Structural conformers of symmetry substituted resorcin[4]arenes

Article abstract of DOI:10.1016/j.molstruc.2003.08.004

Methylresorcin[4]arenes in the C_2h and C_4v symmetrical chair and crown conformers, and resorcin[4]arene in the C _2v symmetrical boat conformation have been synthesized from the typical one-pot acid-catalyzed reaction and s

Full text of DOI:10.1016/j.molstruc.2003.08.004

Journal of Molecular Structure 659 (2003) 119–128
www.elsevier.com/locate/molstruc
Structural conformers of symmetry substituted resorcin[4]arenes
Shaobin Miaoa, Richard D. Adamsb, Dian-Shun Guoc, Qian-Feng Zhanga,b,
*
aDepartment of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, Anhui 243002, China
bDepartment of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, SC 29208, USA
cDepartment of Chemistry, Shandong Normal University, Jinan 250014, China
Received 23 June 2003; revised 2 August 2003; accepted 7 August 2003
Abstract
Methylresorcin[4]arenes in the C2h and C4v symmetrical chair and crown conformers, and resorcin[4]arene in the C2v
symmetrical boat conformation have been synthesized from the typical one-pot acid-catalyzed reaction and structurally
characterized. Solvation of organic molecules in the crystalline state of the chair and boat isomers shows inter-resorcin[4]arene
interactions held together by intermolecular hydrogen bonds involving solvate molecules. The intramolecular hydrogen bonds
naturally form in the crown isomer of the substituted resorcin[4]arenes.
q 2003 Elsevier B.V. All rights reserved.
Keywords: Structure; Resorcin[4]arene; Hydrogen-bonding; Self-assembly; Supramolecular chemistry
1. Introduction
on the reaction conditions, with the chair and the
crown conformers being the kinetically and thermo-
dynamically determined products, respectively.
Atwood et al. reported the syntheses of resorci-
n[4]arenes containing substituted phenyl rings as the
R groups and found that the isolated product only
has the chair isomer [3–5]. Cram and coworkers
also found that the condensation of 2-methylresor-
cinol with benzaldehyde gave methylresorcin[4]ar-
ene exclusively in the chair conformation (.97%),
indicating the possible influence of the methyl group
on the conformation of the methyl-resorcin[4]arene
[6,7]. Indeed, most of crown isomer resorcin[4]ar-
enes may be isolated from the reaction of alkyl
aldehydes with resorcinol [8]. Thus, the formation
of four stereoisomers shown as Chart 1 is interest-
ingly influenced by the presence of the alkyl or aryl
substituents R from the aldehydes.
Resorcin[4]arenes or substituted resorcin[4]arenes
are easily obtained by acid-catalyzed condensation
of resorcinol or substituted resorcinols with a variety
of aliphatic as well as aromatic aldehydes in a
simple one-pot reaction [1]. The main product often
adopts four different conformers (Chart 1), crown
(rccc, C4v), boat (rcct, C2v), chair (rctt, C2h), and
¨
saddle (rtct, D2d). Hogberg described the conden-
sation of various benzaldehydes with resorcinol and
found the only two different stereoisomeric octols
were formed, namely, the chair and the crown
conformers [2]. The ratio of both isomers depends
*
Corresponding author. Tel.: þ865552400551; fax:
þ865552400552.
E-mail address: zhangqf@ahut.edu.cn (Q.-F. Zhang).
0022-2860/03/$ - see front matter q 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2003.08.004

