Effect of adding bromine sensors to the central linker of new diquinoline derivative

Article abstract of DOI:10.1080/15421400802406489

Designing a selective lattice inclusion host had been challenging and fulfilling. Using 3 as a building block, we introduced bromine sensors to the central linker and investigate its effect on inclusion properties. An unexpected result was obtained when a pure sample of the diquinoline derivative 4 was crystallised from tetrahydrofuran. Unlike host 3, the diquinoline 4 did not include any guest molecules.

Full text of DOI:10.1080/15421400802406489

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Effect of Adding Bromine
Sensors to the Central Linker
of New Diquinoline Derivative
Solhe F. Alshahateet a
a Department of Chemistry , Mutah University ,
Mutah , Al-Karak , Jordan
Published online: 31 Aug 2012.
To cite this article: Solhe F. Alshahateet (2008) Effect of Adding Bromine Sensors
to the Central Linker of New Diquinoline Derivative, Molecular Crystals and Liquid
Crystals, 493:1, 95-102, DOI: 10.1080/15421400802406489
To link to this article: http://dx.doi.org/10.1080/15421400802406489
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Mol. Cryst. Liq. Cryst., Vol. 493, pp. 95–102, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400802406489
Effect of Adding Bromine Sensors to the Central Linker
of New Diquinoline Derivative
Solhe F. Alshahateet
Department of Chemistry, Mutah University, Mutah, Al-Karak, Jordan
Designing a selective lattice inclusion host had been challenging and fulfilling.
Using 3 as a building block, we introduced bromine sensors to the central linker
and investigate its effect on inclusion properties. An unexpected result was
obtained when a pure sample of the diquinoline derivative 4 was crystallised
from tetrahydrofuran. Unlike host 3, the diquinoline 4 did not include any guest
molecules.
Keywords: bromine sensors; inclusion compounds; supramolecular synthon; X-ray
crystal structure
INTRODUCTION
Recently, we have been investigating the design and properties of new
lattice inclusion hosts based on racemic V-shaped diheteroaromatic
structures that are unable to employ strong hydrogen bonding interac-
tions during crystal formation using the general crystal engineering
design illustrated in Fig. 1 [1–4]. The target molecules are constructed
from three distinct structural components; two planar aromatic wings,
a flexible central linker group able to provide molecular C2 symmetry,
and two exo-oriented sensor groups. The synthetic methodology used
to prepare such compounds, comprises a simple modular process
whereby the two aromatic wings are condensed onto the central cyclic
linker group, and then the synthesis is completed by substitution of
the benzylic sensor groups.
This new family of host molecules does not contain functional
groups (such as OH, NH2, or CO2H) that are capable of strong
Address correspondence to Solhe F. Alshahateet, Department of Chemistry, Mutah
University, P.O. Box 7, Mutah, Al-Karak 61710, Jordan. E-mail: s_alshahateet@mutah.
edu.jo
95

96
S. F. Alshahateet
FIGURE 1 General schematic design for new lattice inclusion hosts, involv-
ing three structural sub-units: aromatic wings, central linker group, and
exo-sensor groups.
hydrogen bonding. Instead, weak host-host and host-guest noncova-
lent bonds (such as aryl face-face and edge-face, halogen-halogen,
halogen-nitrogen, and edge-edge C-H N dimer interactions) can
occur. Competition between these weak interactions results in the
best overall net energy that affords the observed lattice inclusion
structure. Hence these new host molecules, and their various
inclusion compounds, provide an excellent means of probing the
interdependence of many of the weaker supramolecular synthons
[5–7].
In this work, we started with 3 as the basic building block. It was a
host for polar guest molecules [8]. By adding bromine sensors to the
central linker, we had been successful in synthesizing compound 4.
Substitution on the central linker in this case provided efficient
packing of the diquinoline molecules without the need of presence
any guest molecules resulting in the formation of non-host 4.
RESULTS AND DISCUSSION
Synthesis of Dinitrodiphenyldiquinoline 3
¨
Compound 3 was synthesized according to Scheme 1 using Friedlander
condensation [9,10]. 2 equivalents of 2-amino-5-nitrobenzophenone 1
and 1 equivalent of racemic bicyclo[3.3.1]nonane-3,7-dione 2 [11] were
dissolved in ethanol with catalytic amount of NaOH and refluxed
overnight to produce a light brown powder of 3 [8].

