Evaluation of Cu(II) bzimpy complexes by 1H-NMR and catalytic activities

Article abstract of DOI:10.1080/00958972.2020.1840561

Copper(II) complexes (3a–d and 4a–d) containing tridentate 2,6-bis(benzimidazole-2-yl) pyridine (bzimpy) were synthesized and characterized by ¹H-NMR, elemental analysis, IR, UV and mass spectroscopy. These complexes were tested as catalysts in transfer hydrogenation (TH). The effects of wingtip substituents on bzimpy ligand to the TH activity of Cu(II) complexes were investigated. Among the catalysts, complex 4d with sterically bulky bzimpy ligand showed the highest catalytic activity in this transformation.

Full text of DOI:10.1080/00958972.2020.1840561

Journal of Coordination Chemistry
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Evaluation of Cu(II) bzimpy complexes by 1H-NMR
and catalytic activities
Salih Günnaz
To cite this article: Salih Günnaz (2020): Evaluation of Cu(II) bzimpy complexes by 1H-NMR and
catalytic activities, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2020.1840561
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JOURNAL OF COORDINATION CHEMISTRY
https://doi.org/10.1080/00958972.2020.1840561
1
Evaluation of Cu(II) bzimpy complexes by H-NMR
and catalytic activities
€
Salih Gunnaz
Department of Chemistry, Ege University, Izmir, Turkey
ABSTRACT
ARTICLE HISTORY
Received 25 June 2020
Accepted 30 September 2020
Copper(II) complexes (3a–d and 4a–d) containing tridentate 2,6-
bis(benzimidazole-2-yl) pyridine (bzimpy) were synthesized and
characterized by 1H-NMR, elemental analysis, IR, UV and mass
spectroscopy. These complexes were tested as catalysts in transfer
hydrogenation (TH). The effects of wingtip substituents on bzimpy
ligand to the TH activity of Cu(II) complexes were investigated.
Among the catalysts, complex 4d with sterically bulky bzimpy lig-
and showed the highest catalytic activity in this transformation.
KEYWORDS
Bzimpy; copper(II)
complexes; NMR; transfer
hydrogenation
1. Introduction
Bzimpy binds to metals with N atoms to form two different five-membered rings that
are thermodynamically stable [1–14]. Bzimpy ligands are frequently studied in medi-
cine [15], magnetism [16], photochemistry [17], materials science [18], solution studies
[19], and homogeneous catalysis [20] due to their practical synthesis and versatile
steric and electronic properties.
There are many studies on synthesis and application of Cu(II) bzimpy complexes
[21–37]. Since Cu(II) complexes are paramagnetic studies have not focused on struc-
1
tural characterization by H-NMR. By shortening relaxation times, paramagnetic metals
cause line expansion and signal shifts. Thus, the spectrum is observed on a wide ppm
scale and as broad signals. One method to prevent this problem is to use a shift
reagent. Shift reagents are Lewis acids that provide spectral simplifications by shifting
€
CONTACT Salih Gunnaz
salih.gunnaz@Ege.edu.tr
Department of Chemistry, Ege University, 35100
Izmir, Turkey
Supplemental data for this article is available online at https://doi.org/10.1080/00958972.2020.1840561.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
S. GÜNNAZ
to various extents the resonance positions of the nuclei present when added to the
solutions of Lewis base substrates. In 1969, Hinckley reported that the dipyridine
adduct of tris-(2,2,6,6-tetramethyl-3,5-heptanedianato) europium(III), Eu(dpm)3(py)2,
caused changes in the proton NMR spectrum of cholesterol monohydrate in carbon
tetrachloride as a direct result of the bonding between the lanthanide metal chelate
and the cholesterol monohydrate [38]. It was then stated that the pyridine-free com-
plex Eu(dpm)3 would be a superior shift reagent [39]. However, the efficiency of
Eu(dpm)3 as a shift reagent is slightly reduced when used with weak Lewis bases, and
the solubility of this chelate is relatively low in non-alcoholic solutions [40]. Rondeau
and Sievers have shown improvements in solubility and Lewis acidity from the use of
tris (1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanthiento) europium(III), Eu(fod)3 [41].
Today, there are many different shift reagents in use. As an alternative to these
reagents, the general structures of which are Lewis acids, in this study we character-
ized cationic Cu(II) bzimpy complexes by 1H-NMR using 3-(trimethylsilyl)propionic-
2,2,3,3-d4 acid sodium salt (TSP-d4).
One of the important and basic reactions in organic chemistry is the reductive con-
version of carbonyl compounds to alcohols. The reduction of carbonyl compounds to
alcohols is usually accomplished with a stoichiometric amount of metal hydride reduc-
tant such as lithium aluminum hydride. This method is limited due to its explosive
nature. In addition, using a metal hydride reductant also produces stoichiometric
amounts of waste. As in Meerwein-Ponndorf-Verley (MPV) type reduction, catalytic
transfer hydrogenation reactions using 2-propanol, which are less toxic hydrogen
donors, are an important method used in converting carbonyl compounds into alco-
hols. In our previous studies, the transfer hydrogenation reactions of Ru, Rh and Ir
based bzimpy ligands were reported [42]. Although these metals exhibited higher
activities in the transfer hydrogenation reaction, their higher costs hinders their
applicability.
