Investigation of photochemical and photophysical properties of novel silicon(IV) phthalocyanines and their μ-oxo dimers

Article abstract of DOI:10.3906/kim-1701-23

The synthesis and characterization of novel tetraalkylthio (SC₆ H₁₃ or SC ₁₂ H₂₅) substituted μ -oxo silicon(IV) phthalocyanines (3a and 3b) and their μ-oxo derivatives (4a and 4b) were described in this study.

Full text of DOI:10.3906/kim-1701-23

Turk J Chem
Turkish Journal of Chemistry
(2017) 41: 803 – 812
¨
http://journals.tubitak.gov.tr/chem/
˙
c
⃝ TUBITAK
doi:10.3906/kim-1701-23
Research Article
Investigation of photochemical and photophysical properties of novel silicon(IV)
phthalocyanines and their µ-oxo dimers
Omer GUNGOR1,2, Mahmut DURMUS¸1, Vefa AHSEN1,∗
1Department of Chemistry, Gebze Technical University, Gebze, Kocaeli, Turkey
2Department of Chemistry Technology, Kocaeli University, Advanced Vocational School
¨
¨
¨
¨
˙
of Hereke Omer Ismet Uzunyol, Kocaeli, Turkey
Received: 10.01.2017
•
Accepted/Published Online: 06.04.2017
•
Final Version: 20.12.2017
Abstract: The synthesis and characterization of novel tetraalkylthio (SC6 H13 or SC12 H25) substituted µ-oxo sili-
con(IV) phthalocyanines (3a and 3b) and their µ-oxo derivatives (4a and 4b) were described in this study. These
silicon(IV) phthalocyanines were characterized using different spectroscopic techniques such as UV-Vis, 1 H NMR, FT-
IR, and mass and elemental analysis, as well. Furthermore, the photophysical (fluorescence quantum yields and lifetimes)
and photochemical (singlet oxygen generation) properties of the newly synthesized silicon(IV) phthalocyanines (3a, 3b,
4a, and 4b) were investigated in dimethylformamide solution. The absorption and fluorescence excitation wavelengths of
the studied silicon(IV) phthalocyanines were blue-shifted when they converted to their µ-oxo dimers. The fluorescence
quantum yield and lifetime values decreased with the substitution of the tetraalkylthio groups on the phthalocyanine
ring. The singlet oxygen generation of the studied silicon(IV) phthalocyanines increased with the formation of the µ-oxo
bridge between two phthalocyanine rings.
Key words: Phthalocyanine, silicon, photochemical, photophysical, singlet oxygen, fluorescence
1. Introduction
Phthalocyanines (Pcs) are among the most extensively studied classes of organic functional materials due to their
delocalized aromatic 18-π electron system, which is closely related to that of the naturally occurring porphyrin
ring.1 Pcs have been widely studies as molecular materials because of their outstanding electronic and optical
properties. Apart from their extensive use as blue and green colorants, they have different applications, such as
in catalytic processes,2 nonlinear optics,3 gas sensors,4 liquid crystals,5 and photodynamic therapy (PDT) of
cancer.6 Furthermore, they are excellent building blocks for supramolecular chemistry.
Metallophthalocyanines have low solubility in most organic solvents. The solubility of these compounds
can be increased by substitution of the Pc framework with various groups. Octasubstituted Pcs are generally
less soluble than tetrasubstituted Pcs in organic solvents due to the high dipole moment of tetrasubstituted
derivatives.7 The 4A group Pcs metallo are of interest because various groups can be attached to the axial
positions on the metal center. Furthermore, some of these Pcs are capable of forming linear stacked polymers,
which represent an effective approach to building metallomacrocyclic conductors.8
The most well-known µ-oxo Pc dimers are those of their silicon(IV) derivatives. These are easily obtained
by refluxing SiPc(OH)2 with K2 CO3 in toluene for several hours. The spectroscopic properties of these dimeric
∗Correspondence: ahsen@gtu.edu.tr
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Pcs have been intensively studied. The Q-band absorptions of dimeric silicon(IV) Pcs were shifted towards a
lower wavelength compared to their monomeric counterparts in the electronic absorption spectra and hence this
became a good example to confirm the exciton model.9
Scientists are very interested in the axially substituted silicon(IV) Pcs due to their superior structural
properties. These compounds are not able to aggregate due to their special structural features and thus avoid
fluorescence quenching.10 They are also very attractive targets for the study of photophysical processes.11
Silicon(IV) Pc derivatives are capable of forming stacked µ-oxo oligomeric structures in which the stacking axis,
formed by Si−O−Si bonds, is orthogonal to the Pc π-planes. These µ-oxo oligomers have been considered
useful in developing molecular electronic devices because of their excellent photophysical and photochemical
stabilities.12−14
In this paper, we report the synthesis of new silicon(IV) phthalocyanines (3a and 3b) bearing alkylthio
groups (SC6 H13 and SC12 H25 ) and their µ-oxo bridged silicon(IV) Pc dimers (4a and 4b). The aim of the
present study is the synthesis of novel Pc compounds as photosensitizers for PDT in cancer treatment. The
