Three new coordination compounds based on 2-phenyl-4-quinolinecarboxylic acid and nitrogenous neutral ligands: Syntheses, structural features, and properties

Article abstract of DOI:10.1002/zaac.201300169

Solvothermal reactions of 2-phenyl-4-quinolinecarboxylic acid (Hpqba) with Cd^II, Co^II, Zn^II and/or 4,4′-bipyridyl (4,4′-bipy), 1,4-bis(imidazol-1-ylmethyl)benzene (biyb), 2,2′-bipyridyl (2,2′-bipy) afford three new coordination compounds of stoichiometries [Cd(pqba)₂(4,4′-bipy)] (1), [Zn(pqba) ₂biyb] (2), and [Co₃(pqba)₆-(2,2′-bipy) ₂] (3). Compounds 1-3 were characterized by elements analysis, IR spectroscopy, thermogravimetry, and single-crystal X-ray diffraction study. Compound 1 has a two-dimensional structure, whereas compound 2 consists of a one-dimensional (1D) network, which is further expanded by π·· ·π stacking interactions to form a 3D supramolecular structure. Complex 3 also exhibits a 3D supramolecular structure completely based on π···π stacking interactions. The pqba ligands adopt μ₁-k¹,k¹, μ₁-k¹, μ₂-k¹,k¹, and μ₂-k ¹,k² coordination modes for compounds 1, 2, and 3. The fluorescence properties were examined on compounds 1 and 2 in the solid state at room temperature. Magnetic susceptibility measurements indicate that in complex 3 antiferromagnetic coupling between adjacent Co^II ions exist. Copyright

Full text of DOI:10.1002/zaac.201300169

ARTICLE
DOI: 10.1002/zaac.201300169
Three New Coordination Compounds Based on 2-Phenyl-4-
quinolinecarboxylic Acid and Nitrogenous Neutral Ligands: Syntheses,
Structural Features, and Properties
Xiang-Yang Hou,[a] Xiao Wang,[a] Feng Fu,*[a] Ji-Jiang Wang,[a] and Long Tang[a]
Keywords: Cadmium; Cobalt; Zinc; Fluorescence; Magnetic properties
Abstract. Solvothermal reactions of 2-phenyl-4-quinolinecarboxylic
acid (Hpqba) with CdII, CoII, ZnII and/or 4,4Ј-bipyridyl (4,4Ј-bipy), supramolecular structure. Complex 3 also exhibits a 3D supramolec-
1,4-bis(imidazol-1-ylmethyl)benzene (biyb), 2,2Ј-bipyridyl (2,2Ј-bipy) ular structure completely based on π···π stacking interactions. The
afford three new coordination compounds of stoichio- pqba ligands adopt μ1-k1,k1, μ1-k1, μ2-k1,k1, and μ2-k1,k2 coordination
metries [Cd(pqba)2(4,4Ј-bipy)] (1), [Zn(pqba)2biyb] (2), and modes for compounds 1, 2, and 3. The fluorescence properties were
[Co3(pqba)6-(2,2Ј-bipy)2] (3). Compounds 1–3 were characterized by examined on compounds 1 and 2 in the solid state at room temperature.
which is further expanded by π···π stacking interactions to form a 3D
elements analysis, IR spectroscopy, thermogravimetry, and single-crys-
tal X-ray diffraction study. Compound 1 has a two-dimensional struc-
ture, whereas compound 2 consists of a one-dimensional (1D) network,
Magnetic susceptibility measurements indicate that in complex 3 anti-
ferromagnetic coupling between adjacent CoII ions exist.
