Synthesis, crystal structures, and selected properties of Cu(II) and Zn(II) complexes with in situ formed 2-hydroxy-N′-(propan-2-ylidene) benzohydrazide

Article abstract of DOI:10.1080/00958972.2012.738813

Cu(C₁₀H₁₁O₂N₂)₂ (1) and [Zn(C₁₀H₁₂O₂N₂) ₂(H₂O)₂](NO₃)₂ (2) were synthesized and characterized by elem

Full text of DOI:10.1080/00958972.2012.738813

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Synthesis, crystal structures,
and selected properties of Cu(II)
and Zn(II) complexes with in situ
formed 2-hydroxy-N′-(propan-2-
ylidene)benzohydrazide
Shunsheng Zhao a , Sijiao Wang a , Xiangrong Liu a , Bei Liang a
Lanlan Li a , Huiwu Cai a & Kanshe Li a
,
a College of Chemistry and Chemical Engineering, Xi’an University
of Science and Technology, 710054, Xi’an, P.R. China
Accepted author version posted online: 11 Oct 2012.Version of
record first published: 30 Oct 2012.
To cite this article: Shunsheng Zhao, Sijiao Wang, Xiangrong Liu, Bei Liang, Lanlan Li, Huiwu
Cai & Kanshe Li (2012): Synthesis, crystal structures, and selected properties of Cu(II) and Zn(II)
complexes with in situ formed 2-hydroxy-N′-(propan-2-ylidene)benzohydrazide, Journal of
Coordination Chemistry, 65:24, 4277-4287
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Journal of Coordination Chemistry
Vol. 65, No. 24, 20 December 2012, 4277–4287
Synthesis, crystal structures, and selected properties
of Cu(II) and Zn(II) complexes with in situ formed
2-hydroxy-N9-(propan-2-ylidene)benzohydrazide
SHUNSHENG ZHAO, SIJIAO WANG, XIANGRONG LIU*, BEI LIANG,
LANLAN LI, HUIWU CAI and KANSHE LI
College of Chemistry and Chemical Engineering, Xi’an University of Science and
Technology, 710054 Xi’an, P.R. China
(Received 12 April 2012; in final form 7 September 2012)
Cu(C10H11O2N2)2 (1) and [Zn(C10H12O2N2)2(H2O)2](NO3)2 (2) were synthesized and charac-
terized by elemental analysis, FT-IR spectra, UV-Vis absorption spectroscopy, and X-ray
single-crystal diffraction. Both complexes show distorted octahedral geometry. In 1, Cu(II) is
coordinated by four oxygen atoms from four ligands and two nitrogen atoms from two ligands.
In 2, Zn(II) is coordinated by two oxygen atoms and two nitrogen atoms from two ligands, and
two water molecules. The crystal structures suggest that original ligand o-carboxybenzaldehyde
salicyloylhydrazone (C15H12O4N2) changed into acetone salicyloylhydrazone (C10H12O2N2).
The TG-DTG curves of these complexes indicate two different decomposition processes. 1 and
2 display catalytic activities to decomposition of hydrogen peroxide. Interaction between the
complexes and DNA studied by UV-Vis titration shows the insert interaction.
Keywords: Synthesis; Crystal structure; Complex; Thermal behavior; DNA Binding ability
1. Introduction
Biological applications of inorganic pharmaceuticals play a key role in clinical therapy.
Examples include cis-platin and corresponding second generation alternatives such as
oxaliplatin and carboplatin serving as chemotherapeutic agents for tumors and as
diagnostic contrast agents such as MRI [1–3]. Transition metals are particularly suitable
for this purpose in that they can adopt a wide variety of coordination numbers,
geometries, and oxidation states in comparison with carbon and other main group
elements [4].
Our interest was attracted to transition metal complexes of acyl hydrazones because
acyl hydrazones have been reported to function as antibacterial, antiviral, antifungal,
and antitumor agents, and for DNA interactions and cleavage [5–8]. Coordination of
bioactive ligands to metal may increase their activity and some bioinactive ligands
acquire activity through coordination. Many complexes derived from hydrazones have
biological activities and are pharmacologically important.
*Corresponding author. Email: xkchemistry@yahoo.com.cn
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.738813

