杯[4]吡咯-卤素、铵离子复合物的理论研究

采用密度泛函理论的M06-2X/6-31G(d, p)方法对杯[4]吡咯(CP)与卤素离子(X^-=F^-, Cl^-, Br^-)及卤素-铵根离子对的各种可能组装体系进行了系统研究. 详细讨论了各体系的结构、结合能、自然键轨道分析(NBO)和Multiwfn波函数分析的情况. 结果显示杯[4]吡咯与卤素阴离子的相互作用主要是氢键, 波函数分析显示在CPCl-和CP-Br-复合物中长程范德华力和空间位阻作用也明显存在. 杯[4]吡咯能与卤素-铵根离子形成稳定的复合物, 主要通过氢键作用、阴-阳离子的静电作用以及阳离子-π相互作用.从理论上探讨了杯[4]吡咯与离子或离子对的2:1组装体系,但相对于1:1组装体系来讲, 2:1体系并不占优势.本文结果进一步表明, 杯[4]吡咯不仅是一种阴离子受体,而且也是一种良好的离子对受体,尤其是对涉及氟离子的客体,更是如此.     

脲基杯[4]二(9-冠-3)对钠-卤素离子对的识别作用

采用Oniom方法(B3LYP/LANL2DZ∶PM3)对脲基取代的二(9-冠-3)杯[4]芳烃衍生物(H)与离子对Na+X-(X=F-,Cl-,Br-)的包合作用进行了理论研究.在上述体系中存在2种包合方式:一是阴、阳离子在包合物中是分离的,阴离子与主体分子的上沿主要以N—H…X-氢键作用;二是阴、阳离子在包合物中存在明显的离子配对作用,阴离子主要以阳离子的配对作用存在.通过对包合物Na+X-/H的结构参数、自然键轨道(NBO)以及结合能分析可知,第1种包合方式更有利.研究表明脲基取代的二(9-冠-3)杯[4]芳烃衍生物可成为有效的离子对识别受体,研究结果进一步加深了杯芳烃类受体对离子对识别机理的认识,为实验上设计合成新型离子对受体提供了理论依据.     

杯[4]吡咯-阴离子体系相互作用的理论研究——杯[4]吡咯-卤素阴离子体系的密度泛函研究

用密度泛函B3LYP/LANL2DZ方法对自由杯[4]吡咯的最低能量构象和卤素阴离子-杯[4]吡咯复合物进行了计算研究.结果表明,杯[4]吡咯与卤素离子能通过彼此间的相互作用形成复合物,并且这种相互作用在本质上应为分子间的氢键相互作用;杯[4]吡咯与卤素阴离子形成的复合物在构型变化、电荷转移、前线轨道及其作用方式、成键布居以及能量和热力学参数等方面均按元素周期律有规律地变化,杯[4]吡咯与卤素阴离子间的相互作用沿元素周期依次减少.     

β-三氰基乙烯取代杯[4]吡咯与阴离子相互作用的密度泛函理论研究

采用密度泛函B3LYP方法对β-三氰基乙烯取代杯[4]吡咯主体分子及其与阴离子(F-、Cl-、CH3COO-、H2PO4-)形成的复合物进行研究。结果表明,β-三氰基乙烯取代杯[4]吡咯可与阴离子以分子间氢键相互作用形成复合物,并且其与阴离子结合能力大小的顺序为F-> CH3COO-> H2PO4-> Cl-,与实验结果基本一致;通过与杯[4]吡咯对比可见,强吸电子取代基的引入增强了主体分子对阴离子的结合能力。本文还从几何构型、振动光谱、NBO分析及前线轨道等方面来阐述β-三氰基乙烯取代杯[4]吡咯与不同阴离子氢键相互作用的本质以及吸电子取代基的引入对杯[4]吡咯与F-和Cl-之间主-客体相互作用的影响。     

分子动力学模拟研究[Bmim][PF_6]+水+醇三元体系的微观结构和分子间相互作用(英文)

