Synthesis and X-ray crystal structure of the asymmetric dithiadiazene BrC6F4NSNSC6H4NO2

Article abstract of DOI:10.1080/10426500490427754

The asymmetric dithiadiazene BrC₆F₄NSNSC ₆H₄NO₂ crystallizes in the space group P-1 and exhibits a 1D polar chain structure linked via structure-directing Br...O₂N synthons.

Full text of DOI:10.1080/10426500490427754

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Phosphorus, Sulfur, and Silicon and the Related
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SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF THE
ASYMMETRIC DITHIADIAZENE BrC6F4NSNSC6H4NO2
Joanna Griffiths a & Jeremy M. Rawson a
a University of Cambridge , Cambridge, United Kingdom
Published online: 12 Aug 2010.
To cite this article: Joanna Griffiths & Jeremy M. Rawson (2004) SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF THE
ASYMMETRIC DITHIADIAZENE BrC6F4NSNSC6H4NO2 , Phosphorus, Sulfur, and Silicon and the Related Elements, 179:4-5, 883-886,
DOI: 10.1080/10426500490427754
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Phosphorus, Sulfur, and Silicon, 179:883–886, 2004
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ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490427754
SYNTHESIS AND X-RAY CRYSTAL STRUCTURE
OF THE ASYMMETRIC DITHIADIAZENE
BrC6F4NSNSC6H4NO2
Joanna Griffiths and Jeremy M. Rawson
University of Cambridge, Cambridge, United Kingdom
(Received August 17, 2003; accepted October 3, 2003)
The asymmetric dithiadiazene BrC6F4NSNSC6H4NO2 crystallizes in
the space group P-1 and exhibits a 1D polar chain structure linked via
. . .
structure-directing Br O2N synthons.
Keywords: Crystal engineering; dithiadiazene; fluorination; supra-
molecular synthons
The design of polar and noncentrosymmetric crystal structures for
nonlinear optical (NLO) applications relies on rational crystal en-
gineering strategies to produce materials with desirable properties.
Two key features are necessary for SHG (second harmonic genera-
tion); firstly a strong molecular hyperpolarisability which is usually
afforded by a polar molecule with donor and acceptor groups linked via a
π-conjugated spacer group,1 secondly, these molecules must crystallise
in noncentrosymmetric space groups.2 Our design strategy has focussed
on the use of perfluorinated donor (D)—acceptor (A) substituted aro-
matics, specifically compounds of general formula DC6F4A. Results
on these single ring systems3 have shown that the formation of polar
chains can be encouraged by the selection of donor and acceptor groups
which are well-recognized as forming linear motifs in the solid-state
(supramolecular synthons). Perfluorination tends to minimize interac-
tions between these polar chains and so favor the formation of polar
acentric structures.4 As an extension of this work, we have begun an
examination of thiazyl chains as π-delocalized spacer groups between
donor-acceptor substituted perfluorinated aromatic rings. The extended
delocalization is expected to enhance the molecular NLO response.
We are grateful to the EPSRC for funding (J. G.) and J. E. Davies for data collection.
Address correspondence to J. M. Rawson, Department of Chemistry, University of
Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. E-mail: jmr31@cus.cam.ac.uk
883

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J. Griffiths and J. M. Rawson
RESULTS AND DISCUSSION
Synthetic routes to asymmetric dithiadiazenes are not well docu-
mented. Syntheses involving chain-scrambling of symmetrically sub-
stituted thiazyl chains have been used with some success,5 although
these reactions have a tendency to be uncontrollable and give a mixture
of products. Conversely, a single report indicated that condensation re-
actions between sulfenyl chlorides (RSCl) and trimethylsilyl protected
sulfur diimides can be used to produce asymmetric dithiadiazenes.5 The
methodology detailed in Scheme 1 represents a clean stepwise synthe-
sis of the target compound, BrC6F4NSNSC6H4NO2 (1) in reasonable
yield, and has been applied to prepare several other similar compounds
in this laboratory.
F
F
F
F
F
F
SOCl2
LiN(SiMe3)2
Br
NSNSiMe3
Br
NSO
Br
NH2
toluene
THF, -40°C
F
F
F
F
F
F
ClS
NO2
THF, -40°C
F
F
NO2
Br
NSNS
F
F
SCHEME 1 Synthesis of 1.
Red needle-like crystals of 1 suitable for x-ray diffraction studies
were grown from a concentrated THF solution at 4◦C. The asymmetric
unit contains a single molecule, which is essentially planar. Within the
. . .
structure, molecules are linked into polar chains by Br O2N synthons
˚
. . .O
(dBr
= 3.118 A, compared to the sum of the van der Waals radii
˚
3.08–3.38 A). Hydrogen bonding between a nitro group in one chain
◦
˚
H. . .O
and aromatic protons in an adjacent chain (dC
results in the antiparallel chain alignment seen in Figure 1.
. . .
= 2.509 A, 146.8 )
Successive layers also align antiparallel, with short S N contacts
˚
. . .N
between layers (dS
Waals radii 3.20–3.63 A) being reinforced by πF πH stacking.
= 3.411 A, compared to the sum of the van der
˚
. . .

