Synthesis and structural characterization of copper(II), cadmium(II) and zinc(II) complexes with 4,5-diazaspirobifluorene and bis-9-biphenyl-4,5-diazafluorenyl peroxide

Article abstract of DOI:10.1016/j.poly.2008.11.023

The synthesis and structural chemistry of four new divalent transition metal complexes of the fluorene ligands 4,5-diazaspirobifluorene (L1) and bis-9-biphenyl-4,5-diazafluorenyl peroxide (L2), [Cu₃(L1)₄(NO₃)₆(H

Full text of DOI:10.1016/j.poly.2008.11.023

Polyhedron 28 (2009) 445–452
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and structural characterization of copper(II), cadmium(II) and zinc(II)
complexes with 4,5-diazaspirobifluorene and
bis-9-biphenyl-4,5-diazafluorenyl peroxide
Min Hong a, Kun Zhang a, Yi-Zhi Li b, Jin Zhu a,
*
a Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry,
Nanjing University, 22 Hankou Road, Nanjing 210093, PR China
b Coordination Chemistry Institute, Nanjing University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 June 2008
Accepted 14 November 2008
Available online 30 December 2008
The synthesis and structural chemistry of four new divalent transition metal complexes of the fluorene
ligands 4,5-diazaspirobifluorene (L1) and bis-9-biphenyl-4,5-diazafluorenyl peroxide (L2), [Cu3(L1)4-
(NO3)6(H2O)2] ꢀ 2CH3CN (1), [Cu(L1)(CH3CO2)2(H2O)] ꢀ 2H2O (2), [Cd(L1)2(NO3)2] ꢀ DMF (3) (DMF = N,N-
dimethylformamide) and [Zn2(L2)(l-Cl)2Cl2] (4) are described. Single-crystal X-ray diffraction analysis
1
reveal that the four complexes exhibit various frameworks due to diverse coordination modes and differ-
ent conformations of ligands L1 or L2, as well as nitrate, acetate or chloro counterions. L1 in complexes 1,
2 and 3 present an asymmetric rigid bidentate ligand with two nitrogen atoms as the donor sites. Novel
complex 4 was formed through complexation between conformationally bent shaped peroxide ligands
and zinc(II) dichlorides that adopt a linear coordination geometry, which can also give rise to extended
polymeric chains with a zigzag secondary structure.
Keywords:
Copper
Cadmium
Zinc
4,5-Diazaspirobifluorene
Bis-9-biphenyl-4,5-diazafluorenyl peroxide
Crystal structure
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
tal complex with the rigid and bulky ligands and the coordination
code of the nitrogen-donor ligands, herein, we report the synthesis,
Organocopper, cadmium and zinc complexes have been widely
explored due to their rich structural chemistry [1] and importance
in organic synthesis [2], and in polymerization chemistry [3], e.g.,
as well-defined catalysts for the copolymerization of CO2 and
epoxides [4]. The applications of these complexes must be based
on the fundamental understanding of their components and struc-
ture chemistry. Hence it is of interest to study the coordination
modes and structural features of the complexes. Several rigid mul-
tidentate oxygen-donor ligands have been used to design and syn-
thesize the metal–organic complexes [5,6]. At the same time, many
rigid bidentate nitrogen-donor ligands, such as 2,20-bipyridine and
its derivatives have also been used to prepare the metal organic
materials [7]. However, the nitrogen-donor ligands with larger vol-
umes are not easy to coordinate with the metal ions because of the
large steric hindrance, and larger crystals suitable for single-crystal
XRD analysis are difficult to obtain due to the low coordination
strength of the nitrogen-donor organic ligands caused by the less
negative charge on the nitrogen compared with the oxygen [8].
The coordination chemistry of the rigid ligand 4,5-diazaspirobiflu-
orene has rarely been reported, except for a complex with silver
ion [9]. In order to study the structure feature of the transition me-
characterization, and crystal structure of copper(II), cadmium(II)
and zinc(II) complexes bearing bipyridine-based N,N-chelate fluo-
rene ligands, 4,5-diazaspirobifluorene (L1) and bis-9-biphenyl-4,5-
diazafluorenyl peroxide (L2). Remarkably, we have obtained the
first zinc complex with peroxide so far, which may have potential
applications in catalysis chemistry in the future.
2. Experimental
2.1. General
All of the reagents were commercially available and used as
purchased. 9-Biphenyl-4,5-diazafluorenol and 4,5-diazaspirobiflu-
orene was prepared according to the literature [10]. Interestingly,
along with the expected 4,5-diazaspirobifluorene, bis-9-biphenyl-
4,5-diazafluorenyl peroxide was unexpectedly formed as a by-
product by the oxidation of 9-biphenyl-4,5-diazafluorenol with
H2SO4/HOAc.
The elemental analysis was carried out with a Perkin–Elmer
240C elemental analyzer. 1H NMR spectra were performed on a
Bruker model Advance DRX 500 spectrometer in DMSO-d6 and
were referenced to TMS. The FT-IR spectra were recorded from
KBr pellets over the range 4000–400 cmꢁ1 with a Vector 22 spec-
trometer. The emission/excitation spectra were recorded with a
* Corresponding author. Tel.: +86 (25) 8368 6291; fax: +86 (25) 8331 7761.
