Acridinylresorcinol as a self-complementary building block of robust hydrogen-bonded 2D nets with coordinative saturation. Preservation of crystal structures upon guest alteration, guest removal, and host modification

Article abstract of DOI:10.1021/ja026704l

Acridinylresorcinol host 3 (9-(3,5-dihydroxy-1-phenyl)acridine) forms such adducts as 3·(benzene), 3·(chloroform), 3·0.5(toluene), and 3·(isobutyl benzoate). Modified acridinol host 4 (9-(3,5-dihydroxy-1-phenyl)-4-hydroxyacridine) having an additional OH group on the acridine ring affords such adducts as 4·(benzene), 4·(chloroform), 4·0.5(toluene)·0.5(water), 4·(methanol)·(water), and 4·(ethyl acetate). In the crystals, hosts 3 and 4 form hydrogen-bonded (O-H...O-H) poly(resorcinol) chains which are linked together via interchain O-H...N hydrogen bonds to give a coordinatively saturated (O-H...O-H...N) 2D net composed of doubly hydrogen-bonded and antiparallel-stacked, self-complementary cyclic dimer 3₂ or 4₂ as a rigidified building block, the otherwise flexible O-H...O-H hydrogen bonds being thereby taken in a cyclophane-like structure. This network turns out to be remarkably well preserved among the above adducts. Guest molecules, which are disordered in many cases, are incorporated in the cavities left. The binding of small polar guests to host 4 is primarily due to hydrogen bonding to the OH group on the acridine ring. The latter therefore acts only as a polarity modifier of preserved cavities. Adduct 3·(benzene), that is, 3₂·2(benzene) readily loses one of two guest molecules bound in each cavity to give a microporous half-filled adduct 3₂·(benzene) which adsorbs 1 mol of benzene to regenerate the starting full adduct without involving a phase change, as confirmed by X-ray powder diffractions and reversible Langmuir-type adsorption/desorption isotherms. The self-complementarity strategy for designing rigid crystal structures is discussed with a particular reference to the possibility of systematic perturbation/variation approaches in crystal engineering.

Full text of DOI:10.1021/ja026704l

Published on Web 09/28/2002
Acridinylresorcinol as a Self-Complementary Building Block
of Robust Hydrogen-Bonded 2D Nets with Coordinative
Saturation. Preservation of Crystal Structures upon Guest
Alteration, Guest Removal, and Host Modification
Toshihiro Tanaka,‡,§ Takashi Tasaki,‡ and Yasuhiro Aoyama*,†,‡
Contribution from the Department of Synthetic Chemistry and Biological Chemistry,
Graduate School of Engineering, Kyoto UniVersity, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan,
and Institute for Fundamental Research of Organic Chemistry, Kyushu UniVersity,
Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
Received April 27, 2002
Abstract: Acridinylresorcinol host 3 (9-(3,5-dihydroxy-1-phenyl)acridine) forms such adducts as 3‚(benzene),
3‚(chloroform), 3‚0.5(toluene), and 3‚(isobutyl benzoate). Modified acridinol host 4 (9-(3,5-dihydroxy-1-
phenyl)-4-hydroxyacridine) having an additional OH group on the acridine ring affords such adducts as
4‚(benzene), 4‚(chloroform), 4‚0.5(toluene)‚0.5(water), 4‚(methanol)‚(water), and 4‚(ethyl acetate). In the
crystals, hosts 3 and 4 form hydrogen-bonded (O-H‚‚‚O-H) poly(resorcinol) chains which are linked
together via interchain O-H‚‚‚N hydrogen bonds to give a coordinatively saturated (O-H‚‚‚O-H‚‚‚N) 2D
net composed of doubly hydrogen-bonded and antiparallel-stacked, self-complementary cyclic dimer 32 or
42 as a rigidified building block, the otherwise flexible O-H‚‚‚O-H hydrogen bonds being thereby taken in
a cyclophane-like structure. This network turns out to be remarkably well preserved among the above
adducts. Guest molecules, which are disordered in many cases, are incorporated in the cavities left. The
binding of small polar guests to host 4 is primarily due to hydrogen bonding to the OH group on the acridine
ring. The latter therefore acts only as a polarity modifier of preserved cavities. Adduct 3‚(benzene), that is,
32‚2(benzene) readily loses one of two guest molecules bound in each cavity to give a microporous half-
filled adduct 32‚(benzene) which adsorbs 1 mol of benzene to regenerate the starting full adduct without
involving a phase change, as confirmed by X-ray powder diffractions and reversible Langmuir-type
adsorption/desorption isotherms. The self-complementarity strategy for designing rigid crystal structures is
discussed with a particular reference to the possibility of systematic perturbation/variation approaches in
crystal engineering.
Introduction
engineering may be to find out a rational strategy by which
otherwise flexible networks can be made robust enough to define
The intermolecular interactions of organic molecules are
generally weak. The organic crystal structures are thus sensitive
to molecular geometry, that is, size, shape, and functionality.1
The packing networks of an inclusion compound normally
collapse when guest molecules are removed, although there are,
in addition to robust metal-coordination networks,2-6 a few
exceptions where the hosts are small building blocks such as
dianin’s compounds,7 the helical tubuland diols,8 and the
diaminotriazine derivative.9 A common challenge in crystal
themselves uniquely. This is all we are concerned about here.
(2) (a) Yaghi, O. M.; Li, G. M.; Li, H. L. Nature 1995, 378, 703-706. (b) Li,
H.; Eddaoudi, M.; O’-Keeffe, M.; Yaghi, O. M. Nature 1999, 402, 276-
279. (c) Chen, B. L.; Eddaoudi, M.; Reineke, T. M.; Kampf, J. W.; O’-
Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2000, 122, 11559-11560.
(d) Eddaoudi, M.; Moler, D. B.; Li, H. L.; Chen, B. L.; Reineke, T. M.;
O’-Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319-330. (e)
Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’-Keefe, M.;
Yaghi, O. M. Science 2002, 295, 469-472.
(3) (a) Kitagawa, S.; Kondo, M. Bull. Chem. Soc. Jpn. 1998, 71, 1739-1753.
(b) Kondo, M.; Okubo, T.; Asami, A.; Noro, S.; Yoshitomi, T.; Kitagawa,
S.; Ishii, T.; Matsuzaka, H.; Seki, K. Angew. Chem., Int. Ed. 1999, 38,
140-143. (c) Noro, S.; Kitagawa, S.; Kondo, M.; Seki, K. Angew. Chem.,
Int. Ed. 2000, 39, 2082-2084. (d) Noro, S.; Kitaura, R.; Kondo, M.;
Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Yamashita, M. J. Am. Chem. Soc.
2002, 124, 2568-2583.
(4) (a) For a notable work on preserved crystal structures with varying
substituents, see: Kiang, Y. H.; Gardner, G. B.; Lee, S.; Xu, Z.; Lobkovsky,
E. B. J. Am. Chem. Soc. 1999, 121, 8204-8215. (b) Gardner, G. B.;
Venkataraman, D.; Moore, J. S.; Lee, S. Nature 1995, 374, 792-795. (c)
Venkataraman, D.; Gardner, G. B.; Lee, S.; Moore, J. S. J. Am. Chem.
Soc. 1995, 117, 11600-11601. (d) Kiang, Y. H.; Gardner, G. B.; Lee, S.;
Xu, Z. T. J. Am. Chem. Soc. 2000, 122, 6871-6883.
(5) (a) Otake, M. Catal. SurV. Jpn. 1998, 2, 209-213. (b) Moulton, B.;
Zaworotko, M. J. Chem. ReV. 2001, 101, 1629-1658. (c) Gudbjartson,
H.; Biradha, K.; Poirier, K. M.; Zaworotko, M. J. J. Am. Chem. Soc. 1999,
121, 2599-2600.
* To whom correspondence should be addressed. E-mail: aoyamay@
sbchem.kyoto-u.ac.jp.
† Kyoto University.
‡ Kyushu University.
§ Present address: Department of Applied Chemistry, Graduate School
of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka
558-8585, Japan.
(1) (a) Kitaigorodsky, A. I. Molecular Crystals and Molecules; Academic
Press: New York, 1973. (b) Wright, J. D. Molecular Crystals; Cambridge
University Press: Cambridge, U.K., 1987. (c) Desiraju, G. R. Crystal
Engineering: The Design of Organic Solids; Elsevier: New York, 1989.
(d) Bishop, R.; Choudhury, S.; Dance, I. J. Chem. Soc., Perkin Trans. 2
1982, 1159-1168.
9
10.1021/ja026704l CCC: $22.00 © 2002 American Chemical Society
J. AM. CHEM. SOC. 2002, 124, 12453-12462
12453

A R T I C L E S
Tanaka et al.
