The generality of architectural isomerism in designer inclusion frameworks

Article abstract of DOI:10.1021/ja0030257

We describe herein new structural isomers of a lamellar host system based on organodisulfonate "pillars" that connect opposing hydrogen-bonded sheets, consisting of topologically complementary guanidinium (G) ions and sulfonate (S) groups, to generate inc

Full text of DOI:10.1021/ja0030257

J. Am. Chem. Soc. 2001, 123, 4421-4431
4421
The Generality of Architectural Isomerism in Designer Inclusion
Frameworks
K. Travis Holman,† Stephen M. Martin, Daniel P. Parker,§ and Michael D. Ward*
Contribution from the Department of Chemical Engineering and Materials Science, UniVersity of
Minnesota, Amundson Hall, 421 Washington AVenue, SE, Minneapolis, Minnesota, 55455
ReceiVed August 14, 2000. ReVised Manuscript ReceiVed December 6, 2000
Abstract: We describe herein new structural isomers of a lamellar host system based on organodisulfonate
“pillars” that connect opposing hydrogen-bonded sheets, consisting of topologically complementary guanidinium
(G) ions and sulfonate (S) groups, to generate inclusion cavities between the sheets. These new isomerss
zigzag brick, double brick, V-brick, and crisscross bilayersexpand significantly on our earlier report of
architectural isomerism displayed by the discrete bilayer and simple brick forms. We demonstrate here that
the discrete bilayer-simple brick isomerism, which was limited to several host-guest combinations based on
the G2(4,4′-biphenyldisulfonate) host and one pair of compounds based on the G2(2,6-naphthalenedisulfonate),
can be generalized to other organodisulfonate pillars. Furthermore, in many cases the selectivity toward the
different framework isomers reflects a rather systematic templating role of the guest molecules and host-
guest recognition during assembly of the lattice. We also describe a convenient approach to identifying and
classifying the innumerable possible host architectures based upon the pillar projection topologies for the GS
sheets and the intersheet connectivities. The discovery of these new architectures reveals a structural versatility
for this class of materials that exceeds initial expectations and observations. Each topology produces different
connectivities between the sheets in the third dimension that endows each framework isomer with uniquely
shaped and sized inclusion cavities, enabling this host system to conform readily to different guests. The
unlimited number of architectures available, combined with the inherent conformational softness and structural
tunability of these host lattices, suggests a near universality for the GS system with respect to guest inclusion.
Introduction
difficult, owing to the relatively narrow distribution of guest
sizes and shapes that typically can be included within a given
host framework. Like crystalline organic solids in general,
structural modifications of the molecular components of a host
usually lead to unpredictable and often undesirable changes in
crystal architecture, frustrating systematic control of structural
features such as inclusion cavity size and shape, and frequently
resulting in loss of inclusion behavior. In principle, these
obstacles can be surmounted with a host system based on
structurally persistent supramolecular building blocks equipped
with components that can be interchanged with retention of the
general structural features and supramolecular connectiVity of
the host lattice.
Over the past few years, we have reported inclusion com-
pounds based on lamellar host frameworks constructed from
guanidinium and organodisulfonate ions that embody the central
axiom of crystal engineering3sthe systematic design and
predictable synthesis of solid state structures through judiciously
chosen molecular components.4 The organic residues of the
organodisulfonate ions in these host frameworks serve as
molecular “pillars” that connect opposing hydrogen-bonded
sheets (Scheme 1) of complementary guanidinium (G) ions and
sulfonate (S) moieties, thereby producing inclusion cavities
Crystalline inclusion compounds1 are of considerable interest
because of their potential use in applications such as optoelec-
tronics, chemical separations, storage of sensitive compounds,
and nanoconfined chemical reactions. Consequently, numerous
strategies for designer organic host lattices are being explored.2
The realization of inclusion compounds, however, can be
* To whom correspondence should be addressed. E-mail: wardx004@
tc.umn.edu.
† Natural Sciences and Engineering Research Council (NSERC) of
Canada Postdoctoral Fellow.
§ University of Minnesota Materials Research Science and Engineering
REU Fellow.
(1) For an introduction to organic inclusion compounds, see: (a) Weber,
E. In Topics in Current Chemistry; Springer-Verlag: Berlin, 1987; Vol.
140. (b) ComprehensiVe Supramolecular Chemistry; Atwood, J. A., Davies,
J. E. D., NacNicol, D. D., Vo¨gtle, F., Lehn, J.-M., Eds.; Elsevier Science:
New York, 1996; Vol. 6. (c) Inclusion Compounds. Structural Aspects of
Inclusion Compounds Formed by Organic Host Lattices; Atwood, J. A.,
Davies, J. E. D., MacNicol, D. D., Eds.; Academic: London, 1984; Vol. 2.
(d) Bishop, R. Chem. Soc. ReV. 1996, 311-319.
(2) (a) Aoyama, Y. In Topics in Current Chemistry; Springer-Verlag:
Berlin, 1998; Vol. 198, p 131. (b) Endo, K.; Ezuhara, T.; Koyanagi, M.;
Masuda, H.; Aoyama, Y. J. Am. Chem. Soc. 1997, 119, 499. (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. (d) Toda, F. In Inclusion Compounds, Atwood, J. A., Davies, J.
E. D., MacNicol, D. D., Eds.; Oxford University Press: 1991; Vol. 4. (e)
Caira, M. R.; Nassimbeni, L. R.; Toda, F.; Vujovic, D. J. Am. Chem. Soc.
2000, 122, 9367. (f) Ermer, O. HelV. Chim. Acta 1991, 74, 825. (g) Ermer,
O. J. Am. Chem. Soc. 1988, 110, 3747. (h) Wang, X.; Simard, M.; Wuest,
J. D. J. Am. Chem. Soc. 1994, 116, 12119. (i) Brunet, P.; Simard, M.; Wuest,
J. D. J. Am. Chem. Soc. 1997, 119, 2737. (j) Biradha, K.; Dennis, D.;
MacKinnon, V. A.; Sharma, C. V. K.; Zaworotko, M. J. J. Am. Chem. Soc.
1998, 120, 11895.
(3) (a) Schmidt, G. M. J. Pure. Appl. Chem. 1971, 27, 647. (b) Desiraju,
G. R. Crystal Engineering: The Design of Organic Solids; Elsevier: New
York, 1989.
(4) (a) Russell, V. A.; Evans, C. C.; Li, W.; Ward, M. D. Science 1997,
276, 575. (b) Swift, J. A.; Reynolds, A. M.; Ward, M. D. Chem. Mater.
1998, 10, 4159. (c) Swift, J. A.; Ward, M. D. Chem. Mater. 2000, 12, 1501.
(d) Evans, C. C.; Sukarto, L.; Ward, M. D. J. Am. Chem. Soc. 1999, 121,
320.
10.1021/ja0030257 CCC: $20.00 © 2001 American Chemical Society
Published on Web 04/19/2001

4422 J. Am. Chem. Soc., Vol. 123, No. 19, 2001
Holman et al.
Scheme 1
continuous in 3-D because pillars projecting from both sides of
each GS sheet connect adjacent sheets. The fundamental
difference between the bilayer and simple brick architectures
is, therefore, associated with the different up/down projections
of the pillars from the GS sheets, or equivalently, their
“projection topologies.”
Architectural isomerism has been observed in several other
hydrogen-bonded compounds9 and appears to have important
ramifications for inclusion behavior. The number of isomers
within each system, however, generally is limited. For example,
1,3-cyclohexanedione can exist in two crystalline architectures,
a guest-free 1-D hydrogen-bonded chain or a discrete host-
guest cycla[6]mer,9a wherein identical tautomeric forms of the
molecule are connected by the same O-H‚‚‚OdC hydrogen
bonds. Metal-organic frameworks can also exhibit architectural
isomerism,10 as exemplified by [Co(4,4′-bipyridine)1.5(NO3)2]n,
which exhibits three architectural isomerssladder, bilayer, and
modified brick wallswith different geometrical arrangements
of the same T-shaped module.10a-c
Scheme 2
We describe herein (i) the discovery of several new GS
architecturesszigzag brick, double brick, and V-bricksthat add
to the aforementioned discrete bilayer and simple brick forms
and suggest that the number of architectures available to this
system is substantial, (ii) a convenient approach to identifying
and classifying these host architectures based upon their pillar
projection topologies and intersheet connectivities, (iii) archi-
tectural isomerism in G2BPDS, G2NDS, and several new GS
hosts based on other organodisulfonate pillars, expanding
significantly our previous observations and demonstrating the
generality of this phenomenon, and (iv) unambiguous evidence
for guest-templating and host-guest recognition during host
framework assembly. The discovery of these new architectures
reveals a structural versatility for this class of materials that
exceeds initial expectations and observations. Each topology
produces different connectivities between the sheets in the third
dimension that endows each framework isomer with uniquely
shaped and sized inclusion cavities, enabling this host system
to conform readily to different guests. The innumerable number
of possible architectures, combined with the inherent confor-
between the GS sheets. The GS sheets are highly persistent,
and more important, the size and character of the inclusion
cavities can be manipulated by the choice of organodisulfonate
pillar without disrupting the supramolecular connectivity of the
GS sheet.
