Synthesis, characterization and DFT study of a new family of pyrazole derivatives

Article abstract of DOI:10.1016/j.poly.2014.06.003

This work deals about the synthesis and characterization of compounds containing the pyrazole core belonging to the family of (E)-4-((3,5-dimethyl-1- (4-R-phenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile, with possible application as ligands in inorganic chemistry. These compounds were obtained by reaction of a substituted arylhydrazine, RC₆H₄NHNH₂, R: 4-OCH₃, 4-CH₃, 4-F, 4-H, 4-Cl, 4-CF₃, 4-CN, 3-Cl, 3-NO₂, 2-Cl and perfluorophenylhydrazine, C₆F ₅-NH₂NH; with a β-diketohydrazone precursor of formula (CH₃CO)₂CNNHC₆H₄4-CN. Analytical techniques (MP and EA) and spectroscopic methods such as UV-Vis, IR, ¹H NMR, ¹³C NMR were employed to characterize the prepared systems. One of the synthesized compounds yielded in ethanol single crystals suitable for X-ray diffraction study. In order to model all the studied compounds and the molecular orbitals involved in the transitions, DFT and TDDFT calculations were performed. The non-variability of the bond distances suggests the robustness of the conjugated structure formed by the RC₆H ₄pyrazoleNNbenzonitrile rings, which is poorly affected by the change of the substituents over the phenyl ring.

Full text of DOI:10.1016/j.poly.2014.06.003

Accepted Manuscript
Synthesis, Characterization and DFT Study of a New Family of Pyrazole De-
rivatives
Rodrigo Faundez, Desmond Macleod-Carey, Ximena Zarate, Carlos Bustos,
Elies Molins, Eduardo Schott
PII:
S0277-5387(14)00402-1
DOI:
http://dx.doi.org/10.1016/j.poly.2014.06.003
POLY 10800
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
17 April 2014
3 June 2014
Please cite this article as: R. Faundez, D. Macleod-Carey, X. Zarate, C. Bustos, E. Molins, E. Schott, Synthesis,
Characterization and DFT Study of a New Family of Pyrazole Derivatives, Polyhedron (2014), doi: http://dx.doi.org/
10.1016/j.poly.2014.06.003
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Synthesis, Characterization and DFT Study of a New
Family of Pyrazole Derivatives
Rodrigo Faundeza,b, Desmond Macleod-Careyc, Ximena Zarateb, Carlos Bustosd, Elies Molinse and
Eduardo Schottb*
aDepartamento de Ciencias Quimicas, Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Macul, Chile.
bLaboratorio de Bionanotecnologia, Universidad Bernardo O'Higgins, General Gana 1702, Santiago, Chile.
cUniversidad Autónoma de Chile, Inorganic Chemistry and Molecular Materials Group, Carlos Antúnez 1920, Santiago,
Chile
dInstituto de Ciencias Quimicas, Universidad Austral de Chile, Avda. Los Robles sin numero, Valdivia, Chile.
eInstitut de Ciencia de Materials de Barcelona (CSIC), Campus de la UAB, 08193 Cerdanyola, Barcelona, Spain
*email:maschotte@gmail.com, Phone:+56-2-24772243
Abstract
This work deals about the synthesis and characterization of compounds containing the pyrazole core
belonging to the family of (E)-4-((3,5-dimethyl-1-(4-R-phenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile,
with possible application as ligands in inorganic chemistry. These compounds were obtained by reaction
of a substituted arilhydrazine, R-C6H4-NHNH2, R: 4-OCH3, 4-CH3, 4-F, 4-H, 4-Cl, 4-CF3, 4-CN, 3-Cl, 3-
NO2, 2-Cl and perfluorophenylhydrazine, C6F5-NH2NH; with a β-diketohydrazone precursor of formula
(CH3CO)2C=N-NH-C6H4-4-CN. Analytical techniques (MP and EA) and spectroscopic methods as UV-
Vis, IR, 1H-NMR, 13C-NMR were employed to characterize the prepared systems. One of the synthesized
compounds yielded in ethanol single crystals suitable for X-Ray diffraction study. In order to model all
the studied compounds and the Molecular Orbitals involved in the transitions, DFT and TDDFT
calculations were performed. The non-variability of the bond distances suggests the robustness of the
conjugated structure formed by the R-C6H4-pyrazole-N=N-benzonitrile rings, which is poorly affected by
the change of the substituents over the phenyl ring.

Introduction
Azole heterocycles are interesting because of their occurrence in the nature and as framework of synthetic
molecules. Most of those molecules show biological activity and wide application in all areas of
coordination chemistry. In the field of coordination chemistry, pyrazoles have attracted considerable
interest because their conjugate bases, pyrazolates, have been found to bind metals in a variety of modes
and, in particular, are very strong bridging ligands.[1–3] For example, pyrazolato complexes have been
used as starting material for chemical vapour deposition, furthermore they have interesting luminescent
properties.[4–7] Most pyrazoles have biological (anti-neoplasic, anti-microbial, anti-inflammatory, anti-
diabetic, in between others) and can also be used as ligands or as precursors of pyrazolate-based ligands
and are accessible by well-established synthetic methods.[2-4,8] These methods are quite general, which
allow the preparation of pyrazoles with a variety of substitution patterns and with different substituents in
several positions of the pyrazole ring.[9–12] Moreover, pyrazole and pyrazolate rings can be included as
part of polydentate ligands.[13–15] In this sense, polypyrazolylborates are the most useful and widely
employed ligands in different areas of coordination chemistry.[16]
The conjugate acids (or protonated forms) of the pyrazoles, namely, the pyrazolium cations, are present in
many salts. The behavior of pyrazolium cations as supramolecular guests toward certain hosts has been
studied and it has been shown that pyrazolium cations play crucial roles in some cases.[17–19]
Complexes that contain one or more pyrazolato ligands can be prepared by reacting the preformed
alkaline pyrazolate salts with suitable metal complexes (e.g., halide complexes, so that the pyrazolate
anion replaces the halide), or by treating the preformed pyrazole complexes with a base.[20] However, the
employment of preformed pyrazolate salts or pyrazole complexes is not required for the synthesis of
metal pyrazolato complexes in many cases, whereas they can be directly formed from the suitable metal
precursor, the pyrazole and a base.[21]

