Neutral and cationic palladium(II) and platinum(II) complexes of 2,2′-dipyridylamine with saccharinate: Syntheses, spectroscopic, structural, fluorescent and thermal studies

Article abstract of DOI:10.1016/j.ica.2010.03.077

Four palladium(II) and platinum(II) complexes of 2,2′-dipyridylamine (dpya) with saccharinate (sac), cis-[Pd(dpya)(sac)₂]·H ₂O (1), cis-[Pt(dpya)(sac)₂]·H₂O (2), [Pd(dpya)₂](sac)₂·2H₂O (3) and [Pt(dpya)₂](sac)₂·2H₂O (4), have been synthesized and characterized by elemental analysis, IR, NMR, TG-DTA and X-ray diffraction. In 1 and 2, the metal ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of dpya, resulting in a neutral square-planar coordination sphere, while in 3 and 4, the metal ions are coordinated by two dpya ligands to generate square-planar cationic species, which are stabilized by two sac counter-ions. The mononuclear species of 1 and 2 interact each other through weak intermolecular N-H?O, C-H?O and π?π interactions to form a three-dimensional network, while the ions of 3 and 4 are connected by N-H?N and OW-H?O hydrogen bonds into one-dimensional chains. On heating at 250 °C, the solid cationic complexes of 3 and 4 convert to corresponding anhydrous neutral complexes of 1 and 2 after elimination of a dpya ligand. In addition, all complexes 1-4 are luminescent at room temperature and their emissions seem to be attributed to the MLCT fluorescence.

Full text of DOI:10.1016/j.ica.2010.03.077

Inorganica Chimica Acta 363 (2010) 2416–2424
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Neutral and cationic palladium(II) and platinum(II) complexes of
0
2
,2 -dipyridylamine with saccharinate: Syntheses, spectroscopic, structural,
fluorescent and thermal studies
Emel Guney , Veysel T. Yilmaz a,*, Orhan Buyukgungor b
a
a
Department of Chemistry, Faculty of Arts and Sciences, Uludag University, 16059 Bursa, Turkey
Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Samsun, Turkey
b
a r t i c l e i n f o
a b s t r a c t
0
Article history:
Four palladium(II) and platinum(II) complexes of 2,2 -dipyridylamine (dpya) with saccharinate (sac), cis-
Received 25 February 2010
Received in revised form 23 March 2010
Accepted 29 March 2010
Available online 9 April 2010
[
(
Pd(dpya)(sac)
2
]ꢀH
2
O
(1), cis-[Pt(dpya)(sac)
2
]ꢀH
2
O
(2), [Pd(dpya)
2
](sac)
2
ꢀ2H
2 2
O (3) and [Pt(dpya) ]
sac) O (4), have been synthesized and characterized by elemental analysis, IR, NMR, TG-DTA and
2
ꢀ2H
2
X-ray diffraction. In 1 and 2, the metal ions are coordinated by two N-bonded sac ligands, and two nitro-
gen atoms of dpya, resulting in a neutral square-planar coordination sphere, while in 3 and 4, the metal
ions are coordinated by two dpya ligands to generate square-planar cationic species, which are stabilized
by two sac counter-ions. The mononuclear species of 1 and 2 interact each other through weak intermo-
Keywords:
Saccharinate
0
lecular N–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀO and
pꢀ ꢀ ꢀp interactions to form a three-dimensional network, while the ions of 3
2
,2 -Dipyridylamine
and 4 are connected by N–Hꢀ ꢀ ꢀN and OW–Hꢀ ꢀ ꢀO hydrogen bonds into one-dimensional chains. On heating
at 250 °C, the solid cationic complexes of 3 and 4 convert to corresponding anhydrous neutral complexes
of 1 and 2 after elimination of a dpya ligand. In addition, all complexes 1–4 are luminescent at room tem-
perature and their emissions seem to be attributed to the MLCT fluorescence.
Palladium(II)
Platinum(II)
Crystal structures
Ó 2010 Elsevier B.V. All rights reserved.
1
. Introduction
Saccharin (sacH, also named 1,1-dioxo-1,2-benzothiazol-3-one
Only three metal complexes of sac with dpya have been re-
ported in recent years [13–15]. The dpya ligand acts in a bidentate
chelating fashion in these complexes. In [Cu(dpya)(sac)
[13,14], one sac is N-bonded, while the other is O-bonded, whereas
in [Cd(dpya) (sac)(H O [15], two sac anions act as a
O)](sac)ꢀH
ligand and a counter-ion, but in [Hg(dpya)(sac) ] [15], both sac
2 2
(H O)]
or o-benzosulfimide) is a well-known artificial sweetener and
readily deprotonates in solutions, forming the corresponding sac-
charinate anion (sac). Owing to the presence of the imino, carbonyl
and sulfonyl donor sites, sac acts as a mono-, bi- or tridentate poly-
functional ligand and coordinates many transition metal ions,
forming complexes from mononuclear species to coordination
polymers. The earlier work in this field has been comprehensively
2
2
2
2
ligands are N-coordinated. On the other hand, palladium(II) and
platinum(II) complexes of sac are rare and only a few complexes
have been reported [16–19]. As part of our continuing study of me-
tal complexes of sac, we have recently reported the palladium(II)
0
0
00
reviewed by Baran and Yilmaz [1].
