Synthesis, characterization, and photoluminescence properties of Cu(II), Co(II), Ni(II), and Zn(II) complexes of N-aminopyrimidine-2-thione

Article abstract of DOI:10.3906/kim-1103-55

This research concentrates on the preparation, characterization, and photoluminescence properties of new Co(II), Ni(II), Cu(II), and Zn(II) complexes of N-aminopyrimidine-2-thione. The ligand and metal complexes were characterized by elemental analysis an

Full text of DOI:10.3906/kim-1103-55

Turk J Chem
35 (2011) , 905 – 914.
¨
˙
c
ꢀ TUBITAK
doi:10.3906/kim-1103-55
Synthesis, characterization, and photoluminescence
properties of Cu(II), Co(II), Ni(II), and Zn(II)
complexes of N-aminopyrimidine-2-thione
1
2
2,∗
¨
˙
¨
Zu¨lbiye ONAL , Hu¨seyin ZENGIN , Mehmet SONMEZ
1Department of Chemistry, Faculty of Science, Erciyes University, Kayseri, 38000, TURKEY
2Department of Chemistry, Faculty of Science and Literature, Gaziantep University,
Gaziantep, 27310, TURKEY
e-mail: msonmez@gantep.edu.tr
Received: 29.03.2011
This research concentrates on the preparation, characterization, and photoluminescence properties of
new Co(II), Ni(II), Cu(II), and Zn(II) complexes of N-aminopyrimidine-2-thione. The ligand and metal
complexes were characterized by elemental analysis and spectroscopic studies such as IR, UV/Vis, API-ES,
NMR, fluorescence, and magnetic susceptibility measurements. The ligand and the resulting metal complexes
gave intense emissions (λmax = 408 nm) upon irradiation by ultraviolet light. The photoluminescence
quantum yields and long excited-state lifetimes of the ligand and its complexes were calculated. The
ligand had photoluminescence quantum yields of 36% and long excited-state lifetimes of 3.40 ns. The
photoluminescence intensities and quantum yields of the metal complexes changed upon complexation with
various metals. These novel complexes may be of interest as organic emitting material for electroluminescent
devices.
Key Words: N-aminopyrimidine-2-thione, metal complex, characterization, photoluminescence
Introduction
Pyrimidine is the parent heterocycle of a very important group of compounds that has been extensively studied
due to their occurrence in living systems.1 Considerable attention has been given to metal(II) complexes of the
polydentate Schiff base ligands of N-aminopyrimidine because of their bioinorganic relevance, which has often
∗Corresponding author
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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
been related to their chelating ability with trace metal ions.2−5 Recent findings of the presence of metal-sulfur
and metal-nitrogen bonds at the active sites of several oxidoreductases have stimulated an immense amount of
interest in pyrimidine chemistry.6,7
New organic materials have attracted much attention over recent years for their light-emitting proper-
ties.8−10 For example, organic polymers that exhibit strong luminescence at low driving voltages, particularly
those that emit in the blue region, are of great interest for flat panel display applications.11,12 Rare earth com-
plexes with low-molecular-weight organic ligands have also been extensively studied to obtain highly fluorescent
materials for application in electroluminescent devices13,14 and laser systems.15 Furthermore, luminescent ma-
terials from these low-molecular-weight organic ligands/rare-earth complexes have been prepared as polymer
matrices due to the ease of processing polymers.16,17 However, difficulty in dispersing the low-molecular-weight
organic ligands/ rare-earth metal complexes into a polymer matrix has hindered progress.
Numerous aromatic amines and polymeric arylamines have also been developed as hole-transport layers in
organic electroluminescent research.18,19 The synthesis, luminescence, and cyclic voltammetric studies of novel
binuclear ruthenium(II) complexes were reported by Yang et al.20 These researchers investigated the single-
photon fluorescence of synthesized ligands and their complexes. They concluded that the spectra of the ligands
were similar because of their structural compatibility; however, for their respective complexes, the fluorescence
emission was completely quenched. The synthesis and fluorescence of N-substituted 1- and 2-aminopyrenes have
been studied, and their absorption and fluorescence spectra as well as fluorescence quantum yields in different
solvents were measured and reported.21 It was shown that the fluorescence quantum yield was dependent on
both the structure and solvent polarity. The fluorescent vic-dioxime-type ligand and its mono- and dinuclear
complexes have been studied.22 It was noted that the fluorescence spectra of the probe showed a clear shift in
excitation wavelength maxima upon metal binding, indicating its potential use as a ratiometric metal indicator.
The fluorescence of the complexes was found to be highly sensitive to both polarity and the protic character
of the solvent used. They allow for new fluorescent chemosensors for several transition metals, synthesized by
conjugating 7-mercapto-4-methylcoumarin fluorophore and vic-dioxime as the metal-chelating moiety. It was
further reported that the fluorescence emission intensity of the ligand decreased dramatically depending on the
complex formation with transition metal ions. The decrease in emission intensities was due to the formation of
the coordination complex of the N-atom on the ligand with the metal ions.
The aim of the present work was to synthesize and characterize Co(II), Ni(II), Cu(II), and Zn(II)
complexes with N-aminopyrimidine-2-thione. An investigation of the optical properties of the ligand and its
various complexes in solution was also carried out. The ligand and its various complexes were found to exhibit
intense photoluminescence upon UV irradiation.
Experimental procedure
Materials and instrumentation
All of the chemicals, including 9,10-diphenylanthracene, dimethyl sulfoxide (DMSO), and methanol, were
purchased from Aldrich Chemical Company and used as received.
Elemental analyses (C, H, N, S) were performed using a LECO CHNS model 932 elemental analyzer. IR
906

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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
spectra were obtained using KBr disks of 4000-400 cm−1 with a Bio-Rad-Win-IR spectrometer. The electronic
spectra in the 200-900 nm range were obtained in dimethylformamide (DMF) on a Unicam UV2-100 UV/Vis
spectrophotometer. Magnetic measurements were carried out by the Gouy method using Hg[Co(SCN)4 ] as
the calibrant. Molar conductance was determined in DMF at room temperature using a Jenway model 4070
conductivity meter. 1 H-NMR and 13 C-NMR spectra were recorded with a Bruker 300-MHz UltraShield
TM-NMR instrument. LC/MS-API-ES mass spectra were recorded using an Agilent model 1100 MSD mass
spectrometer. The single-photon fluorescence spectra were collected on a PerkinElmer LS55 luminescence
spectrometer. All of the samples were prepared in spectrophotometric-grade DMSO and analyzed in a 1 cm
optical path quartz cuvette. The solution concentration of the ligands and the complexes in DMSO was 1.0
× 10−5 mol L−1 and the samples were excited at a wavelength of 256 nm. The photoluminescence quantum
efficiencies were calculated using 9,10-diphenylanthracene as the standard.23−25
Preparation of the ligand (LH)
1-Amino-5-(4-methylbenzoyl)-4-(4-methylphenyl)-1H-pyrimidine-2-thione (LH, 1) was prepared according to
the literature method by a 2-step synthesis process.26,27 5-(4-Methylbenzoyl)-4-(4-methylphenyl)-1-(methylphen-
ylmethylenamino)-1H−pyrimidine-2-thione was obtained from acetophenonthiosemicarbazone with 4-(4-meth-
ylbenzoyl)-5-(4-methylphenyl)furan-2,3-dione. In acidic solution, from the hydrolysis of 5-(4-methylbenzoyl)-
4-(4-methylphenyl)-1-(methylphenylmethylenamino)-1H-pyrimidine-2-thione, 1-amino-5-(4-methylbenzoyl)-4-
(4-methylphenyl)-1H -pyrimidine-2-thione was obtained. To a solution of 1 g of 5-(4-methylbenzoyl)-4-(4-
methylphenyl)-1-(methylphenylmethylenamino)-1H-pyrimidine-2-thione in 20 mL of butanol, 20 mL of water
and 5 mL of acetic acid were added, and the mixture was heated under reflux for 45-50 min. Upon cooling,
0.46 g (58%) of 1 was recrystallized from butanol; mp 202 ◦ C; IR (KBr): υ = 3262 (-NH2), 3069 (aromatic
C-H), 2930 (aliphatic C-H), 1653 s (C=O), 1598-1462 m (C=C and C=N), 1160, 835 cm−1 (C=S); 1 H-NMR
(DMSO): δ = 7.71-6.99 (9H, ArH), 7.26 (s, 2H, N-NH2), 2.24 ppm (s, 3H, COArCH3), and 2.19 ppm (s, 3H,
ArCH3). Anal. Calcd. for C19 H17 N3 OS: C, 68.06; H, 5.11; N, 12.53; S, 9.56. Found: C, 67.93; H, 4.82; N,
12.24; S, 9.62%. UV/Vis [λ (nm)]: 266, 304.
