
Angel KaiferUniversity of Miami | UM · Department of Chemistry
Angel Kaifer
Ph.D., Univ. of Puerto Rico
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Introduction
Cucurbit[n]urils, Pillar[n]arenes
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Publications
Publications (307)
While oxidized pillar[5]arenes with 1-5 benzoquinone units are known, very few examples of oxidized pillar[6]arenes have been reported. We describe here the synthesis, characterization and electrochemical behavior of a series of macrocyclic hosts prepared by the stepwise oxidation of 1,4-diethoxypillar[6]arene, resulting in high-yield and high-puri...
The host-guest binding interactions between a series of zwitterionic, symmetric viologens and the cucurbit[7]uril host were investigated using NMR and UV-Vis spectroscopic techniques. The nature of the viologen side arms had strong effects on the kinetics of association and dissociation and weaker, more uniform influence on the thermodynamic stabil...
Although bioluminescent molecular beacons designed around resonance quenchers have shown higher signal-to-noise ratios and increased sensitivity compared with fluorescent beacon systems, bioluminescence quenching is still comparatively inefficient. A more elegant solution to inefficient quenching can be realized by designing a competitive inhibitor...
This work addresses the effects of supramolecular complexation by cucurbit[7]uril (CB[7]) on the cell potential of aqueous batteries based on ferrocene and 4,4’‐bipyridinum (viologen) electroactive materials. It was previously known that the oxidation potential of cationic ferrocene derivatives is shifted to more positive values by the formation of...
Partial oxidation of the pillar[5]arene macrocyle with Fe(III) leads to the isolation of a fibrous purple solid with high porosity. Experimental and computational data indicate that the solid material is primarily composed of macrocycles in which two of the hydroquinone units have been oxidized to benzoquinone units. Self-assembly takes place throu...
This chapter focuses on the proficiency of cucurbit[7]uril and cucurbit[8]uril (CB[7,8]) as appropriate hosts for the complexation of aromatic stimuli-responsive guests, which translates into a wide variety of switchable assemblies. These CB[7,8]-based responsive aggregates will be analysed throughout the text both on the basis of the source of ext...
This chapter focuses on non-covalent complexes formed by cucurbituril hosts with redox active guests, defined as molecules containing a residue capable of reversible electron transfer at accessible potentials. Primarily, we will be concerned with cobaltocenium, ferrocene and viologen derivatives as guests, and cucurbit[7]uril (CB[7]) and cucurbit[8...
This chapter summarizes research work showing that electrostatic interactions may have considerable effects on the stability of complexes formed by the cucurbit[n]uril hosts. Focusing primarily on work carried out by the author's research group with the cucurbit[7]uril (CB[7]) molecular receptor, this review highlights the role played by electrosta...
A series of bis(pyridinium)-xylylene derivatives bearing carboxylate terminal groups were investigated as guests for the cucurbit[7]uril host in aqueous solution. While the presence of the terminal carboxylates has a modest effect on the thermodynamic stability of the complexes, the kinetics of complex association/dissociation is strongly affected....
Interferon‐γ (IFN‐γ) is a 144‐amino acid long N‐terminal methionylated recombinant protein and is a potent multifunctional cytokine which is secreted primarily by activated NK cells and T cells. Originally came to attention due to its anti‐viral activities, IFN‐γ can also act as an anti‐proliferative, and immunoregulator, as well as a proinflammato...
The use of cucurbit[8]uril as a molecular host has emerged in the chemical literature as a reliable strategy for the creation of dynamic chemical systems, owing to its ability to form homo‐ and heteroternary complexes in aqueous media with appropriate molecular switches as guests. In this manner, CB[8]‐based supramolecular switches can be designed...
The use of cucurbit[8]uril as molecular host has emerged in the chemical literature as a reliable strategy for the creation of dynamic chemical systems, due to its ability to form homo and heteroternary complexes in aqueous media with appropriate molecular switches as guests. In that manner, CB[8]‐based supramolecular switches can be designed in a...
We present a simple, direct method to prepare monohydroxylated-cucurbit[7]uril (CB7-OH) through the direct oxidation of its precursor host, cucurbit[7]uril (CB7). Although the conversion takes place in low yield (14%), the isolation of CB7-OH from the reaction mixture is straightforward and the unreacted CB7 can be easily recovered. ITC measurement...