Furthermore, pyrazoles are able to fully accept or donate H+. In this sense the basic site of the pyrazole
molecule can act as a hydrogen-bond acceptor, whereas the N–H group can act as a hydrogen-bond donor.
The ability of this N–H group to act as a hydrogen-bond donor is the main reason why pyrazoles are
important molecules in supramolecular chemistry. The particular type of aggregation that occurs in the
solid-state structure of N–H pyrazoles has been found to be largely dependent on the substitution pattern
of the pyrazole ring.[22,23]
In a previous communication, preliminary results have been reported about the synthesis of a large library
of pyrazoles.[24–27] In the herein review, an extensive report on the synthesis, characterization and
theoretical
studies
of
a
series
of
(E)-4-((3,5-dimethyl-1-(4-R-phenyl)-1H-pyrazol-4-
yl)diazenyl)benzonitrile, see Figure 1, was made (with R= 4-OCH3 (1), 4- CH3 (2), 4-H (3), 4-F (4), 4-Cl
(5), 4-CF3 (6), 4-CN (7), 3-Cl (8), 3-N02 (9), 2-Cl (10)) and perfluorophenylhydrazine (11)). Suitable
crystals of 11 for X-Ray diffraction studies were obtained, in order to corroborate the proposed structure.
Furthermore, DFT and TDDFT calculations were performed to determine the composition of the frontier
molecular orbitals (FMO), to model the UV-Vis transition and to assign their character.
Figure 1. General structure of the studied pyrazoles and the corresponding numeration used for the NMR
assignation. The pyrazole ring is shown in blue and R- are: 4-OCH3 (1). 4-CH3 (2), 4-H (3), 4-F (4), 4-Cl
(5), 4-CF3 (6), 4-CN (7), 3-Cl (8), 3-N02 (9), 2-Cl (10), and -C6F5 (11).

Experimental
Chemicals
Aniline, 4-aminobenzonitrile, acetylacetone, sodium nitrite, acetic acid, hydrochloric acid, sodium
hydroxide and substituted hydrazine R-C6H4-NHNH2 (R= 4-OCH3 (1). 4- CH3 (2), 4-H (3), 4-F (4), 4-Cl
(5), 4-CF3 (6), 4-CN (7), 3-Cl (8), 3-NO2 (9), 2-Cl (10)) and perfluorophenylhydrazine (11) were
purchased from Sigma-Aldrich. Besides, solvents: methanol, ethanol, diethyl ether, acetone CDCl3 and
DMSO-d6, were purchased from usual commercial sources, like the Merck, Fisher and J.T. Baker
providers. All the precursors and solvents were used without further purification. - diketohydrazone
precursor, 4-(2-(2,4-dioxopentane-3-yliden)hydrazine)benzonitrile, was obtained as described in
literature[27–29] and its structure was checked by IR spectroscopy.
Physical measurements
Uncorrected melting points, MP, were determined on digital STUARD, SMP10 apparatus. Elemental
analysis, EA, was obtained from a FISONS, EA 1118 microanalyses using sulfanilamide as standard. UV-
Vis spectra were recorded between 600 and 235 nm, in quartz cells with 1 cm length pass, using a Perking
Elmer, Lambda 35 spectrophotometer. Concentrated solutions of each compound (5.0x10-4 mol/L) were
used and a dilution to 2.5x10-5 mol/L. The infra-red spectra, IR, were obtained in solid state on an ATR
Jasco, PR0450-S, mounted on a Jasco, FT/IR-4200 equipment. Depending of the solubility of
compounds, 1H-NMR, 13C-NMR and HMBC spectra were recorded by the standard methods in CDCl3 or
DMSO-d6, using 5 mm i.d. glass tubes and the internal solvent signals as reference, in a Buker, Avance
1
13
AM 400 spectrophotometer. Assignment of H- and C-NMR signals are reported using the numeration
of Figure 1.
Data collection

Highly redundant single crystal X-Ray diffraction data set of 11 was collected at room temperature on a
Bruker AXS SMART APEX CCD diffractometer using monochromatic MoKa radiation, λ=0.71069 Å
and a 0,3° separation between frames. Crystal data, data collection and structure refinement parameters
are shown in Table 1, while Table 2 contains the selected bond lengths and Figure 2 exhibits an ORTEP
view of the molecule. Data integration was performed using SAINT program contained in the
diffractometer software package. The structure was solved by using direct methods and Fourier's
difference maps and refined by least squares on F2 with anisotropic displacement parameters for non-H
atoms. All hydrogen atoms are in calculated positions and were refined riding on their parent atoms. All
performed calculations to solve the structure, to refine the model proposed and to obtain the results were
carried out with the computer programs WinGX[30,31].
Table 1. Crystal data and data collection and refinement parameters of the X-ray crystal structure of
compound 11.
Empirical formula
Weight formula
Temperature
C18H10F5N5
391.31
294(2) K
Wavelength
0.71073 Å
Crystal system
Spatial group
Cell parameters
Orthorhombic
Fdd2
a= 19.335(7) Å, α= 90°
b= 47.422(10) Å, β= 90°
c = 7.545(3) Å, γ = 90°
Cell volume
6918(4) Å3
16
Z
Calculated density
Absorption coefficient
1.503 g/cc3
0.132 mm-1

F(000)
3168
Crystal size
0.30 x 0.21 x 0.18 mm3
Θ range for data collection
1.72 a 25.99°
0≤ h ≤23, 0≤ k ≤58, -9≤ l
Indices range
≤9
7235
Reflections collected
Independent reflections
3263 [R(int) = 0.0451]
99.9 %
Full value of θ=25.99°
Minimum and maximum
transmission
0.9767 y 0.9616
Full-matrix least-squares
on F2
Refinement method
Data/ restraints/ parameters
S (Goodness-of-fit on F2)
3263/7/264
0.838
R1 = 0.0485, wR2 =
0.0765
Final R index with [I > 2σ(I)]
R1 = 0.1748, wR2 =
R index all data
0.0998
0.183 y -0.134 ē×Å-3
Major difference peak/ hole
Table 2. Calculated selected bond distances for the complete family of studied compounds and the
experimental (exp.) report for compound 11. All the data is in Å.
1
2
3
4
5
6
7
8
9
10
11
11exp
1.265 1.265 1.265 1.264 1.264 1.264 1.263 1.264 1.263 1.264 1.263 1.188
1.377 1.377 1.377 1.377 1.377 1.378 1.378 1.377 1.378 1.378 1.379 1.372
1.375 1.376 1.376 1.377 1.377 1.378 1.379 1.377 1.379 1.377 1.379 1.446
1.414 1.415 1.415 1.423 1.415 1.415 1.415 1.415 1.415 1.415 1.416 1.567
1.429 1.429 1.429 1.429 1.429 1.429 1.429 1.429 1.429 1.429 1.429 1.420
1.156 1.156 1.156 1.156 1.156 1.156 1.156 1.156 1.156 1.156 1.156 1.141
1.360 1.509 1.084 1.349 1.756 1.503 1.156 1.758 1.482 1.752 1.333 1.343
1.424 1.424 1.424 1.415 1.421 1.420 1.417 1.421 1.418 1.423 1.411 1.408
1.317 1.317 1.316 1.317 1.316 1.316 1.315 1.316 1.316 1.317 1.316 1.320
N=Nazo
N-Npyr
C4-Npyr
Npyr-C11
C9-C10
C10≡N
C-R
Nazo-C6
Npyr=C2
General Procedure

