2
K.A. Vinogradova et al. / Polyhedron 57 (2013) 1–13
between a lone pair donor and an electron-deficient
p
-ring are
compressed air (Vfin ꢂ 1 ml). The precipitate was filtered off,
washed with EtOH and dried in the ambient air. Yield: 80 mg
(88%). Anal. Calc. for C24H23Br2CuN5: C, 47.7; H, 3.8; N, 11.6; Cu,
10.5. Found: C, 47.2; H, 4.1; N, 11.5; Cu, 10.3%.
regarded as a new supramolecular bond [35–44]. Another point
concerns with the luminescent properties of these compounds.
Indeed, the [CuL2]BF4ꢀH2O complex was found to demonstrate
orange photoluminescence [32]. As a continuation of our research
in this field we endeavored to synthesize a series of copper halide
complexes with L taking into account the possibility of supramolec-
2.3. Synthesis of [CuL2Br2] (2)
ular self-assemblies formation due to lp–
potential manifestation of luminescence.
p interactions and the
A solution of CuBr2 (0.075 mmol, 16.6 mg) in EtOH (2 ml) was
added dropwise, with stirring, to a solution of L (0.15 mmol,
57 mg) in EtOH (4 ml). The color of the mixture became dark green
and, when the volume of the reaction mixture became ca. 5 ml, yel-
low-green precipitate appeared. The excess of EtOH was removed
by the stream of the compressed air (Vfin ꢂ 1 ml). The precipitate
was filtered off, washed with EtOH and dried in the ambient air.
Yield: 61 mg (82%). Anal. Calc. for C48H46Br2CuN10: C, 58.5; H,
4.7; N, 14.2; Cu, 6.5. Found: C, 58.1; H, 4.6; N, 13.8; Cu, 6.5%. Single
crystals of [CuL2Br2] suitable for X-ray single crystal analysis were
obtained by slow crystallization from mixture EtOH/CHCl3 (1:1).
It should be mentioned in this context that copper(I) complexes
and clusters are regarded as promising candidates for the develop-
ment of organic light-emitting diodes (OLED) and sensors and rep-
resent one of important classes of luminescent metal compounds
based on a relatively abundant, inexpensive and non-toxic element
showing interesting photophysic properties [45–49]. A number of
pyrazolatopyridine- and pyrazolylpyridine-based luminescent
copper(I) complexes has been reported [50–62]. As for pyrazolyl-
pyrimidine-based luminescent copper(I) complexes, to the best
of our knowledge there is only one example of such compounds,
[CuL2]BF4ꢀH2O [32], while luminescent copper(I) halide complexes
with pyrazolylpyrimidines have not been studied in this field.
In this paper we report the synthesis of a series of copper(II),
mixed-valence copper(I,II) and copper(I) halide complexes with
pyrazolylpyrimidine ligand L, namely, [CuLBr]2[Cu2Br6] (1), [CuL2
Br2] (2), [Cu2L2Cl3]ꢀMeCN (3), [Cu2L2Cl3]ꢀCHCl3 (4), [Cu2L2Br3]ꢀEtOH
(5), [Cu2L2Br3]ꢀCHCl3 (6), [CuLCl] (7), [CuLBr] (8) and [Cu2L2I2] (9).
Copper(I) complexes were found to display bright yellow
photoluminescence.
2.4. Synthesis of [Cu2L2Cl3]ꢀMeCN (3)
A solution of CuCl (0.054 mmol, 5.4 mg) in MeCN (1 ml) was
added dropwise, with stirring, to
a solution of [CuL2Cl2]
(0.036 mmol, 32.6 mg) in the mixture of MeCN (2 ml) and CHCl3
(2 ml). The color of the solution turned from dark green to bright
emerald green. In several days some turbidity was observed and
the solution was filtered. Large well-shaped green single crystals
formed in a week. The crystals were filtered off, washed with
MeCN and dried in ambient air. Yield: 21.3 mg (56%). According
to the X-ray data, the composition of the crystals was indentified
as [Cu2L2Cl3]ꢀMeCN.
