Organometallic complexes for nonlinear optics. 52. Syntheses, structural, spectroscopic, quadratic nonlinear optical, and theoretical studies of Ru(C 2C6H4R-4)(κ2-dppf) (η5-C5H5)

Article abstract of DOI:10.1016/j.jorganchem.2012.12.039

The synthesis of Ru(CCC₆H₄-4-NO₂) (κ²-dppf)(η⁵-C₅H₅) (1) is reported, together with spectroscopic, X-ray structural, linear optical and quadratic nonlinear optical (NLO) studies

Full text of DOI:10.1016/j.jorganchem.2012.12.039

Journal of Organometallic Chemistry 730 (2013) 108e115
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Organometallic complexes for nonlinear optics. 52. Syntheses, structural,
spectroscopic, quadratic nonlinear optical, and theoretical studies
of Ru(C2C6H4R-4)(
k
2-dppf)(
h
5-C5H5) (R ¼ H, NO2)
,
Bandar A. Babgi a b, Ahmed Al-Hindawi a, Graeme J. Moxeya, Fazira I. Abdul Razak a, Marie P. Cifuentes a,
Erandi Kulasekera a, Robert Stranger a, Ayele Teshome c, Inge Asselberghs c, Koen Clays c,
,
Mark G. Humphreya
*
a Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
b Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
c Laboratory of Chemical and Biological Dynamics, Centre for Research on Molecular Electronics and Photonics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven,
Belgium
a r t i c l e i n f o
a b s t r a c t
The synthesis of Ru(C^CC6H4-4-NO2)(k h
2-dppf)( 5-C5H5) (1) is reported, together with spectroscopic,
Article history:
Received 30 September 2012
Received in revised form
30 December 2012
X-ray structural, linear optical and quadratic nonlinear optical (NLO) studies of 1 and Ru(C^CPh)
(
k
2-dppf)( 5-C5H5) (2), the last-mentioned using the hyper-Rayleigh scattering technique at 1064 nm.
h
Quadratic nonlinearities for these dppf-containing complexes are comparable to those of their dppe-
containing analogues and significantly greater than carbonyl-containing analogues. The linear optical
and quadratic NLO properties of 1, 2 and their dppe-containing analogues have been rationalized by
time-dependent density functional theory calculations.
Accepted 31 December 2012
Dedicated to the memory of Professor Gor-
don Stone, an inspirational organometallic
chemist.
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
Crystal structure
Ruthenium
Alkynyl
Nonlinear optics
Density functional theory calculations
1. Introduction
We have previously probed the effect of acceptor group incor-
poration and
p-bridge modification at metal alkynyl complexes,
The nonlinear optical (NLO) properties of organometallic com-
plexes have come under considerable scrutiny during the past
twenty years [1e4], the majority of studies being focused on
quadratic nonlinearities and on complexes with a donor-bridge-
acceptor composition. The field of organometallics in nonlinear
optics was given initial impetus from the promising outcomes of
studies with metallocenyl complexes [5], but more recently alkynyl
complexes have also attracted significant attention [6e8]. Amongst
metal alkynyl complexes, those of ruthenium are some of the most
important due to their facile high-yielding syntheses [9,10],
enhanced NLO coefficients [11,12], ease of use in construction of
multimetallic complexes such as dendrimers [13], and reversible
redox properties which afford the possibility of NLO switching [14].
reporting the syntheses and NLO properties (by both electric field-
induced second-harmonic generation, EFISH, and the hyper-
Rayleigh scattering technique, HRS) of complexes of general for-
mula Ru(4-C^CC6H4X)(PPh3)2(
complexes increase on proceeding to a strongly dipolar system
-system lengthening (proceeding
h
5-C5H5). Nonlinearities of these
(replacing X ¼ H by X ¼ NO2) and
p
from X ¼ NO2 to X ¼ C6H4-4-NO2, C^CC6H4-4-NO2, N]CHC6H4-4-
NO2, and Z- and E-CH]CHC6H4-4-NO2, with the last-mentioned
being the most efficient in terms of its quadratic NLO perfor-
mance) [15e18]. We then explored the effect of metal and co-ligand
variation in the series of complexes M(4-C^CC6H4-4-
NO2)(L2)(
h
5-C5H5) (M ¼ Fe, Ru, Os, L2 ¼ dppe; M ¼ Ru, Os,
L ¼ PPh3; M ¼ Ru, L ¼ CO), for which quadratic nonlinearities
increase as M ¼ Fe ꢀ Ru ꢀ Os and L ¼ CO < phosphines [19]. The
more subtle co-ligand modification (replacing 2 ꢁ PPh3 with dppe)
afforded unclear results, with bHRS data for M(4-C^CC6H4-4-
* Corresponding author. Tel.: þ61 2 6125 2927; fax: þ61 2 6125 0750.
