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

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• three synthetic strategies that have been developed to create and strengthen cooperativity, i.e., (i) incorporation of a hydrogen-bonded network; (ii) incorporation of π-stacking moieties; and (iii) coordination of bridging ligands. The thermal ST behavior is commonly expressed in terms of the molar

• with single-crystal structure studies one can unravel the structures of existing networks of hydrogen bonding or specific orderings of π-stacking. Although they are not a prerequisite for thermal ST to take place, such features take part or at least aid in the cooperative interactions involved in the

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

Regioselective synthesis of 7,8-dihydroimidazo[5,1-c][1,2,4]triazine-3,6(2H,4H)-dione derivatives: A new drug-like heterocyclic scaffold

• Nikolay T. Tzvetkov,
• Harald Euler and
• Christa E. Müller

Beilstein J. Org. Chem. 2012, 8, 1584–1593, doi:10.3762/bjoc.8.181

• possibly central nervous system), structural novelty, synthetic accessibility, and the possibility for broad structural variations. In particular, we planned to introduce sp3-hybridized carbon atoms, to avoid completely flat aromatic structures that are prone to low solubility in water due to π-stacking

The crystal structure of the Dess–Martin periodinane

• Albert Schröckeneder,
• Desiree Stichnoth,
• Peter Mayer and
• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 1523–1527, doi:10.3762/bjoc.8.172

• , however, no π-stacking interactions. Least-square planes of the four oxygen atoms bound covalently to iodine are nearly parallel to the c-axis (deviation angle 0.79(4)°). Conclusion In conclusion, we have determined the solid-state structure of the Dess–Martin periodinane (1), a popular reagent in organic

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

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• the glycosyl donor and acceptor, as was previously anticipated. Rather, in addition to these factors, interactions (π-stacking) of the protecting groups in close proximity to, as well as distant from, the reaction centers play an important role in determining the stereoselectivity of intramolecular

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

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• studies this fused heterocycle was found to be more metabolically stable compared to earlier leads that contained a simple piperazine ring. Furthermore, the triazolopiperazine is not only involved in a tight H-bond network within the active site of DPP-IV, but also in π-stacking with the aromatic ring of

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• class of small molecules that can form reversible supramolecular gels in organic solvents or aqueous solutions [1][2][3][4][5][6][7][8][9]. Non-covalent interactions such as hydrogen bonding, hydrophobic interactions, and π–π stacking are the main driving forces for the self-assembly of the gelators

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• amphiphilic tetraalkylammonium derivative that exhibits three different benzene-containing concave sites to which an organic substrate may associate by attractive van der Waals interactions or π-stacking. Moreover, additional functionalities, e.g., hydroxy or amino groups, may be attached to the benzene rings

• of the semibullvalene structure to enable additional hydrogen bonding with the substrate. Also, the benzene rings may be further annelated with additional aromatic units to increase the potential π-stacking area [13]. Most notably, dibenzosemibullvalenes are chiral compounds, so that the propensity

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• were studied. In non-polar solvents such as cyclohexane, this quaterthiophene π-system formed fibril aggregates with an H-type molecular arrangement due to synergistic effect of hydrogen bonding and π-stacking. The self-assembled fibres were found to gelate numerous organic solvents of diverse polarity

• -type aggregate to monomeric building blocks at elevated temperature. The self-assembly of T1 at such low concentrations can be attributed to the synergistic effect of π-π-stacking among the oligothiophene chromophores and intermolecular hydrogen bonding between the amide groups of the neighbouring

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• motif for materials applications. For example, benzyl and thienyl annelated TTF derivatives and analogues have been shown to perform well as semiconductor materials in organic field effect transistors (OFETs) [21][22]. This has been attributed to the enhanced π–π stacking of the extended aromatic groups

Differences between β-Ala and Gly-Gly in the design of amino acids-based hydrogels

• Andreea Pasc,
• Firmin Obounou Akong,
• Sedat Cosgun and
• Christine Gérardin

Beilstein J. Org. Chem. 2010, 6, 973–977, doi:10.3762/bjoc.6.109

• properties were related to hydrogen bonding, hydrophobic interactions and π-π stacking. Herein, β-Ala-His-EO2-Alk was fully characterised by FT-IR, NMR, SAXS and SEM and the gelation mechanism is discussed. It appears that the number of amide groups determines the self-assembling behaviour into 1D or 2D/3D

