The term "supramolecule" appeared as early as the 1930s, but it was only 50 years later that it received attention in the scientific community. Supramolecular chemistry can be defined as "supramolecular chemistry", which is a complex and organized whole chemistry composed of several chemical species through intermolecular interaction. In this whole, each component still maintains some inherent physical and chemical properties. At the same time, due to mutual influence or interference, it shows some overall functions. The microscopic unit of supramolecular system is composed of several or even many molecules or ions of different compounds or other particles with certain chemical properties, which can exist alone. The aggregation number can be determined or uncertain, which is essentially different from strictly determining the number of atoms in a molecule. There is some cohesion (relative to the valence bond of * * *) to aggregate the basic microscopic units of multiple components into "supramolecules".

1 Classification of Supramolecular Compounds

1. 1 heteropoly acid supramolecular compound

Heteropoly acid is a kind of metal oxygen cluster, which is generally in a cage structure and is an excellent acceptor molecule. It can combine with inorganic molecules, ions and other substrates to form supramolecular compounds. As a new type of electrical, magnetic and nonlinear optical material, it has great development value. 3. The synthesis and functional development of novel Keg-gin and Dawson polyacid supramolecular compounds have attracted more and more researchers' attention. Dawson-type phosphomolybdic heteropoly acid hydroquinone supermolecular membrane and pyridine Dawson-type phosphomolybdic heteropoly acid supermolecular membrane modified electrode were synthesized. It was found that the catalytic peak current of the membrane electrode for ascorbic acid had a good linear relationship with its concentration in the range of 0.35 ~ 0.50 mol/L. Gold and other six people synthesized 9- tungstophosphoric acid/crystal violet supramolecular compounds, and their photochromic properties were investigated, that is, the synthesized compounds were photosensitive. The diffuse reflection of sunlight will make it blue. Wang et al. 7 synthesized phosphomolybdic heteropoly acid -L- cysteine self-assembled supramolecular membrane electrode, and found that the membrane electrode had obvious electrocatalytic reduction effect on NO2- in acidic solution. Bi Lihua et al. 8. Synthesis of polyacid supramolecular compounds. It is found for the first time that heteropoly acid supramolecular compounds can exhibit smectic liquid crystal behavior when dissolved in appropriate organic solvents. Liu Shuxia et al. 9 synthesized a supramolecular compound (C10H18O62.6CH3 CN 8H2O) from Dawson-type arsenic molybdic acid and amantadine. The compound has reversible photochromic properties, and the possible photochromic mechanism is proposed.

1.2 polyamine supramolecular compound

Because tetramine dioxygen system can effectively stabilize the high valence oxidation states of transition metal ions such as Cu (Ⅱ) and Ni (Ⅱ), if tetramine dioxygen is connected with a fluorescent group, the quenching or enhancement of the fluorescence of the photosensitive substance is closely related to whether there is electron transfer between the connected tetramine dioxygen complex and the photosensitive substance, that is, the quenching or opening of the fluorescence can be adjusted by metal ions, which plays the role of an optical switch. Substituted 8- hydroxyquinoline was synthesized by Su et al.

Macrocyclic crown ethers have attracted much attention because of their self-assembly performance and molecular recognition ability. Recently, crown ether has become an important building block for building host molecules in supramolecular systems. Li Hui et al. 1 1 Using the molecular recognition ability of crown ether and the photosensitivity of anthraquinone molecule, a new azacrown ether was designed and synthesized to replace anthraquinone molecule, and a supramolecule was formed with this molecule as the main molecule and rare earth ions as the guest.

1.3 porphyrin supramolecular compound

The supramolecular function of porphyrin and its metal complexes and analogues has been applied to the analysis of biological related substances, showing a more attractive prospect and will promote the application of supramolecular complexes in analytical chemistry.

1.4 Dendritic Supramolecular Compound

Dendrimer is a relatively new synthetic polymer that appeared in the mid-1980s. Bo Shan Zhi et al. 12 synthesized dendritic macromolecules with anionic porphyrin as the core and dendritic cation as the outer layer for the first time. Dendrimer complex is assembled based on electrostatic force between porphyrin anion and dendrimer cation. Lanthanide metal ions (Ln3+) such as Tb3+ and Eu3+ are excellent luminescent materials with long lifetime (microsecond level), narrow wavelength and super sensitivity to the environment. However, lanthanide metal ions only have weak luminescence in aqueous solution. Zhu et al. 13 synthesized an amphiphilic hybrid block polymer of polyether dendrimer and polyacrylic acid linear polymer. The research shows that polyether dendrimers can greatly improve the luminescence intensity of Tb3+ through energy transfer.

