Amide-appended porphyrins as scaffolds for catenanes, rotaxanes and anion receptors

Article abstract of DOI:10.1039/b411583j

The synthesis of a porphyrin with an over-arching strap incorporating an isophthalamide unit produced both a porphyrin monomer with a potentially H-bonding receptor site, and a [2]catenane. Although both compounds exhibit fluxional behaviour, ¹

Full text of DOI:10.1039/b411583j

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P A P E R
Amide-appended porphyrins as scaffolds for catenanes, rotaxanes
and anion receptors
Maxwell J. Gunter,* Sandra M. Farquhar and Kathleen M. Mullen
Division of Chemistry, School of Biological, Biomedical and Molecular Sciences, University of
New England, Armidale, NSW 2351 Australia. E-mail: mgunter@pobox.une.edu.au;
Fax: þ612 6773 3268; Tel: þ612 6773 2767
Received (in Durham, UK) 28th July 2004, Accepted 17th September 2004
First published as an Advance Article on the web 4th November 2004
The synthesis of a porphyrin with an over-arching strap incorporating an isophthalamide unit produced both
a porphyrin monomer with a potentially H-bonding receptor site, and a [2]catenane. Although both
1
compounds exhibit fluxional behaviour, H NMR and MS data was used to distinguish them, and was
interpreted in terms of the dynamics of each system. The self-complementarity of the isophthalamide unit
provides an ideal building block for assembling [2]pseudorotaxanes with similarly functionalised threads.
This was illustrated by the self-assembly of a ruthenium–porphyrin stoppered rotaxane under
thermodynamically controlled conditions, by simple mixing of the strapped porphyrin, a complementary
thread unit containing an isophthalamide central unit and pyridine-attached ends, and a ruthenium carbonyl
porphyrin. The strapped porphyrin was also shown to act as a receptor for chloride ion, and its binding
ability with other H-bonding isophthalamide guests was found to be modulated by the presence of chloride
ion. Chloride complexation was observed in both metallated and free base porphyrin monomers as well as
the rotaxanes counterparts, but no anion binding was observed for the catenane.
more recently with the elegant work of Leigh,20 Beer,21,22
Introduction
Smith17,18,23 and Schalley,24 amongst others. Of particular
relevance are those which are receptors for anions,21,22 espe-
cially chloride, and where the anion has been incorporated as a
template in the molecular assembly.
Incorporation of the porphyrin macrocycle into components
for molecular machinery1 and molecular scale electronic de-
vices2 allows for a variety of stimuli that are necessary for the
control of specific mechanical motion. This has been success-
fully demonstrated in at least several catenane and rotaxane
systems.3–6 We have utilised various strapped and superstruc-
tured porphyrins for catenane and rotaxane production, in-
cluding bipyridinium and diimide moieties.7–9 By exploiting the
inherent properties of the inbuilt porphyrin, we have shown
that the dynamic behaviour of these systems can be controlled
by such factors as temperature,6,9,10 chemical change5,6,11 (e.g.,
protonation, metallation vs. free base), photophysical stimuli
and electrochemistry.4,12 We had recognised the alternatives
offered by the neutral diimides compared to the charged
bipyridinium systems,8,13 especially in the assembly of (pseu-
do)rotaxanes under thermodynamically controlled condi-
tions.14,15
Since the advent of the hydrogen-bonded amide-based ro-
taxanes and catenane synthetic methodology,16 we have been
intrigued by the possibility of incorporating this motif into
porphyrinic assemblies. Apart from their inherent chemical
novelty, we were particularly interested in the possibility of an
expected solvent- and anion-dependent behaviour which might
present yet further means by which the dynamic properties of
the systems could be modified. Furthermore, an additional
binding motif allows for more flexibility in the design of future
addressable multi-station rotaxanes and catenanes. We now
demonstrate how the concepts of hydrogen-bonded amide-
based catenanes, rotaxanes and anion receptors can indeed
be applied to produce a new series of dynamic porphyrin
supramolecules with exciting potential.
The target fundamental unit in our case was a porphyrin
strapped with a potential hydrogen-bonding amide compo-
nent, exemplified by A (Fig. 1). Such a superstructure over the
porphyrin macrocycle could then form a scaffold for comple-
mentary H-bond-capable guests in the form of pseudorotax-
anes, which might be then capped with appropriate end-groups
to produce functional rotaxanes. Alternatively, depending on
the synthetic route chosen to the strapped porphyrin, [2]cate-
nane production might be optimised. In any case, the strapped
porphyrins offer an anion receptor geometrically constrained
to be adjacent to a porphyrin subunit. The possibilities offered
by such an arrangement are numerous. For example: the anion
binding can be modulated by the nature of the positively
charged metal ion in the porphyrin; the binding of trivalent
metal ions (e.g. Fe31, Rh31) with anionic axial ligands might
be enhanced and geometrically enforced; anion binding can be
monitored by a change in fluorescence of a suitably chosen
metalloderivative; binding of H-bonding guests can be attenu-
ated by the presence of anions; and metal-ion dependent anion
selectivity can be anticipated. A viable synthetic pathway to
such a base system was thus required, so that its potential
within these and perhaps other roles could be assessed.