In a 100 mL round-bottomed flask were added: 2,6x10-3 mol of the β-diketohydrazone 4-(2-(2,4-dioxo
pentane-3-yliden)hydrazine)benzonitrile, 0.60g; 30 mL of ethanol, 5 mL of glacial acetic acid, and
substituted hydrazine, R-C6H4-NHNH2 (R= 4-OCH3 1, 2,9x10-3 mol, 0,53 g; 4-CH3 2, 3x10-3 mol, 0.50 g;
4-H 3, 3.2x10-2 mol, 3.51 g; 4-F 4, 3.1x10-3 mol, 0.50 g; 4-Cl 5, 3.0x10-3, 0.53 g; 4-CF3 6, 2.7x10-3 mol,
0.48 g; 4-CN 7, 3.1x10-3 mol, 0.52 g; 3-Cl 8, 3.0x10-3 mol, 0.53 g; 3-NO2 9, 2.9x10-3 mol, 0.54 g; 2-Cl
10, 3.0x10-3 mol, 0.53 g. and perfluorophenylhydrazine 11, 2.6x10-3 mol, 0.51 g. The reaction mixture
was heated at reflux temperature stirring magnetically during 18 h. For precipitation of each compound
the mixture was cooled to -18ºC by 2 h and by addition of around 25 mL of water. The yellow-orange
solids were filtered by suction, washed with abundant water and dried under vacuum at 40ºC by 24 h. All
compounds were recrystallized from ethanol/H2O mixtures of variable composition or pure ethanol,
except compound 3 which was recrystallized from 1:1 THF/EtOH.
Analysis
Compound (1) (E)-4-((1-(4-methoxyphenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
65% Recryst. From EtOH. MP: 154ºC. EA: for C19H17N5O (Mι: 331,37 g/mol): Calc(%): C, 68.87; H,
5.17; N, 21.13; Found(%):C, 69.21; H, 5.28; N, 21.54. UV-Vis in THF 2.50 x 10-3 mole/L, λmax, nm(logε):
λ1: 459sh λ2: 358(4.51) λ3: 243(4.35). IR, ν(cm-1): ν(C-H, Ar): 3045w, 3032w; ν(C-H, Alif.): 2990w,
2977w, 2931w; ν(C≡N): 2222s; ν(C=N), ν(N=N) or ν(C=C): 1610w, 1591w, 1548m, 1520s, 1467m; ν(N-
1
N): 1390s; ν(R): 2835w. H-NMR (400 MHz, DMSO-d6) δ(ppm): 7.99 (d, J = 8.6 Hz, 2H), 7.89 (d, J =
13
8.6 Hz, 2H), 7.57 – 7.44 (m, 2H), 7.19 – 6.98 (m, 2H), 3.83 (s, 3H), 2.59 (s, 3H), 2.47 (s, 3H). C-NMR
(DMSO-d6) δ(ppm): 159.03, 155.21, 142.34, 141.20, 135.75, 133.64, 131.36, 126.20, 122.24, 118.69,
114.40, 111.45, 55.50, 14.01, 10.89.
Compound (2) (E)-4-((3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield: 60% Recryst.
From EtOH/H2O 9:1. MP: 200-201ºC. EA: for C19H17N5 (Mι:315,37 g/mol): Calc(%): C, 72.36; H, 5.53;
N, 22,21; Found(%):C, 73.16; H, 5.72; N, 22.27 UV-Vis in THF 2.50 x 10-3 mole/L, λmax, nm(logε): λ1:
456sh λ2: 357(4.59) λ3: 236(4.41). IR, ν(cm-1): ν (C-H, Ar.): 3050w, 3035w; ν(C-H, Alif.): 2987w,

1
2925w; ν(C≡N): 2221s; ν(C=N ), ν(N=N) or ν(C=C): 1598w, 1548m, 1521s; ν(N-N): 1393s. HNMR
(400 MHz, DMSO-d6), δ (ppm): 8.03 – 7.95 (m, 2H), 7.90 (d, J = 8.6 Hz, 2H), 7.49 (d, J = 8.3 Hz, 2H),
13
7.38 (d, J = 8.2 Hz, 2H), 2.63 (s, 3H), 2.49 (s, 3H), 2.40 (s, 3H). C-NMR (DMSO-d6) δ(ppm): 155.14,
142.44, 140.77, 137.78, 135.87, 135.79, 133.37, 129.51, 124.33, 122.04, 118.39, 111.36, 20.41, 13.63,
10.73
Compound (3) (E)-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield: 98% Recryst.
From EtOH/THF. MP: 176-177 ºC. EA: for C18H15N5 (Mι: 301,35 g/mol): Calc(%): C, 71.79; H, 5.02; N,
23.24; Found(%):C, 72.03; H, 5.13; N, 24.36. UV-Vis in THF 2.92 x 10-3 mole/L, λmax, nm(logε): 450sh;
355 (4.71); 284sh. IR, ν(cm-1): ν(C-H, Ar): 3087w, 3058w; ν(C-H, Alif.): 2990w, 2930w; ν(C≡N): 2221s;
1
ν(C=N ), ν(N=N) or ν(C=C): 1596w, 1551s, 1512s; ν(N-N): 1393s. H-NMR (400 MHz, DMSO-d6)
δ(ppm): 8.00 (d, J = 8.6 Hz, 2H), 7.90 (d, J = 8.6 Hz, 2H), 7.61 (ddd, J = 15.3, 8.3, 4.8 Hz, 4H), 7.50 (dt,
J = 9.2, 4.2 Hz, 1H), 2.65 (s, 3H), 2.48 (s, 3H). 13C-NMR (DMSO-d6) δ(ppm): 155.16, 142.58, 141.47,
138.40, 136.01, 133.65, 129.35, 128.35, 124.60, 122.29, 118.67, 111.57, 14.08, 10.99.
Compound (4) (E)-4-((1-(4-fluorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
86% Recryst. From EtOH. MP: 181-182ºC. EA: for C18H14FN5 (Mι: 319.34 g/mol): Calc(%): C, 67.70; H,
4.42; N, 21.93; Found(%):C, 68.00; H, 4.64; N, 22.14. UV-Vis in EtOH 2.50 x 10-3 mole/L, λmax
,
nm(logε): 456sh; 354 (4.72); 269sh. IR, ν(cm-1): ν(C-H, ar): 3087w, 3067w, 3052w; ν(C-H, alif.): 2992w,
1
2971w, 2930w; ν(C≡N): 2221s; ν(C=N ), ν(N=N) or ν(C=C): 1595s, 1552s, 1507s; ν(NN): 1396s. H-
NMR (400 MHz, DMSO-d6) δ (ppm): 8.00 (d, J = 8.6 Hz, 2H), 7.90 (d, J = 8.6 Hz, 2H), 7.68 (m, J =
10.4, 5.2, 2.8 Hz, 2H), 7.47 – 7.37 (m, 2H), 2.63 (s, 3H), 2.48 (s, 3H). 13C-NMR (DMSO-d6) δ(ppm):
162.69, 160.25, 155.14, 142.60, 141.66, 136.28, 135.92, 134.84, 133.67, 127.02, 126.93, 122.30, 118.67,
116.34, 116.11, 111.61, 14.05, 10.86.
Compound (5) (E)-4-((1-(4-chorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
70% Recryst. From Toluene. MP: 215-216ºC. EA: for C18H14ClN5 (Mι: 335.79 g/mol): Calc(%): C, 64.38;
H, 4.20; N, 20.86; Found(%):C, 65.10; H, 4.35; N, 21.71. UV-Vis in Toluene 2.29 x 10-3 mole/L, λmax
nm(logε): 445sh; 355 (4.46); 257sh. IR, ν(cm-1): ν(C-H, ar): 3049w; ν(C-H,alif.): 2986w, 2968w, 2927w;
,

