Preparation and study of pyridothienopyrazines and their Ruthenium(II) complexes: A new family of bidentate ligands

Article abstract of DOI:10.1016/j.tet.2011.01.066

The Friedl?nder condensation of 3-aminothieno[2,3-b]pyrazine-2- carboxaldehyde with either methyl ketones or carbocyclic and heterocyclic ketones leads to a family of new bidentate ligands containing a pyridothienopyrazine coordinating unit. Complexation

Full text of DOI:10.1016/j.tet.2011.01.066

Tetrahedron 67 (2011) 2035e2043
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Preparation and study of pyridothienopyrazines and their Ruthenium(II)
complexes: a new family of bidentate ligands
*
*
ꢀ
ꢀ
Antonio Fernandez-Mato, Jose María Quintela , Carlos Peinador , Carlos Platas-Iglesias
~
~
Departamento de Química Fundamental, Facultad de Ciencias, Universidade da Coruna, Campus A Zapateira, 15008 A Coruna, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
€
The Friedlander condensation of 3-aminothieno[2,3-b]pyrazine-2-carboxaldehyde with either methyl
Received 2 December 2010
Received in revised form 13 January 2011
Accepted 22 January 2011
Available online 28 January 2011
ketones or carbocyclic and heterocyclic ketones leads to a family of new bidentate ligands containing
a pyridothienopyrazine coordinating unit. Complexation with [Ru(bpy)2Cl2] affords the corresponding
six-coordinated Ru(II) complexes. The structures were analyzed by 1H NMR spectroscopy, which shows
shielding effects reflecting significant interligand
physical properties of the ligands and their metallic complexes have been also examined.
Ó 2011 Elsevier Ltd. All rights reserved.
p-stacking interaction in the complexes. The photo-
Keywords:
Bidentate ligands
Heteroleptics Ru(II)-complexes
Pyridothienopyrazine
€
Friedlander condensation
Heterodinuclear complexes
1. Introduction
many of its modern applications to areas, such as supramolecular
and bioinorganic chemistry.4 The tripyridyl analogue of bpy is
2,20:60,200-terpyridine (tpy), which behaves as a tridentate chelator
but enjoys many of the same coordination properties as bpy.5
Currently, an increasing important area of ligand design involves
the synthesis and study of new photochemically active ligands and
their use as chelating ligands.6 Indeed, linearly fused heteroacenes
Heteroaromatic rings are important constituents of drugs and
bioactive molecules. In addition, they have also received wide at-
tention because of their ability to function as effective ligands to
couple metal centers in a covalent manner resulting in polymetallic
complexes that often possess new and interesting properties.
Heteroaromatic nitrogen ligands have found wide applications on
the new generation of molecules with extended applications in
several important research and technological fields, including
bioactive drugs, nonlinear optical materials, and other applications
in optoelectronic devices.1 In recent years, numerous efforts have
been undertaken to develop efficient and selective methods for the
preparation of polydentate ligands suitable for self-assembly
processes.2 Many of these ligands have been bi- or tri-dentate
chelators in which a pyridine ring is the coordinating unit. Thus,
two of the most extensively studied bidentate ligands employed in
coordination chemistry are 2,20-bipyridine (bpy) and 1,10-phe-
nantroline (phen) (Fig. 1). The latter may be considered as a 3,30-
etheno-bridged derivative of the former. The steric requirements of
both ligands are very similar, and differences in the properties of
their metal complexes may be mostly attributed to electronic dif-
ferences arising from the greater electronegativity of phen.3 These
ligands and related N-heterocycles are widely employed as metal-
binding components in all aspects of coordination chemistry, and in
occupy a prominent position of research in
p-conjugated small
molecules because of their attractive electronic and optical prop-
erties.7 Among these heteroacenes, sulfur or/and nitrogen atoms
are introduced widely to tune the solid-state structure and elec-
tronic structure of organic semiconductors while overcoming some
drawbacks of acenes, such as low solubility and unstability.8 Re-
cently, we reported the synthesis and examination of the electronic
absorption and emission spectra of new 2-[1,8]naphthyridinyl and
N
N
N
N
N
N
N
phen
N
tpy
bpy
S
N
N
N
N
4,5-diazafluorene
pyridothienopyrazine (ptp)
* Corresponding authors. E-mail address: carlos.peinador@udc.es (C. Peinador).
Fig. 1. Structures of bidentate and tridentate ligands.
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.01.066

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2036
bis(2-[1,8]naphthyridinyl) fused ligands with multidentate binding
sites.9 On the basis of such precedents, and as part of a programme
of investigating the synthesis and study of new heterocyclic li-
gands10 and their use in coordination and supramolecular chem-
istry and self-assembly processes,11 here we report the synthesis
and a comprehensive study on the photophysical properties of
Similarly, treatment of aminoaldehyde 1 with aliphatic methyl
ketones led to the corresponding 8-substituted pyridothienopyr-
azine compounds (Scheme 2). It should be noted that the con-
densation with unsymmetrical aliphatic ketones gives two different
products depending on which a-carbon is used for bond formation.
Ring closure under the base-catalyzed condensation of 1 with ethyl
a
family of new bidentate ligands. That triheterocyclic pir-
methyl ketone or methyl phenethyl ketone was found to occur
idothienopyrazine chelator ligand skeleton ptp (Fig. 1) may be
considered as a 6,60-sulfur-bridged aza-analogue of bpy and is
expected to be applicable as appropriate chelating ligand in various
photomaterials. To the best of our knowledge, this is the first report
of bipyridine-, phenantroline-, or 4,6-diazafluorene-like ligands
with a sulfur-bridging atom. A simple and straightforward syn-
thesis of the ligands has therefore been developed and the target
compounds have been characterized in detail. The electronic
properties have been studied by using electronic absorption and
emission spectroscopy. The photophysical properties of their me-
tallic complexes have been also examined.
preferentially at the a-CH3 carbon, even though the isomeric
products have been isolated from the reaction mixture with
regioselectivity ratios in the formation of 8-monosubstituted ver-
sus 7,8-disubstituted products from 70:30 to 80:20, respectively.
€
The regiochemistry of the Friedlander reaction depends on the
experimental conditions. We found that the best results were
obtained when ethanolic potassium hydroxide was used. However,
other catalysts, including SnCl2$2H2O, CeCl3$7H2O, HCl, pyrrolidine
or piperidine, also promoted the reaction successfully, but the
regioselectivity and the yields were lower.
S
S
S
CHO
NH2
N
N
N
CH3COCH2R
KOH, EtOH
R
2. Results and discussion
2.1. Synthesis
N
N
N
N
N
R
Me
1
4n,o
3m-o
3m R = H
4n R = CH3
4o R = CH2Ph
3n R = CH3
3o R = CH2Ph
Amino carbonyl compounds are important building blocks in
the synthesis of nitrogen-containing products, and are widely used
by chemists in heterocyclic chemistry and in the pharmaceutical
Scheme 2. Preparation of pyridothienopyrazine derivatives 3meo and 4n,o.
€
industry. The Friedlander reaction is still one of the simplest
€
methods for the preparation of a variety of annulated and bisan-
Analogously, the classical Friedlander reaction has been ex-
nulated pyridines.12 In its most general form, the Friedlander
€
tended and applied to cyclic ketones. Thus, we thought that similar
polycyclic compounds containing a fused pyridothienopyrazine
moiety 6aeg could be afforded by the reaction of 1 with carbocyclic
or heterocyclic ketones through this conversion. Indeed, amino-
aldehyde 1 reacts with 1-indanone giving rise to adduct 7 in 80%
yield (Scheme 3). Consequently, the availability and structural
reaction is the base- or acid-promoted condensation of an aromatic
2-amino-substituted carbonyl compound with an appropriately
substituted carbonyl derivative containing a reactive a-methylene
group followed by cyclodehydration.13 To make the title condensed
pyridothienopyrazine ligands accessible in large quantities, we
have devised a simple and convenient synthesis starting from
3-aminothieno[2,3-b]pyrazine-2-carboxaldehyde 1.14 The initial
objective starts with the preparation of 2-aryl and 2-heteroaryl
ligands 3ael. To this end, the base-catalyzed reaction of the
aminoaldehyde 1 with aryl and heteroaryl ketones 2ael provides
the corresponding 8-aryl and 8-heteroarylpyrido[20,30:4,5]thieno
[2,3-b]pyrazine derivatives 3ael in acceptable to very good yields of
50e93% (Scheme 1).
