[2] Pseudorotaxanes, [2]rotaxanes and metal-organic rotaxane frameworks containing tetra-substituted dibenzo[24]crown-8 wheels

Article abstract of DOI:10.1039/c2ob25200g

[2]Pseudorotaxanes, [2]rotaxanes and metal-organic rotaxane framework materials that utilise DB24C8 as the wheel component are well known and structural variations based on changing the axle component are common. Studies in which the DB24C8 wheel is structurally modified are much more limited. Herein, is described the synthesis of symmetrical DB24C8 analogues containing four CH₂OR (R = CH₂CH₂CH₃, CH ₂(C₆H₅), C₆H₅ and C ₆H₄(4-COOEt)) substituents on the 4 and 5 positions of the aromatic rings. The effect of these molecular appendages on the stability and structures of the interpenetrated and interlocked molecules derived from these new wheels is described. The major effects are an increase in association constants for the formation of [2]pseudorotaxanes relative to DB24C8, the crystal packing of [2]rotaxanes and a change on the internal structure of a 2D MORF (R = C₆H₅) compared to DB24C8.

Full text of DOI:10.1039/c2ob25200g

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PAPER
[2]Pseudorotaxanes, [2]rotaxanes and metal–organic rotaxane frameworks
containing tetra-substituted dibenzo[24]crown-8 wheels†‡
Darren J. Mercer, Joe Yacoub, Kelong Zhu, Stephanie K. Loeb and Stephen J. Loeb*
Received 26th January 2012, Accepted 3rd April 2012
DOI: 10.1039/c2ob25200g
[2]Pseudorotaxanes, [2]rotaxanes and metal–organic rotaxane framework materials that utilise DB24C8 as
the wheel component are well known and structural variations based on changing the axle component are
common. Studies in which the DB24C8 wheel is structurally modified are much more limited. Herein, is
described the synthesis of symmetrical DB24C8 analogues containing four CH2OR (R = CH2CH2CH3,
CH2(C6H5), C6H5 and C6H4(4-COOEt)) substituents on the 4 and 5 positions of the aromatic rings. The
effect of these molecular appendages on the stability and structures of the interpenetrated and interlocked
molecules derived from these new wheels is described. The major effects are an increase in association
constants for the formation of [2]pseudorotaxanes relative to DB24C8, the crystal packing of [2]rotaxanes
and a change on the internal structure of a 2D MORF (R = C6H5) compared to DB24C8.
benzonaphtho[24]crown-8 (BN24C8)6 and dinaphtho[24]crown-
Introduction
8 (DN24C8)7 are capable of forming interpenetrated structures
The formation of interpenetrated pseudorotaxane molecules
involves the molecular recognition, via non-covalent inter-
actions, between a linear “axle” and a macrocyclic “wheel”.1
One of the most commonly employed wheels for the formation
of these unique chemical species is the macrocyclic polyether
dibenzo[24]crown-8 (DB24C8).2 DB24C8 is a good hydrogen
bond acceptor and it was demonstrated early on that the internal
diameter and flexibility of this particular crown size was suitable
for the threading of simple aromatics guests.2l The presence of
two electron-rich catechol rings also endows DB24C8 with a
penchant for π-stacking with many of the electron poor axles
used in these template pairings.2
Most detailed studies on [2]pseudorotaxane formation utilising
DB24C8 have focussed on varying the structural nature of the
axle, while variations in the structure of the macrocyclic wheel
are much more limited. There are two ways to vary the structure
of the DB24C8 wheel in these systems without changing the
essential donor array and ring size. One is to change the nature
of the aromatic ring and it has been established that other
24-membered crown ethers such as [24]crown-8 (24C8),3
benzo[24]crown-8 (B24C8),4 naphtho[24]crown-8 (N24C8),5
very similar to DB24C8. The other way would be to simply add
substituents to the existing aromatic rings of DB24C8. Although
this seems straightforward there are a number of problems. To
add a single substituent to only one of the aromatic rings of
DB24C8 requires incorporating the substituent prior to ring for-
mation and a tedious stepwise building up of the 24-membered
ring.8 Achieving mono-substitution on each of the aromatic rings
is much more straightforward since DB24C8 can be used directly
as the starting material, but this produces syn and anti isomers
that are often difficult to separate and yield [2]pseudorotaxanes
with different association constants; i.e. mixtures cannot be used.9
In this article, we outline a simple two step methodology for
adding flexible CH2OR groups of various sizes to the 4- and 5-
positions of each of the two aromatic rings of DB24C8, resulting
in new symmetrical, tetra-substituted versions of DB24C8.10 The
effect of these substituents on the formation constants and struc-
ture of [2]pseudorotaxanes involving a series of 1,2-bis(pyridi-
nium)ethane axles is investigated along with conversion into
permanently interlocked [2]rotaxanes. To explore applications;
(1) a [2]rotaxane ligand incorporating one of the new crown
ether wheels was prepared and coordinated to Ru(II) – the struc-
tures of the ligand and complex are described and (2) the effect
of including a tetra-substituted wheel into the internal structure of
a metal–organic rotaxane framework (MORF)11 is also reported.
Department of Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada, N9B 3P4. E-mail: loeb@uwindsor.ca;
Fax: +1 519 973 7098; Tel: +1 519 253 3000
Results and discussion
†Electronic supplementary information (ESI) available: 1H and 13C
NMR spectra for all crown ethers and [2]rotaxanes. CCDC
864507–864513. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c2ob25200g
Crown ether synthesis
The initial tetra-functionalization of DB24C8 was accomplished
‡This article is part of the Organic & Biomolecular Chemistry 10th
Anniversary issue.
utilising
a
modified version of
a
preparation involving
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem.

bromomethylation with paraformaldehyde and HBr in acetic
acid.12 The product 2a was produced in excellent yield and
could be isolated as a crystalline, white solid in gram quantities
from commercially available DB24C8 (Scheme 1). Replacement
of all four bromides by OR groups (R = CH2CH2CH3,
CH2(C6H5), C6H5 and C6H4(4-COOEt)) was accomplished
using simple substitution chemistry involving exchange of
bromide for alkoxide. The four new crown ethers were obtained
as white crystalline solids in good yields (Scheme 1).
3b X = C5H4N, 3c, X = C5H4N+Bn) substituted at the 4-position
of the pyridinium ring were used to determine the effect of
crown ether substitutions on [2]pseudorotaxane formation
(Scheme 2). Association constants (Ka) and binding energies
(ΔG°) for 12 new [2]pseudorotaxanes were measured in CD3CN
at 298 K by 1H NMR spectroscopy using the single-point
method appropriate for systems undergoing slow exchange on
the NMR timescale. The results are summarized in Table 1 and
compared to previously recorded values for DB24C8.3g,n,14
There are two basic trends observed for the association con-
stants of these 12 interpenetrated molecules. Firstly, it is
expected that the presence of four CH2OR substituents would
make the aromatic rings of the crown ether more electron rich
1
The new crown ethers 2b–2e were characterized by H NMR
spectroscopy and ESI-MS. The major common characteristics of
the 1H NMR spectra were (1) the addition of a new resonance in
the range 4.47–5.14 ppm due to the addition of a CH2O methyl-
ene group, (2) simplification of the aromatic region in which
only a single singlet resonance was now observed in the range
of 6.95–7.10 ppm and (3) new resonances due to the appended
R-groups.
