主-客体化学研究进展

以分子识别为基础的主－客体化学作为新兴交叉学科，已成为当今研究的热点。本文概述了主体分子的类型、结构特征、分子识别特性及其在某些领域的应用。参考文献56篇。     

Host-Guest Chemistry of Truncated Tetrahedral Imine Cages with Ammonium Ions

Three shape-persistent [4+4] imine cages with truncated tetrahedral geometry with different window sizes were studied as hosts for the encapsulation of tetra-n-alkylammonium salts of various bulkiness. In various solvents the cages behave differently. For instance, in dichloromethane the cage with smallest window size takes up NEt₄⁺ but not NMe₄ ^{+ ,} which is in contrast to the two cages with larger windows hosting both ions. To find out the reason for this, kinetic experiments were carried out to determine the velocity of uptake but also to deduce the activation barriers for these processes. To support the experimental results, calculations for the guest uptakes have been performed by molecular mechanics’ simulations. Finally, the complexation of pharmaceutical interested compounds, such as acetylcholine, muscarine or denatonium have been determined by NMR experiments.     

综合化学实验:苯并21冠7和二级铵盐主客体相互作用的研究*

冠醚的发现开创了一门新的学科--超分子化学。本院开设的“综合化学实验”首次引入这类物质的合成和表征,通过醚化反应合成了典型的冠类化合物--苯并21冠7(B21C7),然后与二级铵盐通过主客体相互作用形成配合物(简称准轮烷);最后采用核磁共振滴定法研究其络合能力。通过本实验的实施,不仅提升了学生的基本实验操作能力,巩固了专业知识的理解,训练了学生的大型仪器测试分析能力;而且拓宽了学生的科研视野,提高了他们的探索创新意识。建议纳入本科高年级和研究生低年级的“综合化学实验”课程。     

Protein-Integrated Hydrogen-Bonded Organic Frameworks: Chemistry and Biomedical Applications

Hydrogen-bonded organic frameworks (HOFs) are porous nanomaterials that offer exceptional biocompatibility and versatility for integrating proteins for biomedical applications. This minireview concisely discusses recent advancements in the chemistry and functionality of protein-HOF interfaces. It particularly focuses on strategic methodologies, such as the careful selection of building blocks and the genetic engineering of proteins, to facilitate protein-HOF interactions. We examine the role of enzyme encapsulation within HOFs, highlighting its capability to preserve enzyme function, a crucial aspect for applications in biosensing and disease diagnosis. Moreover, we discuss the emerging utility of nanoscale HOFs for intracellular protein delivery, illustrating their applicability as nanoreactors for intracellular catalysis and neuroprotective biorthogonal catalysis within cellular compartments. We highlight the significant advancement of designing biodegradable HOFs tailored for cytosolic protein delivery, underscoring their promising application in targeted cancer therapies. Finally, we provide a perspective viewpoint on the design of biocompatible protein-HOF assemblies, underlining their promising prospects in drug delivery, disease diagnosis, and broader biomedical applications.     

Strength and Nature of Host-Guest Interactions in Metal-Organic Frameworks from a Quantum-Chemical Perspective

Metal-organic frameworks (MOFs) offer a convenient means for capturing, transporting, and releasing small molecules. Their rational design requires an in-depth understanding of the underlying non-covalent host-guest interactions, and the ability to easily and rapidly pre-screen candidate architectures in silico. In this work, we devised a recipe for computing the strength and analysing the nature of the host-guest interactions in MOFs. By assessing a range of density functional theory methods across periodic and finite supramolecular cluster scale we find that appropriately constructed clusters readily reproduce the key interactions occurring in periodic models at a fraction of the computational cost. Host-guest interaction energies can be reliably computed with dispersion-corrected density functional theory methods; however, decoding their precise nature demands insights from energy decomposition schemes and quantum-chemical tools for bonding analysis such as the quantum theory of atoms in molecules, the non-covalent interactions index or the density overlap regions indicator.     

Synthesis and host-guest properties of pillar[6]arenes

A facile method for the synthesis of pillar[6]arenes was developed.A series of pillar[6]arenes were prepared with FeCl 3 as catalyst and chloroform as solvent at room temperature in moderate yields(30%-40%).Their host-guest properties with n-cetyltrimethyl ammonium bromide were investigated by 1 HNMR.The results showed that high selectivity in the host-guest relationship became apparent between pillar[6]arenes and pillar[5]arenes based on the different size of the inner cavity.     

