Cyclopalladated 3,5-disubstituted 2-(2′-pyridyl)pyrroles complexed to 8-hydroxyquinoline or 4-hydroxyacridine

Article abstract of DOI:10.1002/ejic.201201341

Four new complexes of general formula [(L_a)Pd(Qui)] (1), [(L_b)Pd(Acr)] (2), [(L_a)Pd(Acr)] (3) and [(L _b)Pd(Acr)] (4) containing methyl (1, 3) or phenyl (2, 4) 3,5-disubstituted chelated 2-(2′-pyridyl)pyrrole lig

Full text of DOI:10.1002/ejic.201201341

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DOI:10.1002/ejic.201201341
Cyclopalladated 3,5-Disubstituted 2-(2Ј-Pyridyl)pyrroles
Complexed to 8-Hydroxyquinoline or 4-Hydroxyacridine
Teresa F. Mastropietro,[a] Elisabeta I. Szerb,[a] Massimo La Deda,[b]
Alessandra Crispini,[b] Mauro Ghedini,[a] and Iolinda Aiello*[a]
Keywords: Palladium / N,O ligands / N,N ligands / Ligand effects / Luminescence
Four new complexes of general formula [(La)Pd(Qui)] (1),
[(Lb)Pd(Acr)] (2), [(La)Pd(Acr)] (3) and [(Lb)Pd(Acr)] (4) con-
taining methyl (1, 3) or phenyl (2, 4) 3,5-disubstituted che-
lated 2-(2Ј-pyridyl)pyrrole ligands (HLa,b) have been synthe-
sized and characterized. For comparative purposes, the anal-
ogous 2-phenylpyridine (HLc) derivatives, [(Lc)Pd(Qui)] (5)
and [(Lc)Pd(Acr)] (6), have also been prepared. Mild syn-
NMR spectroscopy. The crystal structures of 1, 4, and 5 reveal
the presence of different isomers for different complexes, de-
pending on both the cyclometallating and ancillary ligands.
The structures of 1–6 allowed us to hypothesize that the an-
cillary ligand may play a predominant role in the formation
of the trans/cis isomers in these systems and that the pyr-
idylpyrrole definitely produces opposite outcomes compared
thetic conditions and reduced reaction times can be em- with the 2-phenylpyridine ligand. Finally, the photophysical
ployed with HLa,b ligands to obtain the products in good
yields, proving the higher reactivity of HLa,b compared with
HLc in cyclopalladation. Depending on the relative disposi-
properties of 1–4 were studied in solution. Although 5 and 6
are emissive, no emission was detected for 1–4 under the
same conditions, the emission quenching being most likely
caused by the thermal deactivating path of the lowest excited
state, which results from a combination of the pyridylpyrrole-
∧
∧
∧
∧
tions of the N N/N O (1–4) or C N/N O (5 and 6) chelating
rings, all the complexes can in principle exist as two isomers.
∧
1
However, in each case, only one isomer was observed by H
localized state with that localized on the N O ligand.
In this context, it is worth recalling the unusual behav-
iour exhibited by the mixed 2-phenylpyridine and 8-hy-
droxyquinoline PdII complex, which shows luminescence at
room temperature.[10] The corresponding 4-hydroxyacridine
derivative has also been synthesized,[11] but its photophysi-
cal properties were not investigated.
Introduction
Cyclopalladation is a very useful synthetic tool for the
preparation of organometallic PdII complexes that are of
interest in many scientific fields, such as catalysis, organic
synthesis and materials science.[1–3] Nevertheless, in the area
of luminescent transition-metal complexes, which include as
important examples complexes containing RuII,[4] OsII,[4,5]
IrIII[6,7] and PtII,[6,8] PdII organometallic or coordination
compounds occupy a less prominent position.[9] Indeed,
PdII complexes generally emit only at low temperatures in
frozen matrices. However, organopalladium compounds are
among the most readily available and simply prepared of
the plethora of luminescent transition-metal complexes and
their properties can be easily modulated by varying the na-
ture of the ancillary ligand.[1–3]
Of the organic compounds that can undergo cyclopallad-
ation with the eventual formation of the thermodynamically
II
∧
very stable five-membered (C N)Pd chelating ring, 2-
phenylpyridine (HLc in Scheme 1) has been extensively ex-
ploited.[1–3] Therefore the HLc molecule may be an interest-
ing and useful reference substrate for testing the reactivity
of new organic species in the synthesis of PdII-containing
metallacycles.
[a] Centro di Eccellenza CEMIF.CAL, LASCAMM
– CR
INSTM, Unità INSTM della Calabria and CNR-IPCF-UOS
di Cosenza – Laboratory Licryl, Dipartimento di Chimica,
Università della Calabria,
87036 Arcavacata di Rende (CS), Italy
Fax: +39-0984-492066
E-mail: iolinda.aiello@ unical.it
Homepage: http://www.unical.it/portale/
[b] Centro di Eccellenza CEMIF.CAL, LASCAMM
– CR
INSTM, Unità INSTM della Calabria and CNR-IPCF-UOS
di Cosenza – Laboratory Licryl, Dipartimento di Scienze
Farmaceutiche, Università della Calabria,
87036 Arcavacata di Rende (CS), Italy
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201201341.
