A study of the complexation of bis(m-phenylene) crown ethers and secondary ammonium ions

Article abstract of DOI:10.1021/jo972162s

Two macrocycles, bis(m-phenylene)-26-crown-8 (1) and bis(m-phenylene)-32-crown-10 (2), were combined with several linear components, dibenzyl- (3·PF₆), di-n-butyl- (4·PFe), and diphenethyl(5·PF₆) ammonium hexafluorophosphate salts. The smaller macrocycle 1 was shown not to complex effectively with any of the ammonium salts in solution by ¹H NMR, but 1:1 complexes were shown to exist in the "gas phase" as [1:3], [1:4], and [1:5] by high-resolution fast atom bombardment mass spectrometry (HRFABMS) and electrospray ionization mass spectrometry (ESIMS). The X-ray crystal structure of macrocycle 1 is reported. The larger macrocycle 2 did form 1:2 complexes with the ammonium salts in solution, which were observed as well in the solid and gas phases. X-ray crystal structures of the pseudorotaxanes [2:(3)₂]·2PF₆ and [2:(5)₂]·2PF₆ were determined and are discussed. The pseudorotaxanes are stabilized by hydrogen bonding between the ammonium hydrogens of the linear salt unit and the oxygens of the crown ether macrocycle. Secondary stabilization also occurs by edge-to-face π stacking.

Full text of DOI:10.1021/jo972162s

7
634
J . Org. Chem. 1998, 63, 7634-7639
A Stu d y of th e Com p lexa tion of Bis(m -P h en ylen e) Cr ow n Eth er s
a n d Secon d a r y Am m on iu m Ion s
†
‡
‡
†
William S. Bryant, Ilia A. Guzei, Arnold L. Rheingold, J oseph S. Merola, and
Harry W. Gibson*,
†
Department of Chemistry, Virginia Polytechnic Institute and State University,
Blacksburg, Virginia 24061, and Department of Chemistry and Biochemistry, University of Delaware,
Newark, Delaware 19716
Received November 26, 1997
Two macrocycles, bis(m-phenylene)-26-crown-8 (1) and bis(m-phenylene)-32-crown-10 (2), were
combined with several linear components, dibenzyl- (3‚PF
6
6
), di-n-butyl- (4‚PF ), and diphenethyl-
(
5‚PF ) ammonium hexafluorophosphate salts. The smaller macrocycle 1 was shown not to complex
6
1
effectively with any of the ammonium salts in solution by H NMR, but 1:1 complexes were shown
to exist in the “gas phase” as [1:3], [1:4], and [1:5] by high-resolution fast atom bombardment mass
spectrometry (HRFABMS) and electrospray ionization mass spectrometry (ESIMS). The X-ray
crystal structure of macrocycle 1 is reported. The larger macrocycle 2 did form 1:2 complexes with
the ammonium salts in solution, which were observed as well in the solid and gas phases. X-ray
crystal structures of the pseudorotaxanes [2:(3)
2
]‚2PF
6
and [2:(5)
2
6
]‚2PF were determined and are
discussed. The pseudorotaxanes are stabilized by hydrogen bonding between the ammonium
hydrogens of the linear salt unit and the oxygens of the crown ether macrocycle. Secondary
stabilization also occurs by edge-to-face π stacking.
In tr od u ction
Scientists have tried to use the phenomenon of self-
assembly by molecular recognition since the discovery
that organic molecules can arrange themselves into
complex arrangements to produce higher ordered molec-
ular assemblies.1 The use of the self-assembly concept
F igu r e 1. Representations of rotaxane and pseudorotaxane.
can lead to the formation of rotaxanes and pseudorotax-
anes, in which a linear unit is threaded through the
cavity of a cyclic unit (Figure 1). Pseudorotaxanes differ
from rotaxanes because they lack bulky end groups on
the linear unit that prevent dethreading of the cyclic
unit.2
Stoddart et al. recently reported on the self-assembly
complexation of o- and p-phenylene crown ethers with
secondary ammonium salts to form pseudorotaxanes.3
The complexes are a result primarily of hydrogen bonding
between the ammonium protons and the ether oxygens
of the crown ether. Further stabilization of the com-
5
developed syntheses of a number of (5-)mono- and (5,5′-)-
6
difunctional derivatives of these crown ethers as precur-
sors to self-assembled supermolecules and polymeric
7
rotaxanes.2
a,c
Because of their symmetric nature, these
substituted bis(m-phenylene) crown ethers can be pre-
pared as pure compounds without isomer separation and
have simpler NMR spectra than those of their substituted
bis(o-phenylene) and bis(p-phenylene) analogues. We
have demonstrated the formation of a variety of polyro-
(
3) (a) Ashton, P. R.; Campbell, P. J .; Chrystal, E. J . T.; Glink, P.
