Supramolecular interactions of [60]- and [70]fullerenes with calix[n]arenes

[60]- and [70]fullerenes have been shown to form 1:1 supramolecular complexes with (i) 24,26-dimethoxy-25,27-dihydroxy-5,11,17,23-tetra(4-tert-butyl)calix[4]arene (1) and (ii) 37,39,41-trimethoxy-38,40,42-trihydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (2) in CCl(4) medium by absorption spectroscopy. Charge transfer absorption bands of the complexes have been located in each of the cases (except [70]fullerene-2 complex) studied from which the vertical ionisation potential of 1 has been obtained. Formation constants of the complexes have been determined at four different temperatures from which the enthalpies and entropies of formation of the complexes have been obtained. Moreover, the formation constant of [70]fullerene-2 complex is higher than that of the [60]fullerene-1 and [60]fullerene-2 complexes at all the four temperatures studied. This has been accounted in terms of greater cavity size of 2 which is a calix[6]arene compared to 1 which is a calix[4]arene and also by the fact that a high degree of preorganisation takes place in case of 2 through intramolecular H-bonding at its lower rim.     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.     

Cucurbit[5]uril, Decamethylcucurbit[5]uril and Cucurbit[6]uril. Synthesis, Solubility and Amine Complex Formation

A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. ¹H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6-diaminohexane complex.     

Metal-driven ligand assembly in the synthesis of cyclodextrin [2] and [3]rotaxanes

Cyclodextrin [2] and [3]rotaxanes have been synthesised by use of a metal-driven ligand formation methodology. The kinetically stable cobalt(III) complexes formed act as either linking or capping groups, the function being selected by manipulation of the reaction conditions to promote the formation of either 2:1 or 1:1 complexes, respectively. In all cases, mixtures of isomers containing different alpha-cyclodextrin orientations were observed. All three orientational isomers of the [3]rotaxane were isolated and structurally characterized by 2D NMR.     

Solution NMR studies of supramolecular complexes of [60]- and [70]fullerenes with mono O-substituted calix[6]arene

Supramolecular complexation of [60]- and [70]fullerenes with 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert butyl)calix[6]arene (I) has been studied in CCl(4) medium by NMR spectrometric method. All of the complexes are found to be stable with 1:1 stoichiometry. Formation constants (K) of the above supramolecular complexes have been determined from systematic variation of NMR chemical shifts of specific protons of I in the presence of [60]- and [70]fullerenes. Trends in the K value suggest that [70]fullerene binds more strongly with I relative to [60]fullerene. Both PM3 and ab initio calculations reveal that the intermolecular interaction in the [70]fullerene/I complex proceeds through quite deep energy minima.     

Tricarbonylchromium complexes of [5]- and [6]metacyclophane: an experimental and theoretical study

Tricarbonylchromium complexes of [5]- and [6]metacyclophane were prepared and the interaction between the Cr(CO)₃ tripod and the cyclophane fragment was evaluated by both an experimental and a theoretical study. The tricarbonylchromium complex of [5]metacyclophane could only be obtained in solution and was characterized by its ¹H NMR spectrum. The tricarbonylchromium complex of [6]metacyclophane was isolated and an X-ray crystal structure was obtained, which reveals that no significant geometric changes occur upon coordination of the severely distorted aromatic ring. Computations on the tricarbonylchromium complexes of m-xylene, [5]- and [6]metacyclophane furthermore demonstrate that the corresponding complexation energy is remarkably unaffected by the degree of distortion of the aromatic ring. Theoretical analyses of the above model systems as well as complexes of planar and artificially deformed benzene with Cr(CO)₃ show that this is primarily the result of two counteracting effects: (i) a stabilization due to an increased back-donation from the metal center to the benzene and (ii) a destabilization due to the increasing strain in the aromatic ring.     

A spectrophotometric study of the charge transfer complexes of [60]fullerene with different tert-butylcalix[4]crowns

Formation of the charge-transfer complexes between various calix[4]crowns (1-4) and [60]fullerene were studied in toluene solution using UV-vis spectrophotometry. The stability constants and the thermodynamic data of the resulting 1:1 complexes were determined and were found to decrease with increasing the size of the crown moiety of the calixcrown. Except the complex of 3, all the complexes were found to be enthalpy stabilized but disfavored in terms of entropy.     