研究离子液体体系的微观结构和分子间相互作用具有重要意义.本文对1-丁基-3-甲基咪唑六氟磷酸盐([Bmim][PF6])+水+乙醇和[Bmim][PF6]+水+异丙醇三元体系进行了分子模拟研究,计算了径向分布函数和不同组成的水-醇混合溶剂与离子液体阴阳离子间的相互作用能,并将其分解为库仑相互作用能和Lennard-Jones(LJ)势能.在此基础上,研究了溶液体系的微观结构、分子间相互作用和相行为.结果表明,水倾向于与离子液体阴离子和阳离子极性部分作用,醇倾向于与阴离子和阳离子非极性部分作用;库仑力主导阴离子-溶剂相互作用,色散力主导阳离子-溶剂相互作用,阴阳离子的缔合状态对色散力影响较小,对库仑力的影响非常显著.     

分子动力学模拟研究[Bmim][PF6]+水+醇三元体系的微观结构和分子间相互作用

研究离子液体体系的微观结构和分子间相互作用具有重要意义. 本文对1-丁基-3-甲基咪唑六氟磷酸盐([Bmim][PF₆])+水+乙醇和[Bmim][PF₆]+水+异丙醇三元体系进行了分子模拟研究, 计算了径向分布函数和不同组成的水-醇混合溶剂与离子液体阴阳离子间的相互作用能, 并将其分解为库仑相互作用能和Lennard-Jones(LJ)势能. 在此基础上, 研究了溶液体系的微观结构、分子间相互作用和相行为. 结果表明, 水倾向于与离子液体阴离子和阳离子极性部分作用, 醇倾向于与阴离子和阳离子非极性部分作用; 库仑力主导阴离子-溶剂相互作用, 色散力主导阳离子-溶剂相互作用, 阴阳离子的缔合状态对色散力影响较小, 对库仑力的影响非常显著.     

带状修饰的杯[4]吡咯对卤素阴离子识别的研究

应用分子力学／分子动力学模拟方法研究了4种带状修饰的杯[4]吡咯对卤素阴离子的识别作用.模拟结果表明, 加入带状修饰链和调节链长可以增强对某种特殊卤素阴离子的识别, 在这个过程中, 卤素阴离子与杯[4]吡咯NH上的氢形成的多氢键使主体分子与阴离子形成稳定复合物, 同时带状修饰链通过改变杯吡咯空腔大小影响主体分子与卤素阴离子的氢键相互作用, 从而调节了对不同阴离子的识别能力.     

β-卤素取代对杯[4]吡咯构象及主-客体相互作用的影响II. 密度泛函理论研究

应用密度泛函理论对杯[4]吡咯及卤素取代杯[4]吡咯模型分子的自由主体以及其卤素离子复合物体系进行计算研究. 结果表明, 杯[4]吡咯β位被卤素拉电子基团取代后, 主体分子的构象特征受吡咯单元的偶极影响; β-卤素取代导致了杯[4]吡咯对卤素离子的结合作用增强, 且当β位为氯取代时, 杯[4]吡咯对卤素离子的结合能力最强. 并从振动光谱、NBO电荷布居、相互作用的前线轨道、“活性”构象的偶极矩和Mulliken成键布居等方面阐述β-卤素取代对杯[4]吡咯与卤素离子之间的主-客体相互作用的影响.     

N-硝基苯基吡咯酰胺对阴离子识别研究

合成了2个N-硝基苯基吡咯酰胺阴离子识别主体. 通过X射线单晶衍射确定了间位硝基取代物的结构, 氢键及π-π相互作用在该化合物的组装过程中起到了决定性的作用. 利用UV-Vis光谱研究了这两个主体对常见无机阴离子的识别, 结果表明， 它们不仅对F-和H2PO4-离子有比较强的识别能力, 而且在识别发生时还伴随着显著的颜色变化, 因此这两个化合物都可作为阴离子的比色传感器.     

