Synthesis and structural studies of mono- and dinuclear Cu(II) complexes with an ONO donor Schiff base ligand: Self-assembly and sulfato-bridged

Article abstract of DOI:10.1016/j.poly.2012.08.057

Five Cu(II) complexes, [CuL(NO₃)] (1), [CuLBr][CuLCH ₃OH]₂Br₂ (2), [CuLN₃] (3), [CuL(ClO₄)]₂ (4) and [H₂OLCu(μ-SO ₄)CuLH₂O] (5), where L is the s

Full text of DOI:10.1016/j.poly.2012.08.057

Polyhedron 48 (2012) 51–57
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and structural studies of mono- and dinuclear Cu(II) complexes
with an ONO donor Schiff base ligand: Self-assembly and sulfato-bridged
Rasoul Vafazadeh a, ,1, Roya Esteghamat-Panah a, Anthony C. Willis b, Anthony F. Hill b
⇑
a Department of Chemistry, Yazd University, Yazd, Iran
b Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Five Cu(II) complexes, [CuL(NO3)] (1), [CuLBr][CuLCH3OH]2Br2 (2), [CuLN3] (3), [CuL(ClO4)]2 (4) and
Received 1 June 2012
Accepted 6 August 2012
Available online 31 August 2012
[H2OLCu(l-SO4)CuLH2O] (5), where L is the salicylaldehyde semicarbazone tridentate Schiff base ligand,
have been synthesized and characterized by elemental analysis, FT-IR, UV–Vis and mass spectroscopy.
The structures of compounds 2, 4 and 5 have been determined by single-crystal X-ray diffraction analy-
ses. The structure of 2 contains both a mononuclear and a dinuclear species as distinct entities. The coor-
dination geometry around the copper(II) ion in the mononuclear species is four coordinated square
planar, whereas the dinuclear complex cation is five coordinated square pyramidal in which each cop-
per(II) ion has a distorted square pyramidal geometry. In the mononuclear species, L acts as a tridentate
ligand and the fourth position at the Cu ion is occupied by the Br anion, while in the dinuclear species,
L acts as a bridging tridentate ligand connecting two Cu(II) ions, so there is an intramolecular copper–
copper separation of 3.034 Å and the apical position of each Cu ion is occupied by the oxygen of a meth-
anol molecule. Complex 4 is a dinuclear species, in which each copper(II) ion exhibits a distorted square
pyramidal geometry, which is similar to complex 2. The L ligand adopts a tridentate bridging mode with a
copper–copper distance of 3.011 Å. The apical position is occupied by a perchlorate anion. The molecular
structure of 5 shows that it is a sulfato bridged dimeric Cu(II) complex with an intramolecular copper–
copper separation of 4.733 Å. The coordination geometry around each copper is five coordinated square
pyramidal with two oxygen and one nitrogen atom from the tridentate ligand, L, and an oxygen from a
coordinated water in equatorial positions and an oxygen from the bridging sulfato group in the axial
position.
Keywords:
Copper complex
Mononuclear
Dinuclear
Self-assembly
Sulfato bridge
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
[15,16], oxalate [17,18] and sulfate [19,20] are common ligands
to build these complexes.
In recent decades considerable research interest has been
shown in the design and synthesis of complexes which present
two or more copper metals held in close proximity [1–3], due to
their potential application as models for the active sites of impor-
tant biological systems [4–6]. Much effort has been devoted to the
synthesis of new multi-nuclear copper complexes for a better
understanding of the various properties of these complexes in bio-
inorganic chemistry [7], medicine [8] and catalysis [9]. There has
been growing interest in using bridging ligands in the synthesis
of di- and multinuclear metal complexes. Ligands which contain
potentially bridging phenoxo or hydroxo oxygen and nitrogen do-
nor atoms have been widely used in the synthesis of multi-nuclear
copper complexes [10–12]. Also, halides [13,14], pseudo-halides
Metal-sulfato complexes are particularly interesting since the
sulfate ion is capable of binding metal centers in many ways. The
number of metals coordinated to a sulfato ligand can be 2, 3, 4,
5, 6, 8 or even 10. The sulfate ligand can adopt two terminal
(monodentate, bidentate chelating) and 16 different bridging coor-
dination modes [21].