Scheme 1. Chemical structures of the HLa,b and HLc ligands.
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In an attempt to extend the range of cyclopalladated sys- palladated fragment towards HQui or HAcr ligands and
tems, attention has recently been devoted to 2-(2Ј-pyridyl)- 3) their photophysical properties. Consequently, four new
pyrrole ligands as these can display steric effects and a complexes have been synthesized and characterized, namely
∧
monoanionic, bidentate N N chelating mode analogous to [(La)Pd(Qui)] (1), [(Lb)Pd(Acr)] (2), [(La)Pd(Acr)] (3) and
HLc. In particular, the unsubstituted 2-(2Ј-pyridyl)pyrrole [(Lb)Pd(Acr)] (4), as reported in Scheme 3, and for compar-
ligands have been poorly studied, probably because of the ative purposes, [(Lc)Pd(Qui)] (5)[10] and [(Lc)Pd(Acr)] (6)[11]
more complicated synthetic procedure required for their have also been prepared (Scheme 2).
preparation.[12–14] In contrast, more attention has been paid
to 3,5-disubstituted 2-(2Ј-pyridyl)pyrroles,[15–24] which can
Results and Discussion
be synthesized by simple reactions between 2-picolylamine
and the appropriate 2,4-diketones.[25]
Synthesis
The 3,5-disubstituted 2-(2Ј-pyridyl)pyrroles considered in
this study contain methyl or phenyl groups in the 3- and 5-
positions (HLa and HLb, respectively, in Scheme 1), which
allows identification of the electronic and/or steric effects
exerted by the different substituents either on the cyclopal-
ladation process or on the derivatives deriving from the sub-
sequent reactions involving the cyclometallated 3,5-disub-
stituted 2-(2Ј-pyridyl)pyrrole intermediates.
The aim of this investigation was to evaluate the chemis-
try of 3,5-disubstituted 2-(2Ј-pyridyl)pyrroles containing
methyl or phenyl groups according to the following points:
1) cyclopalladation, 2) the reactivity of the resulting cyclo-
Compounds 5[10] and 6[11] were prepared according to
the two-step synthetic procedures reported in the literature,
which first required the formation of the dinuclear acetato-
bridged cyclopalladated precursor [(Lc)Pd(μ-OAc)]2 fol-
lowed by the bridge-splitting reaction with a suitable ancil-
lary ligand.[3] A similar protocol was adopted for the prepa-
ration of the [(La)Pd(μ-OAc)]2 (I)[23] and [(Lb)Pd(μ-OAc)]2
(II) acetato-bridged intermediates. Although the [(Lc)Pd(μ-
OAc)]2 precursor was prepared in acetic acid at 50 °C,
milder conditions and shorter reaction times were employed
in the synthesis of I and II with HLa,b ligands. In particular,
the reaction was carried out in dichloromethane at room
temperature to yield the desired products in good yields.
The new complexes 1–4 were prepared from I or II by a
base-assisted bridge-splitting reaction with HQui or HAcr
(Scheme 3). Complexes 1–4 were fully characterized by IR
1
and H NMR spectroscopy and elemental analysis, which
confirmed the expected compositions (see the Exptl. Sect.).
The elemental analyses properly account for the expected
stoichiometry, whereas the FTIR spectra of 1–4 each show
a strong band at about 1600 cm–1, absent in the spectra of
HLa and HLb, in the region of C=N and C=C signals, a
Scheme 2. Structures of the PdII complexes 5 and 6.
Scheme 3. Synthesis of complexes 1–4. Reagents and conditions: (i) PdII acetate, CH2Cl2, 25 °C, 2 h; (ii) 8-hydroxyquinoline, Na2CO3,
EtOH, 25 °C, 12 h; (iii) 4-hydroxyacridine, Na2CO3, EtOH, 25 °C, 12 h.
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characteristic of cyclometallated bonding. Moreover, for 1
and 3, the medium band that appears at around 2924 cm–1
is attributable to the stretching of the methyl groups on the
La moiety. Finally, the absence of OH stretching, present in
IR spectra of HQui and HAcr at about 3300 cm–1, confirms
the coordination of the ancillary ligands.
In principle, all the complexes can exist as two isomers,
∧
∧
depending on the relative positions of the N N/N O (1–4)
∧
∧
or C N/N O (5 and 6) chelating rings. However, in all
cases, the presence of only one isomer was confirmed by 1H
NMR spectroscopy performed on products isolated from
reactions. The signals were assigned by comparison with the
spectra of the corresponding precursors. In particular, as a
general trend, the protons of 1 and 2 have lower chemical
shifts with respect to the free HQui ligand, whereas in 3
and 4 the signals of the protons shift to higher values with
respect to the free HAcr ligand.
Figure 1. Absorption and emission spectra of 5 and 6 in CH2Cl2
at room temperature.
