Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• the phthalimidyl anion within the chiral pocket of the phosphate catalyst to form complex 55, before enantioselective addition to the iminium ion affords product 56. NHPI esters can also engage in π–π interactions with electron-rich species to generate charge-transfer complexes that can absorb light

Electron-beam-promoted fullerene dimerization in nanotubes: insights from DFT computations

• Laura Abella,
• Gerard Novell-Leruth,
• Josep M. Ricart,
• Josep M. Poblet and
• Antonio Rodríguez-Fortea

Beilstein J. Org. Chem. 2024, 20, 92–100, doi:10.3762/bjoc.20.10

• Computational methods). This significant amount of energy, which could be overestimated, comes from the π–π interactions between the C60 surface and the CNT wall and is modelled in a first approximation using Grimme’s corrections to the dispersion energy [16]. This interaction energy is comparable to those in

• similar systems with π–π interactions, as for example a “buckyball catcher” complex with C60 or the interlayer interaction between graphene sheets [16]. It is found to be significantly smaller than for C60@C240 [17], but larger than for C60@C540 and C60@C960 nanoonions [18]. The encapsulation energy of

• % of the total encapsulation energy. As a consequence of the effective π−π interactions, the larger the contact between the fullerene dimer surface and the CNT wall the larger the encapsulation energy. This significant interaction is also apparent from an inspection of the electronic structure of the

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• compound 29 is perpendicular with respect to the herringbone pattern and the related structures (see Figure 10, bottom). Compound 25 packs with an intramolecular distance of 3.41 Å between the planes of the π-systems. Neither compound 26 nor 29 shows π–π interactions in the crystal packing. The large

• bulkiness of the TIPS groups along with the tert-butyl groups in compound 26 prevent these interactions, while for compound 29, the lack of π–π interactions can be ascribed to the methylene bridges as the hydrogens along with the tert-butyl groups prevent good overlap of the π-systems. Table 3 lists the

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• (Figure 2) were designed to be obtained from precursors containing two 1,4-dioxobenzene fragments required to facilitate π–π interactions with the pyridine unit in the axle (compound 6 in Scheme 1) and confer stability to the supramolecular complex necessary for the formation of [2]rotaxanes. For the

Charge carrier transport in perylene-based and pyrene-based columnar liquid crystals

• Alessandro L. Alves,
• Simone V. Bernardino,
• Carlos H. Stadtlober,
• Edivandro Girotto,
• Giliandro Farias,
• Rodney M. do Nascimento,
• Sergio F. Curcio,
• Thiago Cazati,
• Marta E. R. Dotto,
• Juliana Eccher,
• Leonardo N. Furini,
• Hugo Gallardo,
• Harald Bock and
• Ivan H. Bechtold

Beilstein J. Org. Chem. 2023, 19, 1755–1765, doi:10.3762/bjoc.19.128

• from strong π–π interactions [7][21][22][23][24]. In this work, we investigated a perylene and a pyrene-based columnar liquid crystal in hole-only and electron-only devices to compare their charge carriying properties. The molecular organization and photophysical performances are coherent with the

• solution, the 6.90 ns lifetime in the film is attributed to monomeric emission. The shortest lifetime of 0.90 ns can be related to the emission of aggregated species driven by π–π interactions [36], contributing to almost 20% of the total emission of 1. The longer lifetime of 2 in film (3.84 ns) can be

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• supramolecular organization of the N-acylhydrazones was also studied through their Hirshfeld surfaces, in which π–π interactions play an important role. When the normalized distance between a molecule and the closest neighbors are plotted (Figures S2A and S2C, and S3A and S3C in Supporting Information File 1

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• the reaction partners in a highly ordered three dimensional transition state through noncovalent interactions (like H-bonding, π–π interactions) thus promoting the stereoselective reaction. Examples of covalent bonding organocatalysts are amines [6][7], N-heterocyclic carbenes [8][9], phosphines [10

• with π–π interactions between the catalyst’s aryl group and the aryl substituent at the nitrogen in the aniline 59 (Scheme 16a) [43]. Recently, Fan and co-workers reported a chiral phosphoric acid P20-assisted enantioselective aza-Friedel–Crafts reaction between α-naphthols 17 and isatin-derived