In the present study, we have explained the synthesis of many
mononuclear and dinuclear copper complexes with a salicylalde-
hyde semicarbazone tridentate Schiff base ligand (as an ONO donor),
and three of these (mono- and dinuclear) have been characterized
structurally by X-ray crystallography.
2. Experimental
2.1. Reagents
⇑
Corresponding author. Tel.: +98 351 8214778; fax: +98 351 7250110.
E-mail address: rvafazadeh@yazduni.ac.ir (R. Vafazadeh).
On sabbatical at Research School of Chemistry, Australian National University,
1
All chemicals were used as supplied by Merck and Fluka
without further purification.
Canberra, ACT 0200, Australia.
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.057

52
R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
2.2. Physical measurements
0.008 mol), sodium acetate (1.5 g, 0.01 mol) and salicylaldehyde
(0.5 g, 0.004 mol) at room temperature for 1 h to give a white pre-
cipitate. The precipitate was filtered, washed with distilled water
Infrared spectra were taken with an Equinox 55 Bruker FT-IR
spectrometer using KBr pellets in the 400–4000 cmÀ1 range.
Absorption spectra were determined in the solvent methanol using
a GBC UV–Vis Cintra 101 spectrophotometer with 1 cm quartz, in
the range 200–800 nm at 25 °C. Elemental analyses (C, H, N) were
performed using a CHNS-O 2400II PARKIN-ELMER elemental ana-
lyzer. Mass spectra were obtained on a ZAB-SEQ4F spectrometer
by the mass spectrometry service of the Australian National
University.
and dried at room temperature. Yield 67%. IR (KBr, cmÀ1):
mC@N
1621,
m
C@O 1682. Electronic spectra in acetone kmax (nm), (log ):
e
328 (0.94), 274 (1.53), 249 (1.58).
2.4.2. Syntheses of [CuL(NO3)].H2O, complex 1
The complex was prepared by a similar reported method [25]. A
solution of copper(II) nitrate trihydrate (0.483 g, 2 mmol) in water
(3 ml) was added to a solution of the HL ligand (0.358 g, 2 mmol) in
methanol (30 ml) and the resulting solution was heated to reflux
for 3 h. The resulting green solution was filtered while hot and
allowed to crystallize at room temperature. After many days, small
green crystals appeared at the bottom of the vessel as the solvents
slowly evaporated. They were washed with ethanol:water (1:1 v/v)
and dried in air. Yield 83%. Anal. Calc. for C8H10CuN4O6: C, 29.86; H,
3.13; N, 17.41. Found: C, 29.28; H, 3.35; N, 17.50%. IR (KBr, cmÀ1):
2.3. X-ray crystallography
Diffraction images were measured at 200 K on a Nonius Kappa
CCD diffractometer using a Mo Ka, graphite monochromator
(k = 0.71073 Å) and data were extracted using the DENZO/SCALE-
PACK package [22]. The structures were solved by direct methods
with SIR92 [23]. The structures were refined on F2 by full matrix
last-squares techniques using the CRYSTALS program package [24].
mC@N 1602,
mC@O 1657. Electronic spectra in methanol kmax (nm),
For complex 2, R1 = 0.036 (5321 reflections with I > 2.0
Rw = 0.065 (all 5898 reflections), for complex 4, R1 = 0.026 (2282
reflection with I > 2.0 (I)), Rw = 0.067 (all 2544 reflections) and
for complex 5, R1 = 0.036 (for 2735 reflections with I > 2.0 (I)),
r
(I)),
(log ): 692 (1.97), 369 (1.92), 277 (2.23), 248 (2.28).
e
r
r
2.4.3. Syntheses of [CuLBr].1.5H2O, complex 2
Rw = 0.097 (all 3102 reflections). Numerical absorption corrections
were applied, Tmin/Tmax = 0.257/0.640, 0.547/0.946 and 0.616/0.928
for complexes 2, 4 and 5, respectively. Atomic coordinates, bond
lengths and angles and displacement parameters have been depos-
ited at the Cambridge Crystallographic Data Centre. Crystallo-
graphic details for the three crystals 2, 4 and 5 are summarized
in Table 1.
