Do C-H...O and C-H...π interactions help to stabilize a non-centrosymmetric structure for racemic 2,3-dibromo-1,3-diphenyl-propan-1-one?

Article abstract of DOI:10.1107/S0108270105036942

The racemic title compound, C₁₅H₁₂Br₂O, crystallizes in a non-centrosymmetric structure and displays a significant non-linear optical response to red light. The crystal packing is influenced by C-H...O and C-H...π interactions. One of the former bonds has a short H...O separation of 2.27 A.

Full text of DOI:10.1107/S0108270105036942

organic compounds
Acta Crystallographica Section C
Crystal Structure
title compound, (I) (Fig. 1), which has a second harmonic
generation (SHG) ef®ciency 0.4 times that of urea.
Communications
The non-centrosymmetric space group of (I) is consistent
with the non-zero SHG signal observed. All the geometric
parameters for (I) lie within their expected ranges (Allen et al.,
ISSN 0108-2701
ꢀ
1
995). A dihedral angle of 22.58 (16) occurs between the
Do CÐHÁ Á ÁO and CÐHÁ Á Áp
interactions help to stabilize a
non-centrosymmetric structure for
racemic 2,3-dibromo-1,3-diphenyl-
propan-1-one?
mean planes of the two benzene rings. With respect to the
C7ÐC8 bond, the atom pairs Br1/Br2, C6/C9 and H7/H8 are
all trans (Table 1). Each molecule of (I) is chiral (the arbi-
trarily chosen asymmetric molecule has R and S con®gurations
for atoms C7 and C8, respectively), but space-group symmetry
generates a racemic 1:1 mix of enantiomers, as might be
expected in terms of the bromination reaction used to prepare
(
I), i.e. trans addition of the two Br atoms has occurred.
a
b
c
William T. A. Harrison, * H. S. Yathirajan, B. K. Sarojini,
However, (I) does not crystallize in a space group with
inversion symmetry and a substantial SHG response arises.
d
b
B. Narayana and H. G. Anilkumar
a
Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen
b
AB24 3UE, Scotland, Department of Studies in Chemistry, University of Mysore,
c
Manasagangotri, Mysore 570 006, India, Department of Chemistry, P. A. College
d
of Engineering, Nadupadavu, Mangalore 574 153, India, and Department of
Chemistry, Mangalore University, Mangalagangotri 574 199, India
Correspondence e-mail: w.harrison@abdn.ac.uk
The crystal packing of (I) appears to be in¯uenced by weak
interactions, including CÐHÁ Á ÁO and CÐHÁ Á Áꢀ bonds
Received 31 October 2005
Accepted 9 November 2005
Online 30 November 2005
(
Table 2). The three CÐHÁ Á ÁO interactions in (I) all link to
the same acceptor O atom. One of the resulting HÁ Á ÁO
Ê
separations is rather short, at 2.27 A. It may be assumed that
these three H atoms are all `activated' (made more acidic) in
terms of the identities of their adjacent atoms (Desiraju &
Steiner, 1999). These CÐHÁ Á ÁO links result in parallel chains
of molecules of (I) propagating in the c direction (Fig. 2).
Within a chain, adjacent molecules, related by the c-glide
operation, are enantiomers. For any adjacent pair of molecules
in a chain, the dihedral angle between their C1-benzene rings
The racemic title compound, C H Br O, crystallizes in a non-
1
5
12
2
centrosymmetric structure and displays a signi®cant non-
linear optical response to red light. The crystal packing is
in¯uenced by CÐHÁ Á ÁO and CÐHÁ Á Áꢀ interactions. One of
Ê
the former bonds has a short HÁ Á ÁO separation of 2.27 A.
ꢀ
is 50.50 (10) . Fig. 2 shows that all the chains propagate in the
Comment
same sense, i.e. all the C O moieties point the same way, and
it is tempting to assume that this `lining up' effect plays a role
in de®ning the SHG properties of (I).
Furthermore, two CÐHÁ Á Áꢀ interactions appear to conso-
lidate the crystal packing in (I) in the b direction. The two H
atoms involved in these interactions are both trans to the CÐ
C bond to the rest of the molecule. When viewed along the c
direction (Fig. 3), it is observed that a herring-bone-like array
of molecules of (I) results, with the CÐHÁ Á Áꢀ bonds forming
in®nite ladder-like chains along [010].
In order to display non-linear optical (NLO) effects, organic
molecular crystals must possess suitable electronic and struc-
tural properties. The former effects, including strong donor±
acceptor intermolecular interactions and delocalized p-elec-
tron systems, are reasonably well understood (Watson et al.,
1
993). The latter effects ± especially the ability to crystallize as
a non-centrosymmetric structure ± are harder to predict and
control.
Among the many organic compounds reported for their
NLO properties, chalcone derivatives are notable for their
excellent blue light transmittance and good crystallizability. It
is observed that the substitution of a bromo group on either of
the benzene rings greatly in¯uences the non-centrosymmetric
crystal packing (Uchida et al., 1998; Tam et al., 1989; Indira et
al., 2002). Bromo groups improve the molecular ®rst-order
hyperpolarizabilities and can effectively reduce dipole±dipole
interactions between the molecules (Zhao et al., 2002).
However, chalcone derivatives often have low melting
temperatures, which can be a drawback with respect to the
applications of these crystals in optical instruments. Chalcone
dibromides usually have higher melting points and are ther-
mally stable. We report here the synthesis and structure of the
Figure 1
A view of (I), showing 50% probability displacement ellipsoids; H atoms
are shown as arbitrary spheres.
o728 # 2005 International Union of Crystallography
DOI: 10.1107/S0108270105036942
Acta Cryst. (2005). C61, o728±o730