Chart 1. Host Molecules
Scheme 3. Preparation of Hosts 3 and 4a
Scheme 1. 2D Net in Adducts 1‚2(Guest)
Scheme 2. 2D Net in Adducts 2‚(Guest)
a (a) 2-Methoxyethoxymethyl chloride, NaH, DMF; (b) 3,5-dimethoxy-
phenylmagnesium chloride, THF; (c) HCl, H2O; (d) aqueous HBr; (e)
K2CO3, Cu, C5H11OH; (f) H2SO4; (g) BBr3, CH2Cl2.
acts as a kind of guest. We report here that the resulting 2D net
with coordinative saturation (O-H‚‚‚O-H‚‚‚N) is remarkably
well preserved upon alteration of the guests, partial guest
desorption, and polar modification of the host.14 Thus, the rigid
network allows a perturbation of preserved cavities and a
systematic variation in guests accommodated therein.4a
Results
Preparation. The network-forming host molecules used in
this work are acridinylresorcinol 3 and its 4-acridinol derivative
4 (Chart 1). Both compounds are obtained from Grignard
reactions of the corresponding protected acridone derivatives 5
and 9, respectively, with dimethoxyphenylmagnesium chloride,
followed by deprotection (Scheme 3). 4-Methoxyacridone (8)
is available from the Ullmann reaction of o-chlorobenzoic acid
and o-anisidine, followed by acid-catalyzed cyclization.
Inclusion Complexation of Host 3. Compound 3 is highly
soluble in polar solvents such as methanol and DMF and
scarcely so in hydrocarbons such as benzene. Upon recrystal-
lization from benzene/methanol, benzene/DMF, or chloroform/
DMF, it exclusively incorporates the less polar component to
give 1:1 adduct 3‚(benzene)15 or 3‚(chloroform). On the other
hand, toluene and many other substituted benzenes (xylene
(o-, m-, and p-), mesitylene, halobenzene (halo ) chloro and
bromo), alkyl benzoate (alkyl ) methyl, ethyl, propyl, isopropyl,
and isobutyl), and diphenyl ether) form 1:0.5 (2:1) (host-to-
guest) adducts. Cyclohexene and 1,3-cyclohexadiene behave
similarly as benzene and afford 1:1 adducts. In marked contrast,
cyclohexane and saturated acyclic hydrocarbons (pentane,
hexane, heptane, 2-methylpentane, 3-methylpentane, and 2,2-
dimethylbutane) are hardly incorporated (guest/3 < 0.1). At-
The bis(resorcinol) and mono(resorcinol) derivatives of
anthracene, 110 and 211 (Chart 1), provide typical examples of
flexible networks. They afford 1:2 and 1:1 (host-to-guest)
adducts with a variety of ketones and esters as guests. Host 1
forms a hydrogen-bonded (O-H‚‚‚O-H) 2D net (Scheme 1),
while host 2 gives 1D chains which are self-assembled into a
pseudo 2D net with what we call an either monomeric (m) or
dimeric (d) lattice pattern in a guest-dependent manner (Scheme
2). The network-forming hydrogen bonds are coordinatively
unsaturated and become saturated upon guest binding
(O-H‚‚‚O-H‚‚‚OdC) via host-guest hydrogen bonding, where
a remarkable induced-fit adjustment of the network to the guest
structures is noted and the network collapses upon guest removal
with a phase change to give a nonporous apohost.12,13 The
present work is concerned about rigidification of the poly-
(resorcinol) network using acridinylresorcinol host 3 (Chart 1)
as a self-complementary building block, where the nitrogen atom
(6) (a) Sawaki, T.; Dewa, T.; Aoyama, Y. J. Am. Chem. Soc. 1998, 120, 8539-
8540. (b) Sawaki, T.; Aoyama, Y. J. Am. Chem. Soc. 1999, 121, 4793-
4798. (c) Saiki, T.; Aoyama, Y. Chem. Lett. 1999, 797-798.
(7) Barrer, R. M.; Shanson, V. H. J. Chem. Soc., Chem. Commun. 1976, 333-
334.
(8) Ung, A. T.; Gizachew, D.; Bishop, R.; Scudder, M. L.; Dance, I. G.; Craig,
D. C. J. Am. Chem. Soc. 1995, 117, 8745-8756.
(9) Brunet, P. B.; Simard, M.; Wuest, J. D. J. Am. Chem. Soc. 1997, 119,
2737-2738.
(10) (a) Aoyama, Y.; Endo, K.; Kobayashi, K.; Masuda, H. Supramol. Chem.
1995, 4, 229-241. (b) Endo, K.; Sawaki, T.; Koyanagi, M.; Kobayashi,
K.; Masuda, H.; Aoyama, Y. J. Am. Chem. Soc. 1995, 117, 8341-8352.
(c) Aoyama, Y.; Endo, K.; Anzai, T.; Yamaguchi, Y.; Sawaki, T.;
Kobayashi, K.; Kanehisa, N.; Hashimoto, H.; Kai, Y.; Masuda, H. J. Am.
Chem. Soc. 1996, 118, 5562-5571. (d) Endo, K.; Koike, T.; Sawaki, T.;
Hayashida, O.; Masuda, H.; Aoyama, Y. J. Am. Chem. Soc. 1997, 119,
4117-4122.
(11) Endo, K.; Ezuhara, T.; Koyanagi, M.; Masuda, H.; Aoyama, Y. J. Am.
Chem. Soc. 1997, 119, 499-505.
(12) Dewa, T.; Endo, K.; Aoyama, Y. J. Am. Chem. Soc. 1998, 120, 8933-
8940.
(13) For the thermodynamic and kinetic analysis of lattice inclusion phenomena,
also see: (a) Caira, M. R.; Nassimbeni, L. R.; Toda, F.; Vujovic, D. J.
Am. Chem. Soc. 2000, 122, 9367-9372. (b) Caira, M. R.; Nassimbeni, L.
R. In ComprehensiVe Supramolecular Chemistry; Lehn, J.-M., Atwood, J.
L., Davies, J. E. D., MacNicol, D. D., Vo¨gtle, F., Eds.; Pergamon Press:
Oxford, 1996; Vol. 6, Chapter 25. (c) Barbour, L. J.; Caira, M. R.;
Nassimbeni, L. R. J. Chem. Soc., Perkin Trans. 2 1993, 2321-2322. (d)
Barbour, L. J.; Caira, M. R.; Coetzee, A.; Nassimbeni, L. R. J. Chem. Soc.,
Perkin Trans. 2 1995, 1345-1349. (e) Caira, M. R.; Horne, A.; Nassimbeni,
L. R.; Toda, F. Supramol. Chem. 1998, 9, 231-237.
(14) A preliminary account of a part of this work appeared in the following:
Tanaka, T.; Endo, K.; Aoyama, Y. Chem. Lett. 2000, 1424-1425.
(15) The simplest way to obtain adduct 3‚(benzene), although not as single
crystals, is to reprecipitate host 3 in methanol upon addition of benzene.
9
12454 J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002

Acridinylresorcinol as a Building Block of 2D Nets
A R T I C L E S
Figure 1. Crystal structure of adduct 3‚(benzene): front view (a) and side view (b) of a molecular sheet, top view of three adjacent sheets (c), and perspective
view along the a axis of the guest-binding cavities (d). la, lc, and ls are interring, interchain, and intersheet distances, respectively. The acridine rings,
resorcinol rings, benzene guests, and hydrogen bonds are shown in red, black, green, and light blue, respectively.
Scheme 4. 2D Net in Adduct 3‚(Benzene)
Figure 2. Packing geometry of guest molecules in a cavity of adducts
3‚(benzene) (a), 3‚(chloroform) (b), 3‚0.5(isobutyl benzoate) (c), and
4‚0.5(toluene)‚0.5(water) (d).
a consequence, the tilt angle (φ) of the acridine rings with respect
tempted complexation of small polar guests such as methanol
and ethyl acetate only results in recovery of host 3 with little
incorporation of the former.
to the poly(resorcinol) chain axis is close to the acridine-
resorcinol dihedral angle (æ). Each cavity incorporates two
benzene molecules which are parallel with each other and
perpendicular with respect to the acridine rings, making a
T-shaped benzene-acridine CH-π contact (Figure 2a). The
sheets are layered in a staggered manner, as shown in the top
view of three adjacent sheets in Figure 1c. The guest-binding
cavities thereby form intersheet channels (Figure 1d). In Table
2 are summarized characteristic angles and distances, including
dihedral (æ) and tilt (φ) angles, acridine-acridine interring
Crystal Structure of Adduct 3‚(Benzene). The crystal
structure of adduct 3‚(benzene) is shown in Figure 1 and Scheme
4 for a schematic illustration, and the crystal data are sum-
marized in Table 1. Host 3 forms a hydrogen-bonded
(O-H‚‚‚O-H) poly(resorcinol) chain with acridinyl rings
sticking out alternately in opposite directions. The chains are
linked together via interchain resorcinol-acridine O-H‚‚‚N
hydrogen bonds to give a coordinatively saturated (O-H‚‚‚O-
H‚‚‚N) 2D net or sheet (front view in Figure 1a and Scheme 4
and side view in Figure 1b); the sheet may also be viewed as
arising from an antiparallel dimer (32 in Scheme 4) of self-
complementary host 3 as a building block. There is little tilting
deviation of the resorcinol rings from the sheet (Figure 1b). As
f
distances la (face-to-face) and lac (center-to-center), interchain
distance lc, and intersheet distance ls in reference to Figure 1
and hydrogen-bond distances lO-O and lO-N
.
