22 November 2019, Volume 30 Issue 11

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  • Zhiyuan Fu, Kai Wang, Bo Zou
    Chinese Chemical Letters. 2019, 30(11): 1883-1894. https://doi.org/10.1016/j.cclet.2019.08.041
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    Organic luminescent materials are very sensitive to external stimuli, such as pressure, temperature, and electric field. The luminescent properties of some organic luminescent materials significantly change under high pressure. Some materials may show luminescence discoloration, whereas some may exhibit luminescence enhancement. These properties have many potential applications in anticounterfeiting, force sensor, data recording and storage, and luminescent devices, thereby greatly attracting the attention of scientists. In this review, the progress of research on these materials at high pressure in recent years is summarized.
  • Wei Miao, Zhaoyang Zhu, Zhongxin Li, Erhong Hao, Lijuan Jiao
    Chinese Chemical Letters. 2019, 30(11): 1895-1902. https://doi.org/10.1016/j.cclet.2019.08.016
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    Novel expanded porphyrinoids with advanced structure features (such as multiple-inner-ring-fusion) have a wide range of benefits (such as multi-metal coordination and facile tunable aromaticity) not offered by their normal porphyrin analogues, and have found wide applications as sensors, fluorescent probes, novel ligands and functionalized NIR organic dyes in various research fields. However, the structures of these expanded porphyrinoids are scarce due to their limited synthetic accessibility. Herein, we summarized the lately reported efficient synthesis of novel expanded porphyrinoids with multipleinner-ring-fusion (up to six-inner-ring-fusion) and smaragdyrins with tunable aromaticity. Their synthesis is either based on an oxidative ring cyclization on linear/macrocyclic oligopyrroles containing N-confused pyrrole unit(s) or a straightforward double SNAr reaction on readily available 3,5-dibromoBODIPY, respectively.
  • Liang Ou, Yunyun Zhou, Bin Wu, Liangliang Zhu
    Chinese Chemical Letters. 2019, 30(11): 1903-1907. https://doi.org/10.1016/j.cclet.2019.08.015
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    Azulene, an isomer of naphthalene, has become one of hot chemical structures in the research field of functional materials, due to its anti-Kasha's rule emissions and unusual physicochemical properties (e.g., photophysical, electrochemical, and photoelectrochemical properties). In the past, the synthesis of azulene-based compounds is relatively inconvenient. Recently, there have been more and more reports about the synthesis strategies of the azulene-based compounds for finely tuning the physicochemical properties. In this article, we introduce several synthetic methods for kinds of azulene-based compounds which has unusual physicochemical properties. With these convenient methods and unique physicochemical properties, azulene-based compounds can be applied into many fields such as specific bioimaging, advanced molecular switches, organic field-effect transistor (OFET), organic light emitting diode (OLED), solar cells, and so forth. And these properties are also summarized here.
  • Bo Lu, Shuya Liu, Dongpeng Yan
    Chinese Chemical Letters. 2019, 30(11): 1908-1922. https://doi.org/10.1016/j.cclet.2019.09.012
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    Recently, molecule-based luminescent materials have been drawing extensive attention due to their desirable properties and promising applications in the fields of sensors, lighting display and cell imaging. Crystalline polymorph is an intriguing phenomenon that the presence of multiple packing and aggregate architectures of the same molecular system. The studies on polymorphs for molecule-based fluorophores provide the opportunities to adjust the mode of molecular packing and photophysical properties, which will help to illustrate the structure-property relationship. In this review, we focus on the recent progress in various feasible methods of molecule-based crystalline polymorphism growth and their adjustable photofunctional properties, which will open up possibilities of variant optical applications. Firstly, several effective ways to prepare and screen polymorphs are sorted out. And then, we discuss the discrepant properties and multifunctional applications (such as sensors, laser and OFET). Finally, the development trends and future prospects of these polymorphs are also briefly introduced.
  • Communications
  • Xujin Qin, Jianlei Han, Dong Yang, Wenjie Chen, Tonghan Zhao, Xue Jin, Peipei Guo, Pengfei Duan
    Chinese Chemical Letters. 2019, 30(11): 1923-1926. https://doi.org/10.1016/j.cclet.2019.04.035
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    Photon upconversion (UC) based on triplet-triplet annihilation (TTA) in quasi-solid or solid state has been attracting much research interest due to its great potential applications. To get effective UC, precisely controlled donor-acceptor interaction is vitally important. Chiral self-assembly provides a powerful approach for sophisticated regulation of molecular interaction. Here we report a chiral self-assembly controlled TTA-UC system composed of chiral acceptor and achiral donor. It is found that racemic mixture of acceptors could form straight fibrous nanostructures, which show strong UC emission, while chiral assemblies for homochiral acceptors emit weak upconverted light. The racemic assemblies allow efficient triplet-triplet energy transfer (TTET) and further realize efficient UC emission, while the homochiral assemblies from chiral acceptor produce twisted nanostructures, suppressing efficient triplet energy transfer and annihilation. The establishment of such chiral self-assembly controlled UC system highlights the potential applications of triplet fusion in optoelectronic materials and provides a new perspective for designing highly effective UC systems.
