Facile microwave synthesis, structural diversity and herbicidal activity of six novel alkaline-earth metal complexes (AECs) based on skeletal isomerization chlorophenoxyacetic acids

Article abstract of DOI:10.1039/c8nj00107c

Six novel AECs of [Sr(o-CPA)₂(H₂O)₄]·(o-CPA) 1, [Ba(o-CPA)₂(H₂O)]·H₂O 2, [Sr(m-CPA)₂(H₂O)₄]·(m-CPA) 3, [Ba(m-CPA)₂(H₂O)₄]₂·2(m-CPA)·H₂O 4, [Sr(p-CPA)₂(H₂O)] 5 and [Ba(p-CPA)₂(H₂O)] 6 (o-CPA = 2-chlorophenoxyacetic acid, m-CPA = 3-chlorophenoxyacetic acid and p-CPA = 4-chlorophenoxyacetic acid) were synthesized by a facile microwave-assistant reaction. The solid-state structures were well established by X-ray crystallography and routine analyses of Fourier transform infrared, elemental analysis, field emission scanning electron microscope (FESEM) and thermogravimetric analysis. The structure data reveal that complexes of 1, 3 and 4 are one-dimensional chains with a zigzag arrangement, while 2, 5 and 6 are (4, 4) rhomboid two-dimensional grid structures. It is noticed that the carboxyl group in these complexes displays multiple coordination modes of μ₂-η¹:η¹ (1, 2, 3, 4, 5 and 6), μ₃-η¹:η² (1, 2, 3 and 4), μ₂-η¹:η² (2), μ₃-η²:η² (5 and 6). Interestingly, the oxygen atoms of flexible -OCH₂- in phenoxy groups take part in coordination behavior with metal centers through the rotation of the C-O and C-C bonds in complexes 2, 5 and 6, while only carboxyl group coordination can be found in complexes 1, 3 and 4. FESEM images indicate that the surface appearances of complexes are totally different from ligands after coordination. All ligands and complexes were evaluated for activity as plant-growth inhibitors against Amaranth (Amaranthus spp.) and barnyard grass. Compared with ligands, complexes 1, 3 and 4 exhibited better response index (RI) values of Shoot elongation against barnyard grass. Moreover, complexes 1, 3 and 4 demonstrated a higher inhibitory activity than 2, 5 and 6. It is significant to develop a new kind of environmentally-friendly herbicide based on these kinds of complexes for their low toxicity and high efficiency.

Full text of DOI:10.1039/c8nj00107c

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The role of atropisomers on the photo-reactivity and fatigue of
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ARTICLE
Facile microwave synthesis, structural diversity and herbicidal
activity of six novel alkaline-earth metal complexes (AECs) based
on skeletal isomerization chlorophenoxyacetic acids
Xiuling Xu, ‡ Fan Hu, ‡ Yuwei Ma, Jinming Gao*, and Qi Shuai*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Six novel alkaline-earth metal complexes of [Sr(o-CPA)2(H2O)4]·(o-CPA) 1, [Ba(o-CPA)2(H2O)]·H2O 2, [Sr(m-
CPA)2(H2O)4]·(m-CPA) 3, [Ba(m-CPA)2(H2O)4]2·2(m-CPA)·H2O 4, [Sr(p-CPA)2(H2O)] 5 and [Ba(p-CPA)2(H2O)] 6 (o-
www.rsc.org/
HCPA
= 2-chlorophenoxyacetic acid, m-HCPA = 3-chlorophenoxyacetic acid and p-HCPA = 4-
chlorophenoxyacetic acid) were synthesized by facile microwave assistant reaction. The solid-state structures
were well established by X-ray crystallography and routine analyses of Fourier transform infrared, elemental
analysis, field emission scanning electron microscope and thermogravimetric analysis. The structure data
reveal that complexes of 1, 3, and 4 are one-dimensional chains with zigzag arrangement, while 2, 5, and 6
are (4, 4) rhomboid two-dimensional grid structures. It is noticed that carboxyl group in these complexes
displays multiple coordination modes of µ2-η1:η1 (1, 2, 3, 4, 5 and 6), µ3-η1:η2 (1, 2, 3 and 4), µ2-η1:η2 (2), µ3-
η2:η2 (5 and 6). Interestingly, oxygen atoms of flexible –OCH2– in phenoxy groups take part in coordination
behavior with metal centers through the rotate of C–O and C–C bonds in complexes 2, 5 and 6 while only
carboxyl groups coordination can be found in complexes 1, 3 and 4. FESEM images indicate that the surface
appearances of complexes are totally different from ligands after coordination. All the ligands and complexes
were evaluated for activity as plant growth inhibitors against Amaranth (Amaranthus spp.) and barnyard
grass. Compared to ligands, complexes 1, 3 and 4 exhibited better RI (response index) values of Shoot
elongation against barnyard grass. Moreover, complexes 1, 3 and 4 demonstrated a higher inhibitory activity
than that of 2, 5 and 6. It’s significant to develop new kind of environment-friendly herbicide based on these
kind of complexes for their low toxicity and high efficiency.
synthesis based on 1,3,5ꢀbenzenetricarboxylic acid. It’s noticed that
higher reaction temperature and longer reaction time are beneficial
Introduction
o
o
for synthesis of AECs (for Mg, 150 C, 24 h;15 for Ca: 180 C, 24
h;16 for Sr: 180 oC, 72 h;17 for Ba: 170 oC, 100 h18). Rigorous reactive
condition would be necessary for AECs synthesis. Microwave
radiation has been widely used to synthesize organic molecules,19
zeolites,20 nanoparticles21 since 1946. Absolute advantages of rapid
reaction time,22 higher yields,23 and uniform product24 have made
microwave synthesis become one of the most convenient method to
get chemical compounds during this period. However, it still keeps
an unremarkable fields in synthesizing coordination compounds. 25ꢀ29
Based on these, we are so interested that whether if hard synthesized
AECs would be obtained in condition of higher frequency and
energy provided by microwave radiation.
In the last few years, unprecedented attention has been paid to design
and fabrication of alkalineꢀearth metal complexes (AECs) stemming
from their fascinating structural diversity and potential applications
in catalysis,1 gas storage and sequestration,2, 3 ion exchange4 and drug
delivery.5 In addition, advantage of lowꢀcost,6 nonꢀtoxic,7 low
molecular weight,8 biocompatibility9 and large abundances10 in the
earth’s crust of alkalineꢀearth metal is another reason to prompt the
development of AECs. Compared to transition and lanthanide
metals, the inherent characters of lacking partly filled dꢀ or fꢀ shells
as well as unpredictable coordination numbers11ꢀ14 of alkalineꢀearth
metal are two main obstacles to prevent development of novel
AECs. Good example has been proved by chemist about AECs
Recent studies revealed that organic ligand is a crucial factor to
influence structures and properties of AECs. Various topologies of
ladders,30 brick walls,31 honeycombs,32 helices,33 and diamond
networks34 would be achieved by wellꢀdesigned ligands especially
the bridging forms. In a sense, the formation of molecular racks and
grids in most cases results from picking up rigid ligands
(terephthalic acid, 2,2'ꢀdipyridyl,35, 36 etc.) while helices results from
selecting flexible ligands (carboxylic acid,37ꢀ39 etc.). Further studies
indicate that interesting structures in large scale constructed by
shuaiqi@nwsuaf.edu.cn jinminggao@nwsuaf.edu.cn
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applying both rigid and flexible ligands. For example, Meng's group 2ꢀchlorophenol,
reported a cadmium complex assembled by mixed ligands of flexible chloroacetate, SrCl2
3ꢀchlorophenol,
6H2O, BaCl2
4ꢀchlorophenol,
·2H2O and other source
ethyl
·
polycarboxylic acids 2,3,3’,4’ꢀtdpa and rigid 4,4'ꢀbpy. First, twoꢀ materials were purchased commercially from Aladdin Reagent
dimensional layers with a chiral helix in this complex were Co. Ltd. (Shanghai, China). All reagents were of analytical
constructed by Cd2+ and a flexible carboxylic acid ligand. Then，a grade and used as received without further purification.
