Synthesis, Characterization, Electrochemical, and Optic Limiting Properties of Novel CoII, CuII, and Double-Decker LuII Phthalocyanines

Article abstract of DOI:10.1002/ejic.200801174

The synthesis, spectroscopic, electrochemical, and optical properties of tetrasubstituted Co^II, Cu^II, and double-decker Lu ^III phthalocyanines are reported. The new compounds were characterized by elemental analysis, IR an

Full text of DOI:10.1002/ejic.200801174

FULL PAPER
DOI: 10.1002/ejic.200801174
Synthesis, Characterization, Electrochemical, and Optic Limiting Properties of
Novel CoII, CuII, and Double-Decker LuIII Phthalocyanines
Sinan Saydam,[a] Engin Yılmaz,[a] Fulya Bag˘cı,[b] H. Gül Yag˘lıog˘lu,[b] Ayhan Elmalı,[b]
Bekir Salih,[c] and Özer Bekarog˘lu*[d]
Keywords: Phthalocyanines / Sandwich complexes / Electrochemistry / Nonlinear optics / Rare earths
The synthesis, spectroscopic, electrochemical, and optical
properties of tetrasubstituted CoII, CuII, and double-decker
LuIII phthalocyanines are reported. The new compounds
were characterized by elemental analysis, IR and UV/Vis
spectroscopy, and MALDI TOF mass spectrometry. Their
electrochemistry was studied by cyclic voltammetry and
Z-scan technique. Whereas 6 and 7 showed good nonlinear
absorption, 5 did not. Optical limiting parameters of the ratio
of the excited state to the ground state absorption cross sec-
tions κ, the effective nonlinear absorption coefficient βeff, the
linear absorption coefficient α0, limiting threshold Fth, and
the saturation density or energy density Fsat values were de-
Osteryoung square-wave voltammetry in nonaqueous me- termined for 6 and 7. The results indicated that both com-
dium. Nonlinear absorption and optical limiting performance
of peripheral-substituted (C30H28N30)4Co (5), (C30H28N30)4-
Cu (6), and [(C30H28N30)4]2Lu (7) were investigated by the
pounds exhibited good optical limiting performances.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
tate the formation of various mesophase supramolecular
structures.
Introduction
Rare-earth diphthalocyanines, especially the lutetium de-
rivative, have become objects of intense investigation.[1–4]
Owing to the characteristic overlapping of the ligand π or-
bitals of rare-earth diphthalocyanine compounds, these
compounds possess a wide range of unique properties,
which makes them suitable for a variety of applications.[5,6]
Many of these applications depend on the nature of the
metal ion incorporated at the center of the phthalocyanin-
ato ring as well as the substituents on the macrocycle. The
characteristics of sandwich complexes are largely related to
the properties of the individual molecules. Various modifi-
cations have been made on these compounds with the goal
of improving their properties as advanced materials. Long
alkyl side chains[7–9] and crown ether[10,11] units are two
As a result of the intermolecular interaction between the
macrocycles, peripherally unsubstituted metal phthalocyan-
ines are practically insoluble in common organic solvents,
which therefore minimizes their applications. The solubility
of phthalocyanines can be improved by introduction of sub-
stituents on the peripheral and nonperipheral sites of the
phthalocyanine ring.
Although there are several ways to synthesize bis(phthalo-
cyaninato)lanthanide complexes, common features include
the relatively high temperatures and long reaction times re-
quired in comparison to monomeric phthalocyanines.[4] Re-
cently, Pushkarev and co-workers[2] suggested a new synthe-
sis method for the preparation of heteroleptic bis- and
tris(phthalocyanine) compounds in high yields. These com-
plexes display unique physical, spectroscopic, and electro-
chemical properties. Among these, bis(phthalocyaninato)lu-
tetium complexes have especially generated a great deal of
interest due to their potential use as electrochromic materi-
als[12–14] and due to their intrinsic conductivity[15] and op-
tical nonlinearity;[16–19] these materials may also be used as
gas sensors[20,21] and field-effect transistors (FETs), and in
display technologies.[22,23]
common functionalities added to the macrocycles to facili-
[a] Fırat University, Faculty of Science and Arts, Department of
Chemistry,
Elazıg˘, Turkey
Fax: +90-424-2330062
[b] Department of Engineering Physics, Faculty of Engineering,
Ankara University,
Ankara, Turkey
Fax: +90-312-2127343
Among the nonlinear optical applications of phthalocy-
anines, their optical limiting (OL) performance is the most
promising.[24,25] The phenomenon of optical limiting is
based on attenuating the light beam when it exceeds a
threshold value and transmitting the ambient light with low
absorption. Optically sensitive elements, especially the hu-
man eye, are hence protected. Optical limiting based on re-
[c] Hacettepe University, Faculty of Science and arts, Department
of Chemistry,
Ankara, Turkey
Fax: +90-312-2992163
[d] Istanbul Technical University, Faculty of Science and Arts, De-
partment of Chemistry,
Maslak, Istanbul, Turkey
Fax: +90-216-216-3860824
E-mail: obek@itu.edu.tr
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Novel CoII, CuII, and Double-Decker LuIII Phthalocyanines
verse saturable absorption in phthalocyanines has been
largely reported in the literature both on the nanosecond
and picosecond time scales at a wavelength of 532 nm.[26–29]
The excellent properties of metal phthalocyanines (MPcs)
as candidates for optical limiting applications originated
not only from their extensive π-electron delocalization and
their thermal and chemical stability, but also from their
processability either by substituting the peripheral or axial
side groups or by changing the central metal ion. A change
in the central metal atom in a Pc can lead to considerable
variation in the relevant nonlinear optical properties (NLO)
and OL properties.[24]
In this study, the synthesis, characterization, and optic
limiting properties of novel CoII (5), CuII (6), and double-
decker LuIII phthalocyanine (7) are reported. Whereas lute-
tium and copper phthalocyanine complexes exhibit the
largest nonlinear absorption, the cobalt phthalocyanine
compound showed very low nonlinear absorption.
