Three copper(II) complexes constructed from a new 1,3,5-triazine derivative ligand

Article abstract of DOI:10.1016/j.poly.2006.07.012

Three new complexes {[Cu(dpdapt)(Hhbd)] · 6H₂O}_n (1) (dpdapt = N,N′-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd = 2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO₄)] · 2H₂O (2) and [Cu(dpdapt)(oxa)] · H₂O (3) (oxa = oxalate dianion) have been synthesized and structurally characterized. The non-covalent interactions of π-π stacking and hydrogen bonding extend complexes 1-3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels. The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.

Full text of DOI:10.1016/j.poly.2006.07.012

Polyhedron 25 (2006) 3533–3542
www.elsevier.com/locate/poly
Three copper(II) complexes constructed from a new
1,3,5-triazine derivative ligand
a
a
a,
a
a
Ya-Pan Wu , Cui-Juan Wang , Yao-Yu Wang *, Ping Liu , Wei-Ping Wu ,
a
b
Qi-Zhen Shi , Shie-Ming Peng
a
Department of Chemistry, Shaanxi Key Laboratory of Physico-inorganic Chemistry, Northwest University, Xi0an 710069, PR China
b
Department of Chemistry, National Taiwan University, Taipei, Taiwan
Received 2 June 2006; accepted 3 July 2006
Available online 25 July 2006
Abstract
Three new complexes {[Cu(dpdapt)(Hhbd)] Æ 6H2O}n (1) (dpdapt = N,N0-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd =
2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO4)] Æ 2H2O (2) and [Cu(dpdapt)(oxa)] Æ H2O (3) (oxa = oxalate dianion) have been
synthesized and structurally characterized. The non-covalent interactions of p–p stacking and hydrogen bonding extend complexes
1–3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D
framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework
encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels.
The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Cu(II) complexes; Crystal structure; Self-assembly; Polymeric chain; Hexameric water clusters; 1D open channel
1. Introduction
plexes [15]. Theoretical calculations reveal that the dpdapt
ligand possesses two structural features: (1) It functions as
a bis-bidentate or a tridentate ligand forming supramolec-
ular complexes. (2) It can possibly display syn–syn–syn–
syn, syn–syn–anti–anti and anti–anti–anti–anti coordina-
tion modes in complexes [15]. As an extension of our
previous work, three new complexes, formulated as
{[Cu(dpdapt)(Hhbd)] Æ 6H2O}n (1), [Cu(dpdapt)(SO4)] Æ
2H2O (2) and [Cu(dpdapt)(oxa)] Æ H2O (3), have been suc-
cessfully synthesized and characterized by single-crystal
X-ray diffraction. The dpdapt ligand adopts an all-anti
configuration in the crystal structures of the three copper
(II) complexes. Complexes 2 and 3 show 2D wavelike
In recent years, tremendous effort has been devoted to
the rational design of metal coordination complexes with
polymeric architectures from transition metals and multi-
functional ligands [1–4]. Rapidly great advances have
been made and a wide array of polymeric networks, and
e.g., chains [5–7], ladders [8], helices [9] and honeycombs
[10] have been obtained. Several factors are known to
influence the architecture of a polymer [9,11–14], notably
the ligand nature (connectivity, topology), the counteri-
ons, and the reaction conditions such as solvent, temper-
ature, and pressure. Along this line, in our group we have
synthesized a new modified 1,3,5-triazine ligand N,N0-
di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine (dpdapt)
(see Chart 1) as a building block for supramolecular com-
2ꢀ
2ꢀ
networks, in which SO4 and C2O4
display chelate
coordination modes, respectively. While complex 1 self-
assembles into a 1D polymeric chain by dicarboxylate
bridges and exhibits a 3D framework with 1D open chan-
nels. Unexpectedly, we found cyclic (H2O)6 clusters
encapsulated within the host framework of 1. These
clusters are connected into 1D arrays by supramolecular
*
Corresponding author. Tel.: +86 29 88303097; fax: +86 29 88303798.
E-mail address: wyaoyu@nwu.edu.cn (Y.-Y. Wang).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.07.012

