Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• capsules were originally assumed to encapsulate anionic guests inside their cavity due to the π-acidic character of the aromatic walls [7][8]. Mattey et al. detected 1:1 complex formation with PF6− and BF4− by mass spectrometry, however, without ion mobility mass spectrometry, the location of the anion

• the π-acidic character of pyridine rings, such as 2-oxo-6-oxypyridine, is rather weak [9][10]. Thus, pyridine[4]arenes may be expected to show a dual binding behavior towards anions and cations [8]. In addition to anion complexes also 2:1 complex formation with neutral carboxylic acids and amides have

• studies with ESI-Q-TOF mass spectrometry. Complex formation was tested with the following series of cationic guests: MeNH3+, Me2NH2+, Me3NH+, Me4N+, EtNH3+, Et2NH2+, Et4N+ and Pr4N+, which were used as the corresponding Cl− or Br− salts. None of the cations MeNH3+, Me2NH2+, Me3NH+, EtNH3+, Et2NH2+ or Pr4N

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• chemistry. Different hydrogen bond donors such as pyrrole N–H and benzene C–H along with the triazolium C5–H have been successfully incorporated within a single macrocyclic framework. The complex formation of anions with the hydrogen bond donors varied according to the polarity of the solvent. It was found

Complexation of chiral amines by resorcin[4]arene sulfonic acids in polar media – circular dichroism and diffusion studies of chirality transfer and solvent dependence

• Bartosz Setner and
• Agnieszka Szumna

Beilstein J. Org. Chem. 2019, 15, 1913–1924, doi:10.3762/bjoc.15.187

• chiral multidentate amino compounds (Figure 1) in polar media (DMSO, methanol, aqueous media). RSA 1 features a hydrophobic cavity and a polar rim of sulfonic acid groups capable of forming electrostatic interactions. We will put a particular emphasis on ordering during complex formation that is

• quantitative. The kinetics of complex formation is fast on the NMR timescale. The complexes exhibit a high degree of ordering that is manifested by chirality transfer observed by diastereotopic splitting (Figure 6c, inset). In this case CD spectra are not diagnostic (CD bands are observed already for chiral

• disintegrates and the observed D is a result of a dynamic exchange between the complex 1(R)-2 with free components 1 and (R)-2. The addition of an extra portion of 1 to 1(R)-2 shifts the chemical equilibrium towards complex formation. Thus, in the mixture [1 + 1(R)-2]DMSO the component (R)-2 is fully consumed

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• intramolecular hydrogen bonding with the ionophore [7][8] is shown in Scheme 1. The complex formation ejects the tautomeric proton and stabilizes the keto tautomer. Several successful tautomeric ligands, based on 4-(phenyldiazenyl)naphthalen-1-ol (1) [8] (2 and 3, Scheme 2) as a tautomeric unit have been

• bonding between the tautomeric OH group and the carbonyl group in the ionophore part. The complex formation, depending on the size and charge of the metal ion, should shift the tautomeric equilibrium towards the keto tautomer and should provide stabilization of the complex. To the best of our knowledge

• complex and the deprotonated ligand, shown in Figure 4, indicates that the complex formation is not related to deprotonation. These results coincide with the results obtained for compound 3 [15]. The complexation abilities of 6 towards some alkaline-earth metal ions were studied and the obtained spectra

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• interactions, evidently help to drive the heterometallic complex formation. Conclusion Formally, halide metathesis as a synthetic technique depends strongly on the relative thermodynamic stabilities of the starting and final metal halide salts, M'X and MX. Practically, however, the reaction solvent is also a

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• further interlocking at the γ-CD. Results and Discussion Building block design and rotaxane synthesis To encourage complex formation with γ-CD, axle 1 was designed with a biphenylene core to bind to the macrocycle through hydrophobic effect. The axle is terminated by 2-aminoethyl azide for CB[6]-mediated

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• structures possessing less elaborate hydrogen bond networks (compare ΔH1/ΔH78 for reaction 2 with those of reactions 1 and 3 in Table 1). Generally, increasing the polarity of the medium (higher dielectric constant) attenuates the energies of complex formation although the enthalpies remain negative. Adding

• , observed earlier for α-CD hydration, hold for β-CD as well: the hot spot of the host molecule with the highest affinity for water molecule(s) is the narrow rim. Interestingly, the α-CD–H2O and β-CD–H2O complex formation is characterized by very close ΔH78 values (−2.6 and −2.8 kcal mol−1, respectively