photophysical properties such as fluorescence quantum yields and lifetimes and photochemical properties such as
singlet oxygen quantum yields of these novel silicon(IV) phthalocyanines were investigated in dimethylformamide
(DMF).
2. Results and discussion
The general synthetic routes for the synthesis of the new compounds (3a, 3b, 4a, and 4b) are given in
Schemes 1 and 2. The peripheral tetra substituted monomeric silicon(IV) Pcs (3a and 3b) were prepared
by cyclotetramerization of alkylthio (SC6 H13 or SC12 H25) substituted isoiminoindolines in the presence of
SiCl4 in quinoline. The most well-known µ-oxo bridged Pc dimers are those of SiPc derivatives. These Pcs are
easily obtained by the refluxing of SiPc(OH)2 and K2 CO3 in a toluene-pyridine solvent mixture for several
hours.9 In this study, the µ-oxo silicon(IV) Pcs 4a and 4b were also synthesized from monomeric counterparts
3a or 3b in the presence of K2 CO3 at reflux temperature in a dry toluene-pyridine solvent mixture.
The synthesized novel compounds were characterized by elemental analysis and standard spectroscopic
methods such as FT-IR, 1 H-NMR, UV-Vis, and mass. The novel Pcs are insoluble in most of the organic
solvents (DMSO, toluene, THF, ethanol). The same property was observed in the unsubstituted dihydroxy
silicon(IV) Pc. The decreased solubility of the new compounds is probably due to the increased hydrogen bonds
on the axial positions (Figure S1).
In the FT-IR spectra of the silicon(IV) Pcs, the broad bands were observed at around 3470 cm−1 and
they were assigned to the O-H vibrations on the central silicon atom. The disappearance of the N-H vibrations
on the vibration peak belongs to diiminoisoindoline compounds (2a and 2b) at 3400 cm−1 can be assigned to
the formation of Pc ring. The Si-Cl peak is also observed at 520 cm−1 for chloro silicon(IV) phthalocyanine.15
In the case of the dihydroxy derivative, this band disappears, while the observation of the vibrations at 835
cm−1 are attributed to O-Si-O antisymmetric stretching vibrations in silicon(IV) Pcs (3a, 3b and 4a and 4b).
For the µ-oxo silicon(IV) Pc (4a and 4b) compounds, a broad band at around 990 cm−1 was assigned to the
Si-O-Si asymmetric stretching vibration. Therefore, evidence for the existence of a Si-O-Si bond in the dimer is
of importance for assigning the structure.16−18 The aliphatic C-H vibrations on the silicon(IV) Pcs were also
observed at around 2925–2850 cm−1 . The C-N stretching vibrations were also observed at around 1042–1044
cm−1 for these compounds (Figures S2–S5).
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NH
NH
CN
CN
CN
NH3
RSH
NaOCH3
MeOH
K2CO3
DMSO
CN
RS
RS
O2N
NH
- R= C H
1a
2a - R= C6H13
2b - R= C12H25
6
13
1b- R= C12H25
SR
OH
SiCl4
RS
N
Quinoline
N
N
Si
OH
N
N
N
N
N
SR
RS
- R= C H
3a
6
13
- R= C H
3b
12 25
Scheme 1. Synthesis of tetraalkylthio substituted silicon(IV) phthalocyanines.
OH
SR
RS
N
N
N
Si
N
N
OH
SR
N
N
N
RS
N
K2CO3
O
N
N
N
SR
RS
Si
N
N
N
SR
Toluene
Pyridine
RS
N
N
N
OH
N
SR
RS
N
N
Si
N
N
N
RS
SR
HO
3a - R= C6H13
3b - R= C12H25
4a - R= C6H13
4b - R= C12H25
Scheme 2. Synthesis of tetraalkylthio substituted dimeric silicon(IV) phthalocyanines (4a and 4b).
The most well-known 1 H NMR spectra of µ-oxo Pc dimers were observed as split into two couples
compared to the monomer counterparts.9 The synthesized silicon(IV) Pcs (3a, 3b and 4a, 4b) showed the
characteristic 1 H NMR spectra in deuterated chloroform. In the 1 H NMR spectra of the monomeric silicon(IV)
phthalocyanine derivatives (3a and 3b), the Si-OH protons were observed at –2.05 ppm for 3a and –2.10 ppm
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for 3b due to the magnetic anisotropy of the Pc core.19 The aromatic protons of Pcs were observed between
8.73 and 8.10 ppm for 3a and between 8.75 and 8.07 ppm for 3b, integrating a total of twelve protons. The
aliphatic CH2 protons were observed at three different regions at around 3.40, 1.75, and 1.25–1.45 ppm due to
their diverse chemical environment and their proximity to the Pc rings. The methyl protons were observed at
around 0.85 ppm, which is higher field than expected due to the magnetic anisotropy effect of the Pc ring.19
In the 1 H NMR spectra of dimeric silicon(IV) Pc derivatives (4a and 4b), the Si-OH protons were observed
at around –2.42 ppm. The aromatic protons on the Pc ring were observed as two sets between 8.75–8.07 and
7.92–7.44 ppm for 4a and between 9.11–8.33 and 8.28–7.97 ppm for 4b, integrating 24 protons. The aliphatic
CH2 protons were observed at three different regions at around 3.56–3.40, 1.82–1.50, and 1.48–1.20 ppm due
to their diverse chemical environment and their proximity to the Pc rings. The methyl protons were observed
at high field at around 0.73–0.52 ppm for 4a and 0.54–0.31 ppm for 4b due to the magnetic anisotropy effect
of the Pc ring.19
The mass spectra of the silicon(IV) Pcs (3a, 3b and 4a, 4b) also confirmed the proposed structures of
the target compounds and the molecular ion peaks were observed at m/z : 1039.74 as [M]+ for 3a (Figure S6),
1376.36 as [M]+ for 3b (Figure S7), 2061.98 as [M]+ for 4a (Figure S8), and 2734.89 as [M]+ for compound 4b
