An uracil-linked hydroxyflavone probe for the recognition of ATP

• Márton Bojtár,
• Péter Zoltán Janzsó-Berend,
• Dávid Mester,
• Dóra Hessz,
• Mihály Kállay,
• Miklós Kubinyi and
• István Bitter

Beilstein J. Org. Chem. 2018, 14, 747–755, doi:10.3762/bjoc.14.63

• -5’-triphosphate, GTP) and the strong solvation of the chemosensor and the analyte in aqueous media, reducing the association constant of their complex, and through that the sensitivity of the sensor [31][32]. The molecular recognition of nucleotides in most chemosensors is achieved by charged

• interactions, which prompted us towards the synthesis of UHF by click chemistry. Fluorescence spectroscopy revealed a selective complexation with ATP with an association constant of around 2∙104 M−1 and a ratiometric response in the excitation spectrum. Results and Discussion Structure and calculations Based

• enhancement is remarkable upon excitation at 470 nm – a 7-fold increase can be observed using this excitation wavelength. No significant changes were recorded in the absorption spectra (Figure S15 in the Supporting Information File 1) using a 10 cm path length cuvette. The association constant was calculated

Structural diversity in the host–guest complexes of the antifolate pemetrexed with native cyclodextrins: gas phase, solution and solid state studies

• Magdalena Ceborska,
• Magdalena Zimnicka,
• Aneta Aniela Kowalska,
• Kajetan Dąbrowa and
• Barbara Repeć

Beilstein J. Org. Chem. 2017, 13, 2252–2263, doi:10.3762/bjoc.13.222

• plots see: Figures S4 and S5 in Supporting Information File 1, for Kas values see Table 1). The changes observed for α-CD were the smallest resulting in the lowest association constant (Kas = 4), suggesting very low affinity of α-CD towards PTX. It is worth to notice that a similar complex stability (β

• anion interactions with hydroxy groups of the α-CD. The highest affinity for binding of PTX at pH 7.4 (physiological buffer, PBS) was observed for β-CD (Ka = 226 ± 4 M−1). γ-CD formed complexes characterized by lower association constant Ka = 32 ± 0.1 M−1, whereas α-CD host was shown to have very low

p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests

• Alena A. Vavilova and
• Ivan I. Stoikov

Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188

• logarithm of the association constant of the resulting complexes increases from the energy gain difference calculated using the semi-empirical PM3 method (Table 4). However, an unambiguous tendency is observed only for spherical substrates (halide ions). But there is no such dependence in the case of

• within the range of 82–114 kcal/mol is observed. The quantum mechanical calculations of the complexes of the thiacalix[4]arenes 2, 3, 6, 7, 9 with CH3CO2− ion are in good agreement with the logarithms of the association constant (Table 4). An increase in the logarithm of the association constant

• equiv), 2-bromo-N-(4’-nitrophenyl)acetamide (6 equiv), Cs2CO3 (6 equiv), acetone, reflux. The difference in the energy gain of the complexes of thiacalix[4]arenes 3 and 9 with a number of anions. The logarithms of the association constant (logKass) of the complexes of the synthesized compounds with

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• dispersion of this nucleus. The authors determined the association constant of the complex of NaPF6 with α-cyclodextrin at the picomole level with a detection volume of 50 nL and using non-deuterated solvents [25]. To conclude with the different coil geometries, microslot NMR microprobes and stripline coils

Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

• Cira Mollings Puentes and
• Thomas J. Wenzel

Beilstein J. Org. Chem. 2017, 13, 43–53, doi:10.3762/bjoc.13.6

• enantiomer of the substrate with the higher association constant has a higher proportion complexed with the P-CD at 5 mM than the substrate enantiomer with the lower association constant. Therefore, resonances of the substrate with the higher association constant are more perturbed in the NMR spectrum. At

• higher concentrations of P-CD (10 or 20 mM), also a higher proportion of the enantiomer with the lower association constant binds to the P-CD, thus enhancing perturbations in the NMR spectrum of this enantiomer and thereby diminishing the extent of enantiomeric differentiation. In some cases, the

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• occur depending on the conformation of the host–guest complex (if the light-sensitive part of the molecule is located within or outside of the cavity), on the complex association constant and on the concentration ratio of the guest to the CD. It was shown that the photodecomposition of MB was enhanced

