Synthesis and electrochemical polymerization of bis-dithienyl cyclophane

Functionalized compressed ring cyclophanes are interesting oligomers because such compounds may provide as interchain connections or recombining fluorescent center when they are polymerized into a conducting polymer. The synthesis and the electro-oxidation of bis-dithienyl cyclophane are reported along with the main electrochemical characteristics of the resulting polymer.     

Alternating conjugated and transannular chromophores: tunable property of fluorene-paracyclophane copolymers via transannular pi-pi interaction

[structure-see text]A series of fluorene-dithia[3.3]paracyclophane copolymers was synthesized by Suzuki coupling reactions of suitable precursors. Transannular pi-pi interactions altered the electronic and optical properties of the polymer backbone significantly. A large red shift in the emission spectrum of the unsubstituted polymer was accompanied by enhanced photoluminescence (PL) efficiency. Substitution in the cyclophane unit resulted in PL quenching.     

A new hexaaza bicyclic cyclophane with dual binding sites

A new C3-symmetric drum-shaped homoditopic haxaamino bicyclic cyclophane and its hexachloride and hexaiodide complexes have been synthesized and characterized and dual recognition of guests has been demonstrated. Single-crystal X-ray analysis illustrates that bicyclic cyclophane has a cavity and side pockets for acetone molecules. The hexaprotonated state of this bicycle shows encapsulation of an iodide inside its cavity, and in hexachloride complex, chloride is recognized as Cl(-)...H2O in each of the three side pockets which are in extensive hydrogen bonding interactions with the water and chlorides. (1)H NMR experiments have also been carried out on hexatosylated cyclophane with the halides to study solution state binding.     

Temperature-dependent and friction-controlled electrochemically induced shuttling along molecular strings associated with electrodes.

The temperature and solvent composition dependence of the electrochemically stimulated rate of shuttling of the redox-active cyclophane, cyclobis(paraquat-p-phenylene), on a molecular string has been studied. The molecular string includes a pi-donor diiminebenzene-site that is associated on one side with an electrode, and stoppered on the other side with an adamantane unit. The cyclophane rests on the pi-donor site, owing to stabilizing pi-donor-acceptor interactions. Electrochemical reduction of the cyclophane units, to the bis-radical cation cyclophane, results in the shuttling of the reduced cyclophane towards the electrode, a process that is driven by the removal of the stabilizing donor-acceptor interactions, and the electrostatic attraction of the reduced product by the electrode. The latter process is energetically downhill, and is temperature-independent. Upon oxidation of the reduced cyclophane that is associated with the electrode, the energetically uphill shuttling of the oxidized cyclophane to the pi-donor site proceeds. The rate of this translocation process has been found to be temperature-dependent, and controlled by the solvent composition. The experimental results have been theoretically analyzed in terms of Kramers' molecular friction model. The theoretical fitting of the experimental results, using solutions of variable composition, reveals that the rate-constants for the uphill reaction in a pure aqueous solution follow the temperature-dependence of the viscosity of water. The results demonstrate the significance of friction phenomena in shuttling processes within molecular machines.     

Electromechanics of a redox-active rotaxane in a monolayer assembly on an electrode

A rotaxane monolayer consisting of the cyclophane, cyclobis(paraquat-p-phenylene) (2), threaded on a "molecular string" that includes a pi-donor diiminobenzene unit and stoppered by an adamantane unit is assembled on a Au electrode. The surface coverage of the electroactive cyclophane unit, E degrees = -0.43 V vs SCE, corresponds to 0.8 x 10(-10) mol.cm(-2). The cyclophane (2) is structurally localized on the molecular string by generating a pi-donor-acceptor complex with the diiminobenzene units of the molecular string. The cyclophane (2) acts as a molecular shuttle, revealing electrochemically driven mechanical translocations along the molecular wire. Reduction of the cyclophane (2) to the respective biradical-dication results in its dissociation from the pi-donor site, and the reduced cyclophane is translocated toward the electrode. Oxidation of the reduced cyclophane reorganizes 2 on the pi-donor-diiminobenzene sites. The positions of the oxidized and reduced cyclophane units are characterized by chronoamperometric and impedance measurements. Using double-step chronoamperometric measurements the dynamics of the translocation of the cyclophane units on the molecular string is characterized. The reduced cyclophane moves toward the electrode with a rate constant corresponding to k(1) = 320 s(-1), whereas the translocation of the oxidized cyclophane from the electrode to the pi-donor binding site proceeds with a rate constant of k(2) = 80 s(-1). Also, in situ electrochemical/contact angle measurements reveal that the electrochemically driven translocation of the cyclophane on the molecular string provides a means to reversibly control the hydrophilic and hydrophobic properties of the surface. The latter system demonstrates the translation of a molecular motion into the macroscopic motion of a water droplet.     