E-mail address: jinz@nju.edu.cn (J. Zhu).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.11.023

446
M. Hong et al. / Polyhedron 28 (2009) 445–452
Hitachi 850 fluorescence spectrophotometer by using 1 ꢂ 10ꢁ4
M
5.94. Found: C, 58.44, H, 3.60, N, 5.99%. 1H NMR (DMSO-d6):
d = 8.35 (d, 2H, H1, J = 4.00), 8.13 (d, 1H, H7, J = 8.00), 7.57 (m, 1H,
H10, J = 30.00), 7.37 (t, 1H, H6, J = 14.50), 7.19 (d, 2H, H3, J = 7.50),
6.97 (t, 1H, H4, J = 12.00), 6.85 (d, 1H, H9, J = 7.00), 6.77 (t, 1H, H8,
J = 14.50), 6.54 (t, 2H, H5, J = 15.00), 5.86 (d, 2H, H2, J = 7.00) (see
Table 4 for the atom numbering arrangement). IR (KBr pellet):
CH3CN solution. Optical absorption spectra were collected on a Shi-
madzu 3100 spectrophotometer at room temperature. The absor-
bance was directly proportional to the concentration of
complexes in the range from 1 ꢂ 10ꢁ4 M to 1 ꢂ 10ꢁ3 M.
2.2. Preparation of [Cu3(L)4(NO3)6(H2O)2] ꢀ 2CH3CN (1)
m = 3435 (s), 1600 (m), 1586 (m), 1473 (w), 1438 (w), 1411 (s),
1161 (m), 1008 (m), 814 (w), 769 (m), 707 (m), 557 (w) cmꢁ1
.
Equimolar amounts of 4,5-diazaspirobifluorene (0.079 g,
0.25 mmol) and Cu(NO3)2 ꢀ 3H2O (0.061 g, 0.25 mmol) were stirred
together in CH3CN (30 ml) at room temperature for 2 h. The result-
ing glaucous solution was filtered and concentrated to 10 ml. Blue
block crystals of complex 1 suitable for X-ray diffraction were ob-
tained in 69% yield by slow diffusion of diethyl ether into the fil-
trate for several days. At room temperature, crystals of complex
1 are unstable and decompose slowly into blue powder over the
course of several days. Anal. Calc. for C96H62Cu3N16O20 (1950.24):
C, 59.12; H, 3.21; N, 11.49. Found: C, 59.36; H, 3.44; N, 11.23%.
1H NMR (DMSO-d6): d = 8.09 (s, 4H, H1,7), 7.44 (s, 4H, H3,4), 7.17
(s, 4H, H5,6), 6.68 (s, 2H, H2), 2.07 (s, 3H, CH3CN) (see Table 4 for
the atom numbering arrangement). IR data (KBr, cmꢁ1): 3447 (s),
3053 (vw), 1578 (w), 1473 (m), 1447 (m), 1406 (s), 1384 (s),
2.6. Crystal structure determination and refinement
Suitable single crystals were selected for indexing and intensity
data were measured with a Bruker Smart Apex CCD diffractometer
with graphite-monochromated Mo Ka radiation (k = 0.71073 Å) at
298 K. The raw data frames were integrated into SHELX-format
reflection files and corrected using the SAINT program. Absorption
corrections based on multiscans were obtained from the SADABS pro-
gram. The structures were solved with direct methods and refined
with full-matrix least-squares techniques using the SHELXS-97 and
SHELXL-97 programs, respectively. Metal atoms in each complex
were located from the E-maps, and other non-hydrogen atoms
were located in successive difference Fourier syntheses, where
they were refined with anisotropic thermal parameters on F2.
The hydrogen atoms of the ligands were generated theoretically
onto the specific atoms and refined isotropically with fixed thermal
factors. The hydrogen atoms of the water molecules were located
using the different Fourier method and refined freely. Further de-
tails for structural analysis are summarized in Tables 1 and 2.
1279 (s), 1169 (w), 1013 (w), 797 (w), 765 (m), 737 (m) cmꢁ1
.
2.3. Preparation of [Cu(L)(CH3CO2)2(H2O)] ꢀ 2H2O (2)
Similar procedures were performed to obtain blue crystals of
complex 2, except that Cu(CH3CO2)2 ꢀ 4H2O was used instead of
Cu(NO3)2 ꢀ 4H2O, yield 55%. Anal. Calc. for C27H26CuN2O7
(554.04): C, 58.53; H, 4.73; N, 5.06. Found: C, 58.33; H, 4.77; N,
5.21%. 1H NMR (DMSO-d6): d = 8.84 (s, 2H, H1), 8.07 = (d, 2H, H7,
J = 7.31), 7.46 (t, 2H, H3, J = 14.11), 7.33 (s, 2H, H4), 7.18 (s, 4H,
H5,6), 6.70 (d, 2H, H2, J = 7.00), 2.45 (s, 6H, CH3CO2) (see Table 4
for the atom numbering arrangement). IR data (KBr, cmꢁ1): 3423
(s), 2927 (w), 1606 (s), 1404 (s), 1339 (w), 1163 (w), 807 (w),
3. Results and discussion
3.1. Synthesis of metal complexes
Complexes 1–4 have been prepared in moderate to good yields
(50–70%) by mixing acetonitrile solutions of ligand L1 or L2 with a
salt of a divalent metal, MII = Cu, Cd, Zn (Scheme 1). Crystal of 1 or 2
can be obtained through slow diffusion of diethyl ether into the
reaction mixture. Otherwise, crystals for cadmium and zinc com-
plex have grown tardily from the solution along with the volatili-
zation of the solvent acetonitrile, respectively. From the crystal
structure of complex 1, we could deduce that ligand L forms a
762 (m), 737 (m), 676 (w) cmꢁ1
.
