Superstructures with cyclodextrins: Chemistry and applications IV

• Gerhard Wenz

Beilstein J. Org. Chem. 2017, 13, 2157–2159, doi:10.3762/bjoc.13.215

• insulin and lysozyme were also conjugated to the guest adamantane. The complexation of these conjugates by pegylated β-CD gives rise to superstructures which provide slow release and maintain full biological activity [21]. Significant progress was also achieved in the field of CD rotaxanes. A [3]-rotaxane

• was assembled from two monosubstituted α-CD rings, α,ω-dodecamethylene diazide axis, and two bulky alkyne stoppers through a copper-catalyzed [2 + 3] cycloaddition in one step. Because of the attached gadolinium complexes, this rotaxane showed a high NMR relaxivity, making it suitable as a probe for

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• bioactive surfaces [8][14], imaging of biochemical processes [15], localization of bioactive compounds inside living cells [16], syntheses of small-molecule screening libraries [17], catenane and rotaxane syntheses [18], in reactions under continuous flow processing [19], polymer and surface science [20][21

Creating molecular macrocycles for anion recognition

• Amar H. Flood

Beilstein J. Org. Chem. 2016, 12, 611–627, doi:10.3762/bjoc.12.60

• plot of anion affinities (40:60 methanol/dichloromethane). (a) Representation and (b) crystal structure of cyanostar-based [3]rotaxane. Crystal structures of cyanostar sandwich around (a) perchlorate and (b) diglyme (molecules shown with stick models and representative electron-density contours). Part

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• coupled with rhodamine B in the presence of N,N'-dicyclohexylcarbodiimide (DCC) and hydroxybenzotriazole (HOBt) in anhydrous DMF under inert atmosphere in order to connect the two moieties through an amide bond. The fluorescent CD derivative was used to observe the movement of a rotaxane immobilized on

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

• evaluated and compared to those of the non-rotaxane counterpart 3. The influence of TM-βCD or TM-γCD encapsulation on the thermal stability, solubility in common organic solvents, film forming ability was also investigated. Polyrotaxane 3·TM-βCD exhibits a hypsochromic shift, while 3·TM-γCD displays a

• bathochromic with respect to the non-rotaxane 3 counterpart. For the diluted CHCl3 solutions the fluorescence lifetimes of all compounds follow a mono-exponential decay with a time constant of ≈0.6 ns. At higher concentration the fluorescence decay remains mono-exponential for 3·TM-βCD and polymers 3, with a

• 3. The resonance peak of the d proton from monomer 2 is upfield shifted by more than 0.06 ppm in the polyrotaxane 3·TM-βCD compared to those of the non-rotaxane 3 counterpart, as shown in Figure 1 and Figure S4 in Supporting Information File 1. The resonance peaks of a–c and a’–c’ protons of 3·TM

Smart molecules for imaging, sensing and health (SMITH)

• Bradley D. Smith

Beilstein J. Org. Chem. 2015, 11, 2540–2548, doi:10.3762/bjoc.11.274

• imaging, ion-pair receptors, rotaxane synthesis, squaraine rotaxanes, and synthtavidin technology. The article concludes with a short perspective of likely future directions in biomedical supramolecular chemistry. Keywords: fluorescence; ion-pair receptors; membrane transport; molecular imaging; rotaxane

• [29]. Rotaxane syntheses Building on literature ideas about “wheeled nucleophiles [30][31].” we prepared the reactive ion-pair in Scheme 4 and trapped the bound phenolate as an uncharged [2]rotaxane structure [32]. The ability of the macrobicyclic receptor to accommodate a solvent separated ion-pair

• was vital for efficient rotaxane formation. The interlocked molecule retained its salt binding ability and association of the ions modulated the rotaxane structural dynamics [33][34]. Squaraine rotaxanes The interests in molecular imaging and rotaxane structures merged in 2005 with the discovery and

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• and nanomaterials is a challenging task. Huang and co-workers [165] have reported a taco complex template method to synthesize a cryptand/paraquat [2]rotaxane and [2]catenane (e.g., 207) by using RCM as a key step. Structural features and interesting bioactivity of the hirsutellones have grabbed the

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• . The crown ether/secondary ammonium ion binding motif [34] is a powerful tool to create well-defined pseudorotaxane structures [35][36][37][38][39], which have also served as precursors in rotaxane syntheses [40][41][42] thus providing access to interlocked, mechanically bound molecules. Based on these

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

Synthesis of an organic-soluble π-conjugated [3]rotaxane via rotation of glucopyranose units in permethylated β-cyclodextrin

• Jun Terao,
• Yohei Konoshima,
• Akitoshi Matono,
• Hiroshi Masai,
• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2014, 10, 2800–2808, doi:10.3762/bjoc.10.297

