Binding properties and self-assembly of C2v- symmetrical resorcin[4]arene tetrabenzoates

Article abstract of DOI:10.1016/j.tet.2012.09.003

In the crystalline state two molecules of resorcin[4]arene tetrabenzoates and four chloride anions form molecular wraps containing two Et ₃NH⁺ cations. The structure and composition of the wraps depend on the length of the alkyl chai

Full text of DOI:10.1016/j.tet.2012.09.003

Tetrahedron 68 (2012) 9429e9434
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Binding properties and self-assembly of C2v-symmetrical resorcin[4]arene
tetrabenzoates
Svetlana V. Shishkina a, Andriy Tarnovskiy b, Vladimir Rozhkov c, Oleg V. Shishkin a, Oleg Lukin d,
,e,f,
*
Alexander Shivanyuk c
a STC “Institute for Single Crystals”, The National Academy of Science of Ukraine, 60 Lenin ave., 61001 Kharkiv, Ukraine
b The Institute of Organic Chemistry, The National Academy of Sciences of Ukraine, 5 Murmanska Str., 02660 Kiev 94, Ukraine
c The Institute of High Technologies, Kyiv National Taras Shevchenko University, 4 Glushkov st., Building 5, 03187 Kiev, Ukraine
d ChemBioCenter Kiev, National Taras Shevchenko University, 62 Volodymyrska str., 01033 Kiev, Ukraine
e Macrochem, 4 Lunacharsky Street, Floor 7, 02002 Kiev, Ukraine
f The Institute of Toxicology and Pharmacology, The National Academy of Medical Sciences, 14 Ejen Pottier Str, 03680 Kiev, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 June 2012
Received in revised form 17 August 2012
Accepted 3 September 2012
Available online 10 September 2012
In the crystalline state two molecules of resorcin[4]arene tetrabenzoates and four chloride anions form
molecular wraps containing two Et3NHþ cations. The structure and composition of the wraps depend on
the length of the alkyl chains at the narrow rim of the macrocycle. Resorcin[4]arene tetrabenzoates
interact with ammonium salts in CDCl3.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Resorcinarenes
Hydrogen bonds
Self-assembly
X-ray crystallography
1. Introduction
crystalline state and in apolar solutions. Only one example of cap-
sular assemblies of tetraesters 2 with Et3NHCl was reported,12
Readily available resorcin[4]arene octaols 11 and their various
derivatives have been used as building blocks for rational design
of container molecules,2 self-assembling capsules,3 and
nanotubes.4
whereas in other cases the re-crystallization of 2$2Et3NHCl resul-
ted in crystals of free tetraesters 2, leaving Et3NHCl in the mother
liquor.
The present research was undertaken in order to study com-
plexation of resorcinarene tetrabenzoates 2 with medium size
alkylammonium salts both in the crystalline state and in solutions.
Regioselective tetraacylation of compounds 15 with arylsulfo-
nylchlorides or (het)aroyl-chlorides in MeCN in the presence of
Et3N gave C2v-symmetrical tetrabenzoates 26 and tetrasulfonates 37
(Fig.1). Compounds 2 and 3 form hydrogen bonded aggregates8 and
molecular capsules9 in the crystalline state and nonpolar solvents.
Chemical modifications of tetraesters 2 and 3 afforded cation re-
ceptors,10 chiral and bridged resorcin[4]arenes11 (Scheme 1).
