Synthesis of 4-Alkyl-4H-1,2,4-triazole Derivatives by Suzuki Cross-Coupling Reactions and Their Luminescence Properties

Article abstract of DOI:10.3390/molecules24030652

New derivatives of 4-alkyl-3,5-diaryl-4H-1,2,4-triazole were synthesized utilizing the Suzuki cross-coupling reaction. The presented methodology comprises of the preparation of bromine-containing 4-alkyl-4H-1,2,4-triazoles and their coupling with different commercially available boronic acids in the presence of ionic liquids or in conventional solvents. The obtained compounds were tested for their luminescence properties.

Full text of DOI:10.3390/molecules24030652

molecules
Article
Synthesis of 4-Alkyl-4H-1,2,4-triazole Derivatives by
Suzuki Cross-Coupling Reactions and Their
Luminescence Properties
Monika Olesiejuk 1 , Agnieszka Kudelko 1,
*
, Marcin Swiatkowski 2 and Rafal Kruszynski 2
1
Department of Chemical Organic Technology and Petrochemistry, The Silesian University of Technology,
Krzywoustego 4, PL-44100 Gliwice, Poland; monika.olesiejuk@polsl.pl
2
Department of X-ray Crystallography and Crystal Chemistry, Institute of General and Ecological Chemistry,
˙
Lodz University of Technology, Zeromskiego 116, PL-90924 Łódz´, Poland;
marcin.swiatkowski@p.lodz.pl (M.S.); rafal.kruszynski@p.lodz.pl (R.K.)
Correspondence: agnieszka.kudelko@polsl.pl; Tel.: +48-32-237-17-29
*
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editor: Philippe Belmont
Received: 24 January 2019; Accepted: 8 February 2019; Published: 12 February 2019
ꢀꢁꢂꢃꢄꢅꢆ
Abstract: New derivatives of 4-alkyl-3,5-diaryl-4H-1,2,4-triazole were synthesized utilizing the
Suzuki cross-coupling reaction. The presented methodology comprises of the preparation of
bromine-containing 4-alkyl-4H-1,2,4-triazoles and their coupling with different commercially
available boronic acids in the presence of ionic liquids or in conventional solvents. The obtained
compounds were tested for their luminescence properties.
Keywords: Suzuki cross-coupling; heterocycles; 1,2,4-triazole derivatives; ionic liquids;
luminescence properties
1. Introduction
Heterocyclic compounds containing 4H-1,2,4-triazole moiety are very attractive due to their
wide range of biological activities [
anti-diabetic [ ] or anti-neuropathic [
and herbicides [ ], and in industry as corrosion inhibitors [
valuable electronic and optical properties [10].
The most popular method for the synthesis of 3,4,5-trisubstituted 4H-1,2,4-triazole core [11
1
6
], such as antibacterial [
] properties. They are also applied in agriculture as fungicides
] or in material science due to their
2], anticancer [3], anticonvulsant [4],
5
7
8,9
,12]
involves the reaction of diacylhydrazines with aromatic amines, in the presence of the dehydrating
0
agent, e.g., phosphorus pentoxide [13], zinc chloride [14] or N,N -diphenylphosphenimidous amide [15].
Other methods include the conversion of other heterocyclic systems, such as 1,3,4-oxadiazoles [16
,17],
1,3,4-thiadiazoles [18] or dihydro-1,2,4,5-tetrazines [19].
Ionic liquids (IL) are considered modern green solvents, mainly due to their low vapor pressure,
good thermal stability, and wide liquid regions [20–22]. Recent reports have also shown that IL can act
as effective catalysts [23–25].
Our previous reports examined diacylhydrazines as potent reagents in the synthesis of
heterocycles such as 1,3,4-oxadiazoles and 1,3,4-thiadiazoles [26 27], which were found to be valuable
units in the synthesis of five-membered rings, allowing the formation of compounds bearing
extended -conjugated systems with excellent optical properties. Herein, we report the synthesis of
,
π
4H-1,2,4-triazole core as a structural analogue of our previously investigated heterocyclic arrangements,
expecting that it will exhibit equally good features.
Molecules 2019, 24, 652; doi:10.3390/molecules24030652
www.mdpi.com/journal/molecules

Molecules 2019, 24, 652
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2. Results and Discussion
Our study began by synthesizing four basic 4-alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazole (3a–d
units (Scheme 1). The starting material in the reaction sequence was N,N -bis(4-bromobenzoyl)hydrazine
)
0
(
1
), which was prepared using previously described methods [26
in 80% yield (entry 3, Table 1) into the more reactive chloro-derivative
pentachloride and in the non-polar solvent toluene. Heating compound
,
28]. Compound
in the presence of phosphorus
with excess butylamine
1 was transformed
2
2
generated the corresponding 4-butyl-4H-1,2,4-triazole derivative 3c (71%, entry 3, Table 1). An attempt
to extend the reaction time only slightly improved the yield (73%, entry 4, Table 1). Using our designed
conditions, three other 4-alkyl-4H-1,2,4-triazole derivatives with phenyl groups with terminally
substituted bromine were synthesized in good yields (3a, 3b, 3d, Scheme 1) and subsequently used as
precursors for Suzuki cross-coupling reactions.
Scheme 1. Synthesis of 4-alkyl-4H-1,2,4-triazole core. Reagents and conditions: (i) PCl5, toluene, reflux,
5 min; (ii) R-NH2, toluene, reflux, 10 h.
Table 1. Products of the reaction of N,N0-bis(4-bromobenzoyl)hydrazine (
N,N -bis[(4-bromophenyl)chloromethylene]hydrazine (2) with butylamine.
1) with PCl5 and
0
Product 2
Product 3c
Entry
1: PCl5 Ratio
(equiv.)
2: Bu-NH2
Ratio (equiv.)
◦
◦
Temp. ( C)
Time (min.)
Yield (%)
Solvent
Temp. ( C)
Time (h)
Yield (%)
1
2
3
4
1:2
1:2
1:2
1:4
20
60
60
5
12
3
80
56
1:2
1:2
1:4
1:4
chloroform
toluene
toluene
61
10
10
10
20
33
50
71
73
110
110
110
110
110
110
5
toluene
In order to select the most favorable conditions for the next stage—Suzuki cross-coupling—the
selected dibromo 1,2,4-triazole derivative 3c was treated with the phenylboronic acid (4a). Due to
the use of a two-phase solvent system, it was necessary to employ a phase transfer catalyst. A better
result was obtained when tetrabutylammonium bromide acted as the catalyst instead of its chloro
counterpart (Table 2, entries 1 and 2). The use of a slight excess of a boronic acid with respect to the
triazole derivative 3c resulted in a significant improvement in yield (Table 2, entries 2 and 3). Then the
influence of the type of base on the reaction yield was investigated (Table 2, entries 3–10). The study
revealed that the best results in the two-phase solvent system were achieved with the use of different
carbonates (Table 2, entries 3–6). Interestingly, it turned out that product 7a can also be obtained in
a single-phase system employing an organic base such as sodium alkoxide. In this case, the best result
was obtained using sodium t-butoxide (Table 2, entry 10).
Using these reaction conditions, new organic hybrids containing a 4-alkyl-4H-1,2,4-triazole
moiety were synthesized (Scheme 2). 4-Alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazoles (3a
–d) were
first heated in an oil bath with excess boronic acids 4a in the presence of 5 mol% palladium
–
n
catalyst Pd(PPh3)4 and 10 mol% phase transfer catalyst NBu4Br. Reactions were conducted
in a two-phase toluene/H2O/EtOH solvent system and monitored by TLC until the initial
4-alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazole (3a–d) was entirely consumed.

Molecules 2019, 24, 652
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Table 2. The conventional Suzuki cross-coupling reaction for 3,5-bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-
triazole (7a).
Entry
3c/4a Ratio (equiv.)
Solvents
PTC Catalyst (equiv.)
Base (equiv.)
Yield (%) a
1
2
3
4
5
6
1:2
1:2
1:2.5
1:2.5
1:2.5
1:2.5
Toluene/H2O/EtOH
Toluene/H2O/EtOH
Toluene/H2O/EtOH
Toluene/H2O/EtOH
Toluene/H2O/EtOH
Toluene/H2O/EtOH
NBu4Cl (0.1)
NBu4Br (0.1)
NBu4Br (0.1)
NBu4Br (0.1)
NBu4Br (0.1)
NBu4Br (0.1)
Li2CO3 (10)
Li2CO3 (10)
Li2CO3 (10)
Na2CO3 (10)
K2CO3 (10)
Cs2CO3 (10)
36
58
89
91
92
87
7
8
9
1:2.5
1:2.5
1:2.5
1:2.5
Toluene/H2O/EtOH
Toluene
NBu4Br (0.1)
K3PO4 (10)
EtONa (10)
iPrONa (10)
tBuONa (10)
8
9
77
88
-
-
-
Toluene
Toluene
10
a
Yield with respect to the 4-butyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazole (3c). Conditions: oil bath 130 ◦C, 5 h.
Scheme 2. The conventional Suzuki cross-coupling reaction for 4-alkyl-3,5-bis(4-bromophenyl)-4H-
1,2,4-triazole moiety. Reagents and conditions: aryl dibromide 3a–d (1.00 mmol), arylboronic acid 4a–n
(2.50 mmol), Pd(PPh3)4 (0.05 mmol), NBu4Br (0.10 mmol), K2CO3 (10 mmol), toluene/H2O/EtOH
◦
(10:6:3 mL), oil bath 130 C, 4–12 h.
An alternative method was sought for 3,5-bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7a
)
synthesis. A commercially available IL was selected based its ability to act both as a solvent and
base necessary in the catalytic cycle.
Aqueous solutions of four different hydroxide IL containing different cations, i.e.,
benzyltrimethylammonium (BTMA-OH), choline (Choline-OH), hexadecyltrimethylammonium
(HDTMA-OH) and tetrabutylammonium (TBA-OH), were tested. Due to the limited solubility of
substrates in these solvents, the addition of 10% non-polar conventional solvent (toluene) was necessary.
Interestingly, among the tested systems, only one IL, Choline-OH, could be used without the addition
of a base, resulting in the formation of the product 7a in 83% yield (entry 4, Table 3). We found that the
IL can be regenerated and recycled into the reaction with only a slight decrease in product yield after
five cycles (Figure 1).
Table 3. The synthesis of 3,5-bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7a) in IL.
Entry
IL (10 mL)
Traditional Solvents (1 mL)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
BTMA-OH
BTMA-OH
Choline-OH
Choline-OH
HDTMA-OH
HDTMA-OH
TBA-OH
Chloroform
Toluene
Chloroform
Toluene
Chloroform
Toluene
Chloroform
Toluene
24
24
24
24
24
24
24
24
-
-
-
83
-
-
-
-
TBA-OH

Molecules 2019, 24, 652
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100
80
60
40
20
0
86
84
83
82
79
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5
Figure 1. Yield of the selected product 7a for the synthesis in choline ionic liquids.
Using our standard conditions, novel sets of compounds containing a 4-alkyl-4H-1,2,4-triazole
moiety were synthesized (Table 4). Generally, compounds containing a 4H-1,2,4-triazole core
substituted with an ethyl or propyl group at the position 4 were synthesized at slightly higher yields
than their counterparts with butyl or hexyl substituents (61–99% for 5a
for 7a–n, 37–93% for 8a–n, Table 4). Interestingly, the lowest yields were obtained for compounds 5m
6m 7m 8m, containing a terminal thiophen-2-yl group (61% for 5m, 52% for 6m, 49% for 7m, 37%
–n, 52–99% for 6a–n, 49–98%
,
,
,
for 8m, Table 4). Other products possesing terminal electron-deficient and electron-rich substituted
phenyl group or other heterocyclic arrangements were produced in relatively higher yields (85–99%
for 5a–l,n, 69–99% for 6a–l,n, 74–98% for 7a–l,n, 62–93% for 8a–l,n, Table 4).
Table 4. 4-Alkyl-3,5-bis(4-arylphenyl)-4H-1,2,4-triazoles 5a–n, 6a–n, 7a–n, 8a–n prepared in Suzuki
cross-coupling reaction.
Central Core
Ar Substituent
5a Y = 87 a
6a Y = 94 a
7a Y = 92 a
8a Y = 92 a
Φ = 0.797/0.886 b
Φ = 0.763/0.848 b
Φ = 0.793/0.882 b
Φ = 0.663/0.737 b
∆ = 102 c
∆ = 99 c
∆ = 99 c
∆ = 100 c
abs
abs
abs
abs
λ
λ
λ
= 281
= 292
= 383
λ
λ
λ
= 282
= 290
= 381
λ
λ
λ
= 282
= 293
= 381
λ
λ
λ
= 282
= 292
= 382
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5b Y = 85 a
6b Y = 81 a
7b Y = 83 a
8b Y = 7 a
Φ = 0.496/0.552 b
Φ = 0.687/0.764 b
Φ = 0.433/0.482 b
Φ = 0.655/0.728 b
∆ = 118 c
∆ = 104 c
∆ = 110 c
∆ = 105 c
abs
abs
abs
abs
λ
λ
λ
= 268
= 286
= 386
λ
λ
λ
= 268
= 286
= 372
λ
λ
λ
= 269
= 282
= 379
λ
λ
λ
= 269
= 283
= 374
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5c Y = 97 a
6c Y = 91 a
7c Y = 96 a
8c Y = 91a
Φ = 0.601/0.668 b
Φ = 0.781/0.869 b
Φ = 0.634/0.705 b
Φ = 0.830/0.923 b
∆ = 113 c
∆ = 97 c
∆ = 97 c
∆ = 97 c
abs
abs
abs
abs
λ
λ
λ
= 283
= 293
= 396
λ
λ
λ
= 284
= 292
= 381
λ
λ
λ
= 285
= 293
= 382
λ
λ
= 284
= 293
= 381
max
ex
max
ex
max
ex
max
ex
H3C
max
em
max
em
max
em
max
em
λ
max
max
max
max
5d Y = 90 a
6d Y = 94 a
7d Y = 79 a
8d Y = 93 a
Φ = 0.363/0.404 b
Φ = 0.523/0.582 b
Φ = 0.262/0.291 b
Φ = 0.593/0.659 b
∆ = 128 c
∆ = 105 c
∆ = 105 c
∆ = 114 c
abs
abs
abs
abs
λ
λ
λ
= 259
= 281
= 387
λ
λ
λ
= 259
= 278
= 364
λ
λ
λ
= 258
= 275
= 363
λ
λ
λ
= 259
= 281
= 373
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5e Y = 91 a
6e Y = 91 a
7e Y = 85 a
8e Y = 88 a
Φ = 0.556/0.618 b
Φ = 0.864/0.961 b
Φ = 0.601/0.668 b
Φ = 0.565/0.629 b
∆ = 132 c
∆ = 84 c
∆ = 85 c
∆ = 90 c
abs
abs
abs
abs
λ
λ
λ
= 296
= 303
= 404
λ
λ
λ
= 296
= 302
= 380
λ
λ
λ
= 295
= 301
= 380
λ
λ
λ
= 296
= 302
= 386
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max

