Three Ternary Rare Earth(III) Complexes Based on 3-[(4,6-Dimethyl-2-pyrimidinyl)thio]-propanoic Acid and 1,10-Phenanthroline: Synthesis, Crystal Structure and Antioxidant Activity

Article abstract of DOI:10.1002/zaac.201500018

Three ternary rare earth [Nd^III (1), Sm^III (2) and Y^III (3)] complexes based on 3-[(4,6-dimethyl-2-pyrimidinyl)thio]-propanoic acid (HL) and 1,10-phenanthroline (Phen) were synthesized and characterized by IR and UV/Vis spectroscopy, TGA, and single-crystal X-ray diffraction. The crystal structures showed that complexes 1-3 contain dinuclear rare earth units bridged by four propionate groups and are of general formula [REL₃(Phen)]₂·nH₂O (for 1 and 2: n = 2; for 3: n = 0). All rare earth ions are nine-coordinate with distorted mono-capped square antiprismatic coordination polyhedra. Complex 1 crystallizes in the monoclinic system, space group P2₁/c with a = 16.241(7) ?, b = 16.095(7) ?, c = 19.169(6) ?, β = 121.48(2)°. Complex 2 crystallizes in the monoclinic system, space group P2₁/c with a = 16.187(5) ?, b = 16.045(4) ?, c = 19.001(4) ?, β = 120.956(18)°. Complex 3 crystallizes in the triclinic system, space group P1 with a = 11.390(6) ?, b = 13.636(6) ?, c = 15.958(7) ?, α = 72.310(17)°, β = 77.548(15)°, γ = 78.288(16)°. The antioxidant activity test shows that all complexes own higher antioxidant activity than free ligands.

Full text of DOI:10.1002/zaac.201500018

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
DOI: 10.1002/zaac.201500018
Three Ternary Rare Earth(III) Complexes Based on 3-[(4,6-Dimethyl-2-
pyrimidinyl)thio]-propanoic Acid and 1,10-Phenanthroline: Synthesis,
Crystal Structure and Antioxidant Activity
Xiao Chen[a] and Jian-Qiang Qu*[a]
Keywords: 1,10-Phenanthroline; 3-[(4,6-Dimethyl-2-pyrimidinyl)thio]-propanoic acid; Rare earths; Crystal structure;
Antioxidant
Abstract. Three ternary rare earth [NdIII (1), SmIII (2) and YIII (3)] tallizes in the monoclinic system, space group P21/c with a =
complexes based on 3-[(4,6-dimethyl-2-pyrimidinyl)thio]-propanoic
acid (HL) and 1,10-phenanthroline (Phen) were synthesized and char-
acterized by IR and UV/Vis spectroscopy, TGA, and single-crystal X-
ray diffraction. The crystal structures showed that complexes 1–3 con-
16.241(7) Å, b = 16.095(7) Å, c = 19.169(6) Å, β = 121.48(2)°. Com-
plex 2 crystallizes in the monoclinic system, space group P21/c with
a = 16.187(5) Å, b = 16.045(4) Å, c = 19.001(4) Å, β = 120.956(18)°.
Complex 3 crystallizes in the triclinic system, space group P1 with
tain dinuclear rare earth units bridged by four propionate groups and a = 11.390(6) Å, b = 13.636(6) Å, c = 15.958(7) Å, α = 72.310(17)°,
are of general formula [REL3(Phen)]2·nH2O (for 1 and 2: n = 2; for 3: β = 77.548(15)°, γ = 78.288(16)°. The antioxidant activity test shows
n = 0). All rare earth ions are nine-coordinate with distorted mono- that all complexes own higher antioxidant activity than free ligands.
capped square antiprismatic coordination polyhedra. Complex 1 crys-
3-[(4,6-dimethyl-2-pyrimidinyl)thio]-propanoic acid (HL) and
Introduction
Phen were synthesized and characterized by IR, UV/Vis, TGA,
In the past few years, transition metal complexes with pyr-
–
and single-crystal X-ray diffraction. The super oxide (O2 ) dis-
imidine derivatives were paid considerable attention thanks to
mutase activity was carried out by the pyrogallol autoxidation
the excellent biological activity of pyrimidine and its deriva-
method.