We also reported that inclusion compounds based on one
particular GS host, namely G2BPDS (BPDS ) 4,4′-biphenyl-
disulfonate), exhibit either a discrete “bilayer” or a continuous
“brick” (hereafter referred to as “simple brick”) architecture
(Scheme 2), wherein the selectivity for these framework isomers
appeared to be governed by the templating action of the guest
molecules.5,6 We characterized this phenomenon as “architec-
tural isomerism,” a term that we reserve for structural isomers
that have the same compositions and identical, well-defined
supramolecular connectivities (e.g., the H-bonded GS sheet),
but differ with respect to the geometrical arrangements, or
topologies, of the chemical subunits.7 Pursuant to our initial
observation of architectural isomerism, we reported one example
of each of these two architectures for the G2NDS host (NDS )
2,6-naphthalenedisulfonate).8
(7) Architectural isomerism can be considered a subset of “supra-
molecular isomerism”. Supramolecular isomerism (see Henniger, T. L.;
MacQuarrie, D. C.; Losier, P.; Rogers, R. D.; Zaworotko, M. J. Angew.
Chem., Int. Ed. Engl. 1997, 36, 972) encompasses structural isomers in
which the supramolecular bonding motifs may be the same or different.
By this definition, supramolecular isomerism is ubiquitous, as it includes
polymorphs and solvates in addition to architectural isomers. Architectural
isomerism can be further distinguished by comparison with host lattices
that do not strictly fulfill the criterion. Although the substituted resorcinol
host in reference 2b may appear to exhibit architectectural isomerism, the
two types of inclusion compounds differ only with respect to a shift registry
of the 1-D hydrogen-bonded chains and are not architectural isomers.
Different host architectures in ref 2c are achieved by changing the host
components, but these hosts are not isomers because their chemical
compositions differ.
(8) Holman, K. T.; Ward, M. D. Angew. Chem., Int. Ed. 2000, 39, 1653.
(9) (a) Etter, M. C.; Urbanczyk-Lipkowska, Z.; Jahn, D. A. J. Am. Chem.
Soc. 1986, 108, 5871. (b) MacGillivray, L. R.; Diamente, P. R.; Reid, J.
L.; Ripmeester, J. A. Chem. Commun. 2000, 359. (c) MacGillivray, L. R.;
Atwood, J. L. J. Am. Chem. Soc. 1997, 119, 6931. (d) MacGillivray, L. R.;
Holman, K. T.; Atwood, J. L. Cryst. Eng. 1998, 1, 87-96. (e) Herbstein,
F. H. In Topics in Current Chemistry; Springer-Verlag: Berlin, 1987; Vol.
140.
The different connectivities in the third dimension exhibited
by the bilayer and simple brick isomers are achievable because
the organodisulfonate pillars can extend from either side of the
GS sheet. In the bilayer form the pillars project from the same
side of each sheet, forming bilamellae that are discrete in the
third dimension. The simple brick architecture, however, is
(10) (a) Losier, P.; Zarowotko, M. J. Angew. Chem., Int. Ed. Engl. 1996,
35, 2779. (b) Power, N. K.; Hennigar, T. L.; Zaworotko, M. J. New J. Chem.
1998, 22, 177. (c) Gudbjartson, H.; Biradha, K.; Poirier, K. M.; Zaworotko,
M. J. J. Am. Chem. Soc. 1999, 121, 2599. (d) Kasai, K.; Aoyagi, M.; Fujita,
M. J. Am. Chem. Soc. 2000, 122, 2140. (e) Battan, S. R.; Robson, R. Angew.
Chem., Int. Ed. 1998, 37, 1460. (f) Hagerman, P. J.; Hagerman, D.; Zubieta,
J. Angew. Chem., Int. Ed. 1999, 38, 2638. (g) Li, H.; Yaghi, O. M. J. Am.
Chem. Soc. 1998, 120, 10569. (h) O’Keefe, M.; Yaghi, O. M. Eur. Chem.
J. 1999, 5, 2796.
(5) Swift, J. A.; Pivovar, A. M.; Reynolds, A. M.; Ward, M. D. J. Am.
Chem. Soc. 1998, 120, 5887.
(6) Holman, K. T.; Pivovar, A. M.; Swift, J. A.; Ward, M. D. Acc. Chem.
Res. 2001, 34, 107.

Architectural Isomerism in Inclusion Frameworks
J. Am. Chem. Soc., Vol. 123, No. 19, 2001 4423
Scheme 3
the BDS pillars, whose molecular planes are orthogonal to the
major GS ribbons (Figure 1, Table 1). Benzene, which has a
slightly larger molecular volume (Vg ) 79 Å3), templates the
formation of the lower density, more open simple brick
architecture, affording G2BDS‚3(benzene). The pillars and
guests are isostructural and exhibit herringbone packing, made
possible by the ability of the BDS pillars to rotate about their
C-S bonds. We reported other isostructural combinations,
G2NDS‚3(naphthalene), G2BPDS‚3(biphenyl), and G2ADS‚
3(anthracene),8 with similar herringbone pillar-guest packings
that mimic the layer motifs in the crystals of their respective
pure guests. The pillar-guest organization in G2BDS‚3(benzene),
however, approaches that of the herringbone layers in the more
densely packed high pressure form of pure benzene rather than
its ambient form.13
The G2ADS host also exhibits bilayer-simple brick isomer-
ism, although with proportionally larger guest molecules.
Naphthalene guests are incorporated in the bilayer framework
as G2ADS‚(naphthalene), but the larger pyrene promotes the
formation of the simple brick G2ADS‚(pyrene). This can be
attributed to the large size of the pyrene guests, which cannot
be accommodated by the undersized inclusion cavities of the
bilayer framework. The pyrene guests are confined within ∼7.5
Å wide channels, perpendicular to the GS major ribbon direction
and flanked by the ADS pillars. G2BDS‚3(benzene) and G2ADS‚
(pyrene) illustrate the extraordinary capacity of the simple brick
mational softness and structural tunability of these host lattices,
suggests a near universality for the GS system with respect to
guest inclusion.
Results and Discussion
Generality of Bilayer-Brick Isomerism and New Brick
Architectures. Previous work in our laboratory with GS
inclusion compounds based on BPDS established architectural
isomerism between the bilayer and “simple” brick frameworks.5,6
These investigations, and complementary studies based on 4,4′-
azobenzenedisulfonate (ABDS) and 2,6-naphthalenedisulfonate
(NDS) pillars,4d,8 have suggested that bilayer-brick isomerism
may be governed by the combined steric demands of the pillars
and guests in the gallery regions between the GS sheets. The
generality of this phenomena is demonstrated herein by several
new examples of bilayer and simple brick host frameworks
constructed with BPDS, NDS, 1,4-benzenedisulfonate (BDS),
and 2,6-anthracenedisulfonate (ADS) pillars, as well as the by
the observation of new architectural isomers with these and other
pillars. Scheme 3 illustrates, in overview form, the extent to
which the results reported herein expand upon our previously
reported efforts. The dashed lines in Scheme 3 represent
architectures that have been reported previously, whereas the
solid lines represent the new examples. This scheme illustrates
that architectural isomerism, wherein more than one isomer is
observed for a given host composition, has been limited to the
G2BPDS and G2NDS hosts. With the exception of G2MDBDS
and G2MDS, the scheme illustrates that some form of archi-
tectural isomerism has now been demonstrated for each host
described here. This illustrates the generality of architectural
isomerism and the likelihood that all of the architectures in
Scheme 3, as well as ones yet undiscovered, are achievable for
numerous organodisulfonate pillars.
