The reactions of 8-hydroxyquinoline with [RuHCl(CO)(PPh3)3]: A new ruthenium(II) carbonyl complex with a N-donor ligand

Article abstract of DOI:10.1016/j.poly.2007.05.026

The reaction of [RuHCl(CO)(PPh₃)₃] with 8-hydroxyquinoline has been examined and a novel ruthenium(II) complex - [RuCl(CO)(PPh₃)₂(C₉H₆NO)] - has been obtained. This compound has been studied by IR, UV-Vis (absorption and emission), ¹H and ³¹P NMR spectroscopy, and X-ray crystallography. The molecular orbital diagram of the complex has been calculated with the density functional theory (DFT) method. The spin-allowed singlet-singlet electronic transitions of the complex have been calculated with the time-dependent DFT method, and the UV-Vis spectrum of the compound has been discussed on this basis.

Full text of DOI:10.1016/j.poly.2007.05.026

Polyhedron 26 (2007) 4201–4208
www.elsevier.com/locate/poly
The reactions of 8-hydroxyquinoline with [RuHCl(CO)(PPh3)3]:
A new ruthenium(II) carbonyl complex with a N-donor ligand
a,
b
c
J.G. Małecki *, R. Kruszynski , Z. Mazurak
a
Department of Inorganic and Coordination Chemistry, Institute of Chemistry, University of Silesia, 9th Szkolna Street, 40-006 Katowice, Poland
_
X-ray Crystallography Laboratory, Institute of General and Ecological Chemistry, Technical University of Ło´dz´, 116 Zeromski Street, 90-924 Ło´dz´, Poland
b
c
Polish Academy of Sciences, Centre of Polymer Chemistry, M. Sklodowskiej-Curie 34, Zabrze 41-819, Poland
Received 17 February 2007; accepted 10 May 2007
Available online 31 May 2007
Abstract
The reaction of [RuHCl(CO)(PPh3)3] with 8-hydroxyquinoline has been examined and a novel ruthenium(II) complex – [RuCl-
1
(CO)(PPh3)2(C9H6NO)] – has been obtained. This compound has been studied by IR, UV–Vis (absorption and emission), H and 31P
NMR spectroscopy, and X-ray crystallography. The molecular orbital diagram of the complex has been calculated with the density func-
tional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the complex have been calculated with the time-
dependent DFT method, and the UV–Vis spectrum of the compound has been discussed on this basis.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Ruthenium carbonyl complexes; 8-Hydroxyquinoline; X-ray structure; UV–Vis spectrum; Luminescence; DFT calculations
1. Introduction
transfer and energy translocation [13,14], molecular elec-
tronic devices [15,16], supramolecular self-assembly pro-
cesses [17–20] and as DNA photoprobes [21–24].
Additionally these compounds contain a delocalized p-elec-
tron system which enlarge their advantages in usage as
luminescent and redox-active compounds [25–32]. On the
other hand, ruthenium compounds containing pyridine
derivatives and carbonyl groups have been extensively
studied because of their high activity in the water-gas shift
reaction and in the reduction of carbon dioxide. It was
found that these compounds participate in electrocatalytic
reduction of CO2 [33], thus the exploration of the chemistry
of such complexes as model species has outstanding impor-
tance [34].
In the chemistry of ruthenium, the coordination chemis-
try of complexes containing pyridine and pyridine deriva-
tives is one of the most studied areas. The wide interest is
this field originates from very rich redox chemistry and
photophysics of these compounds. Even small changes in
the coordination environment around ruthenium play a
key role in altering the redox properties of its complexes
and thus complexation of ruthenium by different ligands
is very interesting and widely studied [1–7]. These attributes
of substituted pyridine containing ruthenium compounds
leads to the application of them in conversion of solar
energy to electrical energy [8–12], in long-range electron
The coordination compounds of transition and non-
transition metals containing 8-hydroxyquinoline complexes
are also very interesting due to their application in OLED
materials [35,36]. 8-Hydroxyquinoline is also commonly
used for analytical determination of transition metals such
as Al3+, Ga3+, Pd2+, etc. [37]. Due to its optoelectronic
efficiency, the interest in the synthesis and properties of
*
Corresponding author.