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S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
2. Results and discussion
Resorcin[4]arenes 1, 2, 5 and 6 were synthesized in
one-pot reaction using a similar procedure to that
outlined by Cram et al. to produce the accordingly
resorcin[4]arenes [1,6]. Condensation of 2-methylre-
sorcinol with p-methylbenzaldehyde in a warm (ca.
70 8C) 1:1 mixture of 95% ethanol and HCl (37% in
water) afforded 94% yield of the methylresorcin[4]ar-
ene 1 exclusively in the chair conformation. Similar
reaction used with resorcinol instead of 2-methylre-
sorcinol gave 87% yield of resorcin[4]arene 2 in the
boat conformation. High temperature and long time in
the course of reaction resulted in a lot of orange
impurities to contaminate with the off-white products,
but recrystallization of 1 and 2 from hot CH3CN
solution may remove a little impurity to give
analytical crystalline products. Compounds 1 and 2
possessed poor solubility properties, only dissolving
in some polar solvents, such as DMF and 2-
methoxyethanol. The chair conformer product was
expectably isolated from the reaction of 2-methylre-
sorcinol and substituted benzaldehyde; while the boat
conformer product was unexpectedly obtained from
the reaction of resorcinol and substituted benzal-
dehyde in a moderate condition. The similar reactants
containing substituted benzaldehyde such as p-
hydroxy- and p-methoxy-benzaldehyde generally
gave the chair conformer products [3,4]. Our present
reaction was repeated more time, we found the yield
of the boat conformer product is influenced by the
reaction temperature and time, namely, the yield in
the boat conformation will be gradually reduced with
the rise of temperature and elongation of the reaction
time. Thus, resorcin[4]arene 2 formed in the boat
isomer is regarded as the kinetically favored product
with the chair isomer thermodynamically more
favored (Scheme 1) [18].
Chart 1.
The supramolecular chemistry of the crown isomer
resorcin[4]arenes is extensively investigated because
the bowl-shaped cavity as a useful building block can
be formed by linking pair of the eight adjacent
phenolic groups of a crown resorcin[4]arene [9–11].
The synthetic chemistry of the crown methylresorci-
n[4]arenes is also well established because four
methyl groups in the bowl-shaped cavitand can be
effectively utilized for the functional derivatization as
the supramolecular templates [12–14]. Although
many examples of the crown isomer have been
structurally authenticated, there are only a few
examples of the chair conformer, and the examples
of the boat conformer are even less in the literature
[15,16]. To further understand the structural con-
formers of symmetry substituted resorcin[4]arenes
[17], we are currently interested to seek resorcin[4]ar-
enes possessing the increased numbers of potential
hydrogen-bonding functionalities in the quest for
more extended self-assembled structures. Herein, we
present the syntheses and structures of new resorci-
n[4]arenes and methylresorcin[4]arenes containing
symmetry C2h chair, C2v boat and C4v crown
conformers. It is therefore expected to extend the
study of supramolecular chemistry of the substituted
resorcin[4]arenes and their functional derivatives.
For the furtherance of understanding the confor-
mers of compounds 1 and 2, both molecular structures
were determined by X-ray diffraction. As shown in
Fig. 1, methylresorcin[4]arene 1 indeed adopts the C2h
symmetrical chair conformation in which two oppo-
site aryl rings of the macrocyclic framework are
˚
coplanar with the deviation of 0.01 A from the least
squares plane, two others are nearly perpendicular to
this plane with the dihedral angle of 86.78. The methyl
groups of these rings in the macrocyclic framework

S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
121
Scheme 1. Reagents and conditions: (i) 95% EtOH, 37% HCl, 65–75 8C; (ii) (CH3CO)2O, CH3CN, RT; (iii) 95% EtOH, 37% HCl, 60–65 8C.
also point in opposite directions. The toluene rings
connected to the bridging carbon atoms assume the
axial positions; two of them point up and two down
leading to dihedral angles of 86.4 and 88.18 with
coplanar resorcinol rings. The average separation
between adjacent oxygen atoms of the resorcinol rings
˚
is 4.02 A which is too long to allow intramolecular
hydrogen-bonding, rather, these groups form hydro-
gen-bonds with the DMF solvent molecules. Fig. 2
shows six DMF molecules around the methylresorci-
n[4]arene, four form hydrogen-bonds with hydroxyl
moieties of resorcinols, two additional DMF mol-
ecules don’t participate in hydrogen-bonding, instead,
filling voids in the crystal lattice. The distances
between the oxygen atoms of hydroxyl groups and
hydrogen-bonded DMF molecules range from 2.724
˚
to 2.836 A. In contrast, resorcin[4]arene 2 shown in
Fig. 3 adopts the C2v boat conformation where the
toluene residues and the resorcinol constituents
segregate into different layers. The two opposite aryl
rings of the macrocyclic framework are almost
˚
coplanar with the deviation of 0.16 A from the least
squares plane, the two others facing each other are
perpendicular to this plane with the average dihedral
Fig. 1. Molecular conformation of the rctt chair resorcarene 1 (side
view), 30% thermal ellipsoids are shown.

