Facile synthesis, crystal structure and bioactivity evaluation of two novel barium complexes based on 2,4,6-trichlorophenoxyacetic acid and o-ferrocenylcarbonyl benzoic acid

Article abstract of DOI:10.1039/c7nj03046k

Two novel Ba(ii) complexes [Ba(TCPA)₂(H₂O)₄] 1 and [Ba(H₂O)₈]·2(o-FcCOC₆H₄COO)·6H₂O 2 [HTCPA = 2,4,6-trichlorophenoxyacetic acid and o-HOOCC₆H₄-COFc = o-ferrocenylcarbonyl benzoic acid] have been synthesized by a facile microwave method. The solid-state structures were well established by means of X-ray crystallography as well as routine analysis of the infrared spectrum (FTIR), elemental analysis, field emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TG). Different polyhedra of tricapped triangular prisms for 1 and dodecahedra for 2 were present. It is worth noting that the central Ba(ii) ion in 1 is nine-coordinated by two carboxylate oxygen atoms from TCPA ligands and seven oxygen atoms from coordinated water molecules. By contrast, the eight-coordinated Ba(ii) in 2 forms barium-water clusters assembled by O-H?O hydrogen-bonds contributed by coordinated water molecules. The uncoordinated o-OOCC₆H₄-COFc ligands in 2 play a key role in the process of charge balance. FESEM images exhibited different surface appearances between the ligand and barium complexes, that is: flower-like HTCPA, branch-like o-HOOCC₆H₄-COFc, block-like complex 1 and corner-truncated cubes for complex 2. The allelopathic activity of the complexes and their corresponding ligands was evaluated against two herbaceous plants of barnyard grass and turnip (Raphanus sativus). All the tested compounds showed certain activity with good RI values. An antifungal bioassay was also carried out in vitro on three strains of Botrytis cinerea Pers., Glomerella cingulata Schr and Cytospora sp. Complex 1 and HTCPA can work against all three tested fungi, whereas o-HOOCC₆H₄-COFc and 2 only worked for Botrytis cinerea Pers. The complex presented in this paper has potential applications in weed control, and this work provides an experimental basis for future studies on Ba-based pesticides.

Full text of DOI:10.1039/c7nj03046k

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PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
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A facile synthesis, crystal structure and bioactivity evaluation of
two novel barium complexes based on 2,4,6-
trichlorophenoxyacetic acid and o-ferrocenylcarbonyl benzoic
Received 00th January 20xx,
Accepted 00th January 20xx
acid
DOI: 10.1039/x0xx00000x
*
Xiuling Xu, Fan Hu and Qi Shuai
www.rsc.org/
2 2 4 2 8 6 4 2
Two novel Ba(II) complexes [Ba(TCPA) (H O) ] 1 and [Ba(H O) ]·2(o-FcCOC H COO)·6H O 2 [HTCPA
=
2,4,6ꢀtrichlorophenoxyacetic acid and o-HOOCC H -COFc = oꢀferrocenylcarbonyl benzoic acid] have
6
4
been synthesized by facile microwave method. The solidꢀstate structures were well established by means of Xꢀ
ray crystallography as well as routine analysis of infrared spectrum (FTIR), elemental analysis, field emission
scanning electron microscope (FESEM) and thermogravimetric analysis (TG). Different polyhedron of
tricapped triangular prism for 1 and dodecahedron for 2 were present. It’s worth noting that central Ba(II) ion
in 1 is nineꢀcoordinated by two carboxylate oxygen atoms from TCPA ligands and seven oxygen atoms from
coordinated water molecules. By contrast, the eightꢀcoordinated Ba(II) in 2 forming bariumꢀwater clusters
assembled by OꢀHꢁꢁꢁO hydrogenꢀbond contributed by coordinate water molecules. The uncoordinated o-
OOCC H -COFc ligands in 2 play a key role in the process of charge balance. FESEM images exhibited
6
4
different surface appearances between ligand and barium complexes, that is: flowerꢀlike HTCPA, branchꢀlike
o-HOOCC H -COFc, blockꢀlike complex 1 and cornerꢀtruncated cubes complex 2. The allelopathic activity
6
4
of the complexes and their corresponding ligands was evaluated against two herbaceous plants of barnyard
grass and turnip (Raphanus sativus). All the tested compounds showed certain activity with good RI values.
