Syntheses, crystal structures, and fluorescence properties of zinc(II) complexes with multi-dentate schiff bases

Article abstract of DOI:10.1134/S1070328413110080

Two new structurally similar mononuclear Schiff base zinc(II) complexes, [ZnBr(ClMP)] (I) and [ZnCl(NMP)] (II) (ClMP = 4-chloro-2-[(3-morpholin-4- ylpropylimino)methyl]phenolate; NMP = 4-nitro-2-[(3-morpholin-4-ylpropylimino) methyl]phenolate), and two new dinuclear Schiff base zinc(II) complexes, [Zn₂(EMP)₂I₂] (III), and [Zn ₂(MPA)(CH₃OH)₂(N₃)₂] (IV) (EMP = 5-diethylamino-2-[(2- dimethylaminoethylimino)methyl]phenolate; MPA = N,N'-bis(3-methoxysalicylidene)propane-1,3-diamine), have been prepared and characterized mainly by single-cyrstal X-ray diffraction. Complex I crystallizes in the monoclinic space group P21/n with unit cell dimensions: a = 15.116(3), b = 9.465(1), c = 23.714(4) A, β = 104.358(2)°, V = 3286.9(8) A³, Z = 8, R₁ = 0.0439, and wR₂ = 0.0736. Complex II crystallizes in the mono- clinic space group P21/c with unit cell dimensions: a = 7.253(2), b = 16.652(4), c = 13.568(3) A, β = 96.600(2)°, V = 1627.8(6) A³, Z = 4, R₁ = 0.0417, and wR₂ = 0.0809. Complex III crystallizes in the mono- clinic space group C2/c with unit cell dimensions: a = 27.962(2), b = 8.246(2), c = 31.605(3) A, β = 90.343(2)°, V = 7287.4(15) A³, Z = 8, R₁ = 0.0721, and wR₂ = 0.1709. Complex IV crystallizes in the monoclinic space group C2/c with unit cell dimensions: a = 20.483(3), b = 11.344(2), c = 14.909(3) A, β = 131.650(1)°, V = 2588.6(7) A³, Z = 4, R₁ = 0.0343, and wR₂ = 0.0792. Each Zn atom in I and II are four-coordinated in a tet- rahedral geometry by the NNO donor set of the Schiff base ligand and one halide atom. The Zn atoms in III are in square pyramidal coordination, and those in IV are in octahedral and tetrahedral coordination. Ther- mal stability and fluorescence properties of the complexes I and II have also been determined. Pleiades Publishing, Ltd., 2013.

Full text of DOI:10.1134/S1070328413110080

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2013, Vol. 39, No. 12, pp. 836–843. © Pleiades Publishing, Ltd., 2013.
Syntheses, Crystal Structures, and Fluorescence Properties
of Zinc(II) Complexes with MultiꢀDentate Schiff Bases1
S. S. Qiana, X. S. Chengb, J. Q. Renb, Z. L. Youb, *, and H. L. Zhua
a School of Life Sciences, Shandong University of Technology, ZiBo, 255049 P.R. China
b Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029 P.R. China
*eꢀmail: hailiang_zhu@163.com
Received February 14, 2012
Abstract—Two new structurally similar mononuclear Schiff base zinc(II) complexes, [ZnBr(ClMP)] (I) and
[ZnCl(NMP)] (II) (ClMP = 4ꢀchloroꢀ2ꢀ[(3ꢀmorpholinꢀ4ꢀylpropylimino)methyl]phenolate; NMP =
4ꢀnitroꢀ2ꢀ[(3ꢀmorpholinꢀ4ꢀylpropylimino)methyl]phenolate), and two new dinuclear Schiff base zinc(II)
complexes, [Zn2(EMP)2I2] (III), and [Zn2(MPA)(CH3OH)2(N3)2] (IV) (EMP = 5ꢀdiethylaminoꢀ2ꢀ[(2ꢀ
dimethylaminoethylimino)methyl]phenolate; MPA = N,N'ꢀbis(3ꢀmethoxysalicylidene)propaneꢀ1,3ꢀdiamine),
