Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• partially due to the fact that the π–π-stacking of pyridines [50] was a competing interaction. The most probable rupture force, used in the KBE model, was due to the coordination complexes. Methods using the whole data set are strongly influenced by the stacking interaction and would have needed heavily

First principle investigation of the linker length effects on the thermodynamics of divalent pseudorotaxanes

• Andreas J. Achazi,
• Doreen Mollenhauer and
• Beate Paulus

Beilstein J. Org. Chem. 2015, 11, 687–692, doi:10.3762/bjoc.11.78

• first principle calculations show clearly that this enhanced binding is due to electronic effects, namely the dispersion interaction of the two linkers. For the shortest linker this interaction results in a nearly ideal π–π stacking. For the two longer linkers ideal packing is not possible due to steric

• dispersive interaction of the linking unit (two phenyl rings and the linker), which in case of the n0 guest fits perfectly on top of the anthracene linker of the DiC8 host. The distance between the linker of the host and the linker of the n0 guest is around 3.7 Å, quite close to an ideal distance for the π–π

• stacking of two benzene rings. The n1 and n2 guest do not perfectly fit with the host (Figure 2). In the n1-case the linker is folded away from the anthracene bridge, and for the n2-case one phenyl ring is twisted away due to steric constraints. The Gibbs energy of association ΔG in the gas phase of the

Synthesis and characterization of pH responsive D-glucosamine based molecular gelators

• Navneet Goyal,
• Hari P. R. Mangunuru,
• Bargav Parikh,
• Sonu Shrestha and
• Guijun Wang

Beilstein J. Org. Chem. 2014, 10, 3111–3121, doi:10.3762/bjoc.10.328

• referred to as supramolecular gelators or molecular gelators. They can form reversible gels in organic solvents, aqueous mixtures, and water. The gelation process is completely driven by weak intermolecular forces such as hydrogen bonding, π–π stacking, hydrophobic forces, and van der Waals forces. The

A one-pot multistep cyclization yielding thiadiazoloimidazole derivatives

• Debabrata Samanta,
• Anup Rana,
• Jan W. Bats and
• Michael Schmittel

Beilstein J. Org. Chem. 2014, 10, 2989–2996, doi:10.3762/bjoc.10.317

• by multiple π–π stacking (slighly displaced) at a distance of 3.36−3.40 Å (Figure 1c) while the iminophenyl groups are connected by weak intermolecular C(phenyl)-H···π(phenyl) contacts. Moreover, Figure 1a shows that the structure is planar except for the phenyl ring attached to the N4 atom (C2–N4–C5

• –C6 = 49.0°). The phenyl ring attached to the N3 atom is nearly coplanar (C1–N3–C3–C4 = 2.5°) with the thiadiazole ring allowing additional delocalization. This coplanar arrangement might help for intercalation into biological molecules using e.g., π–π stacking, C–H···π or ion–dipole interactions

• –π stacking. To take the solvent into consideration, the thermochemical analyses were performed in dichloromethane using the COSMO model with gas phase optimized geometries. Originally, DMAP should be hydrogen bonded to both amide protons in complex 8 increasing the nucleophilicity of both N-centers

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• organic field-effect transistors [24][25]. The DPP-based conjugated polymers usually show good electron and hole mobility and promising PCE values in OPVs due to large intermolecular interactions through π–π stacking. Nguyen et al. have investigated the DPP core in small molecules for OPVs with excellent

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• stacked dimers within the DNA minor groove similar to the crystal structure of close analogue (Figure 4, right). Conversely, the AP5 and AP6 aliphatic linkers are long enough to allow self-folding and easy intramolecular π–π stacking of adenine with DBTAA (Figure 4, upper right). During the binding event

• left – note the stacking of DBTAA and adenine) and AP3 (lower left – note the short linker which does not allow for the stacking of DBTAA and adenine); (right) detail of three molecules packing in crystal by π–π stacking of parallel DBTAA rings with a distance of ca. 3 Å (see [13] and Figure 8 therein

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• chain, due to poor solvency of styrene in CO2. It was anticipated that π–π stacking between phenyl groups is a main contributor to the viscosity increase, through its provision of a fundamental intermolecular force needed to raise viscosity in a system. The optimum composition of polymers for viscosity

Influence of perylenediimide–pyrene supramolecular interactions on the stability of DNA-based hybrids: Importance of electrostatic complementarity

• Christian B. Winiger,
• Simon M. Langenegger,
• Oleg Khorev and
• Robert Häner

Beilstein J. Org. Chem. 2014, 10, 1589–1595, doi:10.3762/bjoc.10.164

• Christian B. Winiger Simon M. Langenegger Oleg Khorev Robert Haner Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland 10.3762/bjoc.10.164 Abstract Aromatic π–π stacking interactions are ubiquitous in nature, medicinal chemistry and materials

