Synthesis and characterisation of D-n-D type Schiff base ligands derived from fluorene and 1,10-phenanthroline and its complexes with ruthenium(ll)

Article abstract of DOI:10.3184/030823409X402537

A fluorene derivative, 9H-fluoren-9-one(diphenylmethylene)hydrazone has been synthesised from the reaction of 4,5-diazafluoren-9-one with benzophenone hydrazone and a 1,10-phenanthroline derivative, N-[(1E,2E)-3-phenylprop-2-en-1- ylidene]-1,10-phenanthro

Full text of DOI:10.3184/030823409X402537

ꢌꢃꢁ RESEARCH PAPER
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Synthesis and characterisation of D–›–D type Schiff base ligands
derived from fluorene and 1,10-phenanthroline and its complexes
with ruthenium(II)
Fikriye Tuncel Elmali*, øbrahim Erden, Nebahat Demirhan and Ulvi Avciata
Chemistry Department, Faculty of Arts and Sciences , Yildiz Technical University, 34210 Esenler, Istanbul, Turkey
A fluorene derivative, 9H-fluoren-9-one(diphenylmethylene)hydrazone has been synthesised from the reaction of 4,5-
diazafluoren-9-one with benzophenone hydrazone and a 1,10-phenanthroline derivative, N-[(1E,2E)-3-phenylprop-2-
en-1-ylidene]-1,10-phenanthrolin-5-amine has been synthesised from the reaction of 5-amino-1,10-phenanthroline
with cinnamaldehyde. Ru(II) complexes of these ligands have been prepared and characterised.
Keywords: Schiff base, '±ʌ±'ꢀꢁFRPSOH[ꢀꢁÀXRUHQHꢀꢁꢂꢀꢂꢃꢄꢁSKHQDQWKUROLQH
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JOURNAL OF CHEMICAL RESEARCH 2009 91
The Ru(II) complexes of (1) and (2)ꢁJLYHꢁZHOOꢄGH¿QHGꢁ1H NMR spectra,
ZKLFKꢁSHUPLWꢁXQDPELJXRXVꢁLGHQWL¿FDWLRQꢁDQGꢁDVVHVVPHQWꢁRIꢁSXULW\ꢆꢁ7KHꢁ
chemical shifts of the signals of the Ru(II) complexes (1) and (2) are
quite similar to those of the free ligands, with the sole exception of
ÀXRUHQHꢁSURWRQVꢁDQGꢁꢂꢀꢂꢃꢄSKHQDQWKUROLQHꢁSURWRQVꢁWKDWꢁPRYHꢁKLJKꢁ¿HOGꢁ
due to the diamagnetic currents produced by the bipyridine rings in the
pseudooctahedral geometry. The proton chemical shifts are assigned by
comparison with those for similar compounds.
Results and discussion
7KHꢁ QHZꢁ ÀXRUHQHꢁ (1) and 1,10-phenanthroline (2) ligands have
EHHQꢁ V\QWKHVLVHGꢁ IURPꢁ WKHꢁ UHDFWLRQꢁ RIꢁ ꢎꢀꢉꢄGLD]DÀXRUHQꢄꢌꢄRQHꢁ
and 5-amino-1,10-phenanthroline with benzophenone hydrazone
and cinnamaldehyde in good yield, as shown in Figs 1 and 2.
Their ruthenium complexes have synthesised and isolated as the
KH[DÀXRURSKRVSKDWHꢁVDOWVꢁꢇ)LJVꢁꢏꢁDQGꢁꢎꢈꢆ
IR spectra
Electronic absorption spectra
In the FTIR spectra of (1) and (2), C=N characteristic stretching
YLEUDWLRQꢁEDQGVꢁRIꢁWKHꢁÀXRUHQHꢀꢁꢂꢀꢂꢃꢄSKHQDQWKUROLQHꢁDQGꢁD]RPHWKLQHꢁ
groups showed at 1594, 1627 and 1577, 1608 cm-1, respectively. The
stretching band of the –NH2 group in the benzophenone hydrazone
DQGꢁ& 2ꢁLQꢁWKHꢁÀXRUHQHꢁJURXSVꢁGLVDSSHDUHGꢁLQꢁWKHꢁ,5ꢁVSHFWUXPꢁRIꢁ(1),
and the stretching bands of the –NH2 group in 1,10-phenanthroline
and C=O group in cinnamaldehyde disappeared in the IR spectrum of
(2). This indicates that the condensation reaction has occurred. In the
,5ꢁ VSHFWUDꢁ RIꢁ WKHꢁ FRPSOH[HVꢀꢁ WKHꢁ ÀXRUHQHꢁ DQGꢁ ꢂꢀꢂꢃꢄSKHQDQWKUROLQHꢁ
stretching bands (C=N) at 1594 and 1627 cm-1 shift to the higher
frequencies 1632 and 1637 cm-1, suggesting the coordination of
nitrogen to the metal ions as shown in Figs 3 and 4. The Schiff
base C=N stretching bands appear at 1577 and 1608 cm-1 for the
free ligands; in the complexes, these bands occur in approximately
the same range, showing that the nitrogen atom of the C=Nazomethine
group is not coordinated to the metal ions.
The ligands and complexes are soluble in common polar organic
solvents, such as ethanol, methanol, and chloroform but partially
soluble in non-polar organic solvents such as benzene and hexane.
The UV-Vis spectra of the ligands and Ru(II) complexes were
recorded in methanol (Figs 5 and 6). The absorption spectra of
the ligands and complexes exhibit metal-to-ligand charge transfer
(MLCT) and ligand-centred (LC) bands. The electronic spectra of
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the region of 226 and 303 nm, assigned to S–S* transition due to
WUDQVLWLRQVꢁLQYROYLQJꢁPROHFXODUꢁRUELWDOVꢁORFDWHGꢁRQꢁWKHꢁÀXRUHQHꢁDQGꢁ
1,10-phenanthroline. The second type of transitions appeared in the
range 336–340 nm and can be assigned to n–S* transitions, due to
transitions involving the molecular orbital of the C=N chromophore.
In the electronic absorption spectra of the Ru(II) complexes, the n–S*
WUDQVLWLRQVꢁGXHꢁWRꢁWKHꢁ& 1ꢁJURXSꢁRIꢁÀXRUHQHꢁDQGꢁꢂꢀꢂꢃꢄSKHQDQWKUROLQHꢁ
shifted to lower energy compared to the free ligands. The spectra of
the complexes show charge- transfer transitions different from the
free ligands which can be seen in the range 430–455 nm.
1H NMR spectra
The 1H NMR spectrum of (1) and (2) were recorded in CDCl3-
d6 solution. The 1H NMR spectrum of (2) FRQ¿UPHGꢁ WKHꢁ SURSRVHGꢁ
structure showing a D2O-exchangeble proton at 8.6 ppm as a singlet
SHDNꢁIRUꢁWKHꢁ+& 1ꢁJURXSꢆꢁ7KHꢁÀXRUHQHꢁRIꢁ(1) and 1,10-phenanthroline
of (2) protons appeared at 8.7–7.7 and 9.0–8.2 ppm as multiplets and
phenyl protons at 7.5–7.1, 7.7–6.9 ppm as multiplets, respectively.
The bipyridine rings protons appeared at 8.0–8.1 ppm as a multiplet.
Mass spectra
In the mass spectra, the molecular ion peaks of (1) and (2) appeared
at m/z: 361.25 (M+1, 100%) and 310.41 (M+1, 100%) in the LC/
06ꢁVSHFWUDꢆꢁ0DVVꢁVSHFWUDOꢁGDWDꢁFRQ¿UPHGꢁWKHꢁSURSRVHGꢁVWUXFWXUHꢁRIꢁ
ligands. In the ES-MS spectra for [Ru(1)(bpy)2] and [Ru(2)(bpy)2]
complexes, the signals 774.51 [M+1], 918.82 [M–PF6]+, 1063.77
N
N
O
H2N
+
N
N
N
N
N
Fig. 1 Formation reaction of (1).
N
N
NH2
O
N
N
+
N
Fig. 2 Formation reaction of (2).
N
N
N
N
N
N
N
N
Ru2
+
+
2
N
Ru
N
N
N
N
N
N
Fig. 3 Proposed structure of [Ru(1)(bpy)2].
Fig. 4 Proposed structure of [Ru(2)(bpy)2].

92 JOURNAL OF CHEMICAL RESEARCH 2009
1.75
1.5
2
1.5
1
(2)
1.25
1
(1)
0.75
[Ru(1)(bpy)2]
0.5
[Ru(1)(bpy)2]
0.5
0
0.25
0
200
250
300
350
400
450
500
Wavelength (nm)
200
250
300
350
400
450
500
Wavelength (nm)
Fig. 5 UV-Vis absorption spectra of (1) and [Ru(1)(bpy)2].
Fig. 6 UV-Vis absorption spectra of (2) and Ru(2)(bpy)2].
[M–2PF6]2+ and 723.93 [M+1], 867.12 [M–PF6]+, 1012.78
[M–2PF6]2+ were observed. The measured molecular weights were
consistent with expected values. Elemental analysis of the ligands
show good agreement with the proposed structures.
Conclusion
The paper describes the synthesis, spectral, and thermal
studies of new Schiff base ligands and their Ru(II) complexes
GHULYHGꢁIURPꢁÀXRUHQHꢁDQGꢁꢂꢀꢂꢃꢄSKHQDQWKUROLQHꢆꢁ6FKLIIꢁEDVHVꢁ
and Ru(II) complexes have known use in a wide variety of
applications, as noted above. We hope that these compounds
might be used in the future for such applications.
Fluorescence spectra
In order to characterise the different emissions observed in various
HQYLURQPHQWVꢀꢁWUDQVLHQWꢁÀXRUHVFHQFHꢁPHDVXUHPHQWVꢁZHUHꢁFDUULHGꢁRXWꢁ
for (1) and (2). Dimethylsulfoxide (DMSO), ethanol, methanol and
chloroform were used as solvents. As a result of several experiments,
RSWLPXPꢁÀXRUHVFHQFHꢁHPLVVLRQVꢁRIꢁWKHꢁ(1) and (2) were obtained in
DMSO at room temperature. It was found that the optimum interval
of concentration was between 1.10-5 M and 1.10-6 M. The emission of
(1) and [Ru(1)(bpy)2@ꢁGLGꢁQRWꢁVKRZꢁJRRGꢁÀXRUHVFHQFHꢁHPLVVLRQVꢁEXWꢁ
the emission band of (2) showed a maximum at 500nm in DMSO.
The emission maximum of the [Ru(2)(bpy)2] shifted to 650 nm,
which is substantially red shifted with respect to the emission spectra
of the MCLT.
Received 2 September 2008; accepted 13 December 2008
Paper 08/0145 doi:10.3184/030823409X402537
Published online: 18 February 2009
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1
2
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WHPSHUDWXUHꢁUDQJHꢆꢁ7KHꢁ¿UVWꢁZHLJKWꢁORVVꢁDSSHDUHGꢁDWꢁꢏꢏꢏ°C (40.44%)
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take place in four stages in the 100–1200°C temperature range.
7KHꢁ¿UVWꢁZHLJKWꢁORVVꢁDSSHDUHGꢁDWꢁꢂꢍꢃ°C (12.05%), a second weight
loss appeared at 297°C (48.81%) and a third at 687°C (19.31%).
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is 21.52%).
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)LJXUHVꢁ DSSURSULDWHꢁ WRꢁ WKHꢁ ÀXRUHVFHQFHꢁ DQGꢁ WKHUPRJUDYLPHWULFꢁ
studies are held by the authors and are available upon request.