Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• columnar arrays [17]. In this type of array the host molecules which are in 1,3-alternate conformations align in a “head-to-tail” fashion with the C60 molecules able to be accommodated within the opposite clefts. Furthermore, within such an arrangement, in addition to the “face-to-face” π–π interactions

Synthesis of a water-soluble 2,2′-biphen[4]arene and its efficient complexation and sensitive fluorescence enhancement towards palmatine and berberine

• Xiayang Huang,
• Xinghua Zhang,
• Tianxin Qian,
• Junwei Ma,
• Lei Cui and
• Chunju Li

Beilstein J. Org. Chem. 2018, 14, 2236–2241, doi:10.3762/bjoc.14.198

• , respectively. π···π interactions, hydrophobic interactions and electrostatic attractions should play important roles in the association process. Although having similar structures, these two guests gave very different association constants. The substitution of 1,3-dioxole for two methoxy groups in P, affording

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

• Ana-Maria Preda,
• Małgorzata Krasowska,
• Lydia Wrobel,
• Philipp Kitschke,
• Phil C. Andrews,
• Jonathan G. MacLellan,
• Lutz Mertens,
• Marcus Korb,
• Tobias Rüffer,
• Heinrich Lang,
• Alexander A. Auer and
• Michael Mehring

Beilstein J. Org. Chem. 2018, 14, 2125–2145, doi:10.3762/bjoc.14.187

• is built up via C–HPh···π intermolecular contacts of T-shape. Noteworthy, polymorph 2a showed bismuth···π and π···π interactions leading to 1D ribbons in the solid state, while 2b did not reveal Bi···π interactions. Thus, it is concluded that Bi···π, π···π and C–H···π interactions must be of similar

• contribute to the overall dispersion from π···π interactions. In case of polymorph 1c the results of the quantification of the interaction energies reveal that this structure is actually not dominated by Bi···π arene interaction, but rather consists of dimers connected by strong π···π interaction (Figure 16

• , 1c-2-1 with −64 kJ mol−1) which are connected by two weaker Bi···π arene contacts (Figure 16, 1c-1-1, −47 kJ mol−1). Figure 17 shows the comparison of the distortion and the interaction energies of Bi···π arene and π stacking dimers. As for BiPh3, Bi···π arene and π···π interactions are of comparable

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• addition, the biphenyl portion of 2+ hosted inside the calix cavity was involved in π···π interactions with the aromatic walls (Figures S11–S13, Supporting Information File 1) and C–H···π interactions with the tert-butyl groups of the calixarene wheel (Figure S13, Supporting Information File 1

A self-assembled photoresponsive gel consisting of chiral nanofibers

• Lei Zou,
• Dan Han,
• Zhiyi Yuan,
• Dongdong Chang and
• Xiang Ma

Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174

• -isomers of azobenzene can stack with each other via π–π interactions. Further, the acylamino group of the glutamic acid moiety at the center of the molecule also promotes this aggregation through hydrogen bonding interactions. Finally, the chirality of glutamic acid may be magnified along with the

Diazirine-functionalized mannosides for photoaffinity labeling: trouble with FimH

• Femke Beiroth,
• Tomas Koudelka,
• Thorsten Overath,
• Stefan D. Knight,
• Andreas Tholey and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1890–1900, doi:10.3762/bjoc.14.163

• binding site, undergoing interactions with the protein surface, which add to affinity. Especially CH–π or π–π interactions of a sugar ligand with the side chains of Y48 and Y137, called the “tyrosine gate” [19][20], are known to considerably increase the affinity of a specific mannoside for FimH

Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

• Rakesh Puttreddy,
• Ngong Kodiah Beyeh,
• S. Maryamdokht Taimoory,
• Daniel Meister,
• John F. Trant and
• Kari Rissanen

Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146

• receptor renders the receptor slightly electron deficient further facilitating π–π interactions. With the larger N-oxide guests 10–12, though the shift changes of the guest are not strong enough to conclusively indicate endo complexation, clear changes in the hydroxy groups suggest interaction via hydrogen

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• structures may provide an explanation for their surprising binding behaviors. Multiple non-covalent interactions, including C–H···O hydrogen bonds, cation···π, C–H···π and π···π interactions, are involved in all the cases. Undoubtedly, cation···π interactions between the core quaternary ammonium ions of the

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• and shape of the guest. It is worth noting that CaNS4 shows better sequestration abilities than CaNS2 towards 6 and 8. This may be justified admitting that the presence of the aromatic linker unit favors the interaction with the aromatic dye, due to the occurrence of effective π···π interactions with

