Synthesis, crystal, molecular and electronic structures of thiocyanate ruthenium complexes with pyridine and its derivatives as ligands

Article abstract of DOI:10.1016/j.poly.2010.03.015

The complexes [Ru(SCN)₂(PPh₃)₂(L)₂], where L = py and γ-pic, and [Ru(SCN)₂(PPh₃)₂(L)], where L = py-2-CH₂NH₂ and py-2-CH₂O, have been prepared an

Full text of DOI:10.1016/j.poly.2010.03.015

Polyhedron 29 (2010) 1973–1979
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, crystal, molecular and electronic structures of thiocyanate
ruthenium complexes with pyridine and its derivatives as 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:
The complexes [Ru(SCN)2(PPh3)2(L)2], where L = py and c-pic, and [Ru(SCN)2(PPh3)2(L)], where L = py-2-
CH2NH2 and py-2-CH2O, have been prepared and studied by IR, NMR, EPR, UV–Vis spectroscopy and
X-ray crystallography. The complexes were prepared in the reactions of [RuCl2(PPh3)3] with pyridine,
Received 17 February 2010
Accepted 12 March 2010
Available online 27 March 2010
c-picoline, 2-(aminomethyl)pyridine and 2-(hydroxymethyl)pyridine in methanol solutions. The elec-
tronic structures of the obtained compounds have been calculated using the DFT/TD-DFT method.
Keywords:
Ruthenium thiocyanate complexes
Pyridine
Ó 2010 Elsevier Ltd. All rights reserved.
c
-Picoline
2-(Aminomethyl)pyridine
2-(Hydroxymethyl)pyridine
X-ray structure
UV–Vis
DFT
TD-DFT
1. Introduction
This paper presents the synthesis, crystal, molecular and elec-
tronic structures, and the spectroscopic characterization of some
In the chemistry of ruthenium, the coordination chemistry of
complexes containing pyridine derivatives is one of the most stud-
ied aspects. 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 plays
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 [1–3]. These attributes of substituted pyridine
containing ruthenium compounds leads to their application in the
conversion of solar energy to electrical energy [4], in long-range
electron transfer and energy translocation [5], molecular electronic
devices [6], supramolecular self-assembly processes [7,8] and as
DNA photoprobes [9]. The molecular and electronic structure of
pyridine and picoline ruthenium(II) chloride complexes were stud-
ied earlier [10,11]. Additionally, thiocyanate ligands tune the spec-
tral and redox properties of ruthenium(II) complexes by
destabilizing the metal t2g orbital. For example, the cis form of
the [Ru(II)(4,40-dicarboxy-2,20-bipyridine)2(NCS)2] complex is one
of the most efficient heterogeneous charge transfer sensitizers
known to date and it is widely used in the nanocrystalline TiO2
solar cell [12].
new thiocyanate ruthenium(II)/(III) complexes with pyridine type
ligands.
2. Experimental
All reagents used for the synthesis of the complexes are com-
mercially available and were used without further purification.
The [RuCl2(PPh3)3] complex was synthesised according to the liter-
ature method [13].
2.1. Synthesis of [Ru(SCN)2(PPh3)2(L)2]
The complexes were synthesized by the reaction between
[RuCl2(PPh3)3] (0.2 g; 2 ꢀ 10ꢁ4 mol), NH4SCN (0.03 g; 4 ꢀ 10ꢁ4
mol) and pyridine,
c-picoline, 2-(aminomethyl)pyridine or 2-
(hydroxymethyl)pyridine (2.1 ꢀ 10ꢁ4 mol). The reaction mixture
was refluxed in methanol (50 cmꢁ3) for 2 h. After this time, it
was cooled and filtered, and crystals suitable for X-ray crystal anal-
ysis were obtained by slow evaporation of the reaction mixture.
2.2. [Ru(SCN)2(PPh3)2(py)2] (1)
Yield 72%. IR (KBr): 3050
m
CH; 2090
m
(CN from SCN); 1601 mCN
,
mC@C
;
E-mail address: gmalecki@us.edu.pl
1480, 1309 d(C–CH plane); 1432
mP–Ph; 1088 d(C–CH
;
in the
in the plane)
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.03.015

1974
J.G. Małecki / Polyhedron 29 (2010) 1973–1979
1011 d(C–H out of the plane); 867
m(SC from SCN); 741 d(C–C out of the plane)
;
group contributions to the molecular orbitals and to prepare the
692 d(C–C in the plane); 524
m
(P–Ph+P–Ru); 504 d(CNS). UV–Vis (methanol;
partial density of states (DOS) and overlap population density of
states (OPDOS) spectra. The PDOS and OPDOS spectra were created
by convoluting the molecular orbital information with Gaussian
curves of unit height and FWHM of 0.3 eV.
log
e
); nm: 435.1 (2.91), 347.5 (3.90), 238.8 (4.86), 208.4 (5.12). 1H
NMR (d, DMSO d6): 8.433 (d, HPy), 7.913 (d, HPy), 7.637–7.129 (m,
PPh3), 7.392 (d, HPy). 31P NMR (d, CDCl3): 45.545 (s, PPh3), 39.853
(s, PPh3).
2.8. Crystal structure determination and refinement
2.3. [Ru(SCN)2(PPh3)2(
c
-pic)2]ꢂCH3OH (2)
Yellow crystals of [Ru(SCN)2(PPh3)2(py)2] (1), [Ru(SCN)2(PPh3)2-
Yield 78%. IR (KBr): 3345 OH; 3051
m
m
ArH; 2917
m
CH; 2100
;
(c
-pic)2]ꢂCH3OH (2), [Ru(SCN)2(PPh3)2(py-2-CH2NH2)] (3) and
m(CN
SCN); 1619 mCN
,
m
C@C; 1480, 1313 d(C–CH
from
in the plane)
[Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH (4) were mounted in turn
on a Xcalibur, Atlas, Gemini ultra Oxford Diffraction automatic dif-
fractometer equipped with a CCD detector, and were used for data
collection. X-ray intensity data were collected with graphite mono-
1432
mP–Ph; 1090 d(C–CH
plane); 1025 d(C–H
plane); 851
in the
out of the
m
(SC from SCN); 808 mPic
_
ring; 743 d(C–C out of the plane); 696 d(C–C in the plane)
; 494 d(CNS). UV–Vis (methanol; log e); nm: 405.7 (2.99),
(P–Ph+P–Ru)
;
524
m
314.1 (3.38), 222.6 (4.86), 212.6 (5.12). 1H NMR (d, DMSO d6):
8.616 (d, HPic), 7.637–7.129 (m, PPh3), 7.390 (d, HPic), 2.507 (d,
CH3(Pic)), 4.095 (OH(MeOH)), 3.346 (CH3(MeOH)). 31P NMR (d, CDCl3):
45.664 (s, PPh3), 39.986 (s, PPh3).
chromated Mo K
295.0(2) K, with the
a
radiation (k = 0.71073 Å) at a temperature of
scan mode. Ewald sphere reflections were
x
collected up to 2h = 50.10. The unit cell parameters were deter-
mined from least-squares refinement of the setting angles of
25 967, 64 443, 14 984 and 11 713 strongest reflections for com-
plexes 1, 2, 3 and 4, 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 direct methods. All the non-hydro-
gen atoms were refined anisotropically using the full-matrix,
least-squares technique on F2. All the hydrogen atoms were found
from difference Fourier synthesis after four cycles of anisotropic
refinement, and were refined as ‘‘riding” on the adjacent atom with
individual isotropic temperature factors equal to 1.2 times the va-
lue of the 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.
2.4. [Ru(SCN)2(PPh3)2(py-2-CH2NH2)] (3)
Yield 67%. IR (KBr): 3413
m
NH2; 3240
m
ArH; 3055, 2916
m
CH; 2106,
;
2074 m(CN SCN); 1608 mCN
,
mC@C; 1480, 1276 d(C–CH
from
in the plane)
1434
m
P–Ph; 1092 d(C–CH
SCN); 750 d(C–C
plane); 964 d(C–H
plane); 878
in the
out of the
m(SC
plane); 699 d(C–C plane); 525
from
out of the
in the
m
(P–Ph+P–Ru); 511 d(CNS). UV–Vis (methanol; log e); nm: 402.4
(1.89), 312.5 (2.71), 253.6 (4.05) sh, 208.7 (4.84). 1H NMR (d,
CDCl3): 8.253 (s, H), 7.757 (m, Py-2-CH2NH2) 7.400–7.104 (m,
PPh3), 4.414 (NH), 1.582 (CH2). 31P NMR (d, CDCl3): 45.276 (d,
2
PPh3); 42.153 (d, PPh3) JAB = 32.19 Hz.
2.5. [Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH (4)
Yield 64%. IR (KBr): 3347
m
OH; 3055
m
ArH; 2939
m
CH; 2106
;
m(CN
1433
m(SC
SCN); 1606 mCN
,
m
C@C; 1480, 1315 d(C–CH
plane); 952 d(C–H
from
in the plane)
m
from
P–Ph; 1091 d(C–CH
plane); 844
3. Results and discussion
in the
out of the
SCN); 743 d(C–C
plane); 697 d(C–C plane); 523
in the
out of the
m
(P–Ph+P–Ru); 513 d(CNS). UV–Vis (methanol; log
e
); nm: 510.6
The reactions of the [RuCl2(PPh3)3] complex with pyridine,
c-picoline, 2-(aminomethyl)pyridine or 2-(hydroxymethyl)pyridine
and ammonium thiocyanate have been performed. Refluxing the
(2.72), 329.2 (2.35), 276.6 (3.14), 215.0 (4.27). 31P NMR (d, CDCl3):
2
55.572 (d, PPh3); 41.640 (d, PPh3) JAB = 36.65 Hz.
starting ruthenium(II) complex with the ligands in methanol leads
2.6. Physical measurements
to the complexes [Ru(SCN)2(PPh3)2(L)2], where L = py and c-pic,
and [Ru(SCN)2(PPh3)2(L)], where L = py-2-CH2NH2 and py-2-
Infrared spectra were recorded on a Nicolet Magna 560 spectro-
photometer in the spectral range 4000–400 cm1 with the sample in
the form of a KBr pellet. Electronic spectra were measured on a Lab
Alliance UV–Vis 8500 spectrophotometer in the range 700–180 nm
in acetonitrile solution. The 1H and 31P NMR spectra were obtained
at room temperature in CDCl3 using a Bruker 400 spectrometer.
EPR spectra were recorded as powder samples at 298 K on a Bruker
EMX-10 spectrometer using 100 kHz field modulation.
CH2O, with good yields. Infrared spectra of the obtained complexes
have characteristic bands due to ligands vibrations. The
of the N-heteroaromatic ligands appear around 1601 cm–1 for 1,
1619 cmꢁ1 for 2, 1608 cmꢁ1 for 3 and 1606 cmꢁ1 for 4. The
CN fre-
mC@N bands
m
quencies of the thiocyanate ligands have maxima close to
2100 cmꢁ1 which is characteristic of S-bonded complexes, but
the electronic and steric effects caused by the N-donor ligands af-
fects the mCN frequency. The mCS and d(CNS) frequencies are observed
at 867, 851, 878, 844 cmꢁ1 and 504, 494, 511, 513 cmꢁ1 for com-
plexes 1, 2, 3 and 4, respectively. Because of the trans symmetry
of the two NCS ligands in the complexes 1, 2 and 4, only one mCN
stretch is visible in the IR spectra, but the bands are broadened
due to the not perfect trans disposition of the thiocyanate ligands.
In the IR spectrum of complex 3, a band with a maximum at
2074 cmꢁ1 is visible, which is assigned to a mCN stretch and indi-
cates the mutually orientation of the SCN ligands is cis. The
31P{1H} NMR spectra of the studied complexes 1 and 2 present
two singlets, and in the spectra of complexes 3 and 4 two doublets,
which are close to each other, are consistent with the structure
confirmed by the X-ray analysis and indicate that the cis conforma-
tion of the PPh3 ligands is kept upon coordination. The less
shielded phosphorus atom in the complex 3 is probably positioned
trans to the thiocyanate group due to the electron-withdrawing
2.7. DFT calculations
The calculations were carried out using the GAUSSIAN09 [14] pro-
gram. The DFT/B3LYP [15,16] method was used for the geometry
optimization and electronic structure determination, and elec-
tronic spectra were calculated by the TD-DFT [17] method. The cal-
culations were performed using the DZVP basis set [18] with f
functions, with exponents of 1.94722036 and 0.748930908 on
the ruthenium atom, and polarization functions for all other
atoms: 6-31 g(2d,p) – sulfur, 6-31 g** – carbon, nitrogen and 6-
31 g(d,p) – hydrogen. The PCM solvent model was used in the
Gaussian calculations with methanol as the solvent. The contribu-
tion of a group to a molecular orbital was calculated using Mullik-
en population analysis. GAUSSSUM 2.2 [19] was used to calculate

J.G. Małecki / Polyhedron 29 (2010) 1973–1979
1975
Table 1
Crystal data and structure refinement details of the complexes [Ru(SCN)2(PPh3)2(py)2] (1), [Ru(SCN)2(PPh3)2(
[Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH (4).
c-pic)2]ꢂCH3OH (2), [Ru(SCN)2(PPh3)2(py-2-CH2NH2)] (3),
1
2
3
4
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C48H40N4P2RuS2
899.97
295.0(2)
monoclinic
P21/c
C51H48N4OP2RuS2
960.08
295.0(2)
trigonal
C44H38N4P2RuS2
849.93
295.0(2)
orthorhombic
P212121
C45H40N3O2P2RuS2
881.93
295.0(2)
orthorhombic
Pca21
R–3
Unit cell dimensions
a (Å)
b (Å)
c (Å)
a
19.8773(4)
10.92370(17)
21.6045(5)
90
35.155(5)
35.155(5)
24.440(5)
90
13.4304(2)
15.2689(2)
19.5698(3)
90
17.6898(3)
12.06743(19)
19.4637(4)
90
b
c
114.142(3)
90
4280.78(14)
4
1.396
0.577
90
120
26158(8)
18
1.096
90
90
90
90
Volume (Å3)
4013.12(10)
4
1.407
0.611
1744
4154.92(13)
4
1.410
0.596
1812
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢁ1
F (0 0 0)
)
0.430
8928
1848
Crystal dimensions (mm)
h Range for data collection (°)
Index ranges
0.39 ꢀ 0.28 ꢀ 0.16
3.53–25.05
ꢁ23 6 h 6 23
ꢁ13 6 k 6 13
ꢁ25 6 l 6 25
40118
0.38 ꢀ 0.14 ꢀ 0.11
3.78–25.05
ꢁ41 6 h 6 41
ꢁ41 6 k 6 41
ꢁ29 6 l 6 29
30841
0.33 ꢀ 0.29 ꢀ 0.20
3.47–25.05
ꢁ15 6 h 6 16
ꢁ18 6 k 6 18
ꢁ22 6 l 6 23
21245
0.17 ꢀ 0.14 ꢀ 0.13
3.37–25.05
ꢁ17 6 h 6 21
ꢁ14 6 k 6 12
ꢁ23 6 l 6 23
20562
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
7498 [R(int) = 0.0329]
7498/0/514
1.028
10 098 [R(int) = 0.0359]
10 098/0/594
1.655
6813 [R(int) = 0.0241]
6813/0/489
0.972
7057 [R(int) = 0.0304]
7057/1/498
1.084
Final R indices [I > 2
r
(I)]
R1 = 0.0287
wR2 = 0.0666
R1 = 0.0415
wR2 = 0.0704
0.394 and ꢁ0.332
R1 = 0.0512
wR2 = 0.1440
R1 = 0.0694
wR2 = 0.1584
1.782 and ꢁ1.796
R1 = 0.0305
wR2 = 0.0709
R1 = 0.0390
wR2 = 0.0730
0.845 and ꢁ0.498
R1 = 0.0296
wR2 = 0.0592
R1 = 0.0421
wR2 = 0.0612
0.547 and ꢁ0.447
R indices (all data)
Largest difference in peak and hole (e Åꢁ3
)
effect of the NCS ligand (in 4 it is in a trans position to an O donor).
The 1H NMR spectra of the complexes displayed sets of signals, gi-
ven in experimental section, that are ascribed to N-heteroaromatic
and triphenylphosphine ligands.
The EPR spectrum of a powder sample of complex 4 at room
temperature at X-band frequencies revealed the absence of any
hyperfine splitting due to interactions with any other nuclei pres-
ent in the complex. In the spectrum two lines are visible with two
different g values (gx = gy = 2.41; gz = 2.10), indicative of magnetic
anisotropy and suggestive of a tetragonal distortion in the octahe-
dral geometry.
3.1. Crystal structure
The [Ru(SCN)2(PPh3)2(py)2] and [Ru(SCN)2(PPh3)2(
c
-pic)2]ꢂ-
CH3OH complexes crystallise in the monoclinic P21/c and trigonal
R–3 space groups, respectively. The complexes with the bidendate
ligands 2-(aminomethyl)pyridine and 2-(hydroxymethyl)pyridine
crystallise in the orthorhombic groups P212121 and Pca21. The
molecular structures of the compounds are shown in Figs. 1–4. Se-
lected bond lengths and angles are listed in Table 2. In all the stud-
ied complexes, the triphenylphosphine ligands are in cis positions
and the pyridine and 4-methylpyridine ligands in complexes 1 and
2 have the same mutual orientation. In the complexes, the ruthe-
nium atoms have an octahedral environment and the maximum
distortion from octahedral is visible in complex 4 where the angle
between the thiocyanate ligands is 171.19(11). The C–N and C–S
bond lengths values fall in the 1.155(3)–1.156(3), 1.171(12)–
1.174(13), 1.089(9)–1.144(6) and 1.146(4)–1.147(4) Å ranges for
compounds 1–4, similar to those observed for thiocyanate com-
plexes. These lengths are contrary to those expected for C„N
and C–S bonds, due to the contribution of two resonance struc-
Fig. 1. ORTEP drawing of [Ru(SCN)2(PPh3)2(py)2] with 50% probability displace-
ment ellipsoids. Hydrogen atoms are omitted for clarity.
and are comparable with the distances in other ruthenium com-
plexes containing these heterocyclic ligands. The Ru–N–C mean
angles are 177.25(9), 176.0(10), 174.8(7) and 175.4(3)° for com-
plexes 1–4, close to the higher value of the range observed [21]
for metal-thiocyanate angles (130–180°) in structures containing
the thiocyanate ion bonded to a metal through its nitrogen atom.
The conformations of the studied compounds are stabilized by
ꢀ
ꢁ
tures: linear (M–+N@C–S–) and bent
for thiocya-
N
C
S
M
nate metal complexes. The Ru–N and Ru–P distances are normal

1976
J.G. Małecki / Polyhedron 29 (2010) 1973–1979
Fig. 4. ORTEP drawing of [Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH with 50% proba-
bility displacement ellipsoids. Hydrogen atoms are omitted for clarity.
eral, the predicted bond lengths and angles are in a good agree-
ment with the values based on the X-ray crystal structure data,
and the general trends observed in the experimental data are well
reproduced in the calculations.
Fig. 2. ORTEP drawing of [Ru(SCN)2(PPh3)2(
displacement ellipsoids. Hydrogen atoms are omitted for clarity.
c-pic)2]ꢂCH3OH with 50% probability
The main differences between the optimized and experimental
geometries of the studied compounds are visible in the Ru(1)–P(2)
distance (ꢃ0.096 Å) for complex 1, N(2)–C(2) ꢃ0.095 Å for 3 and in
the angles Ru(1)–N(1)–C(1) – 3.8° for 1, N(1)–Ru(1)–N(2) – 3.5° for
3 and 6.1° Ru(1)–N(2)–C(2) for 4.
3.3. Electronic structure and NBO analysis
In the studied complexes, the HOMO and HOMOꢁ1 molecular
orbitals are composed of the d ruthenium and pSCN orbitals with
participation of 34, 35, 27% and 23% dRu (HOMO) and 64, 62, 69,
76% pSCN in complexes 1, 2, 3 and 4, respectively. The LUMO and
LUMO+1 orbitals in compounds 1, 2 and 3 are localized on the N-
donor ligands (above 90%), and in complex 4 on the py-2-CH2O
(36%) and PPh3 (37%) ligands with a contribution of dRu (27%).
The ruthenium d orbitals play a significant role in the HOMOꢁ4,
HOMOꢁ5 and HOMOꢁ6 molecular orbitals of the studied com-
pounds and LUMO+2 (29, 20%), LUMO+16 (16, 27%) and LUMO+17
(46, 50%) in complexes with monodendate N-heteroaromatic li-
gands. In the virtual molecular orbitals of complex 3 large contri-
bution of dRu is visible in LUMO+13 (41%) and LUMO+14 (34%). In
the case of the ruthenium(III) complex 4 LUMO orbitals with
meaningful contribution of dRu are LUMO, LUMO+1, LUMO+3 (
a
spin) and LUMO+4 (b spin). HOMO–2 and HOMO–3 are localized
on the thiocyanate ligands (above 90%) for all the studied
compounds.
Fig. 3. ORTEP drawing of [Ru(SCN)2(PPh3)2(py-2-CH2NH2)] with 50% probability
In the frontier region, neighboring orbitals may show quasi-
degenerate energy levels. In such cases, consideration of only the
HOMO and LUMO may not yield a realistic description of the fron-
tier orbitals. For this reason, the density of states (DOS) and overlap
population density of states (OPDOS) in terms of Mulliken popula-
tion analysis were calculated using the GAUSSSUM program. They pro-
vide a pictorial representation of the MO compositions and their
contributions to chemical bonding. The DOS and OPDOS diagrams
for complexes 1 and 3 are shown in Fig. 5. The DOS plots mainly
present the composition of the fragment orbitals contributing to
the molecular orbitals. The OPDOS can enable us to ascertain the
displacement ellipsoids. Hydrogen atoms are omitted for clarity.
intra- and intermolecular weak hydrogen bonds, the data of which
are collected in Table 3.
3.2. Optimized geometries
The geometries of the studied complexes were optimized in sin-
glet states using the DFT method with the B3LYP functional. The
optimized geometric parameters are gathered in Table 2. In gen-

J.G. Małecki / Polyhedron 29 (2010) 1973–1979
1977
Table 2
Selected bond lengths (Å) and angles (°) for [Ru(SCN)2(PPh3)2(py)2] (1), [Ru(SCN)2(PPh3)2(
c
-pic)2] (2), [Ru(SCN)2(PPh3)2(py-2-CH2NH2)] (3) and [Ru(SCN)2(PPh3)2(py-2-
CH2O)]ꢂCH3OH (4) with the optimized geometry values.
1
2
3
4
Exp
Calc
Exp
Calc
Exp
Calc
Exp
Calc
Bond lengths (Å)
Ru(1)–N(1)
Ru(1)–N(2)
Ru(1)–N(3)
Ru(1)–N(4)
Ru(1)–P(1)
Ru(1)–P(2)
S(1)–C(1)
2.0460(19)
2.0383(19)
2.1584(19)
2.1537(18)
2.3786(6)
2.3552(6)
1.624(3)
1.156(3)
1.624(3)
1.155(3)
2.0739
2.0717
2.2134
2.2210
2.4517
2.4513
1.6321
1.1854
1.6333
1.1849
2.023(8)
2.030(9)
2.166(9)
2.179(8)
2.355(3)
2.359(3)
1.627(10)
1.171(12)
1.617(11)
1.174(13)
2.0448
2.0452
2.1719
2.1822
2.3931
2.3952
1.6243
1.1848
1.6235
1.1852
2.079(4)
2.058(5)
2.129(4)
2.136(4)
2.3344(13)
2.3332(13)
1.671(9)
1.144(6)
1.632(5)
1.089(9)
2.0761
2.0468
2.1468
2.1473
2.3831
2.3563
1.6214
1.1856
1.6234
1.1839
Ru(1)–N(1)
Ru(1)–N(2)
Ru(1)–N(3)
Ru(1)–O(1)
Ru(1)–P(1)
Ru(1)–P(2)
S(1)–C(1)
N(1)–C(1)
S(2)–C(2)
N(2)–C(2)
2.033(3)
2.034(3)
2.162(3)
2.216(2)
2.3077(9)
2.3318(10)
1.622(4)
1.146(4)
1.636(4)
1.147(4)
2.0228
2.0433
2.1895
1.9783
2.3390
2.3917
1.6199
1.1859
1.6228
1.1881
N(1)–C(1)
S(2)–C(2)
N(2)–C(2)
Angles (°)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–N(3)
N(2)–Ru(1)–N(3)
N(1)–Ru(1)–N(4)
N(2)–Ru(1)–N(4)
N(3)–Ru(1)–N(4)
N(1)–Ru(1)–P(1)
N(2)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(4)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
N(2)–Ru(1)–P(2)
N(3)–Ru(1)–P(2)
N(4)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
S(1)–C(1)–N(1)
S(2)–C(2)–N(2)
Ru(1)–N(1)–C(1)
Ru(1)–N(2)–C(2)
175.86(7)
88.99(7)
88.47(7)
87.96(7)
88.42(7)
81.02(7)
97.59(5)
85.69(5)
90.38(5)
169.71(5)
86.97(5)
95.00(5)
169.79(5)
89.47(5)
99.43(2)
177.1(2)
177.7(2)
177.01(18)
177.5(2)
174.80
89.01
87.36
87.31
88.51
82.28
97.32
85.83
90.72
170.35
86.90
96.70
168.98
88.25
99.31
178.54
179.45
173.19
173.90
174.7(4)
89.2(3)
87.9(4)
86.8(3)
88.5(3)
83.0(3)
88.2(3)
96.0(3)
87.7(2)
169.5(2)
96.6(3)
85.9(3)
171.2(2)
90.6(2)
99.10(11)
178.7(11)
176.5(13)
176.5(9)
175.5(10)
174.87
89.17
87.58
87.29
88.29
82.59
86.98
96.59
87.79
169.00
97.12
85.98
170.75
90.88
99.27
179.36
178.25
173.91
173.29
88.0(2)
81.04(17)
91.8(2)
91.54
80.49
91.71
81.10
168.39
78.33
172.89
94.77
93.43
94.80
83.20
96.51
163.08
92.01
99.17
177.86
171.01
174.46
172.98
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–N(3)
N(2)–Ru(1)–N(3)
N(1)–Ru(1)–O(1)
N(2)–Ru(1)–O(1)
N(3)–Ru(1)–O(1)
N(1)–Ru(1)–P(1)
N(2)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
O(1)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
N(2)–Ru(1)–P(2)
N(3)–Ru(1)–P(2)
O(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
S(1)–C(1)–N(1)
S(2)–C(2)–N(2)
Ru(1)–N(1)–C(1)
Ru(1)–N(2)–C(2)
171.19(11)
83.24(10)
90.65(11)
89.77(10)
82.53(10)
75.40(11)
99.20(8)
87.91(8)
98.12(8)
168.33(7)
87.41(8)
96.95(9)
163.42(7)
90.95(7)
96.86(3)
175.7(4)
179.9(5)
176.0(3)
174.7(3)
176.51
85.63
90.88
92.34
87.00
81.99(17)
166.64(18)
77.94(16)
174.57(13)
94.33(15)
94.00(12)
94.88(12)
85.49(13)
95.25(19)
164.57(12)
92.82(11)
99.13(4)
79.19
95.91
87.44
97.01
170.65
84.50
95.90
162.06
84.58
100.15
177.63
178.85
179.93
168.57
177.9(5)
171.6(16)
175.7(4)
173.9(7)
bonding, non-bonding and anti-bonding characteristics with re-
spect to particular fragments. A positive value in the OPDOS plots
means a bonding interaction, while a negative value represents an
anti-bonding interaction and a value near zero indicates a non-
bonding interaction.
As can be see from the OPDOS plots, the thiocyanate ligands
have significant anti-bonding character in the HOMO and
HOMOꢁ1 molecular orbitals and bonding character in lower
HOMO orbitals. The interactions of N-heteroaromatic ligands with
Ru(II) d orbitals have negative values in the frontier HOMO orbi-
tals. In the frontier occupied and virtual molecular orbitals values
of the interaction between ruthenium and the studied pyridine
Table 3
Hydrogen bonds for [Ru(SCN)2(PPh3)2(py)2] (1), [Ru(SCN)2(PPh3)2(c-pic)2] (2)
[Ru(SCN)2(PPh3)2(py-2-CH2NH2)] (3) and [Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH (4)
(Å and o).
D–Hꢂ ꢂ ꢂA
1
d(D–H)
d(Hꢂ ꢂ ꢂA)
d(Dꢂ ꢂ ꢂA)
<(DHA)
C(8)–H(8)ꢂ ꢂ ꢂN(1)
C(14)–H(14)ꢂ ꢂ ꢂN(1)
C(3)–H(3)ꢂ ꢂ ꢂN(2)
C(12)–H(12)ꢂ ꢂ ꢂN(2)
C(26)–H(26)ꢂ ꢂ ꢂN(2)
C(36)–H(36)ꢂ ꢂ ꢂN(2)
0.93
0.93
0.93
0.93
0.93
0.93
2.43
2.42
2.61
2.51
2.59
2.59
2.984(3)
3.166(3)
3.065(3)
3.017(3)
3.367(3)
3.167(3)
118.0
137.5
110.9
114.4
140.9
120.6
compounds indicate the ligands act as strong
p-acceptors. This
conclusion is confirmed by the mentioned further stabilization en-
ergy and Mayer bond orders, which are the following 1: Ru–P
1.539, 1.553; Ru–N(py) 0.724, 0.737; Ru–N(NCS) 0.953, 0.944; 2:
Ru–P 1.598, 1.592; Ru–N(
0.751, 0.740; Ru–N(NCS) 0.980,
c
-pic)
0.970; 3: Ru–P 1.653, 1.636, Ru–N(py-2-CH2NH2) 0.740, 0.826; Ru–
N(NCS) 0.976, 1.77; 4: Ru–P 0.784, 0.677; Ru–N(py-2-CH2O) 0.459;
Ru–O 0.872, Ru–N(NCS) 0.572, 0.545.
The occupancies of the ruthenium d orbitals, obtained from NBO
analysis, are as follows 1: dxy – 0.94; dxz – 1.83; dyz – 1.86; dx2ꢁy2
2
C(3)–H(3)ꢂ ꢂ ꢂN(1)
C(7)–H(7)ꢂ ꢂ ꢂN(2)
C(13)–H(13)ꢂ ꢂ ꢂN(2)
C(16)–H(16)ꢂ ꢂ ꢂN(2)
C(40)–H(40)ꢂ ꢂ ꢂN(1)
C(46)–H(46)ꢂ ꢂ ꢂN(2)
0.93
0.93
0.93
0.93
0.93
0.93
2.45
2.50
2.61
2.41
2.51
2.60
2.999(15)
2.997(15)
3.065(15)
3.066(15)
3.253(17)
3.358(17)
117.7
113.5
111.0
127.4
138.8
139.3
–
1.86; dz2 – 0.83, 2: dxy – 0.99; dxz – 1.85; dyz – 1.85; dx2-y2 – 1.83; dz2
– 0.82, 3: dxy – 0.99; dxz – 1.87; dyz – 1.85; dx2-y2 – 1.81; dz2 – 0.80,
4: dxy – 1.22; dxz – 1.53; dyz – 1.16; dx2-y2 – 1.70; dz2 – 1.31. The data
suggest that the donation from N-donor ligands to dRu orbitals
plays a role in the electronic structure of the complexes and to
determine the donation, the stabilization energies1 were calcu-
lated. These analyses have shown that the lone pairs localized on
3
C(7)–H(7)ꢂ ꢂ ꢂN(2)
C(22)–H(22)ꢂ ꢂ ꢂN(2)
C(32)–H(32)ꢂ ꢂ ꢂN(2)
C(32)–H(32)ꢂ ꢂ ꢂN(1)
C(19)–H(19)ꢂ ꢂ ꢂS(1) #1
0.93
0.93
0.93
0.93
0.93
2.55
2.37
2.43
2.61
2.87
3.102(9)
3.154(7)
3.224(11)
3.101(8)
3.481(6)
118.4
142.4
143.6
113.3
124.0
4
the N atom of SCNꢁ and py,
c-pic, py-2-CH2NH2 and py-2-CH2O
C(20)–H(20)ꢂ ꢂ ꢂN(1)
C(44)–H(44)ꢂ ꢂ ꢂN(1)
C(10)–H(10)ꢂ ꢂ ꢂN(2)
C(28)–H(28)ꢂ ꢂ ꢂN(2)
C(20)–H(20)ꢂ ꢂ ꢂN(1)
0.93
0.93
0.93
0.93
0.93
2.50
2.55
2.50
2.55
2.50
3.215(5)
3.348(5)
3.296(5)
3.200(5)
3.215(5)
133.9
144.6
143.6
127.2
133.9
1
D
Eij (kcal/mol) associated with delocalization is estimated by the second-order
Eij = qi (F(i,j)2)/(ej
i) where qi is the donor orbital occupancy, e,i ej
perturbative as:
D
ꢁ
e
are diagonal elements (orbital energies) and F(i,j) is the off-diagonal NBO Fock or
#1 1/2 + x, 3/2 ꢁ y, 2 ꢁ z.
Kohn–Sham matrix element.

1978
J.G. Małecki / Polyhedron 29 (2010) 1973–1979
Fig. 5. The density of states (DOS) and overlap partial density of states (OPDOS) diagrams for the complexes [Ru(SCN)2(PPh3)2(py)2] (1) and [Ru(SCN)2(PPh3)2(py-2-CH2NH2)]
(3).
ligands in the studied complexes donate the charge to ruthenium,
and the stabilization energies ( Eij) are 578.06, 636.4, 598.27,
tween the central ruthenium ion and the N-donor ligands in the
studied complexes are displayed. Taking into account the Mayer
bond orders, stabilization energy, values of interactions of N-donor
ligands with dRu orbitals and bonding energy, the results suggest
D
288.2 kcal/mol and 353.40, 383.63, 406.07, 415.24 kcal/mol for
complexes 1, 2, 3 and 4, respectively. The back donation from
ruthenium to the N-heteroaromatic ligands in the complexes 1,
2, 3 and 4 have values 59.71, 61.96, 60.47 and 46.72 kcal/mol,
respectively.
that pyridine and 2-(hydroxymethyl)pyridine as well
and 2-(aminomethyl)pyridine ligands are comparable pairwise in
terms of their -acceptor properties, and pyridine is weakest one.
c-picoline
p
The energy decomposition analysis of the studied complexes,
based on the work of Morokuma [22] and the extended transition
state (ETS) partitioning scheme of Ziegler [23], has been carried out
using the ADF program (Release 2008) [24] at the B3LYP/TZP level.
The binding energies of the compounds were calculated as the dif-
ference between the energy of the complexes with optimized
3.4. Electronic spectra
The complexes presented bands in the UV–Vis spectra resulting
from d ? d transitions, that are assigned to 1A1 ? 1T1 and
1A1 ? 1T2 transitions, with maxima at 435.1 nm (22 983 cmꢁ1),
geometries and the energies of the optimized ligands pyridine,
c
-
and 347.5 nm (28 777 cmꢁ1
)
for compound 1, 405.7 nm
(24 649 cmꢁ1), 314.1 nm (31 837 cmꢁ1
for and 402.4 nm
(24 851 cmꢁ1), 312.5 nm (31 995 cmꢁ1) for complex 3. The bands
picoline, 2-(aminomethyl)pyridine, 2-(hydroxymethyl)pyridine
and [Ru(SCN)2(PPh3)2] fragment. A general theoretical background
on the bond energy decomposition scheme can be found in a re-
view paper [25]. In Table 4 the results of energy decomposition
analysis calculated for the complexes in the gas phase and more
realistically in methanol solvent are listed. As can be seen, the ki-
netic energies of the studied complexes play an important role
for the [Ru(SCN)2(PPh3)2] – L binding in solution.
)
2
attributed to pbC6H6 ? 3dphosphorus
,
p
?
p
and
p
?
p
tran-
*
*
C@C
C@N
sitions are observed at 238.8, 208.4 nm, 222.6, 212.6 nm and 253.6,
208.7 nm for complexes 1, 2 and 3, respectively. The values of the
ligand field parameter 10Dq, calculated on the basis of the posi-
tions and molar extinction coefficients of electronic bands for the
investigated complexes, are equal to 24 380 cmꢁ1 for 1,
26 899 cmꢁ1 for complex 2 and 27 222 cmꢁ1 for compound 3. Ra-
In order to make a comparison between the p-acceptor proper-
ties of the studied N-heteroaromatic ligands, in Fig. 6 the overlap
partial density of states (OPDOS) diagrams for the interaction be-
cah’s parameters are equal to B = 386 cmꢁ1, 479 cmꢁ1, 476 cmꢁ1
C = 1537 cmꢁ1 1907 cmꢁ1 1896 cmꢁ1 and the nephelauxetic
,
,
,

J.G. Małecki / Polyhedron 29 (2010) 1973–1979
1979
Table 4
Energy decomposition analysis for complexes [Ru(SCN)2(PPh3)2(py)2] (1), [Ru(SCN)2(PPh3)2(c-pic)2] (2), [Ru(SCN)2(PPh3)2(py-2-CH2 NH2)] (3) and [Ru(SCN)2(PPh3)2(py-2-CH2O)]
(4) as the [Ru(SCN)2(PPh3)2] fragment and the py,
c
-pic, py-2-CH2NH2, py-2-CH2O ligands (energies in kcal molꢁ1).
Energy (kcal/mol) [Ru(SCN)2(PPh3)2(py)2]
[Ru(SCN)2(PPh3)2(
c
-pic)2]
[Ru(SCN)2(PPh3)2(py-2-CH2NH2)]
[Ru(SCN)2(PPh3)2(py-2-CH2O)]
Gas phase
CH3OH solvent
Gas phase
CH3OH solvent
Gas phase
CH3OH solvent
Gas phase
CH3OH solvent
D
D
D
D
D
D
Eelstat
Ekinetic
ECoulomb
EXC
Esolvation
E
ꢁ136.37
240.43
ꢁ87.09
ꢁ81.20
ꢁ137.71
314.67
ꢁ139.42
ꢁ96.65
ꢁ23.16
ꢁ82.27
ꢁ154.34
324.95
ꢁ154.34
395.18
ꢁ183.65
ꢁ113.89
ꢁ22.68
ꢁ79.37
ꢁ213.12
323.31
ꢁ213.12
340.06
ꢁ237.23
397.00
ꢁ237.23
478.68
ꢁ133.63
ꢁ151.16
ꢁ141.72
ꢁ201.96
ꢁ40.39
ꢁ240.23
ꢁ301.24
ꢁ127.56
ꢁ21.97
(Steric+OrbInt)
ꢁ99.06
ꢁ185.44
ꢁ111.95
ꢁ64.24
ꢁ62.09
ꢁ226.42
ꢁ257.13
ꢁ192.41
ꢁ209.32
4. Supplementary data
CCDC 758952, 761475, 760151 and 759146 contain the supple-
mentary crystallographic data for the complexes [Ru(SCN)2(PPh3)2-
(py)2], [Ru(SCN)2(PPh3)2(c-pic)2]ꢂCH3OH [Ru(SCN)2(PPh3)2(py-2-
CH2NH2)] and [Ru(SCN)2(PPh3)2(py-2-CH2O)]ꢂCH3OH, respectively.
These data can be obtained free of charge via http://www.ccdc.ca-
m.ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Center, 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 at the Wroclaw Centre for
Networking and Supercomputing (http://www.wcss.wroc.pl).
References
[1] X.-Y. Lu, H.-J. Xu, X.-T. Chen, Inorg. Chem. Commun. 12 (2009) 887.
[2] V. Dragutan, I. Dragutan, L. Delaude, A. Demonceau, Coord. Chem. Rev. 251
(2007) 765.
[3] J.B. Coe, J.S. Glenwright, Coord. Chem. Rev. 203 (2000) 5.
[4] E.A. Medlycott, G.S. Hanan, Coord. Chem. Rev. 250 (2006) 1763.
[5] J. Otsuki, T. Akasaka, K. Araki, Coord. Chem. Rev. 252 (2008) 32.
[6] F. Puntoriero, S. Campagna, A.-M. Stadler, J.-M. Lehn, Coord. Chem. Rev. 252
(2008) 2480.
Fig. 6. The overlap partial density of states (OPDOS) diagrams for the interaction
between the ruthenium central ion and the N-donor ligands in the studied
complexes.
[7] Yu.E. Alexeev, B.I. Kharisov, T.C.H. Garcia, A.D. Garnovskii, Coord. Chem. Rev.
254 (2010) 794.
[8] H.E. Toma, K. Araki, Coord. Chem. Rev. 196 (2000) 307.
[9] Li-Feng Tan, H. Chao, K.-Ch. Zhen, J.-J. Fei, F. Wang, Y.-F. Zhou, L.-N. Ji,
Polyhedron 26 (2007) 5458.
parameters are b55 = 0.54, 0.67 and 0.66 for compounds 1, 2 and 3,
respectively. The spectroscopic parameters have been calculated
on the basis of the pseudooctahedral geometry of these complexes.
The calculations of the C parameter have been based on intercom-
bination transitions (1A1 ? 3T1; 1A1 ? 3T2) covered by the bands
observed in the visible energy region of the spectra.
The ruthenium(III) complex with the 2-(hydroxymethyl)pyri-
dine ligand displayed bands at 510.6, 329.2, 276.6 and 215.0 nm,
and for this compound bands are expected in the NIR region. The
spectrum in this energy range was not measured and for that rea-
son the 10Dq and Racah’s parameters were not determined for the
complex. Based on the calculated electronic spectrum, the first
experimental band is attributed to HOMO–5/6 ? LUMO transitions
[10] J.G. Małecki, M. Jaworska, R. Kruszynski, R. Gil-Bortnowska, Polyhedron 24
(2005) 1445.
[11] R. Kruszynski, J.G. Małecki, Acta. Crystallogr., Sect. E63 (2007) m3052.
[12] Md.K. Nazeeruddin, A. Kay, I. Rodicio, R. Humphry-Baker, E. Müller, N.
Vlachopoulos, M. Grätzel, J. Am. Chem. Soc. 115 (1993) 6382.
[13] T.A. Stephenson, G. Wilkonson, J. Inorg. Nucl. Chem. 28 (1966) 945.
[14] 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.
(68%, 34%) and has d ? d character with
a contribution of
d ? p*PPh3/Py-2-CH2O charge transfer transitions. In the energy re-
gion adequate to the experimental bands with maxima at 329.2
and 276.6 nm, HOMO ? LUMO+1(a)/2(b) (81%) and HOMO ? LU-
MO+4 (67%), HOMOꢁ23(b) ? LUMO(b) (64%) transitions were cal-
culated, among others, therefore these bands have MLCT and LMCT
character. The highest energy band is assigned to LLCT transitions.
In summary, the four new ruthenium complexes with thiocya-
nate, triphenylphosphine and N-heteroaromatic ligands have been
synthesized and their crystal structures determined. In the struc-
tures of all the studied complexes, the triphenylphosphine ligands
are in cis positions. The electronic structures of the obtained com-
plexes were calculated. The collected data from NBO, Mayer bond
[15] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[16] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[17] 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.
[18] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chim. Acta 97 (1997)
119.
[19] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comput. Chem. 29 (2008) 839.
[20] Dolomanov et al., Appl. Crystallogr., Sect. 42 (2009) 339.
[21] M.G.B. Drew, A.H. Bin-Othman, S.M. Nelson, J. Chem. Soc., Dalton Trans. (1976)
1394.
orders and energy decomposition analyses indicate that the
acceptor properties of pyridine and 2-(hydroxymethyl)pyridine,
as well as -picoline and 2-(aminomethyl)pyridine, are compara-
p-
[22] K.J. Morokuma, Chem. Phys. 55 (1971) 1236.
[23] T. Ziegler, A. Rauk, Theor. Chim. Acta 46 (1977) 1.
[24] ADF2009.01, SCM, Theoretical Chemistry, Vrije Universiteit, Amsterdam, The
Netherlands, <http://www.scm.com>.
[25] F.M. Bickelhaupt, E.J. Baerends, Kohn-Sham, Predicting and understanding
chemistry, in: K.B. Lipkowitz, D.B. Boyd (Eds.), Rev. Comput. Chem., vol. 15,
Wiley-VCH, New York, 2000, p. 1.
c
ble in pairs. The values of the ligand field parameter 10Dq and Ra-
cah’s parameters were calculated for the studied compounds 1, 2
and 3.