This work is concerned with the properties of cucurbit[n]uril (CBn) host portals. The carbonyl oxygens lining each of the cavity openings on these hosts give rise to a rim of negative charge density, which often has strong effects on guest binding processes. The negative effect that carboxylates exert on guest binding to cucurbit[7]uril (CB7) is de...
Bambusurils are a family of receptor molecules related to the cucurbit[n]urils and appreciated for their high affinities to inorganic anions. Here we show that a bambusuril macrocycle bearing carboxylate functional groups on its portals can form external complexes with bipyridinium cationic guests in aqueous solution. The apparent binding affinitie...
The electrochemical reduction of five partially oxidized pillar[5]arenes containing variable numbers (1-5) of quinone units was investigated in acetonitrile and dichloromethane solutions. The cathodic voltammetric behavior of all the macrocyclic compounds containing two or more quinone units indicates the existence of detectable levels of electroni...
Bioorthogonal conjugation eliminates the shortcomings of classical conjugation methods. The conjugation of antibodies to reporter proteins, such as bioluminescent protein, can be controlled with orthogonal conjugation methods. Here we report a bioluminescent immunoassay for the sensitive detection of interferon-γ (IFN-γ) that utilizes orthogonal co...
In aqueous media the host cucurbit[7]uril (CB7) forms inclusion complexes of high thermodynamic stability with ferrocenyl-containing guests. These complexes are characterized by the inclusion of the ferrocenyl group inside the CB7 cavity, primarily driven by hydrophobic forces. This mini-review provides a summary of the properties of these inclusio...
Myeloid cells play a key role in tumor progression and metastasis by providing nourishment and immune protection, as well as facilitating cancer invasion and seeding to distal sites. Although advances have been made in understanding the biology of these tumor-educated myeloid cells (TEMCs), their intrinsic plasticity challenges our further understa...
The binding interactions between a novel ferrocenyl-guanidinium derivative (FcG+) and the macrocyclic hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solution. 1H NMR spectroscopic experiments indicated that both hosts form stable 1:1 inclusion complexes with FcG+, in which the ferrocenyl group is engulfed by the...
Cucurbit[7]uril (CB7) is a macrocycle with ability to form the most stable supramolecular complexes in water ever reported for artificial receptor. Its use for design of advanced functional materials is however very limited as there is no example of fully reversible CB7 based supramolecular complex enabling repetitious dissociation / association co...
The ability of diferrocenylsilanediol, Fc2Si(OH)2 (5), and 1,1,3,3- tetraferrocenyldisiloxane-1,3-diol, Fc2(HO)Si−O−Si(OH)Fc2 (6), to act as new electroactive anion receptors for either acetate or chloride anions has been investigated in solution, in the solid state, and in the gas phase. 1H NMR spectroscopic titrations with anions reveal that the...
The self-assembly in aqueous solution of the well-known cyclophane, cyclobis(paraquat-p-phenylene) (BB4+), and two cucurbit[7]uril (CB7) hosts around a simple hydroquinol-based, diamine guest (GH22+) was investigated by 1H NMR and electronic absorption spectroscopies, electrospray mass spectrometry and DFT computations. The formation of a quaternar...
The binding interactions between the cyclohexanocucurbit[6]uril (Cy6CB6) host and a series of dialkyl-4,4'-bipyridinium (viologen) dicationic guests were investigated in the solution phase, using 1H NMR spectroscopy, and in the solid phase, using X-ray diffraction methods. In D2O solution, methyl viologen (MV2+) and ethyl viologen (EV2+) form 1:1 c...
The cathodic voltammetric behavior of pillar[5]quinone was investigated in dichloromethane solution. Our data show that the symmetry of the macrocycle has a pronounced effect on the electron uptake sequence. The uptake of the first five electrons follows a 2-1-2 pattern and only a total of eight electrons could be injected into the macrocycle under...
The cathodic voltammetric behavior of N,N'-dimethyl-4,4'-bipyridinium (methylviologen, MV2+), N,N'-dipropyl-4,4'-bipyridinium (propylviologen, PV2+), N,N'-dibutyl-4,4'-bipyridinium (butylviologen, BV2+) and N-hexyl-N'-ethyl-4,4'-bipyridinium (hexyl-ethylviologen, HEV2+) was investigated in aqueous solution containing variable concentrations of sodi...
