Tuning photophysical properties with ancillary ligands in Ru(II) mono-diimine complexes

Article abstract of DOI:10.1016/j.jorganchem.2008.11.048

The series of complexes [XRu(CO)(L-L)(L′)₂][PF₆] (X = H, TFA, Cl; L-L = 2,2′-bipyridyl, 1,10-phenanthroline, 5-amino-1,10-phenanthroline and 4,4′-dicarboxylic-2,2′-bipyridyl; L′₂ = 2PPh₃, Ph₂PC_2<

Full text of DOI:10.1016/j.jorganchem.2008.11.048

Journal of Organometallic Chemistry 694 (2009) 988–1000
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Tuning photophysical properties with ancillary ligands in Ru(II)
mono-diimine complexes
Ayesha Sharmin a, Reuben C. Darlington a, Kenneth I. Hardcastle b, Mauro Ravera c, Edward Rosenberg a,
,
*
J.B. Alexander Ross a,
*
a Department of Chemistry and Bio-Chemistry, University of Montana, Missoula, MT 59812, USA
b Department of Chemistry, Emory University, Atlanta, GA 30322, USA
c Dipartimento di Scienze dell_Ambiente e della Vita, Universita‘ del Piemonte Orientale ‘‘Amedeo Avogadro”, Spalto Marengo 33, 15100 Alessandria, Italy
a r t i c l e i n f o
a b s t r a c t
The series of complexes [XRu(CO)(L–L)(L0)2][PF6] (X = H, TFA, Cl; L–L = 2,20-bipyridyl, 1,10-phenanthro-
line, 5-amino-1,10-phenanthroline and 4,40-dicarboxylic-2,20-bipyridyl; L02 = 2PPh3, Ph2PC2H4PPh2,
Ph2PCH@CHPPh2) have been synthesized from the starting complex K[Ru(CO)3(TFA)3] (TFA = CF3CO2)
by first reacting with the phosphine ligand, followed by reaction with the L–L and anion exchange with
NaPF6. In the case of L–L = phenanthroline and L02 = 2PPh3, the neutral complex Ru(Ph3P)(CO)(1,10-phe-
nanthroline)(TFA)2 is also obtained and its solid state structure is reported. Solid state structures are also
reported for the cationic complexes where L–L = phenanthroline, L2 = 2PPh3 and X = Cl and for L–L = 2,20-
Article history:
Received 16 October 2008
Received in revised form 19 November 2008
Accepted 20 November 2008
Available online 30 November 2008
Keywords:
Ruthenium complexes
Metal-to-ligand charge-transfer
Photophysical properties
Electrochemistry
bipyridyl, L2 = 2PPh3 and X = H. All the complexes were characterized in solution by a combination of 1
H
and 31P NMR, IR, mass spectrometry and elemental analyses. The purpose of the project was to synthesize
a series of complexes that exhibit a range of excited-state lifetimes and that have large Stokes shifts, high
quantum yields and high intrinsic polarizations associated with their metal-to-ligand charge-transfer
(MLCT) emissions. To a large degree these goals have been realized in that excited-state lifetimes in
Phosphine ligands
the range of 100 ns to over 1 ls are observed. The lifetimes are sensitive to both solvent and the presence
of oxygen. The measured quantum yields and intrinsic anisotropies are higher than for previously
reported Ru(II) complexes. Interestingly, the neutral complex with one phosphine ligand shows no MLCT
emission. Under the conditions of synthesis some of the initially formed complexes with X = TFA are con-
verted to the corresponding hydrides or in the presence of chlorinated solvents to the corresponding
chlorides, testifying to the lability of the TFA Ligand. The compounds show multiple reduction potentials
which are chemically and electrochemically reversible in a few cases as examined by cyclic voltammetry.
The relationships between the observed photophysical properties of the complexes and the nature of the
ligands on the Ru(II) is discussed.
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
tions on membranes [1–4]. The luminescent behavior of these
complexes arises from the MLCT (metal-to-ligand charge-transfer)
Transition metal luminescent complexes containing one or
more diimine ligands typically have excited-state lifetimes ranging
from about 100 ns to 10 ls. Because the lifetimes of these lumino-
phores are long compared to fluorescent dyes that are used as bio-
logical probes, time-gated detection can be used to suppress
interfering auto-fluorescence from the biological sample. In addi-
tion, highly polarized emission from some of these complexes
has stimulated interest in using them as biophysical probes for
studying the dynamics of macromolecular assemblies and interac-
band. Because the emission of metal–ligand complexes (MLCs) is
dominated by the MLCT transition, the MLCs behave like a single
chromophoric unit, and they have high chemical and photochemi-
cal stabilities under physiological conditions. As a result of these
favorable properties, MLCs are finding new applications in bio-
physical chemistry, clinical chemistry and DNA diagnostics [5,6].
Because the energy gap law determines the luminescent proper-
ties of these complexes, several criteria must be satisfied to observe
luminescence from their MLCT state [7–10]. The ligand field must
be strong enough to raise the d–d state above the MLCT state
[11]. This is the reason why [Fe(L–L)3]2+ are not luminescent
(non-radiative decay), but [Ru(L–L)3]2+ show radiative decay and
hence useful luminescence (L–L = 2,2 bipyridyl, 1,10-phenanthro-
line and their derivatives). However, the energy of the excited-state
* Corresponding authors. Tel: +1 406 243 2592; fax: +1 406 243 6026
(E. Rosenberg); tel./fax: +1 406 243 4227 (J.B. Alexander Ross).
E-mail addresses: edward.rosenberg@mso.umt.edu (E. Rosenberg), sandy.ross@
umontana.edu (J.B. Alexander Ross).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.048

