Synthesis of silica gel-bound acridino-18-crown-6 ether and preliminary studies on its metal ion selectivity

Starting from commercially available and relatively cheap chemicals a novel silica gel-bound acridino-18-crown-6 ether was prepared. Selectivity of the latter stationary phase toward different metal ions was studied. The stationary phase showed appreciable selectivity for Ag⁺, Cu²⁺, and Hg²⁺ ions.     

含萘并呋喃基团冠醚的合成及离子选择性研究

以2-羟基-1-萘甲醛和2-羟甲基冠醚为原料,合成3种新的含萘并呋喃基团冠醚(3a-3c),并经1 H NMR,13C NMR,MS及元素分析确证.碱金属和碱土金属离子的加入对体系的最大吸收波长影响不大.Li+使3b摩尔吸光度变大,Ca2+和Ba2+引起3a-3c最大发射波长λem发生相对较大红移,同时使其荧光强度降低.     

On the role of the indenyl effect in controlling intramolecular hydride transfer in iron carbonyl complexes

Density functional theory reveals multiple pathways for intramolecular hydride transfer in the cyclopentadienyl and indenyl species (η⁵-C₅H₅)Fe(CO)₃H and (η⁵-C₉H₇)Fe(CO)₃H. The ability of the indenyl ligand to undergo facile η⁵- to η³-‘ring slippage’ stabilises the isomer where the hydride is bonded directly to the metal, which opens up a low-energy pathway for hydride transfer from CO to metal.     

Oxymethylcrowned chromene: photoswitchable stoichiometry of metal ion complex and ion-responsive photochromism

Chromene derivatives bearing oxymethyl-12-crown-4 (1), -15-crown-5 (2), -18-crown-6 (3) ether moieties, and non-cyclic analogue (4) were synthesized, and their metal ion binding properties and photochromism were examined. NMR titration with alkali metal ions revealed that 1 formed a 1:2 complex (metal ion: ligand) with Na⁺, while Li⁺ afforded a 1:1 complex of 1. In cases of K⁺ and Rb⁺, the complexes were a mixture of 1:1 and 1:2 complexes, but the formation of 1:1 complex was observed again with Cs⁺. Under UV irradiation, however, the complex stoichiometry of 1 with all alkali metal ions was 1:1. As a comparison of NMR spectra between the Li⁺ and Na⁺ complexes of 1 indicated considerable upfield shift for the chromene moiety of the Na⁺ complex, π-π stacking of the chromene moiety seems to induce formation of the 1:2 complex. These results indicate that the chromene moiety is not only to show photochromism but also to induce aggregation to form the 1:2 complex resulted in switching of the complex stoichiometry by UV irradiation. The formation of 1:2 complex appeared only with 1 because flexibility of the crown moieties for 2 and 3 interfered the formation of 1:2 complex. Studies on photochromism in the presence of a metal ion demonstrated that the chromene derivatives bearing crown ether moieties show ion-responsive photochromism depending on the metal ion binding ability of their crown ether moieties.     

Density functional theoretical study on attachment sites of Mg<Superscript>2+</Superscript> and Ca<Superscript>2+</Superscript> and metal ion affinity to Crenulatin molecule

Crenulatin (C₂₅H₂₀O₁₀) is a flavonol derivative and has been isolated from the roots of Rhodiola crenulata (Hook. F. et Thoms.), a widely used medicinal herb. Magnesium and calcium cations play an important physiological role in biological systems. In this work, interactions of magnesium and calcium divalent cations with Crenulatin molecule were studied. Density functional theory (DFT) was used to determine coordination geometries and absolute metal ion affinities (MIA) for all possible stable complexes. The results show that calcium and magnesium cations are able to interact with the Crenulatin molecule through mono-, bi-, and tricoordination. B3LYP/6-31G(d) bond energies for all complexes reveal that magnesium cation has a greater affinity to Crenulatin molecule than calcium cation. The calculated value of Mg²⁺ cation affinity, including the zero-point vibrational energy (ZPE) and basis set superposition error (BSSE), is 231.8 kcal mol⁻¹ for the most stable complex. Entropy (ΔS) and free energy (ΔG) variations for the metalation processes considered here have also been reported. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inositol derived crown ethers: effect of auxiliary protecting groups and the relative orientation of crown ether oxygen atoms on their metal ion binding ability

The binding constants of crown ethers prepared from tetra-O-substituted myo- and scyllo-inositol derivatives and 2-O-substituted myo- and scyllo-inositol-1,3,5-orthoformates, with metal picrates show that the O-substituents and the relative orientation of the crown ether oxygen atoms contribute significantly to the binding of crown ethers with metal ions. In particular, the binding efficiency of myo-inositol derived crown ethers to silver and potassium ions could be enhanced by introducing benzyl ethers in the inositol ring. Hence binding efficacy and selectivity of metal ions to inositol derived crown ethers can be tuned by varying substituents on the myo-inositol ring and/or the relative orientation of crown ether oxygen atoms.     