The crystal structure of adduct 3‚(benzene) is apparently
similar to those of 1:1 adducts of anthracenylresorcinol host 2,
for example, 2‚(ethyl acetate), in the dimeric (d) lattice pattern
9
J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002 12455

A R T I C L E S
Tanaka et al.
Table 1. Crystallographic Data of Various Adducts
3‚0.5(isobutyl
benzoate)
3‚(benzene)
3‚(chloroform)
3‚0.5(benzene)a
3‚0.5(toluene)a
C22.5H17NO2
333.38
orange
formula
formula weight
crystal habit and
color
C25H19NO2
365.43
orange prisms
C20H14NO2Cl3
406.70
orange prisms
C
24.5H20NO3
376.43
orange prisms
C22H16NO2
326.37
orange
crystal system
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/n
8.866(2)
14.024(2)
15.393(1)
99.34(1)
1888.6(4)
4
1.285
0.081
295
8.913(2)
13.957(2)
15.099(3)
100.47(1)
1847.0(5)
4
1.462
0.51
295
8.874(2)
13.998(2)
15.604(1)
97.480(9)
1921.8(4)
4
1.301
0.086
295
8.8490
14.1284
15.2494
99.528
1880
8.9000
14.0578
15.2366
99.842
1878
â (deg)
V (Å3)
Z
d
calc (g/cm3)
µ (mm-1
T (K)
)
no. reflns measured
no. unique reflns
4811
4347
4595
4258
4899
4423
(Rint ) 0.063)
2254
(Rint ) 0.025)
2728
(Rint ) 0.034)
2078
no. reflns used
(I > 3σ(I))
no. parameters
reflection/parameter
273
8.26
0.046, 0.080
0.98
289
9.44
0.056, 0.100
1.27
268
7.75
0.081, 0.138
1.70
b
R,b Rw
GOFb
final diff four.
map (e- Å-3
max 0.20,
min -0.20
max 0.32,
min -0.46
max 0.39,
min -0.31
)
4‚0.5(toluene)
4‚(methanol)
4‚(benzene)
4‚(chloroform)
‚0.5(H O)
‚(H O)
2
4‚(ethyl acetate)
4
2
formula
C25H19NO3
381.43
orange prisms
C20H14NO3Cl3
422.69
orange prisms
C
22.5H18NO3.5
C20H19NO5
353.37
orange prisms
C23H21NO5
391.42
orange prisms
C19H13NO3
303.32
orange prisms
formula weight
crystal habit and
color
358.39
orange prisms
crystal system
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/n
8.986(4)
14.010(3)
15.591 (3)
99.60 (3)
1935.3 (9)
4
1.309
0.086
295
9.127(2)
13.960(1)
15.169(2)
101.02(1)
1897.1(4)
4
1.480
0.503
295
9.004(2)
14.001(2)
15.273(2)
100.16(2)
1895.2(6)
4
1.256
0.085
295
8.923(5)
13.966(3)
15.197(4)
100.84(3)
1860.0(1)
4
1.262
0.091
295
9.315(4)
14.040(4)
14.713 (3)
101.91(2)
1882.8(1)
4
1.381
0.098
295
7.431(4)
9.034(7)
21.104(4)
92.42(3)
1415.4(1)
4
1.423
0.097
295
â (deg)
V (Å3)
Z
d
calc (g/cm3)
µ (mm-1
T (K)
)
no. reflns measured
no. unique reflns
4918
4445
4812
4355
4816
4354
4744
4288
4768
4320
3718
3250
(Rint ) 0.100)
1839
(Rint ) 0.032)
2043
(Rint ) 0.085)
1619
(Rint ) 0.083)
2107
(Rint ) 0.031)
1542
(Rint ) 0.071)
1089
no. reflns used
(I > 3σ(I))
no. parameters
reflection/parameter
294
6.26
0.054, 0.094
1.19
298
6.86
0.057, 0.096
1.20
263
6.16
0.072, 0.115
1.46
252
8.36
0.075, 0.126
1.58
255
6.05
0.082, 0.130
1.62
217
5.02
0.074, 0.109
1.36
b
R,b Rw
GOFb
final diff four.
map (e- Å-3
max 0.19,
min -0.27
max 0.22,
min -0.32
max 0.39,
min -0.27
max 0.58,
min -0.36
max 0.60,
min -0.44
max 0.55,
min -0.40
)
a Cell parameters were derived from analysis of powder diffractions.19 b R ) ∑ ||Fo| - |Fc||/∑ |Fo|, Rw ) [∑w(|Fo| - |Fc|)2/∑ wFo ]1/2, GOF ) [∑w(|Fo|
2
- |Fc|)2/(no. refls - no. params)]1/2
.
(Scheme 2). In each case, an antiparallel dimer (32 or 22) of the
host actually serves as a building block. The difference lies in
rigidity and selectivity. In the case of 32, the head (O-H) and
the tail (N) are hydrogen bonded in a self-complementary
manner via an O-H group of another building block to give a
rigid cyclophane-like structure (Scheme 4), while 22 (Scheme
2) is a flexible stack, which, depending on the type of guests,
readily dissociates into a monomeric (m) lattice pattern. Building
blocks 32 and 22 lead to coordinatively saturated and unsaturated
networks, respectively, resulting in a remarkable alteration in
guest-binding selectivities, that is, less polar guests for host 3
and more polar ones for host 2.
Adducts 3‚(Chloroform), 3‚0.5(Isobutyl Benzoate), and 3‚
0.5(Toluene). Chloroform represents less polar nonaromatic
guests. Isobutyl benzoate is representative of potential hydrogen-
bonding guests as well as substituted benzenes that give rise to
the 1:0.5 (2:1) host-to-guest ratio. The crystal structures of
adducts 3‚(chloroform) and 3‚0.5(isobutyl benzoate) turn out
to be closely related with each other and with that of the benzene
adduct described above.16 They share the chain/sheet/layer motif
9
12456 J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002

Acridinylresorcinol as a Building Block of 2D Nets
A R T I C L E S
Table 2. Characteristic Angles and Distances in the Crystals of Various Adductsa
3‚0.5(isobutyl
4‚0.5(toluene)
4‚(methanol)
3‚(benzene)
3‚(chloroform)
benzoate)
4‚(benzene)
4‚(chloroform)
‚0.5(H O)
‚(H O)
2
4‚(ethyl acetate)
2
æ (deg)
φ (deg)
lac (Å)
la(1)f (Å)
la(2)f (Å)
lc (Å)
71
73
14.02
3.7
9.7
9.48
7.10
2.76
2.68
69
76
13.96
3.7
9.7
9.44
7.01
2.74
2.67
66
71
14.00
3.7
9.5
9.46
7.25
2.75
2.69
73
73
14.01
3.8
9.7
9.63
7.18
2.76
2.81
72
76
13.96
3.8
9.7
9.57
7.10
2.75
2.78
70
68
14.00
3.8
9.2
9.52
7.11
2.75
2.80
68
68
13.97
3.8
9.0
9.51
7.00
2.71
2.77
74
76
14.04
3.8
9.9
9.48
7.07
2.76
2.75
ls (Å)
l
l
O-O (Å)
O-N (Å)
a Definitions are as follows, referring to Figures 1 and 4: æ, acridine-resorcinol dihedral angle; φ, tilt angle of acridine rings with respect to a hydrogen-
c
f
f
bonded poly(resorcinol) chain; la , center-to-center interring distance for a neighboring pair of acridine rings along a poly(resorcinol) chain; la(1) and la(2)
,
face-to-face interring distances for neighboring pairs of acridine rings in neighboring poly(resorcinol) chains; lc, interchain distance; ls, intersheet distance;
lO-O, O-O distance for the hydrogen-bonded O-H‚‚‚O-H moiety; lO-N, O-N distance for the hydrogen-bonded O-H‚‚‚N moiety.
polar guests. Competition between ethyl acetate and benzene,
toluene, or chloroform, for example, results in an exclusive
incorporation of the latter. In its absence, however, host 4, but
not 3 (vide supra), is capable of complexing small polar guests
such as ethyl acetate and methanol. In addition, water is often
co-included. As a result, such adducts as 4‚(benzene), 4‚
(chloroform), 4‚0.5(toluene)‚0.5(water), 4‚(methanol)‚(water),
and 4‚(ethyl acetate) are obtained as single crystals. The IR
spectra of the former two anhydrous adducts show a sharp νO-H
absorption at 3250 cm-1 for a free OH group assignable to the
acridinyl OH. It must therefore be free from hydrogen bonding.
