Three asymmetric Salamo-type copper(II) and cobalt(II) complexes: Syntheses, structures and fluorescent properties

Article abstract of DOI:10.1016/j.poly.2016.12.010

Three new supramolecular complexes, [Cu(HL¹)] (1), [Cu(L²)H₂O] (2) and [Co₂(L²)₂]·3CH₃CN (3), were designed and synthesized by the reaction of 5-hydroxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H₃L¹) with Cu(II) acetate hydrate (for 1); and 6-methoxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H₂L²) with Cu(II) acetate hydrate (for 2) and cobalt(II) acetate tetrahydrate (for 3), respectively, and were characterized by element analyses, X-ray crystallography, FT-IR, UV–Vis and fluorescence spectra. Complex 1 is mononuclear and tetra-coordinated and adopts a distorted square-planar geometry, likewise, complex 2 is mononuclear and penta-coordinated with a square-pyramidal geometry, however, complex 3 is dinuclear with the two Co(II) atoms having the same coordination environments and adopt a trigonal bipyramidal geometry. These self-assembling complexes form different dimensional supramolecular structures through inter- and intramolecular hydrogen bonds. Meanwhile, photophysical properties of the three complexes have also been discussed. Furthermore, the fluorescence behaviors of the two Cu(II) complexes in DMF are discussed.

Full text of DOI:10.1016/j.poly.2016.12.010

Polyhedron 123 (2017) 305–315
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Three asymmetric Salamo-type copper(II) and cobalt(II) complexes:
Syntheses, structures and fluorescent properties
⇑
Yin-Juan Dong, Xiu-Yan Dong, Wen-Kui Dong , Yang Zhang, Li-Sha Zhang
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, PR China
a r t i c l e i n f o
a b s t r a c t
1
2
2
Article history:
Three new supramolecular complexes, [Cu(HL )] (1), [Cu(L )H O] (2) and [Co (L ) ]ꢀ3CH CN (3), were
2
2
2
3
Received 11 October 2016
Accepted 7 December 2016
Available online 18 December 2016
0
0
0
designed and synthesized by the reaction of 5-hydroxy-4 ,6 -dibromo-2,2 -[ethylenediyldioxybis
L ) with Cu(II) acetate hydrate (for 1); and 6-methoxy-4 ,6 -dibromo-
,2 -[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H
1
0
0
(
nitrilomethylidyne)]diphenol (H
3
0
2
2
2
L ) with Cu(II) acetate hydrate (for 2) and
cobalt(II) acetate tetrahydrate (for 3), respectively, and were characterized by element analyses, X-ray
crystallography, FT-IR, UV–Vis and fluorescence spectra. Complex 1 is mononuclear and tetra-coordi-
nated and adopts a distorted square-planar geometry, likewise, complex 2 is mononuclear and penta-
coordinated with a square-pyramidal geometry, however, complex 3 is dinuclear with the two Co(II)
atoms having the same coordination environments and adopt a trigonal bipyramidal geometry. These
self-assembling complexes form different dimensional supramolecular structures through inter- and
intramolecular hydrogen bonds. Meanwhile, photophysical properties of the three complexes have also
been discussed. Furthermore, the fluorescence behaviors of the two Cu(II) complexes in DMF are
discussed.
Keywords:
Asymmetric Salamo-type ligand
Complex
Synthesis
Crystal structure
Fluorescence property
Ó 2016 Elsevier Ltd. All rights reserved.
1
. Introduction
The coordination chemistry of transition metal complexes with
tetraalkylene, or longer alkylene chains) [29]. The chain length of
the Salen complexes is one of the important factors that affect
the electrochemical and spectroscopic properties of the central
metal. Photoluminescence has been one of the highlights in mod-
ern coordination chemistry owing to potential applications in
luminescent devices [30], which have been also observed for
Salen-type compounds and their transition metal complexes [31–
35]. In recent years, Cu(II) complexes with Salen-type ligands have
drawn much attention for their photoluminescent characteristics
[36,37].
Salen-type ligands has achieved a considerable attention in the last
decades [1–9], because of their redox-chemistry, unusual magnetic
and structural properties, as well as their usage as models for met-
alloproteinase [10–18], and catalysts for oxidation and polymeriza-
tion reactions [10,13,14,19]. It is important to introduce suitable
functional groups into the organic moiety of the ligands in order
to improve or tune the properties of these metal complexes
[
20–28]. Of particular is the steric and electronic effects of the sub-
Selective syntheses of these asymmetrical ligands is important
because electronic and steric effects of the ligands on Salen-
metal-assisted catalysis may be controlled by the introduction of
different substituents into the two benzene rings [38]. It has been
reported that metal complexes derived from asymmetrical Sal-
amo-type ligands sometimes exhibit better enantioselectivities
when compared with their symmetric counterparts [39].
In this paper, we describe the syntheses, spectroscopic charac-
terization and fluorescent properties of the newly designed asym-
stituents of salicyclic and aniline rings which are the key factors in
various reactions such as the epoxidation, symmetrical or asym-
metrical Salen-based catalysis, polymerization catalysis and the
electron transfer reactivity of the metal atoms with ligands bearing
bulky tert-butyl substituents. For instance, symmetrical or asym-
metrical Salen catalysts and electron-donating and -withdrawing
groups are utilized to fine tune the nonlinear optical properties
of the Cu(II) complexes of the Salen analogues. There are also some
reports on the modification of the methylene chain length of the
Salen complexes, including longer Salen analogues (trialkylene,
1
2
metric Salamo-type ligands, H
(II) complexes.