Results and discussion
The preparation of the precursor dialdehyde 1 was straightfor-
ward, by condensation of 3-t-butylisophthaloyl dichloride and
m-hydroxyaniline, followed by chain extension with 2-(2-chlor-
oethoxy)ethanol and subsequent reaction with salicylaldehyde.
Condensation with the dipyrromethane 2 under standard con-
ditions (Scheme 1) produced two major isolable porphyrinic
components which were identified by mass spectral and NMR
The design was based on analogous ditopic receptors con-
taining an overarching diamide as a H-bonding receptor
module.17–19 The isophthalamide subunit has formed the basis
for numerous rotaxane and catenane structures, particularly
T h i s j o u r n a l i s & T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 4 4 3 – 1 4 4 9
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Fig. 1 Diagram indicating possible roles for amide strapped porphyr-
in A as a component for supramolecular assemblies and anion receptor
systems.
Scheme 1 Reagents and conditions: (i) trichloroacetic acid, THF, rt,
N2, 5 h; (ii) o-chloranil, rt, N2, 18 h; (iii) 3a Zn(OAc)2, MeOH/CHCl3;
(iv) for 3b: 2 M HCl/H2O wash.
techniques as the amide strapped porphyrin 3a (11%) and the
[2]catenane 4 (5%).
(cf. 20 Hz in 3a), indicative of greater facial discrimination of
the porphyrin subunits.
ESI and FAB mass spectrometry allowed easy distinction
between the monomeric structure 3a and the catenated dimer 4;
while both showed mass peaks at m/z 1269.7 [M þ H1] and
1204 [M–Zn], the catenane 4 also showed a significant peak at
2539.6 [M0 þ H1] indicative of a dimeric structure, and
demonstrated no significant fragmentation between this peak
and the monomer peak at 1269.7, a feature characteristic of
interlocked molecules.
The NMR spectrum of 3a (Fig. 2) is consistent with its
strapped structure, where the shielding of the protons in the
strap is attenuated as a function of distance from the porphyr-
in. The resonances associated with the t-butyl (1.33 ppm) and
H-40 (8.06 ppm)w positions are similar to those of the analo-
gous, non-porphyrinic system synthesised by Smith,17,23 and
thus are clearly removed from any shielding by the porphyrin.z
There were no NOE interactions detected between the por-
phyrin subunit and resonances such as the t-butyl or H-40,
which is also indicative of a monomeric species rather than an
interlocked dimer.
Compound 4 displayed some particularly diagnostic reso-
nances in its 1H NMR compared to 3a (Fig. 2). The protons at
position H-20 and H-40 have been significantly deshielded
(Dd 0.85 and 0.15 ppm respectively) when compared to the
monomeric species 3, analogous to the deshielding of the
corresponding resonances of the more symmetrical benzylic
system synthesised by Leigh and co-workers.25 Protons H-18
and H-19 are also shifted upfield in 4 compared to 3a, as a
result of shielding by the isophthaloyl group of the second ring.
The observed diastereotopicity in the protons H-4 on the
periphery of the porphyrin is much larger in 4 at 150 Hz
Conversely, the t-butyl resonance has also been deshielded
(Dd 0.18 ppm) in 4 which would be expected if the interlocking
porphyrins adopt the conformation shown in Scheme 1 with
the rings of the [2]catenane offset with respect to each other.
This is analogous to non-porphyrinic amide [2]catenanes which
have been shown to have a similar offset orientation in order to
maximise hydrogen bonding interactions. This results in an
unsymmetrical structure where the axis through the isophtha-
loyl groups of each of the interlocked rings are angled to each
other. Furthermore, the flexible straps in these systems allow
further conformational mobility with respect to positional
orientation and dihedral angles between the amide and por-
phyrin planes. Significant NOE interactions were observed
between the protons at position H-40 and H-4 of the porphyrin,
and between H-20 and H-200 which are consistent with
inter-ring interactions in the structure depicted in Scheme 1.
No such correlations were observed for the monomeric
structure 3a.
The meso-hydrogen H-1 on the porphyrin in 4 is also
deshielded and somewhat broadened compared to that in
3a which suggests a dynamic process. At low temperatures
(238 K), this signal splits into two, and other porphyrinic and
strap resonances also show signs of separated environments at
lower temperatures. This is indicative of a dynamic process
which could involve either ‘rocking’ of one amide ring relative
to the other, or a ‘flipping’ of the second interlocked ring from
one side of the first porphyrin to the other. It is also significant
that no analogous dynamic processes were observed for 3a
over the same temperature range.
