Nondegenerate π-donor/π-acceptor [2]catenanes containing proton-ionizable 1H-1,2,4-triazole subunits: Synthesis and spontaneous resolution

Article abstract of DOI:10.1002/chem.200601144

Chirality can hold the key to inducing directionality of motion in components of molecular devices. With this idea in mind, we describe here 1) the template-directed synthesis of two [2]catenanes wherein cyclobis(paraquat-p- phenylene) is interlocked with

Full text of DOI:10.1002/chem.200601144

DOI: 10.1002/chem.200601144
Nondegenerate p-Donor/p-Acceptor [2]Catenanes Containing Proton-
Ionizable 1H-1,2,4-Triazole Subunits: Synthesis and Spontaneous Resolution
Ermitas Alcalde,[a] Lluïsa PØrez-García,*[a] Susana Ramos,[a] J. Fraser Stoddart,[b]
[c]
Andrew J. P. White, and David J. Williams*[c]
Abstract: Chirality can hold the key to
inducing directionality of motion in
components of molecular devices. With
this idea in mind, we describe here
1) the template-directed synthesis of
two [2]catenanes wherein cyclobis(par-
aquat-p-phenylene) is interlocked with
polyether macrocycles containing, in
addition to one 3,5-bis(oxymethylene)-
1H-1,2,4-triazole unit, either one 1,4-di-
oxybenzene or one 1,5-dioxynaphtha-
lene ring system. We also report 2) the
full characterization of both [2]cate-
nanes by fast atom bombardment mass
spectrometry (FABMS), X-ray crystal-
lography, and dynamic 1H NMR spec-
troscopy. We reveal 3) the fact that the
[2]catenanes not only exist, both in the
solution-state and in the solid-state, as
strictly one of the two possible transla-
tional isomers, but that they also exhib-
it spontaneous resolution on crystalli-
zation leading to formation of homo-
chiral crystals, as indicated by X-ray
crystallography and circular dichroism
(CD) experiments. Finally, we com-
ment 4) on the chances of switching
these catenanes chemically.
Keywords: catenanes · self-assem-
bly
·
spontaneous resolution
·
·
supramolecular
chemistry
template synthesis
Introduction
that utilize noncovalent interactions as a major element of
the self-assembly methodology,[3] as well as interdisciplinary
research leading to singular approaches for the construction
of molecular devices.[4] Furthermore, stereochemistry can
induce directionality of motion,[5] and therefore chirality can
be regarded as a control element for the construction of mo-
Catenanes and related molecular architectures[1] have been
transformed from mere chemical and intellectual curiosities
into key elements in the fabrication of nanoscale devices, in-
cluding light- and redox-driven switches and most recently
molecular logic gates.[2] A decisive contribution to these ad-
vances has been the development of templated syntheses
lecular switches and binary optical data-storage devices.[6]
A
vast number of configurational,[7] conformational,[8] or topo-
logically[9] chiral interlocked systems has been described,
and a major effort has been made to isolate them in an
enantiomerically pure form.[10] Among them, only one ex-
ample is known of the spontaneous resolution of a [2]cat-
enane having elements of planar chirality,[11] although this
was a degenerate (nonswitchable) case.
[a] Prof. E. Alcalde, Dr. L. PØrez-García, Dr. S. Ramos
Laboratori de Química Orgànica
Facultat de Farmàcia and Institut de Nanoci›ncia i Nanotecnologia
Universitat de Barcelona
Avda. Joan XXIII s/n, 08028-Barcelona (Spain)
Fax : (+34)93-402-1396
Incorporation of betainic subunits, for example, based on
imidazoliummethylene 1,2,4-triazolate, into oligopolar and
oligocationic macrocyclic scaffolds[12] has been one of our re-
search interests and provided cyclophanes with a variety of
properties such as anion binding.[13] In a project aiming at
the preparation of betainic catenanes,[14] the design of inter-
locked structures calls on previous experience of our groups.
In this context, incorporation of proton-ionizable hetero-
aromatic systems, for example, 1H-1,2,4-triazole units,[12,15]
into mechanically interlocked structures is interesting for
different reasons and permits examination of the character-
istics of these entities, based on their distinctive properties:
E-mail: mlperez@ub.edu
[b] Prof. J. F. Stoddart
Department of Chemistry and Biochemistry
University of California at Los Angeles
405 Hilgard Avenue, Los Angeles, CA 90095-1569 (USA)
Fax : (+1)310-206-2843
[c] Dr. A. J. P. White, Prof. D. J. Williams
Department of Chemistry, Imperial College
South Kensington, London SW72AY (UK)
Fax : (+44)171-594-5804
E-mail: d.williams01@ic.ac.uk
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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FULL PAPER
1) 1H-1,2,4-triazole units are good hydrogen-bond donors,
2) they exhibit prototropic annular tautomerism, 3) they can
be regarded as ligands for a variety of transition metal
ions,[16] 4) the 3,5-bis(methylene)-1H-1,2,4-triazole fragment
has a weak p-donor character[17] which could modulate the
translational isomerism in dissymmetric catenanes, 5) its
acid/base properties, that is, the 1H-1,2,4-triazole/1,2,4-tria-
zolate equilibrium can in principle be exploited as an ele-
ment of a switch for the construction of molecular machines,
and 6) the triazole unit is also advantageous for incorpora-
tion of these molecules onto surfaces, as it is easily function-
alized.
In this work we have explored the use of 1H-1,2,4-tria-
zole/triazolate subunits as building blocks for the construc-
tion of p-donor/p-acceptor catenanes based on paraquat res-
idues and p-electron-rich units,[18] aiming at the preparation
and study of the properties of oligocationic and oligopolar
catenanes and their potential use as molecular switches.
We describe here the synthesis of the [2]catenanes
13·4PF6 and 14·4PF6, which incorporate the tetracationic cy-
clophane cyclobis(paraquat-p-phenylene) as the p-electron-
deficient component and a macrocyclic polyether as the p-
electron-rich component incorporating either one 1,4-dioxy-
benzene or 1,5-dioxynaphthalene ring and one 3,5-bis(oxy-
methylene)-1H-1,2,4-triazole unit. We report on the charac-
terization of 13·4PF6 and 14·4PF6 by fast atom bombard-
ment mass spectrometry (FABMS), X-ray crystallography,
1
and dynamic H NMR spectroscopy.
The most remarkable aspect of these new [2]catenanes is
their existence both in solution and in the solid state as only
one of the two possible translational isomers. Furthermore,
both [2]catenanes exhibit spontaneous resolution on crystal-
lization to form homochiral crystals (of the same type of
chirality), as determined by X-ray crystallography and circu-
Abstract in Catalan: La quiralitat pot ser la clau per induir
direccionalitat al moviment per al disseny de dispositius mo-
leculars. Amb aquesta idea en ment, en aquest article descri-
vim 1) la síntesi dirigida per plantilla de dos [2]catenans que
a la seva estructura entrellacen un ciclofà tetracatiònic (ciclo-
bis(paraquat-p-fenil›) amb poli›ters macrocíclics que conte-
nen, a mes d’una unitat de 3,5-bis(oximetilen)-1H-1,2,4-tri-
lar dichroism experiments. The potential use of the proton-
ionizable 1H-1,2,4-triazole moieties as elements of switches
was also examined, but the tetracationic macrocycle is ex-
tremely unstable in the presence of 1,2,4-triazolate anions.
Results and Discussion
azole, un anell d’ 1,4-dihidroxibenz› o 1,5-dihidroxinaftal›.
TambØ detallem 2) la total caracterització dels dos [2]ca-
tenans mitjanÅant espectrometria de masses per bombardeig
d’àtoms ràpids (FABMS), cristal·lografia de raigs-X i espec-
troscòpia dinàmica de 1H NMR. Es remarcable 3) que els
[2]catenans existeixen, tant en dissolució com a l’estat sòlid,
com un de dos possibles isòmers translacionals. A mØs,
tambØ experimenten resolució espontània per cristal·lització,
conduint a la formació de cristalls homoquirals, tal com s’ha
demostrat per cristal·lografia de raigs-X i experiments de di-
croïsme circular (CD). Finalment, comentem 4) sobre el po-
tencial d’actuar com interruptors controlats químicament
d’aquests catenans.
Synthesis: Preparation of macrocyclic polyether 7 was at-
tempted by two procedures (Scheme 1), both of which in-
volved the protected macrocycle 4 as key intermediate. Ini-
tially, synthesis of 4 was attempted by using CsCl as tem-
plate in a one-pot reaction, following a procedure previously
used for the synthesis of various dissymmetric crown ethers
containing
However, reaction of the tetrahydropyranyl-protected bis-
(chloromethyl)triazole 1[20] and tetraethylene glycol in equi-
1-methyl-3,5-bis(methylene)-1H-pyrazole.[19]
AHCTREUNG
molar proportion and using dimethoxyethane (DME) as the
solvent under a variety of conditions did not lead to isola-
tion of 4. Instead, reaction of 1 with an excess of tetraethy-
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L. PØrez-García, D. J. Williams et al.
Scheme 1. Synthesis of the macrocyclic polyethers 7, 8, and 9: a) one-pot, NaH, CsCl, DME, reflux; b) NaH, 608C; c) NaH, NaI, DMF, 808C; d) pTsCl,
NaOH, H2O/THF; e) Cs2CO3, CsOTs, DMF, 808C; f) Cs2CO3, CsOTs, DMF, 1008C; g) 1.5n HCl/MeOH, RT.
lene glycol and NaH afforded bis-alcohol 2 in 62% yield.
