Copper(II) complexes with 4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic acid: Syntheses, crystal structures and antifungal activities

Article abstract of DOI:10.1016/j.jssc.2014.04.012

Reaction of Cu(II) with an asymmetric semi-rigid organic ligand 4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic acid (HL), yielded five compounds, [Cu _0.5L]_n (1), [Cu(HL)₂Cl₂]_n (2), [Cu(HL)₂Cl₂(H₂O)] (3), [Cu(L) ₂(H₂O)]_n (4) and [Cu(L)(phen)(HCO ₂)]_n (5), which have been fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. As for compounds 1, 2 and 5, Cu(II) is bridged through HL, Cl^-, and formic acid, respectively, featuring 1D chain-structure. In compound 3, Cu(II) with hexahedral coordination sphere is assembled through hydrogen-bonding into 3D supramolecular framework. In compound 4, 1D chain units -Cu-O-Cu-O- are ligand-bridged into a 3D network. All compounds were tested on fungi (Fusarium graminearum, Altemaria solani, Macrophoma kawatsukai, Alternaria alternata and Colletotrichum gloeosporioides). Compound 1 exhibits a better antifungal effect compared to other compounds. An effect of structure on the antifungal activity has also been correlated.

Full text of DOI:10.1016/j.jssc.2014.04.012

Journal of Solid State Chemistry 215 (2014) 292–299
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Copper(II) complexes with 4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic
acid: Syntheses, crystal structures and antifungal activities
a
b
a,
nn
Pingping Xiong a,1, Jie Li b,1, Huaiyu Bu b, , Qing Wei , Ruolin Zhang , Sanping Chen
n
a Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science,
Northwest University, Xi'an 710069, China
b Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Shaanxi Provincial Key Laboratory of Biotechnology,
Xi'an 710069, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of Cu(II) with an asymmetric semi-rigid organic ligand 4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic
acid (HL), yielded five compounds, [Cu0.5L]n (1), [Cu(HL)2Cl2]n (2), [Cu(HL)2Cl2(H2O)] (3), [Cu(L)2(H2O)]n
(4) and [Cu(L)(phen)(HCO2)]n (5), which have been fully characterized by infrared spectroscopy,
elemental analysis, and single-crystal X-ray diffraction. As for compounds 1, 2 and 5, Cu(II) is bridged
through HL, Cl-, and formic acid, respectively, featuring 1D chain-structure. In compound 3, Cu(II) with
hexahedral coordination sphere is assembled through hydrogen-bonding into 3D supramolecular
framework. In compound 4, 1D chain units –Cu–O–Cu–O– are ligand-bridged into a 3D network. All
compounds were tested on fungi (Fusarium graminearum, Altemaria solani, Macrophoma kawatsukai,
Alternaria alternata and Colletotrichum gloeosporioides). Compound 1 exhibits a better antifungal effect
compared to other compounds. An effect of structure on the antifungal activity has also been correlated.
& 2014 Elsevier Inc. All rights reserved.
Received 22 December 2013
Received in revised form
7 April 2014
Accepted 20 April 2014
Available online 29 April 2014
Keywords:
Copper(II) compound
4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic acid
Crystal structure
Antifungal activity
1. Introduction
antifungal activity, expand the bactericidal spectrum and renovate
the issue about resistance of sterilization [12]. To explore a new
1H-1, 2, 4-triazole derivatives as a broad-spectrum, highly
effective antifungal fungicide, has been much concerned [1].
Remarkably, triazoles inhibit sterol 14R-demethylase, thus inter-
fere with fungal cell-wall formation [2]. Its outstanding pesticide
effect contributes to the development prospect of triazole-based
compounds [1]. So far, the pesticides on market are mainly
composed of these triazole fungicides, such as difenoconazole,
diniconazole, tebuconazole, flutriafol, hexaconazole and cyproco-
nazole [3–7].
Compared to conventional triazole fungicides, the metal coor-
dination compounds pesticides could be utilized as a kind of
controlled release formulations which has the capacity of alleviat-
ing the toxicity and decreasing the pesticide residue [8]. In
addition to the excellent characteristics of the original, the new
pesticide metal coordination compounds also have the advantages
of increasing efficacy, even the stability of the original drug,
reducing pesticide dosage, as well as other biological functions
[9–11]. The modification in structure of triazole can influence the
metal coordination compound pesticide has a profound potential
of development and utilization in agricultures [13].