Ionic recognition by thiacalixarenes: binding of alkali and heavy metal ions by thiacalix[4]arene-bis-crown[n] ethers

The binding properties of two thiacalix[4]arene-bis-crown[n] derivatives (n = 5 and 6) were examined through extraction experiments. The stability constants of the resulting complexes in methanol were determined. The replacement of the bridging CH2 groups by sulfur atoms leads to a strong decrease in both extraction and complexation levels of alkali metal ions but does not affect the selectivity within the series of crown ethers. The stability of complexes with heavy metal ions does not change markedly on passing from thiacalix[4]arene-bis-crown[n] ethers to their calix[4]arene-bis-crown[n] counterparts; therefore no clear-cut conclusions about the possible interactions between these cations and the sulfur atoms can be drawn.     

Supramolecular polymeric complexes of calix[8]arenes

Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied, and previously unknown ternary polymeric complexes of calix[8]arenes of the ion-ion (polymer-calixarene-uranyl ion) and ion-hydrophilic molecule-hydrophobic molecule (polymer-calixarene-fullerene) types were prepared.     

Efficient functionalizations of heteroatom-bridged calix[2]arene[2]triazines on the larger rim

Heteroatom-bridged dichlorinated calix[2]arene[2]triazines, which were synthesized from the fragment coupling reactions of cyanuric chloride and various aromatic dinucleophiles, are a unique type of platform for the construction of functional macrocyclic host molecules. Utilizing a very convenient and straightforward nucleophilic displacement reaction of dichlorinated tetraoxacalix[2]arene[2]triazine by various chelating group-containing amines, a number of functionalized tetraoxacalix[2]arene[2]triazines on the larger rim were efficiently synthesized in good yields. The resulting tetraoxacalix[2]arene[2]triazines armed with two 2,2'-bi(pyridinyl)amino or two bis(2-pyridinemethyl)amino groups selectively formed 1:1 complexes with Cu2+ ion through most probably a chelating interaction effect.     

Self-assembly and dynamics of [2]- and [3]rotaxanes with a dinuclear macrocycle containing reversible Os-N coordinate bonds

With a dinuclear macrocycle 2 that contains weak reversible OsVI-N coordinate bonds, self-assembly and equilibrium dynamics of [2]- and [3]rotaxanes have been investigated. When the macrocycle 2 was mixed together with threads 4a-e, which all contain an adipamide station but different sizes of end groups, [2]pseudorotaxane- and rotaxane-like complexes were immediately formed with large association constants of >7 x 103M(-1) in CDCl3 at 298 K. Exchange dynamics, explored by 2D-EXSY experiments, suggest that assembly and disassembly of complexes occur through two distinct pathways, slipping or clipping, and this depends on the size of the end groups. The slipping pathway is predominant with smaller end groups that give pseudorotaxane-like complexes, while the clipping pathway is observed with larger end groups that yield rotaxane-like complexes. Under the same conditions, exchange barriers (deltaG++) were 14.3 kcalmol(-1) for 4a and 16.7 kcalmol(-1) for 4d, and indicate that the slipping process is at least one order of magnitude faster than the clipping process. Using threads 13a and 13b that contain two adipamide groups, more complicated systems have been investigated in which [2]rotaxane, [3]rotaxane, and free components are in equilibrium. Concentration- and temperature-dependent 1H NMR spectroscopic studies allowed the identification of all possible elements and the determination of their relative distributions in solution. For example, the relative distribution of the free components, [2]rotaxane, and [3]rotaxane are 30, 45, and 25 %, respectively, in a mixture of 2 (2mM) and 13a (2mM) in CDCl3 at 10 degrees C. However, [3]rotaxane exists nearly quantitatively in a mixture of 2 (4 mM) and 13 a (2 mM) in CDCl3 at a low temperature - 10 degrees C.     