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
989
is closer to the ground state for the Os–MLCs. Consequently, they
typically show weak luminescence; the smaller energy gap facili-
tates non-radiative decay [5]. The luminescence of these complexes
is phosphorescence from the triplet state. Because of the strong
spin–orbit coupling, the intersystem crossing from the initially ex-
cited singlet state is very efficient, and the triplet excited-state yield
is close to unity. In addition, the degree of singlet–triplet mixing di-
rectly affects the radiative vs. non-radiative decay rates, and thus
affects the lifetime of the resulting triplet excited-state. In particu-
lar, increased singlet–triplet mixing results in shorter triplet ex-
cited-state lifetimes.
complexes. It would be desirable to have the ability to tune the life-
time of the excited-state so that one could tailor a particular probe
to a particular dynamical process in a bio-macromolecule. It would
also be desirable to have complexes that contain only one chelating
heterocycle, because this would decrease the molecular symmetry,
which would have the effect of increasing the anisotropy of the
luminescence. Combining all of these desired features into the
synthesis of a luminescent probe is a challenging task. However,
by making use of the easily-substituted ruthenium complex
K[Ru(CO)3(TFA)3] [23] and the well-known fact that the incorpora-
tion of p-acid ligands [5,16,24] into complexes containing chelating
When excited with polarized light, the emission from asymmet-
ric MLCT complexes is also polarized, which makes these com-
plexes useful for studying dynamics; in general, complexes with
non-identical diimine ligands show higher fundamental anisotro-
pies than the more symmetrical complexes. The first such complex
reported was [Ru(bpy)2(dcbpy)]2+ (dcbpy = 4,40-dicarboxy-2,20-
bipyridyl). This dicarboxy derivative showed higher fundamental
anisotropies than [Ru(bpy)3]2+. Introducing electron withdrawing
groups on the diimine ligand resulted in red-shifted emission
and an increase in emission anisotropy, which suggests that one li-
gand is accepting an electron preferentially in the MLCT transition
[1,12–14]. The possibility of improving the fundamental anisot-
ropy with a single chromophoric ligand in metal–ligand complexes
is based on results for Re(I) complexes (e.g. [Re(4,7-dimethyl-
phen)(CO)3(4-carboxy-Py)(PF6)]) [4,15].
A limitation of most metal–ligand complexes is low quantum
yield. However, the electronic effect of ligands on the energy gap
can be utilized to increase quantum efficiency. Previous studies
[16] have shown that replacing diimines with chelating phosphine
ligands results in increased quantum yields of [Os(phen)(dppene)]2+
and [Os(phen)2(dppene)]2+ (dppene = diphenylphosphinoethylene)
compared to [Os(phen)3]2+ (Q = 0.518, 0.138 and 0.016 respec-
tively). Therefore, careful selection of metal and ligands can gener-
ate MLCs with spectroscopic and physical properties useful for the
study of specific biological systems [5,9,17–20]. For example, we
recently reported the synthesis, electrochemical and electrogener-
ated chemiluminescence studies of [Ru(bpy)2{2-(4-methylpyri-
dine-2-yl)benzo[d]-X-azole}(PF6)2] [21]. This study focused on
the development of novel electrogenerated chemiluminescence
devices suitable for the detection of different biological analytes
of clinical and environmental interest. Also, Lakowicz and cowork-
ers have reported the use of the long-lifetime probe [Re(4,7-di-
methyl-phen)(CO)3(4-carboxy-Py)(PF6)] to study overall rotational
motion in lipid vesicles and microsecond dynamics of cell mem-
branes [2–4]. The limitation of this type of complex is that the liga-
tion around the metal is not amenable to further modification
because the carbonyls are difficult to substitute, making it difficult
to further alter the excited-state lifetime.
nitrogen heterocycles has the effect of prolonging the excited-state
lifetime [16], we have developed synthetic pathways to complexes
having most, if not all, of the desired photophysical properties. In
this study, we report the synthesis of a series of complexes [XRu
(CO)(L–L)(L0)2][PF6] (X = H, TFA, Cl; L–L = 2,20-bipyridyl, 1,10-
phenanthroline, 5-amino-1,10-phenanthroline and 4,40-dicarbox-
ylic-2,20-bipyridyl; (L0)2 = 2PPh3, Ph2PC2H4PPh2, Ph2PC2H2PPh2).
2. Experimental
2.1. General methods and materials
Reactions were carried out under a nitrogen atmosphere, but
purification was carried out in air using preparative thin layer
chromatography (10 ꢀ 20 cm plates coated with 1 mm silica gel
PF 60254-EM Science). Activated neutral alumina (size) was also
used to purify compounds by column chromatography. Solvents
were reagent grade. Tetrahydrofuran was distilled from benzophe-
none ketyl and methylene chloride and acetonitrile were distilled
from calcium hydride. Ruthenium carbonyl was purchased from
Strem Chemicals. 2,2-bipyridyl, 1,10-phenantroline, 4,40-dicar-
boxy-2,2-bipyridyl and 5-amino-1,10-phenanthroline (Aldrich)
were used as received. 1H NMR spectra were obtained on a Varian
400 MHz Unity Plus or a Varian NMR Systems 500 MHz spectrom-
eter. Infrared spectra were obtained on a Thermo-Nicolet 633 FT-IR
spectrometer. Elemental analyses were performed by Schwarzkopf
Microanalytical Labs, Woodside, NY. ESI-MS spectra ware obtained
on a Watts/Micromass LCT using 80% MeCN as carrier solvent.
Some of the spectra showed the presence of Na+ associated with
the molecular ion due to the extensive use of salt solutions with
this instrument which has contaminated the analyzer.
2.2. Crystal structure analysis
Suitable crystals of 5, 6 and 10 were coated with Paratone N oil,
suspended in a small fiber loop and placed in a cooled nitrogen gas
stream at 173 K on a Bruker D8 SMART APEX CCD sealed tube diffrac-
tometer with graphite-monochromated Mo K
a (0.71073 Å) radia-
To develop better MLC probes for application to specific biolog-
ical systems, a deeper understanding of the probe’s photophysical
properties is required. Recently, we reported photophysical and
computational studies of [Re(CO)3{2-(4-methyl pyridine-2-yl)
tion. Data were measured using a series of combinations of phi
and omega scans with 10 s frame exposures and 0.30 frame widths.
Data collection, indexing and initial cell refinements were all car-
ried out using SMART [25] software. Frame integration and final cell
refinements were done using SAINT [26] software. The final cell
parameters were determined from least-squares refinement on
2481 and 5705 reflections, respectively. The SADABS [27] program
was used to carry out absorption corrections. The structure was
solved using the Patterson method and difference Fourier tech-
niques (SHELXTL, V6.12) [28]. Hydrogen atoms were placed in their
expected chemical positions using the HFIX command and were
included in the final cycles of least-squares with isotropic Uij’s re-
lated to the atom’s ridden upon. All non-hydrogen atoms were re-
fined anisotropically. Scattering factors and anomalous dispersion
corrections are taken from the International Tables for X-ray Crystal-
lography [29]. Structure solution, refinement, six graphics and
benzo[d]-X-azol}L]
and
[Re(CO)3{2-(4-methylpyridine-2-yl)
benzo[d]-X-azol-2-yl}(4-methylquinolin)L]+. The purpose of these
studies was to investigate the effect of the organic ligand on the
optical properties and electronic structure of the reported com-
plexes [22]. The results showed that the photophysical properties
depended on the nature of X (N > S > O) and L (py and Cl). The
pyridinyl nitrogen is a better electron donor for the Ru(II), and this
donor results in a higher quantum yield and longer excited-state
lifetime relative to the S and O containing heterocycles.
Ideally, one would like to develop a series of complexes where
the MLCT band is red-shifted and well-separated from the intra-
ligand transitions and where the intensity of the MLCT transition
is stronger than observed for previously reported Ru(II) diimine

990
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
Table 1
IR, NMR and ESI-MS data.
a
Compound
IR (m
CO, cmꢁ1
)
1H NMR (d, ppm)b
31PNMR (d, ppm)b
ESI-MSc (m/z)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
2061vs, 2001vs, 1692vs
2066vs, 2004vs, 1691vs
2077vs, 2006vs, 1692vs
1993vs, 1688s
1982s, 1703vs
1992vs, 1680s
1992s, 1727s, 1680m
1944s, 1730s
1942s
1988vs, 1692m
1987vs, 1704m
1992vs, 1691m
1988vs, 1706m
1990vs, 1685m
1977s
7.8–7.2 (30H)
7.8–7.0 (20H), 3.6–3.4 (2H), 2.01 (2H)
7.8–6.9 (22H)
8.9–8.2 (6H), 7.9–6.8 (32H)
9.4–8.2 (6H), 7.8–6.9 (17H)
29.52(s, 2P)
794 [MꢁTFA]
–
–
869 [MꢁPF6]
685 [MꢁTFA]
923 [MꢁPF6]
–
45.8 (s, 1P), 44.07(s, 1P)
53.99(s, 1P), 53.47(s, 1P)
26.6(s, 2P), ꢁ155(1P)
28.3(s, 1P), ꢁ155(1P)
28.98 (s, 2P), ꢁ155 (1P)
–
50.9 (2P), ꢁ155 (1P)
50.45 (2P), ꢁ155 (1P)
45.24 (2P), ꢁ155 (1P)
53.96 (2P), ꢁ155 (1P)
49.93 (2P), ꢁ155 (1P)
53.93 (2P), ꢁ155 (1P)
53.9 (2P), ꢁ155 (1P)
74.8 (2P), ꢁ155 (1P)
9.1–8.4 (6H), 7.8–6.9 (32H),
–
11.7 (2H), 9.1–8.5 (4H), 6.9–8.1 (32H), ꢁ11.09 (1H)
9.0–8.2 (6H), 7.8–6.9 (32H), ꢁ11.07 (1H)
8.6–7.9 (4H), 7.7–6.6 (23H), 3.6–3.3 (2H), 2.04 (2H)
9.4–8.2 (6H), 8.0–6.7 (22H), 3.5–3.3 (2H), 2.04 (2H)
8.8–8.2 (4H), 7.9–7.2 (23H), 7.0–6.8 (3H)
8.9–8.1 (6H), 7.8–6.8 (24H)
943[MꢁPF6+2Na+]
811 [MꢁPF6]
967 [M+H+]
941 [M+]
965 [M+H+]
939 [M+]
8.75–8.05 (5H), 7.8–7.0 (22H), 4.9–4.6 (2H)
8.3–7.9 (5H), 7.8–6.8 (22H), 4.0 (2H), ꢁ7.4 (1H)
835 [MꢁPF6]
723 [MꢁPF6]
a
Data were collected in KBr.
Data were collected in Acetone d6.
Data were collected in 80% acetonitrile.
b
c
generation of publication materials were performed by using
SHELXTL, V6.12 software. Additional details of data collection and
structure refinement are given in Table 2.
emission path on the opposite side of the sample cuvette, was
set at the magic angle (54.7° to vertically polarized excitation)
for determination of the luminescence lifetime. The fluorescence
intensity decay was calculated by fitting the data to a single expo-
nential decay model; here I(t) is the time dependent intensity and
I0 is the intensity at time 0.
2.3. Electrochemistry
A PAR 263A electrochemical analyzer (EG&G Princeton Applied
Research, Oak Ridge, TN, USA) interfaced to a personal computer
running PAR M270 electrochemical software was used for the elec-
trochemical measurements. A standard three-electrode cell was
designed to allow the tip of the reference electrode (saturated cal-
omel electrode, SCE) to closely approach the working (a glassy car-
bon disk, diameter 0.1 cm, sealed in epoxy resin), and the auxiliary
(a Pt wire) electrodes. All measurements were carried out under
nitrogen in CH2Cl2 solutions containing 0.1 M [NBu4]PF6 as sup-
porting electrolyte and the metal complexes at 1.0 ꢀ 10ꢁ3 M. All
potentials are reported vs. the ferrocene/ferrocinium redox couple,
added as an internal standard (E°0 (Fc/Fc+) = +0.41 V vs. SCE [i]). Po-
sitive-feedback IR compensation was applied routinely [30].
IðtÞ ¼ I0 expðꢁt=
s
Þ
ð2Þ
In the time-resolved anisotropy experiment, the depolarization
of the emitted light that results from molecular rotation is given by
5
X
I
VVðtÞ ꢁ IVHðtÞ
Uj
rðtÞ ¼
¼
bjeꢁt=
ð3Þ
I
VVðtÞ þ 2IVVðtÞ
j¼1
where IVV(t) and IVH(t) represent the vertical and horizontal decays,
respectively, obtained using vertical excitation. The pre-exponential
factors, bj, are trigonometric functions of the angles between the
excitation and emission transition dipole moments of the probe
and the symmetry axes of the ellipsoid of revolution [32], and the
sum of bj is the limiting anisotropy at zero time, r0, when no motion
has occurred. The denominator of Eq. (3) is the total intensity decay,
I(t),
2.4. Luminescence spectroscopy
Steady state UV–Vis absorption spectra and emission spectra
were recorded on a Molecular Devices Spectra Max M2. The quan-
n
X
si
tum yields (
oxygen were calculated using Eq. (1), relative to a Rhodamine B
standard ( = 0.7 3, in ethanol), where abs is the absorbance
U) for the luminescent complexes in the presence of
IVVðtÞ þ 2IVHðtÞ ¼ IðtÞ ¼
a
ieꢁt=
ð4Þ
i¼1
U
where si is the lifetime and ai is the amplitude of the ith compo-
nent; the magic angle decay is I(t)/3.
(<0.05) at the excitation wavelength (420 nm), and area is the inte-
grated emission spectrum corrected for the wavelength-dependent
quantum efficiency of the instrument [31].
The anisotropy decay data were analyzed using the software
package FLUOFIT PRO (PicoQuant, Berlin). For anisotropy analysis,
the individual vertical and horizontal decays, IVV(t) and IVH(t),
respectively, were fit simultaneously according to the following
relationships:
abs Rhodamine area Ru
area Rhodamine abs Ru
U
¼
ꢀ
ꢀ 0:73
ð1Þ
$
%
Time-resolved luminescence decay and anisotropy decay mea-
n
X
X
1
3
si
Uj
IVVðtÞ ¼ G
a
ieꢁt= 1 þ 2ðr1 þ
bjeꢁt=
ð5aÞ
ð5bÞ
surements were performed by time-correlated single-photon
counting (TCSPC), using the Quantum Northwest FLASC 1000 sam-
ple chamber (Spokane, WA). In the FLASC 1000, the vertical (V or 0°
to vertically polarized excitation) and horizontal (H or 90°) emis-
sion components are separated on one side of the sample cuvette,
orthogonal to the excitation path, by a beam-splitting Glan-
Thompson polarizer (Karl Lambrecht, Chicago, IL). This allows
simultaneous detection of the V and H anisotropy decay compo-
nents by separate detectors, which assures data collection under
identical excitation conditions. A variable-angle polarizer, in the
i¼1
j¼1
$
%
n
X
X
1
IVHðtÞ ¼
3
si
Uj
a
ieꢁt= 1 ꢁ ðr1 þ
bjeꢁt=
i¼1
j¼1
R
where r is the anisotropy at infinite time [33], and G = IHV dt/
IHH dt is a factor, obtained using horizontal excitation, that corrects
for the difference in the efficiencies of the V and H detection chan-
nels; under ideal conditions G ꢂ 1 [34,35].
1
R

