Polymers or supramolecules generated from a new V-shaped bis-monodentate ligand and the effect of steric hindrance on coordination modes of the ligand

Article abstract of DOI:10.1002/ejic.200600052

A new V-shaped bis-monodentate ligand L (L = 2,3′-dipyridylamine) (1) has been designed and synthesized by alkylation reaction of pyridylamine. An investigation of the charge distributions of the coordination atoms and single-point energy calculations of four conformers of ligand L based on the geometry of conformers optimized by the DFT (density functional theory) method was carried out. The results show that the four conformers of ligand L take on two stable and two less stable configurations. Theory forecasts that two relatively stable configurations present in complexes as probable coordination motifs of the ligand, and that steric hindrance of pyridine nitrogen atoms in isomers will affect its coordination ability together with the electronic factor. This forecast has been demonstrated by the coordination chemistry of ligand L, that is, configuration (a) and (b) of the ligand occur in the following reported complexes, which combines with Ag^I or Cu ^II through two coordination modes (bidentate bridging or a monodentate mode) resulting in coordination polymers {[Ag (L) ₂]NO₃}_n (2), [Cu₂(L) ₂(maa)₄]_n (maa = methacrylic acid) (3), and the mononuclear molecule [Cu(L)₄]-(ClO₄)₂· 2CH₃CH₂OH (4). The ligand assumes different coordination modes in the three complexes because of different levels of steric hindrance of the pyridine nitrogen atoms in the conformers. Interestingly, polymers 2 and 3 assume a 1D helical structure and a linear framework, respectively, and 4 has a 2D supramolecular architecture induced from hydrogen bond interactions. In addition, the magnetic properties of 3 have been explored, which shows a strong antiferromagnetic interaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600052

FULL PAPER
DOI: 10.1002/ejic.200600052
Polymers or Supramolecules Generated From a New V-Shaped Bis-
monodentate Ligand and the Effect of Steric Hindrance on Coordination
Modes of the Ligand
Caihua Zhou,[a,b] Yaoyu Wang,*[a] Dongsheng Li,[a,b] Lijun Zhou,[a] Ping Liu,[a] and
[a]
Qizhen Shi
Keywords: Dipyridylamine / Helical structure / Density functional study / Silver / Copper
A new V-shaped bis-monodentate ligand L (L = 2,3Ј-dipyrid-
ylamine) (1) has been designed and synthesized by alky-
lation reaction of pyridylamine. An investigation of the
charge distributions of the coordination atoms and single-
point energy calculations of four conformers of ligand L
based on the geometry of conformers optimized by the DFT
(density functional theory) method was carried out. The re-
sults show that the four conformers of ligand L take on two
stable and two less stable configurations. Theory forecasts
that two relatively stable configurations present in complexes
as probable coordination motifs of the ligand, and that steric
hindrance of pyridine nitrogen atoms in isomers will affect its
coordination ability together with the electronic factor. This
forecast has been demonstrated by the coordination chemis-
try of ligand L, that is, configuration (a) and (b) of the ligand
occur in the following reported complexes, which combines
with AgI or CuII through two coordination modes (bidentate
bridging or a monodentate mode) resulting in coordination
polymers {[Ag (L)2]NO3}n (2), [Cu2(L)2(maa)4]n (maa = meth-
acrylic acid) (3), and the mononuclear molecule [Cu(L)4]-
(ClO4)2·2CH3CH2OH (4). The ligand assumes different coor-
dination modes in the three complexes because of different
levels of steric hindrance of the pyridine nitrogen atoms in
the conformers. Interestingly, polymers 2 and 3 assume a 1D
helical structure and a linear framework, respectively, and 4
has a 2D supramolecular architecture induced from hydro-
gen bond interactions. In addition, the magnetic properties
of 3 have been explored, which shows a strong antiferromag-
netic interaction.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
of the donor groups plays an extremely important role in
dictating polymer topology. So far, much of the research
has been concentrated on the exploitation of angular li-
gands with a molecular angle, such as ligands with a T-
shape, V-shape etc, in the construction of versatile coordi-
nation polymer architectures.[7–9] Especially, bidentate
bridging ligands with a V-shaped structure have been widely
used to construct coordination frameworks with a helical
structure because of its flexional characteristic and the con-
figuration stability of binding metal ions.[10,11] On the basis
of the V-shaped exo-bidentate ligand, 2,2Ј-bis(4-pyridyl-
eneoxy)-1,1Ј-binaphthalene[12] and 4,4Ј-oxy-bis(benzo-
ate),[13] several novel helical complexes have been prepared.