Re-crystallization of complexes 3$2Et3NHCl from MeCN or EtOH
resulted in negatively charged, hydrogen bonded dimeric hollow
assemblies including two Et3NHþ cations.12 The structure of the
dimeric assemblies was shown to be independent on the type of
arylsulfonyl groups and radicals at the methine bridges of 3. Crystal
structures and spectroscopic studies of tetrasulfonates 3 revealed
the formation of intermolecular hydrogen bonds S]O/HeO in the
2. Results and discussion
Tetrabenzoates 2a and 2b were synthesized through tetraacy-
lation of the corresponding resorcin[4]arene octaols 1 with benzoyl
chloride (MeCN, Et3N, rt). Model octabenzoate 4 was obtained
through the complete acylation of compound 1b with benzoyl
chloride (THF, Et3N, rt). Compounds 2a and 2b precipitated from
the reaction mixtures together with Et3NHCl. Washing the pre-
cipitate with water removed the unbound salt and gave crystalline
complexes 2a,b$2Et3NHCl the stoichiometry of which was de-
termined by 1H NMR spectroscopy. Individual compounds 2a and
2b were obtained through multiple washings of chloroform solu-
tion of the complexes with water. Slow crystallization of tetra-
benzoate 2a from MeCN/H2O (95:5) gave transparent colorless
* Corresponding author. Tel.: þ38 (0)44 5510628; e-mail address: a.shivanyuk@
gmail.com (A. Shivanyuk).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.09.003

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S.V. Shishkina et al. / Tetrahedron 68 (2012) 9429e9434
Fig. 1. (a) Molecular structure of 2a$5MeCN. One of two crystallographically independent molecules is shown. Non-hydrogen bonded MeCN molecules are omitted for the sake of
clarity. (b) Fragment of crystal packing. Hydrogen bonds are shown in broken lines.
Scheme 1.
crystals, which, although unstable without mother liquor, were
suitable for single crystal X-ray diffraction studies.
In the crystalline state a molecule of 2a adopts a boat confor-
mation (Fig. 1) in which the acylated resorcinol rings are quasi-
coplanar and the unsubstituted resorcinol rings are nearly parallel.
Fig. 2. (a) Molecular structure of 4 in 4$4MeCN; (b) infinite columns of molecules 4
As indicated by interatomic distances four OH groups of 2a are sol-
vated by four ordered hydrogen bonded acetonitrile molecules and
no C]O/HO hydrogen bonds are formed. The intramolecular
along the crystallographic a-axis (side view); (c) top view.
ꢀ
interactions as indicated by d(CeO)¼3.28e3.39 A. The cavities
formed by benzoyl groups and n-propyl chains of molecules 4 are
filled by ordered MeCN molecules. The channels between the col-
umns of molecules 4 are also occupied by MeCN molecules. As
indicated by intermolecular distances the MeCN molecules are in-
volved in dipoleedipole interactions between each other and
fragments of molecules 4.
Slow crystallization of 2a$2Et3NHCl from MeCN/H2O (95:5)
resulted in diffraction quality crystals of composition
2a$2Et3NHCl$2MeCN$2H2O. In the crystalline state the molecule of
2a adopts a boat conformation (Fig. 3a and b) similar to that in
ꢀ
HOeC]O distances (2.9e3.2 A) indicate four rather strong dipo-
leedipole interactions. Two ordered MeCN molecules are not hy-
drogen bonded and fill what otherwise would be voids in the crystal.
Crystallization of octabenzoate 4 from MeCN/H2O (95:5) resul-
ted in diffraction quality crystals of solvate 4$4 MeCN. In the crys-
talline state molecule 4 adopts a boat conformation (Fig. 2).
The dihedral angles between quasi-parallel and quasi-coplanar
resorcinol rings are 29.7ꢀ and 1.0ꢀ, respectively. Along the crystal-
lographic a-axis molecules 4 are stacked to form infinite columns
(Fig. 2b and c) stabilized by multiple intermolecular CeH/O

S.V. Shishkina et al. / Tetrahedron 68 (2012) 9429e9434
9431
Fig. 3. Molecular structure of 2a$2Et3NHCl$2MeCN$2H2O (top (a) and side (b) views);
(c) hydrogen bonded dimeric capsules. Et3NHþ cations are omitted for clarity. Selected
distances between hydrogen bonded atoms.
2a$5MeCN. Dihedral angle between the acylated resorcinol units is
70.6ꢀ whereas the angle between the resorcinol rings equals to
40.5ꢀ.
Fig. 4. (a) Molecular structure of 2b$2Et3NHCl$MeCN. Two pairs of symmetry-related
Et3NHþ cations are shown; (b, c) dimeric capsule in the crystalline state.
ꢀ
The HeO/C]O distances (2.96 and 3.25 A) indicate two
intramolecular dipoleedipole attractions as in 2a$5MeCN.
