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91.
Fullerene molecules have nano-scale cavities in which various metal or metal clusters of different sizes can be embedded to form metallofullerenes with unique core-shell structures. The physical and chemical properties of metallofullerenes can be modified through the interaction between the encapsulated metals and the fullerene cages. As such, the investigation of metallofullerenes with novel structures has been a principal research focus in the field of fullerenes. In this study, we investigated the size matching effect between encapsulated clusters and fullerene cages for the endohedral metal carbonitride clusterfullerenes in order to discover new metallofullerenes. The stability and electronic structure of the metallofullerenes formed by encapsulating M3NC clusters (M = Y, La, Gd) into D2(186)-C96 and D2(35)-C88 fullerenes were studied using quantum chemical calculations. It was found that the fullerene cages formed stable structures by accepting six electrons transferred from the encapsulated clusters. The change in configuration of the encapsulated clusters was clarified by a comparison with the corresponding M3N@C2n metal nitride clusterfullerenes; the size matching effect between M3NC cluster and fullerene cage was elucidated on the basis of the calculated results and previous studies on Sc3NC@Ih(7)-C80. For the D2(186)-C96 fullerene, the Gd3NC cluster was found to have smaller changes in the configuration as compared with the La3NC cluster, proving that Gd3NC is more suitable than La3NC for encapsulation in the D2(186)-C96 fullerene cage. In addition, it was determined that the La3NC cluster requires a large structural change to maintain its planar configuration. For the D2(35)-C88 fullerene cage, the Y3NC cluster is more suitable than Gd3NC for encapsulation owing to the smaller size of the Y3NC cluster. The spatial distribution of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of Gd3NC@D2(186)-C96 were found to be similar to those of Gd3N@D2(186)-C96. However, a unique endohedral cluster-based occupied molecular orbital was found for Gd3NC@D2(186)-C96. This orbital is derived from the interaction between the NC unit and the Gd atoms. The spatial distribution of the HOMO of Y3NC@D2(35)-C88 is similar to that of Y3N@D2(35)-C88, while the LUMO of Y3NC@D2(35)-C88 has a much larger contribution from the endohedral cluster as compared to Y3N@D2(35)-C88. Thus, the addition of a carbon atom in the cluster has a remarkable impact on the electronic structure of the metallofullerenes. With respect to structural characteristics, we found that the three fullerene cages, D2(186)-C96, D2(35)-C88, and Ih(7)-C80, have a uniform distribution of five-membered carbon atom rings; these fullerenes can be greatly stabilized in the form of C2n6- anions. However, the formation mechanism of fullerenes and metallofullerenes, at present, is poorly understood. Based on the structural analysis, we propose a direct mechanism for the formation of fullerenes without the Stone-Wales isomerization, i.e., the rearrangement of five-membered rings through the addition of carbon atoms and the transformation into larger carbon cages while maintaining stable structural units. 相似文献
92.
A series of highly fluorescent, pyrene-modified oligo(2,7-fluorene ethynylene)s were synthesized and fully characterized. Different emissions were observed between pyrene-end-capped and pyrene-centered oligo(2,7-fluorene ethynylene)s. Moreover, these oligomers were applied to fabricate organic light-emitting diodes (OLEDs), and bright blue or green electroluminescence (EL) with good device performances was achieved in multilayer OLEDs. These pyrene-modified oligo(2,7-fluorene ethynylene)s could be used as optoelectronics materials or models to investigate fluorescent structure-property relationship of fluorene derivatives. 相似文献
93.
94.
Zigzag molecules from pyrene-modified carbazole oligomers: synthesis, characterization, and application in OLEDs 总被引:1,自引:0,他引:1
A series of monodisperse, pyrene-modified oligocarbazoles were synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag molecular backbone and stable, size-independent absorption, and emission were observed from these oligomers in solutions because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures (types 1-4) based on these oligomers were fabricated and investigated. Pyrene-modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 presented an external quantum efficiency of 0.69% and a maximum brightness of 1782 cd/m2 at 13.5 V, which indicated these oligomers were promising optoelectric materials. 相似文献
95.
Zujin Zhang 《Acta Appl Math》2017,149(1):139-144
This paper studies the 3D generalized MHD system with fractional diffusion terms \((-\triangle)^{\alpha}\boldsymbol{u}\) and \((-\triangle )^{\beta}\boldsymbol{b}\) with \(0<\alpha<\frac{5}{4}\leq\beta\), and establishes a regularity criterion involving the velocity gradient in Besov spaces of negative order. This improves Fan et al. (Math. Phys. Anal. Geom. 17:333–340, 2014) a lot. 相似文献
96.