based carboxylic acid) and have been well used in the prepara-
tion of various complexes owing to their rich coordination
modes.[3] In contrast, the use of 2-phenyl-4-quinolinecarbox-
ylic acid ligands with huge skeleton to construct functional
coordination polymers or supramolecular structure has been
less investigated to date.[4] This ligand has four obvious char-
acteristics: first, Hpqba adopts various coordination modes
when it coordinates to metals, although its only carboxylate
arm; secondly, it has larger conjugated π systems (three benz-
ene rings), π···π stacking, and/or C–H···π interactions, which
may play important roles in the formation of their complexes,
especially in the aspect of linking the dinuclear or multinuclear
discrete subunits or low-dimensional entities into higher-di-
mensional supramolecular frameworks; third, the carboxylic
groups can propagate magnetic super exchange between cen-
tral metal atoms; fourth, rigid ligands containing multi benzene
rings and suitable metal ion form complexes having fluores-
cence properties.
Considering all the aspects stated above, to design com-
plexes showing interesting architectures, magnetic behavior,
and fluorescence properties, we have chosen the CoII, ZnII,
CdII ions and the Hpqba ligand. And the introduction of
2,2Ј-bipyridyl-like bidentate chelating or 1,4-bis(imidazol-1-
ylmethyl)benzene and 4,4Ј-bipyridyl-like linear bridging mole-
cules into the reaction systems, as auxiliary ligands, may gen-
erate interesting coordination architectures. Herein, we report
the synthesis and characterization of compounds 1–3, namely,
[Cd(pqba)2(4,4Ј-bipy)] (1), [Zn(pqba)2biyb] (2), and
[Co3(pqba)6(2,2Ј-bipy)2] (3). The crystal structures, fluores-
cence properties, and magnetic properties of these new com-
pounds are studied in detail.
Introduction
The search for complexes with intriguing architectures[1]
and desired properties assembled by coordination bonds and/
or weak supramolecular interactions such as π···π stacking is
of current interest and great importance because these materi-
als can exhibit a variety of physical properties such as magnet-
ism, fluorescence properties, and gas adsorption, etc.[2] Studies
in this field have been focused on the rational design and syn-
thesis of novel frameworks and the relationships between their
structures and properties, however, remains a great challenge.
The observation of coordination complexes constructed from
organic ligands and metal ions through a self-assembly route
has been explored, and many efforts have been devoted to use
of organic ligands as co-ligands to bridge metal ions to form
infinite network structures. Among various organic ligands,
multicarboxylate organic ligands are often selected as linkers
because of their abundant coordination modes to metal ions,
allowing for various architectures and supramolecular struc-
tures. Recently, rigid ligands are usually the typical building
elements in the multidimensional networks (such as 4-quinol-
inecarboxylate acid, 9-acridinecarboxylic acid, anthracene-9-
carboxylic acid, adamantane-1-carboxylic acid, quinoline-
* Prof. Dr. F. Fu
Fax: + 86-911-2332037
E-Mail: wx2248@126.com
[a] Department of Chemistry and Chemical Engineering
Shaanxi Key Laboratory of Chemical Reaction Engineering,
Yan’an University
Yan’an, Shaanxi 716000, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201300169 or from the au-
thor.
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Z. Anorg. Allg. Chem. 2013, 639, (7), 1254–1260

Coordination Compounds Based on 2-Phenyl-4-quinolinecarboxylic Acid and Nitrogenous Neutral Ligands
C46H34O4N6Zn (800.16): calcd: C 69.05, H 4.28, N 10.50%; found:C
Experimental Section
68.87, H 4.36, N 10.41%. IR (KBr): ν˜ = 3045 (m), 1678 (s), 1630 (s),
1630 (s), 1567 (s), 1365 (s), 1326 (s), 1276 (w), 1107 (m), 1065 (w),
874 (w), 787 (w) cm–1 (Figure S1b).