Macrocyclization of 2 with 1 by using NaH and NaI in DMF
yielded 7% of bis-protected macrocycle 4, which was depro-
tected in acidic medium to give macrocyclic polyether 7
(Scheme 1).
Macrocyclic polyethers 8 and 9 were both obtained in
three steps from intermediate 2 by tosylation, macrocycliza-
tion by reaction of the bis-tosylate 3 with 1,4-dihydroxyben-
zene and 1,5-dihydroxynaphthalene in basic medium
(cesium carbonate in DMF) to give protected macrocycles 5
(26%) and 6 (8%) respectively, and deprotection in acidic
medium (Scheme 1).
The [2]catenanes 13·4PF6 and 14·4PF6 were assembled by
a template-directed methodology (Scheme 2). Reaction of
[21a]
10·2PF6
and 11 in the presence of the appropriate macro-
cyclic polyether 8 containing one 1,4-dioxybenzene unit and
one 3,5-bis(oxymethylene)-1H-1,2,4-triazole unit as p-donor
recognition motifs under high-pressure conditions (10 kbar)
gave [2]catenane 13·4PF6 in 34% yield after counterion ex-
change (Scheme 2). In this case, the reaction performed at
room pressure afforded [2]catenane 13·4PF6 with no signifi-
cant difference in yield (33%). Following a similar proce-
dure with macrocyclic polyether 9 containing one 1,5-dioxy-
naphthalene unit and one 3,5-bis(oxymethylene)-1H-1,2,4-
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p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
action of 10·2PF6 with 11 in the presence of the polyether 7
containing two 3,5-bis(methylene)-1H-1,2,4-triazole units
(Scheme 2), and the only product formed was cyclobis(para-
quat-p-phenylene) 15·4PF6 in 17% yield. This smaller affini-
ty is a consequence of the weaker p-donor character and the
smaller p surface of the 1,2,4-triazole unit, along with the
fact that no oxygen atoms are directly linked to it.[22,23]
Complexation studies: Complexation was studied by UV/
1
Vis and H NMR techniques in acetonitrile solution. First,
the absence of any charge-transfer band for an equimolecu-
lar mixture of cyclobis(paraquat-p-phenylene) 15·4PF6 and
the extended open-chain polyether containing one 1,2,4-tria-
zole unit 16 in CH3CN indicates the lack of p–p interactions
between the two components, and therefore the complex
formed is extremely weak or it does not form at all. Also,
an equimolar mixture of the same components in CD3CN at
258C did not indicate formation of a complex, with no
1
changes in the H NMR chemical shifts of the components.
Under the same conditions, an equimolar mixture of
15·4PF6, 16, and extended polyether 17 containing one 1,4-
dioxybenzene unit,[21a] led to exclusive formation of the 1:1
complex between 15·4PF6 and 17 (see Scheme S1 and
Table S1 in the Supporting Information). The high prefer-
ence of the tetracationic cyclophane for the 1,4-dioxyben-
zene units compared with the 3,5-bis(methylene)triazole
units may explain their different efficiencies as templates in
the formation of the [2]catenanes and the isomer selectivity
observed in the catenanes both in solution and the solid
state (see below).
Scheme 2. Template-directed synthesis of the [2]catenanes 13·4PF6 and
14·4PF6: a) DMF, RT, 10 kbar, 3 days; b) NH4PF6, H2O.
Mass spectrometry: All polyethers 2–9 and 16 containing
the 1H-1,2,4-triazole unit were characterized by positive-ion
ESIMS (see Table S2 in the Supporting Information).
triazole gave [2]catenane 14·4PF6 in 65% yield. Once again,
the 1,5-dioxynaphthalene unit shows its better ability as
template for formation of the p-acceptor cyclophane within
[2]catenanes of this type. Clearly, these yields indicate that
the 3,5-bis(oxymethylene)-1H-1,2,4-triazole is a less efficient
recognition unit for the formation of these [2]catenanes, re-
flecting the relatively weak p-donating ability[17] (see com-
plexation studies below) in comparison to previously de-
scribed [2]catenanes containing macrocyclic polyethers in-
corporating 1,4-dioxybenzene, 1,5-dioxynaphthalene, and p-
xylyl aromatic units.[21] Additional evidence is provided by
two facts: 1) no complexation is evident between open-chain
polyether derivatives of 3,5-bis(methylene)-1H-1,2,4-triazole
and cyclobis(paraquat-p-phenylene) (see below),[12] and
2) under the same conditions, no catenane is formed by re-
The structures of [2]catenanes 13·4PF6 and 14·4PF6 were
characterized by positive-ion FABMS, which revealed peaks
characteristic of successive loss of one, two, three, and four
ꢀ
PF6 counterions from the molecular ion. An additional
peak corresponding to the dicationic fragment after the loss
of two counterions is also observed. Peaks corresponding to
ꢀ
the loss of one, two, and three PF6 counterions from the
free cyclophane component of the [2]catenanes are ob-
served, along with characteristic loss of the neutral crown
ether component of the fragmented [2]catenane (Table 1).
A doubly charged ion is also observed for both catenanes
ꢀ
13·4PF6 and 14·4PF6 corresponding to the loss of two PF6
counterions (Table 1). For 13·4PF6 peaks were also observed
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L. PØrez-García, D. J. Williams et al.
for association of the macrocyclic polyether component
with Li [CE+Li]+ and Na [CE+Na]+, respectively
(Table 1).
X-ray crystallography: Single crystals of 13·4PF6 and
14·4PF6 suitable for X-ray crystallography[24,25] were grown
by vapor diffusion of iPr2O into MeCN solutions.[26] Re-
markably, both sets of single crystals belong to the same
chiral space group and so contain only one pure enantio-
mer in the solid state, that is, spontaneous resolution occurs
on crystallization.[27] Although this is not an uncommon
phenomenon, it is, to our knowledge, the first time[28] that
[2]catenanes of the p-donor/p-acceptor variety have under-
gone spontaneous resolution where 1) the basis for the chir-
ality[29] is helical and planar and 2) inversion between enan-
tiomers involves a co-conformational change[30] and either a
conformational change or a prototropic annular tautomer-
ism.[17] Figure 1 shows the inversion between two pairs of
enantiomers, that is, (pR)-(P) and (pS)-(M), and (pR)-(M)
and (pS)-(P), via diastereoisomers in a mutual fashion that
requires sequential operation of two independent processes.
The first involves rocking[21a] of the macrocyclic polyether
ring with respect to the tetracationic cyclophane (process
I), and the second involves either rotation of the triazole
ꢀ
ring about its C3 C5 axis (process II) or a 1,2-shift of the
proton on the triazole ring (process II’). These last two pro-
cesses have stereochemically identical outcome. The struc-
tures represented in Figure 1 show changes associated with
process II related to rotation of the triazole ring about its
ꢀ
C3 C5 axis, although an equivalent figure could be drawn
considering the prototropic tautomerism (process II’). An-
other stereochemically relevant transformation is process
III, which involves exchange of the inside and alongside bi-
pyridinium units as a consequence of a pirouetting move-
ment by the triazole unit in the macrocyclic polyether. Ap-
plication of this transformation to the molecules of the
[2]catenanes 13·4PF6 and 14·4PF6 leads to the same result
as the transformation related to process I (exchange of dia-
stereomers). The absolute stereochemical descriptors intro-
duced in Figure 1 are defined and explained in Figure 2,
and the structural parameters for the [2]catenanes 13·4PF6
and 14·4PF6 are collected in Table 2 (see also Table S3 in
the Supporting Information).
The solid-state (absolute) structure (Figure 3) of [2]cat-
enane 134+ reveals, as expected, the presence of only one
translational isomer. The macrocyclic polyether is threaded
through the center of the tetracationic cyclophane, with the
1,4-dioxybenzene ring positioned inside the tetracationic
cyclophane, sandwiched between the p-electron-deficient
bipyridinium units, with the bis(oxymethyl)-1,2,4-triazole
unit (the location of the hydrogen atoms on one of the ni-
trogen atoms is clearly defined) lying alongside. The sepa-
rations between the p-electron-deficient bipyridinium units
and the p-electron-rich hydroquinone ring are very similar
to those observed[21a] in the [2]catenane wherein cyclobis-
AHCTREUNG
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p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
phane, while the triazole ring
lies only approximately along-
side and is noticeably removed
from the overlaying position
observed in 134+
. Consistent
with the stronger p–p stacking
interaction between the 1,5-di-
oxynaphthalene ring system
(cf., the hydroquinone ring)
and the bipyridinium units, the
mean interplanar separations
are reduced by more than 0.1 Š
with respect to those in 134+
.
The sliding away of the triazole
ring results in its lying above
the plane of the tetracationic
cyclophane
with
negligible
overlapwith either of the two
pyridinium rings. Disorder of
the triazole ring and one of its
adjacent CH2OCH2 groups re-
sults in two slightly different
orientations: the major confor-
mation is depicted in Figure 4.
Also, the position of the ring
hydrogen atom could not be de-
termined. Intra-[2]catenane sta-
bilizing interactions include the
ꢀ
usual complement of C H···O
ꢀ
and C H···p hydrogen bonds,
which supplement the p–p
stacking interactions (a–d in
Figure 4). Surprisingly, despite
the presence of three ordered
Figure 1. Processes I and II for interconverting diastereoisomers and inverting enantiomers of [2]catenane
134+. Process I corresponds to a change in helical chirality, while process II represents alteration of planar
A
ꢀ
PF6 anions, there are no short
axes of the inside hydroquinone ring to the mean planes of
the tetracationic cyclophanes (t, Table 2). The interplanar
separation (ca. 3.57 Š) between the alongside triazole ring
system and the inside bipyridinium unit is greater than the
stacking separations (<3.4 Š) previously observed[31] with
pyridyl rings. The p–p stacking interactions are supplement-
F···[2]catenane contacts. Again, extended polar stacks are
not formed, nor are there any noteworthy inter-[2]catenane
short contacts, though one CH2···p-xylylene separation is
analogous to that described for 13·4PF6 but with an even
longer H···p distance of 3.19 Š.
In the case of [2]catenane 14·4PF6 containing a 1,5-dioxy-
naphthalene ring system, the successive processes of inter-
conversion between diastereoisomers that lead to inversion
of enantiomers is different from that described for the
[2]catenane containing a 1,4-dioxybenzene ring (Figure 1),
and only two descriptors are used here, because helicity and
planar chirality at the dioxynaphthalene subunit are interde-
pendent. Process IV in 144+ corresponds to the 1,5-dioxy-
naphthalene ring systemꢁs leaving the cavity of the tetracat-
ionic cyclophane, rotating around the axis of its central
carbon–carbon bond, and re-entering the cavity with a dif-
ferent relative orientation. This process is tantamount to its
having undergone rocking (process I in 134+). The full se-
quence of events is illustrated in Figure 5.
ꢀ
ꢀ
ed by intra-[2]catenane C H···O and C H···p interactions
ꢀ
(a–e in Figure 3). There is no intra-[2]catenane N H···X hy-
drogen bond involving the triazole ring; the ring hydrogen
atom is directed toward the only ordered PF6 ion with for-
ꢀ
ꢀ
mation of an N H···F hydrogen bond (N···F 2.97, H···F
ꢀ
2.14 Š; N H···F 1538). Surprisingly, no continuous polar
stacks are formed and the shortest inter-[2]catenane contact
of any significance is from one of the methylene hydrogen
atoms of the tetracationic cyclophane in one molecule to
one of the p-xylylene spacers in the next, though the H···p
distance is long (3.10 Š).
The solid-state (absolute) structure (Figure 4) of 144+[26] is
again chiral; it has the same source of conformational chiral-
ity as that of 13·4PF6 and contains only a single conforma-
tional enantiomer.[32] The p-electron-rich 1,5-dioxynaphtha-
lene ring system is positioned inside the tetracationic cyclo-
Circular dichroism in the solid state: The phenomenon of
spontaneous resolution operating in these [2]catenanes con-
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L. PØrez-García, D. J. Williams et al.
[a]
Table 2. Structural parameters for compounds 13·4PF6 and 14·4PF6.
Parameter
13·4PF6
14·4PF6
qi [8][b]
20
19
qa [8][b]
yi [8][c]
ya [8][c]
fE [8][d]
fF [8][d]
t [8][e]
16
26
26
12
11
42
10
22
22
16
14
38
A···B [Š]
C···D [Š]
E···F [Š]
A···C [Š]
A···D [Š]
C···B [Š]
A···E [Š]
A···F [Š]
w [8]
7.06
7.07
10.22
3.53
3.57
3.57
5.01
5.22
107.8(4)
109.0(5)
108.5(4)
109.2(5)
6.86
6.81
10.39
3.40
3.41
3.89
5.20
5.19
108.5(5)
108.5(4)
107.3(5)
109.0(5)
Figure 2. Definition of the absolute stereochemical descriptors. Helicities
of plus and minus are indicated by P and M, respectively. We give the
solid-line ring (containing oxygen atoms) higher priority than the dotted-
line ring (containing nitrogen atoms) and, on that basis, display the solid-
line ring in front of the dotted-lined ring when observing the helicity gen-
erated by the two rings. The planar chirality is denoted by pR and pS for
clockwise and anticlockwise, respectively.
x [8]
y [8]
z [8]
taining 3,5-bis(oxymethyl)-1H-1,2,4-triazole subunits needed
confirmation. When chirality is of conformational origin,
spontaneous resolution takes place under racemizing condi-
tions, for which just a few examples are well studied.[27] In
the case of [2]catenanes 13·4PF6 and 14·4PF6, from the mul-
tiple co-conformations existing in solution, four can be re-
garded as prevalent (see Figures 1 and 5): those arising from
both prototropic tautomerism and conformational enantio-
merism phenomena.[33] In addition to the X-ray study, we
complemented the investigation of spontaneous resolution
by using solid-state circular dichroism.[34]
[a] For the angles q and y, the subscripts “i” and “a” refer to the inside
and alongside ring systems, respectively. Distances to the ring systems A
to F are calculated from centroid to centroid. [b] The twist angle q is de-
fined as the average of the moduli of the four normalized torsional
ꢀ
angles about the central C C bond within the bipyridinium unit. [c] The
bowing angle y is the supplement of the angle subtended by the two N+
ꢀ
CH2 bonds emanating from the bipyridinium ring system. [d] The
ꢀ
bowing angle f is the supplement of the sum of the angles of the C CH2
bonds emanating from the spacer rings (E and F) and the associated ring
plane. [e] The tilt angle t is the angle between the O···O vector of the
inside O,O’-substituted aromatic ring and the mean plane of the four
corner methylene carbons atoms of the tetracationic cyclophane.
Crystallization of [2]catenane 13·4PF6 under the same
conditions used to obtain single crystals suitable for X-ray
crystallography, that is, by vapor diffusion of iPr2O into a so-
lution of 13·4PF6 in MeCN, yielded small red crystals (300–
500 mg) with no morphological indication that they consti-
tute enantiomorphic crystals. From a mixture of such crys-
tals, we separated manually 14 apparent monocrystals and
used them to prepare KBr disks.[35] From these samples,
three exhibited a Cotton effect at about 400 nm associated
with a p–p transition between the bipyridinium units and
the 1,4-dioxybenzene ring present in the [2]catenane.[36] The
other 11 crystals were presumably twinned. The solid-state
circular dichroism (CD) spectra of enantiomorphic crystals,
which exhibit maxima at 397 nm (De=+0.11 Lmolꢀ1 cmꢀ1)
and 403 nm (De=ꢀ0.18 Lmolꢀ1 cmꢀ1), are shown in
Figure 6. Although no correlation of the optical properties
has been made with the X-ray (absolute) structure of the
[2]catenane, the solid-state CD experiments demonstrate
the presence in a single crystal of a pure single enantio-
mer—presumably either (pR)-(P) or (pS)-(M)—in the solid
state, that is, chiral induction and spontaneous resolution
occur to give a conglomerate under freely racemizing condi-
tions. Unfortunately, we have not been able to obtain any
solid-state CD spectra for [2]catenane 14·4PF6, due to the
small size of the crystals it forms.
Dynamic NMR spectroscopy: Previous studies on p-donor/
p-acceptor [2]catenanes[21] were of great value for the full
assignment of the NMR spectra of the macrocyclic poly-
ethers and [2]catenanes of this work. Unambiguous assign-
ments for the [2]catenanes 13·4PF6 and 14·4PF6 were possi-
ble by using HMBC, HMQC, COSY-2D and ROESY-2D
techniques (Table 3; see also Table S4 in the Supporting In-
formation for data on the polyether components).
The [2]catenanes 13·4PF6 and 14·4PF6 exhibit dynamic
behavior in solution, observed by NMR spectroscopy, conse-
quence of a number of dynamic processes operating in solu-
3970
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Chem. Eur. J. 2007, 13, 3964 – 3979

p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
The overwhelming presence of one translational isomer in
the case of both [2]catenanes in solution renders it impossi-
1
ble to probe, by dynamic H NMR spectroscopy, the rate of
the circumrotation process that interchanges the hydroqui-
none ring in 13·4PF6 and the 1,5-dioxynaphthalene ring
system in 14·4PF6, however fleetingly, with their cyclically
appended 3,5-bis(methylene)-1H-1,2,4-triazole units.
Thus, it is clear that circumrotation of the macrocyclic
polyether through the cavity of the tetracationic cyclophane
does not occur, with no exchange of the 1,4-dioxybenzene
and 3,5-bis(oxymethyl)-1H-1,2,4-triazole rings between the
inside and alongside positions on the NMR timescale. This
statement is based on two observations, 1) warming the
CD3CN solution to 343 K did not cause any shift or broad-
ening of either the aromatic hydrogen atoms of the 1,4-diox-
ybenzene ring or the methylene hydrogen atoms linked to
the triazole unit; 2) on cooling to 233 K the chemical shifts
of these protons do not experience any significant variation
(see Figure S1 in the Supporting Information). Consequent-
ly, control of the translational isomerism over a wide range
of temperatures is operative, with total preference for one
translational isomer, as observed in the solid state.
Figure 3. Ball-and-stick representation of the solid-state molecular struc-
ture of the (pR)-(P) isomer of 134+ showing the intra[2]catenane hydro-
gen-bonding interactions. Hydrogen-bond geometric parameters C···O,
ꢀ
H···O [Š], C H···O [8] are a) 3.37, 2.44, 144; b) 3.24, 2.44, 140; c) 3.41,
ꢀ
2.49, 159. The CH/p interactions have H···p [Š], C H···p [8] of d) 2.70,
169; e) 2.99, 158.
Nonetheless, by cooling a solution of [2]catenane 13·4PF6
in CD3COCD3 (Figure 7), it was possible (Table 4) to identi-
fy three different kinetic processes: 1) rocking[37] of the 1,4-
dioxybenzene ring inside the tetracationic cyclophane cavity
(process I in Figure 1), 2) exchange of the inside and along-
side bipyridinium units as a consequence of a pirouetting
movement by the triazole unit in the macrocyclic polyether
(process III), and 3) prototropic tautomerism of the 1H-
1,2,4-triazole unit (equivalent to process II’ in Figure 1).
In common with the behavior in CD3CN solution, the
room-temperature spectrum of 13·4PF6 in CD3COCD3 (Fig-
ure 7a) shows only one signal for both the 1,4-dioxybenzene
(d=3.90 ppm) and 3,5-bis(oxymethylene)-1H-1,2,4-triazole
(d=4.22 ppm) units, that is, they are located inside and
alongside the tetracationic cavity, respectively. These signals
do not experience any shift on cooling the solution, that is,
the circumrotation of the macrocyclic polyether does not
take place on the NMR timescale at these temperatures.
On cooling the CD3COCD3 solution, the 1,4-dioxyben-
zene proton signals showed clear broadening, and (Fig-
ure 7c) their separation into two broad signals at 210 K indi-
cates that rocking of the 1,4-dioxybenzene ring inside the
tetracationic cyclophane cavity (Process I in Figure 1) is
slowing down. At 193 K (Figure 7d) the process is already
frozen on the NMR timescale, as indicated by the existence
of two signals of equal intensity at d=2.12 and 5.58 ppm
that exhibit the maximum shift difference (Dd=3.46 ppm)
corresponding to the the protons oriented towards the p-
xylyl spacer face and the outside of the cavity, respectively,
as confirmed by COSY-2D and NOESY-2D experiments.
The coalescence of this signal at 218 K allowed calculation
of the energy barriers associated with the process as DG°c =
9.0 kcalmolꢀ1 (Process I, Table 4).
Figure 4. Ball-and-stick representation of the solid-state structure of the
(pR/pS)-(pS) isomer of 144+ showing the intra-[2]catenane hydrogen
bonding interactions. Hydrogen-bond geometric parameters C···O,
ꢀ
H···O [Š], C H···O [8] are a) 3.23, 2.34, 154; b) 3.42, 2.50, 162. The CH/p
ꢀ
interactions have H···p [Š], C H···p [8] of c) 2.54, 148; d) 2.50, 150.
tion, as described for similar compounds.[21a] The most dis-
1
tinctive feature of the H NMR spectra of the [2]catenanes
13·4PF6 and 14·4PF6, recorded in both CD3CN and
CD3COCD3 solutions, is the presence of only one transla-
tional isomer in which the triazole units occupy the along-
side positions with respect to the tetracationic cyclophanes,
as illustrated in Scheme 2. This conclusion is based on the
observation that, in the spectrum of 13·4PF6 recorded in
CD3CN solution, the 1,4-dioxybenzene ring protons resonate
as a singlet at d=3.56 ppm, which indicates[21a] that the ring
is residing inside the tetracationic cyclophane: the protons
on the methylene groups attached to the triazole unit
appear as a singlet at d=4.20 ppm, a modest 0.40 ppm up-
field from where they resonate in free macrocyclic polyether 8.
The protons of the tetracationic cyclophane also exhibit
temperature dependence. The exchange of the aromatic pro-
Chem. Eur. J. 2007, 13, 3964 – 3979
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3971

L. PØrez-García, D. J. Williams et al.
tons occupying the inside and
alongside positions of the mac-
rocyclic polyether is fast at
room
temperature
in
CD3COCD3, as indicated by the
sharpness and good resolution
of the corresponding signals
(Figure 7a). As the solution is
cooled, the a-CH, b-CH, and
the xylyl protons experience
broadening, that is, this process
slows down. As seen in Fig-
ure 7d, at 193 K the process is
frozen and all these protons
appear at different chemical
shifts, and in particular, the b-
CH and a-CH protons each
appear as two doublets (corre-
sponding to the protons occupy-
ing the inside and the alongside
positions of the macrocyclic
polyether) centered at d=8.52
and 9.52 ppm, respectively, as
confirmed by a COSY-2D ex-
periment. The coalescence of
these protons at 210 K (Fig-
ure 7c) allowed the calculation
of a energy barrier associated
with the process of DG°c =
10.0 kcalmolꢀ1 (process III,
Table 4).
Figure 5. Processes II and IV for interconverting diastereoisomers and inverting enantiomers in [2]catenane
144+. Process IV corresponds to a change in the planar chirality of the 1,5-dioxynaphthalene ring system, and
process II represents alteration of the planar chirality of the 3,5-bis(methylene)-1H-1,2,4-triazole unit. The de-
scriptors of absolute stereochemistry are defined in Figure 2.
The resonances correspond-
ing to the protons of the meth-
ylene groupattached to the
1,2,4-triazole ring are also tem-
perature-dependent. At room
temperature in CD3COCD3 they appear as an already slight-
ly broad signal at d=4.21 ppm, which experiences broaden-
ing and, after coalescence at 270 K, appears as two equally
intense singlets (Figure 7b). The maximum separation at
210 K for these singlets appearing at d=3.90 and
d
4.07 ppm (Dd=0.17 ppm) indicates that the process has
frozen at this temperature. The dynamic process corre-
sponds to the prototropic tautomerism, and its associated
energy barrier was calculated as DG°c =12.6 kcalmolꢀ1 (pro-
cess II’, Table 4).
The three kinetic processes identified are thus associated
with energy barriers[38]of 9.0, 10.0, and 12.6 kcalmolꢀ1, re-
spectively. The DG° value of 10.0 kcalmolꢀ1 is considerably
less than that (11.2 kcalmolꢀ1) observed for the pirouetting
process in the prototypical [2]catenane incorporating two
1,4-dioxybenzene residues in the ring, and this reflects the
much weaker p–p stacking interaction between a triazole
ring and a bipyridinium unit. Finally, the DG° value of
12.6 kcalmolꢀ1 is smaller than those reported[39] for other
1H-1,2,4-triazole units, and possibly indicates that it does
not enter into any strong hydrogen bonding interactions
Figure 6. Solid-state CD spectra of “enantiomorphic crystals” of [2]cat-
enane 13·4PF6.
3972
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Chem. Eur. J. 2007, 13, 3964 – 3979

p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
1
Table 3. Selected H NMR (500 MHz) data for [2]catenanes 13·4PF6, 14·4PF6 and their free components 8, 9 and 15·4PF6.[a]
Tetracationic component
bCH C6H4
Macrocyclic polyether
OC6H4O CH2-T
aCH
8.88
–
8.94
CH2N+
H4/8
H3/7
H2/6
OCH2
[b]
[b]
[c]
[b]
[c]
15·4PF6
8[b]
13·4PF6
8.18 7.54
5.76
–
5.73
–
–
–
–
–
–
–
–
–
–
–
–
–
–
6.77
3.56
4.60
4.20
4.00/3.71/3.56–3.70
3.93–3.34
7.79
7.80
A
N
N
G
N
ACHTREUNG
13·4PF6
9[b]
14·4PF6
6.08
–
–
–
2.48
–
–
6.01
–
–
6.27
2.82–4.03
4.28/3.96/3.80/3.70–3.69
4.31–3.37 4.30/4.21/4.05/3.90/3.73/3.57/3.44/3.37
–
4.50
8.87
8.03
7.32
ꢀ4.31
G
(ꢀ5.32)
(ꢀ1.29)
(ꢀ0.55)
14·4PF6
2.78
6.27
6.46
ꢀ4.36
3.41–4.50 4.50/4.33/4.12/3.97/3.81/3.65/3.50/3.41
[a] The values in parentheses are chemical shift differences (Dd) between the free component and the [2]catenane. [b] CD3CN (300 MHz).
[c] CD3COCD3 (500 MHz).
ꢀ
(N H···X) in solution, as also observed in the solid-state
structure reported above.
Similar dynamic behavior in solution was observed for
catenane 14·4PF6. The room-temperature
d values in
CD3CN of d=6.27, 6.01, and 2.48 ppm for the H-2/6, H-3/7,
and H-4/8 protons of the 1,5-dioxynaphthalene ring system
in the spectrum of 14·4PF6 are indicative[40] of the position it
occupies inside the tetracationic cyclophane in this [2]cat-
enane. The absence of significant shifts on warming or cool-
ing the solution (Figure 8) indicates a lack of circumrota-
tion.
The aromatic protons of the tetracationic cyclophane also
have signals which exchange positions: slowly at room tem-
perature as shown by the appearance of two broad signals
for each of the a- and b-CH protons, which on warming the
solution appeared as a average resonance signal as a conse-
quence of faster exchange of these protons (Figure 8).
On the other hand, cooling a solution of the [2]catenane
14·4PF6 in CD3COCD3 (Figure 9) to 198 K results in split-
ting of the a- and b-CH proton signals, that is, freezing of
the dynamic processes (II, II’, III, and IV) takes place in
this catenane. In particular, the CH2N+ methylene groupis
affected, the singlet of which at room temperature splits
into two signals at 253 K. The DG° value of 14.2 kcalmolꢀ1
for the bipyridinium exchange process is in good agreement
with energy barriers reported in the literature[40] for reorgan-
ization of 1,5-dioxynaphthalene ring systems, the local C2h
symmetry of which causes separation of a-CH bipyridinium
protons in p–p stacked systems into two signals, with respect
to the tetracationic cyclophane by leaving its cavity and thus
allowing mutual reorientation (process IV) to occur
(Table 4).
The prototropic tautomerism could also be evaluated by
following the coalescence of the signals for the methylene
hydrogen atoms linked to the 1,2,4-triazole unit, which
evolves from a singlet at room temperature to two signals
(d=4.00 and 4.66 ppm) at 198 K (Figure 9). In comparison
with 13·4PF6 ,the DG° value of 11.4 kcalmolꢀ1 for the tauto-
merism process in [2]catenane 14·4PF6 is even smaller.
Chemical switchability: Due to the presence of the proton-
ionizable 1H-1,2,4-triazole group, switching of the transla-
tional isomers was attempted by using pH to reversibly in-
Figure 7. 1H NMR spectrum of [2]catenane 13·4PF6 in CD3COCD3 at
a) 298 K; b) 253 K; c) 210 K; d) 193 K.
Chem. Eur. J. 2007, 13, 3964 – 3979
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3973

L. PØrez-García, D. J. Williams et al.
Table 4. Kinetic and thermodynamic parameters[a] obtained from the
temperature-dependent 1H NMR spectra of [2]catenanes 13·4PF6 and
14·4PF6 in solution.
cifically, the use of diisopropylethylamine partially depro-
tonated the 1,2,4-triazole ring in [2]catenane 13·4PF6
(Scheme 3), and decomposition products were immediately
observed in the mixture; after 48 h no traces of starting ma-
terials could be detected. The use of stronger bases, such as
DBU or an anion-exchange resin (AER) fully deprotonated
the triazole unit, but only decomposition products were
formed.
To confirm that the instability of the bis(methylene)bipyr-
idinium unit was caused by the triazolate ring, two experi-
ments were carried out (Scheme 4). First, [2]catenane
13·4PF6 was mixed in CD3CN with (4-dimethylaminopyridi-
nio)methyl-1,2,4-triazolate (18)[43] (Scheme 4); 1H NMR
spectra only showed the formation of decomposition prod-
Compound Probe
protons
Dn[b]
kc[c] Tc[d] DGc°[e]
Process[f]
[Hz]
[sꢀ1
]
[K]
[kcalmolꢀ1
]
13·4PF6
OC6H4O
a-CH bipy
OCH2Tr
OCH2Tr
CH2N+
1725 3832 218
9.0
10.0
12.6
11.4
14.2
I
73
149
333
50
161 210
331 270
738 253
111 290
III
II’
II’
IV
14·4PF6
[a] Determined by variable-temperature 1H NMR spectroscopy
(500 MHz) in CD3CN above room temperature and in CD3COCD3
below room temperature. [b] Limiting frequency separation. [c] Rate con-
stant at the coalescence temperature. [d] Coalescence temperature.
[e] Free-energy barrier at the coalescence temperature calculated from
the Eyring equation. [f] Processes discussed in the text and for calcula-
tions of rate constants and free-energy barriers, see reference [38].
Figure 8. 1H NMR spectrum of [2]catenane 14·4PF6 in CD3CN at
a) 298 K; b) 363 K.
terconvert the 1H-1,2,4-triazole/1,2,4-triazolate system.[41]
Although a priori the instability of 4,4’-bipyridinium units to
bases and/or nucleophiles is an issue, some examples are
known that indicate its stability towards pyridine and trie-
thylamine[41b] or Hünigꢁs base.[41c,d] Furthermore, once the bi-
pyridinium units are within the catenane structure, addition-
al stability can be expected on account of the stabilizing p-
donor/p-acceptor interactions.
When 13·4PF6 was treated with hindered bases such as
1
iPr2NEt and DBU in CD3CN solution (Scheme 3), H NMR
spectroscopy revealed the onset of switching as a conse-
quence of deprotonation of the 1H-1,2,4-triazole ring to give
the 1,2,4-triazolate anion.[42] However, rapid decomposition
of the deprotonated compound was observed, presumably
because of the labile nature of the bipyridinium units in the
tetracationic cyclophane component of the [2]catenane. Spe-
Figure 9. 1H NMR spectrum of the [2]catenane 14·4PF6 in CD3COCD3 at
a) 298 K; b) 253 K; c) 243 K; d) 198 K.
3974
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Chem. Eur. J. 2007, 13, 3964 – 3979

p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
Scheme 3. Treatment of [2]catenane 13·4PF6 with different bases.
ucts. Second, paraquat bis(hexafluorophosphate) (20·2PF6)
was mixed with the triazolate-containing macrocyclic poly-
ether 19 in CD3CN solution (Scheme 4); the equimolecular
mixture turned blue and then green and the signals corre-
sponding to the bipyridinium aromatic protons experienced
broadening until they almost disappeared, as shown by
1H NMR spectroscopy, owing to the presence of paramag-
netic bipyridinium-derived species in solution. These experi-
ments manifest the extreme instability of the bipyridinium
units of the tetracationic cyclophane within the catenane to-
wards strong bases such as 1,2,4-triazolate ions.[44] Thus, the
catenane architecture provides no additional stability to the
bipyridinium units towards triazolate anions. These results
presents us with a considerable challenge to be addressed
before the prospect of pH-driven molecular machines and
switches can be realized, although it does rule out its use in
systems which contain different p-electron-deficient macro-
cycles.
Scheme 4. Effect of triazolate ions on different 4,4’-bipyridinium deriva-
tives.
they both undergo spontaneous resolution under conditions
for which the enantiomers racemize rapidly in solution. In
the light of the very large number of solid-state structures of
[2]catenanes of this kind which do not resolve spontaneously
on crystallization, these two examples each containing a 3,5-
bis(methylene)-1H-1,2,4-triazole unit, appear to be excep-
tional at this time. The reasons may be associated with the
disturbance in the crystal of the well-established continuous
polar p-donor/p-acceptor stack, as well as the well-known
tautomerism of the proton on the triazole ring, but in any
case is a structure-based property: The incorporation of the
triazole ring seems to favor symmetry breaking. These are
the first cases of spontaneous resolution in nondegenerate
catenanes.
Conclusion
The two [2]catenanes described here constitute rare exam-
ples of selective isomerization processes. First, they exist,
both in solution and in the solid-state, as only one of two
possible translational isomers. Second, on crystallization,
The triazole ring will allow attachment of these catenanes
to appropriately activated surfaces. To exploit the new struc-
Chem. Eur. J. 2007, 13, 3964 – 3979
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3975

L. PØrez-García, D. J. Williams et al.
3,5-Bis(2-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}ethoxy)methyl-1-(tetra-
hydro-2-pyranyl)-1H-1,2,4-triazole (2): 3,5-Bis(chloromethyl)-1-tetrahy-
dropyranyl-1H-1,2,4-triazole (1)[20] (2.0 g, 8 mmol) was added to a solu-
tion of NaH (0.81 g, 32 mmol) in tetraethylene glycol (41 mL) under N2
and was stirred for 48 h at 608C. After this mixture had cooled to room
temperature, H2O (100 mL) was added, and the solution was extracted
with Et2O (3”50 mL) and CH2Cl2 (4”50 mL). The CH2Cl2 layers were
combined, washed with H2O (2”50 mL), and dried (MgSO4), and the sol-
vent removed. The residue was purified by column chromatography
(SiO2, CH2Cl2/MeOH increasing polarity) to yield 2 as a colorless oil
(2.8 g, 62%). 1H NMR (500 MHz, CDCl3, 258C, TMS): d=5.59 (dd, J=
ture-based properties and functional possibilities of these
catenanes, further study is merited, and undoubtedly the po-
tential for controllable chirality offers promising perspec-
tives for the construction of molecular electronic and chi-
roptical devices.
Experimental Section
9.6, 2.6 Hz, 1H, H2
J=13.0 Hz, 2H, CH2-3), 4.00 (m, 1H, H6
3.62 (m, 1H, H6 (THP)), 2.70 (brs, 2H, OH), 2.29 (m, 1H, H5
2.04 (m, 1H, H4(THP)), 1.91 (m, 1H, H5(THP)), 1.67 (m, 1H, H4
1.67 (m, 1H, H3(THP)), 1.56 ppm (m, 1H, H3(THP)); 13C NMR
ACHTREUNG
General methods: Melting point: CTP-MP 300 hot-plate apparatus with
AHCTREUNG
ASTM 2C thermometer. IR (KBr disks): Nicolet 205 FT spectrophotom-
ACHTREUNG
1
eter. H NMR: Varian Gemini 200, Varian Gemini 350, and Varian VXR
A
N
ACHTREUNG
500 spectrometers (200 MHz, and 350, and 500 MHz). 13C NMR: Varian
Gemini 200 and Varian Gemini 300 spectrometer (50.3 and 75.4 MHz).
HMQC and HMBC: Varian VXR 500 spectrometer (500 MHz). COSY-
2D and ROESY-2D: Bruker 500 spectrometer (500 MHz). NMR spectra
A
ACHTREUNG
(50.3 MHz, CDCl3, 258C, TMS): d=159.7, 152.8, 84.0, 72.4, 70.45, 70.4,
70.3, 70.2, 70.1, 70.0, 69.8, 67.7, 66.0, 63.5, 61.5, 61.4, 29.6, 24.6, 22.2 ppm;
ESI-MS (60 eV): m/z (%): 1132 (1) [2M++H], 589 (8) [M+Na], 566
(100) [M++H], 482 (6) [M+ꢀTHP+H]; elemental analysis calcd (%) for
C25H47N3O11: C 53.1, H 8.4, N 7.4; found: C 53.4, H 8.5, N 7.6.
were
determined
in
[D]chloroform,
[D6]dimethylsulfoxide,
[D3]acetonitrile, [D4]methanol, or [D6]acetone, and chemical shifts are
expressed in parts per million (d) relative to the central peak of the sol-
vent. ESMS and FABMS: VG-Quattro mass spectrometer. TLC was per-
formed on Merck precoated 60 F254 silica gel plates in the solvent system
methanol/2m ammonium chloride/nitromethane (6/3/1) as developing sol-
vent; and the spots were located with UV light and developed with a
10% aqueous solution of potassium iodide or 3% aqueous solution of
hexachloroplatinic acid. Chromatography: SDS silica oxide 60 ACC (30–
75 mm) and Merck aluminum oxide 90 standardized. UV/Vis: CARY-
Varian spectrophotometer. When a rotary evaporator was used, the bath
temperature was 258C. In general, the compounds were dried overnight
at 258C in a vacuum oven. Microanalyses were performed on a Carbo
Erba Fisons EA1108 analyzer in the Serveis Científico-T›cnics (UB).
HR-MS: Autospec/VG analyzer, recorded in the Departament de Quími-
ca Orgànica Biològica (C.S.I.C.) de Barcelona. Experiments at high pres-
sure were performed in an Andreas Hofer press at 14 kbar; reactions
were carried out in a thermally sealed Teflon tube located in the press
cylinder with n-hexane as the external solvent. Solvents were distilled
under nitrogen or argon over a variety of drying agents.[45] DMF and
DME were distilled over calcium hydride and stored with molecular
sieves (4 Š). CH3CN was of HPLC grade (SDS) and dried with molecu-
lar sieves (4 Š). When an anionic exchange resin was used, the previously
established protocol was employed.[12]
1-(Tetrahydro-2-pyranyl)-3,5-bis(2-{2-[2-(2-p-toluensulfonylethoxy)eth-
A
2.65 mmol) in H2O/THF (1/1, 4 mL) was added to a suspension of NaOH
(0.30 g, 7.42 mmol) in H2O (2 mL) cooled to 0–58C. After this a solution
of tosyl chloride (1.06 g, 5.57 mmol) in THF (2 mL) was added over
0.5 h, keeping the temperature between 0 and 58C. After stirring for 3 h,
the reaction mixture was poured into an ice/water mixture (10 mL) and
extracted with toluene (20 mL). The organic layer was washed with a
0.5m aqueous solution of NaOH (2”15 mL) and dried with MgSO4. Re-
1
moval of the solvent afforded 3 as a colorless oil (1.64 g, 71%). H NMR
(200 MHz, CDCl3, 258C, TMS): d=7.64 (dd, J=8.0 Hz, 4H, H2,6
ACHTREUNG
7.21 (dd, J=8.0 Hz, 4H, H3,5
ACHTREUNG
AHCTREUNG
AHCTREUNG
A
N
ACHTREUNG
A
ACHTREUNG
258C, TMS): d=158.9, 152.4, 144.3, 132.3, 129.3, 127.4, 83.7, 70.1, 70.0,
69.95, 69.9, 69.8, 69.6, 69.5, 68.9, 68.8, 68.1, 67.4, 65.7, 63.2, 29.3, 24.3,
21.8, 21.2 ppm; ESI-MS (60 eV): m/z (%): 898 (5) [M++Na], 875 (34)
[M++H], 790 (50) [M+ꢀTHP+H], 720 (100) [M+ꢀOTs+H]; elemental
analysis calcd (%) for C39H59N3O15S2: C 53.6, H 6.8, N 4.8; found: C 53.3,
H 6.8, N 5.1.
Materials: Commercial compounds: Ammonium hexafluorophosphate,
1,4-bis(bromomethyl)benzene (11), 1,8-diazabiciclo[5.4.0]undec-7-ene
R
17
ACHTREUNG
(DBU), 1,4-dihydroxybenzene, 1,5-dihydroxynaphthalene, diisopropyle-
thylamine, and NaH 95% dry were purchased from Aldrich. Compounds
prepared according to literature procedures: 3,5-bis(chloromethyl)-1H-
A
ACHTREUNG
drous DMF (30 mL) was added under argon over 30 min to a degassed
suspension of NaH (116 mg, 4.60 mmol) and NaI (584 mg, 3.90 mmol) in
1,2,4-triazole hydrochloride,[12] 3,5-bis(chloromethyl)-1-(tetrahydro-2-pyr-
[21a]
anyl)-1H-1,2,4-triazole (1),[20] 10·2PF6,
cyclobis(paraquat-p-phenylene)
anhydrous DMF (80 mL). After 15 min
a solution of 1 (443 mg,
(15·4PF6)[21a] 1,4-bis[2-(2-hydroxyethoxy)ethoxy]benzene (17),[21a] (4-di-
methylaminopyridinio)methyl-1,2,4-triazolate (18),[43] 1,1’-dimethyl-4,4’-
bipyridinium bis(hexafluorophosphate) (Paraquat) (20·2PF6).[21a]
1.77 mmol) in anhydrous DMF (40 mL) was added under argon over
15 min. The reaction mixture was then heated at 808C for 6 d. After cool-
ing to room temperature, the suspension was filtered, and the solvent re-
moved in vacuo. The residue was partitioned between CH2Cl2 (70 mL)
and H2O (150 mL). The aqueous phase was extracted again with CH2Cl2
(3”70 mL), and the organic extracts were concentrated in vacuo.
Column chromatography (SiO2, CH2Cl2/MeOH increasing polarity) af-
forded 4 as a pale yellow oil (0.96 g, 7%). 1H NMR (200 MHz, CDCl3,
CD spectroscopy: CD spectra were recorded on a JASCO 720 spectro-
photometer. The samples were prepared as KBr disks by mixing about
50 mg of dried KBr (Aldrich, 98%, dried under vacuum-pump pressure
at 1008C for 5 h) and 0.3–0.6 mg of sample. The mixture was milled and
compressed at 10 tonnes for 10 min. The thickness of the disks was mea-
sured to be between 15 and 25 mm. The initially transparent disks became
opaque with time, and this affected the resolution of the CD spectra;
therefore, all disks were prepared immediately before analysis. The cor-
rect position of the sample was confirmed by checking that the light
beam was passing through the disk. For each sample the disk was rotated
manually 3–5 times to avoid linear dichroic effects. Prior to the analysis
of samples a spectrum of a pure KBr disk was registered and subtracted
from the spectra recorded by using the mathematical treatment in the
Standard Analysis JASCO CD program. The molar elipticity values were
calculated as 7.8·105 degcm2 gmolꢀ1 and ꢀ8.6·10ꢀ5 degcm2 gmolꢀ1 for the
positive and negative spectra, respectively.
258C, TMS): d=5.58 (dd, J=9.4, 2.2 Hz, 2H, H2
13.2 Hz, 4H, CH2-5), 4.57 (dd, J=13.1 Hz, 4H, CH2-3), 4.02 (m, 4H, H6-
(THP)), 3.62 (m, 32H, CH2O), 2.29 (m, 2H, H5(THP)), 2.04 (m, 2H, H4-
(THP)), 1.91 (m, 2H, H5(THP)), 1.67 (m, 2H, H4
(THP)), 1.67 (m, 2H,
H3(THP)), 1.56 ppm (m, 2H, H3(THP)); 13C NMR (50.3 MHz, CDCl3,
A
A
ACHTREUNG
A
N
ACHTREUNG
A
ACHTREUNG
258C, TMS): d=159.6, 152.9, 84.2, 70.6, 70.5, 70.4, 70.3, 70.1, 69.9, 69.8,
67.8, 66.1, 63.7, 29.7, 24.7, 22.3 ppm; ESI-MS (60 eV): m/z (%):765 (12)
[M++Na], 743 (100) [M++H], 288 (72) [M2+ꢀ2THP+2H].
36-(Tetrahydro-2-pyranyl)-2,5,8,11,14,21,24,27,30,33-decaoxa[14]para-
A
N
3976
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 3964 – 3979

p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
over 15 min to a degassed suspension of CsCO3 (7.5 g, 22.9 mmol) in an-
3.70 ppm (m, 32H, OCH2); 13C NMR (50.3 MHz, CDCl3, 258C, TMS):
d=157.8, 152.7, 115.5, 70.5, 70.4, 70.3, 70.2, 70.0, 69.6, 67.8, 65.7 ppm;
ESI-MS (60 eV): m/z (%): 556 (100) [M++H]; HRMS calcd for
C26H41N3O10: 555.2799; found: 555.2791;
hydrous DMF (160 mL). After 15 min
a solution of CsOTs (1.4 g,
4.58 mmol), tetrabutylammonium iodide (TBAI, 0.17 g, 0.46 mmol), and
3 (1.85 g, 2.12 mmol) in anhydrous DMF (310 mL) was added over
15 min. After this the reaction mixture was heated at 808C for six days.
After cooling to room temperature, the suspension was filtered, washed
with anhydrous DMF (50 mL), and the solvent was removed in vacuo.
The brown residue was partitioned between CH2Cl2 (100 mL) and H2O
(200 mL). The aqueous phase was extracted again with CH2Cl2 (4”
70 mL) and washed with a saturated solution of NaCl (150 mL). The or-
ganic extracts were dried (MgSO4) and concentrated in vacuo. Column
chromatography (SiO2, CH2Cl2/MeOH increasing polarity) afforded 5 as
a colorless oil (0.35 g, 26%). 1H NMR (200 MHz, CDCl3, 258C, TMS):
2,5,8,11,14,22,25,28,31,34-Decaoxa
N
N
cle 6 (0.095 g, 0.14 mmol) was deprotected by dissolution in MeOH/1.5n
HCl (5 mL). After stirring for 4 h at room temperature the solution was
evaporated in vacuo. The oil obtained was dissolved in H2O (20 mL) and
neutralized with Na2CO3 until pH 7–8. The aqueous solution was extract-
ed with CH2Cl2 (3”15 mL), dried (MgSO4), and concentrated in vacuo. 9
was obtained as a yellow oil (80 mg, 96%); 1H NMR (500 MHz, CDCl3,
258C, TMS): d=7.80 (d, J=7.8 Hz, 2H, H2,6), 7.30 (dd, J=7.9 Hz, 2H,
H3,7), 6.82 (d, J=8.4 Hz, 2H, H4,8), 4.50 (s, 4H, CH2), 4.28–3.70 ppm (m,
32H,OCH2); 13C NMR (50.3 MHz, CDCl3, 258C, TMS): d=157.2, 126.5,
125.0, 105.7, 70.8, 70.5, 69.6, 67.7, 65.4 ppm; ESI-MS (60 eV): m/z (%):
606 (100) [M++H].
d=6.75 (s, 4H, C6H4), 5.52 (dd, J=9.4, 2.4 Hz, 1H, H2
J=13.2 Hz, 2H, CH2-5), 4.50 (dd, J=12.3 Hz, 2H, CH2-3), 4.02 (m, 2H,
H6
(THP)), 4.00 (m, 4H, CH2O(a)), 3.71 (m, 4H, CH2O(b)), 3.63 (m,
24H, CH2O), 2.29 (m, 1H, H5(THP)), 2.04 (m, 1H, H4
(THP)), 1.91 (m,
1H, H5(THP)), 1.67 (m, 1H, H4(THP)), 1.67 (m, 1H, H3
(THP)),
1.56 ppm (m, 1H, H3(THP)); 13C NMR (50.3 MHz, CDCl3, 258C, TMS):
A
ACHTREUNG
A
ACHTREUNG
{[2]-[2,5,8,11,14,21,24,27,30,33-Decaoxa[14]paracyclo[14]
A
A
N
ACHTREUNG
AHCTREUNG
ACHTREUNG
kis(hexafluorophosphate)
[2,5,8,11,14,21,24,27,30,33,36-
(13·4PF6)
and
{[2]-
tri-
d=159.6, 152.8, 152.7, 115.4, 83.9, 70.6, 70.5, 70.4, 70.35, 70.3, 70.2, 70.0,
69.9, 69.7, 69.5, 67.9, 67.6, 66.0, 63.5, 29.5, 24.5, 22.1 ppm; ESI-MS
(60 eV): m/z (%): 1279 (4) [2M++H], 662 (5) [M++Na], 640 (100) [M+
+H], 556 (4) [M+ꢀTHP+H]; HRMS calcd for C31H49N3O11: 639.3393;
found: 639.3367.
G
A
N
azolophane][2,11,22,31-tetraazonia[1.0.1.1.0.1]paracyclophane]catenane}
R
tetrakis(hexafluorophosphate) 14·2PF6: 10·2PF6 (1 mmol), 1,4-bis(bro-
momethyl)benzene (11) (1.1 mmol), and 8 or 9 (2.5 mmol) were dissolved
in dry DMF (2 mL) in a high-pressure vessel which was pressurized to
10 kbar for three days at room temperature. The colored suspension ob-
tained was poured into Et2O (30 mL) and the precipitate was filtered off,
washed with Et2O (2”5mL), and dried. The residue was purified by
column chromatography (SiO2, MeOH/NH4Cl 2m/CH3NO2 5.5/3/1.5).
The fractions containing the product were combined and concentrated,
and the residue was dissolved in H2O (5 mL) before a saturated aqueous
NH4PF6 solution was added until no further precipitation occurred. The
suspension was filtered off, and the solid recrystallized from MeCN/iPr2O
to give 13·4PF6 or 14·4PF6 as a red or violet solid, respectively. 13·4PF6
(34%): m.p. 244–2458C; 1H NMR (500 MHz, CD3CN, 258C): d=8.94 (d,
J=7.0 Hz, 8H, a-CH), 7.79 (d, J=7.0 Hz, 8H, b-CH), 7.80 (s, 8H, C6H4),
5.73 (s, 8H, CH2N+), 4.20 (s, 4H, CH2), 3.56 (s, 4H, H1,4(DB)), 3.93–
3.34 ppm (m, 32H, OCH2); FABMS (10 eV): m/z (%): 1679 (1) [M+
+Na], 1511 (9) [M+ꢀPF6], 1366 (22) [M+ꢀ2PF6], 1221 (8) [M+ꢀ3PF6],
1076 (3) [Mꢀ4PF6]+, 956 (5) [M+ꢀPF6ꢀCE], 811 (28) [M+ꢀ2PF6ꢀCE],
683 (24) [M2++2PF6], 666 (17) [M+ꢀ3PF6ꢀCE], 562 (100) [CE++Li];
elemental analysis calcd (%) for C62H73N7O10F24P4·1H2O: C 44.5, H 4.5,
N 5.8; found: C 44.7, H 4.9, N 6.2. 14·4PF6 (65%): m.p. 252–2548C;
1H NMR (500 MHz, CD3CN, ꢀ408C): d=8.96 and 8.75 (2”d, J=6.0 Hz,
8H, a-CH), 8.06 and 7.91 (s, 8H, C6H4), 7.37 and 7.18 (2”d, J=5.0 Hz,
8H, b -CH), 6.17 (d, J=8.0 Hz, 2H), 5.95 (dd, J=8.0 Hz, 2H), 5.75–5.83
(m, 8H, CH2N+), 4.22 (s, 4H, CH2), 4.28–3.31 (m, 32H, OCH2),
2.31 ppm (d, J=8.0 Hz, 2H); FABMS (10 eV): m/z (%): 1271 (77) [M+
ꢀ3PF6], 1126 (13) [Mꢀ4PF6]+, 956 (18) [M+ꢀPF6ꢀCE], 810 (90) [M+
ꢀ2PF6ꢀCE], 708 (36) [M2+ +2PF6], 666 (100) [M+ꢀ3PF6ꢀEC]; elemen-
tal analysis calcd (%) for C66H75N7O10F24P4: C 46.5, H 4.4, N 5.7; found:
C 46.4, H 4.6, N 5.4.
40-(Tetrahydro-2-pyranyl)-2,5,8,11,14,25,28,31,34,37-decaoxa[14]-
A
N
(365 mg, 2.28 mmol) was added to a degassed suspension of Cs2CO3
(14.8 g, 45.6 mmol) and CsOTs (1.38 g, 4.56 mmol) in anhydrous DMF
(400 mL) at 808C. After 45 min a solution of 3 (2 g, 2.28 mmol) in anhy-
drous DMF (230 mL) was added, and the reaction mixture was then
heated at 1008C for six days. After cooling to room temperature, the sus-
pension was filtered and washed with DMF (50 mL), and the solvent was
removed in vacuo. The brown residue was partitioned between CH2Cl2
(100 mL), H2O (200 mL), and asaturated solution of NaCl (50 mL). The
aqueous phase was extracted again with CH2Cl2 (2x100 mL), and the or-
ganic extracts were concentrated in vacuo. Column chromatography
(SiO2, CH2Cl2/MeOH increasing polarity) afforded 6 as a yellow oil
(0.13 g, 8%). 1H NMR (200 MHz, CDCl3, 258C, TMS): d=7.82 (dd, J=
8.2, 3.2 Hz, 2H, H2,6
(Naph), 5.48 (dd, J=9.6, 2.6 Hz, 1H, H2
2H, CH2-5), 4.50 (dd, J=12.3 Hz, 2H, CH2-3), 4.27 (m, 4H, CH2Oa),
3.95 (m, 4H, CH2Ob), 3.95 (m, 1H, H6
(THP)), 3.60 (m, 24H, CH2O),
2.29 (m, 1H, H5(THP)), 2.04 (m, 1H, H4(THP)), 1.91 (m, 1H, H5
(THP)),
1.67 (m, 1H, H4(THP)), 1.67 (m, 1H, H3(THP)), 1.56 ppm (m, 1H, H3-
(THP)); 13C NMR (50.3 MHz, CDCl3, 258C, TMS): d=159.4, 154.2,
A
N
A
ACHTREUNG
AHCTREUNG
A
N
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
154.1, 152.7, 126.6, 124.9, 114.5, 114.3, 105.7, 84.0, 71.0, 70.9, 70.7, 70.6,
70.5, 70.4, 70.2, 70.0, 69.8, 69.7, 67.9, 67.7, 66.0, 63.5, 61.6, 29.6, 24.6,
22.2 ppm; ESI-MS (60 eV): m/z (%): 690 (100) [M++H], 606 (14) [M+
ꢀTHP+H]; HRMS calcd for C35H51N3O11: 689.3426; found: 689.3523.
2,5,8,11,14,22,25,28,31,34-Decaoxa
N
N
0.054 mmol) was dissolved in MeOH/1.5n HCl (2 mL). After stirring for
4 h at room temperature the solution was evaporated in vacuo. The oil
obtained was dissolved in H2O (5 mL) and neutralized with Na2CO3 until
pH 7–8. The aqueous solution was extracted with CH2Cl2 (6”5mL),
dried (MgSO4), and concentrated in vacuo. 4 was obtained as a colorless
oil (25 mg, 80%). 1H NMR (200 MHz, CDCl3, 258C, TMS): d=4.71 (s,
8H, CH2), 3.69 ppm (m, 32H, CH2O); 13C NMR (50.3 MHz, CDCl3,
258C, TMS): d=156.6, 69.4, 69.3, 69.2, 69.0, 64.6 ppm; ESI-MS (60 eV):
m/z (%): 597 (86) [M++Na], 575 (100) [M++H]; HRMS calcd for
C24H42N6O10: 574.6285; found: 574.6297.
In a similar procedure using macrocyclic polyether 7, no formation of
catenane 12·4PF6 was observed, and only the tetracationic cyclophane
15·4PF6[21a] was isolated (17%).
3,5-Bis(2-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}ethoxy)methyl-1H-1,2,4-
triazole (16): A solution of 2 (520 mg,0.92 mmol) in 1.5n MeOH/HCl
(20 mL) was stirred for 4 h at room temperature and then the solution
was evaporated in vacuo. The oil obtained was dissolved in H2O (20 mL)
and neutralized with Na2CO3 until pH 7–8. The aqueous solution was ex-
tracted with CH2Cl2 (3”10 mL), dried (MgSO4), and concentrated in
vacuo. 16 was obtained as a colorless oil (77%).1H NMR (200 MHz,
CDCl3, 258C, TMS): d=4.52 (s, 4H, CH2), 3.50 (m, 32H, CH2O);
13C NMR (50.3 MHz, CDCl3, 258C, TMS): d=157.7, 72.2, 72.0, 69.9, 69.8,
69.5, 69.4, 69.3, 65.5, 60.7, 60.6 ppm; ESIMS (60 eV): m/z (%): 504 (10)
[M++Na], 482 (100) [M++H], 963 (1) [2M++H]; HRMS calcd for
C20H39N3O10: 481.2641; found: 481.2635.
2,5,8,11,14,21,24,27,30,33-Decaoxa[14]paracyclo[14](3,5)triazolophane
U
(8): A solution of macrocycle 5 (0.16 g, 0.25 mmol) in MeOH/1.5n HCl
(8 mL) was stirred for 4 h at room temperature, and the solution was
evaporated in vacuo. The oil obtained was dissolved in H2O (20 mL) and
neutralized with Na2CO3 until pH 7–8. The aqueous solution was extract-
ed with CH2Cl2 (4”10 mL), dried (MgSO4) and concentrated in vacuo. 8
was obtained as a colorless oil (0.125 g, 90%); 1H NMR (500 MHz,
CDCl3, 258C, TMS): d=6.77 (s, 4H, C6H4), 4.60 (s, 4H, CH2), 4.03–
Sodium 2,5,8,11,14,21,24,27,30,33-decaoxa[14]paracyclo[14]
A
(19): Macrocyclic polyether 8 (20 mg, 0.036 mmol) was added to a sus-
Chem. Eur. J. 2007, 13, 3964 – 3979
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3977

L. PØrez-García, D. J. Williams et al.
pension of sodium hydroxide (4 mg, 0.1 mmol) in dry acetonitrile (2 mL),
and the mixture was vigorously stirred at room temperature for 4 h. The
suspension was then filtered and the solution concentrated in vacuo. 19
was obtained as a colorless oil (83%). H NMR (200 MHz, CDCl3, 258C,
TMS): d=6.82 (s, 4H, C6H4), 4.51 (s, 4H, CH2), 3.55–4.04 ppm (m, 32H,
White, D. J. Williams, Chem. Eur. J. 2003, 9, 543–556; d) S. A.
Vignon, J. Wong, H. R. Tseng, J. F. Stoddart, Org. Lett. 2004, 6,
1095–1098.
1
[9] a) F. Vçgtle, T. Dünnwald, T. Schmidt, Acc. Chem. Res. 1996, 29,
451–460; b) J.-C. Chambron, D. K. Mitchell, J.-P. Sauvage, J. Am.
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CH2O).
[10] For resolution of chiral interlocked structures, see also the following
articles and the references therein: a) J. C. Chambron, C. Dietrich-
Buchecker, G. Rapenne, J. P. Sauvage, Chirality 1998, 10, 125–133;
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2003, 42, 442–445; e) O. Lukin, T. Kubota, Y. Okamoto, A. Kauf-
mann, F. Vogtle, Chem. Eur. J. 2004, 10, 2084–2810.
Acknowledgements
This research was financially supported by the Dirección General de In-
vestigación (MEC-Spain) through projects CTQ2006-11821/BQU and
TEC2005-07996-C02-02/MIC and the Generalitat de Catalunya
(2005SGR00158). S.R. thanks the Universitat de Barcelona for a fellow-
ship. We are most grateful to Dr. David B. Amabilino of the Institut de
Ci›ncia de Materials (CSIC, Barcelona) and Prof. Ernest L. Eliel of the
University of North Carolina (Chapel Hill) for stimulating and helpful
discussions. We also thank Mr. Scott A. Vignon from the University of
California, Los Angeles, for some illustrative material. The authors are
grateful to the referees for constructive criticism.
[11] P. R. Ashton, S. E. Boyd, S. Menzer, D. Pasini, F. M. Raymo, N.
Spencer, J. F. Stoddart, A. J. P. White, D. J. Williams, P. G. Wyatt,
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[12] E. Alcalde, M. Alemany, N. Mesquida, L. PØrez-García, S. Ramos,
M. L. Rodriguez, Chem. Eur. J. 2002, 8, 474–484, and references
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PØrez-García, Eur. J. Org. Chem. 2006, 3988–3996.
[14] To our knowledge only two examples of zwitterionic rotaxanes have
been reported: a) based on a-cyclodextrin: R. Rahimah, A. E.
Kaifer, J. Am. Chem. Soc. 1991, 113, 8188–8190; betainic[2]rotax-
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[18] For preliminary reports on some aspects of this work, see: a) E. Al-
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A. J. P. White, D. J. Williams, Mendeleev Commun. 2003, 100–102;
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3978
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 3964 – 3979

p-Donor/p-Acceptor [2]Catenanes
FULL PAPER
[23] 3,5-Dioxy-1H-1,2,4-triazole units are synthetically less accessible
than the derivatives described here: A. Zumbrunn, Synthesis 1998,
1357–1361.
[32] The extent of the spontaneous resolution process might depend not
only on the catenane architecture but also on the conditions of the
crystallization; poor quality crystals obtained from an evaporating
acetone solution led to only poor refinement factors from X-ray dif-
fraction data. The collected data showed two independent molecules
in a centrosymmetric monoclinic space group, that is, no spontane-
ous resolution had taken place. In this case, the crystals had grown
under different conditions implying faster nucleation. This consti-
tutes the first example of polymorphism in this family of com-
pounds.
[33] An equal number of co-conformations are possible for the series of
translational isomers containing 1H-1,2,4-triazole units inside the
cavity of the tetracationic cyclophane.
[34] CD spectra of dissolved single crystals in solution in a range of tem-
peratures from 25 to ꢀ408C seem to indicate the preferential forma-
tion of one conformational enantiomer at low temperature, but the
very low intensities of the Cotton effects indicate rapid isomeriza-
tion upon dissolution.
[24] a) Crystal data for 13·4PF6·2.6MeCN·H2O: [C62H73N7O10]-
ACHTREUNG
102.17(1)8, V=1971.5(2) Š3, Z=1, 1calcd =1.500 gcmꢀ3
,
m(CuKa)=
C
reflections, F2 refinement, R1 =0.050, wR2 =0.133, 5966 independent
observed reflections (jFo j>4s
b) Crystal data for 14·3.2PF6·0.8ClO4·3MeCN: [C66H75N7O10]-
(PF6)3.2(ClO4)0.8·3MeCN, M=1793.0, triclinic, P1 (no. 1), a=
12.302(1), b=13.807(2), c=14.229(2) Š, a=113.48(1), b=102.84(1),
g=104.33(1)8, V=2003.1(4) Š3, Z=1, 1calcd =1.486 gcmꢀ3
m-
(CuKa)=1.96 mmꢀ1, T=183 K, red rhombs; 6407 independent mea-
sured reflections, F2 refinement, R1 =0.059, wR2 =0.160, 5806 inde-
A
A
ACHTREUNG
,
ACHTREUNG
pendent observed reflections (jFo j>4s(jFoj), 2qꢁ1288), 1195 pa-
T
rameters.
[25] Data were collected on a Siemens P4/PC diffractometer by using w
scans. The structures were solved by direct methods and refined
based on F2 using the SHELXTL program system a) SHELXTL PC
version 5.03, Siemens Analytical X-Ray Instruments, Inc., Madison,
WI, 1994; b) SHELXTL PC version 5.1, Bruker AXS, Madison, WI,
1997. The absolute structures of 13·4PF6 and 14·3.2PF6·0.8ClO4
were determined by a combination of R-factor tests (for 13·4PF6,
R1+ =0.0502, R1ꢀ =0.0521; for 14·3.2PF6·0.8ClO4, R1+ =0.0591,
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[38] The kinetic data were obtained by the coalescence method, whereby
the rate constant kc at the coalescence temperature Tc was obtained
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from the approximate expression kc =p(Dn)/(2)1/2, where Dn is the
limiting difference (in Hz) between the exchanging proton resonan-
ces at low temperature. The Eyring equation was used to calculate
DG°c values from kc at Tc.
R1ꢀ =0.0605) and by use of Flack parameters (for 13·4PF6, x+
=
0.06(6); for 14·3.2PF6·0.8ClO4, x+ =+0.12(6)]. CCDC-190346 and
CCDC-190347 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from the Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data
request/cif.
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ꢀ
ꢀ
PF6 ion is overlaid by a partial-occupancy ClO4 ion in a ratio of
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ꢀ
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a p-donor/p-acceptor[2]catenane,
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I. V. Karpin, O. N. Chupakhin, Khim. Tekhnol. Vody Khim. Get.
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[44] S. Ramos, PhD Thesis, Faculty of Pharmacy, University of Barcelona
(Spain), 2002.
[45] D. D. Perrin, L. F. Armarego, P urification of Laboratory Chemicals,
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Received: August 8, 2006
Revised: November 23, 2006
Published online: March 1, 2007
Chem. Eur. J. 2007, 13, 3964 – 3979
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3979