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

• could not be verified and the anions were assumed to interact with the pyridinearene cavity. Inclusion complexes of anions within pyridinearene dimers were also theoretically studied by DFT calculations, but using a truncated pyridinearene dimer model [8]. However, previous studies have also shown that

• as for [12 + H]+ (384.8 ± 0.41 Å2) and smaller than for the [12 + Na]+ complex, thus indicating inclusion complexation. This clearly indicates that the Me4N+ complex of 12 has the same rotation average diameter as the protonated dimer and thus the cation is encapsulated inside the cavity. Calculated

• ]arene dimer in [12 + PF6]− and the heterodimer [1·2 + PF6]−, but interestingly the abundance of [1·2 + PF6]− was half of [12 + PF6]−, and PF6− complexes with 2 or 22 had even lower abundances. This clearly shows that the anion has a higher affinity to pyridinearene than to resorcinarene. Inclusion

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• switching to the Z isomer was accompanied by the release of one of the two guests from the cage and the formation of a 1:1 cage/Z-arylazopyrazole inclusion complex. DFT calculations suggest that this process involves a dramatic change in the conformation of the cage. Back-isomerization was induced with

• green light and resulted in the initial 1:2 cage/E-arylazopyrazole complex. This back-isomerization reaction also proceeded in the dark, with a rate significantly higher than in the absence of the cage. Keywords: arylazopyrazoles; coordination cages; inclusion complexes; molecular switches

• on the prototypical arylazopyrazole 1 [35] (Scheme 1) and a previously reported [48] metal–organic cage 2 (see Figure 1). We have recently demonstrated that various azobenzenes formed 2:1 inclusion complexes with 2 [49] and hypothesized, based on the structural similarity between azobenzenes and

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB₂-type host–guest-conjugated amphiphilic molecules for controlled drug delivery

• Yang Bai,
• Cai-ping Liu,
• Di Chen,
• Long-hai Zhuo,
• Huai-tian Bu and
• Wei Tian

Beilstein J. Org. Chem. 2019, 15, 1925–1932, doi:10.3762/bjoc.15.188

• utilized as host units to construct these stimuli-responsive supramolecular self-assemblies [21][22][23][24][25][26][27]. For example, β-CD can form inclusion complexes with guests such as azobenzene [28][29], ferrocene [30][31] and benzimidazole [32][33][34] to construct light-, redox-, and pH-responsive

• was adjusted to 5.0, accompanied with morphology transitions from FSSAs to spherical self-assemblies (SSAs) due to the pH-induced dissociation of β-CD/BM inclusion complexes (Scheme 1c,d), and the hydrophilic–hydrophobic interaction-induced formation of spherical micelles with BM units as inner

• to BM protons in D2O was 3.75, which is slightly bigger than that of 3.46 in DMSO-d6 (Figure 2a) due to the shielding effect of host–guest inclusion. The proton peak ratios of 2,4,3,5,6-H protons of β-CD to BM protons in DCl/D2O was 24.96 (Figure 2c), which is bigger than that of the ratio of 3.75 in

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

• chemistry. In the present study we demonstrate that resorcin[4]arene sulfonic acid (RSA) interacts with chiral amines (amino acid derivatives and aminocavitands) to form inclusion complexes and capsules based on electrostatic interactions. The complexes were characterized by circular dichroism and DOSY NMR

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

• ]∞ and [(C6H6)KA']∞ (3.04 Å in the poorer quality [(toluene)KA']∞ structure), and 3.06 Å in [KA'(dme)]∞ [24]. This suggests that the K+…[A'] interaction is a robust one, and its structure potentially capable of serving as a kind of template for inclusion (see below). Formation of the heterometallic allyl

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

• -conjugated polymers [29][30][31]. On the other hand, γ-CD is relatively less employed in the synthesis of mechanically interlocked molecules despite of its ability to form interesting 1:2 inclusion complexes, and there are only few examples of rotaxane and catenane featuring γ-CD as an interlocked macrocycle