Materials and Methods: All available solvents and starting materials
of analytical grade in the experiments were obtained from commercial
sources and used without further purification. Powder X-ray diffraction
(PXRD) measurements were performed with a Bruker D8 Advance X- Syntheses of [Co3(pqba)6(2,2Ј-bipy)2] (3): A mixture of Hpqba
ray diffractometer using Cu-Kα radiation (λ = 1.5418 Å), in which the (0.2 mmol, 0.0496 g), (2,2Ј-bipy)2 (0.2 mmol, 0.0312 g), and cobalt
X-ray tube was operated at 40 kV and 40 mA. Elemental analysis (C, acetate (0.3 mmol, 0.0747 g) was added to 15 mL of methanol/di-
H, N) was determined with a Perkin-Elmer 2400 type elemental ana-
lyzer. Infrared spectra were recorded with a Bruker EQUINOX-55
spectrophotometer in the range 400–4000cm–1 using KBr disks. Ther-
methyl fumarate (1:1, v/v). The final mixture was placed in a 25 mL
poly(tetrafluoroethylene)-lined stainless steel container under autoge-
nous pressure, heated at 100 °C for 4 d, and cooled to 20 °C at
mogravimetric analyses were recorded with a NETZSCH STA 449C 3 °C·h–1. A large quanitity of red crystals was obtained. Yield 76%
thermal analyzer. Photoluminescence analyses of the solid samples (based on Co). C116H76Co3N10O12 (1978.66): calcd: C 70.41, H 3.87,
were performed with an Edinburgh Instrument F920 fluorescence spec-
trometer at ambient temperature.
N 7.08%; found: C 69.57, H 3.84, N 7.22%. IR (KBr): ν˜ = 3112 (m),
1716 (s), 1674 (s), 1643 (s), 1506 (s), 1403 (s), 1323 (s), 1276 (w),
1147 (m), 1083 (w), 872 (w), 798 (w), 760 (w) cm–1 (Figure S1c).
Syntheses of [Cd(pqba)2(4,4Ј-bipy)] (1): A mixture of Hpqba
(0.2 mmol, 0.0496g), 4,4Ј-bipy (0.2 mmol, 0.0312g), and CdCO3
Crystal Structure Determination: X-ray crystallographic data for the
(0.2 mmol, 0.0345g) in 15 mL mixed solution of methanol /dimethyl compounds 1–3 were collected at room temperature with a Bruker
fumarate (1:1, v/v) was sealed into a 25 mL poly(tetrafluoroethylene)- Smart-1000CCD diffractometer. Graphite monochromated Mo-Kα (λ =
lined stainless steel container under autogenous pressure, heated at
130 °C for 3 d, and cooled to 20 °C at 4 °C·h–1. Colorless prismatic
single crystals suitable for X-ray analyses were obtained. The crystals
were collected by filtration, washed with distilled water and methanol,
and dried at room temperature. Yield 60% (based on Cd).
C42H28O4N4Cd (765.12): calcd: C 65.93, H 3.69, N 7.32%; found: C
65.87, H 3.72, N 7.21%. IR (KBr): ν˜ = 3060 (m), 1649 (s), 1630 (s),
1622 (s), 1535 (s), 1383 (s), 1335 (s), 1281 (w), 1177 (m), 1095 (w),
866 (w), 807 (w), 776 (w) cm–1 (Figure S1a, Supporting Information).
0.71073 Å) radiation was used. All absorption corrections were applied
using the multiscan program SADABS. The structures of compounds
1–3 was solved by direct methods using the SHELXS-97[5] and refined
on F2 by the full-matrix least-squares methods using the SHELXL-
97program package.[6] Atoms were located from iterative examination
of difference F-maps following least-squares renements of the earlier
models. Hydrogen atoms were placed in calculated positions and in-
cluded as riding atoms with isotropic displacement parameters 1.2
times Ueq of the attached carbon atoms. The crystal data and refine-
ment details of the compounds are summarized in Table 1, and selected
bond lengths and angles are listed in Table 2.