E-mail addresses: gmalecki@us.edu.pl (J.G. Małecki), rafal.kruszyns-
ki@p.lodz.pl (R. Kruszynski), mazurak@cchp-pan.zabrze.pl (Z. Mazur-
ak).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.05.026

4202
J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
compounds containing 8-hydroxyquinoline and transition
metals has recently increased [38–41]. The title compound
joins the benefits of ruthenium coordination compounds
and complexes containing 8-hydroxyquinoline and
carbonyl groups, thus its synthesis and determination of
its properties were undertaken.
Anal. Calc. for C46H36ClNO2P2Ru: C, 66.31; H, 4.35;
Cl, 4.25; N, 1.68; O, 3.84; P, 7.43; Ru, 12.13. Found: C,
66.30; H, 4.33; N, 1.66%.
IR (KBr): 3056 mCH; 2987 mCH–phenyl; 1938 mC„O; 1569
m
CN; 1462 d(C–CH
plane); 1434 mPh(P–Ph); 1373
in the
(mring + mCH); 1324 (dCH); 1094 d(C–CH
plane) + mCO;
in the
In this paper we present the synthesis, crystal, molecular
and electronic structure, and luminescence and spectro-
scopic characterization of a new ruthenium(II) carbonyl
complex with the 8-hydroxyquinoline ligand.
742 d(C–C out of the plane); 693 d(C–C in the plane); 604 mP–Ph
.
31P NMR (d, CDCl3): (s, PPh3) 31.41.
UV–Vis (nm) in CH2Cl2 (loge): 417.4 (4.54); 328.2
(4.90); 259.6 (5.11); 221.2 (4.92).
2. Experimental
2.4. Crystal structure determination and refinement
All reagents used in the synthesis of the complex are
commercially available and were used without further puri-
fication. The [RuHCl(CO)(PPh3)3] complex was synthe-
sized by a published procedure [42].
A yellow prism of the studied complex was mounted on
a KM-4-CCD automatic diffractometer equipped with a
CCD detector, and used for data collection. X-ray inten-
sity data were collected with graphite-monochromated
˚
Mo Ka radiation (k = 0.71073 A) at the temperature
291.0(3) K, with the x scan mode. The full Ewald sphere
reflections were collected up to 2h = 50.24ꢁ. The unit cell
parameters were determined from least-squares refinement
of the setting angles of 9369 strongest reflections for the
complex. Details concerning crystal data and refinement
are given in Table 1. Monitoring of 173 reflection intensi-
ties on reference frames measured every 40 frames show
7.32% decay of intensity. During the data reduction the
above decay correction coefficient was taken into account.
Lorentz, polarization, and numerical absorption [49] cor-
2.1. Physical measurements
Infrared spectra were recorded on a Nicolet Magna 560
spectrophotometer in the spectral range 4000–400 cmꢀ1
with the sample in the form of a KBr pellet. Electronic
spectra were measured on a spectrophotometer Lab Alli-
ance UV–Vis 8500 in the range 800–200 nm in dichloro-
methane solution. Elemental analyses (C, H, N) were
performed on a Perkin–Elemer CHN–2400 analyzer. The
1H NMR spectrum was obtained at room temperature
in CDCl3 using an INOVA 300 spectrometer. Lumines-
cence measurements were made on a Jobin-Yvon (SPEX)
FLUOROLOG-3.12 spectrofluorometer at room tem-
perature.
Table 1
Crystal data and structure refinement details of [RuCl(CO)(PPh3)2-
(C9H6NO)]
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C46H36ClNO2P2Ru
833.22
291.0(3)
monoclinic
P21/c
2.2. DFT calculations
The GAUSSIAN-03 program [43] was used in the calcula-
tions. The geometry optimization was carried out with the
DFT method with the use of B3LYP functional [44,45].
The electronic transitions were calculated with the PCM
model [46] with dichloromethane as the solvent. The calcu-
lation was performed using the DZVP basis set [47] with f
functions with exponents 1.94722036 and 0.748930908 on
the ruthenium atom, and polarization functions for all
other atoms: 6-31g(2d,p) – chlorine, 6-31g** – carbon, nitro-
gen, oxygen and 6-31g(d,p) on hydrogen atoms. Natural
bond orbital (NBO) calculations were performed with the
NBO code [48] included in GAUSSIAN-03.