tives.[1] As expected, these metal complexes own higher ac-
tivity than free ligands in versatile areas, like antiproliferative
activity,[2] antimicrobial activity[3] and antitumor activity.[4]
Owing to the capacity of inhibits hydroxyl radical formation,
Results and Discussion
All complexes are stable in air at room temperature and sol-
uble in CH2Cl2, dimethyl formamide (DMF), and dimethyl
sulfoxide (DMSO), but insoluble in water, ethanol, ethyl acet-
ate, cyclohexane, cyclohexanone, acrylonitrile, and ether.
Phen, a well-known chelating ligand, could reduce the severity
of alloxan-induced diabetes in rats and relieved alloxan-in-
duced toxicity in human fibroblastas in culture.[5] And former
study have illustrated that the copper complexes of 1,10-phen-
anthroline (Phen) derivatives owns a remarkable superoxide
anion dismutase activity, and this activity partly depends on
the steric and field effects of ligands involved.[6]
IR Spectroscopy
Despite the excellent antitumor activity of pyrimidine, to
the best of our knowledge, few scientists pay attention on the
antioxidant activity of ternary rare earth complex with pyrim-
idine derivatives and 1,10-phenanthroline. Meanwhile, former
researchers have proved that free radicals may impair human
body through damaging the nucleic acid, protein etc.[7] Hence,
in this paper, three new ternary rare earth complexes based on
The values of main IR absorption peaks in the spectra of the
ligands and complexes are listed in Table 1. IR spectra of the
three complexes were similar, but differed from those of the
free ligands. For carboxylic acid, the characteristic peak of
ν(C=O) disappeared and was substituted by the symmetric
stretching vibration (νs) peak and asymmetric stretching vi-
bration peak (νas) after deprotonation, and this phenomenon
could be proved in the spectrum of sodium salt of HL. In the
complexes 1–3 spectra, the peak of ν(C=O) (1706 cm–1) in HL
spectra disappeared and was replaced by asymmetric stretching
peaks νas (1540–1549 cm–1) and symmetric stretching peaks νs
(1426–1427 cm–1), which proved that L– coordinates with
REIII through carboxyl group.[4] The characteristic peaks of
Phen can be found in the spectra of complexes and confirmed
after compared with homoleptic complexes of REIII and HL.
* Ass. Prof. Dr. J.-Q. Qu
E-Mail: jqqu@tju.edu.cn
[a] Department of Chemistry, School of Science
and Collaborative Innovation Center of Chemical Science and
Engineering
Tianjin University
Tianjin 300072, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201500018 or from the au-
thor.
Z. Anorg. Allg. Chem. 2015, 641, (7), 1301–1306
1301
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 1. Main IR absorption peaks /cm–1 of ligands and complexes 1–3.
Compound
ν(Phen)
ν(C=C)
ν(HL)
ν(OH)
δ(C–C)
δ(C–H) ν(RE–N)a) ν(Me)
ν(Py)b)
νas
νs
ν(C=O)
ν(RE–O)a)
Phen
HL
NaLc)
1
2
3
1618
–
–
1600
1603
1608
841
–
–
846
846
846
733
–
–
731
731
730
–
–
–
544
544
544
–
–
–
–
1537
1544
1549
1540
–
–
1413
1426
1427
1427
–
1706
–
–
–
–
–
–
–
418
418
418
–
–
–
3421
3421
–
2927
2927
2921
2925
2922
1585
1590
1582
1581
1581
a) RE = Rare earth. b) Py = Pyrimidine ring. c) NaL = sodium salt of 3-[(4,6-dimethyl-2-pyrimidinyl)thio]-propanoic acid.
