Structural diversity and properties of four complexes with 4-acyl pyrazolone derivative

Article abstract of DOI:10.1016/j.poly.2013.03.024

Four new complexes {[Zn(HL)(H₂O)(DMF)](NO₃)} _n (1), [Cd(HL)₂]_n (2), {[Mn(HL) ₂]·CH₃CN·2H₂O} (3) and {[Mn(L)(μ₂-EtOH)]}_n (4) (H₂L = N-(1-phenyl-3-methyl-4-benzal-pyrazolone-5)-nicotinic hydrazide) have been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single crystal X-ray diffraction. The structural analyses reveal that complexes 1, 2 and 3, formed by H₂L with metal nitrate, have Zigzag chain, double-stranded chain and mononuclear structures, respectively, and the ligands adopt three different coordination modes in these complexes. While, complex 4, formed by H₂L with manganese acetate, represents a 2D network structure with dinuclear units bridged by ethanol molecules. These result demonstrated that the metal atom and counteranion have certain influences on the structures of resulting complexes. In addition, the fluorescent properties of 1 and 2 and the magnetism of 4 were investigated.

Full text of DOI:10.1016/j.poly.2013.03.024

Polyhedron 55 (2013) 209–215
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural diversity and properties of four complexes with 4-acyl
pyrazolone derivative
⇑
⇑
He Li, Guan-Cheng Xu , Li Zhang, Ji-Xi Guo, Dian-Zeng Jia
Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of
Applied Chemistry, Xinjiang University, Urumqi, 830046 Xinjiang, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new complexes {[Zn(HL)(H2O)(DMF)](NO3)}n (1), [Cd(HL)2]n (2), {[Mn(HL)2]ꢀCH3CNꢀ2H2O} (3) and
Received 13 February 2013
Accepted 13 March 2013
Available online 21 March 2013
{[Mn(L)(l2-EtOH)]}n (4) (H2L = N-(1-phenyl-3-methyl-4-benzal-pyrazolone-5)-nicotinic hydrazide) have
been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single crystal
X-ray diffraction. The structural analyses reveal that complexes 1, 2 and 3, formed by H2L with metal
nitrate, have Zigzag chain, double-stranded chain and mononuclear structures, respectively, and the
ligands adopt three different coordination modes in these complexes. While, complex 4, formed by
H2L with manganese acetate, represents a 2D network structure with dinuclear units bridged by ethanol
molecules. These result demonstrated that the metal atom and counteranion have certain influences on
the structures of resulting complexes. In addition, the fluorescent properties of 1 and 2 and the magne-
tism of 4 were investigated.
Keywords:
Coordination polymer
Pyrazolone derivative
Crystal structure
Fluorescent property
Magnetism
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
struction and property of a series of transition and lanthanon metal
complexes [11–13]. The results showed that 4-acyl pyrazolone
The rational design and assembly of metal–organic coordina-
tion polymers have received remarkable attention not only due
to their fascinating structural diversities [1,2], but also for the po-
tential discovery of novel functional materials, which may have
applications in the areas including optical, electronic, magnetic
fields, gas storage, ion-exchange and catalysis [3,4]. Up to now,
though a great number of coordination polymers with various
structures have been reported, it is still a long-term challenge to
exactly predict and control the structures of resulting coordination
polymers, because the structures of complexes are frequently
influenced by various factors such as the metal atom, organic li-
gand, counteranion, the ratio of ligand to metal ion, reaction condi-
tions, and so on [5,6]. Among them, the proper choice of organic
ligand is the key factor governing the structure of coordination
polymer. Thus, rational design and prepare of new multidentate li-
gand is one of the central tasks [7].