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
991
Reaction of 2 (210 mg, 0.23 mmol) with 4,40-dicarboxy-bipyridyl
(56 mg, 0.23 mmol) in ethylene glycol (25 mL) at 140 °C for 72 h fol-
lowed by addition of aqueous NH4PF6 (1.0 g/10 mL) resulted in a
mixture of [Ru{P(C6H5)3}2(4,40-dicarboxy-bipyridyl)(CO)TFA][PF6]
(8) and [HRu{P(C6H5)3}2(4,40-dicarboxy-bipyridyl)(CO)][PF6] (9).
Dissolving the mixture in hot ethanol yielded only [HRu{P(C6
H5)3}2(4,40-dicarboxy-bipyridyl)(CO)][PF6] (9) (102 mg, 54%) (Anal.
Calc. for C49H39O5P3F6Ru1N2: C, 56.38; H, 3.77, N, 2.69. Found: C,
57.1; H, 3.88, N, 2.62%).
3. Synthesis
The reactive starting complex K[Ru(CF3CO2)3(CO)3] (1) was syn-
thesized according to the published procedure [23]. Spectroscopic
data for the new compounds are summarized in Table 1. Elemental
analyses were obtained only for the final diimine complexes. In
some cases the lability of the TFA ligand led to elemental analyses
slightly out of the required range for carbon content (>0.5%, com-
pounds 7, 11, 15). Mass spectral and spectroscopic data verify iden-
tity and purity of these complexes (Table 1).
Re-crystallization of 7 from hot ethanol gave pale yellow crys-
tals of [HRu{P(C6H5)3}2(2,20-bipyridyl)(CO)][PF6] (10).
3.1. Synthesis of [Ru{P(C6H5)3}2(CO)2(TFA)2] (2),
[Ru(
[Ru{
g
2(C6H5)2PC2H4P(C6H5)2)(CO)2(TFA)2] (3) and
g
3.3. Reaction of of [Ru{g
2(C6H5)2PC2H4P(C6H5)2}(CO)2(TFA)2] (3) with
2(C6H5)2PC2H2P(C6H5)2}(CO)2(TFA)2] (4)
1,10-phenanthroline and 2,20-bipyridyl
An acetone solution (30 mL) of K[Ru(CF3CO2)3(CO)3] (1)
(100 mg, 0.18 mmol) and triphenylphosphine (94 mg, 0.36 mmol)
was refluxed for 24 h. The solvent was removed by a rotary evap-
orator and the residue was chromatographed by TLC on silica gel.
Elution with hexane/acetone (9:1 v/v) gave two bands. The slower
moving band afforded Ru{P(C6H5)3}2(CO)2(TFA)2] (2) (66 mg, 41%)
as a white powder after recrystallization from hexane/acetone at
RT.
Compound 3 (120 mg, 0.153 mmole) was heated with 1,10-phe-
nanthroline (83 mg, 0.461mmole) in ethylene glycol (15 mL) at
140 °C for 72 h, The color of the reaction mixture turned to deep
orange. An orange precipitate of [(CO)(TFA)Ru{
g
2(C6H5)2PC2H4P
(C6H5)2}(
g
2C12H8N2)][PF6] (11) (84 mg, 56%) was obtained by add-
ing aqueous NH4PF6 (1.0 g/10 mL) to the reaction mixture. The res-
idue was then filtered and washed tree times with DI water and
three times with diethyl ether and dried under vacuum (Anal. Calc.
for C41H32O3P3F9Ru1N2: C, 51.0; H, 3.33, N, 2.91. Found: C, 51.9; H,
3.65, N, 3.21%).
A mixture of 1 (250 mg, 0.44 mmole) and diphenylphosphino-
ethane (dppe) (195 mg, 0.48 mmole) was refluxed in an ether–ace-
tone (10 mL/10 mL) solvent for 2 h under N2. The color of the
solution changed from yellow to green. The solvent was removed
by a rotary evaporator, taken up into acetone and separated on
TLC. Elution with acetone/hexane [1:3 (v/v)] developed two bands.
The faster moving yellow band yielded a small amount of 1 and the
A similar reaction of compound 2 (120 mg, 0.153 mmole) with
2,20-bipyridyl (71 mg, 0.46 mmole) in ethylene glycol (15 mL) at
140 °C for 72 h followed by addition of aqueous NH4PF6 (1.0 g/
10 mL) gave [(CO)(TFA)Ru{g g
2(C6H5)2PC2H4P(C6H5)2}( 2C10H8N2)]
[PF6] (12) (80 mg, 55%) (Anal. Calc. for C39H32O3P3F9Ru1N2: C,
49.7; H, 3.41. Found: C, 50.1; H, 3.72%).
slower moving green band afforded [Ru(g
2(C6H5)2PC2H4P
(C6H5)2)(CO)2(TFA)2] (3) (120 mg, 35%).
Reaction of 1 (250 mg, 0.44 mmol) with diphenylphosphinoeth-
ylene (194 mg, 0.48 mmol) in refluxing ether–acetone (10 mL/
10 mL) solvent followed by similar chromatographic separation
afforded [Ru(
40%).
3.4. Reaction of of [Ru{g
2(C6H5)2PC2H2P(C6H5)2}(CO)2(TFA)2] (4) with
1,10-phenanthroline, 2,20-bipyridyl and 5-amino-1,10-phenanthroline
g
2(C6H5)2PC2H2P(C6H5)2)(CO)2(TFA)2] (4) (140 mg,
A mixture of 4 (130 mg, 0.167 mmole) and 1,10-phenanthroline
(86 mg, 0.48 mmole) in ethylene glycol (15 mL) was heated at
140 °C for 72 h. Addition of aqueous NH4PF6 (1.0 g/10 mL) to the
reaction mixture yielded the yellow precipitate of [(CO)(TFA)
3.2. Reaction of [Ru{P(C6H5)3}2(CO)2(TFA)2] (2) with 1,10-
phenanthroline and 2,20-bipyridyl
Ru{g
2(C6H5)2PC2H2P(C6H5)2}(
g
-2C12H8N2)][PF6]
(13)
(95 mg,
The reaction of 2 (100 mg, 0.11 mmole) with 1,10-phenanthro-
line (40 mg, 0.22 mmole) in refluxing toluene for 72 h resulted in
an orange solution. The solvent was removed on a rotary evapora-
tor and the oily residue was dissolved in acetone and placed onto a
column of neutral alumina. Elution with hexane/CH2Cl2 [3:1 (v/v)]
gave two bands. The slower moving orange band gave
[Ru{P(C6H5)3}2(1,10phenanthroline)(CO)Cl][PF6] (5) (35 mg, 36%)
as orange crystals after adding aqueous ammonium hexafluoro-
phosphate and recrystallization from hexane/CH2Cl2 (Anal. Calc.
for C49H38O1P3F6Ru1N2Cl1: C, 58.5; H, 3.83; N, 2.78. Found: C,
58.2; H, 3.62, N, 3.06%). The faster moving yellow band yielded
[Ru{P(C6H5)3}(1,10-phenanthroline)(CO)((TFA)2] (6) (25 mg, 29%) as
yellow crystals after re-crystallization from hexane/CH2Cl2 (Anal.
Calc. for C35H23N2P1O5F6Ru1: C, 53.77; H, 2.97. Found: C, 54.16; H,
2.78%).
59%). The residue was then filtered and washed tree times with
DI water and three times with diethyl ether and dried under vac-
uum (Anal. Calc. for C41H30O3P3F9Ru1N2: C, 51.1; H, 3.11. Found:
C, 51.6; H, 2.97%).
A similar reaction of compound 4 (140 mg, 0.18 mmole) with
2,20-bipyridyl (71 mg, 0.46 mmole) in ethylene glycol (15 mL) at
140 °C for 72 h followed by addition of aqueous NH4PF6
(1.0 g/10 mL) afforded [(CO)(TFA)Ru{
g
2(C6H5)2PC2H4P(C6H5)2}
(g
2C10H8 N2)][PF6] 14 (65 mg, 45%) (Anal. Calc. for C39H30O3P3-
F9Ru1N2: C, 49.89; H, 3.19. Found: C, 50.26; H, 3.42%).
The reaction of compound 4 (140 mg, 0.18 mmole) with 5-
amino-1,10-phenanthroline (39 mg, 0.19 mmole) in ethylene
glycol (15 mL) at 140 °C for 72 h followed by addition of aqueous
NH4PF6 (1.0 g/10 mL) and purification on an activated
alumina column (elution with CH2Cl2/MeCN, [2:1 v/v]) gave
The reaction of 2 (100 mg, 0.11 mmole) with 2,20-bipyridyl
(35 mg, 0.22 mmole) in ethylene glycol (15 mL) at 140 °C for 72 h
produced an orange solution. A deep yellow precipitate was ob-
tained by the addition of aqueous NH4PF6 (1.0 g/10 mL). The pre-
cipitate was dissolved in CH2Cl2 and chromatographed on a
column of activated alumina (Hexane/CH2Cl2, [1:1 v/v]) yielding
the compound [Ru{P(C6H5)3}2(2,20-bipyridyl)(CO)TFA][PF6] (7)
(48 mg, 47%) as a deep yellow powder (Anal. Calc. for C49H38O3P3-
F9Ru1N2: C, 55.44; H, 3.68, N, 2.69. Found: C, 56.06; H, 3.88, N,
3.28%).
[(CO)Ru({g g
2(C6H5)2 PC2H2P(C6H5)2}TFA( 2C10H9N3)][PF6] (15)
(80 mg, 55%). It was not possible to obtain good elemental
analysis for this compound probably owing to the lability of
the TFA.
The addition of conc. Hydrochloric acid or aqueous NaCl to a
methanol solution of 15 afforded hydride complex [HRu({
H5)2PC2H4P(C6H5)2}(CO)(
2C10H9N3)][PF6] (16). The mass spectra
showed trace of the chloride product [ClRu({
2(C6H5)2PC2
H4P(C6H5)2}(CO)(
2C10H9N3)][PF6] present with the hydride com-
plex. ESI-MS: m/z 924 [M+Na] (Calc. M = 902).
g
2(C6
g
g
g