Photophysical Characterization
The photophysical properties of complexes 1–6 were ex-
amined in CH2Cl2 at room temperature (Table 1).
Table 1. Photophysical data in CH2Cl2 solution at room tempera-
ture.
λabs [nm]
λem [nm]
Φ [%]
1
240, 275, 340, 422
no
no
no
no
540
675
no
no
no
no
0.60
1.9
2
240, 275, 340, 400, 505(sh)
300, 330, 370(sh), 410, 525
300, 330, 365(sh), 410, 525
263, 290, 320, 340, 434
300, 350(sh), 530
3
4
5[a]
6
Figure 2. Absorption spectra of complexes 1–4 in CH2Cl2 at room
temperature.
[a] Data taken from ref.[10]
.
As previously reported,[10] the absorption spectrum of 5
(Figure 1) shows two main bands at 263 and 434 nm, and stitution of La by Lb. The band attributed to the N N li-
The spectrum of 2 (Figure 2) shows the effect of the sub-
∧
a series of shoulders, typical of the Lc (263, 290 and gand is redshifted with respect to the spectrum of 1 (see
320 nm)[26,27]
and
Qui
(263,
340
and also the absorption spectra of the pure ligands HLa and
434 nm)[28–30] ligands. In particular, the HOMO–LUMO HLc in Figure S1 in the Supporting Information), causing
transition originates the 434 nm band due to an intraligand the appearance of a low-intensity band at 505 nm, whereas
charge transfer (ILCT) involving the two aromatic rings of the Qui bands are slightly blueshifted.
Qui. The replacement of HQui with HAcr in 6 does not
The spectrum of 4 (Figure 2), in comparison with that of
appreciably modify the spectral shape with respect to 5, 3, shows the superimposition of the low-energy bands of
merely producing a redshift in the absorption bands attrib- the Lc- and Acr-localized transitions, which results in an
∧
uted to the N O ligand (i.e., 300, 350 and 530 nm) due to enlarged band at about 525 nm, whereas the other transi-
the extended aromatic delocalization (Figure 1). The ab- tion remained the same.
sorption spectrum of 1 (Figure 2) shows two relatively in-
The PhPy-containing complexes, that is, 5 and 6, show
tense bands, at 340 and 422 nm, plus a band at 275 nm. By an emission peak centred at 540[10] and 675 nm, respectively
comparison with the spectrum of 5, it is possible to attri- (Table 1 and Figure 1). In 1–4, in which the cyclometallat-
bute the first two bands to the superimposition of La- and ing HLc is replaced by HLa,b, no emission was detected un-
Qui-localized transitions, whereas the band at 275 nm is due der the same conditions, although the HLa and HLb free
to a π–π* transition in the phenyl ring of Qui.
ligands are emissive. The luminescence of 5 and 6 can be
In the spectrum of 3 (Figure 2), the bands due to the attributed to the deactivation of the ILCT state localized on
∧
∧
transition localized on the N O ligand are redshifted (370 the N O ligand. In the other complexes, the pyridylpyrrole-
∧
and 525 nm) with respect to 1 due to the more extended centred states match those localized on the N O ligand,
aromatic delocalization of Acr compared with Qui.
most likely causing emission quenching.
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Structural Analysis
complexes were observed depending on both the cyclo-
metallating and ancillary ligands. Because HLc is exten-
sively used in the synthesis of cyclopalladated derivatives, a
survey of the Cambridge Structural Database (CSD) v. 5.29
(update to October 2012) demonstrates the prevalence of
Single crystals of 1, 4, 5 and 6 were obtained from a
dichloromethane solution of each compound kept in a satu-
rated atmosphere of cyclohexane vapour, used as non-sol-
vent. Because the crystals of 6 were of poor quality, the
collected X-ray data were only sufficient for a raw structure
determination, precluding any further refinement of the
model and, consequently, detailed discussion.
The asymmetric units of 1, 4 and 5 are made up of a
single monomeric complex, as shown in Figure 3. The PdII
is located in a slightly (1 and 5) or highly (4) distorted
∧
∧
the trans-(N,N) arrangement in similar C N/N O systems
containing HLc as the cyclometallated ligand. Accordingly,
in 5, the N(2) atom of the Qui ancillary ligand is bound
trans to the N(1) atom of the phenyl ring of the HLc ligand
(Figure 3). The slight elongation of the Pd(1)–O(1) bond
length [2.09(2) Å] confirms the trans influence of the cyclo-
metallated carbon atom, as has been observed in other sim-
ilar complexes.[31] In contrast, the raw structure determi-
nation (see Figure S2 in the Supporting Information) of 6,
in which the Qui ligand has been replaced by Acr, reveals a
∧
square-planar environment defined by the substituted N N
∧
∧
(1 and 4) or C N (5) ligands and the chelating N O ancil-
lary ligands. A greater degree of distortion from planarity
of the coordination geometry around the PdII metal centre
is observed in 4 [minimum and maximum deviations from
the mean plane of 0.148(1) Å for N(3) and 0.177(1) Å for
N(1), respectively, with the PdII atom lying in the plane],
and is most likely due to the steric effects exerted by the
bulky phenyl substituent groups present on the Lb ligand.
