Lindqvist型多酸亚胺衍生物的理论研究及设计

多金属氧酸盐的修饰化学是近年发展起来的一个热点研究领域,其中多酸的亚胺化是一种非常有效的使多酸有机官能化的方法.有机胺能够将其π电子扩展到无机框架,产生较强的d-π相互作用,从而多金属氧酸盐有机胺衍生物和远程有机官能团可以作为构筑单元构建更为复杂的多金属氧酸盐-有机杂化材料.本文综述了作者研究小组运用密度泛函理论方法研究系列Lindqvist型多酸亚胺衍生物的稳定性、成键特征和非线性光学性质,深入探讨该类有机-无机杂化衍生物非线性光学性质的起源.     

Soft Matter Approaches for Enhancing the Catalytic Capabilities of Polyoxometalate Clusters

In this minireview, we discuss the recent efforts on expanding the catalytic capabilities of polyoxometalates (POM) through emulsion catalysis approaches with novel catalytic-active POM–organic hybrid clusters as emulsifiers. The hybrid emulsifiers include surfactant encapsulated POM complexes, molecular POMs–organic hybrids, and POM-based solid nanoparticles. With such novel approaches the catalytic efficiency of the POMs can be significantly improved by enhancing the compatibility of the POMs with organic media, providing catalytic interface for biphasic reactions, as well as easier preparation, and better recyclability. Particularly, a simple, green chemistry method to prepare metal nanoparticle materials with POMs as both reducing and capping agents in aqueous is reviewed.     

多酸配位聚合物的制备与表征——推荐一个综合化学实验

介绍了一个综合化学新实验--多酸配位聚合物的制备与表征。通过杂多酸和有机配体的合成、多酸配位聚合物的制备和性能表征,使学生了解多酸配位聚合物这一无机合成化学前沿领域,在引导学生进行材料合成及性质表征的过程中,提高学生对已学知识融会贯通的能力,提升学生学习化学的兴趣。本实验综合了无机、有机化学知识点以及实验、仪器操作和数据分析能力的培养,可纳入高年级综合化学实验。     

Aliphatic Organoimido Derivatives of Polyoxometalates Containing a Bioactive Ligand

A series of aliphatic organoimido derivatives of hexamolybdate based on amantadine, namely (nBu₄N)₂[Mo₆O₁₈(?NC₁₀H₁₅)] ( 1 ), (nBu₄N)₂ {cis‐[Mo₆O₁₇(?NC₁₀H₁₅)₂]} ( 2 ), (nBu₄N)₂{trans‐[Mo₆O₁₇(?NC₁₀H₁₅)₂]} ( 3 ), and (nBu₄N)₂[Mo₆O₁₆(?NC₁₀H₁₅)₃] ( 4 ), was synthesized in reasonable yield by dehydration with N,N′‐dicyclohexylcarbodiimide (DCC). They were characterized by IR and UV/Vis spectroscopy, elemental analysis, ESI mass spectrometry, and single‐crystal X‐ray structure analysis. The spectral and structural similarities and differences between monosubstituted, cis‐disubstituted, and trans‐disubstituted organoimido derivatives were elucidated and may provide guidance for related work on organoimido‐functionalized Lindqvist‐type polyoxometalates. In addition, trans‐disubstituted and polysubstituted derivatives containing aliphatic organoimido ligands have not yet been reported, and the crystal structure of the trans isomer may lead us to a deeper understanding of disubstituted derivatives. Furthermore, proliferation and morphology of MCF‐7 cells were studied with compound 1 . The present results show that the DCC‐dehydrating protocol could be an efficient approach to covalently graft bioactive ligands such as amantadine onto POMs and enhance their application in clinical cancer treatment.     

多酸层层自组装复合材料应用的研究进展

多金属氧酸盐(简称多酸)具有独特的分子结构、性质的多样性和可调性,其在磁学、光电化学、材料化学、催化和生物医学等领域均有着潜在的应用。 近年来,层层自组装技术被广泛用于多酸超薄膜组装,进一步拓展了多酸的应用范围。 本文主要介绍基于静电相互作用的层层自组装方法制备的多酸基功能性超薄膜复合材料(平面薄膜、中空微胶囊和微球)在光催化、电催化、光致变色、电致变色、磁学、气体传感和光电催化等领域的研究进展并对其进行了展望。     

Layer-by-layer assembly of polyoxometalates into microcapsules

The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.     