mesoꢀdimensional structure were formed by connect the adjacent 1HNMR spectra were recorded on
a Bruker 500 MHz
heterogeneous chiral helical layers using the rigid ligand 4,4'ꢀbpy.40 spectrometer in DMSOꢀd6 with tetramethylsilane as an internal
At present, a large numbers of intriguing structures are synthesized standard. Microwave synthesis was proceeded on a CEM
by applying both flexible and rigid ligands,41ꢀ44 however, complexes Discover SP singleꢀmode microwave synthesis reactor.
assembled by one ligand with both rigid and flexible block still Elemental analyses (C and H) was carried out on a Vario
keeps a relatively rare research field. From a structural point of MACRO cube elemental analyzer. IR spectra were recorded on
view, chlorophenoxyacetic acid is one kind of specific ligands a BRUKER TENSOR 27 spectrophotometer within 400ꢀ4000
including both flexible and rigid parts. The strong conjugated actions cmꢀ1 using the samples prepared as pellets with KBr. Field
between the carbonꢀcarbon double bonds and weakened strain in the emission scanning electron microscope measurements were
benzene ring provide rigid unit while the –OCH2– spacer group and performed on a FEI Nova Nano SEM 450 from Life Science
–COOH are flexible.45 Since the herbicidal activity of 2,4ꢀ Research Core Services (LSRCS). TG analysis was performed
o
chlorophenoxyacetic acid were founded by Zimerman P W and on a SHIMADZU TAꢀ60ws from 25 to 1000 C at a heating
Hitchcock A E in 1942,46 chlorophenoxyacetic acids have opened up rate of 10 oC minꢀ1 in N2 atmosphere.
a new field of organic selective herbicide due to their high herbicide
General synthesis and characterization
activity, low toxicity, good selectivity, broad spectrum and low
residue.47, 48 Chlorophenoxyacetic acid herbicides usually achieving
Synthesis of the ligands
herbicidal effects by disrupt hormone balance or inhibit the synthesis
of nucleic acids and proteins in plants. Up to now, research on
oꢀHCPA, mꢀHCPA and pꢀHCPA ligands (Scheme 1) were
chlorophenoxyacetic acids including magnetic properties of the
synthesised by the following microwave methods: a mixture of
transition metal complexes49, 50 and the fluorescence properties of the
corresponding phenols (5 mmol), ethyl chloroacetate (0.62 g, 5
rare earth complexes51ꢀ53 have been widely studied. It’s significant to
mmol), K2CO3 (0.42 g, 5 mmol) and KI (0.17 g, 1 mmol) in 3 mL of
extend research about chlorophenoxyacetic acids and further
DMF was stirred for 30 min in a 10 mL microwave tube. The
discovery more complexes especially AECs with interesting
thoroughly mixed resulting solution was irradiated in a commercial
structures and biological activity.54
microwave oven for 4 min at 200 W. Then followed by adding 5 mL
In this paper, six novel alkalineꢀearth metal (Sr, Ba) complexes
of NaOH (2 M) and continue irradiated 5 min at 500 W. After
[Sr(oꢀCPA)2(H2O)4]·(oꢀCPA) 1, [Ba(oꢀCPA)2(H2O)]·H2O 2, [Sr(mꢀ
cooling to room temperature, the resulting aqueous solution was
CPA)2(H2O)4]·(mꢀCPA) 3, [Ba(mꢀCPA)2(H2O)4]2·2(mꢀCPA)·H2O
acidified (pH=6) by addition of a 1M HCl solution under vigorous
4, [Sr(pꢀHCPA)2(H2O)] 5 and [Ba(pꢀCPA)2(H2O)] 6 based on three
stirring, extracted and the white solid product was purified by
chlorophenoxyacetic acids were synthesized by facile microwave
1
column chromatography. Found oꢀHCPA (Yield: 89 %) H NMR
method. The obtained AECs were structurally characterized by
(500 MHz, DMSO): δ 13.21 (s, 1H), 7.53 (d, 1H), 7.37 (t, J = 11.4,
4.4 Hz, 1H), 7.12 (d, J = 8.3 Hz, 1H), 7.06 (t, J = 7.6 Hz, 1H), 4.90
(s, 2H); 13C NMR (125 MHz, DMSO): δ 169.73, 153.18, 130.06,
128.12, 121.87, 121.22, 113.61, 64.94; MALDIꢀTOF (m/z):
186.9985 (M+1),calcd for C8H7ClO3. Melting point：145ꢀ147 C.
singleꢀcrystal Xꢀray diffraction analysis, Fourier transform infrared,
elemental analysis, field emission scanning electron microscope and
thermogravimetric analysis. The structure data reveal that complexes
of 1, 3, and 4 are oneꢀdimensional chains with zigzag arrangement,
o
while 2, 5, and 6 are (4, 4) rhomboid twoꢀdimensional grid structures.
1
mꢀHCPA (Yield: 88 %): H NMR (500 MHz, DMSO) δ 13.17 (s,
Interestingly, oxygen atoms of flexible –OCH2– in phenoxy groups
1H), 7.40 (t, J = 8.3 Hz, 1H), 7.14 ꢀ 7.07 (m, 1H), 7.03 ꢀ 6.97 (m,
1H), 4.83 (s, 1H) 13C NMR (125 MHz, DMSO): δ 169.86, 158.71,
133.68, 130.81, 120.98, 114.63, 113.57, 64.65; MALDIꢀTOF (m/z):
186.9979 (M+1), calcd for C8H7ClO3. Melting point：108ꢀ110 C.
take part in coordination behavior with metal centers through the
rotate of C–O and C–C bonds in complexes 2, 5 and 6 while only
carboxyl groups coordination can be found in complexes 1, 3 and 4.
o
Moreover, all the ligands and complexes were evaluated for activity
1
pꢀHCPA (Yield: 91 %): H NMR (500 MHz, DMSO) δ 13.15 (s,
as plant growth inhibitors against Amaranth (Amaranthus spp.) and
1H), 7.45 ꢀ 7.38 (m, 2H), 7.07 ꢀ 6.98 (m, 2H), 4.78 (s, 2H). 13C NMR
(125 MHz, DMSO): δ 170.44, 157.12, 129.67, 125.19, 116.75,
barnyard grass. Compared to ligands, complexes 1, 3 and 4 exhibited
better RI values of Shoot elongation against barnyard grass.
65.19; MALDIꢀTOF (m/z): 186.9988 (M+1), calcd for C8H7ClO3.
Melting point：157ꢀ158 oC.
Experimental
Materials and physical measurements
2 | J. Name., 2012, 00, 1-3
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Scheme 1 Schematic illustration of microwave synthesized coordination polymers used for herbicides.
solution to room temperature. Elemental analysis calcd. (%) for
C16H16Cl2O8Ba: C, 35.26; H, 2.95. Found: C, 35.26; H, 2.94. IR
Synthesis of complex 1
o
ꢀHCPA (93.30 mg, 0.5 mmol) was dissolved in deionized
water (10 mL) and NaOH (20 mg, 0.5 mmol) was added. After
30 min stirring, SrCl2 6H2O (266.62 mg, 0.25 mmol) in
(KBr, cmꢀ1):
v
(OꢀH): 3186 b; vasym(COOꢀ):1603 s; vsym(COOꢀ):
1487 s, 1445 s;
v(ArꢀOꢀC): 1067 s, 1040 s; v(ꢀCH2ꢀ): 605 m.
