Complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (dafo = 4,5-diazafluoren-9-one, tphpo = triphenylphosphine oxide) with chiral metal centers. Helical packing induced by π-π stacking interactions of dafo rings

Article abstract of DOI:10.1016/S0022-2860(03)00325-9

The first complex of 4,5-diazafluoren-9-one (dafo) and cadmium: [Cd(dafo)₂(tphpo)(CH₃COO)]ClO₄ (triphenylphosphine oxide = tphpo) is a quaternary complex with chiral metal centers and crystallizes in a monoclinic cell with space group P2(1)/n. Cadmium centers with 7-fold coordination adopt a distorted monocapped trigonal prismatic geometry. Two oxygen atoms of acetate and one oxygen atom of triphenylphosphine oxide form the top triangle of the trigonal prism, while three nitrogen atoms from two daft groups construct the bigger bottom triangle. The last nitrogen atom of daft groups occupies the monocapped position. Here, daft molecules display two different coordination patterns, namely unsymmetric and symmetric chelation. Moreover, the interesting linking of screw related cations is fabricated by inter-molecular π-π stacking interactions in the complex.

Full text of DOI:10.1016/S0022-2860(03)00325-9

Journal of Molecular Structure 655 (2003) 467–472
www.elsevier.com/locate/molstruc
Complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (dafo ¼ 4,5-
diazafluoren-9-one, tphpo ¼ triphenylphosphine oxide) with chiral
metal centers. Helical packing induced by p–p stacking
interactions of dafo rings
*
B.-L. Wu, H.-Y. Zhang , Q.-A. Wu, H.-W. Hou, Y. Zh
Department of Chemistry, Zhengzhou University, Zhengzhou 450052, People’s Republic of China
Received 15 April 2003; revised 14 May 2003; accepted 15 May 2003
Abstract
The first complex of 4,5-diazafluoren-9-one (dafo) and cadmium: [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (triphenylphosphine
oxide ¼ tphpo) is a quaternary complex with chiral metal centers and crystallizes in a monoclinic cell with space group P2ð1Þ=n:
Cadmium centers with 7-fold coordination adopt a distorted monocapped trigonal prismatic geometry. Two oxygen atoms of
acetate and one oxygen atom of triphenylphosphine oxide form the top triangle of the trigonal prism, while three nitrogen atoms
from two dafo groups construct the bigger bottom triangle. The last nitrogen atom of dafo groups occupies the monocapped
position. Here, dafo molecules display two different coordination patterns, namely unsymmetric and symmetric chelation.
Moreover, the interesting linking of screw related cations is fabricated by inter-molecular p–p stacking interactions in the
complex.
q 2003 Elsevier B.V. All rights reserved.
Keywords: 4,5-Diazafluoren-9-one; Quaternary complex of cadmium; Chiral molecule; p–p Stacking interaction
1. Introduction
been studied well [1,2]. Further studies on dafo
complexes have discovered that dafo often adopts
monodentate coordination or unsymmetric chelation
in its copper (II), nickel (II) or cobalt (II) complexes
[3–6], unlike complexes of 1,10-phenanthroline
where it usually acts as symmetrically chelating
ligand. Sindhu Menon and M. N. Rajasekharan first
reported two different coordination fashions of dafo in
a copper complex [7], and gave the rational
explanation that a much larger chelate bite for this
4,5-Diazafluoren-9-one (dafo) is a derivative of
1,10-phenanthroline (phen) and has been expected to
be a superior ligand with plentiful coordination
chemistry. However, in contrast with 1,10-phenan-
throline, dafo forms rather fewer complexes with
transition metals. Its Ru (II) and Eu (III) complexes
having potential applications in optical field have
˚
ligand (N· · ·N: dafo, 3.00 A; bipy, 2.62 A; phen,
˚
2.64 A) resulting from the presence of a rigid five-
numbered ring constrains the symmetrically
˚
*
Corresponding author. Tel.: þ863717763675; fax:
þ863717761744.
E-mail address: wzhy@zzu.edu.cn (H.-Y. Zhang).
0022-2860/03/$ - see front matter q 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-2860(03)00325-9