X-ray quality crystals were obtained for 2d and the structure is
shown in Fig. 1. The structure has a crystallographically
imposed centre of symmetry and the macrocycle adopts an open,
S-shaped conformation which is similar to that found for
DB24C8.13 The pairs of CH2O(C6H5) groups on each aromatic
ring are oriented on the same side of the catechol ring.
[2]Pseudorotaxane formation
Three representative 1,2-bis(pyridinium)ethane axles with
phenyl, 4-pyridyl and 4-benzyl-pyridinum groups (3a X = C6H5,
Scheme 2 Formation of [2]pseudorotaxanes. (i) CD3CN, 2.0 × 10−3
M, 298 K. All counterions are triflate, (OTf− = CF3SO3−).
a
Table 1 Complete listing of Ka
and ΔG° values for [2]
pseudorotaxanes in CD3CN solution (2.0 × 10−3 M) at 298 K
[2]Pseudorotaxane
Ka a (×102 M−1
)
ΔG° (kJ mol−1
)
[3a⊂1]2+
4.0
11.5
7.3
12.6
8.8
−14.8
−17.5
−17.1
−17.7
−16.8
[3a⊂2b]2+
[3a⊂2c]2+
[3a⊂2d]2+
[3a⊂2e]2+
Scheme 1 Synthesis of tetra-substituted derivatives of DB24C8. (i)
2a: (CH2O)n, 33% HBr/CH3COOH, RT, 2 days, no stirring; (ii) 2b, 2c:
ROH, 2a, NaH, THF, reflux, 24 h; 2d, 2e: ROH, 2a, K2CO3, CH3CN,
reflux, 5 days.
[3b⊂1]2+
9.3
18.0
6.6
16.2
11.9
−16.9
−18.4
−16.0
−18.3
−17.7
[3b⊂2b]2+
[3b⊂2c]2+
[3b⊂2d]2+
[3b⊂2e]2+
[3c⊂1]4+
10.0
26.6
5.9
8.2
4.3
−10.0
−19.6
−16.7
−16.6
−15.1
[3c⊂2b]4+
[3c⊂2c]4+
[3c⊂2d]4+
[3c⊂2e]4+
a All values were recorded at 500 MHz and determined using the single
point method applicable to slow exchange on the NMR timescale. Errors
are estimated at <10%.
Fig. 1 Ball-and-stick representation of the single-crystal X-ray struc-
ture of crown ether macrocycle 2d.
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2012

Fig. 2 Ball-and-stick representation of the single-crystal X-ray struc-
ture of [2]pseudorotaxane [3a⊂2d]2+. Counterions and H-atoms not
involved in hydrogen-bonding are omitted for clarity.
resulting in an increase in the strength of the non-covalent inter-
actions between these wheels and the three electron deficient
axles. This is indeed the case for the smallest R-group, n-propyl,
as an increase in association constant is observed with each axle
relative to DB24C8.3g Secondly, [2]pseudorotaxane formation
with the tetracationic axle [3c]4+ would be predicted to be the
most favourable due to increased ion–dipole interactions, but
with crowns 2c–2e the association constants are actually lower
than were observed for DB24C8.3g It is thus likely that for larger
and less flexible appendages, steric interactions between the axle
and wheel are an overriding negative influence resulting in a
reduced association constant. Although, this subtle interplay
between electronic and steric effects makes it difficult to predict
the degree of interaction between any single pair of axle and
wheel, these observations are consistent with a straightforward
thermodynamically driven molecular recognition event which
results in [2]pseudorotaxane formation as described previously
for simpler systems involving DB24C8.3g,n,14
Scheme 3 Synthesis of [2]rotaxanes. (i) 5 : 1 eq. crown ether to eq.
axle, 4 eq. of 4-tert-butylbenzyl bromide in CH3CN, RT, 7 days. (ii)
MeNO2, sat’d [Na][CF3SO3](aq). Reported yields are after extensive
work-up and chromatography. All counterions are triflate, (OTf−
=
CF3SO3−).
The single-crystal X-ray structure of [2]pseudrotaxane
[3a⊂2d][OTf]2 was determined and the cationic portion is
shown in Fig. 2. The dicationic axle [3a]2+ is threaded through
the central cavity of macrocycle 2d and held in place via N+⋯O
ion–dipole interactions, a series of eight C–H⋯O hydrogen
bonds and significant π-stacking interactions between the elec-
tron-poor pyridinium rings and electron-rich catechol rings. This
is consistent with the interactions previously identified for
[2]pseudorotaxanes containing DB24C83g and observed in sol-
ution for this study with crown ethers 2b–2e. The four substitu-
ents of crown ether 2d are oriented to one side of the attached
aromatic ring, similar to the structure of 2d, with π-stacking of
the axle pyridinium ring occurring on the opposite face; i.e. there
are no significant intramolecular interactions between any of the
six substituent phenyl groups on either the axle or the wheel.
(Table 2). In particular, resonances for ethylene protons a and
α-pyridinium protons are shifted to higher frequency
b
(0.26–0.34 ppm) due to significant hydrogen-bonding, while
shifts to lower frequencies (0.22–0.50 ppm) for pyridinium
peaks c and d and catechol protons j can be attributed to π-stack-
ing between the electron poor and electron rich aromatic rings.
The chemical shift changes upon going from naked axle [4]4+ to
[2]rotaxane are identical to those observed upon formation of
[4⊂1]4+ which contains the parent crown ether DB24C8.12 For
the [2]rotaxanes with the most flexible R-groups on the wheel
([4⊂2b]4+, [4⊂2c]4+) there are no major differences in chemical
shifts when incorporating a tetra-substituted crown ether in place
of DB24C8. This infers that these groups, although presenting
potential steric barriers to initial interpenetration, do not substan-
tially impact the structure of the final interlocked molecule.
There are, however, some differences observed for chemical shift
data for the [2]rotaxanes with less flexible R-groups ([4⊂2d]4+,
[4⊂2e]4+). It appears that the aromatic rings of the substituent
R-groups interact with the benzylic f and aromatic g and h
protons of the stopper shielding these groups resulting in shifts
to lower frequency (0.17–0.41 ppm).
