Synthesis and crystal structure of charge transfer complex (CTC) of 2-aminobenzothiazole with its Schiff base

Article abstract of DOI:10.1007/s10870-011-0185-5

A novel charge transfer complex (CTC), C₁₄H₁₀N ₂OS·C₇H₆N₂S was synthesized by the reaction of 2-aminobenzothiazole (ABT) with its derivative Schiff base (2-((benzo[d]thiazol-2-ylimino) methyl) phenol is abbreviated as BYMBP) in THF. This complex was characterized by ¹HNMR, ¹³CNMR, IR and UV-vis. Crystal structure of the complex has been determined by X-ray diffraction. The crystal is triclinic, space group P-1 with the unit cell parameters a = 9.7732(5), b = 9.9936(4), c = 11.0193(7) A and α = 71.901(9), b = 78.686(10), c = 70.397(9)°, Z = 2, R = 0.0499. wR₂ = 0.1190. The structure of the title complex was fully optimized at the RB3LYP/6-311++g(d,p) level of theory and CTC's π-π stacking interaction, bond lengths (A) and angles (°) were calculated. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s10870-011-0185-5

J Chem Crystallogr (2011) 41:1844–1849
DOI 10.1007/s10870-011-0185-5
ORIGINAL PAPER
Synthesis and Crystal Structure of Charge Transfer Complex
(CTC) of 2-Aminobenzothiazole with Its Schiff Base
Huihong Li
Yong Zhang
•
Jing Li
•
•
Hongxia Chen
•
Dan Huang
Received: 1 May 2011 / Accepted: 26 September 2011 / Published online: 12 October 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A novel charge transfer complex (CTC),
C H N OSÁC H N S was synthesized by the reaction of
weak intermolecular interactions: p–p stacking, C–HÁÁÁp
and C–HÁÁÁN interactions, and these interactions bring
about charge transfer. Charge transfer compounds are
important components of optical material and have
gradually been an active research area. Among these,
D-A compounds exhibit particular optical properties
because of their unique molecular structure, so they have
been extensively investigated and widely used in lumi-
nescent, photoconductive, nonlinear optical material and
so on [1–14]. Based on these features, more and more
groups focus their research on charge transfer compounds,
of which the ligands containing the conjugate systems of
sulphur and nitrogen are widely studied currently. Ama-
nym had studied charge transfer complexes of Schiff
bases derived from 2-aminobenzothiazole with some
acidic and nonacidic acceptors [15]. Dumur et al. has
reported Q-TTF-Q(1) and Q-TTF-Q(2), these complexes
by themselves contain electron donor–acceptor (EDA)
which leads to charge transfer [16]. Liu et al. have shown
charge transfer complex TTF–TCNAQ [17]. These phe-
nomena are originated from interaction between electron
donor and acceptor molecules in biomolecular equilib-
rium or in model compounds with intramolecular inter-
action, which has been an important topic of research in
physical chemistry and biochemistry for many decades
1
4
10
2
7 6 2
2
-aminobenzothiazole (ABT) with its derivative Schiff
base (2-((benzo[d]thiazol-2-ylimino) methyl) phenol is
abbreviated as BYMBP) in THF. This complex was char-
1
13
acterized by HNMR, CNMR, IR and UV–vis. Crystal
structure of the complex has been determined by X-ray
diffraction. The crystal is triclinic, space group P-1 with the
unit cell parameters a = 9.7732(5), b = 9.9936(4),
˚
c = 11.0193(7) A and a = 71.901(9), b = 78.686(10),
c = 70.397(9)°, Z = 2, R = 0.0499. wR = 0.1190. The
2
structure of the title complex was fully optimized at the
RB3LYP/6-311??g(d,p) level of theory and CTC’s p–p
˚
stacking interaction, bond lengths (A) and angles (°) were
calculated.
Keywords Charge transfer complexes Á Schiff bases Á
X-ray diffraction Á p–p Stacking Á Theoretical calculations
Introduction
The arrangements of the molecules forming the packed
arrays are controlled by the interplay of several different
[
1–14]. So, syntheses of these complexes are always an
attractive theme in the area of physical chemistry and
biochemistry.