992
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
4.1.1. Reaction of the chelating phosphine complexes with the diimine
ligands
The reactions of complex 3 with 1,10-phenanthroline or 2,20-
bipyridyl in ethylene glycol formed [(CO)(TFA)Ru{
2(C6H5)2
PC2H4P(C6H5)2}(
2C12H8N2)][PF6] (11) and [(CO)(TFA)Ru{ 2(C6H5)2
PC2H4P(C6H5)2}(
2C10H8N2)][PF6] (12) in 56% and 55% yield,
4. Results and discussion
4.1. Compound synthesis and reaction pathways
The phosphine complexes [Ru{P(C6H5)3}2(CO)2(TFA)2] (2),
g
g
g
g
[Ru(g g
2(C6H5)2PC2H4P(C6H5)2)(CO)2(TFA)2] (3) and [Ru{ 2(C6H5)2PC2
respectively (Scheme 5). Similarly, heating complex 4 with 1,10-
H2P(C6H5)2}(CO)2(TFA)2] (4) were prepared (Scheme 1), and a series
of stepwise reactions shown in Schemes 2–7 show the preparation
of the luminescent ruthenium MLC complexes of formula [XRu(CO)
(diimine)(L)2][PF6] as well as the non-luminescent [(TFA)2Ru
(CO)(2,20-bpy)(PPh3)]. The stepwise carbonyl and TFA (TFA = trifluo-
roacetate) ligand replacement reactions were monitored by IR and
31PNMR spectroscopic methods.
The Reaction of 2 with 1,10-phenanthroline in refluxing toluene for
72 h followed by chromatographicseparation with an alumina column
and crystallization from CH2Cl2/hexane yielded [Ru{P(C6H5)3}2(1,10-
phenanthroline)(CO)Cl][PF6] (5) and [Ru{P(C6H5)3}(1,10-phenanthro-
line)(CO)((TFA)2] (6) in 36% and 29% yields, respectively (Scheme 2).
The reaction of Compound 2 with 2,20-bipyridyl or 4,40-dicarboxy-
2,20-bipyridyl in ethylene glycol at 140 °C gave [Ru{P(C6H5)3}2
(2,20-bipyridyl)(CO)TFA][PF6] (7) and [Ru{P(C6H5)3}2(4,40-dicarboxy-
phenanthroline or 2,20-bipyridyl in ethylene glycol at 140 °C
afforded [(CO)(TFA)Ru{
(13) and [(CO)(TFA)Ru{
g
2(C6H5)2PC2H2P(C6H5)2}(
g
g
2C12H8 N2)][PF6]
2(C6H5)2 PC2H4P(C6H5)2}-( 2C10H8N2)]
g
[PF6] (14) in 59% and 45% yields, respectively (Scheme 6). Reaction
of 4 with bio-conjugable ligand 5-amino-1,10-phenanthroline in
ethylene glycol at 140 °C gave [(CO)Ru({
P(C6H5)2}TFA(
2C10H9N3)] [PF6] (15) in 55% yield (Scheme 6).
g
2(C6H5)2PC2H4-
g
All these complexes were characterized by elemental analysis,
infrared, 1H NMR, 31P–{1H} NMR, UV–Vis and mass spectral data (Ta-
ble 1). Due to the presence of the labile ligand TFA, these complexes
are unstable in solution, and we were not able to obtain good quality
crystals for X-ray crystallographic analysis. Addition of Conc. HCl or
aqueousNaClsolution to the methanolsolutionof 15produced com-
plex [HRu({
along with trace amount of [Ru{
(CO)(
2C10H9N3)Cl][PF6]. The ESI-MS gave an m/z = 924, due to
g
2(C6H5)2PC2H4P(C6H5)2}(CO)(
g
2C10H9N3)][PF6] (16)
g
2(C6H5)2PC2H4P(C6H5)2}
bipyridyl)(CO)TFA][PF6]
(8)
with
a
small
amount
of
[HRu{P(C6H5)3}2(4,40-dicarboxybipyridyl)(CO)][PF6] (9), respectively.
Crystallization of 7 and the mixture of 8 and 9 from hot ethanol yielded
only the hydride complexes as [HRu{P(C6H5)3}2(2,20-bipyri-
dyl)(CO)][PF6] (10) and [HRu{P(C6H5)3}2(4,40-dicarboxy-bipyri-
dyl)(CO)][PF6] (9), respectively (Scheme 3). All these complexes were
characterized by elemental analysis, infrared, 1H NMR, 31P–{1H}
NMR, UV–Vis and mass spectral data (Table 1). The structure of the
complexes 5, 6 and 10 was further investigated by single crystal
X-ray diffraction analysis.
g
formation of the Na+ adduct, shows the presence of this compound
as a mixture with the hydride compound (Scheme 7). The hydride
complex was confirmed by the observed pentaplet at ꢁ7.4. A
probable route to hydride formation in the H2O/MeOH solution is
shown in Scheme 8. There is a possibility that the reaction with
HCl and NaCl is catalyzed by the H+ present in the solution. It is
predicted that the complex 15 loses the labile ligand, TFA, followed
by the coordination of H2O. Protonation of this bound water
molecule then facilitates hydride transfer to the metal center.
Complex 7 contains the labile ligand TFA (trifluoroacetate) trans
to the N of the bipyridyl ligand. In solution, the complex can lose
the TFA ligand to form the trigonal–bipyramidal intermediate with
a vacant coordination site. Coordinative solvents like alcohols can
coordinate to the vacant site trans to the N of the bipyridyl ligand,
which then undergoes ejection of a proton to form a methoxide
complex, and then b-elimination to give the hydride complex. A
proposed mechanism for hydride formation is shown in Scheme 4.
4.2. Solid state structures of compounds 5, 6 and 10
The solid state structures of 5, 6 and 10 are shown in Fig. 1, crys-
tal data are given in Table 2 and selected distances and angles are
given in Tables 3–5. Complexes 5 and 10 contain two mono-den-
tate triphenylphosphine ligands trans to each other and complex
+ L
acetone/ether
reflux
2
L
2
2 = 2 PPh
3
3 = Ph PC H PPh
2
2
4
2
4 = Ph PC H PPh
2
2
2
2
Ph
Ph
P
Ph
Ph
PPh3
P
CO
CO
TFA
TFA
Ph
Ph
TFA
Ph
Ph
TFA
CO
CO
CO
P
Ru
PPh3
2
P
Ru
Ru
CO
TFA
4
TFA
3
Scheme 1.

