Synthesis and spectroelectrochemical studies of mixed heteroleptic chelate complexes of ruthenium(II) with 1,8-bis(2-pyridyl)-3,6-dithiaoctane (pdto) and substituted 1,10-phenanthrolines

Article abstract of DOI:10.1021/ic025849q

Reaction of dichlorotris(triphenylphosphine) ruthenium(II) [RuCl₂(PPh₃)₃] with 1,8-bis(2-pyridyl)-3,6-dithiaoctane (pdto), a (N₂S₂) tetradentate donor, yields a new compound [Ru(pdto)(PPh₃)Cl]Cl (1), which has been fully characterized. ¹H and ³¹P NMR studies of 1 in acetonitrile at several temperatures show the substitution of both coordinated chloride and triphenylphosphine with two molecules of acetonitrile, as confirmed by the isolation of the complex [Ru(pdto)(CH₃CN)₂]Cl₂ (2). Cyclic voltammetric and spectroelectrochemical techniques allowed us to determine the electrochemical behavior of compound 1. The substitution of the chloride and triphenylphosphine by acetonitrile molecules in the Ru(II) coordination sphere of compound 1 was also established by electrochemical studies. The easy substitution of this complex led us to use it as starting material to synthesize the substituted phenanthroline coordination compounds with (pdto) and ruthenium(II), [Ru(pdto)(4,7-diphenyl-1,10-phenanthroline)]Cl₂· 4H₂O (3), [Ru(pdto)(1,10-phenanthroline)]Cl₂·5H₂O (4), [Ru(pdto)(5,6-dimethyl-1,10-phenanthroline)]Cl₂· ·5H₂O (5), [Ru(pdto)- (4,7-dimethyl-1,10-phenanthroline)]Cl₂·3H₂O (6), and [Ru(pdto)(3,4,7,8-tetramethyl-1,10-phenanthroline)]Cl₂ ·4H₂O (7). These compounds were fully characterized, and the crystal structure of 4 was obtained. Cyclic voltammetric and spectroelectrochemical techniques allowed us to determine their electrochemical behavior. The electrochemical oxidation processes in these compounds are related to the oxidation of ionic chlorides, and to the reversible transformation from RU(II) to Ru(III). On the other hand, a single reduction process is associated to the reduction of the substituted phenanthroline in the coordination compound. The E_1/2 (phen/phen^-) and E_1/2 (Ru^II/Ru^III) for the compounds (3-7) were evaluated, and, as expected, the modification of the substituted 1,10-phenanthrolines in the complexes also modifies the redox potentials. Correlations of both electrochemical potentials with pK_a of the free 1,10-phenathrolines, λ_max MLCT transition band, and chemical shifts of phenanthrolines in these complexes were found, possibly as a consequence of the change in the electron density of the Ru(II) and the coordinated phenanthroline.

Full text of DOI:10.1021/ic025849q

Inorg. Chem. 2003, 42, 1825−1834
Synthesis and Spectroelectrochemical Studies of Mixed Heteroleptic
Chelate Complexes of Ruthenium(II) with
,8-Bis(2-pyridyl)-3,6-dithiaoctane (pdto) and Substituted
,10-Phenanthrolines
1
1
†
,†
‡
†
Luis A. Ortiz-Frade, Lena Ruiz-Ram ´ı rez,* Ignacio Gonz a´ lez, Armando Mar ´ı n-Becerra,
Manuel Alcarazo,†,§ Jos e´ G. Alvarado-Rodriguez, and Rafael Moreno-Esparza
|
†
Departamento de Qu ´ı mica Inorg a´ nica, Facultad de Qu ´ı mica, UniVersidad Nacional Aut o´ noma de
M e´ xico, AV. UniVersidad 3000, Ciudad UniVersitaria, M e´ xico, D.F., 04510, Mexico,
Departamento de Qu ´ı mica, UniVersidad Aut o´ noma Metropolitana-Iztapalapa, M e´ xico, D.F.,
PO Box 55-534, 09340, Mexico, and Centro de InVestigaciones Qu ´ı micas, UniVersidad Aut o´ noma
del Estado de Hidalgo, U. UniVersitaria km. 4.5, Carretera Pachuca-Tulancingo
42074, Pachuca, Hidalgo, Mexico
Received July 4, 2002
Reaction of dichlorotris(triphenylphosphine) ruthenium(II) [RuCl ] with 1,8-bis(2-pyridyl)-3,6-dithiaoctane (pdto),
2
(PPh
3
)
3
a (N ) tetradentate donor, yields a new compound [Ru(pdto)(PPh )Cl]Cl (1), which has been fully characterized.
2
S
2
3
1
31
H and P NMR studies of 1 in acetonitrile at several temperatures show the substitution of both coordinated
chloride and triphenylphosphine with two molecules of acetonitrile, as confirmed by the isolation of the complex
3 2 2
[Ru(pdto)(CH CN) ]Cl (2). Cyclic voltammetric and spectroelectrochemical techniques allowed us to determine the
electrochemical behavior of compound 1. The substitution of the chloride and triphenylphosphine by acetonitrile
molecules in the Ru(II) coordination sphere of compound 1 was also established by electrochemical studies. The
easy substitution of this complex led us to use it as starting material to synthesize the substituted phenanthroline
coordination compounds with (pdto) and ruthenium(II), [Ru(pdto)(4,7-diphenyl-1,10-phenanthroline)]Cl
Ru(pdto)(1,10-phenanthroline)]Cl ‚5H O (4), [Ru(pdto)(5,6-dimethyl-1,10-phenanthroline)]Cl ‚5H O (5), [Ru(pdto)-
4,7-dimethyl-1,10-phenanthroline)]Cl ‚3H O (6), and [Ru(pdto)(3,4,7,8-tetramethyl-1,10-phenanthroline)]Cl ‚4H
7). These compounds were fully characterized, and the crystal structure of 4 was obtained. Cyclic voltammetric
2
‚4H
2
O (3),
[
2
2
2
2
(
2
2
2
2
O
(
and spectroelectrochemical techniques allowed us to determine their electrochemical behavior. The electrochemical
oxidation processes in these compounds are related to the oxidation of ionic chlorides, and to the reversible
transformation from Ru(II) to Ru(III). On the other hand, a single reduction process is associated to the reduction
-
II
III
of the substituted phenanthroline in the coordination compound. The E1/2 (phen/phen ) and E1/2 (Ru /Ru ) for the
compounds (3−7) were evaluated, and, as expected, the modification of the substituted 1,10-phenanthrolines in
a
the complexes also modifies the redox potentials. Correlations of both electrochemical potentials with pK of the
free 1,10-phenathrolines, λmax MLCT transition band, and chemical shifts of phenanthrolines in these complexes
were found, possibly as a consequence of the change in the electron density of the Ru(II) and the coordinated
phenanthroline.
Introduction
transfer. These complexes show fluorescence in the visible
region, which has been used to study macromolecular
assemblies useful in biochemistry and clinical diagnosis.1
Ru(II) polypyridine complexes have played a key role in
the development of photochemistry and electron and energy
-8
§
*
To whom correspondence should be addressed. E-mail: lena@
As student from INTERCAMPUS and Intercambio Acad e´ mico UNAM
servidor.unam.mx.
program exchange. Present address: Instituto de Investigaciones Qu ´ı micas,
Departamento de Bioorganica, Sevilla, Spain.
†
Universidad Nacional Aut o´ noma de M e´ xico.
‡
|
Universidad Aut o´ noma Metropolitana-Iztapalapa.
Universidad Aut o´ noma del Estado de Hidalgo.
1
0.1021/ic025849q CCC: $25.00 © 2003 American Chemical Society
Inorganic Chemistry, Vol. 42, No. 6, 2003 1825
Published on Web 02/15/2003

Ortiz-Frade et al.
The intermolecular interactions and the nature of the ligand
are two important factors in these molecular assemblies. It
has been shown that redox behavior of these complexes
depends on the nature of the ligands, and there is a correlation
II
III
between their spectroscopic properties and Ru /Ru redox
9
-13
potential.
On the other hand, complexes of pdto with Cu(II), Cu(I),
Pt(II), Pd(II), Ni(II), Ru(II), Co(II), and Hg(II) have been
14-30
reported in the literature.
In all the complexes, the ligand
1,8-bis(2-pyridyl)-3,6-dithiaoctane, pdto (Figure 1), presents
a high flexibility toward the preferential geometry of the
central atom. Additionally, interactions of pdto complexes
with cyclodextrines31 and DNA have been demonstrated
Figure 1. Structure of ligand 1,8-bis(2-pyridyl)-3,6-dithiaoctane (pdto)
and the substituted 1,10-phenanthrolines used for the synthesis of complexes
32
3-5.