2.4. Preparation of [Cd(L)2(NO3)2] ꢀ DMF (3)
A mixture with a stoichiometric 2:1 solution of ligand L1
(0.079 g, 0.50 mmol) and Cd(NO3)2 ꢀ 4H2O (0.077 g, 0.25 mmol) in
CH3CN (30 ml) were stirred together for 2 h at room temperature.
The clear solution thus obtained was evaporated under vacuum to
form a white solid and recrystallized from CH2Cl2–DMF to give col-
orless crystals, yield 70%. Anal. Calc. for C52H42CdN8O8 (1019.34): C,
61.27; H, 4.15; N, 10.99. Found: C, 61.09; H, 3.99; N, 10.46%. 1H
NMR (DMSO-d6): d = 8.71 (d, 2H, H1, J = 3.34), 8.07 = (d, 2H, H7,
J = 7.61), 7.96 (s, 1H, DMF–H), 7.45 (d, 2H, H3, J = 7.49), 7.26
(t, 2H, H4, J = 6.88), 7.16 (d, 4H, H5,6, J = 7.08), 6.70 (d, 2H, H2,
J = 7.64), 2.89, 2.73 (s, 6H, DMF–CH3) (see Table 4 for the atom
numbering arrangement). IR data (KBr, cmꢁ1): 3449 (w), 3074
(w), 2922 (w), 1661 (s), 1582 (m), 1432 (s), 1408 (s), 1383 (s),
1298 (s), 1166 (w), 1089 (w), 1028 (w), 954 (w), 803 (w), 762
Table 1
Crystallographic data for complex 1–3.
Complex 1
Complex 2
Complex 3
Formula
C96H66Cu3N16O2
1954.27
C27H26CuN2O7
554.04
monoclinic
P21/c
C52H42CdN8O8
1019.34
monoclinic
P21/c
Formula weight
Crystal system
Space group
Crystal size (mm)
a (Å)
triclinic
ꢀ
P1
0.21 ꢂ 0.19 ꢂ 0.16 0.23 ꢂ 0.15 ꢂ 0.11 0.30 ꢂ 0.24 ꢂ 0.22
12.2642(18)
12.9474(19)
15.649(2)
86.468(2)
75.369(2)
63.026(2)
2138.7(5)
1
10.0594(13)
23.117(3)
11.4744(15)
90
108.732(2)
90
2527.0(6)
4
1.456
12.0376(7)
15.9870(10)
13.0900(8)
90
113.4070(10)
90
2311.8(2)
2
1.464
b (Å)
c (Å)
(m), 738 (m), 652 (w) cmꢁ1
2.5. Preparation of [Zn2(L2)(
solution containing anhydrous zinc dichloride (0.071 g,
.
a
(°)
b (°)
(°)
l
-Cl)2Cl2]1 (4)
c
V (Å3)
Z
A
Dcalc (g cmꢁ3
F(000)
)
1.517
1001
0.825
0.50 mmol) and bis-9-biphenyl-4,5-diazafluorenyl peroxide
(0.168 g, 0.25 mmol) in CH3CN (30 ml) was stirred for 2 h at room
temperature. The resulting light brown solution was filtered, and
then it was left open for slow evaporation of the solvent at room
temperature. After standing for two weeks, small needle-like crys-
tals of complex 4 were obtained, yield 50%. Because the growing
rate of crystal is too fast, the structure quality of complex 4 is
not high. Calc. for C23H15Cl2N2OZn (471.64): C 58.57, H 3.21, N
1148
0.914
1044
0.538
1.040
l
(mmꢁ1
)
Goodness-of-fit on
1.013
1.049
F2 (S)
Data collected
11693
13716
12500
Unique data (Rint
R1, wR2 [I > 2 (I)]
R1, wR2 [all data]
)
8247 (0.0313)
0.0660, 0.1527
0.0898, 0.1597
4947 (0.0532)
0.0624, 0.1228
0.0891, 0.1286
4527 (0.0515)
0.0622, 0.1263
0.0856, 0.1311
r

M. Hong et al. / Polyhedron 28 (2009) 445–452
447
Table 2
ecules. Thus, the structure of [Cu3(L1)4(NO3)6(H2O)2] ꢀ 2CH3CN
is best represented by the formula [Cu(L1)2
Crystallographic data for 9-biphenyl-4,5-diazafluorenol and complex 4.
(H2O)2] ꢀ [Cu(L1)(NO3)3]2 ꢀ 2CH3CN, and for clarity, of two mole-
cules with identical structures only one is shown in Fig. 1. From
crystal structure of complex 1 we can see that the coordination
geometry of Cu1 center is unusual in that the elongated Jahn–Tell-
er axis of the molecule lies along the N–Cu–N vector [Cu1–
N2 = 2.631(2) Å] and not in the O–Cu–O axis [Cu1–
O1 = 2.002(3) Å], which is occupied by water molecules. To our
knowledge, this is one of only two examples of N2O2N02 coordina-
tion to a Cu(II) center with two water molecules bound trans in
the equatorial plane and the nitrogen atoms of the chelates direc-
ted along the J–T axis. [12] This N2X2N02 geometry has been ob-
served in other Cu(II) complexes with the 4,ꢁ5-diazafluorene
template and other anions such as Clꢁ, Brꢁ or NO3 [12,13], while
complexes with transition metals other than Cu(II) (e.g., Re(I), [14]
Co(II) [15]) typically exhibit a more symmetrical coordination.