With this background in mind, our research has focused
on designing new V-shaped ligands and investigating the
rational control of their self-assembly with metal centers.
In our previous work, we successfully constructed helical
structural supramolecular complexes [14] using the V-shaped
3,4Ј-dipyridylamine ligand. Continuing our investigations
on the coordination properties of V-shaped dipyridylamine
ligands, we designed another new V-shaped bis-mono-
dentate 2,3Ј-dipyridylamine ligand. Particularly, this V-
shaped molecule is an isomer of the well-documented mole-
cule 2,2Ј-dipyridylamine, which is widely used as a chelate
Introduction
Crystal engineering of coordination polymers and supra-
molecules have attracted a lot of attention due to their po-
tential as functional materials, as well as their intriguing
compositions and topologies. Considerable progress has
been made on theoretical forecasting and practical ap-
proaches aimed at controlling the topology structure and
geometry of the networks.[1–3] However, the general and
precise principles for the solid structures of the target prod-
ucts are still subjective because the self-assembly process is
highly influenced by several factors such as the structure
of ligands, the coordination preference of metal ions, the
coordination behavior of counterions, and the solvent sys-
tem.[4–6] The chemical structure of the organic ligands in-
cluding the molecular angle, length, and relative orientation
[a] Department of Chemistry and Shaanxi Key Laboratory of
Physico-inorganic Chemistry, Northwest University,
Xi’an 710069, P. R. China
Fax: +86-29-88373398,
E-mail: wyaoyu@nwu.edu.cn
[b] Department of Chemistry and Chemical Engineering, Yan’an
University,
Yan’an 716000, P. R. China
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C. H. Zhou, Y. Y. Wang, D. S. Li, L. J. Zhou, P. Liu, Q. Z. Shi
FULL PAPER
ligand in its amine form, or as a tridentate ligand in its
deprotonated form.[15,16] In order to investigate the possible
coordination modes of 2,3Ј-dipyridylamine compared to
2,2Ј-dipyridylamine, we explored the electronic effect of co-
ordination atoms, the single-point energy calculations of
four conformers of 2,3Ј-dipyridylamine based on the geom-
etry of four conformers optimized by the DFT method. Ac-
cording to these guidelines, we used 2,3Ј-dipyridylamine as
the ligand to coordinate with AgI and CuII, and obtained
two 1D polymers with a helical or linear structure and one
2D supramolecule. Herein, we report the syntheses, crystal
structures, and characterization of properties of ligand (1)
and three complexes, namely {[Ag(L)2]NO3}n (2), [Cu2-
(L)2(maa)4]n (3), and [Cu(L)4](ClO4)2·2CH3CH2OH (4). At
the same time, the magnetic properties of 3 have also been
studied.
Figure 1. Perspective view of N–H···N hydrogen bonds and π-π
stacking interactions in ligand 1. [N2–N(3A) 3.0949(18) Å; N2–
H···N(3A) 168.1(1)°; the distance between the centers of the pyridyl
rings is 3.48(8) Å, the angle is 12.5427(4)° between two planes].
Results and Discussion
Description of the Structures
Ligand 1
In addition, single-point energy calculations and charge
distributions for four conformers of the ligand have been
The single-crystal X-ray structural analysis shows that carried out at DFT levels. Two stable and two less stable
ligand 1 crystallizes in an orthorhombic system. From the configurations have been obtained by structural optimiza-
crystal structure of the ligand, it can be seen that the ligand tion of the four conformers; the electronic layouts of the
forms zigzag chains in the solid state, and the molecules are four conformers are shown in Figure 2. Single point ener-
held together by a series of N–H···N hydrogen bonds [N2– gies of conformers (a), (b), (c), and (d) are –550.46003,
N(3A) 3.0949(18) Å; N2–H···N(3A) 168.1(1)°]. The two –550.46214, –550.40317, and –550.40293 hartree, and the
pyridine rings in the ligand are twisted with a dihedral angle HOMO–LUMO energy gaps are 0.17477, 0.17273, 0.16899,
of 12.5427(4)°, the ligand molecules are associated in pairs, and 0.16735 eV, respectively. These data reveal that configu-
in a head-to-tail arrangement showing π-π stacking interac- rations (a) and (b) are relatively more stable than (c) and
tions [the distance between the centers of the pyridyl rings (d). From the charge layouts of the four conformers, it can
is 3.48(8) Å, the dihedral angle is 12.5427(4)°], and give rise be seen that N1 and N3 each have an approximately equal
to a two-dimensional supramolecular structure (Figure 1).
donor electron ability in the four conformational isomers
Figure 2. The four optimized conformations of the ligand 1, as well as the calculated electron distributions.
