Constructing a series of azide-bridged CuII magnetic low-dimensional coordination polymers by using pybox ligands

Article abstract of DOI:10.1002/ejic.201300107

Four azide-copper coordination polymers, [Cu₂L ¹(N₃)₄]_n, [Cu₂L ²(N₃)₄]_n, [Cu₂L ^3R(N₃)₄]_n, and [Cu₂L ^3S(N₃)₄]_n, were synthesized by using pybox [pyridine-2,6-bis(oxazolines)] as coligands {L¹: 2,6-bis(4,5-dihydrooxazol-2-yl)pyridine; L²: 2,6-bis(5,6-dihydro-4H- 1,3-oxazin-2-yl)pyridine; L^{3R or 3S}: 2,6-bis[(R or S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}. Compounds 1 and 2 possess similar 1D infinite azide-copper hexagonal tapes with three types of N₃ bridges (two single end-on N₃ bridges and one double end-on N ₃ bridge). Compounds 3R and 3S possess an azide-copper 2D honeycomb layer with two types of N₃ bridges (a single end-to-end N₃ bridge and a double end-on N₃ bridge). The chirality of these enantiopure layered structures is controlled by the addition of the chiral pybox ligand in the synthesis, which is very rare for the reported azide-copper coordination polymers. The double end-on N₃ bridge transfers mainly ferromagnetic exchange coupling interactions in these four compounds. Owing to the steric hindrance of the pybox ligands, the interchain and interlayer separations are broadened, which weakens the magnetic interactions between them. Thus, no long-range ferromagnetic ordering was observed above 1.8 K. A magnetostructural correlation was also discussed in detail. A series of pybox ligands were used as effective coligands to construct four azide-copper low-dimensional coordination polymers. Two of these polymers possess similar 1D infinite azide-copper hexagonal tapes and the other two possess a very interesting enantiopure 2D honeycomb layer structure. Magnetic studies revealed the weak ferromagnetic characters of these complexes.

Full text of DOI:10.1002/ejic.201300107

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Magnetic Coordination Polymers
Y.-Y. Zhu, C. Cui, N. Li, B.-W. Wang,*
Z.-M. Wang, S. Gao* ..................... 1–12
Constructing a Series of Azide-Bridged
CuII Magnetic Low-Dimensional Coordi-
nation Polymers by using Pybox Ligands
Keywords: Coordination polymers / Cop-
per / N ligands / Magnetic properties
A series of pybox ligands were used as ef-
fective coligands to construct four azide–
copper low-dimensional coordination poly-
mers. Two of these polymers possess simi-
lar 1D infinite azide–copper hexagonal
tapes and the other two possess a very
interesting enantiopure 2D honeycomb
layer structure. Magnetic studies revealed
the weak ferromagnetic characters of these
complexes.
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DOI:10.1002/ejic.201300107
Constructing a Series of Azide-Bridged CuII Magnetic
Low-Dimensional Coordination Polymers by using Pybox
Ligands
Yuan-Yuan Zhu,[a,b] Chang Cui,[a] Ning Li,[a] Bing-Wu Wang,*[a]
Zhe-Ming Wang,[a] and Song Gao*[a]
Keywords: Coordination polymers / Copper / N ligands / Magnetic properties
Four azide–copper coordination polymers, [Cu2L1(N3)4]n,
[Cu2L2(N3)4]n, [Cu2L3R(N3)4]n, and [Cu2L3S(N3)4]n, were syn-
enantiopure layered structures is controlled by the addition
of the chiral pybox ligand in the synthesis, which is very rare
thesized by using pybox [pyridine-2,6-bis(oxazolines)] as co- for the reported azide–copper coordination polymers. The
ligands {L1: 2,6-bis(4,5-dihydrooxazol-2-yl)pyridine; L2: 2,6-
double end-on N3 bridge transfers mainly ferromagnetic ex-
change coupling interactions in these four compounds. Ow-
ing to the steric hindrance of the pybox ligands, the in-
or
bis(5,6-dihydro-4H-1,3-oxazin-2-yl)pyridine; L3R
3S: 2,6-
bis[(R or S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}. Com-
pounds 1 and 2 possess similar 1D infinite azide–copper hex- terchain and interlayer separations are broadened, which
agonal tapes with three types of N3 bridges (two single end- weakens the magnetic interactions between them. Thus, no
on N3 bridges and one double end-on N3 bridge). Com- long-range ferromagnetic ordering was observed above
pounds 3R and 3S possess an azide–copper 2D honeycomb
layer with two types of N3 bridges (a single end-to-end N3
bridge and a double end-on N3 bridge). The chirality of these
1.8 K. A magnetostructural correlation was also discussed in
detail.
can be coordinated in an elongated octahedral (six coordi-
nated) or square-pyramidal (five coordinated) geometry,
which allows the formation of rich coordination modes. On
the other hand, the Cu2+ ion has only one unpaired elec-
tron; the spin-related energy spectrum is nearly the simplest
one amongst the paramagnetic 3d transition-metal ions,
and it is thus more convenient to theoretically analyze this
system than other magnetic systems.[5] As a versatile bridg-
ing ligand, the azide ion could link two or more metal ions
in various modes, for example, μ-1,1 [end-on (EO)], μ-1,3
[end-to-end (EE)], μ-1,1,1, μ-1,1,3, and so forth, which thus
gives rise to a variety of 0D to 3D polynuclear complexes.[6]
With the participation of various coligands, the azide–cop-
per system might be one of the most complicated coordina-
tion polymer systems.[7] For coordination chemists, the syn-
thesis of azide–copper coordination polymers with new top-
ologies and interesting magnetic properties is still a chal-
lenge. Some important rules of magnetostructural corre-
lation have also been obtained for azide–copper systems.
Most of the reported azide–copper compounds are poly-
nuclear clusters and 1D chain complexes. Given the broad
interest in magnetostructural correlation studies, several 2D
and 3D complexes have been synthesized and magnetically
characterized.[8] Previous studies demonstrated that 2D and
3D azide–copper compounds display very complicated and
interesting magnetic properties because of their rich coordi-
nation modes. Among these systems, coligands greatly de-
termine the diversity of the coordination modes. Most co-
Introduction
Recently, the construction of low-dimensional coordina-
tion polymers has attracted great attention by researchers in
the field of molecular magnetism because these compounds
possess structural diversity and unusual magnetic properties
as well as magnetostructural correlations.[1] Up to now,
many 1D expanded chains, 2D layers, and 3D networks
have been reported, and the magnetic behavior of these sys-
tems has also been studied carefully.[2] Among the magnetic
3d transition-metal compounds with short bridging ligands
–
of one to three atoms (O2–, OH–, CN–, N3 , HCOO–,
–
C2O42–, N2 , etc.),[3] several studies were focused on the az-
ide–copper system from the viewpoint of prolific coordina-
tion structure and magnetostructural correlation.[4] On the
one hand, as a result of the Jahn–Teller effect, the Cu2+ ion
[a] Beijing National Laboratory of Molecular Science (BNLMS),
College of Chemistry and Molecular Engineering, State Key
Laboratory of Rare Earth Materials Chemistry and
Applications, Peking University,
Beijing 100871, P. R. China
Fax: +86-10-6275-1708
E-mail: wangbw@pku.edu.cn
gaosong@pku.edu.cn
Homepage: http://www.chem.pku.edu.cn/mmm/
[b] Key Laboratory of Advanced Functional Materials and
Devices, Anhui Province, School of Chemical Engineering,
Hefei University of Technology,
Anhui 230009, P. R. China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201300107.