Syntheses of [Zn(pqba)2biyb] (2): A mixture of Hpqba (0.2 mmol,
0.0496 g), biyb (0.2 mmol, 0.0477 g), and zinc acetate (0.3 mmol,
0.0659 g) was added to 15 mL of methanol/dimethyl fumarate (1:2, v/
Crystallographic data (excluding structure factors) for the structures in
v). The final mixture was placed in a 25 mL poly(tetrafluoroethylene)- this paper have been deposited with the Cambridge Crystallographic
lined stainless steel container under autogenous pressure, heated at
110 °C for 3 d, and cooled to 20 °C at 5 °C·h–1. Colorless crystals
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting the de-
suitable for X-ray analyses were obtained. Yield 56% (based on Zn). pository numbers CCDC-919473, CCDC-919476, and CCDC-919475
Table 1. Crystal data for compounds 1–3.
1
2
3
Measurement temperature
293(2)
296(2)
293(2)
Empirical formula
Formula weight
C42H28CdN4O4
765.08
C46H34N6O4Zn
800.16
C116H76Co3N10O12
1978.66
Crystal system
Space group
triclinic
P1
monoclinic
C2/c
triclinic
P1
¯
¯
a /Å
b /Å
c /Å
α /°
9.895(2)
12.243(2)
15.499(3)
108.61(3)
99.89(3)
106.24(3)
1636.5(6)
1.553
25.862(5)
11.243(2)
14.830(3)
90
114.620(4)
90
12.8796(6)
13.8874(6)
15.2458(7)
108.0540(10)
107.0250(10)
101.6760(10)
2346.65(18)
1.400
β /°
γ /°
V /Å3
3920.1(13)
1.356
Dc/ Mg·m–3
θ range for data collection /°
Indices range (h,k,l)
3.11 to 25.05
–12 Յ h Ն 12
–15 Յ k Ն 13
–15 Յ l Ն 20
0.71073
14505
7354 / 0 / 460
776
1.73 to 25.09
–30 Յ h Ն 30
–13 Յ k Ն 10
–17 Յ l Ն 17
0.71073
9731
3495 / 0 / 258
1656
1.75 to 25.50
–11 Յ h Ն 15
–16 Յ k Ն 16
–17 Յ l Ն 18
0.71073
24914
8666/ 0 / 599
1019
λ (Mo-Kα) /Å
Reflections collected
Data / restraints / parameters
F(000)
Final R
R indices (all data)
Z
R1 = 0.0585, wR2 = 0.1635
R1 = 0.0789, wR2 = 0.1706
2
R1 = 0.0485,wR2 = 0.1231
R1 = 0.0748, wR2 = 0.1557
4
R1 = 0.0539,wR2 = 0.1370
R1 = 0.0746,wR2 = 0.1552
1
Z. Anorg. Allg. Chem. 2013, 1254–1260
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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X.-Y. Hou, X. Wang, F. Fu, J.-J. Wang, L. Tang
ARTICLE
Table 2. Selected bond lengths /Å and angles /° of compounds 1–3.
1
Cd1–O1
2.241(4)
2.247(4)
84.26(15)
79.81(16)
Cd1–O2#1
Cd1–N4
O3–Cd1–N4
O3–Cd1–N3
2.314(4)
2.365(5)
95.42(17)
85.25(17)
Cd1–O3
Cd1–N3
O4#2–Cd1–N4
O1–Cd1–N3
2.318(4)
2.386(5)
99.75(16)
95.41(16)
Cd1–O4#2
O1–Cd1–O3
O4#2–Cd1–N3
Symmetry codes: #1: 2–x, 2–y, 1–z; #2: 1–x, 2–y, 1–z
2
Zn1–O1
O1– Zn1–N2#1
1.942(3)
111.40(12)
Zn1–N2
O1#1–Zn1–N2#1
2.000(3)
117.27(13)
O1–Zn1–O1#1
N2–Zn1–N2#1
93.73(17)
106.00(17)
Symmetry codes: #1: –x, y, 1.5–z.