In this paper, we selected the 4-(1H-1, 2, 4-trizol-1-ylmethyl)
benzoic acid as the ligand, where oxygen atoms in the carboxylic
group and N atoms from the triazole ring both are apt to
coordinate with Cu ions. As well-known, the coordination modes
of the carboxyl oxygen can be roughly summarized as monoden-
tate-coordinated, chelating-coordinated and bridging-coordinated
[14,15]. Based on flexible coordination modes of carboxylic group
and antifungal activity of trizole molecule, five copper(II) coordi-
nation compounds were synthesized and structurally character-
ized. Antifungal tests showed that compound 1 exhibited the best
antifungal activity.
2. Experimental
2.1. Materials and methods
Elemental analyses were performed on an Elementar Vario EL
III analyzer. IR spectra were recorded on a Tensor 27 spectrometer
(Bruker Optics, Ettlingen, Germany) as KBr pellets in the range of
4000–400 cmꢀ1. Powder X-ray diffraction (PXRD) patterns were
obtained on a Bruker D8 ADVANCE X-ray powder diffractometer
n
Corresponding author.
nn
Corresponding author. Tel./fax: þ86 2988302604.
E-mail addresses: 7213792@qq.com (H. Bu), sanpingchen@126.com,
sanpingchen312@gmail.com (S. Chen).
1
These authors contributed equally to this work.
http://dx.doi.org/10.1016/j.jssc.2014.04.012
0022-4596/& 2014 Elsevier Inc. All rights reserved.

P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
293
COOH
HOOC
N
N
KOH
HN
N
＋
N
H2O
BrH2C
N
Scheme 1. Synthesis of the ligand.
with Cu Kα radiation (λ¼1.5405 Å). Thermogravimetric measure-
ments were carried out from room temperature to 1000 1C for 1–5
in simulated nitrogen atmosphere using a NETRZSCH STA 449C
Elemental analysis calculated for C20H20Cl2CuN6O5: C 42.94%,
H 3.58%, N 15.03%; found: C 43.15%, H 3.45%, N 14.95%.
equipment with a heating rate of 10 1C minꢀ1
.
2.2.5. Preparation of [Cu(L)2(H2O)]n (4)
Just like the compounds 1 and 2, compound 4 was obtained in
the same way. At 140 1C, the yield of compound 4 and the crystal
shape are much better. Blue lump crystals were isolated by hands
in 15% yield (based on HL). 1H NMR (400 MHz, DMSO-d6): δ 8.925
(s, 1H, CH), 8.315 (s, 1H, CH), 7.954 (d, 2H, p-C6H4), 7.364 (d, 2H,
p-C6H4), 5.818 (s, 2H, CH2). IR (KBr pellet, cmꢀ1): 3455(b), 1633(s),
1556(w), 1382(m), 1287(w), 1131(w), 1019(w), 759(m), 673(w) (Fig.
S1). Elemental analysis calculated for C20H18CuN6O5: C 49.39%, H
3.70%, N 17.29%; found: C 49.22%, H 3.99%, N 17.17%.
2.2. Synthesis
2.2.1. Preparation of 4-(1H-1, 2, 4-trizol-1-ylmethyl) benzoic acid
(HL)
The ligand was synthesized using
a literature procedure
(Scheme 1) [16,17]. IR (KBr pellet, cmꢀ1) for HL: 3453, 3119,
2952, 2363, 1914, 1694, 1515, 1433, 1275, 1141, 1011, 919, 731, and
677. m. p 215.1–215.5 1C.