Pyrazolone-5, especially 4-acyl pyrazolone, form an important
class of organic compounds and represent considerable scientific
and applied interest in biological and analytical applications, metal
extractants, dyes, etc [8,9]. On the other hand, the Schiff base
derivatives of 4-acyl pyrazolone are less explored, even though
these ligand are known to show appealing complexation properties
[10]. In recent years, we have devoted our effort to the design and
synthesis of 4-acyl pyrazolone Schiff base derivatives and the con-
derivatives have potential to form different types of complexes
due to the multiple coordination sites and the tautomeric effect
of enol form and keto form, and they can adopt different coordina-
tion modes to bond with metal atoms. Furthermore, some 4-acyl
pyrazolone derivatives and their Cu(II) complexes possess interest-
ing strong antibacterial activity [14]. In order to further investigate
the coordination ability and complexation behavior of pyrazolone-
based ligands, we extended our investigation to the syntheses of
new 4-acyl pyrazolone derivatives and their metal complexes. This
paper presents the syntheses, characterization and structural
diversity of four new complexes, {[Zn(HL)(H2O)(DMF)](NO3)}n
(1), [Cd(HL)2]n (2), {[Mn(HL)2]ꢀCH3CNꢀ2H2O} (3) and {[Mn(L)(l2
-
EtOH)]}n (4). These complexes demonstrated Zigzag chain, dou-
ble-stranded chain, mononuclear and 2D network structures.
Meanwhile, the ligands adopt three kinds of coordination modes
in these complexes. Furthermore, the influences of the metal atom
and counteranion on the structures of the complexes were dis-
cussed. The fluorescent properties of 1 and 2 and the magnetism
of 4 were investigated.
2. Experimental section
2.1. Materials and general physical measurements
⇑
1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone, nicotinic hydra-
zide and other chemicals and solvents were analytical-grade
Corresponding authors. Tel./fax: +86 991 8588883.
E-mail address: jdz0991@gmail.com (D.-Z. Jia).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.03.024

210
H. Li et al. / Polyhedron 55 (2013) 209–215
commercial products and were directly used without further
purification.
C, 50.78; H, 4.43; N, 15.94. Found: C, 51.17; H, 4.22; N, 15.88%.
IR(cmꢁ1, KBr): 3371(m), 3155(m), 2928(m), 1661(s), 1628(s),
1603(s), 1576(s), 1485(s), 1435(s), 1385(s), 1317(s), 1205(w),
1153(w), 1136(m), 1107(m), 1053(m), 1026(m), 920(m), 849(w),
766(m), 706(m), 705(m), 692(m), 660(m), 550(w).
The elemental analyses were made on FLASH EA 1112 Series
NCHS-O analyzer. Melting point was measured with a TECH XT-6
melting point apparatus. IR spectra were recorded on a BRUKER
VERTEX-70 spectrophotometer within 400–4000 cmꢁ1 with the
samples prepared as pellets with KBr. TG curves of the complexes
were recorded with a NETZSCH STA 449F3 thermal analyzer at the
scanning rate of 10 K minꢁ1 in the flowing air atmosphere. The
fluorescence spectra of ligand and complexes 1 and 2 were studied
using Hitachi F-4500 fluorescence spectrophotometer with a Xe arc
lamp as the light source at room temperature. Variable tempera-
ture magnetic data were obtained using a Quantum Design SQUID
MPMS 7XL system. Background corrections for the sample holder
assembly and diamagnetic components of the complexes were
applied.
2.3.2. [Cd(HL)2]n (2)
The procedure for preparation of complex 2 is similar to that of
1 except using Cd(NO3)2ꢀ4H2O (0.0925 g, 0.3 mmol) instead of
Zn(NO3)2ꢀ6H2O. Yellow block crystals were obtained by slow evap-
oration of the resulting clear solution in 60% yield. Anal. Calcd. for
C
46H36N10O4Cd: C, 61.03; H, 4.01; N, 15.47. Found: C, 61.28; H,
4.15; N, 15.19%. IR(cmꢁ1
,
KBr): 3435(m), 3059(w), 2926(w),
1657(m), 1618(m), 1543(s), 1499(s), 1416(s), 1385(s), 1200(m),
1051(m), 1028(m), 1012(m), 839(m), 764(m), 731(m), 696(m),
630(w), 588(w).