A solution of copper(II) nitrate trihydrate (0.483 g, 2 mmol) in
water (3 ml) was added to a solution of the HL ligand (0.358 g,
2 mmol) in methanol (30 ml) and the resulting solution was stirred
at room temperature for 30 min, followed by dropwise addition of
an aqueous solution of KBr (0.238 g, 2 mmol dissolved in 5 ml of
water). The mixture was heated to reflux for 3 h then the resulting
green solution was filtered while hot and allowed to crystallize at
room temperature. After many days, green block-shaped crystals
appeared upon slow evaporation of the solvents at room tempera-
ture, and these were washed with ethanol:water (1:1 v/v) and dried
in air. Yield 80%. Anal. Calc. for C8H11CuN3O3.5: C, 27.56; H, 3.18; N,
2.4. Syntheses
2.4.1. Syntheses of the Schiff base ligand, HL
The salicylaldehyde semicarbazone tridentate Schiff base HL
was prepared by the reported method [25], by condensation in
an aqueous solution containing semicarbazide hydrochloride (1 g,
12.05. Found: C, 27.45; H, 3.11; N, 11.92%. IR (KBr, cmÀ1):
1602, C@O 1646. Electronic spectra in methanol kmax (nm), (log
694 (2.01), 370 (1.95), 276 (2.23), 250 (2.28).
mC@N
m
e):
Table 1
Crystallographic data of the complexes 2, 4 and 5.
Compound
2
4
5
Chemical formula
Formula weight
Temperature (K)
Space group
C
38H56ÁBr4Cu4N12O14
C16H16Cl2Cu2N6O12
682.34
200
C16H2Cu2N6O10S.6H2O
723.62
200
1478.73
200
Triclinic, P1, Z = 1
ꢀ
Monoclinic, P21/c, Z = 2
Monoclinic, C2/c, Z = 4
Unit cell dimensions
a (Å)
b (Å)
c (Å)
9.4489 (2)
6.0660 (2)
21.7887 (6)
8.4847 (2)
90
95.7887 (6)
90
24.1917 (5)
6.9678 (1)
16.6088 (3)
90
104.8556 (10)
90
11.3188 (6)
13.3303 (2)
72.8679 (13)
79.9779 (19)
73.3396 (18)
1298.96 (6)
a
(°)
b (°)
c
(°)
V (Å3)
1115.73 (5)
2706.05 (8)
F(000)
736
1.890
684
2.031
1488
1.776
DCalc (g cmÀ3
)
Crystal size (mm)
0.42 Â 0.06 Â 0.03 mm
0.33 Â 0.28 Â 0.03 mm
0.44 Â 0.20 Â 0.06 mm
l
(mmÀ1
)
4.76
2.23
1.73
h range (°)
3–27.5
2.6–27.5
2.7–27.5
Limiting indices
À12 6 h 6 11
À14 6 k 6 14
À17 6 l 6 17
0.025
À7 6 h 6 7
À28 6 k 6 28
À10 6 l 6 10
0.026
À31 6 h 6 30
À7 6 k 6 9
À21 6 l 6 21
0.036
r
R[F2 > 2 (F2)]
wR(F2) (all data)
0.065*
0.067**
0.097***
*
**
w = 1/[
w = 1/[
w = 1/[
r
r
r
2(F2) + (0.03P)2 + 1.02P], where P = (max(F02,0) + 2Fc2)/3.
2(F2) + (0.03P)2 + 1.18P], where P = (max(F02,0) + 2Fc2)/3.
2(F2) + (0.06P)2 + 7.69P], where P = (max(F02,0) + 2Fc2)/3.
