Solvent-controlled assembly of crystal structures: From centrosymmetric structure to noncentrosymmetric structure

Article abstract of DOI:10.1016/j.molstruc.2015.10.094

Reported here are two isomeric organic crystals and two HgI₂-based coordination compounds by solvo(hydro)thermal method: [(TPTA)·H₂O]_n (1, Cc), [(TPTA)·H₂O]_n (2, Pbca), [Hg_1.5I₃(

Full text of DOI:10.1016/j.molstruc.2015.10.094

Journal of Molecular Structure 1106 (2016) 114e120
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Solvent-controlled assembly of crystal structures: From
centrosymmetric structure to noncentrosymmetric structure
Le Zhang, Lilong Dang, Feng Luo, Xuefeng Feng*
School of Biology, Chemistry and Material Science, East China University of Technology, Nanchang 344000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Reported here are two isomeric organic crystals and two HgI2-based coordination compounds by sol-
vo(hydro)thermal method: [(TPTA)$H2O]n (1, Cc), [(TPTA)$H2O]n (2, Pbca), [Hg1.5I3(TP-
Received 28 August 2015
Received in revised form
27 October 2015
Accepted 28 October 2015
Available online 2 November 2015
TA)0.5(CH3CN)$(H2O)0.5 n
]
(3, P21) and [HgI2(TPTA)$H2O]n (4, P21/c) (TPTA ¼ N,N0,N00-tris(3-pyridyl)
trimesic amide). Single crystal X-ray diffraction show that they afford noncentrosymmetric and
centrosymmetric structures, respectively. Note that this kind of formations can be precisely controlled by
changing the reaction solvent, thus indicating a facile method towards generating noncentrosymmetric
structure.
Keywords:
HgI2
© 2015 Elsevier B.V. All rights reserved.
Centrosymmetric structure
Solvo(hydro)thermal method
Noncentrosymmetric structure
1. Introduction
effective and straightforward approach [15,16]. Then, we can use of
asymmetric ligand or flexible ligand to prepare non-
Synthesis and design of coordination compounds (CCs) have
attracted ever increasing interest due to not only their structural
novelty but also promising applications in the fields of adsorptions,
catalysis, luminescence, magnetism, conductivity, nonlinear optics
(NLO), etc [1e4]. However, the formation of the CCs is highly
influenced by various reaction conditions, such as solvent system,
reaction temperature, pH value of the solution, ratio of ligand to
metal ion, and coordination geometry of central metals and organic
ligands [5e8].
In particular, the coordination compounds (CCs) crystals with
noncentrosymmetric structures (NCS) have received significant
attention, owing to the extensive potential applications in ferro-
electric, pyroelectric, piezoelectric, and second harmonic genera-
tion (SHG) properties [9e11]. Furthermore, to date, it remains a
considerable challenge to control the structures to NCS [12,13].
Generally, noncentrosymmetric materials can be well-designed by
using preferred coordination geometries of metal centers and/or
carefully chosen bridging ligands [14]. Several methods have been
developed to synthesize coordination compounds with non-
centrosymmetric structures. First of all, it is to use optically pure
chiral multidentate ligands, which has been proved to be the most
centrosymmetric materials [17]. Moreover, noncentrosymmetric
compounds can be also obtained through unpredictable sponta-
neous resolution and topology-building [18,19]. The investigation
of spontaneous resolution has been carried out by many re-
searchers during the past decades. It has been found that sponta-
neous resolution occurs in the course of crystallization is closely
related to many external factors which are similar as to the for-
mation of CCs [20e22]. Therefore, it is such a challenging work to
accurately control the crystals from centrosymmetric structure to
noncentrosymmetric structure by changing the reaction condi-
tions. Herein, based on a tripodal ligand of N,N0,N00-tris(3-pyridyl)
trimesic amide (TPTA), we found that the presence of a small
quantity of water molecules as co-solvents would control the final
structures from centrosymmetry to noncentrosymmetry.