[2]Rotaxane synthesis
[2]Pseudorotaxanes comprising pyridine terminated axle [3b]2+
were alkylated with bulky t-butylbenzyl groups to yield perma-
nently interlocked [2]rotaxanes [4⊂2b]4+, [4⊂2c]4+, [4⊂2d]4+
and [4⊂2e]4+ (Scheme 3).15 The products could be isolated as
Single-crystal X-ray structures were determined for [2]rotax-
anes [4⊂2c][OTf]4 and [4⊂2d][OTf]4 which contain four
CH2OCH2C6H5 and CH2OC6H5 groups respectively attached to
the crown ether wheel. Figs. 3 and 4 show the cationic portions
[4⊂2c]4+ and [4⊂2d]4+. In both structures, the terminal tert-
butylbenzyl groups are bent away from and oriented on opposite
sides of the central core of the [2]rotaxane. For [4⊂2c]4+, the
orange-red solids in moderate yields after chromatography and
−
counter-ion exchange to CF3SO3
.
1H NMR spectra for [2]rotaxanes [4⊂2b]4+, [4⊂2c]4+,
[4⊂2d]4+ and [4⊂2e]4+ in CD3CN show evidence of the original
intramolecular interactions used to template the molecules which
are now permanently a part of these interlocked species
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem.

Table 2 Selected 1H NMR chemical shifts for crown ethers 2b–2e, dumbbell [4]4+ and [2]rotaxanes [4⊂2b]4+, [4⊂2c]4+, [4⊂2d]4+ and [4⊂2e]4+
derived from pyridine terminated axle [3b]2+ a
δ(Δδ) Values (ppm)
Proton
[4]4+
[4⊂2b]4+
[4⊂2c]4+
[4⊂2d]4+
[4⊂2e]4+
a
b
c
d
e
f
g
h
i
5.27
9.03
8.48
8.43
9.00
5.79
7.44
7.54
1.32
5.57 (+0.30)
9.32 (+0.29)
8.13 (−0.35)
8.04 (−0.39)
8.92 (−0.08)
5.80 (+0.01)
7.50 (+0.06)
7.60 (+0.06)
1.36 (+0.04)
5.57 (+0.30)
9.32 (+0.29)
8.14 (−0.34)
7.93 (−0.50)
8.53 (−0.47)
5.81 (+0.02)
7.39 (−0.05)
7.53 (−0.01)
1.30 (−0.02)
5.53 (+0.26)
9.37 (+0.34)
8.26 (−0.22)
8.20 (−0.23)
8.84 (−0.16)
5.62 (−0.17)
7.03 (−0.41)
7.25 (−0.29)
1.23 (−0.09)
5.61 (+0.34)
9.36 (+0.33)
8.23 (−0.25)
8.17 (−0.26)
8.86 (−0.14)
5.62 (−0.17)
7.25 (−0.19)
7.35 (−0.19)
1.22 (−0.10)
Proton
Crown
[4⊂2b]4+
[4⊂2c]4+
[4⊂2d]4+
[4⊂2e]4+
j (2b)
j (2c)
j (2d)
j (2e)
k (2b)
k (2c)
k (2d)
k (2e)
6.95
6.95
7.10
7.10
4.43
4.47
5.09
5.14
6.64 (−0.31)
—
—
—
4.04 (−0.39)
—
—
—
—
6.69 (−0.26)
—
—
—
4.11 (−0.36)
—
—
—
—
—
—
6.86 (-0.24)
—
—
—
4.68 (−0.41)
—
—
6.86 (−0.24)
—
—
—
4.76 (−0.38)
a All spectra were recorded at 500 MHz in MeCN-d3 at 298 K. The labelling key can be found in Scheme 3.
Fig. 3 Ball-and-stick representation of the single-crystal X-ray struc-
ture of [2]rotaxane [4⊂2c]4+. Counterions and H-atoms are omitted for
clarity.
Fig. 4 Ball-and-stick representation of the single-crystal X-ray struc-
ture of [2]rotaxane [4⊂2d]4+. Counterions and H-atoms are omitted for
clarity.
CH2OCH2C6H5 groups are all positioned on the same side of the
central core as the tert-butylbenzyl units. However, for [4⊂2d]4+,
one of the CH2OC6H5 groups is oriented on the opposite side of
the core, away from the tert-butylbenzyl stopper, while the other
OC6H5 group is involved in C–H⋯π interactions between the
benzylic CH2 group of the stopper and the CH2OC6H5 substitu-
ent aromatic ring. In order to be involved in this extra interaction
between axle and wheel, the two components must be signifi-
cantly misaligned – the angle between the vectors of the long
axis of the axle and wheel is 23°, whereas this value is 6° for
[4⊂1]4+ and is only 7° in [4⊂2c]4+ containing the more flexible
OCH2C6H5 groups.15a It is likely that orientation of the
R-groups in the solid state is dictated to a large extent by opti-
mizing crystal packing but the observed intramolecular inter-
actions must contribute in some fashion to the co-conformational
preference and overall stability of the [2]rotaxane.
Even though several large inflexible substituents might
initially act as a steric barrier to the formation of a [2]pseudo-
rotaxane, once the two components involved are permanently
interlocked as a [2]rotaxane, optimization of non-covalent inter-
actions will occur to stabilize the whole assembly. It was of inter-
est then to examine the influence of these substituted crown
ethers on the formation and structure of transition metal com-
plexes3l,h,5,16 and metal organic rotaxane framework
materials11,17 derived from these new [2]pseudorotaxane and
[2]rotaxanes.
A [2]rotaxane terpyridine ligand and complexation with Ru2+
It has been previously demonstrated that [2]pseudorotaxanes
with terminal coordinating groups, such as [3b⊂DB24C8]2+, are
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2012

capable of acting as ligands for transition metals, but care must
be taken during synthesis to preserve the non-covalent inter-
actions that stabilize the interpenetrated pair – by for example
excluding heat or competitive solvents.15a,17,18 Alternately, if the
stopper of a [2]rotaxane contains a group for binding metals, the
permanently interlocked [2]rotaxane can act directly as a ligand
without the need for special precautions during synthesis.16,19
This is especially relevant if complexation of an inert metal
centre is targeted as these syntheses often require forcing condi-
tions.3c,h,19 We have previously prepared a [2]rotaxane ligand
with a DB24C8 wheel and stoppers that contains chelating ter-
pyridine groups.16c Herein, we report an analogous [2]rotaxane
ligand containing crown ether wheel 2e and its subsequent
coordination to two [Ru(terpy)]2+ fragments.
The [2]rotaxane ligand [5⊂2e]4+, containing terpy chelating
groups, was prepared in analogous fashion to the [2]rotaxanes
[4⊂(2b–e)]4+ but using 4′-(4-bromobenzyl)-2,2′,6′,2′′-terpyridine
as the stoppering reagent in place of tert-butylbenzyl bromide
1
(Scheme 4).16c The H NMR spectrum of [5⊂2e]4+ was similar
to that observed for [4⊂2e]4+ with addition peaks attributable to
the two terpyridine groups (7.47–8.76 ppm).
