Synthesis, Crystal Structures, and Photophysical Properties Investigations of Two New Pyridinium Complexes Containing [Sm(TTA)4]- and [Eu(TTA)4]-

Article abstract of DOI:10.1080/15533174.2015.1004427

Two new lanthanide(III) complexes were designed and synthesized: DAS[M(TTA)₄]^-, (M = Sm [1], M = Eu [2]), each of them contained one trans-4-[4'-(N, N-dimethylamino)styryl]-N-methyl pyridinium (DAS) cationic moiety, four 2-thenoyltrifluoroacetone anions (TTA-), and one cationic lanthanide(III). Herein, the structures were confirmed by single-crystal X-ray diffraction analysis. The results revealed that the central lanthanide(III) atom was fashionable eight-coordinated with square-antiprismatic coordination environment. Meanwhile, the photophysical properties of 1 and 2 were investigated by fluorescence spectra. It was proposed that there was an antenna effect and the energy transfer took place from the DAS cationic moiety to lanthanide(III) ions.

Full text of DOI:10.1080/15533174.2015.1004427

Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry
ISSN: 1553-3174 (Print) 1553-3182 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt20
Synthesis, crystal structures and photophysical
properties investigations of two new pyridinium
complexes containing [Sm(TTA)4]− and [Eu(TTA)4]−
Guo-Cui Zhang, Dan-Dan Li, Ming Kong, Jian Su, Hong-Ping Zhou, Jie-Ying Wu
& Yu-Peng Tian
To cite this article: Guo-Cui Zhang, Dan-Dan Li, Ming Kong, Jian Su, Hong-Ping Zhou, Jie-
Ying Wu & Yu-Peng Tian (2016): Synthesis, crystal structures and photophysical properties
investigations of two new pyridinium complexes containing [Sm(TTA)4]− and [Eu(TTA)4]−,
Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, DOI:
10.1080/15533174.2015.1004427
To link to this article: http://dx.doi.org/10.1080/15533174.2015.1004427
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Date: 03 March 2016, At: 07:41

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Synthesis, crystal structures and photophysical properties investigations of two new
pyridinium complexes containing [Sm(TTA)4]- and [Eu(TTA)4]-
Guo-Cui Zhang, Dan-Dan Li, Ming Kong, Jian Su, Hong-Ping Zhou, Jie-Ying Wu, Yu-Peng
Tian*
Department of Chemistry, Key Laboratory of Functional Inorganic Materials Chemistry of Anhui
Province, Anhui University, Hefei 230039, P. R. China
*Corresponding author. E-mail address: yptian@ahu.edu.cn
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Abstract
Two new lanthanide(III) complexes were designed and synthesized: DAS[M(TTA)4]-, (M = Sm,
(1), M = Eu, (2)), each of them contained one trans-4-[4’-(N, N-dimethylamino)styryl]-N-methyl
pyridinium (DAS) cationic moity, four 2-thenoyltrifluoroacetone anions (TTA-), and one cationic
lanthanide(III). Herein, the structures were confirmed by single crystal X-ray diffraction
analysis. The results revealed that the central lanthanide (III) atom was fashionable
eight-coordinated with square-antiprismatic coordination environment. Meanwhile, the
photophysical properties of 1 and 2 were investigated by fluorescence (FL) spectra. It was
proposed that there was antenna effect and the energy transfer took place from the DAS cationic
moity to lanthanide (III) ions.
Keywords
Samarium(III) complex; Europium(III) complex; Fluorescence spectra; X-ray diffraction
analysis; Energy transfer
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1. Introduction
The luminescence of lanthanide(III) complexes had raised considerable interest, owing to their
unique luminescence properties, high color purity, long luminescence lifetimes, and insensitivity
to environmental quenching.[1-6] And they also had potential applications in biological systems,
optical amplification, magnetic properties luminescent materials.[7-12]
In fact, the emission color depended on the lanthanide ion, but was mostly up to the
environment of a given lanthanide ion.[13] To the best of our knowledge, that lanthanides(III) had
affinity to donor atoms, so the ligands including oxygen atoms could be widely used in the
[14]
synthesis of lanthanide complexes.