Crystal Structures of Uranyl Ion Complexes of Tetrahydroxy[3.1.3.1]metacyclophane (Homocalix[4]arene)

The first crystal structures of complexes of tetrahydroxy-[3.1.3.1]metacyclophanes, also termed homocalix[4]arenes, are reported. In the two uranyl ion complexes obtained, with different para-substituents, the complex core is analogous to that in tetrahomodioxacalix[4]arene complexes, with the cation in a tetra-phenoxide, distorted square-planar environment. The packing in one of these complexes comprises two different arrangements, one of them being a columnar stacking of complex molecules with sandwiched triethylammonium counter-ions hydrogen bonded to one complex and held by cation–π and CH–π interactions within the cavity of the other neighbouring one.     

Charge Transfer in the Electron Donor-Acceptor Complexes of [60]Fullerene/PM567 and [70]Fullerene/PM567

UV-Vis spectroscopic investigations of electron donor-acceptor complexes of [60]- and [70]fullerenes with a well-known laser dye, viz., 4,4-difluoro-1,3,5,7,8-pentamethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indecene (PM567), are reported in toluene solutions. Absorption bands due to charge transfer (CT) transitions have been located in the visible region. The vertical ionization potential of PM567 has been determined utilizing Mulliken’s equation. A possible mechanism for the interaction between the electronic subsystems of [60]- and [70]fullerenes with PM567 is discussed. Oscillator strengths, resonance energies and electronic coupling elements of the CT complexes were estimated. Formation constant data and ab initio calculations suggest that PM567 binds more tightly with [60]fullerene compared to [70]fullerene.     

Synthesis and self-assembly of novel calix[4]arenocrowns: formation of calix[4]areno[2]catenanes

A series of novel calix[4]arenocrowns 1a-c were efficiently synthesized by a one-pot reaction of calix[4]monohydroquinone diacetate 5 with ditosylate 6 and its analogues in the presence of sodium hydroxide. It was found that the calix[4]arenocrowns could form stable pseudorotaxane-type complexes 2a-c with paraquat, and further self-assemble into calix[4]areno[2]catenanes 3a-c with dicationic salt 8 and p-bis(bromomethyl)benzene.     

Isolated supramolecular [Ru(bpy)3]-viologen-[Ru(bpy)3] complexes with trapped CB[7,8] and photoinduced electron-transfer study in nonaqueous solution

The synthesis of two supramolecular diruthenium complexes, 1 ?CB[7] and 1 ?CB[8] (CB[n]=cucurbit[n]uril), which contain the respective host CB[7] and CB[8], were synthesized and isolated. In the case of host CB[8], the desired supramolecular complex was obtained by utilizing dihydroxynapthalene as a template during the synthesis. The ¹H NMR spectra, electrochemistry, and photochemistry of these supramolecular complexes were performed in nonaqueous solution. The results show that both CB[7,8] hosts mainly bind to the linker part in solution in acetonitrile. This binding also lowers the oxidation potential of the ruthenium metal center and hinders the quenching effect by the viologen moiety. It has also been shown that external methylviologen can be included into 1 ?CB[8]. Analysis with NMR spectroscopy, electrochemistry, and photochemistry clearly shows a viologen radical dimer formation between the bound viologen and free methylviologen, thereby showing that the unique abilities of the CB[8] host can be utilized even in nonaqueous solution.     

Study of electron donor-acceptor complexes of tri-n-octyl amine with [60]- and [70]fullerenes and some other electron acceptors by absorption spectrophotometric method

Electron donor-acceptor (EDA) complexes of tri-n-octylamine (TOA) with [60]- and [70]fullerenes and some other electron acceptors have been studied in chloroform medium by absorption spectrophotometric technique. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potential of TOA was determined utilizing CT transition energy. Oscillator strengths, transition dipole strengths and resonance energies for all the complexes have been calculated. [60]Fullerene/TOA and [70]fullerene/TOA complexes are found to decay slowly with time. Kinetics of these reactions have been studied and activation energies for such processes have been estimated. Ab initio calculations suggest that complexation of [70]fullerene with TOA is enthalpy favoured.     