S
N
X
N
N
6a-g
S
5a,6a X = O
5b,6b X = S
5e,6e X = -
5f,6f X = CH2
N
5c,6c X = NCH2Ph
5d,6d X = NCOCH3
5g,6g X = CH2CH2
N
N
S
N
N
N
7
S
O
CHO +
RCOCH3
N
N
R
NH2
1
2a-l
3a-l
O
X
KOH, EtOH
CHO
NH2
5a-g
3a (61%)
3b (93%)
2g R =
2h R =
2a R =
2b R =
3g (72%)
3h (74%)
N
KOH, EtOH
S
N
S
S
O
N
Br
1
2c R =
3c (72%)
3d (69%)
NR
2i R =
2j R =
3i (71%)
3j (88%)
R
CN
O
N
O
O
R
2d R =
O
S
S
N
N
S
R
R
N
2k R =
2l R =
3k (58%)
3l (84%)
N
N
2e R =
2f R =
N
3e (71%)
3f (50%)
N
N
N
N
R
NH2
O
8a R = H
8b R = CN
9a R = H
9b R = CH3
NO2
N
Scheme 3. Synthesis of pyridothienopyrazines 6aeg, 7, 8a,b, and pyrimidopyr-
idothienopyrazines 9a,b.
€
Scheme 1. Synthesis of pyridothienopyrazines 3ael via Friedlander annulations.

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2037
variety of cyclic ketones provide an easy and direct access to
a number of fused heterocyclic systems for which in many cases
alternate annulation methods are not readily available.
were determined in acetonitrile at 25 ꢀC upon excitation at the
corresponding lmax absorption wavelengths, and the results are
given in Table 1. The Ff values for these systems cover a wide range
from 3f, which only shows a very low quantum yield (0.0080), to 3c
and 3d, which exhibited higher fluorescence efficiency levels (0.26
With the intent to introduce more diversity in the products
€
employing this strategy, it was decided to carry out the Friedlander
reaction with other reactive
a
-methylene groups. Thus,1 condenses
and 0.28, respectively). As a result of the more extended p-de-
with acetonitrile to give the 7-amino adduct 8a, whereas its
condensation with malononitrile takes place via intramolecular
addition of the amino group to the cyano function on the in-
termediate produced by initial intermolecular condensation to give
the amino-cyano derivative 8b (Scheme 3). Similar condensations
with barbituric or 1,3-dimethylbarbituric acids yielded pyr-
imidothienopyrazines 9a,b.
localization, quantum yields remain high even in those compounds
exhibiting longer emission wavelengths. It is also worth mention-
ing that the Stokes shifts of the new ligands vary in the range of
62e160 nm, correlating nicely with the increasing longitudinal
organization of the molecule.15
2.3. Complexation with Ru(II)
All bridging ligands were unambiguously characterized by 1H
NMR, 13C NMR, MS, and elemental analyses. Thus, for example, the
Ru(II) was selected as a central ion for studying the complexa-
tion ability of our briged analogues of bipyridine. The Ru(II) com-
plexes were prepared from equimolecular amounts of [Ru
(bpy)2Cl2] and the appropriate ligand (L) in ethanol/water. The
resulting dichloride [Ru(bpy)2L]Cl2 complexes were isolated in ac-
ceptable to good yields (61e80%) (Scheme 4). For [Ru(bpy)28b]Cl2
complex, dichloride salt can be converted into the corresponding
organic-soluble hexafluorophosphate with NH4PF6.
1H NMR spectra of 3aeo show two doublets at
d
¼7.20e8.40 and
8.10e8.50 (J¼8.5 Hz) due to the protons of the pyridine skeleton.
The pyrazine ring was also distinguished by two doublets at
d
¼8.67e8.78 and 8.80e8.94 (J¼2.4 Hz) due to the H-3 and H-2
protons, respectively. On the other hand, the structural de-
termination of 3a was unequivocally established by the X-ray
structure determination of a monocrystal (Fig. 2).
N
Ru
N
N
S
N
N
N
N
N
S
S
·2Cl
N
N
6b
EtOH/H2O
S
[Ru(bpy)26b(Cl2)
N
Ru
N
N
N
Cl
Cl
Fig. 2. Crystal X-ray structure of compound 3a represented by thermal ellipsoids at the
50% level. Hydrogen atoms have been omitted for clarity. The color-labeling scheme is
as follows: carbon (gray), nitrogen (blue), and sulfur (yellow).
6
S
N
7
3
2
3
R1
N
Ru
N
N
N
N
N
N
N
2
R2
S
2.2. Electronic spectroscopy
·2X
N
EtOH/H2O
6
R2
UVevis absorption spectra of the ligands 3a, 3cee, and 3l were
recorded in acetonitrile at room temperature, and the results are
shown in Table 1. Quantum yields were also determined. The
maximum of the emission band shifts from 412 nm for 3a to
430 nm for 3c and 471 nm for 3d, reflecting a steady progression to
lower energy with increasing the delocalization of the system. The
pyrene group significantly stabilized the energy of the excited-state
7
R1
R2
4-pyridyl
Ligand
3e
R1
H
Complex
[Ru(bpy)23e(Cl2)]
3l
[Ru(bpy)23l(Cl2)]
[Ru(bpy)23m(Cl2)]
H
H
4-nitrophenyl
CH3
by enhancement of conjugation via delocalization of
p electrons
3m
8b
along the pyrene backbone. Consequently, 3d showed a huge
bathochromic shift of the luminescence compared to 3a (lmax¼471
vs 412 nm). The fluorescence quantum yields (Ff) for the systems
[Ru(bpy)28b(PF6)2]
CN
NH2
Scheme 4. Synthesis of Ruthenium(II) complexes.
Unfortunately, we were not able to grow suitable crystals, but
electrospray ionization mass spectrometry (ESI-MS) and NMR
spectroscopy were used to elucidate the formation of complexes
and their composition. The HRMS-ESI supported the proposed
structures showing m/z values and isotopic pattern distributions in
excellent agreement with the calculated ones (see Experimental
section). A comparison between the calculated mass distribution
pattern for the doubly charged species [Ru(bpy)28b]þ2 and the
experimental data unambiguously confirms the formation of the
desired complex. Moreover, the reaction of pyridothienopyrazine
(ptp) ligands with [Ru(bpy)2Cl2] in ethanol/water produced
changes in their 1H NMR spectra that are consistent with the for-
mation of the corresponding complexes. Table 2 compares char-
acteristic chemical shifts for H-2, H-3, H-6, and H-7 into the free
Table 1
Photophysical data for pyridothienopyrazine derivatives 3
Absorptiona lmax
[nm] (log
Emissionb lmax
[nm] 298 K
FEM
Stokes
shift
c
Compd
3
)
3a
3c
3d
3f
3l
265 (4.04), 319 (4.02)
328 (3.30)
256 (4.03), 311 (3.99)
294 (3.90)
412
430
471
372
375
0.09
0.26
0.28
0.008
0.02
93
102
160
78
313 (310)
62
a
Solvent: CH3CN (10ꢁ5 M) at 25 ꢀC.
b
Solvent: CH3CN (5ꢂ10ꢁ5 M) at 25 ꢀC. The spectra were recorded upon excitation
on the long-wavelength absorption maxima.
c
Fluorescence quantum yields (FEM) values were determined in acetonitrile so-
lution at 25 ꢀC, using 8,10-diphenyl anthracene as standard (FEM¼0.95, in ethanol),
by excitation on lmax absorption wavelengths.

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2038
Table 2
a
1H NMR data (Dd
) for the Ru(II) complexes
Ligand
Complex
H-2
H-3
H-6
H-7
3e
3l
3m
8b
[Ru(bpy)23e]Cl2
[Ru(bpy)23l]Cl2
[Ru(bpy)23m]Cl2
[Ru(bpy)28b](PF6)2
ꢁ0.74
ꢁ0.90
ꢁ0.64
ꢁ0.96
0.11
0.20
0.33
0.19
0.85
1.27
1.23
0.70
ꢁ0.37
ꢁ0.05
0.16
a
The
d values are compared to those of the corresponding ligand.
ligands and their corresponding complexes (see Scheme 4 for la-
beling). The ptp protons are assigned on the basis of their chemical
shifts, multiplicity, and an analysis of their 2D-COSY spectra, and
the data are summarized in Table 2. The 1H NMR spectra indicate
that upon coordination to Ru the protons at the 3 and 6 positions of
the pyridothienopyrazine shift downfield (Table 2 and dotted lines
in Fig. 3), which can be attributed to a decreased charge density on
the ligand as a consequence of the formation of the Rueligand
bonds, thereby causing a deshielding effect. Consequently, the H-3
protons of the pyrazine units shifted to larger frequencies (averaged
shift: Dd¼þ0.11e0.33 ppm), whereas the chemical shifts of the H-6
pyridine protons were strongly affected (averaged shift:
Dd¼þ0.70e1.27 ppm). Although H-3 is subject to the same effect as
H-6, it is less pronounced most likely due to back bonding existence
in the charge transfer from metal-to-ligand. This back donation is
very important in the spectroscopic properties of Ru(II) complexes
and its effects are more pronounced in the proximity of the metal
center. On the contrary, the H-2 protons of the complexes are
shifted upfield (Dd¼ꢁ0.64 to 0.96 ppm) from those of the pyr-
idothienopyrazine moiety of the corresponding free ligands (Table
2 and solid line in Fig. 3). The H-2 protons point toward the face of
the central pyridine ring of the orthogonal bpy ligand (see Fig. 4),
causing it to be shielded and shifted upfield. The effect is largely
diminished for the more remote H-3 protons.