2.2. Synthesis of the ligand H2L
2.3.3. {[Mn(HL)2]ꢀCH3CNꢀ2H2O} (3)
The 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (10 mmol)
was dissolved in 40 mL of hot anhydrous ethanol, and a few drops
of acetic acid were added as a catalyst. An ethanol solution of nic-
otinic hydrazide (10 mmol) was added dropwise with constant
stirring. The yellow precipitate was then formed and the mixture
was further refluxed for about 4 h. Upon cooling, the solid was col-
lected by filtration, washed with ethanol and dried in air. The prod-
uct was recrystallized from anhydrous ethanol as yellow block
crystals in 84% yield. M.p.: 193–194 °C. Anal. calc. for
A
ethanol (6 mL) solution of Mn(NO3)2ꢀ4H2O (0.0753 g,
0.3 mmol) was added dropwise to a solution of ligand H2L
(0.1192 g, 0.3 mmol) in acetonitrile (9 mL) and ethanol (3 mL) with
stirring to give a clear solution. The reaction mixture was stirred
for an hour and filtered. Yellow block crystals suitable for X-ray
analysis were obtained by slow evaporation of the filtrate for
two weeks in 57% yield. Anal. calc. for C48H43N11O6Mn: C, 62.34;
H, 4.69; N, 16.66. Found: C, 62.43; H, 4.39; N, 16.52%. IR(cmꢁ1
,
KBr): 3365(m), 3269(m), 2968(m), 2848(m), 1668(m), 1603(s),
1566(s), 1523(m), 1473(s), 1435(s), 1396(m), 1369(s), 1333(m),
1151(m), 1049(m), 1028(m), 1012(m), 914(m), 845(w), 781(m),
760(m), 704(m), 658(w).
C23H19N5O2: C, 69.50; H, 4.82; N, 17.63. Found: C, 69.26; H, 4.67;
N, 17.83%. IR(cmꢁ1, KBr): 3437(m), 3130(w), 2980(m), 1649(s),
1593(s), 1537(s), 1518(s), 1499(s), 1418(m), 1385(s), 1146(m),
1055(m), 1026(w), 1011(m), 833(w), 773(m), 754(m), 706(m),
644(m), 576(m).
2.3.4. {[Mn(L)(l2-EtOH)]}n (4)
2.3. Preparation of the complexes and basic analytical data
The ethanol solution (10 mL) of Mn(OAc)2ꢀ4H2O (0.2451 g,
1 mmol) was added slowly to the ligand (0.3974 g, 1 mmol) in ace-
tonitrile (20 mL). The brown clear solution was stirred for an hour
and filtered. Brown block single crystals were obtained by slow
evaporation of the filtrate at room temperature. Yield: 45%. Anal.
calc. for C25H23N5O3Mn: C, 60.36; H, 4.86; N, 14.08. Found: C,
60.87; H, 4.70; N, 14.15%. IR(cmꢁ1, KBr): 3030(w), 2972(m),
2962(m), 2916(m), 2897(m), 2862(m), 1591(s), 1566(s), 1525(s),
1485(s), 1439(s), 1381(m), 1338(m), 1144(m), 1084(m), 1041(s),
1028(m), 924(m), 891(m), 842(w), 782(w), 756(m), 710(m),
690(m), 658(m), 603(w).
2.3.1. {[Zn(HL)(H2O)(DMF)](NO3)}n (1)
The ligand H2L (0.1192 g, 0.3 mmol) was dissolved in a mixed
solvent of 9 mL acetonitrile and 3 mL N,N-dimethylformamide
(DMF). To this solution was added dropwise an acetonitrile
(6 mL) solution of Zn(NO3)2ꢀ6H2O (0.0892 g, 0.3 mmol) with con-
stant stirring at room temperature. The mixture was filtered after
stirring for ca. 1 h and the filtrate was allowed to evaporate slowly
at ambient temperature. The light-yellow block crystals were ob-
tained in 63% yield after several days. Anal. Calc. for C26H27N7O7Zn:
Table 1
Crystal and structure refinement data for 1–4.
Complex
1
2
3
4
Formula
C
26H27N7O7Zn
C46H36N10O4Cd
905.26
monoclinic
C2/c
22.996(5)
19.443(4)
13.889(3)
90.00
C48H43N11O6Mn
924.87
orthorhombic
P bca
14.806(3)
19.507(4)
31.462(6)
90.00
C25H23N5O3Mn
496.42
monoclinic
P 21/c
11.565(5)
18.363(8)
11.474(5)
90.00
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
614.92
monoclinic
P21/c
10.284(2)
12.043(2)
23.178(5)
90.00
a
(°)
b (°)
93.45(3)
90.00
2865.3(1)
4
124.06(3)
90.00
5144.6(2)
4
90.00
90.00
9087(3)
8
1.352
102.846(7)
90.00
2375.8(17)
4
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.425
1.169
1.388
Rint
0.0347
1. 064
0.0760
1.146
0.0683
1.006
0.0625
1.086
Goodness-of-fit (GOF) on F2
R1 [I > 2
wR2 [I > 2
Residuals (e Åꢁ3
r
(I)]
0.0337
0.0855
ꢁ0.434, 0.345
0.0562
0.1421
ꢁ1.110, 0.718
0.0613
0.1541
ꢁ0.466, 0.344
0.0610
0.1208
ꢁ0.623, 0.361
r(I)]
)

H. Li et al. / Polyhedron 55 (2013) 209–215
211
2.4. X-ray crystallography
applied to the collected data and the structure of 2 was refined
again [17]. In 4, the C12-C17 atoms of the phenyl group were dis-
ordered into two positions with site occupancy factors of 0.45 and
0.55, respectively. The details of the crystal parameters, data col-
lection and refinements for complexes 1–4 are summarized in
Table 1. Selected bond lengths and angles with their estimated
standard deviations are listed in Table S1. Summary for hydrogen
bond data are listed in Table S2.