Such an absorption is absent in the spectra of the remaining
three adducts containing small polar guests. Adduct 4‚(ethyl
acetate) also shows a νCdO at 1710 cm-1, which is shifted by
44 cm-1 to a lower wavenumber from that of ethyl acetate as
a neat liquid. There is little doubt that these small polar guests
are hydrogen bonded to the acridinyl OH group.
Figure 3. X-ray powder diffractions for adducts 3‚(benzene) (a), 3‚0.5-
(toluene) (b), 3‚0.5(benzene) (c), and guest-free apohost 3 (d).
X-ray crystallography reveals that all of the adducts contain
the same O-H‚‚‚O-H‚‚‚N network as described above. Thus,
modified host 4 forms a dimeric building block 42, the building
blocks are assembled into a sheet, and the sheets are layered in
a staggered manner in exactly the same way as in the case of
parent host 3 (Scheme 4). In no case is the acridinyl OH group
involved in the network.17 In Figure 4 is shown, as an example,
the network structure in adduct 4‚(ethyl acetate), which is closely
related to that of adduct 3‚(benzene) shown in Figure 1. This is
confirmed in more detail from an inspection of Tables 1 and 2,
where a remarkable similarity in the cell parameters and cavity-
defining angles and distances among all of the adducts of hosts
3 and 4 is noted. The crystal structures are not simply maintained
but actually preserved upon the introduction of an otherwise
potential OH group into the host (3 f 4).
Adducts 4‚(benzene) and 4‚(chloroform) incorporate two
guest molecules in each cavity in a similar manner as in 3‚
(benzene) and 3‚(chloroform) (Figure 2a and b). The toluene
adduct 4‚0.5(toluene)‚0.5(water) or 42‚(toluene)‚(water) contains
1 mol of toluene and water per cavity. The toluene is disordered
in two locations with a 0.5 occupancy (Figure 2d) in a similar
manner as the benzoate guest in adduct 3‚0.5(isobutyl benzoate)
(Figure 2c), while water is completely disordered. This is also
the case for the methanol and water guests in adduct 4‚
in common, and the cell parameters (a, b, c, â, and V in Table
1) and characteristic angles and distances (Table 2) which define
the size and shape of guest-binding cavities are similar for the
three (benzene, chloroform, and isobutyl benzoate) adducts,
despite a span in the number and type of included guest
molecules. An interesting addition in this regard is the 1:0.5
toluene adduct 3‚0.5(toluene) in comparison with the 1:1
benzene adduct. Although, unfortunately, the quality of the
former adduct is not good enough to allow single-crystal X-ray
diffraction, powder-diffraction analyses show that the two
adducts are very similar to each other, having almost identical
diffraction patterns (Figure 3a and b) and cell parameters (Table
1).
In adduct 3‚(chloroform), each cavity incorporates two guest
molecules with one of three chlorine atoms pointing to the
acridine ring (Figure 2b). Adduct 3‚0.5(isobutyl benzoate)
exhibits no host-guest hydrogen bonding, as confirmed also
by IR spectroscopy showing no complexation-induced shift in
νCdO for the ester guest. Each cavity binds a single molecule
of isobutyl benzoate, which is disordered in two locations with
an occupancy of 0.5 each (Figure 2c). This is also true for the
toluene adduct as shown below and may reflect a poor packing
efficiency of a single guest molecule bound in a big cavity.
Modified Acridinol Host 4 and Its Adducts. As for
selectivity, modified acridinol host 4 retains what is character-
istic of parent host 3, that is, a remarkable preference for less
(17) The acridinyl OH group in all of the adducts of host 4 is disordered in two
positions, appearing as either 4-OH or 5-OH. The R values become lowest
when the occupancy ratios of 0.36:0.64, 0.40:0.60, 0.35:0.65, 0.74:0.26,
and 0.82:0.18 are given to adducts 4‚(benzene), 4‚(chloroform), 4‚0.5-
(toluene)‚0.5(water), 4‚(methanol)‚(water), and 4‚(ethyl acetate), respec-
tively.
(16) It is interesting to note that the chloroform adduct dipped in benzene
undergoes partial guest exchange while maintaining the single crystallinity.
9
J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002 12457

A R T I C L E S
Tanaka et al.
Figure 4. Crystal structure of adduct 4‚(ethyl acetate): front view (a) and side view (b) of a molecular sheet. The colors and the angles and distances have
the same meanings as in Figure 1. The acridinyl OH groups are shown in pink. Guest molecules which are disordered are not shown.
(methanol)‚(water). In the ethyl acetate adduct, the guest
molecules as a whole are disordered again, although the carbonyl
oxygen is detected at a distance of 2.75 Å from the oxygen
atom of the acridinol. There is little doubt that these small polar
guests are hydrogen bonded to the acridinyl OH group.
Nevertheless, they are disordered. This may reflect a high degree
of conformational flexibility of the O-H‚‚‚OdC (in the case
of ethyl acetate) hydrogen bond and hence, again, a poor packing
efficiency for a guest bound in the rigid cavity incapable of
induced-fit adjustment.
Microporosity in Half-Filled Benzene Adduct 3‚0.5-
(Benzene). When left at room temperature in vacuo, benzene
adduct 3‚(benzene) or 32‚2(benzene) loses one of two guest
molecules in each cavity. The resulting half-filled adduct 3‚
0.5(benzene) or 32‚(benzene) readily regenerates the original
full adduct upon uptake of 1 mol (per cavity) of benzene with
a Langmuir-type adsorption/desorption isotherm (Figure 5a). The
small extent of hysteresis observed may be explained in terms
of the so-called capillary condensation. Otherwise, it may be
due to developing defects of irreversible nature. The full and
half adducts show essentially the same X-ray powder diffractions
(Figure 3a and c).18 These results indicate that the crystal
structure is maintained with no phase change during the
Figure 5. Adsorption (O) and desorption (b) isotherms for gaseous benzene
(a), cyclohexene (b), 2,2-dimethylbutane (c), and hexane (d) at 25 °C. The
interconversion of the present full and half adducts, as illustrated
in Scheme 4. The cell parameters (derived from analysis of
powder diffractions)19 of the latter, that is, 3‚0.5(benzene), are
almost identical with those of the former, that is, 3‚(benzene),
as well as not surprisingly with those of the 1:0.5 toluene adduct
3‚0.5(toluene) (Table 1). The half adduct should contain a void
equivalent to a molecule of benzene per cavity and must
therefore be microporous. A diagnostic Langmuir-type isotherm
is not specific to benzene but also applicable to other hydro-
carbons such as cyclopentane (∼0.6), cyclohexane (∼0.5),
cyclohexene (∼0.5), 2,2-dimethylbutane (∼0.25), 2-methylpen-
amount of guest adsorbed was calculated from the pressure difference (Pcal
- Pe), where Pcal is the calculated pressure if there were no guest adsorption,
and Pe is the observed equilibrium pressure, at which the change in pressure
in 9999 s (a) or 3600 s (b-d) had become smaller than 1% of the pressure
at that point. All operations were computer-controlled and automatic. V
(mL) refers to the standard state.
tane (∼0.2), and hexane (∼0.1) with varying guest/host ratios,
shown in parentheses, at saturation binding (Figure 5b, c, and
d for cyclohexene, 2,2-dimethylbutane, and hexane, respectively,
as examples).20 The decreasing (guest/host)sat in this order may
reflect a compactness or rigidity control of the present guest
binding in preserved, rigid micropores.
(18) Simulation (CrystalStructure Analysis Package, Molecular Structure Corp.)
based on the crystal structure of benzene full-adduct 3‚(benzene) with a
hypothetical occupancy of 0.5 for each benzene molecule in the cavity
reproduces the observed powder diffractions of half-adduct 3‚0.5(benzene)
very well. These results suggest that the single benzene molecule in the
cavity of 3‚0.5(benzene) is disordered in two locations in a similar manner
as in toluene adducts 3‚0.5(toluene) and 4‚0.5(toluene)‚0.5(water).
(19) Takagi, Y.; Taniguchi, T.; Hori, K. J. Ceram. Soc. Jpn. 1993, 101, 373-
376.
When heated in vacuo, the benzene adduct loses all of the
guest molecules to give a guest-free apohost 3,21 whose X-ray
(20) Small polar molecules such as ethyl acetate and acetone are also guests of
half-adduct 3‚0.5(benzene) and give Langmuir-type isotherms.
(21) Thermogravimetry indicates that all of the benzene molecules are lost at
e110 °C.
