Design, synthesis and reactivity with dichloro-bis(triphenylphosphine) platinum(II) of two triazenide compounds

Article abstract of DOI:10.1016/j.ica.2011.02.091

In the presence of sodium nitrite, the reaction of methyl anthranilate and 2-aminopyridine or o-aminobenzoic acid gives two triazenes, 1-[(2-carboxymethyl) benzene]-3-[2-pyridine]triazene (HL) and 1-[(2-carboxymethyl)benzene]-3-[o- aminobenzoic acid]triaz

Full text of DOI:10.1016/j.ica.2011.02.091

Inorganica Chimica Acta 373 (2011) 276–281
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Note
Design, synthesis and reactivity with dichloro-bis(triphenylphosphine)
platinum(II) of two triazenide compounds
Xiao-hua Xie a,b, Jin-ye Chen a, Wei-quan Xu a, Er-xuan He a, Shu-zhong Zhan a,
⇑
a College of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
b College of Chinese Language and Culture of Jinan University, 510610 Guangzhou, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 April 2010
Received in revised form 23 February 2011
Accepted 26 February 2011
Available online 6 March 2011
In the presence of sodium nitrite, the reaction of methyl anthranilate and 2-aminopyridine or
o-aminobenzoic acid gives two triazenes, 1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene (HL)
and 1-[(2-carboxymethyl)benzene]-3-[o-aminobenzoic acid]triazene (H2L0), respectively. In the presence
of Et3N, the reaction of Pt(PPh3)2Cl2 and HL or H2L0 produces two triazenido platinum(II) complexes,
Pt(PPh3)2(L)Cl (1) and Pt(PPh3)2(L0) (2), respectively, which have been characterized by X-ray crystallog-
raphy, 31P NMR spectra, UV–Vis spectra, emission spectra and cyclic voltammetry. When excited at
310 nm, complexes 1 and 2 show luminescence at 432 and 442 nm, respectively, which is consistent with
the trend of the lowest-energy absorption wavelengths of 1 (376 nm) and 2 (379 nm). Complexes 1 and 2
exhibit one or two redox waves and follow the order 1 (0.97 V) ? 2 (0.89 and 0.07 V), which is also in
accordance with the trend of the lowest-energy absorption spectra of 1 (376 nm) and 2 (379 nm).
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Triazenes
Crystal structures
Luminescence
Electrochemical properties
1. Introduction
and H2L0 were prepared by modification of a literature procedure
[18].
Tꢀhe study of metal complexes containing triazenido [RN@N–
NR0] ligands has increased greatly during the past two decades,
because of their potential reactivity in relation to their several
modes of coordination [1,2]. Triazenido compounds can serve as
a monodentate (a), a bidentate chelating (b) and a bridging ligand
(c) (Scheme 1) [3–11]. Although complexes with 1,3-(aryl) triaz-
enes are well known [12–14], relatively few complexes with other
triazenido ligands have been developed [15,16].
2.1. Physical measurements
Electronic spectra were recorded on a Hitachi U-3010 (UV–Vis)
spectrophotometer for the solution in CH3CN. 1H NMR spectra
were measured on a Bruker AM 500 spectrometer in CDCl3. 31P
NMR spectra were measured on a Bruker AV 600 spectrometer in
CD2Cl2, chemical shifts were quoted to 85% H3PO4. Electrochemical
experiments were carried out with an Auto Lab instrument with a
With this mind, we have extended our interests to the design,
synthesis and reactivity with transition metals of new triazenido
ligands (Scheme 1d), which can delocalize electron density and
platinum wire working electrode,
a platinum plate counter
electrode, and an AgCl/Ag electrode as the reference electrode.