Hetero-Coencapsulation within a Supramolecular Cage: Moving away from the Statistical Distribution of Different Guests

Beside sensing and delivery, another peculiar property arising from confinement in discrete molecular hosts comes from the possibility to have in close proximity, and in defined position, two different molecules (hetero-coencapsulation). This phenomenon can be tuned considering steric and electronic properties of the guests. In this work, a study on the parameters affecting homo- and hetero-coencapsulation processes within a supramolecular cage is reported. In particular, different benzoate guests were bound within a supramolecular cage containing two metal-binding sites and the experimental binding thermodynamics measured. Unexpectedly, from competition experiments it was observed that the maximum concentration of hetero-coencapsulation is achieved if a weakly binding guest is used to partially displace a strongly binding guest.     

Covalent Organic Frameworks and Cage Compounds: Design and Applications of Polymeric and Discrete Organic Scaffolds

Porous organic materials are an emerging class of functional nanostructures with unprecedented properties. Dynamic covalent assembly of small organic building blocks under thermodynamic control is utilized for the intriguingly simple formation of complex molecular architectures in one‐pot procedures. In this Review, we aim to analyze the basic design principles that govern the formation of either covalent organic frameworks as crystalline porous polymers or covalent organic cage compounds as shape‐persistent molecular objects. Common synthetic procedures and characterization techniques will be discussed as well as more advanced strategies such as postsynthetic modification or self‐sorting. When appropriate, comparisons are drawn between polymeric frameworks and discrete organic cages in terms of their underlying properties. Furthermore, we highlight the potential of these materials for applications ranging from gas storage to catalysis and organic electronics.     

Shape‐Controlled Synthesis and Self‐Sorting of Covalent Organic Cage Compounds

The directional bonding approach is a powerful tool to rationally control both shape and stoichiometry of three‐dimensional objects built from rigid building blocks under dynamic covalent conditions. Co‐condensation of catechol‐functionalized tribenzotriquinacene derivatives which have 90° angles between the reactive sites and diboronic acids with bite angles of 60°, 120°, and 180°, led to the efficient formation of, respectively, bipyramidal, tetrahedral, or cubic covalent organic cage compounds in a predictable manner. Investigations on the self‐sorting of ternary mixtures containing two competitive boronic acids revealed either narcissistic or social self‐sorting depending on the stability of the segregated cages relative to feasible three‐component assemblies.     

Selective and Reversible Solvent Uptake in Tetra-4-(4-pyridyl)phenylmethane-based Supramolecular Organic Frameworks

The dynamic behavior of supramolecular organic frameworks (SOFs) based on the rigid tetra-4-(4-pyridyl)phenylmethane ( TPPM) organic tecton has been elucidated through 3D electron diffraction, X-ray powder diffraction and differential scanning calorimetry (DSC) analysis. The SOF undergoes a reversible single-crystal-to-single-crystal transformation when exposed to vapours of selected organic solvents, moving from a closed structure with isolated small voids to an expanded structure with solvated channels along the b axis. The observed selectivity is dictated by the fitting of the guest in the expanded SOF, following the degree of packing coefficient. The effect of solvent uptake on TPPM solid-state fluorescence was investigated, evidencing a significant variation in the emission profile only in the presence of chloroform.     

无机化学与物理化学课程的协调教学

根据无机化学和物理化学的内容设置及特点, 结合教学实践, 探讨了2者在教学过程中的有机配合和协调统一。无机化学教学应以知识的衔接和实际应用为主, 而物理化学教学则要侧重知识点的挖掘和提升。2者的协调有助于提高课堂利用率, 促进学生学习能力和科学思维的培养。     

Iron Porphyrins Embedded into a Supramolecular Porous Organic Cage for Electrochemical CO2 Reduction in Water

A porous organic cage composed of six iron tetraphenylporphyrins was used as a supramolecular catalyst for electrochemical CO₂‐to‐CO conversion. This strategy enhances active site exposure and substrate diffusion relative to the monomeric catalyst, resulting in CO generation with near‐quantitative Faradaic efficiency in pH 7.3 water, with activities reaching 55 250 turnovers. These results provide a starting point for the design of supramolecular catalysts that can exploit the properties of the surrounding matrix yet retain the tunability of the original molecular unit.     

Protein Assays on Organic Electronics: Rational Device and Material Designs for Organic Transistor-Based Sensors

Artificial receptor-based protein assays have various attractive features such as a long-term stability, a low-cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field-effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on-site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET-based protein assays including the rational design strategies for devices and sensing materials.     

