Synthesis, structural analysis, and photophysical properties of bi-1,2,3-triazoles

Article abstract of DOI:10.1007/s11224-019-01390-1

Structural insights of a group of bi-1,2,3-triazoles derived from oxidative CuAAC are described through an X-ray crystallography study, distinguishing a dihedral angle which is ranged from 76.45 to 86.39° between the two 1,2,3-triazole rings. In addition,

Full text of DOI:10.1007/s11224-019-01390-1

Structural Chemistry
https://doi.org/10.1007/s11224-019-01390-1
ORIGINAL RESEARCH
Synthesis, structural analysis, and photophysical
properties of bi-1,2,3-triazoles
Ivette Santana-Martínez1 & María Teresa Ramírez-Palma1 & Javier Sánchez-Escalera1 & Diego Martínez-Otero1
Marco A. García-Eleno1 & Alejandro Dorazco-González1 & Erick Cuevas-Yañez1
&
Received: 15 May 2019 /Accepted: 27 June 2019
#
Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
Structural insights of a group of bi-1,2,3-triazoles derived from oxidative CuAAC are described through an X-ray crystallography
study, distinguishing a dihedral angle which is ranged from 76.45 to 86.39° between the two 1,2,3-triazole rings. In addition,
compound 1 containing a phenyl moiety displays a strong blue emission (λem = 394 nm); this structure-related
photoluminescence is attributed to the rigidity of the molecule and the conjugation between phenyl groups and the triazole
fragments.
.
.
.
Keywords Bi-1,2,3-triazole Crystal structure Dihedral angle Fluorescent emission
Introduction
aromatic rings linked by a single bond forming the biaryl
part of the molecule. For example, Zhu and coworkers
found rigid axially chiral structures in bi-1,2,3-triazoles
with a broader range of dihedral angle distribution than
that of BINAPs which provide more opportunities for li-
gand design in catalysis area [5].
5,5′-(1,2,3-Triazolyl)-1,2,3-triazoles, usually known as bi-
1,2,3-triazoles, are promising molecules derived from oxida-
tive copper-catalyzed azide-alkyne cycloaddition (CuAAC)
[1, 2]. Since their discovery by Angell and Burgess [3], the
number of works about the synthesis of bi-1,2,3-triazoles have
increased considerably in recent years; however, there are few
reports which describe structural and other physical character-
istics [4–11].
Bi-1,2,3-triazole structure is similar to other biaryl com-
pounds such as binaphthyls [12–14], bipyridines [15],
biimidazoles [16, 17], bipyrazoles [18, 19], and 4,4′-bi-
1,2,4-triazoles [20, 21]. This characteristic converts bi-
1,2,3-triazoles in potential useful ligands for catalysis with
the advantage that these compounds are easily available
from oxidative CuAAC reaction. Hence, structural studies
in bi-1,2,3-triazoles are important in order to describe
properties such as possible coordination sites and stable
conformations, especially those which are related to the
On the other hand, there is a significant current interest in
the development of fluorescent triazole derivatives owing to
their well-known biological properties that offer promise for
medical applications and more recently due to their use as
optical molecular sensors for ionic species [22]. Particularly,
the emission upon excitation is a physical property that has
been found several applications lately in sensing of inorganic
anions [23–25], color emitting devices [26], and metal
chemosensing characterization of 1,2,3-triazole-based
regioisomers [27–29]. The photophysical properties of organ-
ic fluorophores are essentially dependent on the conjugated
aromatic rings, planarity of the system, solvation environ-
ment, and substituent groups in the fluorescent core [22, 30].
In this context, CuAAC reaction has allowed the preparation
of a wide variety of triazole-based molecules, from modest
push-pull chromophores/fluorophores [31, 32] to multipolar
structures with non-linear optical responses such as two-
photon absorption [33]. In this regard, the abovementioned
photophysical properties have not been already described for
bi-1,2,3-triazoles, and only some reported transition metal
complexes of bi-1,2,3-triazoles exhibit these characteristics
[34–37].
* Erick Cuevas-Yañez
ecuevasy@uaemex.mx
1
Centro Conjunto de Investigación en Química Sustentable
UAEM-UNAM, Universidad Autónoma del Estado de México,
Carretera Toluca-Atlacomulco Km 14.5, 50200 Toluca, State of
Mexico, Mexico