Although the PdNNCC (1)/PdNCCC (5) and PdNCCO
five-membered rings, defined by the coordinated ligands at
the Pd metal centre, are almost planar in 1 and 5, a con-
siderable deviation from planarity is observed in 4 [maxi-
mum deviations of 0.103(1) Å at N(2) and 0.117(1) Å at
O(1) for the Pd(1)N(1)N(2)C(5)C(6) and Pd(1)N(3)C(22)
C(27)O(1) rings, respectively]. Moreover, the dihedral angle
in 4 between the two chelated rings of 16.0(1)° proves the
severe distortion due to the bulky phenyl substituent groups
present on the Lb ligand in comparison with the analogous
values found in 1 and 5 of 1.9(1) and 2.9(1)°, respectively.
∧
∧
cis-(N,N) arrangement of the C N/N O system. Even if
the low quality of the collected X-ray data of 6 precludes
any further discussion, literature data seems to corroborate
the structure of 6. Indeed, an analogous cis-(N,N) isomer
has recently been described for a PdII cyclometallated com-
plex containing a substituted Lc ligand and Acr as the ancil-
lary ligand.[11] When the cyclopalladated HLc ligand is sub-
stituted by HLa,b and therefore the coordinated carbon
atom is replaced by the nitrogen donor atom of the pyrrolic
ring, the opposite isomer is isolated. Indeed, the X-ray
structural determination reveals a cis-(N,N) disposition in
1 and an inversion of the arrangement when the Qui ligand
is replaced by Acr [trans-(N,N) in 4]. Moreover, the slightly
reduced elongation of the Pd(1)–O(1) bond [1.999(2) Å] in
4 suggests a less pronounced trans influence of the pyrrolic
nitrogen atom compared with the cyclometallated carbon
atom. Even if it is difficult to provide an unequivocal expla-
nation for the formation of a specific isomer in the solid
state, the structures of 1, 4, 5 and 6 suggest a possible de-
pendence of the N,N arrangement on either the specific
pyridylpyrrole and the ancillary ligand. On this basis, we
can hypothesize that the ancillary ligand could play a pre-
dominant role in the formation of the trans/cis isomers in
these systems and that the pyridylpyrrole definitely pro-
duces opposite outcomes to those with the 2-phenylpyridine
ligand.
The three PdII derivatives 1, 4 and 5 display crystal pack-
ing in which the molecules stack with plane-to-plane dis-
tances compatible with π···π interactions (3.3–3.8 Å). In 1
and 5, the molecules stack to form a 1D motif along the a
crystallographic direction (Figure 4). In 1, three successive
molecules stack with different interplanar distances and de-
gree of overlap. In particular, the shortest distances are ob-
served between pairs of molecules; the PdNCCO five-mem-
bered rings establish aromatic interactions with the phenyl
ring of the La ligand [distance between centroids of
3.457(2) Å; Figure 4]. A weaker interaction is present be-
tween the PdNCCO five-membered rings of complexes of
Figure 3. Asymmetric units of 1, 4 and 5 showing the atomic num-
bering scheme.
As already pointed out, the new complexes can exist as consecutive dimers [distance between centroids of
two isomers, depending on the relative positions of the 3.704(2) Å]. In 5, the PdNCCC and PdNCCO five-mem-
∧
∧
∧
∧
N N/N O (for 1–4) or C N/N O (for 5 and 6) chelating bered rings of neighbouring molecules are involved in the
rings. However, in all cases, only one isomer was isolated in shortest aromatic interactions [distance between the
the crystalline solid state, and different isomers for different centroid of 3.482(2) Å; Figure 4]. Although the PdII metal
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∧
∧
centres are uniformly separated in 5 [distance of 5.457 Å], arrangement of the C N/N O chelating system has also
shorter (3.479 Å) and longer (4.814 Å) Pd···Pd distances recently been described for a PdII complex containing a
alternate along the chain in 1.
substituted 2-phenylpyridine as the cyclometallated ligand
and Acr as co-ligand.[11] Significantly, the opposite arrange-
ment was observed in the Lb derivatives containing Qui (2)
or Acr (4). Indeed, if we compare the nitrogen donor atom
of the pyrrolic ring of the Lb ligand to the carbon atom of
Lc, the cis-(N,N) and trans-(N,N) dispositions are observed
in 1 and 4, respectively. Moreover, the slightly reduced
elongation of the metal-to-ligand bond trans to the pyrrolic
nitrogen atom suggests a less pronounced trans influence of
the pyrrolic nitrogen atom with respect to the cyclometall-
ated carbon atom. Even if is difficult to provide an unequiv-
ocal explanation for the formation of specific isomers in the
solid state, the structures of 1, 4 and 5 suggests a possible
dependence of the N,N arrangement on either Lb or Lc and
the ancillary ligands, the effect produced by the pyridylpyr-
roles being definitely opposite to that of the 2-phenylpyr-
idine ligand.