have been prepared and characterized mainly by singleꢀcyrstal Xꢀray diffraction. Complex
monoclinic space group 21/ with unit cell dimensions: = 15.116(3), = 9.465(1), = 23.714(4)
104.358(2) = 8, 1 = 0.0439, and wR2 = 0.0736. Complex II crystallizes in the monoꢀ
= 3286.9(8) Å3
clinic space group 21/ with unit cell dimensions: = 7.253(2), = 16.652(4), = 13.568(3)
96.600(2) = 4, 1 = 0.0417, and wR2 = 0.0809. Complex III crystallizes in the monoꢀ
= 1627.8(6) Å3
clinic space group 2/ with unit cell dimensions: = 27.962(2), = 8.246(2), = 31.605(3) = 90.343(2)
= 7287.4(15) Å3
= 8, 1 = 0.0721, and wR2 = 0.1709. Complex IV crystallizes in the monoclinic space
group 2/ with unit cell dimensions: = 20.483(3), = 11.344(2), = 14.909(3) = 131.650(1)
2588.6(7) Å3
= 4, 1 = 0.0343, and wR2 = 0.0792. Each Zn atom in and II are fourꢀcoordinated in a tetꢀ
rahedral geometry by the NNO donor set of the Schiff base ligand and one halide atom. The Zn atoms in III
I crystallizes in the
P
n
,
a
b
c
Å,
β
=
°,
V
Z
R
P
c
a
b
c
Å,
β
=
°,
V
,
Z
R
C
c
a
b
c
Å,
β
°,
V
,
Z
R
C
c
a
b
c
Å
,
β
°, V =
,
Z
R
I
are in square pyramidal coordination, and those in IV are in octahedral and tetrahedral coordination. Therꢀ
mal stability and fluorescence properties of the complexes I and II have also been determined.
DOI: 10.1134/S1070328413110080
INTRODUCTION
our work on the Schiff base complexes [11–13], we reꢀ
port in this paper the syntheses, crystal structures,
thermal stability, and fluorescene properties of four
new Schiff base zinc(II) complexes, [ZnBr(ClMP)]
Schiff base complexes have been received considerꢀ
able attention for their importance in the fields of coꢀ
ordination chemistry related to catalysis and enzymatꢀ
ic reactions, magnetism and molecular architectures
[1–5]. Zinc is an important element in biological sysꢀ
tems, functions as the active site of hydrolytic enꢀ
zymes, such as carboxypeptidase and carbonic anhyꢀ
drase where it is in a hardꢀdonor coordination enviꢀ
ronment of nitrogen and oxygen atoms [6]. Schiff base
zinc complexes have been proved to possess interesting
(
I
), [ZnCl(NMP)] (II), [Zn2(EMP)2I2] (III), and
[Zn2(MPA)(CH3OH)2(N3)2] (IV) (ClMP = 4ꢀchloꢀ
roꢀ2ꢀ[(3ꢀmorpholinꢀ4ꢀylpropylimino)methyl]phenolaꢀ
te, NMP = 4ꢀnitroꢀ2ꢀ[(3ꢀmorpholinꢀ4ꢀylpropylimiꢀ
no)methyl]phenolate, EMP = 5ꢀdiethylaminoꢀ2ꢀ[(2ꢀdiꢀ
methylaminoethylimino)methyl]phenolate, MPA = N,N'ꢀ
fluorescence properties [7–10]. As a continuation of bis(3ꢀmethoxysalicylidene)propaneꢀ1,3ꢀdiamine).
Cl
O2N
N
N
N
N
O
O
OH
HClMP
OH
HNMP
N
N
N
N
OH
HO
N
OH
O
O
HEMP
H MPA
2
1
The article is published in the original.
836

SYNTHESES, CRYSTAL STRUCTURES, AND FLUORESCENCE PROPERTIES
837
EXPERIMENTAL
stand in air for a few days. Colourless blockꢀshaped
crystals suitable for Xꢀray single crystal analysis were
formed at the bottom of the vessel. The isolated product
was washed three times with cold EtOH, and dried in a
vacuum over anhydrous CaCl2. The yield was 15.5 mg
(36% on the basis of HClMP).
