(Bipyridine)(terpyridine)(4-iodophenylcyanamide)ruthenium(II) complex: Crystallography, electronic absorption spectroscopy, cyclic voltammetry and EPR measurements

Article abstract of DOI:10.1016/S0020-1693(01)00382-6

The complex [Ru(bpy)(tpy)(Ipcyd)]⁺ (where bpy: 2,2′-bipyridine, tpy: 2,2′:6′,2″-terpyridine and Ipcyd: 4-iodophenylcyanamide anion) has been synthesized. An extensive characterization was carried out using IR, ¹H and ¹³C NMR, ES-MS, UV-Vis, electrochemistry, EPR and X-ray single crystal diffraction analysis. Cyclic voltammogram shows an irreversible anodic peak around 0.7 V/ECS, the shape of the wave is typical of an electrochemical-chemical (EC) mechanism with an half-life time in the order of seconds for the generated species. Oxidation of the title compound has been investigated in order to explore its ability as a magnetic probe for further electronic studies on dinuclear complexes. The EPR spectrum at 100 K of the monooxidized species displays g⊥ = 2.00 and g∥ = 1.96 attributed to the presence of a radical coming from the phenylcyanamide oxidation, in relative good agreement with EH and ZINDO calculations.

Full text of DOI:10.1016/S0020-1693(01)00382-6

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 316 (2001) 79–88
(Bipyridine)(terpyridine)(4-iodophenylcyanamide)ruthenium(II)
complex: crystallography, electronic absorption spectroscopy,
cyclic voltammetry and EPR measurements
Elodie Sondaz, Andre´ Gourdon, Jean-Pierre Launay, Jacques Bonvoisin *
Molecular Electronics Group, CEMES/CNRS, 29 Rue Jeanne Mar6ig, BP4347, 31055 Toulouse Cedex 4, France
Received 4 October 2000; accepted 8 February 2001
Abstract
The complex [Ru(bpy)(tpy)(Ipcyd)]+ (where bpy: 2,2%-bipyridine, tpy: 2,2%:6%,2%%-terpyridine and Ipcyd: 4-iodophenylcyanamide
anion) has been synthesized. An extensive characterization was carried out using IR, 1H and 13C NMR, ES-MS, UV–Vis,
electrochemistry, EPR and X-ray single crystal diffraction analysis. Cyclic voltammogram shows an irreversible anodic peak
around 0.7 V/ECS, the shape of the wave is typical of an electrochemical-chemical (EC) mechanism with an half-life time in the
order of seconds for the generated species. Oxidation of the title compound has been investigated in order to explore its ability
as a magnetic probe for further electronic studies on dinuclear complexes. The EPR spectrum at 100 K of the monooxidized
species displays gÞ=2.00 and gꢀꢀ=1.96 attributed to the presence of a radical coming from the phenylcyanamide oxidation, in
relative good agreement with EH and ZINDO calculations. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ruthenium complexes; Cyanamide complexes; Electrochemistry; Crystal structures
1. Introduction
in order to still have access to the degree of the inner
electronic communicability. One alternative is to choose
paramagnetic compounds and to measure the magnetic
coupling between the paramagnetic redox sites through
the bridging ligand. There is no doubt that magnetic
coupling is another way of measuring the electron
communication through a molecule [2]. It remains that
the correlation between the magnetic coupling parame-
ter J and the electronic coupling parameter Vab has still
to be settled. This magnetic coupling J can be experi-
mentally given by magnetic susceptibility or EPR tech-
niques, this last technique revealing very efficient in
some recent examples [3].
The first step in this strategy is to find good candi-
dates giving a strong interaction between distant para-
magnetic sites. There are very few systems which satisfy
this criterion. R.J. Crutchley found that the NCN
group as a coordination site can be the basis for ligands
that are extremely efficient to mediate magnetic interac-
tion [4]. Since these ligands are at the same time very
efficient for electron transfer within a molecule [5], the
NCN group was selected for this study, in association
In the molecular electronics field, it is important to
know how the electron, the ultimate source of informa-
tion at this scale, passes through a molecule, since the
goal is to make molecular wires, diodes, switches, etc.