As designed, [5⊂2e]4+ is capable of acting as a binucleating
ligand via two terminal terpyridine groups. Refluxing [5⊂2e]
[OTf]4 with two equivalents of [RuCl3(terpy)] in an EtOH–H2O
solution produced, after anion exchange to triflate, the complex
[(Ru(terpy))2(5⊂2e)][OTf]8. The 1H NMR data for dumbbell
[5]4+, [2]rotaxane ligand [5⊂2e]4+ and the Ru(II) complexes [(Ru
(terpy))2(5)]8+ and [(Ru(terpy))2(5⊂2e)]8+ are summarized in
Table 3. The chemical shift differences between the dumbbell
[5]4+ and the [2]rotaxane [5⊂2e]4+ are similar to those observed
for the [2]rotaxanes [4⊂(2b–e)]4+; protons a and b are shifted to
higher frequency (0.32–0.35 ppm) due to hydrogen-bonding,
while pyridinium peaks c and d and catechol protons s shift to
lower frequencies (0.19–0.22 ppm) due to π-stacking. Coordi-
nation to Ru(II) yielding [(Ru(terpy))2(5)]8+, causes significant
coordination shifts to lower frequencies for terpyridine protons
j – m (0.06–1.29 ppm) with the largest shift for proton m being
attributed to the change in ligand conformation from transoid to
cisoid. For [(Ru(terpy))2(5⊂2e)]8+, similar chemical shift
changes are observed due to a combination of both rotaxane for-
mation and coordination to Ru(II).16c
The single-crystal X-ray structures of both [5⊂2e][OTf]4 and
[(Ru(terpy))2(5⊂2e)][OTf]8 were determined and the cationic
portions of these molecules are shown in Fig. 5. In both struc-
tures, pairs of CH2OC6H4(4-COOEt) groups on the ends of each
Scheme 4 Synthesis of [2]rotaxane ligand. (i) 2 equiv. of 4′-(4-bromo-
benzyl)-2,2′,6′,2′′-terpyridine, MeNO2, RT, 7 days followed by anion
exchange by stirring the MeNO2 layered with NaOTf(aq).
Table 3 Selected 1H NMR chemical shifts for dumbbell [5]4+, [2]rotaxane [5⊂2e]4+ and complexes [(Ru(terpy))2(5)]8+ and [(Ru(terpy))2(5⊂2e)]8+ a
δ(Δδ) Values (ppm)
Proton
[5]4+
[5⊂2e]4+
[(Ru(terpy))2(5)]8+
[(Ru(terpy))2(5⊂2e)]8+
a
b
c
d
e
f
g
h
i
5.27
9.04
8.49
8.46
9.04
5.94
7.71
8.04
8.76
8.70
7.98
7.46
8.70
5.62 (+0.35)
9.36 (+0.32)
8.27 (−0.22)
8.27 (−0.19)
8.98 (−0.06)
5.77 (−0.17)
7.71 (0.00)
7.52 (−0.52)
8.57 (−0.19)
8.73 (+0.03)
7.99 (+0.01)
7.47 (+0.01)
8.70 (0.00)
5.34 (+0.07)
9.19 (+0.15)
8.58 (+0.09)
8.58 (+0.12)
9.14 (+0.10)
6.04 (+0.10)
7.88 (+0.17)
8.34 (+0.30)
9.03 (+0.27)
8.50 (−0.20)
7.92 (−0.06)
7.16 (−0.30)
7.41 (−1.29)
5.67 (+0.40)
9.43 (+0.39)
8.42 (−0.07)
8.42 (−0.04)
9.11 (+0.07)
5.87 (−0.07)
8.09 (+0.38)
7.69 (−0.35)
8.83 (−0.07)
8.51 (−0.19)
7.92 (−0.06)
7.19 (−0.25)
7.45 (−1.25)
j
k
l
m
Proton
2eb
[5⊂2e]4+
[(Ru(terpy))2(5)]8+
[(Ru(terpy))2(5⊂2e)]8+
p
q
r
7.90
7.03
5.14
7.10
7.88 (−0.02)
6.94 (−0.09)
4.64 (−0.50)
6.84 (−0.16)
—
—
—
—
7.92 (+0.02)
7.03 (0.00)
4.81 (−0.33)
6.92 (−0.18)
s
a All spectra were recorded at 500 MHz in MeCN-d3 at 298 K. The labelling key can be found in Scheme 4. b Shifts are from 2e.
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem.

Fig. 5 Top: A ball-and-stick representation of the single-crystal X-ray structure of [2]rotaxane ligand [5⊂2e]4+. Bottom: A ball-and-stick represen-
tation of the single-crystal X-ray structure of binuclear complex [(Ru(terpy))2(5⊂2e)]8+. Counterions and H-atoms are omitted for clarity.
crown ether bracket the stoppering group with one
CH2OC6H4(4-COOEt) substituent involved in π-stacking with a
pyridine group of the terpy stopper and the other interacting with
the linking phenyl unit (protons g and h) via an edge-on C–
H⋯π interaction. Thus, the longer, functionalized stoppers on
the axle are capable of interacting directly with the extended sub-
stituents of the wheel in an intramolecular fashion. This concept
could potentially be used to link axle and wheel via coordination
chemistry or perhaps use a wheel donor as a hemi-labile ligand.
A metal–organic rotaxane framework
[2]Pseudorotaxanes and [2]rotaxanes have also been used as
ligand/linkers in the creation of metal–organic framework
(MOF) materials.11,17 However, to date, there have been no
reports of a metal–organic rotaxane framework (MORF) in
which the skeletal framework could be kept constant and the
nature of the interlocked wheel component varied in order to
observe the effect on structure and/or materials properties. This
is undoubtedly because very few MORFs are known as their
synthesis/crystallization is often difficult. We previously reported
a MORF which is a 2D network comprised of [3b⊂DB24C8]2+
linkers and [Cd(H2O)2]2+ nodes.17a In an attempt to prepare an
analogous MORF with a tetra-substituted crown ether, 2 equiva-
lents of [3b⊂2d][BF4]2 were combined with 1 equivalent of
[Cd(H2O)6][BF4]2 in MeNO2 solution which after partial evapor-
ation produced a yellow crystalline material in ∼40% yield.
Single-crystal X-ray crystallography showed this material to
have formula {[Cd(H2O)2(3b⊂2d)(3b)][BF4]6·(MeNO2)23}. The
Fig. 6 Ball-and-stick representation of the single-crystal X-ray struc-
structure is a 2D network, as designed, with [3b]2+ linkers
ture of metal–organic rotaxane framework [Cd(H2O)2(3b⊂2d)(3b)]n
joining [Cd(H2O)2]2+ metal centres (Fig. 6). This is exactly the
showing one square grid. Counterions and H-atoms are omitted for
same square grid arrangement previously observed for {[Cd
(H2O)(BF4)(3b⊂DB24C8)2]}n when [3b⊂DB24C8]2+ was used
as the linker allowing for direct comparison of two MORFs that
differ only by the nature of their crown ether wheel.17a
clarity.
