Molecular self-induced configuration for improving dissymmetry factors in tetradentate platinum(Ⅱ) enantiomers cycloaddition

Two pairs of Pt(Ⅱ) enantiomers((RR)/(SS)-Py Pt,((RR)/(SS)-Py: N,N’-(1,2-diphenylethane-1,2-diyl)dipicolinamide;(RR)-P/M-QPt,((RR)/(SS)-Q: N,N’-((1R,2R)-1,2-diphenylethane-1,2-diyl)bis(quinoline-2-carboxamide)) were synthesized, respectively, with good circularly polarized luminescence(CPL) and tunable dissymmetry factors(g) by molecular self-induction with(RR)/(SS)-1,2-diphenylethane-1,2-diamine as carbon chiral sources. In the(RR)-P-QPt and(SS)-M-QPt, specific P-and M-configurations were effectively induced from intrinsic chiral carbon centres(R or S), ingeniously avoiding the racemic mixture formation and chiral separation. Furthermore, the chirality originating from both chiral carbon centres and helicene-like structure improves the g factor significantly, which provides a new molecular design strategy for chiral Pt(II) enantiomers with good CPL properties.

The Dissymmetry of Friction Stir Welding Joints and Va-riable Polarity Plasma Arc Welding Joints Study

2219 aluminum alloys welding joints were prepared by Friction stir welding (FSW) and Variable polarity plasma arc welding (VPPAW).The microstructure of joints was characterized by means of OM,SEM,and EDX.Microhardness measurements was performed to differentiate the joint zones and to evaluate the symmetry level of the joints with the help of nano-indentation experiment.The dissymmetry of microstructure and mechanical properties was found both in FSW joint and VPPAW joint.The dissymmetry in FSW joint can not be suppressed due to the nature of the mixing head,but the symmetry and satisfactory welding joint can be obtained by changing the working pattern of VPPAW.

Research on Search Laws of Image Guided Missile

When image guided missile adopts guided search and common search law to search ground targets, under some conditions the movement of image on the monitor screen will be dissymmetrical, which is harmful for shooter to acquire and capture targets. To remove the dissymmetry of the image movement, such common search laws as parallel search law, ＂X＂ style search law, search law of one-dimension visual effect and cone search law are improved and designed again. Simulation results show that the dissymmetry can be removed by adopting all the above four improved search laws, but the search track of improved cone search law has serious transmutation compared with the original search track. The other three improved search laws have little transmutation of the search track, and they all can keep the main characters of the original search law. Study resuits are helpful for image guided missile in adopting guided search to choose appropriate search law.

Dissymmetric flow phenomenon in a multistrand tundish

The dissymmetric flow phenomenon exists in a symmetric multistrand tundish. It was studied by the physical simulation experiment. The fundamental flow characteristic of dissymmetry was analyzed. The asymmetry of the flow field, the temperature field, and the inclusions distribution without flow-control devices （FCDs） were compared with those with FCDs. It is proved that the asymmetry of the flow and temperature field along the outlets at the long range is more obvious. The symmetric FCDs installation has a slight effect on the dissymmetric temperature field, simultaneously, the symmetry of the average residence time and the fluid flow pattern has improved, and the fluid flow in the tundish has been more reasonable. In case of a symmetric multistrand tundish having a large volume, the influence of the dissymmetric phenomenon should be considered and the flow behaviors in the whole tundish should be studied completely.

Chiral thermally activated delayed fluorescence materials for circularly polarized organic light-emitting diodes

Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material science.Benefiting from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,etc.Due to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical applications.The ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two elements.This review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device performance.Furthermore,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.

Efficient circularly polarized photoluminescence and electroluminescence of chiral spiro-skeleton-based thermally activated delayed fluorescence molecules

Chiral thermally activated delayed fluorescence(TADF) molecules showing circularly polarized luminescence(CPL) have great potential in 3D displays. However, the relationships among CPL property, device performance and molecule structure are still not clear. In this article, we develop a strategy to promote dissymmetry factors without sacrifice in device performance and study the impact of molecule structures towards CPL property. Three novel TADF enantiomers are synthesized and studied.(R/S)-SCN with diminutive cyano group as an acceptor shows dissymmetry factor |gPL| ≈ 1.4×10^(-3) and noticeable organic light-emitting diode(OLED) performances with a maximum external quantum efficiency(EQEmax) of 23.0%. For(R/S)-SPHCN, the prolonged electron withdrawing group benzonitrile enhances |gPL| up to 3.6×10^(-3) with decreased device EQEmaxof 15.4%. By further replacing benzonitrile with(trifluoromethyl)pyridine, the enantiomers of(R/S)-SCFPY show similar |gPL| factors of 3.5×10^(-3) and device EQE_(max)up to 23.3%, which represents the highest efficiency among sprio-type TADF materials based OLEDs. Furthermore, the OLEDs also show obvious circularly polarized electroluminescence with gELfactors of-1.4/1.8×10^(-3),-3.6/3.6×10^(-3) and-3.7/3.6×10^(-3), respectively. These results indecate by delicate functional group engineering, high g factor can be achieved while maintaining decent device performances. Besides,(R/S)-SCFPY represents an impressive TADF emitter, which shows promoted g factor and recorded high device EQE_(max)among similar molecules.

Circularly polarized luminescent self-organized helical superstructures:From materials and stimulus-responsiveness to applications

Circularly polarized luminescence(CPL)has gained considerable attention in various systems and has rapidly developed into an emerging research field.To meet the needs of actual applications in diverse fields,a high luminescence dissymmetry factor(glum)and tunable optical performance of CPL would be the most urgent pursuit for researchers.Accordingly,many emerging CPL materials and various strategies have been developed to address these critical issues.Emissive cholesteric liquid crystals(CLCs),that is,luminescent self-organized helical superstructures,are considered to be ideal candidates for constructing CPL-active materials,as they not only exhibit high glum values,but also enable flexible optical control of CPL.This review mainly summarizes the characteristics of CPL based on CLCs as the bulk phase doped with different emitters,including aggregated induced emission molecules,conventional organic small molecules,polymer emitters,metal-organic complex emitters,and luminescent nanoparticles.In addition,the recent significant progress in stimulus-responsive CPL based on emissive CLCs in terms of several types of stimuli,including light,electricity,temperature,mechanical force,and multiple stimuli is presented.Finally,a short perspective on the opportunities and challenges associated with CPL-active materials based on the CLC field is provided.This review is anticipated to offer new insights and guidelines for developing CLC-based CPL-active materials for broader applications.