Synthesis, crystal structures, and nonlinear optic and thermal properties of two diiodocarbazole derivatives

Article abstract of DOI:10.3184/174751917X14839766277297

Two 3,6-diiodocarbazole derivatives were prepared from the iodination of the corresponding phenylcarbazole. 3,6-Diiodo-9-phenylcarbazole crystallises in the chiral space group P2₁ and shows good second-harmonic generation effects. Thermogravime

Full text of DOI:10.3184/174751917X14839766277297

JOURNAL OF CHEMICAL RESEARCH 2017
VOL. 41 FEBRUARY, 79–81
RESEARCH PAPER 79
Synthesis, crystal structures, and nonlinear optic and thermal properties of
two diiodocarbazole derivatives
Gui-Mei Tanga*, Rui-Hai Chia, Wen-Zhu Wana, Yong-Tao Wanga*, Yue-Zhi Cuia, and Seik Weng Ngb
aDepartment of Chemical Engineering, Shandong Provincial Key Laboratory of Fine Chemicals, Qilu University of Technology, Jinan 250353, China
bChemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
Two3,6-diiodocarbazolederivativeswerepreparedfromtheiodinationofthecorrespondingphenylcarbazole.3,6-Diiodo-9-phenylcarbazole
crystallises in the chiral space group P21 and shows good second-harmonic generation effects. Thermogravimetric analysis of the two
compounds shows high thermal stabilities, in which the decomposition temperature for 1 and 2 are 273 and 308 °C, respectively.
Keywords: phenylcarbazole, iodination, infrared spectra, UV-Vis and NMR spectra, X-ray diffraction, crystal structures, nonlinear optics
Carbazoles are an important type of heterocyclic organic
compounds in the field of organic fluorescence materials, gas
absorption, and separation and nonlinear optics1–3 as they have
efficient hole-transporting capability and electronic properties.4–6
More importantly, the synthesis and characterisation of
iodocarbazoles are of interest. Most iodocarbazoles are obtained
by iodination using a mixture of KI and KIO3 under acidic
conditions.7,8
In particular, di- and poly-iodocarbazole derivatives have
attracted much attention because they are key intermediates in the
design and development of interesting optoelectronic materials.7–11
Notably, diiodocarbazole compounds play a key role in the design
and development of novel optoelectronic materials. However, there
is little of knowledge of the relationship between structure and
properties for these compounds in solid state. Thus, determining
detailed structural information and the structure–property
relationships for diiodocarbazoles still remains a formidable
challenge.
Prompted by these elegant studies on the interesting properties
of carbazole derivatives, and understanding the importance of
the structure–property relationships of organic iodo-compounds,
we synthesised two derivatives containing a 3,6-diiodocarbazole
moiety: 3,6-diiodo-9-phenylcarbazole (1) and 9-(4-bromophenyl)-
3,6-diiodocarbazole (2) (Schemes 1 and 2), and characterised them
by FTIR, UV-Vis, 1H NMR, and single-crystal X-ray diffraction.
Compounds 1 and 2 crystallised in chiral and centrosymmetric
space groups, respectively. In addition, we investigated their
thermal properties in detail and the nonlinear optic properties of
compound 1 were studied.
X-ray diffraction analysis of compound 1 revealed that it
crystallises in the chiral space group P21. As illustrated in Fig. 1,
in an asymmetric unit, there are two unique molecules of 1. The
first molecule contains I1 and I2 groups. The C–I bond distances
are 2.124 (9) and 2.054 (10) Å. There is two-fold disorder of the
9-position phenyl group and the dihedral angle between the phenyl
group and the five-member ring is about 43.9°. Interestingly, the
dihedral angles between the three fused rings Cg1–Cg2, Cg2–Cg3,
and Cg1–Cg3 (where Cg1, Cg2 and Cg3 are C1–C2–C3–C4–
C5–C6, N1–C6–C1–C7–C12, and C7–C8–C9–C10–C11–C12,
respectively) are 2.36°, 6.84°, and 4.6°, respectively, indicating that
the whole carbazole moiety is rather planar.
