Tetracopper complexes with two-mode cubane-like Cu4O4 core from similar hydroxyl-rich salicylaldehyde Schiff bases: Structure and magnetic properties

Article abstract of DOI:10.1016/j.poly.2016.02.042

The reaction of water-soluble hydroxyl-rich salicylaldehyde Schiff base ligands with the metal salt Cu(OAc)₂·H₂O affords three novel tetracopper complexes via solvothermal method: [Cu₄(H₂L1)₄]·CH

Full text of DOI:10.1016/j.poly.2016.02.042

Polyhedron 110 (2016) 182–187
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Tetracopper complexes with two-mode cubane-like Cu4O4 core
from similar hydroxyl-rich salicylaldehyde Schiff bases: Structure
and magnetic properties
⇑
⇑
Bing Yang, Jiali Pan, Xianggao Meng, Jinge Cao, Yuyi Li, Fengping Xiao , Dongfeng Li
Department of Chemistry, Central China Normal University, Wuhan 430079, Hubei, China1
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of water-soluble hydroxyl-rich salicylaldehyde Schiff base ligands with the metal salt
Cu(OAc)2ꢀH2O affords three novel tetracopper complexes via solvothermal method:
[Cu4(H2L1)4]ꢀCH3OH(1), [Cu4(HL2)2(Py)2(OAc)2](2), [Cu4(HL3)2(Py)2(OAc)2](3). The X-ray crystal
structures reveal the cubane Cu4O4 for complex 1 with 3-alkoxo bridges and quasi-stepped cubane
Received 10 December 2015
Accepted 26 February 2016
Available online 4 March 2016
l
Cu4O4 for 2 and 3 bearing two central copper atoms bridged by two alkoxy groups and two peripheral
copper atoms bridged with central copper atoms by one another alkoxy oxygen. Temperature-dependent
magnetic measurements indicate that the dominant ferromagnetic interactions among metal ions within
the cubic core of 1 with J1 = +27.44 cmꢁ1, J2 = ꢁ0.21 cmꢁ1 (g = 2.1157) while there are antiferromagnetic
interactions between two metal centers in 3 with J1 = ꢁ268 cmꢁ1, J2 = ꢁ297 cmꢁ1 (g = 2.068).
Ó 2016 Published by Elsevier Ltd.
Keywords:
Tetracopper complexes
Hydroxyl-rich Schiff base
Crystal structures
Hydrogen bonding
Magnetic property
1. Introduction
reported besides of pentanuclear Mn complexes with similar
ligands from Reedijk and co-workers [15a,16,17].
Multinuclear transition-metal complexes have attracted intense
interests these years due to their interesting architectures and pos-
sible utility in many fields such as catalysis, clathrate separation,
molecular sieving, magnetochemistry and bioinorganic chemistry
[1–5]. Among them, multinuclear copper(II) complexes, especially
the cubane-like Cu4O4 complexes, have been studied from a mag-
netic structure point of view with experimental and theoretical
approaches [6,7]. Polydentate ligands bearing endogenous bridging
and chelating groups are usually adopted to effectively encapsulate
metal ions and promote intramolecular superexchange interac-
tions [8–10]. For example, hydroxy-rich polydentate Schiff-base
ligands synthesized via 1,3-diamino-2-propanol/or 2-amino-1,3-
propanediol are extensively utilized to bridge metal ions for the
preparation of polynuclear complexes with various core structures
including Cu, Mn, Fe, Ni and even heteronuclear of Co and Fe, Cu
and Mo [11–15]. Some multinuclear complexes constructed by sal-
icylaldehyde Schiff base possessing alkoxyl groups have also been
Inspired by these work mentioned above, three tetranuclear
cupric complexes [Cu4(H2L1)4]ꢀCH3OH(1), [Cu4(HL2)2(Py)2]ꢀ
(OAc)2(2) and [Cu4(HL3)2(Py)2]ꢀ(OAc)2(3) have been solvother-
mally synthesized via the reaction of copper salt and relative Schiff
base ligands (H4L1 = 2-((1,3-dihydroxy-2-(hydroxymethyl)propan-
2-ylimino)methyl)phenol), H4L2 = 2-((1,3-dihydroxy-2-(hydrox-
ymethyl)propan-2-ylimino)methyl)-4-chlorophenol, H4L3 = 2-((1,
3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino)methyl)-4-bro-
mophenol) (Scheme 1) in ethanol.