Struct Chem
In connection with other projects, we some time ago initi-
ated studies on the synthesis of bi-1,2,3-triazoles, few exam-
ples of which were then known, as well as thorough structural
and photophysical property studies about this kind of com-
pounds. In light of the new discoveries about this topic, we
consider disclosing our most recent results in this area.
Scheme 1 Synthesis of bi-1,2,3-triazoles
Experimental
diffractometer. Three standard reflections every 97 reflections
were used to monitor the crystal stability. The structure was
solved by direct methods; missing atoms were found by dif-
ference Fourier synthesis, and refined on F2 by a full-matrix
least-squares procedure using anisotropic displacement pa-
rameters using SHELX-97. Crystallographic data for the
structure reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre (CCDC). Copies of
available materials can be obtained free of charge on applica-
tion to the director of CCDC (12 Union Road, Cambridge
CB2 IEZ, UK (facsimile: (44) 01223 336033); e-mail:
deposit@ccdc.ac.uk).
General
The starting materials were purchased from Aldrich Chemical
Co. and were used without further purification. Solvents were
distilled before use. The tartrate-NaOH solution (Fehling B
solution) was prepared dissolving sodium hydroxide (23.5 g,
0.04 mol) and tartaric acid (18.3 g, 0.012 mol) in H2O
(100 mL). The CuSO4 solution (Fehling A solution) was pre-
.
pared by dissolving CuSO4 5H2O (9.89 g, 0.039 mol) in H2O
(100 mL). Silica plates of 0.20-mm thickness were used for
thin layer chromatography. Melting points were determined
with a Krüss Optronic melting point apparatus and they are
uncorrected. 1H and 13C NMR spectra were recorded using a
Bruker AVANCE 300 or a Varian 500-MHz instrument; the
chemical shifts (δ) are given in ppm relative to TMS as inter-
nal standard (0.00). For analytical purposes, the mass spectra
were recorded on a Shimadzu GCMS-QP2010 Plus in the EI
mode, 70 eV, 200 °C via direct inlet probe. Only the molecular
and parent ions (m/z) are reported. IR spectra were recorded
on a Bruker TENSOR 27 FT instrument.
The absorption and emission spectra were recorded from
methanolic solutions of compounds 1–5 (10 μM and 2 μM
respectively) in a quartz cuvette placed in a compartment of
spectrophotometer thermostated at 25.0° 0.1 on a Cary-100
Agilent UV-vis spectrophotometer and Cary Eclipse Agilent
fluorescence spectrophotometer. Emission quantum yields
were determined using L-tryptophan in a degassed aqueous
solution as the standard (Φ = 0.13; ex = 280 nm).
General procedure for the synthesis
of bi-1,2,3-triazoles
The corresponding azide (1 mmol) and alkyne (1 mmol) were
added to a solution of glucose (0.045 g, 0.25 mmol) in H2O
(1 mL) and MeOH (5 mL). The mixture was treated succes-
sively with the tartrate-NaOH solution (Fehling B solution,
0.1 mL) and CuSO4 solution (Fehling A solution, 0.25 mL,
0.1 mmol). The resulting mixture was stirred at 0 °C for 24 h.
The solvent was removed under reduced pressure and the final
product was purified by column chromatography (SiO2,
hexane/AcOEt 8:2).
3,3′-Dibenzyl-5, 5′-diphenyl—3H, 3′H-[4,4′] bi
[[1,2,3]triazolyl] (1). White solid, mp. 110 °C. IR (KBr) ѵ =
1
695, 721, 973, 1219, 1296, 1452, 3100 cm−1. H RMN:
(500 MHz, DMSO-d6) δ 7.4 (m, 4H), 7.14–7.25 (m, 6H),
7.07–7.20 (m, 6H), 6.81 (d, 4H), 4.81 (d, 2H), 4.74 (d, 2H)
ppm. 13C RMN (125 MHz, DMSO-d6) δ 147.22, 134.04,
129.54, 129.24, 129.07, 128.98, 128.77, 128.36, 125.81,
52.63 ppm; MS [EI+] m/z (%) 468 [M]+ (40), 349 [M-
Differential scanning calorimetry (DSC) studies were per-
formed on the Netzsch STA 449 F3 Jupiter for experiment A
at a rate of 10 °C/min and 1 °C/min, atmosphere: high purity
nitrogen. For experiment B, at a heating and cooling rate of
5 °C/min, atmosphere: helium BIP and nitrogen, both exper-
iments in aluminum crucible, with a hole in the lid.
Table 1 Synthesis of bi-1,2,3-triazoles
Compound
R1
R2
% yield
For the RX diffraction studies, crystals of compounds 2–7
were obtained by slow evaporation of a dilute MeOH solution.
Crystallographic data for compounds were collected on a
Bruker SMART APEX DUO three-circle diffractometer
equipped with an Apex II CCD detector using MoKα (λ =
0.71073 Å (Incoatec IμS microsource and Helios optic mono-
chromator); the temperature of collections was − 173 °C
(100 K)). Suitable crystals were coated with hydrocarbon
oil, picked up with a nylon loop, and mounted the
1
2
3
4
5
6
7
CH2Ph
CH2Ph
CH2Ph
CH2Ph
CH2Ph
(CH2)3Ph
CH2Ph
Ph
68
90
65
77
70
78
50
CH2O(2-Cl)C6H4
CH2O(4-Cl)C6H4
CH2O(4-Br)C6H4
CH2O(4-CH3)C6H4
Ph
CH2OH

