Synthesis and electrochemical studies of η5-monocyclopentadienylruthenium(II) complexes with substituted thiophene nitrile ligands. Crystal structure of [Ru(η5-C5H5)(dppe)(NC{SC4H2}2</

Article abstract of DOI:10.1016/j.jorganchem.2009.04.025

A systematic series of η⁵-monocyclopentadienylruthenium(II) complexes with substituted thiophene nitrile ligands of general formula [Ru(η⁵-C₅H₅)(P_P)(NC{SC₄H₂}_nNO₂)][P

Full text of DOI:10.1016/j.jorganchem.2009.04.025

Journal of Organometallic Chemistry 694 (2009) 2888–2897
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and electrochemical studies of
g
5-monocyclopentadienylruthenium(II)
complexes with substituted thiophene nitrile ligands. Crystal structure
of [Ru(
g
5-C5H5)(dppe)(NC{SC4H2}2NO2)][PF6]
b
M. Helena Garcia a, , Paulo J. Mendes , M. Paula Robalo c,d, M. Teresa Duarte c, Nelson Lopes e
*
a Centro de Ciências Moleculares e Materiais, Faculdade de Ciências da Universidade de Lisboa, Ed.C8, Campo Grande, 1749-016 Lisboa, Portugal
b Centro de Química de Évora, Universidade de Évora, Rua Romão Ramalho 59, 7002-554 Évora, Portugal
c Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
d Departamento de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa, Portugal
e Grupo de Lasers e Plasmas, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
a r t i c l e i n f o
a b s t r a c t
5-monocyclopentadienylruthenium(II) complexes with substituted thiophene
5-C5H5)(P_P)(NC{SC4H2}nNO2)][PF6] (P_P = dppe, (+)-diop; n = 1–
Article history:
A systematic series of
nitrile ligands of general formula [Ru(
g
Received 13 February 2009
Received in revised form 17 April 2009
Accepted 20 April 2009
g
3) has been synthesized and characterized. Spectroscopic and electrochemical data were used in order
to get an insight on the molecular nonlinear optical properties of these complexes when compared to
those found for the reported thiophene iron(II) and p-benzonitrile or 1,2-di-(2-thienyl)-ethene derived
Available online 3 May 2009
iron(II)/ruthenium(II) related complexes. The compound [Ru(g
5-C5H5)(dppe)(NC{SC4H2}2NO2)][PF6]
Keywords:
Ruthenium(II)
Monocyclopentadienyl
Thiophene ligands
Cyclic voltammetry
Second harmonic generation
was also characterized by X-ray diffraction. The solid state nonlinear optical properties of the chiral com-
pounds were also evaluated by Kurtz powder technique with a Nd:YAG laser emitting at 1064 nm.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
[12–16], which revealed to be much more efficient donor groups
for second-order NLO purposes than the traditional organic donor
The exploitation of organometallic chemistry for the synthesis
of new compounds with nonlinear optical (NLO) properties has
been mainly motivated by the optical devices technology [1]. The
significant work already published in this area during the last
two decades [2–11] is in agreement with the general understand-
ing that second-order nonlinearities are strongly related to asym-
metric push–pull systems, both in organic and organometallic
molecular materials. In the case of metallo-organic compounds,
the metal centre can be bound to a highly polarizable conjugated
backbone, acting hence as an electron releasing or withdrawing
group. Consequently, strong charge-transfer (CT) transitions can
occur, leading to high molecular first hyperpolarizabilities (b).
Moreover, the position of these CT bands, usually appearing at
the visible region, can be tuned by variation of the coligands
and/or the metal itself, to optimize the hyperpolarizability through
(near) resonant enhancement. This is the case of the general family
groups (NMe2, NH2, etc.), leading therefore to higher b values.
Recently we found significant values of quadratic hyperpolariz-
abilities in complexes combining the organometallic donor
fragment {FeCp(P_P)} (P_P = dppe, (+)-diop) with conjugated
thiophene derived ligands. Measurements by hyper-Rayleigh scat-
tering (HRS), in [FeCp(dppe)(NC{SC4H2}nNO2)][PF6] compounds
with 1, 2 or 3 thiophene units presented values of b of 455, 710
and 910 ꢀ 10ꢁ30 esu, respectively, measured at 1064 nm [16].
Nevertheless, high values of b do not lead necessarily to good
NLO efficiencies at the macroscopic level since the second-order
NLO effects are strongly influenced by the crystal packing. Thus,
crystallization in
a non-centrosymmetric space group is a
necessary criterion (not absolute) when solid state properties are
evaluated, this being guaranteed in the present compounds by
the chiral coligand, (+)-diop.
In order to get some hint about the solid state second harmonic
generation efficiencies of the general family of compounds
[FeCp(P_P)(NC{SC4H2}nNO2)][PF6] we had extended our studies to
the analogous family of ruthenium derivatives, which have the
advantage of a higher transparency than the iron ones, at the sec-
ond harmonic wavelength (532 nm) of the used Nd:YAG laser.
These studies on bulk materials become very important when solid
of
g
5-monocyclopentadienyliron(II)/ruthenium(II) complexes pre-
senting benzene- or thiophene-based conjugated ligands coordi-
nated to the metal centre through nitrile or acetylide linkages
* Corresponding author.
E-mail addresses: lena.garcia@fc.ul.pt, i017@alfa.ist.utl.pt (M.H. Garcia).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.04.025

M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
2889
state applications are envisaged. The present paper reports the
synthesis, characterization and electrochemical studies of a sys-
tematic series of
[16] and 1,2-di-(2-thienyl)-ethene iron(II) and ruthenium(II) [18]
complexes leads to the following trend:
g
5-monocyclopentadienylruthenium(II) com-
plexes with nitro-substituted thiophene nitrile ligands of general
formula [RuCp(P_P)(NC{SC4H2}nNO2)][PF6] (P_P = dppe, (+)-diop;
n = 1–3). The chiral (+)-diop coligand, as mentioned above, is used
to favour the formation of a non-centrosymmetrical crystal struc-
tures, required for macroscopic second-order NLO. Spectroscopic
and cyclic voltammetric data are compared with the values re-
Fe-(thio)-NO2 > Fe-(thio)-C(H)@C(H)-(thio)-NO2 ꢂ Fe-(thio)2-
NO2 > Ru-(thio)-NO2 > Ru-(thio)-C(H)@C(H)-(thio)-NO2 ꢂ Ru-
(thio)2-NO2 > Fe-(thio)3-NO2 > Ru-(thio)3-NO2.
The magnitude of
p-backdonation interaction is higher for
iron(II) compounds as expected considering the better
p-donor
ported for other related
g
5-monocyclopentadienyliron/ruthenium
ability of the iron(II) moiety. Moreover in both iron(II) and ruthe-
nium(II) families no significant differences are observed between
the bithiophene derivatives and the ones possessing the vinylidene
unit between the two thiophene rings. This behavior can ulti-
mately give some insight on the trend of the corresponding first
hyperpolarizabilities [16,19].
complexes and are evaluated at the light of the possible known
electronic factors, responsible for the NLO properties. Preliminary
evaluation of the efficiency on doubling frequency of a Nd:YAG
laser emitting at 1064 nm was carried out for the ruthenium
compounds possessing (+)-diop as coligand, [RuCp((+)-diop)-
(NC{SC4H2}nNO2)][PF6] and one of the iron analogous, namely
[FeCp((+)-diop)(NC{SC4H2}2NO2)][PF6] by Kurtz powder technique.
