Molecular tweezers as synthetic receptors: molecular recognition of neutral and cationic aromatic substrates. A comparison between the supramolecular structures in crystal and in solution

Klrner, Frank-Gerrit; Burkert, Ulrich; Kamieth, Markus; Boese, Roland

doi:10.1002/1099-1395(200010)13:10<604::aid-poc271>3.0.co;2-7

Cited by 42 publications

(30 citation statements)

References 22 publications

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“…Molecular tweezer T , which comprises one naphthalene and four benzene components bridged by four methylene units, was prepared and purified as previously reported (Figure 1). 14 NMR spectroscopy (see Supporting Information for details) showed that tweezer T forms a stable 1:1 complex with 4,4′‐ N , N ‐bis(3,5‐di‐ tert ‐butylbenzyl)bipyridinium [ D 0 ] 2+ . Solvent‐dependent binding constants ( K a =730 M −1 in [D 6 ]acetone/CDCl 3 (2:1) and K a =8400 M −1 in CD 2 Cl 2 ), and complexation‐induced upfield shifts of the chemical shifts for the protons of the guest (Δ δ max =1.01 or 0.91 ppm (H o ), and 4.12 or 3.22 ppm (H m )) were determined by 1 H NMR titration experiments (500 MHz, Bruker DRX 500) at 25 °C, and the 1:1 stoichiometry of the complex was determined through Job plot analysis.…”

Section: Half‐wave Potentials Versus Sce (Saturated Calomel Electrodementioning

confidence: 99%

Tweezering the Core of a Dendrimer: A Photophysical and Electrochemical Study

Balzani¹,

Ceroni²,

Giansante³

et al. 2005

Angew Chem Int Ed

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Section: Half‐wave Potentials Versus Sce (Saturated Calomel Electrodementioning

confidence: 99%

Tweezering the Core of a Dendrimer: A Photophysical and Electrochemical Study

Balzani¹,

Ceroni²,

Giansante³

et al. 2005

Angew Chem Int Ed

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“…We recently described the syntheses and some supramolecular properties of the new host molecules 1 a , b 26–29 and 2 a ,30 named molecular tweezers and clips 31. The size and shape of their cavities depends on the number of methylene bridges and on the size of the aromatic spacer units (benzene or naphthalene).…”

Section: Introductionmentioning

confidence: 99%

Dynamics in Host–Guest Complexes of Molecular Tweezers and Clips

Lobert

Bandmann

Burkert

et al. 2006

Chemistry A European J

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The dynamics in the host-guest complexes of the molecular tweezers 1 a,b and clips 2 a,b with 1,2,4,5-tetracyanobenzene (TCNB, 3) and tropylium tetrafluoroborate (4) as guest molecules were analyzed by temperature-dependent 1H NMR spectroscopy. The TCNB complexes of tweezers 1 a,b were found to be particularly stable (dissociation barrier: DeltaG(++)=16.8 and 15.7 kcal mol(-1), respectively), more stable than the TCNB complexes of clips 2 a,b and the tropylium complex of tweezer 1 b (dissociation barrier: DeltaG(++)=12.4, 11.2, and 12.3 kcal mol(-1), respectively). A detailed analysis of the kinetic and thermodynamic data (especially the negative entropies of activation found for complex dissociation) suggests that in the transition state of dissociation the guest molecule is still clipped between the aromatic tips of the host molecule. The 1H NMR analysis of the TCNB complexes 3@1 b and 3@2 a at low temperatures (T<-80 degrees C) showed that 3 undergoes fast rotation inside the cavity of tweezer 1 b or clip 2 a (rotational barrier: DeltaG( not equal)=11.7 and 8.3 kcal mol(-1), respectively). This rotation of a guest molecule inside the host cavity can be considered to be the dynamic equilibration of noncovalent conformers. In the case of clip complex 3@2 a the association and rotational barriers are smaller by DeltaDeltaG(++)=3-4 kcal mol(-1) than those in tweezer complexes 3@1 a,b. This can be explained by the more open topology of the trimethylene-bridged clips compared to the tetramethylene-bridged tweezers. Finally, the bromo substituents in the newly prepared clip 2 b have a substantial effect on the kinetics and thermodynamics of complex formation. Clip 2 b forms weaker complexes with (TCNB, 3) and tetracyanoquinodimethane (TCNQ, 12) and a more stable complex with 2,4,7-trinitrofluoren-9-ylidene (TNF, 13) than the parent clip 2 a. These results can be explained by a less negative electrostatic potential surface (EPS) inside the cavity and a larger van der Waals contact surface of 2 b compared to 2 a. In the case of the highly electron-deficient guest molecules TCNB and TCNQ the attractive electrostatic interaction is predominant and hence responsible for the thermodynamic complex stability, whereas in the case of TNF with its extended pi system, dispersion forces are more important for host-guest binding.

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“…Low affinities were found towards most common transition metals ( K d in µ m : Fe 2+ 130, Fe 3+ 220, Cu 2+ 530) as well as alkali (Cs + 1350) and alkali‐earth metals (Ca 2+ , Mg 2+ >2000), and these affinities contrasted with the exceptionally high affinity for Zn 2+ ions ( K d = 5 µ m ) . Moreover, lysine and zinc ions can be complexed simultaneously by 2 , as evidenced by 1 H NMR spectroscopy: in the fluorescence titrations of tweezers with included lysine residues, the addition of Zn 2+ ions leads to a further fluorescence decrease, but the drastic upfield shifts of the encapsulated lysine side‐chain CH 2 groups remain (this is not the case with Cs + ions, which are included in the tweezers themselves) . Most likely, free lysine moieties are threaded through the tweezers cavity, whereas the Zn 2+ cation is chelated above the cavity by both phosphate residues.…”

Section: Resultsmentioning

confidence: 99%

Molecular Tweezers Inhibit PARP‐1 by a New Mechanism

Wilch

Talbiersky

Berchner‐Pfannschmidt

et al. 2017

Eur J Org Chem

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The inhibition of PARP‐1 (poly[ADP‐ribose]polymerase 1), a key enzyme for DNA quality control, has been achieved with synthetic molecular tweezers through a noncompetitive mechanism with an IC50 value of 3 µm. Displacement as well as electrophoretic mobility shift assays and molecular dynamics experiments point to a simultaneous inclusion of lysine side‐chains in the cavity of the tweezers and the coordination of one phosphate arm to the central Zn2+ ion of the zinc finger; thereby, lesioned DNA is displaced.

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Molecular tweezers as synthetic receptors: molecular recognition of neutral and cationic aromatic substrates. A comparison between the supramolecular structures in crystal and in solution

Cited by 42 publications

References 22 publications

Tweezering the Core of a Dendrimer: A Photophysical and Electrochemical Study

Tweezering the Core of a Dendrimer: A Photophysical and Electrochemical Study

Dynamics in Host–Guest Complexes of Molecular Tweezers and Clips

Molecular Tweezers Inhibit PARP‐1 by a New Mechanism

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