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Polymers or Supramolecules Generated From a New V-Shaped Bis-monodentate Ligand
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(but each N1’s donor electron ability is slightly stronger mation. In the three synthetic complexes, we find that the
than that of each N3), if only considering their electronic ligand only takes on the coordination motifs of configura-
effect.[17] However, we can see that the steric hindrance of tion (a) and (b). Configuration (b) presents in complex 4,
N1 in configuration (b) and (d) is obviously larger than in which combines with metal ions in a monodentate mode,
configuration (a) and (c). Considering steric hindrance and configuration (a) appears in polymers 2 and 3, which
might affect the coordination ability of N1 in different con- links with metal ions in a bidentate bridging mode. There-
figurations, we further investigated the coordination prop- fore, the difference in the coordination ability of N1 be-
erties of ligand 1 with transition metal ions by experimental tween configuration (a) and (b) mainly results from the dif-
means. Fortunately, the experimental results prove this esti- ference in the steric hindrance of N1.
Figure 3. (a) The helical chain of 2; (b) π-π packing interactions between helical chains; (c) the 3D structure formed by hydrogen-bonding
and Ag···O weak interactions between adjacent layers.
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C. H. Zhou, Y. Y. Wang, D. S. Li, L. J. Zhou, P. Liu, Q. Z. Shi
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{[Ag(L)2]NO3}n (2)
3.310(2), 3.250(2) Å, C–H···O 146.63(1), and 150.35(3)°]
and Ag···O weak interactions, resulting in a 3D supramo-
lecular structure (Figure 3c).
The single-crystal X-ray data shows the structure of 2
consists of one-dimensional (1D) cationic polymeric
–
{[Ag(L)2]}+ chains and uncoordinated NO3 anions. The
n
ligand adopts a N,N-bidentate bridging coordination mode
by using two pyridine nitrogen atoms to coordinate to the
AgI centers forming a 1D helical chain (Figure 3, a). The
[Cu2(L)2(maa)4]n (3)
The structure of 3 consists of linear dinuclear one-dimen-
bond angle of N1–Ag1–N(3A) is 165.09(6)°, and the bond sional polymeric [Cu2(L)2(maa)4]n chains (Figure 4, a). The
lengths of Ag1–N1 and Ag1–N(3A) are 2.193(2) and basal unit of the chain is a dinuclear CuII subunit of the
2.196(2) Å, respectively, which are the typical values for paddle-wheel type, the two copper atoms are located at
AgI–Npy coordination distances.[18–21] The helices, parallel equivalent sites in the dinuclear unit. Each copper atom has
to the [010] direction, are generated around a twofold screw a square pyramid coordination environment, with four oxy-
axis presented in the space group P21/n. Pyridine rings gen atoms from four methacrylic groups, forming an equa-
through centers of inversion from adjacent helical chains torial plane, and one pyridyl nitrogen atom, occupying an
indicate significant π-π stacking interactions. Pyridine rings axis place. The axial Cu–N distance is longer than the
involving π-π stacking are absolutely parallel and the dis- average Cu–O bond length. So the coordination geometry
tances between their centroids are 3.769(6) and 3.593(8) Å, around the copper() atom can be regarded as a distorted
(Figure 3, b). Not only do the intermolecular π-π stacking square pyramid, and the Jahn–Teller effect in the polymer
interactions stabilize the helical frameworks but they also manifests itself as an asymmetric elongation along the axial
produce a two-dimensional layer parallel to the crystallo- direction. In the structure of 3, four methacrylic acid
graphic bc plane, the same as most reported similar helical groups are bound to the copper() atoms in the form of a
structures.[22,23]
symmetrical bridging mode (syn,syn-η1:η1:µ2), thus forming
A striking feature of 2 is the stacking pattern in the solid a Cu2(maa)4 paddle-wheel type linked by L ligands. Just as
state. The packing diagram of 2 shows that the NO3– coun- those reported coordination polymers containing the pad-
terions are sandwiched between two layers, and every layer dle-wheel type,[24,25] the bridging ligand is located in an ax-
interacts with other close layers by two groups of C–H···O ial position in the paddle-wheel type structure. On the other
hydrogen bonds between uncoordinated oxygen atoms of hand, this big paddle-wheel type group hinders further tor-
–
NO3 and carbon atoms of the pyridine rings [C–O sion of the two pyridine rings of the bridging ligand, and
Figure 4. (a) Repeat units of the infinite coordination polymer of 3; (b) The two-dimensional network of 3 viewed along the a axis.
