Orientation effects on C2(5)-C2'(5')linked bioxazole isomers synthesized via regioselective and sequential C—H arylation

Bis(4-fluorophenyl) substituted oxazole(2,5-Oxz) and C2(5)-C2'(5') linked bioxazole isomers(C2-C2'_BOxz,C2-C5'_BOxz and C5-C5'_BOxz) were concisely synthesized via palladium-catalyzed regioselective and sequential C-H arylation in 1-3 reaction steps along with 20%-83% of total yields from oxazole and4-bromofluorobenzene.The linking orientation plays a key role in the packing geometry and photophysical properties of C2-C2'_BOxz,C2-C5'_BOxz and C5-C5'_BOxz.These bioxazole isomers in solid state showed significant differences in photoluminescence quantum yields(PLQY)(0.33,0.25 and 0.04,respectively),delayed fluorescence properties and powder X-ray diffraction(PXRD) patterns,suggesting the divergence in intermolecular interactions.The theoretically calculated gradient isosurfaces and complexation energies indicate the existence of intense π-π interactions between molecular layers,which are in good agreement with the variation trend of optical properties.

In Situ Fabrication of Superfine Perovskite Composite Nanofibers with Ultrahigh Stability by One‑Step Electrospinning Toward White Light‑Emitting Diode

All-inorganic CsPbX_(3)(X=Cl,Br,I)perovskite nanocrystals(NCs)are emerging as promising candidate materials for optoelectronic devices due to their splendid optical and electrical properties.However,the intrinsic instability greatly limits their practical application.Herein,a feasible strategy is proposed for fabricating highly stable and luminescent CsPbBr_(3)@PVDF-HFP/PS nanofibers by combining one-step electrospinning method with 1H,1H,2H,2H-perfluorodecyltrimethoxysi-lane(PFDTMS)-assisted post-treatment.The bright-emitting CsPbBr_(3) NCs can be effectively encapsulated within polymer nanofibers,which exhibit ultrafine diameter of only 88.1±2.8 nm and high photoluminescence quantum yield(PLQY)of 87.9%via rationally optimizing the electrospinning parameters,concentration of perovskite precursors and ligands.Most importantly,the superhydrophobic surface structures of nanofibers are formed by the hydrolysis and condensation of PFDTMS under moist environment.Benefiting from the double effective protection of polymer matrices and hydrophobic PFDTMS oligomers against moisture erosion,the CsPbBr_(3)@PVDF-HFP/PS nanofibers present an obviously improved stability,which can retain 90%initial PL intensity after water immersion for 70 days.Furthermore,an efficient white light-emitting diode with wide color gamut covering 117%of National Television System Committee(NTSC)standard is successfully fabricated based on the composite nanofiber membranes,suggesting their promising prospect for solid-state lighting and display applications.