Anchoring pyrazolines on a 2,2′:6′,2″-terpyridine backbone

Article abstract of DOI:10.1016/j.molstruc.2017.07.057

Introducing pyrazoline derivatives into the classical 2,2′:6′,2″-terpyridine (2,2′:6′,2″-tpy) backbone leads to the synthesis of a new class of compounds, 4′-pyrazolinyl-2,2′:6′,2″-tpys. Six such derivatives bearing differently substituted pyrazolines hav

Full text of DOI:10.1016/j.molstruc.2017.07.057

Journal of Molecular Structure 1148 (2017) 397e403
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
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Anchoring pyrazolines on a 2,2 :6 ,2 -terpyridine backbone
a
a
a
b
b
b, *
E Liu , Li Li , Hangxing Xiong , Corinna Chan , Jessica Cheng , Guoqi Zhang
a
Hubei Key Laboratory of Drug Synthesis and Optimization, Jingchu University of Technology, Hubei 448000, China
Department of Sciences, John Jay College and the Graduate Center, The City University of New York, New York, NY 10019, USA
b
a r t i c l e i n f o
a b s t r a c t
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Introducing pyrazoline derivatives into the classical 2,2 :6 ,2 -terpyridine (2,2 :6 ,2 -tpy) backbone leads
Article history:
Received 2 June 2017
Received in revised form
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to the synthesis of a new class of compounds, 4 -pyrazolinyl-2,2 :6 ,2 -tpys. Six such derivatives bearing
differently substituted pyrazolines have been synthesized with a facile two-step procedure using simple
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July 2017
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chalcone compounds and 4 -hydrazino-2,2 :6 ,2 -tpy as starting materials, and they were fully charac-
terized by IR, NMR, MS and elemental analysis. Two representative crystal structures have been deter-
mined by single crystal X-ray diffraction analysis. The solid state structures reveal the presence of two
enantiomers as a racemate in each of these compounds and the arrangement between aromatic rings in
both tpy and pyrazoline domains can be affected by the substituents. The intermolecular packing is
Accepted 20 July 2017
Available online 24 July 2017
Keywords:
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,2 :6 ,2 -Terpyridine
2
mainly driven by the
sorption and emission behaviors of the new compounds were also investigated.
© 2017 Elsevier B.V. All rights reserved.
p-stacking interactions between aromatic regions. The solution electronic ab-
Pyrazoline
Crystal structure
p-Stacking
Fluoresence
1
. Introduction
explored in the past decades [26e34]. Due to its easiness of syn-
0
thesis, introducing an additional functional group in the 4 -position
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0
00
Pyrazolines are well known in organic chemistry and represent
a class of important N-heterocyclic compounds [1]. A large number
of pyrazoline derivatives have been found to display considerable
biological activities [2]. In the past decades, extensive research has
been conducted to establish the prominent biological effects of
pryazolines, such as antimicrobial, antimycobacterial, antifungal,
antiamoebic, anti-inflammatory, analgesic, antidepressant and
anticancer activities [3e10]. As a result, the synthesis and modifi-
cation of pyrazolines with various substituents on the 5-membered
ring have become a focus of research. In addition, aryl-substituted
pyrazolines are highly blue fluorescent materials and have been
used as whitening or brightening reagents [11,12]. Some function-
alized pyrazolines have also found extended applications in elec-
tro- and photo-luminescence materials and chemosensors [13e16].
of 2,2 :6 ,2 -tpy is a popular way while pursuing specific catalytic
and materials properties, which resulted in the synthesis of a
tremendous amount of interesting supramolecular compounds
0
0
00
containing 2,2 :6 ,2 -tpy moieties [35]. Despite of the extensive
0
0
00
efforts on the functionalization of 2,2 :6 ,2 -tpy, the direct
anchoring of a pyrazoline unit on the 2,2 :6 ,2 -tpy backbone is,
surprisingly, unknown.
0
0
00
0
Herein, we report for the first time the synthesis of a series of 4 -
0
0
00
pyrazolinyl-2,2 :6 ,2 -tpy derivatives. The spectroscopic, photo-
physical and structural characterization of the new pyrazoline-tpy
compounds are described. These new class of compounds are
anticipated to show intriguing coordination chemistry and fluo-
rescence sensing properties upon complexation with transition
metal ions, as well as potential biological activities. Prior to a
thorough investigation on their metal coordination chemistry,
herein we present our results on the synthesis and characterization
of the free ligands.
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,2 :6 ,2 -tpy is a classical ligand with a convergent N coordi-
2
0
0
00
nation site [17]. The derivatives of 2,2 :6 ,2 -tpy have played an
important role as strong chelating agents for transition metals
thanks to their ability to form structurally defined metal complexes
displaying interesting photo/electrochemical and catalytic proper-
2. Experimental
0
0
00
ties [18e25]. Therefore, the functionalization of 2,2 :6 ,2 -tpy on
different positions of its three aromatic rings has been extensively
2.1. General
Solvents and reagents were purchased from Fisher Scientific or
Sigma-Aldrich in the US. All reactions were performed under
ambient conditions (under air). H, C and 2D NMR spectrum was
*
Corresponding author.
E-mail address: guzhang@jjay.cuny.edu (G. Zhang).
1
13
http://dx.doi.org/10.1016/j.molstruc.2017.07.057
022-2860/© 2017 Elsevier B.V. All rights reserved.