The amide-strapped porphyrin 3a, as well as functioning as a
component of the symmetrical [2]catenane 4, is a versatile
building block for more elaborate systems. For example,
unsymmetrical [2]catenanes are now available by known syn-
thetic procedures using pre-formed 3a or 3b and other por-
phyrinic or non-porphyrinic macrocycle precursors for the
second link of the catenane. Alternatively, 3a or 3b can also
function as the loop component for rotaxanes assembled by
hydrogen-bonding motifs. We illustrate this by the reversible
w Non-systematic numbering for NMR assignments is shown in
Scheme 1.
z It should be noted that the length and flexibility of the ethyleneoxy
linkages allows considerable conformational freedom in the molecule,
with the amide moiety free to lay over laterally, and not restricted to a
vertical alignment as might be implied by the drawing in Scheme 1.
1444
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 4 4 3 – 1 4 4 9

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Fig. 2 1H NMR spectra in CD2Cl2 at 303 K of amide-strapped porphyrin 3a (top) and catenane 4 (bottom). Lines indicate significant shifts of
important resonances.
assembly of a metalloporphyrin-stoppered, porphyrin-looped,
rotaxane. The successful assembly of this system also confirms
the monomeric nature of 3, compared to the catenane 4, which
showed no evidence of pseudorotaxane or stoppered rotaxane
formation under similar conditions.
The thread component 5 for this thermodynamically as-
sembled rotaxane was easily synthesised by condensation of
the homologue of the hydroxy-precursor of 1 with nicotinic
anhydride. The protocol for the formation of the rotaxane was
the same as we have used previously for the self-assembly of
dibenzo-crown ethers with diimide thread components and
metalloporphyrin stoppers14 (Scheme 2). Thus, admixing 3b
1
with 5 in 1 : 1 stoichiometric ratio produced changes in the H
NMR spectrum indicative of a rapidly exchanging system, and
consistent with reversible binding of the thread within the loop
of 3b. At lower temperatures, the equilibrium is shifted towards
pseudorotaxane formation, and exchange becomes slower.
This pseudo-rotaxane formation is also solvent dependent;
the presence of even trace amounts of methanol precludes
significant binding of the thread, presumably because of com-
peting H-bonding with solvent. Chloroform is also suitable as a
solvent, but the spectra are somewhat broadened compared to
those in dichloromethane. It should also be noted that the
spectra are broadened by aggregation at too high a concentra-
tion. An additional problem encountered with solutions in
dichloromethane or chloroform is a slow change of the spec-
trum over time (hours to days), which we attribute to an effect
of chloride ion from slow solvent decomposition (the effect of
chloride binding from added chloride is discussed below).
Addition of two equivalents of carbonyl-meso-tetrakis(3,5-di-
t-butylphenyl)porphyrinatoruthenium(II) 6 to the pseudorotax-
ane system of 3b plus 5 resulted in a spectrum characteristic of
the more slowly exchanging rotaxane 7 (Fig. 3). The assign-
ment of the NMR spectrum was aided by the usual 2-D
techniques, but most importantly, the shifts associated with
the central units of the rotaxane (i.e. protons 20, 40 and NH)
correspond closely to those of the [2]catenane 4.
In particular the NH protons have broadened under the
baseline and the 20 protons have shifted downfield of the 40
protons (Dd 0.77 for 20 of the thread unit, and 0.55 for 20 of the
porphyrin strap). Significant shifts are also seen in the protons
20 and 21 as a result of shielding by the isophthaloyl group
in the porphyrin. All of these effects are mirrored in the
catenane 4.
As a result of the Ru porphyrin coordination, the resonances
of the terminal pyridine units are all shifted well upfield and are
hidden under other resonances. By analogy with previously
reported coordinatively assembled rotaxanes,14 these peaks would
be expected to be in the regions 6.7, 5.3, 2.2 and 1.8 ppm, and they
could be identified by COSY techniques. No other significant
shifts were detected in the polyether chains of the thread unit,
Scheme 2 Reagents and conditions: mix stoichiometric quantities,
CD2Cl2.
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 4 4 3 – 1 4 4 9
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Fig. 4 Partial 1H NMR spectrum in CD2Cl2 at 303 K for 3b (top) and
3b þ Cl– (bottom). Lines indicate shifts of selected resonances.
Fig. 3 Partial 1H NMR spectra in CD2Cl2 at 303 K for 3b þ 5 (top), 7
(bottom). Lines indicate shifts of selected resonances. Numbers in bold
correspond to 5, those underlined to 3, and Ru porphyrin and pyridine
resonances are indicated Ru and py.
the previously prepared solutions of the catenane, metallated
and free base porphyrin monomer, the pseudorotaxane (3b þ
5) and rotaxane 7 (Scheme 3). All experiments were performed
in dry, non-protic CD2Cl2 as the solvent. The samples were
briefly sonicated in the presence of excess (insoluble) ammo-
nium salt and allowed to equilibrate until there was no further
change in the NMR spectrum (1–3 h).