Struct Chem

Struct Chem
Fig. 1 ORTEP diagrams for compounds 1 (a), 2 (b), 3 (c), 4 (d), 5 (e), 6 (f), and 7 (g)
C7H7N2]+ (35), 321 [M-C7H7N4]+ (35), 91 [C6H5CH2]+
(100).
3,3′-Dibenzyl-5,5′-bis-(2-chlorophenoxymethyl)-3H,3′
H-[4,4′]bi[[1,2,3]triazolyl] (2). White solid mp. 92 °C. IR
(KBr) ѵ = 3062, 3028, 2916, 2850, 1715, 1589, 1484, 1447,
1276, 1244, 1228, 1060, 1042, 1002, 860, 825, 747, 737, 709,
695, 670, cm−1. 1H RMN: (500 MHz, DMSO-d6) δ7.41 (dd,
2H), 7.31 (m, 4H), 7.28 (m, 6H), 7.22 (m 2H), 6.94 (m, 2H),
5.09 (d, 2H) 4.95 (d, 2H), 4.77 (d, 2H) 4.64 (d, 2H) ppm. 13
C
RMN (125 MHz, DMSO-d6) δ 153.24, 144.65, 134.52,

Struct Chem
Fig. 2 TG thermogram and DSC curve of compound 1
130.43, 129.23, 128.58, 128.30, 122.5, 121.65, 114.35, 61.75,
52.44 ppm. MS [EI+] m/z (%) 596 [M]+ (10), 526 [M-Cl2]+
(20), 119 [C7H7N2]+ (20), 91 [C7H7]+ (100). Elemental anal-
ysis calculated: C, 64.33; H, 4.39; N, 14.07, found: C, 64.31;
H, 4.27; N, 14.05.
3,3′-Dibenzyl-5,5′-bis-(4-chlorophenoxymethyl)-3H,3′
H-[4,4′]bi[[1,2,3]triazolyl] (3). White solid; mp.70 °C. IR
(KBr) ѵ = 3141, 2925, 2853, 1886, 1731, 1579, 1490, 1239,
1221, 993, 830, 815, 756, 720, 649, 515, 473 cm−1; 1H RMN:
(500 MHz, DMSO-d6) δ 7.19-7.34 (m, 14H.) 6.93 (d, 2H)
Fig. 3 DSC heating and cooling scan of compound 1

