Hexadecachloro-substituted lanthanide(III) phthalocyaninates and their hybrid conjugates with gold nanoparticles: Synthesis and optical properties

Article abstract of DOI:10.1016/j.poly.2017.06.048

Novel hexadecachloro-substituted Eu, Er and Lu monophthalocyaninates were prepared via two alternative ways: lanthanide ion templated tetramerization of tetrachlorophthalonitrile and metallation of the corresponding phthalocyanine ligand. Target complexes

Full text of DOI:10.1016/j.poly.2017.06.048

Accepted Manuscript
Hexadecachloro-substituted lanthanide(III) phthalocyaninates and their hybrid
conjugates with gold nanoparticles: synthesis and optical properties
Elena A. Kuzmina, Tatiana V. Dubinina, Anton V. Zasedatelev, Anton V.
Baranikov, Maria I. Makedonskaya, Tolganay B. Egorova, Larisa G. Tomilova
PII:
S0277-5387(17)30466-7
DOI:
http://dx.doi.org/10.1016/j.poly.2017.06.048
POLY 12729
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
27 April 2017
28 June 2017
Please cite this article as: E.A. Kuzmina, T.V. Dubinina, A.V. Zasedatelev, A.V. Baranikov, M.I. Makedonskaya,
T.B. Egorova, L.G. Tomilova, Hexadecachloro-substituted lanthanide(III) phthalocyaninates and their hybrid
conjugates with gold nanoparticles: synthesis and optical properties, Polyhedron (2017), doi: http://dx.doi.org/
1
0.1016/j.poly.2017.06.048
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Нexadecachloro-substituted lanthanide(III) phthalocyaninates
and their hybrid conjugates with gold nanoparticles: synthesis
and optical properties
a
*a,b
c
Elena A. Kuzmina , Tatiana V. Dubinina , Anton V. Zasedatelev , Anton V.
c
a
a
a,b
Baranikov , Maria I. Makedonskaya , Tolganay B. Egorova and Larisa G. Tomilova
a
Department of Chemistry, M.V. Lomonosov Moscow State University, 1 Leninskie Gory, Moscow, 119991, Russian
Federation. Fax: +7 495 939 0290; Tel: +7 495 939 1243; E-mail: dubinina.t.vid@gmail.com.
b
Institute of Physiologically Active Compounds, Russian Academy of Sciences, 1 Severny proezd, Chernogolovka,
Moscow Region, 142432, Russian Federation. Fax: +7 496 524 9508; E-mail: tom@org.chem.msu.ru.
c
Skolkovo Institute of Science and Technology, 3 Nobel street, Moscow, 143026, Russian Federation. Fax: +7 495
2
80 14 81; E-mail: a.zasedatelev@skoltech.ru
Received date (to be automatically inserted after your manuscript is submitted)
Accepted date (to be automatically inserted after your manuscript is accepted)
ABSTRACT: Novel hexadecachloro-substituted Eu, Er and Lu monophthalocyaninates were prepared
via two alternative ways: lanthanide ion templated tetramerization of tetrachlorophthalonitrile and
metallation of the corresponding phthalocyanine ligand. Target complexes were identified by mass
spectrometry and fourier transform infrared spectroscopy. Aggregation behaviour of these compounds
was investigated using UV-vis and fluorescence spectroscopy. Hybrid nanoparticle conjugates
composed of the gold cores (20 and 30 nm in diameter) covered by the layers of target phthalocyanines
were obtained. The formation of phthalocyanine shell on the surface of nanoparticles and its elemental
composition were examined using transmission electron microscopy experiments. Reverse saturable
absorption effect was found in solution of the erbium complex utilizing z-scan technique. Furthermore,
significant increase in the effect was observed in hybrid nanoparticles due to their plasmonic properties.
KEYWORDS: phthalocyanine, nonlinear optical properties, gold nanoparticles, hybrid conjugates,
UV-vis spectroscopy
*
Correspondence to: Tatiana V. Dubinina, email: dubinina.t.vid@gmail.com, tel: +7 (495)-9391243, fax: +7 (495)-9390290