(Figure S9). Furthermore, the mass spectra of the dimers (4a, 4b) show that they did not consist of a trimer.
The UV-Vis absorption spectra of monomeric (3a and 3b) and dimeric (4a and 4b) silicon(IV) Pcs
were measured in DMF solutions. The µ-oxo silicon(IV) Pc dimers generally exhibit approximately 30 nm
blue-shifted Q-band absorption when compared to their corresponding monomer counterparts.20 It is generally
agreed that the blue shift of the Q-bands with respect to the dimer is due to an excitonic interaction of the
transition dipoles of the coplanar silicon(IV) Pc units having central symmetry along the Si−O−Si axis, with
no significant molecular orbital overlap. The UV-Vis absorption spectra of the studied monomeric (3a and 3b)
and dimeric (4a and 4b) silicon(IV) Pcs in DMF solutions are supplied in Figure 1 for comparison purposes.
The single narrow Q-bands were observed at 696, 695, 665, and 661 nm for compounds 3a, 3b, 4a, and 4b
in this solvent, respectively (Table 1). The absorption spectra of the monomer and µ-oxo dimer are in good
agreement with previously reported data.20
1
0.8
3a
3b
4a
4b
0.6
0.4
0.2
0
300
400
500
600
700
800
Wavelength (nm)
Figure 1. UV-Vis absorption spectra of compounds 3a, 3b, 4a, and 4b in DMF. Concentration = 1 × 10−5 M.
2.1. Aggregation studies
Aggregation is usually depicted as a coplanar association of rings progressing from monomer to dimer and higher
order complexes. It is dependent on the concentration and nature of the used solvent, nature of the substituents,
complexed metal ions, and temperature.21 In the aggregation state, the electronic structures of the complexed
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Table 1. Absorption, excitation, and emission spectral data for the monomeric (3a and 3b) and µ-oxo dimeric (4a
and 4b) silicon(IV) phthalocyanines in DMF.
Stokes shift,
Compound λmax (nm) log ε λEx (nm) λEm (nm)
∆
(nm)
Stokes
3a
3b
4a
4b
SiPc
696
695
665
661
697
4.85
4.86
4.90
4.94
4.04
700
700
662
662
700
710
710
664
666
709
10
10
2
4
9
λmax : Absorption maximum, λEx : excitation maximum, λEm : emission maximum.
Pc rings are perturbed, resulting in alternation of the ground and excited state electronic structures.22 In this
study, the aggregation behaviors of monomeric (3a and 3b) and µ-oxo dimeric (4a and 4b) silicon(IV) Pcs
were investigated at different concentrations in DMF. We complied with the Beer–Lambert law for all of these
compounds at concentrations ranging from 1.2 × 10−5 to 2.0 × 10−6 M. None of the studied Pc compounds
showed any aggregation at these concentration ranges in DMF (Figure S10 for 3a, Figure S11 for 3b, Figure
S12 for 4a, Figure S13 for 4b).
400
300
200
100
0
1
Excitation
Emission
Absorption
0.8
0.6
0.4
0.2
0
500
600
700
800
Wavelength (nm)
Figure 2. Electronic absorption, fluorescence emission, and excitation spectra for compound 4a in DMF. Excitation
wavelength is 620 nm.
2.2. Fluorescence quantum yields and lifetimes
Figures 2 and 3 show the electronic absorption, fluorescence emission, and excitation spectra of µ-oxo dimeric
silicon(IV) Pcs (4a and 4b) in DMF. The peak maxima of the fluorescence emission and excitation spectra
of the studied compounds (3a, 3b, 4a, and 4b) in DMF are listed in Table 1. Florescence emission peaks
were observed at 664 and 666 nm for µ-oxo dimeric silicon(IV) Pcs (4a and 4b) and at 710 nm for the
monomeric compounds (3a and 3b) in DMF (Table 1). While the observed Stokes shifts (λems − λexc) of the
studied monomeric silicon(IV) Pcs (3a and 3b) were higher, these values of dimeric derivative Pcs (4a and
4b) were lower than those of unsubstituted silicon(IV) Pc in DMF.23 The excitation spectra of the studied
silicon(IV) Pcs were similar to the absorption spectra of these compounds and both were mirror images of
the fluorescence emission spectra in DMF. All studied compounds showed similar electronic absorption and
fluorescence excitation spectra. This suggests that the nuclear configurations of the ground and excited states
of these compounds were similar and these compounds were not affected by excitation in DMF.
The fluorescence quantum yields (ΦF ) of silicon(IV) Pcs (3a, 3b, 4a, and 4b) in DMF are given in
Table 2. The ΦF values of all studied alkylthio substituted silicon(IV) Pcs were lower than those of standard
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400
300
200
100
0
1
Excitation
0.8
0.6
0.4
0.2
0
Emission
Absorption
500
600
700
Wavelength (nm)
800
Figure 3. Electronic absorption, fluorescence emission, and excitation spectra for compound 4b in DMF. Excitation
wavelength is 620 nm.
8500
6500
Prompt
4500
2500
500
Decay
1600
1700
1800
Channels
1900
2000
4
0
1630
1830
2030
2230
2430
-4
Channels
Figure 4. Time correlated single photon counting (TCSPC) trace for compound 4a in DMF with residuals. Excitation
wavelength = 665 nm.
unsubstituted silicon(IV) Pc in DMF. The µ-oxo dimeric silicon(IV) Pcs (4a and 4b) showed higher fluorescence
quantum yields (ΦF ) than their monomeric counterparts (3a and 3b) in DMF.
