Implications of stoichiometry-controlled structural changeover between heteroleptic trigonal [Cu(phenAr2)(py)]+ and tetragonal [Cu(phenAr2)(py)2]+ motifs for solution and solid-state supramolecular self-assembly

Article abstract of DOI:10.1021/ic301286w

A stoichiometric variant of the HETPYP concept (HETeroleptic PYridine and Phenanthroline metal complexes) opens the venue to heteroleptic metallosupramolecular HETPYP-I assemblies both in solution and the solid state, involving the trigonal [Cu(phenAr₂)(py)]⁺ coordination motif (phenAr₂ = 2,9-diarylphenanthroline; py = various oligopyridines). Combining the same building blocks at another stoichiometric ratio furnished metallosupramolecular HETPYP-II aggregates in the solid state, now based on the tetrahedral [Cu(phenAr₂)(py)₂] ⁺ coordination motif. Thus, a stoichiometry-controlled structural changeover based on the relative amounts of oligopyridines leads from a discrete assembly with trigonally coordinated copper(I) centers to a coordination polymer with tetrahedrally coordinated copper(I) ions, as shown by solid state studies. In solution, the analysis of both stoichiometric variants indicates that the HETPYP-I structure is congruent with that in the solid state, while the HETPYP-II assembly, as established through DOSY NMR and dynamic light scattering measurements, is only oligomeric at low temperature. At room temperature, i.e. due to entropic costs, the latter assembly prefers to keep unsaturated coordination sites that are in rapid exchange, making it an interesting system as a dynamic protecting group and for constitutional dynamic materials through the exchange and reshuffling of components.

Full text of DOI:10.1021/ic301286w

Article
pubs.acs.org/IC
Implications of Stoichiometry-Controlled Structural Changeover
Between Heteroleptic Trigonal [Cu(phenAr2)(py)]+ and Tetragonal
[Cu(phenAr2)(py)2]+ Motifs for Solution and Solid-State
Supramolecular Self-Assembly
Subhadip Neogi,*,‡ Gregor Schnakenburg,§ Yvonne Lorenz,§ Marianne Engeser,§
and Michael Schmittel*,‡
‡Center of Micro and Nanochemistry and Engineering, Organische Chemie I, Universitat Siegen, Adolf-Reichwein-Strasse 2, D-57068
̈
Siegen, Germany
§Fachgruppe Chemie der Universitat Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany
̈
S
* Supporting Information
ABSTRACT: A stoichiometric variant of the HETPYP
concept (HETeroleptic PYridine and Phenanthroline metal
complexes) opens the venue to heteroleptic metallosupramo-
lecular HETPYP-I assemblies both in solution and the solid
state, involving the trigonal [Cu(phenAr2)(py)]+ coordination
motif (phenAr2 = 2,9-diarylphenanthroline; py = various
oligopyridines). Combining the same building blocks at
another stoichiometric ratio furnished metallosupramolecular
HETPYP-II aggregates in the solid state, now based on the
tetrahedral [Cu(phenAr2)(py)2]+ coordination motif. Thus, a
stoichiometry-controlled structural changeover based on the
relative amounts of oligopyridines leads from a discrete
assembly with trigonally coordinated copper(I) centers to a
coordination polymer with tetrahedrally coordinated copper(I) ions, as shown by solid state studies. In solution, the analysis of
both stoichiometric variants indicates that the HETPYP-I structure is congruent with that in the solid state, while the HETPYP-II
assembly, as established through DOSY NMR and dynamic light scattering measurements, is only oligomeric at low temperature.
At room temperature, i.e. due to entropic costs, the latter assembly prefers to keep “unsaturated” coordination sites that are in
rapid exchange, making it an interesting system as a dynamic protecting group and for constitutional dynamic materials through
the exchange and reshuffling of components.
more components being available.6 Unsurprisingly, the
INTRODUCTION
■
successful self-assembly of multiple components into discrete
Over the past two decades, metallosupramolecular chemistry
has witnessed forceful research activities to unravel the
mysteries of self-assembly furnishing well-defined, discrete
heteroleptic structures is still much less documented.3,7 Herein,
we will present not only a new three-component self-assembly
system, but also its use in reversible structural changeovers,
architectures under thermodynamic control from a collection of
two, three, or even more components.1 On one side, current
simply controlled by the stoichiometric ratio of the
components. Such protocols may open the perspective to
research aims at developing huge highly symmetric supra-
molecular entities, such as virus analogs,2 making multiple use
switching emergent properties of multicomponent systems
through the deliberate addition and removal of components.
of a single component (in combination with metal ions as a
At present, additive-triggered structural changeovers in
glue), while on the other side intricate self-sorting protocols are
supramolecular systems are hardly known.8 Hupp and Nguyen
searched to build more and more geometrically irregular
multicomponent aggregates.3 Interest in the latter4 emerges not
elaborated a loop to square conversion by rigidifying the
bridging ligand through addition of Zn2+ to a salene binding
only because of academic fascination with intricate structures,
site.9 Utilizing the reaction of an alkyne with Co2(CO)8 for
but also due to possible emergent properties of multi-
supramolecule-to-supramolecule transformations, Stang and co-
workers developed the conversion of a [6 + 6] hexagon to two
component aggregates, a feature well-known in biological
systems.5 The increased complexity, however, goes along with
an augmented number of possible reaction products and thus
raises the question, how to control the formation of a single
discrete supramolecule in a fully dynamic setting with more and
Received: June 18, 2012
Published: September 26, 2012
© 2012 American Chemical Society
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Scheme 1. Three Different Possibilities of Heteroleptic Complexation in the HETPYP Concept
Scheme 2. Ligands Used in the Present Study (With Atom Numbering Scheme)
[3 + 3] hexagons and of a triangle-square mixture to [2 + 2]
rhomboids.10 Reversible interconversion of a metallosupramo-
lecular triangle and a coordination polymer was effected by
changing the solvent that acts as an axial ligand on the bridging
copper ions, as described by Mirkin.8b Obviously, such
transformations should not mistaken for supramolecular
isomerism.11,12
For inducing structural alterations through addition of
components, the highly dynamic coordination motif [M-
(phenAr2)(py)]+ seemed most promising to us. Unlike L =
phenanthroline or terpyridine,20 the nonchelate ligand pyridine
provides a much weaker binding to the metal ion thus offering
an increased dynamics.21 On the basis of these considerations,
we recently developed the HETPYP (heteroleptic pyridine and
phenanthroline metal complexes) concept,15 in which the
central copper(I) ion sets up a tetrahedral coordination
scenario with one phenanthroline and two pyridine ligands.
In our quest to control supramolecular structures by
stoichiometry, we envisioned that the HETPYP approach
may be ideal by virtue of various Cu+−N(py) bonding settings.
To our perception, three different possibilities may arise in
HETPYP assemblies (see Scheme 1): (a) a HETPYP-II
coordination as reported previously by us,15,16b (b) a
trisheteroleptic complex (HETPYP-III) arising from a [M-
(phenAr2)]+ unit and two dissimilar pyridine ligands (similar to
the end-capped Pt2+ or Pd2+ metal ions reported by Fujita and
co-workers),22 and (c) formation of a new tricoordinated23
HETPYP-I type complex, in which a single pyridine ligand is
attached to the frustrated [M(phenAr2)]+ center.
For setting up stoichiometry-responsive multicomponent
systems and their structural conversions, we envisaged to use a
heteroleptic complexation unit that is both tolerant to different
lengths/angles of the ligands and to different coordination
angles/scenarios at the metal site. As possible coordination
units for such transformations, one may identify end-capped
square-planar palladium and platinum units as these corner-
stones allow for combinations with a variety of ligands, such as
pyridines, alkynes, carboxylates, and nitriles, leading to exciting
heteroleptic metallosupramolecular structures.13,14 A similarly
attractive cornerstone is the complex [M(phenAr2)]+ with its
sterically shielded 2,9-diarylphenanthroline (phenAr2), because
in our earlier work it has proven itself as a versatile building unit
for a large number of supramolecular heteroleptic aggre-
gates.15−19 Notably, the [M(phenAr2)]+ unit cannot combine
with a second phenAr2. Thus, the system remains in a
coordinatively frustrated situation until it coordinates to a
second slim ligand L (L: pyridine (py),15,16a phenanthro-
line,17,18 or terpyridine19) to fill the vacant site(s) by generating
the complex [M(phenAr2)(L)]+.
Herein, we describe how one can set up (i) trigonally
coordinated copper(I) centers (HETPYP-I) as novel building
blocks for discrete supramolecular assemblies and (ii) a
stoichiometry-dependent changeover between discrete [Cu-
(phenAr2)(py)]+ assemblies (HETPYP-I) and coordination
polymers in the solid state, the latter based on tetrahedral
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Table 1. Summary of Crystallographic Data for C1(I), C1(II), C2, C3(II), and C4(I)
C1(I)
C1(II)
C2
C3(II)
C4(I)
formula
fw
C84H72Cl4Cu2F12N6P2
1724.30
C42H36CuF6N4P
805.26
C76H68Cu2F6N6O6S2Cl4
1608.36
C80H72Cu2F6N8P
1417.51
C122H111Cl2Cu3F18N9OP3
2415.63
cryst syst
space group
a (Å)
b (Å)
c (Å)
triclinic
orthorhombic
Pna21
triclinic
monoclinic
P21/n
monoclinic
C2/c
P1
̅
P1
̅
0.861(10)
12.328(12)
14.657(15)
91.22(4)
103.27(3)
95.78(3)
1898.3(3)
1
18.924(4)
10.675(3)
18.521(5)
11.204(15)
12.427(16)
13.711(16)
94.47(4)
102.37(4)
101.74(4)
1810.7(4)
1
14.548(7)
36.735(17)
16.967(8)
41.081(3)
23.644(16)
27.532(18)
α
β (deg)
γ
V (Å3)
95.55(10)
117.06(3)
3741.41(17)
4
9025.3(7)
4
23814(3)
8
Z
Dcalcd (g cm−3
)
1.508
1.430
0.693
1656
1.475
1.043
0.541
2940
1.348
0.697
9936
μ (mm−1
)
0.824
0.866
F(000)
882
826
T (min.)
T (max.)
0.673
0.706
0.934
1.045
0.0458
0.1211
0.846
0.909
0.938
0.917
0.1178
0.2317
0.756
0.959
1.221
0.1091
0.3108
0.952
0.950
GOF on F2
1.045
1.026
R1 [I > 2σ(I)]
R2 [I > 2σ(I)]
0.0322
0.0834
0.0748
0.1719
Figure 1. Side view (left) and top view (right) of the crystal structure for complex C1(I).
[Cu(phenAr2)(py)2]+ complexes (HETPYP-II). The origin of
the change is based solely on the reversible attachment of one
versus two pyridine ligands at the frustrated [Cu(phenAr2)]+
site (Scheme 1). In solution, on the basis of 1D and 2D NMR,
DOSY NMR, ESI-FTICR mass spectrometry, and dynamic
light scattering (DLS) data, we see the same structural
changeover.
HETPYP-I design was proven by X-ray diffraction analysis.
Orange-colored single crystals, suitable for the X-ray study,
were grown by slow diffusion of diethyl ether into a
dichlorobenzene solution of C1(I). The compound crystallizes
in the triclinic space group P1 (Table 1) with the asymmetric
̅
unit consisting of one copper(I) ion, ligand 1, one-half of ligand
−
3, a PF6 anion, and a 1,2-dichlorobenzene solvent molecule.
The copper(I) ion is linked unsymmetrically to the two
nitrogens of the phenanthroline (2.10 Å and 1.98 Å) and one
pyridine nitrogen (1.90 Å) thus accepting only three dative
RESULTS AND DISCUSSION
■
All ligands used in this study are depicted in Scheme 2. 4,4′-
Bipyridine (2) is commercially available, while ligands 1, 3, and
4 were prepared according to literature procedures.24 For
convenience, HETPYP-I and HETPYP-II complexes based on
identical ligands are denoted as Cn(I) and Cn(II), respectively.
Solid State Studies. Self-Assembly of Bipyridine 3 and
[Cu(1)]+ (Complexes C1(I), C1(II), and C2). As a starting point to
elaborate HETPYP-I vs HETPYP-II self-assembly, we decided
to evaluate the heteroleptic complexation scenario of 1, 3, and
[Cu(MeCN)4]PF6. Because pyridines typically form homo-
leptic complexes in the presence of many metal ions,25 it
seemed reasonable to avoid formation of any unwanted
homoleptic complex right at the onset by combining all
components sequentially. Keeping this in mind, 1 was first fed
with one equivalent of Cu+ in dichloromethane-d2 to form the
capped and coordinatively frustrated metal monoligand
complex [Cu(1)]+. After mixing ligand 3 with [Cu(1)]+ in a
1:2 ratio, the color of the solution immediately turned from
yellow to orange. Heteroleptic complexation along the
−
coordination bonds (Figure 1). The PF6 anion is situated on
one side of the [Cu(1)]+ motif exhibiting only negligible
interaction with the copper(I) ion (3.25 Å).26 While the
trigonal copper(I) motif is rare, it has been documented
previously with various ligands in mononuclear complexes23,27
and within an oligonuclear oligopyridine helicate with all L−
Cu−L angles at ∼120°.28
The less-commonly Y-shaped geometry (one angle com-
pressed from 120°, the other two expanded), as observed
herein, occurs only when a chelating ligand forces one of the
angles to be narrower than the expected 120° trigonal planar
geometry.27 Each ligand 3 connects two copper(I) phenanthro-
line units (Figure 1) to form a discrete dumbbell-shaped
structure with a Cu···Cu separation of 13.45 Å, with the planes
of phenanthroline and pyridine rings being perpendicular to
each other. One of the mesityl groups of 1 is found to be
slanted somewhat toward the bipyridine plane (Figure 1, side
view) thus experiencing strong π-stacking interactions with the
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pyridine ring (3.59 Å). Another strong π-stacking interaction is
observed between the pyridine ring and the dichlorobenzene
solvent molecule (3.80 Å). These strong secondary interactions
appear to stabilize the overall structure. The overall two-
dimensional (2D) packing diagram with its one-dimensional
channel structure is depicted in Figure 2. The channels are
−
filled with solvent molecules and PF6 anions.
Figure 3. View of the 2D packing arrangement of complex C1(II) with
PF6− anions (shown in a space filling mode) inside the channel. Inset
shows the zigzag motif of an individual chain structure. Hydrogen
atoms were omitted for clarity. Color code: 1, red; 3, blue; copper,
cyan.
the [Cu(CF3SO3)(toluene)] complex as a copper(I) source.