The capacity for the electron on going from one side to
the other side of the molecule is quantitatively given by
the so-called electronic coupling parameter Vab. One
can have an experimental access to this parameter by
UV–Vis near IR spectroscopy through the intervalence
transition in a binuclear complex [1]. This is a rather
well established method but it has experimental limits.
The most constraining one is associated with the dis-
tance between the redox sites in a molecule. Indeed,
,
when this distance is about ca 25 A, the intervalence
transition becomes almost undetectable, i.e. under the
sensitivity limit of the apparatus. Therefore, for such
long molecules, it is important to find alternative ways
* Corresponding author. Tel: +33-5-6225 7852; fax: +33-5-6225
7999.
E-mail address: jbonvoisin@cemes.fr (J. Bonvoisin).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00382-6

80
E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
with a functionalized part for further extension. Indeed,
the iodide group was chosen as an efficient reaction
center for further Sonogashira coupling [6]. In this
paper, the title diamagnetic Ru(II) complex was firstly
synthesized and characterized by crystallography, to
develop the synthetic and interpretative tools necessary
to obtain long range dinuclear compounds. Secondly its
oxidation was studied, with the aim of generating para-
magnetic Ru(III) complex.
(100 cm3). After complete addition of the benzoyl chlo-
ride, the reaction mixture was allowed to reflux 10 min.
4-Iodoaniline (18.9 g, 0.09 mol) in acetone (50 cm3) was
added dropwise to the refluxing reaction mixture and
the reflux was kept for 45 min. The solution turned
brown. The product was then poured into cold water
(800 cm3) to ensure complete precipitation of the yellow
thiourea derivative. Vigorous stirring was necessary to
solubilize the NH4Cl by-product. The product was
filtered, washed with water and dried under vacuum
(31.6 g, 96%).
The thiourea derivative (7.3 g, 19 mmol) was dis-
solved in 2M sodium hydroxide (200 cm3) by boiling
for 10 min. The solution was cooled to 65°C, and a
solution of lead(II) acetate trihydrate (7.2 g, 19.1 mmol)
in water (60 cm3) was slowly added. The reaction was
allowed to continue for 7 min, the black lead sulfide
precipitate was filtered and the filtrate was cooled in an
ice bath. Glacial acetic acid (25 ml) was added to
neutralize the filtrate and precipitate the neutral ligand.
The white product was filtered, washed copiously with
cold water and air-dried. [I(C6H4)NHCN] (4.0 g, 87%),
Dec. pt 95°C (Found: C, 34.6; H, 2.1; N, 11.1%
C7H5IN2 requires C, 34.5; H, 2.1; N, 11.5%); IR w/
cm−1 2239s (CꢀN); EI mass spectrum m/z 244.0 re-
quires 244.0; lH(CDCl3) 7.64 (d, 2Hm, J=8.99 Hz),
6.75 (d, 2Ho, J=8.99 Hz), 6.15 (s, 1H, N–H),
lC(CDCl3) 139.0 Cm, 137.4 C1, 117.8 Co, 110.9 CꢀN,
86.8 Cp.
2. Experimental
2.1. Materials
All chemicals and solvents were reagent grade or
better. [Ru(tpy)Cl3] [7] and [Ru(tpy)(bpy)Cl]PF6 [8]
were prepared according to literature procedures. 4-
Iodoaniline was purchased from Aldrich. RuCl3 was
purchased from Strem Chemicals. Weakly acidic Brock-
mann I type alumina (Aldrich) was used.
2.2. Measurements
Elemental analyses were performed by the Service
d’Analyse du LCC (Toulouse). Electrospray (positive
mode) and Electronic Impact mass spectra were ob-
tained with Perkin–Elmer Sciex (Nermag R10-R10). IR
were recorded in KBr pellets and nujol mulls on a
Perkin Elmer FT-IR 1725. UV–Vis electronic spectra
2.3.2. [Ru(tpy)(bpy)(Ipcyd)]PF6
were obtained with a Shimadzu UV-3100. H and 13C
1
The synthesis was adapted from a literature proce-
dure [10]. To deaerated acetone (100 cm3) were added
506 mg of [Ru(tpy)(bpy)Cl]PF6 (0.75 mmol) and a
slight molar excess of AgPF6 (1.0 mmol), the resulting
solution was then refluxed with stirring for 4 h under
argon. A tenfold excess of ligand IpcydH (7.5 mmol)
was added, and the solution was stirred under argon
with reflux for 4 h, then at room temperature overnight.