There are shifts for ν(C=C) from 1618 cm–1 (free ligand) to to 180 °C belongs to the remove of two lattice water mol-
about 1600–1608 cm–1 (complexes), and δ(C–H) from ecules.[11] No weight loss was found in this region for 3, which
733 cm–1 (free ligand) to 730–731 cm–1 (complexes), which indicated that no water molecules exist. These results are well
indicates that the Phen ligand coordinates with rare earth ions consistent with the X-ray crystal structure. The decomposition
through nitrogen atoms.[8] The new peaks of RE–N of coordination framework starts at about 217 °C (1), 217 °C
(544 cm–1) and RE–O (418 cm–1) in the spectra of the com- (2), and 218 °C (3).
plexes further proved the coordination of Phen and HL with
REIII.[9] The broad peak (3421 cm–1) in the spectra of 1 and 2
belongs to lattice water.[4] All the above results can be further
confirmed by single-crystal X-ray diffraction.
UV/Vis Spectroscopy
Figure 1 shows the UV/Vis spectra of the free ligands, the
sodium salt of HL, and complexes 1–3 from 235 nm to
340 nm. The maximum absorption wavelengths (λmax) of HL
and Phen are at 248.8 nm and 264.6 nm, respectively. Mean-
while, the spectrum of deprotonated HL was measured with a
tiny red shift (0.8 nm) to 249.6 nm. The λmax values of com-
plexes 1–3 are almost the same: 254.8 nm (1), 254.8 nm (2),
and 254.6 nm (3), which assigned to an intramolecular charge
transfer interaction and indicated that both L– group and Phen
are coordinated with rare earth ions successfully.[10]
Figure 2. Thermogravimetric curves of complexes 1–3.
Description of the Crystal Structures
The details of crystallographic data of 1–3 are listed in
Table 2. Some selected interatomic distances are compiled in
Table 3. The selected interatomic angles are listed in Table S1
(see Supporting Information).
The structures of complexes 1 and 2 are isostructural with
space group P21/c (Figure 3a for 1, Figure 4a for 2). Rare earth
ions are nine-coordinate forming a very common distorted
mono-capped square antiprism (Figure 3b for 1, Figure 4b for
2), which could be found in the reported lanthanide complexes
[Ln(PDA)3(H2O)]·2H2O [Ln
=
Nd, Sm] and [Nd(α-
C10H7CH2COO)3(C12H8N2)]2 as well.[12] Two rare earth ions
are bridged by four L– groups with bidentate bridging mode
and tridentate bridging mode. The remaining L– groups and
Phen coordinated with the central metal ions as bidentate che-
lating group through oxygen atoms and nitrogen atoms, respec-
tively. The distances of Nd(Sm)–O bonds are in the range of
2.418 Å to 2.589 Å (Sm–O bond: 2.391 Å to 2.557 Å) and the
Figure 1. UV/Vis spectra of the ligands and complexes 1–3.
Thermogravimetric Analysis
Thermogravimetric analysis of complexes 1–3 are shown in mean distance of the Nd(Sm)–N bond is 2.653 Å (Sm–N bond:
Figure 2. The weight loss of complexes 1 and 2 (for 1: obsd. 2.612 Å). Bidentate bridging groups own the largest O–C–O
2.1%, calcd. 1.9%; for 2: obsd. 2.1%, calcd. 1.8%) from 30 angles (1: O1–C13–O2, 125.4°; 2: O5–C31–O6, 125.4°), and
Z. Anorg. Allg. Chem. 2015, 1301–1306
1302
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 2. Crystallographic data for complexes 1–3.