˚
a (A)
15.6122(7)
20.6761(11)
24.8752(12)
90.00
101.676(4)
90.00
7863.5(7)
8
1.408
0.587
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
3408
Crystal dimensions (mm)
h Range for data collection (ꢁ)
Index ranges
0.403 · 0.258 · 0.169
2.69–25.12
ꢀ18 6 h 6 18,
ꢀ21 6 k 6 24,
ꢀ29 6 l 6 29
14011
9005 (0.0988)
9005/0/955
1.103
2.3. Synthesis of [RuCl(CO)(PPh3)2(C9H6NO)]
Reflections collected
A suspension of [RuHCl(CO)(PPh3)3] (0.95 g; 1 · 10ꢀ3
mol) and 8-hydroxyquinoline (0.36 g; 2 · 10ꢀ3 mol) in
dimethoxyethane (100 cmꢀ3) was refluxed until the solid
dissolved, then the solution was cooled and filtered. Yellow
crystals suitable for X-ray crystal analysis were obtained by
slow evaporation of the reaction mixture. Yield: 81%.
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
)
R1 = 0.1288, wR2 = 0.1455
R1 = 0.0633, wR2 = 0.1202
0.631 and ꢀ0.553
ꢀ3
˚
Largest difference in peak and hole (e A
)

J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
4203
rections were applied. The structure was solved by the
Patterson method combined with a partial structure
expansion procedure. All the non-hydrogen atoms were
refined anisotropically using the full-matrix least-squares
technique on F2. The hydrogen atoms were found from
difference Fourier synthesis after four cycles of anisotropic
refinement, and refined as ‘‘riding’’ on the adjacent atom
with individual isotropic temperature factors equal to 1.2
times the value of the equivalent temperature factor of
the parent atom, with geometry idealization after each
cycle. SHELXS-97 [50], SHELXL-97 [51] and SHELXTL [52] pro-
grams were used for all the calculations. Atomic scattering
factors were those incorporated in the computer
programs.
1434 cmꢀ1 indicates the presence of triphenylphosphine
ligands. The singlet at 31.41 ppm in the 31P NMR spec-
trum indicates both triphenylphosphoine ligands in the
studied complex are equivalent and are mutually trans
disposed.
3.1. Crystal structure
The [RuCl(CO)(PPh3)2(C9H6NO)] complex crystallises
in the monoclinic P21/c group and the crystal structure
is built up of two independent molecules in the asymmet-
ric unit. Both molecules have the same conformation (the
root mean square deviation of superimposed molecules
˚
atoms is 0.133 A and the most distant O(2) atoms are sep-
˚
arated by 0.335 A). The relative orientation of the mole-
3. Results and discussion
cules is depicted in Fig. 1, which also shows the
displacement ellipsoids of the non-hydrogen atoms. These
two molecules are twisted with respect to one another by
62.81(4)ꢁ, which prevents the existence of higher crystallo-
graphic symmetry. The structural drawing is presented in
Fig. 2. The most important angles and bond lengths for
the complex are reported in Table 2. The weak intra-
and intermolecular hydrogen bonds [53,54] are presented
in Table 3.
The reaction of the complex [RuHCl(CO)(PPh3)3] with
8-hydroxyquinoline has been performed. Refluxing a
ruthenium carbonyl hydrido complex with an excess of
8–hydroxyquinoline in dimethoxyethane leads to the com-
plex [RuCl(CO)(PPh3)2(C9H6NO)] in good yield. The ele-
mental analysis of the complex is in good agreement with
its formulation. The IR spectrum of the complex is consis-
tent with its molecular structure. The bands of C„O and
C@N stretching modes are observed at 1938 and
1569 cmꢀ1, respectively. The mPh(P–Ph) absorption band at
The ruthenium atom in the complex [RuCl(CO)-
(PPh3)2(C9H6NO)] is in a distorted octahedral environment
with trans triphenylphosphine ligands (average P–Ru–P
Fig. 1. Relative orientation of two molecules of the [RuHCl(CO)(PPh3)2(C9H6NO)] complex in the asymmetric unit. The displacement ellipsoids are
drawn with 50% probability.