9
12458 J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002

Acridinylresorcinol as a Building Block of 2D Nets
A R T I C L E S
Table 3. Similarity in Longitudinal and Angular Parameters in the Crystal Structures of Various Adducts
difference in % betweend
average (maximal deviation in %)a
[3‚(guest)]av and
[4‚(guest)]av
3‚(benzene)and
4‚(benzene)
3‚(benzene)and
3‚0.5(benzene)
4‚(benzene)and
4‚(ethyl acetate)
b
c
parameter
[3‚(guest)]av
[4‚(guest)]av
a (Å)
b (Å)
c (Å)
8.880 (+0.37, -0.35)
14.033 (+0.68, -0.54)
15.316 (+1.9, -1.4)
99.33 (+1.1, -1.9)
1883 (+2.1, -1.9)
69 (+3.4, -3.9)
9.071 (+2.7, -1.6)
13.995 (+0.32, -0.25)
15.189 (+2.6, -3.1)
100.71 (+1.2, -1.1)
1894 (+ 2.2, -1.8)
71 (+3.6, -4.8)
2.1
0.3
0.8
1.4
0.6
4
1.3
0.1
1.3
0.3
2.4
3
0
0.1
3
0.2
0.7
0.9
0.2
0.5
3.6
0.2
5.8
2.3
2.8
1
4
0.2
0
â (deg)
V (Å3)
æ (deg)
φ (deg)
lac (Å)
la(1)f (Å)
la(2)f (Å)
lc (Å)
73 (+3.6, -3.2)
72 (+5.3, -5.8)
2
13.99 (+0.2, -0.2)
3.7 (0, 0)
9.63 (+0.7, -1.4)
9.46 (+0.2, -0.2)
7.12 (+1.8, -1.5)
14.00 (+0.3, -0.3)
3.8 (0, 0)
9.50 (+4.2, -5.3)
9.54 (+0.9, -0.6)
7.09 (+1.2, -1.3)
∼0
3
1.4
0.9
0.4
0
1.6
1.1
2
1.6
1.5
ls (Å)
a 100‚[(max or min) - av]/av, where max, min, and av are the maximal, minimal, and average ([3‚(guest)]av or [4‚(guest)]av) values among the adducts
in concern, respectively. b Average value among adducts 3‚(benzene), 3‚(chloroform), 3‚0.5(isobutyl benzoate), 3‚0.5(benzene), and 3‚0.5(toluene) with
c
respect to a, b, c, â, and V and among adducts 3‚(benzene), 3‚(chloroform), and 3‚0.5(isobutyl benzoate) with respect to æ, φ, la , la(1)f, la(2)f, lc, and ls.
c Average value among adducts 4‚(benzene), 4‚(chloroform), 4‚0.5(toluene)‚0.5(water), 4‚(methanol)‚(water), and 4‚(ethyl acetate). d 100‚(max - min)/av,
where max, min, and av are the larger, smaller, and average ((max + min)/2) values for a pair of adducts in concern, respectively.
as hydrogen-bond donors and acceptors, respectively (top view
of columns in Figure 6c).
Discussion
Coordinative Saturation and Preservation of Crystal
Structures. All of the adducts of hosts 3 and 4 investigated
here share a common space group (P21/n), and the packing mode
of dimeric building block 32 or 42 is well preserved. The
similarity, among adducts, of the cell parameters (a, b, c, â,
and V in Table 1) and geometrical ones (Table 2) defining the
conformation (æ) and orientation (φ) of the host molecule and
the chain/sheet/layer structures (interring (la), interchain (lc), and
intersheet (ls) distances) becomes clearer when the average
values ([3‚(guest)]av and [4‚(guest)]av) and maximal deviations
therein (in percent in parentheses) for the adducts of 3 and 4
are taken (Table 3; columns 2 and 3, respectively). The
characteristic angles (æ and φ) and lengths (la, lc, and ls) vary
only within (4% among adducts 3‚(guest) and (6% among
4‚(guest), and the cell parameters are constant within (2% and
(3% for 3‚(guest) and 4‚(guest), respectively. Moreover, the
Figure 6. Crystal structure of guest-free apohost 4: side view of a stacked
difference between [3‚(guest)]av and [4‚(guest)]av is remarkably
small (e4%) for all of the parameters (column 4). This is true
for any pair of adducts, for example, 3‚(benzene) and 4‚
acridine column (a and b) and top view of columns (laf ) 3.6 Å, lac ) 7.43
Å, lc(1) ) 10.55 Å, and lc(2) ) 9.03 Å).
(benzene) having the same guest with different hosts (column
5), 3‚(benzene) and 3‚0.5(benzene) having different numbers
of guest with the same host (column 6), and 4‚(benzene) and
4‚(ethyl acetate) having guests of different polarity types with
the same host (column 7).
powder diffractions (Figure 3d) are different from those of 3‚
(benzene) and 3‚0.5(benzene) (Figure 3a and c). A phase change
must have taken place; the network described above is not so
robust as to sustain guest-free cavities. So far, host 3 resists to
give good single crystals. In the case of modified host 4, crystals
enough to allow single-crystal X-ray diffraction are obtained
by sublimation. The crystal structure of apohost 4 is completely
nonporous (Figure 6). The acridinol moiety forms an intra-
molecular O-H‚‚‚N hydrogen bond. The resorcinol rings, on
the other hand, afford an intermolecular hydrogen-bonded
(O-H‚‚‚O-H) poly(resorcinol) chain with acridine moieties
sticking out in the same direction. A couple of chains come
Is there any molecule to which an OH group can be
introduced without causing a big change in crystal structures,4a
as in the present case of 3 f 4? The acridinyl OH group in
host 4 is just a spectator of network formation but is not
necessarily “dead”. It is capable of modifying the polarity
character of the cavities involving aromatic walls of low to
moderate polarity, so that polar guests become accommodable.
Such a wide variation in guests as observed here, that is, from
benzene, toluene, and chloroform through esters to methanol
and water22 in preserved cavities, is hardly met. At the same
time, the unprecedentedly high intrinsic apolar/polar (benzene/
f
together in such a way as to give a tightly packed (la ) 3.6 Å)
acridine column (Figure 6a and b). The columns are linked
together via intercolumn O-H‚‚‚O hydrogen bonds involv-
ing the coordinatively unsaturated resorcinol OH groups
(O-H‚‚‚O-H) and the acridinyl OH groups (O-H‚‚‚N) acting
(22) When treated with water, adduct 4‚(methanol)‚(water) readily affords diaquo
adduct 4‚2(water).
9
J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002 12459

A R T I C L E S
Tanaka et al.
hydrogen-bonding and π-stacking interactions. With such a
fixation of æ, the orientation of the hydrogen bond will also be
fixed if a preferred linear O-H‚‚‚O bond is assumed. This, in
turn, fixes the relative geometry of the two resorcinol rings
linked by the hydrogen bond and hence the inter(building block)
geometry including the tilt angle (φ) and interring (la) and
interchain (lc) distances. Thus, the flexibility-causing freedoms
associated with anthracenyl hosts 1 and 2 are mostly frozen
here. The structure of the derived 2D network (Scheme 4) is
self-definable or autodetermined as far as it is formed. With
the present included guests as a space filler, such a network is
in fact formed with little guest-dependence and with no
interference by such polar guests as esters, methanol, and water,
which are either rejected by host 3 or bound only to the spectator
OH group of host 4. Varying host/guest ratios and crystal-
lographic disorder of the guests are reminiscent of the incapabil-
ity of the host network to adjust to guest structures.3,9
Langmuir-type Adsorption/Desorption of Organic Guests.
Pores may be generated in some robust metal-coordination
polymers when included guest molecules including labile
metal-ligands are removed without much affecting the host
network.2-6 The microporosity of such guest-off materials can
be demonstrated on the basis of maintenance of the phase during
the guest-on/guest-off process in concern. This is usually done
by referring to similar X-ray powder diffractions (XRPD) of
the guest-off and guest-on species and to Langmuir-type
adsorption/desorption isotherms24 for small, inert guests such
as N2 and CH4.2,3,25,26 In particular cases, microporosity can be
demonstrated directly by single-crystal X-ray diffraction.2c
Hydrogen-bonded networks, on the other hand, are far less
robust and collapse in the absence of guests. Exceptional cases
are some 3D hydrogen-bonded networks which accommodate
various guests with different host/guest ratios and survive
(partial) guest desorption, as demonstrated mainly on the basis
of powder-diffraction evidence.8,9 The present half-filled adduct
3‚0.5(benzene) or 32‚(benzene) provides a novel example of
hydrogen-bonded microporous materials in that (1) a 2D
network is involved and (2) the microporosity is evidenced on
criteria of both XRPD and isotherm. This is probably the first
demonstration of stoichiometric and reversible Langmuir-type
adsorption/desorption of such a sizable organic molecule as
benzene as a guest and a metal-free organic solid as an
adsorbent.