and platinum(II) complexes of sac with 2,2 :6 ,2 -terpyridine
0
0
2
,2 -Dipyridylamine (dpya) is an aromatic amine. It behaves as a
(terpy) [20] and 2,2 -bipyridine (bpy) [21]. In the present work,
neutral or monoanionic ligand. The NH group is usually not in-
volved in coordination because of geometrical constraints and
the two pyridine rings are flexible in their coordination to metal
centers, leading to different coordination modes such as monoden-
tate, chelating bidentate and bridging tridentate [2–7]. In recent
years, palladium(II) and platinum(II) complexes of dpya have re-
ceived increasing attention and have been investigated due to their
use as potential anticancer agents [8–12].
we report the synthesis, characterization and crystal structures of
new palladium(II) and platinum(II) complexes of dpya containing
sac. The new complexes are classified into two groups such as
neutral complexes, cis-[Pd(dpya)(sac)
(sac) O (2), and cationic complexes, [Pd(dpya)
]ꢀH
(3) and [Pt(dpya) ](sac) O (4). In complexes 1–4, the dpya
ꢀ2H
2
]ꢀH
2
O (1) and cis-[Pt(dpya)-
2
2
2
](sac)
2
2
ꢀ2H O
2
2
2
ligand behaves as a bidentate chelating ligand. However, both sac
anions in the neutral complexes coordinate the metal(II) ions,
while these sac anions in the cationic complexes are present as
counter-ions, remaining in the outside coordination sphere.
Furthermore, the luminescent and thermal properties of these
complexes have also been studied.
*
Corresponding author.
E-mail address: vtyilmaz@uludag.edu.tr (V.T. Yilmaz).
0
020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.03.077

E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
2417
2
. Experimental
.1. Materials and measurements
M(dpya)Cl ] was prepared according to the literature methods
tion of dpya (1 mmol) in methanol (10 ml) and this suspension
was set to reflux overnight. Then, the resulting solution was fil-
2
tered off and mixed with a 5 ml aqueous solution of Na(sac)ꢀ2H
1 mmol, 0.24 g). This solution was stirred at 60 °C for 2 h and
evaporated to about 10 ml. Well shaped yellow crystals of
2
O
(
[
2
II
II
II
II
(
M = Pd [9] and Pt [9,22]). Other chemicals were purchased and
[M(dpya)
within a day.
2
](sac)
2
ꢀ2H
2
O (3 for Pd and 4 for Pt ) were obtained
used without further purification. Elemental analyses for C, H,
and N were performed using a Costech elemental analyser. UV–
Vis spectra were measured on a Shimadzu 1700UV spectropho-
ꢂ5
2.2.1. [Pd(dpya)(sac)
Yield 86%. M.p. 280–290 °C (decomp.). Anal. Calc. for
Pd: C, 43.7; H, 2.9; N, 10.6. Found: C, 43.5; H, 3.2;
N, 10.7%. H NMR (400 MHz, DMSO-d ): d 11.41 (s, 1H, NH),
2
]ꢀH
2
O (1)
tometer using 1 ꢁ 10 M DMSO/water solutions (1:1) in the
2
6
00–800 nm range. IR spectra were recorded on a Thermo Nicolet
700 FT-IR spectrophotometer as KBr pellets in the frequency
24 19 5 7 2
C H N O S
1
ꢂ1
1
13
6
range 4000–400 cm
corded on a Varian Mercuryplus spectrometer. Thermal analysis
curves (TG and DTA) were obtained from a Seiko Exstar TG/DTA
.
H NMR and C NMR spectra were re-
0
0
5
6
6
5
8
7
H
.22–8.20 (d, 2H, H and H ), 8.01–7.97 (t, 2H, H and H ), 7.78–
0
3
sac
3
.69 (m, 8H, H ), 7.40–7.38 (d, 2H, H and H ), 7.14–7.11 (t, 2H,
0
4
4
13
6
and H ). C NMR (400 MHz, DMSO-d ): d 165.60, 150.10,
6
200 thermal analyser in a flowing air atmosphere with a heating
ꢂ1
149.56, 142.36, 142.03, 133.44, 133.27, 130.97, 123.68, 120.21,
rate of 10 K min using a sample size of 5–10 mg and platinum
ꢂ1
ꢂ3
119.83, 114.77. (Solid KBr pellet):
(OH), 3296w
028m (CH), 2923w
(CN), 1530m, 1479vs
m
(cm ) 3569m
m
(OH), 3484sb
(CH),
(CO), 1590s
(C@C), 1420w, 1338w
), 1175vs (SO ), 1161vs
as(CNS), 903w, 874w, 778s,
crucibles. Excitation and emission spectra of 1 ꢁ 10 M DMSO/
m
3
m
m
m
m
(NH), 3243w, 3194m, 3136w, 3087m
(CH), 2848w (CH), 1659vs
(C@C), 1436w
), 1248s as(SO
), 1125m, 1058w, 1025w, 967s
m
water solutions (1:1) were recorded at room temperature with a
Varian Cary Eclipse spectrophotometer equipped with a Xe pulse
lamp of 75 kW.
m
m
m
m
m
m
s
(CNS), 1294vs
(SO
m
as(SO
2
m
2
m
s
2
s
2
m
2.2. Synthesis of the palladium(II) and platinum(II) complexes
7
54s, 678m, 596s, 565m, 535s.