• -phenylene) and oligothiophene with a pseudo-linked [3]rotaxane structure by full rotation of glucopyranose units via a flipping (tumbling) mechanism in the π-conjugated guest having two permethylated β-cyclodextrin units at both ends. We also succeeded in the synthesis of an organic-soluble fixed [3

• ]rotaxane by a cross-coupling or complexation reaction of thus formed pseudo linked [3]rotaxane. Oligo(para-phenylene), oligothiophene, and porphyrin derivatives were used as π-conjugated guests with stopper groups. Keywords: cross-coupling reaction; insulated π-conjugated molecule; oligothiophene

• ; permethylated cyclodextrin; [3]rotaxane; Introduction Insulated molecular wires (IMWs) [1][2], which feature π-conjugated polymer chains covered by protective sheaths, have attracted considerable attention as next-generation mono-molecular electronic devices because of their potential conductivity and

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane

• Kazuaki Kato,
• Katsunari Inoue,
• Masabumi Kudo and
• Kohzo Ito

Beilstein J. Org. Chem. 2014, 10, 2573–2579, doi:10.3762/bjoc.10.269

• the rotaxane structures [11]. GPRs with poly(ε-caprolactone) (PCL) as a flexible graft chain, which exhibits a much lower glass transition temperature than PMMA, have been cross-linked to yield flexible elastomers [11]. Such elastomers exhibit an excellent scratch resistance, and thus can be employed

Host–guest-driven color change in water: influence of cyclodextrin on the structure of a copper complex of poly((4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl)methacrylamide-co-dimethylacrylamide)

• Nils Retzmann,
• Gero Maatz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2480–2483, doi:10.3762/bjoc.10.259

• of CD–dye hydrogels by addition of metal ions, as well as the sensing of copper ions using cyclodextrin–dye rotaxane [10][11]. Herewith we thus wish to describe our recent results about the synthesis of a water-soluble polymer bearing a novel azo dye and the presumed formation of complexes with Cu

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units

• Aurica Farcas,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert,
• Flavian Farcas,
• Iuliana Stoica and
• Anton Airinei

Beilstein J. Org. Chem. 2014, 10, 2145–2156, doi:10.3762/bjoc.10.222

• -dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane

• 4 counterpart. The fluorescence lifetimes of polyrotaxanes follow a mono-exponential decay with a value of τ = 1.14 ns compared with the non-rotaxane, where a bi-exponential decay composed of a main component with a relative short time of τ1 = 0.88 (57.08%) and a minor component with a longer

• granular morphology with a lower dispersity supported by a smaller roughness exponent compared with the non-rotaxane counterpart. Keywords: cyclodextrins; energy band gaps; fluorescence lifetimes; persilylated cyclodextrins; supramolecular encapsulation; surface morphology; Introduction Semiconducting π

Substitution effect and effect of axle’s flexibility at (pseudo-)rotaxanes

• Friedrich Malberg,
• Jan Gerit Brandenburg,
• Werner Reckien,
• Oldamur Hollóczki,
• Stefan Grimme and
• Barbara Kirchner

Beilstein J. Org. Chem. 2014, 10, 1299–1307, doi:10.3762/bjoc.10.131

• molecular shuttles [9][10] via shifting the axle back and forth within the wheel. The Stoddart group synthesized the first rotaxane-based molecular shuttle in 1991 [11]. It consisted of a tetracationic wheel, which was able to move back and forth between two identical hydroquinol stations. These

• symmetrically surrounded a polyether axle, which was terminated at the ends by large triisopropylsilyl stoppers [11]. Other rotaxane systems were also studied. For instance, Leigh and coworkers synthesized several rotaxane shuttles in the last years [12]. Many of these rotaxanes are based on a benzylic amide

• published a further interesting application of rotaxanes [16][17]. The axle consisted of a peptide, which can be released from the wheel by the according reaction, thus allowing the rotaxane to function as a high-precision delivery system. The authors introduced a system, which – in contrast to the first

Molecular assembly of amino acid interlinked, topologically symmetric, π-complementary donor–acceptor–donor triads

• M. B. Avinash,
• K. V. Sandeepa and
• T. Govindaraju

Beilstein J. Org. Chem. 2013, 9, 1565–1571, doi:10.3762/bjoc.9.178

• [18], catenane [19], rotaxane [20], self-healable supramolecular polymer [21], aromatic stacking within a coordination cage [22], superamphiphile [23] and thermochromic [24] materials. Notably, Wilson et al. have reported preferential π-stacking of pyrene and NDI amongst a pool of π-electron D-A

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

• Narcisa Marangoci,
• Rodinel Ardeleanu,
• Laura Ursu,
• Constanta Ibanescu,
• Maricel Danu,
• Mariana Pinteala and
• Bogdan C. Simionescu