In addition, as for 2-thenoyltrifluoroacetone (HTTA),
which had the structure of β-diketonatecan, could play a great role in constructing molecular
frameworks as building block and it had much better advantages of transporting energy to
lanthanide(III). [13]
Notably, organic pyridinium salts molecules tended to interact with another neighboring
molecules through intramolecular charge balance, which could obtain a large conjugated
structures.[15] They pertained to the frequent use of designing various chemosensors for some
highly specific metal ions, fluorescent probes for DNA and RNA detection in biological systems,
single-molecule magnets as well as photodynamic cancer therapy.[16-23]
The structures with the type of Q+ [Ln(TTA)4]- were studied a lot,[24] however, it was a great
challenge to search for new luminescent materials. Spurred by the idea, we had synthesized
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DAS[M(TTA)4]-, (M = Sm, (1), M = Eu, (2)), which were supposed to open up new
characteristics and intriguing applications with a light-harvesting antenna.
2. Experimental section
2.1 Measurements and Methods
Chemical reagents used in the study were bought of analytical grade, and some of them were
synthesized and purified. Mass spectra were obtained with MALDI-TOF-MS. IR spectra were
located from NEXUS 870 (Nicolet) spectrophotometer in the range of 400-4000 cm-1 using a
powder sample on a KBr plate. Fluorescence spectra of solid state were determined by F-4500
FL Spectrophotometer.
2.2 Crystal Structure Determination and Refinement
X-ray diffraction data were collected on a Bruker Smart 1000 CCD area detector
diffractometer. Both of the radiation sources were MoK (λ = 0.71073 Å). Empirical absorption
correction was applied to the data. The structures were solved by direct methods and refined by
full-matrix least-squares methods on F2. All the nonhydrogen atoms were located from the trial
structure and then refined anisotropically by SHELXTL. All structures were solved by direct
methods with SHELXL-97. The hydrogen atom positions were geometrically idealized and
generated in idealized positions and fixed displacement parameters. Details of the crystal
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parameters, data collections and refinements were listed in Table 1, and selected bond distances
and angles of complexes 1 and 2 were given in Table 2 and Table 3, respectively.
2.3 Synthesis of Complexes 1 and 2 (Scheme 1).
2.3.1 Preparation of 1,4-Dimethylpyridinium iodide
1,4-Dimethylpyridinium iodide was prepared according to a literature method [25]
.
2.3.2 Preparation of Trans-4-[4’-(N, N-Dimethylamino)styryl]-N-methyl pyridinium iodide
(DASI)
DASI was prepared according to the literature method [26]
.
2.3.3 Preparation of Samarium(III) complex (complex 1)
Complex 1 was prepared according to a literature method [27]. Obtained orange powder with
yield of 43%. Found: M+ (MS/ESI), 1034.121. Anal. Calc. for C48H35F12N2O8S4Sm (%): C,
45.24; H, 2.77; N, 2.20. Found: C, 45.39; H, 2.68; N, 2.12. IR (KBr, cm-1) selected bands: 3423
(s), 3083 (s), 2916 (s), 1603 (w), 1534 (m), 1476 (s), 1411(m),1356 (s), 1302 (m), 1137 (m), 933
(s), 829 (s) 786 (s).
2.3.4 Preparation of Europium(III) complex (complex 2)
Complex 2 was prepared according to a literature method [27]. Afforded red powder with the
yield of 40%. Found: M+ (MS/ESI), 1035.076. Anal. Calc. for C48H35EuF12N2O8S4 (%): C, 45.18;
H, 2.76; N, 2.20. Found: C, 45.29; H, 2.88; N, 2.17. IR (KBr, cm-1) selected bands: 3444 (s),
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3083 (s), 2916 (s), 1604 (w), 1577 (m), 1535 (m), 1509 (m), 1477(m), 1412 (s), 1357 (s), 1303
(m), 1136 (m), 936 (s), 828 (s), 785 (s).