The cucurbit[7]uril (CB7) host forms rotaxane-type complexes with dumbbell-shaped, cationic guests bis(3,5-dimethoxybenzyl)-4,4'-bipyridinium (1(2+)) and bis(3,5-diethoxybenzyl)-4,4'-bipyridinium (2(2+)). The kinetics of complex formation is slower with the latter guest because of its bulkier end groups. Rotaxane formation was found to be thermodyn...
This work focuses on the effect of cucurbit[n]uril (CBn) hosts on the microenvironment of molecular subunits that are located adjacent to the CBn binding site in inclusion complexes. The set of data presented here includes previously reported electrochemical and electron paramagnetic resonance spectroscopic data, primarily obtained with ferrocene-c...
The cucurbit[n]uril (CBn) host family consists of a group of rigid macrocyclic hosts with barrel-like shapes and limited solubility in aqueous media. These hosts are capable of reaching high binding affinities with positively charged hydrophobic guests. In optimum cases, equilibrium association constant (K) values as high as 1017 M–1 have been repo...
A supramolecular complex between benzoates and a bambusuril crystallizes out immediately after mixing in chloroform but only in the presence of residual water molecules. In this complex each of the two portals of the macrocycle is occupied by one benzoate. Carboxylate groups are connected through hydrogen bonding interactions with one molecule of w...
We prepared a new series of bisaminoferrocenyl triazine derivatives and investigated their anodic voltammetric behavior. The electronic nature of the third substituent on the triazine nucleus, that is, its electronic donor/acceptor character determines the level of interactions between the two ferrocenyl centers as measured by the separation betwee...
The binding interactions between two cucurbit[n]uril hosts (n = 7, 8, CB7 and CB8) and the three new guests 1,1′-bis(cyclohexylammoniomethyl)ferrocene (1H22+), 1,1′-bis(cyclohexylmethylammoniomethyl)ferrocene (2H22+), and 1,1′-bis(cyclohexyldimethylammoniomethyl)ferrocene (32+) were investigated in aqueous solution using 1H NMR spectroscopy, voltam...
The formation of inclusion complexes between the cucurbit[7]uril host and a cationic guest containing ferrocenylmethyl and adamantyl residues connected to an ammonium nitrogen initially leads to a ~1:1 mixture of two isomeric microscopic complexes, which evolves as a function of time towards the thermodynamically stable mixture, dominated by the ad...
Stick it to them! Underwater adhesion becomes possible by taking advantage of highly stable host-guest complexes formed between cucurbit[7]uril hosts and ferrocenyl residues. The formation of multiple noncovalent complexes between the two complementary surfaces gives rise to strong adhesive forces resulting in a "supramolecular velcro" system that...
The binding properties of the cucurbit[7]uril host with three structurally related ferrocene-containing guests, ferrocenyltrimethylammonium, ferrocenylmethyltrimethylammonium and ferrocenylethyltrimethylammonium, have been investigated using (1)H NMR spectroscopy, mass spectrometry, voltammetry and computational methods. The experimental and comput...
(Ferrocenylmethyl)methylammonium (1H(+)) is an excellent cationic guest for inclusion complexation by the cucurbit[7]uril host. However, deprotonation of the guest leads to a decrease of 14.8 kJ mol(-1) in the overall stability of its inclusion complex, and one-electron oxidation of the guest's ferrocene residue further diminishes the complex stabi...
Six equivalents of N,N'-bis(4-aminobenzyl)urea, 12 equivalents of 2-formylpyridine and four equivalents of FeSO(4) or NiSO(4) undergo subcomponent self-assembly in aqueous solution to form tetrahedral cages around a single, encapsulated sulfate anion.
Six- and seven-membered cucurbiturils form inclusion complexes with a lutidine derivative. These inclusion complexes differ in the binding mode, stability, kinetics of complexation, and sensitivity toward basic media.
