Controlled orientation of polyconjugated guest molecules in tunable host cavities

Published on Web 09/24/2010

Controlled Orientation of Polyconjugated Guest Molecules in

Tunable Host Cavities

Airon C. Soegiarto, Angiolina Comotti,* and Michael D. Ward*

Department of Materials Science and INSTM, UniVersity of Milano Bicocca, Via R. Cozzi 53,

20125 Milan, Italy, and Molecular Design Institute, Department of Chemistry, New York

UniVersity, 100 Washington Square East, New York, New York 10003-6688, United States

Received July 9, 2010; E-mail: mdw3@nyu.edu

Abstract: Linear conjugated guest molecules with high aspect ratios form inclusion compounds with

guanidinium organodisulfonate (GDS) host frameworks in which organodisulfonate “pillars” connect opposing

GS sheets to generate lamellar architectures that reﬂect templating by the guest. Through judicious selection

of pillars having adjustable lengths (l_S-S, as measured by the separation between distal sulfur atoms) and

guests of various lengths (l_g), the framework architecture can be controlled systematically in a manner that

enables regulation of the guest orientation and aggregation in the host framework. Inclusion compounds

for which l_g/l_S-Se 0.9 exhibit a bilayer architecture with 1-D channels containing guests oriented parallel

to the long axis of the pillar. Guests with values of l_gcomparable to l_S-S, however, promote the formation

of a brick architecture in which the guests and the pillar are arranged in a herringbone motif. Surprisingly,

longer guests (l_g) 1.25l_S-S) favor the formation of the bilayer architecture despite their larger volume

because the guests are forced to align end-to-end as single-ﬁle arrays due to the vertical constraints of the

1-D channels. Bithiophene and biphenyl guests (l_g< l_S-S) are exceptional, promoting bilayer structures in

which turnstile rotations of the pillars afford an unusual motif in which the guests are isolated from one

another. The ability to synthesize a large family of compounds based on a common supramolecular building

block (the GS sheet) permits construction of a structural “phase diagram” based on two simple molecular

parameters, l_gand l_S-S, that can be used to sort the inclusion compounds according to their framework

architectures and enable prediction of crystal structures for new host-guest combinations. The effects of

these different framework architectures and packing motifs is manifested as bathochromic shifts in the

absorption and emission spectra of the guests compared with their spectra in methanol solutions. This

behavior is supported by ab initio TDDFT calculations that reproduce the bathochromic shifts associated

with the effects of guest-guest and guest-host interactions, combined with conformational constraints

imposed on the guest molecules by the rigid host framework.

Introduction

functional molecules and computational prediction of crystal

structure, however, generally has proven elusive owing to the

Polyconjugated molecules have substantial potential in elec-

tronics, ranging from light-emitting diodes to nonlinear optical

devices to thin-ﬁlm transistors.¹The optical and electronic

properties of these compounds are governed by optical absorp-

tion, charge generation, and carrier transport, which typically

are cooperative effects that depend on the arrangement of

molecular constituents in the solid state.²Consequently, the

ability to regulate solid-state structure is crucial to advancements

in functional molecular crystals. Control of the organization of

numerous noncovalent interactions that contribute to crystal

packing.³This limitation has led to a reliance on empirical

principles to direct molecular assembly into desired solid-state

architectures based on molecular symmetry and structure-

directing interactions such as hydrogen bonding or metal

coordination.^4,5One effective strategy involves the use of robust

host frameworks that encapsulate functional guest molecules

in molecular-scale cavities with tailored shapes, sizes, and

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10.1021/ja106106d  2010 American Chemical Society

J. AM. CHEM. SOC. 2010, 132, 14603–14616 14603

A R T I C L E S

Soegiarto et al.

Scheme 1

chemical environments that enable systematic regulation of solid

state properties.^6-9This approach promises to simplify the

synthesis of molecular materials by decoupling the design of

structure, provided by the host framework, from function,

introduced by the guest molecules. Furthermore, inclusion of

guests in host frameworks can improve their thermal and

chemical stability.¹⁰

can be engineered reliably through the introduction of inter-

changeable organic groups.^15-18The organic residues of dis-

ulfonates serve as “pillars” that connect opposing GS sheets

and enforce the creation of cavities, occupied by guest mol-

ecules. The size and chemical character of the cavities can be

adjusted through judicious selection of the pillars.¹⁹The

persistence of the 2-D GS network toward the introduction of

While numerous organic host frameworks have been re-

ported,¹¹few exist that are amenable to systematic modiﬁcation

with retention of global architecture, thus limiting the inclusion

of guest molecules with wide-ranging shapes and sizes in a

predictable and reliable manner. Indeed, structural modiﬁcation

of a particular host to accommodate a given guest usually results

in unexpected changes in crystal architecture, often with loss

of inclusion properties.¹²This obstacle can be surmounted

through the use of host frameworks with structurally robust

n-dimensional supramolecular networks that simplify engineer-

ing to the last remaining 3-n dimensions and permit the

introduction of structural components without loss of architec-

ture.¹³Our laboratory has reported a series of crystalline

materials based on guanidinium cations (G ) (C(NH₂)₃⁺) and

the sulfonate moieties of organomonosulfonates (MS; S )

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R-SO₃^-)¹⁴or organodisulfonate anions (DS; S ) ^-O₃S-R-SO₃).

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14604 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

Scheme 2

a wide range of organic pillars and guests can be attributed to

the existence of charge-assisted N-H· · ·O-S hydrogen bonds

as well as several mechanisms for optimizing packing, including

an inherent structural compliance of the GS sheet (through

puckering), the availability of an alternative “shifted ribbon”

motif in which GS ribbons are joined by only a single

N-H· · ·O-S hydrogen bond between the cations and anions,

and access to multiple architectural isomers characterized by

different cavity sizes and shapes.

Cavity metrics and shape depend not only on the molecular

structure of the organodisulfonate pillars but also on the

arrangement of the pillars between the GS sheets. The GS

inclusion compounds exhibit numerous architectures, each

endowed with uniquely sized and shaped cavities, with different

connectivities between the GS sheets resulting from different

“projection topologies” from either side of the 2-D GS sheet.²⁰

The guest molecules act as steric templates that steer the

assembly of the host frameworks toward architectural isomers

that optimize host-guest and guest-guest packing.²¹To date,

nine unique architectural isomers have been discovered,^8,22,23

the most common being the “bilayer” and the more open “simple

brick” (Scheme 2), the latter achieved by templating with larger

guest molecules.²¹

the height of the inclusion cavity, thus frustrating the BL_|

architecture. Commensurism between the long axis of the guest

and the 1-D channel can stabilize the BL_⊥architecture further.

In principle, because the 1-D channels are effectively inﬁnite,

guests of any length, including macromolecules, are potential

candidates for inclusion.²⁴

GDS inclusion compounds with the bilayer architecture

typically conﬁne guests in their 1-D channels such that the long

axes of the guests are nominally parallel to the long axis of the

organodisulfonate pillar, that is, in a “vertical” orientation, herein

denoted as BL_|(Scheme 2; the 2-D ordering of the pillars and

guests in each architecture, viewed perpendicular to the layers,

can be gleaned from the ﬁgures contained within Results and

Discussion). Guests with larger volumes typically promote the

formation of the more open brick frameworks, the most common

being the simple brick form. The 1-D channels in the bilayer

architecture, however, do not preclude alignment of the long

axis of a linear guest perpendicular to the long axis of the

supporting pillar provided the guest has a cross section that can

be accommodated by the channel. This arrangement, denoted

as BL_⊥, would be more likely for guests with lengths that exceed

We demonstrate herein that the framework architecture of

the GDS inclusion compounds and the corresponding arrange-

ment of the linear π-conjugated guest molecules can be regulated

through judicious selection of pillar and guest combinations

based on their relative lengths rather than their relative volumes.

Various guest conﬁgurations, edge-to-edge, face-to-edge, end-

to-end, were realized by the systematic transition from the BL_|

to simple brick to BL_⊥architecture, achieved with increasing

values of the guest length relative to the pillar. This behavior

further reveals the role of guest templating and host-guest

recognition during host framework assembly but illustrates that

guest length can serve as a structure director as well as guest

volume. The control of guest arrangement in the solid-state GS

frameworks enabled tuning of the optical properties of the guests

due to conﬁnement in the host matrix, manifested as batho-

chromic shifts in the absorption and emission spectra of the

guests compared with their spectra in methanol solutions. Ab

initio time-dependent density functional theory (TDDFT) cal-

culations reproduce the bathochromic shifts associated with the

effects of guest-guest and guest-host interactions, combined

with conformational constraints imposed on the guest molecules

by the rigid host framework. The ability to direct the orientation

of the guest molecules in these frameworks suggests a new route

to the design and synthesis of functional materials that require

controlled alignment for modulation of electronic properties and

solid-state reactivity.

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Results and Discussion

Architectural Isomerism and Design. Examination of more

than 250 GDS inclusion compounds previously produced in our

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10, 4159. (b) Evans, C. C.; Sukarto, L.; Ward, M. D. J. Am. Chem.

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Chem. Soc. 2001, 123, 4421.

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Chem. Soc. 1998, 120, 5887.

(22) The various architectural isomers 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 a detailed discussion, see ref 20.

(23) These architectures include simple bilayer, crisscross bilayer, simple

brick, zigzag brick, double brick, V-brick, double zigzag brick, chevron

brick, and the chevron bilayer.