Results and Discussion
Synthesis and Characterization
Starting from 1 and 2, compound 3 was obtained in 65%
yield by a base-catalyzed nucleophilic nitro group displace-
ment reaction. The reaction was carried out in a single step
by using K2CO3 as the nitro displacing base at 70–90 °C in
dry DMF under an argon atmosphere. The reaction of 3
with ammonia in methanol by the catalysis of sodium meth-
oxide at reflux temperature gave compound 4 in 90% yield.
Phthalocyanine complexes of 5 and 6 were prepared by the
general synthetic route given in Scheme 1. Bis(phthalocyan-
inato)lutetium(III) complex was prepared by the reaction
Scheme 1. (i) K2CO3, DMF, Ar; (ii) NH3, CH3ONa; (iii)
Co(CH3COO)2·4H2O, DMF, Ar; (iv) Cu(CH3COO)2·2H2O, DMF,
Ar; (v) Lu(CH3COO)3·H2O, DBU, octanol, Ar.
of 4 and lutetium(III)acetate monohydrate in octanol, cata- peared at 747 cm–1. The aromatic C-H bending vibrations
lyzed by DBU at elevated temperatures under an argon at- appeared at 1400 and 1273 cm–1. The band at 700 cm–1 was
mosphere for 12 h. The mixture was then precipitated in assigned to the C–C macrocycle ring deformation.[31] The
water (250 mL). Product 7 was obtained and isolated by 1H NMR spectra were also in good agreement with the syn-
column chromatography on silica gel (THF/methanol, 10:1) thesized compounds. The 1H NMR spectrum of compound
in 25% yield. Compounds 5, 6, and 7 are soluble in acetone, 3 has two singlet at 1.72 and 1.86 ppm, corresponding to
chloroform, DCM, THF, DMF, and DMSO.
two methyl groups each. The aromatic protons appeared
The spectroscopic characterization of newly synthesized between 6.76 and 7.84 ppm corresponding to 18 protons.
1
1
compounds performed by H NMR, IR, and UV/Vis spec- Compound 4 has a similar H NMR spectrum to that of 3
troscopy and mass spectrometry are in accordance with the except for the =NH protons, which appeared at 8.5 ppm as
proposed structures. The IR spectrum of 3 exhibits charac- a broad peak to confirm the presence of the =NH group.
teristic frequencies at 3110–3008 (Ar-H), 2900–2840 (CH3),
The UV/Vis spectra of 5 and 6 in THF displayed charac-
2226 (CϵN), 1594–1486 (C=C), 1250–1278 (Ar-O-C), and teristic absorption bands around 615 and 680 nm in the Q-
1495 and 1457 cm–1 (Ar-H). The absence of a nitrile peak band region (Figure 1). The Q-band was attributed to a
at 2226 cm–1 in 3 and the emergence of new peaks at 3500– πǞπ* transition from the highest occupied molecular or-
3200 (N-H) and 1650 cm–1 (=NH) are a good indication of bital (HOMO) to the lowest unoccupied molecular orbital
the formation of 4. The IR spectrum of 5 exhibit two bands (LUMO) of the phthalocyanine ring. The other band (B
at 3083 and 3053 cm–1 and are assigned to the symmetric band) in the UV region at 335 nm is due to the transition
and asymmetric stretching vibration of –CH in the aromatic from the deeper π levels to the LUMO.
ring, and those at 2965, 2927 and 2852, 2874 cm–1 are as-
Double-decker complexes are regarded as single-hole
signed to the symmetric and asymmetric stretching vi- complexes in which an unpaired electron is present in one
bration of alkyl –CH groups. The band appearing at of the macrocyclic ligands.[32,33] The UV/Vis spectra of 7
1601 cm–1 was assigned to the aromatic C=C stretching vi- taken in THF, showed the characteristic double-decker
bration and those at 1494 cm–1 to the stretching vibration phthalocyanine lutetium complex with the Q-band at
of C=N.[30] A peak for the substituted benzene ring ap- 684 nm and weak vibronic band at 615 nm that is responsi-
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topic peak distributions of the protonated molecular ions is
given as the inset spectrum in Figure 2.
Besides the protonated molecular ion peak of the com-
plexes, only very few peaks at low intensities were observed
as fragmented ions. However, the clean spectra showed the
high stability of these complexes under the laser shots and
mass spectrometric conditions and also the high purity of
the synthesized complexes.
Electrochemical Measurements
The voltammetric measurements of 5, 6, and 7 were car-
ried out on a glassy carbon (GC) electrode in DCM or
DMF, tetrabutylammonium tetrafluoroborate (TBATFB)
as supporting electrolyte by cyclic voltammetry (CV) and
Osteryoung square-wave voltammetry (SWV). The relevant
data are given in Table 1. All lanthanide bis(phthalocyan-
ine) complexes can undergo multiple reductions of the con-
jugated macrocycle. The electrochemical behavior of 5 was
investigated in DCM by CV and SWV. Compound 5
showed both oxidation and reductions waves labeled O1
and O2 and R1, R2, and R3 within the electrochemical win-
dow of DCM containing 0.1  TBATFB. All These pro-
cesses can be attributed to the successive addition and re-
moval of one electron to ligand-based orbitals of the bis-
(phthalocyaninato) complex.[36–38] The measured half-wave
redox potentials for 5 in DCM solution containing
TBATFB as the supporting electrolyte are listed in Table 1,
which also includes selected data from the literature for the
related compounds. Osteryoung SWV of 5 in the same me-
dium displayed oxidation and reduction potentials more
clearly. Three reductions waves labeled R1, R2, and R3,
E1/2 = –0.10, –1.30, and –1.70, with two oxidation waves
labeled O1 and O2, E1/2 = 0.32 and 0.64 V vs. Fc/Fc+ have
been observed, respectively. The separation between the re-
duction and oxidation peak potentials and the variation in
the peak potentials with the scan rate for all the processes
lies between 60 and 90 mV, showing their reversible or qua-
sireversible nature.