1
ν(C≡N): 2221s; ν(C=N ), ν(N=N) or ν(C=C): 1595w, 1552s, 1507s; ν(N-N): 1393s. HNMR (400 MHz,
DMSO-d6) δ(ppm): 7.99 (d, J = 8.5 Hz, 2H), 7.91 (d, J = 8.5 Hz, 2H), 7.71 – 7.57 (m, 4H), 2.67 (s, 3H),
2.50 (s, 3H). 13C-NMR (DMSO-d6) δ(ppm): 155.06, 142.82, 141.24, 137.14, 133.40, 132.60, 129.13,
126.10, 124.17, 122.10, 118.36, 111.53, 13.67, 10.72.
Compound (6) (E)-4-(3,5-dimethyl-1-(4-(trifluoromethyl)phenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile.
Yield: 60% Recryst. From EtOH. MP: 144-145ºC. EA: for C19H14F3N5 (Mι: 369.34g/mol): Calc(%): C,
61.79; H, 3.82; N, 18.96; Found(%):C, 62.86; H, 3.87; N, 20.41. UV-Vis in EtOH 2.41 x 10-3 mole/L,
λmax, nm(logε): 446sh; 354 (4.89); 263sh. IR, ν(cm-1): ν(C-H, Ar): 3085w, 3056w; ν(C-H, Alif.): 2998w,
1
2933w; ν(C≡N): 2228s; ν(C=N ), ν(N=N) or ν(C=C): 1672w, 1616s, 1556m, 1525m; ν(N-N): 1396s. H-
NMR (400 MHz, DMSO-d6) δ(ppm): 8.05-7.85 (m, 8H), 2.74 (s, 3H), 2.51 (s, 3H). 13C-NMR (DMSO-d6)
δ (ppm): 154.98, 143.17, 142.99, 141.69, 141.50, 136.26, 133.40, 128.56 128.25, 127.93, 127.61, 126.36,
126.32, 126.28, 126.25, 124.66, 122.14, 118.33, 111.66, 13.75, 10.85.
Compound (7) (E)-4-((1-(4-isocyanophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
91% Recryst. From EtOH. MP: 208-209ºC. EA: for C19H14N6 (Mι: 323.35 g/mol): Calc(%): C, 69.25; H,
4.32; N, 25.75; Found(%):C, 69.75; H, 4.20; N, 25.88. UV-Vis in EtOH 2.73 x 10-3 mole/L, λmax
,
nm(logε): 449sh; 353 (4.59); 261sh. IR, ν(cm-1): ν(C-H, Ar): 3120w, 3065w; ν(C-H, Alif.): 2985w,
1
2936w; ν(C≡N): 2224s; ν(C=N ), ν(N=N) or ν(C=C): 1602m, 1583w, 1552m, 1514s; ν(N-N): 1385s. H-
NMR (400 MHz, DMSO-d6) δ(ppm): 8.03 (d, J = 7.9 Hz, 2H), 7.98 (d, J = 7.8 Hz, 2H), 8-10-7.80 (m,
13
4H), 2.74 (s, 3H), 2.50 (s, 3H). C-NMR (DMSO-d6) δ(ppm): 154.91, 143.36, 141.83, 141.77, 136.38,
133.37, 133.35, 124.47, 122.14, 118.30, 117.94, 111.70, 110.32, 13.79, 10.92.
Compound (8) (E)-4-((1-(3-Chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
75% Recryst. From EtOH. MP: 172ºC. EA: for C18H14ClN5 (Mι: 335.79 g/mol): Calc(%): C, 64.38; H,
4.20; N, 20.86; Found(%):C, 65.03; H, 4.19; N, 21.05. UV-Vis in EtOH 2.50 x 10-3 mole/L, λmax
,
nm(logε): 452sh; 353 (4.77); 257sh. IR, ν(cm-1): ν(C-H, Ar): 3088w, 3066w; ν(C-H, Alif.): 2994w,
2932w, 2923w; ν(C≡N): 2220s; ν(C=N ), ν(N=N) or ν(C=C): 1593s, 1585s, 1551s, 1504s; ν(N-N): 1391s.
1H-NMR (400 MHz, DMSO-d6) δ(ppm): 8.01 (d, J = 8.6 Hz, 2H), 7.92 (d, J = 8.6 Hz, 2H), 7.76 (d, J =