• orientation, possibly due to inter-ring interactions with the CB[6], to give the [6]rotaxane as one single stereoisomer. Considering the ability of γ-CD to form stable 1:2 inclusion complexes, these singly threaded [n]rotaxanes could serve as an entry point to other high order interlocked structures by

• by LC–MS. Contrary to most reports on the inclusion of simple aromatic or poly(ethylene glycol) in γ-CD where a 2:1 binding stoichiometry was observed, LC–MS analysis of the reaction mixture containing a 2:1 molar ratio of 1/γ-CD stoppered by 2 showed only the [3]rotaxane 3R (93%, m/z = 798.0, 4

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• hindrance of the mannose and peptide part during the inclusion process of the adamantane [37][39]. It is well known that vaccine adjuvants can enhance or modulate the Th1/Th2-bias of an induced immune response. Interferon-γ (as a Th1 cytokine) and IL-4 (as a Th2 cytokine) induce isotype switching to IgG2a

• for target inhibition of liver metastasis [51]. Therefore, the presented mannosylated desmuramyl peptides with incorporated adamantane will be further explored in order to get a better insight into possible PRR crosstalk. Namely, inclusion of adamantane into carriers such as liposomes can additionally

Host–guest interactions in nor-seco-cucurbit[10]uril: novel guest-dependent molecular recognition and stereoisomerism

• Xiaodong Zhang,
• Wei Wu,
• Zhu Tao and
• Xin-Long Ni

Beilstein J. Org. Chem. 2019, 15, 1705–1711, doi:10.3762/bjoc.15.166

• encapsulation of this moiety. Pyrene group, that are too large for the individual CB[6]–CB[7] sized cavities of ns-CB[10] [23], it is thus believed that the upfield shift of the pyrene protons is attributed the intermolecular π–π stacking between the two pyrenyl moieties as proposed in the plausible inclusion

• and TΔS = −21.66 kJ·mol−1 for inclusion complex G1·host-1; ΔH = −65.77 kJ·mol−1 and TΔS = −26.46 kJ·mol−1 for the inclusion complex G2·host-1; ΔH = −39.01 kJ·mol−1 and TΔS = −1.02 kJ·mol−1 for the inclusion complex G1·host-2); while only the formation of the inclusion complexes of host-2 with G2 is

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

• .15.163 Abstract Cyclodextrins (CDs) are native host systems with inherent ability to form inclusion complexes with various molecular entities, mostly hydrophobic substances. Host cyclodextrins are accommodative to water molecules as well and contain water in the native state. For β-cyclodextrin (β-CD

• ; hydration; macrocycles; thermodynamic characteristics; Introduction Cyclodextrins (CDs), a family of enzymatically modified starches, are widely used as host macrocycles in forming inclusion complexes with various molecular entities of interest to food industry, pharmacology, cosmetics, catalysis, and

• process of water inclusion into β-CD is energetically favorable. Both experiments and theory agree that up to ten water molecules can be accommodated internally by the β-CD host. The first incoming water molecules cluster around the narrow belt due to the higher electron density concentrated in this

Mechanochemistry II

• José G. Hernández

Beilstein J. Org. Chem. 2019, 15, 1521–1522, doi:10.3762/bjoc.15.154

• strategy for the future of chemical synthesis. In fact, the potential of mechanochemistry in various domains of research, industry and in commercial entities has been recently recognized by the IUPAC after the inclusion of mechanochemistry among the ten chemical innovations that will change our world [2

Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

• Andrea Rodil,
• Alexandra M. Z. Slawin,
• Nawaf Al-Maharik,
• Ren Tomita and
• David O’Hagan

Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

• ether 3 as shown in Figure 2. Therefore, there is potential for the inclusion of this motif in candidate molecules without a significant increase in log P. Having explored synthetic routes and log P evaluations, we now report our initial studies on the metabolism of the ArSCF2CH3 substituent. In this

Efficiency Eff_syn of complex syntheses as multicomponent reactions, its algorithm and calculations based on concrete criteria