I
2
3
1
1
1
12
14
4
9
13
N
R
10
5
15
8
6
7
1
2
R = H ( )
In the second molecule, the C–I bond lengths are 2.043 (9)
and 2.120 (9) Å, which are comparable to those in the first
molecule. The 9-position phenyl group in the carbazole group
I
Br ( )
Scheme 1
I
i
N
R
N
R
I
1
R = H ( )
2
Br ( )
Reaction conditions: i) KI, KIO3, glacial acetic acid, 135 oC, 18 h
Scheme 2
* Correspondent. E-mail: ceswyt@qlu.edu.cn

80 JOURNAL OF CHEMICAL RESEARCH 2016
Fig. 1 A perspective of compound 1.
the corresponding dihedral angle in compound 1, which can
be attributed to the stereo-hindrance effect of the substituent
bromo group. Compared with the structure of compound 1, the
phenyl group at the 9-position of the carbazole ring in 2 does
not display disorder.
Given that compound 1 crystallised in the chiral space
group P21, the effect of second-harmonic generation (SHG)
for compound 1 was investigated. The primary experimental
results revealed that compound 1 is SHG active, and displays
a moderate SHG efficiency. The effect of SHG for compound 1
is twice than that of KH2PO4, which may be mainly attributed
to a good donor–acceptor system (Scheme 1) and the orderly
arrangement of the organic moieties. The experimental results
further identified the arrangement of the organic moieties
obtained by the single-crystal structure mentioned above.
In summary, we successfully obtained two compounds,
3,6-diiodo-9-phenylcarbazole and 9-(4-bromophenyl)-3,6-
diiodocarbazole, which were structurally characterised by
FTIR, UV-Vis, 1H-NMR, elemental analysis, and single-crystal
X-ray diffraction. Both compounds displayed good thermal
stability. Single-crystal diffraction analysis revealed packing
interactions in the structures of the compounds. Interestingly, the
packing interactions in 9-(4-bromophenyl)-3,6-diiodocarbazole
with a bromine substituent were obviously stronger than those
of 3,6-diiodo-9-phenylcarbazole. Furthermore, compound
1 showed strong SHG efficiency, and may be a promising
nonlinear optic material. The design and development of other
diiodocarbazole-based derivatives is ongoing in our laboratory.
Fig. 2 A perspective of compound 2.
also occurs in the formation of two-fold disorder. The dihedral
angles between the N-phenyl group and the five-member ring
are observed to be 52.6° and 47.4°. As a result, the average
dihedral angle is 50°, which is much higher than that in the first
molecule.
X-ray diffraction of compound 2 revealed that it crystallises
in the space group P21/c. As shown in Fig. 2, there is only one
molecule of 2 in the asymmetric unit. The molecule contains
two kinds of halogen atoms: Br and I. The C–I bond distances
are 2.094 (8) and 2.090 (8) Å, which are comparable to those
in compound 1. The Br–C bond length is 1.909 (7) Å. The bond
length of N1–C13 (1.422 (9) Å) in the Br-phenyl ring is obviously
longer than that of N1–C6 (1.389 (10) Å) or N1–C12 (1.400 (10)
Å) in the carbazolyl ring and shorter than the common C–N
bond (1.52 Å), which indicates the formation of conjugation
between the carbazole group and the Br-phenyl group. In the
carbazole group, the dihedral angles of the adjacent aromatic
rings are 0.40°, 0.65°, and 0.67° for Cg1–Cg2, Cg2–Cg3, and
Cg3–Cg1 (Cg1, Cg2, and Cg3 represent C1–C2–C3–C4–C5–
C6, N1–C6–C1–C7–C12, and C7–C8–C9–C10–C11–C12,
respectively), respectively. Interestingly, the whole carbazole
ring has a co-planar structure, which can be ascribed to the
small dihedral angle (average 0.66°) between the three aromatic
rings of the carbazole group. Obviously, this dihedral angle is
smaller than the corresponding dihedral angle in compound 1,
which may be due to the disordered structure of the N-phenyl
group. A dihedral angel of 53.8° in compound 2 is observed
between the Br-phenyl group and the five-member ring in the
carbazole system. This dihedral angle is much larger than
Experimental
9-Phenylcarbazole and 9-(4-bromophenyl)carbazole were obtained
from Zhengzhou HQ material Co., Ltd. and Puyang Chemical
Factory, respectively. Potassium iodide and sodium thiosulfate
pentahydrate were purchased from The Third Plant of Tianjin
Chemical Reagent. Potassium iodate and acetic acid are obtained
from Tianjin Bo Di Chemical Co., Ltd. and Jinan Reagent General
Factory, respectively. The reagents and solvents employed were used
as received without further purification. Elemental analyses were
performed on an Elementar Vario EL III microanalyser. The FTIR
spectra were recorded from KBr pellets in the range 400–4000 cm−1
on a Bruker spectrometer. NMR spectra were recorded using a Bruker
Advances 400 spectrometer at 400 MHz for samples dissolved in
CDCl3 and held at room temperature. The absorption spectra were
recorded with an absorption spectrophotometer model TU-1900/1901.