• is confirmed to depend on a fine balance between different factors, namely Coulomb and π···π interactions, and steric effects. The importance of a compromise between these factors for the complexation into calixresorcinarenes has been recently assessed [42]. Moreover, in analogy with the bahavior

• sequestering agents towards model pollutants such as p-nitroaniline derivatives and dyes. Our results indicate that the absorption equilibrium is affected by a combination of hydrophobic effects, Coulomb and π…π interactions, as a function of the molecular size and shape. Moreover, significant pH-dependent

Steric “attraction”: not by dispersion alone

• Ganna Gryn’ova and
• Clémence Corminboeuf

Beilstein J. Org. Chem. 2018, 14, 1482–1490, doi:10.3762/bjoc.14.125

• interaction distances. In the present work, we have performed a direct comparison between the sp2 and sp3-rich hydrocarbons and quantified the ECpen term of their intermolecular interactions. The electrostatic effects are, not surprisingly, important in systems with strong π–π interactions. Our results

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

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

• structure of the complex is similar to the DEHF∙ATP complex. However, an additional π-stacking interaction is formed between the adenine and the uracil groups creating a so-called “double-sandwich” structure. In the other case, the π–π interactions vanish and the complex is stabilized through the base-pair

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• wanted to use the aromatic ring system previously developed by Roth et al. [39] as a nucleobase analogue to furnish greater π–π interactions with the natural bases and possibly also to increased hydrophobic effects. A new strategy for the preparation of tC analogues was used, starting from 5-iodo or 5

Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• interactions, π–π interactions, desolvation effects and entropy-unfavorable conformational dynamic restraints. Polarimetry is confirmed as a very useful and versatile tool for the investigation of supramolecular interactions with chiral hosts, even in complex systems involving multiple equilibria. Keywords

• outlines an important role assumed by π–π interactions. In fact, the small aromatic imidazolium cation 5 is appreciably included into CAP−2, although with a relatively small binding constant (K = 250 ± 20 M−1; ΔΘ = −14.6 ± 0.4 deg dm−1 M−1). It is interesting to notice that significant affinity towards CAP

• −2 is also shown by neutral nitroaniline derivatives 8 and 10, providing further confirmation that π–π interactions play an important role. Nevertheless, it is also worth noting here that the importance of electrostatic effects has been already outlined by Schneider and Schneider [32], who examined

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• distance is 3.437(4) Å. Consequently, π–π interactions must be considered for this structure [51][52]. Bond lengths and angles of the reported crystal structures 4b, 5, and 6 are in the expected range. The tricyclic 1H-benzo[f]isoindole-1,3(2H)-dionyl moiety in 4b, 5 and the corresponding 3-imino-1-oxo-2,3

• 5 (left) and a centrosymmetric dimer formation by π–π interactions (right) (ellipsoids are drawn at the 40% probability level). The ORTEP-type plot of the asymmetric unit of the crystal structure 6 (top) and π-stacking interactions (bottom) (ellipsoids are drawn at the 40% probability level

Mechanochemical Knoevenagel condensation investigated in situ

• Sebastian Haferkamp,
• Franziska Fischer,
• Werner Kraus and
• Franziska Emmerling

Beilstein J. Org. Chem. 2017, 13, 2010–2014, doi:10.3762/bjoc.13.197

• interactions such as hydrogen bonds, halogen bonds, and π∙∙∙π interactions [16][17][18][19]. For example, Toda et al. reported yields of 97% for Aldol condensations in the absence of any solvents [20]. Kaupp et al. described the first Knoevenagel condensation in a ball mill [21]. Compared to conventional

Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

• Spyros D. Chatziefthimiou,
• Mario Inclán,
• Petros Giastas,
• Athanasios Papakyriakou,
• Konstantina Yannakopoulou and
• Irene M. Mavridis

Beilstein J. Org. Chem. 2017, 13, 1572–1582, doi:10.3762/bjoc.13.157

• to the secondary hydroxy level, apparently in order to optimize the π···π interactions between the indole planes (Figure 2 and Figure 3, Table 1). The above suggest a tight fit of the guest inside the cavity. On the other hand, the aliphatic part of NAcTrp, positioned in the space between dimers

• stability of the complex (a) no strong π···π interactions at 3.5 Å can be established in the middle of the β-CD dimer as in L-NAcTrp (Figure 5); (b) the aliphatic moieties of β-CD–L-NAcPhe protruding from the primary sides between dimers do not interact directly or even indirectly via β-CD hydroxy groups

Correlation of surface pressure and hue of planarizable push–pull chromophores at the air/water interface

• Frederik Neuhaus,
• Fabio Zobi,
• Gerald Brezesinski,
• Marta Dal Molin,
• Stefan Matile and
• Andreas Zumbuehl