2.2.2. Preparation of [Cu0.5L]n (1)
2.2.6. Preparation of [Cu(L)(phen)(HCO2)]n (5)
A
mixture of HL (20.3 mg, 0.10 mmol) and CuCl2 ꢁ 2H2O
A mixture of HL (20.3 mg, 0.10 mmol), CuCl2.2H2O (17.0 mg,
0.10 mmol), l,10-phenanthroline (19.8 mg, 0.10 mmol) and N,N-
dimethylformamide (DMF)/H2O (2:3, v/v), which were sealed in
a 10 mL Teflon-lined stainless steel autoclave. The mixture has
been heated at 140 1C for 10 h and cooled to 100 1C at a rate of
5 1C hꢀ1. Upon being held at 100 1C for 72 h, the system was
cooled to room temperature at a rate of 5 1C hꢀ1. The resulting
solution was filtered and transfered in the vial for seven days. Blue
triangular shape crystals were isolated and washed with EtOH
repeatedly. (Yield: 75%, based on HL). 1H NMR (400 MHz, DMSO-
d6): δ 9.455(s, 1H, –HCO), 8.682 (s, 1H, CH), 8.602 (d, 2H, –C5H3N),
8.068 (d, 2H, –C5H3N), 8.024 (s, 1H, CH), 7.924 (d, 2H, p-C6H4),
7.618 (d, 2H, –C6H2), 7.307 (t, 2H, –C5H3N), 7.286 (d, 2H, p-C6H4),
5.018 (s, 2H, CH2). IR (KBr pellet, cmꢀ1): 3441 (b), 1628 (s), 1594
(s), 1382 (m), 1018 (m), 852 (m), 723 (m), 678 (m) (Fig. S1).
Elemental analysis calculated for C23H17CuN5O4: C 56.22%, H
3.46%, N 14.26%; found: C 56.15%, H 3.60%, N 14.19%.
(17.0 mg, 0.10 mmol) was dissolved in distilled H2O (3 mL), which
were sealed in a 10 mL Teflon-lined stainless steel autoclave. The
mixture was heated at 140 1C for 72 h, cooled to 100 1C at a rate of
5 1C hꢀ1, and held at this temperature for 10 h. Then, it was cooled
to room temperature at a rate of 5 1C hꢀ1. Purple lump crystals
were isolated in 45% yield (based on HL). 1H NMR (400 MHz,
DMSO-d6): δ 8.650 (s, 1H, CH), 8.004 (s, 1H, CH), 7.933 (d, 2H, p-
C6H4), 7.331 (d, 2H, p-C6H4), 5.540 (s, 2H, CH2). IR (KBr pellet,
cmꢀ1): 3455 (b), 1608 (s), 1562 (m), 1371 (s), 1288 (m), 1119 (m),
736 (m), 674 (m) (Fig. S1). Elemental analysis calculated for
C
20H16CuN6O4: C 51.29%, H 3.41%, N 17.95%; found: C 51.11%, H
3.74%, N 17.80%.
2.2.3. Preparation of [Cu(HL)2Cl2]n (2)
Compound 2 was synthesized by the identical pathway with
compound 1. In the above method, the purple lump crystals (1)
can be obtained while a small amount of blue–green block crystals
(2) can be received at the same time. In order to improve the yield
of compound 2, the temperature was increased to 160 or 180 1C,
then almost only compound 2 left. Since the color and the shape
are different for each other, we simply separate them by hands.
Blue–green block crystals were isolated in 65% yield (based on HL).
1H NMR (400 MHz, DMSO-d6): δ 13.083 (s, 1H, COOH), 8.737 (s, 1H,
CH), 8.183 (s, 1H, CH), 7.926 (d, 2H, p-C6H4), 7.309 (d, 2H, p-C6H4),
5.723 (s, 2H, CH2). IR (KBr pellet, cmꢀ1): 3444(b), 1616(s), 1564(s),
1374(s), 1279(m), 1123(m), 1001(m), 768(m), 742(s), 673(m) (Fig.
S1). Elemental analysis calculated for C20H18Cl2CuN6O4: C 44.38%,
H 3.33%, N 15.53%; found: C 44.25%, H 3.63%, N 15.36%.
2.3. Single-crystal structure determination
Selected the suitable single crystals of 1–5, then mounted them
onto thin glass fibers and performed the single crystals at 20 1C on
a Bruker SMART APEX CCD-based diffractometer in air. All struc-
tures were solved by direct methods and refined with full-matrix
least-squares refinements based on F2 using SHELXS-97 and
SHELXL-97 [18]. Crystal data, data collection parameters, and
refinements for 1–5 are listed in Table 1. The interatomic bond
distances and bond angles of 1–5 are given in the Suporting
information (Tables S1–S5). CCDC numbers: 970263 and 970264
for 1 and 4, 970266-970268 for 5, 3 and 2, respectively.