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
993
PPh3
PPh3
N
N
+
TFA
TFA
CO
CO
1. Toluene, reflux
2. Aq. NH4PF6
N
N
TFA
OC
+
Ru
-
Ru
PF6
PPh3
PPh3
5
2
+
TFA
N
TFA
OC
Ru
N
PPh3
6
Scheme 2.
PPh3
R
PPh3
R
1. ethylene glycol,
140oC
+
TFA
TFA
N
N
CO
N
TFA
OC
+
Ru
-
Ru
PF6
CO
N
2. Aq. NH4PF6
PPh3
PPh3
R
R
2
7, R = H
8, R = COOH
Ethanol
reflux
PPh3
R
+
H
N
N
-
Ru
PF6
OC
PPh3
R
9, R = COOH
10, R = H
Scheme 3.
R
R
PPh3
PPh3
+
2+
N
N
N
N
F3 CC OO
OC
CF3COO-
+
OC
Ru
Ru
PPh3
PPh3
R
R
7, R =H
8, R = COOH
R
R
PPh3
PPh3
R
PPh3
H
2+
2+
N
+
N
H3CH 2CO
H3CH 2CO
OC
N
N
+
-H+
+H -
H
Ru
Ru
Ru
OC
N
N
OC
PPh3
-elimination
β
PPh3
R
R
PPh3
10, R =H
R
9, R =COOH
+
CF3 COOH
+ CH3CH O
Scheme 4.

994
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
Ph
Ph
P
N
+
N
CO
CO
Ph
Ph
P
Ru
TFA
diimine
TFA
11 1,10 phenanthroline
12 2,2' bipyridine
3
Ethylene glycol
140 oC
Aq. NH4PF6
Ph
Ph
Ph
Ph
P
P
+
+
CO
N
CO
N
Ph
Ph
Ph
Ph
P
P
Ru
Ru
_
PF6
_
PF6
TFA
TFA
N
N
11
12
Scheme 5.
Ph
Ph
P
Ph
Ph
CO
CO
P
N
N
+
Ru
diimine
TFA
TFA
13 1,10 phenanthroline
14 2,2' bipyridine
4
15 5-amino-1,10 phenanthroline
Ethylene glycol
140 oC
Aq. NH4PF6
Ph
Ph
Ph
Ph
Ph
+
+
Ph
P
_
PF6
P
_
_
CO
N
+
CO
P
Ph
Ph
PF6
Ph
PF6
P
CO
N
P
Ph
Ph
Ru
P
Ru
N
Ph
Ru
N
N
TFA
TFA
TFA
N
NH2
13
15
14
Scheme 6.
6 contains only one triphenylphosphine ligand. The presence of
[PF6] anion assures the positive charge on 5 and 10 whereas com-
plex 6 is a neutral complex as it contains two TFA ligands cis with
respect to each other.
The ligands in these complexes are arranged in close to octahe-
dral geometry around the Ru atom. The chelating bi-dentate dii-
mine ligands in 5, 6 and 10 are bound to the Ru(II) with a bite
angle 78.19(13), 79.2(13) and 74.5(17)°, respectively. This struc-
tural feature is similar to other Ru–diimine complexes [23,36].
The Ru–N phenanthroline (2.06–2.13 Å) and Ru–N bipyridine
(2.10–2.16 Å) bond lengths of the coordinated diimine ligands are
also comparable to those observed in other Ru–diimine complexes
[36]. All these complexes contain one carbonyl ligand attached to
the metal center and the Ru–C bond lengths of 5, 6 and 10
[1.866(9), 1.864(4) and 1.816(15) Å] are similar to those observed
for similar Os and Re complexes [36–38]. The exchange of Cl for

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
995
1750 cmꢁ1, which are easily distinguishable from organic CO fre-
quencies. The M–CO signals are very sensitive to the electronic
properties of the other ligands present on the metal. The observed
changes in the carbonyl stretching region are due to the replace-
ment of CO ligands by phosphines and diimine ligands, respec-
tively. Introduction of electron rich ligands such as Ph3P, dppe
and dppene decreased the energy of the M-CO bands. Phosphine
compounds 2–4 showed two strong M–CO stretches at 2066 and
2002 cmꢁ1, confirming that they are di-carbonyl complexes; the
strong mCO at 1696 cmꢁ1 is due to the two CF3COOꢁ ligands.
The complexes 5–16 have only one M–CO ligand, and usually the
strong M–CO stretch appears at 1995–1985 cmꢁ1 for the non-hy-
dride complexes. Replacement of CF3COOꢁ by the more electron-
donating hydride ligand shifts mCO to lower energy in complexes
9, 10 and 16. A strong absorption at 1734 cmꢁ1 was also observed
for the carboxyl groups of 4,40-dicarboxy-2,2-bipyridyl of 8 and 9.
Raman spectra of the metal hydrides show characteristic mM–H
stretches at 1800–2000 cmꢁ1 [39]. Raman spectra of complexes 9
and 10 have mM–H at 1920 and 1950 cmꢁ1, respectively.
Ph
Ph
_
PF6
+
P
CO
N
Ph
Ph
P
conc .HCl
or
Aq. NaCl
Ru
N
+
TFA
NH2
MeOH
RT
15
Ph
P
Ph
P
Ph
Ph
+
+
Ph
Ph
H
Ph
Ph
Cl
CO
P
N
-
P
-
PF
6
PF
6
Ru
N
Ru
N
+
CO
N
4.3.2. NMR spectral analysis
The 1H and 31P NMR spectra of these complexes obtained in ace-
tone d6 are consistent with the predicted structures. NMR spectral
analysis was an important tool to assign the presence of the termi-
nal hydride ligand in the complexes 9, 10 and 15. The aromatic re-
gion of the 1H spectra is complex due to presence of phenyl protons
of phosphines ligands and the aromatic protons of diimine ligands.
The chemical shifts and coupling constants are listed in Table 1.
The phenyl protons of PPh3 (complexes 2 and 5–10) and chelating
phosphines (complexes 3, 4 and 11–16) appear as multiplets at d
7.2–7.6 ppm. The CH@CH protons of diphenylphosphinoethylene
are observed around d 6.4–6.9 ppm and the alkyl protons of
diphenylphosphinoethane are observed around d 2.03–3.6 ppm.
The M–H resonance appears as a triplet at d ꢁ11.09 (J = 20 Hz)
and ꢁ11.07 (J = 20 Hz) for complexes 9 and 10, respectively. In
the case of complex 16, the pentuplet is observed at d ꢁ7.7 ppm
(J = 20 Hz).
H2N
H2N
16
17
Scheme 7.
TFA ligand in complex 5 resulted in disordering of the CO and Cl li-
gands. The hydride ligand in the equatorial position of complex 10
is trans to N(2) of the bipyridine ligand and Ru–H bond length is
2.04(5). The presence of this hydride was confirmed by 1H NMR.
4.3. Spectroscopic characterization
4.3.1. Infrared spectral analysis
The infrared spectra of the metal bound carbonyl stretching re-
gion (mCO) provided important information about the stepwise li-
gand substitutions performed on the precursor 1. All of the
complexes synthesized contain metal-coordinated carbonyl
ligands. M–CO shows CO stretching modes around 2150–
The 31P NMR spectra greatly facilitated structural characteriza-
tion of these complexes. The chemical shift of the metal bound
phosphines ligands are in good agreement with the similar Ru(II)
OCOCF3
CO
Ph
H2N
+
Ph
2+
Ph
N
N
Ph
P
Ru
N
P
MeOH / H2O
Ru
+ CF3COO-
H2N
P
N
P
Ph
Ph
CO
Ph
Ph
15
-H2O
+H2O
NH2
NH2
N
Ph
Ph
Ph
Ph
Ph
2+
H+
N
N
N
+
P
P
Ru
O
Ru
H
CO
CO
P
P
Ph
Ph
Ph
H
H
16
+H2O
+CF3COOH
Scheme 8.

