Irreversible and reversible formation of a [2]rotaxane containing platinum(ii) complex with an N-alkyl bipyridinium ligand as the axis component

Article abstract of DOI:10.1039/b610087b

An N-Alkyl bipyridinium having a polymethylene chain and a bulky aryl group at the end, [4,4′-bpy-N-(CH₂)₁₀OC₆H ₃-3,5-^tBu₂]Cl ([1a]Cl), reacts with K[PtCl ₃(dmso)] to produce the

Full text of DOI:10.1039/b610087b

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PAPER
www.rsc.org/dalton | Dalton Transactions
Irreversible and reversible formation of a [2]rotaxane containing platinum(II)
complex with an N-alkyl bipyridinium ligand as the axis component†
Yuji Suzaki, Toshiaki Taira and Kohtaro Osakada*
Received 14th July 2006, Accepted 4th October 2006
First published as an Advance Article on the web 25th October 2006
DOI: 10.1039/b610087b
An N-Alkyl bipyridinium having a polymethylene chain and a bulky aryl group at the end,
[4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-tBu2]Cl ([1a]Cl), reacts with K[PtCl3(dmso)] to produce the Pt complex
with the N-alkyl bipyridinium ligand [Cl2(dmso)Pt{4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-tBu2}][PtCl3(dmso)]
as a 6 : 1 mixture of trans and cis isomers ([trans-2a][PtCl3(dmso)] and [cis-2a][PtCl3(dmso)]). Addition
of a-cyclodextrin (a-CD) to a solution of [1a]Cl in dmso-d6/D2O (3 : 1) forms [2]pseudorotaxane
[{4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-tBu2}·(a-CD)]Cl ([3a]Cl) which is equilibrated with [1a]Cl and a-CD in
solution. The reaction of K[PtCl3(dmso)] with [3a]Cl affords the [2]rotaxane
[trans-Cl2(dmso)Pt{4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-tBu2}·(a-CD)][PtCl3(dmso)]
([trans-4a][PtCl3(dmso)]) which contains a-CD and [trans-2a][PtCl3(dmso)] as the cyclic and axis
components, respectively. Dissolution of a mixture of [trans-2a][PtCl3(dmso)], [cis-2a][PtCl3(dmso)] and
a-CD in dmso-d6/D2O (3 : 1) forms a mixture of the rotaxanes containing [trans-4a-d6][PtCl3(dmso)]
and [cis-4a-d6][PtCl3(dmso)]. The reaction involves partial dissociation of the bipyridinium from Pt of
[trans-2a][PtCl3(dmso)] or [cis-2a][PtCl3(dmso)] to yield [1a][PtCl3(dmso)] and formation of
pseudorotaxane with a-CD, followed by recoordination of the bipyridinium to the Pt. The reversible
formation of the Pt–N coordination bond is studied in a dmso solution of the N-butyl compounds
[trans-Cl2(dmso)Pt{4,4ꢀ-bpy-N-nBu}][PtCl3(dmso)] ([trans-2b][PtCl3(dmso)]).
Introduction
Rotaxanes and pseudorotaxanes have attracted growing attention
because of their interlocked structure as well as their unique
chemical and physical properties.1,2 Cyclodextrins (CDs) possess
a hydrophobic cavity and can form rotaxanes with various
hydrophobic guest molecules in aqueous solution.3 Rotaxanes and
polyrotaxanes composed of a-CD and guest molecule with linear
alkyl groups have been applied to intelligent materials such as
molecular tubes,4 conductive polymers,5 drug delivery systems,6
and topological gels.7 Although sterically bulky organic groups
Scheme 1
are employed as the stoppers at the end of the axis molecules,
transition metals with ligands also play roles as bulky stoppers of
rotaxanes and kinetically stabilized rotaxanes.8 Macartney et al.
reported that diiron complexes [(NC)5Fe{pyz(CH2)nR}Fe(CN)5]4−
(pyz = pyrazinium, R = pyrazinium or 4,4ꢀ-bpy) and a-CD formed
rotaxanes via partial dissociation of the Fe–N bond (Scheme 1).9
Recent studies on pseudorotaxanes of CD with bispyridinylalkane
have revealed that a-CD prefers to reside at the alkyl chain of
the axis component rather than the positively charged pyridinium
group.2,10
containing rotaxane is stable in aqueous solution but it exhibits
dynamic behavior in dmso-d6–D2O. Chemical properties of related
[2]pseudorotaxanes and Pt complexes are also described.
Results and discussion
N-Alkyl bipyridinium compounds [4,4ꢀ-bpy-N-R]Cl ([1a]Cl: R =
(CH2)10OC6H3-3,5-tBu2; [1b]Cl: R = nBu), were prepared by
reaction of 4,4ꢀ-bipyridine with the chloroalkanes in DMF, as
shown in eqn (1).
In this paper, we report the synthesis of a new [2]rotaxane
that has a-CD and a Pt complex with an alkylbipyridinium
ligand as the cyclic and axis components, respectively. The Pt-
Chemical Resources Laboratory R1-3, Tokyo Institute of Technol-
ogy, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan. E-mail:
kosakada@res.titech.ac.jp; Fax: +81-45-924-5224; Tel: +81-45-924-5224
† Electronic supplementary information (ESI) available: Additional crystal
structure details, 1H NMR spectra of [1a]Cl, the mixture of [1a]Cl and a-
CD and [trans-4a][PtCl3(dmso)]. See DOI: 10.1039/b610087b
(1)
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Both compounds are soluble in water and were characterized by
NMR spectroscopy, ESIMS (electrospray ionization mass spec-
trometry) and elemental analysis. Reactions of K[PtCl3(dmso)]
with [1a]Cl and with [1b]Cl produced the platinum complexes with
[PtCl3(dmso)]− as counter anion, as shown in eqn (2).
