Intermolecular Interactions and Chiral Recognition in Water

用~1H核磁共振波谱研究了对甲基苯甲酸(p-CH_3-Ph-CO_2^-)和烷酸阴离子(CnCO_2^-)与环糊精(CDS)在非质子极性溶剂DMSO-d_6中的氢键络合反应。虽然未解离的p-甲基苯甲酸p-CH_3-Ph-CO_2H不与硫化镉相互作用，但p-CH_3-Ph-CO_2^-通过氢键作用与α-，β-、γ-等天然硫化镉结合，结合常数(K)较大。少量D_2O的加入抑制了氢键络合物的形成，表明在水溶液中，以致密的羟基为氢键供体的简单主体与以CO_2~(2-)为氢键受体的客体之间几乎不发生氢键作用。质子化七(6-氨基-6-脱氧)…More-β-CD(Per-NH_3^-β-CD)与单价客体阴离子形成稳定的包合物。Per-NH_3~(2-)-Δ-CD与对甲基苯甲酸根阴离子(p-CH_3-Ph-CO_2~(-1))的络合反应的热焓(ΔH)为3.8±0.7kJ mol^~(-1)，熵为88.6±2.2J moL^~(-1)~(-1)·g~(-1)。热力学参数表明，p-CH_3-Ph-CO_2^-包结过程中p-CH_3-Ph-CO_2^-进入Per-NH_3^-β-Cd空腔的熵增加主要是由于主客体离子的脱水作用造成的。在Per-NH_3^-β-Cd空腔中，醋酸盐阴离子不被包合，而丁酸和己酸阴离子形成包合物。烷酸阴离子的络合作用是以熵为主的。结果表明，四(对磺基苯基)卟啉四阴离子(TPPS)与β-CD(TMe-β-Cd)形成1：2的包合物(TMe-TMe-Cd)(卟啉：Cd=1：2)，需要库仑相互作用和包结作用才能实现较大的脱水熵。该体系在水中的K值太大，无法测定。这样的系统有望成为检测血红蛋白和/或肌红蛋白的良好模型。本文研究了Fe(III)TPP与TMe-β-Cd形成的络合物。在pH=5的条件下，TMe-β-Cd在水中形成稳定的1：2络合物，而Cd包合物的化学计量比由于卟啉环净电荷的作用而改变。Cd-卟啉络合物表现出ClO_4~-和ClO_4~-的轴向配位行为。较少

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