Figure 7. Schematic representation of intermolecular hydrogen bonds in
the anthracenyl system (hosts 1 and 2) (a) and the acridinyl system (hosts
3 and 4) (b).
methanol, chloroform/DMF, toluene/ethyl acetate, etc.) selectiv-
ity of hosts 3 and 4 should not be overlooked. These phenomena
are undoubtedly related to each other and may be understood
primarily in terms of coordinative saturation of the present
network, which gives a low sensitivity, at best, to polar
functional groups of the guests and polar modification of the
host. However, what is really significant here is the way in
which coordinative saturation freezes flexibilities. Before dis-
cussing this, we have to spend some time on the reference
anthracenyl hosts 1 and 2.
Self-Complementary Building Block and Network Rigid-
ity. The flexibility of the anthracenyl system arises, in reference
to Figure 7a, from the conformational (æ) and orientational (φ)
freedom of the host, the rotational freedom around the C-OH
bond which governs the orientation of the key intermolecular
hydrogen bond (O-H‚‚‚O-H) and hence that of guest molecule
bound via hydrogen bonding thereto, and the conformational
freedom of the guest. They cooperate or manipulate to give the
best induced-fit adjustment to the guest molecules with varying
size and shape. Thus, the crystal structures (cell constants,
geometrical parameters (æ, φ, la (anthracene-anthracene), lc,
and ls), and even crystal system and space group), and hence
powder diffractions as well, of adducts 1‚2(guest) and 2‚(guest)
are rendered highly guest-dependent,23 although the strict
stoichiometry (1:2 for 1 and 1:1 for 2) and similar network
motifs (Scheme 1 or 2) are shared by the adducts. Guest
molecules are generally well-packed and well-positioned without
undergoing crystallographic disorder.
In the case of self-complementary hosts 3 and 4, the key
intermolecular hydrogen bond (O-H‚‚‚O-H) as well as the
f
nitrogen atom as a guest are contained in a π-stacked (la(1)
)
Concluding Remarks
3.7 Å in 32 and 3.8 Å in 42 (Table 2)) cyclophane-like structure
(Figure 7b). The molecular conformation, that is, dihedral angle
(æ), must be fixed at a certain narrow range (actually, æ = 69°
in 3‚(guest) and 71° in 4‚(guest), Table 3) to allow simultaneous
To summarize, self-complementary hosts 3 and 4 form a
coordinatively saturated 2D net, which is well preserved upon
(24) Sigmoidal or threshold-type isotherms are observed in the case when
complexation is accompanied by a phase change. For a comprehensive
discussion, see ref 12. Also see: (a) Dewa, T.; Aoyama, Y. Chem. Lett.
2000, 854-855. (b) Ariga, K.; Endo, K.; Aoyama, Y.; Okahata, Y. Colloids
Surf., A 2000, 169, 177-186. (c) Matsuura, K.; Ariga, K.; Endo, K.;
Aoyama, Y.; Okahata, Y. Chem.-Eur. J. 2000, 6, 1750-1756. (d) Dewa,
T.; Saiki, T.; Imai, Y.; Endo, K.; Aoyama, Y. Bull. Chem. Soc. Jpn. 2000,
73, 2123-2127. (e) Naito, M.; Sasaki, Y.; Dewa, T.; Aoyama, Y.; Okahata,
Y. J. Am. Chem. Soc. 2001, 123, 11037-11041.
(25) (a) Fletcher, A. J.; Cussen, E. J.; Prior, T. J.; Rosseinsky, M. J.; Kepert, C.
J.; Thomas, K. M. J. Am. Chem. Soc. 2001, 123, 10001-10011. (b) Kepert,
C. J.; Prior, T. J.; Rosseinsky, M. J. J. Am. Chem Soc. 2000, 122, 5158-
5168. (c) Rujiwatra, A.; Kepert, C. J.; Claridge, J. B.; Rosseinsky, M. J.;
Kumagai, H.; Kurmoo, M. J. Am. Chem. Soc. 2001, 123, 10584-10594.
(26) (a) Yaghi, O. M.; Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. J. Am.
Chem. Soc. 1998, 120, 8571-8572. (b) Reineke, T. M.; Eddaoudi, M.;
O’-Keeffe, M.; Yaghi, O. M. Angew. Chem., Int. Ed. 1999, 38, 2590-
2594. (c) Eddaoudi, M.; Li, H. L.; Yaghi, O. M. J. Am. Chem. Soc. 2000,
122, 1391-1397. (d) Chen, B. L.; Eddaoudi, M.; Hyde, S. T.; O’-Keeffe,
M.; Yaghi, O. M. Science 2001, 291, 1021-1023.
(23) A selected comparison is among adducts 1‚2(4-heptanone), 1‚2(6-unde-
canone), and 1‚2(ethyl acetate). Adduct 1‚2(4-heptanone): monoclinic, P21/
n, a ) 8.973 Å, b ) 13.739 Å, c ) 15.320 Å, â ) 104.11°, V ) 1831.8
Å3, Z ) 2, d ) 1.13 g/cm3. Adduct 1‚2(6-undecanone): monoclinic, P21/
n, a ) 9.375 Å, b ) 13.519 Å, c ) 17.547 Å, â ) 92.36°, V ) 2222.2 Å3,
Z ) 2, d ) 1.10 g/cm3. Adduct 1‚2(ethyl acetate): monoclinic, P21/n, a )
12.847 Å, b ) 9.579 Å, c ) 13.343 Å, â ) 115.24°, V ) 1485.2 Å3, Z )
2, d ) 1.276 g/cm3. Another comparison is among adducts 1‚2(methyl
benzoate), 1‚2(ethyl benzoate), and 1‚2(isobutyl benzoate). Adduct 1‚
2(methyl benzoate): monoclinic, C2/c, a ) 13.396 Å, b ) 20.395 Å, c )
13.918 Å, â ) 117.012°, V ) 3387.9 Å3, Z ) 4, d ) 1.31 g/cm3, æ )
72.4° and 58.3°, lac ) 13.40 Å, laf ) 13.35 Å, lc ) 10.20 Å, ls ) 6.20 Å.
Adduct 1‚2(ethyl benzoate): monoclinic, P21/n, a ) 9.033 Å, b ) 13.885
Å, c ) 15.244 Å, â ) 104.32°, V ) 1852.5 Å3, Z ) 2, d ) 1.25 g/cm3, æ
) 72.4°, lac ) 13.89 Å, laf ) 12.43 Å, lc ) 9.77 Å, ls ) 6.83 Å. Adduct
1‚2(isobutyl benzoate): monoclinic, P21/n, a ) 9.534 Å, b ) 13.479 Å, c
) 15.572 Å, â ) 100.77°, V ) 1966.0 Å3, Z ) 2, d ) 1.27 g/cm3, æ )
89.8°, lac ) 13.48 Å, laf ) 12.22 Å, lc ) 9.86 Å, ls ) 7.40 Å.
9
12460 J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002

Acridinylresorcinol as a Building Block of 2D Nets
A R T I C L E S
3.81 (both t, both 2H, OCH2CH2O), 5.84 (s, 2H, NCH2O), 7.36 (m,
2H, Ar-H), 7.80-7.94 (m, 4H, Ar-H), 8.31 (dd, 2H, Ar-H). Found:
C, 72.31; H, 6.25; N, 5.09%. Calcd for C17H17NO3: C, 72.07; H, 6.05;
N, 4.94%.
alteration of the guests, partial (but not complete) loss of guest,
and polar modification of the host. The rigidity of the network
originates in the cooperation of self-complementary hydrogen
bonding and π-stacking, which leads to a highly structure-
regulating cyclophane-like motif. In this regard, dimeric building
blocks 32 and 42 may represent a supramolecular synthon of
CdC double bonds used as a conformation-fixed building block
of covalent architectures. In principle, the self-complementarity
strategy is applicable not only to the OH group, a commonest
network former in crystal engineering, but also to other
functionalities such as amine, amide, and ligated metal ion, and
thus provides a new tool of designing crystal structures,
especially rigid crystal structures.
Perturbation or variation may also be a key word of this work.
It is only through a systematic variation in guests in preserved
cavities that the guest-binding selectivity can be rigorously
evaluated. The role of the acridinyl OH group in modified host
4 is a kind of substituent effect.4a Various substituents might
also be introduced as selectivity-controllers, as sensing chro-
mophores or fluorophores, or as catalytic sites. The perturbation
methods play key roles in establishing structure-property
correlations in solution chemistry. This is, however, not the case
for molecular crystals, because perturbation, for example,
different substituents or different guests, often lead to different
crystal structures. To exaggerate, one crystal structure represents
one chemistry. The real significance of this work, we believe,
lies in that it refers to the possibility of such a perturbation
approach in crystal engineering.
