[2]Pseudorotaxanes based on naphtho-21-crown-7 and secondary dialkylammonium salts: Remarkably improved association constants among four threaded structures

Article abstract of DOI:10.1002/cjoc.201400049

This research article is focused on the recognition interaction of a new host naphtho-21-crown-7 and four secondary dialkylammonium salts. In acetone, they can form 1:1 host-guest complexes which belong to slow-exchange systems. We also found the differen

Full text of DOI:10.1002/cjoc.201400049

FULL PAPER
DOI: 10.1002/cjoc.201400049
[
2]Pseudorotaxanes Based on Naphtho-21-crown-7 and Sec-
ondary Dialkylammonium Salts: Remarkably Improved Asso-
ciation Constants Among Four Threaded Structures
,a,c
b
a
a
a
Qizhong Zhou,* Yan Luo, Huajiang Jiang, Yuyuan Ye, Quan Zhang,
a
,a
Guoliang Dai, and Rener Chen*
a
Department of Chemistry, Taizhou University, Taizhou, Zhejiang 318000, China
b
Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
c
Department of Chemistry, Fudan University, Shanghai 200433, China
This research article is focused on the recognition interaction of a new host naphtho-21-crown-7 and four sec-
ondary dialkylammonium salts. In acetone, they can form 1 ∶ 1 host-guest complexes which belong to
slow-exchange systems. We also found the differences of binding affinity and binding selectivity between the host
and its complementary guest moieties, which could be ascribed to the aromatic π-π stacking effect and the acidity
increase of N-methylene and ammonium hydrogens due to the increasing electron withdrawing ability from butyl to
methoxyphenyl to phenyl to p-cyanophenyl substituents in the recognition motif.
Keywords crown ethers, host-guest systems, pseudorotaxanes, secondary ammonium salts
[
42]
Introduction
self-sorting selectivities. Philp developed a method of
[
43]
low temperature capture of pseudorotaxanes.
Crown ethers have been widely used in fabricating
threaded structures as host molecules for organic salts,
Pseudorotaxanes, known as mechanically inter-
locked molecular architectures which were fabricated
from linear molecular components surrounded by mac-
rocyclic components, have attracted great interest and
widely have been studied throughout the world.
[38-40]
such as paraquat derivatives
and secondary dial-
[42]
kylammonium salts.
A rotaxane had been synthesized in 74% yield from
benzo-21-crown-7 containing 21 atoms in the macrocy-
cle and a secondary dialkylammonium salt different
from the previously widely accepted point that a mac-
rocycle needs at least 24 C, N, O, or S atoms for the
Pseudorotaxanes as synthetic templates were widely
[
1-11]
[12-17]
used to construct rotaxanes,
catenanes
which have potential ap-
plication in intelligent material such as molecular de-
and su-
[
18-30]
pramolecular polymers,
[31]
[32]
vice, artificial molecular machine, molecular elec-
[4]
well-threading of an alkyl group into its cavity.
[
33]
[34-37]
tronic device and new functional materials,
etc.
We want to improve host-guest interactions in order
to construct more stable threaded structures.
In this paper, we synthesized a new host naph-
tho-21-crown-7 and studied the recognition interaction
of naphtho-21-crown-7 and four secondary dialkylam-
monium salts.
Pseudorataxanes as threaded structures attracted
much interest from supramolecuar scientist because of
their topological importance but also due to their many
potential applications. Recently, Gibson reported
[
2]pseudorotaxane and pseudocryptand-type poly[2]-
pseudorotaxane based on bis(meta-phenylene)-32-
crown-10 and paraquat derivatives, pseudocryptand-
type [2]pseudorotaxanes based on bis(meta-phenylene)-
[
38]
Experimental
[
39]
3
2-crown-10 derivatives and paraquats,
docryptand-type [3]pseudorotaxane based on a bis-
meta-phenylene)-32-crown-10 derivative and bispara-
and pseu-
Compounds 1, G1, G3 and G4 were prepared ac-
cording to the previously reported method. H NMR
was run on Varian Unity INOVA 400 MHz spectrome-
ter with TMS as internal standard. C NMR was meas-
ured on Bruker AVANCE DMX 500 MHz spectrome-
ter.
[5] 1
(
[
40]
13
quat derivatives. Ganguly et al. demonstrated folding
[41]
and unfolding movements in a [2]pseudorotaxane.
Schalley has found [4]pseudorotaxanes with remarkable
*
E-mail: qizhongchou@tzc.edu.cn (Q. Zhou); cre@tzc.edu.cn (R. Chen); Tel.: 0086-0576-88660177
Received January 21, 2014; accepted April 3, 2014; published online April 22, 2014.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400049 or from the author.
Chin. J. Chem. 2014, 32, 319—323
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
319