• by stabilizing Ag/TiO2 nanoparticles with β-CD, but applying β-CD in excess the rate of degradation decreased dramatically [46]. The association constant of IBR/β-CD complex falls in the range of 103–104 M−1 [47][48], while that of MB/β-CD is less than 103 M−1 [49][50]. According to NMR studies IBR

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• selected as a non-ionic molecule with a high association constant to α-CD (Ka = 134 M−1 ) [70]. In the presence of C6 diol, the reaction yields dropped to 63–72%, whereas the molecular weights of the polymers increased (22.9 and 19.4 kDa in entries 3 and 6, respectively). It is considered that by

Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu²⁺

• Rahman Hosseinzadeh,
• Mohammad Nemati,
• Reza Zadmard and
• Maryam Mohadjerani

Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163

• interaction with Cu2+. The 1:1 stoichiometry of the obtained complex has been determined by Job’s plot. The association constant determined by fluorescence titration was found to be 1.8 × 106 M−1. The sensor showed a linear response toward Cu2+ in the concentration range from 1 to 10 µM with a detection limit

• fluorescence intensity spectrum showed a gradual decrease up to 5 equiv of Cu2+. With higher Cu2+ concentrations the fluorescence quenched completely (Figure 5a). The stoichiometry of the complex was found to be 1:1 between L and Cu2+ based on the Job’s plot and its association constant was calculated using

• allows a suitable complex formation with a copper ion (Scheme 3). To show the high selectivity of chemosensor L for copper ions, the association constant and limit of detection (LOD) were compared with those reported for other related chemosensors (Table 1). It should be emphasized that due to different

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• results, the high association constant observed with γ-CD is mainly due to a good fitting of the pyrimidine ring into the cavity, while one ethoxy substituent protruding from the lower rim. In the cases of α- and β-CD, the phosphoryl residue is located outside the cavity. For α- and β-CD, the methyl

• TRIMEB and its 73% reduction of hydrolysis. Another study was later carried out with DIMEB in the same experimental conditions [57] and showed that this CD, characterized by a significantly high association constant, was the strongest inhibitor of fenitrothion hydrolysis (decrease of 84% – Table 4). It

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• bind 9-propyladenine in chloroform with a very high association constant of Kassoc = 120,000 M−1 [17][18][19]. What role do the hydrogen bonding and aromatic stacking play? As seen in Figure 4, this system provides an excellent example of what Jencks called “complex additivity of binding energies” [20

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins – new media for capillary separation techniques

• Gabor Benkovics,
• Ondrej Hodek,
• Martina Havlikova,
• Zuzana Bosakova,
• Pavel Coufal,
• Milo Malanga,
• Eva Fenyvesi,
• Andras Darcsi,
• Szabolcs Beni and
• Jindrich Jindrich

Beilstein J. Org. Chem. 2016, 12, 97–109, doi:10.3762/bjoc.12.11

• between the cinnamyl moiety and the α-CD cavity would not be strong enough to hold together such large aggregates. According to Boutellier [15] the degree of polymerization (DPmax) for a SP is given by the association constant between the interacting components and by the concentration of the self

Size-controlled and redox-responsive supramolecular nanoparticles

• Raquel Mejia-Ariza,
• Gavin A. Kronig and
• Jurriaan Huskens

Beilstein J. Org. Chem. 2015, 11, 2388–2399, doi:10.3762/bjoc.11.260

• synthesized by a reaction of 1-(chlorocarbonyl)ferrocene with the terminal amino group of methoxypoly(ethylene glycol)amine (Mw = 5000 g/mol) in dichloromethane, using an excess of triethylamine as a base, followed by precipitation from diethyl ether. To evaluate the association constant of the Fc moiety with

Conformational equilibrium in supramolecular chemistry: Dibutyltriuret case

• Karina Mroczyńska,
• Małgorzata Kaczorowska,
• Erkki Kolehmainen,
• Ireneusz Grubecki,
• Marek Pietrzak and
• Borys Ośmiałowski

Beilstein J. Org. Chem. 2015, 11, 2105–2116, doi:10.3762/bjoc.11.227

• association or the relative population of rotamers [50]. In the current study these forces coexist with other ones in the same molecule. Results and Discussion Studies by NMR techniques Properties of 1 The dilution studies for 1 provided its self-association constant Kself = 170 M−1 (CDCl3, rt, Supporting