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S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
Fig. 2. The intermolecular hydrogen bonds between chair isomer 1 (top view) and DMF solvents are clearly shown.
angle of 86.28. The toluene rings connected to the
bridging carbon atoms act as four-legged piano stool,
all of them point down leading to the tilt angles of
91.8–97.48 with the macrocyclic framework plane.
The long distances between neighboring oxygen
atoms of the resorcinol rings (O1· · ·O4 ¼ 4.55 and
˚
O2· · ·O7 ¼ 4.26 A) clearly indicate that the boat
isomer of 2 precludes the intramolecular hydrogen
Fig. 3. Molecular conformation of the rcct boat resorcarene 2 (side view), 30% thermal ellipsoids are shown.

S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
123
Fig. 4. The intermolecular hydrogen bonds between boat isomer 2 (top view) and DMF solvents are clearly shown.
bonding among the hydroxyl groups on the aromatic
resorcinol rings. Thus, intermolecular hydrogen bonds
are formed between hydroxyl groups and DMF
solvent molecules. Fig. 4 shows six DMF molecules
and one boat-shaped resorcin[4]arene molecule 2.
Five DMF form hydrogen bonds with hydroxyl
moieties of resorcinols, one additional DMF molecule
just fills voids in the crystal lattice. It is interesting to
note that each of the hydroxyl groups of the central
aromatic macrocyclic rings form single hydrogen-
bonds to a DMF molecule with O· · ·O distances
gave octakis-(acetoxy)-resorcin[4]arene 3 or 4,
respectively, which was sufficiently soluble in
CH2Cl2, acetone and toluene for the characterization.
Single crystal of 3 was therefore isolated from CH2Cl2
solution. In accordance with NMR spectroscopic and
mass spectrometric data, 3 and 4 were found to be the
peracelyated cyclic calixarene tetramers of their
according 1 and 2, respectively. Thus, similar to
methylresorcin[4]-arene 1, the rctt isomer 3 adopts a
chair conformation with C2h symmetry; similarly,
resorcin[4]arene 4 is also expected for the boat
conformation of the rcct isomer. The conformational
assignment for 3 was confirmed by the single-crystal
X-ray analysis shown in Fig. 5. Thus, acetylation of
the rctt and rcct isomers cannot affect their according
˚
ranging from 2.642 to 2.742 A.
Cram and coworkers have confirmed that the
limitation of low solubility of resorcin[4]arenes is
potentially due to conformationally mobile groups
substituted in the 4-positions of the phenyls [6,7].
Compounds 1 and 2 with four toluene moieties can be
only dissolved in the very polar solvents such as
DMSO and DMF, and are sparsely soluble in THF and
CH2Cl2. In order to improve the solubility in apolar
media, peracetylation was performed. Treatment 1 or
2 with 8 equiv. acetic anhydride in CH3CN solution
¨
conformers, as Hogberg’s conformation [2] and the
previous results reported [6,19].
Although resorcinarenes and substituted resorci-
narenes have large and extended surfaces for
intermolecular interactions, the special feature for
bowl-shaped cavitand construction having strong
intramolecular hydrogen bonds may provide

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S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
Fig. 5. Molecular conformation of the rcct chair 3 seen from side view, 30% thermal ellipsoids are shown.
functional groups for further elaboration needed [20].
For example, the study of multicomponent supramo-
lecular assemblies held by hydrogen-bonding and
functional molecular cavitands is mostly motivated
from the interesting ccc crown conformer with C4v
symmetry [9,10,21,22]. The condensation of isovaler-
aldehyde with resorcinol or 2-methylresorcinol
afforded the ccc isomer compound 5 or 6 with tetra-
iso-butyl groups, which was unambiguously con-
firmed by NMR spectral data and single-crystal X-ray
diffraction analyses. Fig. 6 shows the structure of
tetramethyl-resorcin[4]arene 5. The molecule adopts a
‘bowl’ structure with four iso-butyl forming ‘legs’ to
attach the bowl. The average dihedral angle between
two adjacent aromatic rings in the bowl is 52.98. It
may be mentioned that the molecule is held together
in the crystal by an extensive network of hydrogen
bonding involving the hydroxyl groups on the bowl
and solvate species (two DMF molecules) (see Fig. 7).
The overall molecule retains the C4 symmetry due to
the orientation in the solution, but the structure of the
bowl-shaped crown conformer with C4v symmetry is
clearly shown in the solid state [23]. This ccc-bowl
structure may provide the highest ability of supramo-
lecular assembly [24].
In summary, we demonstrated structural confor-
mers of symmetry substituted resorcin[4]arenes by X-
ray crystallography. Condensation of aliphatic
aldehydes and resorcinol or 2-methylresorcinol yields
ccc-bowl-shaped crown conformation with C4v sym-
metry. With 4-substituted benzaldehydes and resorci-
nol or 2-methyl-resorcinol, either ctt-chair product
with C2h symmetry or cct-boat product with C2v
symmetry was produced. It is clear to indicate that
methyl moieties of substituted resorcin[4]arenes may
result in the structural stereoselectivities. The remark-
able thing about the results is that given the large
numbers of effects, the stereoselectivities are high