9-(3,5-Dimethoxyphenyl)acridine (6).28 Into a solution of N-
protected acridone 5 (3.85 g, 13.6 mmol) in THF (60 mL) was added
dropwise under nitrogen at -77 °C a THF solution (27 mL) of 3,5-
dimethoxyphenylmagnesium chloride, obtained from magnesium (1.09
g, 44.9 mmol) and 1-chloro-3,5-dimethoxybenzene (5.17 g, 30.0 mmol)
in the presence of dibromoethane (100 µL). The mixture was stirred at
room temperature for 24 h, treated successively with aqueous HCl and
aqueous K2CO3, and extracted with chloroform. The crude product was
chromatographed after usual workup. The main component eluted with
chloroform was washed with methanol and dried at 100 °C in vacuo
to give dimethoxy derivative 6 (4.01 g, 12.7 mmol, 93%) as a pale-
1
yellow solid: mp 199-200 °C. TLC Rf ) 0.25 (CHCl3). H NMR
(CDCl3): δ 3.83 (s, 6H, OCH3), 6.59 (d with J ) 2.2 Hz, 2H, Ar-H),
6.67 (t with J ) 2.2 Hz, 1H, Ar-H), 7.40-7.50 (m, 2H, Ar-H), 7.70-
7.80 (m, 4H, Ar-H), 8.27 (d with J ) 8.7 Hz, 2H, Ar-H). Found: C,
79.72; H, 5.43; N, 4.46%. Calcd for C21H17NO2: C, 79.98; H, 5.43; N,
4.44%.
9-(3,5-Dihydroxyphenyl)acridine (3).29 A mixture of dimethoxy
derivative 6 (1.60 g, 5.06 mmol) and concentrated hydrobromic acid
(47% HBr, 100 mL) was refluxed under nitrogen for 2 h. The mixture
was allowed to cool to room temperature, neutralized with aqueous
K2CO3, and extracted with ethyl acetate. The crude product was
chromatographed after usual workup. The main component eluted with
ethyl acetate was taken in methanol, reprecipitated upon addition of
diethyl ether, and dried at 170 °C in vacuo to give dihydroxy compound
3 (1.11 g, 3.86 mmol, 77%) as pale-yellow powders: mp > 280 °C
(dec). TLC Rf ) 0.65 (ethyl acetate). 1H NMR (DMSO-d6): δ 6.26 (d
with J ) 2.0 Hz, 2H, Ar-H), 6.44 (t with J ) 2.0 Hz, 1H, Ar-H),
7.52-7.57 (m, 2H, Ar-H), 7.75 (d with J ) 8.7 Hz, 2H, Ar-H), 7.81-
7.86 (m, 2H, Ar-H), 8.18 (d with J ) 8.7 Hz, 2H, Ar-H), 9.60 (s,
2H, OH). 13C NMR (DMSO-d6): δ 102.38, 108.30, 124.00, 125.83,
126.48, 129.12, 130.15, 136.69, 146.90, 148.06, 158.42. MS (FAB+)
(M + H)+ ) 288. Found: C, 79.45; H, 4.67; N, 4.73%. Calcd for
C19H13NO2: C, 79.43; H, 4.56; N, 4.88%.
Experimental Section
General Procedures. THF was distilled from benzophenone ketyl
and dichloromethane from calcium hydride. Other solvents for prepara-
tive purposes and as guests were dried by standard methods. TLC and
column chromatography were carried out with silica gel 60 F254 plates
(Merck) and Wakogel C-200 (Wako), respectively. Melting points were
measured on a Yanako MP-500D melting point apparatus. Microanaly-
ses were performed at the microanalysis center of Kyushu University.
NMR and IR spectra were taken on a Bruker DPX 400 spectrometer
and a JASCO IR-810 spectrophotometer, respectively. Mass spectra
were obtained with a JEOL JMS-700/700S spectrometer. Thermo-
gravimetry was performed by using a Seiko Denshi TG/DTA 220U
thermal analysis system at a heating rate of 10 °C/min, in a similar
manner as described.12 Binding isotherms were recorded with a
BELSORP 18 automated gas adsorption apparatus, in a similar manner
as reported.12 X-ray powder diffractions were obtained with a Rigaku
diffractometer RINT 2000V.
N-(2-Methoxyethoxymethyl)-9-acridone (5).27 A DMF solution
(250 mL) of 9(10H)-acridone (9.76 g, 50.0 mmol) was added to sodium
hydride (2.40 g, 60% in oil), which had been repeatedly washed with
hexane, and the mixture was stirred at room temperature under nitrogen
for 30 min. To the resulting mixture was added dropwise 2-methoxy-
ethoxymethyl chloride (8.0 g, 64 mmol) at 0 °C. The mixture was stirred
for 2 h at room temperature, treated with water, and extracted with
ethyl acetate. The extract was washed successively with water and
aqueous NaCl, dried on Na2SO4, and evaporated. The residue was
chromatographed. The main component eluted with ethyl acetate was
dried at 80 °C in vacuo to give N-protected acridone 5 (10.9 g, 38.5
mmol, 77%) as a pale-yellow solid: mp 180-181 °C. TLC Rf ) 0.43
(ethyl acetate). 1H NMR (DMSO-d6): δ 3.26 (s, 3H, OCH3), 3.53 and
4-Methoxy-9(10H)-acridone (8).30 Anthranilic acid derivative 7 was
obtained in a yield of 88% by Ullmann reaction of o-chlorobenzoic
acid and o-anisidine.31 A mixture of compound 7 (80.1 g, 0.33 mol)
and concentrated sulfuric acid (200 mL) was stirred at 100 °C under
atmosphere for 4 h. Hot water (80-90 °C, 1 L) was added slowly, and
the mixture was stirred at 100 °C for further 1 h and allowed to cool.
Insoluble materials were recovered by filtration and taken in an aqueous
solution (800 mL) of Na2CO3 (61 g, 0.57 mol). The mixture was stirred
at 100 °C for 5 min. Insoluble materials were recovered by filtration
and washed with water and then with hot methanol, and dried at 100
°C in vacuo to give acridone derivative 8 (37.3 g, 0.166 mol, 50%) as
a pale-green solid. 1H NMR (DMSO-d6): δ 4.04 (s, 3H, OCH3), 7.16-
7.21 (m, 1H, Ar-H), 7.22-7.27 (m, 1H, Ar-H), 7.33 (d with J ) 2.0
Hz, 1H, Ar-H), 7.66-7.72 (m, 1H, Ar-H), 7.80 (d with J ) 2.0 Hz,
1H, Ar-H), 7.93 (d with J ) 2.0 Hz, 1H, Ar-H), 8.20 (d with J )
2.0 Hz, 1H, Ar-H), 11.21 (s, 1H, NH).
N-(2-Methoxyethoxymethyl)-4-methoxy-9-acridone (9).27 This
compound was obtained (yield, 65%) as a yellow solid in a similar
manner as parent acridone derivative 5. Compound 9: mp 95-96 °C.
1
TLC Rf ) 0.72 (ethyl acetate). H NMR (DMSO-d6): δ 3.18 (s, 3H,
(28) Grignard reactions were carried out according to the procedures shown in
ref 27a,b.
(29) Deprotection with HBr was carried out according to the procedures shown
in: (a) King, F. E.; Sherred, G. A. J. Chem. Soc. 1942, 415-416. (b)
Hartshorn, S. L.; Baird, S. L., Jr. J. Am. Chem. Soc. 1946, 68, 1562-
1563.
(30) Cyclization was performed according to the procedure shown in: Brock-
mann, H.; Muxfeldt, H.; Haese, G. Chem. Ber. 1957, 90, 44-49.
(31) For the general procedure of Ullmann reactions, see: Fanta, P. E. Chem.
ReV. 1964, 64, 613-632.
(27) N-Alkylation was performed according to the procedures shown in: (a)
Whitten, J. P.; Matthews, D. P.; McCarthy, J. R. J. Org. Chem. 1986, 51,
1891-1894. (b) Zeng, Z. J.; Zimmerman, S. C. Tetrahedron Lett. 1988,
29, 5123-5124. (c) McConnaughie, A. W.; Jenkins, T. C. J. Med. Chem.
1995, 38, 3488-3501.
9
J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002 12461

A R T I C L E S
Tanaka et al.
OCH2CH2OCH3), 3.37-3.41 and 3.45-3.50 (both m, both 2H, OCH2-
CH2O), 3.96 (s, 3H, Ar-OCH3), 5.77 (s, 2H, NCH2O), 7.27-7.38 (m,
2H, Ar-H), 7.44-7.48 (m, 1H, Ar-H), 7.76-7.82 (m, 1H, Ar-H),
7.84-7.89 (m, 2H, Ar-H), 8.17-8.21 (m, 1H, Ar-H). Found: C,
69.16; H, 6.06; N, 4.52%. Calcd for C18H19NO4: C, 68.99; H, 6.11; N,
4.47%.
