Synthesis of organometallic Ru(II) and Fe(II) complexes containing fused rings hemi-helical ligands as chromophores. Evaluation of non-linear optical properties by HRS

Article abstract of DOI:10.1016/j.jorganchem.2008.05.035

A new family of three-legged piano stool structured organometallic compounds containing the fragment η⁵-cyclopentadienyl-ruthenium(II)/iron(II) has been synthesized to evaluate the existence of electronic metal to ligand charge transfer upon coordination of the novel benzodithiophene ligands (BDT), benzo[1,2-b;4,3-b′]dithiophen-2-carbonitrile (L1) and benzo[1,2-b;4,3-b′]dithiophen-2′nitro-2-carbonitrile (L2). All the compounds were characterized by ¹H, ¹³C, ³¹P NMR, IR and UV-Vis. spectroscopies and their electrochemistry studied by cyclic voltammetry. The X-ray structures of [Ru(η⁵-C₅H₅)(PPh₃)₂(NCC₁₀H₅S₂)][PF₆] (1Ru), [Ru(η⁵-C₅H₅)(PPh₃)₂(NCC₁₀H₅S₂)][CF₃SO₃] (1′Ru), [Ru(η⁵-C₅H₅)(DPPE)(NCC₁₀H₅S₂)][PF₆] 2Ru and [Fe(η⁵-C₅H₅)(DPPE)(NCC₁₀H₅S₂)][PF₆] (2Fe) were determined by X-ray diffraction showing centric crystallization on groups P over(1, ?) and P2₁/n, respectively. Quadratic hyperpolarizabilities (β) of some of the complexes (2Fe, 2Ru and 3Fe) have been determined by hyper-Rayleigh scattering (HRS) measurements at a fundamental wavelength of 1500 nm, to minimize the probability of fluorescence due to two-photon absorption and to reduce the effect of resonance enhancement, in order to estimate static β values.

Full text of DOI:10.1016/j.jorganchem.2008.05.035

Journal of Organometallic Chemistry 693 (2008) 2987–2999
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of organometallic Ru(II) and Fe(II) complexes containing fused rings
hemi-helical ligands as chromophores. Evaluation of non-linear optical properties
by HRS
a
b
b
b,c
M. Helena Garcia a, , Pedro Florindo , M. Fátima M. Piedade , M. Teresa Duarte , M. Paula Robalo
,
*
Jürgen Heck d, Christian Wittenburg d, Jan Holtmann d, Emanuela Licandro e
a Centro de Ciências Moleculares e Materiais, Faculdade de Ciências da Universidade de Lisboa, Edificio C8, Campo Grande, 1749-016 Lisboa, Portugal
b Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
c Departamento de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa, Portugal
d Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther- King-Platz 6, D-20146 Hamburg, Germany
e Dipartimento de Chimica Organica e Industriale, Università degli Studi di Milano, Via C. Golgi, 19, 20133 Milano, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 April 2008
Received in revised form 7 May 2008
Accepted 7 May 2008
Available online 31 July 2008
A new family of three-legged piano stool structured organometallic compounds containing the fragment
5-cyclopentadienyl-ruthenium(II)/iron(II) has been synthesized to evaluate the existence of electronic
g
metal to ligand charge transfer upon coordination of the novel benzodithiophene ligands (BDT),
benzo[1,2-b;4,3-b0]dithiophen-2-carbonitrile (L1) and benzo[1,2-b;4,3-b0]dithiophen-20nitro-2-carboni-
trile (L2). All the compounds were characterized by 1H, 13C, 31P NMR, IR and UV–Vis. spectroscopies
and their electrochemistry studied by cyclic voltammetry. The X-ray structures of [Ru(g
5-C5H5)(PPh3)2-
Dedicated to the memory of Professor
Alberto Romão Dias.
(NCC10H5S2)][PF6] (1Ru), [Ru(
g g -
5-C5H5)(PPh3)2(NCC10H5S2)][CF3SO3] (10Ru), [Ru( 5-C5H5)(DPPE)(NCC10
H5S2)][PF6] 2Ru and [Fe(
g
5-C5H5)(DPPE)(NCC10H5S2)][PF6] (2Fe) were determined by X-ray diffraction
ꢀ
showing centric crystallization on groups P1 and P21/n, respectively.
Keywords:
Quadratic hyperpolarizabilities (b) of some of the complexes (2Fe, 2Ru and 3Fe) have been determined
by hyper-Rayleigh scattering (HRS) measurements at a fundamental wavelength of 1500 nm, to minimize
the probability of fluorescence due to two-photon absorption and to reduce the effect of resonance
enhancement, in order to estimate static b values.
Ruthenium(II)
Iron(II)
Benzodithiophene
Nonlinear optics
Hyper-Rayleigh scattering (HRS)
Monocyclopentadienyl complexes
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
plane, have been found of potential interest for second-order opti-
cal nonlinearities, due to the charge delocalization through a
The search for new organometallic materials with nonlinear
optical (NLO) properties has been an area of considerable interest
due to its relevance to optical device technology [1–6].
dmetal
by the families of
–
p*ligand interaction. This is widely illustrated in the literature
g
5-monocyclopentadienyl iron and ruthenium
molecular materials presenting p-nitrobenzonitriles [7–10], p-nitro-
benzoacetylides [11–13], nitrothienylacetylides [14] and thiophene
derivatives [15].
The high values of first molecular hyperpolarizability (b) found
in organometallic compounds has been related to low energy elec-
tronic metal-to-ligand or ligand-to-metal charge transfer excita-
tions. In addition, this charge transfer energy can be tuned by
variation of the metal itself and its oxidation state, ligand environ-
ment and coordination geometries in order to optimize the second
order NLO response. Significant results have been achieved in
push–pull systems in which the metal centre, bonded to a polariz-
able organic conjugated backbone (chromophore), acts as an elec-
tron releasing or withdrawing group [1–6]. In particular, structures
presenting the metal centre and the chromophore in the same
Although the first molecular hyperpolarizability of purely
organic push–pull molecules increases strongly with the length
of the conjugated chain [16,17], this is not the case for the benz-
oderivatives, due to the torsion angle between the rings. Neverthe-
less, the extension of conjugation turns out effective by insertion of
a vinylene unit between two phenyl rings. Yet, extended conju-
gated chain in systems based on thiophene rings, is expected to
present an improved planarity since the torsion angle between
rings can become quite small. In accordance, ab initio calculations
[18] suggests that for terthiophene, although the gas-phase
structure is not planar, the conformational inter-conversion energy
is very low and sensitive to the chemical environment. Also a
* Corresponding author. Tel.: +351 217500972; fax: +351 217500088.
E-mail addresses: lena.garcia@ist.utl.pt, i017@alfa.ist.utl.pt (M.H. Garcia).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.05.035