E-mail address: Mark.Humphrey@anu.edu.au (M.G. Humphrey).
NO2)(L2)(
h
5-C5H5) suggesting (M ¼ Ru, L2 ¼ 2PPh3) < (M ¼ Ru,
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.12.039

B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
109
L2 ¼ dppe) and (M ¼ Os, L2 ¼ 2PPh3) z (M ¼ Os, L2 ¼ dppe) (within
the error margins of the experiment). We have now returned to this
question of the effect of co-ligand variation on quadratic non-
linearity in metal alkynyl complexes (and thereby the potential of
tuning the response), and report herein the synthesis of the new
Solutions containing ca 1 ꢁ 10ꢃ3 M complex were maintained
under nitrogen. Measurements were carried out at room tem-
perature using Pt disc working-, Pt wire auxiliary- and Ag/AgCl
reference electrodes, such that the ferrocene/ferrocenium redox
couple was located at 0.56 V (peak separation ca. 0.10 V). Scan
complex Ru(C^CC6H4-4-NO2)(
k
2-dppf)(
h
5-C5H5) incorporating
rates were typically 100 mV sꢃ1
.
the electro-active bidentate ligand 1,2-bis(diphenylphosphino)fer-
rocene, structural studies of both this complex and its non-nitro
2.3. Synthesis of Ru(C^CC6H4-4-NO2)(
k h
2-dppf)( 5-C5H5) (1)
analogue Ru(C^CPh)(k h
2-dppf)( 5-C5H5), spectroscopic and elec-
trochemical characterization of these complexes, quadratic non-
linearities from hyper-Rayleigh scattering measurements at
1064 nm, comparison to related extant experimental data, and
theoretical studies employing density functional theory (DFT) and
time-dependent DFT (TD-DFT) to rationalize the experimental
outcomes.
RuCl(
k
2-dppf)( 5-C5H5) (210.2 mg, 0.278 mmol) and
h
HC^CC6H4-4-NO2 (41.5 mg, 0.282 mmol) were added to a flask
containing MeOH (20 ml). A solution of NaOMe in MeOH (7.00 ml,
0.1 M) was added and the orange mixture was stirred at reflux
until the formation of a red solution (ca. 15 min). The red solution
was cooled to room temperature, resulting in the precipitation of
a red powder that was collected by filtration, affording 1 (184.3 mg,
77%). Crystals of 1 suitable for single-crystal X-ray structural study
were grown by slow diffusion of methanol into a dichloromethane
2. Experimental
solution at room temperature. Elemental analysis (C47H37FeNO2
2.1. General experimental conditions and starting materials
-
P2Ru): calcd.: C: 65.14, H: 4.30, N: 1.62%. Found: C: 65.30, H: 4.18,
N: 1.35%. HR ESI MS (C47H37FeNO2P2Ru): calculated: 882.0927,
found: 882.0944. UVevis (CH2Cl2): 469 nm (1.74), 273 nm (1.42).
1H NMR (CDCl3): 3.95, 4.04, 4.11, 5.06 (4 s, 4 ꢁ 2H, H1, H2, H3, H4),
4.27 (s, 5H, H10), 7.08 (d, JHH ¼ 9 Hz, 2H, H14), 7.18e7.73 (m, 20H, H7,
H8, H9), 7.99 (d, JHH ¼ 9 Hz, 2H, H15). 13C NMR (CDCl3): 68.3, 71.3,
73.2, 76.0 (C1, C2, C3, C4), 80.8 (C12), 85.0 (C10), 88.3 (t, JCP ¼ 35 Hz,
C5), 115.6 (C11), 123.9 (C14), 127.3 (m), 128.8, 129.3, 134.0 (m) (C7, C8,
C9), 130.5 (C15), 137.5 (C13), 140.4 (m, C6), 142.7 (C16). 31P NMR
(CDCl3): 55.9.
All reactions were performed under a nitrogen atmosphere with
the use of Schlenk techniques unless otherwise stated. Dichloro-
methane was dried by distilling over calcium hydride; all other
solvents were used as received. Petrol is a fraction of petroleum
spirits of boiling range 60e80 ꢂC. Chromatography was performed
on ungraded basic alumina. Phenylacetylene (Aldrich) was used as
received. The following were prepared by the literature procedures:
RuCl(k h
2-dppf)( 5-C5H5) [20], HC^CC6H4-4-NO2 [21].
