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2. Conformation-Dependent Response to the Protonation of Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0): A Route to Pseudorotaxane-Like Structures.
- Author
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Szyszko B, Przewoźnik M, Białek MJ, Białońska A, Chmielewski PJ, and Latos-Grażyński L
- Subjects
- Hydrogenation, Molecular Conformation, Rotaxanes chemical synthesis, Stereoisomerism, Anions chemistry, Rotaxanes chemistry
- Abstract
Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0), an expanded carbaporphyrinoid incorporating two phenanthrenylene moieties, exists as two separate, yet interconvertible, locked stereoisomers. These species demonstrate complex dynamic behavior upon protonation, consisting in multiple conformational rearrangements and anion-binding events. The formation of one of the final dicationic forms is accompanied by the inclusion of a complex anion(s) within the macrocyclic cavity yielding a pseudorotaxane-like host-guest complex. Protonation with trifluoroacetic or dichloroacetic acids followed by neutralization afforded a conformation-switching cycle, which involves six structurally different species. Analogous acidification with chiral 10-camphorsulfonic acid and subsequent neutralization generated one of the free base stereoisomers with enantiomeric excess. Therefore, it was shown that the simple acid-base chemistry of diphenanthrioctaphyrin can act as stimulus, inducing chirality into the system, allowing for the manipulation of the stereochemical information imprinted into the enantiomers of the macrocycle., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2020
- Full Text
- View/download PDF
3. Electrostatic barriers in rotaxanes and pseudorotaxanes.
- Author
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Hmadeh M, Fahrenbach AC, Basu S, Trabolsi A, Benítez D, Li H, Albrecht-Gary AM, Elhabiri M, and Stoddart JF
- Subjects
- Magnetic Resonance Spectroscopy, Models, Molecular, Thermodynamics, Pyridinium Compounds chemistry, Rotaxanes chemistry
- Abstract
The ability to control the kinetic barriers governing the relative motions of the components in mechanically interlocked molecules is important for future applications of these compounds in molecular electronic devices. In this Full Paper, we demonstrate that bipyridinium (BIPY(2+)) dications fulfill the role as effective electrostatic barriers for controlling the shuttling and threading behavior for rotaxanes and pseudorotaxanes in aqueous environments. A degenerate [2]rotaxane, composed of two 1,5-dioxynaphthalene (DNP) units flanking a central BIPY(2+) unit in the dumbbell component and encircled by the cyclobis(paraquat-p-phenylene) (CBPQT(4+)) tetracationic cyclophane, has been synthesized employing a threading-followed-by-stoppering approach. Variable-temperature (1)H NMR spectroscopy reveals that the barrier to shuttling of the CBPQT(4+) ring over the central BIPY(2+) unit is in excess of 17 kcal mol(-1) at 343 K. Further information about the nature of the BIPY(2+) unit as an electrostatic barrier was gleaned from related supramolecular systems, utilizing two threads composed of either two DNP units flanking a central BIPY(2+) moiety or a central DNP unit flanked by a BIPY(2+) moiety. The threading and dethreading processes of the CBPQT(4+) ring with these compounds, which were investigated by spectrophotometric techniques, reveal that the BIPY(2+) unit is responsible for affecting both the thermodynamics and kinetics of pseudorotaxane formation by means of an intramolecular self-folding (through donor-acceptor interactions with the DNP unit), in addition to Coulombic repulsion. In particular, the free energy barrier to threading (ΔG(f)(++)) of the CBPQT(4+) for the case of the thread composed of a DNP flanked by two BIPY(2+) units was found to be as high as 21.7 kcal mol(-1) at room temperature. These results demonstrate that we can effectively employ the BIPY(2+) unit to serve as electrostatic barriers in water in order to gain control over the motions of the CBPQT(4+) ring in both mechanically interlocked and supramolecular systems., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2011
- Full Text
- View/download PDF
4. Synthesis and function of double-stranded helical polymers and oligomers.
- Author
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Furusho Y and Yashima E
- Subjects
- Models, Molecular, Molecular Structure, Polymerization, Thermodynamics, Amidines chemistry, Carboxylic Acids chemistry, Peptide Nucleic Acids chemistry, Resorcinols chemistry, Rotaxanes chemistry
- Abstract
The design and synthesis of artificial helical polymers and oligomers has attracted much interest, in connection with fascinating biological helices and their sophisticated functions as well as possible applications in novel chiral materials. The last half-century has seen a significant advancement in the synthesis of single-stranded helical polymers and oligomers, since the discovery of the helical structure of isotactic polypropylene. In contrast, the chemistry of double-stranded helical counterparts is still premature. This paper highlights our recent achievements in the synthesis, structures, and functions of double-stranded helical polymers and oligomers, stressing an important role of supramolecular chemistry in the design and synthesis of double helices with a controlled helical sense., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2011
- Full Text
- View/download PDF
5. Hydrogen-bonding-mediated dynamic covalent synthesis of macrocycles and capsules: new receptors for aliphatic ammonium ions and the formation of pseudo[3]rotaxanes.
- Author
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Xu XN, Wang L, Wang GT, Lin JB, Li GY, Jiang XK, and Li ZT
- Subjects
- Hydrogen Bonding, Magnetic Resonance Spectroscopy, Molecular Structure, Rotaxanes chemistry, Models, Molecular, Quaternary Ammonium Compounds chemistry, Rotaxanes chemical synthesis
- Abstract
This paper describes a novel, highly efficient approach to the self-assembly of monomacrocycles and two-layered capsules by using dynamic covalent chemistry. Intramolecular hydrogen-bonding was used to preorganize aromatic amide-based monomers that contain aldehyde and tert-butoxycarbonylamino units. As a result, in the presence of an excess of trifluoroacetic acid (TFA), four monomers could self-couple to produce macrocycles selectively through the formation of three imine or hydrazone bonds. Three dipodal precursors were also prepared by connecting two hydrogen-bonded segments with a flexible linker. In the presence of TFA, these precursors could also self-couple, leading to the exclusive formation of two-layered capsules. As a result of intramolecular hydrogen-bonding, all the macrocycles and capsules were stable in solution and could be purified by simple recrystallization. The new capsules were able to form complexes with linear propylenediammonium derivatives to give unique two-layered pseudo[3]rotaxanes.
- Published
- 2009
- Full Text
- View/download PDF
6. Molecular Catenanes, Rotaxanes and Knots : A Journey Through the World of Molecular Topology
- Author
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Jean-Pierre Sauvage, Christiane Dietrich-Buchecker, Jean-Pierre Sauvage, and Christiane Dietrich-Buchecker
- Subjects
- Rotaxanes, Catenanes, Knot theory
- Abstract
This journey through the fascinating world of molecular topology focuses on catenanes, rotaxanes and knots, their synthesis, properties, and applications and the theory of interlocking and interpenetrating molecules. Nearly one hundred years of progress have passed since Willstatter's speculative vision of a molecule consisting of two interlinked rings. But even today the synthesis of such structures are a challenge to the creativity of synthetic chemists. These molecules are not only of academic interest, since they occur naturally. In such molecules as DNA, knots and related topological features play a key role in biochemical processes. In addition, extensive research on the properties of polyrotaxanes and polycatenanes show potential applications as molecular magnets, wires or switches. Twelve international leading experts in the field present the broad and impressive spectrum of the topology of these molecules, from theoretical aspects and new pathways in synthesis to probing their properties. All researchers working in this interdisciplinary area, whether organic, inorganic or polymer chemists, as well as material scientists, will welcome this comprehensive and up-to-date work as an inspiring source for creative research ideas.
- Published
- 1999
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