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Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
2.2. Synthesis of {[Cu(dpdapt)(Hhbd)] Æ 6H2O}n (1)
A methanol suspension (15 mL) of dpdapt (68.2 mg,
0.2 mmol) was added slowly dropwise to methanol
(15 mL) dissolved Cu(Hhbd) (42.3 mg, 0.22 mmol). The
resulting mixture was stirred for 30 min and then filtered.
The aqua filtrate solution was transferred a tube and evap-
orated at room temperature. After two months, deep blue
crystals were obtained. Yield: 65%. Anal. Calc. for
C23H31CuN7O11 (645.09): C, 41.78; H, 4.74; N, 14.83.
Found: C, 41.91; H, 4.70; N, 14.72%. IR spectrum
(cmꢀ1): 3425(w), 2923(w), 1640(s), 1592(m), 1502(w),
1469(s), 1429(s), 1381(s), 1242(w), 1195(w), 1157(w),
1023(w), 891(w), 821(w), 773(m), 703(w), 633(w), 525(w).
2.3. Synthesis of [Cu(dpdapt)(SO4)] Æ 2H2O (2)
CuSO4 Æ 5H2O (50.0 mg, 0.2 mmol) was dissolved in
methanol (15 mL) and mixed with a methanol suspension
(15 mL) of dpdapt (68.2 mg, 0.2 mmol) and then stirred
for 1 h. Diffused in Et2O after filtration, finally blue crystals
were produced. Yield: 59%. Anal. Calc. for C19H19Cu-
N7O6S (537.01): C, 42.50; H, 3.57; N, 18.26. Found: C,
42.32; H, 3.43; N, 18.38%. IR spectrum (cmꢀ1): 3493(w),
2925(w), 1636(s), 1587(s), 1502(m), 1469(s), 1434(s),
1242(w), 1195(w), 1162(w), 977(w), 867(w), 832(w),
770(m), 696(w), 634(w), 517(w), 432(w).
Chart 1. N,N0-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine(dp dapt).
association running along the 1D open channels. A recent
report described a discrete ice-like hexameric water cluster
stabilized by a cyano-bridged trimetallic complex [16,17].
Here, the hexameric water cluster is unique and unlike
the previously published hexamer water clusters [16–22].
There is mounting evidence of the presence of ordered
water clusters in the active clefts of proteins such as
dimeric haemoglobin, crambin, actinidin and carbonic
anhydrase, however, positional information for the waters
and their nature is still preliminary [16,17]. As water
molecules play an important role in contributing to con-
formation, stability, function and dynamics of biomacro-
molecules, the new 1D water clusters arrays may provide
insight into the hydrogen-bonding motif of the aqueous
environment in living systems and enhance understanding
of the 1D water morphologies.
2.4. Synthesis of [Cu(dpdapt)(oxa)] Æ H2O (3)
Cu(oxa) (30.3 mg, 0.2 mmol) was dissolved in methanol
(15 mL) and mixed with a methanol suspension (15 mL) of
dpdapt (68.2 mg, 0.2 mmol) and then stirred for 2 h. Green
crystals 3 were obtained after the mixture was allowed to
stand at room temperature for a month. Yield: 60%. Anal.
Calc. for C21H17CuN7O5 (510.96): C, 51.16; H, 3.07; N,
19.89. Found: C, 51.33; H, 2.94; N, 19.73%. IR spectrum
(cmꢀ1): 3411(w), 2913(w), 1665(s), 1573(m), 1510(w),
1466(s), 1385(s), 1269(w), 1240(w), 1202(w), 1157(w),
1115(w), 1059(w), 1023(w), 779(m), 706(w), 627(w), 524(w).
2. Experimental
2.1. Materials and physical measurements
2.5. Crystallographic data collection and structure
determination
The new ligand N,N0-di(2-pyridyl)-2,4-diamino-6-
phenyl-1,3,5-triazine was synthesized according to the
literature method [15]. All other reagents and solvents
employed were commercially available and used as received
without further purification. Infrared spectra on KBr pel-
lets were recorded on a Nicolet 170SX FT-IR spectropho-
tometer in the range 4000–400 cmꢀ1. Electronic spectra
were taken on a Cary 300 Bio UV–Vis spectrophotometer
in the range 200–800 nm at ambient temperature. Elemen-
tal analysis was conducted with a Perkin–Elmer model
240C instrument. Fluorescence experiments used a HIT-
ACHI F-4500 Fluorescence spectrophotometer and were
measured in methanol. Thermal analysis was performed
on a NETZSCH STA 449C microanalyzer in a nitrogen
Single-crystal X-ray diffraction of complexes 1, 2 and 3
were performed on a BRUKER SMART 1000 CCD dif-
fractometer equipped with a graphite crystal monochroma-
tor situated in the incident beam for data collection.
Crystallographic data were collected with Mo Ka radiation
˚
(k = 0.71073 A) for the three complexes at 296(2) K. The
structures were solved by direct methods and refined by
full-matrix least-squares method on F2 values using SHELXL
97 and SHELXL 97 programs, respectively [23,24]. Single
crystal X-ray structural analysis shows the hydroxyl group
might lie on one of the two adjacent methylenes, which
would present the hydroxyl group disordered in a half-
occupied position in complex 1. All non-hydrogen atoms
atmosphere at a heating rate of 10 ꢁC minꢀ1
.

Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
3535
were refined with anisotropic displacement parameters.
3. Results and discussion
Hydrogen atoms of all water molecules in complex 1 were
not visible in the difference Fourier map. In complexes 2
and 3, the hydrogen atoms of the lattice water molecules
could be trustfully inferred from analysis of the difference
Fourier map. Crystal data, data collection and refinement
parameters for three complexes are shown in Table 1,
and selected bond lengths and bond angles are listed in
Table 2.
3.1. Description of the crystal structures
A single crystal X-ray structural analysis shows 1
crystallizes in monoclinic space group C2/c. Each copper
atom has a slightly distorted [CuN3O2] trigonal bipyramid
geometry. Owing to the symmetry of the ligand, each cop-
per atom lies on a two-fold axis in the subunit (Fig. 1). The
Table 1
Crystallographic data and structure refinement for 1, 2 and 3
Complex
1
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C23H31CuN7O11
645.09
296(2)
monoclinic
C2/c
16.372(3)
17.534(4)
10.867(2)
116.330(3)
2796.1(10)
4
C19H19CuN7O6S
537.01
296(2)
orthorhombic
Pnnm
C21H17CuN7O5
510.96
296(2)
monoclinic
P21/n
9.7005(16)
17.487(3)
13.373(2)
110.366(3)
2126.7(6)
4
˚
a (A)
15.911(2)
11.4246(15)
12.2370(16)
90
2224.5(5)
4
1.603
1.128
1100
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg mꢀ3
)
1.532
0.852
1340
1.596
1.078
1044
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm)
0.35 · 0.08 · 0.04
0.71073
0.29 · 0.20 · 0.10
0.71073
0.20 · 0.14 · 0.06
0.71073
˚
k (A)
h Range (ꢁ)
Reflections collected
1.81–25.04
7046
2.10–25.09
10914
2.00–25.10
10792
Limiting indices
ꢀ16 6 h 6 19,
ꢀ19 6 k 6 20,
ꢀ12 6 l 6 12
0.0503
1.044
0.0548, 0.1419
0.0756, 0.1561
ꢀ18 6 h 6 18,
ꢀ13 6 k 6 10,
ꢀ14 6 l 6 14
0.0377
1.038
0.0372, 0.0934
0.0478, 0.1002
ꢀ11 6 h 6 8,
ꢀ19 6 k 6 20,
ꢀ15 6 l 6 15
0.0483
1.016
0.0483, 0.1148
0.0854, 0.1352
Rint
Goodness-of-fit on F2
b
R1a, wR2 [I > 2r(I)]
R1, wR2 (all data)
P
P
a
R = iFoj ꢀ jFci/ jFoj.
P
P
2
2 1=2
b
wR2 ¼ ½ ½wðF 2o ꢀ F c2Þ ꢁ= ½ðF 2oÞ ꢁꢁ
.
Table 2
Selected bond lengths (A) and angles (ꢁ) of complexes 1, 2 and 3
˚
1
2
3
Bond lengths
Cu1–N1#1
Cu1–N1
Cu1–N3
Cu1–O1#1
Cu1–O1
1.978(3)
1.978(3)
2.032(4)
2.096(3)
2.096(3)
Cu1–N1
Cu1–N1#2
Cu1–N4
Cu1–O2
Cu1–O3
1.979(2)
Cu1–N1
Cu1–N3
Cu1–N7
Cu1–O1
Cu1–O2
2.013(3)
1.954(3)
2.068(3)
1.912(3)
2.064(3)
1.979(2)
1.949(3)
2.208(3)
1.961(2)
Bond angles
N3–Cu1–O1
N3–Cu1–O1#1
O1–Cu1–O1#1
N1–Cu1–N1#1
134.3(9)
134.3(9)
91.6(2)
N1–Cu1–N1#2
O2–Cu1–N1#2
N1–Cu1–O2
130.4(5)
N1–Cu1–N7
N1–Cu1–O2
N7–Cu1–O2
N3–Cu1–O1
122.6(1)
133.4(1)
103.9(2)
170.9(1)
114.5(8)
114.5(8)
163.2(9)
174.2(2)
N4–Cu1–O3
Hydrogen bonds
N2–Hꢂ ꢂ ꢂO2a
O3–Hꢂ ꢂ ꢂO4
2.832(4)
2.729(2)
2.819(3)
N2–Hꢂ ꢂ ꢂO4b
O4–Hꢂ ꢂ ꢂO1c
O4–Hꢂ ꢂ ꢂO4
2.794(5)
2.738(4)
2.763(5)
O9–Hꢂ ꢂ ꢂO3d
O9–Hꢂ ꢂ ꢂO4e
N2–Hꢂ ꢂ ꢂO9f
2.687(5)
2.855(5)
2.730(5)
O3–Hꢂ ꢂ ꢂO6
Symmetry codes: #1: ꢀx + 1, y, ꢀz + 1/2; #2: x, y, ꢀz + 1; (a) ꢀx + 1, ꢀy + 2, ꢀz + 1; (b) x, y, ꢀz + 1; (c) x + 1/2, ꢀy + 1/2, z + 1/2; (d) x, y, z ꢀ 1;
(e) x + 1/2, ꢀy + 1/2, z ꢀ 1/2; (f) x ꢀ 1, y, z + 1.

