Copper(II) and copper(I) tetrafluoroborate complexes with 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L): Synthesis, structures and luminescence

Article abstract of DOI:10.1016/j.ica.2012.02.004

Copper(II) and copper(I) complexes, [Cu^IIL₂(BF ₄)₂]·0.5H₂O, [Cu^IL ₂](BF₄)·2MeCN and [Cu^IL ₂](BF₄)·H₂O, with 4-(3,5-diphenyl-1H- pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) have been synthesized. The compound [Cu^IIL₂(BF₄)₂]·0. 5H₂O was obtained in the M:L = 1:1 and 1:2 molar ratios in EtOH solutions. It represents an example of a complex containing coordinated BF ₄^- anion. The Cu-F(BF₃) distances, 1.964(2) and 2.000(2) , are the shortest for copper tetrafluoroborate complexes. The compounds [Cu^IL₂](BF₄)·2MeCN and [Cu^IL₂](BF₄)·H₂O were obtained in the M:L = 1:1 and 1:2 molar ratios in MeCN solutions. According to X-ray data, the molecules of L in the structures of [Cu^IIL ₂(BF₄)₂]·0.5H₂O and [Cu ^IL₂](BF₄)·2MeCN are coordinated to the copper atoms through N²(pyrazole) and N³(pyrimidine) atoms. The complex [Cu^IL₂](BF₄)·2MeCN is unstable in the ambient air and transforms into [Cu^IL ₂(BF₄)]·H₂O. The complex [Cu ^IL₂](BF₄)·H₂O was found to display orange photoluminescence.

Full text of DOI:10.1016/j.ica.2012.02.004

Inorganica Chimica Acta 386 (2012) 116–121
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Copper(II) and copper(I) tetrafluoroborate complexes with
4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L):
Synthesis, structures and luminescence
Katerina A. Vinogradova a, Viktor P. Krivopalov b, Elena B. Nikolaenkova b, Natalia V. Pervukhina a,
Dmitrii Yu. Naumov a, Lilia A. Sheludyakova a,c, Mark B. Bushuev a,c,
⇑
a Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, 3, Akad. Lavrentiev Ave., Novosibirsk 630090, Russia
b N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, 9, Akad. Lavrentiev Ave., Novosibirsk 630090, Russia
c Novosibirsk State University (National Research University), Department of Natural Sciences, 2, Pirogova Str., Novosibirsk 630090, Russia
a r t i c l e i n f o
a b s t r a c t
Copper(II) and copper(I) complexes, [CuIIL2(BF4)2]Á0.5H2O, [CuIL2](BF4)Á2MeCN and [CuIL2](BF4)ÁH2O, with
4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) have been synthesized. The com-
pound [CuIIL2(BF4)2]Á0.5H2O was obtained in the M:L = 1:1 and 1:2 molar ratios in EtOH solutions. It rep-
Article history:
Received 1 December 2011
Received in revised form 31 January 2012
Accepted 2 February 2012
Available online 11 February 2012
À
resents an example of a complex containing coordinated BF4 anion. The Cu–F(BF3) distances, 1.964(2)
and 2.000(2) Å, are the shortest for copper tetrafluoroborate complexes. The compounds
[CuIL2](BF4)Á2MeCN and [CuIL2](BF4)ÁH2O were obtained in the M:L = 1:1 and 1:2 molar ratios in MeCN
solutions. According to X-ray data, the molecules of L in the structures of [CuIIL2(BF4)2]Á0.5H2O and
[CuIL2](BF4)Á2MeCN are coordinated to the copper atoms through N2(pyrazole) and N3(pyrimidine)
atoms. The complex [CuIL2](BF4)Á2MeCN is unstable in the ambient air and transforms into
[CuIL2(BF4)]ÁH2O. The complex [CuIL2](BF4)ÁH2O was found to display orange photoluminescence.