***

R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
53
2.4.4. Syntheses of [CuLN3], complex 3
The coordination geometry around the copper(II) ion in mono-
nuclear 2A is four coordinated square planer, whereas in the dinu-
clear complex cation, 2B, each copper(II) ion is five coordinated
square pyramidal. In mononuclear 2A, L acts as a tridentate ligand
which forms one five membered and one six membered chelate
ring with the Cu(II) metal centre, and the fourth position at the
Cu ion is occupied by the Br anion. In the dinuclear cation 2B,
the L ligand acts as a bridging tridentate ligand connecting the
two Cu(II) ions with an intramolecular copper–copper separation
of 3.034(5) Å, and the apical position is occupied by the oxygen
of a methanol molecule. The geometry of copper in the dinuclear
complex 2B is best described as distorted square pyramidal with
A solution of copper(II) nitrate trihydrate (0.483 g, 2 mmol) in
water (3 ml) was added to a solution of the HL ligand (0.358 g,
2 mmol) in methanol (30 ml). The resulting solution was heated
to reflux for 3 h and a green solution resulted. An aqueous solution
of NaN3 (0.26 g, 2 mmol dissolved in 5 ml of water) was added to
the green solution and the mixture was stirred at room temperature
for 2 h. The resulting green precipitates were collected by filtration
and washed with ethanol and dried in air. Yield 68%. Anal. Calc. for
C8H8CuN6O2: C, 33.86; H, 2.84; N, 29.62. Found: C, 33.51; H, 2.58; N,
30.00%. IR (KBr, cmÀ1):
mC@N 1602,
m
C@O 1660,
m
N3 2063. Elec-
tronic spectra in methanol kmax (nm), (log
e): 713 (1.82), 368
(1.86), 280 (1.85), 250 (2.14).
the Addison parameter
which and b are largest angles;
amid and = 0 for a regular square pyramid [26].
s
= 0.04, where
s
= (
a
À b)/60,
a > b, in
a
s
= 1 for a regular trigonal bipyr-
s
2.4.5. Syntheses of [CuL(ClO4)]2, complex 4
The Cu–N(imino) and Cu–O(carbonyl) bond distances for the
two crystallographically different copper(II) centers (mono- and
dinuclear species) are very similar. However, the Cu–O(phenoxo)
bond length in the mononuclear complex is shorter than the corre-
sponding ones in the dinuclear complex (Table 2), which is in good
agreement with analogous complexes observed in the literature
[1,10,27]. This could be due to the fact that in the dinuclear com-
plex 2B, the bridging phenoxo interaction with the Cu atom is
weaker than the terminal phenoxo interaction with the Cu center
in the mononuclear complex 2A. The angles of Cu(II) with two do-
nor atoms in cis positions for the mono- and dinuclear species are
in the range 80.78(7)–92.88(4) and 78.96(6)–107.21(6)° and with
two donor atoms in trans positions, 163.76(5)–173.03(6) and
171.44(7)–173.81(6)°, respectively (Table 2). The methanol mole-
cules and the NH2 amide group of the Schiff base ligand play a sig-
nificant role in the H bonding network; all the hydrogen bonds
lengths with the corresponding angles are listed in Table 3.
A solution of perchloric acid (0.12 ml, 2 mmol) in methanol
(40 ml) was added to solution of the HL ligand (0.358 g, 2 mmol)
in methanol (30 ml) and the resulting solution was stirred at room
temperature for 30 min, followed by slow addition of copper(II)
nitrate trihydrate (0.483 g, 2 mmol). The resulting solution was stir-
red for 24 h at room temperature then filtered and green precipi-
tates were obtained by evaporation of the solvent. The green solid
product was recrystallized from methanol/2-propanol (5:2 v/v).
Green block-shaped crystals appeared upon slow evaporation of
the solvents and these were washed with ethanol and dried in air.