Single crystals of complexes 1 and 2 were obtained by evaporating slowly of methanol
solutions covered by acetonitrile at room temperature.
3. Results and Discussion
3.1 Crystal Structures of 1 and 2
As Table 1 shown, complexes 1 and 2 were isomorphous and isostructural in the P21/n space
group. Samarium was next to europium in the periodic table of elements, so they behaved similar
in some certain aspects. From the data above, the Sm-O distances ranged from 2.339 (7) Å to
2.425 (6) Å, and the Eu-O distances ranged from 2.363 (5) Å to 2.426 (4) Å. Both of them had a
distorted square antiprism environment around the lanthanide(III) site, with eight metal- oxygen
bonds. In addition, in Table 2, the average bond lengths of C-O and the average of O-Eu-O
angles of 1 (1.259 Å, 70.49º) were a little larger than that of in Table 3 (1.255 Å, 70.38º),
respectively, and the average of C-C-C angles of 1 (122.88º) was just a little smaller than that of
2 (123.08º).
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According to X-ray crystallography，the crystal structures of complexes 1 and 2 were shown in
Fig.1 and Fig.2, and these structures were absolute equal except the lanthanide(III) cation moiety.
The molecule unit was asymmetric with one lanthanide(III) ion coordinated closely with four
bidentate TTA- anions ligands and one pyridinium cation, and all hydrogen atoms were deleted
from their previous positions. The anionic TTA- appeared as typical O,O-chelates, which
generated a new distorted square antiprism with the two square planes from (O1~O2~O5~O6)
and (O3~O4~O7~O8). The Samarium(III) coordination environment with two distorted square
antiprisms was shown in Fig.3a and that of Europium(III) complex was in Fig.4a. This kind of
coordination configuration around lanthanide(III) was typical eight-coordinated, which leaded
the low structural symmetry in complexes 1 and 2.
In the crystal, the neighboring molecules of 1 were linked by intermolecular S(1)-S(4)
C(20)-H(20)···O(5) and C(10)-H(10)···F(4) hydrogen bonding interactions to form a
one-dimensional structure as shown in Fig.3b. The distances of S(1)-S(4) C(20)-H(20)···O(5)
and C(10)-H(10)···F(4) hydrogen bonds lengths were 3.5617 (5) Å, 2.7086 (6) Å and 2.6322 (13)
Å, respectively. It also existed weak C–H···π, C(7)-H(7)···F(4) and C(30)-H(30)···H(16A)
interactions. On the basis of Fig.3b, the adjacent layers were linked by C(6)-H(6)···C(18)
(2.7908 (11) Å) bonding interactions to form two-dimensional packing diagram (Fig.3c).
Furthermore, we could obtain three-dimensional crystal packing via weak C(18)-H(18)···C(27)
(2.8773 (16) Å) intermolecular bonding under the help of the two-dimensional diagram (Fig.3d).
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As for the one-dimensional chain of complex 2 was shown in Fig.4b via C(26)-H(26)···F(10)
and C(42)-H(42)···F(12) are 2.5458 (9) Å and 2.6234 (10) Å, respectively. Similar with 1, there
were also C(38)-H(38)···F(12), C–H···π, and C(45)-H(45)···C(13) interactions. The adjacent
molecules were linked to each other via intermolecular C(39)-H(39)···C(3) and
C(38)-H(38)···F(12) and C(26)-H(26)···F(10) (2.7757 (9) Å, 2.4651 (10) Å and 2.5488 (9) Å,
respectively), which formed two-dimensional structure of 2 (Fig.4c). Three-dimensional packing
diagram was generated via C(19)-H(19)···F(5) hydrogen bond on the basis of its
two-dimensional layers, as shown in Fig.4d. The distance of hydrogen bond C(19)-H(19)···F(5)
was 2.567 Å. All results revealed that hydrogen bonds were very important for molecules to form
relevant multidimensional structures.