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ligands used in the reported complexes are commercially at roughly 2120 to 1970 cm–1 (a sharp peak at 2063 cm–1
available. Chiral ligands, however, were seldom used. In the and a shoulder at 2048 cm–1) is observed, which suggests
field of organic chemistry, pybox [pyridine-2,6-bis(oxaz- the presence of two different bridging modes of azide.
oline)] is a privileged chiral catalyst that is widely used in
asymmetric catalytic reactions.[9] In the field of inorganic
chemistry, this type of ligand has also been utilized to con-
struct rare earth complexes in the study of luminescent
properties.[10] Successful attempts to construct enantiopure
molecular magnets are rare; however, Li et al. obtained a
chiral single-molecule magnet (SMM) by using a bidentate
chiral box [bis(oxazoline)] ligand.[11] Chiral magnets appear
to be good candidates for presenting a cross-effect of circu-
lar dichroism (CD) and magnetochiral dichroism
(MChD).[12] The study of enantiopure chiral molecule
based magnets has been a topic of growing interest for syn-
thetic chemists.[13] Therefore, we tried to synthesize novel
azide–copper complexes with new topologies by utilizing
this new type of organic chiral ligand and hoped that this
Figure 1. IR spectra of compounds 1, 2, 3R, and 3S.
ligand could be an effective coligand to construct molecule-
based magnets, especially those that are enantiopure. In this
article, we report the synthesis, structure, and magnetic
Crystal Structures
properties of a series of azide-bridged Cu2+ complexes by
For convenience in the description of structure and the
analysis of magnetism, some structural parameters are de-
fined in advance. The trigonality index τ = (β – α)/60, in
which β and α are two largest L–Cu–L (L = ligand) angles
of the coordination sphere (τ = 0 infers a perfect square-
pyramid and τ = 1 infers a perfect trigonal-bipyramid),
which can be used to describe the degree of distortion of the
utilizing pybox as a coligand.
Results and Discussion
Synthesis and IR Spectra
Three pybox-type ligands, 2,6-bis(4,5-dihydrooxazol-2- basal plane of the Cu2+ coordination geometry. The index d
yl)pyridine (L1), 2,6-bis(5,6-dihydro-4H-1,3-oxazin-2-yl)- is the deviation of the Cu2+ ion from the basal plane. The
pyridine (L2), and 2,6-bis[(R and S)-4-benzyl-4,5-dihydro- index δ is the dihedral angle of the two basal planes of the
oxazol-2-yl]pyridine (L3R and L3S), were used as coligands neighboring Cu2+ coordination geometry. The index Δ is
to synthesize azide–copper complexes (Scheme 1). A de- the dihedral angle of the azide-bridged Cu–(EE-N3)–Cu.
tailed synthesis procedure can be found in the Supporting The index θ is the bond angle of EO azide-bridged Cu–N–
Information. Chiral ligands L3R and L3S were synthesized Cu.
from (R and S)-phenylglycinol, their commercially available
chiral sources, in several steps.
The crystallographic and refinement details of these four
compounds are summarized in Table 6.[14,15] Although the
The IR spectra of compounds 1, 2, 3R, and 3S display four compounds are of the general formula [Cu2(N3)4L]n,
characteristic bands of the azide on the basis of their bridg- their topologies are significantly different. The Cu2+ ions
ing modes (Figure 1). In the region expected for νas(N3) ab- form a 1D hexagonal tape in compounds 1 and 2, and only
sorption, compound 1 exhibits three well-separated neigh- small differences in the link angle as a result of structural
boring sharp and strong bands (2084, 2059, and 2041 cm–1) differences in the pybox coligands are observed. Compara-
and a shoulder peak (2031 cm–1), which is attributed to the tively, the Cu2+ ions form 2D honeycomb layers in com-
presence of the four tapes of bridging modes of azide (two pounds 3R and 3S. In 1 and 2, one type of Cu2+ ions are
single EO N3, a double EO N3, and a terminal N3). For bridged by two EO N3 anions and the other type of Cu2+
–
compound 2, four well-separated neighboring sharp and ions are bridged by four EO N3 anions and N3 as a ter-
strong bands (2085, 2060, 2051, and 2025 cm–1) are ob- minal ligand, in which all the Cu2+ ions are five coordi-
served for the same azide bridging modes as those observed nated. Compounds 3R and 3S are enantiomeric complexes,
for 1. For compounds 3R and 3S, a very strong broad band in which the Cu2+ ions are alternately bridged by two types
Scheme 1. Structures of four pybox ligands.
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of EE N3 anions and a pair of double EO N3 anions. All they are bound asymmetrically to the Cu2+ ions with Cu–
the Cu2+ ions are identical and are also five coordinated. N distances of 1.981 Å (Cu2) and 2.003 Å (Cu2Ј, at –x +
More structural details concerning the specific compounds 2, –y + 2, –z), and the Cu2–N13–Cu2Ј angle is 103.06°. The
are discussed below.
terminal azide anions are bound to Cu2+ ions with a Cu–
N distance of 1.954 Å, and the Cu2–N10–N12 angle is
115.41°. The three types of azide bridges and the one ter-
minal azide anion are almost linear; the N–N distances in
the azide anions are approximately equal to each other, and
the longer bonds involving the nitrogen atom are linked to
the Cu2+ ions. This is consistent with the structural results
obtained with the other EO azide-bridging complexes.[4a]
Pybox ligand L1 stacks parallel in the two sides of the chain
and separate the different chains well; the shortest distance
of the Cu2+ ions between the neighboring chains is 8.886 Å.