Complexes 1 and 2 were synthesized by the following method.
AgNO
3
(1 mmol, 0.17 g) was added to a suspension of [M(dpya)Cl
2
]
2.2.2. [Pt(dpya)(sac)
Yield 80%. M.p. 307–318 °C (decomp.). Anal. Calc. for
Pt: C, 38.5; H, 2.6; N, 9.4. Found: C, 38.2; H, 2.9; N,
9.7%. H NMR (400 MHz, DMSO-d ): d 11.36 (s, 1H, NH), 8.35–
2
]ꢀH
2
O (2)
(
0.5 mmol) in water (200 ml) and then, this suspension was re-
fluxed for 6 h. After cooling to room temperature, the precipitate
of AgCl was removed by filtering through Celite paste to obtain a
clear solution. The filtrate was concentrated to 25 ml and followed
24 19 5 7 2
C H N O S
1
6
0
0
5
6
6
5
8.12 (d, 2H, H and H ), 7.95–7.85 (t, 2H, H and H ), 7.83–7.60
0
sac
3
3
4
by the addition of Na(sac)ꢀ2H
2
O (1 mmol, 0.24 g) and stirred at
O, a poly-
(m, 8H, H ), 7.35–7.14 (d, 2H, H and H ), 7.14–6.90 (t, 2H, H
0
4
13
6
0 °C for 30 min. As soon as the addition of Na(sac)ꢀ2H
2
and H ).
C
NMR (400 MHz, DMSO-d
6
):
d
165.25, 150.32,
crystalline yellow precipitate was formed. The final suspension
was cooled to room temperature and filtered off to remove the yel-
146.85, 142.20, 141.38, 133.18, 133.01, 131.66, 123.80, 120.41,
ꢂ1
119.98, 116.07. (Solid KBr pellet):
3297w, 3195m (NH), 3137w, 3079m
2920w (CH), 1652vs (CO), 1591m
(C@C), 1435w (C@C), 1339w (CNS), 1305vs
as(SO ), 1177vs (SO ), 1160vs
m
(cm
)
3448sb
m
(OH),
(CH),
(CN), 1532m, 1485vs
as(SO ), 1258vs
II
II
low solid [M(dpya)(sac)
crystalline yellow powders were recrystallized from a mixture of
water and DMSO (1:1).
2
]ꢀH
2
O (1 for Pd and 2 for Pt ). The poly-
m
m(CH), 3022m m
m
m
m
m
m
m
m
m
s
m
2
For the synthesis of complexes 3 and 4, a suspension of
2
m
s
2
m
s
(SO
2
), 1129s, 1058w, 969s
[
M(dpya)Cl
2
] (0.5 mmol) in water (50 ml) was mixed with a solu-
as(CNS), 758s, 677s, 595vs, 566s, 525m.
Table 1
Crystallographic data and structure refinement for 1–4.
Complex
1
2
3
4
Formula
M
T (K)
C
24
H
19
N
5
O
7 2
S Pd
C
24
H
17
5
N O
S
6 2
Pt
C
34
H
30
N
8
O
8 2
S Pd
34 30 8 8 2
C H N O S Pt
659.96
295(2)
0.71073
730.64
295(2)
0.71073
849.18
295(2)
0.71073
937.87
295(2)
0.71073
k (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1ꢀ
triclinic
P1ꢀ
9.6972(7)
9.9176(9)
13.2449(10)
85.926(6)
86.758(6)
81.811(7)
1256.24(17)
2
monoclinic
P2 /c
11.0900(5)
12.8646(5)
16.1348(7)
90
131.338(2)
90
1728.35(13)
2
monoclinic
P2 /c
11.0789(4)
12.8623(3)
16.1324(6)
90
131.393(2)
90
1724.59(10)
2
1
1
9.8338(7)
9.7194(6)
13.3028(8)
87.173(5)
85.591(5)
81.862(6)
1253.98(14)
2
1.748
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
ꢂ3
calcd (g cm
ꢂ1
)
1.929
5.802
1.632
0.723
1.806
4.255
(mm
)
0.963
F(0 0 0)
h Range (°)
Index range
664
1.54–26.50
708
2.08–26.50
864
2.31–26.50
928
2.31–26.50
ꢂ12 6 h 6 12,
ꢂ12 6 h 6 12,
ꢂ13 6 h 6 13,
ꢂ13 6 h 6 13,
ꢂ12 6 k 6 12, ꢂ16 6 l 6 16
ꢂ12 6 k 6 12, ꢂ16 6 l 6 16
ꢂ16 6 k 6 16, ꢂ20 6 l 6 20
ꢂ16 6 k 6 16, ꢂ20 6 l 6 20
Reflections collected
Data/parameters
Goodness-of-fit (GOF) on F
18 366
5198/358
1.060
12 239
5145/343
1.051
18 825
3578/247
1.048
22 372
3570/248
1.068
2
R
wR
1
[I > 2
r
]
0.0425
0.1059
0.0716
0.1416
0.0349
0.0751
0.0204
0.0489
2

2
418
E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
H
N
H
N
N
N
2
Na(sac)
o
M
N
N
in H O 60 C
O
S
O
C
2
O
in H O
2
M
N
N
S
O
reflux
C
O
O N
NO3
3
(aq)
2
AgNO3
O
Neutral
H
N
o
2
50 C
II
II
(
M = Pd or Pt )
N
N
-
dpya
M
Cl
in H O
Cl
2
2
+
H
N
H
N
reflux
2
dpya
O
S
O
N
N
N
N
N
N
N
N
2
Na(sac)
M
M
N
o
in H O 60 C
2
C
O
2
N
H
N
H
(aq)
Cationic
Scheme 1. Synthesis of complexes 1–4.