Thermogravimetric analysis data were collected with a TA SDT
Q600 analyser in N2 at a heating rate of 10 °C min−1 in the range of
20–750 °C. Kurtz powder SHG measurements were performed on
ground samples of crystalline compound 1 with a synchroscan streak
camera (Hamamatsu Model C1587, 8 ps resolution) connected to

JOURNAL OF CHEMICAL RESEARCH 2016 81
a polychromator as the detector system, and an optical parametric
generator (Spectra Physics, Model: OPA-800C) pumped by a mode-
locked Ti:sapphire laser oscillator–amplifier system (Spectra Physics,
Model: Hurricane) as the pump source. The powder second-harmonic
signals were compared with that of KH2PO4 to determine the relative
SHG efficiencies of compounds 1 and 2, respectively.
Synthesis of 3,6-diiodo-9-phenylcarbazole (1)
A mixture of 9-phenylcarbazole (0.2433 g, 0.1 mmol), potassium
iodide (0.6640 g, 4.0 mmol) and potassium iodate (0.4277 g, 2.0
mmol) was refluxed for 18 h in glacial acetic acid (50 mL). The colour
of the solution changed from purple to chocolate brown. After the
reaction was completed, the mixture was left to cool naturally. The
precipitate was separated and washed with 10% sodium hyposulfite
solution (50 mL) and distilled water (30 mL) successively. The white
needles obtained were further dried and recrystallised from alcohol to
give compound 1 as white crystals: m.p. 185–186 °C; yield 0.3703 g
(74.8%); 1H NMR (400 MHz, Chloroform-d1): δ 8.40 (s, 2H), 7.71–7.58
(m, 4H), 7.50 (t, J = 9.4 Hz, 3H), 7.16 (d, J = 8.6 Hz, 2H); FTIR (KBr)
(cm−1): 3134(s), 1595(m), 1500(w), 1463(s), 1427(s), 1400(s), 1278(m),
1228(s), 1014(m), 867(w), 798(m), 756(m), 696(w), 630(w), 565(w),
563(w). Anal. calcd for C18H11I2N: C, 43.67; H, 2.24; N, 2.83; found: C,
43.54; H, 2.23; N, 2.84%.
Single-crystal structure determinations of compounds 1 and 2 were
measured by a Bruker Smart CCD diffractometer equipped with
graphite–monochromator Mo Kα radiation (λ = 0.71073 Å). The
lattice parameters were obtained by a least-squares refinement of the
diffraction data. All the measured independent reflections were used in
the structural analysis, and semi-empirical absorption corrections were
applied using the SADABS program.12 The program SAINT was used
for integration of the diffraction profiles.13 The structure was solved by
direct methods using the SHELXS program of the SHELXTL package
and refined with SHELXL.14,15 All non-hydrogen atoms were located
in successive difference Fourier syntheses. The final refinement was
performed by full-matrix least-squares methods with anisotropic
thermal parameters for all the non-hydrogen atoms based on F2. The
hydrogen atoms were placed in the calculated sites and included in the
final refinement in the riding model approximation with displacement
parameters derived from the parent atoms to which they were bonded.
Special computations for the crystal structure discussions were carried
out with PLATON for Windows.16 A summary of the crystallographic
data and structure refinements are listed in Table 1. The IR, UV-
Synthesis of 9-(4-bromophenyl)-3,6-diiodocarbazole (2)
The preparation procedure for compound 2 was similar to that
for 1 except that 9-(4-bromophenyl) carbazole took the place of
9-phenylcarbazole. The pink crystals obtained were further dried and
recrystallised from alcohol to give compound 2 as pale yellow crystals:
yield 0.472 g (82.22%); m.p. 234–235 °C; 1H NMR (400 MHz,
Chloroform-d1): δ 8.39 (s, 2H), 7.75 (d, J = 8.1 Hz, 2H), 7.68 (d, J = 8.6
Hz, 2H), 7.37 (d, J = 8.1 Hz, 2H), 7.12 (d, J = 8.6 Hz, 2H); FTIR (KBr)
(cm−1): 3134(s), 1585(w), 1490(s), 1425(s), 1400(s), 1226(m), 1068(m),
933(s), 867(s), 827(s), 794(s), 630(m), 563(m), 497(w). Anal. calcd
for C18H10BrI2N: C, 37.67; H, 1.76; N, 2.44; found: C, 37.45; H, 1.75; N,
2.45%.