Fig. 4. Calculated structures of [Ru(bpy)23l]þ2 (left) and [Ru(bpy)23m]þ2 (right)
systems.
by the rotation about de 2,20-bond. For heteroleptic complexes like
[Ru(bpy)23e]Cl2 or [Ru(bpy)23m]Cl2, the substituents tend toward
perpendicular orientation, which minimizes the steric hindrance
with bipyridine ancillary ligands.16 This orientation is stabilized by
p p interactions between the aromatic substituent and one or-
ꢁ
thogonal pyridine ring, which facilitates interligand communica-
tion. Fig. 4 depicts computer simulations for the complexes [Ru
(bpy)23l]Cl2 and [Ru(bpy)23m]Cl2 using the software package
Gaussian 03. The structure of [Ru(bpy)23l]Cl2 shows a near co-
planarity between the p-nitrophenyl ring and one bipyridine of the
auxiliary ligand. The calculated structure of [Ru(bpy)23m]Cl2 dis-
plays the proximity of the methyl substituent to a bipyridine li-
gands, causing the shielding of its protons in the NMR spectra with
respect to their position observed for the free ligand
(
Dd¼þ0.14 ppm). Thus, the calculated structure for this compound
is consistent with spectroscopic data collected.
2.4. Photophysical studies
The arrangement of the 8-substituents as regarding to the pyr-
idothienopyrazine nucleus depends on the dihedral angle
a defined
Since the spectroscopic and electronic properties of metal
complexes will depend to a great extent on ligand structure, it was
of interest to investigate the absorption and emission properties for
these systems. UVevis spectra were recorded in acetonitrile, and
the relevant data are compiled in Table 3. The pyridothienopyrazine
nucleus (ptp) may be considered as a 2,20-bipyridine aza-analogue
bridged at the 6 and 60 positions with a single sulfur unit, which is
both more delocalized and more electronegative, making it a much
better charge acceptor.17 This difference is evidenced by the ab-
sorption maxima observed in the absorption spectra of our free
ptps ligands (294e348 nm), when compared to the long-wave-
length absorption of bpy at 284 nm.18 It is noteworthy that the
more planar and extensively conjugated is the ptp derivative, the
more is shifted the absorption band to lower energies. This is in line
with previous studies that showed that when bpy is bridged at the
6 and 60 positions with a single methylene unit, the resulting dia-
zafluorene exhibits a bathochromic shift as would be expected for
a more rigid, planar molecule.17 The absorption graphs for the
heteroleptics complexes (Fig. 5) are similar, and the higher energy
transitions are observed in the range 280e295 nm, corresponding
Fig. 3. Partial 1H NMR spectra (CD3CN, 298 K, 500 MHz) of ligand 6b (top) and the [Ru
(bpy)26b]Cl2 complex (bottom).
Table 3
Photophysical data for ligands 3e, 3l,m, 6b, 8b and their complex derivatives
c
c
Ligand
Absorptiona
lmax [nm] (log
Emissionb lmax
[nm] 298 K
FEM
Stokes
shift
Complex
Absorptiona lmax
[nm] (log
284 (3.43)
282 (4.77), 425 (4.39)
290 (3.50)
Emissionb lmax
[nm] 298 K
FEM
Stokes
shift
3
)
3
)
3f
3l
3m
6b
8b
294 (3.90)
313 (3.10)
239 (4.64), 304 (4.47)
252 (5.01), 348 (4.38)
251 (4.25), 321 (4.09)
372
375
380
375
480
0.008
0.02
0.01
0.04
0.25
78
62
76
27
169
[Ru(bpy)23f]Cl2
[Ru(bpy)23l]Cl2
[Ru(bpy)23m]Cl2
[Ru(bpy)26b]Cl2
[Ru(bpy)28b](PF6)2
465
545
470
550
600
0.09
n.d.
0.03
0.03
0.19
43
120
180
96
284 (4.00), 434 (3.87)
285(4.24), 435(3.80)
315
a
Solvent: CH3CN (10ꢁ5 M) at 25 ꢀC.
b
c
Solvent: CH3CN (5ꢂ10ꢁ5 M) at 25 ꢀC. Excitation at the long-wavelength absorption maximum.
Fluorescence quantum yields were determined in CH3CN at 25 ꢀC, using Rhodamine B in ethanol as standard (FEM¼0.65), at lmax of absorption wavelengths.

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2039
derivatives show emission maxima shifted 10e100 nm to a shorter
wavelengths, again indicating that the replacement of a bpy ligand
by a ptp derivative increases the energy difference between the
ground state and the excited charge-transfer state.
In conclusion, a simple method for the preparation of pyr-
€
idothienopyrazines (ptp) is presented based on the Friedlander
condensation of 3-aminothieno[2,3-b]pyrazine-2-carbaldehyde
with ketones. Using this method, a family of new bidentate bridged
ligands for transition metals were prepared and their complexation
abilities toward Ruthenium(II) were demonstrated. The photo-
physical properties of the ligands and their Ruthenium(II) com-
plexes have been also examined. Further studies on this interesting
family of ligands are underway and will include variation of the
heterodinuclear complexes and the self-assembly of ligand-bridged
supramolecular structures.
3. Experimental section
3.1. General
Fig. 5. Absorption graphs for the heteroleptics Ru(II)-complexes measured in 10ꢁ5
CH3CN solutions at room temperature.
M
All reagents used were commercial grade chemicals from freshly
opened containers. Merck 60 HF254þ366 foils were used for thin
layer chromatography (TLC) and Merck 60 (230e400 mesh) silica
gel for flash chromatography. NMR spectra were obtained in
a Bruker Avance 500 instrument equipped with a dual cryoprobe
for 1H and 13C or in a Bruker Avance 300 spectrometer. TMS was
used as an internal reference. IR spectra were recorded as potas-
sium bromide disks. Mass spectrometry experiments were carried
out in a Thermo MAT95XP spectrometer for low resolution EI and
FAB using thioglycerol or 3-nitrobenzyl alcohol (3-NBA) as matrix
(FAB), or in an LC-Q-q-TOF Applied Biosystems QSTAR Elite spec-
trometer for low- and high-resolution ESI. Electronic spectra were
measured on a PerkineElmer Lambda 900 spectrophotometer.
Fluorescence spectra were obtained with a Hitachi F-2000 lumi-
nescence spectrometer. Melting points were measured using Stuart
Scientific SMP3 apparatus and are uncorrected. Microanalyses were
performed by the elemental analyses general service of the Uni-
to
p
ꢁ
p
*
transitions between the aromatic rings of the bipyridine
ligands, and transitions between these bipyridines and the ptp
nucleus attributed to intraligand
p
ꢁ
p transitions by comparison
*
with the spectrum of [Ru(bpy)3]2þ. The visible region of the
absorption spectra, at 420e440 nm, is characterized by the pres-
ence of medium-intensity absorption bands that can be attributed
to metal-to-ligand-charge-transfer (MLCT) transitions. These bands
can be attributed to the promotion of an electron from a metal
d orbital to a
comparison of these values with the MLCT band observed for [Ru
(bpy)3]2þ
derivatives they are observed at shorter wavelengths. This hyp-
sochromic shift is due to ground-state stabilization and de-
stabilization of the excited state because of poor ptp ligand
donation, reflecting the influence of the more electronegative
pyridothienopyrazine ligand.
p
*
orbital on the most electronegative ligand.4a,b
A
(lmax¼452 nm) shows that for the complexes with ptp
The difference in the electronegativity of ptp versus bpy be-
comes apparent when one examines the emission spectra of [Ru
(bpy)2L]2þ complexes. Luminescence measurements were recorded
in acetonitrile and the relevant data are shown in Table 3 and Fig. 6.
For most of the complexes the emission intensity is poor, the
spectra showing a long-wavelength component in the range
450e610 nm. When we compared the luminescence properties of
~
versity of A Coruna.
3.2. Computational methods
Full geometry optimizations of [Ru(bpy)23l]2þ and [Ru
(bpy)23m]2þ systems were performed at the HF level by using the
Gaussian 03 program package (Revision C.01). In these calculations
we used the standard 6-31G basis set for C, H, and N atoms, while
for Ru the LanL2DZ valence and effective core potential functions
were used. The stationary points found on the potential energy
surfaces as a result of the geometry optimizations have been tested
to represent energy minima rather than saddle points via frequency
analysis.