INTRODUCTION
Phthalocyanines and their analogues containing electron-withdrawing substituents attract significant research
interest due to a wide range of applications. Presence of n-type conductivity [1, 2] allows using of these compounds
in organic field-effect transistors and chemical transducers [1]. Furthermore, these complexes can be prospective
building blocks for the formation of push-pull molecules, revealing nonlinear optical properties [3]. In addition, gas-
sensing properties were described for the perchlorinated zinc phthalocyanine [4].
Electron-deficient porphyrazine core can be obtained alternatively either by annelation of electron-deficient
heterocycles [5-7] or by introduction of electron-withdrawing substituents [8, 9]. Thanks to high availability of the
initial phthalonitriles and capable of further structural modification (e.g. through nucleophilic substitution or cross-
coupling reactions) halogen-substituted phthalocyanines are the most attractive derivatives of this type. Typical
disadvantages of these compounds resulted from their low solubility: the intrinsic aggregation tendency [1], which
usually leads to the broadening and decrease in intensity of the main absorption band (Q-band). Hence, the formation
of the high-quality thin films requires application of the relatively expensive vapor deposition technique.
This disadvantage can be overcome employing the synthesis of phthalocyanine complexes with the lanthanide
ions. The presence of axial ligands and high coordination ability of lanthanides improves solubility of the target
complexes.
Recently, we demonstrated, that it is possible to form hybrid gold nanoparticles covered by tetra-tert-
butylphthalocyaninato aluminum chloride through axial ligand exchange reaction at the aluminum center of the
phthalocyanine [10]. Further growth of phthalocyanine shell is associated with π-πstacking interactions between the
phthalocyanine ligands. Great enhancement of the molar absorption coefficient caused by intense plasmonic near
field acting on the phthalocyanine shell was established [10]. Present study further extends this work dealing with the
synthesis and investigation of optical properties of hexadecachloro-substituted phthalocyaninates of lanthanides and
hybrid Au nanoparticles covered by these complexes. Thanks to their tendency to form the most stable single-decker
complexes [11-13], the elements of the middle (Eu) and end of lanthanide series (Er and Lu) were chosen as central
ions.
MATERIAL AND METHODS

