Cobalt-catalyzed amination of aziridines and azetidines toward 1,2- and 1,3-diamines.

Diamines play important roles in synthetic organic chemistry and thus facilitate life and materials sciences. Herein we report a cobalt-catalyzed ring opening, nucleophilic amination of aziridines and azetidines with N-fluorosulfonamides toward a wide range of 1,2- and 1,3-diamine derivatives in moderate to good yields under mild conditions.

Spatial Attention Frustum: A 3D Object Detection Method Focusing on Occluded Objects.

Achieving the accurate perception of occluded objects for autonomous vehicles is a challenging problem. Human vision can always quickly locate important object regions in complex external scenes, while other regions are only roughly analysed or ignored, defined as the visual attention mechanism. However, the perception system of autonomous vehicles cannot know which part of the point cloud is in the region of interest. Therefore, it is meaningful to explore how to use the visual attention mechanism in the perception system of autonomous driving. In this paper, we propose the model of the spatial attention frustum to solve object occlusion in 3D object detection. The spatial attention frustum can suppress unimportant features and allocate limited neural computing resources to critical parts of the scene, thereby providing greater relevance and easier processing for higher-level perceptual reasoning tasks. To ensure that our method maintains good reasoning ability when faced with occluded objects with only a partial structure, we propose a local feature aggregation module to capture more complex local features of the point cloud. Finally, we discuss the projection constraint relationship between the 3D bounding box and the 2D bounding box and propose a joint anchor box projection loss function, which will help to improve the overall performance of our method. The results of the KITTI dataset show that our proposed method can effectively improve the detection accuracy of occluded objects. Our method achieves 89.46%, 79.91% and 75.53% detection accuracy in the easy, moderate, and hard difficulty levels of the car category, and achieves a 6.97% performance improvement especially in the hard category with a high degree of occlusion. Our one-stage method does not need to rely on another refining stage, comparable to the accuracy of the two-stage method.

Application in Anticounterfeiting for Multistimuli Smart Luminescent Materials Based on MOF-on-MOF.

The generation of smart responsive materials that can perform multiple drastic optical outputs upon different triggers provides a good platform to encode and hide the information and create multilevel security. In this paper, a smart multiresponsive MOF-on-MOF material was reported using one MOF (HPU-14) as a platform to grow ZIF-8 on the outer layer, combining different emitter centers such as anthracene (ANT) and lanthanide ions (Ln3+) confined into two MOFs. Due to the existence of ANT in the pores of ZIF-8, this composite material can exhibit reversible photoswitching behavior under a 365 nm ultraviolet (UV) lamp and enable "resetting and reusing" dynamic anticounterfeiting application. Meanwhile, when treated by an acid/alkali gas, this material can also display reversible switching behavior under 254 nm UV irradiation, which is attributed to the loading of Ln3+ on HPU-14. We demonstrated that this excellent practical anticounterfeiting material can decipher the right information only by following a strict stimuli sequence. Therefore, this MOF-on-MOF material synthesis technology for sophisticated counterfeiters, which makes the protected information highly secure, could open a new way to design multilevel anticounterfeiting materials.

Postsynthesis Strategy of Functional Zn-MOF Sensors for the Detection of ClO- and DPA.

Active species were introduced into MOFs to prepare multifunctional fluorescent probes by a stepwise postsynthetic modulation strategy. First, two-dimensional HPU-16 (HPU = Henan Polytechnic University; HPU-16 = Zn(L)2(H2O); HL = 2-(5-pyridin-4-yl-5H-[1,2,4]triazol-3-yl)-pyrazine) was transformed into three-dimensional HPU-17 ({Zn3(L)2(btc)2(H2O)}n) through a crystal dissolution-recrystallization process. Second, linker replacement was used to introduce -NH2 into the HPU-17 to generate functional NH2-HPU-17 via a single-crystal to single-crystal transformation. The functional amino groups caused NH2-HPU-17 to show a significant response to ClO-. Because of the interaction of amino groups and ClO-, the fluorescence of NH2-HPU-17 gradually changed from blue to yellow-green. More interestingly, NH2-HPU-17 could encapsulate Tb3+ and sensitize the visible-emitting characteristic fluorescence of Tb3+ in aqueous solution. Then, newly generated Tb3+@NH2-HPU-17 could serve as an effective probe for the determination of DPA. This work paves a new way for the design and modulation of ratiometric fluorescence probes for the selective and sensitive detection of special molecules.