·
deionized water (5 mL) were added drop wise. The reaction Synthesis of complex 3
mixture was transfered to a 25 mL microwave tube and heated
by microwave under autogenous pressure at 100 C for 1 h at
100 W. The solution was reduced in volume and left for slow
A water solution containing SrCl2
·6H2O (266.62 mg, 0.25
o
mmol), ꢀHCPA (93.30 mg, 0.5 mmol) was stirred for 20 min
m
at room temperature, then the pH of the mixture was adjusted to
7 by adding drops of 10 % sodium hydroxide solution. Finally,
evaporation, the colorless single crystals
1 were obtained (yield:
76 %, based on Sr(II)). Elemental analysis calcd. (%) for
C16H20Cl2O10Sr: C, 36.18; H, 3.77. Found: C, 36.17; H, 3.77.
o
the mixture was heated at 100 C at 150 W for 3 h under
autogeneous pressure in a 25 mL microwave tube. The
IR (KBr, cmꢀ1):
v
(OꢀH): 3412 b; vasym(COOꢀ):1609 s; vsym(COOꢀ
colorless crystals of
3 were obtained after the reaction solution
): 1484 s, 1429 s;
v(ArꢀOꢀC): 1134s, 1063s; v(ꢀCH2ꢀ): 604m.
was cooled down gradually, and washed with distilled water.
Yield: 69 %, based on Sr(II). Elemental analysis calcd. (%) for
C16H20Cl2O10Sr: C, 36.16; H, 3.78. Found: C, 36.17; H, 3.77.
Synthesis of complex 2
Complex
of BaCl2
solution (10 mL) of
2
·
was prepared by addition of stoichiometric amounts
2H2O (61.07 mg, 0.25 mmol) to a hot aqueous
ꢀHCPA (93.30 mg, 0.5 mmol). The pH
IR (KBr, cmꢀ1):
): 1479 s, 1434 s;
v
(OꢀH): 3525 b; vasym(COOꢀ):1625 s; vsym(COOꢀ
(ArꢀOꢀC): 1099 s, 1075 s; (ꢀCH2ꢀ): 679 m.
v
v
o
was then adjusted to 7 with NaOH (20 mg, 0.5 mmol). The Synthesis of complex 4
resulting solution was sealed in a 25 mL microwave tube and
m
ꢀHCPA (93.30 mg, 0.5 mmol) was added to the solution of
o
heated at 100 C for 1 h at 120 W. Colorless single crystals
2
BaCl2 2H2O (10 mL). Afterwards, the pH value of the solution
was adjusted to 7 using aqueous sodium hydroxide solution
·
were obtained (yield: 71 %, based on Ba(II)). After cooling the
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o
(10 %). Going on stirring under 100 C at 160 W for 1 h, the displacement parameters for nonꢀH atoms using SHELXTL.55 All
colorless solution was obtained. After cooling to room nonꢀhydrogen atoms and hydrogen atoms were refined
temperature and left for slow evaporation, some colorless stickꢀ geometrically. Structural plots were generated with Diamond.
like crystals were collected by filtration, washed with distilled Crystallographic data has been deposited with the Cambridge
water (yield: 59 %, based on Ba(II)). Elemental analysis calcd. Crystallographic Data Centre, CCDC 1546820 for complex 1,
(%) for C32H42Cl4O21Ba2: C, 32.58; H, 3.55. Found: C, 32.57; 1546821 for complex 2, 1546822 for complex 3, 1546823 for
H, 3.56. IR (KBr, cmꢀ1):
sym(COOꢀ): 1477 s, 1424 s;
v
(OꢀH): 3456 b;
v
asym(COOꢀ):1579 s; complex 4, 1546824 for complex 5, 1546853 for complex 6. These
(ꢀCH2ꢀ): data can be obtained free of charge via
v
v(ArꢀOꢀC): 1047 s, 948 s; v
678 m.
www.ccdc.can.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Centre, 12 Union Road, Cambridge CB2 1EZ,
U.K., fax (+44) 1223ꢀ336033, or deposit@ccdc.cam.ac.uk). The
Synthesis of complex 5
A mixture of SrCl2
mg, 0.5 mmol) and
·
p
6H2O (266.62 mg, 0.25 mmol), NaOH (20 summary of the crystallographic data
ꢀHCPA (93.30 mg, 0.5 mmol) in water (10 and structure refinement for 1–6 are listed in Table 1. Selected bond
mL) was stirred for 30 min at room temperature. The resulting lengths and angles for 1–6 are summarized in Table S1. Bond
solution was sealed in a 25 mL microwave tube and heated at lengths (Å) and angles (°) of hydrogenꢀbond for 1–6 are summarized
100 oC, 130 W for 1 h. Colorless single crystals of
5 were in Table S2.
obtained (yield: 77 %, based on Sr(II)). Elemental analysis
calcd. (%) for C16H14Cl2O7Sr: C, 40.28; H, 2.95. Found: C,
Allelopathic Bioassay
40.27; H, 2.94. IR (KBr, cmꢀ1): (OꢀH): 3617 b; vasym(COOꢀ The seeds of two herbaceous plants, Amaranth (Amaranthus spp.),
v
):1629 s; vsym(COOꢀ): 1575 s, 1492 s;
(ꢀCH2ꢀ): 636 m.
v(ArꢀOꢀC): 1050 s, 1011 s; and barnyard grass were used for the bioassay. The procedure was
v
conducted according to the reported protocol.56 First, the plant seeds
were rinsed with running water for 2 h, then soaked in 0.3 % KMnO4
for 15 min, and flushed until they were colorless. The ligands and
Synthesis of complex 6
For the preparation of complexes 6, 5 mmol of pꢀHCPA and complexes, positive (control glyphosate) and blank solvent
deionized water (10 mL) were placed together in a 25 mL methanol, were added to 12ꢀwell plates with filter paper to serial
microwave tube and deprotonated by adding NaOH (0.2 mmol) concentration gradient of 50 to 200 ppm. After the evaporation of
until the pH=7. Then 0.25 mmol of BaCl2
·2H2O were added, methanol, the plant seeds were sown in the microdishes of 12ꢀwell
after vigorous stirring for five minutes. The mixture was heated plates and irrigated with deionized water. Triplicate experiments
o
o
by microwave under autogenous pressure at 100 C for 1 h at were conducted. The plates were then incubated at 24 C for 90 h,
200 W and then cooled to room temperature and filtered. The and the germination rates were calculated according to eq 1.
colourless crystals of suitable for the Xꢀray diffraction were Allelopathic effects [response index (RI)] were calculated according
obtained directly on the filter paper. Yield: 78 %, based on to eq 2.
Ba(II). Elemental analysis calcd. (%) for C16H14Cl2O7Ba: C,
36.48; H, 2.67. Found: C, 36.47; H, 2.66. IR (KBr, cmꢀ1):
v
(Oꢀ
H): 3572 b; vasym(COOꢀ):1576 s; vsym(COOꢀ): 1492 s, 1442 s;
(ArꢀOꢀC): 1048 s, 1008 s; (ꢀCH2ꢀ): 632 m.
germination rate %
ꢀ
ꢁ
⁄
= ꢀnumber of germinated seedsꢁ ꢀtotal number of seedsꢁ
v
v
1
Single-crystal X-ray structure determinations
)
All crystallographic data was collected on a Bruker SMART CCD
areaꢀdetector diffractometer at 298(2)
K
with graphite If T > C, then RI = 1 – C / T ; if T < C, then RI = T / C − 1
monochromatized MoꢀKα radiation (λ=0.71073 Å) in ω scan mode,
and the data reduction was performed using Bruker SAINT. The
2
crystal structures were resolved by direct methods and refined with ) Where T is the length of the treatment, C is the length of the blank
fullꢀmatrix leastꢀsquares refinement on F2 with anisotropic control, and RI is the response index.