1
2
3
Empirical formula
Formula weight
Crystal system
T /K
C78H86N16Nd2O14S6
1952.47
monoclinic
294(2)
C78H86N16O14S6Sm2
1964.69
monoclinic
294(2)
C78H82N16O12S6Y2
1805.78
triclinic
294(2)
Space group
a /Å
b /Å
c /Å
α /°
P21/c
16.241(7)
16.095(7)
19.169(6)
90
121.48(2)
90
4273(3)
P21/c
16.187(5)
16.045(4)
19.001(4)
P1
11.390(6)
13.636(6)
15.958(7)
72.310(17)
77.548(15)
78.288(16)
2280.3(18)
1.315
90
β /°
γ /°
120.956(18)
90
4232.0(19)
1.542
0.29ϫ0.13ϫ0.04
2
Volume /Å3
ρ /g·cm–3
Crystal size /mm3
Z
1.517
0.30ϫ0.13ϫ0.05
2
0.23ϫ0.17ϫ0.14
2
F(000)
1988
1.419
1996
1.593
932
1.467
μ /mm–1
Index ranges
–19 Յ h Յ 19
–19 Յ k Յ 19
–22 Յ l Յ 22
7537 / 2 / 529
0.9324, 0.6756
36144 / 7537 [R(int) = 0.0977]
1.050
–20 Յ h Յ 20
–20 Յ k Յ 20
–24 Յ l Յ 24
9666 / 0 / 538
0.9390, 0.6551
43676 / 9666 [R(int) = 0.0716]
1.060
–13 Յ h Յ 13
–16 Յ k Յ 15
–18 Յ l Յ 18
8033 / 0 / 520
0.8210, 0.7291
Data/restraints/ parameters
Max. and min. transmission
Reflections collected / unique
GOF
19725 / 8033 [R(int) = 0.0586]
1.096
R1, wR2 [I Ͼ 2σ(I)]
R1, wR2 (all data)
0.0446, 0.1100
0.0503, 0.1172
0.0396, 0.0969
0.0478, 0.1042
1.732 and –1.109
0.0539, 0.1749
0.0598, 0.1811
1.524 and –0.448
Largest diff peak and hole / e·Å–3 1.896 and –1.374
Table 3. Selected interatomic distances /Å for complexes 1–3.
1
Nd(1)–O(2)#1
Nd(1)–O(5)#1
Nd(1)–O(1)
2.418(3)
2.419(3)
2.444(3)
Nd(1)–O(6)
Nd(1)–O(5)
2.567(3)
2.589(3)
Nd(1)–O(4)
Nd(1)–O(3)
2.478(3)
2.540(3)
Nd(1)–N(1)
Nd(1)–N(2)
2.630(4)
2.676(4)
Nd(1)–Nd(1)#1 3.9998(13)
Symmetry codes: #1 –x,–y+2,–z+1.
2
Sm(1)–O(5)
2.391(2)
Sm(1)–O(2)
Sm(1)–O(1)
2.555(3)
2.557(2)
Sm(1)–O(4)
Sm(1)–O(3)
2.446(3)
2.521(3)
Sm(1)–N(1)
Sm(1)–N(2)
2.597(3)
2.640(3)
Sm(1)–O(1)#1 2.392(2)
Sm(1)–O(6)#1 2.403(2)
Sm(1)–Sm(1)#1 3.9622(8)
Symmetry codes: #1 –x, –y+2, –z+1.
3
Y(1)–O(4)#1
Y(1)–O(5)#1
Y(1)–O(3)
2.307(3)
2.316(3)
2.352(3)
Y(1)–O(1)
Y(1)–O(5)
Y(1)–Y(1)#1
2.530(3)
2.570(3)
3.9261(15)
Y(1)–O(2)
Y(1)–O(6)
2.375(3)
2.412(3)
Y(1)–N(1)
Y(1)–N(2)
2.605(3)
2.559(3)
Symmetry codes: #1 –x, –y+1, –z+1.
the next are bidentate chelating groups (1: O3–C22–O4, tate chelating mode could be found between YIII ions and the
121.7°; 2: O3–C22–O4, 121.3°) and tridentate bridging groups left L– group or Phen molecule. It is obvious that the coordina-
(1: O5–C31–O6, 120.3°; 2: O1–C13–O2, 120.6°). The coordi- tion environment of YIII is similar to NdIII and SmIII.