2. Results and discussion
2.1. Synthesis and characterization
The pentadentate ligands H4L1-3 were synthesized via amine-
aldehyde condensation of salicylaldehyde/or its derivatives with
OH
N
OH
OH
OH
⇑
Corresponding authors at: Department of Chemistry, Central China Normal
University, 152 Luoyu Road, Hongshan District, 430079 Wuhan, China. Fax: +86 027
67862900.
X
E-mail addresses: fpxiao@mail.ccnu.edu.cn (F. Xiao), Lidf@mail.ccnu.edu.cn
X=H, H4L1; Cl, H4L2; Br, H4L3
(D. Li).
1
http://www.chem.ccnu.edu.cn.
Scheme 1. The ligands: X = H, H4L1; Cl, H4L2; Br, H4L3.
http://dx.doi.org/10.1016/j.poly.2016.02.042
0277-5387/Ó 2016 Published by Elsevier Ltd.

B. Yang et al. / Polyhedron 110 (2016) 182–187
183
2-amino-2-hydroxymethyl-propane-1,3-diol(Tris) in ethanol. The
reactions of these ligands and 3 equiv of Cu(OAc)2ꢀH2O in the
presence of pyridine give two kinds of Cu4O4 complexes 1–3.
quasi-square-plane and the axial coordination site is occupied by
the rest of 3-O(Cu1–O1 = 1.9015(10), Cu1–N1 = 1.9224(12),
Cu1–O2 = 1.9428(10), Cu1–O2#3 = 1.94239(10), and Cu1–O2#1
2.5407(10) Å). In the other words, the metal centers linked by a
3-alkoxo-oxygen atom of the Schiff base to develop a cubic
l
=
l
2.1.1. Crystal structure of [Cu4(H2L1)4]ꢀCH3CH2OH (1)
Cu4O4 arrangement of the metal and oxygen atoms. More bond
lengths and angles were provided in Table S1.
Complex 1 is composed by Cu(II), deprotonation dianionic back-
bone ligand H2L1 and one lattice ethanol molecule without second
ligand with the rate of them is 4:4:1. But the crystals will become
gradual efflorescence at room temperature when they are out of
the mother liquor due to the slow loss of the lattice solvent mole-
cules (Fig. S1).
Additionally, each ligand in 1 has two uncoordinated hydroxyl
groups to form much abundant hydrogen bonds. One molecular
interacts with four neighbors via eight hydrogen bonds between
uncoordinated O atoms to form a tetrahedral structure (Fig. 2a).
The Oꢀ ꢀ ꢀO distances of O4–H4Aꢀ ꢀ ꢀO1 and O3–H3Aꢀ ꢀ ꢀO4 are
2.659(1) and 2.712(1) Å, respectively, and bond angles of them
are 174(3)° and 177(2)° (Table S2). Then the tetrahedral structure
interacts with neighbors to form 3-D hydrogen bond networks. It is
noteworthy that if each cubic tetracopper molecule was
considered as a hydrogen-bonded connected node, the final 3D
hydrogen-bonded network in complex 1 can be topologically
simplified as an uninodal 4-connected net with the long and
short schläfli symbol of 66 and 62.62.62.62.62.62, respectively
(Fig. 2b).