Stable photochromism and controllable reduction properties of surfactant-encapsulated polyoxometalate/silica hybrid films

In this paper, we present a novel strategy for fabricating polyoxometalate (POM)-based photochromic silica hybrid films. To combine metal nanoparticles (NPs) into the POMs embedded silica matrix, furthermore, we realized the controllable in situ synthesis of metal NPs in the film by utilizing the reduction property of POMs existing in the reduced state. Through electrostatic encapsulation with hydroxyl-terminated surfactants, the POMs with good redox property can be covalently grafted onto a silica matrix by means of a sol-gel approach, and stable silica sol-gel thin films containing surfactant-encapsulated POMs can be obtained. The functional hybrid film exhibits both the transparent and easily processible properties of silica matrix and the stable and reversible photochromism of POMs. In addition, well-dispersed POMs in a hydrophobic microenvironment within the hybrid film can be used as reductants for the in situ synthesis of metal NPs. More significantly, the size and location of NPs can be tuned by controlling the adsorption time of metal ions and mask blocking the surface. The hybrid film containing both POMs and metal NPs with patterned morphology can be obtained, which has potential applications in optical display, memory, catalysis, microelectronic devices and antibacterial materials.     

RNA-selective cross-pairing of backbone-extended pyrrolidine-amide oligonucleotide mimics (bePOMs)

Pyrrolidine-amide oligonucleotide mimics (POMs) can cross-pair strongly with complementary parallel and antiparallel DNA and RNA targets in a sequence-specific fashion. As a result POMs have significant potential for applications including in vivo gene silencing, diagnostics and bioanalysis. To further modulate the DNA- and RNA-recognition properties and fine-tune the physiochemical properties of POMs for nucleic acid targeting, backbone-extended pyrrolidine-amide oligonucleotide mimics (bePOM I and II) were introduced. The bePOMs differ from the original POMs through the insertion of an additional methylene group into the backbone units, which increases the flexibility of the oligomers. bePOM I and II oligomers were synthesised using solid-phase peptide chemistry. Interestingly, UV thermal denaturation and circular dichroism studies reveals bePOM I and II can hybridise with complementary RNA, but not DNA.     

Density functional theory study on the first hyperpolarizabilities of organoimido derivatives of hexamolybdates

The first hyperpolarizabilities and origin of nonlinear optical (NLO) properties of arylimido molybdate derivatives have been investigated by density functional theory (DFT). The molecular orbital character analysis reveals that organoimido-to-polyanion charge transfer may be responsible for the NLO properties of this kind of molybdate derivatives. The NLO study shows intra-ion charge transfer is helpful to increase the first hyperpolarizability of arylimido molybdate derivatives. The lengthening of organoimido pi-conjugation enhances the betavec value. System 4 has the largest betavec value at the static electronic field, 1.238 x 10(-27)esu. Orbital analysis shows that the degree of charge transfer between polyanion cluster and organic segment was increased when the second organoimido polyanion was introduced. The present investigation provides important insight into NLO origin and properties of polyanion arylimido molybdate derivatives.     

Theoretical studies on phosphoraniminato derivatives of Keggin-type polyoxometalates [PW11O39{MVNPPh3}]3− (M = Fe,Ru): Electronic structures and bonding features

Transition metal phosphoraniminato derivatives of Keggin-type polyoxometalates(POMs) are important intermediates in N-transfer reactions.Density functional theory(DFT) has been employed to calculate the electronic structures,bonding features and redox properties of the iron and ruthenium phosphoraniminato derivatives of Keggin-type POMs,[PW11O39{MVNPPh3}] 3-(M = Fe,Ru).Our DFT calculations show that both anions have the same qualitative M-N single bond features.However,the calculations predict that the FeN system possesses a lower energy and more accessible metalnitrogen antibonding orbital than the RuN system.This results in a greater weakening of the Fe-N bond in the reduction process,and thus enhances its N-transfer reactivity.     