Materials and measurements. Commercially availꢀ
able 5ꢀchlorosalicylaldehyde, 5ꢀnitrosalicylaldehyde,
4ꢀdiethylaminosalicylaldehyde, 3ꢀmethoxysalicylalꢀ
dehyde, N,Nꢀdimethylethaneꢀ1,2ꢀdiamine, propaneꢀ
1,3ꢀdiamine, and 3ꢀmorpholinꢀ4ꢀylpropylamine were
purchased from Aldrich and used without further puꢀ
rification. Other solvents and reagents were made in
China and used as received. The Schiff base H2MPA
was prepared according to the literature procedure
[14]. C, H and N elemental analyses were performed
with a PerkinElmer elemental analyser. Thermal staꢀ
bility analysis was performed on a PerkinElmer Pyris
Diamond TGꢀDTA thermal analyses system. Fluoresꢀ
cence spectra were recorded with an Fꢀ2500 FL Specꢀ
trophotometer analyzer.
Synthesis of the Schiff base HClMP. 5ꢀChlorosaliꢀ
cylaldehyde (1.0 mmol, 0.156 g) and 3ꢀmorpholinꢀ4ꢀ
ylpropylamine (1.0 mmol, 0.144 g) were dissolved in
EtOH (20 mL) with stirring. The mixture was stirred
for about 30 min at room temperature to give a yellow
solution. The solvent was evaporated to give yellow
gummy product of HClMP.
For C14H18N2O2ClBrZn
anal. calcd., %:
Found, %:
C, 39.4;
C, 39.2;
H, 4.2;
H, 4.3;
N, 6.6.
N, 6.5.
Synthesis of II. A MeOH solution (5 mL) of ZnCl2
(0.1 mmol, 13.6 mg) was added to a MeOH solution
(10 mL) of HNMP (0.1 mmol, 29.3 mg) with stirring.
The mixture was stirred for 30 min to give a clear coꢀ
lourless solution. The resulting solution was allowed to
stand in air for a few days. Colourless blockꢀshaped
crystals suitable for Xꢀray single crystal analysis were
formed at the bottom of the vessel. The isolated product
was washed three times with cold EtOH, and dried in a
vacuum over anhydrous CaCl2. The yield was 17.0 mg
(43% on the basis of HNMP).
For C14H19N2O2Cl
For C14H18N3O4ClZn
anal. calcd., %: C, 59.5;
Found, %: C, 59.4;
H, 6.8;
H, 6.7;
N, 9.9.
anal. calcd., %: C, 42.8;
Found, %: C, 42.6;
H, 4.6;
H, 4.6;
N, 10.7.
N, 10.5.
N, 10.0.
Synthesis of the Schiff base HMP. 5ꢀNitrosalicylꢀ
aldehyde (1.0 mmol, 0.167 g) and 3ꢀmorpholinꢀ4ꢀylꢀ
propylamine (1.0 mmol, 0.144 g) were dissolved in
EtOH (20 mL) with stirring. The mixture was stirred
for about 30 min at room temperature to give a yellow
solution. The solvent was evaporated to give yellow
gummy product of HNMP.
Synthesis of III. A MeOH solution (5 mL) of ZnI2
(0.2 mmol, 62.0 mg) was added to a MeOH solution
(10 mL) of HEMP (0.1 mmol, 26.3 mg) with stirring.
The mixture was stirred for 30 min to give a clear light
yellow solution. The resulting solution was allowed to
stand in air for a few days. Light yellow blockꢀshaped
crystals suitable for Xꢀray single crystal analysis were
formed at the bottom of the vessel. The isolated product
was washed three times with cold EtOH, and dried in a
vacuum over anhydrous CaCl2. The yield was 41.0 mg
(45% on the basis of HEMP).
For C14H19N3O4
anal. calcd., %: C, 57.3;
Found, %: C, 57.1;
H, 6.5;
H, 6.6;
N, 14.3.
N, 14.5.