Finally, the photophysical properties of 1–4 have been
studied in solution. Although 5 and 6 are emissive in solu-
tion,[10] no emission was detected for 1–4 under the same
conditions. As previously reported,[10] the luminescence of
5 and 6 can be attributed to the deactivation of the ILCT
Figure 4. Molecular packing diagrams of 1 and 5.
∧
In 4, the stacking interactions, frustrated by the presence
of the bulky phenyl substituents, are limited to two mole-
cules (Figure 5), aromatic interactions occurring between
the phenyl rings of the Lc ligands [distance between the
centroids of the N(1)C(5) rings of 3.860(3) Å]. The shortest
Pd···Pd distance is 6.015 Å.
state localized on the N O ligand. In 1–4, the pyridylpyr-
∧
role-centred states match those localized on the N O li-
gands, most likely causing the emission quenching.
Experimental Section
Materials and Methods: PdII acetate, HQui, HAcr and solvents
were used as supplied from Sigma–Aldrich. Compounds HLa,[25]
HLb,[25] [(La)Pd(μ-OAc)]2 (I),[23] [(Lc)Pd(Qui)] (1)[10] and [(Lc)-
Pd(Acr)] (2)[11] were prepared following literature methods. The
thermal behaviour was monitored with a Zeiss Axioscope polariz-
ing microscope equipped with a Linkam CO 600 heating stage.
Elemental analyses were performed with a Perkin–Elmer 2400
CHNS/O analyser. FTIR spectra were recorded with a Perkin–El-
1
mer Spectrum 100 FTIR spectrometer. H NMR spectra were re-
corded with a Bruker WM-300 spectrometer in CDCl3 solution
with Me4Si as internal standard. UV/Vis absorption spectra were
recorded with a Perkin–Elmer Lambda 900 spectrophotometer and
the emission spectra (all confirmed by the excitation spectra) with
a Perkin–Elmer LS-50B fluorimeter. Luminescence quantum yields
were determined by using the optical dilution method[32] with [Ru(-
bipy)3]-
Cl2 (bipy = 2,2Ј-bipyridine; Φ = 0.028 in aerated aqueous solu-
tion[33]) as the standard. Experimental errors are as follows: absorp-
tion and emission maxima, Ϯ2 nm; molar absorption coefficients,
10%; luminescence quantum yields, 20%.
Figure 5. Aromatic interactions between pairs of molecules in 4.
Conclusions
Four new PdII complexes of general formula [(La)-
Pd(Qui)] (1), [(Lb)Pd(Qui)] (2), [(La)Pd(Acr)] (3) and [(Lb)-
Pd(Acr)] (4) containing methyl (1, 3) or phenyl (2, 4) 3,5-
substututed 2-(2Ј-pyridyl)pyrroles ligands have been synthe-
sized and characterized. Moreover, for comparative pur-
poses, [(Lc)Pd(Qui)] (5) and [(Lc)Pd(Acr)] (6) have also been
prepared.
Syntheses
[(Lb)Pd(μ-OAc)]2 (II): The product was obtained as an orange solid
by a procedure similar to that previously used for the preparation
of I.[23] Yield: 60% (0.10 g), m.p. 280 °C (decomp.). FTIR (KBr):
The crystal structures of 1, 4 and 5 were determined by
single-crystal X-ray diffraction studies. The usual trans-
ν
max = 1602 (s), 1561 (s), 1491 (s), 1431 (m), 761 (s), 697 (m) cm–1.
˜
∧
∧
(N,N) arrangement was observed in the C N/N O system
of 5 containing Qui as the ancillary ligand. It is noteworthy
that the opposite cis-(N,N) geometry is present in 6 in
1H NMR (300 MHz, CDCl3): δ = 8.38 (d, 2 H, 6Ј-H), 8.23 (d, 4
H, Ph-H), 7.96 (d, 4 H, Ph-H), 7.58–7.05 (12 H, overlapped peaks,
Ph-H), 6.93 (d, 2 H, 3-H), 6.76 (t, 2 H, 4Ј-H), 6.53 (s, 2 H, 4-H),
which the Acr replaces the Qui ligand. The same cis-(N,N) 5.94 (t, 2 H, 5Ј-H), 2.09 (s, 6 H, CH3) ppm. C46H36N4O4Pd2
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(921.64): calcd. C 59.95, H 3.94, N 6.08; found C 60.21, H 4.30, N
5.93.
Table 2. Details of data collection and structure refinements for 1a,
4b and 5c.
Complexes 1–4 were prepared in a similar manner by using the
appropriate complex I or II and HQui or HAcr. A typical prepara-
tion is reported for complex 1.