1.5 liquid crystal supramolecular compound

Side-chain liquid crystal polymers have the dual characteristics of small molecular liquid crystals and high molecular materials. In Supramolecular Liquid Crystal 14, Yan Hua specifically discussed the internal relationship between supramolecular and liquid crystal, and discussed the molecular engineering and thermodynamics of supramolecular liquid crystal. CoCo Lee et al. 15 synthesized acrylic liquid crystal polymer with p-nitroazobenzene as mesogenic group from the perspective of molecular design. Nitro group as electron acceptor and alkoxy group as electron donor on liquid crystal box can form delocalized π electron system with benzene ring and NN. The preliminary study shows that this kind of polymer orientation film prepared by corona polarization method has second-order nonlinear optical properties. Guandong Zhong 1 6 was synthesized from 4,4'-dicarboxylic acid1,6 diphenoxy n-hexane and 4,4'-bipyridine with equal molar.

1.6 phthalocyanine supramolecular compound

Tian Hongjian et al. 17 synthesized meso- tetra (4 ′-sulfophenyl) porphyrin zinc complex with negative charge substituent and zinc complex with 2,9,16,23 tetra (4 ′-n, n, n trimethyl) phenoxyphthalocyanine quaternary ammonium iodide with positive charge substituent, and their compositions were determined by Job photometric titration. It is a face-to-face heterodimer or sandwich heterodimer supramolecular arrangement. It is found that porphyrin and phthalocyanine can quench each other's fluorescence in supramolecular system. The transient absorption spectra of porphyrin positive ions at 600 ~ 650 nm and phthalocyanine negative ions at 550 ~ 600 nm were observed by nanosecond laser flash photolysis technique. The results show that there is a photoinduced electron transfer process between molecules in supramolecular system.

Synthesis of Two Supramolecular Compounds

2. 1 molecular self-assembly

In recent years, molecular self-assembly has attracted much attention as a new chemical synthesis method. Writing medical papers, especially compounds with molecular size of 1 ~ 100 nm, are generally difficult to obtain by ordinary chemical synthesis methods. Recently, Yan et al. 18 synthesized a tube with a length of cm, a diameter of mm and a wall of 400nm by supramolecular self-assembly method, which became supramolecular chemical synthesis.

Yajuan Liu et al. 19 constructed supramolecular nanotubes with a diameter of about 5μm through the self-assembly process of a pair of complementary molecular components 5(4 dodecyloxy styryl 2,4,6 (1 h, 3H) pyrimidinone and 4 amino 2,6 docosalkylamino13,5 triazine. The study of temperature-dependent Fourier transform infrared spectroscopy shows that the diameter of nanotubes is about 5 μ m. Non-valence bond interactions such as hydrogen bond, π-π interaction and van der Waals force lead to the formation of supramolecular nanotubes. Reinhoudt et al reported organometallic dendrimers with as many as 47 palladium complexes. Quasi-elastic light scattering experiment (QELS), atomic force microscope (AFM) and transmission electron microscope (TEM) show that the aggregate is spherical with a diameter of 200nm, and the dendrimer platinum complex synthesized by Puddephatt reaches the fourth generation.

2.2 template synthesis

1992, researchers of Mobil company synthesized silica and aluminosilicate with mesoporous structure for the first time using supramolecular liquid crystal template of cationic surfactant, among which MCM-4 120 with hexagonal mesoporous channels was the most representative.

The synthesis and properties of rotaxanes with cyclodextrins (α-CD, β-CD, γ-CD) are particularly attractive. The edge of cyclodextrin is hydrophilic and the inner cavity is hydrophobic. Cyclohexane can be formed by self-recognition of cyclodextrin as the main body and hydrophobic guest molecules. Liu Yu 2 1 has made a deep study on molecular recognition and assembly with cyclodextrin as receptor. Isnin and others successfully synthesized asymmetric rotaxane. One end of the molecule is dimethyl (ferrocenyl methyl) ammonium salt, and the other end is naphthalene 2 sulfonate. Stoddart et al. used polyvinyl alcohol to react with α-CD, and the terminal group was 2,4 dinitrobenzene. The pearl necklace rotaxane containing 20 ~ 23 α-CDs was obtained. Stoddart and others synthesized a series of terpenoids at room temperature. At room temperature, terpenoids were obtained by using terphenyl 34 crown 10(BPP34CI0) as template, and the yield was as high as 70%.