Herein we extend the use of the bzimpy ligand for synthesis and characterization
of earth-abundant, inexpensive and non-toxic copper(II) complexes. Complexes charac-
1
terized by H-NMR using TSP-d4 in dmso-d6 were screened for TH of aldehydes and
ketones with 2-propanol. To the best of our knowledge, this is the first example for
application of Cu(II)-bzimpy complexes in TH reactions.
2. Results and discussion
2.1. Synthesis and characterization of compounds
The ligands used and the synthesis and reaction routes to the Cu(II) complexes are
presented in Scheme 1.
Synthesized compounds were characterized by elemental analysis and NMR and IR
spectra. The bzimpy ligands were synthesized according to the steps illustrated in
Scheme 1. At the first step, 2,6-bis(benzimidazol-2-yl) pyridine (1a) and 2,6-bis(5,6-
dimethylbenzimimidazol-2-yl) pyridine (2a) were prepared by reaction of pyridine-2,6-
dicarboxylic acid with o-phenylenediamine and 4,5-dimethylbenzene-1,2-diamine in
polyphosphoric acid (PPA). Bzimpy ligands (1b–d, 2b–d) were obtained via the alkyl-
ation of 1a and 2a with benzyl chloride, 2,4,6-trimethylbenzyl bromide, and

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3
Scheme 1. Preparation of Cu(II)-bzimpy complexes studied in this work.
pentamethyl benzyl bromide in the presence of KOH in acetone at reflux. The ligands
1
(1b–d, 2b–d) are soluble in chlorinated solvents, alcohols, and DMSO. In H-NMR spec-
tra, the Py-Hp and Py-Hm protons were observed as doublets and triplets in a 2:1 ratio
at around d 8.11–8.56 ppm. Signals at d 45.8–48.1 ppm corresponded to the benzylic
methylene carbon resonances for 1b–d and 2b–d.
Copper(II) complexes (3a–d and 4a–d) were obtained by mixing equimolar amounts
of CuCl2ꢀ2H2O and 1a–d, 2a–d at 40 ꢁC in CH3OH. The complexes were characterized
1
by H-NMR, elemental analysis, IR and mass spectroscopy. Complexes are stable in air
and soluble in DMSO, moderately soluble in acetonitrile and slightly soluble in metha-
nol and water. The mass spectra of the complexes show molecular ion peaks at m/z of
409–785 due to the molecular ion [CuClL]þ. The IR spectral data for the free ligand
and the Cu(II) complexes with their relative assignments have been studied to

4
S. GÜNNAZ
Table 1. IR Comparison between complexes and ligands.
mC¼C (cmꢂ1
)
mC¼N (cmꢂ1
)
1a
1b
1c
1d
2a
2b
2c
2d
1601
1585
1587
1586
1600
1587
1599
1597
3a
3b
3c
3d
4a
4b
4c
4d
1605
1598
1598
1596
1612
1599
1603
1602
1a
1b
1c
1d
2a
2b
2c
2d
1573
1570
1570
1571
1574
1569
1571
1568
3a
3b
3c
3d
4a
4b
4c
4d
1577
1574
1576
1572
1578
1579
1575
1574
Figure 1. 1H-NMR spectrum of the paramagnetic 3d complex in dmso-d6.
characterize their structures. The IR spectrum of free bzimpy (1a) shows characteristic
absorption bands of the benzimidazole pyridine group at 1573 and 1436 cmꢂ1
assigned to mC ¼ C and mC ¼ N, respectively. The results were found to be in good
agreement with the literature [23–25]. For free bzimpy a strong band is found at
1573 cmꢂ1, attributed to mC ¼ N of the benzimidazole group, which showed a medium
band at 1577 cmꢂ1 in the Cu(II) complex. IR spectral data for free ligand and the Cu(II)
complexes (3a–d and 4a–d) together with their assignments are presented in Table 1.
The UV-vis absorption spectra were recorded at 2.0 ꢃ 10ꢂ5 mol/L in DMSO at room
temperature. The complexes have absorptions at 360–420 nm. The maximum absorp-
ꢄ
tions are located at 360–395 nm, which can be assigned to p!p transitions. There is
one more peak observed at 385–420 nm for each complex which arises from the met-
al–ligand charge transfer. The results are compatible with the literature [23, 24,
26, 31].
1
2.2. Characterization of 3a–d and 4a–d by H-NMR
1
The H-NMR spectra of complexes containing paramagnetic metals are observed on a
1
very wide ppm scale. Figure 1 demonstrates the H-NMR spectrum of 3d in dmso-d6.
In this spectrum, the peaks are quite broad and it is not possible to calculate the inte-
gral field. TSP-d4 was used to convert this complex spectrum into a spectrum suitable
for first order analysis.