Regulation of dynamic structure of cyclophanes by their complexation with the porphyrin

Dithia[3.3]metacyclophanes which consist of the pyridine unit connecting to the different positions of the parent cyclophane skeleton have been prepared. Conformational change has been observed for the cyclophane having a 4-substituted pyridine unit by binding to the porphyrin. In contrast the porphyrin binding has no influence on conformational behavior of the cyclophane having a 3-substituted pyridine unit.     

The electrochemical polymerisation of a [2]rotaxane

We report the synthesis of a dithienylpyrrole-stoppered rotaxane and its subsequent electrochemical polymerisation onto a platinum working electrode surface. We have shown that the tetracationic cyclophane moiety of the rotaxane does not impair electropolymerisation of this derivative. Indeed, functionalised films can be conveniently prepared by oxidative polymerisation of the dithienylpyrrole stopper units, to yield a network of rotaxane units interconnected by a conducting polymer backbone.     

Preparation and multivalently enhanced guest-binding affinity of water-soluble cyclophane heptadecamers

Water-soluble cyclophane heptadecamers (17a and 17b), which were constructed with the core cyclophane heptadecamer and 36 polar side chains with a terminal galactose or glucose residue, respectively, were prepared. An analogous cyclophane pentamer (5a) was also prepared. The stoichiometry for the complex of the cyclophane oligomers with fluorescence guests such as TNS was confirmed to be 1:1 host:guest by a Job plot. The guest-binding affinity of cyclophane heptadecamers 17a and 17b was much enhanced relative to that of a corresponding monocyclic cyclophane (1a), i.e., the 1:1 binding constant (K) values for 17a with TNS, 2,6-ANS, and 1,8-ANS were ca. 1700-, 1600-, and 1500-fold larger than those of 1a for the identical guests, respectively, which reflects the multivalency effects in macrocycles. Meanwhile, the corresponding K values for the cyclophane pentamer 5a with TNS, 2,6-ANS, and 1,8-ANS were ca. 250-, 250-, and 110-fold larger than those of 1a for the identical guest, respectively.     

季戊四醇衍生的咪唑鎓化合物的合成及其对阴离子的光谱响应

咪唑鎓本身带有正电荷,2-位碳氢(C2-H)具有一定的酸性,是一种良好的氢键供体,能与阴离子形成氢键。因此,咪唑鎓可以识别各种无机阴离子和生物体内重要的阴离子。本文利用四(1-咪唑甲基)甲烷的独特结构,通过烷基化反应,合成了多咪唑鎓盐2、含有多功能臂的双咪唑鎓盐3和咪唑鎓环番4。采用荧光发射光谱法研究了咪唑鎓盐2、3、4对阴离子(Cl~-、Br~-、I~-、CH_3COO~-、PhCOO~-、HSO_4~-)的光谱响应。结果表明,咪唑鎓盐2和咪唑鎓环番4a加入Cl~-,荧光强度明显增强;咪唑鎓盐3a加入PhCOO~-,荧光强度明显减弱;咪唑鎓盐3b和咪唑鎓环番4b加入I~-,荧光强度明显增强。     

Synthesis, characterization and complexation studies of some novel cyclophane amides and sulfonamides

A series of tricyclic tetraamides have been synthesized and were characterized from spectral and XRD studies. XRD studies revealed that the pyridine-based tricyclic cyclophane amide exists with twisted phenyl rings. All the cyclophane compounds form charge-transfer (CT) complexes with TCNQ. Metal ion complexation studies show that the cyclophane amides are more selective towards Cu(II) ions rather than Ni(II) and Cd(II) ions.     