  • Xiaolong Zhang, Yifei Han, Guangyao Liu, Feng Wang
    Chinese Chemical Letters. 2019, 30(11): 1927-1930. https://doi.org/10.1016/j.cclet.2019.05.007
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    Two host-guest systems have been constructed, by employing structurally similar terpyridine platinum (II) macrocycle and molecular tweezer as the synthetic receptors. The macrocycle/guest complex displays low-energy emission signal, reinforced non-covalent binding affinity, and enhanced photosensitization capability than those of the molecular tweezer/guest one. The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt(II) Pt(II) metal-metal bonds in host-guest complexation structures.
  • Gangyuan Li, Hao Ye, Fucheng Zhu, Yan Geng, Jianzhong Fan, Jianping Ma, Chihaya Adachi, Yu-Bin Dong
    Chinese Chemical Letters. 2019, 30(11): 1931-1934. https://doi.org/10.1016/j.cclet.2019.08.006
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    By applying two donor-acceptor motif molecules, 5,10-di(pyridin-4-yl)-5,10-dihydrophenazine (L1) and 10,10'-di(pyridin-3-yl)-10H,10'H-9,9'-spiroacridine (L2), as ligands and CuI/AgCF3CO2 as metal salt, we synthesized three coordination polymers, namely, {Cu4(L1)2I4} (CP1), {Cu(L2)I·CHCl3} (CP2) and {Ag(L2)CO2CF3·CHCl3} (CP3). X-ray crystallographic analysis revealed that three coordination polymers all feature one-dimensional (1D) linear chains which are consisting of molecular boxlike units. In comparison with low photoluminescence quantum yield (PLQY) of two ligands, three coordination polymers, CP1, CP2 and CP3, present more intense photoluminescence with PLQY of 15%, 46% and 34% at room temperature respectively. The PL emission of CP1 and CP2 at room temperature could be attributed to the fast phosphorescence with lifetime both around 5 ms due to effective intersystem crossing (ISC). Whilst, it is worth noting that CP3 exhibit thermally activated delayed fluorescence (TADF) emission at room temperature.
  • Xuan Wang, Nan Gan, Mingxing Gu, Kun Ling, Chaoqun Ma, Huili Ma, Wei Yao, Yujian Zhang, Huifang Shi, Zhongfu An, Wei Huang
    Chinese Chemical Letters. 2019, 30(11): 1935-1938. https://doi.org/10.1016/j.cclet.2018.12.023
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    Ultralong organic phosphorescent materials have invoked considerable attention for their great potential in sensing, data encryption, information anti-counterfeiting and so forth. However, effective ways to achieve highly efficient ultralong organic phosphorescence (UOP) in metal-free organic materials remain a great challenge. Herein, we designed three isomers based on asymmetric triazines with various bromine substituted positions. Impressively, phosphorescence efficiency of p-BrAT in solid state can reach up to 9.7% with a long lifetime of 386 ms, which was one of the highest efficient UOP materials reported so far. Theoretical calculations further demonstrated that para-substitution exhibited the most effective radiative transition for triplet excitons. These results will provide an effective approach to achieving highly efficient UOP materials.
  • Nan Liu, Peng-Zhong Chen, Jian-Xin Wang, Li-Ya Niu, Qing-Zheng Yang
    Chinese Chemical Letters. 2019, 30(11): 1939-1941. https://doi.org/10.1016/j.cclet.2019.04.058
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    Difluoroboron β-diketonate (BF2bdk) complexes have attracted much attention due to their outstanding photophysical properties. However, BF2bdk with near-infrared fluorescence usually suffer from emission quenching in solid state due to the π-π stacking in aggregation. Herein, we report a BF2bdk dye exhibiting donor-acceptor (D-A) structure with the difluoroboron moiety acting as the electron acceptor and the aminonaphthalene as the electron donor. It processes intense molar extinction coefficient, large Stokes shift and strong fluorescence in red/NIR region in both solution and aggregations. It was used for NIR imaging in living cells.
  • Lingzhi Ma, Tianfeng Yang, Zeyuan Zhang, Siping Yin, Zhongxiao Song, Wen Shi, Dake Chu, Yanmin Zhang, Mingming Zhang
    Chinese Chemical Letters. 2019, 30(11): 1942-1946. https://doi.org/10.1016/j.cclet.2019.07.043
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    In this work, a near-infrared emissive dipyridyl ligand was synthesized and used to prepare three platinum(II) metallacycles with different shapes via metal-coordination-driven self-assembly with different platinum(II) precursors. These metallacycles were further used for both cell imaging and cancer therapy, offering a new type of theranostic agents towards cancer treatment.
  • Yue Shen, Xiaohui Tang, Yuwei Xu, Haichao Liu, Shitong Zhang, Bing Yang, Yuguang Ma
    Chinese Chemical Letters. 2019, 30(11): 1947-1950. https://doi.org/10.1016/j.cclet.2019.07.059
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    Organic solid-state luminescent materials with high-efficiency deep-red emission have attracted considerable interest in recent years. Constructing donor-acceptor (D-A) type molecules has been one of most commonly used strategies to achieve deep-red emission, but it is always difficult to achieve high photoluminescence (PL) quantum yield (ηPL) due to forbidden charge-transfer state. Herein, we report a new D-A type molecule 4-(7-(4-(diphenylamino)phenyl)-9-oxo-9H-fluoren-2-yl)benzonitrile (TPAFOCN), deriving from donor-acceptor-donor (D-A-D) type 2,7-bis(4-(diphenylamino)phenyl)-9H-fluoren-9-one (DTPA-FO) with a fluorescence maximum of 627 nm in solids. This molecular design enables a transformation of acceptor from fluorenone (FO) itself to 4-(9-oxo-9H-fluoren-2-yl) benzonitrile (FOCN). Compared with DTPA-FO, the introduction of cyanophenyl not only shifts the emission of TPA-FOCN to deep red with a fluorescence maximum of 668 nm in solids, but also maintains the high ηPL of 10%. Additionally, a solution-processed non-doped organic light-emitting diode (OLED) was fabricated with TPA-FOCN as emitter. TPA-FOCN device showed a maximum luminous efficiency of 0.13 cd/A and a maximum external quantum efficiency (EQE) of 0.22% with CIE coordinates of (0.64, 0.35). This work provides a valuable strategy for the rational design of high-efficiency deep-red emission materials using cyanophenyl as an ancillary acceptor.
  • Shuai Tan, Xiugang Wu, Yanqiong Zheng, Yafei Wang
    Chinese Chemical Letters. 2019, 30(11): 1951-1954. https://doi.org/10.1016/j.cclet.2019.08.003
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    Utilization of intermolecular Friedel-Crafts and intramolecular condensation reaction, novel 1,3-di-(pyridine-2-yl)benzene(N,C,N terdentate) skeleton with electro-withdrawing group in 6' position of pyridyl and a cyclization between 6' position of pyridyl and 6 position of benzyl ring were firstly designed and synthesized. The structures of these novel N,C,N terdentate were confirmed by NMR, MS and X-ray single crystalanalyses. The photophysical properties of these compounds were briefly explored.
  • Wenbo Yuan, Hannan Yang, Mucan Zhang, Die Hu, Shigang Wan, Zijing Li, Changsheng Shi, Ning Sun, Youtian Tao, Wei Huang
    Chinese Chemical Letters. 2019, 30(11): 1955-1958. https://doi.org/10.1016/j.cclet.2019.08.019
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    The highest efficiency thermally activated delayed fluorescence (TADF) emitters in OLEDs are mostly based on twisted donor/acceptor (D/A) type organic molecules. Herein, we report the rational molecular design on twisted all ortho-linked carbazole/oxadiazole (Cz/OXD) hybrids with tunable D-A interactions by adjusting the numbers of donor/acceptor units and electron-donating abilities. Singlet-triplet energy bandgaps (ΔEST) are facilely tuned from~0.4, 0.15 to~0 eV in D-A, D-A-D to A-D-A type compounds. This variation correlates well with triplet-excited-state frontier orbital spatial separation efficiency. NonTADF feature with solid state photoluminescence quantum yield (PLQY)<10% is observed in D-A type 2CzOXD and D-A-D type 4CzOXD. Owing to the extremely low ΔEST for efficient reverse intersystem crossing, strong TADF with PLQY of 71%-92% is achieved in A-D-A type 4CzDOXD and 4tCzDOXD. High external quantum efficiency from 19.4% to 22.6% is achieved in A-D-A typed 4CzDOXD and 4tCzDOXD.
  • Lili Sun, Ning Sun, Lubing Bai, Xiang An, Bin Liu, Chen Sun, Lixiang Fan, Chuanxin Wei, Yamin Han, Mengna Yu, Jinyi Lin, Dan Lu, Ning Wang, Linghai Xie, Kang Shen, Xinwen Zhang, Yanan Xu, Juan Cabanillas-Gonzalez, Wei Huang
    Chinese Chemical Letters. 2019, 30(11): 1959-1964. https://doi.org/10.1016/j.cclet.2019.08.048
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    The control of the condensed superstructure of light-emitting conjugated polymers (LCPs) is a crucial factor to obtain high performance and stable organic optoelectronic devices. Side-chain engineering strategy is an effective platform to tune inter chain aggregation and photophysical behaviour of LCPs. Herein, we systematically investigated the alkyl-chain branched effecton the conformational transition and photophysical behaviour of polydiarylfluorenes toward efficient blue optoelectronic devices. The branched side chain will improve materials solubility to inhibit interchain aggregation in solution according to DLS and optical analysis, which is useful to obtain high quality film. Therefore, our branched PEODPF, POYDPF pristine film present high luminance efficiency of 36.1% and 39.6%, enhanced about 20% relative to that of PODPF. Compared to the liner-type sides' chain, these branched chains also suppress chain planarization and improve film morphological stability effectively. Interestingly, the branched polymer also had excellent stable amplified spontaneous emission (ASE) behaviour with low threshold (4.72 μJ/cm2) and a center peak of 465 nm, even thermal annealing at 220℃ in the air atmosphere. Therefore, side-chain branched strategy for LCPs is an effective means to control interchain aggregation, film morphology and photophysical property of LCPs.
  • Qiang Wang, Qingqing Chen, Guoyu Jiang, Mengting Xia, Mengjiao Wang, Yongdong Li, Xiaoming Ma, Jianguo Wang, Xinggui Gu
    Chinese Chemical Letters. 2019, 30(11): 1965-1968. https://doi.org/10.1016/j.cclet.2019.08.037
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    An AIEgen decorated porphyrin (TPETPyP) was easily obtained through a one-step reaction. The bulky TPE in TPETPyP greatly impeded the intermolecular π-π stacking of the porphyrin core, which significantly suppressed aggregation-caused quenching (ACQ) effect of TPETPyP in aqueous solution. The four pyridinium salts formed in TPETPyP also render the whole molecule water solubility, which eliminated its aggregation. TPETPyP exhibited 1O2 quantum yield as high as 0.85 in PBS. Moreover, it also showed high binding affinity to proteins, the major biotarget of 1O2. The high 1O2 quantum yield plus the great binding ability of TPETPyP toward proteins makes it a highly-efficient protein photocleaving agent. Protein electrophoresis experiments demonstrated that TPETPyP can photocleave BSA upon visible light irradiation, indicating that TPETPyP can act as a promising photosensitizer (PS) in PDT. The work here will provide a facile strategy to utilize AIEgens modified traditional PSs for photodynamic therapy (PDT).
  • Bing Yang, Jianfeng Zhao, Zepeng Wang, Zhenlin Yang, Zongqiong Lin, Yanni Zhang, Jiewei Li, Linghai Xie, Zhongfu An, Hongmei Zhang, Jiena Weng, Wei Huang
    Chinese Chemical Letters. 2019, 30(11): 1969-1973. https://doi.org/10.1016/j.cclet.2019.08.054
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    Two electron-deficient azaacenes including di- and tetra-cyanodiazafluorene (DCAF and TCAF) with the advantages of deep lowest unoccupied molecular orbital (LUMO), green-synthesis, low-cost, simply purification method, excellent yields have been obtained, characterized and used as electron injection materials (EIMs) in three groups of electroluminescence devices. Device B with TCAF as EIM exhibited the best performance including turn-on voltage of 5.0 V, stronger maximum luminance intensity of 31,549 cd/m2, higher luminance efficiency of 62.34 cd/A and larger power efficiency of 21.74 lm/W which are 0.53, 6.7, 9.3 and 15.3 times than that of device A with DCAF as EIMs, respectively. The enhanced interfacial electron injection ability of TCAF than that of DCAF is supported by its better electron mobility in electron-only device, deeper LUMO (-4.52 eV), and stronger electronic affinity. Best external quantum efficiency of 16.56% was achieved with optimized thicknesses of TCAF as EIM and TPBi as electron transporting layer. As a new comer of acceptor family, TCAF would push forward organic electronics with more fascinating and significant applications.
  • Yanni Zhang, Jianfeng Zhao, Caixia Zhu, Lifang Bian, Huifang Shi, Shiming Zhang, Huili Ma, Wei Huang
    Chinese Chemical Letters. 2019, 30(11): 1974-1978. https://doi.org/10.1016/j.cclet.2019.09.005
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    Organic phosphorescence materials demonstrate potential optoelectronic applications due to their remarkably ultralong organic phosphorescence (UOP) lifetime and abundant optical characteristics prior to the fluorescence materials. For a better insight into the intrinsic relationship among regioisomeric molecules, crystalline interactions, and phosphorescence properties, three crystalline dicarbazol-9-yl pyrazine-based regioisomers with para-, meta- and ortho-convergent substitutions (p-DCzP, m-DCzP, and o-DCzP) were designed and presented gradually increased UOP lifetimes prolonging from 63.14,127.93 to 350.46 ms, respectively, due to the regioisomerism effect (RIE) which would be an effective strategy for better understanding of structure-property of UOP materials.
  • Hongxia Lai, Ting Zhao, Yurong Deng, Chunyin Fan, Wanhua Wu, Cheng Yang
    Chinese Chemical Letters. 2019, 30(11): 1979-1983. https://doi.org/10.1016/j.cclet.2019.09.009
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    Water-soluble triplet sensitizer with permethyl-β-cyclodextrin (PMCD) grafting on a Schiff-base Pt (II) complex (Pt-2), in which PMCD unit serves as a host for binding the acceptors and the Schiff-base Pt(II) complex serves as a triplet sensitizer, was synthesized to investigate the effect of supramolecular complexation and assembly on the triplet-triplet annihilation upconversion emission in water. 9, 10-Diphenylanthracence (DPA) carboxylate (A-1) and its dimer (A-2) in which two DPA carboxylate were covalently linked with an alkyl chain were synthesized as triplet acceptors which also play a role of guest molecules for PMCD. A-1 and A-2 showed high affinity with PMCD, and A-2 can readily aggregate in water and form micron sized assemblies due to the hydrophobic effect and π-π stacking of anthracene core in A-2. The efficiency of TTA-UC was demonstrated to be enhanced by a synergistic effect of host-guest complexation of Pt-2 with A-2 and the self-aggregation of the acceptor A-2, which facilitated the energy transfer and energy fusion among donor and acceptor.
  • Ni Yan, Jiale Song, Fengyan Wang, Longwang Kan, Jiahang Song, Weiling Wang, Wenqiang Ma, Weidong Zhang, Gang He
    Chinese Chemical Letters. 2019, 30(11): 1984-1988. https://doi.org/10.1016/j.cclet.2019.09.039
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    Two highly emissive pyrenoviologen derivatives were synthesized and used to fabricate fluorescent sensors for detection of picric acid (PA) with good sensitivity and selectivity. The sensitivity of the sensor was attributed to the specific electrostatic association effect of the cationic pyrenoviologens to the picrate anions, which also gave the sensor special selectivity among other compounds with similar structure. The electron transfer between them was attributed to the fluorescence response. Fluorescence lifetime measurements revealed that the quenching is static in nature. The novel and efficient pyrenoviologen derivatives-based sensors offered a strategy to fabricate real-life PA sensor.
  • Xiang Chen, Jue-Wen Zhao, Xu-Hui Zheng, Jie-Ji Zhu, Guo-Xi Yang, Shan-Shun Tang, Qing-Xiao Tong, Si-Lu Tao
    Chinese Chemical Letters. 2019, 30(11): 1989-1993. https://doi.org/10.1016/j.cclet.2019.09.013
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    Phosphorescent and thermally activated delayed fluorescence (TADF) emitters can break through the spin statistics rules and achieve great success in external quantum efficiency (over 5%). However, maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes. Hence, we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99% of the maximum external quantum efficiency (EQEmax) maintained even at a high luminance of 1000 cd/cm2 based non-doped devices. When doping the two materials in CBP (4,4'-bis(N-carbazolyl)-1,1'-biphenyl), the doped devices still exhibited excellent stability at high brightness with CIEy ≈ 0.07 and low turn-on voltage of only 2.8 V. The state-ofthe-art low efficiency roll-off makes the new materials attractive for potential applications. It is the first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs, which helps us understand the mechanism more intuitively and deeply.