As shown in Fig. 1, complex 1 is cubic tetracopper molecule
with the distances of Cuꢀ ꢀ ꢀCu in ‘‘4 + 2” class (Cu1ꢀ ꢀ ꢀCu1#2
=
Cu1ꢀ ꢀ ꢀCu1#3 = Cu1#ꢀ ꢀ ꢀCu1#3 = Cu1#1ꢀ ꢀ ꢀCu1#2 = 3.1268(3),
Cu1ꢀ ꢀ ꢀ
Cu1#1 = Cu1#2ꢀ ꢀ ꢀCu1#3 = 3.5491(3) Å (Symmetry Code #1: 2 ꢁ x,
0.5 ꢁ y, z, #2: 0.75 ꢁ y, 1.25 ꢁ x, 2.25 ꢁ z, #3: 1.25 ꢁ y, 0.75 ꢁ x,
2.25 ꢁ z)) (Table S3) and each Cu(II) center is a five-coordinated
distorted square-pyramidal coordination sphere (4 + 1) with four
O atoms and one N atom from H2L1. Among of them, one
phenol-O atoms, two bridging
l3-alkoxo- and one N atom form a
2.1.2. Crystal structure of [Cu4(HL2)2(Py)2(OAc)2](2)
Complex 2 is a stable tetracopper coordination complex with
the ratio of Cu (II) ions:ligand HL2:acetate:pyridine = 4:2:2:2 out
of the solution at room temperature (Figs. 3 and S1). And single-
crystal X-ray analysis reveals that it is a chair-like/or stepped
tetranuclear copper(II) structure although synthesis of it is similar
to 1, in which four copper(II) cations are fixed by two trianionic
HL2 and two acetate ions. In 2, two Cu2+ ions are adopted in differ-
ent types of coordination environments: the Cu1 atom displays
square planar geometry (3 + 1) with three oxygen atoms O1 and
O2 from Schiff base ligand and O5 from bridging
l
2-OAcꢁ, one
nitrogen atom N3 from HL2 (Cu1–O1 = 1.905(2), Cu1–O2 = 1.931
(2), Cu1–O5 = 1.952(2), and Cu1–N3 = 1.948(2) Å), and the Cu2
center is a five-coordinated distorted square-pyramidal sphere.
The centrosymmetric Cu2 and Cu2# are bridged by two
l2-alkoxo
oxygen atoms (O3 and O3#) which associate with the other coordi-
nated oxygen (O2 and O6/O2# and O6#) to generate a square-plane
(Cu2–O3# = 1.920(2), Cu2–O2 = 1.941(2), Cu2–O3 = 1.946(2), and
Cu2–O6 = 1.982(2) Å (Symmetry Code #: ꢁx, 1 ꢁ y, 1 ꢁ z)); and
the N2 atom of the pyridine occupying the axial site (Cu2–N2 =
2.240(3) Å) results to square-pyramidal sphere (Table S1).
Fig. 1. ORTEP diagram of 1 (in order to clear, the ethanol has been deleted).
Fig. 2. (a) Packing structure by hydrogen bonds and (b) topological simplified diagram of the 3D hydrogen-bonded network, in which the tetranuclear copper(II) unit was
shown as purple balls. (Colour online.)

184
B. Yang et al. / Polyhedron 110 (2016) 182–187
Fig. 3. ORTEP diagram of 2.
Fig. 5. ORTEP diagram of 3.
Comparing to 1, there is only one uncoordinated hydroxyl
group in 2, which results to less hydrogen bonds (Fig. 4). Every
molecule interacts with two neighbors to form hydrogen-bonded
one-dimensional (1-D) chains via intermolecular hydrogen-bond-
ing interactions between coordinated phenol O atom and hydroxyl
O atom. The Oꢀ ꢀ ꢀO distance within the chains is 2.8475(35) Å and
bond angle of O4–H4ꢀ ꢀ ꢀO1a is 148.759(3)° (Symmetry Code a:
ꢁ1 + x, y, z) (Table S2).