Two molecules of 2a are hydrogen bonded to four chloride an-
ions and four water molecules (Fig. 3c) and form a multicomponent
hydrogen bonded wrap having two portals on both sides of the
cavity. Hydrogen bonded water molecules bridge the neighboring
chloride anions and link them to the carbonyl oxygen atoms of the
benzoyl fragments. Theþ molecular wrap is filled with two
are included in the cavity. The distance between the nitrogen atoms
of the encapsulated cations (7.6 A) is nearly the same as in
ꢀ
2a$2Et3NHCl$2MeCN$2H2O (Fig. 4) and in previously reported di-
meric hollow structures of C2v-symmetrical resorcinarene tetra-
sulfonates 3.12 Thus, the relatively small differences in structures of
2a and 2b cause considerable differences in the crystal structures of
their complexes with Et3NHCl.
ꢀ
symmetry-related Et3NH , which are separated by 6.6 A (NeN
distance) and hydrogen bonded to water molecules. The shortest
distance between the nitrogen of included Et3NHþ and the chloride
ꢀ
anion (4.29 A) is considerably longer than the NeCl distance in the
2.1. Solution studies
crystal of Et3NHCl (3.08 A),13 where cations and anions are directly
ꢀ
hydrogen bonded. The methylene and methyl protons of the en-
In the presence of tropylium or tetramethylammonium cations
self-complementary resorcin[4]-arenetetraesters 2 form dimeric
capsules in CDCl3 stabilized by eight OeH/O]C hydrogen bonds
and four stacking interactions between (het)aroyl fragments.9 The
capsulated Et3NHCl form close contacts (d(CeC)¼2.99, d(CeO)¼
ꢀ
2.55 A) with carbon atoms of the aromatic rings and carbonyl ox-
ygens of molecules 2, which may be attributed to CH/p and CH/O
hydrogen bonding. The two non-encapsulated Et3NHþ assume
well-defined positions and are hydrogen bonded to chloride anions
as in pure Et3NHCl. Thus, a crystal of 2a$2Et3NHCl$2MeCN$2H2O
contains both contact and solvent separated ion pairs of Et3NHCl.
The IR spectrum of tetrabenzoate 2a in the solid state (KBr
guest cations form CH/p and pep bonds to the p-basic interiors of
the capsules. Molecular mechanics calculations14 revealed that
Et3NHþ is too bulky to be included in the dimeric capsule, which
explains the formation of extended solid state capsules in
2a$2Et3NH Cl$2MeCN$2H2O and 2b$2Et3NHCl$MeCN.
pellets) contains a broad band with a maximum at 3455 cmꢁ1
,
The fact that the carbonyl groups of resorcinarene tetra-
benzoates do not form intramolecular hydrogen bonds suggested
that compounds 2 might bind alkylammonium salts through the
inclusion of cations into the resorcinarene cavity and hydrogen
bonding of anions to the OH groups.15
which indicates groups forming weak hydrogen bonds of the
phenolic OH groups. In the IR spectrum of solid 2a$2Et3NH the OH
groups appear as a broad band with maximum at 3197 cmꢁ1, which
most probably indicates the formation of hydrogen bonds
OeH/Clꢁ as found in the crystal structure described above.
Slow crystallization of 2b$2Et3NHCl from MeCN/H2O (95:5) gave
diffraction quality crystals of compositions 2a$2Et3NHCl$MeCN.
In the crystalline state a molecule of 2b adopts a boat conformation
(Fig. 4a) in which the acylated resorcinol rings are quasi-coplanar
(dihedral angle 158.8ꢀ), whereas the unsubstituted ones are nearly
parallel (dihedral angle 24.2ꢀ).