2988
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
semi-empirical calculation, indicating that the structure of bithi-
ophene becomes planar in water solution [19], supports the
assumption of easier planarity on oligothiophene compounds.
Our recent studies in complexes containing the organometallic
donor fragment [FeCp(P–P)]+ (P–P = DPPE, (+)-DIOP) and conjugated
S
O
S
i)
H
S
2
1
ii)
thiophene derived ligands, showed an improved electronic
p-cou-
plingbetweenthe
g
5-cyclopentadienylironfragmentand the
p-sys-
tem of the conjugated thiophene ligands, when compared to the
previously reported p-benzonitrile analogues [15]. As a result, the
first hyperpolarizabilities at 1.064 lm are indeed higher than for
S
S
S
H
O
iv)
3
S
4
the related benzonitrile compounds, and they could be scaled up
by increasing the conjugation length, leading to the high b 910 ꢀ
10ꢁ30 esu for the complex with three thiophene units. Nevertheless,
the increased conjugation originated by that chain-lengthening can
also be on the basis of a lowering of the charge-transfer (CT) effi-
ciency, as was suggested by our published electrochemical and spec-
troscopic experimental data and also by the solvatochromic studies.
The constancy of b0 ꢂ 100 ꢀ 10ꢁ30 esu upon chain-lengthening is a
consequence of the compensation of two favourable effects, namely
the increasing of conjugation length and the lowering of the charge
transfer efficiency [15].
iii)
v)
S
S
NO
2
C
N
S
S
5
O N
2
L1
iii)
S
Therefore, it seems that the exploitation of promising thiophene
based ligands for NLO purposes, should not be limited to the chain
lengthening alternative, within this family of organometallic com-
pounds, but instead, other alternatives seem to be quite pertinent.
In this work we explore the potentialities of new benzo[1,2-
b;4,3-b0]dithiophene based chromophores where the fused rings
structure guarantees the rigidity of the ligand to be coordinated
on the same plan of the metal centre, in a family of cyclopentadi-
enyl iron/ruthenium derivatives.
C
N
S
L2
i) 1- dry THF, TiCl4, - 20 ºC ; 2- Zn dust, reflux; ii) hν, I2, air, toluene,
r.t.; iii) HNO3/Ac2O; iv) 1- dry THF, N2, - 78 ºC, n-BuLi; 2- DMF;
v) 1-H2 NOH.HCl, py, -30 ºC; 2-Ac2O, reflux
Scheme 1.
Although some reports concerning the NLO properties of thio-
phene-based organometallic complexes have been published, they
are mainly about ferrocenyl and tricarbonyl chromium arene
derivatives [20–26] in which the metal is unfavourably placed out-
side of the conjugation plane [27], in contrast with the present
complexes and our previously reported oligothiophene containing
complexes [15].
A new class of compounds for second-order NLO materials was
developed, combining the organometallic donor fragment [MCp-
(L_L)]+, (M = Ru(II), L_L = DPPE, 2PPh3and TMEDA; M = Fe(II),
L_L = DPPE) with the benzodithiophene functionalized molecules
(BDT), namely benzo[1,2-b;4,3-b0]dithiophen-2-carbonitrile (L1)
and benzo[1,2-b;4,3-b0]dithiophen-20-nitro-2-carbonitrile (L2).
The coligand TMEDA (N,N,N0,N0-tetramethyl-ethylenediamine) was
introduced in these studies to evaluate the ability of [RuCp(TME-
DA)]+ fragment as donor group comparatively to the well studied
[RuCp(P_P)]+. Spectroscopic and cyclic voltammetry data were ana-
The new nitrile ligands, obtained with yields of 84% (L1) and
46% (L2), and the compounds 3 and 5, were fully characterized
by IR, 1H and 13C NMR spectroscopies and the elemental analysis
were in accordance with the proposed formulations. The solid state
FT-IR spectra (KBr pellets) showed the characteristic stretching
vibration of the nitrile functional group at ꢂ2215 cmꢁ1 for both
compounds. In addition, L2 presented also the vibrations attrib-
uted to the NO2 group, at ꢂ1515 and 1335 cmꢁ1
.
2.2. Synthesis of the Ru(II)/Fe(II) complexes
Complexes of general formula [M(g
5-C5H5)(LL)(BDT)][Z], with
Z = PFꢁ6 and/or CF3SO3ꢁ; (LL) = DPPE, 2PPh3 and TMEDA when
M = Ru(II) and (LL) = DPPE when M = Fe(II); BDT = benzo[1,2-b;4,3-
b0]dithiophen-2-carbonitrile (Y = H) and benzo[1,2-b;4,3-b0]dithio-
phen-20-nitro-2-carbonitrile (Y = NO2), were prepared, as shown in
Scheme 2, by halide abstraction with TlPF6 (or AgCF3SO3) from the
lyzed to get some understanding about the electronic
between the
5-cyclopentadienyliron/ruthenium fragment and
the -system of the benzodithiophene derived ligands. Quadratic
p-coupling
g
p
parent neutral complexes [M(g
5-C5H5)(LL)X] (M = Fe(II), X = I;
hyperpolarizabilities of three compounds of this family have been
determined by hyper-Rayleigh scattering (HRS) measurements at
the fundamental wavelength of 1500 nm. These measurements re-
vealed that the first hyperpolarizabilities are lower than expected.
M = Ru(II), X = Cl ), in acetone, in the presence of an adequate excess
of the corresponding nitrile.
The reactions were carried out at reflux, stirring overnight un-
der inert atmosphere. The compounds were recrystallized by slow
diffusion of n-heptane or n-hexane in acetone or dichloromethane
solutions, giving crystalline yellow or orange products. With the
exception of compound [Ru(g
5-C5H5)(TMEDA)(NCC10H5S2)][PF6]
2. Results and discussion
(4Ru), which was very air sensitive, all the compounds were fairly
stable to air and moisture, either in the solid state or in solution
and were obtained in good yields (70–90%). Attempts to character-
2.1. Synthesis of the benzodithiophene derived ligands (BDT)
ize the iron analogue [Fe(g
5-C5H5)(TMEDA)(NCC10H5S2)][PF6] were
The synthesis of the BDT ligands, benzo[1,2-b;4,3-b0]dithio-
phen-2-carbonitrile (L1) and benzo[1,2-b;4,3-b0]dithiophen-20-ni-
tro-2-carbonitrile (L2) is summarized in Scheme 1. The aldehyde
starting material was prepared with good yield, by generation of
unsuccessful, due to the instability of the compound. The formula-
tion of all the new compounds is supported by analytical data,
FT-IR and 1H, 13C, 31P NMR spectroscopic data. The solid state FT-
IR spectra (KBr pellets) of the complexes presented a large number
of bands which identify the presence of the various coligands.
the benzodithiophene
a-anion with n-BuLi and subsequent treat-
ment with DMF, following Ref. [28].

M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
2989
Table 1
Selected 1H NMR data for BDT ligands, free and coordinated to Ru/Fe organometallic
Y
fragments
TlZ or AgZ
Compound
Proton number
S
X
M
[Z]
H11
H10
H7
H6
H3
Cp
(CH ) CO
3 2
L
C
N
M
L
L1
8.05
8.12
8.19
8.07
8.07
8.05
8.05
8.06
8.02
7.86
7.87
8.05
9.08
8.71
8.09
8.09
8.12
7.93
7.94
8.12
8.35
8.24
8.25
8.29
8.28
8.19
8.18
8.25
8.26
8.18
8.93
8.58
8.64
7.59
7.53
8.94
8.95
7.83
S
L
1Ru
10Ru
2Ru
2Fe
4Ru
L2
4.75
4.78
4.99
4.63
4.54
L
1Ru M=Ru(II); (LL) = 2PPh3; Y=H ; Z= PF6
1’Ru M=Ru(II); (LL) = 2PPh3; Y=H ; Z= CF3SO3
2Ru M=Ru(II); (LL) = DPPE; Y=H; Z= PF6
2Fe M=Fe(II); (LL) = DPPE; Y=H; Z= PF6
3Fe M=Fe(II); (LL) = DPPE; Y=NO2; Z= PF6
4Ru M=Ru(II); (LL) = TMEDA; Y=H; Z= PF6
3Fe
4.76
shielded 0.37 ppm in 3Fe, and only 0.18 ppm in 2Fe. The upfield
shift of these protons, with special relevance for H10, indicates a
shielding due to an electronic flow throughout the ligand towards
the NO2 electron withdrawing group, coming from the metal cen-
Scheme 2.
tre, due to a
p-backdonation effect involving the coordinated ni-
trile group. This
p
-backdonation flow also confirmed by the NC
Typical bands were used to confirm the presence of the cyclopen-
tadienyl ligand (ꢃ3060 cmꢁ1), the PF6ꢁ anion (840 and 560 cmꢁ1
)
stretching frequencies on the infrared spectra of all the com-
pounds, was well illustrated by the negative shift of ꢂꢁ20 cmꢁ1
the CF3SOꢁ3 anion (1253 cmꢁ1) and the coordinated nitrile (
mNC from
2215 to 2190 cmꢁ1) in all the studied complexes. As observed before
for other ruthenium and iron related compounds, negative shifts up
observed for mNC in compound 3Fe. Nevertheless this effect of back-
donation leads to an increased electronic density through the coor-
dinated ligand only for compound 3Fe, since for all the other
compounds this effect was only relevant for the thiophene ring
functionalised with the nitrile, i.e. the ring closest to the metal cen-
tre. Moreover, in the case of the TMEDA derivative 4Ru, the effect
to ꢁ20 cmꢁ1 were found for
mNC by comparison to the corresponding
values of the uncoordinated nitrile. This effect has been attributed to
p
-backdonation due to
p bonding between the d orbitals of the me-
tal and the
p
* orbital of the nitrile group, this leading to a decreased
of
p-backdonation was only noticed by the measurable negative
N„C bond order [8].
shift of ꢁ20 cmꢁ1on the N„C stretching vibration since the 1H
1H NMR chemical shifts of the cyclopentadienyl ring are dis-
played in the characteristic range of monocationic ruthenium(II)
and iron(II) complexes. The coordination of the BDT derived ni-
triles leads to a shielding of most of the protons, particularly the
one bonded to the adjacent carbon of the NC group (H3 in Fig. 1).
The upfield shift was more significant along the family 1Ru to
3Fe. For compound 1Ru, with PPh3 as coligands, a maintenance
of the positions of the aromatic protons upon coordination of the
ligand is observed, with exception of H3, for which a shift of
ꢁ0.35 ppm was observed. Nevertheless, the analogous compound
2Ru, with the better donating coligand DPPE replacing PPh3,
showed a negative shift of ꢁ1.34 ppm for H3 and also small nega-
tive shifts for all the protons of the BDT ligands (see Table 1).
The shielding effect on H3 in the coordinated ligand, became
more evident for the iron analogue 2Fe, for which H3 was shifted
to higher field by 1.4 ppm, although the other protons suffered
about the same shielding as the 2Ru analogue. The electron with-
drawing effect of NO2 in compound 3Fe causes clearly an electronic
delocalization throughout the coordinated ligand. Comparison of
the chemical shifts of 3Fe and 2Fe to the ones of the respective
uncoordinated ligands L1 and L2, showed that while the proton
H3, adjacent to CN group, was shielded 1.12 ppm (3Fe) and
1.40 ppm (2Fe) the proton H10, adjacent to the NO2 group, was
NMR chemical shifts of the chromophore nitrile ligand remained
unchanged after coordination. The effect of p-backdonation was al-
ready found in our previous studies involving monocyclopentadie-
nyliron(II) and ruthenium(II) phosphine containing fragments
possessing other chromophore ligands also coordinated by the ni-
trile functional group [7–10].
13C NMR data for this family of compounds confirm the evi-
dence found for proton spectra. The Cp ring chemical shifts are in
the range usually observed for Ru(II) and Fe(II) cationic derivatives,
a significant deshielding ( up to ꢂ14 ppm) being observed on the
carbon of the N„C functional group upon coordination, except
for compound 4Ru which chemical shift remained unchanged after
coordination. All the other carbons of the chromophore ligand
were only slightly deshielded or remained almost unchanged for
the entire family of compounds.
31P{1H} NMR data of the complexes showed a single sharp sig-
nal for the phosphine coligands revealing an expected deshielding
upon coordination, according to the
ligands.
r donor character of these
2.3. UV–Vis studies
The optical absorption spectra of all complexes [M(g5
-
C5H5)(L_L)(BDT)][PF6] were recorded in 10ꢁ4 M dichloromethane
and methanol solutions (Table 2) in order to identify the M L
charge transfer and
complexes.
p–
p* absorption bands expected for these
The electronic spectra of all the compounds showed two intense
absorption bands in the UV region, attributed to electronic transi-
tions occurring both in the organometallic fragment {MCp(LL)}+
(k ꢂ 235 nm) and in the BDT coordinated chromophores (k
ꢂ280–340 nm). Additionally, for the compounds containing DDPE
as coligand, namely [Ru(
C5H5)(DPPE)(L1)][PF6] (2Fe) and [Fe(
g -
5-C5H5)(DPPE)(L1)][PF6] (2Ru), [Fe(g5
g
5-C5H5)(DPPE)(L2)][PF6]
(3Fe), evidence was found for the existence of charge transfer
(CT) bands, appearing as shoulders on the intense absorption band
Fig. 1. Numbering scheme for NMR spectral assignments of Ru/Fe complexes and
free BDT ligands.