Energetic of molecular interface at metal-organic heterojunction: the case of thiophenethiolate chemisorbed on Au(111)

To probe the cooperativity of charge transfer between organoimido and hexamolybdate, and enhance the second-order nonlinear optical (NLO) response of organoimido derivatives of hexamolybdates, electronic structures and second-order NLO properties of a series of charge-transfer covalently bonded organoimido derived hexamolybdate complexes with donor-(π conjugated bridge)-acceptor-(π conjugated bridge)-donor or acceptor-(π conjugated bridge)-donor-(π conjugated bridge)-acceptor structures were studied by density functional theory. Studies show that different combinations of the donor, acceptor, heterocycle, –C≡C– and –N=N– moieties, and orientation of heterocycle remarkably affect the second-order NLO responses. The complexes containing electronic acceptor matched with the direction of charge transfer possess remarkable large molecular second-order polarizabilities. Electronic transitions to crucial excited states show that x-polarized transition, contributed to the off-diagonal second-order polarizabiliy tensor (β_zxx), possesses lower excited energy compared with z-polarized transition which accounted for the diagonal second-order polarizabiliy tensor (β_zzz) and thus led to the large in-plane nonlinear anisotropy (u = β_zxx/β_zzz) value, as well as good two-dimensional (2-D) second-order NLO properties. These complexes can be used as excellent 2-D second-order NLO materials from the standpoint of both large β and u values.     

六钼酸盐有机胺杂化衍生物与SARS-CoV 3CLpro相互作用的分子动力学模拟

采用分子动力学模拟方法, 在分子水平上探讨六钼酸盐有机杂化衍生物潜在的抗SARS病毒活性. 3CLpro主蛋白酶是冠状病毒复制和转录过程中起关键作用的功能蛋白, 因此采用SARS-CoV 3CLpro作为靶标进行抗SARS病毒的药物设计. 使用Insight II软件包中的Biopolymer, Discover 3, Profile-3D和Affinity等模块, 研究 POMs/3CLpro相互作用的结合位点和作用性质. 研究其能量变化规律, 探讨了多酸化合物对SARS病毒可能的抑制机理. 研究结果表明, POMs与3CLpro在酶的催化活性位点处有较强的结合力. 形成的复合物主要以静电相互作用相结合, 氢键相互作用对复合物的相对稳定性有一定影响. 对于POMs/3CLpro复合物, 有机胺基团取代的POMs所带负电荷比未取代体系的高, 比3CLpro的结合能更高, 这与POMs的相关量子化学计算结果吻合.     

多酸在电催化析氢反应中的应用研究进展

电催化水裂解是一种可持续用于生产可再生氢能源的技术。然而,开发高效稳定、低成本的析氢电催化剂仍是一项具有挑战性的任务。多金属氧酸盐(多酸)是一种离散的金属氧簇合物,通常由氧配体和高价的钒(V)、钼(VI)、钨(VI)金属构成。由于多酸含有丰富的氧化还原活性金属中心,因此,近几年来,多酸在水裂解应用研究方面备受关注。本综述将聚焦于多酸在电催化水裂解析氢的应用研究进展。本文还突出强调了电催化析氢目前面临的主要问题,以及对多酸基催化剂及作为催化剂前体在电催化析氢方面的应用及发展前景做了展望。     

Electrochemical-reduction-assisted Assembly of Pd NPs/Polyoxometalates/Graphene Ternary Nanocomposite and Its Electrocatalytic Performance toward Formic Acid Oxidation

A novel ternary nanocomposite, Pd nanoparticles(NPs)/polyoxometalates(POMs)/reduced graphene oxide(rGO), was prepared by a green, mild, electrochemical-reductionassisted assembly. It is worth noting that the Keggin-type POM acts as an electrocatalyst as well as a bridging molecule. During the reduction process, POMs transfer the electrons from the electrode to GO, leading to a deep reduction of GO and the content of oxygen-containing groups is decreased to around 6.1%. Meanwhile, the strong adsorption effect between the POM clusters and rGO nanosheets induces the spontaneous assembly of POM on r GO in a uniformly dispersed state, forming a nanocomposite. The ternary Pd NPs/POMs/rGO nanocomposite exhibits higher electrocatalytic activities, better electrochemical stability, and higher resistance to CO poisoning than the Pd/C catalyst towards the formic acid oxidation(FAOR). Especially, the Pd/PW_(12)/rGO exhibits the best electrocatalytic performance among three Pd/POMs/rGO composites(POMs = PW_(12), SiW_(12), PMo_(12)).     

