Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• through hydrogen bonding and metal ion coordination in nonpolar solvents [66][67][68]. Compared with NDI, PDI has more aromatic rings to generate stronger intermolecular π−π stacking, leading to molecular aggregates more easily, and these aggregates or supramolecular assemblies can give rise to desirable

• in the above-tested five solvent systems were also recorded. Because of the relatively weaker π–π stacking effect of the NDI units comparing with PDI units, 2 has a better solubility in the organic solvents. Consequently, the UV–vis absorption bands of 2 in all the organic solvents can be clearly

• were investigated. As shown in Figure 2a, micelle-like assemblies of 1 were observed, while, because of the higher polarity of MeCN, the aggregation of 1 through π–π stacking was considerably enhanced forming linear assemblies (Figure 2b). Interestingly, when imposed to an aqueous medium through adding

Efficient synthesis of pyrazolopyridines containing a chromane backbone through domino reaction

• Razieh Navari,
• Saeed Balalaie,
• Saber Mehrparvar,
• Fatemeh Darvish,
• Frank Rominger,
• Fatima Hamdan and
• Sattar Mirzaie

Beilstein J. Org. Chem. 2019, 15, 874–880, doi:10.3762/bjoc.15.85

• of the product (Figure 2). Meanwhile, via hydrogen bridges and the solvent molecules (water and ethanol) the molecules build pairs with π–π stacking of the aromatic systems. To examine the scope and generality of our reaction, other (arylhydrazono)methyl-4H-chromen-4-ones were synthesized and their

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

• lengths reveal no anomalies and are similar to those in [Zn2L(μ-OAc)]+. There are no π–π stacking interactions between the azobenzene moieties. However, the [Zn2L(μ-azo-OH)]+ and [Zn2L(μ-azo-O)] complexes are connected by a OH···O hydrogen bond of length 2.46 Å (O3a···O3b, not shown in Figure 4). [Zn2L(μ

• , respectively. These values compare well with those in 3' and other [Zn2L(μ-carboxylato)]+ complexes. The [Zn2L(μ-azo-NMe2)]+ complexes in 5 assemble in pairs (Figure 5) most likely via π···π stacking interactions, as manifested by the distance of 3.34 Å between the planes through the azobenzene moieties. [Cd2L

• radius of Cd2+. The Cd···Cd distance is at 3.399 Å. Virtually the same values are observed in [Cd2L(μ-OAc)]+ [10]. As in 5 π–π stacking of the azo-carboxylato co-ligands occurs (Figure 7). The shortest distance between two carbon atoms of adjacent benzene rings is at 3.41 Å. [Ni2L(μ-Azo-NMe2)]ClO4·xEtOH

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• functionalized compounds are rare [19][20][21][22][23]. In contrary to azobenzenes, diazocines 1 are stable in their cis configuration. The bent cis isomer is less prone to π–π stacking which is known to reduce the switching efficiency (Figure 1a) [19][24]. The reverse stability of the cis and trans isomers in

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

• Grimme [54] and Iverson et al. [55] on the unreflected use of terms such as C–H···π, or π···π stacking previously. In most cases, these interactions rely on London dispersion forces rather than special types of bonding due to the π system. Crystal structures In all of the presented compounds, the

Functionalization of graphene: does the organic chemistry matter?

• Artur Kasprzak,
• Agnieszka Zuchowska and
• Magdalena Poplawska

Beilstein J. Org. Chem. 2018, 14, 2018–2026, doi:10.3762/bjoc.14.177

• , was assigned to the stretching vibrations of the alkyl chain (commonly observed at up to 2980 cm−1); this absorption band corresponds to the N–H stretching vibrations of NH3+. The further reaction with amphotericin B, which is a compound containing unsaturated bonds, was most plausibly a result of π–π