0

398
E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
E2
E3
obtained at room temperature on a Bruker III 500 MHz spectrom-
eter with TMS as an internal standard. Electrospray mass spectra
were recorded using a Finnigan MAT LCQ mass spectrometer.
Infrared spectra were recorded on a Shimadzu FTIR-8400 S spec-
trophotometer with solid samples on a Golden Gate diamond ATR
accessory. Solution electronic absorption spectra were recorded on
a Varian-Cary 5000 spectrophotometer. Fluorescence spectra were
recorded on a Shimadzu F-4500 spectrophotometer. Chalcones 1e6
J ¼ 8.0 Hz, 2H, H ), 7.08 (d, J ¼ 8.0 Hz, 2H, H ), 5.62 (dd, J ¼ 4.8,
C5
C4
12.0 Hz, 1H, H ), 3.88 (dd, J ¼ 12.0, 17.0 Hz, 1H, H ), 3.20 (dd,
0
C4
CH3 13
J ¼ 4.8, 17.0 Hz, 1H, H ), 2.24 (s, 3H, H ). C NMR (126 MHz,
A2
B2
B4
C3
3
CDCl ) d/ ppm 157.1 (C ), 156.1 (C ), 151.3 (C ), 149.8 (C ), 149.2
A6
E1
E4
A4
D1
E3
(C ), 138.6 (C ), 137.7 (C ), 136.8 (C ), 132.4 (C ), 130.1 (C ),
D4
D3
D2
E2
A5
129.5 (C ), 128.8 (C ), 126.6 (C ), 125.9 (C ), 123.6 (C ), 121.6
(C ), 105.4 (CB3), 62.7 (CC5), 43.7 (C ), 21.3 (C ). ESI-MS (CH
A3
C4
CH3
2
2
Cl /
þ
MeOH) m/z 468.3 [M þ H ] (base peak, calc. 468.2), 490.1
0
0
0
00
þ
and 4 -hydrazino-2,2 :6 ,2 -terpyridine were synthesized accord-
ing to the literature method [36,37].
[M þ Na ] (calc. 490.2). Anal. Calc. for C31
25 5 2
H N $1.75H O, C 74.60, H
5.23, N 14.15%; Found C 74.30, H 5.23 N 14.15%.
2.2. Synthesis of 7
2.4. Synthesis of 9
0
0
0
00
0
0
0
00
4
-Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
4 -Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
chalcone 1 (20.8 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
under N in a 25 mL round-bottom flask equipped with a magnetic
bar and condenser, to which K CO (13.8 mg, 0.010 mmol) was added.
chalcone 3 (23.8 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
2
under N
2
in a 25 mL round-bottom flask equipped with a magnetic
CO (13.8 mg, 0.010 mmol) was
2
3
bar and condenser, to which K
2
3
The solution was heated to reflux under rigorous stirring for 3.5 h,
after which the resulting mixture was cooled slowly to room tem-
perature. White solid of 7 was collected by filtration under vacuum,
added. The solution was heated to reflux under rigorous stirring for
4 h, after which the resulting mixture was cooled slowly to room
temperature. White solid of 9 was collected by filtration under
washed with cold ethanol (2 ꢀ 2 mL) and dried in vacuo over P
2
O
5
.
vacuum, washed with cold ethanol (2 ꢀ 1 mL) and dried in vacuo
ꢁ
Yield: 30.0 mg (66%). Singe crystals were grown by slow evaporation
over P
2
O
5
. Yield: 32.0 mg (66%). M.p.: 215e216 C. UVevis
lmax/nm
ꢁ
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ
of a CH
(
(
1
2
Cl
2
/MeOH solution of 7. M.p.: 264e265 C. UVevis
l
max/nm
(5.0 ꢀ 10 mol dm , THF): 280 (ε/10 dm mol cm 1, 42.4), 359
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ1
ꢂ1
5.0 ꢀ 10 mol dm , THF), 279 (ε/10 dm mol cm 46.7), 355
(2.04), 380sh (0.634). FT-IR (solid, cm ): 3055 w, 2833s 1599 m,
ꢂ1
2.20), 377sh (1.02). FT-IR (solid, cm ): 3057 w, 3026 w, 1599 m,
580 s, 1562 s, 1545 m, 1466 s, 1445 m, 1410 m, 1346 m, 1304 w,
256 w, 1236 m, 1132 m, 1115 m, 1074 w, 1030 m, 1009 m, 984 m,
95 w, 872 m, 856 m, 791 m, 766 m, 756 m, 732 m, 689s, 671 s, 621 m.