The crystallographic data of the complexes 1–3 were collected
at 293(2) K on a Rigaku R-axis Spider diffractometer with graphite
monochromatic Mo Ka radiation (k = 0.71073 Å). The structures
were solved by direct methods using SHELXS-97 and were refined
by full matrix least-squares methods using SHELXL-97 [15]. Aniso-
tropic displacement parameters were refined for all non-hydrogen
atoms. The data collection for 4 was performed on a Bruker SMART
1000 CCD diffractometer at 293 K. Semi-empirical absorption cor-
rection was applied using the SADABS program [16]. The structure
was solved by direct method and refined by full-matrix least
square on F2 using the SHELXTL-97 program. The structure of 2 pos-
sesses large solvent accessible volume, but the difference Fourier
revealed no meaningful electron density that could be reliably as-
signed to the solvent. Thus, the SQUEEZE routine of PLATON was
3. Results and discussion
3.1. Crystal structural description
3.1.1. Crystal structure of {[Zn(HL)(H2O)(DMF)](NO3)}n (1)
The crystal structure of 1 is exhibited in Fig. 1a with an atom
numbering scheme. Its asymmetric unit contains one Zn(II) center,
Fig. 1. (a) Crystal structure of 1 with atom numbering scheme. (b) The infinite zigzag chain structure along b axis of 1. The coordinated solvent molecules are omitted for
clarity. (c) The chains are further linked by hydrogen bonds to generate a 3D framework. The hydrogen bonds are indicated by the dashed lines.

212
H. Li et al. / Polyhedron 55 (2013) 209–215
one ligand anion HLꢁ, one water, one N,N-dimethylformamide
(DMF) molecules and one nitrate anion for charge balance. Each
Zn(II) atom is coordinated by O1, N3 and O2 atoms from one ligand
anion HLꢁ, one N5A atom (A: ꢁx + 1, y + 1/2, ꢁz + 3/2) from an-
other ligand anion, and two O atoms (O3 and O4) from the coordi-
nated DMF and water molecules to forms an octahedron geometry.
The O1, O2, N3, N5A atoms consist of the equatorial plane with the
least square plane deviation of 0.0400 Å, and the Zn(II) atom strays
from the equatorial plane 0.1659 Å. The Zn–O/N bond distances in
equatorial plane are in the range of 2.007(2) to 2.098(2) Å. The ax-
ial positions are occupied by O3 and O4 from the DMF and water
molecules with the bond lengths of 2.323(2) and 2.069(2) Å. The
angels of O1–Zn–O2, N3–Zn–N5A and O3–Zn–O4 are 164.83(6)°,
165.24(7)° and 175.38(7)°, respectively, which are deviated from
the theoretical value of 180°. Therefore, the local coordination
geometry around the Zn(II) center can be described as a distorted
octahedron. On the other hand, the ligand acts as negative mono-
valent tetradentate linker to bond with two Zn(II) atoms, in which
the O1, N3 and O2 atoms coordinate with Zn1(II) atom in meridi-
onal fashion, and the pyridyl N5 atom of the lateral chain bonds
with another Zn1A atom. Such connection mode gives rise to zig-
zag chain structure of complex 1 with the Znꢀ ꢀ ꢀZn separation of
7.253 Å along the b axis as illustrated in Fig. 1b.
In complex 1, the chains are further linked by hydrogen bonds
to form a 3D framework. The coordinated water molecules and ni-
trate anions play a vital role in the formation of this architecture.