T.; Menzer, S.; Philp, D.; Spencer, N.; Stoddart, J . F.; Tasker, P. T.;
Williams, D. J . Angew. Chem., Int. Ed. Engl. 1995, 34, 1865. (b) Ashton,
P. R.; Campbell, P. J .; Chrystal, E. J . T.; Glink, P. T.; Menzer, S.; Philp,
D.; Spencer, N.; Stoddart, J . F.; Tasker, P. T.; Williams, D. J . Angew.
Chem., Int. Ed. Engl. 1995, 34, 1869. (c) Ashton, P. R.; Glink, P. T.;
Martinez-Diaz, M.-V.; Stoddart, J . F.; White, A. J . P.; Williams, D. J .
Angew. Chem., Int. Ed. Engl. 1996, 35, 1930. (d) Ashton, P. R.;
Chrystal, E. J . T.; Glink, P. T.; Menzer, S.; Schiavo, C.; Spencer, N.;
Stoddart, J . F.; Tasker, P. T.; White, A. J . P.; Williams, D. J . Chem.s
Eur. J . 1996, 2, 709. (e) Ashton, P. R.; Glink, P. T.; Stoddart, J . F.;
Tasker, P. T.; White, A. J . P.; Williams, D. J . Chem.sEur. J . 1996, 2,
729.
plexes is achieved through π-orbital interactions of the
aromatic rings of both species.4 However, m-phenylene
crown ethers were not discussed. Bis(m-phenylene)
crown ethers are of special interest to us because we have
†
Virginia Polytechnic Institute and State University.
University of Delaware.
‡
(1) (a) Singer, S. J .; Nicholson, G. L. Science 1972, 175, 720. (b)
Pedersen, C. J . Angew. Chem., Int. Ed. Engl. 1988, 27, 1021. (c) Lehn,
J .-M. Angew. Chem., Int. Ed. Engl. 1988, 27, 89. (d) Cram, D. J . Angew.
Chem., Int. Ed. Engl. 1988, 27, 1009. (e) Lindsey, J . S. New J . Chem.
(4) Raymo, F. M.; Houk, K. N.; Stoddart, J . F. Private communica-
tion.
1
991, 15, 153. (f) Philp, D.; Stoddart, J . F. Synlett 1991, 445. (g) Lehn,
(5) Nagvekar, D. S.; Yamaguchi, N.; Wang, F.; Bryant, W. S.; Gibson,
H. W. J . Org. Chem. 1997, 62, 4798.
J .-M. Science 1993, 260, 1762. (h) Lehn, J .-M. Supramolecular
ChemistrysConcepts and Perspectives; VCH: Weinheim, Germany,
1
(6) (a) Delaviz, Y.; Gibson, H. W. Org. Prep. Proced. Int. 1991, 23,
382. (b) Gibson, H. W.; Delaviz, Y. Polymer 1994, 34, 1109. (c) Delaviz,
Y.; Merola, J . S.; Berg, M. A. G.; Gibson, H. W. J . Org. Chem. 1995,
60, 516. (d) Nagvekar, D. S.; Gibson, H. W. Org. Prep. Proced. Int. 1997,
29, 237. (e) Nagvekar, D. S.; Gibson, H. W. Can. J . Chem. 1997, 75,
1375.
995. (i) Philp, D.; Stoddart, J . F. Angew. Chem., Int. Ed. Engl. 1996,
5, 1155. (j) Feiters, M. C.; Fyfe, M. C. T.; Martinez-Diaz, M.-V.;
3
Menzer, S.; Nolte, R. J . M.; Stoddart, J . F.; van Kan, P. J . M.; Williams,
D. J . J . Am. Chem. Soc. 1997, 119, 8119.
(2) (a) Gong, C.; Gibson, H. W. Curr. Opin. Solid State Mater. Sci.
1
3
998, 2, 647. (b) Fyfe, M. C. T.; Stoddart, J . F. Acc. Chem. Res. 1997,
0, 393. (c) Gibson, H. W. In Large Ring Molecules; Semlyen, J . A.,
(7) Yamaguchi, N.; Nagvekar, D. S.; Gibson, H. W. Angew. Chem.,
Int. Ed. Engl. 1998, 37, 2361. Yamaguchi, N.; Hamilton, L. M.; Gibson,
H. W. Angew. Chem., Int. Ed. Engl. 1998, in press. Yamaguchi, N.;
Gibson, H. W. Angew. Chem., Int. Ed. Engl. 1998, in press.