4278
S. Zhao et al.
Interactions of DNA with small molecules can serve as a foundation for design of
new types of pharmaceutical molecules. Interaction models of transition metal
complexes with DNA and their subsequent applications in molecular biology attract
attention. In particular, interest has been generated in DNA binding and DNA cleavage
by redox and photoactive metal complexes in order to explore sequence specificities of
DNA binding using intercalating ligands [9–11].
There is no literature available on the synthesis, structural characterization, and
interaction studies of Cu(II) and Zn(II) complexes containing 2-hydroxy-N0-(propan-2-
ylidene)benzohydrazide, stimulating our interest in synthesis, structure, DNA binding,
cleavage, protein binding, and antioxidant properties of Cu and Zn complexes
containing the above hydrazone. Structures of the new complexes were established by
single-crystal X-ray diffraction and spectroscopic data. In addition, investigations on
thermal decomposition of the complexes and their catalytic activity in the decompo-
sition of hydrogen peroxide were also undertaken.
2. Experimental
2.1. Measurements
Elemental analyses were carried out on a P.E.2400-II instrument. IR spectra were
recorded on a P.E.983 FT-IR spectrophotometer with KBr pellets. UV-Vis spectra were
obtained on a TU-1900 spectrophotometer using DMF as solvent at 10ꢀ5 mol Lꢀ1
Crystal structures were determined using a Bruker SMART APEX CCD diffractometer
.
˚
equipped with graphite monochromated Mo-Ka radiation (ꢀ ¼ 0. 71 073 A). Thermal
data were collected on a Q1000DSC þ LNCSꢀþ1 FACS Q600SDT instrument in nitrogen
at heating rates of 5ꢁC, 10ꢁC, and 15ꢁC min from 30ꢁC to 800ꢁC.
2.2. Materials and synthesis
All chemicals are reagent grade and used as purchased without purification. The
CT-DNA was purchased from Sigma Company. CT-DNA was dissolved in Tris-HCl
buffer (0.1 mol Lꢀ1, pH ¼ 7.25). 2-((Salicyloylhydrazono)methyl)benzoic acid was
prepared according to a previously reported method [12].
2.2.1. Synthesis of bis[2-hydroxy-N0-(propan-2-ylidene)benzohydrazonato]copper(II) (1).
To a solution of Cu(NO3)2 ꢂ 3H2O (0.11 g, 0.4 mmol) in DMF (10 mL), a solution of the
2-((salicyloylhydrazono)methyl)benzoic acid (0.23 g, 0.8 mmol) in DMF (10 mL) was
added. The color of the reaction mixture changed from blue to green. The mixture was
stirred at 50ꢁC in a water bath for 1 h. An aliquot of the resulting solution was analyzed
to determine the complex formed. The remaining solution was kept in a sealed bottle
containing acetone, allowing acetone to slowly evaporate at room temperature. Dark
green crystals of Cu(C10H11O2N2)2 were obtained 2 weeks later. The crystals were
collected by filtration, washed with methanol, and finally dried. Anal. Calcd for
Cu(C10H11O2N2)2 (%): C, 53.86; H, 4.97; N, 12.56; O, 14.35. Found (%): C, 53.81;
H, 4.85; N, 12.55; O, 15.58.