The 1H NMR spectrum of tetrabenzoate 2a measured in CDCl3
contains four singlets for the CH protons of the resorcinol rings,
a triplet for the protons of the methine bridges, and one set of signals
for the ethyl and phenyl groups (Fig. 5 (top)). The OH groups emerge
as a very broad singlet or do not emerge at all most probably due to
the rapid exchange with the protons of residual water in CDCl3. This
can be explained by weakness of hydrogen bonds. The 2D NOESY
experiment revealed that the singlets at 6.91 and 6.84 ppm corre-
spond to the protons in positions 5 of the resorcinol rings. Relatively
small differences in the chemical shifts of these signals indicate that
Eight OH groups form hydrogen bonds to four chloride anions
resulting in the negatively charged dimeric wrap-like assembly
(Fig. 4b). Two Et3NHþ-cations hydrogen bonded to chloride anions

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S.V. Shishkina et al. / Tetrahedron 68 (2012) 9429e9434
Fig. 5. 1H NMR spectrum (300 MHz, CDCl3, 295 K) of 2a (top) and 2aþ2Et3NHCl
(bottom).
molecules 2a assume in solution a somewhat distorted crown (cone)
conformation rather than the pinched boat conformation.16 The
addition of 2 M equiv of Et3NHCl results in downfield shifts of the
proton signals (Fig. 5 bottom) of the resorcinol rings (0.15e0.4 ppm)
and benzoyl fragments (0.1e0.15 ppm). The methylene protons of
Et3NHþ underwent up-field shift of 0.3 ppm most probably due to
shielding effects of aromatic rings of 2a. The NMR dilution experi-
ment revealed that the complex between 2a and Et3NHCl is not
stable on the NMR time scale at ambient temperature.
The model NMR dilution experiments revealed that the addition
of 2 M equiv of Et3NHCl to the solution of resorcinol in CDCl3
resulted in a downfield shift (0.2 ppm) of the signal of protons in
position 2 while all other signals did not change their shape and
position. Thus the change of chemical shifts of protons in positions
5 of the resorcinol rings of 2a and 2b may indicate a conformational
change of the resorcinarene skeleton.
Decreasing the temperature to 223 K results in broadening and
splitting the 1H NMR signals of 2aþ2Et3NHCl. A broad signal at
ꢁ0.47 ppm indicates the inclusion of Et3NHþ in the basic cavity of
2a or its hydrogen bonding oligomers.3c,17 Unfortunately, the poor
quality of the 1H NMR spectra did not allow to establish stoichi-
ometry of complexes between 2a and Et3NHCl at 223 K. It seems
likely that OH groups of 2a form hydrogen bonds to chloride anions
of Et3NHCl in CDCl3.
Fig. 6. 1H NMR spectrum (300 MHz, CDCl3, 295 K) of 2c (a), 2cþH2NCH2CH2OH$2HCl
(b), and 2cþ3 t-BuNH3Cl (c).
saturated solutions revealed a 1:4 molar ratio between resorci-
narene tetrabenzoates and
changes (shifting, broadening, splitting of the signals) for the
resorcinarene components. Since -proline is poorly soluble in
L-proline and considerable spectral
L
CDCl3 this ratio may indicate the stoichiometry of the lipophilic
complex formed. The model experiment with octabenzoate 4
revealed no considerable extraction of L-proline into CDCl3. Al-
though the detailed structure of this complex could not be inferred
from the NMR data it seems plausible that benzoyl and hydroxyl
groups of 2a and 2b can bind four L-proline molecules through C(O)
Oꢁ/HO, NþH2/O]C and NþH2/O interactions.
Sonication of a suspension of H2NCH2CH2OH$HCl in solution of
2d in CDCl3 for 8 h resulted in extraction of equimolar quantity of
the salt according to integration of signals in the 1H NMR spectrum
of the solution (Fig. 6b). The presence of H2NCH2CH2OH$HCl in-
duces considerable changes in positions of protons of the resorcinol
rings and methyne bridges of 2b (Fig. 6a and b) and leads to the
splitting of signals of diastereotopic methylene protons H3.
The addition of t-BuNH3Cl to a solution of 2b in CDCl3 results in
a considerable change in positions and shape of 1H NMR signals for
2b (Fig. 6c), which indicates complexation. Remarkably the
methyne protons of the bridges emerge as doublet of doublets due
to spinespin coupling with the diastereotopic protons of the
neighboring methylene groups. Dilution experiments revealed that
the complex between 2b and t-BuNH3Cl was not stable on the NMR
time scale at 295 K. It should be noted that Me4Nþ, which is com-
parable in size to t-BuNHþ3 forms highly stable dimeric capsules
with 2b stabilized by hydrogen bonds and stacking interactions.