2. Experimental
2.1. Materials and methods
Commercially available reagents were used throughout without
further purification and TPTA was synthesized according to the
literature method [23e26]. Elemental analyses for C, H, and N were
performed with a PerkineElmer 2400 Series II element analyzer.
Thermogravimetric analysis (TGA) experiments were carried out
with a DuPont Thermal Analyzer from room temperature to 800 ꢀC
* Corresponding author.
E-mail address: wlnczhcd@163.com (X. Feng).
http://dx.doi.org/10.1016/j.molstruc.2015.10.094
0022-2860/© 2015 Elsevier B.V. All rights reserved.

L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
115
Table 1
5 mL DMF was mixed in a Teflon container and sealed in an auto-
clave. The autoclave was heated to 115 ꢀC in a programmable oven,
and this temperature was maintained for three days before it was
cooled to room temperature. Light yellow bar-type crystals were
obtained. EA analysis (%): calc. C/63.15, N/18.41, H/4.42; exp. C/
63.14, N/18.42, H/4.45.
Selected bond lengths/Å and bond angles/ꢀ for 3 and 4.
Compound 3
Hg(1)eN(2)
Hg(1)eI(3)
Hg(1)eI(4)
Hg(1)eI(4B)
Hg(2)eN(1)
Hg(2)eI (1)
Hg(2)eI(2)
Hg(2)eI(1A)
Hg(3)eN(3)
Hg(3)eI(5)
Hg(3)eI(5B)
Hg(3)eI(6)
Hg(3)eI(6A)
2.376(7)
2.6321(7)
2.6650(7)
3.1741(7)
2.413(6)
2.6347(7)
2.6341(7)
3.3248(7)
2.392(7)
N(2)eHg(1)eI(3)
N(2)eHg(1)eI(4)
I(3) eHg(1) eI(4)
N(2)eHg(1)eI(4B)
I(3)eHg(1)eI(4B)
I(4)eHg(1)eI(4B)
N(1)eHg(2)eI(1)
N(1) eHg(2) eI(1A)
I(2)eHg(2)eI(1)
104.09(17)
102.08(17)
149.87(3)
90.47(18)
102.66(2)
91.74(2)
99.23(19)
97.9(2)
158.80(2)
93.79(2)
2.4. Synthesis of [Hg1.5I3(TPTA)0.5(CH3CN)·(H2O)0.5]n (3)
The mixture of HgI2 (0.2 mmol) and TPTA(0.2 mmol) in the 5 ml
acetonitrile and 1 mL H2O solution was stirred for 30 min, and then
transferred to a Teflon container and sealed in an autoclave. The
autoclave was heated to 160 ꢀC in a programmable oven, and this
temperature was maintained for three days before it was cooled to
room temperature (cooling rate 3ꢀC/h). Light yellow crystals were
obtained in the yield of 65% based on Hg. EA analysis (%): calc. C/
17.70, N/5.90, H/1.27; exp. C/17.73, N/5.90, H/1.26.
2.6731(7)
3.5271(7)
2.6305(7)
3.3960(7)
I(2)eHg(2)eI(1A)
I(1)eHg(2)eI(1A)
N(3)eHg(3)eI(6)
N(3) eHg(3) eI(5)
I(6)eHg(3)eI(5)
89.01(2)
102.64(16)
100.99(17)
156.36(3)
91.74(2)
Hg(1)eI(4)eHg(1A)
Hg(2)eI(1)eHg(2B)
89.01(2)
Compound 4
Hg(1)eN(1)
Hg(1)eN(6A)
Hg(1)eI(1)
Hg(1)eI(2)
Hg(1)eN(6B)
2.396(6)
2.441(6)
2.6290(9)
2.6581(9)
2.441(6)
N(1)eHg(1)eN(6A)
N(1)eHg(1)eI(1)
N(6)eHg(1)eI(1A)
N(1)eHg(1)eN(2)
N(6)eHg(1)eI(2A)
I(1)eHg(1)eI(2)
88.5(2)
104.17(16)
103.01(15)
106.43(16)
100.97(16)
141.26(3)
2.5. Synthesis of [HgI2(TPTA)·H2O]n (4)
The mixture of HgI2 (0.2 mmol) and TPTA(0.2 mmol) in the 5 ml
acetonitrile solution was stirred for 30 min, and then transferred to
a Teflon container and sealed in an autoclave. The autoclave was
heated to 160 ꢀC in a programmable oven, and this temperature
was maintained for three days before it was cooled to room tem-
perature (cooling rate 3ꢀC/h). Light brown crystals were obtained in
the yield of 68% based on Hg. EA analysis (%): calc. C/32.29, N/
9.41,H/2.03; exp. C/32.27, N/9.45, H/2.01.