nation number, coordination arrangement, and the interatomic
The Y–O interatomic distances range from 2.307 Å to
distances and angles in complexes 1 and 2 are similar to the 2.570 Å and the mean distance of Y–N bond is 2.582 Å. Com-
statistics found in the published ternary rare earth complexes pared with tridentate bridging group (O5–C31–O6: 120.0°)
[Nd(2-Cl-4,5-dfba)3PhenH2O]2 and [Sm(o-MBA)3Phen]2.[13]
and bidentate chelating group (O1–C13–O2: 120.6°), the bi-
With respect to complex 3, Figure 5a and b show the mole- dentate bridging group (O3–C22–O4: 126.3°) owns the largest
cular structure of complex 3 and the coordination arrangement O–C–O angle. The structure of complex 3 is similar to that of
of the YIII ion, respectively. Complex 3 is a dual core structure reported ternary rare earth complexes Y2(crot)6(Phen)2·2H2O
with space group P1 and two YIII ions are bridged together by and Y2(crot)6(mPhen)2·2H2O.[14] π–π interactions just exist in
four L– groups, with two of them in bidentate bridging mode 3 between Phen of nearby molecules with a centroid-centroid
and the remaining two in tridentate bridging mode. The biden- distance of 3.667(4) Å (Figure 6).
Z. Anorg. Allg. Chem. 2015, 1301–1306
1303
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
It is obvious that complex 3 has a different molecular struc-
ture compared with complex 1 and 2. This difference may re-
lated to the π–π interactions existing in complex 3, but the
exact reasons of this difference still need to be further investi-
gated. However, the coordination numbers of all the complexes
are 9 and the coordination arrangements of the three com-
plexes are completely the same: distorted mono-capped square
antiprism with two nitrogen atoms from Phen molecule and
seven oxygen atoms from L– groups.
Antioxidant Activity
Some investigations have shown that compared with free
Figure 3. (a) Crystal structure of [NdL3(Phen)]2·2H2O (1). Hydrogen
atoms and lattice water molecules are omitted for clarity; (b) coordina- ligand, their transition metal complexes may own a higher anti-
tion arrangement of the NdIII atom in 1.
oxidant activity.[15] Hence, the antioxidant activities of free li-
gands and complexes 1–3 were investigated. Free ligand HL
(IC50 = 2.53 mmol·L–1) expressed an obvious antioxidant ac-
tivity. However, no noticeable activity was found for Phen un-
der pyrogallol autoxidation method. As expected, the antioxi-
dant activity tests illustrate that complexes 1–3 (for 1: IC50
= 0.11 mmol·L–1; for 2: IC50 = 0.11 mmol·L–1; for 3: IC50
=
0.10 mmol·L–1) possess much higher activity than free ligand
HL. Meanwhile, the antioxidant activity of complexes 1–3 is
higher than the reported copper(II)-dipeptide complexes
Cu(Gly·Ala)·2H2O (8.00 mmol·L–1) and Cu(Gly·Gly)·3H2O
(1.32 mmol·L–1), but lower than Cu(glygly)(HPB)(Cl)·2H2O
(3.83 μmmol·L–1).[16]
It is believed that this conclusion may be helpful in prepar-
ing more high-performance antioxidants.
Figure 4. (a) Crystal structure of [SmL3(Phen)]2·2H2O (2). Hydrogen
atoms and lattice water molecules are omitted for clarity; (b) coordina-
tion arrangement of the SmIII atom in 2.
Conclusions
In this work,
a
new ligand 3-[(4,6-dimethyl-2-
pyrimidinyl)thio]-propanoic acid was synthesized and its ter-
nary rare earth [NdIII (1), SmIII (2) and Y(III) (3)] complexes
based on 1,10-phenanthroline (Phen) were obtained and well
characterized with IR, UV/Vis, TGA, and single X-ray diffrac-
tion. The three complexes have dinuclear structures in which
two rare earth ions bridged by four L– groups with a general
formula of [REL3(Phen)]2·nH2O (for 1 and 2: n = 2; for 3: n
= 0). Herein, pioneering work on the antioxidant activity of
ternary rare earth complexes based on pyrimidine derivatives
and 1,10-phenanthroline was done. Investigations on the super
–
oxide (O2 ) dismutase activity of free ligands and complexes
1–3 illustrated that the three complexes own higher activity
than the free ligands HL and Phen, which confirms the former
result that transition metal complexes may exhibit higher anti-
oxidant activity than the corresponding free ligand. This con-
clusion provides a new way to prepare more effective antioxi-
dants.
Figure 5. (a) Crystal structure of [YL3(Phen)]2 (3). Hydrogen atoms
are omitted for clarity; b) coordination arrangement of the YIII atom
in 3.