2.2. Calculations
A number of local energy minima are expected for compounds
2. Two major energy minima are different boat conformations of
the resorcinarene macrocycle and many local energy minima cor-
respond to a variety of arrangements of benzoyl groups. Molecular
mechanics (MM) study of the C2v-symmetrical resorcinarene tet-
rabenzoates using the MMX force field was performed as follows.
The structure of 2 was energy-minimized starting from the two
boat conformations with parallel and co-planar unsubstituted
resorcinol rings (Fig. 7). The energy barrier between these confor-
mations was sufficiently high to prevent their interconversion
during the geometry optimization. In both conformations the ar-
rangement of the benzoyl groups was optimized using the dihedral
driver procedure (see Experimental part). The lowest energy cor-
responds to the boat conformation having parallel diacylated res-
orcinol rings (structure A, Fig. 7). Despite the presence of four
intramolecular hydrogen bonds, the second boat conformation
with co-planar diacylated resorcinol rings was found to be
Solutions of tetrabenzoates 2a and 2b in CDCl3 extract
L-proline
from solid phase. The 1H NMR spectroscopic studies of the

S.V. Shishkina et al. / Tetrahedron 68 (2012) 9429e9434
9433
of the hollow assemblies. Thus, depending on the nature of the
guest resorcinarene tetrabenzoates form closed dimeric positively
charges molecular capsules, hydrogen bonded solvates or nano-
sized molecular wraps.
4. Experimental part
4.1. General methods and procedures
All reactions were carried out under open atmosphere with no
precautions taken to exclude ambient moisture. Melting points
were measured with a Buchi melting points apparatus are un-
corrected. 1H and 13C NMR spectra were measured on a Bruker
Avance DRX 500 (500 and 125 MHz, respectively) with TMS as an
internal standard. IR spectra were measured on a Vertex 70
spectrometer.
Fig. 7. MMX force field optimized conformations of C2v-symmetrical resorcinarene
tetrabenzoates.
4.2. General procedure for the preparation of tetrabenzoates 2
Triethylamine (20 mmol) was added in one portion to a stirred
solution of 2 (5 mmol) in dry MeCN (50 ml) and the suspension
formed was stirred for 10 min. Benzoylchloride (20 mmol) was
added to the suspension at vigorous shaking. The precipitate was
dissolved and in 5 min a white solid started to crystallize from the
reaction mixture. The reaction mixture was stirred for 8 h, the
precipitated was filtered off, washed with acetonitrile (2ꢂ20 ml),
and was recrystallized from MeCN/H2O to give analytically pure
2$2Et3NCl. A solution of 2$2Et3NCl (1 g) in CHCl3 (50 ml) was
washed with water (5ꢂ50 ml), the organic layer was separated,
filtered through paper filter, and evaporated in vacuo.
energetically less favorable by about 5 kcal/mol. Given the rela-
tively low precision of molecular mechanics calculations of flexible
structures, either of the boat conformations could be favored in
solution or in the crystalline state depending on experimental
conditions. The main factor influencing the preferred boat con-
former of 2 seems to be the solvent that can either stabilize or
disrupt intramolecular hydrogen bonds.
In optimized conformation C, four hydroxyl groups cannot
form intramolecular hydrogen bonds to the neighboring oxygen
atoms and can be involved in intermolecular hydrogen bonding
like in the crystalline state. Conformation C is predicted to be to
be less stable than conformation A by 15 kcal/mol, probably due
to the lack of intramolecular hydrogen bonding. Hydrogen
bonding between the hydroxyl groups of conformation C and
four MeCN molecules results in a complex the energy of which is
5 kcal/mol lower than the sum of energy of conformer A and four
nonbonding acetonitrile molecules. Although the MM calculation
does not take into account the entropic factors, these results
correlate with the observed capacity of compounds 2 to form
hydrogen bonds to solvent molecules or/and chloride anions (as
described above).