3
Co1–O3
Co1–O6
Co2–O1
O3–Co1–O2
O1–Co2–O4#1
2.012(2)
2.214(3)
2.063(2)
95.09(11)
86.61(10)
Co1–O2
Co1–N5
Co2–O5
N5–Co1–N4
O1–Co2–O5
2.062(3)
2.094(3)
2.121(2)
76.34(13)
90.35(10)
Co1–O5
Co1–N4
Co2–O4
O5–Co1–O6
O4#1–Co2–O5
2.157(2)
2.146(3)
2.066(2)
59.66(9)
90.25(9)
Symmetry codes: #1: 1–x, 1–y, 1–z.
for complexes 1, 2, and
3 (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk)
Supporting Information (see footnote on the first page of this article):
IR spectra, additional figures of the π•••π stacking interactions; exper-
imental and simulated PXRD patterns, and TGA curves for complexes
1–3.
Results and Discussion
Structural Description of Compounds 1–3
Crystal Structure of[Cd(pqba)2(4,4Ј-bipy)] (1)
X-ray crystallographic analysis revealed that 1 crystallizes
¯
in the triclinic P1 space group, and its structure features a 2D
coordination network. As shown in Figure 1a, the asymmetric
unit of compound 1 contains one CdII cation, two pqba anions,
and one 4,4Ј-bipy molecule. The coordination environment
around the Cd1 adopts slightly distorted octahedral coordina-
tion arrangement with four carboxylate oxygen atoms (O1, O3,
O2#1, O4#2) from four pqba ligands, and two nitrogen atoms
(N3, N4) from two 4,4Ј-bipy molecules, whereas the O1 and
O4#2 atoms exist in the equatorial positions. The Cd1–O
lengths are in the range of 2.241(4)–2.318(4) Å and the Cd1–
N lengths are in the range of 2.365(5) Å and 2.386(5) Å. The
selected bond lengths and angles are listed in Table 2. All bond
lengths and angles in 1 are within normal ranges and compar-
able with those observed in other reported Cd2+-carboxyl-
ates.[7]
It is obvious that the angles of O–C–O for two pqba ligands
around each Cd1 cation are not the same, 126.47°, 125.74° for
each O–C–O. The angles between the two planes are 24.4°
Figure 1. (a) Coordination environment of the CdII ion in 1. The hy-
and 29.8° (Figure S2a, Supporting Information). One plane is drogen atoms are omitted for clarity. Symmetry codes: #1: 2–x, 2–y,
1–z; #2: 1–x, 2–y, 1–z. (b) View of 1D chain constructed by carboxyl
along the a axis of 1. (c) View of 2D framework by 4,4Ј-bipy along
the b axis of 1. The pqba anions are omitted for clarity.
formed by a single benzene ring and the other is formed by a
quinol.
In compound 1, the pqba anions adopts a μ2-k1,k1 coordina-
tion mode to bridge two central Cd1 atoms (Scheme 1c). If the
4,4Ј-bipy ligand is omitted, each of the CdII atoms are bridged dimensional infinite chains along the a axis with a Cd1···Cd1
by carboxylate oxygen atoms (O1, O2, O3, O4) to form one- separation of 4.917(4) and 4.982 Å (Figure 1b). The eight-
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Coordination Compounds Based on 2-Phenyl-4-quinolinecarboxylic Acid and Nitrogenous Neutral Ligands
ear 4,4Ј-bipy ligand form the 2D coordination network, as
shown in Figure 1c. The 4,4Ј-bipy molecule adopts a bis(mon-
odentate) coordination mode to bridge two central cadmium
atoms. This is particularly mentioned that two 4,4Ј-bipy mole-
cules of linking metal cadmium are not in the same plane,
and the angle between the two planes is 63.2° (Figure S2b,
Supporting Information).