1.6 Hz, 1H), 7.67 – 7.55 (m, 3H), 2.70 (s, 3H), 2.49 (s, 3H). 13C-NMR (DMSO-d6) δ(ppm): 155.09,
142.87, 142.08, 139.64, 136.14, 133.69, 133.61, 131.01, 128.24, 124.33, 123.18, 122.35, 118.65, 111.72,
14.14, 10.93.
Compound (9) (E)-4-(3,5-dimethyl-1-(3-nitrophenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield: 90%
Recryst. From EtOH/THF. MP: 188ºC. EA: for C18H14N5O2 (Mι: 346.34g/mol): Calc(%): C, 62.42; H,
4.07; N, 24.27; Found(%):C, 62.86; H, 4,06; N, 24.49. UV-Vis in EtOH/THF 2.51 x 10-3 mole/L, λmax
,
nm(logε): 454sh; 351 (4.65); 255sh. IR, ν(cm-1): ν(C-H, Ar): 3092w; ν(C-H, Alif.): 2990w, 2967w,
1
2923w; ν(C≡N): 2226s; ν(C=N ), ν(N=N) or ν(C=C): 1617w, 1599w, 1557m, 1536s; ν(N-N): 1398s. H-
NMR (400 MHz, DMSO-d6) δ(ppm): 8.61–7.32 (m, 8H), 2.75 (s, 3H), 2.52 (s, 3H). 13C-NMR (DMSO-d6)
δ(ppm): 154.94, 148.14, 143.27, 141.90, 139.12, 136.20, 133.39, 130.69, 130.06, 122.43, 122.14, 118.79,
118.32, 111.69, 13.74, 10.77.
Compound (10) (E)-4-((1-(2-Chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
70% Recryst. From EtOH. MP: 154ºC. EA: for C18H14ClN5 (Mι: 335.79 g/mol): Calc(%): C, 64.38; H,
4.20; N, 20.86; Found(%):C, 64.77; H, 4.21; N, 21.20. UV-Vis in EtOH 2.50 x 10-3 mole/L, λmax
,
nm(logε): 435sh; 348(4.38); 240(4.03). IR, ν(cm-1): ν(C-H, Ar.): 3093w, 3065w, 3046w; ν(C-H, Alif.):
2981w, 2964w, 2922w; ν(C≡N): 2226s; ν(C=N ), ν(N=N) or ν(C=C): 1589w, 1579w, 1550s, 1505s; ν(N-
1
N): 1395s. H-NMR (400 MHz, DMSO-d6) δ (ppm): 7.99 (d, J = 7.6 Hz, 2H), 7.91 (d, J = 7.7 Hz, 2H),
7.75 (d, J = 7.7 Hz, 1H), 7.61 (dt, J = 14.8, 7.0 Hz, 3H), 2.50 (s, 3H), 2.43 (s, 3H). 13C-NMR (DMSO-d6)
δ (ppm): 155.08, 143.15, 141.74, 135.50, 135.13, 133.38, 131.40, 130.76, 130.08, 129.71, 128.23, 122.08,
118.36, 111.53, 13.45, 10.03.
Compound (11) (E)-4-(3,5-dimethyl-1-(perfluorophenyl)-1H-pyrazol-4-yl)diazenyl)benzonitrile. Yield:
85% Recryst. From EtOH. MP: 183ºC. EA: for C18H10F5N5 (Mι: 391.09: Calc(%): C, 55.25; H, 2.58; N,
17.90; Found(%): C, 55.74; H, 2.35; N, 18.52. UV-Vis in EtOH 2.50 x 10-3 mole/L, λmax, nm(logε): 435sh;
340 (4.43); 239 (4.17). IR, ν(cm-1): ν(C-H, Ar.): not found; ν(C-H, Alif.): 2931w; ν(C≡N): 2227s; ν(C=N
1
), ν(N=N) or ν(C=C): 1602w, 1563w, 1536s, 1513s; ν(N-N): 1401s. H-NMR (400 MHz, DMSO-d6) δ

(ppm): 8.01 (d, J = 7.6 Hz, 2H), 7.93 (d, J = 7.8 Hz, 2H), 2.55 (s, 3H), 2.50 (s, 3H). 13C-NMR (DMSO-d6)
δ (ppm): 154.85, 143.62, 136.28, 135.41, 133.44, 122.26, 112.02, 13.41, 9.46.
Computational Methods
The Gaussian 03 computational package[32] was used to perform ground-state geometry optimization
calculations employing Becke’s three-parameter hybrid exchange functional and the Lee−Yang−Parr non-
local correlation functional B3LYP[33–35] and 6-31G* basis set was used for C, N, O, and H atoms and
the LANL2DZ basis set[36,37] with an effective core potential for I.[38] Time-dependent density
functional theory calculations were also performed using this methodology, and the first 60 singlet excited
states were calculated. Calculations by the first-principles method were used to obtain accurate excitation
energies and oscillator strengths. We modelled the solvent with the polarizable continuum model using
Ethanol as the solvent.[39]
Results and Discussion
Structure and Geometrical Parameters
Figure 2 presents the crystal structure of 11, while Table 1 provides a survey of crystallographic and
refinement data; Table 2 shows some selected bond distances. The structure has been well refined with
final indices, [I>2σ(l)], of R1=0.0485 and wR2=0.0765, Table 1. The relevant characteristics, Figure 2, are
(i) the presence of the β-diketohydrazone bonded to a pyrazole core, confirming the route followed by the
reaction, see proposed mechanism in the SI, and (ii) the planarity of the β-diketohydrazone bonded to the
pyrazole core, see torsion angles in the SI.

Figure 2. ORTEP representation of a molecule of compound 11 from its X-ray crystal structure showing
the atom numbering and the displacement ellipsoids at 50% probability level (H atoms are drawn as
circles of arbitrary radii).
By the DFT optimization of all the synthesized compounds we could make the comparison of the
geometrical parameters as the substituents are changed over the phenyl ring bonded to the pyrazole core.
The change of the substituents from an electron-donor substituent to another having an electron-acceptor
character does not influence the calculated geometrical parameters of 1-11. Also, as it is observed in Table
2, the calculated geometrical parameters are in good agreement with those obtained from the
crystallographic study. This non-variability of the bond distances gives us a hint about the robustness of
the conjugated structure formed by the phenyl-pyrazole-N=N-benzonitrile rings, which is poorly affected
by the change of the -R substituents over the phenyl ring.
NMR spectroscopy
NMR assignments are made according to the numeration in Figure 1. A summary of the signals found in
1
the H-NMR spectra for 1-11 are shown in the supplementary information, see Table S1. According to
Figure 1, the most important features of the 1H-NMR spectra are the presence of: i) variable multiplicity
resonances in the range 8.61-6.98 ppm, which correspond to the aromatic protons; ii) a singlet in the