The tapes are packed through weak C–H···O hydrogen-
Structure of Compound 1
The structure of compound 1 (Figure 2) consists of an
azide–copper 1D hexagonal tape with three types of N3
–
bridges as linkers, and this compound crystallizes in the
monoclinic space group P21/n. There are two crystallo-
graphically independent Cu2+ ions, which are all five coor-
dinated with distorted square-pyramidal geometry. The tri-
gonality index τ of the Cu1 and Cu2 atoms is 0.180 and
0.297, respectively, which indicates that the coordination of
these two Cu2+ ions is close to square-pyramid coordina-
tion geometry. One type of Cu2+ ions (Cu1) is coordinated
by two different single EO bridging azide anions, and the
othr three nitrogen atoms come from the L1 ligand. One
nitrogen atom (N4) of the single EO bridging azide and
three nitrogen atoms (N1, N2, and N3) of the L1 ligand
comprise the basal plane, and the axial coordination sites
are occupied by the nitrogen atom (N7) of another single
EO bridging azide. The single EO bridging azide anions in
the basal plane (N4) are bound asymmetrically to the two
types of Cu2+ ions with Cu–N distances of 1.944 Å (N4–
Cu1) and 2.675 Å (N4–Cu2), and the Cu1–N4–Cu2 angle
is 123.79°. Another type of single EO bridging azide anion
in the axial coordination sites is also bound asymmetrically
to the two types of Cu2+ ions with Cu–N distances of
2.424 Å (Cu1) and 1.980 Å (Cu2), and the Cu1–N7–Cu2
angle is 117.40°; the Cu–N distance (Cu1–N7) in the axial
position is elongated because of the Jahn–Teller effect. An-
other type of Cu2+ ions (Cu2) are all coordinated by azide
anions. Besides the two single EO bridging azide anions
mentioned above, three others are a pair of double EO
bridging azide anions and a terminal azide anion. Two EO
Figure 3. View of the crystal packing of compound 1 along the b
axis.
Table 1. Selected bond lengths and angles for complex 1.[a]
Bond lengths [Å]
azide anions of a double EO N3 bridge are identical, and Cu1–N4
1.944(3)
1.976(3)
2.033(3)
2.056(3)
2.425(3)
Cu2–N10
Cu2–N7
Cu2–N13
Cu2–N13#1
N13–Cu2#1
1.954(3)
1.980(3)
1.981(4)
2.002(4)
2.002(4)
Cu1–N2
Cu1–N1
Cu1–N3
Cu1–N7
Bond angles [°]
N4–Cu1–N2
N4–Cu1–N1
N2–Cu1–N1
N4–Cu1–N3
N2–Cu1–N3
N1–Cu1–N3
N4–Cu1–N7
N2–Cu1–N7
N1–Cu1–N7
N3–Cu1–N7
N10–Cu2–N7
N10–Cu2–N13
N7–Cu2–N13
168.25(14)
99.14(13)
78.67(13)
102.63(13)
78.80(13)
157.42(13)
103.87(13)
87.81(12)
92.96(12)
87.62(11)
96.85(14)
169.67(14)
93.49(14)
C11–N3–Cu1
C4–N2–Cu1
C8–N2–Cu1
N5–N4–Cu1
C3–N1–Cu1
C1–N1–Cu1
N11–N10–Cu2
N14–N13–Cu2
139.4(3)
119.3(2)
119.3(2)
116.8(3)
113.7(2)
139.3(3)
114.4(2)
125.3(3)
N14–N13–Cu2#1 131.0(3)
Cu2–N13–Cu2#1 103.09(16)
N8–N7–Cu2
N8–N7–Cu1
Cu2–N7–Cu1
N12–N11–N10
N15–N14–N13
N6–N5–N4
125.3(3)
113.8(2)
117.41(14)
177.8(4)
178.0(5)
176.9(4)
175.6(4)
N10–Cu2–N13#1 93.79(14)
N7–Cu2–N13#1 151.84(16)
N13–Cu2–N13#1 76.91(16)
Figure 2. (a) Crystal structure of 1. Hydrogen atoms are omitted
for clarity. (b) 1D hexagonal Cu2+ chain bridged by EE and EO
azides.
C9–N3–Cu1
112.6(2)
N9–N8–N7
[a] Symmetry operation: #1 –x + 2, –y + 2, –z.
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bonding interactions of the neighboring oxazole rings along Table 2. Selected bond lengths and angles for complex 2.[a]
the b axis (dH···O = 2.579 Å) to form the 3D structure (Fig-
ure 3; see also Figure S12 in the Supporting Information).
Selected bond lengths and angles of compound 1 are listed
Bond lengths [Å]
Cu1–N4
Cu1–N2
Cu1–N1
1.938(2)
1.943(2)
2.042(2)
2.080(2)
2.364(2)
Cu2–N10
Cu2–N7
Cu2–N13#1
Cu2–N13
N13–Cu2#1
1.967(2)
1.980(2)
2.001(2)
2.004(2)
2.001(2)
in Table 1.
Considering the topology of the Cu2+ ions, the tape is Cu1–N3
formed by parallel six-membered Cu2+ rings. In 2005, our
Cu1–N7
group reported two finite azide–copper tapes consisting of
eight-membered copper rings,[4b] in which the neighboring
eight-membered rings share three Cu2+ ions. In compound
1, the neighboring six-membered rings share two Cu2+ ions.
These results all demonstrate the rich coordination modes
of the azide–copper system.
Bond angles [°]
N4–Cu1–N2
N4–Cu1–N1
N2–Cu1–N1
N4–Cu1–N3
N2–Cu1–N3
N1–Cu1–N3
N4–Cu1–N7
N2–Cu1–N7
N1–Cu1–N7
N3–Cu1–N7
N10–Cu2–N7
161.31(10)
95.40(9)
79.28(9)
105.43(9)
79.05(9)
158.32(9)
104.15(9)
94.26(9)
96.01(8)
84.84(8)
96.19(10)
C4–N1–Cu1
C1–N1–Cu1
C5–N2–Cu1
C9–N2–Cu1
N5–N4–Cu1
113.78(17)
127.00(16)
118.80(17)
119.29(17)
120.52(19)
N14–N13–Cu2#1 126.69(19)
N14–N13–Cu2
Cu2a-N13–Cu2
C10–N3–Cu1
C13–N3–Cu1
N8–N7–Cu2
N8–N7–Cu1
Cu2–N7–Cu1
N12–N11–N10
N15–N14–N13
N9–N8–N7
129.73(19)
103.57(10)
112.84(17)
127.16(17)
123.71(19)
114.95(17)
115.97(10)
177.6(3)
Structure of Compound 2
Compound 2 (Figure 4) also crystallizes in the mono-
clinic space group P21/n and possesses the same topology
as that of 1. The oxazole ring in L1 is close to the plane,
the oxazine ring in L2; however, it is obviously twisted. The
structural differences of the two coligands results in some
differences in the bond lengths and angles in the two com-
pounds. The detailed data can be seen from Tables 1 and 2.
Detailed differences in the structures will also be discussed
in the magnetostructural correlation study section (see be-
low). Similar to compound 1, weak C–H···O hydrogen-
bonding interactions between neighboring tapes in 2 were
also observed [Figure 5, dH···O = 2.520 Å; see also Fig-
ure S13 in the Supporting Information).
N10–Cu2–N13#1 92.82(10)
N7–Cu2–N13#1
N10–Cu2–N13
N7–Cu2–N13
N13#1-Cu2–N13 76.43(10)
N11–N10–Cu2 117.14(18)
157.08(10)
169.19(9)
93.46(9)
179.0(3)
176.1(3)
176.6(3)
N6–N5–N4
[a] Symmetry operation: #1 –x + 2, –y, –z.