[Ru(bpy)3]2þ
(
lmax¼620 nm), the complexes of bridged ptp
3.3. Crystallographic material
Crystallographic data (excluding structural factors) for 3a have
been deposited in the Cambridge Crystallographic Data Center as
supplementary publication number CCDC 674102. These data can
be obtained free of charge from the Cambridge Crystallographic
Data Center via www.ccdc.cam.ac.uk/data_request/cif.
3.4. Substituted pyrido[20,30:4,5]thieno[2,3-b]pyrazines.
General procedure (3aeo, 4n,o, 6aeg, 7, 8a,b, and 9a,b)
A solution of 1 (0.1 g, 0.55 mmol), a suitable aryl or heteroaryl
methyl ketone 2 (0.66 mmol), and a catalytic amount of 10% etha-
nolic potassium hydroxide in ethanol (10 mL) was refluxed until all
starting material had disappeared as checked by TLC (1e24 h). The
Fig. 6. Emission graphs for the heteroleptics Ru(II)-complexes measured in 5ꢂ10ꢁ5
M
CH3CN solutions at room temperature.

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2040
solvent was evaporated, and the resulting residue was recrystal-
lized from ethanol or purified by medium-pressure chromatogra-
phy on silica gel.
1H NMR (CDCl3, 300 MHz)
d: 7.36e7.39 (m, 2H, Py), 7.82e7.84 (m,
2H, Py); 8.40 (d, J¼9.4 Hz, 1H), 8.64e8.90 (m, 3H). 13C NMR (CDCl3,
75 MHz) d: 121.3, 121.9, 132.2, 135.4, 139.6, 141.0, 149.5. MS (FAB) m/
z 265 [(MH)þ, 100]. Anal. Calcd C14H8N4S: C, 63.62; H, 3.05; N, 21.20.
3. 4.1. 8 -Phenylpyrido[2 0, 30: 4, 5]thieno[ 2, 3-b] pyrazine
Found: C, 63.39; H, 3.21; N, 21.28.
(3a). Recrystallized from ethanol; yield (61%); white solid; mp:
221e225 ꢀC. IR (KBr) 3050, 1738, 1545, 1493, 1451, 1342 cmꢁ1
.
1H
3.4.7. 8-(Pyrid-30-yl)-pyrido[20,50:3,5]thieno[2,3-b]pyrazine
(3g). Recrystallized from ethanol; yield (79%); yellow crystals; mp:
230e232 ꢀC. IR (KBr) 3046, 1681, 1483, 1140 cmꢁ1. 1H NMR (CDCl3,
NMR (CDCl3, 300 MHz) d: 7.47e7.57 (m, 2H, ArH); 8.03 (d, 1H,
J¼8.5 Hz, H-6); 8.25e8.28 (m, 3H, ArH); 8.32 (d, 1H, J¼8.5 Hz, H-7);
8.71 (d, 1H, J¼2.4 Hz, H-3); 8.90 (d, 1H, J¼2.4 Hz, H-2). 13C NMR
300 MHz)
d
: 8.03 (d, 1H, J¼8.5 Hz, H-6), 8.38 (d, 1H, J¼8.5 Hz, H-7),
(CDCl3, 75 MHz)
d
: 120.5, 127.2, 129.0, 131.1, 141.5, 142.1, 152.2. MS
8.40e8.65 (m, 3H, Py); 8.78 (d, 1H, J¼2.4 Hz, H-3); 8.93 (d, 1H,
(FAB) m/z 264 [(MH)þ, 20]. Anal. Calcd for C15H9N3S: C, 68.42; H,
J¼2.4 Hz, H-2); 9.18 (s,1H). 13C NMR (CDCl3, 75 MHz)
d: 120.6, 123.7,
3.45; N, 15.96. Found: C, 68.11; H, 3.21; N, 15.78.
132.3, 133.6, 134.2, 135.1, 142.4, 143.7, 144.8, 148.0, 148.4, 150.3,
153.9, 157.5. MS (FAB) m/z 265 [(MH)þ, 70]. Anal. Calcd C14H8N4S: C,
63.62; H, 3.05; N, 21.20; S, 12.13. Found: C, 63.22; H, 3.12; N, 21.33;
S, 12.33.
3.4.2. 8-(Naphthacen-20-yl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3b). Recrystallized from ethanol; yield (93%); white solid; mp:
186e188 ꢀC. IR (KBr) 3045, 2852, 1652, 1530, 1454, 1402, 1339 cmꢁ1
.
1H NMR (CDCl3, 300 MHz)
d
: 7.43e7.49 (m, 3H, ArH); 7.77e7.97 (m,
3.4.8. 8-(Thien-20-yl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
4H, ArH); 8.09e8.14 (m,1H); 8.38 (d,1H, J¼8.5 Hz, H-6); 8.69 (d,1H,
(3h). Recrystallized from (CH2Cl2); yield (74%); yellow solid; mp:
J¼2.4 Hz, H-3); 8.85 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
250e251 ꢀC. IR (KBr) 3047, 1738, 1542, 1480, 1431, 1166 cmꢁ1 1H
.
75 MHz)
d: 125.2, 125.3, 125.8, 126.6, 128.2, 129.1, 131.2, 131.3, 132.8,
NMR (CDCl3, 300 MHz) d: 7.45e7.49 (m, 1H, thienyl); 7.92e7.96 (m,
133.7, 137.7, 142.2, 143.4, 145.1, 147.7, 157.3, 158.2. MS (FAB) m/z 314
[(MH)þ, 100]. Anal. Calcd for C19H11N3S: C, 72.82; H, 3.54; N, 13.41.
Found: C, 72.36; H, 3.75; N, 13.12.
2H, thienyl); 8.09e8.11 (m, 1H); 8.25 (d, 1H, J¼8.5 Hz, H-7); 8.71 (d,
1H, J¼2.4 Hz, H-3); 8.92 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
75 MHz) d: 119.0, 125.5, 128.4, 132.4, 142.1, 143.2, 151.8, 157.5. MS
(FAB) m/z 270 [(MHþ),100]. Anal. Calcd C13H7N3S2: C, 57.97; H, 2.62;
3.4.3. 8-(Phenanthren-20-yl)-pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3c). Recrystallized from CH2Cl2/hexane, 6:4; yield (72%); paleyel-
low solid; mp: 219e220 ꢀC. IR (KBr) 2921, 1714, 1598, 1564,
N, 15.60. Found: C, 57.59; H, 2.99; N, 15.12.
3.4.9. 8-(50-Bromothien-20-yl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
1178 cmꢁ1
.
1H NMR (CDCl3, 300 MHz)
d: 7.61e7.73 (m, 2H, ArH);
(3i). Recrystallized from (CH2Cl2); yield (69%); yellow solid; mp:
7.80 (d, 1H, J¼8.8 Hz, H-7); 7.90e7.93 (m, 2H, ArH); 8.20 (d, 1H,
J¼8.5 Hz, H-6); 8.37 (d, 1H, J¼8.5 Hz); 8.53e8.55 (m, 1H, ArH); 8.71;
8.73e8.79 (m, 2H, ArH); 8.81 (d, 1H, J¼8.0 Hz, ArH); 8.94 (d, 1H,
253e255 ꢀC. IR (KBr) 3048, 2323, 1569, 1419, 1214 cmꢁ1 1H NMR
.
(CDCl3, 300 MHz)
d
: 7.12 (d, 1H, J¼3.9 Hz, thienyl); 7.52 (d, 1H,
J¼3.9 Hz, thienyl); 7.83 (d, 1H, J¼8.5 Hz, H-6); 8.25 (d, 1H, J¼8.5 Hz,
J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d: 121.0, 122.9, 123.3,
H-7); 8.69 (d, 1H, J¼2.4 Hz, H-3); 8.90 (d, 1H, J¼2.4 Hz, H-2). 13C
125.4, 126.7, 126.9, 127.3, 127.4, 128.6, 130.0, 131.0, 131.9, 132.2,
132.4, 133.0, 136.4, 142.3, 144.5, 145.1, 147.8. MS (FAB) m/z 364
[(MH)þ, 70]. Anal. Calcd for C23H13N3S: C, 76.01; H, 3.61; N, 11.56; S,
8.82. Found: C, 76.31; H, 3.56; N, 11.51; S, 8.62.
NMR (CDCl3, 75 MHz) d: 116.1, 118.7, 125.7, 131.0, 132.0, 132.7, 142.5,
143.6, 144.7, 145.6, 147.6, 151.0, 157.7. MS (FAB) m/z 348 [(MHþ), 95].