9-(3,5-Dimethoxyphenyl)-4-methoxyacridine (10).28 This com-
pound was obtained (yield, 37%) as a yellow solid in a similar manner
as parent acridine derivative 6. Compound 10: mp 186-187 °C. TLC
Rf ) 0.36 (CHCl3). 1H NMR (DMSO-d6): δ 3.84 (s, 6H, Dmp-OCH3;
Dmp ) dimethoxyphenyl), 4.19 (s, 3H, Acr-OCH3; Acr ) acridinyl),
6.58 (d with J ) 2.3 Hz, 2H, Dmp-H), 6.73 (t with J ) 2.3 Hz, 1H,
Dmp-H), 7.19 (d with J ) 8.7 Hz, 1H, Acr-H), 7.40-7.45 (m, 2H,
Acr-H), 7.51-7.57 (m, 1H, Acr-H), 7.63-7.66 (d, 1H, Acr-H),
7.79-7.85 (m, 1H, Acr-H), 8.22 (d with J ) 8.7 Hz, 1H, Acr-H).
Found: C, 76.01; H, 5.61; N, 3.94%. Calcd for C22H19NO3: C, 76.50;
H, 5.54; N, 4.06%.
orange prisms. Found: C, 56.97; H, 3.43; N, 3.26%. Calcd for C20H14-
Cl3NO3: C, 56.83; H, 3.34; N, 3.31%. Adduct 4‚0.5(toluene)‚0.5(water)
(method B with ethyl acetate) as orange prisms. Found: C, 75.09; H,
5.17; N, 3.74%. Calcd for C22.5H18NO3.5: C, 75.39; H, 5.06; N, 3.91%.
Adduct 4‚(methanol)‚(water) (method C) as orange prisms. Found: C,
68.35; H, 5.11; N, 3.90%. Calcd for C20H19NO5: C, 67.98; H, 5.42; N,
3.96%. Adduct 4‚(ethyl acetate) (method C) as orange prisms. Found:
C, 70.28; H, 5.42; N, 3.39%. Calcd for C23H21NO5: C, 70.58; H, 5.41;
N, 3.58%.
Treatment of full-adduct 3‚(benzene) at 250 mmHg at room
temperature for 3 days gave the half-adduct 3‚0.5(benzene). Single
crystals of apohost 4 were obtained by sublimation when adduct 4‚
(ethyl acetate) was heated at 180 °C in vacuo (1 mmHg) for 3 days.
X-ray Crystal Structure Determinations. Diffraction data were
collected on a Rigaku AFC7R four-circle automated diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.71069 Å). Single
crystals were mounted on a glass fiber. A linear absorption correction
was applied in each case. The intensities of three standard reflections
were monitored after every 150 reflections were taken; the decay of
intensities was within 2%. The intensity data collected by using the
ω-2θ scan technique were corrected for both Lorentz and polarization
effects. The unit-cell parameters used for refinement were determined
by least-squares calculations on the setting angles of 25 reflections.
The structures were solved by a combination of the direct method
using SIR92 program and the Fourier techniques using DIRDIF99. Non-
hydrogen atoms of hosts 3 and 4 were refined anisotropically. The
hydroxyl hydrogen atoms in the resorcinol rings were located by
difference Fourier maps, and the rest in the host molecules were
introduced at calculated positions (C-H ) 0.95 Å). All of these
hydrogen atoms were refined isotropically. Non-hydrogen and hydrogen
atoms of guests benzene and chloroform were refined anisotropically
and isotropically, respectively, in a similar manner as those in the hosts.
Non-hydrogen atoms in other guests were refined isotropically. The
weighting scheme w-1 ) [σ2(Fo) + (0.0005Fo)2] was employed for all
of the adducts. Atomic scattering factors and anomalous dispersion
terms were taken from International Tables for X-ray Crystallography.34
Calculations were performed by using the CrystalStructure crystal-
lographic software package of the Molecular Structure Corp., and the
crystal structures were visualized by using the Cerius2 set of computer
programs of Molecular Simulation Inc.
9-(3,5-Dihydroxyphenyl)-4-acridinol (4).32 Into a dichloromethane
solution (250 mL) of trimethoxy derivative 10 (6.96 g, 20.2 mmol)
was added dropwise slowly a solution (40 mL) of BBr3 (28.3 mL, 88.3
mmol) in dichloromethane (40 mL) at 0 °C. After the addition was
complete, the mixture was further stirred at room temperature for 12
h, treated with water, and extracted with ethyl acetate. The crude product
was chromatographed after usual workup. The main component eluted
with ethyl acetate was dried at 100 °C in vacuo to give trihydroxy
compound 4 (4.54 g, 15.0 mmol, 74%) as yellow powders: mp > 230
°C (dec). TLC Rf ) 0.57 (ethyl acetate). 1H NMR (DMSO-d6): δ 6.24
(d with J ) 2.0 Hz, 2H, Dhp-H; Dhp ) dihydroxyphenyl), 6.42 (d
with J ) 2.0 Hz, 1H, Dhp-H), 7.09-7.18 (m, 2H, Acr-H; Acr )
acridinyl), 7.35-7.40 (m, 1H, Acr-H), 7.52-7.57 (m, 1H, Acr-H),
7.73 (d with J ) 8.6 Hz, 1H, Acr-H), 7.81-7.86 (m, 1H, Acr-H),
8.24 (d with J ) 8.8 Hz, 1H, Acr-H), 9.60 (s, 2H, Dhp-OH), 9.82
(bs, 1H, Acr-OH). 13C NMR (DMSO-d6): δ 158.37, 152.60, 146.87,
146.21, 140.14, 139.97, 129.94, 129.02, 126.63, 126.48, 126.02, 124.82,
124.36, 116.33, 109.26, 108.20, 102.31. MS (FAB+) (M + H)+
)
304. Found: C, 75.09; H, 4.32; N, 4.56%. Calcd for C19H13NO3: C,
75.24; H, 4.32; N, 4.62%.
Adducts and Apohost. Adducts were obtained by recrystallization
of hosts 3 and 4 in one of three ways. In method A, the guest vapor
was allowed to diffuse into a solution of the host in methanol, DMF,
or ethyl acetate. In method B, a solution of the host in methanol/guest
or ethyl acetate/guest was left open to allow methanol or ethyl acetate
to evaporate gradually. In method C, a solution of the host in guest
was left open to allow the solvent (guest) to evaporate gradually. The
compositions of the adducts were determined by 1H NMR integration,
elemental analyses, and thermogravimetry. Adduct 3‚(benzene) (method
A with DMF or methanol) as orange prisms. Found: C, 82.07; H, 5.26;
N, 3.81%. Calcd for C25H19NO2: C, 82.17; H, 5.24; N, 3.83%. Adduct
3‚0.5 (toluene) (method B with methanol) as orange prisms. Found:
C, 80.69; H, 5.26; N, 4.04%. Calcd for C22.5H17NO2: C, 81.06; H, 5.14;
N, 4.20%. Adduct 3‚(chloroform) (method A with DMF) as orange
prisms.33 Found: C, 60.07; H, 3.71; N, 3.76%. Calcd for C20H14Cl3-
NO2: C, 59.07; H, 3.47; N, 3.44%. Adduct 3‚0.5 (isobutyl benzoate)
(method B with methanol) as orange prisms. Found: C, 77.88; H, 5.32;
N, 3.73%. Calcd for C24.5H20NO3: C, 78.17; H, 5.36; N, 3.72%. Adduct
4‚(benzene) (method B with ethyl acetate) as orange prisms. Found:
C, 78.81; H, 5.04; N, 3.64%. Calcd for C25H19NO3: C, 78.72; H, 5.02;
N, 3.67%. Adduct 4‚(chloroform) (method A with ethyl acetate) as
Acknowledgment. This work was supported by grant-in-aids
for COE Research (no. 08CE2005) in Kyushu University and
for Scientific Research (no. 13555220) in Kyoto University from
the Ministry of Education, Science, Sports, and Culture, Japan,
and also by CREST of Japan Science and Technology Corpora-
tion (JST).
Supporting Information Available: X-ray structural informa-
tion for adducts 3‚(benzene), 3‚(chloroform), 3‚(isobutyl ben-
zoate), 4‚(benzene), 4‚(chloroform), 4‚0.5(toluene)‚0.5(water),
4‚(methanol)‚(water), and 4‚(ethyl acetate) and apohost 4,
including tables of crystal and refinement data, atomic coordi-
nates and thermal parameters, bond lengths and angles, aniso-
tropic displacement values, torsion angles, nonbonded contacts
out to 3.60 Å, and thermal ellipsoid figures (PDF). They are
also available in CIF format. This material is available free of
charge via the Internet at http://pubs.acs.org.
JA026704L
(32) Deprotection with BBr3 was performed according to the procedure shown
in: Bonner, T. G.; Bourne, F. J.; McNally, S. J. Chem. Soc. 1960, 2929-
2934.
(34) Creagh, D. C.; McAuley, W. J. In International Tables for X-ray
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol C.
(33) On standing, adduct 3‚(chloroform) gradually loses some of the included
guest molecules.
9
12462 J. AM. CHEM. SOC. VOL. 124, NO. 42, 2002