2.1.3. Crystal structure of [Cu4(HL3)2(Py)2(OAc)2](3)
The single-crystal structure of complex 3 is similar to 2 (Fig. 5)
with distance of Cu1ꢀ ꢀ ꢀCu2 = 2.8855(8), Cu2ꢀ ꢀ ꢀCu2# = 3.0158(10),
Cu1ꢀ ꢀ ꢀCu2# = 4.7796(14) and Cu1ꢀ ꢀ ꢀCu1# = 7.2970(9) Å (Table S3)
and the same packing pattern in addition to intermolecular hydro-
gen-bonded 1D chain (Fig. S2).
2.2. Electronic spectra
Fig. 6. UV–Vis spectra for complexes 1–3 in ethanol.
The absorption spectra of 1 and 2 show one weak band centered
at 360 and 380 nm, respectively (Fig. 6), which can be attributed to
alkoxido- and/or phenoxido-to-copper(II) ligand-to-metal charge-
transfer (LMCT) transition [18], while there is no obvious absorp-
tion for 3 maybe due to the low dissolubility of it in ethanol. The
intense absorption band observed below 250 nm and the shoulder
band from 250 to 300 nm should be correlated to the intra-ligand
charge-transfer transitions involving the entire conjugation system
2.3. Magnetic properties
For complexes 1 and 3 magnetic susceptibility measurements
were performed for air-dried powdered samples in the tempera-
ture range from 2 to 300 K at an applied field of 1000 Oe. As shown
in Fig. 7, the
v
mT product of complex 1 is 1.811 cm3 K molꢁ1 at
of ligand (p ?
p⁄) associated with C@N linkages (n ? p⁄). Unfortu-
room temperature which is obviously higher than the value
expected for four magnetically isolated copper(II) ions (1.5 cm3
K molꢁ1 for SCu = 1/2, g = 2). With the lowering of the temperature,
nately, no low intensity band above 450 nm belonged to the d–d
transition of the copper(II) ion has been observed like the litera-
tures [19].
the
vmT value increases continuously to reach a maximum of
Fig. 4. Self-assembly of the complex 2 via hydrogen bonds into an 1D chain.

B. Yang et al. / Polyhedron 110 (2016) 182–187
185
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
2.3
2.2
2.1
2.0
1.9
1.8
1.0
0.8
0.6
0.4
0.2
0.0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Cu
J2
J1
Cu
J1
J1
J2
Cu
Cu
J1
J1
Cu
J2
Cu
J1
Cu
Cu
0
50
100
150
200
250
300
0
50
100
150
200
250
300
T(K)
MT vs. T and vM vs. T (inset) for complex 3 in the temperature range
T(K)
MT vs. T and vM vs. T (inset) for complex 1 in the temperature range
Fig. 8. Plots of
of 1.8–300 K.
v
Fig. 7. Plots of
of 1.8–300 K.
v
2.23 cm3 K molꢁ1 around 14 K. Both of them suggest that the total
spin ground state of ST = 2 with the four spins (S = 1/2) presents
dominant ferromagnetic interactions within the cubic unit. Then,
the zero-field splitting effects (ZFS) of the S = 2 ground state cause
copper atoms are bridged by two alkoxy bridges while the
peripheral copper atoms are bridged by one alkoxy oxygen [24].
The conventional Hamiltonian (Eq. (2)) can be adopted to the curve
fitting of magnetic property for interaction of the tetracopper units.
the
imum [20]. And the temperature-dependence magnetic suscepti-
bilities obeys the Curie–Weiss law
v
mT drops suddenly to 1.78 cm3 K molꢁ1 at 2 K from the max-
H ¼ ꢁJ1ðS1S2 þ S3S4Þ ꢁ J2S2S3
ð2Þ
vm = C/(T ꢁ h) with a Weiss
Then the values giving the best fit (2–300 K) for
3
are,
The
constant h = 1.79 K and a Curie constant C = 4.15 cm3 K molꢁ1, indi-
cating also a ferromagnetic interaction between the metal centers.