All reactions were monitored by thin-layer chromatography (TLC) and UV-vis until complete disappearance of the
starting reagents unless otherwise specified. TLC was performed using Merck Aluminium Oxide F254 neutral flexible
plates. Electronic absorption (UV/Vis) spectra were recorded on a ThermoSpectronic Helios-α spectrophotometer
using quartz cells (1×1 cm). Matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectra
were taken on a VISION-2000 mass spectrometer with 2,5-dihydroxybenzoic acid (DHB) as the matrix. High-
resolution MALDI mass spectra were registered on a Bruker ULTRAFLEX II TOF/TOF instrument with DHB as the
matrix. The salts, Mg(OAc) ·4H O, Eu(OAc) ·3H O, Er(OAc) ·4H O, Lu(OAc) ·4H O were dried at 70ºСfor 3 h
2
2
3
2
3
2
3
2
immediately before use. Tetrachlorophthalonitrile (98%, Sigma-Aldrich), gold nanoparticles 20 nm diameter
1
1
(
stabilized suspension in citrate buffer, c=7.2×10 particles/mL, Aldrich) and gold nanoparticles 30 nm diameter
1
1
(
stabilized suspension in citrate buffer, c=1.8×10 particles/mL, Aldrich) were used as received.
The fluorescence spectra were recorded on a Cary Eclipse spectrometer in quartz cells (1×1 cm). Spectral resolution:
Δλ = 1.5 nm.
-
1
FTIR spectra were measured using IR 200 Thermonicolet spectrometer. Spectral resolution: Δλ = 4 cm .
Z-scan measurements were carried out using optical parametric amplifier (Coherent OPerA SOLO) pumped by high
energy Ti:sapphire regenerative amplifier system (Coherent Libra-HE) providing TEM00 beam with the emission
wavelength of 570 nm. Pulse duration and repetition rate were 100 fs and 100 Hz respectively. The beam was tightly
2
focused by 100 mm focal-length lens providing up to 55 GW/cm peak intensity in the focus. Energy of pulses were
in a range from 68 to 75 nJ. All measurements were done in THF solution at room temperature using a 3 mm quartz
cuvette.
Synthesis
(
a) Approach with tetrachlorophthalonitrile
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato europium acetate 1a:
Tetrachlorophthalonitrile (213.0 mg, 0.80 mmol), Eu(OAc) ·3H O (76.4 mg, 0.20 mmol) and 1,8-
3
2
diazabicyclo[5.4.0]undec-7-ene (119 µL, 0.80 mmol) were stirred in 3 mL of boiling isoamil alcohol for 4 h (TLC-
control: SiO , F , toluene). The reaction mixture was cooled to room temperature and a MeOH:H O (4:1 V/V)
2
254
2
o
mixture was added. The precipitate was filtered and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C
2
to give compound 1a (110.8 mg, 44%). UV-vis (THF): λmax (nm) (I/I ) 378 (0.56); 644 (0.35); 696 (1.00). IR
max
-
1
(
(
(
vaseline oil): ν (cm ) 1050 - 1095 (st C-Cl); 1549 - 1580 (γ pyrrole); 1325 – 1418 ( С- О) ; 1549 – 1614 ( С= О) . MS
MALDI-TOF): m/z 1180 [M-OAc-Cl]; 1216 [M-OAc]; 1267 [M]; 1362 [M-OAc+DHB]; 1517 [M-OAc+2DHB]. MS
MALDI-TOF/TOF): m/z Found: [M] 1267.4602; molecular formula C H Cl EuN O requires [M] 1267.4608.
3
4
3
16
8
2
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato erbium acetate 1b:
Tetrachlorophthalonitrile (213.0 mg, 0.80 mmol), Er(OAc) ·4H O (83.0 mg, 0.20 mmol) and 1,8-
3
2