Supramolecularity of New Diquinoline Derivative
97
SCHEME 1 Synthetic route for diquinolines 3 and 4.
Synthesis of Dibromodinitrodiphenyldiquinoline 4
Radical bromination at the benzylic positions of diquinoline 3 was achi-
eved using N-bromosuccinimide (NBS) in trifluoromethylbenzene to
give the racemic dibromodinitrodiquinoline 4 in 75% yield (Scheme 1).
The highly regio- and stereo-selective outcomes of such NBS substitution
reactions have been discussed in recent publications [12,13].
Crystallization of Compound 4
A solvent free sample of diquinoline 4 was obtained after crystalliza-
tion from tetrahydrofuran. Crystallization from a variety of other
solvents also gave no evidence of guest inclusion by 4 (confirmed by
1H NMR and FTIR). The crystal data for inclusion compounds and
structure refinements were shown in Table 1.

98
S. F. Alshahateet
TABLE 1 Crystal Data and Structure Refinements
Empirical formula
Formula weight
Temperature
C35H22Br2N4O4
722.39
223(2) K
˚
Wavelength
0.71073 A
Crystal system
Space group
Unit cell dimensions
Monoclinic
C2=c
a ¼ 90ꢀ.
˚
a ¼ 17.2093(13) A
b ¼ 116.942(2)ꢀ.
c ¼ 90ꢀ.
˚
b ¼ 10.7231(8) A
˚
c ¼ 18.1962(13) A
3
˚
Volume
2993.4(4) A
Z
4
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
1.603 Mg=m3
2.756 mmꢁ1
1448
0.60 ꢂ 0.08 ꢂ 0.03 mm3
2.32 to 27.50ꢀ
ꢁ22 ꢃ n ꢃ 10, ꢁ13 ꢃ k ꢃ 13,
ꢁ23 ꢃ ꢃ 23
Reflections collected
10368
Independent reflections
Completeness to theta ¼ 27.50ꢀ
Absorption correction
Max. and min. transmission
Refinement method
3440 [R(int) ¼ 0.0410]
100.0%
Sadabs, (Sheldrick 2001)
0.9219 and 0.2886
Full-matrix least-squares on F2
3440=0=204
Data=restraints=parameters
Goodness-of-fit on F2
1.057
Final R indices [I > 2sigma(I)]
R indices (all data)
Largest diff. peak and hole
R1 ¼ 0.0559, wR2 ¼ 0.1429
R1 ¼ 0.0830, wR2 ¼ 0.1563
ꢁ3
˚
1.609 and ꢁ0.340 e.A
Crystal Structure of 4
Crystallization of 4 from tetrahydrofuran yielded crystals of the
solvent free compound in the monoclinic space group C2=c with
z ¼ 4. The asymmetric unit contains one half of the molecule
C35H22Br2N4O4. The whole molecule is generated by the 2-fold
rotation. Analysis of the crystal structure of solid 4 indicated aryl-
nitrogen interactions with C-H N and C-H N distances of 3.00 and
˚
3.83 A, respectively. Figure 2 illustrates two molecules of 4 interacting
together.
Further analysis of the crystal structure of 4 revealed the absence of
the ubiquitous edge-edge aryl C-H N dimer interaction frequently
observed in crystal structures of our previous diquinoline derivatives
[14]. This interaction was replaced with the previously unobserved
Centrosymmetric double Br H-C-Ar hydrogen interaction between

Supramolecularity of New Diquinoline Derivative
99
FIGURE 2 Part of the crystal structure of 4 showing two molecules of 4
interacting together. Color code: C ¼ gray, N ¼ blue, H ¼ white, O ¼ red, and
Br ¼ dark red.
opposite enantiomers of 4. This gave a dimer between two host
molecules of opposite chirality with C-H Br distances of 3.22 and
˚
3.05 A in each motif (Fig. 3).
In addition, bromine atoms were found to interact with the oxygen
˚
atoms of the nitro group with Br O distance of 3.45 A which should pro-
vide extra packing stability between the diquinoline molecules (Fig. 4).
FIGURE 3 Centrosymmetric double Br H-C-Ar hydrogen interaction between
˚
opposite enantiomers of 4 with C-H---Br distances of 3.22 and 3.05 A in each
motif. Color code: C ¼ gray, N ¼ blue, H ¼ white, O ¼ red, and Br ¼ dark red.