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Polymers or Supramolecules Generated From a New V-Shaped Bis-monodentate Ligand
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causes the formation of a neutral one-dimensional linear (Figure 4b) through C–H···O [C···O 3.513(5) Å, C–H···O
chain rather than a helical chain. The chains self-organize 159.18(2)°] hydrogen bonds and C–H···π interaction [C–
and produce a two-dimensional supramolecular structure H···π 3.012(6) Å].
Figure 5. (a) ORTEP views showing the metal environment in the cation of 4; (b) Perspective view of hydrogen-bonding and Cu–O weak
interactions in 4 (top), and 2D packing view along the b axis (bottom).
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[Cu(L)4](ClO4)2·2CH3CH2OH (4)
IR Spectra and TGA Analysis
Single-crystal X-ray diffraction analysis reveals that 4 is a
neutral, mononuclear molecule with the CuII atom in a
square coordination geometry with four pyridine nitrogen
atoms of the four different dipyridylamine ligands (Fig-
ure 5, a). From the data about the N–Cu–N bond angles
[89.14(14), 90.23(10), 90.23(10), and 90.42(13)°] and the
Cu–N bond lengths [2.011(2), 2.011(2), 2.019(2), and
2.019(2) Å], it can be seen that the CuII ions together with
the four nitrogen atoms form a perfect square geometry,
and this ideal quadrangle structure is rare in the coordina-
tion geometry of CuII. A twofold rotary axis along the b
axis direction presenting in space group C2/c is the typically
symmetrical operation of 4. The dihedral angles between
two pyridine planes are about 28.106(2), 28.106(2),
23.418(2), and 23.418(2)° in the four ligands respectively,
which are obviously larger than the free ligand 1. This indi-
cates that the ligand coordinated to the metal CuII pro-
moted flexion of the σC–N bond. Interestingly, the four li-
gands all adopt a monodentate coordination mode and they
all present in 4 as configuration (b), which further proves
the theoretical judgment that the coordination ability of N1
atoms in configuration (b) has been reduced by a steric bar-
IR spectra of the three complexes and the L ligand were
recorded as KBr pellets in the range 4000–400 cm–1. Ligand
1 shows a broad band at 3535 cm–1, which can be assigned
as the stretch absorption of ν(N–H). The next group of
bands appears at 3071 cm–1, corresponding to stretching vi-
brations of ν(C–H). Skeletal vibration of the pyridine ring
shows a strong band at 1503 cm–1. Because of the formation
of intermolecular coordination bonds and hydrogen bonds,
these absorption peaks are significantly shifted to lower fre-
quencies in three complexes. In 2, ν(N–H), ν(C–H), and the
pyridine ring skeleton exhibit at 3448, 3017, and 1484 cm–1,
respectively; there is a strong absorption appearing at
1355.15 cm–1 for the noncoordinated anions of nitrate
–
(NO3 ). While in 3 the three characteristic peaks appear at
3526, 2923, and 1496 cm–1. Another characteristic absorp-
tion for 3 is concerned with the values of asymmetric and
symmetric stretching frequencies for the COO– groups. The
difference between νas(COO) and νs(COO) in comparison
to the corresponding values in ionic species is currently em-
ployed to determine a characteristic coordination mode of
the carboxylate group.[30] For 3, the complex shows strong
bands corresponding to νas(COO) and νs(COO) at 1601 and
1415 cm–1, respectively. The ∆ν is 186 cm–1, close to the cor-
responding values for the sodium methacrylic (178 cm–1),
indicating that the methacrylic groups coordinate to metal
ions in a symmetrical bridging mode (syn,syn-η1:η1:µ2), in
agreement with the paddle-wheel type structure of 3. The
IR spectra of 4 is similar to 2, ν (N–H), ν (C–H), and the
pyridine ring skeleton exhibit at 3621, 3206, and 1501 cm–1,
respectively. There is a slight red shift in 4 compared to 2
and 3 because of the more conjugated pyridine rings pres-
enting in 4. Meanwhile, a strong absorption band appears
–
rier. Two O atoms of the uncoordinated ClO4 anions form
the acceptors of C(4)–H···O(3) [C–O 3.277(5) Å, C–H···O
140.36(2)°] intermolecular hydrogen bonds and CuII···O(1)
weak interactions, which link the discrete units to form a
2D supramolecular structure together with the N(2)–
H···N(6) [N–N 3.130(4) Å, N–H···N 176.69(3)°] inter-
molecular hydrogen bonds (Figure 5, b). In this complex,
the uncoordinated ClO4– anions are an essential part of the
structure, which act as a key linker in the 2D supra-
–
molecular structure, similar to BF4 in the reported com-
plex [(CH3OH)2Co(L)4](BF4)4.[26] However, the ethonal
molecule present in complex 4 only functioned as an ac-
ceptor of intramolecular hydrogen bonds between the oxy-
gen atoms of ethonal and amino nitrogen atoms of the li-
gand, which has little influence on the extended structure
of complex 4.