Figure 5. View of the crystal packing of compound 2 along the b
axis.
consists of an azide–copper 2D honeycomb layer with two
types of azide bridges. There is only one crystallographi-
cally independent Cu2+ ion, which is five coordinated with
distorted square-pyramidal geometry. The trigonality index
τ of the Cu2+ ion is 0.22. The Cu2+ ion is coordinated by
two different single EE bridging azide anions, a pair of
double EO bridging azide anions, and one nitrogen atom in
the oxazole ring of the L3R ligand. One nitrogen atom (N2)
of the L3R ligand, two EO azide-bridged nitrogen atoms
Figure 4. (a) Crystal structure of 2. Hydrogen atoms are omitted
for clarity. (b) 1D hexagonal Cu2+ chain bridged by EE and EO
azides.
Structures of Compounds 3R and 3S
Compound 3R and 3S are enantiomers and crystallize in (N6 and N6#1; symmetry code #1 = –x + 2, y, –z + 1),
the chiral space group C2, and the absolute structure pa- and one EE azide-bridged nitrogen atom (N3) comprise the
rameters (flack parameters)[16] are 0.094 for 3R and 0.000 basal plane, and the axial coordination sites are occupied
for 3S. For 3R as an example, its structure (Figure 6, a) by the nitrogen atom (N5) of another EE bridging azide.
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The EE bridging azide anions in the basal plane and the Two neighboring Cu2+ ions are coordinated with one pybox
axially coordinated azide anions are identical in crystal- ligand, which makes the distance between them very short,
lography and are coordinated with the Cu2+ ions at dif- so the coordination of pyridine becomes unfavorable. The
ferent ends. The Cu–N distance of the basal plane is structures of the honeycomb Cu2+ 2D layers of 3R and 3S
1.952 Å (Cu1–N3), and that of the axial site is 2.385 Å demonstrate that the chirality information was successfully
(Cu1–N5#2; symmetry code #2 = –x + 3/2, y + 1/2, –z + transferred from the chiral pybox ligands to the coordina-
1). The pair of double EO bridging azide anions are iden- tion polymers. This represents the successful construction
tical, which are bound asymmetrically to Cu2+ with Cu–N of enantiopure 2D layers from chiral coligands. No signifi-
distances of 2.040 Å (Cu1–N6) and 2.017 Å (Cu1–N6#1), cant π–π stacking or weak hydrogen bonds are observed
and the Cu1–N6–Cu1#1 angle is 88.07°. The angle is between the neighboring 2D layers (Figure S14, Supporting
smaller than that in compounds 1 and 2, so the distance Information). Thus, the 3D structure is assembled from the
of the neighboring Cu2+ ions is very short (2.820 Å). One 2D layer only through van der Waals forces. The shortest
nitrogen atom (N2) in the oxazole ring of the L3R ligand is distance of the Cu2+ ions between the neighboring layers
bound to the Cu2+ ion with a Cu–N distance of 1.989 Å is 12.457 Å (Figure 7; Figure S14, Supporting Information).
(Cu1–N2), and the other N atom (N2#1) in the oxazole Selected bond lengths and angles of compound 3R are
ring is bound to the neighboring Cu2+ ions. Owing to the listed in Table 3.
steric hindrance of the substituent group, the nitrogen atom
(N1) in the pyridine ring of the ligand is not coordinated.
Table 3. Selected bond lengths and angles for complex 3R.[a]
Bond lengths [Å]
Cu1–N3
Cu1–N2
Cu1–N6#1
Cu1–N6
1.952(8)
1.989(7)
2.017(8)
2.041(7)
Cu1–N5#2
Cu1–Cu1#1
N6–Cu1#1
N5–Cu1#3
2.385(8)
2.820(2)
2.017(8)
2.385(8)
Bond angles [°]
N3–Cu1–N2
96.1(3)
93.3(3)
156.6(3)
169.5(3)
92.2(3)
76.6(4)
92.9(4)
100.5(3)
N6a–Cu1–Cu1#1 46.3(2)
N6–Cu1–Cu1#1 45.6(2)
N5b–Cu1–Cu1#1 125.2(2)
N3–Cu1–N6#1
N2–Cu1–N6#1
N3–Cu1–N6
N7–N6–Cu1#1
N7–N6–Cu1
Cu1a–N6–Cu1
C4–N2–Cu1
C6–N2–Cu1
N4–N3–Cu1
N4–N5–Cu1#3
N8–N7–N6
121.9(6)
124.4(6)
88.1(3)
124.5(6)
126.7(6)
124.2(7)
170.7(9)
176.8(10)
176.6(10)
N2–Cu1–N6
N6a–Cu1–N6
N3–Cu1–N5#2
N2–Cu1–N5#2
N6a–Cu1–N5#2 100.4(3)
N6–Cu1–N5#2
N3–Cu1–Cu1#1
N2–Cu1–Cu1#1
91.9(3)
124.6(3)
111.8(2)
N5–N4–N3
[a] Symmetry operations: #1 –x + 2, y, –z + 1; #2 –x + 3/2, y +
1/2, –z + 1; #3 –x + 3/2, y – 1/2, –z + 1.
Figure 6. (a) Crystal structure of 3R. Hydrogen atoms are omitted
for clarity. (b) Enantiopure honeycomb Cu2+ 2D layers of 3R and
3S bridged by EE and EO azides.
Magnetic Studies
The magnetic measurements were performed on poly-
crystalline samples of compounds 1, 2, 3R, and 3S by using
a SQUID (superconducting quantum interference device)
magnetometer. Enantiomers 3R and 3S exhibit identical
magnetic behavior. Thus, the magnetic discussion below
concerns only 1, 2, and 3R. All compounds show apparent
ferromagnetic interactions, but no long-range ferromagnetic
ordering is observed above 1.8 K for these compounds.
The χMT versus T plot of 1 under an applied field of
1 kOe is shown in Figure 8 (χM is the molar magnetic
susceptibility per two Cu2+ ions). At room temperature,
χMT is equal to 0.89 cm3 mol–1 K, which is slightly higher
than that expected for two uncoupled Cu2+ ions (χMT =
0.375 cm3 Kmol–1 for an S = 1/2 ion with g = 2). The χMT
value increases upon cooling very slowly and reaches a
maximum at 6.5 K (χMT = 0.95 cm3 mol–1 K) and decreases
to 0.93 cm3 mol–1 K at 2 K, which is almost a straight hori-
Figure 7. View of the crystal packing of compound 3R along the b
axis.
–1
zontal line. The temperature dependence of χM from 2 to
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300 K obeys the Curie–Weiss law with a small positive
Weiss constant θ of 0.83 K (see Figure 8). The small posi-
tive θ value and the very slow increase in the plot of χMT
versus T suggest a very weak ferromagnetic interaction.