Cu(II) and Zn(II) benzohydrazide
Table 1. Crystallographic data for 1 and 2.
4279
1
2
Empirical formula
Formula weight
Crystal color
Crystal system
Space group
Unit cell dimensions (A, )
C
445.96
Dark green
Monoclinic
P2(1)/n
20H22N4O4Cu
C20H28N6O12Zn
609.85
Yellow
Monoclinic
P2(1)/n
ꢁ
˚
a
b
c
6.2989(10)
16.085(3)
9.7177(15)
97.241(2)
976.7(3), 2
1.516
1.153
7.456(4)
9.943(5)
17.198(8)
98.098(8)
1262.2(10), 2
1.605
1.048
ꢁ
Volume (A ), Z
3
˚
Calculated density (Mg mꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
)
462
632
Crystal size (mm3)
ꢂ range for data collection (ꢁ)
Limiting indices
0.31 ꢃ 0.27 ꢃ 0.15
2.46–25.10
ꢀ7 ꢄ h ꢄ 6;
ꢀ19 ꢄ k ꢄ 15;
ꢀ9 ꢄ l ꢄ 11
4819/1737
[R(int) ¼ 0.0199]
1.098
0.33 ꢃ 0.27 ꢃ 0.14
2.37–25.09
ꢀ8 ꢄ h ꢄ 8;
ꢀ11 ꢄ k ꢄ 11;
ꢀ20 ꢄ l ꢄ 14
5908/2229
[R(int) ¼ 0.0629]
0.999
Reflections collected/unique
Independent reflection
Goodness-of-fit on F2
R indices [I 4 2ꢃ(I)] R1, wR2
R indices (all data) R1, wR2
0.0273, 0.0776
0.0340, 0.0814
0.0676, 0.1711
0.0831, 0.1786
2.2.2. Synthesis of {bis[2-hydroxy-N0-(propan-2-ylidene)benzohydrazide]}(dihydrato)
zinc(II) nitrate (2). This complex was prepared by reacting a CH2Cl2 (7 mL) solution
of Zn(NO3)2 ꢂ 6H2O (0.15 g, 0.4 mmol) with
a
DMF (7 mL) solution of
2-((salicyloylhydrazono)methyl)benzoic acid (0.23 g, 0.8 mmol) at 50ꢁC in a water
bath for 1 h. An aliquot of the resulting solution was analyzed to determine the complex
formed. The remaining solution was kept in a sealed bottle containing acetone and the
acetone slowly evaporated at room temperature. After 2 weeks, yellow crystals
appeared. The crystals were collected by filtration, washed with methanol and finally
dried. Anal. Calcd for [Zn(C10H12O2N2)2(H2O)2](NO3)2 (%): C, 39.39; H, 4.63;
N, 13.78; O, 31.48. Found (%): C, 39.35; H, 4.62; N, 13.56; O, 31.37.
2.2.3. Crystallographic studies. Crystallographic information for 1 and 2 is listed in
table 1. Determination of unit cell parameters and data collections were performed with
˚
Mo-Ka radiation (ꢀ ¼ 0.71073 A). The structures were solved by direct methods and
semi-empirical absorption correction using SHELXTL-97. Non-hydrogen atoms were
located with difference Fourier synthesis and hydrogen atoms were generated
geometrically. The CCDC reference numbers for 1 and 2 are 721329 and 733609,
respectively.
2.2.4. Decomposition of hydrogen peroxide. A mixture of 1 (1 mL, 1 mol Lꢀ1) and
hydrogen peroxide (20 mL, 15%) was put aside for 1 d (20ꢁC), then the hydrogen
peroxide left was titrated with potassium permanganate standard solution and the
percentage of the hydrogen peroxide decomposition was calculated according to the
titration result. Method used for 2, ligand, copper nitrate, or zinc nitrate was same as
that for 1.

