Synthesis, crystal, molecular and electronic structures of hydride carbonyl ruthenium(II) complexes with pyridine and its derivative ligands

Article abstract of DOI:10.1016/j.poly.2010.09.028

[RuHCl(CO)(PPh₃)₂(py)], [RuHCl(CO)(PPh ₃)₂(pyIm)] and [RuCl(CO)(PPh₃) ₂(pyoh)]·2CH₃OH complexes (where py = pyridine, pyIm = imidazo[1,2-α]pyridine, pyoh = 2-hydroxy-6-methylpyri

Full text of DOI:10.1016/j.poly.2010.09.028

Polyhedron 30 (2011) 79–85
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, crystal, molecular and electronic structures of hydride carbonyl
ruthenium(II) complexes with pyridine and its derivative ligands
J.G. Małecki
Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2010
Accepted 23 September 2010
Available online 1 October 2010
[RuHCl(CO)(PPh3)2(py)], [RuHCl(CO)(PPh3)2(pyIm)] and [RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH complexes
(where py = pyridine, pyIm = imidazo[1,2-a]pyridine, pyoh = 2-hydroxy-6-methylpyridine) have been
prepared and studied by IR, NMR, UV–Vis spectroscopy and X-ray crystallography. Electronic structures
and bonding of the complexes were defined on the basis of DFT method, and the pyridine derivative
ligands were compared on the basis of their donor–acceptor properties. Values of the ligand field param-
eter 10Dq and Racah’s parameters were estimated for the studied compounds, and the luminescence
properties were determined.
Keywords:
Ruthenium hydride–carbonyl complexes
Pyridine
Imidazo[1,2-a]pyridine
Ó 2010 Elsevier Ltd. All rights reserved.
2-Hydroxy-6-methylpyridine
X-ray structure
UV–Vis
Luminescence
DFT
TD-DFT
1. Introduction
ruthenium polypyridyl complexes have been researched exten-
sively for decades as photochemical molecular devices due to their
Chemistry of ruthenium complexes with nitrogen-containing li-
gands has been attracting continuous attention due to their variety
of structures, reactivities, and photophysical and photochemical
properties [1–3]. The azine ligands have energetically low lying
excellent chemical stability, facial electron transfer, strong lumi-
nescence and emission and relatively long-lived excited states
[8,9]. Among the studied hydride-carbonyl ruthenium(II) com-
plexes with pyridine derivatives ligands, the simple [RuHCl(CO)
(py)(PPh3)2] complex has not been described like the complexes
p-antibonding orbitals, which can accept electrons from filled me-
tal d orbitals. In consequence, they can exhibit charge transfer
bands with interesting spectroscopic properties in the visible re-
gion [4]. Ligands containing pyridine ring are wide studied and
with imidazo[1,2-a]pyridine and 2-hydroxy-6-methylpyridine li-
gands. DFT and TDDFT calculations were performed to establish
the nature of orbitals involved in transition processes and to corre-
late the structural parameters with the spectroscopic properties of
the complexes.
their
p-donor properties are interesting. Its combination with
other donor atoms should in principle afford complexes with tun-
able spectroscopic properties [5,6]. The hydride ligand – a powerful
r
-donor – is found to be very efficient at compensating the elec-
2. Experimental
tron deficiency at the metal central ion in complexes. The ‘‘trans
effect” of Hꢁ ligand and the interaction between CO and N-donor
ligands in trans positions to one another are stabilizing factors
which explain stability of these complexes [7].
Besides, luminescent metal complexes are a fascinating class of
molecules that have found applications in many areas, among
which luminescent Ru(II) bipyridyl compounds have been exten-
sively studied. The ruthenium(II) metal to ligand charge transfer
(MLCT) compounds are known to display long lived luminescence
life times. They are also extremely photo stable. In particular,
All reagents used for the synthesis of the complex are commer-
cially available and have been used without further purification.
The [RuHCl(CO)(PPh3)3] complex was synthesized according to
the literature method [10].
2.1. Syntheses of [RuHCl(CO)(PPh3)2(L)] complexes L = pyridine (py),
imidazo[1,2-a]pyridine (pyIm), 2-hydroxy-6-methylpyridine
The complex was synthesized in a reaction between [RuHCl
(CO)(PPh3)3] (1 ꢂ 10ꢁ4 mol) and pyridine, imidazo[1,2-
a]pyridine
E-mail address: gmalecki@us.edu.pl
or 2-hydroxy-6-methylpyridine (1 ꢂ 10ꢁ4 mol) in methanol solution
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.09.028

80
J.G. Małecki / Polyhedron 30 (2011) 79–85
(50 cmꢁ3). The mixture of the compounds was refluxed in metha-
nol by 3 h. After this time, it was cooled and filtered. The crystals
suitable for X-ray crystal analysis were obtained by slow evapora-
tion of the reaction mixture.
Compound 1: Yield 78%. Anal. Calc. for C42H36ClNOP2Ru: C,
65.58; H, 4.72; N, 1.82. Found: C, 66.04; H, 4.69; N, 1.85%.
