Photoluminescence and energy transfer in Tb/Mn co-doped ZnAl2O4 glass ceramics

We report on Tb³⁺ as efficient sensitizer for red photoemission from Mn²⁺-centers in ZnO-B₂O₃-Al₂O₃-Si₂O-Na₂O-SrO glasses and corresponding gahnite glass ceramics. In comparison to singly or co-doped glasses, the glass ceramics exhibit significantly increased emission intensity. Structural considerations, ESR, and dynamic luminescence spectroscopy indicate partial incorporation of Mn²⁺ as well as Tb³⁺ into the crystalline phase, the former on octahedral Zn²⁺-sites. Interionic distance and charge transfer probability between both species depend on crystallization conditions. This enables control of the energy transfer process and, hence, tunability of the color of photoemission by simultaneous emission from Tb³⁺ and Mn²⁺ centers. Concentration quenching in Mn²⁺-singly doped materials was found at a critical dopant concentration of about 1.0 mol%. The energy transfer process was studied in detail by dynamic as well as static luminescence spectroscopy. Spectroscopic results suggest the application of the studied materials as single or dual-mode emitting phosphor for luminescent lighting.     

Convenient and rapid synthesis of α-aminonitriles starting directly from nitro compounds in water

A distinct approach for the synthesis of α-aminonitriles has been discovered by three-component reaction of nitroarenes, aldehydes, and TMSCN using indium in dilute aqueous HCl at room temperature. The products were formed in high yields (86-96%) within a short period of time (5-20 min). This one-pot conversion consists of the following steps: (i) reduction of nitro compounds to amines, (ii) formation of imines from amines and aldehydes and (iii) addition of cyanide anion to the imines.     

A distinct approach for the rapid synthesis of homoallylic amines starting directly from nitro compounds in water

Three-component reactions of nitroarenes, benzaldehydes, and allyltributylstannane using indium in dilute aqueous HCl at room temperature afford the corresponding homoallylic amines in high yields within 5-10 min. The conversion in one-pot synthesis involves the following steps: (i) reduction of nitro compounds to amines, (ii) formation of imines from amines and aldehydes, and (iii) allylation of imines.     

Stereoselective total synthesis of dodoneine

The stereoselective total synthesis of the naturally occurring bioactive dihydropyranone dodoneine has been achieved involving the Sharpless asymmetric epoxidation, 1,3-syn diastereoselective reduction and Grubb’s ring-closing metathesis as key steps.     

Anhydrous proton-conducting organic–inorganic hybrid membranes synthesized from tetramethoxysilane/methyltrimethoxysilane/diisopropyl phosphite and ionic liquid

Inorganic–organic hybrid membranes were prepared by sol–gel process with tetramethoxysilane/methyltrimethoxysilane/diisopropyl phosphite and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) ionic liquid as precursors. The Fourier transform infrared spectroscopy (FT-IR) and ³¹P, ²⁹Si, ¹H, ¹³C, and ¹⁹F nuclear magnetic resonance measurements have shown good chemical stability and complexation of (POH[(CH₃)₂CHO]₂) with [BMIMBF₄] ionic liquid in the fabricated hybrid membranes. The influence of the textural properties of all the prepared composite membranes could be interpreted from nitrogen adsorption–desorption measurements. The average pore size was increased proportionally with the ionic liquid weight percent ratio in the host phosphosilicate matrix from 2.59 to 11.71 nm, respectively. Thermogravimetric analysis and differential thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 260 °C. Thermal stability of the hybrid membranes was significantly enhanced by the presence of inorganic SiO₂ framework and high stability of [BF₄] anion. For all the composite membranes, the conductivities were measured within the temperature range (−30 °C) to 150 °C, and a maximum conductivity of 7 × 10⁻³ S/cm at 150 °C was achieved for 40 wt.% ionic liquid-based composite membrane under nonhumidified conditions.     