100
S. F. Alshahateet
FIGURE 4 Two molecules of 4 with same chirality interact via Br O with a
˚
distance of 3.45 A.
CONCLUSIONS
In this article we synthesised compound 4 in which we expected that it
would behave in a similar manner to 3 perhaps even giving isostruc-
tural outcomes, but this proved not to be the case. In moving from com-
pound 3 to 4 the only molecular change is replacement of a benzylic
hydrogen atom by a bromine atom. This minor alteration results in
considerable supramolecular change and molecules of 4 pack quite
differently. Indeed compound 4 no longer includes the guests trapped
by 3. On a supramolecular level the bromine atom offers new possibi-
lities for intermolecular attractions and as a result, this potential host
molecule is able to adopt new efficient lattice packing without guest
inclusion.
EXPERIMENTAL
Melting points were determined using a Bu¨chi melting point B-540
apparatus. NMR spectra were recorded using a Bruker 400 MHz stan-
dard bore instrument with Quad Nuclear Probe (QNP) and carbon
substitution information was determined using the Distortionless
Enhancement of Polarization Transfer (DEPT) procedure. Mass spec-
trometry data were recorded using a Finnigan TSQ 7000 machine.
Elemental analyses for C, H, N, O, and Br were determined using a
Perkin-Elmer PE 2400 or platinum sample pans.
7a,15a-Dibromo-2,10-dinitro-8,16-diphenyl-6,7,14,15-
tetrahydro-7,15-methanocycloocta[1,2-b:5,6-b0]diquinoline (4)
A solution of NBS (0.45 g, 2.54 mmol) and 3 (0.58 g, 1.02 mmol) in
trifluoromethylbenzene (40 mL) was refluxed overnight and then the

Supramolecularity of New Diquinoline Derivative
101
resulting mixture was allowed to cool. Succinimide was filtered off,
washed with additional trifluoromethylbenzene (20 mL), and then
the combined filtrate was evaporated under reduced pressure to give
a lightyellow solid. Crystallization from THF gave colourless crystals
of 4 (0.56 g, 75%), mp 168 170ꢀC. Elemental analysis: experimental
(calculated), %C: 58.19(58.14), %H: 3.07 (3.03), %N: 7.76 (7.70),
1
%Br: 22.12 (22.20), %O: 8.86 (8.90). H NMR (DMSO) d 2.95 (s, 2H),
4.04 (d, 2H), 5.28 (d, 2H), 7.415–7.474 (m, 4H), 7.714–7.829 (m, 6H),
8.089–8.113 (m, 2H), 8.302–8.307 (m, 2H), 8.377–8.383 (m, 2H); 13C
NMR (CD3SOCD3) d 19.78 (CH2), 38.01(CH), 52.76 (CH), 123.25
(CH), 123.43 (CH), 126.97 (C), 128.45 (CH), 128.59 (C), 129.25 (CH),
129.75 (CH), 129.85 (CH), 129.90 (CH), 130.99 (CH), 133.47 (C),
146.05 (C), 149.44 (C), 152.08 (C), 157.43 (C); MS (ESI, m=z þ>10%):
630.2 (10), 710.1 (31), 712.1 (75), 723.1 (100), 725.0 (45), 726.1 (20).
Solution and Refinement of the Crystal Structure
Single-crystal X-ray diffraction experiments were carried out on a
Bruker SMART Apex 1000 diffractometer equipped with a CCD detec-
tor and Mo-Ka sealed tube at 223(2) K. SMART [14] was used for col-
lecting frame data, indexing reflection, and determination of lattice
parameters. SAINT [15] was used for integration of intensity of reflec-
tions and scaling. SADABS [16] was used for absorption correction and
SHELXTL [17] for space group, structure determination, and least-
square refinements on F2. All hydrogen atoms were placed in calcu-
lated positions for the purpose of structure factor calculation. All
nonhydrogen atoms were refined anisotropically [17], and all hydro-
gen atoms were included in calculated positions with isotropic thermal
motion linked to that of the bonded atom.
SUPPORTING INFORMATION AVALIABLE
Crystallographic data (cif) have been deposited with the Cambridge
Structural Data Centre (CCDC), CCDC reference number 684344.
Copies of the data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: þ44(0)-1223
336033 or E-mail: deposit@ccdc.cam.ac.uk).
ACKNOWLEDGMENTS
The author would like to thank Mutah University for the support
needed for this research, the Agency for Science, Technology, and
Research (AꢄSTAR, Singapore) for the financial support, Prof. Koh

102
S. F. Alshahateet
Lip Lin and Ms. Tan Geok Kheng from the National University of
Singapore for their technical support and assistance. Great thanks
are also due to Prof. Roger Bishop who was the first one to introduce
and design the modular for this study. Special thanks are due to
Dr. Zaher Juddeh (Nanyang Technological University, Singapore)
for technical support and assistance in running some of the experi-
ments reported in this article.
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