2
.2.3. [Pd(dpya)
2
](sac)
2
ꢀ2H
2
O (3)
3293sb
1650vs
m
m
(NH), 3130w, 3071w
(CO), 1626vs (CO), 1585vs
(C@C), 1417w, 1358w, 1338w
as(SO ), 1168vs (SO ), 1155vs
1053w, 1025w, 968m as(CNS), 952m, 903w, 787m, 765s, 745m,
m
(CH), 2981w
(CN), 1534m, 1472vs
(CNS), 1270s
(SO ), 1119w,
m(CH), 2901w,
Yield 85%. M.p. 330–338 °C (decomp.). Anal. Calc. for
Pd: C, 48.1; H, 3.6; N, 13.2. Found: C, 48.4; H, 3.4;
): d 11.65 (s, 2H, NH),
m
m
C
34
30
H N
8
O
8
S
2
m(C@C), 1435m
m
m
s
mas(-
1
N, 13.5%. H NMR (400 MHz, DMSO-d
8
7
6
SO ), 1251s
2
m
2
m
s
2
m
s
2
0
0
5
6
6
5
.20–8.17 (m, 4H, H and H ), 8.09–8.03 (m, 4H, H and H ),
m
0
3
sac
3
.77–7.53 (m, 8H, H ), 7.47–7.41 (d, 4H, H and H ), 7.14–7.08
675m, 637w, 605m, 543m, 461w.
0
4
4
13
(
m, 4H, H and H ). C NMR (400 MHz, DMSO-d
6
): d 165.57,
1
1
54.82, 150.06, 147.82, 142.30, 137.94, 132.04, 131.47, 122.96,
ꢂ1
2.2.4. [Pt(dpya) ](sac) ꢀ2H O (4)
2
2
2
20.23, 119.60, 116.24. (Solid KBr pellet):
m (cm ) 3385sb m(OH),
Yield 80%. M.p. 350–360 °C (decomp.). Anal. Calc. for
C H
34 30
N
8
O
S
8 2
Pd: C, 43.5; H, 3.2; N, 12.0. Found: C, 43.7; H, 3.0;
Table 2
Electronic and photoluminescence spectral dataa for 1–4.
Table 3
Selected FT-IR spectral data for 1–4.
a
Compounds
UV–Vis (k/nm)
Excitation
Emission
(k/nm)
ꢂ1
ꢂ1
(
e
/dm3 mol cm
)
(k/nm)
Assignment
1
2
3
4
dpya
270 (27 080)
17 (16 700)
336
353
m
(OH)
3569m,
3448sb
3385sb
3571sb,
3415sb
3305w
3064w–
2846w
1655vs,
1641vs
1326s
3
3484sb
m
m
(NH)
(CH)
3296w
3087m–
3195m
3097m–
2920w
1652vs
3293w
3071w,
2981w
1650vs,
1626vs
1338w
1270s, 1251s 1266vs,
1247vs
1168vs,
1155vs
968m
Na(sac)
273 (2022)
285
323
429
373
1
257 (22 286)
2848w
301 (13 576)
m(CO)
1659vs
2
245 (74 020)
330
383
3
4
06 (13 209)
23 (6812)
m
m
s
(CNS)
as(SO
1338w
1294vs,
1339w
1305vs,
1258vs
1177vs,
1160vs
969s
2
)
1
248s
1175vs,
161vs
967s
3
4
253 (20 391)
00 (19 504)
325
324
410
386
m
s
(SO
2
)
1152vs
3
1
249 (35 752)
06 (19 380)
mas(CNS)
954s
3
a
ꢂ1
Frequencies in cm
. b = broad; m = medium; w = weak; vw = very weak;
a
2
In DMSO/H O (1:1).
vs = very strong; s = strong.