The precipitated AgCl was removed by filtration on
Celite, solid NH4PF6 was added to the filtrate, and the
solution concentrated to 50 cm3. Diethyl ether (300
cm3) was added. After stirring, the orange precipitate
was filtered, washed with diethyl ether and dried under
vacuum.
The complex was purified by column chromatogra-
phy (acidic alumina, CH3CN+C6H5CH3; 40/60), the
yellow ligand being separated from the dark red com-
plex. Recrystallisation was achieved by diffusing tolu-
ene into an acetonitrile solution of the complex. Black
needles (518.9 mg, 78%) were obtained. (Found: C,
44.0; H, 2.1; N, 11.5% C32H23IN7F6PRu requires C,
43.7; H, 2.6; N, 11.1%); IR w/cm−1 2175s and 2150w
(NCN); ES mass spectrum (CH3CN) m/z: 734.0 [M−
PF6]+ requires 734.0; lH(CD3CN): 9.74 (1H, d, 5.78
Hz), 8.61 (d, 1H, 8.17 Hz), 8.51 (d, 2H, 7.97 Hz), 8.40
NMR spectra were recorded on Bruker WF-250 and
Bruker AMX-400 in CDCl3 and CD3CN solution. The
solvent signal was used as internal reference at lH: 7.26
ppm and lC: 77.0 ppm (CDCl3) and lH: 1.96 ppm and
lC: 1.2 and 118.1 (CD3CN). Cyclic voltammograms
were obtained with an Autolab system (PGSTAT 100)
in acetonitrile and dichloromethane (0.1 M tetrabutyl-
ammonium hexafluorophosphate, TBAH) at 25°C. A
three-electrode cell was used comprising a 1 mm Pt-disk
working electrode, a Pt wire auxiliary electrode, and an
aqueous saturated calomel (SCE) reference electrode.
EPR experiments were performed with a Bruker X-
band ESP 300 E fitted out with a Bruker B-NM20
gaussmeter. The external magnetic field was calibrated
with a microwave bridge EIP548 wavemeter.
2.3. Syntheses
2.3.1. 4-Iodophenylcyanamide (IpcydH)
IpcydH was prepared via the general procedure given
for phenylcyanamide derivatives [9]. Benzoyl chloride
(12.6 g, 0.09 mol) in acetone (100 cm3) was added
dropwise to a magnetically stirred, refluxing solution of
ammonium thiocyanate (6.8 g, 0.09 mol) in acetone

E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
81
−
(d, 2H, 7.97 Hz), 8.31 (m, 2H), 8.15 (t, 1H, 7.77 Hz),
7.95 (m, 3H), 7.71 (m, 3H), 7.33 (m, 3H), 6.99 (t, 1H,
5.58 Hz), phenyl ring: 7.10 (2H, d, 8.77 Hz) and 5.88
(2H, d, 8.77 Hz); lC(CD3CN) bpy ring: 158.5 Cf, 156.2
Ce, 152.6 Ca, 152.2 Cj, 137.2 Cc, 136.4 Ch, 127.7 Cb,
126.5 Ci, 124.1 Cd, 123.6 Cg, tpy ring: 158.7 C2, 158.1
C2%, 152.8 C6, 134.9 C4%, 138.0 C4, 127.9 C5, 124.2 C3,
123.2 C3%, ligand, 137.6 Cm, 122.0 Co, 152.2 C1, 77.7
Cp.
PF6 counterion as shown by high residual electron
density around the phosphorus atom.
2.5. EPR measurements
[Ru(bpy)(tpy)Cl]PF6 was oxidized totally by electrol-
ysis in dichloromethane and frozen in liquid nitrogen
before being analyzed at 100 K. A signal of Ru(III) was
observed. Because of its instability, [Ru(bpy)(tpy)-
(Ipcyd)]2+ was partially generated electrochemically in
situ in the EPR tube at 273 K, then the temperature
was allowed to decrease until 100K during the electrol-
ysis. A signal with a g near the 2.0023 free electron
value was observed, then the product was warmed until
273 K and frozen again, then no more signal was
observed. The simulations were obtained with SIMFO-
NIA software [15].
2.4. Crystal structure determination of
[Ru(tpy)(bpy)(Ipcyd)]PF6
Dark prismatic crystals of the complex were grown
by slow diffusion of toluene in an acetonitrile solution
of the complex. A summary of the crystal data is given
in Table 1. The diffraction intensities were collected [11]
on a Nonius KappaCCD diffractometer at 293 K with
,
molybdenum radiation (0.71073 A). The structure was
2.6. Extended Hu¨ckel calculation
solved by direct methods [12] and successive difference
−
Fourier maps. The PF6
anion was found severely
Extended Hu¨ckel calculation was made on [Ru(bpy)-
(tpy)(Ipcyd)]+ using the crystallographic coordinates.
Standard parameters were used, except for ruthenium
atom where we took −12.5 eV for the Ru(4d) orbital
as suggested by Launay et al. [16]. Molecular orbitals
have been visualized with the cacao software [17].
ZINDO/1 calculation was performed by using hyper-
chem software [18] with default parameters. The shape
of the resulting HOMO and LUMO are in perfect
agreement with EH results.
disordered around the phosphorus atom. It was mod-
elled over two sites with occupation factors of 0.5. The
fluorine atoms were then refined isotropically with soft
restrains [13]. H atoms were recalculated after each
refinement cycle. Refinement was done by full matrix
least squares. Calculations were performed with the
Crystals Package [14]. The full experimental details,
atomic parameters and the complete listing of bond
lengths and angles are available as supplementary data.
The refinement of this structure is slightly high with
Rf=0.065 and this may result from disorder of the
3. Results and discussion
Table 1
3.1. Synthesis and characterization
Crystallographic data and refinement parameters
Formula
C32H23F6IN7PRu
monoclinic
878.52
The procedure is an adaptation of the synthesis of
chalcogenoether complexes [10]. The Ru(II) complex is
synthesized by a reaction involving Ag(I) abstraction of
chloride from [Ru(bpy)(tpy)Cl]+ in acetone. Introduc-
tion of the IpcydH ligand in tenfold excess leads to the
desired complex. Unlike Crutchley’s phenylcyanamides
[19], iodophenylcyanamide is stable at 60°C so the
Ru(II) complex can be formed at acetone refluxing
temperature; high purity and good yields are obtained.
Deprotonation of the ligand is proved by the observa-
tion of the wNCN band around 2150 cm−1 in the IR
spectrum of the complex, compared to the neutral
ligand vibration wCN at 2239 cm−1 [9]. According to
literature, this wNCN band is shifted to lower energies
(ca. 2080–2100 cm−1) for Ru(III) pentaammine com-
pounds [4].
Crystal system
Fw (g mol−1
)
Space group
P21/c
,
a (A)
11.4153(1)
13.2964(1)
23.52561(3)
100.9175(6)
3506.22(6)
4
1.44
1.66
60.24
250081
0.018
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
v(Mo Ka) (cm−1
)
zcalc (g cm−3
2qmax (°)
)
Total no. of reflections
Rint
No. of unique reflections with I\4|(I)
Absorption correction
Tmin/max
7107
spherical
0.53/0.57
0.065
0.075
1.06
a
Rf
b
Rw
1H NMR of the complex (Fig. 1) allows an easy
distinction of the chloride precursor by the doublets of
the phenyl protons from the ligand Ipcyd at 7.10 and
5.88 ppm. Those signals are coupled with a constant
GOF
a Rf=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b Rw=(S wꢀFoꢀ−ꢀFcꢀ)2/S wꢀFoꢀ )
.
2 1/2

/
316
(
7
Fig. 1. 1H NMR of [Ru(bpy)(tpy)Cl]PF6 (A) and [Ru(bpy)(tpy)(Ipcyd)]PF6 (B) in CD3CN.

E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
83
Table 2
bipyridine and terpyridine protons come from correla-
tion spectroscopy (COSY). The 13C NMR signal as-
a
,
Selected bond lengths (A) and bond angles (°)
1
signments were based on the heteronuclear 2D H–13C
Bond lengths
correlation spectroscopy (HMQC and HMBC).
Electrospray mass spectrum is consistent with the
formula. It shows the molecular peak positively charged
by the loss of the hexafluorophosphate ion at m/z: 734
and the fragment [Ru(bpy)(tpy)]+ at m/z: 490.
Ru(1)–N(16)
Ru(1)–N(26)
Ru(1)–N(36)
Ru(1)–N(46)
Ru(1)–N(56)
2.068(3)
1.970(3)
2.073(3)
2.053(3)
2.076(3)
Ru(1)–N(69)
N(67)–C(66)
N(67)–C(68)
N(69)–C(68)
2.078(3)
1.395(6)
1.294(6)
1.133(5)
Bond angles
N(16)–Ru(1)–N(26) 79.87(14)
N(46)–Ru(1)–N(56) 78.55(14)
N(16)–Ru(1)–N(36) 159.50(13) N(16)–Ru(1)–N(69) 88.22(14)
3.2. X-ray structure
N(26)–Ru(1)–N(36) 79.65(13)
N(16)–Ru(1)–N(46) 93.09(14)
N(26)–Ru(1)–N(46) 95.68(13)
N(36)–Ru(1)–N(46) 89.81(13)
N(26)–Ru(1)–N(69) 90.98(13)
N(36)–Ru(1)–N(69) 91.25(13)
N(46)–Ru(1)–N(69) 73.33(14)
N(56)–Ru(1)–N(69) 94.79(14)
Crystal structure data for [Ru(bpy)(tpy)(Ipcyd)]PF6
and selected bond lengths and angles are respectively
given in Tables 1 and 2. Fig. 2 shows the ortep [21]
drawing of the [Ru(bpy)(tpy)(Ipcyd)]+ cation and the
numbering scheme used in Table 2. This structure is
similar to the one obtained by Rasmussen et al. for
[Ru(tpy)(bpy)(CH3CN)]2+ [22]. Small angle C(66)–
N(67)–C(68) (120.4(4)°), long distance N(67)–C(68)
N(16)–Ru(1)–N(56) 102.98(13) Ru(1)–N(69)–C(68) 174.5(3)
N(26)–Ru(1)–N(56) 173.63(13) N(67)–C(68)–N(69) 173.0(5)
N(36)–Ru(1)–N(56) 97.49(13)
C(66)–N(67)–C(68) 120.4(4)
a Angle between the C(61)–C(66) mean plane and the tpy mean
plane: 103.3(1)°. Angle between the C(61)–C(66) mean plane and the
bpy mean plane: 27.9(1)°. Torsion angle C(68)–N(67)–C(66)–C(65):
7.0(3)°.
,
,
(1.294(6) A), short distance C(68)–N(69) (1.133(5) A)
and the large angle C(68)–N(69)–Ru(1) (174.5(3)°) are
consistent with the resonance structure A coordinated
to the metal ion via the nitrile lone pair, rather than
with the B form [23].
By referring to the Cambridge Structural Database
[24], one can observe that the bond distance between
N(69) and C(68) is very typical of a CN triple bond in
,
CN–Ru(II) (median value 1.13 A). The angle between
the bipyridine mean plane and the iodophenyl-
cyanamide mean plane is about 30°.
There is an apparent contradiction between X-ray
and Infrared data: Infrared data show two distinct
absorption bands in KBr disks or nujol mull: a strong
one at 2175 cm−1 and a weaker one at 2150 cm−1. The
presence of two bands is usually interpreted as the
presence of two conformers where cyanamide ligands
are inequivalent [4,23]. Note however that this was
proposed for Ru(III) complexes. Yet for this study, the
X-ray structure strictly demonstrates the presence of
only one conformation. In fact, it probably means that
the X-ray analysis was made on only one kind of
crystals.
Fig. 2. ortep drawing of the cation [Ru(bpy)(tpy)(Ipcyd)]+ along with
the atom numbering scheme (probability level of 30%).
JHH=8.77 Hz. The Ha bipyridine proton which points
toward the ligand is characteristic. It undergoes the
influence of the substituent because of its privileged
position; the crystal structure shows a short intramolec-
,
ular contact of 2.636(3) A between N69 of the
cyanamide ligand and H55 (the one attached to C55) of
the bipyridine moiety (see crystal structure section). The
upfield shift from 10.2 to 9.74 ppm upon substitution of
the chloride atom by the Ipcyd molecule is due to the
larger diamagnetic anisotropy of iodophenylcyanamide
vs. chloride [20]. The assignments of the remaining
3.3. UV–Vis absorption
The [Ru(II)(bpy)(tpy)(Ipcyd)]+ spectrum in dichloro-
methane (Fig. 3) shows, in the visible region; two broad
bands (439 and 495 nm). The attribution of the charge
transfer transition of [Ru(II)(bpy)(tpy)L]n+ salts has

84
E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
Fig. 3. UV–Vis spectrum of [Ru(bpy)(tpy)(Ipcyd)]PF6. Insert: enlargement of the specified area.
Table 3
UV–Vis absorption bands and redox potential
Absorption bands, u (nm) (m×10−3, dm3 mol−1 cm−1
)
Electrochemical data,
E V/SCE (DE, mV)
p*’p
Charge-transfer transition
ERuIII/II
IpcydH in CH3CN
203 (35), 244 (32), 285 (6.3)
[Ru(II)(bpy)(tpy)(Ipcyd)]+ in CH2Cl2 242 (26), 283 (44), 316 (30), 358sh (7.1)
MLCT, 498 (6.0), 453 (5.4) 0.698 a
0.871 (73) −1.42 (73)
−1.38 (70)
[Ru(II)(bpy)(tpy)Cl]+ in CH2Cl2
[Ru(III)(bpy)(tpy)Cl]2+ in CH3CN
240 (41), 282 (38), 294 (43), 318 (38), 360sh (8.6) MLCT, 505 (12.0)
319 (8.2) LMCT, 402 (2.9)
a Anodic potential of the half-wave attributed to an EC mechanism.
Fig. 4. Cyclic voltammograms of [Ru(bpy)(tpy)(Ipcyd)]PF6 in CH3CN for different scan rates.

E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
85
Fig. 5. Experimental (top) EPR spectrum of [Ru(bpy)(tpy)Cl]2+ in frozen CH2Cl2 (100 K) and simulated (bottom).
been largely documented [22,25]. Thus, in the present
case, the band at 495 nm can be assigned to dp (Ru(II))“
p* (tpy) MLCT transition, indeed tpy moiety presents a
more extended p system than bpy one, then gives more
stable p* orbitals and thus lower excited energy state. The
second band at 439 nm can be assigned to dp (Ru(II))“
p* (bpy) transition. The absence of solvatochromism on
these bands corroborates these attributions.
Upon oxidation, the large MLCT band of the chloro
complex disappears and a smaller band at 402 nm as-
signed to a ligand p“dp (Ru(III)) (LMCT) charge trans-
fer transition grows.

86
E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
3.4. Electrochemistry
is observed. Successive ligand-based reductions are ob-
served in the negative region. These reductions corre-
spond to the formation of radical anions as electrons
are added to the p* orbitals of the polypyridyl ligands.
The first wave, well-defined, has been assigned to terpy
reduction [26] in agreement with the calculation de-
scribed below. The other waves, less well-resolved espe-
Cyclic voltammetry (CV) data for the complexes are
given in Table 3. The E1/2 potentials were determined
from the average of the anodic and cathodic peak
potentials except for [Ru(bpy)(tpy)(Ipcyd)]+/2+ which
shows an irreversible wave where only the anodic peak
Fig. 6. Experimental (top) EPR spectrum of [Ru(bpy)(tpy)(Ipcyd)]2+ in frozen CH2Cl2 (100 K) and simulated (bottom).

E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
87
Fig. 7. Results from Extended Hu¨ckel calculation for [Ru(bpy)(tpy)(Ipcyd)]+: (A) HOMO; (B) LUMO.
pyridine fragment. This corroborates the terpyridine
reduction assignment in CV experiment.
cially in dichloromethane, are assumed to correspond
to bpy and tpy reductions, respectively.