Table 2. Photophysical and photochemical data for the monomeric (3a and 3b) and µ-oxo dimeric (4a and 4b)
silicon(IV) phthalocyanines in DMF.
Compound ΦF
3a
τF (ns) Φ∆
0.09
3.85
3.98
4.21
4.13
0.10
0.11
0.18
0.19
0.12a
3b
4a
4b
SiPc
0.09
0.15
0.14
0.52a 4.91
aData from Ref. [23].
Fluorescence lifetime (τF ) refers to the average time a molecule stays in its excited state before returning
to its ground state by emitting. Many factors such as internal conversion, intersystem crossing, aggregation,
and used solvent affect the fluorescence lifetime of a photosensitizer.24 Fluorescence lifetime (τF ) values of the
synthesized Pc complexes (3a, 3b, 4a, and 4b) were measured by a time correlated single photon counting
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(TCSPC) method in DMF solutions. Fluorescence lifetime spectra were given in Figure 4 for compound 4a as
an example in DMF solution.
2.3. Singlet oxygen quantum yields
Singlet oxygen is generated as a result of a bimolecular interaction between the triplet state of a photosensitizer
and the ground state (triplet) molecular oxygen and is quantified as singlet oxygen quantum yield (Φ∆).24 In
this study, the generated singlet oxygen by silicon(IV) Pcs (3a, 3b, 4a, and 4b) was determined using UV-Vis
spectroscopy. The absorption decay of 1,3-diphenylisobenzofuran (DPBF) was monitored at 417 nm during light
irradiation using a photochemical set-up.25,26 No change was observed in the Q-band intensities of the studied
silicon(IV) Pcs during the Φ∆ determinations, indicating that the used light irradiation (30 V) did not degrade
the studied Pcs (Figure 5 for Pc 4b and Figures S14-S17 for phthalocyanines 3a, 3b, and 4a, respectively).
The Φ∆ values of the synthesized silicon(IV) Pcs (3a, 3b, 4a, and 4b) and unsubstituted silicon(IV) Pc are
given in Table 2. These values of monomeric silicon(IV) Pcs (3a and 3b) in DMF were found lower than those
for unsubstituted silicon(IV) Pc. These values of dimeric silicon(IV) Pcs (4a and 4b) were higher than those
for unsubstituted silicon(IV) Pc in DMF, which means that these Pcs can be used as photosensitizers for PDT
applications.
1
1
y =-0.03x + 0.7469
0.8
R² = 0.9321
0.6
0.8
0.6
0.4
0.2
0
0 s
0.4
0.2
0
-1
1
3
5
7
9
11 13 15
5 s
Time (s)
10 s
15 s
300
400
500
Wavelength (nm)
600
700
800
Figure 5. Electronic absorption spectral changes of compound 4b during the determination of singlet oxygen quantum
yield in DMF at a concentration of 1 × 10−5 M.
2.4. Conclusions
In the presented work, the synthesis of tetraalkylthio (SC6 H13 and SC12 H25) substituted monomeric (3a and
3b) and µ-oxo dimeric (4a and 4b) silicon(IV) Pcs was described and these Pcs were fully characterized by
elemental analysis and the standard spectral data such as FT-IR, 1 H NMR, UV-Vis, and mass spectra. The
photophysical and photochemical properties including fluorescence quantum yields, lifetimes, and singlet oxygen
generation of all these silicon(IV) Pcs were also described and compared with unsubstituted SiPc. In solution,
the absorption spectra of the new compounds (3a, 3b, 4a, and 4b) showed monomeric behavior evidenced by
a single (narrow) Q-band, typical of metallated Pc complexes in DMF. The dimerization of the Pc rings by the
µ-oxo silicon bridge caused approximately 30 nm of blue-shift to the absorption wavelength of the Q-band. The
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photophysical (fluorescence quantum yields and lifetimes) values of monomeric silicon(IV) Pcs (3a and 3b) were
found lower than those of unsubstituted SiPc in DMF. The µ-oxo silicon(IV) Pcs (4a and 4b) showed higher
singlet oxygen quantum yields than unsubstituted SiPc and the monomeric counterparts (3a and 3b). As a
result, the µ-oxo silicon(IV) Pcs (4a and 4b) offer potential as candidate photosensitizers for the treatment of
cancer by PDT.
3. Experimental
3.1. Materials and methods
The used materials and equipment are given in the Supplementary information. Photophysical and photochem-
ical parameters were calculated according to previous literature.27
3.2. Synthesis
4-Hexylthiophthalonitrile (1a), 4-dodecylthiophthalonitrile (1b), 1,3-dihydro-1,3-diimino-6-(n-hexylthio)-isoimi-
noindoline (2a) and 1,3-dihydro-1,3-diimino-6-(n-dodecylthio)-isoiminoindoline (2b) were synthesized, purified,
and characterized according to the literature procedures.28−30
3.2.1. 1,3-Dihydro-1,3-diimino-6-(n-hexylthio)-isoiminoindoline (2a)
To a solution of 1a (3.26 g, 2.04 mmol) in dry methanol (150 mL) under an argon atmosphere, sodium methoxide
(0.165 g, 3.06 mmol) was added. Anhydrous ammonia was bubbled through the mixture for 6 h at reflux
temperature. The ammonia inlet was stopped and the volume of the solution was reduced to 50 mL under
reduced pressure. With crystallization from MeOH/acetone 1:5 (v/v), 2a was obtained as pale yellow crystals.
Yield: 2.96 g, 85%, Mp = 165 ◦ C (dec.). FT-IR νmax /cm−1 : 3400 (NH), 2951–2923 (aliphatic C-H), 1641,
1593, 1536, 1455, 1380, 1320, 1289, 1237, 1154, 1075, 885, 813, 729, 678. 1 H NMR (CDCl3) (δ: ppm): 8.22
(br, N-H, 3H), 7.40 (m, Ar-H, 3H), 2.87 (t, J = 7.3 Hz, S-CH2 , 2H), 1.60 (q, S-C-CH2 , 2H), 1.25–1.28 (m,