Figure 1. UV/Vis spectra of 5, 6, and 7 in THF.
ble for the color of the compound (Figure 1). For the
homoleptic bis(phthalocyaninato)lutetium(III) complexes,
two weak π–radical–anion bands near 450 (shoulder) and
910 nm are also seen. This is the characteristic absorption
band for double-decker (phthalocyaninato)rare-earth(III)
complexes, which arises due to the transition from the
forth-occupied HOMO to the SOMO and from the SOMO
to the LUMO, respectively.[33–35] The other band in the UV
region of the spectrum at 370 nm (B band) arises from the
transition of the deeper π level to the LUMO of conjugated
18π electron systems.[3]
High-resolution MALDI mass spectra of all complexes
were obtained by using the positive ion and reflectron mode
in various novel MALDI matrices, and one of them is given
in Figure 2 for 7 as an example. The high-resolution
MALDI mass spectra of the complexes were obtained in
IAA, DNB, and dithranol matrices for 5, 6, and 7, respec-
tively. Isotopic molecular ion peak distributions of the com-
plexes were calculated and compared to the theoretical dis-
tributions of the complexes. It was found that all theoretical
isotopic distributions of the complexes were matched ex-
actly with the experimental results. These experimental iso-
The HOMO level of bis(phthalocyaninato) complexes re-
sults from a splitting of the 4au π-HOMO of the mono-
phthalocyanine due to interactions between both rings and
leads to a complex whose HOMO is occupied by only one
electron, giving a radical character to the compound. These
types of compounds should be reducible by a total of five
electrons.[34] The bis(phthalocyaninato)rare-earth(III) com-
plexes are known to be radicals, and the HOMO is semi-
occupied (SOMO). The absorption band at 920 nm in the
electronic spectrum is attributed to the electronic transition
from the SOMO to the degenerate LUMO.[37] Because the
HOMO is the semi-occupied molecular orbital (SOMO) in
sandwich-type phthalocyanine complexes, the first re-
duction of 5 occurs at much lower reduction potentials than
those of monophthalocyanines. The first ring reduction of
monomeric phthalocyanine occurs usually at potentials
more negative than –0.60 V vs. SCE.[5] In contrast, com-
pound 5 is reduced at a potential that is considerably more
Figure 2. The positive-ion and reflectron mode MALDI-MS spec-
trum of 7 (lutetium) was obtained in dithranol (1,8-dihydroxy-10H-
anthracen-9-one) (20 mgmL–1 tetrahydrofuran) MALDI matrix by
using nitrogen laser accumulating 50 laser shots. Inset spectrum
shows expanded molecular mass region of the complex.
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Novel CoII, CuII, and Double-Decker LuIII Phthalocyanines
Table 1. Redox potentials of Lu[(C30H28N3O)4]2 and selected double-decker (phthalocyaninato)lutetium(III) complexes.
Compounds
Solvent/Supporting electrolyte
RE[a]
O2
O1
R1
R2
R3
∆E1
Ref.[b]
Lu[(C30H28N3O)4]2
Lu2[(Pc)(–2)(Pc)(–1)]2
MPc2
Lu(Pc)2
Lu2Pc4
CoPc
CuPc
DCM/TBATFB
THF/TBAP
DCM/TBAP
PhCN/TBAPF6
DCM/TBAP
DMF/TBATFB
DMF/TBATFB
Fc/Fc+ 0.64
0.32
0.34
0.40
–0.05
0.06
0.01
–0.10
–0.06
–0.02
–0.46
–0.32
–0.88
–1.42
–1.30
–0.84
–1.10
–1.54
–1.09
–2.03
–1.94
–1.70
–1.14
–1.33
–1.92
–1.31
–2.43
0.42
0.40
0.42
0.41
0.40
0.89
1.32
tw
[12]
Fc/Fc+
[37]
[38]
[44]
SCE
Fc/Fc+
Fc/Fc+
Fc/Fc+ 0.44
Fc/Fc+ 0.15
tw
tw
–0.10
[a] RE: Reference electrode, ∆E1 = O1 – R1, at 0.100 Vs–1 scan rate. [b] tw: this work.
positive with respect to that of monophthalocyanines. The havior, with five redox processes (E1/2 vs. Fc/Fc+) labeled
electrochemical properties of 5 are similar to those of pre- O2 = 0.440 V, O1 = 0.01 V, R1 = –0.88 V, R2 = –2.030 V,
viously reported double-decker lutetium phthalocyanine and R3 = –2.425 V. The first reduction and first oxidation
compounds. This can be revealed by the similar potential processes are metal based in polar coordinating solvents,
difference between the first oxidation and the first reduction which is a well-known electrochemical behavior of CoPc
potentials, ∆E°1/2 and between the first of the first re- complexes in coordinating solvents such as DMF and
duction and the second reduction processes ∆E°1/2 = 0.42 V, DMSO.[45] Therefore, the first reduction and the first oxi-
which also have good agreement with the previously re- dation of 6 could be assigned to CoIII(Pc–2)/CoII(Pc–2)
ported results of the bis(phthalocyaninato)lutetium com- (O1) and CoII(Pc–2)/CoI(Pc–2) (R1) redox couples and the
pounds recorded in DCM.[39–41] The electrode reactions of second and the third reductions and the second oxidation
5 are schematically shown in Scheme 2.
processes are Pc-ring-based and assigned to CoI(Pc–2)/CoI-
(Pc–3) (R2), CoI(Pc–3)/CoI(Pc–4) (R3), and CoIII(Pc–1)/
CoIII(Pc–2) (O2), respectively. The separation between the
metal center reduction and oxidation processes (O1–R1 =
0.89 V), which reflects the HOMO–LUMO gap of the com-
plex, is comparable to the reported CoPc complexes.[42] The
number of electrons transferred for each redox process is
determined by the chronocoulometric studies and it showed
that each redox process is approximately equal to unity.
