1,3 Di­bromo­azulene

organic papers

Acta Cryst.(2005). E61, o941–o943 doi:10.1107/S1600536805006811 Chenet al. _C

10H6Br2

o941

Structure Reports Online

ISSN 1600-5368

1,3-Dibromoazulene

Xue-Yi Chen,aJerry R. Dias,a Doug R. Powell,bJ. David Van Horna* and Thomas C.

Sandreczkia

a_{Department of Chemistry, University of}

Missouri–Kansas City, 5110 Rockhill Road, Kansas City, MO 64110, USA, andb_Department

of Chemistry, University of Kansas, Mallott Hall, Room 6044, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582, USA

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study

T= 100 K

Mean(C–C) = 0.002 A˚

Rfactor = 0.016

wRfactor = 0.046

Data-to-parameter ratio = 16.1

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2005 International Union of Crystallography Printed in Great Britain – all rights reserved

In the structure of 1,3-dibromoazulene, C10H6Br2, the planar

molecule sits on a crystallographic mirror plane. The Br atoms are attached to the five-membered ring adjacent to the ring fusion. Head-to-tail charge–charge interactions due to partial positive charges on ring H atoms and partial negative charges within the aromatic ring system attract adjacent 1,3-dibromo-azulene molecules together. This causes them to arrange themselves in a zigzag pattern that allows close packing of the oppositely charged groups.

Comment

Polyazulene and its derivatives are of scientific and practical interest, because they are highly conjugated hydrocarbons that can be made electrically conductive and highly para-magnetic (Wanget al., 2003; Wang, Lai & Han, 2004; Wang, Xu

et al., 2004). One important physical property of a polyazulene that can be tailored is its solubility, which requires appropriate derivatization of the azulene monomer unit. Halogenated azulenes are known to be useful as monomeric building blocks for polyazulene and its derivatives (Wang & Lai, 2003). They are also precursors for the synthesis of dumbbell-shaped alkyl-bridged diazulenyl compounds (Elwahy, 2002). The crystal structures of aromatic halogenated azulenes, however, have not been described in the literature to date. This report of the crystal structure of 1,3-dibromoazulene, (I), and a related report on 1,3-diiodoazulene (Chenet al., 2005), are a portion of our continuing work involving the preparation and analysis of electrically conductive azulene-containing polymers.

Pertinent to this report is the crystal structure of the parent azulene (Robertson et al., 1962), which crystallizes in the monoclinic space group P21/a. Other related structures, also

having monoclinic space groups, include two variously substituted azulenes (Lohr et al., 1984; Wong et al., 1984) which both crystallize in the space groupP21/c, and a fused

bis-azulene (Vogelet al., 1984) found in the space groupP21/n.

This is in contrast with the orthorhombic structure of the dibromoazulene presented here. The related diiodoazulene is

also monoclinic, but is found in the space groupCc(Chenet al., 2005).

A calculation comparing the parent azulene with dibromoazulene [HF/6–31 G(d,p) level, full natural bond orbital analysis; Frischet al., 2003)] indicates that the presence of the Br atoms substantially polarizes the ring current toward the five-membered ring, with significant charge on the C atoms attached to the Br atoms. The calculation also helps to explain the head-to-ring and bromine-to-ring interactions observed in the crystal structure as being of a dipolar (or charge–charge) nature. Finally, the Br atoms have very little calculated charge, which may account for the short intermolecular Br Br distance observed in the solid state.

In the crystal structure of (I), individual molecules lie on a crystallographic mirror plane that passes through atoms C1 and C6, bisecting the fused five- and seven-membered rings. The rings are planar, but stack in an offset herring-bone pattern that apparently maximizes the dipolar interactions between molecules in the same stack. The distance between atom C6 of one molecule and atoms C3 and C30_{of the ring}

fusion bond of a neighboring molecule in the same stack is about 2.76 A˚ (Fig. 2), indicating a strong interaction between the positively charged seven-membered ring and the nega-tively charged five-membered ring. The only significant close contacts between adjacent stacks are intermolecular Br Br interactions [3.549 (2) A˚ ].

Experimental

Compound (I) was obtained by reacting 1.0 equivalent of azulene with 2.1 equivalents ofN-bromosuccinimide in dichloromethane at room temperature overnight (Elwahy, 2002). The solvent was then removed under vacuum below 273 K. Purification was accomplished by column chromatography, using neutral alumina as substrate and hexanes as eluent. Dark-blue blocks were obtained by slow evaporation of the solvent.