(
(
(
(
(
(
(
(
(
1) Friedman, A. E.; Chambron J.-C.; Sauvague, J. P.; Turro, N. J.; Barton,
J. K. J. Am. Chem. Soc. 1990, 112, 4960-4962.
2) Jenkis, Y.; Friedman, A. E.; Turro, N. J.; Barton, J. K. Biochemistry
byelectrochemical methods. The flexibility of pdto, the
photochemical properties of Ru(II) polypyridine complexes,
and the possible intermolecular interactions with biomol-
ecules direct us to synthesize complexes capable of forming
macromolecular assemblies as new prospective probes for
biochemistry and clinical diagnosis.
1
992, 31, 10809-10816.
3) Holmlin, R. E.; Stemp, E. D. A.; Barton J. K. Inorg. Chem. 1998, 37,
9-34.
4) Li, L.; Szamacinski, H.; Lakowicz, J. R. Biospectroscopy 1997, 3,
55-159.
5) Li, L.; Szamacinski, H.; Lakowicz, J. R. Anal. Biochem. 1997, 244,
0-85.
6) Terpetsching, E.; Szamacinski, H.; Lakowicz, J. R. Anal. Biochem.
2
1
8
This work presents the synthesis and characterization of
1995, 227, 140-147.
different coordination compounds of Ru(II) with pdto and
7) Youn, H.; Terpetsching, E.; Szamacinski, H.; Lakowicz, J. R. Anal.
Biochem. 1995, 232, 24-30.
n
different substituted 1,10-phenanthrolines, [Ru(pdto)L ]Cl
2
,
where n ) 1-5 (Figure 1). Several substituted phenanthro-
lines were used to obtain complexes 3-7 in order to modify
electrochemical and possibly photochemical properties.
Electrochemical studies of these complexes were performed
in order to understand the influence of the nature of ligands
in the redox behavior. Due to the easy replacement of
chloride and triphenylphosphine ligands (in cis position), the
8) Murtaza, Z.; Chang, Q.; Rao, G.; Lin., H.; Lakowicz, J. R. Anal.
Biochem. 1997, 247, 216-222.
9) Lever, A. B. P. Inorg. Chem. 1990, 29, 1271-1285.
(
(
(
(
10) Masui, H.; Lever, A. B. P.; Dodsworth, E. S. Inorg. Chem. 1993, 32,
258-267.
11) Vlcek, A. A.; Dodsworth, E. S.; Pierro, W. J.; Lever, A. B. P. Inorg.
Chem. 1995, 34, 1906-1913.
12) Dovletoglou, A.; Adeyemi, A. S.; Meyer, T. J. Inorg. Chem. 1996,
35, 5, 4120-4127 and references therein.
13) Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.;
Zelewsky, A. Coord. Chem. ReV. 1998, 84, 85-277.
3
complex [Ru(pdto)(PPh )Cl]Cl (1) was used as the starting
(
(
14) Goodwin, H. A.; Lions, F. J. Am. Chem. Soc. 1960, 82, 5013-5023.
material for the complexes 3-7. This substitution can be
observed using NMR, X-ray diffraction, and conductivity
measurements. Additionally electrochemical studies were
also used as a supplementary technique to demonstrate this
fact.
15) Worrell, J. H.; Genova, J. J.; Dubois, T. D. J. Inorg. Nucl. Chem.
1978, 40, 441-446.
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
16) Amundsen, A. R.; Whelan, J.; Bosnich, B. J. Am. Chem. Soc. 1977,
99, 6730-6739.
17) Thompson, M.; Whelan, J.; Zemon, D. J.; Bosnich, B.; Solomon, E.
I.; Gray, H. B. J. Am. Chem. Soc. 1979, 101, 2482-2483.
18) Sakaguchi, U.; Addison, A. W. J. Chem. Soc., Dalton Trans. 1979,
600-608.
Experimental Section
19) Brubaker, G. R.; Brown, J. N.; Yoo, M. K.; Kinsey, R. A.; Kutchan,
T. M.; Mottel, E. A. Inorg. Chem. 1979, 18, 299-302.
20) Castineiras, A.; Paredes, M. V.; Hiller, W. Acta Crystallogr., Sect. C:
Cryst. Struct. Commun. 1984, 40, 2078-2079.
21) Castineiras, A.; Hiller, W.; Paredes, M. V.; Sordo, J.; Str a¨ hle, J. Acta
Crystallogr., Sect. A: Found. Crystallogr. 1984, 40, C302.
22) Castineiras, A.; Hiller, W.; Paredes, M. V.; Sordo, J.; Str a¨ hle, J. Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 1985, 41, 41.
23) Humphery, D. G.; Fallon, G. D.; Murray, K. S. J. Chem. Soc., Chem.
Commun. 1988, 1356-1361.
24) Castineiras, A.; Diaz, G.; Florencio, F.; Garc ´ı a-Blanco, S.; Mart ´ı nez-
Carrera, S. J. Cristallogr. Spectrosc. Res. 1988, 18, 395-401.
25) Castineiras, A.; Diaz, G.; Florencio, F.; Garc ´ı a-Blanco, S.; Mart ´ı nez-
Carrera, S. Z. Anorg. Allg. Chem. 1988, 101, 567.
Chemicals and Reagents. The ligands 4,7-diphenyl-1,10-
1
2
phenanthroline (L ), 1,10-phenanthroline (L ), 5,6-dimethyl-1,10-
3
4
phenanthroline (L ), 4,7-dimethyl-1,10-phenanthroline (L ), and
5
3,4,7,8-tetramethyl-1,10-phenanthroline (L ) and all chemicals and
solvents for synthesis and characterization were purchased from
Aldrich Chemical Co. and used without further purification.
1,8-Bis(2-pyridyl)-3,6-dithioctane (pdto) was prepared by the
14
method described by Goodwin and Lions. Yield: 70%. Elemental
anal. Calcd for C16
Found: C, 63.1; H, 6.2; N, 9.7; S, 20.5.
Dichlorotris(triphenylphosphine) ruthenium(II) [RuCl
was prepared by a modification of the reported technique as
follows: RuCl (H O) (1.00 g, 3.81 mmol) was dissolved in 50
20 2 2
H N S : C, 63.1; H, 6.6; N, 9.2; S, 20.1.
26) Bermejo, E.; Castineiras, A.; Dom ´ı nguez, A. R.; Str a¨ hle, J.; Hiller,
W. Acta Crystallogr., Sect. C 1993, C49, 324.
2 3 3
(PPh ) ]
33
27) Pavlischchuk, V. V.; Koltilov, S. V.;. Michael, E. S.; Prushan, J.;
Addison, A. W. Inorg. Chim. Acta 1998, 278, 217-222.
3
2
3
28) Bermejo, E.; Castineiras, A.; Dom ´ı nguez, A. R.; Str a¨ hle, J.; Hiller,
W. Acta Crystallogr., Sect. C 1993, 49, 1918-1920.
mL of methanol, and a 6-fold excess of triphenylphosphine (6.00
g, 22.86 mmol) was added. The solution was heated under reflux
for 4 h. A brown solid was filtered and washed several times with
diethyl ether to eliminate the excess of triphenylphosphine. Yield:
29) Davies, K. M. Whyte, K. D. Gilbert, A. H. Inorg. Chim. Acta 1990,
1
77, 121-126.
30) Davies, K. M. Whyte, K. D. Liebermann, J. Mahr, J. A. Polyhedron
991, 10, 1647-1651.
31) Sivagnanam, U.; Palaniandavar, M. J. Chem. Soc., Dalton Trans. 1996,
609-2615.
32) Mahadevan, S.; Palaniandavar, M. Inorg. Chim. Acta 1997, 254, 291-
02.
1
94%. Elemental anal. Calcd for C54
2
H45RuCl : C, 67.6; H, 4.7.
Found: C, 67.0; H, 4.9.
2
3
(33) La Placa, S. J.; Ibers, J. A. Inorg. Chem. 1965, 4, 778-783.
1826 Inorganic Chemistry, Vol. 42, No. 6, 2003

Ru(II) Complexes with pdto and 1,10-Phenanthrolines
Chloro triphenylphosphine 1,8-bis(2-pyridyl)-3,6-dithiaoctane
Table 1. Crystal Data Collection for Complexes
ruthenium(II) chloride, [Ru(pdto)Cl(PPh
pdto (0.304 g, 1.0 mmol) was added to a solution of [Ru(PPh
Cl ] (0.957 g, 1.0 mmol) previously dissolved in 50 mL of methanol.