4280
S. Zhao et al.
2.2.5. Interaction of CT-DNA. Mixed solutions of 1 (1.0 ꢃ 10ꢀ4 mol Lꢀ1) and DNA
(various concentrations) in buffer solution (pH ¼ 7.3) were put aside for 30 min and
then UV-Vis absorption spectra were measured at room temperature. The method used
for 2 was the same as that for 1.
3. Results and discussion
3.1. Structure description
3.1.1. In situ characterization of bis(N0-2-carboxybenzylidene-2-hydroxybenzohydrazo-
nato)copper(II), intermediate a. For the preparation of 1, a green reaction solution is
obtained when mixing DMF solution of ligand (colorless) and copper nitrate (blue).
Molar conductivity measurement (11.3 S m2 molꢀ1) of the resulting reaction solution
indicates that intermediate a exists as a non-electrolyte [13]. Existence of phenolic
(ꢄ ¼ 11.79 ppm) and carboxylic group (ꢄ ¼ 13.87 ppm) protons in 1H-NMR spectrum of
the complex solution demonstrates the proposed structure with amide group
deprotonated. Comparing to the ligand, the band of the azomethine n ! ꢅ* transition
in UV-Vis absorption spectra of the reaction solution shifts to lower frequencies, also
indicating that the imine nitrogen is involved in coordination. When acetone is allowed
to penetrate slowly into the solution, the o-carboxybenzaldehyde in intermediate a is
replaced by acetone with coordination bonds unbroken. Similar ligand reactions with
coordination bond unbroken could be found in the previous report [14].
3.1.2. In situ characterization of [bis(N0-2-carboxybenzylidene-2-hydroxybenzohydrazide)
(dihydrato)]zinc(II), intermediate b. In contrast with 1, for 2, the solution remains
colorless when mixing DMF solution of ligand (colorless) and zinc nitrate (colorless).
Molar conductivity measurement (219.1 S m2 molꢀ1) of the reaction solution indicates
that intermediate b exists as a bivalent electrolyte, which suggests the complex cation
1
with neutral ligands and two accompanying NOꢀ3 . H-NMR spectrum of the complex
solution shows existence of phenolic (ꢄ ¼ 11.73 ppm), carboxylic (ꢄ ¼ 13.09 ppm), and
amide (ꢄ ¼ 2.15 ppm) protons, consistent with the proposed structure of intermediate b.
When acetone is allowed to penetrate slowly into the solution, the o-carboxybenzalde-
hyde in intermediate b is replaced by acetone with coordination bonds unbroken,
consistent with the reaction in formation of 1.
3.1.3. Structure description of 1. The crystal structure and packing diagram of 1 are
shown in figures 1 and 2, respectively. Selected bond lengths and angles are listed in
table 2. Hydrogen bonding geometry is given in table 3.
As figure 2 and table 2 show, each Cu(II) adopts a distorted octahedral geometry in
which the basal plane is formed by coordination of two imino nitrogen atoms and two
carbonyl oxygen atoms from two ligands; the axial sites are occupied by two phenolic
hydroxyl oxygen atoms from two other ligands with a relatively weak interaction.
The bond lengths of Cu–O and Cu–N are in agreement with previously reported data
˚
of complexes with similar structures [15–17]. Cu–O bond length (1.903 A) is a little
shorter than that of Cu–N, which means oxygen has better coordination ability with

Cu(II) and Zn(II) benzohydrazide
4281
Figure 1. Crystal structure of 1 (symmetry transformations used to generate equivalent atoms: A ꢀx ꢀ 2,
ꢀy þ 1, ꢀz).
Figure 2. Layer structure of 1 (symmetry transformations used to generate equivalent molecules: A x, y, z; B
x þ 1, y, z; C x þ 2, y, z; D x þ 3, y, z; AA ꢀx ꢀ 2, ꢀy þ 1, ꢀz; AB ꢀx ꢀ 1, ꢀy þ 1, ꢀz; AC ꢀx, ꢀy þ 1, ꢀz;
AD ꢀx þ 1, ꢀy þ 1, ꢀz).
Cu(II) than does nitrogen [18]. The two five-membered chelate rings are essentially
planar (Cu1–N1–N2–C1–O1 and Cu1–N1A–N1A–C1A–O1A). The C1–N2 bond
˚
length is 1.319(3) A, shorter than that of C–N single bond (1.47 A) but longer than
˚
˚
that of C¼N double bond (1.273 A), due to conjugation between C¼O and C¼N. The
˚
˚
O1–C1 bond length is 1.285(2) A, between C¼O double bond (1.233 A) and C–O single
˚
bond (1.336 A). Inter-unit coordination of metals and ligands from different unsym-
metrical units makes 1 a coordination polymer and stacking interaction induces the
z-type 3-D structure, as shown in figure 2.
3.1.4. Structure description of 2. In 2, the Zn(II) is six coordinate with a distorted
octahedral geometry. The crystal structure and layer structure are shown in
figures 3 and 4. The six-coordinate groups are two imino nitrogen atoms and two