Crystal data

C10H6Br2

Mr= 285.97

Orthorhombic,Pnma a= 8.3575 (14) A˚

b= 15.114 (2) A˚

c= 7.1840 (12) A˚

V= 907.4 (2) A˚3

Z= 4

Dx= 2.093 Mg m

3

MoKradiation Cell parameters from 4195

reflections = 2.7–26.0

= 8.87 mm1

T= 100 (2) K Block, blue

0.280.200.20 mm

Data collection

Bruker APEX diffractometer !scans

Absorption correction: multi-scan (SADABS; Bruker, 2002)

Tmin= 0.120,Tmax= 0.170

7311 measured reflections 931 independent reflections

870 reflections withI> 2(I)

Rint= 0.024

max= 26.0

h=10!10

k=18!18

l=8!8

Refinement

Refinement onF2 R[F2_{> 2(F}2_{)] = 0.016}

wR(F2) = 0.046

S= 0.96 931 reflections 58 parameters

H-atom parameters constrained

w= 1/[2

(Fo2) + (0.03P)2

+ 0.6P]

whereP= (Fo2+ 2Fc2)/3

(/)max= 0.001 max= 0.48 e A˚

3 min=0.36 e A˚ 3

Table 1

Selected geometric parameters (A˚ ,_).

Br1—C2 1.879 (2)

C1—C2 1.399 (2)

C2—C3 1.396 (2)

C3—C4 1.386 (2)

C3—C3i 1.499 (2)

C4—C5 1.392 (2)

C5—C6 1.395 (2)

C2i

—C1—C2 107.0 (2)

C3—C2—C1 110.9 (2)

C4—C3—C3i

127.6 (1)

Br1—C2—C3—C3i 179.4 (1)

Symmetry codes: (i)x;yþ3 2;z.

organic papers

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10H6Br2 Acta Cryst.(2005). E61, o941–o943

Figure 2

A view of the packing of (I), showing the zigzag stack of the dibromo-substituted azulene molecules. Charge–charge interactions of parallel [3.24 (1) A˚ ] and herringbone [3.36 (1) A˚] geometry are indicated by dashed lines.

Figure 1

A perspective view of (I) with the atom-numbering scheme [symmetry code: (i)x,y+ 3

All H atoms were included in calculated positions using a riding model, with C—H = 0.95 A˚ and withUiso(H) = 1.2Ueq(C).

Data collection:SMART(Bruker, 1998); cell refinement:SAINT

(Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 1998); program(s) used to refine structure:SHELXTL; molecular graphics:ORTEP3(Farrugia, 1997); software used to prepare material for publication:SHELXTL.

The authors thank the National Science Foundation (grant No. CHE-0079282) and the University of Kansas for funds to acquire the diffractometer and computers used in this work.

References

Bruker (1998). SMART (Version 5.625), SAINT (Version 6.22) and

SHELXTL(Version 6.12). Bruker AXS, Inc., Madison, Wisconsin, USA. Bruker (2002). SADABS (Version 2.04). Bruker AXS, Inc., Madison,

Wisconsin, USA.

Chen, X.-Y., Dias, J. R., Powell, D. R., Van Horn, J. D. & Sandreczki, T. C. (2005).Acta Cryst.E61, o944–o946.

Elwahy, A. H. M. (2002).Tetrahedron Lett.43, 711–714.

Frisch, M. J., Trucks, G. W., Schlegel, H. B., Scuseria, G. E., Robb, M. A., Cheeseman, J. R., Montgomery, J. A., Vreven, T. Jr, Kudin, K. N., Burant, J. C., Millam, J. M., Iyengar, S. S., Tomasi, J., Barone, V., Mennucci, B.et al.

(2003).GAUSSIAN03. Revision B04. Gaussian Inc., Pittsburgh, Pennsyl-vania, USA.

Farrugia, L. J. (1997).J. Appl. Cryst.30, 565.

Lohr, H.-G., Engel, A., Josel, H.-P., Vogtle, F., Schuh, W. & Puff, H. (1984).J. Org. Chem.49, 1621–1627.

Robertson, J. M., Shearer, H. M. M., Sim, G. A. & Watson, D. G. (1962).Acta Cryst.15, 1–8.

Vogel, E., Wieland, H., Schmalstieg, L. & Lex, J. (1984).Angew. Chem. Int. Ed. Engl.23, 717–719.

Wang, F. & Lai, Y.-H. (2003).Macromolecules,36, 536–538.

Wang, F., Lai, Y.-H. & Han, M.-Y. (2004).Macromolecules,37, 3222–3230. Wang, F., Lai, Y.-H., Kocherginsky, N. M. & Kosteski, Y. Y. (2003).Org. Lett.5,

995–998.

Wang, W., Xu, J., Lai, Y.-H. & Wang, F. (2004).Macromolecules,37, 3546– 3553.