H. Li Á J. Li Á D. Huang (&)
In this paper, synthesis and crystal structure of a new
charge transfer complex was reported. In addition, the
structural details of the complex have been investigated
using RB3LYP/6-311??g(d,p) calculations [18]. In the
Key Laboratory of Eco-Textile (Jiangnan University) of Ministry
of Education, 214112 Wuxi, China
e-mail: huangdan6@163.com
H. Chen Á Y. Zhang Á D. Huang
˚
gas phase, p–p stacking interaction, bond lengths (A) and
angles ( ) were calculated, and charge transfer (CT) can be
Key Laboratory of Organic Synthesis of Jiangsu Province,
College of Chemistry, Chemical Engineering and Materials
Science, Soochow University, 215123 Suzhou, China
o
seen in its molecule.
1
23

J Chem Crystallogr (2011) 41:1844–1849
Experimental
1845
1
3
7.01–6.97 (m, 1 H, Ar); CNMR (CDC1 , 75 MHz) (d,
3
ppm): 169.2, 167.6, 162.2, 151.7, 135.6, 134.8, 134.3, 126.9,
-
1
General
125.5, 123.2, 122.0, 120.0, 118.5, 117.9. IR(KBr, cm ):
300 (bs), 3055(s), 2949(s), 2873(s), 1606(v), 1570(vs),
3
Melting points were determined in sealed argon-filled
capillaries and uncorrected. Carbon, hydrogen, and nitro-
gen analyse were performed by direct combustion on a
Carlo Erba-1110 instrument; quoted data are the average of
at least two independent determinations. The IR spectra
were recorded on a Nicolet-550 FTIR spectrometer as KBr
pellets. The single crystal X-ray diffraction data were
recorded on a Rigaku Mercury CCD X-ray diffractometer.
1502(m), 1452(m), 1377(s), 1284(m), 1174(m), 1149(m),
1063(m), 901(s), 800(s), 754(s), 723(m), 679(m), 617(m).
Synthesis and Character of Charge Transfer Complex
(CTC)
The CTC was prepared by mixing the equimolar amounts
of BYMBP and ABT in THF at 60 °C for 8 h, during the
time the pale yellow color changed gradually to yellow.
The precipitate was removed from the reaction mixture by
centrifugation, and THF was completely evaporated in
vacuum, and ethanol was added to extract the product.
Insoluble CTC was purified by being heated with ethanol
several times to remove any contaminants, and the com-
plex was filtered off, dried in vacuum. The crystal was
grown from an ethanol-toluene mixture (1:10). Yellow
microcrystals were obtained at room temperature in a few
days, m.p.: 176–178 °C (dec). Anal. Calc. for C H N
1
13
H NMR and C NMR spectra were recorded on a Unity
Inova-300 spectrometer. UV–vis spectra were recorded on
a Shimadzu UV-3150 spectrometer. All calculations were
carried out with the RB3LYP/6-311??g(d,p) [18].
Synthesis
Synthesis and Character of Schiff Bases (BYMBP)
2
-Aminobenzthiazole (ABT): The aniline (0.1 mol) and
2
1 16 4
ammonium thiocyanate (0.2 mol) in 150 mL of glacial
acetic acid were cooled in an ice bath and stirred
mechanically. To the solution, bromine (0.2 mol) in 25 mL
of glacial acetic acid was added dropwise at such a rate to
keep the temperature below 10 °C throughout the addition.
Stirring was continued for additional thirty minutes after
the bromine addition. The precipitate of the benzthiazole
hydrobromide was collected, dissolved in hot water and
basified with a saturated sodium carbonate solution. The
free substituted benzthiazol was collected, washed with
water and dried under vacuum. Recrystallization from the
OS : C, 62.35; H, 3.99; N, 13.85; S, 15.85%. Found: C,
2
1
62.35; H, 3.99; N, 13.85; S, 15.85%. HNMR (CDC1 ,
3
300 MHz) (d, ppm): 12.24 (s, 1 H, OH), 9.29 (s, 1 H,
CH=N), 7.99 (d, J = 8.2 Hz, 1 H, Ar), 7.86 (d,
J = 7.8 Hz, 1 H, Ar), 7.61–7.46 (ovm, 5 H, Ar), 7.38 (t,
J = 7.7 Hz, 1 H, Ar), 7.32 (t, J = 7.7 Hz, 1 H, Ar), 7.14
(t, J = 7.8 Hz, 1 H, Ar), 7.07 (d, J = 8.4 Hz, 1 H, Ar),
7.01 (t, J = 7.6 Hz, 1 H, Ar), 5.25 (brs, 2 H, –NH );
2
1
3
CNMR (CDC1 , 75 MHz) (d, ppm): 170.4, 167.6, 135.7,
3
134.3, 127.0, 126.2, 125.5, 123.2, 122.6, 122.0, 121.1,
-
1
120.1, 119.5, 118.6, 118.5, 117.9. IR(KBr, cm ):
3340(s,b), 3275(s,b), 3072(s), 2764(m), 2650(m), 1661(s),
1606(s), 1571(vs), 1541(s), 1501(s), 1478(s), 1448(s),
1316(m), 1288(s), 1255(m), 1239(m), 1182(s), 1149(s),
1123(m), 1064(m), 1017(m), 968(w), 931(w), 893(m),
889(s), 849(m), 788(m), 754(s), 724(s), 692(s).
