A novel coordination mode of 4,5-diazafluorene-9-one quinaldinoylhydrazone (HL) to nickel and the crystal structure of [Ni(L)2(Py) 2](H2O)2 (Py = pyridine)

Article abstract of DOI:10.1016/S0022-2860(03)00419-8

A new ligand 4,5-diazafluorene-9-one quinaldinoylhydrazone (HL) has been designed and synthesized. Ni(II) complex [Ni(L)₂(Py) ₂](H₂O)₂ has been prepared by the reaction of HL, pyridine(Py) with the NiSO₄ 6H₂O. The crystal belongs to triclinic system, P-1 space group. The crystallographic data are: a = 10.531(2) ?, b = 11.748(2) ?, c = 10.342(2) ?, α = 115.19(3)°, β = 90.70(3)°, ￡ = 86.46(3)°. The crystal structure data indicated that the Ni(II) ion was coordinated through two oxygen and two nitrogen atoms from two HL ligands and nitrogen atoms from two pyridine molecules. Ni(II) ion is a six-coordination in the center of the octahedron. The crystal was stabilized by the intermolecular π-π stacking between the diazafluorene planes in adjacent molecules.

Full text of DOI:10.1016/S0022-2860(03)00419-8

Journal of Molecular Structure 658 (2003) 59–64
www.elsevier.com/locate/molstruc
A novel coordination mode of 4,5-diazafluorene-9-one
quinaldinoylhydrazone (HL) to nickel and the crystal structure
of [Ni(L) (Py) ](H O) (Py ¼ Pyridine)
2
2
2
2
*
Chen Xu, Hong-Yan Mao, Hong-Yun Zhang , Qing-An Wu, Hong-Lei Liu,
Hong-Wei Hou, Yu Zhu, Gang Li
Department of chemistry, ZhengZhou University, ZhengZhou 450052, China
Received 27 May 2003; revised 25 June 2003; accepted 25 June 2003
Abstract
A new ligand 4,5-diazafluorene-9-one quinaldinoylhydrazone (HL) has been designed and synthesized. Ni(II) complex
Ni(L) (Py) ](H O) has been prepared by the reaction of HL, pyridine(Py) with the NiSO 6H O. The crystal belongs to
[
2
2
2
2
4
2
˚
˚
˚
triclinic system, P-1 space group. The crystallographic data are: a ¼ 10:531ð2Þ A, b ¼ 11:748ð2Þ A, c ¼ 10:342ð2Þ A, a ¼
1
15:19ð3Þ8; b ¼ 90:70ð3Þ8; g ¼ 86:46ð3Þ8: The crystal structure data indicated that the Ni(II) ion was coordinated through two
oxygen and two nitrogen atoms from two HL ligands and nitrogen atoms from two pyridine molecules. Ni(II) ion is a six-
coordination in the center of the octahedron. The crystal was stabilized by the intermolecular p–p stacking between the
diazafluorene planes in adjacent molecules.
q 2003 Elsevier B.V. All rights reserved.
Keywords: 4,5-Diazafluorene-9-one quinaldinoylhydrazone; Ni(II) complex crystal structure; p–p Stacking
1
. Introduction
a versatile building block for construction of
polypyridyl bridged ligand. On some conditions, it
can coordinate to some metal ions with two nitrogen
atoms [3,4]. 4,5-Diazafluorene-9-one, its derivatives
and theirs complexes have special structures and
properties [5–7], which has been widely reported. Its
aroylhydrazone should have many coordination
modes. Literature has reported they coordinated to
the metal ion with enolic oxygen (sulfur) and
azomethine nitrogen atoms forming a five-member
chelating ring [8,9]. In order to further investigate the
coordination mode of 4,5-diazafluorene-9-one aroyl-
hydrazone, in this paper, we researched the synthesis
Aroylhydrazones are important polydentate
ligands. Due to their biologically activity and variable
bonding when forming complexes with metal ions, the
coordination chemistry of aroylhydrazones has
attracted much attention from chemists in recent
years [1,2]. 4,5-Diazafluorene-9-one is a special
polypyridyl ligand, which has been proven to be
*
Corresponding author. Tel.: þ86-3717763675; fax: þ86-
3717761744.
E-mail address: wzhy917@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)00419-8