3 2
L and H L and their Cu(II) and Co
⇑
Corresponding author.
E-mail address: dongwk@126.com (W.-K. Dong).
http://dx.doi.org/10.1016/j.poly.2016.12.010
277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
0

3
06
Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
O
O
N
O
NH2
O
N
O
N
O
OH
H2N O
O NH2
R1
R2
Br
OH
Br
OH
Br
OH HO
Br
Br
Br
R2
R1
1
H3L : R1 = OH, R2 = H.
2
H2L : R2 = OCH3, R1 = H.
Scheme 1. The synthetic route of two asymmetric Salamo-type ligands.
1
2
2
. Experimental
.1. Materials and instruments
,5-Dibromo-2-hydroxybenzaldehyde, 2,4-dihydroxybenzalde-
2.2. Syntheses of H
3
L and H
2
L
2
The synthetic route to two asymmetric Salamo-type ligands
1
2
H
3
L and H
1,2-Bis(aminooxy)ethane was synthesized according to
reported methods [36,40]. Yield, 78.4%. Anal. Calc. for C
C, 26.08; H, 8.76; N, 30.42. Found: C, 25.96; H, 8.90; N, 30.35%.
2
L is shown in Scheme 1.
3
hyde and 2-hydroxy-3-methoxybenzaldehyde were purchased
from Aldrich and used without further purification. Other reagents
and solvents were analytical grade reagents from Tianjin Chemical
Reagent Factory.
C, H, and N analyses were obtained using a GmbH VarioEL V3.00
automatic elemental analysis instrument. Elemental analyses for
metals were detected by an IRIS ER/SWP-1 ICP atomic emission
spectrometer. FT-IR spectra were recorded on a VERTEX70 FT-IR
spectrophotometer, with samples prepared as KBr (500–
2 8 2 2
H N O :
Initially, the intermediate compound, monooxime 2-hydroxy-
3,5-dibromobenzaldehyde O-(2-(aminooxy)ethyl) oxime was pre-
pared by the reaction of 3,5-dibromo-2-hydroxybenzaldehyde
(4 mmol) in ethanol (80 mL) with excess 1,2-bis(aminooxy)ethane
(8 mmol) in ethanol (60 mL), and was heated at 50–55 °C for 6 h.
The obtained mixture contained the desired monooxime and a
small amount of dioxime. The pure monooxime was obtained after
ꢁ1
ꢁ1
4
000 cm ) and CsI (100–500 cm ) pellets. UV–Vis absorption
silica gel chromatographic (SiO
2
, chloroform/ethyl acetate, 20:1)
and fluorescence spectra were recorded on a Shimadzu UV-2550
spectrometer and Perkin-Elmer LS-55 spectrometer, respectively.
H NMR spectra were determined by German Bruker AVANCE
DRX-400 spectrometer. Melting points were obtained by the use
of an X4 microscopic melting point apparatus made in Beijing
Taike Instrument Limited Company and the thermometer was
uncorrected. X-ray single-crystal structures were determined on
a Bruker Smart APEX CCD area detector.
separation of the crude product, and was obtained as stable crys-
tals. Yield, 61.6%. m.p. 100–102 °C. Anal. Calc. for C
C, 30.54; H, 2.85; N, 7.91. Found: C, 30.59; H, 2.79; N, 7.87%.
NMR (400 MHz, CDCl
9
H
10Br
2
N
2
O
3
:
H
1
1
3
): 3.98 (t, J = 4.5 Hz, 2H), 4.39 (t, J = 4.5 Hz,
2H), 5.54 (brs, 2H), 6.89 (d, J = 9.0 Hz, 1H), 7.36 (dd, J = 9.0,
2.5 Hz, 1H), 8.12 (s, 1H), 9.85 (s, 1H).
Finally, the asymmetrical Salamo derivative product, 5-
0
0
0
hydroxy-4 ,6 -dibromo-2,2 -[ethylenediyldioxybis(nitrilomethyli-
Table 1
Crystal data and structure refinement for complexes 1, 2 and 3.
CCDC deposit number
Empirical formula
Formula weight
T (K)
1433366
12Br
535.64
293(2)
0.71073
1433367
16Br
567.67
298(2)
0.71073
1433368
4 2 7 10
37Br Co N O
1213.27
293(2)
C
16
H
2
CuN
2
O
5
C
17
H
2
CuN
2
O
6
C
40
H
k (Å)
0.71073
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
monoclinic
P 2(1)/c
monoclinic
P 2(1)/c
triclinic
P1ꢀ
16.3506(15)
10.2289(7)
10.7001(11)
92.8420(10)
90.00
104.839(2)
1729.9(3)
4
11.1458(9)
13.6328(12)
13.0070(13)
90
98.9240(10)
90
1952.5(3)
2
1.931
11.8954(14)
14.3538(14)
14.3855(16)
94.5440(10)
104.731(2)
98.8210(10)
2329.4(4)
2
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
3
calc (Mg/m )
2.057
5.913
1.730
4.204
ꢁ
1
(mm
)
5.249
F (000)
1044
1116
1200
Crystal size (mm)
h (°)
0.20 ꢂ 0.11 ꢂ 0.06
0.34 ꢂ 0.32 ꢂ 0.30
0.43 ꢂ 0.23 ꢂ 0.14
2.58–25.01
2.69–25.02
2.55–25.02
Index ranges
Reflections collected
Independent reflections (Rint
Completeness to h = 25.02 (%)
Data/restraints/parameters
Goodness of fit (GOF) on F2
ꢁ19 6 h 6 19, ꢁ12 6 k 6 11, ꢁ12 6 l 6 12
ꢁ9 6 h 6 13, ꢁ16 6 k 6 14, ꢁ15 6 l 6 15
ꢁ14 6 h 6 14, ꢁ12 6 k 6 17, ꢁ17 6 l 6 16
9339
9613
14615
)
3058 (0.0638)
99.9
3058/0/235
1.071
3438 (0.0602)
99.6
3438/0/254
1.034
8203 (0.0861)
99.9
8203/0/573
1.014
R
1
0.0453
0.0451
0.0702
wR
2
[I > 2
r
(I)]
0.0977
0.772 and ꢁ0.777
0.1002
0.843 and ꢁ0.572
0.1236
0.862 and ꢁ0.621
maximum,minimum (e Å 3
)
ꢁ
D
q

Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
307
Fig. 1. Molecular structure of complex 1 with the atom numbering. Thermal ellipsoids are plotted at 30% probability level.