1H NMR resonances for the cyclopentadienyl ring are in the
range usually observed for monocationic ruthenium(II) complexes
and depends mainly of the phosphine coligand being more
shielded for (+)-diop complexes. The phosphine 1H NMR reso-
nances are also relatively insensitive to the nature of the aromatic
nitrile. Considering the thiophene ligand protons, an overall shield-
ing effect upon coordination was observed, especially for the H3
protons (see Table 1 and Fig. 2 for numbering scheme), indicating
2. Results and discussion
2.1. Synthesis and spectroscopic studies
The complexes (Fig. 1) were prepared by chloride abstraction of
[RuCp(P_P)Cl] (P_P = dppe or (+)-diop) (dppe: 1,2-bis(diphenyl-
phosphino)ethane; (+)-diop: (+)-2,3-O-isopropylidene-2,3-dihy-
droxy-1,4-bis(diphenylphosphino)butane) with TlPF6 in the
presence of an excess of the appropriate thiophene ligand in meth-
anol or methanol/dichloromethane mixture, according to the
solubility of the reactants, at room temperature. After workup,
orange-reddish microcrystalline products of [RuCp(P_P)(NC{SC4H2}n-
NO2)][PF6] (P_P = dppe, n = 1 (1a), n = 2 (2a), n = 3 (3a); P_P = (+)-
diop, n = 1 (1b), n = 2 (2b), n = 3 (3b)) were obtained with yields
in the range of 40–78%. The new compounds are fairly stable to-
wards oxidation in air and to moisture both in the solid state and
in solution. Formulation of the new compounds was supported
by analytical data, IR and 1H, 13C and 31P NMR spectroscopies.
The molar conductivities of ca. 10ꢁ3 M solutions of the complexes
an electronic flow towards the aromatic ligand due to p-backdona-
tion involving the metal centre. The same overall behavior on the
1H NMR resonances was found in the similar iron(II) derivatives
[16] and the 1,2-di-(2-thienyl)-ethene iron(II) and ruthenium(II)
related compounds [18].
13C NMR data generally confirm the evidences found in pro-
ton spectra and show the same behavior presented in the related
iron(II) compounds [16]. The Cp ring resonances are in the range
usually observed for monocationic ruthenium(II) complexes and
depends mainly on the phosphine coligand as observed in 1H
NMR spectra. Also, the phosphine signals are relatively insensitive
to the nature of the aromatic thiophene ligands. Considering the
thiophene ligands, an expected deshielding on the NC carbon upon
coordination was observed, whereas for the ring carbons more
significant changes were observed for the carbons closest to the
nitrile group (see Table 2), in agreement with the trends observed
in the 1H NMR spectra.
in nitromethane, placed in the range 82–89
X
ꢁ1 cm2 molꢁ1, are
consistent with the values reported for 1:1 type electrolytes [17].
Typical IR bands confirm the presence of the cyclopentadienyl
31P NMR data for the complexes showed one singlet for dppe
whereas for the (+)-diop coligand the resonances are characterized
by two doublets, revealing the presence of two inequivalent phos-
phorous atoms.
The optical absorption spectra of all complexes were recorded
using 5.0 ꢀ 10ꢁ5 M solutions in dichloromethane and DMF in order
to identify metal-to-ligand and intraligand charge transfer bands
(MLCT and ILCT, respectively), expected for these complexes. The
spectra for 1a–3a in dichloromethane typify the behavior of the
compounds studied in this work (Fig. 3) and the optical data are
ꢁ
ligand (ca. 3120–3040 cmꢁ1), the PF6 anion (840 and 550 cmꢁ1
)
and the coordinated nitrile (2205–2225 cmꢁ1) in all the complexes.
Comparison of m(N„C) upon coordination of the thiophene ligands
to ruthenium(II) centres reveals a negative shift of ꢁ5 to ꢁ20 cmꢁ1
for 1a, 1b and 2b and a positive shift of +5 to +25 cmꢁ1 for the
remaining complexes (IR data of the nitrile ligands are from Ref.
[16]). The negative shifts have been related with enhanced
p-back-
donation from the metal d orbitals to the
p
* orbital of the NC group,
which leads to a decrease in the N„C bond order. In the present
study the observed values show that the thiophene chain length-
ening leads to a less effective p-backdonation interaction. Compar-
ison of these shifts with those found on related thiophene iron(II)
Table 1
Differences on NMR 1H resonances of thiophene ligands upon coordination to the
Ru(II) organometallic fragments.a,b
Compound
D
dc (ppm)
H3
H4
H7
H8
H11
H12
1a
1b
2a
2b
3a
3b
ꢁ0.59
ꢁ0.17
ꢁ0.85
ꢁ0.30
ꢁ0.68
ꢁ0.31
ꢁ0.30
ꢁ0.11
ꢁ0.26
ꢁ0.01
ꢁ0.60
ꢁ0.03
–
–
–
–
–
–
–
–
0.00
0.01
–
–
–
–
ꢁ0.09
ꢁ0.02
ꢁ0.10
ꢁ0.03
ꢁ0.06
ꢁ0.03
ꢁ0.03
0.00
ꢁ0.02
0.00
a
In CDCl3 except 3a and 3b (in CD2Cl2).
For 1H NMR resonances of thiophene ligands see Ref. [16].
b
c
dcomplex ꢁ dfree
.
ligand
Fig. 1. Structural formulae of the complexes [RuCp(P_P)(NC{SC4H2}nNO2)][PF6].

2890
M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
summarized in Table 3. The spectra of all compounds are charac-
terized by the presence of absorption bands which assignment
was based on the spectra of the free ligands and the organometallic
fragments [RuCp(P_P)]+. The electronic transition of the organome-
tallic moiety (k ꢃ 253–265 nm) and of the uncoordinated thio-
phene ligands (k ꢃ 289–442 nm) can be clearly recognized in the
spectra of all the complexes. An important feature for the com-
pounds 1a and 1b is the appearance of two new weak broad
bands in the visible region (k ꢃ 388–485 nm) assigned to MLCT
Fig. 2. Numbering scheme for NMR spectral assignments of Ru complexes and free
ligands.
Table 2
Differences on NMR 13C resonances of thiophene ligands upon coordination to the Ru(II) organometallic fragments.a,b
Compound
D
dc (ppm)
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
1a
1b
2a
2b
3a
3b
3.12
5.81
7.17
9.60
6.92
10.76
1.91
1.85
ꢁ1.15
ꢁ2.05
ꢁ1.91
ꢁ2.25
2.25
3.24
2.00
2.60
1.05
1.67
0.50
0.97
0.38
0.91
0.61
0.69
ꢁ1.11
ꢁ0.60
ꢁ0.16
0.63
1.00
1.96
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
0.04
0.27
–
–
–
–
0.32
ꢁ0.12
ꢁ0.44
ꢁ0.24
0.46
0.70
ꢁ0.21
0.43
ꢁ1.21
ꢁ0.65
0.22
0.34
ꢁ0.24
ꢁ0.05
0.41
0.32
ꢁ0.22
ꢁ0.10
ꢁ0.02
ꢁ0.26
0.23
0.20
a
In CDCl3 except 3a and 3b (in CD2Cl2).
For 13C NMR resonances of thiophene ligands see Ref. [16].
b
c
dcomplex ꢁ dfree
.
ligand
Fig. 3. Absorption spectra of [RuCp(dppe)(NC{SC4H2}nNO2)][PF6] (n = 1: 1a, n = 2: 2a, n = 3: 3a) recorded in CH2Cl2 (5.0 ꢀ 10ꢁ5 M). Top figure shows absorption spectra for the
free thiophene ligands NC{SC4H2}nNO2 (n = 1: L1, n = 2: L2, n = 3: L3) taken from Ref. [16] and RuCp(dppe)Cl in the same experimental conditions for comparison.

M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
2891
Table 3
chemical behavior of Ru(II) complexes was studied by cyclic
voltammetry in dichloromethane and acetonitrile, between the
limits imposed by the solvents. The cyclic voltammetry of the free
thiophene ligands was reported elsewhere [16]. As an example, the
electrochemical response for 2a in dichloromethane is shown in
Fig. 4, and the most relevant data for redox changes exhibited by
all the complexes in dichloromethane and acetonitrile are summa-
rized in Tables 5 and 6.
The electrochemical behavior in dichloromethane is character-
ized by the presence of one quasi-reversible redox process attrib-
uted to Ru(II)/Ru(III) couple, in the range 1.17–1.41 V, and two
reductive processes occurring on the coordinated nitrile ligands.