On the other hand, the environment of Cu2 center is square
pyramidal. The basal plane is built by a nitrogen atom from the li-
gand L1 and three oxygen atoms of three nitrate groups, whereas
the apical position is occupied by the other nitrogen atom of the
bidentate ligand L1. Main bond distances and angles for non-
hydrogen atoms are listed in Table 3. Meanwhile, the structure
analysis indicates that biphenyl and 2,20-bipyridine units in two
kinds of coordinated ligand L1 are both perpendicularly cross-
linked by a carbon atom. The dihedral angles between the mean
planes of the two units are 88.6° (L1 coordinated to Cu1) and
91.5° (L1 coordinated to Cu2), which are very similar to that in
the crystal structure of the free ligand L1 we have reported previ-
ously [16].
9-Biphenyl-4,5-diazafluorenol
Complex 4
Formula
C46H32N4O2
672.76
orthorhombic
P212121
0.25 ꢂ 0.15 ꢂ 0.11
8.0633(6)
15.4115(11)
27.940(2)
90
90
90
3472.1(4)
4
1.287
1408
0.080
1.000
18394
3659 (0.0962)
0.0350, 0.0618
0.0529, 0.0664
C23H15ZnCl2N2O
471.64
monoclinic
P21/c
0.20 ꢂ 0.13 ꢂ 0.11
8.8988(12)
18.567(3)
12.2080(17)
90
94.785(2)
90
2010.0(5)
4
1.559
956
Formula weight
Crystal system
Space group
Crystal size (mm)
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
V (Å3)
Z
Dcalc (g cmꢁ3
F(000)
)
l
(mmꢁ1
)
1.505
0.756
10863
3940 (0.1107)
0.0504, 0.0604
0.1502, 0.0721
Goodness-of-fit on F2 (S)
Data collected
Unique data (Rint
R1, wR2 [I > 2 (I)]
R1, wR2 [all data]
)
r
4:3 complex with copper(II) nitrate (Fig. 1), although the reaction
was processed in a 1:1 ratio.
Reactions of ligand L1 with one equivalent of copper(II) acetate
yielded complex 2 whose chemical analysis suggested a 1:1 ratio of
ligand to metal salt. This result parallels the reaction of substituted
2,20-bipyridine with copper(II) acetate which forms a simple four-
coordinate 1:1 complex [11]. In contrast, crystals from a mixture of
ligand L1 and cadmium(II) nitrate with a 2:1 ratio in DMF/CH2Cl2
were shown by X-ray crystallography to be a DMF solvate.
The addition of ligand L2 in a 1:2 ratio to a acetonitrile solution
of ZnCl2 after two weeks, accompanied with slow evaporation of
the solvent at room temperature, results in small needle-like crys-
tals of complex 4.
Interestingly, as can be seen from Fig. 2, a one-dimensional
supramolecular chain is formed by intermolecular hydrogen bond-
ing involving the water molecules coordinated to the copper center
which chelated by two bidentate ligands L1 and the nitrate oxygen
atoms coordinated to the other copper center (Table 4). Undoubt-
edly, these hydrogen bonds contribute to the stability of the whole
crystal structure.
3.2. X-ray crystallography
3.2.2. [Cu(L1)(CH3CO2)2(H2O)] ꢀ 2H2O (2)
Single crystals suitable for X-ray analysis could be obtained for
all five compounds in this study. The solved crystal structures are
shown in Figs. 1, 3, 5, 6 and 9, and the selected bond lengths and
angles are collected in Table 3.
Copper(II) acetate forms a variety of structures with unsubsti-
tuted 2,20-bipyridine. The formation of multinuclear systems con-
taining two or three copper ions [17–19], polymers [20] and a
mononuclear cation [21] [Cu(bipy)2(acetate)]+ are facilitated by
the possibility of acetate either acting as a bidentate ligand, or
using one oxygen atom to bridge two metal centers. To determine
the structure feature of the complex formed by 2,20-bipyridine-
based ligand L1 and copper(II) acetate, complex 2 was synthesized
3.2.1. [Cu3(L1)4(NO3)6(H2O)2] ꢀ 2CH3CN (1)
Single-crystal X-ray study reveals that the asymmetric unit of
complex 1 consists of three crystallographically independent mol-
Cu(NO3)2 3H2O
[Cu3(L1)4(NO3)6(H2O)2] 2CH3CN (1)
N
N
Cu(CH3CO2)2 H2O
Cd(NO3)2 4H2O
[Cu(L1)(CH3CO2)2(H2O)] 2H2O (2)
[Cd(L1)2(NO3)2] DMF
(3)
HO
(L1)
N
H2SO4/HOAc
(DMF = N,N-dimethylformamide)
N
N
ZnCl2
[Zn2(L2)Cl4]∞
(4)
O
N
N
O
N
(L2)
Scheme 1. Synthetic routes of the ligands L1, L2 and complexes 1–4.

448
M. Hong et al. / Polyhedron 28 (2009) 445–452
Fig. 1. X-ray single crystal structure of complex 1 (thermal ellipsoids at 30% probability).