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• ]. Excimers are formed when pyrene moieties form supramolecular complexes by intermolecular or intramolecular π–π interactions, causing a significant shift of single pyrene bands to longer wavelengths. Pyrenes are often used as a sensor part of receptor molecules, so their excimer bands switch on/off to

• applications [9]. These compounds have a very large aromatic surface suitable to form self-assembled supramolecular structures by intermolecular π–π interactions and showed excimer fluorescence in thin film and in the solid state. Kawai et al. reported exciplex formation between pyrene and guanine in polar

• representative geometries that account for most of the population of each system are presented in Figure 2. The results showed that both conjugates, irrespective of their protonation state, prefer stacked conformations, with favorable π–π interactions among aromatic fragments. Interestingly, this also holds even

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• intermolecular π–π interactions between the fluorophores leading to delocalization of excitons or excimers in the solid state would be responsible for the bathochromic shifts of λmax,abs and λmax,fl and lowering of Φfl with change of state from solution to solid [34][35][36]. The τfl-solid values of OTK-2 and

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• to poor solubility as a consequence of strong π–π interactions between the planar molecules [4]. Thus, attaching solubilising alkyl chains is necessary [5]. A common way to further decrease the HOMO–LUMO gap is attaching electron-donating and electron-accepting groups. Electron-rich units raise the

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• quenched due to aggregation-caused quenching (ACQ) [10]. Generally, the restriction of intermolecular π–π interactions in highly planar compounds plays a key role in aggregate structures exhibiting fluorescence [5][6][10]. In addition, intramolecular mechanisms, such as intramolecular rotation (RIR

• ΦH2O/ΦEtOH values of 0.07 and 0.12, respectively, which were 7.0 and 15 times higher than those in ethanol (non-aggregated form). Because compounds 4a–e form an A–D–A system, charge disproportionation may affect intermolecular π–π interactions and lead to AIEE. The enhanced fluorescence was almost

• completely quenched by the addition of an 0.1 M HCl solution to solutions of compounds 4a and 4e (Figure 3). This result indicated that the protonation of the secondary amine disrupted the intermolecular π–π interactions or planarity of compounds 4 (Figure 4), and the rigid structure in solution was involved

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• ][36][37][38], anion templates [39][40], ammonium crown ether templates [41], and templates based on π–π interactions [42]. In 2004, Sauvage and co-workers have used a Cu(I)-based passive metal template approach to synthesize a [2]catenane containing an optically pure BINOL unit in each macrocycle [43

• supramolecular template strategies that have been developed in the past decades, including passive metal templates, active metal templates, anion templates, ammonium crown ether templates, and templates based on π–π interactions. This has opened the way for the application of the resulting chiral MIMs. The

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• stereoselectivity. Moreover, the chiral phosphoric acid group attains a bifunctional role by activating both partners via hydrogen bonds, and the chiral backbone of the catalyst controls the stereoselectivity through steric effects and π–π interactions. Moreover, Li and co-workers recently developed CPA-catalyzed

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• of Photonic Technology (IPHT), e. V. Jena, Albert-Einstein-Straße 9, 07745 Jena, Germany 10.3762/bjoc.17.166 Abstract The self-healing behavior of two supramolecular polymers based on π–π-interactions featuring different polymer backbones is presented. For this purpose, these polymers were

• behavior was also quantified in detail using an indenter. Keywords: characterization of polymers; π–π-interactions; self-healing polymers; supramolecular polymers; Introduction Damage inflicted on different materials is omnipresent. Consequently, nature established a mechanism dealing with this problem

• previous studies, several of these interactions were already applied such as metal–ligand interactions [13][14], hydrogen bonds [15][16] or halogen bonds [17]. Furthermore, π–π interactions also feature a reversible behavior and were therefore utilized for the design of different self-healing polymers [18

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• , but also to cation–H or π–π interactions. Some of the advantages of multidentate, supramolecular anion-binding catalysis were recently exploited by the Feringa group, who designed an anion-binding catalyst 86 that fuses the known triazole binding properties with a light-switchable molecular motor. In

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• such as β-lactoglobulin, lysozyme or crystallins is based on a complex interplay of various attractive forces such as hydrogen bonding, electrostatic as well as π–π interactions and hydrophobic effects [302][304][305] Several studies show that in the

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• substituents. Previously we have shown for a simpler model system that the PSA correlates with the interaction of the molecules, in particular, the dye–dye electrostatic repulsion [31]. Hence, the lower the PSA the better the dye molecules can interact with each other through π–π interactions. Comparing the