七、八元瓜环对盐酸雷尼替丁的包合作用及缓释性能

研究了七元瓜环(Q[7])和八元瓜环(Q[8])与盐酸雷尼替丁(RH)的包合作用及包合物的体外药物缓释性能.采用紫外-可见光谱法测定了体系的包合比、包合稳定常数和药物累积释放度;用1H NMR技术考察了体系主-客体的包合作用.结果表明,Q[7]和Q[8]与RH在酸性及中性条件下均能发生1∶1包合作用,包合稳定常数分别为1.21×104和2.06×104 L/mol;在碱性条件下则不发生包合作用.原药RH,Q[7]-RH及Q[8]-RH包合物在人工胃液(pH=1.2)中的60 min累积释放度分别为89.1%,56.6%和38.4%;而在人工肠液(pH=6.8)中三者的60 min累积释放度分别为90.2%,58.7%和38.0%.实验结果表明,Q[7]及Q[8]包合对RH有明显的体外缓释作用.     

[Z]-1-[2-(三芳基锡基)乙烯基]环辛醇的合成和性质

本文用三苯基氢化锡、三对甲苯基氢化锡作为锡氢化试剂与1-乙炔基环辛醇进行反应, 合成了两个有机锡化合物: [Z]-1-[2-(三苯基锡基)乙烯基]环辛醇(1)和[Z]-1-[2-(三对甲苯基锡基)乙烯基]环辛醇(2), 并测定了1的晶体结构。1和2分别与ICl, Br2, I~2反应, 得到六个有机锡一卤化物和三个有机锡二卤化物(3-11)。有机锡二卤化物6和一卤化物5与KOH乙醇溶液反应, 分别得到相应的锡氧化物和锡氢氧化物(12, 13)。有机锡二卤化物8分别与含氮双齿配体[2,2'-联吡啶(Bipy),5-硝基-1,10-邻菲罗啉(Nphen),8-羟基喹啉(Oxin)]反应, 得到三个相应的配合物(14-16)。十六个新化合物通过元素分析、锡含量测定、IR、^1H NMR测定对其结构进行了表征, 同时提出了1和2的生成反应历程。     

Energies of charge transfer and supramolecular interactions of some mono O-substituted calix[6]arenes with [60]fullerene by absorption spectrometric method

Equilibria for the formation of supramolecular complexes of [60]fullerene with a series of mono O-substituted calix[6]arenes, namely: (i) 37-methoxy-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (1), (ii) 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (2), (iii) 37-phenacyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (3), (iv) 37-ethylester-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (4) and (v) 37-benzyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (5) have been studied in CCl4 medium by absorption spectroscopic technique. The stoichiometry has been found to be 1:1 ([60]fullerene:calix[6]arene) in each case. An absorption band due to charge transfer (CT) transition is observed in each case in the visible region. The vertical ionisation potentials (I(D)(v)) of all the calix[6]arenes under study have been estimated utilising CT transition energy. The experimental I(D)(v) values also yield a good estimate of the electron affinity of [60]fullerene. The degrees of CT in the ground state of the complexes have been found to be very low (about 0.15%). Resonance energy of the complexes have been estimated. Thermodynamic parameters for the supramolecular complex formation of [60]fullerene with mono O-substituted calix[6]arene receptors are reported. It is observed that among the calix[6]arenes under the present study, only 1 and 4 form inclusion complexes with [60]fullerene. This has also been substantiated by theoretical calculation using PM3 method. Thus presence of one substituent group (of different types) on the lower rim of the calix[6]arene molecule has been shown to govern the host-guest complexation process.     

Calix[6]pyrrole and hybrid calix[n]furan[m]pyrroles (n+m=6): syntheses and host-guest chemistry

Calix[6]pyrrole 2 and the "hybrid systems" calix[3]furan[3]pyrrole 12, calix[2]furan[4]pyrrole 13, and calix[1]furan[5]pyrrole 14, have been synthesized by increasing conversion of the furan units present in the readily accessible calix[6]furan 3 to pyrroles. The host-guest chemistry of these novel macrocycles towards a number of anions, including halogen ions, dihydrogen phosphate, hydrogen sulfate, nitrate, and cyanide has been investigated in solution by (1)H NMR titration techniques and/or phase transfer experiments. The solid-state structures of the free receptors 2, 12, and 13, the 1:1 complexes of calix[6]pyrrole 2 with chloride and bromide, and the 1:1 complex of 14 with chloride are also reported.