Palladium(II) complexes of 5-substituted isatin thiosemicarbazones: Synthesis,spectroscopic characterization,biological evaluation and in silico docking studies

Substituted heterocyclic (isatin) appended thiosemicarbazone ligands (L1–L3) are synthesized by condensation of substituted isatin molecule with N(4)-phenyl-3-thiosemicarbazide in good yields. The palladium(II) complexes are synthesized from ligands (L1–L3) and PdCl₂, with a general formula [PdCl(X-C₁₅H₁₀N₄OS)] where X?=?5-chloro (1), 5-bromo (2), and 5-nitro (3). Both analytical and spectroscopic methods have been used for the analysis and characterization of the synthesized compounds. The antimicrobial activity results observed that complexes, 1 and 2 have registered potent antibacterial activity against B. subtilis and K. pneumoniae and also complex 2 has shown good antifungal activity against the micro organisms. The antioxidant activity analysis revealed that the complex 3 showed significant activity with IC₅₀ values 7.24?±?0.09?µM. Moreover, the in vitro antiproliferative activity results suggested that complex 3 exhibited high activity against HeLa cell line compared with the standard with the IC₅₀ value 16.52?±?1.08?µM. The docking results correlate well.     

Synthesis,characterization, and antidiabetic activity of 6‐methoxyimidazo[1,2‐b]pyridazine derivatives

The present article describes the synthesis, characterization, and antidiabetic activity of 6‐methoxyimidazo[1,2‐b]pyridazine derivatives 7a‐l . The synthetic sequence for the preparation of these derivatives involves the following prominent reactions: (a) Step 1: involves the high‐pressure amination reaction; (b) Step 2: involves the Zinc oxide nanoparticle‐catalyzed cyclization reaction; (c) Step 3: involves the methoxylation; (d) Step 4: involves the bromination reaction; (e) Step 5: involves the Suzuki coupling reaction; (f) Step 6: involves the reduction of the –NO₂ group; (g) Step 7: involves Boc protection of the 1^o amino group (h) Step 8: involves diazotization of the amine group and finally the last of the synthesis (i) Step 9: involves the saponification of the ethyl ester group. Furthermore, the structures of the newly synthesized 6‐methoxyimidazo[1,2‐b]pyridazine derivatives 7a–l were determined using ¹H NMR, ¹³C NMR, and Mass and IR spectroscopic analyses. These derivatives were evaluated for their antidiabetic property and the results revealed that most of the compounds exhibited significant potency. It is worth mentioning that compounds 7b (69.87%), 7f (69.0%), 7h (68.79%), and 7l (68.61%) with substitution R = para‐NH₂, para‐COOH, meta‐NH₂, and meta‐COOH, respectively, showed significant (good) hypoglycemic activity when compared to the standard drug insulin (50 mg/kg b.w) in reducing the blood glucose level.     

Proton-conducting hybrid membranes for medium temperature (>100 °C) fuel cells

Hybrid membranes doped with silicotungstic acid (STA) were prepared by sol–gel process with 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, phosphoric acid, and tetraethoxysilane as chemical precursors. The thermogravimetry and differential thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 350 °C. Relatively, a high proton conductivity of 2.85 × 10⁻² S/cm was obtained for 10 mol% STA-doped hybrid membrane at 120 °C under 90% RH. The hydrogen permeability was found to decrease in the temperature range 20–120 °C from 1.64 × 10⁻¹⁰ to 1.36 × 10⁻¹⁰ mol/cm.s.Pa.     

A Benzofuranoid and Two Clerodane Diterpenoids from Pulicaria wightiana

Methyl 5‐formyl‐1‐benzofuran‐6‐carboxylate ( 1 ) and the two clerodane diterpenes, methyl 6‐oxocleroda‐3,13‐dien‐15,16‐olid‐18‐oate ( 2 ) and 2β‐(2‐methylbutanoyl)cleroda‐3,13‐dien‐15,16‐olid‐18‐oic acid ( 3 ), together with 15 known compounds, were isolated from the aerial parts of Pulicaria wightiana. The structures of the new compounds 1, 2 , and 3 were established by spectroscopic (mainly 1D‐ and 2D‐NMR) methods.