Hexaaminobenzene derivatives: synthesis and unusual oxidation behavior

The syntheses and the electrochemical behavior of the monomeric peralkylated hexaamino(1,3)metacyclophane 4, the dimeric dodecaamino(1,3)cyclophane 5a, and the dodecaamino(1,3,5)cyclophane 6 are described. Electrochemical measurements show that the hexaaminobenzene units in 4 and 5a undergo an unusually slow two-electron transfer attributed to the deformation of the rings into bis-cyanine cations when oxidized to the respective dication. Further oxidations to tri-, tetra-, and hexacationic units occur at more positive potentials. In the dimeric structures, no interaction between the rings can be seen in the (1,3)cyclophane, but strong interaction for the (1,3,5)cyclophane is observed.     

Synthesis, complexation studies and biological activity of some novel mono and tricyclic cyclophane amides and cyclophane sulfonamides

A series of mono, tricyclic cyclophane tetraamides and cyclophane sulfonamides have been synthesized and characterized from spectral and XRD studies. All the cyclophane amides form charge transfer (CT) complex with TCNQ. The cyclophane amides show moderate to good anti-inflammatory activity. Some of them were active against Gram positive (Klebsiella pneumonia) and Gram negative (Escherichia coli and Staphylococcus aureus) human pathogens.     

The tuneable complexation of gold nanoparticles

Mixed monolayer protected gold nanoparticles have been fabricated incorporating 1,5-dialkyloxynaphthalene moieties that are capable of forming complexes with the tetracationic cyclophane cyclobis(paraquat-p-phenylene); electrochemical reduction of the cyclophane or the addition of tetrathiafulvalene results in disassembly of the complexes.     

Tetrathiafulvalenenaphthalenophanes: planar chirality and cis/trans photoisomerization

A cyclophane incorporating one 1,5-dioxynaphthalene ring system and one tetrathiafulvalene (TTF) unit bridged by [SCH(2)CH(2)O] linkages has been synthesized. In this cyclophane, the TTF unit can adopt either cis or trans configurations. In addition, the 1, 5-dioxynaphthalene ring system imposes one element of planar chirality on this cyclophane. A second element of planar chirality is introduced by the trans form of the TTF unit. Thus, the cyclophane exists in diastereoisomeric forms as three pairs of enantiomers. The enantiomeric pairs associated with the cis form of the TTF unit, as well as one of those associated with the trans form, have been isolated by crystallization, and their structures assigned in the solid state by single-crystal X-ray analyses. In solution, cis/trans isomerization occurs when either the cis or the trans form of the cyclophane is exposed to light. The photoisomerization reaction can be followed by (1)H NMR and UV-vis spectroscopies, as well as by HPLC. The photoisomerization quantum yield has been measured at two different excitation wavelengths (406 and 313 nm). In both cases, the trans --> cis process (Phi = 0.20 at 406 nm) is much more efficient than the reverse cis --> trans process (Phi = 0.030 at 406 nm). Since the absorption spectra of the trans and cis isomers are different and the quantum yield of the trans --> cis photoisomerization reaction depends on the excitation wavelength, the mole fraction of the two diastereoisomers present at the photostationary state depends on the wavelength of the exciting light. No isomerization occurs when the solutions, regardless of the mole fraction of the two diastereoisomers, are stored in the dark.     

