Synthesis and photoluminescence of Zinc(II) complexes with tetrafluoroterephthalic acid (H2L). Crystal structure of coordination polymer [Zn(H2O)4(L) ? 4H2O] n

Article abstract of DOI:10.1134/S1070328411090041

Complexes Zn(H₂O)₄(L) (I) and Zn(H₂O)(L) (II) (H₂L = p-HOOCC₆F₄COOH) are synthesized. Single crystals of compound [Zn(H₂O)₄(L) ? 4H ₂O] _n (III) a

Full text of DOI:10.1134/S1070328411090041

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2011, Vol. 37, No. 9, pp. 650–656. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.V. Larionov, L.I. Myachina, R.F. Klevtsova, L.A. Glinskaya, N.V. Kurat’eva, E.M. Uskov, M.I. Rakhmanoa, V.M. Karpov, V.E. Platonov, V.P. Fadeeva,
2011, published in Koordinatsionnaya Khimiya, 2011, Vol. 37, No. 9, pp. 651–657.
Synthesis and Photoluminescence of Zinc(II) Complexes
with Tetrafluoroterephthalic Acid (H2L). Crystal Structure
of Coordination Polymer [Zn(H2O)4(L) · 4H2O]n
1
S. V. Larionova, *, L. I. Myachinaa, R. F. Klevtsovaa, , L. A. Glinskayaa, N. V. Kurat’evaa,
E. M. Uskova, M. I. Rakhmanova, V. M. Karpovb, V. E. Platonovb, and V. P. Fadeevab
a Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences,
pr. Akad. Lavrent’eva 3, Novosibirsk, 630090 Russia
b Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090 Russia
* Eꢀmail: lar@niic.nsc.ru
Received January 17, 2011
Abstract—Complexes Zn(H2O)4(L) (I) and Zn(H2O)(L) (II) (H2L = pꢀHOOCC6F4COOH) are syntheꢀ
sized. Single crystals of compound [Zn(H2O)4(L) · 4H2O]n (III) are grown. According to the Xꢀray diffracꢀ
tion data, the crystal structure of compound III is built of zigzag chains of coordination polymer Zn(H2O)4(L)
and molecules of water of crystallization. The chain contains ions Zn2+, whose octahedral coordination sphere
includes the O atoms of four water molecules and two O atoms of the deprotonated carboxyl groups. The chains in
structure III are joined by a system of hydrogen bonds of coordinated water molecules and molecules of water of
crystallization. The photoluminescence spectrum of H2L exhibits the band with
λ
max = 368 nm. The spectra of
compounds III , and II contain bands at 322, 340, and 353 nm, respectively.
,
I
DOI: 10.1134/S1070328411090041
1
Presently, considerable attention is given to the
EXPERIMENTAL
synthesis and studies of the structure and properties of
coordination of metals with aromatic acids bearing
several carboxyl groups. This is due to various polyꢀ
meric structures of the solid phases formed, resulting
in the formation of pores of various diameters. Specific
features of the structure of the coordination polymers
provide the inclusion of various compounds into pores
of molecules and the manifestation of diverse funcꢀ
tional properties (luminescence, hydrogen storage)
[1, 2]. One of the simplest representatives of the
studied dibasic aromatic acids is terephthalic acid
Terephthalic acid was synthesized according to a
known procedure [13]. The following reagents were
used in the synthesis of the complex: Zn(CH3COO)2
·
2H2O and ZnO (reagent grade), EtOH (rectificate),
and MeOH (highꢀpurity grade). Alcohols were not
dehydrated.
Synthesis of
raaquazinc Zn(H2O)4(L) (I). Procedure
~50 ) solutions of H2L (0.48 g, 2 mmol) in EtOH
(3 ml) and Zn(CH3COO)2 2H2O (0.37 g, 1.7 mmol)
(
µ
ꢀtetrafluoroterephthalato)tetꢀ
1.