Table 1. Crystallographic Data and Structure Refinement Details for 1ꢀ6.
Complex
1
2
3
4
5
6
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a, Å
C16H20Cl2O10Sr
530.84
C16H16Cl2O8Ba
544.53
C16H20Cl2O10Sr C32H42Cl4O21Ba2 C16H14Cl2O7Sr
C16H14Cl2O7Ba
526.51
298(2)
530.84
1179.14
298(2)
476.79
298(2)
298(2)
298(2)
298(2)
Triclinic
Pꢀ1
Monoclinic
P2(1)/c
Triclinic
Pꢀ1
Triclinic
Pꢀ1
Monoclinic
P2(1)/n
6.4624(6)
7.1964(7)
38.762(4)
90
Monoclinic
P2(1)
6.928(2)
7.487(3)
20.058(7)
96.780(6)
16.999(3)
7.7090(4)
13.979(3)
90
6.837(2)
7.377(3)
20.863(7)
95.035(6)
7.1090(10)
7.4780(10)
21.187(4)
82.464(3)
6.598
b, Å
7.511
c, Å
19.292
90
α (°)
4 | J. Name., 2012, 00, 1-3
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β
γ
(°)
(°)
91.281(6)
95.550(6)
1027.7(6)
2
92.294(3)
90.00
1830.5(6)
4
95.389(5)
91.338(6)
1043.1(6)
2
89.801(2)
87.715(3)
1115.7(3)
2
90.8980
90
96.99
90
Volume (Å3)
1802.5(3)
4
949.0
2
Z
Dc/g cmꢀ3
1.715
1.976
2.504
1064
1.690
1.755
1.757
3.324
952
1.843
2.408
512
µ
F
(mmꢀ1)
2.934
2.891
2.069
(000)
536
536
582
Crystal size (mm)
0.30×0.30×0.25
0.40×0.40×0.30 0.30×0.28×0.12 0.18×0.12×0.08 0.30×0.30×0.20 0.32×0.30×0.28
ꢀ9≤
ꢀ9≤
ꢀ26≤
Reflections collected 6957/493
h
≤9
≤8
≤25
ꢀ22≤
ꢀ9≤ ≤10
ꢀ12≤ ≤18
h
≤21
ꢀ8≤
h
≤8
≤6
≤25
ꢀ7≤
ꢀ9≤
ꢀ27≤
h
≤9
≤9
≤26
ꢀ8≤
h
≤8
≤9
≤40
ꢀ8≤
h
≤7
≤9
≤23
Index Range
k
k
ꢀ8≤k
k
ꢀ9≤k
ꢀ8≤k
l
l
ꢀ23≤
l
l
ꢀ50≤
l
ꢀ21≤l
11874/45
0.0375
5789/381
0.0445
7359/5010
0.0532
11931/4182
0.0243
5543/3295
0.0179
R
(int)
0.0488
Completeness (%)
GooF
97.5
99.2
98.3
98.3
99.8
99.9
1.004
1.264
1.066
1.187
1.115
1.147
R1=0.0896
wR2=0.2432
R1=0.1093
wR2=0.2702
2.202 and ꢀ3.092
R1=0.034
wR2=0.1012
R1=0.0414
wR2=0.1023
R1=0.065
wR2=0.1955
R1=0.0832
wR2=0.2110
R1=0.0584
wR2=0.1574
R1=0.0625
wR2=0.1722
R1=0.040
wR2=0.1435
R1=0.0583
wR2=0.1553
R1=0.0267
wR2=0.0753
R1=0.0273
wR2=0.0760
R1
,
wR2 [I>2sigma(I)]
wR2 (all data)
R1
,
ꢁρmax,ꢁρmin(e Å−3
)
0.969 and ꢀ3.839 1.235 and ꢀ1.438 2.908 and ꢀ1.113 0.694 and ꢀ1.192 1.204 and ꢀ0.621
oꢀCPA ligands, one lattice oꢀCPA ligand and four coordinated H2O
molecules. The central Sr (II) ions, exhibiting a tricapped triangular
prism coordination geometry, with the caps (O1, O2A, O1B) of the
three plane construct by the oxygen atoms of O3WꢀO3WBꢀO4Wꢀ
O1W, O1WꢀO4WꢀO2WCꢀO2W and O3WꢀO3WBꢀO2WCꢀO2W.
The central Sr(II) is nineꢀcoordinated by three carboxylate oxygen
Results and Discussion
Structure descriptions
The crystal structure of [Sr(
o-CPA)2(H2O)4]·(o-CPA) 1
atoms (O1, O1B, O2A) and six oxygen atoms (O1W, O2B, O2W,
O2WC, O3W, O4W) from coordinated H2O molecules. The length
of the SrꢀO bonds range from 2.570(6) Å to 2.844(5) Å, with the
average value of 2.678 Å, which are within the normal range.57
Singleꢀcrystal Xꢀray diffraction reveals that complex
1
crystallizes in
triclinic system with the space group pꢀ1. Fig. 1(a) shows the
coordination environments of Sr(II) ions. The asymmetric unit
contains one crystallographically unique Sr(II) ion, two coordinated
Fig. 1 (a) The coordination environment and coordination polyhedron of Sr(II) ion in 1. (b) and (c) are different coordination modes utilized by carboxyl group in
complex 1. All the hydrogen atoms are filtered.
In
1, the totally deprotonated carboxyl from oꢀCPA ligands appearing alternatively. The lengths of the two wings between the
displays two different coordination modes of µ2ꢀη1:η1 and µ3ꢀη1:η2 neighboring Sr(II) ions are d1=4.1189 and d2=3.790 Å, the
(Fig. 1(b) and (c)), which linked neighbouring Sr(II) ions together Sr···Sr···Sr torsion angle for the wings is α=122.110 (Fig. 2(b)).
with the coordinated water molecules to generate a metalꢀbased 1D
chain along the b axis (Fig. 2(a)). An interesting structural feature
for the 1D chains is zigzag arrangement with wingꢀlike shape
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O5B, O3AꢀO1WꢀO3ꢀO1WC and O5BꢀO4ꢀO3ꢀO1WC, respectively.
The BaꢀO covalent bond distances are within the range of 2.724 (2)ꢀ
3.054 (2) Å, which is consistent quite well with the other barium
complexes reported.
Fig. 2(a) A view showing the 1D chain along the
b axis. (b) The wingꢀlike zigzag
chain. All the hydrogen atoms are filtered.
As shown in Fig 3, uncoordinated oꢀCPA (the blue part) insert to
the two adjacent 1D chain with the assist of hydrogen bonds between
Fig. 4 The coordination environment (a) and coordination polyhedron (b) of Sr(II)
ion in 2. (c), (d) and (e) are the different coordination modes of carboxyl displayed
in 2. All the hydrogen atoms are filtered.
carboxylate oxygen and coordinated water, thus,
supramolecular layer structure is formed.
a
2D
Single crystal Xꢀray structure analysis reveals that compound
2
originate a (4, 4) rhomboid 2D grid structure (Fig. 5(a), 5(b)),
whereas the carboxyl group utilized three different coordination
modes: µ3ꢀη1:η2, µ2ꢀη1:η2 and µ2ꢀη1:η1. Within each grid, the
rhomboid windows have dimensions of 6.9953×4.3671 Å with
angles of 63.931 and 116.069° (defined by Ba···Ba distances and
Ba···Ba···Ba angles). The Ba–O bond lengths vary from 2.724(2) to
3.054(2) Å, which are within the normal range .58
Fig. 3 A view of the 2D layer along the ac plan. All the hydrogen atoms are
filtered.
