A novel cyclophane-anthracene complex

Article abstract of DOI:10.1016/S0040-4039(02)01033-X

A cyclophane host formed by connecting the oxygen atoms of two α,α′-di-(4-hydroxyphenyl)-1,4-diisopropylbenzene units with two pentamethylene spacers forms a unique solid-state complex with anthracene.

Full text of DOI:10.1016/S0040-4039(02)01033-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 5017–5019
A novel cyclophane–anthracene complex
Richard A. Bartsch,a,* Piotr Kus,a,b N. Kent Dalleyc and Xiaolan Kouc
aDepartment of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
bDepartment of Chemistry, Silesian University, 9 Szkolna Street, 40-006 Katowice, Poland
cDepartment of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602-5700, USA
Received 18 April 2002; revised 24 May 2002; accepted 30 May 2002
Abstract—A cyclophane host formed by connecting the oxygen atoms of two a,a%-di-(4-hydroxyphenyl)-1,4-diisopropylbenzene
units with two pentamethylene spacers forms a unique solid-state complex with anthracene. © 2002 Elsevier Science Ltd. All
rights reserved.
In the design and synthesis of new molecular receptors,
cyclophanes play an important role.1,2 Molecular guests
are complexed within the central cavities of these
macrocyclic receptors. We are using the relatively unex-
plored bisphenol 13 (Scheme 1) as a p electron-rich,
hydrophobic unit for the construction of a new family
of cyclophanes.
host molecules. Since it was envisioned that the aro-
matic guest would be contained within a walled enclo-
sure, such cyclophane hosts are termed ‘corrals’.4
Recently, we described the preparation of cyclophane
host 4 and the solid-state structure for the complex of
this corral with a p-xylene guest.4 In this structure, the
p-xylene guest was encapsulated within the central cav-
ity of the cyclophane.
In connecting the oxygen atoms of two molecules of 1
with two multi-methylene spacers, rigidity of the two
a,a%-di-(4-oxyphenyl)-1,4-diisopropylbenzene
units
Changing the number of carbons in the multi-methyl-
ene spacers from three to five should expand the central
cavity in the cyclophane so it can complex larger aro-
matic guest molecules. We now report the synthesis of
host 5 and the solid-state structure of its complex with
an anthracene guest.
should provide open structures in which the dimensions
of the central cavity can be systematically varied by
changing the number of carbon atoms in the spacers.
Complexation of aromatic guests within their central
cavities should be facilitated by p interactions with the
Scheme 1. Two-step synthesis of cyclophane host 5.
Keywords: host–guest; molecular recognition; solid-state structure.
* Corresponding author.
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)01033-X

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R. A. Bartsch et al. / Tetrahedron Letters 43 (2002) 5017–5019
Figure 1. Top (left) and side (right) view for the solid-state structure of the 5-anthracene complex.
Reaction of bisphenol 1 with a large excess of 1,5-
dibromopentane and potassium carbonate in DMF at
room temperature for 15 h gave an 80% yield of
dibromide 3.5 A mixture of equivalent amounts of
bisphenol 1 and dibromide 3 with cesium carbonate in
DMF was stirred at 60–70°C for 6 days to provide a
70% yield of cyclophane 57 as a white solid.
1
By H NMR spectroscopy,9 no complexation of tolu-
ene, p-xylene, or naphthalene molecules by cyclophane
Figure 2. Host molecules for reported cyclophane–aromatic
5 in deuteriochloroform was evident. However, mixing
of deuteriochloroform solutions of the cyclophane host
and anthracene gave an immediate formation of a white
crystalline precipitate with a melting point similar to
that of host 5. Under more controlled conditions, crys-
tals were grown by slow evaporation of a chloroform–
dichloromethane solution of equimolar cyclophane 5
and anthracene. Combustion analysis of the crystals
revealed a one-to-one complex of host 5 and anthracene
guest.10 In contrast, no complexes were formed by slow
evaporation of chloroform–dichloromethane solutions
of 5 and naphthalene, phenanthrene, or pyrene. Crys-
tals suitable for structure determination by X-ray dif-
fraction were obtained by slow evaporation of the
chloroform–dichloromethane solution of equimolar 5
and anthracene and the solid-state structure for the
5-anthracene complex was determined.11 Computer
drawings of top and side views are shown in Fig. 1. As
is readily evident, the anthracene guest is encapsulated
within the cavity of the cyclophane host. The dihedral
angles between the planes of the three benzene rings at
each end of the cyclophane host are 73.9, 95.3, and
133.7° for ring 1–ring 2, ring 2–ring 3, and ring 1–ring
3 (ring 3 is the C20–C25 benzene ring). The dihedral
angle between the least-squares planes of the host and
guest is 18.8°. Both the host and the guest lie about the
same inversion center. The cyclophane cavity has a
rectangular shape with dimensions of approximately 15
quest complexes.
angles between the least squares plane of the guest and
benzene rings 1, 2, and 3 are 77.5, 124.6, and 61.7°,
respectively.
This
suggests
edge-to-face
p
interactions14,15 between the guest and benzene rings 1
and 3 of the host in the complex.
Koga and co-workers have determined the solid-state
structure of a complex of durene16 with related
cyclophane 6 (Fig. 2) and assessed interactions of this
cyclophane host with naphthalene in acidic aqueous
solution.17 In both the solid state and in solution, the
aromatic guest was perpendicular to the plane of the
host. A similar perpendicular arrangement was calcu-
lated for the complex of benzene with the N-alkylated
analogue 7.18 Therefore, the nearly coplanar arrange-
ment of the host and guest planes in the 5-anthracene
complex is quite unexpected. Studies to determine the
causative factor(s) for this unusual orientation of the
aromatic guest within the cyclophane host cavity are in
progress.
Acknowledgements
Support of the portions of this research conducted at
Texas Tech University by the Welch Foundation
(Grant D-775) is gratefully acknowledged.
,
,
A (C12a···C13) for one side and approximately 10 A
(C3···O26) for the other. This provides sufficient space
for the anthracene guest to lie nearly flat in the middle
of the intramolecular cavity of the host with the termi-
nal edges of the anthracene pointing toward the aro-
matic portions of the host. The distances from the
centroid of ring 3 to the nearest proton of the guest is
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