Qiuhua Zhu Yilin Zhang Han Nie Zujin Zhao Shuwen Liu Kam Sing Wong Ben Zhong Tang 《Chemical science》2015,6(8):4690-4697
Racemic C6-unsubstituted tetrahydropyrimidines (THPs) are a series of fluorophores with a strong aggregation-induced emission (AIE) effect. However, they do not possess the structural features of conventional AIE compounds. In order to understand their AIE mechanism, here, the influences of the molecular packing mode and the conformation on the optical properties of THPs were investigated using seven crystalline polymorphs of three THPs (1–3). The racemic THPs 1–3 have low-conjugated and highly flexible molecular structures, and hence show practically no emission in different organic solvents. However, the fluorescence quantum yields of their polymorphs are up to 93%, and the maximum excitation (λ ex) and emission (λ em) wavelengths of the polymorphs are long at 409 and 484 nm, respectively. Single-crystal structures and theoretical calculation of the HOMOs and LUMOs based on the molecular conformations of these polymorphs indicate that the polymorphs with the shortest λ ex and λ em values possess a RS-packing mode (R- and S-enantiomers self-assemble as paired anti-parallel lines) and a more twisted conformation without through-space conjugation between the dicarboxylates, but the polymorphs with longer λ ex and λ em values adopt a RR/SS-packing mode (R- and S-enantiomers self-assemble as unpaired zigzag lines) and a less twisted conformation with through-space conjugation between the dicarboxylates. The molecular conformations of 1–3 in all these polymorphs are stereo and more twisted than those in solution. Although 1–3 are poorly conjugated, the radiative rate constants (k r) of their polymorphs are as large as conventional fluorophores (0.41–1.03 × 108 s–1) because of improved electronic conjugation by both through-bond and through-space interactions. Based on the obtained results, it can be deduced that the strong AIE arises not only from the restriction of intramolecular motion but also from enhanced electronic coupling and radiatively-favored inter-crossed local excitation (LE) and intramolecular charge transfer (ICT) excitation states. The abnormal molecular structures, easily-controllable self-assembly of the R- and S-enantiomers, and the strong AIE effect make THPs very useful fluorophores for applications and theoretical research. 相似文献
97.
纳米团簇的超分子自组装 总被引:10,自引:0,他引:10
在纳米材料的应用过程中, 纳米团簇或纳米粒子的组装将是非常关键的一步。纳米团簇的超分子化学组装方法可分为两类, 即胶态晶体法和模板法。胶态晶体法是利用胶体溶液的自组装特性将纳米团簇组装成超晶格, 可得到二维或三维有序的超晶格。模板法是利用纳米团簇与组装模板间的识别作用来带动团簇的组装, 可应用的模板有固体膜、单分子膜、有机分子、生物分子等。其中, 单分子膜模板是研究最多也是最为成熟的一种; 生物分子间严密的分子识别功能使其成为非常有发展前途的组装模板, 而且用生物分子模板有可能实现不同纳米团簇间的组装。 相似文献
98.
99.
Jian-Cai Huang Guang-Ming Ye Maoxing Yu Ruishan Huang Prof. Zujin Zhao Prof. Anjun Qin Dr. Shu-Ting Wu Prof. Zenghong Xie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(22):6760-6766
Recently, scientists have reported a range of chiral fluorescence materials or chiral composites that can emit circularly polarized luminescence. Herein, two achiral metal–organic colloidal solutions were studied, showing active circularly polarized luminescence, which is observed in vortex stirring. The absolute values for glum are 0.05 and 0.03 and the plus or minus sign of glum depends on the colloidal structure and stirring direction, which make the property easy to manipulate. Further, the host–guest interaction study suggests both electrostatic interactions and coordination bonding may influence the chiroptical property from the colloidal solution to the guest molecule. Rhodamine 6G and its carboxylic acid derivative exhibit good quantum yields and acceptable glum values in the colloidal solution. 相似文献
100.
Dr. Ziqi Hu Aman Ullah Dr. Helena Prima-Garcia Sang-Hyun Chin Dr. Yuanyuan Wang Dr. Juan Aragó Prof. Zujin Shi Dr. Alejandro Gaita-Ariño Prof. Eugenio Coronado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13242-13248
To design molecular spin qubits with enhanced quantum coherence, a control of the coupling between the local vibrations and the spin states is crucial, which could be realized in principle by engineering molecular structures via coordination chemistry. To this end, understanding the underlying structural factors that govern the spin relaxation is a central topic. Here, we report the investigation of the spin dynamics in a series of chemically designed europium(II)-based endohedral metallofullerenes (EMFs). By introducing a unique structural difference, i. e. metal-cage binding site, while keeping other molecular parameters constant between different complexes, these manifest the key role of the three low-energy metal-displacing vibrations in mediating the spin-lattice relaxation times (T1). The temperature dependence of T1 can thus be normalized by the frequencies of these low energy vibrations to show an unprecedentedly universal behavior for EMFs in frozen CS2 solution. Our theoretical analysis indicates that this structural difference determines not only the vibrational rigidity but also spin-vibration coupling in these EMF-based qubit candidates. 相似文献