2990
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
Table 2
ison of these electronic spectra is shown in Fig. 3. The effect of the
Optical spectra data for complexes [M(g
5-C5H5)(L_L)(BDT)][PF6], 1Ru, 2Ru, 2Fe, 3Fe,
introduction of one acceptor group on benzo[1,2-b;4,3-b0]dithioph-
ene (3), either NC or NO2, leads to the expected bathochromic shift
on the observed bands, as can be observed on the spectra of L1 and
compound 5. Moreover, when both groups are competing in the
same molecule, such as the case of L2, the stronger accepting effect
of NO2 is predominant as can be clearly observed by comparison of
L2 and 5.
4Ru, and the free L1 and L2 ligands, in dichloromethane and methanol (ca. 10ꢁ4 M)
solutions
Compound
kmax (nm) (e )
, Mꢁ1 cmꢁ1
CH2Cl2
MeOH
–
Benzo[1,2-b;4,3-b0]dithiophene (3)
Benzo[1,2-b;4,3-b0]-2-nitrodithiophene (5)
251 (12,500)
289 (14,300)
299 (sh)
264 (4800)
285 (390)
379 (7800)
269 (12,600)
276 (sh)
–
–
2.4. X-ray structural studies of complexes 1Ru, 10Ru, 2Ru and 2Fe
Compounds [Ru(
g
5-C5H5)(PPh3)2(NCC10H5S2)][PF6] ꢄ (CH3)2CO
Benzo[1,2-b;4,3-b0]dithiophen-
2-carbonitrile (L1)
(1Ru) and [Fe(
g
5-C5H5)(DPPE)(NCC10H5S2)][PF6] ꢄ (CH3)2CO ꢄ H2O
315 (24,300)
349 (23,800)
351 (23,500)
336 (19,000)
320 (13,200)
347 (sh)
(2Fe) were recrystalized by slow diffusion of n-heptane in acetone
[Ru(
[Ru(g5-C5H5)(PPh3)2(L1)][CF3SO3] (10Ru)
[Ru(
5-C5H5)(dppe)(L1)][PF6] (2Ru)
5-C5H5)(dppe)(L1)][PF6] (2Fe)
g
5-C5H5)(PPh3)2(L1)][PF6] (1Ru)
345 (23,400)
346 (22,900)
345 (22,400)
317 (11,200)
347 (sh)
solutions and compound [Ru(g
5-C5H5)(DPPE)(NCC10H5S2)][PF6]
(2Ru) by slow diffusion of n-hexane in an acetone solution, afford-
ing suitable crystals for X-ray diffraction studies. Orange crystals of
g
[Fe(g
[Ru(
g
5-C5H5)(PPh3)2(NCC10H5S2)][CF3SO3] ꢄ 0.5CH2Cl2 (10Ru) were
367 (sh)
363 (sh)
obtained by slow diffusion of n-hexane in a dichloromethane solu-
tion. This compound was found to crystallize with two indepen-
dent molecules in the asymmetric unit (Z0 = 2). Selected bond
distances and angles are presented in Table 3, as well as the torsion
angles.
423 (sh)
416 (sh)
[Ru(g
5-C5H5)(tmeda) (L1)][PF6] (4Ru)
269 (11,700)
315 (19,000)
272 (6800)
364 (6400)
361 (15,800)
460 (sh)
267 (11,700)
313 (17,700)
–
Benzo[1,2-b;4,3-b0]ditiophen-20-nitro-
2-carbonitrile (L2)
[Fe(g
5-C5H5)(dppe)(L2)][PF6] (3Fe)
355 (14,600)
460 (sh)
The molecular structures of the cations 1Ru+, 10Ru+, 2Ru+ and
2Fe+ are shown in Fig. 4–7.
sh: shoulder.
All the complexes present the usual three-legged piano stool
geometry around the metal atom, confirmed by the N–M–P angles,
close to 90° (see Table 3) with the remaining C(g
5-centroid)–M–X
of the BDT ligand, in the visible region of the spectra. The batho-
chromic shift observed for most of the bands when dichlorometh-
ane was substituted by methanol is compatible with the origin of
these bands. Further studies in solvents of different polarities, to
examine the solvatochromic effect, were limited by the low solu-
bility of the compounds. Fig. 2 depicts the electronic spectra of
the iron compounds 2Fe and 3Fe, together with the spectra of
the related free BDT ligands, L1 and L2 for comparison.
For a better understanding of the electronic spectra of the stud-
ied compounds and the L1 and L2 uncoordinated ligands, addi-
tional studies were also carried out on the parent unsubstituted
chromophore benzo[1,2-b;4,3-b0]dithiophene (3), and on the re-
lated compound benzo[1,2-b;4,3-b0]-2-nitrodithiophene (5) (see
Scheme 1) to evaluate the effect of the substituting groups NC
and NO2 on the benzodithiophene parent molecule 3. The compar-
(with X = N or P) angles between 117.84(5)° and 130.6(6)°. Also, in
all compounds, the benzodithiophene ligand is essentially planar
with torsion angles between rings ranging from 175.0(5)° to
179.9(5)° (see Table 3).
All the Ru compounds show bond distances Ru–N as well the
N–C placed in the range of the ones found for similar cyclope-
ntadienyldiphosphine complexes with thiophene based nitriles
ligands [29] (Ru–N 1.977–2.023 Å and N–C 1.139–1.178 Å) but
smaller, in general, than the ones found in cyclopentadienyldi-
phosphine complexes with NCPh ligands presented in Table 4.
Although some results in this table, such as for example Ru–N dis-
tances, might suggest some evidence for
p-backdonation on the
compounds of the present study, compared to other related ni-
triles, a careful study of the other coordination geometrical param-
Fig. 2. Electronic spectra of [Fe(
C5H5)(DPPE)(L2)][PF6]3Fe (—), compared to the free ligands L1 (cdots) and L2
g
5-C5H5)(DPPE)(L1)][PF6]2Fe (–ꢄ–), and [Fe(g5
-
Fig. 3. Electronic spectra of free ligands L1 (–––) and L2 (–ꢄ–), compared to the
unsubstituted benzodithiophene, 3 (—), and nitrobenzodithiophene, 5 (ꢄ ꢄ ꢄ).
(–ꢄꢄ–).