Anal. Calcd C13H6N3S2Br: C, 44.84; H, 1.74; N, 12.07; S, 18.42. Found:
C, 44.54; H, 1.34; N, 11.68; S, 18.03.
3.4.4. 6-(Pyren-20-yl)-pyrido[40,50:4,5]thieno[2,3-b]pyrazine
(3d). Recrystallized from CH2Cl2/hexane, 1:1; yield (69%); yellow
solid; mp: 262e264 ꢀC. IR (KBr) 3038, 2324, 1789, 1585, 1433,
3.4.10. 8-(Furan-20-yl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3j). Recrystallized from Et2O/hexane 1:1; yield (88%); pale yellow
solid; mp: 184e186 ꢀC. IR (KBr) 2917, 2849, 1595, 1488, 1339,
1328, 1132 cmꢁ1
.
1H NMR (CDCl3, 300 MHz)
d
: 8.00 (d, 1H,
1176 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 6.62e6.65 (m, 1H, furyl);
J¼8.3 Hz, ArH); 8.03 (d, 1H, J¼5.6 Hz, ArH); 8.05 (d, 1H, J¼7.6 Hz,
ArH); 8.09 (d, 1H, J¼9.3 Hz, ArH); 8.15 (s, 1H, ArH); 8.22e8.24 (m,
2H, ArH); 8.29 (d, 1H, J¼7.9 Hz, H-6); 8.36 (d, 1H, J¼7.9 Hz, H-7);
8.41e8.45 (m, 2H, ArH); 8.71 (d, 1H, J¼2.4 Hz, H-3); 8.89 (d, 1H,
7.45 (d, 1H, J¼3.5 Hz, furyl); 7.61e7.65 (m, 1H, furyl); 7.99 (d, 1H,
J¼8.5 Hz, H-6); 8.28 (d, 1H, J¼8.5 Hz, H-7); 8.70 (d, 1H, J¼2.4 Hz, H-
3); 8.89 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d: 110.0,
112.4, 119.0, 128.7, 131.8, 132.3, 142.2, 143.4, 144.8, 147.4, 148.6,
153.0. MS (FAB) m/z 254 [(MHþ), 90]. Anal. Calcd C13H7N3OS: C,
61.65; H, 2.79; N,16.59; S, 12.66. Found: C, 61.42; H, 2.98; N,16.17; S,
12.20.
J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d: 124.6, 124.8, 125.5,
126.1, 127.5, 128.1, 128.3, 128.4, 129.0, 131.4, 132.8, 135.1, 142.4,
143.6, 145.2, 148.1, 157.2, 158.7. MS (FAB) m/z 388 [(MH)þ, 50].
Anal. Calcd for C25H13N3S: C, 77.50; H, 3.38; N, 10.98; S, 8.28.
Found: C, 77.47; H, 3.38; N, 10.67; S, 8.47.
3.4.11. 8-(Thiazol-20-yl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3k). Recrystallized from CH2Cl2; yield (58%); yellow solid; mp:
3.4.5. 8-(Pyri-20-yl)-pyrido[20,30:4,5]thieno[2,3-b]pyrazine
215e217 ꢀC. IR (KBr) 2353, 1567, 1543, 1446, 1326, 1309, 1083 cmꢁ1
.
(3e). Recrystallized from CH2Cl2; yield (71%); yellow solid; mp:
1H NMR (CDCl3, 300 MHz)
d
: 7.55 (d, 1H, J¼2.7 Hz, thiazolyl); 7.96
245e247 ꢀC. IR (KBr) 3089, 3047, 1599, 1341, 1281, 1179 cmꢁ1
.
1H
(d, 1H, J¼2.7 Hz, thiazolyl); 8.34 (d, 1H, J¼8.5 Hz, H-6); 8.53 (d, 1H,
NMR (CD3CN, 500 MHz)
d
: 7.83 (d, 1H, J¼8.5 Hz, H-6), 7.96 (d, 1H,
J¼8.5 Hz, H-7); 8.70 (d, 1H, J¼2.4 Hz, H-3); 8.93 (d, 1H, J¼2.4 Hz, H-
J¼8.5 Hz, H-7), 8.00e8.05 (m, 4H, Py); 8.43 (d, 1H, J¼8.5 Hz, H-3),
2). 13C NMR (CDCl3, 75 MHz)
d: 120.0, 122.0, 132.4, 145.1, 142.2,
8.61 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3, 125 MHz)
d: 121.4,
143.5, 143.9, 151.2. MS (FAB) m/z 271 [(MHþ), 90]. Anal. Calcd
C12H6N4S2: C, 53.32; H, 2.24; N, 20.73. Found: C, 53.57; H, 2.54; N,
20.86.
121.6, 134.2, 134.7, 143.3, 144.4, 144.9, 145.5, 147.8, 151.0, 152.9,
157.4. MS (FAB) m/z 265 [(MH)þ, 80]. Anal. Calcd C14H8N4S: C,
63.62; H, 3.05; N, 21.20; S, 12.13. Found: C, 63.31; H, 2.90; N, 21.55;
S, 12.24.
3.4.12. 8-(40-Nitrophenyl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3l). Recrystallized from CH2Cl2/hexane 3:7; yield (84%); yellow
solid; mp: 289e291 ꢀC. IR (KBr) 3075, 1672, 1601, 1508, 1335,
3.4.6. 8-(Pyrid-40-yl)-pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3f). Recrystallized from ethanol; yield (50%); yellow crystals; mp:
1093 cmꢁ1. 1H NMR (CD3CN, 500 MHz)
6); 7.50e7.56 (m, 4H); 7.72 (d, 1H, J¼8.5 Hz, H-7); 8.45 (d, 1H,
d
: 7.55 (d, 1H, J¼8.5 Hz, H-
233e235 ꢀC. IR (KBr) 3050, 1738, 1545, 1493, 1451, 1342, 1183 cmꢁ1
.

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2041
J¼2.4 Hz, H-3); 8.66 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
27.8, 30.9, 33.8, 136.1, 137.9, 138.6, 145.9, 148.9, 149.6, 150.8, 161.4,
162.0. MS (FAB) m/z 244 [(MHþ), 100]. Anal. Calcd C12H9N3OS: C,
59.24; H, 3.73; N, 17.27; S, 13.18. Found: C, 59.51; H, 3.87; N, 17.70; S,
13.53.
125 MHz) d: 121.0, 124.0, 128.2, 132.4, 134.3, 142.5, 143.9, 144.3,
144.7, 148.1, 153.8. MS (FAB) m/z 309 [(MHþ), 95]. Anal. Calcd
C15H8N4O2S: C, 58.43; H, 2.62; N, 18.17; S, 10.40. Found: C, 58.40; H,
2.95; N, 18.52; S, 10.01.
3.4.19. 6,7-Dihydro-(9H)-thiopyran[300,400:50,60]pyrido[20,30:4,5]
thieno[2,3-c]pyrazine (6b). Recrystallized from AcOEt/hexane 4:6;
yield (79%); yellow solid; mp: 204e206 ꢀC. IR (KBr) 3178, 1713,
1648, 1621, 1428, 1345, 1262, 1076 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
3.4.13. 8-Methylpyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3m). Recrystallized from AcOEt/hexane 3:7; yield (87%); yellow
solid; mp: 176e178 ꢀC. IR (KBr) 3094, 3046, 2918, 2852, 1979, 1635,
1570, 1545, 1343, 1155 cmꢁ1. 1H NMR (CD3CN, 500 MHz)
d: 3.11 (s,
d
: 3.10 (t, 2H, J¼6.5 Hz); 3.51 (t, 2H, J¼6.5 Hz); 3.96 (s, 2H); 7.98 (s,
3H); 7.36 (d, 1H, J¼8.5 Hz, H-6); 7.53 (d, 1H, J¼8.5 Hz, H-7); 8.32 (d,
1H); 8.65 (d, 1H, J¼2.4 Hz); 8.82 (d, 1H, J¼2.4 Hz). 13C NMR (CDCl3,
1H, J¼2.4 Hz, H-3); 8.54 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
75 MHz) d: 26.4, 30.1, 33.8, 129.7, 131.6, 132.2, 142.0, 143.1, 144.7,
75 MHz)
d
: 24.6, 123.7, 131.2, 131.5, 142.0, 143.1, 144.8, 147.1, 157.1,
145.9, 156.5, 157.1. MS (FAB) m/z 260 [(MHþ), 40]. Anal. Calcd
C12H9N3S2: C, 55.57; H, 3.50; N, 16.20; S, 24.73. Found: C, 55.25; H,
3.19; N, 16.65; S, 24.91.