Table 2
Selected bond distances (Å) and bond angles (°) for complexes 1, 2 and 3.
Bond
Distance
Bond
Distance
1.883(5)
Bond
Distance
1.996(6)
1
Cu1–O3
Cu1–N2
1.921(4)
1.920(5)
Cu1–O4
Cu1–N1
2
Cu1–O3
Cu1–O5
1.939(4)
1.941(5)
Cu1–N1
Cu1–N2
1.963(6)
2.028(5)
Cu1–O6
2.240(4)
3
Co1–O3
Co1–O4
Co2–O4
Co2–O9
1.923(8)
2.075(6)
1.992(6)
2.086(6)
Co1–O9
Co1–N2
Co2–N3
1.972(6)
2.081(8)
2.048(8)
Co1–N1
Co2–O8
Co2–N4
2.056(8)
1.908(7)
2.074(9)
Bond
Angle
Bond
Angle
Bond
Angle
1
[
Cu(HL )]
O4–Cu1–N2
O4–Cu1–O3
2
92.4(2)
88.54(19)
O4–Cu1–N1
N2–Cu1–O3
157.6(2)
152.6(2)
N2–Cu1–N1
O3–Cu1–N1
99.1(2)
89.9(2)
[
2
Cu(L )H O]
O3–Cu1–O5
O3–Cu1–N1
O5–Cu1–N1
O3–Cu1–N2
2
87.52(18)
87.7(2)
159.7(2)
176.6(2)
O5–Cu1–N2
N1–Cu1–N2
O3–Cu1–O6
89.2(2)
95.0(2)
91.10(17)
O5–Cu1–O6
N1–Cu1–O6
N2–Cu1–O6
103.29(18)
96.5(2)
90.67(19)
[
Co
2
(L )
2
]ꢀ3CH
3
CN
O3–Co1–O9
O3–Co1–N1
O9–Co1–N1
O3–Co1–O4
O4–Co2–N3
N3–Co2–N4
N3–Co2–O9
120.7(3)
89.7(4)
102.4(3)
100.1(3)
102.4(3)
90.8(4)
O9–Co1–O4
N1–Co1–O4
O3–Co1–N2
O9–Co1–N2
O8–Co2–N4
O8–Co2–O9
N4–Co2–O9
76.3(2)
N1–Co1–N2
O4–Co1–N2
O8–Co2–O4
O8–Co2–N3
O4–Co2–N2
O4–Co2–O9
91.5(3)
81.1(3)
122.8(3)
89.8(3)
125.9(3)
75.6(3)
169.4(4)
110.5(3)
126.7(3)
109.3(3)
101.1(3)
81.4(3)
168.1(4)
dyne)]diphenol (H
,5-dibromobenzaldehyde O-(2-(aminooxy)ethyl) oxime (1 mmol)
in ethanol (20 mL) with appropriate 2,4-dihydroxybenzaldehyde
1 mmol) in ethanol (20 mL), and was heated at 50–55 °C for 5 h
3
L1) was obtained by the reaction of 2-hydroxy-
1H), 7.35 (dd, J = 8.6 Hz, 2.5 Hz, 1H), 8.16 (s, 1H), 8.23 (s, 1H),
3
9.72 (s, 1H), 9.77 (s, 1H), 10.38 (s, 1H).
0
0
The second asymmetrical Salamo-type ligand, 6-methoxy-4 ,6 -
0
(
dibromo-2,2 -[ethylenediyldioxybis(nitrilomethylidyne)]diphenol
1
2
and yielded pale pink H
28 °C. Anal. Calc. for C16
Found: C, 40.60; H, 2.89; N, 5.96%. H NMR (400 MHz, DMSO-
d6): 4.48–4.50 (m, 4H, CH ), 6.88 (d, J = 8.6 Hz, 1H), 6.92 (t,
J = 7.8 Hz, 1H), 6.98 (d, J = 7.8 Hz, 1H), 7.16 (dd, J = 7.8 Hz, 1.5 Hz,
3
L
powder. Yield, 68.3%. m.p. 127–
(H
2
L ) was synthesized according to the analogous method
1
H14Br
N
2 2
O
5
: C, 40.53; H, 2.98; N, 5.91.
described above [37,41]. Yield, 75.2%. m.p. 137–138 °C. Anal. Calc.
for C17 : C, 41.83; H, 3.30; N, 5.74. Found: C, 41.91; H,
3.41; N, 5.66%. H NMR (400 MHz, DMSO-d6, d, ppm) d: 3.92 (s,
3H), 4.46–4.49 (m, 4H, CH ), 6.88 (d, J = 8.6 Hz, 1H), 6.92 (t,
1
H
2 2 5
16Br N O
1
2
2

3
08
Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
J = 7.8 Hz, 1H), 6.96 (d, J = 7.8 Hz, 1H), 7.14 (dd, J = 7.8 Hz, 1.5 Hz,
Co
2
N
7
O
10 ([Co
2
(L
2
)
2
]ꢀ3CH
3
CN): C, 39.60; H, 3.07; N, 8.08; Co, 9.71.