Yield 83%. Anal. Calc. for C16H16Cl2Cu2N6O12: C, 28.16; H, 2.36; N,
12.32. Found: C, 28.44; H, 2.31; N, 12.00%. IR (KBr, cmÀ1):
1602, C@O 1654, ClO4 1047. Electronic spectra in methanol kmax
(nm), (log ): 689 (1.99), 371 (2.05), 277 (2.36), 248 (2.42).
mC@N
m
m
e
2.4.6. Syntheses of [H2OLCu(-SO4)CuLH2O]Á6H2O, complex 5
A solution of copper(II) sulfate pentahydrate (0.499 g, 2 mmol)
in water (3 ml) was added to a solution of the HL ligand (0.358 g,
2 mmol) in methanol (30 ml) and the resulting solution was heated
to reflux for 4 h. The resulting green precipitates were collected by
filtration and washed with ethanol and dried in air. The green solid
product was recrystallized from water. Green block-shaped crystals
appeared upon slow evaporation of the solvents and these were
washed with ethanol and dried in air. Yield 63%. Anal. Calc. for
3.1.2. Description of complex 4
Complex 4 crystallized in the monoclinic space group P21/c. The
molecular structure of the complex, with labeling of selected
atoms, is shown in Fig. 3. Selected bond lengths and angles are
listed in Table 2. There is disorder in the packing of the perchlorate
group over two positions, which have relative occupancies which
refined to 78%:22%.
From the crystal structure, it has been found that in complex 4
the coordination geometry around each copper is slightly distorted
square pyramidal, where the four equatorial positions are occupied
by three oxygen atoms (O12 of carbonyl, O1 and O1⁄ from
C
16H32Cu2N6O16S: C, 26.59; H, 4.46; N, 11.61. Found: C, 26.59; H,
4.26; N, 11.65%. IR (KBr, cmÀ1):
C@N 1602, C@O 1655. Electronic
): 693 (2.40), 358 (4.33), 292 (4.47).
m
m
spectra in H2O kmax (nm), (log
e
l
-phenolato groups) and one nitrogen (N9 of the imine Schiff
base), while the axial position is occupied by one oxygen atom
(O14) of perchlorate anion. The axial Cu–O14 bond is
2.510(6) Å, which is longer than the equatorial Cu–O bonds
[1.944(1), 1.958(1) and 1.965(2) Å], as expected [28–30].
3. Result and discussion
3.1. Crystal structures
a
3.1.1. Description of complex 2
The angles at Cu(II) between two donor atoms in cis positions
are in the range 79.03(6)–107.31(6)° and between two donor
atoms in trans positions, 170.82(6)–173.38(6)° (Table 2). The Addi-
son parameter for the copper atom is 0.04 [26]. The deviation of
copper(II) from the basal plane towards the axially coordinated site
is 0.041 Å. In complex 4 the Cu1Á Á ÁCu2 separation is 3.011(5) Å,
which is close to the value for complex 2 and other complexes re-
ported by Thompson (ranging from 2.997 to 3.1184 Å) [31], and it
is larger than the value reported by Ray (2.903 Å) [32] and Dutta
(2.911 Å) [33]. The perchlorate ions play a significant role in the
H bonding network. The major hydrogen bonds lengths with the
corresponding angles are listed in Table 4.
Single crystals of complex 2 suitable for X-ray were obtained
from a saturated solution of 2 in methanol. The crystals lose solvent
very readily and need to be kept in methanol until the last moment,
and then rapidly coated with oil and transferred to the cold stream
of the diffractometer. The complex crystallized in the triclinic space
ꢀ
group P1. The molecular structure of the complex, with labeling of
selected atoms, is shown in Fig. 1, and an assembly of the complex,
when longer Cu. . .Br contacts are included, is shown in Fig. 2. Se-
lected bond lengths and angles are listed in Table 2. The crystal
structure of 2, shown in Fig. 2, includes two independent parts,
namely, species 2A, which is a discrete mononuclear complex
[CuLBr], and species 2B, the dinuclear complex [Cu2L2(CH3OH)2]Br2.
There are also weak intermolecular non-covalent interactions
involving the coordinatively unsaturated metal ions of the mono-
and dinuclear complexes with the bromide anions, with Cu. . .Br
distances of 3.045(3) and 3.107(3) Å (Fig. 2).
3.1.3. Description of complex 5
Complex 5 crystallized in the monoclinic space group C2/c. The
molecular structure of the complex, with labeling of selected atoms,
is shown in Fig. 4, and selected bond lengths and angles are listed in

54
R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
Fig. 1. The crystal structure of the complex 2, (A) mononuclear complexes, [CuLBr] and (B) the dinuclear complex, [Cu2L2(CH3OH)2] cation with labeling of selected atoms.
