Synthesis, structure and third-order nonlinear optical properties of 1,3,5-triazine-based Zn(II) three-dimensional supramolecule

Article abstract of DOI:10.1016/j.molstruc.2004.03.008

A novel zinc(II) 1,3,5-triazine-based complex [Zn(TIPT)Cl ₂]·2CH₃OH (1) (TIPT=2,4,6-tri(2-ispropylidene-1-ly) hydrazono-1,3,5-triazine) was prepared and structurally characterized by means of X-ray single crystal diffraction. The zinc(II) atom is coordinated at a distorted triangle bispyramid by three nitrogen atoms from TIPT and two Cl ^- anions. This compound exhibits a three-dimensional solid-state structure constituted by N-H?O, O-H?Cl, N-H?Cl and C-H?Cl hydrogen bonds. The third-order nonlinear optical properties were determined by Z-scan techniques. The results indicate the compound exhibit strong self-focusing effect, and the hyperpolarizability γ value is 8.26×10^-30esu. Its thermal properties were also determined in air.

Full text of DOI:10.1016/j.molstruc.2004.03.008

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Journal of Molecular Structure 693 (2004) 217–224
www.elsevier.com/locate/molstruc
Synthesis, structure and third-order nonlinear optical properties
of 1,3,5-triazine-based Zn(II) three-dimensional supramolecule
*
Fan Yaoting, Li Gang , Li Zifeng, Hou Hongwei, Mao Hairong
Department of Chemistry, Zhengzhou University, Henan 450052, P. R. China
Received 24 December 2003; revised 3 March 2004; accepted 4 March 2004
Abstract
A novel zinc(II) 1,3,5-triazine-based complex [Zn(TIPT)Cl2]·2CH3OH (1) (TIPT ¼ 2,4,6-tri(2-ispropylidene-1-ly)hydrazono-1,3,
5-triazine) was prepared and structurally characterized by means of X-ray single crystal diffraction. The zinc(II) atom is coordinated at a
distorted triangle bispyramid by three nitrogen atoms from TIPT and two Cl2 anions. This compound exhibits a three-dimensional solid-state
structure constituted by N–H· · ·O, O–H· · ·Cl, N–H· · ·Cl and C–H· · ·Cl hydrogen bonds. The third-order nonlinear optical properties were
determined by Z-scan techniques. The results indicate the compound exhibit strong self-focusing effect, and the hyperpolarizability g value is
8.26 £ 10230 esu. Its thermal properties were also determined in air.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Zinc(II); Supramolecular compound; Hydrogen bonds; NLO properties
1. Introduction
in polyfluorophenyl palladium(II) complexes with 2,4,6-
Tris(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine [3c] and so on
[3d–3f,4]. More recently, we found that there are a very
large number of complexes synthesized by the reaction of
N-containing 2,4,6-trisubstituted-1,3,5-triazines with metal
ions [4]. That is to say, in order to synthesize more
interesting compounds with 1,3,5-triazine moieties system-
atically, the development of these types of 1,3,5-triazine-
based ligands is of importance.
Recently, strong interest has been focused on the self-
assembly of supramolecular architectures prepared from
multifunctional ligands and transition metals [1,2]. Conse-
quently there has been a steady rise in attempts to design
organic molecules as bi- or poly-dentate ligands that can
form supramolecular systems via covalent or non-covalent
interactions. Of these ligands 1,3,5-triazine derivatives have
been demonstrated to be versatile ligands for the synthesis
of metal complex materials with a variety of structural
architectures. By careful control of the synthesis conditions
and the organic species employed, it has been proven
possible to synthesize many 2D and 3D supramolecular
networks [3,4]. For example Bhattacharya and co-workers
have reported a novel organic porous solids with channel
and layered structures from 1,3,5-triazine-2,4,6-triamine-
hexaacetic acid and its Ca(II) salts [3a]. Galan–Mascaros
et al. have also studied the structure and magnetic properties
of the 1D chain compound {K[Fe(1,3,5-triazine-2,4,
6-tricarboxylate)(H2O)2]2H2O}n [3b]. Carrion and co-
workers have described five different fluxional processes
On the other hand, since 1987s, metal–organic com-
pounds with nonlinear optical (NLO) properties have been
attracting a great deal of attention [5,6]. Compared to
organic molecules, metal–organic complexes have some
definitive advantages such as tunability of the polarizablity
by changing the oxidation state of metal atoms or by
variation of ligands [6]. Up to now, several reports about
second-order NLO properties of 1,3,5-triazine derivatives
were published [7], but 1,3,5-triazine-based complexes have
drawn little attention especially the investigations of third-
order NLO properties [3g] in this context.