First, the adjacent chains are linked by O4–H4WAꢀ ꢀ ꢀN2 hydrogen
bonds between the coordinated water molecules and the ligands
to form a 2D network (Fig. S1 in ESI). The distance of O4ꢀ ꢀ ꢀN2 is
2.786(3) Å with the angle O–Hꢀ ꢀ ꢀN being 165.00°. In addition, the
O atoms of the nitrate anions act as acceptors to form O–Hꢀ ꢀ ꢀO,
N–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀO hydrogen bonds with water molecules and
the ligands. These hydrogen bonds further link the 2D networks
to generate 3D framework structure as illustrated in Fig. 1c.
Fig. 2. (a) Crystal structure of 2 with the coordination environment around the
Cd(II) center. (b) The double-stranded chain structure of 2 along the c axis. The
phenyl groups on 1,4-positions of the ligands are omitted for clarity.
to form a 12-membered Cd2(HL)2 irregular ring with a Cdꢀ ꢀ ꢀCd sep-
aration of 7.459 Å and the adjacent rings shared one Cd(II) atom to
generate a double-stranded chain structure extended along the c
axis as shown in Fig. 2b. There are N–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀO hydrogen
bonds in the chains, which help in stabilizing the structure (Fig. S2
in ESI).
3.1.2. Crystal structure of [Cd(HL)2]n (2)
To investigate the influence of metal atom on the structure of
the complex, the reactions of ligand H2L with Cd(NO3)2ꢀ6H2O or
Mn(NO3)2ꢀ4H2O were carried out, and complexes 2 and 3, respec-
tively, were obtained and their structures were determined by X-
ray crystallographic analyses. It is interesting to find that 2 features
double-stranded chain structure, rather than Zigzag chain struc-
ture of 1, and 3 is a mononuclear compound. Meanwhile, the li-
gands in complexes 1–3 adopt different coordination modes. The
results provide a nice example that metal atoms with different
coordination features play an important role in determining the
structures of the complexes.
The crystal structure of 2 with atom numbering scheme is
shown in Fig. 2a. Each Cd(II) atom is coordinated by N3, O2, N3A
and O2A atoms from two ligand anions and two pyridyl N atoms
(N5B and N5C) from the other two ligand anions (A: ꢁx + 1, y,
ꢁz + 1/2. B: ꢁx + 1, ꢁy + 1, ꢁz + 1. C: x, ꢁy + 1, z ꢁ 1/2.). The bond
lengths of Cd1–O2, Cd1–N3 and Cd1–N5 are 2.337(3), 2.382(3)
and 2.419(3) Å, respectively, and the coordination angles around
Cd1(II) atom are varying from 67.33(1)° to 154.28(2)° (Table S1).
Therefore, the local coordination geometry of the Cd(II) atom can
be described as a serious distorted octahedral with N4O2 donor set.
On the other hand, the ligand acts as a mononegative tridentate
bridging linker to bond with two different Cd(II) atoms. It is note-
worthy that only azomethine N3, enolic O2 and pyridyl N5 atoms
take part in the coordination with metal atoms. While the O1 atom
of the pyrazolone ring is free of coordination in complex 2. The
unexpected coordination performance of H2L is different from that
in complex 1 and it is also very rare in the reported complexes of
pyrazolone derivatives. By closer inspection of the structure, two
antiparallel ligand anions HLꢁ bridge two adjacent Cd(II) atoms
3.1.3. Crystal structure of {[Mn(HL)2]ꢀCH3CNꢀ2H2O} (3)
Complex 3 has a mononuclear structure and the asymmetric
unit of 3 contains one Mn(II) atom, two ligand anion HLꢁ, one lat-
tice acetonitrile and two lattice water molecules. The structure of
the [Mn(HL)2] motif is shown in Fig. 3a with an atom numbering
scheme. Each Mn(II) atom with octahedral geometry is coordinated
by O1, N3, O2 atoms from one ligand anion and O3, N8, O4 atoms
from another ligand anion to form a MnN2O4 coordination environ-
ment. The O3, O4, N3 and N8 atoms comprise the equatorial plane
with the least square plane deviation of 0.0345 Å, and the Mn(II)
atom strays from the equatorial plane 0.0237 Å, which indicates
that the Mn(II) atom almost lies in the plane. The Mn–O3, Mn–
O4, Mn–N3 and Mn–N8 bond lengths are 2.084(2), 2.191(2),
2.233(3) and 2.210(3) Å, respectively. The axial positions are occu-
pied by O1 and O2 atoms with bond distances of 2.107(2) and
2.212(2) Å. The bond angels of O3–Mn–O4, N3–Mn–N8 and O1–
Mn–O2 are 157.53(9)°, 176.93(1)° and 151.59(9)°, respectively,
which are deviated from the theoretical value of 180°. Therefore,
the local coordination geometry around the Mn(II) center can be
described as highly distorted octahedron.