4204
J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
122.5ꢁ to 146.8ꢁ) and two linking the phosphine phenyl
˚
C–H and O (Dꢁ ꢁ ꢁA distance 2.885(6) and 2.884(6) A and
D–Hꢁ ꢁ ꢁA angle 117.0ꢁ and 100.1ꢁ). One intermolecular
hydrogen bond is observed, C(89)–H(89)ꢁ ꢁ ꢁO(52)(#1
˚
ꢀx + 1, y ꢀ 1/2, ꢀz + 1/2) (Dꢁ ꢁ ꢁA distance 3.470(9) A;
D–Hꢁ ꢁ ꢁA angle 171.1ꢁ).
O
N
3.2. Geometry optimization
Ru
(C H ) P
P(C H )
6 5 3
6
5 3
The geometry of the studied complex was optimized by
the DFT method with the B3LYP functional. The opti-
mized geometry parameters for the [RuCl(CO)(PPh3)2-
(C9H6NO)] complex are gathered in Table 2. In general,
the predicted bond lengths and angles are in agreement
with the values based upon the X-ray crystal structure
data, and the general trends observed in the experimental
data are reproduced in the calculations. The calculated
bond lengths and angles for [RuCl(CO)(PPh3)2(C9H6NO)]
agree with the experimental results; the largest difference is
OC
Cl
Fig. 2. Structural drawing of [RuHCl(CO)(PPh3)2(C9H6NO)].
angle 177.62(5)ꢁ). The carbonyl ligand is in trans position
to the hydroxyquinoline N donor atom (average C–Ru–
N angle 170.8(3)ꢁ) and the chloride ion lies trans to the
hydroxyquinoline oxygen atom with an average angle of
171.07(11)ꢁ. All Ru–ligand distances, such as Ru–Cl
2.4183(18), Ru–P 2.4105(14), 2.4106(14), Ru–N 2.1270(4),
˚
found for the C(43)–O(2) bond (ꢂ0.25 A). The maximum
difference between the calculated and experimental angles
are visible for N(1)–Ru(1)–P(1) and C(46)–Ru(1)–O(1)
and are close to 2.1ꢁ and 2.0ꢁ, respectively.
˚
Ru–C 1.9585(7) and Ru–O 2.0770(3) A, are normal and
are comparable with distances in other ruthenium com-
plexes containing heterocyclic ligands [55–58]. The C(46)–
O(2) bond shows some shortening in comparison with typ-
ical distances in CO substituents, but similar distances can
be found in several compounds [59–76].
3.3. Electronic structure and NBO analysis
In the studied complex, the occupied dxy and dxz ruthe-
nium orbitals participate in backdonation from the central
metal ion to the carbonyl ligand. The largest contribution
of the pRu–CO bonding interaction is visible in the Hꢀ1
and Hꢀ3 orbitals. The pRꢃ u–CO orbitals are also distributed
The conformation of the molecule is stabilized by five
weak intramolecular hydrogen bonds, three between the
phenyl CH and the Cl ligand (Dꢁ ꢁ ꢁA distance varies from
˚
3.334(7) to 3.492(6) A and D–Hꢁ ꢁ ꢁA angle varies from
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for [RuCl(CO)(PPh3)2(C9H6NO)]
Experimental
Calculated
˚
Bond lengths (A)
Ru(1)–C(46)
Ru(1)–O(1)
Ru(1)–N(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–Cl(1)
C(46)–O(2)
1.975(7)
2.076(3)
2.127(4)
2.4128(14)
2.4089(14)
2.4097(18)
0.884(7)
Ru(52)–C(96)
Ru(52)–O(51)
Ru(52)–N(51)
Ru(52)–P(51)
Ru(52)–P(52)
Ru(52)–Cl(51)
