Intermolecular Interactions and Chiral Recognition in Water

本文用^1HNMR研究了在非质子极性溶剂DMSO-d 6中对甲基苯甲酸根（p-CH_3-Ph-CO_2^-）和链烷酸根（CnCO_2 ^-）与环糊精（CD）的氢键络合作用。未解离的对甲基苯甲酸（p-CH_3-Ph-CO_2 H）不与CD相互作用，但p-CH_3-Ph-CO_2^-通过氢键作用与α-、β-和γ-CD等天然CD以较大的结合常数（K）结合。少量D_2O的加入抑制了氢键复合物的形成，在水溶液中，以高密度OH基团为氢键供体的简单主体与以CO_2 ~（2-）基团为氢键受体的客体之间几乎不发生氢键相互作用，并测定了多价环糊精阳离子和阴离子与带相反电荷客体络合的热力学参数2 O，含0.02 M NaCl，通过^1H NMR光谱法测定。质子化七（6-氨基-6-脱氧） 关于我们 -β-CD（per-NH_3^+-β-CD）与一价客体阴离子形成稳定的包合物。对甲基苯甲酸根阴离子（p-CH_3-Ph-CO_2^-）与per-NH_3^+-β-CD络合的焓变（ΔH）为3.8±0.7 kJ·mol ~（-1），熵变（ΔS）<-1>为88.6±2.2 J·mol ~（-1）·<-1>K ~（-1）<-1>。热力学参数表明，对-CH_3-Ph-CO_2^-包合到per-NH_3^+-β-CD空腔中的过程中，主客体离子的脱水作用是导致包合过程熵增加的主要原因。乙酸根阴离子未被包合到per-NH3 ^+-β-CD空腔中，而丁酸根和己酸根阴离子形成包合物。链烷酸根阴离子的络合是熵占主导地位。四对磺酸基苯基卟啉四阴离子（TPPS）与全甲基化β-CD（TMe-β-CD）形成1：2的包合物（卟啉：CD=1：2）。该体系在水中的K值太大，无法测定。预期这样的系统充当血红蛋白和/或肌红蛋白的良好模型。研究了Fe（Ⅲ）TPPS与TMe-β-CD组成的体系，在pH&gt;5的水中，TPPS的Fe（Ⅲ）配合物与TMe-β-CD也形成了非常稳定的1：2的配合物，而CD的包合物的化学计量比由于卟啉环的净电荷的作用而变为1：1。CD-卟啉配合物表现出Cl^-和ClO_4^-轴向连接的新行为。少

Complexation of p-methylbenzoate (p-CH_3-Ph-CO_2^-) and alkanoate anions (CnCO_2^-) with cyclodextrins (CDs) through hydrogen bonding in an aprotic polar solvent, DMSO-d_6, has been studied by means of ^1H NMR spectroscopy. Although undissociated p-methylbenzoic acid, p-CH_3-Ph-CO_2H, does not interact with CDs, p-CH_3-Ph-CO_2^- is bound to native CDs such as α-, β-, and γ-CDs with fairly large binding constants (K) through hydrogen-bonding interactions. Addition of small amounts of D_2O suppresses the formation of the hydrogen-bonded complexes, suggesting that hydrogen-bonding interactions between simple host having dense OH groups as hydrogen-bond donors and guest having the CO_2^- group as a hydrogen-bond acceptor hardly occur in aqueous solution.Thermodynamic parameters for complexation of polyvalent cyclodextrin cation and anion with oppositely charged guests have been determined in D_2O containing 0.02 M NaCl by means of ^1H NMR spectroscopy. Protonated heptakis (6-amino-6-deoxy) … More -β-CD (per-NH_3^+-β-CD) forms stable inclusion complexes with monovalent guest anions. The enthalpy (ΔH) and entropy changes (ΔS) for complexation of per-NH_3^+-β-CD with p-methylbenzoate anion (p-CH_3-Ph-CO_2^-) are 3.8±0.7 kJ mol^<-1> and 88.6±2.2 J mol^<-1>K^<-1>, respectively. The thermodynamic parameters clearly indicate that dehydration from both the host and guest ions accounts for the entropic gain in inclusion process of p-CH_3-Ph-CO_2^- into the per-NH_3^+-β-CD cavity. The acetate anion is not included into the per-NH_3^+-β-CD cavity, while the butanoate and hexanoate anions form the inclusion complexes. The complexation of the alkanoate anions is entropically dominated. Judging from these results, it may be concluded that Coulomb interactions cooperated with inclusion are required for realizing the large entropic gain due to extended dehydration.Tetrakis (p-sulfonatophenyl) porphyrin tetraanion (TPPS) forms an extremely stable 1 : 2 inclusion complex of permethylated β-CD (TMe-β-CD)(porphyrin : CD=1 : 2). The K value for this system in water is too large to be determined. Such a system is expected to act as a good model for hemoglobin and/or myoglobin. The we studied the system composed of Fe (III) TPPS and TMe-β-CD.The Fe (III) complex of TPPS also form a very stable 1 : 2 complex of TMe-β-CD in water at pH>5, while the stoichiometry of the CD inclusion complex is altered to 1 : 1 because of the effort of the net charge of the porphyrin ring. The CD-porphyrin complex shows a novel behavior of axial ligation of Cl^- and ClO_4^-. Less