In addition, low intense redox waves at Ep/2 ꢂ 0.12 V and
Epa ꢂ ꢁ0.95 V were found and attributed to decomposition prod-
ucts originated by the second reductive process since these waves
vanish when the potential is reverted immediately after the first
reductive process (Fig. 4). A difference of 60–100 mV on Ru(II)/
Ru(III) couple was found from 1 to 2 compounds, whereas between
2 and 3 the difference is only 10–30 mV. This behavior is analogous
to the one observed for similar iron(II) complexes [16] and can be
explained by a less effective release of electronic density from the
metal centre to the acceptor nitro group with the extension of the
aromatic system. These results confirm the evidences of the spec-
troscopic data discussed above, namely the relative magnitude of
Selected electronic spectral data for [RuCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes in
dichloromethane solution (ca. 5.0 ꢀ 10ꢁ5 M).
Compound
k, nm (10ꢁ4
e)
1a
1b
2a
2b
3a
3b
253 (sh), 289 (0.97), 389 (0.58), 485 (0.24)
265 (sh), 292 (sh), 388 (0.66), 471 (0.38)
254 (sh), 329 (sh), 396 (1.62), 452 (0.51)
264 (sh), 322 (sh), 395 (2.02), 442 (0.33)
257 (sh), 429 (2.39)
262 (sh), 442 (1.97)
transitions. For the compounds with two and three thiophene
rings, these MLCT transitions are more difficult to assign due to
the possible overlapping with the ILCT transition associated to
the thiophene chromophores.
In order to clarify this hypothesis a fit with multiple GAUSSIANS
bands were applied to the spectra of these compounds, which re-
veal longest wavelength absorption bands at 452 nm (2a) and
442 nm (2b) that are compatible with MLCT transitions. However,
these bands were not clearly found for 3a and 3b due to the com-
plete overlapping with ILCT transition related to the ligand L3. In
fact, the MLCT transitions seems to shift to higher energies with
increasing conjugation length while the intraligand bands shift to
lower energies, this giving a complete overlapping of these bands
for the compounds with three thiophene rings. The same behavior
was already found in the similar iron(II) complexes [16]. Compared
to these iron(II) complexes, the MLCT bands on the ruthenium(II)
derivatives are shifted to higher energies. According to the well
known two-level-model (TLM) [20] this behavior can ultimately
lead to lower quadratic hyperpolarizabilities for the ruthenium(II)
complexes. On the basis of this model, it might be expected similar
quadratic hyperpolarizabilities for 2a and for the thiophen-2-yl-vi-
nyl-thiophene ruthenium(II) derivative [18] since no significant
differences on the energies of the corresponding lowest-energy
bands were found.
The most relevant results concerning the solvatochromic
behavior of all compounds are summarized in Table 4. Although
these results must be carefully analyzed due to the broadening of
the bands, which lead to some uncertainty in the attribution of
kmax values, the studies showed a slight bathochromic shift on
the MLCT bands for the compounds 1a and 1b upon increasing
the polarity of the solvent. This positive solvatochromic behavior
is characteristic of electronic transitions with an increase of the di-
pole moment upon photo-excitation.
the metal-ligand
p-backdonation, which was found to decrease
as the conjugation length of the nitrile ligand increases. Replacing
dppe coligand by (+)-diop gives an expected increase of the redox
potential of the Ru(II)/Ru(III) couple, which agrees with the relative
donating ability of the two organometallic fragments. As the
HOMO energy can be related to the Ru(II)/Ru(III) potential
[16,21] the results discussed above show that this orbital, as ex-
pected, is destabilized by dppe and, in a less extent, by the chain
lengthening of the thiophene ligand. These overall results are illus-
trated in Fig. 5, in which electrochemical data for similar iron(II)
complexes were also added for comparison.
As mentioned above, all complexes show two redox processes
at negative potentials, occurring at the coordinated thiophene li-
gands. The first redox couple, in the range ꢁ0.56 V to ꢁ0.86 V, is
reversible or quasi-reversible and corresponds to the formation
of the anionic radical. The results show that LUMO, which energy
can be related to this first reduction potential [16,21], is destabi-
lized as the chain-length of the thiophene ligand increases and is
2.2. Electrochemical studies
In order to get an insight on the electron richness of the organo-
metallic fragment and the coordinated chromophores, the electro-
Table 4
Relevant solvatochromic data for [RuCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes.
Compound
k (nm)
CH2Cl2
DMF
1a
1b
2a
2b
389
485
408
504
388
471
419
485
396
452
418
481
395
442
407
474
3a
3b
428
442
454
445
Fig. 4. Cyclic voltammograms of 2a in dichloromethane showing both oxidative
and reductive processes (—) and the first reductive process (- - -) at scan rate of
200 mV/s.

2892
M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
Table 5
Electrochemical data for [RuCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes in CH2Cl2.
Compound
Epc (V)
Epa (V)
Ep/2 (V)
Epa ꢁ Epc (mV)
Ic/Ia
1a
1.23
ꢁ0.65
ꢁ1.35
1.33
ꢁ0.56
–
1.28
ꢁ0.61
–
100
90
–
0.6
1
–
1b
2a
2b
3a
3b
1.35
ꢁ0.61
ꢁ1.23
1.12
ꢁ0.82
ꢁ1.27
1.47
ꢁ0.5
ꢁ1.1
1.23
ꢁ0.72
ꢁ1.15
1.41
ꢁ0.56
–
120
110
–
0.8
1
–
1.18
ꢁ0.77
ꢁ1.21
1.35
ꢁ0.76
ꢁ1.17
1.17
ꢁ0.86
ꢁ1.19
1.32
ꢁ0.88
ꢁ1.19
110
100
120
0.7
1
1
1.29
ꢁ0.8
1.4
110
90
90
0.7
1
1
ꢁ0.71
ꢁ1.21
ꢁ1.12
1.11
ꢁ0.91
ꢁ1.24
1.26
ꢁ0.93
ꢁ1.23
1.22
ꢁ0.81
ꢁ1.15
1.37
ꢁ0.82
ꢁ1.15
110
100
90
0.8
1
0.6
110
110
80
0.6
0.8
0.6
Fig. 5. Trends on oxidation potentials, in CH2Cl2, for Ru(II) and Fe(II)
[MCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes. Iron data collected from Ref. [16].
Table 6
Electrochemical data for [RuCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes in acetonitrile.
Table 7
Compound
Epc (V)
Epa (V)
Ep/2 (V)
Epa ꢁ Epc (mV)
–
–
60
70
Ic/Ia
Estimation of HOMOꢁLUMO gaps based on electrochemical data in CH2Cl2 for
[MCp(P_P)(NC{SC4H2}nNO2)][PF6] complexes.
1a
–
1.16
–
–
–
–
–
1
1
1.00a
ꢁ0.62
ꢁ1.27
Compound
Eox ꢁ Ered (V)
ꢁ0.56
ꢁ0.6
Ru
Fea
ꢁ1.2
ꢁ1.24
[MCp(dppe)(NC{SC4H2}NO2)]+
[MCp((+)-diop)(NC{SC4H2}NO2)]+
[MCp(dppe)(NC{SC4H2}2NO2)]+
[MCp((+)-diop)(NC{SC4H2}2NO2)]+
[MCp(dppe)(NC{SC4H2}3NO2)]+
[MCp((+)-diop)(NC{SC4H2}3NO2)]+
1.89
1.97
1.95
2.11
2.03
2.20
1.50
1.64
1.63
1.76
1.69
1.84
1b
2a
2b
3a
–
1.35
–
–
–
–
–
80
–
–
–
0.9
–
1.16b
ꢁ0.58
ꢁ1.3
ꢁ0.5
ꢁ0.54
ꢁ1.01
–
–
1.09
–
–
–
–
–
70
70
–
–
1
1
1.00a
ꢁ0.79
ꢁ1.22
a
ꢁ0.72
ꢁ0.76
Data taken from Ref. [16] for comparison.