Therefore, the electrochemical reactions corresponding to
all waves in the voltammogram are stepwise one-electron
processes. The ratios of the anodic to cathodic peak cur-
rents (ia to ic) for couples for all the waves are close to unity,
suggesting a reversible/quasireversible redox processes.
Scheme 2. The one-electron redox processes of Lu[(C30H28N3O)4]2.
The difference in the redox potentials of O1 and R1 (∆E1)
represents the energy for putting a second electron in the
SOMO of the neutral double-decker radical [M(Pc)2] or to
remove one of the two electrons from the HOMO of the
reduced species [M(Pc)2]–.[37] As the first oxidation step and
first reduction step involve the HOMO and the LUMO of
the molecule, the energy difference between these two redox
processes corresponds to its electrochemical molecular
bandgap. The peak separations and the variation of the
peak potentials with the scan rate for these redox processes
were usually within the range of quasireversible behavior,
which indicates that the complex has potential to be a mo-
lecular semiconductor.[42,43] Solubility in common organic
solvents, thermal stability up to 300 °C, and the small elec-
tron-pairing energy necessary for the bis(phthalocyani-
nato)lutetium(III) complex makes it a good candidate to
find application in electronics.
In contrast to the HOMO level of double-decker or
bis(phthalocyanine)s, the LUMO of monometallophthalo-
cyanines has doubly degenerate eg symmetry and can there-
fore accept up to four electrons.[39] The redox properties of
6 and 7 were studied by using CV and SWV in DMF, and
typical voltammograms of 6 and 7 are shown in Figures 3
and 4. The potential values and assignments are summa-
Figure 3. Cyclic and square-wave (inset) voltammograms of 6 in
rized in Table 1. Complex 6 showed good voltammetric be- DMF containing 0.1  TBAFB, scan rate: 100 mVs–1.
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where q0(z) is given by:
where z0 is the Rayleigh range of the beam and leff is the
effective sample length containing linear absorption coeffi-
cient, α0 and true optical path through the sample, L inside.
The open-aperture spectra of 6 and 7 are given in Fig-
ure 5. The effective nonlinear absorption coefficients are de-
picted as a function of the focal intensity. The decrease in
βI with an increase in focal intensity can be attributed to
the fact that higher odd order nonlinear absorptions take
part. In order to compare with the literature, βI values at I0
= 0.5 GWcm–2 were found from the βI–I0 graphs.[26]
To fit the open-aperture data and obtain optical limiting
parameters κ and FSat, rate equations for a five-level system
were solved; nonlinear absorption coefficients were derived
and inserted into a propagation formalism. Then normal-
ized transmission as a function of fluence is obtained as
follows:[47]
Figure 4. Cyclic and square-wave (inset) voltammograms of 7 in
DMF containing 0.1  TBAFB, scan rate: 100 mVs–1.
Figure 4 represents the CV and SW voltammogram of 7
and they display four redox processes assigned to the
phthalocyanine ring oxidation and reduction, labeled O2,
O1, R1, and R2. The first and second reduction waves were
observed at –1.42 and –1.94 V and the oxidation waves ap-
peared at –0.10 and 0.15 V, respectively, at a scan rate of
0.100 Vs–1. Osteryoung SW voltammogram of 7 suggests
that all four redox processes have quasireversible character
The open-aperture spectra were manipulated and nor-
(Figure 4). The separation of the firs reduction and the first malized transmissions (TNorm) were plotted against energy
oxidation processes (–1.32 V) reflects the HOMO–LUMO density per pulse (F) for 6 and 7 by using the above equa-
gap of the CuPc complexes. Although R1, R2, and O2 seem tion (Figure 6).
to be reversible processes, O1 of 7 is quasireversible, which
is illustrated by the SW voltammogram of the complex performance by only one parameter, such as βI. Preferably,
comparing the anodic to cathodic peak current. the optical limiting efficiency of materials should be defined
It is not reasonable to characterize the optical limiting
The good optical limiting properties of phthalocyanines with a combination of some “yardsticks” such as the satu-
arise from their extensive π-electron delocalization, good ration energy density (FSat), the ratio of the excited state to
chemical and thermal stabilities, and also from their great ground state absorption cross sections (κ), besides the effec-
opportunity to be tailored by either substituting a metal tive nonlinear absorption coefficient (βI). Note that a good
atom to the core and/or by substituting different peripheral optical limiter must have high κ, low Fsat, and high βeff val-
and axial ligands. Especially, changing the metal atom has ues. In comparison to the literature, it is not easy to esti-
tremendous effect on optical limiting performance of the Pc mate which Pcs will be the better optical limiters, as most
compound.[24] In this study, this strategy has been followed of the materials do not satisfy all the conditions for good
by changing the metal atom with Lu, Cu, and Co while optical limiting behavior.
keeping the substitution groups the same. Among these
Rare-earth-substituted phthalocyanines are sandwich-
compounds, 6 and 7 exhibited good optical limiting per- type compounds where the metal resides between two Pc
formance, but 5 did not show any optical limiting behavior. rings. To the best of our knowledge, there are no studies on
Blau and co-workers presented the values of optical limiting the optical limiting performance of rare-earth-substituted
parameters of structurally different phthalocyanine deriva- phthalocyanines manipulated from open-aperture Z-scan
tives containing ZnII, CoII, NiII, PdII, GaII, and InIII metal data to obtain κ, Fsat, and βeff values. Therefore, we can
atoms manipulated by the Z-scan technique.[27] In this only compare the nonlinear absorption coefficient βI with
study, CoPc or NiPc monomers are found out to be the the literature. The wavelength dependence of the nonlinear
weakest nonlinear absorbers among the 39 different kinds absorption coefficient of a bis(phthalocyanine) NdPc2 was
of investigated Pc compounds.