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Copper(II)
Copper(I)
Pyrazolylpyrimidines
N-ligands
Weakly coordinated anions
Luminescence
1. Introduction
abundant and non-toxic element showing interesting photophysic
properties [37–42]. The examples of copper(I) complexes with pyr-
Acting as ligands, hybrid heteroaromatic compounds containing
pyrazolylpyrimidine core can adopt various coordination modes
forming mono-, di- or oligonuclear complexes with transition met-
als [1–32]. 4-(Pyrazolyl)pyrimidines, although they have been stud-
ied somewhat less than 2-(pyrazolyl)pyrimidines, also can be
regarded as one of the platforms for the design of complexes mani-
festing various functional properties. Ruthenium(II) complexes with
4-pyrazolylpyrimidines have been reported as materials with redox
properties[25]. Copper(II)complexeswiththese ligandsrevealmag-
netic activity [21]. Some of these complexes have been recognized as
appealing objects for the design of supramolecular self-assemblies
[18–20,32]. Another field of potential application of these com-
pounds concerns with their luminescent properties [28–31].
azolyl- and pyrazolatopyridine ligands have also been reported
[43–53]. Since copper(II) quenches luminescence, the examples
of copper(I,II) and copper(II) luminescent complexes are rather
scarce [48,54,55]. To date, luminescent copper complexes with 4-
pyrazolylpyrimidines have not been reported.
In this context, as a logical continuation of our research in the
field of coordination chemistry of metal complexes with pyrazolyl-
pyrimidines (for our latest results see [56]) we were endeavored to
synthesize luminescent copper complexes with 4-pyrazolylpyrim-
idines. Earlier we synthesized 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-
(piperidin-1-yl)pyrimidine (L) and studied its coordination behavior
toward copper(II), zinc(II) and cadmium(II) chlorides [56,57]. Free
L as well as zinc(II) and cadmium(II) complexes with this ligand
demonstrate bright blue luminescence [56]. Continuing our re-
search in this field, we made an attempt to pass from zinc(II) and
cadmium(II) luminescent complexes with L to other potentially
luminescent systems, namely, copper(I) and copper(II) complexes
with L. In the present paper we report the synthesis and crystal
structures of copper(II) and copper(I) tetrafluoroborate complexes
with L. The complex [CuIIL2(BF4)2]Á0.5H2O represents an example of
Luminescent compounds are the base for the development of
organic light-emitting diodes (OLED) and sensors [33–36].
Copper(I) complexes and clusters are currently one of important
classes of luminescent metal compounds based on a relatively
⇑
Corresponding author at: Nikolaev Institute of Inorganic Chemistry, Siberian
Branch of Russian Academy of Sciences, 3, Akad. Lavrentiev Ave., Novosibirsk
630090, Russia.
À
a complex containing coordinated BF4 anion, the Cu–F(BF3)
distances are the shortest for copper tetrafluoroborate complexes.
E-mail addresses: bushuev@niic.nsc.ru, mark.bushuev@gmail.com (M.B. Bushuev).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.02.004

K.A. Vinogradova et al. / Inorganica Chimica Acta 386 (2012) 116–121
117
The complex [CuIL2](BF4)ÁH2O manifests orange luminescence and
represents the first example of luminescent copper complexes with
4-pyrazolylpyrimidines.
solution was added to a solution of L (0.10 mmol, 38.1 mg) in
MeCN (4 ml). The reaction mixture was concentrated to 2 ml and
the orange precipitate appeared. It was filtered off, washed with
MeCN and dried in the ambient air. Yield: 94 mg (72%). Anal. Calc.
for C48H48BCuF4N10O: C, 61.9; H, 5.2; N, 15.0. Found: C, 61.8; H,
5.5; N, 15.0%.