(2)
The product obtained from [1a]Cl and K[PtCl3(dmso)] con-
tains two isomers of [Cl2(dmso)Pt(4,4ꢀ-bpy-N-(CH2)10OC6H3-
3,5-tBu2)][PtCl3(dmso)] with trans and cis Pt centers ([trans-
2a][PtCl3(dmso)] and [cis-2a][PtCl3(dmso)]), in a ratio of 6 : 1,
while the reaction with [1b]Cl produces [trans-2b][PtCl3(dmso)]
as a single product. Fig. 1 depicts the molecular structure
of [trans-2b][PtCl3(dmso)] determined by X-ray crystallography.
Four coordination sites of the square-planar Pt(II) center of the
cationic complex are occupied by the pyridyl group, dmso and two
trans Cl ligands. The dmso ligands coordinate to the Pt centers
through their sulfur atoms.
Fig. 2 1H NMR spectra of (a) [1a]Cl in dmso-d6–D2O, (b) the mixture of
[1a]Cl and a-CD in dmso-d6–D2O, and (c) isolated [trans-4a][PtCl3(dmso)]
dissolved in D2O.
at lower magnetic field positions than those of [1a]Cl. The signals
of both [1a]Cl and [3a]Cl are broadened. Only a set of the signals
is observed for the pseudorotaxane [3a]Cl, although two isomers
due to different orientations of the a-CD could be expected.10,11
These results may be rationalized by assuming the same aromatic
peak positions between the isomers due to complexation of a-
CD with the alkyl chain by hydrophobic interactions.2,10 1H NMR
signals of CH2 hydrogens of 1a are shifted upon complexation
with a-CD similarly to other axis molecules composed of alkyl
chain and pyridinium end groups.10 Alternatively, a small signal
observed at d 6.71 in Fig. 2(b) may be assigned to a minor isomer of
the pseudorotaxane with different orientations of the a-CD ring.
ROESY measurement of the solution did not provide any further
information on details of the structures of the pseudorotaxane.
[1a◦]Cl and [3a]Cl in the solution attain equilibrium within 5 min
at 25 C. Fig. 3 shows the Job plots obtained from 1H NMR peak
area ratio of e and eꢀ of the mixtures of [1a]Cl and a-CD with
different molar ratios. The concentration of the pseudorotaxane
formed reaches a maximum at an equal amount of the initially
added [1a]Cl and a-CD, indicating formation of [3a]Cl by 1 :
1 complexation of a-CD and [1a]Cl. The plots fit well with the
curve based on 1 : 1 complexation with association constant
Ka = 44 M−1. The association constant is smaller than those for
formation of the pseudorotaxane with a similar axis component
[{bpy(CH2)nbpy}·(a-CD)]I2 (n = 8–12) (72–3700 M−1 in D2O).9
Formation of the [2]pseudorotaxane [3a]Cl was confirmed also by
ESIMS which showed the parent peak of [3a]+ at m/z = 1473.8
(calc. 1473.7). Addition of a-CD to a D2O solution of [1b]Cl shows
little change in the 1H NMR spectrum, indicating that [1b]Cl and
a-CD does not form a stable [2]pseudorotaxane. Low stability of
the pseudorotaxane of a-CD with [1b]Cl can be attributed to too
short a butyl chain to form a stable inclusion complex with a-CD.
Fig. 1 ORTEP drawing of [trans-2b][PtCl3(dmso)] with 50% probability.
Hydrogen atoms are omitted for clarity.
Dissolution of a-CD and [1a]Cl in dmso-d6–D2O (3 :
1) forms [2]pseudorotaxane [{4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-
tBu2}·(a-CD)]Cl ([3a]Cl) as shown in eqn (3).
(3)
Fig. 2(a) and (b) show the 1H NMR spectra of [1a]Cl before and
after addition of a-CD, respectively. The latter spectrum contains
signals of the pseudorotaxane [3a]Cl (eꢀ, fꢀ and dꢀ) whose positions
(d 6.58, 6.92 and 9.03) differ from the corresponding signals of
[1a]Cl (d 6.61, 6.90 and 8.98). Signals of the CH2 hydrogens at
b-positions of N and O atoms of the axis molecule are observed
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of the Pt-containing rotaxanes. [trans-4a-d6][PtCl3(dmso)] and [cis-
4a-d6][PtCl3(dmso)], as shown in eqn (5).
(5)
Fig. 3 Job plots of the concentration of [3a]Cl formed from mixtures of
[1a]Cl and a-CD as a function of the molar fraction of [1a]Cl to a-CD
employed in dmso-d6–D2O (3 : 1). Sum of the concentrations of the two
components ([[1a]Cl]0 + [a-CD]0) was fixed to 10 mM in all cases. The
curve calculated by assuming formation of a 1 : 1 pseudorotaxane with an
association constant of 44 M−1 is shown.
Dmso ligands bonded to the cationic Pt center are replaced com-
pletely with dmso-d6, while the dmso ligands of [PtCl3(dmso)]− do
not exchange with the solvent. Fig. 4 plots time-dependent change
of concentration of rotaxanes and pseudorotaxanes monitored by
1H NMR spectroscopy. The compounds attain equilibrium in 20 h
at 25 ◦C.