Steroid Cyclophanes as Artificial Cell-surface Receptors. Molecular Recognition and its Consequence in Signal Transduction Behavior

Steroid cyclophanes, bearing four bile acid moieties covalently placed on a tetraazaparacyclophane skeleton, were designed and synthesized as artificial cell-surface receptors. Guest-binding behavior of the steroid cyclophanes embedded in a bilayer membrane formed with a synthetic peptide lipid was clarified by means of fluorescence and circular dichroism spectroscopy. We found that the steroid cyclophane effectively bound aromatic guests in both bilayer membranes and aqueous solution. In addition, copper(II) ions acted as a guest species for the steroid cyclophane and a competitive inhibitor toward a NADH-dependent lactate dehydrogenase (LDH). On these grounds, we constituted a supramolecular assembly as an artificial signaling system in combination with the steroid cyclophane, a cationic peptide lipid, and LDH. As a consequence, the steroid cyclophane acted as an effective artificial cell-surface receptor being capable of transmitting an external signal to the enzyme in collaboration with copper(II) ions as a signal transmitter.     

A New Class of Polyconjugated Systems: Synthesis and Properties of Polymetacyclophanes

A unique polyconjugated systems having longitudinal π-electron overlaps was synthesized by using a metacyclophane monomer, 8, 16-dihydroxy-[2,2]-metacyclophane. The monomer was synthesized according to Tashiro's method and was converted to two types of polycyclophanes. One was obtained as a quinoid-type polymer from FeCI₃ -catalyzed oxidative coupling of the 2,5-disubstituted phenols. The polymer obtained was composed of [2,2,] -metacyclophane units polymerized via a diphenoquinone linkage. Amorphous, bright reddish-orange powders were obtained quantitatively under mild reaction condition. Another one was a phenol-type polymer that contained [2,2] -metacyclophane units linked with a 4,4′-dihydroxybiphenyl skeleton. This polymer was obtained by way of a unique polycondensation reaction characteristic of cyclophane compounds. The polymer obtained had a fine whisker form with a golden luster and partial crystallinity. The structures of these polymers were confirmed by various spectroscopic methods and elemental analysis. The electrical conductivity of both polymers was of almost the same order of magnitude (10^?8 S/cm). When doped with sulfuric acid (H₂SO₄) vapor, the phenol-type polymer exhibited a conductivity of 0.25 S/cm, which was much higher than that of the quinoidtype polymer (10^?4 S/cm).     

The synthesis of a pyrrole-functionalized cyclobis(paraquat-p-phenylene) derivative and its corresponding [2]rotaxane and [2]catenane and their subsequent deposition onto an electrode surface

We report the convenient synthesis of a pyrrole-functionalized tetracationic cyclophane, [2]rotaxane, and [2]catenane. X-ray crystallography has confirmed the interlocked structure of the catenane. We have investigated the solution properties of these systems using solution electrochemistry, NMR, and UV-vis spectroscopy. We have also demonstrated that it is possible to immobilize these systems onto a platinum working electrode surface. We have shown that films of the cyclophane have the ability to undergo complexation with a dialkyloxynaphthalene derivative.     

Ultra-high pressure synthesis of a tetrathiafulvalene-diquat cyclophane

Quaternization of a tetrathiafulvalene (TTF)/2,2′-bipyridine cyclophane under 10 kbar of pressure yields a TTF-diquat donor-acceptor cyclophane revealing distinct charge-transfer interactions.     

Synthesis and X-ray crystallographic characterization of a (1,3,5)cyclophane with three amide N-H groups surrounding a central cavity. A neutral host for anion complexation.

A short synthesis of 2.15.28-trioxo-3,16,29-triaza-6,19,32-trithia-[7.7.7](1,3,5)cyclophane(1) is described. An X-ray crystallographic analysis shows that the cyclophane exists in an extended conformation with three amide N-H groups directed approximately inward toward the central cavity.     

“黑洞型”缺电子联吡啶环蕃的合成

利用2,3,5,6-四氟-1,4-苯二甲酸为原料, 经过酯化、还原及溴代, 合成1,4-二溴甲基-2,3,5,6-四氟苯. 以其为原料在低温下利用模板效应合成高度缺电子的“黑洞型”缺电子联吡啶环蕃化合物, 经过连续液液萃取及离子交换得到“黑洞型”缺电子联吡啶环蕃单体. 产品经¹H NMR, ¹³C NMR, MS表征. 利用变温核磁共振技术研究“黑洞型”缺电子联吡啶环蕃与经典的双环(百草枯-对苯撑)型缺电子联吡啶环蕃在溶液中的变化.