The zinc and free base porphyrins 3a and 3b showed clear
evidence of chloride binding, with significant shifts analogous
to those observed in Beer’s systems22 (Fig. 4). Obvious down-
field shifts of the 20, and 200 protons (Dd 0.84 and 0.30 ppm
respectively) and the reappearance of the NH proton signal in a
highly deshielded position (d 10.46 ppm) are symptomatic of
anion binding. Analogous shifts for both the porphyrin and
thread protons were also observed when a mixture of the
thread component 5 and the free base porphyrin 3b was treated
with chloride. The spectrum was different to the sum of the
individual spectra of chloride-bound thread component 5 and
porphyrin 3b, indicating that pseudorotaxane formation of 3b
with 5 is templated by chloride ion. Rotaxane 7 also showed
evidence of similar anion-induced shifts after being exposed to
chloride anions.
Somewhat surprisingly, the catenane 4 showed no evidence
for anion binding under similar conditions. This indicates a
steric constraint of the covalently interlocked species which
presumably precludes the conformation required for anion
binding. Thus, whether chloride ion can act as a template in
the formation of the catenane during the porphyrin forming
reaction warrants further investigation, but the prognosis
is poor.y
Conclusion
Porphyrins strapped with potential H-bonding amide super-
structures based on isophthalamide units are clearly versatile
components for a variety of new structures. Here we have
demonstrated that much of the corresponding chemistry that is
available for simpler analogues is readily transferable to these
porphyrinic systems, and thus routes to porphyrin-containing
catenanes, psuedo-rotaxanes, rotaxanes, and anion receptors
of various types has now become available. The advantages of
the in-built porphyrin sub-units are self-evident, in that it
Scheme 3 Reagents and conditions: CD2Cl2, excess Me4NCl (solid),
sonication.
as these are too far removed from the shielding influence of the
Ru porphyrin.
Having obtained the catenane, porphyrin monomer and
both a pseudorotaxane and a reversibly coordinated rotaxane,
a preliminary investigation of the capacity for anion binding
and templating was undertaken. The effect of chloride ion was
examined by the addition of tetramethylammonium chloride to
y Although the product catenane may not be stabilised by chloride,
there is a distinct possibility that a transition state towards it may well
be, given that the pseudorotaxane structure shows evidence for chlor-
ide ion templation.
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5-tert-Butyl-N,N0-bis-{3-[2-(2-hydroxyethoxy)ethoxy]phenyl}-
1,3-benzenediamide (9)
allows provision for both a detection and trigger functionality,
depending on the chosen system. The dynamics of the system
can be modified by a wide variety of factors, including tem-
perature, solvent, anion, and metallation state. Within these
sets, the porphyrin moiety allows additional stimulation by
photophysical, electrochemical or chemical means. A modifi-
cation of the synthesis of the catenane, by initial synthesis of
the monomeric unit 3 and subsequent stepwise catenation with
the components of a different porphyrinic unit, allows for a
route to unsymmetrical catenanes where inter-porphyrin com-
munication and stimulation could be examined. The scope for
these versatile systems is considerable.
A mixture of diol 8 (1 g, 2.5 mmol) and K2CO3 (1.59 g, 11.48
mmol) in MeCN (dry, 100 ml) was heated, with stirring, under N2
(30 min). 2-(2-Chloroethoxy)ethanol (800 mg, 6.42 mmol) was
then added and the mixture was refluxed for 5 days. The mixture
was then cooled to room temperature and filtered to remove
potassium salts. The solvent was then evaporated and the residue
was taked up in EtOAc (100 ml), washed with HCl (dilute, 2 ꢀ 50
ml), water (50 ml) and dried (Na2SO4). The solvent was then
removed in vacuo to yield 9 as an oily yellow solid (1.3 g, 95%);
mp 66 1C; dH (300 MHz, d6-acetone) 9.69 (2H, s, NH), 8.29 (1H,
t, J 1.5, isophthal H-2), 8.15 (2H, d, J 1.5, isophthal H-4), 7.58
(2H, t, J 2, Ar H-2), 7.36 (2H, d, J 8, Ar H-6), 7.21 (2H, t, J 8, Ar
H-5), 6.68 (2H, d, J 8, Ar H-4), 4.10 (4H, t, J 5, OCH2), 3.80 (4H,
t, J 5, OCH2), 3.66–3.57 (8H, m, 2 ꢀ OCH2), 3.1–2.9 (2H, bs,
OH), 1.35 (9H, s, t-butyl); m/z (EI) 580.2783 [M1 requires
580.2785], 384 [(Mꢁ C10H14NO3)1 requires 384.46].
Experimental
General
All solvents were distilled before use, using standard proce-
dures: tetrahydrofuran (THF) was distilled over benzophenone
and sodium under N2; triethylamine (Et3N) was distilled over
CaH2; dimethylformamide (DMF) was dried over type 4 A
molecular sieves. Column chromatography used Aldrich silica
gel (grade 9385, 230–400 mesh).
1H NMR spectra were acquired using a 300 MHz Bruker
Avance 300 spectrometer at 303 K, unless otherwise stated.
Chemical shifts (d) are reported in parts per million relative to
residual solvent. Coupling constants (J) are reported in Hz.