For the experiments performed in CH3CN as solvent (ca. 1.1 ꢁ
10ꢀ5 mol Lꢀ1) containing in 0.1 mol Lꢀ1 tetra-n-butylammonium
perchlorate (TBAP) as supporting electrolyte, the potentials were
referenced to an AgCl/Ag electrode. Luminescent spectra were re-
corded on a LS-55 Perkin–Elmer fluorescence spectrophotometer
at room temperature.
donate
p electron density to the metal atoms and control the orga-
nization of metal complexes [17]. In our lab, two triazenes, namely
1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene (HL) and
1-[(2-carboxymethyl)benzene]-3-[o-aminobenzoic acid]triazene
(H2L0) have been synthesized and characterized. The reaction of
Pt(PPh3)2Cl2 and HL or H2L0 gives two platinum(II) complexes
Pt(PPh3)2(L)Cl (1) and Pt(PPh3)2(L0) (2), respectively. In this paper,
we describe the synthesis and characterization of the two new
triazenes, as well as the platinum(II) complexes thereof.
2.2. Synthesis
2.2.1. Synthesis of HL
2. Experimental
A solution of methyl anthranilate (10 mmol) in water (5 mL)
was mixed with 1 mol Lꢀ1 HCl (30 mL, 30 mmol) at 0 °C. An
aqueous solution (15%) of sodium nitrite (15 mmol) was added
dropwise with stirring. Once the amine was dissolved, a solution
of 2-aminopyridine in ethanol (10 mmol) was added at 0 °C and
the mixture was stirred for 8 h. The reaction mixture was
All reactions were performed under air. All chemicals were pur-
chased and were used without further purification. Triazenes HL
⇑
Corresponding author. Fax: +86 20 87112053.
E-mail address: shzhzhan@scut.edu.cn (S.-z. Zhan).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.02.091

X.-h. Xie et al. / Inorganica Chimica Acta 373 (2011) 276–281
277
Table 1 listed details of the crystal parameters, data collection
and refinement for HL, 1 and 2. The selected bond distances and
angles for HL, 1 and 2 were listed in Tables 2–4.
Table 1
Crystallographic data for HL, 1, and 2.
Scheme 1. Generic triazenido binding modes and new triazenes.
Parameter
HL
1
2
Empirical formula
Formula weight
k (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
13H12N4O2
C49H44ClN4O2P2Pt C51H43N3O4P2Pt
256.27
0.71073
monoclinic
P2(1)/c
1013.36
0.71073
monoclinic
P2(1)/c
1018.91
0.71073
orthorhombic
Pbca
neutralized with a 15% aqueous of CH3CO2Na to give a yellow pre-
cipitate. The reaction mixture was filtered, and the solid was puri-
fied by crystallization at ꢀ4 °C from 8:2 ethyl acetate/hexanes to
obtain yellow crystals, which were collected and dried in vacuo
(1.9 g, 71%). Anal. Calc. for C13H12N4O2: C, 60.9; H, 4.7; N, 21.9.
Found: C, 60.17; H, 5.04; N, 21.56%. 1H NMR (CDCl3, ppm): d 8.58
(d, J = 1 Hz, 1H, py), 8.05 (d, J = 2.6 Hz, 1H, Py), 7.96 (d, J = 2.8 Hz,
1H, Py), 7.82 (t, J = 2.7 Hz, 1H, Py), 7.60 (t, J = 2.7 Hz, 2H, Ar), 7.25
(t, J = 1.7 Hz, 1H, Ar), 7.16 (t, J = 2.7 Hz, 1 Hz, Ar), 3.97 (s, 3H, –
OCH3).