diazabicyclo[5.4.0]undec-7-ene (119 µL, 0.80 mmol) were stirred in 3 mL of boiling isoamil alcohol for 4 h (TLC-
control: SiO , F , toluene). The reaction mixture was cooled to room temperature and a MeOH:H O (4:1 V/V)
2
254
2
o
mixture was added. The precipitate was filtered and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C
2
to give compound 1b (164.2 mg, 64%). UV-vis (THF): λmax (nm) (I/I ) 361 (0.61); 639 (0.37); 696 (1.00). IR
max
-
1
(
vaseline oil): ν (cm ) 1026-1095 (st C-Cl); 1556 (γ pyrrole); 1377 ( С- О) ; 1556 ( С= О) . MS (MALDI-TOF): m/z 1194
[
M-OAc-Cl]; 1212 [M-OAc-Cl+H O]; 1229 [M-OAc]; 1247 [M-OAc+H O]; 1346 [M-OAc-Cl+DHB]. MS (MALDI-
2
2
TOF/TOF): m/z Found: [M-OAc] 1229.4486; molecular formula C Cl ErN requires [M-OAc] 1229.4447.
3
2
16
8
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato lutetium acetate 1c:
Tetrachlorophthalonitrile (213.0 mg, 0.80 mmol), Lu(OAc) ·4H O (85.6 mg, 0.20 mmol) and 1,8-
3
2
diazabicyclo[5.4.0]undec-7-ene (119 µL, 0.80 mmol) were stirred in 3 mL of boiling isoamil alcohol for 4 h (TLC-
control: SiO , F , toluene). The reaction mixture was cooled to room temperature and a MeOH:H O (4:1 V/V)
2
254
2
o
mixture was added. The precipitate was filtered and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C
2
to give compound 1c (202.0 mg, 78%). UV-vis (THF): λmax (nm) (I/I ) 363 (0.68); 642 (0.33); 699 (1.00). IR
max
-
1
(
vaseline oil): ν (cm ) 1091 (st C-Cl); 1554 (γ pyrrole); 1377 ( С- О) ; 1554 ( С= О) . MS (MALDI-TOF): m/z 1444
[
M+DHB]; 1502 [M-OAc-Cl+2DHB]; 1536 [M-OAc+2DHB]; 1597 [M+2DHB]; 1655 [M-Cl+3DHB]; 1692 [M-
OAc+3DHB]. MS (MALDI-TOF/TOF): m/z Found: [M-OAc+2DHB] 1536.5028; molecular formula
C H Cl LuN O requires [M-OAc+2DHB] 1536.5046.
4
6
10
16
8
8
(
b) Approach with hexadecachlorophthalocyanine
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato magnesium 2:
Tetrachlorophthalonitrile (426.0 mg, 1.60 mmol), Mg(OAc) ·4H O (172.0 mg, 0.40 mmol) and 1,8-
2
2
diazabicyclo[5.4.0]undec-7-ene (238 µL, 1.60 mmol) were stirred in 6 mL of boiling isoamil alcohol for 4 h (TLC-
control: SiO , F , toluene). The reaction mixture was cooled to room temperature and a MeOH:H O (4:1 V/V)
2
254
2
o
mixture was added. The precipitate was filtered and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C
2
to give compound 2 (321.0 mg, 74%). UV-vis (THF): λmax (nm) (I/I ) 365 (0.51); 646 (0.45); 695 (1.00). IR (vaseline
max
-
1
oil): ν (cm ) 1051 - 1101 (st C-Cl); 1556 (γ pyrrole). MS (MALDI-TOF): m/z 1009 [M-2Cl]; 1027 [M-2Cl+H O];
2
1
045 [M-Cl]; 1063 [M-Cl+H O]; 1081 [M+H]. MS (MALDI-TOF/TOF): m/z Found: [M+H] 1080.5202; molecular
2
formula C HCl MgN requires [M+H] 1080.5191.
3
2
16
8
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyanine 3: The magnesium
complex 2 (216.0 mg, 0.20 mmol) was dissolved in concentrated sulphuric acid (10 mL). This solution was poured
into the ice. A green precipitate formed at the same time. This precipitate was filtered and washed with water until
the neutral pH and MeOH to give 3 (186.0 mg, 87%). UV-vis (THF): λmax (nm) (I/I ) 358 (0.76); 659 (1.00); 697
max
-
1
(
0.95). IR (vaseline oil): ν (cm ) 1039 - 1105 (st C-Cl); 1564 (γ pyrrole); 3300 (st NH). MS (MALDI-TOF): m/z 995

[
[
M-2Cl]; 1012 [M-2Cl+H O]; 1030 [M-Cl]; 1048 [M-Cl+H O]; 1058 [M+H]. MS (MALDI-TOF/TOF): m/z Found:
2
2
M+H] 1058.5468; molecular formula C H Cl N requires [M+H] 1058.5497.
3
2
3
16
8
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato europium acetate 1a:
A mixture of ligand 3 (164.5 mg, 0.15 mmol) and Eu(OAc) ·3H O (57.3 mg, 0.15 mmol) was refluxed in 3 mL of 1,2-
3
2
dichlorobenzene (o-DCB) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (37 µL, 0.25 mmol) for 4 h (TLC-
control: SiO , F , toluene). The reaction mixture was cooled to room temperature and a MeOH:H O (4:1 V/V)
2
254
2
o
mixture was added. The precipitate was filtered and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C
2
to give compound 1a (155.0 mg, 81%). The characteristics were identical with those obtained by method (a).
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato erbium acetate 1b:
Ligand 3 (78 mg, 0.070 mmol), Er(OAc) ·4H O (29 mg, 0.076 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene (18 µL,
3
2
0
.12 mmol) were stirred in 3 mL of boiling o-DCB for 4 h (TLC-control: SiO , F , toluene). The reaction mixture
2
254
was cooled to room temperature and a MeOH:H O (4:1 V/V) mixture was added. The precipitate was filtered and
2
o
washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C to give compound 1b (61 mg, 68%). The
2
characteristics were identical with those obtained by method (a).
Preparation of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninato lutetium acetate 1c:
Ligand 3 (80 mg, 0.075 mmol), Lu(OAc) ·4H O (32 mg, 0.075 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene (18
3
2
µL, 0.12 mmol) were stirred in 3 mL of boiling o-DCB for 4 h (TLC-control: SiO , F , toluene). The reaction
2
254
mixture was cooled to room temperature and a MeOH:H O (4:1 V/V) mixture was added. The precipitate was filtered
2
o
and washed with a MeOH:H O (4:1 V/V) mixture and dried at 70 C to give compound 1c (77.5 mg, 80%). The
2
characteristics were identical with those obtained by method (a).
Preparation of phthalocyanines 1a-c - gold nanoparticles hybrids. General procedure:
The synthesis of hybrids based on gold nanoparticles with a diameter of 20 and 30 nm was carried out by mixing the
-
4
solutions of gold nanoparticles (1 vol part) in water and a solution of the phthalocyanine in THF (C=10 M, 9 vol
parts). The resulting mixture was kept at room temperature for 2 h.
RESULTS AND DISCUSSION
Synthesis and identification
There are two general synthetic approaches to the lanthanide monophthalocyanine compounds [13]. According to the
template method, complexes are obtained starting from corresponding phthalonitriles [14]. The main disadvantage of
this approach is of oligomeric and polymeric derivatives of the starting nitrile. Within the second approach the target
lanthanide phthalocyaninates are synthesized from the corresponding phthalocyanine ligands [11, 15]. The drawback

of this method is the presence of two additional stages: preliminary formation of the magnesium complex and its
demetallation.
In the present work both synthetic approaches to phthalocyanine complexes of lanthanides were implemented for
their qualitative comparison (Scheme 1).
Scheme 1. Synthesis of phthalocyanine complexes 1a-c.
Template assembly of the compounds 1ac (Method A) was performed in boiling isoamyl alcohol. Selectivity of the
monophthalocyanine formation was provided by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), coordination of which to
the lanthanide central ion results in steric hindrance and prevents undesirable formation of the sandwich-type
complexes [16]. Due to the possibility of nucleophilic substitution typical for the electron-deficient systems, the use
of DBU as a base is preferred rather than employement of alkoxide ions [17]. Decrease of the yields going from
3
+
lutetium (1c) to europium (1a) complex can be explained by increase of the Ln ionic radius, which is obviously not
favorable for template macrocyclization due to steric reasons.
According to the second approach (Scheme 1, Method B) preliminarily formed magnesium complex 2 was
demetallated by concentrated sulfuric acid to give ligand 3. The lanthanide single-deckers 1ac were obtained in
boiling o-DCB using DBU as a base, by analogy with the previously described procedure [11, 18]. The selective
formation of monophthalocyanine complexes 1 was observed without any traces of the double-decker complexes. The
total yield of europium complex 1a (52%) is higher than the yield, which was obtained within the method A (Scheme
1
). However, in the case of compounds 1b and 1c the first approach turned to be more effective.
All the compounds obtained were characterized by MALDI TOF and high resolution MALDI TOF/TOF mass
spectrometry. The high resolution spectra of the target heavy molecular weight lanthanide monophthalocyanines
demonstrate good agreement between the observed and calculated mass patterns (see Experimental part). Molecular

ions were observed for complexes 1a, 2 and 3. The additional fragmentation of peripheral chlorine atoms and axial
acetate groups was found. Besides that, the formation of conjugates with the matrix (DHB) under lazer ionization was
observed. This phenomenon can be explained by high mobility of axial ions in lanthanide monophthalocyaninates,
which can be perfectly applied to obtain heteroleptic complexes [12, 19]. As an example, the mass spectra of the
compounds 1a-c are shown in Fig. 1.