S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
125
Fig. 6. Molecular conformation of the rccc crown resorcarene 5 seen from side view, showing intermolecular hydrogen bonds.
Fig. 7. Unit-cell contents for 5·2DMF, viewed along b axis. The intermolecular hydrogen bonds were showed at dash lines.

126
S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
enough to provide practical yields of highly desirable
starting materials for cavitand and carcerend
syntheses.
meta to CH3), 6.82 (d, J ¼ 7.8 Hz, 4H, ArH, ortho to
CH3), 8.44 (bs, 8H, ArOH). MS (FAB): m/z 905.3
(Mþ, calcd 905.1). Anal. calcd for C60H56O8·H2O: C,
78.07; H, 6.33. Found: C, 78.21; H, 6.42.
rcct-2,8,14,20-Tetrakis-(4-methylphenyl)-resorci-
n[4]arene 2. Yield 10.52 g (87%) of off-white solid:
mp . 304 8C. 1H NMR [300 MHz, (CD3)2SO, ppm]:
d 2.26 (s, 12H, ArCH3), 5.50 (s, 4H, Ar3CH), 6.09 (s,
4H, ArH, ortho to OH), 6.24 (bs, 4H, ArH, meta to
OH), 6.54 (d, J ¼ 7.6 Hz, 4H, ArH, meta to CH3),
6.78 (d, J ¼ 7.6 Hz, 4H, ArH, ortho to CH3), 8.62 (bs,
8H, ArOH). MS (FAB): m/z 849.1 (Mþ, calcd 849.0).
Anal. calcd for C56H48O8·2H2O: C, 76.00; H, 5.92.
Found: C, 76.23; H, 6.07.
3. Experimental section
3.1. General
All reactions were carried out under a nitrogen
atmosphere, and solvents were purified, if necessary,
by standard procedure prior to use. Ethanol (95%) was
used as received. Dimethylformamide (DMF) and
˚
acetic anhydride were stored over 4 A molecular
sieves. 2-methylresorcinol, resorcinol, p-methylben-
zaldehyde, isovaleraldehyde and acetic anhydride
were purchased from Aldrich and used as received.
Infrared spectra were recorded on a Nicolet 170sx FT-
rctt-2,8,14,20-Tetrakis-(4-methylphenyl)-4,6,10,12,
18,22,24-octakis-(acetoxy)-5,11,17,23-tetramethyl-
resorcin[4]arene 3. Yield 1.79 g (91%) of white solid:
1
mp . 330 8C. H NMR [300 MHz, CDCl3, ppm]: d
1
IR spectrophotometer as solutions in CaF2 cells. H
1.92 (s, 12H, ArCH3), 2.15 (s, 24H, CH3CO), 2.26 (s,
12H, ArCH3), 5.51 (s, 4H, Ar3CH), 6.52 (d,
J ¼ 7.6 Hz, 4H, ArH, meta to CH3), 6.86 (d,
J ¼ 7.6 Hz, 4H, ArH, ortho to CH3). MS (FAB): m/z
1241.9 (Mþ, calcd 1241.4). Anal. calcd for C76H72-
O16·CH2Cl2: C, 69.73; H, 5.62. Found: C, 69.67; H,
5.71.
NMR spectra were recorded on a Bruker DPX-300