Compound
1
4
5
Formula
Mr
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C20H17N3OPd C34H23N3OPd C20H14N2OPd
421.77
monoclinic
P21/n
7.6366(10)
18.261(2)
12.2581(16)
90
103.253(6)
90
1663.9(4)
4
1.684
1.128
2.04–28.28
33425
4124, 0.0448
226
595.95
monoclinic
P21/n
10.496(6)
12.578(7)
19.561(11)
90
92.96(3)°
90
2579(2)
4
1.535
0.753
1.93–28.23
38836
6366, 0.0665
352
404.73
orthorhombic
P212121
5.4510(18)
10.460(3)
26.045(9)
90
90
90
1485.1(9)
4
1.810
1.258
1.56–32.78
33749
5360, 0.0483
217
0.0310
0.0530
1.023
[(La)Pd(Qui)] (1): HQui (0.05 g, 0.32 mmol) with an excess of
Na2CO3 (0.25 g, 2.36 mmol) was added to a suspension of I (0.10 g,
0.15 mmol) in EtOH. After stirring the reaction mixture at room
temperature for 12 h, the brown precipitate formed was filtered off
and washed with EtOH and H2O. The pure product was obtained
as an orange solid after recrystallization from CHCl3/cyclohexane,
α [°]
β [°]
γ [°]
yield 60% (0.04 g), m.p. 191 °C. FTIR (KBr): ν
= 2924 (m),
˜
max
V [Å3]
1602 (s), 1574 (s), 1491 (s), 1381 (s), 1321 (s), 1109 (s), 759 (s) cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.35 (d, 1 H, a-H), 8.10 (d, 1 H,
6Ј-H), 7.57 (t, 1 H, 4Ј-H), 7.33 (m, 2 H, c,b-H), 7.21 (m, 2 H, d,e-
H), 6.97 (d, 1 H, f-H), 6.85 (d, 1 H, 3Ј-H), 6.71 (t, 1 H, 5Ј-H),
5.76 (s, 1 H, 4-H), 2.98 (s, 3 H, CH3), 2.41 (s, 3 H, CH3) ppm.
C20H17N3OPd (421.79): calcd. C 56.95, H 4.06, N 9.96; found C
56.93, H 4.02, N 9.94.
Z
ρcalcd [gcm–3]
μ [mm–1]
θ range [°]
Data collected
Unique data, Rint
Parameters
R1 [obsd. data]
wR2 [all data]
GOF
0.0314
0.0636
1.029
0.0346
0.0756
1.052
[(Lb)Pd(Acr)] (2): Yellow solid, yield 88% (0.10 g), m.p. 241 °C.
FTIR (KBr): ν
= 1741 (w), 1599 (m), 1560 (s), 1499 (s), 1466
˜
max
(s), 1318 (m), 1114 (w), 762 (s) cm–1. H NMR (CDCl3): δ = 8.54
(d, 1 H, a-H), 8.30 (d, 1 H, 6Ј-H), 7.97 (d, 1 H, c-H), 7.87 (d, 1 H,
3Ј-H), 7.60–7.00 (13 H, overlapped peaks, 4Ј,d,f-H), 6.90 (t, 1 H,
e-H), 6.65 (t, 1 H, b-H), 6.52 (t, 1 H, 5Ј-H), 5.68 (s, 1 H, 4-H) ppm.
C30H21N3OPd (545.93): calcd. C 66.00, H 3.88, N 7.70; found C
65.98, H 3.87, N 7.67.
1
Table 3. Selected bond lengths [Å] and angles [°] for complexes 1,
4 and 5.
1
4
[(La)Pd(Acr)] (3): Violet solid, yield 57% (0.04 g), m.p. 206 °C.
Pd(1)–N(1)
Pd(1)–N(2)
Pd(1)–N(3)
Pd(1)–O(1)
N(1)–Pd(1)–N(3)
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(3)–Pd(1)–N(2)
N(3)–Pd(1)–O(1)
N(2)–Pd(1)–O(1)
2.048(2)
1.988(2)
2.083(2)
1.9817(19)
105.41(9)
80.29(9)
172.64(9)
174.09(9)
81.82(9)
92.45(9)
2.005(2)
2.044(2)
2.064(2)
1.9987(19)
168.09(8)
79.52(9)
91.90(9)
109.08(9)
81.05(9)
166.49(8)
FTIR (KBr): νmax = 2926 (m), 1602 (s), 1542 (s), 1519 (s), 1488 (s),
˜
1
1462 (s), 1394 (m), 1328 (m), 1273 (m), 1156 (m), 762 (s) cm–1. H
NMR (CDCl3): δ = 8.85 (s, 1 H, e-H), 8.45 (m, 2 H, 6Ј-H, a-H),
7.90 (d, 1 H, d-H), 7.65–7.20 (5 H, overlapped peaks, Ph-H,
4Ј,b,c,f,g-H), 7.14 (d, 1 H, 3Ј-H), 7.05 (d, 1 H, h-H), 6.77 (t, 1 H, 5Ј-
H), 5.78 (s, 1 H, 4-H), 2.50 (s, 3 H, CH3), 2.40 (s, 3 H, CH3) ppm.
C24H19N3OPd (471.85): calcd. C 61.09, H 4.06, N 8.91; found C
61.10, H 4.08, N 8.93.
