First examples of Co(II), Ni(II), and Cu(II) coordination compounds with 1-(pyrid-2-yl)-1H-tetrazole: Synthesis, structure and properties

Article abstract of DOI:10.1016/j.poly.2020.114750

Coordination compounds of cobalt(II), nickel(II), and copper(II) with a poly nitrogen-containing heterocyclic ligand 1-(pyrid-2-yl)-1H-tetrazole (1-Pytz) such as [Cu(1-Pytz)₂Cl₂]_n, [M(1-Pytz)₂(H₂O)Cl₂] (M = Co, Ni), [M(1-Pytz)₂(C₂N₃)₂]_n (M = Co, Ni) have been synthesized. The compounds have been studied by means of infrared diffuse reflectance spectroscopy, single-crystal and powder X-ray diffraction, and static magnetic susceptibility. The studies on the μ_eff(T) for the [Cu(1-Pytz)₂Cl₂]_n, [Co(1-Pytz)₂(C₂N₃)₂]_n and [Ni(1-Pytz)₂(C₂N₃)₂]_n polynuclear complexes in the temperature range of 2–300 K have shown that exchange interactions between spins of metal ions are weak.

Full text of DOI:10.1016/j.poly.2020.114750

Journal Pre-proofs
First examples of co(ii), ni(ii) and cu(ii) coordination compounds with 1-(pyr‐
id-2-yl)-1h-tetrazole: synthesis, structure and properties
Alina D. Ivanova, Yury V. Grigoriev, Vladislav Yu. Komarov, Taisiya S.
Sukhikh, Artem S. Bogomyakov, Liliya A. Sheludyakova, Ludmila G.
Lavrenova
PII:
S0277-5387(20)30407-1
DOI:
Reference:
https://doi.org/10.1016/j.poly.2020.114750
POLY 114750
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
19 June 2020
31 July 2020
12 August 2020
Please cite this article as: A.D. Ivanova, Y.V. Grigoriev, V. Yu. Komarov, T.S. Sukhikh, A.S. Bogomyakov, L.A.
Sheludyakova, L.G. Lavrenova, First examples of co(ii), ni(ii) and cu(ii) coordination compounds with 1-
(pyrid-2-yl)-1h-tetrazole: synthesis, structure and properties, Polyhedron (2020), doi: https://doi.org/10.1016/
j.poly.2020.114750
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УДК 541.49+548.736+
FIRST EXAMPLES OF Co(II), Ni(II) AND Cu(II) COORDINATION COMPOUNDS
WITH 1-(PYRID-2-YL)-1H-TETRAZOLЕ: SYNTHESIS, STRUCTURE AND PROPERTIES
Alina D. Ivanovaa,*, Yury V. Grigorievb, Vladislav Yu. Komarova,c, Taisiya S. Sukhikha,
Artem S. Bogomyakovc,d, Liliya A. Sheludyakovaa, Ludmila G. Lavrenovaa,c
aNikolaev Institute of Inorganic Chemistry SB RAS,
Russia, 630090 Novosibirsk, Akademika Lavrentieva ave., 3
bResearch Institute for Physical Chemical Problems of Belarusian State University,
Belarus, 220006 Minsk, Leningradskaya str., 14
cNovosibirsk State University, Russia, 630090 Novosibirsk, Pirogova str., 2
dInternational Tomography Center SB RAS, Novosibirsk, Russia, Institutskaya str., 3a
e-mail: ivanova@niic.nsc.ru
_____________________________________________________________________________
ABSTRACT
Coordination compounds of cobalt(II), nickel(II), and copper(II) with a poly nitrogen-containing
heterocyclic ligand 1-(pyrid-2-yl)-1H-tetrazole (1-Pytz) such as [Cu(1-Pytz)2Cl2]n, [M(1-Pytz)2(H2O)Cl2]
(M = Co, Ni), [M(1-Pytz)2(C2N3)2]n (M = Co , Ni) have been synthesized. The compounds have been
studied by means of infrared diffuse reflectance spectroscopy, single-crystal and powder X-ray
diffraction, and static magnetic susceptibility. The studies on the µeff(T) for the [Cu(1-Pytz)2Cl2]n, [Co(1-
Pytz)2(C2N3)2]n and [Ni(1-Pytz)2(C2N3)2]n polynuclear complexes in the temperature range of 2-300 K
have shown that exchange interactions between spins of metal ions are weak.
Keywords:
3d metals
1-(pyrid-2-yl)-1H-tetrazole
Complex
X-ray structure
Magnetic properties
1. Introduction
Tetrazole derivatives are promising objects for studying in the field of coordination
chemistry. Owing to the presence of four nitrogen atoms in the tetrazole ring capable of forming
coordination bonds, the use of tetrazoles as ligands allows one to obtain a wide range of metal
complexes with specific properties [1–4]. Among tetrazole-containing mononuclear metal
complexes, compounds have been found that exhibit low temperature spin crossover (SCO),
including photoinduced SCO, as well as luminescent properties [5–8]. A number of complexes
of the Co(II), Ni(II), Cu(II) halides with 1-alkyltetrazoles having a layered structure exhibit
exchange interactions of ferromagnetic nature [9–11].
Coordination polymers and organometallic backbones that form multinuclear metal
complexes with tetrazole derivatives are characterized by high heat resistance, high porosity, the
1