1580 s, 1562 s, 1543 m, 1510 m, 1462 s, 1447 m, 1408 m, 1348 m,
1302 w,1246 s, 1177 m, 1105 m, 1099 m, 1032 m, 1018 m, 984, 891 w,
1
1
8
868 w, 827 m, 793 s, 758 s, 744 s, 735 m, 687 s, 671 s, 621 m. H NMR
A6
(500 MHz, CDCl
3
)
d
/ppm 8.66 (d, J ¼ 4.6 Hz, 2H, H ), 8.52 (d,
1
A6
A3
B3 D2
H NMR (500 MHz, CDCl
3
)
d
8.65 (d, J ¼ 4.7 Hz, 2H, H ), 8.52 (d,
J ¼ 7.9 Hz, 2H, H ), 8.09 (s, 2H, H ), 7.82 (d, J ¼ 7.2 Hz, 2H, H ),
A3
B3
D2
A4 D3
J ¼ 7.9 Hz, 2H, H ), 8.09 (s, 2H, H ), 7.82 (d, J ¼ 7.1 Hz, 2H, H ), 7.77
7.78 (td, J ¼ 1.6, 7.7 Hz, 2H, H ), 7.40 (t, J ¼ 7.3 Hz, 2H, H ), 7.36 (t,
D4 A5
A4
D3
(
H
td, J ¼ 1.6, 7.8 Hz, 2H, H ), 7.40 (t, J ¼ 7.2 Hz, 2H, H ), 7.37 (m, 1H,
J ¼ 7.2 Hz, 1H, H ), 7.26 (overlapping, m, 2H, H ), 7.24 (over-
E2 E3
D4
E2
E3
), 7.33 (d, J ¼ 7.2 Hz, 2H, H ), 7.30 (overlapping, m, 2H, H ), 7.26
lapping, 2H, H ), 6.80 (d, J ¼ 8.7 Hz, 2H, H ), 5.61 (dd, J ¼ 4.7,
C5 C4
A5
E4
(
1
overlapping, m, 2H, H ), 7.20 (t, J ¼ 7.2 Hz, 1H, H ), 5.65 (dd, J ¼ 4.8,
12.0 Hz, 1H, H ), 3.87 (dd, J ¼ 12.0, 17.0 Hz, 1H, H ), 3.69 (s, 3H,
0
C5
C4
CH3
C4 13
2.1 Hz, 1H, H ), 3.91 (dd, J ¼ 12.1, 17.0 Hz,1H, H ), 3.23 (dd, J ¼ 4.9,
H
), 3.20 (dd, J ¼ 4.8, 17.0 Hz, 1H, H ). C NMR (126 MHz, CDCl
3
)
0
C4 13
A2
E4
A2
B2
B4
C3
1
(
7.1 Hz, 1H, H ). C NMR (126 MHz, CDCl
3
)
d
/ ppm 157.1 (C ),156.2
d/ ppm 159.3 (C ), 157.1 (C ), 156.1 (C ), 151.3 (C ), 149.8 (C ),
B2
B4
C3
A6
E1
A4
A6
A4
E1
D1
D4
C ),151.3 (C ),149.8 (C ),149.2 (C ),141.5 (C ),136.8 (C ),132.3
149.2 (C ), 136.8 (C ), 133.6 (C ), 132.4 (C ), 129.5 (C ), 128.8
(C ), 127.2 (C ), 126.6 (C ), 123.6 (C ), 121.6 (C ), 114.7 (C ),
105.4 (C ), 62.5 (C ), 55.4 (C ), 43.7 (C ). ESI-MS (CH Cl /
2 2
D1
D4
E3
D3
E4
D2
D3
E2
D2
A5
A3
E3
(
C
), 129.56 (C ), 129.42 (C ), 128.8 (C ), 128.1 (C ), 126.6 (C ),
26.0 (C ), 123.6 (C ), 121.5 (C ), 105.4 (C ), 63.0 (C ), 43.6 (C ).
E2
A5
A3
B3
C5
C4
B3
C5
CH3
C4
1
þ
þ
þ
ESI-MS (CH
[
Cl
2 2
/MeOH) m/z 454.6 [M þ H ] (calc. 454.6), 476.3
MeOH) m/z 484.6 [M þ H ] (calc. 484.2), 506.3 [M þ Na ] (base
þ
þ
þ
M þ Na ] (base peak, calc. 476.2), 929.7 [2 M þ Na ] (calc. 929.4).
peak, calc. 506.2), 989.7 [2 M þ Na ] (calc. 989.4). Anal. Calc. for
23 5 2
Anal. Calc. for C30H N $1/3H O, C 78.41, H 5.19, N 15.24%; Found C
31 25 5 2
C H N O$0.5H O, C 75.59, H 5.32, N 14.22%; Found, C 75.13, H
7
8.56, H 5.20, N 15.46%.
5.17, N 14.03%.