The reaction mixture was heated under reflux for 3 h, cooled, and
concentrated, and a yellow powder appeared. This powder was
washed several times with diethyl ether to eliminate the excess of
triphenylphosphine and was then recrystallized with dichloro-
methane, from which a yellow crystalline solid (1) was filtered off.
3
)]Cl (1). Reagent grade
1
a
2
4
3 3
) -
empirical formula
C34H35ClF6N2- C20H28Cl2N4-
O0.5P2RuS2 OCl2RuS2
852.22 576.55
C28H28Cl2N4-
O3.5RuS2
712.63
2
fw
temp, K
wavelength, Å
cryst syst
space group
lattice params
a, Å
291(2)
294(2)
293(2)
0.71073
monoclinic
P21/c
0.71073
monoclinic
C2/c
0.71073
monoclinic
I2/a
35 2 2 2
Yield: 90%. Elemental anal. Calcd for C34H N S PRuCl : C, 55.3;
10.9879(7)
23.126(2)
14.470(1)
93.710(2)
3669.3(4)
4
13.601(1)
16.312(1)
11.326(1)
102.16(1)
2456.5(3)
4
22.689(1)
11.922(1)
25.835(2)
109.06(1)
6605(3)
8
H, 4.8; N, 3.8; S, 8.7. Found: C, 55.1; H, 4.8; N, 3.7; S, 8.5. FAB-
b, Å
c, Å
+
2
-1
(
+): m/z 703 [Ru(pdto)Cl(PPh
Chloro triphenylphosphine 1,8-bis(2-pyridyl)-3,6-dithiaoctane
ruthenium(II) hexafluorophosphate [Ru(pdto)Cl(PPh )]PF (1a).
.031 mmol (0.0203 g) of 1 was dissolved in 25 mL of methanol
3
)] . Λ ) 125.2 S cm mol .
â, deg
vol, Å3
3
6
Z
3
density (calcd), mg/m 1.543
1.559
1.045
1.433
0.798
0
-
1
abs coeff, mm
final R indices
I > 2σ(I)]
R indices
(all data)
0.760
and then treated with equimolecular quantities of ammonium
hexafluorophosphate (0.0044 g) to induce crystallization. Suitable
yellow crystals for X-ray diffraction were obtained 1a. Yield: 80%.
R1 ) 0.0561
R1 ) 0.0388
R1 ) 0.0448
[
wR2 ) 0.0831 wR2 ) 0.1263 wR2 ) 0.1293
R1 ) 0.1661
R1 ) 0.0402
R1 ) 0.0792
35 2 2 2 6
Elemental anal. Calcd for C34H N S P RuClF : C, 48.1; H, 4.2;
wR2 ) 0.1083 wR2 ) 0.1270 wR2 ) 0.1418
N, 3.3; S, 7.5. Found: C, 48.8; H, 4.2; N, 3.6; S, 7.5. FAB(+):
+
m/z 703 [Ru(pdto)Cl(PPh
3
)] .
SX102A mass spectrometer with a matrix of nitrobenzyl alcohol
and dissolved in CH CN. A VARIAN Unity Inova spectrometer
was used to record all NMR spectra, H (300 MHz), C (75.5
MHz), and 31P spectra (121 MHz); TMS and H
PO were used as
reference, and acetonitrile-d was used as solvent. A Hewlett-
Bis(acetonitrile)1,8-bis(2-pyridyl)-3,6-dithiaoctane ruthenium-
II) chloride, [Ru(pdto)(CH CN) ]Cl (2). 1 (0.0556 g, 0.1 mmol)
3
1
13
(
3
2
2
was added to 50 mL of acetonitrile. The mixture was heated under
reflux for 4 h, cooled, and concentrated to 5 mL, and finally, by
addition of 20 mL of diethyl ether, an orange precipitate was
isolated. Suitable crystals for X-ray analysis were obtained from
3
4
3
Packard 5484A diode array spectrophotometer was used to acquire
UV-vis spectra, using acetonitrile as solvent. Conductivities were
measured with a SUNTEX model SC170 conductivity meter. The
conductivity data were obtained at sample concentrations of ca.
acetonitrile. Yield: 95%. Elemental anal. Calcd for C20
RuCl : C, 43.0; H, 4.7; N, 10.0; S, 11.5. Found: C, 43.1; H, 4.7;
N, 10.1; S, 11.5. Λ ) 250 S cm mol
26 4 2
H N S -
2
2
-1
-4
.
1 × 10 M in acetonitrile solutions at 25.0((0.5) °C. All
Synthesis of the Substituted Phenanthroline pdto Ru(II)
electrochemical measurements were performed in acetonitrile
(HPLC grade) solution containing 0.1 M tetra-N-butylammonium
tetrafluoroborate (TBATFB) as supporting electrolyte. A poten-
tiostat/galvanostat EG&G PARC model 273 controlled by PC
software was used. A typical three-electrode array was employed
for all electrochemical measurements: platinum disk as working
electrode, platinum wire as counter electrode, and a pseudo
reference electrode of silver wire immersed in an acetonitrile
solution with 0.1 M tetra-N-butylammonium chloride (TBACl). All
solutions were bubbled with nitrogen prior each measurement. All
voltammograms were initiated from open circuit potential (Eocp),
and the scan potential was obtained in both positive and negative
directions. All the potentials were reported versus the couple Fc/
Complexes. All of these coordination complexes were prepared
n
following the next procedure: 0.1 mmol of L was added to 0.0738
3
g (0.1 mmol) of [Ru(pdto)(PPh )Cl]Cl, previously dissolved in 50
mL of methanol. The mixture was heated under reflux for 3 h,
cooled, and concentrated to 5 mL, and finally, by addition of 20
mL of ether, in all cases an orange precipitate was isolated.
1
[
Ru(pdto)(L )]Cl
phenanthroline)]Cl ‚4H
RuCl : C, 54.5; H, 4.9; N, 6.4; S, 7.3. Found: C,
2
‚4H
2
O (3). [Ru(pdto)(4,7-diphenyl-1,10-
2
2
O. Yield: 75%. Elemental anal. Calcd for
C
40
H
O N
44 4 4
S
2
2
2
-1
5
4.8; H, 4.9; N, 6.3; S, 7.4. Λ ) 170 S cm mol
2
[
Ru(pdto)(L )]Cl
2 2
‚5H O (4). [Ru(pdto)(1,10-phenanthroline)]-
Cl
2 2 38 5 4 2
‚5H O. Yield: 94%. Elemental anal. Calcd for C28H O N S -
+
34
Fc according to IUPAC convention.
RuCl
.5; S, 8.5. Λ ) 275 S cm mol . Suitable crystals for X-ray
2
: C, 45.6; H, 5.1; N, 7.5; S, 8.6. Found: C, 45.2; H 5.1; N,
2
-1
7
X-ray Analysis of Compounds 1a, 2, and 4. X-ray diffraction
data were collected with a Bruker 6000 CCD area detector
diffractometer and analyzed using monochromated Mo KR X-ray
radiation (λ ) 0.71073 Å). The crystal dimensions of the analyzed
crystals 1a, 2, and 4 were respectively 0.25 × 0.18 × 0.11 mm,
0.4 × 0.25 × 0.2 mm, and 0.3 × 0.2 × 0.19 mm. Unit cell
parameters along with data collection and refinement details for
compounds 1a, 2, and 4 are listed in Table 1. All structures were
analysis for this compound were obtained from a mixture of
acetonitrile-water (6:1).
3
[
Ru(pdto)(L )]Cl
2
‚5H
‚5H O. Yield: 65%. Elemental anal. Calcd for
: C, 46.4; H, 5.5; N, 7.2; S, 8.3. Found: C,
2
O (5). [Ru(pdto)(5,6-dimethyl-1,10-
phenanthroline)]Cl
RuCl
2
2
C
4
30
H
O N
42 5 4
S
2
2
2
-1
6.0; H 5.3; N, 7.2; S, 8.5. Λ ) 273 S cm mol
4
[
Ru(pdto)(L )]Cl
2
‚3H
‚3H O. Yield: 70%. Elemental anal. Calcd for
: C, 45.6; H, 5.1; N, 7.5; S, 8.6. Found: C,
2
O (6). [Ru(pdto)(4,7-dimethyl-1,10-
35
phenanthroline)]Cl
RuCl
2
2
solved by Patterson methods using SHELXS 97-2. Least-squares
2
C
4
30
H
O N
38 3 4
S
2
2
refinement based on F was carried out by full-matrix method of
2
-1
36
5.2; H, 5.1; N, 7.5; S, 8.5. Λ ) 243 S cm mol
SHELXL-97-2. All non-hydrogen atoms were refined with
5
anisotropic thermal parameters. Location of hydrogen atoms was
generated geometrically and included in the refinement with an
[
Ru(pdto)(L )]Cl
2
.4H
‚4H
RuCl : C, 49.0; H, 5.7; N, 7.1; S, 8.2. Found:
C, 49.1; H, 5.6; N, 7.0; S, 8.1. Λ ) 252 S cm mol
2
O (7). [Ru(pdto)(3,4,7,8-tetramethyl-1,-
1
0-phenanthroline)]Cl
2
2
O. Yield: 91%. Elemental anal.Calcd
for C32
H O
44 4
N
4
S
2
2
2
-1
(34) Gritzner, G.; K u¨ ta J., Pure Appl. Chem. 1984, 4, 461-466.