ꢁ1.15
ꢁ1.18
–
1.29
–
–
–
–
–
90
90
–
–
0.9
0.9
on LUMO, as previously discussed and also recently reported in
the study of the related thiophen-2-yl-vinyl-thiophene derivatives
[18]. Similar trends were observed on similar iron(II) complexes
[16] but higher HOMOꢁLUMO gaps are found for ruthenium(II)
complexes. This is mainly due to the stabilization of the HOMO
orbitals for the ruthenium(II) derivatives, since the LUMO energies
are almost unaffected by changing the metal fragment. In fact, the
oxidation potentials for ruthenium(II) compounds are ca. 0.38 V
higher than the iron(II) ones, whereas the first reduction potentials
are very similar for both metals, considering the same thiophene
ligand [16]. These results are in agreement with the better donor
character of the iron(II) fragment.
1.16b
ꢁ0.78
ꢁ1.19
ꢁ0.69
ꢁ0.74
ꢁ1.1
ꢁ1.15
–
–
1.54
1.08
–
–
–
–
–
–
–
60
60
–
–
–
1
1.00a
ꢁ0.87
ꢁ1.24
ꢁ0.81
ꢁ0.84
ꢁ1.18
ꢁ1.21
0.9
3b
–
–
1.6
1.27
–
–
–
–
–
–
–
70
80
–
–
–
0.7
0.8
1.16b
ꢁ0.86
ꢁ1.23
ꢁ0.79
ꢁ0.83
ꢁ1.15
ꢁ1.19
Our previous observation that thiophene ligands can be substi-
tuted by the acetonitrile solvent during the oxidative process in the
electrochemical experiments [16], was also found for these ruthe-
nium(II) compounds. In fact, our electrochemical studies in aceto-
nitrile showed that the Ru(II)/Ru(III) oxidation have no cathodic
counterpart for all the studied complexes. Moreover, a new catho-
dic wave arises at 1.00 V for the complexes with dppe and at 1.16 V
for (+)-diop complexes independently of the coordinated thio-
phene ligand (see Table 6). These cathodic potentials were as-
signed to the reduction of the 17-electron species
[RuCp(P_P)(NCCH3)]2+ since the values are consistent with those
found in separate electrochemical experiments for the redox cou-
ple of [RuCp(P_P)(NCCH3)][PF6] compounds. These results seem
to indicate that the 17-electron species [RuCp(P_P)(NC{SC4H2}n-
NO2)]2+, formed on the electrode surface at the oxidation potential,
undergo fast substitution of thiophene ligand by acetonitrile sol-
vent molecule, leading to the [RuCp(P_P)(NCCH3)]2+ species.
a,b
Waves assigned to reduction of [RuIIICp(P_P)(NCMe)]2+ (see text).
only slightly affected by the nature of the phosphine coligand. The
second reduction is reversible or quasi-reversible for the com-
pounds 2 and 3 whereas for compounds with one thiophene ring
one fully irreversible wave was found. On the basis of HOMOꢁLU-
MO gap, as expressed by the difference between the Ep/2 for the
oxidation process and the Ep/2 for the first reduction process, the
results show that this gap depends on the phosphine coligand
and the chain lengthening of the thiophene ligand (Table 7). As ex-
pected, the lower HOMOꢁLUMO gaps observed for dppe com-
plexes are mainly due to the higher energies of the HOMOs since
LUMOs, mainly located on thiophene ligands, are only slightly af-
fected by the nature of the phosphine coligand. The chain length-
ening of the thiophene ligands lead to an increase of the
HOMOꢁLUMO gap, mainly as a result of the destabilizing effect

M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
2893
The electrochemical experiments in acetonitrile showed the
same general trend on the oxidation and reduction potentials by
varying the phosphines co-ligands and the thiophene chromoph-
ores that was observed in dichloromethane.
suggest some evidence for a slight poorer degree of
p
-backdona-
tion for 2a when compared to [RuCp(dppe)(NC(C4H2S)C(H)C(H)
(C4H2S)NO2)][PF6], supported also by the spectroscopic data. The
nitrile group shows an almost linear geometry with the C1–N1–
Ru1 and N1–C1–C2 angles being 175.4(5)° and 177.0(7)°, respec-
tively. The dihedral angle between the planes of the thiophene
rings (17.6°) is higher than the corresponding one in the related
2.3. X-ray structural studies
Crystals of [RuCp(dppe)(NC{SC4H2}2NO2)][PF6] were obtained
by slow diffusion of n-hexane in a dichloromethane solution at
room temperature. The molecular structure of 2a (Fig. 6 and Table
8 for selected bond distances and angles) was established by X-ray
diffraction analysis. The overall geometry around ruthenium can
be described as pseudo-octahedral, on the assumption that the
cyclopentadienyl group takes up three coordination sites. The
structural data derived from the geometry around the metal,
namely the P1–Ru1–P2, N1–Ru1–P1 and N1–Ru1–Cp angles are
similar to the other cyclopentadienyl complexes reported in the lit-
erature [22,23].
The bond lengths Ru–P and Ru–Cp and P1–Ru–P2 angle re sim-
ilar to those found in the analogous complex [RuCp(dppe)(p-
NC{C6H4}2NO2)][PF6] [22] and are within the values found in the
literature [23b,23d]. The Ru1–N1 distance, 2.005(5) Å, is slightly
higher than the one found for [RuCp(dppe)(NC(C4H2S)C(H)C(H)
(C4H2S)NO2)][PF6] and shorter than other ruthenium complexes
containing nitriles (Table 9). The nitrile bond distance, very similar
to the one observed for [RuCp(dppe)(NC(C4H2S)C(H)C(H)(C4H2S)-
NO2)][PF6], although marginally shorter, is comparable with the
other complexes and indicate a triple bond character. These results
compound
[RuCp(dppe)(NC(C4H2S)C(H)C(H)(C4H2S)NO2)][PF6]
(8.39°) [18], resulting in a somewhat lower planarity for the pres-
ent compounds. The dihedral angle between the thiophene rings
may in fact have some influence in the loss of charge transfer effi-
ciency with increasing conjugated length, as suggested for the
compounds [FeCp(dppe)(NC{C4H2S}nNO2)][PF6] (n = 2, 3) [16]. Dis-
tances and angles within the thiophene rings are consistent with
the retention of aromaticity, in particular there is no obvious bond
length alternation which would be expected for an appreciable
quinoidal contribution.
The crystal packing of 2a is centrosymmetric due to the crystal-
lization in the monoclinic space group P21/n with four independent
molecules in the unit cell, making this compound unsuitable for
solid state NLO purposes. However multiple intermolecular hydro-
gen bonding motif in the solid state are observed involving the
PF6ꢁ counterion and several hydrogens of the cationic counterpart.
2.4. Second-order NLO characterization
The nonlinear optical properties, namely the second harmonic
generation (SHG), of compounds [RuCp((+)-diop)(NC{SC4H2}n-
Fig. 6. Molecular structure of the [RuCp(dppe)(NC{SC4H2}2NO2)]+, showing the labelling scheme. Hydrogen atoms have been omitted for clarity.
Table 8
Selected bond lengths (Å) and angles (°) for [RuCp(dppe)(NC{SC4H2}2NO2)][PF6] (2a).
Bond lengths (Å)
Angles (°)
Ru1–N1
Ru1–Cpa
Ru1–C21
Ru1–P1
2.005(5)
1.8637
N1–C1
C1–C2
C2–C3
C3–C4
C4–C5
C2–S1
C5–S1
C5–C6
C6–C7
C7–C8
C8–C9
C6–S2
C9–S2
C9–N2
N2–O1
N2–O2
1.143(6)
1.407(7)
1.358(8)
1.394(8)
1.363(8)
1.726(6)
1.719(5)
1.443(7)
1.355(8)
1.398(8)
1.330(9)
1.722(5)
1.692(6)
1.458(8)
1.187(7)
1.235(7)
N1–Ru1–C21
C21–Ru1–P1
C21–Ru1–P2
N1–Ru1–Cpa
N1–Ru1–P1
N1–Ru1–P2
P1–Ru1–P2
154.3(2)
118.2(2)
101.7(2)
122.7
85.0(1)
91.1(1)
83.92(5)
133.4
C211–P2–Ru1
C221–P2–Ru1
C131–P1–Ru1
C231–P2–Ru1
C231–C131–P1
C131–C231–P2
C1–N1–Ru1
N1–C1–C2
112.7(2)
118.7(2)
108.7(2)
109.5(2)
107.4(4)
109.6(4)
175.4(5)
177.0(7)
119.1(6)
114.3(6)
2.186(6)
2.293(1)
2.286(1)
1.379(9)
1.411(9)
1.392 (9)
1.40(1)
1.402(9)
1.827(6)
1.827(6)
1.857(5)
1.823(6)
1.834(6)
1.841(6)
Ru1–P2
C21–C22
C22–C23
C23–C24
C24–C25
C25–C21
P1–C111
P1–C121
P1–C131
P2–C211
P2–C221
P2–C231
Ru1–P1–Cpa
Ru1–P2–Cpa
C111–P1–Ru1
C121–P1–Ru1
126.9
120.6(2)
114.8(2)
C9–N2–O1
C9–N2–O2
a
Cp centroid.

2894
M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
Table 9
Structural data for monocyclopentadienylruthenium(II) derivatives with nitrile ligands.
Compound
Bond lengths (Å)
Ru–N1
Angles (°)
Ref.
N1–C1
C1–C2
Ru–N1–C1
N1–C1–C2
[RuCp(dppe)(NC{SC4H2}2NO2)][PF6]
[RuCp(dppe)(NC(C4H2S)C(H)C(H) (C4H2S)NO2)][PF6]
[RuCp(dppe)(p-NC(C6H4)2NO2)][PF6]
[RuCl2(CO)2(NCC6H5)2]
[RuCp(PPh3)2(p-NC(C6H4)2OEt)][PF6]
[RuCl4(NCC6H5)2][Bu4N]
2.005(5)
1.997(5)
2.021
2.119(2)
2.041(5)
2.024
1.144(6)
1.148(8)
1.126
1.138(8)
–
1.407(7)
1.436(10)
1.46
1.439(9)
–
175.4(5)
175.8(5)
175.8
175.5(1)
–
177.1(7)
176.4(7)
176.1(12)
177.1(20)
–
This work
[18]
[22]
[24a]
[24b]
[25]
1.124
1.447
176.3
–
2.002
1.135
NO2)][PF6] (n = 1–3) and [FeCp((+)-diop)(NC{SC4H2}2NO2)][PF6]
[16] were evaluated with our experimental set up [26], for mea-
surements by the Kurtz powder technique [27]. The studies were
performed at the Nd:YAG laser fundamental wavelength
(1064 nm) considering the reasonable transparence of the samples
at 532 nm, the second harmonic wavelength. The efficiency in dou-
bling the laser frequency was only detectable for the [RuCp((+)-
diop)(NC{SC4H2}NO2)][PF6] (1b) complex, which emitted a signal
approximately 100 times smaller than the standard urea. For the
other studied compounds the emitted signals were negligible. It
is important to become aware that the results obtained by this
technique are very difficult to interpret in terms of molecular
structure-property relationships, since they depend not only on
the molecular hyperpolarizability b but also very strongly of the
solid state effects, such as for example, the crystal packing struc-
ture, grain size and the phase matching properties. To better
understand the results of the present study, it would be crucial
to consider the X-ray data relative to the precise orientation of
the molecules in the crystal and, even more important, the angle
between the molecular charge transfer axis (typically along the do-
nor–acceptor axis) and the polar crystal axis. It is known that there
is an optimum value for this angle which depends of the crystal
space group in order to allow quadratic phase-matched interac-
tions [28–30]. Thus, the poor values found for these compounds
can be probably explained by a significant deviation from the opti-
mal phase matching direction. Finally, it is important to point out
that these preliminary studies did not account for fluorescence and
grain size of the samples. Some work is in progress to obtain crys-
tals suitable for X-ray studies.
bithiophene derivative when compared to that found in related
thiophen-2-yl-vinyl-thiophene reported in the literature, we ex-
pected comparable quadratic hyperpolarizabilities for these com-
plexes. Finally, in spite of the somewhat lower b values expected
for the (+)-diop complexes, the SHG efficiencies found by Kurtz
powder technique, in the preliminary tests carried out in the pres-
ent study, were unsatisfactory and can probably find some justifi-
cation in the multiple factors related with the used method.
4. Experimental
4.1. General procedures
All preparations and manipulations of the complexes described
in this work were carried out under nitrogen or argon atmosphere
using standard Schlenck techniques. Solvents were purified
according to the usual methods [31]. Solid state IR spectra were ta-
ken on a Perkin–Elmer 457 spectrophotometer with KBr pellets;
only significant bands are cited in the text. 1H, 13C and 31P NMR
spectra were recorded on a Varian Unity 300 spectrometer at probe
temperature. The 1H and 13C chemical shifts are reported in parts
per million (ppm) downfield from internal Me4Si and the 31P
NMR spectra are reported in ppm downfield from external stan-
dard 85% H3PO4. Coupling constants are reported in Hz. Spectral
assignments follow the numbering scheme shown in Fig. 2. Elec-
tronic spectra were recorded at room temperature on a Shimadzu
UV-1202 spectrometer. Melting points were obtained using a Reic-
hert Thermovar. The molar conductivities of 1 mM solutions of the
complexes in nitromethane were recorded with a Schott CGB55
Konduktometer at room temperature. Microanalyses were ob-
tained at the Laboratório de Análises, Instituto Superior Técnico,
using a Fisons Instruments EA1108 system. Data acquisition, inte-
gration and handling were performed using a PC with the software
package Eager-200 (Carbo Erba Instruments).
3. Conclusions
A new family of Ru(II) half-sandwich complexes was synthes-
ised and fully characterized. As already found for the previously re-
ported related thiophene iron(II) complexes, spectroscopic and
The starting ruthenium(II) complexes [RuCp(dppe)Cl],
[RuCp((+)-diop)Cl] [32] and thiophene ligands 5-nitrothiophene-
2-carbonitrile (L1), 50-nitro-2,20-bithiophene-5-carbonitrile (L2)
and 500-nitro-2,20:50,200-terthiophene-5-carbonitrile (L3) [16] were
prepared as reported.
electrochemical data suggest an improved electronic
between the
5-cyclopentadienylruthenium(II) moiety and the
-system of the conjugated thiophene ligands, when compared
p-coupling
g
p
to the previously reported p-benzonitrile analogues. However, a
poorer electron-donor effect from the metal centre towards NO2
acceptor group is found for the complexes studied in this work.
Also, spectroscopic, electrochemical and crystallographic data
show marginally differences between the [RuCp(dppe)-
(NC{C4H2S}2NO2)][PF6] and the related [RuCp(dppe)(NC(C4H2S)-
C(H)@C(H)(C4H2S)NO2)][PF6] complex, despite some improved
electronic coupling between the organometallic fragment and the
nitrile ligand for the thiophene-vinyl derivative. Thus, the overall
data suggest an expected improvement of the quadratic hyperpo-
larisabilities for the complexes studied in the present work when
compared to those found in p-benzonitrile derivatives. Neverthe-
less these values are expected lower than the similar thiophene
iron(II) complexes. Despite some poorer electronic coupling
between the ruthenium(II) fragment and the nitrile ligand for the
4.2. Synthesis of the complexes
All
the
complexes
[RuCp(P_P)(NC{SC4H2}nNO2)][PF6]
(P_P = dppe or (+)-diop; n = 1, 2 or 3) were prepared as follows:
TlPF6 (0.37 mmol) was added to a solution of [RuCp(P_P)Cl]
(0.33 mmol) and the appropriate thiophene derivative (0.39 mmol)
in methanol or a mixture of methanol/dichloromethane according
to the solubility of the reactants. The suspension was stirred at
room temperature for 16–96 h. A change was observed from yel-
low-orange to orange-reddish with simultaneous precipitation of
TlCl and some desired product. After filtration, the solvent was
evaporated under vacuum and the solid residue washed several
times with diethyl ether/dichloromethane mixture to remove the

M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
2895
3
3
excess of thiophene ligand derivative. Furthermore, the desired
product co-precipitated with TlCl was solubilized with dichloro-
methane and filtered to remove the thallium salt. The solvent
was evaporated under vacuum and the solid obtained was recrys-
tallized together with previous isolated residue from dichloro-
methane/n-hexane or dichloromethane/diethyl ether giving the
desired complexes as orange-reddish microcrystalline products.