The major difference between the two square grid structures is
that the new version containing crown ether 2d with four
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2012

Conclusions
Derivatives of the ubiquitous macrocycle DB2C8 containing
four CH2OR groups appended to the two aromatic rings are
readily available in good yield following two simple steps from
commercially available starting materials. The formation of
[2]pseudorotaxanes with 1,2-bis(pyridinium)ethane axles is
favourable in acetonitrile solvent and association constants are
comparable to those for the same axles with DB24C8. Simple
[2]rotaxanes and [2]rotaxane ligands with terpyridine groups can
be prepared via the threading-followed-by-stoppering method-
ology. Coordination to an inert Ru(II) metal centre was shown to
be straightforward and it was established that the appendages
from a substituted crown ether wheel are capable of interacting
with these coordination sites. Most significantly it was demon-
strated that a series of structurally related metal–organic rotaxane
frameworks (MORFs) is possible in which the crown ether com-
ponent can be thought of as a supramolecular additive for poten-
tially tuning the internal properties of these porous materials.
Experimental
General
Phenol, benzyl alcohol, ethyl(4-hydroxy)benzoate, 4-tert-butyl-
benzyl bromide, sodium triflate, sodium borohydride, DB24C8,
2,2′ : 6′,2′′-terpyridine, RuCl3·xH2O, and cadmium(II) tetrafluoro-
borate were obtained from Sigma-Aldrich and used as received.
Axles3g [3a][OTf]2, [3b][OTf]2 and [3c][OTf]2, [RuCl3-
(terpy)]20 and 4′-(4-bromobenzyl)-2,2′,6′,2′′-terpyridine21 were
synthesized according to literature procedures. Deuterated sol-
vents were obtained from Cambridge Isotope Laboratories and
used as received. Solvents were dried using an Innovative Tech-
nologies Solvent Purification System. Thin layer chromatography
(TLC) was performed using Merck Silica gel 60 F254 plates and
viewed under UV light. Column chromatography was performed
Fig. 7 Space-filling representation of a 2 × 3 section of the 2D square
network of: top, previously reported [Cd(H2O)(BF4)(3b⊂DB24C8)2]n
and bottom, [Cd(H2O)2(3b⊂2d)(3b)]n (this work).
CH2OC6H5 groups has one of the axle linkers missing the crown
ether; i.e. one of the linkers is not a rotaxane but a naked axle.17b
It appears as that the four CH2OC6H5 appendages on an adjacent
rotaxane take on the role of sheltering the axle normally accom-
plished by threading on a wheel and rotaxane formation. Fig. 7
shows space-filling views of the two 2D MORFs. The axle and
the metal components yield two MORFs with identical metal–
organic frameworks while the interlocked wheel component can
be thought of as a supramolecular additive which does not
perturb the structure of the coordination polymer. It may be poss-
ible to use this as method to tune the internal properties and/or
structure of the cavities in porous MORFs – for example making
them hydrophobic or hydrophilic depending on the crown ether
substituents. Preliminary results from a poorly resolved X-ray
structure involving the same metal and axles with crown ether
2b, containing smaller n-propyl groups, appears to show that all
linkers are rotaxanes analogous to the previously reported
MORF [Cd(H2O)(BF4)(3b⊂DB24C8)2]n (top, Fig. 7). If so, this
would infer that large groups such as those in [Cd-
(H2O)2(3b⊂2d)(3b)]n (top, Fig. 7) are required to compensate
for rotaxane formation and that smaller more flexible groups
might perhaps be better for full saturation and filling the internal
pores usually occupied by solvent. Work in this concept is
ongoing.
1
using Silicycle Ultra Pure Silica Gel (230–400 mesh). H NMR
experiments were performed on a Bruker Avance 500 instrument
using the deuterated solvent as lock and the residual solvent or
TMS as the internal reference. High-resolution mass spec-
trometry experiments were performed on a Micromass LCT
electro-spray-ionization time-of-flight mass spectrometer in lock-
mass mode. Solutions of 50–100 ng μL−1 were prepared in
MeCN–H2O (1 : 1) (unless otherwise indicated) and injected for
analysis at a rate of 5 μL min−1 using a syringe pump.
Preparation of crown ether 2a. DB24C8 (0.200 g,
0.446 mmol), paraformaldehyde (0.121 g, 4.01 mmol) and 33%
hydrobromic acid in acetic acid (1.3 mL) were stirred until all
the solids had dissolved. The mixture was then left to stand
without stirring for 3 days while a white precipitate formed. The
solid was collected by filtration, washed consecutively with
water, ethanol, and diethyl ether and then air dried. The solid
was recrystallized from MeCN. Yield: 0.316 g, 86%. MP:
1
201–205 °C. H NMR (500 MHz, CDCl3): δ 6.83 (4H, s), 4.59
(8H, s), 4.15 (8H, m), 3.90 (8H, m), 3.79 (8H, m).
Preparation of crown ether 2b. Sodium metal was dissolved
in dry n-propanol (30 mL) and 2a (1.00 g, 1.21 mmol) added
with stirring under N2. The mixture was refluxed for 12 h. After
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem.

cooling, H2O was added drop-wise with great care to destroy any
excess Na(s). The solvent was evaporated and the residue parti-
tioned between CH2Cl2 and H2O. The organic layer was washed
with H2O (2 × 50 mL) and then dried with anhydrous MgSO4.
Yield: 0.828 g, 92%. MP: 72–75 °C. 1H NMR (500 MHz,
CD3CN): δ 6.95 (4H, s), 4.43 (8H, s), 4.10 (8H, m), 3.78 (8H,
m), 3.67 (8H, s), 3.39 (8H, t, J = 6.6 Hz), 1.57 (8H, m, J = 6.6,
7.3 Hz), 0.91 (12H, q, J = 7.3 Hz). 13C NMR (125 MHz,
CD3CN): δ 148.5, 130.8, 115.3, 72.4, 71.4, 70.3, 70.2, 69.6,
23.5, 10.8. ESI-MS: m/z [2b + K]+ calcd 775.4035, found
775.4007.
CH3CN (10 mL) and stirred overnight. 4-t-Butylbenzyl bromide
(0.150 g, 0.660 mmol) was added and the mixture stirred for 4
days. The solvent was removed and the residue stirred in CH2Cl2
(25 mL) for 30 min. The solid that remained was filtered and the
filtrate was evaporated. The orange solid was dissolved in a two
layer solution of MeNO2/NaOTf(aq) and stirred overnight. The
organic layer was separated and dried with anhydrous MgSO4.