Wong, H. N. C., So, K. P. & Mak, T. C. W. (1984).Z. Kristallogr.169, 117–125.

organic papers

Acta Cryst.(2005). E61, o941–o943 Chenet al. _C

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Acta Cryst. (2005). E61, o941–o943

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Acta Cryst. (2005). E61, o941–o943 [https://doi.org/10.1107/S1600536805006811]

1,3-Dibromoazulene

Xue-Yi Chen, Jerry R. Dias, Doug R. Powell, J. David Van Horn and Thomas C. Sandreczki

1,3-Dibromoazulene

Crystal data C10H6Br2 Mr = 285.97

Orthorhombic, Pnma Hall symbol: -P 2ac 2n a = 8.3575 (14) Å b = 15.114 (2) Å c = 7.1840 (12) Å V = 907.4 (2) Å3 Z = 4

F(000) = 544

Dx = 2.093 Mg m−3

Melting point: 76.5 K

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 4195 reflections θ = 2.7–26.0°

µ = 8.87 mm−1 T = 100 K Block, blue

0.28 × 0.20 × 0.20 mm

Data collection Bruker APEX

diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

ω scans

Absorption correction: multi-scan (SADABS; Bruker, 2002) Tmin = 0.120, Tmax = 0.170

7311 measured reflections 931 independent reflections 870 reflections with I > 2σ(I) Rint = 0.024

θmax = 26.0°, θmin = 2.7° h = −10→10

k = −18→18 l = −8→8

Refinement Refinement on F2

Least-squares matrix: full R[F2 _{> 2σ(F}2_{)] = 0.016} wR(F2_{) = 0.046} S = 0.96 931 reflections 58 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

Hydrogen site location: inferred from neighbouring sites

H-atom parameters constrained w = 1/[σ2_(F

o2) + (0.03P)2 + 0.6P]

where P = (Fo2 + 2Fc2)/3

(Δ/σ)max = 0.001

Δρmax = 0.48 e Å−3

Δρmin = −0.36 e Å−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full

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Acta Cryst. (2005). E61, o941–o943

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_,

conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) is used}

only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2

are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2₎

x y z Uiso*/Ueq

Br1 0.46263 (2) 0.558729 (11) 0.79056 (2) 0.02160 (10) C1 0.4714 (3) 0.7500 0.8153 (3) 0.0160 (5) H1 0.5204 0.7500 0.9347 0.019* C2 0.4286 (2) 0.67563 (12) 0.7108 (2) 0.0157 (4) C3 0.36081 (18) 0.70040 (10) 0.5410 (2) 0.0147 (3) C4 0.30704 (19) 0.64441 (11) 0.4015 (2) 0.0169 (3) H4 0.3153 0.5829 0.4272 0.020* C5 0.2426 (2) 0.66626 (12) 0.2288 (2) 0.0202 (4) H5 0.2130 0.6177 0.1522 0.024* C6 0.2156 (3) 0.7500 0.1533 (3) 0.0199 (5) H6 0.1719 0.7500 0.0312 0.024*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Br1 0.02695 (14) 0.01187 (13) 0.02598 (15) 0.00155 (6) −0.00326 (7) 0.00492 (6) C1 0.0167 (12) 0.0139 (13) 0.0175 (11) 0.000 0.0004 (9) 0.000 C2 0.0171 (8) 0.0100 (8) 0.0200 (9) 0.0008 (7) 0.0018 (6) 0.0017 (6) C3 0.0133 (7) 0.0109 (9) 0.0198 (8) 0.0012 (6) 0.0023 (6) 0.0008 (6) C4 0.0162 (8) 0.0137 (8) 0.0208 (8) −0.0001 (6) 0.0022 (7) −0.0005 (6) C5 0.0181 (8) 0.0201 (10) 0.0223 (8) −0.0016 (8) −0.0012 (7) −0.0066 (7) C6 0.0159 (11) 0.0292 (14) 0.0145 (11) 0.000 −0.0005 (10) 0.000

Geometric parameters (Å, º)

Br1—C2 1.879 (2) C4—C5 1.392 (2) C1—C2 1.399 (2) C4—H4 0.9500 C1—H1 0.9500 C5—C6 1.395 (2) C2—C3 1.396 (2) C5—H5 0.9500 C3—C4 1.386 (2) C6—H6 0.9500 C3—C3i _{1.499 (2)}

C2i_{—C1—C2 107.0 (2) C3—C4—C5 128.65 (16)}

C2i_{—C1—H1 126.5 C3—C4—H4 115.7}

C2—C1—H1 126.5 C5—C4—H4 115.7 C3—C2—C1 110.9 (2) C4—C5—C6 128.62 (18) C3—C2—Br1 125.45 (13) C4—C5—H5 115.7 C1—C2—Br1 123.59 (13) C6—C5—H5 115.7 C4—C3—C2 126.81 (15) C5i_{—C6—C5 130.2 (2)}

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C2—C3—C3i _{105.56 (10) C5—C6—H6 114.9}

C2i_{—C1—C2—C3 0.6 (3) Br1—C2—C3—C3}i _{−179.4 (1)}

C2i_{—C1—C2—Br1 179.63 (7) C2—C3—C4—C5 −178.26 (18)}

C1—C2—C3—C4 178.89 (17) C3i_{—C3—C4—C5 0.9 (2)}

Br1—C2—C3—C4 −0.1 (2) C3—C4—C5—C6 −0.2 (3) C1—C2—C3—C3i _{−0.39 (16) C4—C5—C6—C5}i _{−1.1 (5)}