C-CH2 -C, 6H), 0.80 (t, J = 6.5 Hz, CH3 , 3H). Mass (ES+), (m/z): Calculated as 261.39 for C14 H19 N3 S;
Found: 262.26 [M+H]+ . Anal. Calcd. for C14 H19 N3 S: C, 64.33%; H, 7.33%; N, 16.08%; Found C, 64.73%; H,
7.52%; N, 15.93%.
3.2.2. Tetrakis (4-hexylthio)dihydroxy silicon(IV) phthalocyanine (3a)
A mixture of the 1,3-dihydro-1,3-diimino-6-(n-hexylthio)-isoiminoindoline (2a) (1 g, 3.82 mmol) in dry quinoline
(5 mL) was stirred at room temperature for 10 min. SiCl4 (0.22 mL, 1.91 mmol) was added to this mixture
and refluxed for 2 h. After this time, the reaction was cooled to room temperature and 5 mL of hydrochloric
acid (36.5%) was then added to the mixture and stirred at 60 ◦ C for 1 h. The formed blue solid product was
filtered and washed with ammonium hydroxide, water, methanol, and ethyl acetate. The pure product was
obtained after drying at 110 ◦ C overnight. Yield: 0.30 g (29%). Mp > 400 ◦ C. FT-IR νmax /cm−1 : 3462
(OH), 2924–2852 (aliphatic C-H), 1600 (C=N), 1517 (C=C), 1451, 1392, 1349, 1312, 1145, 1068, 1042, 929,
900, 835 (Si-OH), 767, 751, 732, 695. 1 H NMR (CDCl3) (δ: ppm): 8.73 (m, Ar-H, 7H), 8.10 (m, Ar-H, 5H),
3.36 (t, J = 3 Hz, S-CH2 , 8H), 1.72 (q, S-C-CH2 , 8H), 1.26–1.42 (m, C-CH2 -C, 24H), 0.84 (t, J = 3 Hz, CH3 ,
12H), –2.05 (s, OH, 2H). UV-Vis (DMF): λmax , nm (log ε): 696 (4.85), 673 (4.43), 636 (4.25), 361 (4.58). Mass
(ES+), (m/z): Calculated as 1039.52 for C56 H66 N8 S4 O2 Si; Found: 1039.74 [M]+ , 1022.80 [M-OH]+ , 922.58
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[M-SC6 H13 ]+ . Anal. Calcd. for C56 H66 N8 S4 O2 Si: C, 64.70%; H, 6.40%; N10.78%; Found C, 64.95%; H,
6.55%; N, 10.63%.
3.2.3. Tetrakis (4-dodecylthio)dihydroxy silicon(IV) phthalocyanine (3b)
A mixture of the 1,3-dihydro-1,3-diimino-6-(n-dodecylthio)-isoiminoindoline (2b) (1 g, 2.89 mmol) in dry
quinoline (5 mL) was stirred at room temperature for 10 min. SiCl4 (0.17 mL, 1.45 mmol) was added to
this mixture and refluxed for 2 h and then it was cooled to room temperature. Next, 5 mL of hydrochloric acid
(36.5%) was added to the mixture and stirred at 60 ◦ C for 1 h. The formed blue solid product was filtered and
washed with ammonium hydroxide, water, methanol, and ethyl acetate. The pure product was obtained after
drying at 110 ◦ C overnight. Yield: 0.25 g (23%). Mp > 400 ◦ C. FT-IR νmax /cm−1 : 3456 (OH), 2919–2851
(aliphatic C-H), 1601 (C=N), 1518 (C=C), 1455, 1396, 1349, 1315, 1267, 1148, 1068, 1044, 931, 831 (Si-OH),
767, 752, 731, 695. 1 H NMR (CDCl3) (δ: ppm): 8.75 (m, Pc-H, 7H), 8.07 (m, Pc-H, 5H), 3.39 (t, J = 3 Hz,
S-CH2 , 8H), 1.76 (q, S-C-CH2 , 8H), 1.29–1.47 (m, C-CH2 -C, 72H), 0.89 (t, J = 3 Hz, CH3 , 12H), –2.10 (s,
OH, 2H). UV-Vis (DMF): λmax , nm (log ε): 695 (4.86), 665 (4.43), 629 (4.28), 364 (4.51). Mass (ES+), (m/z):
Calculated as 1376.15 for C80 H114 N8 S4 O2 Si; Found: 1376.36 [M]+ , 1359.06 [M-OH]+ , 1344.80 [M-2OH]+ ,
1190.64 [M-SC12 H25 ]+ . Anal. Calcd. for C80 H114 N8 S4 O2 Si: C, 69.82%; H, 8.35%; N, 8.14%; Found C,
69.93%; H, 8.48%; N, 8.36%.
3.2.4. General procedure for the synthesis of 4a and 4b
The tetraalkylthio substituted silicon(IV) phthalocyanine (3a or 3b) [3a (0.2 g, 0.19 mmol), 3b (0.2 g, 0.15
mmol)] was dissolved in a mixture of dry toluene (5 mL) and dry pyridine (5 mL). Anhydrous K2 CO3 [13.30
mg (0.1 mmol) for 3a and 10.04 mg, (0.07 mmol) for 3b] was added to this solution and refluxed for 2 h. The
solvent was removed after this time. The resulting blue solid product was obtained after washing with water,
acetone, and ethyl acetate.
4a: Yield: 0.1 g (51%). Mp > 400 ◦ C. FT-IR νmax /cm−1 : 3463 (OH), 2924–2851 (aliphatic C-H),
1601 (C=N), 1518 (C=C), 1454, 1392, 1314, 1260, 1144, 1068, 1043, 986 (Si-O-Si), 929, 832 (Si-OH), 815, 768,
751. 1 H NMR (CDCl3) (δ: ppm): 9.01–8.30 (m, Pc-H, 16H), 7.92–7.44 (m, Pc-H, 8H), 3.55–3.41 (m, S-CH2 ,
16H), 1.82–1.70 (m, S-C-CH2 , 16H), 1.42–1.31 (m, CH2 , 48H), 0.73–0.52 (m, CH3 , 24H), –2.42 (s, OH, 2H).
UV-Vis (DMF): λmax , nm (log ε): 665 (4.90), 628 (4.52), 594 (4.34), 361 (4.74). MS (ES+), (m/z): Calculated
as 2061.02 for C112 H130 N16 S8 O3 Si2 ; Found: 2061.98. [M]+ , 2044.93 [M-OH]+ , 1039.63 [M-Pc]+ , 1022.60
[M-Pc-OH]+ . Anal. Calcd. for C112 H130 N16 S8 O3 Si2 : C, 65.27%; H, 6.36%; N, 10.87%; found C, 65.93%; H,
6.29%; N, 11.03%.
4b: Yield: 0.095 g (48%). Mp > 400 ◦ C. FT-IR νmax /cm−1 : 3469 (OH), 2923–2852 (aliphatic C-H),
1601 (C=N), 1519 (C=C), 1454, 1352, 1312, 1147, 1070, 1042, 995 (Si-O-Si), 930, 831 (Si-OH), 817, 768, 751,
732. 1 H NMR (CDCl3) (δ: ppm): 9.11–8.93 (m, Pc-H, 16H), 8.28–7.97 (m, Pc-H, 8H), 3.56–3.42 (m, S-CH2 ,
16H), 1.73–1.50 (m, S-C-CH2 , 16H), 1.48–1.20 (m, CH2 , 144H), 0.54–0.31 (m, CH3 , 24H), –2.34 (s, OH, 2H).
UV-Vis (DMF): λmax , nm (log ε): 661 (4.94), 630 (4.51), 594 (4.34), 368 (4.74). MS (ES+), (m/z): Calculated
as 2734.29 for C160 H226 N16 S8 O3 Si2 ; Found: 2734.89 [M]+ , 2718.30 [M-OH]+ , 2516.91 [M-SC12 H25 -OH]+ ,
1359.16 [M-Pc-OH]+ . Anal. Calcd. for C160 H226 N16 S8 O3 Si2 : C, 70.28%; H, 8.33%; N, 8.20%; Found C,
70.43%; H, 8.29%; N, 8.56%.
811