2.3. Synthesis of 8
2.5. Synthesis of 10
0
0
0
00
0
0
0
00
4
-Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
4 -Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
chalcone 2 (22.2 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
under N in a 25 mL round-bottom flask equipped with a magnetic
bar and condenser, to which K CO (13.8 mg, 0.010 mmol) was
added. The solution was heated to reflux under rigorous stirring for
h, after which the resulting mixture was cooled to room tem-
chalcone 4 (25.1 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
2
under N
bar and condenser, to which K
2
in a 25 mL round-bottom flask equipped with a magnetic
CO (13.8 mg, 0.010 mmol) was
2
3
2
3
added. The solution was heated to reflux under rigorous stirring for
4 h, after which the resulting mixture was cooled slowly to room
temperature. White solid of 10 was collected by filtration under
6
perature. The solution was then concentrated to 2.0 mL and Et
2
O
ꢂ3
ꢁ
(
2.0 cm ) was added. The solution was further cooled to ꢂ18 C
vacuum, washed with cold ethanol (2 ꢀ 1 mL) and dried in vacuo
ꢁ
overnight to give yellow precipitate, which was collected by
over P
2
O
5
. Yield: 18.0 mg (36%). M.p.: 243e244 C. UVevis
lmax/nm
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ1
filtration under vacuum, washed with Et
vacuo over P
2
O (2 ꢀ 1 mL) and dried in
(5.0 ꢀ 10 mol dm , THF): 278 (ε/10 dm mol cm 44.0), 360
ꢁ
ꢂ1
2
O
5
. Yield: 20.5 mg (44%). M.p.: 209e210 C. UVevis
(2.06), 378sh (1.20). FT-IR (solid, cm ): 3051 w, 2887 w, 1597 m,
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ1
lmax/nm (5.0 ꢀ 10 mol dm , THF): 279 (ε/10 dm mol cm
1580 s, 1562 s, 1543 m, 1518 m, 1468 s, 1445 m, 1408 m, 1346 m,
1254 w, 1234 w, 1188 w, 1165 w, 1113 s, 1092 w, 1032 w, 984 w,
ꢂ1
41.4), 354 (2.00), 375sh (1.18). FT-IR (solid, cm ): 3013 w, 1597 m,
1
578 s, 1560 s, 1543 m, 1466 s, 1445 s, 1410 s, 1348 m, 1302 w,
943 w, 895 m, 874w, 852 m, 814 s, 189 s, 756 s, 744 s, 735 m, 688 s,
1
1
9
6
8
H
254 w, 1234 m, 1178 w, 1132 m, 1109 m, 1092 m, 1032 m, 1011 m,
671 s, 621 m. H NMR (500 MHz, CDCl
3
)
d
/ppm 8.66 (d, J ¼ 4.1 Hz,
A6
A3
B3
82 m, 874 m, 858 m, 814 s, 791 s, 758 s, 735 s, 687 s, 671 s, 658 s,
2H, H ), 8.51 (d, J ¼ 7.9 Hz, 2H, H ), 8.11 (s, 2H, H ), 7.82 (d,
1
A6
D2 A4
21 s. H NMR (500 MHz, CDCl
3
)
d
/ppm 8.66 (d, J ¼ 4.4 Hz, 2H, H ),
J ¼ 7.2 Hz, 2H, H ), 7.77 (td, J ¼ 1.7, 7.8 Hz, 2H, H ), 7.40 (t,
D3 D4
A3
B3
.52 (d, J ¼ 7.9 Hz, 2H, H ), 8.09 (s, 2H, H ), 7.82 (d, J ¼ 7.3 Hz, 2H,
J ¼ 7.3 Hz, 2H, H ), 7.35 (t, J ¼ 7.2 Hz,1H, H ), 7.26 (overlapping, m,
A5 E2 E3
D2
A4
D3
), 7.77 (td, J ¼ 1.4, 7.8 Hz, 2H, H ), 7.40 (t, J ¼ 7.3 Hz, 2H, H ),
2H, H ), 7.18 (d, J ¼ 8.7 Hz, 2H, H ), 6.62 (d, J ¼ 8.8 Hz, 2H, H ),
C5 C4
D4
A5
7.35 (t, J ¼ 7.1 Hz, 1H, H ), 7.26 (overlapping, m, 2H, H ), 7.21 (d,
5.58 (dd, J ¼ 4.6,11.9 Hz,1H, H ), 3.84 (dd, J ¼ 11.9,17.0 Hz,1H, H ),

E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
399
C4 13
0
0
C4
C4
3
.20 (dd, J ¼ 4.7, 17.0 Hz, 1H, H ), 2.85 (s, 6H, HCH3). 13C NMR
(dd, J ¼ 13.5,17.5 Hz,1H, H ), 3.68 (dd, J ¼ 10.3,17.6 Hz,1H, H ).
B4
C
A2
B2
B4
A2
B2
(
(
126 MHz, CDCl
C
3
)
d
/ ppm 157.2 (C ), 156.1 (C ), 151.4 (C ), 150.2
3
NMR (126 MHz, CDCl ) d/ ppm 156.8 (C ), 156.0 (C ), 151.9 (C ),
E4
C3
A6
A4
D1
D4
C3
A6
A4
E4a
D1
), 149.9 (C ), 149.2 (C ), 136.8 (C ), 132.6 (C ), 129.4 (C ),
149.9 (C ), 148.9 (C ), 136.5 (C ), 132.3 (C ), 132.2 (C ), 131.6
E1
D3
E2
D2
A5
E9
E1a
E5
E4
E5a
E8a
1
29.2 (C ), 128.7 (C ), 126.9 (C ), 126.6 (C ), 123.5 (C ), 121.6
(C ), 130.8 (C ), 130.3 (C ), 130.1 (C ), 130.0 (C ), 129.7 (C ),
A3
), 113.1 (CE3), 105.4 (CB3), 62.6 (C ), 43.7 (C ), 40.7 (C ). ESI-
C5
C4
CH3
E10
D4
D3
E2
E7
(
C
129.5 (C ), 129.3 (C ), 128.9 (C ), 127.4 (C ), 126.9 (C ), 126.7
þ
D2
E6
E3
E8
A5
E1
MS (CH
2
Cl
2
/MeOH) m/z 497.1 [M þ H ] (base peak and the only
(C ), 125.2 (C ), 125.0 (C ), 123.8 (C ), 123.3 (C ), 122.7 (C ),
A3
B3
C5
C4
peak, calc. 497.3). Anal. Calc. for C32
Found C 76.89, H 5.79, N 16.72%.
H
28
N
6
, C 77.39, H 5.68, N 16.92%;
2 2
121.1 (C ),105.8 (C ), 59.3 (C ), 42.4 (C ). ESI-MS (CH Cl /MeOH)
þ
þ
m/z 554.6 [M þ H ] (calc. 554.2), 576.3 [M þ Na ] (base peak, calc.