Zhou et al.
FULL PAPER
Synthesis of naphtho-21-crown-7 (H1)
Results and Discussion
A suspension of 2,3-dihydroxynaphthalene (2.70 g,
6.9 mmol), compound 1 (10.00 g, 16.9 mmol), potas-
sium carbonate (7.00 g, 50.7 mmol) and potassium
hexafluorophosphate (4.66 g, 25.3 mmol) in acetonitrile
The structures of naphtho-21-crown-7 and four sec-
ondary dialkylammonium salts were showcased in
Scheme 1.
1
(
350 mL) was stirred at reflux under nitrogen atmos-
Scheme 1 The structures of naphtho-21-crown-7 and four sec-
phere for 72 h. The reaction mixture was cooled to room
temperature. Then, the reaction mixture was filtered.
After the organic solvent in organic phase was evapo-
rated, dichloromethane (50 mL) was used to dissolve
this residue. The organic phase was washed with so-
dium hydroxide (50 mL, 2 mol/L). Then, the separated
organic phase was dried over sodium sulfate. The or-
ganic solution was concentrated. The crude product thus
obtained was subjected to column chromatography over
silica gel column and elution done with mobile phase of
dichloromethane/acetonitrile (10∶1, V∶V), the desired
fraction thus eluted was evaporated under vacuum to
ondary dialkylammonium salts
H6
H5
H7
H4
H8
H2
H3
O
H1
O
H9
O
O
O
O
O
H1
H10 H12
PF -
PF -
6
6
N
N
H
2
H
2
afford a white solid (2.3 g, 33%)
O
H11 H13
G2
1
G1
3 3
H NMR (400 MHz, CD COCD ) δ: 7.67－7.73 (m,
PF -
PF6-
6
2
H), 7.25－7.32 (m, 4H), 4.24 (t, J＝4.8 Hz, 4H), 3.92
(
4
t, J＝4.8 Hz, 4H), 3.75 (t, J＝4.8 Hz, 4H), 3.66 (t, J＝
.8 Hz, 4H), 3.55－3.62 (m, 8H); C NMR (100 MHz,
N
N
H
1
3
H2
2
NC
G3
G4
CD COCD ) δ: 149.4, 129.5, 126.3, 123.9, 108.0, 71.0,
3
3
+
7
4
4
0.8, 70.4, 69.3, 68.9; ESI-MS m/z: 424.2 [M＋NH ] ,
29.1 [M ＋ Na] . HRMS-EI calcd for C H O :
4
The synthesis of naphtho-21-crown-7 was illustrated
in Eq. 1. Compound 1 reacted with 2,3-dihydroxy-
+
2
2
30
7
06.1992, found 406.1994.
naphthalene in the presence of K
CH
2
CO
3
and KPF
6
in
Synthesis of G2
3
CN to afford naphtho-21-crown-7 in 33% yield.
A solution of p-methoxybenzaldehyde (10.27 g, 75.4
mmol) and n-butylamine (5.50 g, 75.2 mmol) in metha-
nol (150 mL) was stirred at reflux overnight. When the
reaction mixture was cooled to room temperature, so-
dium borohydride (4.00 g, 105.3 mmol) was added into
the mixture in several portions. Then the mixture was
stirred at room temperature for 24 h. After completion
of the reaction, water (50 mL) was used to quench the
reaction. The mixture was filtered and methanol was
distilled off. The residue was extracted with dichloro-
methane and the extract was concentrated to get a yel-
low oil. After the oil was added to a hydrochloric acid
solution and stirred for a moment, a white precipitate
formed. The mixture was filtered and the solid was dis-
solved in water to get a saturated solution. The solution
was added to a saturated ammonium hexafluorophos-
phate solution to produce a precipitate. It was collected
by suction filtration and recrystallized from deionized
water three times to afford G2 (3.31 g, 23.3%) as a
OH
O
O
OTs
OH
H1
(1)
O
Ts
O
K2CO3, KPF6, CH3CN
reflux
O
O
1
The synthesis of G2 was shown in Eq. 2.
p-Methoxybenzaldehyde reacted with n-butylamine to
give a reaction mixture, followed by reduction with
4
NaBH . After completion of the reaction, water was
used to quench the reaction. Then, the residue was
treated with a hydrochloric acid solution then with a
saturated NH
white solid.
4 6
PF solution to produce G2 (23.3%) as a
1
) reflux
O
2) NaBH4
O
+ H N
G2
(2)
3
3) HCl
4
) NH PF6
4
1
white solid.
The H NMR spectrum (Figure 1) of an equimolar
solution of naphtho-21-crown-7 (H1) and G1 in ace-
1
3 3
H NMR (400 MHz, CD COCD ) δ: 7.49 (d, J＝8.8
Hz, 2H), 7.00 (d, J＝8.8 Hz, 2H), 4.50 (s, 2H), 3.80 (s,
H), 3.38 (t, J＝8.0 Hz, 2H), 1.77－1.88 (m, 2H), 1.37
1.50 (m, 2H), 0.92 (t, J＝7.6 Hz, 3H); ESI-MS m/z:
6
tone-d showcases three sets of resonances for uncom-
3
－
plexed H1, uncomplexed G1, and the complex between
H1 and G1, indicating slow-exchange complexation on
＋
＋
1
[44]
1
94.1 [M−PF ] , 121.1 [M−PF −C H N] . HREIMS
4 5 6
the H NMR time scale. Proton NMR of H , H , H ,
6
6
4
11
＋
m/z calcd for [M−HPF ] C H NO: 193.1467, found
10 11 12
H , H , H and H13 split into two parts after com-
plexation. This implied the threading of G1 through the
6
12 19
1
93.1473.
320
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 319—323