2.2. Instrumentation
2.4. Synthesis of Ru(C^CPh)(k h
2-dppf)( 5-C5H5) (2)
Microanalyses were carried out at the Australian National
University. UVevis spectra of solutions in 1 cm quartz cells were
recorded using a Cary 5 spectrophotometer; bands are reported in
the form wavelength (nm) [extinction coefficient, 104 Mꢃ1 cmꢃ1].
The infrared spectra were recorded as KBr discs using a Perkine
This complex has been prepared previously by an alternative
procedure in 98% yield [22]. RuCl(
2-dppf)( 5-C5H5) (113.7 mg,
k
h
0.15 mmol) and HC^CPh (0.05 ml, 0.46 mmol) were added to
a flask containing MeOH (15 ml). A solution of NaOMe in MeOH
(7.00 ml, 0.1 M) was added and the orange mixture was stirred at
reflux until the formation of a red solution (ca. 15 min). The red
solution was cooled to room temperature, resulting in the precip-
itation of a yellow powder that was collected by filtration, affording
2 (103.0 mg, 83%). Crystals of 2 suitable for X-ray diffraction study
were grown by slow diffusion of methanol into a dichloromethane
solution at room temperature. UVevis (CH2Cl2): 402 nm (0.14),
311 nm (2.18), 273 nm (1.36). 31P NMR (CDCl3): 56.0.
Elmer System 2000 FT-IR; peaks are reported in cmꢃ1 1H
.
(300 MHz) and 13C (75 MHz) NMR spectra were recorded using an
Inova-300 NMR spectrometer and 31P NMR spectra (121 MHz)
were recorded using a Varian Mercury-300 FT NMR spectrometer.
The spectra are referenced to residual chloroform (7.26 ppm),
CDCl3 (77.0 ppm), or external H3PO4 (0.0 ppm), respectively; atom
labelling follows the numbering scheme in Chart 1. The high
resolution ESI mass spectrum (HR ESI MS) was obtained utilizing
a Bruker Apex 4.7T FTICR-MS instrument. Cyclic voltammetry
measurements were recorded using a MacLab 400 interface and
MacLab potentiostat from ADInstruments. The supporting elec-
trolyte was 0.1 M ðNBun4ÞPF6 in distilled, deoxygenated CH2Cl2.
2.5. Structure determinations
Intensity data were collected using an Enraf-Nonius KAPPA CCD
ꢀ
at 200 K with Mo K
a
radiation (
l
¼ 0.7170 A). Suitable crystals were
immersed in viscous hydrocarbon oil and mounted on a glass fibre
that was mounted on the diffractometer. Using psi and omega scans
Nt (total) reflections were measured, which were reduced to No
unique reflections, with Fo > 2s(Fo) being considered “observed”.
Data were initially processed and corrected for absorption using the
programs DENZO [23] and SORTAV [24]. The structures were solved
using direct methods, and observed reflections were used in least
squares refinement on F2, with anisotropic thermal parameters
refined for non-hydrogen atoms. Hydrogen atoms were con-
strained in calculated positions and refined with a riding model.
Structure solutions and refinements were performed using the
programs SHELXS-97 and SHELXL-97 [25] through the graphical
interface Olex2 [26], which was also used to generate the figures.
Crystal data for 1: C47H37FeNO2P2Ru, M ¼ 866.64, red block,
0.10 ꢁ 0.10 ꢁ 0.09 mm3, triclinic, space group P-1 (no. 2),
ꢀ
Chart 1. NMR labelling scheme for 1.