Crystal Structure of [Zn(pqba)2biyb] (2)
X-ray single-crystal diffraction reveals that complex 2 has a
1D coordination polymer, which expand 3D supramolecules
via strong π···π stacking interactions. Complex 2 crystallized
in the monoclinic C2/c space group. As shown in Figure 2a,
each asymmetric unit contains of one Zn2+ ions, two pqba an-
ionic ligands, and one biyb ligand. Zn1 is four-coordinated by
two carboxylate oxygen atoms (O1, O1#1) from two pqba li-
gands and two nitrogen atoms (N2, N2#1) from two biyb li-
gands to form a slight distorted tetrahedral arrangement. The
bond lengths of Zn–N/O are in the range from 1.942(3) to
2.000(3) Å, and the O–Zn–O(N) angles around the central ions
vary from 93.73(17)° to 117.27(13)°. The selected interatomic
Scheme 1. The coordination mode of the pqba ligand.
membered ring, [Cd2(μ2-CO2)2] with the angles of two O–C– distances and angles are listed in Table 2. which are closely
O are 125.74° and 126.47°, is formed between in the one- similar to those observed in four-coordinate zinc complexes
dimensional chain. These one-dimensional chains and the lin- with oxygen donor and nitrogen donor ligands.[8]
Figure 2. (a) Coordination environment of the ZnII ion in 2. Hydrogen atoms are omitted for clarity. Symmetry codes: #1: –x, y, 1.5–z.
(b) View of 1D chain constructed by biyb ligand along the c axis and 2D supramolecular structure by π–π stacking interactions along the b axis
of 2. (c) View of 3D supramolecular structure by π–π stacking interactions along the a axis.
Z. Anorg. Allg. Chem. 2013, 1254–1260
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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X.-Y. Hou, X. Wang, F. Fu, J.-J. Wang, L. Tang
ARTICLE
There is only one unique kind of coordination mode of the
pqba ligand in compound 2, the carboxylic oxygen atom of the
pqba ligand is coordinated with ZnII by μ1-k1 mode
(Scheme 1b). The pqba ligand contributes to coordination
number around each metal ion. If the pqba ligand is omitted,
as shown in Figure 2b, compound 2 forms a one-dimensional
zigzag chains structure along the c axis through biyb ligand
coordinated zinc(II) ions with a Zn···Zn distance of 14.630 Å.
In one-dimensional chains, the pqba ligands seem to act as
“wings”, whereas the biyb and ZnII acts as “trunk”, thus, they
compose a butter-fly-like structure (Figure S3a, Supporting In-
formation). In 2, there are π···π stacking interactions
(centroid···centroid distances: 4.071 Å, centroid···plane dis-
tances: 3.490 Å) between two adjacent 1D zigzag chains,
whose interaction changes the framework from 1D zigzag
chains to 2D structure in the bc plane (Figure 2c). Further,
stong π···π stacking interaction (centroid···centroid distances:
3.639 Å, centroid···plane distances: 3.365 Å) (Figure S3b, Sup-
porting Information) exists between adjacent 2D structure, and
it play important roles in the assembly process of the 3D supra-
molecular architecture (Figure 2c).
Crystal Structure of [Co3(pqba)6(2,2’-bipy)2] (3)
Compound 3 is engaged in the formation of π–π stacking
interaction between the mononuclear units leading to the con-
struction of the three-dimensional supramolecules. X-ray
analysis reveals that compound 3 crystallizes in the triclinic
¯
P1 space group. As shown in Figure 3a, compound 3 consists Figure 3. (a) Schematic description of the Co3 unit and its coordination
of one and a half CoII ions, three pqba anionic ligands, and a
2,2Ј-bipy ligand. The six-coordinate Co1(II) adopts distorted
[CoO4N2] octahedron arrangement, where four oxygen atoms
come from three dierent pqba anionic ligands [Co1–O3:
environment in 3. The hydrogen and part of the carbon atoms are
omitted for clarity. Symmetry codes: #1: 1–x, 1–y, 1–z. (b) The 3D
supramolecular structure by π–π stacking interactions of 3.