Host-Guest Interaction in Ethylene and Ethane Separation on Zeolitic Imidazolate Frameworks as Revealed by Solid-State NMR Spectroscopy

The separation of ethane/ethylene mixture by using metal-organic frameworks (MOFs) as adsorbents is strongly associated with the pore size-sieving effect and the adsorbent-adsorbate interaction. Herein, solid-state NMR spectroscopy is utilized to explore the host-guest interaction and ethane/ethylene separation mechanism on zeolitic imidazolate frameworks (ZIFs). Preferential access to the ZIF-8 and ZIF-8-90 frameworks by ethane compared to ethylene is directly visualized from two-dimensional ¹H-¹H spin diffusion MAS NMR spectroscopy and further verified by computational density distributions. The ¹H MAS NMR spectroscopy provides an alternative for straightforwardly extracting the adsorption selectivity of ethane/ethylene mixture at 1.1∼9.6 bar in ZIFs, which is consistent with the IAST predictions.     

绿色化学理念下的无机及分析化学实验

根据理工类高等院校无机及分析化学实验课的特点, 结合基础化学实验中心实验条件, 从合理设置实验、减少试剂用量、取代有毒试剂、回收利用等方面对无机及分析化学实验进行了系列改革和实践, 使大部分实验实现了绿色化。减少了废渣、废液、废气对环境的污染, 降低了实验成本, 取得了良好的环境效益和经济效益。同时, 对学生进行了有效地绿色化学实践教育。     

Improved Acid Resistance of a Metal–Organic Cage Enables Cargo Release and Exchange between Hosts

The use of di(2‐pyridyl)ketone in subcomponent self‐assembly is introduced. When combined with a flexible triamine and zinc bis(trifluoromethanesulfonyl)imide, this ketone formed a new Zn₄L₄ tetrahedron 1 bearing twelve uncoordinated pyridyl units around its metal‐ion vertices. The acid stability of 1 was found to be greater than that of the analogous tetrahedron 2 built from 2‐formylpyridine. Intriguingly, the peripheral presence of additional pyridine rings in 1 resulted in distinct guest binding behavior from that of 2 , affecting guest scope as well as binding affinities. The different stabilities and guest affinities of capsules 1 and 2 enabled the design of systems whereby different cargoes could be moved between cages using acid and base as chemical stimuli.     

Chemistry in Confinement: Copper and Palladium Catalyzed Ecofriendly Organic Transformations within Porous Frameworks

A concise account on the use of transition metals copper (Cu) and palladium (Pd), as their cations as well as nanoparticles exchanged/immobilized onto porous frameworks such as zeolites, metal organic frameworks (MOFs), covalent organic polymers (COPs) and hollow nanostructures, functioning as catalysts in organic synthesis is presented. This biomimetic account, “focusing on catalytic systems in confinement” within zero‐dimensional microenvironments and second sphere coordination covers primarily results from our group on N‐sulfonylketenimine mediated cycloaddition, hydrogenation and C−C bond forming reactions, thus providing an interesting insight into the versatility and utility of these Cu and Pd catalysts. Other significant advantages and green credentials of confinement such as stability, selectivity, reusability, promotion of multicomponent reactions, use of green solvents, atom economy, and use of ambient conditions are highlighted at appropriate places. In the final section, our views on the current achievements and the future prospects in this area are summarized.     

基础有机化学教学与前沿科学研究的融合——共价有机骨架材料的成键方式

作为材料研究领域的明星,共价有机框架材料的研究是基于有机化学反应的成功选择和合成条件的不断优化。本文探讨将共价有机框架材料的成键方式引入有机化学教学课堂的途径,阐述有机化学反应在新型纳米材料设计合成中的应用。科教融合教学模式不仅能够培养学生掌握知识、运用知识解决实际复杂问题的能力;同时可以调动学生的学习兴趣、拓展科研视野、激发科研热情;更能在科研成果中增强学生的专业认同感、培养学生的创新意识和社会担当。科教融合是实现创新人才培养的一个重要环节。     

象形分子在有机化学及有机合成化学教学中的应用

激发学生学习兴趣,是提高课堂教学效果的关键。从化学科普网站收集象形分子,并用于有机化学及有机合成化学的课堂教学。通过象形分子形象逼真、妙趣横生、幽默及具艺术魅力的特点,调动学生学习的积极性和主动性,激发学习兴趣和热情,进而提高课堂趣味性,使教学内容形象生动。提高了教与学的效率和水平。