157.9. MS (FAB) m/z 202 [(MHþ), 100]. Anal. Calcd C10H7N3S: C,
59.68; H, 3.51; N, 20.88; S, 15.93. Found: C, 59.95; H, 3.60; N, 20.81;
S, 15.64.
3.4.20. 8-Benzoyl-6,7,8,9-tetrahydropyrazine[40,30:4,5]thieno[2,3-b]
[1,6]naphthyridine (6c). Recrystallized from AcOEt/hexane 4:6;
yield (82%); yellow solid; mp: 211e213 ꢀC. IR (KBr) 2934, 2817,
3 . 4.14. 8 -E thyl pyr id o [2 0, 30:4 , 5 ]t hien o[ 2 , 3- b] pyra zin e
(3n). Recrystallized fꢀrom AcOEt/hexane 4:6; yield (44%); yellow
solid; mp: 155e157 C. IR (KBr) 2921, 2852, 1652, 1530, 1454,
1668, 1597, 1432, 1081 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 2.91 (t,
1402, 1339, 1184 cmꢁ1
.
1H NMR (CD3CN, 300 MHz)
d
: 1.18 (t, 3H,
2H, J¼5.9 Hz); 3.16 (t, 2H, J¼5.9 Hz); 3.76 (s, 2H); 3.80 (s, 2H);
J¼6.6 Hz, CH3); 2.81 (q, 2H, J¼6.6 Hz, CH2); 7.36 (d, 1H, J¼8.5 Hz,
7.36e7.40 (m, 5H); 8.33 (s, 1H); 8.78 (d, 1H, J¼2.4 Hz); 8.89 (d, 1H,
H-6); 7.53 (d, 1H, J¼8.5 Hz, H-7); 8.32 (d, 1H, J¼2.4 Hz, H-3);
J¼2.4 Hz). 13C NMR (CDCl3, 75 MHz)
d: 31.4, 49.1, 54.1, 60.4, 126.2,
8.80 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d
: 23.0,
127.4, 127.9, 128.7, 130.6, 137.5, 140.5, 141.4, 142.5, 143.1, 144.7, 153.9,
155.8. MS (FAB) m/z 333 [(MHþ), 100]. Anal. Calcd C19H16N4S: C,
68.65; H, 4.85; N,16.85; S, 9.65. Found: C, 68.48; H, 4.75; N,16.75; S,
10.02.
29.9, 131.4, 132.3, 134.2, 141.8, 142.7, 145.0, 145.1, 156.9, 157.4. MS
(FAB) m/z 216 [(MHþ), 100]. Anal. Calcd C11H9N3S: C, 61.37; H,
4.21; N, 19.52; S, 14.89. Found: C, 61.62; H, 4.55; N, 19.20; S,
14.63.
3.4.21. 8-Acetyl-6,7,8,9-tetrahydropyrazine[40,30:4,5]thieno[2,3-b]
[1,6]naphthyridine (6d). Recrystallized from AcOEt/hexane 6:4;
yield (76%); yellow solid; mp: 234e236 ꢀC. IR (KBr) 2922, 2878,
3.4.15. 7,8-Dimethylpyrido[20,30:4,5]thieno[2,3-b]pyrazine
(4n). Recrystallized from AcOEt/hexane 4:6; yield (23%); yellow
solid; mp: 280 ꢀC (dec). IR (KBr) 3156, 1666, 1598, 1337, 1097,
1752, 1656, 1544, 1321, 1147 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 2.01
1034 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d
: 2.46 (s, 3H, CH3); 2.72 (s,
(s, 3H); 3.42e3.71 (m, 4H); 3.93 (s, 3H); 7.93 (s. 1H); 8.71 (d, 1H,
J¼2.4 Hz); 8.77 (d, 1H, J¼2.4 Hz). MS (FAB) m/z 285 [(MHþ), 100].
Anal. Calcd C14H12N4OS: C, 59.14; H, 4.25; N, 19.70; S, 11.28. Found:
C, 59.69; H, 4.44; N, 19.93; S, 11.53.
3H, CH3); 7.93 (s, 1H, H-6); 8.8.59 (d, 1H, J¼2.4 Hz, H-3); 8.76 (d, 1H,
J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d: 27.3, 34.3, 140.2, 141.1,
141.2, 141.9, 142.2, 143.5, 144.1. MS (FAB) m/z 216 [(MHþ), 100]. Anal.
Calcd C11H9N3S: C, 61.37; H, 4.21; N, 19.52; S, 14.89. Found: C, 61.21;
H, 4.40; N, 19.70; S, 14.69.
3.4.22. 7,8-Dihydro-(6H)-cyclopenta[100,200:50,60]pyrido[20,30:4,5]
thieno[2,3-b]pyrazine (6e). Recrystallized from AcOEt/hexane 1:1;
yield (71%); pale yellow solid; mp: 189e191 ꢀC. IR (KBr) 3043, 2951,
1572, 1531, 1432, 1341, 1174, 1032 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
3.4.16. 8-(20-Phenylethyl)pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(3o). Recrystallized from CH2Cl2; yield (45%); yellow solid; mp:
150e152 ꢀC. IR (KBr) 3053, 3028, 2851, 1448, 1345, 1178 cmꢁ1
.
1H
d
: 2.26 (q, 2H, J¼7.6 Hz); 3.12 (t, 2H, J¼7.6 Hz); 3.24 (t, 2H, J¼7.6 Hz);
NMR (CDCl3, 300 MHz)
d
: 3.17e3.22 (m, 2H); 3.36e3.41 (m, 2H);
8.01 (s, 1H); 8.61 (d, 1H, J¼2.4 Hz); 8.79 (d, 1H, J¼2.4 Hz). 13C NMR
7.20e7.33 (m, 6H); 8.12 (d, 1H, J¼8.4 Hz, H-7); 8.68 (d, 1H, J¼2.4 Hz,
(CDCl3, 75 MHz) d: 23.2, 31.1, 34.0, 123.8, 126.6, 131.3, 138.7, 141.9,
H-3); 8.87 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3, 75 MHz)
d
: 36.3,
142.2, 142.6, 143.2, 166.2. MS (FAB) m/z 228 [(MHþ), 90], 202 (15).
Anal. Calcd C12H9N3S: C, 63.41; H, 3.99; N, 18.49; S, 14.11. Found: C,
63.22; H, 4.08; N, 18.34; S, 14.36.
41.2, 123.5, 126.4, 128.1, 128.5, 131.8, 132.0, 141.2, 142.0, 143.2, 145.0,
147.3, 157.6, 160.9. MS (FAB) m/z 292 [(MHþ), 100]. Anal. Calcd
C17H13N3S: C, 70.08; H, 4.50; N, 14.42; S, 11.00. Found: C, 69.81; H,
4.76; N, 14.57; S, 10.86.
3.4.23. 6,7,8,9-Tetrahydropyrido[40,30:4,5]thieno[3,2-b]quinoline
(6f). Recrystallized from AcOEt/hexane 3:7; yield (73%); pale yel-
low solid; mp: 170e172 ꢀC. IR (KBr) 3040, 2938, 1528, 1394, 1204,
3.4.17. 7-Benzyl-8-methylpyrido[20,30:4,5]thieno[2,3-b]pyrazine
(4o). Recrystallized from CH2Cl2; yield (11%); pale yellow solid;
1154, 1084 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 1.75e2.04 (m, 4H);
mp: 162e164 ꢀC. NMR (CDCl3, 300 MHz)
d: 2.77 (s, 3H); 4.18 (s, 2H);
3.01 (t, 2H, J¼6.5 Hz); 3.22 (t, 2H, J¼6.5 Hz); 7.90 (s, 1H); 8.61 (d, 1H,
7.17e7.19 (m, 2H); 7.19e7.35 (m, 3H); 7.85 (s, 1H); 8.62 (d, 1H,
J¼2.4 Hz); 8.78 (d, 1H, J¼2.4 Hz). 13C NMR (CDCl3, 75 MHz)
d: 22.5,
J¼2.4 Hz, H-3); 8.80 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
22.9, 29.7, 32.8, 131.1, 131.7, 133.8, 141.7, 142.7, 145.1, 145.2, 157.0,
157.6. MS (FAB) m/z 242 [(MHþ), 100]. Anal. Calcd C13H11N3S: C,
64.70; H, 4.59; N,17.41; S,13.29. Found: C, 64.45; H, 4.54; N,17.43; S,
13.58.
75 MHz) d: 36.3, 40.2, 123.5, 126.0, 128.3, 128.5, 131.3, 132.0, 141.2,
142.0, 143.2, 144.9, 147.3, 157.2. MS (FAB) m/z 292 [(MHþ), 60]. Anal.
Calcd C17H13N3S: C, 70.08; H, 4.50; N, 14.42; S, 11.00. Found: C,
69.84; H, 4.65; N, 14.21; S, 11.20.