Deuterated solvents were purchased from Aldrich and stored
over type 3 A molecular sieves after opening. COSY-45, gra-
dient COSY, one-bond C–H correlation (HMQC), long-range
C–H correlation (HMBC), NOESY, gradient NOESY two-
dimensional NMR experiments employed the standard Bruker
parameters. DEPT, NOE difference and saturation transfer
experiments, as well selective gradient NOE experiments utilised
standard Bruker pulse programs. 1H NMR assignments of
porphyrin-based molecules use the non-systematic numbering
displayed in Scheme 1; for the pseudorotaxane 3 þ 5, rotaxane 7
and related compounds, the protons of the thread component
polyether chain are numbered from the carbon adjacent to the
nicotinic ester group (C16) to C21 at the phenoxy end.
Melting points were determined using a Reichert micro-
scopic hot-stage apparatus.
5-tert-Butyl-N,N0-bis-[3-{2-[2-(4-toluenesulfonyloxy)
ethoxy]ethoxy}phenyl]-1,3-benzenediamide (10)
The extended diol 9 (2 g, 3.75 mmol) in CH2Cl2 (50 ml) and
Et3N (2 ml) was stirred at room temperature for 30 min. p-
Toluenesulfonyl chloride (1.79 g, 9.39 mmol) in CH2Cl2 (50 ml)
and Et3N (2 ml) was then added and the whole was stirred for
40 h. The solution was then poured onto ice and washed with
HCl (dilute, 50 ml), water (50 ml), dried (Na2SO4) and finally
dried in vacuo to yield the product 10 as an oily, pale yellow
solid (2 g, 63%) which was used crude in the subsequent
reaction; dH (300 MHz, d6-acetone) 9.69 (2H, s, NH), 8.34
(1H, t, J 1.5, isophthal H–2), 8.20 (2H, d, J 1.5, isophthal H-4),
7.79 (4H, d, J 8, tosyl-H), 7.58 (2H, t, J 2, Ar H-2), 7.43 (4H, d,
J 8, tosyl-H), 7.36 (2H, d, J 8, Ar H-6), 7.21 (2H, t, J 8, Ar H-
5), 6.68 (2H, d, J 8, Ar H-4), 4.20 (4H, t, J 5, OCH2), 4.05 (4H,
t, J 5, OCH2), 3.76–3.69 (8H, m, 2 ꢀ OCH2), 2.42 (6H, s, tosyl-
CH3), 1.35 (9H, s, t-butyl).
FAB and ESI mass spectrometry was carried out by CSIRO
Molecular Science at the Ian Wark Laboratory, Clayton, and
high resolution ESI was performed at the Centre for Molecular
Architecture, Rockhampton.
5-tert-Butyl-N,N0-bis-(3-hydroxyphenyl)-1,3-benzenediamide (8)
5-tert-Butyl-N,N0-bis-[3-{2-[2-(2-formylphenoxy)ethoxy]
ethoxy}phenyl]-1,3-benzenediamide (1)
3-Aminophenol (1 g, 9.16 mmol), 5-tert-butyl-isophthaloyl
dichloride (1.08 g, 4.17 mmol) and MeCN (dry, 50 ml) were
stirred together under N2 (30 min). Et3N (1.37 ml, 9.88 mmol)
was then added via syringe and the mixture was left to stir
overnight. The mixture was then filtered and the remaining
solution was then added to EtOAc (100 ml) and washed with
dilute HCl (2 ꢀ 50 ml), water (50 ml) and dried (Na2SO4). The
solvent was removed in vacuo to yield 8 as a white solid (1.6 g,
95%); mp 160–161 1C; dH (300 MHz, d6-acetone) 9.56 (2H, s,
NH), 8.29 (1H, t, J 1.5, isophthal H-2), 8.15 (2H, d, J 1.5,
isophthal H-4), 7.50 (2H, t, J 2, Ar H-2), 7.20 (2H, d, J 8, Ar
H-6), 7.15 (2H, t, J 8, Ar H-5), 6.60 (2H, d, J 8, Ar H-4), 2.9–2.7
(2H, bs, OH); m/z (EI) 404.1736 [M1 requires 404.1736],
296.13 [M-C6H6NO1 requires 296.35].