The CH3NO2 solution was filtered and the solvent evaporated.
The residue was stirred in toluene. Yield 0.038 g, 25%. MP:
183–190 °C (dec). NMR (500 MHz, CD3CN): δ 9.32 (4H, d, J
= 5.9 Hz), 8.92 (4H, d, J = 6.9 Hz), 8.13 (4H, d, J = 6.9 Hz),
8.04 (4H, d, J = 6.8 Hz), 7.60 (4H, d, J = 8.4 Hz), 7.50 (4H, d, J
= 8.4 Hz), 6.64 (4H, s), 5.80 (4H, s), 5.57 (4H, s), 4.04–3.94
(32H, m), 3.23 (4H, t, J = 6.7 Hz), 1.54 (8H, dd, J = 6.7, 7.4
Hz), 1.36 (12H, s), 0.90 (12H, t, J = 7.4 Hz). ESI-MS: m/z
[4⊂2b + 2OTf]2+ calcd 834.3731, found 834.3736.
Preparation of crown ether 2c. NaH (118 mg, 4.88 mmol)
and benzyl alcohol (527 mg, 4.88 mmol) in dry THF (30 mL)
were stirred for 2 h at room temperature followed by the addition
of 2a (1.00 g, 1.21 mmol). The mixture was refluxed for 1.5
days, cooled to room temperature and H2O (4 mL) added with
care. THF was removed under vacuum and the residual oil dis-
solved in CH2Cl2 (50 mL) and washed with 1 M NaHCO3 (3 ×
50 mL) and H2O (50 mL) and then dried with anhydrous
MgSO4. The CH2Cl2 was removed and the residue stirred in
diethyl ether. Yield: 0.836 g, 74%. MP: 60–63 °C. 1H NMR
(500 MHz, CD3CN): δ 7.31 (20H, m), 6.95 (4H, s), 4.47 (8H,
s), 4.45 (8H, s), 4.09 (8H, m), 3.76 (8H, m), 3.65 (8H, s). 13C
NMR (125 MHz, CD3CN): δ 148.6, 144.4, 130.4, 129.1, 128.5,
128.2, 115.6, 72.6, 71.4, 70.2, 69.9, 69.6. ESI-MS: m/z
[2c + K]+ calcd 967.4035, found 967.4070.
Preparation of [2]rotaxane [4⊂2c][OTf]4. 3b[OTf]2 (0.050 g,
0.078 mmol), 2c (0.145 g, 0.157 mmol) was dissolved in
CH3CN (10 mL) and stirred overnight. 4-t-Butylbenzylbromide
(0.150 g, 0.660 mmol) was added, and stirred for 4 days. The
solvent was removed, and was stirred in CH2Cl2 (25 mL) for
30 minutes. The solid that remained was filtered, and the filtrate
was evaporated. The orange solid was dissolved in a two layer
solution of MeNO2/NaOTf(aq) stirred overnight. The organic
layer was separated, dried with MgSO4. The CH3NO2 solution
was filtered and solvent evaporated. The residue was stirred in
toluene. X-ray quality crystals were grown by the slow diffusion
of isopropyl ether into a saturated CH3CN solution. Yield
0.025g, 15%. MP: 177–185 °C (dec). 1H NMR (500 MHz,
CD3CN): δ 9.32 (4H, d, J = 6.8), 8.53 (4H, d, J = 6.8), 8.14
(4H, d, J = 6.8), 7.93 (4H, d, J = 6.8), 7.53 (4H, d, J = 8.4),
7.38–7.35 (12H, m), 7.31–7.28 (8H, m), 6.67 (4H, s), 5.55 (4H,
s), 5.47 (4H, s), 4.35 (8H, s), 4.11 (8H, s), 4.04–3.99 (24H, m),
1.28 (18H, s). ESI-MS: m/z [4⊂2c + 2OTf]2+ calcd 930.3731,
found 930.3765.
Preparation of crown ether 2d. To a solution of 2a (1.00 g,
1.22 mmol) and phenol (0.459 g, 4.88 mmol) in CH3CN
(30 mL) was added K2CO3 and the mixture stirred under N2 at
reflux for 5 days. The solvent was evaporated and the residue
partitioned between CH2Cl2 and H2O. The organic layer was
washed with H2O (2 × 50 mL), dried with anhydrous MgSO4
and recrystallized from CH3CN. X-Ray quality crystals were
grown by the slow diffusion of hexanes into a saturated CHCl3
solution. Yield: 0.806 g, 76%. MP: 135–136 °C. 1H NMR
(500 MHz, CD3CN): δ 7.27 (8H, t, J = 8.0 Hz), 7.03 (4H, s),
6.92 (12H, m), 5.05 (8H, s), 4.14 (8H, m), 3.85 (8H, m), 3.78
(8H, m). 13C NMR (125 MHz, CD2Cl2): δ 159.0, 148.9, 129.7,
128.6, 121.2, 115.6, 71.4, 70.0, 69.7, 67.8. ESI-MS: m/z
[2d + Na]+ calcd 895.3669, found 895.3658.
Preparation of [2]rotaxane [4⊂2d][OTf]4. 3b[OTf]2 (0.050 g,
0.078 mmol) and 2d (0.140 g, 0.160 mmol) were dissolved in
CH3CN (10 mL) and stirred overnight. 4-tert-Butylbenzyl
bromide (0.150 g, 0.660 mmol) was added and the mixture
stirred for 4 days. The solvent was removed and the residue was
stirred with CH2Cl2 (25 mL) for 30 minutes. The solid that
remained was removed and the filtrate evaporated. The resulting
orange solid was dissolved in a two layer solution of MeNO2/
NaOTf(aq) and stirred overnight. The organic layer was separ-
ated and dried with anhydrous MgSO4. The CH3NO2 solution
was filtered and solvent evaporated. The residue was stirred in
toluene. X-ray quality crystals were grown by the slow diffusion
of iso-propyl ether into a saturated CH3CN solution. Yield
0.030 g, 30%. MP: 181–185 °C (dec). 1H NMR (500 MHz,
CD3CN): δ 9.37 (4H, d, J = 6.6 Hz), 8.84 (4H, d, J = 6.6 Hz),
8.26 (4H, d, J = 6.6 Hz), 8.20 (4H, d, J = 6.6 Hz), 7.35 (8H, dd,
J = 8.0 Hz), 7.25 (4H, d, J = 7.7 Hz), 7.03 (4H, d, J = 7.7 Hz),
6.92 (8H, d, J = 8.0 Hz), 6.86 (8H, s), 5.62 (8H, s), 5.53 (8H, s),
4.68 (8H, s), 4.08–4.02 (24H, m), 1.23 (18H, s). ESI-MS: m/z
[4⊂2d + OTf]3+ calcd 551.9104, found 551.9100.
