Covers
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Probing
the Electrostatic Barrier of Tetrathiafulvalene Dications using a
Tetra‐stable Donor–Acceptor [2]Rotaxane (Cover
Feature)
Control of directionality is of
paramount
importance if rectified motion in electroactive molecular machines
should be realized. As illustrated in the cover artwork, the
tetracationic ring (blue) in a tetraoxidized [2]rotaxane can follow two
different tracks; it transpires that it is easier for the ring to
follow a track in which it has to move across a
monopyrrolotetrathiafulvalene dication (dark green) compared to the
track in which it moves across a tetrathiafulvalene dication (light
green).
M. Jensen, R. Kristensen, S. S. Andersen, D. Bendixen, and J. O. Jeppesen*
Chem. Eur. J., 2020, in press
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Naphtho[1,2‐b:5,6‐b′]dithiophene
Building Blocks and their Complexation with Cyclobis(paraquat‐p‐phenylene)
(Cover
Feature)
Collaboration
with K. Takimiya (RIKEN
Center for Emergent Matter Science)
The Cover
Feature shows how two electron donors compete for the cavity of the
electron accepting tetracationic macrocycle cyclobis(paraquat‐p‐phenylene)
(CBPQT4+). Addition of the weak donor naptho[1,2‐b:5,6‐b']dithio-
phene
(NDT) to a colorless solution of CBPQT4+ leads
to
the formation of a
relatively weak complex (NDT⊂CBPQT4+) in which
NDT is located inside
CBPQT4+ as evidenced by a color change from
colorless to amber orange.
Subsequent, addition of the strong donor tetrathiafulvalene (TTF)
produces another color change from amber orange to green as a
consequence of decomplexation of NDT⊂CBPQT4+ and
formation of a very
strong complex (TTF⊂CBPQT4+) in which CBPQT4+
now encircles TTF.
M. Jensen, G. Olsen, R. Kristensen, K. Takimiya, J. O. Jeppesen*
Eur. J. Org. Chem.
2019,
7532–7540
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Design and Sensing Properties of a
Self-Assembled Supramolecular Oligomer (Cover Picture)
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Collaboration
with J. L. Sessler (UTX)
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Supramolecular polymers
are a class of macromolecules stabilized by weak non-covalent
interactions. These self-assembled aggregates typically undergo
stimuli-induced reversible assembly and disassembly. They thus hold
great promise as so-called functional materials. In this work, we
present the design, synthesis, and responsive behavior of a short
supramolecular oligomeric system based on two hetero-complementary
subunits. These “monomers” consist of a
tetrathiafulvalene-functionalized calix[4]pyrrole (TTF-C[4]P) and a
glycol diester-linked
bis-2,5,7-trinitrodicyanomethylenefluorene-4-carboxylate (TNDCF),
respectively. We show that when mixed in organic solvents, such as CHCl3,
CH2ClCH2Cl, and
methylcyclohexane, supramolecular aggregation takes place to produce
short oligomers stabilized by hydrogen bonding and donor–acceptor
charge-transfer (CT) interactions. The self-associated materials were
characterized by 1H NMR and UV/Vis/NIR
absorption spectroscopy, as well as by concentration- and
temperature-dependent absorption spectroscopy and dynamic light
scattering (DLS) analyses of both the monomeric and oligomerized
species. The self-associated system produced from TTF-C[4]P and TNDCF
exhibits a concentration-dependent aggregation behavior typical of
supramolecular polymers. Further support for the proposed self-assembly
came from theoretical calculations. The fluorescence emitting
properties of TNDCF are quenched under conditions that promote the
formation of supramolecular aggregates containing TTF-C[4]P and TNDCF.
This quenching effect has been utilized as a probe for the detection of
substrates in the form of anions (i.e., chloride) and nitroaromatic
explosives (i.e., 1,3,5-trinitrobenzene). Specifically, the addition of
these substrates to mixtures of TTF-C[4]P and TNDCF produced a
fluorescence “turn-on” response.
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S.
Bähring, L. Martín-Gomis, G. Olsen, K. A. Nielsen, D. S. Kim, T.
Duedal, Á. Sastre-Santos, J.
O. Jeppesen*, J. L. Sessler* |
Chem.
Eur. J. 2016, 22,
1958–1967
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Synthesis and Recognition
Properties of
Higher Order Tetrathiafulvalene (TTF) Calix [n]pyrroles (n = 4−6) (Inside Front Cover)
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Collaboration
with J. L. Sessler (UTX)
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Two
new benzoTTF-annulated calix[n]pyrroles (n = 5 and 6) were synthesized
via a one-step acid catalyzed condensation reaction and fully
characterized via single crystallographic analyses. As compared to the
known tetra-TTF annulated calix[4]pyrrole, which is also produced under
the conditions of the condensation reaction, the expanded
calix[n]pyrroles (n = 5 and 6) are characterized by a larger cavity
size and a higher number of TTF units (albeit the same empirical
formula). Analysis of the binding isotherms obtained from UV-Vis
spectroscopic titrations carried out in CHCl3;
in the presence of both
anionic (Cl−, Br−, I−,
CH3COO−,
H2PO4−,
and HSO4−) and neutral
(1,3,5-trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT)
substrates revealed that as a general rule the calix[6]pyrrole
derivative proved to be the most efficient molecular receptor for
anions, while the calix[4]pyrrole congener proves most effective for
the recognition of TNB and TNT. These findings are rationalized in
terms of the number of electron rich TTF subunits and NH hydrogen bond
donor groups within the series, as well as an ability to adopt
conformations suitable for substrate recognition, and are supported by
solid state structural analyses.
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J.
S. Park, C. Bejger, K. R. Larsen, K. A. Nielsen, A. Jana, V. M. Lynch, J. O. Jeppesen,*
D. Kim,* J. L. Sessler* |
Chem.
Science 2012,
3,
2685–2689
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Quantifying the Working
Stroke of
Tetrathiafulvalene-based Electrochemically-driven Linear Motor-molecules
(Front Cover)
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Collaboration
with J. F. Stoddart (UCLA)
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Charged
with the energy electrostatic repulsion, a mechanically-interlocked
[2]rotaxane can overcome its barrier to freedom within two minutes.
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S.
Nygaard, B. W. Laursen, A. H. Flood, C. N. Hansen, J. O. Jeppesen,*
J. F. Stoddart* |
Chem.
Commun. 2006,
144-146
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Ground-State Equilibrium
Thermodynamics and
Switching Kinetics of Bistable [2]Rotaxanes Switched in Solution,
Polymer Gels, and Molecular Electronic Devices (Front Cover) |
Collaboration
with J. F. Stoddart (UCLA) and
J. R. Heath (Caltech)
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Join
the highway where, irrespective of the environment, be it solution,
self-assembled monolayers,polymer matrices, or molecular switch tunnel
junctions—and independently of the bistable molecular switches, be they
catenanes or rotaxanes—a single and generic switching mechanism is
observed for all bistable mechanically interlocked molecules, as
described by J. F. Stoddart, J. R. Heath, J. O. Jeppesen et al. on p.
261 ff. The cover picture is designed from a concept by Amar Flood
enriched by Scott Vignon; the artwork for the front cover was produced
by Anthony Pease [the cover artwork was produced using POVTree by Gena
Obukhov (implementing TomTree by Tom Aust) and stsky.inc by Jaime Vives
Piqueres].
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J.
W. Choi, A. H. Flood, D. W. Steuerman, S. Nygaard, A. B. Braunschweig,
N. N. P. Moonen, B. W. Laursen, Y. Luo, E. DeIonno, A. J. Peters, J. O. Jeppesen,*
K. Xu, J. F. Stoddart,* and J. R. Heath* |
Chem.
Eur. J. 2006,
12,
261–279
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Nanoscale
Molecular-Switch Devices Fabricated by Imprint Lithography
(Front Cover) |
Collaboration
with J. F. Stoddart (UCLA) and
Hewlett–Packard
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Nanoscale
molecular-electronic devices comprising a single molecular monolayer of
bistable [2]rotaxanes sandwiched between two 40-nm metal electrodes
were fabricated using imprint lithography. Bistable current–voltage
characteristics with high on–off ratios and reversible switching
properties were observed. Such devices may function as basic elements
for future ultradense electronic circuitry.
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Y.
Chen, D. A. A. Ohlberg, X. Li, D. R. Stewart, R. S. Williams, J. O. Jeppesen, K.
A. Nielsen, J. F. Stoddart, D. L. Olynick and E. Anderson |
Appl.
Phys. Lett. 2003,
82,
1610–1612
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Pyrrolo-Tetrathiafulvalenes
and Their Applications in Molecular and Supramolecular Chemistry
(Front Cover)
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The
cover picture shows the molecular structure (center) of the parent
pyrrolo-tetrathiafulvalene, which has been incorporated into a number
of molecular and supramolecular systems, such as cyclophanes (upper
right), rotaxanes (lower right), porphyrins (lower left), and
calixpyrroles (upper left). The synthesis and physical properties of
the parent pyrrolo-tetrathiafulvalenes, followed by a journey through
their applications in macrocyclic, molecular, and supramolecular
chemistry, are described in the Microreview by J. O. Jeppesen and J.
Becher on p. 3245 ff.
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J. O. Jeppesen*
and Jan Becher* |
Eur.
J. Org. Chem. 2003,
3245–3266
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Two-Dimensional
Molecular Electronic Circuits (Front Cover) |
Collaboration
with J. F. Stoddart (UCLA) and
J. R. Heath (Caltech)
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The
cover picture shows part of a twodimensional crossbar circuit in which
amphiphilic bistable [2]rotaxane molecules are oriented and clustered
in the form of a monolayer between polysilicon wires (yellow) and top
electrodes (gray and white) of titanium topped by aluminum. For 2D
circuit measurements, a relay-switching matrix can be used to achieve
independent control over every wire when operating a device as a
rewritable 64-bit random access memory circuit or as an XOR logic gate,
for example. Junctions can be opened or closed by splitting the address
voltage across the top and bottom wires that define the junction, while
all other wires are held at ground. After some strings of bits have
been configured into the memory, the entire memory is read out by
applying a small voltage to the top electrode and grounding the bottom
wire through a current preamplifier, while again, all other wires are
grounded.
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Y.
Luo, C. P. Collier, J.
O. Jeppesen, K. A. Nielsen, E. Delonno, G. Ho, J. Perkins,
H.-R. Tseng, T. Yamamoto, J. F. Stoddart and J. R. Heath |
ChemPhysChem. 2002,
3,
519–525
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