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Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
Fig. 1. Repeat unit of the infinite coordination polymer of 1. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms and water
molecules are omitted for clarity.
copper (II) ion is coordinated to three nitrogen atoms from
the dpdapt ligand, and two oxygen atoms from two differ-
ent Hhbd dianions. The two pyridyl rings of the dpdapt
ligand are nearly coplanar with a dihedral angle of ca.
4.5ꢁ. It is worthwhile to note that the Hhbd dianions bridge
copper centers to create a 1D polymeric chain running
along the a axis with an adjacent Cuꢂ ꢂ ꢂCu distance of
˚
8.957(2) A. The dpdapt ligands lie on both sides of this
1D chain in an antiparallel fashion. Interestingly, these
1D polymeric chains self-assemble to generate a 2D
Fig. 2. View of the 2D supramolecular structure of complex 1 self-assembled by hydrogen bonds and p–p stacking interactions.

Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
3537
supramolecular architecture under the direction of hydro-
associated by strong O–Hꢂ ꢂ ꢂO hydrogen bonds into cyclic
centrosymmetric hexamers that adopt a hexagon configu-
ration (Fig. 4(a)). The geometric parameters of the hexa-
mers are summarized in Table 3. The average distance
˚
gen bonding (Namido–Hꢂ ꢂ ꢂOcarbonyl, 2.832(4) A) and p–p
stacking interactions between the pyridyl and triazine ring
˚
with a center-to-center distance of 3.55 A and with a dihe-
˚
dral angle of ca. 2.7ꢁ (Symmetry code: ꢀx, ꢀy, ꢀz) (Fig. 2).
There are also significant hydrogen bonds involving hydro-
xyl oxygen atoms (O3AD, O3BD) of the dicarboxylate
ligands and aqua oxygen atoms (O4AC, O6AC, O4CC,
O5AC, O5BC, O6CC) from lattice water molecules. These
observed hydrogen bonding interactions, with the donor–
acceptor distances, are shown in Tables 2 and 3. These
interactions generate the final 3D framework that feature
between the oxygen atoms is 2.838(6) A, which is very
˚
similar to the Oꢂ ꢂ ꢂO distance of 2.85 A in liquid water
[25]. Unlike the previously reported hexamer clusters
[16–22], here it is noteworthy that the water hexamer clus-
ters are self-assembled along the channels by interhex-
amer O6ꢂ ꢂ ꢂO6 hydrogen bonds to give extended 1D
arrays consisting of six-membered rings of water
(Fig. 4(a)). When viewed down the crystallographic c axis,
more interestingly, an adjacent hexameric water cluster is
not complete superposition but is in a slipped stacking
mode (Fig. 4(b)).
˚
1D open channels (14.626 · 15.110 A) when viewed along
the c axis (Fig. 3).
The most remarkable feature in 1 is that these 1D
channels are occupied by six water molecules, which are
Additionally, the hydrogen bonding between water mol-
ecules and the hydroxyl oxygen atoms of dicarboxylate
ligands plays an important role in contributing to the sta-
bility of the 1D hexameric water cluster arrays. This supra-
molecular association of water molecules in arrays is
presumably enforced by the shape and the condition of
the interior of the host’s channel. These results further
illustrate the structural diversity possible for water clusters
and the sensitive dependence of their structures on the nat-
ure of their environment.
Table 3
˚
Geometrical parameters [A, ꢁ] for the cyclic water hexamers in complex 1
O–Hꢂ ꢂ ꢂO
Oꢂ ꢂ ꢂO
Oꢂ ꢂ ꢂOꢂ ꢂ ꢂO
O4ꢂ ꢂ ꢂO5ꢂ ꢂ ꢂO6
O5ꢂ ꢂ ꢂO6ꢂ ꢂ ꢂO4
O6ꢂ ꢂ ꢂO4ꢂ ꢂ ꢂO5
O4–Hꢂ ꢂ ꢂO5a
O4–Hꢂ ꢂ ꢂO6
O5–Hꢂ ꢂ ꢂO6
O6–Hꢂ ꢂ ꢂO6
2.783(9)
2.844(5)
2.887(5)
2.633(1)
107.44(2)
128.73(2)
123.72(2)
Symmetry codes: (a) ꢀx + 3/2, y ꢀ 1/2, ꢀz + 3/2.
Fig. 3. View of the 3D supramolecular framework of complex 1 that contains 1D open channels encapsulating arrays of cyclic (H2O)6 clusters.