þ
576.2), 1129.7 [2 M þ Na ] (calc. 1129.4). Anal. Calc. for
2.6. Synthesis of 11
38 27 5 2
C H N $0.5H O, C 81.12, H 5.02, N 12.45%; Found C 81.57, H 4.74, N
12.62%.
0
0 0 00
-Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
4
chalcone 5 (23.8 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
under N in a 25 mL round-bottom flask equipped with a magnetic
bar and condenser, to which K CO (13.8 mg, 0.010 mmol) was
added. The solution was heated to reflux under rigorous stirring for
.5 h, after which the resulting mixture was cooled slowly to room
temperature. White solid of 11 was collected by filtration under
vacuum, washed with cold ethanol (2 ꢀ 1 mL) and dried in vacuo
2.8. X-ray structural determinations
2
2
3
Suitable crystals of 7 and 12 were mounted on a Cryoloop with oil
at 123 K. Data were collected on a Bruker APEXII diffractometer and
CRYSTALS were used for the data reduction, solution and refine-
ment. Structure was solved by direct methods. All non-hydrogen
atoms were refined anisotropically by full matrix least squares on
4
ꢁ
2
over P
(
(
1
1
2
O
5
. Yield: 30.0 mg (66%). M.p.: 238e239 C. UVevis
l
max/nm
F and all hydrogen atoms were placed in calculated positions with
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ1
5.0 ꢀ 10 mol dm , THF): 279 (ε/10 dm mol cm 41.5), 353
appropriate riding parameters. Due to the decay of diffused CHCl
solvents in the crystal of 12 during data collection, the structure was
refined at a relatively high R level. Crystal structures and packing
3
ꢂ1
2.76), 380sh (0.784). FT-IR (solid, cm ): 3040 w, 1599 s, 1578 s,
562 s, 1543 m, 1516 w, 1466 s, 1408 m, 1346 w, 1306 w, 1248 s,
175 m, 1111 m, 1034 m, 982 m, 856 m, 829 s, 795 s, 773 m, 743 m,
f
figures were drawn with the program Mercury v. 2.4 [38]. The
crystallographic refinement data are listed below.
1
7
8
H
02 m, 675 s, 658 s, 636 m, 621 m. H NMR (500 MHz, CDCl
3
)
d
/ppm
A6
A3
.64 (d, J ¼ 4.5 Hz, 2H, H ), 8.51 (d, J ¼ 7.9 Hz, 2H, H ), 8.06 (s, 2H,
7: C30
H
23
N
5
, M ¼ 453.55, colorless needle, monoclinic, space
B3
A4þD2
E2
), 7.77 (overlapping, 4H, H
), 7.33 (t, J ¼ 7.7 Hz, 2H, H ), 7.29
group P21/n, a ¼ 18.2004 (8), b ¼ 5.5954(3), c ¼ 22.8030(9) Å,
E3
A5
3
ꢂ3
(
overlapping, 2H, H ), 7.26 (overlapping, m, 2H, H ), 7.20 (t,
b
m
¼ 100.818(2), U ¼ 2280.95 (18) Å , Z ¼ 4, D
c
¼ 1.321 mg m
,
E4
D3
ꢂ1
J ¼ 7.0 Hz, 1H, H ), 6.92 (d, J ¼ 8.5 Hz, 2H, H ), 5.62 (dd, J ¼ 8.3 Hz,
(Mo-K
a
) ¼ 0.080 mm , T ¼ 123 K. Total 57269 reflections, 4459
C5
C4
CH3
1
H, H ), 3.88 (dd, J ¼ 12.1, 17.0 Hz, 1H, H ), 3.83 (s, 3H, H ), 3.19
unique. Refinement of 8203 reflections (316 parameters) with
I > 2 (I) converged at final R all data ¼ 0.0382),
¼ 0.0320 (R
wR all data ¼ 0.0754), GOF ¼ 1.1153.
¼ 0.0520 (wR
12·3(CHCl ): C41
, M ¼ 911.80, colorless block, monoclinic,
space group P2
/c, a ¼ 14.9087(13), b ¼ 9.7891(8), c ¼ 27.404(2) Å,
0
C4 13
(
dd, J ¼ 4.7, 17.0 Hz, 1H, H ). C NMR (126 MHz, CDCl
3
)
d/ ppm
s
1
1
D4
A2
B2
B4
A6
1
60.9 (C ), 157.1 (C ), 156.0 (C ), 151.3 (C ), 149.1 (C ), 141.7
2
2
E1
A4
E3
D2
E4
E2
(
C
), 136.8 (C ), 129.4 (C ), 128.1 (C ), 128.0 (C ), 126.0 (C ),
3
9 5
H30Cl N
D1
A5
B3
1
25.0 (C ), 123.6 (C ), 121.6 (CA3), 114.2 (CD3), 105.4 (C ), 62.8
1
C5
CH3
C4
C3
3
ꢂ3
, m
(
C
), 55.6 (C ), 43.8 (C ), C not observed. ESI-MS (CH
2
Cl
2
/
b
K
¼ 96.628 (5), U ¼ 3972.7(6) Å , Z ¼ 4, D
c
¼ 1.524 mg m
) ¼ 0.674 mm , T ¼ 123 K. Total 54941 reflections, 6911 unique.