Warm
(
°
C
·
pꢀ ). Coordination polymer
HOOCC6H4COOH (H2L1
in EtOH (3 ml) were mixed, and the mixture was
stored at room temperature. A finely crystalline white
powder gradually precipitated from the solution. Next
day the precipitate was filtered off with suction,
washed with EtOH and hexane, and dried in air. The
yield was 0.55 g (87%).
compounds H2L1 with ions Zn2+ [3, 4], Cr3+, and Fe3+
were synthesized [5–8]. The Zn(II) compounds
Zn(H2O)2(L1) and Zn(H2O)(L1) exhibit photolumiꢀ
nescence at λmax = 402 nm (λexc = 260 nm) and 344,
385 nm (λexc = 279 nm), respectively [4]. The synthesis
of the luminescent Zn(II) complexes is a topical probꢀ
lem [9, 10]. Therefore, it is of interest to synthesize the
Zn(II) compounds with perfluorinated aromatic
dicarboxylic acids, because the introduction of F
atoms into the composition of organic ligands favors
luminescence [11, 12].
For C8H8F4O8Zn
anal. calcd., %:
Found, %:
C, 25.7; H 2.1; F, 20.4; Zn, 17.5.
C, 26.0; H 2.0; F, 20.6 Zn, 18.1.
Procedure 2. Zinc oxide (0.2 g, 2 mmol) was added
to a warm solution of H2L (0.64 g, 2.7 mmol) in
MeOH (20 ml). The mixture was stirred at room temꢀ
perature for 6 h, and the precipitate was filtered off
with suction, washed with EtOH and hexane, and
dried in air. The yield was 0.66 g (72%).
This work is aimed at synthesizing the Zn(II) complexes
with tetrafluoroterephthalic acid
pꢀHOOCC6F4COOH
and at studying their structures and luminescence
properties.
1
Deceased.
650

SYNTHESIS AND PHOTOLUMINESCENCE OF ZINC(II) COMPLEXES
651
mated power diffractometer (
R
= 192 mm, Cu
K
radiꢀ
α
For C8H8F4O8Zn
ation, Ni filter) in the range from
2
θ
3
°
to 60 .
°
anal. calcd., %: С, 25.7; H, 2.1; F, 20.4; Zn, 17.5.
Xꢀray diffraction analysis of compound III. Unit cell
parameters and reflection intensities were measured at
low temperature (150 K) on a Bruker X8 Apex CCD
automated diffractometer equipped with a twoꢀcoorꢀ
dinate detector according to a standard procedure
Found, %:
C, 25.9; H, 2.0; F, 20.5; Zn, 17.8.
The thermal analysis (TA) of complex
that its mass loss on heating occurred in three stages.
According to the thermal gravimetry (TG) data, the
I showed
(
Mo
K
radiation,
λ
= 0.71073 Å, graphite monochroꢀ
α
mass loss was 14.6% at the first stage (50–80 С). This
°
mator). The crystallographic characteristics and
details of the Xꢀray diffraction experiment and strucꢀ
ture refinement for compound III are given in Table 1.
The structure was solved by a direct method and
refined by the fullꢀmatrix leastꢀsquares method on F2
in the anisotropic (for nonꢀhydrogen atoms) approxiꢀ
mation using the SHELXLꢀ97 program package [16].
The positions of the hydrogen atoms of the water molꢀ
ecules were localized from the difference electron
density synthesis and included into refinement in the
isotropic approximation along with nonꢀhydrogen
atoms. Selected interatomic distances and bond angles
are listed in Table 2. The full tables of the coordinates
of atoms, bond lengths, and bond angles were deposꢀ
ited with the Cambridge Crystallographic Data Centre
(no. 802247); deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk/data_request/cif) and are availꢀ
able from the authors.
corresponds to the loss of three water molecules (the
calculated content of three water molecules in comꢀ
pound
in the DTA (differential thermal analysis) curve. The
product formed is stable up to 150 . At the second
stage (150–195 ) the mass loss is 4.7%, which correꢀ
sponds to the loss of one more water molecule. The
endotherm in the DTA curve at 190 corresponds to
I
is 14.5%). The endotherm is observed at 70 С
°
°
С
°
С
°
С
this process. The total mass loss in two stages is 19.3%,
and the calculated water content in Zn(H2O)4(L) is
also 19.3%. The third stage of mass loss corresponding
to the decomposition of the dehydrated complex
begins at 270
exotherm at 375
Synthesis of (
Zn(H2O)(L) (II) A weighed sample of complex
heated in a desiccator at 100 for 3 h. The mass loss
was 14.5%.