3.2 Fluorescence Spectra Studies
The spectroscopic studies were investigated by the fluorescence spectra in solid state. The
emission spectra of pyridinium iodide (DASI, ex = 470 nm), Sm(TTA)4TBA (ex = 346 nm), 1
(ex = 346 nm), 1 (ex = 416 nm) and 1 (ex = 470 nm) were shown in Fig. 5. The emission spectra
of pyridinium iodide (DASI, ex=470 nm), Eu(TTA)4TBA (ex = 376 nm), 2 (ex = 376 nm), 2 (ex
= 443 nm) and 2 (ex = 470 nm) were shown in Fig.6. For the DASI, the characteristic band was
at 670 nm. Characteristic bands from the Sm(III) cation were observed around 568 nm
(5G5/2⟶6H5/2)，607 nm (5G5/2⟶6H7/2)，650 nm (5G5/2⟶6H9/2), respectively. And characteristic
emission bands from the Eu(III) cation were about 594 nm (5D0⟶7F1), and 613 nm (5D0⟶7F2),
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respectively. The most strongest emission band of Sm(III) cation was at 607 nm (5G5/2⟶6H7/2)
with orange light. However, Eu(III) cation was at 613 nm (5D0⟶7F2), emiting red light. Although
the bands of complexes 1 and 2 were also around 590 nm and 670 nm, which were respectively
from M(III) cations (M = Sm, M = Eu) and DASI, with much more intense emission bands. The
results proposed that the energy transfer took place from DASI to lanthanide (III) ions with an
antenna effect .
4. Conclusions
In summary, two new lanthanide(III) complexes were presented including the synthesis,
structures and the fluorescence properties. From the single crystal X-ray diffraction analysis,
lanthanide(III) site can be approximately described as a distorted square antiprism, with two
square planes. The multidimensional structures of 1 and 2 were presented respectively. In
addition, the results of fluorescence spectra revealed that characteristic emission bands of
complexes 1 and 2 were from lanthanide(III) cations and pyridinium moity, which may
supported that there was antenna effect and the energy transfer may took place from the DASI to
the lanthanide(III) ions.
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Acknowledgements
This work was supported by a grant for the National Natural Science Foundation of China
(21271004, 51372003, 21271003), the Natural Science Foundation of Anhui Province
(1208085MB22), Ministry of Education Funded Projects Focus on returned overseas scholar,
Program for New Century Excellent Talents in University (China), Doctoral Program Foundation
of Ministry of Education of China (20113401110004).
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Table 1 Crystal data and structure refinements for compounds 1 and 2.