996
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
a
b
c
Fig. 1. Solid state structure of (a) C49H38ClF6N3O4P3Ru1 (5), (b) C35H23F6N2O5P1Ru1 (6) and (c) C47H39F6N2O1P3Ru1 (10) showing the 90% probability thermal elipsoids and the
calculated positions of the hydride and hydrogen atoms.
phosphine complexes. Complexes 2, 5, 6 and 7 show singlet reso-
nances at 26–30 ppm, relative to external H3PO4, due to the PPh3
ligands. The sharp singlet observed for these complexes (2, 5 and
7) indicated that the two phosphorous nuclei are magnetically
equivalent, and therefore are trans to each other. In the chelating
phosphine complexes, the two phosphorous nuclei must be cis to
each other and therefore two singlets at 45.8 and 45.07 ppm for
complex 3 and at 53.9 and 53.4 ppm for complex 4 are observed.
The 31P–31P coupling is apparently small in these complexes. The
observation of two resonances in the 31P NMR for 3 and 4 requires
that one of the two remaining CO ligands and one of the two
remaining TFA ligands are trans to each phosphorous. Otherwise
the molecule would have a plane of symmetry and one 31P NMR
resonance would be observed. However, when the diimine ligand
is introduced, only one sharp signal for the chelating phosphine li-
gand is observed. This indicates that complexes 11–16 have a sym-
metry component that makes the two phosphorous nuclei
equivalent (Schemes 2, 3 and 5). With the exception of complex
6, complexes 5–16 all contain [PF6] as a counter ion, which ap-
peared in the 31P NMR as a septet at ꢁ155 ppm with an integrated

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
997
Table 2
Summary of crystal data and structure refinement for compound 5, 6 and 10.
Compound
5
6
10
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C49H38ClF6N3O4P3Ru
1076.25
173(2)
C35H23F6N2O5PRu
797.59
173(2)
1.54178
Monoclinic
P2(1)/n
C47H39F6N2OP3Ru
955.78
173(2)
0.71073
0.71073
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
12.0192(8)
11.0644(2)
11.848(3)
b (Å)
13.8790(9)
20.2377(4)
13.558(3)
c (Å)
14.7094(9)
15.1820(3)
14.869(4)
a
b (°)
(°)
92.1380(10)
99.2250(10)
103.3140(10)
2349.9(3)
90
93.896
90
89.908(4)
81.975(4)
79.685(4)
2326.2(9)
c
(°)
Volume (Å3)
3391.67(11)
Z
2
4
2
Dcalc (Mg/m3)
1.521
0.565
1090
1.562
4.882
1600
1.365
0.500
972
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm3)
0.285 ꢀ 0.235 ꢀ 0.133
0.35 ꢀ 0.15 ꢀ 0.15
0.19 ꢀ 0.12 ꢀ 0.12
1.76–23.82
ꢁ13 ꢃ h ꢃ 13, ꢁ15 ꢃ k ꢃ 15,
ꢁ16 ꢃ l ꢃ 16
20092
h Range for data collection (°)
Index ranges
1.41–28.37
3.64–66.38
ꢁ16 ꢃ h ꢃ 16, ꢁ18 ꢃ k ꢃ 18,
ꢁ19 ꢃ l ꢃ 19
34911
ꢁ12 ꢃ h ꢃ ꢃ 13, ꢁ23 ꢃ k ꢃ 23,
ꢁ17 ꢃ l ꢃ 17
19108
Reflections collected
Independent reflections [Rint
Completeness to h = 66.38°
Data/restraints/parameters
Goodness-of-fit on F2
]
11720 [0.0373]
99.5%
11720/2/614
1.154
5716 [0.0237]
95.9%
5716/0/279
13496 [0.0668]
100.0%
13496/3/358
1.082
1.069
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0619, wR2 = 0.1487
R1 = 0.0701, wR2 = 0.1532
1.112 and ꢁ2.227
R1 = 0.0432, wR2 = 0.1350
R1 = 0.0453, wR2 = 0.1368
2.196 and ꢁ0.512
R1 = 0.0877, wR2 = 0.1852
R1 = 0.1300, wR2 = 0.2079
1.223 and ꢁ1.916
Largest difference peak and hole
(e Åꢁ3
)
Table 3
Selected bond distances (Å) and angles (°) for C49H38ClF6N2OP3Ru1 (5).
4.4. Electrochemistry
The redox properties of the series of Ru carbonyl complexes (7,
9, 10, 13, 14 and 15) were determined by cyclic voltammetry. The
cyclic voltammetric (CV) responses are, generally speaking, not
well resolved and have as many as four ill-defined peaks.
In the bipyridyl-based complexes (7, 9 and 10), a series of four
redox steps are observed. It is likely that both metal- and ligand-
centered reductions occur, but it is not possible to discriminate
them on the basis of the obtained CVs. As an example, we show
in Fig. 2 the cyclic voltammetric (CV) response on a glassy carbon
electrode (GC) of a CH2Cl2/0.1 M [NBu4]PF6 solution of 7 at a
0.2 V sꢁ1 scan rate (v). Apparently, only the first peak couple (E°0
(A/A0) = ꢁ1.02 V vs. SCE) is chemically reversible, although the sec-
ond and the third (Ep,c (B) = ꢁ1.76 V, and Ep,c (C) = ꢁ2.06 V vs. Fc/
Fc+, respectively) show a hint of a return peak in the reverse scan,
in particular when the fourth peak (Ep,c = (D) ꢁ2.30 V vs. Fc/Fc+) is
not traversed. The other complexes of the series show similar
behavior and number of peaks. Changing the scan rates to 0.5
and 1.0 V sꢁ1 did not significantly change the appearance of the
voltammograms.
N(1)–Ru(1)
N(2)–Ru(1)
P(1)–Ru(1)
P(2)–Ru(1)
2.110(3)
2.127(3)
2.3732(9)
2.3782(9)
2.480(5)
93.3(6)
89.5(3)
167.7(3)
88.7(3)
90.89(8)
90.3(3)
90.28(8)
177.88(3)
4.9(4)
163.22(15)
90.14(9)
94.6(3)
97.66(12)
89.36(8)
C(1T)–O(1T)
C(1T)–Ru(1)
C(2T)–O(2T)
C(2T)–Ru(1)
1.222(8)
1.866(9)
1.193(8)
1.891(11)
2.475(3)
177.1(4)
99.0(4)
78.19(13)
90.7(3)
88.99(8)
87.5(3)
92.98(8)
97.5(4)
85.32(15)
88.20(9)
1.6(5)
175.81(12)
89.61(8)
98.86(16)
Cl(2)–Ru(1)
Cl(1)–Ru(1)
C(1T)–Ru(1)–C(2T)
C(2T)–Ru(1)–N(1)
C(2T)–Ru(1)–N(2)
C(1T)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
C(1T)–Ru(1)–P(2)
N(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
C(2T)–Ru(1)–Cl(1)
N(2)–Ru(1)–Cl(1)
P(2)–Ru(1)–Cl(1)
C(2T)–Ru(1)–Cl(2)
N(2)–Ru(1)–Cl(2)
P(2)–Ru(1)–Cl(2)
C(1T)–Ru(1)–N(1)
C(1T)–Ru(1)–N(2)
N(1)–Ru(1)–N(2)
C(2T)–Ru(1)–P(1)
N(2)–Ru(1)–P(1)
C(2T)–Ru(1)–P(2)
N(2)–Ru(1)–P(2)
C(1T)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1)
C(1T)–Ru(1)–Cl(2)
N(1)–Ru(1)–Cl(2)
P(1)–Ru(1)–Cl(2)
Cl(1)–Ru(1)–Cl(2)
Table 4
Selected bond distances (Å) and angles (°) for C35H23F6N2O5P1Ru1 (6).
Table 5
N(1)–Ru(1)
N(2)–Ru(1)
O(2)–Ru(1)
O(4)–Ru(1)
C(31)–Ru(1)–N(1)
C(31)–Ru(1)–O(2)
N(1)–Ru(1)–O(2)
C(31)–Ru(1)–N(2)
N(1)–Ru(1)–N(2)
O(2)–Ru(1)–N(2)
2.062(3)
2.133(3)
2.086(3)
2.148(3)
93.95(16)
99.28(15)
165.79(12)
173.27(15)
79.40(13)
87.25(12)
C(31)–O(1)
C(31)–Ru(1)
P(1)–Ru(1)
1.145(5)
1.864(4)
2.3020(10)
Selected bond distances (Å) and angles (°) for C47H39F6N2O1P3Ru1 (10).
N(1)–Ru(1)
N(2)–Ru(1)
P(1)–Ru(1)
Ru(1)–H(1)
O(1)–C(47)–Ru(1)
C(47)–Ru(1)–N(2)
C(47)–Ru(1)–P(1)
N(2)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
N(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
2.102(6)
2.163(6)
2.347(5)
2.040(5)
174.5(14)
105.1(5)
88.9(5)
94.7(2)
89.5(2)
174.8(2)
81.0
C(47)–O(1)
C(47)–Ru(1)
P(2)–Ru(1)
1.151(18)
1.816(15)
2.349(5)
C(31)–Ru(1)–O(4)
N(1)–Ru(1)–O(4)
O(2)–Ru(1)–O(4)
N(2)–Ru(1)–O(4)
C(31)–Ru(1)–P(1)
95.47(15)
88.54(12)
85.08(11)
83.44(11)
88.53(13)
C(47)–Ru(1)–N(1)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–P(1)
C(47)–Ru(1)–P(2)
N(2)–Ru(1)–P(2)
C(47)–Ru(1)–H(1)
N(2)–Ru(1)–H(1)
P(2)–Ru(1)–H(1)
179.2(5)
74.20(17)
91.0(2)
90.7(5)
90.4(2)
99.8
155.0
92.4
relative intensity of 1:2 when compared with the phosphine ligand
resonances.
82.5