C(96)–O(52)
1.942(7)
2.078(3)
2.127(4)
2.4081(14)
2.4123(14)
2.4270(16)
0.932(6)
1.876
2.106
2.182
2.466
2.467
2.482
1.159
Bond angles (ꢁ)
C(46)–Ru(1)–O(1)
C(46)–Ru(1)–N(1)
O(1)–Ru(1)–N(1)
C(46)–Ru(1)–P(2)
O(1)–Ru(1)–P(2)
N(1)–Ru(1)–P(2)
C(46)–Ru(1)–Cl(1)
O(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(1)
P(2)–Ru(1)–Cl(1)
C(46)–Ru(1)–P(1)
O(1)–Ru(1)–P(1)
P(2)–Ru(1)–P(1)
Cl(1)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
92.2(3)
171.6(3)
79.32(16)
90.6(2)
88.76(10)
88.84(11)
96.8(2)
170.84(11)
91.59(13)
89.94(5)
91.7(2)
90.48(10)
177.58(5)
90.44(5)
88.76(11)
C(96)–Ru(52)–O(51)
C(96)–Ru(52)–N(51)
O(51)–Ru(52)–N(51)
C(96)–Ru(52)–P(52)
O(51)–Ru(52)–P(52)
N(51)–Ru(52)–P(52)
C(96)–Ru(52)–Cl(51)
O(51)–Ru(52)–Cl(51)
N(51)–Ru(52)–Cl(51)
P(52)–Ru(52)–Cl(51)
C(96)–Ru(52)–P(51)
O(51)–Ru(52)–P(51)
P(51)–Ru(52)–P(52)
P(51)–Ru(52)–Cl(51)
N(51)–Ru(52)–P(51)
90.1(2)
170.0(2)
93.18
171.22
78.04
88.96
91.09
91.20
97.72
169.10
91.06
89.09
88.97
91.08
177.08
89.15
91.16
79.89(15)
90.27(18)
88.78(10)
88.48(11)
98.57(19)
171.29(11)
91.41(12)
90.59(5)
92.04(18)
91.67(10)
177.65(5)
88.62(5)
89.33(11)

J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
4205
Table 3
Table 4
˚
Hydrogen bonds for [RuCl(CO)(PPh3)2(C9H6NO)] (A and ꢁ)
The energy and character of selected occupied and virtual MOs for
[RuCl(CO)(PPh3)2(C9H6NO)]
D–Hꢁ ꢁ ꢁA
C(6)–H(6)ꢁ ꢁ ꢁCl(1)
d(D–H)
d(Hꢁ ꢁ ꢁA)
d(Dꢁ ꢁ ꢁA)
\(DHA)
MO
Energy
Character
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
2.70
2.34
2.68
2.57
2.74
2.79
2.40
2.69
2.77
2.55
3.452(6)
2.885(6)
3.492(6)
2.884(6)
3.334(7)
3.455(6)
2.972(6)
3.452(6)
3.360(6)
3.470(9)
138.9
117.0
146.8
100.1
122.5
129.6
119.4
139.8
122.3
171.1
C(12)–H(12)ꢁ ꢁ ꢁO(1)
C(24)–H(24)ꢁ ꢁ ꢁCl(1)
C(30)–H(30)ꢁ ꢁ ꢁO(1)
C(37)–H(37)ꢁ ꢁ ꢁCl(1)
C(56)–H(56)ꢁ ꢁ ꢁCl(51)
C(62)–H(62)ꢁ ꢁ ꢁO(51)
C(74)–H(74)ꢁ ꢁ ꢁCl(51)
C(87)–H(87)ꢁ ꢁ ꢁCl(51)
C(89)–H(89)ꢁ ꢁ ꢁO(52)#1
Hꢀ15
Hꢀ14
Hꢀ13
Hꢀ12
Hꢀ11
Hꢀ10
Hꢀ9
Hꢀ8
Hꢀ7
Hꢀ6
Hꢀ5
Hꢀ4
Hꢀ3
Hꢀ2
Hꢀ1
H
L
L+1
L+2
L+3
L+4
L+5
L+6
L+7
ꢀ6.797
ꢀ6.776
ꢀ6.723
ꢀ6.651
ꢀ6.614
ꢀ6.596
ꢀ6.581
ꢀ6.514
ꢀ6.486
ꢀ6.404
ꢀ6.365
ꢀ6.019
ꢀ5.748
ꢀ5.095
ꢀ4.788
ꢀ4.272
ꢀ1.034
ꢀ0.563
ꢀ0.487
ꢀ0.408
ꢀ0.249
ꢀ0.134
ꢀ0.027
0.052
pPPh
3
pPPh
3
pPPh
3
pPPh
3
pPPh
3
pPPh
3
pPPh
3
pPPh þ pCl
3
pPPh þ phq
3
pPPh þ pCl
3
Symmetry transformations used to generate equivalent atoms: #1 ꢀx + 1,
pPPh þ phq
3
y ꢀ 1/2, ꢀz + 1/2.
dRu + nP
dRu þ pꢃCO
dRu þ pꢃCl
dRu þ pꢃCl þ pꢃCO
dRu þ pꢃO
pꢃhq
among several unoccupied molecular orbitals. Their contri-
bution is visible in L+14, L+15. The HOMO orbital of the
[RuCl(CO)(PPh3)2(C9H6NO)] complex is composed of the
dxz metal orbital and the hydroxyquinoline oxygen p orbi-
tal in an anti-bonding arrangement. The LUMO orbital is
localized on the hydroxyquinoline ring. The dz2 orbital of
the Ru atom makes the largest contribution to L+2 and,
whereas L+4, L+14 and L+15 have dx2ꢀy2 character.