1
2
CCDC
981462
789624
Empirical formula
Formula weight
C48H35SmF12N2O8S4 C48H35EuF12N2O8S4
1274.37
1275.98
Crystal system
Monoclinic
Monoclinic
Space group Crystal size
P21/n 0.30 x 0.20 x 0.22/n 0.17 x 0.12 x 0.11 mm
1
mm
Unit cell dimensions
a= 10.497(5)Å
b= 21.838 (5)Å
c= 23.321 (5)Å
β= 101.209 (5)°
5244(3)Å3
4
a= 10.491(5)Å
b= 21.840(5)Å
c= 23.324(5)Å
β= 101.134(5)°
5243(3) Å3
4
Volume
Z
Dc (mg m-3)
1.614
1.616
 (mm-1)
1.374
1.451
Reflns. Collected
Reflns. Unique
Parameters
25971
37429
8999
12152
679
698
Goodness-of-fit on F2
1.088
0.990
R1, wR2 [I>2sigma(I)]
R1 = 0.0694 wR2 =R1 = 0.0638 wR2 = 0.132
0.1553
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Table 2. Selected bond lengths (Å) and angles (º) for compound 1
Sm(1)-O(1)
Sm(1)-O(3)
2.400(6)
2.379(6)
2.396(6)
2.339(7)
1.244(11)
1.283(11)
1.251(11)
1.295(12)
70.4(2)
Sm(1)-O(2)
Sm(1)-O(4)
2.425(6)
2.396(6)
2.413(6)
2.407(6)
1.239(12)
1.261(11)
1.216(11)
1.250(11)
70.9(2)
Sm(1)-O(5)
Sm(1)-O(6)
Sm(1)-O(7)
Sm(1)-O(8)
O(1)-C(43)
O(2)-C(45)
O(3)-C(46)
O(4)-C(48)
O(5)-C(39)
O(6)-C(37)
O(7)-C(40)
O(8)-C(42)
O(1)-Sm(1)-O(2)
O(5)-Sm(1)-O(6)
C(39)-C(38)-C(37)
C(45)-C(44)-C(43)
O(3)-Sm(1)-O(4)
O(7)-Sm(1)-O(8)
C(42)-C(41)-C(40)
C(46)-C(47)-C(48)
70.3(2)
69.9(2)
122.2(9)
123.0(10)
123.4(9)
123.7(9)
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Table 3. Selected bond lengths (Å) and angles (º) for compound 2
Eu(1)-O(1)
Eu(1)-O(3)
2.426(4)
2.380(4)
2.402(4)
1.282(7)
1.247(8)
1.242(7)
1.242(7)
Eu(1)-O(2)
Eu(1)-O(4)
2.375(4)
2.383(4)
2.384(5)
2.363(5)
1.255(7)
1.254(8)
1.273(8)
1.257(8)
70.61(15)
70.92(16)
123.5(7)
123.8(6)
Eu(1)-O(5)
Eu(1)-O(6)
Eu(1)-O(7)
Eu(1)-O(8)
O(1)-C(7)
O(2)-C(5)
O(3)-C(13)
O(4)-C(15)
O(5)-C(21)
O(6)-C(23)
O(7)-C(31)
O(8)-C(29)
1.262(7)
O(2)-Eu(1)-O(1)
O(6)-Eu(1)-O(5)
C(7)-C(6)-C(5)
C(23)-C(22)-C(21)
69.95(14)
O(3)-Eu(1)-O(4)
O(8)-Eu(1)-O(7)
C(15)-C(14)-C(13)
C(31)-C(30)-C(29)
70.48(16)
121.9(6)
122.3(7)
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Fig.1. The molecular structure of complex 1; H atoms are omitted for clarity.
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Fig.2. The molecular structure of complex 2; H atoms are omitted for clarity.
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Fig.3. (a) The distorted square antiprism of Sm(III) coordination environment; (b) 1D structure
of complex 1 showing the weak interactions; (c) 2D structure of complex 1 showing the weak
interactions; (d) 3D structure of complex 1 showing the weak interactions; (In order to clear,
hydrogen atoms are deleted)
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Fig.4. (a) The distorted square antiprism of Eu(III) coordination environment; (b) 1D structure
of complex 2 showing the weak interactions; (c) 2D structure of complex 2 showing the weak
interactions; (d) 3D structure of complex 2 showing the weak interactions; (In order to clear,
hydrogen atoms are deleted)
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Fig.5. The emission spectra of pyridinium iodide (DASI, ex = 470 nm), Sm(TTA-)4TBA (ex
= 346 nm), 1 (ex = 346 nm), 1 (ex = 470 nm) and 1 (ex = 416 nm) in the solid state.
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Fig.6. The emission spectra of pyridinium iodide (DASI, ex = 470 nm),
Eu(TTA-)4TBA (ex = 376 nm), 2 (ex = 376 nm), 2 (ex = 470 nm) and 2 (ex = 443 nm) in
solid state.
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Scheme 1 Synthesis routes of complexes 1 and 2.
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