¨
GUNGOR et al./Turk J Chem
¨
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¨
812

Supplementary information
Investigation of photochemical and photophysical properties of novel silicon(IV)
phthalocyanines and their μ-oxo dimers.
Ömer GÜNGÖR, Mahmut DURMUŞ, Vefa AHSEN
1

Materials
1,3-diphenylisobenzofuran (DPBF), and sodium were purchased from Fluka. Silica gel 60 for
column chromatography, toluene, pyridine, quinoline and SiCl4 were purchased from Merck.
All other reagents and solvents were reagent grade quality and were obtained from
commercial suppliers. Toluene was distilled from sodium before use.
Equipments
UV–Vis spectra were recorded with a Shimadzu 2001 UV spectrophotometer. Fluorescence
excitation and emission spectra were recorded on a Varian Cary Eclipse spectrofluorometer
using 1 cm pathlength cuvettes at room temperature. Infrared spectra were recorded on a
Perkin Elmer Spectrum BX FT-IR system. The mass spectra were recorded on a Bruker Micro
1
ES+ system. H NMR spectra were recorded in CDCl3 solutions on a Varian 500 MHz
spectrometer using TMS as an internal reference.
Photo-irradiations were done using a General Electric quartz line lamp (300 W). A 600 nm
glass cut off filter (Schott) and a water filter were used to filter off ultraviolet and infrared
radiations, respectively. An interference filter (Intor, 670 nm with a band width of 40 nm) was
additionally placed in the light path before the sample. Light intensities were measured with a
POWER MAX5100 (Molelectron detector incorporated) power meter.
Photophysical parameters
Photophysical and photochemical values were calculated according to previous literature.1
Silicon phthalocyanine was used as standard compound.
References
[1]
Durmus, M.; Yaman, H.; Göl, C.; Ahsen, V.; Nyokong. T. Dyes and Pigments. 2011,
91, 153-163.
2