Struct Chem
Fig. 4 DSC heating and cooling scan of compound 2
6.69 (d, 2H) 5.75 (s, 4H) 5.07 (d, 4H) ppm; 13C RMN
(125 MHz, DMSO-d6) δ 157.28, 143.15, 136.41, 129.68,
129.22, 128.63, 128.39, 125.21, 117,116.99, 61.81,
53.31 ppm. MS [EI+] m/z (%) 596 [M]+ (5), 92 [C7H8]+
(100). Elemental analysis calculated: C, 64.33; H, 4.39; N,
14.07, found: C, 64.10; H, 4.48; N, 13.77.
3,3′-Dibenzyl-5,5′-bis-(4-bromophenoxymethyl)-3H,3′
H-[4,4′]bi[[1,2,3]triazolyl] (4). White solid, mp. 68 °C; IR
(KBr) ѵ = 2952, 2922, 2853, 1577, 1483, 1459, 1337,1336,
1285,1237, 1211, 1118, 1000, 858,809, 730, 706, 615, 592,
507 cm−1. 1H RMN: (500 MHz, DMSO-d6) δ 7.39 (m, 4H),
7.17–7.31 (m, 10H), 6.93 (s, 4H), 5.57 (s, 4H) 5.18 (s, 4H)
ppm. 13C RMN (125 MHz, DMSO-d6) δ 164.85, 137.3,
133.85, 131.85, 117.7, 114.45, 76.47, 40.21, 39.79, 39.62,
39.45 ppm. MS [EI+] m/z (%) 684 [M]+ (5), 526 [M-Br2]+
(30), 119 [C7H7N2]+ (20), 92 [C7H8]+ (100). Elemental
analysis calculated: C, 55.99; H, 3.82; N, 12.24, found: C,
55.13; H, 4.00; N, 12.05.
3,3′-Dibenzyl-5,5′-bis-p-tolyloxymethyl-3H,3′
H-[4,4′]bi[[1,2,3]triazolyl] (5) White solid, m.p. 85 °C. IR
(KBr) ѵ = 3064, 3032, 2923, 2857, 1725, 1611, 1568,
1509, 1456, 1290, 1228, 1177, 1027, 1016, 813, 709,
1
511 cm−1. H RMN: (500 MHz, DMSO-d6) δ 7.31 (ddd,
6H), 7.07 (m, 4H), 6.93 (d, 4H), 6.57 (d, 4H), 5.15 (d,
Table 3 Dihedral angles
(°) formed by triazole
Compound
Dihedral angle (°)
rings in bi-1,2,3-triazoles
1
2
3
4
5
6
7
82.07
77.93
80.64
81.28
83.58
86.39
76.45
Fig. 5 Orthogonal conformation in the triazole rings in compound 6

Struct Chem
Fig. 6 Intramolecular interactions C–H—pi found in compound 6
2H), 5.03 (d, 2H), 4.58 (d, 2H), 4.44 (d, 2H), 2.21 (s, 6H)
ppm. 13C RMN (125 MHz, DMSO-d6) δ 155.61, 145.39,
134.69, 129.94, 129.28, 128.11, 122.4, 115.40, 114.73,
60.66, 52.25, 20.045 ppm. MS [EI+] m/z (%) 556 [M]+
(5), 91 [C7H7]+ (100). Elemental analysis calculated: C,
72.99; H, 4.98; N, 15.96, found: C, 72.93; H, 4.91; N,
15.95.
5,5′-Diphenyl-3,3′-bis-(3-phenylpropyl)-3H,3′
H-[4,4′]bi[[1,2,3]triazolyl] (6). White solid, m. p. 131 °C. IR
1
(ATR) ѵ = 2915, 2862, 1439 cm−1. H NMR (300 MHz,
CDCl3) δ 7.79 (m, 4H), 7.42–7.20 (m, 2H), 3.79 (dd, 4H),
2.57 (t, 4H), 1.98 (t, 2H). 13C NMR (75 MHz, CDCl3) δ
147.1, 141.6, 131.9, 129.2, 128.9, 128.6, 127.9, 126.3,
122.8, 49.3, 34.2, 25.7. MS [EI+] m/z (%) 552 [M]+ (5), 91
Fig. 7 Dimer formed by the C–H—N2 interaction in the crystal packing of compound 6. Symmetry code (i) = − x, 1 − y, 1 − z