(I)
¼ 0.1079
(Mo-
þ
þ
ꢂ1
MeOH) m/z 484.7 [M þ H ] (calc. 484.2), 506.3 [M þ Na ] (base
a
þ
peak, calc. 506.2), 989.7 [2 M þ Na ] (calc. 989.4). Anal. Calc. for
Refinement of 11001 reflections (496 parameters) with I > 2
converged at final R all data ¼ 0.1253), wR
¼ 0.1017 (R
(wR
all data ¼ 0.1569), GOF ¼ 0.9751.
s
C
31
H
25
N
5
O$H
2
O, C 74.23, H 5.43, N 13.96%; Found C 74.52, H 5.19, N
1
1
2
14.00%.
2
2.7. Synthesis of 12
3. Results and discussion
0
0
0
00
4
-Hydrazino-2,2 :6 ,2 -terpyridine (29.0 mg, 0.11 mmol) and
3.1. Synthesis and characterization
chalcone 6 (30.8 mg, 0.10 mmol) were dissolved in ethanol (5 mL)
under N in a 25 mL round-bottom flask equipped with a magnetic
bar and condenser, to which K CO (13.8 mg, 0.010 mmol) was
added. The solution was heated to reflux under rigorous stirring for
6 h, after which the resulting mixture was cooled slowly to room
0
0
0
00
2
The functionalization in the 4 -position of 2,2 :6 ,2 -tpy utilizes
0
0
0
00
2
3
mainly two intermediates up to now, 4 -chloro-2,2 :6 ,2 -tpy and
its precursor 2,6-bis-(pyrid-2-yl)-4-pyridone [28,30]. In contrast,
there were numerous reports on the nucleophilic aromatic sub-
1
0 0 0 00
stitution of the chlorine-function in 4 -chloro-2,2 :6 ,2 -tpy, readily
temperature. White solid of 12 was collected by filtration under
0 0 0 00
leading to 4 -R-alkoxy-2,2 :6 ,2 -tpys [28]. Likewise, the same type
vacuum, washed with cold ethanol (2 ꢀ 1 mL) and dried in vacuo
ꢁ
0
0
0
00
over P
2
O
5
. Yield: 20.0 mg (36%). M.p.: 276e277 C. Single crystals
of reaction also afforded 4 -hydrazino-2,2 :6 ,2 -tpy when hydra-
zine was used as a nucleophile. Accordingly, the facile condensation
3
were grown by slow evaporation of a solution of 12 in CDCl . UVevis
ꢂ6
ꢂ3
4
3
ꢂ1
ꢂ1
0 0 0 00
of 4 -hydrazino-2,2 :6 ,2 -tpy with aromatic aldehydes led to a
l
max/nm (5.0 ꢀ 10 mol dm , THF), 258(ε/10 dm mol cm
0
0
0
00
2
(
8.8): 279 (43.3), 357 (2.70), 372sh (2.32), 394sh (0.200). FT-IR
solid, cm ): 3049 w, 2953 m, 1597 m, 1578 s, 1560 s, 1545 s,
variety of 4 -hydrazone-2,2 :6 ,2 -tpys, whose properties and co-
ordination chemistry have been revealed earlier [39e41]. Alterna-
tively, we envisaged that it would be equally straightforward to
ꢂ1
1462 s, 1445 s, 1408 s, 1346 m, 1312 w, 1159 w, 1113 m, 1092 m,
0 0 00
prepare pyrazoline-containing 2,2 :6 ,2 -tpys through the conven-
1
6
059 m, 1038 s, 984 m, 953 m, 879 m, 860 s, 833 m, 789 s, 727 s,
1
0
0
0
00
87 s, 671 s, 642 m, 615 m. H NMR (500 MHz, CDCl
3
)
d
/ppm 8.72 (d,
tional pyrazoline condensation between 4 -hydrazino-2,2 :6 ,2 -
tpy and chalcones under basic conditions. Therefore, our synthesis
began with the preparation of several substituted aromatic chal-
cones 1e6 as shown in Scheme 1. The synthesis of 1e6 was ach-
ieved in high yields under basic conditions by using the method
reported in the literature [36]. In the next step, the stoichiometric
reaction was conducted by using the resultant chalcones 1e6 and
E1
E10
A6
J ¼ 9.0 Hz, 1H, H ), 8.44 (s, 1H, H ), 8.37 (d, J ¼ 3.6 Hz, 2H, H ),
A3
E4
8
.27 (d, J ¼ 7.9 Hz, 2H, H ), 8.11 (d, J ¼ 8.5 Hz, 1H, H ), 8.04 (d,
E8 D2
J ¼ 8.7 Hz, 1H, H ), 7.99 (overlapping, 2H, H ), 7.93 (overlapping,
E5
E2
A4
1
H, H ), 7.75 (m, 1H, H ), 7.63 (overlapping, 2H, H ), 7.61 (over-
E3
D3
lapping, 1H, H ), 7.46 (t, J ¼ 7.3 Hz, 2H, H ), 7.42 (t, J ¼ 7.2 Hz, 1H,
D4
E6
E7
H
), 7.32 (overlapping, 1H, H ), 7.29 (overlapping, 1H, H ), 7.12
A5
C5
0 0 0 00
2 3
1.0 equiv. of 4 -hydrazino-2,2 :6 ,2 -tpy in the presence of K CO
(
dd, J ¼ 5.1, 6.6 Hz, 2H, H ), 6.90 (dd, J ¼ 10.4, 13.2 Hz,1H, H ), 4.09

400
E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
O
O
base
O
+
2
R
EtOH, RT
1
R
R1
R2
1 2
, R = H, R = H
1
2
3
4
5
O
1 2
, R = H, R = CH3
1 2
, R = H, R = OCH3
1 2
, R = H, R = N(CH3)2
1 2
, R = OCH , R = H
6
3
1
R
O
D
H N
2
H
4
N
N
2
R
C
5
1
R
2
R
N
E
N
N
N
3
B
N
K CO (10 mol%), EtOH, reflux
2 3
N
A
N
6
1
R
5
3
D
2
3
4
4
1
4
1 2
7, R = H, R = H; 66%
1a
5
4a
10
5a
C
N
E
9
1 2
8, R = H, R = CH ; 44%
N
8
8a
3
5
1 2
9, R = H, R = OCH ; 66%
3
7
6
3
B
N
N
A
N
1 2
10, R = H, R = N(CH ) ; 36%
6
5
3 2
1 2
11, R = OCH , R = H; 41%
3
3
4
12, 36%
Scheme 1. The synthesis of chalcones 1e6 and pyrazoline-tpy 7e12 with atom-labeling for NMR assignments.