Symmetry code: (A): 1 þ x, y, z; (B): ꢁ1þx, y, z.
in a nitrogen atmosphere at a heating rate of 10 ꢀC minꢁ1. In the
measurements of emission and excitation spectra, the pass width is
5.0 nm.
2.2. Synthesis of [(TPTA)·H2O]n (1)
2.6. Crystallographic measurements
N,N0,N00-tris(3-pyridyl) trimesic amide(TPTA) (0.2 mmol) with
5 mL DMF and 1 mL H2O was mixed in a Teflon container and sealed
in an autoclave. The autoclave was heated to 115 ꢀC in a program-
mable oven, and this temperature was maintained for three days
before it was cooled to room temperature. Light yellow block-
shaped crystals were obtained. EA analysis (%): calc. C/63.15, N/
18.41, H/4.42; exp. C/63.17, N/18.48, H/4.40.
Single-crystal diffraction intensity data were collected on Bruker
Smart Breeze CCD employing graphite-monochromated Mo-K
a
radiation (
l
¼ 0.71073 Å) at 296(2)K, the measurement method is
phi and omega scans, and corrected with SADABS program. The
structures were solved by direct methods and all non-hydrogen
atoms were subjected to anisotropic refinement by full matrix
least-squares on F2 using SHELXTS 97 and SHELXTL 97 program
[29,30]. Non-hydrogen atoms were refined anisotropically and
hydrogen atoms were placed in calculated positions and refined
isotropically using a riding model. The important interatomic dis-
tances and angles are listed in Table 1, and The crystallographic data
2.3. Synthesis of [(TPTA)·H2O]n (2)
N,N0,N00-tris(3-pyridyl) trimesic amide(TPTA) (0.2 mmol) with
Table 2
Crystal data, experimental conditions, and structure refinement parameters of 1, 2, 3 and 4.
1
2
3
4
Empirical formula
Formula weight/g mol
Temperature/K
Wavelength/Å
C24H20O5N6
456.46
296(2)
C24H20N6 O3
456.46
296(2)
C14H12Hg1.5I3N4O2
949.86
296(2)
C24H18Hg I2N6O3
892.83
296(2)
0.71073
0.71073
0.71073
0.71073
Crystal size/mm
Crystal system
0.30 ꢂ 0.28 ꢂ 0.25
Monoclinic
Cc
0.20 ꢂ 0.20 ꢂ 0.18
Orthorhombic
Pbca
0.20 ꢂ 0.20 ꢂ 0.19
Monoclinic
P21
0.20 ꢂ 0.20 ꢂ 0.18
Monoclinic
P21/c
Space group
D
calc/g cmꢁ3
1.423
1.404
2.934
2.369
a/Å
b/Å
c/Å
17.7919(14)
14.5737(9)
8.3397(7)
99.900(5)
2130.2(3)
4
8.1083(15)
22.087(4)
24.109(4)
90.00
4317.6(13)
8
4.2062(3)
14.429(5)
19.984(7)
8.724(3)
95.681(9)
2503.2(15)
4
29.6215(19)
17.2646(10)
91.269(3)
2150.5(2)
4
ꢀ
b
/
V/Å3
Z
F(000)
q
952
1.82e25.00ꢀ
8049
1904
1.69e25.00ꢀ
16981
1676
1.37e25.00ꢀ
15040
1656
1.75e25.00ꢀ
16463
range for data collection/ꢀ
Reflections collected
R
0.0429
0.0627
0.0513
0.0457
int
GooF
Final R indices [I <2
R indices (all data)
Largest diff. peak and hole/e Åꢁ3
1.079
1.071
1.111
1.100
[a]
s
(I)]
R1 ¼ 0.0456, wR2 ¼ 0.0845
R1 ¼ 0.0587, wR2 ¼ 0.0948
0.128, ꢁ0.158
R1 ¼ 0.0595, wR2 ¼ 0.1252
R1 ¼ 0.0982, wR2 ¼ 0.1442
0.203, ꢁ0.209
R1 ¼ 0.0646, wR2 ¼ 0.1573
R1 ¼ 0.0668, wR2 ¼ 0.1599
4.112, ꢁ2.160
R1 ¼ 0.0395, wR2 ¼ 0.1036
R1 ¼ 0.0430, wR2 ¼ 0.1070
1.431, ꢁ1.655
[b]

116
L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
Scheme 1. The conformations of the ligand in crystal structures (trans and cis are defined based on the relative orientation of the amide oxygen and the pyridyl nitrogen. trans-
conformation means the two atoms are in the opposite side. cis-conformation means that the pyridine nitrogen atom and the amide oxygen atom of the ligand are in the same side).