Ed.; J ohn Wiley and Sons: New York, 1996; Chapter 6, p 191. (d)
Amabilino, D. B.; Stoddart, J . F. Chem. Rev. 1995, 95, 2725.
1
0.1021/jo972162s CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/06/1998

Complexation of Crown Ethers and Ammonium Ions
J . Org. Chem., Vol. 63, No. 22, 1998 7635
bardment mass spectrometry (HRFABMS) that dibenzo-
2
4-crown-8 (DB24C8, 6) can complex with dibenzyl-
ammonium ions (3‚PF ) and di-n-butylammonium ions
4‚PF
) in 1:1 stoichiometries.3 The complexes were
6
(
6
shown to exist in pseudorotaxane forms in the solid state.
However, we observe that when the 26-membered meta
analogue 1 is placed in solution (CD
3
CN, CDCl
3
, or
acetone-d ) with 3‚PF , 4‚PF , or 5‚PF
6
6
6
6
, there is no
9
change in the chemical shifts of the proton signals, even
though the cavity size of the molecule is large enough to
allow threading to take place.10 Another indication of the
lack of complexation was the observation that 3‚PF
6
, 4‚
PF , and 5‚PF do not dissolve in the presence of 1 in
6
6
chloroform. Stoddart et al. have demonstrated that these
chloroform-insoluble salts become soluble by complex-
3
ation in the presence of DB24C8. As noted by Peder-
sen11 and Izatt et al. with dibenzo-18-crown-6 (DB18C6,
7
12
F igu r e 2. Bis(m-phenylene)-26-crown-8 (1), bis(m-phenylene)-
), an unfavorable crown ether conformation may be the
reason no detectable complexation of 1 takes place in
solution.
3
2-crown-10 (2), dibenzyl- (3‚PF
6
), di-n-butyl- (4‚PF
6
), and
diphenethyl- (5‚PF ) ammonium hexafluorophosphates, di-
6
benzo-24-crown-8 (6), dibenzo-18-crown-6 (7), and bis(p-phe-
nylene)-34-crown-10 (8).
However, 1:1 complexes, perhaps [2]pseudorotaxanes,
of 1 with 3‚PF
6
, 4‚PF
6
6
, and 5‚PF were determined to
exist by HRFABMS and electrospray ionization mass
spectrometry (ESIMS). Solids obtained by evaporation
of equimolar solutions of the components gave peaks at
m/z 646.5, 578.5, and 674.6, respectively, corresponding
to the 1:1 complex cations [1:3], [1:4], and [1:5] (Figures
4
-6) for ESIMS. A comparison of the peak intensities
of the ammonium salt and the complex in each spectrum
gives a relative indication of the strength of the com-
plexation. In Figures 4 and 5, the peaks for the com-
plexes are 2 times as intense as the peaks for the salts;
this indicates that fairly stable complexes exist. How-
ever, in Figure 6 the peak for the salt is about 6 times as
intense as the peak for the complex. This indicates that
the complex 1:5 is not as strong as 1:3 or 1:4. Attempts
to grow crystals of these complexes suitable for X-ray
crystallography have so far been futile.
F igu r e 3. Possible pseudorotaxane products from mixtures
of crown ethers and secondary ammonium salts.
Cr ysta l Str u ctu r e of 1. A crystal suitable for X-ray
crystallographic analysis was obtained by slow evapora-
6
tion of an acetone solution containing both 1 and 5‚PF .
taxanes from these macrocycles via hydrogen bonding.1a,8
Therefore, the complexations of the 26- and 32-membered
bis(m-phenylene) crown ethers 1 and 2 with several
The crystals formed were of 1 alone (Figure 7). The
structure of the macrocycle differs from that of previously
reported phenylene-based macrocycles.1
3-15
Instead of
secondary ammonium salts (3‚PF
were investigated (Figure 2). The possible pseudorotax-
anes that can be assembled are shown in Figure 3.