H
O
N
N
N
N
Si
N
N
N
N
O
H
H
O
N
N
N
N
N
Si
N
N
N
O
H
Figure S1. Intermolecular hydrogen bonding in dihydroxy silicon phthalocyanine.
94
92
90
88
86
84
82
80
78
76
74
72
70
68
66
64
62
60
58
2852.15
3462.56
1517.93
1451.18
1600.46 1312.53
2924.07
643.61
1145.50
%T
695.46
830.5
4
1349.62
929.34
732.44
815.97
1042.42
1392.86
767.20
1068.11
1000
751.78
4000
3500
3000
2500
2000
1500
Wavenumbers (cm- 1
)
Figure S2. IR spectrum of compound 3a.
3

90
85
80
75
70
65
60
55
50
45
40
3456.23
628.11
643.64
1518.50
1148.71
1396.95
%T
1601.07
1267.28
695.64
1455.83
2851.32
1044.78
995.021315.25
731.66
831.94
816.41
1068.53
2919.94
1349.87
767.28
752.05
9679.7301.01
4000
3500
3000
2500
2000
)
1500
1000
Wavenumbers (cm- 1
Figure S3. IR spectrum of compound 3b.
94
92
90
88
86
84
82
80
78
76
74
72
70
68
66
64
62
60
58
56
54
2851.32
1519.13
3463.25
1454.23
1312.53
643.61
2924.17
1145.50
1601.64
900.02
992.93
%T
695.46
832.63
1352.13
929.34
815.97
1042.42
732.44
1393.16
1068.11
1000
7687.2501.52
4000
3500
3000
2500
2000
1500
Wavenumbers (cm- 1
)
Figure S4. IR spectrum of compound 4a.
4

94
92
90
88
86
84
82
80
78
76
74
72
70
68
66
64
62
60
58
56
54
2852.19
1518.88
3469.15
1312.53
1454.31
1145.50
2923.58
900.02
695.46
831.23
%T
1601.43
1352.13
928.86
1042.42
817.97
732.44
1393.16
1068.64
768.20
751.26
4000
3500
3000
2500
2000
1500
1000
Wavenumbers (cm- 1
)
Figure S5. IR spectrum of compound 4b.
5

SC6H13
H13C6S
OH
N
N
N
Si
N
N
N
N
N
SC6H13
H13C6S
SC6H13
H13C6S
OH
N
N
N
Si
N
N
OH
N
N
SC6H13
N
H13C6S
OH
N
H13C6S
N
N
Si
N
N
OH
N
N
N
SC6H13
SC6H13
H13C6S
H13C6S
OH
N
N
N
Si
N
N
N
N
N
H13C6S
Figure S6. Mass spectrum (ES+) of compound 3a.
SC12H25
H25C12S
OH
N
N
N
Si
N
N
N
N
SC12H25
N
SC12H25
H25C12
S
OH
H25C12S
N
SC12H25
N
N
Si
N
H25C12S
N
OH
N
N
N
N
N
N
Si
N
N
SC12H25
N
N
H25C12
S
N
SC12H25
H25C12S
SC12H25
SC12H25
H25C12S
OH
N
H25C12S
N
N
N
Si
N
N
N
N
OH
N
Si
N
N
N
N
N
N
N
H25C12S
H25C12S
SC12H25
H25C12S
OH
N
N
N
Si
N
N
N
N
N
H25C12S
Figure S7. Mass spectrum (ES+) of compound 3b.
5

O
SC6H13
C6H13
S
N
N
N
N
Si
N
N
N
N
O
SC6H13
SC6H13
C6H13
S
S
C6H13
N
N
N
N
N
Si
N
N
N
C6H13
S
SC6H13
SC6H13
SC6H13
H13C6
S
OH
H13C6
S
OH
N
N
N
N
N
Si
N
N
Si
N
N
N
N
N
N
SC6H13
SC6H13
N
SC6H13
N
N
SC6H13
H13C6
S
H13C6
S
O
H13C6
S
OH
N
H13C6
S
N
N
N
N
Si
N
N
Si
N
N
N
N
N
N
SC6H13
N
N
SC6H13
H13C6
S
N
O
O
H13C6
S
Figure S8. Mass spectrum (ES+) of compound 4a.
SC12H25
SC12H25
H25C12
S
OH
H25C12
S
OH
N
N
N
N
Si
N
N
N
Si
N
N
N
N
N
N
N
N
SC12H25
N
SC12H25
SC12H25
O
H25C12
S
SC12H25
O
H25C12
S
OH
H25C12
S
SC12H25
H25C12
S
N
N
N
H25C12
S
N
N
Si
N
N
Si
N
N
N
N
N
N
N
N
N
Si
N
N
N
N
SC12H25
N
SC12H25
OH
N
N
N
SC12H25
H25C12
S
H25C12
S
SC12H25
H25C12
S
H25C12
S
OH
N
N
N
N
Si
N
N
N
N
SC12H25
O
H25C12
S
SC12H25
H25C12
S
N
N
N
Si
N
N
N
N
N
SC12H25
Figure S9. Mass spectrum (ES+) of compound 4b.
7