[
2]Pseudorotaxanes Based on Naphtho-21-crown-7 and Secondary Dialkylammonium Salts
1
Figure 1 Partial H NMR spectra (400 MHz, CD
3
COCD
3
, room temperature) of 16.00 mmol/L H1 (a), 16.00 mmol/L H1 and G1 (b),
and 16.00 mmol/L secondary dialkylammnium salt G1 (c).
cavity of H1 to form a pseudorotaxane. In the same way,
complexations of H1 with secondary ammonium salts
G2 and G3 and G4 were also found to be slow-ex-
change systems.
6
H1•G2, H1•G3 and H1•G4 in acetone-d were deter-
−1
−1
mined to be 775 (±77) L•mol , 930 (±91) L•mol
−1
and 1473 (±102) L•mol , respectively (Supporting
Information).
The stoichiometry of the complexes between H1•G1,
was determined to be 1∶1 and confirmed by an elec-
Some observed values are higher than the corre-
−1
a
sponding K values of 615 (±36) L•mol (B21C7•G2),
−1
trospray ionization mass spectrum (ESI-MS) m/z: 536.1
and 1062(±102) L•mol (B21C7•G4) for B21C7-
＋
]
[4]
[
H1•G1−PF
6
(Figure 2).
based complexes, indicating that the aromatic π-π
The stoichiometries of the complexes between H1
stacking effect in naphtho-21-crown-7/secondary dial-
and G2, between H1 and G3, and between H1 and G4
were also determined to be 1∶1 and confirmed by an
electrospray ionization mass spectrum (ESI-MS) m/z:
kylammonium salts system is larger than B21C7/sec-
ondary dialkylammonium salts system. The K increase
a
from H1•G1 to H1•G2, H1•G3 and H1•G4 is a result of
the acidity increase of N-methylene and ammonium hy-
drogens due to the increasing electron withdrawing abil-
ity from butyl to methoxyphenyl to phenyl to p-cyano-
phenyl substituents.
＋
＋
6
00.1 [H1•G2−PF
6
] , 570.1 [H1•G3−PF
6
] , and 595.1
(see Supporting Information).
＋
]
[
H1•G4−PF
6
Since the stoichiometries of all four complexation
systems were determined to be 1∶1, then the associa-
[
4,42]
tion constants (K
were determined to be 467 (±51) L•mol (Figure 3).
The association constants (K ) of 1∶1 complexes of
a
) of 1∶1 complexes
of H1•G1
The proposed host-guest interaction model was ex-
plained in Scheme 2 according to previous litera-
−
1
[4,45-49]
a
tures.
There exist host-guest interaction between
＋
＋
] , 445.1 [H1＋
Figure 2 Electrospray ionization mass spectrum of a solution of H1 and G1. m/z: 130.2 [G1–PF
6
] , 424.2 [H1＋NH
4
＋
＋
K] , 536.1 [H1•G1–PF ] .
6
Chin. J. Chem. 2014, 32, 319—323
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
321

Zhou et al.
FULL PAPER
1
Figure 3 H NMR spectrum (400 MHz, CD COCD , room temperature) of 16.00 mmol/L H1 and G1. The association constant K
3
3
a, H1•G1
−
3
value calculated from integrations of complexed and uncomplexed peaks of H
5
of H1 is [(0.92/1.30)×16.00×10 ]/[(1−0.92/1.30)×
−
3 2
−1
1
6.00×10 ] ＝518 L•mol . The association constant K
a, H1•G1
value calculated from integrations of complexed and uncomplexed peaks
−3
−3 2
−1
of H11 of G1 is [(1.00/1.47)×16.00×10 ]/[(1−1.00/1.47)×16.00×10 ] ＝416 L•mol . Therefore, Ka, H1•G1＝(518＋416)/2＝467(±51)
−
1
L•mol .
Scheme 2 Proposed host-guest interaction model (for example
H1•G3)
on naphtho-21-crown-7/secondary dialkylammonium
salt system are on the progress.
O
O
Acknowledgement
O
-
This work was supported by the National Natural
Science Foundation of China (Nos. 21172166 and
N
O
PF6
H
O
H
O
2
1203135) and China Postdoctoral Science Foundation
O
(
No. 2013M541456), Natural Science Foundation of
Zhejiang Province (No. LY14B020012) and University
Students' Science and Technology Innovation Program
of Zhejiang Province (No. 2013R428016).
crown ether and dialkylammonium salts, and π-π stack-
ing interaction.
[
4,45-49]
Conclusions
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5
(Cheng, F.)
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