• stacking. As mentioned above in the discussion of reaction mechanisms, water molecules significantly lower the reaction rates for the desired nucleophiles. Importantly, water molecules also influence the hydrolysis of the activated carboxyl groups (Figure 2, step d and Figure 3, step f). Water should

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

• by three-dimensional networks through self-assembly have drawn significant attention in the past decades. They are normally fabricated by means of noncovalent intermolecular interactions [3], such as π–π stacking, hydrogen bonding, van der Waals forces, hydrophobic, electrostatic, host–guest and

• construct optically controlled systems [17][30][32][33][34][35]. This moiety is also frequently employed as a building block because of its strong π–π stacking in nonpolar solvents. Herein, a novel compound 3 containing both chiral L-glutamic lipid and azobenzene was designed and synthesized (Scheme 1). It

• and π–π stacking in DMSO. However, beautiful acicular fibers could be detected on the surface treated with a chloroform solution, and a dendritic network was observed on the sample made from benzene solution (Figure S9, Supporting Information File 1). The photoresponsiveness of compound 3 was also

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

• cages [10]. Intermolecular interactions in hydrocarbons are also subject to significant dispersion contribution. In the unsaturated systems, from benzene dimer to higher acenes and, ultimately, graphenes, dispersion is increasingly the key force behind the π–π stacking interactions [11]. Large and flat

• electrostatic contribution to it [25]. For example, “dispersion dominates and electrostatics commands” is the ‘punch line’ of the 2017 computational study on the σ–σ, σ–π and π–π stacking interactions between benzene, cyclohexane and some of their fluorinated derivatives [26]. The authors show that while

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

• including formation of metallophilic d8···d8 interactions and/or π–π stacking of the coordinating ligands [67][92] as well as excited-state interactions such as formation of excimers [93][94]. Although they may be usefully employed to shift both absorption and emission spectra

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

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

• optimized geometries are presented in Figure 2. The investigation of the DEHF∙ATP 1:1 complex revealed a sandwich structure, which is held together by a π–π stacking- and an H-bond interaction. The triphosphate group is positioned near ring C of the DEHF and the π-stacking occurs between the adenine group

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• luminance of 100 cd/m2, slightly red-shifted compared to the emission observed for doped OLEDs. Clearly, the specific design of D6 and its highly twisted structure efficiently weakened the π–π-stacking interactions, providing a general design rule for the elaboration of TADF emitters insensitive to the

Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives

• Leonid S. Kikot',
• Catherine Yu. Kulygina,
• Alexander Yu. Lyapunov,
• Svetlana V. Shishkina,
• Roman I. Zubatyuk,
• Tatiana Yu. Bogaschenko and
• Tatiana I. Kirichenko

Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203

• π–π stacking and C–H∙∙∙X (X = N, O, F ...) interactions. The stability of inclusion complexes based on molecular clips and paraquat derivatives depends on two factors: 1) the value of the positive charge on the dipyridinium fragment of paraquat derivatives, the distribution of which is well

• paraquat, the following moieties may be involved: the glycoluril fragment (hydrogen bonds involving the oxygen atoms of the carbonyl groups), the catechol part of the crown ether fragments (π–π stacking interactions) and the polyether chains of benzocrown ethers (C–H···О interactions). The first two

• complexation constant of the clip 6 with paraquat (7), which was: lgK = 1.46 ± 0.01 (−ΔG = 1.96 ± 0.02 kcal/mol). The complex of clip 6 with paraquat (7) may be stabilized through π–π stacking interactions of the electron-deficient aromatic rings of paraquat and the electron donating veratrol fragments of the

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• solvent-free mechanomilling [50]. By varying the electron density on the aromatic aldehydes, it was observed that electron deficient aldehydes provided a better yield with excellent stereo selectivity over electron rich systems. The observed result suggests that a π–π stacking interaction between electron

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• described as the Langmuir–Freundlich isotherm [47]. The polymer matrix has higher adsorption capacity for 4-NP due to π–π stacking interactions, which can encourage 4-NP molecules to enter the polymer channel to form the adsorbed species [54]. At the same time, the hydrogen atom is introduced onto the