1
0.8
0.6
0.4
0.2
0
0.9
0.6
0.3
1.20E-05
1.00E-05
8.00E-06
6.00E-06
4.00E-06
2.00E-06
y = 76764x - 0.0308
R² = 0.9954
0
0.00E+00
4.00E-06
8.00E-06
1.20E-05
Concentration (M)
300
400
600
700
800
500Wavelength (nm)
Figure S10. UV-Vis spectra of compound 3a in DMF at different concentrations.
1
0.9
0.6
0.3
y = 62144x + 0.0927
R² = 0.9984
0.8
0.6
0.4
0.2
0
1.20E-05
1.00E-05
8.00E-06
6.00E-06
4.00E-06
2.00E-06
0
-5.08E-21
4.00E-06
8.00E-06
1.20E-05
Concentration (M)
300
400
500
600
Wavelength (nm)
700
800
Figure S11. UV-Vis spectra of compound 3b in DMF at different concentrations.
8

1
0.8
0.6
0.4
0.2
0
y = 63381x + 0.1301
0.9
0.6
0.3
0
R² = 0.9945
1.20E-05
1.00E-05
8.00E-06
6.00E-06
4.00E-06
2.00E-06
0.00E+00
5.00E-06
1.00E-05
1.50E-05
Concentration (M)
300
400
500
600
700
800
Wavelength (nm)
Figure S12. UV-Vis spectra of compound 4a in DMF at different concentrations.
1
0.9
0.6
0.3
0
y = 44860x +0.4477
R² = 0.9963
1.20E-05
1.00E-05
8.00E-06
6.00E-06
4.00E-06
0.8
0.6
0.4
0.2
0
2.00E-06
6.00E-06
1.00E-05
1.40E-05
Concentration (M)
300
400
500
600
700
800
Wavelength (nm)
Figure S13. UV-Vis spectra of compound 4b in DMF at different concentrations.
9

0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
y = -0.0026x + 0.7114
R² = 0.9951
0 s
5 s
10 s
15 s
20 s
25 s
30 s
0
20
40
Time
300
400
500
600
700
800
Wavelength (nm)
Figure 14. Electronic absorption spectral changes for DPBF during the determination of
singlet oxygen quantum yield in DMF.
1
0.9
0.6
0.3
0
y = -0.0289x+ 0.7671
R² = 0.97
0 s
0.8
0.6
0.4
0.2
0
5 s
10 s
15 s
20 s
0
5
10
15
20
Time (s)
300
400
500
Wavelenght (nm)
600
700
800
Figure S15. Electronic absorption spectral changes for compound 3a during the
determination of singlet oxygen quantum yield in DMF at a concentration of 1×10-5 M.
10

0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.9
0.6
0.3
0
y = -0.0313x + 0.6894
R² = 0.9461
0 s
5 s
10 s
15 s
20 s
25 s
30 s
0
5
10
15
Time (s)
300
400
500
600
Wavelength (nm)
700
800
Figure S16. Electronic absorption spectral changes for compound 3b during the
determination of singlet oxygen quantum yield in DMF at a concentration of 1×10-5 M.
1
1.2
y = -0.0392x + 0.778
0.8
R² = 0.9635
0 s
0.4
0.8
0
5 s
0
5
10
15
Time (s)
0.6
0.4
0.2
0
10 s
15 s
300
400
500
Wavelength (nm)
600
700
800
Figure S17. Electronic absorption spectral changes for compound 4a during the
determination of singlet oxygen quantum yield in DMF at a concentration of 1×10-5 M.
11

0.8
0.6
0.4
0.2
0
DPBF
3a
3b
4a
4b
0
5
10
15
Time (s)
Figure S18. DPBF absorption spectral changes for compound DPBF, 3a, 3b, 4a, and 4b
during the determination of singlet oxygen quantum yield in DMF.
8500
Prompt
6500
Decay
Fit
4500
2500
500
1600
1700
1800
1900
2000
Channels
4
0
Residuals
1630
-4
1830
2030
2230
2430
Channels
Figure S19. Time correlated single photon counting (TCSPC) trace for compound 3a in DMF
with residuals. Excitation wavelength= 710 nm.
12

8500
6500
4500
2500
500
Prompt
Decay
Fit
1600
1700
1800
1900
2000
Channels
Residuals
4
0
1630
1830
2030
2230
2430
-4
Channels
Figure S20. Time correlated single photon counting (TCSPC) trace for compound 3b in DMF
with residuals. Excitation wavelength= 708 nm.
8500
6500
Prompt
4500
2500
500
Decay
Fit
1600
1700
1800
1900
2000
Channels
4
0
Residuals
1630
1830
2030
2230
2430
-4
Channels
Figure S21. Time correlated single photon counting (TCSPC) trace for compound 4a in DMF
with residuals. Excitation wavelength= 665 nm.
13

8500
6500
4500
2500
500
Prompt
Decay
Fit
1600
1700
1800
Channels
1900
2000
4
0
Residuals
1630
1830
2030
Channels
2230
2430
-4
Figure S22. Time correlated single photon counting (TCSPC) trace for compound 4b in DMF
with residuals. Excitation wavelength= 667 nm.
10000
SiPc
IRF
1000
Fit
100
10
1
85
105
125
145
165
Time (ns)
Figure S23. Time correlated single photon counting (TCSPC) trace for compound SiPcCl2 in
DMF with residuals. Excitation wavelength= 709 nm.
14