From open aperture Z-scan experimental data, nonlinear sorption coefficient as that of NdPc2 measured at 532 nm.
studied.[48] Compound 7 has almost the same nonlinear ab-
absorption coefficients of 6 and 7 were calculated at various
In a recent review,[26] optical limiting parameters (βeff, α0,
focal intensities by using the theory previously reported.[46] FSat, and κ) are taken into account for 39 materials. In this
The normalized transmission as a function of position z, review, it was found that βeff ranges in the order of 10–10 to
TNorm(z), is given by:
10–8 cmW–1, FSat in the order of 1 to 170 Jcm–2, and κ in
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Novel CoII, CuII, and Double-Decker LuIII Phthalocyanines
Figure 5. Normalized Z-scan experiment results for 6 and 7 under open-aperture configuration. Solid lines represent theoretical fits.
[Fsat value for (Ciso5H11)8Cu is 4.6 Jcm–2], and high βeff
value of 1.9ϫ10–7 cmW–1 at 0.5 GWcm–2 intensity [βeff
value for (Ciso5H11)8Cu is 6.4ϫ10–8 cmW–1 at
0.5 GWcm–2 intensity].
OL is a nonlinear effect consisting of a decrease in the
transmittance of a sample under high intensity or fluence
illumination. Ideally, the transmitted intensity should re-
main constant (or even decrease to a small value) above a
certain limiting threshold. The nonlinear response should
possess a low limiting threshold. Therefore, the limiting
threshold (Fth) is also taken into account as an optical limit-
ing parameter. In the literature, the Fth value is usually
greater than 1 Jcm–2.[24,26,50] Compound 6 exhibits very low
Fth value of 0.5 Jcm–2. The Fth value for the investigated
LuPc2 compound was found to be 1.8 Jcm–2, and this value
is comparable with that of EuPc2.[50]
Figure 6. Plots of normalized transmission against incident pulse
energy density for 6 and 7. Solid lines represent theoretical fits.
Conclusions
the order of 1 to 27. Investigated compound 7 has a high
In conclusion, both compounds have a good combina-
βI value (7.76ϫ10–8 cmW–1), a very high κ value (15.3), tion of optical limiting parameters between a relatively high
and a low FSat value (2.98 Jcm–2). Wang et al. pointed out absorption cross section κ, a very low energy dependent
the importance of the atomic radii of rare-earth elements saturation Fsat, a relatively high effective nonlinear absorp-
on the optical limiting performance.[49] In this study, al- tion coefficient βeff, and a low limiting threshold Fth. The
though Gd was a heavier atom than Eu, Eu[Pc(OC5H11)8]2 OL performances of both compounds may be attributed to
exhibited better optical limiting performance. It was con- the effectiveness of peripheral side groups as a result of the
cluded that the bigger the ion radius, the smaller the prob- improved electron mobility.
ability of π–π interactions and, therefore, the longer the
In this work, the synthesis, characterization, and optical
triplet-state lifetime. Despite the fact that Lu is a light rare- limiting properties of new bis(phthalocyaninato)co-
earth element, compound 7 exhibits good optical limiting balt(II), -copper(II), and sandwich -lutetium(III) complexes
performance.
were accomplished. Electrochemical studies of 5 showed
As the linear absorption coefficient of compound 6 is that the complex undergoes five redox couples with a
close to that of (Ciso5H11)8Cu with isopentyl substitution HOMO–LUMO gap of ∆E1/2 = 0.42 V. Solubility in com-
groups,[26] one can compare the OL performances of these mon organic solvents, thermal stability up to 300 °C, and
compounds. Compound 6 exhibits a high κ value of 13.6 [κ the small electron-pairing energy necessary for 5, make it a
value for (Ciso5H11)8Cu is 8.8], low Fsat value of 0.98 Jcm–2 good candidate for electronic applications. Complex 6
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Ö. Bekaroglu et al.
˘
FULL PAPER
4-[2-(2H-1,2,3-Benzotriazol-2-yl)-4,6-bis(2-phenylpropan-2-yl)phen-
oxy]phthalonitrile (3): A mixture of 1 (2.24 g, 5 mmol) and 2
(0.87 g, 5 mmol) in dry DMF (25 mL) was stirred at 70–90 °C for
10 min and then the fine powder of dry K2CO3 (2.10 g, 15 mmol)
was added portionwise over 1 h under an argon atmosphere. The
reaction was then stirred for 12 h under an argon blanket. Then,
the reaction mixture was poured into water (500 mL), and the pre-
cipitate formed was filtered, washed with water, and dried in air.
The crude product was crystallized from ethanol. Product 3 is solu-
ble in ethanol, methanol, CHCl3, THF, DMF, and DMSO. Yield:
showed good voltammetric behavior, with five redox pro-
cesses; the first reduction and first oxidation processes are
metal based. Complex 7 displayed four redox processes, all
assigned to the phthalocyanine ring oxidation and re-
duction.
It was found that, although both bis(phthalocyaninato)
copper(II) and -lutetium(III) complexes have good optical
limiting properties, (phthalocyaninato)cobalt(II) in contrast
did not.
1.87 g (65%). M.p. 94–97 °C. IR (KBr disc): ν =3110–3008 (Ar-H),
˜
2900–2840 (-CH3), 2226 (-CN), 1594–1486 (-C=C-), 1250–1278
(Ar-O-C), 1495 and 1457 (Ar-H) cm–1. 1H NMR (400 MHz,
CDCl3): δ = 1.72 (s 6 H), 1.85 (s 6 H), 6.42 (s 1 H), 6.75 (s 1 H),
6.76–7.00 (m 4 H), 7.23–7.43 (m 9 H), 7.66–7.84 (m 4 H) ppm.
C38H31N5O (573.67): calcd. C 79.56, H 5.45, N 12.21; found 79.40,
H 5.23, N 12.43.