Synthesis of the Schiff base HEMP. 4ꢀDiethylamiꢀ
nosalicylaldehyde (1.0 mmol, 0.193 g) and N,Nꢀdiꢀ
methylethaneꢀ1,2ꢀdiamine (1.0 mmol, 0.088 g) were
dissolved in EtOH (20 mL) with stirring. The mixture
was stirred for about 30 min at room temperature to
give an orange solution. The solvent was evaporated to
give orange gummy product of HEMP.
For C30H47N6O2I2Zn2
anal. calcd., %: C, 39.7;
Found, %: C, 39.5;
H, 5.2;
H, 5.3;
N, 9.3.
N, 9.2.
Synthesis of IV. A MeOH solution (5 mL) of
Zn(NO3)2 6H2O (0.2 mmol, 54.3 mg) was added to
For C15H25N3O
⋅
the mixture of a MeOH solution (10 mL) of H2MPA
(0.1 mmol, 34.2 mg) and sodium azide (0.2 mmol,
13.0 mg) with stirring. The mixture was stirred for
30 min to give a clear colourless solution. The resultꢀ
ing solution was allowed to stand in air for a few days.
Colourless blockꢀshaped crystals suitable for Xꢀray
single crystal analysis were formed at the bottom of the
anal. calcd., %: C, 68.4;
Found, %: C, 68.3;
H, 9.6;
H, 9.6;
N, 16.0.
N, 15.8.
Synthesis of I. A MeOH solution (5 mL) of ZnBr2
(0.1 mmol, 22.5 mg) was added to a MeOH solution
(10 mL) of HClMP (0.1 mmol, 28.2 mg) with stirring.
The mixture was stirred for 30 min to give a clear coꢀ
lourless solution. The resulting solution was allowed to vessel. The isolated product was washed three times with
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
No. 12
2013

838
QIAN et al.
Table 1. Crystallographic and experimental data for the complexes I–IV
Value
Parameter
I
II
393.1
III
IV
Fw
427.0
908.3
619.2
Crystal shape/color
Crystal system
Space group
Block/colourless
Monoclinic
Block/colourless
Monoclinic
Block/colourless
Monoclinic
Block/colourless
Monoclinic
P
21/n
P
21/
c
C
2/
c
C2/c
a
, Å
, Å
, Å
15.116(3)
9.465(1)
23.714(4)
104.358(2)
3286.9(8)
8
7.253(2)
16.652(4)
13.568(3)
96.600(2)
1627.8(6)
4
27.962(2)
8.246(2)
31.605(3)
90.343(2)
7287.4(15)
8
20.483(3)
11.344(2)
14.909(3)
131.650(1)
2588.6(7)
4
b
c
β
V
Z
, deg
, Å3
T
, K
298(2)
298(2)
1.695
298(2)
298(2)
μ(Mo
K
), mm–1
4.092
3.045
1.905
α
ρcalcd, g cm–3
1.726
1.604
1.656
1.589
F(000)
1712
808
3608
1272
Crystal size, mm
Tmin
0.17
×
0.15
×
0.15
0.27
×
0.23
×
0.23
0.27
×
0.23
×
0.23
0.28
×
0.27 × 0.23
0.5430
0.5788
7005
3627
379
0.6575
0.6965
3556
2479
208
0.4936
0.5410
7919
5377
387
0.6175
0.6684
2958
2039
188
Tmax
Reflections collected
Observed reflections (
Parameters
I
≥
2σ(I))
Restraints
0
0
0
8
Goodness of fit on F 2
0.952
1.007
1.095
1.022
R1
,
,
wR2
(
I
≥
2
σ
(
I
))*
0.0439, 0.0736
0.1207, 0.0923
0.0417, 0.0809
0.0747, 0.0911
0.0721, 0.1709
0.1077, 0.1916
0.0343, 0.0792
0.0599, 0.0899
R1
wR2 (all data)*
*
R
=
Σ
||F
| – |F
||/
Σ
|F
|, wR = [
Σ
w
(Fo2
–
Fc2)2
/ w
(Fo2)2]1 2.