(
10 mol%), respectively. Consequently, the desired pyrazoline-tpy
products 7e12 were harvested in 36e66% yields when the re-
actions were carried out in ethanol upon refluxing for 3.5e16 h
(Scheme 1). The products are well soluble in CHCl
3 2 2
, CH Cl , DMF or
DMSO, but poorly soluble in acetone, methanol or acetonitrile.
1
Compounds 7e12 were fully characterized by UVevis, FT-IR, H
and 1 C NMR spectroscopy, ESI-MS spectrometer and elemental
analysis. The mass spectra of all compounds show peak envelops
3
C21
C23
1
13
matched with those calculated. The H and C NMR spectra of these
new compounds in CDCl were assigned by 2D techniques and were
3
C22
N6
in complete agreement with the molecular structures shown in
Scheme 1. It is worth noting that a new stereogenic center was
C25
N3
C24
C7
C5
generated on C atom upon the formation of pyrazolinyl moiety
C4
N5
and the diastereotopic protons on C sense the presence of this
stereogenic center in 1H NMR spectra for all compounds. For
C8
C9
C10
C11
instance, the diastereotopic protons in 7 appear as two dd signals at
N11
C5
C6
N1
Fig. 2. An ORTEP presentation of the X-ray structure of 7 with thermal ellipsoids
plotted at the 50% probability level. Selected bond parameters: N5eN6 ¼ 1.3782(14),
N5eC24
¼
1.4707(16), N6eC22
¼
1.2920(15), C21eC22
¼
1.4637(16),
C22eC23 ¼ 1.5064(18), C23eC24 ¼ 1.5516(16), C24eC25 ¼ 1.5164(16) Å; Dihedral
Fig. 1. The 1H NMR spectra of 7 and 12.
angle: N1eC10eC11eN11 ¼ 7.19, N3eC5eC6eN1 ¼ 13.23, N6eN5eC8eC9 ¼ 4.19 .
ꢁ

E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
401
3.2. Crystal structures of 7 and 12
To further confirm the molecular structures of the new
pyrazoline-tpy compounds, crystals of 7 and 12 were grown and
the structures were determined by single-crystal X-ray diffraction
analysis. Colorless needles of 7 were obtained by slow evaporation
2 2
of a CH Cl /MeOH solution of the compound over three days. X-ray
structural analysis unambiguously confirmed its structure as
illustrated in Scheme. 1. The ORTEP representation of the crystal
structure of 7 is shown in Fig. 2 and relevant bond parameters are
listed in the caption. 7 crystallizes in the monoclinic space group
P21/n and the asymmetric unit includes one molecule of 7. The
bond lengths and angles of the terpyridine domain are unexcep-
0
0
00
tional and close to those of known 2,2 :6 ,2 -tpy derivatives. The X-
ray structure shows that the tpy domain is close to being planar and
adopts the expected trans, trans-conformation as found in most tpy
derivatives [39e41]. Two side pyridine rings deviate slightly from
the plane of central pyridine and the dihedral angles between side
Fig. 3. The molecular packing in 7 along the crystallographic b axis, highlighting two
types of -stacking interactions with space-filling representation.
p
ꢁ
and central pyridines are 7.19 and 13.23 , respectively. The pyr-
azolinyl ring is almost coplanar with the central pyridine, as well as
the phenyl ring containing C21, and the torsional angles between
these rings are 4.19 and 2.28 , respectively. In addition, the phenyl
3
7
3
.91 and 3.23 ppmwith different coupling constants, respectively. In
C4
ꢁ
e11, the chemical shifts for H vary slightly between 3.91 and
.88 ppm for one proton and 3.23e3.19 for another one. However, in
ring on the tetrahedral C24 atom is twisted away from the plane
C5
C4
ꢁ
compound 12 containing an anthryl group at C the two H pro-
tons shift downfield to 4.09 and 3.68 ppm, respectively. In addition,
H
while it remains constantly in the range of 5.65e5.58 ppm for 7e11.
Fig.1 shows a comparison of the H NMR spectra for these protons in
7
(<N5eC24eC25 ¼ 68.07(2) ) as expected, minimizing the steric
interactions. The stereogenic C24 adopts an S-configuration (Fig. 2)
and the R-enantiomer of 7 is also observed in the unit cell. Inter-
C5
for compound 12 is notably downfield shifted to 6.90 ppm,
molecular packing is dominated by
crystallographic b axis as shown in Fig. 3. The
involve packing between the pyrazoline-phenyl groups as well as
the tpy domains and the shortest inter-atomic distances for the
p…p
interactions along the
1
p…p
interactions
and 12.
p
-
C19
C17
C20
C18
N5
C16
N4
C8
C7
C9
C10
C6
C5
N3
N1
C11
N2
Fig. 4. An ORTEP structure of 12 with thermal ellipsoids plotted at the 50% probability level. Three CHCl
N4eN5 ¼ 1.381(6), N5eC18 ¼ 1.294(6), C18eC17 ¼ 1.504(7), C17eC16 ¼ 1.535(7), N4eC16 ¼ 1.486(6) Å; Dihedral angle: N1eC5eC6eC7 ¼ 34.43, N3eC11eC10eC9 ¼ 25.85 .
3
molecules are omitted for clarity. Selected bond parameters:
ꢁ

402
E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
UVevis and fluorescence spectra. The THF solution of these at room
temperature all display intense, high energy absorption centered at
80 nm from ligand-centered * ) transition, except that
compound 12 also shows a higher energy band at 258 nm. Less
intense * ) transition bands also appear as broad peaks at
2
p
p
p
p
between 320 and 390 nm. Compared to the absorption of tpy
moiety [42], the obvious red shift upon the introduction of the
aromatic rings pendant pyrazoline substituents corresponds to a
lowering in energy of the ligand
p* orbitals. In addition, the char-
acteristic fine peaks for anthracene are observed in the absorption
of 12, while the peaks are slightly red shifted. (see Fig. 6)
The fluorescent emission spectra of these compounds were also
recorded in THF solution with the same concentration as for UVevis
measurements (Fig. 7). Compounds 7e9 displayed very similarly
blue fluorescence centered at 400 and 419 nm, while excited at
Fig. 5. The molecular packing mode in 12 along the crystallographic b axis.
stacking were found to be approximately 3.664 and 3.535 Å,
respectively (see Fig. 3).
355 nm. Compound 10 shows fluorescence with two similar peaks,
Single crystals of 12·3CHCl
a CHCl solution. Despite of the decay of crystals due to the loss of
interstitial CHCl molecules during the data collection which
resulted in relatively poor quality of data, the main structure of 12
was clearly established. 12·3CHCl crystallizes in the monoclinic
space group P2 /c and the asymmetric unit includes one molecule
3
were grown by slow evaporation of
yet with decreased intensity. In contrast, the emission band of 11
features a single peak band and shifted to 442 nm, with the in-
tensity being close to that of 10. This indicates that the electronic
substituents on the pyrazoline unit have a significant impact on the
emission spectra of the compounds, although their UVevis spectra
were very close. Surprisingly, compound 12 is non-emissive under
the same conditions, which is presumably attributed to the excited
state energy transfer between the tpy-pyrazoline and anthrance
chromophores. Preliminary studies on the fluorescence properties
of 12 upon complexation with metal ions show that the emission
could be intrigued by the introduction of zinc ions in the solution.
Details on the influence of metal ions in the emission of these
compounds will be reported in due course.
3
3
3
1
of 12 (Fig. 4). Like 7, the tpy domain adopts the trans, trans-
conformation and two enantiomers of 12 are also observed in the
unit cell. Due to the presence of an anthryl group on the pyrazolinyl
unit, the planes of three pyridyl rings are severely distorted, while
all bond lengths remain very close to those in 7. The dihedral angles
between the central pyridine and side pyridines are 34.43 and
ꢁ
2
5.85 , respectively. In the molecular packing mode, the anthryl
group is mainly responsible for intermolecular
p-stacking in-
teractions (Fig. 5). The interactions occur between the anthryl
group and pyrazolinyl or pyridyl rings of adjacent molecules and
the shortest interatomic distances are around 3.295 and 3.586 Å,
p…p
4. Conclusion
In conclusion, we herein report the synthesis and character-
respectively. In addition, non-classical CeH…
also found between the anthracene moieties. The solvent CHCl
molecules reside in cavities formed by the packing of 12, hydrogen
p hydrogen bonds are
0
0
00
ization of six new 2,2 :6 ,2 -tpy derivatives by anchoring aromatic
3
0
substituted pyrazolines on the 4 -position. The facile pyrazoline
0
0
0
00
condensation between 4 -hydrazino-2,2 :6 ,2 -tpy and simple
chalcones allows for the synthesis of such compounds containing
multiple chromophores with high purity and in moderate to good
yields. This represents the first example of synthesis of pyrazoline-
tpy derivatives. The aromatic substituents on the pyrzaoline moiety
were found to play a role in affecting both the solid state molecular
structure and emission properties. The fluorescence properties
bonded to the side-arm pyridine N atoms (H/N 2.464 Å, C/N
ꢁ
3
.139(3) Å, CeH/N 125 ).
3.3. UVevis and fluorescence
The new compounds 7e12 were further characterized by
Fig. 6. UVevis spectra of compounds 7e12 in THF (c ¼ 5 ꢀ 10ꢂ6 M) at room
ꢂ6
Fig. 7. The fluorescence spectra of compounds 7e12 in THF (c ¼ 5 ꢀ 10 M) at room
temperature.
temperature. Excitation wavelengh ¼ 355 nm.

E. Liu et al. / Journal of Molecular Structure 1148 (2017) 397e403
403
corresponding to metal sensing behavior might be worth further
investigating, whereas studies on the coordination chemistry of
these compounds are currently in progress.
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