An aqueous reaction of K[PtCl3(dmso)] with [1a]Cl in the
presence of a-CD forms [2]rotaxane [trans-4a][PtCl3(dmso)] which
is isolated in 53% yield (eqn (4)).
(4)
Fig. 2(c) shows the 1H NMR spectrum of isolated [trans-
4a][PtCl3(dmso)] in D2O at room temperature. A set of the
signals due to the rotaxane is observed in the regions of aromatic
and aliphatic hydrogens, and they do not change over 24 h at
room temperature. Consequently, the cationic rotaxane [trans-4a],
having Pt complex as the bulky end group of the axis component,
keeps the interlocked structure in D2O at room temperature. Since
the distance between the two trans Cl ligands Cl(1) and Cl(2) of
Fig.
from a-CD (28 mM) and [cis-2a][PtCl3(dmso)]/[trans-2a][PtCl3(dmso)]
([[cis-2a][PtCl3(dmso)]] [[trans-2a][PtCl3(dmso)]] 2.8 mM) in
dmso-d6–D2O (3 : 1) at 25 ◦C.
4
Profile of formation of rotaxanes and pseudorotaxanes
+
=
Scheme 2 depicts the plausible mechanism for formation of
the Pt-containing rotaxane from [cis-2a][PtCl3(dmso)], [trans-
2a][PtCl3(dmso)] and a-CD. A 6 : 1 mixture of [trans-
˚
[trans-2b][PtCl3(dmso)] (4.58 A) is similar to size of the cavity of
3
˚
a-CD (4.7 A), the PtCl2(dmso) group is too bulky to pass through
˚
the cavity of a-CD (the van der Waals radius of Cl = 1.75 A). High
2a][PtCl3(dmso)] and [cis-2a][PtCl3(dmso)], prepared in H2O, is
converted to a mixture of [1a][PtCl3(dmso)], PtCl2(dmso-d6)2,
[cis-2a][PtCl3(dmso)] and [trans-2a][PtCl3(dmso)] in dmso-d6–
D2O (3 : 1) by reversible dissociation and recoordination of
the bipyridinium ligand. [1a][PtCl3(dmso)] and a-CD produces
pseudorotaxane [3a][PtCl3(dmso)] which undergoes end-capping
by PtCl2(dmso)2 to form the rotaxane [cis-4a][PtCl3(dmso)]/[trans-
4a][PtCl3(dmso)], as shown in eqns (3) and (4). The total reaction
requires almost 20 h for completion and is much slower than
the pseudorotaxane formation (eqn (3)) and the end-capping of
it (eqn (4)). Consequently a series of the reactions shown in
Scheme 2 contains the initial dissociation of PtCl2L unit from
the bipyridinium ligand as the rate-determining step.
stability of the [2]rotaxane in D2O solution suggests that it does not
undergo dissociation of the pyridyl ligand. Dissolution of [trans-
4a][PtCl3(dmso)] in dmso-d6, however, results in formation of
a mixture of [cis-2a-d6][PtCl3(dmso)], [trans-2a-d6][PtCl3(dmso)],
[1a][PtCl3(dmso)] and a-CD; 80% of [trans-4a][PtCl3(dmso)] is
consumed within 5 min at room temperature. The dethreading of
the axis molecule from [trans-4a], giving [trans-2a-d6], is induced
by partial decoordination of the pyridyl group from Pt.
Reaction of a-CD with the Pt complex having the N-alkyl-
4,4ꢀ-bipyridine ligand in dmso-d6–D2O ([[cis-2a][PtCl3(dmso)]]0 +
[[trans-2a][PtCl3(dmso)]]0 = 2.8 mM ([cis-2a][PtCl3(dmso)]/[trans-
2a][PtCl3(dmso)] = 6 : 1), [a-CD]0 = 28 mM) also yields a mixture
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Scheme 2
Reversible formation of the Pt–N coordination bond, ac-
companied by cis–trans isomerization, is observed in dmso
solutions of the N-butyl compounds also. Dissolution of
[trans-2b][PtCl3(dmso)] in dmso-d6 gives a mixture containing
[trans-2b-d6][PtCl3(dmso)], [cis-2b-d6][PtCl3(dmso)] and [1b][PtCl3-
(dmso)] ([[trans-2b-d6][PtCl3(dmso)]] : [[cis-2b-d6][PtCl3(dmso)]] :
[[1b][PtCl3(dmso)]] = 28 : 52 : 20) after 30 h as shown in eqn (6).
Fig. 5 Profile of the reaction of (a) [trans-2b][PtCl3(dmso)] and (b)
PtCl2(dmso)2 with [1b]Cl in dmso-d6 at 25 ◦C.
(7)
Fig. 5(b) shows the profile of the reaction. [trans-2b-d6]Cl is
formed as the initial product, but it is further isomerized into
the thermodynamically more stable cis-complex to give a mixture
containing [trans-2b-d6]Cl, [cis-2b-d6]Cl and [1b]Cl in 24 : 38 : 38
ratio after 34 h.
[trans-2b][PtCl3(dmso)] is stable in nitromethane-d3 for 12 h
at 25 ◦C, while addition of dmso (4 equiv.) to the solution of
[trans-2b][PtCl3(dmso)] at 50 ◦C causes isomerization to afford
[cis-2b][PtCl3(dmso)] as shown in eqn (8).