°
С. The process is accompanied by the
°
С.
µ
ꢀtetrafluoroterephthalato)aquazinc
.
I
was
°
С
For C H F O Zn
8 2 4 5
RESULTS AND DISCUSSION
Found, %: Zn 20.8.
anal. calcd., %: Zn 20.5.
The Zn(II) compounds with terephthalic acid,
Zn(H2O)2(L1) and Zn(H2O)(L1), were synthesized [4]
by the hydrothermal reaction of ZnO and the acid in
The substance is stable on storage in air.
Synthesis of ꢀtetrafluoroterephthalato)tetꢀ
raaquazinc tetrahydrate [Zn(H2O)4(L) 4H2O]n (III)
weighed sample of compound , which was syntheꢀ
sized according to procedure 2, was dissolved on heatꢀ
ing in a minimum amount of H2O, and the beaker with
the solution was covered with a watch crystal and left
(
µ
water (autoclave, 160
pound using two procedures by the reaction of tetꢀ
rafluoroterephthalic acid (having higher acidity) with
Zn(CH3COO)2 2H2O or ZnO in alcohol media at
temperatures not higher than 50 without an autoꢀ
clave. Water in complex synthesized by the second
°
С, 48 h). We synthesized comꢀ
·
. A
I
I
·
°
С
I
to stand in air. Transparent crystals precipitated after procedure is present due to its formation in the reacꢀ
tion and to the presence of water in methanol. The difꢀ
fraction patterns of the samples of complex syntheꢀ
sized using two procedures are identical, indicating
their similar structures. Compared to the Zn(II) comꢀ
several days. Outside the mother liquor the crystals in
air gradually grew turbid and disintegrated.
I
Analyses to C, H, and F were carried out similarly
to a procedure described [14]. The Zn content was
determined by complexonometric titration (Trilon B,
eriochrome black T as an indicator). The TA curves
were obtained using a TG 209 F1 Iris® thermobalance
(NETZSCH). The sample weight was 20 mg (Al cruꢀ
cible, helium atmosphere, heating rate 10 deg/min,
plexes with terephthalic acid [4], complex I contains
more water molecules (four). It is most likely that the
coordination to the Zn2+ ions of fluorineꢀcontaining
anions L2–, whose donor ability is lower than that of
the terephthalic acid anions, enhances the capability
of the acceptors (Zn2+ ions) of adding water moleꢀ
cules. The TA data indicate the difference in binding
temperature range 20–600 С). The experimental
°
results were processed using the standard Proteus
Analysis program package [15]. The excitation and
photoluminescence (PLM) spectra of compounds
of water molecules during the dehydration of complex I.
In addition, these data showed the possibility to obtain
product II containing only one water molecule by
heating of complex I.
H2L and
Cary Eclipse spectrofluorimeter at 300 K under equivaꢀ
lent conditions for all samples (500 V, 5ꢀnm gap). Xꢀray crystals of compound III have the composition
I–III in the solid phase were obtained on a
According to the Xꢀray diffraction data, single
phase analysis was carried out on a DRONꢀ3M autoꢀ Zn(H2O)4(L)
·
4H2O. Crystal structure III consists of
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

652
LARIONOV et al.