E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
2419
1
N, 11.9%. H NMR (400 MHz, DMSO-d
8
6
): d 11.54 (s, 2H, NH), 8.13–
2.3. X-ray crystallography
0
0
5
6
6
5
.08 (m, 4H, H and H ), 7.87–7.84 (dd, 4H, H and H ), 7.65–7.53
0
m, 8H, H ), 7.51–7.47 (d, 4H, H3 and H ), 7.16–7.11 (m, 4H, H
sac
3
4
The intensity data of the complexes 1–4 were collected using a
STOE IPDS 2 diffractometer with graphite-monochromated Mo Ka
(
0
4
13
and H ).
C
NMR (400 MHz, DMSO-d
6
):
d
168.20, 152.30,
1
1
50.24, 145.69, 142.83, 135.23, 132.05, 131.49, 122.96, 121.04,
radiation (k = 0.71073 Å). The structures were solved by direct
methods and refined on F with the SHELX-97 program [23]. All
ꢂ1
2
19.60, 115.65. (Solid KBr pellet):
m
(cm ) 3571sb
m
(OH), 3415sb
(CH), 2958w (CH),
(CO), 1585vs (CN), 1535s,
(C@C), 1420w, 1376s, 1326s (CNS),
as(SO ), 1152vs (SO ), 1124vs, 1054w,
as(CNS), 895w, 827s, 787m, 768vs, 679s, 659m,
m
2
1
1
1
6
(OH), 3305w
m
(NH), 3191w, 3135w, 3064w
(CH), 1655vs (CO), 1641vs
(C@C), 1439m
as(SO ), 1247vs
m
m
non-hydrogen atoms were found from the difference Fourier map
and refined anisotropically. The crystals of complex 2 were extre-
mely small (0.04 ꢁ 0.08 ꢁ 0.012 mm), which greatly influenced
the quality of the data of this compound. Additionally, a rather
high peak, which can be evaluated as the water O atom, remained
as residue. Attempts to fix it as an O atom failed, however, due to
846w
480vs
266vs
m
m
m
m
m
m
m
m
m
s
2
2
m
s
2
034m, 954s
03vs, 543s, 472w, 446w.
m
Fig. 1. (a) Molecular structure of cis-[Pd(dpya)(sac)
2
]ꢀH
2
O (1). C–H hydrogen atoms were omitted for clarity. (b) A two-dimensional layer in 1 viewed down a.

2
420
E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
insufficient quality of the data for 2. Hydrogen atoms bonded to C
and N atoms were refined using a riding model, with C–H = 0.96–
to those of complexes 3 and 4 containing uncoordinated sac anions
[20]. The signals of C NMR are consistent with the structures of
the metal complexes.
1
3
0
.97 Å and N–H = 0.86–0.91 Å. The constraint Uiso(H) = 1.2 Ueq(C
and N) or 1.5 Ueq(methyl C) was applied. The water hydrogen
atoms are refined freely. The details of data collection, refinement
and crystallographic data are summarized in Table 1.
3.2. Description of crystal structures
The molecular structures of complex 1 and 2 are shown in Figs.
1
a and 2, respectively. Selected bond distances and angles are
3
. Results and discussion
listed in Table 4. Both complexes are isomorphous with a triclinic
space group P1. The structures of 1 and 2 consist of a lattice water
ꢀ
3.1. Synthesis and characterization
molecule and neutral [M(dpya)(sac)
2
] units, but the lattice water in
could not be fixed due to the data quality as explained in Section
.3. The dpya ligand chelates the palladium(II) or platinum(II) ions
2
2
As shown in Scheme 1, a two-step reaction sequence was used
to prepare new palladium(II) and platinum(II) complexes of sac. In
the first step of the synthesis of bis(sac)palladium(II) and plati-
via two pyridyl N atoms to form a six-membered ring. The square-
planar coordination around the metal(II) ions is completed by two
N atoms of two sac anions at the cis positions, leading to a neutral
II
II
num(II) complexes, the chlorides of [M(dpya)Cl
were removed by AgNO to obtain [M(dpya)(NO
and in the second step, the reaction of the [M(dpya)(NO
with Na(sac) afforded the yellow solid complexes of [Pd(dpya)
sac) O (1) and [Pt(dpya)(sac) ]ꢀH O (2). In the preparation of
]ꢀH
bis(dpya)palladium(II) and platinum(II) complexes, firstly
M(dpya)Cl ] was reacted with an excess of dpya and then, the
addition of Na(sac) resulted in the formation of yellow solid com-
plexes [Pd(dpya) ](sac) O (3) and [Pt(dpya) ](sac) ꢀ2H O (4).