Experimental Section
Materials and General Methods: All starting reagents were commer-
cially available as reagent grade and were used without further purifi-
cation. Rare earth chlorides were prepared by the reaction of rare earth
oxide (Yuelong, China) with HCl. Infrared (IR) spectra were recorded
Figure 6. π–π interactions in complex 3. Hydrogen atoms and part of
the L– groups are omitted for clarity.
Z. Anorg. Allg. Chem. 2015, 1301–1306
1304
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
with an ALPHA FT-IR spectrometer (Bruker, Germany) in the region
with a spectrum showing a very intensive peak at about 320 nm. The
of 4000–400 cm–1 by using KBr pellets. UV/Vis spectra were carried superoxide free radical inhibition activity of sample could be acquired
out with a UT-1901 (Persee, China) from 340 nm to 235 nm in CH2Cl2.
Thermogravimetric analyses (TGA) were taken with a STA 409 PC
(NETZSCH, Germany) in a nitrogen atmosphere from room tempera-
ture to 1000 °C with a heating rate of 10 K·min–1. The single-crystal
X-ray diffraction was carried out with a XtaLAB mini (Rigaku, Japan)
at 294(2) K. The antioxidant activity of both free ligands and com-
plexes was carried out by pyrogallol autoxidation method.
after compared with the pyrogallol autoxidation rate.[19]
The samples (1: 0.0269 g; 2: 0.0264 g; 3: 0.0266 g) were dissolved in
DMF (1.0 mL) and diluted with water to 50.00 mL.
A mixture (5.00 mL), containing Tris-HCl (2.00 mL, pH = 8.3), dis-
tilled water (2.70 mL), and pyrogallol (0.30 mL, 6.0 mmol·L–1) was
transferred to the quartz absorption cells. The values of absorption,
measured at 319.2 nm, were recorded for 4.0 min. The slope of absorp-
tion-time curve stands for the pyrogallol autoxidant rate (ν0).
Synthesis of 4,6-Dimethyl-2-pyrimidineethiol:[4] An ethanol solution
(60.0 mL) of thiourea (7.61 g, 100 mmol) and acetyl acetone (10.2 mL)
was heated to reflux at 80 °C for 0.5 h. Afterwards concentrated HCl
(16.8 mL) was added slowly. The reflux conditions were kept for fur-
ther 2 h and the mixture was cooled to room temperature overnight.
The yellow crystals were obtained with filtration, washed with a small
amount of water and dried in vacuo. Yield: 62.1%.
Tris-HCl (2.00 mL, pH = 8.3) and the sample (0.10 mL, 0.20 mL,
0.50 mL, 1.0 mL, 1.5 mL, 2.0 mL, 2.5 mL) were mixed. Distilled
water was added till the volume arrived at 4.70 mL. Pyrogallol
(0.30 mL, 6.0 mmol·L–1) was added into the mixture at last. The values
of absorption, measured at 319.2 nm, were recorded for 4.0 min. The
slopes of absorption-time curves stand for the sample antioxidant rate
(νt).
Synthesis of 3-[(4,6-Dimethyl-2-pyrimidinyl)thio]-propanoic Acid:
(see Figure 7) A distilled water (50.0 mL) solution of 3-chloropropi-
onic acid (4.34 g, 40.0 mmol), NaOH (3.20 g, 80.0 mmol), and 4,6-
dimethyl-2-pyrimidineethiol (5.61 g, 40.0 mmol) was heated to reflux
80 °C for 1.5 h, filtered while hot, and cooled to room temperature.
Afterwards, concentrated HCl was dropped to obtain the white precipi-
tation. The white crystals were collected after recrystallized from 50%
ethanol, filtered, washed with a small amount of water and dried in
vacuo. Yield: 75.8%. IR (KBr): ν˜ = 3697 (s), 1706 (s), 1586 (s), 1535
(m), 1430 (m), 1340 (s), 1249 (s), 1164 (m), 950 (w), 887 (w), 859
(w), 815 (w), 547 (w) cm–1. UV/Vis (λmax, CH2Cl2): 248.8 nm.