468
B.-L. Wu et al. / Journal of Molecular Structure 655 (2003) 467–472
chelating ability of dafo. Herein, we report
another example [Cd(dafo)2(tphpo)(CH3COO)]ClO4
(tphpo ¼ triphenylphosphine oxide), where dafo also
displays two different chelating coordination styles,
one-second as a symmetrically chelating ligand and
the other as the unsymmetric.
stacking interactions between dafo rings are very
strong, which induce the helical linking of cations to
be formed in crystal. Moreover, those cadmium
centers have chirality owing to coordination
environments.
Apart from adduct of tetrabromocadmate (II) with
protonated dafo where dafo just acts as a counter ion
[8], from our knowledge, no complex of dafo with
subgroup IIB metals has been reported. The title
complex is the first complex of dafo with cadmium
and also the first complex of triphenylphosphine oxide
and cadmium. In the complex, inter-molecular p–p
2. Experimental
2.1. Equipments and measurements
Elemental analyses were performed with a Carlo–
Erba 1106 elemental analyzer. IR spectral was
recorded on a FTS-40 infrared spectrophotometer
using KBr discs in the 4000–400 cm21regions.
Crystal structure was determined on a Rigaku–
Raxis-IV X-ray diffractometer.
Table 1
Crystal data for complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4
Empirical formula
Formula weight
Temperature
C42H30CdClN4O9P
913.52
291(2) K
˚
0.71073 A
Table 2
Wavelength
˚
Selected bond lengths (A) and bond angles (8) for [Cd(dafo)2(-
tphpo)(CH3COO)]ClO4
Crystal system,
space group
Monoclinic, P2ð1Þ=n
˚
˚
Bond lengths
Unit cell dimensions a ¼ 12.796(3) A
a ¼ 90
˚
˚
Cd1–O5
Cd1–O4
Cd1–N4
Cd1–O3
Cd1–N1
Cd1–N2
Cd1–N3
2.324(3)
2.3394(4)
2.398(3)
2.408(3)
2.457(4)
2.478(4)
2.587(4)
b ¼ 13.424(3) A
b ¼ 105.21(3)
˚
˚
c ¼ 24.039(1) A
g ¼ 90
Volume
3984.6(14) A3
Z; Calculated density 4, 1.523 Mg/m3
Absorption
coefficient
0.717 mm21
Fð000Þ
1848
Bond angles
O5–Cd1–O4
O5–Cd1–N4
O4–Cd1–N4
O5–Cd1–O3
O4–Cd1–O3
N5–Cd1–O3
O5–Cd1–N1
O4–Cd1–N1
N4–Cd1–N1
O53–Cd1–N1
O5–Cd1–N2
O4–Cd1–N2
N4–Cd1–N2
O3–Cd1–N2
N1–Cd1–N2
O5–Cd1–N3
O4–Cd1–N3
N4–Cd1–N3
O3–Cd1–N3
N1–Cd1–N3
N2–Cd1–N3
Crystal size
Theta range for
data collection
Index ranges
0.25 £ 0.20 £ 0.20 mm
˚
1.65–25.00
91.82(2)
75.55(12)
140.27(13)
92.42(12)
54.39(13)
159.92(13)
158.50(12)
103.89(13)
100.09(13)
85.17(13)
85.15(13)
129.68(12)
87.32(12)
75.52(13)
73.54(13)
115.42(12)
80.25(13)
72.17(13)
127.90(13)
82.15(13)
144.85(13)
0 # h # 15;
215 # k # 15;
228 # l # 27
9968/6005
Reflections
collected/unique
Completeness
to 2u ¼ 25:00
Refinement method
½RðintÞ ¼ 0:0375ꢀ
88.57%
Full-matrix
least-squares on F2
Data/restraints/
parameters
6005/0/524
Goodness-of-fit
on F2
0.996
Final R indices
½I . 2sðIÞꢀ
R1 ¼ 0.0457,
wR2 ¼ 0.0776
R indices (all data)
R1 ¼ 0.0958,
wR2 ¼ 0.0868
Largest diff. peak
and hole
0.472 and 20.448 e A23