6
, 4‚PF
6
, and 5‚PF
6
)
the “all-gauche” conformation of the polyether bridges
adopted by other macrocycles, there exist two trans bonds
(C5-C6 and C17-C18). The cavity of the macrocycle is
collapsed, and the overall shape of the macrocycle is
reminiscent of DB24C8.12 However, the phenyl rings in
Resu lts a n d Discu ssion
1
are almost opposite each other along the short axis
I. Com p lexa tion of 26-Mem ber ed Ma cr ocycle 1
(centroid-centroid distance 7.12 Å) rather than along the
long axis. They also exist in an edge-to-edge conforma-
tion rather than the more open face-to-face orientation.
w ith Am m on iu m Sa lts. Stoddart et al. have demon-
1
strated by H NMR and high-resolution fast atom bom-
1
(8) (a) Gibson, H. W.; Liu, S.; Gong, C.; J oseph, E. Macromolecules
(9) H NMR and LRFABMS spectra have been submitted as
1
1
1
1
997, 30, 3711. (b) Gong, C.; Gibson, H. W. J . Am. Chem. Soc. 1997,
19, 5862. (c) Gong, C.; Gibson, H. W. Macromol. Chem. Phys. 1997,
98, 2321. (d) Gong, C.; J i, Q.; Glass, T. E.; Gibson, H. Macromolecules
997, 30, 4807. (e) Gong, C.; Gibson, H. W. Angew. Chem., Int. Ed.
Supporting Information.
(10) The minimum number of cyclic C, N, or O atoms required for
the threading of a polymethylene chain is 22. See: Harrison, I. T. J .
Chem. Soc., Chem. Commun. 1972, 231.
(11) Pedersen, C. J . J . Am. Chem. Soc. 1967, 89, 7017.
(12) Izatt, R. M.; Lamb, J . D.; Izatt, N. E.; Rossiter, B. E., J r.;
Christensen, J . L.; Haymore, B. L. J . Am. Chem. Soc. 1979, 101, 6273.
(13) Hanson, I. R.; Hughes, D. L.; Truter, M. R. J . Chem. Soc., Perkin
Trans. 2 1976, 972.
(14) Allwood, B. L.; Shahriari-Zavareh, H.; Stoddart, J . F.; Williams,
D. J . J . Chem. Soc., Chem. Commun. 1987, 1058.
(15) (a) Allwood, B. L.; Spencer, N.; Shahriari-Zavareh, H.; Stoddart,
J . F.; Williams, D. J . J . Chem. Soc., Chem. Commun. 1987, 1061. (b)
Slawin, A. M. Z.; Spencer, N.; Stoddart, J . F.; Williams, D. J . J . Chem.
Soc., Chem. Commun. 1987, 1070.
Engl. 1997, 36, 2331. (f) Gong, C.; Gibson, H. W. J . Am. Chem. Soc.
997, 119, 8585. (g) Gibson, H. W.; Nagvekar, D. S.; Powell, J .; Gong,
1
C.; Bryant, W. S. Tetrahedron 1997, 59, 15197. (h) Gong, C.; Gibson,
H. W. Angew. Chem., Int. Ed. Engl. 1997, 36, 2331. (i) Gong, C.; Gibson,
H. W. Macromolecules 1997, 30, 8524. (j) Gong, C.; Gibson, H. W.
Angew. Chem., Int. Ed. Engl. 1998, 37, 310. (k) Gong, C.; Gibson, H.
W. Macromolecules 1998, 31, 308. (l) Gong, C.; Subramanian, C.; J i,
Q.; Gibson, H. W. Macromolecules 1998, 31, 1814. (m) Gibson, H. W.;
Gong, C.; Liu, S.; Nagvekar, D. Macromol. Symp. 1998, 128, 89. (n)
Gong, C.; Balanda, P. B.; Gibson, H. W. Macromolecules 1998, 31, 5278.
(o) Gong, C.; Gibson, H. W. Macromol. Chem. Phys. 1998, 199, in press.

7
636 J . Org. Chem., Vol. 63, No. 22, 1998
Bryant et al.
6
F igu r e 4. ESIMS for a 1:1 mixture of 1 and 3‚PF .
6
F igu r e 5. ESIMS for a 1:1 mixture of 1 and 4‚PF .
II. Com p lexa tion of 32-Mem ber ed Ma cr ocycle 2
w ith Am m on iu m Sa lts. Encouraged by the result that
relative to that for [2:(3)
2
]‚PF
6
was ∼400:1. Also observed
was a peak at m/z 734.2, which is the [2]pseudorotaxane
[2:3]. The peak intensity for [2:3] was approximately
90% as large as that of 2 alone.9
bis(p-phenylene)-34-crown-10 (BPP34C10, 8) forms a [3]-
3
pseudorotaxane with 3‚PF
6
, we investigated the com-
plexation between 2 and 3‚PF
6
. Because the threading
X-ray crystallography confirmed the [3]pseudorotaxane
and dethreading processes are fast on the NMR time
scale, one observes a time-averaged coalesced signal for
structure for [2:(3) ]‚2PF6 (Figure 8). The complex
2
resides on an inversion center, with two N-H- -O hy-
9
the “complexed” and “uncomplexed” forms. The overall
1
association constant, as measured by H NMR (CD
3
CN),
(
16) The overall association constant was determined by a titration
method where [3‚PF ] . [2]. For the method, see: Dobson, B.; Foster,
R.; Bright, A. A. S.; Foreman, M. I.; Gorton, J . J . Chem. Soc. B 1971,
286. The association constant for the 2:1 complex between 3‚PF and
-
2 16
was ∼5 ( 2 M
.