Fig. 5 A view of the 2D layer along the ac plan. All the hydrogen atoms are
The crystal structure of [Ba(o-CPA)2(H2O)]·H2O 2
filtered.
The crystal structure reveals that
2
crystallizes in P2(1)/c space
group of the monoclinic system. Fig. 4 exhibits that the asymmetric
unit includes one Ba(II) ions, two oꢀCPA ligands, one coordinated
water molecule and one lattice water molecule. Centre Ba(II) is nine
coordinated (Fig. 4(a)), connected by six oxygen atoms from
carboxyl (O2, O3, O3A, O5B, O6, O6C), one oxygen atom (O4)
from phenoxy group of oꢀCPA ligand, two oxygen atoms of O1W
and O1WC from coordinated water molecules. As shown in Fig. 4(b),
The crystal structure of [Sr(
Refinement data revealed that
with space group Pꢀ1. Similar to
of one Sr(II) ions, two ꢀCPA ligands, four coordinated water
and one lattice ꢀCPA molecules. Different from , the Sr(II)
involved in distorted bicapped trigonal prism coordination
geometry, where O1W, O2W and O6 form the top plane of the
trigonal prism, and the bottom plane is completed by O3W,
O3WC and O6B, while O4W and O5A capped two
quadrilateral faces formed by O1WꢀO2WꢀO3WCꢀO3W and
m
-CPA) 2(H2O)4]·(
crystallized in triclinic system
, the asymmetric unit consists
m-CPA) 3
3
1
m
m
1
similar to
1, coordination geometry around Ba(II) ions in 2 are
distorted tricapped triangular prism, with the caps (O6, O6C, O2) of
the three plane construct by the oxygen atoms of O4ꢀO1WꢀO3Aꢀ
6 | J. Name., 2012, 00, 1-3
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O2WꢀO3WCꢀO6BꢀO6, respectively (Fig. 6 (a)). The Sr–O bond η1
ARTICLE
:
η1 and
µ
3ꢀη1
:
η2 coordination modes (Fig. 6(b) (c)) to
lengths vary from 2.548(5) to 2.717(5) Å, which are within the coordinate to the Sr(II) centre (Fig. 7(b), the yellow part),
normal range . 59
whereas another ꢀCPA ligand (Fig. 7(b), the blue part) has no
In , two Sr (II) are bridged by two coordinated water and coordination interactions with metals. The uncoordinated
two carboxyl groups which from ꢀCPA ligands and further CPA molecules play an important role of balancing the charge,
generate a binuclear secondary building unit (SBU) Sr2( it also link neighboring chains which further form the 2D layer
m
3
mꢀ
m
mꢀ
CPA)2(H2O)2 equivalent to a paddle wheel, producing the by formation of two kinds intermolecular hydrogen bonds (Fig.
Sr···Sr distance of 3.9215 Å. Neighbouring SBUs connect to 7(b), the pink part), one formed by coordinate water and
each other via sharing the carboxyl of
m
ꢀCPA ligands to oxygen atom from phenoxy, another constructed by carboxyl
produce a 1D chain extending along the
b
axis (Fig. 7(a)). group oxygen atoms and coordinate water, the distances of
Similar to 1, the carboxy group of mꢀCPA ligands utilize µ2ꢀ donorꢀacceptor distance vary from 2.75 to 3.21 Å.
Fig. 6 (a) The coordination environment and coordination polyhedron of Sr(II) ion in 3. (b) and (c) are the coordination modes of carboxy group. All the hydrogen atoms
are filtered.
Fig. 7 (a) A view of the SBU and 1D chain along the
b
axis. (b) The 2D layer. All the hydrogen atoms are filtered.
O1WꢀO1WBꢀO4WꢀO3W, respectively. Which is anchored by
three oxygens (O4, O4B and O5A) coming from carboxyl, as
well as six oxygens (O1W, O1WB, O2W, O2WA, O3W, O4W)
deriving from coordinated water molecules. The Ba−O bond
lengths vary from 2.700(4) to 2.871(4) Å, which are within the
The crystal structure of [Ba(
m-CPA)2(H2O)4]2·2(m-CPA)·H2O 4
The centrosymmetric dimer found in the crystal structure of
4
is
shown in Fig. 8. Singleꢀcrystal Xꢀray diffraction analysis
revealed that crystallized in triclinic crystal system, ꢀ1 space
4
P
group. The coordination environment and coordination
polyhedron of Ba(II) is presented in Fig. 8 with atom
normal range.60 Similar to
ligands utilize µ2
η1 η1 and µ3
coordinate to the Ba(II) centre.
The {Ba1( ꢀCPA)3(H2O)6} and {Ba2(
tricapped triangular share two oxygen atoms from coordinated
water and two ꢀCPA ligands to form a binuclear unit
containing an inorganic SBU [Ba( ꢀCPA)2(H2O)4]2·H2O, in
3
, the carboxy group of
mꢀCPA
ꢀ
:
ꢀ :
η1 η2 coordination modes to
numbering scheme. The asymmetric unit of
crystallographically independent Ba(II) atoms, four coordinated
ꢀCPA ligands, eight coordinated water molecules, two
uncoordinated ꢀCPA ligands and one lattice water molecule.
As illustrated in Fig. 8(b), both Ba1 and Ba2 are the nineꢀ
coordinate and locates in slightly distorted tricapped
4 possesses two
m
mꢀCPA)3(H2O)6}
m
m
m
m
a
which the Ba···Ba distance is 4.0042 Å. The adjacent inorganic
SBUs are bridged by double coordinate water form a 1D
triangular prism coordination sphere, with the caps (O5A, O4C,
O4B) of the three plane construct by the oxygen atoms of
O3WꢀO2WAꢀO2WꢀO2WA, O1WꢀO2WAꢀO2WꢀO1WB and
straight chain along the
b axis. (Fig. 9(a)).
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ARTICLE
Fig. 8 The coordination environment (a) and coordination polyhedron of Ba(II) ion (b) in 4. All the hydrogen atoms are filtered.
Different from
chain is the formation of the two interwoven quadrilateral (Fig.9(b)B).
between the two SBUs, one completed by Ba1ꢀO4ꢀBa2ꢀO4B, The ꢀCPA molecule can be regarded as a bidentate
and another constructed by Ba1ꢀO1WꢀBa2ꢀO1WB, (the blue bridging ligand to link coordinate water of neighboring chains.
circle part and show in Fig.9(b)A). While for compound , only In this manner, the 1D chains as a whole are involved in
3, an interesting structural feature for the 1D water (O1W, O2W, O4W) did not connect with others
m
3
one quadrilateral formed by Sr1ꢀO6ꢀSr2ꢀO6B, and coordinated hydrogen bonding interactions with neighboring chains to form
a 2D layer parallel to the ab plan.
Fig. 9 (a) A view of the SBU and 1D chain along the
b
axis. (b) Interwoven quadrilateral in
are filtered.
4 and quadrilateral in 3. (c) The 2D layer. All the hydrogen atoms
ligands, one oxygen atoms (O3) from phenoxy group of pꢀCPA
The crystal structure of [Sr(
Compounds and are isostructural differing only with respect
to the metal ion. Take the structure of to be described in detail
here for example. Crystal of have the centrosymmetric
crystallized in the 2(1)/n space group of the monoclinic
system, with an asymmetric unit consisting of one Sr(II) ion,
two ꢀCPA ligands, and one coordinated water molecule. As
p-CPA)2(H2O)] 5
and one water oxygen (O1W) from coordinated water. The
coordination geometry around Sr(II) ion could be described as a
distorted bicapped trigonal prism, where O4, O1 and O4C form
the top plane of the trigonal prism, and the bottom plane is
completed by O2A, O5B, and O1W, while O3 and O5C capped
two quadrilateral faces formed by O2AꢀO5BꢀO1ꢀO4 and O5Bꢀ
O1ꢀO4CꢀO1W, respectively. The Sr–O bond lengths vary from
2.473(3) to 2.948(3) Å, which are within the normal range . 61, 62
5
6
5
5
P
p
shown in Fig. 10(a), Sr(II) is eightꢀcoordinated with six
carboxyl oxygen atoms (O1, O2A, O4, O4C, O5B, O5C) from
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Fig. 10 (a) The coordination environment and (b) coordination polyhedron of Sr(II) ion in
hydrogen atoms are filtered.
5. (c) and (d) are the coordination modes of carboxy. All the
The carboxyl group of pꢀCPA ligand showed two kind of connecting nodes because four Sr(II) is connected by carboxyl
coordination modes µ3ꢀη2:η2 and µ2ꢀη1:η1 in Fig. 10 (c) and (d).. As oxygen atoms of pꢀCPA and forming fourꢀmembered ring.
for compound
5, the molecular structures are extended into a 2D Therefore, the 2D structure can be represented as a 4ꢀconnect
layer architecture. Similar to
1
, the Sr(II) can be regarded as fourꢀ topology. Fig. 11 (b).
Fig. 11 (a) The 2D layer of 5 (b) Topological representation of the 2D topology of 5. All the hydrogen atoms are filtered.
Structures comparison of complexes 1-6
Complexes , derived from three similar substitutional complexes
chlorophenoxyacetic acids, have both many similarities and , and
specific structural features. It is indicated that these compounds with twoꢀdimensional structures. The uncoordinated ligands (in
mainly belong to triclinic and monoclinic system. Carboxyl ) play an important role of balancing the charge, it also
group shows the diversity of coordination modes, such as µ2ꢀ link neighboring chains which further form the 2D layer by
η1:η1 ( ), µ3ꢀη1:η2 ( ), µ2ꢀη1:η2 ( ), µ3ꢀη2:η2 (
). formation of hydrogen bonds. And more notably, the oxygen
The big radius of Sr(II) and Ba(II) cause an unpredictable atoms of phenoxy group participate in the coordination process
coordination numbers (9 or 8) and different coordination was found in the complexes ( ), which is scarcely found in
present in all the complexes
and . The structure data reveal that complexes of
were oneꢀdimensional structure and others (
1ꢀ6, but lattice water only exists in
1
ꢀ
6
2
4
1
,
3
4
2, 5, 6)
1, 3, 4
1
,
2
,
3,
4
,
5,
6
1,
2
,
3,
4
2
5, 6
2, 5, 6
polyhedron (bicapped trigonal prism corresponds to chlorophenoxyacetic acid based complexes. In the meantime,
coordination numbers 8, while tricapped triangular prism this phenomenon can confirm the –OCH2– spacer group of
corresponds to coordination numbers 9). Coordinated water was ligands was flexible through the rotate of C–O and C–C bonds.
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Thermogravimetric analysis of complexes 1-6
BaO). For complex
1
, the first weight loss of 13.57% below
The TG analysis was performed in N2 atmosphere at a heating 175.53 oC is consistent with the removal of its lattice water
rate of 10 oC minꢀ1 on powder samples of
curves are shown in Fig. 12. The TG results reveal that all of 648.07 oC can be ascribed to the release of
1
–
6
, and the TG (calcd 13.56%), and the weight loss of 66.93% from 175.73 to
ꢀCPA organic
o
the six compounds have three weightꢀloss stages. The first step ligands. Upon further heating, the coordinated ligands were lost
shows an initial weight loss below 200 oC which can be until the residue was SrO (Table S3.). By the formation of
attributed to the removal of four coordinated water molecules. intermolecular O
Upon further heating, the following two weight losses can be ligands in complex
ascribed to the decomposition of organic ligands. The but the firm chemical bond is present in
remaining residue corresponds to formation of oxide (SrO or better thermodynamic
ꢀ
H···O hydrogen bonds, the uncoordinated
1
,
3
and inserted to the 2D layer structure,
4
2
,
5
and
6
, thus, has a
stability.
Fig. 12 TG curves of the complexes 1–6.
structures were formed. mꢀHCPA ligands look like coral, after
coordinated with Sr(II), spheroid with bright edges and dark inner
FESEM characterizing of ligands and complexes
Fig. 13 shows the typical FESEM micrograph of the ligands and
complexes. It can be seen clearly that surface appearance change
dramatically after coordinated. The ligands of oꢀHCPA were starꢀ
liked structure, after coordinated with Sr(II), it exhibits sheetꢀliked
structure with smooth edge; after coordination with Ba(II), rootꢀliked
were formed, after coordination with Ba(II), stripꢀliked complex
with wrinkled edge were formed. Grassꢀliked pꢀHCPA ligands
interact with Sr(II) and Ba(II), rodꢀliked complex and flakeꢀliked
complex were formed.
4
5
6
10 | J. Name., 2012, 00, 1-3
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ARTICLE
Fig. 13. FESEM images of the ligands and complexes. (1) FESEM images for
o
ꢀHCPA, (2) FESEM images for complex 1, (3) FESEM images for complex 2, (4)
FESEM images for coordination polymer
mꢀHCPA, (5) FESEM images for complex 3, (6) FESEM images for complex 4, (7) FESEM images for pꢀHCPA, (8) FESEM
images for complex 5, (9) FESEM images for complex 6.
inhibition of seedling growth. (1) The determined RI values of Shoot
elongation revealed complexes and were more active than the
corresponding ligands oꢀCPA and mꢀCPA). (2) For the six
complexes, complexes 1, 3 and 4 demonstrated a higher inhibitory
activity than that of complexes and . (3) The structureꢀ
allelopathic activity relationship analysis indicated that complexes of
and with oneꢀdimensional chains structures gave the more
potent inhibition of seedling growth compared to complexes of
and with twoꢀdimensional network structures. The overall
observed growth inhibitory effects order revealed to be the following:
pꢀCPA mꢀCPA oꢀCPA . In addition,
screening of compounds for their allelopathic activity revealed that
these complexes possess weaker inhibitory action than the
corresponding ligands in the range from 50 to 200 ppm.
Evaluation of Allelopathic Activity
1
,
3
4
All isolated compounds were evaluated for allelopathic activity
against Amaranth (Amaranthus spp.) and barnyard grass seeds by
determining the germination rates and seedling growth (root and
shoot elongation) with respect to the control, glyphosate, a broadꢀ
spectrum 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.
(
2
,
5
6
1
,
3
4
2, 5
6
3
>
>
4
>
>
1
>
5
>
6
>
> 2
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 against the tested barnyard grass.
The results are presented in Table 2. Our results revealed that all
1ꢀ6
administered experimental agents, caused
a
doseꢀdependent
Table 2. Allelopathic Effects on barnyard grass of ligands and complexes.
Germination rate
100 150
0.50
0.92
Shoot elongation
100 150
ꢀ0.30
ꢀ0.37
（
RI）
Root elongation
100 150
ꢀ0.86
ꢀ0.71
（RI）
50
0.83
0.67
200
0.75
0.58
50
ꢀ0.28
ꢀ0.30
200
ꢀ0.54
ꢀ0.62
50
ꢀ0.71
ꢀ0.64
200
ꢀ0.91
ꢀ0.82
0.58
0.58
ꢀ0.44
ꢀ0.46
ꢀ0.89
ꢀ0.79
o
ꢀCPA
1
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Journal Name
0.92
0.75
0.83
0.42
ꢀ0.26
ꢀ0.29
ꢀ0.38
ꢀ0.47
ꢀ0.41
ꢀ0.69
ꢀ0.64
ꢀ0.81
2
0.75
0.83
0.58
0.92
0.58
0.75
0.25
0.92
ꢀ0.30
ꢀ0.38
ꢀ0.52
ꢀ0.64
ꢀ0.65
ꢀ0.67
ꢀ0.67
ꢀ0.68
ꢀ0.94
ꢀ0.73
ꢀ0.97
ꢀ0.82
ꢀ0.97
ꢀ0.83
ꢀ0.97
ꢀ0.94
mꢀCPA
3
0.75
1.00
0.92
0.42
ꢀ0.31
ꢀ0.58
ꢀ0.67
ꢀ0.87
ꢀ0.91
ꢀ0.95
ꢀ0.97
ꢀ0.97
4
0.58
0.83
0.83
0.92
0.50
0.75
0.75
0.92
ꢀ0.31
ꢀ0.29
ꢀ0.64
ꢀ0.64
ꢀ0.74
ꢀ0.67
ꢀ0.89
ꢀ0.68
ꢀ0.85
ꢀ0.82
ꢀ0.91
ꢀ0.83
ꢀ0.92
ꢀ0.86
ꢀ0.94
ꢀ0.94
pꢀCPA
5
0.83
0.83
0.67
0.75
ꢀ0.28
ꢀ0.10
ꢀ0.62
ꢀ0.17
ꢀ0.71
ꢀ0.19
ꢀ0.88
ꢀ0.25
ꢀ0.80
ꢀ0.34
ꢀ0.87
ꢀ0.42
ꢀ0.95
ꢀ0.43
ꢀ0.96
ꢀ0.47
6
0.67
0.83
0.75
0.83
0.75
0.83
0.92
0.83
gp
ck
The authors gratefully acknowledge the financial supports from the
National Natural Science Foundation of China (Grant No. 21473136,
Grant No. 21103140).
Conclusions
In summary, we have synthesized six AECs based on isomeric
chlorophenoxyacetic ligands. Their structures were well
characterized by Single Xꢀray diffraction, Fourier transform infrared,
elemental analysis, field emission scanning electron microscope and
thermogravimetric analysis. The structure data reveal that complexes
Notes and references
1
A. E. Platero Prats, V. A. de la PenaꢀO'Shea, M. Iglesias, N.
Snejko, A. Monge and E. GutierrezꢀPuebla, ChemCatChem
2010, 2, 147ꢀ149.
,
2
3
4
5
6
7
8
9
K. S. Asha, M. Makkitaya, A. Sirohi, L. Yadav, G. Sheet and
S. Mandal, CrystEngComm, 2016, 18, 1046ꢀ1053.
Y. Wang, W. Liu, F. Huang, T. Zou and Z. Lin,
CrystEngComm, 2012, 14, 7165ꢀ7169.
Y. X. Sun, Y. Y. Sun, H. Zheng, H. L. Wang, Y. Han, Y.
Yang and L. Wang, CrystEngComm, 2016, 18, 8664ꢀ8671.
of
1
,
3
, and
4
are oneꢀdimensional chains with zigzag arrangement,
while
2,
5
, and are (4, 4) rhomboid twoꢀdimensional grid
6
structures. The carboxyl groups exhibiting various coordination
modes of µ2ꢀη1:η1 µ2ꢀη1:η2 µ3ꢀη1:η2 and µ3ꢀη2:η2 in these complexes.
,
,
Interestingly, oxygen atoms of flexible –OCH2– in phenoxy groups
take part in coordination behavior with metal centers through the
H. S. He, K. R. Rodgers and A. M. Arif, J. Inorg. Biochem
2004, 98, 667ꢀ676.
,
rotate of C–O and C–C bonds in complexes
carboxyl groups coordination can be found in complexes
Coordinated water was present in all the complexes
lattice water only exists in complexes and
uncoordinated ligands (in
2,
5
and
6
while only
S. Cai, Z. He, W. Wu, F. Liu, X. Huang, S. Zheng, J. Fan and
W. Zhang, CrystEngComm, 2017, 19, 3003ꢀ3016.
R. M. Nair, M. R. Sudarsanakumar, S. Suma, M. Kurup and P.
Antharjanam, Inorg. Chem. Commun., 2016, 63, 81ꢀ85.
M. B. Khan, H. Khan, M. U. Shah and S. Khan, Nat. Prod.
Res., 2016, 30, 935ꢀ940.
1
,
3
and 4.
1
ꢀ
6
, but
The
2
4.
1,
3,
4) play an important role of
K. Manna, P. Ji, F. X. Greene and W. Lin, J. Am. Chem. Soc.
2016, 138, 7488ꢀ7491.
,
balancing the charge. They also contribute to formation of 2D
layer by linking neighboring chains through OꢀHꢂꢂꢂO hydrogen
bonds. FESEM images indicate that the ligand's surface appearance
changed dramatically after coordinated with Sr(II) or Ba(II): starꢀlike
10 A. Peccerillo, S. R. Taylor, Contrib. Mineral Petr., 1976, 58,
63ꢀ81.
11 Q. Zhou, J. Qian and C. Zhang, J. Mol. Struct., 2016, 1119,
340ꢀ345.
12 S. C. Rosca, C. Dinoi, E. Caytan, V. Dorcet, M. Etienne, J. F.
Carpentier and Y. Sarazin, Chem.ꢀEur. J., 2016, 22, 6505ꢀ
6509.
13 J. Li, C. Wang, X. Gao, F. Zhao, K. Zhao, X. Fan, G. Zhang,
W. Zhang and Z. Gao, Polyhedron, 2016, 106, 58ꢀ64.
14 S. Varma and S. B. Rempe, Biophys. Chem., 2006, 124, 192ꢀ
199.
15 M. Mazaj, T. B. Celic, G. Mali, M. Rangus, V. Kaucic and N.
Z. Logar, Crystal Growth & Design, 2013, 13, 3825ꢀ3834.
16 R. K. Vakiti, B. D. Garabato, N. P. Schieber, M. J. Rucks, Y.
Cao, C. Webb, J. B. Maddox, A. Celestian, W. Pan and B.
Yan, Crystal Growth & Design, 2012, 12, 3937ꢀ3943.
17 D. T. Tran, D. Chu, A. G. Oliver and S. R. J. Oliver, Inorg.
Chem. Commun., 2009, 12, 351ꢀ354.
for oꢀHCPA, sheetꢀlike for
HCPA, spheroidꢀlike for , stripꢀliked for
HCPA, rodꢀliked for and flakeꢀliked for . Allelopathic activities
indicated that and are more effective than the ligands,
1, rootꢀlike for
2, coralꢀlike for mꢀ
3
4, grassꢀliked for pꢀ
5
6
1
,
3
4
especially to barnyard grass. The presented microwave synthesis
could be further applied into construction transition metal and rare
earth metal coordination compounds in crystal engineering. It’s
significant to develop new kind of environmentꢀfriendly herbicide
based on these kinds of complexes for their low toxicity and high
efficiency.
Acknowledgements
12 | J. Name., 2012, 00, 1-3
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Journal Name
ARTICLE
18 K. R. Ma, Y. L. Zhu, Q. F. Yin, H. Y. Hu and F. Ma, J. Chem. 45 Z. Wang, H. H. Zhang, Y. P. Chen, C. C. Huang, R. Q. Sun,
Res., 2010, 34, 705ꢀ709.
19 P. Lidstrom, J. Tierney, B. Wathey and J. Westman,
Tetrahedron, 2001, 57, 10229.
20 M. Ghasemi, H. Javadian, N. Ghasemi, S. Agarwal and V. K.
Gupta, J. Mol. Liq., 2016, 215, 161ꢀ169.
21 R. C. Hoffmann, S. Sanctis, E. Erdem, S. Weber and J. J.
Schneider, J. Mater. Chem. C, 2016, 4, 7345ꢀ7352.
Y. N. Cao and X. H. Yu, J. Solid. State. Chem, 2006, 179,
1536ꢀ1544.
46 P. W. Zimmerman, A. E. Hitchcock, Contrib. Boyce.
Thompson. Inst, 1942, 12, 321ꢀ44.
47 Y. C. Zhang, J. D. Li, Henan Agricultural Sciences, 2001, 11,
13ꢀ15.
48 A. H. Lu, H. B. He, Journal of Huazhong Normal University
(Natural Science Edition), 1999, 33, 543ꢀ546.
49 C. DendrinouꢀSamara, S. Katsamakas, C. Raptopoulou, A.
22 P. George, N. R. Dhabarde and P. Chowdhury, Mater. Lett
2017, 186, 151ꢀ154.
,
23 A. de la Hoz, A. DiazꢀOrtiz and A. Moreno, Chem. Soc. Rev.
2005, 34, 164ꢀ178.
,
Terzis, V. Tangoulis and D. P. Kessissoglou, Polyhedron
2007, 26, 763ꢀ772.
,
24 S. Tyrrell, M. SwadzbaꢀKwasny and P. Nockemann, J. Mater. 50 V. Tangoulis, G. Psomas, C. DendrinouSamara, C. P.
Chem. A, 2014, 2, 2616ꢀ2622.
25 K. Zhang, J. Dai, Y. H. Wang, M. H. Zeng and M. Kurmoo,
Dalton Trans., 2013, 42, 5439ꢀ46.
26 L.Q. Wei, K. Zhang, Y. C. Feng, Y. H. Wang, M. H. Zeng,
and M. Kurmoo, Inorg. Chem., 2011, 50, 7274ꢀ83.
Raptopoulou, A. Terzis and D. P. Kessissoglou, Inorg. Chem.
1996, 35, 7655ꢀ7660.
51 D. Y. Ma, H. F. Guo, L. Qin, Y. Pan, K. Lu and J. Q. Liu, J.
Coord. Chem., 2012, 65, 3424ꢀ3432.
52 D. Y. Ma, K. Lu, H. F. Guo, Y. Pan and J. Q. Liu, J. Mol.
Struct., 2012, 1021, 179ꢀ186.
,
27 L.
Q Wei, B. W. Li, S. Hu and M. H. Zeng,
CrystEngComm., 2010, 13 , 510ꢀ516.
28 Y. L. Zhou, M. H. Zeng, L. Q. Wei, B. W. Li, and M.
Kurmoo, Chem. Mater, 2010, 22, 4295ꢀ4303.
29 M. H. Zeng, Y. L. Zhou, W. X. Zhang, M. Du, and H. L. Sun,
Crystal Growth & Design., 2010, 10, 20ꢀ24.
53 Z. Wang, D. Liu, H. Zhang, C. Huang, Y. Cao and X. Yu, J.
Coord. Chem., 2008, 61, 419ꢀ425.
54 C. DendrinouꢀSamara, G. Psomas, C. P. Raptopoulou and D.
P. Kessissoglou, J. Inorg. Biochem., 2001, 83, 7ꢀ16.
55 G. M. Sheldrick, Acta. Crystallogr. C, 2015, 71, 3ꢀ8.
30 K. Kose, J. Motoyanagi, T. Kusukawa, A. Osuka and A. 56 Q. Zhang, S. Q. Wang, H. Y. Tang, X. J. Li, L. Zhang, J.
Tsuda, Angew. Chem., Int. Ed., 2015, 54, 8673ꢀ8678. Xiao, J. M. Gao, J. Agr. Food. Chem., 2013, 61, 11447ꢀ11452.
31 A. Dogaru, C. Pichon, R. Ababei, D. Mitcov, C. Maxim, L. 57 B. Freitag, J. Pahl and C. Farber and S. Harder,
Toupet, C. Mathoniere, R. Clerac and M. Andruh,
Polyhedron, 2014, 75, 146ꢀ152.
32 R. Zhang, X. Zeng, M. Prehm, F. Liu, S. Grimm, M. Geuss,
Organometallics, DOI: 10.1021/acs.organomet.7b00871.
58 H. S. Huang, Z.M. Li, G. T. Zhang, T. L. Zhang and W. H.
Hu, Main. Group. Chem., 2014, 13, 117ꢀ127.
M. Steinhart, C. Tschierske and G. Ungar, ACS Nano, 2014, 8, 59 L. R. Canaval, S. Hadisaputra and T. S. Hofer, Phys. Chem.
4500ꢀ4509.
Chem. Phys., 2015, 17, 16359ꢀ16366.
33 S. Leung and V. Yam, Chem. Sci., 2013, 4, 4228–4234.
34 W. Fujita, A. Tokumitu, Y. Fujii and H. Kikuchi,
CrystEngComm, 2016, 18, 8614ꢀ8621.
60 R. Drisya, U. S. S. Mol, P. R. S. Chandran, C. K. Simi, M. R.
Sudarsanakumar and P. K. S. Antharjanam, Main. Group.
Chem., 2017, 16, 241ꢀ254.
35 J. Gu, X. Liang, Y. Cui, J. Wu, Z. Shi and A. M. Kirillov, 61 K. S. Asha, M. Makkitaya, A. Sirohi, L. Yadav, G. Sheet and
CrystEngComm, 2017, 19, 2570ꢀ2588. S. Mandal, Crystengcomm 2016, 18, 1046ꢀ1053.
36 S. Feng, W. Li, F. Guo, X. Cao, Luminescence, 2014, 29, 62 F. Gschwind and M. Jansen, Acta. Crystallogr. E., 2012, 68
791ꢀ797.
(Pt 11), m1319.
37 R. Patra, H. M. Titi and I. Goldberg, CrystEngComm, 2013,
15, 2863ꢀ2872.
38 T. Wang, C. L. Zhang, Z. M. Ju and H. G. Zheng, Dalton
Trans., 2015, 44, 6926ꢀ6935.
39 S. Huf, S. Kruegener, T. Hirth, S. Rupp and S. Zibek, Eur. J.
Lipid. Sci. Tech., 2011, 113, 548ꢀ561.
40 Y. Su, S. Zang, Y. Li, H. Zhu and Q. Meng, Crystal Growth
& Design., 2007, 7, 1277ꢀ1283.
41 D. N. Dybtsev, H. Chun and K. Kim, Angew. Chem., Int. Ed.
2004, 43, 5033ꢀ5036.
,
42 Y. Q. Zheng, J. L. Lin and Z. P. Kong, Inorg. Chem., 2004,
43, 2590ꢀ2596.
43 G. Y. Wu, Y. X. Ren, Z. Yin, F. Sun, M. H. Zeng and M.
Kurmoo, RSC Adv., 2014, 4, 24183ꢀ24188.
44 J. M. Li, Y. G. Zhang, J. H. Chen, L. Rui, Q. M. Wang and X.
T. Wu, Polyhedron, 2000, 19, 1117ꢀ1121.
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DOI: 10.1039/C8NJ00107C
Text: Facile microwave synthesis, structural diversity and herbicidal activity of six
novel alkaline-earth metal complexes (AECs) based on skeletal isomerization
chlorophenoxyacetic acids