Fourier-transform spectrometer with reference to
SiMe4. Mass spectra were obtained on a Finnigan
TSQ-700 spectrometer.
3.2. General procedure
rcct-2,8, 14, 20- Tetrakis- (4-methylphenyl)- 4,6,10,
12,18,22,24,-octakis-(acetoxy)-resorcin[4]arene 4.
A solution of 50 mmol of 2-methylresorcinol or
resorcinol in 50 ml of 95% ethanol and 10 ml of
concentrated hydrochloric acid was combined with 1
equiv. of the according aldehyde in a dropwise
manner under cooling with ice. The mixture was
then kept warm at about 65 8C for 12 h under
nitrogen. After cooling to room temperature, the
precipitate was collected, washed with a little cold
ethanol, and dried in vacuo. An acetonitrile solution
of 2 mmol of methylresorcin[4]arene 1 or resorci-
n[4]arene 2 was added with 8 equiv. acetic
anhydride at room temperature. The reaction
solution was stirred for 2 h, the solvent was
removed in vacuo. The residue was recrystallized
from acetone/dichloromethane solution to give pure
colorless crystalline product.
1
Yield 1.62 g (84%) of white solid: mp . 315 8C. H
NMR [300 MHz, CDCl3, ppm]: d 2.17 (s, 24H,
CH3CO), 2.28 (s, 12H, ArCH3), 5.52 (s, 4H, Ar3CH),
6.13 (s, 4H, ArH, ortho to OCOCH3), 6.29 (bs, 4H,
ArH, meta to OCOCH3), 6.58 (d, J ¼ 7.6 Hz, 4H,
ArH, meta to CH3), 6.77 (d, J ¼ 7.6 Hz, 4H, ArH,
ortho to CH3). MS (FAB): m/z 1185.5 (Mþ, calcd
1185.3). Anal. calcd for C72H64O16·H2O: C, 71.87; H,
5.53. Found: C, 72.45; H, 5.62.
rccc-2,8,14,20-Tetrakis-(iso-butyl)-5,11,17,23-tet-
ramethyl-resorcin[4]arene 5. Yield 12.56 g (74%)
1
of white solid: mp . 300 8C. H NMR [300 MHz,
(CD3)2CO, ppm]: d 0.95 (d, J ¼ 6.8 Hz, 24H,
CH (CH3)2), 1.52 (m, 4H, CH(CH3)2), 2.10(t, J ¼ 7.4
Hz, 8H, CH2), 2.31 (s, 12H, ArCH3), 4.52 (t, 4H,
Ar2CHCH2), 7.04 (s, 4H, ArH), 7.22 (d, J ¼ 7.4 Hz,
4H, ArH, meta to CH3), 7.58 (d, J ¼ 7.4 Hz, 4H,
ArH, ortho to CH3), 8.23 (bs, 8H, ArOH). MS
(FAB): m/z 758.8 (Mþ, calcd 759.0). Anal. calcd
for C48H54O8: C, 75.96; H, 7.17. Found: C, 75.72;
H, 7.13.
rctt-2,8,14,20- Tetrakis- (4-methylphenyl)- 5,11,17,
23-tetramethyl-resorcin[4]arene 1. Yield 12.56 g
(94%) of off-white solid: mp . 315 8C. 1H NMR
[300 MHz, (CD3)2SO, ppm]: d 1.98 (s, 12H, ArCH3),
2.25 (s, 12H, ArCH3), 5.48 (s, 4H, Ar3CH), 6.22 (s,
4H, ArH, meta to OH), 6.43 (d, J ¼ 7.8 Hz, 4H, ArH,