Molecules 2019, 24, 652
5 of 20
Table 4. Cont.
Central Core
Ar Substituent
5f Y = 99 a
6f Y = 95 a
7f Y = 8 a
8f Y = 83 a
Φ = 0.770/0.856 b
Φ = 0.699/0.777 b
Φ = 0.680/0.756 b
Φ = 0.583/0.648 b
∆ = 100 c
∆ = 99 c
∆ = 97 c
∆ = 100 c
abs
abs
abs
abs
λ
λ
λ
= 282
= 297
= 382
λ
λ
λ
= 283
= 298
= 382
λ
λ
λ
= 284
= 296
= 381
λ
λ
λ
= 284
= 299
= 384
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5g Y = 94 a
6g Y = 91 a
7g Y = 91 a
8g Y = 85 a
Φ = 0.052/0.057 b
Φ = 0.027/0.031 b
Φ = 0.016/0.018 b
Φ = 0.010/0.011 b
∆ = 105 c
∆ = 104 c
∆ = 119 c
∆ = 109 c
abs
abs
abs
abs
λ
λ
λ
= 275
= 300
= 380
λ
λ
λ
= 276
= 290
= 380
λ
λ
λ
= 276
= 310
= 295
λ
λ
λ
= 276
= 310
= 285
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5h Y = 99a
6h Y = 99 a
7h Y = 98 a
8h Y = 78 a
Φ = 0.323/0.360 b
Φ = 0.298/0.331 b
Φ = 0.328/0.364 b
Φ = 0.131/0.146 b
∆ = 126 c
∆ = 123 c
∆ = 125 c
∆ = 122 c
abs
abs
abs
abs
λ
λ
λ
= 280
= 292
= 406
λ
λ
λ
= 282
= 290
= 405
λ
λ
λ
= 281
= 292
= 406
λ
λ
λ
= 281
= 293
= 403
max
ex
max
ex
max
ex
max
ex
H2N
max
em
max
em
max
em
max
em
max
max
max
max
5i Y = 89a
6i Y = 90 a
7i Y = 87 a
8i Y = 86 a
Φ = 0.574/0.638 b
Φ = 0.363/0.403 b
Φ > 0.98 b,d
Φ = 0.560/0.623 b
∆ = 107 c
∆ = 107 c
∆ = 169 c
∆ = 107 c
abs
abs
abs
abs
λ
λ
λ
= 280
= 291
= 387
λ
λ
λ
= 281
= 291
= 388
λ
λ
λ
= 281
= 324
= 450
λ
λ
λ
= 281
= 292
= 388
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5j Y = 93a
6j Y = 69 a
7j Y = 74 a
8j Y = 83 a
Φ = 0.557/0.619 b
Φ = 0.612/0.680 b
Φ = 0.149/0.165 b
Φ = 0.262/0.291 b
∆ = 95 c
∆ = 97 c
∆ = 148 c
∆ = 147 c
abs
abs
abs
abs
λ
λ
λ
= 284
= 291
= 379
λ
λ
λ
= 284
= 292
= 381
λ
λ
λ
= 285
= 299
= 433
λ
λ
λ
= 284
= 300
= 431
max
ex
max
ex
max
ex
max
ex
max
max
em
max
em
max
em
em
max
max
max
max
5k Y = 92 a
Φ > 0.98 b,d
6k Y = 96 a
Φ > 0.98 b,d
7k Y = 75 a
8k Y = 89 a
Φ > 0.98 b,d
Φ = 0.857/0.953 b
∆ = 85 c
∆ = 83 b
∆ = 91 c
∆ = 85 c
abs
abs
abs
abs
λ
λ
λ
= 310
= 314
= 395
λ
λ
λ
= 311
= 314
= 394
λ
λ
λ
= 310
= 316
= 401
λ
λ
λ
= 310
= 314
= 395
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5l Y = 91a
6l Y = 92 a
7l Y = 94a
8l Y = 69 a
Φ = 0.658/0.732 b
Φ = 0.622/0.691 b
Φ = 0.642/0.714 b
Φ = 0.580/0.645 b
∆ = 91 c
∆ = 93 c
∆ = 102 c
∆ = 95 c
abs
abs
abs
abs
λ
λ
λ
= 283
= 293
= 374
λ
λ
λ
= 284
= 292
= 377
λ
λ
λ
= 285
= 294
= 387
λ
λ
λ
= 284
= 293
= 379
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5m Y = 61 a
6m Y = 52 a
7m Y = 49 a
8m Y = 37 a
Φ = 0.716/0.796 b
Φ = 0.750/0.834 b
Φ = 0.685/0.762 b
Φ = 0.753/0.837 b
∆ = 87 c
∆ = 85 c
∆ = 89 c
∆ = 85 c
abs
abs
abs
abs
λ
λ
λ
= 311
= 316
= 398
λ
λ
λ
= 312
= 315
= 397
λ
λ
λ
= 312
= 320
= 401
λ
λ
λ
= 312
= 316
= 397
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
5n Y = 90a
6n Y = 90a
7n Y = 77 a
8n Y = 62 a
Φ = 0.545/0.605 b
Φ = 0.793/0.881 b
Φ = 0.513/0.570 b
Φ = 0.524/0.583 b
∆ = 111 c
∆ = 85 c
∆ = 104 c
∆ = 95 c
abs
abs
abs
abs
λ
λ
λ
= 290
= 301
= 401
λ
λ
λ
= 290
= 298
= 382
λ
λ
λ
= 289
= 302
= 393
λ
λ
λ
= 290
= 299
= 385
max
ex
max
ex
max
ex
max
ex
max
em
max
em
max
em
max
em
max
max
max
max
a The reaction yield (Y) [%]. b Quantum yield (
Φ
) [29]. Quinine sulfate [30] and trans,trans-1,4-diphenyl-1,3-butadiene [31
]
c
em
abs
were used as standards. Stokes shift (
∆
) from the equation ∆ = λ
− λ . Wavelength determined from the 3D
max
max
d
emission spectrum [nm]. Exact value cannot be determined due to nonlinearity of standard/sample dependence
[29] in the Φ region 0.97–1.00.
All the final products were screened for their luminescence properties, displaying strong
fluorescent properties. The only exception occurred for compounds 5–8g containing a nitrophenyl

Molecules 2019, 24, 652
6 of 20
moiety (Table 4), due the presence of a strong electron withdrawing -NO2 group, which diminished
the electron density within an aromatic system and subsequently changed the energy of delocalized
orbitals accompanied by a decrease in population of fluorescent transitions. Generally, compounds
containing aliphatic chains with an even number of carbon atoms exhibit longer emission wavelengths,
than those of odd numbers (Table 4). This effect was independent from the absorption or excitation
wavelengths (Figure 2a,b). The wavelengths of absorption and excitation maxima depended mainly on
the Ar substituent type, i.e., for the same Ar substituent, these wavelengths are similar (Figure 2c,d).
(a)
(b)
(d)
(c)
Figure 2. Absorption-emission or excitation-emission maxima of studied compounds: (
emission maxima of studied compounds containing ethyl (5a–n), propyl (6a–n), butyl (7a–n) and
hexyl (8a–n) substituents; ( ) excitation-emission maxima of studied compounds containing ethyl
5a–n), propyl (6a–n), butyl (7a–n) and hexyl (8a–n) substituents; ( ) absorption-emission maxima of
a) Absorption-
b
(
c
studied compounds containing different aryl substituents; (d) excitation-emission maxima of studied
compounds containing different aryl substituents.
The calculated quantum yields (
Φ
) correlated with registered values of fluorescence (larger
and absorption was
fluorescence leads to larger , Figure 3a), whereas no relationship between the
Φ
Φ
observed (Figure 3b). This meant that the emission mechanism was similar in all compounds and the
differences in values of absorption originated from the variation in the amount of electromagnetic
energy (photons) transformed into internal energy. The 3D fluorescence spectra in most cases displayed
one well-shaped maximum, originating from the absorption-emission effects occurring within the
central moiety. The exceptions are compounds 6i and 8i, containing 4-pyridyl substituent (spectrum
of compound 6i contains two maxima, and of 8i exhibits large broadening at longer emission
wavelengths). The presence of a fluorescent substituent (pyridyl) caused the formation of the second
re-emission effect, partially overlapped with the fluorescence of the central moiety, influencing the
shape of the emission spectrum. These changes were also observed in other synthesized compounds
containing the pyridyl moiety (5i, 7i, 5j–8j); however, the broadening was less visible due to a smaller

Molecules 2019, 24, 652
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shift and larger overlap of the emission maxima. In all cases, the n→π* absorption transitions are the
main origin of excited states leading to subsequent fluorescence.
(a)
(b)
Figure 3. Quantum yield of studied compounds: (
a
) Quantum yield and intensity of fluorescence of
ex
studied compounds; (b) Quantum yield of fluorescence and absorbance at excitation wavelength (
λ
)
max
of studied compounds.
The determined optimal excitation wavelengths are similar to those registered for 1,2,4-triazole
and certain bromo derivatives; however, in our case, the calculated quantum yields were much
greater than the ones for 1,2,4-triazole and the above-mentioned derivatives (up to four orders of
magnitudes, e.g., Φ1,2,4-triazole = 5
wavelengths at global maxima of 3D fluorescence spectra vary from 75 nm to 168 nm, with the most
×
104) [32]. The differences between the excitation and emission
populated value at ca. 80 nm (Figure 4). The largest shift in wavelengths occurred for compound 7b
which upon absorption of ultraviolet light emitted a strong blue fluorescence. Such shift is rare, as
typically fluorescent compounds possess emission wavelengths separated by less than 100 nm from
excitation wavelengths. Upon irradiation by UV light, 7i emitted a blue light and compounds 7j and
8j emitted a violet light visible by the naked eye.
,
em
ex
Figure 4. The distribution of the ∆λ = λ
− λ
for the studied compounds.
max
max
3. Experimental
3.1. General Information
Melting points were measured on a Stuart SMP3 melting point apparatus. The 1H-NMR and
13C-NMR spectra were recorded on an Agilent 400-NMR spectrometer in CDCl3 solution using TMS as
−1
the internal standard. FT-IR spectra were performed between 4000 and 650 cm using a FT-IR Nicolet
6700 apparatus with a Smart iTR accessory. UV-Vis spectra were registered at room temperature in
CH2Cl2 on a Jasco V-660 spectrophotometer. Fluorescence spectra were registered at room temperature
in CH2Cl2 using a Jasco F-6300 fluorescence spectrophotometer. High-resolution mass spectra were
recorded on a Waters ACQUITY UPLC/Xevo G2QT instrument. Thin-layer chromatography was