architecture to adapt to the steric demands of the guest molecules
through puckering of the conformationally flexible GS sheet
about its major ribbon edges (defined by the interribbon angle
θIR, see Figure 1). Puckering allows the host to significantly
adjust its inclusion cavity volume, Vinc, and “shrink-wrap” about
the guests. This, combined with rotation of the pillars about
their C-S bonds, provides the host framework with a route to
optimized host-guest interactions, similar to behavior described
(12) Bilayer host frameworks often exhibit a “shifted ribbon”, rather than
quasihexagonal, GS sheet motif. The shifted-ribbon motif is generated by
a translation of adjacent GS ribbons by up to one-half of the ribbon repeat
distance. This minor structural variation is thought to be a consequence of
subtle steric packing forces between the pillars and guests. Because the
supramolecular connectivities of the quasihexagonal and shifted-ribbon motif
differ, frameworks with different GS motifs can be regarded as supra-
molecular isomers but technically are not architectural isomers. For every
pillar that adopts a bilayer framework we have observed at least one example
that exhibits the quasihexagonal sheet motif. Thus, the bilayer framework
can be regarded as a true architectural isomer of its corresponding brick
forms.
(13) The observation of nonambient herringbone packing can be attributed
to the structural incompatibility of the GS host lattice and the ambient motif.
The 2-D herringbone motif of the ambient and high pressure form of benzene
have lattice dimensions of 7.44 Å × 6.92 Å (area/benzene molecule )
51.5 Å2) and 7.35 Å × 5.38 Å (area/benzene molecule ) 39.5 Å2),
respectively. The pillar-guest layers in G2BDS‚3(benzene) exhibit lattices
of 7.65 Å × 11.62 Å, corresponding to 7.65 Å × 5.81 Å (area ) 44.5 Å2)
if the crystallographic symmetry of the layers is ignored. Pillar-guest
packing with the ambient density would require a lattice dimension normal
to the GS ribbon of 2 × 6.92 Å ) 13.84 Å, which exceeds the width of
two GS ribbons (2 Å × 6.5 Å ) 13.0 Å). Equivalently, the area required
by the ambient phase exceeds the available area of 48.75 Å2 in a framework
having a flat quasihexagonal GS sheet. The actual area occupied by the
benzene pillars and guests is less than this ideal value owing to puckering
of the GS host, which effectively exerts an internal lattice pressure that
enforces the denser packing of benzene guests and benzene pillar fragments.
Systematic Architectural Isomerism with Arene Pillars.
With small guests such as tetrahydrofuran (volume of guest,
Vg ) 73 Å3)11 the smallest pillar, BDS, adopts a typical bilayer
framework with quasihexagonal GS sheets.12 The guests in
G2BDS‚(tetrahydrofuran) are included in cavities flanked by
(11) Molecular volume calculations were performed using MSI Cerius2
v.3.5. Vg values are obtained using a Connolly (van der Waals) surface
model with a probe radius of zero and a dot density of 100 Å-1. These
values tend to be systematically lower, by up to ca. 6%, than those
determined by traditional means (see Kitaigorodski, A. I. Molecular Crystals
and Molecules; Academic Press: New York, 1973; pp. 18-21). Vinc values
are obtained by determining the “available volume” (probe radius ) 0.5
Å, grid spacing of “fine”) in the unit cell after removal of guests and
normalizing to one host formula unit. Vhost values are calculated by
subtracting the “available volume” from the unit cell volume and normal-
izing to one host formula unit. These values are consistent, to within 5 Å3,
among different inclusion compounds of the same host.

4424 J. Am. Chem. Soc., Vol. 123, No. 19, 2001
Holman et al.
Table 1. Summary of Crystallographic Data for Reported Compounds
compound
formula
formula wt
crystal system monoclinic
G2BDS‚(thf) G2BDS‚3(benzene) G2BDS‚2(p-xylene) G2BDS‚2(o-xylene) G2BDS‚2(naphthalene) G2NDS‚(benzene) G2NDS‚(p-xylene)
C
12H24N6O7S2
C26H34N6O6S2
590.72
monoclinic
P21/n
C24H36N6O7S2
568.70
orthorhombic
Pbca
C24H36N6O6S2
568.70
orthorhombic
Pbca
C12H24N6O7S2
612.72
orthorhombic
Pbca
C18H24N6O6S2
484.56
triclinic
C20H28N6O6S2
512.60
triclinic
428.49
space group
color
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
temp (K)
Z
Cmcm
colorless
7.5299(6)
12.465(1)
21.430(2)
90
P1h
P1h
colorless
7.6465(6)
11.6218(9)
17.625(2)
90
96.211(1)
90
1557.1(2)
173(2)
colorless
13.4285(9)
12.5989(9)
17.785(2)
90
90
90
3008.9(4)
173(2)
2
colorless
13.1459(8)
12.4292(8)
18.882(2)
90
90
90
3085.3(3)
173(2)
2
colorless
13.360(1)
12.647(1)
18.168(2)
90
90
90
3069.8(4)
173(2)
2
colorless
6.2166(3)
7.1847(4)
13.1213(7)
74.725(1)
83.331(1)
85.826(1)
560.98(5)
173(2)
colorless
7.2609(9)
7.4075(9)
13.154(2)
89.189(2)
77.186(2)
62.193(2)
560.98(2)
173(2)
90
90
2011.4(3)
173(2)
4
2
1
1
R1 [I > 2σ(I)] 0.0318
wR2 [I > 2σ(I)] 0.0875
0.0418
0.1130
1.19
0.0344
0.0971
1.06
0.0424
0.1201
1.081
0.0326
0.0795
1.026
0.0338
0.0882
1.037
0.0343
0.0941
1.075
G.O.F.
1.097
compound
G2NDS‚3(o-xylene) G2NDS‚2(1-MN) G2NDS‚2(pyrene) G2BPDS‚2(perylene) G2ADS‚(p-xylene) G2ADS‚(o-xylene) G2ADS‚(naphthalene)
formula
formula wt
crystal system
space group
color
a (Å)
b (Å)
c (Å)
R (deg)
C
36H48N6O6S2
C34H38N6O6S2
690.82
orthorhombic
Pbca
colorless
13.3756(3)
12.4586(3)
22.3040(5)
90
90
90
3716.8(2)
173(2)
4
C44H38N6O6S2
810.92
orthorhombic
Pbca
colorless
13.4471(4)
12.1155(4)
23.9856(7)
90
90
90
3907.7(2)
173(2)
4
C54H44N6O6S2
937.08
orthorhombic
Pbca
orange
13.6864(7)
12.4544(7)
26.473(2)
90
90
90
4512.4(4)
173(2)
4
C24H30N6O6S2
562.66
triclinic
C24H30N6O6S2
562.66
triclinic
C26H28N6O6S2
584.66
triclinic
724.92
monoclinic
P21/n
colorless
7.5334(6)
12.2651(9)
20.621(2)
90
96.645(1)
90
1892.5(3)
173(2)
2
P1h
P1h
P1h
pale yellow
6.2024(4)
7.1901(5)
15.184(1)
80.859(1)
82.235(1)
85.208(1)
661.1(1)
173(2)
pale yellow
6.2001(5)
7.3015(6)
15.145(2)
103.134(2)
94.777(1)
92.607(2)
663.0(1)
173(2)
pale yellow
6.2127(6)
7.19775(7)
15.372(2)
78.105(2)
81.376(2)
87.493(2)
664.9(1)
173(2)
â (deg)
γ (deg)
V (Å3)
temp (K)
Z
1
1
1
R1 [I > 2σ(I)]
wR2 [I > 2σ(I)]
G.O.F.