• (sigmoidal, see Supporting Information File 1, Figure S11 (inset)). It is fair to mention that the association constant is loaded with an error higher than in our previous publications and should be treated as an approximate value. This is due to the fact that the titration curves were fitted to have the

• equilibrium in 1 cause that the general interaction scheme is non-specific yielding a non-linear change of the association constant. On the other hand the regular changes of anion properties are expressed by some regular tendency in the partial titration-derived data (discussion in Supporting Information File

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• showed two reversible two-electron redox waves at −0.03 and 0.38 V vs Fc/Fc+ in benzonitrile under normal conditions [25][60]. Conducting nanostructure formation from star-shaped oligo-TTFs Although pristine TTF does not self-associate in solution due to the low association constant for dimerization, the

• of mixed valence dimers [18][73], the association constant Ka of 31•+ measured in CH2Cl2–MeCN 4:1 assuming an infinite association model [74] is large (Ka = 3.12 ± 0.48 × 105 M−1 at 298 K) owing to 18 sulfur atoms in 31. Therefore, the oxidation of 31 solution (0.1 mM) in CH2Cl2 first forms (31)22

• association constant in solution (Ka in toluene-d8 at 303 K = 634 M−1 (30), 101 M−1 (31)) [67][68]. Both 30 and 31 fibers showed roughly the same behavior for doping with iodine, and the color of fibers quickly changed from bluish purple to dark brown due to the partial oxidation of 30 and 31 as shown Figure

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• , confirming the formation of the 1:1 complex (m-DNB@clip 3) (Figure 9 left). The association constant was determined to be Ka = (7 ± 3) × 103 M−1 by exploiting the Job plot analysis according to literature [66]. Despite many efforts devoted to the search for a complexation of m-DNB using molecular clip 4, we

• addition of sensor 4. The construction of the Job plot is in agreement with the 1:1 binding stoichiometry between clip 4 and F4-TCNQ with a maximum centered at a molar ratio of 0.5 (Figure 9 right). The high association constant Ka = (1.3 ± 0.8) × 106 M−1 in CH2Cl2 confirms that this rigidified molecular

Fluoride-driven ‘turn on’ ESPT in the binding with a novel benzimidazole-based sensor

• Kai Liu,
• Xiaojun Zhao,
• Qingxiang Liu,
• Jianzhong Huo,
• Bolin Zhu and
• Shihua Diao

Beilstein J. Org. Chem. 2015, 11, 563–567, doi:10.3762/bjoc.11.61

• changes with two well-defined isosbestic points (344, 270 nm) indicated the formation of a single complex between BIP and fluoride [2]. Evidence for 1:1 complex formation was also validated by non-linear least-square analysis [31] for BIP with F−. The association constant, calculated from the UV−vis plot

• binding constant of BIP with F− was also determined by nonlinear regression based on spectrofluorometric titration. Good nonlinear curve fits (R = 0.9907) also indicated the formation of an 1:1 stoichiometric complex of BIP with F− (see Figure S2 in Supporting Information File 1). The association constant

Synthesis and surface grafting of a β-cyclodextrin dimer facilitating cooperative inclusion of 2,6-ANS

• Lars W. Städe,
• Thorbjørn T. Nielsen,
• Laurent Duroux,
• Reinhard Wimmer,
• Kyoko Shimizu and
• Kim L. Larsen

Beilstein J. Org. Chem. 2015, 11, 514–523, doi:10.3762/bjoc.11.58

• spectroscopy, it is shown that the free β-CD dimer forms a 1:1 complex with the fluorescent guest molecule, 2-anilinonaphthalene-6-sulfonic acid (otherwise known not to form 1:2 complexes with parent β-CD), with an apparent association constant of 7300 M−1. Further, it is shown using total internal reflection

• recorded at different concentrations of β-CD dimer (Figure 6a) and parent β-CD (Figure 6b) at equilibrium. The apparent association constant (Ka) was determined by plotting the variation in FI at 420 nm as a function of the β-CD dimer (Figure 6a, insert) and parent β-CD (Figure 6b, insert) concentration

Formation of nanoparticles by cooperative inclusion between (S)-camptothecin-modified dextrans and β-cyclodextrin polymers