The crystal structure reveals that the Cu4O4 core of 1 belongs to
the ‘‘cubane [4 + 2] class” structure with four short and two long
Cuꢀ ꢀ ꢀCu distances [6] and it belongs to C4h point group. So, the spin
Hamiltonian can be considered as two different exchange con-
stants, J1 and J2, between the spin Si. Then, the following spin
Hamiltonian (Eq. (1)) has been used.
J1 = ꢁ268 cmꢁ1
,
J2 = ꢁ297 cmꢁ1
,
g = 2.068, R = 7.8 * 10ꢁ7
.
values of the exchange constants J1 and J2 state also strong
antiferromagnetic interactions in this stepped cubic Cu4O4 core
due to the large Cu–O–Cu angles with
\ Cu1–O2–Cu2 =
96.169(14)° and \ Cu2–O3–Cu2# = 101.857(15)° [24,25].
3. Conclusions
In this paper, we present the synthesis and crystal structure of
three tetranuclear Cu-containing complexes in two different kinds
of mode with similar hydroxyl-rich salicylaldehyde Schiff base
ligands. Complex 1 exhibits the ‘‘cubane [4 + 2] class” Cu4O4 struc-
ture with dominant ferromagnetic interactions among four metal
centers. And rich hydrogen bonds from the uncoordinated hydro-
xyl groups result to 3D network with a hexagon topological struc-
ture. The four metal ions within 2 and 3 are linked by two
trianionic HL2 and HL3 respectively, forming a stepped structure
with square-planar and distorted square-pyramidal geometries of
copper centers. Different from 1, the molar paramagnetic suscepti-
bilities vm are corrected by the antiferromagnetic interactions
among the multinuclear Cu atoms in 3, and less hydrogen bonds
form 1D chain only.
H ¼ ꢁJ1ðS1S2 þ S2S3 þ S3S4 þ S1S3Þ ꢁ J2ðS1S3 þ S2S4Þ
In which, S1, S2, S3, and S4 are the spin operators
(S1 = S2 = S3 = S4 = 1/2). A good agreement with the experimental
ð1Þ
data for complex
1 is obtained with the parameters: J1 =
+27.44 cmꢁ1, J2 = ꢁ0.21 cmꢁ1, g = 2.1157, R = 1.0 * 10ꢁ5. The domi-
nant ferromagnetic interaction of 1 from the J1 which depends
mainly on the geometry including the value of the Cu–O–Cu angle
and the relative orientation of the magnetic orbitals [6c,19b,21],
although J2 exhibits a weak antiferromagnetic coupling. These
values of exchange parameters in fit not exactly same with the
ones previously reported on the [Cu4O4] cubane series with
similar ligands because of the different angles of Cu–O–Cu and
distances of Cuꢀ ꢀ ꢀCu [6,22].
The magnetic property of 3 is shown in Fig. 8 with vm versus T
and
v
vmT versus T. Different from 1, all of data including the lower
mT value of 1.21 cm3 K molꢁ1 at room temperature, the continu-
4. Experimental
ous decreasing of vmT with lowering temperature and the negative
Weiss constant (C = 1.14 cm3 K molꢁ1, h = ꢁ18.4 K) suggest antifer-
romagnetic interactions among the stepped cubane unit, even
there are a small amount of paramagnetic impurities indicated
from the increasing of the vm at low temperature. At the same
4.1. Materials and measurements
The starting materials were purchased from commercial
sources and used without further purification. 1H NMR spectra
were obtained at a Varian Mercury 400 MHz spectrometer. Chem-
ical shifts are reported in d relative to TMS. IR spectra were mea-
sured as KBr pellets on a Perkin-Elmer spectrometer in the range
of 400–4000 cmꢁ1. Elemental analyses were performed on a Vario
EL111 CHNSO elemental analytical instrument for C, H, N and
Perkin-Elmer OPTIMA 2000 DV Optical Emission Spectrometer
for Cu. Powder X-ray diffraction were recorded by Y-2000.
time, the
vmT values at low-temperature are nearly consist with
an ST = 0 ground state, which are confirmed by the observed
change of the vm values at low temperatures [23].
