Macrocyclic bis(ureas) as ligands for anion complexation

• Claudia Kretschmer,
• Gertrud Dittmann and
• Johannes Beck

Beilstein J. Org. Chem. 2014, 10, 1834–1839, doi:10.3762/bjoc.10.193

• formed (Figure 4). To ensure the composition of the host–guest complexes Job plots were used. The function molar fraction vs the product of molar fraction multiplied by the shift change Δδ allows for the determination of the molar fractions of host and guest. From the maximum of the extrapolated curve

• , indicating a complex of two bis(urea) molecules and one chloride ion. For the smaller macrocyclus 1 the Job plots do not show a distinct plateau after addition of one equivalent of anion. Here, doubtless an interaction is present but apparently not a distinct host–guest complex formation. The binding

Why a diaminopyrrolic tripodal receptor binds mannosides in acetonitrile but not in water?

• Diogo Vila-Viçosa,
• Oscar Francesconi and
• Miguel Machuqueiro

Beilstein J. Org. Chem. 2014, 10, 1513–1523, doi:10.3762/bjoc.10.156

• in water [14]. In fact, this receptor family [11][12][13] could only be tested in water at slightly acidic conditions, due to solubility reasons, and proved to be very inefficient [14]. Unraveling the molecular details of these host–guest interactions is crucial to understand their different

Homochiral BINOL-based macrocycles with π-electron-rich, electron-withdrawing or extended spacing units as receptors for C₆₀

• Marco Caricato,
• Silvia Díez González,
• Idoia Arandia Ariño and
• Dario Pasini

Beilstein J. Org. Chem. 2014, 10, 1308–1316, doi:10.3762/bjoc.10.132

• complexes in solution give insights into the role of nonspecific host–guest interactions (such as π–π stacking) for the overall stabilization of the complexes. We are currently designing binaphthyl-based hosts for the enantioselective recognition and separation of higher fullerenes and chiral nanotubes

Molecular recognition of isomeric protonated amino acid esters monitored by ESI-mass spectrometry

• Andrea Liesenfeld and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 825–831, doi:10.3762/bjoc.10.78

• demonstrate the relevance of dispersive interactions for the overall binding event. These effects also provide hints for the relative spatial orientation of the guest molecules within the host–guest complex, and thereby prove the importance of the spirobifluorene moiety for the observed binding of the

• . However, mass spectrometry has become a major analytical tool in supramolecular chemistry in recent years [19][20][21] and seemed to be perfectly suited in this case, since we were planning to recognise the amino acid derivatives in form of their protonated alkyl esters anyway. Thus, the host–guest

• quasi-isomer is performed to reveal the relative affinity of a receptor towards the different isomers. In this way, the mass spectrometric analysis easily allows direct identification of the individual host–guest complexes. This is usually more complicated with other techniques such as, e.g., NMR

Towards allosteric receptors – synthesis of β-cyclodextrin-functionalised 2,2’-bipyridines and their metal complexes

• Christopher Kremer,
• Gregor Schnakenburg and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 814–824, doi:10.3762/bjoc.10.77

• tool to study the host–guest chemistry of these systems in the future, however, we did not investigate these further. Interestingly, the copper(I) complexes of 2 were much less sensitive to oxidation. This might be a consequence of the steric crowding caused by the 6,6’-disubstitution of the bipyridine

• metal complexes’ host–guest chemistry at a later stage in a quantitative manner, however, a 1:2 metal-to-ligand stoichiometry like in the [Zn(1)2]-complexes is not very easy to study because one has to deal with a very complicated equilibrium between 1:2:2, 1:2:1, 1:2:0 and even more complicated metal

• dimeric complexes with 4,4'-disubstituted bipyridine 1. However, such a 1:2 effector–bipyridine ratio could lead to a difficult-to-handle host–guest chemistry when it comes to binding of additional guest molecules due to very complicated equilibria between 1:2:2, 1:2:1, 1:2:0 and even more complicated

Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

• Malamatenia D. Manouilidou,
• Yannis G. Lazarou,
• Irene M. Mavridis and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 774–783, doi:10.3762/bjoc.10.73

• aqueous solution as shown by DLS [39] and DOSY measurements at different concentrations [38][40][41]; it is therefore reasonable to assume that a part of the aggregation of the dimer is due to the β-CD moieties. Finally, given that in any host–guest solution in the fast exchange regime in the NMR time

End-group-functionalized poly(N,N-diethylacrylamide) via free-radical chain transfer polymerization: Influence of sulfur oxidation and cyclodextrin on self-organization and cloud points in water