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Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
Fig. 4. (a) Extended 1D array consisting of six-membered rings of water molecules in the 3D framework of complex 1. The hydrogen bond Oꢂ ꢂ ꢂO
˚
distances [A]: O5ABꢂ ꢂ ꢂO4AB, 2.783(9); O4ABꢂ ꢂ ꢂO6AB, 2.844(5); O6ABꢂ ꢂ ꢂO5BB, 2.887(5). (b) View of hexameric water cluster array in the 1D open
channels of complex 1. Black and grey represent the different array of an adjacent cyclic (H2O)6 cluster. Dotted lines show the hydrogen bonding between
water molecules.
dianion and in a tridentate fashion to one triazine-N atom
(N4) and two pyridine-N atoms (N1, N1A). The two
pyridyl rings of the dpdapt ligand are non-coplanar with
a dihedral angle of ca. 52.2ꢁ. In mononuclear [Cu(dpdapt)
(SO4)] Æ 2H2O, the bond angles N1–Cu1–N1A (130.4(5)ꢁ),
N1A–Cu1–O2 (114.5(8)ꢁ) and O2–Cu1–N1 (114.5(8)ꢁ)
add up to approximately to 360ꢁ and the angle N4–Cu1–
O3 is close to 180ꢁ, so the coordinated geometry of the cen-
tral copper can be described as a distorted trigonal bipyra-
mid configuration, Cu1, N1, N1A, O2 forming the
equatorial plane and N4, O3 occupying the axial positions.
The lattice water molecules act as a hydrogen bond donor/
acceptor, forming hydrogen bonds with the oxygen atoms
of the sulfate anion and the amido nitrogen atoms (as
shown in Table 2), to give rise to a 2D network structure
in the ac plane as shown in Fig. 6.
Complexes 3 and 1 have the same crystal system and
different space group, and complex 3 displays a P21/n
space group. The central copper(II) is five-coordinate
being bonded in a bidentate fashion to two oxygen atoms
(O1, O2) of an oxalate dianion and in a tridentate fashion
to one triazine-N atom (N3) and two pyridine-N atoms
(N1, N7) (Fig. 7). The dihedral angle between the two
Fig. 5. ORTEP view of [Cu(dpdapt)(SO4)] Æ 2H2O (2) with 30% proba-
bility ellipsoids. The water molecules are omitted here.
pyridyl ring planes of the dpdapt ligand is 38.9ꢁ. The
bonds distance to the terminal triazine N3 (Cu1–N3) is
˚
1.954(3) A and the distance with the pyridyl donors N1
˚
and N7 are 2.013(3) and 2.068(3) A, respectively. The
The molecular structure of 2 is shown in Fig. 5. The
complex crystallizes in the orthorhombic space group
Pnnm. The Cu1 is five-coordinate being bonded in a biden-
tate fashion to two oxygen atoms (O2, O3) of the sulfate
˚
average Cu–N bond length is observed to be 2.011(9) A,
which is longer than that of 1. Both Cu–N bond lengths
are typical of those found for five-coordinate Cu(II)-l-

Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
3539
Fig. 6. View of the 2D network of [Cu(dpdapt)(SO4)] Æ 2H2O (2) constructed through two kinds of hydrogen bonds (O–Hꢂ ꢂ ꢂO, N–Hꢂ ꢂ ꢂO) in the ac plane.
Fig. 7. Perspective view of the coordination environment of the copper atom in the complex [Cu(dpdapt)(oxa)] Æ H2O (3). Thermal ellipsoids are drawn at
the 30% probability level. One water molecule is omitted here.
pmea analogues [26]. The adjacent monomeric entity is
interconnected through hydrogen bonding interactions
involving the oxygen atoms of the lattice water molecule
and the oxalate dianion and the amido nitrogen atoms
(Table 2), to generate a 2D wavelike network in the ac
plane (Fig. 8).