Electrochemical Continuous-Flow Scholl Reaction toward Polycyclic Aromatic Hydrocarbons.

The preparation of polycyclic aromatic hydrocarbons (PAHs) by the Scholl reaction is typically performed by using superstoichiometric oxidants. Herein, we develop an electrochemical continuous-flow Scholl reaction to access PAHs that features a reduction in the use of supporting electrolytes and easy scale-up without changing the reaction conditions and setups. This reaction allows the synthesis of distorted PAHs containing three [5]helicene units that possess intriguing electronic and optical properties.

Current-Controlled Electrochemical Approach Toward Mono- and Trifluorinated Isoindolin-1-one Derivatives.

An electrochemical intramolecular 5-exo-dig aza-cyclization of 2-alkynylbenzamides and subsequent nucleophilic fluorination have been developed to afford the highly selective synthesis of mono- and trifluorinated isoindolin-1-one derivatives. This work demonstrates the unique capability of synthetic electrochemistry in controlling reaction selectivity through the applied electrolytic parameters. In addition, the obtained monofluorinated 3-methyleneisoindolin-1-one (19) displays interesting photophysical properties that are not observed in its nonfluorinated analog.

VOC transport in an occupied residence: Measurements and predictions via deep learning.

Monitoring and prediction of volatile organic compounds (VOCs) in realistic indoor settings are essential for source characterization, apportionment, and exposure assessment, while it has seldom been examined previously. In this study, we conducted a field campaign on ten typical VOCs in an occupied residence, and obtained the time-resolved VOC dynamics. Feature importance analysis illustrated that air change rate (ACR) has the greatest impact on the VOC concentration levels. We applied three multi-feature (temperature, relative humidity, ACR) deep learning models to predict the VOC concentrations over ten days in the residence, indicating that the long short-term memory (LSTM) model owns the best performance, with predictions the closest to the observed data, compared with the other two models, i.e., recurrent neural network (RNN) model and gated recurrent unit (GRU) model. We also found that human activities could significantly affect VOC emissions in some observed erupted peaks. Our study provides a promising pathway of estimating long-term transport characteristics and exposures of VOCs under varied conditions in realistic indoor environments via deep learning.

Synthesis of Indeno[1,2-c]furans via Cobalt-Catalyzed Radical-Polar Crossover [3 + 2] Cycloaddition of o-Alkynylaryl ß-Dicarbonyls.

Fused polycyclic furans are privileged structural scaffolds in materials chemistry, including organic semiconductors. Specifically, indeno[1,2-c]furans are an interesting type of polycyclic furans featuring a fused furan and indenone framework. Unfortunately, limited studies on their photophysical properties have been performed, probably owing to the lack of efficient and straightforward approaches to those compounds. Herein, we have developed a cobalt-catalyzed radical-polar crossover cyclization of the readily available o-alkynylaryl ß-carbonyls to afford diverse indeno[1,2-c]furans. Photophysical and DFT calculations were also carried out, suggesting that the obtained indeno[1,2-c]furans exhibit promising electronic and optical properties.

A luminescent terbium coordination complex as multifunctional sensing platform.

In this paper, we report the synthesis of a multifunctional fluorescent probe Tb-CP, Tb(HL)(EtOH)2(NO3)2 (HPU-10) (H2L = 2,6-bis-(5-pyridin-4-yl-1H-[1,2,4]triazol-3-yl)- pyridine), and demonstrate that this novel chemosensor has the property of ratiometric detection of Zn2+ and Cd2+. The detection limit of HPU-10 sensing Zn2+ and Cd2+ is 0.319 and 0.965 µM, respectively. The sensing mechanism can be explained by (i) the decomposition of HPU-10 and (ii) the recombination of Zn2+ or Cd2+ with ligand forming 2HL--Zn2+ or 2HL--Cd2+, respectively. Moreover, the fluorescent sensor HPU-10 can detect the nitroaromatic compound 2, 4-DNP via a fluorescence quenching mechanism. The detection limits obtained from linear regression curve plots of 2, 4-DNP is calculated to be 1.69 µM. In addition, the possible use of the probe coated paper for tracing the target analytes has also been presented.