(6)
Fig. 5(a) plots the profile of the reaction monitored by 1H
NMR spectroscopy. Exchange of the dmso ligand of the cationic
parts, [trans-2b] and [cis-2b], with dmso-d6 was completed within
20 min, whereas the counter anion [PtCl3(dmso)]− did not undergo
exchange of the dmso ligand throughout the reaction. Presence of
[1b][PtCl3(dmso)] in the reaction mixture suggested accompanying
formation of PtCl2(dmso-d6)2, although it was not detected by
the 1H NMR spectra. A similar equilibrated mixture of the
compounds with chloro counter anion is obtained by the reaction
of [1b]Cl and PtCl2(dmso)2 in dmso-d6 (eqn (7)).
(8)
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Fig. 6 shows the 1H NMR spectra of the reaction mixture
2 min and 150 h after addition of dmso. A small signal of methyl
hydrogens of PtCl2(dmso)2 is observed at d 3.52 after 150 h.
Fig. 7 plots the profile of the isomerization reaction monitored
1
by H NMR spectroscopy. The mixture attains equilibrium after
100 h to form a mixture containing [trans-2b][PtCl3(dmso)],
[cis-2b][PtCl3(dmso)] and [1b][PtCl3(dmso)] in 53 : 45 : 2 ratio.
These results indicate that the isomerization between [trans-
2b][PtCl3(dmso)] and [cis-2b][PtCl3(dmso)] is induced by addition
of dmso to the complex. The reaction induced by a small amount
of dmso (4 equiv. to Pt) (Fig. 7) is slower than the reaction in dmso
(Fig. 5(a)).
Scheme 3
effect of concentration of dmso on the reaction rate supports the
pathway in Scheme 3.12,13
In summary, we have demonstrated the synthesis of new [2]ro-
taxanes composed of a-CD and bipyridinium ligand of a platinum
complex as well as the platinum complexes without rotaxane struc-
ture. The Pt–N coordination bond of the bipyridinium platinum
complex undergoes reversible dissociation and association upon
addition of dmso to the complexes in D2O and CD3NO2. Partial
dissociation of the bipyridinium from the Pt center enables formal
slippage of a-CD from the rotaxane. Different reactivity of the Pt–
N bond toward dissociation depending on the solvent enabled
switching in formation and degradation of the Pt-containing
rotaxane.
Experimental
General
Fig. 6 1H NMR spectra of [trans-2b][PtCl3(dmso)] in nitromethane-d3
(a) 2 min after addition of dmso (4 equiv.) and (b) after 150 h.
Dried solvents were purchased from Kanto Chemical Co., Inc.
K[PtCl3(dmso)] and PtCl2(dmso)2 were prepared by the literature
method.13,14 Other chemicals were commercially available. NMR
1
spectra (1H, 13C{ H}) were recorded on Varian MERCURY300
and JEOL EX-400 spectrometers. The chemical shifts in the mixed
solvent (dmso-d6–D2O = 3 : 1) were referenced with respect to
dmso-d5 (d 2.49) as internal standard. IR absorption spectra were
recorded on Shimadzu FT/IR-8100 spectrometers. JASCO V-530
UV/VIS spectrometer was used for UV absorption measurements.
Electrospray ionization mass spectrometry (ESIMS) was recorded
on a ThermoQuest Finnigan LCQ Duo. Elemental analyses were
carried out with a Yanaco MT-5 CHN autorecorder.
Cl(CH2)10OC6H3-3,5-tBu2. A DMF (25 mL) solution con-
taining 3,5-di-tert-butylphenol (4.0 g, 19 mmol), NaOH (1.6 g,
40 mmol) and Cl(CH2)10Cl (8.2 mL, 39 mmol) was stirred for 25 h
at 110 ◦C. The reaction was quenched by addition of 1 M HCl in
H2O, and the organic product was extracted with Et2O and dried
over MgSO4. Evaporation of the solvent give a crude product
which was purified by SiO2 column chromatography (hexane–
CH2Cl2 = 30 : 1) to give Cl(CH2)10OC6H3-3,5-tBu2 as a colorless
Fig. 7 Profile of the reaction of dmso with [trans-2b][PtCl3(dmso)] in
nitromethane-d3 at 50 ◦C (eqn (8)).
1
Scheme 3 depicts a plausible mechanism that accounts for the
reactions in eqns (6)–(8). cis–trans Isomerization of the complex
with bipyridinium ligand is initiated by coordination of dmso to
Pt of [cis-2b]. Formation of an associative intermediate A and its
structure change via Berry pseudorotation lead to the complex
with trans geometry of the Pt center as shown in (i). Pathway
(ii) involves elimination of the N-butyl bipyridinium to generate
PtCl2(dmso)2 and [1b]Cl. An alternative dissociative pathway may
also be possible for the cis–trans isomerization, although positive
oil (1.9 g, 5.0 mmol, 27%). H NMR (300 MHz, CDCl3, r.t.): d
1.30–1.57 (m, 30H, CH2, CH3), 1.78–1.90 (m, 4H, CH2), 3.58 (t,
2H, ClCH2, J(HH) = 7 Hz), 4.03 (t, 2H, OCH2, J(HH) = 7 Hz),
1
6.83 (s, 2H, ortho-C6H3), 7.08 (s, 1H, papa-C6H3). 13C{ H} NMR
(75.5 MHz, CDCl3, r.t.): d 26.1 (CH2), 26.8 (CH2), 28.8 (CH2), 29.4
(4C, CH2), 31.4 (CH3), 32.6 (CH2), 34.9 (CCH3), 45.0 (ClCH2),
67.6 (OCH2), 108.8 (ortho-C6H3), 114,7 (para-C6H3), 152.0 (meta-
C6H3), 158.7 (C6H3). HRMS: Anal. Calc. for C24H41ClO: 380.2846.