M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
2991
Table 3
Detailed analysis of the geometric parameters in the four com-
pounds, led us to notice that in compounds 2Ru and 2Fe, the BDT
ligand is almost perpendicular with respect to the plane defined by
the metal atom, the centroid of the cyclopentadienyl and the N1
and C1 atoms making a dihedral angle of 83.4(1)° and 86.5(1)°,
respectively, while for 1Ru the thiophene lies in a slightly twisted
arrangement (dihedral angle 34.7(2)°). This, we thought, was due
to the larger cone angle of the triphenylphosphine ligands (145°)
in comparison with the cone angle of the diphenylphosphinoeth-
ane ligand (125°). However, in compound 10Ru, that has coordi-
nated triphenylphosphine ligands, the two independent
molecules in the unit cell, Fig. 8, are quite different: molecule
labelled A the thiophene ligand has an arrangement similar to
compounds 2Ru and 2Fe, i.e., the thiophene ligand is almost per-
pendicular with respect to the plane defined above, dihedral angle
of 71.2(1)°, while the molecule labelled B has an arrangement anal-
ogous to the cation of compound 1Ru where the BDT ligand is
almost coplanar to this plane (dihedral angle 22.1(1)°). In a survey
in CSD [34] of similar organometallic compounds with either Ru or
Fe, PPh3, DPPE and nitriles or acetylides derivatives, no trend was
observed. So the different arrangements can be attributed to an
interplay of energetic stability and stereochemical hindrance.
Analysing the stereochemical arrangements, the geometrical
parameters to take in account should be the cone angle, the mono
or bidentate behaviour of the phosphine, the size of the ligand and
the supramolecular interactions in the crystal packing.
The different position of the BDT ligand in molecule A and B of
10Ru complex can be explained by the different supramolecular
hydrogen bonding interactions between the CF3SO3 anion and
the ligand. In anion B only one of the oxygen atoms (O1B) interacts
with two different hydrogens atoms, one from the adjacent carbon
(C3B) of the BDT ligand and the other from the C15B carbon of the
Cp ligand, forming a chelated hydrogen bond [35]. In the case of
anion A these interactions are also established but through two dif-
ferent oxygen atoms of the triflate anion (O2A and O3A) with the
hydrogen H3A of the BDT ligand and the H15A of the Cp ligand
of cation A (see Table 5 and Fig. 8).
Selected bond lengths and bond and torsion angles for 1Ru, 10Ru, 2Ru, 2Fe
Compound
1Ru
10Ru
2Ru
2Fe
Bond lengths (Å)
M–Cp
1.8539(12)
1.995(6)
1.117(10)
2.343(2)
2.352(2)
1.8590(5);
1.8648(6)
2.025(5);
2.016(6)
1.153(8);
1.151(9)
2.3313(17);
2.3258(18)
2.3600(17);
2.3334(18)
1.8639(4)
2.018(4)
1.7132(7)
1.8639(4)
1.154(6)
M–N(1)
N(1)–C(1)
M(1)–P(1)
M(1)–P(2)
C(ar)–C(ar)
1.149(6)
2.2918(13)
2.3041(12)
2.2145(15)
2.2088(15)
1.357–1.414 1.349–1.413 1.358–1.407 1.366–1.391
Angles (°)
N(1)–M(1)–P(1)
91.27(18)
87.82(19)
104.83(7)
126.53(18)
117.84(5)
121.48(6)
176.6(7)
87.61(15);
88.76(16)
92.92(15);
94.90(17)
99.33(6);
100.57(6)
126.55(14);
124.63(15)
121.52(5);
119.98(5)
120.75(4);
120.82(5)
176.3(5);
169.8(6)
87.41(12)
92.82(11)
83.76(4)
92.66(13)
84.73(13)
86.83(6)
N(1)–M(1)–P(2)
P(2)–M(1)–P(1)
Cp–M(1)–N(1)
Cp–M(1)–P(1)
Cp–M(1)–P(2)
M(1)–N(1)–C(1)
N(1)–C(1)–C(2)
124.64(11)
129.39(3)
126.03(4)
176.7(4)
124.94(12)
124.48(5)
130.55(5)
176.6(4)
176.0(9)
173.4(7);
178.6(7)
176.3(6)
178.1(5)
Torsion angles (°)
M(1)–N(1)–C(1)–C(2) 43(21)
ꢁ39(13);
ꢁ127(34)
ꢁ107(6);
164(35)
ꢁ116(9)
73(9)
133(13)
ꢁ175(10)
6(15)
N(1)–C(1)–C(2)–C(3)
N(1)–C(1)–C(2)–S(1)
C(1)–C(2)–C(3)–C(4)
C(2)–C(3)–C(4)–C(9)
ꢁ43(13)
137(12)
177.8(7)
ꢁ176.9(9)
68(6);
ꢁ103(9)
ꢁ175.0(5)
176.6(5)
ꢁ16(36)
175.6(6);
176.6(7)
ꢁ179.9(6);
ꢁ176.7(7)
ꢁ177.7(4)
177.5(5)
The crystal packing of 1Ru discloses a very interesting supra-
molecular array, that displays holes in the a direction (Fig. 9), sug-
gesting that this network can possibly be used as a selectively
storing guests material [36,37]. This particular array is formed by
intermolecular hydrogen bonds between one fluorine atom (F3)
of the anion with the previously mentioned hydrogen atoms of
the carbons of the BDT and carbon of the Cp, respectively H3 and
H11, like in molecule A of the 10Ru complex; but it is further ex-
tended, due to the interaction of the anion and the solvent mole-
cule (F2ꢄ ꢄ ꢄH20f-C202) and the short hydrogen bond of the
oxygen of the solvent molecule with both H7 and H12, again from
the BDT and Cp ligands of the cation, respectively (see Table 5).
This supramolecular geometry implies that two cation molecules
have no direct connection and their interactions are always medi-
ated by the presence of the anion and solvent molecule, giving rise
to the observed porosity, with holes of about 8 Å. This arrangement
seems to be a result of the configuration of the BDT ligand towards
the plane defined by the metal atom, the centroid of the cyclopen-
tadienyl and the N1 and C1 atoms, as in molecule B of the com-
pound 10Ru.
Fig. 4. ORTEP of the cation of compound Ru(
1Ru.
g
5-C5H5)(PPh3)2(L1)][PF6] ꢄ (CH3)2CO,
As expected, the variation of the counter-ion in the cationic
complex [Ru(
leads to very different arrays in the solid state, as can be seen on
Fig. 9. While 1Ru discloses very interesting supramolecular
g
5-C5H5)(PPh3)2(NCC10H5S2)]+ from PFꢁ6 to CF3SO3ꢁ
eters do not led us to any conclusion or evidence about the signif-
icance of this effect.
a
‘‘Accordingly, also in complex 2Fe the Fe–N and N–C bond
lengths (1.8639(4) and 1.154(6) Å, respectively) are within the val-
ues found for complex [CpFe(DPPE)(NCSC4H2CH@CHSC4H3)][PF6]
(1.869(9) and 1.152(12) Å, respectively) [29] where also only spec-
troscopic evidence for back-donation was found”.
arrangement, the crystal packing of the compound 10Ru has a much
more closed packing, due to the high number of hydrogen bonds of
both anions present in the asymmetric unit. CF3SO3 anion B has a
bifurcated hydrogen bond with molecule B, as described above,
while atom O2B interacts with a phenyl group of a symmetry related

2992
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
Fig. 5. ORTEP of the cation of compound Ru(g5-C5H5)(PPh3)2(L1)][CF3SO3] ꢄ 0.5CH2Cl2, 10Ru. The numbering A and B shows the two different independent molecules in the
unit cell (see text).
by a hydrogen bond between the external sulphur of the BDT li-
gand with an hydrogen of the ethylene fragment of the phosphine,
leading to the formation of a pseudo-dimeric motif (Fig. 10).
The analysis of the crystalline structure of compound 2Fe re-
veals that it also forms pseudo-dimeric units, via intermolecular
interactions with the PF6, almost bisecting the ab plane. These di-
mers are reinforced through
(Fig. 11).
p–p interactions of the BDT ligand
2.5. Electrochemical studies
In order to obtain an insight on the electron richness of the
organometallic fragment and on the coordinated BDT ligands, the
electrochemical behaviour of Ru(II) and Fe(II) compounds and also
the free BDT chromophores L1 and L2, were studied by cyclic vol-
tammetry in dichloromethane and acetonitrile, between the limits
imposed by the solvents. Similar studies were also carried out on
the related molecules benzo[1,2-b;4,3-b0]dithiophene (3) and ben-
zo[1,2-b;4,3-b0]-20-nitrodithiophene (5) (see Scheme 1) for a better
understanding on the behaviour of the ligands L1 and L2. Tables 6
and 7 summarize the electrochemical data obtained for all the
studied compounds in dichloromethane and acetonitrile, respec-
Fig. 6. ORTEP of the cation of compound [Ru(g
5-C5H5)(dppe)(L1)][PF6], 2Ru.
tively, at room temperature and at the scan rate of 200 mV sꢁ1
.
Studies carried out at scan rates of 50 and 100 mV sꢁ1 showed
the same results. The electrochemistry of the free ligand L1 was
characterized by an irreversible oxidation at Epa value of +1.48 V
in dichloromethane and no reductive processes were found at neg-
ative potentials. The behaviour of L1 in acetonitrile was quite dif-
ferent, since besides the oxidation process occurring at
Epa = +1.38 V, with a very weak counterpart at Epc = +1.28 V, one
reductive process was also observed presenting a cathodic wave
at Epc = ꢁ1.70 V with a very small counterpart at Epa = ꢁ1.56 V.
The related compound 3 presented only one anodic process occur-
ring in both solvents at a somehow higher potential than L1,
Epa = +1.55 V (CH2Cl2) and Epa = +1.45 V (CH3CN). For this com-
pound, no reductive processes were observed. The cyclic voltamo-
gram of the ligand L2, shows clearly the influence of the good
acceptor NO2 group, presenting two irreversible redox processes
at Epc = ꢁ0.88 (Epa = ꢁ0.76 V) and Epc = ꢁ1.29 (Epa = ꢁ1.17 V) in
dichloromethane, and also one additional cathodic wave at
Epc = ꢁ1.50 V. In acetonitrile the three processes were also ob-
served at lower potentials, displaying two irreversible processes
at Epc = ꢁ0.85 (Epa = ꢁ0.77) V and Epc = ꢁ1.26 (Epa = ꢁ1.14) V. In
this solvent, the third reducing process at Epc = ꢁ1.57 V showed a
small anodic counterpart at Epa = ꢁ1.43 V. As would be expected,
the related molecule 5 shows also two irreversible redox processes
Fig. 7. ORTEP of the cation of compound Fe(
CO ꢄ H2O, 2Fe.
g
5-C5H5)(dppe)(L1)][PF6] ꢄ (CH3)2-
cation B and, moreover, a fluorine atom of the same anion still inter-
acts with a phenyl group of another symmetry generated B molecule.
At the same time, two of the oxygen atoms (O2A and O3A) of anion A
interact with one A cation, while O1A interacts with another A cat-
ion. This complex tridimensional hydrogen bonds system explains
the two diverse packings obtained. This is further complicated due
to the presence of one dichloromethane molecule, which interacts
with both cations at the same time.
Compound 2Ru forms chains along the a direction due to the
interaction of the PF6 molecule connecting two successive cations
(see Table 5). This supramolecular packing is further enhanced