organic compounds
If the acceptor benzene ring is considered, then in each case
it is notable that a Br atom is located roughly opposite the CÐ
(I). The crystal packing of (I), viewed approximately down
[010], is available as a ®gure in the supplementary material.
ꢀ
HÁ Á Áꢀ interaction (Fig. 3) (H13Á Á Áꢀ1Á Á ÁBr2 = 168 and H3Á Á Á
ꢀ
ꢀ
2Á Á ÁBr1 = 163 ; ꢀ1 is the centroid of atoms C1±C6 and ꢀ2 is
Experimental
the centroid of atoms C10±C15). While this cannot be
considered to be a BrÁ Á Áꢀ `bond' of any kind [the BrÁ Á Áꢀ
Chalcone (1,3-diphenyl-2-propen-1-one) (20.8 g 0.1 mol) was treated
with 30% bromine in acetic acid until the orange colour of the
solution just persisted. After stirring for 30 min, the contents of the
¯ask were poured onto crushed ice and the resulting crude solid was
collected by ®ltration. The compound was dried and recrystallized as
clear blocks of (I) from ethanol in 85% yield (m.p. 396±398 K).
Ê
separations of 3.661 and 3.884 A are greater than the van der
Ê
Waals separation of 3.55 A for Br (1.85 A) plus the half-
Ê
Ê
thickness (1.70 A) of a benzene ring], it is possible that this
kind of intermolecular contact in¯uences the SHG response of
2
Analysis for C15H12Br O requires: C 48.95, H 3.29%; found: C 48.91,
H 3.26%. The SHG ef®ciency of (I), normalized to that of urea, was
measured by a standard powder technique (Kurtz & Perry, 1968)
using an Nd:YAG laser.
Crystal data
�
3
C
15
H12Br
2
O
D
x
= 1.763 Mg m
M
r
= 368.07
Monoclinic, Cc
Mo Kꢂ radiation
Cell parameters from 4476
re¯ections
Ê
a = 20.6762 (7) A
Ê
b = 7.2443 (2) A
ꢀ
ꢃ = 2.9±27.5
Ê
c = 10.3501 (3) A
� 1
ꢄ = 5.83 mm
T = 120 (2) K
ꢀ
ꢁ
= 116.575 (2)
Ê
3
V = 1386.50 (7) A
Z = 4
Block, colourless
0.48 Â 0.32 Â 0.18 mm
Data collection
Nonius KappaCCD diffractometer
and ' scans
Absorption correction: multi-scan
SADABS; Bruker, 1999)
min = 0.138, Tmax = 0.350
2889 re¯ections with I > 2ꢅ(I)
!
Rint = 0.029
ꢀ
ꢃ
max = 27.5
(
T
h = � 26 ! 26
k = � 9 ! 9
9
3
478 measured re¯ections
011 independent re¯ections
l = � 12 ! 13
Re®nement
Figure 2
2
Re®nement on F
2
(Á/ꢅ)max = 0.001
Aview of (I), showing how the three CÐHÁ Á ÁO interactions link adjacent
molecules into parallel chains propagating in (001). H atoms not involved
in the interactions shown have been omitted. [Symmetry codes: (i) x,
2
Ê
� 3
Áꢆmax = 1.05 e A
R[F > 2ꢅ(F )] = 0.026
wR(F ) = 0.058
2
Ê
� 3
Áꢆmin = � 0.74 e A
S = 1.05
3011 re¯ections
Extinction correction: SHELXL97
Extinction coef®cient: 0.0035 (2)
Absolute structure: Flack (1983),
1416 Friedel pairs
1
2
1
2
�
y + 1, z � ; (ii) x, � y + 1, z + .]
164 parameters
H-atom parameters constrained
w = 1/[ꢅ (F ) + 3.0761P]
2
2
o
Flack parameter: 0.022 (11)
2
2
c
where P = (Fo + 2F )/3
Table 1
Selected torsion angles ( ).
ꢀ
C6ÐC7ÐC8ÐC9
169.9 (3)
Br1ÐC7ÐC8ÐBr2
175.33 (16)
Table 2
Intermolecular interactions (A, ).
Ê
ꢀ
ꢀ1 is the centroid of the C1±C6 ring and ꢀ2 is the centroid of the C10±C15
ring.
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
i
i
C5ÐH5Á Á ÁO1
C8ÐH8Á Á ÁO1
0.95
1.00
0.95
0.95
0.95
2.55
2.27
2.57
2.91
2.99
3.469 (4)
3.237 (4)
3.370 (4)
3.629 (4)
3.590 (3)
162
163
142
133
123
i
C11ÐH11Á Á ÁO1
iii
Figure 3
C13ÐH13Á Á Áꢀ1
iv
A detail of (I), showing how CÐHÁ Á Áꢀ interactions involving atoms H3
and H13 provide coherence between herring-bone-like sheets of
molecules. Note also how a Br atom is positioned approximately trans
to every CÐHÁ Á Áꢀ bond (see Comment). H atoms not involved in the
interactions shown have been omitted. [Symmetry codes: (v) x, y + 1, z;
C3ÐH3Á Á Áꢀ2
1
2
1
2
3
2
1
2
1
2
1
2
1
Symmetry codes: (i) x; � y ‡ 1; z � ; (iii) x ‡ ; � y ‡ ; z ‡ ; (iv) x � ; � y ‡ ; z �
.
2
Ê
The H atoms were positioned geometrically (CÐH = 0.95±1.00 A)
and re®ned as riding, with Uiso(H) = 1.2Ueq(carrier).
(vi) x, y � 1, z.]
ꢁ
Acta Cryst. (2005). C61, o728±o730
Harrison et al.
15 2
C H12Br O
o729