On the other hand, the ligand H2L is in the deprotonated form
by losing one hydrogen atom and functions as negative monova-
lent tridentate chelating agent coordinated to one Mn(II) atom in
meridional fashion and generate a mononuclear complex. The

H. Li et al. / Polyhedron 55 (2013) 209–215
213
Fig. 3. (a) Crystal structure of 3 with the coordination environment around the
Mn(II) center. The phenyl groups on 1-position of pyrazolone rings are omitted for
clarity. (b) The mononuclear units are connected by the intermolecular hydrogen
bonds to form chain structure. The hydrogen bonds are indicated by the dashed
lines.
remarkable feature of 3 is that the pyridyl N5 atom in the lateral
chain was not coordinate with the Mn(II) atom. The crystal packing
diagram of 3 is shown in Fig. 3b, the mononuclear units are linked
by the intermolecular hydrogen bonds C44–H44ꢀ ꢀ ꢀN4 to form a
chain structure.
Complexes 1–3 were synthesized by the reactions of ligand H2L
with M(NO3)2ꢀnH2O (M = Zn, Cd, Mn) under the mixed solvent con-
dition. But complexes 1–3 have different structures. Complex 1 has
a Zigzag chain structure, while 2 and 3 feature double-stranded
chain and mononuclear structure, respectively. In complexes 1–3,
the ligands H2L act as mononegtive agent coordinated with the
metal atoms. It is worth notice that ligands adopt three different
coordination modes in 1–3. These results indicated that the metal
atoms with different features have a significant effect on the for-
mation and structures of the resulting complexes [18].
Fig. 4. (a) Crystal structure of 4 with atom numbering scheme. The C12–C17 atoms
of the phenyl group at the 3-position were disordered into two positions with site
occupancy factors of 0.45 and 0.55, respectively. (b) The 2D network structure of 4.
nated by O1, N3 and O2 atoms from one ligand anion L2ꢁ, one N5B
atom from another ligand anion, and two O atoms (O3 and O3A)
from two bridging ethanol molecules to form an octahedron geom-
etry with N4O2 donor sets (A: ꢁx + 1, ꢁy + 2, ꢁz. B: x, ꢁy + 3/2,
z ꢁ 1/2.). The O1, O2, N3 and O3A atoms consist of the equatorial
plane with the least square plane deviation of 0.1094 Å, and the
Mn1(II) ion strays from the equatorial plane 0.0251 Å, which indi-
cates that the Mn1(II) atom nearly lies in the equatorial plane. The
axial positions are occupied by O3 and N5B atoms with the bond
distances of 2.208(2) and 2.398(3) Å. The bond distances of
Mn1–O1, Mn1–O2, Mn1–N3 and Mn1–O3A in the equatorial plane
are 1.916(3), 1.925(3), 1.990(3), 1.873(2) Å, respectively. It is obvi-
ous that the axial bond distances are longer than the bond dis-
tances of the equatorial plane, The bond angels of O1–Mn1–O2,
N3–Mn1–O3A and O3–Mn1–N5B are 167.94(1)°, 171.77(1)° and
176.84(1)°, respectively, which are deviated from the theoretical
value of 180°. All these observations implied that the geometry
around the Mn1(II) atom in 4 should be an elongated distorted
octahedron.
3.1.4. Crystal structure of {[Mn(L)(l2-EtOH)]}n (4)
In order to further investigate the influence of the anion on the
structures of the complexes, reactions of the ligand H2L with
M(OAc)2ꢀnH2O (M = Zn, Cd and Mn) were carried out. Although
great effort was made, only complex {[Mn(L)(l2-EtOH)]}n (4) was
obtained from H2L and Mn(OAc)2ꢀ4H2O. X-ray crystallographic
analysis indicates that complex 4 has a 2D network structure,
rather than a mononuclear structure as observed in 3. The results
showed that the anions may have influence on the structures of
the resulting complexes [19].
