D.-M. Du et al. / Journal of Molecular Structure 560 (2001) 23±28
27
at room temperature resulted in the loss of four mole-
cules of hydrogen bromide, and gave the diacetylene 2
as pale yellow crystals in 68% yield [9]. Diacetylene 2
was subjected to Diels±Alder cycloaddition with
der Waals contact and aromatic p±p stacking. It
can be expected that p±p stacking through overlap-
ping of pyridine ring with the dimethoxy-substituted
benzene ring may play an important role in inclusion
behavior. In fact, in the unit cell, the deviations of the
six atoms of guest molecule from the nearest mean
plane of dimethoxy-substituted benzene ring are 3.40,
4
,7-dimethoxyisobenzofuran, produced in situ
from 4,7-dimethoxy-1-hydroxyphthalan [10] in
acid condition, to afford endoxide 3 in 85%
yield. Deoxydenation of endoxide 3 with low-
valent titanium gave 1,4,11,14-tetramethoxy-diben-
zo[b,n]tetraphenylene 4 as colorless crystals in
Ê
3.63, 3.91, 4.36, 4.76 and 4.96 A, respectively. The
intermolecular interaction is re¯ected by the fact
that in the central eight-membered ring, the
torsion angle of 270.3(6)8 about the C(1)±C(32)
bond is signi®cantly larger than those [67.4(6),
66.0(6), and 267.9(6)8] about the other three
single bonds. The measured dimensions of the
8
9% yield [5] (Scheme 1).
:1 inclusion compound 5 was obtained as air-
1
stable, colorless ¯at prisms upon slow evaporation
of a solution of 4 in pyridine. Its 1:1 stoichiometry
and structure were established by means of elemental
analysis and X-ray crystallography. Crystal data and
experimental conditions are shown in Table 1. The
fractional atomic coordinates and equivalent isotropic
temperature factors for the crystal structure of inclu-
sion compound 5, along with their estimated standard
deviations, are presented in Table 2.
Fig. 1 depicts the molecular structure of host
compound 4, and the molecular packing of 1:1 inclu-
sion compound 5 in unit cell is given in Fig. 2. X-ray
analysis has shown that the 1,4,11,14-tetramethoxy-
dibenzo[b,n]tetraphenylene host molecule 4 has
normal molecular dimensions and the central cyclooc-
tatetraene ring is boat-shaped with C±C and CyC
bonds alternating around it. Two substituted naphthy-
lene rings and two benzene rings are disposed above
and below the mean plane of the molecule, the
resulting molecular con®guration of 4 enables it to
function as an ef®cient host for inclusion of guest
molecules.
Ê
central ring are C±C 1.494(4), CyC 1.408(6) A,
C±C±C 121.58.
Interestingly, the parent nonfunctionalized diben-
zo[b,n]tetraphenylene which has the same C2D
symmetry with compound 4, has shown no inclusion
ability [3]. X-ray analysis has shown that this inclu-
sion compound differs from the clathrate of tetraphe-
nylene with regard to stoichiometry, mode of
accommodation [1,2]. Host molecule 4 exhibits
selective inclusion behavior, it does not form any
crystalline adduct with benzene, tetrahydrofuran, 1,4-
dioxane, cyclohexane and 2-methylpyridine, and it
selectively includes pyridine forming a 1:1 crystalline
complex.
Acknowledgements
We gratefully thank Professor Henry N.C. Wong
and Professor Thomas C.W. Mak (The Chinese
University of Hong Kong) for their valuable guidance
and discussion of this project. This project was
partially supported by the National Natural Science
Foundation of China (Grant No. 29872023), Ministry
of Education of China (research funds for Chinese
scholars returning from abroad) and China Post-
doctoral Science Foundation.
As shown in Fig. 2, the host molecules are
connected by intermolecular face-to-face p±p inter-
action between pairs of centrosymmetrically-related
substituted naphthylene rings (the interplanar spacing
Ê
Ê
is 3.48 A and centroid-to-centroid distance is 3.55 A)
to form a zigzag chain running parallel to the b axis.
Owing to the uncertainty and disorder of the position
of nitrogen atom in guest molecule pyridine, carbon
atom was used instead of nitrogen atom in X-ray
crystal structure solution and re®nement procedure.
Two centrosymmetrically-related six-membered ring
guest molecules (pyridine) are enclosed in the cavity
surrounded by eight host molecules, and the main
intermolecular interaction can be ascribed to Van
References
[
[
1] T.C.W. Mak, H.N.C. Wong, Top. Curr. Chem. 140 (1987)
41±164.
1
2] N.Z. Huang, T.C.W. Mak, J. Chem. Soc. Chem. Commun.
(1982) 543±544.
Du, Da-Ming
