Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 6, pp. 940−944.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © Yu.G. Vlasov, S.S. Levichev, A.A. Kruchinin, 2012, pblished in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 6, pp. 960−964.
AND INDUSTRIAL ORGANIC CHEMISTRY
Interaction of a Bispyrazole-Based Ligand
with Metal Cations in Ethanol
Yu. G. Vlasov, S. S. Levichev, and A. A. Kruchinin
St. Petersburg State University, St. Petersburg, Russia
Received April 13, 2012
Abstract—A new ligand based on two pyrazole cycles linked with each other was synthesized. Its interaction with
Cu(II), Ni(II), Co(II), Mn(II), Cr(III), Zn(II), and Cd(II) cations in ethanol was studied by the spectrophotometric
Bispyrazole ligands can be considered as building
blocks for obtaining sorbents and creating optical chemi-
cal sensors, and their metal complexes can ﬁ nd applica-
tion for solid-phase hydrogen storage and as catalysts.
Coordination compounds of bispyrazole-based ligands
with copper, zinc, cadmium, and cobalt are thermally
stable up to 300°C that open a prospect of their applica-
tion under such conditions where only inorganic materials
 were used earlier.
The bispyrazole ligand of a general type represents
two pyrazole cycles, connected by a bridge. It is possible
to adjust complex-forming properties of the ligand by
synthesizing compounds with various length and structure
of the bridge and also by attaching the bridge to various
points of a pyrazole cycle. Within the limits of this con-
cept it is possible to obtain both a strictly selective ligand
in relation to zinc or copper  and a universal sorbent
with ﬂ exible framework .
The bridge of the ligand synthesized in this work
contains a benzene ring without substituents, which
can be modiﬁ ed by various functional groups after the
comprehensive completion of the synthesis. It enables us
to adjust properties of a whole ligand without carrying out
anew all stages of the synthesis. In the published works
the main attention is paid to the application of bispyrazole
ligands as sorbents [3, 4] or of their metal complexes
for hydrogen solid-phase storage [5, 6] and as catalysts
. The interaction of the ligand with cations is studied
in a solid state by means of the X-ray crystal analysis
[1–6], trying to make the complex as stable as possible.
In this work the bispyrazole ligand is considered as a
receptor for a sensory material. A stable complex with
a cation is not required for such an application, whereas
the study of a complex formation in a solution is of
The aim of this work was to study reactions of the
synthesized new ligand with metal cations in ethanol
solutions by the spectrophotometric method.
The ligand 1,2-bis[(3,5-dimethylyrazole-1-yl)-
methyl]-benzene (В1) was synthesized in a strongly
alkaline medium according to the scheme.
The procedure described in  served as the basis for
the synthesis. It was adapted for this work by the replace-
ment of a solvent and also by the optimization of tem-
perature and time of the intermediate stages fulﬁ llment.
All reagents were purchased in Sigma-Aldrich Company.
The procedure for the ligand B1 synthesis with a yield
of 68%, which we have developed, is given below: to
22 g (0.4 mol) of powdery KOH suspended in 100 ml of
1-methyl-2-pyrrolidone, 19.2 g (0.2 mol) of 3,5-dimethyl-
1H-pyrazole (P) were added. The resulting suspension
was intensively stirred with heating up to 70–80°C within
1 h. Then the reaction mixture was cooled up to 20–30°C