A Reduced-Symmetry Heterobimetallic [PdPtL4]4+ Cage: Assembly, Guest Binding, and Stimulus-Induced Switching

Article abstract of DOI:10.1002/anie.202003220

A strategy is presented that enables the quantitative assembly of a heterobimetallic [PdPtL₄]⁴⁺ cage. The presence of two different metal ions (Pd^II and Pt^II) with differing labilities enables the cage to be opened and closed selectively at one end upon treatment with suitable stimuli. Combining an inert Pt^II tetrapyridylaldehyde complex with a suitably substituted pyridylamine and Pd^II ions led to the assembly of the cage. ¹H and DOSY NMR spectroscopy and ESI mass spectrometry data were consistent with the quantitative formation of the cage, and the heterobimetallic structure was confirmed using single-crystal X-ray crystallography. The structure of the host–guest adduct with a 2,6-diaminoanthraquinone guest molecule was determined. Addition of N,N′-dimethylaminopyridine (DMAP) resulted in the formation of the open-cage [PtL₄]²⁺ compound and [Pd(DMAP)₄]²⁺ complex. This process could then be reversed, with the reformation of the cage, upon addition of p-toluenesulfonic acid (TsOH).

Full text of DOI:10.1002/anie.202003220

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
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Accepted Article
Title: A low symmetry heterobimetallic [PdPtL4]4+ cage: assembly,
guest binding and stimulus-induced switching
Authors: Lynn S Lisboa, James A Findlay, L James Wright, Christian G
Hartinger, and James David Crowley
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202003220
Angew. Chem. 10.1002/ange.202003220
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10.1002/anie.202003220
Angewandte Chemie International Edition
RESEARCH ARTICLE
A reduced symmetry heterobimetallic [PdPtL4]4+ cage: assembly,
guest binding and stimulus-induced switching
Lynn S. Lisboa,[a] James A. Findlay,[a] L. James Wright,[b] Christian G. Hartinger,[b] and James D.
Crowley*[a]
[a]
L. S. Lisboa, Dr. J. A. Findlay and Prof. J. D. Crowley
Department of Chemistry
University of Otago
PO Box 56, Dunedin 9054, New Zealand
E-mail: jcrowley@chemistry.otago.ac.nz
[b]
Prof. C. G. Hartinger and Prof. L. J. Wright
School of Chemical Sciences
University of Auckland
Private Bag 92019, Auckland 1142, New Zealand
Supporting information for this article is given via a link at the end of the document.
Abstract: As part of efforts to enhance the applications of self-
assembled metallosupramolecular architectures (MSAs) there is
considerable current interest in the development of lower symmetry
heterometallic systems. Herein we report a strategy that enables the
Homometallic M2L4 cage-like systems (where M is a square
planar metal ion, commonly palladium(II)) are one of the most
studied sub-classes of MSAs (Figure 1).[4] Since the early work of
McMorran and Steel,[5] there have been many [Pd2L4]4+ cages
synthesized, ranging in size from small to large.[4, 6] The molecular
recognition properties of the [Pd2L4]4+ cages have been
extensively examined, with systems that can bind both neutral[7]
and anionic[8] guests, including drugs[9] and pollutants,[10]
quantitative assembly of
a reduced symmetry heterobimetallic
[PdPtL4]4+ cage C. We anticipated that the presence of two different
metal ions (Pd(II) and Pt(II)) with differing labilities could enable the
cage to be “opened” and “closed” selectively at one end upon
treatment with suitable stimuli. Combining an inert platinum(II)
tetrapyridylaldehyde complex with a suitably substituted pyridylamine
and Pd(II) ions led to the assembly of C. 1H and DOSY nuclear
magnetic resonance spectroscopy (NMR) and electrospray ionization
mass spectrometry (ESIMS) data were consistent with the
quantitative formation of the cage and the heterobimetallic structure
was confirmed using single crystal X-ray crystallography. The cage C
was shown to bind quinone guest molecules. The structure of the
reported.
Additionally,
the
redox,[11]
photophysical,[12]
biological,[12e, 13] and catalytic[14] properties of these types of cages
have also been explored and others have developed switchable
systems that can either change shape or release guest molecules
15]
on demand.[9,
For the most part, these results have been
achieved using high symmetry [Pd2L4]4+ cages. Related [Pt2L4]4+
systems are known but are far less common, presumably
because the relatively inert nature[16] of Pt(II) (in comparison to the
more labile Pd(II)) makes the self-assembly process more
difficult.[17]
host-guest adduct with
a 2,6-diaminoanthraquinone (G) guest
molecule was determined using X-ray crystallography. Additionally,
the system was shown to be stimuli responsive and could be opened
and closed on demand. Addition of N,N'-dimethylaminopyridine
(DMAP) to the cage C resulted in the formation of the “open-cage”
[Pt(L)4]2+ compound and [Pd(DMAP)4]2+ complex. This new type of
stimulus-induced cage opening is similar to
a
flower
blossoming/blooming. This process could then be reversed, with the
reformation of C, upon the addition of p-toluenesulfonic acid (TsOH).
When DMAP was added to the host-guest adduct, [CG]4+, the guest
was released from C. The host-guest adduct was subsequently
restored upon addition of TsOH.
Figure 1. Cartoon representations of homometallic [Pd2L4]4+ (right) and [Pt2L4]4+
(left) cages. A lower symmetry heterobimetallic [PdPtL4]4+ cage (center). Colors:
palladium(II) = purple, platinum(II) = pink, grey = semi rigid di-monodentate
linker ligand.
Introduction
There is a growing number of lower symmetry [Pd2L4]4+
cages that have either been generated with lower symmetry
ligands[18] or with two or more different types of ligands[19]
incorporated into the cage architecture. Several discrete
heterometallic [PdXMXLY] structures[3] (where M = Ti(IV),[20]
Over the past three decades, there has been considerable
interest in self-assembled metallosupramolecular architectures
(MSAs). The general principles for the synthesis of high symmetry
assemblies[1] are now well understood and a range of interesting
applications of MSAs are emerging.[2] To further enhance these
nascent applications, there has been an up-surge in efforts to
develop lower symmetry cage systems, especially those that
utilize two different metals with dissimilar coordination
properties.[3]
22]
24]
Zn(II),[21] Fe(II),[6b,
Fe(III),[23] Ru(II),[6e,
Ir(III),[25] Al(III)[26]
Zr(IV),[27] and lanthanide ions (Ln)[28] have been reported but there
are very few [PdXPtXLY] systems[29] and, thus far, to the best of our
knowledge, there have been no reports of a reduced symmetry
heterobimetallic [PdPtL4]4+ cage system (Figure 1 center).
1
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10.1002/anie.202003220
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RESEARCH ARTICLE
Herein we describe a method for the quantitative assembly
of a heterobimetallic [PdPtL4]4+ cage. Additionally, we examine
the stimuli responsiveness, as well as guest binding and release
of this cage.
formation, the aldehyde and amine resonances of 1 and 2,
respectively, were replaced by a signal (Hi, δ = 8.95 ppm)
consistent with imine formation and the α-pyridyl peaks (Ha and
Hb) were shifted downfield, relative to 2, indicating coordination to
the Pd(II) ion. The new set of peaks were also different to those
observed for the free ligand L (Figure 1d and Supporting
Information, Figures S9-10). 1H DOSY NMR spectrum of the
reaction mixture revealed that all the new resonances have the
same diffusion coefficient (DC = 1.22 × 10-10 m2 s-1) suggesting
clean formation of one product (Supporting Information, Figure
S11 and Table S1). Furthermore, this diffusion coefficient was
different to those found for 1 and 2 and consistent with the
formation of a larger architecture (Supporting Information, Table
S1). Electrospray ionization mass spectrometry (ESIMS) data
obtained from the solution of the reaction mixture also supported
the formation of the cage C. The major peak observed at m/z =
358.5741 was consistent with the formulation [PdPtL4]4+ and the
observed isotope pattern matched that calculated for this 4+ ion
(Supporting Information, Figure S8).
Results and Discussion
Inspired by the subcomponent self-assembly method[1f, 30] and
dynamic covalent cage systems,[31] we have devised an approach
to a reduced symmetry heterobimetallic [PdPtL4]4+ cage. We
reasoned that combining an inert platinum(II) tetrapyridylaldehyde
complex[32] with a suitably substituted pyridylamine and a labile
Pd(II) complex should lead to the assembly of a heterometallic
[PdPtL4]4+ cage through the reversible formation of imine and Pd-
pyridyl bonds (Scheme 1).
The relatively inert platinum(II) complex [Pt(3-
pyridylcarboxyaldehyde)4](BF4)2 (1) was synthesized in good yield
(95%) by heating 3-pyridylcarboxyaldehyde (4 equiv.),
[Pt(DMSO)2Cl2] (1 equiv.) and AgBF4 (3 equiv.) in acetonitrile at
60 °C for 20 h (Supporting Information, Scheme 1, Scheme S1,
Figures S1-S3). 3-[2-(3-Pyridinyl)ethynyl]benzenamine (2) was
synthesized in modest yield (43%) using a Sonogashira coupling
between the commercially available 3-ethynylpyridine and 3-
iodoaniline (Supporting Information, Figures S4-S5).
The cage C was isolated as a colorless solid in 87% yield
from the [D6]DMSO solution of the reaction mixture by addition of
excess ethyl acetate. The colorless solid was dissolved in
nitromethane and diethyl ether was vapor-diffused into the
solution to provide colorless crystals of quality suitable for single
crystal X-ray diffraction analysis. The molecular structure
determined from the X-ray data (Supporting Information, Table S2
Figure S14) is given in Scheme 1 and provides confirmation for
the formation of the reduced symmetry [PdPtL4](BF4)4 cage, C. As
expected, the four bridging ligands are oriented so that the cage
has different coordination environments at each end. At one end
the Pd(II) ion is coordinated to the four pyridyl alkyne groups of
the bridging ligands while the Pt(II) ion is bound to four
pyridylimines (Scheme 1 and Supporting Information). The metal-
pyridyl bond distances are consistent with those observed in
related molecules and the Pd-Pt distance (11.52 Å) is similar to
those found in related homometallic pyridyl alkyne-type cages.[7d,
8a, 9-10, 12b, 12e, 13b, 13f, 14c, 17f, 33] The cage C adopts a slight helical twist
-
and the cavity contains a BF4 anion (positioned towards the
pyridyl alkyne end) and a nitromethane molecule (found close to
the pyridylimine end). Both guests form hydrogen bonds to the
acidic α-pyridyl hydrogen atoms (Supporting Information, Figure
S14).
Having confirmed the formation of the reduced symmetry
heterometallic cage C, we next examined the host-guest (HG)
chemistry of the system. Homobimetallic [Pd2L4]4+ cages have
been shown previously to bind a variety of neutral and anionic
guest molecules. Lusby and co-workers,[7d, 14c] and others[8a] have
reported that benzoquinone (BQ) will bind within the cavity of
homobimetallic [Pd2L4]4+ cages through hydrogen bonding
interactions between the carbonyl groups of the guest and the
acidic α-pyridyl hydrogen atoms of the coordinated pyridyl group
of the host. However, the same authors also showed the HG
interaction with neutral guests is weakened by competition with
anions and solvents.[7d] As the solid state structure of C showed a
BF4- anion bound within the cavity of the cage, we first examined
this interaction in solution using 19F NMR spectroscopy
([D6]DMSO, 298 K). The NMR data suggested that the
BF4− anions were, at least weakly, interacting with the cage,
presumably in a similar fashion to that observed in the X-ray
structure, because the resonance due to the BF4− anions
Scheme 1. Synthesis of the [PdPtL4](BF4)4 cage (C): (i) 1 (1 eq.), 2 (4 eq.), and
[Pd(CH3CN)4](BF4)2 (1 eq.), [D6]DMSO, RT, 1 h. The ball and stick structures 1
(one possible conformation) and 2 are SPARTAN’16® models, whereas the stick
model of C is the molecular structure determined by X-ray diffraction analysis:
selected bond lengths (Å) Pt1-N4 = 2.08(3), Pt1-N9 = 2.08(4), Pt1-N3 = 2.04(4),
Pt1-N12 = 2.02(3), Pd1-N10 = 2.01(2), Pd1-N7 = 2.04(3), Pd1-N1 = 2.03(3),
Pd1-N6 = 2.00(2), Pt1-Pd1 = 11.52(2). Color: pink = platinum, purple =
palladium, light blue = nitrogen, red = oxygen, grey = carbon, white = hydrogen.
Solvent molecules and counterions were omitted for clarity.
The platinum(II) complex, 1, [Pd(CH3CN)4](BF4)2 and 2 were
then combined in [D6]DMSO at room temperature (RT) and the
reaction monitored using 1H NMR spectroscopy (Scheme 1,
Figure 1 and Supporting Information, Figures S6-S8). Within 1 h,
the signals (Figure 1a and c) of the platinum(II) aldehyde complex
(1) and amine 2 had completely disappeared and were replaced
by a new series of resonances (Figure 1b). Diagnostic of cage
of C was shifted (Δδ
=
0.2 ppm) relative to that of
NaBF4 (Supporting Information, Figure S15).
2
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RESEARCH ARTICLE
Figure 1. Stacked partial 1H NMR spectra (400 MHz, [D6]DMSO, 298 K) of a) compound 2, b) cage C, c) complex 1 and d) ligand L
Nevertheless, since the Pd-Pt distance (11.52 Å) of C was
similar to the Pd-Pd distances found in homometallic pyridyl
alkyne-type cages,[7d, 8a, 9-10, 12b, 12e, 13b, 13f, 14c, 17f, 33] we decided to
investigate HG interactions between C and selected neutral guest
molecules that had been found to bind within [Pd2L4]4+ cages. In
the first instance we examined the interaction of BQ with the cage
C using 1H NMR spectroscopy ([D6]DMSO, 298 K). Upon titration
of BQ into a [D6]DMSO solution of C very modest complexation
induced shifts (CIS) of the protons (Ha, Hb, Hm, Hl and Hi) of C were
observed (Δδ = 0.04 – 0.13 ppm, in the presence of 50 equiv. of
guest). This indicated that BQ does interact with C, albeit weakly.
Fitting the titration data to a 1:1 binding model using Bindfit
(supramolecular.org)[34] gave a binding constant (K) of 23.3 ± 0.8
M-1 for the [C BQ]4+ interaction (Supporting Information, Figures
S16-S19). Presumably, the modest binding interaction was caused
by competition with the BF4− anions and DMSO solvent molecules.
In an effort to achieve a stronger HG interaction, we
examined some larger quinone guests including anthraquinone,
2,6-diaminoanthraquinone (G) and 6,13-pentacenequinone.
However, the limited solubility of these compounds in [D6]DMSO
restricted our studies to G. Addition of G (1 equiv.) to the cage C
in [D6]DMSO resulted in a substantial change in the resonances
of the cage as indicated by the 1H NMR spectrum of the mixture
(Figure 2b). The resonances of the cage C were shifted and
doubled upon addition of G to the solution. In addition, peaks due
to free cage C, as well as free and bound G, could all be
discerned. The data suggested that G is bound within C and the
exchange between free and bound states is slow on the NMR
timescale. Due to the slow exchange (both inter- and intra-
molecular) the C and G peaks of the CG host-guest adduct were
doubled. The low symmetry of the cage coupled with the slow
exchange led to the number of host-guest signals doubling. When
G is bound it removes the four-fold symmetry of the cage as the
amino groups of G are nearer to two of the metal bound pyridyl
units but the other two pyridyl units are near a hydrogen on the
guest (vide infra, Scheme 2). The integration of the bound host
and guest signals suggested that one G molecule was interacting
with C. Upon titration of more G into the solution the peaks due to
the free cage eventually disappear leaving only the signals due to
the CG host-guest adduct and the excess free G (Supporting
Information, Figure S21). ESIMS data obtained on the 1:1 mixture
of C and G in [D6]DMSO provided additional support for the
formation of the CG host-guest adduct (Supporting Information,
Figure S20). While a series of peaks due to the empty cage with
different numbers of counterions was observed, two peaks
consistent with C forming a 1:1 host-guest adduct with G
(Supporting Information) were also present (m/z = 418.0981
([CG]4+) and 566.4655 ([CG(BF4)]3+), respectively). Using a 1:1
binding model, we were able to estimate the binding constant (K)
to be 2900 ± 300 M-1 for the system (Supporting Information,
Figures S21-S22). Vapor diffusion of ethylacetate into a 1:1
mixture of C and G in DMSO provided small single crystals that
could be used for X-ray diffraction analysis. While the intensity of
diffraction was weak and there was some positional disorder in
the cage unit, the cationic cage and the presence of the guest G
(and the anions) could clearly be observed confirming the
formation of a 1:1 host-guest adduct (Scheme 2 and Supporting
Information, Figure S23). As was observed in related
[Pd2L4]4+quinone host-guest adducts,[7d, 14b] there are hydrogen
bonding interactions between the carbonyl groups of the guest
and the acidic α-pyridyl hydrogen atoms of the coordinated pyridyl
group of the cage (Scheme 2 and Supporting Information, Figure
S23).
Having confirmed that C would act as a host for guest
molecules, we next examined if the presence of two different
metal ions (Pd(II) and Pt(II)) with differing labilities could be
exploited to “open” and “close” the cage selectively at one end
upon treatment with a suitable stimulus. We postulated that
addition of N,N'-dimethylaminopyridine (DMAP) to the reduced
symmetry [PdPtL4](BF4)4 cage C should remove the more labile
Pd(II) ions from the cage while leaving the more inert Pt(II) ions
coordinated to the four ligands L. This would lead to the cage
opening in a similar way to a flower blossoming/blooming. Several
switchable [Pd2L4]4+ cages are known and a range of different
stimuli have been used to generate switching.[9, 15] In most cases,
the stimulus results in complete decomposition of the cage or
rearrangement into new metallosupramolecular architectures.
Here, we chose to use DMAP as a competitive ligand for Pd(II) as
we[9] and others[35] have previously shown that addition of this very
basic ligand will remove Pd(II) from metallosupramolecular
architectures as [Pd(DMAP)4]2+ with release of the free ligands.
Furthermore, this process is completely reversible, and addition
of acid to the [Pd(DMAP)4]2+:ligand mixtures that are produced
results in protonation and dissociation of the more basic DMAP
ligands with reformation of the initial metallosupramolecular
architectures.
3
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10.1002/anie.202003220
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RESEARCH ARTICLE
Figure 2. Stacked partial 1H NMR spectra (400 MHz, [D6]DMSO, 298 K) of a) cage C, b) GC complex at a 1:1 ratio, and c) 2,6-diaminoanthraquinone (G). Proton
peak labels: blue; C of GC complex, orange; G of GC complex, green; G. The prime symbols on host and guest proton labels of the CG host-guest adduct
indicate the doubling of these resonances due to desymmetrization caused by the lower symmetry of C and slow guest exchange (both inter- and intra-molecular
exchange).
Initially, we titrated DMAP into a [D6]DMSO solution of C and
1
monitored the reaction using H NMR spectroscopy (Supporting
Information, Figures S24 and S25). As the amount of DMAP was
increased (from 0-5 equiv.), the resonances for C slowly
decreased and two new sets of peaks appeared. One set of peaks
was consistent with the formation of [Pd(DMAP)4]2+, as expected,
and the other set of peaks was assigned to the complex,
[Pt(L)4]2+. No signals were observed for free L. 2D COSY and
NOESY NMR spectra enabled the full assignments to be made
for [Pt(L)4]2+ and the observed chemical shifts for the pyridyl
proton resonances were consistent with one pyridyl(imine) unit of
L
being complexed to the Pt(II) ion while the second
pyridyl(alkyne) unit was not coordinated. ESIMS data obtained on
the 1:4 mixture of C and DMAP in [D6]DMSO provided additional
support for the formation of [Pt(L)4]2+ (m/z = 664.2042) and
[Pd(DMAP)4]2+ (m/z = 297.0913) (Supporting Information, Figure
S26).
Addition of p-toluenesulfonic acid (TsOH, 4 equiv.) to the 1:4
mixture of
C
and DMAP in [D6]DMSO led to the
protonation/dissociation of the DMAP ligands and reformation of
the heterobimetallic cage C, confirming that the stimulus induced
opening of the cage is completely reversible (Supporting
Information, Figure S24). Having demonstrated that C was able
to open and close on demand, we then examined if this could be
used to release and then rebind guest molecules (Scheme 2). The
[CG]4+ host-guest adduct was generated by adding 1 equiv. of G
to a [D6]DMSO solution of C (1 equiv.). The resulting host-guest
complex was then treated with DMAP (4 equiv.) and the reaction
1
1
monitored using H NMR spectroscopy (Figure 3). The H NMR
spectrum (Figure 3b) showed that addition of the DMAP resulted
in the formation of [Pt(L)4]2+ and [Pd(DMAP)4]2+ with liberation of
the guest G (Scheme 2). In a process that paralleled that
observed with the empty cage C, addition of TsOH (4 equiv.) to
the mixture resulted in protonation/dissociation of the DMAP
ligands on Pd(II) with accompanying reformation of the cage C
and, importantly, reuptake of the guest G to form the [CG]4+ host-
guest adduct.
Scheme 2. Reversible release and re-binding of G from C by the addition of 4
eq. TsOH and 4 eq. DMAP, respectively. The ball and stick structure of [PtL4]2+
(one possible conformation) is a SPARTAN’16® model. The stick model of GC
is the solid-state X-ray crystal structure (distances (Å): Pt1-Pd1 = 11.7310(8),
N7-N5A = 3.67(2), N7-N2B = 3.84(2), O2-C24A = 3.43(1), O2-C15A = 3.34(1),
O2-C5A = 3.464(9), O2-C34A = 3.35(1)). Color: pink = platinum, purple =
palladium, light blue = nitrogen, red = oxygen, grey = carbon, white = hydrogen.
Solvent molecules and counterions are omitted for clarity.
4
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10.1002/anie.202003220
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RESEARCH ARTICLE
Figure 3. Stacked partial 1H NMR spectra (400 MHz, [D6]DMSO, 298 K) of a) GC at a 1:1 ratio, b) open Pt complex with the addition of DMAP, and c)
reformation of the cage into GC with the addition of TsOH.
related higher symmetry [Pd2L4]4+ and [Pt2L4]4+ cages. We are
currently examining these properties and attempting to extend the
methodology
metallosupramolecular architectures.
to
other
(larger)
heterobimetallic
Conclusion
Herein we have developed a method that enables the quantitative
assembly of a reduced symmetry, heterobimetallic [PdPtL4]4+
cage C. Combining an inert platinum(II) tetrapyridylaldehyde
complex with a suitably substituted pyridylamine and Pd(II) ions
led to the assembly of the heterobimetallic [PdPtL4]4+ cage
through the reversible formation of imine and relatively labile Pd-
Acknowledgements
LSL thanks the University of Otago for a PhD Scholarship. JDC
thanks the University of Otago, Department of Chemistry and the
MacDiarmid Institute for Advanced Materials and Nanotechnology
for funding. All authors are grateful to the Marsden Fund for
supporting this work through a grant (UOA1726).
1
pyridyl bonds. H and DOSY NMR and ESI-mass spectra were
consistent of the quantitative formation of the cage and the
heterobimetallic structure was confirmed using X-ray
crystallography. The heterobimetallic [PdPtL4]4+ cage displayed a
similarly sized cavity to known homometallic [Pd2L4]4+ cages. Like
the known [Pd2L4]4+ cages, C was shown to bind quinone guest
molecules using 1H NMR spectroscopy. The larger 2,6-
diaminoanthraquinone (G) interacted with the cage quite strongly
(K = 2900 ± 300 M-1) and the host-guest adduct could be detected
using ESIMS. The structure of the [CG]4+ host-guest adduct was
also determined using X-ray crystallography.
Importantly, the deliberate design of the cage with inert
Pt(II)-pyridyl donor bonds at one end and relatively labile Pd(II)-
pyridyl donor bonds at the other end enabled the cage to be
opened and closed reversibly and in a controlled manner. This
new type of stimulus-induced cage opening can be viewed as
similar to the blossoming/blooming of a flower and is distinct from
the mechanisms observed in previously reported homometallic
stimuli-responsive cages. The stimuli-responsive behavior of C
was achieved by sequential addition of the basic ligand DMAP,
followed by the acid TsOH. Thus, the addition of 4 equivalents of
DMAP to C resulted in cage opening through removal of the
relatively labile Pd(II) ion from the cage as [Pd(DMAP)4]2+ and
formation of the [Pt(L)4]2+ “open-cage”. Subsequent addition of
TsOH to the mixture then resulted in protonation/dissociation of
the DMAP ligands from [Pd(DMAP)4]2+ and reformation of C.
When this process was carried out on the host-guest adduct,
[CG]4+, DMAP addition resulted in the formation of [Pt(L)4]2+ and
[Pd(DMAP)4]2+ with release of the guest G. Upon addition of
TsOH to this reaction mixture, the host-guest adduct, [CG]4+,
was restored.
Keywords: metallosupramolecular architectures • cages • stimuli
responsive • host-guest • heterometallic
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5
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Entry for the Table of Contents
Insert graphic for Table of Contents here. ((Please ensure your graphic is in one of following formats))
Insert text for Table of Contents here. A method for the quantative assembly of the heterobimetallic cage, [PdPtL4]4+, is described.
The cage is shown to interact with quinone guest molecules in a 1:1 fashion. The cage can be selectively and reversibly opened then
re-closed at the Pd(II) end by the sequential addition of base then acid. Guest molecules can be reversibly released/bound during this
process.
Institute and/or researcher Twitter usernames: @CrowleyGroup @HartingerHub
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