A fluoresceinophane: 19,4,16-trioxa-1(2,10)-anthracena-2(1,2)- benzenacyclohexadeca-phane-17,3(19 H)-dione

Article abstract of DOI:10.1107/S0108270107008566

A novel macrocycle containing fluorescein, the highly fluorescent title compound, C31H32O5, has a xanthene core and a benzyl unit that are planar. The latter is rotated by 72.99 (3)° from the xanthene mean plane. The C11 alkyl tether and the xanthene grou

Full text of DOI:10.1107/S0108270107008566

organic compounds
Acta Crystallographica Section C
Crystal Structure
of our macrocycle was achieved in three relatively easy steps
starting from ¯uorescein.
Communications
ISSN 0108-2701
9
A fluoresceinophane: 1 ,4,16-trioxa-
(2,10)-anthracena-2(1,2)-benzena-
1
7
9
cyclohexadecaphane-1 ,3(1 H)-dione
The structure of (I) consists of two planar aryl units linked
by an undecanyl alkyl tether. The aryl units are twisted with
respect to one another because of the steric hindrance
between atom H15 and atoms H2 and H11 (all bonded to the
C atoms of the same numbers; Fig. 1) that would result from
the coplanarity of the two aryl rings. The angle between the
St e phane Dufresne, Sergio Andr e s P e rez Guar Áõ n and
W. G. Skene*
Department of Chemistry, University of Montreal, CP 6128, succ. Centre-ville,
Montr e al, Qu e bec, Canada H3C 3J7
ꢀ
ꢀ
two mean planes of the aryl units is 72.99 (3) . The 17.01 twist
from perpendicularity allows the macrocycle to accommodate
the long tether chain, as shown in Fig. 1. This is in contrast with
linear ¯uorescein derivatives whose xanthene±benzyl mean
Correspondence e-mail: w.skene@umontreal.ca
Received 15 December 2006
Accepted 20 February 2007
Online 11 May 2007
ꢀ
planes are rotated by between 85 and 90 (Cody, 1987;
Tremayne et al., 1997; Willner et al., 1997; Ajtai & Burghardt,
A novel macrocycle containing ¯uorescein, the highly
¯uorescent title compound, C H O , has a xanthene core
and a benzyl unit that are planar. The latter is rotated by
1
995; Wang et al., 2001). The intramolecular CÐHÁ Á Áꢀ inter-
31 32 5
action C23ÐH23AÁ Á ÁCg1, where Cg1 is the centroid of the
C1±C6 ring, also contributes to the observed conformation.
The xanthene group consists of three different six-
membered rings, namely the central pyran ring and the
terminal quinone and benzene rings. These individual rings
are generally dif®cult to identify unequivocally by common
ꢀ
7
2.99 (3) from the xanthene mean plane. The C alkyl tether
1
1
and the xanthene group adopt a cage-like structure and the
xanthene adopts a quinoid-type con®guration. The compound
crystallizes as a racemic mixture with one molecule of each
isomer per unit cell. Even though the planes described by the
xanthene and the benzene rings of different molecules are
1
techniques such as H NMR. Despite these challenges, the
bond distances of the different elements that comprise the
three unique rings were expected to be substantially dissim-
ilar, allowing them to be observed in the isolated crystal
structure. It is, therefore, not surprising that the isolated
xanthene is unsymmetric, with longer bond distances on the
side containing the alkyl chain. For example, C2ÐC3 and
Ê
separated by 3.341 (4) and 3.73 (1) A, respectively, there is
insuf®cient overlap between the aryl units to promote
ꢀ-stacking.
Comment
Ê
The investigation of macrocycles has been pursued recently
along many avenues of science, due to the potential applica-
tions of these compounds as nanomolecular machines (Stod-
dart & Tseng, 2002; Balzani et al., 2000). Many interesting
properties can be obtained by incorporating steric elements
into the macrocycle that increase activation barriers such as
that to rotation (Feringa, 2001; Kelly et al., 1994). These
properties are responsible for novel devices such as ®eld-effect
transducers, molecular sensors, switches, etc. Because of these
activation barriers, macrocycles can be used as actuators and
are useful for temperature probes or monitors. Macrocyclic
formation is, however, challenging and numerous dif®culties
are encountered during the synthesis of such nanoactuators.
Consequently, macrocycles have attracted much attention in
order to ®nd more ef®cient protocols for their synthesis and
for the preparation of new materials with desired functional
properties. We have incorporated ¯uorescein as a core unit in
the title compound, (I), because this ¯uorescent scaffold
ensures that unique photophysical properties can be obtained.
The bene®ts of our approach are the ease and versatility of the
macrocyclic synthesis, which can ultimately be used for the
synthesis of macrocycles with various ring sizes. The synthesis
C5ÐC6 are 0.036 (4) and 0.030 (4) A longer than their
respective counterparts C10ÐC11 and C7ÐC8, and C1ÐC13
Ê
is also 0.070 (4) A longer than its corresponding C12ÐC13
bond. Even though the O1ÐC7 and O1ÐC6 bond distances
are identical, the C1ÐC13 and C12ÐC13 bond distances are
considerably different, further contributing to the unsym-
metric nature of the molecule.
Figure 1
A drawing of (I), showing the atom-numbering scheme. Displacement
ellipsoids are drawn at the 30% probability level and H atoms are shown
as small spheres of arbitrary radii.
o350 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107008566
Acta Cryst. (2007). C63, o350±o352

organic compounds
ꢀ
The C12ÐC13 bond is understood to have greater double-
bond character owing to its shorter length relative to C1Ð
C13. This con®guration confers an aromatic character on the
corresponding torsion angle of 71.7 (2) . No disorder was
found in the structure, even with the long C11 tether. Even
though the alkyl chain forms a rectangular cage-like structure
with the xanthene group, no solvent was found within the
structure. The cavity size was the same for both isomers and
Ê
xanthene. The O2ÐC9 bond is also 0.112 (4) A shorter than
Ê
O5ÐC4, which is 0.079 (5) A shorter than the reported value
Ê
Ê
for a similar ¯uorescein (Yamaguchi et al., 1997). The O2ÐC9
and O5ÐC4 bond distances correspond to a ketone and an
aryl ether group, respectively, which cannot be readily iden-
ti®ed by other standard characterization techniques. The
presence of these two different groups further contributes to
the unsymmetric nature of the ¯uorescein. The combined
bond distances con®rm that the xanthene consists of three
different six-membered rings. These different aromatic rings
collectively contribute to the high ¯uorescence exhibited by
this compound. Moreover, of the many known conformations
of ¯uorescein, the isolated structure con®rms that the highly
conjugated quinoid conformation is formed.
was calculated to be 7.88 (1) A wide and 3.762 (6) A in height.
The height was calculated according to the absolute distance
between the planes of the xanthene and the alkyl chain, while
the width was calculated from the distance between the two
average mean planes described by C14/C19/C20 and C27±C29.
The xanthene groups of different isomers adopt an anti-
parallel arrangement in the crystal lattice. Conversely, the
benzyl units of the two isomers are parallel. The arrangement
of the xanthene and the benzyl groups affords a close-packed
network that is present in the crystal lattice involving the two
inversion-related molecules of (I) (Fig. 2), which extends
along the z direction. Even though ꢀ-stacking is common for
such highly conjugated compounds, no such interactions were
found for (I). Despite the xanthene±xanthene and benzene±
benzene plane distances being ideal for ꢀ-interactions at
Owing to the possible rotation around the C13ÐC14 bond,
the long alkyl chain can potentially lie on either side of the
xanthene face. This leads to two possible isomers. The asym-
Ê
metric molecules has a C12ÐC3ÐC14ÐC19 torsion angle of
ꢀ
3.341 (4) and 3.73 (1) A, respectively, the aryl units do not
�
71.7 (2) . Since the compound crystallizes in the P1 space
group there is an exact inversion-related molecule with the
overlap. In fact, the centroid±centroid distances of xanthene
and benzene are much greater, resulting in no apparent
intermolecular interactions. However, a van der Waals inter-
action occurs between the alkyl chains of two molecules
Ê
separated by 3.89 (1) A. The observed van der Waals inter-
actions take place between two different isomers.
A total of three unique intermolecular CÐHÁ Á ÁO hydrogen
bonds are present and these are responsible for the supra-
molecular network represented in Fig. 3. Two such inter-
actions occur between C5ÐH5Á Á ÁO2 of two separate
molecules. There are two additional donor±acceptor bonds
involving C8ÐH8Á Á ÁO1. These two donor±acceptor pairs are
Ê
separated by 3.355 (2) and 3.4639 (19) A, respectively, and
form a dimer-like structure. Two additional hydrogen bonds
occur between two complementary C10ÐH10Á Á ÁO3 units of
two molecules. More speci®cally, a nontraditional donor±
acceptor±donor±acceptor hydrogen-bonding motif was found
between the two isolated isomers involving the xanthene unit,
leading to a dimer-like arrangement. This is illustrated in Fig. 3,
Figure 2
The three-dimensional network of (I), demonstrating the van der Waals
interactions between the alkyl chains.
Figure 3
The supramolecular structure of (I), showing the intramolecular CÐHÁ Á ÁO bonding giving a dimer-like structure. [Symmetry codes: (i) � x + 1, � y + 2,
�
z + 1; (ii) � x + 1, � y + 2, � z + 2; (iii) x, y, z + 1; (iv) x, y, z � 1; (v) � x + 1, � y + 2, � z.]
ꢁ
Acta Cryst. (2007). C63, o350±o352
Dufresne et al.
C H
31 32
O
5
o351

organic compounds
which also shows the interactions between the two isomers
i
Table 2
ꢀ
i
i
i
i
Hydrogen-bond geometry ( AÊ , ).
involving O2Á Á ÁH5 ÐC5 , O1Á Á ÁH8 ÐC8 , O2 Á Á ÁH5ÐC5 and
i
O1 Á Á ÁH8ÐC8 [details are given in Table 2; symmetry code: (i)
Cg1 is the centroid of the C1±C6 ring.
�
x + 1, � y + 2, � z + 1]. Hydrogen bonds between atoms O3
ii
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
and H10 [symmetry code: (ii) � x + 1, � y + 2, � z + 2] and the
i
iv
i
i
other isomer involving O3 and H10 [symmetry code: (iv) x,
y, z � 1] were also observed. All these intermolecular
C5ÐH5Á Á ÁO2
C8ÐH8Á Á ÁO1
0.95
0.95
0.95
0.99
2.51
2.60
2.47
2.93
3.355 (2)
3.4639 (19)
3.3454 (19)
3.82 (2)
149 (2)
151 (3)
154 (2)
150 (2)
ii
C10ÐH10Á Á ÁO3
Ê
distances are less than 3.5 A and the DÐHÁ Á ÁA angles are ca
C23ÐH23AÁ Á ÁCg1
ꢀ
150 , so they can therefore be categorized as ideal hydrogen
bonds.
Symmetry codes: (i) � x ‡ 1; � y ‡ 2; � z ‡ 1; (ii) � x ‡ 1; � y ‡ 2; � z ‡ 2.
H atoms were placed in calculated positions, with CÐH = 0.93±
Ê
.97 A, and included in the re®nement in the riding-model approx-
Experimental
0
imation, with Uiso(H) = 1.2Ueq(C).
Fluorescein (2.73 g) was dissolved in methanol (200 ml) along with a
catalytic amount of concentrated sulfuric acid. The orange±red
solution was re¯uxed for 12 h and was then poured into ice±water
Data collection: SMART (Bruker, 2003); cell re®nement: SMART;
data reduction: SAINT (Bruker, 2004); program(s) used to solve
structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
ORTEP-3 (Farrugia, 1997) and SHELXTL (Bruker, 1997); software
used to prepare material for publication: UdMX (Marris, 2004).
(100 ml). The resulting precipitate was ®ltered off to yield the product
as an orange solid. This isolated product (1.67 g) was added to
dimethylformamide (100 ml) followed by potassium carbonate
(1.43 g) and 11-bromoundecan-1-ol (1.28 g), and the mixture was
heated at 333 K for 2 d. The resulting red precipitate was ®ltered off
and washed with aqueous sodium hydroxide. The product was solu-
bilized in anhydrous tetrahydrofuran along with sodium hydride. The
mixture was subsequently re¯uxed for 8 h and the title compound,
The authors acknowledge ®nancial support from the
Natural Sciences and Engineering Research Council, Canada,
Fonds de Recherche sur la Nature et les Technologies, and
Canada Foundation for Innovation. Gratitude is extended to
Dr M. Simard for assistance with the crystal structure analysis.
SD thanks the Universit e de Montr e al for a graduate scho-
larship.
(I), was isolated in 41% yield after column chromatography.
Compound (I) was crystallized by slow diffusion of hexanes into a
saturated solution of the compound in diisopropyl ether.
Crystal data
ꢀ
C
31
32
H O
5
ꢃ = 92.167 (3)
Ê
3
M
r
= 484.57
Triclinic, P1
a = 7.9010 (9) A
V = 1276.0 (2) A
Z = 2
Ê
Cu Kꢁ radiation
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SQ3058). Services for accessing these data are
described at the back of the journal.
Ê
� 1
b = 12.7844 (13) A
ꢄ = 0.68 mm
T = 100 (2) K
Ê
c = 12.9683 (14) A
ꢀ
ꢁ
= 91.895 (2)
0.18 Â 0.16 Â 0.11 mm
ꢀ
ꢂ = 102.655 (3)
Data collection
References
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Absorption correction: multi-scan
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R
int = 0.024
(SADABS; Sheldrick, 1996)
5 standard re¯ections
frequency: 1080 min
intensity decay: none
T
min = 0.804, Tmax = 0.931
699 measured re¯ections
831 independent re¯ections
4
3
Re®nement
2
2
R[F > 2ꢅ(F )] = 0.041
wR(F ) = 0.129
325 parameters
H-atom parameters constrained
2
Ê
� 3
Áꢆmax = 0.24 e A
S = 1.07
3
Áꢆmin = � 0.24 e AÊ
� 3
831 re¯ections
Table 1
Selected geometric parameters (A, ).
Ê
ꢀ
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O2ÐC9
O5ÐC4
O5ÐC31
C1ÐC13
C2ÐC3
1.252 (2)
C5ÐC6
C7ÐC8
C10ÐC11
C12ÐC13
1.390 (2)
1.360 (2)
1.352 (2)
1.379 (2)
4
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1.4542 (17)
1.449 (2)
3
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1.388 (2)
C12ÐC13ÐC14
120.80 (13)
C1ÐC13ÐC14
119.87 (13)
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ꢁ
o352 Dufresne et al.
31 32
C H O
5
Acta Cryst. (2007). C63, o350±o352