1
9
H), 7.35 (dd, J = 8.6 Hz, 2.5 Hz, 1H), 8.16 (s, 1H), 8.22 (s, 1H),
.75 (s, 1H), 10.36 (s, 1H).
Found: C, 38.98; H, 3.01; N, 8.24; Co, 9.56%.
2.6. X-ray crystal structure determination
2
.3. Synthesis of complex 1
1
2
The single crystals of the complexes [Cu(HL )] (1), [Cu(L )H
2
O]
2
(
2) and [Co
0.20 ꢂ 0.11 ꢂ 0.06 mm ,
2
(L )
2
]ꢀ3CH
3
CN (3) with approximate dimensions of
A solution of Cu(II) acetate hydrate (1.9 mg, 0.01 mmol) in etha-
3
3
1
0.34 ꢂ 0.32 ꢂ 0.30 mm
.43 ꢂ 0.23 ꢂ 0.14 mm , respectively, were placed on a Bruker
Smart 1000 CCD area detector. The diffraction data were collected
using a graphite monochromated Mo K radiation (k = 0.71073 Å)
at 298(2) K, 298(2) K and 293(2) K for 1, 2 and 3, respectively.
The structures were solved by using the program SHELXL-97 and
Fourier difference techniques, and refined by full-matrix least-
and
nol (2 mL) was added dropwisely to a solution of H
0
the color turned dark-green, while the mixture was filtered and
the filtrate allowed to stand at room temperature for about one
month. The solvent was partially evaporated and red-brown pris-
matic crystals suitable for X-ray crystallographic analysis were
3
L
(4.75 mg,
3
0
.01 mmol) in acetone (2 mL) at room temperature. Immediately
a
obtained. Yield, 46.9%. Anal. Calc. for
C
16
H12Br
2
CuN
2 5
O ([Cu
2
1
squares method on F . All hydrogen atoms were added theoreti-
cally. The crystal and experimental data are shown in Table 1.
(
HL )]): C, 35.88; H, 2.26; N, 5.23; Cu, 11.86. Found: C, 35.54; H,
2
.36; N, 5.10; Cu, 11.90%.
3
. Results and discussion
.1. Crystal structures
3.1.1. The crystal structure and supramolecular interactions of [Cu
2
.4. Synthesis of complex 2
3
A solution of Cu(II) acetate hydrate (1.9 mg, 0.01 mmol) in
methanol/acetonitrile (2:1) (3 mL) was added dropwisely to a solu-
tion of H L (4.88 mg, 0.01 mmol) in acetone (2 mL) at room tem-
2
perature. The color of the mixed solution immediately turned
brown, the mixture was filtered and the filtrate allowed to stand
at room temperature for about three weeks. The solvent was par-
tially evaporated and several dark-brown block-like single crystals
2
1
(
HL )], 1
The crystal structure of the Cu(II) complex, 1 is shown in Fig. 1.
The Selected bond distances (Å) and bond angles (°) for the three
complexes are listed in Table 2.
The complex 1 crystallizes in the monoclinic, space group P2(1)/
c with Z = 4. The molecular structure of 1 consists of one Cu(II)
atom and one deprotonated (HL ) unit. In fact, this mononuclear
Cu(II) complex is similar to the previously reported Salen or
Salamo-type complexes [41], for instance, the Cu(II) atoms of [Cu
suitable for X-ray crystallographic analysis were obtained. Yield,
2
5
2
1
3.9%. Anal. Calc. for C17
H
16Br
2 2
CuN O
6
([Cu(L )H
2
O]): C, 35.97; H,
1
2ꢁ
.84; N, 4.93; Cu, 11.19. Found: C, 35.85; H, 2.76; N, 5.23; Cu,
1.26%.
(
2
Salamo)], [Cu(3-MeOSalamo)] (H Salamo = 1,2-bis(salicylide-
2
.5. Synthesis of complex 3
neaminooxy)ethane) [42] and [Cu(PnSalen)] [43] have a square
planar geometry. The coordination geometry around Cu(II) atom
can be best described as a slight distortion toward tetrahedral
geometry from the square planar structure, where the Cu(II) atom
A
solution of cobalt(II) acetate tetrahydrate (2.48 mg,
0
.010 mmol) in methanol (3 mL) was added dropwisely to a solu-
2
tion of H
2
L
(4.88 mg, 0.1 mmol) in acetonitrile (3 mL) at room
2 2
lies in cis-N O cavity by two oxime nitrogen (N1 and N2) atoms
temperature. The color of the solution immediately turned pale
yellow, and the mixture was allowed to stand at room temperature
for about two weeks. After the solvent was partially evaporated,
several brown block-shaped single crystals suitable for X-ray crys-
tallographic analysis were obtained. The crystal was unstable,
and two phenoxo oxygen (O3 and O4) atoms.
In the complex 1, the dihedral angle between the coordination
planes of N1–Cu1–O3 and N2–Cu1–O4 is 34.36(4)°, which is larger
than that of the reported complexes with symmetric Salen-type
bisoxime ligands [44]. This significant enlargement indicates that
1
2ꢁ
easily weathered in the air. Yield, 66.3%. Anal. Calc. for C40
H37Br
4
-
the (HL ) unit has serious distortion probably as a result of its
Table 3
Hydrogen bonding distances (Å) and bond angles (°) for complexes 1, 2 and 3.