For long distances of Cu1ꢀ ꢀ ꢀCu2 and Cu1ꢀ ꢀ ꢀCu1# in complex 3,
the magnetic exchange in the stepped unit can be modeled as
Cu(S1)–J1–Cu(S2)–J2–Cu(S3)–J1–Cu(S4), here, J1 and J2 are expected
to be different due to the two types of copper atoms: the central

186
B. Yang et al. / Polyhedron 110 (2016) 182–187
Table 1
4.2. Preparation
Crystallographic data of complexes 1–3.
The ligands and their relative complexes have been synthesized
according to the route in the Scheme 2.
Complex
1
2
3
Empirical
formula
C
46H58Cu4
C18H19ClCu2N2O6 C36H38Br2Cu4N4O12
N4O17
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
1193.12
100(2)
tetragonal
I4(1)/a
17.0466(10)
17.0466(10)
16.7448(10)
90°
90°
90°
4865.8(5)
4
521.88
296(2)
triclinic
1132.68
296(2)
4.2.1. Preparation of H4L1
A
mixture of tris(hydroxymethyl)methyl aminomethane
triclinic
(1.215 g, 10 mmol) and salicylaldehyde (1.220 g, 10 mmol) in
anhydrous ethanol (30 mL) was heated at 100 °C for about 3 h.
Then the white crystals of ligand H4L1 were obtained after remov-
ing the solvent in approximate 88% yield. 1H NMR (400 MHz,
DMSO-d6, 25 °C, d ppm): d = 14.51 (1H, s, ArOH), 8.55(1H, s, CH@N),
7.41 (1H, d, o-ArH), 7.29 (1H,t, p-ArH), 6.08 (2H, t, m-ArH), 4.72,
ꢀ
ꢀ
P1
P1
8.4161(11)
10.7638(14)
11.3804(15)
102.776(2)
101.360(2)
99.618(2)
961.5(2)
2
8.389(3)
10.935(3)
11.349(4)
103.431(4)
100.988(5)
99.376(4)
970.3(5)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
(3H, t, -OH), 3.6 (6H, d, ꢁCH2). IR (KBr):
m = 3326(s) 2809 (m),
1643 (s), 1477 (m), 1052 (m) cmꢁ1
.
Z
l
(mmꢁ1
)
1.802
2.390
4.290
Goodness-of-fit
(GOF) on F2
Final R indices
[I > 2d(I)]
1.057
1.164
1.073
4.2.2. Preparation of H4L2
H4L2 was synthesized similar to ligand H4L1 with the reaction
of tris(hydroxymethyl)methyl aminomethane (1.215 g, 10 mmol)
and 5-Cl-salicylaldehyde (1.575 g, 10 mmol) in approximate 95%
yield. 1H NMR (400 MHz, DMSO-d6, 25 °C, d ppm): d = 14.68 (1H,
s, ArOH), 8.53 (1H, s, CH@N), 7.51 (IH, d, o-ArH),7.28 (1H, t
p-ArH), 6.75 (1H, d, m-ArH), 4.79 (3H, t, –OH), 3.61(6H, d, –CH2).