Fig.1. MALDI TOF mass spectra of compounds 1a-c, isotopic pattern (inset А) and simulated MS pattern (inset B).
FTIR spectra for all target complexes were recorded in vaseline oil. Stretching vibrations of C-Cl bonds were
-
1
observed in the region of 1026-1105 cm . Skeletal vibrations of pyrrol fragments occupy the region from 1549 to
-
1
-1
-1
1
580 cm . In the case of complexes of lanthanide complexes 1ac the bands at 1325-1418 cm and at 1549-1614 cm
were assigned to C-O and C=O vibrations respectively.
Fig.2. FTIR spectra of lutetium phthalocyaninate 1c in vaseline oil (A) and lutetium (III) acetate in ZnSe (B).
Notably, the same values were observed for acetates in literature [20] and for the salts used herein. For instance, the
spectra of the lutetium complex 1c and lutetium (III) acetate are shown in Fig. 2.
UV-vis and fluorescence spectroscopy
In the UV-vis spectra of lanthanide phthalocyaninates 1ac the type of central ion does not affect the position of the
Q-band (Fig. 3).
Fig.3. UV-vis spectra of europium 1a (solid line), erbium 1b (dashed line) and lutetium 1c (dotted line) complexes in THF.
For complexes 1 and 2 low resolution of the Q-band vibrational satellites and their increased intensity comparing to
the Q-band was observed. The strongest aggregation picture was observed for magnesium complex 2, which does not

contain axial ligand. The aggregation behaviour of complexes 1 and 2 can be explained by the intermolecular
interactions between the electron-deficient periphery and the electron-releasing porphyrazine core of the neighboring
molecules.
In order to prove this hypothesis fluorescence and excitation spectra were measured for complex 2 (Fig. 4). The
Stokes shift of the Q-band is 12 nm. This value is 3 times higher, than Stokes shift in pyrazinoporphyrazines, which
were described by us earlier [6].
Fig.4. UV-vis (solid line) and fluorescence (dashed line) spectra (λ = 380 nm) of 2 in THF (A). Excitation spectrum (λ = 707
ex
em
nm) of 2 in THF (B).
In contrast to absorption spectra, Q band vibrational satellites are well-resolved in the excitation spectra and their
intensity is lower, than one for absorption spectra. This follows from the fact that the excitation spectra correspond to
the shape of nonaggregated complexes.
Identification and optical properties of hybrids
Hybrids of Au nanoparticles and phthalocyanine complexes 1a-c were prepared in THF solutions. In visible range
two main absorption bands were observed: in 520-540 nm region, which can be refered to the absorption band of Au
nanoparticles, and near 700 nm, which can be refered to the Q-band of the phthalocyanine part of hybrids (Table 1).