The FABMS results corroborate the
formation of a 1:2 complex by the presence of a peak at
6
1
6
m/z 1077.6, corresponding to the [3]pseudorotaxane
3
4
bis(p-phenylene)-34-crown-10 was estimated to be higher (∼10 -10
-
1
[2:(3)
2
]‚PF
6
. The ratio of peak intensities for 2 alone
M
[sic]).

Complexation of Crown Ethers and Ammonium Ions
J . Org. Chem., Vol. 63, No. 22, 1998 7637
6
F igu r e 6. ESIMS for a 1:1 mixture of 1 and 5‚PF .
F igu r e 8. Side-on and top views of the X-ray structure of the
pseudorotaxane [2:(3)
for clarity). The hydrogen bonds have the following distances
2
6 6
]‚2PF (PF anions have been omitted
and angles: [N-O] 3.02 Å, 2.88 Å; [H-O] 2.12 Å, 1.98 Å;
[N-H- -O] 176°, 170°. The aromatic-aromatic edge-to-face
interactions have the following parameters: centroid-centroid
distance, 5.50 Å; C-H- -centroid angle, 140°; H-centroid
distance, 3.48 Å.
must be noted, however, that the interaction is a second-
ary stabilization interaction and that hydrogen bonding
is the much stronger, primary stabilizing variable in
these systems. Using CPK models, it was found that the
addition of two extra methylene units to the ammonium
salt 3‚PF
6
6
to give 5‚PF might make it possible to increase
the face-to-face π stacking affinity and thus increase the
F igu r e 7. X-ray structure of 26-membered macrocycle 1 (a)
contribution of the secondary stabilizing interaction.
ORTEP drawing and (b) space-filling representation.
The formation of the [3]pseudorotaxane [2:(5)
caused a small change in the chemical shifts for the time-
averaged proton signals of both species.9 FABMS de-
tected only a 1:1 complex, as evidenced by a peak at m/z
62.2, which may correspond to the pseudorotaxane
2
]‚2PF
6
drogen bonds per ammonium salt stabilizing the interac-
tion. The hydrogen bonds involve alternate 1,3-ether
oxygens [O(2), O(3); O(2a), O(3a)] on the same ethyl-
eneoxy bridge. Further stabilization occurs from two
aromatic-aromatic edge-to-face interactions17 between
one of the ortho aromatic hydrogen atoms of each
ammonium ion and a resorcinol ring. There appear to
be no strong stabilizing interactions between the com-
plexes in the crystal lattice.
7
complex [2:5]. The peak intensity for [2:5] was ap-
9
proximately 55% as large as that of 2 alone. Both of
these observations suggest a lower association constant
for this system than that for the complex between 2 and
‚PF . The lower association constant is probably due
6
3
to the decreased acidity of the benzylic methylene groups
and the ammonium center. Because there is no longer
Stoddart et al. have demonstrated that face-to-face π
stacking further stabilizes the complexation of some of
the crown ether/ammonium salt pseudorotaxanes.3 It
2
an sp carbon beta to the ammonium center, the through-
bond effects that increase the acidity of the ammonium
center in 3‚PF
X-ray crystallography did confirm the structure of the
3]pseudorotaxane [2:(5) ]‚2PF (Figure 9). The complex
is stabilized by two N-H- -O hydrogen bonds per am-
6
are not as profound in 5‚PF
6
.
(
17) (a) J orgensen, W. L.; Severance, D. L. J . Am. Chem. Soc. 1990,
1
12, 4768. (b) Grossel, M. C.; Cheetham, A. K.; Hope, D. A.; Weston,
S. C. J . Org. Chem. 1993, 58, 6651. (c) Paliwal, S.; Geib, G.; Wilcox, C.
S. J . Am. Chem. Soc. 1994, 116, 4497.
[
2
6

7
638 J . Org. Chem., Vol. 63, No. 22, 1998
Bryant et al.
ether to form pseudorotaxanes has been demonstrated
here. The 32-membered crown ether 2 forms complexes
-
2
in solution as determined by NMR (K
a
≈ 5 M in
acetone-d at 22 °C). The complexes are stable enough
6
to be detected in the gas phase by MS and were obtained
in single crystal form. However, it appears that the 26-
membered macrocycle 1 does not efficiently form com-
plexes in solution, but such structures were observed by
MS.