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Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
˚
Fig. 8. View of the 2D supramolecular network of [Cu(dpdapt)(oxa)] Æ H2O (3) formed by hydrogen bonds (O9AL–Hꢂ ꢂ ꢂO3AJ, 2.687(5) A, O9AL–
˚
˚
Hꢂ ꢂ ꢂO4AB, 2.855(5) A; N2BD–Hꢂ ꢂ ꢂO9AL, 2.730(5) A). The hydrogen atoms of the lattice water molecules and the organic ligand are omitted for clarity
here.
Although the structures of 1, 2 and 3 exhibit the
coordination character of the dpdapt ligand in part, the
framework structures of the three complexes are rare for
inorganic triazine compounds. To the best of our knowl-
edge only one dimeric unit of a transition-metal complex
based on 1,3,5-tris(2-pyridyl)triazine (tpt) has been
reported [27], but no solvent molecules effect and p–p inter-
actions were discussed. Additionally, in our previous
works, two complexes have been reported [15], which show
ladder and layer frameworks via intermolecular and intra-
molecular hydrogen bonds, respectively. However, we
discuss here the action of guest solvent molecules in con-
structing the three complexes. There are hexameric, dimeric
and one water molecule located in the lattices of complexes
1, 2 and 3, respectively. It is the water molecules that
extend complexes 2 and 3 into 2D supramolecular net-
works. While in 1, water molecules form a hexagon config-
uration in the adjacent 1D polymeric chains, Furthermore,
the individual water hexamer self-assembles 1D chains by
interhexamer hydrogen bonds, which exert a great influ-
ence on extending the architecture of complex 1.
exhibit mas(OCO) and ms(OCO) vibrations of the carboxyl-
ate groups that occur at 1640 and 1381 cmꢀ1 for 1 and
1665 and 1385 cmꢀ1 for 3. D[mas(OCO)–ms(OCO)] >
200 cmꢀ1 for complexes 1 and 3, and the value reveals that
the carboxylate is coordinated in a monodentate fashion,
which is consistent with the results of the X-ray analysis.
These data confirm the involvement of acid radical ligands
and ligand dpdapt in the copper complexation. The UV–
Vis spectra of the complexes are recorded in methanol
and are characterized by several spectral regions. The
absorption bands in the range 260–285 nm for the dpdapt
ligand are ligand-centered (LC) due to p–p* transitions.
The peak at 300 nm for complexes 1, 2 and 3 is due to
the d–d transition and the low-energy bands at 300, 302
and 297 nm are assigned to metal-to-ligand charge transfer
transitions (MLCT) [28,29]. This slight shift of absorption
bands of the complexes relative to that of dpdapt is caused
by the effect of metal-to-ligand charge transfer transitions.
The luminescence data were obtained in methanol at
room temperature. It was reported that the dpdapt ligand
showed a strongest emission peak at 375.4 nm with an exci-
tation peak at 330.0 nm [15]. The emission bands for com-
plexes 1, 2 and 3 can be attributed to intraligand