2.1.1. Physical measurements
Infrared spectra were recorded on a Nicolet Magna 560 spectro-
photometer in the spectral range 4000–400 cmꢁ1 using KBr pellets.
Electronic spectra were measured on a Lab Alliance UV–Vis 8500
spectrophotometer in the range of 500–180 nm in methanol solu-
tion. The 1H and 31P NMR spectra were obtained at room temper-
ature in CDCl3 using Bruker 400 spectrometer. Luminescence
measurements were made on a F-2500 FL spectrophotometer at
room temperature. Elemental analyses (C, H, N) were performed
on a Perkin–Elmer CHN-2400 analyzer.
IR (KBr): 3053
m
ArH; 1995
m
(Ru-H); 1920
m
(CO); 1600
1432 mPh(P–Ph);
m
(CN); 1586
1091
m(C@C)
;
1480, 1311 d(C–CH
;
in the plane)
d(C–CH in the plane); 998 d(C–H out of the plane); 745 d(C–C out of the plane)
;
695 d(C–C
plane); 520 m(P–Ph+P–Ru). UV–Vis (methanol; log e):
in the
370.1 (1.13), 330.8 (1.90), 270.4 (2.96), 211.5 (4.98). 1H NMR
(d, CDCl3): 7.720–7.124 (m, PPh3, py), ꢁ13.491 (t, HRu). 31P NMR
(d, CDCl3): 45.709 (s, PPh3). Luminescence: exc = 370 nm, emis-
sion = 430 nm; exc = 331 nm, emission = 380 nm.
2.1.2. DFT calculations
The calculations were carried out using GAUSSIAN09 [11]
program. The DFT/B3LYP/CAM-B3LYP [12–14] method was used
for the geometry optimization and electronic structure determi-
nation, and electronic spectra were calculated by TD-DFT [15]
method. The calculations were performed using the DZVP basis
Compound 2: Yield 83%. Anal. Calc. for C44H37ClN2OP2Ru: C,
65.39; H, 4.61; N, 3.47. Found: C, 65.24; H, 4.69; N, 3.49%. IR
(KBr): 3050
1480, 1313 d(C–CH in the plane); 1433
1028 d(C–H out of the plane); 741 d(C–C out of the plane); 693 d(C–C in the plane)
m
ArH; 2016
m
(Ru-H); 1900
m
(CO); 1635
m
(CN); 1571 m(C@C)
;
mPh(P–Ph); 1092 d(C–CH in the plane)
;
;
set [16] with
0.748930908 on ruthenium atom, and polarization functions
**
f functions with exponents 1.94722036 and
519
m(P–Ph+P–Ru). UV–Vis (methanol; log e): 360.3 (1.23), 310.2
(2.90), 265.1 (3.86), 211.3 (5.02). 1H NMR (d, CDCl3): 8.141 (s,
1Himidazole), 7.574–7.176 (m, PPh3, pyIm), ꢁ13.322 (t, HRu). 31P
NMR (d, CDCl3): 45.376 (s, PPh3). Luminescence: exc = 360 nm,
emission = 420 nm; exc = 310 nm, emission = 370 nm.
for all other atoms: 6-31g
– sulfur, carbon, nitrogen and
6-31g – hydrogen. The PCM (Polarizable Continuum Model) sol-
vent model was used in the GAUSSIAN calculations with methanol
as the solvent. Natural bond orbital (NBO) calculations were
performed with the NBO code [17] included in GAUSSIAN09. The
contribution of a group to a molecular orbital was calculated
using Mulliken population analysis. GAUSSSUM 2.2 [18] was used
to calculate group contributions to the molecular orbitals and
to prepare the partial density of states (DOS) and overlap pop-
ulation density of states (OPDOS) spectra. The DOS and OPDOS
spectra were created by convoluting the molecular orbital infor-
mation with GAUSSIAN curves of unit height and FWHM (Full
Width at Half Maximum) of 0.3 eV. Mayer bond orders were
calculated with use of QMFORGE program [19].
Compound 3: Yield 83%. Anal. Calc. for C45H44ClNO4P2Ru: C,
62.75; H, 5.15; N, 1.63. Found: C, 62.79; H, 5.23; N, 1.59%. IR
(KBr): 3435
1471 d(C–CH in the plane); 1435
745 d(C–C plane); 696 d(C–C
m
OH; 3052
m
ArH; 1940
Ph(P–Ph); 1092 dOH; 1028 d(C–H out of the plane)
plane); 522 (P–Ph+P–Ru)..
e): 368.8 (1.23), 291.6 (2.90), 261.0 (2.81),
m(CO); 1712 m(CN); 1601 m(C@C);
m
;
m
out of the
in the
UV–Vis (methanol; log
216.4 (4.92). 1H NMR (d, CDCl3): 7.283–6.857 (m, PPh3, pyo),
2.508 (s, CH3), 3.260, 2.618 (CH3OH). 31P NMR (d, CDCl3): 45.681,
40.035 (d, PPh3). Luminescence: exc = 360 nm, emission = 415 nm;
exc = 292 nm, emission = 375 and 450 nm.