Moreover, at 1.8 K, the field-dependent magnetization ini-
tially linearly increases in the low-field region, and then in-
creases slowly in the high-field region and reaches 1.93 Nβ
at 50 kOe (Figure S15, Supporting Information), which is
only a little smaller than the expected saturation value
(2.0 Nβ for Cu2+ assuming g = 2.00). It also confirms the
very weak ferromagnetic characteristics of 1. No peak is
found in the alternating current (ac) susceptibility at vari-
ous frequencies in the absence of a direct current (dc) field
from 2 to 10 K (Figure S17, Supporting Information). This
result demonstrates no long-range ferromagnetic ordering
above 2 K.
–1
Figure 9. Plots of χMT and χM versus T for 2 under a field of
1 kOe.
ferromagnetic interaction between the adjacent Cu2+ ions
through the 2 EO azide bridges is stronger than the antifer-
romagnetic interaction between the adjacent Cu2+ ions
linked by the EE azide bridge. Relative to 1 and 2, the big-
ger θ value and the abrupt increase in χMT versus T for 3
indicate the ferromagnetic interaction of 3R is the strongest
amongst the three compounds. Field-dependent magnetiza-
tion also supports this conclusion. It initially increases
quickly in the low-field region, and then increases slowly
and linearly with the applied field and finally reaches
2.17 Nβ at 50 kOe (Figure S21, Supporting Information).
This value is a little larger than the expected saturation
value (2.0 Nβ); however, similar to compounds 1 and 2, no
long-range ferromagnetic ordering is observed above 2 K
(Figure S23, Supporting Information).
–1
Figure 8. Plots of χMT and χM versus T for 1 under a field of
1 kOe.
The magnetic behavior of 2 is similar to that of 1. The
χMT versus T plot of 2 is shown in Figure 9 (χM is the
molar magnetic susceptibility per two Cu2+ ions). At room
temperature, χMT is equal to 0.91 cm3 mol–1 K, which is
slightly higher than that expected for two uncoupled Cu2+
ions (0.75 cm3 mol–1 K). It increases upon cooling very
slowly above 50 K, and then increases very quickly until
to 2 K (χMT = 1.31 cm3 mol–1 K). No maximum of χMT is
–1
observed above 2 K. The temperature dependence of χM
from 2 to 300 K obeys the Curie–Weiss law with a small
positive Weiss constant θ of 0.93 K (Figure 9). Moreover,
the field-dependent magnetization at 1.8 K is similar to that
of 1 (Figure S18, Supporting Information). The successive
increase in χMT and the positive θ value suggest that the
ferromagnetic interaction is a little stronger than that of 1.
Similar to 1, no long-range ferromagnetic ordering is ob-
served above 2 K (Figure S20, Supporting Information).
The χMT versus T plot of 3R is shown in Figure 10. At
Figure 10. Plots of χM and χMT versus T for 3R under a field of
1 kOe.
Magnetostructural Correlation
The magnetic studies demonstrate that, for all com-
room temperature, χMT is equal to 1.16 cm3 mol–1 K, which pounds, the ferromagnetic exchange is dominant. Unfortu-
is higher than that expected for two uncoupled Cu2+ ions nately, the exchange pathways of compounds 1–3 cannot
(0.75 cm3 mol–1 K). It increases upon cooling moderately be simply modeled because of the complicated geometrical
above 10 K, and then increases very quickly to 2 K (χMT = structures of the complexes. The magnetostructural corre-
3.83 cm3 mol–1 K). No maximum of χMT is observed above lation of azide–copper compounds, however, has been
–1
2 K. The temperature dependence of χM from 100 to studied comprehensively, both experimentally and theore-
300 K obeys the Curie–Weiss law with a positive Weiss con- tically. Some rules were proposed on the basis of the various
stant θ of 10.95 K (Figure 10), and the plot below 100 K types of azide–copper compounds. Therefore, we tried to
is slightly derivative from the linear fitting. The successive map the magnetic exchange interactions of the different
increase in χMT and the positive θ value suggest that the types of azide bridges in this series of compounds.
Eur. J. Inorg. Chem. 0000, 0–0
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The exchange interactions transferred by double EO az- some analogical structures with similar geometry param-
ides were deeply investigated.[4a,5,17] For a symmetric double eters, the values of the coupling parameter |J| usually are
EO azide bridge, three structural parameters impose signifi- less than 5 cm–1. Though the experimental data are limited,
cant influences on the magnetic interaction: (1) The Cu–N– some rules can be obtained. For an asymmetric single EO
Cu angle (α): the ferromagnetic interactions decreases with azide bridge, the longer Cu–Cu distance (typically Ͼ3.50 Å)
increased α angle and 104 (from experiment) or 108° (from and the larger value of τ (typically Ͼ0.2) will lead to a
computation) is the boundary. (2) The Cu–N bond lengths weaker antiferromagnetic interaction. Thus, in compounds
and the Cu–Cu distances: smaller distances tend to ferro- 1 and 2, the antiferromagnetic interaction transferred by
magnetic coupling. (3) The distortion of the coordination the two types of single EO azide bridges is very weak.
geometry: the distortion is not conducive to the efficient
delocalization of the magnetic orbital and so reduces the 1,3-bridging mode in this series of compounds. To summa-
interaction. rize some reported 1D uniform systems, the single EE azide
The single EE azide bridge of compound 3 is the only
As mentioned in the above structure section, the three bridging mode transmits a weak ferromagnetic interaction,
compounds all contain a symmetric double EO azide including some examples with similar geometry parameters
bridge, and the bond lengths and angle are listed in Table 4. compared to the EE azide bridge in compound 3R.[19]
The α angles of the three compounds are all smaller than Therefore, the EE azide bridge of compound 3R may also
104° and the Cu–N and Cu–N–Cu distances are also of transfer a weak ferromagnetic interaction.
normal length. The small τ values reveal that the distortion
From the view of magnetic coupling, this series of cop-
from the square-pyramid is not obvious. By combining per(II) azide coordination polymers can roughly be treated
these data with theoretical rules and reported results, it can as dinuclear copper(II) complexes with a double EO azide
be concluded that the double EO azide bridge in the three bridge that can transfer a strong ferromagnetic interaction.
compounds all transfer ferromagnetic interaction. The For compounds 1 and 2, the dinuclear units are linked by
smallest α angle and the Cu–Cu distances of compound 3R two types of single EO azide bridges along one direction.
suggest that this compound exhibits the strongest ferromag- The magnetic interaction transferred by two single EO az-
netic coupling amongst the three compounds. This conclu- ide bridges is very weak, which probably is antiferromag-
sion is also consistent with the results of magnetic measure- netic coupling. For compound 3R, the dinuclear units are
ments.
linked by a type of single EE azide bridge along the plane.
The EE azide bridge transfers a very weak ferromagnetic
interaction. Overall, in the three compounds, the ferromag-
netic interaction is dominant.