a ¼ 9.926(2), b ¼ 12.406(3), c ¼ 15.571(3) A,
a
¼ 97.23(3),

110
B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
3
ꢂ
ꢀ
b
¼ 99.29(3),
g
¼ 99.36(3) , V ¼ 1844.1(6) A , Z ¼ 2, Dc ¼ 1.561 g/
cm3, F000 ¼ 884,
m
¼ 0.933 mmꢃ1, 2qmax ¼ 55.0ꢂ, 35,613 reflections
collected, 8438 unique (Rint
¼
0.0358). Final GoF
¼
1.192,
R1 ¼0.0278, wR2 ¼ 0.0813, R indices based on 7392 reflections with
I > 2
s
(I) (refinement on F2), 487 parameters, 0 restraints. Crystal
data for 2$CH2Cl2: C48H40Cl2FeP2Ru, M ¼ 906.56, yellow block,
0.12 ꢁ 0.10 ꢁ 0.09 mm3, monoclinic, space group P21/n (No. 14),
ꢀ
a ¼ 10.232(2), b ¼ 23.572(5), c ¼ 17.482(4) A,
b
¼ 93.51(3)ꢂ,
V ¼ 4208.7(14) A , Z ¼ 4, Dc ¼ 1.431 g/cm3, F000 ¼ 1848,
3
ꢀ
m
¼ 0.939 mmꢃ1, 2qmax ¼ 55.8ꢂ, 60,857 reflections collected, 9777
unique (Rint
¼
0.0538). Final GoF
¼
1.063, R1
¼
0.0839,
(I)
wR2 ¼ 0.2449, R indices based on 7119 reflections with I > 2
s
(refinement on F2), 500 parameters, 156 restraints. CCDC 899522e
899523. Variata. For compound 2, atoms C41eC47 of the phenyl-
alkynyl moiety exhibited positional disorder. This disorder
was successfully modelled using a two-position model with
0.49894(0.00707):0.50106 occupancy levels, in conjunction with
geometry restraints. The anisotropic displacement parameters of
these atoms were also restrained. The unit cell of 2 contains four
dichloromethane molecules that have been treated as a diffuse
contribution to the overall scattering without specific atom posi-
tions by PLATON SQUEEZE [27].
Fig. 1. Molecular structure of Ru(C^CC6H4-4-NO2)(k h
2-dppf)( 5-C5H5) (1), with ther-
mal ellipsoids set at the 30% probability level. Hydrogen atoms have been omitted for
clarity. Selected bond lengths and angles: RueC40 2.033(2), RueP1 2.282(1), RueP2
ꢀ
2.283(1), C40^C41 1.186(3), C41eC42 1.434(3) A, RueC40^C41 178.4(2), C40^C41eC42
167.3(3), P1eRueP2 95.93(3)ꢂ.
2.6. Hyper-Rayleigh scattering measurements
An injection-seeded Nd:YAG laser (Q-switched Nd:YAG Quanta
Ray GCR5, 1.064 mm, 8 ns pulses, 10 Hz) was focused into a cylin-
zeta plus polarization (TZP) Slaterorbital basis sets forall atoms. UVe
vis spectra were calculated using the statistical average of orbital
potentials (SAOP) functional [35] with the same TZP basis sets. Cal-
drical cell (7 ml) containing the sample. The intensity of the inci-
dent beam was varied by rotation of a half-wave plate placed
between crossed polarizers. Part of the laser pulse was sampled by
a photodiode to measure the vertically polarized incident light
intensity. The frequency doubled light was collected by an efficient
condenser system and detected by a photomultiplier. The harmonic
scattering and linear scattering were distinguished by appropriate
filters; gated integrators were used to obtain intensities of the
incident and harmonic scattered light. The absence of a lumines-
cence contribution to the harmonic signal was confirmed by using
interference filters at different wavelengths near 532 nm. All
measurements were performed in tetrahydrofuran using 4-
culated
b values were obtained using the Taylor series convention.
For clarity, the approximate location of the Cartesian axes for the
calculations are (with reference to Fig.1) Ru1eC40eC41eN1 (x axis),
and through Ru1 and orthogonal to the plane of the figure (z axis),
with the y axis orthogonal to these x and z axes.
3. Results and discussion
3.1. Synthesis and characterization
nitroaniline (
b
¼ 21.4 ꢁ 10ꢃ30 esu) as a reference. Reported
The alkynyl complexes were prepared using extensions of
established methodologies (Scheme 1), and the new complex 1 was
characterized by a combination of IR, 1H, 13C, and 31P NMR spec-
troscopies and mass spectrometry. The IR spectra contain charac-
b
values were obtained using the so-called “B convention”, which
incorporates the 1/2! and 1/3! factors from the Taylor series
expansion. Solutions were sufficiently dilute that absorption of
scattered light was negligible. Further details regarding ns HRS
studies employing a Nd:YAG laser are given in Refs. [28] and [29].
teristic
n
(C^C) bands at 2039 (1) and 2073 cmꢃ1 (2) for the
stretching mode of the metal-bound alkynyl group, with the
anticipated shift to lower frequency on introduction of a nitro
group. The 31P NMR spectra contain one singlet resonance at 55.9
(1) and 56.0 ppm (2), while the high resolution mass spectrum of 1
shows a peak corresponding to the molecular ion.