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• photocatalytic reaction with a rate acceleration facilitated by supramolecular host–guest interactions and hybrid materials are typically assisted by noncovalent forces, including Coulomb and van der Waals forces, hydrogen bonding, and π–π interactions. For potential supramolecular photocatalysts, they should

• of two different crown ether-substituted molecules, styrylbenzothiazole and cinnamic acid [18]. In this system, the Ba2+ cation can preorganize the two crown ether-substituted molecules into a supramolecular complex (Figure 2), which was further stabilized by hydrogen bonding and π–π interactions

Control over size, shape, and photonics of self-assembled organic nanocrystals

• Chen Shahar,
• Yaron Tidhar,
• Yunmin Jung,
• Haim Weissman,
• Sidney R. Cohen,
• Ronit Bitton,
• Iddo Pinkas,
• Gilad Haran and
• Boris Rybtchinski

Beilstein J. Org. Chem. 2021, 17, 42–51, doi:10.3762/bjoc.17.5

• ]. We have reported on 2D crystalline self-assembled systems based on a hierarchical assembly mode promoted by hydrophobic and π–π interactions [36]. Yet, the size and shape of these systems could not be controlled beyond the 2D morphology. We report herein on the aqueous self-assembly of organic

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• completed by the close contacts between carbonyl oxygen atoms (of the urea group) and S atoms (of DMSO), indicating possible chalcogen interactions [47][48], and the C=O···S=O distances were 3.269 and 3.308 Å (Figure 3a). The molecular packing was further strengthened by the π–π interactions of the p

• -acetylphenylalaninate. Design of chiral calix[4]arene-based receptors for anions. X-ray structure of 4a: (a) Top view into the cavity. (b) Side view of the same cavity. X-ray structure of 7a: (a) Hydrogen bonding interactions (black) in a dimeric motif, chalcogen interactions are shown in green. (b) π–π interactions in

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• parallel (see Figure 2B), the centroid distance between the rings reaches up to 4.985 Å, suggesting that the intermolecular π–π interactions are absent. In addition to these interactions, there also exist weak supramolecular N–H interactions. Firstly, two Me units form dimeric structures that are connected

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• -8 (DBC8, Figure 1), which bind through noncovalent interactions. In detail, these interactions are strong hydrogen bonds between ether oxygen atoms and ammonium protons. In addition, weaker C–H···O hydrogen bonds with the CH2 groups adjacent to the ammonium nitrogen as well as π–π-interactions

• , maximized π–π-interactions with the axle because of the 84° torsional angle between the resorcinol and the NDI unit. Consequently, the complexation of NDIC8 is less enthalpically favored than that of TTFC8. However, the more rigid structure of NDIC8 also leads to a lower degree of conformational fixation in

• the pseudorotaxane of NDIC8, and thus to a more favorable binding entropy compared to the pseudorotaxane of TTFC8. For TTFC8, the increased binding enthalpy can be explained by additional π–π-interactions between the naphthalene and TTF unit of the crown ether and the ammonium axle, resulting in a

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• hydrophobic effect and to host–guest π–π interactions. Hydrophobic surface simulations showed that TBTQ-(OG)6 and C60 forms an amphiphilic supramolecular host–guest complex, which further assembles to microspheres with diameters of 0.3–3.5 μm, as determined by scanning electron microscopy. Keywords

• -membered rings of C60 were calculated to be 3.541 and 3.702 Å, respectively. These results suggest significant host–guest π–π interactions between TBTQ-(OG)6 and C60 [57]. In order to intuitively assess the hydrophilicity and hydrophobicity of the complex, the hydrophobic surface diagram was generated and

• the host–guest complexes is primarily due to hydrophobic effects and π–π interactions. The TBTQ-(OG)6 C60 complex was found to further assemble to microspheres with diameters of 0.3–3.5 μm. The inclusion complexation between TBTQ-(OG)6 and fullerenes in aqueous solution may shed light on potential

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• secondary structures, which lead to nanostructured materials [16][17]. Noncovalent interactions, such as hydrogen bonding, van der Waals interactions, hydrophobic interactions, electrostatic interactions, and π–π interactions [18][19][20][21][22] are common driving forces in peptide self-assembly. These