–
at 1131 cm–1 for the noncoordinated ClO4 anions. The
bands appearing below 600 cm–1 may be assigned to the M–
N frequencies for the three complexes.
The thermogravimetric analysis (TGA) reveals the weight
loss of 2 occurs in two stages. The first stage occurs between
208.7 and 428.6 °C with a weight loss of 66.99%, which is
It is worth noting that 4 has a higher stability than the equivalent to the loss of the ligands (calculated to be
organic ligand owing to the fact that the single point energy 66.83%). The total thermal effect of decomposition and
(–2397.66179 hartree) of 4 is far lower than that of 1. The oxidation of the ligand causes an exothermic peak at
HOMO–LUMO energy gap of 4 is 0.1332 eV, and the li- 216.5 C. When the temperature is above 440 °C, the
gand has a high contribution to the front orbit of 4. In AgNO3 begins to decompose and metal silver is the final
addition, comparing this new ligand with 2,2Ј-dipyridyl- product, which constitutes 20.86% (calculated to be
amine, we find that there are several differences between 20.93%). In contrast to 2, the TGA shows that the weight
them: (i) 2,3Ј-dipyridylamine is a monodentate or bidentate of 3 remains almost unchanged from 40 to 180 °C. In the
ligand, and 2,2Ј-dipyridylamine is a chelate or monodentate temperature range 180–400 °C, the complex undergoes a
ligand[27] in their amine form; (ii) 2,3Ј-dipyridylamine is an large weight loss of 76.67%, which represents weight loss
asymmetrical V-shaped molecule that may produce different from L and the methacrylic groups (calculated to be
conformers in complexes, and 2,2Ј-dipyridylamine is a sym- 79.12%). The DSC curve shows an exothermic peak at
metrical molecule that generally has three coordination 218.4 °C, and the final product is CuO in 21.33% yield (cal-
modes, syn-syn, syn-anti, and anti-anti;[28] (iii) the syn-syn culated to be 20.88%). Complex 4 has undergone two steps
conformation of 2,2Ј-dipyridylamine builds many linear of weight loss. The first weight loss occurs at 50–180 °C,
conformations of metal complexes in its deprotonated corresponding to the loss of ethanol molecules. The higher
form,[29] and 2,3Ј-dipyridylamine can not form linear chains temperature for the release of ethanol molecules is due to
of metal atoms.
the strong hydrogen bonds involving ethanol molecules in
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Polymers or Supramolecules Generated From a New V-Shaped Bis-monodentate Ligand
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4. At this step, the experimental percentage weight loss is
8.01% (calculated to be 8.85%). The following steps of
Conclusions
In summary, a new V-shaped ligand 1 has been designed
and synthesized. Density functional calculations at the
B3LYP level of theory provide a satisfactory forecast for
coordination properties of the ligand with metal ions. That
is, two relatively stable conformers of the ligand combine
with metal ions by different coordination modes. On the
basis of ligand 1, we have synthesized three novel com-
plexes, {[Ag (L)2]NO3}n (2), [Cu2(L)2(maa)4]n (maa = meth-
acrylic acid) (3), and [Cu(L)4](ClO4)2·2CH3CH2OH (4).
Interestingly, polymers 2 and 3 assume a 1D helical struc-
ture and a linear framework, respectively, and 4 has a 2D
supramolecular structure. Although the two relatively stable
configurations of the ligand have very similar single-point
energies and charge distributions, they form different coor-
dination modes in the three complexes. These results indi-
cate that the steric factors of the N atoms play important
roles in the coordination modes of the dipyridylamine li-
gand, which may help us to understand the influence of
organic spacers in determining the type and topology of the
product.
weight loss represent the pyrolysis of the organic ligand.