Table 1
Crystal data and structure refinement details of [RuHCl(CO)(py)(PPh3)2] (1), [RuHCl(CO)(PPh3)2(pyIm)] (2) and [RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH (3) complexes.
1
2
3
Empirical formula
Formula weight
T (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
42H36ClNOP2Ru
C44H37ClN2OP2Ru
808.22
295.0(2)
monoclinic
P21/c
C43H36ClNO2P2Ru, 2(CH4O)
861.27
769.18
298.0(2)
monoclinic
P21/n
295.0(2)
triclinic
ꢀ
P1
15.8866(12)
14.1353(8)
16.0535(15)
90
11.069(2)
24.400(5)
28.016(6)
90
11.277(2)
11.535(3)
18.133(5)
76.19(2)
b (Å)
c (Å)
a
(°)
b (°)
97.903(7)
90
3570.8(5)
4
1.431
0.638
92.41(3)
90
7560(3)
8
1.420
0.607
3312
88.818(12)
80.45(2)
2258.4(10)
2
1.267
0.517
c
(°)
V (Å3)
Z
DCalc. (Mg/m3)
Absorption coefficient (mmꢁ1
F(0 0 0)
)
1576
888
Crystal dimensions (mm)
h Range for data collection (°)
Index ranges
0.17 ꢂ 0.16 ꢂ 0.07
3.37–25.05
ꢁ18 6 h 6 15
ꢁ16 6 k 6 16
ꢁ16 6 l 6 19
10 291
0.22 ꢂ 0.21 ꢂ 0.06
3.40–25.05
ꢁ13 6 h 6 10
ꢁ23 6 k 6 28
ꢁ33 6 l 6 25
33 103
0.34 ꢂ 0.27 ꢂ 0.14
3.47–25.05
ꢁ13 6 h 6 13
ꢁ13 6 k 6 13
ꢁ21 6 l 6 21
40 553
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
)
6315 (0.0740)
6315/0/437
0.990
13 342 (0.0298)
13 342/0/927
1.022
7972 (0.0342)
7972/0/490
1.068
Final R indices [I > 2
r
(I)]
R1 = 0.0397
wR2 = 0.0714
R1 = 0.0768
wR2 = 0.0819
1.003 and ꢁ0.638
R1 = 0.0381
wR2 = 0.0800
R1 = 0.0600
wR2 = 0.0844
0.421 and ꢁ0.543
R1 = 0.0418
wR2 = 0.1224
R1 = 0.0512
wR2 = 0.1285
1.250 and ꢁ0.646
R indices (all data)
Largest difference in peak and hole (e Åꢁ3
)

J.G. Małecki / Polyhedron 30 (2011) 79–85
81
Fig. 1. ORTEP drawing of [RuHCl(CO)(py)(PPh3)2] (1), [RuHCl(CO)(PPh3)2(pyIm)] (2) and [RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH (3) with 50% probability displacement ellipsoids.
Hydrogen atoms (except Ru–H) and solvent molecules are omitted for clarity.
2.2. Crystal structures determination and refinement
trix, least-squares technique on F2. The Ru–H hydrogen atoms were
found from difference Fourier synthesis after four cycles of aniso-
tropic refinement, and refined as ‘‘riding” on the adjacent atom
with individual isotropic temperature factor equal 1.2 times the
value of equivalent temperature factor of the parent atom, with
geometry idealization after each cycle. The OLEX2 [20] program
was used for all the calculations. Atomic scattering factors were
those incorporated in the computer programs.
Crystals of [RuHCl(CO)(py)(PPh3)2] (1), [RuHCl(CO)(PPh3)2
(pyIm)] (2) and [RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH (3) were
mounted in turn on an Xcalibur, Atlas, Gemini ultra Oxford Diffrac-
tion automatic diffractometer equipped with a CCD detector, and
used for data collection. X-ray intensity data were collected with
graphite monochromated Mo K
perature 298.0(2) K (1) or 295.0(2) K (2), (3), with
a
radiation (k = 0.71073 Å) at tem-
scan mode.
x
Ewald sphere reflections were collected up to 2h = 50.10. The unit
cell parameters were determined from least-squares refinement of
the setting angles of 4074, 14 943 and 25 105 strongest reflections
for complexes 1, 2 and 3, respectively. Details concerning crystal
data and refinement are gathered in Table 1. During the data
reduction, the decay correction coefficient was taken into account.