Table 1. Positions of the main absorption bands of hybrid nanoparticles in visible region.
Hybrid
λ(nm)
1
1
1
1
1
1
a+Au (20 nm)
a+Au (30 nm)
b+Au (20 nm)
b+Au (30 nm)
c+Au (20 nm)
c+Au (30 nm)
526; 699
527; 706
527; 697
534;705
527; 702
531; 703
In comparison with pure complexes 1a-c Q-bands of the hybrids are bathochromically shifted up to 705 and 706 nm
in the case of complexes 1a and 1b, respectively (Table 1, Fig. 5).
Notheworthy, the most bathochromic shift was found for hybrids with Au (30 nm). In the case of hybrids with Au (20 nm)
Q-band possesses a smaller red-shift (1-3 nm). According to the literature data, similar bathochromic shift was observed
in the case of Au nanoparticles covered by phthalocyaninato indium chloride [21].
Fig.5. UV-vis spectra of hybrid 1b+Au (30 nm) (solid line), Au (30 nm) (dashed line) and complex 1b (dotted line) in THF.
By the analogy with our previous investigation [10], considering the mechanism of the hybrid conjugates formation,
we suggest that axial ligand exchange reaction at the lanthanide center of the phthalocyanine (acetate to the anion of
citrate OH group) can be considered as the most probable route.
TEM images show the formation of phthalocyanine shell on the surface of gold (Fig. 6). Elemental composition
correlates well with the proposed structure and shows the presence of Cl and Eu elements from phthalocyanine and
Au - from nanoparticles.

Fig.6. TEM image of hybrid 1a+Au (20 nm) (1) and elemental composition of the marked regions A and B (2).
According to the TEM data, phthalocyanine shell is not homogeneous, its size occupies the range of 4-14 nm. This
probably resulted from the aggregation of phthalocyanine molecules on the surface of gold nanoparticles.
Nonlinear optical (NLO) properties of the samples were studied in accordance with well-known single-beam Z-
scan technique first reported by Sheik-Bahae et al [22].
Herein we examined NLO properties of the samples based on 1b compound conjugated with 20 nm and 30 nm
-
10
-11
gold nanoparticles with the following concentrations: 1.2·10 and 3.0·10 M. Open-aperture z-scan data are
represented in Fig. 7. In order to extract nonlinear absorption coefficient we fit the result by well-established equation
based on the solution of nonlinear wave equation in the paraxial approximation for Gaussian beam [23].
where
– the nonlinear absorption coefficient,
effective thickness of sample,
– on-axis intensity in focus (z=0, r=0, t=0),
– the linear absorption coefficeint, - Rayleigh range.
–

Fig.7 Open-aperture Z-scan curves of compound 1b – a, compound 1b + Au (20 nm) – b, compound 1b + Au (30
nm) – c in THF solution.
Reverse saturable absorption (RSA) effect which was found out in the experiment is not a surprising result for
phthalocyanines since the wavelength of excitation lies in transparent region of compound 1b (Fig.1b). Indeed, in that
case the absorption cross-section of
singlet-singlet transition appears to be less than the excited state
absorption cross-section of
singlet-singlet transition (Fig. 8). Taking into acount typical values of lifetime in
st
the 1 excited single state for the most of the phthalocyanine compounds (~5 ns) as well as ultrashort pulse duration
(100 fs) we can neglect occupancy of the triplet states.
st
Fig.8 Scheme of optical transitions induced by the nonresonant excitation. S
0
– ground state (singlet), S
1
– 1 excited
th
singlet state, S
N
– N excited singlet state.
Typically gold nanoparticles demonstate strong saturable absorption effect caused by hot eleсtrons and localized
surface plasmon resonance (LSPR) [24]. Open-aperture Z-scan curves for the bare nanoparticles reveal saturable
absorption effect explicilty (Fig. 9). Applying analytical model mentioned above the nonlinear coefficients β were
-
12
-12
found to be equal to -3·10 cm/W and -7·10 cm/W for 20 and 30 nm gold nanoparticles respectively. Since the
compound 1b and gold particles exhibit oposite sign nonlinearities having nearly the same amplitudes, their linear
superposition should result in decrease of total effect. Nevertheless, one can clearly see pronounced RSA effect for
hybrid nanoparticles (Fig. 7b,c). This indicates dominant role of the phthalocyanine nonlinearity in the overall
response of the hybrid sample enhanced by gold nanoparticles.