4.2.1. Compound 2a. Yield 37%. Mp >300 ꢀC (MeCN). 1H NMR
(500 MHz, CDCl3)
d
(ppm): 7.99 (d, J¼7.6 Hz, 8H, CH), 7.48 (t,
J¼7.3 Hz, 4H), 7.22 (t, J¼8.4 Hz, 8H, CH), 6.91 (s, 2H, CH), 6.84 (s, 2H,
CH), 6.71 (s, 2H, CH), 6.11 (s, 2H, CH), 4.41 (t, J¼7.5 Hz, 4H, CH),
2.10e1.91 (m, 8H, CH2), 0.91 (t, J¼7.0 Hz, 12H, CH3). 13C NMR
(125 MHz, DMSO-d6)
d (ppm): 164.59, 154.03, 145.71, 135.98,
134.09, 130.17, 129.31, 127.81, 125.39, 125.39, 120.32, 116.45, 102.63,
95.95, 36.86, 28.70, 13.12. Anal. Found %: C, 75.28; H, 5.74. Anal.
Calcd for C64H56O12 %: C, 75.59; H, 5.51.
4.2.2. Compound 2b. Yield 32%. Mp >300 ꢀC (MeCN). 1H NMR
Density functional theory calculations with B3LYP/cc-pvdz basis
set confirmed the conclusions of the above MM studies of resor-
cinarene tetrabenzoate 2a and its complex with acetonitrile.
(500 MHz, CDCl3)
d
(ppm): 8.02 (d, J¼7.0 Hz, 8H, CH), 7.48 (t,
J¼7.3 Hz, 4H, CH), 7.23 (t, J¼8.4 Hz, 8H, CH), 6.89 (s, 2H, CH), 6.86 (s,
2H), 6.12 (s, 2H, CH), 4.48 (t, J¼7.3 Hz, 4H, CH), 2.08e1.84 (m, 8H,
CH2), 1.45e1.14 (m, 8H, CH2), 0.89 (t, J¼7.3 Hz, 12H, CH3). 13C NMR
3. Conclusions
(125 MHz, DMSO-d6) d (ppm): 164.60, 154.08, 145.52, 136.26,
134.09, 130.17, 129.28, 127.96, 125.38, 120.05, 116.43, 102.73, 95.97,
37.30, 34.32, 20.98, 14.34. Anal. Found %: C, 75.93; H, 6.12. Anal.
Calcd for C68H64O48 %: C, 76.11; H, 5.97.
The disposition of four OH and benzoyl groups on the wide rim
of resorcinarene tetrabenzoate 2 does not allow the formation of
strong intramolecular C]O/H-O hydrogen bonds. Such a geome-
try of molecules 2 facilitates the formation of intermolecular hy-
drogen bonds between the OH groups and hydrogen bond
acceptors such as MeCN and H2O molecules, or chloride anions. The
self-complementarity of molecules 4 is the main reason for the
formation of dimeric hydrogen bonded capsules around such
complementary guests like tropylium and tetramethylammonium
cations. In this case the molecular capsule is stabilized through
eight intramolecular hydrogen bonds and four pairs of weaker
stacking interactions while the anion is involved predominantly in
electrostatic interaction with the nanosized capsular cation. The co-
crystallization of tetrabenzoates 2a and 2b with Et3NHCl results in
the formation of nanosized wrap-like structure encapsulating two
Et3NHþ cations. In this case the chloride anions are the components
4.2.3. Compound 4. Compound 1b (1 g, 1.67 mmol) and Et3N (2.1 g,
20.04 mmol) were dissolved in THF (100 ml). Benzoyl chloride
(2.82 g, 20.04 mmol) was slowly added to the solution under vig-
orous stirring. The mixture was stirred for 12 h at room tempera-
ture and the solvent was evaporated. The residue was partitioned
between water and CH2Cl2 (50:50 ml). The organic layer was col-
lected, washed with water (3ꢂ25 ml), and dried over Na2SO4. The
solvent was evaporated and the product was recrystallized from
MeCN to furnish the product as white crystals. Yield 33% (not op-
timized). 1H NMR (CDCl3)
d (ppm): 7.92 (br s, 8H, CH), 7.81 (br s, 8H,
CH), 7.70 (s, 2H, CH), 7.58 (br m, 8H, CH), 7.41 (br m, 10H, CH), 7.34
(br m, 8H, CH), 7.05 (s, 2H, CH), 6.58 (s, 2H, CH), 4.50 (br m, 4H, CH),
2.21 (br m, 4H, CH2), 2.03 (br m, 4H, CH2), 1.24 (br m, 4H, CH2), 1.22

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S.V. Shishkina et al. / Tetrahedron 68 (2012) 9429e9434