D–Hꢀ ꢀ ꢀA
d(D–H)
d(H–A)
d(D–A)
\D–H–A
Type
Symmetry code
1
O5–H5ꢀ ꢀ ꢀO3
C1–H1Aꢀ ꢀ ꢀO3
C13–H13ꢀ ꢀ ꢀO4
C16–H16ꢀ ꢀ ꢀO5
0.82
0.97
0.93
0.93
1.98
2.51
2.6
2.715(6)
3.380(8)
3.521(8)
3.490(8)
149
149
169
162
Inter
Inter
Inter
Inter
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
x, 1/2 ꢁ y, 1/2 + z
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, ꢁ1/2 + y, 1/2 ꢁ z
2.59
2
O6–H6Cꢀ ꢀ ꢀO3
O6–H6Cꢀ ꢀ ꢀO4
O6–H6Dꢀ ꢀ ꢀO5
O6–H6Dꢀ ꢀ ꢀBr1
C11–H11ꢀ ꢀ ꢀO3
C17–H17ꢀ ꢀ ꢀO4
0.85
0.85
0.85
0.85
0.93
0.93
2.1
2.2
2.14
2.82
2.38
2.61
2.837(6)
2.867(7)
2.871(6)
3.380(4)
3.305(8)
3.390(9)
144
135
144
125
172
141
Inter
Inter
Inter
Inter
Inter
Inter
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
x, 3/2 ꢁ y, 1/2 + z
x, 3/2 ꢁ y, ꢁ1/2 + z
3
C17–H17Aꢀ ꢀ ꢀO6
C34–H34Aꢀ ꢀ ꢀO1
C9–H9ꢀ ꢀ ꢀO1
0.96
0.96
0.93
0.97
0.96
0.96
2.59
2.65
2.72
2.63
2.93
2.7
3.521(14)
3.527(1)
3.249(1)
3.220(6)
3.816(11)
3.632(1)
163
152
117
120
154
163
Inter
Inter
Inter
Inter
Intra
Intra
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, 2 ꢁ y, ꢁz
1 ꢁ x, 2 ꢁ y, ꢁz
1 + x, y, z
C19–H19Aꢀ ꢀ ꢀN5
C36–H36Aꢀ ꢀ ꢀBr3
C36–H36Bꢀ ꢀ ꢀO4

Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
309
1
Fig. 2. Supermolecular structures of [Cu(HL )]. (a). View of the 1D chain motif within complex 1 along the c axis; (b) View of the 2D layered motif along the bc plane; (c) Part
of 3D supramolecular network through intermolecular interactions.

3
10
Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
Fig. 3. Molecular structure of complex 2 with the atom numbering. Thermal ellipsoids are plotted at 30% probability level.
asymmetricity. Meanwhile, the dihedral angle between the mean
plane of Cu–O3–C5–C4–C3–N1 and its adjacent phenyl ring is
Cu1–O5, 1.941(5) Å; Cu1–N1, 1.963(6) Å; Cu1–N2, 2.028(5) Å),
and one oxygen atom (O6) of the coordinated water molecule
occupies the axial position (Cu1–O8, 2.240(4) Å). The axial bond
distance Cu1–O6 is longer than all of the others which formed
the basal plane. More typical Cu–O bond length of the apical water
molecule in such square pyramidal molecule is the value of 2.369
9
.30(3)° while Cu–O4–C12–C11–C10–N2 and its adjacent phenyl
ring is 3.61(3)°. Furthermore, the deviation of Cu1 atom from the
coordination plane is 0.046(2) Å while those of the four donor
N1, N2, O3 and O4) atoms from their mean plane are 0.373(3),
2 2
N O
(
ꢁ
0.376(4), ꢁ0.428(3) and 0.432(3) Å, respectively. All show that
2
(2) Å found in [Cu(MeO-Salen)(H O)] [53].
1
2ꢁ
the Salamo-type (HL ) moiety is not planar, but has a twisted
geometry.
Four coordination atoms in the basal plane are deviated slightly
from the mean plane, with N2 and O3 above average by 0.144(3) Å
and 0.163(3) Å, and N1 and O5 below average by 0.148(3) Å and
0.158(3) Å, respectively. Meanwhile, the Cu(II) atom is 0.181(3) Å
displaced from the mean plane. The dihedral angle between the
coordination plane of O3–Cu1–N1 and that of O5–Cu1–N2 is
Notably, there are a large number of intermolecular hydrogen
bonds in the complex 1. The hydrogen bond data are summarized
in Table 3. Complex 1 shows the existence of a weak intramolecu-
lar C1–H1Aꢀ ꢀ ꢀO3 hydrogen bond between the methylene groups
1
2ꢁ
from the O-alkyl chain of (HL ) unit and phenolic oxygen (O3)
atom. The complex monomer links adjacent molecules through
C1-H1AꢀꢀꢀO3 hydrogen bond interactions into an infinite 1D
supramolecular chain along the a-axis (Fig. 2a). Furthermore, this
linkage is further stabilized by three pairs of intermolecular O(5)
2 2
19.77(3)°. In addition, the mean plane (N O ) and sal(1) (2-
hydroxy-3-methoxybenzaldehyde) have a dihedral angle of 18.25
(3)°, and the dihedral angle of sal(2) (3,5-dibromo-2-hydroxyben-
zaldehyde) with the mean plane is 29.65(4)°. These could be attrib-
uted to the asymmetric composition too.