Subtle role of polyatomic anions in molecular construction: structures and properties of AgX bearing 2,4'-thiobis(pyridine) (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-))

Studies on the subtle effects and roles of polyatomic anions in the self-assembly of a series of AgX complexes with 2,4'-Py(2)S (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-); 2,4'-Py(2)S = 2,4'-thiobis(pyridine)) have been carried out. The formation of products appears to be primarily associated with a suitable combination of the skewed conformers of 2,4'-Py(2)S and a variety of coordination geometries of Ag(I) ions. The molecular construction via self-assembly is delicately dependent upon the nature of the anions. Coordinating anions afford the 1:1 adducts [Ag(2,4'-Py(2)S)X] (X(-) = NO(3)(-) and CF(3)CO(2)(-)), whereas noncoordinating anions form the 3:4 adducts [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Each structure seems to be constructed by competition between pi-pi interactions of 2,4'-Py(2)S spacers vs Ag.X interactions. For ClO(4)(-) and PF(6)(-), an anion-free network consisting of linear Ag(I) and trigonal Ag(I) in a 1:2 ratio has been obtained whereas, for the coordinating anions NO(3)(-) and CF(3)CO(2)(-), an anion-bridged helix sheet and an anion-bridged cyclic dimer chain, respectively, have been assembled. For a moderately coordinating anion, CF(3)SO(3)(-), the 3:4 adduct [Ag(3)(2,4'-Py(2)S)(4)](CF(3)SO(3))(3) has been obtained similarly to the noncoordinating anions, but its structure is a double strand via both face-to-face (pi-pi) stackings and Ag.Ag interactions, in contrast to the noncoordinating anions. The anion exchanges of [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = BF(4)(-), ClO(4)(-), and PF(6)(-)) with BF(4)(-), ClO(4)(-), and PF(6)(-) in aqueous media indicate that a [BF(4)(-)] analogue is isostructural with [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Furthermore, the anion exchangeability for the noncoordinating anion compounds and the X-ray data for the coordinating anion compounds establish the coordinating order to be NO(3)(-) > CF(3)CO(2)(-) > CF(3)SO(3)(-) > PF(6)(-) > ClO(4)(-) > BF(4)(-).     

Modified calix[4]pyrrole receptor: solution thermodynamics of anion complexation and a preliminary account on the phosphate extraction ability of its oligomer

A modified calix[4]pyrrole, namely meso-tetramethyl-tetrakis-(4-hydroxyphenyl) calix[4]pyrrole, 1, has been synthesized and characterized. (1)H NMR investigations in various deuterated solvents seems to indicate that this receptor interacts with acetone-d(6). The solution thermodynamics of 1 in various solvents is reported. Complexation studies in CD(3)CN show that the NH and OH functionalities of 1 are the active sites of its interaction with the fluoride and the dihydrogen phosphate anions. The composition of the anion complexes was established through conductance measurements. In all cases, 1:1 complexes are formed. The thermodynamics of anion complexation in acetonitrile and N,N-dimethylformamide is discussed comparatively with previous reported data for the parent calix[4]pyrrole, 2, and these anions in these solvents. The medium effect on anion complexation is discussed in terms of the solvation properties of the reactants and the product in acetonitrile and N,N-dimethylformamide. An oligomeric material containing 1 as anchor group was synthesized and characterized by mass spectrometry. Preliminary studies have been performed to assess the extracting properties of this oligomer for the removal of phosphates from aqueous solutions. The effects of pH, temperature on the extraction of this anion salt from water, as well as the kinetics of the process (fast) were investigated.     