4282
S. Zhao et al.
ꢁ
˚
Table 2. Selected bond lengths (A) and angles ( ) for 1 and 2.
1
2
Cu(1)–O(1)#1
Cu(1)–O(1)
Cu(1)–N(1)#1
Cu(1)–N(1)
Cu(1)–O(2)#3
Cu(1)–O(2)#4
N(1)–C(8)
N(1)–N(2)
N(2)–C(1)
O(1)–C(1)
O(2)–C(7)
1.9029(14)
1.9029(14)
2.0547(18)
2.0547(18)
2.7561(17)
2.7561(17)
1.288(3)
1.402(2)
1.319(3)
1.285(2)
1.363(3)
Zn(1)–O(1)
2.050(3)
2.050(3)
2.193(3)
2.193(3)
2.102(3)
2.102(3)
1.276(5)
1.385(5)
1.335(5)
1.205(5)
1.221(5)
Zn(1)–O(1)#2
Zn(1)–N(1)
Zn(1)–N(1)#2
Zn(1)–O(2)
Zn(1)–O(2)#2
N(1)–C(2)
N(1)–N(2)
N(2)–C(4)
N(3)–O(6)
N(3)–O(4)
O(1)#1–Cu(1)–O(1)
O(1)#1–Cu(1)–N(1)#1
O(1)–Cu(1)–N(1)#1
O(1)#1–Cu(1)–N(1)
O(1)–Cu(1)–N(1)
N(1)#1–Cu(1)–N(1)
O(2)#3–Zn(1)–O(2)#4
O(2)#3–Cu(1)–N(1)
O(2)#3–Cu(1)–O(1)
180.0
O(1)#2–Zn(1)–O(1)
O(1)#2–Zn(1)–N(1)#2
O(1)–Zn(1)–N(1)#2
O(1)#2–Zn(1)–N(1)
O(1)–Zn(1)–N(1)
N(1)#1–Zn(1)–N(1)
O(2)–Zn(1)–O(2)#2
O(2)–Zn(1)–N(1)
180.0
80.83(6)
99.17(6)
99.17(6)
76.54(12)
103.46(13)
103.46(13)
76.54(12)
180.000(1)
180.0(2)
80.83(6)
180.00(8)
180.00(5)
88.298(55)
91.785(58)
88.19(15)
88.91(15)
O(2)–Zn(1)–O(1)
Symmetry transformations used to generate equivalent atoms: #1 ꢀxꢀ2, ꢀy þ 1,ꢀz; #2 ꢀx,ꢀy,ꢀz þ 1; #3 x ꢀ 1, y, z; #4
ꢀx ꢀ 1, ꢀy þ 1, ꢀz.
Table 3. Hydrogen bonding geometry (A, ꢁ).
˚
D–Hꢂ ꢂ ꢂA
d (D–H)
d (Hꢂ ꢂ ꢂA)
d (Dꢂ ꢂ ꢂA)
ff(DHA)
1
2
O(2)–H(2A)ꢂ ꢂ ꢂN(2)
N(2)–H(2)ꢂ ꢂ ꢂO(3)
0.77(2)
0.86
0.82
0.87
0.85
1.90(2)
1.90
1.86
1.92
1.87
2.579(2)
2.576
2.665
2.770
2.720(5)
148(2)
134.3
169.2
163.7
174.9
O(3)–H(3)ꢂ ꢂ ꢂO(5)#5
O(2)–H(2A)ꢂ ꢂ ꢂO(4)
O(2)–H(2B)ꢂ ꢂ ꢂO(5)#6
Symmetry transformations used to generate equivalent atoms: #5 ꢀx þ 1, ꢀy þ 1, ꢀz þ 1; #6 ꢀx þ 1, ꢀy, ꢀz þ 1.
Figure 3. Crystal structure of 2 (symmetry transformations used to generate equivalent atoms: A ꢀx, ꢀy,
ꢀz þ 1).