The remarkable indifference of alkali metal cation binding constants to sidearm thioether and sulfoxide donors in azalariat ethers

The first example of a lariat ether containing a sulfur sidearm donor is reported here along with a comparison of cation binding strengths to Na⁺ and K⁺. The binding strength differs remarkably little from analogs completely lacking a sidearm donor group and similar results are observed for the novel sulfoxide analog.     

Synthesis and metal ion complexation of spin labeled 18-crown-6 ethers containing an acridone or an acridine fluorophore unit

Double (spin and fluorescence) labeled pyrroline derivatives of crown ethers containing an acridone or an acridine fluorophore unit (1 and 2) and their diamagnetic analogues (3 and 4) were synthesized. Their fluorescent behavior as well as their complexation properties toward selected metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺) were examined.     

Theoretical design of a fluorescence sensor with configuration-transformed metal ion recognition of aza-18-crown-6

A novel configuration-transformed metal-ion-recognizing fluorescent molecular sensor was designed. The ground state geometries of the free ligand L(L₁, L₂)and their metal ion complex L/Mⁿ⁺ have been investigated theoretically by density functional theory (DFT). The interaction of L and a series of alkaline earth metal ions have been carried out by the natural bond orbital (NBO) and mayer bond order. The calculated results reveal that the metal ion Sr²⁺ has strong interaction with the free ligand L. The excited states, absorption spectra and fluorescence emission spectra of the free ligands L₁, L₂ and their complexes L/Mⁿ⁺ were performed by the time-density functional theory (TD-DFT). The UV-vis results show that the absorption peak of L₂/Sr²⁺ has an obvious change compared with that of L₂, which indicates that the free ligand L₂ can specifically identify the metal ion Sr²⁺. Furthermore, L₂/Sr²⁺ is superior fluorescent molecular sensor compared with other molecules.     

The hapticity of cyclooctatetraene in its first row mononuclear transition metal carbonyl complexes: Several examples of octahapto coordination

The two cyclooctatetraene metal carbonyls that have been synthesized are the tetrahapto derivative (η⁴-C₈H₈)Fe(CO)₃ and the hexahapto derivative (η⁶-C₈H₈)Cr(CO)₃ using the reactions of cyclooctatetraene with Fe(CO)₅ and with fac-(CH₃CN)₃Cr(CO)₃, respectively. Related C₈H₈M(CO)_n (M = Ti, V, Cr, Mn, Fe, Co, Ni; n = 4, 3, 2, 1) species have now been investigated by density functional theory in order to explore the scope of cyclooctatetraene metal carbonyl chemistry. In this connection, the existence of octahapto (η⁸-C₈H₈)M(CO)_n species is predicted as long as the central metal M does not exceed the 18-electron configuration by receiving eight electrons from the η⁸-C₈H₈ ring. Thus the lowest energy structures (η⁸-C₈H₈)Ti(CO)_n (n = 3, 2, 1), (η⁸-C₈H₈)M(CO)_n (M = V, Cr; n = 2, 1), and (η⁸-C₈H₈)Mn(CO) all have octahapto η⁸-C₈H₈ rings. An exception is (η⁶-C₈H₈)Fe(CO), with a hexahapto η⁶-C₈H₈ ring and thus only a 16-electron configuration for the iron atom. Hexahapto (η⁶-C₈H₈)M(CO)_n structures are predicted for the known (η⁶-C₈H₈)Cr(CO)₃ as well as the unknown (η⁶-C₈H₈)Ti(CO)₄, (η⁶-C₈H₈)V(CO)₃, (η⁶-C₈H₈)Mn(CO)₂, and (η⁶-C₈H₈)Fe(CO)₂ with 18, 18, 17, 17, and 18 electron configurations, respectively, for the central metal atoms. There are two types of tetrahapto C₈H₈M(CO)_n complexes. In the 1,2,3,4-tetrahapto (η⁴-C₈H₈)M(CO)_n complexes two adjacent CC double bonds, forming a 1,3-diene unit similar to butadiene, are bonded to the metal atom. In the 1,2,5,6-tetrahapto (η^2,2-C₈H₈)M(CO)₃ derivatives two non-adjacent CC double bonds of the C₈H₈ ring are bonded to the metal atom. The known (η⁴-C₈H₈)Fe(CO)₃ is a 1,2,3,4-tetrahapto complex. The unknown isomeric 1,2,5,6-tetrahapto complex (η^2,2-C₈H₈)Fe(CO)₃ is predicted to lie ∼15 kcal/mol above (η⁴-C₈H₈)Fe(CO)₃. The related 1,2,5,6-tetrahapto complexes (η^2,2-C₈H₈)Cr(CO)₄, (η^2,2-C₈H₈)Mn(CO)₄, [(η^2,2-C₈H₈)Mn(CO)₃]⁻, (η^2,2-C₈H₈)Co(CO)₂, and (η^2,2-C₈H₈)Ni(CO)₂ are all predicted to be low-energy structures.     