range 2.75-2.50 ppm, which correspond to C5-H protons of the methyl group CH3-C=C; iii) a singlet
located in the range 2.52-2.47 ppm, which corresponds to the protons 1C-H of the methyl group CH3-
C=N and iv) 1 and 2 show the typical signals attributed to the methyl groups of the -R substituents
(CH3O- 1 and CH3- 2) located at 2.40 and 3.83 ppm, respectively.
The relative integration found for the signals H-Ar, 1C-H, 5C-H and H-R are 8:3:3:3 in 1 and 2; 5:3:3 in 3,
8:3:3 in 4-10 and 4:3:3 in 11; which are consistent with the structure for each substituted pyrazole.
13
The signals found in the C-NMR spectra are summarized in the supplementary information, see Table
S2. Compounds 1-11 show the typical resonances C1, C2, C3, C4 and C5, located at positions almost
invariable, that are commonly found in the pyrazole ring. The signals associated to C1, C2, C3, C4 and C5
are located in the ranges 11.26-9.46, 144.68-142.44, 137.14-131.73, 143.62-140.77 and 14.37-13.41 ppm,
respectively. All the synthesized pyrazole show a signal in the range 112.02-111.36 ppm which is assigned
to the C10 carbon of the nitrile group, C≡N. Besides, the non-fluorinated compounds show all the signals
associated to the phenyl ring and to the corresponding substituent. However, compounds 4, 6 and 11,
13
which are fluorinated, show split signals due to the C-F coupling. Detailed C-NMR spectra of 4 and 6
are shown in the supplementary information. In compound 4 the C-F magnetic couplings of the carbons
C14, C12 and C13 are doublets located at 161.47 (d, J=245.7 Hz), 126.97 (d, J=8.9 Hz), 116.23 (d, J=23.1
Hz) ppm, respectively; C11 is a slightly deformed singlet located at 134.84 ppm. On the other hand,
compound 6 shows no signal for C15, C13 and C14 which should appear as quartets, while C11 and C12 are
formally singlet, located at 134.01 and 118.74 ppm, respectively, see Figure S1. Finally, it was not
possible to find the signals of the quaternary aromatic carbons in the perfluorophenyl group in 11. This is
due to the presence of couplings with more than one bond, which generates signals with high multiplicity
that could not be distinguished from the background noise of the spectrum.
Optical Properties

Absorption bands found in the UV-vis spectra of 1-11 are collated in Table 3. The main characteristic of
the spectra is determined by the general structure of the molecules. Each molecule has a double bond -
N=N- (azo group) which is directly conjugated with one benzene rings and with the pyrazole ring. This
fragment has an extensive electronic delocalization, therefore it is possible to predict the presence of a
main absorption band associated to a π-delocalized system, that involves the fragment -N=N-, and other
mainly associated internal transitions that emerge from the benzene rings and/or pyrazole system.
Table 3. Experimental (λexp) and calculated (λTh) wavelengths, logarithm of the extinction coefficient
(logε), energy in eV (E), oscillator strength multiplied by 100 (fx100), active MOs and their percentage
contributions for compounds 1-11 in THF.
% Orbtial Contribution
Comp.
1
E
logε
fx100
λexp
459sh.
359
λTh
476
346
252
2.603
3.579
4.928
0.09
HOMO-1
→
→
→
→
LUMO
LUMO
94
94
32
46
4.51
4.35
65.36 HOMO-2
243
5.11
HOMO-6
HOMO
LUMO
LUMO+1
2.601
3.184
3.677
456sh.
357
236
477
389
337
0.07
107.76
30.66 HOMO-2
HOMO-1
HOMO
→
→
→
LUMO
LUMO+1
LUMO+1
100
100
100
2
3
4.59
4.41
2.600
3.248
4.492
450sh.
355
284sh.
477
382
276
0.10
117.24
4.37
HOMO-1
HOMO
HOMO-6
HOMO
→
→
→
→
LUMO
LUMO
LUMO
100
100
46
4.71
4.72
4.46
4.89
LUMO+1
50
2.601
3.238
4.843
456sh.
354
269sh.
477
383
256
0.08
112.88
1.33
HOMO-1
HOMO
HOMO
HOMO
→
→
→
→
LUMO
LUMO
LUMO+1
LUMO+2
100
100
26
4
52
2.597
3.237
4.843
445sh.
355
257
477
383
256
0.04
121.81
4.03
HOMO-1
HOMO
HOMO-6
HOMO
→
→
→
→
LUMO
LUMO
LUMO
100
100
63
5
6
LUMO+3
22
2.592
3.294
4.494
446sh.
354
263sh.
478
376
276
0.01
133.85
6.48
HOMO-1
HOMO
HOMO-5
→
→
→
LUMO
LUMO
LUMO
100
100
26

HOMO-4
HOMO
→
→
LUMO
LUMO+1
22
52
2.586
3.268
4.689
449sh.
353
261sh.
480
379
264
0.04
146.14
32.98 HOMO-2
HOMO-1
HOMO
→
→
→
LUMO
LUMO
LUMO+1
100
100
97
7
8
4.59
4.77
4.65
2.595
3.281
4.784
452sh.
353
257sh.
478
378
259
HOMO-1
HOMO
HOMO
→
→
→
LUMO
LUMO
LUMO+1
100
100
81
125.58
16.03
2.593
3.315
4.751
454sh.
351
255sh.
478
374
261
0.01
128.77
17.80 HOMO-5
HOMO-1
HOMO
→
→
→
LUMO+2
LUMO+2
LUMO+2
94
100
26
9
2.611
3.410
5.155
435sh.
348
240
475
364
241
0.01
127.89
10.98
HOMO-1
HOMO
HOMO
→
→
→
LUMO
LUMO
LUMO+3
100
100
67
10
11
4.38
4.03
2.609
3.444
5.185
435sh.
340
239
475
360
239
0.01
131.48
12.99 HOMO-2
HOMO-1
HOMO
→
→
→
LUMO
LUMO
LUMO+1
100
100
97
4.43
4.17
In this sense and in accordance with the structure of the compounds, we can determine that the first
absorption band, λ1, located in the range of 435-459 nm, of low intensity that appears as shoulder is
attributed to a transition π*←n, that involves the azo bridge. While the second absorption band, λ2,
located in the range 340-357 nm, shows the highest extinction coefficient (logε=4.38-4.89) and is
attributed to a transition π*←π. This transition involves the pyrazole and the benzonitrile rings. The
remaining absorption band located at higher energy corresponds to λ3 and is assigned of the type π*←π.
Again, a similar behaviour of the previous transitions is observed.
All the former assignations were corroborated using TD-DFT calculation. An example of the involved
MOs for compound 11 is presented in Figure 3. The image including all the studied compounds can be
found in the supplementary information, Figure S2. In Table 3 are shown the experimental and calculated
absorption maximum and the corresponding orbital contribution. As observed, λ1 and λ2 involve mainly