• as electrostatic, hydrogen bonding, dipole–dipole, π–π stacking and hydrophobic/van der Waals interactions. Since the cross-links between fibres are non-covalent in nature, LMWHs exhibit thermoreversibility, rapid response to external stimuli (i.e., stirring, sonication). Among these LMWHs, amino

• hydrophilic and hydrophobic modules, as well as the number of H-donor and H-acceptor centers, or π–π stacking. Therefore the appropriate balance between all these factors must be determined. As a part of the ongoing research carried out in our laboratory on the self-assembled systems of amino acids-based

Pyridinium based amphiphilic hydrogelators as potential antibacterial agents

• Sayanti Brahmachari,
• Sisir Debnath,
• Sounak Dutta and
• Prasanta Kumar Das

Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101

• hydrophobic interactions is mandatory for any gelation process. Non-covalent interactions such as hydrogen bonding, ionic interactions, π–π stacking or van der Waals forces play a pivotal role in self-assembled gelation [12]. Tuning the structure of gelator molecules leads to a better understanding of the

• gelation. The planar aromatic moiety favors π–π stacking interactions between the molecules and leads to the formation of 3D networks of viscoelastic gels [25][26][27]. Interestingly, among all these aromatic rings, the positively charged pyridine (pyridinium) unit is well known to impart antibacterial

• pyridinium moieties in order to exploit its favorable π–π stacking interaction towards self-assembled gelation as well as an ability to kill bacteria. Furthermore, a very simple method of synthesizing such amphiphilic antibacterial hydrogelators with pyridinium units would definitely boost its importance and

Chiral gels derived from secondary ammonium salts of (1R,3S)-(+)-camphoric acid

• Tapas Kumar Adalder,
• N. N. Adarsh,
• Ravish Sankolli and
• Parthasarathi Dastidar

Beilstein J. Org. Chem. 2010, 6, 848–858, doi:10.3762/bjoc.6.100

• can be of two kinds – chemical or polymeric and physical or supramolecular. While covalent bonds are responsible for the formation of 3-D networks in chemical gels, various non-covalent interactions such as hydrogen bonding, π-π stacking, hydrophobic, van der Waals forces etc. are required to form gel

• sustained by weak π-π stacking interactions (3.926 Å) involving the phenyl groups of the neighboring 2-D sheets (Figure 6). Crystals of DCHADC 1 was grown from m-xylene. It was crystallized in the non-centrosymmetric monoclinic space group P21. The C–O distance of the carboxylic acid moieties are 1.226(10

Organic gelators and hydrogelators

• Jean-Pierre Desvergne

Beilstein J. Org. Chem. 2010, 6, 846–847, doi:10.3762/bjoc.6.99

• liquid) which behaves as a visco-elastic material (soft matter) due to the immobilization of solvent molecules in a three-dimensional network. This network results from the self-assembly of the gelling agent into fibres via non-covalent interactions such as hydrogen bonding, π–π stacking, van der Waals

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• lengths and angles for the crystal structures can be found in the supporting information. All structures show the expected bond length and angles. The packing diagrams reveal space filling packing without any π-stacking between the molecules. Polymerizations Since the goal of this research was the

En route to photoaffinity labeling of the bacterial lectin FimH

• Thisbe K. Lindhorst,
• Michaela Märten,
• Andreas Fuchs and
• Stefan D. Knight

Beilstein J. Org. Chem. 2010, 6, 810–822, doi:10.3762/bjoc.6.91

• residues Tyr48 and Tyr137 (‘tyrosine gate’) that can form favorable interactions with appropriate mannosidic aglycone moieties, such as π-π-stacking with the phenyl group of benzyl mannosides [14]. In a preceding work, we synthesized the three corresponding photoactive α-D-mannosides, 1, 2, and 3 (Figure

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• compounds tend to associate via π–π-stacking, and b) radical additions to alkynes usually proceed with significantly lower relative rates (30–50%) than those to the corresponding alkenes [7]. Taking these findings and the observed regioselectivity of the cycloaddition into consideration, the maximum

9,10-Dioxa-1,2-diaza-anthracene derivatives from tetrafluoropyridazine

• Graham Pattison,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2010, 6, No. 45, doi:10.3762/bjoc.6.45

• , parallel to the [101] direction and π···π stacking interactions (shortest interatomic distance C5···C3 is 3.336 Å), and short C–H···O contacts (C···O 3.387 Å) bind adjacent chains in the [100] and [010] directions, respectively. Again, the regiospecificity of these reaction processes occurs because of the