2.7. Theoretical studies
Calculations were performed using the Amsterdam Density
Functional (ADF) program [30], version ADF2012.01. Scalar rela-
tivistic effects were treated via the zeroth-order regular approx-
imation (ZORA) method [31]. Geometry optimizations were
undertaken without any symmetry constraints using the Beckee
Perdew (BP) exchange-correlation [32e34] functional with triple
We have previously reported the cyclic voltammetric response
of complexes of general formula Ru(C^CC6H4-4-NO2)(L2)(h5
-
C5H5), for which the potentials of the formally RuII/III oxidation
processes increase on proceeding from L2 ¼ dppe (0.67 V) [19] to
(PPh3)2 (0.73 V) [15] and then (CO)2 (0.86 V) [19], consistent with
Scheme 1. Syntheses of ruthenium alkynyl complexes 1 and 2.

B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
111
Table 1
expectations of decreasing electron density at the metal centre in
proceeding from electron-donating alkyldiarylphosphines to tri-
arylphosphines and then electron-withdrawing carbonyl ligands.
Complex 1 was investigated in the same way, revealing two
oxidation processes [FeII/III 0.73 V; RuII/III 1.00 V], the dppf ligand-
centred oxidation rendering the ruthenium centre considerably
more difficult to oxidize. Redox switching of optical non-
linearities has attracted significant attention [36,37]. The rever-
sible stepwise oxidation of 1 suggests that this complex may
have potential in this regard because the donor nature of the
ligated ruthenium centre in this formally donor-bridge-acceptor
composition will be attenuated or “switched off” following oxi-
dation, which should lead to a diminution of quadratic optical
nonlinearity.
The identities of 1 and 2 were confirmed by single-crystal X-ray
diffraction studies; the molecular structures are illustrated in Figs. 1
and 2, the captions including selected bond lengths and angles
which fall within the ranges of those reported previously for related
structures. Full bond lengths and angles are provided in
Supplementary material.
Experimental linear optical and quadratic nonlinear response parameters for 1, 2
and related complexes.
Complex
lmax (nm)
, 104 Mꢃ1 cmꢃ1
]
b1064
b0
Ref.
[15]
a
[
3
(10ꢃ30 esu)b (10ꢃ30 esu)c
Ru(C^CPh)(PPh3)2
310 [2.0]
311 [2.2]
460 [1.1]
364 [1.6]
447 [1.8]
469 [1.7]
16
120
468
58
10
72
(h
5-C5H5)
Ru(C^CPh)(dppf)
5-C5H5) (2)
Ru(4-C^CC6H4NO2)
(PPh3)2(
5-C5H5)
Ru(4-C^CC6H4NO2)
(CO)2(
5-C5H5)
Ru(4-C^CC6H4NO2)
(dppe)(
5-C5H5)
Ru(4-C^CC6H4NO2)
(dppf)(
5-C5H5) (1)
This
work
[15]
(h
96
h
27
[19]
[19]
h
664
770
161
165
h
This
work
h
a
Dichloromethane solvent.
Measurements were carried out in THF; all complexes are optically transparent
b
at 1064 nm. Errors ꢄ 10%.
c
Corrected for resonance enhancement at 532 nm using the two-level model
with b0
¼
b
[1 ꢃ (2lmax/1064)2][1 ꢃ (lmax/1064)2].
3.2. Linear optical and quadratic nonlinear optical studies
coefficient, perhaps indicating the presence of another transition
contributing to the band at ca. 310 nm in the spectra of the non-
nitro complexes. Amongst the nitro-containing complexes,
replacing the (comparatively) electron-withdrawing carbonyl li-
gands with electron-donating phosphines results in a significant
Absorption maxima and intensities from electronic spectra of
1 and 2, together with those of related complexes, are collected in
Table 1. We have previously assigned the low-energy transitions
in ruthenium alkynyl complexes of this type as metal-to-ligand
charge transfer (MLCT) in character [15]. The two-level model
suggests that strong low-energy transitions involving significant
charge displacement (such as the MLCT transitions for these
complexes) are correlated with significant quadratic nonlinearity,
so understanding the effect of systematic complex modification
red-shift in lmax
.