Σ
1
o
c
o
2
cold EtOH and dried in a vacuum over anhydrous CaCl2. absorption corrections were performed using the
SADABS program [16]. The structures were solved
by direct methods and refined against F 2 by fullꢀmaꢀ
trix leastꢀsquares methods using the SHELXTL verꢀ
sion 5.1 [17]. All of the nonꢀhydrogen atoms were reꢀ
fined anisotropically. The methanol H atom in IV was
located from a difference Fourier map and refined isoꢀ
The yield was 33.5 mg (54% on the basis of HMPA).
For C21H28N8O6Zn2
anal. calcd., %:
Found, %:
C, 40.7;
C, 40.8;
H, 4.6;
H, 4.5;
N, 18.1.
N, 18.0.
tropically with O–H distance restrained to 0.85(1) Å.
Xꢀray structure determination. Diffraction intensiꢀ
ties for the complexes IV were collected at 298(2) K
using a Bruker SMART 1K areaꢀdetector with Mo
The remaining H atoms were placed in idealized posiꢀ
tions and constrained to ride on their parent atoms.
The crystallographic data for the complexes are sumꢀ
I–
K
α
radiation ( = 0.71073 Å). The collected data were reꢀ
λ
duced using the SAINT program [15], and multiꢀscan marized in Table 1. Selected bond lengths and angles
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
No. 12
2013

SYNTHESES, CRYSTAL STRUCTURES, AND FLUORESCENCE PROPERTIES
839
Table 2. Selected bond lengths (Å) and angles (deg) in
complexes IV
are given in Table 2. Supplementary material has been
deposited with the Cambridge Crystallographic Data
Centre (nos. 866689 (
and 638069 (IV)); deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk).
I– *
I
), 866690 (II), 866855 (III),
Bond
d
, Å
Bond
d, Å
I
Zn(1)–O(1)
Zn(1)–N(2)
Zn(2)–O(3)
Zn(2)–N(4)
1.915(3) Zn(1)–N(1)
2.089(3) Zn(1)–Br(1)
1.911(3) Zn(2)–N(3)
2.107(4) Zn(2)–Br(2)
II
1.925(2) Zn(1)–N(1)
2.075(2) Zn(1)–Cl(1)
III
1.985(5) Zn(1)–N(1)
2.086(6) Zn(1)–N(2)
2.584(1) Zn(2)–O(1)
2.028(5) Zn(2)–N(4)
2.200(8) Zn(2)–I(2)
IV
2.026(2) Zn(1)–N(1)
2.279(2) Zn(2)–N(2)
2.036(2)
1.985(4)
2.3386(8)
2.000(3)
2.3454(9)
RESULTS AND DISCUSSION
The molecular structures of complexes I and II are
shown in Fig. 1a and 1b, respectively. The structures of
the complexes are very similar to each other. There two
Zn(1)–O(1)
Zn(1)–N(2)
1.991(2)
2.2128(10)
independent molecules in the asymmetric unit of I.
The Zn atom in each of the complexes is coordinated
by the phenolate O, imine N, and morpholine N atꢀ
oms of the Schiff base ligand and one halide atom (Br
for I and Cl for II). The stereochemistry around the
Zn atoms in the complexes can be described as distortꢀ
ed tetrahedral configuration. The coordinate bond anꢀ
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–I(1)
Zn(2)–O(2)
Zn(2)–N(5)
2.069(8)
2.240(8)
2.081(5)
2.103(8)
2.582(1)
gles range from 95.1(2)
95.4(1) to 122.5(1) for II, indicating the difference
from the ideal values of 109 28 for the perfect tetraheꢀ
°
to 118.9(1)° for I and from
°
°
°
′
Zn(1)–O(1)
Zn(1)–O(3)
Zn(2)–O(1)
2.041(2)
1.958(2)
dral geometry. The distorsion of the tetrahedral coorꢀ
dination is mainly caused by the tensile force of the
Schiff base ligands. The Zn–O and Zn–N bond
lengths in the complexes are similar to each other, and
all of which are comparable to the corresponding valꢀ
ues observed in other Schiff base zinc(II) complexes
[18, 19]. As expected, the coordinate bonds involving
amine atoms are longer than those involving imine atꢀ
oms [20].