998
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
Fig. 2. CV of a 1.0 mM solution of 7 in CH2Cl2 containing 0.10 M [NBu4][PF6], at a GC working electrode;
v
= 0.2 V sꢁ1 (d starting potential).
The phenanthroline-based series of complexes exhibit consider-
to Ru(I) couple, while the complex and more negative potentials
are the result of electron donation to the diimine ligand and/or
the phenyl rings on the phosphine ligands [40]. There is consider-
able precedent for such multiple electron transfers to diimine li-
gands in related Ru(II) complexes [40]. However, we cannot
differentiate at this time whether the CO and phosphine ligands
are also participating as electron acceptors. The different reduction
potentials and the different degrees of redox-wave-overlap are
consistent with this interpretation. The observation of a reversible
oxidation wave for complex 5 makes this complex a good candi-
date for electrochemiluminescence studies.
able overlap of the observed redox wave CVs. Only complex 5
shows three well-resolved, chemically and electrochemically
reversible, redox steps: two reductions (E°0 (E/E0) = ꢁ1.70, and E°0
(F/F0) = ꢁ1.93 V vs. Fc/Fc+, respectively), accompanied by an oxida-
tion in the positive scan (E°0 (G/G0) = +1.04 V vs. Fc/Fc+) (Fig. 3). The
closely related 7 does not show this reversible oxidation, probably
owing to the differences between the electronic properties be-
tween the phenanthroline and bipyridyl ligands.
A reasonable interpretation of the multiple redox couples ob-
served for complexes 5 and 7 is that the first reduction is the Ru(II)
Fig. 3. CV of a 1.0 mM solution of 5 in CH2Cl2 containing 0.10 M [NBu4][PF6], at a GC working electrode;
v
= 0.2 V sꢁ1 (d starting potential).

A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
999
Table 6
The other compounds in the series also show complex electro-
chemical behavior, preventing meaningful tabulation of the elec-
trochemical parameters.
UV–Vis absorption and emission data for 5–7 and 9–15.
Compound
kabs MLCT(nm)
kExcitation (nm)
kEm (nm) Ua
s (ns)
5
6
7
9
10
11
12
13
14
15
420b
410b
420b
450
425
410
425
450
450
450
450
450
450
470
595b
–
0.08
–
110 (330)b,c
–
4.5. Photophysical properties of 5–16
611b
647
607
590b
610b
590b
610
607
0.12
0.30
0.11
0.12
0.08
0.09
0.07
0.25
185 (680)b,c
720 (2630)c
847
4.5.1. Absorption spectra
445
The UV–Vis absorption spectra of the synthesized complexes 5–
15 were measured at room temperature in ethanol and/or acetoni-
trile solution (Table 6). The absorption spectra were also recorded
in water for complexes 10 and 15, as both of these complexes have
bio-conjugable functional groups. The ruthenium complexes
[(CO)LRu(diimine)(L2)][PF6] have six d electrons in the three t2
orbitals, and the diimine ligand provides low-energy p* orbitals
that upon excitation can accept an electron from the electron-rich
metal center. Consequently, these complexes display weak absorp-
tion bands around 400–500 nm due to the singlet metal-to-ligand
charge-transfer (1MLCT) [5]. The strong absorption bands below
445b
450b
440b
445
106 (325)c
180
126
190
450
250 (570)c
The photophysical studies were done making solution in acetonitrile and ethanol.
a
Referenced to 0.73 Quinine disulfate in H2SO4 (dilute) (31). Estimated error in
relative yields is nearly 15%. Rhodamine emission is in the same region as the MLCT
transition.
b
Solvent was acetonitrile.
The lifetime was recorded after exclusion of oxygen by purging Ar for 30 min in
c
ethanol solution. The MLCT absorptions are broad.
390 nm are assigned to intra-ligand charge-transfer (p–p and n–p).
0.55
a
0.45
0.35
0.25
0.15
0.05
260
310
360
410
460
510
560
-0.05
wavelength, nm
b
600
650
700
750
800
wavelength, nm
Fig. 4. (a) Absorption and (b) emission spectra of 9 in ethanol.