It is to be pointed out that 1,3,5-triazine-based complexes
usually consist of two parts: aromatic triazine-containing
ligands and metal ions, both the two parts may make a
contribution to optical nonlinearity. Herein, we synthesized
a new 1,3,5-triazine-containing ligand, 2,4,6-tri(2-ispropy-
lidene-1-ly)hydrazono-1,3,5-triazine, and the corresponding
*
Corresponding author. Tel.: þ86-371-7767164; fax: þ86-371-
7761744.
E-mail address: gangli@zzu.edu.cn (L. Gang).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.03.008

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F. Yaoting et al. / Journal of Molecular Structure 693 (2004) 217–224
Zn(II) complex [Zn(TIPT)Cl2]·2CH3OH (1). The crystal
structure of complex 1 was characterized by X-ray
diffraction. The zinc(II) ion is in a distorted triangle
bispyramidal environment with three nitrogen atoms from
TIPT and two Cl- anions. This compound exhibits four kinds
of hydrogen bonds N–H· · ·O, O–H· · ·Cl, N–H· · ·Cl and
C–H· · ·Cl, which may extend the [Zn(TIPT)Cl2] units into
1D chains, and further into a 3D solid-state structure.
Moreover, compound 1 has strong third-order NLO
refractive properties. The calculated hyperpolarizability g
values is 8.26 £ 10230 esu, which can be comparable to
some reported clusters and ferrocenyl complexes.
C3H9N9: C: 21.52; H: 5.31; N: 73.79%. Found: C: 21.04; H:
5.04; N: 73.79%. THDT was insoluble in water, ethanol,
benzene, and acetone.
Secondly, the target ligand TIPT was prepared: a mixture
of THDT (0.428 g, 2.5 mmol), acetone (25 ml), and H2O
(15 ml) was refluxed gently until all of the THDT solids
were dissolved. The resulting clearly mixture was cooled
and the residual acetone removed by rotary evaporation.
When the resulting solution was cooled and placed for half
day, a white precipitation can be obtained by filtration. The
solid may be recrystallised from MeOH; yield 0.696 g,
(95.5%). IR (cm21): 3376 (s), 2915 (w), 1584 (s), 1505 (s),
1423 (s), 1371 (m), 1275 (m), 1153 (s), 1099 (w), 807 (s),
674 (m), 642 (m). Anal. Calcd For C12H21N9: C: 49.47; H:
7.26; N: 43.27%. Found: C: 49.82; H: 6.95; N: 43.52%. 1H
NMR (400 MHz, CD3OD): d 2.05 (s, 3H, NH), 1.82–1.88
(s, 18H, CH3). TIPT was soluble in methanol, hot water and
the mixture of water and acetone.
2. Experimental
2.1. Materials and physical techniques
All chemicals were of reagent grade quality obtained
from commercial sources and used without further
purification.
2.3. Preparation of [Zn(TIPT)Cl2]·2CH3OH (1)
A solution of TIPT (0.0146 g, 0.05 mmol) in methanol
(10 ml) was added dropwise to a solution of ZnCl2·6H2O
(0.0148 g, 0.05 mmol) in methanol (10 ml). The resulting
solution was heated and refluxed for 2 h, then filtered. The
colorless filtrate was allowed to stand at room temperature.
Colorless crystals suitable for X-ray single crystals analysis
were obtained over 8 h in 71% yield. IR (cm21): 3254 (m),
2945 (w), 1627 (m), 1581 (s), 1537 (s), 1507 (m), 1430 (m),
1373 (w), 1341 (w), 1304 (w), 1278 (m), 1157 (m), 1111
(w), 799 (m), 683 (w), 650 (w). Anal. Calcd for C14H29
Cl2N9O2Zn: C: 34.19; H: 5.94; N: 25.64%. Found: C: 34.53;
H: 5.60; N: 25.67%.
IR data were recorded on a Nicolet NEXUS 470-FTIR
spectrophotometer with KBr pellets in the 400–4000 cm21
region. UV/VIS spectra were performed on a HP 8453
spectrophotometer. Elemental analyses (C, H and N) were
1
carried out on a Carlo-Erba1106 Elemental Analyzer. H
NMR spectra were recorded at RT on Bruker DPX 400
spectrometers. TGA–DTA measurements were performed
by heating the sample from 20 to 700 8C at a rate of
10 8C min21 in air on a Perkin Elmer DTA-7 differential
thermal analyzer.
2.2. Preparation of 2,4,6-tri(2-ispropylidene-1-ly)
hydrazono-1,3,5-triazine (TIPT)
2.4. Crystallography
The ligand TIPT was prepared by two steps as follows
(See Scheme 1):
Crystal data and experimental details for compound 1
are contained in Table 1. All measurements were made on
a Bruker CCD-AREA imaging plate area detector
with graphite monochromated Mo-Ka radiation (l ¼
dimensions of 0.30 £ 0.30 £ 0.20 mm3. All data were
collected at a temperature of 180(2) K using the v–2u
scan technique and corrected for Lorenz-polarization
effects. A correction for secondary extinction was applied.
The structure were solved by direct methods and
expanded using the Fourier technique. The non-hydrogen
Compound 2,4,6-trihydrazino-1,3,5-triazine (THDT)
was firstly synthesized by following method: adding 2,4,6-
trichloro-1,3,5-triazine (3.7 g, 20 mmol) (85%, 30 ml) to a
stirred aqueous solution of NH2NH2·H2O (85%, 30 ml).
After the reaction mixture was stirred and refluxed for 3 h,
then cooled and filtered to give a white solid. The solid
product was then washed with water until pH ¼ 7, and air-
dried, yield, 3.0 g (87%). IR (cm21): 3310 (s), 2919 (w),
1566 (s), 1433 (s), 1220 (m), 1172 (m), 1121 (m), 1071(s),
934(s), 801 (s), 729(m), 616 (m), 488(w). Anal. Calcd For
˚
0.71073 A). The sample selected for investigation has
Scheme 1.

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F. Yaoting et al. / Journal of Molecular Structure 693 (2004) 217–224
219
Table 1
to be 35 ^ 5 mm (half-with at 1=e2 maximum). The interval
between the laser pulses was chosen to be ,5 s for
operational convenience. The incident and transmitted pulse
energies were measured simultaneously by two Laser
Precision detectors (RjP-735 energy probes), which were
linked to a computer by an IEEE interface [9]. The NLO
properties of the sample were manifested by moving the
sample along the axis of the incident beam (Z-direction)
with respect to the focal point. An aperture of 0.5 mm in
radius was placed in front of the detector to assist the
measurement of the self-focusing effect.
Crystallographic data and structure refinement for 1
Formula
C14H29O2N9Cl2Zn
Fw
491.73
Crystal syst
Monoclinic
Crystal size (mm) space group
˚
a (A)
˚
b (A)
0.30 £ 0.30 £ 0.20 P2ð1Þ=c
9.1027(16)
12.280(2)
˚
C (A)
20.574(4)
a (8)
b (8)
g (8)
90
96.301(2)
90
3
˚
V (A )
2285.8(7)
Dc (Mg m23
)
1.429
Z
4
m (mm21
)
1.336
3. Results and discussion
Reflens collected/unique
Data/restraints/parameters
Refinement method
Final R indices
11797/4467 RðintÞ ¼ 0:0344
446/0/468
3.1. Syntheses
Full-matrix ileast-squares on F2
R1 ¼ 0:0565; wR2 ¼ 0:1082
R1 ¼ 0:0674; wR2 ¼ 0:1128
1.177
The utilization of 2,4,6-trichloro-1,3,5-triazine as
‘parent’ material is an effective route for preparation of a
novel multidentate ligand containing 1,3,5-triazine. Our
experimental process reveals that the target product 2,4,6-
tri(2-ispropylidene-1-ly)hydrazono-1,3,5-triazine (TIPT)
was obtained in good yield under relatively mild conditions.
It is noted that under the varied molar ratio of ligand
TIPT and Zn2þ ion from 1:1 to 1:3, the same compound
[Zn(TIPT)Cl2]·2CH3OH (1) can be obtained. That is to say,
one TIPT only can coordinate to one Zn2þ ion forming a
mononuclear complex. The similar case can be found in a
related 1,3,5-triazine derivative, 2,4,6-tris(2-pyridyl)-1,3,5-
triazine (TPT). People’s studies show that when TPT
functions as a tridentate ligand, the coordination of second
metal to is not usually observed due to deactivation of the
triazine ring by the inductive effect of the first metal and as a
result of steric interactions between the hydrogen atoms and
the metal ion [10]. We presume that the same deactivation
of the triazine ring can occur in our preparation process, thus
the polynuclear complex with the TIPT ligand was not
easily obtained.
R indices (all data)
Goodness-of-fit on F2
23
˚
Drmin and Drmax=e A
20.375 and 0.644
atoms were refined with anisotropic thermal parameters.
Hydrogen atoms were included but not refined. The final
cycle of full-matrix least-squares refinement was based on
4467 observed reflections and 275 variable parameters. All
calculations were performed using the SHELX-97 crystal-
lographic software package [8]. Selected bond lengths and
bond angles are listed in Table 2.
2.5. NLO measurement
A DMF solution for complex 1 was placed in a 1 mm
quartz cuvette for NLO measurements. The nonlinear
refraction was measured with a linearly polarized laser
light (l ¼ 532 nm; pulse widths ¼ 7 ns) generated from a
Q-switched and frequency-doubled Nd-YAG laser. The
spatial profiles of the optical pulses were nearly Gaussian.
The laser beam was focused with a 25 cm focal-length
focusing mirror. The radius of the beam waist was measured
3.2. Crystal Structure of [Zn(TIPT)Cl2]·2CH3OH (1)
Table 2
˚
Selected bond distances (A) and angles (deg) for 1
The molecular structure of complex 1 was determined by
single crystal X-ray diffraction analysis. The molecule
crystallizes in the space group P2ð1Þ=c: The perspective
view together with the atomic numbering scheme is
illustrated in Fig. 1.
Zn(1)–N(3)
2.013(3)
2.377(3)
2.310(3)
1.279(4)
1.393(4)
1.356(4)
1.378(4)
129.32(9)
114.92(4)
103.02(8)
146.01(10)
99.45(8)
132.4(2)
109.5(2)
133.7(2)
Zn(1)–Cl(1)
2.2114(11)
2.2534(10)
1.279(4)
1.383(4)
1.354(4)
1.345(4)
1.267(5)
Zn(1)–N(5)
Zn(1)–Cl(2)
Zn(1)–N(1)
C(2)–N(1)
C(5)–N(5)
N(1)–N(2)
The Zn(II) ion is at a five-coordinated geometry in which
nitrogen atom N3 from TIPT ligand and two Cl2 anions
occupy the equatorial plane, two nitrogen atoms N1 and N5
from TIPT ligand occupy the axial positions. Deviation of Zn
atoms from the mean plane formed by the three equatorial
˚
atoms is about 0.0754 A and the maximum deviation of any
˚
equatorial atom from the mean plane is 0.0237 A. Zn–N
N(1)–N(2)
N(2)–C(7)
N(4)–C(8)
N(8)–C(9)
N(8)–N(9)
N(9)–C(10)
Cl(1)–Zn(1)–N(3)
Cl(1)–Zn(1)–Cl(2)
Cl(1)–Zn(1)–N(1)
N(1)–Zn(1)–N(5)
Cl(2)–Zn(1)–N(5)
C(2)–N(1)–Zn(1)
N(2)–N(1)–Zn(1)
C(5)–N(5)–Zn(1)
Cl(2)–Zn(1)–N(3)
N(3)–Zn(1)–N(1)
Cl(2)–Zn(1)–N(1)
Cl(1)–Zn(1)–N(5)
N(3)–Zn(1)–N(5)
C(1)–C(2)–N(1)
N(2)–C(7)–N(3)
N(4)–N(5)–Zn(1)
115.68(9)
73.31(11)
97.29(8)
96.40(8)
72.79(10)
117.8(3)
115.9(3)
108.4(2)
˚
distances range from 2.013(3) to 2.376(3) A, while Zn–Cl
˚
distances are 2.2114(11) and 2.2536(10) A, respectively.
The bond angles around Zn(II) ion vary from 72.79(10)8 to

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F. Yaoting et al. / Journal of Molecular Structure 693 (2004) 217–224
and [Zn(tp)(4,40-bipy)] (tp ¼ terephthalate) (Zn-N:
˚
2.154(2)–2.186(3) A) [11b], and those of Zn(II) Schiff
base complex [ZnCl2(L2)] (L2 ¼ 1,2-bis(ferrocen-l-
˚
ylmethyleneamino)ethane) (Zn–N: 2.063(3)–2.073(4) A)
[12]. The dihedral angle between the triazine rings and the
planes Cl1–Cl2–N3 is 87.68.
Interestingly, in the solid state structure of 1,
[Zn(TIPT)Cl2] and CH3OH are joined together by hydrogen
bonds forming a three-dimensional supramolecule. It can be
seen from Fig. 2 that the coordinated Cl2 anions, crystal-
lized methanol molecules and NH units are involved in the
hydrogen bonds between the neighboring [Zn(TIPT)Cl2]
units forming an infinite {[Zn(TIPT)Cl2]·2CH3OH}n chain.
There are three kinds of hydrogen bonds. One is between O2
unit of the crystallized methanol molecule and N8H of one
[Zn(TIPT)Cl2] unit [N8· · ·O2 ¼ 2.892, H8D· · ·O2 ¼
˚
2.031 A, N8–H8D· · ·O2 ¼ 168.808]. The other arises
from the interaction of O2H of the crystallization methanol
molecule with Cl2 of another [Zn(TIPT)Cl2] unit
˚
[Cl· · ·O2 ¼ 3.283, H2· · ·Cl2 ¼ 2.518 A, O2–H2· · ·Cl2 ¼
151.858]. The third originates from N2H of the
[Zn(TIPT)Cl2] unit with Cl2 of neighboring [Zn(TIPT)Cl2]
˚
unit [Cl· · ·N2 ¼ 3.351, H2D· · ·Cl2 ¼ 2.539 A, N2–H2D· · ·
Cl2 ¼ 170.578]. At the same time, the hydrogen bonds
between O2H units of the crystallized methanol molecule
and N6 units of neighboring [Zn(TIPT)Cl2] unit serve to
link the {[Zn(TIPT)Cl2]·2CH3OH}n chains into two-dimen-
sional sheets. Viewed from b-axis, different sheets stack by
the weak hydrogen bonds C–H· · ·Cl and the Van der Waals
interactions forming three-dimensional structure(Fig. 3).
Fig. 4 shows its solid-state structure along a-axis.
Fig. 1. ORTEP drawing with atom-labeling scheme of 1. The hydrogen
atoms are omitted for clarity.
146.01(10)8. The geometry about the five-coordinate zinc
atom can best be described as slightly distorted trigonal
bipyramidal coordination sphere, with equatorial angles in
the range 114.92(4)–129.32(9)8, and an axial angle N(1)–
Zn(1)–N(5) of 146.01(10)8. The Zn–N distances can be
comparable to those of other Zn(II) coordination polymers,
for example [Zn(4,40-bipy)(H2O)3(ClO4)](ClO4)·(4,40-
3.3. Thermogravimetric Analysis (TGA)
The TG-DTA of complex 1 was determined in the
range of 20-700 8C in air. TG data shows that the 1 is
stable up to 37.7 8C, then loses weight from 37.7 to 98.5 8C
˚
bipy)1.5·H2O (Zn–N: 2.104(2)–2.117(2) A) [11a]
Fig. 2. The one-dimensional chain supported by hydrogen bonding of 1.