Synthesis of stable azide and alkyne functionalized phosphoramidite nucleosides

The use of CuAAC chemistry to crosslink and stabilize oligonucleotides has been limited by the incompatibility of azides with the phosphoramidites used in automated oligonucleotide synthesis. Herein we report optimized reaction conditions to synthesize azide derivatives of thymidine and cytidine phosphoramidites. Investigation of the stability of the novel phosphoramidites using ³¹P NMR at room temperature showed less than 10% degradation after 6?h. The azide modified thymidine was successfully utilized as an internal modifier in the standard phosphoramidite synthesis of a DNA sequence. The synthesized azide and alkyne derivatives of pyrimidines will allow efficient incorporation of azide and alkyne click pairs into nucleic acids, thus widening the applicability of click chemistry in investigating the chemistry of nucleic acids.     

Transition Metal Complexes Containing Functionalized Organoimido and Phosphaneiminato Ligands

Two different types of modified imido and phosphaneiminato ligands are investigated, namely chelate ligands and redox‐functionalised ligands. The first examples of di(organoimido)chromium as well as di(phosphaneiminato)titanium and niobium chelates are described. Furthermore, the first complexes containing redox‐functionalised organoimido ligands are presented, together with the first structurally characterised redox‐functionalised phosphaneiminato complex. Compounds of the type [(RN)₂M(CH₂Ph)₂] (M = Cr, Mo) are used as catalysts for the (co‐)polymerisation of the polar olefins methyl methacrylate, acrylonitrile and vinyl acetate. A range of X‐ray crystal structure determinations provide clear evidence for the quantum‐chemical result that, similar to organoimido complexes, the potential energy well for the angle at the nitrogen atom is very shallow for phosphaneiminato complexes.     

The urea renaissance

Over the last decade the use of urea derivatives as useful reagents, catalysts, and structural features in organic chemistry has increased rapidly. They now find utility as hydrogen-bond donors in organocatalysts and anion transporters, as important scaffolds in supramolecular chemistry, as lithiation directors, amination substrates, and promoters of metalation, and as substrates for novel rearrangement reactions. Highlighted herein is the remarkably rapid and recent development of the chemistry of ureas, which for many years had been considered unreactive, intractable, and of little value.     

Solid‐State Dynamics of Uranyl Polyoxometalates

Understanding fundamental uranyl polyoxometalate (POM) chemistry in solution and the solid state is the first step to defining its future role in the development of new actinide materials and separation processes that are vital to every step of the nuclear fuel cycle. Many solid‐state geometries of uranyl POMs have been described, but we are only beginning to understand their chemical behavior, which thus far includes the role of templates in their self‐assembly, and the dynamics of encapsulated species in solution. This study provides unprecedented detail into the exchange dynamics of the encapsulated species in the solid state through Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy. Although it was previously recognized that capsule‐like molybdate and uranyl POMs exchange encapsulated species when dissolved in water, analogous exchange in the solid state has not been documented, or even considered. Here, we observe the extremely high rate of transport of Li⁺ and aqua species across the uranyl shell in the solid state, a process that is affected by both temperature and pore blocking by larger species. These results highlight the untapped potential of emergent f‐block element materials and vesicle‐like POMs.     

Mono-lacunary PrIII-Polyoxotungstate： Epoxidation of Alkenes with Unusual Selectivity

The utilization of polyoxometalates (POMs) or their derivatives as homogeneous or heterogeneous catalysts in alkene epoxidation is a subject of considerable research activity[1]. The limitation to the use of POMs in these catalytic reactions is either their relatively low selectivity in epoxide formation or applicability for a rather limited type of alkenes. Therefore, it would be beneficial if the catalysts bear high selectivity for epoxidation and are applicable for a rather wide variety of alkenes, which is desirable in industrial processes and also vital for the selection of an ideal catalyst[2]. In search for an efficient and practical epoxidation method to utilize aqueous H2O2 as terminal oxidant, we focus on the rare-earth complexes with lacunary POM ligands.     

Nanoscale polyoxometalate‐based inorganic/organic hybrids

The latest advances in the area of polyoxometalate (POM)‐based inorganic/organic hybrid materials prepared by self‐assembly, covalent modification, and supramolecular interactions are presented. This Review is composed of five sections and documents the effect of organic cations on the formation of novel POMs, surfactant encapsulated POM‐based hybrids, polymeric POM/organic hybrid materials, POMs‐containing ionic crystals, and covalently functionalized POMs. In addition to their role in the charge‐balancing, of anionic POMs, the crucial role of organic cations in the formation and functionalization of POM‐based hybrid materials is discussed. DOI 10.1002/tcr.201100002