Effect of molecular packing on corannulene-based materials electroluminescence

The present investigation reports for the first time a detailed theoretical analysis of the optical absorption spectra of corannulene-based materials using state-of-the-art first-principles many-body GW-BSE theory. The study specifically addresses the nature of optical excitations for predictions regarding suitability for device fabrication. The well-defined structure-correlation relationship in functionalized corannulenes is used in a focused investigation of the predicted optoelectronic properties in both the isolated state and bulk crystals. The findings suggest that the excitonic properties are strongly dependent on the specific substituent group as well as the crystalline arrangement. Arylethynyl-substituted corannulene derivatives are shown to be the most suitable for device purposes.     

Catalytic enantioselective synthesis of glutamic acid derivatives via tandem conjugate addition-elimination of activated allylic acetates under chiral PTC conditions

A new, general, and practical procedure for the asymmetric synthesis of 4-alkylidenyl glutamic acid derivatives via a catalytic enantioselective tandem conjugate addition-elimination on allylic acetates under chiral phase-transfer conditions is reported. A variety of structural types of allylic acetates have been reacted with the benzophenone imine of glycine tert-butyl ester to give the products in good to excellent yields and enantioselectivities (63-92% yield, 80-97% ee, 8 cases).     

Preparation and Spectral Analysis of Nickel-containing Aluminophosphate Molecular Sieves of Type-5

Diffuse reflectance spectroscopy was used to studynickel ion positions in the aluminophosphate molecularsieves of the AlPO-5 type. Nickel ions wereintroduced into the reactant mixture of thealuminophosphate and the synthesis carried outhydrothermally through various methods of gel, clearsolution and diluted suspension. The visibleabsorption spectra obtained of the dried, hydrated andcalcined materials were studied. A distinct andwell-defined triplet absorption band observed at about625, 580 and 540 nm was assigned to tetrahedralframework-substituted nickel(II) ions. A relativelystrong band at about 400 nm and two broad bands withsimilar intensity at 730 and 660 nm were assigned tooctahedral nickel species. These 730 and 660 nm bandsare observable only in the sample where nickel cationswere incorporated merely in the octahedralextra-framework sites by ion-exchange treatment ofSAPO-5. According to the synthesis procedure used,the amount of tetrahedral framework-substituted nickelions in comparison with octahedral ones can beevaluated from the intensities of the characteristicbands of the 4- and 6-coordinated nickel ions. Thereis much more octahedral nickel compared with thetetrahedral ones estimated in the light of theintensity data taking into account the absorptivitiesof nickel (II) symmetries. This work showed thatusing our synthesis procedure of a dilutedsuspension will result in preparing NiAPO-5 molecular sieve with more nickel cationsincorporated in the framework sites ofthe aluminophosphate. A very small quantity of thesecations remain in their sites at temperatures as highas 550°C.     

Chiral synthesis of functionalized tetrahydropyridines: gamma-aminobutyric acid uptake inhibitor analogues

[Chemical reaction: See text] A convenient preparation of functionalized chiral tetrahydropyridine-3-carboxylates from nitriles in 68-90% enantiomeric excess (ee) via allylboration, followed by a conjugate addition-elimination and ring-closing metathesis, has been developed. Thus, the treatment of the acetate derived from vinylalumination of formaldehyde by use of [alpha-(ethoxycarbonyl)vinyl]diisobutylaluminum with chiral beta-substituted and beta-unsubstituted homoallylic amines, prepared in >98% diastereomeric excess (de) and 68-90% ee via allylboration of the corresponding N-aluminoimines, furnished functionalized aminodienes, which underwent ring-closing metathesis to provide chiral C5-C6 disubstituted tetrahydropyridine-3-carboxylates. This methodology has been applied for the synthesis of a chiral C6-substituted tetrahydropyridine with known GABA-inhibiting properties at low concentrations.