In some of the lowest unoccupied molecular orbitals of
[RuCl(CO)(PPh3)2(C9H6NO)], the contribution of the
phosphorous orbitals is visible (L+1, L+2, L+3). In classi-
cal concepts empty phosphorous 3d orbitals are used in the
p-back bonding between the metal center and the phos-
phine ligand. Now it is generally recognized that d orbitals
have very high energy and play only a minor role in the
pM–PR3 bond formation [77]. In the p-back bonding
between the metal center and the phosphine ligand, the
r*(P–C) orbitals are involved. The HOMO–LUMO gap
is 3.24 eV. The energy and character of the selected frontier
molecular orbitals are given in Table 4.
pꢃPPh þ nP
3
dRu þ pꢃ þ nP
pꢃPPh þ PnPPh
3
3
dRu þ pꢃ
PPh3
pꢃPPh
3
pPPh þ pꢃhq
3
pꢃPPh
3
L+8
L+9
0.106
0.180
0.207
0.268
0.301
0.312
0.537
1.140
pꢃPPh
3
pꢃPPh
3
L+10
L+11
L+12
L+13
L+14
L+15
pꢃPPh
3
pꢃPPh
3
pꢃPPh
3
pꢃPPh
3
dRu þ pꢃCO
dRu þ pꢃCO
H denotes HOMO; L denotes LUMO.
Table 5
The occupancies and hybridization of the calculated Ru–C and C–O
natural bond orbitals (NBOs) of [RuCl(CO)(PPh3)2(C9H6NO)]
The natural bond orbital (NBO) rAB can be written in
terms of two directed valence hybrids (HHOs) hA and hB
on atoms A and B:
BD
Occupancy
Hybridization of NBO
(2-center bond)
Ru(1)–C(46)
C(46)–O(2)
1.955 (0.309) 0.513(sd3.75
1.998 (0.080) 0.533(sp61.70d0.20
1.997 (0.091) 0.532(sp)C + 0.847(p)O
1.995 (0.018) 0.546(sp2.26 C + 0.838(sp0.39
) )
Ru + 0.859(sp0.47
C
rAB ¼ cAhA þ cBhB
where cA and cB are polarization coefficients. Each valence
bonding NBO must in turn be paired with a corresponding
valence anti-bonding NBO:
)
C + 0.846(sp34.32d0.23
)
O
)
)
O
rꢃAB ¼ cBhA ꢀ cAhB
tals are polarized towards the carbon atom, and the C–O
bond orbitals are polarized towards the oxygen end. The
oxygen atom of the carbonyl ligand has one lone pair
(LP) orbital. The occupancies and hybridization of the
CO and Ru–C bonds are gathered in Table 5 (anti-bonding
NBOs are given in round brackets).
Not detected in NBO analysis, the Ru–N(hq) and
Ru–O(hq) bonds have a character consisting of predomi-
nantly Coulomb-type interactions between the central ion
and the 8-hydroxyquinoline ligand [78].
to complete the span of the valence space. The Lewis-type
(donor) NBOs are thereby complemented by the non-Le-
wis-type (acceptor) NBOs that are formally empty in an
idealized Lewis picture. The interactions between ‘‘filled’’
Lewis-type NBOs and ‘‘empty’’ non-Lewis NBOs lead to
loss of occupancy from the localized NBOs of the idealized
Lewis structure into the empty non-Lewis orbitals, and
they are referred to as ‘‘delocalization’’ corrections to the
zeroth-order natural Lewis structure.
For the carbonyl group of the investigated complex,
three natural bond orbitals were detected for the C–O
bond, and one for the Ru–C bond. The Ru–C bond orbi-
The calculated charge on the ruthenium atom in the
complex [RuCl(CO)(PPh3)2(C9H6NO)] is considerable
lower than the formal charge of +2, and is close to 0.21.