1
Vis, H-NMR and thermogravimetric analysis data are provided in
the Electronic Supplementary Information. Selected bond lengths
and angles are given in Table S1 in the Electronic Supplementary
Information. Corresponding packing interactions data for compounds
1 and 2 are listed in Tables S2 and S3 in the Electronic Supplementary
Information.
Acknowledgements
This work was financially supported by J09LB03,
BS2011CL034, and NSFC (No. 21276149).
Table 1 Crystal data and structure refinement parameters for 1 and 2
Electronic Supplementary Information
Compound
Chemical formula
Formula mass
Crystal system
a/Å
1
2
The ESI is available through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data.
C18H11I2N
495.08
monoclinic
12.3621 (9)
4.8724 (4)
27.031(2)
90.00
103.1897 (9)
90.00
1585.2 (2)
293 (2)
P21
C18H9BrI2N
573.98
monoclinic
4.4724 (4)
13.9377 (12)
27.172 (2)
90.00
90.0720 (10)
90.00
1693.8 (3)
293 (2)
P21/c
Received 10 December 2016; accepted 20 December 2016
Paper 1604476 DOI: 10.3184/174751917X14839766277297
Published online: 10 February 2017
b/Å
c/Å
References
α/°
β/°
γ/°
1
B.R. Rosen, E.W. Werner, A.G. O’Brien and P.S. Baran, J. Am. Chem. Soc.,
2014, 136, 5571.
2
3
4
5
S. Qiao, Z. Du and R. Yang, J. Mater. Chem. A, 2014, 2, 1877.
X. Sun, Y. Wang and Y. Lei, Chem. Soc. Rev., 2015, 44, 8019.
J.L. Li and A.C. Grimsdale, Chem. Soc. Rev., 2010, 39, 2399.
K. Shizu, J. Lee, H. Tanaka, H. Nomura, T. Yasuda, H. Kaji and C. Adachi,
Pure Appl. Chem., 2015, 87, 627.
Unit cell volume/Å3
Temperature/K
Space group
6
7
Y. Tao, C. Yang and J. Qin, Chem. Soc. Rev., 2011, 40, 2943.
Z. Zhao, J.-H. Li, X. Chen, X. Wang, P. Lu and Y. Yang, J. Org. Chem.,
2009, 74, 383.
D. Raksasorn, S. Namuangruk, N. Prachumrak, T. Sudyoadsuk, V.
Promarak, M. Sukwattanasinitt and P. Rashatasakhon, RSC Adv., 2015, 5,
72841.
No. of formula units per unit cell, Z
Radiation type
Absorption coefficient, μ/mm−1
No. of reflections measured
No. of independent reflections
Rint
Final R1 values (I > 2σ(I))a
Final wR(F2) values (I > 2σ(I))b
Final R1 values (all data)a
Final wR(F2) values (all data)b
Goodness of fit on F2
CCDC number
4
Mo K
3.960
14083
4
Mo K
6.068
18577
8
7166
3825
9
M.J. Xiong, Z.H. Li and M.S. Wong, Aust. J. Chem., 2007, 60, 603.
0.0338
0.0421
0.0826
0.0629
0.0934
1.026
0.0567
0.0468
0.0919
0.0824
0.1017
10 G.G. Abashev, E.V. Shklyaeva, R.V. Syutkin, K.Y. Lebedev, I.V. Osorgina,
V.A. Romanova and A.Y. Bushueva, Solid State Sci., 2008, 10, 1710.
11 B. Gupta, A.K. Singh, A.A. Melvin and R. Prakash, Solid State Sci., 2014,
35, 56.
12 G.M. Sheldrick, SADABS, University of Göttingen, Göttingen, 1996 and
2003.
13 Bruker and AXS, SAINT software reference manual, Madison, WI, 1998.
14 G.M. Sheldrick, SHELXTL NT Version 5.1. Program for solution and
refinement of crystal structures, University of Göttingen, Göttingen, 1997.
15 G.M. Sheldrick, Acta Crystallogr. Sect. A, 2008, 64, 112.
16 A.L. Spek, J. Appl. Cryst., 2003, 36, 7.
1.057
1437027
1437026
aR1 = Σ||Fo| − |Fc||/ Σ|Fo|.
bwR2 = [Σ[w(Fo − Fc )2] / Σ[w(Fo )2]]1/2.
2
2
2