3.4.24. 7,8,9,10-Tetrahydro-(6H)-cyclohepta[100,200:50,60]pyrido
[20,30:4,5]thieno[2,3-b]pyrazine (6g). Recrystallized from AcOEt/
hexane 1:1; yield (71%); yellow solid; mp: 148e150 ꢀC. IR (KBr)
3.4.18. 6,7-Dihydro-(9H)-pyran[300,400:50,60]pyrido[20,30:4,5]thieno
[2,3-c]pyrazine (6a). Recrystallized from AcOEt/hexane 2:8; yield
(77%); yellow crystals; mp: 218e220 ꢀC. IR (KBr) 3132, 1704, 1615,
2921, 2851, 1650, 1399, 1141 cmꢁ1 1H NMR (CDCl3, 300 MHz)
. d:
1423,1367,1306, 898 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d
: 3.52 (t, 2H,
1.73e1.90 (m, 6H); 2.92e2.97 (m, 2H); 3.27e3.33 (m, 2H); 7.90 (s,
J¼6.3 Hz); 3.90 (t, 2H, J¼6.3 Hz); 4.26 (s, 2H); 8.11 (s, 1H); 8.68 (d,
1H); 8.58 (d, 1H, J¼2.4 Hz); 8.76 (d, 1H, J¼2.4 Hz). 13C NMR (CDCl3,
1H, J¼2.4 Hz); 8.84 (d, 1H, J¼2.4 Hz). 13C NMR (CDCl3, 75 MHz)
d:
75 MHz) d: 26.6, 28.1, 32.2, 35.9, 39.3, 130.7, 132.3, 139.6, 141.8,

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A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2042
142.5, 144.5,145.8, 156.8, 163.3. MS (FAB) m/z 256 [(MHþ), 90]. Anal.
Calcd C14H13N3S: C, 65.85; H, 5.13; N, 16.46; S, 12.56. Found: C,
65.79; H, 5.39; N, 16.42; S, 12.40.
1H, J¼6.2 Hz), 7.32 (m, 2H), 7.43 (t, 1H, J¼6.2 Hz), 7.45 (t, 1H,
J¼6.9 Hz), 7.59 (d, 1H, J¼8.5 Hz, H-7), 7.70 (t, 1H, J¼7.9 Hz),
7.84e7.86 (m, 1H), 7.87 (t, 1H, J¼3.0 Hz, H-2), 7.94 (t, 1H, J¼7.8 Hz),
8.05e8.13 (m, 5H), 8.19 (d, 1H, J¼5.4 Hz), 8.38 (d, 2H, J¼7.8 Hz),
8.45e8.47 (m, 3H), 8.54 (d, 1H, J¼3.0 Hz, H-3), 8.68 (d, 1H, J¼8.5 Hz,
3.4.25. 6H-Indene[100,200:50,60]pyrido[20,30:4,5]thieno[2,3-b]pyrazine
(7). Recrystallized ethanol/acetone; yield (80%); yellow crystals;
mp: 240e242 ꢀC. IR (KBr) 3190, 2919, 2851, 1666, 1573, 1548, 1513,
H-6). 13C NMR (D2O, 125 MHz)
d: 123.2, 123.6, 124.1, 124.4, 126.9,
127.1, 127.2, 127.4, 127.8, 128.5, 133.8, 134.4, 135.1, 137.5, 138.4, 138.5,
138.6, 139.2, 144.3, 145.1, 146.1, 148.7, 149.1, 150.8, 152.1, 152.4, 153.0,
153.7, 153.9, 157.0, 157.1, 157.8, 161.3. HRMS-ESI (m/z) calcd for
[MꢁClꢁ]þ 713.0571, found 713.0536; calcd for [Mꢁ2Clꢁ]2þ
339.0438, found 339.0450. Anal. Calcd C34H24Cl2N8RuS: C, 54.55; H,
3.23; N, 14.97; S, 4.28. Found: C, 54.01; H, 3.41; N, 15.10; S, 4.67.
1244 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 4.07 (s, 1H); 7.74e7.77 (m,
5H); 8.22 (s, 1H); 8.62 (d, 1H, J¼2.4 Hz); 8.70 (d, 1H, J¼2.4 Hz). 13C
NMR (CDCl3, 75 MHz) d: 31.0, 108.9, 122.5, 123.6, 125.8, 126.7, 127.4,
129.8, 133.3, 137.7, 140.7, 140.8, 142.1, 142.5, 148.2, 155.0. MS (FAB)
m/z 276 [(MHþ), 100]. Anal. Calcd C16H9N3S: C, 69.80; H, 3.29; N,
15.26; S, 11.65. Found: C, 69.47; H, 3.56; N, 15.67; S, 11.30.
3.5.2. [Ru(bpy)23l]Cl2. Acetone/H2O (1:1) as eluent; yield (65%);
3. 4. 26. 8-Aminopyrido[20, 30:4,5]thieno[2, 3-b]pyrazine
(8a). Recrystallized from AcOEt/hexane 3:7; yield (77%); yellow
crystals; mp: 256e258 ꢀC. IR (KBr) 3460, 3340, 2920, 2851, 1731,
black solid. 1H NMR (CD3CN, 500 MHz)
d
: 6.91 (t, 1H, J¼6.9 Hz), 7.22
(d, 1H, J¼5.7 Hz), 7.31e7.35 (m, 2H), 7.41e7.48 (m, 1H), 7.50e7.57
(m, 3H), 7.67 (d, 1H, J¼8.5 Hz, H-7), 7.76e7.81 (m, 2HþH-2),
7.94e8.02 (m, 2H), 8.11e8.17 (m, 3H), 8.26(m, 1H, J¼5.7 Hz),
8.43e8.53 (m, 4H), 8.65 (d, 1H, J¼3.0 Hz, H-3), 8.82 (d, 1H,
1621, 1519, 1186 cmꢁ1 1H NMR (CDCl3, 300 MHz)
. d: 4.88 (s, 2H);
6.84 (d, 1H, J¼8.5 Hz, H-7); 7.98 (d, 1H, J¼8.5 Hz, H-6); 8.62 (d, 1H,
J¼2.4 Hz, H-3); 8.77 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
J¼8.5 Hz). 13C NMR (CD3CN, 125 MHz)
d: 123.4, 123.8, 126.8, 127.0,
75 MHz)
d
: 111.5, 128.8, 130.9, 132.2, 132.9, 133.5, 141.7, 141.8, 142.7.
127.5, 127.6, 127.7, 128.2, 128.3, 133.6, 136.8, 138.5, 142.6, 144.9,
148.1, 148.5, 150.9, 151.1, 152.5, 153.2, 154.1, 155.1, 156.8, 156.9, 157.1,
158.1, 162.3. HRMS-ESI (m/z) calcd for [Mꢁ2Clꢁ]2þ 361.0387, found
361.0394. Anal. Calcd C35H24Cl2N8O2RuS: C, 53.03; H, 3.05; N, 14.14;
S, 4.05. Found: C, 52.87; H, 3.01; N, 14.35; S, 3.88.
MS (FAB) m/z 203 [(MHþ), 40]. Anal. Calcd C9H6N4S: C, 53.45; H,
2.99; N, 27.70; S, 15.86. Found: C, 53.81; H, 2.84; N, 27.65; S, 15.70.
3.4.27. 8-Amino-7-cyanopyrido[20,30:4,5]thieno[2,3-b]pyrazine
(8b). Recrystallized from ethanol; yield (89%); yellow crystals; mp:
>300 ꢀC. IR (KBr) 3489, 3139, 2216,1633,1580,1344,1190, 974 cmꢁ1
.
3.5.3. [Ru(bpy)23m]Cl2. Acetone/CH3CN/H2O (8:1:1) as eluent;
1H NMR (CDCl3, 300 MHz)
d
: 6.93 (s, 2H); 7.76 (s, 1H, H-6); 8.32 (d,
yield (60%); black solid. 1H NMR (CD3CN, 500 MHz)
d: 2.76 (s, 3H),
1H, J¼2.4 Hz, H-3); 8.70 (d, 1H, J¼2.4 Hz, H-2). 13C NMR (CDCl3,
7.40e7.49 (m, 4H), 7.60 (d, 1H, J¼6.9 Hz), 7.69 (d, 1H, J¼8.5 Hz, H-7),
7.80 (d, 1H, J¼5.6 Hz), 7.90 (t, 1H, J¼3.0 Hz, H-2), 8.06e8.16 (m, 6H),
8.59 (d, 1H, J¼8.5 Hz, H-6), 8.65 (d, 1H, J¼3.0 Hz, H-3), 8.67e8.70
75 MHz) d: 92.2, 116.5, 120.2, 139.0, 142.7, 142.8, 143.7, 144.5, 149.7,
158.4. MS (FAB) m/z 228 [(MHþ), 50]. Anal. Calcd C10H5N5S: C, 52.85;
H, 2.22; N, 30.82; S,14.11. Found: C, 52.66; H, 2.41; N, 30.68; S,14.35.