and 3.5176 Å along the a axis, and 3.9159 Å, 3.7322 Å, and
3.9771 Å, 4.3737 Å along the b axis, respectively. π···Stacking
interactions can be viewed as medium to strong if they exhibit
rather short centroid···centroid distances (Ͻ3.8 Å) together
with large slip angles (β, γ Ͻ 25°) and vertical displacements
(d Ͻ 1.5 Å). In comparison, weak π···stackings show rather
short centroid···centroid contacts (Ͼ4.0 Å), small slip angles
(β, γ Ͼ 30°) and vertical displacements (d Ͼ 2.0 Å), which
translate into a sizeable overlap of the aromatic planes.[10] Ob-
viously, these π···π stacking interactions increase the stability
of the whole crystal structure of 3.
2.012(2) Å, Co1–O2: 2.062(3) Å, Co1–O5: 2.157(2) Å, and
Co1–O6: 2.214(3) Å.], two nitrogen atoms are from one 2,2Ј-
bipy molecule [Co1–N5: 2.094(3) Å, Co1–N4: 2.146(3) Å],
which O5 and N5 atoms in the equatorial positions. The Co2
is also distorted [CoO6] octahedrally coordinated, bound to six
oxygen atoms from six pqba anions, where the O1 and O1#1
atoms are in the equatorial positions. The bond lengths of
Co2–O are 2.063(2), 2.063(2), 2.121(2), 2.121(2), 2.065(2),
2.065(2) Å, respectively. The selected interatomic distances
and angles for 3 are listed in Table 2. All bond lengths and
angles are comparable to those observed in other CoII com-
plexes.[9]
The pqba anionic ligands adopt two coordination modes:
one is μ2-k1,k1 coordination mode to bridge two central cobalt
atoms, another is μ2-k1,k2 mode connecting with two cations
PXRD and TG Results
The purity of compounds 1–3 is confirmed by powder
(Scheme 1a and d). The linear trinuclear cobalt cluster unit PXRD analyses. The PXRD experimental and computer-simu-
[Co3(pqba)6bipy2] is formed, which is centrosymmetric lated patterns of the corresponding complexes are shown in the
through the connection of two μ2-CO2 and two μ2-CO2. The Supporting Information (Figures S5), in which the main peaks
angle of Co1–Co2–Co1#1 is 180.00° and a Co···Co separation of the experimental spectra of 1–3 are almost consistent with
is 3.459 Å in the trinuclear basic unit. Each trinuclear basic its simulated spectra.
unit is connected by π···π stacking interaction (Figure S4a–c,
In order to estimate the stability of the frameworks, thermal
Supporting Information) to form a 3D supramolecular architec- gravimetric analysis (TG) of 1–3 was carried out from 30 °C
ture (Figure 3b). The interplanar and centroid···centroid dis- to 900 °C in a nitrogen atmosphere (Figure S6, Supporting In-
tances are 3.9159 Å and 3.9772 Å along the c axis, 3.4062 formation). Complexes 1–3 show similar thermal behaviors.