Complexation was carried out in dichloromethane by reacting
[Cu(1)]+/3 in a 2:1 ratio affording complex C2, from which
single crystals were grown as red needles by slow evaporation of
dichloromethane. The X-ray analysis reveals that the metal ion
is bound to two nitrogens of phenanthroline 1 (2.10 Å and 2.00
Å) and one nitrogen atom of ligand 3 (1.93 Å), while the fourth
coordination site is now filled at 2.34 Å distance with one
oxygen atom of the triflate anion, leading to a distorted
tetrahedral geometry at each copper(I) center (Figure 4). The
overall structure of complex C2 was found to be quite similar to
that of complex C1(I) considering the spatial orientation of
ligands 1 and 3, except that the central copper(I) ion is now
tetra-coordinated. Strong π−π stacking interactions exist
between the pyridine ring and one of the mesityl groups of
ligand 1 (3.63 Å). On the basis of the above results, we
conclude that the complexation scenario, i.e. trigonal vs
tetrahedral coordination at the copper(I) center, depends on
the properties of the anion furnishing weak or strong binding.
Self-Assembly of 2 and [Cu(1)]+ (Complexes C3(I) and
C3(II)). To evaluate the impact of shortening the distance
between two nitrogen donor centers in the bipyridine and thus
an increasing steric repulsion between the caps, 3 is replaced by
the shorter bipyridine 2 (Scheme 2). We envisaged that the
smallest heteroleptic assembly formed at lowest entropic costs
following the HETPYP-I strategy ([Cu(1)]+/2 = 2:1) should
be [Cu2(1)2(2)]2+. Unfortunately, though single crystals of
relatively big size and good shape were obtained by different
methods, all crystals proved to be unstable during diffraction
measurements. Nevertheless, formation of the desired complex
C3(I) was attested by the ESI-FTICR mass spectrometry data,
with the molecular ion being readily detected by its correct
isotopic pattern and exact mass (see Supporting Information,
Figure S12).
Figure 2. Two dimensional packing diagram of C1(I) along the
crystallographic a axis, showing 1,2-dichlorobenzene solvent molecules
and PF6 anions embedded inside the one-dimensional channels.
−
Color code: 1, red; 3, blue; copper, cyan.
Changing the ratio of ligands 1, 3, and [Cu(MeCN)4]PF6 to
1:1:1 caused a visible color difference and block shaped red
crystals of C1(II) were isolated by slow diffusion of diethyl ether
into a dichloromethane solution of the complex. X-ray analysis
revealed the formation of a zigzag chain structure. Each of the
Cu+ ions is now tetrahedrally coordinated by four N atoms with
ligation from phenanthroline 1 and two pyridines, the latter
stemming from two different molecules of 3. As depicted in
Figure 3, the zigzag chains are arranged in a side-by-side
manner to produce a 2D array along the ac plane, showing
extensive π−π-stacking interactions (3.69 Å) between the
phenanthroline moiety and a pyridine ring of the neighboring
array. Close inspection of the copper(I) centers in an individual
chain in C1(II) divulges that, unlike in C1(I), the pyridine rings
are not positioned in the shielding region of 1. The steric
hindrance between the mesityl groups and the pyridine ortho
protons enforces the loss of ligand coplanarity in 3 promoting
the more common tetrahedral (albeit distorted) geometry at
the copper(I) center.
The above structural alteration from a discrete heteroleptic
assembly in C1(I) to a polymeric chain structure in C1(II) by
changing the stoichiometric ratio of [Cu(1)]+/ 3 may therefore
be viewed as a supramolecular modification, whereby the
geometry (and coordination number) of the involved copper(I)
center expands from trigonal (3) to tetrahedral (4) in the solid
state.
In another set of experiments, addition of 1 equiv of 2 to a
1:1 mixture of 1 and [Cu(MeCN)4]PF6 in dichloromethane
caused a conversion from C3(I) → C3(II), as revealed by the
resulting solid state structure. Small red crystals of complex
To explore the effects of the counteranion on the HETPYP-I
complex formation, the above reaction was modified by using
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Figure 4. Side view (left) and top view (right) of the crystal structure for complex C2.
C3(II), suitable for X-ray analysis, were obtained by a method
similar to that used for C1(II). The solid state structure of C3(II)
reveals that each copper(I) center is tetrahedrally bound to
both nitrogens of one phenanthroline and two nitrogen atoms
belonging to different bipyridine ligands. The overall structure
can be viewed as a one-dimensional (1D) chain arrangement
with the [Cu(1)]+ motif acting as a capping unit and the 4,4′-
bipyridine ligand extending the framework (Figure 5). The
complex with ligand 4 (Scheme 2) was initiated. Single crystals
were grown as orange blocks by diffusion of diethyl ether into a
dichloromethane solution of capped [Cu(1)]+ complex and
ligand 4 (at 3:1 ratio). The crystals are very sensitive to air and
loose crystallinity immediately when taken out of the mother
liquor. Data collection could only be done at low temperature
by wrapping in oil prior to mounting. The coordination
environment about the copper(I) ions in C4(I) follows a
distorted trigonal geometry with ligation from two N atoms of
1 and one pyridine N atom of 4. In C4(I), the tripyridine ligand
adopts a nearly planar molecular structure joining three
crystallographically independent [Cu(1)]+ centers using its
−
long aromatic arms. The PF6 anion (5.1 Å) and dichloro-
methane solvent molecule (4.9 Å) are quite far away from any
metal ion and are hence not bound to Cu+ (Supporting
Information, Figure S32). A wide variation of bond distances
and bond angles is observed at the three Cu+−N(py) units,
although they lie within a range observed in other Cu+−
N(pyridine) structures.15,27 Figure 6 represents a view of the
−
Figure 5. Crystal packing of complex C3(II) along c axis, with PF6
anions (shown in space filling mode) located in between the 2D layers.
Inset shows the twist in the chain structure. Color code: 1, red; 2, blue;
copper, cyan. All hydrogen atoms were omitted for clarity.
structure of C3(II) is different from the zigzag chain structure of
C1(II) in a way that the neighboring bipyridines 2 to the
[Cu2(1)22] building block unit are aligned in a syn−anti−syn−
anti orientation (Cu1−Cu2−Cu3−Cu4 = 7.7° and Cu2−Cu3−
Cu4−Cu5 = 179.4°), providing a notable twist to the polymer
chain (Figure 5, inset), whereas in the later structure C1(II), the
longer bipyridines 3 run always anti (Cu1−Cu2−Cu3−Cu4 =
180.0°). Both structures are different from the helicate structure
reported previously.15
Figure 6. A perspective view of C4(I) showing intra- and
intermolecular secondary interactions. Solvent molecules, anions, and
hydrogen atoms are omitted for clarity.
discrete assembly of C4(I) down the c axis, accentuating the Y-
like arrangement of all Cu+ ions and the 180° rotation of every
alternate phenanthroline ring along the b axis. In this structure,
the phenanthroline ligands are oriented with respect to each
other in such a way that the “bottom side” of ligand 1 may
come into contact (3.5 Å) with another aromatic plane of the
neighboring assembly to maximize π−π stacking. This turns the
phenanthroline rings slightly offset and causes an unusual
trigonal distortion at the copper(I) center.
Self-Assembly of 4 and [Cu(1)]+ (Complex C4(I)
=
[Cu3(1)3(4)](PF6)3)). To probe the formation of a trifold
HETPYP-I complex with three [Cu(1)]+ caps on a tripyridine
ligand to afford a [Cu3(phenAr2)3(py)]3+ assembly (here, py
represents a tripyridine ligand), the reaction of the [Cu(1)]+
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Mimicking the Solid State Structure of C4(II)
=
signals, with the chemical shifts of the pyridine α and β protons
of 3 (for the numbering of the protons, see Scheme 2) being
drastically moved from 8.63 to 7.00 ppm and from 7.43 to 7.20
ppm, respectively (Table 2). Such finding is in line with the
[Cu3(1)3(4)2]3+. The reaction of [Cu(1)]+ and ligand 4 (3: 2
molar ratio) furnished a molecular assembly in solution that is
denoted as C4(II) in the following. Since all efforts to grow
single crystals of C4(II) remained unsuccessful, we substituted
ligand 4 by its methylated congener 4Me (see Scheme 2).
Reaction of 4Me and [Cu(1)]+ in a 2: 3 molar ratio in
Table 2. Diagnostic Shifts for Pyridine Protons in Various
HETPYP-I and HETPYP-II Structures
1
dichloromethane-d2 furnishes an H NMR spectrum that is
a
b
b
,
c
b
b,c
complex
C1(I)
δ
(Hα)
7.00
Δδ (Hα)
δ
(Hβ)
7.20
Δδ (Hβ)
identical to the spectrum of the assembly C4(II), except for the
additional methyl groups (see Figure S21 in the Supporting
Information). The full agreement of the solution state NMR
0.68
0.09
(II)
C1S
7.68
7.17
7.78
6.88
7.64
7.29
7.32
7.39
7.18
7.29
C3(I)
0.61
0.07
0.11
characteristics of C4(II) and C4Me(II) suggests that the solid state
(II)
(II)
assembly C4(II) should be well represented by that of C4Me
=
C3S
C4(I)
0.76
[Cu3(1)3(4Me)2]3+ that is literature known.15 The latter
(II)
C4S
structure (Figure 7, another view of the honeycomb structure
a
b
c
Recorded in CD2Cl2. In ppm. 1H NMR shift difference for Hα or
(II)
Hβ between CnS and Cn(I).
symmetric encapsulation of the pyridine rings into the cavity of
the electron-rich mesityl groups of 1. 3-H and 4-H protons (see
Scheme 2) of the phenanthroline residue are downfield shifted
to 7.94 and 8.72 ppm, respectively, due to metal complexation.
DOSY NMR indicates the formation of a single species in
solution (Supporting Information). ESI-FTICR mass spectra
obtained at very soft ionization conditions provide a clear clue
for the existence of a discrete assembly in the gas phase as they
show signals corresponding to the molecular ion of C1(I) in its
singly charged form [Cu2(1)2(3)(PF6)]+ at m/z = 1285.3 with
correct isotopic pattern and exact mass (Supporting Informa-
tion, Figure S3). Nevertheless, a significant amount of
fragmentation by loss of the neutral complex [Cu(1)(PF6)]
turned out to be inevitable, leading to the base peak at m/z
659.2, which is assigned to the heteroleptic mononuclear
species [Cu(1)(3)]+. According to the gas-phase results, the
strongly bound [Cu(1)]+ entities of C1(I) stay intact, while the
significantly weaker bound pyridine ligands dissociate off in the
presence of excess energy.
Changing the ratio of ligands 1, 3, and [Cu(MeCN)4]PF6 to
1:1:1 leads to a shift of the pyridine α and β protons of 3 from
8.63 to 7.68 ppm and from 7.43 to 7.29 ppm, respectively, a
much smaller upfield shift in comparison to that found for
Figure 7. Top view of honeycomb like two-dimensional arrangement
in C4Me
anions and solvate molecules were omitted for clarity.
.
15 Color code: 1, red; 4Me, blue; copper, cyan. All H-atoms,
(II)
1
C1(I). The H NMR spectrum therefore points toward the
in the original paper) is characterized by a broken honeycomb
network, where every individual [Cu(1)]+ cap is connected
with two pyridines stemming from two different ligands 4Me,
resulting in a tetrahedral arrangement at each copper(I) center.
The above annotations have successfully demonstrated that
for various combinations of [Cu(1)]+ and oligopyridines, that
is, 1−4, the stoichiometric ratio reliably commands the
outcome of the solid state structure resulting in either a
discrete HETPYP-I or oligomeric HETPYP-II structure. The
present study further indicates the important role that weakly
coordinating counterions may play in such supramolecular
structure alteration.
Solution State Studies. Self-Assembly of Bipyridine 3
and [Cu(1)]+ in Solution. At first, an oligomeric coordination
scenario, as detected in all solid-state HETPYP-II assemblies,
seems rather unlikely in solution due to the unfavorable
entropic costs. We thus studied how HETPYP-I and HETPYP-
II assemblies would manifest themselves in solution.
formation of an aggregate containing other structural elements.
Clearly, both α and β pyridine protons experience less shielding
from the mesityl group of 1. Although the ESI-FTICR MS
(even under very soft ionization condition) exhibits only signals
of small fragments due to weak [Cu2(3)]2+---N(py) bonding,
the DOSY spectrum shows a single species (Supporting
Information). Surprisingly, the diffusion coefficient of the
aggregate derived from DOSY (D = 10.2 × 10−10 m2 s−1; rH =
0.51 nm) was found to be larger than that for C1(I) (D = 8.6 ×
10−10 m2 s−1; rH = 0.60 nm). These numbers suggest that the
HETPYP assembly at a ratio of [Cu(1)]+/ 3 = 1: 1 ought to be
smaller in solution than C1(I). To resolve this issue, dynamic
light scattering (DLS) measurements were undertaken in
dichloromethane. The DLS data reveal a monomodal size
distribution for both assemblies (Supporting Information,
Figure S8) allowing to establish the hydrodynamic diameter
as d = 1.12 nm (for the unknown assembly at a ratio of
[Cu(1)]+/ 3 = 1: 1) and 1.30 nm (for C1(I)). Both diameters
are in full agreement with the size determination from the
DOSY NMR (Supporting Information, Table S2). Assessing
several different possible arrangements of ligand 3 and the
As a representative example for all cases studied so far, the
structure of C1(I) and C1(II) in CD2Cl2 was intimately analyzed.
1
The H NMR spectrum of C1(I) reveals only one set of sharp
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Inorganic Chemistry
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[Cu(1)]+ cap at a ratio 1:1, the simplest model according to
Occam’s razor is the one in which a [Cu(1)]+ cap is only
attached to one pyridine of ligand 3 with the other pyridine of
the same ligand remaining uncoordinated (Scheme 3, a and b).
Scheme 3. Possible Associations of Bipyridine 3 with the
Capped [Cu(1)]+ Complex, When Used in 1:2 and 1:1
a
Stoichiometry in Solution
Figure 8. Variable temperature 1H NMR spectra (partial spectrum) of
C1(I) and C1S(II), all in CD2Cl2. Color code: C1(I), green; C1S(II), pink;
pyα, red stars; pyβ, blue stars.
Quite in contrast, the assembly at [Cu(1)]+/ 3 = 1:1 shows
notable upfield shifts of both the phenanthroline and pyridine α
protons upon lowering the temperature. The pyridine α
protons experience progressive upfield shifts and finally end
up as broad singlet at −80 °C. At this temperature, the pyridine
protons reveal a shift close to that of the HETPYP-I scenario
(Figure 8). However, no peaks corresponding to free ligand 3
are observed, which excludes scenario d in eq 2 (Scheme 3).
Because both pyridine terminals of 3 experience the same NMR
signal shift at all temperatures, the bipyridine terminals have
rapidly to exchange their environment by detaching and
reattaching to the copper caps (assembly a and b in Scheme
3). At −80 °C, this swapping motion is becoming slower as
seen from the pyridine α protons that show peak broadening by
coalescence. With decreasing temperature, the mesityl hydro-
gens experience a significant upfield shift that should be
indicative for a tetracoordination at copper.17,18 Considering a
free energy balance between enthaplic gain through maximum
site occupancy and entropic costs, we thus expect the solution
assembly of [Cu(1)]+/ 3 = 1:1 at −80 °C to shift more and
more toward structure (c) either as a dimeric or even
oligomeric entity (Scheme 3). Notably, the latter structure
a
To show the exchange processes, the two pyridine rings of 3 are
colored differently.
Most likely, the copper(I) center in [Cu(1)(3)]+ is coordinated
in a trigonal fashion as in C1(I). Because of very rapid exchange,
the average pyridine NMR resonance are placed almost halfway
(Table 2 and Figure S8 in Supporting Information) between
that of C1(I) and 3. This model is furthermore justified because
1
the room temperature H NMR spectrum of the aggregate
exhibits no signals of a free ligand 3. Thus, an equilibrium
involving species d, as depicted in Scheme 3, seems unlikely.
Further insight was obtained upon probing the mixture
[Cu(1)]+/ 3 at ratios 1:1 and 2:1 (C1(I)) using different
temperatures (Figure 8). Upon decreasing the temperature of
the C1(I) assembly, only the pyridine α protons experience a
pronounced upfield shift (from 7.00 ppm at 25 °C to 6.20 ppm
at −80 °C) associated with incessant peak sharpening. None of
the phenanthroline protons changes its shift, which indicates
that the phen-Cu+-py linkage remains intact. Thus, the
observations suggest that the C1(I) assembly is dynamic at
room temperature due to rotation about the long axis of 3 (see
process (1) in Scheme 3). Once the temperature reaches −80
°C, a more rigid conformation is attained, in which the pyridine
α protons experience strong shielding effects by the mesityl
groups.
closely resembles a subpart of the solid state structure of C1(II)
.
Clearly, the solution structure of [Cu(1)]+/ 3 = 1:1 is
complex and temperature dependent. Thus, in the following
this aggregate in solution will be denoted as C1S(II). It seems
that at room temperature the structure is best described as a
complex [Cu(1)(3)]+ with one pyridine terminal of 3 left
uncoordinated (see a + b in Scheme 3), while at low
temperature due to decreasing entropic costs of larger
aggregates, we see a shift toward a dimeric or even oligomeric
structure that is largely similar to the polymeric solid state
structure.
The dynamic nature of the C1S
corroborated by a H NMR titration experiment, showing that
after addition of one equivalent [Cu(1)]+ to a solution of
C1S(II), the original spectrum of C1(I) is fully reconstituted
(Supporting Information, Figure S7).
(II)
assembly is further
1
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Inorganic Chemistry
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For the other systems as well, that is, CnS(II) and Cn(I), a fully
analogous behavior may be derived from their H NMR data
SMP-20 instrument and are uncorrected. Infrared spectra were
recorded on a Perkin-Elmer 1750 FT-IR spectrometer with the
software of IRDM 1700. Elemental analysis measurements were done
using the EA 3000 CHNS. Mass spectra were recorded on a Bruker
APEX IV Fourier transform ion cyclotron resonance (FT-ICR) mass
spectrometer. Dynamic light scattering (DLS) data were acquired at
20 °C in dichloromethane on a Malvern Zetasizer (Zetasizer Nano,
Malvern Instruments GmbH, Germany).
1
(Table 2) and in some cases is further supported by DOSY and
DLS measurements (see Supporting Information, Table S2).
The analogy of all systems is best read out from the Δδ (Hα)
values that represent the difference of δ (Hα) of HETPYP-I and
HETPYP-II assemblies. For all pairs CnS(II) and Cn(I) with n =
1, 3, and 4, the Δδ value is remarkably constant.
X-ray Structural Studies. For complexes C1(I), C1(II), C2, and
C4(I): Data collection, Bruker APEX2; cell refinement, Bruker
SAINT;29 data reduction, Bruker SAINT. Program used to solve
structure: SHELXS97.30 Program used to refine structure:
SHELXL97.30 Molecular graphics: Bruker SHELXTL.31 Software
used to prepare material for publication: Bruker SHELXTL. The X-
ray single-crystal diffraction data for complex C3(II) was collected on a
SIEMENS SMART diffractometer. The structures were solved using
SHELXS-9730 and refined by full-matrix least-squares analysis.
Hydrogen atoms were generated theoretically onto the specific
atoms and refined isotropically with fixed thermal factors. The non-
H atoms were refined with anisotropic thermal parameters (for details
see Supporting Information). CCDC reference nos. 836993−836996
contain the supplementary crystallographic data of C1(I), C1(II), C2,
and C4(I). The data can also be obtained free of charge at www.ccdc.
cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; Fax:
(Internet.)+44−1223/336−033; E- mail:deposit@ccdc.cam.ac.uk].
Synthesis and Characterization of C1(I). Ligand 115 (4.16 mg,
10.0 μmol) and [Cu(MeCN4)]PF6 (3.73 mg, 10.0 μmol) were
dissolved in dichloromethane (0.50 mL) affording a slightly yellow
solution. Then, 310 (0.90 mg, 5.0 μmol) was added resulting in an
orange solution. After removal of the solvents, the solid residue was
analyzed without any further purification. Single crystals, suitable for
X-ray study, were grown by slow diffusion of diethylether into a 1,2-
dichlorobenzene solution of C1(I). For the solid state characterization,
see X-ray structural analysis. Yield: quantitative. mp = 148 °C. IR
(KBr): ν = 2918, 2857, 1612, 1586, 1508, 1481, 1426, 1381, 1361,
1298, 1216, 1148, 1111, 1030, 841, 651, 625, 557 cm−1. 1H NMR (400
MHz, CD2Cl2): δ = 8.72 (d, J = 8.3 Hz, 4H, 4-H), 8.18 (s, 4H, 5-H),
7.94 (d, J = 8.3 Hz, 4H, 3-H), 7.20 (d, J = 5.1 Hz, 4H, β-H), 7.00 (d, J
= 5.1 Hz, 4H, α-H), 6.98 (s, 8H, m-H), 2.36 (s, 12H, b-H) 2.04 (s,
24H, a-H). 13C NMR (100 MHz, CD2Cl2): δ = 161.0, 150.2, 144.0,
140.0, 139.9, 137.3, 136.2, 132.0, 129.2, 128.3, 127.6, 127.3, 127.2,
92.2, 21.2, 20.5. FTICR-MS Calcd. for [Cu2(1)2(3)(PF6)]+: m/z
1 2 8 5 . 3 ; f o u n d m / z 1 2 8 5 . 3 . A n a l . C a l c d f o r
C72H64Cu2F12N6P2·0.5CH2Cl2 = ([Cu2(1)2(3)(PF6)2]·0.5CH2Cl2):
C, 59.12; H, 4.45; N, 5.71. Found: C, 59.19; H, 4.67; N, 5.39.
Synthesis and Characterization of C3(I). Ligand 1 (4.16 mg,
10.0 μmol) and [Cu(MeCN4)]PF6 (3.73 mg, 10.0 μmol) were
dissolved in dichloromethane (0.50 mL) affording a slightly yellow
hue. Then, 2 (0.78 mg, 5.0 μmol) was added resulting in an orange
solution. After removal of the solvents the solid residue was analyzed
without any further purification. Yield: Quantitative. mp: 135 °C. IR
(KBr): ν = 2919, 2858, 1609, 1505, 1482, 1444, 1410, 1379, 1356,
Thus, the solution structure of all Cns(I) is best represented
by that of the discrete species Cn(I) as documented through
(II)
solid state analysis. Using the insight received on system C1S
,
however, it is clear that for other Cns(II), as well a
tetracoordinated copper(I) center, that is, a HETPYP-II
structure, is only plausible at rather low temperature. At
room temperature, tetracoordination is no longer thermo-
chemically competitive, because any oligomeric assembly would
generate too high entropic costs (−TΔS). Obviously, the
entropic costs of copper(I) tetracoordination in the solid state
are much less relevant as the observed polymeric structure is
strongly supported by extensive interlayer π−π stacking
interactions because of the parallel packing of the one-
dimensional chains.
CONCLUSION
■
In conclusion, the aforementioned results in solution, solid
state and gas phase demonstrate the successful utilization of
2,9-dimesityl phenanthroline as a cap for tricoordinated
copper(I) centers in heteroleptic [Cun(phenAr2)n(py)]n+
assemblies, by choosing the appropriate di- and tripyridyl
ligands, using the HETPYP protocol. Based on solid state
evidence, we see a stoichiometry-dependent structural change-
over, with the concomitant coordination at copper(I) changing
from trigonal (HETPYP-I) to tetrahedral (HETPYP-II)
depending on the amount of pyridine ligands. While
HETPYP-I derived species Cn(I) are discrete supramolecules
both in solid state and solution, the HETPYP-II assemblies
Cn(II) are characterized by their polymeric nature in the solid.
In solution, there is a structural changeover depending on the
temperature. At low temperature, the “di- and oligomeric”
solution structure is reminiscent of the solid-state structure, but
it breaks down to “monomeric” [Cu(1)(3)]+ units at higher
temperature due to entropic reasons.
The dynamic nature of both assemblies in solution was
(I)
(II)
proven by the reversible interconversion of CnS and CnS
assemblies upon titration with the required components. Such
dynamic modulation may allow to introduce novel stimuli-
dependent properties, a particularly attractive feature of
functional dynamic materials, for example through modifying
constitution by exchange and reshuffling components.
1
1297, 1217, 1147, 1110, 1067, 840, 625, 558 cm−1. H NMR (400
MHz, CD2Cl2): δ = 8.72 (d, J = 8.3 Hz, 4H, 4-H), 8.18 (s, 4H, 5-H),
7.95 (d, J = 8.3 Hz, 4H, 3-H), 7.32 (br, 4H, β-H), 7.17 (br, 4H, α-H),
6.98 (s, 8H, m-H), 2.33 (s, 12H, b-H) 2.04 (s, 24H, a-H). 13C NMR
(100 MHz, CD2Cl2): δ = 160.9, 151.0, 145.6, 144.0, 139.7, 139.5,
137.4, 136.2, 129.1, 128.4, 127.5, 127.2, 122.1, 116.9 (CN of
acetonitrile), 21.2, 20.4, 2.0 (CH3 of acetonitrile). FTICR-MS Calcd.
for [Cu2(1)2(2)(PF6)]+: m/z 1259.3; found m/z 1259.3. Anal. Calcd.
for C70H64Cu2F12N6P2 [Cu2(1)2(2)(PF6)2]: C, 59.78; H, 4.59; N,
5.98. Found: C, 59.44; H, 4.98; N, 6.13.
EXPERIMENTAL SECTION
■
General Methods. All commercial reagents were used without
further purification. The purification and drying of the solvents was
accomplished according to standard protocols. Confirmation of the
structures of all products was obtained by H NMR and 13C NMR
1
spectroscopy (Bruker Avance 400 spectrometer) as well as DOSY
NMR (Varian VNMR-S 600 MHz spectrometer) using the deuterated
solvent as the lock and residual solvent as the internal reference. The
following abbreviations were utilized to describe peak patterns: s =
singlet, d = doublet, t = triplet, dd = doublet of doublet, br = broad
and m = multiplet. Numbering of carbon atoms of the molecular
formulas shown in the Experimental Section is used only for
assignments of the NMR signal and is not in accordance with the
Synthesis and Characterization of C4(I). Ligand 1 (4.16 mg,
10.0 μmol) and [Cu(MeCN4)]PF6 (3.73 mg, 10.0 μmol) were
dissolved in dichloromethane (0.50 mL) assuming a slightly yellow
color. Then, 414d (1.27 mg, 3.33 μmol) was added resulting in an
orange solution. After removal of the solvents, the solid residue was
analyzed without any further purification. Single crystals suitable for X-
ray analysis were obtained by slow diffusion of diethylether into a
IUPAC nomenclature rules. Melting points were measured on a Buchi
̈
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Inorganic Chemistry
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dichloromethane solution of C4(I). For the solid state characterization,
see the X-ray structural analysis. Yield: quantitative. mp: 220 °C. IR
(KBr): ν = 2917, 2857, 2215, 1608, 1587, 1558, 1480, 1425, 1380,
W.; Frankenberger, E. A.; Griffith, J. P.; Hecht, H.-J.; Johnson, J. E.;
Kamer, G.; Luo, M.; Mosser, A. G.; Rueckert, R. R.; Sherry, B.; Vriend,
G. Nature 1985, 317, 145.
1
1359, 1296, 1215, 1147, 1110, 1030, 840, 650, 624, 557 cm−1. H
́
(6) (a) Angurell, I.; Ferrer, M.; Gutierrez, A.; Martínez, M.;
NMR (400 MHz, CD2Cl2): δ = 8.72 (d, J = 8.3 Hz, 6H, 4-H), 8.18 (s,
6H, 5-H), 7.94 (d, J = 8.3 Hz, 6H, 3-H), 7.88 (s, 3H, c-H), 7.18 (br,
6H, β-H), 6.99 (s, 12H, m-H), 6.88 (br, 6H, α-H), 2.38 (s, 18H, b-H)
2.04 (s, 36H, a-H). 13C NMR (100 MHz, CD2Cl2): δ = 161.0, 150.1,
144.0, 139.9, 139.7, 137.3, 136.3, 136.2, 132.9, 129.2, 128.3, 127.6,
127.2, 126.9, 123.4, 116.9 (CN of acetonitrile), 94.4, 87.6, 21.2, 20.5,
2.08 (CH3 of acetonitrile). FTICR-MS: Calcd. for [Cu3(1)3(4)-
(PF6)]2+: m/z 983.3; found m/z 983.3. Anal. Calcd. for
C117H99Cu3F18N9P3·MeCN ([Cu3(1)3(4)(PF6)3]·MeCN): C, 62.21;
H, 4.47; N, 6.10. Found: C, 62.42; H, 4.60; N, 6.24.
Rodríguez, L.; Rossell, O.; Engeser, M. Chem.Eur. J. 2010, 16,
13960. (b) Saha, M. L.; Schmittel, M. Org. Biomol. Chem. 2012, 10,
4651.
(7) (a) Lehn, J.-M.; Eliseev, A. V. Science 2001, 291, 2331.
(b) Northrop, B. H.; Yang, H.-B.; Stang, P. J. Inorg. Chem. 2008, 47,
11257. (c) Zheng, Y.-R.; Yang, H.-B.; Northrop, B. H.; Ghosh, K.;
Stang, P. J. Inorg. Chem. 2008, 47, 4706. (d) Zheng, Y.-R.; Northrop,
B. H.; Yang, H.-B.; Zhao, L.; Stang, P. J. J. Org. Chem. 2009, 74, 3554.
(e) Zheng, Y.-R.; Yang, H.-B.; Ghosh, K.; Zhao, L.; Stang, P. J.
Chem.Eur. J. 2009, 15, 7203.
(8) (a) Sun, S.-S.; Anspach, J. A.; Lees, A. J. Inorg. Chem. 2002, 41,
1862. (b) Heo, J.; Jeon, Y.-M.; Mirkin, C. A. J. Am. Chem. Soc. 2007,
129, 7712. (c) Dublin, S. N.; Conticello, V. P. J. Am. Chem. Soc. 2008,
130, 49.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details of synthesis, characterization for all Cn(II)
,
CnS(II), and C2 complexes, NMR spectra, DLS, FT-IR and
mass spectrometric data, views of the single crystal X-ray
structures. X-ray crystallographic data for C1(I), C1(II), C2,
C3(II), and C4(I) in CIF format are provided. This material is
available free of charge via the Internet at http://pubs.acs.org.
(9) Sun, S.-S.; Stern, C. L.; Nguyen, S. T.; Hupp, J. T. J. Am. Chem.
Soc. 2004, 126, 6314.
(10) Zhao, L.; Northrop, B. H.; Stang, P. J. J. Am. Chem. Soc. 2008,
130, 11886.
(11) Abourahma, H.; Moulton, B.; Kravtsov, V.; Zaworotko, M. J. J.
Am. Chem. Soc. 2002, 124, 9990.
(12) Halper, S. R.; Cohen, S. M. Angew. Chem., Int. Ed. 2004, 43,
2385.
(13) (a) Tashiro, S.; Kobayashi, M.; Fujita, M. J. Am. Chem. Soc.
2006, 128, 9280. (b) Suzuki, K.; Kawano, M.; Sato, S.; Fujita, M. J. Am.
́
Chem. Soc. 2007, 129, 10652. (c) Ferrer, M.; Gutierrez, A.; Mounir,
M.; Rossell, O.; Ruiz, E.; Rang, A.; Engeser, M. Inorg. Chem. 2007, 46,
3395. (d) Yamauchi, Y.; Yoshizawa, M.; Fujita, M. J. Am. Chem. Soc.
2008, 130, 5832. (e) Rang, A.; Engeser, M.; Maier, M. M.; Nieger, M.;
Lindner, W.; Schalley, C. A. Chem.Eur. J. 2008, 14, 3855. (f) Ono,
K.; Klosterman, J. K.; Yoshizawa, M.; Sekiguchi, K.; Tahara, T.; Fujita,
AUTHOR INFORMATION
Corresponding Author
*E-mail: schmittel@chemie.uni-siegen.de.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are indebted to the DFG for continued support and to the
Alexander von Humboldt Foundation for a stipend to S.N. We
thank Dr. J. W. Bats (Frankfurt) for measuring the X-ray data of
M. J. Am. Chem. Soc. 2009, 131, 12526. (g) Ferrer, M.; Gutier
Rodríguez, L.; Rossell, O.; Ruiz, E.; Engeser, M.; Lorenz, Y.; Schilling,
R.; Gomez-Sahl, P.; Martín, A. Organometallics 2012, 31, 1533.
́
rez, A.;
C3(II)
.
́
(14) (a) Yuan, Q.-H.; Yan, C.-J.; Yan, H.-J.; Wan, L.-J.; Northrop, B.
H.; Jude, H.; Stang, P. J. J. Am. Chem. Soc. 2008, 130, 8878. (b) Rang,
REFERENCES
■
A.; Nieger, M.; Engeser, M.; Lutzen, A.; Schalley, C. A. Chem.
̈
(1) (a) Lehn, J.-M. Supramolecular Chemistry: Concepts and
Perspectives; VCH: Weinheim, Germany, 1995. (b) Batten, S. R.;
Robson, R. Angew. Chem., Int. Ed. 1998, 37. (c) Atwood, J. L.; Steed., J.
W. Encyclopedia of Supramolecular Chemistry; Marcel Dekker Ltd.:
New York, 2004.
(2) (a) Ghosh, K.; Yang, H.-B; Northrop, B. H.; Lyndon, M. M.;
Zheng, Y.-R.; Muddiman, D. C.; Stang, P. J. J. Am. Chem. Soc. 2008,
130, 5320. (b) Zhao, L.; Ghosh, K.; Zheng, Y.; Lyndon, M. M.;
Williams, T. I.; Stang, P. J. Inorg. Chem. 2009, 48, 5590. (c) Lee, J.;
Ghosh, K.; Stang., P. J. J. Am. Chem. Soc. 2009, 131, 12028.
(d) Kikuchi, T.; Sato, S.; Fujita, M. J. Am. Chem. Soc. 2010, 132, 15930.
(e) Inokuma, Y.; Kawano, M.; Fujita, M. Nat. Chem. 2011, 3, 349.
(3) (a) Mahata, K.; Schmittel, M. J. Am. Chem. Soc. 2009, 131, 16544.
(b) Jiang, W.; Schalley, C. A. Proc. Natl. Acad. Sci. U.S.A. 2009, 106,
10425. (c) Schmittel, M.; Samanta, S. K. J. Org. Chem. 2010, 75, 5911.
(d) Mahata, K.; Saha, M. L.; Schmittel, M. J. Am. Chem. Soc. 2010, 132,
Commun. 2008, 4789. (c) Zhao, Z.; Zheng, Y.-R.; Wang, M.; Pollock,
J. B.; Stang, P. J. Inorg. Chem. 2010, 49, 8653. (d) Zheng, Y. R.; Zhao,
Z.; Wang, M.; Ghosh, K.; Pollock, J. B.; Cook, T. R.; Stang, P. J. J. Am.
Chem. Soc. 2010, 132, 16873. (e) Wang, M.; Vajpayee, V.;
Shanmugaraju, S.; Zheng, Y. R.; Zhao, Z.; Kim, H.; Mukherjee, P.
S.; Chi, K.-W.; Stang, P. J. Inorg. Chem. 2011, 50, 1506.
(15) Schmittel, M.; He, B.; Fan, J.; Bats, J. W.; Engeser, M.;
Schlosser, M.; Deiseroth, H. J. Inorg. Chem. 2009, 48, 8192.
(16) (a) Samanta, S. K.; Samanta, D.; Bats, J. W.; Schmittel, M. J. Org.
Chem. 2011, 76, 7466. (b) We now use the name HETPYP-II for
assemblies as reported in ref 15.
(17) (a) Schmittel, M.; Luning, U.; Meder, M.; Ganz, A.; Michel, C.;
̈
Herderich, M. Heterocycl. Commun. 1997, 3, 493. (b) Schmittel, M.;
Kalsani, V.; Bats, J. W. Inorg. Chem. 2005, 44, 4115. (c) De, S.; Mahata,
K.; Schmittel, M. Chem. Soc. Rev. 2010, 39, 1555.
(18) (a) Schmittel, M.; Ganz, A.; Fenske, D. Org. Lett. 2002, 4, 2289.
(b) Schmittel, M.; Ammon, H.; Kalsani, V.; Wiegrefe, A.; Michel, C.
Chem. Commun. 2002, 2566. (c) Schmittel, M.; Kalsani, V.; Fenske, D.;
Wiegrefe, A. Chem. Commun. 2004, 490. (d) Schmittel, M.; Kishore, R.
S. K. Org. Lett. 2004, 6, 1923. (e) Kishore, R. S. K.; Paululat, T.;
Schmittel, M. Chem.Eur. J. 2006, 12, 8136. (f) Schmittel, M.;
Kishore, R. S. K.; Bats, J. W. Org. Biomol. Chem. 2007, 5, 78. (g) Fan,
J.; Bats, J. W.; Schmittel, M. Inorg. Chem. 2009, 48, 6338. (h) Schmittel,
M.; Mahata, K. Chem. Commun. 2010, 46, 4163.
15933. (e) Jiang, W.; Schafer, A.; Mohr, P. C.; Schalley, C. A. J. Am.
̈
Chem. Soc. 2010, 132, 2309. (f) Jiang, W.; Nowosinski, K.; Low, N. L.;
̈
Dzyuba, E. V.; Klautzsch, F.; Schafer, A.; Huuskonen, J.; Rissanen, K.;
Schalley, C. A. J. Am. Chem. Soc. 2012, 134, 1860.
̈
(4) (a) Cairns, A. J.; Perman, J. A.; Wojtas, L.; Kravtsov, V. C.;
Alkordi, M. H.; Eddaoudi, M.; Zaworotko, M. J. J. Am. Chem. Soc.
2008, 130, 1560. (b) Sun, Q.-F.; Iwasa, J.; Ogawa, D.; Ishido, Y.; Sato,
S.; Ozeki, T.; Sei, Y.; Yamaguchi, K.; Fujita, M. Science 2010, 328,
1144. (c) Li, D.; Zhou, W.; Landskron, K.; Sato, S.; Kiely, C. J.; Fujita,
M.; Liu, T. Angew. Chem., Int. Ed. 2011, 50, 5182.
(5) (a) Abad-Zapatero, C.; Abdel-Meguid, S. S.; Johnson, J. E.; Leslie,
A. G. W.; Rayment, I.; Rossmann, M. G.; Suck, D.; Tsukihara, T.
Nature 1980, 286, 33. (b) Rossmann, M. G.; Arnold, E.; Erickson, J.
(19) (a) Schmittel, M.; Kalsani, V.; Mal, P.; Bats, J. W. Inorg. Chem.
2006, 45, 6370. (b) Schmittel, M.; Kalsani, V.; Michel, C.; Mal, P.;
Ammon, H.; Jackel, F.; Rabe, J. P. Chem.Eur. J. 2007, 13, 6223.
̈
(c) Schmittel, M.; He, B.; Kalsani, V.; Bats., J. W. Org. Biomol. Chem.
10840
dx.doi.org/10.1021/ic301286w | Inorg. Chem. 2012, 51, 10832−10841

Inorganic Chemistry
Article
2007, 5, 2395. (d) Schmittel, M.; Mal, P. Chem. Commun. 2008, 960.
(e) Schmittel, M.; He, B.; Mal, P. Org. Lett. 2008, 10, 2513.
(20) (a) Schmittel, M.; Ganz, A. Chem. Commun. 1997, 999.
(b) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40, 2022.
(c) Yamanaka, M.; Yamada, Y.; Sei, Y.; Yamaguchi, K.; Kobayashi, K. J.
Am. Chem. Soc. 2006, 128, 1531. (d) Weilandt, T.; Troff, R. W.; Saxell,
H.; Rissanen, K.; Schalley, C. A. Inorg. Chem. 2008, 47, 7588 The
combination of several bi- or tridentate ligands at dynamically binding
metal centers in supramolecular assemblies operates at the cost of a
slow kinetics and thus would not be ideal for a model study on the
interconversion of supramolecules..
(21) (a) Fujita, M.; Oguro, D.; Miyazawa, M.; Oka, H.; Yamaguchi,
K.; Ogura, K. Nature 1995, 378, 469. (b) Olenyuk, B.; Whiteford, J. A.;
Fechtenkotter, A.; Stang, P. J. Nature 1999, 398, 796. (c) Yoshizawa,
̈
M.; Nakagawa, J.; Kumazawa, K.; Nagao, M.; Kawano, M.; Ozeki, T.;
Fujita, M. Angew. Chem., Int. Ed. 2005, 44, 1810. (d) Fujita, M.;
Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem. Res. 2005, 38, 371.
(e) Sato, S.; Lida, J.; Suzuki, K.; Kawano, M.; Ozeki, T.; Fujita, M.
Science 2006, 313, 1273.
(22) Yoshizawa, M.; Nagao, M.; Kumazawa, K.; Fujita, M. J.
Organomet. Chem. 2005, 690, 5383.
(23) Lopez, S.; Keller, S. W. Inorg. Chem. 1999, 38, 1883.
(24) (a) Schmittel, M.; Kalsani, V.; Kishore, R. S. K.; Colfen, H.;
̈
Bats, J. W. J. Am. Chem. Soc. 2005, 127, 11544. (b) Schmittel, M.; He,
B. Chem. Commun. 2008, 4723. (c) Schmittel, M.; Michel, C.; Liu, S.-
X.; Schildbach, D.; Fenske, D. Eur. J. Inorg. Chem. 2001, 1155. (d) Ogi,
S.; Ikeda, T.; Wakabayashi, R.; Shinkai, S.; Takeuchi, M. Chem.Eur.
J. 2010, 16, 8285.
(25) (a) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am. Chem.
Soc. 1994, 116, 1151. (b) Blake, A. J.; Hill, S. J.; Hubberstey, P.; Li, W.
S. J. Chem. Soc., Dalton Trans. 1997, 913. (c) Noguchi, D.; Tanaka, H.;
Kondo, A.; Kajiro, H.; Noguchi, H.; Ohba, T.; Kanoh, H.; Kaneko, K.
J. Am. Chem. Soc. 2008, 130, 6367.
(26) (a) MacGillivray, L. R.; Subramanian, S.; Zaworotko, M. J. J.
Chem. Soc., Chem. Commun. 1994, 1325. (b) Blake, A. J.; Hill, S. J.;
Hubberstey, P.; Li, W. S. J. Chem. Soc., Dalton Trans. 1998, 909.
(27) (a) Lewis, D. F.; Lippard, S. J.; Welcker, P. S. J. Am. Chem. Soc.
1970, 92, 3805. (b) Kappenstein, C.; Hugel, R. P. Inorg. Chem. 1978,
17, 1945. (c) Sorrell, T. N.; Malachowski, M. R.; Jameson, D. M. Inorg.
Chem. 1982, 21, 3250. (d) Munakata, M.; Maekawa, M.; Kitagawa, S.;
Matsuyama, S.; Masuda, H. Inorg. Chem. 1989, 28, 4300. (e) Chou, C.-
C.; Su, C.-C.; Yeh, A. Inorg. Chem. 2005, 44, 6122. (f) Chou, C.-C.;
Liu, H.-J.; Chao, L. H.-C. Chem. Commun. 2009, 6382.
(28) Potts, K. T.; Horwitz, C. P.; Fessak, A.; Keshavarz-K, M.; Nash,
K. E.; Toscano, P. J. J. Am. Chem. Soc. 1993, 115, 10444.
(29) SAINT, version 6.02; Bruker AXS: Madison, WI, 1999.
(30) Sheldrick, G. M. SHELXS-97 and SHELXL-97: Program for the
Crystal Structure Solution and Refinement; University of Gottingen:
̈
Goottingen, Germany, 1997.
̈
(31) Sheldrick, G. M. SHELXTL Reference Manual, version 5.1;
Bruker AXS: Madison, WI, 1997.
10841
dx.doi.org/10.1021/ic301286w | Inorg. Chem. 2012, 51, 10832−10841