Fig. 2. 1D linear chain of complex 1 via the intermolecular hydrogen bonding, dashed lines indicate the intermolecular hydrogen bonds.
in our case, which was characterized by X-ray crystallography. The
molecular structure is shown in Fig. 3, which is different from the
mononuclear copper(II) complexes mentioned above. The crystal
structure of 2 consists of mononuclear units in which the copper(II)
center surrounding is square pyramidal. A nitrogen atom (N2) from
the bidentate ligand L1 is in the apical position. Two oxygen atoms
(O2 and O4) from the monodentate acetate groups, one oxygen
atoms (O1) from a water molecule and the other nitrogen atom
of ligand L1 (N1) build the basal plane. The Cu–N bond distances
are similar to those observed in the foregoing mononuclear five-
coordinate molecular structure of complex 1. However, the Cu–O
(water oxygen atom) [1.961(3) Å] is slight shorter than the one
[2.002(3) Å] observed in the foregoing another six-coordinate
molecular structure of complex 1. N1, O1, O2, and O4 atoms fall
on
a plane: the largest deviation from the mean plane is
ꢁ0.0273 Å for O1. The copper(II) ion is 0.032(3) Å out of this plane.
The value of the axial copper-nitrogen distance is 2.489(3) Å,
which is much longer than the observed one [2.037(3) Å] in the
quadrilateral plane.
In 2 there are no
p–p aromatic interactions between the biphe-
Fig. 3. X-ray single crystal structure of complex 2 (thermal ellipsoids at 30%
probability).
nyl or bipyridyl rings, Fig. 4, but there are several sets of intermo-

M. Hong et al. / Polyhedron 28 (2009) 445–452
449
Fig. 4. Perspective view of the one-dimensional chain of complex 2, dashed lines indicate the weak interaction and the intermolecular hydrogen bonds.
slightly longer than the other [2.447(4) and 2.329(3) Å]. Two
nitrate counterions occupy the apical position, d(Cd–O) =
2.411(5) Å. The bite angle of the ligand L1 [77.14°] indicates
that there is a certain strain in the six-membered chelate ring.
´
According to the literatures, this is the first example of N2O2N2
coordination to a Cd(II) center with four nitrogens of the chelates
bound in the equatorial plane and two trans nitrates directed along
the J–T axis. [22,23] Similar N2O2N02 geometry has been observed in
other Cd(II) complex with the 4,5-diazafluorene template and an-
ions NO3ꢁ, while it typically exhibit a more symmetrical coordina-
tion by adopting cis structures for two nitrate anions and two
bidentate ligands (e.g., 40,50-diaza-90-(4,5-bis(ethylthio)-1,3-
dithiole-2-ylidene)-fluorene) [23].
Fig. 5. Molecular structure of complex 3. Thermal ellipsoids are at the 30%
probability level.
3.2.4. [Zn2(L2)(l-Cl)2Cl2]1 (4)
A section of the one-dimensional polymer [Zn2(L2)(
l-Cl)2Cl2]1
is illustrated in Fig. 6; selected intramolecular distances and angles
are presented in Table 3. The asymmetric unit contains only one-
half of the molecules, the remainder being generated by a center
of symmetry located on the O–O bond. The structure features of
the peroxide group in 4 are similar to those of ap-9-(o-isopropyl-
phenyl)-9-fluorenyl peroxide. [24] They include a C–O–O–C dihe-
dral angle of 180°, and C–O and O–O distances of 1.433(4) and
1.473(5) Å, respectively. One phenyl ring of the biphenyl group is
nearly perpendicular to their respective fluorenyl rings [79.7°],
and the other is parallel to the fluorenyl ring [21.3°]. Meanwhile,
the symmetry requires the two fluorene-ring planes connected
by the O–O bond to be anti-parallel, which is also the case for
the corresponding four phenyl-ring planes. In the similar fluorene
lecular hydrogen bonding (see Table 4) between the waters of crys-
tallization and the coordinated acetic groups which link the adja-
cent molecules into an infinite one-dimensional supramolecular
chain (Fig. 4).
3.2.3. [Cd(L1)2(NO3)2] ꢀ DMF (3)
The crystal structure of complex 3 unambiguously confirms the
[Cd(L1)2] stoichiometry as well as the bidentate nature of the li-
gand L1 (Fig. 5). The cadmium atom lies on a crystallographic
inversion center. N4O2 coordination polyhedron around the Cd(II)
center is Jahn–Teller distorted octahedron. Four N atoms from
the two ligands L1 coordinate to the Cd(II) center in the equatorial
plane, wherein, for each ligand moiety, one Cd–N distance is
Fig. 6. View of a selected unit of the chain polymer 4 (thermal ellipsoids at 30% probability).

450
M. Hong et al. / Polyhedron 28 (2009) 445–452
Table 3
Table 4
Selected bond lengths (Å) and angles for complexes 1–4.
Hydrogen bonding geometries for complexes 1 and 2 (Å and °).