Because of its small cavity size, 1 can only form 1:1
complexes with ammonium salt moieties, thus simplify-
ing analyses of possible systems that incorporate its
structure. However because the complexation does not
occur to an appropriate extent in solution, the 26-
membered macrocycle is not a suitable choice for use in
supramolecular assembly with secondary ammonium ion
species but does offer opportunities for selective su-
pramolecular self-assembly.
The formation of a variety of novel supramolecular
structures, including main-chain and side-chain polyro-
taxanes,1
a,c,8
based on the above-mentioned ammonium
salt moieties and bis(m-phenylene)-32-crown-10 units
does appear possible and is currently under study in our
laboratories.
Exp er im en ta l Section
Gen er a l Meth od s. Reagent grade reactants and solvents
were used as received unless otherwise specified. Bis(m-
1
8
phenylene)-26-crown-8 (1), bis(m-phenylene)-32-crown-10
F igu r e 9. Side-on and top views of the X-ray structure of the
pseudorotaxane [2:(5) (PF anions have been omitted
for clarity). The hydrogen bonds have the following distances
1
9
3a
(
2), dibenzylammonium hexafluorophosphate (3‚PF
di-n-butylammonium hexafluorophosphate (4‚PF
prepared by literature methods. H NMR spectra were
recorded at ambient temperature on a 400-MHz spectrometer.
6
3
), and
were
2
]‚2PF
6
6
a
6
)
1
and angles: [N-O] 2.85 Å, 2.84 Å; [H-O] 1.96 Å, 1.93 Å;
[N-H- -O] 165°, 175°. The aromatic-aromatic edge-to-face
Dip h en eth yla m m on iu m Hexa flu or op h osph a te (5‚P F
A solution of C CH CHO (5.38 g, 44.8 mmol), C CH CH
NH
6
).
interactions have the following parameters: centroid-centroid
distance, 4.83 Å; C-H- -centroid angle, 142°; H-centroid
distance, 2.80 Å.
6
H
5
2
6
H
5
2
2
-
2
(5.45 g, 45.0 mmol), and ∼75 mL of toluene was heated
at reflux with a Dean-Stark trap for 2 h and then cooled to
room temperature. The solvent was removed by rotoevapo-
monium salt involving alternate 1,3-ether oxygens [O(2),
O(3); O(2a), O(3a)] on the same ethyleneoxy bridge.
There is also further stabilization by two aromatic-
aromatic edge-to-face interactions. However in this case,
the interactions occur between the aromatic rings of the
two ammonium ions and not the benzyl groups with the
resorcinol rings of the macrocycle. Thus, the anticipated
π stacking of 5‚PF with 2 was not observed. There
6
appear to be no strong stabilizing interactions between
the complexes in the crystal lattice.
ration to give a yellow oil. The oil was dissolved in CH
100 mL), and NaBH (1.7 g, 44.8 mmol) was added over 1 h.
The resulting suspension was heated at reflux for 15 min.
Deionized (DI) H O (100 mL) was then added. The solvent
was removed by rotoevaporation, and another 100 mL of DI
O was added at ∼0 °C. A tacky, yellow oil was observed,
and the H O was decanted. CH OH (25 mL) was added to
3
OH
(
4
2
H
2
2
3
the oil followed by 2 M HCl (250 mL) at ∼0 °C. The resulting
solution was stirred for 2 h. A yellow oil was observed in the
bottom of the flask. The CH
3 2
OH/H O layer was decanted. The
solvents were removed by rotoevaporation to give a yellow
solid. Mp: 264.8-266.2 °C (lit. 265-266 °C). 1H NMR (400
MHz, DMSO-d , ambient T): δ 7.26 (m, 10H), 2.94 (m, 8H).