ability of a selective sorbtion of gases, etc. [12–18]. At that, the manifold structural features and
properties of the obtained complexes is connected not only with the presence of a tetrazole
fragment in the ligand molecule, but also, to a considerable extent, with the structure of the
substituent in the tetrazole ring and the nature of the metal used as a complexing agent [1].
In this connection, pyridyltetrazoles, whose coordination to the metal can be effected by
nitrogen atoms belonging both to the tetrazole ring, and to the pyridine one, are of interest as
potential ligands. In contrast to 5-pyridyltetrazoles, whose coordination chemistry has been
thouroughly studied [19–29], the complex compounds of 1-(pyrid-2-yl)-1H-tetrazole (1-Pytz), first
synthesized more than 20 years ago [30], have not been obtained up till now. The only
theoretical investigation of Ir(III) complex with 1-Pytz has been reported [31]. Moreover,
synthesized metal complexes of 1-(pyrid-2-yl)-1H-tetrazole with any substituents are limited to
one example, viz. Be compound with a hydroxy-pyridyl derivative, whose crystal structure was
not determined [32]. The compounds described in this paper represent the examples of first
synthesized complexes with the 1-Pytz ligand.
This work is a continuation of our studies concerning the coordination chemistry of
tetrazole derivatives and is devoted to the synthesis and studies of the structure and properties of
Cu (II), Co (II), Ni (II) complexes with 1-(pyrid-2-yl)-1H-tetrazole.
2. Experimental
2.1. Materials and instrumentation9
All the reagents were obtained from Sigma Aldrich and used without purification. The
elemental analysis (C, H, N) was performed at the Analytical laboratory of Nikolaev Institute of
Inorganic Chemistry, SB RAS using a EuroVector EURO EA 3000 (Italy) analyzer. The 1H and
13C NMR spectra were registered using a Bruker Avance 500 NMR spectrometer. The observed
chemical shifts were referenced to solvent signals (δH 2.50, δC 39,43 ppm). The IR absorption
spectra were registered using a Scimitar FTS 2000 spectrometer in the range from 400 to 4000
cm–1. The samples under investigation were prepared in the form of suspensions in Nujol and in
fluorinated oils. Diffuse reflectance spectra were registered using a Shimadzu UV-3101 PC
scanning spectrophotometer at a room temperature. The thermogravimetric (TG) and differential
scanning calorimetry (DSC) curves have been obtained using a NETZSCH STA429
thermoanalyzer in a dynamic nitrogen atmosphere in the temperature range from a room
temperature up to 500 °C (aluminum oxide at a heating rate amounting to 10 °C/min, and a
weighed sample portion ranging from 1 to 3 mg). Temperature-dependent magnetic
susceptibility measurements were carried out using a MPMSXL Quantum Design SQUID
2

magnetometer within the temperature range from 2 to 330 K with magnetic field of up to 5 kOe.
The observed susceptibility data were corrected for the sample holder and underlying
diamagnetism by using Pascal’s constants. The values of the effective magnetic moment were
1