M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
2993
Ref.
Table 4
Comparison the geometrical parameters for ruthenium and iron derivatives containing MCp(phosphine) nitrile cations and the ones presented in this work
Compound
M–N (Å)
N–C (Å)
C–C (Å)
M–N–C (°)
N–C–C (°)
[RuCp(PPh3)2(NCPh)][PF6]
2.037(1)
2.023(2)
2.031(13)
2.031(1)
2.037(1)
1.995(6)
2.025(5);
2.016(6)
2.018(4)
1.892(2)
1.874(11)
1.875(13)
1.902(9)
1.8639(4)
1.145(2)
1.146(2)
1.137(18)
1.149(2)
1.145(2)
1.117(10)
1.153(8);
1.151(9)
1.149(6)
1.141(3)
1.129(14)
1.390(19)
1.142(15)
1.154(6)
1.440(2)
1.442(3)
1.42(2)
171.70(12)
171.24(15)
177.2(12)
173.52(14)
171.7(1)
176.6(7)
176.3(5);
169:8(6)
177.84(16)
177.8(2)
178.6(15)
175.15(18)
177.8(2)
176.0(9)
173.4(7);
178.6(7)
176.3(6)
174.5(2)
177.4(15)
178.0(16)
172.8(13)
178.1(5)
[30]
[30]
[14]
[30]
[31]
[RuCp(PPh3)2(NCPhNO2)][PF6]
[RuCp{(+)-DIOP}(NCPhNO2)][PF6]
[RuCp(PPh3)2(NCPhNMe2)][PF6]
[RuCp(PPh3)2{NCPh}][PF6]
1.424(2)
1.440(2)
1.464(12)
1.402(9);
1.416(10)
1.400(7)
1.444(3)
1.42(2)
a
[RuCp(PPh3)2(L1)][PF6] ꢄ (CH3)2CO
–
–
a
[RuCp(PPh3)2(L1)][CF3SO3] ꢄ 0.5CH2Cl2
a
[RuCp(DPPE)(L1)][PF6]
[FeCp(DPPE)(NCPh)]PF6
[FeCp(DPPE)(NCPhNO2)][PF6]
[FeCp(DPPE)(NCPhNO2)][I]
[FeCp(PROPHOS)(NCPhNO2)][PF6]
[FeCp(DPPE)(L1)][PF6] ꢄ (CH3)2CO ꢄ H2O
176.7(4)
–
172.16(18)
176.6(11)
175.6(11)
172.0(10)
176.6(4)
[30]
[9]
1.40(2)
1.421(15)
1.427(8)
[32]
[33]
a
–
a
This work; DPPE = 1,2-bis(diphenylphosphino)ethane; PROPHOS = (R)-(+)-1,2-Bis(diphenylphosphino)- propane.
found spectroscopic data, in particular the 1H NMR experimental
results discussed before for compound 3Fe.
The general behaviour of the ruthenium compounds in both sol-
vents was characterised by one oxidation process RuII/RuIII, with
Epa in the range 1.10–1.40 V with a very small cathodic counter-
part, while the iron analogues show a non reversible FeII/FeIII redox
process, with Ep/2 placed in the range 0.70–0.90 V. For all the stud-
ied compounds, the electrochemical processes were easier in ace-
tonitrile, as expected. Comparison of the values presented on
Tables 6 and 7 for compounds possessing the coordinated BDT li-
gand L1, namely 1Ru, 2Ru and 2Fewith the ones of the free com-
pound L1, reveals some differences. In fact, as mentioned above,
although no reductive processes were observed for L1 in CH2Cl2,
its electrochemical behaviour in CH3CN was more complex, show-
ing a reductive process at Epc = ꢁ1.70 V with the corresponding
anodic wave at Epa = ꢁ1.56 V. After coordination, this reductive
process attributed to ligand L1 occurs at less negative potentials
for all the complexes possessing this ligand at Epc = ꢁ1.53 V for
1Ru, Epc = ꢁ1,61 V for 2Ru, and Epc = ꢁ1.55 V for 2Fe, revealing
the easier reducing ability of the coordinated ligand L1.
Fig. 8. Supramolecular interactions responsible for the different positioning of the
BDT ligand towards the plane defined by the metal atom, the centroid of the
cyclopentadienyl and the N1 and C1 atoms, in the two molecules of the unit cell of
10Ru complex.
Regardless all the spectroscopic data for compound 2Fe point
out for some evidence of
p-backbonding, corroborated by the X-
ray data (Fe–N shorter distance than usual and the NC distance
compatible with a double bond), the electrochemical behaviour
of this compound is similar to the ruthenium related ones.
Table 5
Intermolecular contacts [Å] for compounds 1Ru, 10Ru, 2Ru, 2Fe
1Ru
10Ru
The electrochemical behaviour of compounds 3Fe and free li-
gand L2, in dichloromethane, is illustrated in Fig. 12. Comparison
of the electrochemistry of compounds 2Fe and 3Fe shows that
compound 3Fe oxidizes ꢂ25 mV at higher potential than 2Fe, in
both solvents, suggesting that the metal centre is more deficient
in electronic density. Accordingly, in compound 3Fe the reduction
on the coordinated ligand L2 became more difficult, showing only
one reductive process that occurs at Epc = ꢁ0.90 V (CH2Cl2) instead
the three reductive processes observed for free L2 (Epc = ꢁ0.88;
ꢁ1.29 and ꢁ1.50 V) in the same solvent. These results can be re-
lated to an easier electronic flow from the metal centre, through
the ligand, towards the nitro group, this being in good agreement
with the 1H and 13C NMR, FT-IR and UV–Vis spectroscopic data,
C3–H3ꢄ ꢄ ꢄF3
2.522(9)
2.588(13)
2.577(11)
2.491(8)
2.459(10)
C3A–H3Aꢄ ꢄ ꢄO2A
C15A–H15Aꢄ ꢄ ꢄO3A
C3B–H3Bꢄ ꢄ ꢄO1B
C15B–H15Bꢄ ꢄ ꢄO1B
2.531(7)
2.551(6)
2.416(9)
2.453(8)
C3–H3ꢄ ꢄ ꢄF2
C11–H11ꢄ ꢄ ꢄF3
C7–H7ꢄ ꢄ ꢄO1
C12–H12ꢄ ꢄ ꢄO1
2Ru
2Fe
C13–H13Aꢄ ꢄ ꢄS2
C223–H223ꢄ ꢄ ꢄF5
C224–H224ꢄ ꢄ ꢄF3
C226–H226ꢄ ꢄ ꢄF4
C216–H216ꢄ ꢄ ꢄF4
C216–H216ꢄ ꢄ ꢄF5
C12–H12ꢄ ꢄ ꢄF4
2.917(2)
2.643(5)
2.435(5)
2.620(5)
2.571(4)
2.654(6)
2.584(5)
C5ꢄ ꢄ ꢄC9
3.383(12)
2.588(4)
2.561(3)
2.470(3)
C10–H10ꢄ ꢄ ꢄF5
C6–H6ꢄ ꢄ ꢄF2
C213–H213ꢄ ꢄ ꢄF2
which suggest an increase of
p-backdonation on compound 3Fe
when compared with 2Fe.
at Epc = ꢁ0.98 V (Epa = ꢁ0.83 V), in dichloromethane, revealing the
presence of NO2. These processes occurred in acetonitrile at
Epc = ꢁ0.94 V (Epa = ꢁ0.80 V) and Epc = ꢁ1.04 V (Epa = ꢁ0.95 V).
Therefore, it seems that the reduction of compound L2 is clearly
easier than the reduction of the related molecules L1, 3 and 5.
These data, suggesting that this compound can potentially act as
a good electron acceptor ligand, are in good agreement with the
2.6. Second harmonic generation (SHG)
In order to study the second harmonic generation, the
complexes 2Ru, 2Fe and 3Fe were subjected to hyper-Rayleigh
scattering (HRS) studies [38]. To avoid the effect of fluorescence
due to two-photon absorption and to obtain as little resonance

2994
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
Fig. 9. Comparison of crystal packing in compounds containing the cationic complexes [Ru(
displaying holes in the a direction; (B) Crystal packing of compound with [CF3SO3] (10Ru) along the a axis, showing the closer packing of the compound.
g
5C5H5)(PPh3)2(L1)]+: (A) Supramolecular array of compound with [PF6] (1Ru),
Fig. 10. Perspective view of the pseudo-dimeric motif of compound [Ru(g
5-C5H5)(DPPE)(L1)][PF6], 2Ru, forming chains along the a direction.
Fig. 11. Dimeric units of compound [Fe(g p–p interactions of the thiophene ligands.
5-C5H5)(PPh3)2(L1)][PF6], 2Fe, showing intermolecular
enhancement as possible [39], the stimulating laser light was
shifted from the original wavelength of the used Nd:YAG laser of
1064 nm to a higher wavelength (1500 nm). Thus, a superposition
of absorptions in the UV–Vis region and the SHG signal (750 nm) is
reduced, which makes the calculated static hyperpolarisability (b0)
[39] more reliable [40,41]. Another important reason for using the
higher wavelength incident beam, is an attempt to discriminate
between a true SHG signal and a two photons absorption induced
fluorescence (TPAF) enhanced signal [42,43]. The 1500 nm incident
beam HRS examinations were achieved using a tuneable optical
parametric oscillator (OPO) based set-up [41]. All measurements
were carried out using Disperse Red 1 (DR1) as an external stan-
dard. The reference hyperpolarisability b of DR1 in CH2Cl2 was cal-
culated by comparison of the slopes of the standard in CH2Cl2 and
CHCl3, to obtain the ratio of bsolute [44]. Using the value
b(CHCl3) = 80 ꢀ 10ꢁ30 esu [45] the hyperpolarisability of DR1 in
CH2Cl2 is estimated to be 70 ꢀ 10ꢁ30 esu. The effect of the refrac-
tive indices of the solvents was corrected using the simple Lorentz
local field [42]. Unfortunately, no SHG intensity could be detected
for 2Ru and 2Fe, although the concentration of the investigated
solutions of 2Fe and 2Ru were considerably high for this method
(>10ꢁ3 M). However, the HRS study of 3Fe results in a measurable,
although weak SHG value. The calculated first hyperpolarizability
amounts to b = 33 ꢀ 10ꢁ30 esu. The corresponding static first
hyperpolarizability is calculated to b0 = 19 ꢀ 10ꢁ30 esu taking into
account the long wavelength absorption which is assigned to a do-
nor–acceptor charge-transfer transition. The failure of a measur-
able SHG for 2Fe and 2Ru can be explained by the weak