Beilstein J. Org. Chem. 2017, 13, 1099–1105, doi:10.3762/bjoc.13.109

• this same condensed phase for the remainder of the experiments. During the first compression, the film organized obviously into a condensed phase. Upon decompression, the monolayer remains in this condensed state due to strong π–π interactions. The following compression cycles reach the exact same

• Å2 is obtained, that mirrors the area per molecule at low surface pressure found in the Langmuir–Pockels experiments. The transition into the densely packed film due to strong π–π interactions around 15 mN/m leads to the smaller area per molecule. Grazing incidence X-ray diffraction (GIXD) The

• ordering phenomenon during the first compression can be explained by π–π interactions between the flipper mechanophores. We therefore characterized the degree of membrane ordering using synchrotron grazing incidence X-ray diffraction. The GIXD data in Supporting Information File 1 shows the absence of any

Interactions between shape-persistent macromolecules as probed by AFM

• Johanna Blass,
• Jessica Brunke,
• Franziska Emmerich,
• Cédric Przybylski,
• Vasil M. Garamus,
• Artem Feoktystov,
• Roland Bennewitz,
• Gerhard Wenz and
• Marcel Albrecht

Beilstein J. Org. Chem. 2017, 13, 938–951, doi:10.3762/bjoc.13.95

• polyconjugated polymers ranged from 6 to 16 nm, depending on the side groups and the method of determination [9][10][11]. Among many supramolecular interactions, such as hydrogen bonding, π–π-interactions or hydrophobic host–guest interactions [12][13][14][15][16], the interactions of cyclodextrins (CDs) with

Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines

• Adrian E. Ion,
• Liliana Cristian,
• Mariana Voicescu,
• Masroor Bangesh,
• Augustin M. Madalan,
• Daniela Bala,
• Constantin Mihailciuc and
• Simona Nica

Beilstein J. Org. Chem. 2016, 12, 1812–1825, doi:10.3762/bjoc.12.171

• terpyridine fragments are involved in π–π interactions (3.56–3.66 Å). The separation between the neighboring azulenyl moieties is higher than 3.85 Å. Photophysical properties The photophysical properties of the azulene-containing terpyridines, 4a and 4b have been investigated by absorption and emission

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

• Valeria Corne,
• Ariel M. Sarotti,
• Carmen Ramirez de Arellano,
• Rolando A. Spanevello and
• Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

• additional effort to understand the extent to which the π–π interactions affect the conformational equilibriums of a system, we next explored the M06-2X/6-31+G(d) PES of acrylate 6d bearing a methoxymethyl group at the benzylic position of the molecule (Figure 5). With the lack of stabilizing π-stacking

Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• interactions. Further edge-to-face H···π [44] and π–π interactions [45][46] (Table 4) between molecules from neighboring layers contribute to the three-dimensional crystal packing (Figure S6 in Supporting Information File 1). Conclusion Several indenopyrone derivatives were synthesized and characterized by NMR

• derivatives 2a–d and 3''b measured in acetonitrile and methylene chloride at rt. Absorption and emission data for dihydroindenopyrone derivatives 2'a–d, 2''b–d and 3''b. Intermolecular H···π and π–π interactions in the crystal of 6a. Supporting Information Supporting Information File 62: Experimental

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

• complicated process and besides the host–guest interaction other additional intermolecular interactions may also take place. Due to the numerous hydroxy groups present in the studied molecules these secondary interactions most probably are the hydrogen-bond interactions between the CD units, or the π–π

• interactions of the cinnamyl moieties. The sum of all these possible interactions results in the large supramolecular aggregates observed by DLS. Effect of competitive additives on the aggregation behavior: DLS and ROESY experiments In order to demonstrate that in the case of the Cin-α-CD the main force which

Synthesis and photophysical characteristics of polyfluorene polyrotaxanes

• Aurica Farcas,
• Giulia Tregnago,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert and
• Franco Cacialli

Beilstein J. Org. Chem. 2015, 11, 2677–2688, doi:10.3762/bjoc.11.288

• synthesis of 1·TM-βCD or 1·TM-γCD in polar protic solvents is driven by hydrophobic interactions in combination with electrostatic, van der Waals or π–π interactions. In comparison, in polar aprotic solvents such as DMF, THF relies mostly on host–guest specific interactions, such as dispersion or dipole

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• from the adjacent strings along [100] take part in π···π interactions, also forming molecular dimers (Figure 7). The shortest C···C distances are C7–C15 and C5–C9 (3.367(2) Å, and 3.410(2) Å, respectively). The presence of π–π-bonded aggregates in the crystal structure of 3a is in line with the