1H and 13C NMR data relative to dppe and (+)-diop coordinated
phosphines are very similar in the ruthenium(II) compounds, and
are described below.
6.55 (d, 1H, H3, JHH = 4.2), 6.98 (d, 1H, H4, JHH = 3.9), 7.16 (d,
3
3
1H, H11, JHH = 4.5), 7.19 (d, 1H, H7, JHH = 3.9), 7.32 (d, 1H, H8,
3JHH = 3.9), 7.85 (d, 1H, H12, JHH = 4.2); 13C NMR (CD2Cl2): d
3
82.84 (g
5-C5H5), 107.11 (C2), 121.03 (NC), 123.84 (C8), 124.63
(C7), 127.85 (C11), 128.05 (C4), 130.23 (C12), 136.59 (C9), 136.80
(C6), 139.96 (C3), 143.84 (C10), 144.36 (C5), 150.27 (C13); 31P
NMR (CD2Cl2): d 79.8. Anal. Calc. for C44H35F6N2O2P3S3Ru: C,
51.41; H, 3.43, N, 2.72; S, 9.36. Found: C, 51.58; H, 3.36, N, 2.67;
S, 9.19%.
Compounds 1a and 2a. For dppe: 1H NMR (CDCl3): 2.56–2.68 (m,
4H, CH2), 7.22–7.29 (m, 4H, C6H5), 7.43–7.54 (m, 8H, C6H5), 7.58 (t,
4.2.4. RuCp((+)-diop)(NC{SC4H2}NO2)PF6 (1b)
56% yield, orange-reddish, recrystallized from CH2Cl2/n-hexane,
3
3
4H, C6H5, JHH = 7.5), 7.78 (m, 4H, C6H5, JHH = 8.5); 13C NMR
m.p. 162 °C (dec.). Molar conductivity (
(KBr) cmꢁ1 (N„C) 2205. 1H NMR (CDCl3): d 4.52 (s, 5H, g5
C5H5), 7.42 (d, 1H, H3, JHH = 4.2), 7.80 (d, 1H, H4, JHH = 4.2); 13C
X
ꢁ1 cm2 molꢁ1) 88.5. IR
1
(CDCl3): d 28.08 (t, CH2, JCP = 23.0), 129.12 and 129.50 (t, Cmeta
,
:
t
-
3JCP = 4.8), 130.58 and 133.03 (t, Cortho 2JCP = 4.8), 130.64 and
,
3
3
131.27 (s, Cpara), 136.98 (t, Cipso
,
1JCP = 2.8).
NMR (CDCl3): d 84.73 (g
5-C5H5), 113.78 (C2), 121.24 (NC),
Compound 3a. For dppe: 1H NMR (CD2Cl2): d 2.58–2.66 (m, 4H,
128.51 (C4), 139.61 (C3), 155.02 (C5); 31P NMR (CDCl3): d 35.5
(2d, JPAPB = 38.1). Anal. Calc. for C41H39F6N2O4P3SRu: C, 51.09; H,
4.08, N, 2.91; S, 3.33. Found: C, 50.95; H, 4.36, N, 2.86; S, 3.02%.
CH2), 7.26–7.32 (m, 4H, C6H5), 7.46–7.50 (m, 6H, C6H5), 7.57–
7.62 (m, 6H, C6H5), 7.76–7.82 (m, 4H, C6H5); 13C NMR (CD2Cl2): d
1
28.23 (t, CH2, JCP = 22.8), 129.41 and 129.66 (t, Cmeta
,
3JCP = 4.9),
130.98 and 131.55 (s, Cpara), 131.09 and 133.36 (t, Cortho
,
4.2.5. RuCp((+)-diop)(NC{SC4H2}2NO2)PF6 (2b)
2JCP = 4.8), 137.25 (t, Cipso 1JCP = 2.8).
,
48% yield, orange-reddish, recrystallized from CH2Cl2/diethyl
Compounds 1b and 2b. For (+)-diop: 1H NMR (CDCl3): d 1.14 (s,
3H, CH3), 1.31 (s, 3H, CH3), 2.31–2.41 (m, 1H, CH), 2.58–2.68 (m,
1H, CH), 3.10–3.31 (m, 2H, CH2), 3.48–3.64 (m, 2H, CH2), 7.11–
7.18 (m, 4H, C6H5), 7.40–7.46 (m, 6H, C6H5), 7.54–7.60 (m, 4H,
C6H5), 7.66–7.72 (m, 4H, C6H5), 7.85–7.92 (m, 2H, C6H5); 13C
NMR (CDCl3): d 26.73 (s, CH3), 26.90 (s, CH3), 29.04 (d, CH2,
ether, m.p. 205–206 °C. Molar conductivity (
X
ꢁ1 cm2 molꢁ1) 86.2.
IR (KBr) cmꢁ1 (N„C) 2210. 1H NMR (CDCl3): d 4.48 (s, 5H, g5
:
t
-
3
3
C5H5), 7.20 (d, 1H, H7, JHH = 4.2), 7.32 (d, 1H, H4, JHH = 3.6), 7.59
(d, 1H, H3, 3JHH = 3.6), 7.86 (d, 1H, H8, 3JHH = 4.2); 13C NMR (CDCl3):
d 84.18 (g
5-C5H5), 108.91 (C2), 122.80 (NC), 125.38 (C7), 126.97
(C4), 128.70 (C8), 140.97 (C3), 141.27 (C6), 141.93 (C5), 151.41
(C9); 31P NMR (CDCl3): d 35.8 (2d, JPAPB = 38.1). Anal. Calc. for
C45H41F6N2O4P3S2Ru: C, 51.68; H, 3.95, N, 2.68; S, 6.13. Found: C,
51.82; H, 4.12, N, 2.59; S, 5.98%.
1
2
1JCP = 21.4), 30.75 (d, CH2, JCP = 3.4), 75.58 (d, CH, JCP = 11.7),
2
78.36 (d, CH, JCP = 6.2), 109.06 (s, C(CH3)2), 128.82–134.34 (m,
C6H5), 138.78 (d, Cipso, ,
1JCP = 47.6), 141.06 (d, Cipso 1JCP = 46.4).
Compound 3b. For (+)-diop: 1H NMR (CD2Cl2): d 1.06 (s, 3H, CH3),
1.26 (s, 3H, CH3), 2.32–2.43 (m, 1H, CH), 2.60–2.67 (m, 1H, CH),
3.15–3.25 (m, 2H, CH2), 3.58–3.70 (m, 2H, CH2), 7.38–7.48 (m,
10H, C6H5), 7.54–7.80 (m, 8H, C6H5), 7.85–7.91 (m, 2H, C6H5); 13C
NMR (CD2Cl2): d 26.85 (s, CH3), 26.98 (s, CH3), 29.19 (d, CH2,
4.2.6. RuCp((+)-diop)(NC{SC4H2}3NO2)PF6 (3b)
40% yield, red, recrystallized from CH2Cl2/diethyl ether, m.p.
145 °C (dec.). Molar conductivity (
cmꢁ1 (N„C) 2215. 1H NMR (CD2Cl2): d 4.41 (s, 5H,
7.17 (d, 1H, H11, JHH = 4.5), 7.20 (d, 1H, H4, JHH = 4.5), 7.26 (d,
X
ꢁ1 cm2 molꢁ1) 81.9. IR (KBr)
:
t
g
5-C5H5),
1
2
3
3
1JCP = 21.0), 32.00 (d, CH2, JCP = 29.0), 75.80 (d, CH, JCP = 11.6),
2
3
3
78.72 (d, CH, JCP = 9.4), 109.41 (s, C(CH3)2), 129.10–134.83 (m,
1H, H7, JHH = 4.2), 7.27 (d, 1H, H3, JHH = 3.9), 7.35 (d, 1H, H8,
3
C6H5), 138.93 (d, Cipso
,
1JCP = 41.8), 141.92 (d, Cipso
,
1JCP = 38.4).
