Synthesis, characterization and molecular structure of ruthenium complexes containing imidazole-2-carboxylic acid derivatives

Article abstract of DOI:10.1016/j.poly.2012.04.020

The ruthenium complexes [Ru(BIm-2-COO)₂(PPh₃) ₂]·CH₃OH·H₂O (1), [RuCl ₂(MeIm-2-COO)(PPh₃)₂] (2) and [Ru(NCS) ₂(MeIm)₂(PPh₃)₂]·CH ₃OH (3) have been prepared and studied by IR, ¹H, ³¹P NMR, UV-Vis spectroscopy and X-ray crystallography. The complexes were synthesized by the reactions of [RuCl₂(PPh₃) ₃] with 1H-benzimidazole-2-carboxylic acid (BIm-2-COOH) or 1-methyl-1H-imidazole-2-carbozylic acid (MeIm-2-COOH) and in the case of complex (3) with admixture of NH₄SCN in methanol solutions. The experimental studies were complemented by quantum chemical calculations which were used to identify the nature of the interactions between the ligands and the central ion and the orbital compositions in the frontier electronic structures. Based on a molecular orbital scheme, the calculated results allowed the interpretation of the UV-Vis spectra obtained at an experimental level. The luminescence properties of the complexes were determined.

Full text of DOI:10.1016/j.poly.2012.04.020

Polyhedron 40 (2012) 125–133
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization and molecular structure of ruthenium complexes
containing imidazole-2-carboxylic acid derivatives
⇑
´
J.G. Małecki , A. Maron
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 ruthenium complexes [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1), [RuCl2(MeIm-2-COO)(PPh3)2] (2)
and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) have been prepared and studied by IR, 1H, 31P NMR, UV–Vis
spectroscopy and X-ray crystallography. The complexes were synthesized by the reactions of
[RuCl2(PPh3)3] with 1H-benzimidazole-2-carboxylic acid (BIm-2-COOH) or 1-methyl-1H-imidazole-2-
carbozylic acid (MeIm-2-COOH) and in the case of complex (3) with admixture of NH4SCN in methanol
solutions. The experimental studies were complemented by quantum chemical calculations which were
used to identify the nature of the interactions between the ligands and the central ion and the orbital
compositions in the frontier electronic structures. Based on a molecular orbital scheme, the calculated
results allowed the interpretation of the UV–Vis spectra obtained at an experimental level. The lumines-
cence properties of the complexes were determined.
Received 5 March 2012
Accepted 17 April 2012
Available online 26 April 2012
Keywords:
Ruthenium complexes
Imidazole derivatives carboxylic acids
X-ray structure
Electronic structure
DFT calculations
Ó 2012 Elsevier Ltd. All rights reserved.
Fluorescence
1. Introduction
In this paper, an experimental and quantum chemical study of
complexes based on RuCl2(PPh3)3 and imidazole derivatives car-
The coordination chemistry of ruthenium is a field of current
growing interest from various viewpoints. The attention of scien-
tists concentrates on synthetic aspects, structural, physicochemical
properties and reactivity. The ruthenium complexes with imidaz-
ole derivative ligands have been attracting continuous attention
due to their properties and applications [1–4]. The compounds
with imidazole moiety, especially heterocyclic derivatives, are
known for their interesting optical properties as well as they are
recognized as a mediator for synthesis reactions and play an
important role in preparing functionalized materials [5,6]. Their
unique fluorescence and chemiluminescence properties are re-
flected in the research aimed at the application of these arrange-
ments in analytical chemistry [5]. The imidazole ring occurs as a
fragment of biologically active molecules, which show antimicro-
bial, cytotoxic, antidepressant actions [3,7,8].
boxylic acid ligands: 1-methyl-1H-imidazole-2-carboxylic acid
and 1H-benzimidazole-2-carboxylic acid is presented. The com-
plex reported in this paper combine the interest in ruthenium
phosphine coordination compounds and complexes containing five
membered azole rings derivative ligands [11–16]. The quantum
chemical study included a characterization of the molecular and
electronic structures of the complexes by analysis of optimized
molecular geometries, electronic populations by using the natural
bond orbitals scheme. The latter was used to identify the nature of
the interactions between the ligands and the central ion. The calcu-
lated density of states showed the interactions and influences the
orbital composition in the frontier electronic structure. The time
dependent density functional theory (TD-DFT) was finally used to
calculate the electronic absorption spectra. Based on a molecular
orbital scheme, these results allowed for the interpretation of the
UV–Vis spectra obtained at an experimental level.
On the other hand, N-heterocyclic carboxylic acids such as
derivatives of pyridine-2-carboxylic acid, pyrazine-2-carboxylic
acid, which are recognized as efficient N–O donors exhibiting
diverse mode of coordination [9], were widely studied recently.
2. Experimental
They are known as a good
p-acceptor and stabilizing factor of
2.1. Synthesis
ruthenium(II) central ions [10]. However, the coordination behav-
ior of imidazole carboxylic acids toward ruthenium central ions is
different and relatively less studied in spite of their interesting
The complex [RuCl2(PPh3)3] was synthesized by literature
method [17]. All other reagents were commercially available and
were used without further purification.
moderate p-donor properties.
The complexes were synthesized in the reactions between
[RuCl2(PPh3)3] (0.19 g, 0.2 mmol) and 1H-benzimidazole-2-carbox-
ylic acid and 1-methyl-1H-imidazole-2-carboxylic acid (0.06 g,
⇑
Corresponding author.
E-mail address: gmalecki@us.edu.pl (J.G. Małecki).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.04.020

´
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
126
0.4 mmol) in CH3OH (80 cm3). In the case of complex (3) to the
reaction mixture the stoichiometric amount of NH4SCN (0.4 mmol)
was added. The mixtures of the compounds were refluxed for
about 2 h. After this time the filtered solutions were cooled and left
out to slow evaporation.
3.17 (s, methanol). 31P NMR (d, DMSO-d6): 46.91 (s, PPh3), 25.50 (s,
PPh3).