Table 4. Main structural parameters for the symmetric double EO
(μ2-1,1-N3) azide bridge of this series of compounds.[a]
Compound
Cu–Cu
[Å]
Cu–N
[Å]
α Cu–N–Cu
τ
[°]
1
2
3R
3.119
3.146
2.820
2.003, 1.981
2.004, 2.000
2.040, 2.017
103.06
103.58
88.07
0.297 (Cu2)
0.202 (Cu2)
0.215
Conclusions
In summary, by using pybox-type ligands L1, L2, L3R
,
[a] α = band angle, τ = trigonality index; for a detailed definition
of the structural parameters, see the section on Crystal Structures.
and L3S as coligands, four new azide–copper compounds,
[Cu2(N3)4L1] (1), [Cu2(N3)4L2] (2), [Cu2(N3)4L3R] (3R), and
The situation in compounds 1 and 2 is complicated. The [Cu2(N3)4L3S] (3S), were successfully obtained. Compounds
corresponding structural parameters of the two types of sin- 1 and 2 possess a similar 1D infinite azide–copper hexago-
gle EO azide bridges and the single EE azide bridge are nal chain with three types of N3 bridges and compound
listed in Table 5.
3R and 3S possess a pair of enantiopure azide–copper 2D
The two types of single EO azide bridges in compounds honeycomb layer with two types of N3 bridges. The honey-
1 and 2 are all asymmetrically linked to the Cu1 and Cu2 comb-type azide–copper compounds are very rare. Com-
ions. According to the experimental data of some reported pounds 3R and 3S represent rare examples of chiral 2D
1D uniform systems, the single EO azide bridging ligand layer azide–copper compounds. The magnetic analysis re-
usually mediates relatively weak magnetic interaction, vealed that the ferromagnetic interaction is dominant in
which is either antiferromagnetic or ferromagnetic.[18] For these four compounds, but no long-range ferromagnetic or-
Table 5. Main structural parameters for the single EO (μ1,1-N3) azide bridge of 1 and 2 and the single EE (μ1,3-N3) azide bridge of 3R.[a]
Compound
Cu–Cu [Å]
Cu–N [Å]
α Cu–N–Cu [°]
τ
d [Å]
δ
Δ [°]
1 (N4)
1 (N7)
2 (N4)
2 (N7)
3R
4.088
3.770
4.113
3.689
6.033
2.675, 1.944
2.424, 1.980
2.620, 1.938
2.364, 1.980
2.385, 1.952
138.79
117.40
128.32
115.97
–
0.180 (Cu1)
0.297 (Cu2)
0.050 (Cu1)
0.202 (Cu2)
0.215
0.133 (Cu1)
0.206 (Cu2)
0.162 (Cu1)
0.206 (Cu2)
0.234
29.47
–
28.34
–
–
–
–
–
73.46
57.08
[a] τ = the trigonality index, d = bond length, δ = dihedral angle of the two basal planes of the neighboring Cu coordination geometry,
Δ = dihedral angle of the azide-bridged Cu–(EE-N3)–Cu; for a detailed definition of the structural parameters, see the section on Crystal
Structures.
Eur. J. Inorg. Chem. 0000, 0–0
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N2,N6-Bis(3-chloropropyl)pyridine-2,6-dicarboxamide (8): Prepared
from 4 and 3-aminopropan-1-ol by following a procedure similar
to that used for 6. White solid (72%). 1H NMR (400 MHz, CDCl3):
δ = 8.36 (d, J = 7.6 Hz, 2 H), 8.10 (br., 2 H), 8.04 (t, J = 7.6 Hz,
1 H), 3.71–3.67 (m, 8 H), 2.16 (quint., J = 6.4 Hz, 4 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 163.9, 148.7, 139.1, 124.9, 42.8, 37.4,
32.0 ppm. MS (ESI): m/z = 318.15 [M + 1]+. C13H17Cl2N3O2
(318.20): calcd. C 49.07, H 5.38, N 13.21; found C 48.94, H 5.37,
N 13.17.
derings were observed above 1.8 K. The four compounds
demonstrate that new magnetic azide metal compounds
could be synthesized by using new organic ligands as co-
ligands, and the magnetic properties can also be mediated
by the structure of the coligands.
Experimental Section
2,6-Bis(5,6-dihydro-4H-1,3-oxazin-2-yl)pyridine (L2): To a solution
of 8 (1.6 g, 5 mmol) in MeCN (15 mL) was added KF/Al2O3 (40%
KF in weight, 5.8 g, 40 mmol), and the mixture was stirred for 2 d.
The solid was filtered off, and the filtrate was washed with water
(15 mL) and brine (15 mL) and then dried with sodium sulfate. The
product was obtained as a white solid (1.16 g, 95%) after the sol-
Reagents and General Procedures: All starting materials are com-
mercially available at analytical grade and were used without fur-
ther purification. All reactions were carried out under aerobic con-
ditions. Elemental analyses were carried out with an Elementary
Vario EL analyzer. IR spectra were recorded with a Nicolet
Magna-IR 750 spectrometer equipped with a Nic-Plan microscope
against pure samples. The magnetic data of compounds were mea-
sured with a Quantum Design MPMS-XL5 SQUID system. The
experimental susceptibility data were corrected for diamagnetism
(Pascal’s parameters)[1] and background by experimental measure-
ment on the sample holder.
1
vent was removed. H NMR (400 MHz, CDCl3): δ = 8.05 (d, J =
7.6 Hz, 2 H), 7.79 (t, J = 8.0 Hz, 1 H), 4.44 (t, J = 5.6 Hz, 4 H),
3.65 (t, J = 5.6 Hz, 4 H), 2.00 (quint., J = 6.0 Hz, 4 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 154.4, 151.0, 137.0, 123.4, 65.5, 42.8,
21.6 ppm. MS (ESI): m/z = 268.08 [M + Na]+. C13H15N3O2·
1/15CH2Cl2 (250.71): calcd. C 62.54, H 6.08, N 16.75; found C
62.42, H 6.15, N 16.79.
Caution! Although not encountered in our experiment, Cu(ClO4)2·
6H2O and complexes of copper ions are potentially highly explosive.
Only small amounts of material should be prepared and handled with
great care.
N2,N6-Bis[(R)-1-chloro-3-phenylpropan-2-yl]pyridine-2,6-dicarbox-
amide (10R): Prepared from 4 and (R)-2-amino-3-phenylpropan-1-
ol by following a procedure similar to that used for 6. White solid
(80%). 1H NMR (400 MHz, CDCl3): δ = 8.35 (d, J = 8.0 Hz, 2 H),
8.07 (d, J = 9.2 Hz, 2 H), 8.06 (t, J = 8.0 Hz, 1 H), 7.36–7.24 (m,
10 H), 4.73–4.65 (m, 2 H), 3.79 (dd, J1 = 11.6, J2 = 4.0 Hz, 2 H),
3.68 (dd, J1 = 11.6, J2 = 3.0 Hz, 2 H), 3.14–3.04 (m, 4 H) ppm.