–
H(5)ꢀ ꢀ ꢀO(3), C(13)–H(13)ꢀ ꢀ ꢀO(4) and C(16)–H(16)ꢀ ꢀ ꢀO(5) interac-
tions to form an infinite 2D-layer supramolecular structure
Fig. 2b). Thus, every complex 1 molecule links the other adjacent
The introduction of a coordinated water molecule in complex 2
successfully leads to the assembly of dimer units by intermolecular
hydrogen bonds. As illustrated in Fig. 4a, four intermolecular
hydrogen bonds, O6–H6Cꢀ ꢀ ꢀO3, O6–H6Cꢀ ꢀ ꢀO4, O6–H6Dꢀ ꢀ ꢀO5 and
O6–H6Dꢀ ꢀ ꢀBr1 are formed. One of the water protons -O6H6C of
the coordinated water molecule in complex 2 is hydrogen-bonded
(
molecules into a novel 3D supramolecular network structure
through these intermolecular interactions (Fig. 2c).
to phenolic oxygen atom (O3) and methoxy oxygen atom (O4) of
2
3
H
.1.2. The crystal structure and supramolecular interactions of [Cu(L )
2 2ꢁ
(
L ) unit of the adjacent molecule. The other of water proton -
2
O], 2
O6H6D of the coordinated water molecule is bound to the coordi-
The crystal structure of complex 2 is shown in Fig. 3. The com-
nated phenolic oxygen atom (O5) and the bromo atom (Br1) of the
2
2ꢁ
plex consists of one Cu(II) atom, one (L ) unit and one coordi-
nated water molecule, and crystallizes in the monoclinic, space
group P2(1)/c with Z = 2. X-ray crystallographic analysis of com-
plex 2 reveals a mononuclear structure which is different from
the earlier reported structures of 1:2 [36], 2:2 [45–47], 2:3 [48]
and 2:4 [48] (L: Cu(II)) in the Salamo-type Cu(II) complexes. The
complex 2, [Cu(L )H O] with the Salamo-type ligand H L was
2 2
obtained from methanol/acetonitrile/acetone solution as an aqua
complex, whereas some of the other Salamo [41] and related (Salen
2 2ꢁ
(
L ) unit of the adjacent molecule. Consequently, these hydrogen
bonding interactions have stabilized a pair of the Cu(II) complex
molecules to form a dimer with the nearest Cuꢀ ꢀ ꢀCu distance of
4
.839(4) Å [54]. Moreover, there exists two weak intermolecular
C11–H11ꢀ ꢀ ꢀO3 and C17–H17ꢀ ꢀ ꢀO4 hydrogen bond interactions.
Simultaneously, each complex 2 molecule is connected to adjacent
molecules forming a Zigzag chain along the c-axis (Fig. 4b). Thus,
each dimer molecule links four other molecules into an infinite
2
2
2
D supramolecular network via intermolecular O–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀO
[
49], Saltn [50,51], Salbn [52] etc) complexes had a tetracoordinate
structure without aqua ligands. The value of = 0.28 clearly indi-
and O–Hꢀ ꢀ ꢀBr hydrogen bond interactions (Fig. 4c).
s
cates that the coordination environment of the Cu(II) atom can
be best described as a square-pyramidal topology with the Cu(II)
atom being penta-coordinated. The two phenolic oxygen atoms
3.1.3. The crystal structure and supramolecular interactions of
2
[Co
2
(L )
2
]ꢀ3CH
3
CN, 3
(
O3 and O5) and the two oxime nitrogen atoms (N1 and N2) of
X-ray crystallographic analysis reveals that the Co(II) dimer
2
2ꢁ
2 2ꢁ
the (L ) unit constitute the basal plane (Cu1–O3, 1.939(4) Å;
consists of two Co(II) atoms, two deprotonated (L ) units and

Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
311
Fig. 4. Supermolecular structures of complex 2. (a) A dimeric unit formed by intermolecular hydrogen bonds. (b) View of the 1D chain motif within the complex along the c
axis; (c) View of the 2D-layered motif along the bc plane.
three uncoordinated acetonitrile molecules (Fig. 5). The complex 3
[55,57,58] and 4:8 [38] (L: Co(II)). The Co1 atom has a trigonal-
bipyramidal geometry ( = 0.712), whose axial positions are occu-
ꢀ
s
crystallizes in the triclinic, space group P1 with Z = 2. The structure
2
of complex 3 can be described as two [Co(L )] unit connected by a
pied by the N1 and O4 donor atoms. Three coordinated atoms (O9–
N2–O3) form the basal plane and the Co1 deviates from the mean
plane by 0.170(3) Å. The dihedral angle of O(3)–Co(1)–N(1) and O
diphenoxy-bridge. Two Co(II) atoms sit in the Salamo moiety, two
oxygen atoms (O4 and O9) bridge two Co(II) atoms. To the best of
2
2ꢁ
2 2ꢁ
our knowledge, the novel 2:2 ((L ) : Co(II)) Salamo-type Co(II)
complex is rarely found reported in comparison to the Salamo-type
Co(II) complexes having the structures of 1:1 [55,56], 2:3
(4)–Co(1)–N(2) is 69.92(4)°, which indicates that (L ) unit has
serious distortion probably due to its asymmetricity. The geometry
of Co2 is similar to that of Co1. The value of
s = 0.703 clearly shows

3
12
Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
Fig. 5. Molecular structure of complex 3 with the atom numbering. Thermal ellipsoids are plotted at 30% probability level.