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

• change is significant and represents the expected red shift. Although contributions from changes in π–π stacking on spectroscopic properties cannot be excluded, the observed red shift in compressed flipper monolayers is consistent with the earlier experiments on the planarization of monomeric flipper

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• interaction between the positively charged amino group in DOX and the negatively charged groups on the CD surface can take place. Also van der Waals and π–π stacking interactions were attributed as contributing factors to the DOX loading and DOX incorporation into the hollow CD cavity. Drug release at acidic

A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation

• Wangkhem P. Singh and
• Rajkumar S. Singh

Beilstein J. Org. Chem. 2017, 13, 138–149, doi:10.3762/bjoc.13.17

• geometry (unlike the planar geometry of say anthracene, pyrene, etc.), π–π stacking will be favoured only between benzene units of different trityl groups. A small library of triphenylmethyl derivatives was synthesized from the corresponding primary alcohols employing a single step reaction and detailed

• planar two-dimensional structures will be similar to the width of TPM-G12 (8.50 Å). The observed d-spacing value of 8.12 Å from powder XRD experiment correlates closely with this value. The weak intensity peak at 22.02° (4.10 Å) may result from π–π stacking between benzene rings of adjacent

• linear molecular arrays and also between two-dimensional planar arrays. The weak intensity peak at 22.39° (3.96 Å) can be attributed to the presence of π–π stacking between benzene rings of adjacent triphenylmethyl groups. Dye absorption studies Dyes are commercially important and are widely used in many

Supramolecular frameworks based on [60]fullerene hexakisadducts

• Andreas Kraft,
• Johannes Stangl,
• Ana-Maria Krause,
• Klaus Müller-Buschbaum and
• Florian Beuerle

Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1

• ][34][35][36][37][38][39][40][41][42][43][44][45] or π–π-stacking [46] that retain porosity in the solid state under activation conditions have been reported so far. One possible way to enhance stability and shape-persistency might be the implementation of polyfunctional building blocks in order to

Synthesis of spiro[isoindole-1,5’-isoxazolidin]-3(2H)-ones as potential inhibitors of the MDM2-p53 interaction

• Salvatore V. Giofrè,
• Santa Cirmi,
• Raffaella Mancuso,
• Francesco Nicolò,
• Giuseppe Lanza,
• Laura Legnani,
• Agata Campisi,
• Maria A. Chiacchio,
• Michele Navarra,
• Bartolo Gabriele and
• Roberto Romeo

Beilstein J. Org. Chem. 2016, 12, 2793–2807, doi:10.3762/bjoc.12.278

• 180° rotation of the isoindolinone core such that the benzyl group and dialkylamide occupy the Leu26 and Phe19 pockets, respectively. The reoriented binding mode, similar to the MI63 analogue, takes advantage of the π–π stacking interaction with His96 of MDM2 and the benzyl moiety of compound 6e, and

Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells

• John A. Love,
• Shu-Hua Chou,
• Ye Huang,
• Guilllermo C. Bazan and
• Thuc-Quyen Nguyen

Beilstein J. Org. Chem. 2016, 12, 2543–2555, doi:10.3762/bjoc.12.249

• reflection, suggesting a quite well-ordered film. Additionally, there is a small peak at 1.79 Å−1, corresponding to a spacing of 3.5 Å, which we attribute to π–π stacking. There is a broad feature centered at Q = 1.5 Å−1 which is seen in both films and at all orientations, which is the convolution of two

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• inclusion between the adamantane groups and the cyclodextrin cavities at the surface of cyclodextrin vesicles (CDVs) results in efficient immobilization of the squaraine on a nanocarrier. In addition, π–π stacking (and hence inactivation) of the squaraine is supressed due to the steric separation of the