2.2. Physical measurements
Infrared spectra were collected on a Perkin Elmer FT-IR spectro-
photometer in the spectral range 4000–450 cmÀ1 with technique
of KBr pellets. Electronic spectra were measured on a Lab Alliance
UV–Vis 8500 spectrophotometer in the range of 1100–180 nm in
methanol solutions. 1H and 31P NMR spectra were obtained at
room temperature in CDCl3 using a Bruker 400 spectrometer.
Luminescence measurements were made in methanolic solutions
on an F-2500 FL spectrophotometer at room temperature.
2.1.1. [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1)
IR (KBr): 3421
m
OH; 3056
m
PhH; 2897, 2746
m
CH; 1637
Ph(P–Ph); 1322, 1299 mCOO
1094 d(C–CH in the plane); 747, 738 d(C–C out of the plane); 691 d(C–C in the
mCOO; 1587
mCN; 1486, 1469 d(C–CH in the plane); 1432
m
;
plane); 520 mP–Ph
.
1H NMR (d, DMSO-d6): d 13.08 (s, NH), 7.72–6.92 (m, PPh3; BIm),
3.49 (methanol), 3.15 (H2O), 2.51 (dt, J = 3.7, 1.9 Hz, DMSO). 31P
NMR (d, DMSO-d6): 48.50 (s, PPh3).
UV–Vis (methanol, k [nm] (loge)): 444 (1.14), 332 (1.97), 305
2.3. DFT calculations
(sh), 265 (2.74), 212 (4.98).
The calculations were carried out using GAUSSIAN09 [18] program.
Molecular geometries of the singlet and doublet ground state of
complexes (1), (3) and (2), respectively were fully optimized in
the gas phase at the B3LYP/DZVP level of theory [19,20]. For each
compound a frequency calculation was carried out, verifying that
the optimized molecular structure obtained corresponds to an en-
ergy minimum, thus only positive frequencies were expected. The
DZVP basis set [21] with f functions with exponents 1.94722036
and 0.748930908 was used to describe the ruthenium atom and
the basis set used for lighter atoms (C, N, O, P, H) was 6-31G with
a set of ‘‘d’’ and ‘‘p’’ polarization functions. The TD-DFT (time
dependent density functional theory) method [22] was employed
to calculate the electronic absorption spectra of the complexes in
the solvent PCM (Polarizable Continuum Model) model. In this
work, 90 singlet excited states was calculated as vertical transi-
tions for the complexes. A natural bond orbital (NBO) analysis
was also made for all complexes using the NBO 5.0 package [23] in-
cluded in GAUSSIAN09. Natural bond orbitals are orbitals localized on
one or two atomic centers, that describe molecular bonding in a
manner similar to a Lewis electron pair structure, and they corre-
spond to an orthonormal set of localized orbitals of maximum
2.1.2. [RuCl2(MeIm-2-COO)(PPh3)2] (2)
IR (KBr): 3446 OH; 3052 PhH; 2924
1509, 1481 d(C–CH plane); 1433
m
m
m
CH; 1673
Ph(P–Ph); 1265, 1178 mCOO
1090 d(C–CH in the plane); 746 d(C–C out of the plane); 694 d(C–C in the plane)
519
m
COO; 1571 mCN
;
;
;
m
in the
m
.
P–Ph
UV–Vis (methanol, k [nm] (log
e
)): 507 (1.16), 440 (1.54), 361
(1.92), 285 (sh), 212 (4.83).
1H NMR (d, DMSO-d6): 7.74–7.32 (m, Im, PPh3), 7.25 (dd, J = 9.4,
5.4 Hz, Im), 7.12 (s, Im), 3.47 (d, J = 46.6 Hz, CH3). 31P NMR (d,
DMSO-d6): 38.42 (s, PPh3), 30.42 (s, PPh3).
2.1.3. [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3)
IR (KBr): 3437 mOH; 3127, 3051 mPhH; 2929 mCH; 2105 m(CN
from
SCN); 1533
mCN(Im); 1480 d(C–CH in the plane); 1431
m
Ph(P–Ph); 1089 d(C–
plane); 1030 (imidazole ring); 828, 806 m(SC
SCN), 741
CH in the
from
d(C–C out of the plane); 698 d(C–C in the plane); 513 d(NCS)
.
UV–Vis (methanol, k [nm] (log )): 380 (1.42), 271 (2.89), 213
e
(4.92).
1H NMR (d, DMSO-d6): d 7.37–7.18 (m, Im, PPh3), 7.09 (d,
J = 2.6 Hz, Im), 6.88 (d, J = 6.5 Hz, Im), 3.49 (t, J = 21.1 Hz, CH3(Im)),
Table 1
Crystal data and structure refinement details of [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1) [RuCl2(MeIm-2-COO)(PPh3)2] (2) and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes.