0.0403
0.1110
1.022
0.0568
0.1569
1.047
0.0371
0.0869
1.019
0.0422
0.1020
1.049
0.0363
0.0964
1.070
0.0381
0.1008
1.064
0.0386
0.1091
1.090
compound
G2ADS‚(pyrene) G2ADS‚3(biphenyl) G2ADS‚2(perylene)
G2ODS
G2ODS‚(hexane) G2PEDS‚(toluene) G2PEDS‚3(acetonitrile)
formula
formula wt
crystal system
space group
color
a (Å)
b (Å)
c (Å)
R (deg)
C
32H30N6O6S2
C52H50N6O6S2
919.10
monoclinic
Pn
pale yellow
7.4697(8)
26.627(3)
11.836(2)
90
92.100(2)
90
2352.5(4)
173(2)
C56H44N6O6S2
961.10
orthorhombic
Pbca
orange
13.789(2)
12.303(1)
26.784(2)
90
90
90
4544.0(7)
173(2)
2
C10H28N6O6S2
392.15
orthorhombic
Pna21
colorless
12.658(2)
42.116(4)
11.596(1)
90
90
90
6182(1)
173(2)
12
C16H42N6O6S2
464.24
orthorhombic
Pnma
colorless
14.426(1)
22.438(2)
7.4303(6)
90
90
90
2405.2(3)
173(2)
4
C21H28N6O7S2
540.62
triclinic
C20H29N9O7S2
571.64
orthorhombic
P212121
colorless
7.4659(4)
13.7874(8)
29.084(2)
90
90
90
2993.8(3)
173(2)
4
658.74
monoclinic
P21/n
pale yellow
7.447(1)
9.873(2)
20.756(3)
90
94.601(3)
90
1521.2(3)
173(2)
2
P1h
colorless
7.5011(9)
12.092(2)
29.989(5)
84.585(1)
86.477(9)
89.23(1)
2702.7(6)
173(2)
â (deg)
γ (deg)
V (Å3)
temp (K)
Z
2
2
R1 [I > 2σ(I)]
wR2 [I > 2σ(I)]
G.O.F.
0.0413
0.0967
0.905
0.0457
0.0702
0.812
0.0439
0.0898
1.06
0.0541
0.1310
1.018
0.0666
0.2163
1.075
0.0511
0.01035
0.877
0.0564
0.01453
1.098
compound
G2PEDS‚(mesitylene)‚(MeOH)
24H36N6O8S2
G2MDS‚(acetone)‚(MeOH)
G2MDBDS‚2(thf)
formula
formula wt
crystal system
space group
color
a (Å)
b (Å)
c (Å)
C
C15H32N6O8S2
488.59
orthorhombic
Cmc21
colorless
7.501(1)
20.576(3)
15.796(2)
90
90
90
2438.1(6)
173(2)
4
C19H38N6O9S2
558.68
orthorhombic
Pnma
colorless
21.1037(8)
7.5867(4)
19.3182(8)
90
90
90
3093.2(2)
173(2)
4
600.71
orthorhombic
P212121
colorless
7.5839(4)
14.2280(8)
27.748(2)
90
90
90
2994.2(3)
173(2)
4
R (deg)
â (deg)
γ (°)
V (Å3)
temp (K)
Z
R1 [I > 2σ(I)]
wR2 [I > 2σ(I)]
G.O.F.
0.0408
0.1044
1.050
0.0317
0.0823
1.098
0.0967
0.2432
1.012

Architectural Isomerism in Inclusion Frameworks
J. Am. Chem. Soc., Vol. 123, No. 19, 2001 4425
Figure 1. GS inclusion compounds exemplifying the bilayer-simple brick isomerism. (a) Bilayer G2BDS‚(tetrahydrofuran) as viewed down
[110], (b) simple brick G2BDS‚3(benzene), (c) bilayer G2ADS‚(naphthalene), (d) simple brick G2ADS‚(pyrene). The host frameworks are drawn
as wireframe and the guests as space-filling. The right-hand panels in (b) and (d) depict the top-down view of the pillar-guest packing within the
gallery regions of the brick frameworks. The guanidinium ions and oxygen atoms of the sulfonates in the GS sheets have been removed for clarity,
and the major ribbons are parallel to the a axes. θIR represents the interribbon puckering angle.
above for G2BDS‚3(benzene). This remarkable flexibility is
typical of simple brick frameworks and allows inclusion
stoichiometries ranging from 1:1 to 1:4, the higher guest
occupancies associated with significantly less puckering. We
recently demonstrated that the maximum inclusion cavity
volume, Vminacx, available in a simple brick host with a given
pillar could be determined through the use of master curves,
based on an analytic function, which describe the dependence
tion sequences for the various up/down combinations and
facilitates the conjecture of possible continuous brick framework
isomers.15
The G2BDS, G2NDS, G2BPDS, and G2ADS compounds
establish the generality of bilayer-simple brick architectural
isomerism and the role of steric complementarity. The projection
topologies I and II are ubiquitous in the GS inclusion
compounds and guanidinium organomonosulfonates.16 The latter
have lamellar “interdigitated bilayer” and “continuously inter-
digitated” architectures that mirror the bilayer and simple brick
inclusion architectures, respectively. The projection topology
in our previously observed G[1-butanesulfonate],16a however,
is a singular exception, adopting a “zigzag” topology (III) in
which the projection of the organosulfonate residues alternate
...up, down... along the major ribbons and ...up, up, down,
down... along the minor ribbons. Given the monosulfonate-
disulfonate homology demonstrated for the bilayer and brick
architectures, this prompted us to explore whether the zigzag
topology could be reproduced in G2[organodisulfonate] frame-
works.
of Vinc on the θIR, the pillar length, and the intrinsic molecular
14
volume of the host, Vhost
.
For a given pillar, the pillar length
and Vhost are constants such that Vinc is solely dependent upon
θIR.
The bilayer and simple brick GS sheets can be distinguished
by their “projection topologies,” which describe the “up/down”
arrangement of the pillars projecting from the sulfonate nodes
on the GS sheets. For convenience, each GS sheet can be
described as consisting of “major” (M) and “minor” (m) GS
ribbons. The pillars in the bilayer frameworks project either all
“up” or all “down” from each sheet as depicted by topology I
in Figure 2. In contrast, in the simple brick architecture the
pillars along each major ribbon project to the same side of the
sheet, but the pillars on adjacent ribbons project to opposite
sides, generating topology II. Consequently, along the major
ribbons the pillars project either all up or all down, but alternate
...up,down,up,down... along the “minor” ribbons. These and
more complicated projection topologies can be described by a
formalism that reveals the symmetry constraints on the projec-
We reported previously that G2[1,4-butanedisulfonate]‚
2(acetonitrile) crystallizes in the bilayer framework with topol-
ogy I. In contrast, G2ODS, crystallized from methanol, forms
a guest-free continuous zigzag brick framework, a new brick
architecture with a projection topology (III) identical to that in
G[1-butanesulfonate] (Figure 3). It may seem surprising that
this framework exists without the inclusion of guests. The
gauche conformations at the terminal C-C-C-S segments (τ
) 89°), and anti conformations within the internal C6 segment,
however, result in an antiparallel orientation of the sulfonate
groups that allows the pillars to bridge opposing GS sheets,
(14) The values of Vinc can be calculated from Vinc ) (Vcell - 2Vhost)/2,
wherein Vinc is normalized to one host formula unit and Vcell is given by
Vcell ) [7.5]‚[13.0 sin(θIR/2)]‚[13.0 cos(θIR/2) + 2l] Å3 where l is the pillar
length, as measured by the S-S separation within the pillar. See ref 6.

4426 J. Am. Chem. Soc., Vol. 123, No. 19, 2001
Holman et al.
but with the long axes of the pillars nearly parallel to the GS
sheets. This orientation affords an average intersheet spacing
of c/2 ) 5.80 Å, substantially less than one may expect on the
basis of the length of the ODS pillar. This structure results in
a packing fraction (0.65) that is on the low end of values typical
of molecular crystals. This suggests that the adoption of the
gauche-(anti)5-gauche pillar conformation and the resulting
interpillar packing is a reasonable low-energy alternative to
inclusion (the energy of the gauche conformation is ∼1 kcal/
mol higher than that of the anti). It is important to note that all
anti ODS pillars oriented perpendicular to the GS sheets could,
in principle, produce an even lower-density zigzag brick
architecture (or possibly other architectures), capable of guest
inclusion. It is reasonable to suggest, however, that open zigzag
brick frameworks are more likely for rigid pillars.