(br m, 4H, CH2), 0.99 (br m, 12H, CH3). Anal. Found %: C, 76.82; H,
6.00. Anal. Calcd for C96H88O16 %: C, 77.00; H, 5.88.
was assumed for the dielectric constant. For optimization of the
arrangement of the benzoyl groups the dihedral driver procedure
was applied in which two torsions for the AreOBz and ArOeBz
bonds were changed with the step of 30ꢀ. From the 144 con-
formers, the lowest energy one was minimized with no con-
straints and taken, in turn, as the starting point for the following
rotations of remaining benzoyl groups. B3LYP calculations19 were
carried out using the PCGAMES/Firefly program20 with cc-pVDZ
basis set.21
4.3. X-ray data collection and crystal structure
determinations
X-ray diffraction data were collected on the «Xcalibur-3» dif-
fractometer (graphite monochromated MoK
a radiation, CCD de-
tector,
u
-scans, 2Qmax¼50ꢀ) at 173 K. The structures were solved by
direct methods using the SHELXTL18 package. Positions of hydrogen
atoms were calculated geometrically and refined by riding them on
the carrier atom with Uiso¼nUeq (n¼1.5 for methyl and hydroxyl
groups and n¼1.2 for other hydrogen atoms). The hydrogen atoms
of hydroxyl groups and water molecules in the structure
2a$2Et3NHCl$2MeCN$2H2O were refined in isotropic approxima-
tion. The crystallographic data and experimental parameters are
listed in Table 1. Final atomic coordinates, geometrical parameters,
and crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre, 11 Union Road, Cambridge CB2 1EZ,
UK (fax: þ44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk). The
deposition numbers are given in Table 1.
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R. M.; Antesberger, J.; Dalgarno, S. J.; Thallapally, P. K.; Atwood, J. L. Angew.
Chem., Int. Ed. 2006, 45, 6221e6224.
Table 1
X-ray crystallographic data
2a$5MeCN
2a$5Et3NHCl$2 4$5MeCN
MeCN$2H2O
2b$2Et3NHCl$
MeCN
5. Tunstad, L. M.; Tucker, J. A.; Dalcanale, E.; Weiser, J.; Bryant, J. A.; Sherman, J. C.;
Helgeson, R. C.; Knobler, C. B.; Cram, D. J. J. Org. Chem. 1989, 54, 1305e1312.
ꢀ
a, A
19.495(4)
29.830(4)
24.615(4)
90
103.24(2)
90
13,934(4)
5196
Monoclinic Monoclinic
P21/c
4
100
0.080
1.173
50
15.359(3)
30.396(6)
16.977(3)
90
9.8208(3)
35.423(1)
25.0371(9) 26.594(1)
22.362(1)
26.420(2)
€
6. Shivanyuk, A.; Paulus, E. F.; Bohmer, V.; Vogt, W. J. Org. Chem. 1998, 63,
ꢀ
b, A
6448e6449.
ꢀ
c, A
7. (a) Lukin, O. V.; Pirozhenko, V. V.; Shivanyuk, A. N. Tetrahedron Lett. 1995, 36,
7725e7728; (b) Lukin, O.; Shivanyuk, A.; Pirozhenko, V. V.; Tsymbal, I. F.;
Kal’chenko, V. I. J. Org. Chem. 1998, 63, 9510e9516.
8. Shivanyuk, A. Chem. Commun. 2001, 1472e1473.
ꢀ
ꢀ
ꢀ
a
,
90
90
92.191(5)
90
15,700(2)
5936
b
,
92.27(1)
90
91.475(3)
90
g
,
€
3
9. (a) Shivanyuk, A.; Paulus, E. F.; Bohmer, V. Angew. Chem., Int. Ed. 1999, 38,
ꢀ
V, A
7920(2)
3096
8707.2(5)
3488
2906e2909; (b) Shivanyuk, A. Tetrahedron 2005, 61, 349e352.