Density-functional investigation of the excited state properties and the Jahn-Teller effect in [CrX6]3− (X=Cl−, Br−)

Summary The luminescence of [CrX₆]^3– X=Br^–, Cl^– has been studied through density functional theory (DFT) using both deMon and ADF codes. Multiplet energies⁴A₂,²E,⁴T₂, and⁴T₁ have been expressed as energies of non-redundant single determinants and calculated as in Ref. [1]. The influence of the metal ligand distance on the multiplet energies has been investigated. Of particular interest to this work is the Jahn-Teller effect distortion. We found that the system moves to a more stable geometry when the axial bond length is compressed and the equatorial one elongated in agreement with the experimental value.     

Unsaturation in trinuclear cobalt carbonyl compounds of the type ECo3(CO)n (E = CH,CF, P,As; n = 9, 8, 7, 6) with Co3E tetrahedrane structures

Theoretical studies on the known trinuclear cobalt carbonyl derivatives ECo₃(CO)₉ (E = CH, CF, P, As) predict structures with carbonyl groups bridging each edge of the Co₃ triangle in contrast with experiment where structures with all terminal carbonyl groups are found in all cases. However, the energy differences are predicted to be rather small ranging from 4 ± 2 kcal/mol for FCCo₃(CO)₉ to 10 ± 3 kcal/mol for AsCo₃(CO)₉. The global minima for the unsaturated ECo₃(CO)_n (n = 8, 7, 6) derivatives generally have two (for n = 8) or three (for n = 7 and 6) carbonyl groups bridging the edges of the Co₃ triangle. However, structures with all terminal carbonyl groups are also found in all cases as well as higher energy structures in which one of the carbonyl groups bridges all three cobalt atoms. The fluoromethinyl derivatives FCCo₃(CO)_n (n = 9, 8, 7) are anomalous since their unbridged structures or structures with a carbonyl group bridging all three cobalt atoms are closer in energy to the doubly or triply bridged global minima than is the case for the other ECo₃(CO)_n derivatives.     

电场对Ni3（dpa）4Cl2金属串配合物结构影响的理论研究

应用密度泛函UBP86方法对具有分子导线潜在应用性的金属串配合物Ni3(dpa)4Cl2进行研究,分析了外电场对配合物的几何构型和电子结构的影响.结果表明,零电场条件下存在沿着Ni63+轴及轴向配体Cl的Ni—Ni及Ni—Cl离域作用.沿金属轴Cl4→Cl5方向施加外电场,可使高电势端的Ni2—Cl4键长增大而Ni1—Ni2键长减小,低电势端的Ni3—Cl5键长减小而Ni1—Ni3键长增大;分子能量降低,偶极矩线性增大;HOMO与LUMO能隙减小,前线占据轨道分布向低电势方向移动且轨道能升高,空轨道分布则向高电势方向移动且轨道能降低,其中沿着金属轴方向离域的前线轨道分布及其轨道能随电场的变化尤为显著.在电场作用下,电荷分布发生改变,低电势端Cl5的负电荷向高电势端Cl4转移,但金属和桥联配体的电荷变化很小;同样,在电场作用下,配合物存在明显的结构变化和电子转移现象,呈现出类似导电过程中电子定向转移的变化规律.     