60
C. Xu et al. / Journal of Molecular Structure 658 (2003) 59–64
and properties of a new ligand 4,5-diazafluorene-9-
one quinaldinoylhydrazone (HL) and its complex,
finding its coordination mode is different from those
of the past literature. It coordinates to the Ni(II) ion
through the enolic oxygen atom of the amide group
and nitrogen atom of the quinaldic group to form a
five-member chelating ring. The crystal was stabilized
by the intermolecular p–p stacking. The structure
was also characterized through IR and single crystal
X-ray diffraction.
6 h in 65–70 8C water bath, then methanol was
distilled to remove 2/3 volumes. The remainder
diluted with 50 ml water was neutralized using
saturated K CO solution to pH 6–7 to appear
2
3
white precipitation. 1.02 g (yield 58%) methyl
quinaldinic carboxylate were obtained by filtrating,
washing using water and drying at 50–60 8C.
Eight millilitre hydrazine hydrate and three
drops of glacial acetic acid were added to 50 ml
ethanol solution containing 1.02 g (5.45 mmol)
methyl quinaldinic carboxylate. The reaction mix-
ture was heated and refluxed for 6 h in 80–85 8C
water bath, then solvent was distilled to remove 4/5
volumes. The remainder was diluted with 50 ml
water to separate white precipitation, then 0.97 g
2
. Experimental
2
.1. Materials and measurement
Nickel sulfate, 1,10-phenanthroline, quinaldinic
(yield 95%) quinaldinic hydrazide were obtained
through filtrating, washing using water and drying
at 50–60 8C.
acid and other reagents were analytic reagent grade.
Melting points were taken on a XT-5 microscope
melting point apparatus. IR spectra were recorded on
a Nicolet IR-470 spectrometer from KBr pellets in
Six drops of acetic acid were added to a mixture of
quinaldinoyl hydrazine (1.87 g, 10 mmol) and 4,5-
diazafluorene-9-one (1.82 g, 10 mmol) in anhydrous
ethanol (30 ml). The resultant solution was heated to
reflux for 3 h, and after cooled, a yellow solid was
collected by filtration, washed with cold ethanol three
times and dried in vacuum. Yield 50%, m.p. 291–
2
1
range 4000–400 cm . Single crystal was measured
on a Rigaku-Raxis-IV X-ray diffractometer.
2.2. Synthesis of 4,5-diazafluorene-9-one
quinaldinoylhydrazone
2
benzene; slightly soluble in methanol, ethanol; easily
93 8C. The ligand (HL) is insoluble in ether,
4
,5-Diazafluorene-9-one (dafo) was prepared by
the method described in the literature [10]. The ligand
HL) was synthesized from quinaldinic acid and 4,5-
2
soluble in DMF, DMSO. IR (cm , KBr disk),
1
3
338ðnN–HÞ; 3048ðnC–HÞ; 1710ðnCyOÞ; 1561, 1511,
492ðnCyNÞ:
(
1
diazafluorene-9-one as follows:
Three millilitres H SO (98%) was slowly added
2
2.3. Synthesis of [Ni(L) (Py) ](H O)
2 2 2 2
4
dropwise to 50 ml methanol solution containing
.63 g (9.4 mmol) quinaldinic acid in 250 ml three-
neck bottle. The reaction mixture was refluxed for
1
Solution (40 ml) of ethanol/DMF (2:1, v/v) of the
HL (0.5 mmol, 0.175 g) and aqueous solution (3 ml)