Salicylaldehyde (725 mg, 5.93 mmol), K2CO3 (2 g, 14.4 mmol)
and MeCN (dry, 100 ml) were heated together, with stirring,
under N2 (30 min). The tosylate 10 (2 g, 2.37 mmol) was then
added and the mixture was refluxed for 2 days. The mixture
was then cooled to room temperature, dried via rotary eva-
porator and partitioned between CH2Cl2 (100 ml) and water
(100 ml). The organic layer was washed with HCl (dilute, 50
ml), water (3 ꢀ 50 ml). The solvent was then removed in vacuo
to yield 1 as a slightly oily yellow solid (1.88 g, 100%); mp
68 1C; dH (300 MHz, CDCl3) 10.46 (2H, s, CHO), 9.10 (2H, s,
NH), 8.12 (1H, s, isophthal H-2), 7.99 (2H, s, isophthal H-4),
7.70 (2H, d, J 6, Ar ald H-3), 7.44 (2H, t, J 6, Ar ald H-4), 7.37
(2H, t, J 1.5, Ar H-2), 7.26 (2H, d, J 6, Ar H-6), 7.10 (2H, t, J 9,
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 4 4 3 – 1 4 4 9
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Ar H-5), 6.91 (4H, m, Ar ald H-5, Ar ald H-6), 6.59 (2H, d, J 6,
Ar H-4), 4.17 (4H, t, J 5, OCH2), 4.05 (4H, t, J 5, OCH2), 3.88
(4H, t, J 5, OCH2), 3.82 (4H, t, J 5, OCH2), 1.23 (9H, s, t-
butyl); dC (75 MHz, CDCl3) 31.0, 35.0, 67.4, 68.2, 69.8, 106.9,
111.0, 113.0, 121.0, 121.9, 125.0, 128.3, 129.7, 134.8, 136.1,
139.5, 152.6, 159.1, 161.3, 166.0, 190.5; m/z (ESI) 811 [(M þ
Na)1 requires 811.89], 789.33 [(M þ H)1 requires 789.91]; m/z
(EI) 788.3311 [M1 requires 788.3309].
ethanol (4 g, 23.7 mmol) was then added and the mixture was
refluxed for 5 days. The mixture was then cooled to room
temperature and filtered to remove potassium salts. The sol-
vent was then evaporated, and the residue was taked up in
EtOAc (100 ml), washed with HCl (dilute, 2 ꢀ 50 ml), water
(50 ml) and dried (Na2SO4). The solvent was then removed
in vacuo to yield 11 as a thick yellow oil (3.25 g, 40%); dH (300
MHz, d6-acetone) 9.64 (2H, s, NH), 8.29 (1H, t, J 1.5,
isophthal H–2), 8.15 (2H, d, J 1.5, isophthal H–4), 7.58 (2H, t,
J 2, Ar H-2), 7.36 (2H, d, J 8, Ar H-6), 7.21 (2H, t, J 8, Ar H-5),
6.68 (2H, d, J 8, Ar H-4), 4.12 (4H, t, J 5, OCH2), 3.83 (4H, t,
J 5, OCH2), 3.66–3.57 (8H, m, 2 ꢀ OCH2), 3.5 (8H, t, J 5, 2 ꢀ
OCH2), 3.1–2.9 (2H, bs, OH), 1.35 (9H, s, t-butyl); m/z (EI)
668.3313 [M1 required 668.3309], ca. 637 [(M-CH3O)1
requires 637.76], ca. 427 [(M-C12H18NO5]1 requires 427.52.
[2]-bis-{2,8,12,18-tetraethyl-3,7,13,17-tetramethyl-5,15
[2,2-{2-[2-[3-N,N0-(5-tert-butyl-1,3-benzenediamido)
phenyl]ethoxy]ethoxy}diphenyl] porphyrinato}-zinc(II)
[2]catenane (4)
and
{2,8,12,18-tetraethyl-3,7,13,17-tetramethyl-5,15[2,2-
{2-[2-[3-N,N0-(5-tert-butyl-1,3-benzenediamido)phenyl]
ethoxy] ethoxy}diphenyl]porphyrinato}-zinc(II) (3a)
5-tert-Butyl-N,N0-bis-[3-{2-[2-(2-nicotinoyloxy)ethoxy]
ethoxy}phenyl]-1,3-benzenediamide (5)
The extended diol 11 (200 mg, 0.299 mmol), nicotinic acid
(148 mg, 1.2 mmol), N-hydroxybenzotriazole (HOBT, 162 mg,
1.2 mmol) and 1-[(3-dimethylamino)propyl]-3-ethylcarbodii-
mide hydrochloride (EDC) (172 mg, 0.90 mmol) were dissolved
in CH2Cl2 (30 ml) before triethylamine (90.8 mg, 0.90 mmol)
was added via a syringe and the solution was stirred at room
temperature under nitrogen in the dark for 4 days. The solvent
was evaporated and the residue was taken up in 6 M HCl and
chloroform. The aqueous layer was separated and neutralised
with NaHCO3 (sat’d. aq.). The product was extracted with
chloroform, dried (Na2SO4) and the solvent removed to yield a
yellow/brown oil which was subjected to column chromato-
graphy using CH2Cl2, CH2Cl2/MeOH (1%) and CH2Cl2/
MeOH (5%) as the eluents to give the product 5 as a dark
yellow oil (150 mg, 57%); dH (300 MHz, CD2Cl2) 9.19 (2H, s,
NH), 8.86 (2H, s, H-py), 8.70 (2H, d, J 1, H-py), 8.27 (2H, d, J
2, H-py), 8.22 (1H, s, H-20), 8.09 (2H, s, H-40), 7.39–7.23 (8H,
m, H-600, H-500, H-200, H-py), 6.69 (2H, dm, J 8, H-400), 4.50
(8H, m, H-19, H-21), 4.09 (4H, m, H-20), 3.85 (12H, m, H-18,
H-17, H-16), 1.36 (9H, s, t-butyl); m/z (ESI-APCI) 879.4 [(M þ
H)1 requires 879.4].