appropriate solvent gave 2-aminobenzthiazol in good yield
1
(
88.5%). m.p.: 129–130 °C. HNMR (CDCl , 300 MHz)
3
(d, ppm): 7.57–7.52 (m, 2 H, ArH), 7.29–7.12 (m, 2 H,
ArH), 5.85 (brs, 2 H, –NH2); CNMR (CDC1 , 75 MHz)
1
3
3
(
d, ppm): 166.4, 152.0, 131.5, 126.0, 122.2, 120.9, 119.0.
IR (KBr, cm ): 3399(s), 3274(m), 3067(s), 2929(m),
-
1
1
1
7
645(s), 1530(s), 1448(s), 1316(m), 1310(m), 1285(m),
123(m), 1017(m), 920(m), 889(m), 741(s), 720(sh),
06(s), 687(m), 484(m).
Results and Discussion
Schiff bases (BTYMP): To a 10 mL EtOH solution of
Synthesis and Molecular Structure of the 1:1 Complex
of ABT with BYMBP
salicylaldehyde and a catalytic amount of formic acid was
added a 5 mL EtOH solution of the appropriate amine
(
0.9 eq.). The mixture was refluxed for 8 h and the solution
BYMBP was prepared as described previously [15], and
treated with 1 equiv of ABT in THF at 60 °C in order to
prepare the corresponding 1:1 complex. The reaction went
smoothly and after workup, the desired 1:1 complex was
isolated in good yield as yellow crystals upon crystalliza-
tion from toluene. Scheme 1 shows the reaction sequence.
The IR spectra of this complex exhibited the strong
stored at 5 °C overnight. The resulting precipitate was col-
lected by suction filtration and washed with Et O
2
(
3 9 10 mL). Yield: 85% of an orange solid, m.p.:
1
1
50–151 °C. HNMR (CDC1 , 300 MHz) (d, ppm): 12.24
3
(
s, 1 H, OH), 9.26 (s, 1 H, CH=N), 7.98 (d, J = 8.2 Hz, 1 H,
Ar), 7.84 (d, J = 7.8 Hz, 1 H, Ar), 7.52–7.45 (ov m, 3 H, Ar),
.40–7.35 (m, 1 H, Ar), 7.06 (d, J = 8.4 Hz, 1 H, Ar),
-
1
7
absorptions near 1571 and 1541 cm indicating partial
123

1
846
J Chem Crystallogr (2011) 41:1844–1849
Scheme 1 Synthesis of
ABT:BYMBP complex
CHO
H
C
NH2
N
Br /HAc
N
S
OH
2
+
NH SCN
N
S
4
NH2
EtOH, cat:formic acid
OH
2
rm
C=N double bond character [19]. This complex was further
characterized by X-ray structure analysis. Figure 1 and 2
show the molecular structure and the packing of the title
compound, respectively. The value of calculation and test
of selected bond lengths and bond angles are given in
Table 1. Single-crystal X-ray structure determination
reveals that one unit cell of the title compound contains
two independent molecules BYMBP and ABT in its crys-
tals. From Fig. 2 we see a very interesting property of
ABT:BYMBP: along the b axis, the nearby units con-
˚
necting with p–p stacking (ca.3.43 A) of thiazole ring
formed a 2D necklace-like supramolecular chain. These
chains formed by N(3)–H(3B)ÁÁÁN(2) and N(3)–
H(3A)ÁÁÁN(4) lying paralleled to each other, resulting in a
two-dimensional hydrogen-bonded layer along the ab and
ac plane, respectively (Fig. 2). The layers are further
extended into a three-dimensional (3D) supramolecular
array through hydrogen-bonded interactions, which are
offset p–p stacking interactions with the face-to-face dis-
˚
tance of ca. 3.43 A between thiazole rings. Each uncoor-
dinated N3 of thiazole from one chain forms an NÁÁÁH–O
hydrogen bond with a hydroxyl group from another nearby
chain. The packing of the title compound can be described
as parallel-sandwich geometry (Fig. 2). In addition,
Fig. 1 Crystal structure of ABT:BYMBP complex
Table 1) in the same formation, and O(1)–H(1)ÁÁÁN(1) are
the last hydrogen bonds which are the weakest in this 1:1
complex. It is very interestingly observed in this 2D array,
and they are four types of hydrogen-bonded patterns A–D.