The anodic peak around 0.7 V/ECS could at first
sight be assigned to the oxidation of the ruthenium
atom of the iodide complex. This wave is shifted to less
positive potentials (ca. 150 mV) compared to the case
of [Ru(bpy)(tpy)Cl]+/2+. This would agree with the
more donor character of the iodophenylcyanamide lig-
and compared to the chloro.
Fig. 4 shows the behavior of the wave at different
scan rates. The reversibility of the wave at 0.7 V/ECS
increases with increasing scan rate, this takes evidence
for an electrochemical–chemical reaction. From those
CV, an approximate half-life time in the order of
seconds has been measured for the primary electro-
chemically generated species [27].
4. Conclusion
In conclusion, full characterization including X-ray
structure determination has been made on the title
complex. CV, EPR, Hu¨ckel and ZINDO calculations
converge to the fact that oxidation of the title com-
pound leads to an unprecedented Ru complex with the
cyanamido organic radical. This last species seems to be
unstable according to the CV and EPR results, and the
desired paramagnetic Ru(III) complex is not obtained.
Nevertheless, the chemical ability of the title compound
to give Sonogashira coupling reactions has been
demonstrated and yields a new class of compounds
which will be described elsewhere. For the future, at-
tempts will be made to add donor substituents on
terminal polypyridine entities in order to lower the
oxidation potential of the Ru(II/III) couple in order to
avoid the formation of unwanted unstable organic rad-
ical. Once obtained the desired functionalized mononu-
clear species, the next step will be to make a long
binuclear molecule and then study magnetic and elec-
tronic coupling.
3.5. EPR measurements
The EPR spectrum of electrogenerated [Ru(bpy)-
(tpy)Cl]2+ is very typical of a low-spin d5 Ru(III) ion
[28] with gx=2.79; gy=2.23 and gz=1.61 (Fig. 5). In
contrast, the EPR spectrum of [Ru(bpy)(tpy)(Ipcyd)]2+
shows an axial signal at gÞ=2.00 and gꢀꢀ=1.96 (Fig.
6), which can be taken as an evidence for the presence
of an organic radical. It would be generated as the
primary species and would subsequently transform to
the secondary species, which is EPR silent (see Section
2.5).
5. Supplementary material
This assumption about an organic radical formation
is substantiated further by extended Hu¨ckel and
ZINDO/1 calculations showing the HOMO (Fig. 7(a))
largely dominated by the phenylcyanamide contribu-
tion. This tends to prove that the ligand should be
oxidized first rather than the metal. It also can be noted
that the LUMO (Fig. 7(b)) is dominated by the ter-
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 157364. Copies of this infor-
mation may be obtained from The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: +44-
1233-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).

88
E. Sondaz et al. / Inorganica Chimica Acta 316 (2001) 79–88
[14] D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge,
Acknowledgements
Crystals, Chemical Crystallography Laboratory, Oxford, UK,
Issue 10, 1997.
[15] WINEPR SIMFONIA ver. 1.25, Bruker Analytische Messtechnik
Gmbh, 1996.
[16] C. Patoux, J.-P. Launay, M. Beley, S. Chodorowski-Kimmes,
J.-P. Collin, S. James, J.-P. Sauvage, J. Am. Chem. Soc. 120
(1998) 3717.
[17] C. Mealli, D.M. Proserpio, J. Chem. Educ. 67 (1990) 399.
[18] Hyperchem™ release 6.01 for Windows, Chemcad, 2000 Hyper-
cube, Inc.
We thank Dominique de Montauzon (Laboratoire de
Chimie de Coordination, Toulouse) for electrochemical
advice and facilities, Alain Mari (Laboratoire de
Chimie de Coordination, Toulouse) for EPR measure-
ments and Christophe Coudret (CEMES) for helpful
suggestions regarding synthetic strategies.
[19] M.L. Naklicki, R.J. Crutchley, Inorg. Chem. 28 (1989) 4226.
[20] A. Gerli, J. Reedijk, M.T. Lakin, A.L. Spek, Inorg. Chem. 34
(1995) 1836.
[21] L.J. Farrugia, J. Appl. Cryst. I (1997) 565.