4206
J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
I0
The charge on the carbon atom of the carbonyl ligand is
positive (+0.59), whereas the oxygen atom is negatively
charged (ꢀ0.30).
I ¼
;
ꢀ
ꢁ
2
mꢀm0
1 þ
c
The charges on the P atoms are positive and close to
1.15; the charge on the chloride ligand is smaller than ꢀ1
(ꢀ0.62), the charge on the hydroxyquinoline ligand is close
to ꢀ0.53. The occupancies of the ruthenium d orbitals,
obtained from NBO analysis, are as follows: dxy ꢀ1.84;
dxz ꢀ1.89; dyz ꢀ0.86; dx2ꢀy2 ꢀ1.25; dz2 ꢀ1.60.
where c ¼ 1=2 spectral width on 1=2 height:
Ninety electronic transitions were calculated using the
TDDFT method and they do not comprise all the experi-
mental absorption bands. The UV–Vis spectrum was calcu-
lated up to ꢂ225 nm, so the shortest wavelength
experimental bands cannot be assigned to the calculated
transitions. However, considering that the solution spectra
of PPh3 and 8-hydroxyquinoline exhibit intense absorption
bands in the 260–200 nm region, some additional intrali-
gand and interligand transitions are expected to be found
at higher energies in the calculations.
The assignments of the calculated transitions to the
experimental bands are based on the criterion of the energy
and oscillator strength of the calculated transitions. In the
description of the electronic transitions only the main com-
ponents of the molecular orbitals are taken into
consideration.
3.4. Electronic spectrum
The experimental and calculated electronic spectra of
[RuCl(CO)(PPh3)2(C9H6NO)] are presented in Fig. 3. The
contour of calculated spectrum was broadening by the
Lorentzian function, calculated by the formula:
The longest wavelength experimental unsymmetrical
broad band, with a maximum at 417.4 nm, is assigned to
the transitions from the HOMO to LUMO and
LUMO + 2 orbitals. As the LUMO orbital is composed
of the p* orbitals of the 8-hydroxyquinoline ring, the tran-
sition is of the Metal–Ligand Charge Transfer type with a
d ! d (Ligand Field) contribution.
The next band, with maximum at 328.2 nm, is
ascribed to the metal–ligand charge transfer transitions
d ! pꢃPPh and d ! phꢃq. In this region the transitions
3
between HOMO and HOMO ꢀ 2 MOs were calculated.
The last calculated transition, attributed to experimental
one at 259.6 nm, proceeds mainly from the d ruthenium
10000
8000
6000
4000
2000
0
200
400
600
800
[nm]
220 240 260 280 300 320 340 360 380 400 420 440 460
Wavelength, nm
450
500
550
nm
600
650
Fig. 3. The UV–Vis spectra of [RuCl(CO)(PPh3)2(C9H6NO)]: (a) exper-
imental and (b) calculated.
Fig. 4. The emission spectrum of [RuCl(CO)(PPh3)2(C9H6NO)].

J.G. Małecki et al. / Polyhedron 26 (2007) 4201–4208
4207
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orbitals with an admiꢃxture of p chloride and p carbonyl
orbitals to pꢃPh and phq, with an admixture of Ligand–
Ligand Charge Transfer transitions (pPPh ! pꢃhq;
3
HOMO ꢀ 5/6 ! LUMO + 1).
The intraligand transition pPPh ! pꢃPPh was calculated
3
3
at 229.9 nm and it can be assumed that the experimental
band at 221.2 nm (not assigned on the basis of the calcu-
lated transitions) is composed of the transitions in the
PPh3 ligands and from p ! p* excitations in the hydroxy-
quinoline ligand. As it was pointed out in the literature,
the TDDFT method gives such transitions at too small
energies [79–87] and we may expect also that this is the case
in our calculations.
The emission property of the studied complex has been
examined in dichloromethane solution at room tempera-
ture. The luminescence spectrum is presented in Fig. 4.
On excitation at 417 nm, an emission peak was observed
at 513 nm and it was independent of the concentration of
the solution. The emission originates from the lowest
energy metal to ligand charge transfer (MLCT) state,
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CCDC 635757 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
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The crystallographic part was financed by funds allo-
cated by the Ministry of Science and Higher Education
to the X-ray Crystallography and Crystal Chemistry
Group, Institute of General and Ecological Chemistry,
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