Figure 1c gives a perspective view of the complex III
together with the atomic labeling system. The complex
is a phenolateꢀO bridged dinuclear zinc(II) comꢀ
pound. Each Zn atom in the complex is fiveꢀcoordiꢀ
nated in a squareꢀpyramidal coordination, with two
phenolate O, one imine N, and one amine N atoms
from two Schiff base ligands EMP defining the basal
Angle
ω
, deg
Angle
ω
, deg
I
O(1)Zn(1)N(1)
N(1)Zn(1)N(2)
N(1)Zn(1)Br(1) 117.55(11) N(2)Zn(1)Br(1) 110.57(10)
O(3)Zn(2)N(3)
N(3)Zn(2)N(4)
N(3)Zn(2)Br(2) 118.94(11) N(4)Zn(2)Br(2) 106.73(10)
95.12(15) O(1)Zn(1)N(2) 117.62(13)
97.88(14) O(1)Zn(1)Br(1) 116.07(10)
95.81(14) O(3)Zn(2)N(4) 121.14(14)
95.50(14) O(3)Zn(2)Br(2) 117.01(11)
II
O(1)Zn(1)N(1)
N(1)Zn(1)N(2)
N(1)Zn(1)Cl(1) 119.18(8) N(2)Zn(1)Cl(1) 106.40(7)
95.41(9) O(1)Zn(1)N(2) 122.48(10)
96.94(10) O(1)Zn(1)Cl(1) 115.39(8)
III
plane, and with one I atom occupying the apical posiꢀ
tion. The substantial distortion of the square pyramids
is revealed by the bond angles among apical and basal
O(1)Zn(1)N(1) 144.1(3) O(1)Zn(1)O(2)
76.4(2)
96.9(3)
N(1)Zn(1)O(2)
N(1)Zn(1)N(2)
O(1)Zn(1)I(1)
83.6(3) O(1)Zn(1)N(2)
79.3(3) O(2)Zn(1)N(2) 139.5(3)
115.0(2) N(1)Zn(1)I(1) 100.1(2)
113.0(2) N(2)Zn(1)I(1) 106.0(2)
75.6(2) O(2)Zn(2)N(4) 135.7(3)
donor atoms, ranging from 100.1(2)
°
to 115.0(2)
° for
Zn(1), and from 107.3(2)° to 113.4(2)° for Zn(2). The
Zn atoms deviate from the leastꢀsquares planes deꢀ O(2)Zn(1)I(1)
fined by the corresponding basal donor atoms in the
direction of the apical positions by 0.674(2) for
Zn(1), and 0.721(2) for Zn(2).
O(2)Zn(2)O(1)
O(1)Zn(2)N(4)
O(1)Zn(2)N(5) 142.4(3) N(4)Zn(2)N(5) 79.3(3)
O(2)Zn(2)I(2) 113.4(2) O(1)Zn(2)I(2) 109.7(2)
N(4)Zn(2)I(2) 109.9(2) N(5)Zn(2)I(2) 107.3(2)
Å
81.7(3) O(2)Zn(2)N(5)
96.2(3)
Å
The coordination number 5 for zinc(II) comꢀ
plexes is very common and usually presents either a
squareꢀpyramidal or a trigonalꢀbipyramidal geomeꢀ
try, or any of the distorted intermediate geometries.
For a pentacoordinated metal center, the distortion
of the coordination environment from squareꢀpyraꢀ
midal to trigonalꢀbipyramidal can be calculated
IV
O(1)Zn(1)O(1
O(1)Zn(1)N(1
O(1)Zn(1)O(3)
N(1)Zn(1)O(3)
O(3)Zn(1)O(3
A
A
)
77.3(1) O(1)Zn(1)N(1)
) 168.7(1) N(1)Zn(1)N(1
92.0(1) O(1)Zn(1)O(3
88.8(1) N(1)Zn(1)O(3
) 178.3(1) N(2)Zn(2)N(2
) 114.6(1) N(2)Zn(2)O(1) 114.4(1)
76.8(1)
91.7(1)
99.5(1)
89.3(1)
90.1(1)
A)
A)
A)
from the Addison distortion index,
as = ( )/60, where and are the largest coꢀ
ordinate angles, and = 0 represents perfect squareꢀ
pyramidal,
midal [21]. In the present complex, the calculated
τ
, which defined
A
A
A) 116.1(2)
τ
β
–
α
α
β
N(2)Zn(2)O(1
τ
τ
= 1 represents perfect trigonalꢀbipyraꢀ O(1)Zn(2)O(1
A)
* Symmetry code for
A: –
x, y, 1/2 – z.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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840
QIAN et al.