15.064(3)
6.197(1)
27.545(6)
90.00
99.30(3)
90.00
12.355(3)
20.634(4)
17.305(4)
90.00
20.555(4)
20.730(4)
21.009(4)
90.00
b (Å)
c (Å)
a
(°)
b (°)
94.30(3)
90.00
90.00
90.00
c
(°)
Z
4
4
8
Dcalc (Mg mꢀ3
F(0 0 0)
)
1.342
1072
3.09–27.48
1.530
1.512
2028
4080
2.2.2. Synthesis of H2L0
The procedure was performed in the same way as that for the
synthesis of HL except that 2-aminopyridine was replaced by
o-aminobenzoic acid. H2L0 was obtained (52%). Anal. Calc. for
h Range for data
collection (°)
Reflections
collected/
unique
Data/restraints/
parameters
Goodness-of-fit
(GOF) on F2
Final R indices
3.08–25.34
3.23–25.35
21 893/5713
30 106/7787
87 771/8179
C
15H13N3O4: C, 60.20; H, 4.35; N, 14.05. Found: C, 60.26; H, 4.34;
5713/0/344
1.154
7787/0/533
1.148
8179/0/551
1.038
N, 14.10%. 1H NMR (CDCl3, ppm): d 8.36 (d, J = 4.8 Hz, 1H, Ar),
8.08 (d, J = 5.0 Hz, 1H, Ar), 7.98 (d, J = 4.8 Hz, 1H, Ar), 7.90 (d,
J = 3.6 Hz, 1H, Ar), 7.62 (m, 2H, Ar), 7.45 (t, J = 2.3 Hz, 1H, Ar),
7.21 (t, J = 2.4 Hz, 1 Hz, Ar), 3.98 (s, 3H, –OCH3).
R1 = 0.1123,
wR2 = 0.3209
R1 = 0.1454,
wR2 = 0.3504
R1 = 0.0470,
wR2 = 0.1125
R1 = 0.0575,
wR2 = 0.1170
R1 = 0.0459,
wR2 = 0.1249
R1 = 0.0781,
wR2 = 0.1460
[I > 2r(I)]
R indices(all data)
2.2.3. Synthesis of Pt(PPh3)2(L)Cl (1)
To a solution, containing ligand HL (0.31 g, 1.2 mmol) and
triethylamine (0.12 g, 1.2 mmol) in CH3OH/CH2Cl2 (20 mL, 1:1),
Pt(PPh3)2Cl2 (0.76 g, 0.96 mmol) was added and stirred for
10 min. The solution was allowed to slowly evaporate to afford
yellow crystals, which were collected and dried in vacuo (0.38 g,
41.4%). Anal. Calc. for C49H44ClN4O2P2Pt: C, 58.03; H, 4.34; N,
5.53. Found: C, 58.14; H, 4.35; N, 5.51%. UV–Vis [CH3CN, kmax/nm
Table 2
Selected bond distances (Å) and angles (°) for HL.
N(2)–N(3)
1.264(4)
1.423(5)
111.8(3)
119.6(3)
N(2)–N(1)
1.336(4)
1.372(5)
113.2(3)
N(3)–C(1)
N(1)–C(9)
N(3)–N(2)–N(1)
N(2)–N(1)–C(9)
N(2)–N(3)–C(1)
(e
/L molꢀ1 cmꢀ1)]: 244 (2.7 ꢁ 104), 376 (1.4 ꢁ 104). 31P NMR
(CD2Cl2, ppm): d 6.61 (d, 1P, JPtP = 1320 Hz), d 13.35 (d, 1P,
JPtP = 1663 Hz).
Table 3
Selected bond distances (Å) and angles (°) for 1.
2.2.4. Synthesis of Pt(PPh3)2(L0) (2)
To a solution, containing ligand H2L0 (0.26 g, 0.89 mmol) and
triethylamine (0.10 g, 1.0 mmol) in CH3OH/CH2Cl2 (20 mL, 1:1),
Pt(PPh3)2Cl2 (0.60 g, 0.76 mmol) was added and stirred for
15 min. The solution was allowed to slowly evaporate to afford
yellow crystals, which were collected and dried in vacuo (0.42 g,
55.7%). Anal. Calc. for C51H43N3O4P2Pt: C, 60.06; H, 4.22; N, 4.12.
Pt(1)–N(1)
Pt(1)–P(1)
N(1)–N(2)
N(3)–N(2)
2.078(5)
2.2724(17)
1.309(7)
1.307(7)
Pt(1)–P(2)
Pt(1)–Cl(1)
N(1)–C(1)
N(3)–C(6)
2.2496(16)
2.3569(16)
1.385(9)
1.429(8)
N(1)–Pt(1)–P(2)
P(2)–Pt(1)–P(1)
P(2)–Pt(1)–Cl(1)
N(2)–N(1)–C(1)
C(1)–N(1)–Pt(1)
N(3)–N(2)–N(1)
89.93(15)
99.28(6)
174.90(6)
116.2(5)
120.3(4)
112.7(5)
N(1)–Pt(1)–P(1)
N(1)–Pt(1)–Cl(1)
P(1)–Pt(1)–Cl(1)
N(2)–N(1)–Pt(1)
N(2)–N(3)–C(6)
170.49(15)
85.81(15)
85.11(6)
123.0(4)
110.5(5)
Found: C, 59.93; H, 4.21; N, 4.13%. UV–Vis [CH3CN, kmax/nm (e/L
molꢀ1 cmꢀ1)]: 248 (3.1 ꢁ 104), 379 (1.7 ꢁ 104). 31P NMR (CD2Cl2,
ppm): d 5.28 (d, 1P, JPtP = 1657 Hz), d 8.96 (d, 1P, JPtP = 1282 Hz).
2.3. X-ray crystallography
Table 4
Selected bond distances (Å) and angles (°) for 2.
Data were collected with a Bruker SMART CCD area detector
using graphite monochromated Mo K
a radiation (0.71073 Å) at
Pt(1)–N(1)
Pt(1)–P(2)
N(1)–N(2)
N(2)–N(3)
N(1)–Pt(1)–O(4)
O(4)–Pt(1)–P(2)
O(4)–Pt(1)–P(1)
N(2)–N(1)–C(1)
C(1)–N(1)–Pt(1)
2.040(5)
2.2396(18)
1.321(8)
1.267(7)
83.5(2)
Pt(1)–O(4)
Pt(1)–P(1)
N(1)–C(1)
2.061(5)
2.2997(18)
1.405(9)
room temperature. All empirical absorption corrections were ap-
plied by using the SADABS program [19]. The structures were solved
using direct methods and the corresponding non-hydrogen atoms
were refined anisotropically. All the hydrogen atoms of the ligands
were placed in calculated positions with fixed isotropic thermal
parameters and included in the structure factor calculations in
the final stage of full-matrix least-squares refinement. All calcula-
tions were performed using the SHELXTL computer program [20].
N(1)–Pt(1)–P(2)
N(1)–Pt(1)–P(1)
P(2)–Pt(1)–P(1)
N(2)–N(1)–Pt(1)
N(3)–N(2)–N(1)
94.13(17)
168.74(17)
96.02(7)
126.5(4)
115.4(6)
174.70(16)
86.74(15)
114.3(6)
118.6(5)

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X.-h. Xie et al. / Inorganica Chimica Acta 373 (2011) 276–281
3. Results and discussion
3.1. Synthesis and characterization
1-[(2-Carboxymethyl)benzene]-3-[2-pyridine]triazene(HL) was
synthesized by the reaction of methyl anthranilate, sodium nitrite,
and 2-aminopyridine in 71% yield. 1H resonances were found in the
range of 8.6–7.1 ppm for the aromatic protons, 3.97 ppm for the
methyl group (Supporting information, Fig. S1 1H NMR spectrum
of HL).
H2L0 was synthesized by the reaction of methyl anthranilate,
sodium nitrite, and o-aminobenzoic acid in 52% yield. 1H reso-
nances were found in the range of 8.1–7.1 ppm for the aromatic
protons, 3.97 ppm for the methoxy group (Supporting information,
Fig. 1. ORTEP plot of HL.
1
Fig. S2 H NMR spectrum of H2L0).
Scheme 2 shows the procedure of the synthesis of complexes 1
and 2. Complex 1 was obtained as orange crystals by the reaction
of HL and Pt(PPh3)2Cl2 in CH3OH/CH2Cl2. The 31P NMR spectrum
of Pt(PPh3)2Cl2 showed one resonance with 195Pt satellite peak at
16.06 ppm (1JPt–P = 2267 Hz) for P atoms of PPh3 (Supporting
information, Fig. S3 31P NMR spectrum of Pt(PPh3)2Cl2). The 31P
NMR spectrum of complex 1 exhibited two resonance with 195Pt
satellite peaks at 6.61 ppm (1JPt–P = 1320 Hz) and 13.35 ppm
(1JPt–P = 1663 Hz) for P atoms of two PPh3 molecules, respectively
(Supporting information, Fig. S4 31P NMR spectrum of complex 1).
Complex 2 was obtained as yellow crystals by the reaction of
H2L0 and Pt(PPh3)2Cl2 in CH3OH/CH2Cl2. The 31P NMR spectrum of
complex 2 showed two resonance with 195Pt satellite peaks at
5.28 ppm (1JPt–P = 1657 Hz) and 8.96 ppm (1JPt–P = 1282 Hz) for P
atoms of two PPh3 molecules, respectively (Supporting informa-
tion, Fig. S5 31P NMR spectrum of complex 2).
3.2. Crystal structures
3.2.1. Crystal structure of HL
X-ray quality crystals of HL were obtained by hexane diffusion
into an ethyl acetate solution of HL. An ORTEP view of HL is
displayed in Fig. 1. HL contains a rigid N(2)@N(3) double bond.
The N(1)–N(2) and N(2)–N(3) bond distances are 1.336(4) and
1.264(4) Å, which are different from those found in 1,3-bis-
(2-carboxymethyl)benzene triazene (1.296(3) and 1.293(3) Å)
[10]. N(1)–N(2)–N(3) bond angle is 111.8(3)°.
Fig. 2. ORTEP plot of complex 1.
the Pt. The Pt–N bond length 2.078(5) Å is in agreement the value
of 2.09(2) reported for trans-[PtH(dtt)-(PPh3)2] (dtt = 1,3-di-p-tol-
yltriazenido) [21] and is slightly shorter than the distance found
in [NBu4][Pt(C6F5)2(PhNNNPh)(Cl)2] (2.1215 Å) [22]. The bond dis-
tance of Pt and Cl (2.3569(16) Å) is slightly longer than that found
in [NBu4][Pt(C6F5)2(PhNNNPh)(Cl)2] [22].
3.2.2. Crystal structure of complex 1
As shown in Fig. 2, the platinum center geometry is square pla-
nar with Pt(1), N(1), Cl(1), P(1) and P(2) atoms lying on a plane. The
Pt atom is coordinated by two P atoms of PPh3 ligands, one chloride
ion, and one nitrogen atom of Lꢀ ligand. Pt–P bond distances are
2.2724(17) and 2.2496(16) Å, respectively. The important feature
of the structure is the monodentate bonding of the Lꢀ ligand to
The two N–N bond lengths (1.309(7) and 1.307(7) Å) are virtu-
ally equal in the monodentate platinum complex 1, owing to the
delocalization of the
p-electrons in the triazenido moiety. The
N(1)–N(2)–N(3) angle takes a value of 112.7(5)°, slightly larger
than that of the free HL ligand (111.8(3)°).
3.2.3. Crystal structure of complex 2
During the reaction of Pt(PPh3)2Cl2 and H2L0, two Clꢀ ions were
2ꢀ
both replaced by an L0 ligand. As shown in Fig. 3, the platinum
atom has a slightly distorted square planar coordination. Complex
2ꢀ
2 is completed by one Pt atom, two cis PPh3 molecules, and one L0
ligand. Compared with complex 1, complex 2 contains one chelate
triazenido ligand (L02ꢀ). The Pt–P bond distances are 2.2997(18)
and 2.2396(18) Å, which are similar to those found in complex 1.
The bond distance of Pt and N is 2.040(5) Å, which is shorter than
that found in complex 1 (2.078(5) Å). The distance of Pt and O is
2.061(5) Å.
Scheme 2. Schematic representation of the synthesis of complexes 1 and 2.

X.-h. Xie et al. / Inorganica Chimica Acta 373 (2011) 276–281
279
6
HL
Pt(PPh ) Cl
3 2
2
5
4
3
2
1
2 min
5 min
10 min
15 min
complex 1
0
200
300
400
500
600
λ/nm
Fig. 4. UV–Vis spectral changes of the reaction of HL and Pt(PPh3)2Cl2.
Fig. 3. ORTEP plot of complex 2.
3.3. Electronic spectra
The electronic spectra of HL, H2L0, Pt(PPh3)2Cl2, 1 and 2 were
recorded in CH3CN (Table 5). HL exhibited two bands at 276 and
363 nm, and H2L0 showed three bands at 229, 257 and 376 nm.
Complex 1 exhibited two bands at 244 and 376 nm, and complex
2 showed two bands at 248 and 379 nm. Compared with those of
HL and H2L0, the absorption maxima of low-energy bands of com-
plexes 1 (376 nm) and 2 (379 nm) were red-shifted to a longer-
wavelength region. This is assignable to spin–orbit coupling from
the heavy atom effect of the platinum(II) ion as well as a Pt ? L
MLCT transition upon deprotonated HL or H2L0 binding to the plat-
inum(II) ion [23].
Scheme 3. The possible mechanism of the formation of complex 1.
The UV–Vis spectra also were used to investigate the reactivity
of Pt(PPh3)2Cl2 and HL or H2L0 and assist the understanding of the
formation of complexes 1 and 2. As shown in Fig. 4, in the presence
of Et3N, after 2 min mixing of Pt(PPh3)2Cl2 and HL at molar ratio
1:1, the UV–Vis spectra showed two new absorbance peaks at
238 and 356 nm. At the same time, the color of the solution chan-
ged from deep-red to light yellow. Furthermore, the intensities of
the absorption band at 356 nm decreased, accompanied by a red
shift from 356 to 358 nm, specifying the formation of complex 1
(Scheme 3). After 15 min, there were no changes in the intensities
of the absorbance, the position of bands, or the color of the
solution.
5.0
H2L'
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
Pt(PPh3)2Cl2
2 min
5 min
10 min
15 min
complex 2
As shown in Fig. 5, after 2 min mixing H2L0 and Pt(PPh3)2Cl2 at
molar ratio 1:1, the UV–Vis spectra showed two new absorbance
peaks at 241, and 366 nm. At the same time, the color of the solu-
tion changed from red to yellow. Furthermore, the intensities of
Table 5
200
300
400
500
600
Photo-physical and electrochemical data for HL, H2L0, 1 and 3 in CH3CN.
λ/nm
CH3CN
CH3CN
CH3CNa
Eox1
Fig. 5. UV–Vis spectral changes of the reaction of H2L0 and Pt(PPh3)2Cl2.
kabs (nm)
kem (nm)
Eox2
Ered
HL
276, 363
229, 257, 376
241
244, 376
248, 379
420
428
399
432
442
1.04
0.97b
0.43
0.96
0.89
1.48
1.26
1.28b
H2L0
absorption bands at 244 and 366 nm decreased, accompanied by
a red shift from 366 to 370 nm, specifying the formation of com-
plex 2 (Scheme 4). After 15 min, there were no further changes
of intensities of the absorbance, the place of bands, or the color
of the solution.
Pt(PPh3)2Cl2
1
2
0.07b
a
Potential in V vs. Ag/AgCl at 100 mV/s.
Peak potential for irreversible wave.
b

280
X.-h. Xie et al. / Inorganica Chimica Acta 373 (2011) 276–281
Scheme 4. The possible mechanism of the formation of complex 2.
Fig. 7. CV of HL, Pt(PPh3)2Cl2 and 1 in CH3CN/0.1 mol Lꢀ1 [Bu4N]ClO4 at 100 mV sꢀ1
scan rate.
3.4. Emission spectra
The emission spectra of HL, H2L0, Pt(PPh3)2Cl2, 1 and 2 were
measured in CH3CN at room temperature. As shown in Fig. 6, when
excited at 310 nm, HL and H2L0 displayed a band at 420 and
428 nm, respectively. The emission energy of complex 1 appeared
at 432 nm, and complex 2 exhibited reduced emission energy at
442 nm. Clearly, compared with that of 1, the emission of 2 is
red-shifted. The emission wavelength 1 (432 nm) < 2 (442 nm) is
consistent with the trend of the lowest-energy absorption
wavelengths of 1 (376 nm) and 2 (379 nm).
3.5. Electrochemical properties
The electrochemical data for complexes 1 and 2, together with
the free ligands HL and H2L0 were summarized in Table 5.
The free ligands HL and H2L0 displayed two redox waves and fol-
lowed the order HL (1.48 and 1.04 V) ? H2L0 (1.26 and 0.97 V). This
is in accordance with the trend of the lowest-energy absorption
spectra of HL (363 nm) and H2L0 (376 nm). Complexes 1 and 2
exhibited one or two redox waves and followed the order 1
(0.97 V) ? 2 (0.89 and 0.07 V). This is also in accordance with the
trend of the lowest-energy absorption spectra of 1 (376 nm) and
2 (379 nm).
Fig. 8. CV of H2L0, Pt(PPh3)2Cl2 and
2
in CH3CN/0.1 mol Lꢀ1 [Bu4N]ClO4 at
100 mV sꢀ1 scan rate.
plex 1 revealed a reversible wave at 0.96 V corresponding to a
one-electron oxidation of 1 (PtIII/PtII), which was anodically shifted
compared to that of the compound Pt(PPh3)2Cl2 (0.429 V), indicat-
ing that it is easier to reduce the Pt(II) ion in 1 than that in
Pt(PPh3)2Cl2.
As shown in Fig. 7, compound Pt(PPh3)2Cl2 exhibited one
reversible redox potential at 0.429 V, and one irreversible oxida-
tion at 1.28 V, which corresponding to two successive one-electron
oxidations of Pt(PPh3)2Cl2 (PtIII/PtII and PtIV/PtIII). The CV of com-
As shown in Fig. 8, the CV of complex 2 revealed one reversible
redox potential at 0.89 V, and one irreversible reduction at 0.07 V.
The former process corresponds to a one-electron oxidation of 2
(PtIII/PtII), and the latter is assigned to a one-electron reduction of
2 (PtII/PtI). The higher platinum-based oxidation potentials for 1
(0.96 V) than for 2 (0.89 V) is due to the electron-deficient nature
of HL, making oxidation of 1 more difficult than that of 2.
In summary, the present study shows that the 1,3-RR0-triazenide
ligands, 1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene and
1-[(2-carboxymethyl)benzene]-3-[o-aminobenzoic acid]triazene
give two new platinum(II) complexes. Currently we are exploring
this further, including the design and synthesis of new triazenes,
as well as their reactivity.
160
HL
H2L'
140
Pt(PPh3)2Cl2
120
complex 1
complex 2
100
80
60
40
20
0
Acknowledgments
This work was supported by the Research Foundation for Re-
turned Chinese Scholars Overseas of Chinese Education Ministry
(No. B7050170), the National Science Foundation of China (No.
350
400
450
500
550
600
Fig. 6. Emission spectra of HL, H2L0, Pt(PPh3)2Cl2, 1 and 2 in CH3CN.

X.-h. Xie et al. / Inorganica Chimica Acta 373 (2011) 276–281
281
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