ꢀ2H
2
] (M = Pt or Pd )
] in solution
] moiety
3
3 2
)
3 2
)
(
2
2
2
2
[
2
2
2
2
2
2
2
As will be discussed in Section 3.4, on heating at around 250 °C
for an hour, complexes 3 and 4 turn into the anhydrous complexes
of 1 and 2, respectively. It is also observed that the anhydrous com-
plexes obtained by the desolvation of 3 and 4 do not gain water of
crystallization upon dispersion in water. All complexes are air-sta-
ble and obtained in high yields (over 80%). Complexes 1 and 2 are
soluble in DMSO and DMF, while 3 and 4 are water-soluble.
The electronic spectra were measured using DMSO/water solu-
tions of the ligands and their complexes. The free dpya displays
two absorption bands in the UV region centered at 270 and
3
17 nm, and that of the free sac appears at 273 nm. These absorp-
*
tion bands are attributed to the
p–p transitions. The UV–Vis spec-
tra of the complexes display a number of distinct bands at 257 and
3
2
01 nm for 1, and 245, 306, 423 nm for 2, 253, 300 nm for 3, and
49, 306 nm for 4 (Table 2). The spectra of complexes 1–4 are dom-
inated mainly by ligand-based strong transitions with considerable
blue shifts.
2
Fig. 2. Molecular structure of cis-[Pt(dpya)(sac) ] (2). C–H hydrogen atoms were
omitted for clarity. Note that a water molecule could not fixed due to the quality of
the intensity data.
Selected FT-IR spectroscopic data for complexes 1–4 are listed
ꢂ1
in Table 3. The broad and intense bands centered over 3400 cm
are attributed to the m(OH) vibrations of the lattice water mole-
cules. The NH stretching of the free dpya ligand appears at
ꢂ1
Table 4
3
258 cm and in the complexes this band is observed in the fre-
a
ꢂ1
Selected bond lengths (Å), angles (°) and hydrogen bonding geometry for 1 and 2.
quency range 3250–3300 cm [24]. The sac moiety gives charac-
teristic IR bands due to the presence of the carbonyl and sulfonyl
groups. The sharp bands between 1625 and 1660 cm are due
1
2
ꢂ1
M1–N1
M1–N2
M1–N4
M1–N5
N1–M1–N2
N1–M1–N4
N1–M1–N5
N2–M1–N4
N2–M1–N5
N4–M1–N5
2.033(3)
2.017(3)
2.031(3)
2.031(3)
89.93(13)
177.98(13)
90.57(13)
91.38(13)
172.84(13)
87.93(13)
2.022(11)
1.986(14)
2.027(10)
1.990(15)
90.8(5)
178.1(6)
90.2(5)
91.1(5)
to the absorption of the carbonyl group. The asymmetric (
and symmetric ( ) stretchings of the SO group are observed as
two strong IR bands at ca. 1305–1245 and 1177–1150 cm
respectively. Both as and stretchings of the sulfonyl group are
usually observed as two split bands. The and as stretching
m
as
)
m
s
2
ꢂ1
,
m
m
s
m
s
m
modes of the CNS moiety of the sac ligands appear at ca. 1330
ꢂ1
174.1(5)
87.8(5)
and 960 cm , respectively.
1
In the H NMR spectra of complexes 1–4, the NH proton appears
as
a
singlet at d = ca. 11.50 ppm, which was observed at
(dpya) ] in CDCl [25]. The pyridine protons
D–Hꢀ ꢀ ꢀA
Hydrogen bonds
1
D–H (Å)
Hꢀ ꢀ ꢀA (Å)
Dꢀ ꢀ ꢀA (Å)
D–Hꢀ ꢀ ꢀA (°)
d = 9.50 ppm for [PdCl
appear as four signals in the range d = 8.35–6.90 ppm, while the
protons of sac are observed between 7.53 and 7.83 ppm as a mul-
tiplet (see Section 2.2). The signals of 3,3 H atoms of dpya in 1–4
shift to the lower frequency compared to those of the free dpya
molecule, whereas those of 5,5 H atoms experience deshielding
upon complexation. The proton resonances of coordinated sac
rings in 1 and 2 slightly shift to the higher frequency compared
2
2
3
O1W–H1Wꢀ ꢀ ꢀO5
0.86(13)
0.85(15)
0.86
2.05(9)
2.38(14)
1.99
2.834(10)
3.090(13)
2.740(4)
152(16)
142(20)
146
0
O1W–H2Wꢀ ꢀ ꢀO1
i
N3–H3Aꢀ ꢀ ꢀO4
0
2
i
N3–H3Aꢀ ꢀ ꢀO4
0.86
2.03
2.785(17)
146
a
Symmetry codes: (i) ꢂx + 1, ꢂy + 1, ꢂz + 1.

E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
2421
coordination sphere (Figs. 1a and 2). The dpya ligand adopts a boat
conformation and the dihedral angle between two py rings is
is slightly distorted from the perfect square-plane and the palla-
dium(II) and platinum(II) ions are displaced from the coordination
plane by 0.076(3) and 0.051(3) Å, respectively. In order to reduce
2
5.32(15)° in 1, and 24.77(13)° in 2. The coordination geometry
Fig. 3. (a) Molecular structure of [Pd(dpya)
2
](sac)
2
ꢀ2H
2
O (3). C–H hydrogen atoms were omitted for clarity. (b) Packing of hydrogen-bonded chains of 3 viewed down a.