[22] S.C. Rasmussen, S.E. Ronco, D.A. Mlsna, M.A. Bil-ladeau,
W.T. Pennington, J.W. Kolis, J.D. Petersen, Inorg. Chem. 34
(1995) 821.
[23] R.J. Crutchley, R. Hynes, E.J. Gabe, Inorg. Chem. 29 (1990)
4921.
[24] F.H. Allen, O. Kennard, Chem. Des. Automation News 8 (1993)
31.
[25] (a) K.J. Takeuchi, M.S. Thompson, D.W. Pipes, T.J. Meyer,
Inorg. Chem. 23 (1984) 1845. (b) N.C. Fletcher, F.R. Keene, J.
Chem. Soc., Dalton Trans. (1998) 2293; P.A. Ander-son, G.F.
Strouse, J.A. Treadway, F.R. Keene, T.J. Meyer, Inorg. Chem.
33 (1994) 3863. (c) S. Ruile, O. Khole, P. Pe´chy, M. Gratzel,
Inorg. Chim. Acta 261 (1997) 129. (d) C.R. Hecker, P.E. Fan-
wick, D.R. Mc Millin, Inorg. Chem. 30 (1991) 659. (e) A. Ben
Altabel, S.B. Ribotta de Gallo, M.E. Folquer, N.E. Katz, Inorg.
Chim. Acta 188 (1991) 67. (f) P.A. Anderson, G.B. Deacon,
K.H. Haarmann, F.R. Keene, T.J. Meyer, D.A. Reitsma, B.W.
Skelton, G.F. Strouse, N.C. Thomas, T.A. Treadway, A.H.
White, Inorg. Chem. 34 (1995) 6145.
[26] R.M. Berger, D.R. McMillin, Inorg. Chem. 27 (1988) 4245.
[27] R.S. Nicholson, I. Shain, Anal. Chem. 36 (1964) 706.
[28] (a) J.S. Griffith, The Theory of Transition-Metal Ions, Ch. 12,
Cambridge University Press, London, 1961, pp. 346–374. (b)
J.B. Raynor, B.G. Jeliazkowa, J. Chem. Soc., Dalton Trans.
(1982) 1185.
References
[1] (a) N.S. Hush, Prog. Inorg. Chem. 8 (1967) 391. (b) S. Woitel-
lier, J.-P. Launay, C.W. Spangler, Inorg. Chem. 28 (1989) 758.
[2] (a) T.R. Felthouse, D.N. Hendrickson, Inorg. Chem. 17 (1978)
2636. (b) R.J. Crutchley, Adv. Inorg. Chem. 41 (1994) 273.
[3] P.K.A. Shonfield, A. Be-hrendt, J.C. Jeffery, J.P. Maher, J.A.
McCleverty, E. Psillakis, M.D. Ward, C. Western, J. Chem.
Soc., Dalton Trans. (1999) 4341.
[4] M.A.S. Aquino, F.L. Lee, E.J. Gabe, C. Bensimon, J.E.
Greedan, R.J. Crutchley, J. Am. Chem. Soc. 114 (1992) 5130.
[5] A.R. Revzani, C.E.B. Evans, R.J. Crutchley, Inorg. Chem. 34
(1995) 4600.
[6] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 50
(1975) 4467.
[7] B.P. Sullivan, J.M. Calvert, T.J. Meyer, Inorg. Chem. 19 (1980)
1404.
[8] J.M. Calvert, H.S. Russell, B.P. Sullivan, J.S. Facci, T.J. Meyer,
R.W. Murray, Inorg. Chem. 22 (1983) 2151.
[9] M.L. Naklicki, R.J. Crutchley, Inorg. Chem. 28 (1989) 1955.
[10] M.J. Root, E. Deutsch, Inorg. Chem. 24 (1985) 1464.
[11] Z. Otwinowski, W. Minor, in: C.W. Carter, R.M. Sweet (Eds.),
Methods Enzymol, vol. 276, Academic Press, New York, 1997,
p. 307.
[12] A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi,
M.C. Burla, G. Polidori, M. Camalli, J. Appl. Cryst. 27 (1994)
435.
[13] J.R. Carruthers, D.J. Watkin, Acta Crystallogr., Sect. A 35
(1979) 698.
.