• Heiner Eckert

Beilstein J. Org. Chem. 2019, 15, 1425–1433, doi:10.3762/bjoc.15.142

• reactions results in the precise value yoa. The algorithm is broad in scope and can be used in many ways as required through the introduction of constants in the variables c1, c2 and invariable C. This permits the inclusion of soft criteria, such as suitable resources, time (see discussion above) and

Reversible end-to-end assembly of selectively functionalized gold nanorods by light-responsive arylazopyrazole–cyclodextrin interaction

• Maximilian Niehues,
• Patricia Tegeder and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2019, 15, 1407–1415, doi:10.3762/bjoc.15.140

• azobenzenes that form inclusion complexes with α- or β-CD exclusively in the trans configuration, not in the cis configuration [26]. This light-responsive interaction has been recently applied by Ma et al. for the end-to-end assembly of AuNR [27]. However, the system showed some limitations as the assembly

• photophysical properties like nearly quantitative isomerization, straight forward synthesis in excellent yields and very long Z-isomer half-life times up to 1000 days due to less steric repulsion [37]. In previous reports we could show that the AAP guest inclusion properties to β-CD are comparable to

• increase the solubility of CTAB and destabilize its double layer. Furthermore, ethanol weakens the hydrophobic effect of the solvent so that the inclusion of CTAB into β-CD is suppressed. The ligand exchange was followed by ζ-potential measurements giving direct information about the surface charge

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• inclusion of Ru(bpy)3 into the hydrophobic cavity of SC8A led to a considerable luminescence enhancement [64]. That is, the photophysical behavior of Ru(II) complexes is rather complicated upon either covalently linking or non-covalently binding with calixarenes. In our present case, the GC5A–Ru(dcbpy)3

• employed (Table 1), indicating its privileged ability to form stable inclusion complexes with a variety of guest molecules. As for Fl, EY, RB, TPPS, AlPcS4 and TPS, a drastic complexation-induced fluorescence quenching without wavelength shifting was observed, which was assumed as the PET mechanism. 2,6

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter

• Indrajit Paul,
• Debabrata Samanta,
• Sudhakar Gaikwad and
• Michael Schmittel

Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137

• -component rectangle [Cu4(1)2(2)2]4+ and the four-component sandwich complex [Cu2(1)(2)(4)]2+ is triggered by inclusion and release of DABCO (4). The fully reversible and clean switching between two multicomponent supramolecular architectures can be monitored by fluorescence changes at the zinc porphyrin

• porphyrin edge capsules to cone-shaped inclusion complexes depending on the presence of C60/C70, however, a process that was not selective for one of the guests [24]. A spectacular case of guest sensing, but not guest-induced recognition, was demonstrated by Clever in a supramolecular cage-to-cage

• , the emission wavelength changes by addition of DABCO. Figure 3c nicely illustrates the shift of the emission band from λ = 602 → 618 nm (λexc = 557 nm) for the conversion of complex 5 → 6 illustrating that DABCO inclusion into the porphyrinic sandwich entails a shift of 16 nm. Finally, a single set of

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• are Xe inclusion complexes that are of special interest as they help to establish laser-polarized 129Xe NMR spectroscopy for the imaging in biological systems [22][23][24][25]. For the formation of Xe cryptophane complexes, cryptophane-1.1.1 has proven to be a very suitable host as it still shows the

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks

• Sebastian Hamer,
• Fynn Röhricht,
• Marius Jakoby,
• Ian A. Howard,
• Xianghui Zhang,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1331–1338, doi:10.3762/bjoc.15.132

• ., on surfaces and in materials. Different strategies have been employed to prepare ordered arrays of rotors in two dimensions, such as the inclusion of rotors in channels on the surface of particular crystals [3] on metal surfaces [4][5][6] or in Langmuir–Blodgett films [7]. Several strategies have

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

• calixarenes (with the same repeating units). The sulfur functionalities are stated to provide better metal complexation [3]. Unmodified calixarenes and thiacalixarenes are sparingly soluble, have chemical and thermal stability and act as host molecules as they possess cavities, but their inclusion properties