New insights on anion recognition by isomers of a calix pyrrole derivative

Two isomeric structures of meso-tetramethyltetrakis(3-hydroxyphenyl)calix[4]pyrrole, 4-alphaalpha betabeta and 4-alphabeta alphabeta, have been isolated and characterized by 1H NMR in different solvents (CD3CN, CD3OD, and DMSO-d6) at 298 K. Standard Gibbs energies of solution derived from solubility data in various solvents were used to calculate the transfer Gibbs energy, delta(t)G(o), of these ligands using acetonitrile as the reference solvent. These results are consistent with the 1H NMR studies in different media that show chemical shift changes observed in the resonances of the NH and the OH protons of these ligands. Solvate formation was observed when these isomers were exposed to saturated atmosphere of N,N-dimethylformamide, dimethyl sulfoxide and propylene carbonate. Anion interaction involving 4-alphaalpha betabeta and 4-alphabeta alphabeta was investigated by 1H NMR in CD3CN while the complex composition was assessed through conductance measurements. Significant differences are observed in the affinity of these ligands for anions as well as in the composition of the fluoride complexes. Thus 4-alphaalpha betabeta shows selectivity for H2PO4(-) in acetonitrile while its isomer 4-alphabeta alphabeta is selective for the fluoride anion. Again the complex composition is altered for the fluoride anion when complexed with 4-alphaalpha betabeta in acetonitrile (1:1 complex) relative to 4-alphabeta alphabeta in the same solvent. The latter isomer shows an enhanced hosting ability for this anion. Thus two anions are taken up per unit of ligand. The thermodynamics of complexation of H2PO4(-) and these ligands in acetonitrile is discussed, and the results are compared with those involving calix[4]pyrrole and this anion in this solvent. It is shown that the isomers interact with two H2PO4(-) anions while one calix[4]pyrrole unit interacts with this anion. This paper demonstrates for the first time that the enthalpy parameter may be a suitable reporter of the number of hydrogen bonds formed when calix[4]pyrrole and its derivatives interact with the dihydrogen phosphate anion in acetonitrile. In moving from acetonitrile to N,N-dimethylformamide, 4-alphaalpha betabeta is unable to enter complexation with most anions, except fluoride, with which the formation of a 1:2 (ligand:anion) complex is demonstrated. The rather versatile behavior of these receptors for anions is explained on the basis of 1H NMR evidence and solvation effects. These investigations highlight the importance of the medium effect on the stability of the complex and reflect the inherent nature of the solvent and its highly significant involvement in the complexation process.     

Conformational features and anion-binding properties of calix[4]pyrrole: a theoretical study

The conformational preference of calix[4]pyrrole and its fluoride and chloride anion-binding properties have been investigated by density functional theory calculations. Geometries were optimized by the BLYP/3-21G and BLYP/6-31G methods, and energies were evaluated with the BLYP/6-31+G method. To model the effect of medium, the SCIPCM solvent model was also employed. Four typical conformations of the parent substituent-free calix[4]pyrrole were studied. Both in the gas phase and in CH(2)Cl(2) solution, the stability sequence is predicted to be 1,3-alternate > partial cone > 1,2-alternate > cone. The cone conformation is predicted to be about 16.0 and 11.4 kcal/mol less stable in the gas phase and CH(2)Cl(2) solution, respectively. This is mainly due to electrostatic repulsions arising from the all-syn pyrrole/pyrrole/pyrrole/pyrrole arrangement present in this conformer. The existence of possible 1:1 and 1:2 anion-binding modes were explored in the case of fluoride anion, and the factors favoring the 1:1 binding mode are discussed. The calculated binding energy for fluoride anion is about 15 kcal/mol larger than that for chloride anion. The calculated binding energy for chloride anion agrees with the experimental value very well. The presence of meso-alkyl substituents destabilizes the cone conformer with respect to the 1,3-alternate conformer and, therefore, reduces the anion-binding affinity by 3-4 kcal/mol. The strength of N-H- - -anion hydrogen bonds in the various structures subject to study were estimated on the basis of the calculated anion-binding energies and the predicted structural deformation energies of substituent-free calix[4]pyrrole.     

Anion Adsorption on an Au Colloid Monolayer Based Cysteamine-Modified Gold Electrode

IntroductionThe metal colloids have been investigated for over l40 years since Faraday['] made thefirst approach on gold colloids. Colloidal Au can be used for catalysis['], microanalysis of pro--tein and biosensors[3J and its fine particles have been expected to be a highly efficient thirdnon1inear optical material[4'5J. However, most studies on the surface chemistry of metal parti-cles have been focused on silver[6], the reason is that the plasmon absorption band of that met-al is very str…     