FMO, while λ3 in some cases lower occupied and higher unoccupied MOs. The description of the FMO
will be discussed in the DFT section.
Figure 3. Diagram of the FMOs of compound 11.
The main stretching absorptions found in the IR spectra of 1-11 are summarized as follows. In general,
the spectra show a stretching ν(C-H) of aromatic protons, about 3000 cm-1 except 11 where no stretching
of these protons were observed, which is due to the presence of the fluorinated substituent. This behaviour
was corroborated with the DFT calculations. In all compounds, immediately under 3000 cm-1 a weak
stretching ν(C-H) is observed. This stretching correspond to the aliphatic 3,5-dimethylpyrazole system. In
case of compounds 1 and 2, this signal includes stretching of the methyl groups present in the aromatic
ring. Furthermore, it is possible to identify in the region 2228-2220 cm-1 in all compounds an intense band
which corresponds to the stretching ν(C≡N) [40,41]. Additionally, there is a set of variable intensity bands

in the region 1672-1501 cm-1 attributed to the stretching ν(C=N), ν(N=N) and ν(C=C) [10,41–44]. It is
also important to mention the signals attributed to the -R substituent of the benzene rings of compounds 1
ν(C-H), 6 ν(C-F) and 11 ν(C-F), located at 2835, 1183, 1116 and 1402 cm-1 respectively. Finally, all
compounds show a stretching located between 1390 and 1401 cm-1 which is attributed to the N-N bond of
the pyrazole ring.
DFT Calculations
The FMO are involved in almost every calculated transitions, vide supra. The FMO of all compounds
show similar characteristics as observed in the supplementary information, see Figure S2. In all cases, the
HOMO is delocalized over the pyrazole ring, the azo group and the benzonitrile ring. The HOMO-1 is
composed in every case mainly by the azo bridge. In terms of the unoccupied MOs the LUMO is mainly
centred over the benzonitrile ring. On the other hand, the LUMO+1 is located almost in every case over
the substituted phenyl ring.
The HOMO, LUMO and GAP energies do not follow any trend. However all the calculated values are
very similar and do not depend on the character of the substituent located over the phenyl substituent.
In order to make the first approach of the reactivity that this compounds might show, the estimated
reactivity indexes (electronic chemical potential (µ), chemical hardness (η), and electrophilicity
(ω))[45,46] are reported in Table 4.
Table 4. HOMO and LUMO orbital energies, HOMO-LUMO GAP and Reactivity indexes, electronic
chemical potential (µ), chemical hardness (η) and electrophilicity (ω), all in eV.
Comp.
HOMO LUMO GAP
µ
η
ω
-6.11
-6.29
-6.36
-2.70
-2.71
-2.73
3.41
3.57
3.63
-4.40
-4.50
-4.54
1.71 5.68
1.79 5.66
1.81 5.68
1
2
3

-6.36
-6.39
-6.48
-6.51
-6.44
-6.51
-6.48
-6.60
-2.74
-2.77
-2.80
-2.86
-2.77
-2.91
-2.72
-2.80
3.62
3.63
3.68
3.65
3.66
3.60
3.77
3.80
-4.55
-4.58
-4.64
-4.69
-4.60
-4.71
-4.60
-4.70
1.81 5.72
1.81 5.78
1.84 5.85
1.82 6.02
1.83 5.79
1.80 6.16
1.88 5.61
1.90 5.81
4
5
6
7
8
9
10
11
η is a measure of the resistance of a chemical species to change its electronic configuration[45]. It is
thought as an indicator, together with electronegativity, of the chemical reactivity and stability of systems.
The highest value for η is shown by 11, which has the perfluorinated substituent and is the most electron-
attracting substituent. On the other hand the smallest value is shown by 1 which has the most electron-
donor substituent. µ characterizes the tendency of escaping of electrons from the equilibrium
system[45,46]; it is then related to the electronic charge rearrangement associated to any chemical
process. This index shows an opposite behaviour to that of η, where the highest value is shown by 1,
which has the most electron donor substituent, and the smallest value is shown by 9 and 11 which have
the most electron-acceptor substituents. Electrophilicity index, ω, could give information comparing two
molecules in which one is an electrophile (or nucleophile) and this is indicated by a higher (or lower)
ω[46]. In this case the highest value of ω was found for compound 9, which has the most electron-
attracting substituent. Comparing compounds with the substituent in position 4-, the highest value was
found for compound 7, which has the most electron-attracting substituent. On the other hand the smallest
value of co was found for compound 10. In case of comparing position 4-, the smallest value for ω was
found for compound 1, which has the most electron-donor substituent.
Conclusion
The high yield synthesis of a new family of pyrazoles of the type (E)-4-((3,5-dimethyl-1-(4-R-phenyl)-
1H-pyrazol-4-yl)diazenyl)benzonitrile is reported. This procedure was performed by reaction of a b-

diketohydrazone 4-(2-(2,4-dioxopentane-3-yliden)hydrazine)benzonitrile with an arylhydrazine
substituted, R-C6H4-NHNH2, R=4-OCH3 1; 4-CH3 2; 4-F, 3; 4-H, 4; 4-Cl, 5; 4-CF3, 6; 4-CN, 7; 3-Cl, 8; 3-
NO2, 9; 2-Cl, 10; and pentafluorophenylhydrazine, NH2NH-C6F5, 11. This reaction has shown that the
condensation of the b-diketohydrazone with arylhydrazine, occurs via a ketodihydrazone intermediary,
which maintained under reflux for 36 h, undergoes an addition reaction with H2O displacement to give the
corresponding pyrazoles. Compounds 1-11 were purified by recrystallization and characterized by
analytical and spectroscopic techniques (UV-Vis, IR and NMR). The crystal and molecular structure of
the compound 11 was determined by single crystal X-ray diffraction. This structure shows a certain
degree of positional disorder for the nitrogen atoms in the fragment –CN=NC-, which may be related with
a vibrational coupled mode of this group. In any case, the fragment has nearly planar geometry (torsion
angle τ(N3Aa- N4Aa- C41 - C42) = 169.6(6)º and τ(N4Aa - N3Aa- C4 - C3) = 0.4(11)º), which can be
related with the extensive electronic delocalization, probably including adjacent rings to the pyrazole ring.
All compounds were modelled by DFT calculations, showing similar geometrical parameters, which is
adduced to the robustness of the conjugated system. Furthermore, TDDFT calculations were performed
showing similar composition of the absorption bands in all the studied compounds.
Acknowledgment
ESV thanks FONDECYT 1130707. CBF thanks FONDECYT 1080269. EMG thanks
EULANETCERMAT (PIRSES-GA-2011-295197).
1
Supplementary Information: The C-F coupling, full MO diagram, UV-Vis spectra, H-NMR, 13C-NMR
and a summary of the crystallographic results can be found in the supplementary information. CCDC
983729 for 11 contains the full supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.