C NMR (100 MHz, DMSO-d , ambient T): δ 137.6, 128.7,
26.8, 40.0, 33.0. The chloride salt was stirred in hot H O,
and solid NH PF was added until precipitation ceased. The
20
The ability of 2 to adapt its conformation to include
different ammonium ions is evident by comparing the
6
1
3
1
3
6
crystal parameters of the pure macrocycle to those of
the macrocycle in [2:(3) ]‚2PF and [2:(5) ]‚2PF (Table
). The all-gauche conformation of the ethyleneoxy
1
2
2
6
2
6
4
6
1
white precipitate was filtered and then dried in a desiccator.
bridges is maintained in both complexes. Although there
appears to be little change in the distances between the
Yield: 12.08 g (72.3%). Mp: 155 °C (sublimes). 1H NMR (400
MHz, CD CN, ambient T): δ 7.31 (m, 10H), 3.23 (t, J ) 8.4
3
1
3
NH
change substantially. The macrocycle in [2:(3)
expands in both dimensions relative to 2 alone, whereas
in [2:(5) ]‚2PF it expands along one axis but shrinks
along the other. Also, the centroid-centroid distances
of the aromatic rings of the macrocycle increase in [2:(3) ]‚
PF but decrease in [2:(5) ]‚2PF relative to pure 2.
2
centers, the dimensions of the macrocyclic cavity
Hz, 8H), 2.94 (t, J ) 8.4 Hz, 8H). C NMR (100 MHz, DMSO-
2
]‚2PF
6
d
6
, ambient T): δ 136.9, 128.6, 126.8, 47.7, 31.5.
Ma ss Sp ectr oscop ic An a lysis of Com p lexes. Equimolar
solutions of both components were made in acetone, and the
solvent was allowed to evaporate slowly. HRFABMS: m/z
2
6
6
1
46.3384 (dev. 0.6), 578.3715 (dev. 3.8), 674.3614 (dev. -11.7),
2
+
+
077.4785 (dev. -4.1), and 762.4224 (dev. 0.8) for [1:3] , [1:4] ,
2
6
2
6
+
+
+
[1:5] , {[2:(3)
2
]‚PF } , and [2:5] , respectively. The matrix was
6
(
18) Lindsten, G.; Wennerstroem, O.; Isaksson, R. J . Org. Chem.
Con clu sion
The threading of secondary ammonium ions through
1
987, 52, 547.
(
(
19) Delaviz, Y.; Gibson, H. W. Polym. Commun. 1991, 32, 103.
20) Yates, P.; Giles, R. G. F.; Farnum, D. G. Can. J . Chem. 1969,
the cavity of the 32-membered bis(m-phenylene) crown
47, 3997.

Complexation of Crown Ethers and Ammonium Ions
J . Org. Chem., Vol. 63, No. 22, 1998 7639
Ta ble 1. Com p a r ison of Cr ysta l P a r a m eter s (in a n gstr om s)
compound or complex
cavity size
centroid-centroid distance of
aromatic rings in macrocycle
mean plane separation between
aromatic rings of macrocycle
distance between the two
NH2 centers
2
[2:(3)2]‚2PF6
[2:(5)2]‚2PF6
7.8 × 4.9
8.2 × 6.7
8.6 × 4.1
8.8
10.3
8.3
7.0
8.2
7.2
5.6
7.0
N/A
Ta ble 2. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s
data
1
[2:(3)2]‚2PF6
[2:(5)2]‚2PF6
formula
C24H32O8
448.51
monoclinic
P21/n
C56H72F12N2O10P2
1223.10
triclinic
P-1
222(2)
C60H80F12N2O10P2
1279.20
monoclinic
P21/n
formula weight (g/mol)
lattice type
space group
T (K)
298(2)
243(2)
a (Å)
b (Å)
c (Å)
11.382(3)
16.111(2)
12.8971(11)
11.0034(2)
11.88170(10)
13.1435(2)
102.9690(1)
113.7160(10)
96.0480(10)
1495.81(4)
1
1.358
1280
0.167
3.5-56.2
12.250(2)
11.294(4)
23.473(3)
R (deg)
â (deg)
102.479(11)
98.522(5)
ø (deg)
3
V (Å )
2309.2(7)
4
1.290
960
0.096
3211.8(12)
2
1.323
1344
0.158
Z
Dc (g cm-3)
F(000)
µ (mm-1)
Θ range (deg)
no. of unique reflections
measured
observed
2.05-22.50
4.0-45.0
2913
6409
5515
370
5.57
22.35
4182
2264
388
6.67
15.89
no. of variables
R (%)
Rw (%)
290
4.26
9.25
3
-NBA. For ESIMS, the samples were diluted to an unknown
For [2:(3)
2
]‚2PF
6
and [2:(5)
2
]‚2PF
6
: X-ray crystallographic
concentration in acetone/methanol (20/80%), and the fragmen-
tor was run at a low fragmentor potential of 27 V: m/z 646.5,
5
data were obtained using a Siemens CCD-detector-equipped
P4 diffractometer (a four-circle SMART system). Structures
were solved with SHELXTL software. The systematic ab-
sences in the diffraction data were consistent for the reported
+
+
+
78.5, and 647.6 for [1:3] , [1:4] , and [1:5] , respectively.