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A R T I C L E S

Soegiarto et al.

Scheme 3

bilayer-simple brick isomerism with guests having larger

volumes templating the simple brick form, group C contravenes

the expected trend based on guest volume, reverting to the

bilayer architecture rather than the zigzag brick form. The bilayer

structures in groups A and C adopt the same pillar projection

topology, but the orientation of the guests differ with respect

to the orientations of the pillars. In group A, the long axis of

the guest is nearly parallel to that of the pillar, denoted as BL_|,

whereas in group C the long axis of the guest is nominally

perpendicular to that of the pillar, denoted as BL_⊥(Scheme 2).

Examination of Table 1 reveals a consistent trend of the

transition from BL_⊥to BL_|with increasing l_S-Sfor a common

guest, that is, with decreasing l_g:l_S-S

.

These libraries produced a total of 32 unique inclusion

compounds of a possible 72 host-guest combinations (Table

2). The inclusion compounds were crystallized by slow evapora-

tion of methanol solutions containing a unique combination of

GDS host and guest, typically resulting in crystals exhibiting a

plate-like morphology (see Supporting Information). The ob-

servation of 32 inclusion compounds further demonstrates the

ability of the GDS hosts to tolerate a wide range of guests,

including ones with large aspect ratios. The absence of the

inclusion compounds based on the remaining 40 combinations

can largely be attributed to pillars that are considerably

undersized compared with the dimensional requirements of the

larger guests.

laboratory have revealed an unusual architectural isomerism in

which the selectivity for various host framework isomers is

governed by the combined steric demands of the organodisul-

fonate pillars and guest molecules. Each of these isomers is

endowed with inclusion cavities having volumes that are

determined primarily by the length and the projection topology

of the pillars from the GS sheet. Generally, for a given pillar,

the framework architecture follows a systematic transition from

bilayer to simple brick to “zigzag” brick with increasing guest

volume, reﬂecting increasingly larger inclusion cavity size and

the role of guest templating during framework assembly.^15,20

As such, framework isomerism has been viewed primarily in

the context of the combined volumes of host pillars and guests,

although guest eccentricity (i.e., disk vs oval-shaped) was found

to play a role in the selectivity for hexagonal cylindrical host

frameworks and lamellar frameworks in GMS inclusion

compounds.

The linear π-conjugated molecules used here differ from most

guests conﬁned previously in the GDS frameworks by their high

aspect ratios (typically >1.6),²⁵allowing examination of the

inﬂuence of guest shape on framework architecture and the

corresponding guest aggregation and orientation in the inclusion

cavities. This investigation is based on libraries of eight GDS

hosts and nine linear π-conjugated guests, characterized by

metric variables l_S-S, measured by the distance between sulfur

atoms in the host pillar, and l_g, the length of the long axis of

the guest (Scheme 3). The guest library consisted of 2,2′-

bithiophene, biphenyl, trans-1,2-di(2-thienyl)ethylene (DTE),

trans-stilbene, trans-azobenzene, bibenzyl, thieno[3,2-b]thio-

phene (TT), 2,2′:5′,2′′-terthiophene, and tetrathiafulvalene (TTF),

with 9.0 e l_ge 14.6 Å. The GDS host library was based on

aliphatic and aromatic pillars, with 6.9 e l_S-Se 17.6 Å.

Inclusion compounds derived from these libraries can be

classiﬁed into three groups according to the l_g:l_S-Sratio: (A)

l_g:l_S-Se 0.92, (B) 1.00 e l_g:l_S-Se 1.10, and (C) l_g:l_S-Sg 1.25

(Table 1). Whereas groups A and B appear to adopt the expected

BL_|Architectures. Twelve GDS inclusion compounds pre-

pared from the libraries in Scheme 3 with l_g:l_S-Se 0.92 were

found to template the formation of the BL_|architecture, in which

the pillars project from the same side, all-up or all-down, of

each GS sheet. These compounds consist of those based on the

G₂BPDS (BPDS ) 4,4′-biphenyldisulfonate) host with the TT

guest, G₂BSPE (BSPE ) 1,2-bis(4-sulfophenoxy)ethane) host

with azobenzene, stilbene, bibenzyl, and DTE, G₂BSPB (BSPB

) 1,4-bis(4-sulfophenoxy)butane) host with terthiophene, and

G₂ABDS (ABDS ) 4,4′-azobenzenedisulfonate), G₂SBDS

(SBDS ) 4,4′-stilbenedisulfonate), and G₂BBDS (BBDS ) 4,4′-

bibenzyldisulfonate) hosts with bithiophene, biphenyl, and TTF.

The GS sheet in these compounds displays a shifted-ribbon motif

rather than quasihexagonal (Scheme 1), producing a lamellar

architecture with 1-D channels along b₁(perpendicular to the

GS ribbon; Scheme 1) having a width of 7.3 ( 0.2 Å (3.8 Å

when adjusted for van der Waals radii). The formation of the

shifted-ribbon motif allows for an expanded channel width

compared with that in the quasihexagonal GS motif (6.5 ( 0.2

Å; 3.0 Å when adjusted for van der Waals radii), thus

accommodating the guest molecules more readily (see Figure

S2, Supporting Information). The heights of the channels are

largely determined by the lengths of the pillars, with a secondary

contribution from slight tilting.

The guests in the channel are arranged edge-to-edge with their

long axes nearly parallel to the pillars, exhibiting face-to-edge

contact with the molecular plane of the surrounding pillars

(Figure 1A,B). In addition to the size of the pillar, the inclusion

cavity volume in the bilayer structure can be inﬂuenced by the

tilt angle of the pillar with respect to the normal axis of the GS

sheet, ꢀ, and the turnstile rotation of the pillar around the C-S

bond (Table 1). For a given pillar, a large ꢀ results in shorter

bilayer heights and smaller inclusion cavity volumes, which are

suitable for guests with smaller volumes. For example, BL_|

compounds with the ABDS pillar reveal an increase of ꢀ from

11.5° for the biphenyl guest (V_g) 155 Å³) to 13.3° for the

bithiophene guest (V_g) 137 Å³). Similarly, for the BSPE pillar

(25) The aspect ratio, l_g/w_g, is determined from the distance between the

two most distant atoms along the length (l_g) and width (w_g) of the

guest, accounting for the van der Waals radii.

9

14606 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

Table 1. Structural Features for GS Inclusion Compounds with the General Formula GDS ·n(guest)

guest

host

compound no.

framework architecture (θ_IR)^e

l_S-S(Å)^a

l_g:l_S-S

n

nV_g(Å³)^b

V_pillar(Å³)^b

V_inc(Å³)^b

V_cell(Å³)^c

TT

G₂BuDS

G₂NDS

G₂BPDS

1

2

3

BL_⊥

6.9

8.5

10.6

1.30

1.06

0.85

1

3

1

108

324

108

75

127

155

240

611

254

516

921

617

V_g) 108 Å³

l_g) 9.0 Å^d

w_g) 6.7 Å^d

l_g/w_g) 1.3

bithiophene

V_g) 137 Å³

l_g) 10.6 Å^d

w_g) 6.5 Å^d

l_g/w_g) 1.6

biphenyl

simple brick (148.7°)

BL_|

G₂NDS

4

5

6

7

8

9

10

11

BL_⊥

8.5

10.6

12.5

12.7

12.9

8.5

1.25

1.00

0.85

0.83

0.82

1.34

1.08

0.91

0.5

3

1

0.5

3

1

68

411

137

77

127

155

170

189

180

127

155

170

212

789

299

320

310

231

825

323

540

1121

682

720

703

559

1158

705

G₂BPDS

G₂ABDS

G₂BBDS

G₂SBDS

G₂NDS

G₂BPDS

G₂ABDS

simple brick (142.7°)

BL_|

BL_⊥

V_g) 155 Å³

l_g) 11.4 Å^d

w_g) 6.4 Å^d

l_g/w_g) 1.8

DTE

simple brick (129.8°)

BL_|

10.6

12.5

465

155

G₂NDS

G₂ABDS

G₂BSPE

12

13

14

BL_⊥

8.5

12.5

14.9

1.58

1.07

0.90

0.5

3

1

83

498

166

127

170

202

215

927

368

548

1279

783

V_g) 166 Å³

l_g) 13.4 Å^d

w_g) 6.6 Å^d

l_g/w_g) 2.0

azobenzene

V_g) 173 Å³

l_g) 13.3 Å^d

w_g) 6.5 Å^d

l_g/w_g) 2.0

stilbene

simple brick (134.9°)

BL_|

G₂NDS

15

16

17

18

19

20

21

22

23

BL_⊥

8.5

12.5

12.7

12.9

14.9

8.5

12.5

12.7

14.9

1.56

1.06

1.05

1.03

0.89

1.61

1.10

1.08

0.92

0.5

3

1

0.5

3

86

519

173

91

549

183

127

170

189

180

202

127

170

189

202

226

935

958

947

376

220

963

975

387

559

1287

1325

1306

788

G₂ABDS

G₂BBDS

G₂SBDS

G₂BSPE

G₂NDS

G₂ABDS

G₂BBDS

G₂BSPE

simple brick (132.3°)

simple brick (131.0°)

simple brick (135.7°)

BL_|

BL_⊥

553

V_g) 183 Å³

l_g) 13.7 Å^d

w_g) 6.6 Å^d

l_g/w_g) 2.1

bibenzyl

simple brick (126.7°)

simple brick (127.8°)