First-principles study of the effect of mechanical strength on ion transport in La-doped LiF-SEI on the Li (001) surface

The solid electrolyte interface (SEI) plays an important role in the lithium–sulfur battery system. It not only protects the stability of the lithium metal anode interface but also inhibits the growth of lithium dendrites during charge and discharge. The relationship between the shape of the SEI and the transport behavior of lithium ions affects the homogeneity of lithium dendrites. In this work, first-principles calculations are used to determine the stable structure and transport properties of the La-doped LiF solid electrolyte interface (La–LiF SEI) on the Li substrate. For the vertical transport of Li ions within the La–LiF SEI, the transport of Li ions in the grain boundary and that in the crystal grain was calculated separately. Regarding the plane diffusion behavior of Li ions between the La–LiF SEI and the lithium anode, the diffusion of Li ions on the surface and interface of the lithium anode were calculated. The effect of critical tensile strain on the diffusion of Li ions on the surface and interface was investigated. The results show that doping with La solves the problem of excessive periodic grain boundary gaps caused by the difference between LiF and Li lattices during the deposition process. The periodic gap is reduced from 0.478 nm to 0.306 nm after La doping. By comparing the migration energy barriers of each path, it is found that lithium ions are more likely to be inserted and extracted at the La–LiF SEI grain boundary. The reason is that the existence of the rare earth element La causes the grain boundary to have a more stable vacancy structure and a smaller transport energy barrier (0.789 eV). The critical tensile strain reduces the diffusion energy barrier (0.813 eV) of Li ions on the surface of the lithium metal anode, which promotes the fast diffusion and uniform deposition of Li ions between the interfaces. The establishment of SEI transport characteristics under the coupling conditions of mechanical stretching and ion transport is expected to improve the Li deposition behavior.     

电场对金属串配合物M3(dpa)4Cl2 (M=Co,Rh, Ir; dpa=dipyridylamide)结构的影响

应用密度泛函理论PBE0 方法研究具有分子导线潜在应用的金属串配合物M₃(dpa)₄Cl₂ (1: M=Co, 2: M=Rh, 3: M=Ir; dpa=dipyridylamide)在电场作用下的几何和电子结构. 结果表明: 配合物基态均是二重态. 1和2的M₃⁶⁺金属链形成三中心三电子σ键, 3 中M₃⁶⁺形成三中心四电子σ键且存在弱的δ键. 随金属原子周期数增大其M―M键增强、LUMO与HOMO能隙减小、金属原子的反铁磁耦合减弱以至消失且自旋密度向配体的离域增强. 在Cl4→Cl5 电场作用下, 低电势端的M3－Cl5 键缩短, 高电势端的M2―Cl4 键增长, M―M平均键长略为缩短, M―M键增强, 有利于分子线的电子传递; 分子能量降低, 偶极矩线性增大. 低电势端Cl5的负电荷向高电势端Cl4 转移, 且3 中金属原子的正电荷由高电势端向低电势端的转移较明显, 自旋电子由低电势端向高电势端金属原子移动, 但桥联配体dpa^-与M和Cl 所在的分子轴间没有电荷转移. 电场使LUMO与HOMO能隙减小, 有利于分子的电子输运. 随金属原子周期数增大, 电场作用下M―M平均键长变化减小, LUMO、HOMO的能级交错现象减少.     

Synthesis and structural studies of hydrazino-crown ethers and thermodynamic studies of their interaction with transition,and post-transition metal ions and methyl ammonium ion

Hydrazino-crown ethers have been synthesized in only 3 or 4 steps starting from 1,2-diacetylhydrazine. The X-ray crystal structure of protonated hydrazino-19-crown-7 (2) showed that one of the hydrazino nitrogen atoms was directed outside the ring cavity. A solvent methanol molecule is held in the cavity of the host ligand by three hydrogen bonds involving two hydrogen atoms bonded to nitrogens of the ligand and the alcohol hydrogen of the methanol. The logK values for the interaction of2 with CH₃NH ₊ ³ , Ag⁺, Pb²⁺, and Cd²⁺ were much less than those for the interaction of symmetrical triaza-l8-crown-6 (5) with the same cations. Hydrazino-crown2 reduced silver ions to silver metal when a solution of2 and silver ions in DMSO was allowed to stand for several days.     