Beilstein J. Org. Chem. 2012, 8, 1610–1618, doi:10.3762/bjoc.8.184

• Polymers, “Gheorghe Asachi” Technical University of Iasi, 700050 Iasi, Romania 10.3762/bjoc.8.184 Abstract An ionic liquid based on polydimethylsiloxane with imidazolium salt brushes was synthesized as a good solvent for β-cyclodextrin-polydimethylsiloxane rotaxane. As expected the PDMS-Im/Br ionic liquid

• had a liquid-like non-Newtonian behavior with rheological parameters dependent on frequency and temperature. The addition of rotaxane to the ionic liquid strengthened the non-Newtonian character of the sample and a type of stable liquid-like network was formed due to the contribution of weak ionic

• polyrotaxane structures. Also, in the present study, we report how the rheological properties are influenced when CD-polydimethylsiloxane rotaxane is dissolved in PDMS-Im/S ionic liquid. Results and Discussion A class of polymers that possesses a unique combination of properties, such as very low Tg values

Synthesis and characterization of low-molecular-weight π-conjugated polymers covered by persilylated β-cyclodextrin

• Aurica Farcas,
• Ana-Maria Resmerita,
• Andreea Stefanache,
• Mihaela Balan and
• Valeria Harabagiu

Beilstein J. Org. Chem. 2012, 8, 1505–1514, doi:10.3762/bjoc.8.170

• morphology and thermal properties of the PDOF-BTc rotaxane copolymer compared to its noncomplexed PDOF-BT homologue. In contrast, the number-average molecular weight (Mn) of PDOF-BTc rotaxane copolymer indicated lower values suggesting that the condensation reaction is subjected to steric effects of the

• materials for use in molecular devices, the construction of mechanically interlocked molecules, such as rotaxanes and polyrotaxanes, has attracted considerable attention [19][20][21][22][23]. A rotaxane assembly comprises a macrocyclic component (host) encircling an axle (guest) through noncovalent

• reaction between DOF and BT, and its properties were compared with the rotaxane PDOF-BTc copolymer. The first step in the preparation of PDOF-BTc polyrotaxane is the threading of the BT monomer through the PS-βCD cavity to form the BTc inclusion complex. BTc obtained as a precipitate from a 2:1 mol/mol

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• converting light into mechanical energy without any battery or power source [47]. Bistable memory device Recently, Stoddart and Venturi's group described a molecular switch using a [2]rotaxane 25, which undergoes mechanical movements triggered by redox processes and can be switched between two

• thermodynamically stable conformations [138]. The energy barriers between these conformations can be controlled kinetically by photochemical modulation. The ring component of the [2]rotaxane is cyclobis(paraquat-p-phenylene) and the dumbbell is comprised of a tetrathiafulvalene unit and a 1,5-dioxynaphthalene as π

• written on the rotaxane when the units of tetrathiafulvalene are oxidized and then blocked in the trans–cis photoisomerization process, on the azobenzene fragment. After writing the information, the oxidized species can be reduced to the original form without loss of data. The data is stored until

Synthesis of multivalent host and guest molecules for the construction of multithreaded diamide pseudorotaxanes

• Nora L. Löw,
• Egor V. Dzyuba,
• Boris Brusilowskij,
• Lena Kaufmann,
• Elisa Franzmann,
• Wolfgang Maison,
• Emily Brandt,
• Daniel Aicher,
• Arno Wiehe and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2012, 8, 234–245, doi:10.3762/bjoc.8.24

• ][32]. The mechanical bond appears particularly suited for this goal, because it connects the axle and wheel strongly, but leaves freedom for the relative movement of the two components. Pseudorotaxanes are the precursors for both rotaxane syntheses by stoppering reactions or catenanes by

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• acid derivative with benzylamine. The overall yield from the oxacalix[3]arene is less than 5%, but, given that the dimerization proceeds in only 14%, this is nevertheless quite impressive. However, in addition to the formation of the molecular capsule, a self-threaded dimer (rotaxane-40) was also

• isolated, which had resulted from an upper-rim substituent threading through the central cavity during dimerization. The existence of the rotaxane structure was deduced from the complexity of the patterns observed in the 1H NMR spectrum compared to that of the capsule. A similar strategy was adopted to

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Templated versus non-templated synthesis of benzo-21-crown-7 and the influence of substituents on its complexing properties

• Wei Jiang and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2010, 6, No. 14, doi:10.3762/bjoc.6.14

• groups is a narrow alkyl chain. By using this binding motif, the so far smallest [2]rotaxane consisting of only 76 atoms and having a molecular weight of not more than 510 Da was synthesized by Chiu and co-workers [25]. More recently, we applied C7 together with dibenzo-24-crown-8 (DB24C8) to the