All calculations were carried out with the RB3LYP/6-
311??g(d,p) [18], and the result of the calculations were
in accordance with the result of using X-Ray.
2
2
-aminobenzothiazole (ABT) acts as
a donor and
-((benzothiazol-2-ylimino)methyl)-4,6-di-tert-butylphenol
(
BYMBP) acts as a acceptor, four ABT occupy the four
apical positions, formed the intermolecular hydrogen bond
and p–p stacking of the complex when two ABT molecules
were antiparallel, simultaneously, each ABT using the
amino nitrogen atom and benzothiazole nitrogen atom of
BYMBP, forms one kind of hydrogen bonds (N(3)–
H(3B)ÁÁÁN(2), Table 1) [20, 21]. Each BYMBP making use
of benzothiazole carbon atom and hydroxyl oxygen atom
forms the other kind of hydrogen bonds (C(10)–
H(10)ÁÁÁO(1), Table 1). Additionally, each ABT making
use of thiazole nitrogen atom and amino nitrogen atom
forms another kind of hydrogen bonds (N(3)–H(3A)ÁÁÁN(4),
RB3LYP/6-311??g(d,p) Calculations
The structures of ABT:BYMBP optimized by the
RB3LYP/6-311??g(d,p) [18] approach are shown in
Fig. 3. The calculated bond lengths, bond and torsion
angles are given in Table 2. Structure (a) shows a monomer
of the 1:1 complex in which the hydroxyl group of
1
23

J Chem Crystallogr (2011) 41:1844–1849
1847
Fig. 2 Packing of the
ABT:BYMBP complex
o
Table 1 Selected bond lengths (A) and angles ( ) for ABT:BYMBP complex
˚
Parameters
X-ray
RB3LYP/6-311??g(d,p)
Parameters
X-ray
RB3LYP/6-311??g(d,p)
S(1)–C(9)
1.734(3)
1.759(2)
0.830
1.757
1.820
0.995
2.121
2.390
2.555
87.84
87.98
108.0
S(2)–C(16)
1.737(3)
1.760(3)
0.898(10)
0.883(10)
1.87
1.764
1.792
1.012
1.011
1.874
S(1)–C(8)
S(2)–C(15)
O(1)–H(1)
N(3)–H(3A)
N(3)–H(3B)
O(1)–H(1)–N(1)
N(3)–H(3B)–N(2)
N(3)–H(3A)–N(4)
C(10)–H(10)–O(1)
C(16)–S(2)–C(15)
C(9)–S(1)–C(8)
C(1)–O(1)–H(1)
2.122(12)
2.064(11)
2.56
89.27(12)
88.66(12)
109.5
H(3A)–N(3)–H(3B)
C(15)–N(3)–H(3B)
C(15)–N(3)–H(3A)
119(3)
114.6
113.5
117.7
118(2)
122.2(18)
All calculations were carried out with the RB3LYP/6-311??g(d,p) level of theory [18]
1 -x ? 1, -y, -z ? 1; #2 -x ? 1, -y ? 1, -z; #3 x, y ? 1, z
#
BYMBP interacts with the amine group of ABT, through
˚
treated as idealized contributions. The structure was solved
and refined using SHELXS-97 programs. Crystal and
refinement data for complex are listed in Table 3.
the N(3)–H(3B)ÁÁÁN(4) hydrogen bond of 2.121 A, shorter
˚
by 0.001 A than in the crystal (Table 2). In the optimized
structure (b) the hydroxyl group of BYMBP is engaged in
the N(3)–H(3A)ÁÁÁN(4) hydrogen bond, which is by 0.326
Ultraviolet Spectral Studies
˚
A longer than in the crystal.