The dialdehyde 1 (0.43 g, 0.54 mmol) and 3,30-diethyl-4,40-
dimethyl-2,20-dipyrrylmethane 2 (0.25 g, 1.1 mmol) were added
to a degassed solution of MeCN (50 ml). Trichloroacetic acid
(B20 mg) was then added and the mixture was left to stir (in
the dark, under N2) for 5 h. o-Chloroanil (0.75 g, 3 mmol) in
THF (20 ml) was added all at once and the mixture was taken
to dryness via rotary evaporator. The residue was run through
a plug of silica using EtOAc as the solvent followed by
insertion of zinc in the usual manner (excess Zn(OAc)2, MeOH/
CHCl3). The residue was then purified via silica column
chromatography using CH2Cl2, CH2Cl2/MeOH (1%) and
CH2Cl2/MeOH (5%) as the eluants to give two major frac-
tions. These fractions were recrystallised from acetone/MeOH
to yield bright purple solids 3 and 4.
4 (35 mg, 5%); dH (300 MHz, CD2Cl2/d3-MeOD) 10.24 (2H,
s, H-1), 8.63 (1H, s, H-20), 8.21 (2H, s, H-40), 7.75–7.69 (4H, m,
H-11, H-12), 7.36–7.28 (6H, m, H-600, H-13, H-14), 7.12 (2H, t, J
9, H-500), 7.05 (2H, m, Ar–H), 6.37 (2H, d, J 9, H-400), 4.24 (4H,
m, H-4), 4.20 (4H, m, H-16), 3.95 (4H, m, H-4), 3.26 (4H, m, H-
17), 2.97 (4H, m, H-19), 2.52 (12H, s, H-7), 2.25 (4H, m, H-18),
1.72 (12H, t, J 6, H-5), 1.50 (9H, s, t-butyl); m/z (ESI) 1269.7
[(M/2 þ H)1 requires 1269.5], 1207.6315 [(M/2ꢁZn þ H)1
requires 1207.6272]; m/z (FAB) 2538.6 [M1 requires 2537.066].
3a (75 mg, 11%), dH (300 MHz, CD2Cl2/d3-MeOD) 10.06
(2H, s, H-1), 8.06 (2H, s, H-40), 7.88 (1H, s, H-20), 7.75 (2H, t, J
6, H-12), 7.67 (2H, d, J 6, H-11), 7.49 (2H, d, J 9, H-600), 7.47–
7.29 (4H, m, H-13, H-14), 7.07 (2H, t, J 9, H-500), 6.49 (2H, m,
H-200), 6.37 (2H, d, J 9, H-400), 4.12 (4H, m, H-16), 3.95 (8H, m,
H-4), 3.22–3.16 (8H, m, H-19, H-17), 2.84 (4H, m, H-18), 2.52
(12H, s, H-7), 1.72 (12H, t, J 6, H-5), 1.33 (9H, s, t-butyl); dC
(75 MHz, CDCl3) 13.5, 17.5, 31.4, 34.1, 66.6, 69.6, 70.7, 96.1,
103.6, 110.9, 111.8, 113.6, 118.0, 121.0, 122.6, 127.5, 130.0,
134.6, 135.7, 138.7, 144.3, 158.8, 159.3; m/z (ESI) 1291.5285
[(M þ Na)1 requires 1291.5227], 1270 [(M þ H)1 requires
1269.5], ca. 1207 [(Mꢁ Zn þ 3H)1 requires 1207.1].
Pseudorotaxane (3b þ 5)
An equimolar mixture of porphyrin 3b and thread 5 were
combined in a NMR tube and allowed to reach equilibrium.
The porphyrin (Hp) and thread (Ht-) resonances were mon-
itored. dH (300 MHz, CD2Cl2) 10.23 (2H, s, Hp-1), 9.06 (2H, br
s, Ht-py), 8.53 (2H, br s, Ht-py), 8.47 (2H, br s, Ht-NH), 8.25
(2H, d, J 6, Ht-py), 8.20 (2H, s, Ht-20), 8.11 (2H, s, Ht-40), 8.06
(2H, s, Hp-40), 7.90 (1H, s, Hp-20), 7.80 (4H, t, J 6, Hp-11, Hp-
12), 7.68 (2H, d, J 9, Hp-600), 7.42–7.21 (12H, m, Hp-13, Hp-14,
Ht-200, Ht-500, Ht-600, Ht-py), 7.14 (2H, t, J 9, Hp-500), 6.71 (2H,
m, Hp-200), 6.65 (2H, d, J 9, Ht-400), 6.37 (2H, d, J 6, Hp-400),
4.49 (8H, m, Ht-19, Ht-20), 4.25 (4H, m, Hp-16), 4.06–4.03 (8H,
m, Ht-18, Ht–21), 3.85–3.77 (8H, m, Ht-16, Ht-17), 3.33 (8H,
m, Hp-17, Hp-19), 2.95 (4H, m, Hp-18), 2.6 (12H, s, Hp-7), 2.21
(12H, t, J 6, Hp-5), 1.30 (9H, s, Hp-t-butyl, Ht-t-butyl).