Found: 380.2845.
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[4,4ꢀ-bpy-N-(CH2)10OC6H3-3,5-tBu2]Cl ([1a]Cl).
A
DMF
C6H3), 8.49 (2H, C10H8N2), 8.95–9.08 (4H, C10H8N2). The low
(20 mL) solution containing 4,4ꢀ-bipyridine (1.6 g, 10 mmol) a◦nd
Cl(CH2)10OC6H3-3,5-tBu2 (1.9 g, 5.0 mmol) was stirred at 100 C
for 22 h. Evaporation of the solvent gave an orange oil which was
washed with Et2O and toluene. Recrystallization from CH2Cl2–
solubility of complexes prevented 13C{ H} NMR measurement.
1
IR (KBr disk, r.t.): mmax/cm−1 2924, 1140 (S O), 1024, 442 (PtS).
=
UV absorption kmax(CHCl3)/nm 249 (e/dm3 mol−1 cm−1 18500).
[trans-2b][PtCl3(dmso)]. To a solution of K[PtCl3(dmso)]
(164 mg, 0.39 mmol) in H2O (4 mL) was adde◦d an aqueous solution
(2 mL) of [1b]Cl (45 mg, 0.18 mmol) at 0 C. The solid formed
immediately was collected by filtration and washed with EtOH
and Et2O. The crude product was purified by recrystallization
from MeNO2–Et2O, washed with EtOH and Et2O and dried under
reduced pressure to give [trans-2b][PtCl3(dmso)] as a white solid
1
Et2O yielded [1a]Cl as a white solid (1.5 g, 2.8 mmol, 55%). H
NMR (300 MHz, dmso-d6, r.t.): d 1.24 (s, 18H, CH3), 1.24–1.44
(12H, CH2), 1.67 (m, 2H, OCH2CH2), 1.94 (m, 2H, NCH2CH2),
3.91 (t, 2H, OCH2, J(HH) = 6 Hz), 4.64 (t, 2H, NCH2, J(HH) =
7 Hz), 6.67 (s, 2H, ortho-C6H3), 6.93 (s, 1H, para-C6H3), 8.04 (d,
2H, C10H8N2, J(HH) = 6 Hz), 8.63 (d, 2H, C10H8N2, J(HH) = 6
Hz), 8.86 (d, 2H, C10H8N2, J(HH) = 6 Hz), 9.23 (d, 2H, C10H8N2,
1
(116 mg, 0.12 mmol, 67%). H NMR (300 MHz, CD3NO2, r.t.):
1
J(HH) = 6 Hz). 13C{ H} NMR (75.5 MHz, dmso-d6, r.t.): d 25.4
d 1.00 (t, 3H, CH3, J(HH) = 8 Hz), 1.48 (m, 2H, CH2), 2.13 (m,
2H, CH2), 3.28 (s, 6H, CH3, J(PtH) = 22 Hz), 3.44 (s, 6H, CH3),
4.77 (t, 2H, CH2, J(HH) = 8 Hz), 8.07 (m, 2H, C10H8N2), 8.49 (d,
2H, C10H8N2, J(HH) = 7 Hz), 8.97 (m, 2H, C10H8N2), 8.99 (d, 2H,
(CH2), 25.6 (CH2), 28.4 (CH2), 28.8 (2C, CH2), 28.9 (2C, CH2),
30.8 (CH2), 31.2 (CH3), 34.6 (CCH3), 60.3 (NCH2), 67.0 (OCH2),
108.6 (ortho-C6H3), 114.0 (para-C6H3), 122.0 (C10H8N2), 125.4
(C10H8N2), 140.9 (C10H8N2), 145.4 (C10H8N2), 151.0 (C10H8N2),
151.6 (C10H8N2), 152.2 (meta-C6H3), 158.3 (ipso-C6H3). Calc.
for C34H49N2ClO·3H2O: C, 69.07; H, 9.38; N, 4.74; Cl, 6.00.
Found: C, 68.98; H, 9.09; N, 4.70; Cl, 6.37%. ESIMS: Calc. for
C34H49N2O: 501.4. Found: m/z = 501.8 [M − Cl]+. UV absorption
kmax(H2O)/nm 261 (e/dm3 mol−1 cm−1 17600).
1
C10H8N2, J(HH) = 7 Hz). 13C{ H} NMR (75.5 MHz, CD3NO2,
r.t.): d 13.8 (CH2CH3), 20.4 (CH2), 34.3 (CH2), 44.1 (SCH3), 44.4
(SCH3), 125.7 (C10H8N2), 128.1 (C10H8N2), 146.5 (C10H8N2), 154.2
(C10H8N2). The signal of the NCH2 carbon was overlapped with
the signal of CD2HNO2 (d 62.8). Calc. for C18H29N2Cl5O2Pt2S2:
C, 23.07; H, 3.12; N, 2.99; S, 6.84; Cl, 18.92. Found: C, 23.02; H,
3.04; N, 3.03; S, 6.70; Cl, 19.14%. IR (KBr disk, r.t.): mmax/cm−1
[4,4ꢀ-bpy-N-nBu]Cl ([1b]Cl). A toluene (20 mL) solution con-
taining 4,4ꢀ-bipyridine (2.5 g, 16 mmol) and nBuCl (12.5 ml,
60 mmol) was refluxed for 96 h. The solid formed by the reaction
was collected by filtration and washed with toluene to give [1b]Cl
=
2917, 1134 (S O), 1022, 442 (PtS).