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C52H40N4O4P2RuCH4OH2O
997.95
295.0(2)
C41H35Cl2N2O2P2Ru
821.62
295.0(2)
C46H42N6P2RuS2CH4O
938.03
295.0(2)
monoclinic
P21/n
triclinic
triclinic
ꢀ
ꢀ
P1
P1
11.2946(10)
11.7551(7)
17.8029(13)
91.873(5)
97.117(7)
91.527(6)
2343.1(3)
2
11.4498(3)
23.6857(7)
24.6905(7)
68.328(3)
88.087(2)
80.807(2)
6140.3(3)
6
11.3365(4)
25.0341(8)
16.4390(5)
90
104.686(3)
90
4512.9(2)
4
1.381
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Å3)
Z
DCalc (mg/m3)
1.414
0.459
1028
1.332
0.627
2514
Absorption coefficient (mmÀ1
F(000)
)
0.553
1936
Crystal dimensions (mm)
Range for data collection (°)
Index ranges
0.31 Â 0.11 Â 0.07
3.47–25.05
À13 ꢀ h ꢀ 13
À14 ꢀ k ꢀ 14
À21 ꢀ l ꢀ 21
24673
0.20 Â 0.09 Â 0.03
3.32–25.05
À13 ꢀ h ꢀ 13
À28 ꢀ k ꢀ 24
À29 ꢀ l ꢀ 27
46356
0.17 Â 0.11 Â 0.06
3.50–25.05
À13 ꢀ h ꢀ 12
À25 ꢀ k ꢀ 29
À19 ꢀ l ꢀ 16
19685
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
8266 (0.0572)
8266/0/600
1.165
21697 (0.0763)
21697/0/1354
0.984
7981 (0.0293)
7981/0/536
1.022
Final R indices [I > 2
r
(I)]
R1 = 0.0524
wR2 = 0.1079
R1 = 0.0786
wR2 = 0.1156
1.289 and À0.933
R1 = 0.0512
wR2 = 0.0986
R1 = 0.0970
wR2 = 0.1166
0.974 and À0.686
R1 = 0.0364
wR2 = 0.0793
R1 = 0.0509
wR2 = 0.084
0.480 and À0.405
R indices (all data)
Largest difference in peak and hole

´
127
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
occupancy. NBO analysis provides the contribution of atomic orbi-
tals (s, p, d) to the NBO and hybrid orbitals for bonded atom
30.42 and 46.91, 25.50 ppm that are consistent with the structure
confirmed by X-ray, indicating that the cis conformation of PPh3 li-
gands were kept upon coordination. The spectrum of complex (1)
shows singlet at 48.50 ppm suggests that the phosphine molecules
are equivalent.
On the IR spectra stretching vibrations for imidazole C@C and
C@N are observed in the 1587–1533 cmÀ1 range. The asymmetric
and symmetric stretches of COO groups gave the bands with
maxima at 1637, 1673 cmÀ1 and 1322, 1299 cmÀ1 and 1265,
1178 cmÀ1, respectively. The carboxyl group stretches in the free
ligands are observed at 1668 cmÀ1 and 1367 cmÀ1. These consider-
r
p
pairs. In this scheme, three NBO hybrid orbitals are defined, bond-
ing orbital (BD), lone pair (LP), and core (CR), which were analyzed
on the atoms directly bonded or presenting some kind of interac-
tion with the ruthenium atom. The contribution of a group (li-
gands, central ion) to a molecular orbital was calculated using
Mulliken population analysis. GaussSum 2.2 [24] was used to cal-
culate group contributions to the molecular orbitals and to prepare
the partial density of states (DOS) spectra. The DOS spectra were
created by convoluting the molecular orbital information with
Gaussian curves of unit height and FWHM (Full Width at Half Max-
imum) of 0.3 eV.
able difference between mas and ms is indicative of strong coordina-
tion of the carboxyl oxygen to the ruthenium(II) acceptor centre.
The mCN frequencies of thiocyanate ligands in complex (3) have
maxima close to 2105 cmÀ1, which is characteristic to S-bonded
complexes, but the electronic and steric effects caused by the N-
donor ligands affect the mCN frequency. The mCS and d(CNS) frequen-
cies are observed at 828, 806 and 513 cmÀ1. Because of a trans
symmetry of two NCS ligands to each other in the complex, on
the spectrum is visible only one mCN stretch, but the bands are
broadening due to not perfect trans disposition of thiocyanate li-
gands. The IR spectra of complexes (1) and (3) are presented on
the Fig. 1.
2.4. Crystal structure determination and refinement
X-ray intensity data were collected with graphite monochro-
mated Mo Ka radiation at temperature of 295.0(2) K, with x scan
mode. Lorentz, polarization and empirical absorption correction
using spherical harmonics implemented in SCALE3 ABSPACK
scaling algorithm [CrysAlis RED, Oxford Diffraction Ltd., Version
1.171.29.2] were applied. The structures were solved by the Patter-
son method and subsequently completed by the difference Fourier
recycling. All the non-hydrogen atoms were refined anisotropically
using full-matrix, least-squares technique. All the hydrogen atoms
were found from difference Fourier synthesis after four cycles of
anisotropic refinement, and refined as ‘‘riding’’ on the adjacent car-
bon atom with individual isotropic temperature factor equal 1.2
times the value of equivalent temperature factor of the parent
atom. The OLEX2 [25] and SHELXS97, SHELXL97 [26] programs were
used for all the calculations. Details concerning crystal data and
refinement are gathered in Table 1.
The structure of complex (2) has a large solvent void probably
due to lose their long-range ordering when solvent molecules
(methanol) leave the crystal. The presence of residual density in
the void has been verified with PLATON/SQUEEZE. In the struc-
tures of complexes (2) and (3) the alerts connected with Hirshfeld
differences between atoms are generated. These alerts are not re-
moved by refinements and may be connected with heavy (metal,
sulphur) atoms in the complexes or with crystals quality. In the
structure of complex (1) the hydrogen atom from methanol OH
group is in short intramolecular contact with phosphine phenyl
CH atom due to calculated geometry of the hydroxyl group. The
localization of the hydrogen by the difference Fourier recycling
has been failed.
3. Results and discussion
The complexes (1) and (2) were synthesized by reaction
between [RuCl2(PPh3)3] and twofold quantities of the ligands in re-
fluxed methanolic solutions. The attempt to synthesize thiocyanate
analogue of complex (2) leads to the ruthenium(II) complex with
decarboxylated imidazole ligand. In the reactions when the molar
ratio of [RuCl2(PPh3)3] to 1-methyl-1H-imidazole-2-carboxylic acid
ligand are 1:1 or 1:2 the same product have been obtained. The 1H
NMR spectra of the complexes show a set of signals corresponding
to the PPh3 and imidazole derivative ligands. The imidazole aro-
matic protons in the spectra of complexes (2) and (3) are visible
at 7.25, 7.12 ppm and 7.09, 6.98 ppm. The imidazole NH proton
indicates signal at 13.08 ppm in the spectrum of complex (1).
The triplets at 3.49 and 3.47 ppm indicate the methyl group in po-
sition 1 in imidazole ring of complexes (2) and (3). The singlets at
3.49 and 3.17 ppm originate from the methanol, which occurs as a
solvent in the structure of the complexes (1) and (3). The 31P NMR
spectra of the (2) and (3) complexes show two singlets at 38.42,
Fig. 1. The experimental and calculated IR spectra of [Ru(BIm-2-COO)2(PPh3)2]Á
CH3OHÁH2O (1) and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes.

´
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
128
3.1. Molecular structures
Ru(1)–O(1) and N(3)–Ru(1)–O(3) angles in complex (1) and
78.78° (average value) for N–Ru–O angle in (2). The angles are
practically the same indicating identical binding of the imidazole
derivative ligands. In the geometry of complex (3) the distortion
is smaller. The largest deviations are in the angles between 1-
methyl-1H-imidazole ligands (83.34(9)°) and isothiocyanate li-
gands (171.37(9)°). The P–Ru–P angles are greater than 90°
(96.85°, 98.30° and 97.51(3)° in (1), (2) and (3) respectively) which
may be attributed to the steric interactions between bulky PPh3
ligands.
The C–N and C–S bond lengths fall in the 1.152(3)–1.156(3) Å
and 1.623(3)–1.633(3) Å ranges for complex (3), similar to those
observed for thiocyanate complexes. These lengths are contrary
to those expected for the C„N and C–S bonds due to the contribu-
tion of the two resonance structures: linear (M–+N„C–S–) and
Crystals of the complexes suitable for single crystal X-ray anal-
yses were obtained by slow evaporation of the reaction mixtures.
The complexes (1) and (2) crystallise in triclinic P1 and the isothi-
ꢀ
ocyanate complex (3) in monoclinic P21/n space groups. The ruthe-
nium(II) complexes crystallise in solvated form with methanol and
water molecules. Fig. 2 presents the molecular structures of the
complexes and the selected bond distances and angles are col-
lected in Table 2. The crystal structure of complex (2) is built up
of three independent molecules in the asymmetric unit. The mole-
cules are twisted one to each other what prevents existence of
higher crystallographic symmetry. The average deviation of the
bond lengths in the three molecules does not outrun 0.014 Å
(Ru–P(1) bond).
The structures of the complexes can be considered as a
distorted octahedral with the largest deviation from the expected
90° bond angles coming from the bite angles of 2-imidazolecarb-
oxylic acids. It equals to 77.81(15)° and 78.07(15)° for N(1)–
bent (
) for thiocyanate metal complexes. The Ru–
N–C(S) ordinary angles are 174.6(2)° and 169.0(2)°. Close to the
higher value of the range observed for metal-thiocyanate angles
Fig. 2. Molecular structures of [Ru(BIm-2-COO)2(PPh3)2] (1), [RuCl2(MeIm-2-COO)(PPh3)2] (2) and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes. Hydrogen atoms and
solvent molecules are omitted for clarity. In the case of complex (2) one molecule from three independent is presented.

Table 2
Selected bond lengths (Å) and angles (°) for [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1), [RuCl2(MeIm-2-COO)(PPh3)2] (2) and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes with the optimized geometry values.
(1)
(2)
(3)
Exp
Calc
Exp
Calc
Exp
Calc
Bond lengths (Å)
N(1)–Ru(1)
N(3)–Ru(1)
O(1)–Ru(1)
O(3)–Ru(1)
2.121(4)
2.129(4)
2.133(4)
2.117(4)
2.3253(16)
2.3351(15)
2.160
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–O(1)
Ru(1)–N(1)
2.3041(13)
2.3724(15)
2.3872(15)
2.4266(14)
2.063(3)
Ru(2)–Cl(3)
Ru(2)–Cl(4)
Ru(2)–P(3)
Ru(2)–P(4)
Ru(2)–O(3)
Ru(2)–N(3)
2.3224(15)
2.3639(14)
2.3597(14)
2.4437(14)
2.059(3)
Ru(3)–Cl(5)
Ru(3)–Cl(6)
Ru(3)–P(5)
Ru(3)–P(6)
Ru(3)–O(5)
Ru(3)–N(5)
2.3225(14)
2.372
2.382
2.459
2.550
2.087
2.119
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–N(98)
Ru(1)–N(99)
2.140(2)
2.179
2.161
2.164
2.164
2.408
2.408
2.3645(15)
2.3939(13)
2.4305(15)
2.054(3)
2.163(2)
2.3462(8)
2.3469(7)
2.023(2)
2.037(2)
2.189
2.436
2.445
2.072
2.078
P(1)–Ru(1)
P(2)–Ru(1)
2.068(4)
2.089(4)
2.084(4)
Angles (°)
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–O(1)
N(1)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
N(3)–Ru(1)–O(1)
N(3)–Ru(1)–P(1)
N(3)–Ru(1)–P(2)
O(1)–Ru(1)–P(1)
O(1)–Ru(1)–P(2)
O(3)–Ru(1)–N(1)
O(3)–Ru(1)–N(3)
O(3)–Ru(1)–O(1)
O(3)–Ru(1)–P(1)
O(3)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
84.00(16)
77.81(15)
89.67(12)
172.96(13)
93.25(15)
173.50(12)
89.55(12)
86.79(11)
99.82(11)
93.79(15)
78.07(15)
168.60(14)
100.99(11)
87.60(11)
96.85(5)
82.69
77.65
89.61
171.35
94.75
171.33
89.60
87.42
99.17
94.76
77.64
169.98
99.18
87.38
98.34
Cl(1)–Ru(1)–Cl(2)
Cl(1)–Ru(1)–P(1)
Cl(1)–Ru(1)–P(2)
Cl(2)–Ru(1)–P(1)
Cl(2)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
O(1)–Ru(1)–Cl(1)
O(1)–Ru(1)–Cl(2)
O(1)–Ru(1)–P(1)
O(1)–Ru(1)–P(2)
O(1)–Ru(1)–N(1)
N(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(2)
N(1)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
99.44(5)
89.79(5)
93.21(5)
87.83(5)
165.31(5)
99.72(5)
168.66(11)
86.12(10)
100.35(11)
80.16(10)
78.81(15)
92.04(12)
82.57(13)
170.39(13)
89.60(12)
Cl(3)–Ru(2)–Cl(4)
Cl(3)–Ru(2)–P(3)
Cl(3)–Ru(2)–P(4)
Cl(4)–Ru(2)–P(3)
P(4)–Ru(2)–Cl(4)
P(4)–Ru(2)–P(3)
O(3)–Ru(2)–Cl(3)
O(3)–Ru(2)–Cl(4)
O(3)–Ru(2)–P(3)
O(3)–Ru(2)–P(4)
O(3)–Ru(2)–N(3)
N(3)–Ru(2)–Cl(3)
N(3)–Ru(2)–Cl(4)
N(3)–Ru(2)–P(3)
N(3)–Ru(2)–P(4)
96.93(5)
95.24(5)
166.52(5)
92.13(5)
87.59(5)
97.74(5)
168.87(10)
86.36(10)
98.64(10)
80.62(10)
78.99(15)
90.72(13)
84.38(11)
171.75(12)
89.71(11)
Cl(6)–Ru(3)–Cl(5)
Cl(5)–Ru(3)–P(5)
Cl(5)–Ru(3)–P(6)
Cl(6)–Ru(3)–P(5)
Cl(6)–Ru(3)–P(6)
P(5)–Ru(3)–P(6)
O(5)–Ru(3)–Cl(5)
O(5)–Ru(3)–Cl(6)
O(5)–Ru(3)–P(5)
O(5)–Ru(3)–P(6)
O(5)–Ru(3)–N(5)
N(5)–Ru(3)–Cl(5)
N(5)–Ru(3)–Cl(6)
N(5)–Ru(3)–P(5)
N(5)–Ru(3)–P(6)
97.25(6)
87.67(5)
168.92(5)
92.64(5)
92.36(5)
97.43(5)
166.76(10)
87.83(11)
99.81(9)
81.62(11)
78.54(15)
82.70(13)
89.94(13)
170.27(13)
91.83(13)
98.32
86.33
168.34
92.93
91.84
98.92
166.28
89.07
99.10
79.85
78.04
83.16
91.31
169.13
90.94
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
N(3)–Ru(1)–P(2)
N(1)–Ru(1)–N(98)
N(1)–Ru(1)–N(99)
N(3)–Ru(1)–N(98)
N(3)–Ru(1)–N(99)
N(98)–Ru(1)–P(1)
N(99)–Ru(1)–P(1)
N(98)–Ru(1)–P(2)
N(99)–Ru(1)–P(2)
N(98)–Ru(1)–N(99)
P(1)–Ru(1)–P(2)
Ru(1)–N(98)–C(98)
Ru(1)–N(99)–C(99)
83.34(9)
90.25(7)
173.13(6)
171.97(7)
88.99(6)
88.25(9)
86.38(9)
85.32(9)
87.35(9)
97.00(7)
89.79(7)
88.73(7)
95.69(7)
171.37(9)
97.51(3)
174.6(2)
169.0(2)
82.32
89.65
170.66
170.06
88.57
87.71
87.09
86.70
87.07
97.68
87.87
88.43
95.82
172.37
99.75
166.14
165.80

´
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
130
Table 3
donor ligands. In the structures, several weak inter- and intramo-
lecular hydrogen bonds exist [27] what is collected in Table 3.
The structures of the complexes (1) and (2) are stabilized by elec-
Hydrogen bonds for [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1), [RuCl2(MeIm-2-
COO)(PPh3)2] (2) and [Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes (Å and °).
D–HÁ Á ÁA
d(D–H)
d(HÁ Á ÁA)
d(DÁ Á ÁA)
<(DHA)
tronic interactions (p–p stacking) between PPh3 phenyl and imi-
dazolecarboxylic acid rings. Fig. 3 presents the alignment of
centroids formed by imidazole and phosphine phenyl rings in the
molecular structure of complex (1). The plane-to-plane distance
between the #Ph(P) centroid, determined by C(17)–C(22) carbons,
and imidazole ring is equal to 3.505 Å and the angle between the
(1)
N(2)–H(2)Á Á ÁO(5) #1
N(4)–H(4)Á Á ÁO(4) #2
O(5)–H(5A)Á Á ÁO(2)
O(6)–H(6B)Á Á ÁO(4) #2
C(11)–H(11)Á Á ÁO(6)
C(24)–H(24)Á Á ÁO(1)
C(30)–H(30)Á Á ÁO(3)
C(32)–H(32)Á Á ÁO(6) #3
C(46)–H(46)Á Á ÁO(1)
(2)
0.86
0.86
0.82
0.85
0.93
0.93
0.93
0.93
0.93
1.92
1.94
1.91
2.57
2.37
2.36
2.32
2.59
2.23
2.757(6)
2.732(6)
2.725(6)
3.01(3)
164.7
152.9
171.5
113.3
156.6
147.1
156.3
128.4
158.1
3.24(3)
normal to #Ph(P) and #Im is 13.03° indicating
action. Similar interactions are visible in the molecules of complex
(2) and the distances vary from 2.417 to 3.612 Å. The stacking
p–p stacking inter-
3.181(8)
3.197(8)
3.25(3)
p–p
3.112(8)
interaction in complex (2) presents the inset in Fig. 3 in which the
electrostatic potential surface is plotted. In the crystal packing of
complex (3) no p–p stacking interactions exist.
C(2)–H(2)–Cl(2)
0.93
0.93
0.96
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.96
0.93
0.93
0.93
0.93
2.70
2.69
2.41
2.21
2.50
2.58
2.59
2.81
2.76
2.57
2.22
2.82
2.55
2.65
2.80
2.35
2.31
2.41
2.61
2.77
3.221(6)
3.422(6)
3.053(8)
3.022(8)
3.143(6)
3.438(5)
3.318(7)
3.601(6)
3.356(7)
3.470(7)
3.027(7)
3.638(7)
3.091(6)
3.468(6)
3.135(5)
3.052(9)
3.100(7)
3.080(8)
3.169(6)
3.430(6)
115.8
136.4
123.9
145.2
126.7
153.5
135.9
143.6
123.2
162.3
144.4
147.2
117.3
147.1
102.5
129.7
142.8
128.7
118.9
129.1
C(7)–H(7)–Cl(5) #4
C(8)–H(8A)–O(2)
C(23)–H(23)–O(1)
C(26)–H(26)–O(1)
C(36)–H(36)–Cl(2)
C(40)–H(40)–O(4) #5
C(43)–H(43)–Cl(1) #6
C(53)–H(53)–Cl(3)
C(56)–H(56)–O(6) #7
C(59)–H(59)–O(3)
C(65)–H(65)–Cl4
C(65)–H(65)–Cl(4)
C(75)–H(75)–Cl(3)
C(75)–H(75)–Cl(4)
C(85)–H(85A)–O(6)
C(94)–H(94)–O(5)
C(106)–H(106)–O(5)
C(116)–H(116)–Cl(5)
C(116)–H(116)–Cl(6)
(3)
3.2. Electronic structure
To gain the electronic structures and bonding properties of the
studied complexes, calculations using the density functional the-
ory (DFT) method with the B3LYP functional of GAUSSIAN09 were car-
ried out. Before the calculations, their geometries were optimized
in singlet or doublet states using the DFT method with the B3LYP
functional. In general, the predicted bond lengths and angles are
in a good agreement with the values based on the X-ray crystal
structure data, and the general trends observed in the experimen-
tal data are well reproduced in the calculations. The interaction be-
tween ligands and central ions manifest itself in charges on the
complex metal ions. The metal ions in the complexes are formally
in di- and tri-valent oxidation states, but the calculated natural
charges are lower than 2+ or 3+ as follows À0.07, À0.13 and
À0.24 in complexes (1), (2) and (3), respectively. The natural
charges indicate that the donations from ligands to central ions
have the advantage over the back donations from metal to ligands.
The interactions between central ions and ligands are presented in
the stabilization energies calculated in NBO analyses. The stabiliza-
tion energy associated with the charge donation from the N-het-
erocyclic ligands to ruthenium(II) and (III) central ions are
380.55, 291.82 and 187.80 kcal/mol and the back donations have
values 69.13, 38.69 and 53.56 kcal/mol in complexes (1), (2) and
(3), respectively. The natural populations of valence d orbitals in
the complexes are 7.23, 7.29 for Ru(II) and 7.03 for Ru(III) and
C(1)–H(1)–N(99)
C(5)–H(5)–N(98)
C(14)–H(14)–N(99)
C(26)–H(26)–N(98)
C(38)–H(38)–N(99)
C(44)–H(44)–N(98)
0.93
0.93
0.93
0.93
0.93
0.93
2.55
2.48
2.59
2.46
2.42
2.50
2.963(4)
2.947(4)
3.394(4)
3.126(4)
3.051(4)
3.312(4)
107.1
111.4
144.6
128.7
125.3
145.5
Symmetry transformations used to generate equivalent atoms: #1 2 À x, 1 À y,
2 À z; #2 1 À x, 1 À y, 1 À z; #3 1 + x, 1 + y, z; #4 x, y, 1 + z; #5 Àx, 1 À y, 1 À z; #6
À1 + x, y, z; #7 1 À x, Ày, 1 À z.
(130–180) in structures containing the thiocyanate ion bonded to a
metal through nitrogen atom. The bond length are normal and
comparable with ruthenium(II)/(III) complexes with N, carboxyl-
Fig. 3. The
p-stacking interactions in the [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1) molecule.

´
131
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
Coulomb-type interactions between the ruthenium central ions
and these ligands are clearly visible in the calculated Wiberg bond
indices whose values are considerably lower than one. The Ru–N
and Ru–O bond indices are similar and close to 0.45 and 0.50.
The Ru–P bond orders are also smaller than 1 (0.7). The indices
for Ru–Cl and Ru–NCS bonds are 0.82 and 0.59 indicate the more
covalent interaction between chloride and ruthenium(III) than iso-
thiocyanate ligand with Ru(II) central ion. The interaction between
ruthenium and imidazole type ligands presents Fig. 4 and one can
see the stronger
p-acceptor property of 1H-benzimidazole-2-car-
boxylic acid and weaker acceptor ability of 1-methyl-1H-imidazole
ligand toward ruthenium(II).
Analysis of the frontier molecular orbitals is useful for under-
standing the spectroscopic properties as electronic absorption
and emission spectra of organometallic complexes. The densities
of states (DOS) in terms of Mulliken population analysis were cal-
culated using the GAUSSSUM program and Fig. 5 presents the compo-
sition of the fragment orbitals contributing to the molecular
orbitals for the complexes. As one can see on the DOS plots of
the complexes, the dRu orbitals play significant role in frontier
HOMO orbitals. The contribution of ruthenium orbitals in the
HOMO to HOMOÀ2 orbitals in complexes (1) and (2) are from
73% to 40%. In the case of complex (3) the dRu orbitals participate
in HOMO, HOMOÀ1 with the percentage of about 37%. In these
molecular orbitals the contribution of chloride and isothiocyanide
ligands in complexes (2) and (3) are visible. In the complex (1) the
1H-benzimidazole-2-carboxylic acid ligand contribute in these
occupied molecular orbitals. The frontier virtual molecular orbitals
Fig. 4. Overlap partial density of states for interactions between ruthenium central
ions and ligands in the complexes.
the populations of valence shells are also similar 8.04, 8.20 and
8.09, respectively. In the case of complexes (2) and (3), except
the 1-methyl-1H-imidazole-2-carboxylic acid or 1-methyl-1H-
imidazole ligands, the chloride or isothiocyanate ligands have an
impact on the valence population of ruthenium central ion. In
the analyses were found that the imidazole derivatives donor
ligands do not show covalent bonding with ruthenium. The
Fig. 5. The density-of-states diagrams for [Ru(BIm-2-COO)2(PPh3)2] (1), [RuCl2(MeIm-2-COO)(PPh3)2] (2) and [Ru(NCS)2(MeIm)2(PPh3)2] (3).

´
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
132
Table 4
The electronic transitions for the (1), (2) and (3) complexes calculated with B3LYP functional by the TDDFT method.
k (nm) (f)
Transitions
Character
Exp. k (nm)
(1)
451.8 (0.0006)
395.3 (0.0034)
383.4 (0.0082)
362.5 (0.0359)
316.5 (0.0015)
309.5 (0.0021)
306.4 (0.0023)
301.8 (0.0125)
294.3 (0.012)
275.0 (0.0126)
271.9 (0.1124)
266.7 (0.0933)
263.6 (0.0505)
(2)
H-1 ? L + 3 (27%), H-1 ? L + 5 (18%), H-1 ? L + 10 (14%), H-1 ? L + 12 (19%)
HOMO ? LUMO (81%)
HOMO ? L + 1 (82%)
d ? d; d ? p⁄
d ? p⁄
444
PPh3
d ? p⁄BImCOO
H-2 ? LUMO (84%)
d ? p⁄BImCOO
332
305
BImCOO
HOMO ? L + 2 (34%), HOMO ? L + 4 (62%)
HOMO ? L + 3 (51%), HOMO ? L + 5 (37%)
H-1 ? L + 3 (45%), H-1 ? L + 5 (46%)
H-2 ? L + 2 (37%), H-2 ? L + 4 (61%)
H-2 ? L + 3 (49%), H-2 ? L + 5 (40%)
H-2 ? L + 7 (75%), H-1 ? L + 8 (14%)
H-4 ? LUMO (62%)
d ? d; d ? p⁄
L
d ? p⁄
L
d ? d; d ? p⁄
d ? d; d ? p⁄L
d ? d; d ? p⁄L
L
d ? p⁄
PPh3
pPPh3
?
p⁄
?
BImCOO
H-7 ? LUMO (68%)
H-7 ? L + 1 (24%), H-6 ? LUMO (13%), H-5 ? L + 1 (37%)
pBImCOO
p⁄
265
BImCOO
pBImCOO/PPh3
?
p⁄
BImCOO
564.2 (0.0012)
551.1 (0.0072)
518.1 (0.0015)
463.8 (0.0048)
H-3(b) ? LUMO(b) (39%), H-2(b) ? LUMO(b) (49%)
H-4(b) ? LUMO(b) (13%), H-3(b) ? LUMO(b) (39%), H-2(b) ? LUMO(b) (38%)
H-4(b) ? LUMO(b) (75%)
p
p
p
L ? dx2Ày2
L ? dx2Ày2
L ? dx2Ày2
507
440
HOMO(a) ? LUMO(a) (11%), H-8(b) ? LUMO(b) (13%), H-6(b) ? LUMO(b) (14%), H-5(b) ? LUMO(b) (11%)
d ? d; pL ? dx2Ày2
447.7 (0.0015)
430.3 (0.001)
409.6 (0.0078)
H-8(b) ? LUMO(b) (30%), H-6(b) ? LUMO(b) (20%), H-5(b) ? LUMO(b) (18%)
H-10(b) ? LUMO(b) (20%), H-9(b) ? LUMO(b) (62%)
H-16(b) ? LUMO(b) (42%), H-13(b) ? LUMO(b) (33%)
H-18(b) ? LUMO(b) (69%)
p
p
p
p
L ? dx2Ày2
MeImCOO/PPh3 ? dx2 Ày2
MeImCOO/PPh3 ? dx2 Ày2
L ? dx2Ày2
370.1 (0.0085)
359.7 (0.003)
297.5 (0.1706)
285.3 (0.0026)
H-2(
a
) ? L + 1(
) ? LUMO(
) ? LUMO(
) ? L + 2( ) (26%)
H-8(b) ? L + 1(b) (10%), HOMO(b) ? L + 4(b) (13%)
H-2( ) ? L + 2( ) (29%), H-1( ) ? L + 2( ) (12%), H-1(b) ? L + 3(b) (10%)
a
) (16%), H-1(
) (19%), H-4(b) ? L + 1(b) (39%)
) (20%), H-11( ) ? LUMO( ) (20%), H-9(
a
) ? L + 1(
a
) (48%)
d ? d
361
285
H-5(a
a
a
p
p
L ? dx2Ày2
L ? dx2Ày2
H-12(
a
a
a
a) ? LUMO(a) (15%)
279.7 (0.0041)
276.9 (0.0178)
272.6 (0.0406)
(3)
H-1(a
a
d ? p⁄
PPh3
d ? d; d ? p⁄
Cl
a
a
a
a
d ? p⁄
PPh3
423.6 (0.0003)
416.4 (0.0004)
401.2 (0.001)
379.4 (0.0024)
371.4 (0.0047)
320.2 (0.0066)
303.1 (0.0028)
301.8 (0.0036)
299.9 (0.0039)
290.9 (0.0141)
273.1 (0.0186)
H-1 ? LUMO (24%), HOMO ? LUMO (30%)
H-1 ? LUMO (23%), HOMO ? LUMO (23%), HOMO ? L + 3 (18%)
H-2 ? LUMO (67%), H-2 ? L + 13 (16%)
d ? d
d ? d
pSCN ? dx2Ày2
H-1 ? LUMO (17%), HOMO ? LUMO (13%), HOMO ? L + 3 (22%), HOMO ? L + 12 (12%)
H-1 ? LUMO (13%), H-1 ? L + 3 (36%), H-1 ? L + 12 (11%), HOMO ? LUMO (11%)
H-2 ? L + 1 (10%), H-2 ? L + 3 (52%), H-2 ? L + 12 (20%)
HOMO ? L + 4 (94%)
H-1 ? L + 4 (94%)
HOMO ? L + 5 (96%)
d ? d
d ? d
380
p
SCN ? dx2Ày2
/
/
p⁄
p⁄
PPh3
PPh3
d ? p⁄
d ? p⁄L
d ? p⁄L
L
H-2 ? LUMO (11%), H-2 ? L + 1 (65%)
p
SCN ? dx2Ày2
d ? pMeIm
d ? d; d ? p⁄
H-3 ? LUMO (53%), HOMO ? L + 9 (12%)
; pSCN ? d
271.6 (0.0197) H-4 ? LUMO (42%), H-1 ? L + 9 (23%)
267.7 (0.024)
256.9 (0.013)
271
PPh3
H-2 ? L + 5 (91%)
H-4 ? L + 1 (78%) H-4 ? L + 3 (8%)
pSCN ?
p⁄
PPh3
d ? p⁄PPh3/dz2
are localised on 1H-benzimidazolecarboxylic acid ligands (with
contributing of dx2 ) in complex (1) and in complexes (2), (3)
The theoretical absorption spectra of the complexes were ob-
tained from the calculation of the singlet excited states with TD-
DFT at the B3LYP/DZVP/6-31g++ level in the methanol solvent
phase. Computation of 100 excited states of the complexes allowed
the interpretation of the experimental spectra to 260–240 nm
range. The selected excited states assigned to the absorption bands
are shown in Table 4. The longest wavelength experimental bands
of electronic spectra of ruthenium(II) complexes (1) and (3) origi-
nates from transitions from HOMO, HOMOÀ1 to virtual molecular
orbitals formed by p⁄-bonding orbitals of imidazole type ligands
and the transitions can be seen as a delocalized MLLCT (Metal–Li-
gand-to-Ligand CT) transitions. The same character can be assigned
to the experimental absorptions at 332 and 271 nm in spectra of
complexes (1) and (3), respectively. The bands observed in the
vicinity of 40000 cm–1 (250 and 265 nm in complex (1)) have been
attributed to intra- and interligand (pbC6H6 ? 3dphosphorus and
Ày2
on the ruthenium dx2
with contribution of antibonding orbitals
Ày2
of triphenylphosphine ligands. The dz2 orbitals of ruthenium cen-
tral ions are visible in LUMO+5 and LUMO+1 in complexes (1)
and (2). In the case of complex (3) this orbital play role in higher
molecular orbitals (LUMO+12/14).
3.3. Experimental and theoretical electronic spectra
The ruthenium(II) complexes (1) and (3) present bands on the
UV–Vis spectra resulted from d ? d transitions, which may be as-
signed to 1A1 ? 1T1 and 1A1 ? 1T2 in octahedron or 1A1 ? 1A2/B1/E
in lower symmetry fields. Based on the pseudo-octahedral geome-
try of the complexes and taking into account the bands with max-
ima at 444, 332 nm and 380, 271 nm, the ligand field parameters
10Dq can be estimated to 24374 and 23786 cmÀ1 for the com-
plexes (1) and (3), respectively. The ruthenium(III) complex (2) dis-
played bands at 507, 440, 361, 285 (sh) and 212 nm and for this
compound are expected the bands in the NIR region. The spectrum
in this energy range was not measured and for this reason the
Racah’s parameters were not determined for the complex.
p
?
p⁄C@C) transitions with admixture of Metal–Ligand Charge
Transfer transitions (dRu and dRu
p⁄Ph). The highest
experimental bands close to 212 nm may result from transitions
?
p⁄
?
N-ligand
in the PPh3 ligands and from
omatic ligands.
p ?
p⁄ excitations in the N-heteroar-
From the data collected in Table 4 one can see that the absorption
bands at 507 nm and 440 nm in complex (2) have Ligand-to-Metal

´
133
J.G. Małecki, A. Maron / Polyhedron 40 (2012) 125–133
spectra of ruthenium(III) complex (2) suggest diamagnetism of
the complex, which was in accordance with the theoretical results
obtained from NBO analysis. The electronic structures of these
complexes, presented in particular by the density of states dia-
grams, have been correlated with their ability to fluorescence
and used to analyze the UV–Vis spectra.
Acknowledgements
The GAUSSIAN-09 calculations were carried out in the Wrocław
Centre for Networking and Supercomputing, WCSS, Wrocław, Po-
land, http://www.wcss.wroc.pl, under calculational Grant No. 18.
Appendix A. Supplementary data
CCDC 850289, 856086 and 867512 contains the supplementary
crystallographic data for the complexes [Ru(BIm-2-COO)2(PPh3)2]Á-
CH3OHÁH2O (1), [RuCl2(MeIm-2-COO)(PPh3)2] (2) and [Ru(NCS)2
(MeIm)2(PPh3)2]ÁCH3OH (3). 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: +44 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk.
Fig. 6. Fluorescence spectra of [Ru(BIm-2-COO)2(PPh3)2]ÁCH3OHÁH2O (1) and
[Ru(NCS)2(MeIm)2(PPh3)2]ÁCH3OH (3) complexes in methanolic solutions.
Charge Transfer character with some mixture of d ? d transitions.
The MLCT transitions were calculated in higher energy adequate
to experimental band at 285 nm. The Ligand Field transitions play
role in the band at 361 nm and can be assigned to 2T2g ? /2A1g
,
References
2T1g transitions.
Emission properties of the complexes (1) and (3) have been
examined in the methanol solutions with concentration of
1 Â 10À3 mol/dm3 at room temperature. Fig. 6 presents the plots
of excitations and emissions spectra. The solutions of the com-
plexes excited at 309 and 302 gave emission peaks with maxima
at 360 and 388 nm. The emissions originating from the lowest
energy metal to ligand charge transfer states, derived from the
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?
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p
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4. Conclusion
Three new complexes of ruthenium with imidazole carboxylic
acid ligands were synthesized and characterized by infra red, pro-
ton and phosphorus nuclear magnetic resonance, electronic
absorption and emission spectroscopy and X-ray crystallography.
In the reaction between 1-methyl-1H-imidazolecarboxylic acid
and [RuCl2(PPh3)3] have been obtained ruthenium(III) chloride
complex, and in the reaction in the presence of ammonium thiocy-
anate the decarboxylation of the ligand occurred and the
ruthenium(II) complex has been prepared. The 1H and 31P NMR
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