• Thorbjørn Terndrup Nielsen,
• Catherine Amiel,
• Laurent Duroux,
• Kim Lambertsen Larsen,
• Lars Wagner Städe,
• Reinhard Wimmer and
• Véronique Wintgens

Beilstein J. Org. Chem. 2015, 11, 147–154, doi:10.3762/bjoc.11.14

• thermodynamic parameters derived assuming a 1:1 complex formation between β-CD and CPT units are given in Table 2. The interactions between the polymers were in both cases exothermic. The apparent association constant (Ka) is more than one order of magnitude higher for D70GP-CPT2 than D10GP-CPT1. The complex

• minor fluorescence intensity (FI) enhancement which is in accordance with the low association constant previously reported in literature in the range of 202–206 M−1 [10][12]. For both of the CPT polymers a vast increase in FI accompanied by an 8 nm blue shift of the emission wavelength in response to

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

• Florian Hamon,
• Claire Blaszkiewicz,
• Marie Buchotte,
• Estelle Banaszak-Léonard,
• Hervé Bricout,
• Sébastien Tilloy,
• Eric Monflier,
• Christine Cézard,
• Laurent Bouteiller,
• Christophe Len and
• Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

• to be an excellent guest for the β-CD cavity, with an association constant Ka ranging from 2·104 M−1 to 4·104 M−1 [35]. This is because the adamantyl residue fits perfectly inside the β-CD cavity. In this present work, we investigated how the affinity between the dimer of adamantane and switchable

• correspond to the complexation of both isomers of AZO-CDim 1. Interestingly, the association constants measured for the ditopic host (about 109 M−1 for the cis isomer and 106 M−1 for the trans isomer) are orders of magnitude larger than the association constant for the monotopic β-CD (Ka = 5·104 M−1). This

• means that the complexation is highly cooperative, particularly in the case of the cis isomer. Although it was not demonstrated, such an additional interaction could explain why the association constant between the trans isomer of the ditopic host AZO-CDim 1 and the ditopic guest ADAdim 4 is

Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

• Véronique Nardello-Rataj and
• Loïc Leclercq

Beilstein J. Org. Chem. 2014, 10, 2603–2622, doi:10.3762/bjoc.10.273

• DCPE by the CD in aqueous solution was proved by 1H NMR. The stoichiometry of the DCPE–γ-CD complex was found to be 1:1 and the association constant was estimated at 1 488 M−1 at 35 °C. In the presence of 2.8 × 10−3 M of γ-CD, the stability of DCPE was enhanced by 2-fold. Moreover, the initial liquid

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

• amount of the chemical shifts in the 1H NMR spectra. Bromide is bound strongly to 2 in the 1:1 binding mode. Nitrate is bound weaker than bromide but still stronger than iodide, and chloride in the 2:1 binding mode shows a high association constant of log K = 7.93. The binding constants for the known

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

• value of the association constant Ka and of the molar absorptivity of the complex εc: where A is the measured absorbance, x is the total concentration of titrant added, εc is the molar absorptivity of the complex, εs is the molar absorbivity of the substrate at the desired wavelength, which could be

• directly determined, C is the total concentration of the titrate (which is a constant quantity), and Ka is the association constant for the 1:1 complex [28]. The data for titrations of 4b with C60 (Figure 4, top) were fitted to a general form of the Hill equation: which can be conveniently rewritten in

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• complex [(SIMes)CuCl(phen)] could be isolated as red crystals and a single crystal X-ray structure shows a distorted tetrahedral coordination geometry at the metal centre. Peak broadening indicative of ligand exchange was observed on the NMR time scale and the association constant of phenanthroline was

The β-cyclodextrin/benzene complex and its hydrogen bonds – a theoretical study using molecular dynamics, quantum mechanics and COSMO-RS

• Jutta Erika Helga Köhler and
• Nicole Grczelschak-Mick

Beilstein J. Org. Chem. 2013, 9, 118–134, doi:10.3762/bjoc.9.15

• shows multiple topologies/configurations (guest up/down) in MD with λ-dynamics [14]. The association constant Ka for α- and β-CD inclusion complexes with several benzene derivatives was investigated by a genetic algorithm [15] and neuronal networks [16]. An overview of quantum mechanical methods to