10. (a) Eisler, D. J.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 6352e6365; (b) Eisler, D.
J.; Kirby, C. W.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 7626e7634; (d) Eisler, D.
J.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 8192e8202.
F(000)
Crystal system
Space group
Z
Monoclinic Monoclinic
P21/n
4
P21/c
4
C2/c
8
100
0.143
1.176
50
€
11. (a) Shivanyuk, A.; Schmidt, C.; Bohmer, V.; Paulus, E. F.; Lukin, O. V.; Vogt, W. J.
T, K
100
100
Am. Chem. Soc. 1998, 120, 4319e4326; (b) Shivanyuk, A.; Rafai Far, A.; Rebek, J.,
Jr. Org. Lett. 2002, 4, 1555e1558; (c) Arnott, G.; Page, P. C.; Heaney, H.; Hunter,
R.; Sampler, E. P. Synlett 2001, 412e414.
m
, mmꢁ1
0.147
1.217
50
0.085
1.262
60
Dcalcd, g/cm3
Qmax, grad
Measured
reflections
2
€
12. Shivanyuk, A.; Paulus, E. F.; Rissanen, K.; Kolehmainen, E.; Bohmer, V. Chem.
41,824
20,623
90,464
54,590
dEur. J. 2001, 7, 1944e1951.
13. James, M. A.; Cameron, T. S.; Knop, O.; Neuman, M.; Falk, M. Can. J. Chem. 1985,
63, 1750e1758.
Independent
reflections
Rint
Reflections
with F>4s(F)
22,159
12,696
25,254
13,643
14. Serena Software, Dr. Kevin E. Gilbert, P.O. 3076, Bloomington, IN 47402.
15. See for example: Winstanley, K. J.; Sayer, A. M.; Smith, D. K. Org. Biomol. Chem.
2006, 4, 1760e1767.
0.133
3730
0.057
6235
0.067
14,494
0.071
9113
16. Abis, L.; Dalcanale, E.; Du Vosel, A.; Spera, S. J. J. Org. Chem. 1988, 53,
5475e5479.
Parameters
1663
981
1144
941
17. For example methyl protons of Et3NHþ encapsulated in hexameric resorcinar-
ene capsules emerge at ꢁ0.08 ppm: (a) Palmer, L.; Shivanyuk, A.; Yamanaka, M.;
Rebek, J., Jr. Chem. Commun. 2005, 857e858.
R1
wR2
S
0.047
0.063
0.534
876625
0.052
0.123
0.813
876624
0.069
0.173
1.027
876627
0.081
0.206
1.026
876626
18. Sheldrick, G. M. SHELXTL PLUS. PC Version A system of computer programs for
the determination of crystal structure from X-ray diffraction data; V. 5.1. 1998,
1998.
CCDC number
19. (a) Hohenberg, P.; Kohn, W. Phys. Rev. 1964, 136, B864eB871; (b) Kohn, W.;
Sham, L. J. Phys. Rev. 1965, 140, A1133eA1138; (c) Miehlich, B.; Savin, A.; Stoll,
H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200e206.
20. Granovsky, A. A. PC GAMES Version 7.0. http://classic.chem.msu.su/gran/
gamess/index.html.
4.4. Calculations
Molecular mechanics calculations were performed using the
MMX force field as implemented in PCMODEL 7.5. Energy mini-
mization was accomplished with a conjugate gradient procedure.
A root-mean-square (rms) gradient of 0.01 kcal/mol or less was
assumed as a condition of energy convergence. A value of 1.5 D
21. (a) Dunning, T. H., Jr. J. Chem. Phys. 1989, 90, 1007e1024; (b) Woon, D. E.;
Dunning, T. H., Jr. J. Chem. Phys. 1994, 100, 2975e2989; (c) Kendall, R. A.;
Dunning, T. H., Jr..; Harrison, R. J. J. Chem. Phys. 1992, 96, 6796e6807; (d) Woon,
D. E.; Dunning, T. H., Jr. J. Chem. Phys. 1993, 98, 1358e1372; (e) Wilson, A. K.;
Woon, D. E.; Peterson, K. A.; Dunning, T. H., Jr. J. Chem. Phys. 1999, 110,
7667e7677.