Pyridine-2,6-dicarbonyl Dichloride (4): To a mixture of pyridine-
2,6-dicarboxylic acid (1.67 g, 10 mmol) in DMF (0.05 mL) was
added SOCl2 (20 mL). The mixture was stirred at reflux for 2 h,
during which time the insoluble powder gradually dissolved. The
excess amount of SOCl2 was recovered by atmospheric distillation,
and the residual amount of SOCl2 was removed under reduced
pressure by adding a small amount of toluene. Product 4 (2.04 g,
100%) was obtained as a pale white solid under vacuum drying.
2,6-Bis[(R)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine (L3R):[21] Pre-
pared from 10R by following a procedure similar to that used for
1
L1. White solid (95%). H NMR (400 MHz, CDCl3): δ = 8.22 (d,
J = 8.0 Hz, 2 H), 7.89 (t, J = 8.0 Hz, 1 H), 7.33–7.30 (m, 4 H),
7.25–7.21 (m, 6 H), 4.69–4.61 (m, 2 H), 4.46 (t, J = 9.0 Hz, 2 H),
4.26 (t, J = 8.0 Hz, 2 H), 3.27 (dd, J1 = 13.6 Hz, J2 = 4.8 Hz, 2 H),
2.74 (dd, J1 = 13.6 Hz, J2 = 9.0 Hz, 2 H) ppm.
N2,N6-Bis(2-hydroxyethyl)pyridine-2,6-dicarboxamide (6): To
a
solution of 2-aminoethanol (1.53 g, 25 mmol) and triethylamine
(4.3 mL, 30 mmol) in dichloromethane (30 mL), cooled in an ice
bath, was added a solution 4 (2.04 g, 10 mmol) in dichloromethane
(30 mL) over 10 min; a white precipitate was generated immedi-
ately. After stirring at room temperature for 1 d, SOCl2 (20 mL)
was added to the reaction mixture, which was cooled in an ice-
bath. The solution was stirred at reflux for 2 h. The white precipi-
tate dissolved, and the color of the solution turned violent. The
solution was concentrated under reduced pressure, and the residual
amount of SOCl2 was removed under reduced pressure by adding
a small amount of toluene. The resulting residue was triturated
with dichloromethane (30 mL). The solution was washed with satu-
rated sodium hydrogen carbonate solution (15 mL), water (15 mL),
and brine (15 mL) and then dried with sodium sulfate. The solvent
was removed, and the crude product was subjected to flash
chromatography [petroleum ether (PE)/EtOAc, 2:1 to 1:1] to give 6
(1.88 g, 65% in two steps) as a white solid. 1H NMR (400 MHz,
CDCl3): δ = 8.38 (d, J = 8.0 Hz, 2 H), 8.29 (br., 2 H), 8.07 (t, J =
7.6 Hz, 1 H), 3.88–3.84 (m, 4 H), 3.76 (t, J = 5.6 Hz, 4 H) ppm.
2,6-Bis[(S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine (L3S):[21] Pre-
pared from (S)-2-amino-3-phenylpropan-1-ol by following a pro-
cedure similar to that used for L3R. White solid (95%).
[Cu2L1(N3)4]n (1): Single crystals were obtained by diffusion. In a
test tube, a solution of NaN3 (26 mg, 0.4 mmol) and L1 (43 mg,
0.2 mmol) in MeOH/CH2Cl2 (10:1, 5 mL) was layered carefully
with blank MeOH/CH2Cl2 solvent (20:1, 3 mL) and then a solution
of Cu(ClO4)2·6H2O (74 mg, 0.2 mmol) in MeOH (5 mL). The tube
was sealed and undisturbed at room temperature for 3 d. Dark-
green needle-like crystals were obtained, yield 67 mg, 65% [based
on Cu(ClO4)2·6H2O]. C11H11Cu2N15O2 (512.40): calcd. C 25.78, H
2.16, N 41.00; found C 26.07, H 2.31, N 40.43. IR (neat): ν = 3338
˜
(w), 3304 (w), 3099 (w), 3066 (w), 3040 (w), 2976 (w), 2084 (s),
2059 (s), 2041 (s), 2031 (m), 1905 (w), 1648 (w), 1626 (w), 1586
(m), 1495 (w), 1476 (w), 1410 (m), 1339 (w), 1295 (w), 1267 (m),
1213 (w), 1193 (w), 1168 (w), 1082 (w), 1032 (w), 1020 (w), 985
(w), 977 (w), 958 (w), 977 (w), 958 (w), 911 (w), 842 (w), 759 (w),
737 (w), 693 (w), 677 (w), 658 (w) cm–1.
2,6-Bis(4,5-dihydrooxazol-2-yl)pyridine (L1):[20] To a solution of 6
(1.45 g, 5 mmol) in methanol (50 mL) was added KOH (0.7 g,
12.5 mmol). The solution was stirred at reflux for 4 h, and white
precipitate was generated during the course of the reaction. The
solution was concentrated under reduced pressure. The resulting
residue was triturated with dichloromethane (30 mL), and the solu-
tion was washed with water (15 mL) and brine (15 mL) and then
[Cu2L2(N3)4]n (2): Single crystals were obtained by diffusion. In a
test tube, a solution of NaN3 (26 mg, 0.4 mmol) and L2 (49 mg,
0.2 mmol) in MeOH/CH2Cl2 (10:1, 5 mL) was layered carefully
with blank MeOH/CH2Cl2 solvent (20:1, 3 mL) and then a solution
of Cu(ClO4)2·6H2O (74 mg, 0.2 mmol) in MeOH (5 mL). The tube
dried with sodium sulfate. L1 (1.03 g, 95%) was obtained as a white was sealed and undisturbed at room temperature for 3 d. Dark-
solid under vacuum drying.
green needle-like crystals were obtained, yield 62 mg, 60% [based
Eur. J. Inorg. Chem. 0000, 0–0
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Table 6. Crystallographic data and structure refinements for 1, 2, 3R, and 3S.
1
2
3R
3S
Formula
C11H11Cu2N15O2
512.43
monoclinic
P21/n
14.955(4)
6.7213(15)
18.182(5)
90
C13H15Cu2N15O2
540.48
monoclinic
P21/n
15.405(4)
6.5456(15)
19.258(5)
90
C12.5H11.5CuN7.5
346.33
monoclinic
C2
13.218(6)
9.273(4)
12.922(6)
90
O
C12.5H11.5CuN7.5
346.33
monoclinic
C2
13.223(3)
9.269(2)
12.925(3)
90
O
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
104.37(4)
90
1770.4(8)
4
95.44(4)
90
1933.1(9)
4
113.99(5)
90
1447.0(11)
4
114.09(3)
90
1446.2(6)
4
γ [°]
V [Å3]
Z
T [K]
173(2)
1024
1.923
2.452
173(2)
1088
1.857
2.251
173(2)
704
1.590
1.523
173(2)
704
1.591
1.524
F(000)
Dcalcd. [gcm–3]
μ [mm–1]
λ [Å]
0.71073
0.21ϫ0.18ϫ0.04
0.9791, 0.9925
1.58, 27.48
14999
4007, 0.0794
3638
271
0.0534
0.1513
1.109
0.71073
0.25ϫ0.12ϫ0.03
0.7851, 1.0000
1.62, 27.48
16504
4430, 0.0426
4171
289
0.0389
0.0858
1.201
0.71073
0.71073
0.2ϫ0.21ϫ0.05
0.6843, 1.0000
1.73, 27.49
4841
2761, 0.0324
2714
204
0.0342
0.0968
1.182
Crystal size [mm3]
Tmin and Tmax
θmin, θmax [°]
No. total reflns.