The Asymmetric Dithiadiazene p-BrC F NSNSC H NO
2
885
6
4
6
4
FIGURE 1 Single layer illustrating antiparallel chains in 1.
CONCLUSIONS
Whilst the formation of one-dimensional polar chains is encouraged
. . .
through the use of the structure-directing Br O2N synthon, interac-
tions between polar chains generate a centric structure which is there-
fore NLO inactive. Key intermolecular interactions promoting the cen-
. . .
. . .
tric structure are πF πH and C H O interactions. Current attempts
to synthesize perfluorinated derivatives in which these features are
absent are underway.
EXPERIMENTAL
Crystal data for 1: C12H4BrF4N3O2S2, M = 442.21, triclinic, space
group P-1, a = 7.5372(15), b = 7.9664(16), c = 13.805(3) α = 103.79(3),
3
˚
β = 90.42(3), γ = 114.63(3), U = 726.4(3) A , T = 180(2)K, Z = 2,
D = 2.022 Mg/m3. Of 8474 reflections measured, 3315 were unique
(R(int) = 0.0435) and were used in all calculations. The final wR2 =
0.0794 (all data), R1 [F2 > 2σ(F2)] = 0.0326. CCDC ******
Preparation of BrC6F4NSNSC6H4NO2
SOCl2 (1.8 ml, 2.716 g, 22.8 mmol) in toluene (20 ml) was added drop-
wise to a rapidly stirred solution of p-BrC6F4NH2 (5.56 g, 22.8 mmol)
in toluene (20 ml) to yield a yellow precipitate. The suspension was
heated to reflux for 5 h then solvents were removed in vacuo to yield
p-BrC6F4NSO as a yellow crystalline solid which was used without fur-
ther purification. A solution of p-BrC6F4NSO (2.90 g, 10 mmol) in THF
(20 ml) was added dropwise to a stirred solution of LiN(SiMe3)2 (1.67 g,
10 mmol) in THF (20 ml) at −40◦C to form a deep red solution. After
stirring for 1 h, the reaction mixture was allowed to warm to 0◦C and

886
J. Griffiths and J. M. Rawson
stirred for a further 1 h. After cooling again to −40◦C, a solution of
p-O2NC6H4SCl (1.85 g, 10 mmol) in THF (20 ml) was added dropwise
to the stirred reaction mixture to give a red/brown precipitate. After
warming to room temperature and stirring for a further 16 h, the reac-
tion mixture was filtered to remove insoluble impurities. The solvents
were removed from the filtrate in vacuo to give the 1 as a red/brown
solid (1.24 g, 27.9%). Anal. Calc. for C12H4F4O2BrN: C 32.6, H 0.9, N 9.5.
Found: C 32.4, H 0.9, N 9.5. EI-MS: 442.9, 440.9 (M+). UV-vis (CHCl3):
457.9 nm, ε = 7.4 × 104 mol dm−3 cm−1
.
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J. Phys. Chem., 95, 10631 (1991).
[2] Ch. Bosshard, K. Sutter, Ph. Preˆtre, et al., Organic Nonlinear Optical Materials
(Gordon and Breach, Basel, 1995).
[3] A. D. Bond, J. Griffiths, J. M. Rawson, and J. Hulliger, J. Chem. Soc., Chem. Commun.,
2488 (2001).
[4] J. Hulliger, P. J. Langley, and S. W. Roth, Cryst. Eng., 1, 177 (1998).
[5] K. Bestari, R. T. Oakley, and A. W. Cordes, Can. J. Chem., 69, 94 (1991).