(a)
C(23)
C(14)
C(24)
N(6)
C(13)
C(22)
C(18)
C(25)
N(2)
C(12)
C(19)
I(1)
C(15)
Zn(1)
C(20)
C(21)
C(11)
N(1)
C(16)
C(17)
O(1)
Zn(2)
I(2)
C(26)
N(4)
C(1)
C(6)
O(2)
C(2)
C(27)
C(30)
C(3)
C(5)
C(4)
N(5)
C(28)
C(9)
C(10)
N(3)
C(29)
C(8)
C(7)
(b)
C(8)
N(1)
C(9)
C(26)
C(7)
C(1)
C(25)
Br(2)
O(4)
C(6)
C(4)
Br(1)
N(4)
C(24)
C(23)
Cl(1)
N(2)
C(10)
C(2)
C(5)
C(27)
Zn(1)
C(14)
Zn(2)
C(28)
C(3)
O(1)
C(11)
C(12)
C(22)
O(3)
C(17)
N(3)
C(16)
C(15)
C(13)
O(2)
C(21)
C(18)
C(20)
C(19)
Cl(2)
(c)
C(8)
C(9)
N(1)
C(10)
C(7)
Cl(1)
C(6)
C(1)
N(2)
O(4)
N(3)
C(11)
Zn(1)
C(2)
C(5)
C(14)
C(12)
O(1)
C(3)
C(4)
O(3)
C(13)
O(2)
Fig. 1. Molecular structure of I (a), II (b), and III (c) at 30% probability displacement.
τ
values are 0.077 for Zn(1) and 0.112 for Zn(2),
suggesting they are best described as distorted Zn(2)–O(2) in complex III is not planar, but presents
squareꢀpyramidal geometry. a slightly distorted roofꢀshape. The Zn···Zn distance in
The fourꢀmembered bridging ring Zn(1)–O(1)–
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SYNTHESES, CRYSTAL STRUCTURES, AND FLUORESCENCE PROPERTIES
841
C(10)
C(9)
C(9A)
N(1)
C(8)
C(1)
N(1
A
)
C(8A
)
O(3)
Zn(1)
O(3A)
C(6)
C(1A
)
C(6A
)
C(11)
C(11A)
C(2A)
C(5A
)
O(1)
O(1A)
C(2)
C(5)
Zn(2)
C(4A)
C(3A)
C(3)
C(4)
O(2
A
)
N(2)
O(2)
N(3)
N(4)
N(2
N(3
N(4
A)
A
)
C(7A)
C(7)
A
)
Fig. 2. Molecular structure of IV at 30% probability displacement. Atoms labled with A are at the symmetry position –
1/2
x, y,
⎯ z.
the complex is 3.194(2)
Å
. The Zn···Zn distance, as
In the crystal structure of IV, molecules are linked
through intermolecular O–H···N hydrogen bonds to
forming 1D chains, as shown in Fig. 3.
well as the coordinate bond lengths in the complex, are
comparable to those in similar dinuclear Schiff base
zinc(II) complexes [22, 23].
Differential thermal (DT) and thermal gravimetric
analyses (TGA) were conducted to examine the stability
Fig. 2 gives a perspective view of the complex IV toꢀ
gether with the atomic labeling system. The complex is
a phenolateꢀO bridged dinuclear zinc(II) compound,
which possesses crystallographic twoꢀfold rotation axꢀ
is symmetry. The inner Zn atom is sixꢀcoordinate in an
octahedral geometry with two phenolate O and two
imine N atoms of the Schiff base ligand MPA defining
the equatorial plane and with two O atoms from two
methanol molecules occupying the axial positions.