• complex formation, ∆Hε, in condensed medium (water, Equation 2): Basis set superposition errors (BSSE) were considered by following the counterpoise approach of Boys and Bernardi as implemented in Gaussian 09 package. The PyMOL software was used for creating the molecular graphics images [24]. M062X/6-31G

A heteroditopic macrocycle as organocatalytic nanoreactor for pyrroloacridinone synthesis in water

• Piyali Sarkar,
• Sayan Sarkar and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2019, 15, 1505–1514, doi:10.3762/bjoc.15.152

• supramolecular assemblies like molecular rotors (pseudorotaxane, rotaxane, catenane), molecular switches, molecular shuttles, etc. [32][33][34][35][36][37][38][39][40][41][42][43]. Furthermore, macrocycles have been applied in the area of ion–ion pair recognition and heterometallic complex formation [44][45][46

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• oxygen of the P=O group. The comparison of 1H, 13C, and 31P NMR spectra of starting 1a and its complex with AlCl3 13 is presented in Figure 3 (see full spectral data in Supporting Information File 1). It is clear that the complex formation led to significant broadening of NMR spectral lines and, mainly

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• especially useful when the crystalline complex formation with the guest is undesirable. The aggregation properties, by the ready-to-associate secondary rim, are considerably affected by these substituents. One of the most important reactions of CDs occurs with oxiranes (epoxides) under basic conditions to

• seen in Figure 2 and Figure 3. Although scaled-up β-CDP has somehow larger particles, complexation studies with methyl orange (MO) only showed small differences. Although complex formation with MO showed similar behaviour to previous reports [13], adsorption capacity seems to be considerably lower than

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• between biological receptors and small ions. The complex formation behavior of water-soluble p-sulfonatocalix[4]arene and thiacalix[4]arene and group IA, IIA and f-block metal cations has been investigated computationally by means of density functional theory computations in the gas phase and in aqueous

• environment. The calculated Gibbs free energy values of the complex formation reaction of these ligands with the bare metal cations suggest a spontaneous and energy-favorable process for all metal cations in the gas phase and only for Na+, Mg2+, Lu3+ cations in water environment. For one of the studied

• formation reactions. Keywords: complex formation; DFT; group IA; IIA and f-block metal cations; macrocycles; p-sulfonatocalix[4]arene; p-sulfonatothiacalix[4]arene; Introduction If macrocycles are pillars of the supramolecular chemistry, then calixarenes (“calix” = vase + “arene”) are the 3rd pillar after

Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• triclinic product. Inclusion of catalyst in the final product, as evidenced by mass spectrometric analysis, suggests this complex polymorphic pathway may be due to seeding effects. Multivariate analysis for the in situ Raman spectra supports this complex formation pathway, and offers a new approach to

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• with the ligand L1 at two different metal-to-ligand ratios (1:1 and 3:2). We also carried out the complexation of bare palladium(II) with the ligand L1 at two different metal-to-ligand ratios (1:2 and 3:4). The complexation reactions performed in DMSO-d6 allowed the monitoring of complex formation and

• to form (e.g., from 4a and L1) and prone to decomposition. As far as trinuclear complex formation is concerned the central pyridine ring of L1 is in a relatively favorable situation, thus the complex 4a could form and 3a was a kinetic product. Conclusion A set of mononuclear and trinuclear complexes

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• chromoionophore and the spectra in Figure 1 were assigned to the formation of the trans-dye–Ba2+ complex [19]. For all dye solutions, a distinct isosbestic point upon titration was observed, indicating only one kind of complex formation even at the highest Ba2+ concentration. To determine the optimal Ba2

• , which is true for the simplest form of complexation [18]: where A0 and A∞ are the absorptions of the chromoionophore at zero and infinite concentration of the metal ion, respectively; A is the absorption at the concentration cM of the metal ion; K is the stability constant of complex formation, and L

• and LM are the ligand and the metal ion complex, respectively. A∞ and K were found by approximation of Equation 1. The stability constant for the complex formation was estimated to be K = 100 ± 15 M−1, 49.4 ± 7.6 M−1 and 44.7 ± 10 M−1 for dyes 4b, 4c and 4d, respectively. For dye 4a the stability

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• similar way to that described in Scheme 3. In this case, the coupled alkyne moiety is again activated by Cu(I) and then base-promoted cyclization occurs. A new copper complex formation with the alkene analogue to 13 (see Scheme 3) facilitates the aromatic nucleophilic substitution by indole or pyrrole

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• salen-type ligand followed by metal-complex formation in the same pot [55]. Otera’s solvent-free approach by which the formation of self-assembled supramolecules could be accelerated [56]. Synthesis of a Pd-based metalla-supramolecular assembly through mechanochemical activation for C–H-bond activation