• . In a first set of experiments, we investigated the photochemical properties of AdSq in acetonitrile (Figure 2). The absorption spectrum shows a peak at 665 nm indicative of the presence of squaraine monomers in the solution. A shoulder around 610 nm indicates aggregation of the squaraine due to π–π

• stacking. A comparison of absorption spectra in different solvents revealed that the amount of aggregation is rather low in acetonitrile or ethanol but increases dramatically if water is used as a solvent (see Figure S1 in Supporting Information File 1). This is in agreement with literature and highlights

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

• Paul B. Geraghty,
• Calvin Lee,
• Jegadesan Subbiah,
• Wallace W. H. Wong,
• James L. Banal,
• Mohammed A. Jameel,
• Trevor A. Smith and
• David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

• evident (Figure 5a). However, λmax is dependent on the degree of formation of π–π stacking and development of the lowest energy transition with two clear sharp peaks at 552 nm and 590 nm (λmax) for BMR, while for BPR λmax is at 594 nm with a shoulder at around 630 nm indicating poor formation of the

• cm−2. BPR shows promise with a high FF (74%), however a lower Voc (0.82 V) and a reduced Jsc (14.3 mA cm−2) reduce the PCE to 8.7%. UV–vis data indicate that under these SVA conditions the π–π stacking is not fully developed indicating that optimizing SVA conditions may lead to improved light

• architecture described above. The collected device data are summarized in Table 5, and the J–V curves are shown in Figure 13. Examination of the BTxR UV–vis data for as-cast films (Figure 5d) indicates that BT8R does not have a well-developed π–π stacking peak in as-cast films, unlike BTR. Also, both BT4R and

Synthesis and characterization of fluorinated azadipyrromethene complexes as acceptors for organic photovoltaics

• Forrest S. Etheridge,
• Roshan J. Fernando,
• Sandra Pejić,
• Matthias Zeller and
• Geneviève Sauvé

Beilstein J. Org. Chem. 2016, 12, 1925–1938, doi:10.3762/bjoc.12.182

• structure is distorted tetrahedral with favorable π–π stacking distances between the proximal phenyl and pyrrole rings of the two separate ligands (Figure 10a and 10b). The distance between centroids is 3.56 Å for Zn(L2)2, compared to 3.63 Å for Zn(ADP)2 [38]. The shorter distance found for Zn(L2)2 suggests

• a stronger interaction between the proximal phenyl and pyrrole rings than in Zn(ADP)2. Unfortunately, it cannot be determined whether the addition of fluorine or phenylacetylene contributed to the shorter π–π stacking distances without a crystal structure for Zn(WS3)2. Intermolecular favorable π–π

• stacking distances are observed between the pyrrolic phenylacetylene arms of two chelates seen on the outside of the unit cell, as well as between the distal phenyl rings of two chelates. Due to the crowded packing and difficulty in obtaining a clear image to convey these observations, the authors invite

From supramolecular chemistry to the nucleosome: studies in biomolecular recognition

• Marcey L. Waters

Beilstein J. Org. Chem. 2016, 12, 1863–1869, doi:10.3762/bjoc.12.175

• -helices; aromatic interactions; β-hairpin peptides; cation–π interactions; dynamic combinatorial chemistry; histone; molecular recognition in water; nucleosome; π–π-stacking; post-translational modification; supramolecular chemistry; Review Childhood influences When thinking about how to start writing

• postdoc. Seminal work probing the electrostatic component of π–π stacking and edge-face aromatic interactions as well as cation–π interactions was being published at the time, as well as tantalizing suggestions about their relevance in biological structure and function. In particular, I was inspired by

• -Sanders Model for π–π stacking from 1990 [4]. (d) Kool’s nonpolar isostere of thymidine from 1995 [5].(e) Gellman’s model for π–π stacking in aqueous solution [6]. (a) Model β-hairpin for investigation of aromatic interactions. (b) Examples of noncovalent interactions studied, from weakest to strongest