Deter m in a tion of Associa tion Con sta n t for [2:(3) ]‚
2
2
3
P F
‚PF
6
. Solutions were made in CD
3
CN; the concentration of
space group for [2:(5)
2
]‚2PF
6
and space groups P 1h and P1 for
was varied from 0.05 to 0.60 M while the concentration
[2:(3) ]‚2PF Even though the E statistics for the latter
2
6
.
6
-3
of 2 was held constant at 5.0 × 10 M. The overall association
constant, K ) K , was determined by observing the change
in the chemical shift for the δ′ proton of 2 and solving the
strongly suggested the noncentrosymmetric space group P1,
both possibilities were explored, but only space group P1h
yielded chemically reasonable and computationally stable
results and refinement. The structures were solved using
direct methods, completed by subsequent difference Fourier
synthesis, and refined by full-matrix least-squares procedures.
In both structures, the crown ethers reside on inversion
1
K
2
6
following equation for both K
1 2
and K :
∆
/[3‚PF ] ) -∆K (1 + [3‚PF ] K ) + K {∆ (1) +
6
o
1
6 o
2
1
o
∆o(2)[3‚PF ] K } (1)
centers. In the case of [2:(5)
and C(10)] are disordered between two positions in a 2:1 ratio
and were refined isotropically.
6
]‚2PF , two carbon atoms [C(9)
6 o
2
2
where ∆
complex [2:3]‚PF
nucleus in pure 2 (δ
for the [2:(3) ]‚2PF complex (δ
of the measured nucleus of 2 in the equilibrium mixture
relative to the line position of the same nucleus in a solution
o
(1) ) chemical shift of the measured nucleus in the
relative to the chemical shift of the same
(2) ) corresponding value
6
2
- δ[2:3]‚PF6); ∆
o
Ack n ow led gm en t. This research was funded by the
National Science Foundation (U.S.A.) (Grant CHE-
521738). Mass spectrometry was provided by the
Washington University Mass Spectrometry Resource,
an NIH Research Resource (Grant P41RRR0954).
2
6
2
- δ[2:(3)2]‚2PF6); ∆ ) line position
9
of 2 alone (δ
amount of 3‚PF
2
- δObs); and [3‚PF
6
6 o
] ) total stoichiometric
in the solution.
Cr ysta llogr a p h ic Str u ctu r a l Deter m in a tion . Crystals
suitable for X-ray crystallography were grown for 1 by slow
Su p p or tin g In for m a tion Ava ila ble: Stacked 1H NMR
plots for 1, 1 + 3‚P F
‚P F , 5‚P F ; LRFABMS for 2 + 3‚P F
data and structure refinements for 1, [2:(3)
6
, 3‚P F
6
, 2, 2 + 3‚P F
6
, 3‚P F
6
, and 2, 2 +
evaporation of an acetone solution and for [2:(3)
2
6
]‚2PF and
5
6
6
6
and 2 + 5‚P F
6
; crystal
[
2:(5) ]‚2PF by vapor diffusion of n-pentane into an equimolar
2
6
2
‚2PF
]‚2PF
6
, and [2:(5)
, and [2:(5)
, and [2:(5)
2
]‚
]‚
acetone solution of both components. Crystal, data collection,
and refinement parameters are given in Table 2.
2
2
PF
6
; bond lengths and angles for 1, [2:(3)
]‚2PF
2
6
2
PF6; atomic coordinates for 1, [2:(3)
2
6
2
]‚2PF
6
;
All software and sources of the scattering factors are
contained in the SHELXTL (version 5.03) program library (G.
Sheldrick, Siemens XRD, Madison, WI). All non-hydrogen
atoms were refined with anisotropic displacement coefficients.
All hydrogen atoms were treated as idealized contributions.
For 1: X-ray crystallographic data were obtained using a
Siemens R3m/v single-crystal diffractometer. Structures were
solved with SHELXTL software.
anisotropic displacement coefficients for 1, [2:(3)
2:(5) ]‚2PF ; H-atom coordinates for [2:(3) ]‚2PF
6
PF (22 pages). This material is contained in libraries on
2
]‚2PF
6
, and
and [2:(5) ]‚
[
2
2
6
2
6 2
microfiche, immediately follows this article in the microfilm
version of this journal, and can be ordered from the ACS; see
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J O972162S