(35) Sheldrick, G. M. SHELXS-97-2. Program for Crystal Stucture Refine-
ment; University of G o¨ ttingen: G o¨ ttingen, Germany, 1997.
Physical Measurements. Fissons Instruments analyzer model
EA 1108 was used for elemental analysis determination, using a
sulfanilamide standard. Mass spectra were obtained in a JEOL
(
36) Sheldrick, G. M. SHELXL-97-2. Program for Crystal Structure
Refinement; University of G o¨ ttingen: G o¨ ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 42, No. 6, 2003 1827

Ortiz-Frade et al.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1a
Cl(1)-Ru(1)
N(1)-Ru(1)
N(2)-Ru(1)
2.441(2)
2.154(5)
2.138(6)
P(1)-Ru(1)
Ru(1)-S(1)
Ru(1)-S(2)
2.398(2)
2.292(2)
2.366 (2)
N(2)-Ru(1)-N(1) 172.8(2)
N(1)-Ru(1)-P(1)
S(1)-Ru(1)-P(1)
S(2)-Ru(1)-P(1)
N(2)-Ru(1)-Cl(1)
N(1)-Ru(1)-Cl(1)
S(2)-Ru(1)-Cl(1)
P(1)-Ru(1)-Cl(1)
92.8(2)
98.0(6)
173.8(1)
89.2(2)
93.0(2)
89.1(1)
85.5(1)
N(2)-Ru(1)-S(1)
N(1)-Ru(1)-S(1)
N(2)-Ru(1)-S(2)
N(1)-Ru(1)-S(2)
S(1)-Ru(1)-S(2)
N(2)-Ru(1)-P(1)
92.4 (2)
84.9(2)
82.9(2)
90.3(2)
87.6(7)
94.2(2)
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 2a
Ru(1)-N(2)#1
Ru(1)-N(1)#1
2.098(4)
2.136(4)
Ru(1)-S(1)
Ru(1)-S(1)#1
2.300(1)
2.300(1)
N(2)-Ru(1)-N(2)#1
N(2)-Ru(1)-N(1)
N(2)-Ru(1)-N(1)#1
83.5(2)
90.9(1))
92.2(1)
N(2)#1-Ru(1)-S(1) 94.5(1)
N(1)-Ru(1)-S(1) 93.5(1)
N(1)#1-Ru(1)-S(1) 83.5(1)
N(1)-Ru(1)-S(1)#1 83.4(1)
S(1)-Ru(1)-S(1)#1 87.9(6)
Figure 2. ORTEP diagram showing the molecular structure of the cation
[Ru(pdto)Cl(PPh )]+ (1a) with 50% probability displacement ellipsoids.
3
N(1)-Ru(1)-N(1)#1 175.8(2)
Table 5. 1H NMR Spectroscopic Data for Complex 1a
N(2)-Ru(1)-S(1)
175.2(1)
a
Symmetry transformations used to generate equivalent atoms:
3
#
1 -x + 1, y, -z + /2.
Table 4. Bond Lengths (Å) and Angles (deg) for 4
Ru(1)-N(4)
Ru(1)-N(3)
Ru(1)-N(2)
2.104(4)
2.112(4)
2.143(4)
Ru(1)-N(1)
Ru(1)-S(1)
Ru(1)-S(2)
2.142(4)
2.312(2)
2.319(1)
N(4)-Ru(1)-N(3)
N(4)-Ru(1)-N(1)
N(3)-Ru(1)-N(1)
N(4)-Ru(1)-N(2)
N(3)-Ru(1)-N(2)
N(1)-Ru(1)-N(2)
N(4)-Ru(1)-S(1)
N(3)-Ru(1)-S(1)
78.1(2)
90.6(2)
89.1(2)
90.8(2)
92.0(2)
178.4(2)
96.7(1)
174.1(1)
N(1)-Ru(1)-S(1)
N(2)-Ru(1)-S(1)
N(4)-Ru(1)-S(2)
N(3)-Ru(1)-S(2)
N(1)-Ru(1)-S(2)
N(2)-Ru(1)-S(2)
S(1)-Ru(1)-S(2)
93.6(1)
85.5(1)
175.0(1)
98.1(1)
86.0(1)
92.6(1)
87.3(1)
δH1 ) 9.86 dd(1); δH2 ) 7.25 ddd(1); δH3 ) 7.65ddd(1); δH4 )
7.30dd(1); δH5,6 ) 4.80 td(1), 3.18 ddd(1); δH7,8 ) 1.95 td(1),
3.50 dd(1); δH9,10 ) 3.05 dd(1), 1.84 ddd(1); δH11,12 ) 2.74 dd(1),
1.84 ddd(1); δH13,14 ) 1.95 ddd(1), 2.82 td(1); δH15,16 ) 3.32 ddd(1),
2
.50 td(1); δH17 ) 6.91 dd(1); δH18 ) 7.59 ddd(1); δH19 )
.55 ddd(1); δH20 ) 8.74 dd(1)
6
isotropic fixed thermal parameter using a “riding” model. Neutral
atom scattering factors and anomalous dispersion corrections were
taken from International Tables for Crystallography. Selected
bond lengths and angles of the compounds 1a, 2, and 4 are listed
in Tables 2, 3, and 4, respectively; molecular structure drawings
were generated using ORTEP3 for Windows.38
J1-2 ) 6.29; J1-3 ) 1.50; J2-3 ) 7.49; J2-4 ) 1.50; J3-4 ) 7.79; J5-7 )
1
2
5.88; J5-8 ) 15.88; J5-6 ) 2.09; J6-7 ) 15.28; J6-8 ) 4.79; J7-8 )
.09; J9-10 ) 2.08; J9-12 ) 4.79; J10-11 ) 10.19; J10-12 ) 4.79;
3
7
J11-12 ) 2.08; J13-14 ) 4.49; J13-16 ) 16.18; J13-15 ) 7.49; J16-14
14.98; J16-15 ) 2.10; J14-15 ) 12.59; J18-20 ) 1.50; J18-19 ) 7.19;
J19-20 ) 5.69; J17-19 ) 1.50; J17-18 ) 7.79
)
Ho,m,p ) 6.62, 7.20, 7.50 (broad signals)
Results and Discussion
a
δ, multiplicity, (integration), J/Hz.
Characterization of the Starting Compound. Elemental
analysis and conductometric measurement are in agreement
with the proposed formulas for 1 and 1a. The FAB mass
the trans influence of the coordinated triphenylphosphine
ligand. The bond lengths Ru(1)-N(1) (2.154(1) Å) and Ru-
(
1)-N(2) (2.138(1) Å) are fairly equivalent.
The H NMR spectrum for 1 at 298 K was obtained in
spectrum peak at (+) m/z 703 corresponding to the fragment
1
+
[Ru(pdto)Cl(PPh
3
)] was detected for both complexes. The
3
acetonitrile-d . Considering that there are no significant
changes in the molecular structure in the solid state and
solution, the unequivocal assignment was achieved with a
molecular structure of 1a has been determined by X-ray
diffraction and is shown in Figure 2. The complex has a
distorted octahedral geometry around the ruthenium(II) with
trans-oriented nitrogen ligand atoms [N(1)-Ru(1)-N(2)
2
D correlated COSY experiment; hydrogen assignments are
listed in Table 5. The high chemical shift value for H (δ )
.86 ppm) compared to the H20 value (δ ) 8.74 ppm) and
their magnetic inequivalence are attributed to the fact that
is closer than H20 to the chloride atom. The broad signals
1
1
72.8(2)°] from the pdto; two cis configurations are also
presented, the first between chloride and triphenylphosphine
Cl(1)-Ru(1)-P(1) 85.5(1)°] and the second between the
9
[
H
1
sulfur atoms from the pdto [S(1)-Ru(1)-S(2) 87.6(1)°]. The
Ru(1)-S(2) bond trans to P(1) is elongated (2.366(2) Å)
compared to Ru(1)-S(1) trans to Cl(1) (2.292(2) Å) due to
1
in H NMR spectrum can be attributed to the restricted
rotation of the aromatic groups of triphenylphosphine: H
, H
The 31P NMR spectrum shows only one signal at δ )
40.01 ppm, which suggests a unique species of phosphorus
o
,
H
m
p
.
