From Cyclophanes to Molecular Machines

Flood, Amar H.; Liu, Yi

doi:10.1002/3527603964.ch19

Cited by 11 publications

(6 citation statements)

References 24 publications

(45 reference statements)

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“…A polymeric ladderphane is defined as multiple layers of cyclophanes , where the tethers are part of the polymeric backbones (Figure a). Structurally, it can be considered as a multiple stranded polymer with planar aromatic linkers.…”

Section: Introductionmentioning

confidence: 99%

Polymeric Ladderphanes

et al. 2009

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A new class of polymers, which have a double-stranded polybinorbornene skeleton with multilayer planar oligoaryl linkers, defined as polymeric ladderphanes, are synthesized. The structures of these ladderphanes are determined by spectroscopic means. Photophysical studies and time-resolved fluorescence spectroscopic investigations reveal that there is a strong interaction between the chromophore linkers. Thus, Soret band splitting in the absorption spectrum of the polymer with porphyrin linker (12e), significant fluorescence quenching with oligoaryl linkers (12b-d), and excimer emission with a terphenylene-diethynylene linker (12a) are characteristic photophysical properties of these polymers. Scanning tunneling microscopy shows that polymers 12b and d exhibit a ladder-like morphology and form a supramolecular assembly leading to a two-dimensional ordered array on a highly oriented pyrolytic graphite surface.

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Section: Introductionmentioning

confidence: 99%

Polymeric Ladderphanes

et al. 2009

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“…The synthetic availability and desirable electronic properties of 1,1′-disubstituted-4,4′-bipyridinium and its derivatives have, to a large extent, driven research in this area and generated numerous cyclophanes in this family. Several rigid polycationic box-like cyclophanes with different shapes, sizes, and electronic properties have been synthesized with a number of desirable properties, including (i) host–guest recognition and complexation, (ii) catalysis, (iii) artificial photosystems, (iv) molecular electronics, (v) live-cell imaging and therapy, , and (vi) molecular machines …”

Section: Introductionmentioning

confidence: 99%

Combining Intra- and Intermolecular Charge Transfer with Polycationic Cyclophanes To Design 2D Tessellations

Cetin¹,

Beldjoudi²,

Roy³

et al. 2019

J. Am. Chem. Soc.

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A series of donor−acceptor (D-A) naphthalene−viologen-based cyclophanes of different shapes, sizes, and symmetries have been synthesized and characterized. Solution optical studies on these cyclophanes reveal the existence of photoinduced intramolecular charge transfer (CT) at 465 nm from naphthalene (D) to viologen (A) units, resulting in a conformational change in the viologen units and the emergence of an emission at 540 nm. The D-A cyclophanes with box-like and hexagon-like shapes offer an opportunity to control the arrangement within 2D layers where D-A interactions direct the superstructures. While a box-like 2,6-disubstituted naphthalene-based tetracationic cyclophane does not form square tiling patterns, a truncated hexagon-like congener self-assembles to form a hexagonal superstructure which, in turn, adopts a hexagonal tiling pattern. Tessellation of the more rigid and highly symmetrical 2,7disubstituted naphthalene-based cyclophanes leads to the formation of 2D square and honeycomb tiling patterns with the boxlike and hexagon-like cyclophanes, respectively. Co-crystallization of the box-like cyclophanes with tetrathiafulvalene (TTF) results in the formation of D-A CT interactions between TTF and viologen units, leading to tubular superstructures. Cocrystallization of the hexagon-like cyclophane with TTF generates well-ordered and uniform tubular superstructures in which the TTF−viologen CT interactions and naphthalene−naphthalene [π•••π] interactions propagate with 2D topology. In the solid state, the TTF−cyclophane co-crystals are paramagnetic and display dual intra-and intermolecular CT behavior at ∼470 and ∼1000 nm, respectively, offering multi-responsive materials with potential pathways for electron transport.

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“…1,2 Accordingly, the synthesis and basic molecular recognition properties of numerous classes of macrocycles including cyclodextrins, calixarenes, cyclophanes, crown ethers, self-assembled systems, and most recently pillararenes have been extensively studied. 1,3,4–6 Importantly, the properties of guest compounds bound within molecular containers are distinct from those of the same compounds free in solution. For example, the lifetime of high energy molecules like cyclobutadiene can be extended, 7 the photophysical properties of encapsulated dyes can be improved, 8 the conformation of natural and non-natural molecules can be controlled, 5,9 the pK a of included guests can be shifted, 10 and the reactions of certain substrates can be catalyzed.…”

Section: Introductionmentioning

confidence: 99%

Acyclic CB[n]-type molecular containers: effect of solubilizing group on their function as solubilizing excipients

2014

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We report the synthesis and x-ray crystal structures of three acyclic CB[n]-type molecular containers (2a, 2h, 2f) that differ in the charge on their solubilizing groups (SO3−, OH, NH3+). The x-ray crystal structures of compounds 2h and 2f reveal a self-folding of the ArOCH2CH2X wall into the cavity driven by π–π interactions, H-bonds and ion-dipole interactions. The need to reverse this self-folding phenomenon upon guest binding decreases the affinity of 2h and 2f toward cationic guests in water relative to 2a as revealed by direct 1H NMR and UV/Vis titrations as well as UV/Vis competition experiments. We determined the pKa of 6-aminocoumarin 7 (pKa = 3.6) on its own and in the presence anionic, neutral, and cationic hosts (2a: pKa = 4.9; 2h: pKa = 4.1; 2f, pKa = 3.4) which reflect in part the relevance of direct ion-ion interactions between the arms of the host and the guest toward the recognition properties of acyclic CB[n]-type containers. Finally, we showed that the weaker binding affinities measured for neutral and positively charged hosts 2h and 2f compared to anionic 2a results in a decreased ability to act as solubilizing agents for either cationic (tamoxifen), neutral (17α–ethynylestradiol), or anionic (indomethacin) drugs in water. The results establish that acyclic CB[n] compounds that bear anionic solubilizing groups are most suitable for development as general purpose solubilizing excipients for insoluble pharmaceutical agents.

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From Cyclophanes to Molecular Machines

Cited by 11 publications

References 24 publications

Polymeric Ladderphanes

Polymeric Ladderphanes

Combining Intra- and Intermolecular Charge Transfer with Polycationic Cyclophanes To Design 2D Tessellations

Acyclic CB[n]-type molecular containers: effect of solubilizing group on their function as solubilizing excipients

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