• medicine. The binding affinities and thermodynamics of p-sulfonato-calix[4]arene upon complexation with different inorganic and organic cations in water have been investigated experimentally by Bonal et al. [30] and Morel et al. [31]. The experiments indicated 1:1 stoichiometry of the inclusion complexes

• anchoring points for the positively charged guests. Cation–π interactions between the monoatomic cations and p-sulfonatocalix[4]arene in water are supposed (but not proven) to take part in the inclusion complex formation [31]. Mendes et al. have carried out molecular dynamics (MD) simulations of association

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

• Ana M. Belenguer,
• Adam A. L. Michalchuk,
• Giulio I. Lampronti and
• Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

• of mixing, these effects are considerably smaller. For such an effect to dominate in the present case, one must assume that no reaction takes place until ideal mixing is achieved, which is unrealistic. Indeed, the inclusion of a mixing term does not affect the onset time for reaction. However, it was

• found that the inclusion of a mixing term does lead to ‘shaping’ of the accumulation profile. Such effects appear necessary to capture the kinetic profile of the lower frequency kinetic curves. This suggests that, while onset time is dependent on frequency and input energy, the mixing (mass transport

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

• the inclusion of the base led to crystallization of the corresponding products 3a–c during the milling process. In contrast, crystallization during the base-free reaction required an ex situ aging step. Figure 1 shows the XRPD pattern of the substrate 2 and the product 3a. Due to the liquid state of

• treatment for a few minutes, before transforming abruptly (over a period of 90 seconds) to the t3a phase. Having observed the inclusion of catalyst into the final product phase (see Figure 3), we suggest this change in polymorphic behavior to result from a templating phenomenon, which dominates at higher

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

• constant was found to be K = 70 ± 15 M−1 which is in good correlation with the published data [22]. These results prompted us to identify the optimal Ba2+ concentration, necessary for a maximum degree of dye–Ba2+ inclusion complex formation. Obviously for a better complexation it is necessary to work with

• reactions. Real-time E/Z-photoisomerization of dyes 4a–d and their complexes The photoisomerization of free dyes 4a–d and dye–Ba2+ inclusion complexes were investigated in real time mode upon irradiation with visible light (λ = 488 nm) close to their absorption maxima. Figure 3a illustrates the

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• engineering [6], energy storage [7], biosensors [8], catalysis [9], and environmental engineering [10]. Various supramolecular host molecules such as cyclodextrins (CDs), calix[n]arenes, and pillar[n]arenes can form host–guest inclusion complexes (ICs) with numerous compounds due to their unique cavity

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• chloride (2), and 1,4-diiodooctafluorobutane and accompanying small solvent guests (methanol, acetonitrile and water) are presented. The guests’ inclusion affects the geometry of the cavity of the receptors 1 and 2, while the divalent halogen bond donor 1,4-diiodooctafluorobutane determines the overall

• guest inclusion in solution. Keywords: capsule; dimeric assemblies; halogen bonding; host–guest chemistry; resorcinarene salts; X-ray crystallography; Introduction The construction of specific supramolecular assemblies based on the directional non-covalent bonding has been a central goal of

• arising from solvent mixtures could be useful in probing the solvation interactions in solution. In the current study, we examine the role of the inclusion guest in determining the final XB structures. Instead of adding 1,4-dioxane as a guest, we use methanol and acetonitrile as both solvent and as

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• paraformaldehyde (Scheme 31a). Subsequently, it was observed that varying the amine component (C-protected amino acids) allowed the obtention of exocyclic elements of diversity as observed in macrocycles 162a and b (Scheme 31b). The process allows the increase of the peptide sequence as well as the inclusion of

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• . Fitting the experimental data of 4 and 7 led to very similar values, namely J = +21.79 cm–1, g = 2.17, D = |3.64| cm–1 and J = +21.70 cm–1, g = 2.22 and D = |4.67| cm–1, respectively. In each case the low-temperature fit was significantly improved by the inclusion of the D parameter, but as stated above