1H-NMR spectra were recorded on a Varian AS 400 Mercury NMR spectrometer
operating at 399.885 MHz and 300 K. The 1H-NMR spectra were recorded with the
standard pulse sequence (s2pul) using a spectral width of 6398 Hz, a data size of

JOURNAL OF COORDINATION CHEMISTRY
5
32768 points, a relaxation delay of 1 s, acquisition time of 2.561 s and the number of
scans are 8.
The samples for NMR analysis were prepared by dissolving in DMSO-d6 containing
10 wt. % TSP-d4.
One-dimensional 1H-NMR spectra of 3a–d and 4a–d in DMSO-d6 are shown in
1
1
Figure 2, and the H-NMR chemical shifts are provided in Table 2. In the H-NMR spec-
tra, the Py-Hp and Py-Hm protons were observed as doublets and triplets in a 2:1 ratio
at d 8.27–8.43 ppm. Signals at d 5.68–6.21 ppm corresponded to the benzylic methy-
lene proton resonances for 3b–d and 4b–d.
2.3. Catalytic studies
Transfer hydrogenation is the addition of hydrogen from another reagent to an unsat-
urated molecule; 2-propanol (IPA) is generally used as the hydrogen source and KOH
as a base for this process. The synthesized Cu(II) bzimpy complexes (3a–d and 4a–d)
were examined as active catalysts for the transfer hydrogenation of 4-chloroacetophe-
none. The conversion of 4-chloroacetophenone to 1-(4-chlorophenyl) ethanol was
selected as a benchmark reaction. The reaction was carried out at 82 ꢁC in open air
with 2-propanol as the hydrogen source and KOH as the base in the presence of
1 mol % catalyst. After 2 h, the sample was taken from the reaction mixture and the
1
conversion was determined by using H-NMR spectroscopy. Catalytic activities of Cu(II)
complexes having H, benzyl, trimethyl benzyl and pentamethyl benzyl wingtips on
bzimpy ligands were compared; the best conversion was obtained with 4d (entry 9).
Increasing steric bulk on wingtip substituent has a positive effect on the catalytic
activity. More important, replacing the H with CH3 on the backbone of benzimidazole
had a significant effect on catalytic activity. The conversion was 43% at 50 ꢁC (entry
10). Replacing KOH with NaOH decreased the conversion of the reaction to 76% (entry
11); Na2CO3 was inactive under the same conditions (entry 12). Since KOH is a stron-
ger base, higher conversion was obtained as addressed in a similar study [43]. In the
experiment with KOH and without catalyst, 41% conversion was observed (entry 13).
No conversion was observed when CuCl2ꢀ2H2O was used in the same reaction condi-
tions instead of Cu(II)-bzimpy, which indicates the critical role of the ligands (entry 15).
Using inert reaction conditions did not improve the yield of the reaction significantly
and the remaining reactions were performed open to air (entry 16). The results are
detailed in Table 3.
To study the scope of the reaction, various aldehydes and ketones were reacted
under optimized conditions (Scheme 2). Alcohols were obtained with high conversions
from ketones bearing electron deficient -Cl, -Br groups. In the same conditions, good
conversions were obtained from ketones bearing electron-donating groups 4-OMe, 4-
NH2 and 3,4-diMe in 24 h. We studied the scope of the TH reaction with various elec-
tron-rich or electron-deficient aldehydes. Under the same reaction conditions, we
obtained benzyl alcohol with 99% conversion from benzaldehyde. In the case of 4-
chloro, 4-bromo, 4-methoxy, 3,4,5-trimethoxy and 4-methyl benzaldehyde, respectively,
79, 86, 99, 96 and 93% conversion were obtained.

6
S. GÜNNAZ
Figure 2. 1H-NMR spectra of 3a–d and 4a–d.

JOURNAL OF COORDINATION CHEMISTRY
7
Table 2. 1H-NMR Chemical shifts (ppm) in DMSO-d6 of 3b–d and 4b–d.
Complex
Py-Hm
Py-Hp
Benzimidazole-H
N-CH2
3a
8.30 (d, 2H,
J ¼ 7.6 Hz)
8.35 (d, 2H,
J ¼ 7.6 Hz)
8.12 (t, 1H,
J ¼ 7.8 Hz)
8.19 (t, 1H,
J ¼ 7.8 Hz)
7.79 (bs, 4H), 7.23–7.19 (m, 4H)
–
3b
3c
7.76 (d, 2H, J ¼ 8.8 Hz),
7.46 (d, 2H,
5.75 (s, 4H)
6.14 (s, 4H)
J ¼ 8.0 Hz), 6.82–6.80
(m, 4H)
8.43 (d, 2H,
J ¼ 8.0 Hz)
8.23 (t, 1H,
J ¼ 8.0 Hz)
7.78 (d, 2H, J ¼ 8.0 Hz),
7.23 (t, 2H,
J ¼ 7.6 Hz), 7.10 (t,
2H, J ¼ 7.6 Hz), 6.79
(d, 2H, J ¼ 4.8 Hz)
7.69 (d, 2H, J ¼ 8.0 Hz),
7.13 (t, 2H,
J ¼ 7.6 Hz), 6.98 (t,
2H, J ¼ 7.6 Hz), 6.64
(d, 2H, J ¼ 8.4 Hz)
7.60 (bs, 4H)
3d
8.38 (d, 2H,
J ¼ 7.6 Hz)
8.21 (t, 1H,
J ¼ 8.0 Hz)
6.20 (s, 4H)
4a
4b
4c
4d
8.23 (d, 2H,
J ¼ 7.6 Hz)
8.27 (d, 2H,
J ¼ 6.4 Hz)
8.34 (d, 2H,
J ¼ 8.0 Hz)
8.28 (d, 2H,
J ¼ 7.6 Hz)
8.07 (t, 1H,
J ¼ 7.6 Hz)
8.11 (t, 1H,
J ¼ 8.0 Hz)
8.15 (t, 1H,
J ¼ 7.8 Hz)
8.10 (t, 1H,
J ¼ 7.8 Hz)
–
7.23 (bs, 2H), 7.52 (bs, 2H)
7.46 (s, 2H), 6.49 (s, 2H)
7.43 (s, 2H), 6.45 (s, 2H)
5.68 (s, 4H)
6.05 (s, 4H)
6.10 (s, 4H)
Table 3. Optimization of reaction conditions.a
Entry
Cat.