• interaction indicating the importance of electrostatic complementarity for aromatic π–π stacking interactions. Keywords: DNA; hybridization; nucleic acids; perylenediimide; pyrene; Introduction When two aromatic molecules are in close proximity they often have a tendency to interact non-covalently in a face

• -to-face stacking arrangement. Face-centered, parallel aromatic π–π stacking interactions have been studied and reviewed in great detail [1][2][3][4][5]. These interactions are especially important for polycyclic aromatic hydrocarbons (PAHs) [6][7]. The interaction is the result of solvophobicity, as

Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA₂DNA triplexes

• Alex Manicardi,
• Lucia Guidi,
• Alice Ghidini and
• Roberto Corradini

Beilstein J. Org. Chem. 2014, 10, 1495–1503, doi:10.3762/bjoc.10.154

• induced by steric factors; moreover the large aromatic portion introduced with the pyrene ring can interact with the flanking bases of the strand through π–π stacking interactions, thus stabilizing the complex formed. For the evaluation of the sum of all this effects we measured the melting temperatures

Homochiral BINOL-based macrocycles with π-electron-rich, electron-withdrawing or extended spacing units as receptors for C₆₀

• Marco Caricato,
• Silvia Díez González,
• Idoia Arandia Ariño and
• Dario Pasini

Beilstein J. Org. Chem. 2014, 10, 1308–1316, doi:10.3762/bjoc.10.132

• complexes in solution give insights into the role of nonspecific host–guest interactions (such as π–π stacking) for the overall stabilization of the complexes. We are currently designing binaphthyl-based hosts for the enantioselective recognition and separation of higher fullerenes and chiral nanotubes

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• disordered water molecules were omitted for clarity) and the intra- and intermolecular π–π-stacking interactions between an inversion symmetry related pair (right, hydrogen atoms were omitted for clarity). Cyclic voltammogram of dyad 8c (recorded in CH2Cl2, T = 298 K, c (8c) = 0.1 mol·L−1, Pt working

Columnar/herringbone dual crystal packing of pyrenylsumanene and its photophysical properties

• Binod Babu Shrestha,
• Shuhei Higashibayashi and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2014, 10, 841–847, doi:10.3762/bjoc.10.80

• unidirectional columnar structures based on π–π stacking while the pyrene moieties generate herringbone structures due to CH–π interactions. The absorption and emission maxima of pyrenylsumanene were both red-shifted relative to those of sumanene and pyrene, owing to the extension of π-conjugation. Monomer

• distance of 3.0 Å (Figure 1f). The π–π stacking of pyrene moieties, however, is not evident in the arrangement. The UV–vis absorption and emission spectra and maxima as well as the quantum yields of 1, 3 and pyrene in CH2Cl2 or in the solid state are summarized in Figure 3 and Table 1. The absorption

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

• Jun Hu,
• Jindan Wu,
• Qian Wang and
• Yong Ju

Beilstein J. Org. Chem. 2013, 9, 2877–2885, doi:10.3762/bjoc.9.324

• driving forces for the formation of such self-assembled fibrillar networks include hydrogen-bonding interaction, van der Waals force, π–π stacking, and donor–acceptor interaction [7][8][9][10]. Since LMWGs are often thermally reversible and the gelation can be triggered by pH or the addition of small

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• . This result can be attributed to relatively efficient π–π stacking [48] The most stable syn-HH dimeric aggregate forms the most stable, and therefore, most abundant complex within the γ-CD cavity and consequently the main photo-product. Hence, the photodimerization of COU within host 2 is a

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• , electrochemistry, light-harvesting materials and so on [1][2][3][4][5][6]. These small molecules self-assemble into regular supramolecular structures through non covalent interactions such as ion–ion, dipole–dipole, hydrogen bonding, π–π stacking, van der Waals, host–guest, and ion coordination, and in so doing

• , including the additional intermolecular contacts from the pending moieties linked at C-3 (usually hydrogen bond and π–π stacking), lead to a primarily one-dimensional long-range growth and finally produce the interconnected 3D self-assembled fibrillar network (SAFIN), which traps the solvent and turns into

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• such as fullerene fragments [4] and liquid-crystalline compounds [5]. Positions C5, C10 and C15 can be functionalised with a range of substituents, commonly saturated alkyl chains, which can enhance the solubility and processability as well as reduce intermolecular π–π stacking [6], but there are also

Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains

• Rohan J. Kumar,
• Jegadesan Subbiah and
• Andrew B. Holmes

Beilstein J. Org. Chem. 2013, 9, 1102–1110, doi:10.3762/bjoc.9.122

• . The final scenario considered here is that the hydrogen-bonding-mediated interaction is immediately followed by a kinetically faster second supramolecular interaction, leading to the observation by 1H NMR of only the rate-limiting first step. π–π stacking interactions are observed for planar aromatic

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• differs from many other docked FimH ligands. Here, the higher affinity for the open-gate FimH can be explained by strong π–π stacking of the first aromatic ring of the azobenzene unit with the tyrosine gate. As both isomers of 2 interact equally well with FimH, they can’t be used to switch type 1 fimbriae

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• conditions in comparison to reactions carried out in solvent could be attributed to lower molecular motion due to increased hydrogen bonding between aldehyde and amidic NH, and more effective π–π-stacking interaction between the phenyl ring of the catalyst and aldehyde. The methyl ester of (S)-proline-(S

• large surface area of the lipophilic residue of the tryptophan, reinforced by the hydrophobic environment created by the addition of water, appears to be responsible for the improvement in diastereoselectivity. These factors also enhance the π–π stacking between the catalyst and aldehyde to form a more

Synthetic glycopeptides and glycoproteins with applications in biological research

• Ulrika Westerlind

Beilstein J. Org. Chem. 2012, 8, 804–818, doi:10.3762/bjoc.8.90

• tyrosine residues form the “tyrosine gate” [134]. By π–π stacking interactions with the aromatic tyrosine residues, monovalent α-mannose ligands containing hydrophobic aglycons, have shown increased binding affinities [128][135][136]. Employing multivalent ligands, the binding affinity to FimH could be

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

• ]. Noncovalent hydrogen bonding, electrostatic interactions, π–π stacking and metal coordination have been used alone and in concert to assemble a broad range of building blocks, from small molecules [4][5][6][7] to polymers [8][9] including dendrimers [10][11]. Among these noncovalent interactions, hydrogen

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• in the space group P21/c (No. 14). The bond distances of O(3)–C and O(1)–C were 1.241(4) Å and 1.228(4) Å, respectively. These correspond to the values of the C=O double bonds. In the crystal packing, molecule layers were formed due to very weak π–π stacking of the aromatic rings (Figure 4

Double N-arylation reaction of polyhalogenated 4,4’-bipyridines. Expedious synthesis of functionalized 2,7-diazacarbazoles

• Mohamed Abboud,
• Emmanuel Aubert and
• Victor Mamane

Beilstein J. Org. Chem. 2012, 8, 253–258, doi:10.3762/bjoc.8.26

• diffraction and show π–π stacking involving the diazacarbazole moieties and the phenyl rings of functionalized groups. Keywords: 4,4’-bipyridine; cross-coupling; crystal packing; diazacarbazole; X-ray diffraction; Introduction Only a few examples of the preparation of diazacarbazoles have been reported [1

• crystal structure, it contributes to the cohesion of the molecular columns through C–H···π hydrogen bonds (H···π = 2.83 Å) (Figure 2a). However, in 12c the methylsulfanylphenyl groups are implied in the π–π stacking (interplanar distances of 3.261 Å and 3.549 Å). Such neighboring molecular columns

• use of the palladium-catalyzed double N-arylation of electron-rich anilines as the key reaction, the diazacarbazoles were regioselectively generated. Crystal structure determination shows that these molecules interact mainly through π–π stacking. The reported synthesis should widen the use of

Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

• Vadim A. Soloshonok and
• Donna J. Nelson

Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85

• with Ar* on Se in a π – π-stacking stabilization [33][34], is reported to give the major product. This produces asymmetric induction favoring the (S)-isomer in the reaction of 2 with the analogous phenyl substituted alkenols 4 (R2 = Ph, R3 = –(CH2)n–OH, n = 2 or 3) [33][34], as shown in Scheme 2 and

• with 4-phenyl-3-buten-1-ol (Scheme 2, Table 4, n = 2) gives product 6 with 84% de in 92% yield. When R = Et, the diastereoselectivity and yield decrease to 34% and 73% respectively. The higher level of asymmetric induction and yield in the case of R = Ph has been attributed to a stabilizing π–π

• stacking of alkene and electrophile substituents [33][34]. Results for 1 and 2 (n = 3) in Table 4 also, in general, follow this pattern. In the reactions of 1 or 2 with alkenols 4 (n = 3) (Scheme 2), the stabilizing effects of phenyl at the developing positive charge at the adjacent carbon are considered