Fig.9 Open-aperture Z-scan curves of 20 nm (a) and 30 nm (b) gold nanoparticles in THF solution.
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12
-12
We found β being much higher for hybrid nanoparticles based on 20 nm (11·10 cm/W) and 30 nm (18·10 cm/W)
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12
gold cores than β of pure compound 1b without gold (3.2·10 cm/W). It should be noted that in the case of resonant
excitation of hybrid nanoparticles based on gold cores and subphthalocyanine compounds [25] significant
enhancement of nonlinearity was found as well. Hereby we first demonstrate increase in nonlinear absorption, which
results in RSA effect utilizing nonresonant excitation. Considerable enhancement in nonlinear absorption for hybrid
nanoparticles presumably relates to high local E-field on the nanoparticle surface which is provided by LSPR. In the
previous study we demonstrated substantial increase in linear absorption of phthalocyanines attached to gold
nanoparticles [10] due to local field factor (LFF). But surface-averaged LFF strongly depends on the particle’s size.
In accordance with theory 30 nm particle provides an average field, which is higher than in the case of 20 nm gold. In
the present research, we observe the highest nonlinear absorption coefficient for hybrid nanoparticles with the largest
gold core that points to the same tendency which was found earlier for the linear absorption.
CONCLUSIONS
Novel hexadecachloro-substituted lanthanide monophthalocyaninates were obtained using template synthesis and
reaction of metallation of phthalocyanine ligand (two-stage method). It was observed, that the yields of erbium and
lutetium complexes were higher in the template approach. However, the total yield of europium complex is higher in
the case of the two-stage method. Target and intermidiate compounds were identified by MALDI TOF mass
spectrometry, IR and UV-vis spectroscopy revealing their tendency to aggregation. UV-vis spectrum of the
nonaggregated complex was registered as the excitation spectrum. Hybrids of Au nanoparticles (20nm and 30nm)
covered by hexadecachloro-substituted lanthanide monophthalocyaninates were prepared. The formation of hybrid
nanoparticles was proven by TEM and UV-vis spectroscopy methods. Elemental composition correlates well with
proposed structure of the conjugates. Considerable enhancement in nonlinear absorption was observed for hybrid

nanoparticles. The highest nonlinear absorption coefficient was found for hybrid particles based on Au (30 nm). This
phenomenon can be explained by increase of the local field factor along with increasing the nanoparticle size.
Acknowledgements
We are grateful to the Russian Scientific Fund (Grant 17-13-01197) for main support of this research. The part of
this work devoted to the investigated of plasmonic properties was supported by the Russian Foundation for Basic
Research (Grant Nos. 16-33-60005, and 16-07-00961) and Council under the President of the Russian Federation for
State Support of Young Scientists and Leading Scientific Schools (Grant MD-2991.2017.3). Transmission electron
microscopy experiments were realized using the equipment of CKP "Nanochemistry and nanomaterials", which was
purchased using the financial resources of the Development Program of M.V. Lomonosov Moscow State University.
The authors acknowledge collaboration with Prof Pavlos Lagoudakis, director of the Hybrid Photonics Laboratories at
the Skolkovo Institute of Science and Technology, for supporting this work by contributing the z-scan measurements.
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Effective approach to perchlorinated lanthanide phthalocyaninates was developed.
Hybrids composed of the gold cores covered by phthalocyanines were obtained.
Aggregation behaviour was investigated using UV-vis and fluorescence spectroscopy.
Enhancement in nonlinear absorption was observed for hybrid nanoparticles.
The highest nonlinear absorption coefficient was found for hybrids with Au 30 nm.

Novel perchlorinated Eu, Er and Lu monophthalocyaninates were prepared. Hybrid nanoparticle
conjugates composed of the gold cores (20 and 30 nm in diameter) covered by the layers of target
phthalocyanines were obtained. Considerable enhancement in nonlinear absorption was observed for
hybrid nanoparticles.