2.2.4. Preparation of [Cu(HL)2Cl2(H2O)](3)
Different with 1 and 2, compound 3 was obtained from mother
liquor of the hydrothermal reaction above. The temperature region
of the hydrothermal reaction must be in the range from 140–
180 1C. Upon being disturbed for four weeks, blue strip crystals
were isolated in 10% yield (based on HL). 1H NMR (400 MHz,
DMSO-d6): δ 13.194 (s, 1H, COOH), 8.949 (s, 1H, CH), 8.294 (s, 1H,
CH), 7.926 (d, 2H, p-C6H4), 7.303 (d, 2H, p-C6H4), 5.818 (s, 2H, CH2).
IR (KBr pellet, cmꢀ1): 3446 (b), 1674 (s), 1610 (m), 1429 (s), 1323
(s), 1293 (s), 1183 (m), 1127 (s), 995 (m), 742 (s), 669 (m) (Fig. S1).
2.4. Antifungal activities tests
The test microorganisms used in this study were Fusarium
graminearum, Altemaria solani, Macrophoma kawatsukai, Alternaria
alternata and Colletotrichum gloeosporioides. The antifungal activ-
ities of the compounds were determined by the radial growth
method (A.MANN 2008) [19]. In this technique, sterilized hot PDA
nutrient medium (composition: potato (200 g), dextrose (15 g),
agar (18 g) and distilled water 1000 mL) and 4 mm diameter hole

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P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
Table 1
Crystallographic data for 1–5.
Empirical formula
C
1
20H16CuN6O4
C20H18Cl2CuN6O4
2
C20H20Cl2CuN6O5
3
C20H18CuN6O5
4
C23H17CuN5O4
5
fw
Cryst syst
a (Å)
b (Å)
c (Å)
α (1)
β (1)
γ (1)
467.94
Monoclinic
5.3239(10)
16.558(3)
10.639(2)
90
93.435(4)
90
936.2(3)
P2(1)/c
2
540.84
558.86
Monoclinic
17.899(2)
8.0675(12)
7.8400(11)
90
95.565(2)
90
1126.8(3)
P2/c
485.94
Monoclinic
23.008(2)
9.4363(9)
9.5393(9)
90
104.9430(10)
90
2001.0(3)
C2/c
490.96
Orthorhombic
9.7494(18)
9.693(2)
21.815(4)
90
90
90
2061.6(7)
Pna2(1)
4
Triclinic
7.5930(14)
7.6304(14)
19.844(4)
83.935(3)
81.248(3)
71.401(3)
1075.0(3)
P-1
V (Å3)
Space group
Z value
F calc (g/cm3)
2
2
4
1.660
1.211
1.671
1.307
1.647
1.253
1.613
1.140
1.582
1.103
m (mmꢀ1
)
Temp (K)
296(2)
1651
0.0690; 0.1480
296(2)
3786
0.0572; 0.1484
296(2)
2002
0.0290; 0.0551
296(2)
1768
0.0320; 0.0833
296(2)
2960
0.0555; 0.0926
No. of observations (I43
s
)
Final Rα indices [I42
s
(I)]: R; Rw
R1¼∑||Fo|ꢀ|Fc||/∑|Fo|. wR2¼{∑[w(Fo2–Fc2)2]/∑[w(Fo2)2]}1/2
.
punch were used. Five final concentration solutions in PDA, 0, 30,
60, 90, and 120 mmol/L, were prepared for compound 1–5, HL,
CuCl2 and l,10-phenanthroline to against F. graminearum respec-
tively. Besides that, five final concentration solutions in PDA of
compound 1 were used to inhibit the growth of other four fungi
(A. solani, M. kawatsukai, A. alternata and C. gloeosporioides).
40 mL PDA with each reagent in 50 mL centrifuge tube was
divided into three Petri dishes and allowed to solidify. Then the
Petri dishes were inculated with 4 mm diameter of the fungi
culture by the hole punch. Petri dishes were incubated at 28 1C for
96 h. Antifungal activities were expressed in terms of diameter of
growth. All the steps of the above were repeated thrice in our
experiment.
compound 2 significantly increased and the rest compounds 1
and 4 disappeared. Only compound 2 left at 180 1C (Fig. S4).
During the period, the reaction equilibriums of Cu(II) with the
ligand shift from one to another with increasing the temperature.
As we noticed, the products at higher temperatures are obtained at
the expense of those at lower temperatures. In term of thermo-
dynamics stability, compounds 1–4 follow the sequence of 1, 4, 3
and 2.