M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
2995
Table 6
ties determined by hyper-Rayleigh scattering (HRS) at 1500 nm,
found for 3Fe the value of b0 = 19 ꢀ 10ꢁ30 esu, while for compounds
2Fe (and also 2Ru) the SHG values was negligible. In spite of, all the
experimental data for compound 3Fe point out for the existence of a
donor-acceptor combination originated by the presence of the
NO2group, the value of SHG found was disappointingly small.
The crystallization of these compounds in centrosymmetric
space groups precludes the evaluation of the NLO properties in
the solid state by Kurtz powder technique.
Electrochemical data for the complexes [M(g
5-C5H5)(LL)(BDT)][PF6], the free BDT
ligands and the related compounds 3 and 5, in CH2Cl2
Compound
Epa
(V)
Epc
(V)
Ep1/2
(V)
Epa ꢁ Epc Ia/Ic
(mV)
Benzo[1,2-b;4,3-b0]dithiophene (3)
1.55
–
–
–
–
–
–
–
–
–
–
–
ꢁ0.16a
Benzo[1,2-b;4,3-b0]-2-
nitrodithiophene (5)
ꢁ0.83 ꢁ0.98
ꢁ0.98 ꢁ1.08
ꢁ0.91 150
ꢁ1.02 100
Benzo[1,2-b;4,3-b0]dithiophen-
2-carbonitrile (L3)
1.48
–
–
–
–
[Ru(
[Ru(
g
g
5-C5H5)(PPh3)2(L1)][PF6] (1Ru)
5-C5H5)(DPPE)(L1)][PF6] (2Ru)
1.37
1.53
1.28
0.89
1.23
1.30 140
–
1.22 120
–
–
–
–
4. Experimental
1.16
0.81
[Fe(g
5-C5H5)(DPPE)(L1)][PF6] (2Fe)
0.85
80
ꢃ1
Benzo[1,2-b;4,3-b0]dithiophen-
20-nitro-2-carbonitrile (L2)
ꢁ0.76 ꢁ0.88
ꢁ0.82 120
–
4.1. General procedures
ꢁ1.17 ꢁ1.29
ꢁ1.23 120
0.9
–
ꢁ1.50
–
–
–
0.87 100
–
–
All the experiments were carried out under dinitrogen atmo-
sphere using standard Schlenk techniques. All the solvents used
were dried using standard methods [46]. Starting materials
[Fe(g
5-C5H5)(DPPE)(L2)][PF6] (3Fe)
0.92
ꢁ0.74 ꢁ0.90
0.82
ꢃ1
–
a
[M(
M = Ru, LL = DPPE and X = I when M = Fe) were prepared following
the methods described in the literature [(i) [Ru(
5-C5H5)(DPPE)Cl]
and [Ru(
5-C5H5)(PPh3)2Cl] [47], (ii) [Fe( 5-C5H5)(DPPE)I] [9];
[Ru(
5-C5H5)(TMEDA)Cl] [48]; Benzo[1,2-b;4,3-b0]ditiophen-2-
g
5-C5H5)(LL)X] (LL = TMEDA, DPPE, 2PPh3 and X = Cl when
Small wave due to products originated by oxidation at 1.55 V.
g
Table 7
g
g
Electrochemical data for the complexes [M(
ligands and the related compounds 3 and 5, in CH3CN
g
5- C5H5)(LL)(BDT)][PF6], the free BDT
g
carbaldehyde [28]. FT-IR spectra were recorded in a Mattson Satel-
ite FT-IR spectrophotometer with KBr pellets; only significant
bands are cited in text. 1H- 13C- and 31P NMR spectra were re-
corded on a Bruker Avance 400 spectrometer at probe tempera-
ture. The 1H (DMSO-d6) and 13C (DMSO-d6) chemical shifts are
reported in parts per million (ppm) downfield from internal Me4Si
and the 31P (DMSO-d6) NMR spectra are reported in ppm downfield
from external standard, 85% H3PO4. Elemental analyses were ob-
tained at Laboratório de Análises, Instituto Superior Técnico, using
a Fisons Instruments EA1108 system. Data acquisition, integration
and handling were performed using a PC with the software pack-
age EAGER-200 (Carlo Erba Instruments). Melting points were ob-
tained on a Reichert Thermovar equipment.
Compound
Epa
(V)
Epc
(V)
Ep1/2
(V)
Epa ꢁ Epc Ia/Ic
(mV)
Benzo[1,2-b;4,3-b0]dithiophene (3)
1.45
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
ꢁ0.02a
Benzo[1,2-b;4,3-b0]-2-
nitrodithiophene (5)
ꢁ0.80 ꢁ0.94
ꢁ0.95 ꢁ1.04
ꢁ0.87 140
ꢁ1.00
90
Benzo[1,2-b;4,3-b0]dithiophen-
2-carbonitrile (L1)
1.38
1.28
1.33 100
ꢁ1.56 ꢁ1.70
ꢁ1.63 140
[Ru(g
5-C5H5)(PPh3)2(L1)][PF6]
1.38
1.13
–
–
–
(1Ru)
1.01
1.07 120
–
–
ꢁ1.53
ꢁ1.70
1.01
–
–
–
–
[Ru(g
5-C5H5)(DPPE)(L1)][PF6]
1.11
0.79
1.06 100
(2Ru)
–
ꢁ1.61
–
–
0.72 140
–
[Fe(g
5-C5H5)( DPPE)(L1)][PF6] (2Fe)
0.65
1.25
0.8
ꢃ1
Electronic spectra were recorded at room temperature on a Jas-
co V-560 spectrometer in the range of 200–900 nm.
–
ꢁ1.55
–
–
Benzo[1,2-b;4,3-b0]dithiophen-
20-nitro-2-carbonitrile (L2)
ꢁ0.77 ꢁ0.85
ꢁ1.14 ꢁ1.26
ꢁ1.43 ꢁ1.57
ꢁ0.81
80
90
ꢁ1.20
ꢁ1.50 140
–
4.2. Synthesis of the hemi-helicene chromophore ligands
[Fe(g
5-C5H5)( DPPE)(L2)][PF6] (3Fe)
0.81
0.64
0.73
–
ꢃ1
–
ꢁ0.73 ꢁ0.86
ꢁ0.79 130
4.2.1. Benzo[1,2-b;4,3-b0]ditiophen-2-carbonitrile (L1)
–
–
ꢁ1.40
ꢁ1.63
–
–
–
–
–
–
A solution of H2NOH ꢄ HCl (0.14 g, 2 mmol) in pyridine (4 mL)
was added to a solution of benzo[1,2-b;4,3-b0]ditiophene (0.19 g,
1 mmol) in pyridine (4 mL) cooled to ꢁ30°C. After stirring for 1 h
at that temperature, acetic anhydride (5 mL) was added and the
mixture was refluxed for 1 h. After cooling the mixture at room
temperature, it was poured on cold water, the precipitate filtered
and dissolved in methylene chloride (30 mL). The solution was
washed with water (3 ꢀ 20 mL), the solvent removed under re-
duced pressure and the product purified by means of flash column
chromatography (eluent: light petroleum/methylene chloride 7:3),
affording 0.18 g (0.84 mmol, yield 84%) of pure benzo[1,2-b;4,3-
b0]ditiophen-2-carbonitrile; m.p. 122–124°C. IR (KBr, cmꢁ1):
a
Small wave due to products originated by oxidation at 1.45 V.
p-backbonding effect which barely compensates the ligand sigma
coordination, as suggested by the spectroscopic and electrochemi-
cal data. The rather high energy shifted electronic excitation of 2Fe
and 2Ru compared to 3Fe which bares an electron accepting func-
tion (NO2), and the measurable SHG for 3Fe confirm this
interpretation.
3. Conclusion/summary
m
(CN) 2215. 1H NMR (DMSO-d6): 8.05(2d, 2H, H10, H11), 8.09(d,
1H, H7, J = 8.8 Hz), 8.25(d, 1H, H6, J=8.8 Hz), 8.93(s,1H, H3). 13C
NMR (DMSO-d6): 107.85(C2), 114.74(CN), 118.43(C7), 122.40(C10),
123.02(C6), 129.57(C11), 132.45(C9), 134.70(C3), 135.00(C4),
136.99(C8), 138.50(C5). Anal. Calc. for C11H5NS2: C, 61.37; H,
2.34; N, 6.51; S, 29.78. Found: C, 61.20; H, 2.06; N, 5.91; S, 30.94%.
With the aim to continue the exploitation of the NLO properties
originated by charge transfer metal-ligand through the interaction
of d –p*NC orbitals, a new family of Ru(II) and Fe(II) piano stool struc-
p
tured was synthesised and fully characterized. The main structural
feature of these compounds is the planarity of the new chromophore
coligands BDT guaranteed by the fused rings skeleton, with one phe-
nyl ring placed between two thiophene units. Spectroscopic evidence
by 1H NMR, UV–Vis, FT-IR and electrochemical studies by cyclic vol-
tammetry, suggested some existence of a weak electronic delocaliza-
4.2.2. Benzo[1,2-b;4,3-b0]ditiophen-20-nitro-2-carbonitrile (L2)
Nitric acid (0.08 mL) was added to a solution of benzo[1,2-b;
4,3-b0]ditiophen-2-carbonitrile (0.22 g, 1 mmol) in acetic anhydride
(4 mL) at room temperature. After 1 h in agitation, the mixture was
poured onto water, extracted with methylene chloride, washed
tion due to the
p-backbonding effect, on the iron derivatives 2Fe and
3Fe. Our preliminary evaluation on the quadratic hyperpolarizabili-

2996
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
g -
Fig. 12. Cyclic voltammograms in dichloromethane, at scan rate of 200 mV sꢁ1: (A) [Fe( 5-C5H5)(DPPE)(L2)][PF6], 3Fe (—), and the free ligand L2 (–––); (B) [Fe(g5
C5H5)(DPPE)(L1)][PF6], 2Fe (—), and the free ligand L1 (–––).
with saturated solution of NaHCO3 and water, dried with
magnesium sulphate and the solvent removed. Recrystallization
from methylene chloride/heptane afforded 0.12 g (0.46 mmol,
yield 46%) of pure benzo[1,2-b;4,3-b0]ditiophen-20-nitro-2-
4.3.2. [Ru(g
5-C5H5)(PPh3)2(NCC10H5S2)][PF6] (1Ru)
Orange; recrystallized from (CH3)2CO/(n-heptane); 77% yield;
m.p. decomposes at ꢃ160 °C; IR (KBr, cmꢁ1):
m(CN) 2214, m )
(PFꢁ6
840; 1H NMR (DMSO-d6): 4.75(s, 5H,
g
5-C5H5), 7.13(m, 12H, C6H5,
carbonitrile; m.p. 130–131°C. IR (KBr, cmꢁ1):
m
(CN) 2216. 1H NMR
PPh3)), 7.36(m, 12H, C6H5, PPh3)), 7.46(m, 6H, C6H5, PPh3)), 8.06(d,
1H, H10, J = 5.6 Hz), 8.09(d, 1H, H7, J = 8.9 Hz), 8.12(d, 1H, H11, J =
5.7 Hz), 8.29(d, 1H, H6, J = 8.8 Hz), 8.58(s, 1H, H3) 13C NMR
(DMSO-d6): 8.26(d, 1H, H6, J = 9.0 Hz), 8.35(d, 1H, H7, J =
9.0 Hz), 8.95(s, 1H, H3), 9.08(s,1H, H10). 13C NMR (DMSO-d6):
110.50(C2), 114.86(C „ N), 123.42(C6), 124.57(C7), 125.51(C10),
132.18(C5), 134.58(C8), 135.00(C3), 139.06(C4), 140.34(C9),
151.97(C11). Anal. Calc. for C11H5NS2: C, 50.76; H, 1.55; N, 10.76;
S, 24.63. Found: C, 50.91; H, 1.34; N, 10.69; S, 24.48%.
(DMSO-d6): 84.37(g
5-C5H5), 107.74(C2), 118.51(C7), 122.36(C10),
123.72(C6), 124.73(CN), 128.48(CH, PPh3), 130.15(CH, PPh3),
130.39(C11), 132.07(C9), 132.91(CH, PPh3), 134.96(Cq, PPh3),
135.25(C4), 135.39(C3), 137.27(C8), 138.94(C5).31P NMR (DMSO-d6):
1
ꢁ144.0(ht, JP,F = 711.5 Hz, PF6), 41.6(s, PPh3). Anal. Calc. for
4.2.3. Benzo[1,2-b;4,3-b0] -20-nitroditiophene (5)
C52H40NS2P3F6Ru: C, 59.43; H, 3.84; N, 1.33; S, 6.10. Found: C,
Nitric acid (0,08 mL) was added to a solution of benzo[1,2-b;4,3-
b0]ditiophene (0.19 g, 1 mmol) in acetic anhydride (4 mL) 5 °C.
After 1 h with stirring, the mixture was poured on to water, ex-
tracted with methylene chloride, washed with saturated solution
of NaHCO3 and water, dried with magnesium sulphate and the
solvent was then removed. Recrystallization from hot ethanol
afforded 0.17 g (0.7 mmol, yield 70%) of pure benzo[1,2-b;4,3-b0]-
59.83; H, 3.47; N, 1.31; S, 6.17%.
4.3.3. [Ru(
g
5-C5H5)(PPh3)2(NCC10H5S2)][CF3SO3] (10Ru)
Orange; recrystallized from CH2Cl2-(n-hexane); 73% yield; m.p.:
decomposes at ꢃ167 °C; IR (KBr, cmꢁ1):
m
g
(CN) 2214,
m )
as(CF3SOꢁ3
1253; 1H NMR (DMSO-d6): 4.78(s, 5H,
5-C5H5), 7.11(m, 12H,
C6H5, PPh3)), 7.30(m, 12H, C6H5, PPh3)), 7.43(m, 6H, C6H5, PPh3)),
2-nitroditiophene; m.p. 118–120°C. IR (KBr, cmꢁ1):
m(NO2) 1515
8.02(d, 1H, H10, J = 5.6 Hz), 8.12(d, 1H, H7, J = 8.9 Hz), 8.19(d, 1H,
and 1334. 1H NMR (DMSO-d6): 8.01(d, 1H, H10, J = 5.2 Hz), 8.05(d,
1H, H7, J = 8.8 Hz), 8.15(d, 1H, H11, J = 5.2 Hz), 8.29(d, 1H, H6,
J = 8.8 Hz), 8.94(s, 1H, H3). 13C NMR (DMSO-d6): 118.62(C6),
122.40(C2), 124.43(C7), 124.55(C10), 129.53(C5), 131.62(C5),
136.66(C8), 137.90(C9), 138.03(C4), 148.17(C11). Anal. Calc. for
H
11, J = 5.7 Hz), 8.28(d, 1H, H6, J = 8.8 Hz), 8.64(s, 1H, H3) 13C NMR
(DMSO-d6): 84.98(g
5-C5H5), 107.80(C2), 118.59(C7), 122.03(C10),
124.01(C6), 124.89(CN), 128.49(CH, PPh3), 130.07(CH, PPh3),
130.51(C11), 132.06(C9), 132.91(CH, PPh3), 135.10(Cq, PPh3),
135.31(C4), 135.41(C3), 137.27(C8), 138.98(C5).31P NMR (DMSO-d6):
42.0(s, PPh3). Anal. Calc. for C53H40NS3P2F3O3Ru: C, 60.33; H, 3.82;
N, 1.33. Found: C, 59.98; H, 3.47; N, 1.38%.
C11H5NS2: C, 51.05; H, 2.14; N, 5.95; S, 27.26. Found: C, 50.73; H,
1.95; N, 5.73; S, 28.66%.
4.3. Synthesis of the complexes
4.3.4. [Ru(
Yellow; recrystallized from (CH3)2CO-(n-hexane); 84% yield;
m.p. 264–268 °C; IR (KBr, cmꢁ1): (PF6ꢁ) 839; 1H NMR
(CN) 2216,
(DMSO-d6): 2.71(m, 2H, –CH2–), 2.75(m, 2H, –CH2–), 4.99(s, 5H,
5-C5H5), 7.41(m, 4H, C6H5, DPPE), 7.59(s,1H, H3), 7.60(m, 12H,
g
5-C5H5)(DPPE)(NCC10H5S2)][PF6] (2Ru)
4.3.1. Preparation of [M(
Complexes [M(
5-C5H5)(LL)(NCR)][PF6] were prepared by
halide abstraction from the parent neutral complexes [M(g5
g
5-C5H5)(LL)(NCR)][PF6]
m
m
g
-
g
C5H5)(LL)X] (1 mmol) with TlPF6 (1 mmol) in acetone, in the
presence of a slight excess (1.1 mmol), of the ligands, benzo[1,2-
b;4,3-b0]ditiophen-2-carbonitrile L1 or benzo[1,2-b;4,3-b0]ditio-
phen-20-nitro-2-carbonitrile (L2) at reflux for 16 h under inert
atmosphere. After cooling to room temperature, filtering and
removing the solvent, the complexes were washed with n-hexane
(3 ꢀ 15 mL) and recrystallized from acetone/n-heptane or n-hex-
ane, giving crystalline products.
C6H5, DPPE), 7.86(d, 1H, H10, J = 5.6 Hz), 7.93(d,1H, H7, J = 8.8 Hz),
7.95(m, 4H, C6H5, DPPE), 8.07(d, 1H, H11, J = 5.6 Hz), 8.19(d, 1H, H6,
J = 8.8 Hz). 13C NMR (DMSO-d6): 26.99(–CH2–, DPPE), 82.42(g5
-
C5H5), 107.13(C2), 118.22(C7), 120.36(CN), 121.96(C10), 123.45(C6),
128.90(CH, DPPE), 130.20(C11), 130.71(CH, DPPE), 131.54(C9),
132.93(CH, DPPE), 134.45(C3), 134.51(C4), 136.07(Cq, DPPE),
137.03(C8), 138.42(C5). 31P NMR (DMSO-d6): ꢁ144.0(ht,
1JP,F = 711.3 Hz, PF6), 78.6(s, DPPE). Anal. Calc. for C42H34NS2P3F6Ru:

M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
2997
C, 54.55; H, 3.71; N, 1.51; S, 6.93. Found: C, 54.42; H, 3.44; N, 1.48; S,
6.91%.
96.38(s, DPPE). Anal. Calc. for C42H33N2O2S2P3F6Fe: C, 54.56; H,
3.60; N, 3.03; S, 6.93. Found: C, 54.74; H, 3.83; N, 2.94; S, 5.29%.
4.3.5. [Fe(
g
5-C5H5)(DPPE)(NCC10H5S2)][PF6] (2Fe)
4.3.7. [Ru(g
5-C5H5)(TMEDA)(NCC10H5S2)][PF6] (4Ru)
Orange redish; recrystallized from (CH3)2CO-(n-heptane); 89%
Yellow; recrystallized from (CH3)2CO-(n-heptane); 70% yield;
yield; m.p. decomposes at ꢃ200 °C; IR (KBr, cmꢁ1):
m
(CN) 2199,
m.p. decomposes at ꢃ140 °C; IR (KBr, cmꢁ1):
m(CN) 2195, m )
(PFꢁ6
m
(PF6ꢁ) 840; 1H NMR (DMSO-d6): 2.71(m, 2H, –CH2–), 2.75(m,
840; 1H NMR (DMSO-d6): 2.53(m, 2H, –CH2–), 2.63(m, 2H, –CH2–),
2H, –CH2–), 4.63(s, 5H,
g
5-C5H5), 7.41(m, 4H, C6H5, DPPE), 7.53(s,
2.87(s, 6H, NCH3), 3.15(s, 6H, NCH3), 4.54(s, 5H, g
5-C5H5), 8.05(2d,
1H, H3), 7.60(m, 12H, C6H5, DPPE), 7.87(d, 1H, H10, J = 5.6 Hz),
2H, H10, H11, J = 5.6 Hz), 8.12(d,1H, H7, J = 8.8 Hz), 8.25(d, 1H, H6,
7.94(d,1H, H7, J = 8.8 Hz), 7.95(m, 4H, C6H5, DPPE), 8.07(d, 1H,
J = 8.8 Hz), 8.94(s, 1H). 13C NMR (DMSO-d6): 59.88(NCH3),
H
11, J = 5.6 Hz), 8.18(d, 1H, H6, J = 8.8 Hz). 13C NMR (DMSO-d6):
59.88(NCH3),
62.15(–CH2–),
74.14(g
5-C5H5),
107.92(C2),
27.05(CH2), 80.07(
123.26(C6), 128.54(CN),
g
5-C5H5), 107.86(C2), 118.19(C7), 121.88(C10),
129.06(CH, DPPE), 129.96(C11),
114.80(CN), 118.52(C7), 122.46(C10), 123.11(C6), 129.66(C11),
132.53(C9), 134.79(C3), 135.07(C4), 137.06(C8), 138.58(C5). 31P NMR
1
131.12(CH, DPPE), 131.51(C9), 132.76 (CH, DPPE), 133.87(C3),
(DMSO-d6): ꢁ144.1(qt, JP,F = 711.5 Hz, PF6). Anal. Calc. for
134.42(C4), 136.08(Cq, DPPE), 136.97(C8), 137.94(C5). 31P NMR
C22H26N3S2PF6Ru: C, 41.12; H, 4.08; N, 6.54; S, 9.98 (error due to
1
(DMSO-d6): ꢁ144.1(qt, JP,F=710.2 Hz, PF6), 96.6(s, DPPE). Anal.
the instability of the compound). Found: C, 39.07; H, 3.26; N, 6.22;
S, 9.34%.
Calc. for C42H34NS2P3F6Fe: C, 57.35; H, 3.90; N, 1.59; S, 7.29. Found:
C, 57.07; H, 3.74; N, 1.50; S, 6.77%.
4.4. Electrochemical experiments
4.3.6. [Fe(g
5-C5H5)(DPPE)(NCC10H5S2NO2)][PF6] (3Fe)
The electrochemical experiments were performed on an EG&G
Princeton Applied Research Model 273A potentiostat/galvanostat
and monitored with a personal computer loaded with Electro-
chemistry PowerSuite v2.51 software from Princeton Applied Re-
search. Cyclic voltammograms were obtained in 0.1 M solutions
of [NBu4][PF6] in CH2Cl2 or CH3CN, using a three-electrode config-
uration with a platinum-disk working electrode (1.0 mm diameter)
probed by a Luggin capillary connected to a silver-wire pseudo-ref-
erence electrode; a Pt wire auxiliary electrode was employed. The
electrochemical experiments were performed under a N2 atmo-
sphere at room temperature. The redox potentials of the complexes
were measured in the presence of ferrocene as the internal
Dark red; recrystallized from (CH3)2CO-(n-heptane); 81% yield;
m.p. decomposes at ꢃ215 °C; IR (KBr, cmꢁ1):
m(CN) 2197, m(NO2)
1517, 1329, m
(PFꢁ6 ) 840; 1H NMR (DMSO-d6): 2.72(m, 2H, –CH2–),
2.86(m, 2H, –CH2–), 4.76(s, 5H,
g
5-C5H5), 7.59(m, 12H, C6H5, DPPE),
7.66(m, 4H, C6H5, DPPE), 7.83(s, 1H, H3), 8.12(m, 4H, C6H5, DPPE),
8.18(d, 1H, H6, J = 8.8 Hz), 8.24(d, 1H, H7, J = 8.8 Hz), 8.71(s, 1H,
H
10). 13C NMR (DMSO-d6): 27.23(–CH2–, DPPE), 80.36( 5-C5H5),
g
110.57(C2), 123.57(C6), 124.68(C7), 125.49(C10), 128.76(CN),
129.12(CH, DPPE), 131.22(CH, DPPE), 132.02(C5), 132.37 (CH, DPPE),
134.58(C3), 134.82(C8), 135.97(Cq, DPPE), 139.10(C4), 140.39(C9)
1
151.92(C11). 31P NMR (DMSO-d6): ꢁ144.07(ht, JP,F = 710.5 Hz, PF6),
Table 8
Data collection and structure refinement parameters for 1Ru, 10Ru, 2Ru and 2Fe
Compound
1Ru
10Ru
2Ru
2Fe
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
55H45F6NOP3RuS2
C107H80Cl2F6N2O6P4Ru2S6
2193.01
150(2)
C42H34F6NP3RuS2
924.80
293(2)
1.54180
Monoclinic
P21/n
C45H40F6FeNO1.33P3S2
942.99
150(1)
0.71073
Monoclinic
P21/n
1108.02
293(2)
1.54180
Triclinic
0.71073
Triclinic
ꢀ
ꢀ
P1
P1
13.415(7)
14.763(8)
17.049(8)
69.02(2)
87.87(2)
65.49(3)
2844(3)
2
1.294
4.186
12.281(2)
13.550(3)
33.005(7)
82.619(6)
84.873(7)
63.176(6)
4858(2)
11.370(3)
14.984(3)
23.765(5)
–
102.25(2)
–
3957(2)
4
1.553
5.868
9.2211(5)
19.5890(13)
23.4609(15)
–
93.240(2)
–
4231.0(5)
4
1.480
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Å3)
Z
2
Calculated density (Mg mꢁ3
)
1.499
0.630
Absorption coefficient (mmꢁ1
)
0.633
F(000)
1130
2232
1872
1939
h Range for data collection (°)
Limiting indices
3.55–66.92
ꢁ15 6 h 6 16
ꢁ16 6 k 6 16
0 6 l 6 20
9756/9756
[0.0000]
1.86–28.61
ꢁ16 6 h 6 12
ꢁ18 6 k 6 18
ꢁ44 6 l 6 42
57,369/24,723
[0.0823]
3.51–66.93
ꢁ13 6 h 6 0
ꢁ17 6 k 6 0
ꢁ18 6 l 6 28
6959/6665
[0.1491]
2.03–20.61
ꢁ9 6 h 6 9
ꢁ19 6 k 6 19
ꢁ23 6 l 6 23
33,367/4296
[0.0728]
Reflections collected/unique
[Rint
]
Completeness to h
Refinement method
66.92 (96.4%)
Full-matrix least-squares on
F2
28.61 (99.2%)
Full-matrix least-squares on
F2
66.93 (94.5%)
Full-matrix least-squares on
F2
20.61 (99.6%)
Full-matrix least-squares on
F2
Data/restraints/parameters
9756/0/623
1.095
24,723/4/1217
0.913
6665/0/497
1.045
4296/0/536
1.181
Goodness-of-fit on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0930;
wR2 = 0.2363
0.0100(7)
1.831 and ꢁ1.488
R1 = 0.0738
wR2 = 0.2010
–
2.169 and ꢁ1.543
R1 = 0.0624
wR2 = 0.1665
0.00067(11)
1.390 and ꢁ2.248
R1 = 0.0338;
wR2 = 0.0897
–
0.461 and ꢁ0.429
Extinction coefficient
Largest difference in peak and hole
(e Åꢁ3
)

2998
M.H. Garcia et al. / Journal of Organometallic Chemistry 693 (2008) 2987–2999
standard and the redox potential values are normally quoted rela-
tive to the SCE by using the ferrocenium/ferrocene redox couple
(Ep/2 = 0.46 or 0.40 V vs. SCE for CH2Cl2 or CH3CN, respectively)
[49].
The supporting electrolyte was purchased from Aldrich Chemi-
cal Co., recrystallized from ethanol, washed with diethyl ether and
dried under vacuum at 110 °C for 24 h. Reagent grade acetonitrile
and dichloromethane were dried over P2O5 and CaH2, respectively,
and distilled under nitrogen atmosphere before use.
E. Licandro acknowledge joint financial support from the Minis-
tero dell’Istruzione, dell’Università della Ricerca Scientifica
(MUR), Rome, and the University of Milan (FIRB project, Bando
2003, Progetto RBNE033KMA, title of the project: ‘‘Molecular com-
pounds and hybrid nanostructured materials with resonant and
non resonant optical properties for photonic devices.”
e
Appendix A. Supplementary material
CCDC 683038, 683039, 683041 and 683040 contain the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2008.05.035.
4.5. Crystal structure determination
X-ray data were collected on a TURBOCAD4 Enraf–Nonius dif-
fractometer with
a rotating anode and Cu Ka1 radiation
(k = 1.5418Å), at room temperature for compounds 1Ru and 2Ru.
Data were corrected for Lorentz and polarization effects and for
absorption by XABS2 empirical method (included in WINGX-version
1.70.01 [50]) for compound 1Ru and by semiempirical methods
based on w-scans [51] for compound 2Ru. Data collection and data
reduction were done with CAD4 and XCAD programs [52].
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