References
[1] G. La Monica, G.A. Ardizzoia, in:, Prog. Inorg. Chem. Vol. 46, 1997, pp. 151–238.
[2] F. Meyer, Eur. J. Inorg. Chem. 2006 (2006) 3789.
[3] M. a Halcrow, Dalton Trans. (2009) 2059.
[4] A. a Mohamed, A. Burini, J.P. Fackler, J. Am. Chem. Soc. 127 (2005) 5012.
[5] M. a Omary, M. a Rawashdeh-Omary, M.W.A. Gonser, O. Elbjeirami, T. Grimes, T.R. Cundari,
H.V.K. Diyabalanage, C.S.P. Gamage, H.V.R. Dias, Inorg. Chem. 44 (2005) 8200.
[6] H.V.R. Dias, H.V.K. Diyabalanage, M.G. Eldabaja, O. Elbjeirami, M. a Rawashdeh-Omary, M. a
Omary, J. Am. Chem. Soc. 127 (2005) 7489.
[7] B. Hu, G. Gahungu, J. Zhang, J. Phys. Chem. A 111 (2007) 4965.
[8] R. Goikhman, T.L. Jacques, D. Sames, J. Am. Chem. Soc. 131 (2009) 3042.
[9] D. a. Mac-Leod-Carey, C. Bustos, E. Schott, L. Alvarez-Thon, M. Fuentealba, Acta Crystallogr. Sect.
E Struct. Reports Online 63 (2007) m670.
[10] B. Yang, Y. Lu, C.-J. Chen, J.-P. Cui, M.-S. Cai, Dye. Pigment. 83 (2009) 144.
[11] R.D. Miller, O. Reiser, J. Heterocycl. Chem. 30 (1993) 755.
[12] K. Makino, H.S. Kim, Y. Kurasawa, J. Heterocycl. Chem. 35 (1998) 489.
[13] R. Mukherjee, Coord. Chem. Rev. 203 (2000) 151.
[14] A. Otero, J. Fernández-Baeza, A. Lara-Sánchez, J. Tejeda, L.F. Sánchez-Barba, Eur. J. Inorg. Chem.
2008 (2008) 5309.
[15] J. Klingele, S. Dechert, F. Meyer, Coord. Chem. Rev. 253 (2009) 2698.
[16] S. Trofimenko, Polyhedron 23 (2004) 197.
[17] S. Kiviniemi, A. Sillanp, M. Nissinen, K. Rissanen, M.T. Lämsä, J. Pursiainen, Chem. Commun.
(1999) 897.
[18] S. Kiviniemi, M. Nissinen, M.T. Lämsä, J. Jalonen, K. Rissanen, J. Pursiainen, New J. Chem. 2000
(2000) 47.
[19] S. Kiviniemi, M. Nissinen, T. Alaviuhkola, K. Rissanen, J. Pursiainen, J. Chem. Soc. Perkin Trans. 2
6 (2001) 2364.
[20] G.A. Ardizzoia, G. LaMonica, A. Maspero, M. Moret, N. Masciocchi, Eur. J. Inorg. Chem. 1998
(1998) 1503.
[21] L.R. Falvello, J. Fornie, A. Martín, V. Sicilia, P. Villarroya, Organometallics 21 (2002) 4604.
[22] K. Umakoshi, Y. Yamauchi, K. Nakamiya, T. Kojima, M. Yamasaki, H. Kawano, M. Onishi, Inorg.
Chem. 42 (2003) 3907.
[23] J. Pérez, L. Riera, Eur. J. Inorg. Chem. 2009 (2009) 4913.

[24] C. Bustos, C. Sanchez, R. Martinez, R. Ugarte, E. Schott, D. Macleodcarey, M. Garland, L.
Espinoza, Dye. Pigment. 74 (2007) 615.
[25] C. Bustos, E. Schott, D. a. Mac-Leod-Carey, A. Ibañez, L. Alvarez-Thon, Acta Crystallogr. Sect. E
Struct. Reports Online 62 (2006) o2499.
[26] C. Bustos, E. Schott, M. Ríos, C. Sánchez, J.-G. Cárcamo, J. Chil. Chem. Soc. 54 (2009) 267.
[27] C. Bustos, M. Pérez-Cerda, L. Alvarez-Thon, E. Barrales-Salcedo, M.T. Garland, Acta Crystallogr.
Sect. E Struct. Reports Online E68 (2012) o353.
[28] V. Bertolasi, P. Gilli, V. Ferretti, K. Vaughan, New J. Chem. 23 (1999) 1261.
[29] H.C. Yao, J. Am. Chem. Soc. 29 (1964) 2959.
[30] G.M. Sheldrick, Acta Crystallogr. Sect. A Found. Crystallogr. 46 (1990) 467.
[31] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[32] M.A.R. M.J. Frisch, G.W. Trucks, H.B. Schlegel, P.M.W. Gill, B.G. Johnson, M.A. J.R. Cheeseman,
T.A. Keith, G.A. Petersson, J.A. Montgomery, K. Raghavachari, B.B.S. Al-Laham, V.G.
Zakrzewski, J.V. Ortiz, J.B. Foresman, J. Cioslowski, J.L. A. Nanayakkara, M. Challacombe, C.Y.
Peng, P.Y. Ayala, W. Chen, M.W. Wong, D.J.D. Andres, E.S. Replogle, R. Gomperts, R.L. Martin,
D.J. Fox, J.S. Binkley, J.A.P. J. Baker, J.P. Stewart, M. Head-Gordon, C. Gonzalez, (n.d.).
[33] A.D. Becke, Phys. Rev. A 38 (1988) 3098.
[34] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[35] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[36] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270.
[37] W.R. Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284.
[38] V.A. Rassolov, M.A. Ratner, J.A. Pople, P.C. Redfern, L.A. Curtiss, J. Comput. Chem. 22 (2001)
976.
[39] M. Cossi, G. Scalmani, N. Rega, V. Barone, J. Chem. Phys. 117 (2002) 43.
[40] M. Onishi, M. Yamaguchi, S. Kumagae, H. Kawano, Y. Arikawa, Inorganica Chim. Acta 359 (2006)
990.
[41] T.E. Ali, Heteroat. Chem. 24 (2013) 426.
[42] M.J. Ahsan, H. Khalilullah, S. Yasmin, S.S. Jadav, J. Govindasamy, Biomed Res. Int. 2013 (2013).
[43] B. Chandrakantha, A.M. Isloor, K. Sridharan, R. Philip, P. Shetty, M. Padaki, Arab. J. Chem. 6
(2013) 97.
[44] M. Asniza, A.M. Issam, H.P.S.A. Khalil, Sains Malaysiana 40 (2011) 765.
[45] R.G. Pearson, J. Mol. Struct. THEOCHEM 255 (1992) 261.
[46] P.K. Chattaraj, S. Giri, Annu. Rep. Prog. Chem.{,} Sect. C Phys. Chem. 105 (2009) 13.

Synthesis and characterization of compounds containing the
pyrazole nuclei