Base
Time (h)
T (ꢁC)
Conv. (%)
1
2
3
4
5
6
7
8
3a
3b
3c
3d
4a
4b
4c
4d
4d
4d
4d
4d
-
4d
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
NaOH
Na2CO3
KOH
–
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
82
82
82
82
82
82
82
82
82
50
82
82
82
82
82
82
32
46
57
62
45
61
70
76
99
43
76
ND
41
ND
ND
92
9
10
11
12
13
14
15
16b
CuCl2ꢀ2H2O
KOH
KOH
4d
aReaction conditions: 4-chloroacetophenone (1.0 mmol), cat. (1 mol%), KOH (1 mol%), 2-PrOH (2.0 mL), 82 ꢁC,
under air.
bReaction was performed under inert system.
3. Conclusion
The preparation and characterization of Cu(II)bzimpy complexes (3a–d and 4a–d) are
reported. Their catalytic activities were investigated for the TH reaction of aldehydes
and ketones. The catalytic activity increased generally with the amount of electron

8
S. GÜNNAZ
Scheme 2. Scope of TH reaction with aldehydes and ketones catalyzed by 4da.
b
aReaction conditions: ketone (1.0 mmol), 4d (1 mol%), KOH (1 mol%), 2-PrOH(2.0 mL), 82 ꢁC, under air. 24h.
density on the metal. Catalyst 4d demonstrated the highest catalytic activity and alco-
hols with up to 99% conversion were obtained within 2 h. Based on these results, it is
thought that the complexes obtained with copper(II), which are quite cheap and
abundant, may be a good alternative to other metals frequently used in the transfer
hydrogenation reaction.

JOURNAL OF COORDINATION CHEMISTRY
9
4. Experimental
4.1. General considerations
Reactions involving air-sensitive components were performed using a Schlenk-type
flask under an argon atmosphere with high vacuum-line techniques. The glass equip-
ment was heated under vacuum in order to remove the oxygen and moisture, and
then filled with argon. The solvents were of analytical grade and distilled under an
argon atmosphere from sodium (ethanol, methanol, diethyl ether, and pentane) and
P2O5 (dichloromethane). Synthesis of bzimpy [44] and preparation of 2,4,6-bromide
and 2,3,4,5,6-pentamethylbenzyl bromide were undertaken according to the literature
[45]. PPA is generally freshly prepared. Approximately 25 mL PPA was obtained by mix-
ing 18 g P2O5 and 10 g 85% H3PO4. The reagents were stirred at 100 ꢁC under a dry
atmosphere until a homogenous, clear viscous liquid was formed. Typically, this pro-
cess takes 24 h. The 1H and 13C NMR spectra were recorded on a Varian AS400
Mercury at Ege University. As solvents, CDCl3 and d6-DMSO were employed, and the J
values were in Hz.
Compound 1a: Yield: 80%. Elemental analysis: calcd (%) for C19H13N5 (311.12): C,
1
73.30; H, 4.21; N, 22.49%. Found: C, 73.18; H, 4.27; N, 22.43%. H NMR (400 MHz, 303 K
DMSO-d6) d: 7.41 (m, 4H, BI-H), 7.76 (m, 4H, BI-H), 8.21 (t, 1H, J ¼ 7.7 Hz, Py-Hp), 8.41 (d,
2H, J ¼ 8.0 Hz, Py-Hm), 13.05 (2H, N-H). 13C NMR (100 MHz, 303 K, DMSO-d6) d: 115.8,
121.6 (2 x BI-C), 124.3 (Py-Cm), 136.4 (Py-Cp), 140.4 (BI-C), 146.1 (Py-Co), 150.5
(N ¼ C-NH).
Compound 2a: Yield: 84%. Elemental analysis: calcd (%) for C23H21N5 (367.18): C,
1
75.18; H, 5.76; N, 19.06%. Found: C, 74.26; H, 5.39; N, 18.74%. H NMR (400 MHz, 303 K,
DMSO-d6) d: 2.37 (s, 12H, BI-CH3), 7.51 (s, 4H, BI-H), 8.11 (t, 1H, J ¼ 7.7 Hz, Py-Hp), 8.26
(d, 2H, J ¼ 8.0 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, DMSO-d6) d: 22.0 (BI-CH3), 121.6
(BI-C), 124.9 (Py-Cm), 130.6 (BI-C), 132.8 (Py-Cp), 139.5 (BI-C), 148.6 (Py-Co), 151.1
(N ¼ C-NH).
4.2. General procedures for the synthesis of 1b–d and 2b–d
2,6-Bis(2-benzimimidazolyl)pyridine or 2,6-bis(5,6-dimethylbenzimimidazol-2-yl)pyridine
(1.6 mmol) and KOH (3.36 mmol) were dissolved in acetone. The mixture was stirred
and heated under reflux for one hour. Then, aryl chloride/bromide (3.2 mmol) was
added and refluxed for six hours. The volatiles were removed under vacuum, and then
the residue was dissolved with DCM (10 mL) and filtered with cannula. Diethyl ether
(20 mL) was added to the solution and the crystals obtained were filtered and dried
under vacuum.
Compound 1b: Yield: 83%. Elemental analysis: calcd (%) for C33H25N5 (491.21): C,
1
80.63; H, 5.13; N, 14.25%. Found: C, 79.91; H, 5.64; N, 13.86%. H NMR (400 MHz, 303 K,
CDCl3) d: 5.55 (s, 4H, N-CH2), 6.81 (dd, 4H, J1 ¼ 8.4 Hz, J2 ¼ 1.6 Hz, BI-H), 7.25 (m, 10H,
Ar-H, 2H, BI-H), 7.88 (d, 2H, J ¼ 8.0 Hz, BI-H), 8.01 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.38 (d, 2H,
J ¼ 8.0 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) d: 48.1 (N-CH2), 111.1, 120.5, 123.2,
124.0 (4 x BI-C), 125.9 (Py-Cm), 126.4, 127.6, 128.9, 136.7 (4 x Ar-C), 137.2 (BI-C), 138.5
(Py-Cp), 143.0 (BI-C), 149.9 (Py-Co), 150.2 (N ¼ C-NH).

10
S. GÜNNAZ
Compound 1c: Yield: 85%. Elemental analysis: calcd (%) for C39H37N5 (575.30): C, 81.36;
H, 6.48; N, 12.16%. Found: C, 80.79; H, 6.56; N, 11.49%. 1H NMR (400 MHz, 303 K, CDCl3) d:
1.93 (s, 12H), 2.19 (s, 6H, Ar-CH3), 6.26 (s, 4H, N-CH2), 6.67 (d, 2H, J ¼ 7.6 Hz, BI-H), 6.71 (s, 4H,
Ar-H), 6.98 (t, 2H, J ¼ 7.7 Hz, BI-H), 7.19 (t, 2H, J ¼ 7.6 Hz, BI-H), 7.76 (d, 2H, J ¼ 7.9 Hz, BI-H),
8.07 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.42 (d, 2H, J ¼ 7.6 Hz, Py-Hm). 13C NMR (100 MHz, 303 K,
CDCl3) d: 19.8, 19.9 (Ar-CH3), 46.8 (N-CH2), 105.9, 115.0, 120.6 (3 x BI-C), 121.1 (Py-Cm), 134.0,
135.1 (2 x Ar-C), 135.2 (BI-C), 142.0 (Py-Cp), 142.3 (BI-C), 149.0 (Py-Co), 155.4 (N ¼ C-NH).
Compound 1d: Yield: 82%. Elemental analysis: calcd (%) for C43H45N5 (631.37): C,
1
81.74; H, 7.18; N, 11.08%. Found: C, 80.08; H, 7.06; N, 11.24%. H NMR (400 MHz, 303 K,
CDCl3) d: 2.02 (s, 12H, Ar-CH3), 2.13 (s, 12H, Ar-CH3), 2.21 (s, 6H, Ar-CH3), 6.18 (s, 4H, N-
CH2), 6.59 (d, 2H, J ¼ 7.6 Hz, BI-H), 7.01 (t, 2H, J ¼ 7.5 Hz, BI-H), 7.22 (t, 2H, J ¼ 7.6 Hz, BI-
H), 7.81 (d, 2H, J ¼ 7.6 Hz, BI-H), 8.11 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.72 (d, 2H, J ¼ 7.8 Hz, Py-
Hm). 13C NMR (100 MHz, 303 K, CDCl3) d: 15.9, 17.7, 19.9 (3 x Ar-CH3), 47.8 (N-CH2),
112.0, 120.0, 122.5, 123.4, 126.1 (5 x BI-C), 128.2, 133.4, 134.9 (3 x Ar-C), 136.0 (BI-C),
137.8 (Py-Cp), 142.4 (BI-C), 149.7 (Py-Co), 150.7 (N ¼ C-N).
Compound 2b: Yield: 79%. Elemental analysis: calcd (%) for C37H33N5 (547.27): C,
1
81.14; H, 6.07; N, 12.79%. Found: C, 80.69; H, 6.21; N, 11.98%. H NMR (400 MHz, 303 K,
CDCl3) d: 2.32 (s, 6H, BI-CH3), 2.38 (s, 6H, BI-CH3), 5.49 (s, 4H, N-CH2), 6.80 (d, 4H,
J ¼ 7.3 Hz, Ar-H), 6.96 (s, 2H, BI-H), 7.19 (m, 6H, Ar-H), 7.62 (s, 2H, BI-H), 7.94 (t, 1H,
J ¼ 7.9 Hz, Py-Hp), 8.30 (d, 2H, J ¼ 7.9 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) d:
20.5, 20.9 (2 x BI-CH3), 47.8 (N-CH2), 110.9, 120.4, 125.6, 126.4 (4 x BI-C), 127.5 (Py-Cm),
128.9, 132.3, 133.5 (3 x Ar-C), 135.4 (BI-C), 137.7 (Ar-C), 138.3 (Py-Cp), 141.8 (BI-C), 149.7
(Py-Co), 150.1 (N ¼ C-N).
Compound 2c: Yield: 84%. Elemental analysis: calcd (%) for C43H45N5 (631.37): C,
1
81.74; H, 7.18; N, 11.08%. Found: C, 81.33; H, 7.03; N, 10.97%. H NMR (400 MHz, 303 K,
CDCl3) d: 2.01 (s, 12H, Ar-CH3), 2.06 (s, 6H, Ar-CH3), 2.14 (s, 6H), 2.24 (s, 6H,BI-CH3), 6.02
(s, 4H, N-CH2), 6.48 (s, 2H, BI-H), 6.72 (s, 4H, Ar-H), 7.55 (s, 2H, BI-H), 8.01 (t, 1H,
J ¼ 7.9 Hz, Py-Hp), 8.38 (d, 2H, J ¼ 7.9 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) d:
20.2, 20.5 (2 x Ar-CH3), 21.0, 21.1 (2 x BI-CH3), 45.8 (N-CH2), 111.9, 120.2, 125.5, 129.2 (4
x BI-C), 129.8 (Py-Cm), 131.7, 132.8 (2 x Ar-C), 134.9 (BI-C), 137.1 (Py-Cp), 137.6 (BI-C),
138.2, 141.7 (2 x Ar-C), 149.9 (Py-Co), 150.5 (N ¼ C-N).
Compound 2d: Yield: 86%. Elemental analysis: calcd (%) for C47H53N5 (687.43): C,
1
82.05; H, 7.77; N, 10.18%. Found: C, 81.76; H, 7.51; N, 10.65%. H NMR (400 MHz, 303 K,
CDCl3) d: 2.07 (s, 12H), 2.13 (s, 6H), 2.15 (s, 12H, Ar-CH3), 2.23 (s, 6H), 2.31 (s, 6H, BI-
CH3), 6.16 (s, 4H, N-CH2), 6.43 (s, 2H), 7.58 (s, 2H, BI-H), 8.04 (t, 1H, J ¼ 7.9 Hz, Py-Hp),
8.39 (d, 2H, J ¼ 7.9 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) d: 16.9, 17.0, 17.3 (3 x
Ar-CH3), 20.4, 21.1 (2 x BI-CH3), 47.4 (N-CH2), 112.3, 120.0, 125.5, 129.3 (4 x BI-C), 131.6
(Py-Cm), 132.6, 133.0 (2 x Ar-C), 133.2 (BI-C), 135.2 (Py-Cp), 138.1 (BI-C), 141.7 (Ar-C),
149.9 (Py-Co), 150.5 (N ¼ C-N).
4.3. General procedures for the synthesis of 3a–d and 4a–d
CuCl2ꢀ2H20 (1 mmol) and ligand (1 mmol) were stirred at 40 ꢁC for 20 min in 10 ml of
MeOH. The resulting green precipitate was filtered and washed with diethylether and
dried in vacuo.

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11
Complex 3a: Yield: 90%. Elemental analysis: calcd (%) for C19H13N5Cl2Cu (443.98): C,
1
51.19; H, 2.94; N, 15.71%. Found: C, 51.21; H, 2.99; N, 15.75%. m/z: 409.03%. H NMR
(400 MHz, 303 K DMSO-d6) d: 7.19–7.23 (m, 4H, BI-H), 7.79 (bs, 4H, BI-H), 8.19 (t, 1H,
J ¼ 7.8 Hz, Py-Hp), 8.30 (d, 2H, J ¼ 7.6 Hz, Py-Hm).
IR (KBr; cmꢂ1): 2903 (m), 2857 (m), 2748 (m), 2639 (m), 1605 (m) (mC¼C), 1587 (m),
1577 (m) (mC¼N), 1495 (m), 1468 (s), 1321 (s), 1143 (w), 1016 (m), 995 (m), 822 (m), 768
(m), 762 (m), 748 (s). UV–Vis (nm): 360, 385.
Complex 3b: Yield: 89%. Elemental analysis: calcd (%) for C33H25N5Cl2Cu (624.08): C,
1
63.31; H, 4.03; N, 11.19%. Found: C, 63.41; H, 4.12; N, 11.26%. m/z: 589.05. H NMR
(400 MHz, 303 K DMSO-d6) d: 5.75 (s, 4H, N-CH2), 6.80–6.82 (m, 4H, BI-H), 7.10–7.17 (m,
6H, Ar-H), 7.23–7.29 (m, 4H, Ar-H), 7.46 (d, 2H, J ¼ 8.0 Hz, BI-H), 7.76 (d, 2H, J ¼ 8.8 Hz,
BI-H), 8.19 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.35 (d, 2H, J ¼ 7.6 Hz, Py-Hm). IR (KBr; cmꢂ1): 2919
(m), 2880 (w), 1638 (m), 1618 (m), 1598 (m) (mC¼C), 1574 (m) (mC¼N), 1511 (m), 1483
(m), 1464 (s), 1435 (s), 1422 (m), 1390 (m), 1338 (m), 1299 (w), 1250 (w), 1209 (w),
1094 (m), 1086 (m), 807 (w), 751 (s). UV–Vis (nm): 380, 390.
Complex 3c: Yield: 92%. Elemental analysis: calcd (%) for C39H37N5Cl2Cu (708.17): C,
65.96; H, 5.25; N, 9.86%. Found: C, 66.03; H, 5.36; N, 9.97%. m/z: 673.20. 1H NMR
(400 MHz, 303 K DMSO-d6) d: 1.99 (s, 12H, Ar-CH3), 2.20 (s, 6H, Ar-CH3), 6.21 (s, 4H, N-
CH2), 6.78 (s, 4H, Ar-H), 6.79 (d, 2H, J ¼ 4.8 Hz, BI-H), 7.10 (t, 2H, J ¼ 7.6 Hz, BI-H), 7.23 (t,
2H, J ¼ 7.6 Hz, BI-H), 7.78 (d, 2H, J ¼ 8.0 Hz, BI-H), 8.31 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.51 (d,
2H, J ¼ 8.0 Hz, Py-Hm). IR (KBr; cmꢂ1): 2967 (m), 2950 (m), 2916 (m), 2859 (w), 1613 (s),
1598 (s) (mC¼C), 1576 (m) (mC¼N), 1515 (m), 1485 (s), 1470 (s), 1457 (s), 1447 (s), 1424
(s), 1390 (m), 1338 (s), 1282 (m), 1023 (w), 1015 (w), 853 (m), 807 (m), 757 (s), 752 (s),
705 (m). UV–Vis (nm): 380, 395.
Complex 3d: Yield: 93%. Elemental analysis: calcd (%) for C43H45N5Cl2Cu (764.23): C,
67.40; H, 5.92; N, 9.14%. Found: C, 67.51; H, 5.98; N, 9.24%. m/z: 729.60%. 1H NMR
(400 MHz, 303 K DMSO-d6) d: 1.90 (s, 12H, Ar-CH3), 1.99 (s, 12H, Ar-CH3), 2.11 (s, 6H, Ar-
CH3), 6.20 (s, 4H, N-CH2), 6.64 (d, 2H, J ¼ 8.4 Hz, BI-H), 6.98 (t, 2H, J ¼ 7.6 Hz, BI-H), 7.13
(t, 2H, J ¼ 7.6 Hz, BI-H), 7.69 (d, 2H, J ¼ 8.0 Hz, BI-H), 8.21 (t, 1H, J ¼ 8.0 Hz, Py-Hp), 8.42
(d, 2H, J ¼ 7.6 Hz, Py-Hm). IR (KBr; cmꢂ1): 2980 (m), 2920 (m), 1596 (s) (mC¼C), 1572 (m)
(mC¼N), 1511 (m), 1483 (s), 1463 (s), 1436 (s), 1421 (s), 1387 (m), 1338 (s), 1158 (w),
1070 (w), 1013 (w), 806 (m), 751 (s). UV–Vis (nm): 390, 405.
Complex 4a: Yield: 88%. Elemental analysis: calcd (%) for C23H21N5Cl2Cu (500.05): C,
1
55.04; H, 4.22; N, 13.95%. Found: C, 55.26; H, 4.18; N, 13.84%. m/z: 465.09. H NMR
(400 MHz, 303 K DMSO-d6) d: 2.42 (s, 12H, BI-CH3), 7.60 (bs, 4H, BI-H), 8.07 (t, 1H,
J ¼ 7.6 Hz, Py-Hp), 8.23 (d, 2H, J ¼ 8.0 Hz, Py-Hm). IR (KBr; cmꢂ1): 2967 (s), 2920 (s), 2881
(s), 2860 (s), 2775 (s), 2703 (s), 2627 (s), 1612 (s) (mC¼C), 1578 (s) (mC¼N), 1557 (s), 1488
(s), 1470 (s), 1386 (m), 1327 (m), 1274 (s), 1159 (s), 1125 (m), 1085 (m), 1014 (s), 999
(s), 969 (s), 852 (s), 823 (s), 686 (m). UV–Vis (nm): 395, 420.
Complex 4b: Yield: 88%. Elemental analysis: calcd (%) for C37H33N5Cl2Cu (680.14): C,
1
65.15; H, 4.88; N, 10.27%. Found: C, 65.23; H, 4.97; N, 10.36%. m/z: 645.18. H NMR
(400 MHz, 303 K DMSO-d6) d: 2.27 (s, 6H, BI-CH3), 2.30 (s, 6H, BI-CH3), 5.68 (s, 4H, N-
CH2), 6.78 (bs, 4H, Ar-H), 7.14 (s, 6H, Ar-H), 7.23 (bs, 2H, BI-H), 7.52 (bs, 2H, BI-H), 8.11
(t, 1H, J ¼ 8.0 Hz, Py-Hp), 8.27 (d, 2H, J ¼ 6.4 Hz, Py-Hm). IR (KBr; cmꢂ1): 2969 (w), 2938
(m), 1646 (m), 1599 (m) (mC¼C), 1579 (m) (mC¼N), 1567 (m), 1510 (m), 1496 (m), 1478 (s),

12
S. GÜNNAZ
1450 (s), 1361 (w), 1347 (m), 1328 (m), 1298 (w), 1269 (m), 1207 (m), 1162 (m), 1106
(m), 1089 (m), 1077 (w), 1022 (m), 1005 (m), 995 (m), 879 (m), 855 (m), 844 (w), 821
(m), 738 (m), 732 (m), 718 (m). UV–Vis (nm): 390, 420.
Complex 4c: Yield: 90%. Elemental analysis: calcd (%) for C43H45N5Cl2Cu (764.23): C,
67.40; H, 5.92; N, 9.14%. Found: C, 66.01; H, 5.81; N, 9.01%. m/z: 729.22. 1H NMR
(400 MHz, 303 K DMSO-d6) d: 1.88 (s, 12H, Ar-CH3), 2.08 (s, 6H, Ar-CH3), 2.12 (s, 6H, BI-
CH3), 2.23 (s, 6H, BI-CH3), 6.05 (s, 4H, N-CH2), 6.49 (s, 2H, BI-H), 6.69 (s, 4H, Ar-H), 7.46
(s, 2H, BI-H), 8.15 (t, 1H, J ¼ 8.0 Hz, Py-Hp), 8.34 (d, 2H, J ¼ 8.0 Hz, Py-Hm). IR (KBr; cmꢂ1):
2969 (m), 2943 (m), 2918 (m), 2860 (m), 1603 (s) (mC¼C), 1575 (m) (mC¼N), 1518 (m),
1506 (m), 1478 (s), 1462 (s), 1450 (s), 1433 (s), 1386 (m), 1333 (m), 1288 (m), 1025 (m),
1002 (m), 861 (m), 852 (m), 838 (m), 807 (m), 690 (m). UV–Vis (nm): 395, 420.
Complex 4d: Yield: 90%. Elemental analysis: calcd (%) for C47H53N5Cl2Cu (820.30): C,
68.64; H, 6.50; N, 8.52%. Found: C, 68.32; H, 6.23; N, 8.27%. m/z: 785.30. 1H NMR
(400 MHz, 303 K DMSO-d6) d: 1.89 (s, 12H, Ar-CH3), 1.99 (s, 12 H, Ar-CH3), 2.04 (s, 6H, Ar-
CH3), 2. 10 (s, 6H, BI-CH3), 2.21 (s, 6H, BI-CH3), 6.10 (s, 4H, N-CH2), 6.45 (s, 2H, BI-H),
7.43 (s, 2H, BI-H), 8.10 (t, 1H, J ¼ 7.8 Hz, Py-Hp), 8.28 (d, 2H, J ¼ 7.6 Hz, Py-Hm). IR (KBr;
cmꢂ1): 2966 (m), 2919 (m), 1602 (s) (mC¼C), 1574 (m) (mC¼N), 1517 (s), 1493 (m), 1454
(s), 1417 (s), 1386 (m), 1377 (m), 1337 (m), 1285 (m), 1215 (w), 1166 (w), 1067 (m),
1050 (m), 1001 (m), 883 (w), 854 (m), 808 (m), 738 (w), 692 (w). UV–Vis (nm): 395, 410.
4.4. General procedure for the TH reactions
A mixture of acetophenone (1 mmol), the catalyst (1 mol %), KOH (1 mmol), and
propan-2-ol (1 mL) were stirred at 82 ꢁC. At the desired reaction times, aliquots were
1
withdrawn from the reaction vessel. The reaction was monitored by H-NMR. The con-
versions were recorded for an average of three runs.
Disclosure statement
No potential conflict of interest was reported by the author.
Funding
This study was funded by Ege University Scientific Research Projects Coordinatorship (EGE-BAP)
with project code: 17-FEN-075. The author is indebted to Ege University for the finan-
cial supports.
ORCID
€
Salih Gunnaz
http://orcid.org/0000-0002-7422-6593
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