Experimental Section
General Remarks: All chemicals used were reagent grade. The sol-
vents were purified according to standard procedures[51] and stored
over molecular sieves. Electrochemical grade tetrabutylammonium
tetrafluoroborate (TBAFB) (Fluka) was used as the supporting
electrolyte in voltammetric measurements in nonaqueous solvents.
Compound 1 was obtained from Aldrich. Compounds 2, 3,and 4
were prepared according to literature procedures.[52] Melting points
were determined with a Electrothermal Digital melting point appa-
ratus (Model IA9100). FTIR spectra were recorded with a Mattson
1000 FTIR spectrometer in the range 400–4000 cm–1 as KBr disks.
1H NMR spectra were determined with a Gemini Varian 200 MHz
NMR spectrometer. Electronic absorption spectra were measured
in THF with an Ocean Optics HR2000 CG UV-NIR diode array
UV/Vis spectrometer in the range 200–1100 nm. Cyclic and square-
wave voltammograms were carried out by using a Gamry Reference
600 Potentiostat/Galvanostat/ZRA. A three-electrode system was
used for CV and SWV measurements in dichloromethane (DCM)
or dimethylformamide (DMF) consisting of a glassy carbon work-
ing electrode, a platinum wire counter electrode, and a platinum
wire quasireference electrode. The ferrocene/ferrocenium couple
(Fc/Fc+) was used as an internal standard and potentials are re-
ported with respect to Fc/Fc+ in nonaqueous solutions. High-pu-
rity argon was used for the deoxygenation of the cell at least 10 min
prior to electrochemical measurements, and the solution was pro-
tected from air by a blanket of argon during the experiments. Mass
spectra were acquired with a Voyager-DETM PRO MALDI-TOF
mass spectrometer (Applied Biosystems, USA) equipped with a ni-
trogen UV-Laser operating at 337 nm. Spectra were recorded in
reflectron and linear modes with an average of 50 shots. Indolin
acrylic acid (IAA) (40 mgmL–1 in methanol), 2,4-dinitrobenzene
(DNB) (40 mgmL–1 in acetonitrile), and Dithranol (1,8-dihydroxy-
10H-anthracen-9-one; 20 mgmL–1 in tetrahydrofuran) matrixes
were used for 5, 6, and 7, respectively. MALDI sample was pre-
pared by mixing the complex (2 mgmL–1 in tetrahydrofuran) with
the matrix solution (1:10) in a 0.5-mL Eppendorf microtube. Fi-
nally, 1 µL of this mixture was deposited on the sample plate, dried
at room temperature, and then analyzed. The second harmonic of
Nd:YAG laser (Quantel Brillant) was used as the excitation light
source with a pulse width of 4 ns and a repetition rate of 10 Hz.
The experiment technique used in the measurements was the Z-
scan technique.[46] In the Z-scan experiment, while sample was
translated along z axis in the vicinity of the focal point of a 20 cm
focal length lens, open-aperture signals were detected with a silicon
detector. The concentrations of 6 and 7 were 1ϫ10–3 and
5-[2-(2H-1,2,3-Benzotriazol-2-yl)-4,6-bis(2-phenylpropan-2-yl)phen-
oxy]-1,3-diiminoisoindoline (4): To
a solution of 3 (1.50 g,
2.61 mmol) in dry methanol (100 mL), was added sodium meth-
oxide (0.082 g, 1.52 mmol). Anhydrous ammonia was bubbled
through the solution under reflux. The course of the reaction was
followed by IR spectroscopic monitoring of the C=N peak at
2226 cm–1. After completion of the reaction, the ammonia inlet was
closed, and the volume of the reaction mixture was reduced to
25 mL under reduced pressure. The mixture was precipitated with
water (250 mL), and the solid was filtered off. The product was
crystallized from methanol/acetone (1:5) to afford 4 as pale yellow
crystals. Yield: 1.40 g (90%). M.p. 128–131 °C. IR (KBr disc): ν =
˜
3500–3200 (NH), 3110–3004 (Ar-H), 2900–2840 (-CH3), 1650
(=NH), 1600–1440 (-C=C-), 1253–1303 (Ar-O-C), 1495 and 1465
1
(Ar-H) cm–1. H NMR (400 MHz, CDCl3): δ = 1.72 (s 6 H), 1.85
(s 6 H), 6.42 (s 1 H), 6.75 (s 1 H), 6.76–7.00 (m 4 H), 7.23–7.43 (m
9 H), 7.66–7.84 (m 4 H), 8.52 (br. 3 H) ppm. C38H34N6O (590.72):
calcd. C 77.26, H 5.80, N 14.23; found C 77.51, H 5.62, N 14.35.
[2,9,16,23-Tetrakis{2-(2H-benzo-1,2,3-triazol-2-yl)-4,6-bis(2-phen-
ylpropan-2-yl)phenoxy}phthalocyaninato]cobalt(II) (5): A mixture of
3 (0.574 g, 1 mmol) and cobalt(III) acetate tetrahydrate (0.063 g,
0.25 mmol) or 3 (0.574 g, 1 mmol) and copper(II) acetate monohy-
drate (0.050 g, 0.25 mmol) in DMF (5 mL) was heated at reflux
under an argon atmosphere for 24 h. After cooling to room tem-
perature, ethanol (10 mL) was added, and the mixture was precipi-
tated with water (250 mL). The green precipitate was filtered off
and washed several times ethanol and acetone and dried in vacuo
at 80 °C. The product is soluble in CHCl3, CH2Cl2, DMF, DMSO,
and THF. Yield: 0.410 g (70%, mixture of regioisomers). M.p.