Cu(II) and Zn(II) benzohydrazide
4283
Figure 4. Layer structure of 2.
Scheme 1. Formation of 1.
carbonyl oxygen atoms from two ligands. There are also two water molecules
occupying the axial sites.
˚
˚
The average Zn–O and Zn–N bond lengths are 2.076 A and 2.193(3) A, respectively,
similar with previous reports [19–21]. The five-membered chelate rings (Zn1–N1–N2–
C4–O1 and Zn1–N1A–N2A–C4A–O1A) are in one plane. The N1–C2 bond length is
˚
˚
˚
1.275(5) A, similar with a C¼N (1.273 A). The O1–C4 bond length is 1.246(5) A, close to
˚
C¼O double bond length (1.233 A). The intramolecular hydrogen bond N2–H2ꢂ ꢂ ꢂO3
ꢁ
˚
(2.576 A, 134.3 ) stabilizes the planarity of the ligand in the complex. Intermolecular
hydrogen bonds (O3–H3ꢂ ꢂ ꢂO5 and O2–H2ꢂ ꢂ ꢂO5) link the complex cations and nitrate
anions to form layers. These flat layers are interconnected by hydrogen bonds between
water and NOꢀ3 to form a network.
3.2. The formation mechanisms of 1 and 2
The formation mechanisms of the complexes are proposed through intermediates a and
b, respectively. Substitution occurs when acetone is allowed to penetrate slowly into the
solution to give 1 and 2, as shown in schemes 1 and 2.

4284
S. Zhao et al.
Scheme 2. Formation of 2.
3.3. IR spectra
The IR spectrum of ligand shows bands at 1606 and 1662 cmꢀ1 assigned to ꢆ(C¼N) and
ꢆ(C¼O), respectively. Moreover, in the IR spectrum of 1 (‘‘Supplementary material’’),
ꢆ(C¼N) and ꢆ(C¼O) shift to 1555 ꢆ(C¼N) and 1605 cmꢀ1 ꢆ(C¼O), and ꢆ(OH/NH,
enol/keto) disappears due to coordination [22, 23]. In the IR spectrum of 2, ꢆ(C¼N)
and ꢆ(C¼O) shift to 1567 ꢆ(C¼N) and 1622 cmꢀ1 ꢆ(C¼O) and an OH vibration could
be assigned to coordinated water. A strong band at 1380 cmꢀ1 in 2 indicates the
existence of non-coordinated nitrate, also evidenced by single-crystal X-ray diffraction.
3.4. UV-Vis absorption spectra
The ligand and complexes in DMF (10ꢀ5 mol Lꢀ1) show absorptions between 200 and
500 nm. The free ligand exhibits a strong absorption at 322 nm, due to intraligand ꢅ–ꢅ*
transition. In 1 and 2, spectra show intense bands at 311 and 313 nm, respectively,
which can be assigned to ꢅ–ꢅ* transitions. The azomethine n ! ꢅ* band is shifted to
lower frequencies, indicating that the imine nitrogen is coordinated to metal [24].
3.5. Thermal analysis
TG-DTG curves of 1 and 2ꢀa1t 10ꢁC minꢀ1 are shown in ‘‘Supplementary materiaꢀl.1’’
TG–DTG curves at 5ꢁC min and 15ꢁC minꢀ1 are similar with that of 10ꢁC min
.
Weight losses and corresponding temperature ranges of the complexes during
decomposition are obtained from these figures.
From figure S2 for 1, there are two distinct stages in decomposition. The first from
100ꢁC to 280ꢁC with a mass loss of 60.0% (Calcd 60.35%) is connected with loss of the
phenol and two methyls. The second decomposition stage occurs from 280ꢁC to 600ꢁC
with a mass loss of 22.24% (Calcd 21.99%), assigned to loss of two five-membered
chelate rings. The remainder, probably CuO, has mass of 16.73% as against the
calculated value of 17.76%.
For 2, there are three stages in the decomposition (‘‘Supplementary material’’). The
first stage from 35ꢁC to 170ꢁC with a mass loss of 12.88% (Calcd 13.19%) is connected
with the loss of coordinated water. The second stage occurs from 170ꢁC to 340ꢁC,
assigned to loss of nitrate and two methyls with a mass loss of 25.00% (Calcd 26.70%).