Lorentz, polarization, and numerical absorption corrections were
applied. The structures were solved by Patterson method. All the
non-hydrogen atoms were refined anisotropically using full-ma-
3. Results and discussion
The [RuHCl(CO)(py)(PPh3)2], [RuHCl(CO)(PPh3)2(pyIm)] and
[RuCl(CO)(PPh3)2(pyoh)] complexes were obtained by the reaction
of [RuHCl(CO)(PPh3)3] with pyridine (py), imidazo[1,2-a]pyridine
(pyIm) or 2-hydroxy-6-methylpyridine (pyoh) in methanol solu-
tions. Elemental analyses of the complexes are in a good agreement
with their formulas. The 1H NMR spectra of the complexes

82
J.G. Małecki / Polyhedron 30 (2011) 79–85
displayed sets of signals, given in experimental section, that where
ascribed to N-heteroaromatic and triphenylphosphine ligands. The
triplets at ꢁ13.491 and ꢁ13.322 ppm indicated the hydride ligand
in complexes 1 and 2, respectively. The singlets in 31P NMR spectra
of the complexes at 45.709 and 45.376 ppm indicated both the tri-
phenylphosphine ligands in the compounds are equivalent and
they are mutually trans disposed. On the 31P NMR spectrum of
complex 3 two doublets at 45.681, 40.035 ppm indicates the cis
configuration of PPh3 ligands.
3.1. Electronic structure
To form an insight in the electronic structures and bonding
properties of the studied complexes, the calculations in the DFT
method were carried out. Before the calculations of electronic
structures of the complexes, their geometries were optimized in
singlet states using the DFT method with the B3LYP functional.
From the data collected in Table 2, one may see that the majority
of differences between the experimental and calculated geometries
are found in the Ru–H(Ru) distance and the angle differences do
not exceed 4°. The stabilization energies calculated in NBO analy-
ses have shown that the lone pairs localized on the N(O)-donor
atoms of ligands in the complexes donate the charge to ruthenium,
In the IR spectrum of complex 1, the ring C@N stretching modes
of the pyridine ligands are present at 1600 cmꢁ1, 1635 cmꢁ1 for
complex 2 and the imidazo[1,2-a]pyridine C@N and C@C stretches
are found at 1635 and 1571 cmꢁ1. The intense bands around 1995
and 2016 cmꢁ1 in IR spectra indicate the presence of hydride li-
gands in the complexes 1 and 2, respectively. The stretching modes
of the carbonyl group are observed at 1920, 1900 and 1940 cmꢁ1
and the stretching modes of the C–H are observed at 3053, 3050
and 3052 cmꢁ1, for complexes 1, 2 and 3, respectively. The phenyl
ring C–H bend mode is visible in the bands with maxima at 1480,
1432, 1311 cmꢁ1 in 1, 1480, 1433, 1313 cmꢁ1 in 2 and 1471, 1435
and 1028 cmꢁ1 in complex 3. The stretching frequency of the Ru–N
bond is at 520 cmꢁ1 in complex 1, 519 cmꢁ1 in 2 and 522 cmꢁ1 in 3.
The complexes crystallize in the monoclinic space group P21/n
and P21/c, 1 and 2, respectively and the complex 3 crystallizes in
and the stabilization energies (DEij) are 118.15, 46.17 and 147.58
kcal/mol for 1, 2 and 3, respectively. The back donations to pyri-
dine type ligands are equal to 24.48, 21.24 and 33.62 kcal/mol
for complexes 1, 2 and 3, respectively. The chloride ligands also do-
nate charge to ruthenium central ions and the energies are equal to
52.52 and 37.04 kcal/mol (back donation 5.57 and 3.02 kcal/mol)
for complexes 1 and 2, respectively. The data suggest that the
donation from ligands to dRu orbitals plays a role in the electronic
structure of the complexes which can be seen in the charges of
ruthenium central ions. The natural atomic charges on the ruthe-
nium central ion in the complexes are ꢁ0.90 in 1, ꢁ0.08 in 2 and
ꢁ0.51 in complexes 3.
ꢀ
the triclinic P1 space group. The crystal structure of complex 2 is
built up of two independent molecules in the asymmetric unit.
Both molecules have the same conformation. The relative
orientation of molecules is depicted in Fig. 1, which also shows
molecular structure of complexes 1, 3 and the displacement ellip-
soids of the non-hydrogen atoms. The selected bond lengths and
angles are listed in Table 2. In the complexes, the ruthenium atom
has a disordered octahedral environment. The longer Ru–H bond in
the complexes 1 compared with 2 is in accordance with infra red
spectral data. The triphenylphosphine ligands in complexes 1 and
2 are in trans positions and in complex 3 these ligands are mutually
in cis. The disposition of PPh3 ligands are in coincidence with 31P
NMR data. In the structures of the complexes, weak hydrogen
bonds [21,22] exist and these are collected in Table 3.
In the HOMO orbitals of the complexes 1 and 2, the d ruthenium
orbitals contribute 51% in complex 1 and 48% in 2, and the chloride
ligands 40% and 43%, respectively. In the electronic structure of
both complexes, dRu orbitals are diffused in the HOMOꢁ1 to
HOMOꢁ7 energy range with participation between 10% and 43%.
In the complex 3 HOMO orbital is composed from pyoh ligand
(82%) and dRu orbitals (11%) and in the LUMO dRu orbitals play sig-
nificant role with contribution of 27% (62% PPh3). The orbitals
HOMOꢁ1, HOMOꢁ2 and HOMOꢁ3 of complex 3 are localized on
the dRu and pCl orbitals. In the lower HOMO orbitals (HOMOꢁ4 to
HOMOꢁ6) the ruthenium d orbitals play significant role with con-
tribution of
p orbitals of triphenylphosphine ligands. The LUMO
orbitals of the complexes 1 and 2 are localized on the pyridine
Table 2
Selected bond lengths (Å) and angles (°) for [RuHCl(CO)(py)(PPh3)2] (1), [RuHCl(CO)(PPh3)2(pyIm)] (2) and [RuCl(CO)(PPh3)2(pyoh)] (3) complexes.
1
2
3
Exp
Calc.
Exp
Exp
Calc.
Exp
Calc.
Bond lengths (Å)
Ru(1)–C(1)
Ru(1)–N(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–Cl(1)
Ru–H1(Ru)
C(1)–O(1)
1.811(7)
1.855 Ru(1)–C(1)
2.276 Ru(1)–N(1)
2.436 Ru(1)–P(1)
2.429 Ru(1)–P(2)
2.596 Ru(1)–Cl(1)
1.610 Ru–H1(Ru)
1.165 C(1)–O(1)
1.799(3)
Ru(2)–C(44)
Ru(2)–N(3)
Ru(2)–P(3)
Ru(2)–P(4)
1.817(3)
1.856 Ru(1)–C(1)
2.250 Ru(1)–N(1)
2.430 Ru(1)–P(1)
2.429 Ru(1)–P(2)
2.594 Ru(1)–Cl(1)
1.600 Ru(1)–O(2)
1.165 C(1)–O(1)
1.817(4)
1.857
2.211(5)
2.367(17)
2.349(18)
2.519(15)
1.820(4)
1.169(9)
2.161(2)
2.346(9)
2.334(9)
2.542(10) Ru(2)–Cl(2)
1.510(2)
1.159(4)
2.186(3)
2.355(9)
2.338(9)
2.518(11)
1.460(3)
1.156(4)
2.090(3)
2.344(10)
2.362(11)
2.417(10)
2.184(2)
1.161(4)
2.141
2.431
2.453
2.460
2.202
1.162
Ru(2)–H2A(Ru)
C(44)–O(2)
Angles (°)
P(1)–Ru(1)–P(2)
C(1)–Ru(1)–Cl(1)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–C(1)
N(1)–Ru(1)–Cl(1)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–C(1)
P(2)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–C(1) 170.60(2)
P(2)–Ru(1)–H(1) 90.4(15)
Cl(1)–Ru(1)–H(1) 173.7(15)
N(1)–Ru(1)–H(1)
C(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
176.77(6)
177.21
100.69
90.79
89.99
89.51
91.05
87.83
92.59
89.52
169.76
91.00
174.00
85.00
85.00
87.00
175.49
P(1)–Ru(1)–P(2)
C(1)–Ru(1)–Cl(1) 105.10(10)
176.45(3)
P(3)–Ru(2)–P(4)
C(44)–Ru(2)–Cl(2)
P(3)–Ru(2)–N(3)
P(3)–Ru(2)–C(44)
N(3)–Ru(2)–Cl(2)
P(4)–Ru(2)–N(3)
P(4)–Ru(2)–C(44)
P(4)–Ru(2)–Cl(2)
P(3)–Ru(2)–Cl(2)
N(4)–Ru(2)–C(44)
P(4)–Ru(2)–H(2A)
176.93(3)
176.29
P(1)–Ru(1)–P(2)
C(1)–Ru(1)–Cl(1)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–C(1)
N(1)–Ru(1)–Cl(1)
P(2)–Ru(1)–N(1) 163.98(7)
P(2)–Ru(1)–C(1)
P(2)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1) 167.95(3)
N(1)–Ru(1)–C(1) 102.28(14)
P(2)–Ru(1)–O(2) 106.16(6)
Cl(1)–Ru(1)–O(2)
N(1)–Ru(1)–O(2)
C(1)–Ru(1)–O(2) 163.92(13)
P(1)–Ru(1)–O(2) 83.70(7)
Ru(1)–C(1)–O(1) 175.4(3)
100.44(4)
101.06
91.92
90.61
94.55
81.48
159.07
93.50
85.13
170.74
102.91
102.33
87.84
61.31
164.08
84.12
174.97
98.34(19)
89.49(14)
91.10(2)
91.03(13)
91.06(14)
87.90(2)
94.02(6)
89.16(6)
102.60(10)
90.77(6)
89.24(9)
84.92(8)
89.87(6)
89.74(9)
95.66(3)
87.38(3)
172.46(12)
86.9(10)
100.70
91.40
89.19
87.21
90.85
88.17
92.89
90.15
172.07
87.00
174.00
86.00
86.00
90.00
176.59
94.98(12)
89.07(7)
94.60(11)
81.77(8)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–C(1)
N(1)–Ru(1)–Cl(1)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–C(1)
P(2)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–C(1) 167.60(12)
P(2)–Ru(1)–H(1) 85.6(9)
Cl(1)–Ru(1)–H(1) 171.7(9)
89.12(6)
90.76(10)
87.29(7)
91.50(6)
87.89(10)
94.26(3)
89.25(3)
89.88(12)
86.87(4)
Cl(2)–Ru(2)–H(2A) 170.6(11)
85.07(7)
61.77(9)
84.4(15)
86.3(15)
86.50(15)
N(1)–Ru(1)–H(1)
C(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
84.4(9)
83.2(9)
90.9(9)
N(3)–Ru(2)–H(2A)
C(44)–Ru(2)–H(2A)
P(3)–Ru(2)–H(2A)
Ru(2)–C(44)–O(2)
86.1(11)
86.4(11)
90.1(10)
176.0(3)
Ru(1)–C(1)–O(1) 174.7(6)
Ru(1)–C(1)–O(1) 173.2(3)

J.G. Małecki / Polyhedron 30 (2011) 79–85
83
Table 3
1 and 45–62% in 2. Fig. 2 shows the partial density-of-states (DOS)
and overlap partial density-of-states (OPDOS) diagrams in terms of
Mulliken population analysis, calculated using the GAUSSSUM pro-
gram, for complexes 2 (the 1 and 2 complexes have similar elec-
tronic structures) and 3. The DOS plot mainly presents the
composition of the fragment orbitals contributing to the molecular
orbitals. As can be seen from the OPDOS plot, the chloride ligands
have significant antibonding character in the HOMO and HOMOꢁ1
molecular orbitals and bonding in lower occupied orbitals. The
interactions of the carbonyl ligand with the Ru(II) d orbitals have
positive values (bonding character) in the frontier HOMO orbitals
and in lower occupied orbitals. In the occupied and virtual molec-
ular orbitals, the values of the interaction between ruthenium and
Hydrogen bonds for [RuHCl(CO)(py)(PPh3)2] (1), [RuH(Cl)(CO)(PPh3)2(pyIm)] (2) and
[RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH (3) complexes (Å and °).
D–Hꢀ ꢀ ꢀA
1
C(5)–H(5)ꢀ ꢀ ꢀCl(1)
C(11)–H(11)ꢀ ꢀ ꢀCl(1)
C(29)–H(29)ꢀ ꢀ ꢀCl(1)
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
<(DHA)
0.93
0.93
0.93
2.66
2.73
2.75
3.332(7)
3.535(8)
3.403(9)
130.0
145.5
127.6
2
C(2)–H(2)ꢀ ꢀ ꢀCl(1)
C(32)–H(32)ꢀ ꢀ ꢀN(1)
C(45)–H(45)ꢀ ꢀ ꢀCl(2)
C(77)–H(77)ꢀ ꢀ ꢀCl(2)
C(5)–H(5)ꢀ ꢀ ꢀO(1) #1
0.93
0.93
0.93
0.93
0.93
2.71
2.82
2.59
2.46
2.49
3.245(4)
3.427(4)
3.147(4)
3.332(4)
3.385(5)
117.4
123.5
118.7
157.2
161.3
3
the pyridine or imidazo[1,2-
indicating that these ligands have similar
This conclusion is confirmed by the proportion of the Ru(II) and
N-heteroaromatic ligand in the frontier molecular orbitals. The 2-
a
]pyridine ligand are comparable,
C(25)–H(25)ꢀ ꢀ ꢀO(2)
C(31)–H(31)ꢀ ꢀ ꢀO(2)
C(98)–H(98C)ꢀ ꢀ ꢀCl(1) #2
0.93
0.93
0.96
2.32
2.54
2.79
3.138(4)
3.141(4)
3.732(13)
146.0
123.0
163.0
p-acceptor properties.
Symmetry transformations used to generate equivalent atoms: #1 ꢁ1 + x, y, z; #2
1 ꢁ x, 1 ꢁ y, 2 ꢁ z.
hydroxy-6-methylpyridine ligand has stronger
p-acceptor proper-
ties than pyridine or imidazo[1,2- ]pyridine as one can see from
a
the OPDOS diagram for complex 3 presented in Fig. 2b. Further-
more, the Mayer bond orders for Ru–N(1) of 0.66 for complex 1,
0.69 for 2 and 0.92 for 3 show the weakness of this bond compared
with the Ru–Cl (1.16, 1.26 and 1.80 in 1, 2 and 3, respectively)
bond. The Ru–CO and Ru–H bonds orders also are much alike in
the complexes with values equal to 2.7 and 1.7, respectively. The
cis arrangement of the bulky PPh3 ligands in the [RuCl(CO)(PPh3)2
(93%) or imidazo[1,2-a]pyridine ligands (97%). Virtual molecular
orbitals with large contribution of dRu are LUMO+1 (12%, 15%,
13% for 1, 2 and 3, respectively), LUMO+2 (21%) in complex 3
and are diffused in energy scope corresponding to LUMO+14 to
LUMO+17 (15–30% in 1; 13–34% in 2) in electronic structures of
complexes 1 and 2. In these unoccupied orbitals, the carbonyl
ligand plays significant role with contributions 44–68% in complex
(pyoh)] complex is probably connected with stronger
p-accepting
ability of phosphines in the cis arrangement than in the trans
Fig. 2. The density of states (DOS) and overlap partial density of states (OPDOS) diagrams for complexes 2 (a) and 3 (b).

84
J.G. Małecki / Polyhedron 30 (2011) 79–85
one, and it has electronic origin. The Mayer orders for Ru–P bond
for complexes 1 and 2 are close each other and have value of
1.40, and in complex 3 it is equal to 1.60. The ruthenium–phos-
phine backdonation leads to a decrease in the electron density on
of ligands nature. The excitations at shorter wavelengths gave
stronger emission peaks. The emission of complex 2 is very intense
compared to complexes 1 and 3 which is connected with the
significant contribution of pyIm ligand in the frontier Homo and
Lumo orbitals. In Fig. 4, the luminescence spectra of the complexes
2 and 3 are presented, and in them (excited at 360 nm), a broaden-
ing and shoulders are visible. The complicated structure of the
luminescence spectrum suggests that more than one state is in-
volved in luminescence process. Hence the luminescence is of IL/
MLCT origin in these systems. The singlet and triplet states of LF
and LMCT type, which are close to the ground state energy can pro-
vide the radiationless deactivation channel for the complexes
which explain relatively small intense of emission.
the metal atom, which in turn causes stronger
r ligand–metal
donation. In this manner the ruthenium central ion is suitable
accepting more charge from N,O-donor ligand as pyoh. Taking into
account the stabilization energy analysis mentioned above, one
can see that the 2-hydroxy-6-methylpyridine ligand is the stron-
gest donor among studied ligands and it favours the cis-PPh3 form
over trans-PPh3 one.
3.2. Electronic spectra
Summarizing, new ruthenium(II) complexes with N-heteroaro-
matic ligands have been synthesized. The molecular structures of
the compounds are determined by X-ray, and the spectroscopic
properties as infrared, 1H, 31P NMR spectra were studied. Based
on the crystal structures, the computational researches were made
in order to determine the electronic structures of the complexes.
In the UV–Vis spectra of the complexes are similar and the max-
ima at 370, 331, 270 and 212 nm for complex 1, 360, 310, 265, 211
for 2 and 368.8, 291.6, 261.0, 216.4 for 3 were measured. The
assignments of the calculated transitions to the experimental
bands are based on the criteria of energy and oscillator strength
of the calculated transitions. In the description of the electronic
transitions, only the main components of the molecular orbitals
are taken into consideration. The electronic transitions were calcu-
lated by use the B3LYP functional and its long range corrected ver-
sion CAM-B3LYP which using the Coulomb-attenuating method. As
one can see from Fig. 3, the use of CAM-B3LYP functional provides
better estimation of excitation energy especially for the transitions
with Charge-Transfer character.
The results were used to compare
p-donor/acceptor properties of
pyridine type ligands. The acceptor/donor properties of N(O)-donor
ligands explained the differences in the triphenylphosphine li-
gands arrangement in the complexes. The ligands with strong do-
nor properties favour the cis-PPh3 form over trans-PPh3 one in the
The first two experimental bands in the electronic spectra of the
complexes are assigned to the transitions between the HOMO ? -
LUMO+1 (69% for 1, 44% for 2, 64% for 3), HOMO ? LUMO (96% for
1, 69% for 2, 48% for 3) and HOMOꢁ1 ? LUMO (93% for 1, 77% for 2,
57% for 3) molecular orbitals. As the HOMO, HOMOꢁ1 and
LUMO+1 are composed of the d ruthenium orbitals with admixture
of
type (d ? d). The LUMOs are localised on the pyridine or
imidazo[1,2- ]pyridine ligands, respectively in complexes 1 or 2
p-chloride (1, 2) or p-PPh3 (3), the transitions are of Ligand Field
a
and Metal–Ligand Charge Transfer transitions are associated with
these.
The bands observed at 270, 265 and 261 nm have been attributed
to the Metal–Ligand Charge Transfer transitions (d ! pꢃPPh3=py=pyIm=Cl).
In this energy region, the transitions between the HOMO ? LU-
MO+4, HOMOꢁ2 ? LUMO+3, HOMOꢁ1 ? LUMO+5/6/7 were cal-
culated. The highest energy bands with maxima at 212 nm and
211 nm are attributed to transitions of the Ligand–Ligand Charge
Transfer type (
p
!
pꢃC@N).
Based on the pseudooctahedral geometry of the complexes and
taking into account the d–d transitions assigned to 1A1 ? 1T1 and
1A1 ? 1T2 in octahedron, the ligand field parameter 10Dq can be
estimated to 19 618 cmꢁ1 for the complex 1, 22 417 cmꢁ1 for 2
and 25 604 cmꢁ1 for complex 3. Adequately, Racah’s parameters
are B = 214, 299 and 479 cmꢁ1, C = 852, 1190 and 1906 cmꢁ1 and
the nepheloauxetic parameter have values b55 = 0.30, 0.42 and
0.67 for complexes 1, 2 and 3, respectively.
The emission characteristics of the complexes have been exam-
ined in the methanol solutions (with concentration of 5 ꢂ 10ꢁ4
mol/dm3) at room temperature. The excitations were executed at
two wavelengths corresponding to maxima of two first electronic
absorptions, i.e., at 370, 331 nm for 1, 360, 310 nm for 2 and 360,
292 nm for complex 3. In all complexes, the emissions with max-
ima at 430, 420, 415 nm and 380, 370 and 375 nm (in the emission
spectrum of complex 3 excited at 292 nm is visible lower intense
band with maximum at 450 nm see Fig. 4) originating from the
lowest energy metal to ligand charge transfer (MLCT) state, derived
from the excitation involving a d
? pligand transition are observed.
p
The assignment is also supported by the analysis of the frontier
orbitals of the corresponding complexes showing a contribution
Fig. 3. The experimental and calculated (B3LYP and CAM-B3LYP functional) UV–Vis
spectra of complexes 1 and 3.

J.G. Małecki / Polyhedron 30 (2011) 79–85
85
Fig. 4. The emissions spectra of the complexes 2 and 3 in the methanolic solutions (c = 5 ꢂ 10ꢁ4 mol/dm3).
[4] M. Chandra, A.N. Sahay, D.S. Pandey, M.C. Puerta, P. Valerga, J. Organomet.
Chem. 648 (2002) 39.
[5] A.K. SinghP. Kumar, M. Yadav, D.S. Pandey, J. Organomet. Chem. 695 (2010) 567.
[6] S. Jasimuddin, Transition Met. Chem. 31 (2006) 724.
[7] B.J. Coe, S.J. Glenwright, Coord. Chem. Rev. 203 (2000) 5.
[8] S. Kannan, M. Sivagamasundari, R. Ramesh, Yu Liu, J. Organomet. Chem. 693
(2008) 2251.
[9] M.U. Raja, N. Gowri, R. Ramesh, Polyhedron 29 (2010) 1175.
[10] N. Ahmad, J.J. Levinson, S.D. Robinson, M.F. Uttely, Inorg. Synth. 15 (1974) 48.
[11] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro,
M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J. M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,
P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,
J.V. Ortiz, J. Cioslowski, D.J. Fox, GAUSSIAN 09, Revision A.1, Gaussian, Inc.,
Wallingford CT, 2009.
complexes. This is connected with stronger
phosphines in the cis arrangement [23].
p-accepting ability of
On the basis of a pseudooctahedral configuration of the com-
plexes and their electronic spectra, the values of the ligand field
parameter 10Dq and Racah’s parameters were estimated. Emission
properties of the complexes have been examined. The emissions
originating from the lowest energy metal to ligand charge transfer
(MLCT) state, derived from the excitation involving a d
? pligand
p
transition are observed. The assignment is supported by the anal-
ysis of the frontier orbitals of the corresponding complexes show-
ing a partial contribution of ligands nature.
Appendix A. Supplementary data
CCDC 769610, CCDC 782764 and CCDC 784018 contain the sup-
plementary crystallographic data for [RuHCl(CO)(py)(PPh3)2],
[RuHCl(CO)(PPh3)2(pyIm)] and [RuCl(CO)(PPh3)2(pyoh)]ꢀ2CH3OH
complexes, respectively. These data can be obtained free of charge
from http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk. Calculations have been carried out in
Wroclaw Centre for Networking and Supercomputing (http://
www.wcss.wroc.pl).
[12] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[13] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[14] T. Yanai, D. Tew, N. Handy, Chem. Phys. Lett. 393 (2004) 51.
[15] M.E. Casida, in: J.M. Seminario (Ed.), Recent Developments and Applications of
Modern Density Functional Theory, Theoretical and Computational Chemistry,
vol. 4, Elsevier, Amsterdam, 1996, p. 391.
[16] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chim. Acc. 97 (1997) 119.
[17] E.D. Glendening, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO (version 3.1).
[18] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comput. Chem. 29 (2008) 839.
[19] Adam L. Tenderholt, QMFORGE, Version 2.1, Stanford University, Stanford, CA,
USA.
[20] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl.
Crystallogr. 42 (2009) 339.
References
[21] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and
Biology, Oxford University Press, 1999.
[22] G.A. Jeffrey, W. Saenger, Hydrogen Bonding in Biological Structures, Springer-
Verlag, 1994.
[1] A. Coleman, C. Brennan, G.J. Vos, T.M. Pryce, Coord. Chem. Rev. 252 (2008)
2585.
[2] K. Naresh Kumar, R. Ramesh, Polyhedron 24 (2005) 1885.
[3] M.J. Clark, Coord. Chem. Rev. 236 (2003) 209.
[23] M. Jaworska, J.G. Małecki, J. Mol. Struct. 784 (2006) 169.