Anion binding studies of fluorinated expanded calixpyrroles

The anion binding properties of fluorinated calix[n]pyrroles (n = 4-6) in aprotic solvents (acetonitrile and DMSO) and modified reaction conditions allowing for the synthesis and isolation of the hitherto missing dodecafluorocalix[6]pyrrole from the condensation of 3,4-difluoro-1H-pyrrole and acetone are described. In acetonitrile solution containing 2% water, the association constants for the 1:1 binding interaction between octafluorocalix[4]pyrrole and chloride anion obtained with isothermal titration calorimetry (ITC) and (1)H NMR titration methods were found to match reasonably well. As compared to its nonfluorinated congener, octafluorocalix[4]pyrrole was found to display enhanced binding affinities for several representative anions in pure acetonitrile as judged from ITC analyses. Similar analyses of the fluorinated calix[n]pyrroles revealed an increase in the relative affinity for bromide over chloride with increasing macrocycle size, as manifest in a decrease in the binding ratio K(a(Cl))/K(a(Br)). Anion binding studies in the solid state, involving single-crystal X-ray diffraction analyses of the chloride and acetate anion complexes of octafluorocalix[4]pyrrole and decafluorocalix[5]pyrrole, respectively, confirmed the expected hydrogen bond interactions between the pyrrolic NH protons and the bound anions.     

Double-cavity calix[4]pyrrole derivative with enhanced capacity for the fluoride anion

A double-cavity calix[4]pyrrole derivative, meso-tetramethyl-tetra[N-(2-phenoxyethyl)-N'-phenylurea]calix[4]pyrrole, 1, with enhanced hosting ability for the fluoride anion has been designed and characterized. Its interaction with anions (fluoride, chloride, bromide, iodide, dihydrogen phosphate, hydrogen sulfate, perchlorate, nitrate, and trifluoromethane sulfonate) was qualitatively and quantitatively assessed through 1H NMR, conductance, and calorimetric studies. The outcome of these investigations demonstrates that 1 interacts only with fluoride and dihydrogen phosphate anions in dipolar aprotic media. However, the composition of these complexes differs in that two units of fluoride are taken per unit of 1, while a 1:1 anion/ligand complex is formed with the dihydrogen phosphate anion. Results from the 1H NMR studies are striking in that these not only provide information about the active sites of the ligand-anion interaction but also allow the establishment of the sequence of events taking place during fluoride complexation. Thus, hydrogen-bond formation between the pyrrolic hydrogen and the fluoride anion is followed by the uptake of a second anion through the same type of interaction, but with the phenyl urea. It is also the latter group that is responsible for the interaction of 1 with the dihydrogen phosphate anion. Finally, this paper illustrates the importance of structural information for the interpretation of the thermodynamics associated with these systems.     

Exploring the dynamics of calix[4]pyrrole: effect of solvent and fluorine substitution

Molecular dynamics simulations show that calix[4]pyrrole (CP) and octafluorocalix[4]pyrrole (8F-CP) are extremely flexible molecules. CP mainly adopts the 1,3-alternate conformation in all the solvents, although the percentage of alternative conformations increases in polar solvents, especially those with good hydrogen-bonding acceptor properties. However, in the case of 8F-CP, the cone conformation is the most populated in some solvents. Transitions between conformers are common and fast, and both CP and 8F-CP can adopt the cone conformation needed for optimum interaction with anions more easily than would be predicted on the basis of previous gas-phase calculations. Furthermore, the present studies show that when a fluoride anion is specifically placed initially in close proximity to CP and 8F-CP in their respective 1,3-alternate conformations, an extremely fast change to the cone conformation is observed in both cases. The results suggest that preorganization does not represent a major impediment to anion-binding for either CP or 8F-CP, and that ion-induced conformational changes can follow different mechanisms depending on the solvent and the chemical substituents present on the calix[4]pyrrole beta-pyrrolic positions.     

Cooperative binding of calix[4]pyrrole-anion complexes and alkylammonium cations in halogenated solvents

Calix[4]pyrrole-chloride interactions are affected not only by the choice of countercation in halogenated solvents, but show a specific dependence on the way in which these cations are bound within the electron rich, bowl-like calix[4]pyrrole cavity formed upon chloride anion complexation. In dichloromethane, the affinities of simple meso-octamethylcalix[4]pyrrole (1) for methyl-, ethyl-, and n-butylammonium chlorides are on the order of 10(5), 10(4), and 10(2) M(-1), respectively, as determined from isothermal titration calorimetry (ITC) analyses. These cation-dependent anion affinity effects, while clearly evident, are less pronounced in other halogenated solvents, such as 1,2-dichloroethane. Support for the proposed cation complexation selectivity is provided by solid state X-ray crystallographic analyses.