2.3 Other methods

Recently, Zhao et al. used the density inclusion method to design and optimize the heterotrimer supramolecule constructed by dimethylglyoxime and benzoic acid through quadruple hydrogen bonds at the level of 6-3 1G, and wrote a thesis title to prove that the trimer formation reaction can proceed spontaneously, and the related heterotrimer 23 was synthesized experimentally.

Zhao Shilong et al. 24 synthesized a new supramolecular compound (bipyh2) 2 (H2P2Mo5O23) H2O under hydrothermal conditions. The results show that heteropolyanions, protonated 4,4 ′-bipyridine and water molecules form an infinite two-dimensional network structure through hydrogen bonds. The formation of supramolecular compounds. Luan Youguo et al. 25 synthesized the compound (h3nch2ch2nh3) 2 (hpo 4) 2mo5o 1 5 by a medium-temperature hydrothermal method, and determined its configuration as1five-membered ring formed by five Mo-o octahedrons connected by * * edges and * * angles, with a group of hpo4 tetrahedrons passing through the upper and lower sides of the ring plane. In addition, H2O 2 P 2 Mo 5 O 234- and H3NCH 2NH3 form a new type of organic-inorganic supramolecular hybrid material through strong hydrogen bonding.

Application of Three Supramolecular Compounds

3. Application of1in photochemistry

Lehn et al. designed a hole-like ligand specially used for light release of alkali metal ions. They use 2- nitrobenzyl ether as a bridge bond of macrocycle, which can be interrupted by ultraviolet light to form monocyclic compounds, and the complexing ability of the latter to alkali metal ions is greatly reduced. Zhang Hairong et al. 26 found that BCD can induce RTP with strong BNS emission in the presence of trace cyclohexane. Yin Wei et al.27 used the quaternary, ternary and binary complexes of Eu2+ with phenanthroline (phen), 2- thienyl trifluoroacetone (TTA) and bipyridine (Dpy) to assemble a series of new supramolecular nano luminescent materials, and compared their luminescent properties. Chen Zhangping 28 synthesized porphyrin crown ether 4,4-dimethylbipyridine supramolecular model compound. It is found that 4,4-dimethylbipyridine can be well combined into the cavity formed by porphyrin and crown ether. Under the illumination condition, the generated stimulated porphyrin molecules can transfer electrons well and form a good optical switch model.

3.2 Application in Piezoelectric Chemical Sensor

The principle of subject-object adaptation in supramolecular chemistry has been widely used in piezoelectric chemical sensors. Supramolecular is used as the sensitive coating of piezoelectric chemical sensor, and through the synergistic effect between molecules, the target molecule can be identified by using the extraordinary spatial structure of supramolecular. The selectivity of the piezoelectric chemical sensor can be significantly improved. Many crown ether derivatives are used as QCM coatings for the determination of organic vapors, such as sensor arrays and pattern recognition, which are recognized in binary, ternary and quaternary organic vapor mixtures, and the guess results are good. Monobenzene 15 crown 5(B 15C5), monombenzene 18 crown 6(B 18C6) and benzene 30 crown 10(DB30C 10) were coated on the electrode of TSM chemical sensor.

Dickert et al. used BCD coated QCM and SAW to determine tetrachloroethylene, and the lower limit of determination could reach several 10-6(Y). Later, they used cross-linked BCD as the coating of QCM to determine chlorobenzene. When a large amount of ether exists (the volume ratio of ether to chlorobenzene is 50000∶ 1), it does not interfere with the determination. The linear range is10×10-6 ~ 500×10-6 (y), which is used to monitor the end point of Grignard reaction. Nelli et al. used resorcinol calixarene derivatives as QCM sensitive coating, which has high selectivity for nitrobenzene, and has selectivity for H2, H2S, NO, SO2 and CH4 under the condition of relative humidity as high as 90%. N-C4H 1O*** does not interfere with the determination. Dermody et al. used various calixarene derivatives to self-assemble molecules on the surface of surface acoustic wave to determine benzene, chlorobenzene and toluene. Pinalli et al. used resorcinol calixarene derivatives to determine the alcohol content in the gas phase. The linear range is/kloc-0 /×10-3 ~ 4. Good reproducibility. Malitesta et al. prepared bionic QCM sensor by molecular imprinting electrosynthesis polymerization. Yao shouzhuo et al. made BAW sensor with coffee as template molecule, and its response range to caffeine was 5.0×10-9 ~1.0×10-4.

At pH8.0, the detection limit is 5.0× 10-9mol/L and the recovery rate is 96. 1% ~ 105.6% 29.

3.3 Recognition of Supramolecular Compounds

Molecular recognition is a process in which the subject (or receptor) selectively binds to the object (or substrate) and produces specific functions. It is the basis of assembly and assembly functions, and also the basis of enzyme and receptor selectivity. Complementarity and pre-organization are two key principles that determine the molecular recognition process. The former determines the selectivity of the recognition process, while the latter determines the bond and ability of the recognition process.

The purpose of recognition of carboxylate and phosphate is to explore the recognition of amino acids, peptides and nucleotides by host molecules, and then to study the catalytic hydrolysis of peptides and nucleic acids. Macrocyclic polyamines and their metal complexes can well identify carboxylate and phosphate host molecules. Complexes containing acridine groups can selectively recognize terephthalic acid through supramolecular self-assembly of Zn2+ complexes. Macrocyclic polyamines will react with Cu (Ⅱ) if there are amino groups that can be coordinated outside the ring.

3- can form a fairly strong complex. For the purpose of molecular recognition, the system can be used as a new model to move the binding site of phosphoric acid.

3.4 Research on Supramolecular Compounds as Molecular Devices

Molecular devices are systems assembled by molecular elements (supramolecular structures), which are designed to perform specific functions under the action of electrons, ions or photons. Liu Qitao 3 1 Cu2 (BPY) 2 (terph) Cl2 4h2o crystal was synthesized with terpenoid alcohol ester of terephthalic acid as ligand, where bpy is 2. Cu3(TMA)(H2O)3n coordination supramolecular crystal can be synthesized with trimellitic acid (TMA) as ligand, which makes it possible to manufacture nano-scale pore materials and realize nano-reactor. Many metal complexes of 8- hydroxyquinoline and 1- phenanthroline are fluorescent and stable. When 8- hydroxyquinoline or 1- phenanthroline is introduced into the macrocycle, because of both of them,

3.5 Application of Supramolecular Compounds in Chromatography and Spectroscopy

Gu et al. 32 prepared 2, 4, 6, 10 and 20 layers of polyvinyl carbazole (PVK) supramolecular films on hydrophobic P-Si by LB technology with eicosanoic acid as auxiliary film-forming substance. The SPS study of the system shows that the surface photovoltage increases with the increase of the number of PVK films, especially in the ultraviolet region. The photovoltaic voltage on the surface tends to be saturated. The photosensitivity of the film to the substrate is mainly caused by the photoconductivity of PVK. Yang Yang et al. 33 successfully separated a series of products of electron-rich hydroquinone polyether chain (HQ), an intermediate in the synthesis of supramolecular compounds, by high performance liquid chromatography.

3.6 Supramolecular catalysis and analytical application of simulated enzyme

The reactivity and catalysis of supramolecules are very similar to the recognition of substrates by enzymes and the participation of substrates in the reaction. For more than ten years, the research on mimetic enzymes (or artificial enzymes) aimed at simulating the molecular recognition and efficient catalytic activity of natural enzymes to substrates has been an important topic in biochemistry and organic chemistry. Among them, the analysis and application of peroxidase mimetic enzyme is particularly prominent. Ci Yunxiang and others combined the effects of amino acids, protein, nucleic acids and some metalloporphyrins on the activity of mimic enzyme with immunoassay technology, and established an enzyme immunoassay method with mimic enzyme as tracer or a nucleic acid sequence analysis method with mimic enzyme as non-radioactive probe.

3.7 Application in Analytical Chemistry

Shinkai and others have made many achievements in studying the molecular assembly behavior of porphyrin derived from boric acid and used it to determine the configuration of sugar molecules. For example, the aggregate of tetra (4- boroylphenyl) porphyrin (TBPP) in aqueous solution and in the presence of sugar molecules, the exciton coupling band (ECB) symbol of circular dichroism (CD), which is specific to the absolute configuration of sugar molecules, can detect the absolute configuration of sugar molecules, and so on.

4 conclusion

At present, the theories and methods of supramolecular chemistry are playing an increasingly important role, and the research of this subject will be more closely integrated with all branches of chemistry. It can be predicted that host-guest chemistry, as the origin of supramolecular chemistry, will promote each other with organic synthetic chemistry, coordination chemistry and biochemistry and make great contributions to life science and energy science. The application of supramolecular chemistry in inorganic chemistry will enable people to obtain various materials with specific functions, such as complexes, crystals, ceramics and so on. Physical chemistry should change the current qualitative scientific situation of supramolecular chemistry, quantitatively describe selective intermolecular forces, molecular recognition, molecular self-assembly and other processes with appropriate variables from micro and macro, improve people's familiarity with supramolecular chemistry, guess and control ability, and finally seek theoretical tools to explain the internal motion law of supramolecular systems and predict the overall function of such systems. 2 .

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