S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
127
Table 1
Crystallographic data for 1·6DMF, 2·6DMF·C7H8, 3·CH2Cl2 and 5·2DMF
Compound
1·6DMF
2·6DMF·C7H8
3·CH2Cl2
5·2DMF
Empirical formula
Formula weight
Crystal system
Space group
C78H98N6O14
1343.62
C81H98N6O14
1379.65
C77H74O16Cl2
1326.16
C54H78N2O16
915.18
Triclinic
P-1
Monoclinic
P21/n
Triclinic
P-1
Triclinic
P-1
˚
a (A)
˚
b (A)
˚
c (A)
10.8167(8)
13.4529(9)
14.3189(10)
70.1390(10)
86.8950(10)
70.5630(10)
1843.9(2)
1
16.027(4)
20.083(5)
23.921(8)
11.898(2)
12.592(3)
13.623(3)
107.575(4)
114.036(4)
94.388(4)
1729.7(6)
1
12.3180(7)
12.4399(7)
18.6562(11)
81.4130(10)
71.210(2)
88.9250(10)
2674.8(3)
2
a (deg)
b (deg)
g (deg)
101.064(6)
3
˚
V (A )
7556(4)
4
Z
rcalcd (g cm23
Radiation
)
1.210
1.213
1.273
1.136
Mo Ka
0.083
Mo Ka
0.083
Mo Ka
0.162
Mo Ka
0.077
m (mm21
T (8C)
)
23(2)
23(2)
23(2)
23(2)
Rs (observed data)
Rs (all data)
R1 ¼ 0.0517
wR2 ¼ 0.1493
R1 ¼ 0.0552
wR2 ¼ 0.1537
1.024
R1 ¼ 0.0668
wR2 ¼ 0.1498
R1 ¼ 0.0933
wR2 ¼ 0.2037
0.979
R1 ¼ 0.0817
wR2 ¼ 0.1555
R1 ¼ 0.1294
wR2 ¼ 0.2709
0.992
R1 ¼ 0.0766
wR2 ¼ 0.1834
R1 ¼ 0.1305
wR2 ¼ 0.2614
1.010
S (GoF on F2)
P
P
P
P
P
2
2
1=2;
2
1=2
R1 ¼ llFol 2 lFcll= lFol; wR2 ¼ ½ wðlFo2l 2 lFc2lÞ = wlFo2l ꢀ S ¼ ½ wðlFol 2 lFclÞ =ðNobs 2 NparamÞꢀ
rccc-2,8,14,20-Tetrakis-(iso-butyl)-resorcin[4]ar-
ene 6. 9.21 g (61%) of white solid: mp . 285 8C. 1H
NMR [300 MHz, CDCl3, ppm]: d 0.96 (d, J ¼ 6.8 Hz,
24H, CH3), 1.51 (m, 4H, CH(CH3)2), 2.13 (t, J ¼ 7.4
Hz, 8H, CH2), 4.52 (t, 4H, Ar2CHCH2), 7.04 (s, 4H,
ArH, ortho to OH), 7.16 (s, 4H, ArH, meta to OH),
8.21 (bs, 8H, ArOH). MS (FAB): m/z 702.3 (Mþ,
calcd 702.8). Anal. calcd for C44H46O8: C, 75.19; H,
6.60. Found: C, 75.03; H, 6.56.
The collected frames were processed with the soft-
ware SAINT [25]. The data was corrected for
absorption using the program SADABS [26]. Struc-
tures were solved by the direct methods and refined by
full-matrix least-squares on F2 using the SHELXTL
software package [27]. All non-hydrogen atoms were
refined anisotropically. The positions of all hydrogen
atoms were generated geometrically (C–H bond fixed
˚
at 0.96 A), assigned isotropic thermal parameters, and
allowed to ride on their respective parent C atoms
before the final cycle of least-squares refinement. One
CH2Cl2 solvent molecule in 3·CH2Cl2 is disordered
and refined with the C–Cl bond distance restraint.
Crystallographic data are summarized in Table 1.
3.3. Analyses of X-ray crystal structure
Single crystals of compounds 1·6DMF,
2·6DMF·C7H8 and 5·2DMF were grown by slow
evaporation of their DMF solutions at room tempera-
ture. Unstable single crystal of compound 3·CH2Cl2,
easily losing solvents in the crystal lattice, was
obtained from their CH2Cl2 solution at 24 8C. X-
ray intensity data for crystals of all compounds were
measured at 23 8C on a Bruker APEX SMART 1000
CCD-based X-ray diffractometer system equipped
with graphite monochromated Mo Ka radiation
4. Supplementary materials
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-
0119/213351-54. Copies of the data can be obtained
˚
(l ¼ 0:71073 A) by using an v scan technique.

128
S. Miao et al. / Journal of Molecular Structure 659 (2003) 119–128
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free of charge on application to The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [Fax:
þ44(0)1223-336033; Email: deposit@ccdc.cam.a-
c.uk].
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Acknowledgements
[12] H. Boerrigter, W. Verboom, D.N. Reinhoudt, J. Org. Chem. 62
(1997) 7148.
This project was sponsored by the Scientific
Research Foundation for the Returned Overseas
Chinese Scholars, State Education Ministry of
China. Acknowledgement is made to the research
funds from Anhui Provincial Natural Science Foun-
dation (grant no. 00045105), the Natural Science
Foundation of Shandong Province (grant no.
Y2000B05) and the USC Nanocenter to RDA. Dr
Q.F. Zhang is grateful to the Postdoctoral Research
Fellowship from University of South Carolina.
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