3k
calculated according to formula
2 , where  is the molar





eff

 T 2  (8T ) 1
2
N А B


magnetic susceptibility corrected for diamagnetism, k is the Boltzmann constant, NA is the
Avogadro's number, µB is the Bohr magneton.
2.2. Synthesis
2.2.1. Synthesis of 1-(pyrid-2-yl)-1H-tetrazole (1-Pytz).
A glacial acetic acid (48 g, 0.8 mol) was added under stirring to a suspension of 2-
aminopyridine (9.4 g, 0.1 mol) and sodium azide (7.8 g, 0.12 mol) in triethylorthoformate (43.8
o
g, 0.3 mol). The mixture was heated under stirring at 100 C for 3 h. The reaction mixture was
cooled to a room temperature, and then a concentrated hydrochloric acid (12 mL) was added.
The reaction mixture was filtered, and filtrate was concentrated under reduced pressure. A crude
residue was washed with water (~100 mL) and dried at a room temperature under vacuum to
obtain the pure target compound in form of a colorless powder (13.4 g, 0.091 mol, 91%). Mp:
o
o
129–130 C (Lit. 125–126,5 C [33]). C6H5N5 (147.14): C 49.05 (calc. 48.98); H 3.61 (calc.
1
3.43); N 47.37 (calc. 47.60)%. HNMR (500 MHz, (CD3)2SO, : 7.64–8.66 (m, 4Н, CHpyridine),
10.19 (s, 1Н, СHtetrazole) ppm.13C NMR (125 MHz, (CD3)2SO, :114.9, 125.3, 140.5, 141.5,
146.4, 149.2 ppm.
2.2.2 Synthesis of [Cu(1-Pytz)2Cl2]n (1)
A solution of 1-Pytz (0.15 g, 0.001 mol) in acetone (10 mL) was added to a solution of
CuCl2·2H2O (0.09 g, 0.0005 mol) in ethanol (10 mL) heated to 60 °C. The reaction mixture was
stirred at 60 °C and, after evaporation to ½ of the initial volume, cooled to 0–5 °C. The resulting
blue-green precipitate [Cu(1-Pytz)2Cl2]n (0.15 g, 71.0%) was filtered off, washed with a small
amount of chilled ethanol and dried in air at a room temperature. Anal. Calc. for
CuC12H10N10Cl2(428.73): C, 33.6; H, 2.4; N, 32.7. Found: C, 33.7; H, 2.3; N, 32.3%.
2.2.3. Synthesis of [Co(1-Pytz)2(H2O)Cl2] (2)
A solution of 1-Pytz (0.37 g, 0.0025 mol) in 10 ml of acetone was added under stirring to
a solution of СоCl2·6H2O (0.31 g, 0.0013 mol) in 7 ml of ethanol. The reaction mixture was
stirred at 60°C and evaporated to ¼ of the initial volume. The solution with no precipitate was
held at a room temperature. The crystals of [Co(1-Pytz)2Cl2(H2O)] with admixture of
[Co(H2O)2Cl2] (revealed via XRPD, vide infra) formed after 24 hours were filtered off and dried
3