Fig. 4. Molecular structure of [Pt(dpya)
2
](sac)
2
ꢀ2H
2
O (4). C–H hydrogen atoms were omitted for clarity.

2
422
E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
steric hindrance, two sac ligands tend to be oriented to the coordi-
nation plane with the dihedral angles 73.12(14)° and 86.70(12)° in
1, and 71.91(13)° and 85.98(12)° in 2. The M–N(sac) distances are
in close agreement with those reported in other palladium(II) and
platinum(II) complexes with sac [17,18,20,21], while the M–
N(dpya) bond distances are typical of those found in palladium(II)
and platinum(II) complexes of the dpya ligand [9,11,12,22,26,27].
The problem with fixing of the water O in 2 makes it difficult to
discuss the hydrogen bonding involving the water of crystalliza-
tion, but as expected, the molecules of 2 show similar packing
characteristics to those of 1. The molecules of 1 are doubly bridged
into dimers by the N–Hꢀ ꢀ ꢀO hydrogen bonds involving the amine H
atoms of dpya and the carbonyl O atoms of sac. The hydrogen-
bonded dimers are extended into a two-dimensional layer by
p
3
(dpya)ꢀ ꢀ ꢀ
.593(9) Å and 3.710(10) Å, respectively (Fig. 1b). Similarly, the
plane-to-plane distances of (dpya) and (sac)
p
(dpya) and
p
(sac)ꢀ ꢀ ꢀ
p(sac) stacking interactions of
p
(dpya)ꢀ ꢀ ꢀ
p
p(sac)ꢀ ꢀ ꢀ
p
stacking interactions in 2 are 3.568(10) and 3.690(10) Å, respec-
tively. The two-dimensional layers are further connected into a
three-dimensional network by weak C–Hꢀ ꢀ ꢀO hydrogen bonds
(
Cꢀ ꢀ ꢀO = 3.02–3.47 Å).
Fig. 5. Emission spectra of complexes 1–4 in DMSO/water solutions (1:1) at room
The molecular structures of complexes 3 and 4 are shown in
temperature.
Figs. 3a and 4, respectively, together with the atom numbering
scheme. Selected bond distances and angles are listed in Table 5.
X-ray analysis of complexes 3 and 4 indicates that they are iso-
p–p
stacking interactions between the py rings of dpya or the phe-
1
structural and crystallize in the monoclinic crystal system (P2 /
nyl rings of sac are present.
2
+
2
c). Both complexes are composed of a complex cation [M(dpya) ]
(
II
II
M = Pd or Pt ), two sac anions and two lattice water molecules. In
3.3. Photoluminescence
the complex cation, the palladium(II) and platinum(II) ions are lo-
cated on the inversion center and coordinated by two dpya ligands
in a bidentate manner, forming a distorted square-planar geome-
try. Again, each dpya molecule shows a boat conformation. Con-
trary to 1 and 2, the sac anions in 3 and 4 do not coordinate the
metal ions, but remain outside the coordination sphere as
counter-ions. The Pd–N(dpya) and Pt–N(dpya) bond lengths are
similar, being within the expected range for square-planar palla-
dium(II) and platinum(II) complexes containing the dpya ligand
The photoluminescent spectra of the ligands and their com-
plexes have been measured using DMSO/water solutions (1:1) at
room temperature. The emission spectra of complexes 1–4 are
illustrated in Fig. 5 and the excitation and emission data are listed
in Table 2. All ligands and their complexes are weakly luminescent
when excited at the absorption wavelengths in the range ca. 245–
3
17 nm. However, the dpya ligand is highly emissive at 353 nm
upon excitation at 336 nm. It was observed that the emission spec-
tra of metal complexes are originated from the dpya ligand. The
emission intensity of the complexes significantly decreases com-
pared to that of the free dpya ligand, but the emission intensity
of 2 is much higher than those of other three complexes. This
enhancement in the emission intensity may be due to low-lying
excited state orbitals of complex 2 [28]. Early studies showed that
[
9,11,12,22,26,27].
Since complexes 3 and 4 are isostructural, they exhibit almost
identical molecular packing interactions (see Table 5). Therefore,
only packing of molecules of 3 is presented in Fig. 3b. In addition
to electrostatic interactions, two sac anions located at either side
of the complex cation interact with the cation via the N–Hꢀ ꢀ ꢀN
and are also doubly bridged by two water molecules leading to
one-dimensional hydrogen-bonded chains running along the crys-
tallographic c axis (Fig. 3b). It is interesting to note that no obvious
the emissions of manganese(II), zinc(II) and cadmium(II) com-
plexes with dpya were attributed to the
*
p–p
intraligand transi-
tions, since upon complexation, the emissions of the metal
complexes are not shifted compared to free dpya ligand [29–33].