The inhibition ratio (Z) of samples could be calculated by the equation:
Z = (1 – νt / ν0)ϫ100%.[20]
The half maximal inhibitory concentration, short for IC50, represents
the concentration of an inhibitor that is required for 50% inhibition
and is commonly used as a measure of sample effectiveness. For the
antioxidant effectiveness of complexes 1–3, the half maximal inhibi-
tory concentration (IC50) values could be calculated using the linear
relation between the inhibitory ratio and concentration logarithm.[21]
X-ray Single Crystal Structure Determination: The X-ray single-
crystal diffraction data of 1–3 were collected with a Rigaku XtaLAB
mini diffractometer (Japan) at 294(2) K with graphite-monochromated
Mo-Kα radiation (λ = 0.71073 Å) and ω scan mode. The semi-empiri-
cal multi scan absorption correction was applied to the X-ray data of
1–3. All the structures were solved by direct method and refined by
full-matrix least-squares methods with SHELXL package.[22]
Hydrogen atoms of complexes 1–3 were positioned at geometrically
calculated positions and refined with fixed isotropic thermal param-
eters.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting
the depository numbers CCDC-1035513 (1), CCDC-1035514 (2),
Figure 7. Synthesis of ligand 3-[(4,6-dimethyl-2-pyrimidinyl)thio]-
propanoic acid (HL).
Synthesis of RE(Phen)2Cl3:[17] An ethanol solution (25.0 mL) of
Phen·H2O (0.79 g, 4.0 mmol) and RECl3·6H2O (2.0 mmol) was stirred and CCDC-1035515 (3) (Fax: +44-1223-336-033; E-Mail:
for 2.0 h at room temperature. The white powder was obtained by
filtration, washed with a small amount of ethanol and further dried in
vacuo. Yield: 86.7% (1), 88.4% (2), 85.9% (3).
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
Supporting Information (see footnote on the first page of this article):
Selected interatomic angles of complexes 1–3.
Synthesis of Complexes 1–3: HL (0.64 g, 3.0 mmol) was dissolved
in 50% methanol (10.0 mL). Afterwards, NH3·H2O was added until
the pH arrived to 6.0. This mixture was added into the 50% methanol
(15.0 mL) solution of RE(Phen)2Cl3 (1.0 mmol). The pH was kept at
6.0 using NH3·H2O, stirred at room temperature for 2.0 h, and filtered.
After three weeks, the colorless block crystals of 1–3 suitable for X-
ray diffraction were obtained from filtrate by slow evaporation at room
temp. Yield: 69.1% (1), 68.7% (2), 65.9% (3).
Acknowledgements
This work was supported by Seed Foundation of Tianjin University
(60302020).
References
Antioxidant Activity: Pyrogallol autoxidized at a very high speed in
aqueous alkaline medium, and several intermediate products and su-
peroxide free radical were apparently formed.[18] Owning to the exis-
tence of intermediate product, the aqueous solution became yellow
[1] a) P. G. Baraldi, B. Cacciari, S. Moro, G. Spalluto, G. Pastorin,
T. Da Ros, K.-N. Klotz, K. Varani, S. Gessi, P. A. Borea, J. Med.
Chem. 2002, 45, 770–780; b) R. L. Levine, N. J. Hoogenraad, N.
Kretchmer, Pediatr. Res. 1974, 8, 724–734.
Z. Anorg. Allg. Chem. 2015, 1301–1306
1305
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
[2] A. B. Caballero, A. Rodríguez-Diéguez, M. Quirós, J. M. Salas, [13] a) K. Tang, J. J. Zhang, D. H. Zhang, N. Ren, L. Z. Yan, Y. Li, J.
Ó. Huertas, I. Ramírez-Macías, F. Olmo, C. Marín, G. Chaves-
Lemaur, R. Gutierrez-Sánchez, M. Sánchez-Moreno, Eur. J. Med.
Chem. 2014, 85, 526–534.
Chem. Thermodyn. 2013, 56, 38–48; b) N. Ren, J. J. Zhang, S. L.
Xu, R. F. Wang, S. P. Wang, Thermochim. Acta 2005, 438, 172–
177.