1000
A. Sharmin et al. / Journal of Organometallic Chemistry 694 (2009) 988–1000
4.5.2. Emission spectra
Acknowledgements
The heavy metal atom (Ru) facilitates intersystem crossing via
spin–orbit coupling, and the emission typically originates from
the lowest lying triplet state (3MLCT) [41]. The absorption and
emission spectra of complex 9 in ethanol is shown in Fig. 4. The
room temperature emission spectra of the complexes 5–16 (except
compound 6) showed red-shifted emission spectra, similar to those
of other known Ru–MLCT complexes (Table 6). Compound 6, con-
taining only one PPh3 ligand, did not have detectable emission at
room temperature. It is significant that for this series of ligands
that it is necessary to have two phosphine ligands in order to ob-
serve emission. This is most likely due to the more electron rich
and more symmetrical structures of the bis-phosphine complexes,
which could reduce distortion in the excited-state. The quantum
This research was supported by Grant CHE-0709738 from the
National Science Foundation (NSF) [E.R.] and by Grants MCB-
0517644 from NSF and RR15583 from the National Center for Re-
search Resources (NCRR), a component of the National Institutes
of Health (NIH) [J.B.A.R.].
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2008.11.048.
References
yields (U) for the luminescent complexes in the presence of oxy-
[1] L. Li, H. Szmacinski, J.R. Lakowicz, Anal. Biochem. 244 (1997) 80.
[2] L. Li, H. Szmacinski, J.R. Lakowicz, Biospectroscopy 3 (1997) 155.
[3] L. Li, H. Szmacinski, J.R. Lakowicz, Anal. Biochem. 247 (1997) 465.
[4] L. Li, Chem. Phys. Lipids 99 (1999) 991.
[5] J.R. Lakowicz, Principles of Fluorescence Spectroscopy, 3rd ed., Springer, New
York, 2006.
gen, listed in Table 6, were calculated relative to a Rhodamine B
standard using Eq. (1). In general, these newly synthesized com-
2þ
plexes showed higher quantum yields than RuðbpyÞ3 (i.e.
U
> 0.06).
Time-resolved luminescence decay measurements were per-
[6] G. Piszczek, Arch. Biochem. Biophys. 453 (2006) 54.
formed by time-correlated single-photon counting (TCSPC). The
data were analyzed by non-linear least-squares as described in
the experimental section. The excited-state lifetimes of the lumi-
nescent complexes containing phenanthroline ligands (5, 11 and
13) are in the range of 110–126 ns. However, complex 15, which
contains amino-phenanthroline ligand, has a lifetime of 250 ns.
The bipyridyl complexes, when lacking the hydride ligand, have
lifetimes of 180–200 ns. The hydride complexes 9 and 10, at room
temperature and in the presence of oxygen, had much longer life-
times of 720 and 847 ns, respectively. The effect of oxygen on the
photophysical properties of complexes 5, 7, 9, 11 and 15 was also
studied by measuring the lifetimes in both air-equilibrated and
deoxygenated solutions in ethanol. The deoxygenated samples
had longer excited-state lifetimes of 330, 680, 2630, 325 and
570 ns, for complexes 5, 7, 9, 11 and 15, respectively.
[7] J.V. Caspar, E.M. Kober, B.P. Sullivan, T.J. Meyer, J. Am. Chem. Soc. 104 (1982)
630.
[8] E.M. Kober, J.L. Marshall, W.J. Dressick, B. Sullivan, J.V. Caspar, T.J. Meyer,
Chem. Phys. Lett. 91 (1982) 91.
[9] E.M. Kober, J.L. Marshall, W.J. Dressick, B.P. Sullivan, J.V. Caspar, T.J. Meyer,
Inorg. Chem. 24 (1985) 755.
[10] C.V. Caspar, T.J. Meyer, J. Phys. Chem. 87 (1983) 952.
[11] C. Garino, S. Ghiani, R. Gobetto, C. Nervi, L. Salassa, V. Ancarani, P. Neyroz, L.
Franklin, J.B.A. Ross, E. Seibert, Inorg. Chem. 44 (2005) 3875.
[12] E. Terpetschnig, H. Szmacinski, H. Malak, J.R. Lakowicz, Biophys. J. 68 (1995)
342.
[13] E. Terpetschnig, H. Szmacinski, J.R. Lakowicz, Anal. Biochem. 227 (1995) 140.
[14] H. Szmacinski, E. Terpetschnig, J.R. Lakowicz, Biophys. Chem. 62 (1996) 109.
[15] X.Q. Guo, F.N. Castellano, L. Li, J.R. Lakowicz, Anal. Chem. 70 (1998) 632.
[16] E.M. Kober, J.V. Caspar, B.P. Sullivan, T.J. Meyer, Inorg. Chem. 27 (1988) 4587.
[17] Felix N. Castellano, Xiang-Qun Guo, L. Li, Henryk Szmacinski, Jeffrey Sipior,
Joseph R. Lakowicz, Proc. SPIE-Int. Soc. Opt. Eng. 3256 (1998) 223.
[18] B.P. Sullivan, J.V. Caspar, T.J. Meyer, Organometallics 3 (1984) 1241.
[19] T.A. Treadway, G.F. Strouse, R.R. Ruminski, T.J. Meyer, Inorg. Chem. 40 (2001)
4508.
[20] T. Tuyen, J.C.M. Nguyen, J. Am. Chem. Soc. 102 (1980) 7383.
[21] C. Garino, S. Ghiani, I. Bottero, R. Gobetto, C. Nervi, L. Salassa, E. Rosenberg, G.
Caputo, G. Viscardi, I. Miletto, M. Milanesio, Eur. Inorg. Chem. 14 (2006) 2839.
[22] A. Albertino, C. Garino, S. Ghiani, R. Gobetto, C. Nervi, L. Salassa, E. Rosenberg,
G. Viscardi, R. Buscaino, G. Croce, M. Milanesio, A. Sharmin, J. Organometal.
Chem. 692 (2007) 1377.
[23] C. Garino, S. Ghiani, R. Gobetto, C. Nervi, L. Salassa, E. Rosenberg, J.B.A. Ross Xi
Chu, K.I. Hardcastle, C. Sabatini, Inorg. Chem. 46 (2007) 8752.
[24] E.M. Kober, B.P. Sullivan, W.J. Dressick, J.V. Caspar, T.J. Meyer, J. Am. Chem. Soc.
102 (1980) 7383.
The anisotropy decay of complex 10 and 15 were studied in
glycerol at 0 °C. The limiting anisotropy, which reflects the angle
between the absorption and emission transition dipole moments,
was 0.124 and 0.07, respectively, for complexes 10 and 15. These
2þ
values are higher than that (<0.01) observed for RuðbpyÞ3 [5].
5. Conclusions
Several important conclusions can be drawn from these results.
First, our original hypothesis that Ru(II) complexes with one dii-
[25] SMART Version 5.628, Bruker AXS Inc., Analytical X-ray Systems, 5465 East
Cheryl Parkway, Madison WI 53711-5373, 2003.
[26] SAINT Version 6.36A, Bruker AXS Inc., Analytical X-ray Systems, 5465 East
Cheryl Parkway, Madison WI 53711-5373, 2002.
mine ligand and ancillary
p-acceptor ligands will have longer ex-
cited-state lifetimes and higher quantum yields than previously
reported for Os(II) complexes has been verified [24]. Furthermore,
this series of complexes exhibit a wide range of excited-state life-
times (110–850 ns), indicating that they will be useful for studying
a wide range of dynamical biomacromolecular processes. The ob-
served Stokes shifts and the emission wavelengths are similar to
those obtained for Ru(II) complexes with two or three diimine li-
gands. The associated higher quantum yields relative to those pre-
viously reported for Ru(II) diimine complexes, also increases their
usefulness. To help develop an understanding of the fundamental
reasons for the observed variations in the photophysical properties
we are now pursuing computational studies. Finally, the synthesis
work reported here demonstrates the usefulness of the starting
material 1 for making diverse ligand substitutions at the Ru(II) cen-
ter. Although the low solubility of these complexes is an obstacle
for using them in aqueous medium, their lipophilicity makes them
promising for applications in lipid/membrane systems.
[27] SADABS Version 2.10, George Sheldrick, University of Göttingen, 2003.
[28] SHELXTL V6.12, Bruker AXS Inc., Analytical X-ray Systems, 5465 East Cheryl
Parkway, Madison WI 53711-5373, 2002.
[29] A.A.J.C. Wilson (Ed.), International Tables for X-ray Crystallography, vol. C.
Kynoch, Academic Publishers, Dordrecht, Tables 6.1.1.4 (pp. 500–502) and
4.2.6.8 (pp. 219–222), 1992.
[30] D. Collini, C. Femoni, M.C. Iapalucci, G. Longoni, P. Zanello, Special Publ. – R
Soc. Chem. (Perspect. Organomet. Chem.) 287 (2003) 183.
[31] C.A. Parker, Photoluminescence of Solutions with Applications to
Photochemistry and Analytical Chemistry, Elsevier, Amsterdam, 1968. p 262.
[32] M.D. Barkley, A.A. Kowalczyk, L. Brand, J. Chem. Phys. 75 (1981) 3581.
[33] R.E. Dale, L.A. Chen, L. Brand, J. Biol. Chem. 252 (1981) 7500.
[34] M.G. Badea, L. Brand, Methods Enzymol. 61 (1979) 378.
[35] J. Paoletti, J.B. Le Pecq, Anal. Biochem. 31 (1969) 33–41.
[36] B. Carlson, Inorg. Chim. Acta 357 (2004) 3967.
[37] G. Croce, M. Milanesio, D. Viterbo, C. Garino, R. Gobetto, C. Nervi, L. Salassa, CR
Chim. 8 (2005) 1676.
[38] C. Garino, T. Ruiu, L. Salassa, A. Albertino, G. Volpi, C. Nervi, R. Gobetto, H.I.
Hardcastle, Eur. J. Inorg. Chem. 23 (2008) 3587.
[39] H. Jacobsen, Helv. Chim. Acta 82 (1999) 297.
[40] S. Zalis, M. Krejcik, V. Drchal, A.A. Vlcek, Inorg. Chem. 34 (1995) 6008.
[41] T.J. Meyer, Pure Appl. Chem. 62 (1990) 1003.