Antifungal bioassay was also carried out in vitro on three strains of Botrytis cinerea Pers., Glomerella
cingulata Schr, and Cytospora sp. Complex 1 and HTCPA can against all the three tested fungus, while o-
HOOCC H -COFc and 2 only worked for Botrytis cinerea Pers. The complex presented in this paper has
6 4
potential applications in weed control, and this work provides an experimental basis for future studies on Baꢀ
based pesticides.
destroying the chemical structure of pesticides, coordination of
herbicide molecules with metal ions is an effective way to improve
Introduction
The need to increase world grain output for the rapidly growing efficiency.16, 17 In recent years, a great number of novel efficient
population is well recognized. Pesticides, controlling weeds pesticides were synthesized in large quantities through the
(
barnyard grass, broadleaf weeds, cyperaceae weeds, etc.) and coordination method and achieved superior results compared with
18ꢀ21
pathogens (Botrytis cinerea Pers., Cytospora sp., etc.), have that of the single ligands.
contributed greatly to the boost farm income. However, for many synthesized the triadimefon copper complex for the first time and
For example, Lei’s group in 2009
1
, 2
years now, excessive use of pesticides has been one of the major proved that the inhibitory effect of the complex on Rhizoctonia leges
22
causes of environment pollution, including air, water, soil and and Rhizoctonia solani was better than that of the ligand. A wide
3
ꢀ8
biological pollution. More and more countries exert great efforts to variety of metal centres have been employed to develop pesticides
develop highly efficient pesticides by structural modification of exhibiting satisfactory results, however, the study of Ba(II) remains
existing compounds (phenoxy carboxylic acids, sulfonyl, pyridazine, largely unexplored. In fact, the toxicity of waterꢀsoluble barium
9
ꢀ15
pyrazoles, triazolinones, uracils and triketones).
Without compounds was caused by altering the cell membrane permeability
23ꢀ27
through blocking K(I) channels.
The development of Baꢀbased
pesticides might be an efficient method to enhance the pesticides
activity.
The abovementioned structural modification that improved the
efficiency of compounds was mainly based on coordination effect of
bioactive ligands with O, S and N atoms to different metal centres.
Chlorophenoxyacetic acid and ferroceneꢀbased carboxylate are two
UVꢀvis spectra of two
complexes and ligands.
28ꢀ32
kinds ligands with excellent bioactivity.
Since the USDA first
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reported the herbicidal effect of 2,4ꢀdichlorophenoxyacetic acid in
944, more and more derivatives with advantages of high efficiency,
1
low consumption and low cost have been developed in the world. As
a kind of organochlorine herbicide, chlorophenoxyacetic acid usually
inhibits the growth of hormones in plants by disrupting their normal
level. On the other side, ferrocene, which was first discovered in
1
951, has captured the imagination of chemists because of its
6 4
Scheme 1 Chemical structure of the HTCPA and o-HOOCC H -COFc ligands.
fascinating sandwich structure and is considered among the
important structural motifs in organometallic chemistry, materials
science and herbicides. Incorporation of a ferrocene fragment into a
molecule of an organic compound often obtained unexpected
biological activity, which is attributed to their different membrane
permeation properties and anomalous metabolism. Most
interestingly, similar to chlorophenoxyacetic acid, ferrocenyl
derivatives also possess a very high level of plant growth regulatory
Experimental
2
.1. Materials and physical measurements
2
,4,6ꢀtrichlorophenol, ethyl chloroacetate, phthalic anhydride,
aluminium chloride and ferrocene were purchased commercially
from Aladdin Reagent Co. Ltd. (Shanghai, China). NMR spectra
were recorded on
tetramethylsilane as an internal standard. Microwave synthesis was
carried out on a CEM Discover SP singleꢀmode microwave synthesis
reactor. Elemental analyses (C and H) were performed on a Vario
MACRO cube elemental analyzer. IR spectra were recorded on a
a Bruker 500 MHz spectrometer with
3
3ꢀ39
activity on a wide variety of crops.
From structural point of view,
difficulties in synthesis of Ba(II) complexes caused by small charge
and large radii would be improved by applying these two kinds of
carboxyl groupꢀcontaining ligands. The various coordination modes
(
Fig. 1) of carboxyl group provide high probability to achieve
ꢀ1
BRUKER TENSOR 27 spectrophotometer within 400ꢀ4000 cm
structural modification of Ba(II) on existing pesticides through
coordination effect. Full utilization of the aboveꢀmentioned carboxyl
groupꢀcontaining ligands to build Ba(II) complexes for efficient
herbicides is significant.