(
37) Wilson, A. J. C., Ed. International Tables for Crystallography; Kluwer
Academic Publishers: Dordrecht, The Netherlands, 1995; Vol. C,
Table 4.2.4.2, p 193.
1
31
atom coordinated to Ru(II). The H and P NMR spectra of
(38) Farrugia, L. ORTEP3 for Windows. J. Appl. Crystallogr. 1997, 30,
565.
complexes 1 and 1a are essentially the same.
1828 Inorganic Chemistry, Vol. 42, No. 6, 2003

Ru(II) Complexes with pdto and 1,10-Phenanthrolines
Figure 3. ORTEP diagram showing the molecular structure of the cation
2
+
[
Ru(pdto)(CH3CN)2] (2) with 50% probability displacement ellipsoids.
Figure 4. ORTEP diagram showing the molecular structure of the cation
[
ellipsoids.
Ru(pdto)(1,10-phenanthroline)]2 (4) with 50% probability displacement
+
Temperature H and 31P NMR and Conductivity
Studies of 1. A H NMR study in acetonitrile-d
1
1
3
was
performed at several temperatures, from 223 to 353 K, with
an increment of 10 K in order to obtain information about
the stability of compound 1. In experiments from 223 to 293
K, a broadening of the signals corresponding to aromatic
protons is observed, this is due to the restricted rotation of
the phenyl protons in the triphenylphosphine coordinated to
the Ru(II) atom. When the temperature was raised to 313
K, three new signals appeared, at 9.65, 9.12, and 7.74 ppm,
while the initial pyridinic aromatic signals for H
1
4
-H and
H17-H20 decreased. This phenomenon persisted until a
temperature of 353 K was reached, when the signal disap-
peared.
31
As pointed out above, the P NMR spectrum of compound
presents only one signal P (δ ) 40.01 ppm) at 293 K.
When the measurement was performed at 303 K, a negligible
shift in the signal P (δ ) 39.96 ppm) and the appearance
of a new signal P at 0.34 ppm were observed. At 353 K the
signal P shifted to 1.25 ppm and the original signal P
1
1
1
2
2
1
disappeared. The 31P NMR spectra of noncoordinated tri-
phenylphosphine at 303 K shows a signal at 0.06 ppm, and
when the sample was warmed to 353 K, a signal at 1.26
ppm was detected. The above results clearly show that in
compound 1 the triphenylphosphine is substituted by aceto-
nitrile as the temperature is increased.
In a polar solvent such as acetonitrile the coordinated
chloride ligand should also be exchanged; this suggestion
was confirmed with a conductometric experiment. The
conductivity of a 10-3 M solution of 1 in acetonitrile at 298
Figure 5. COSY experiment for 4, recorded at 300 MHz. Acetonitrile-d3
was employed as solvent.
array [N(2)-Ru(1)-N(2)#1, 83.5(2)°]; sulfur atoms are also
in a cis configuration [S(1)-Ru(1)-S(1)#1, 87.9(1)°].
In order to fully characterize 2, the synthesis from 1 in
acetonitrile was done, and the solid obtained from this
-
1
2
-1
K was κ ) 136.5 µS cm (Λ ) 125.2 S cm mol ),
corresponding to a 1:1 electrolyte. When the solution was
warmed to 353 K and later on was cooled to room
temperature, the conductivity value increased to κ ) 2030
1
synthesis was characterized. H NMR spectrum of compound
2 in acetonitrile was also obtained. The NMR spectra of
compound 2 presents three signals with the same chemical
-
1
1
µS cm . From the above solution yellow crystals were
recovered, and the structure was determined by X-ray
diffraction techniques; two acetonitrile molecules are coor-
dinated to Ru(II), corresponding to the compound [Ru(pdto)-
shift values as those observed in the H NMR spectra for
-
3
compound 1 from 313 to 353 K. The conductivity of a 10
M solution, at 298 K in acetonitrile solution for this
compound, corresponds to a 1:2 electrolyte, κ ) 2050 µS
-
1
2
-1
(CH CN) ]Cl
3 2 2
(2), see Figure 3. The complex has a distorted
cm , Λ ) 250 S cm mol .
octahedral geometry around the ruthenium(II) with trans-
oriented nitrogen ligand atoms [N(1)#1-Ru(1)-N(1), 175.8-
From this discussion, it is feasible to conclude that, in polar
solvents, both ligands (chloride and triphenylphosphine) are
easily substituted by solvent molecules.
(2)°] from the pdto and two molecules of acetonitrile in cis
Inorganic Chemistry, Vol. 42, No. 6, 2003 1829

Ortiz-Frade et al.
Figure 6. HETCOR experiment for 4, recorded at 300 MHz. Acetonitrile-d3 was employed as solvent.
Characterization of the Substituted Phenanthroline
pdto Ru(II) Complexes. Conductivity measurements and
elemental analyses for all the compounds correspond to the
proposed formulas (3-7).
The crystal structure of molecule 4 obtained by X-ray
diffraction is shown in Figure 4. This complex has a slightly
distorted octahedral geometry around the ruthenium(II) with
the pdto nitrogen atoms [N(1)-Ru(1)-N(2), 178.4(2)°] in
trans position and the two nitrogen atoms of 1,10-phenan-
throline [N(3)-Ru(1)-N(4), 78.1(2)°] in a cis arrangement;
the sulfur atoms are also in a cis configuration [S(1)-Ru-
(
1)-S(2), 87.3(1)°].
1H and 13C NMR spectra for 4 at 298 K in acetonitrile-d
3
were acquired. Assuming again that there are no significant
changes in the molecular structure going from solid state to
Figure 7. Cyclic voltammograms of compound 1 in the presence of 0.1
M TBABF4 in acetonitrile. The scan potential was initiated from Eocp to
positive direction. Scan rate: 200 mV s . Each experiment was acquired
1
13
solution, unequivocal H and C NMR assignments were
achieved by 2D correlated COSY (Figure 5) and HETCOR
-
1
at a different concentration of 1: (a) 0.365, (b) 1.422, (c) 2.01, and (d)
1
13
(
Figure 6) experiments, H and C assignments of the
2.70 mM.
molecules (3-5) are listed in Tables 6 and 7. NMR spectra
for the compounds (3, 5, 6, and 7) are very similar to the
spectrum of 4, excluding the signals due to the substituents
of the corresponding 1,10-phenanthrolines; the signals for
ligand pdto are basically the same. The magnetic equivalence
of hydrogen and carbon in the coordinated pdto ligand, for
all the compounds, suggest a trans configuration of the
pyridine rings.
at different concentrations were performed (Figure 7). When
the potential scan was initiated in the positive direction, in
the lowest concentration of 1 (Figure 7a), an anodic oxidation
signal (I
was inverted) are presented. Additionally, a second oxidation
signal (I *) and a reduction signal (I *), see Figure 7c,d,
a c
) and a reduction signal (I ) (after the scan potential
a
c
appear when the concentration of 1 increases.
Table 8 shows the selected electronic spectra absorption
data for compounds 3-7. The spectra for all complexes are
analogous, and all show six bands (3 MLCT, 2 LC, and 1
MC transition bands). The strongest absorption band in the
UV region can be assigned as an intraligand LC (π f π*)
transition. Alternatively the absorption band in the visible
region near 400 nm can be assigned to a metal-to-ligand
charge-transfer (MLCT) transition (due to (phenanthroline),
by analogy to spectral assignments of similar absorption in
To obtain information on the electrochemical process,
controlled potential coulometry and spectroelectrochemical
studies were also performed. Two electrons per molecule
were determined by coulometry at a potential more positive
+
than the peak I
a
(1.13 V/Fc-Fc ); a change in solution color
from yellow to green was observed. Cyclic voltammograms
were recorded before and after electrolysis. In both cases,
the scan potential was initiated from the open circuit
+
potential, Eocp ) -0.240 V/Fc-Fc (before electrolysis) and
II
2+ 13
+
the compounds [Ru (phen)
3
] .
E
ocp) 0.633 V/Fc-Fc (after electrolysis). From the cyclic
Electrochemical Studies of the Starting Material Com-
pound 1. Cyclic voltammetric experiments for compound 1
voltammogram obtained in the positive direction after the
electrolysis, the absence of an oxidation signal suggests the
1830 Inorganic Chemistry, Vol. 42, No. 6, 2003

Ru(II) Complexes with pdto and 1,10-Phenanthrolines
Table 6. 1H NMR Spectroscopic Data for Complexes 3-7a
Table 7. 13C NMR Spectroscopic Data for Compounds 3-7
3
δCa ) 153.9; δCb ) 123.8; δCc ) 138.3; δCd ) 127.4; δCa* )
1
1
1
50.6; δCe ) 26.6; δCf ) 31.6; δCg ) 34.0, δC2 ) δC9 )
57.3; δC3 ) δC8 ) 127.0; δC4 ) δC7 ) 148.8; δC5 ) δC6 )
25.8; δC11 ) δC12 ) 163.9; δC13 ) δC14 ) 135.5; δC(4)φ )
3
δHa ) 8.81 d(2); δHb ) 7.08 ddd (2); δHc ) 7.57 td(2); δHd )
7.10 dd (2); δHe,e′ ) 2.25 td(2), 3.76 ddd (2); δHf,f′ ) 3.74 td(2),
3.29 ddd (2); δHg,g′ ) 3.18d(2), 2.19 d(2); Ja-b ) 6.00; Jb-c )
7.50; Jb-d ) 1.50; Jc-a ) 1.50; Jc-d ) 7.50; Jc-a ) 1.20;
o,m 129.8, p129.1, φ128.5
δCa ) 153.8; δCb ) 123.6; δCc ) 138.3; δCd ) 127.2; δCa* )
4
5
6
7
Je-e′ ) 2.10; Je-f ) 12.60; Je-f′ ) 12.60; Je′-f ) 12.60;
Je′-f′ ) 5.10; Jf-f′ ) 2.10; Jg-g′ ) 9.90, δH2 ) 10.34 d(2);
δH3 ) 8.16 d (2); δH5 ) 8.01 s(2); δ(4)C6H5 ) (7.678-7.592)
m(12); J2-3 ) 5.70
1
1
1
48.2; δCe ) 26.4; δCf ) 31.9; δCg ) 34.2, δC2 ) δC9 )
57.6; δC3 ) δC8 ) 126.8; δC4 ) δC7 )138.7, δC5 ) δC6 )
28.0; δC11 ) δC12 ) 163.8; δC13 ) δC14 ) 130.6
δCa ) 153.8; δCb ) 123.6; δCc ) 138.3; δCd ) 127.3; δCa* )
1
4
5
δHa ) 8.73 d(2); δHb ) 7.02 ddd (2); δHc ) 7.53 td(2); δHd )
47.3; δCe ) 26.4; δCf ) 31.8; δCg ) 34.1, δC2 ) δC9 ) 156.4;
7.12 dd (2); δHe,e′ ) 2.22 td(2), 3.75 ddd (2); δHf,f′ ) 3.40 td(2),
3.33 ddd (2); δHg,g′ ) 3.17d(2), 2.17 d(2); Ja-b ) 6.30; Jb-c )
7.50; Jb-d ) 1.50; Jc-a ) 1.50; Jc-d ) 7.50; Jc-a ) 1.20; Je-e′ )
2.10; Je-f ) 12.90; Je-f′ ) 12.90; Je′-f ) 12.90; Je′-f′ ) 5.10;
δC3 ) δC8 ) 126.4; δC4 ) δC7 )135.4; δC5 ) 131.0 ) δC6;
δC11 ) δC12 ) 163.8; δC13 ) δC14 ) 133.0; δC(5)CH3 ) 14.6
δCa ) 153.8; δCb ) 123.5; δCc ) 138.2; δCd ) 127.3; δCa* )
1
47.7; δCe ) 26.3; δCf ) 31.6; δCg ) 34.0; δC2 ) δC9 ) 157.0;
Jf-f′ ) 2.10; Jg-g′ ) 9.60, δH2 ) 10.32 d(2); δH3 ) 8.25 dd (2);
δH4 ) 8.73 d(2); δH5 ) 7.12 s (2); J2-3 ) 4.50; J3-4 ) 8.40
δHa ) 8.72 dd(2); δHb ) 7.00 ddd (2); δHc ) 7.44 td(2); δHd )
δC3 ) δC8 ) 127.2; δC4 ) δC7 ) 149.2; δC5 ) δC6 ) 124.2;
δC11 ) δC12 ) 163.8; δC13 ) δC14 ) 130.0; δC(4)CH3 ) 18.1
δCa ) 154.1; δCb ) 123.5; δCc ) 138.1; δCd ) 127.2; δCa* ) 146.7;
δCe ) 26.4; δCf ) 31.6; δCg ) 34.2, δC2 ) δC9 ) 157.7; δC3 )
δC8 ) 129.0; δC4 ) δC7 ) 146.9; δC5 ) δC6 ) 123.5; δC11 )
δC12 ) 163.8; δC13 ) δC14 ) 136.0; δC(3)CH3 ) 14.2;
δC(4)CH3 ) 17.2
7
3
1
1
.11 dd (2); δHe,e′ ) 2.22 td(2), 3.75 ddd (2); δHf,f′ ) 3.39 td(2),
.26 ddd (2); δHg,g′ ) 3.17d(2), 2.17 d(2); Ja-b ) 6.90; Ja-c )
.20; Jb-c ) 7.50; Jb-d ) 1.50; Jc-d ) 7.50; Je-e′ ) 2.10; Je-f )
2.60; Je-f′ ) 12.60; Je′-f ) 12.60; Je′-f′ ) 5.10; Jf-f′ ) 2.10;
Jg-g′ ) 9.90, δH2 ) 10.26 d(2); δH3 ) 8.23 dd (2); δH4 )
8
.86 dd(2); δ(5)CH3 ) 2.72 s(6); J2-3 ) 4.20; J3-4 ) 8.70;
Table 8. UV-Visible Spectroscopic Data for Compounds 3-7
λmax, nm
J4-1 ) 1.20
6
7
δHa ) 8.72 dd(2); δHb ) 7.00 ddd (2); δHc ) 7.52 td(2); δHd )
7.11 dd (2); δHe,e′ ) 2.22 td(2), 3.71 ddd (2); δHf,f′ ) 3.38 td(2),
3.28 ddd (2); δHg,g′ ) 3.15d(2), 2.15 d(2); Ja-b ) 6.00; Ja-c )
1.50; Jb-c ) 7.50; Jb-d ) 1.50; Jc-d ) 7.50; Je-e′ ) 2.10; Je-f )
12.90; Je-f′ ) 12.90; Je′-f ) 12.90; Je′-f′ ) 5.10; Jf-f′ ) 2.10;
ꢀ, M-1 cm-1)
(
compd
MLCTa,d
238
LCa,c,d
MCa
MLCTb
MLCTa
3
282
no
320
412
Jg-g′ ) 9.90, δH2 ) 10.13 d(2); δH3 ) 8.08 d (2); δH5 )
.24 s(2); δ(4)CH3 ) 2.94 s(6); J2-3 ) 5.70
δHa ) 8.72 dd(2); δHb ) 7.01 ddd (2); δHc ) 7.52 td(2); δHd )
(
20841)
235
23425)
244
5138)
239
24135)
232
21492)
(27910)
269
(25258)
276
(30136)
269
(24263)
273
(10927)
330
(7780)
328
(10530)
337
(8549)
334
(5902)
400
(4835)
432
(5138)
397
(6301)
392
8
4
5
6
7
295
(8789)
300
(13780)
294
(10364)
304
(
7
3
1
.11 dd (2); δHe,e′ ) 2.19 td(2), 3.75 ddd (2); δHf,f′ ) 3.39td(2),
.26 ddd (2); δHg,g′ ) 3.16 d(2), 2.14 d(2); Ja-b ) 6.00; Ja-c )
.50; Jb-c ) 7.80; Jb-d ) 1.50; Jc-d ) 7.80; Je-e′ ) 2.10;
(
Je-f ) 12.90; Je-f′ ) 12.90; Je′-f ) 12.90; Je′-f′ ) 5.10; Jf-f′ )
(
2
2
.10; Jg-g′ ) 9.90, δH2 ) 9.91 s(2); δH5 ) 8.24 s(2); δ(3)CH3 )
.80 s(6); δ(4)CH3 ) 2.81 s(6)
(
(32071)
(11844)
(8489)
(7006)
a
δ, multiplicity, (integration), J/Hz.
a
b
Transition due to the coordination of 1,10-phenanthrolines. Transition
c
due to the coordination of pdto. Intra-ligand LC ( π f π*) transition.
d
In all complexes a transition at 252 nm LC (π f π*), due to pdto is also
complete oxidation of compound 1; meanwhile when the
scan potential was initiated in the negative direction, the
chemical species formed after the electrolysis presents a very
well-defined reversible electrochemical reduction process.
A spectroelectrochemical study with an optical transparent
thin layer electrode (OTTLE), made of platinum minigrid,
at potential 1.13 V/Fc-Fc was carried out. The experiment
was monitored every 30 s (Figure 8 depicts results for 60 s
intervals). A decrease of the absorbance in 358 nm MLCT
d f π*) and the appearance of a new band with maximum
no
presented. Not observed.
However, from the coulometric experiment two electrons per
molecule were established, and there is one additional
electron in the electrochemical process; thus the simultaneous
oxidation of another chemical species during the electrolysis
of 1 is presented. For this reason an electrochemical study
of ligand in the absence of Ru(II) was performed. When the
potential was started in the positive direction, only a single
oxidation signal was observed at the anodic peak potential
value of Epa ) 0.63 V/Fc-Fc ; when the scan was
completed, no corresponding reduction signal peak was
detected. By controlled potential coulometry at a potential
value more positive than Epa (0.83 V/Fc-Fc ), two electrons
39
+
(
+
40
absorption at 525 nm during the electrolysis suggest the
oxidation of the central atom from Ru(II) to Ru(III). This
transformation requires only one electron per molecule.
+
(
39) DeAngellis, T. P.; Heineman, W. R. J. Chem. Educ. 1976, 53, 594-
97.
40) Ruiz-Ramirez, L.; Stephenson, T. A. J. Chem. Soc., Dalton Trans.
973, 1770-1782.
per molecule were established.
The simultaneous oxidation of Ru(II) and pdto must be
discarded because three electrons per molecule would be
5
(
1
Inorganic Chemistry, Vol. 42, No. 6, 2003 1831

Ortiz-Frade et al.
Figure 8. Spectroelectrochemical study in OTTLE made of platinum
minigrid for 1 mM compound 1 (in the presence of 0.1 M TBABF4 in
+
acetonitrile) during controlled potential electrolysis at 1.13 V/Fc-Fc ). Each
spectrum was acquired every 60 s.
Figure 10. Cyclic voltammograms for 1.00 mM of compound 4 in the
presence of 0.1 M TBABF4 in acetonitrile. The scan potential was initiated
-
1
from Eocp to negative direction. Scan rate 1000 mV s
.
observed, and when the potential scan was reversed E-λ, three
oxidation signals (I , II , III ) were observed. As the cycle
was completed, two reduction signals (II , III ) are also
a
a
a
c
c
observed. On the other hand, when the potential scan was
started in the positive direction, the same signals are
observed; this fact demonstrates that signals II and III are
independent of signal I. The independence of the oxidation
signals II
switching potentials E+λ. Each oxidation signal has respec-
tively a corresponding reduction signal (II , III ).
a a
and III was established by modifying the
c
c
The cathodic peak potential value Epc(I) obtained for signal
+
I
c
was -1.733 V/Fc-Fc , and the corresponding anodic peak
+
Figure 9. Cyclic voltammograms for 1 mM compound 1, in the presence
potential value Epa(I) for signal I
a
was -1.645 V/Fc-Fc ; a
of 0.1 M TBABF4 in acetonitrile. The scan potential was initiated from
quasi-reversible electrochemical behavior is presented. The
-
1
Eocp to positive direction. Scan rate: 200 mV s . Different amounts of
ionic chloride as TBACl were added: (a) 0, (b) 1, (c) 2, (d) 3, and (e) 4
mM.
-1
∆
p
E was independent of scan rate (0.1-1 V s ), and the
1/2
cathodic peak current was proportional to V , indicating that
4
1
process I is a diffusion-controlled process.
The cathodic and anodic peak potential values for signals
and II pa(II) and Epc(II) are 0.601 and 0.357 V/Fc-
Fc , respectively. The high ∆E indicates the presence of
chemical reaction coupled to the electron transfer in process
required, and the experimental evidence shows that only two
electrons per molecule are involved in the oxidation of 1. In
order to explain these two electrons per molecule involved
in this process, the simultaneous oxidation of Ru(II) and ionic
chloride was proposed. To confirm this, cyclic voltammetric
experiments of compound 1 in the presence of tetra-N-
butylammonium chloride (TBACl), at different concentra-
tions were carried out. When the ionic chloride was added,
II
a
c
E
+
p
4
1
II.
The anodic peak potential value Epa(III) obtained for signal
+
III
a
was 1.080 V/Fc-Fc , and the cathodic peak potential
+
value Epc(III) for signal III
c
was 0.989 V/Fc-Fc ; a quasi-
Figure 9, the currents associated with the oxidation (I
reduction (I ) signals clearly are increased, Figure 9b-d,
while only a small increase of signals I * and I * was
a
) and
reversible electrochemical behavior is also observed.
In order to assign the electrochemical process associated
with process I, a spectroelectrochemical study in optical
c
a
c
observed. Furthermore, a cyclic voltammetry experiment of
a 1.40 mM new solution of compound 1 was obtained after
warming to 353 K and then cooling to room temperature;
3
8
transparent thin layer electrode (OTTLE) was performed;
+
the applied potential was -1.870 V/Fc-Fc (more negative
than Epc(I)), and the electrolysis was monitored every 30 s
an increase in the current associated with the oxidation (I
a
)
(Figure 11 depicts results for 60 s intervals). During the
and reduction (I ) signals was observed. This confirms the
c
electrolysis, the absorbance decreased for all signals, par-
ticularly at 269 nm LC (π f π*); this is evidence of the
reduction of the 1,10-phenanthroline ligand. A one-electron
reduction for this process was established by controlled
potential electrolysis. One-electron electrochemical reduction
of 1,10-phenanthrolines coordinated to Ru(II) and Cu(II) have
exchange of the coordinated chloride by acetonitrile releasing
ionic chlorides for the oxidation process.
Electrochemistry of the Substituted Phenanthroline
pdto Ru(II) Complexes. In all the electrochemical experi-
ments, a 1 mM solution of each compound in supporting
electrolyte (0.1 M TBATFB in acetonitrile) was used. Figure
1
3,42
been reported.
1
0 shows a typical voltammogram of compound 4 obtained
in a platinum electrode. When the potential scan was initiated
in the negative direction, one reduction signal (I ) was
(
41) Bard, A. J.; Faulkner, L. R. Electrochemical Methods, Fundamentals
c
and Applications; John Wiley and Sons: New York, 1980.
1832 Inorganic Chemistry, Vol. 42, No. 6, 2003

Ru(II) Complexes with pdto and 1,10-Phenanthrolines
Figure 12. Spectroelectrochemical study in OTTLE made of platinum
Figure 11. Spectroelectrochemical study in OTTLE made of platinum
minigrid for 1 mmol dm-3 compound 4 (in the presence of 0.1 M TBABF4
in acetonitrile) during controlled potential electrolysis at -1.87 V/Fc-Fc .
Each spectrum was acquired every 60 s.
minigrid for 1 mM compound 4 (in the presence of 0.1 M TBABF in
4
+
acetonitrile) during controlled potential electrolysis at 1.13 V/Fc-Fc . Each
+
spectrum was acquired every 60 s.
Table 9. Electrochemical Potentials for Complexes 3-7
A controlled potential coulometry at potential more
positive than Epa(II) (0.700 V/Fc-Fc ) for a new solution
E1/2b
+
pKaa
II
III
phen/phen-
compd
Ru /Ru
of 4 established an oxidation of two electrons per molecule;
no changes in the solution color were observed during the
electrolysis. After electrolysis, disappearance of the electro-
chemical signal associated with process II was observed and
the values of the peak potentials Epa(I), Epc(I) and Epa(III),
3
4
5
6
7
4.8
4.86
5.6
5.95
6.31
1.042
1.037
1.050
1.020
0.997
-1.644
-1.689
-1.720
-1.805
-1.911
a
pKa of free phenanthroline. b Redox potential, E1/2 ) (Epa + Epc)/2,
1
E
pc(III) remain unchanged. These facts suggest that process
-
reported vs ferrocene in 0.1 M TBABF4-CH3CN. Scan rate 1 V s
.
II corresponds to the oxidation of species outside the
coordination sphere of the Ru(II); thus this process may
correspond to the oxidation of the two ionic chloride atoms
from complex 4. This is in agreement with the fact that two
electrons per molecule in the coulometric test at Epa(II) were
obtained (one electron per chloride to form chlorine). In order
to confirm this, cyclic voltammetric experiments of com-
pound 4 in the presence of different amounts of tetra-N-
butylammonium chloride (TBACl) were performed. When
chlorides were added to the solution, an increase in the anodic
and cathodic current peaks associated with electrochemical
process II was observed; simultaneously the currents and the
potentials associated with processes I and III remain un-
changed. These facts confirm that this electrochemical
process corresponds to the chloride ions. As it was previously
demonstrated in complex 1 of this work, the electrochemical
oxidation of the coordinated pdto ligand in the Ru(II) is not
observed.
The half-wave potential was evaluated with the half sum of
the anodic and cathodic peak potentials, E ) (E + E ),
1
/2
pa
pc
II
III
for the electrochemical processes III (Ru /Ru ) and I (phen/
-
phen ) for all the compounds.
Correlations. The E1/2 (phen/phen ) and E (Ru /Ru )
-
II
III
1/2
values for each complex and the pK for each corresponding
a
free substituted phenanthroline are listed in Table 9. In this
table it is observed that the potential for the process (phen/
-
phen ) increases linearly as the pK of the free substituted
a
phenanthrolines increase; this demonstrates that the nature
of the phenanthroline is determinant in the phen reduction
process. This correlation between the potential E1 (phen/
/2
-
phen ) in the complexes and the pK of free phenanthrolines
a
was found to have the equation E1/2 ) -0.150 pK - 0.9278,
a
with a correlation coefficient r ) 0.9432. There have been
reported correlations for Ru(II) polypyridine complexes in
-
which the potential values E1/2 (phen/phen ) are dependent
Finally, to obtain information of signal III, the solution
recovered after controlled potential coulometry at Epa(II) was
again electrolyzed at Epa(III), and one electron per initial
molecule was established during the electrolysis. The solution
color changes from yellow to green, and this fact suggests
the oxidation of Ru(II) to Ru(III). This was confirmed by
on several properties of the free ligand, due to the nature,
1
3
position, and number of substituents. Also Sanna and co-
4
2
-
workers have obtained E (phen/phen ) values for Cu(II)
1
/2
phenanthroline complexes, which have an inverse correlation
with pK . The π*-acceptor properties of the phenanthrolines
a
are not easily evaluated, but an experimental parameter
+
an spectroelectrochemical study, at 1.130 V/Fc-Fc , Figure
widely accepted to indirectly measure these properties is the
-
12. The decrease of ligand metal charge transfer (MLCT)
half-wave potential for the phen/phen reduction; moreover
transitions bands (330 and 400 nm) for Ru(II) complex and
the appearance of a new absorption maximum at 600 nm
that corresponds to a Ru(III) compound were observed. The
electrochemical behavior for compounds 3, 5, 6, and 7 is
very similar to that observed for 4, though there are changes
in the values of peak potentials; this will be discussed below.
similar studies of quantitative analysis of ligands and effect
(QALE) have suggested that the π*-acceptor properties of a
ligand decrease regularly as their σ basicity increases.4
This is in agreement with our experimental evidence, i.e.,
the 4,7-diphenyl-1,10-phenanthroline ligand, in their corre-
sponding complex (3), has a high π*-acceptor character (low
3,44
(
42) Sanna, G.; Pio, M. I.; Zoroddu, M. A.; Seeber, R. Inorg. Chim. Acta
(43) Tollman, C. A. Chem. ReV. 1977, 77, 313-348.
(44) Drago, R. S.; Joerg S. J. Am. Chem. Soc. 1996, 118, 2654-2663.
1993, 208, 153-158.
Inorganic Chemistry, Vol. 42, No. 6, 2003 1833

Ortiz-Frade et al.
-
pK
a
) that causes a low potential E1/2 (phen/phen ). On the
complexes with substituted phenanthrolines is ∆λMLCT. A
other hand, the complex with 3,4,7,8-tetramethyl-1,10-
linear correlation was obtained with an equation ∆E1/2
0.0041∆λMLCT + 0.0152, and r ) 0.9554.
)
phenanthroline (7) has a low π*-acceptor character (high
-
pK
a
), which increases the potential E1/2 (phen/phen ).
Summary
We also observed a linear correlation among the chemical
shift of the ortho hydrogen δH of the coordinated 1,10-
A new compound 1 can be converted into 2 in acetonitrile
solution by heating. This was confirmed by NMR studies,
X-ray diffraction, and electrochemistry. The electrochemical
behavior of compound 1 was studied by cyclic voltammetry,
controlled potential coulometry, and spectroelectrochemical
studies. The simultaneous oxidation of ionic chloride and
Ru(II) was observed.
2
phenanthroline, from Table 6, and the potential values E1/2
-
of (phen/phen ). The equation obtained was E1/2 ) 0.588
δH - 7.7543 with a correlation coefficient r ) -0.989. If
2
the chemical shift measures the extent to which the nucleus
is shielded, then this can be related to the acidity of the
coordinated ligand. In this case shielding δH of the ortho
2
A new family of compounds with possible photochemical
properties was synthesized and fully characterized by
elemental analysis, X-ray diffraction, and NMR spectra. It
was established by cyclic voltammetry, controlled potential
coulometry, and spectroelectrochemical studies in acetonitrile
that all these complexes present two oxidation processes:
the oxidation of the ionic chlorides and the oxidation of the
Ru(II). Additionally a monoelectronic reduction on the
phenanthrolines coordinated to the Ru(II) was also observed.
The electrochemical processes of the coordination com-
pounds described in this work are affected by the electron-
donating and electron-withdrawing properties of the ligands,
due to the nature, number, and position of the substituents
hydrogen nucleus can be also related to the π*-acceptor
character of the phenanthroline.
A rough tendency can also be observed for the potential
II
III
(
Ru /Ru ) values with pK
ligands with a higher pK
This can be explained in terms of the stronger σ capability
higher pK ) resulting in a higher electron density over the
a
, Table 9. The complexes of the
show a low oxidation potential.
a
(
a
Ru(II) and consequently in a lower oxidation of the
complexes. Within the context of ligand field theory, the
correlation connecting the E1/2 values of the complexes and
the pK of the ligands has been attributed to the spherical
a
density of the donor atoms at the antibonding d orbitals.
Thus, complexes formed with ligands with high electron
a
on the 1,10-phenanthroline. Stronger σ ability (higher pK )
results in lower electron density over Ru(II) and consequently
density on their donor atoms (high pK
a
) will show lower
4
5
E
1/2 values than those formed with weaker bases. These
in a lower oxidation of the complexes. This was confirmed
correlations have been studied for Ru(II)-Schiff base
II
III
by the series of correlations between the E1/2 Ru /Ru and
the pK , δH , and ∆λmax (MLCT), respectively. The ligands
L with low pK will decrease the electron density in the
complexes derived from substituted salicylaldimines and
triphenylphosphine.46
a
2
n
a
A correlation can also be observed for the chemical shift
rest of the molecule and consequently are easier to reduce
and more difficult to oxidize.
of the ortho hydrogen δH
,10-phenanthroline coordinated, and the E1/2 (Ru /Ru ) was
obtained. This also suggests that the electrochemical potential
2
of the corresponding substituted
II
III
1
Acknowledgment. The authors thank DGAPA-UNAM
(IN212500) and CONACyT (3700PE) for financial support.
L.A.O.-F. thanks CONACyT for a scholarship. M.A. thanks
INTERCAMPUS and Intercambio Acad e´ mico UNAM PRO-
GRAM EXCHANGE for financial support from the ex-
change program. The authors thank USAI-Facultad Qu ´ı mica
UNAM and, particularly, G. Duarte, R. Del Villar, and O.
Ya n˜ ez for technical support.
II
III
(
Ru /Ru ) is a function of the electron density distribution
produced by the substituent on the 1,10-phenanthrolines.
In order to obtain a correlation between the electrochemical
II
III
and spectrochemical properties, the E1/2 (Ru /Ru ) and the
max of the MLCT absorption near 400 nm, were selected.
λ
The difference between E1/2 of complex with nonsubstituted
phenanthroline and E1/2 of the complexes with substituted
phenanthrolines is ∆E1/2; and the difference between λmax of
complex with nonsubstituted phenanthroline and λmax of the
Supporting Information Available: X-ray crystallographic file
in CIF format for the structural determination of complexes 1a, 2,
and 4. This material is available free of charge via the Internet at
http://pubs.acs.org.
(
(
45) Lintvedt, R. L.; Fenton D. E. Inorg. Chem. 1980, 19, 569-571.
46) Mar ´ı n-Becerra, A.; Ruiz-Ram ´ı rez, L.; Moreno-Esparza, R.; Del R ´ı o,
P. J. F. J. Coord. Chem. 1993, 29, 359-370.
IC025849Q
1834 Inorganic Chemistry, Vol. 42, No. 6, 2003