3JHH = 3.9), 7.87 (d, 1H, H12, JHH = 4.5); 13C NMR (CD2Cl2): d
84.20 (g
5-C5H5), 106.77 (C2), 123.96 (C8), 124.87 (NC), 125.27
4.2.1. [RuCp(dppe)(NC{SC4H2}NO2)PF6 (1a)
78% yield, red, recrystallized from CH2Cl2/n-hexane, m.p. 224–
226 °C. Molar conductivity (
ꢁ1 cm2 molꢁ1) 87.4. IR (KBr) cmꢁ1
(N„C) 2220. 1H NMR (CDCl3): d 4.87 (s, 5H, 5-C5H5), 7.00 (d,
1H, H3, JHH = 4.5), 7.61 (d, 1H, H4, JHH = 4.5); 13C NMR (CDCl3):
(C7), 128.18 (C11), 128.13 (C4), 130.46 (C12), 136.50 (C9), 137.00
(C6), 140.58 (C3), 143.80 (C10), 145.32 (C5), 150.49 (C13); 31P
X
:
NMR (CD2Cl2):
d
36.0 (2d, JPAPB = 38.1). Anal. Calc. for
t
g
C49H43F6N2O4P3S3Ru: C, 52.17; H, 3.84, N, 2.48; S, 8.53. Found: C,
52.29; H, 3.92, N, 2.39; S, 8.37%.
3
3
d
83.27
(g
5-C5H5), 113.84 (C2), 118.55 (NC), 128.04 (C4),
g
138.62 (C3), 154.51 (C5); 31P NMR (CDCl3): d 79.3. Anal. Calc.
4.3. Electrochemical studies
for C36H31F6N2O2P3SRu: C, 50.06; H, 3.62, N, 3.24; S, 3.71. Found:
C, 50.32; H, 3.65, N, 3.08; S, 3.42%.
The electrochemistry instrumentation consisted of a EG&A
Princeton Applied Research Model 273A Potentiometer and exper-
iments were monitored in a PC computer loaded with Model 270
Electrochemical Analysis Software 3.00 of EG&A from Princeton
Applied Research. Potentials were referred to a calomel electrode
containing a saturated solution of potassium chloride. The working
electrode was a 2-mm piece of platinum wire for voltammetry. The
secondary electrode was a platinum wire coil. Cyclic voltammetry
experiments were performed at room temperature and ꢁ20 °C in a
PAR polarographic cell. Solutions studied were 1 mM in solute and
0.1 M in tetrabutylammonium hexafluorophosphate as supporting
electrolyte. The electrochemical system was checked with a 1 mM
solution of ferrocene in acetonitrile and dichloromethane for
which the ferrocinium/ferrocene electrochemical parameters
(Ep/2 = 0.38 V in acetonitrile and Ep/2 = 0.41 V in dichloromethane;
4.2.2. RuCp(dppe)(NC{SC4H2}2NO2)PF6 (2a)
72% yield, orange; recrystallized from CH2Cl2/n-hexane, m.p.
255 °C (dec.). Molar conductivity (
cmꢁ1 (N„C) 2225. 1H NMR (CDCl3): d 4.85 (s, 5H,
6.76 (d, 1H, H3, JHH = 4.2), 7.07 (d, 1H, H4, JHH = 4.2), 7.13 (d,
X
ꢁ1 cm2 molꢁ1) 86.8. IR (KBr)
:
t
g
5-C5H5),
3
3
3
3
1H, H7, JHH = 4.2), 7.83 (d, 1H, H8, JHH = 4.2); 13C NMR (CDCl3):
d 82.74 (
5-C5H5), 109.81 (C2), 120.37 (NC), 125.14 (C7), 126.44
g
(C4), 128.14 (C8), 140.37 (C3), 141.14 (C5), 141.71 (C6), 151.22
(C9); 31P NMR (CDCl3): d 79.6. Anal. Calc. for C40H33F6N2O2P3S2Ru:
C, 50.80; H, 3.52, N, 2.96; S, 6.78. Found: C, 50.92; H, 3.64, N, 2.88;
S, 6.51%.
4.2.3. RuCp(dppe)(NC{SC4H2}3NO2)PF6 (3a)
68% yield, red, recrystallized from CH2Cl2/diethyl ether, m.p.
DE = 60–70 mV; Ia/Ic = 1) were in good agreement with the litera-
ture [33,34]. The electrolyte was purchased from Aldrich Chemical
Co., recrystallized from ethanol, washed with diethyl ether, and
246–247 °C. Molar conductivity (
X
ꢁ1 cm2 molꢁ1) 84.3. IR (KBr)
cmꢁ1 (N„C) 2215. 1H NMR (CD2Cl2): d 4.84 (s, 5H, 5-C5H5),
:
t
g

2896
M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
dried under vacuum at 110 °C for 24 h. Reagent grade acetonitrile
and dichloromethane, were dried over P2O5 and CaH2, respectively,
and distilled before use under argon atmosphere. An argon atmo-
sphere was maintained over the solution during the experiments.
nated directly by a Nd:YAG laser at low power (50 mJ per pulse),
producing 40 ns pulses with a repetition rate of 10 Hz. The voltage
from the photomultiplier was measured by the oscilloscope, which
is triggered by the signal itself. The photomultiplier voltage and the
neutral density filter area were optimized to obtain a good signal to
noise relation and prevent the saturation of the photomultiplier.
The oscilloscope measured the time integral of the photomultiplier
voltage automatically, which is proportional to the SHG efficiency.
The oscilloscope also performed, automatically, the average over
several laser shots. The SHG efficiency measurement of the urea
reference sample was performed under the same experimental
conditions as those of each test sample. For details of our experi-
mental set-up see reference [26].
The procedure for the measurements is as follows: the materials
were mulled to a fine powder and compacted in a mount and then
installed in the sample holder. Samples grain sizes were not stan-
dardized. For this reason, signals between individual measure-
ments were seen to vary in some cases by as much as 20%. For
a proper comparison with the urea reference material the mea-
surements were averaged over several laser thermal cycles.
4.4. Crystal structure determination of the complex 2a
X-ray data were collected on a MACH3 Enraf–Nonius diffrac-
tometer using graphite-monochromated Mo
K
a
radiation
(k = 0.71073 Å), at room temperature. As a general procedure, the
intensity of three standard reflections was measured periodically
every 2 h. This procedure did not reveal any appreciable decay.
Using the CAD4 software, intensity data were corrected for Lorentz
and polarization effects. The position of the Ru atom was obtained
by a tridimensional Patterson synthesis, while all the other non-
hydrogen atoms were located in subsequent difference Fourier
maps. All non-hydrogen atoms were refined by full-matrix least-
squares on F2 with anisotropic thermal motion parameters
whereas H-atoms were placed in idealised positions and allowed
to refine isotropically riding on the parent C atom. The structure
was solved by direct methods with SIR97 [35] and refined by full-
matrix least-squares on F2 with SHELXL97 [36] both included in the
package of programs WINGX-VERSION 1.70.01 [37]. Graphical represen-
tations were prepared using ORTEP3 [38] and Mercury 1.1.2 [39]. A
summary of the crystal data, structure solution and refinement
parameters are given in Table 10. Lists of observed and calculated
structure factors, tables of final atomic coordinates, anisotropic
thermal parameters for all non-hydrogen atoms, hydrogen atomic
coordinates, bond lengths and angles, and inter- and intramolecu-
lar contact distances are available from the authors and have been
deposited as Supplementary material.
Appendix A. Supplementary material
CCDC 718609 contains the supplementary crystallographic data
for 2a. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2009.04.025.
References
4.5. Kurtz powder SHG measurements
[1] D.J. Williams, Angew. Chem., Int. Ed. Engl. 23 (1984) 690.
[2] H.S. Nalwa, Appl. Organomet. Chem. 5 (1991) 349.