3.2. Crystal structure analysis
Among five titled compounds, as shown in Fig. 1, the oxygen
atoms of the carboxylic group could coordinate with Cu(II) in
terminal monodentate or bidentate, and the N atom from the
triazole ring monodentate-bonds with Cu(II).
3. Results and discussion
3.2.1. Structure analysis of compound 1
3.1. Temperature effect on the reaction system
In compound 1, the crystallographically unique copper(II) atom
adopts a distorted octahedral coordination sphere, with four
carboxylate O atoms from the different carboxylate groups, biden-
tate coordination in the equatorial plane, and two N donors from
triazoles in the axial positions (Fig. 2a).
As shown in Fig. 2b, each copper(II) atom coordinates with four
ligands, and each ligand coordinates to two Cu ions. As a bridging
ligand, triazole N atoms and carboxylate O atoms are involved in
coordination with Cu(II) to form an infinite double Z-shaped 1D
chain. In each approximately rectangular ring, the Cu(II)–Cu(II)
contact is around 10.639 Å. In parallel with the two 1D chains, the
shortest interchain Cu(II)–Cu(II) contact is 5.324 Å.
In order to explore the temperature effect on the formation of
the different compounds from the same system of Cu(II)–4-(1H-1,
2, 4-trizol-1-ylmethyl) benzoic acid. As described in preparation of
compounds, compounds 1–4 were simultaneously generated at
140 1C, like the colored ribbons. Decreasing the temperature down
to 120 1C, the final products included a lot of purple crystals and a
handful of blue microcrystallines, which were identified to be
compounds 1 and 4 by PXRD, respectively (Fig. S2). Further cooling
to 90 1C, a great number of purple crystals were structurally
characterized as compound 1, as shown in Fig. S3. That is to say,
only one target was obtained. As for the temperatures below 90 1C,
there was not any powder or crystalline samples formed except
the start materials. It is concluded that, the thermodynamics-
controlled temperature regions range from room temperature to
90 1C for 1 and from room temperature to 120 1C for 4, respec-
tively. The temperature region of 90–120 1C are the kinetics-
controlled process for 4, in which the trace powder samples grow
to be crystalline product. According to the above experimental
fact, the activation energy of compound 1 is the minimum among
the four compounds. With the increase of temperature, the other
compounds successively grew, owing to exceeding their activation
energy. Accordingly, the reaction is mainly controlled by thermo-
dynamics below 120 1C. Compound 1 is the most thermodynami-
cally stable among these compounds.
3.2.2. Structure analysis of compounds 2 and 3
As shown in Fig. 3a, compound 2 contains two crystallographi-
cally independent Cu(II) ions, Cu1 and Cu2, which lie at an
inversion center and possess different geometries. Cu1 adopts a
distorted octahedral coordination sphere, with four Cl atoms in the
equatorial plane, and two N donors from triazoles in the axial
positions. Cu2 takes a square-planar environment, with two Cl
atoms occupying the equatorial plane, and two N donors from
triazoles occupying the axial positions. The adjacent Cu(II) centers
are bridged by chloride atoms in μ2-bridging bidentate mode into
zigzag 1D infinite chains (Fig. 3b).
In compound 3, the crystallographically unique copper(II) atom
adopts a distorted hexahedral coordination sphere, with two N
donors from triazole in the axial positions, one O atom from the
Increasing the reaction temperature to 160 1C, the amounts of 1
and
4 markedly drop compared with those at 140 1C, and

P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
295
O
O
O
Cu
Cu
O
N
N
N
N
N
N
Cu
Cu
O
O
Cu
HO
N
N
O
N
N
N
N
Cu
Fig. 1. Four kinds of coordination pattern with the metal atoms of the ligand (a–d).
Fig. 2. (a) The coordination configuration of 1. (b) The 1D wavelike chain of 1.
Fig. 3. (a) The coordination environment of 2. (b) The zigzag chain in 2, the chlorine atoms are regarded as bridging atoms.
water molecules and two Cl atoms coordination in the equatorial
3.2.3. Structure analysis of compound 4
plane. The carboxyl oxygen atoms do not participate in coordina-
tion, and the compound exists as a separate molecule (Fig. 4a). As
presented in Fig. 4b, Cu(II) with hexahedral coordination sphere
are assembled through hydrogen-bonding into 3D supramolecule
structure.