ꢁ
1
that the coordination environment of the Co2 atom is close to trig-
onal bipyramidal geometry in which the axial site is occupied by
O9 and N3 atoms. The dihedral angle between the coordination
plane of O(8)–Co(2)–N(3) and that of O(4)–Co(2)–N(4) is 71.17
observed at 1203, 1230 and 1244 cm for complexes 1, 2 and 3,
respectively. The Ar–O stretching frequencies are shifted to lower
frequencies, indicating that the M–O bonds are formed between
the Cu(II) or Co(II) atoms and oxygen atoms of the phenolic groups.
In addition, infrared spectrum of complex 2 shows the expected
(
4)°. This is different from the reported structures of its analogues
ꢁ1
Cu(Salen) [59] and Cu(Salamo) [41], which form slightly pyrami-
dalized square planar geometries, and could be stabilized by the
intermolecular contacts between copper and oxygen atoms to form
a head-to-tail dimer.
absorption bands at ca. 3415, 1636, and 547 cm which could
be assigned to the coordinated water molecule, as is substantiated
by the crystal structure, indicating the presence of one coordinated
water molecule [57].
The special thing about Co(II) dimer lies in its self-assembly
array linked by intramolecular and intermolecular hydrogen
bonds. As a result of the three uncoordinated acetonitrile, complex
The far-infrared spectra of complexes 1, 2 and 3 were also
obtained in the region 500–100 cm in order to identify frequen-
cies due to the M–O and M–N bonds. The IR spectra of the Cu(II)
ꢁ1
3
supramolecular structure experiences a huge change. The Co(II)
dimer via three intermolecular C(17)–H(17A)ꢀ ꢀ ꢀO(6), C(34)–H
34A)ꢀ ꢀ ꢀO(1) and C(9)–H(9)ꢀ ꢀ ꢀO(1) hydrogen bonds links neighbor-
complexes show1m(Cu–N) and
m(Cu–O) vibration absorption frequen-
ꢁ
ꢁ1
ꢁ1
cies at 511 cm
and 439 cm
for complex 1, 495 cm
and
ꢁ
1
(
423 cm for complex 2, respectively [60], and complex 3 shows
ꢁ1
ing molecules into an infinite 1D chain supramolecular structure
along the c axis (Fig. 6a). Interestingly, an unconnected acetonitrile
molecule provides a hydrogen bond donor and acceptor. Thus, this
linkage is further stabilized by one intermolecular hydrogen bond
C(19)–H(19A)ꢀ ꢀ ꢀN(5) and two pairs of intramolecule hydrogen
bonds C(36)–H(36A)ꢀ ꢀ ꢀBr(3), C(36)–H(36B)ꢀ ꢀ ꢀO(4) to form an infi-
nite 2D supramolecular layered structure (Fig. 6b).
m(Co–N) and m(Co–O) vibration absorption frequencies at 489 cm
ꢁ1
and 446 cm , respectively. As pointed out by Percy and Thornton
[61], the metal–oxygen and metal-nitrogen frequency assignments
are at times very difficult.
3.3. Uv–Vis absorption spectra study
The UV–Vis absorption spectra of the free ligands H
3 2
L1 and H L2
3
.2. FT-IR spectra analysis
and their corresponding complexes 1, 2 and 3 were determined in
ꢁ5
ꢁ1
5
.0 ꢂ 10 mol L DMF solution, and are shown in Fig. 7a and b,
The IR spectra of the free ligands H
3
L1 and H
2
L2 and their corre-
respectively.
sponding Cu(II) and Co(II) complexes exhibit various bands in the
It can be seen that the absorption peaks of the three complexes
1, 2 and 3 are obviously different from those of the free ligands
H L and H L upon complexation. The UV–Vis absorption spectra
3 2
ꢁ
1
5
00–4000 cm region. The most important FT-IR bands for the
1
2
ligands and the Cu(II) and Co(II) complexes are given in Table 4.
1
2
The free ligands H
3
L and H
2
L
exhibit characteristic C@N stretch-
of the free ligands consist of two relatively intense bands centered
ꢁ1
1
2
ing bands at 1614 and 1622 cm , while those of complexes 1, 2
and 3 are observed at 1605, 1601 and 1607 cm , respectively.
The C@N stretching frequencies are shifted to lower frequencies
by ca. 9, 11 and 15 cm for 1, 2 and 3, respectively, upon complex-
ation, indicating a decrease in the C@N bond order due to the coor-
dinated bonds of the Cu(II) and Co(II) atoms with the oxime
nitrogen lone pair [57].
at 274 and 313 nm for H
could be assigned to the
3
L , and 273 and 320 nm for H
2
L
which
ꢁ
1
⁄
p
–
p
transitions of the benzene rings of
1
3
salicylaldehyde units [62]. Compared with the free ligands H L
and H L , the absorption bands at 313 and 320 nm disappear from
2
ꢁ1
2
the UV–Vis spectra of complexes 1, 2 and 3, which indicate that the
oxime nitrogen atoms are involved in coordination to the Cu(II)
⁄
and Co(II) atoms [49]. The intraligand
p
–p
transitions of the ben-
The Ar–O stretching frequency appears as a strong band within
zene rings of salicylaldehyde units are slightly shifted in the corre-
sponding complexes and appear at 293, 280 and 269 nm for
complexes 1, 2 and 3, respectively. Moreover, the new absorption
bands are observed at 364, 380 and 375 nm for complexes 1, 2
ꢁ1
1
263–1213 cm range as reported for similar salen-type ligands.