B.-L. Wu et al. / Journal of Molecular Structure 655 (2003) 467–472
469
2.2. Materials and reagents
2.3. Preparation of complex
[Cd(dafo)2(tphpo)(CH3COO)]ClO4
Except for 4,5-diazafluoren-9-one being syn-
thesized through the method of literature [6], others
were used as purchased from creditable companies
without further purification.
The mixture of Cd(CH3COO)2·4H2O (0.067 g,
0.25 mmol), dafo (0.091 g, 0.5 mmol) and
15 ml absolute ethyl alcohol was put into a 100 ml
Fig. 1. (a) An ORTEP diagram of the asymmetric unit of complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (omitted hydrogen atoms for clarity). (b)
Polyhedral representation of the monocapped trigonal prismatic coordination environments around metal centers.

470
B.-L. Wu et al. / Journal of Molecular Structure 655 (2003) 467–472
three-necked flask. After being added ten drops of
acetic acid, the mixture was heated at refluxed
temperature in water-bath for 3 h. Then 2 ml benzene
soution of 0.13 g (0.5 mmol) triphenylphine was put
into this system which continued to reflux for another
1 h.Twomilliliteralcoholsolutionof0.122 g(1 mmol)
NaClO4 was added to earlier-mentioned system, the
mixture was refluxed for final 10 min. After being kept
untouched overnight, this mixture was filtrated and the
filtratewas letevaporatenaturallyatroomtemperature.
After half year, yellow needle crystal appeared.
Filtrated, washed with ether and dried naturally, pure
title complex of 0.16 g was obtained (yield 60%)
(Found: C, 55.20; H, 3.28; N, 6.40%. C42H30CuClN4-
O9P requires: C, 55.17; H, 3.28; N, 6.13%). Selected IR
spectra: 3441, 3075, 1729, 1592, 1574, 1440, 1414,
through gradual evaporation for half year. Due to
exposed to air during the preparation of the title
complex, triphenylphosphine was oxidized into tri-
phenylphosphine oxide [9], which is consistent with
the results of crystallography and IR spectra.
3.2. Crystal structure
X-ray diffraction results show that the title
complex is a quaternary complex of cadmium (II)
coordinating with dafo, tphpo and acetate. Cad-
mium centers with 7-fold coordination adopt
distorted monocapped trigonal prismatic geometry
as shown in Fig. 1(a). Three oxygen atoms of O3,
1156, 1105, 765, 725, 542 cm21
.
2.4. X-ray crystallography
A
single
crystal
of
dimension
0.25 £ 0.20 £ 0.20 mm3 was mounted on a Rigaku–
Raxis-IV X-ray diffractometer using graphite mono-
chromated Mo Ka ðl ¼ 0:071073 nmÞ radiation at
291(2) K. A total of 9968 reflections were measured
over the ranges 1:65 # 2u # 25:00; 0 # h # 15;
215 # k # 15; 228 # l # 27; yielding 6005 unique
reflections. Raw data were corrected and the structure
was solved using the SHELX-97 program. Non-hydro-
gen atoms were located by direct phase determination
and subjected to anisotropic refinement. The full-
matrix least-squares calculations on F2 were applied
on the final refinement. The refinement converged at
R1 ¼ 0:0457 and wR2 ¼ 0:0776 values for reflections
with I . 2sðIÞ: The unit cell parameters, along with
data collection and refinement details were tabulated in
Table 1, while other correlated data were also listed in
Table 2. Full atomic data are available as a file in CIF
format, deposited with the Cambridge Crystallo-
graphic Data Center (No. 199387).
3. Results and discussion
3.1. Synthesis
Fig. 2. Helical chains of cations formed by p–p stacking interaction
in complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (viewed down b
axis).
The title complex was synthesized using fractional
step method and its single crystal was obtained

B.-L. Wu et al. / Journal of Molecular Structure 655 (2003) 467–472
471
O4 and O5 and three nitrogen atoms of N1, N3 and
N4 construct top and bottom triangle of trigonal
prism, respectively, while N2 from the capped
position coordinates to Cd1. From the bond lengths
and angles tabulated in Table 2, it can be
postulated that the bottom triangle of the prism is
larger than the top triangle (see Fig. 1(b)).
center [Cd(dafo)2(tphpo)(CH3COO)]þ belongs to C1
point group and displays chirality. In crystal cell,
however, these four metal centers arrange in internal
compensation.
There are two-typed p–p stacking interactions in
the crystal as shown in Fig. 2. The distance of phenyl
ring C23AC24AC25AC26AC27AC28A and dafo
ring C17AC18AC19AC20AC21AN4A ranges from
In this complex, dafo displays two chelating
coordination patterns. Half of the dafo adopt
unsymmetrically chelating coordination with Cd1–
˚
3.525 to 3.807 A, indicating weaker intra-molecular
p–p stacking interaction that stabilizes the configur-
ation of the title complex. Meanwhile, stronger inter-
molecular p–p stacking interactions with distance
˚
˚
N3 of 2.587(4) A and Cd1–N4 of 2.398(3) A, while
the other half adopting symmetrically chelating
˚
coordination with Cd1–N1 of 2.457(4) A and
˚
from 3.490 to 3.553 A offset between adjacent dafo
˚
Cd1–N2 of 2.478(4) A. Acetate ions chelate to
cadmium centers, with bond lengths of Cd1–O3 and
˚
Cd1–O4 being 2.408(3) and 2.339(4) A, respect-
rings of different cations, which conduct discrete
cations in helical arrangement (clearly shown in
Fig. 2). These helical chains pile up along a axis in the
crystal, while perchlorate ions and triphenylphosphine
groups occupy cavities between these chains (shown
in Fig. 3).
ively. Meanwhile, oxygen atom O5 from triphenyl-
phosphine oxide coordinates to Cd1 with bond
˚
length of 2.324(3) A. The symmetry of the metal
Fig. 3. Crystal packing of complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4, occupants of ClO24 and ¼ PPh3 in the cavities formed by the helical
chains.

472
B.-L. Wu et al. / Journal of Molecular Structure 655 (2003) 467–472
[3] S. Menon, M.V. Rajasekharan, Polyhedron 17 (1998) 2463.
Acknowledgements
[4] Z.-L. Lu, Ch.-Y. Duan, Y.-P. Tian, X.-Z. You, Inorg. Chem. 35
(1996) 2253.
We thank Henan Education Department (approved
No: 20011500027) and the Natural Science Foun-
dation of Henan Province (approved No:
0211020300) for support.
[5] X.-H. Shi, X.-Z. You, C. Li, R.-G. Xiong, Transition Met.
Chem. 20 (1995) 191.
[6] Y.-X. Wang, W. Perez, G.-Y. Zhang, D.P. Rillema, Inorg.
Chem. 37 (1998) 2051.
[7] S. Menon, M.V. Rajasekharan, Inorg. Chem. 36 (1997)
4983.
References
[8] K. Ravikumas, N.V. Lakshmi, G.Y.S.K. Swamy, K.C. Mohan,
Acta. Cryst. C:51 (1995) 1556.
[9] Q.Y. Xing, R.Q. Xu, Zh. Zhou, W.W. Fei, Basic Organic
Chemistry, Version 2, People’s Education Press, Peking, 1994,
pp. 1111.
[1] L.J. Henderson, F.R. Fronczek, W.R. Cherry, J. Am. Chem.
Soc. 106 (1984) 5876.
[2] Y.-X.Chen,D.-J.Xu,Y.-Zh.Xu,Appl.Chem.,(Ch)14(1997)78.