Struct Chem
Table 4 Photophysical properties
bi-1,2,3-triazoles 1-5 in CH3OH
Compound R2
λ
(nm)
max abs
Extinction coefficient Emission
Quantum
RFIc
(M−1 cm−1
)
(nm)a
yield (%)b
1
2
3
4
5
Ph
244; 286 1.3 × 105; 5.8 × 104
243; 262 7.6 × 104; 3.7 × 104;
242; 263 6.8 × 104; 3.8 × 104
242; 267 5.3 × 104; 3.0 × 104
384
361
355
341
338
10.4
5.8
5.2
3.4
4.5
–
CH2O(2-Cl)C6H4
CH2O(4-Cl)C6H4
CH2O(4-Br)C6H4
0.43
0.40
0.23
0.29
CH2O(4-CH3)C6H4 242; 265 3.5 × 104; 1.7 × 104
a λexc = 286 nm
b Relative to L-tryptophan
c RFI relative fluorescence intensity normalized with respect to 1
[C7H7]+ (100). Elemental analysis calculated: C, 78.23; H,
6.57; N, 15.21, found: C, 78.29; H, 6.52; N, 15.16.
Compounds 1–7 were fully characterized by the conven-
tional spectroscopic techniques. Moreover, these compounds
were crystalline solids suitable for X-ray crystallography stud-
ies. Crystallographic data and structural refinement parame-
ters of compounds 1–7 are summarized in Table 2 and the
corresponding ORTEP representations are shown in Fig. 1,
confirming the proposed structure for these compounds.
Single-crystal X-ray diffraction analysis performed on com-
pounds 1–7 revealed some interesting facts. For example, crystal
structure of bi-1,2,3-triazole 1 represents a new polymorphic
form of this compound which previously crystallized in an or-
thorhombic crystal system under a centrosymmetric space group
Pbca [11]. In this case, the new polymorph of 1 crystallized in a
triclinic crystal system under a space group P-11 with 4 mole-
cules in the asymmetric unit, two of them displaying disorder in
the phenyl moiety (molecule a in Fig. 1). In order to corroborate
the presence of polymorphs in compound 1, simultaneous TGA
and DSC studies were determined with a heating rate of
10 °C/min (Fig. 2). TG thermogram of 1 shows only an impor-
tant weight loss which takes place at above 350 °C associated to
the molecule degradation and demonstrating that this product is
neither a solvated, nor a hydrated form of compound 1, while the
DSC curve of this sample displays an endothermic process at
141.1 °C. A second sample was analyzed under a cycle plotted in
( 3 , 3 ′ - D i b e n z y l - 5 ′ - h y d r o x y m e t h y l - 3 H , 3 ′
H-[4,4′]bi[[1,2,3]triazolyl]-5-yl)-methanol (7) White solid,
m.p. 85 °C. IR (KBr) ѵ = 3350, 2923, 2857, 1611, 1568,
1509, 1456, 1290, 1230 cm−1 1H RMN: (500 MHz,
.
DMSO-d6) δ 7.31 (ddd, 6H), 7.07 (m, 4H), 6.93 (d, 4H),
6.57 (d, 4H), 5.15 (d, 2H), 5.03 (d, 2H), 4.58 (d, 2H), 4.44
(d, 2H) ppm. 13C RMN (125 MHz, DMSO-d6) δ 141.4, 136.8,
129.94, 129.3, 128.1, 121.9, 59.7, 52.1 ppm. MS [EI+] m/z
(%) 376 [M]+ (5), 375 [M-H]+ (10), 92 [C7H8]+ (100).
Elemental analysis calculated: C, 63.82; H, 5.36; N, 22.33,
found: C, 63.83; H, 5.29; N, 22.25.
Results and discussion
The initial experiments were aimed to prepare bi-1,2,3-triazoles
through an adaptation of a previous work by our group (Scheme
1) [11, 38]. Thus, treatment of diverse azides with the appropriate
alkynes in the presence of catalytic amounts of a Fehling
Reagent-glucose-NaOH system at 0 °C afforded the correspond-
ing bi-1,2,3-triazoles 1–7 in 65–90% yields (Table 1).
Fig. 8 Absorption and fluorescence spectra of compounds 1–5 (10 μM and 2 μM for UV-vis and fluorescence respectively, λex = 280 nm) in CH3OH