(m, 4H). 13C NMR (CD3CN, 125 MHz)
d: 21.7, 124.6, 124.7, 127.6, 127.7,
128.1, 128.2, 131.5, 134.2, 138.2, 138.3, 138.5, 144.0, 146.6, 148.8,
150.8, 152.5, 152.6, 152.8, 154.1, 157.0, 157.1, 157.6, 158.2, 164.0.
HRMS-ESI (m/z) calcd for [Mꢁ2Clꢁ]þ2 307.5389, found 307.5396.
Anal. Calcd C30H23Cl2N7RuS: C, 52.56; H, 3.38; N, 14.30; S, 4.68.
Found: C, 52.79; H, 3.15; N, 14.99; S, 4.37.
3.4.28. 2,4-Dioxo-1,2,3,4-tetrahydropyrimido[200,300:50,60]pyrido
[20,30:4,5]thieno[2,3-b]pyrazine (9a). Recrystallized from AcOEt;
yield (70%); yellow solid; mp: >300 ꢀC. IR (KBr) 3115, 2917, 2819,
1667,1613,1562,1266,1093 cmꢁ1. 1H NMR (CDCl3, 300 MHz)
d: 6.71
(s, 1H); 7.55 (s, 1H); 8.37 (s. 1H); 8.73 (d, 1H, J¼2.4 Hz); 8.85 (d, 1H,
J¼2.4 Hz). 13C NMR (CDCl3, 75 MHz)
d
: 56.5, 79.4, 114.9, 123.0, 136.6,
3.5.4. [Ru(bpy)26b]Cl2. Acetone/H2O (1:1) as eluent; yield (69%);
142.6, 143.5, 143.6, 144.1, 144.2, 146.1, 157.4, 158.0. MS (ESI) m/z 271.
Anal. Calcd C11H5N5O2S: C, 48.71; H, 1.86; N, 25.85; S, 11.82. Found:
C, 48.59; H, 1.97; N, 25.79; S, 11.57.
black solid. 1H NMR (D2O, 500 MHz)
d: 2.32e2.36 (m, 2H),
2.60e2.67 (m, 4H), 3.72 (d, 1H, J¼16.0 Hz), 3.91 (d, 1H, J¼16.0 Hz),
7.25e7.32 (m, 4H), 7.64 (d, 1H, J¼6.4 Hz), 7.74 (d, 1H, J¼5.9 Hz), 7.88
(d, 1H, J¼5.9 Hz), 7.91e8.00 (m, 5H), 8.28 (s, 1H), 8.32 (d, 1H,
3.4.29. 1,3-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimido
[ 2 00, 3 00: 5 0, 6 0] p y r i d o [ 2 0, 3 0: 4 , 5 ] t h i e n o [ 2 , 3 - b ] p y r a z i n e
(9b). Recrystallized from ethanol; yield (76%); yellow crystals; mp:
J¼3.0 Hz), 8.41e8.50 (m, 4H). 13C NMR (D2O, 125 MHz)
d: 25.4, 30.2,
31.0, 124.2, 124.3, 127.2, 127.5, 131.4, 132.7, 135.6, 138.1, 138.2, 138.4,
143.6, 145.3, 149.2, 151.8, 152.2, 152.5, 153.1, 153.4, 157.0, 157.1, 157.2,
158.1, 162.1. HRMS-ESI (m/z) calcd for [Mꢁ2Clꢁ]þ2 336.5322, found
336.5338. Anal. Calcd C32H25Cl2N7RuS2: C, 51.68; H, 3.39; N,13.18; S,
8.62. Found: C, 51.90; H, 3.12; N, 13.73; S, 8.91.
291e293 ꢀC. IR (KBr) 3178, 1713, 1648, 1428, 1345, 1076 cmꢁ1 1H
.
NMR (CDCl3, 300 MHz) d: 2.89 (s, 3H); 3.08 (s, 3H); 8.41 (d, 1H,
J¼2.4 Hz); 8.47 (d, 1H, J¼2.4 Hz); 8.87 (s, 1H). 13C NMR (CDCl3,
75 MHz) d: 27.2, 28.3, 118.8, 123.6, 138.9, 143.5, 143.8, 147.2, 151.2,
152.4, 154.8, 155.7. MS (FAB) m/z 300 [(MHþ), 100]. Anal. Calcd
C13H9N5O2S: C, 52.17; H, 3.03; N, 23.40; S, 10.71. Found: C, 52.64; H,
3.41; N, 23.22; S, 10.41.
3.5.5. [Ru(bpy)28b](PF6)2. Acetone as eluent; yield (79%); black
solid. 1H NMR (CD3CN, 500 MHz)
d: 5.00 (s, 2H), 7.40e7.54 (m, 3H),
7.65e7.68 (m, 2H), 7.74 (d, 1H, J¼3.0 Hz), 7.85e7.94 (m, 2H),
8.09e8.16 (m, 4H), 8.43e8.37 (m, 1H), 8.48e8.61 (m, 5H), 8.66 (s,
3.5. Preparation of Ru(II) complexes
1H). 13C NMR (CD3CN, 125 MHz)
d: 124.3, 124.5, 124.9, 127.7, 128.0,
128.4, 134.4, 138.4, 138.5, 139.9, 140.3, 144.1, 144.7, 146.5, 147.4,
To prepare the Ru(II) complexes, a mixture of [Ru(bpy)2Cl2]
(200 mg, 1.11 mmol) and the appropriate ligand (3e, 3l, 3m, 6b or
8b) (1.11 mmol), in ethanol/water (1:3) (15 mL), was heated under
reflux in an inert atmosphere of argon until all starting materials
had disappeared as checked by TLC. The suspension was concen-
trated in vacuo and the residue was purified by column chroma-
tography on silica gel.
152.6, 152.7, 152.9, 154.5, 154.6. HRMS-ESI (m/z) calcd for
[Mꢁ2PFꢁ6 ]þ2
320.5336,
found
320.5336.
Anal.
Calcd
C30H21F12N9P2RuS: C, 37.27; H, 3.02; N, 15.94; S, 3.42. Found: C,
37.47; H, 2.88; N, 15.76; S, 3.12.
Acknowledgements
ꢀ
The authors are indebted to Centro de Computacion de Galicia for
3.5.1. [Ru(bpy)23e]Cl2. Acetone/H2O (1:1) as eluent; yield (61%);
providing the computer facilities. This research was supported by
black solid. 1H NMR (D2O, 500 MHz)
d
: 6.94 (t, 1H, J¼6.9 Hz), 7.23 (t,
Xunta de Galicia (PGIDIT06PXIB103224PR), Ministerio de Educacion
ꢀ

ꢀ
A. Fernandez-Mato et al. / Tetrahedron 67 (2011) 2035e2043
2043
8. (a) Du, C.; Guo, Y.; Liu, Y.; Qiu, W.; Zhang, H.; Gao, X.; Liu, Y.; Qi, T.; Lu, K.; Yu, G.
Chem. Mater. 2008, 20, 4188; (b) Ma, Y.; Sun, Y.; Liu, Y.; Gao, J.; Chen, S.; Sun, X.;
Qiu, W.; Yu, G.; Cui, G.; Hu, W.; Zhu, D. J. Mater. Chem. 2005, 15, 4894; (c) Qi, T.;
Guo, Y.; Liu, Y.; Xi, H.; Zhang, H.; Gao, X.; Liu, Y.; Lu, K.; Du, C.; Yu, G.; Zhu, D.
Chem. Commun. 2008, 6227.
y Cultura of Spain, and FEDER (CTQ2007-63839/BQU). A.F.-M. ac-
knowledges a predoctoral fellowship from Xunta de Galicia.
Supplementary data
ꢀ
9. Fernandez-Mato, A.; Blanco, G.; Quintela, J. M.; Peinador, C. Tetrahedron 2008,
64, 3446.
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2011.01.066.
ꢀ
10. (a) Blanco, G.; Fernandez-Mato, A.; Quintela, J. M.; Peinador, C. Synthesis 2009,
ꢀ
438; (b) Blanco, G.; Fernandez-Mato, A.; Quintela, J. M.; Peinador, C. Tetrahedron
2008, 64, 11136; (c) Blanco, G.; Quintela, J. M.; Peinador, C. Synthesis 2008, 1397;
(d) Blanco, G.; Quintela, J. M.; Peinador, C. Tetrahedron 2008, 64, 1333; (e) Al-
varez-Sarandes, R.; Peinador, C.; Quintela, J. M. Tetrahedron 2001, 57, 5413.
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