[2]Pseudorotaxane ([3a]Cl). To a solution of [1a]Cl (2.4 mg,
4.4 × 10−3 mmol) in dmso-d6–D2O (1.2 mL–0.4 mL) was added
a-CD (42.8 mg, 4.4 × 10−2 mmol). A part of the solution was
transferred into an NMR tube and1H NMR spectra were recorded
periodically. The solution contained [1a]Cl and [3a]Cl. 1H NMR
data of [3a]Cl (300 MHz, dmso-d6–D2O (3 : 1), r.t.): d 1.18–1.42
(12H, CH2-axis), 1.21 (s, 18H, CH3), 1.46–1.66 (2H, OCH2CH2),
1.84–2.06 (2H, NCH2CH2), 3.16–3.80 (36H, CH-a-CD), 3.86*
(2H, OCH2), 3.92–4.36 (6H, CH-a-CD), 4.46–4.64 (2H, NCH2),
6.58 (s, 2H, ortho-C6H3), 6.92 (s, 1H, para-C6H3), 7.92 (2H,
C10H8N2), 8.36–8.44 (2H, C10H8N2), 8.74–8.80 (2H, C10H8N2), 9.03
(d, 2H, C10H8N2, J(HH) = 7 Hz). The peak with an asterisk was
overlapped significantly with the signal of the solvent. ESIMS:
Calc. for C70H109N2O31: 1473.7. Found: m/z = 1473.8 [M − Cl]+.
1
as a white solid (468 mg, 1.9 mmol, 12%). H NMR (300 MHz,
dmso-d6, r.t.): d 0.92 (t, 3H, CH3, J(HH) =8 Hz), 1.32 (m, 2H,
CH2), 1.93 (m, 2H, CH2), 4.65 (t, 3H, NCH2, J(HH) = 8 Hz),
8.04 (d, 2H, C5H4N, J(HH) = 6 Hz), 8.64 (d, 2H, C10H8N2,
J(HH) = 6 Hz), 8.86 (d, 2H, C10H8N2, J(HH) = 6 Hz), 9.25 (d,
1
2H, C10H8N2, J(HH) = 6 Hz). 13C{ H} NMR (100 MHz, dmso-
d6, r.t.): d 13.3 (CH3), 18.7 (CH2), 32.7 (CH2), 60.0 (NCH2), 121.8
(C10H8N2), 125.2 (C10H8N2), 140.8 (C10H8N2), 145.3 (C10H8N2),
150.8 (C10H8N2), 151.8 (C10H8N2). Calc. for C14H17N2Cl·0.25H2O:
C, 66.40; H, 6.96; N, 11.06; Cl, 14.00. Found: C, 66.60; H, 7.08;
N, 11.03; Cl, 14.08%. ESIMS: Calc. for C14H17N2: 213.1. Found:
m/z = 213.5 [M − Cl]+.
[trans-2a][PtCl3(dmso)]/[cis-2a][PtCl3(dmso)]. To a solution
of K[PtCl3(dmso)] (200 mg, 0.48 mmol) in H2O (2 mL) was added
an aqueous solution (4.0 mL) of [1a]Cl (60 mg, 0.12 mmol) at
Reaction of a-CD with [1b]Cl). [1b]Cl (10 mg, 0.04 mmol) and
a-CD (39 mg, 0.04 mmol) were charged to an NMR tube. After
addition of D2O (0.7 mL) to the mixture, the 1H NMR spectrum
showed almost exactly the signals of [1b]Cl.
0
◦C. The solution was stirred for 3 min and the solid formed
was collected by filtration, washed with water and dried under
reduced pressure to give a mixture of [trans-2a][PtCl3(dmso)]/[cis-
2a][PtCl3(dmso)] (= 6 : 1) as a yellow solid (95 mg, 0.077 mmol,
67%). Calc. for C38H61N2Cl5O3Pt2S2: C, 37.24; H, 5.02; N, 2.29;
S, 5.23; Cl, 14.47. Found: C, 37.53; H, 5.07; N, 2.33; S, 5.00; Cl,
14.84%.
1H NMR data of [trans-2a][PtCl3(dmso)] (300 MHz, CD3NO2,
r.t.): d 8.06 (d, 2H, J(HH) = 7 Hz). 1H NMR data of [cis-
2a][PtCl3(dmso)] (300 MHz, CD3NO2, r.t.): d 7.99 (d, 2H,
J(HH) = 7 Hz). Other signals of [trans-2a][PtCl3(dmso)] and
[cis-2a][PtCl3(dmso)] were not distinguished from each other
due to severe overlapping; d 1.30 (s, 18H, C(CH3)3), 1.30–1.44
(12H, CH2), 1.76 (m, 2H, OCH2CH2), 2.16 (m, 2H, NCH2CH2),
3.28 (s, 6H, PtCl3{SO(CH3)2}, J(PtH) = 22 Hz), 3.44 (br, 6H,
PtCl2{SO(CH3)2}), 4.00 (t, 2H, OCH2, J(HH) = 7 Hz), 4.77 (t, 2H,
NCH2, J(HH) = 7 Hz), 6.78 (s, 2H, ortho-C6H3), 7.10 (s, 1H, para-
[trans-4a][PtCl3(dmso)]. To a solution of K[PtCl3(dmso)]
(126 mg, 0.30 mmol) in H2O (6 mL) was added a solution of
[1a]Cl (80 mg, 0.15 mmol) and a-CD (584 mg, 0.60 mmol) in H2O
(12 mL) at 0 ◦C to cause immediate separation of a colorless solid
which was collected by filtration. The crude product was washed
with cold water and dried in vacuo to give [trans-4a][PtCl3(dmso)]
(167 mg, 0.076 mmol, 53%). 1H NMR (300 MHz, D2O, r.t.):
d 1.13 (s, 18H, CCH3), 1.29–1.34 (br, 12H, CH2), 1.46 (br, 2H,
OCH2CH2), 1.98 (br, 2H, NCH2CH2), 3.34–3.74 (m, 36H, CH,
CH2), 3.40 (s, 12H, SCH3), 3.83 (br, 2H, OCH2), 4.89 (s, 6H,
CH-a-CD), 6.67 (s, 2H, ortho-C6H3), 7.04 (s, 1H, para-C6H3),
7.91 (d, 2H, C10H8N2, J(HH) = 7 Hz), 8.28 (d, 2H, C10H8N2,
J(HH) = 6 Hz), 8.74 (d, 2H, C10H8N2, J(HH) = 6 Hz), 8.88
(d, 2H, C10H8N2, J(HH) = 6 Hz). The low solubility of [trans-
1
4a][PtCl3(dmso)] in D2O prevents 13C{ H} NMR measurement.