No. uniq. reflns, Rint
No. obs. [IՆ2σ(I)]
No. params
R1 [IՆ2σ(I)]
wR2 (all data)
S
0.23ϫ0.21ϫ0.05
0.6843, 1.0000
1.72, 26.40
5908
2907, 0.0584
2788
204
0.0734
0.2083
1.153
Δρ[a] [eÅ–3]
Max. and mean Δ/σ[b]
+0.95, –0.76
0.001, 0.000
+0.41, –0.31
0.001, 0.000
+2.32, –0.84
0.000, 0.000
+0.49, –0.54
0.000, 0.000
[a] Max. and min. residual density. [b] Max. and mean shift/σ.
on Cu(ClO4)2·6H2O]. C13H15Cu2N15O2 (540.45): calcd. C 28.89, H
1575 (w), 1496 (w), 1478 (w), 1454 (w), 1408 (w), 1381 (w), 1350
(w), 1335 (w), 1280 (w), 1251 (w), 1211 (w), 1185 (w), 1157 (w),
1094 (w), 1050 (w), 1031 (w), 1019 (w), 1000 (w), 982 (w), 962 (w),
2.80, N 38.88; found C 28.11, H 2.73, N 39.33. IR (neat): ν = 3330
˜
(w), 3076 (w), 3052 (w), 3019 (w), 2975 (w), 2958 (w), 2905 (w),
2085 (s), 2060 (s), 2051 (s), 2025 (m), 1648 (m), 1633 (m), 1593 (m), 938 (w), 861 (w), 837 (w), 749 (w), 732 (w), 702 (w), 683 (w), 660
1483 (w), 1466 (w), 1438 (w), 1397 (m), 1368 (w), 1340 (w), 1312 (w), 611 (w) cm–1.
(w), 1282 (m), 1219 (m), 1199 (w), 1157 (w), 1120 (w), 1076 (w),
X-ray Crystallography and Physical Measurements: The X-ray mea-
surements of 1 and 2 were carried out with a Saturn724+ CCD
diffractometer with Confocal-monochromator Mo-Kα radiation
(λ = 0.71073 Å) at 173 K. Intensities were collected by using Crys-
talClear (Rigaku Inc., 2008) technique, and absorption effects were
collected by using the multiscan technique. The X-ray measure-
ments of 3R and 3S were carried out with a Saturn724+ CCD
diffractometer with graphite-monochromator Mo-Kα radiation
(λ = 0.71073 Å) at 173 K. Intensities were collected by using Crys-
talClear (Rigaku Inc., 2008) technique, and absorption effects were
collected by using the Numerical technique. The structures of 3R
and 3S were solved by using the SHELXS-97 program[14] and re-
fined by a full-matrix least-squares technique based on F2 by using
the SHELXL 97 program.[15] Crystallography data and refinement
results are listed in Table 6 and selected bond lengths and angles
in Tables 1–3.
1061 (w), 1035 (w), 976 (w), 930 (w), 892 (w), 849 (w), 838 (w), 811
(w), 760 (w), 747 (w), 684 (w), 665 (w) cm–1.
[Cu2L3R(N3)4]n (3R): Single crystals were obtained by slow evapora-
tion. To a solution of L3R (80 mg, 0.2 mmol) and NaN3 (26 mg,
0.4 mmol) in MeOH (10 mL) was added a solution of Cu(ClO4)2·
6H2O (74 mg, 0.2 mmol) in MeOH (10 mL) whilst stirring. After
filtration, the dark-green solution was left at room temperature for
2 d, and dark-green plate single crystals were obtained, yield 90 mg,
65%. C25H23Cu2N15O2 (692.65): calcd. C 43.35, H 3.35, N 30.33;
found C 43.32, H 3.37, N 30.16. IR (neat): ν = 3367 (w), 3077 (w),
˜
3031 (w), 2983 (w), 2938 (w), 2064 (s), 1650 (m), 1639 (w), 1605
(w), 1575 (w), 1497 (w), 1478 (w), 1455 (w), 1408 (w), 1381 (w),
1350 (w), 1335 (w), 1280 (w), 1250 (w), 1211 (w), 1185 (w), 1157
(w), 1095 (w), 1050 (w), 1031 (w), 1019 (w), 999 (w), 982 (w), 962
(w), 938 (w), 862 (w), 837 (w), 749 (w), 732 (w), 702 (w), 683 (w),
660 (w), 611 (w) cm–1.
[Cu2L3S(N3)4]n (3S): Single crystals were obtained by slow evapora-
tion. To a solution of L3S (80 mg, 0.2 mmol) and NaN3 (26 mg,
0.4 mmol) in MeOH (10 mL) was added a solution of Cu(ClO4)2·
6H2O (74 mg, 0.2 mmol) in MeOH (10 mL) whilst stirring. After
filtration, the dark-green solution was left at room temperature for
2 d, and dark-green plate single crystals were obtained, yield 90 mg,
65%. C25H23Cu2N15O2 (692.65): calcd. C 43.35, H 3.35, N 30.33;
CCDC-832864 (for 1), -832865 (for 2), -832866 (for 3R), and
-832867 (for 3S) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Detailed synthetic procedures, characterization data, magnetic
analysis, further measurements, and crystal structures.
found C 43.42, H 3.34, N 30.02. IR (neat): ν = 3362 (w), 3076 (w),
˜
3030 (w), 2982 (w), 2938 (w), 2063 (s), 2048 (s), 1650 (w), 1639 (w),
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I30107
/KAP1
Date: 18-04-13 15:44:22
Pages: 12
www.eurjic.org
FULL PAPER
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Acknowledgments
This work was financially supported by the National Natural Sci-
ence Foundation of China (NSFC) (grant numbers 90922033 and
21071008), Beijing Natural Science Foundation of China (BJSFC)
(grant number 2122023), and the National Basic Research Program
of China (grant numbers 2010CB934601, 2013CB933401). Y.-Y. Z.
is thankful for the financial support by the Open Fund of Beijing
National Laboratory for Molecular Sciences (BNLMS).
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Received: January 24, 2013
Published Online: ᭿
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