5-tert-Butyl-N,N0-bis-[3-{2-[2-(2-hydroxyethoxy) ethoxy]
ethoxy}phenyl]-1,3-benzenediamide (11)
Metalloporphyrin-stoppered rotaxane (7)
An equimolar mixture of strapped porphyrin 3b, thread 5 were
combined in an NMR tube. Two equivalents of ruthenium
carbonyl porphyrin 6 was added and the solution was allowed
to equilibrate (10 min). The porphyrin (Hp), thread (Htꢁ) and
ruthenium porphyrin (HRuPꢁ) resonances were monitored. dH
(300 MHz, CD2Cl2) 10.22 (2H, s, Hp-1), 8.97 (1H, br s, Ht-200),
8.72 (16H, s, HRuP-Ru), 8.45 (3H, br s, Ht-NH, Hp-20), 8.30
(1H, s, Ht-20), 8.23 (4H, m, Ht-40, Hp-40), 8.10 (18H, m, Ht-40,
The diol 8 (5 g, 12.4 mmol) and K2CO3 (7.95 g, 57.5 mmol)
were suspended in MeCN (dry, 200 ml) and heated, with
stirring, under N2 for 30 min. 2-[2-(2-Chloroethoxy)ethoxy]
H
RuP-Ru), 8.01 (2H, m, Hp-40), 7.90 (5H, m, Hp-20, Hp-11,
Hp-12), 7.82 (8H, s, HRuP-Ru), 7.67 (2H, d, J 6, Hp-600),
1448
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 4 4 3 – 1 4 4 9

View Article Online
7.42–7.11 (23H, m, Hp-13, Hp-14, Hp-20, Hp-600, Hp-500, Hp-500,
Hp-400, Ht-200, Ht-200, Ht-500, Ht-500, Ht-600, Ht-600), 6.78–6.55 (9H,
m, Hp-400, Ht-py, Ht-200, Ht-400, Ht-400), 4.47 (4H, m, Ht-19), 4.26
(4H, m, Hp-16), 4.06 (4H, m, Ht-20), 3.95 (12H, m, 4, Ht-21),
3.79 (4H, m, Ht-18), 3.65 (4H, m, Ht-17), 3.48–3.33 (12H, m,
Hp-17, Hp-19, Ht-16), 2.97 (4H, m, Hp-18), 2.59 (12H, s, Hp-7),
2.23 (12H, m, Hp-5), 1.54 (72H, s, HRuP-t-butyl), 1.42 (9H, s,
Hp-t-butyl, Ht-t-butyl). As previously observed for coordina-
tively stoppered rotaxanes,14 only mass peaks corresponding to
the component entities were observed in ESI mass spectra: m/z
(ESI) 1207.6 [3b (M þ H)1 requires 1207.6], 879.4 [5 (M þ H)1
requires 879.4], 1191 [6 (M þ H)1 requires 1191.6].
4
L. Flamigni, A. M. Talarico, S. Serroni, F. Puntoriero, M. J.
Gunter, M. R. Johnston and T. P. Jeynes, Chem. Eur. J., 2003
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M. J. Gunter and M. R. Johnston, Chem. Commun., 1994, 829.
M. J. Gunter, S. M. Farquhar and T. P. Jeynes, Org. Biomol.
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M. J. Gunter, Eur. J. Org. Chem., 2004, 1655.
M. J. Gunter and S. M. Farquhar, Org. Biomol. Chem., 2003, 1,
3450.
M. J. Gunter, T. P. Jeynes and P. Turner, Eur. J. Org. Chem.,
2004, 193.
5
6
7
8
9
10 M. J. Gunter, D. C. R. Hockless, M. R. Johnston, B. W. Skelton
and A. H. White, J. Am. Chem. Soc., 1994, 116, 4810.
11 M. J. Gunter and S. M. Farquhar, J. Porphyrins Phthalocyanines,
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12 (a) L. Flamigni, A. M. Talarico, M. J. Gunter, M. R. Johnston
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General procedure for chloride binding
A small crystal of tetramethylammonium chloride was added
to NMR samples of the host molecules in CD2Cl2. In each case
the sample was sonicated for 2 min and then allowed to
equilibrate (5 min–several h) until there was no further change
in the spectrum. Spectral shifts are shown in Fig. 4 and
discussed in the text.
13 J. G. Hansen, N. Feeder, D. G. Hamilton, M. J. Gunter, J. Becher
and J. K. M. Sanders, Org. Lett., 2000, 2, 449.
14 M. J. Gunter, N. Bampos, K. D. Johnstone and J. K. M. Sanders,
New J. Chem., 2001, 25, 166.
15 K. D. Johnstone, N. Bampos, J. K. M. Sanders and M. J. Gunter,
Chem. Commun., 2003, 1396.
Acknowledgements
This work was supported by the Australian Research Council.
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