organic compounds
Data collection: COLLECT (Nonius, 1998); cell re®nement:
SCALEPACK (Otwinowski & Minor, 1997); data reduction:
SCALEPACK, DENZO (Otwinowski & Minor, 1997) and SORTAV
Blessing, R. H. (1995). Acta Cryst. A51, 33±38.
Bruker (1999). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Desiraju, G. R. & Steiner, T. (1999). The Weak Hydrogen Bond in Structural
Chemistry and Biology, p. 50. Oxford University Press.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Flack, H. D. (1983). Acta Cryst. A39, 876±881.
Indira, J., Karat, P. P. & Sarojini, B. K. (2002). J. Cryst. Growth, 242, 209±
(
(
(
Blessing, 1995); program(s) used to solve structure: SHELXS97
Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97
Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997),
214.
ATOMS (Shape Software, 2003) and PLATON (Spek, 2003); soft-
ware used to prepare material for publication: SHELXL97.
Kurtz, S. K. & Perry, T. T. (1968). J. Appl. Phys. 39, 3798±3813.
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276,
Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M.
Sweet, pp. 307±326. New York: Academic Press.
Shape Software (2003). ATOMS. Shape Software, 525 Hidden Valley Road,
Kingsport, Tennessee, USA.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of
G oÈ ttingen, Germany.
Spek, A. L. (2003). J. Appl. Cryst. 36, 7±13.
The authors thank the EPSRC National Crystallography
Service (University of Southampton, England) for the data
collection. HGA thanks the University of Mysore for provi-
sion of facilities.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FG1880). Services for accessing these data are
described at the back of the journal.
Tam, W., Guerin, B., Calabrese, J. C. & Stevenson, S. H. (1989). Chem. Phys.
Lett. 154, 93±96.
Uchida, T., Kozawa, K., Sakai, T., Aoki, M., Yoguchi, H., Abduryim, A. &
Watanabe, Y. (1998). Mol. Cryst. Liq. Cryst. 315, 135±140.
Watson, G. J. R., Turner, A. B. & Allen, S. (1993). Organic Materials for
Non-linear Optics III, edited by G. J. Ashwell & D. Bloor. RSC
Special Publication No. 137, pp. 112±117. London: Royal Society of
Chemistry.
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ꢁ
o730 Harrison et al.
C
15
2
H12Br O
Acta Cryst. (2005). C61, o728±o730