Fig. 2. A view of via apical metal–halide interaction the [CuLBr]2[Cu2L2(CH3OH)2]Br2 assembly.

R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
55
Table 2
Selected bond lengths (Å) and angles (°) in complexes 2, 4 and 5.a
Complex 2A
Cu1–Br1
Cu–O1
Cu–O12
Cu1–N9
Cu1. . .Br2
2.379 (3)
1.894 (2)
1.993 (3)
1.949 (2)
3.045 (3)
N9–Cu1–O1
N9–Cu1–O12
Br1–Cu1–O1
Br1–Cu1–O12
Br1–Cu1–N9
N9–Cu1–O12
Cu1–Br2–Cu2
92.31 (7)
80.78 (7)
94.04 (5)
92.88 (4)
163.8 (5)
173.0 (7)
175.7 (1)
Complex 2B
Cu2–O21
Cu2–O32
Cu2–N29
Cu2–O21⁄
Cu2–O41
Cu2. . .Br2
Cu. . .Cu
1.956 (1)
1.984 (2)
1.942 (2)
1.975 (1)
2.443 (2)
3.107 (3)
3.034
N29–Cu2–O21
N29–Cu2–O32
O21–Cu2–O21⁄
O32–Cu2–O21⁄
Cu1–N9–C10–C11
O21–Cu2–O32
N29–Cu2–O21⁄
92.48 (7)
81.35 (7)
78.96 (6)
107.2 (6)
90.30 (1)
173.8 (6)
171.4 (7)
Complex 4
Cu1–O1⁄
Cu1–O1
Cu1–O12
Cu1–O14
Cu1–N9
C2–O1
C11–O12
C8–N9
Cu. . .Cu
1.958 (1)
1.944 (1)
1.965 (2)
2.510 (6)
1.932 (2)
1.356 (2)
1.260 (3)
1.281 (3)
3.011
N9–Cu1–O1⁄
O12–Cu1–O1
O14–Cu1–O1
N9–Cu1–O1
N9–Cu1–O12
O14–Cl1–O16
O15–Cl1–O16
170.8 (6)
173.3 (6)
95.84 (2)
92.26 (6)
81.31 (7)
110.7 (4)
108.8 (3)
Fig. 3. The molecular structure of 4 with labeling of selected atoms, ellipsoids
shows 30% probability levels.
Complex 5
Cu1–O1
Cu1–O12
Cu1–O14
Cu1–O15
Cu1–N9
C2–O1
C11–O12
C8–N9
Cu. . .Cu
1.882 (2)
1.980 (2)
2.010 (2)
2.202 (3)
1.936 (5)
1.329 (3)
1.262 (3)
1.287(3)
4.733
O1–Cu1–O12
N9–Cu1–O14
O1–Cu1–O15
N9–Cu1–O1
N9–Cu1–O12
O15–S1–O16
O15⁄–S1–O16
172.9 (8)
155.2 (8)
98.71 (1)
92.38 (8)
80.81 (8)
110.6 (2)
107.7 (2)
Table 4
Hydrogen bonding (Å) and angles (°) for 4.
D–H. . .A
D–H
H. . .A
D. . .A
D–H. . .A
N10–H101. . .O15vi
N10–H101. . .O115vi
N13–H131. . .O16vi
N13–H131. . .O17xi
N13–H131. . .O115vi
N13–H132. . .O15ii
N13–H132. . .O117ii
0.78 (3)
0.78 (3)
0.85 (3)
0.85 (3)
0.85 (3)
0.78 (3)
0.78 (3)
2.26 (3)
2.06 (3)
2.55 (3)
2.49 (3)
2.49 (3)
2.38 (3)
2.22 (3)
3.003 (3)
2.792 (3)
3.157 (3)
3.051 (3)
3.181 (3)
3.153 (3)
2.950 (3)
159 (3)
156 (3)
129 (3)
124 (3)
139 (3)
168 (3)
156 (3)
a
Symmetry codes: Àx + 1, Ày + 1, Àz + 1.
Table 3
Hydrogen bonding (Å) and angles (°) for 2.
Symmetry codes: (ii) x À 1, y, z; (vi) x, Ày + 1/2, z + 1/2; (xi) x À 1, Ày + 1/2, z + 1/2.
D–H. . .A
D–H
H. . .A
D. . .A
D–H. . .A
with analogous systems observed in the literature [34–36]. The
sulfato ligand has a distorted tetrahedral symmetry. The angle at
the sulfur atom for the two oxygen atoms coordinated to the copper
centers is the largest (O15–S1–O15⁄ = 113.0(2)°), whereas the angle
at the sulfur atom of the unbound two oxygen atoms is the smallest
(O16–S1–O16⁄ = 107.1(4)°). The Cu. . .Cu distance is 4.733(1) Å,
which is much longer than the van-der waals radii sum for copper
(2.8 Å), [37], showing that there is no interaction between the cop-
per atoms. In this crystal structure there are hydrogen bonding con-
tacts, and they are listed in Table 5.
In complex 4, by a self-assembly process, two [CuL] building
blocks follow with perchlorate anions to give the neutral dinuclear
complex. The anionic phenolic oxygen atoms act as bridges connect-
ing two Cu(II) ions. This proves that the phenoxo oxygen is a stronger
donor center than the perchlorate oxygen [38]. However, in com-
plexes 1, 3 and 5, and also in CuLCl [25], there is no self-assembly
via intermolecular interactions with anionic phenolic oxygen atoms.
The probable reason for this observation is that the phenoxo oxygen
is a weaker donor than nitrato, azido, sulfato and chloro anions. In
complex 2, the crystal structure includes both mononuclear and
dinuclear complexes, which is probably due to the similarity of
donation strength of the phenoxo oxygen and the Br anion.
N13–H131. . .O12ii
N13–H132. . .O41vi
N33–H331. . .O51iv
N33–H332. . .O61i
O51–H511. . .O1
0.87 (3)
0.84 (3)
0.85 (3)
0.81 (3)
0.81 (2)
2.24 (3)
2.17 (3)
2.07 (3)
2.13 (3)
2.09 (2)
3.063 (4)
3.003 (4)
2.883 (4)
2.928 (4)
2.883(4)
156 (3)
171 (3)
160 (3)
170 (3)
164 (3)
Symmetry codes: (i) Àx + 1, Ày + 1, Àz + 1; (ii) Àx, Ày, Àz + 1; (iv) Àx, Ày + 1, Àz + 1;
(vi) x, y À 1, z.
Table 2. There is disorder in the packing of the sulfato group over
two positions, which have relative occupancies which refined to
68%:32%. The molecular structure shows that it is a centrosymmet-
ric sulfato bridged dimeric Cu(II) complex with a [Cu2L2(l-SO4)]
unit, i.e. the 2.1100 coordinated sulfato mode [21]. The coordina-
tion geometry around each the central copper is five coordinated
square pyramidal with two oxygen and one nitrogen atom from
the tridentate ligand HL (O1, N9 and O12) and an oxygen from
the coordinated water (O14) in equatorial positions and an oxygen
from the bridging sulfato group (O15) in the axial position. The an-
gles at Cu(II) between two donor atoms in cis positions are in the
range 80.81(8)–117.41(10)° and between two donor atoms in trans
positions, 155.17(8)–172.86(8)°. The Addison parameter for the
copper atom is 0.29 [26]. The Cu(II) atom deviates 0.233 Å from
the mean square base towards the apical position. As shown in
Table 2, similar to complex 2B and 4, the Cu–O bond length in the
apical position (Cu1–O15 = 2.202(3) Å) is longer than the Cu–O
bond lengths in the equatorial positions (Cu1–O1 = 1.882(2), Cu1–
O12 = 1.980(2) and Cu1–O14 = 2.010(2) Å), which is consistent
3.2. Infrared spectra
A comparison of the spectra of the free ligand and the com-
plexes indicates that the ligand is coordinated to the copper center.

56
R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
Fig. 4. The molecular structure of 5 with labeling of selected atoms, ellipsoids shows 30% probability levels.
The IR spectrum of the free tridentate ligand HL shows bands at
1265, 1621 and 1682 cmÀ1, which are assigned as
C–O, C@N
and C@O, respectively. The strong
C@N band at 1602 cmÀ1 for
Table 5
m
m
Hydrogen bonding (Å) and angles (°) for 5.
m
m
complexes 1–5 and the
mC@O band is shifted approximately
D–H. . .A
D–H
H. . .A
D. . .A
D–H. . .A
ꢀ25 cmÀ1 toward lower energy in comparison with the free ligand,
N10–H101. . .O16iv
N10–H101. . .O151iv
N13–H131. . .O18
N13–H132. . .O19xii
O14–H141. . .O1ix
O14–H142. . .O16iii
O14–H142. . .O161iii
O17–H171. . .O12
O17–H172. . .O18vii
O18–H181. . .O17
O18–H182. . .O19
O19–H191. . .O16xi
O19–H191. . .O161xi
O19–H192. . .O17vii
0.85
0.85
0.86
0.85
0.81
0.79
0.79
0.79
0.78
0.78
0.80
0.79
0.79
0.81
1.98
2.29
2.18
2.15
1.93
2.22
1.84
2.08
2.07
2.02
2.06
2.26
2.06
2.11
2.806 (4)
2.913 (4)
3.034 (4)
3.000 (4)
2.660 (4)
2.946 (4)
2.603 (4)
2.822 (4)
2.842 (4)
2.789 (4)
2.855 (4)
2.934 (4)
2.830 (4)
2.916 (4)
163
131
177
174
150
152
160
156
172
168
170
144
162
170
which indicates coordination of the imine nitrogen atom and the
carbonyl group to the copper ion [39]. Conversely, the mC–O band
is shifted approximately ꢀ35 cmÀ1 toward higher energies com-
pared with the free ligand, which suggests coordination of the
deprotonated phenolic oxygen to the copper ion in complexes
1–5 [40,41].
The use of IR spectroscopy to distinguish between uncoordi-
nated, monodentate and bidentate (chelate or bridge) SO42À is sim-
ple and interesting. The free sulfate ion belongs to the Td point group,
has four vibrational modes,
(bending symmetric, IR inactive),
tive) and m4 (bending asymmetric, IR active). The spectrum of the
sulfate ion shows two bands at about 1104 cmÀ1
and
613 cmÀ1
4) [42]. When it forms a complex, its symmetry will be
decreased to C3v (as a monodentate ligand) or C2v (as a bidentate
m
1 (stretching symmetric, IR inactive), m2
m3 (stretching asymmetric, IR ac-
Symmetry codes: (iii) Àx + 1, y À 1, Àz + 1/2; (iv) Àx + 1, Ày + 1, Àz + 1; (vii) Àx + 1/
2, yÀ1/2, Àz + 1/2; (ix) Àx + 1. Y, Àz + 1/2; (xi) xÀ1/2, yÀ1/2, z; (xii) Àx + 1/2, Ày + 1/
2. Àz + 1.
(m3)
(m
Scheme 1.

R. Vafazadeh et al. / Polyhedron 48 (2012) 51–57
57
ligand) and the
m
3 and
m
4 bands will be split. In addition, the
m
1 and m2
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.poly.2012.08.057.
modes become active with the decrease in symmetry [21,42].
In complex 5, broad bands around 1110 cmÀ1 are observed (
m3),
which can be resolved into three bands at 1143, 1110 and
1036 cmÀ1. Furthermore, the m4 mode appears at 618 cmÀ1 and
the m2 mode appears with weak intensity at 983 cmÀ1. These re-
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Acknowledgments
The authors are grateful to the Yazd University and the Australian
National University for partial support of this work. We thank Dr.
Hayedeh Javadzadeh Shahshahani for reading the manuscript and
her valuable comments.
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CCDC 884622–884624 contains the supplementary crystallo-
graphic data for 2, 4 and 5, respectively. 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