Complex 1
Cu1–O1
Cu1–N1
Cu1–N2
D–HꢀꢀꢀA
Complexe 1
HꢀꢀꢀA
DꢀꢀꢀA
D–HꢀꢀꢀA
2.002(3)
1.983(3)
2.631(2)
2.070(3)
161.5(1)
80.92(1)
88.86(2)
171.0(2)
Cu2–O5
Cu2–O8
Cu2–N4
Cu2–N3
O2–Cu2–O5
O8–Cu2–N3
O8–Cu2–N4
1.916(3)
2.008(3)
2.037(3)
2.348(4)
82.57(2)
86.20(1)
91.54(1)
O(1)-H(1C)ꢀꢀꢀO(4)i
O(1)-H(1C)ꢀꢀꢀN(5)i
O(1)-H(1D)ꢀꢀꢀO(10)ii
2.10(6)
2.62(6)
1.83(6)
3.010(5)
3.571(5)
2.751(4)
157(5)
171(4)
160(5)
Cu2–O2
O2–Cu2–N4
O2–Cu2–N3
O1–Cu1–N1
O8–Cu2–O5
Complexe 2
O(1)-H(1A)ꢀꢀꢀO(3)iii
O(6)-H(6A)ꢀꢀꢀO(7)iii
O(1)-H(1B)ꢀꢀꢀO(5)iii
O(7)-H(7A)ꢀꢀꢀO(6)iv
O(6)-H(6B)ꢀꢀꢀO(2)
1.69(5)
2.08(6)
1.90(6)
2.15(6)
2.29(6)
2.637(4)
2.820(5)
2.689(4)
2.903(5)
2.959(4)
173(4)
157(5)
157(5)
175(6)
137(5)
Complex 2
Cu1–O1
Cu1–O2
1.962(3)
1.948(3)
1.936(3)
88.41(1)
89.11(1)
178.3(1)
Cu1–N1
Cu1–N2
2.037(3)
2.489(3)
Cu1–O4
Symmetry codes: i, ꢁx, ꢁy + 2, ꢁz + 1; ii, x ꢁ 1, y, z; iii, ꢁx + 1, ꢁy + 1, ꢁz + 1; iv, x, y,
z ꢁ 1.
O1–Cu1–O2
O1–Cu1–O4
O1–Cu1–N1
O2–Cu1–O4
O2–Cu1–N1
177.12(1)
91.74(1)
Complex 3
Cd1–N1
Cd1–N2
O1–Cd1–N1
O1–Cd1–N2
Because of the flexibility of the ligand L2, the geometry arrange-
ment between the biphenyl and 2,20-bipyridine units in complex 4
differentiates markedly from that of the ligand L1. The most inter-
esting characteristic is that one of the phenyl ring is approximately
paralleled to the 2,20-bipyridyl ring.
2.433(3)
2.332(3)
103.4(2)
84.10(1)
Cd1–O1
2.411(5)
N1–Cd1–N2
O1–Cd1–N1ii
102.7(1)
76.75(1)
Complex 4
Zn1–N2
Zn1–Cl1
Zn1–Cl2
N2–Zn1–Cl1
Cl2–Zn1–Cl1
N1–Zn1–Cl1
N2–Zn1–Cl2iii
Cl2–Zn1–Cl2iii
C11–O1–O1iv
2.075(3)
2.185(1)
2.233(1)
113.9(1)
121.2(5)
96.26(10)
88.23(1)
86.14(5)
104.7(3)
Zn1–N1
2.447(4)
2.718(1)
1.473(5)
124.75(1)
78.78(1)
91.41(1)
99.99(5)
162.3(1)
The role of
in metal–organic coordination compounds has been a topic of
much interest. [25,26] In the present complex, interaction
involving the 9-biphenyl-4,5-diazafluorenyl peroxide is also ob-
served (Fig. 7). The centroid–centroid distance (d) between the
phenyl and the bipyridyl rings is 3.495 Å and their interplanar an-
p–p stacking interaction in the stability of structures
Zn1–Cl2iii
O1–O1iv
p–p
N2–Zn1–Cl2
N2–Zn1–N1
N1–Zn1–Cl2
Cl1–Zn1–Cl2iii
N1–Zn1–Cl2iii
gle (h) is 20.9°. It should be noted that the intramolecular
p–p
interactions play an important role for the structural stability.
Symmetry codes: i, ꢁx, ꢁy + 2, ꢁz + 1; ii, ꢁx + 1, ꢁy + 1, ꢁz + 2; iii, ꢁx + 1, ꢁy, ꢁz + 2;
iv, ꢁx, ꢁy, ꢁz + 1.
All efforts to obtain the crystal structure of the ligand L2 were
not successful so far. However, we have determined the structure
of the precursor of the ligands L1 and L2, 9-biphenyl-4,5-diazaflu-
orenol. As it is shown from Fig. 8, in each independent fluorenol
molecule there is an intramolecular
p–p interaction which is extre-
peroxide mentioned above [24], there only exists the perpendicu-
lar phenyl ring.
mely identical with the interaction observed in complex 4. So
p-p
In complex 4, zinc(II) centers are linked by bis-9-biphenyl-4,5-
diazafluorenyl peroxide ligands to form an infinite zigzag chain.
Terminal and bridged chloro groups complete the distorted trigo-
nal–bipyramidal coordination around each metal ion. The coordi-
nation geometry of 4 is novel, in which one nitrogen atoms (N2,
from the ligand L2) and two chloride ions (Cl1, Cl2) are in the basal
plane, another nitrogen atom of the ligand (N1) and a chloride ion
Cl2i from the neighboring molecular unit occupy the axial position
[symmetry code i: 1 ꢁ x, 2 ꢁ y, ꢁz]. The distortion of the trigonal-
bipyramid is indicated by the fact that the basal donor atoms not
planar but deviate by as much as 0.0176 Å from their least-squares
plane, and by the angle of N1–Zn1–Cl2i [162.3(1)°]. As usual in the
case of zinc(II) compounds, the axial Zn–Cl distance [2.718(1) Å] is
much longer than the ones in the basal plane [2.233(1) and
2.185(1) Å].
An additional structural feature of interest is the involvement of
four-membered Zn2Cl2 ring. The four-membered ring is coplanar
completely with four atoms Zn1, Cl2, Zn1i and Cl2i. The Zn–Zn dis-
tance in the coordination dimmer is 3.630 Å, which is comparable
with the Zn–Zn distance of 3.620 Å in the reported [ZnCl2(l-
Fig. 8. Intramolecular
rings in the complex 4.
p–p stacking interaction between the phenyl and fluorenyl
bipy)] (bipy = 4,40-bipyridine) polymer [1a].
1
Fig. 7. Perspective view of the one-dimensional polymeric chain of complex 4.

M. Hong et al. / Polyhedron 28 (2009) 445–452
451
Fig. 9. X-ray single crystal structure of 9-biphenyl-4,5-diazafluorenol (30% probability thermal ellipsoids): showing the parallel stacking of the intermolecular fluorene
domains or the intramolecular fluorene and phenyl rings.
Table 5
1H NMR spectroscopic data for complexes containing L1 or L2.
6
4
8
7
7
5
2
9
6
2
5
O
4
10
3
3
N
N
N
N
1
1
2
L1
L2
Hydrogen
8.09 (1,7-H)
8.84 (1-H)
8.71 (1-H)
8.35 (1-H)
6.97 (4-H)
1
2
3
4
7.44 (3,4-H)
7.46 (3-H)
7.45 (3-H)
8.13 (7-H)
6.85 (9-H)
7.17 (5,6-H)
7.33 (4-H)
7.26 (4-H)
7.57 (10-H)
6.77 (8-H)
6.68 (2-H)
6.70 (2-H)
6.70 (2-H)
7.19 (3-H)
5.86 (2-H)
8.07 (7-H)
8.07 (7-H)
7.18 (5,6-H)
7.16 (5,6-H)
7.37 (6-H)
6.54 (5-H)
it can be concluded that, when the biphenyl group is not fully fixed
to the 9-position carbon atom appeared in the ligand L1, the con-
formation of one phenyl ring perpendicular to the fluorenyl ring
and the other parallel is the most stable. Meanwhile, there also ex-
ists intermolecular p–p interaction for the fluorenyl rings between
two adjacent 9-biphenyl-4,5-diazafluorenol in the unit cell, which
contributes to the stability of the whole crystal structure.
3.3. 1H NMR spectroscopy
All 1H NMR spectra were measured in DMSO-d6 for consistency.
The 1H NMR chemical shifts for complexes 1–4 are shown in Table
5.
From the 1H NMR spectra of complexes 1–4 we can see that, dif-
ferent metal ions or coordination geometry have less affect on the
chemical shift of the ligands in the complex except complex 1. Both
complex 2 and 3 exhibit six sets of aromatic hydrogen between
6.70 and 8.84 ppm. Only obvious difference for the protons at the
1 ortho-position of nitrogen-donor atoms can be found. But for
complex 1, due to the existence of two kinds of coordination geom-
etry between ligand L1 and copper center, and the environment of
some aromatic hydrogen have mixed a lot and shown only four
Fig. 10. Absorption spectra of L1 (a) and complex1 (b), 2 (c), 3 (d) at 298 K in
CH3CN.

452
M. Hong et al. / Polyhedron 28 (2009) 445–452
nyl-4,5-diazafluorenol. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2008.11.023.
References
[1] (a) C.H. Hu, U. Englert, Angew. Chem., Int. Ed. 44 (2005) 2281;
(b) S.N. Wang, J.F. Bai, Y.Z. Li, M. Scheer, X.Z. You, Cryst. Eng. Commun. 9
(2007) 228;
(c) M. Kontturi, E. Laurila, R. Mattsson, S. Peraniemi, J.J. Vepsalainen, M.
Ahlgren, Inorg. Chem. 44 (2002) 2400;
(d) K. Hanson, N. Calin, D. Bugaris, M. Scancella, S.C. Sevov, J. Am. Chem. Soc.
126 (2004) 10502;
(e) Z .Y. Du, X.L. Li, Q.Y. Liu, J.G. Mao, Cryst. Growth Des. 7 (2007) 1501.
[2] (a) T. Marino, N. Russo, M. Toscano, J. Am. Chem. Soc. 127 (2005) 4242;
(b) J.S. Casas, E.E. Castellano, M.D. Couce, J. Ellena, A. Sanchez, J. Sordo, C.
Taboada, J. Inorg. Biochem. 100 (2006) 124.
[3] Z.Y. Chai, C. Zheng, Z.X. Wang, Organometallics 27 (2008) 1626.
[4] (a) Y.L. Xiao, Z. Wang, K. Ding, Chem. Eur. J. 11 (2005) 3668;
(b) M. Walther, K. Wermann, M. Lutsche, W. Gunther, H. Gorls, E. Anders. J.
Org. Chem. 71 (2006) 1399;
(c) I. Kim, S.M. Kim, C.S. Ha, D.W. Park, Macromol. Rapid Commun. 25 (2004)
888.
[5] J. Kim, B. Chen, T.M. Reineke, H. Li, M. Eddaoudi, D.B. Moler, M. O’Keeffe, O.M.
Yaghi, J. Am. Chem. Soc. 423 (2003) 705.
Fig. 11. Emission spectra of the free ligand L1 (a) and complex 1 (b), 2 (c), 3 (d) in
CH3CN solution at room temperature, excited at 333 nm (the peaks with a star are
assigned to the scattering of the excitation; inset: excitation spectrum of the
fluorescent species).
types of chemical shifts in the 1H NMR spectra. Just like the proton
environment of ligand L2 themselves, the 1H NMR spectra of com-
plex 4 shows ten sets of different types of aromatic hydrogen.
[6] O.M. Yaghi, M. O’Keefe, N.W. Ockwig, H.K. Chae, M. Eddaoudi, J. Kim, Nature
423 (2003) 705.
[7] N.C. Fletcher, T.C. Robinson, A. Behrendt, J.C. Jeffery, Z.R. Reeves, M.D. Ward, J.
Chem. Soc., Dalton Trans. (1999) 2999.
[8] H.R. Khavasi, A. Abedi, V. Amani, B. Notash, N. Safari, Polyhedron 27 (2008)
1848.
3.4. UV–Vis and fluorescent spectra of complexes 1–3
The UV–Vis spectral data of the ligand L1 and the three com-
plexes in acetonitrile were measured. The dominant vibronic
[9] C.C. Wang, C.H. Yang, S.M. Tseng, S.Y. Lin, T.Y. Wu, M.R. Fuh, G.H. Lee, K.T.
Wong, R.T. Chen, Y.M. Cheng, P.T. Chou, Inorg. Chem. 43 (2004) 4781.
[10] K.T. Wong, R.T. Chen, FC. Fang, C.C. Wu, Y.T. Lin, Org. Lett. 7 (2005) 1979.
[11] C.R. Rice, S. Onions, N. Vidal, J.D. Wallis, M.C. Senna, M. Pilkington, H. Stoeckli-
Evans, Eur. J. Inorg. Chem. (2002) 1985.
absorption peaks in complexes 1–3 at ꢃ294, ꢃ305, and ꢃ322 nm
*
can be ascribed to the ligand-centered (LC)
p–p
transitions. These
[12] S. Menon, M.V. Rajasekharan, Polyhedron 17 (1998) 2463.
[13] B.J. Kraft, H.J. Eppley, J.C. Huffman, J.M. Zaleski, J. Am. Chem. Soc. 124 (2002)
272.
[14] V.W.W. Yam, K.Z. Wang, C.R. Wang, Y. Yang, K.K. Cheung, Organometallics 17
(1998) 2440.
[15] X.H. Shi, X.Z. You, C. Li, R.G. Xiong, K.B. Yu, Transition Met. Chem. 20 (1995)
191.
[16] M. Hong, C. Teng, J. Zhu, Acta Crystallogr., Sect. E 63 (2007) o3304.
[17] G. Christou, S.P. Perlepes, E. Libby, K. Folting, J.C. Huffman, R.J. Webb, D.N.
Hendrickson, Inorg. Chem. 29 (1990) 3657.
[18] G. Christou, S.P. Perlepes, K. Folting, J.C. Huffman, R.J. Webb, D.N. Hendrickson,
J. Chem. Soc., Chem. Commun. (1990) 746.
[19] S. Meenakumari, S.K. Tiwary, A.R. Chakravarty, Inorg. Chem. 33 (1994) 2085.
[20] S.P. Perlepes, E. Libby, W.E. Streib, K. Folting, G. Christou, Polyhedron 11 (1992)
923.
[21] B.J. Hathaway, N. Ray, D. Kennedy, N.O. Brien, B. Murphy, Acta Crystallogr.,
Sect. B 36 (1980) 1371.
[22] P.F. Rodesiler, R.W. Turner, N.G. Charles, E.A.H. Griffith, E.L. Amma, Inorg.
Chem. 23 (1984) 999.
spectral assignments were made on the basis of their spectral sim-
ilarities with those of free ligand L1 (see Fig. 10) and a silver(I)
complex with L1 [9]. Furthermore, for complex 1 and 3, the Cu(II)
and Cd(II) d–d transitions are observed as a single broad feature
centered at 334 nm, consistent with a 6-coordinate mixed N, O
coordination environment. [27]
In acetonitrile (CH3CN), both the ligand L1 and corresponding
metal complexes are emissive; fluorescent emission at UV wave-
length (354 nm) of the free ligand L1 can be attributed to the li-
*
gand-centered
p –p relaxation (Fig. 11). Ligand-based emission
bands (ꢃ354 nm) are preserved in the corresponding Cu or Cd
complexes, but the Ag complex reported previously is intrinsically
nonluminescent throughout 350–800 nm in any organic solvent
[9].
[23] Q.Y. Zhu, Y. Zhang, J. Dai, X.F. Huan, Chin. J. Inorg. Chem. 22 (2006) 1170.
Acknowledgements
[24] P.D. Robinson, Y. Hou, C.Y. Meyers, Acta Crystallogr., Sect.
9900147.
C 55 (1999)
[25] A. Dutta, S.K. Pati, J. Chem. Phys. 118 (2003) 8420.
[26] Y.B. Dong, P. Wang, J.P. Ma, X.X. Zhao, H.Y. Wang, B. Tang, R.Q. Huang, J. Am.
Chem. Soc. 129 (2007) 4872.
[27] A.B.P. Lever, E.S. Dodsworth, in: E.I. Solomon, A.B.P. Lever (Eds.),
Electrochemistry, Charge-Transfer Spectroscopy, and Electronic Structure,
vol. 2, John Wiley and Sons, New York, 1999, p. 227.
J.Z. acknowledges support from the National Basic Research
Program of China (2007CB925103), the National Natural Science
Foundation of China (No. 20604011) and the program for New Cen-
tury Excellent Talents in University (NCET-06-0451).
Appendix A. Supplementary data
CCDC 671903, 668544, 668545, 668546, and 690767 contain
the supplementary crystallographic data for 1, 2, 3, 4 and 9-biphe-