Cu(II) and Zn(II) benzohydrazide
4285
Table 4. The catalytic properties of compound for decomposi-
tion of hydrogen peroxide.
Decomposition
percent of H2O2 (%)
Compound
Cu(NO3)2 ꢂ 3H2O
Zn(NO3)2 ꢂ 6H2O
Ligand
90.5
80.2
85
Complex 1
Complex 2
99.8
96.7
The third stage, from 340ꢁC to 800ꢁC, with a mass loss of 32.82% (Calcd 34.08%), is
assigned to loss of phenol. When the temperature is 800ꢁC, the remaining mass of
29.1% could be assigned to Zn and coordinated atoms (Calcd 29.5%). This indicates
that 2 decomposes incompletely at 800ꢁC.
3.6. The catalytic activity of 1 and 2
The test of catalytic decomposition activity to hydrogen peroxide shows that 1 and 2
have good catalytic activity (table 4). In the same concentration of the catalyst, the
metal salts and their complexes have catalytic decomposition activity. The ligand also
has some catalytic activity. The complexes perform much better catalytic ability than
corresponding salts and ligand.
3.7. DNA binding study
UV-Vis spectroscopy is an effective method for examining the binding of DNA with
metal complexes [26]. The potential binding abilities of ligand, 1 and 2 to CT-DNA
were studied by UV-Vis absorption spectroscopy. Figure 5 and figures S4 and S5
(‘‘Supplementary material’’) show the intensity variation of intraligand ꢅ–ꢅ* transition
of the ligand, 1 and 2 upon addition of CT-DNA with an increasing concentration.
Hypochromism of 11% for ligand, 3% for 1 and 1% for 2 was observed (table 5).
Although this is not definitive, hypochromism observed for other complexes in the
presence of CT-DNA is taken as a sign of an intercalative binding mode, where stacking
interactions between the aromatic chromophore of the complex and the base pairs of
DNA modulate the absorption characteristics of the metal complexes [27]. Comparing
with previous reports [28], we proposed that the hypochromism observed in UV spectra
is due to the partial/moderate intercalation of the ligand within the complexes. The
extent of the hypochromism is commonly consistent with the strength of intercalative
interaction. Our results imply that our ligand is similar to TACN [28] and bpa-R [29],
which do not intercalate very strongly or deeply between the DNA base pairs.
4. Conclusion
Two complexes with same coordination geometry were synthesized and characterized.
The structures of the complexes show original ligand changed into acetone

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S. Zhao et al.
Figure 5. Changes in the absorption spectra of 1 on titration with increasing CT-DNA concentration
(0–50 mmol Lꢀ1).
Table 5. The changes of the UV-Vis spectrum after interaction between compounds and
DNA.
ꢀmax (nm)
Compound
Free state
Bound state
Dꢀ
Absorbance changes (%)
Ligand
Complex 1
Complex 2
322
311
313
298
299
300
ꢀ24
ꢀ12
ꢀ13
11
3
1
salicyloylhydrazone and the nitrate in 2 is not coordinated. Thermal decomposition
of 1 is divided into two stages, while 2 is divided into three stages. Catalytic activity to
decomposition of hydrogen peroxide shows that 1 displays better activity than 2. The
modes of CT-DNA binding to ligand, 1 and 2 have been proposed as moderate
intercalation.
Supplementary material
CCDC 721329 and 733609 contain the supplementary crystallographic data for 1 and 2.
The data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/conts/retrieving.html.

Cu(II) and Zn(II) benzohydrazide
4287
Acknowledgments
The authors are grateful to National Natural Science Foundation of China
(Nos. 21073139, 21103135, and 51173145), Scientific Research Program Funded by
Shaanxi Provincial Education Commission (Nos. 07JK317 and 12JK0622), Natural
Science Basic Research Plan in Shaanxi Province of China (No. 2011JQ2011), the Open
Foundation of the Laboratory of Space Materials Science and Technology of NWPU,
and Cultivation Foundation of Xi’an University of Science and Technology (Program
No. 2010QJD030) for supporting this research.
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