通过SAPO-34分子筛笼中引入金属物种提升甲醇制烯烃反应中乙烯选择性

低碳烯烃(乙烯、丙烯)是化学工业极其重要的基本原料.甲醇制烯烃(MTO)反应是重要的烯烃生产石油替代路线.其中,磷酸硅铝类SAPO-34分子筛在MTO反应中表现出优异的低碳烯烃选择性.与丙烯相比,乙烯具有更高的经济附加值,因此提升MTO反应中乙烯的选择性有着重要的意义.本文采用传统离子交换法(CIE)、模板辅助离子引入法(TII)和醇相离子交换法(AIE)对SAPO-34分子筛进行金属Zn、Cu改性,利用多种表征手段对金属Zn、Cu改性SAPO-34分子筛的物理结构、化学组成、金属物种状态与分布、酸性及扩散性质等进行表征.首先,对金属Zn、Cu改性SAPO-34分子筛的物理结构和化学组成进行分析.X射线衍射表明,相比AIE法,CIE法和TII法改性基本保持SAPO-34分子筛的结晶度.X射线荧光分析表明,相比Co、Ni,金属Zn、Cu更易引入SAPO-34分子筛.N2物理吸附-脱附表明,CIE法改性能够保持SAPO-34分子筛的BET比表面积和微孔孔容.其次,考察了金属Zn、Cu改性SAPO-34分子筛中金属物种的状态.氢气-程序升温还原(H2-TPR)和X射线光电子能谱(XPS)结果表明,Zn物种主要以孤立态的Zn2+阳离子形式存在.H2-TPR、XPS、紫外-可见光谱和电子顺磁共振谱结果表明,Cu物种主要以孤立态的Cu2+阳离子以及部分CuO形式存在.继而对金属Zn、Cu改性SAPO-34分子筛中金属物种的分布进行表征.XPS表明,Zn阳离子改性的SAPO-34表层富硅、富Zn,呈类核壳结构;XPS和扫描式电镜-能量色散X射线光谱结果表明,Cu物种在Cu改性SAPO-34分子筛中均匀分布.进一步研究了金属Zn、Cu改性SAPO-34分子筛中酸性的变化.氨气-程序升温脱附和核磁共振氢谱结果表明,Zn、Cu改性SAPO-34酸性位点的酸量降低.最后,对金属Zn、Cu改性SAPO-34分子筛的扩散性质进行分析.智能重量分析表明,Zn、Cu阳离子的引入降低探针分子(乙烷、丙烷)的扩散系数,推断Zn、Cu阳离子的引入增加对MTO反应产物的扩散限制.热重表明,Zn阳离子改性SAPO-34分子筛反应初期积炭量略微增加.综上所述,Zn阳离子改性SAPO-34催化剂表层富硅、富Zn,呈现类核壳结构.Zn阳离子的引入增加对MTO反应产物的扩散限制,而且Zn阳离子的引入促进MTO反应初始阶段的碳沉积.因此,Zn阳离子改性SAPO-34分子筛显著增加MTO反应产物的扩散限制,对分子尺寸较大的反应产物的扩散限制更为明显,从而提高MTO反应初始阶段的乙烯选择性,增大乙烯/丙烯比.     

Activity and selectivity of Ni nanoclusters in the selective hydrogenation of acetylene: A computational investigation

In this work, the Ni_n (n = 2–10) nanoclusters were investigated to design new catalysts for the selective hydrogenation of acetylene. Our results show that among the Ni_n nanoclusters, the Ni₆ nanocluster can be used as a catalyst in the reactions of hydrogenation. In the presence of the Ni₆ nanocluster, the E_a of the forward step in the reaction of conversion of vinyl to ethylene was 21.21 kJ/mol lower than that of the reverse step in the reaction of conversion of acetylene to vinyl. Also, the E_a of the forward step in the reaction of conversion of ethyl to ethane was 96.59 kJ/mol higher than that of the reverse step in the reaction of conversion of ethylene to ethyl. According to the obtained results, the Ni₆ nanocluster can selectively act in the hydrogenation of a mixture of acetylene and ethylene.     

Density functional study of the lithiation of cyclic vinyl ethers in solution

Lithiation of three cyclic vinyl ethers—2,3-dihydrofuran, 3,4-dihydro-2H-pyran, and 2,3-dihydrooxepin in ethereal solution are investigated at the density functional theory level of B3LYP/6-31++G(d,p). Several solvation models were used, including the microsolvation model, the continuum models such as the Onsager model, the polarized continuum models, and the isodensity polarized continuum model, and the mixed discrete-continuum model. Both the microsolvation and the mixed discrete-continuum model gave results consistent with experiments. Theoretical calculations also indicate that lithiation of 2,3-dihydrooxepin undergoes allylic lithiation concomitant with ring opening.