Ͼ300 °C. UV/Vis (THF): λ (log ε) = 670 (4.46), 615 (4.12), 335
(4.31), (sh.) nm. IR (KBr pellet): ν = 30591, 1736, 1615, 1467, 1402,
˜
1364, 1270, 1235, 1094, 958, 746, 700 cm–1. C152H124CoN20O4
(2353.68): calcd. C 77.65, H 5.31, N 11.90; found C 76.45, H 5.43,
N 12.21. MS (MALDI-TOF): m/z = [M + H]+ 2352–2358 (because
of isotopic distribution).
[2,9,16,23-Tetrakis{2-(2H-benzo-1,2,3-triazol-2-yl)}-4,6-bis(2-phen-
ylpropan-2-yl)(phenoxy)phthalocyaninato]copper(II) (6): Synthe-
sized by a procedure similar to that above for 5. The product is
soluble in CHCl3, CH2Cl2, DMF, DMSO, and THF. Yield: 0.385 g
(65%, mixture of regioisomers). M.p. Ͼ300 °C. UV/Vis (THF): λ
2ϫ10–3

with
a
linear absorption coefficient of 2.54 and
(log ε) = 680 (4.27), 615 (4.10), 355 (4.21) nm. IR (KBr pellet): ν
˜
1.94 cm–1, respectively. All samples were placed in a quartz cell of
1 mm thickness and dimethyl sulfoxide was used as the solvent. As
the samples were taken in a 1 mm cuvette, thin lens condition was
satisfied.
= 3057, 2966, 1614, 1494, 1465, 1401, 1325, 1233, 1092, 950, 746,
700 cm–1. C152H124CuN20O4 (2358.29): calcd. C 77.44, H 5.30, N
11.88; found C 76.98, H 5.16, N 12.11. MS (MALDI-TOF): 2356–
2362 (because of isotopic distribution).
2102
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Eur. J. Inorg. Chem. 2009, 2096–2103

Novel CoII, CuII, and Double-Decker LuIII Phthalocyanines
[20] J. Jiang, W. Liu, K. W. Poon, D. Du, D. P. Arnold, D. K. P. Ng,
Eur. J. Inorg. Chem. 2000, 205.
Bis[tetrakis-2,9,16,23-{2-(2H-1,2,3-benzotriazol-2-yl)}-4,6-bis(2-
phenylpropan-2-yl)phenoxy Phthalocyaninato]lutetium(III) (7): A
mixture of 4 (0.300 g, 0.51 mmol), lutetium acetate monohydrate
(0.023 g, 0.063 mmol), and DBU (0.25 mL) was heated at reflux in
n-octanol (3.0 mL) under an argon atmosphere for 12 h. The prod-
uct was precipitated with methanol (50 mL) and filtered off. Then,
the product was dissolved in THF and purified by silica-gel column
chromatography (THF/methanol, 10:1). The dark green product
was collected and precipitated in water, filtered off, and dried in
vacuo at 80 °C. Yield: 0.074 g (25%). UV/Vis (THF): λ (log ε) =
[21] A. Arrieta, M. L. Rodriguez-Mendez, J. A. de Saja, Sens. Actu-
ators B 2003, 95, 357.
[22] M. M. Nicholson, Ind. Eng. Chem. Prod. Res. Dev. 1982, 21,
261.
[23] C. Piechocki, J. Simon, J. J. Andre, D. Guillon, P. Petit, A.
Skoulios, P. Weber, Chem. Phys. Lett. 1985, 122, 124.
[24] G. de la Torre, P. Vazquez, F. A. Lopez, T. Torres, Chem. Rev.
2004, 104, 3723.
[25] T. Ceyhan, M. Yüksek, H. G. Yaglıoglu, B. Salih, M. K. Erbil,
˘
˘
A. Elmalı, Ö. Bekaroglu, Dalton Trans. 2008, 2407.
˘
450 (4.41) (sh.), 615 (4.40), 685 (5.13) nm. IR (KBr pellet): ν =
˜
[26] S. M. O’Flaherty, S. V. Hold, M. J. Cook, T. Torres, Y. Chen,
M. Hanack, W. J. Blau, Adv. Mater. 2003, 15, 19.
[27] C. G. Claessen, W. J. Blau, M. Cook, M. Hanack, R. J. M.
Nolte, T. Torres, D. Torres, Monatsh. Chem. 2001, 132, 3.
[28] P. Wang, S. Zhang, P. Wu, C. Ye, H. Liu, F. Xi, Chem. Phys.
Lett. 2001, 340, 261.
3081, 3054, 3021, 2962, 2924, 2854, 1601, 1494, 1468, 1401, 1340,
1295, 1273, 1235, 1094, 1032, 940, 852, 747, 700 cm–1.
C304H248LuN40O8 (4764.45): calcd. C 76.64, H 5.25, N 11.76; found
C 76.28, H 5.42, N 11.37. MS (MALDI-TOF): m/z = 4762–4772
[M + H]+ (because of isotopic distribution).
[29] Y. Chen, D. Wang, Y. Li, Y. Nie, Proc. SPIE-Int. Soc. Opt.
Eng. 2003, 33, 4797.
[30] A. A. M. Farag, Optics Laser Technol. 2007, 39, 728.
[31] R. Seoudi, G. S. El-Bahy, Z. A. El Sayed, J. Mol. Struct. 2005,
753, 119.
[32] J. Sleven, C. Gorller-Walrand, K. Binnemans, Mater. Sci. Eng.,
C 2001, 18, 229.
[33] Y. Z. Bian, R. M. Wang, D. Wang, P. H. Zhu, R. J. Li, J. M.
Dou, W. Liu, C. F. Choi, H. S. Chan, C. Q. Ma, D. K. P. Ng,
J. Z. Jiang, Helv. Chim. Acta 2004, 87, 2581.
[34] N. Ishikawa, J. Porphyrins Phthalocyanines 2001, 5, 87.
[35] S. H. Bo, D. H. Tang, X. H. Liu, Z. Zhen, Dyes Pigm. 2008,
76, 35.
[36] R. J. Li, X. X. Zhang, N. Pan, P. H. Zhu, N. Kobayashi, J. Z.