The quadratic nonlinearities of 1 and 2 have been determined at
1064 nm using the hyper-Rayleigh scattering technique; the re-
sults are given in Table 1, together with the two-level corrected
values, and data for related complexes. Problems with the two-
level model have been discussed previously by us [38]; while it
is not considered adequate for donor-bridge-acceptor organome-
tallics such as those in this report, it may be useful in comparing
closely related complexes. With this caveat in mind, one can
compare the data. Both experimental and two-level corrected
nonlinearities increase significantly on proceeding from non-nitro-
to nitro-containing complexes (as expected when replacing
a donor-bridge with a donor-bridge-acceptor composition). For the
nitro-containing complexes, experimental and two-level corrected
data undergo substantial increase on proceeding from electron-
withdrawing co-ligand CO to electron-donating triphenylphos-
phine with a further increase seen in proceeding to the bidentate
diphosphines. The dppf complexes from the present study are of
particular interest; they possibly exhibit the largest nonlinearities
within this family of complexes (although the experimental and
two-level-corrected data for 1 are comparable to those of its dppe-
containing analogue within experimental error margins). Coupled
to their aforementioned redox activity, they afford the intriguing
possibility of redox switching the quadratic NLO performance by
sequential oxidation at the ferrocenyl unit and then the ruthenium
centre.
on lmax and
are important. For these complexes, introduction of
3
a nitro group (and thereby creating a strong donor-bridge-
acceptor composition) results in a significant red-shift of the
optical absorption maximum from ca. 310 nm to ca. 460 nm;
there is
a concomitant slight reduction in the extinction
3.3. Theoretical studies
TD-DFTcalculations of 1, 2, and their dppe-containing analogues
were undertaken to rationalize the linear optical and quadratic
nonlinear optical behaviours. Although the TD-DFT calculations
computed the 200 lowest energy dipole-allowed excitations for
each complex, in general only transitions with calculated oscillator
strengths of 0.04 atomic units or greater below 35,000 cmꢃ1 were
considered in the analysis to follow. The calculated transition en-
ergies, oscillator strengths [f], and main orbital contributions
involved in the excitations are listed in Table 2 for all four
Fig. 2. Molecular structure of Ru(C^CPh)(k h
2-dppf)( 5-C5H5) (2), with thermal ellip-
soids set at the 30% probability level. Hydrogen atoms and the disorder component of
the phenylalkynyl moiety have been omitted for clarity. Selected bond lengths and
angles: RueC40 2.015(8), RueP1 2.272(2), RueP2 2.273(2), C40^C41 1.26(5), C41eC42
1.49(5) A, RueC40^C41 173(3), C40^C41eC42 161(5), P1eRueP2 96.87(6)ꢂ.
ꢀ

112
B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
Table 2
Observed and calculated optical transitions for 1, 2, Ru(C^CPh)(dppe)(
h
5-C5H5) and Ru(4-C^CC6H4NO2)(dppe)(
h
5-C5H5).a
Complex
nmax
[
3 ] (exp)
nmax [f] (calcd)
Composition (wt%)
Major assignment
Ru(C^CPh)(dppe)(
h
5-C5H5)
30,950 [1.91]
28,280 [0.09]
29,952 [0.19]
30,637 [0.07]
17,600 [0.47]
26,392 [0.06]
29,467 [0.07]
32,066 [0.04]
32,434 [0.08]
170a / 180a (51%)
170a / 180a (36%)
170a / 181a (81%)
182a / 183a (89%)
179a / 183a (61%)
173a / 183a (41%)
179a / 185a (45%)
181a / 194a (40%)
Rudxz
Rudxz
Rudxz
þ
þ
þ
p
p
p
C
C
C
2 / Rudyz
2 / Rudyz
2 / Rudyz
þ
þ
þ
p*C2Ph
p*C2Ph
p*C2Ph þ Ppz
Ru(4-C^CC6H4NO2)(dppe)(