[(Lb)Pd(Acr)] (4): Orange solid, yield 60% (0.08 g), m.p. 236 °C
5
(partial decomp.). FTIR (KBr): ν
= 1598 (m), 1520 (m), 1489
˜
max
Pd(1)–N(1)
Pd(1)–C(7)
Pd(1)–N(2)
Pd(1)–O(1)
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–C(7)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–C(7)
N(2)–Pd(1)–O(1)
C(7)–Pd(1)–O(1)
2.011(2)
2.001(2)
2.064(2)
2.0894(19)
173.48(8)
80.90(9)
93.36(8)
105.08(9)
80.69(8)
174.20(9)
(m), 1465 (s), 1395 (m), 1271 (m), 1159 (m), 761 (s) cm–1. 1H NMR
(CDCl3): δ = 8.53 (s, 1 H, e-H), 8.51 (d, 1 H, a-H), 7.99 (d, 1 H,
6Ј-H), 7.65–7.13 (17 H, overlapped peaks, Ph-H, 3Ј,4Ј,b,c,d,f,g-H),
7.08 (d, 1 H, h-H), 6.85 (t, 1 H, 5Ј-H), 6.43 (s, 1 H, 4-H) ppm.
C34H23N3OPd (595.99): calcd. C 68.52, H 3.89, N 7.05; found C
68.49, H 3.86, N 7.03.
X-ray Crystallography: Single-crystal XRD data for 1, 4 and 5 were
collected at room temperature with a Bruker–Nonius X8APEXII
CCD area detector system equipped with a graphite monochroma-
tor with radiation Mo-Kα (λ = 0.71073 Å). Different sets of data
were recorded and solved to verify the repeatability of the crystalli-
zation, however, only the best data are reported herein. The data
were processed through the SAINT[34] reduction and SADABS[35]
absorption software. The structures were solved by direct methods
by using the SHELXTL-NT[36] structure determination package
and refined by full-matrix least-squares methods based on F2. In
general, all non-hydrogen atoms were refined anisotropically and
hydrogen atoms were included as idealized riding atoms. The final
geometrical calculations and the graphical manipulations were car-
ried out by using the XP utility of the SHELXTL system and DIA-
MOND program.[37] Cell parameters and final refinement data are
given in Table 2. Selected interatomic bond lengths and angles are
given in Table 3.
In the case of 6, only the unit cell parameters are reported (see the
Supporting Information). Unfortunately, the poor crystal quality
of 6 (completeness of 99.8% per 2θ of 44.4°) together with the low
quality of the collected X-ray data (Rint = 0.16 per 2294 unique
reflections), make its structure unpublishable. However, even if the
poor X-ray data precludes further discussion, the raw structure of
6, obtained from an initial structural determination, reveal a cis-
∧
∧
(N,N) arrangement of the C N/N O system.
CCDC-907952 (for 1), -907953 (for 4) and -907954 (for 5) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Eur. J. Inorg. Chem. 0000, 0–0
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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/KAP1
Date: 08-02-13 11:10:11
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FULL PAPER
[17] A. T. Luedtke, K. I. Goldberg, Inorg. Chem. 2007, 46, 8496–
8498.
[18] P.-I. Shih, C. H. Chien, C. Y. Chuang, C. F. Shu, C. H. Yang,
J. H. Chen, Y. Chi, J. Mater. Chem. 2007, 17, 1692–1698.
[19] J.-L. Chen, C.-H. Lin, J.-H. Chen, Y. Chi, Y.-C. Chiu, P.-T.
Chou, C.-H. Lai, G.-H. Lee, A. J. Carty, Inorg. Chem. 2008,
47, 5154–5161.
Supporting Information (see footnote on the first page of this arti-
cle): Absorption spectra of the HLa and HLb ligands, cell param-
eters and asymmetric unit of 6.
Acknowledgments
[20] A. T. Luedtke, K. I. Goldberg, Angew. Chem. 2008, 120, 7808;
The work was supported by the Ministero dell’Istruzione, dell’Uni-
versità e della Ricerca (MIUR) through the Progetti di Ricerca di
Interesse Nazionale (PRIN 2007 - 2007WJMF2W). I. A. thanks
Alessia Aprea for help in the synthesis.
Angew. Chem. Int. Ed. 2008, 47, 7694–7696.
[21] J. L. McBee, J. Escalada, T. D. Tilley, J. Am. Chem. Soc. 2009,
131, 12703–12713.
[22] J. L. McBee, T. D. Tilley, Organometallics 2009, 28, 3947–3952.
[23] D. Pucci, I. Aiello, A. Aprea, A. Bellusci, A. Crispini, M.
Ghedini, Chem. Commun. 2009, 1550–1552.
[1] J. Dupont, C. S. Consorti, J. Spencer, Chem. Rev. 2005, 105,
2527–2572.
[2] M. Ghedini, I. Aiello, A. Crispini, A. Golemme, M. La Deda,
D. Pucci, Coord. Chem. Rev. 2006, 250, 1373–1390.
[3] J. Dupont, M. Pfeffer (Eds.), Palladacycles, Wiley-VCH,
Weinheim, Germany, 2008.