Molecules 2019, 24, 652
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performed on silica gel 60 F254 (Merck, Darmstadt, Germany) TLC plates using CHCl3/EtOAc (5:1 v/v)
as the mobile phase. All reagents were purchased from commercial sources and used without further
purification. Aqueous solutions of four different hydroxide IL (Merck) containing different cations
including: benzyltrimethylammonium hydroxide solution 40 wt. % in H2O (BTMA-OH), choline
hydroxide solution 46 wt. % in H2O (Choline-OH), hexadecyltrimethylammonium hydroxide solution
10 wt. % in H2O (HDTMA-OH) and tetrabutylammonium hydroxide solution 40 wt. % in H2O
(TBA-OH) were tested. Copies of the 1H-NMR and 13C-NMR spectra and 3D emission spectra of the
compounds are available in the online Supplementary Materials.
3.2. Synthesis and Characterization
3.2.1. Procedure for the Synthesis of Precursor 2
0
0
N,N -Bis[(4-bromophenyl)chloromethylene]hydrazine (2). A mixture of N,N -bis(4-bromobenzoyl)hydrazine
(
1
, 3.981 g, 0.01 mol) with phosphorus pentachloride (4.164 g, 0.02 mol) in toluene (70 mL) was heated
◦
under reflux in an oil bath (130 C) for 5 min. The clear yellow solution was evaporated under
vacuum. The residue was then dissolved in chloroform (50 mL) and transferred to a separating funnel.
The organic layer was washed with distilled water (5
×
50 mL), dried over MgSO4 and concentrated
using a rotary evaporator. The crude yellow residue was purified by column chromatography (silica gel,
CHCl3 as the mobile phase) to give N,N0-bis[(4-bromophenyl)chloromethylene]hydrazine (
2, 3.490 g,
80% yield) as a light cream solid mp 143–145 ◦C (lit. [33]: 144–145 ◦C).
3.2.2. General Procedure for the Synthesis of Suzuki Cross-Coupling Precursors:
4-alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazoles (3a–d)
To a cooled, vigorously stirred solution of N,N0-bis[(4-bromophenyl)chloromethylene]hydrazine
(2, 4.349 g, 0.01 mol) in toluene (50 mL), the appropriate amine (0.04 mol) was added. The solution
was stirred in an ice bath for 3 h and then at room temperature overnight, followed by heating
for an additional 10 h before being concentrated using a rotary evaporator. The crude residue was
purified by column chromatography (silica gel, CHCl3/EtOAc, 5:1 v/v as the mobile phase) to give
4-alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazole (3a–d).
3,5-Bis(4-bromophenyl)-4-ethyl-4H-1,2,4-triazole (3a). White solid in 78% yield, 3.175 g, m.p. 214–215 ◦C;
UV (CH2Cl2)
λ
max 257.5 nm (ε·10−3 33.3 cm−1M−1); IR (ATR)
ν
: 2966, 1597, 1473, 1457, 1431, 1379, 1080,
1.07 (t, J = 7.2 Hz, 3H,
1067, 1009, 968, 824, 794, 753, 737, 730, 665 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
CH3), 4.08 (q, J = 7.2 Hz, 2H, CH2), 7.52 (d, J = 8.4 Hz, 4H, ArH), 7.65 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR
(100 MHz, CDCl3):
15.8, 40.0, 124.9, 126.4, 130.4, 132.3, 154.5; HRMS m/z calcd for (C16H13N3Br2 + H+):
405.9549; found: 405.9544.
δ
◦
3,5-Bis(4-bromophenyl)-4-propyl-4H-1,2,4-triazole (3b). White solid in 80% yield, 3.369 g, m.p. 208–210 C;
UV (CH2Cl2)
λ
max
258.5 nm (ε·10−3 27.7 cm−1M−1); IR (ATR)
ν: 2955, 2930, 2869, 1468, 1455, 1429,
1401, 1379, 1349, 1269, 1105, 1091, 1069, 1010, 967, 849, 827, 800, 746 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.63 (t, J = 7.2 Hz, 3H, CH3), 1.41 (sext, J = 7.2 Hz, 2H, CH2), 4.03 (t, J = 7.2 Hz, 2H, CH2), 7.54
(
d, J = 8.4 Hz, 4H, ArH), 7.68 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.6, 23.4, 46.6,
124.8, 126.6, 130.4, 132.3, 154.8; HRMS m/z calcd for (C17H15N3Br2 + H+): 419.9705; found: 419.9701.
3,5-Bis(4-bromophenyl)-4-butyl-4H-1,2,4-triazole (3c). White solid in 71% yield, 3.085 g, m.p. 220–223 ◦C;
UV (CH2Cl2)
λ
max 258.0 nm (ε·10−3 28.0 cm−1M−1); IR (ATR)
ν
: 2963, 2927, 2856, 1468, 1430, 1400, 1382,
0.67 (t, J = 7.6 Hz,
1268, 1096, 1069, 1011, 973, 846, 826, 756, 744, 720 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 1.01 (sext, J = 7.6 Hz, 2H, CH2), 1.35 (quin, J = 7.6 Hz, 2H, CH2), 4.06 (t, J = 7.6 Hz, 2H, CH2),
7.54 (d, J = 8.4 Hz, 4H, ArH), 7.67 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.1, 19.2,
31.9, 44.8, 124.7, 126.5, 130.4, 132.3, 154.8; HRMS m/z calcd for (C18H17N3Br2 + H+): 433.9862; found:
433.9863.

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◦
3,5-Bis(4-bromophenyl)-4-hexyl-4H-1,2,4-triazole (3d). White solid in 62% yield, 2.872 g, m.p. 168–169 C;
UV (CH2Cl2)
λ
max
258.0 nm (ε·10−3 31.3 cm−1M−1); IR (ATR)
ν
: 2951, 2931, 2860, 1599, 1464, 1417,
1398, 1381, 1353, 1331, 1147, 1101, 1071, 1014, 977, 853, 842, 825, 772, 753, 734, 720 cm−1; H-NMR
1
(400 MHz, CDCl3):
δ
0.76 (t, J = 7.2 Hz, 3H, CH3), 0.98 (m, 4H, 2
×
CH2), 1.00 (quin, J = 7.2 Hz, 2H,
CH2), 1.36 (quin, J = 7.2 Hz, 2H, CH2), 4.05 (t, J = 7.2 Hz, 2H, CH2), 7.54 (d, J = 8.4 Hz, 4H, ArH), 7.68
(d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.7, 22.2, 25.6, 29.8, 30.6, 45.0, 124.7, 126.6,
130.4, 132.3, 154.8; HRMS m/z calcd for (C20H21N3Br2 + H+): 462.0175; found: 462.0177.
3.2.3. General Procedure for Conventional Suzuki Cross-Coupling Reactions. Synthesis of
4-Alkyl-3,5-bis(4-arylphenyl)-4H-1,2,4-triazoles 5a–n, 6a–n, 7a–n, 8a–n
To a mixture of 4-alkyl-3,5-bis(4-bromophenyl)-4H-1,2,4-triazole (3a–d, 1.00 mmol), the corresponding
boronic acid (4a–n, 2.50 mmol), palladium catalyst Pd(PPh3)4 (0.058 g, 0.05 mmol), phase transfer
catalyst NBu4Br (0.032 g, 0.10 mmol) and base K2CO3 (1.382 g, 10.00 mmol), toluene (9 mL), H2O
(6 mL) and EtOH (3 mL) were added. The mixture was heated under reflux in an oil bath (130 ◦C) for
4–12 h (reaction was monitored by TLC). After cooling, chloroform (50 mL) was added and the solution
transferred to a separating funnel. The aqueous layer was extracted with chloroform (2 × 10 mL).
The combined organic layers were filtered through a silica gel plug (10 mL), which was then flushed
with CHCl3/EtOAc (5:1 v/v). The filtrate was dried over MgSO4 and then concentrated using a rotary
evaporator. The product was precipitated using EtOAc (5 mL), filtered, washed with fresh EtOAc and
air-dried to give the corresponding pure 4-alkyl-3,5-bis(4-arylphenyl)-4H-1,2,4-triazole (5a–n
, 6a–n,
7a–n, 8a–n).
3,5-Bis(biphenyl-4-yl)-4-ethyl-4H-1,2,4-triazole (5a). Beige solid in 87% yield, 0.348 g, m.p. 229–231 ◦C;
UV (CH2Cl2)
λ
281.0 nm (ε·10−3 36.0 cm−1M−1); IR (ATR)
ν
1
: 3029, 2965, 1471, 1456, 1445, 1420,
max
1340, 1083, 1076, 1007, 968, 847, 765, 750, 730, 695, 598 cm−1; H-NMR (400 MHz, CDCl3):
δ
1.16
(
t, J = 7.2 Hz, 3H, CH3), 4.23 (q, J = 7.2 Hz, 2H, CH2), 7.39 (t, J = 7.2 Hz, 2H, ArH), 7.47 (t, J = 7.2 Hz,
4H, ArH), 7.64 (d, J = 7.2 Hz, 4H, ArH), 7.74–7.78 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
15.9,
40.0, 127.2, 127.6, 127.9, 128.3, 128.9, 129.3, 140.0, 142.9, 155.1; HRMS m/z calcd for (C28H23N3 + H+):
402.1965; found: 402.1963.
4-Ethyl-3,5-bis(20-methylbiphenyl-4-yl)-4H-1,2,4-triazole (5b). White solid in 85% yield, 0.366 g, m.p.
247–250 ◦C; UV (CH2Cl2)
λ
268.0 nm (ε·10−3 32.6 cm−1M−1); IR (ATR)
ν: 3060, 3016, 1473, 1454,
max
1425, 1379, 1109, 1051, 1007, 968, 849, 842, 835, 807, 765, 743, 729 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
1.22 (t, J = 7.2 Hz, 3H, CH3), 2.32 (s, 6H, 2
×
CH3), 4.27 (q, J = 7.2 Hz, 2H, CH2), 7.28–7.31 (m, 8H,
16.0,
ArH), 7.50 (d, J = 8.4 Hz, 4H, ArH), 7.75 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
20.4, 40.0, 125.9, 126.2, 127.7, 128.7, 129.6, 129.8, 130.5, 135.3, 140.9, 143.8, 155.2; HRMS m/z calcd for
(C30H27N3 + H+): 430.2278; found: 430.2274.
4-Ethyl-3,5-bis(30-methylbiphenyl-4-yl)-4H-1,2,4-triazole (5c). White solid in 97% yield, 0.417 g, m.p.
194–195 ◦C; UV (CH2Cl2)
λ
283.0 nm (ε·10−3 41.3 cm−1M−1); IR (ATR)
ν: 3015, 2983, 1740, 1474,
max
1418, 1371, 1337, 1236, 1113, 1083, 1042, 1018, 968, 853, 842, 780, 755, 730, 609 cm−1; 1H-NMR (400 MHz,
CDCl3):
δ
1.17 (t, J = 7.2 Hz, 3H, CH3), 2.45 (s, 6H, 2
×
CH3), 4.23 (q, J = 7.2 Hz, 2H, CH2), 7.22
(d, J = 7.6 Hz, 2H, ArH), 7.37 (t, J = 7.6 Hz, 2H, ArH), 7.45–7.47 (m, 4H, ArH), 7.61–7.63 (m, 8H, ArH);
13C-NMR (100 MHz, CDCl3):
δ 15.9, 21.5, 40.0, 124.3, 126.5, 127.6, 127.9, 128.7, 128.8, 129.3, 138.6, 140.1,
143.0, 155.2; HRMS m/z calcd for (C30H27N3 + H+): 430.2278; found: 430.2279.
4-Ethyl-3,5-bis(20,60-dimethylbiphenyl-4-yl)-4H-1,2,4-triazole (5d). White solid in 90% yield, 0.412 g, m.p.
326–329 ◦C; UV (CH2Cl2)
λ
259.0 nm (ε·10−3 28.5 cm−1M−1); IR (ATR)
ν
: 2984, 2917, 1482, 1466,
1.22
max
1442, 1426, 1384, 1163, 1112, 1004, 963, 846, 773, 728, 719 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.2 Hz, 3H, CH3), 2.08 (s, 12H, 4
×
CH3), 4.29 (q, J = 7.2 Hz, 2H, CH2), 7.14 (d, J = 7.2 Hz, 4H,
ArH), 7.19–7.23 (m, 2H, ArH), 7.34 (d, J = 8.4 Hz, 4H, ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR

Molecules 2019, 24, 652
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(100 MHz, CDCl3):
δ
15.8, 20.8, 40.0, 126.2, 127.4, 129.1, 129.8, 135.8, 140.8, 143.2, 155.3; HRMS m/z
calcd for (C32H31N3 + H+): 458.2591; found: 458.2593.
4-Ethyl-3,5-bis(20-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (5e). Creamy solid in 91% yield, 0.420 g, m.p.
189–190 ◦C; UV (CH2Cl2)
λ
max
272.0 nm (ε·10−3 33.0 cm−1M−1) and 296.0 (33.2); IR (ATR)
ν: 3016,
2941, 2838, 1595, 1493, 1470, 1432, 1400, 1258, 1244, 1123, 1053, 1021, 1004, 964, 855, 835, 803, 749, 734,
727 cm−1; 1H-NMR (400 MHz, CDCl3):
(q, J = 7.2 Hz, 2H, CH2), 7.02 (d, J = 8.4 Hz, 2H, ArH), 7.07 (t, J = 7.6 Hz, 2H, ArH), 7.35–7.40 (m, 4H,
ArH), 7.71 (d, J = 8.4 Hz, 4H, ArH), 7.75 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
16.0,
δ
1.20 (t, J = 7.2 Hz, 3H, CH3), 3.85 (s, 6H, 2
×
OCH3), 4.26
δ
40.0, 55.6, 111.4, 121.0, 126.2, 128.5, 129.2, 129.6, 130.5, 130.8, 140.3, 155.3, 156.5; HRMS m/z calcd for
(C30H27N3O2 + H+): 462.2176; found: 462.2175.
4-Ethyl-3,5-bis(30-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (5f). White solid in 99% yield, 0.457 g, m.p.
191–192 ◦C; UV (CH2Cl2)
λ
max
282.0 nm (ε·10−3 31.6 cm−1M−1); IR (ATR)
ν: 3007, 2953, 2836, 1737,
1609, 1583, 1474, 1437, 1417, 1294, 1268, 1212, 1170, 1114, 1095, 1082, 1053, 1030, 1014, 853, 840, 768,
753, 730 cm−1; 1H-NMR (400 MHz, CDCl3):
(q, J = 7.2 Hz, 2H, CH2), 6.95 (dd, J = 8.0 and 2.4 Hz, 2H, ArH), 7.19 (t, J = 2.4 Hz, 2H, ArH), 7.23–7.26
(m, 2H, ArH), 7.41 (t, J = 8.0 Hz, 2H, ArH), 7.74–7.78 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ1.18 (t, J = 7.2 Hz, 3H, CH3), 3.90 (s, 6H, 2
×
OCH3), 4.24
δ
15.9, 40.0, 55.4, 113.0, 113.3, 119.7, 126.8, 127.7, 129.3, 130.0, 141.6, 142.7, 155.1, 160.1; HRMS m/z calcd
for (C30H27N3O2 + H+): 462.2176; found: 462.2170.
4-Ethyl-3,5-bis(30-nitrobiphenyl-4-yl)-4H-1,2,4-triazole (5g). Yellow solid in 94% yield, 0.462 g, m.p.
246–248 ◦C; UV (CH2Cl2)
λ
275.0 nm (ε·10−3 57.4 cm−1M−1); IR (ATR)
ν
: 3076, 1517, 1485, 1469,
max
1346, 1287, 1103, 1086, 1010, 963, 877, 854, 837, 804, 776, 729, 798, 692 cm−1; H-NMR (400 MHz,
1
CDCl3):
δ 1.20 (t, J = 7.2 Hz, 3H, CH3), 4.26 (q, J = 7.2 Hz, 2H, CH2), 7.69 (t, J = 8.0 Hz, 2H, ArH), 7.83
(
d, J = 8.4 Hz, 4H, ArH), 7.87 (d, J = 8.4 Hz, 4H, ArH), 8.00 (d, J = 8.0 Hz, 2H, ArH), 8.28 (d, J = 8.0 Hz
,
2H, ArH), 8.54 (s, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.9, 40.1, 122.0, 122.7, 127.8, 127.9,
129.7, 130.0, 133.0, 140.4, 141.7, 148.9, 154.9; HRMS m/z calcd for (C28H21N5O4 + H+): 492.1666;
found: 492.1678.
3,5-Bis(30-aminobiphenyl-4-yl)-4-ethyl-4H-1,2,4-triazole (5h). Beige solid in 99% yield, 0.428 g, m.p.
232–234 ◦C; UV (CH2Cl2)
λ
258.0 nm (ε·10−3 28.5 cm−1M−1) and 280.0 (32.2); IR (ATR)
ν: 3455,
max
3426, 3348, 3305, 3188, 3046, 1621, 1598, 1566, 1473, 1448, 1426, 1313, 971, 888, 867, 840, 777, 748 cm−1
;
,
,
1H-NMR (400 MHz, CDCl3):
2H, CH2), 6.72 (d, J = 7.6 Hz, 2H, ArH), 6.97 (s, 2H, ArH), 7.05 (d, J = 7.6 Hz, 2H, ArH), 7.27 (t, J = 7.6 Hz
δ
1.16 (t, J = 7.2 Hz, 3H, CH3), 3.80 (br.s, 4H, 2
×
NH2), 4.22 (q, J = 7.2 Hz
2H, ArH), 7.72-7.75 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.9, 40.0, 113.8, 114.7, 117.6,
126.5, 127.5, 129.2, 129.9, 141.3, 143.0, 146.9, 155.2; HRMS m/z calcd for (C28H25N5 + H+): 432.2183;
found: 432.2169.
4-Ethyl-3,5-bis[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (5i). Grey solid in 89% yield, 0.359 g, m.p.
248–251 ◦C; UV (CH2Cl2)
λ
280.0 nm (ε·10−3 31.0 cm−1M−1); IR (ATR)
ν
: 3067, 1594, 1541, 1474,
1.19 (t, J = 7.2 Hz,
max
1411, 1221, 993, 969, 858, 808, 771, 751, 733, 664 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 4.25 (q, J = 7.2 Hz, 2H, CH2), 7.57 (d, J = 6.0 Hz, 4H, ArH), 7.82 (d, J = 8.4 Hz, 4H, ArH),
7.85 (d, J = 8.4 Hz, 4H, ArH), 8.72 (d, J = 6.0 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.9, 40.1,
121.6, 127.6, 128.3, 129.6, 139.9, 147.1, 150.5, 154.8; HRMS m/z calcd for (C26H21N5 + H+): 404.1870;
found: 404.1868.
4-Ethyl-3,5-bis[4-(pyridin-3-yl)phenyl]-4H-1,2,4-triazole (5j). Yellow solid in 93% yield, 0.374 g, m.p.
199–202 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 54.8 cm−1M−1); IR (ATR)
ν
: 3025, 1464, 1433, 1416,
1.19 (t, J = 7.2 Hz,
max
1383, 1025, 999, 971, 855, 848, 806, 772, 749, 712 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 4.26 (q, J = 7.2 Hz, 2H, CH2), 7.42 (dd, J = 7.6 and 5.2 Hz, 2H, ArH), 7.77 (d, J = 8.4 Hz, 4H,
ArH), 7.84 (d, J = 8.4 Hz, 4H, ArH), 7.95 (d, J = 7.6 Hz, 2H, ArH), 8.66 (dd, J = 5.2 and 1.6 Hz, 2H, ArH),
8.93 (d, J = 1.6 Hz, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
15.9, 40.1, 123.7, 127.4, 127.7, 129.6, 134.4,
135.5, 139.6, 148.3, 149.1, 154.9; HRMS m/z calcd for (C26H21N5 + H+): 404.1870; found: 404.1870.

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4-Ethyl-3,5-bis[4-(furan-2-yl)phenyl]-4H-1,2,4-triazole (5k). Creamy solid in 92% yield, 0.351 g, m.p.
236–237 ◦C; UV (CH2Cl2)
λ
310.0 nm (ε·10−3 53.0 cm−1M−1); IR (ATR)
ν: 3114, 1615, 1493, 1471,
max
1189, 1158, 1083, 1007, 967, 905, 884, 848, 833, 809, 792, 744, 719 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
1.13 (t, J = 7.2 Hz, 3H, CH3), 4.19 (q, J = 7.2 Hz, 2H, CH2), 6.52 (dd, J = 3.6 and 2.0 Hz, 2H, ArH), 6.78
d, J = 3.6 Hz, 2H, ArH), 7.53 (d, J = 2.0 Hz, 2H, ArH), 7.71 (d, J = 8.8 Hz, 4H, ArH), 7.83 (d, J = 8.8 Hz,
(
4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.7, 40.0, 106.4, 111.9, 124.1, 126.3, 129.2, 132.3, 142.8, 153.0,
155.1; HRMS m/z calcd for (C24H19N3O2 + H+): 382.1550; found: 382.1554.
4-Ethyl-3,5-bis[4-(furan-3-yl)phenyl]-4H-1,2,4-triazole (5l). Creamy solid in 91% yield, 0.347 g, m.p.
246–248 ◦C; UV (CH2Cl2)
λ
283.0 nm (ε·10−3 27.7 cm−1M−1); IR (ATR)
ν: 3143, 2969, 1507, 1472,
max
1403, 1350, 1195, 1162, 1115, 1084, 1054, 1016, 923, 872, 843, 785, 760, 739 cm−1; 1H-NMR (400 MHz,
CDCl3):
δ 1.13 (t, J = 7.2 Hz, 3H, CH3), 4.18 (q, J = 7.2 Hz, 2H, CH2), 6.76 (dd, J = 1.6 and 0.8 Hz, 2H,
ArH), 7.53 (t, J = 1.6 Hz, 2H, ArH), 7.65 (d, J = 8.8 Hz, 4H, ArH), 7.71 (d, J = 8.8 Hz, 4H, ArH), 7.83
(
dd, J = 1.6 and 0.8 Hz, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.8, 39.9, 108.7, 125.7, 126.2, 126.3,
129.4, 134.2, 139.2, 144.1, 155.1; HRMS m/z calcd for (C24H19N3O2 + H+): 382.1550; found: 382.1548.
4-Ethyl-3,5-bis[4-(thiophen-2-yl)phenyl]-4H-1,2,4-triazole (5m). Creamy solid in 61% yield, 0.254 g, m.p.
239–242 ◦C; UV (CH2Cl2)
λ
311.0 nm (ε·10−3 43.2 cm−1M−1); IR (ATR)
ν: 3089, 3004, 2961, 1470,
max
1428, 1353, 1260, 1216, 1194, 1116, 1081, 1012, 967, 959, 853, 843, 819, 785, 773, 740, 704, 693 cm−1
;
1H-NMR (400 MHz, CDCl3):
and 3.6 Hz, 2H, ArH), 7.35 (d, J = 5.2 Hz, 2H, ArH), 7.42 (d, J = 3.6 Hz, 2H, ArH), 7.70 (d, J = 8.4 Hz, 4H,
δ 1.14 (t, J = 7.2 Hz, 3H, CH3), 4.20 (q, J = 7.2 Hz, 2H, CH2), 7.12 (dd, J = 5.2
ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 15.8, 40.0, 124.0, 125.8, 126.2, 126.5,
128.3, 129.4, 136.0, 143.1, 155.0; HRMS m/z calcd for (C24H19N3S2 + H+): 414.1093; found: 414.1077.
4-Ethyl-3,5-bis[4-(thiophen-3-yl)phenyl]-4H-1,2,4-triazole (5n). Beige solid in 90% yield, 0.372 g, m.p.
265–266 ◦C; UV (CH2Cl2)
λ
290.0 nm (ε·10−3 42.5 cm−1M−1); IR (ATR)
ν: 3094, 2962, 1470, 1352,
max
1278, 1205, 1119, 1083, 1017, 968, 870, 843, 780, 760, 733, 695, 667, 631 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
1.14 (t, J = 7.2 Hz, 3H, CH3), 4.20 (q, J = 7.2 Hz, 2H, CH2), 7.43-7.47 (m, 4H, ArH), 7.57 (dd, J = 2.8
and 1.6 Hz, 2H, ArH), 7.72 (d, J = 8.4 Hz, 4H, ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz,
CDCl3): 15.8, 40.0, 121.3, 126.1, 126.3, 126.7, 126.8, 129.4, 137.4, 141.2, 155.1; HRMS m/z calcd for
(C24H19N3S2 + H+): 414.1093; found: 414.1102.
δ
◦
3,5-Bis(biphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6a). Creamy solid in 94% yield, 0.391 g, m.p. 285–288 C;
UV (CH2Cl2)
λ
max
282.0 nm (ε·10−3 41.8 cm−1M−1); IR (ATR)
ν: 3058, 2958, 2934, 2874, 1467, 1446,
1420, 1397, 1385, 1349, 1005, 969, 843, 802, 767, 745, 734, 724, 688 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.68 (t, J = 7.6 Hz, 3H, CH3), 1.50 (sext, J = 7.6 Hz, 2H, CH2), 4.16 (t, J = 7.6 Hz, 2H, CH2), 7.40
(
t, J = 7.2 Hz, 2H, ArH), 7.49 (t, J = 7.2 Hz, 4H, ArH), 7.67 (d, J = 7.2 Hz, 4H, ArH), 7.75–7.79 (m, 8H,
ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.7, 23.5, 46.6, 126.7, 127.1, 127.6, 127.9, 128.9, 129.3, 140.0, 142.8,
155.4; HRMS m/z calcd for (C29H25N3 + H+): 416.2121; found: 416.2120.
3,5-Bis(20-methylbiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6b). White solid in 81% yield, 0.360 g, m.p.
230–232 ◦C; UV (CH2Cl2)
λ
268.0 nm (ε·10−3 37.9 cm−1M−1); IR (ATR)
ν
: 3052, 2961, 2873, 1474,
0.71
CH3), 4.19 (t, J = 7.2 Hz, 2H,
CH2), 7.28–7.31 (m, 8H, ArH), 7.50 (d, J = 8.0 Hz, 4H, ArH), 7.75 (d, J = 8.0 Hz, 4H, ArH); 13C-NMR
max
1425, 1382, 1112, 1093, 1007, 972, 864, 847, 768, 747, 722 cm−1; H-NMR (400 MHz, CDCl3):
δ
1
(t, J = 7.2 Hz, 3H, CH3), 1.54 (sext, J = 7.2 Hz, 2H, CH2), 2.32 (s, 6H, 2
×
(100 MHz, CDCl3):
δ 10.7, 20.4, 23.5, 46.6, 125.9, 126.3, 127.7, 128.7, 129.6, 129.8, 130.5, 135.3, 140.9,
143.8, 155.5; HRMS m/z calcd for (C31H29N3 + H+): 444.2434; found: 444.2432.
3,5-Bis(30-methylbiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6c). White solid in 91% yield, 0.404 g, m.p.
223–225 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 45.2 cm−1M−1); IR (ATR)
ν: 3050, 2967, 2877, 1607,
max
1470, 1414, 1382, 1336, 1093, 1020, 969, 863, 852, 838, 775, 752, 725 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.68 (t, J = 7.6 Hz, 3H, CH3), 1.50 (sext, J = 7.6 Hz, 2H, CH2), 2.45 (s, 6H, 2
2H, CH2), 7.22 (d, J = 7.6 Hz, 2H, ArH), 7.38 (t, J = 7.6 Hz, 2H, ArH), 7.45–7.48 (m, 4H, ArH), 7.74–7.77
×
CH3), 4.15 (t, J = 7.6 Hz,

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(m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
10.7, 21.5, 23.5, 46.6, 124.3, 126.6, 127.6, 127.9, 128.7, 128.9,
129.3, 138.6, 140.0, 142.9, 155.5; HRMS m/z calcd for (C31H29N3 + H+): 444.2434; found: 444.2430.
0
0
3,5-Bis(2 ,6 -dimethylbiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6d). White solid in 94% yield, 0.444 g, m.p.
285–286 ◦C; UV (CH2Cl2)
1379, 1092, 1004, 973, 863, 841, 765, 751, 729 cm−1; 1H-NMR (400 MHz, CDCl3):
λ
max
259.0 nm (ε·10−3 29.5 cm−1M−1); IR (ATR)
ν
: 3035, 2969, 1466, 1424,
0.69 (t, J = 7.2 Hz,
δ
3H, CH3), 1.53 (sext, J = 7.2 Hz, 2H, CH2), 2.07 (s, 12H, 4
×
CH3), 4.20 (t, J = 7.2 Hz, 2H, CH2), 7.14
(
d, J = 7.2 Hz, 4H, ArH), 7.19–7.23 (m, 2H, ArH), 7.33 (d, J = 8.4 Hz, 4H, ArH), 7.77 (d, J = 8.4 Hz, 4H,
ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.7, 20.8, 23.4, 46.6, 99.1, 126.3, 127.4, 129.1, 129.8, 135.8, 140.8,
143.1, 155.6; HRMS m/z calcd for (C33H33N3 + H+): 472.2747; found: 472.2744.
3,5-Bis(20-methoxybiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6e). White solid in 91% yield, 0.433 g, m.p.
198–199 ◦C; UV (CH2Cl2)
λ
273.0 nm (ε·10−3 27.7 cm−1M−1) and 296.0 (28.6); IR (ATR)
ν: 3037,
max
2933, 2830, 1598, 1495, 1465, 1421, 1257, 1239, 1122, 1112, 1055, 1024, 1005, 860, 839, 803, 735, 721 cm−1
;
1H-NMR (400 MHz, CDCl3):
OCH3), 4.18 (t, J = 7.6 Hz, 2H, CH2), 7.02 (d, J = 8.4 Hz, 2H, ArH), 7.07 (t, J = 7.6 Hz, 2H, ArH),
7.35-7.40 (m, 4H, ArH), 7.70 (d, J = 8.4 Hz, 4H, ArH), 7.74 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz,
δ 0.71 (t, J = 7.6 Hz, 3H, CH3), 1.55 (sext, J = 7.6 Hz, 2H, CH2), 3.85 (s, 6H,
2
×
CDCl3):
δ 10.7, 23.5, 46.6, 55.6, 111.4, 121.0, 126.3, 128.5, 129.2, 129.6, 130.0, 130.8, 140.3, 155.6, 156.5;
HRMS m/z calcd for (C31H29N3O2 + H+): 476.2333; found: 476.2332.
3,5-Bis(30-methoxybiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6f). White solid in 95% yield, 0.452 g, m.p.
193–195 ◦C; UV (CH2Cl2)
λ
283.0 nm (ε·10−3 35.5 cm−1M−1); IR (ATR)
ν: 2969, 2836, 1600, 1592,
max
1560, 1463, 1418, 1301, 1219, 1166, 1050, 1029, 1016, 858, 869, 849, 840, 795, 778, 753, 744 cm−1; 1H-NMR
(400 MHz, CDCl3):
δ 0.68 (t, J = 7.6 Hz, 3H, CH3), 1.50 (sext, J = 7.6 Hz, 2H, CH2), 3.90 (s, 6H,
2 × OCH3), 4.15 (t, J = 7.6 Hz, 2H, CH2), 6.95 (dd, J = 8.0 and 2.4 Hz, 2H, ArH), 7.19 (t, J = 2.4 Hz,
2H, ArH), 7.23–7.26 (m, 2H, ArH), 7.40 (t, J = 8.0 Hz, 2H, ArH), 7.74–7.78 (m, 8H, ArH); 13C-NMR
(100 MHz, CDCl3):
δ 10.7, 23.5, 46.6, 55.4, 112.9, 113.3, 119.6, 126.9, 127.6, 129.3, 130.0, 141.5, 142.6,
155.4, 160.1; HRMS m/z calcd for (C31H29N3O2 + H+): 476.2333; found: 476.2334.
3,5-Bis(30-nitrobiphenyl-4-yl)-4-propyl-4H-1,2,4-triazole (6g). Creamy solid in 91% yield, 0.460 g, m.p.
291–293 ◦C; UV (CH2Cl2)
λ
276.0 nm (ε·10−3 47.3 cm−1M−1); IR (ATR)
ν: 3034, 2969, 2872, 1521,
max
1488, 1468, 1344, 1294, 1104, 876, 852, 840, 802, 777, 759, 742, 723 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.70 (t, J = 7.2 Hz, 3H, CH3), 1.52 (sext, J = 7.2 Hz, 2H, CH2), 4.19 (t, J = 7.2 Hz, 2H, CH2), 7.68
t, J = 7.6 Hz, 2H, ArH), 7.82 (d, J = 8.4 Hz, 4H, ArH), 7.86 (d, J = 8.4 Hz, 4H, ArH), 8.00 (dd, J = 7.6
and 2.0 Hz, 2H, ArH), 8.27 (dd, J = 7.6 and 2.0 Hz, 2H, ArH), 8.54 (t, J = 2.0 Hz, 2H, ArH); 13C-NMR
(
(100 MHz, CDCl3):
δ 10.7, 23.6, 46.8, 122.0, 122.7, 127.8, 128.0, 129.7, 130.0, 133.0, 137.2, 140.3, 141.7,
155.2; HRMS m/z calcd for (C29H23N5O4 + H+): 506.1823; found: 506.1811.
3,5-Bis(3◦0-aminobiphenyl-4-yl)-4-propyl-4H-1,2−,43-triazole (6h). Beige solid in 99% yield, 0.428 g, m.p.
216–218 C; UV (CH2Cl2)
λ
235.0 nm (ε·10 27.0 cm−1M−1), 258.0 (29.2) and 282.0 (33.9); IR (ATR)
max
−1
ν
: 3441, 3407, 3336, 3143, 2961, 1601, 1586, 1564, 1479, 1431, 1324, 1233, 993, 893, 842, 775, 743, 714 cm
;
1H-NMR (400 MHz, CDCl3):
(br.s, 4H, 2x NH2), 4.13 (t, J = 7.2 Hz, 2H, CH2), 6.72 (dd, J = 8.0 and 2.0 Hz, 2H, ArH), 6.98 (t, J = 2.0 Hz
2H, ArH), 7.05 (dd, J = 8.0 and 2.0 Hz, 2H, ArH), 7.27 (t, J = 8.0 Hz, 2H, ArH), 7.72–7.74 (m, 8H, ArH);
δ 0.67 (t, J = 7.2 Hz, 3H, CH3), 1.49 (sext, J = 7.2 Hz, 2H, CH2), 3.80
,
13C-NMR (100 MHz, CDCl3):
δ 10.7, 23.5, 46.6, 113.8, 114.7, 117.5, 126.6, 127.5, 129.2, 129.9, 141.2, 143.0,
146.9, 155.5; HRMS m/z calcd for (C29H27N5 + H+): 446.2339; found: 446.2348.
4-Propyl-3,5-bis[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (6i). Creamy solid in 90% yield, 0.376 g, m.p.
237–240 ◦C; UV (CH2Cl2)
λ
281.0 nm (ε·10−3 36.5 cm−1M−1); IR (ATR)
ν
: 2957, 1596, 1541, 1471,
0.69 (t, J = 7.6 Hz,
max
1408, 1347, 1217, 992, 969, 859, 812, 772, 752, 737 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 1.50 (sext, J = 7.6 Hz, 2H, CH2), 4.17 (t, J = 7.6 Hz, 2H, CH2), 7.58 (d, J = 6.0 Hz, 4H, ArH),
7.81–7.84 (m, 8H, ArH), 8.73 (d, J = 6.0 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.7, 23.5, 46.7,
121.6, 127.6, 128.4, 129.6, 139.8, 147.1, 150.5, 155.2; HRMS m/z calcd for (C27H23N5 + H+): 418.2026;
found: 418.2022.

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4-Propyl-3,5-bis[4-(pyridin-3-yl)phenyl]-4H-1,2,4-triazole (6j). Creamy solid in 69% yield, 0.288 g, m.p.
212–215 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 40.6 cm−1M−1); IR (ATR)
ν
: 3035, 2965, 2875, 1470,
0.69
max
1426, 1414, 1383, 1339, 1025, 1001, 970, 851, 799, 749, 707 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.6 Hz, 3H, CH3), 1.51 (sext, J = 7.6 Hz, 2H, CH2), 4.18 (t, J = 7.6 Hz, 2H, CH2), 7.42 (dd, J = 8.0
and 4.8 Hz, 2H, ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH), 7.83 (d, J = 8.4 Hz, 4H, ArH), 7.95 (dt, J = 8.0 and 1.6
Hz, 2H, ArH), 8.66 (dd, J = 4.8 and 1.6 Hz, 2H, ArH), 8.93 (d, J = 1.6 Hz, 2H, ArH); 13C-NMR (100 MHz,
CDCl3):
δ 10.7, 23.5, 46.7, 123.7, 127.5, 127.7, 129.6, 134.4, 135.5, 139.5, 148.3, 149.1, 155.2; HRMS m/z
calcd for (C27H23N5 + H+): 418.2026; found: 418.2028.
3,5-Bis[4-(furan-2-yl)phenyl]-4-propyl-4H-1,2,4-triazole (6k). Beige solid in 96% yield, 0.379 g, m.p.
279–281 ◦C; UV (CH2Cl2)
λ
311.0 nm (ε·10−3 63.6 cm−1M−1); IR (ATR)
ν: 2960, 1615, 1491, 1465,
max
1351, 1282, 1220, 1116, 1076, 1020, 1010, 903, 862, 839, 815, 805, 757, 735, 663 cm−1; 1H-NMR (400 MHz,
CDCl3):
δ 0.64 (t, J = 7.6 Hz, 3H, CH3), 1.45 (sext, J = 7.6 Hz, 2H, CH2), 4.10 (t, J = 7.6 Hz, 2H, CH2),
6.53 (dd, J = 3.6 and 2.0 Hz, 2H, ArH), 6.78 (d, J = 3.6 Hz, 2H, ArH), 7.53 (d, J = 2.0 Hz, 2H, ArH),
7.71 (d, J = 8.8 Hz, 4H, ArH), 7.83 (d, J = 8.8 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.7, 23.4,
46.7, 106.4, 111.9, 124.1, 126.4, 129.2, 132.3, 142.8, 153.0, 155.4; HRMS m/z calcd for (C25H21N3O2 + H+):
396.1707; found: 396.1709.
3,5-Bis[4-(furan-3-yl)phenyl]-4-propyl-4H-1,2,4-triazole (6l). Creamy solid in 92% yield, 0.363 g, m.p.
299–303 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 35.3 cm−1M−1); IR (ATR)
ν
: 3141, 1507, 1471, 1351,
0.65 (t, J = 7.6 Hz,
max
1162, 1115, 1055, 1015, 923, 872, 843, 785, 754, 739 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 1.46 (sext, J = 7.6 Hz, 2H, CH2), 4.10 (t, J = 7.6 Hz, 2H, CH2), 6.77 (dd, J = 2.0 and 1.2 Hz, 2H,
ArH), 7.53 (d, J = 2.0 Hz, 2H, ArH), 7.65 (d, J = 8.8 Hz, 4H, ArH), 7.70 (d, J = 8.8 Hz, 4H, ArH), 7.84
(
d, J = 1.2 Hz, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 10.7, 23.4, 46.6, 108.6, 125.7, 126.2, 126.3, 129.4,
134.2, 139.2, 144.1, 155.4; HRMS m/z calcd for (C25H21N3O2 + H+): 396.1707; found: 396.1710.
4-Propyl-3,5-bis[4-(thiophen-2-yl)phenyl]-4H-1,2,4-triazole (6m). Grey solid in 52% yield, 0.223 g, m.p.
283–285 ◦C; UV (CH2Cl2)
λ
312.0 nm (ε·10−3 36.4 cm−1M−1); IR (ATR)
ν: 3091, 2959, 2873, 1469,
max
1427, 1398, 1352, 1260, 1216, 1193, 1116, 1093, 1013, 970, 959, 844, 819, 757, 741, 707, 694 cm−1; 1H-NMR
(400 MHz, CDCl3):
δ 0.66 (t, J = 7.6 Hz, 3H, CH3), 1.48 (sext, J = 7.6 Hz, 2H, CH2), 4.12 (t, J = 7.6 Hz, 2H,
CH2), 7.13 (dd, J = 4.8 and 3.6 Hz, 2H, ArH), 7.36 (d, J = 4.8 Hz, 2H, ArH), 7.43 (d, J = 3.6 Hz, 2H, ArH),
7.71 (d, J = 8.4 Hz, 4H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3): δ 10.7, 23.5, 46.7,
124.0, 125.8, 126.2, 126.6, 128.3, 129.4, 136.0, 143.2, 155.3; HRMS m/z calcd for (C25H21N3S2 + H+): 428.1250;
found: 428.1241.
4-Propyl-3,5-bis[4-(thiophen-3-yl)phenyl]-4H-1,2,4-triazole (6n). Beige solid in 90% yield, 0.385 g, m.p.
302–305 ◦C; UV (CH2Cl2)
λ
290.0 nm (ε·10−3 44.8 cm−1M−1); IR (ATR)
ν: 3094, 2966, 1467, 1423,
max
1402, 1352, 1206, 1197, 1117, 1089, 1017, 970, 871, 843, 781, 753, 743, 732, 720 cm−1; 1H -NMR (400 MHz,
CDCl3):
δ 0.66 (t, J = 7.6 Hz, 3H, CH3), 1.48 (sext, J = 7.6 Hz, 2H, CH2), 4.13 (t, J = 7.6 Hz, 2H, CH2),
7.44 (dd, J = 5.2 and 3.2 Hz, 2H, ArH), 7.47 (dd, J = 5.2 and 1.6 Hz, 2H, ArH), 7.58 (dd, J = 3.2 and
1.6 Hz, 2H, ArH), 7.73 (d, J = 8.4 Hz, 4H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz,
CDCl3):
δ 10.7, 23.5, 46.6, 121.3, 126.1, 126.4, 126.7, 126.8, 129.4, 137.4, 141.2, 155.4; HRMS m/z calcd for
(C25H21N3S2 + H+): 428.1250; found: 428.1259.
◦
3,5-Bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7a). Creamy solid in 92% yield, 0.396 g, m.p. 297–300 C;
UV (CH2Cl2)
λ
max
282.0 nm (ε·10−3 41.9 cm−1M−1); IR (ATR)
ν: 3034, 2953, 2926, 2859, 1472, 1447,
1423, 1384, 1211, 1121, 1098, 1005, 973, 842, 768, 753, 741, 723, 688 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.69 (t, J = 7.6 Hz, 3H, CH3), 1.07 (sext, J = 7.6 Hz, 2H, CH2), 1.45 (quin, J = 7.6 Hz, 2H, CH2), 4.19
(
t, J = 7.6 Hz, 2H, CH2), 7.40 (t, J = 7.2 Hz, 2H, ArH), 7.49 (t, J = 7.2 Hz, 4H, ArH), 7.67 (d, J = 7.2 Hz, 4H,
ArH), 7.75-7.79 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.0, 44.8, 126.6, 127.1, 127.6,
127.9, 128.9, 129.3, 140.0, 142.8, 155.4; HRMS m/z calcd for (C30H27N3 + H+): 430.2278; found: 430.2277.
4-Butyl-3,5-bis(20-methylbiphenyl-4-yl)-4H-1,2,4-triazole (7b). Grey solid in 83% yield, 0.380 g, m.p.
182–183 ◦C; UV (CH2Cl2)
λ
max
269.0 nm (ε·10−3 32.6 cm−1M−1); IR (ATR)
ν: 3051, 3015, 2963, 2926,

Molecules 2019, 24, 652
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2859, 1470, 1460, 1421, 1383, 1355, 1326, 1109, 1008, 970, 863, 854, 840, 807, 766, 745, 734, 724 cm−1
1H-NMR (400 MHz, CDCl3):
0.70 (t, J = 7.2 Hz, 3H, CH3), 1.10 (sext, J = 7.2 Hz, 2H, CH2), 1.48 (quin,
J = 7.2 Hz, 2H, CH2), 2.32 (s, 6H, 2 CH3), 4.21 (t, J = 7.2 Hz, 2H, CH2), 7.28–7.31 (m, 8H, ArH), 7.50
(d, J = 8.4 Hz, 4H, ArH), 7.74 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
13.2, 19.3, 20.4,
;
δ
×
δ
32.1, 44.7, 125.9, 126.3, 127.7, 128.7, 129.6, 129.8, 130.5, 135.3, 140.9, 143.8, 155.5; HRMS m/z calcd for
(C32H31N3 + H+): 458.2591; found: 458.2588.
4-Butyl-3,5-bis(30-methylbiphenyl-4-yl)-4H-1,2,4-triazole (7c). White solid in 96% yield, 0.440 g, m.p.
211–213 ◦C; UV (CH2Cl2)
λ
285.0 nm (ε·10−3 44.9 cm−1M−1); IR (ATR)
ν
: 3020, 2960, 2872, 1607,
max
1466, 1416, 1340, 1262, 1111, 1094, 1039, 1019, 972, 862, 855, 845, 780, 761, 749, 608 cm−1; H-NMR
1
(400 MHz, CDCl3):
2H, CH2), 2.45 (s, 6H, 2
t, J = 7.6 Hz, 2H, ArH), 7.45–7.49 (m, 4H, ArH), 7.75–7.79 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
0.69 (t, J = 7.2 Hz, 3H, CH3), 1.06 (sext, J = 7.2 Hz, 2H, CH2), 1.45 (quin, J = 7.2 Hz
,
×
CH3), 4.18 (t, J = 7.2 Hz, 2H, CH2), 7.22 (d, J = 7.6 Hz, 2H, ArH), 7.38
(
δ
13.2, 19.3, 21.5, 32.1, 44.8, 124.3, 126.6, 127.6, 127.9, 128.7, 128.9, 129.3, 138.6, 140.0, 142.9, 155.4; HRMS
m/z calcd for (C32H31N3 + H+): 458.2591; found: 458.2592.
4-Butyl-3◦,5-bis(20,60-dimethylbiphenyl-4-yl)-4H-1,2,4-triazole (7d). White solid in 79% yield, 0.384 g, m.p.
269–271 C; UV (CH2Cl2)
λ
258.0 nm (ε·10-3 31.1 cm−1M−1); IR (ATR)
ν: 3035, 2969, 1464, 851,
δ 0.66 (t, J = 7.2 Hz, 3H, CH3), 1.07 (sext, J = 7.2 Hz,
max
839, 778, 751 cm−1; 1H-NMR (400 MHz, CDCl3):
2H, CH2), 1.47 (quin, J = 7.2 Hz, 2H, CH2), 2.07 (s, 12H, 4
×
CH3), 4.23 (t, J = 7.2 Hz, 2H, CH2), 7.15
(
d, J = 7.2 Hz, 4H, ArH), 7.19–7.23 (m, 2H, ArH), 7.34 (d, J = 8.4 Hz, 4H, ArH), 7.76 (d, J = 8.4 Hz, 4H,
ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.0, 19.1, 20.8, 31.9, 44.5, 126.3, 127.4, 129.1, 129.8, 135.8, 140.8,
143.1, 155.5; HRMS m/z calcd for (C34H35N3 + H+): 486.2904; found: 486.2901.
4-Butyl-3,5-bis(20-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (7e). White solid in 85% yield, 0.417 g, m.p.
190–193 ◦C; UV (CH2Cl2)
λ
max
272.0 nm (ε·10−3 29.5 cm−1M−1) and 295.0 (28.3); IR (ATR)
ν: 2956,
2932, 2832, 1597, 1582, 1493, 1462, 1423, 1258, 1239, 1122, 1056, 1025, 1005, 974, 866, 837, 801, 756,
736 cm−1; 1H-NMR (400 MHz, CDCl3):
1.49 (quin, J = 7.6 Hz, 2H, CH2), 3.85 (s, 6H, 2
Hz, 2H, ArH), 7.07 (t, J = 7.6 Hz, 2H, ArH), 7.35–7.40 (m, 4H, ArH), 7.70 (d, J = 8.4 Hz, 4H, ArH), 7.73
δ
0.71 (t, J = 7.6 Hz, 3H, CH3), 1.10 (sext, J = 7.6 Hz, 2H, CH2),
OCH3), 4.20 (t, J = 7.6 Hz, 2H, CH2), 7.02 (d, J = 7.6
×
(
d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.4, 32.0, 44.8, 55.6, 111.5, 121.0, 126.3,
128.5, 129.2, 129.7, 130.0, 130.8, 140.3, 155.5, 156.5; HRMS m/z calcd for (C32H31N3O2 + H+): 490.2489;
found: 490.2491.
4-Butyl-3,5-bis(30-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (7f). Grey solid in 82% yield, 0.402 g, m.p.
182–184 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10-3 33.5 cm−1M−1); IR (ATR)
ν
: 2954, 2930, 2830, 1608,
max
1583, 1560, 1474, 1421, 1297, 1212, 1172, 1055, 1033, 1015, 856, 839, 779, 752, 693 cm−1; H-NMR
1
(400 MHz, CDCl3):
2H, CH2), 3.90 (s, 6H, 2
7.19 (t, J = 2.4 Hz, 2H, ArH), 7.24–7.26 (m, 2H, ArH), 7.40 (t, J = 8.0 Hz, 2H, ArH), 7.74–7.78 (m, 8H,
δ
0.69 (t, J = 7.6 Hz, 3H, CH3), 1.07 (sext, J = 7.6 Hz, 2H, CH2), 1.45 (quin, J = 7.6 Hz,
×
OCH3), 4.19 (t, J = 7.6 Hz, 2H, CH2), 6.95 (dd, J = 8.0 and 2.4 Hz, 2H, ArH),
ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.1, 44.8, 55.4, 112.9, 113.3, 119.6, 126.8, 127.6, 129.3,
130.0, 141.5, 142.6, 155.4, 160.1; HRMS m/z calcd for (C32H31N3O2 + H+): 490.2489; found: 490.2492.
4-Butyl-3,5-bis(30-nitrobiphenyl-4-yl)-4H-1,2,4-triazole (7g). Creamy solid in 91% yield, 0.473 g, m.p.
252–253 ◦C; UV (CH2Cl2)
λ
max
276.0 nm (ε·10−3 46.9 cm−1M−1); IR (ATR)
ν: 3099, 2926, 2861, 1522,
1490, 1467, 1347, 1292, 1102, 1018, 973, 876, 850, 832, 799, 780, 740, 724, 704 cm−1; 1H-NMR (400 MHz,
CDCl3):
CH2), 4.22 (t, J = 7.6 Hz, 2H, CH2), 7.68 (t, J = 8.0 Hz, 2H, ArH), 7.82 (d, J = 8.4 Hz, 4H, ArH), 7.86
d, J = 8.4 Hz, 4H, ArH), 8.00 (dd, J = 8.0 and 2.0 Hz, 2H, ArH), 8.27 (dd, J = 8.0 and 2.0 Hz, 2H, ArH),
δ 0.71 (t, J = 7.6 Hz, 3H, CH3), 1.09 (sext, J = 7.6 Hz, 2H, CH2), 1.47 (quin, J = 7.6 Hz, 2H,
(
8.54 (t, J = 2.0 Hz, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.1, 45.0, 122.0, 122.7, 127.7,
128.0, 129.7, 130.0, 133.0, 140.3, 141.7, 148.9, 155.1; HRMS m/z calcd for (C30H25N5O4 + H+): 520.1979;
found: 520.1967.

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3,5-Bis(3◦0-aminobiphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7h). Beige solid in 98% yield, 0.451 g, m.p.
−3
244–246 C; UV (CH2Cl2)
ν
λ
max
232.0 nm (ε·10 27.7 cm−1M−1), 258.0 (29.6) and 281.0 (34.1); IR (ATR)
: 3428, 3348, 2955, 2926, 2871, 1619, 1601, 1588, 1472, 1449, 1422, 1318, 1229, 1172, 973, 836, 777, 755,
744, 665 cm−1; H-NMR (400 MHz, CDCl3):
2H, CH2), 1.43 (quin, J = 7.2 Hz, 2H, CH2), 3.81 (br.s, 4H, 2
6.72 (dd, J = 8.0 and 2.0 Hz, 2H, ArH), 6.98 (t, J = 2.0 Hz, 2H, ArH), 7.05 (dd, J = 8.0 and 2.0 Hz, 2H,
ArH), 7.26 (t, J = 8.0 Hz, 2H, ArH), 7.71–7.75 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
13.2, 19.3,
δ
0.68 (t, J = 7.2 Hz, 3H, CH3), 1.05 (sext, J = 7.2 Hz,
NH2), 4.17 (t, J = 7.2 Hz, 2H, CH2),
1
×
δ
32.0, 44.8, 113.7, 114.7, 117.5, 126.6, 127.5, 129.2, 129.9, 141.2, 143.0, 147.0, 155.4; HRMS m/z calcd for
(C30H29N5 + H+): 460.2496; found: 460.2479.
4-Butyl-3,5-bis[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (7i). Creamy solid in 92% yield, 0.397 g, m.p.
258–259 ◦C; UV (CH2Cl2)
λ
281.0 nm (ε·10−3 33.7 cm−1M−1); IR (ATR)
ν
: 2963, 1595, 1540, 1471,
max
1407, 1217, 971, 857, 811, 771, 757, 736 cm−1; H-NMR (400 MHz, CDCl3):
δ 0.70 (t, J = 7.6 Hz, 3H,
1
CH3), 1.07 (sext, J = 7.6 Hz, 2H, CH2), 1.45 (quin, J = 7.6 Hz, 2H, CH2), 4.21 (t, J = 7.6 Hz, 2H, CH2), 7.58
(d, J = 6.0 Hz, 4H, ArH), 7.81–7.85 (m, 8H, ArH), 8.73 (d, J = 6.0 Hz, 4H, ArH); 13C-NMR (100 MHz,
CDCl3):
δ 13.2, 19.3, 32.1, 44.9, 121.6, 127.6, 128.4, 129.6, 139.8, 147.1, 150.5, 155.1; HRMS m/z calcd for
(C28H25N5 + H+): 432.2183; found: 432.2180.
4-Butyl-3,5-bis[4-(pyridin-3-yl)phenyl]-4H-1,2,4-triazole (7j). White solid in 74% yield, 0.320 g, m.p.
207–209 ◦C; UV (CH2Cl2)
λ
285.0 nm (ε·10−3 40.4 cm−1M−1); IR (ATR)
ν: 3033, 2929, 2870, 1575,
max
1468, 1428, 1413, 1386, 1024, 1000, 972, 853, 803, 774, 746, 710 cm−1; H-NMR (400 MHz, CDCl3):
1
δ
0.70 (t, J = 7.2 Hz, 3H, CH3), 1.08 (sext, J = 7.2 Hz, 2H, CH2), 1.46 (quin, J = 7.2 Hz, 2H, CH2),
4.21 (t, J = 7.2 Hz, 2H, CH2), 7.42 (dd, J = 7.6 and 4.8 Hz, 2H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH),
7.84 (d, J = 8.4 Hz, 4H, ArH), 7.95 (dt, J = 7.6 and 1.6 Hz, 2H, ArH), 8.66 (dd, J = 4.8 and 1.6 Hz, 2H,
ArH), 8.93 (d, J = 1.6 Hz, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.1, 44.9, 123.7, 127.5,
127.6, 129.6, 134.4, 135.5, 139.5, 148.3, 149.1, 155.2; HRMS m/z calcd for (C28H25N5 + H+): 432.2183;
found: 432.2181.
4-Butyl-3,5-bis[4-(furan-2-yl)phenyl]-4H-1,2,4-triazole (7k). Creamy solid in 75% yield, 0.307 g, m.p.
264–267 ◦C; UV (CH2Cl2)
λ
310.0 nm (ε·10-3 43.6 cm−1M−1); IR (ATR)
ν: 2956, 2926, 2871, 1615,
max
1491, 1471, 1220, 1189, 1157, 1115, 1008, 972, 904, 884, 848, 805, 773, 735, 702 cm−1; 1H-NMR (400 MHz,
CDCl3):
δ 0.66 (t, J = 7.6 Hz, 3H, CH3), 1.03 (sext, J = 7.6 Hz, 2H, CH2), 1.40 (quin, J = 7.6 Hz, 2H,
CH2), 4.14 (t, J = 7.6 Hz, 2H, CH2), 6.53 (dd, J = 3.2 and 1.6 Hz, 2H, ArH), 6.78 (d, J = 3.2 Hz, 2H, ArH),
7.53 (d, J = 1.6 Hz, 2H, ArH), 7.71 (d, J = 8.4 Hz, 4H, ArH), 7.83 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR
(100 MHz, CDCl3):
δ 13.2, 19.3, 32.0, 44.8, 106.4, 111.9, 124.1, 126.4, 129.2, 132.3, 142.8, 153.0, 155.4;
HRMS m/z calcd for (C26H23N3O2 + H+): 410.1863; found: 410.1866.
4-Butyl-3,5-bis[4-(furan-3-yl)phenyl]-4H-1,2,4-triazole (7l). Yellow solid in 94% yield, 0.384 g, m.p.
274–277 ◦C; UV (CH2Cl2)
λ
285.0 nm (ε·10−3 37.3 cm−1M−1); IR (ATR)
ν: 3134, 2960, 1507, 1469,
max
1194, 1162, 1115, 1094, 1054, 1015, 975, 923, 873, 842, 785, 749 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
0.67 (t, J = 7.6 Hz, 3H, CH3), 1.04 (sext, J = 7.6 Hz, 2H, CH2), 1.41 (quin, J = 7.6 Hz, 2H, CH2), 4.14
t, J = 7.6 Hz, 2H, CH2), 6.77 (d, J = 1.6 Hz, 2H, ArH), 7.53 (d, J = 1.6 Hz, 2H, ArH), 7.65 (d, J = 8.8 Hz,
(
4H, ArH), 7.71 (d, J = 8.8 Hz, 4H, ArH), 7.83 (s, 2H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.0,
44.8, 108.6, 125.7, 126.2, 126.3, 129.4, 134.2, 139.2, 144.0, 155.4; HRMS m/z calcd for (C26H23N3O2 + H+):
410.1863; found: 410.1867.
4-Butyl-3,5-bis[4-(thiophen-2-yl)phenyl]-4H-1,2,4-triazole (7m). Grey solid in 49% yield, 0.216 g, m.p.
289–292 ◦C; UV (CH2Cl2)
λ
312.0 nm (ε·10−3 37.4 cm−1M−1); IR (ATR)
ν
: 2955, 1472, 1426, 1400,
0.68 (t, J = 7.6 Hz,
max
1215, 1193, 1115, 1099, 974, 844, 819, 742, 695 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
3H, CH3), 1.05 (sext, J = 7.6 Hz, 2H, CH2), 1.43 (quin, J = 7.6 Hz, 2H, CH2), 4.15 (t, J = 7.6 Hz, 2H, CH2),
7.13 (dd, J = 4.8 and 3.6 Hz, 2H, ArH), 7.36 (d, J = 4.8 Hz, 2H, ArH), 7.43 (d, J = 3.6 Hz, 2H, ArH), 7.70
(d, J = 8.4 Hz, 4H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.0,

Molecules 2019, 24, 652
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44.9, 124.0, 125.8, 126.2, 126.6, 128.3, 129.4, 136.0, 143.2, 155.3; HRMS m/z calcd for (C26H23N3S2 + H+):
442.1406; found: 442.1412.
4-Butyl-3◦,5-bis[4-(thiophen-3-yl)phenyl]-4H-1,2,4-triazole (7n). Beige solid in 77% yield, 0.342 g, m.p.
288–290 C; UV (CH2Cl2)
λ
289.0 nm (ε·10−3 37.4 cm−1M−1); IR (ATR)
ν: 3067, 2955, 2872,
max
1470, 1428, 1363, 1196, 1094, 1014, 973, 867, 841, 782, 746, 688 cm−1; H-NMR (400 MHz, CDCl3):
1
δ
0.68 (t, J = 7.6 Hz, 3H, CH3), 1.04 (sext, J = 7.6 Hz, 2H, CH2), 1.41 (quin, J = 7.6 Hz, 2H, CH2), 4.13
(
t, J = 7.6 Hz, 2H, CH2), 7.43–7.47 (m, 2H, ArH), 7.56–7,59 (m, 2H, ArH), 7.68–7.78 (m, 10H, ArH);
13C-NMR (100 MHz, CDCl3):
δ 13.2, 19.3, 32.0, 44.8, 121.4, 126.1, 126.2, 126.7, 126.8, 129.4, 132.3, 141.2,
154.6; HRMS m/z calcd for (C26H23N3S2 + H+): 442.1406; found: 442.1397.
3,5-Bis(biphenyl-4-yl)-4-hexyl-4H-1,2,4-triazole (8a). White solid in 92% yield, 0.421 g, m.p. 240–242 ◦C;
UV (CH2Cl2)
λ
max 282.0 nm (ε·10-3 45.4 cm−1M−1); IR (ATR)
ν
: 3028, 2926, 2855, 1474, 1444, 1429, 1379,
0.73 (t, J = 7.6 Hz, 3H,
1072, 1007, 967, 858, 847, 835, 767, 738, 695 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
CH3), 1.00–1.11 (m, 6H, 3
×
CH2), 1.46 (quin, J = 7.6 Hz, 2H, CH2), 4.18 (t, J = 7.6 Hz, 2H, CH2), 7.40
(
t, J = 7.2 Hz, 2H, ArH), 7.49 (t, J = 7.2 Hz, 4H, ArH), 7.67 (d, J = 7.2 Hz, 4H, ArH), 7.75–7.79 (m, 8H,
ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.8, 22.2, 25.7, 29.9, 30.7, 45.0, 126.7, 127.1, 127.6, 127.9, 128.9,
129.3, 140.1, 142.8, 155.4; HRMS m/z calcd for (C32H31N3 + H+): 458.2591; found: 458.2588.
4-Hexyl-3,5-bis(20-methylbiphenyl-4-yl)-4H-1,2,4-triazole (8b). White solid in 72% yield, 0.350 g, m.p.
185–186 ◦C; UV (CH2Cl2)
λ
269.0 nm (ε·10−3 31.5 cm−1M−1); IR (ATR)
ν
: 3022, 2955, 2929, 2857,
0.75
max
1470, 1425, 1378, 1261, 1099, 1007, 966, 840, 766, 743, 723 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.2 Hz, 3H, CH3), 1.01–1.13 (m, 6H, 3
×
CH2), 1.49 (quin, J = 7.2 Hz, 2H, CH2), 2.32 (s, 6H,
2 × CH3), 4.20 (t, J = 7.6 Hz, 2H, CH2), 7.27–7.32 (m, 8H, ArH), 7.50 (d, J = 8.4 Hz, 4H, ArH), 7.75
(d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.8, 20.4, 22.1, 25.6, 29.9, 30.7, 44.9, 125.9,
126.3, 127.7, 128.7, 129.6, 129.8, 130.5, 135.3, 140.9, 143.8, 155.5; HRMS m/z calcd for (C34H35N3 + H+):
486.2904; found: 486.2905.
4-Hexyl-3,5-bis(30-methylbiphenyl-4-yl)-4H-1,2,4-triazole (8c). White solid in 91% yield, 0.442 g, m.p.
217–218 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 40.3 cm−1M−1); IR (ATR)
ν
: 3017, 2929, 2863, 1607,
0.73
max
1468, 1416, 1380, 1338, 1112, 1017, 968, 855, 843, 754, 691 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.2 Hz, 3H, CH3), 1.01–1.11 (m, 6H, 3
2 × CH3), 4.17 (t, J = 7.6 Hz, 2H, CH2), 7.22 (d, J = 7.6 Hz, 2H, ArH), 7.37 (t, J = 7.6 Hz, 2H, ArH),
7.45–7.48 (m, 4H, ArH), 7.74–7.77 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
13.8, 21.5, 22.2, 25.7,
×
CH2), 1.45 (quin, J = 7.2 Hz, 2H, CH2), 2.45 (s, 6H,
δ
29.9, 30.7, 45.0, 124.2, 126.6, 127.6, 127.9, 128.7, 128.8, 129.2, 138.6, 140.1, 142.9, 155.4; HRMS m/z calcd
for (C34H35N3 + H+): 486.2904; found: 486.2902.
4-Hexyl-3,5-bis(20,60-dimethylbiphenyl-4-yl)-4H-1,2,4-triazole (8d). White solid in 93% yield, 0.478 g, m.p.
200–202 ◦C; UV (CH2Cl2)
λ
259.0 nm (ε·10−3 26.8 cm−1M−1); IR (ATR)
ν
: 3014, 2954, 2930, 2855,
0.75
max
1464, 1418, 1380, 1260, 1096, 1005, 969, 852, 839, 770, 737 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.2 Hz, 3H, CH3), 1.00–1.13 (m, 6H, 3
×
×
CH2), 1.48 (quin, J = 7.2 Hz, 2H, CH2), 2.07 (s, 12H,
CH3), 4.22 (t, J = 7.6 Hz, 2H, CH2), 7.14 (d, J = 7.2 Hz, 4H, ArH), 7.19–7.23 (m, 2H, ArH), 7.34
13.7, 20.8, 22.1,
4
(
d, J = 8.4 Hz, 4H, ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ
25.6, 29.7, 30.6, 44.9, 115.6, 126.3, 127.4, 129.1, 129.8, 135.8, 140.8, 143.1, 155.6; HRMS m/z calcd for
(C36H39N3 + H+): 514.3217; found: 514.3217.
4-Hexyl-3,5-bis(20-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (8e). Creamy solid in 88% yield, 0.456 g, m.p.
171–172 ◦C; UV (CH2Cl2)
λ
max
273.0 nm (ε·10−3 28.1 cm−1M−1) and 296.0 (28.8); IR (ATR)
ν: 3049,
2953, 2860, 1599, 1494, 1467, 1433, 1421, 1257, 1235, 1179, 1125, 1112, 1029, 1016, 1005, 861, 841, 801,
1
748, 737, 721 cm−1; H-NMR (400 MHz, CDCl3):
δ
0.76 (t, J = 7.2 Hz, 3H, CH3), 1.02–1.13 (m, 6H,
OCH3), 4.20 (t, J = 7.6 Hz, 2H, CH2), 7.03
d, J = 8.4 Hz, 2H, ArH), 7.07 (t, J = 7.6 Hz, 2H, ArH), 7.34–7.40 (m, 4H, ArH), 7.70 (d, J = 8.4 Hz, 4H, ArH),
7.73 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
13.8, 22.2, 25.7, 30.0, 30.7, 44.9, 55.6, 111.5,
3 × CH2), 1.50 (quin, J = 7.2 Hz, 2H, CH2), 3.85 (s, 6H, 2
×
(
δ

Molecules 2019, 24, 652
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121.0, 126.3, 128.5, 129.2, 129.7, 130.0, 130.8, 140.3, 155.5, 156.5; HRMS m/z calcd for (C34H35N3O2 + H+):
518.2802; found: 518.2800.
4-Hexyl-3,5-bis(30-methoxybiphenyl-4-yl)-4H-1,2,4-triazole (8f). White solid in 83% yield, 0.430 g, m.p.
182–184 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 33.6 cm−1M−1); IR (ATR)
ν: 3036, 2954, 2931, 2853,
max
1599, 1590, 1476, 1461, 1428, 1414, 1323, 1300, 1221, 1177, 1049, 1035, 1022, 861, 834, 788, 747 cm−1
;
1H-NMR (400 MHz, CDCl3):
quin, J = 7.2 Hz, 2H, CH2), 3.90 (s, 6H, 2
2.4 Hz, 2H, ArH), 7.19 (d, J = 2.4 Hz, 2H, ArH), 7.23–7.27 (m, 2H, ArH), 7.40 (t, J = 8.0 Hz, 2H, ArH),
δ
0.73 (t, J = 7.2 Hz, 3H, CH3), 1.01–1.10 (m, 6H, 3
×
CH2), 1.46
(
×
OCH3), 4.18 (t, J = 7.2 Hz, 2H, CH2), 6.95 (dd, J = 8.0 and
7.74–7.78 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.8, 22.2, 25.7, 29.9, 30.7, 45.0, 55.4, 113.0,
113.3, 119.6, 126.9, 127.6, 129.3, 130.0, 141.6, 142.6, 155.4, 160.1; HRMS m/z calcd for (C34H35N3O2 + H+):
518.2802; found: 518.2801.
4-Hexyl-◦3,5-bis(30-nitrobiphenyl-4-yl)-4H-1,2,4-triazole (8g). Creamy solid in 85% yield, 0.466 g, m.p.
223–225 C; UV (CH2Cl2)
λ
max 276.0 nm (ε·10-3 48.3 cm−1M−1); IR (ATR)
ν: 3086, 2927, 2857, 1522, 1472,
1344, 1294, 1105, 1085, 968, 877, 843, 813, 778, 730, 702, 684 cm−1; 1H-NMR (400 MHz, CDCl3):
δ 0.74
(
t, J = 7.2 Hz, 3H, CH3), 1.01–1.13 (m, 6H, 3
×
CH2), 1.47 (quin, J = 7.6 Hz, 2H, CH2), 4.21 (t, J = 7.6 Hz,
2H, CH2), 7.68 (t, J = 7.6 Hz, 2H, ArH), 7.82 (d, J = 8.4 Hz, 4H, ArH), 7.86 (d, J = 8.4 Hz, 4H, ArH), 8.00
(dd, J = 7.6 and 2.0 Hz, 2H, ArH), 8.27 (dd, J = 7.6 and 2.0 Hz, 2H, ArH), 8.53 (t, J = 2.0 Hz, 2H, ArH);
13C-NMR (100 MHz, CDCl3):
δ 13.8, 22.2, 25.7, 30.0, 30.7, 45.1, 122.0, 122.7, 127.7, 128.0, 129.7, 130.0,
133.0, 140.3, 141.7, 148.8, 155.1; HRMS m/z calcd for (C32H29N5O4 + H+): 548.2292; found: 548.2299.
3,5-Bis(3◦0-aminobiphenyl-4-yl)-4-hexyl-4H-1,2,4-triazole (8h). Beige solid in 78% yield, 0.381 g, m.p.
−3
181–183 C; UV (CH2Cl2)
ν
λ
max
233.0 nm (ε·10 30.3 cm−1M−1), 258.0 (32.8) and 281.0 (37.7); IR (ATR)
: 3442, 3369, 3200, 3034, 2956, 2926, 2856, 1617, 1601, 1586, 1562, 1474, 1427, 1321, 1227, 1166, 993, 888,
835, 780, 746, 722 cm−1; 1H-NMR (400 MHz, CDCl3):
3 × CH2), 1.44 (quin, J = 7.2 Hz, 2H, CH2), 3.78 (br.s, 4H, 2
(dd, J = 7.6 and 2.0 Hz, 2H, ArH), 6.98 (t, J = 2.0 Hz, 2H, ArH), 7.05 (dd, J = 7.6 and 2.0 Hz, 2H, ArH),
7.26 (t, J = 7.6 Hz, 2H, ArH), 7.72–7.74 (m, 8H, ArH); 13C-NMR (100 MHz, CDCl3):
13.8, 22.2, 25.6,
δ
0.73 (t, J = 7.2 Hz, 3H, CH3), 0.98–1.10 (m, 6H,
NH2), 4.16 (t, J = 7.6 Hz, 2H, CH2), 6.73
×
δ
29.9, 30.7, 45.0, 113.7, 114.7, 117.5, 126.6, 127.5, 129.2, 129.9, 141.2, 143.0, 146.9, 155.4; HRMS m/z calcd
for (C32H33N5 + H+): 488.2809; found: 488.2817.
4-Hexyl-3,5-bis[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (8i). White solid in 86% yield, 0.396 g, m.p.
205–207 ◦C; UV (CH2Cl2)
λ
281.0 nm (ε·10−3 46.6 cm−1M−1); IR (ATR)
ν
: 2924, 2855, 1595, 1540,
0.73
max
1471, 1408, 1216, 993, 967, 857, 812, 771, 753, 737, 667 cm−1; H-NMR (400 MHz, CDCl3):
δ
1
(
t, J = 7.2 Hz, 3H, CH3), 0.99-1.11 (m, 6H, 3
×
CH2), 1.46 (quin, J = 7.2 Hz, 2H, CH2), 4.20 (t, J = 7.2 Hz,
2H, CH2), 7.58 (d, J = 6.0 Hz, 4H, ArH), 7.82–7.85 (m, 8H, ArH), 8.73 (d, J = 6.0 Hz, 4H, ArH); 13C-NMR
(100 MHz, CDCl3):
δ 13.8, 22.1, 25.6, 29.9, 30.7, 45.1, 121.6, 127.6, 128.4, 129.6, 139.8, 147.1, 150.5, 155.1;
HRMS m/z calcd for (C30H29N5 + H+): 460.2496; found: 460.2499.
4-Hexyl-3,5-bis[4-(pyridin-3-yl)phenyl]-4H-1,2,4-triazole (8j). Creamy solid in 83% yield, 0.382 g, m.p.
198–199 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 41.6 cm−1M−1); IR (ATR)
ν
: 2927, 2855, 1574, 1469,
0.73
max
1415, 1380, 1102, 1026, 1001, 967, 849, 839, 804, 751, 709 cm−1; H-NMR (400 MHz, CDCl3):
δ
1
(
t, J = 7.2 Hz, 3H, CH3), 1.00–1.11 (m, 6H, 3
2H, CH2), 7.42 (dd, J = 8.0 and 4.8 Hz, 2H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH), 7.83 (d, J = 8.4 Hz, 4H,
ArH), 7.96 (dt, J = 8.0 and 1.6 Hz, 2H, ArH), 8.66 (dd, J = 4.8 and 1.6 Hz, 2H, ArH), 8.94 (d, J = 1.6 Hz
×
CH2), 1.47 (quin, J = 7.2 Hz, 2H, CH2), 4.20 (t, J = 7.2 Hz,
,
2H, ArH); 13C-NMR (100 MHz, CDCl3):
134.4, 135.5, 139.5, 148.3, 149.1, 155.2; HRMS m/z calcd for (C30H29N5 + H+): 460.2496; found: 460.2497.
δ 13.8, 22.2, 25.7, 29.9, 30.7, 45.1, 123.7, 127.5, 127.7, 129.6,
3,5-Bis[4-(furan-2-yl)phenyl]-4-hexyl-4H-1,2,4-triazole (8k). Creamy solid in 89% yield, 0.390 g, m.p.
◦
199–202 C; UV (CH2Cl2)
λ
max
310.0 nm (ε·10−3 37.8 cm−1M−1); IR (ATR)
ν
: 2933, 1687, 1611,
0.72
1473, 1374, 1259, 1180, 1092, 1009, 903, 844, 800, 731, 664 cm−1; 1H-NMR (400 MHz, CDCl3):
δ
(
t, J = 7.2 Hz, 3H, CH3), 0.97–1.10 (m, 6H, 3
×
CH2), 1.41 (quin, J = 7.2 Hz, 2H, CH2), 4.13 (t, J = 7.6 Hz,
2H, CH2), 6.53 (dd, J = 3.6 and 2.0 Hz, 2H, ArH), 6.78 (d, J = 3.6 Hz, 2H, ArH), 7.53 (d, J = 2.0 Hz, 2H,

Molecules 2019, 24, 652
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ArH), 7.70 (d, J = 8.8 Hz, 4H, ArH), 7.83 (d, J = 8.8 Hz, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 13.7,
22.2, 25.7, 29.8, 30.7, 45.0, 106.4, 111.9, 124.1, 126.3, 129.2, 132.3, 142.8, 153.0, 155.3; HRMS m/z calcd for
(C28H27N3O2 + H+): 438.2176; found: 438.2175.
3,5-Bis[4-(furan-3-yl)phenyl]-4-hexyl-4H-1,2,4-triazole (8l). Yellow solid in 69% yield, 0.302 g, m.p.
175–178 ◦C; UV (CH2Cl2)
λ
284.0 nm (ε·10−3 17.8 cm−1M−1); IR (ATR)
ν
: 3093, 2933, 2864, 1740,
max
1615, 1475, 1429, 1261, 1164, 1116, 1055, 1015, 957, 922, 873, 839, 785, 750, 723, 695 cm−1; H-NMR
1
(400 MHz, CDCl3):
δ
0.73 (t, J = 7.2 Hz, 3H, CH3), 0.97–1.10 (m, 6H, 3
×
CH2), 1.41 (quin, J = 7.2 Hz, 2H,
CH2), 4.13 (t, J = 7.6 Hz, 2H, CH2), 6.77 (dd, J = 2.0 and 1.2 Hz, 2H, ArH), 7.53 (d, J = 2.0 Hz, 2H, ArH),
7.65 (d, J = 8.8 Hz, 4H, ArH), 7.69 (d, J = 8.8 Hz, 4H, ArH), 7.83 (d, J = 1.2 Hz, 2H, ArH); 13C-NMR
(100 MHz, CDCl3):
δ 13.8, 22.2, 25.7, 29.8, 30.7, 45.0, 108.6, 125.7, 126.1, 126.2, 129.3, 134.2, 139.2, 144.0,
155.3; HRMS m/z calcd for (C28H27N3O2 + H+): 438.2176; found: 438.2173.
4-Hexyl-3,5-bis[4-(thiophen-2-yl)phenyl]-4H-1,2,4-triazole (8m). Beige solid in 37% yield, 0.174 g, m.p.
219–220 ◦C; UV (CH2Cl2)
λ
312.0 nm (ε·10−3 42.0 cm−1M−1); IR (ATR)
ν: 2954, 2923, 2853, 1611,
max
1471, 1427, 1400, 1377, 1351, 1259, 1213, 1115, 959, 848, 818, 776, 752, 662 cm−1; 1H-NMR (400 MHz,
CDCl3):
δ
0.73 (t, J = 7.2 Hz, 3H, CH3), 0.99–1.09 (m, 6H, 3
×
CH2), 1.43 (quin, J = 7.2 Hz, 2H, CH2),
4.14 (t, J = 7.2 Hz, 2H, CH2), 7.13 (dd, J = 4.8 and 3.6 Hz, 2H, ArH), 7.36 (d, J = 4.8 Hz, 2H, ArH),
7.43 (d, J = 3.6 Hz, 2H, ArH), 7.71 (d, J = 8.4 Hz, 4H, ArH), 7.78 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR
(100 MHz, CDCl3):
δ 13.8, 22.2, 25.7, 29.9, 30.7, 45.0, 124.0, 125.8, 126.2, 126.6, 128.3, 129.4, 136.0, 143.2,
155.3; HRMS m/z calcd for (C28H27N3S2 + H+): 470.1719; found: 470.1707.
4-Hexyl-3,5-bis[4-(thiophen-3-yl)phenyl]-4H-1,2,4-triazole (8−n1). Creamy solid in 62% yield, 0.291 g, m.p.
237–239 ◦C; UV (CH2Cl2)
λ
290.0 nm (ε·10−3 39.6 cm
M ν: 3065, 2925, 2856, 1614,
−1); IR (ATR)
max
1467, 1426, 1355, 1260, 1194, 1100, 1014, 864, 846, 781, 749 cm−1; 1H-NMR (400 MHz, CDCl3):
δ 0.73
(
t, J = 7.2 Hz, 3H, CH3), 0.98–1.09 (m, 6H, 3
×
CH2), 1.43 (quin, J = 7.2 Hz, 2H, CH2), 4.15 (t, J = 7.2 Hz,
2H, CH2), 7.44 (dd, J = 5.2 and 2.8 Hz, 2H, ArH), 7.47 (dd, J = 5.2 and 1.6 Hz, 2H, ArH), 7.57 (dd, J = 2.8
and 1.6 Hz, 2H, ArH), 7.72 (d, J = 8.4 Hz, 4H, ArH), 7.77 (d, J = 8.4 Hz, 4H, ArH); 13C-NMR (100 MHz,
CDCl3):
δ 13.8, 22.2, 25.7, 29.9, 30.7, 45.0, 121.3, 126.1, 126.4, 126.7, 126.8, 129.4, 137.3, 141.2, 155.4;
HRMS m/z calcd for (C28H27N3S2 + H+): 470.1719; found: 470.1728.
3.2.4. An IL Alternative Approach for Suzuki Cross-Coupling Reaction. Synthesis of
3,5-Bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7a)
To a mixture of 3,5-bis(4-bromophenyl)-4-butyl-4H-1,2,4-triazole (3c, 0.435 g, 1.00 mmol), phenylboronic
acid (4a, 0.305 g, 2.50 mmol) and Pd(PPh3)4 (0.058 g, 0.05 mmol), aq. choline hydroxide solution
46 wt.% (Choline-OH, 10 mL) and toluene (1 mL) were added. The mixture was heated under
◦
reflux in an oil bath (130 C) for 24 h (reaction was monitored by TLC). After cooling, chloroform
(50 mL) was added and then transferred to a separating funnel. The IL was extracted with chloroform
(
2 × 10 mL). The remaining IL after extraction can be used for the next cycle. The combined chloroform
layers were filtered through a silica gel plug (10 mL), which was then flushed with CHCl3/EtOAc
(5:1 v/v). The filtrate was dried over MgSO4 and concentrated using a rotary evaporator. The product
was precipitated using EtOAc (5 mL), filtered, washed with fresh EtOAc and air-dried to give
3,5-bis(biphenyl-4-yl)-4-butyl-4H-1,2,4-triazole (7a) in 83% yield.
4. Conclusions
We developed an efficient methodology for the synthesis of four series of 4H-1,2,4-triazole
derivatives conjugated to different aromatic and heteroaromatic arrangements via 1,4-phenylene
linker. The final Suzuki cross-coupling reactions of the intermediate 4-alkyl-3,5-bis(4-bromophenyl)-
4H-1,2,4-triazoles and boronic acids were conducted by both conventional and alternative ionic liquid
(IL) approach. The application of IL in the transformation resulted in the formation of the selected
product in high yield with the possibility of regeneration of this green solvent and its subsequent
recycling with only a slight decrease in product yield. Generally, products were obtained in excellent

Molecules 2019, 24, 652
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yields at each stage of a few-step methodology. The presence of alkyl substituent on the ring nitrogen
atom enhances the solubility of the final products, which is particularly important for their potential
application in the production of optoelectronic devices. Strong fluorescence has been observed
for almost all compounds, except products containing a terminal 3-nitrophenyl substituent. High
fluorescence quantum yields were observed, reaching up to 98%, dependent on the nature of terminal
substituents, suggesting conjugation extending over all five rings of the investigated systems.
Supplementary Materials: Copies of the 1H-NMR and 13C-NMR spectra and 3D emission spectra of the
compounds are available in the online Supplementary Materials.
Author Contributions: M.O. and A.K. conceived and designed the experiments. M.O. performed the experiments.
M.S. performed the emission measurements. M.O. wrote the manuscript with the help of A.K. and R.K. All authors
read and approved the final manuscript.
Funding: Partial financial support for this research work, awarded by Polish National Science Centre grant
UMO-2016/23/N/ST5/02036, is gratefully acknowledged.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds 3a–d, 5c–g, 6c–g, 7c–g, 8c–g are available from the authors.
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