The crystal structure of 4 is shown in Fig. 4a with atom number-
ing scheme. The asymmetric unit contains one crystallographically
independent Mn(II) center, one ligand anion L2ꢁ and one l2
-
bridged ethanol molecule. It is interesting that two Mn(II) atoms
(Mn1 and Mn1A) are bridged by two 2-O atoms of the ethanol
molecules and form a dinuclear unit. Each Mn1(II) is hexa-coordi-
l

214
H. Li et al. / Polyhedron 55 (2013) 209–215
In the dinuclear unit, two Mn(II) atoms are bridged by two
l
2-O
the Zn(II) ion is difficult to oxidize or reduce due to its d10 config-
uration [21]. Thus, it can be ascribed to the intraligand transitions.
Furthermore, Compared with the luminescence of ligand, 1 results
in much higher emission energy and a large red shift of 102 nm,
which may be attributed to the coordination of Zn(II) atom to
the ligand. The incorporation of Zn(II) effectively increases the con-
formational rigidity of the ligand and reduces the nonradiative de-
cay of the intraligand excited state [22]. The good fluorescence
efficiency indicated that 1 may be a good candidate for fluorescent
materials.
atoms (O3 and O3A) from ethanol molecules to define a planar cen-
trosymmetric parallelogram, in which the side lengths are 2.208(2)
and 1.873(2) Å. The bond angles of Mn1–O3–Mn1A and O3A–
Mn1–O3 are 98.12° and 81.88°. The Mnꢀ ꢀ ꢀMn intermetallic dis-
tance is 3.091 Å.
In addition, the ligand H2L is in the deprotonated form by losing
two hydrogen atoms and functions as negative bivalent tetraden-
tate coordination unit to bridge two dinuclear units and give rise
to a 2D network structure as indicated in Fig. 4b.
In comparison, the structure of 4 is different from 3. Firstly, the
solvent ethanol molecule acts as bridging co-ligand and connects
two Mn(II) atoms to form dinuclear unit in 4. While in 3, the sol-
vent ethanol molecule did not take part in the coordination. Fur-
thermore, in 4, the ligand functions as negative bivalent
tetradentate unit to bond with two octahedral Mn(II) atoms. But
in 3, the ligand acts as negative monovalent tridentate unit coordi-
nated with one Mn(II) atom. These results indicated that the anions
have a certain effect on coordination mode of the ligands and
structures of the resulting complexes.
3.4. Magnetic property
The temperature variable magnetic susceptibility of complex 4
was measured in the range of 2–300 K under 2 kOe applied field
as shown in Fig. S6. At 300 K,
v
MT is 8.84 cm3 molꢁ1 K, which is
close to the expected spin-only value of 8.75 cm3 molꢁ1 K for two
Mn(II) ions with S = 5/2. The magnetic susceptibility data in the
range of 20–300 K obey the Curie–Weiss law,
vM = C/(T ꢁ h), with
Curie constant C = 9.17 cm3 molꢁ1 K and negative Weiss constants
h of ꢁ9.04 K, which indicates the antiferromagnetic interaction be-
3.2. Thermal analyses
tween Mn(II) ions. The magnetic susceptibility vM increases as the
temperature decreases and reaches a maximum of 0.296 cm3 -
molꢁ1 at 14.0 K and then sharply goes down, suggesting the pres-
ence of possible antiferromagnetic ordering in this compound
(Fig. S7). The Neel temperature, TN, was determined from the
To estimate the stability of the complexes, thermogravimetric
measurements for complexes 1–4 were carried out and the results
were shown in Fig. S3 in ESI. The TG curve of 1 shows a weight loss
of 15.96% from 84 to 156 °C, corresponding to the removal of coor-
dinated water and DMF molecules of each formula unit (Calc.:
14.82%). Then the decomposition of the ligand and nitrate anion
was followed. Weight constancy is attained at around 490 °C. The
end product, estimated as ZnO, has an observed mass of 14.52%
compared with the calculated value of 13.24%. Complex 2 exhibits
a continuous weight loss in the temperature range of 115–640 °C.