[4] Y. Chi, P.-T. Chou, Chem. Soc. Rev. 2007, 36, 1421–1431.
[5] D. Kumarresan, K. Shankar, S. Vaidya, R. H. Schmehl, Top.
Curr. Chem. 2007, 281, 101–142.
[6] W.-Y. Wong, C.-l. Ho, J. Mater. Chem. 2009, 19, 4457–4482.
[7] L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura, F. Barigel-
letti, Top. Curr. Chem. 2007, 281, 143–203.
[24] J. G. Andino, J. A. Flores, J. A. Karty, J. P. Massa, H. Park,
N. P. Tsvetkov, R. J. Wolfe, K. G. Caulton, Inorg. Chem. 2010,
49, 7626–76298.
[25] J. J. Klappa, A. E. Rich, K. McNeill, Org. Lett. 2002, 4, 435–
437.
[26] I. Aiello, M. Ghedini, M. La Deda, J. Lumin. 2002, 96, 249–
259.
[27] C. A. Craig, R. J. Watts, Inorg. Chem. 1989, 28, 309–313.
[28] W. E. Ohnesorge, L. B. Rogers, Spectrochim. Acta 1959, 14, 27–
40.
[29] H. Yersin, D. Donges, J. K. Nagle, R. Sitters, M. Glasbeek,
Inorg. Chem. 2000, 39, 770–777.
[8] J. A. G. Williams, Top. Curr. Chem. 2007, 281, 205–268.
[9] F. Neve, in: Palladacycles (Eds.: J. Dupont, M. Pfeffer), Wiley-
VCH, Weinheim, Germany, 2008, pp. 285–389.
[10] M. Ghedini, I. Aiello, M. La Deda, A. Grisolia, Chem. Com-
mun. 2003, 2198–2199.
[11] D. Pucci, V. Albertini, R. Bloise, A. Bellusci, A. Cataldi, C. V.
Catapano, M. Ghedini, A. Crispini, J. Inorg. Biochem. 2006,
100, 1575–1578.
[30] a) A. S. Bailey, R. J. P. Williams, J. D. Wright, J. Chem. Soc.
1965, 2579–2587; b) M. Goldman, E. L. Wehry, Anal. Chem.
1970, 42, 1178–1185; c) E. Bardez, A. Chatelain, B. Larrey, B.
Valeur, J. Phys. Chem. 1994, 98, 2357–2366.
[31] J. L. Serrano, L. Garcia, J. Perez, E. Perez, J. Garcia, G. San-
chez, G. Lopez, M. Liu, Eur. J. Inorg. Chem. 2008, 4797–4806.
[32] J. N. Demas, G. A. Crosby, J. Phys. Chem. 1971, 75, 991–1024.
[33] K. Nakamaru, Bull. Chem. Soc. Jpn. 1982, 55, 2697–2705.
[34] SAINT, v. 6.45, Bruker AXS Inc., Madison, WI, USA, 2003.
[35] G. M. Sheldrick, SADABS, v. 2.10, Bruker AXS Inc., Madison,
WI, USA, 2003.
[12] J. Firl, Chem. Ber. 1968, 101, 218.
[13] K. Seki, K. Ohkura, M. Terishima, Heterocycles 1984, 22,
2347–2350.
[14] W. E. Noland, K. P. Cole, D. Britton, Acta Crystallogr. Sect.
C: Cryst. Struct. Commun. 2003, 59, o263–o267.
[15] J. J. Klappa, S. A. Geers, S. J. Schmidtke, L. A. MacManus-
Spencer, K. McNeill, Dalton Trans. 2004, 883–891.
[16] S. Schouteeten, O. R. Allen, A. D. Haley, G. L. Ong, G. D.
Jones, D. A. Vicic, J. Organomet. Chem. 2006, 691, 4975–4981.
[36] G. M. Sheldrick, SHELXTL-NT, v. 5.1, Bruker AXS Inc.,
Madison, WI, USA, 1999.
[37] DIAMOND, v. 3.1b, Crystal Impact GbR, Brandeburg & H.
Putz GBR, Bonn, Germany, 2006.
Received: November 5, 2012
Published Online: ᭿
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I21341
/KAP1
Date: 08-02-13 11:10:11
Pages: 8
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FULL PAPER
Cyclopalladated Complexes
T. F. Mastropietro, E. I. Szerb,
M. La Deda, A. Crispini, M. Ghedini,
I. Aiello* ........................................... 1–8
Cyclopalladated 3,5-Disubstituted 2-(2Ј-
Pyridyl)pyrroles Complexed to 8-Hydroxy-
quinoline or 4-Hydroxyacridine
Keywords: Palladium / N,O ligands / N,N
ligands / Ligand effects / Luminescence
New cyclopalladated complexes with 3,5-
disubstituted 2-(2Ј-pyridyl)pyrroles and 4-
hydroxyquinoline or 4-hydroxyquinoline as
ancillary ligands have been prepared and
characterized by single-crystal X-ray dif-
fraction analysis and UV/Vis spectrophoto-
metry.
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim