STUDY ON THE THROUGH-SPACE AND THROUGH-BOND INTERACTIONS IN TRICYCLO 4,2,2,2 DODECADIENE-1.5

Through-space interactions of pi orbiatl and sigma orbital in molecule tricycle 4,2,2,2,dodecadiene -1.5 were studied by means of DV-X alpha SVF method using a model molecule that consists of two ethylenes with interdeck distance D. The results show the through-space interactions of the title molecule decrease with the increasing of D,the through-space interactions of pi orbital are larger than that of sigma orbital. Furthermore, through-bond interactions of the pi orbtial and sigma orbital were analyzed basing on the calculations of the electronic structure of the title molecule. Both through-space and through-bond interactions are Large and,the net interactions are small. The calculated ionization potential energies of the title molecule which were obtained by transition-state procedure are in good agreement with the PE spectroscopy.

Manipulation of the through-space interactions in diphenylmethane

Through-space interaction(TSI)has been proven to play an important role in the newly emerging clusteroluminescence(CL)phenomenon.However,it is still a big challenge to manipulate the TSI at the molecular level due to the unclear relationship between the non-conjugated structure and TSI properties.Herein,the TSI in diphenylmethane is manipulated by breaking its symmetric structures and changing the isolated subunits.Finally,the CL wavelength and efficiency of diphenylmethane are successfully regulated at the aggregate state.

The superiority of nonconjugated structures in fluorescence:through-space vs.through-bond charge transfer

Constructing charge transfer(CT)state by introducing donor(D)and acceptor(A)is an efficient strategy to regulate the photophysical properties of luminescent materials.Traditional CT-type luminophores are built onπ-conjugated fused-ring structures,which always show hybrid CT/locally excited(LE)states and luminescence quenching effect in the aggregate state.In this work,eight conjugated biphenyl(BP)and nonconjugated diphenylmethane(DPM)derivatives with different donors and acceptors are synthesized to investigate the CT properties.Systematic photophysical characterization and theoretical calculation demonstrate that the through-space CT(TSCT)in nonconjugated DA-DPM exhibit superior photophysical performance than the conjugated DA-BP with through-bond CT(TBCT),the main manifestations are as follows:(1)TSCT luminophores produce longer maximum emission wavelength(λ_(em))than the corresponding TBCT ones.For example,the longest λ_(em)of DMA-CN-DPM(DMA,dimethylamino)is 621 nm but the corresponding λ_(em)of DMA-CN-BP is only 480 nm.(2)TSCT-based DA-DPM demonstrates more sensitive responsiveness to environmental stimuli such as temperature and polarity.(3)Complete separation of the the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)distribution exists in all kinds of conformation of DA-DPM,which was hard to realize in conjugated DA-BP.

Effects of nonaromatic through-bond conjugation and through-space conjugation on the photoluminescence of nontraditional luminogens

Photoluminescence(PL)mechanisms of nontraditional luminogens(NTLs)have attracted great interest,and they are generally explained with intra/intermolecular through-space conjugation(TSC)of nonconventional chromophores.Here a new concept of nonaromatic through-bond conjugation(TBC)is proposed and it is proved that it plays an important role in the PL of NTLs.The PL behaviors of the three respective isomers of cyclohexanedione and gemdimethyl-1,3-cyclohexanedione were studied and correlated with their chemical and aggregate structures.These compounds show differentfluorescence emissions as well as dif-ferent concentration,excitation and solvent-dependent emissions.The compounds which undergo keto-enol tautomerism and hence with a conjugated ketone-enol structure(i.e.,nonaromatic TBC)show more red-shifted emissions.TBC effect reduces the energy gaps and facilitates the formation of stronger TSC in the aggre-gate state.The compounds in the ketone-enol form are also prone to occur excited state intra/intermolecular proton transfer(ESIPT).The cooperative effect of nonaro-matic TBC and TSC determines the PL behaviors of NTLs.This work provides a novel understanding of the PL mechanisms of NTLs and is of great importance for directing the design and synthesis of novel NTLs.

Lighting up aggregate emission of perylene diimide by leveraging polymerization-mediated through-space charge transfer and π-π stacking

The molecular engineering of fluorescent organic/polymeric materials,specifically those emitting in the deep red to near-infrared spectrum,is vital for advancements in optoelectronics and biomedicine.Perylene diimide(PDI),a well-known fluorescent scaffold,offers high thermal and photophysical stability but suffers from fluorescence quenching in solid or aggregate states due to intenseπ-πinteractions.To mitigate this,simple and versatile methods for strong PDI aggregate emission without extensive synthetic demands are highly desirable but still lacking.Here,we report a straightforward strategy to enhance the solid-state emission of PDI by introducing certain degree of through-space charge transfer(TSCT)via controlled radical polymerization,which can efficiently distort the typical face-to-face PDI stacking,enabling greatly enhanced deep red emission.This is achieved by growing electron-donating star-shape styrenic(co)polymers from a multidirectional electron-accepting PDI initiator.The incorporation of polycyclic aromatic monomers further shifted the emission into the near-infrared region,albeit with a reduced intensity.Overall,the emission of the PDI-based TSCT polymers can be systematically manipulated by leveraging the balance between PDI stacking and the TSCT degree,as confirmed by both experimental study and theoretical calculations.Our approach circumvents complex synthetic procedures,offering highly emissive materials with large Stokes shifts and showing broad potential for optoelectronic technology.

Fjord-Type AIEgens Based on Inherent Through-Space Conjugation

Through-space conjugation(TSC)is a noncovalently electronic interaction that is emerging as a potential complement to through-bond conjugation(TBC)-based strategies for constructing luminescent materials.However,the design of efficient luminogens based on TSC is currently challenging due to a lack of established structure-property understanding.This is particularly true in the case of luminogens displaying aggregation-induced emission(AIE)effects.In this work,three terphenyl derivatives were prepared,and their photophysical properties were systemically studied.It was found that relative to the corresponding m-and p-linked analogues,the electronic interaction of TBC is weakened while the strength of TSC is commensurately enhanced in the constitutional isomer containing an o-linked fjordtype subunit.Within this set of luminogens,the presence of a fjord-type arrangement promotes a transformation from aggregation-caused quenching to AIE.Further investigations involving congeneric quaterphenyl and pentphenyl isomers support the universality of the fjord-type unit as a framework for synthesizing AIE-active luminogens(AIEgens)with inherent TSC.This work not only provides a novel set of AIEgens but also establishes the utility of TSC in controlling the photophysical properties of nonconventional and twisted luminogens.

Through-Space Conjugation: A Thriving Alternative for Optoelectronic Materials

Efficient electronic coupling is the key to constructing optoelectronic functionalπsystems.Generally,the delocalization ofπelectrons must comply with the framework constructed by covalent bonds(typicallyσbonds),representing classic through-bond conjuga-tion.However,through-space conjugation offers an alternative that achieves spatial electron communica-tionwith closely stacked π systems instead of covalent bonds thus enabling multidimensional energy and charge transport.

Through-space charge transfer blue polymers containing acridan donor and oxygen-bridged triphenylboron acceptor for highly efficient solution-processed organic light-emitting diodes

Three kinds of through-space charge transfer(TSCT)blue polymers containing non-conjugated polystyrene backbone together with spatially-separated acridan donor and oxygen-bridged triphenylboron acceptors having different substituents of tert-butyl,hydrogen and fluorine are designed and synthesized.The designed TSCT blue polymers possess photoluminescence quantum yields up to 70%in solid-state film,single-triplet energy splitting below 0.1 eV,and typical thermally activated delayed fluorescence(TADF)effect.Meanwhile,the resulting polymers exhibit aggregation-induced emission(AIE)effect with emission intensity increased by up to^27 folds from solution to aggregation state.By changing the substituent of acceptors to tune the charge transfer strength,blue emission with peaks from 444 to 480 nm can be realized for the resulting polymers.Solution-processed organic light-emitting diodes based on the polymers exhibit excellent device performance with Commission Internationale de L’Eclairage(CIE)coordinates of(0.16,0.27),together with the maximum luminous efficiency of 30.7 cd A-1 and maximum external quantum efficiency of 15.0%,which is the best device efficiency for blue TADF polymers.

Through-space charge transfer polymers for solution-processed organic light-emitting diodes

Through-space charge transfer(TSCT)polymers are an attractive class of luminescent polymers with spatial donor/acceptor architecture and thermally activated delayed fluorescence effect,different from conventional luminescent polymers with conjugated donor-acceptor structure and through-bond charge transfer emission.Their emission comes from the intramolecular charge transfer by through-space pathway because the donor and acceptor segments are spatially proximate to each other in each repeating unit but are physically separated by nonconjugated polymer backbone.In this review,recent advances in TSCT polymers with linear,bottlebrush,and dendritic architectures are presented,with the focus on their molecular design,photophysical behavior,and device performance.We hope that this review shall provide a useful insight of new luminescent polymers with TSCT effect for use in solution-processed organic light-emitting diodes.

Recent advances of folded tetraphenylethene derivatives featuring through-space conjugation

Through-space conjugated molecules are interesting building blocks for the construction of functional materials that allow multi-dimensional transport of carrier and energy.However,the well explored through-space conjugated molecules are quite limited,which defers their structure-property correlation establishment and wide-scale application.In this review,we introduce a kind of newly-emerging folded tetraphenylethene derivatives featuring through-space conjugation.Their synthesis,crystal and electronic structures,and optical properties are described,and their representative applications as bipolar charge-transporting materials in organic light-emitting diodes and as single-molecule wires in molecular devices are presented,which are anticipated to provide guidance for the further expansion of through-space conjugated systems.

Carbazole ring: A delicate rack for constructing thermally activated delayed fluorescent compounds with through-space charge transfer

Three carbazole derivatives, Ac PTC, Px PTC and Pt PTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine,phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of a single carbazole ring via phenylene, are designed and synthesized. X-ray diffraction analysis of Ac PTC reveals that there exist multiple π-π interactions between the donor and acceptor groups to form a sandwich-like structural unit with edge-to-face interaction model. The compounds thus show obvious thermally activated delayed fluorescence with through-space charge transfer character and possess considerable photoluminescence quantum yields of up to 73% in doped films with sky-blue to yellow emissions. The solution-processed electroluminescent devices achieve the highest maximum external quantum efficiencies of 10.0%, 11% and 5.6% for Ac PTC, Px PTC and Pt PTC, respectively, with small efficiency roll-offs.

Construction of chiral through-space luminophores via symmetry breaking triggered by sequenced chlorination

The construction of molecular chirality is crucial for exploring novel luminophores with chiroptical properties.Classic asymmetric synthesis of chiral center or axial is not powerful enough on through-space architecture.Accessible methodologies for breaking molecular symmetry could be promising but remain less investigated.Herein,we report a novel methodology for constructing chiral through-space luminophores via simple chlorination on bridged carbazole motifs.The chlorination breaks the molecular symmetry and thus results in molecular chirality by eliminating the mirror plane or rotating axis.Interestingly,continuous multiple chlorinations can rebuild and break the symmetry of the skeleton in succession.Several chiral and achiral isomeric analogues are synthesized and characterized with impressive chiroptical properties.Results of chiral high performance liquid chromatography(HPLC),single-crystal X-ray diffraction,kinetic racemization,and chiroptical property investigation demonstrate the effectiveness of our rational design strategy.It provides a feasible methodology for exploring novel chiral luminescent materials based on versatile though-space skeletons.

Acceptor modulation for improving thermally activated delayed fluorescence emitter in through-space charge transfer on spiroskeletons

Through-space charge transfer(TSCT)is regarded as an effective way to develop thermally activated delayed fluorescence(TADF)emitters.Based on this strategy,many molecular frameworks have been proposed,among which spirobased scaffolds have been extensively studied due to their unique advantages.In this work,we developed three emitters SPS,SPO,and SPON,which were constructed with the same donor and various acceptors to explore the influence of acceptor modulation at the C9 position of fluorene for spirostructure TSCT emitters.The results show that the acceptor with too weak electronwithdrawing ability will cause the emitter to not have TADF properties,while the acceptor with too much steric hindrance will weaken the face-to-faceπ-πstacking interaction between donor/acceptor(D/A).Since SPO balances the electron-withdrawing strength and steric hindrance of the acceptor,it achieves the highest external quantum efficiency(EQE)of 17.75%.This work shows that appropriate acceptor selection is essential for the TADF properties and high efficiency of the spirobased scaffold TSCT emitter.

Controllable Secondary Through-Space Interaction and Clusteroluminescence

Nonconjugated clusteroluminogens(CLgens),such as proteins and polystyrene,have become increasingly important in photophysics.They show many advantages over traditional conjugated dyes with fused aromatic rings in biological applications.However,CLgens have historically been unheeded because of their weak visible emissions in the aggregate state,namely clusteroluminescence(CL).Changing the electronic structures of CLgens by precisely regulating the intramolecular throughspace interaction(TSI)to improve their photophysical properties remains an enormous challenge.Herein,we propose a general strategy to construct a higher-level intramolecular TSI,namely secondary TSI constructed by the primary TSI and a TSI linker,in multi-aryl-substituted alkanes(MAAs).By introducing methyl and phenyl into 1,1,3,3-tetraphenylpropane,the modified MAAs show efficient CL with high luminescence quantum yield(-40%)and long emission wavelength(-530 nm).Then,comprehensive experiments and theoretical studies demonstrate that molecular rigidity and overlap of subunits play pivotal roles in improving these hierarchical TSIs.This work not only provides a feasible strategy to achieve controllable manipulation of hierarchical TSIs and CL but also establishes comprehensive TSI-based aggregate photophysics.

Synthesis and Properties of a Through-Space Interacting Diradicaloid

Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.

Ⅰ期非小细胞肺癌患者肺穿刺活检是否增加胸膜复发和气腔播散的风险

近年来,随着肺结节的比例升高,术前经皮肺穿刺活检或经支气管镜活检越来越受到重视。大量临床证据也证实,Ⅰ期非小细胞肺癌(non-small cell lung cancer,NSCLC)的肺穿刺活检是安全可行的。但是,由于肺磨玻璃结节的组织学特点,与实性结节相比穿刺时更容易发生出血或咳嗽,肿瘤细胞在血流或气流冲击下可能会沿着肺泡壁或针道种植,导致胸膜复发和气腔播散(spread through air spaces,STAS),尤其是胸膜下结节合并有脏层胸膜侵犯和淋巴细胞浸润时需要慎重选择。

教育数字化转型赋能教育强国建设的空间逻辑

空间是数字时代理解教育变革的重要维度。教育空间在数字化转型过程中被赋予新的空间形态和功能,悄然改变着教育实践变革的形式和程度,教育数字化转型对教育空间的形塑能够为教育强国建设注入新的动能。基于空间理论审视教育数字化转型赋能教育强国建设的深层逻辑,应构建“空间机遇-空间诉求-目标对接”的分析框架,既要厘清教育数字化转型赋能教育强国建设的空间机遇,以物质空间重塑提升教育实力,以精神空间重塑强化教育功能,以实践空间重塑重构教育生态;也要分析教育强国建设之于教育数字化转型的空间诉求,以物质空间资源整合助推教育自身之强,以精神空间价值引领助推教育服务之强,以实践空间制度创新助推教育认同之强;最终探寻教育数字化转型赋能教育强国建设的空间路向,促进二者实现教育供给与需求层面的目标对接,以物质空间治理为教育强国建设奠基,以精神空间治理为教育强国建设储能,以实践空间治理为教育强国建设谋远。

面向地电极电流场透地通信的两阶段长相关信号捕获方法

地电极电流场透地通信可以为地下强遮蔽空间信息传输提供解决方案。针对接收的电流场信号信噪比(SNR)低、易畸变且受载波频偏影响大导致捕获困难的问题,该文设计一种长同步信号帧结构,在此基础上提出一种联合频偏粗估计和精估计的两阶段长相关信号捕获算法。该算法第1阶段利用接收时域信号中的训练符号,依据最大似然算法进行采样间隔偏差粗估计,并计算采样点补偿间隔粗估计值。第2阶段结合粗估计值和接收信噪比,确定采样点补偿间隔精估计值的遍历范围,进而设计本地补偿后的长相关模板信号,实现电流场信号的精确捕获。本研究在距离地面30.26 m的地下强遮蔽空间中进行了算法性能验证。实验结果表明,与传统的滑动相关算法相比,该文所提算法具有更高的捕获成功概率。

无刷双馈风力发电机低电压穿越控制策略研究

针对无刷双馈风力发电系统,稳态时,采用基于空间矢量调制(Space Vector Modulation,SVM)的直接功率控制(Direct Power Control,DPC)技术。在电网电压对称跌落条件下,理论分析功率绕组磁链与控制绕组电压的关系,对于故障期间控制绕组会产生较大的过电流,严重时可能损害变流器功率器件的问题,在原有的控制方案中引入前馈控制。通过将可观测的功率绕组电流进行微分运算后得到反映控制绕组反电势的直接干扰量,将其经前馈控制器引入到控制电压的参考值端,形成一种基于前馈控制的SVM-DPC复合控制。仿真结果表明,基于功率绕组电流微分前馈控制的复合控制策略可以在一定程度上抑制控制绕组过电流,能为无刷双馈风力发电机实现低电压穿越提供参考。

肺癌气道播散的影像学研究进展

肺癌气道播散(STAS)是指肿瘤细胞以微乳头状细胞团、实性细胞巢或单个细胞等形式存在于主瘤体之外的气道中。随着肺癌研究的不断深入,预测肺癌STAS在诊治和预后中有重要的价值,因此在2015年世界卫生组织将其确定为肺腺癌的一种新的侵袭方式。近年来,利用影像学方法预测STAS的有无已经成为研究的热点。目前相关研究的结果已证实了影像学预测STAS的可行性,进一步深入的研究对发现更加可靠和准确的影像学预测方法十分必要。本文就STAS的病理学、临床意义及影像学方面的研究进展予以综述。