However, in the present work, the emission energies of 1–4 are
much lower than those of the free dpya, with the red-shifts varying
from 50 to 85 nm (Table 2 and Fig. 5). These observations clearly
indicate a metal-to-ligand charge transfer (MLCT) at the excited
state [28,34].
Table 5
a
Selected bond lengths (Å), angles (°) and hydrogen bonding geometry for 3 and 4.
3
4
M1–N1
M1–N2
N1–M1–N2
N1–M1–N2
2.026(2)
2.016(2)
86.78(8)
93.22(8)
2.023(2)
2.016(2)
87.30(9)
92.70(9)
i
3.4. Thermal decomposition
D–Hꢀ ꢀ ꢀA
Hydrogen bonds
D–H (Å)
Hꢀ ꢀ ꢀA (Å)
Dꢀ ꢀ ꢀA (Å)
D–Hꢀ ꢀ ꢀA (°)
The thermal stability and thermal decomposition behaviors of
3
complexes 1–4 were studied by TG and DTA at the atmosphere
of air in the temperature range 25–900 °C. The TG and DTA curves
are illustrated in Fig. 6 and the thermoanalytical data are presented
in Table 6. In general, all complexes dehydrate in the range of 35–
160 °C. Then, the endothermic elimination of the dpya ligands
takes place and it is followed by the highly exothermic decompo-
sition of the sac moiety. It is clearly observed that the dehydration
temperatures of the cationic complexes (3 and 4) are significantly
higher than those of the neutral complexes (1 and 2). This may be
ii
N3–H3Aꢀ ꢀ ꢀN4
0.86
0.83(8)
0.83(4)
2.13
2.06(8)
2.23(5)
2.907(3)
2.884(4)
3.047(5)
150
168(5)
167(6)
iii
O1W–H1Wꢀ ꢀ ꢀO3
iv
O1W–H2WꢀꢀꢀO2
4
ii
N3–H3Aꢀ ꢀ ꢀN4
0.86
0.83(8)
0.84(5)
2.14
2.06(8)
2.23(5)
2.908(3)
2.885(4)
3.064(5)
148
173(6)
176(8)
iii
iv
O1W–H1Wꢀ ꢀ ꢀO3
O1W–H2Wꢀ ꢀ ꢀO2
a
Symmetry codes: (i) ꢂx + 1, ꢂy + 1, ꢂz + 1; (ii) x, y, z ꢂ 1; (iii) ꢂx + 1, y + 1/2,
ꢂz + 3/2; (iv) x, ꢂy + 3/2, z ꢂ 1/2.

E. Guney et al. / Inorganica Chimica Acta 363 (2010) 2416–2424
2423
palladium(II) complexes is PdO, which decomposes to metallic Pd
over ca. 780 °C, while the platinum(II) complexes directly produce
metallic Pt.
The most important observation is that the cationic complexes
of 3 and 4 turn into corresponding neutral complexes of 1 and 2 at
around 250 °C. The solid complexes formed at that temperature are
thermally stable up to 285 °C for 1 and 330 °C for 2. This is shown
as a plateau in the TG curves (Fig. 6). In a separate experiment,
complexes 3 and 4 were heated at 250 °C for an hour. The solid
polycrystalline decomposition products were characterized by ele-
mental analysis, IR and NMR techniques, and shown to be high
purity anhydrous 1 and 2. These results clearly show that 1 and
2
can readily be synthesized from 3 and 4 by a solid-state decom-
position followed by an inter-conversion mechanism, in which two
sac counter-ions become involved in coordination with palla-
dium(II) or platinum(II) subject to the removal of a bidentate dpya
ligand (see Scheme 1).
4
. Conclusions
In this study, two neutral complexes, cis-[Pd(dpya)(sac)
2
]ꢀH
2
O
(
[
1) and cis-[Pt(dpya)(sac)
2
]ꢀH
2
O (2), and two cationic complexes,
](sac) O (4), have
ꢀ2H
Pd(dpya) ](sac) O (3) and [Pt(dpya)
2
2
ꢀ2H
2
2
2
2
been synthesized and characterized by various techniques includ-
ing elemental analysis, IR, NMR and crystallography. The neutral
complexes contain two N-coordinated sac ligands, while in the cat-
ionic complexes sac acts as a counter-ion. On heating at around
2
50 °C, the solid cationic complexes 3 and 4 transform to the cor-
responding solid neutral complexes 1 and 2 after elimination of a
dpya ligand. The solid-state decomposition of the cationic com-
plexes can be used as an alternative method for the preparation
of the neutral complexes. All complexes are fluorescent due to
MLCT transitions.
5
. Supplementary material
CCDC 767469, 767470, 767471 and 767472 contain the supple-
mentary crystallographic data for 1, 2, 3 and 4. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
Fig. 6. DTA and TG curves of 1–4.
This work is a part of a Research Project 106T664. We thank
TUBITAK for the financial support given to the Project.
Table 6
Thermoanalytical data for 1–4.
Stage Temperature
DTAmax
(°C)
Mass loss
(%)
Solid residue
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a
b
range (°C)
[
[
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