Struct Chem
Fig. 9 Absorption (a) and fluorescence (b) spectra of 1 (10 μM and 2 μM for UV-vis and fluorescence respectively, λex = 280 nm) in CH3OH. The inset
shows solution of A under irradiation at 365 nm UV light
Fig. 3 (heating-cooling-heating rates of 1 °C/min); the DSC scan
shows three small endothermic peaks of crystallization at 133.2,
135.9, and 138.1 °C which indicate the existence of 3 polymor-
phic forms.
small structural changes; an example is the regioisomerism
which dramatically modifies the molecular absorption and
emission attributes in these compounds [25, 32]. Taking this
point into consideration, we explored the effect of substituent
− R2 (see Table 1) on the photophysical properties of bi-1,2,3-
triazoles 1–5. The basic photophysical properties (absorption
maxima, emission, and quantum yields) of 1–5 in methanolic
solutions are collected in Table 4 and the corresponding UV-
vis and fluorescence spectra are plotted in Fig. 8.
All compounds display good solubility in methanol and the
corresponding solutions were used for further studies.
Compound 1 exhibits a strong blue emission under ambient
conditions with bands centered at 384 upon excitation at
286 nm, as shown in Fig. 9. Solutions of 2–3 present a modest
emission at 361 and 355 nm respectively. In contrast, com-
pounds 4–5 display very low fluorescence. One particular
point is that insertion of an electron-donating group
(halophenoxymethyl groups in compounds 2–4 and
tolyloxymethyl group in compound 5 at the C-4 triazole posi-
tion in 1,1′-dibenzyl-bis(1,2,3-triazole) fragment induces a
considerable quenching of the emission accompanied by sig-
nificant blue-shift of 23-46 nm in the position of the longest
wavelength bands.
According to RFI parameter with respect to bi-1,2,3-tri-
azole 1, the effect of substitution of the bi-1,2,3-triazole core
on the decrease in the emission can be described as phenyl >
2-chlorophenoxymethyl > 4-chlorophenoxymethyl >
tolyloxymethyl. This trend is consistent with the quantum
yield values determined (Table 4). Similar photochemical
properties with UV/blue-light emission in the range of 316–
422 nm have been reported previously for a series of aryl-
1,2,3-triazoles derivatives with Stokes shift in the range of
38–94 nm [39]. Thus, the emission performance effect of sub-
stituent group at C-4 position on 3,3′- dibenzyl -5, 5′-
diphenyl-bi-1,2,3-triazolyl fragment as a fluorescence core
A similar behavior was observed in compound 2, which
crystallized with 2 molecules in the asymmetric unit
(molecule b in Fig. 1). Two polymorphs were detected in
compound 2 through a DSC heating-cooling cycle curve anal-
ysis which exhibits two small endothermic peaks of crystalli-
zation at − 28.7 °C and − 31.2 °C respectively (Fig. 4).
A noteworthy feature found in compounds 1–7 is an almost
orthogonal conformation between triazole rings similar to other
reported bi-1,2,3-triazoles [5]. Dihedral angles formed by triazole
rings are presented in Table 3 and exhibit a range from 76.45 to
86.39°.
For example, dihedral angle N(1)-C(10)-C(27)-N(4) in
compound 6 is 86.39(13)° (Fig. 5). In addition, the presence
of a C–H—pi interaction between the C(22)-H(22) and the
centroid of phenyl ring at 5-position of triazole determines a
distance of 3.7658(17) Å between these two elements and a
dihedral angle C(10)-C(11)-C(12)-C(17) of 23.84(17)° (Fig.
6). Similar distance and dihedral angle are observed from
interactions of the opposite C(5)-H(5)/5′-phenyl-1′,2′,3′-
triazolyl system. These elements suggest the presence of a
rigid axially structure along C10–C27 bond which is favored
by the C–H—pi interactions.
In the crystal packing some intermolecular interactions
have been found. C-H—N2 interactions, C(20)i-H(20A)i—
N(2) and C(18)i-H(18B)i—N(2) H—N are 2.55 and 2.70 Å
respectively forming a dimer in the unit cell as a show in the
Fig. 7. The angles C–H–N are close to 150°, the distance
ppC(20)i-N(2) is 3.5913(14) Å, and the distance C(18)i-N(2)
is 3.4728(13) Å with a symmetry code (i) − x, 1 − y, 1 − z.
1,2,3-Triazole-based molecular compounds have shown a
large diversity of photophysical properties as a function of

Struct Chem
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can be elucidated as follows: (1) the emission is considerably
higher when bi-1,2,3-triazole fragment contains rigid substit-
uents such as phenyl. It is well known that rigidity increase in
small fluorescent molecules reduces the energy loss through
non-radiative processes such as vibrations [39, 40]; (2) a sig-
nificant quenching is observed by insertion of electro-
donating groups; this optical effect is not unexpected, because
the emission in organic fluorophores is favored by the combi-
nation of a strongly electron-donating moiety conjugated
through to π-linker to a strongly electron-accepting one
(push-pull system) [41, 42]; and (3) the highest fluorescent
emission in bi-1,2,3-triazole 1 compared with the other stud-
ied compounds can be assigned to a good conjugation be-
tween phenyl group and triazole ring (dihedral angles between
0.5 and 20°). These results reveal the potential influence of
some C-4 substituent groups on photophysical properties of
bi-1,2,3-triazole derivatives. Hence, the strong emission of 1
is possible through a combination provided by a straightfor-
ward synthesis from the click chemistry approach, turning this
molecule into a promising candidate for the design of more
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Conclusion
In summary, the structure of some bi-1,2,3-triazoles was elu-
cidated, showing dihedral angles in the crystalline structure of
some bi-1,2,3-triazoles which suggest the presence of a rigid
axially chiral structure, and therefore, atropisomers, such as
Zhu and coworkers have proposed for other bi-1,2,3-triazoles
[5]. This rigidity, in combination with a significant conjuga-
tion effect through homocyclic and heterocyclic rings, also
produces an outstanding fluorescent emission in bi-1,2,3-tri-
azole 1 that has not been registered in this kind of compounds
and will open new study lines about these molecules. The
elements herein described suggest that bi-1,2,3-triazoles will
enjoy widespread applications in the future.
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Acknowledgments The authors would like to thank N. Zavala, A. Nuñez,
and L. Triana for the technical support.
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Funding information Financial support from CONACYT is gratefully
acknowledged.
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Compliance with ethical standards
Conflict of interest The authors declare that they have no competing
interests.
19. Luque R, Baruwati B, Varma RS (2010) Magnetically separable
nanoferrite-anchored glutathione: aqueous homocoupling of
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