The residues above 500 °C have a composition of CuO, and
the observed residue percentage is 7.31% (calculated to be
7.69%).
Magnetic Properties
Variable-temperature magnetic susceptibility measure-
ments over a 5–300 K range were carried out for 3. The
temperature dependence of magnetic susceptibilities χM and
χMT of complex 3 is shown in Figure 6. It should be noted
that polymer 3 exhibits two types of magnetic exchange in-
teraction between two CuII ions; one is through short brid-
ges via the methacrylic groups and the other is through a
long bridge via L. Actually, because of the long L ligand
fragment, the possibility of overlap of the magnetic orbital
through the C and N atoms of L is negligible. Hence, the
Cu2(maa)4 unit of paddle-wheel type plays an important
role in the magnetic properties of polymer 3. This type of
antiferromagnetic interaction is strong because unpaired
electron density from both Cu ions is transferred to the
same orbital of the bridging methacrylic groups. The χM
curve is typical for a very strong antiferromagnetic coupling
with a small amount of paramagnetic impurities: the molar
magnetic susceptibility decreases to a minimum and then
Experimental Section
Physical Measurements: Elemental analyses (C,H,N) were deter-
mined with a Perkin–Elmer 240C elemental analyzer. Infrared spec-
suddenly increases when the temperature is lowered, at- tra on KBr pellets were recorded with a Bruker EQUINOX-55
spectrometer in the range of 4000–400 cm–1. Thermal analyses were
taining a maximum. The magnetic datafit to a Bleaney–
Bowers equation,[31,32] which was derived from the spin
performed with a Netzsch STA 449C microanalyzer with a heating
rate of 10 °C·min–1 under air. Magnetic measurements were carried
out on a polycrystalline sample with a SQUID magnetometer op-
Hamiltonian H = –JS1S2. The best-fit parameters are –2J
= 316 cm–1, g = 2.09, and R = 6.8·10–4 (R = Σ[(χMT)obs
–
erating in the 5–300 K temperature range with an applied field of
5 kOe. Diamagnetic corrections were estimated from Pascal con-
stants. 1H NMR spectra were recorded with a Varian INOVA 400-
MHz spectrometer. Electronic spectra were recorded with a Cary
300 Bio UV/Visible spectrophotometer. Mass spectra were ob-
tained with a JEOL HX-110 HF double focusing spectrometer op-
erating in the positive ion detection mode.
(χMT)calc]2/Σ[(χMT)obs 1/2). In contrast to the reported dinu-
]
clear CuII carboxylates, such as Cu2(C10H9O2)4(C2H5OH)2
(–2J = 242 cm–1),[33] Cu2(C7H15COO)4 (–2J = 320 cm–1),
and Cu2(C7H15COO)4(C6H7N)2 (–2J = 300 cm–1),[34] poly-
mer 3 (–2J = 316 cm–1) shows a considerably stronger anti-
ferromagnetic interaction.
Figure 6. Plot of χM (᭺) (left scale) and χM T (ᮀ) (right scale) per CuII ion vs. T for 3. The solid lines represent the best fit to the
modified Bleaney–Bowers expression.
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The Synthesis of Ligand 1: The reagents and solvents were pur-
chased from commercial sources (Aldrich) and used as received.
The 2,3Ј-dipyridylamine ligand was obtained as follows (Scheme 1):
2-aminopyridine (2.80 g, 34.8 mmol) and NaOBu (6.90 g,
72.9 mmol) were added to a 200 mL flask under nitrogen. Then the
solution of 3-bromopyridine (3.44 mL, 34.8 mmol) and dry ben-
zene (100 mL) were added to the container. The resulting solution
was stirred for 72 h under reflux, and then cooled to room tempera-
ture. The original product was filtered and washed with dry ben-
zene and water several times. The final product was purified by
column chromatography on silica gel (dichloromethane/hexane,
1:1) to afford a colorless crystalline solid (4.16 g, 69.82%).
C10H9N3 (171.20): calcd. C 70.17, H 5.263, N 24.54; found C 69.98,
Scheme 1. The preparation of ligand 2,3Ј-dipyridylamine.
3
3
3
1 H, J = 5.8, J = 5.4, 4-H), 7.27 (d, 1 H, J = 5.8 Hz, 5-H), 6.80
3
3
(d, 2 H, J = 6.3 Hz, 6-H), 8.25 (d, 2 H, J = 3 Hz, 7-H) ppm.