The electronic absorption spectra of the donor (ABT),
acceptors (BYMBP) and the resulting complex in ethanol
were recorded by UV–vis with a 1 cm quartz cell at room
temperature. The ultraviolet spectra of these compounds
are shown in Fig. 4. ABT:BYMBP compound shows a
moderately intense absorption band at 376 nm, while such
a band is absent in the parent ABT. However, at 326 nm
for the parent BYMBP, the CT band with a red shift, Dk
X-Ray Crystallography
Diffraction data were collected on a Rigaku Mercury CCD
area detector. The structure was solved by direct methods
and refined by full-matrix least-squares procedures based
2
on |F| . All non-hydrogen atoms were refined with aniso-
tropic displacement coefficients. Hydrogen atoms were
123

1
848
J Chem Crystallogr (2011) 41:1844–1849
Fig. 3 The optimized structures
of ABT:BYMBP by the
RB3LYP/6-311??g(d,p)
method, a monomer connected
by the N(3)–H(3B)ÁÁÁN(4)
hydrogen bond, b monomer
connected by N(3)–
H(3A)ÁÁÁN(4) hydrogen bond
˚
Table 2 Experimental and calculated bond lengths (A)
˚
Hydrogen bond lengths (A)
X-ray
RB3LYP/6-311??g(d,p)
and p–p stacking
N(3)–H(3A)ÁÁÁN(4)
N(3)–H(3B)ÁÁÁN(2)
O(1)–H(1)ÁÁÁN(1)
C(10)–H(10)ÁÁÁO(1)
p–p stacking
2.064
2.122
1.87
2.390
2.121
1.874
2.555
2.56
˚
3.43 A
˚
3.43 A
Table 3 Crystallographic data for complex
Complex
Formula
21 16 4 2
C H N OS
F
w
404.50
223(2)
Fig. 4 Absorption spectra of ABT, BYMBP and ABT:BYMBP
(
-
10 mol L ) in ethanol
6
-1
T (K)
Crystal system
Space group
Triclinic
P-1
˚
a (A)
about 50 nm, indicates that BYMBP is an efficient electron
acceptor, which makes the charge transfer (CT) easier.
Thus, ABT:BYMBP compound is a good D-A compound.
9.7732(5)
9.9936(4)
˚
b (A)
˚
c (A)
11.0193(7)
78.686(10)
958.61(9)
2
b (deg)
3
V (A )
˚
Conclusion
Z
D
calc
1.401
-
1
The 1:1 complex of BYMBP with ABT was obtained.
According to the structure analysis, three chemistry inter-
actions can be seen in its structure, p–p stacking, hydrogen
bond and charge transfer. Synthesizing more 1:1 complex
remains an important task for further research.
l (mm
F (000)
Crystal size (mm)
)
0.298
420
0.30 9 0.22 9 0.08
H
max (°)
25.50
8295
3535
2724
263
Reflections collected
Independent reflections
Observed reflections
Parameters refined
R
Supplementary Data
0.0499
0.1190
1.061
Additional crystallographic data have been deposited at the
Cambridge Crystallographic Data Centre, CCDC reference
number is 746489 for the complex. The data can be
wR
2
2
GOF on F
1
23

J Chem Crystallogr (2011) 41:1844–1849
1849
obtained free of charge from 178 www.ccdc.cam.ac.uk/
conts/retrieving.html (or from CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax:?44 1223 336 033; e-mail:
deposit@ccdc.cam.ac.uk.)
13. Dozal A, Keyzer H, Kin HK, Way WW (2000) Int J Antimicrob
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Acknowledgments We are grateful for the support from the Open
Project Program (KJS1007) of Key Lab. of Organic Synthesis
17. Wu JC, Liu SX, Neels A, Derf FL, Salle M, Decurtins S (2007)
Tetrahedron 63:11282
(
Soochow University) of Jiangsu Province.
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