• Sebastian Reinelt,
• Daniel Steinke and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 680–691, doi:10.3762/bjoc.10.61

• functionalization is supported by 1H NMR-, SEC-, FTIR- and MALDI–TOF measurements. Keywords: chain-transfer polymerization; cyclodextrins; end-group functionalization; host–guest interaction; lower critical solution temperature (LCST); poly(N,N-diethylacrylamide); Introduction Supramolecular chemistry was first

• ]. Some publications make use of free-radical chain transfer polymerization and subsequent polymer post-modification [25][27][35][36]. The scope of our investigation was the preparation of multiple-stimuli-responsive PDEAAm polymers possessing hydrophobic end-groups suitable for host–guest interactions

• addition the solution properties of polymers 8a–d and 9a–d as a function of temperature were also evaluated in the presence of different amounts of RAMEB-CD. In general, the 4-tert-butylphenyl as well as the 4-tert-octylphenyl end-group are able to build host-guest inclusion complexes with the RAMEB-CD

Novel supramolecular affinity materials based on (−)-isosteviol as molecular templates

• Christina Lohoelter,
• Malte Brutschy,
• Daniel Lubczyk and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2013, 9, 2821–2833, doi:10.3762/bjoc.9.317

• ][52], molecular machinery [53][54] and supramolecular host–guest chemistry [55][56]. With an angle of 120° between its aromatic moieties, it exhibits a rigid geometry with a defined alignment of functional groups (Figure 3, left). Next to classical convergent–concave structures, architectures with a

Synthesis of enantiopure sugar-decorated six-armed triptycene derivatives

• Paola Bonaccorsi,
• Maria Luisa Di Gioia,
• Antonella Leggio,
• Lucio Minuti,
• Teresa Papalia,
• Carlo Siciliano,
• Andrea Temperini and
• Anna Barattucci

Beilstein J. Org. Chem. 2013, 9, 2410–2416, doi:10.3762/bjoc.9.278

• functionalization of either its arene units or the bridged positions of its bicyclooctatriene system. This allows for the development of a range of structurally different triptycene-based derivatives [1]. Triptycene derivatives have also been used as building blocks for the synthesis of new molecules in host–guest

• applications not only as glycoconjugates in glycochemistry, but also as interesting candidates for host–guest interactions by presenting a rigid lipophilic core surrounded by hydrophilic sugar moieties assembled on a rotor skeleton. The six-armed sugar-decorated triptycene derivatives might constitute a new

Structure elucidation of β-cyclodextrin–xylazine complex by a combination of quantitative ¹H–¹H ROESY and molecular dynamics studies

• Syed Mashhood Ali,
• Kehkeshan Fatma and
• Snehal Dhokale

Beilstein J. Org. Chem. 2013, 9, 1917–1924, doi:10.3762/bjoc.9.226

• science and is the basis for most of the vital biological processes [1]. The basis of supramolecular chemistry is molecular recognition where host and guest species interact with each other and exist as a single system. These host–guest systems symbolize simplest examples of supramolecular systems in

• stoichiometry and binding constant of host–guest complexes, 1H NMR titration experiments are most common. These titration experiments give Δδ data for many independent signals which can independently be used to determine the stoichiometry and binding constant. Several NMR versions of Benesi–Hildebrand equations

• . 1H–1H ROESY studies ROESY is an important tool for the study of large molecules and provides information on the through-space proximity of protons [19]. The host–guest interactions are displayed as intermolecular peaks between cavity protons and part of the guest involved in complexation. The

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• ]. Formation of 2:2 complexes with β-CD and 1:2 (host/guest) sandwich complexes with γ-CD were made responsible for the observed increase in the quantum yields. The photodimerization of unmodified ANT could be performed for the first time homogenously in aqueous solution, because of the high solubilities of

• quantum yields and molar fractions of the syn-HH isomer, listed in Table 5, are in good agreement with the measured values, listed in Table 4. It also shoes, that the binding constant K, calculated according to the law of mass action for the 1:2 (host/guest) complex, tremendously increases with the salt

• topochemical reaction. This type of topochemical control happening in solution is much more applicable than the classical topochemical control occurring in the crystalline state [3][43][49]. Conclusion Aromatic guests ANT, ACE, and COU form 1:2 (host/guest) complexes within γ-CD thioethers 1–7, which

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• , electrochemistry, light-harvesting materials and so on [1][2][3][4][5][6]. These small molecules self-assemble into regular supramolecular structures through non covalent interactions such as ion–ion, dipole–dipole, hydrogen bonding, π–π stacking, van der Waals, host–guest, and ion coordination, and in so doing

Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production

• Sándor B. Ötvös,
• Ádám Georgiádes,
• István M. Mándity,
• Lóránd Kiss and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1508–1516, doi:10.3762/bjoc.9.172

• chemistry and drug discovery as biosensing probes, in immunoassays and in host–guest chemistry [71]. Ferrocene-substituted amino acids have been of significant importance in the investigation of the secondary structures of different peptides and foldamers [72]. Thus, conjugates of the azido-functionalized β

Linkage of α-cyclodextrin-terminated poly(dimethylsiloxanes) by inclusion of quasi bifunctional ferrocene

• Helmut Ritter,
• Berit Knudsen and
• Valerij Durnev

Beilstein J. Org. Chem. 2013, 9, 1278–1284, doi:10.3762/bjoc.9.144

• verified by the shifts of the protons in the 1H NMR spectra and in the correlation signals of the 2D ROESY NMR spectra. Keywords: cyclodextrins; ferrocene; host–guest systems; polysiloxanes; supramolecular chemistry; Introduction Polymers containing cyclodextrins (CD) covalently or supramolecularly

• dimethylsiloxane unit. The results of the IR, 1H NMR and mass spectroscopy strongly support the existence of the described derivatives. The terminally α-CD-functionalized poly(dimethylsiloxanes) 4 and 5 were subsequently used as host molecules component for the following complexation reactions. Host–guest

• interactions of the siloxane derivatives with ferrocene Linking of the obtained polydimethyl and disiloxane derivatives through host–guest interactions with single ferrocene molecules generates supramolecular, connected siloxane chains. The guest molecule ferrocene was therefore dissolved in chloroform and

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

• Svetlana Begel,
• Ralph Puchta and
• Rudi van Eldik

Beilstein J. Org. Chem. 2013, 9, 1252–1268, doi:10.3762/bjoc.9.142

• the widest range in both host–guest systems, see Table 9. The illustrated occurrence evidences the importance of the possible alteration of the angles between the CH2 groups and the Nsp3 bridgehead for optimal matching between the host and the guest molecules. The stereochemistry of all investigated

Space filling of β-cyclodextrin and β-cyclodextrin derivatives by volatile hydrophobic guests

• Sophie Fourmentin,
• Anca Ciobanu,
• David Landy and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1185–1191, doi:10.3762/bjoc.9.133

• was still inferior to unity (0.69), which indicated that the host–guest interactions were partially compensated by reduced solvation and loss of freedom of the host–guest system. One way to further improve the hydrophobic binding potential of a host in water is to add a salt such as NaCl [42]. From

Superstructures of fluorescent cyclodextrin via click-reaction

• Arkadius Maciollek,
• Helmut Ritter and
• Rainer Beckert

Beilstein J. Org. Chem. 2013, 9, 827–831, doi:10.3762/bjoc.9.94

• , Humboldtstr. 10, 07743 Jena, Germany 10.3762/bjoc.9.94 Abstract Mono-(6-azido-6-deoxy)-β-cyclodextrin (CD) was covalently attached to an alkyne-modified 5-methyl-2-(pyridin-2-yl)thiazol-4-ol yielding a fluorophore containing CD in a click-type reaction. Intermolecular complexes were formed by poly(host–guest

• the elongated noncovalent polymeric structures collapse. Keywords: fluorescent dye; cyclodextrins; host–guest interaction; supramolecular polymer; Introduction Most small heterocyclic molecules show low fluorescence. However, as we reported earlier, substituted 4-hydroxythiazoles have a high

• and Discussion The water-soluble fluorescent cyclodextrin was synthesized via copper-catalyzed cycloaddition (Scheme 1). The existence of the resulting product was confirmed by MALDI–TOF spectrometry, 1H NMR and IR spectroscopy. The formation of host–guest structures between the thiazole functionality

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

• Dyanne L. Cruickshank,
• Natalia M. Rougier,
• Raquel V. Vico,
• Susan A. Bourne,
• Elba I. Buján,
• Mino R. Caira and
• Rita H. de Rossi

Beilstein J. Org. Chem. 2013, 9, 106–117, doi:10.3762/bjoc.9.14

• solution containing 2% dioxane at 25 °C and in the presence of the native cyclodextrins α-CD, β-CD, γ-CD as well as the permethylated derivatives TRIMEA and TRIMEB, was performed [6]. This revealed weak host–guest association in the case of α-CD and insoluble complex formation in the case of the host

• guest from the inclusion complex resulted in an estimated 17.9 ± 0.3% (n = 2) mass loss, which is in good agreement with the theoretical value of 17.2% for a 1:1 host–guest complex. The complex stoichiometry deduced from thermal analysis was subsequently confirmed by NMR spectroscopy, as described below

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• 75.0 ppm. The symmetric diol 25 crystallizes from ethanol with one equivalent of included water. Stoichiometric host/guest associates have often been observed for this class of compounds [16]. The NMR spectra of 25 show only a small number of signals due to the symmetry of the molecule. In the 13C NMR

Influence of cyclodextrin on the solubility and the polymerization of (meth)acrylated Triton^® X-100

• Melanie Kemnitz and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 2176–2183, doi:10.3762/bjoc.8.245

• , and fluorescence studies, were used to determine the equilibrium constant [4][5][6][7][8][9][10][11][12]. The results also differ in the stoichiometry of the formed complexes [4][7][9][10][11]. Host/guest ratios of 1:1 [4][7], 2:1 [9] and the coexistence of 1:1 and 2:1 [10][11] complexes of β-CD and

• RAMEB-CD The reaction of Triton® X-100 (1) with methacryloyl chloride and acryloyl chloride gave the corresponding methacrylic ester 2 [2] and acrylic ester 3, respectively. Both monomers 2 and 3 were insoluble in water, but readily formed water-soluble host–guest complexes with RAMEB-CD (4 to 7) within

• possible after the complexation of (meth)acrylated Triton® X-100 (2 and 3) with RAMEB-CD (Scheme 3). The polymers 10 and 12 complexed with 1 equiv of RAMEB-CD precipitated during the polymerization, whereas the double complexed polymers 11 and 13 did not precipitate, as a consequence of the stronger host

New enzymatically polymerized copolymers from 4-tert-butylphenol and 4-ferrocenylphenol and their modification and inclusion complexes with β-cyclodextrin

• Adam Mondrzyk,
• Beate Mondrzik,
• Sabrina Gingter and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 2118–2123, doi:10.3762/bjoc.8.238

• investigated until now. Hence, in the present paper we report the HRP-catalyzed synthesis of novel copolymers from 2 and 3. Click reaction of the propargyl modified polyphenol 5 with mono-(6-azido-6-deoxy)-β-cyclodextrin (6) was also investigated. Based on former studies, host–guest structures were created [24

• subsequent click chemistry with N3-β-CD. The covalently bound cyclodextrin moiety and the covalently bound Fc or tert-butyl group form host/guest complexes as proven by DLS measurement. The cyclic voltammetry data shows that the central iron atom of the Fc moiety is present in the copolymer and can be

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• observed. Additionally, this azo-dye-end-group-labeled polymer was complexed with hyperbranched polyglycerol (HPG) decorated with β-CD to generate hedgehog-like superstructures. Keywords: azo-dye; cyclodextrins; end-group functionalization; host–guest interaction; supramolecular aggregation; Introduction

• functionalization by condensation with an azo dye. We also investigated the host–guest interaction of the azo-dye-labeled end group with randomly methylated β-cyclodextrin (RAMEB-CD), and with HPG bearing β-CD on top. Thus, the focus of the present study was directed towards the preparation and superstructure

• predominant form in the red acidic aqueous solution [17][18][19]. Due to our general interest in the use of CD in polymer chemistry [3], the interaction of polymer 6 with RAMEB-CD was investigated. The proposed formation of the host–guest structure between the azo-dye end group and the RAMEB-CD cavity was

Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1890–1895, doi:10.3762/bjoc.8.218

• ]. The host–guest complexes, so-called cyclodextrin inclusion compounds, find many applications such as solubilization of pharmaceutical drugs, dispersion of cosmetics, catalysis, or chromatographic separation of enantiomers [2][7][8]. Application of β-CD 1 is hampered by its low solubility of 18.8 g L−1

• host–guest complexes. Thermodynamic data obtained for the guests 4-tert-butylbenzoate and adamantane-1-carboxylate are listed in Table 1 and Table 2, respectively. Remarkable differences in the binding constants for 4-tert-butylbenzoate were found for the β-CD derivatives 2–7. The completely methylated

Molecular solubilization of fullerene C₆₀ in water by γ-cyclodextrin thioethers

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1644–1651, doi:10.3762/bjoc.8.188

• hampered by the toxicities of the employed organic solvents or surfactants. The most successful strategy to carry the extremely hydrophobic C60 molecule into water is the use of appropriate water-soluble carriers that can form host–guest complexes, such as calixarenes [19][20] and cyclodextrins (CDs) [21