Preparation of the complexes
After 0.335 g (1.00 mmol) of LH (1) was dissolved in 25 mL of chloroform and 25 mL of methanol, a solution of
0.5 mmol Co(CH3 COO)2·4H2 O (0.125 g), Ni(CH3 COO)2·4H2 O (0.124 g), Cu(CH3 COO)2·H2 O (0.100 g),
and Zn(CH3 COO)2·2H2 O (0.110 g) methanol was added dropwise with continuous stirring. The mixture was
stirred further for 1 h at 60 ◦ C. The precipitate was filtered off, washed with diethyl ether followed by cold
methanol, and dried in a vacuum desiccator.
[CoL2 ]·H2 O (2): Yield was 306 mg (82%), mp 230 ◦ C. Anal. Calcd. for C38 H34 CoN6 O3 S2 (745.00
g mol−1): C, 61.20; H, 4.60; N, 11.27; S, 8.60. Found: C, 61.03; H, 4.34; N, 11.40; S, 9.00%. Selected IR data
(KBr, ν cm−1): 3440 ν (OH/H2 O), 3327 ν (NH), 3059 (C-Hpyrimidine), 1646 ν (C=O), 1602-1521 (C=C and
C=N), 1173, 873 ν (C=S), 476 (M-N). UV/Vis [λ (nm)]: 268, 274, 417. μeff, 2.04 BM, Λo (S cm2 mol−1
)
13.11. API-ES: m/z 747.0 [59 Co(L)2 +2].
[NiL2 ]2 ·H2 O (3): Yield was 298 mg (88%), mp 263 ◦ C. Anal. Calcd. for C38 H32 N6 NiO3 S2 (735.71
907

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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
g mol−1): C, 61.97; H, 4.52; N, 11.41; S, 8.71. Found: C, 61.70; H, 4.43; N, 11.61; S, 9.15%. Selected IR data,
ν (cm−1): 3412 ν (OH/H2 O), 3325 ν (NH), 3059 (C-Hpyrimidine), 1649 ν (C=O), 1602-1523 (C=C and C=N),
1169, 891 ν (C=S), 477 (M-N). UV/Vis [λ (nm)]: 268, 290, 370, 460, 556. μeff, Dia, Λo (S cm2 mol−1) 3.50.
API-ES: m/z 1475.1 [58 Ni2 L4 +H2 O+3]; 726.9 [58 NiL2 ]+ .
[CuL2 ]2 (4): Yield was 355 mg (49%), mp 227 ◦ C. Anal. Calcd. for C76 H64 Co2 N12 O6 S4 (1462.2 g
mol−1): C, 62.32; H, 4.40; N, 11.48; S, 8.76. Found: C, 62.49; H, 4.47; N, 11.62; S, 9.22%. Selected IR data,
ν (cm−1): 3327 ν (NH), 3059 (C-Hpyrimidine), 1657 ν (C=O), 1603 (C=Npyrimidine), 1169, 890 ν (C=S), 486
(M-N). UV/Vis [λ (nm)]: 282, 310, 378, 432, 678. μeff, 1.81 BM, Λo (S cm2 mol−1) 11.12. API-ES: m/z
1463.1 ([CuL2 ]2 +1); m/z 733.2 [CuL2 +1].
[ZnL2 ] (5): Yield was 225 mg (61%), mp 251 ◦ C. Anal. Calcd. for C38 H32 N6 O3 S2 Zn (732.00 g
mol−1): C, 62.16; H, 4.39; N, 11.45; S, 8.73. Found: C, 61.76; H, 4.40; N, 11.46; S, 9.00%. Selected IR data,
ν (cm−1): 3309 ν (NH), 3058 (C-Hpyrimidine), 1642 ν (C=O), 1601 (C=Npyrimidine), 1169, 875 ν (C=S), 492
ν (M-N). 1 H-NMR (DMSO, ppm): δ = 8.55 (s, 2 H, C-Hpyrimidine), 7.13 (d, J = 8.06 Hz, 4H, (Pym)Ph-Hm),
7.25 (d, J = 8.06 Hz, 4H, (CO)Ph-Hm), 7.34 (d, J = 8.07 Hz, 4H, (Pym)Ph-Ho), 7.67 (d, J = 8.10 Hz,
4H, (Pym)Ph-Ho), 2.51, 2.23 ppm (s, 12H, 4 × CH3).13 C-NMR (DMSO-d6 , ppm), δ 191.62 (OC-Ar), 174.85
(C=S, pyrimidine), 161.42 (-C6, pyrimidine), 145.22-120.64 (C, aromatic), 21.64, 21.32 (CH3). UV/Vis [λ
(nm)]: 266, 304, 356. μeff, Dia, Λo (S cm2 mol−1) 4.56. API-ES: m/z 733.8 [ZnL2 +1].
Results and discussion
Synthesis
1-Aminopyrimidine-2(1H)-thione (LH, 1) was prepared according to the literature method by a 2-step synthesis
process.26,27 The ligand and its complexes were very stable at room temperature in the solid state. The ligand
is soluble in common organic solvents, but its metal complexes are generally only soluble in DMF and DMSO.
The microanalytical data of the complexes revealed a metal:ligand stoichiometry of 1:2, corresponding to a
square planar geometry of [M(L)2 ] or [M(L)2 ]2·nH2 O (Figure 1). These analytical data are in good agreement
with the proposed stoichiometry of the complexes. The molar conductivities of compounds 2-5 in DMF at 25
◦ C are in the range of 3.50-13.11 Ω−1 cm2 mol−1 , indicating nonelectrolytes.28
CH3
O
H
CH3
N
S
N
N
M
N
N
N
S
H3C
N
H
O
O
H3C
CH3
CH3
H
N
O
O
H
N
CH3
CH3
S
N
S
N
N
N
M
M
N
N
S
H3C
N
H
N
S
H3C
N
H
O
H3C
H3C
M = Co(II), Zn(II)
M = Cu(II), Ni(II)
Figure 1. Proposed chemical structure of the metal complexes.
908

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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
Structural study
Characteristic IR bands of the ligand were assigned at 3262 cm−1 ν (NH2), 3069 cm−1 ν (C–H pyrimidine ring),
l652 cm−1 ν (C=O benzoyl), 1602 (C=Npyrimidine), 1160, and 835 ν (C=S) vibrations.29,30 IR spectra of the
complexes were compared with that of the free ligand to show changes during complexation. Co(II), Ni(II),
Cu(II), and Zn(II) complexes of the ligand at 3241 cm−1 for υ(NH) primer amine asymmetric-symmetric
stretching vibration bands vanished, and the sec-amine peak was observed at 3309-3423 cm−1 . The ν (C=S)
vibration at 1160 and 835 cm−1 in the free ligand shifted to a higher frequency, to approximately 1170 and 870
cm−1 , after complexation, due to coordination with the sulfur atom of the thione group to the metal ion.29−31
This situation indicated coordination of sulfur and nitrogen to the metal(II) ion.32 Thus, a metal-ligand bond
formed over the NH2 group, which lost one proton of the ligand.33 The low frequency region of the spectra
revealed the presence of a new medium-intensity band between 470 and 490 cm−1 due to ν (M–N) vibrations.33
The UV/Vis spectral data of the compounds in DMF are presented in the experimental section. There
were 2 absorption bands, assigned to n-π * and π − π * transitions, in the electronic spectrum of the ligand.
These transitions were also observed in the spectra of the complexes, but they were shifted toward lower and
higher frequencies, confirming the coordination of the ligand to the metallic ions.34
The electronic absorption spectrum of the Ni(II) complex showed 2 bands, at 565 and 650 nm, which
1
1
1
1
were attributed to the A1g → A2g and A1g → B2g transitions.35 These transitions, as well as the measured
value of the magnetic moment (μeff = 0), suggested a square-planar stereochemistry for the compound.
Since the zinc ion has a d10 configuration, the absorption at 390 nm could be assigned to a charge-transfer
transition. However, taking into account the spectrum and the configuration of the zinc(II) ion, a tetrahedral
geometry may be assumed for its complex.34,36
The electronic absorption spectrum of the copper complex exhibited bands at 440 and 645 nm, which
2
2
2
2
could be assigned to the B1g → A1g and B1g → E1g transitions. These transitions, together with the
measured value of the magnetic moment (μeff = 1.88 BM), suggested a square-planar stereochemistry for
this compound. The values for the effective magnetic moment obtained from the measurements of magnetic
susceptibility (1.77-1.80 BM) were characteristic for copper(II) ions of a square-planar local configuration.37
DMSO-d6 was used as a solvent for 1 H-NMR and 13 C-NMR spectra. In the 1 H-NMR spectrum of 1-
amino-5-(4-methylbenzoyl)-4-(4-methylphenyl)-1H-pyrimidine-2-thione, a singlet signal at δ 7.26 ppm assigned
to the NH2 band on the pyrimidine molecule was observed.27 The 1 H-NMR spectrum of the Zn(II) complex
is shown in Figure 2. In the spectra of the diamagnetic Zn(II) complexes, the low field signals due to the NH2
protons disappeared, indicating the replacement of these protons by the metal ion. The multiplets in the region
of δ 7.74-7.11 ppm were due to aromatic protons, and singlets in the region of 2.51 and 2.23 ppm were due to
the methyl protons in the free ligand.27 On the basis of the above discussion, a square-planar structure can be
suggested for the Zn(II) complex (Figure 1).
The 13 C-NMR spectrum of the Zn(II) complex is shown in Figure 3. It displayed characteristic signals
at 191.62, 174.85, and 161.42 ppm due to the (OC-Ar), (C=O, pyrimidine), and (-C6, pyrimidine ring) of
the Zn(II) complexes, respectively. The singlets at δ 145.22-120.64 and 21.64 and 21.32 ppm were due to the
aromatic and methyl carbons of the complex.38
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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
Figure 2. 1 H-NMR spectrum of Zn(II) complex.
Figure 3. 13 C-NMR spectrum of Zn(II) complex.
910

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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
The LC/MS-API-ES spectra of the [CoL2 ]·H2 O, [NiL2 ]2·H2 O, [CuL2 ]2 , and [ZnL2 ] complexes showed
molecular ion peaks [59 Co(L)2 +2], [58 Ni2 L4 +H2 O+3], [[CuL2 ]2 +1], and [ZnL2 +1] at m/z 747.0, 1475.1,
1463.1, and 733.8, respectively. All of the compounds were consistent with the molecular ion fragment and
support the proposed structure of the complexes. The Co(II) and Ni(II) complexes had one additional water of
crystallization. Single crystals of the compounds could not be isolated.
Fluorescence measurements
The optical properties of the ligand and its various complexes were explored using UV/Vis and photolumines-
cence. Absorption and photoluminescence spectra were studied for solutions of the ligand excited at 256 nm.
The most striking feature was that the ligand gave an intense emission upon irradiation by UV light. The
photoluminescence spectrum of the ligand in DMSO is shown in Figure 4. Maximum luminescent intensity was
observed at 408 nm, and the full width at half maximum was 116 nm. The ligand exhibited a photoluminescence
quantum yield of 36% and a long excited-state lifetime of 3.40 ns. The high quantum yields resulted from the
π -electron’s extensive delocalization, forming a large conjugated system in the ligand structure.
800
Ex. of 5
Ex. of 4
Ex. of 1
Ex. of 3
Ex. of 2
Em. of 5
Em. of 4
Em. of 1
Em. of 3
Em. of 2
700
600
500
400
300
200
100
0
160
220
280
340
400
460
520
580
Wavelength (nm)
Figure 4. Photoluminescence spectra of the ligand and its various complexes in DMSO; samples were excited at 256
nm.
Figure 4 also shows the comparison of excitation and emission spectra of the ligand and its various
complexes in the solvent DMSO. The complexes, the preparation of which is described in the experimental
section, were used for the luminescent measurements. The photoluminescence intensities and quantum yields
of the metal complexes changed with respect to that of the ligand upon complexation with various metals. As
seen in Figure 4, the ligand exhibited an excitation maximum wavelength at 260 nm, which shifted to 272 nm
upon binding to the transition metal ions. Furthermore, a decrease in the excitation intensity of the ligand
was observed depending on complex formation with Co and Ni transition metal ions. However, an increase in
excitation intensity of the ligand was observed depending on complex formation with Cu2+ and Zn2+ metal
911

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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
ions. When excited at 260 nm, the ligand showed an emission maximum at 408 nm, which shifted to 439 nm
upon binding to the transition metal ions (Figure 4). Thus, it is evident that the fluorescence emission intensity
of the ligand decreases dramatically depending on the complex formation with the transition metal ions. The
decrease of emission intensities is due to the formation of the coordination complex of the S and N atom in the
ligand with the metal ions. These coordination complexes make the energy transfer possible from the excited
state of the ligand to the metal ions, thus increasing the nonradiated transition of the ligand excited state and
decreasing the fluorescence emission. However, the degree of the fluorescence quenching increases upon complex
formation with metal ions, which have lower d-orbital electron numbers. The decreases in emission maxima
were in the order of Zn2+ < Cu2+ < Ni2+ < Co2+ for the synthesized complexes (Figure 4). This clearly
implicates an interaction between the metal and the ligand.
The emission of the ligand, being inhibited in this case, is dependent on the presence of a metal ion, and
the ligand photoluminescence in DMSO is regarded as being dependent on the d-block metals that are effective in
DMSO solutions. Quenching of fluorescence of the ligand by transition metal ions during complexation is a rather
common phenomenon, which can be explained by processes including magnetic perturbation, redox-activity, and
electronic energy transfer.39,40 Enhancement of fluorescence through complexation is, however, of much interest,
as it opens up the opportunity for photochemical applications of these complexes.41,42 It can be seen in Figure
4 that upon complexation of the ligand, the photoluminescence intensities and quantum yields of the Cu2+ and
Zn2+ metal complexes increase. The increase in intensity is due to the formation of a metal-to-ligand ratio of
1:2, resulting in larger molecule formation. There are 2 driving forces competing here: the interaction between
the metal and ligand due to complexation results in a reduction of photoluminescence intensities, while the
formation of the metal-to-ligand ratio of 1:2 leads to an increase in photoluminescence intensities and thus the
formation of larger molecules. The first instance, where there is a reduction of photoluminescence, is greater
for the Co and Ni complexes, while the second case applies for the Cu and Zn complexes. Additionally, upon
Table. Photoluminescence data for the ligand and its various complexes.
Entity
λmax Ex (nm) In Ex
λmax Em (nm)
In Em φf (%) τf (ns)
LH (1)
260
(226, 241, 269)
258
615
520
563
699
787
408
(355, 379, 435, 471)
374
608
515
557
691
778
36
32
34
40
44
3.40
2.99
3.17
3.75
4.10
L-Co (2)
L-Ni (3)
L-Cu (4)
L-Zn (5)
(219, 236, 267)
259
(353, 402, 433, 465)
405
(225, 242, 268)
269
(354, 379, 436, 468)
439
(226, 242, 259)
272
(359, 384, 411, 476)
436
L-Zn (5) (226, 242, 258)
(359, 379, 413, 486)
λmax Ex: maximum excitation wavelength, In Ex: maximum excitation intensity,
λmax Em: maximum emission wavelength, In Em: maximum emission intensity,
φf : quantum yield, τf : excited-state lifetime; L: ligand.
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Synthesis, characterization, and photoluminescence..., Z. ONAL, et al.
complexation of the ligand, the maximum photoluminescence peak shifted from 408 to 439 nm, and other peaks
and shoulder peaks became more intense and obvious. Some electrons of the atoms or moieties of this ligand
become affected by the inserted metal ions. This emission wavelength difference can probably be used for
tuning in photoluminescent devices. The photoluminescence data for the ligand and its various complexes are
summarized in the Table. The photoluminescent properties of these compounds may indicate a great deal of
potential for numerous optical and electronic applications.
Conclusion
In this study, the synthesis, spectroscopic characterization, and photoluminescence properties of a N-aminopyri-
midine-2-thione ligand and its various complexes were presented. The structures of the metal complexes
were characterized with UV/Vis, FT-IR, 1 H- and 13 C-NMR, and magnetic susceptibility and electrolytic
measurement techniques. The ligand was found to exhibit an intense photoluminescence at 408 nm, and
the complexes showed great changes in maximum luminescence intensities and quantum efficiencies. Upon
complexation, the luminescence peak shifted from 408 to 439 nm. These compounds may be interesting materials
for application in electroluminescent devices.
Acknowledgements
¨
˙
The authors wish to thank TUBITAK for financial support (Project No: 104M367). We would also like to
thank the Departments of Chemistry of Gaziantep University and Erciyes University.
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