2. Experimental
2.1. General
2.5. Synthesis of [Cu2L2Cl3]ꢀCHCl3 (4)
4-(3,5-Diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine
(L), [CuL2Cl]2[Cu2Cl4] and [CuL2Cl2] were prepared according to the
reported procedure [33]. All other reagents and solvents were com-
mercially available and were used without additional purification.
The syntheses of 3, 4, 7 and 8 were performed under an inert atmo-
sphere of argon. IR absorption spectra were recorded on a Scimitar
FTS 2000 spectrometer (375–4000 cmꢁ1) and on a VERTEX-80
spectrometer (100–600 cmꢁ1). Elemental analysis (C, H, N) was
performed with a EuroEA3000 analyzer using standard technique.
Copper content was determined by complexometric titration, the
simples were mineralized in a mixture of concentrated H2SO4
and HClO4. X-ray powder diffraction data were obtained with a
A powder of CuCl (0.038 mmol, 3.7 mg) was added to a stirred
solution of [CuL2Cl2] (0.038 mmol, 33.8 mg) in the mixture of
MeCN (2 ml) and CHCl3 (3 ml). When CuCl dissolved, the color of
the mixture became dark green. In a week some turbidity was ob-
served and the solution was filtered. Additional amount of CuCl
(2.0 mg) was added to the resulting transparent solution. Large
well-shaped green single crystals formed in a week. The crystals
were filtered off, washed with MeCN and dried in ambient air.
Yield: 11.2 mg (30%). Anal. Calc. for C49H47Cl6Cu2N10: C, 52.7; H,
4.2; N, 12.6. Found: C, 53.0; H, 4.4; N, 12.8%. According to the X-
ray data, the composition of the crystals was indentified as
[Cu2L2Cl3]ꢀCHCl3.
DRON-3M automated diffractometer (R = 192 mm, Cu K
a radia-
tion, Ni-filter, scintillation point detector with amplitude discrim-
ination) at room temperature. X-ray powder diffraction patterns
are given in Supporting Information (Figs. 1S–5S). Luminescence
spectra of the solid samples were recorded on a fluorescence spec-
trophotometer Cary Eclipse (Varian). The emission spectra of the
complexes were recorded at room temperature under the follow-
ing experimental conditions: kexc = 350 and 450 nm, V = 500 V,
whereas the spectrum of the ligand was recorded at kexc = 320 nm,
V = 500 V. In addition, the emission spectra of [Cu2L2I2] were
2.6. Synthesis of [Cu2L2Br3]ꢀEtOH (5)
A hot solution of L (0.15 mmol, 57 mg) in EtOH (4 ml) was
added to a hot stirred solution of CuBr2 (0.15 mmol, 34 mg) in
EtOH (2 ml). The color of the solution became dark brown. In ca.
10 min green brown precipitate appeared. The reaction mixture
was stirred for 1 h. The excess of solvent was removed by evapora-
tion, the precipitate became dark green. The precipitate was fil-
tered off, washed with EtOH and dried in dessicator over KOH.
The precipitate looked visually somewhat inhomogeneous. Yield:
63 mg. Anal. Calc. for C50H52Br3Cu2N10O: Cu, 10.8. Found: Cu,
10.7%.
recorded on a fluorescence spectrophotometer DFS-24; kexc
313 nm, T = 300 and 77 K.
=
2.2. Synthesis of [CuL2Br]2[Cu2Br6] (1)
Dark brown well-shaped single crystals suitable for X-ray anal-
ysis were obtained by slow crystallization from the mother solu-
tion. Their composition was indentified as [Cu2L2Br3]ꢀEtOH.
Recrystallization of the powder from CHCl3 in 4 days gave dark
brown crystals. According to the X-ray single crystal data the com-
position of this crystals was indentified as [Cu2L2Br3]ꢀCHCl3.
A solution of L (0.15 mmol, 57 mg) in EtOH (6 ml) was added
dropwise, with stirring, to a solution of CuBr2 (0.15 mmol, 34 mg)
in EtOH (2 ml). The color of resulting solution became brown and
brown precipitate appeared. The reaction mixture was stirred for
30 min, the excess of EtOH was removed by the stream of the