h
5-C5H5)
20,500 [1.58]
32,550 [0.68]
Rudx2ꢃy2 þ Ppy
þ
p
C2C6H4NO2
/
p*C2C6H4NO2
Rudx2ꢃy2
þ
p
C2C6H4NO2
þ
þ
p
Cp / p*C2C6H4NO2
p
(dppe) / p*C2C6H4NO2
Rudx2ꢃy2
Rudxy
þ
pC2C6H4NO2
pCp / Rudxz
þ
p*dppe
þ
p
C2 / Rudxz
þ
p*C2C6H4NO2
Ru(C^CPh)(dppf)(
h
5-C5H5) (2)
24,500 [0.15]
32,150 [2.82]
24,077 [0.01]
25,547 [0.01]
29,368 [0.05]
29,864 [0.04]
207a / 213a (83%)
206a / 213a (92%)
207a / 221a (37%)
206a / 219a (17%)
205a / 216a (15%)
210a / 224a (12%)
204a / 212a (58%)
206a / 221a (37%)
Fedz2 þ Rudxy
Fedz2 þ Rudxy
Fedz2 þ Rudxy
/
/
/
p*(dppe)
p*(dppe)
p*C2Ph
Fedz2/dx2ꢃy2 þ Rudx2ꢃy2 / Fedxy
þ
p*(dppe)
Fedx2ꢃy2 / Fedyz þ Rudyz
þ
p*(dppe)
p*Cp
C2Ph / p*(dppe)
p*C2Ph
Rudz2
Rudz2
Fedz2 þ Rudx2ꢃy2
þ
þ
p
p
C2Ph / Rudxz
þ
31,511 [0.05]
31,659 [0.06]
/
Ru(4-C^CC6H4NO2)(dppf)(
h
5-C5H5) (1)
21,160 [3.02]
34,000 [2.20]
19,028 [0.35]
27,846 [0.04]
32,031 [0.08]
34,773 [0.07]
219a / 222a (39%)
206a / 222a (47%)
199a / 222a (57%)
216a / 236a (28%)
Rudz2 þ Fedz2
þ
p
C2C6H4NO2
(dppe) / p*C2C6H4NO2
C2C6H4NO2
Cp / p*C2C6H4NO2
p*C2C6H4NO2
/
p*C2C6H4NO2
Opx
þ
pC2
þ
p
Rudxz
þ
p
þ
p
Fedx2ꢃy2 þ Rudx2ꢃy2 / Rudxz
þ
Calculated and observed nmax in cmꢃ1; [ ] in 104 Mꢃ1 cmꢃ1; calcd oscillator strength [f].
3
a
complexes along with the observed band positions. The position
and relative intensities (depicted as vertical lines) of the calculated
transitions are also shown alongside the experimental UVevis
spectra in Fig. 3. Plots of the main occupied and virtual molecular
orbitals involved in the calculated transitions are shown in Fig. 4.
The calculated absorption spectra indicate that there is negli-
gible spectral intensity below 17,000 and 28,000 cmꢃ1, respectively,
for the nitro and non-nitro substituted species, in agreement with
the experimental spectra. The introduction of the nitro substituent
on the axial phenyl group results in a red-shift of the main lowest
energy band in the experimental spectra between 10,000 and
11,000 cmꢃ1 for 1 and Ru(4-C^CC6H4NO2)(dppe)( 5-C5H5), and
h
this shift is nicely reproduced in the calculated spectra. Based
on the observed band positions for Ru(C^CPh)(dppe)(h5
C5H5) and 2, and also their nitro-substituted analogues Ru(4-
C^CC6H4NO2)(dppe)(
5-C5H5) and 1, it appears that replacing
-
h
Fig. 3. Calculated and experimental absorption spectra for 1 (top left), 2 (top right), Ru(C^CPh)(dppe)(h h
5-C5H5) (bottom left) and Ru(4-C^CC6H4NO2)(dppe)( 5-C5H5) (bottom
right).

B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
113
Fig. 4. Major occupied and virtual molecular orbitals involved in the calculated transitions for (a) 1, (b) 2, (c) Ru(4-C^CC6H4NO2)(dppe)(h -
5-C5H5), and (d) Ru(C^CPh)(dppe)(h5
C5H5).
the dppe ligand by dppf has only a minor effect, at least for the
lowest energy transitions, and this is borne out in the calculated
spectra in that these bands have only minor contributions from the
phosphine-based donor ligands.
to higher energy, in the vicinity of 26,000 to 35,000 cmꢃ1, which
can be assigned to transitions arising from orbitals with Ru,
C2C6H4NO2 p and Cp
p character to orbitals largely localized on the
C2C6H4NO2 fragment. A very weak band is observed around
24,500 cmꢃ1 in complex 2 which, on the basis of the calculations,
can be attributed primarily to an internal charge transfer transition
on the dppf ligand. A similar weak band in the vicinity of
23,500 cmꢃ1 is also predicted for the corresponding nitro-
substituted complex 1 but, presumably, is obscured by the main
lowest energy band now positioned at approximately 22,000 cmꢃ1
due to the red-shift noted above.