at room temperature in air. For elemental analysis, the crystals were ground to homogeneous
state. Anal. Calc. for CoC12H12N10Cl2O (442.13): C, 32.6; H, 2.7; N, 31.7. The best phase
mixture fit is 90.0 mol.% [Co(1-Pytz)2(H2O)Cl2] and 10.0 mol.% [Co(H2O)2Cl2],
CoC10.8H11.2N9.0O1.1Cl2 (414.51): C, 31.3; H, 2.7; N, 31.4, Found: C, 31.7; H, 3.1; N, 30.0%.
2.2.3. Synthesis of [Ni(1-Pytz)2(H2O)Cl2] (3)
A solution of 1-Pytz (0.15 g, 0.001 mol) in acetone (10 mL) was added to a solution of
NiCl2·6H2O (0.12 g, 0.0005 mol) in ethanol (10 mL) heated to 60 °C. The reaction mixture was
stirred at 60 °C and, after evaporation to ½ of the initial volume, cooled to 0–5 °C. The resulting
precipitate of [Ni(1-Pytz)2Cl2(H2O)] (0.14 g, 63.0%) was filtered off, washed with a small
amount of chilled ethanol and dried in air at a room temperature. Anal. Calc. for
NiC12H12N10Cl2O (441.89): C, 32.6; H, 2.7; N, 31.7. Found: C, 32.3; H, 2.8; N, 31.5%.
2.2.4.Synthesis of [Co(1-Pytz)2(C2N3)2]n (4)
A solution of 1-Pytz (0.29 g, 0.002 mol) in acetone (10 mL) was added to a solution of
Co(NO3)2·6H2O (0.12 g, 0.0005 mol) and NaN(CN)2 (0.27 g, 0.003 mol) in a mixture of ethanol
(15 mL) – water (5 mL). The reaction mixture was stirred at 60 °C and after evaporation to ½ of
the initial volume was held in a refrigerator. The crystals of [Co(1-Pytz)2(C2N3)2]n (0.2 g, 82.0%)
formed after 24 hours were filtered off and dried at a room temperature in air. Anal. Calc. for
CoC16H10N16 (485.29): C, 39.6; H, 2.1; N, 46.2. Found: C, 39.6; H, 2.1; N, 45.7%.
2.2.5.Synthesis of [Ni(1-Pytz)2(C2N3)2]n (5)
A solution of 1-Pytz (0.29 g, 0.002 mol) in acetone (10 mL) was added to a solution of
Ni(NO3)2·6H2O (0.12 g, 0.0005 mol) and NaN(CN)2 (0.27 g, 0.003 mol) in a mixture of ethanol
(15 mL) – water (5 mL). The reaction mixture was stirred at 60 °C, and after the evaporation to
½ of the initial volume, the formed precipitate of [Ni(1-Pytz)2(C2N3)2]n (0.16 g, 66.0%) was
filtered off and dried at a room temperature in air. Anal. Calc. for NiC16H10N16 (485.05): C, 39.6;
H, 2.1; N, 46.2. Found: C, 39.7; H, 2.1; N, 46.5%.
2.3. X-ray structure determination
Crystals of 1 and 3 suitable for single crystal X-ray diffraction analysis were obtained by
slow evaporation of the mother liquor from the corresponding syntheses; crystals of 2 and 4 were
harvested directly from the solid product. Single-crystal XRD data for compounds 1, 2, 3, 4 were
registered using a Bruker Apex DUO diffractometer equipped with a 4K CCD area detector
employing graphite-monochromated MoKα radiation (λ = 0.71073 Å) (Table S1). The φ-and ω-
4