5350 | Dalton Trans., 2006, 5345–5351
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Calc. for C74H121N2Cl5O33Pt2S2·H2O: C, 40.10; H, 5.59; N, 1.26; S,
2.89. Found: C, 39.92; H, 5.84; N, 1.42; S, 2.76%. UV absorption
kmax(H2O)/nm 268 (e/dm3 mol−1 cm−1 19000).
acknowledges the scholarship by Japan Society for the Promotion
of Science. We are grateful to Professor Munetaka Akita of our
institute for ESIMS measurements.
Reaction of dmso-d6 with [trans-2b][PtCl3(dmso)]. [trans-
2b][PtCl3(dmso)] (7.0 mg, 7.5 × 10−3 mmol) was charged to an
NMR tube. After addition of dmso-d6 (0.75 mL) and a drop of
mesitylene as an internal standard, the tube was capped with a
References
1 G. Schill, Catenanes, rotaxanes, and knots, Organic Chemistry, Aca-
demic Press, New York, 1971, vol. 22; G. Schill, Molecular Catenanes,
Rotaxanes and Knots, ed. J.-P. Sauvage and C. Dietrich-Buchecker,
Wiley-VCH, Weinheim, 1999.
1
rubber septum. H NMR spectra were recorded occasionally to
monitor the concentration of the species based on the internal
standard. The NMR tube was kept in a thermostat bath (25 ◦C)
and stored when not being actively monitored.
2 D. B. Amabilino and J. F. Stoddart, Chem. Rev., 1995, 95, 2725; R.
Ja¨ger and F. Vo¨gtle, Angew. Chem., Int. Ed. Engl., 1997, 36, 930;
S. A. Nepogodiev and J. F. Stoddart, Chem. Rev., 1998, 98, 1959; J.-C.
Chambron and J.-P. Sauvage, Chem.–Eur. J., 1998, 4, 1362; T. J. Hubin
and D. H. Busch, Coord. Chem. Rev., 2000, 200–202, 5; T. Takata and
N. Kihara, Rev. Heteroat. Chem., 2000, 22, 197; V. Balzani, A. Credi,
F. M. Raymo and J. F. Stoddart, Angew. Chem., Int. Ed., 2000, 39, 3348;
K. Kim, Chem. Soc. Rev., 2002, 31, 96; J.-P. Collin and J.-P. Sauvage,
Chem. Lett., 2005, 34, 742; K. Osakada, T. Sakano, M. Horie and Y.
Suzaki, Coord. Chem. Rev., 2006, 250, 1012.
3 J. Szejtli, Topics in Inclusion Science: Cyclodextrin Technology, Kluwer
Academic, Boston, MA, 1988; J. F. Stoddart, Carbohydr. Res., 1989,
192, xii; G. Wenz, Angew. Chem., Int. Ed. Engl., 1994, 33, 803; A.
Harada, Coord. Chem. Rev., 1996, 148, 115; A. Harada, Carbohydr.
Polym., 1997, 34, 183; A. Harada, Acc. Chem. Res., 2001, 34, 456.
4 A. Harada, J. Li and M. Kamachi, Nature, 1992, 356, 325.
5 K. Yoshida, T. Shimomura, K. Ito and R. Hayakawa, Langmuir, 1999,
15, 910; C. Lagrost, J.-C. Lacroix, K. I. Chane-Ching, M. Jouini, S.
Aeiyach and P.-C. Lacaze, Adv. Mater., 1999, 11, 664; T. Shimomura,
K. Yoshida, K. Ito and R. Hayakawa, Polym. Adv. Technol., 2000, 11,
837; A. Farcas and M. Grigoras, J. Optoelectron. Adv. Mater., 2000,
2, 525; R. V. Belosludov, H. Sato, A. A. Farajian, H. Mizuseki and
Y. Kawazoe, Mol. Cryst. Liq. Cryst., 2003, 406, 195; Y. Takashima,
Y. Oizumi, K. Sakamoto, M. Miyauchi, S. Kamitori and A. Harada,
Macromolecules, 2004, 37, 3962; I. Yamaguchi, K. Kashiwagi and T.
Yamamoto, Macromol. Rapid Commun., 2004, 25, 1163; M. van den
Boogaard, G. Bonnet, P. van’t Hof, Y. Wang, C. Brochon, P. van Hutten,
A. Lapp and G. Hadziioannou, Chem. Mater., 2004, 16, 4383.
6 N. Yui, Supramolecular Design for Biological Applications, CRC Press,
Boca Raton, FL, 2002; N. Yui and T. Ooya, J. Artif. Organs, 2004, 7,
62.