using the samples prepared as pellets with KBr. Field emission
scanning electron microscope measurements were performed on a
FEI Nova Nano SEM 450 from Life Science Research Core Services
(
LSRCS) of Northwest A&F University. TG analysis was performed
o
on a SHIMADZU TAꢀ60ws from 25 to 1000 C at a heating rate of
o
ꢀ1
1
2
2
2
0 C min in N atmosphere.
.2. Synthesis of the ligands and complexes
.2. 1. Synthesis of the ligand HTCPA
The ligands were prepared by the microwave reaction as shown in
Scheme 2. In a microwave tube, 2.4.6ꢀchlorophenol (5 mmol, 987
mg) was dissolved in dry N, Nꢀdimethylformamide (2 mL) followed
2 3
with 2 mL aqueous solution of K CO (691.05 mg, 5 mmol), ethyl
chloroacetate (5 mmol, 0.61 g) and KI (166 mg, 1 mmol). The
o
reaction mixture was allowed to irradiate for 4 min at 100 C under
2
00 W. Then 5 mL of NaOH (2 M) was added to the mixture and
o
Fig. 1 The coordination modes of carboxyl.
irradiated for 5 min at 150 C under 500 W. The resulting solution
was acidified (pH = 6) by adding of a 1 M hydrochloric acid solution
under vigorous stirring after the mixture cooled to room temperature.
The crude product was purified by column chromatography on silica
gel using petroleum ether: ethyl acetate (4:1, v/v) as the eluent. Then
HTCPA ligand as white solids was obtained. Yield: 83 %. Found H
NMR (DMSO/TMS, 500 MHz, ppm): δ 13.25 (s, 1H), 7.81 (s, 2H),
4
Since the first discovery of the microwave by Percy Spencer in 1946,
microwave radiation method has been widely applied to synthsize
40ꢀ42
organic molecules, zeolites, nanoparticles, etc.
However,
microwave synthesis has not been well applied to synthesize
complexes compared to traditional solvent and hydrothermal
method. Our previous works have successfully synthesized Mg(II),
1
.68 (s, 2H).
43ꢀ46
Ca(II), Sr(II) complexes through rapid microwave method.
This
work was the deeper study about microwave method applied in
Ba(II) complexes synthesize. Herein, two novel complexes
2 2 4 2 8 6 4 2
[Ba(TCPA) (H O) ] 1 and [Ba(H O) ]·2(o-FcCOC H COO)·6H O
2
[HTCPA = 2,4,6ꢀtrichlorophenoxyacetic acid and o-HOOCC H -
6 4
COFc = oꢀferrocenylcarbonyl benzoic acid] were synthesized for the
Scheme 2 Microwave synthesis of the HTCPA ligand.
first time. Their solidꢀstate structures are well established by means
of Xꢀray crystallography as well as routine analysis of infrared 2.2. 2. Synthesis of the ligand o-HOOCC H -COFc
6
4
spectrum, elemental analysis, field emission scanning electron
microscope and thermogravimetric analysis. Allelopathic activity of
ligands and complexes with turnip (Raphanus sativus) and barnyard
grass have been evaluated. The Antifungal bioassay on three strains,
Botrytis cinerea Pers., Glomerella cingulata Schr, Cytospora sp were
also reported.
In a 250 mL roundꢀbottom flask, a mixture of phthalic anhydride
5.92 g, 40 mM) and aluminium chloride (10.67 g, 80 mM) in
dichloromethane (80 mL) were stirred for 15 min under a nitrogen
atmosphere at room temperature. Next, a solution of ferrocene (7.44
(
2 2
g, 40 mM) dissolved in CH Cl (80 mL) was added dropwise in 30
2
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min. After refluxed for 4 h, the resulting mixture was diluted with 2
M hydrochloric acid solution (25 mL) and the organic layer was
separated, then the aqueous layer was extracted with CH
combined organic layers were dried over anhydrous MgSO
2
Cl
2
. The
and
4
concentrated under reduced pressure. The crude product was purified
by column chromatography on silica gel using petroleum ether: ethyl
acetate (6:1, v/v) as the eluent. Then o-HOOCC
was obtained as a yellow solid. Yield: 76 %. Found H NMR
CDC1 /TMS, 500 MHz, ppm): δ 8.04 (s, 1H), 7.68 (d, J = 23.4 Hz,
H), 7.61 – 7.52 (m, 1H), 4.62 (s, 2H), 4.55 (s, 2H), 4.22 (s, 4H).
6 4
H -COFc ligand
1
(
3
2
Fig. 2 Crystals images of complexes 1 and 2.
2
.3. Single-crystal X-ray structure determinations
All crystallographic data were collected on a Bruker SMART CCD
areaꢀdetector diffractometer at 298(2) with graphite
K
monochromatized MoꢀKα radiation (λ = 0.71073 Å) in ω scan mode,
the data reduction was performed using Bruker SAINT. The crystal
structures were resolved by direct methods and refined with fullꢀ
6 4
Scheme 3 Microwave synthesis of the o-HOOCC H -COFc ligand.
2
matrix leastꢀsquares refinement on F with anisotropic displacement
2
2 2 4
.2. 3. Synthesis of compounds [Ba(TCPA) (H O) ] 1
47
parameters for nonꢀH atoms using SHELXTL. All atoms were
refined geometrically. Structural plots were generated with
Diamond. A summary of crystallographic data for 1 and 2 is
presented in Table S1. Bond lengths (Å) and angles (°) of bond for 1
An appropriate amount of NaOH solution (0.2 mM, 0.5 mL) was
added dropwise to HTCPA ethanol solution (0.2 mM, 0.5 mL)
under stirring to adjust the pH value to approximately 7. Then the
2 2
BaCl ·2H O (0.1 mmol, 24.43 mg) dissolved in distilled water (5 and 2 are given in Table S2. Crystallographic data have been
mL) was added into this mixture under stirring with the molar ratio deposited with the Cambridge Crystallographic Data Centre, CCDC
2+
of Ba : HTCPA = 1 : 2. Finally, the mixture was transferred into a number 1546818 for 1, 940743 for 2. These data can be obtained
2
1
5 mL microwave tube. The mixture was heated by microwave at free of charge via www.ccdc.can.ac.uk/conts/retrieving.html (or from
00 C for 1 h at 140 W and then cooled to room temperature, the Cambridge Crystallographic Centre, 12 Union Road, Cambridge
o
continued to be cultivated by slowly evaporating the filtrate at room CB2
1EZ,
U.K.,
fax
(+44)
1223ꢀ336033,
or
temperature. The colorless, block crystals (Fig. 2(1)) suitable for Xꢀ deposit@ccdc.cam.ac.uk).
ray diffraction were obtained. Yield: 32 %, based on Ba. Anal. calc.
2
.4. Allelopathic Bioassay
for BaC16
6
H16Cl O10: C, 26.73; H, 2.23 %. Found: C, 26.77; H,
ꢀ
1
ꢀ
2
.31 %. IR data (cm ): v(OꢀH): 3279 b; vasym(COO ): 1734 s; The seeds of two herbaceous plants, barnyard grass and turnip
sym(COO ): 1709 s; v(ArꢀOꢀC): 1461 s, 1425 s, 1141, 1084 s; v(ꢀ (Raphanus sativus), were used for the bioassay. The procedure was
ꢀ
v
CH
.2.
FcCOC
2
ꢀ): 672 m.
conducted according to the following steps. The plant seeds were
washed with running water for 2 h, soaked in 0.3 % KMnO for 15
4
2
4.
Synthesis
O 2
of
compounds
[Ba(H O) ]·2(o-
2 8
min, flushed until they were colorless. The compounds, positive
control (glyphosate) and blank solvent methanol, were added to 12ꢀ
6
H
4
COO)·6H
2
For the preparation of complexes 2, 5 mmol of oꢀHOOCC H - well plates with filter paper to serial concentration gradient of 50–
6
4
COFc and deionized water (10 mL) were placed together in a 25 mL 200 ppm. After the evaporation of methanol, the plant seeds were
microwave tube, and deprotonated by adding NaOH (0.2 mM) until sown in the micro dishes and irrigated with deionized water.
the pH=7. After the vigorous stirring for five minutes, 0.25 mmol of Triplicate experiments were conducted. The plates were incubated at
BaCl
2
·2H
2
O added. Then the mixture was heated by microwave 24 °C for 90 h. The germination rates were calculated according to
under autogenous pressure at 100 C for 1 h at 200 W and cooled to eq 1, and allelopathic effects [response index (RI)] were calculated
room temperature. The crystal was obtained by slowly evaporating according to eq 2.
o
the filtrate at room temperature. The redꢀbrown, block crystals (Fig.
germination rate (%)= (number of germinated seeds)/ (total number
of seeds)
2(2)) suitable for the Xꢀray diffraction were obtained directly on the
filter paper. Yield: 78 %, based on Ba. Elemental analysis calcd. (%)
for BaC36 20: C, 40.92; H, 5.11. Found: C, 40.91; H, 5.13. IR
H
54Fe
2
O
1)
2)
ꢀ
1
ꢀ
(
v
1
KBr, cm ): v(OꢀH): 3448 s, 3065 m; vasym(COO ): 1695 s,
If T > C，then RI = 1 – C / T ; if T < C, then RI = T / C− 1
ꢀ
sym(COO ): 1584 m; v(Ar): 1448 s, 1393 m, 1293 s, v(ferrocene):
121 s, 931s, 754 s, 653 s, 481 s.
Where T is the length of the treatment, C is the length of the blank
control, and RI is the response index.
2
.5．Antifungal bioassay
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The tested phytopathogenic fungi (Botrytis cinerea Pers, was prepared for each strain. The final acetone concentration did not
Glomerella cingulata Schr, Cytospora sp) were provided by Shaan exceed 0.5 % of the final volume in both control and treated cultures.
xi Key Laboratory of Natural Products & Chemical Biology, College Compoundꢀamended agar medium was dispersed aseptically onto 9ꢀ
of Chemistry & Pharmacy, Northwest A&F University. The tested cmꢀdiameter glass Petri dishes (10 mL/dish). Each dish was
fungi were maintain cultured on potato dextrose agar (PDA) slants at inoculated with three mycelial discs (4 mm diameter) cut from the
4
°C and subcultured in Petri dishes prior to testing. The in vitro periphery of actively growing colonies. Three replicate plates for
antifungal activity of the tested compounds was evaluated by the each fungus were incubated at 28 (±2) °C for all test fungi. Control
mycelial growth inhibitory rate method. Solutions of each compound plates containing media mixed with acetone (1 mL) were included.
were prepared by dissolving the appropriate amount of compound in Having cultured for 60 h, the mycelial growth of fungi (mm) in both
acetone. Equal volumes of acetone containing diluted compounds treated (T) and control (C) Petri dishes was measured diametrically
were added to sterile cool agar media (PDA) to give suitable in two different directions (decussation method) till the fungal
concentrations for each substance. A zeroꢀconcentration treatment growth in the control dishes was almost complete. The percentage of
(control plate), containing the same percentage of acetone to ensure growth inhibition (I) was calculated according to eq 3.
equivalent concentrations of these components in all the treatments,
I (%) = [(CꢀT)/C]ꢁ100
3）
Scheme 4 Schematic illustration of microwave synthesized complexes used for bacteriostat and herbicides.
O1WC, O2W, O3W, O3WB) from coordinated H O molecules. The
length of the Ba−O bonds range from 2.718(7) to 2.953(6) Å, with
the average value of 2.824 Å. The crystal structure of
2
3
. Results and Discussion
3
3
.1. Structural description for 1 and 2
[
Ba(TCPA) (H O) ] shows that the compound is a oneꢀdimensional
2 2 4
.1.1. The crystal structure of [Ba(TCPA) (H O) ] 1
2
2
4
polymer with [Ba(TCPA) (H O) ] repeat units. The repeat unit is
2
2
7
infinitely extended along the aꢀaxis crystallographic direction to
generate a metalꢀbased 1D chain, as shown in Fig. S6. An interesting
structural feature for the 1D chains is all of the Ba(II) ions lie on a
straight line. The lengths of the two neighboring Ba(II) ions are
d=4.2229 Å, and the Ba···Ba···Ba torsion angle for the wings is
α=180 (Fig. S6).
The coordination of TCPA ligands involves carboxylato oxygen
atoms in one coordination modes in each dimeric unit. The TCPA
ligands act as monodentate ligands bound to the Ba(II) atom through
O(3) atom，and the BaꢀO bond length was d= 2.76Å. Each 1D chain
was linked by hydrogen bonds to form a 2ꢀD layered network in abꢀ
plane of the cell in which the TCPA ligands point alternately up and
down (Fig. S7). Neighboring layered networks are further connected
into a 3ꢀD supramolecular framework through van der waals forces
Fig. 3 The coordination environment and coordination polyhedron of Ba(II) in 1.
Singleꢀcrystal Xꢀray diffraction analysis reveals that 1 crystallizes in
Orthorhombic crystal system, Pbcm space group. The coordination
environment and coordination polyhedron of Ba(II) is presented with
atom numbering scheme (Fig. 3). The asymmetric unit consists of
one crystallographically independent Ba(II) ion, two TCPA ligands
and four coordinated water molecules. The central Ba (II) ion
exhibiting a tricapped triangular prism coordination geometry, with
the caps (O2W, O3A, O3) of the three plane construct by the oxygen
atoms of O1WꢀO1WBꢀO1WCꢀO1WA, O1WAꢀO1WCꢀO3WBꢀO3W
(
Fig. S8).
3
2
2 8 6 4 2
.1.2. The crystal structure of [Ba(H O) ]·2(o-FcCOC H COO)·6H O
and O3WꢀO3WBꢀO1WBꢀO1W. The central Ba (II) ion is nineꢀ Xꢀray diffraction reveals that complex 2 is a coꢀcrystal structure and
coordinated by two carboxylate oxygen atoms (O3, O3A) from two crystallizes in the triclinic crystal system with the space group of Pꢀ1.
TCPA ligands and seven oxygen atoms (O1W, O1WA, O1WB, There are one crystallographically independent Ba(II) ion, two o-
4
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OOCC H -COFc ligands, eight coordinated water molecules and
The adjacent 1D linear chains are selfꢀassembled to form a 2D
6
4
six lattice water (O15, O16, O17, O18, O19, O20) in the asymmetric supramolecular layer with the π…π stacking interactions along the
unit. One Ba(II) ion and eight water molecules (O7, O8, O9, O10, ab plan (Fig. S10). Neighboring layered networks are further
2
+
O11, O12，O13, O14) form the bariumꢀwater clusters [Ba(H
2
O)
8
]
connected into a 3ꢀD supramolecular framework through van der
waals forces (Fig. S11).
with the Ba−O distance ranging from 2.69(2) to 2.890(11) Å which
is in agreement with other complexes containing Ba(II) centers (Fig.
), and the coꢀcrystal structure formed by o-OOCC H -COFc and
6 4
3
.1.3. Structures comparison of complex 1 and 2
7
2
+
[
Ba(H
2
O)
8
]
in ratio of 2:1.
Complex 1 and 2, derived from two kinds of carboxylic acid ligands,
both have many similarities and own structural features. In each
asymmetric unit contain one Ba(II), two ligands and different
numbers of coordinated water molecules. Different coordination
polyhedron was present in these two complexes (tricapped triangular
prism corresponds to coordination numbers
9 in 1, while
dodecahedron arrangement corresponds to coordination numbers 8
in 2). It is interesting to note, that the Ba(II) in 2 forming bariumꢀ
water clusters with coordinate water rather than coordinate to o-
6 4
OOCC H -COFc ligands, so a coꢀcrystal structure presented. The
structure analysis show that weak interaction play an important role
in forming the multidimensional structure, such as 1D chains is
linked by hydrogen bonds to form a 2ꢀD layered in 1, while the
adjacent 1D linear chains are selfꢀassembled to form a 2D
supramolecular layer with the π…π stacking interactions along the
ab plan in 2.
Fig. 4 The coordination environment of Ba(II) in 2.
The coordination polyhedron around the Ba(II) atom could be best
described as dodecahedron arrangement which constructed by O11ꢀ
O8ꢀO14, O8ꢀO11ꢀO9, O9ꢀO11ꢀO10, O10ꢀO11ꢀO14, O14ꢀO10ꢀO7,
O8ꢀ07ꢀO14, O8ꢀO7ꢀO12, O13ꢀO10ꢀO7, O7ꢀO12ꢀO13, O12ꢀ013ꢀO8,
O9ꢀO13ꢀO10 and O8ꢀO13ꢀO9. (Fig. 5).
3
.2.Thermogravimetric analysis of complexes 1 and 2
The TGꢀDTG analysis curves recorded reveals that the structures of
complexes show different thermal decomposition behavior (Fig. 6).
TGꢀDTG curves of 1 and 2 were measured at the heating rate of 10
o
ꢀ1
o
C min in the temperature range from 25 to 1000 C under the N
2
o
o
atmosphere. For the first step, in the ranges of 25 C–243.89 C,
complex 1 lost four coordinated water molecules (The experimental
mass loss was 15.956 %; the calculated mass loss was 13.675 %),
the DTG trace gives one endothermic peak at 137.22 °C (Fig. 6(1)).
And for complex 2, in the ranges of 25 C–217.38 C for the loss of
eight coordinated water and six lattice water (the experimental mass
loss was 23.843 %; the calculated mass loss was 23.867 %), on the
o
o
o
DTG curve，the peak temperatures was 148.38 C (Fig. 6(2)). For
compound 1，in the subsequent steps, there is another 54.762 %
o
(
calculated 57.204 %) weight loss up to 1000 C. These weight
Fig. 5 The coordination polyhedron of Ba(II) in 2.
losses are due to the complete decomposition of the compound and
For complex 2, although the o-OOCC H -COFc anions did not leaving the residues of BaO (observed 29.282 %; calculated
6
4
direct coordinated with Ba(II) atom, but hydrogen bond interactions 29.121 %)，the DTG curve shows that there are one peaks at 337.49
2+
ꢀ
o
between [Ba(H
2
O)
6
]
and ꢀCOO of ferrocenyl carboxyl (Fig. S9.)
C. For complex 2, following decomposition belongs to the
played an important role in the formation of sandwich 1D chains continuous collapse of the frameworks with a value of 61.349 %
o
structure with ligand anions as outer layer and centre metal cation as (Calcd. 61.613 %) at the temperature range of 217.21–1000 C, the
o
interlayer along bꢀaxis. The uncoordinated o-OOCC
6
H
4
-COFc DTG curve shows that there are one peaks at 519.40 C in the
o
molecules play an important role of balancing the charge, and they temperature range of 496.179–573.48 C. To the end, the complex is
also bridge the neighboring Ba(II) by the formation of hydrogen completely degraded into BaO(FeO)2 (observed 14.808 %;
bonds between coordinated water molecules and carboxyl oxygen calculated 14.522 %) for
atoms.
2
after the final decomposition.
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Fig. 6 TG and DTG curves of the complexes 1 and 2.
3
.3. FESEM characterizing of Ligands and complexes
3
.4. Evaluation of Allelopathic Activity
The FESEM images of HTCPA, complex 1, o-HOOCC H -COFc
6
4
All isolated compounds were evaluated for allelopathic activity
against barnyard grass and turnip (Raphanus sativus) using our
previously reported assay by determining the germination rates and
seedling growth (root and shoot elongation) with respect to the
control, glyphosate, a broadꢀspectrum systemic herbicide. The RI
was selected as an evaluation indicator, which ranges from −1 to 1,
with positive values indicating stimulation by the treatments and
negative values indicating inhibition by them, the RI was considered
to be superior to the T/C statistical method and easy to interpret
because it is simply the proportional reduction of the treatment
relative to the control. As shown in Table 3, whether the complexes
or ligands can inhibit the elongation of barnyard grass, while most
being less active than the positive control glyphosate.With the
increase of the solution concentration, moderate to strong growth
inhibitory effects (shoot elongation and root elongation) were
observed for all of the compounds.
and complex 2 are shown in Fig. 7. The HTCPA were flowerꢀliked.
However, after coordinated, the complex 1 change to homogeneous
clumpyꢀliked sheets with the smooth surface. Similarly, a distinct
change in morphology from shaly bedded to cornerꢀtruncated cubes
was observed upon addition of Ba(II) ion to the solution containing
6 4
o-HOOCC H -COFc ligands.
In general, 2,4,6ꢀtrichlorophenoxyacetic acid demonstrated stronger
inhibitory activity than that of the complex 2. In particular, HTCPA
showed the prominent inhibition of shoot and root elongation (ꢀ
0
.32~ꢀ0.41 and ꢀ0.33~ꢀ0.47, respectively) at 50~200 ppm compared
to those of the control glyphosate (ꢀ0.31~ꢀ0.39 and ꢀ0.31~ꢀ0.43,
respectively). In contrast, o-OOCC H -COFc and 2 containing a
6
4
benzoyl side chain and a ferrocene group showed weaker inhibition.
However, complex 2 are more superior than o-OOCC H -COFc
6
4
ligand. Our results revealed that all administered experimental
agents, caused a doseꢀdependent inhibition of seedling growth. The
overall observed growth inhibitory effects order revealed to be the
Fig. 7 FESEM images of the ligands and complexes. (1) FESEM images for
HTCPA, (2) FESEM images for complex 1, (3) FESEM images for o-OOCC
COFc and (4) FESEM images for complex 2.
6 4
H -
following: HTCPA > 1 > 2 > o-OOCC H -COFc.
6 4
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Table 1 Allelopathic Effects on barnyard grass of ligand and complexes 1 and 2
Germination rate
100 150
Shoot elongation（RI）
50 100 150 200
Root elongation（RI）
Compound
5
0
200
50
100
150
200
HTCPA
1
0.72 0.67 0.72 0.72 ꢀ0.32 ꢀ0.36 ꢀ0.39 ꢀ0.41 ꢀ0.33 ꢀ0.37 ꢀ0.41 ꢀ0.47
0.94 0.89 0.72 0.94 ꢀ0.28 ꢀ0.31 ꢀ0.32 ꢀ0.35 ꢀ0.24 ꢀ0.26 ꢀ0.30 ꢀ0.37
o-OOCC
6
H
4
-COFc 0.50 0.55 0.61 0.56 ꢀ0.18 ꢀ0.20 ꢀ0.27 ꢀ0.30 ꢀ0.21 ꢀ0.24 ꢀ0.26 ꢀ0.32
0.72 0.83 0.61 0.78 ꢀ0.21 ꢀ0.23 ꢀ0.28 ꢀ0.33 ꢀ0.23 ꢀ0.25 ꢀ0.27 ꢀ0.34
0.50 0.61 0.72 0.89 ꢀ0.31 ꢀ0.34 ꢀ0.37 ꢀ0.39 ꢀ0.31 ꢀ0.34 ꢀ0.40 ꢀ0.43
0.50 0.44 0.89 0.83
2
Gp
Ck
.