The octahedron is elongated as evidenced by the longꢀ
er distances of the axial bonds than those of the equaꢀ
torial bonds. The outer Zn atom is fourꢀcoordinated in
of complexes
the first step started at about 220
at about 378 C, corresponding to the loss of the Br
ligand. The observed weight loss of 18.5% is very close
to the calculated value (18.7%). The second step, from
380 to 610 C, corresponds to the loss of the Schiff base
I
and II. For the DT–TGA of
I (Fig. 4a),
°C and was completed
°
°
ligand and the formation of the final product (ZnO).
The observed weight loss of 63.5% in this step is close
to the calculated value (62.3%). The total weight loss
of 82.0% is close to the calculated value (81.0%). For
the DT–TGA of II (Fig. 4b), the first step started at
about 230°C and was completed at about 290°C, corꢀ
a tetrahedral geometry by two O atoms of MPA and responding to the loss of the Cl ligand. The observed
weight loss of 9.4% is close to the calculated value
(9.0%). The second step, from 300 to 637 C, correꢀ
two N atoms from two azide ligands. The substantial
distortion of the tetrahedral coordination is revealed
°
sponds to the loss of the Schiff base ligand and the forꢀ
mation of the final product (ZnO). The observed
weight loss of 71.5% in this step is close to the calcuꢀ
lated value (70.2%). The total weight loss of 80.9% is
close to the calculated value (79.3%).
by the coordinate bond angles, ranging from 76.8(1)
to 116.1(2) . The Zn···Zn distance in the complex is
3.177(2) . The dihedral angle between two benzene
rings of MPA is 3.1(2) . The azide ligands are nearly
linear and show bent coordination mode with the
Zn(2) atom [N(2)–N(3)–N(4)/Zn(2)–N(2)–N(3) =
°
°
Å
°
Owing to the excellent luminescent properties of
d10 metal ions, the solid state photoluminescence of
the complexes were investigated at room temperature.
176.0(3)°/130.9(2)°]. The Zn···Zn distance, as well as
the coordinate bond lengths in the complex are comꢀ
parable to those in III and in other similar dinuclear
Schiff base zinc(II) complexes [22, 23].
For
I, upon excitation at 367 nm, the emission spectrum
of the complex shows one emission band at 449 nm
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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842
QIAN et al.
x
0
z
y
Fig. 3. The 1D chain structure of IV, viewed along the
y
axis. Hydrogen bonds are drawn as dashed lines.
(a)
(a)
449
–5
10000
100
80
60
40
20
0
–10
–15
–20
–25
–30
–35
–40
8000
6000
4000
2000
0
200
400
Temperature,
600
400
450
500
Wavelenght, nm
550
600
°
C
(b)
(b)
20
469
100
80
60
40
20
0
2000
10
419
0
1500
1000
–10
–20
–30
–40
200
400 600
Temperature,
800
1000
450
500
Wavelenght, nm
550
600
°
C
Fig. 5. Solid state fluorescent emission spectrum of
and II (b).
I (a)
Fig. 4. DT–TGA curve of
I
(a) and II (b).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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SYNTHESES, CRYSTAL STRUCTURES, AND FLUORESCENCE PROPERTIES
843
11. You, Z.ꢀL., Ni, L.ꢀL., Shi, D.ꢀH., et al., Eur. J. Med.
Chem., 2010, vol. 45, no. 7, p. 3196.
12. You, Z.ꢀL., Shi, D.ꢀH., and Zhu, H.ꢀL., Inorg. Chem.
Commun., 2006, vol. 9, no. 6, p. 642.
13. You, Z.ꢀL. and Zhu, H.ꢀL., Z. Anorg. Allg. Chem., 2006,
(Fig. 5a). For II, upon excitation at 367 nm, the emisꢀ
sion spectrum of the complex shows two emission
bands at 419 and 469 nm (Fig. 5b).
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