ꢁ1
1
2
These bands occur at 1265 and 1246 cm
3 2
for H L and H L ,
respectively. However, the Ar–O stretching frequencies are

Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
313
Fig. 6. Supermolecule structures of complex 3. (a) View of the 1D chain motif within complex 3 along the c axis; (b) Part of 2D supramolecular layered structure via
intermolecular and intramolecular hydrogen bond interactions.
Table 4
The most important FT-IR bands for the ligands and complexes 1, 2 and 3 (cmꢁ1).
Compound
L1
Cu(HL )]
m
(C@N)
m
(Ar–O)
Ph ring (C–H)
m
O–H
d
(H–O–H)
q
H2O
m
(M–O)
m(
M–N)
H
[
3
1614s
1605s
162s
1601s
1607s
1265s
1480
3408w
3420w
3408w
3415s
2926s
1
1203m
1246m
1230m
1244m
1435vs
1438vs
1476vs
1454vs
511w
439w
2
2
H L
2
[
[
Cu(L )H
2
O]
]ꢀ3CH
1636
547
495w
489w
423w
446w
2
Co
2
(L )
2
3
CN
⁄
and 3, respectively, and assigned to L ? M charge-transfer (LMCT)
at 273 nm, which should be assigned to the intraligand
p–
p
tran-
transitions which are characteristic of the transition metal com-
sition [64]. The Cu(II) complex 1 shows an intense broad photolu-
plexes with N
2
O
2
coordination sphere [63].
minescence with maximum emission at 462 nm upon excitation at
3
51 nm, which is slightly red-shifted by 46 nm compared to that of
1
the ligand H
3
L .
3.4. Fluorescence properties
The emission spectra of H
2
L2 and its corresponding complex 2
2
The fluorescent properties of H
plex 1 were investigated at room temperature (Fig. 8a). The ligand
H L exhibits an intense emission peak at 416 nm upon excitation
3
L1 and its corresponding com-
3
2
are shown in Fig. 8b. In comparison with the corresponding H L
with the maximum emission wavelength at 417 nm when excited
with 290 nm, the complex 2 exhibits red-shift with the maximum
1

3
14
Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
Fig. 8. Emission spectra of the ligands and their corresponding complexes. (a) H
3
L1
---) and its Cu(II) complex (—) in DMF (C = 5 ꢂ 10 mol/1, kex = 273 and 351 nm,
ꢁ
5
(
k
Fig. 7. UV–Vis absorption spectra of the ligands and their corresponding
2
1
ꢁ5 ꢁ1
em = 416 and 462 nm); (b)
H
2
L
(---) and its Cu(II) complex (—) in DMF
complexes. (a) H
3
L
(—) and its Cu(II) complex 1 (---) in DMF (5 ꢂ 10
L ); (b)
ꢁ
5
ꢁ1
2
(C = 5 ꢂ 10 mol L , kex = 290 and 354 nm, kem = 417 and 473 nm).
H L (—) and its Cu(II) (---) and Co(II) (————) complexes 2 and 3, respectively, in
DMF (5 ꢂ 10 mol L ).
2
ꢁ
5
ꢁ1
1
2
2
formula [Cu(HL )] (1), [Cu(L )H
2
O] (2) and [Co
2
(L )
2
]ꢀ3CH
3
CN (3)
1
2
with asymmetric Salamo-type ligands H
3
L and H
2
L , were synthe-
emission wavelength kmax = 473 nm when excited at 354 nm,
which could be assigned to the LMCT [65].
sized and structurally characterized. In FT-IR spectra of complexes
, 2 and 3, the M–N vibrational absorption frequencies
1
mM–O and m
The blue emissions for complexes 1 and 2 have been observed.
These complexes, having the same molar concentrations as the
ligands, display enhanced emission intensities compared to their
have been observed. Meanwhile, the Cu(II) in complexes 1 and 2
exhibit blue emission with the maximum emission wavelengths
at 462 and 473 nm, respectively. The structures of complexes 1, 2
and 3 have serious distortion probably as a result of the introduc-
tion of different substituents into the two benzene rings of the
asymmetric Salamo-type ligands.
1
2
3 2
corresponding ligands H L and H L when excited with the similar
amount of energy. Fluorescence enhancements through complexa-
tion are of much interest as it opens up the opportunity for photo-
chemical applications of these complexes. The fluorescence of the
1
2
3 2
free ligands H L and H L are probably quenched by the occur-
rence of a photoinduced electron transfer (PET) process due to
the presence of a lone pair of nitrogen atoms. As such, the process
Acknowledgements
1
2
is prevented by the complexation of the ligands H
3 2
L and H L with
This work was supported by the National Natural Science
Foundation of China (21361015), Graduate Student Guidance Team
Building Fund of Lanzhou Jiaotong University (260001) and the
Science and Technology support funds of Lanzhou Jiaotong
University (ZC2012003), which are gratefully acknowledged.
Cu(II) atoms. Thus, the fluorescence intensities may be effectively
enhanced by the coordination of Cu(II) atoms. Meanwhile, the
1
2
3 2
chelation of the ligands H L and H L to Cu(II) atoms increases
the rigidity of the ligands and therefore reduces the loss of energy
via vibrational motions, which might increase the emission
efficiency.
Appendix A. Supplementary data
4
. Conclusions
CCDC 1433366, 1433367, and 1433368 contains the supple-
mentary crystallographic data for 1–3. 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
According to the above data and discussion, three new
supramolecular Cu(II) and Co(II) complexes with the chemical

Y.-J. Dong et al. / Polyhedron 123 (2017) 305–315
315
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk.
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