[3] A. A. Osowole, G. A. Kolawole, R. Kempe, O. E. Fagade, Synth. [14] A. M. Atria, J. C. Munoz, A. Soto, M. T. Garland, R. Baggio,
React. Inorg. Met.-Org. Nano-Met. Chem. 2009, 39, 165–174.
[4] J. Q. Qu, L. F. Wang, Y. Q. Liu, Y. M. Song, Y. Y. Wang, X. F.
Jia, J. Rare Earths 2006, 24, 15–19.
[5] D. L. Eizric, M. A. De Lúcio, A. C. Boschero, M. E. Hoffmann,
J. Free Radic. Biol. Med. 1986, 2, 189–192.
Acta Crystallogr., Sect. C 2003, 59, m416–m420.
[15] a) Y. Li, Zh. Y. Yang, J. Fluoresc. 2010, 20, 329–342; b) Q. Wang,
Zh. Y. Yang, G. F. Qi, D. D. Qing, Biometals 2009, 22, 927–940;
c) H. Wu, Y. Bai, Y. Zhang, G. Pan, J. Kong, F. Shi, X. Wang, Z.
Anorg. Allg. Chem. 2014, 640, 2062–2071.
[6] G. J. Bijloo, H. Van der Goot, A. Bast, H. Timmerman, J. Inorg.
Biochem. 1990, 40, 237–244.
[7] H. I. Ismil, K. W. Chen, A. A. Mariod, M. Ismail, Food Chem.
2010, 119, 643–647.
[8] S. X. Xiao, H. W. Gu, J. J. Zhang, H. Xiao, J. Ding, X. Lu, Int.
J. Thermophys. 2012, 33, 289–299.
[9] J. Q. Qu, L. Qu, Q. H. Yang, L. F. Wang, Chem. Pap. 2009, 63,
426–431.
[16] a) X. B. Fu, Z. H. Lin, H. F. Liu, X. Y. Le, Spectrochim. Acta Part
A 2014, 122, 22–33; b) R. G. Bhirud, T. S. Srivastava, Inorg.
Chim. Acta 1991, 179, 125–131.
[17] X. M. Xie, Z. Zeng, Lanzhou Daxue Xuebao Ziran Kexueban
2003, 39, 64–67.
[18] S. Marklund, G. Marklund, Eur. J. Biochem. 1974, 47, 469–474.
[19] J. Sun, H. He, B. J. Xie, J. Agric. Food Chem. 2004, 52, 6646–
6652.
[10] a) W. J. Chai, W. X. Li, X. J. Sun, T. Ren, X. Y. Shi, J. Lumin.
2011, 131, 225–230; b) S. Benabid, T. Douadi, H. Debab, M.
[20] Y. Lu, Y. Tang, H. Gao, Z. Zhang, H. Wang, Appl. Organomet.
Chem. 2007, 21, 211–217.
De Backer, F. X. Sauvage, Synth. React. Inorg. Met.-Org. Nano- [21] a) M. Sakuma, Appl. Entomol. Zool. 1998, 33, 339–347; b) L.
Met. Chem. 2012, 42, 1–8.
[11] S. Jin, D. Wang, Synth. React. Inorg. Met.-Org. Nano-Met. Chem.
2013, 43, 562–574.
[12] a) Z. Chen, W. Xiong, Z. Zhang, F. Liang, Z. Anorg. Allg. Chem.
2010, 636, 1392–1396; b) H. T. Xia, Y. F. Liu, G. J. Lu, D. Q.
Wang, Synth. React. Inorg. Met.-Org. Nano-Met. Chem. 2012, 42,
145–153.
Xu, X. H. Wang, R. Y. Luo, S. Q. Lu, Z. J. Guo, M. A. Wang, Y.
Liu, L. G. Zhou, J. Integr. Agric. 2015, 14, 80–87.
[22] G. M. Sheldrick, SHELXL-97, University of Göttingen,
Göttingen, Germany, 1997.
Received: January 11, 2015
Published Online: April 29, 2015
Z. Anorg. Allg. Chem. 2015, 1301–1306
1306
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim