A new screw shaped coordination compound for crystal engineering: Synthesis, crystal structure and nonlinear optical effect of o-chlorophenylthiourea zinc (II) diacetylacetonate

Article abstract of DOI:10.1016/j.inoche.2006.05.034

This paper presents the synthesis and crystal structure of a new screw shaped square-pyramidal coordination compound, Zn(OCPT)(acac)₂(OCPT is o-chlorophenylthiourea). In the molecule, the tail length is almost equal to the width of the head . The compound crystallizes in a noncentrosymmetric structure. The molecules are arranged in almost parallel direction.The compound showed the powder SHG (second harmonic generation) effect of about 1.5 times as large as that of KDP.

Full text of DOI:10.1016/j.inoche.2006.05.034

Inorganic Chemistry Communications 9 (2006) 986–988
www.elsevier.com/locate/inoche
A new screw shaped coordination compound for crystal
engineering: Synthesis, crystal structure and nonlinear optical
effect of o-chlorophenylthiourea zinc (II) diacetylacetonate
a
a
a
a
a,
b,
*
Xu Su , Gang Zhang , Tao Liu , Lianqing Chen , Jingui Qin *, Chuangtian Chen
a
Department of Chemistry, Wuhan University, Wuhan 430072, China
Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100080, China
b
Received 1 May 2006; accepted 20 May 2006
Available online 9 June 2006
Abstract
This paper presents the synthesis and crystal structure of a new screw shaped square–pyramidal coordination compound, Zn(OCP-
T)(acac)2(OCPT is o-chlorophenylthiourea). In the molecule, the ‘‘tail’’ length is almost equal to the width of the ‘‘head’’. The compound
crystallizes in a noncentrosymmetric structure. The molecules are arranged in almost parallel direction.The compound showed the pow-
der SHG (second harmonic generation) effect of about 1.5 times as large as that of KDP.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Coordination compound; Crystal structure; Nonlinear optics; Crystal engineering
Nonlinear optical (NLO) materials have played impor-
tant role in the opto-electronic technology [1,2]. To show
NLO effect, the crystal or film must form noncentrosym-
metric (NCS) arrangement of the molecules that also pos-
sess no centrosymmetry [3]. Organic NLO chromophores
are normally linear molecules with D–p–A character (D:
electron donor, A: electron acceptor, p: conjugated bridge).
This type of molecules exhibit quite large dipole moment,
and interact each other by Coulombic force. In most cases,
this interaction leads to the centrosymmetrical arrange-
ment of the molecules, and hence no second harmonic gen-
eration (SHG) effect could be observed.
It has been called ‘‘Crystal Engineering’’ of NLO mate-
rials to form NCS arrangement of the chromophores in
crystals or other types of the solids. This is one of the great
challenges in the area though there have been some
approaches to increase the chance for formation of NCS
arrangement, such as the usage of the hydrogen bonding,
chiral molecule, LB film and poled polymer among the oth-
ers. It was recently reported that the polar chromophores
could arrange favorably to form NCS packing in poled
polymer films if bulky groups are attached to one or both
sides of the chromophore molecules since the distance
between the neighboring polar molecules are enlarged
and the Coulombic interaction of the polar chromophores
will be suppressed [4,5].
We have summarized in a review article [6] that
square–pyramidal coordination compounds, L Æ Zn(acac)2,
have a high probability to form NCS crystals. For exam-
ple, phenylthiourea zinc (II) diacetylacetonate (PZDA)
(see Fig. 1a) crystallized in an almost parallel arrangement
of the molecules and showed SHG effect 10 times as large
as that of KDP [7]. Later Anthony and Radhakrishnan
have further called L Æ Zn(acac)2 as the screw shaped
molecules, and presented one of the compounds, Zn(dim-
ethylpyridene)(acac)2,formed perfect assembly by self-
poling [8]. Three years ago,four compounds of the type
of L Æ Zn(acac)2 with extended conjugation length of L
were synthesized in the hope to increase NLO property
(see Fig. 1b). However all four compounds crystallize in
*
Corresponding authors. Tel./fax: +86 27 68756757.
E-mail address: jgqin@whu.edu.cn (J. Qin).
1387-7003/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.05.034

X. Su et al. / Inorganic Chemistry Communications 9 (2006) 986–988
987
Cl
X
O
S
O
NH2
H2O
+
N
N
NH4SCN
H
H
Cl
Cl
Reflux
N
HN
O
NH
O
HN
NH
O
2
2
C
S
C
S
Cl
Cl
HN NH2
NaOH
acetone-ZDA
NH
S
(acac)H/acetone=2:1
S
Zn
O O
Zn
O O
45oC
O
Zn
H2N
O
O
O
O
b
a
Scheme 1.
Fig. 1. (a) The molecule of PZDA; (b) the coordination compounds with
long ligands.
centrosymmetric space groups, and showed no SHG effect
[9,10]. It seemed to us that the screw shape of the mole-
cule can not guarantee the formation of NCS, and it
may be necessary to consider the ratio of the length to
the width in the ‘‘screw’’. In our case, the compounds
in Refs. [8,9] may be a little too long, and the ratio is a
little too high. Therefore we have recently synthesized
some new L Æ Zn(acac)2 with a shorter L. This paper
describes the synthesis,crystal structure and NLO prop-
erty of one compound,namely (o-chlorophenylthiourea
zinc(II) diacetylacetonate.
The synthetic route is illustrated in Scheme 1. The ligand
o-chlorophenylthiourea was synthesized by an operation
described in Ref. [11]. The acetone zinc (II) diacetylaceto-
nate (acetone–ZDA) was prepared according to the litera-
ture [12]. The coordination compound was prepared by
reaction of (2-chloro-phenyl)-thiourea with acetone solu-
tion of equimolar acetone–ZDA at 45 ꢁC for about 5 h.
The product was purified by recrystallization from a mix-
ture of acetone and acetylacetone (2:1 volume ratio). The
ligand and the coordination compound were characterized
by IR and EA.1
Single crystals of the coordination compound were
grown from an acetone–acetylacetone (1:1) solution by
solvent evaporation in air and the structure was deter-
mined by X-ray single crystal structure analysis.2 The
ORTEP drawing of the compound with numbered atoms
Fig. 2. ORTEP view of the molecular structure of coordination com-
pound. Selected Bond lengths (A) and Angels (ꢁ): Zn(1)-O(1) 2.011(11),
´
˚
Zn(1)-O(2) 2.054(9), Zn(1)-O(3) 2.063(10), Zn(1)-O(4) 2.011(9), Zn(1)-S(1)
2.380(4), C(7)-N(2) 1.274(19), C(7)-N(1) 1.329(18), C(7)-S(1) 1.704(13),
C(9)-O(1) 1.219(19), C(11)-O(2) 1.243(17), C(14)-O(3) 1.238(16), C(16)-
O(4), 1.295(17), C(6)-Cl(1) 1.696(17), C(5)-N(1) 1.43(2); O(4)-Zn(1)-O(1)
144.0(5), O(4)-Zn(1)-O(2) 83.4(4), O(1)-Zn(1)-O(2) 87.7(5), O(4)-Zn(1)-
O(3) 88.9(4), O(1)-Zn(1)-O(3) 85.7(4), O(2)-Zn(1)-O(3) 156.9(5), O(4)-
Zn(1)-S(1) 109.3(3), O(1)-Zn(1)-S(1) 106.6(4), O(2)-Zn(1)-S(1) 100.7(4),
O(3)-Zn(1)-S(1) 102.4(3).
1
Ligand: Yield 72%. IR data (KBr, cmÀ1): 3415.2, 3187.6, 3270.5,
3066.4, 1618.8, 1579.5, 1501.1, 1453.2, 1481.4, 1233.4, 1057.4, 804.5, 614.2.
Anal. (%), Found: C: 44.90, H: 3.92, N: 15.22, S: 17.01; (Calcd.: C: 45.04,
H: 3.78, N: 15.01, S: 17.18). Coordination compound: Yield 59%. IR data
(KBr, cmÀ1): 3392.0, 3165.2, 3265.2, 3032.2, 2954.6, 2916.0, 1633.9,
1591.7, 1521.5, 1494.0, 1454.9, 1264.8, 1186.5, 1015.7, 800.5, 761.1.
Anal.(%), Found: C: 45.44, H: 4.58, N: 6.20, S: 7.22; (Calcd.: C: 45.26, H:
4.70, N: 6.22, S: 7.12).
is shown in Fig. 2. The zinc atom is coordinated to four
oxygen atoms of two (acac) groups and one sulfur atom
of ligand to form a square–pyramid configuration. The
whole molecule can be seen as a screw, in which two
(acac) groups form the ‘‘head’’ and the ligand forms the
‘‘tail’’. The ratio of the tail length to the head width is
nearly 1:1. Four ZnAO bond lengths are not equal but
2
Crystal data for compound: C17H20ClN2O4SZn, M = 449.23, mono-
˚
˚
˚
clinic, space group Pc, a = 7.534(3) A, b = 14.314(5) A, c = 9.316(3) A,
3
3
˚
b = 95.113(6)ꢁ, V = 1000.6(6) A , T = 292(2) K, Z = 2, Dc = 1.491 g/cm ,
l = 1.489 mmÀ1, F(000) = 462, k = 0.71073 A. Of 2301 reflections mea-
˚
sured, 1625 were unique (Rint = 0.0181) and were used in all calculations.
The final R1[I > 2r(I)] = 0.0701, wR2 = 0.1814 (all data). The CCDC #:
605779.
˚
have a disparity of about 0.05 A at maximum. The

988
X. Su et al. / Inorganic Chemistry Communications 9 (2006) 986–988
Fig. 3. The crystal packing along a direction.
˚
C(7)AS bond length is 1.704(13) A, which is between
Acknowledgement
˚
˚
1.82 A for CAS single bond and 1.56 A for C@S double
bond [11].
The authors are grateful to the National Key Funda-
mental Research Program (973 program) of China for
financial support.
Fig. 3 is the crystal structure along a axis. All the screw
shaped molecules orient in such an almost perfect direction
that they parallel to each other along the c axis (with an
angle of about 30ꢁ between two tails). The screw tails are
located between every two screw’s heads. This molecular
alignment benefits the accumulation of the first molecular
hyperpolarizability (b) and hence to exhibit a noticeable
SHG value.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.inoche.
2006.05.034.
The SHG effect was investigated using the Kurtz powder
technique [13]. A Nd:YAG laser with pulse duration of 8 ns
was utilized to generate fundamental 1064 nm light. The
microcrystalline potassium dihydrogen phosphate (KDP)
was served as the standard. The result showed that the
intensity of the frequency signal of the compound was
about 1.5 times as large as that of KDP. No SHG signal
was found for the ligand. The UV–Vis absorption maxima
of the ligand and the coordination compound are at 295
and 321 nm, respectively. They both do not absorb at
532 nm.
References
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In summary, a new screw shaped square–pyramidal
coordination compound, Zn(OCPT)(acac)2, in which the
tail length is almost equal to the width of the head,was syn-
thesized. In the crystal the molecules are arranged in
almost parallel direction. And the powder SHG effect of
the compound is about 1.5 · KDP. This result may indi-
cate that the screw shaped dipole molecules should possess
adequate ratio of the tail length to the head width so that
they have more chance to form noncentrosymmetric and
favorable alignment of the chromophores in crystals for
NLO effect.
[12] E.L. Lippert, M.R. Truter, J. Chem. Soc. (1960) 4996.
[13] S.K. Kurtz, T.T. Perry, J. Appl. Phys. 39 (1968) 3798.