C. Xu et al. / Journal of Molecular Structure 658 (2003) 59–64
61
of the NiSO 6H O (0.25 mmol, 0.066 g) were
4
3. Discussion and results
2
mixed together, then five drops of pyridine were
added to the above mentioned solution. Red single
crystal suitable for X-ray structure analyses
was obtained by slow evaporation of solvent at
3.1. IR spectroscopy
A comparison of the IR spectrum of the ligand
(HL) with that of the Ni(II) complex reveals
interesting features. The free ligand (HL) can exhibit
keto–enol tautomerism, however, the nðCyOÞ at
2
1
room temperature after two months. IR (cm , KBr
disk), 3424ðn
Þ; 3065ðnC–HÞ, 1597, 1562, 1524,
C–O
HO–H
1
496ðn Þ; 1030ðn
CyN
Þ:
2
1
21
1
710 cm and the nðN–HÞ at 3338 cm appeared
in IR spectrum of the ligand (HL), indicating the
ligand (HL) remains as the keto tautomer. But the two
bands above disappear in IR spectrum of the complex,
2
.4. Crystal structure determination
Intensity data of [Ni(L) (Py) ](H O) were
2
2
2
2
2
1
21
while two new bands at 1030 cm , 1597 cm is
assigned to nðC–OÞ; nðCyNÞ; indicating that the HL
coordinates to Ni(II) ion in enol-form. The absorption
measured on a Rigaku-Raxis-IV X-ray diffractometer
using graphite-monochromated Mo Ka radiation
ꢀ
ðl ¼ 0:71073 AÞ at 291(2) K. 2958 reflections were
2
1
at 1562 cm for the CyN stretching vibration in the
diazafluorene ring of the complex has not changed
much [11], which shows the non-coordination of this
fragment. All of this evidence indicates that the ligand
measured over the ranges 1:92 < 2u < 25:00; 0 <
h # 12; 213 # k # 13; 212 # I # 12; yielding
2
958 unique reflections. Raw data were corrected
and the structure was solved using the SHELX-97
program, non-hydrogen atoms were located by direct
phase determination and subjected to anisotropic
refinement. The full-matrix least-squares calculation
(HL) coordinates to Ni(II) ion through oxygen atom of
the depronated enolic aroylhydrazone group and
nitrogen atom of quinaldic ring while the diazafluor-
ene is free. IR spectra also suggest that the complex
contained water molecules as shown by nðH–OHÞ at
2
on F were applied on the final refinement. The
refinement converged at R ¼ 0:0567 and WR ¼
1
2
2
1
3424 cm
.
0
:1424 values for reflection with I . 2sðIÞ: Details of
crystal structure determination are summarized in
Table 1. Full atomic data are available as a file in CIF
format, deposited with the CCDC (No. 200267).
3.2. Structure of Ni(II) complex
The structure consist of [Ni(L) (Py) ] molecules
2
2
and water molecules. The selected bond lengths and
Table 1
Crystal date and structure refinement
Table 2
˚
Selected bond length (A) and angle (8)
Formula
52
C H
38
N
12NiO
4
Formula weight
953.65
Red
Color
Ni(1)–O(1)
Ni(1)–O(1)A
Ni(1)–N(1)
Ni(1)–N(1)A
Ni(1)–N(6)
Ni(1)–N(6)A
C(1)–N(1)
2.009(3)
2.009(3)
2.149(3)
2.149(3)
2.129(4)
2.129(4)
1.384(5)
1.325(5)
1.486(6)
1.274(5)
1.320(5)
1.376(5)
1.286(5)
1.330(6)
1.328(6)
1.340(7)
C(16)–N(5)
1.347(6)
115.4(3)
120.4(4)
123.1(4)
180.0(3)
180.0(18)
180.0(2)
90.56(14)
89.44(14)
79.12(12)
100.88(12)
131.4(3)
92.86(14)
126.4(4)
115.5(3)
117.7(4)
3
Crystal size
024 £ 0.20 £ 0.20 mm
Ni(1)–O(1)–C(10)
Ni(1)–N(6)–C(22)
Ni(1)–N(6)–C(26)
O(1)–Ni(1)–O(1)A
N(6)–Ni(1)–N(6)A
N(1)–Ni(1)–N(1)A
O(1)–Ni(1)–N(6)
O(1)–Ni(1)–N(6)A
O(1)–Ni(1)–N(1)
O(1)–Ni(1)–N(1)A
Ni(1)–N(1)–C(1)
N(6)–Ni(1)–N(1)
O(1)–C(10)–N(2)
N(1)–C(9)–C(10)
O(1)–C(10)–C(9)
Crystal system
Triclinic
Space group
p-1
˚
10.531(2) A
˚
11.748(2) A
a
b
˚
10.342(2) A
c
a
115.19(3)8
90.70(3)8
86.46(3)8
N(1)–C(9)
b
C(9)–C(10)
C(10)–O(1)
C(10)–N(2)
N(2)–N(3)
N(3)–C(21)
N(4)–C(11)
N(4)–C(15)
C(20)–N(5)
g
3
˚
V
1155.4(4) A
Z
1
3
1.371(mg m )
D(Calc.)
Fð000Þ
494
2
Goodness-of-fit on F
R indices
1.103
R ¼ 0:0691; WR ¼ 0:1472
1
2