Preparation of crown ether 2e. To a solution of 2a (1.00 g,
1.22 mmol) and ethyl(4-hydroxy)benzoate (0.810 g, 4.88 mmol)
in degassed MeCN (30 mL) was added K2CO3 and the mixture
stirred under N2 at reflux for 5 days. The solvent was then evap-
orated and the residue partitioned between CH2Cl2 and H2O.
The organic layer was washed with H2O (2 × 50 mL) and then
dried with anhydrous MgSO4 and recrystallized from CH3CN.
1
Yield: 0.877 g, 62%. MP: 120–123 °C. H NMR (500 MHz,
CD3CN): δ 7.95 (8H, d, J = 8.4 Hz), 7.03 (4H, s), 6.97 (8H, d, J
= 8.4 Hz), 5.11 (8H, s), 4.30 (8H, q, J = 7.0 Hz), 4.15 (8H, m),
3.85 (8H, m), 3.75 (8H, m), 1.35 (12H, t, J = 7.0 Hz). 13C NMR
(125 MHz, CD2Cl2): δ 166.5, 162.7, 149.4, 131.9, 128.3, 124.0,
116.0, 114.9, 71.6, 70.3, 70.0, 68.3, 61.1, 14.7. ESI-MS: m/z
[2e + Na]+ calcd 1183.4515, found 1183.4524.
Preparation of [2]rotaxane [4⊂2b][OTf]4. 3b[OTf]2 (0.050 g,
0.078 mmol), 2b (0.115 g, 0.157 mmol) were dissolved in
Preparation of [2]rotaxane [4⊂2e][OTf]4. 3b[OTf]2 (0.050 g,
0.078 mmol) and 2e (0.185 g, 0.159 mmol) were dissolved in
Org. Biomol. Chem.
This journal is © The Royal Society of Chemistry 2012

CH3CN (10 mL) and 4-t-butylbenzyl bromide (0.150 g,
0.660 mmol) added. The mixture was stirred for 4 days. The
solvent was removed and the residue was stirred in CH2Cl2
(25 mL) for 30 min. The solid that remained was filtered and the
filtrate was evaporated. The remaining orange solid was dis-
solved in a two layer solution of MeNO2/NaOTf(aq) and stirred
overnight. The organic layer was separated and dried with anhy-
drous MgSO4. The CH3NO2 was removed by evaporation and
the residue stirred in toluene. X-ray quality crystals were grown
by the slow diffusion of iso-propyl ether into a saturated CH3CN
J = 8.3 Hz), 6.97 (8H, d, J = 8.8 Hz), 6.86 (4H, s), 5.62 (4H, s),
5.61 (4H, s), 4.76 (8H, s), 4.33 (8H, q, J = 7.1 Hz), 4.02–4.08
(24H, m), 1.36 (8H, t, J = 7.1 Hz), 1.22 (18H, s). ESI-MS: m/z
[4⊂2e + OTf]3+ calcd 647.9385, found 647.9409.
Preparation of [2]rotaxane, [5⊂2e][OTf]4. 3b[OTf]2 (0.050 g,
0.078 mmol) and 2e (0.185 g, 0.159 mmol) were dissolved in
MeNO2 (10 mL) and stirred overnight. 4′-(4-Bromobenzyl)-
2,2′,6′,2′′-terpyridine (0.189 g, 0.147 mmol) was dissolved in
CH2Cl2, and the mixture was stirred for 7 days. The organic
layer was removed, and the orange solid stirred between MeNO2
and NaOTf(aq) stirred overnight. The organic layer was separ-
ated, dried with anhydrous MgSO4 and evaporated. The residue
was stirred in toluene. The orange solid was dissolved in
1
solution. Yield 0.037 g, 20%. MP: 188–193 °C (dec). H NMR
(500 MHz, CD3CN): δ 9.36 (4H, d, J = 6.8 Hz), 8.86 (4H, d,
J = 6.9 Hz), 8.23 (4H, d, J = 6.8 Hz), 8.17 (4H, d, J = 6.6 Hz),
7.99 (8H, d, J = 8.8 Hz), 7.35 (8H, d, J = 8.3 Hz), 7.25 (8H, d,
Table 4 A summary of crystal data collection, solution and structure refinement parameters for single-crystal structure determinations
Compound
2d·(CHCl3)
[3a⊂2d][BF4]2·(CH3NO2)6
[4⊂2c][OTf]4·(H2O)2
[4⊂2d][OTf]4·(CH3CN)3.5(H2O)1.5
CCDC number
Formula
Formula weight
Crystal system
Space group
T (K)
864512
C53H57Cl3O12
992.34
864511
C82H94B2F8N8O24
1749.27
Monoclinic
C2/c (15)
173(2)
864513
C104H116F12N4O26S4
2194.25
Monoclinic
C2/c (15)
173(2)
864507
C107H119.5F12N7.5O25.5S4
2274.84
Triclinic
Triclinic
ˉ
ˉ
P1 (2)
P1 (2)
173(2)
173(2)
a (Å)
b (Å)
c (Å)
α (°)
12.554(4)
13.774(5)
15.329(5)
80.404(5)
68.495(4)
89.969(5)
2426.4(15)
2
37.627(6)
12.680(2)
20.775(3)
—
123.038(2)
—
8309(2)
4
1.398
27.729(3)
16.863(2)
23.505(3)
—
106.757(1)
—
10 524(2)
4
1.385
16.478(4)
17.317(4)
22.065(5)
78.7863)
78.864(3)
65.622(3)
5580(2)
2
β (°)
γ (°)
V (Å3)
Z
ρ, g cm−3
1.358
0.253
1.354
0.180
μ, mm−1
0.114
0.188
Reflections
Variables/restraints
R1 [I > 2σ(I)]a
R1 (all data)
R2w [I > 2σ(I)]b
R2w (all data)
GoF on F2
8433
565/0
0.1434
0.2106
0.3560
0.3936
1.165
8470
8956
757/275
0.1090
0.1499
0.2910
0.3206
1.097
19 587
1462/537
0.1114
0.1636
0.3178
0.3647
1.291
451/55
0.1216
0.1669
0.3558
0.3818
1.296
Compound
[5⊂2e][OTf]4·(CH3CN)2(H2O)7 [(Ru(terpy))2(5⊂2e)][OTf]8·(CH3CN)2(H2O)3 [Cd(H2O)2(3b⊂2d)(3b)][BF4]6·(CH3NO2)23
CCDC number
Formula
Formula weight
Crystal system
Space group
T (K)
864510
138H144F12N12O39S4
864509
C172H158F24N18O47Ru2S8
4143.78
Monoclinic
P21/n (14)
173(2)
18.248(9)
20.018(10)
28.528(14)
—
92.355(8)
—
10 412(9)
2
864508
C119H169B6CdF24N31O60
3627.11
Monoclinic
Pc (7)
C
2950.90
Monoclinic
P21/c (14)
173(2)
21.417(3)
25.553(3)
13.838(2)
—
103.228(2)
—
7372(2)
2
173(2)
a (Å)
b (Å)
20.057(3)
22.223(3)
18.474(3)
—
109.497(2)
—
7763(2)
2
1.552
c (Å)
α (o)
β (o)
γ (o)
V (Å3)
Z
ρ, g cm−3
μ, mm−1
Reflections
1.329
0.161
12 927
1.322
0.321
10 811
0.270
27 335
Variables/restraints 920/0
709/596
0.226
0.4242
0.4545
0.5573
1174/534
0.0855
0.1188
0.2214
0.2405
R1 [I > 2σ(I)]a
R1 (all data)
0.1361
0.2414
0.2818
0.3449
1.104
R2w [I > 2σ(I)]b
R2w (all data)
GoF on F2
1.292
0.929
2 2
2 2
2
a R1 = Σ ||Fo| − |Fc||/ Σ |Fo|. b R2w = [Σ[w(Fo2 − Fc ) ]/Σ[w(Fo ) ]]1/2, where w = q[σ2(Fo ) + (aP)2 + bP]−1
.