Compounds 4 and 1 are twin generated. Because of their sig-
nificantly different colors, it is easy to separate them. In compound 4,
the crystallographically unique copper(II) atom adopts the same
coordination configuration as that of compound 1, with two N atoms
donors from triazole, two carboxylate O atoms from the carboxylate

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P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
Fig. 4. (a) The coordination unit of 3. (b–d) Two kinds of hydrogen bonds and the 3D structure.
group monodentate coordination in the equatorial plane, and two O
atoms from the water molecules coordinated in the axial positions
(Fig. 5a). In each distorted rectangular ring, the Cu(II)–Cu(II) bond
distance is 12.209 Å, which is longer than that in compound 1.
In compound 4 (Fig. 5b), O atoms as bridging atom connect
with Cu(II), forming an inorganic zigzag chain –Cu–O–Cu–O–. In
the 1D zigzag chains, the shortest Cu(II)–Cu(II) bond distance is
4.770 Å. The –Cu–O–Cu–O– 1D zigzag chains are ligand-bridged,
leading to a 2D layer. The 2D layers are further ligand-bridged into
a 3D network structure.
3.3. X-ray powder diffraction and thermal analysis
As shown in the Supporting information (Fig. S5), X-ray powder
diffraction patterns of the samples of 1–5 are quite similar to the
simulated data of the crystal structure.
To examine the thermal stability of 1–5, the thermogravimetric
analyses for crystal samples of 1–5 were performed under a
simulated nitrogen atmosphere with a heating rate of 10 1C minꢀ1
from room temperature up to 1000 1C. The compounds are thermally
stable up to 285, 254, 250, 252, and 180 1C for 1–5, respectively. With
increasing temperature, the whole frameworks of the compounds
collapse (exp. 42.21%, 48.75%, 39.28%, 46.36%, and 33.31% for 1–5).
Following that, the intermediates are slowly decomposed, and do not
form stable substances until 1000 1C. As shown in Fig. S6, compound
1 shows the highest thermostability, which is consistent with the fact
that compound 1 is the most thermodynamically stable among these
compounds.
3.2.4. Structure analysis of compound 5
In compound 5, the N,N-dimethylformamide (DMF) is hydro-
lyzed to formic acid molecule. The N atoms from triazole are not
involved in coordination. Two N atoms donors from 1,10-phenan-
throline and one O atom from the formic acid molecule coordinate
to Cu(II) in the equatorial plane. Two carboxylate O atoms in the
carboxylate group and one O atom from the formic acid molecule
participate in coordination in the axial positions (Fig. 6a).
Compared with compound 2, compound 5 has a different
inorganic zigzag chains –Cu–O–C–O–Cu–O–C–O– and the formic
acid molecule are used as a bridging ligand. The copper(II) atoms
are linked together through the formic acid molecule with the
shortest Cu(II)–Cu(II) bond distance is 5.728 Å (Fig. 6b).
3.4. Antifungal activities of copper(II) compounds
The primordial data were supposed to be calculated according
to the following formulas: 1) Pure increment (mm)¼Average
diameters of coloniesꢀ4 mm diameter of fungal culture; 2)
Percentage of antifungal (%)¼[(Pure increment of controlꢀPure
increment of treatment)]/Pure increment of control ꢂ 100%.

P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
297
Fig. 5. (a) The coordination environment of 4. (b, c) The inorganic zigzag chains –Cu–O–Cu–O– and the 3D network structure.
Fig. 6. (a) The central atom coordination configuration of 5. (b) The zigzag chain in (5), showing the formic acid molecule bridging of the copper(II) centers.
According to the results and analysis, five compounds show the
higher inhibition effect than those of HL, CuCl2 and 1,10-phenan-
throline (Figs. 7 and S7). For instance, antifungal percentage of
compounds 1–5 are 72.468%, 63.660%, 68.293%, 70.196%, and
65.796%, respectively. Whereas HL, CuCl2 and 1,10-phenanthroline
depict antifungal percentage of 61.908%, 24.154%, and 56.337% at
120 mmol/L. It is worth mentioning that HL, CuCl2 and l,10-
phenanthroline have a certain degree of antimicrobial effect.