2. Experimental
2.1. General
2.5. X-ray crystallographic study
4-(3,5-Diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine
(L) has been prepared according to the reported procedure [57]. All
other reagents and solvents were commercially available and were
used without additional purification. All syntheses of copper(I)
coordination compounds were performed in deoxygenated solvents
under an inert atmosphere of argon. IR absorption spectra were
recorded on a Scimitar FTS 2000 spectrometer at 400–3800 cmÀ1
and on a VERTEX-80 spectrometer at 100–600 cmÀ1. Elemental
analysis (C, H, N) was performed with a EuroEA3000 analyzer using
standard technique. The excitation and emission spectra of 3 were
recorded on a fluorescence spectrophotometer Cary Eclipse (Varian)
at room temperature (V = 800 V, kexc = 320 nm).
Single crystal data for 1 and 2 were collected at 150 K with Mo
Ka radiation (k = 0.71073 Å) using a Bruker Nonius X8Apex CCD
diffractometer equipped with graphite monochromator. The SMART
software was used for data collection and also for indexing the
reflections and determining the unit cell parameters; the collected
data were integrated using SAINT software [58]. The structures were
solved by direct methods and refined by full-matrix least-squares
calculations using SHELXTL software [59]. All the non-H atoms were
refined in the anisotropic approximation. The crystallographic
parameters of the studied compounds are given in Table 1.
3. Results and discussion
2.2. Synthesis of [CuIIL2(BF4)2]Á0.5H2O (1)
3.1. Synthetic aspects
2.2.1. Method 1
A solution of L (0.021 mmol, 8.1 mg) in EtOH (0.5 ml) was added
to a solution of Cu(BF4)2Á6H2O (0.021 mmol, 7.3 mg) in EtOH
(1.5 ml). The resulting green solution was allowed to stay for a
month. This resulted in the formation of light green crystals. They
were filtered off, washed with EtOH and dried in the ambient air.
The composition of the crystals, [CuIIL2(BF4)2]Á0.5H2O, has been
determined by X-ray diffraction.
The copper(II) complex 1 has been prepared by a reaction of
CuII(BF4)2Á6H2O and L in EtOH. To study the effect of the metal-
to-ligand molar ratio on the stoichiometry of the products, the
1:1 and 1:2 metal-to-ligand molar ratios have been applied for
the synthesis (Scheme 1). As the result, irrespective of the M:L
molar ratio in both cases we have isolated the product with 1:2
metal-to-ligand stoichiometry. IR-spectra and X-ray powder dif-
fraction patterns of the products which have been obtained in
the 1:1 and 1:2 metal-to-ligand molar ratios are identical. Note-
2.2.2. Method 2
À
Cu(BF4)2Á6H2O (0.010 mmol, 3.5 mg) and
L (0.020 mmol,
worthy, despite of the fact that BF4 anion is usually regarded as
7.6 mg) were dissolved in EtOH (3 ml). Resulting light green solu-
tion was stirred with heating. When the volume of the solution be-
came ca. 1 ml, the mixture was cooled down to the room
temperature. Light green transparent crystals appeared in a day.
They were filtered off, washed with EtOH and dried in the ambient
air. Yield: 6.0 mg (54%). Anal. Calc. for C48H47B2CuF8N10O0.5: C,
57.1; H, 4.7; N, 13.9. Found: C, 56.7; H, 4.8; N, 13.7%.
noncoordinating or weakly coordinating one [60–62], we were ablÀe
to obtain copper(II) complex compound with coordinated BF4
(structural details and comments see below).
The copper(I) complexes, 2 and 3, have been synthesized in
MeCN solutions under an inert atmosphere of argon to prevent oxi-
dation of Cu(I). These complexes have been prepared in the follow-
ing way. At the first stage, we reduced CuII(BF4)2(solv) by Cu0 in
MeCN solution producing CuIBF4(solv). At the second stage, a reac-
tion of CuIBF4(solv) and L in MeCN has been performed. Instead,
the reaction of CuII(BF4)2 with L in the presence of copper powder
as a reductant can be regarded as an alternative that also affords
the same copper(I) complexes. Surprisingly, the reaction per-
formed using the CuI:L = 1:1 molar ratio produced single crystals
of 2 having 1:2 stoichiometry. To prepare this complex as a powder
product we performed the reaction between CuIBF4(solv) and L in
the CuI:L = 1:2 molar ratio and obtained complex 3. In several days
single crystals of 2 become non-transparent and crack due to loss
of MeCN molecules and inclusion of H2O molecules, yielding yel-
low powder of 3. Elemental analysis and IR spectroscopic data
for 3 and decomposition product of single crystals of 2 are identical
that induces to think that the molecular structures of 2 and 3 are
similar.