Indeed, the zigzag brick architecture is observed in the 1:2
inclusion compounds G2BDS‚2(p-xylene), G2BDS‚2(o-xylene),
and G2BDS‚2(naphthalene) (Figure 4). The guests effectively
serve as templates for this architecture and are confined as face-
to-face dimers within the inclusion cavities generated by the
zigzag arrangement of pillars between the GS sheets. The sheets
are puckered like an egg carton rather than the pleated puckering
exhibited by the simple brick form. The dimers exhibit edge-
to-face ordering with the BDS pillars and with arene dimers in
neighboring inclusion cavities (the intermolecular dihedral
angles associated with this packing are provided in Figure 4).
It is interesting to note that naphthalene, p-xylene, and o-xylene
do not adopt these face-to-face geometries within their native
crystal structures.17-19
Figure 2. Top-view representations of the projection topologies of
the organodisulfonate pillars on each individual GS sheet in the four
architectural isomers that have been observed in GS hosts. Filled and
open circles depict pillars projecting above and below the sheet,
respectively. The “up” pillars connect to the adjacent GS sheet above
the plane of the page and the “down” pillars connect to the adjacent
GS sheet below the plane of the page. The guanidinium ions sit on the
undecorated nodes of the quasihexagonal tiling. The solid and dashed
lines represent the major ribbons, M, and the minor ribbons, m(1) and
m(2), respectively. The parallelograms depict the translational repeat
unit of each sheet.
(15) The topologies for the bilayer and continuous architectures can be
described by a formalism, M(n)ud((nn))m(1)u(1)m(2)u(2), where M(n), m(1) and
d(1)
d(2)
m(2) denote n number of major and two minor ribbons, respectively, and
u and d are indices that describe the projection sequence of the pillars on
the respective ribbons. The number of M(n) terms required for an
unambiguous description the projection topology of a given sheet is equal
to the number of rows that define a unit translation in the GS sheet along
the direction perpendicular to the major ribbon. The major ribbons are
chosen, by convention, as those that describe the repeating sequence normal
to these ribbons with the least number of M(n) terms. The full notations
for projection topologies of the bilayer (I) and simple brick (II) isomers
are M01 M01 and M01 M10m(1)11m(2)11, respectively, although the shorter de-
scriptions M10 M01 and M01 M10 define these two isomers unambiguously. The
toplogies of adjacent sheets are related to each other by reflection. The
projection topologies of the zigzag (III) and double-brick isomer (IV) can
be described in a similar manner using this formalism. Architectures with
identical numbers of up and down pillars on each sheet, like the simple
brick form, can be described universally as
Figure 3. (a) Zigzag brick, guest-free G2ODS. The projection topology
of the ODS pillars is identical to that adopted by the monosulfonate
salt G[1-butanesulfonate].
where the i, j, k terms need not be identical for the different ribbons but
The G2NDS host framework exhibits similar trends with
respect to steric complementarity and architectural isomerism,
but with proportionally larger guest molecules. The longer NDS
pillar provides more inclusion volume compared to BDS. Thus,
benzene and p-xylene, which template simple brick and zigzag
brick architectures, respectively, for G2BDS, can be accom-
modated in the bilayer framework of G2NDS, affording G2NDS‚
(benzene)20 and G2NDS‚(p-xylene). The apparent inability of
the larger naphthalene guest to fit within the undersized inclusion
cavities of the G2NDS bilayer framework allows it to template
the formation of the simple brick architecture in G2NDS‚
3(naphthalene). We presume that this architecture is also favored
by the achievement of near-ideal herringbone pillar-guest
packing. Interestingly, G2NDS‚3(o-xylene) adopts a simple brick
u(1)
u(2)
ik )
ik )
u(n) and
∑
∑
∑
k)1,2,3,...
k)1,2,3,...
n
d(1)
d(2)
ik )
ik )
d(n).
∑
∑
∑
k)1,2,3,...
k)1,2,3,...
n
These summation rules are useful because they establish the repeat interval
of the projection sequence, which becomes more difficult to assign as the
sequence intervals contain more terms in more complex topologies.
(16) (a) Russell, V. A.; Etter M. C.; Ward, M. D. J. Am. Chem. Soc.
1994, 116, 1941. (b) Russell, V. A.; Etter M. C.; Ward, M. D. Chem. Mater.
1994, 6, 1206. (c) Russell, V. A.; Ward, M. D. Acta Crystallogr. 1996,
B52, 209. (d) Russell. V. A.; Ward, M. D. J. Mater. Chem. 1997, 7, 1123.
(e) Russell, V. A.; Ward, M. D. New J. Chem. 1998, 149.
(17) Biswas Indian J. Phys. 1960, 34, 263.
(18) van Koningsveld, H.; van den Berg, A. J.; Jansen, J. C.; de Goede,
R. Acta Crystallogr., Sect. B 1986, 42, 491.
(19) Abrahams, S. C.; Robertson, J. M.; White, J. G. Acta Crystallogr.
1949, 2, 233.
(20) The host framework in G2NDS‚(benzene) exhibits the shifted-ribbon
motif.

Architectural Isomerism in Inclusion Frameworks
J. Am. Chem. Soc., Vol. 123, No. 19, 2001 4427
Figure 4. Zigzag brick inclusion compounds: (a) G2BDS‚2(naphthalene). (b) G2NDS‚2(pyrene). (c) G2ADS‚2(perylene), and (d) G2BPDS‚
2(perylene). The major ribbons are parallel to the a axes.
architecture, illustrating that factors other than simple sterics,
such as guest shape, sometimes play an important structure-
directing role.
architecture for G2NDS, it is accommodated by the bilayer
frameworks of G2BPDS and G2ADS as 1:1 inclusion com-
pounds. The simple brick architectures of G2BPDS and G2ADS
can be formed, however, with rather large guests, as illustrated
by G2BPDS‚3(biphenyl), G2ADS‚3(biphenyl), and the afore-
mentioned highly puckered 1:1 compound, G2ADS‚(pyrene).
Despite numerous attempts, we have not yet been able to prepare
the corresponding pyrene inclusion compound of G2BPDS. In
a trend that parallels the isomerism observed for the G2BDS
and G2NDS hosts, a further increase in guest size to perylene
affords the zigzag brick architectures in G2BPDS‚2(perylene)
and G2ADS‚2(perylene). As with the pyrene dimers in the
zigzag G2NDS, the perylene dimers in these compounds adopt
a face-to-face configuration, with an interplanar separation of
3.42 Å, that is identical to that observed in R-perylene.22 We
have also demonstrated that the G2ABDS host, with the even
longer ABDS pillar, can accommodate still larger guest
molecules (e.g., 1,4-divinylbenzene) in a bilayer framework.4d
As mentioned above, we recently established that, for a given
simple brick host, Vinc depends on the interribbon puckering
angle, θIR, according to a simple analytic function.14 Notably,
Vminacx, the overall maximum achievable inclusion cavity volume
(normalized to host stoichiometry, Z, Table 1), is not achieVed
when the GS sheets are flat. The observed Vinc values in G2BDS‚
3(benzene) (θIR ) 132°), G2NDS‚3(naphthalene) (θIR ) 133°),
Architectural isomerism for G2NDS can be extended to the
zigzag brick by using the larger 1-methylnaphthalene(1-MN)
and pyrene guests, which afford G2NDS‚2(1-methylnaphthalene)
and G2NDS‚2(pyrene). Like the corresponding zigzag brick
G2BDS compounds, the guests are situated as face-to-face arene
dimers, exhibiting edge-to-face contacts with the four surround-
ing NDS pillars and the guest dimers of adjacent cavities.
Notably, the local structure of the pyrene dimers is essentially
identical to that observed for the dimers in single crystals of
pure pyrene, with identical interplanar separations (3.43 Å) and
offset geometry.21 Given the observation of non-native face-
to-face dimers of naphthalene, o-xylene and p-xylene in the
zigzag brick G2BDS compounds, we surmise that the pyrene
dimers in G2NDS‚2(pyrene) reflect an optimization of guest-
guest and host-guest interactions rather than a strong structure-
directing role for the pyrene dimers.
The steric origins of architectural isomerism are also evident
in G2BPDS and G2ADS inclusion compounds. As one would
expect on the basis of the size and length of the pillars, the
inclusion compounds of p-xylene and o-xylene adopt the bilayer
G2BPDS‚3(biphenyl) (θIR ) 130°), and G2ADS‚3(biphenyl) (θIR
max
) 130°) are near their respective V
predicted by this
inc
function. In contrast, the highly puckered simple brick com-
pound G2ADS‚(pyrene) (θIR ) 110°) has a Vinc that is
max
significantly smaller than V for this host.
inc
We surmise that the egg-carton puckering of the zigzag brick
structures also serves to increase Vinc, beyond what would be
architecture with a 1:1 stoichiometry. Although naphthalene is
large enough to template the formation of a simple brick
(22) Camerman, A.; Trotter, J. Proc. R. Soc. London, Ser. A 1964, 279,
(21) Camerman, A.; Trotter, J. Acta Crystallogr. 1965, 18, 636.
129.

4428 J. Am. Chem. Soc., Vol. 123, No. 19, 2001
Holman et al.
Table 2. Selected Structural Features for GS Inclusion Compounds Exhibiting the Bilayer, Simple Brick, and Zigzag Brick Architectures
host
nguest
architectural isomer
Vg a (Å3)
nVg (Å3)
Vinc a (Å3)
Vcell b (Å3)
G2BDS
tetrahydrofuran
3(benzene)
2(p-xylene)
2(o-xylene)
2(naphthalene)
benzene
bilayer
73
79
112
112
122
79
73
237
224
224
244
79
235
505
484
503
499
250
296
635
683
618
666
303
299
301
823
793
307
309
311
407
822
782
503
778
752
771
767
561
607
946
994
929
977
638
634
636
1158
1128
661
663
665
761
1176
1136
Vhost a ) 268 Å3
simple brick
zigzag brick
zigzag brick
zigzag brick
bilayer
G2NDS
Vhost a ) 311 Å3
p-xylene
bilayer
112
112
122
139
181
112
112
122
147
224
112
112
122
181
147
224
112
336
366
278
362
112
112
122
441
448
112
112
122
181
441
448
3(o-xylene)
3(naphthalene)c
2(1-methylnaphthalene)
2(pyrene)
simple brick
simple brick
zigzag brick
zigzag brick
bilayer
bilayer
bilayer
simple brick
zigzag brick
bilayer
bilayer
bilayer
G2BPDS
p-xylened
Vhost a ) 335 Å3
o-xylened
naphthalenee
3(biphenyl)c
2(perylene)
p-xylene
G2ADS
Vhost a ) 354 Å3
o-xylene
naphthalene
pyrene
3(biphenyl)
2(perylene)
simple brick
simple brick
zigzag brick
b
a See ref 11. Vcell values are unit cell volumes that have been normalized to one host formula unit. c See ref 8. d See ref 4b. e See ref 5.
provided with a flat sheet, to allow optimization of host-guest
packing within the gallery regions, in a manner similar to the
simple brick form. The general trends observed for guest
templating of the zigzag G2BDS, G2NDS, G2BPDS, and
G2ADS hosts suggest a size threshold beyond which guests
cannot be accommodated within the simple brick form. The
simple and zigzag brick isomers, however, differ only with
respect to the connectiVity between the sheets such that the
volume occupied by the pillars between the GS sheets is
in contrast to the range (1:1 to 1:4) of stoichiometries observed
for the simple brick.
The observation of stoichiometric inclusion reflects the
propensity of the GS hosts to form commensurate inclusion
compounds, in contrast to other well-known channel inclusion
hosts such as urea and perhydrotriphenylene.24 This character-
istic can be attributed to the conformational softness of the
frameworks, the combination of puckering and pillar rotation
permitting inclusion with commensurate registry between the
host and guests. The availability of the brick frameworks appears
to provide an alternative option for the inclusion of guests that,
based on their dimensions, would otherwise appear suitable for
inclusion in the corresponding bilayer isomer. For example, the
length of the short axis of naphthalene is identical to long axis
of benzene, and the lengths of the short axes of pyrene and
perylene are identical to the long axis of naphthalene. The
benzene and naphthalene guests in the bilayer compounds
G2NDS‚(benzene), G2BPDS‚(naphthalene), and G2ADS‚(naph-
thalene) are oriented with their long axes parallel to the pillar
axes. This would suggest that bilayer structures could be
observed for naphthalene in G2NDS, and pyrene and perylene
in G2BPDS and G2ADS if the guests were properly oriented.
Instead, we observe commensurate brick architectures in
G2NDS‚3(naphthalene), G2BPDS‚2(perylene), G2ADS‚(pyrene)
and G2ADS‚2(perylene). This argues that commensurate inclu-
sion of these guests in the bilayer frameworks is difficult.
identical for these isomers. Consequently, for a given pillar,
max
inc
both architectures possess essentially the same V . Indeed,
the observed values of Vinc, as well as Vcell (normalized by Z,
Table 1), for the slightly puckered simple brick and zigzag brick
max
inc
architectures are similar (Table 2). Although the overall V is
identical for the two frameworks, the size and shape of the
individual cavities are different.
The similarity of the Vinc values for the simple and zigzag
brick is reflected in their 1:3 and 1:2 inclusion stoichiometries,
respectively. The incorporation of larger guest molecules in the
zigzag brick allows inclusion of only two equivalents of guest
per host, as compared to three smaller guests for the simple
brick. The products nVg, where n is the number of guest
molecules and Vg is the guest volume, are similar for the simple
and zigzag brick compounds (Table 2). Although the values of
nVg in Table 2 appear significantly smaller than their corre-
sponding Vinc values, they are comparable if packing fraction
typical of the GS inclusion compounds (∼0.68) is taken into
account.23 This behavior indicates that certain large guests
template a projection topology that allows the formation of
differently sized and shaped inclusion cavities capable of
accommodating these guests, albeit in reduced quantity. The
Vinc values for the zigzag brick architecture are more uniform
than those of the simple brick. This reflects a greater rigidity
of the zigzag brick, for which extensive puckering is frustrated
by the absence of a 1-D hydrogen-bonding “hinge” that exists
in the simple brick. This is manifested in inclusion stoichiom-
etries of these hosts, with only 1:2 observed for the zigzag brick,
The systematic and rather predictable behavior exhibited by
these hosts illustrates their extraordinary adaptability to differ-
ently sized and shaped guests. The guests effectively serve as
templates, generating their respective frameworks through a type
of “molecular imprinting,” reminiscent of the structure-directing
influence of molecular templates during the synthesis of
microporous silica and polymers.25-28 We note that topologies
(24) (a)Hollingsworth, M. E.; Brown, M. E.; Hillier, A. C.; Santasiero,
B. D.; Chaney, J. D. Science 1996, 273, 1355. Brown, M. E.; Chaney, J.
D.; Santarsiero, B. D.; Hollingsworth, M. D. Chem. Mater. 1996, 8, 1588.
Hoss, R.; Koenig, O.; Kramer-Hoss, V.; Berger, U.; Rogin, P.; Hulliger, J.
Angew. Chem., Int. Ed. Engl. 1996, 35, 1664. Konig, O.; Burgi, H.-B.;
Armbruster, Th.; Hulliger, J.; Weber, Th. J. Am. Chem. Soc. 1997, 119,
1062. (b) Quintel, A.; Hulliger, J.; Wubbenhorst, M. J. Phys. Chem. B 1998,
102, 4277. (c) Harris, K. D. M. Chem. Soc. ReV. 1997, 26, 279.
(25) Katz, A.; Davis, M. E. Nature 2000, 403, 286.
(23) The packing fraction (PF) for each inclusion compound can be
calculated by PF ) (Vhost + nVg)/Vcell. The values obtained in this way
tend to be slightly low, reflecting a systematic error in the reported Vg
values.11

Architectural Isomerism in Inclusion Frameworks
J. Am. Chem. Soc., Vol. 123, No. 19, 2001 4429
Figure 5. Double-brick inclusion compounds: (a) G2ODS‚(hexane) (θIR ) 77°, 156°). The disordered hexane guest molecules have been removed
for clarity. (b) G2PEDS‚(mesitylene)‚(methanol) (θIR ) 70°, 162°). (c) G2 (MDBDS)‚2(tetrahydrofuran) (θIR ) 121°, 148°). The major ribbons are
normal to the plane of the page.
I-IV have analogues in solid-state inorganic chemistry, specif-
ically the patterns of interstitial cations between cubic close
packed layers of anions.29 In this respect, the locations of the
pillars between the GS sheets of the bilayer isomer resemble
the locations of the metal ions in MoS2. Similarly, the brick,
zigzag brick, and double brick isomers have topologies identical
to those of CaCl2, R-PbO2, and ê-Nb2C, respectively. We
anticipate, however, that the GS hosts can afford more topolo-
gies than are possible for the inorganic counterparts, owing to
the templating role of the guests, whereby guest molecules force
the pillars into topological configurations to accommodate the
size and shape of the guests.
Architectural Isomers with Bent Pillars. In principle, the
2-D infinite character of the GS sheet allows an indefinite
number of projection topologies that can produce different
continuous brick architectures. The pillars described in the
-
preceding section, including ODS, possess antiparallel C-SO3
bond vectors such that pillars can be regarded as “straight”.
We have discovered that “bent” pillars PEDS (4,4′-phenyl
etherdisulfonate), MDBDS (2-methoxy-4,6-dimethyl-1,5-ben-
zenedisulfonate), and MDS (mesitylenedisulfonate), as well as
ODS, can generate a framework isomer with a “double brick”
projection topology (IV) that can be regarded as a higher order
form of the simple brick framework. The pillars in topology
IV project from the same side of the sheet along adjacent pairs
of major GS ribbons, alternating their projection on the next
adjacent pair. This configuration has the potential to create very
wide channels (19.5 Å as measured between ribbons, center-
to-center), separated by narrower channels having a 6.5 Å width.
The formation of such wide channels is precluded, however,
by the rather extensive puckering exhibited by the GS sheets
in these compounds. The puckering involves bending between
pairs of adjacent GS ribbons30 and needs to be described by
two unique θIR values. Although presently we have observed
the double brick isomer with only these pillars, we cannot
identify any obvious structural features that would preclude its
formation with others.
Figure 6. GS sheet projection topologies of four as yet undiscovered
frameworks. The number of up and down projections is identical in
each example. These represent a small subset of an unlimited number
of combinations.
n-octane, crystallization from methanol solutions containing
n-pentane or n-hexane affords the double brick inclusion
compounds G2ODS‚(n-pentane) and G2ODS‚(n-hexane) (Figure
5). This demonstrates that alkanedisulfonates, as well as
arenedisulfonates, are capable of architectural isomerism. The
guests and the pillars are highly disordered in these compounds,
but the predominant conformation of the pillar is (anti)5-
gauche-anti. The ...up,up,down,down... projection sequence,
perpendicular to the major GS ribbon, can be deduced by tracing
the structure along one of the puckered GS sheets.
Architectural isomerism is also observed for G2PEDS, with
toluene guests promoting the formation of a bilayer framework
with the composition G2PEDS‚(toluene). Other guests, however,
form inclusion compounds that adopt the double brick structure,
as observed for G2PEDS‚(mesitylene)‚(methanol) and G2PEDS‚
3(acetonitrile). The guests occupy “pockets” because channels
that otherwise would exist along the b axis, orthogonal to the
GS ribbons, are pinched off by the puckering. The double brick
framework in G2(MDBDS)‚2(tetrahydrofuran) is less corrugated
than in the G2PEDS compounds, reflecting the shorter pillar
Although G2ODS forms a guest-free phase when crystallized
from methanol, as well as from methanol in the presence of
(26) Whitcombe, M. J.; Rodriguez, M. E.; Villar, P.; Vulfson, E. J. Am.
Chem. Soc. 1995, 117, 7105.
(27) Vlatakis, G.; Anderson, L. I.; Mu¨ller, R.; Mosbach, K. Nature 1993,
361, 645.
(28) Shea, K. J. Trends Polym. Sci. 1994, 2, 166.
(29) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford
University Press: Oxford, UK, 1984; pp 167-178.
(30) We have recently observed that the GS sheets in G2PEDS and
G2MDS can roll into closed tubes containing an even number of GS ribbons;
manuscript in preparation.

4430 J. Am. Chem. Soc., Vol. 123, No. 19, 2001
Holman et al.
only with respect to the registry of adjacent major ribbons.
Overall, the number of pillars projecting from each side of the
sheet is the same.
One can also anticipate an unlimited number of other brick
isomers in which the number of pillars that project “up” from
a given GS sheet differ from the number projecting “down.”
Although such configurations are possible in principle, their
syntheses may be difficult because such isomers will possess
two distinctly different gallery regions, most likely requiring
the simultaneous inclusion of two differently sized and shaped
guests. This is illustrated by the hypothetical example with
topology IX in Figure 7.
Connectivity Isomerism. It also is important to consider the
possibility of another form of architectural isomerism based on
the connectiVity of the sheets. For example, the bilayer
framework of G2BPDS‚2(methanol)4a exhibits projection topol-
ogy I, but the BPDS pillars crisscross when viewed along the
ribbon direction, producing a “crisscross bilayer” architectural
isomer (bilayer I-A, Figure 8). This differs from the 3-D
connectivity typically observed for the vast majority of bilayer
inclusion compounds (also with projection topology I), as
exemplified by G2BDS‚(tetrahydrofuran), in which the pillars
are eclipsed when viewed along the ribbon direction. Similarly,
the connectivity of the sheets in G2MDS‚(methanol)‚(acetone)
differs from that observed in the aforementioned double brick
structures, adopting a “V-brick” architecture IV-A. The GS
sheets in IV-A have the same projection topology of the double
brick architecture, but the sheets are connected together differ-
ently. Such connectivity isomers add even more structural
variety to the considerable number of possible architectures
available through different projection topologies.
Figure 7. Projection topology and a side view of a hypothetical
inclusion compound in which the number of pillars projecting up from
the GS sheet is different from the number projecting down. In this
example, the projections alternate layer-to-layer as ...n, 2n, n, 2n...,
where n is the number of pillars.
length, higher guest occupancy, and protrusion of MDBDS
methyl groups into the region between adjacent pillars, all of
which contribute to space-filling between the GS sheets. As
with PEDS, the MDBDS pillars within the ribbon pairs that
define the puckering unit have opposed orientations. The
observation of these inclusion compounds demonstrates that the
lamellar character can be preserved even though the (pillar)C-
S(sulfonate) bond vectors are not antiparallel.
Other Possible Topologies. The infinite 2-D character of
the GS sheet suggests an unlimited number of projection
topologies and, therefore, an unlimited number of possible
continuous brick-like framework isomers. Each isomer will
possess a unique inclusion cavity shape as a consequence of
the topology-dependent connectivity of the sheets, suggesting
that guests must be carefully chosen to template these archi-
tectures. We anticipate that projection topology schemes, with
accompanying molecular modeling, can serve as a rough guide
to choosing guest templates that will promote the formation of
new framework architectures. Figure 6 illustrates four examples
of as yet unknown topologies (V-VIII) based on an equal
number of “up“ and “down“ pillars on each sheet. Topology V
can be regarded as a second-order version of the zigzag topology
IV, differing with respect to the width of the channels flanked
by the pillars. Topology VI is a variant of V, differing only
with respect to the registry of adjacent major ribbons (horizon-
tal). Topology VII depicts a configuration in which each major
ribbon has twice as many pillars in the “up” projection as
“down”, or vice-versa, and topology VIII is a variant that differs
Conclusions
These examples illustrate the remarkable structural diversity
of these lamellar GS inclusion compounds. The ability to access
various architectural isomers with tunable components, based
on a common supramolecular building block, removes the
constraint of a fixed-sized inclusion environment that limits the
choice of guest molecules. Instead, the soft and topologically
adaptable GS host frameworks can respond to the size and shape
requirements of the guest molecules, while the inclusion cavity
environment and framework topology can be adjusted by the
choice of pillar. We anticipate that carefully designed guest
templates can produce new topologies based on the GS
Figure 8. (a) The discrete “crisscross bilayer” connectivity isomer I-A in G2BPDS‚2(methanol), as viewed along the major GS ribbons. The
pillars crisscross when viewed along the GS ribbon direction, connecting ribbons that are not directly opposed. (b) The V-brick connectivity isomer
IV-A, which has the same projection topology as the double-brick architecture, observed in G2MDS‚(methanol)‚(acetone).

Architectural Isomerism in Inclusion Frameworks
J. Am. Chem. Soc., Vol. 123, No. 19, 2001 4431
[Guanidinium]2[mesitylenedisulfonate], G2MDS. Chlorosulfonic
acid (6.36 mL; 11.1 g, 95.7 mmol) was added slowly via syringe to a
chilled (-15 °C) round-bottom flask containing 50 mL of anhydrous
chloroform and 5.00 g (5.79 mL; 41.6 mmol) of mesitylene, all under
a nitrogen atmosphere. After 15 min, the chloroform and excess
chlorosulfonic acid were decanted from the oily residue. The oil was
further rinsed with chloroform (20 mL), dissolved in acetone, and then
treated with an acetone solution of G[BF4]. The G2MDS‚(acetone)n
precipitate was filtered and dried under vacuum to give 3.47 g (8.73
mmol) of pure G2MDS (21% yield). 1H NMR (dimethyl sulfoxide-d6,
200 MHz, J/Hz): δ 6.96 (s, 12H, G), 6.68 (s, 1H, Ar-H), 2.80 (s, 3H,
2-CH3), 2.44 (s, 6H, 4,6-CH3).
hydrogen-bonded network. The adaptability of the GS hosts
endows them with considerable versatility for chemical separa-
tions and synthesis of new functional materials for applications
such as magnetics and optoelectronics. The GS inclusion
compounds with pyrene and perylene guests also demonstrate
that the spatial organization and aggregation of guest molecules
can be controlled, suggesting interesting opportunities for
examination of their optical and electronic properties in the
confined host matrix. The confinement of guests in these host
matrices also suggests possibilities for controlling reactions
between a well-defined number of molecules in discrete cavities,
for example, dimerization of the guests in the zigzag brick
architecture.
[Guanidinium]2[2-methoxy-4,6-dimethyl-1,5-benzenedisul-
fonate], G2MDBDS. Chlorosulfonic acid (5.62 mL; 9.83 g, 84.4 mmol)
was added slowly via syringe to a chilled (-15 °C) round-bottom flask
containing 100 mL of anhydrous chloroform and 5.00 g (5.19 mL; 36.7
mmol) of 3,5-dimethylanisole, all under a nitrogen atmosphere. After
thirty minutes, the chloroform was evaporated and the oily residue
dissolved in acetone. The solution was then treated with an acetone
solution of G[BF4] to precipitate G2MDBDS‚(acetone)n as a white
powder. The precipitate was filtered and dried under vacuum to give
4.27 g (10.3 mmol) of pure G2MDBDS apohost (28% yield). 1H NMR
(dimethyl sulfoxide-d6, 200 MHz, J/Hz): δ 6.97 (s, 12H, G), 6.53 (s,
1H, 3-H), 3.64 (s, 3H, OCH3), 2.76 (s, 3H, 6-CH3) 2.47 (s, 3H, 4-CH3).
[Guanidinium]2[4,4′-phenyl Etherdisulfonate], G2PEDS. Chloro-
sulfonic acid (4.43 mL; 7.88 g, 67.6 mmol) was added slowly via
syringe to a chilled (-15 °C) round-bottom flask containing 20 mL of
anhydrous chloroform and 5.00 g (4.66 mL; 29.4 mmol) of phenyl
ether, all under a nitrogen atmosphere. After fifteen minutes, the
chloroform and excess chlorosulfonic acid are decanted from the oily
residue. The oil was further rinsed with chloroform (20 mL), dissolved
in acetone, and then treated with an acetone solution of G[BF4]. The
G2PEDS‚(acetone)n precipitate was filtered and dried under vacuum
Experimental Section
Materials and General Procedures. 4,4-Biphenyldisulfonic acid
was purchased from TCI America. The potassium salt of 2,6-anthracene
disulfonate,31 the sodium salt of 1,8-octanedisulfonate,32 and [CpFe(1,4-
dicholorobenzene)][PF6]33 were prepared according to published pro-
cedures. All solvents and other starting materials were purchased as
ACS grade from Aldrich and were used as received. Metal salts of the
sulfonic acids were converted to the acid form by passing them through
an Amberlyst 36(wet) ion-exchange column. G2NDS, G2BPDS,
G2ADS, and G2ODS precipitate, as acetone clathrates, by direct reaction
of guanidinium tetrafluoroborate, prepared by neutralization of guani-
dinium carbonate with tetrafluoroboric acid, with the corresponding
disulfonic acid in acetone. These compounds readily lose enclathrated
acetone under ambient conditions to yield pure guanidinium organo-
disulfonate apohosts. The compounds reported here were crystallized
from methanolic solutions containing the dissolved apohost and the
corresponding guest where applicable. The stoichiometries of the
resulting inclusion compounds tend to be independent of the host:guest
stoichiometric ratios during crystallization. The stoichiometries of all
inclusion compounds were confirmed by 1H NMR spectroscopy in
addition to single-crystal structure determinations. 1H NMR spectra were
recorded on a Varian INOVA 200 MHz spectrometer.
[Guanidinium]2[1,4-benzenedisulfonate], G2BDS. [CpFe(1,4-di-
cholorobenzene)][PF6] (2.50 g, 6.05 mmol) was added to a 200 mL
aqueous solution containing 7.65 g (60.7 mmol) of Na2SO3. The mixture
was refluxed, in the absence of light, for several hours at which point
the iron compound had completely dissolved. The resulting solution
was photolyzed, with several intermittent filtrations, in direct sunlight
for several days. The resulting nearly clear solution was treated with
BaCl2(aq), and the BaSO3 precipitate removed by centrifugation, until
a precipitate no longer formed. Any excess barium can be precipitated
as BaSO4 by the addition of small amounts of H2SO4. After centrifuga-
tion, the cloudy solution was filtered through Celite and evaporated to
give a crude mixture of mostly sodium 1,4-benzenedisulfonate and
NaCl. The solid was redissolved in water and passed through an
Amberlyst 36(wet) ion-exchange column, after which the water was
evaporated and the residue dissolved in acetone. Treatment of this
solution with an acetone solution of G[BF4] resulted in the immediate
precipitation of G2BDS‚(acetone), which was filtered and dried under
vacuum to give 1.41 g (3.96 mmol) of pure, white G2BDS apohost
(65% yield). 1H NMR (dimethyl sulfoxide-d6, 200 MHz, J/Hz): δ 7.42
(s, 4H, Ar-H), 6.93 (s, 12H, G).
1
to give 9.22 g (20.5 mmol) of pure, white G2PEDS (70% yield). H
2
NMR (dimethyl sulfoxide-d6, 200 MHz, J/Hz): δ 7.62 (d, 4H, J )
2
12, 2-H), 6.96 (d, 4H, J ) 12, 3-H), 6.92 (s, 12H, G).
Crystallography. Experimental parameters pertaining to the single-
crystal X-ray analyses are given in Table 1 (see Supporting Informa-
tion). Data were collected on either Siemens or Bruker CCD platform
diffractometers with graphite monochromated Mo KR radiation (λ )
0.71073 Å) at 173(2) K. The structures were solved by direct methods
and refined with full-matrix least-squares/difference Fourier analysis
using the SHLEX-97 suite of software.34 All non-hydrogen atoms were
refined with anisotropic displacement parameters and all hydrogen
atoms were placed in idealized positions and refined with a riding
model. Data were corrected for the effects of absorption using
SADABS.
Acknowledgment. This work was supported in part by the
MRSEC program of the National Science Foundation under
Award Number DMR-9809364 and the NSF Division of
Materials Research (DMR-9908627). K.T.H. also gratefully
acknowledges a postdoctoral fellowship from NSERC of
Canada.
Supporting Information Available: X-ray experimental
details in the form of a crystallographic information file (CIF)
have been deposited. This material is available free of charge
via the Internet at http://pubs.acs.org.
(31) Acquavella, M. F.; Evans, M. E.; Farraher, S. W.; Ne´voret, C. J.;
Abelt, C. J. J. Org. Chem. 1994, 59, 2894-2897.
(32) Stone, G. C. H. J. Am. Chem. Soc. 1936, 58, 488.
(33) Khand, I. U.; Pauson, P. L.; Watts, W. F. J. Chem. Soc. (C) 1968,
2261.
JA0030257
(34) SHELX-97, G. M. Sheldrick, University of Go¨ttingen, 1997.