scan techniques were used to measure intensities. Data reduction and absorption correction were
performed using APEX2 suite [34]. The crystal structure were solved using a SHELXT [35]
and refined using a SHELXL [36] programs with OLEX2 GUI [37]. Atomic displacement
parameters for nonhydrogen atoms were refined anisotropically. The positions of hydrogen
atoms were calculated corresponding to their geometrical conditions, and refined with the use of
a riding model. In structures of 2 and 3, H atoms of coordinated water were located from Fourier
difference map and were refined with restraints on O–H bonds (DFIX 0.86 0.01) and fixed Uiso
at 1.5 times of the corresponding O atoms. The H–O–H angles of 106(2) and 103(2)° for 2 and 3
respectively were reasonable, while the O–H bonds were directed to hydrogen bond acceptors N
and Cl.
Powder XRD was carried out using a Shimadzu XRD-7000 diffractometer (CuKα
radiation, Ni filter, 2θ angle range from 5° to 60°) using point NaI scintillation detector SC-1003
(for 1, 3, 5; 2θ scan step 0.030°) or linear Dectris MYTHEN2 R 1K (for 2, 4; 2θ reduction step
0.014°) detector at ambient conditions. Polycrystalline samples of 1–5 were slightly ground up
with heptane in an agate mortar, the resulting suspensions were deposited on the polished side of
a glass holder, and a smooth ∼100 μm layers formed after drying. X-ray powder diffraction
patterns of the complexes are given in ESI (Fig. S1 – S5) Simulated X-ray powder diffraction
patterns of compounds 1, 3–5 are in good agreement with the experimental X-ray powder
diffraction patterns. Diffraction patterns (measured for 4 independent samples) of 2 revealed that
along with the [Co(1-Pytz)2(H2O)Cl2] phase (the crystal structure determined in the present
work) it contains an impurity phase, which was recognized as [Co(H2O)2Cl2] [38] (CHN-based
admixture phase content is ~10 mol.%, ~4 wt.%). Similarity of the diffraction patterns of 4 and 5
indicates their isostructurality.
3. Results and discussion
3.1. Synthesis and characterization
It is well-known that a heterocyclization of primary amines with sodium azide and
triethyl orthoformate is a convenient method for obtaining a wide range of 1-substituted
tetrazoles [39]. We have used this method to obtain 1-(pyrid-2-yl)-1H-tetrazole (1-Pytz). The
reaction proceeds smoothly in glacial acetic acid under heating and at a ratio of 2-aminopyridine
: triethylorthoformate : sodium azide : acetic acid amounting to 1 : 3 : 1.2 : 8, which results in
obtaining the target 1-Pytz with a 91% yield (Scheme 1). According to the thermogravimetry
(TG) and scanning differential calorimetry (DSC) data, the 1-Pytz melts at a temperature of
about 129 ° C. Upon further heating of the sample, both thermal decomposition and partial
evaporation thereof is observed (Fig. S6). The total mass loss upon heating to 500°C amounted
to about 82%.
5

Scheme 1. Synthesis of 1-(pyrid-2-yl)-1H-tetrazole.
The synthesis of 1-Pytz complexes has been performed using different solvents at
different M : 1-Pytz ratios, depending on the nature of the complexing metal. According to XRD
data, all the compounds obtained are crystalline ones; they are stable in air for a long time. The
presence of water molecules in the complexes has been determined using elemental analysis,
XRD, and IR spectroscopy.
Scheme 2. Synthesis of M(II) complexes (M = Co, Ni, Cu) with 1-Pytz.
3.2. Crystal structures
According to single crystal X-Ray analysis, compound 1 exhibits a square planar (shape
similarity factor [40, 41] S(D4h) = 0.46) coordination environment of Cu (CuCl2N2) by two 1-
Pytz ligands and two chloride ions (Fig. 1). The coordination sphere is complemented to an
octahedral one (S(Oh) = 3.13) by shortened Cu···Cl contacts (3.02 Å) between the neighboring
molecules.
Compounds 2 and 3 are isostructural to each other. They contain two 1-Pytz ligands, two
chloride ions, and one aqua ligand (Fig. 2) which form the coordination sphere of the metal
(MCl2N3O) with S(Oh) = 1.04 and 0.91 for 2 and 3 respectively. Compound 4 has a polymeric
6

structure owing to bridging N(CN)2 ligands (Fig. 3). The coordination environment of Co (CoN6)
represented by four N(CN)2 and two 1-Pytz ligands is close to a regular octahedron (S(Oh) =
0.02). Compound 5 was not characterized by single crystal XRD analysis; powder XRD analysis
revealed that compound 5 is isostructural with compound 4.
Fig. 1. The structure of 1. Atomic displacement ellipsoids are shown at the 50% probability
level. Hydrogen atoms are shown as spheres.
Fig. 2. The structure of 2 and 3 by the example of the latter. Atomic displacement ellipsoids are
shown at the 50% probability level. Hydrogen atoms are shown as spheres.
7