R1 = 0.0259,
wR2 = 0.0717
R1 = 0.0359,
wR2 = 0.1089
R1 = 0.0438,
wR2 = 0.1224
radiation (k = 0.71073 Å); and unit cell dimensions were obtained
with least-squares refinements. The program Bruke SAINT7 was used
for reduction date. All structures were solved by direct methods
using SHELXS-97 (Sheldrick, 1990) and refined with SHELXL-97
(Sheldrick, 1997) [26]; non-hydrogen atoms were located in
successive difference Fourier syntheses. The final refinement was
performed by full matrix least-squares methods with anisotropic
thermal parameters for non-hydrogen atoms on F2. The hydrogen
atoms were treated by a mixture of independent and constrained
refinement. Crystallographic data and experimental details for
structural analyses are summarized in Table 1.
IR (KBr):
m = 3391 (s), 2928 (w), 2827 (w), 1634 (s), 1541 (m),
1043 (s) cmꢁ1
.
4.2.3. Preparation of H4L3
H4L3 was synthesized via similar the reaction of tris(hydrox-
ymethyl) methyl aminomethane (1.215 g, 10 mmol) and 5-Br-sali-
cylaldehyde (2.009 g, 10 mmol) in approximate 85% yield. 1H NMR
(400 MHz, DMSO-d6, 25 °C, d ppm): d = 14.70 (1H, s, ArOH), 8.52
(1H, s, CH@N), 7.63 (1H, d, o-ArH), 7.36 (1H,t, p-ArH), 6.72 (1H,
d, m-ArH), 4.79(3H, t, –OH), 3.61(6H, d, –CH2). IR (KBr):
(s), 2882 (w), 1625 (s), 1533 (m), 1320 (w) 1172 (w), 1052 (m)
cmꢁ1
m = 3400
Acknowledgements
.
Financial support from the National Science Council of the
Republic of China (NSFC 21101067) and the Self-determined
Research Funds of Central China Normal University from the
Colleges’ Basic Research and Operation of Ministry of Education,
China (No. CCNU14A05013) is gratefully acknowledged.
4.2.4. Preparation of complexes 1–3
Similar method has been used to prepare complexes 1–3 with
the ratio of backbone ligand:Cu(OAc)2ꢀH2O:pyridine = 1:3:2 in
ethanol (8 ml) which were heated in a Teflon-lined at 100 °C for
12 h via programmed controlling temperature with 20 °C/h. Then
obtain dark-green crystals for X-ray diffraction and the crystal-
phase purity of the bulk samples were evidenced by the consis-
tence of theoretical and experimental PXRD patterns (see Fig. S3).
Elemental Anal. for complexes: Calc. for 1 (C46H58Cu4N4O17): Cu,
21.30; C, 46.31; H, 4.90; N, 4.70. Found: Cu, 21.19; C, 46.19; H,
4.91; N, 4.69%; 2 (C18H19ClCu2N2O6): Cu, 24.35; C, 41.42; H, 3.67;
N, 5.37. Found: Cu, 24.48; C, 41.52; H, 3.65; N, 5.35%; 3 (C36H38 Br2-
Cu4N4O1): Cu, 22.44; C, 38.17; H, 3.38; N, 4.95. Found: Cu, 24.34; C,
38.07; H, 3.39; N, 4.80%.
Appendix A. Supplementary data
CCDC 1440270, 1440285 and 1440347 contains the supplemen-
tary crystallographic data for complexes 2, 3 and 1 respectively.
These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Sup-
plementary data associated with this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.poly.2016.02.042.
4.3. Crystal structure determination
Single-crystal X-ray diffraction measurement for complexes
1–3 were carried out on a Bruker Smart APEX CCD-based diffrac-
tometer equipped with a graphite crystal monochromator for data
collection at 292(2) K/or 100 K. The determinations of unit cell
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parameters and data collections were performed with Mo K
a
OH
1(x=H)
CHO
OH
OH
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2(x=Cl)
3(x=Br)
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NH2
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Scheme 2. The synthesis of the ligands (X = H, H4L1; Cl, H4L2; Br, H4L3) and the
relative coordinated multinuclear complexes 1–3.

B. Yang et al. / Polyhedron 110 (2016) 182–187
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