The Synthesis of the Complexes
The formation of 2, 3, and 4 with experimental conditions are
shown in Scheme 2, their syntheses are given in the sequel.
H 5.210, N 24.66. IR (KBr): ν
= 3535 (s), 3434 (s), 3294 (s),
{[Ag(L)2]NO3}n (2):
A solution of silver() nitrate (16.9 mg,
˜
max
3172 (s), 3071 (m), 3000 (m), 1643 (m), 1592 (m), 1503 (s), 1476 0.1 mmol) in CH2Cl2 (10 mL) was added to a solution of L
(s), 1421 (s), 1270 (m), 1210 (m), 1051 (s), 902 (m), 824 (m), 732.44
(17.1 mg, 0.1 mmol) in CH2Cl2 (10 mL). The reaction mixture was
stirred at 25 °C for 1 h, and then the solvent was removed under
reduced pressure. The resulting white powder was partially dis-
solved in acetonitrile (5 mL) (CH3CN). The mixture was filtered,
(s), 677 (m), 574 (w) cm–1. UV/Vis (λ/nm): 320, 260, 220. MS
1
(FAB): m/z (%) = 171.2 (L). H NMR (CDCl3): δ = 8.59 (s, 1 H,
3
1-H), 7.05 (s, 1 H, 2-H), 8.02 (d, 1 H, J = 4.4 Hz, 3-H), 7.54 (dd,
Scheme 2. The formation of 2, 3, and 4 with experimental conditions.
2444
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Eur. J. Inorg. Chem. 2006, 2437–2446

Polymers or Supramolecules Generated From a New V-Shaped Bis-monodentate Ligand
FULL PAPER
Table 1. Crystal data and structure refinements for 1–4.
Complex
1
2
3
4
Empirical formula
Formula mass
Temperature [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C10H9N3
171.20
273(2)
orthorhombic
Pbca
9.2018(3)
11.9210(5)
15.6331(6)
90
C10H8AgN4O3
340.07
273(2)
monoclinic
P21/n
8.293(3)
14.174(4)
9.751(3)
90
101.064(5)
90
1125.0(6)
4
2.008
1.798
C26H29Cu2N3O8
638.68
273(2)
C44H48Cl2CuN12O10
1039.38
296(2)
monoclinic
C2/c
27.767(4)
10.7067(14)
18.144(2)
90
115.891(9)
90
4852.6(11)
4
1.423
0.629
21562
triclinic
¯
P1
9.092(8)
9.229(8)
17.335(15)
93.786(13)
91.981(15)
97.735(14)
1437(2)
2
90
90
γ [°]
V [Å3]
1714.87(11)
8
1.326
0.084
720
Z
Dcalcd.[g·cm–3]
µ [mm–1]
F [000]
1.572
0.829
714
668
θ [°]
2.61–25.09
2.57–29.15
2769/0/164
1.045
2.23–29.19
6693/0/357
0.999
1.63–25.10
4315/0/314
1.073
Data/restraints/parameters 1521/0/119
Goodness-of-fit on F2
1.043
0.0417, 0.1069
[a]
R1 wR2 [I Ͼ 2σ(I)]
0.0220, 0.0581
0.0455, 0.1268
0.0474, 0.1205
[a] R1 = Σ(||Fo| – |Fc|)/Σ|Fo|; wR2 = [Σw(Fo – Fc ) /Σw(Fo2)2]1/2
.
2
2 2
and diethyl ether vapor was diffused into this solution. After se-
veral days, suitable single crystals for X-ray diffraction could be
obtained from the acetonitrile solution. Yield: 83.98% (28.56 mg).
C10H8AgN4O3 (340.07): calcd. C 35.19, H 2.34, N 16.42; found C
35.13, H 2.40, N 16.67.
Table 2. Selected bond lengths [Å] and angles [°] for 1–4.
Ligand 1
C(6)–N(3)
1.324(2)
1.339(2)
129.87(13)
C1–N(1)
C(5)–N(1)
1.329(2)
1.350(2)
C(10)–N(3)
C(1)–N(2)–C(7)
[Cu2(L)2(maa)4]n (3): Cu2(maa)4·2H2O was prepared according to a
similar method reported previously in the literature.[35] A methanol
solution (20 mL) of L (17.1 mg, 0.1 mmol) was slowly added to
a solution of Cu2(maa)4·2H2O (50.4 mg, 0.1 mmol) dissolved in
methanol/ethanol (20 mL, v/v = 1:1). The resultant solution was
allowed to evaporate slowly for several days at room temperature,
and block-shaped green crystals of 1 were obtained. Yield: 66.82%
(42.63 mg). C26H29Cu2N3O8 (638.68): calcd. C 50.13, H 5.48, N
10.96; found: C 50.12, H 5.45, N 10.94.
Complex 2
Ag(1)–N(1)
N(1)–Ag(1)–N(3A)
2.193(2)
165.09(6)
Ag(1)–N(3A)
2.196(2)
Complex 3
Cu(1)–O(7)A
Cu(1)–O(6)
Cu(1)–N(1)
Cu(2)–N(3)
O(7A)–Cu(1)–O(6)
O(6)–Cu(1)–O(5)
O(7A)–Cu(1)–N(1)
O(4)–Cu(2)–N(3)
O(3)–Cu(2)–N(3)
1.960(3)
1.964(3)
2.193(3)
2.183(3)
89.64(12) O(6)–Cu(1)–O(8)
90.33(12) O(8)–Cu(1)–O(5)
94.32(11) O(6)–Cu(1)–N(1)
98.89(13) O(1)–Cu(2)–N(3)
95.11(12) O(2)–Cu(2)–N(3)
Cu(1)–O(8)
Cu(1)–O(5)
Cu(1)–Cu(1A)
Cu(2)–Cu(2A)
1.970(3)
1.970(3)
2.6280(19)
2.6416(18)
168.32(10)
88.27(12)
93.92(12)
96.92(12)
93.12(13)
[Cu(L)4](ClO4)2·2CH3CH2OH (4): The solution of Cu(ClO4)2·
6H2O (37.05 mg, 0.1 mmol) in ethanol (10 mL) was carefully lay-
ered on top of a solution of L (68.4 mg, 0.4 mmol) in chloroform
(10 mL) in a test tube. After several days at room temperature,
yellow green single crystals appeared at the boundary between eth-
Complex 4
anol and chloroform with
a yield of 63.66% (66.17 mg).
C44H48Cl2CuN12O10 (1039.38): calcd. C 50.85, H 4.65, N 16.17;
found C 50.87, H 4.60, N 16.14.
Cu(1)–N(1)
Cu(1)–N(4)
N(1)–Cu(1)–N(1A)
2.011(2)
2.019(2)
89.14(14) N(1)–Cu(1)–N(4)
Cu(1)–N(1A)
Cu(1)–N(4A)
2.011(2)
2.019(2)
90.23(10)
Crystal Data Collection and Refinement: Diffraction experiments
for 1, 2, 3, and 4 were carried out with Mo-Kα radiation using a
Bruker SMART APEXCCD diffractometer at 273(2) K for 1, 2, 3,
and 296(2) K for 4. A summary of the crystallographic data and
structure refinement is given in Table 1, and selected bond lengths
and angles of the four complexes are listed in Table 2. All structures
were solved by direct methods and refined with the full-matrix le-
ast-squares technique on F2 using the SHELXS-97[36] and
SHELXL-97[37] programs. All non-hydrogen atoms were refined
anisotropically.
N(1A)–Cu(1)–N(4A) 90.23(10) N(4)–Cu(1)–N(4A) 90.42(13)
Symmetry code: A: x–1/2, –y+1/2, –z for 1, –x+3/2, y–1/2,
–z+1/2 for 2, –x+2, –y+2, –z for 3 and –x+1, y, –z+3/2 for 4.
Calculation Details: The single-point energy and the orbit calcula-
tions based on the geometry of the free ligand and complex 4 were
optimized by the DFT method using the B3LYP/LanL2DZ basis
set in the Gaussian 03 program.[38] The data analyses were per-
formed with Hyperchem 7.5 and GaussView 3.0.
X-ray crystallographic data in CIF format for the structures re-
ported in this paper have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC-277949 (for 1), -277950 (for 2), Acknowledgments
-277951 (for 3), and -294858 (for 4). These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
This work was supported by the National Natural Science Founda-
tion of China (Grant No. 20471048) and TRAPOYT.
Eur. J. Inorg. Chem. 2006, 2437–2446
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2445

C. H. Zhou, Y. Y. Wang, D. S. Li, L. J. Zhou, P. Liu, Q. Z. Shi
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Received: January 18, 2006
Published Online: April 20, 2006
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Eur. J. Inorg. Chem. 2006, 2437–2446