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem.

CH3CN and iso-propyl ether was slowly diffused into the sol-
ution to give an orange solid. Yield: 0.065 g, 30%. MP:
166–172 °C (dec). 1H NMR (500 MHz, CD3CN): δ 9.36 (4H, d,
J = 6.7 Hz), 8.98 (4H, d, J = 6.7 Hz), 8.73 (4H, d, J = 4.5 Hz),
8.70 (4H, d, J = 7.8 Hz), 8.57 (4H, s), 8.27 (4H, m), 8.00 (4H,
d, J = 8.1, 1.7 Hz), 7.87 (8H, d, J = 8.8 Hz), 7.71 (4H, d, J = 8.0
Hz), 7.52 (4H, d, J = 8.0 Hz), 7.46 (4H, dd, J = 7.8, 1.7 Hz),
6.93 (4H, d, J = 8.8 Hz), 6.84 (4H, s), 5.77 (4H, s), 5.62 (4H, s),
4.64 (8H,s) 4.14 (12H, q, J = 7.1 Hz), 4.06–4.13 (12H, m), 1.21
(8H, t, J = 7.0 Hz). ESI-MS: m/z [5⊂2e + 2OTf]2+ calcd
1221.4011, found 1221.4041.
and anomalous dispersion coefficients are contained in the
SHELXTL 5.03 program library.22 All X-ray crystal structure
graphics were created using the program DIAMOND.23
A
summary of crystal data collection, solution and structure refine-
ment parameters are listed in Table 4. Details of the X-ray struc-
ture solutions can be found in the CIF format files deposited
with the CCDC (numbers are listed in Table 4)†. This includes
any problems with crystal quality, data collection or solution
refinement that resulted in high residuals, as well as a description
of any restraints necessary to attain the chemically reasonable
models shown.
Preparation of complex [(Ru(terpy))2(5⊂2e)][OTf]8. To a sol-
ution of [5⊂2e][OTf]4 (0.030 g, 0.0109 mmol) dissolved in 1 : 1
EtOH–H2O solution was added solid [RuCl3(terpy)] (0.010 g,
0.020 mmol) and the mixture was brought to reflux for 24 h to
give a deep red solution. The reaction mixture was cooled to
room temperature and filtered through a Celite pad and washed
with EtOH until the eluent was colourless. The filtrate was then
reduced to half the volume and the addition of NaOTf produced
a red precipitate. The red solid was dissolved in CH3CN and iso-
propyl ether slowly diffused into the solution give a red solid in
Acknowledgements
The authors thank NSERC of Canada for providing funds in the
form of a Discovery Grant to S. J. L.
Notes and references
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1
quantitative yield. H NMR (500 MHz, CD3CN): δ 9.43 (4H, d,
J = 6.4 Hz), 9.11 (4H, d, J = 6.4 Hz), 8.83 (4H, s), 8.77 (4H, d,
J = 8.1 Hz), 8.59 (4H, d, J = 8.1 Hz), 8.51 (4H, d, J = 8.1 Hz),
8.43 (4H, m), 8.42 (4H, m), 8.41 (4H, m), 8.09 (4H, d, J = 8.1
Hz), 7.93 (4H, m), 7.92 (4H, m), 7.91 (8H, m), 7.69 (4H, d, J =
8.1 Hz), 7.45 (4H, d, J = 5.2 Hz), 7.37 (4H, m, J = 5.3 Hz), 7.19
(4H, dd, J = 6.4, 6.3 Hz), 7.18 (4H, dd, J = 6.4, 6.3 Hz), 7.03
(4H, d, J = 8.7 Hz), 6.92 (4H, s), 5.87 (4H, s), 5.67 (4H, m),
4.81 (8H, s), 4.13–4.06 (12H, m), 4.13–4.06 (24H, m), 1.21
(8H, t, J = 7.0 Hz). UV-vis: λmax = 486 nm. ESI-MS: m/z [(Ru-
(terpy))2(5⊂2e) + 4OTf]4+ calcd 852.6761, found 852.6795.
Preparation of MORF [Cd(H2O)2(3b⊂2d)(3b)][BF4]6. To a
solution of 3b[BF4]2, (13 mg, 0.025 mmol) in MeNO2 (1 mL)
was added 2 equivalents of 2d (42 mg, 0.048 mmol). The result-
ing solution was stirred at room temperature for 1 h at which
time [Cd(H2O)6][BF4]2 (5 mg, 13 mmol) dissolved in MeNO2–
MeOH (0.5 mL) was added. Slow diffusion of isopropyl ether
into the MeNO2 produced yellow crystals. Yield ∼40%; deter-
mined to be a homogeneous sample by optical microscopy and
identified as having formula {[Cd(H2O)2(3b⊂2d)(3b)][BF4]6.
(MeNO2)23} by single-crystal X-ray crystallography.
Single-crystal X-ray structure determinations. Crystals were
mounted on a short glass fibre attached to a tapered copper pin.
A full hemisphere of data were collected with 30 second frames
on a Brüker APEX diffractometer fitted with a CCD based detec-
tor using MoKα radiation (0.71073 Å). Decay (<1%) was moni-
tored by 50 standard data frames measured at the beginning and
end of data collections. Diffraction data and unit-cell parameters
were consistent with the assigned space groups. Lorentzian
polarization corrections and empirical absorption corrections,
based on redundant data at varying effective azimuthal angles,
were applied to the data set. The structure was solved by direct
methods, completed by subsequent Fourier syntheses and refined
with full-matrix least-squares methods against |F2| data. All non-
hydrogen atoms were refined anisotropically. All hydrogen
atoms were treated as idealized contributions. Scattering factors
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