[3] N.J. Long, Angew. Chem., Int. Ed. Engl. 34 (1995) 21.
[4] S.R. Marder, in: D.W. Bruce, D. O’Hare (Eds.), Inorganic Materials, 2nd ed.,
Wiley, Chichester, 1996, p. 121.
[5] T. Verbiest, S. Houbrechts, M. Kauranen, K. Clays, A. Persoons, J. Mater. Chem. 7
(1997) 2175.
[6] I.R. Whittall, A.M. McDonagh, M.G. Humphrey, M. Samoc, Adv. Organomet.
Chem. 42 (1998) 291.
The efficiency on Second Harmonic Generation of compounds
[RuCp((+)-diop)(NC{SC4H2}nNO2)][PF6] 1b, 2b and 3b and
[FeCp((+)-diop)(NC{SC4H2}2NO2)][PF6] was measured in our labo-
ratories using the Kurtz powder method [27]. The measurements
were performed at the fundamental wavelength of 1064 nm origi-
[7] E. Goovaerts, W.E. Wenseleers, M.H. Garcia, G.H. Cross, in: H.S. Nalwa (Ed.),
Handbook of Advanced Electronic and Photonic Materials, vol. 9, 2001, p. 127
(Chapter 3).
Table 10
[8] S. Di Bella, Chem. Soc. Rev. 30 (2001) 355.
Data collection and structure refinement parameters for 2a.
[9] C.E. Powell, M.G. Humphrey, Coord. Chem. Rev. 248 (2004) 725.
[10] E. Cariati, M. Pizzotti, D. Roberto, F. Tessore, R. Ugo, Coord. Chem. Rev. 250
(2006) 1210.
[11] J.P. Morral, G.T. Dalton, M.G. Humphrey, M. Samoc, Adv. Organomet. Chem. 55
(2008) 61.
[12] M.H. Garcia, A.R. Dias, M. Paula Robalo, M.G. Humphrey, A.M. Mc Donagh, S.
Urst, E. Goovaerts, W. Wenseleers, Organometallics 21 (2002) 2107.
[13] E. Goovaerts, W. Wenseleers, P. Hepp, M.H. Garcia, M.P. Robalo, A.R. Dias,
M.F.M. Piedade, M.T. Duarte, Chem. Phys. Lett. 367 (2003) 390.
[14] M.H. Garcia, Paulo J. Mendes, A. Romão Dias, J. Organomet. Chem. 690 (2005)
4063.
Compound
2a
Chemical formula
Molecular weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C40H33F6N2O2P3RuS2
945.85
293(2)
0.71069
Monoclinic
P21/n
13.0721(10)
20.2434(1)
b (Å)
[15] M.P. Robalo, A. Teixeira, M.H. Garcia, M.F.M. Piedade, M.T. Duarte, A.R. Dias, J.
Campo, W. Wenseleers, E. Goovaerts, Eur. J. Inorg. Chem. (2006) 2175.
[16] M.H. Garcia, P.J. Mendes, M.P. Robalo, A.R. Dias, J. Campo, W. Wenseleers, E.
Goovaerts, J. Organomet. Chem. 692 (2007) 3027.
c (Å)
15.6906(1)
90.0
101.349(1)
90.0
4070.9(5)
4
1.543
0.591
1912
1.66–24.97
ꢁ15 6 h 6 15; 0 6 k 6 24; 0 6 l 6 18
7436/7160 [0.0252]
Full-matrix least-squares on F2
7160/0/538
a
(°)
b (°)
c
(°)
[17] W.J. Geary, Coord. Chem. Rev. 7 (1977) 81.
V (Å3)
[18] M.H. Garcia, Pedro Florindo, M. Fátima, M. Piedade, M. Teresa Duarte, M. Paula
Robalo, Etienne Goovaerts, Wim Wenseleers, J. Organomet. Chem. 694 (2009)
433.
Z
Dc (g cmꢁ3
)
Absorption coefficient (mmꢁ1
)
[19] W. Wenseleers, A.W. Gerbrandij, E. Goovaerts, M.H. Garcia, M. Paula Robalo,
Paulo J. Mendes, João C. Rodrigues, A.R. Dias, J. Mater. Chem. 8 (1998) 925.
[20] J.L. Oudar, D.S. Chemla, J. Chem. Phys. 66 (1977) 2664.
[21] M.H. Garcia, M.P. Robalo, A.R. Dias, M.F.M. Piedade, A. Galvão, M.T. Duarte, W.
Wenseleers, E. Goovaerts, J. Organomet. Chem. 619 (2001) 252.
[22] João C. Rodrigues, Síntese de Novos Materiais Organometálicos com
Propriedades de Não Linearidade Óptica, Ph.D. thesis, Faculdade de Ciências
da Universidade de Lisboa, 1999.
F(0 0 0)
Theta range for data collection (°)
Limiting indices
Reflections collected/unique [R(int)
Refinement method
]
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
1.100
[23] (a) M.I. Bruce, C. Ean, D.N. Duffy, M.G. Humphrey, G.A. Koutsantonis, J.
Organomet. Chem. 295 (1985) C40;
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0518; wR2 = 0.0947
R1 = 0.0928; wR2 = 0.1171
0.658 and ꢁ0.424
Largest difference peak and hole (e Åꢁ3
)
(b) M.I. Bruce, P.A. Humphrey, M.R. Snowe, E.R.T. Tiekink, J. Organomet. Chem.
303 (1986) 417;

M.H. Garcia et al. / Journal of Organometallic Chemistry 694 (2009) 2888–2897
2897
(c) M.I. Bruce, A. Catlow, M.G. Humphrey, G.A. Koutsantonis, M.R. Snow, E.R.T.
Tiekink, J. Organomet. Chem. 388 (1988) 59;
(d) W.A. Schenk, T. Stur, E. Dombrowski, Inorg. Chem. 31 (1992) 723;
(e) W.H. Pearson, J.E. Shade, J.E. Brown, E. Bitterwolf, Acta Crystallogr. C (1996)
1106.
[30] Ziss, J.F. Nicoud, M. Coquillay, J. Chem. Phys. 81 (1984) 4160.
[31] D.D. Perrin, W.L.F. Amarego, D.R. Perrin, Purification of Laboratory Chemicals,
2nd ed., Pergamon, New York, 1980.
[32] G.S. Ashby, M.I. Bruce, I.B. Tomkins, R.C. Wallis, Aust. J. Chem. 32 (1979) 1003.
[33] I.V. Nelson, R.T. Iwamoto, Anal. Chem. 35 (1961) 867.
[24] (a) J.C. Daran, Y. Jeannin, C. Rigault, Acta Crystallogr. C 40 (1984) 249;
(b) J.F. Costello, S.G. Davies, R.M. Highcock, M.E.C. Polywka, M.W. Poulter, T.
Richardson, G.G. Roberts, J. Chem. Soc., Dalton Trans. (1997) 105.
[25] C.M. Duff, G.A. Heath, A.C. Willist, Acta Crystallogr. C 46 (1990) 2320.
[26] M.H. Garcia, J.C. Rodrigues, A. Romão Dias, M.F.M. Piedade, M.T. Duarte, M.P.
Robalo, N. Lopes, J. Organomet. Chem. 632 (2001) 133.
[34] R.R. Gagné, Carl A. Koval, G.C. Lisensky, Inorg. Chem. 19 (1980) 2855.
[35] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, G. Giacovazzo, A. Guagliardi,
A.G.G. Moliterini, G. Polidoro, R. Spagna, J. Appl. Cryst. 32 (1999) 115.
[36] G.M. Sheldrick, SHELXL-97: Program for the Refinement of Crystal Structure,
University of Gottingen, Germany, 1997.
[37] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.
[27] S.K. Kurtz, T.T. Perry, J. Appl. Phys. 39 (1968) 3798.
[38] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[28] J. Ziss, J.L. Oudar, Phys. Rev. A 26 (1982) 2016.
[29] J. Ziss, J.L. Oudar, Phys. Rev. A 26 (1982) 2028.
[39] C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M.
Towler, J. Van de Streek, J. Appl. Cryst. 39 (2006) 453.