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

• , for k0[HO–], k2K2[HO–], and K2, respectively. From these data k2 = 0.14 × 10–3 s–1 can be obtained and this is a measure of the rate of the reaction taking place within the DIMEB cavity. The association constant determined for DIMEB and 1, viz. (1.69 ± 0.9) × 103 M–1 is significantly higher than the

• higher association constant reported here for fenitrothion complexation with DIMEB in aqueous solution compared with previous data for its complexation with β-CD and TRIMEB results in more effective protection of the insecticide molecule from hydrolytic degradation. Kinetic data of the type established

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• molecules between VP and β-CD. Actually, the association constant of α-CD with decamethylene is much higher than that of β-CD with decamethylene [24]. Consequently, the association constant plays an important role in gel formation. To confirm a supramolecular hydrogel formed by crosslinking VP with the α,α

Impact of cyclodextrins on the behavior of amphiphilic ligands in aqueous organometallic catalysis

• Hervé Bricout,
• Estelle Léonard,
• Christophe Len,
• David Landy,
• Frédéric Hapiot and
• Eric Monflier

Beilstein J. Org. Chem. 2012, 8, 1479–1484, doi:10.3762/bjoc.8.167

• supramolecularly interact with β-CDs. For example, addition of a stoichiometric amount of RAME-β-CD on aqueous solutions of water-soluble phosphanes 1–4 led to the formation of phosphaneRAME-β-CD supramolecular complexes. The stoichiometry and association constant Kass of these complexes were measured by

High-affinity multivalent wheat germ agglutinin ligands by one-pot click reaction

• Henning S. G. Beckmann,
• Heiko M. Möller and
• Valentin Wittmann

Beilstein J. Org. Chem. 2012, 8, 819–826, doi:10.3762/bjoc.8.91

• . The association constant for the WGA–N,N’-diacetylchitobiose interaction, for example, has been determined to be K ≈ 5 × 103 to 2 × 104 M–1. The corresponding value for binding to GlcNAc is K ≈ 2 × 102 to 1.3 × 103 M−1 [47]. This prompted us to design a series of multivalent WGA ligands containing two

Azobenzene dye-coupled quadruply hydrogen-bonding modules as colorimetric indicators for supramolecular interactions

• Yagang Zhang and
• Steven C. Zimmerman

Beilstein J. Org. Chem. 2012, 8, 486–495, doi:10.3762/bjoc.8.55

• -modified PBA ranged from viscous liquids to gels depending on the loading of UPy groups on the polymer backbone (Figure 5). The supramolecular coupling of DAN and DeUG units and DAN and UPy units has been well studied. Thus, the association constant (Kassoc) for the DAN–DeUG heterocomplex was measured as

A ferrocene redox-active triazolium macrocycle that binds and senses chloride

• Nicholas G. White and
• Paul D. Beer

Beilstein J. Org. Chem. 2012, 8, 246–252, doi:10.3762/bjoc.8.25

• larger halide, iodide, is only weakly bound. The addition of small amounts (<1 equiv) of dihydrogen phosphate caused precipitation and, hence, no association constant could be calculated. Electrochemical Investigations The ability of 5·2PF6 to sense anions electrochemically was investigated by cyclic

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• affect the binding of ammonium cations. Katoh’s N-hydroxypyrazinone-containing oxacalix[3]arene 23 extracted n-BuNH3+ picrate and t-BuNH3+ picrate better in the presence of Ga3+, indicating cooperation between the two binding sites [38]. The association constant for n-HexNH3+ picrate was found to be 4375

• [53]. Capsule 46 was shown to bind to C60 by the presence of two peaks in the 13C NMR spectrum, which did not coalesce even at 90 °C. 1H NMR was used to determine an association constant of 54 M−1 in Cl2CDCDCl2 at 60 °C. An asymmetric capsule incorporating an oxacalix[3]arene and three Zn(II)porphyrin

• moieties, 52, was also able to bind C60 in a similar fashion with an association constant of 60 M−1 in toluene-d8 at −30 °C [86]. Another strategy to promote fullerene inclusion in an oxacalix[3]arene was to link the two by a triethylene glycol tether to form a molecular cup-and-ball 53 [87]. In addition

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• these data, the association constant for the protonated monovanadate HVO42− with 1 is about 103.8 M−1, while the association constant for V2O74− is Ka = 106.2 M−1. The pKa value for the coordinated divanadate is 8.4 and therewith, 1.9 pKa units lower than for the uncoordinated V2O74− ion. The binding of

• a second Zn-benzylcyclene unit proceeds with an association constant of 103.5 M−1. Consequently, the affinity of the divanadate for both the proton and the second Zn-benzylcyclene is lowered by the coordination of the first Zn-benzylcyclene unit. A speciation diagram for the titration at pH 9.5

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

• Jens Eckelmann,
• Vittorio Saggiomo,
• Svenja Fischmann and
• Ulrich Lüning

Beilstein J. Org. Chem. 2012, 8, 11–17, doi:10.3762/bjoc.8.2

• halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated Kass of pyridine-N-oxide of ca. 40 M−1, NMR titration confirms 25 M−1. Keywords: anion binding; association constant; estimation of binding constants

• constants were identified. Estimation rather than an exact determination of Kass would be fair enough. Once a good candidate is recognized, a standard determination of the association constant, for example, by NMR titration, can be done. With Δδmax unknown, the magnitude of the CIS cannot distinguish

• Supporting Information File 1, page S12), Kass for the best binder to 1, pyridine-N-oxide (PyNO), was estimated to be ca. 40 M−1. A subsequent NMR titration of host 1 with PyNO provided an association constant of 25 M−1 (see Supporting Information File 1). Remarkably, chloride ions are only very weakly bound

Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution

• Xiao-bo Zhou,
• Wing-Hong Chan,
• Albert W. M. Lee and
• Chi-Chung Yeung

Beilstein J. Org. Chem. 2011, 7, 1508–1515, doi:10.3762/bjoc.7.176

• , acetonitrile (ACN) emerged as the best cosolvent, among other polar solvents, to favor the formation of the most stable complex between the probe and Cys, as characterized by the highest association constant. When a higher content of water was used, the association constant of Cd2+–ACAQ and L-cysteine

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

• Xiao-bo Zhou,
• Yuk-Wang Yip,
• Wing-Hong Chan and
• Albert W. M. Lee

Beilstein J. Org. Chem. 2011, 7, 75–81, doi:10.3762/bjoc.7.11

• present in aspartates weakened their interaction with sensor 1, presumably due to non-bonding repulsions. In contrast, in comparison with the association constant between sensor 1 and glutarate, sensor 1 exhibited a stronger binding affinity to D- and L-glutamate (Table 2). Interestingly, a marginal

• association constant of sensor 2 and D-glutamate is one order of magnitude greater than that of sensor 2 and glutarate. In addition to the carboxylate–thiourea interactions, additional H-bond interactions could arise from the alcohol group of the host and the amino group of the guest. A three site binding

Preparation, structures and preliminary host–guest studies of fluorinated syn-bis-quinoxaline molecular tweezers

• Markus Etzkorn,
• Jacob C. Timmerman,
• Matthew D. Brooker,
• Xin Yu and
• Michael Gerken

Beilstein J. Org. Chem. 2010, 6, No. 39, doi:10.3762/bjoc.6.39

• substituents on the electrostatic potential within the cleft is paramount in the facilitation of this interaction between host and guest. Korenaga and Sakai have already noted that N,N,N′,N′-tetramethyl-p-phenylendiamine displays a stronger association constant with molecular tweezer 1 when compared to several

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• stoichiometry between a specific host and guest – or dynamic, where the binding of the first guest to the first binding site of a receptor affects the association constant of a second guest with a second binding site. Either positive allosteric binding – the first guest increases the association constant of the

• second guest – or negative allosteric binding – the first guest decreases the association constant with the second – can occur [30]. Positive allostery or co-operativity [31][32] is desireable for synthetic receptors. In most cases the host forms a cavity in which guest molecules are complexed as the

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• of excess F− ion) abstracts a HF fragment to give [HF2]−. A higher association constant was observed for fluoride ion than for other ions due to its strong hydrogen-bonding ability, small size, and better selectivity which resulted in a strong binding with receptor 1 [50]. Fluorescence study

Size selective recognition of small esters by a negative allosteric hemicarcerand

• Holger Staats and
• Arne Lützen

Beilstein J. Org. Chem. 2010, 6, No. 10, doi:10.3762/bjoc.6.10

• esters 5–7, however, did not result in any significant shifts indicating size-selective discrimination of the different esters. In order to evaluate this phenomenon further we performed an NMR titration to determine the association constant for the binding of the arguably best guest ethyl acetate

• assuming a 1:1 stoichiometry of the resulting host-guest complex (Figure 2). Analysis of the binding isotherms by non-linear regression revealed only a small association constant of K = 9 ± 1 M−1 which, however, was not unexpected given the fact that binding occurs mainly due to quite weak dispersive

• did not reach any saturation and the analysis of these curves did result in an association constant K < 1 M−1. This, however, indicates that the recognition behaviour of 2 can indeed be controlled in a heterotropic negative cooperative allosteric fashion (Scheme 3). Having established this first

Recognition properties of receptors consisting of imidazole and indole recognition units towards carbohydrates

• Monika Mazik and
• André Hartmann

Beilstein J. Org. Chem. 2010, 6, No. 9, doi:10.3762/bjoc.6.9

• and 5 with these monosaccharides to be much more favorable than those with the α-anomers 7a and 9. The curve fitting of the titration data for 4 and β-glucoside 6a suggested the existence of 1:1 and 2:1 receptor–sugar complexes in CDCl3 solutions with a stronger association constant for 1:1 binding

• and a weaker association constant for the 2:1 receptor–sugar complex (this model was further supported by the mole ratio plots). The binding constants, however, were too large to be accurately determined by the NMR spectroscopic method (K11 > 105 and K21 ~ 104 M−1; see Table 3; for a review discussing

• chloroform solution (with stronger association constant for 1:1 binding and a weaker association constant for 2:1 receptor–sugar complex). In both cases, 4•11 and 5•11, the binding constants in CDCl3 were too large to be accurately determined by the NMR spectroscopic method (see Table 3). After the addition

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• experiments are used to quantify the dimerization constants, as well as the association constant values of the 1:1 complexes formed between the receptors and a series of diamides and dipeptides. The receptors show moderate levels of selectivity in the molecular recognition of the hydrogen-bonding pattern

• substrate (ΔΔG01 (fumaramide-succinamide) = −2.46 kcal/mol and ΔΔG02 (fumaramide-succinamide) = −2.79 kcal/mol). When the association constant values obtained for the DAAD hydrogen-bonding pattern are compared, it becomes evident that both cyclic receptors exhibited a marked preference for the diamides in

• temperature show that the variation in chemical shift fits a simple theoretical dimerization model, although higher order aggregation cannot be ruled out. Using 1H NMR titration experiments we have determined the association constant values of the 1:1 complexes formed between receptors 1, 2, 15, and 17 and a

Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state

• Carolin Rether,
• Wilhelm Sicking,
• Roland Boese and
• Carsten Schmuck

Beilstein J. Org. Chem. 2010, 6, No. 3, doi:10.3762/bjoc.6.3

• stability is too large to evaluate with an estimated association constant of Kass> 1010 M−1. Even in water dimerisation still takes place (Kass = 170 M−1) [13]. The stability of the dimer 1·1 is significantly larger than the simple Coulomb-interactions of point charges, suggesting that indeed the formation

An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III) ions

• Markus Albrecht,
• Olga Osetska,
• Thomas Abel,
• Gebhard Haberhauer and
• Eva Ziegler

Beilstein J. Org. Chem. 2009, 5, No. 78, doi:10.3762/bjoc.5.78

• Equation 1. It represents a simple association constant which involves all protonation/deprotonation and metal ion coordination steps. The virtual association constants of the complexation systems were calculated by non-linear-square fitting according to the Benesi–Hildebrand equation from the UV