Jiang, J. Porphyrins Phthalocyanines 2005, 9, 40.
[37] P. H. Zhu, F. L. Lu, N. Pan, D. P. Arnold, S. Y. Zhang, J. Z.
Jiang, Eur. J. Inorg. Chem. 2004, 510.
Acknowledgments
We gratefully acknowledge financial support of the Scientific and
Technical Research Council of Turkey (TUBITAK, Project No:
105T240 and 107T708) and the Research Funds of Ankara Univer-
sity, Turkish State of Planning Organization (DPT) under grant
number 2003K12019010-7, and in part by the Turkish Academy of
Sciences (TUBA).
˙
[1] N. Kobayashi, Coord. Chem. Rev. 2002, 227, 129.
[2] V. E. Pushkarev, E. V. Shulishov, Y. V. Tomilov, L. G. Tomilova,
Tetrahedron Lett. 2007, 48, 5269.
[3] T. Ceyhan, M. Korkmaz, M. K. Erbil, Ö. Bekarog˘lu, J. Porphy-
rins Phthalocyanines 2005, 9, 423.
[4] S. Abdurrahmanog˘lu, A. R. Özkaya, M. Bulut, Ö. Bekarog˘lu,
Dalton Trans. 2004, 4022.
[5] C. C. Leznoff, A. B. P. Lever, Phthalocyanines: Properties and
Applications, VCH, New York, 1993, vol. 3.
[38] F. Guyon, A. Pondaven, J. M. Kerbaol, M. L’Her, Inorg. Chem.
1998, 37, 569.
[39] K. M. Kadish, T. Nakanishi, A. Gurek, V. Ahsen, I. Yilmaz,
J. Phys. Chem. B 2001, 105, 9817.
[6] H. S. Nalwa, Supramolecular Photo-sensitive and Electro-active [40] M. L’Her, Y. Cozien, J. Courtot-Coupez, J. Electroanal. Chem.
Materials, Academic Press, New York, 2001, vol. 3.
[7] T. Komatsu, K. Ohta, T. Fujimoto, I. Yamamoto, J. Mater.
Chem. 1994, 4, 533.
1983, 157, 397.
[41] K. Takahashi, Y. Tomita, Y. Hada, K. Tsubota, M. Handa, K.
Kasuga, K. Sogabe, T. Kokii, Chem. Lett. 1992, 759.
[42] M. Bouvet, J. Simon, Chem. Phys. Lett. 1990, 172, 299.
[8] J. Simon, C. Sirlin, Pure Appl. Chem. 1989, 61, 1625.
[9] T. Komatsu, K. Ohta, T. Watanabe, H. Ikemoto, T. Fujimoto, [43] J. Simon, J. Andea, Molecular Semiconductors, Springer, Berlin,
I. Yamamoto, J. Mater. Chem. 1994, 4, 537.
[10] N. Ishikawa, Y. Kaizu, Chem. Lett. 1998, 183.
[11] F. Steybe, J. Simon, New J. Chem. 1998, 22, 1305.
[12] J. Jiang, J. Xie, M. T. M. Choi, Y. Yan, S. Sun, D. K. P. Ng, J.
Porphyrins Phthalocyanines 1999, 3, 322.
[13] L. Gaffo, D. Goncalves, A. Dhanabalan, W. C. Moreira, O. N.
Oliveira, Synth. Met. 2001, 124, 351.
Germany, 1985.
[44] A. Koca, T. Ceyhan, M. K. Erbil, A. R. Özkaya, Ö. Bekarog˘lu,
Chem. Phys. 2007, 340, 283.
[45] M. Özer, A. Altindal, A. R. Özkaya, M. Bulut, Ö. Bekarog˘lu,
Synth. Met. 2005, 155, 222.
[46] M. Sheik-Bahae, A. A. Said, T.-H. Wei, D. J. Hagan, E. W.
Van Stryland, IEEE J. Quantum Electron. 1990, 26, 760.
[47] S. M. O’Flaherty, J. J. Doyle, W. J. Blau, Phys. Chem. B 2004,
108, 17313.
[14] P. R. Somani, S. Radhakrishnan, Mater. Chem. Phys. 2002, 77,
117.
[15] F. Guyon, A. Pondaven, P. Guenot, M. L’Her, Inorg. Chem.
1994, 33, 4787.
[16] V. Chauke, M. Durmus, T. Nyokong, J. Photochem. Photobiol.,
A 2007, 192, 179.
[48] K. P. Unnikrishnan, J. Thomas, V. P. N. Nampoori, C. P. G.
Vallabhan, Appl. Phys. B 2002, 75, 871.
[49] X. Wang, C. Liu, Q.-H. Gong, Y. Huang, C. Huang, Opt. Com-
mun. 2001, 197, 83.
[17] Y. Chen, J. Doyle, Y. Liu, A. Strevens, Y. Lin, M. E. EI-Khouly,
Y. Araki, W. J. Blau, O. Ito, J. Photochem. Photobiol., A 2007,
185, 263.
[18] B. Derkowska, M. Wojdyla, R. Czaplicki, W. Bala, B. Sahra-
oui, Optics Commun. 2007, 274, 206.
[19] S. T. Fu, X. J. Zhu, G. J. Zhou, W. Y. Wong, C. Ye, W. K.
Wong, Z. Y. Li, Eur. J. Inorg. Chem. 2007, 2004.
[50] X. Wang, C.-l. Liu, Q.-H. Gong, Y.-Y. Huang, C.-H. Huang,
J.-Z. Jiang, Appl. Phys. A 2002, 75, 497.
[51] W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory
Chemicals, 5th ed., Butterworth/Heinemann, Tokyo, 2003.
[52] N. Ozan, Ö. Bekarog˘lu, Polyhedron 2003, 22, 819.
Received: December 3, 2008
Published Online: March 28, 2009
Eur. J. Inorg. Chem. 2009, 2096–2103
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2103