Fig. 3. The structure of 4. Atomic displacement ellipsoids are shown at the 50% probability
level. Hydrogen atoms are shown as spheres.
The 1-Pytz ligand in complexes 1–4 tends to act as a monodentate and bidentate ligand that
coordinates via N4 atom (IUPAC atom numbering) of the tetrazole moiety or both N4 and N of
the pyridine moiety (for atom numbering, see Fig. S7). The monodentate ligand exhibits a
conformation with a torsion angle N–N–C–N between the tetrazole and pyridine moieties close
to 180° (Table 1). A close analogue of 1-Pytz, viz. 2-(1H-1,2,4-triazol-1-yl)pyridine (1-Pytrz)
and its derivatives, exhibit a similar coordination mode and a similar conformation in most
structurally characterized complexes (see, for example, [42–44]). In complexes 2 and 3, one of
1-Pytz ligands has such a conformation that differs from the others in the rotation of the pyridine
moiety along C–N1 bond so that the torsion N–N–C–N angle is close to zero. This conformation
promotes a chelate coordination mode of the ligand. A few complexes with 1-Pytrz, e.g. [Re(1-
Pytrz)(CO)3Br] [45] exhibit a similar chelate coordination mode of the ligand. This mode is
likely destabilized by intramolecular steric repulsion interactions between H atoms of C–H
groups (Fig. S7). Two intramolecular C–H···N contacts contribute little to the thermodynamic
stability of the monodentate conformation. Thus, there is competition between the two different
conformations of 1-Pytz and its analogues: the monodentate one and the chelate one. The
tendency to the chelate conformation of 1-Pytrz is facilitated by the presence of auxiliary donor
groups forming a five-membered metallocycle with the N atom inherent in the tetrazole or
pyridine ring, e.g. the carboxylate group [46]. In addition to the reduced steric repulsion between
8

H atoms, the monodentate coordination mode should be preferable owing to a more negative
charge at the N4 atom of the tetrazole comparing to the N2 one [47, 48].
Compounds 2 and 3 exhibit intermolecular hydrogen bonds such as O–H···N (2.78 Å)
with the pyridine nitrogen, and O–H···Cl (3.05 Å) (Fig. 4). The former bind the molecules into
pairs, whereas the latter bind them into a layer. The layers are linked to give a 3D structure via π-
π head-to-tail interactions between the tetrazole and pyridine moieties (Fig. S9) with an
intercentroid distance of 3.82 Å.
Fig. 4. The structure of a layer consisting of hydrogen bonded molecules of 2 and 3 by the
example of the latter that exhibits intermolecular hydrogen bonds shown in dashed green (O–
H···Cl) and blue (O–H···N) lines. Hydrogen atoms not participating in the hydrogen bonds are
omitted.
Structures 1 and 4 exhibit π-π stacking interactions between the tetrazole and pyridine
moieties (Fig. S9) in a head-to-head manner (the intercentroid distance amounting to 3.88 Å) for
1, and in a head-to-tail manner (the intercentroid distances amounting to 3.62 and 4.56 Å) for 4.
Table 1. Selected bond distances (Å), torsion angles (degrees) and the shortest distances M…M
(Å) in the structures 1, 2, 3, 4. For the distances, the standard uncertainty is less than 2·10–3 Å.
M–N (1-Pytz)
1 2.00
M–A (Cl, N(CN)2) M–O (H2O) N–N–C–N (1-Pytz) M…M
2.29, 3.02
–
177.5(2)
3.88
6.40
6.34
7.26
2 2.11, 2.17, 2.19 2.36, 2.40
3 2.06, 2.11, 2.12 2.35, 2.39
2.11
2.07
–
169.1(1), 7.8(2)
169.0(2), 7.0(2)
176.7(1)
4 2.16
2.11, 2.11
9

The main vibrational frequencies in the IR spectra of 1-Pytz and complexes 1–5
are presented in Table 2. The spectra of 1-Pytz and the complexes within a high-
frequency spectral range from 3120 to 3039 cm-1 exhibit stretching vibration bands
inherent in CH groups. Spectra of 2 and 3 in the range of 3494–3211 cm-1 show the bands
of stretching vibrations ν (O–H) inherent in intrasphere water molecules. Changes in the
positions of the bands are observed in the spectra of complexes 1–5 in the range of
stretching and bending vibrations of the ring (1600–1470 cm-1), which indicates the fact
that the 1-Pytz ligand coordinates to the metal through nitrogen atoms, which is in a
good agreement with the obtained X-ray diffraction data. The bands in the spectrum of
NaN(CN)2, in the range of 2100–2300 cm–1, are shifted during complexation mainly to
the high-frequency region. This suggests bidentate-bridged coordination of cyanamide
ions [49, 50], which is confirmed by X-ray diffraction data. In the low-frequency spectral
range, in the case of the synthesized complexes there are bands that are not observed in
the free ligand spectrum. The bands in the range of 270–230 cm–1 exhibited in the spectra
of all the complexes can be attributed to M–N stretching vibrations, whereas the bands
observed in the range of 310–280 cm–1 in the spectra of 1–3 can be attributed to
stretching vibrations ν(M–Cl). Data analysis table 2 shows that the IR spectra of
complexes 4 and 5 are very close in all spectral regions.
Table 2. Main vibrational frequencies in the IR spectra of 1-Pytz and complexes 1–5.
Compound
3
Attribution
1
2
4
5
NaN(CN)2
1-Pytz
3305
3211
3494
3387
3279
3146
3108
3076
3049
1626
1607
1572
1529
1487
ν(H2O)
3120
3100
3069
3039
3154
3095
3086
3062
3145
3078
3053
3130
3111
3126
3107
3079 sh
ν(CH)
1631
1604
1573
1532
1485
(H2O)
Rring
1598
1575
1527
1468
1597
1570
1489
1596
1577
1482
1597
1575
1484
νs+νas(C–N)
νas(CN)
νs(CN)
2301
2249
2177
2298
2253
2183
2287
2233
2182
479
254
232
338
483
271
247
352
ν(M–O)
ν(M–N)
248
236
301
269
250
287
266
ν(M–Cl)
295пл
10

The number and the position of the bands in diffuse reflectance spectra 1–5 correspond to
the literature data [51] and indicate that all the complexes have an octahedral structure of the
coordination polyhedron. The splitting parameters  have been estimated. The position of the
bands in the spectra, the attribution thereof, as well as the obtained  values are presented in
Table 3.
Table 3. Characteristics of diffuse reflection spectra for complexes 1–5.
·10-3, cm-1
№
Compound
Attribution

max, nm
2E2T2
4T1(F) 4T1(P)
4T14T2
1
2
[Cu(1-Pytz)2Cl2]n
[Co(1-Pytz)2(H2O)Cl2]
695
530
1313
400
650
1173
14,4
8,7
3A23T1(P)
3A23T1(F)
3A23T2
3
[Ni(1-Pytz)2(H2O)Cl2]
8,5
4T1(F) 4T1(P)
4T14T2
4
5
[Co(1-Pytz)2(C2N3)2]n
[Ni(1-Pytz)2(C2N3)2]n
485
1095
367
590
958
10,4
10,4
3A23T1(P)
3A23T1(F)
3A23T2
The μeff(T) dependence for complex 1 is shown in Fig. 5. The µeff value at 300 K is 1.78
µB and is in good agreement with the theoretical spin only one of 1.73 µB for one paramagnetic
center with spin S = 1/2 with a g factor of 2. The µeff almost does not change with lowering
temperature downto 70 K, and below 70 K decreases to to 1.29 µB at 5 K. The 1/χ(T)
dependence obeys the Curie-Weiss law with the best fit values of C and θ of 0.413 K·cm3/mol
and –2.9 K. The decreasing of µeff below 70 K and negative value of the Weiss constant indicate
domination of antiferromagnetic exchange interactions between spins of Cu(II) ions. Analysis of
the μeff(T) dependence with an uniform chain model (spin-Hamiltonian H = –2J·∑SiSi+1) [52]
gives the best fit values of g-factor and exchange coupling parameter J of 2.11±0.01 and –
1.96±0.01 cm–1 respectively.
11

1/, mol/cm3
eff, B
1.8
600
400
200
1.6
1.4
1.2
1.0
0
0
100
200
300
T, K
Fig. 5. The µeff(T) and 1/χ(T) dependences for complex [Cu(1-Pytz)2Cl2]n (1).
The μeff(T) and 1/χ(T) dependencies for complexes 4 and 5 are shown in Fig. 6. The μeff
values are 5.09 and 3.23 µB at 300 K and are in good agreement with typical values for one
Co(II) and Ni(II) ions for complexes 4 and 5, respectively. The 1/χ(T) dependencies are linear
and obey the Curie-Weiss law with the best fit parameters C and θ of 3.55 K·cm3/mol and –27.6
K for complex 4 and 1.17 K·cm3/mol and –0.52 K for complex 5. Small Weiss constant value
and constancy of the μeff value in the wide temperature range indicate absence of significant
exchange interactions between spins of Ni(II) ions in the complex 5. The large negative Weiss
constant and a decreasing of the μeff below 150 K are caused by spin-orbit coupling, that typical
for Co(II) ions in the octahedral environment. The μeff value at low temperatures is in good
agreement with a theoretical one of 3.87 µB for one paramagnetic center with spin S = 3/2.
12

1/, mol/cm3
eff, B
5
200
4
100
3
0
0
100
200
300
T, K
Fig. 6. The µeff(T) and 1/χ(T) dependencies for complexes [Co(1-Pytz)2(C2N3)2]n (4) (●
and ○) and [Ni(1-Pytz)2(C2N3)2]n (5) (■ and □).
4. Conclusions
By using interaction between 1-(pyrid-2-yl)-1H-tetrazole and Co(II), Ni(II) and Cu(II) salts,
novel coordination compounds with this ligand have been synthesized. The obtained complexes
have been studied by means of infrared diffuse reflectance spectroscopy, single-crystal and
powder X-ray diffraction, and static magnetic susceptibility. Depending on the nature of the
metal ion, on the anion, and on the synthesis conditions, the ligand can be coordinated both
monodentally to the N(4) atom of the tetrazole ring and in a bidentate-cyclic way with the
formation of the five-membered metal-containing cycle MCN3 with the participation of the N(2)
nitrogen atom belonging to the tetrazole ring, and the N atom belonging to the pyridine ring,
which results in the formation of mononuclear or polynuclear structures. The conclusions about
the structure of complex 5 were made based on a comparison of powder X-ray diffraction
patterns and IR spectroscopy data for complexes 4 and 5, which have an identical composition. It
has been shown that, antiferromagnetic exchange interactions occur between spins of copper(II)
ions in the [Cu(1-Pytz)2Cl2]n complex at a low temperature and exchange interactions between
spins of paramagnetic metal ions in the complexes 4 and 5 are weak.
Acknowledgements
The authors express gratitude to N. P. Kоrоtkevich for the registration of diffraction
patterns and I. V. Yushina for the registration of diffuse reflectance spectra.
Funding
13

The research was partially supported by the Russian Science Foundation (the research project
No. 20-63-46026).
Appendix A. Supplementary data
CCDC 2010561-2010564 contain the supplementary crystallographic data. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223- 336-033; or e-mail: deposit@ccdc.cam.ac.uk.
14

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Alina D. Ivanova: Investigation; Yury V. Grigoriev: Investigation; Vladislav Yu. Komarov:
Investigation; Taisiya S. Sukhikh: Investigation; Artem S. Bogomyakov: Investigation; Liliya A.
Sheludyakova: Investigation; Ludmila G. Lavrenova: Conceptualization, Methodology, Writing -
Original Draft.
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests:
17

Novel coordination compounds of cobalt(II), nickel(II), and copper(II) with 1-(pyrid-2-yl)-1H-
tetrazole have been synthesized. The ligand can be coordinated both monodentally and in a bidentate-
cyclic way. The studies on the µeff(T) for the polynuclear copper(II) have shown antiferromagnetic
exchange interactions between copper(II) ions to occur at a low temperature.
Novel complexes of 3d-metals with 1-(pyrid-2-yl)-1H-tetrazole have been synthesized
Ligand can be coordinated both monodentally and in a bidentate-cyclic way
Polynuclear Cu(II) have shown exchange interactions between Cu(II) ions to occur
18