Fig. 1. View of the molecular structure of L for the asymmetric unit in 1 (a) and 2 (b).
for compounds 1, 2, 3 and 4 are listed in Table 2.
Data Centre (CCDC) also discloses that TPTA ligand in the cis-cis-
trans-conformation and trans-trans-cis-conformation usually re-
sults in acentric coordination compounds, by contrast, TPTA ligand
in the cis-cis-cis-conformation and trans-trans-trans-conformation
often generate centrosymmetric coordination compounds. This is
well consistent with our results, indicating that acentric or
centrosymmetric feature of TPTA or TPTA coordination compounds
is highly relative to the conformation of TPTA ligands.
3. Results and discussion
Organic molecular crystals 1 and 2 are isomers. 1 was synthe-
sized with N,N0,N00-tris(3-pyridyl) trimesic amide(TPTA) in DMF-
water(5 mL/1 mL) solution at 115 ꢀC. The preparation of 2 is similar
to that of 1 except that the solvent mixture was replaced with DMF
(5 mL). Single crystal X-ray diffraction reveals that 1 crystallizes in
the monoclinic acentric Cc space group with Flack
factor ꢁ0.201(12), while 2 crystallizes in the orthorhombic space
group Pbca. The coordination compound 3 was synthesized with
HgI2 and TPTA ligand in acetonitrile-water(5 mL/1 mL) solution by
solvo(hydro)thermal reaction at 160 ꢀC, while the coordination
compound 4 was obtained under the same synthetic conditions but
in acetonitrile (5 mL).
Single crystal X-ray diffraction reveals that compound 3 crys-
tallizes in the acentric P21 monoclinic space group with Flack factor
of 0.1, whereas compound 4 crystallizes in the P21/c monoclinic
space group. X-ray diffraction reveals that the C3-symmetric
triangular ligand of TPTA in 1, 2, 3, 4 perform these conformations
as follows: cis-cis-trans, cis-cis-cis, trans-trans-cis, cis-cis-cis
(Scheme 1), where cis-conformation means that the pyridine ni-
trogen atom and the amide oxygen atom of the ligand are in the
same side, and trans-conformation means that the two atoms are in
the opposite side. Then, a query on Cambridge Crystallographic
3.1. Crystal structures
The asymmetric unit of both 1 and 2 containing one N,N0,N00-
tris(3-pyridyl) trimesic amide (TPTA) molecule and one isolated
water molecule are shown in Fig. 1. The terminal pyridyl groups of 1
are not co-planar with the central phenyl ring plane with dihedral
angles of ca. 8.76ꢀ, 27.40ꢀ, 9.45ꢀ(Fig. 1a), while in 2 the corre-
sponding values are ca. 37.47ꢀ, 25.23ꢀ, 20.23ꢀ, indicating more
intense distortion of the TPTA ligand in 2 (Fig. 1b). TPTA molecules
in 1 create a two-dimensional (2D) layer along c axis through
NeH/O (NeH/O ¼ 2.773(2), 2.786(2), 3.061(2) Å/161.40(4),
160.62(4), 160.85(4)ꢀ) and OeH/N (OeH/N ¼ 2.847(3), 2.869(3)
Å/174.37(4), 169.80(4)ꢀ) hydrogen bonds between the amide
groups (Fig. 2a, c). While in 2, it also create a two-dimensional (2D)
layer but V-shaped along
a
direction through NeH/O
(NeH/O
¼
2.996(2), 2.998(2) Å/150.69(4), 159.46(4)ꢀ) and
OeH/N (OeH/N ¼ 2.767(3), 2.942(3) Å/165.77(4), 170.59(4)ꢀ)

L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
117
Fig. 2. (a) The hydrogen bonds of compound 1 are represented by yellow dashed lines. (b) The hydrogen bonds of compound 2 are represented by yellow dashed lines. (c) Layered-
stacking structure of compound 1 along c direction. (d) V-shaped layer stacking structure of compound 2 along a direction. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)
hydrogen bonds between the amide groups (Fig. 2b, d).
As for compound 3, TPTA ligand in the trans-trans-cis-confor-
mation acts as a trigonal bridge to combine three Hg(II) centers
together. The asymmetric unit contains three unique Hg(II) ion-
s(Fig. 3). Both Hg1, Hg2 show the four-coordinated tetrahedral
geometry but Hg3 shows the five-coordinated pyramidal geometry
Fig. 3. The coordination surrounding around metal ions Hg(II) in 3. Symmetry transformations used to generate equivalent atoms: A: 1 þ x, y, z; B: ꢁ1þx, y, z. All hydrogen atoms
are omitted for clarity.

118
L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
Fig. 4. (a) The one-dimensional columnar pillar with sideboard-like channel of compound 3; (b) The one-dimensional columnar pillar stacking structure of compound 3.
Fig. 5. The coordination surrounding around metal ions Hg(II) in 4. Symmetry transformations used to generate equivalent atoms: A: 1 þ x, y, z; B: ꢁ1þx, y, z. All hydrogen atoms
are omitted for clarity.
and the coordination surrounding of them is described in detail
below. Hg1 is coordinated by N2 from TPTA ligand and I3, I4, I4B
(B: ꢁ1þx, y, z) from iodine ions Iꢁ; Hg2 is coordinated by N1 from
TPTA ligand and I1, I2, I1A (A: 1 þ x, y, z) from iodine ions Iꢁ; Hg3 is
coordinated by N3 from TPTA ligand and I5, I5B, I6, I6A from iodine
ions Iꢁ. The lengths of HgeI bond range from 2.631 Å to 3.527 Å,
Fig. 6. View of the one-dimensional chain structure of compound 4 (yellow stick represented screw axis). (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)

L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
119
which are all less than the sum of Hg (2.3 Å) and I (1.98 Å) van der
Waals radius. And the bond lengths of Hg1eN2, Hg2eN1 and
Hg3eN3 are 2.376(7)Å, 2.413(6)Å and 2.392(7)Å. The three termi-
nal pyridyl groups of TPTA are not co-planar with the central
benzene ring plane, giving the dihedral angles of ca. 20.16ꢀ, 28.27ꢀ,
20.24ꢀ.
Compound [HgI2(TPTA)$H2O]n (4) presents different structure
from 3, and the coordination surrounding drawing is shown in
Fig. 5, the asymmetric unit of 4 only contains one crystallography-
independent Hg(II) ion, which displays the four-coordinated
HgI2N2 tetrahedral geometry completed by two iodine atoms (I1,
I2) and two TPTA nitrogen atoms (N1, N6). The bond lengths of
Hg1eI1 and Hg1eI2 are 2.6290(9)Å, 2.6581(9)Å, respectively, while
the bond lengths of Hg1eN1 and Hg1eN2 are 2.396(6)Å, 2.6581(9)
Å. For TPTA ligand in the cis-cis-cis conformation, it takes the
bridging mode to connect with two Hg(II) ions with one pyridyl
nitrogen atom uncoordinated, and the corresponding dihedral an-
gles are ca. 13.58ꢀ, 59.38ꢀ, 34.49ꢀ, also indicating more intense
distortion of the TPTA ligand in 4. As shown in Fig. 4a, the Hg(II)
ions of 3 are integrated together to create a 1D columnar pillar with
sideboard-like channel (Fig. 4a, b). Nevertheless, in 4, along a axis
direction, the Hg(II) ions are integrated together to create a 1D
chain with a screw axis (Fig. 6).
Fig. 8. The solid-state emission spectrum of compound 3 and compound 4.
the TPTA ligand, and the red shift (9 nm, 6 nm) is mainly due to a
metal-to-ligand or ligand to-metal charge transfer [28].
3.2. TG-DTA, and photoluminescence properties
4. Conclusion
The thermostability of 3 and 4 are explored by TG studies at
35e800 ꢀC (Fig. 7). Thermogravimetric analysis of 3 reveals that the
weight loss (exp. 10.0%) in the temperature range of 35e200 ꢀC is
derived from one water molecule and two acetonitrile molecule
(calc. 10.5%). For 4, the first weight loss, 1.8%, at 35e150 ꢀC is
ascribed to the loss of one guest water molecules (calc. 2.0%). And
then the chemical decomposition temperature is estimated around
300 ꢀC. Compared with 3 and 4, we can obviously see that com-
pound 4 has higher thermal stability than 3.
The solid-state photoluminescence properties of 3 and 4 were
measured. As shown in Fig. 8, an intense emission of 3 occurs at
444 nm with an excitation wavelength of 313 nm, and 4 also dis-
plays one distinct emission peak at 441 nm under an excitation
wavelength of 322 nm. As we know, the emission is mainly derived
In conclusion, we successfully synthesized two isomeric organic
crystals and two HgI2-based coordination compounds using C3-
symmetric triangular ligand TPTA by solvo(hydro)thermal method.
We through a good deal of the literature researches find that the
compound structures are strongly correlated with the conforma-
tion of C3-symmetric triangular ligand. In the synthesis of com-
pound 1 and 3, we used some water as co-solvents to obtain two
noncentrosymmetric structures with TPTA ligands in cis-cis-trans-
conformation or trans-trans-cis-conformation. Importantly, based
on a tripodal ligand of N,N0,N00-tris(3-pyridyl) trimesic amide
(TPTA), we found that the presence of a small quantity of water
molecules as co-solvents would control the final structures from
centrosymmetry to noncentrosymmetry. To some extent, the re-
sults have opened a facile method towards generating non-
centrosymmetric structure.
from the
p*/n or p*/p transition. Meanwhile, the free TPTA
ligand exhibits a 435 nm blue emission under 320 nm excitation
[27], which indicates that the emissions of 3 and 4 originate from
Acknowledgment
This work was supported by the Foundation of Radioactive ge-
ology and National Defense Key Laboratory of exploration tech-
nology (2011RGET011), and Jiangxi Province Key Laboratory of
science and mass spectrometry instrument (JXMS201105), the
natural science foundation of Jiangxi Province (20122BAB213015),
and the science and technology project of Jiangxi Province
(20121BBG70011), and the Innovation Fund Designated for Grad-
uate Students of Jiangxi Province (YC2015-S274).
Appendix A. Supplementary materials
Crystallographic data (excluding structure factors) for the
structures in this paper have been deposited with the Cambridge
Crystallographic Data Centre, CCDC, 12 Union Road, Cambridge
CB21EZ, UK. Copies of the data can be obtained free of charge on
quoting the depository numbers CCDC-1061831 (1), CCDC-1061832
(2), CCDC-1061833 (3) and CCDC-1061831 (4) (Fax: þ44-1223-336-
033; E-Mail: deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
Fig. 7. The thermostability of 3 compound and compound 4.

120
L. Zhang et al. / Journal of Molecular Structure 1106 (2016) 114e120
[16] E.V. Anokhina, A.J. Jacobson, J. Am. Chem. Soc. 126 (2004) 3044.
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