On the basis of the data in Table 2, the main band at around
31,000 cmꢃ1 for Ru(C^CPh)(dppe)( 5-C5H5) can be assigned to
h
transitions originating from the 170a orbital, dominated by Rudxz
and C2 p character, to the 180a or 181a p* orbitals which are mostly
localized on the C2Ph fragment. For the corresponding nitro
substituted complex Ru(4-C^CC6H4NO2)(dppe)(h
5-C5H5), the
lowest energy band is red-shifted, as noted above, but can be
attributed to a transition from the 182a orbital possessing Rudx2ꢃy2
The first hyperpolarizability,
b, is a third rank tensor with 27
and C2C6H4NO2
p character, to the 183a orbital which is mostly of
components. Application of Kleinman symmetry [39] reduces the
C2C6H4NO2 p* character. In the case of the dppf complex 2, the main
band at approximately 32,500 cmꢃ1 is assigned to transitions from
the 204a, 206a and 207a orbitals, comprising a mixture of Rudz2/
number of unique components, allowing
following expression:
b
to be calculated from the
h
ꢀ
ꢁ
ꢀ
ꢁ
2
btot
¼
bxxx
þ
bxyy
bzxx
þ
bxzz 2 þ byyy
þ
byzz
þ
byxx
dx2ꢃy2, Fedz2 and C2Ph
p character, to the 212a, 219a and 221a levels
which are primarily p* orbitals on either the C2Ph fragment or dppf
ligand. For complex 1, the main (red-shifted) band at around
21,000 cmꢃ1 is assigned to a transition from the 219a orbital,
comprising Ru/Fedz2 and C2C6H4NO2 p character, to the 222a orbital
which is primarily of C2C6H4NO2 p* character.
i
1=2
ꢀ
ꢁ
2
þ
bzzz
þ
þ
bzyy
(1)
The calculated components of
b
and resulting btot value based on
the above equation are listed in Table 3 along with the experimental
value b0,exp that is obtained from the frequency dependent value
measured at 1064 nm using the two-level approximation [5]:
In addition, for the nitro-substituted complexes, 1 and Ru(4-
b
C^CC6H4NO2)(dppe)(h
5-C5H5), several weak bands are observed

114
B.A. Babgi et al. / Journal of Organometallic Chemistry 730 (2013) 108e115
Table 3
Calculated and observed NLO data for 1, 2, Ru(C^CPh)(dppe)(
h
5-C5H5) and Ru(4-C^CC6H4NO2)(dppe)(
h
5-C5H5).a
Complex
bxxx
bxyy
bxzz
1.0
byyy
byzz
byxx
bzzz
1.1
1.0
ꢃ1.1
0.6
bzxx
bzyy
btot
19.0
158.2
13.8
b0,exp
Ru(C^CPh)(dppe)(
Ru(4-C^CC6H4NO2)(dppe)(
Ru(C^CPh)(dppf)(
Ru(4-C^CC6H4NO2)(dppf)(
h
5-C5H5)
ꢃ11.8
ꢃ1.6
ꢃ8.0
4.1
ꢃ0.2
2.7
0.4
13.2
55.3
9.5
7.7
36.0
6.4
4.7
6.9
0.0
3.6
h
5-C5H5)
ꢃ114.5
ꢃ8.3
ꢃ19.5
ꢃ0.7
ꢃ4.7
161
72
165
h
5-C5H5) (2)
0.0
ꢃ0.8
h
5-C5H5) (1)
ꢃ109.2
ꢃ14.2
ꢃ8.6
2.5
3.5
48.9
36.7
148.7
a
Calculated and observed
b
in units of 10ꢃ30 esu; btot determined from equation (1); b0,exp evaluated using equation (2) (see Table 1).
h
ih
i
work. M.G.H. is an ARC Australian Professorial Fellow, M.P.C. is an
ARC Australian Research Fellow, and I.A. was a Postdoctoral Fellow
of FWO-Vlaanderen.
b0;exp
¼
bexp 1 ꢃ ð
l
max=1064Þ2 1 ꢃ ð2
l
max=1064Þ2
(2)
Addition of the nitro group on the axial phenylalkynyl fragment
in both complexes 1 and Ru(4-C^CC6H4NO2)(dppe)(h
5-C5H5) re-
Appendix A. Supplementary material
sults in an increase in the calculated btot values of between 135 and
140 ꢁ 10ꢃ30 esu. While the same level of enhancement is not evi-
dent in the experimental data for the dppf complex (1), a significant
increase of 93 ꢁ 10ꢃ30 esu in b0,exp is nonetheless observed, which
is consistent with other related group 8 metal alkynyl systems in
which a nitro substituent has been introduced on the axial phe-
nylalkynyl group [8].
CCDC 899522 (1) and CCDC 899523 (2) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Although none of the four complexes possess any symmetry,
a pseudo mirror plane exists in the xz plane, bisecting the Ru centre,
C2Ph/C2C6H4NO2 group and the Cp ring. Consequently, the calcu-
lated values for byyy and byzz are close to zero. For complexes 1 and
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