A major challenge in the pursuit of dynamic materials is the dichotomy between reversible structure and electronic conjugation. Guided by the precedence for N‐heterocyclic carbenes (NHCs) to dimerize, couple with electrophiles and bind to transition metals, we proposed that linearly opposed bis(NHC)s could, in a similar manner, afford unsaturated h...
The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6‐trioxytriphenyl‐amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The...
We report the effect of transition metal deposition on the conductivity of single‐walled carbon nanotube (SWNT) networks. The slow evaporation of small amounts of highly mobile transition metal atoms significantly reduces the resistance of SWNT thin films; we suggest that Cr, Fe, and Ti atoms form bis‐hexahapto complexes at the SWNT sidewalls, ther...
On the basis of the highly stable G2H (2 : 1) ternary complex formed by two methyl viologen cation radicals inside the cavity of cucurbit[8]uril, we prepared three monocationic 4‐phenylpyridinium derivatives: 1‐(hydroxyethyl)‐4‐phenyl‐pyridinium (1+) bromide, 1‐(octaethyleneglycol)‐4‐phenyl‐pyridinium (2+) chloride, and 4‐[4‐(methoxymethoxy)phenyl]...
A series of fully‐substituted 5,6‐benzoquinolines covalently fused to the chlolestane framework has been synthesized to serve as model compounds for the poorly characterized components found in the heaviest fractions of petroleum, namely the asphaltenes. Acid‐catalyzed cyclocondensation of an aromatic imine with 5‐α‐cholestan‐3‐one gives 5,6‐benzoq...
The solvent dependency of the ground‐state distribution as well as the electrochemical switching behavior in a redox‐active bistable donor–acceptor [2]catenane, containing bisthiotetrathiafulvalene (STTFS) and 1,5‐dioxynaphthalene (DNP) recognition sites incorporated within a macrocyclic polyether encircled by the cyclobis(paraquat‐p‐phenylene) (CB...
Deprotonation of the two terminal COOH groups on a 4,4'-bipyridinium linear derivative leads to a pronounced slow down on the kinetics of threading and unthreading by the cucurbit[7]uril host.
The inclusion of three bulky guests, adamantyl(ferrocenylmethyl)amine (2), adamantylferrocenecarboxylamide (3), and 1,1'-bis(adamantylaminomethyl)ferrocene (4), inside dimeric molecular capsules formed by an octaacid deep-cavity cavitand (1) was investigated using (1)H NMR spectroscopy and voltammetric techniques. Guests 2 and 3 were encapsulated i...
DNA-based vaccines hold promise to outperform conventional antigen-based vaccines by virtue of many unique features. However, DNA vaccines have thus far fallen short of expectations, due in part to poor targeting of professional antigen-presenting cells (APC) and low immunogenicity. In this study, we describe a new platform for effective and select...
The formation of highly stable inclusion complexes in aqueous solution between the organometallic cobaltocenium cation (Cob(+)) and the hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) was used to develop a simple method, based on UV-vis titrations, to assay the purity of samples of these two hosts. The equilibrium association constant (K) of...
A new heterometallic electroactive compound having the ferrocenyl moiety attached to the platinum atom through an amidine functionality has been prepared via Pt(II)-mediated nucleophilic addition of β-aminoethylferrocene to a benzonitrile ligand. This neutral receptor shows remarkable electrochemical anion-sensing redox response to H(2)PO(4)(-).
Inclusion of guests inside molecular capsules may have pronounced effects on their chemical reactivity. This article provides a quick summary of research on the electrochemical reactivity of encapsulated redox-active guests. A brief account of the results obtained with simple hosts, such as cyclodextrins and cucurbiturils, starts the article. Howev...
Narrow bandgap conjugated polymers in combination with fullerene acceptors are under intense investigation in the field of organic photovoltaics (OPVs). The open circuit voltage, and thereby the power conversion efficiency, of the devices is related to the offset of the frontier orbital energy levels of the donor and acceptor components, which are...
The extent of methylation of the central nitrogen in (ferrocenylmethyl)tempammonium guests determines the main binding site for complexation by the cucurbit[8]uril host.
Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however...
Research on the chemistry of cucurbit[n]uril (CBn) hosts has picked up and maintained an impressive pace in the last decade, primarily due to the isolation of hosts with relatively larger cavity sizes, such as CB7 and CB8. This review article summarizes our involvement in this research effort, with particular emphasis on the binding of redox active...