For complex 3, the first weight loss (8.38%) in the range of 63–
150 °C corresponds to the departure of one lattice acetonitrile
and two water molecules. The weight loss is consistent with the
calculated value (8.33%). Then, no marked weight loss is observed
until 260 °C. After that temperature, the decomposition of the li-
gand anions was followed in the temperature range of 260–
460 °C. The observed mass loss (82.21%) coincides with the calcu-
lated value (82.70%). The final residue is qualitatively proved to be
Mn2O3, the observed mass of 9.14% as against the calculated value
of 8.53%. Compared with 1–3, complex 4 shows more better ther-
mal stability. No weight loss is observed from room temperature to
240 °C. After that temperature, the compound begins to decom-
pose following a process of continuous weight loss of the coordi-
nated ethanol molecule and ligand anion. The observed mass loss
is 84.27%, which is consistent with the theoretical value of
84.10%. The decomposition completes at 455 °C and the end prod-
uct, estimated as Mn2O3, has the observed mass of 15.73% as
against the calculated value of 15.90%.
peak of d(
vMT)/dT at 9.0 K (inset of Fig. S7) [23]. The ratios of
TN/T( M,max) = 0.643 do show the low-dimensional antiferromag-
v
netic ordering character [24].
Taking into account the two-dimensional character of the com-
plex 4, the 2-D square lattice can be treated as alternating uniform
[MnIIMnII] dimmers with the exchange constant J and interdimmer
interactions zJ0. And the magnetic susceptibility data was fitted by
means of the analytical expression derived by Curély for an infinite
2D square lattice composed of the dimmer Mn2 (S = 5/2) isotropi-
cally coupled [25]. The molar magnetic susceptibility of the dim-
mer [26] can be expressed as given in Eq. (1), and the molar
magnetic susceptibility of the dimmer is written as in Eq. (2). Then
the magnetic susceptibility of the 2D compound is as shown in Eq.
(3), in which u = coth(JdSd(Sd + 1)/kT) ꢁ kT/JdSd(Sd + 1). The best fit-
ting in the temperature range of 50–300 K gives J = ꢁ1.67 cmꢁ1
,
ꢁ
P
zJ0 = ꢁ0.03 cmꢁ1, g = 2.02 with R = 9.96 ꢂ 10ꢁ4 {R = [(
vMT)obs
P
(
v
MT)calc]2/
(
v
MT)obs2}. The negative value of exchange coupling
through the oxygen bridges further suggests antiferromagnetic
interaction in the Mn(II) dimmer.
Ng2b2
vdimer
¼
3kT
ꢀ
ꢁ
6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT
ꢂ
ð1Þ
1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
Ng2b2
3kT
vd
¼
SdðSd þ 1Þ
3.3. Fluorescent properties
ꢀ
ꢁ
6 e2J=kT þ 5e6J=kT þ 14e12J=kT þ 30e20J=kT þ 55e30J=kT
Metal–organic coordination polymers with d10 metal atom and
organic ligand are promising candidates for photoactive materials
with potential applications [20]. Therefore, the solid-state fluores-
cent spectra of the free ligand H2L, complexes 1 and 2 were re-
corded at room temperature, as shown in Fig. S4. The emission
spectra of the free ligand H2L and 2 both display broad band at
SdðSd þ 1Þ ¼
ð2Þ
ð3Þ
1 þ 3e2J=kT þ 5e6J=kT þ 7e12J=kT þ 9e20J=kT þ 11e30J=kT
2
Ng2b2 ð1 þ uÞ
v
¼
2 SdðSd þ 1Þ
3kT
ð1 ꢁ uÞ
ca. 404 nm upon excitation at 251 nm, which may due to the p⁄
–
p
or p⁄–n electronic transitions, since the ligand cation of 2 has
4. Conclusions
the similar structure with that of the free ligand (Fig. S5). While
1 exhibits intense fluorescence emission band at ca. 506 nm upon
excitation at 434 nm. The emission of 1 is neither metal-to-ligand
charge transfer (MLCT) nor ligand-to-metal transfer (LMCT) since
In summary, four complexes with multidentate 4-acyl pyrazo-
lone Schiff-base derivative have been prepared and structurally
characterized. The different structures of these complexes

H. Li et al. / Polyhedron 55 (2013) 209–215
215
_
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China (No. 21161019), the Natural Science Foundation of Xinjiang
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Appendix A. Supplementary data
CCDC reference numbers 917283–917286 contain the supple-
mentary crystallographic data for complexes 1–4, respectively.
These data can be obtained free of charge via http://www.ccdc.
cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
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fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Sup-
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