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• near various carbon atoms in the main polymer chain. Apart from this, the intensity of the bending vibrations of carboxyl groups at 1700 cm−1 and of ether groups at 1030–1080 cm−1 increases as well. Results and Discussion Study of the complex formation between Cp2TiCl2 and AlEt2Cl It is known that the

• only at Ti/Al ratios above 1:1, therefore, the ratio of Ti/Al equal to 1:1.5 was further used. During this complex formation, generation of cyclopentadiene (CPD) trimers, resulting from the interaction between the cyclopentadiene ring of bis(cyclopentadienyl)titanium dichloride and dicyclopentadiene

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• form γ-CD–C60 complexes. Our electrospinning system employs a highly volatile solvent, HFIP. We initially examined γ-CD–C60 complex formation in HFIP. C60 (16 mg/mL, pre-ground by an agate mortar) was added into 15 w/v % γ-CD/HFIP and kept under sonication for a few days. After removing the residual

• –36 h (Figure 2b and Figure S1 in Supporting Information File 1). Although complex formation occurs without sonication, the color of the obtained solution was fairly weak (data not shown). Shortening of the time to reach equilibrium in the γ-CD–C60 inclusion complex formation was reported by

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• to interact with the crucial residues in the basic ridge which are known to be essential for the in vitro complex formation of ExoI with SSB [73], a finding that supports the low IC50 value exhibited by this molecule. Remarkably, these four compounds were also able to disrupt the complex formation of

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• complexes π-electron-rich aromatic compounds such as dihydroxynaphthalenes or dihydroxybenzenes. The π-donor TTF (1) also forms a 1:1 complex 13 with this host molecule as shown in solution experiments and by crystallography. The complex formation is immediately visible by an emergent green color of these

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• linkers. In addition, each amide moiety, upon deprotonation (a requirement for complex formation), would provide a formal negative charge on the ligand, thus resulting in increased complex stability while reducing the number of spectator anions associated with the two metals. Different combinations of

• ligand with three nitrogen donor atoms per metal center. Ligand 16-H2 was found to undergo complex formation with various copper, zinc, palladium and nickel salts. Figure 3 shows the X-ray crystal structure of 16·Ni2(OAc)2, obtained from ligand 16-H2 and two equivalents of nickel(ΙΙ) acetate. The

• obtained, preliminary experiments have shown that ligand 22-H2 undergoes complex formation with various nickel and palladium salts [58]. Pyrazole-bridged bisoxazoline ligands. The synthesis of an analog of bisoxazoline ligand 16-H2 in which the naphthyridine bridge is replaced with a pyrazole linker is

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• complex formation was calculated as a difference between free energy of calix[4]arene + ADP/ATP complex and isolated calix[4]arene and ADP/ATP dianion. The complex structures corresponding to the minimum energy as well as supramolecular binding motif of ADP and ATP are presented in Figure 4. As can be

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• -dipyrromethene (BODIPY) dyes as a new class of fluorophores for the design of reporter dyes for supramolecular host–guest complex formation with cucurbit[7]uril (CB7). The BODIPYs contain a protonatable aniline nitrogen in the meso-position of the BODIPY chromophore, which was functionalized with known binding

• too slow to equilibrate during the titration within reasonable time (Figure S19, Supporting Information File 1). The pKa values of the host–dye complex were independently determined by pH titrations in presence of excess CB7 and analysed assuming quantitative complex formation (Figure 4). Overall, the

• complex formation of the BODIPY core, the photostability of the dyes was not affected by CB7 complex formation (Figure S20, Supporting Information File 1). The compatibility of BODIPYs with common excitation sources and filter sets also enables their use in fluorescence microscopy. To demonstrate, we have

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• other pillar[5]arenes [17][20], and were assigned as the proton signals from the methylene protons of the 1,4-dicyanobutane in the cavity of pillar[5]arene 3. The complex formation of 3 and 1,4-dicyanobutane indicates the displacement of the alkyl chain ring from the inside to the outside of the cavity

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• preferred to the one where the oxazoline ring formation occurs first (the barriers of the ring closure are consistently higher than those of the aryl transfers). It is also interesting to note that in some cases the initial complex formation is the rate determining step along the aryl-transfer path although

• in most cases the differences in the two barrier heights are very small. The full set of reactions also shows that the aryl transfer as the first step after the complex formation with the catalyst is preferred over the route where the ring closure precedes the aryl transfer. Only three cases from the