acid, TCPA will attack proteins of Botrytis cinerea Pers. In the
conditions that the concentration was 100 mg/L, the o-OOCC
COFc and 2 resulted inactive against Glomerella cingulata Schr (ꢀ
.51 and ꢀ0.69) and Cytospora sp. (ꢀ3.97 and ꢀ5.02), whereas
HTCPA and 1 show a moderate antibacterial activity (23.47, 25.90,
.59, 6.65 respectivly). In fact, ferrocene has certain biological
3
.5. Evaluation of Antifungal bioassay
6
4
H -
Preliminary in vitro screening results of the title compounds for
antifungal activities against three phytopathogenic fungi (Botrytis
cinerea Pers., Glomerella cingulata Schr，Cytospora sp.) are listed
in Table 2. The results indicated that some of the synthetic
0
5
compounds exhibited over 25.90 % growth inhibition against compatibility, at low concentrations, meanwhile the optimum
mycelial growth of these tested fungi at concentrations of 100 mg/L.
concentrations was 100mg/L and rich Ba(II) couldpromote the
growth of Glomerella cingulata Schr and Cytospora sp. As an
overall result, compounds HTCPA and 1 resulted active against all
The determined I values revealed that both ligands and complexes
are active against Botrytis cinerea Pers and the complexes are more
active than the ligands. It is noteworthy that the I values of complex
6 4
the tested fungus. While o-HOOCC H -COFc and 2 only worked
for Botrytis cinerea Pers but not for Glomerella cingulata Schr,
Cytospora sp. Although the activity of the two complexes is weaker
than the positive control, we still hope that the experimental results
can provide a reference for peers and encourage more chemist to
develop efficient antibacterial agents.
1
were 14.29, and 2 were 19.00, respectively, indicating that
complex 2 possesses better activities than 1. In fact, the main
difference between 1 and 2 is that there are three substituted chlorine
atoms on the ligand in 1 while ferrocene benzoyl in 2. As one kind
of organic chloride fungicides, similar to 2,4ꢀdichlorophenoxyacetic
Table 2 Growth Inhibition [%] of three plant pathogenic fungi by ligands and complexes (conc. 100 mg/L)
Compound
HTCPA
Botrytis cinerea Pers.
17.43
Glomerella cingulata Schr
23.47
Cytospora sp.
5.59
1
19.00
13.21
14.29
78.91
25.90
ꢀ0.51
ꢀ0.69
89.93
6.65
o-HOOCC
6
H
4
-COFc
ꢀ3.97
ꢀ5.02
84.71
2
Carbendazim
o-HOOCC
6
H
4
-COFc and characterized their structures by Xꢀray
Conclusions
diffraction methods, IR, elemental analysis, field emission scanning
In summary, we presented two Ba(II) complexes based on HTCPA, electron microscope and thermogravimetric analysis. In complex 1,
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the central Ba (II) ions is nineꢀcoordinated by two carboxylate 10. X. Yu, Y. Liu, Y. Li and Q. Wang, J. Agr. Food Chem., 2016,
oxygen atoms and seven oxygen atoms from coordinated H
molecules, while compound 2 coordinates to eight oxygen atoms
which come from coordinated H O molecules. The carboxyl group
of HTCPA in 1 exhibits monodentate coordination mode, and the
uncoordinated o-OOCC -COFc ligands in 2 play a key role in the
process of charge balance. The title complexes 1 and 2 can also selfꢀ
2
O
64, 3034ꢀ3040.
1
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like for complex 1, shaly bedded for o-HOOCC
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331.
elongation were ꢀ0.23, ꢀ0.25, ꢀ0.27, and ꢀ0.34). Further, to verify the 16. C. DendrinouꢀSamara, L. Alevizopoulou, L. Iordanidis, E.
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Samaras and D. P. Kessissoglou, J. Inorg. Biochem., 2002, 89,
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7. R. P. Sharma, A. Saini, J. Kumar, S. Kumar, P. Venugopalan
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Acknowledgements
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A table of contents entry.
With a microwave method， two novel Ba(II) complexes were first synthesized and their allelopathic and
antifungal activity evaluated.