Table 1. Crystallographic characteristics and experimental Table 2. Selected interatomic distances and bond angles in
and refinement details for the structure of compound III the structure of compound III
Parameter
Empirical formula
Value
Bond
d,
Å
Bond
d, Å
C8H16F4O12Zn
445.58
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–O(3)
O(3)–C(1)
O(4)–C(1)
C(1)–C(2)
C(2)–C(4a)
C(2)–C(3)
C(3)–F(3)
C(3)–C(4)
2.0944(6) O(1)–H(11)
2.1336(6) O(1)–H(12)
2.1027(6) O(2)–H(21)
1.2654(9) O(2)–H(22)
0.81(2)
0.80(2)
0.87(2)
0.87(2)
0.78(2)
0.87(2)
0.77(2)
0.77(2)
1.3425(8)
FW
Crystal system
Triclinic
Space group
P
1
a
,
Å
Å
Å
6.8435(2)
6.8435(2)
8.7154(3)
88.605(1)
70.943(1)
88.916(1)
388.00(2)
1; 1.907
1.2474(9) O(1
w
)–H(1a)
)–H(1b)
)–H(2a)
)–H(2b)
b,
1.510(1) O(1
w
c,
α, deg
1.391(1) O(2
w
w
β,deg
1.391(1) O(2
γ
, deg
Å3
(calcd.), mg/cm3
1.3418(9) C(4)–F(4)
1.385(1)
V
,
Z
;
ρ
, mm–1
Crystal sizes, mm
can range, , deg
1.690
Angle
ω
, deg
Angle
ω
, deg
μ
0.50
×
0.32 × 0.20
O(1a)Zn(1)O(3) 91.39(2) C(4a)C(2)C(3) 116.98(6)
O(1)Zn(1)O(3) 88.61(2) C(4a)C(2)C(1) 120.90(6)
O(1a)Zn(1)O(2) 91.47(2) C(3)C(2)C(1)
θ
2.47–35.00
4596
Number of measured reflections
Number of independent reflections
Rint
122.10(6)
118.53(6)
120.09(6)
121.37(7)
118.42(6)
3218
O(1)Zn(1)O(2)
O(3)Zn(1)O(2)
88.53(2) F(3)C(3)C(4)
88.61(2) F(3)C(3)C(2)
0.0116
3168
Number of reflections with
I
> 2σ(I)
Number of refined parameters
147
O(3a)Zn(1)O(2) 91.39(2) C(4)C(3)C(2)
C(1)O(3)Zn(1) 128.43(5) F(4)C(4)C(3)
Goodnessꢀofꢀfit on F2
1.061
R
R
factor (
I
> 2
σ
(
I
))
R1 = 0.0193,
wR2 = 0.0535
O(4)C(1)O(3)
O(4)C(1)C(2)
O(3)C(1)C(2)
126.23(7) F(4)C(4)C(2a) 119.90(6)
117.99(6) C(3)C(4)C(2a) 121.65(7)
115.77(6)
factor (on all
I
hkl):
R1 = 0.0196
wR2 = 0.0536
Residual electron density (max/min)e/
Å3 0.534/–0.520
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SYNTHESIS AND PHOTOLUMINESCENCE OF ZINC(II) COMPLEXES
653
0
y
x
Fig. 1. Packing of oneꢀdimensional chains of the coordination polymer Zn(H O) (L) and molecules of water of crystallization in
2
4
structure III in projection on the plane (001).
oneꢀdimensional chains of the molecular coordinaꢀ plane of five atoms O(3)O(4)C(1)O(1a)H(12a); the
tion polymer Zn(H2O)4(L) and molecules of water of average deviation of the atoms of this fragment being
crystallization (Fig. 1). It is seen in projection on the 0.035(5) Å.
plane (001) that the chains are zigzag and the angle
The polymeric Zn(II) complex with H2L1
,
Zn(1)O(3)C(1) is 128.4 . The polymer chains contain
°
Zn(H2O)2(L1), is also oneꢀdimensional and chain in
structure, but the coordination polyhedron of the Zn
atom is the ZnO4 tetrahedron [4]. The octahedral
coordination polyhedron ZnО6 has previously been
the Zn2+ ions occupying the partial positions in the
symmetry centers. The octahedral coordination
sphere of the Zn2+ ion includes the O atoms of four
coordinated water molecules (Zn–O 2.0944(6) and
2.1336(6) Å) and two O(3) atoms of the deprotonated
found in the ionic compound [{Zn(H2O)4BETC}2–
carboxyl groups of two bridging ligands L2–
2.1027(6)
11.238 Å. The structure contains strong hydrogen
(Zn–О
C4H12 N22+
· 4H2O]n (BETC = 1,2,4,5ꢀbenzenetetraꢀ
Å). The distance Zn⋅⋅⋅Zn in the chain is
carboxylate ion) in which the fragment
Zn(H2O)4BETC2– is a chain coordination polymer
[17]. The crystal structure of this compound contains
the same number of molecules of water of crystallizaꢀ
bonds O–H⋅⋅⋅O between the uncoordinated O atoms of
ligands L2– and two of four coordinated water moleꢀ
cules (О(1)⋅⋅⋅О(4а) 2.665(1) Å, angle O(1)H(12)O(4a)
tion as in structure III
.