Although the complexes 1–3 have the same metal-to-ligand
stoichiometry, tetrafluoroborate anion in the structures of cop-
per(I) complexes, 2 and 3, does not coordinate to copper in contrast
to the structure of copper(II) compound, 1. Such Àa difference can
result from (i) the inability of relatively small BF4 anion to cause
the precipitation of bulky [CuIIL2]2+ cation and to form ionic comÀ-
plex [CuIIL2](BF4)2, and (ii) the inability of CuI to coordinate BF4
due to more ‘‘soft’’ character of CuI with respect to CuII in terms
of Pearson’s classification.
2.3. Synthesis of [CuIL2]BF4Á2MeCN (2)
A mixture of Cu(BF4)2Á6H2O (0.020 mmol, 6.9 mg) and copper
powder was stirred with heating in MeCN (1 ml). When the color
of the solution turned from light blue to colorless, the resulting
solution was added to a solution of L (0.040 mmol, 15.3 mg) in
MeCN (2 ml). After that, the mixture was allowed to stay at room
temperature. The orange crystals appeared in ca. 2–3 days. They
were filtered off and dried in the ambient air. These crystals were
used for X-ray diffraction analysis and their composition was iden-
tified as [CuIL2](BF4)Á2MeCN. In several days orange crystals begin
to crack and became non-transparent. In a week all crystals trans-
form to yellow powder. The elemental analysis and IR spectrum of
this product correspond to the complex [CuIL2]BF4ÁH2O (3),
containing H2O molecules instead of MeCN. Anal. Calc. for
C
48H48BCuF4N10O ([CuIL2]BF4ÁH2O): C, 61.9; H, 5.2; N, 15.0. Found:
C, 62.5; H, 5.2; N, 15.2%.
2.4. Synthesis of [CuIL2]BF4ÁH2O (3)
A mixture of Cu(BF4)2Á6H2O (0.025 mmol, 8.6 mg) and copper
powder was stirred with heating in MeCN (2 ml). When the color
of the solution turned from light blue to colorless, the resulting

118
K.A. Vinogradova et al. / Inorganica Chimica Acta 386 (2012) 116–121
Table 1
Crystal data and structure refinement for the compounds 1 and 2.
Compound
1
2
Empirical formula
C
48H47B2CuF8N10O0.50
C52H52BCuF4N12
995.41
orthorhombic
Pbcn
16.0300(9)
20.4734(11)
14.7541(6)
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
1009.12
monoclinic
C2/c
39.0462(12)
12.8815(4)
36.9840(11)
95.152(1)
18527(1)
b (°)
V (Å3)
4842.1(4)
Z
16
4
T (K)
150(2)
1.447
0.553
150(2)
1.365
0.517
Dcalc (g cmÀ3
)
l
(mmÀ1
)
Crystal size (mm3)
h Range for data collection (°)
Index ranges
0.35 Â 0.30 Â 0.20
0.32 Â 0.21 Â 0.15
1.59–26.37
2.12–26.37
À35 6 h 6 48
À16 6 k 6 13
À41 6 l 6 46
52935
À20 6 h 6 20
À25 6 k 6 25
À11 6 l 6 18
31971
Reflections collected
Independent reflections (Rint
Completeness to h
Absorption correction
)
18926 (0.0201)
99.9% (25.00°)
SADABS
4950 (0.0363)
99.8% (25.00°)
SADABS
Maximum and minimum transmission
Refinement method
0.8975 and 0.8301
full-matrix least-squares on F2
18926/0/1321
1.037
0.9265 and 0.8520
full-matrix least-squares on F2
4950/29/327
1.048
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0538, wR2 = 0.1460
R1 = 0.0654, wR2 = 0.1523
1.544 and À0.815
R1 = 0.0453, wR2 = 0.1263
R1 = 0.0677, wR2 = 0.1381
0.960 and À1.011
Largest difference in peak and hole (e ÅÀ3
)
2
N
N
N
N
3N
CuII(BF4)2
L
Cu0
MeCN, T
CuII(BF4)2
CuIBF4
CuIBF4
CuII:L = 1:1 or 1:2
EtOH
CuI:L = 1:1
MeCN
CuI:L = 1:2
MeCN
[CuIIL2(BF4)2]·0.5H2O [CuIL2]BF4·2MeCNainmthbeient air
[CuIL2]BF4·H2O
3
( )
(1)
2
( )
Scheme 1. Synthesis of the complexes.
Thus, the following transformations were carried out
(Scheme 1).
3.2. Crystal structures of 1 and 2
The crystal structure of 1 can be regarded as molecular, while
this of 2 is ionic. The unit cell of 1 contains two crystallographically
independent Cu atoms: Cu(1) and Cu(2). In both complexes, 1 and
2, two molecules of L are coordinated to copper atoms through
N2(pyrazole) and N3(pyrimidine) atoms adopting thus bidentate
chelating coordination mode. The pyrazole, pyrimidine and phenyl
rings are planar to within 0.03 Å for 1 and 0.01 Å for 2. The angles
between the planes of pyrazole and pyrimidine rings for the com-
Fig. 1. The structure of the crystallographically independent molecule
[Cu(1)L2(BF4)2] in 1 (hydrogen atoms are omitted for clarity).
of the ligand coordination is the closing of two non-planar CuCN3
chelate cycles.
The geometry around each copper atoms, Cu(1) and Cu(2), in 1
is distorted octahedral (Fig. 1 and Fig. 1S). The crystal structure of 1
contains the complex molecules [CuIIL2(BF4)2] as well as non-coor-
dinated H2O molecules. Similarly to our previous results [57], the
Cu–N2(pyrazole) bond length is longer than Cu–N3(pyrimidine)
one (Table 2). An interesting feature of the structure is the
plex
1 are 5.9 and 13.6° for [Cu(1)L2(BF4)2]; these for
[Cu(2)L2(BF4)2] are 4.6° and 11.1°. This angle for the complex 2 is
16.7°. The piperidino-group adopts chair conformation. At the
same time, in the structure of 1 one of the piperidino-groups
belonging to the [Cu(1)L2(BF4)2] fragment is disordered. The result

K.A. Vinogradova et al. / Inorganica Chimica Acta 386 (2012) 116–121
119
Table 2
Selected bond lengths (Å) and angles (°) for 1 and 2.
Compound 1
Cu(1)–F(11)
Cu(1)–N(13)
Cu(1)–N(23)
Cu(1)–N(11)
1.964(2)
1.971(2)
1.975(2)
2.095(2)
2.317(2)
2.905(2)
1.966(2)
1.967(2)
2.000(2)
2.107(2)
2.238(2)
2.737(2)
92.22(9)
92.04(9)
174.20(9)
153.60(9)
N(13)–Cu(1)–N(11)
78.29(8)
99.46(9)
124.36(9)
99.36(9)
74.97(8)
81.76(8)
178.30(9)
92.04(9)
89.62(9)
78.78(9)
99.74(9)
160.72(9)
102.17(9)
76.78(9)
113.99(9)
84.70(9)
N(23)–Cu(1)–N(11)
F(11)–Cu(1)–N(21)
N(13)–Cu(1)–N(21)
N(23)–Cu(1)–N(21)
N(11)–Cu(1)–N(21)
N(43)–Cu(2)–N(33)
N(43)–Cu(2)–F(21)
N(33)–Cu(2)–F(21)
N(43)–Cu(2)–N(41)
N(33)–Cu(2)–N(41)
F(21)–Cu(2)–N(41)
N(43)–Cu(2)–N(31)
N(33)–Cu(2)–N(31)
F(21)–Cu(2)–N(31)
N(41)–Cu(2)–N(31)
Cu(1)–N(21)
Cu(1)Á Á ÁF(31)
Cu(2)–N(43)
Cu(2)–N(33)
Cu(2)–F(21)
Cu(2)–N(41)
Cu(2)–N(31)
Cu(2)Á Á ÁF(44)
F(11)–Cu(1)–N(13)
F(11)–Cu(1)–N(23)
N(13)–Cu(1)–N(23)
F(11)–Cu(1)–N(11)
Compound 2
Cu(1)–N(3)
2.002(2)
2.002(2)
2.053(2)
2.053(2)
120.85(11)
N(3)–Cu(1)–N(1)#1
N(3)#1–Cu(1)–N(1)#1
N(3)–Cu(1)–N(1)
N(3)#1–Cu(1)–N(1)
N(1)#1–Cu(1)–N(1)
135.53(8)
80.75(8)
80.75(8)
135.53(8)
111.87(11)
Fig. 3. The structure of [CuIL2]+ cation in 2.
Cu(1)–N(3)#1
Cu(1)–N(1)#1
Cu(1)–N(1)
The crystal structure of 2 is composed of [CuIL2]+ and BF4À ions,
the molecules of MeCN are non-coordinated. The geometry around
copper atom is distorted tetrahedral (Fig. 3). In the crystal struc-
ture of 2 the intermolecular contacts between N(1S) and C(7)
atoms of the pyrimidine and C(2) atom of the pyrazole rings
(N(1S)Á Á ÁC(7) 3.443 Å, N(1S)Á Á ÁC(2) 3.584 Å) were observed.
N(3)–Cu(1)–N(3)#1
À
coordination of BF4 anion usually being regarded as noncoordi-
nating or weakly coordinated anion. According to the Cambridge
Structural Database (Version 5.32; updates Nov 2010, Feb 2011,
May 2011, Aug 2011), there are 1329 crystal structures of copper
tetrafluoroborate complexes (including both copper(I) and cop-
per(II)) and there are only 93 structures of copper complexes with
3.3. IR-spectra
Table 3 contains main IR spectroscopic data for L and the com-
plexes 1 and 3. The bands of stretching-deformation vibrations of
the (hetero)aromatic rings in IR-spectra of the complexes shifted
with respect to their positions in the spectrum of L. The far-IR spec-
tra of the complexes exhibit the bands of the stretching vibrations
of the Cu–N bonds. These observations suggest the coordination of
the heterocyclic rings of L molecule in 1 and 3. The vibrations of
À
coordinated BF4 ligand between them. The Cu–F(BF3) distances
for the complexes with coordinated BF4 ligand fall into the range
À
2.012–2.847 Å (Fig. 2S). Among these compounds, there are only
four copper(II) complexes with the distances below than 2.3 Å
[63–66]. In the structure of 1, each complex unÀit, [Cu(1)L2(BF4)2]
and [Cu(2)L2(BF4)2], contains monodentate BF4 anion, the Cu–
F(BF3) distances are 1.964(2) and 2.000(2) Å for Cu(1) and Cu(2),
respectively. Thus, these distances are the shortest for copper tet-
tetrafluoroborate anion, m4 and
split (Table 3). In contrast to the spectrum of 1, only a broad band
of 4 and a band of 3 were observed in the spectra of 3 and freshly
m3, in the spectrum of 1 are clearly
À
rafluoroborate complexes. The second BF4 anion (for each unit,
m
m
[Cu(1)L2(BF4)2] and [Cu(2)L2(BF4)2]) can be regarded as weakly
coordinated ligand, corresponding distances are 2.905(2) and
2.737(2) Å for [Cu(1)L2(BF4)2] and [Cu(2)L2(BF4)2], respectively. In
prepared sample of 2. These observÀations provide an additional
evidence for the coordination ofÀBF4 in 1 and are in accordance
with outer-spheric nature of BF4 in 2 and 3. The high-frequency
region of the spectra of the complexes 1 and 3 contains also bands
the crystal packing it should outline the presence of p–p stacking
(3580–3450 cmÀ1) which can definitely be assigned to the
m(OH)
interactions between phenyl groups of neighboring complex
molecules (centroid–centroid distance is 3.585(4) Å, distance be-
tween corresponding adjacent planes is 3.233(4) Å) (Fig. 2).
vibrations indicating the presence of non-coordinated H2O mole-
cules. The spectrum of freshly prepared sample of 2 contains also
À
Fig. 2. The
p
–p
interactions in the structure of 1 (hydrogen atoms and weakly coordinated BF4 anions are omitted for clarity).

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K.A. Vinogradova et al. / Inorganica Chimica Acta 386 (2012) 116–121
Table 3
The main vibration frequencies in IR spectra (cmÀ1) of the compounds.
Compound
L
(
m
+ d)ring
m
3(B–F)
m
4(B–F)
m(Cu–N)
1605, 1591, 1552,
1531, 1487
1625, 1568, 1554,
1504, 1486
1615, 1542, 1503,
1485
1616, 1544, 1503,
1486
[CuIIL2(BF4)2]Á
0.5H2O
1092, 1043,
984,
1054
534, 520
531
290, 252
275, 257
[CuIL2]BF4Á
2MeCN
[CuIL2]BF4ÁH2O
1057
529
a band which can be assigned to the stretching vibrations of the
C„N bonds indicating the presence of MeCN molecules
(2248 cmÀ1). The spectrum of 3 and the spectrum of decomposi-
tion product of single crystals of 2 are practically identical which
indicates that, in the ambient air, the single crystals of 2 loss MeCN
molecules and include H2O transforming into 3.
Fig. 4. The excitation (dashed line) and emission (solid line) spectra of 3.
À
3.4. Coordination of BF4 anion in 1
fluoroborate complexes could favor the coordination of BF4À anion
along with the formation of short Cu–F(BF3) coordination bonds.
Thus, our results, togeÀther with the results of Cano and co-workers
demonstrate that BF4 anion acting as the ligand can be coordi-
nated to copper(II) as a ‘‘conventional’’ instead of weakly coordi-
nating ligand.
À
An interesting moment concerns with coordination of BF4 an-
ion. According to the data on coordinating ability indices, aTM, pro-
posed recently by Diaz-Torres and Alvarez as
a quantifying
measure of coordinating abilities of anions and solvent molecules
[67], the tetrafluoroborate anion, with aTM = À1.1, is one of the
weakest anion-coordinators. Taking into account the data on
copper tetrafluoroborate complexes (see Section 3.2), the value of
coordinating ability index for tetrafluoroborate anion toward cop-
per, aCu, calculated according to Diaz-Torres and Alvarez [67], is
also equal to À1.1. This indicates that the coordination ability of
tetrafluoroborate anion toward copper is practically the same as
it is regarding other transition metals. Nevertheless, starting this
work, we were endeavored to prepare copper(II) complexes with
3.5. Photoluminescence
The copper(I) complex, 3, manifests orange luminescence in the
solid state. The excitation and emission spectra are displayed in
Fig. 4. The emission spectrum of the compound 3 displays the wide
emission band with a maximum at 612 nm. The maximum of emis-
sion for the complex shifts toward higher wavelengths relatively to
the corresponding maxima in the spectra of free L as well as zinc(II)
and cadmium(II) complexes with L [56]. Since that copper(I) can
easily be oxidized and, on the other hand, the molecules of L have
easily accessed p⁄-orbitals, it seems to be reasonable that, upon the
excitation of 3, the metal-to-ligand charge transfer (MLCT) takes
place and luminescence originates from these MLCT excited states.
The copper(II) complex, 1, does not show luminescent properties.
À
À
coordinated BF4 anion. We believed that BF4 anion is small en-
ough to cause the precipitation of bulky [CuIIL2]2+ cation and to
form ionic [CuIIL2](BF4)2 complex instead of molecular
[CuIIL2(BF4)2] one containing coordinated tetrafluoroborato-li-
gands. Our approach was successful and we obtained a complex
with the Cu–F(BF3) distances of 1.964(2) and 2.000(2) Å being
the shortest for copper tetrafluoroborate complexes. Thus, this
À
coordination of BF4 anion cannot be regarded as semi-coordina-
tion, but as ‘‘normal’’ or ‘‘conventional’’ coordination. It ought to
note that despite of the fact that the reaction mixture contained
some amount of water (since the synthesis of 1 was performed
in 96% EtOH and the hexahydrate of copper(II) tetrafluoroborate
was used as the copper(II)-containing starting reagent) this did
not obstruct coordination of BF4À anion to copper(II) and H2O mol-
ecules were found to be included into the crystal structure of 1 as
outer-spheric molecules instead of ligands. This observation pro-
vides an additional example that the presence of some amount of
water in the reaction mixture in some cases does not prevent the
coordination of tetrafluoroborate.
Interestingly, the short Cu–F(BF3) distance of 2.068 Å, being the
shortest for copper(II) tetrafluoroborate complexes until our com-
plex was obtained, was observed by Cano and co-workers for
copper(II) tetrafluoroborate complex with 2-(3,5-bis(buthoxyphe-
nyl)-1H-pyrazol-1-yl)pyridine [63]. The ligand used by Cano and
co-workers somewhat resembles our ligand L used in the present
work. Indeed, in both cases the pyrazolyl group contains two bulky
substituents (phenyl or substituted phenyl groups) and, on the
other hand, the C6(pyridine) and C2(pyrimidine) positions (i.e. the
4. Comments and conclusion
In summary, we have synthesized a series of copper(I) and cop-
per(II) tetrafluoroborate complexes based on a bidentate chelating
ligand L. The M:L = 1:1 and 1:2 molar ratios afforded complexes
with Cu:L = 1:2 stoichiometry. According to X-ray data,
[CuIL2](BF4)Á2MeCN and [CuIIL2(BF4)2]Á0.5H2O complexes have dis-
torted tetrahedral and octahedral coordination cores, respectively.
The compound [CuIL2](BF4)ÁH2O was found to exhibit orange lumi-
nescence while [CuIIL2(BF4)2]Á0.5H2O is non-luminescent. Thus, the
complex [CuIL2](BF4)ÁH2O represents the first example of lumines-
cent copper complexes with 4-pyrazolylpyrimidinesÀ. Another
noteworthy moment concerns with coordination of BF4 anion to
copper(II) in [CuIIL2(BF4)2]Á0.5H2O. The Cu–F(BF3) distances,
1.964(2) and 2.000(2) Å, are the shortest for copper tetrafluorobo-
rate complexes.
Acknowledgements
a
-positions to N(azine) atom participating in coordination) are free
The authors are grateful to Prof. Stanislav V. Larionov for his
attention to this work and useful discussions. The authors thank
Dr. Olga S. Koshcheeva and Dr. Anna P. Zubareva for CHN-analysis,
from any substituents. Thus, it seems to be reasonable that the
employing of related ligands for the synthesis of copper(II) tetra-

K.A. Vinogradova et al. / Inorganica Chimica Acta 386 (2012) 116–121
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Appendix A. Supplementary material
CCDC 855801 and 855802 contain the supplementary crystallo-
graphic 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. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.ica.2012.02.004.
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