The binding interactions between two paramagnetic cobaltocenium guests and the hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated using a combination of electronic absorption, NMR, and electron paramagnetic resonance (EPR) spectroscopies, mass spectrometry, and X-ray crystallography. Guest 1, (4-amido-2,2,6,6-tetramethylpiperid...
Tetrathiafulvalene (TTF) is trapped inside a dimeric capsule formed by two octaacid, deep-cavity cavitands in aqueous solution. While the first one-electron oxidation of TTF is strongly hindered by encapsulation, the capsular assembly is eventually destabilized upon oxidation of the guest.
This review summarizes recent work on the chemistry of inclusion complexes formed between redox active guests and cucurbit [n]uril hosts. The large majority of the surveyed research concerns the hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8), while the guests are 4,4'-bipyridinium (viologen) and ferrocene derivatives. The work includes dendr...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The redox-active guests (ferrocenylmethyl)trimethylammonium (2 +) and methylviologen (5 2+) form stable complexes with the cucurbit[7]uril host (CB7) in aqueous solution. In this work, we report a method to transfer these cationic inclusion complexes – as their hexafluorophosphate salts – to less polar, non-aqueous solvents, such as CH3CN, dimethyl...
The utilization of ferrocene as a component of supramolecular systems is surveyed. The electroactivity of ferrocene affords a convenient tool to characterize these systems and, in some instances, provides a mechanism to control their properties.
The thermodynamic functions that describe the complexation of a series of four carboxylic acid guests and two related quaternary ammonium derivatives with β-cyclodextrin were measured using flow calorimetry at 298 K in aqueous media in the presence and in the absence of large concentrations of urea. The relative differences of the thermodynamic par...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Introduction Thermodynamic and Kinetic Considerations Cyclodextrin and Cucurbituril Complexation of Redox-Active Guests Electrochemistry of Inclusion Complexes Formed by Cavitand-Type Hosts Conclusions and Outlook Acknowledgments References
This manuscript presents a summary of recent research work on the electrochemical behaviour of redox active guests fully or almost fully encapsulated by suitable molecular receptors or molecular capsules. From the standpoint of their voltammetric behaviour the cyclodextrins have been shown to be very dynamic hosts, which hamper the observation of d...
The interactions of pinacyanol chloride (PIN), a cationic cyanine dye, with the anionic polyelectrolyte poly(acrylic acid, sodium salt) (PAA) towards enhancing H-aggregation were investigated by electronic absorption spectroscopy. We employed the cucurbit[7]uril (CB7) host to control the formation of these aggregates via host–guest binding interact...
EPR experiments in water-saturated CH(2)Cl(2) solution clearly indicate that oxotempo is not included inside hexameric molecular capsules of resorcin[4]arene. In fact, the tumbling rate of oxotempo only experiences minor changes when resorcinarene is present in the solution. However, NMR spectroscopic data suggest that oxotempo engages in labile hy...
While the direct electrochemical oxidation of ferrocene encapsulated inside a dimeric molecular capsule is essentially suppressed, a cationic ferrocene derivative binds to the capsule's external surface and acts as an effective electrochemical mediator.
Smaller members of water-soluble sulfonated calixarenes have been extensively explored in the context of host-guest complexation, supramolecular chemistry, and potential sensors. However, larger members especially eight-membered calixarene (CA[8]) has received much less attention because of its floppy nature and tendency to exist as a mixture of co...
In quarantine: Nitroxide spin probes are encapsulated by hexameric resorcinarene molecular capsules in dichloromethane solutions (see picture). A substantial reduction in the tumbling rates occurs upon encapsulation of two cationic probes and one neutral probe. As the molecular volume of the probe increases, the tumbling rate of the probe reflects...
We have investigated the formation of inclusion complexes between the host cucurbit[7]uril (CB7) and three cationic and four neutral ferrocene-containing guests: (ferrocenylmethyl)trimethylammonium (2(+)), butyl(ferrocenylmethyl)-dimethylammonium (3(+)), (ferrocenylmethyl)heptyldimethylammonium (4(+)), hydroxymethylferrocene (5), (((methoxy)-ethoxy...
Controlling aggregation : The formation of H‐ and J‐aggregates by cyanine dyes can be significantly enhanced by poly(styrenesulfonate) and further controlled though host–guest complexation with the cucurbit[7]uril host (see picture). magnified image
The presence of anionic polyelectrolytes enhances the tendency of cationic cyanine dyes to form aggr...
This chapter reviews the growing body of data on the binding interactions between dendrimers and two types of well-established
molecular hosts: cyclodextrins and cucurbit[n]urils. Dendrimers are highly branched macromolecules to which functional groups can be attached in spatially defined locations.
The attachment of guest functional groups to dend...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The binding interactions between two cyanine dyes, pseudoisocyanine (PIC) and pinacyanol (PIN), and the cucurbit[n]uril hosts, cucurbit[7]uril (CB7) and cucurbit[6]uril (CB6), were investigated by electronic absorption spectroscopy and DFT computational methods. The CB7 host forms more stable complexes with both dyes than CB6 and the computational...
The cucurbit[6]uril (CB6) host forms stable complexes with 2-aminoethanethiol (cysteamine) and a derivative that contains a bulky terminal group attached to the amine group, as well as with the related disulfide cystamine. In these complexes, the thiol or the disulfide group is encapsulated inside the host cavity. The CB6-complexed thiols show dras...
The preparation and characterization of a new series of dendrimers containing two identical aminoferrocenyl units and a Fréchet dendron around a triazine nucleus is described. A sizable degree of electronic communication between the two redox active ferrocenyl residues was detected in dichloromethane solution containing tetrabutylammonium tetra(pen...
Five new 4,4'-bipyridinium (viologen) core dendrimers containing a Frechet (Fn, n = 1-3, first to third generation) and a Newkome (Nn, n = 1-3) dendron linked to each of the termini of the viologen residue were prepared and characterized. These macromolecules (FnNn) were prepared according to synthetic methodology already developed by our group. Th...
The formation in aqueous solution of kinetically stable inclusion complexes between a deep-cavity cavitand and several redox active ferrocene derivatives was demonstrated using (1)H NMR spectroscopy. The electrochemical kinetics of the inclusion complexes was strongly attenuated as compared to that observed with the free guests.
Ureido pyrimidinedione derivatives with phenyl, 1-naphthyl and 2-naphthyl substituents form stable dimers via quadruple hydrogen bonding, but the 1-naphthyl derivative presents an unexpected tautomer in the solid state.
(Figure Presented) As easy as pi: The spacious 870-Å3 cavity of CB[10] is able to accommodate free base and metalated tetra(N-methylpyridyl) porphyrins inside. The complexes blend the advantageous recognition and photophysical properties of these two classes of macrocycles and promote the formationtern ary complexes (see picture) inwater through π-...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
In aqueous media the deep-cavity cavitand octaacid 1 forms stable dimeric molecular capsules 1(2), which are stabilized by hydrophobic effects. In this work we investigate the binding interactions in aqueous solution between these capsules and the redox active guests, ferrocene (Fc) and three 4,4'-bipyridinium (viologen) dications: methyl viologen...
The molecular host cucurbit[7]uril forms an extremely stable inclusion complex with the dicationic ferrocene derivative bis(trimethylammoniomethyl)ferrocene in aqueous solution. The equilibrium association constant for this host-guest pair is 3 × 10¹⁵ M⁻¹ (K d = 3 × 10⁻¹⁶ M), equivalent to that exhibited by the avidin–biotin pair. Although purely s...
Hydrogen bonding is one of the most important intermolecular forces in molecular self-assembly or non-covalent synthesis.
It is now possible to prepare rather large supramolecular assemblies (>1,000Da) held together by hydrogen bonds between their
molecular building blocks. From the standpoint of electrochemistry, this opens up interesting research...
This book describes the electrochemical behavior of supramolecular systems. Special emphasis will be given to the electrochemistry of host-guest complexes, monolayer and multilayer assemblies, dendrimers, and other supramolecular assemblies. A fundamental theme throughout the book is to explore the effects that supramolecular structure exerts on th...
The Concept of Electrochemical SwitchingSwitchable Binding in a Redox-Active Cation HostElectrochemical Switching as a Means of Controlling Molecular Devices and Other StructuresReferences