62
C. Xu et al. / Journal of Molecular Structure 658 (2003) 59–64
Fig. 1. ORTEP drawing of the coordination sphere of the Nickel atom with atom numbering scheme (a) and perspective view of the ab plane of
the two-dimensional layer structure (b).
bond angles are listed in Table 2. Fig. 1(a) shows an
ORTEP drawing of the Ni(II) complex with the atom
numbering and Fig. 1(b) is a perspective view of the
two-dimensional layer structure. The molecules
packing in the complex is shown in Fig. 2.
The Ni(II) ion has a coordination geometry that
approximates to octahedral. The ligand (HL) coordi-
nates to Ni(II) as a mono-negative bi-dentate ligand
with enolic oxygen atom of amide group and nitrogen
atom of quinaldic group. The atomic distance data:

C. Xu et al. / Journal of Molecular Structure 658 (2003) 59–64
63
2 2 2 2
Fig. 2. Packing diagram of the unit cell of [Ni(L) (Py) ](H O) looking down the c axis.
˚
Ni(1)–O(1) ¼ Ni(1)–O(1)A ¼ 2.009(3) A, Ni(1)–
neighboring ligand (HL). The center-to-center separ-
˚
ation between the two diazafluorene rings is 3.414 A
˚
N(1) ¼ Ni(1)–N(1)A ¼ 2.149(3) A, Ni(1)–N(6) ¼
˚
Ni(1)–N(6)A ¼ 2.129(4) A, and bond angle data:
(Fig. 1(b)). The water molecules in the crystal lattice
exist as water of crystallization, because they are not
directly bonded to the Ni(II) ion and the ligand (HL).
Table 2 showed that the CyNazomethine bond
˚
(1.286(5) A) is shorter than those of other complexes
˚
(1.295(3), 1.307(3), 1.309(3) A) [8,9], indicating that
O(1)–Ni(1)–O(1)A ¼ 180.0(3)8,
N(6)–Ni(1)–
N(6)A ¼ 180.0(18)8, N(1)–Ni(1)–N(1)A ¼ 180.(2)8,
O(1)–Ni(1)–N(6)A ¼ 90.56(14)8, O(1)–Ni(1)–
N(6) ¼ 89.44(14)8. It can be seen from these par-
ameters that O(1), O(1), N(1), N(1)A atoms from two
ligand (HL) in the equatorial geometry, forming a
parallelogram, while the two nitrogen atoms from the
pyridine occupying the axial site. Ni(II) ion was six-
coordination in the center of the octahedron.
N
azomethine is free. The literature reported that aroylhy-
drazonemoietychelatingtothemetalionsformingfive-
membered rings via the amide oxygen and
azomethine nitrogen atoms [8]. However, the ligand
HL) coordinated to Ni(II) ion forming five-membered
rings and the azomethine nitrogen atom is
(
Least-squares planarity analysis shows that the
diazafluorene plane and the quinaldic plane are almost
coplanar (dihedral angle is 8.88). This is due to the
free. Instead, nitrogen atom of the quinaldic ring
coordinates to Ni(II) ion. The result shows that the
coordinating activity of the nitrogen atom of the
quinaldic ring is stronger than the azomethine nitrogen
atom of the aroylhydrazone group.
2
small torsion angle of N–N–C–O (1.68) and the sp
hybridization of the carbon atoms C(21) (diazafluor-
ene) and C(10) (amide) [8]. The two diazafluorene
rings of neighboring molecules are parallel on each
other (dihedral angle is 08), indicating the strong
intermolecular stacking interaction between the two
As we know, 1,10-phenanthroline is a strong
chelating ligand. The coordinating activity of the 4,5-

64
C. Xu et al. / Journal of Molecular Structure 658 (2003) 59–64
diazafluorene-9-one derived from 1,10-phenanthro-
line has been reduced because of the effect of the
carbonyl group. The 4,5-diazafluorene-9-one easily
coordinates to metal ions only in acidic medium. In
general, the coordinating activity of the azomethine
nitrogen atom and amide oxygen atom of 4,5-
diazafluorene-9-one aroylhydrazone is stronger than
the two nitrogen of 4,5-diazafluorene. If the aromatic
group of the aroylhydrazone is a strong electron-
attract substituent, the coordinating activity of the
azomethine nitrogen atom will be reduced, instead,
coordinating atoms of aromatic group can coordinate
to metal ion. This coordination mode of the ligand
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