Reaction of PtCl2(dmso)2 with [1b]Cl. PtCl2(dmso)2 (3.2 mg,
7.5 × 10−3 mmol) was charged to an NMR tube. After addition of
a dmso-d6 (0.75 mL) solution of [1b]Cl (1.9 mg, 7.5 × 10−3 mmol)
and a drop of mesitylene as an internal standard, the tube was
capped with a rubbe◦r septum. The NMR sample was kept in a
1
thermostat bath (25 C) and its H NMR spectra were recorded
periodically to monitor the concentration of the species based on
the internal standard.
Isomerization of [trans-2b][PtCl3(dmso)]. [trans-2b][PtCl3-
(dmso)] (3.6 mg, 3.8 × 10−3 mmol) was charged to an NMR
tube. After addition of CD3NO2 (0.75 mL), dmso (1.1 lL, 1.5 ×
10−2 mmol) and a drop of mesitylene as an internal standard, the
tube was capped with◦a rubber septum. The NMR sample was
kept in an oil bath (50 C) and its 1H NMR spectra were recorded
periodically to monitor the concentration of the species based on
the internal standard.
Crystal structure determination
Crystals of [trans-2b][PtCl3(dmso)] suitable for X-ray diffraction
study were obtained by recrystallization from MeNO2–Et2O and
mounted in a glass capillary tube. The data was collected to
a maximum 2h value of 55◦. Omega scans of several intense
reflections, made prior to data collection, had an average width
at half-height of 0.26◦ with a take-off angle of 6.0◦. Calculations
were carried out by using the program package CrystalStructureTM
for Windows.15 The structure was solved by direct methods and
expanded using Fourier techniques.
7 Y. Okumura and K. Ito, Adv. Mater., 2001, 13, 485.
8 H. Ogino, J. Am. Chem. Soc., 1981, 103, 1303; H. Ogino and K. Ohata,
Inorg. Chem., 1984, 23, 3312; H. Ogino, New J. Chem., 1993, 17, 683.
9 R. S. Wylie and D. H. Macartney, J. Am. Chem. Soc., 1992, 114, 3136;
R. S. Wylie and D. H. Macartney, Supramol. Chem., 1993, 3, 29; D. H.
Macartney and C. A. Wadding, Inorg. Chem., 1994, 33, 5912.
10 T. Oshikiri, Y. Takashima, H. Yamaguchi and A. Harada, J. Am. Chem.
Soc., 2005, 127, 12186.
11 R. Isnin and A. E. Kaifer, J. Am. Chem. Soc., 1991, 113, 8188.
12 Examples on reports on the isomerization reaction of the platinum
complexes: Y. N. Kukushkin, Y. E. Vyazmenskii and L. I. Zorina,
Z. Neorg. Khim., 1968, 13, 3052, (Chem. Abstr., 1969, 70, 33907z); P.-C.
Kong and F. D. Rochon, Can. J. Chem., 1978, 56, 441; M. D. Reily,
K. Wilkowski, K. Shinozuka and L. G. Marzilli, Inorg. Chem., 1985,
24, 37; J. H. Price, J. P. Birk and B. B. Wayland, Inorg. Chem., 1978,
17, 2245; G. Annibale, M. Bonivento, L. Canovese, L. Cattalini, G.
Michelon and M. L. Tobe, Inorg. Chem., 1985, 24, 797; A. P. S. Fontes,
A. Oskarsson, K. Lo¨vqvist and N. Farrell, Inorg. Chem., 2001, 40,
1745; R. Romeo and M. L. Tobe, Inorg. Chem., 1974, 13, 1991; D. A.
de Vekki, V. N. Spevak and N. K. Skvortsov, Russ. J. Coord. Chem.,
2001, 27, 579, (Chem. Abstr., 2001, 134, 326608v); G. Annibale, M.
Bonivento, L. Cattalini and M. L. Tobe, J. Chem. Soc., Dalton Trans.,
1992, 3433.
Crystal data for [trans-2b][PtCl3(dmso)]. C18H29Cl5N2O2Pt2S2,
Mr = 937.00, monoclinic, space group P21/a (no. 14), a =
◦
˚
13.771(3), b = 21.19(1), c = 9.604(2) A, b = 96.80(2) , V = 2782(2)
3
−3
˚
A , Z = 4, Dc = 2.237 g cm , no. of unique reflections = 6382,
no. of variables = 309, goodness of fit = 0.934, R = 0.054 (I ≥
2r(I)), Rw = 0.072 (I ≥ 2r(I)).
CCDC reference number 614949.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b610087b
Acknowledgements
13 Y. N. Kukushkin, Y. E. Vyaz’menskii and L. I. Zorina, Russ. J. Inorg.
Chem., 1968, 13, 1573.
This work was supported by Grants-in-Aid for Scientific Research
from the Ministry of Education, Science, Sports and Culture,
Japan and by a 21st Century COE Program “Creation of
Molecular Diversity and Development of Functionalities”. Y. S.
14 J. H. Price, A. N. Williamson, R. F. Schramm and B. B. Wayland, Inorg.
Chem., 1972, 11, 1280.
15 Crystal Structure: Crystal analysis package, Rigaku corporation and
Rigaku/MSC Inc., 2000–2006.
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The Royal Society of Chemistry 2006
Dalton Trans., 2006, 5345–5351 | 5351
©