161
°
). This results in the formation of sixꢀmembered
Hꢀcycles ZnCO3H related by the symmetry center
The polymer chains in the structure of compound
(Figs. 2a, 2b). The cycle has an envelope conformation III are joined by the system of hydrogen bonds of the
with the Zn(1) atom shifted by 0.411(3) Å from the coordinated and crystallization water molecules. Figꢀ
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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654
LARIONOV et al.
(а)
O(4a)
H(12)
O(1)
F(4)
F(3)
O(2a)
C(1a)
C(4)
C(3)
Zn(1)
O(3)
O(3a)
C(2a)
C(2)
C(1)
O(2)
O(1a)
H(12a)
C(3a)
C(4a)
O(4)
F(3a)
F(4a)
(b)
O(4)
H(12a)
O(1a)
O(2a)
F(4a)
C(1)
C(2)
F(3a)
C(4a)
C(3a)
C(3)
C(4)
O(3a)
F(3)
C(2a)
F(4)
Zn(1)
O(3)
C(1a)
O(1)
O(2)
H(12)
O(4a)
Fig. 2. Structure of the independent fragment of the chain coordination polymer Zn(H O) (L) in structure III in two projections
2
4
(a, b) with enumerated nonꢀhydrogen atoms (thermal ellipsoids are shown at the 50% probability level).
ure 3 shows the mutual arrangement of polymer chains possessing rather high PLM intensity (Fig. 4). The
in structure III, whose packing forms channels along
the direction [100] ~3 Å in size. The channels are
PLM spectra of the samples of complex
by two procedures has the asymmetric band with
I synthesized
×
3
occupied by molecules of water of crystallization.
Therefore, complex III can be classified as an incluꢀ
sion compound.
λmax = 340 nm. The PLM spectrum of compound II
,
unlike that of Zn(H2O)(L1), contains one asymmetric
band with λmax = 353 nm. The PLM spectrum of
inclusion compound III exhibits one band with λmax
322 nm. Therefore, there is a considerable hypsochroꢀ
mic shift of the bands in the PLM spectra of comꢀ
pounds I–III compared to the spectrum of H2L. The
shift increases with an increase in the amount of water
molecules in these compounds. The PLM intensity of
=
We believe that the structure of complex I is analoꢀ
gous to that of the coordination polymer Zn(H2O)4(L)
in structure III. The structure of complex II seems to
be more complicated by analogy to the trimeric comꢀ
plex Zn(H2O)(L1)
.
The PLM excitation spectrum of acid H2L exhibits
two bands with λmax = 290 and 340 nm (Fig. 4). The
excitation spectra of complexes I and II contain only
one broad band with λmax ~293 and ~292 nm, respecꢀ
tively. The band is broader for complex II. Based on
these data, we chose the excitation wavelength during
recording the PLM spectra (λexc = 290 nm). The PLM
spectrum of acid H2L exhibits one somewhat asymꢀ
complexes
I and II decreases slightly compared to
H2L. The PLM intensity of inclusion compound III
bearing four molecules of water of crystallization is
much lower than that of complexes
I and II. Thereꢀ
fore, the coordination of the tetrafluoroterephthalate
anions to the Zn2+ ions does not increases the PLM
intensity of compounds I–III compared to the PLM
metric band in the UV spectral region (λmax = 368 nm) intensity of acid H2L
.
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SYNTHESIS AND PHOTOLUMINESCENCE OF ZINC(II) COMPLEXES
655
0
z
y
Fig. 3. Chain packing in crystal structure III in projection to the plane (100) and the arrangement of molecules of water of crysꢀ
tallization in the channels formed.
600
400
1
1
3
200
3
4
4
0
200
300
400
500
λ
, nm
Fig. 4. Excitation and photoluminescence spectra of (
1) H L, (2) Zn(H O)(L), (3) Zn(H O) (L), and (4) [Zn(H O) (L) ·
2 2 2 4 2 4
4H O]n; = 500 V, 5ꢀnm gap, = 290 nm.
V
λ
2
exc
The results of the studies showed that photolumiꢀ
nescent coordination polymers of zinc(II) can be synꢀ
thesized from perfluoroaromatic dicarboxylic acids.
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