H⋅⋅⋅F and C−H⋅⋅⋅Br interactions in this molecule that were quantified by Hirshfeld surface analysis. The polarization (P) vs. electric field (E) hysteresis loop measurements on 2 gave a remnant polarization (P_r) of 14.4 μC cm⁻² at room temperature. Flexible polymer composites with various (5, 10, 15 and 20) weight percentages (wt%) of 2 in thermoplastic polyurethane (TPU) were prepared and tested for mechanical energy harvesting applications. A notable peak-to-peak output voltage of 20 V, maximum current density of 1.1 μA cm⁻² and power density of 21.1 μW cm⁻² were recorded for the 15 wt% 2 -TPU composite device. Furthermore, the voltage output generated from this device was utilized to rapidly charge a 100 μF capacitor, with stored energies and measured charges of 156 μJ and 121.6 μC, respectively.     

Flavonoids from Andrographis viscosula

Phytochemical investigation of the whole plant of Andrographis viscosula has led to the isolation of three new 2'-oxygenated flavonoids, (2R)-5-hydroxy-7,2',3'-trimethoxyflavanone (1), 7,2',5'-trimethoxyflavone (2), 5,7,2',3'-tetramethoxyflavone (3), and eight known flavones, 5,7,2'-trimethoxyflavone (4), 5,7,2',4',5'-pentamethoxyflavone (5), echioidinin (6), 5,2',6'-trihydroxy-7-methoxyflavone (7), 5-hydroxy-7,2'-dimethoxyflavone (8), echioidin (9), echioidinin 5-O-glucoside (10), and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-glucoside (11). The structures of 1-11 were elucidated by physical and spectral methods, including extensive 2D NMR studies. The presence of 2'-oxygenated flavonoids is apparently restricted to Andrographis species in Acanthaceae. Therefore, 2'-oxygenated flavonoids are regarded as chemotaxonomic markers of Andrographis genus in the Acanthaceae family.