fluorescent emission of the coordinated dpdapt ligand.
The emission peak for complex 1 is at 310.8 nm, for com-
plex 2 at 330.6 nm and for complex 3 at 320.2 nm, and their
emission spectra show strong peaks at 448.6, 414.2 and
423.6 nm, respectively. Compared with the excitation–
emission spectrum of the ligand, obvious enhancement of
the fluoroscence intensities is realized in complexes 1, 2
and 3; the emission bands for three complexes are red-
shifted. This drastic shift can be attributed to the strong
hydrogen-bonding interactions between the water
3.2. Spectroscopic properties
The IR spectra of the three complexes were performed
as KBr pellets in the range 4000–400 cmꢀ1. In complex 1,
the bands around 1425 and 1496 cmꢀ1 for the ligand dpd-
apt, attributed to the C@N groups, are shifted to 1469 and
1592 cmꢀ1. In complex 2, the corresponding bands for the
C@N groups are shifted to 1469 and 1587 cmꢀ1, the bands
corresponding to SO4 are at 634 cmꢀ1. The correspond-
2ꢀ
ing bands for the C@N groups for 3 are shifted to 1466
and 1573 cmꢀ1, respectively. Furthermore, the spectra

Y.-P. Wu et al. / Polyhedron 25 (2006) 3533–3542
3541
molecules and the nearby O atoms of acid radical ligands
Appendix A. Supplementary material
that change the donor–acceptor character of the dpdapt
moieties. These peaks of the emission spectra are probably
assigned to intramolecular charge transfer (ICT) transi-
tions [30].
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic Data
Centre, CCDC No. 294,845 for 1, 294,843 for 2 and
294,844 for 3. Copies of this information may be obtained
free of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44 1223 336 033; e-mail:
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.poly.
2006.07.012.
3.3. Thermogravimetric analysis
Thermogravimetric analysis (TGA) for complexes 1, 2
and 3 were recorded under a nitrogen atmosphere. The
TGA result for complex 1 shows an initial weight loss of
16.07% at about 200 ꢁC, corresponding to the removal of
six water molecules per formula unit (16.35% calculated).
Heating above 500 ꢁC results in complete collapse of com-
plex 1 accompanied by a rapid mass change as the organic
component burns off. The two water molecules in complex
2 are lost at about 115 ꢁC with mass loss of 5.39% (5.72%,
calculated). Heating above 450 ꢁC leads complete collapse
of complex 2. Complex 3 loses its one water molecule at
about 118 ꢁC, leading to a 3.32% loss of the formula unit
(3.53%, calculated). The complete collapse of 3 is showed
above 470 ꢁC.
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Acknowledgements
This work was supported by the National Natural Sci-
ence Foundation of China (No. 20471048) and TRAP-
OYT, and Specialized Research Found for the Doctoral
Program of Higher Education (No. 20050697005).

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