However, their antifungal rate are far below the titled copper(II)
compounds, especially compound 1 (Table 2).
Among the five novel compounds, compound 1 presents the best
antifungal activity compared to compounds 2–5. Visually, diameters
of fungal culture under treatment of compound 1 are markedly
smaller than those of other groups including HL and CuCl2. At the

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P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
Fig. 7. Drug concentration–effect curves of compounds 1–5, HL, CuCl2, and l,10-phenanthroline against Fusarium graminearum.
Table 2
Antifungal activities of compounds 1–5, HL, CuCl2, and l,10-phenanthroline against Fusarium graminearum.
Antifungal drugs
Drug concentration–effect curves
R
EC50 (μmol Lꢀ1
)
Compound 1
Compound 2
Compound 3
Compound 4
Compound 5
L
y¼5.0334xꢀ3.509
y¼4.5483xꢀ3.2612
y¼4.6459xꢀ2.9746
y¼5.0522xꢀ3.7133
y¼4.6284xꢀ3.1176
y¼8.0151xꢀ10.77
y¼7.8479xꢀ11.008
0.9633
0.8536
0.9703
0.9712
0.9944
0.9804
0.9767
49.0343
65.50885
85.72352
53.05178
56.74139
92.78975
109.5973
l,10-phenanthroline
CuCl2
The inhibition ration of CuCl2 is so low that drug concentration–effect curves is not available
Fig. 8. Drug concentration–effect curves of compound 1 against five kinds of fungi.
identical concentration, the antifungal percentage of compound 1 is
the highest. The antifungal percentage of the compound 1 ranges
from 40.540% to 72.468% with the increase of concentration. The
antifungal percentage of compound 2 is the lowest, which varies
from 37.721% to 63.660%. And we could draw a conclusion that the
antifungal activity of compound 1 is superior to those of the other
compounds.
Due to the superiority of compound 1, we made use of it to test
other four fungi (A. solani, M. kawatsukai, A. alternata, and C.
gloeosporioides) (Fig. S8). All the fungi are retarded by compound 1
to some extent, among which F. graminearum shows the highest
retardance with an antifungal percentage of 72.468% at 120 mmol/L
(Fig. 8 and Table 3).
It is conceivable that ligands contain electron-withdrawing
substituents such as ꢀCl, have greater antifungal activity than
electron-donating substituents [20]. Videlicet, the compounds
with electron-withdrawing substituents will show a better anti-
fungal activity. However, the chlorine atoms in compounds 2 and 3
lead to only minor increases in the antifungal activities compared
to the ligand HL. Notably, inhibition percentage of compounds 1

P. Xiong et al. / Journal of Solid State Chemistry 215 (2014) 292–299
299
Table 3
Antifungal activity of compound 1 against five kinds of fungi.
Acknowledgments
We gratefully acknowledge the financial support from the
National Natural Science Foundation of China (Grant nos.
31201534, 21373162 and 21173168), and the Science Research
Projects of Department of Shaanxi Provincial Government (Grant
nos. 2010JK882, 2010JQ2007, 11JS110 and 11JK0578).
Fungi
Drug concentration–effect
curves
R
EC50
(μmol Lꢀ1
)
Fusarium graminearum
Altemaria solani
y¼5.0334xꢀ3.509
y¼9.1983xꢀ13.051
0.9633 49.0343
0.9782 91.70647
0.9600 91.28512
0.9780 97.43164
0.9897 94.55837
Macrophoma kawatsukai y¼10.034xꢀ14.671
Alternaria alternata
Colletotrichum
y¼7.7721xꢀ10.456
y¼8.6322xꢀ12.055
gloeosporioides
Appendix A. Supporting information
and 4 are higher than those of compounds (2 and 3) which have
electron-withdrawing substituents. Compared to that in the com-
pound 3 (0D, the intramolecular hydrogen bonds assemble the 0D
structure into a 3D network structure), the effect of the electron-
withdrawing substituents is more significant in compound 2,
which is the reason for compound 2 shows the lowest antifungal
activity behavior [3,21–25]. As for compounds 1 and 4, the
complexity and stability of structures probably affect their anti-
fungal activity. Generally speaking, simple structures (compound
1) have larger possibilities to have good antifungal activity.
Supplementary data associated with this article can be found in
the online version at http://dx.doi.org/10.1016/j.jssc.2014.04.012.
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