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Coordination Compounds Based on 2-Phenyl-4-quinolinecarboxylic Acid and Nitrogenous Neutral Ligands
For compound 1, it reveals that a continuous weight loss of attributed to the π*Ǟπ transition) for the Hpqba ligand,
64.7% occurs from 255 to 420 °C, which can be attributed to respectively. Compared with the emission spectra of the Hpqba
the release of pqba anion (calcd. 64.9%). Further, the second ligand, compounds 1 and 2 are all blue-shifted, and the emis-
weight loss from 430 to 700 °C is attributed to the release of sion peaks of complexes 1 and 2 are blue-shifted 95 and
4,4Ј-bipy molecule. The remaining residue corresponds to the 65 nm, respectively. It is well-known that both zinc and cad-
formation of CdO (obsd. 16.5%; calcd. 16.8%). For 2, the rst mium ions are difficult to be oxidized or reduced, owing to
weight loss in the temperature range of 275–470 °C is consis- their stable d10 configurations. As a result, the observed emis-
tent with the removal of pqba anion (obsd 61.6%; calcd. sions of 1 and 2 can probably be attributed to the intraligand
62.1%). The second weight loss from 510 to 720 °C is attrib- fluorescent emission of Hpqba, which is modified by metal
uted to the collapse of the bipy molecule. The remaining resi- coordination.[11] Both 1 and 2 may be suitable as excellent
due corresponds to the formation of ZnO (obsd 10.7%; calcd. candidates of fluorescent materials.
10.2%). For 3, the rst weight loss in the temperature range of
180–380 °C is consistent with the removal of the pqba anion
(obsd 75.4%; calcd. 75.3%). The second weight loss from 380
Magnetic Properties of 3
to 620 °C is attributed to the collapse of the 2,2Ј-bipy mole-
cule. The remaining residue corresponds to the formation of
CoO (obsd 11.7%; calcd. 11.4%).
Complex 3 containing 3d magnetic metal ions (Co), so their
magnetic properties should be interesting to be investigated.
The magnetic measurements were performed on polycrystal-
line samples of 3 using a MPMS-XL-7 magnetometer under
an applied field of 1000 Oe in the temperature range of 1.8–
300 K. At room temperature, magnetic susceptibility data per
Luminescence Properties of 1 and 2
The luminescence properties of the free ligand Hpqba, and Co3 unit for 1 shows a χMT value of 8.51 cm3·K·mol–1 (Fig-
complexes 1 and 2, are investigated in the solid state at room ure 5), which is much higher than the spin only value of three
temperature, as shown in Figure 4. These compounds exhibit high-spin CoII ion (5.63 cm3·K·mol–1, S = 3/2, g = 2.0), due to
strong emission with a broad band. Emission bands are ob- signicant orbital contribution.[12] The χMT value of polymer 3
served at 410 nm (λex = 380 nm) for 1, 440 nm (λex = 380 nm) decreases with decreasing temperature down to a minimum
for 2, and 505 nm (the intense emission at 415 nm, which is value of 2.77 cm3·K·mol–1 at 2 K, which indicates an intraclus-
Figure 4. Fluorescence properties of Hpqba ligand and complexes 1 and 2 in solid state at room temperature.
Z. Anorg. Allg. Chem. 2013, 1254–1260
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1259

X.-Y. Hou, X. Wang, F. Fu, J.-J. Wang, L. Tang
ARTICLE
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Figure 5. Temperature dependence of magnetic susceptibility in the
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Conclusions
Three new complexes [Cd(pqba)2(4,4Ј-bipy)] (1),
[Zn(pqba)2biyb] (2), and [Co3(pqba)6(2,2Ј-bipy)2] (3) were
synthesized by self-assembly reactions of pqba anion ligands,
4,4Ј-bipy, 2,2Ј-bipy, or biyb neutral ligands, and CdII, CoII,
ZnII system. The pqba ligand with unusual coordination
modes, neutral ligands, and metal ions common control the
dimensional architectures and properties of complexes 1–3.
Especially, photoluminescence measurements indicate that the
compounds 1 and 2 show strong luminescence. The tempera-
ture dependence of magnetic susceptibilities was studied, and
antiferromagnetic was observed for compound 3. It is believed
that the presented results of complexes 1–3 provide new infor-
mation regarding synthetic strategy, luminescence, and mag-
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Acknowledgements
15, 55.
This project supported by the Natural Scientific Research Foundation
of Shaanxi Provincial Education Office of China (No. 11JK0583).
Received: March 24, 2013
Published Online: May 25, 2013
1260
www.zaac.wiley-vch.de
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 1254–1260