BL_|

1315

1342

800

1

G₂NDS

24

25

26

27

28

BL_⊥

8.5

12.5

12.7

12.9

14.9

1.61

1.10

1.08

1.06

0.92

0.5

3

1

94

567

189

127

170

189

180

202

231

964

984

988

385

563

1317

1351

1350

798

V_g) 189 Å³

l_g) 13.7 Å^d

w_g) 6.7 Å^d

l_g/w_g) 2.0

G₂ABDS

G₂BBDS

G₂SBDS

G₂BSPE

simple brick (130.7°)

simple brick (134.0°)

simple brick (133.8°)

BL_|

^al_S-Sdescribes the intramolecular separation between distal sulfur atoms in each pillar. ^bMolecular volume (V_g, V_pillar, V_inc) calculations were

performed using Accelrys Materials Studio v.4.2 modeling suite. The volumes of the guest molecules and organodisulfonate pillars, V_gand V_pillar

,

respectively, were obtained using a Connolly (van der Waals) surface using a probe radius of zero and ultraﬁne grid spacing. The values of V_pillar

exclude the volume of the sulfonate groups, when combined would contribute 95 Å³(average). The volumes tend to be systematically lower, by up to

ca. 6%, than those determined by traditional means (see Kitaigorodskii, A. I. In Molecular Crystals and Molecules; Academic Press: New York, 1973;

pp 18-21). The volumes of each inclusion cavity, V_inc, were determined with a Connolly surface using probe radius ) 0.5 Å and an ultraﬁne grid

c

spacing, after removal of guests and normalizing to one host formula unit. V_cellvalues are unit cell volumes obtained from crystallographic data

normalized to one host formula unit. ^dThe length and width of the guest molecules, l_gand w_g, respectively, correspond to the “major” and “minor” axis

e

of the guests after accounting for van der Waals radii. θ_IRvalues given in this column are applicable for only the simple brick architectures.

ꢀ decreases from 14° for azobenzene (V_g) 173 Å³) to 8.3° for

bibenzyl (V_g) 189 Å³) to 6.3° for stilbene (V_g) 183 Å³).

Exceptions to this trend were observed, however; for example

G₂BSPE·(DTE) (ꢀ ) 9.7°, V_g) 166 Å³).

Simple Brick Architectures. Thirteen inclusion compounds

with l_g:l_S-S≈ 1.0 adopt simple brick architectures, as illustrated

by the G₂BPDS host with bithiophene and biphenyl, G₂NDS

(NDS ) 2,6-naphthalenedisulfonate) host with TT, and in

G₂ABDS, G₂SBDS, and G₂BBDS hosts with azobenzene,

stilbene, bibenzyl, DTE, and terthiophene (Figure 3). In contrast

to the bilayer structures, which are discrete along the third

dimension, the simple brick architectures are continuous in all

three dimensions because the pillars project from both sides of

each GS sheet, the pillar orientations alternating “up-down” on

adjacent GS ribbons. This framework isomerism affords an

inclusion cavity volume that is nominally twice that of the

corresponding bilayer framework.

The simple brick framework can be described by three

mutually orthogonal lattice parameters (Scheme 2),²⁶a₁, b₁, d_⊥,

which essentially idealize the simple brick framework as an

orthorhombic lattice. Although deviations from this ideal

orthorhombic symmetry are common owing to the softness of

the host framework, they typically are slight, resulting in

Host frameworks constructed with nonrigid pillars such as

BSPB can achieve dense packing that reﬂects conformational

ﬂexibility of the pillar. This is evident in the crystal structure

of G₂BSPB·(terthiophene) in which the central butyl linker of

the pillar adopts the gauche-anti-gauche conformation (Figure

2) instead of the all-anti conformation, thus allowing the

G₂BSPB host framework to shrink-wrap around the terthiophene

guest molecule. This compound adopts the quasihexagonal GS

sheet motif, producing a 1-D channel, with a width of ca. 6.4

Å (2.9 Å when adjusted for van der Waals radii), along the

b-axis. These channels would be expected to be too narrow for

guest inclusion, but the BSPB pillars maximize inclusion cavity

volume by distorting and bundling in pairs, to accommodate

the guests. Within these channels, the terthiophene guests align

with their long axes nearly parallel with the long axis of the

pillars, but with a face-to-edge conﬁguration, in contrast with

the edge-to-edge conﬁguration of the guest molecules observed

in other BL_|structures.

(26) The lattice parameters b₁and d_⊥depend on θ_IR, according to simple

mathematical functions (see ref 15). The d_⊥lattice parameter also

depends on the length of the organodisulfonate pillar, l_S-S

.

9

J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010 14607

A R T I C L E S

Soegiarto et al.

Table 2. Crystallographic Data for GS Inclusion Compounds

G₂BuDS·(TT) 1

G₂NDS·3(TT) 2

G₂BPDS·(TT) 3

G₂NDS·¹/₂(bithiophene) 4

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

C₁₂H₂₄N₆O₆S₄

476.61

C₃₀H₃₀N₆O₆S₈

827.08

monoclinic

P2₁/n

colorless

7.6803(5)

20.1103(13)

11.9293(8)

90

92.0190(10)

90

1841.4(2)

100(2)

C₂₀H₂₄N₆O₆S₄

572.69

C₃₂H₄₂N₁₂O₁₂S₆

979.14

triclinic

j

P1

colorless

7.2548(15)

7.5417(16)

11.167(3)

98.349(4)

98.643(4)

118.152(3)

516.0(2)

100(2)

colorless

7.2917(4)

12.1492(7)

15.2108(9)

68.0590(10)

80.6340(10)

86.1180(10)

1233.20(12)

100(2)

colorless

7.1188(5)

12.3016(9)

13.0373(9)

81.629(4)

75.620(3)

79.022(4)

1079.89(13)

100(2)

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

1

2

1

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0668

0.1956

1.149

0.0704

0.2170

1.057

0.0475

0.1549

1.104

0.0440

0.1296

1.045

G₂BPDS·3(bithiophene) 5

C₃₈H₃₈N₆O₆S₈

931.22

G₂ABDS·(bithiophene) 6

C₂₂H₂₆N₈O₆S₄

626.75

G₂BBDS·(bithiophene) 7

C₂₄H₃₀N₆O₆S₄

626.78

G₂SBDS·(bithiophene) 8

C₂₄H₂₈N₆O₆S₄

624.76

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

monoclinic

P2₁/n

triclinic

j

P1

colorless

7.5783(18)

11.932(3)

24.791(6)

90

90.963(4)

90

2241.4(9)

200(2)

orange

colorless

6.1495(5)

7.2725(6)

16.2688(14)

96.933(5)

91.913(5)

93.743(5)

720.09(10)

100(2)

brown

6.1289(3)

7.1528(4)

15.7075(8)

93.882(3)

96.130(3)

93.115(3)

681.77(6)

100(2)

6.1517(4)

7.2099(5)

16.0369(10)

94.010(4)

96.867(4)

93.349(3)

702.85(8)

100(2)

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

2

1

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0427

0.1170

1.119

0.0378

0.1071

1.044

0.0347

0.0917

1.099

0.0304

0.0793

1.04

G₂NDS·¹/₂(biphenyl) 9

C₃₆H₄₆N₁₂O₁₂S₄

967.08

G₂BPDS·3(biphenyl)⁴⁰10

G₂ABDS·(biphenyl) 11

C₂₆H₃₀N₈O₆S₂

614.70

G₂NDS·¹/₂(DTE) 12

C₃₄H₄₄N₁₂O₁₂S₆

1005.17

triclinic

P1

colorless

7.1367(6)

12.4838(10)

12.6842(11)

83.869(2)

77.676(2)

85.366(2)

1095.76(16)

100(2)

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

C₅₀H₅₀N₆O₆S₂

-

monoclinic

P2₁/n

colorless

7.6612(6)

26.306(2)

11.4887(9)

90

90.458(2)

90

2315.307

173

triclinic

P1

triclinic

j

P1

colorless

7.1426(9)

12.7521(15)

13.1674(16)

91.845(2)

104.765(2)

104.145(2)

1118.8(2)

200(2)

orange

6.1627(4)

7.2125(5)

16.0535(11)

95.2630(10)

94.7580(10)

94.6110(10)

705.31(8)

200(2)

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

1

2

1

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0374

0.1095

1.040

0.0359

-

0.0319

0.0899

1.055

0.0500

0.1557

1.187

G₂ABDS·3(DTE) 13

C₄₄H₄₄N₈O₆S₈

1037.35

monoclinic

P2₁/n

G₂BSPE·(DTE) 14

C₂₆H₃₂N₆O₈S₄

684.82

G₂NDS·¹/₂(azobenzene) 15

C₃₆H₄₆N₁₄O₁₂S₄

995.10

G₂ABDS·3(azobenzene) 16

C₅₀H₅₀N₁₄O₆S₂

1007.16

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

triclinic

P1

orange

monoclinic

P2₁/n

j

P1

orange

colorless

6.0857(8)

7.2198(10)

18.138(3)

94.606(2)

99.461(2)

91.746(2)

782.79(18)

200(2)

dark orange

7.5750(11)

29.220(4)

11.6324(18)

90

90.103(3)

90

2574.7(7)

200(2)

7.573(2)

11.721(4)

28.831(9)

90

91.220(6)

90

2558.7(14)

200(2)

2

7.1097(5)

12.6139(10)

13.8091(11)

110.9790(10)

101.8200(10)

93.9510(10)

1118.01(15)

200(2)

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

1

2

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0685

0.1961

1.028

0.0376

0.1058

1.069

0.0308

0.1005

1.052

0.0290

0.0825

1.039

9

14608 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

Table 2. Continued

G₂BBDS·3(azobenzene) 17

G₂SBDS·3(azobenzene) 18

G₂BSPE·(azobenzene) 19

G₂NDS·¹/₂(stilbene) 20

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

C₅₂H₅₄N₁₂O₆S₂

1007.19

monoclinic

P2₁/n

C₅₂H₅₂N₁₂O₆S₂

1005.18

monoclinic

P2₁/n

C₂₈H₃₄N₈O₈S₂

674.75

C₃₈H₄₈N₁₂O₁₂S₄

993.12

triclinic

j

P1

orange

colorless

7.1176(5)

12.5978(8)

12.6173(8)

85.8500(10)

87.6160(10)

78.7700(10)

1106.34(13)

200(2)

7.6405(4)

30.4156(18)

11.4061(6)

90

90.7260(10)

90

2650.5(3)

200(2)

2

7.6142(5)

29.502(2)

11.6308(8)

90

90.100(3)

90

2612.7(3)

200(2)

2

6.1014(4)

7.3115(5)

17.9047(13)

91.1680(10)

97.0620(10)

95.9110(10)

788.02(9)

200(2)

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

1

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0438

0.1152

1.026

0.0441

0.1051

1.063

0.0346

0.1099

1.019

0.0324

0.1059

1.043

G₂ABDS·3(stilbene) 21

C₅₆H₅₆N₈O₆S₂

1001.21

monoclinic

P2₁/n

G₂BBDS·3(stilbene) 22

C₅₈H₆₀N₆O₆S₂

1001.24

monoclinic

P2₁/n

G₂BSPE·(stilbene) 23

C₃₀H₃₆N₆O₈S₂

672.77

G₂NDS·¹/₂(bibenzyl) 24

C₃₈H₅₀N₁₂O₁₂S₄

995.14

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

triclinic

P1

j

P1

orange

colorless

7.6384(5)

30.908(2)

11.3694(7)

90

90.7390(10)

90

2683.9(3)

200(2)

colorless

6.0960(4)

7.2875(4)

18.3630(11)

97.1930(10)

98.1780(10)

92.0110(10)

799.96(8)

200(2)

colorless

7.1652(5)

12.5807(10)

25.0454(19)

94.2600(10)

91.0190(10)

91.2990(10)

2250.4(3)

200(2)

7.6038(5)

30.2564(19)

11.4283(7)

90

90.0430(10)

90

2629.2(3)

200(2)

2

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

2

1

2

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0368

0.0966

1.037

0.0407

0.0986

1.066

0.0333

0.0907

1.038

0.0459

0.1433

1.045

G₂ABDS·3(bibenzyl) 25

C₅₆H₆₂N₈O₆S₂

1007.26

monoclinic

P2₁/n

G₂BBDS·3(bibenzyl) 26

C₅₈H₆₆N₆O₆S₂

1007.29

monoclinic

P2₁/n

G₂SBDS·3(bibenzyl) 27

C₅₈H₆₄N₆O₆S₂

1005.27

monoclinic

P2₁/n

G₂BSPE·(bibenzyl) 28

C₃₀H₃₈N₆O₈S₂

674.78

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

triclinic

j

P1

orange

colorless

7.7503(6)

30.182(2)

11.5482(9)

90

90.583(2)

90

2701.2(4)

173(2)

colorless

7.7596(5)

30.2152(19)

11.5130(7)

90

90.7390(10)

90

2699.1(3)

200(2)

colorless

6.1532(8)

7.2222(10)

18.283(2)

95.493(2)

98.852(2)

92.424(2)

797.77(18)

200(2)

7.7072(6)

29.840(2)

11.4574(9)

90

90.7480(10)

90

2634.8(4)

100(2)

2

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

2

1

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0320

0.0847

1.044

0.0435

0.1071

1.028

0.0377

0.0957

1.029

0.0307

0.1006

1.111

G₂ABDS·(TTF) 29

C₂₀H₂₄N₈O₆S₆

664.83

G₂SBDS·(TTF) 30

C₂₂H₂₆N₆O₆S₆

662.85

monoclinic

C2

G₂ABDS·3(terthiophene) 31

G₂BSPB·(terthiophene) 32

C₃₀H₃₆N₆O₈S₅

768.95

formula

formula wt

crystal system

space group

color

a (Å)

b (Å)

c (Å)

C₅₀H₄₄N₈O₆S₁₁

1205.59

monoclinic

P2₁/n

triclinic

monoclinic

P2₁/n

j

P1

dark green

6.2754(13)

7.1880(15)

15.396(3)

91.838(3)

95.848(3)

96.074(3)

686.4(2)

100(2)

red

orange

light yellow

12.3178(7)

7.4997(4)

38.947(2)

90

96.277(2)

90

3576.4(4)

200(2)

34.320(4)

8.1261(8)

10.1674(10)

90

99.663(3)

90

2795.3(5)

100(2)

4

7.6167(12)

31.632(5)

11.2812(17)

90

90.604(2)

90

2717.8(7)

200(2)

2

R (deg)

ꢁ (deg)

γ (deg)

V (Å³)

temp (K)

Z

1

4

R₁[I > 2σ(I)]

wR₂[I > 2σ(I)]

G.O.F.

0.0584

0.1765

1.186

0.0259

0.0709

1.054

0.0432

0.1190

1.051

0.0872

0.2108

1.076

9

J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010 14609

A R T I C L E S

Soegiarto et al.

Figure 3. Simple brick structures of (A) G₂BPDS · 3(bithiophene); (B)

G₂ABDS·3(stilbene). The hosts have been rendered as ball-and-sticks and

the guests as space-ﬁlling models.

Figure 1. Discrete BL_|structures as viewed along the a axis (top) and

pillar-guest packing as viewed along the c axis (bottom) of: (A)

G₂BSPE·(azobenzene); (B) G₂SBDS·(bithiophene). The hosts have been

rendered as ball-and-sticks and the guests as space-ﬁlling models. In the

bottom panel, the G ions have been removed for clarity.

Figure 4. Herringbone (face-to-edge) pillar-guest packing in the ac plane

of (A) G₂ABDS·3(stilbene); (B) G₂BBDS·3(azobenzene); (C) G₂BPDS·

3(bithiophene). The G ions and sulfonate oxygen atoms have been removed

for clarity. Sulfur atoms are yellow. Carbon atoms of the pillar are purple.

Parts A-C are space-ﬁlling models. (D) Schematic view, normal to the

GS sheet, of the herringbone pillar-guest packing in the simple brick

framework, with a 1:3 stoichiometry of pillar (purple) to guest (gray). The

pillars projecting below the sheet are depicted as open circles. The

herringbone motif resembles the native crystalline packing of the pure guest

molecules and that of other aromatic hydrocarbons.

Figure 2. The BL_|structure of G₂BSPB·(terthiophene) as viewed along

the b axis. The gauche-anti-gauche conformation adopted by the butyl group

of the BSBP pillar allows the host framework to densely pack the

terthiophene guest molecules, which exhibit face-to-edge conﬁguration in

the channel (top). The hosts have been rendered as ball-and-sticks and the

guests as space-ﬁlling models (colored cyan and pink to aid visualization).

In the bottom panel, the guests have been removed to highlight the bundling

of the pillars into purple-green pairs.

architecture can adjust its inclusion cavity volume slightly

through tilting of the pillars, the inclusion cavity volume of the

simple brick architecture can adapt to the steric requirements

of the guest by puckering about a hydrogen-bond “hinge” joining

adjacent GS ribbons, deﬁned by an inter-ribbon puckering angle,

θ_IR(Scheme 2). When combined with conformational and

turnstile-like rotational freedom of the pillars, puckering enables

the host framework to shrink-wrap about guest molecules and

achieve dense packing. We have demonstrated previously¹⁵that

the maximum inclusion cavity volume is achieved in an ideal

simple brick framework when the inter-ribbon puckering angle

is approximately 130° rather than 180° (i.e., no puckering).

Indeed, in all our simple brick inclusion compounds, the inter-

ribbon puckering angles average 130° (Table 1). Interestingly

the stilbene and azobenzene moieties in G₂ABDS·3(stilbene)

and G₂SBDS·3(azobenzene) reverse their roles as host and

guest. The organic moieties exhibit face-to-edge packing similar

to that observed in the herringbone layers of crystalline stilbene

or azobenzene. Stilbene and azobenzene molecules in the pure

monoclinic unit cells with ꢁ angles near 90°. For example, ꢁ )

91.220° and 90.043° for G₂ABDS · 3(DTE) and G₂ABDS ·

3(stilbene) respectively, due to a modest misregistry of adjacent

hydrogen-bonded ribbons along the ribbon direction a₁.

The simple brick inclusion compounds are essentially isos-

tructural with the distribution of the guests and the pillars

between the GS sheets organized in a “herringbone” motif (face-

to-edge) packing arrangement, a common packing arrangement

for aromatic molecules (Figure 4). The 1:3 pillar:guest stoichi-

ometry suggests that the organodisulfonate pillars effectively

replace every fourth molecule of the guest in an otherwise guest-

only herringbone motif. Whereas the host:guest stoichiometry

of the BL_|is 1:1, the simple brick architecture typically exhibits

1:3 stoichiometry, larger than that expected for an idealized

doubling of the available volume (Table 1). Whereas the bilayer

9

14610 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

to-center distance of 12.6 Å between aligned guests is double

the center-to-center distance between adjacent NDS moieties).

The 1-D channels of the BL_⊥architecture have a rectangular-

shaped cross-section of 3.5 × 4.9 Å²(calculated on the basis

of the crystallographic data and the van der Waals radii), closely

matching the cross-section of the guests (as determined by V_g/

l_g). Each channel is ﬂanked by nonpolar naphthalene units and

polar GS sheets. The G₂NDS BL_⊥architecture creates a cavity

environment conducive to host-guest C-H · · · π contacts

(d_{C-H· · ·π}) 3.3 - 3.6 Å) while precluding edge-to-edge and

face-to-edge guest-guest interactions.

In the G₂NDS BL_⊥architecture, the pillars lining the channel

walls display a dihedral angle between the molecular planes of

the pillars on alternating adjacent GS ribbons, ω, of ap-

proximately 20°. For example, ω ) 22.5° for the NDS pillars

in G₂NDS·¹/₂(stilbene) (Figure 5A, bottom). The energy barrier

for turnstile rotation around the C-S bond is small (a few kJ/

mol, as calculated at the B3LYP/6-311G(d,p) level; see Sup-

porting Information). The resulting conformational freedom

allows for facile optimization of host-guest packing, which

ranges from guests conﬁned in well-deﬁned channels (ω e 45°)

to isolated pockets (ω > 45°). Bithiophene and biphenyl guests

in the G₂NDS host adopt the BL_⊥architecture, but the 1-D

channels are interrupted by the naphthalene moiety of the pillars,

which rotate out-of-plane, with ω ) 68.8° and 46.5°, respec-

tively (Figure 5B). This conﬁguration effectively encapsulates

the guests in cage-like cavities such that they are isolated from

one another (Figure 6). This conﬁguration may be a consequence

of the smaller length of bithiophene and biphenyl compared

with stilbene, azobenzene, and DTE, which are too long to ﬁt

inside these cage-like cavities.

The bilayer framework also can maximize packing efﬁciency

through tilting of the pillars with respect to the mean plane of

the GS sheet. In the G₂NDS BL_⊥architecture, the tilt of the

pillars alternates ribbon-to-ribbon to generate two distinct tilt

angles, ꢀ₁and ꢀ₂, producing GS sheets that are rippled in two

dimensions. The ꢀ₁and ꢀ₂angles scale inversely with the size

of the guest molecules, revealing that the host framework adjusts

systematically to the steric requirements of the guests. For

example, for the NDS pillar, ꢀ₁and ꢀ₂decrease from 10° and

27°, respectively, for bithiophene (V_g) 137 Å³) (Figure 5B,

top) to 9.3° and 10.6° for stilbene (V_g) 183 Å³) (Figure 5A,

top).

The TT guest also was included in the shorter G₂BuDS host

with the BL_⊥architecture (Figure 7). Due to its small length (l_g

) 9 Å, the smallest in the library of Scheme 3), however, TT

spans only one ribbon of the GS sheet, forming an inclusion

compound with a host:guest ratio of 1:1 instead of 1:0.5.

Furthermore, the aliphatic residue of the pillar does not show

any dihedral or tilting angle. Although the aspect ratio of TT

(1.3) is smaller than the typical values for the other guests in

the library, it ﬁts the trend of guest orientation on l_g:l_S-Sobserved

for the other inclusion compounds.

The BL_⊥architecture is a new occurrence in GDS inclusion

compounds. For a given pillar, the GS framework typically

prefers the zigzag brick architecture when a guest is too large

to ﬁt into the simple brick framework cavities. For example, a

pyrene guest with V_g) 187 Å³templates the zigzag brick

architecture in G₂NDS host although the volume of pyrene is

comparable to that of azobenzene, stilbene, and bibenzyl (Table

1). A similar case is observed for 1-methylnaphthalene; with

V_g) 144 Å³, this guest is nearly the same volume as biphenyl

and bithiophene. Both pyrene and 1-methylnaphthalene have

Figure 5. Discrete BL_⊥structures as viewed along the c axis (top) and

1

j

pillar-guest packing in the (1 40) plane (bottom) of: (A) G₂NDS· /₂(stilbene);

(B) G₂NDS·¹/₂(bithiophene). The hosts have been rendered as ball-and-

sticks and the guests as space-ﬁlling models. In the bottom panel, the G

ions have been removed for clarity.

compounds are tilted with respect to the 2-D layers such that

the molecules are offset along their long axes by one-half the

length of the molecule. The stilbene and azobenzene moieties

in the inclusion compounds, however, are not tilted and do not

exhibit this offset, revealing structural enforcement on host-guest

packing provided by the GS sheet (see Supporting Informa-

tion).²⁷

BL_⊥Architectures. Inclusion of π-conjugated molecules with

l_gg 1.25 l_S-Sproduced seven compounds that crystallize in a

BL_⊥architecture (Figure 5), including the G₂NDS host with

azobenzene, bibenzyl, DTE, stilbene, biphenyl, and bithiophene,

and the G₂BuDS (BuDS ) 1,4-butanedisulfonate) host with TT.

The BL_⊥architecture differs from previously reported GDS

compounds. The long axis of the guests is aligned perpendicular

to the long axis of the pillars, such that the long axis of the

guests coincides with the channel direction. This reﬂects a steric

frustration of the BL_|framework when the pillar is too short to

accommodate the guest in the vertical orientation. Consequently,

the inclusion compound adopts a conﬁguration in which the

guests are arranged end-to-end in a single ﬁle along the channel

rather than the edge-to-edge conﬁguration observed in the BL_|

architecture.

The G₂NDS BL_⊥architecture has the same GS sheet

projection topology as in the BL_|case but with some notable

differences. Each guest in the channel spans two periods of the

ribbons along the channel direction (the crystallographic c-axis

in the case of G₂NDS·¹/₂(stilbene), Figure 5A; b₁in Scheme

1), generating an unusual host:guest stoichiometry of 1:0.5. The

guest arrays are commensurate with the host lattice (the center-

(27) (a) Harada, J.; Ogawa, K. J. Am. Chem. Soc. 2004, 126, 3539. (b)

Chaloner, P. A.; Gunatunga, S. R.; Hitchcock, P. B. Acta Crystallogr.,

Sect. C: Cryst. Struct. Commun. 1994, 50, 1941. (c) Bouwstra, J. A.;

Schouten, A.; Kroon, J.; Helmholdt, R. B. Acta Crystallogr., Sect. C:

Cryst. Struct. Commun. 1985, 41, 420. (d) Ruban, G.; Zobel, D. Acta

Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1975, 31, 2632.

(e) Harada, J.; Ogawa, K. Struct. Chem. 2001, 12, 243. (f) Charbon-

neau, G.-P.; Delugeard, Y. Acta Crystallogr., Sect. B: Struct. Crys-

tallogr. Cryst. Chem. 1977, 33, 1586.

9

J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010 14611

A R T I C L E S

Soegiarto et al.

Figure 6. (A) The end-to-end arrangement of the azobenzene guests in the 1-D channels of the BL_⊥G₂NDS·¹/₂(azobenzene) as viewed along the a axis.

(B) Completely isolated bithiophene guests nestled within the “cage”-like cavity of the BL_⊥G₂NDS·¹/₂(bithiophene) as viewed along the a axis. In both

cases, the long axis of the guests is nearly orthogonal to that of the pillar. The hosts have been rendered as ball-and-sticks and the guests as space-ﬁlling

models. In addition, the carbon atoms of the NDS pillars are colored purple to aid visualization.

Figure 7. BL_⊥structure of G₂BuDS·(TT) as viewed along: (A) the b axis

or the channel direction; (B) the a axis highlighting the end-to-end

conﬁguration of the TT guests. The hosts have been rendered as ball-and-

sticks and the guests as space-ﬁlling models. In addition, the carbon atoms

of the BuDS pillars in (B) are colored purple to aid visualization.

an aspect ratio of 1.2, which is much smaller than those of the

elongated guests herein studied (from 1.6 to 2.1, with the

exception of TT). This implies that the formation of the BL_⊥

structure can be attributed to the high aspect ratio of the guests,

which steers templating of 1-D channels while frustrating the

Figure 8. Structural phase diagram for GDS inclusion compounds sorted

zigzag brick framework, which does not have 1-D cavities due

according to distinct sectors deﬁned by the value of l_g:l_S-S. Blue circles

to the zigzag arrangement of adjacent GS ribbons. This

phenomenon further reinforces the role of guest-templating

effects in GS framework assembly, not unlike the templating

mechanism proposed for the formation of zeolite and inorganic

networks.²⁸

(b) denote BL_⊥compounds, red diamonds ((, )) denote simple brick

compounds, and green triangles (2, ∆) denote BL_|compounds. Filled

symbols ((, 2, b) refer to 32 inclusion compounds reported herein and

unﬁlled symbols (), ∆) refer to 27 inclusion compounds that had been

previously reported and were formed with polyacene-based guests. The

diagram actually contains 59 entries, but only 49 are visible because several

compounds overlap.

Structural Phase Diagram. The GDS hosts can form a variety

of lamellar architectures, each endowed with inclusion cavities

of different sizes and shapes, exhibiting conformational ﬂex-

ibility that permit the optimization of the host-host and

host-guest interactions and thus the accommodation of a wide

variety of guests in the voids. The discovery of a new

arrangement of the guest with respect to the hosts, realized by

varying the length of the organic groups, reveals the inherent

ability of these compounds to optimize packing while retaining

the hydrogen-bond connectivity of the GS sheet and the overall

lamellar organization. Using l_gand l_S-S, a “structural phase

diagram”¹⁴(Figure 8) can be constructed to illustrate the

relationship between simple, well-deﬁned molecular parameters

and the host framework architecture of the inclusion compounds.

Figure 8 describes the positions of 59 inclusion compounds on

this diagram, including new compounds reported herein (ﬁlled

symbols) as well as others reported previously that contain

polyacene guests (unﬁlled symbols), which also are rigid and

conjugated. The phase diagram reveals that the different

architectures are located in distinct sectors according to their

l_g/l_S-Sratios.

< 1.25, typically reside in the two rightmost sectors, illustrating

the general trend from the BL_|to the simple brick architecture

with increasing guest volume, relative to the pillar volume, as

well as increasing l_g:l_S-S. These compounds, which consist of

polyacene pillars NDS, BPDS, and ADS (2,6-anthracenedisul-

fonate) (l_S-S) 8.5, 10.6, and 10.8 Å, respectively), crystallize

as either the BL_|or simple brick, depending on the relative sizes

of the pillars and guests. Generally, pillars without bulky

substituents favor bilayer frameworks when small guests are

included, whereas brick frameworks are templated by large

guests. The transition from BL_|to simple brick resulting from

increases in l_g:l_S-Sis apparent by inspection of Figure 8. For

example, the G₂BPDS host forms the BL_|architecture with

guests having 9.1 e l_ge 10.4 Å, including monosubstituted

naphthalene guests C₁₀H₇X (X ) Br, Cl, CH₃) and 1,2- and

1,5-dimethylnaphthalene. The simple brick architecture, how-

ever, is observed for guests having 10.7 e l_ge 11.6 Å as well

as monosubstituted naphthalenes bearing bulkier substituents

such as C₁₀H₇X (X ) I, NO₂, CN) and the remaining eight

dimethylnaphthalenes.²¹Similarly, the G₂ADS host forms the

BL_|architecture for guests such as naphthalene and tetrathi-

afulvalene (l_g) 9.2 and 10.6 Å, respectively) but the simple

brick architecture for larger guests such as pyrene, anthracene,

Previously reported GDS inclusion compounds in Figure 8

(unﬁlled symbols), which were restricted to guests with l_g:l_S-S

(28) Davis, M. E.; Katz, A. J.; Ahmad, W. R. Chem. Mater. 1996, 8, 1820.

9

14612 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

Table 3. Absorption (λ_max) and Emission (λ_em) Wavelengths and

Stokes Shift (λ_em- λ_max) for the Inclusion Compounds

architecture, exhibit bathochromic shifts (i.e., red-shifted)

compared with the absorption maxima in solution (<10^-5M).

The bathochromic shifts are the result of the balance among

various factors, including the increase of effective conjugation

length associated with molecular geometry (i.e., planar vs

nonplanar) as well as host-guest and guest-guest interactions.

The inﬂuence of these factors on the electronic transitions

of the guests was investigated by performing ab initio calcula-

tions. The electronic transition energies of the conjugated guests,

as encapsulated in the various inclusion frameworks, and as

isolated molecules or molecular aggregates (with structures

extracted from the crystal structures of the inclusion com-

pounds), were calculated using time-dependent density func-

tional theory (TDDFT), which is regarded as a reliable

computational method for evaluating the ground and low-lying

excited state spectrum of conjugated molecules,³⁰at the PBE0/

6-311G(d,p) level. The PBE0 hybrid functional is extremely

efﬁcient for accurately reproducing experimental values and

absorption spectra in several applications.³¹

The bithiophene guests in G₂NDS·¹/₂(bithiophene) exhibited

an experimentally measured bathochromic shift of 33 nm in

the absorption wavelength (λ_max) compared with λ_maxfor

bithiophene alone in methanol. The inﬂuence of host-guest

interactions on the optical properties were calculated using an

inclusion compound environment mimicking the packing ar-

rangements of the guest molecules within the cavities, as

determined by single crystal X-ray diffraction of the inclusion

compound. Bithiophene guests in the G₂NDS host framework

reside in cage-like cavities, largely isolated from one another,

surrounded by NDS pillars and GS sheets (Figure 6B). The

calculations for bithiophene conﬁned in the cage-like cavity of

G₂NDS·¹/₂(bithiophene), which is formed by four NDS and four

G moieties, revealed an electronic transition at λ_max,calc) 330

nm (see Supporting Information), in excellent agreement with

the experimental data (λ_max) 335 nm).³²The calculated

electronic transition wavelength is red-shifted by 28 nm

compared to that calculated for the isolated guest molecule,

comparing favorably with the aforementioned shift observed

experimentally and supporting the importance of host-guest

interactions.

compound

architecture

λ_max(nm) λ_em(nm) λ_em- λ_max(nm)

G₂NDS·¹/₂(bithiophene) BL_⊥

G₂BPDS·3(bithiophene) simple brick

G₂BBDS·(bithiophene) BL_|

335

336

334

307

302

338

431

384

372

391

358

396

384

375

410

346

387

353

355

349

348

96

48

38

84

56

58

48

43

93

39

57

21

23

31

bithiophene

-

bithiophene (in MeOH)

G₂NDS·¹/₂(stilbene)

G₂BBDS·3(stilbene)

G₂BSPE·(stilbene)

stilbene

-

BL_⊥

simple brick 336^a

BL_|

-

332^a

317

stilbene (in MeOH)

307^a

330^b

G₂NDS·¹/₂(azobenzene) BL_⊥

G₂BBDS·3(azobenzene) simple brick 332^b

G₂BSPE·(azobenzene) BL_|

azobenzene

332^b

318^b

317^b

-

azobenzene (in MeOH)

^aThis λ_maxvalue corresponds to the electronic transition with the

longest wavelength. Other absorption maxima with roughly equal

intensities to that of λ_maxare present at 318, 302, and 290 nm in the

spectra. ^bAnother absorption maxima with much lower intensities than

that of λ_maxare present at about 445 nm.

and biphenyl (l_g≈ 11.5 Å). The simple brick architecture is

also preferred in isostructural host-guest combinations,

G₂NDS · 3(naphthalene), G₂BPDS · 3(biphenyl), and G₂ADS ·

3(anthracene), with herringbone pillar-guest packing that mimic

the layer motifs in the crystals of their respective pure guests.²⁰

These structures reveal that dependence of the selectivity for

BL_|, and simple brick architectures can be explained by l_g:l_S-S

as well as V_g:V_pillar. In contrast, the examples in the BL_⊥sector

can only be explained by l_g:l_S-S

.

Figure 8 includes examples for which only two of the three

architectures were observed for a common guest, speciﬁcally

inclusion compounds containing terthiophene or TTF guests

(Table S1, Supporting Information). Terthiophene forms the BL_|

architecture with ABDS and SBDS hosts. In the case of

G₂ABDS·(TTF), the π-π stacking between ABDS and TTF

imparts a dark green color due to formation of a charge-transfer

complex²⁹wherein ABDS is the electron acceptor and TTF the

electron donor.

A more expansive structural phase diagram constructed from

a more diverse set of pillar-guest combinations (>250 GDS

inclusion compounds) exhibits similar architectural sorting,

although the phase boundaries are not as distinct as in Figure 8

(Figure S5, Supporting Information). Nonetheless, these struc-

tural phase diagrams illustrate that architectural isomers sharing

a common supramolecular building block, in this case the two-

dimensional GS sheets, can be sorted according to simple

molecular parameters, promising structure prediction for un-

tested host-guest combinations.

Optical Properties of the Photoactive Guests Included

within the GDS Hosts. The three framework isomers described

above result in distinct guest-guest aggregation and host-guest

packing motifs, which can be expected to inﬂuence the optical

absorption and emission of the guests conﬁned within the

framework cavities. This can only be demonstrated for inclusion

compounds based on a host and guest without overlapping

absorption and emission bands as in the combinations of

G₂NDS, G₂BPDS, G₂BBDS, and G₂BSPE hosts and bithiophene,

stilbene, and azobenzene guests (Table 3). The absorption bands

of these guests in the GDS host frameworks, regardless of

The experimentally observed bathochromic shift (7 and 13

nm, based on λ_max) 324 and 330 nm) for azobenzene in the

G₂NDS host matched the shift of 5 and 12 nm (based on λ_max,calc

) 321 and 328 nm) calculated for a single azobenzene guest

surrounded by four NDS and four G moieties of the G₂NDS

host. Similarly, the experimental bathochromic shift for trans-

(30) Runge, E.; Gross, E. K. U. Phys. ReV. Lett. 1984, 52, 997.

(31) (a) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,

3865. (b) Adamo, C.; Barone, V. J. Chem. Phys. 1999, 110, 6158. (c)

Cossi, M.; Barone, V. J. Chem. Phys. 2001, 115, 4708. (d) Jacquemin,

D.; Preat, J.; Wathelet, V.; Fontaine, M.; Perpe`te, E. A. J. Am. Chem.

Soc. 2006, 128, 2072. (e) Santoro, F.; Lami, A.; Improta, R.; Barone,

V. J. Chem. Phys. 2008, 128, 224311.

(32) The bithiophene guests in the inclusion compounds are trans-planar

with the dihedral (S-C-C-S) angle of 180°. Computations reveal

that the torsional energy barrier between two bithiophene conformers

with a dihedral (S-C-C-S) angle of 150° (the minimum) and 180°

(trans-planar) is approximately 0.3 kcal/mol (∼0.5Nk_BT at room

temperature). The maximum energy barrier, between two conformers

with a dihedral (S-C-C-S) angle of 150° and 90°, was calculated

to be approximately 2 kcal/mol (∼3Nk_BT at room temperature). These

relatively small barriers suggest that multiple conformers coexist in

solution and in the gas phase (Figure S8, Supporting Information).

Also see: (a) Takayanagi, M.; Gejo, T.; Hanazaki, I. J. Phys. Chem.

1994, 98, 12893. (b) Chadwick, J. E.; Kohler, B. E. J. Phys. Chem.

1994, 98, 3631.

(29) Evans, C. C. Conﬁnement of Dyes in Nanometer-Scale Domains. Ph.D.

Dissertation, University of Minnesota, Minneapolis, MN, 1998.

9

J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010 14613

A R T I C L E S

Soegiarto et al.

stilbene in G₂NDS (31 nm; λ_max) 338 nm) is in good agreement

with the shift of 17 and 29 nm calculated for a single stilbene

guest in the same host environment.^33,34Formation of J-type

aggregates, in which neighboring molecules adopt a head-to-

tail arrangement, also should be considered because they are

often associated with bathochromic shifts compared with the

isolated molecules.³⁵These shifts have been explained by

molecular exciton theory, which invokes coupling of transition

moments between neighboring molecules that splits the lowest

singlet excited state (Davydov splitting). The transition to the

lower Davydov level, which is responsible for the bathochromic

shift, is optically allowed for J-type aggregates whereas the

transition to the upper Davydov level is optically forbidden. In

the case of stilbene and azobenzene in G₂NDS host (with BL_⊥

architecture), the guests align end-to-end along the 1-D channel,

like J-type aggregates (Figure 6A). Notably, calculations

revealed small bathochromic shifts of ∼3 and 5 nm, respectively,

for pairs of azobenzene and stilbene guests (without the host)

having the J-aggregate-like motifs observed in their respective

inclusion compounds. The relatively small shifts calculated for

the J-aggregate-like motifs further supports an important role

for host-guest interactions in the optical properties and only a

minor contribution to the optical properties from guest-guest

interaction. Interestingly, the inﬂuence of the host is dramatic

compared with typical solvents, as the effect of solvent polarity

on λ_maxis negligible (as measured in hexane, cyclohexane,

benzene, acetonitrile, and methanol).³⁶Attempts to compare the

optical properties for bithiophene, azobenzene, and stilbene

guests included within the BL_|architecture and their host-free

molecular or aggregate forms were precluded by the large

number of atoms to be considered in the computationally

demanding high-level TDDFT methods.³⁷

The emission wavelength (λ_em) for guests in the GDS host

frameworks also exhibit bathochromic shifts compared with their

respective values in dilute solutions (Figure 9). The largest shifts

were recorded for bithiophene, stilbene, and azobenzene guests

conﬁned within hosts having the BL_⊥architecture. For example,

a bathochromic shift of 73 nm (λ_em) 431 nm) was observed

for bithiophene in G₂NDS host (BL_⊥), compared with λ_emin

any of the aforementioned solvents. In contrast, bithiophene in

G₂BPDS (simple brick) and G₂BBDS (BL_|) hosts exhibited a

Figure 9. The photoluminescence spectra of bithiophene, trans-stilbene,

and trans-azobenzene in various GDS host frameworks. The spectra of the

guests alone dissolved in methanol (10^-5M) are provided for comparison.

The bathochromic shift can be gleaned from the λ_emvalues (emission) in

methanol, denoted by the vertical dashed line. All intensity values are

normalized. The range of λ_maxvalues (absorption) for each guest chro-

mophore in the inclusion compounds is denoted by the vertical gray band.

The actual λ_maxvalues are provided in Table 3.

bathochromic shift of only 36 and 14 nm, respectively. The

emission bands of bithiophene and azobenzene guests in their

respective inclusion compounds are broad and featureless.

Stilbene guests exhibit multiple peaks corresponding to elec-

tronic relaxation to different vibrational energy levels of the

ground state in G₂BBDS and G₂BSPE, but broad featureless

bands in G₂NDS.³⁸Curiously, the Stokes shift, the difference

between the absorption and emission maxima, is larger for the

chromophores embedded in the inclusion compounds compared

with their respective values in solution. This may seem

surprising, as the magnitude of the Stokes shift usually increases

for molecules due to geometry changes or solvent reorganiza-

tion,³⁹which would be expected to be less in the constrained

environment of the solid-state host than in solution. The

chromophores examined here, however, lack substantial dipolar

character, which would be expected to produce small Stokes

(33) (a) Chen, P. C.; Chieh, Y. C. J. Mol. Struct. (THEOCHEM) 2003,

624, 191. (b) Brown, E. V.; Granneman, G. R. J. Am. Chem. Soc.

1975, 97, 621. (c) Champagne, B. B.; Pfanstiel, J. F.; Plusquellic, D. F.;

Pratt, D. W.; van Herpen, W. M.; Meerts, W. L. J. Phys. Chem. 1990,

94, 6.

(34) The minimum energy conformation for free trans-stilbene and trans-

azobenzene is reported as planar, as found in the GDS inclusion

compounds. Consequently, the contribution of conformational effects

to the bathochromic shifts for these compounds is negligible.

(35) Cornil, J.; Beljonne, D.; Calbert, J.-P.; Bre´das, J.-L. AdV. Mater. 2001,

13, 1053.

(36) A small red shift (<2 nm) has been reported for bithiophene with

increasing solvent polarity. See: (a) Di Ce´sare, N.; Belleteˆte, M.;

Raymond, F.; Leclerc, M.; Durocher, G. J. Phys. Chem. A 1997, 101,

776. (b) Meng, S.; Ma, J.; Jiang, Y. J. Phys. Chem. B 2007, 111,

4128.

(37) Although computations for a complete inclusion cavity based on four

BBDS pillars, four G ions, and a single bithiophene guest were not

possible due to the large number of atoms involved, calculation with

a lower number of host molecules (four BBDS pillars, two G ions)

and one guest revealed a bathochromic shift of 14 nm, much less than

the experimental value of 32 nm. Calculation at the same level

predicted a hypsochromic shift (blue-shift) of ∼3 nm for two

bithiophene guests (without host) with the edge-to-edge motif observed

in the G₂BBDS inclusion compound. These results further reinforce

a more important role for host-guest interactions in the bathochromic

shifts compared with guest-guest interactions.

(38) Waldeck, D. H. Chem. ReV. 1991, 91, 415.

(39) Anslyn, E. V.; Dougherty, D. A. In Modern Physical Organic

Chemistry; University Science Books: Sausalito, 2006; pp 942-

946.

(40) CSD Reference Code MAXZUG Holman, K. T.; Ward, M. D. Angew.

Chem., Int. Ed. 2000, 39, 1653.

9

14614 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Tunable Host Cavities

A R T I C L E S

of 4,4′-disulfostilbene,⁴²and the sodium salt of 1,4-butanedisul-

fonate⁴³were prepared according to published procedures. All

solvents and other starting materials were purchased as ReagentPlus

or ACS reagent grade from Aldrich, Acros (Geel, Belgium), or Alfa

Aesar (Ward Hill, MA) 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, G₂ABDS, G₂SBDS, and G₂BuDS precipitate, as acetone

clathrates, by direct reaction of guanidinium tetraﬂuoroborate,

prepared by neutralization of guanidinium carbonate with tetraﬂuo-

roboric acid, with the corresponding disulfonic acid in acetone.

These compounds readily lose enclathrated acetone under ambient

conditions to yield pure guanidinium organodisulfonate apohosts.

The inclusion compounds reported here were crystallized from

methanolic solutions (by slow evaporation method) 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

shifts regardless of the environment. This is supported by the

observation of a negligible dependence of λ_emfor each guest

on the polarity of the solvent (hexane, cyclohexane, benzene,

acetonitrile, methanol). This suggests that other factors con-

tribute to the energetic relaxation of the excited state and the

associated Stokes shifts in the inclusion compounds, possibly

coupling of the excited state with lattice phonons or with the

excited states of other guest chromophores, which could be

enhanced by the degree of guest alignment and small intermo-

lecular distances in the solid state compared with dilute

solutions.

Conclusions

The architecture of GDS host frameworks and the orientation

of linear π-conjugated guest molecules in 1-D channels can be

regulated systematically based on the relative lengths of the

pillar and the guest. Increasing values of l_g:l_S-Sare accompanied

by a systematic transition in the framework architecture from

the BL_|to simple brick to BL_⊥, and consequently, a change in

the aggregation motifs of the conﬁned guests from edge-to-edge

to face-to-edge to end-to-end. The framework architecture types

can be sorted in a “structural phase diagram” according to simple

molecular parameters, l_gand l_S-S, which can be used for

structure prediction in this class of compounds. Although the

BL_|and simple brick architectures have been well documented

in the past, the formation of the BL_⊥architecture (with l_gg

1.25 l_S-S) is unprecedented and appears to be associated with

guests having high aspect ratios. The BL_⊥architecture can

generate either a 1-D channel or a cage-like cavity depending

on the length of the conﬁned guests; for example, stilbene guests

in G₂NDS host (BL_⊥; l_g:l_S-S) 1.61) are arranged end-to-end

along the 1-D channel whereas bithiophene guests in the same

host (BL_⊥; l_g:l_S-S) 1.25) are isolated in cage-like cavities. The

effects of the various host and/or guest aggregation motifs on

the optical properties of the conﬁned guests are manifested in

the bathochromic shifts in the absorption and emission spectra

relative to those in dilute solution. The shifts in the absorption

bands were corroborated by ab initio computations (using

TDDFT at the PBE0/6-311G(d,p) level) based on the structures

of the host-guest aggregates observed in the crystalline state.

The ability of the GDS hosts to adapt to different size and shape

requirements of the guests by forming various architectures that

can be sorted according to simple molecular parameters reveals

the exceptional capability of these hosts for regulating guest

aggregation in a reliable and predictable manner. Additionally,

the host components in GDS compounds are often π-conjugated

and, therefore, may contribute to energy and charge transfer

processes in a manner that modulates the optical properties

derived from the conﬁned guests. Collectively, these features

suggest promising pathways to the design and synthesis of

functional materials.

1

conﬁrmed by H NMR spectroscopy in addition to single-crystal

structure determinations. ¹H NMR spectra were recorded on a

Bruker AV-400 spectrometer operating at 400 MHz.

[Guanidinium]₂[1,4-bis(4-sulfophenoxy)butane], G₂BSPB. An

ethanolic solution containing 1:1 molar ratio of NaOH (1.72 g, 43

mmol) and 4-hydroxybenzenesulfonic acid sodium salt dihydrate

(10 g, 43 mmol) was prepared and reﬂuxed for 30 min. 1,4-

Dibromobutane (4.64 g, 21.5 mmol) was then added to the solution,

and the reaction was left to reﬂux for a further 100 h. After the

reaction ended, the mixture was rotary-evaporated to remove the

ethanol solvent. The remaining solid residue, which contained

the sodium salt of BSPB, was dissolved in water and converted to

the acid form by passing them through an Amberlyst 36(wet) ion-

exchange column. After the water had been rotary-evaporated, the

BSPB acid was dissolved in acetone and then treated with an

acetone solution of G[BF₄]. The G₂BSPB ·(acetone)_nprecipitate

was ﬁltered and dried under vacuum to give 5.46 g (10.5 mmol) of

1

pure, white G₂BSPB (50% yield). H NMR (dimethyl sulfoxide-

d₆, 400 MHz, J/Hz): δ 7.50 (d, 4H, ²J ) 8, 2-H), 6.95 (s, 12H, G),

2

6.86 (d, 4H, J ) 8, 3-H), 4.04 (m, 4H, O-CH₂), 1.86 (m, 4H,

1-CH₂).

Crystallography. Experimental parameters pertaining to the

single-crystal X-ray analyses are given in Table 2 (see Supporting

Information). Data were collected on Bruker SMART APEX II

CCD platform diffractometer with graphite monochromated Mo KR

radiation (λ ) 0.71073 Å) at 100(2) K or 200(2) K. The structures

were solved by direct methods and reﬁned with full-matrix least-

squares/difference Fourier analysis using the APEX2 (fully inte-

grated with SHELX-97) suite of software.⁴⁴All 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. The data collection of compound

G₂NDS·¹/₂(DTE) was carried out at 15-ID ChemMatCARS beam-

line, Advanced Photon Source, Argonne National Laboratory, using

a Bruker SMART APEXII CCD detector. Data were collected at

100 K with a wavelength of 0.44280 Å with an exposure time of

0.6 s per frame and a crystal-detector distance of 5.5 cm.

Fluorescence. Fluorescence measurements were performed using

a Hitachi F-2500 ﬂuorescence spectrophotometer, equipped with a

150 W xenon light source. Liquid samples were placed inside

Fisherbrand* disposable polystyrene four-clear-sided cuvettes pur-

chased from Fisher Scientiﬁc. In the case of solid samples, several

Experimental Section

Materials and General Procedures. Guanidine carbonate salt,

tetraﬂuoroboric acid, 2,6-naphthalenedisulfonic acid disodium salt,

Amberlyst 36 (wet) ion-exchange resin, 2,2′-bithiophene, bibenzyl,

azobenzene, trans-stilbene, biphenyl, 2,2′:5′,2′′-terthiophene, and

tetrathiafulvalene were purchased from Sigma-Aldrich (Milwaukee,

WI). 4,4′-Biphenyldisulfonic acid and thieno[3,2-b]thiophene were

purchased from TCI America (Tokyo, Japan). These chemicals were

used without further puriﬁcation. G₂BBDS and G₂BSPE apohosts,⁸

the sodium salt of 4,4′-azobenzenedisulfonate,⁴¹the sodium salt

(42) (a) Moore, F. J. J. Am. Chem. Soc. 1903, 25, 622. (b) van Es, T.;

Backeberg, O. G.; Morrison, I. J. South Afr. Chem. Inst. 1964, 17,

95.

(43) Stone, G. C. H. J. Am. Chem. Soc. 1936, 58, 488.

(44) (a) Sheldrick, G. M. SHELX-97; University of Go¨ttingen: Go¨ttingen,

Germany, 1997. (b) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found.

Crystallogr. 2008, 64, 112.

(41) Clarke, H. T. J. Org. Chem. 1971, 36, 3816.

9

J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010 14615

A R T I C L E S

Soegiarto et al.

single crystals of a given compound were placed at the bottom of

a glass NMR tube cut to ﬁt into the cuvette holder of the

spectrophotometer. The excitation slit width was set at 2.5 nm. The

emission slit widths (2, 5, or 10 nm) were adjusted to enhance

intensity values. Data were collected at a scan speed of 300 nm/

min and a photomultiplier (PMT) detector voltage of 400 V.

Transmittance and Reﬂectance Absorption. Both transmittance

(for liquid samples placed in quartz cuvette) and reﬂectance (for

solid samples) absorption measurements were performed using a

Perkin-Elmer Lambda 950 UV/vis Spectrometer. Reﬂectance

measurements were performed in total reﬂectance mode by attaching

an 8° wedge to the sample port of a 60-mm integrating sphere. All

solid crystalline samples were lightly ground into polycrystalline

powders, loaded into a 1.25-in. diameter sample cup, mixed with

BaSO₄(95% by weight) as a diluent, and pressed ﬁrmly to create

a smooth sample surface. The sample cup was then attached onto

the sample port of the integrating sphere. The UV/vis slit width

was ﬁxed at 2 nm. The photomultiplier detector gain was 30, and

its integration (response) time was 0.20 s. Absorbance values (A)

were converted from % reﬂectance (%R) according to A )

-log(%R).

Computational Study. Calculations of the electronic transition

energy between the ground and excited (singlet and/or triplet) states

were performed with the Gaussian03 program package⁴⁵using time-

dependent density functional theory (TDDFT) at the PBE0/6-

311G(d,p) level. PBE0 is built on the Perdew-Burke-Ernzerhof

pure functional, in which the exchange is weighted (75% DFT/

25% Hartree-Fock) accordingly to theoretical considerations.

Electronic transition energy calculations for the guests in the

inclusion compounds and as isolated molecules were based on

molecular geometries extracted from the crystal structures as

determined by single crystal X-ray diffraction. In addition, the

oscillator strength, f, for each electronic transition was calculated.

The coefﬁcient f is related to the molar extinction coefﬁcient of

that transition, and hence the transition with the highest f is assigned

as the calculated absorption maxima (λ_max,calc) that can be compared

with the experimental absorption maxima (λ_max). Conformational

analysis of the guests was performed using density functional theory

(DFT) at the PBE0/6-311G(d,p) level and was based on the

geometry-optimized molecular structure of the guests at various

predetermined dihedral angles.

Acknowledgment. The authors thank Samuel Hawxwell and

Chunhua (Tony) Hu of the New York University Molecular Design

Institute, Yu-Sheng Chen of ChemMatCARS, APS, and Charles

Campana of Bruker Inc. for their assistance in crystal structure

determinations. Bernardo Moltrasio and Maurizio Cossi are ac-

knowledged for helpful suggestions on computational calculations.

This work was supported in part by the Fondazione Cariplo and

the NSF Division of Materials Research (DMR-0906576). Use of

the Advanced Photon Source was supported by the U.S. Department

of Energy, Ofﬁce of Science, Ofﬁce of Basic Energy Sciences,

under Contract No. DE-AC02-06CH11357. ChemMatCARS Sector

15 is principally supported by the National Science Foundation/

Department of Energy under grant number CHE-0535644.

Supporting Information Available: Crystal images with face

indexing, various schematics of crystal structures and additional

structural phase diagrams, ab initio calculation details, individual

absorption and emission spectra, structural features of com-

pounds 29-32, crystallographic information ﬁles (CIFs), and

complete citation for reference 45. This material is available

free of charge via the Internet at http://pubs.acs.org.

(45) Frisch, M. J., et al. Gaussian 03 (ReVision C.02); Gaussian, Inc.:

Wallingford, CT, 2004.

JA106106D

9

14616 J. AM. CHEM. SOC. VOL. 132, NO. 41, 2010

Article Doi

Controlled orientation of polyconjugated guest molecules in tunable host cavities

DOI: 10.1021/ja106106d

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Authors:

Article abstract of DOI:10.1021/ja106106d

Full text of DOI:10.1021/ja106106d

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