Preparation and Electrochemical and Optical Properties of α-Alkoxyphthalocyanines with β-Pyridylthio Groups

Article abstract of DOI:10.1002/ejic.201900766

Phthalocyanines (Pcs) 5a-Mg, 5b-Mg, 6a-Mg, and 6b-Mg with eight alkoxy groups at α-positions and 2- or 4-pyridylthio groups at the β-positions, were prepared from 3,6-dialkoxy-4,5-dipyridylthiophthalonitriles. Magnesium complexes 5a-Mg, 5b-Mg, and 6a-Mg were treated with trifluoroacetic acid to produce free-base compounds 5a-2H, 5b-2H, and 6a-2H. In the UV/Vis spectra, Q-band absorption of Mg and free-base Pcs appeared near 760 nm and 780 nm, respectively, in chloroform and 745 nm and 760 nm, respectively, in methanol. Emission spectra of these Pcs showed small Stokes shifts in chloroform and methanol. Reactions of 5a-Mg, 5b-Mg, and 5b-2H with methyl iodide produced the corresponding Pcs 7a-Mg, 7b-Mg, and 7b-2H with methyl pyridinium groups, respectively. After methylation of the pyridine nitrogen, the Pcs were moderately soluble in water but had little solubility in chloroform. The UV/Vis and emission spectra of methylated Pcs 7a-Mg, 7b-Mg, and 7b-2H were obtained in methanol and water. Photobleaching of diphenylisobenzofuran (DPBF) was examined in methanol in the presence of Pcs 7b-Mg and 7b-2H, and was monitored by UV/Vis spectroscopy.

Full text of DOI:10.1002/ejic.201900766

DOI: 10.1002/ejic.201900766
Full Paper
Phthalocyanines
Preparation and Electrochemical and Optical Properties of
α-Alkoxyphthalocyanines with ꢀ-Pyridylthio Groups
Takeshi Kimura*,[a] Chiko Kudo,[a] and Shiduko Nakajo[a]
Abstract: Phthalocyanines (Pcs) 5a-Mg, 5b-Mg, 6a-Mg, and in chloroform and methanol. Reactions of 5a-Mg, 5b-Mg, and
6b-Mg with eight alkoxy groups at α-positions and 2- or 4- 5b-2H with methyl iodide produced the corresponding Pcs 7a-
pyridylthio groups at the ꢀ-positions, were prepared from 3,6- Mg, 7b-Mg, and 7b-2H with methyl pyridinium groups, respec-
dialkoxy-4,5-dipyridylthiophthalonitriles. Magnesium complexes tively. After methylation of the pyridine nitrogen, the Pcs were
5a-Mg, 5b-Mg, and 6a-Mg were treated with trifluoroacetic moderately soluble in water but had little solubility in chloro-
acid to produce free-base compounds 5a-2H, 5b-2H, and form. The UV/Vis and emission spectra of methylated Pcs 7a-
6a-2H. In the UV/Vis spectra, Q-band absorption of Mg and Mg, 7b-Mg, and 7b-2H were obtained in methanol and water.
free-base Pcs appeared near 760 nm and 780 nm, respectively, Photobleaching of diphenylisobenzofuran (DPBF) was exam-
in chloroform and 745 nm and 760 nm, respectively, in meth- ined in methanol in the presence of Pcs 7b-Mg and 7b-2H, and
anol. Emission spectra of these Pcs showed small Stokes shifts was monitored by UV/Vis spectroscopy.
Introduction
about Pcs containing both α-alkoxy and ꢀ-pyridylthio substitu-
ents are rare. Through previous studies about tetraazaporphy-
rins and Pcs,[13] we were interested in Pcs soluble in both or-
ganic solvent and water. To construct Pcs with pyridylthio and
alkoxy groups, 3,6-dialkoxy-4,5-dipyridylthiophthalonitrile was
prepared from dichlorodicyano-p-benzoquinone via two-step
reactions. This paper describes the preparation and structure
determination of Pcs with eight alkoxy groups at α-positions
and 2- or 4-pyridylthio groups at ꢀ-positions along with their
optical and electrochemical properties. In addition, cationic
species were prepared by treatment of pyridylthio groups of
Pcs with methyl iodide to solubilize Pcs in water and the photo-
bleaching of diphenylisobenzofuran (DPBF) with ambient light
was examined in methanol in the presence of Pcs 7b-Mg and
7b-2H.
Phthalocyanines (Pcs) and related compounds have actual or
potential ability as catalysts, optoelectronic devices, and sensi-
tizers for photodynamic therapy of cancer.[1,2] The most attract-
ive properties of Pcs for application to new functional materials
include: possession of a multi-step redox system from the ex-
panded π-conjugation system; a strong Q-band absorption and
related emission in the near-infrared region; and efficacy to
generate a singlet oxygen upon irradiation. However, many Pcs
have the disadvantage of low solubility in common solvents.
Although Pcs have been used as photosensitizers, their effect
may be disabled by self-quenching upon aggregation in solu-
tion.[1b,1c,2b] Substituents, such as alkyl groups and heteroatoms
at the α or ꢀ positions of the Pc core and axial ligands on the
central metal atoms, can improve the solubility of Pcs in organic
solvents, preventing aggregation in solution and promoting
easy purification by chromatography, recrystallization, and re-
precipitation.[3,4] In addition, α-substituents of Pcs can shift the Results and Discussion
Q-band absorption to lower energy [near-infrared] field com-
pared to ꢀ-substituents.[3] On the other hand, the ability of
Preparation of 3,6-Dialkoxy-4,5-dipyridylthiophthalonitrile
ammonium,[5] methylpyridinium,[6] sulfonic,[7] cyclodextrin,[8]
and peptide groups[9] to increase the solubility of Pcs in water,
have led to their application as photo-sensitizers for photody-
namic therapy. The results depended on the efficacy of the Pc
to generate singlet oxygen.[1c,2b] Although many reports exist
about Pcs with pyridyl,[10] pyridyloxy,[11] and pyridylthio groups
at the ꢀ-positions as water soluble compounds,[12] reports
ꢀ-Octa(4-pyridylthio)phthalocyanine has been studied as a rea-
gent for photodynamic therapy. However, this compound is in-
soluble in organic solvents such as chloroform, and the λmax
absorption in the UV/Vis spectrum is observed near 650 nm.[12]
To improve the solubility of this compound in organic sol-
vents and shift the Q band absorption to lower energy field,
substituents such as alkyl, alkoxy, and alkylthio groups could be
introduced at the α-positions.[3] Therefore, we tried to prepare
3,6-dialkoxy-4,5-dipyridylthiophthalonitrile (Scheme 1). Accord-
ing to a method reported previously, 3,6-dibutoxy-4,5-dichloro-
phthalonitrile (1) and 3,6-dioctyloxy-4,5-dichlorophthalonitrile
(2) were prepared by reduction of DDQ with sodium hydrogen
[a] Center for Instrumental Analysis, Iwate University,
4–3-5 Ueda, Morioka, Iwate 020–8551, Japan
E-mail: kimura@iwate-u.ac.jp
http://www.ccrd.iwate-u.ac.jp/kimura/index.html
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201900766.
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sulfite followed by butylation and octylation of the 3,6-dihy- have alkoxy groups at α-positions, they showed high solubility
droxy-4,5-dichlorophthalonitrile produced.[14]
in organic solvents. The structures of all Pcs obtained were de-
termined by 1H NMR spectra and high-resolution fast atom
bombardment mass spectrometry (HR-FAB-MS); the corre-
sponding molecular ion peaks were observed as M+ or MH+;
5a-Mg: m/z =1984.5805 [M+]; 5b-Mg: m/z =1984.5927 [M+]; 6a-
Mg: m/z = 2434.0935 [MH+]; 6b-Mg: m/z = 2434.0834 [MH+];
5a-2H: m/z = 1963.6171 [MH+]; 5b-2H: m/z = 1963.6171 [MH+];
6a-2H: m/z = 2411.1214 [M+].
UV/Vis Absorption and Emission Spectra of
Phthalocyanines
Scheme 1. Preparation of phthalonitriles 3 and 4.
It is expected that the two chlorine atoms of compounds
1and 2 can be substituted with nucleophiles, because reaction
of mercaptopyridine and 4,5-dichlorophthalonitrile was re-
ported.[6,11,12,15] Therefore, a slightly modified procedure was
used to construct the starting phthalonitriles. Compounds 1
and 2 were treated with 2-mercaptopyridine or 4-mercaptopyri-
dine in the presence of potassium carbonate in DMF at 90 °C
for 6 h under Ar. The reaction gave the desired products, 3,6-
dialkoxy-4,5-dipyridylthiophthalonitriles 3a (57 %), 3b (25 %),
4a (37 %), and 4b (4 %).
The UV/Vis spectra of Pcs obtained in chloroform showed
strong Q-band absorption at λ
=764.5 nm for 5a-Mg,
max
761.0 nm for 5b-Mg, 762.0 nm for 6a-Mg, 762.0 nm for 6b-Mg,
787.0 nm for 5a-2H, 782.0 nm for 5b-2H, and 785.5 nm for 6a-
2H (Figure 1a and Table 1). The Q band absorption of these Pcs
appear at the lower energy field than that of ꢀ-octa(4-pyridyl-
thio)phthalocyanine, suggesting that the effect of α-alkoxy
groups amounts to more than 110 nm (ca. 2200 cm–1) in these
Pcs. Since the magnesium complexes are D4h symmetry, the Q-
band absorption in chloroform was sharp compared with those
of metal-free Pcs. The Q-band absorption of free-base Pcs ap-
peared at a lower energy field than those of magnesium Pcs.
The weak absorption of 5a-Mg and 5b-Mg near 830 nm may
be originated from partial aggregation of the molecules.
Preparation of Phthalocyanines
Several methods are available for preparing free base or metal-
ated Pcs. Typically, compound 3a was treated with magnesium
butoxide in 1-butanol at 110 °C for 18 h (Scheme 2). The result-
ing green solid was purified by column chromatography to give
α-octa(butoxy)-ꢀ-octa(2-pyridylthio)Pc (5a-Mg) in 50 % yield. In
this reaction, the compound whose 2-pyridylthio groups were
substituted with butoxy groups was not obtained under the
reaction conditions. Treatment of 3b, 4a, and 4b with a similar
procedure produced Pcs 5b-Mg, 6a-Mg, and 6b-Mg in 60 %,
48 %, and 60 % yields, respectively. The central magnesium
atom of the products was eliminated easily by reaction with
strong acid. Pc 5a-Mg was treated with trifluoroacetic acid (TFA)
in chloroform at 60 °C for 15 min to produce demetallated Pc
5a-2H in 93 % yield after purification with column chromatog-
raphy. Using a similar treatment, 5b-2H and 6a-2H were ob-
tained in 38 % and 48 % yields, respectively. Since the products
Figure 1. UV/Vis spectra of 5a-Mg, 5b-Mg, 5a-2H, and 5b-2H, obtained in (a)
chloroform and (b) methanol (1.0 × 10–5 M).
In methanol solution, the Q-band absorption of Pcs was ob-
served at λ
=745.0 nm for 5a-Mg, 748.5 nm for 5b-Mg,
max
749.5 nm for 6a-Mg, 746.0 nm for 6b-Mg, 769.5 nm for 5a-2H,
758.5 nm for 5b-2H, and 770.0 nm for 6a-2H (Figure 1b and
Scheme 2. Preparation of phthalocyanines 5 and 6.
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Table 1. UV/Vis [λmax (nm)] and emission [λe (nm)] spectra of phthalocyanines.[a]
Solvent
λmax [nm], (ε)
Δλmax [nm]
λe [nm]
Δλe [nm]
Stokes shift [nm]
5a-Mg
5b-Mg
5a-2H
5b-2H
6a-Mg
6b-Mg
6a-2H
CHCl3
MeOH
CHCl3
MeOH
CHCl3
MeOH
CHCl3
MeOH
CHCl3
MeOH
CHCl3
MeOH
CHCl3
MeOH
764.5 (189000)
745.0 (199000)
761.0 (170000)
748.5 (171000)
787.0 (181000)
769.5 (30700)
782.0 (140000)
758.5 (132000)
762.0 (177000)
749.5 (168000)
762.0 (204000)
746.0 (198000)
785.5 (191000)
749.5 (156000)
19.5
–
12.5
–
17.5
–
23.5
–
13.0
–
16.0
–
36.0
–
804
782
792
777
822
798
817
804
789
776
781
765
814
800
22
–
12
–
34
–
13
–
13
–
16
–
14
–
40
37
31
29
35
29
35
46
27
27
19
19
29
51
[a] Δλmax = λmax (CHCl3) – λmax (MeOH); Δλe = λe (CHCl3) – λe (MeOH).
Table 1). The Q-band absorption of magnesium Pcs obtained in
methanol also was sharp compared with free-base Pcs for
which Q-band absorption appeared at lower energy field than
those of magnesium Pcs. The solubility of 5a-2H in methanol
was lower than that of the other compounds and the absorp-
tion also was weaker.
The emission spectra of Pcs were measured in chloroform;
the molecules were excited with 350 nm light (Figure 2a and
Table 1). The spectra showed strong emission at λ e = 804 nm
for 5a-Mg, 792 nm for 5b-Mg, 822 nm for 5a-2H, and 817 nm
for 5b-2H, together with a moderate emission peak near
900 nm. In the methanol solution, the emission spectra were
obtained using 400 nm light as excitation, which produced a
maximum peak at λ e = 782 nm for 5a-Mg, 777 nm for 5b-Mg,
798 nm for 5a-2H, and 804 nm for 5b-2H (Figure 2b and
Table 1). Since 5a-2H was insoluble in methanol, only weak
emission could be observed in this solvent. Apparently, Pcs
showed solvatochromism in the UV/Vis and emission spectra
between chloroform and methanol, and a small Stokes shift
was observed in the spectra. As mentioned above, magnesium
atoms were eliminated easily from Mg complexes. In the UV/Vis
spectra obtained in methanol, the Q-band absorption of 5b-
Mg (748.5 nm) was different than that of free base Pc, 5b-2H
(758.5 nm). Thus, the stability of Mg-Pcs can be assessed using
aqueous acetic acid and aqueous hydrochloric acid. The aque-
ous acetic acid solution of 5b-Mg at pH 2.5 showed the Q band
at 749 nm, suggesting that demetallation of 5b-Mg did not
proceed. In contrast, when 5b-Mg was dissolved in aqueous
hydrochloric acid at pH 3.2, the Q band was observed at
761 nm. Apparently, the magnesium atom was eliminated from
5b-Mg in solution; therefore, elimination of magnesium atom
from 5b-Mg proceed more easily in aqueous hydrochloric acid
than in aqueous acetic acid.
Figure 2. Emission spectra of 5a-Mg, 5b-Mg, 5a-2H, and 5b-2H, obtained in
(a) chloroform and (b) methanol (1.0 × 10–5 M).
quasi-reversible couple at E1/2 = 0.48 V and irreversible peaks
at Ep = 0.83 V and 1.30 V, the reduction potentials are two
quasi-reversible couples at E1/2 = –0.44 and –1.12 V. Compound
5b-Mg showed a quasi-reversible couple and an irreversible
peak during oxidation at E1/2 = 0.56 V and Ep= 1.06 V, and two
quasi-reversible couples during reduction at E1/2 = –0.45 and
–1.02 V. While the oxidation potentials of 6a-Mg were a reversi-
ble couple and an irreversible peak at E1/2 = 0.45 V and
Ep= 1.20 V, the reduction potentials were two quasi-reversible
couples at E1/2 = –0.49 and –1.06 V. Although the oxidation
Oxidation and Reduction Potentials of Phthalocyanines
The electrochemical properties were determined using cyclic potentials of free-base derivatives 5a-2H, 5b-2H, and 6a-2H
voltammetry with Ag/AgNO3 as a reference electrode (Figure 3 were irreversible, they showed quasi-reversible reduction po-
and Table 2). It is known that the charge of Mg (II) does not tentials. The first oxidation and first reduction potentials of
change during the CV measurement of the magnesium Pc de- magnesium complexes showed the cathode shift compared to
rivatives.[16] Although the oxidation potentials of 5a-Mg were a free-base Pcs, except for the first reduction potential of 5a-2H.
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Table 2. Oxidation and reduction potentials of phthalocyanines.[a]
4thRed
3rdRed
2ndRed
1stRed
1stOxid
2ndOxid
3rdOxid
1.30[c]
ΔE1
ΔE2[e]
5a-Mg
5b-Mg
5a-2H
5b-2H
6a-Mg
6a-2H
–1.12[b]
–1.02[b]
–0.78[b]
–1.13[b]
–1.06[b]
–1.10[b]
–0.44[b]
–0.45[b]
–0.37[b]
–0.72[b]
–0.49[b]
–0.73[b]
0.48[b]
0.56[b]
0.89[c]
0.82[c]
0.45[d]
1.00[c]
0.83[c]
1.06[c]
0.92
1.01
1.26
1.54
0.94
1.73
1.62
1.62
1.57
1.59
1.62
1.58
–1.87[b]
–1.37[b]
1.20[c]
–1.87[b]
[a] Electrolyte, 0.1
M
nBu4N+ClO4–/CH2Cl2; Reference electrode, Ag/AgNO3; Counter electrode, Pt; Working electrode, glassy-carbon; Scan rate, 200 mV/s.
[b] Quasi-reversible (E1/2/V). [c] Irreversible (Ep/V); ΔE1 = [1stOxid – 1stRed], and. [d] Reversible (E1/2/V). [e] ΔE2 was calculated using λmax (nm) in UV/Vis spectra.
ium groups on the core ring showed fragment peaks of lost
methyl groups and iodide ions as molecular ion peaks.[11a,12b]
Scheme 3. Methylation of phthalocyanines.
UV/Vis Absorption and Emission Spectra for 7a-Mg, 7b-Mg,
7b-2H
nBu4N+ClO4
/
–
The UV/Vis and emission spectra of methylated Pcs 7a-Mg,
7b-Mg, and 7b-2H were obtained in methanol and water. The
2-methylpyridinium derivative had lower solubility in water
than 4-methylpyridinium derivatives; therefore, the results for
7b-Mg, and 7b-2H are shown in Figure 4. The UV/Vis spectra
of 7b-Mg measured in methanol, tap water, and ion-exchanged
water (IEW) showed Q-band absorption around λ max = 745 nm.
Similarly, the UV/Vis spectra of 7b-2H obtained in methanol,
tap water, and ion-exchanged water showed Q-band absorp-
tion near λ max = 750 nm.
The emission spectra of 7a-Mg, 7b-Mg, and 7b-2H were ob-
tained in methanol and water. Since the 2-methylpyridinium
derivative showed lower solubility in water than 4-methyl-
pyridinium derivatives, the results of 7b-Mg and 7b-2H are
shown in Figure 5. The emission spectra of 7b-Mg obtained in
methanol, tap water, and ion-exchanged water showed Q-band
absorption near λ max = 766 nm.
Figure 3. Cyclic voltammogram of 5a-2H and 5b-2H; 0.1
M
CH2Cl2; reference electrode, Ag/AgNO3; counter electrode, Pt; working elec-
trode, glassy-carbon; scan rate, 200 mV/s.
Methylation of the Pyridine Nitrogen
Although Pcs obtained showed good solubility in organic sol-
vent, polar and hydrophilic substituents were introduced to
promote solubility in polar solvents such as water. Pyridinium
salts can promote solubility of Pcs soluble in water. To introduce
methyl groups on the pyridine nitrogen atoms substituted on
Pcs, Li et al. and Pereira et al. used methyl iodide, while Nyo-
kong et al. used dimethyl sulfate.[6,12] Based on these proce-
dures, 5a-Mg was treated with methyl iodide at reflux tempera-
ture for 24 h, producing the corresponding quaternized product
7a-Mg in 69 % yield. The Pcs 5b-Mg and 5b-2H also were
treated with methyl iodide to produce 7b-Mg and 7b-2H in
56 % and 30 % yields, respectively (Scheme 3). Reaction of 5a-
1,3-Diphenylisobenzofuran (DPBF) readily reacts with singlet
2H with methyl iodide produced an insoluble solid. The struc- oxygen via 1,4-cycloaddition to produce the cyclic peroxide.
tures of Pcs 7a-Mg, 7b-Mg, and 7b-2H obtained were deter- However, the product then immediately decomposes to 1,2-
mined by NMR spectra and matrix-assisted laser desorption dibenzoylbenzene.[17] Although DPBF shows a strong absorp-
ionization time-of-flight mass spectrometry (MALDI-TOF-MS); tion at 412 nm in the UV/Vis spectrum, 2-dibenzoylbenzene has
7a-Mg: m/z = 2022.4405 [M–7CH3–8I + Na]+; 7b-Mg: m/z = no absorption in that area. The presence of singlet oxygen can
2022.4849 [M–7CH3–8I + Na]+; 7b-2H: m/z = 2024.5093 [M– be determined by monitoring the absorbance of DPBF.[12a,18]
7CH3–8I + 2Na]+. It was reported that Pcs with methylpyridin- The photobleaching of the absorbance of DPBF was investi-
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15 min. After 60 min, a decrease in the absorption of DPBF
became small. The concentration of Pcs in the solution was
based on the molar extinction coefficient; 7b-Mg: 3.5 × 10–6 M,
7b-2H: 1.8 × 10–6 M. As shown in Figure 6a, the absorption of
DPBF at 410 nm decreased over time.
Figure 4. UV/Vis spectra of (a) 7b-Mg and (b) 7b-2H obtained in methanol,
water, and ion-exchanged water (IEW) (1.0 × 10–5 M).
Figure 6. (a) Photobleaching of DPBF absorbance upon ambient light in
methanol in the absence of Pc and in the presence of Pc 7b-2H; (b) Plot of
ln [DPBFAbs] vs. reaction time.
Although the oxidation of DPBF is a two-molecule reaction,
the concentration of oxygen was expected to be larger than
that of DPBF.[19] Therefore, the oxidation reaction was treated
as a pseudo-first-order reaction with respect to DPBF concentra-
tion. Figure 6b shows the plot of ln [DPBFAbs] vs. reaction time.
The absorption value of [DPBFAbs] was calculated as [DPBFAbs(t)
– DPBFAbs(120)]; DPBFAbs(t) is absorption of DPBF at each time
(t = 0–105) and DPBFAbs (120) is final absorption. The slope on
the linear graph of ln [DPBFAbs] was greater in the presence of
7b-Mg and 7b-2H than in the absence of Pcs. Furthermore, the
results showed 7b-2H was more effective at generating singlet
oxygen than 7b-Mg was.
Conclusions
Figure 5. Emission spectra of (a) 7b-Mg and (b) 7b-2H obtained in methanol,
water, and ion-exchanged water (IEW) (1.0 × 10–5 M).
Phthalocyanine derivatives with eight alkoxy groups at α-posi-
tions and 2- or 4-pyridylthio groups at ꢀ-positions were pre-
gated with ambient light in methanol in the presence of Pcs pared, and the products showed good solubility in organic sol-
7b-Mg and 7b-2H for 120 min (Figure 6). The spectra were vents and good to moderate solubility in methanol and water
obtained at intervals of 15 min or 30 min, except for first after methylation of the pyridine nitrogen. The structure of
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1
3,6-Dibutoxy-4,5-di(4-pyridylthio)phthalonitrile (3b). 37 %; yel-
low crystal; mp: 98–101.5 °C; H NMR (500 MHz, CDCl3, 25 °C, TMS)
δ = 0.87 (t, J = 7.5 Hz, 6H, CH3), 1.33 (sext, J = 7.5 Hz, 4H, CH2), 1.61
(quint, J = 6.5 Hz, 4H, CH2), 4.16 (t, J = 6.5 Hz, 4H, CH2), 6.87(dd, J =
4.7, 1.5 Hz, 4H, Py-H), 8.40(dd, J = 4.7, 1.5 Hz, 4H, Py-H); 13C NMR
(126 MHz, CDCl3, 25 °C, TMS) δ = 13.5, 18.6, 31.7, 76.3, 111.2, 112.4,
121.1, 138.9, 145.6, 149.8, 159.2; HR-FAB-MS (m/z) 490.1502 [M+];
calcd. for C26H26N4O2S2 = 490.1497.
the product was determined by H NMR, FABMS, and MALDI-
TOF-MS. The UV/Vis spectra of Pcs obtained in chloroform and
methanol, showed Q-band absorption in the near-infrared re-
gion. These compounds produced emissions in chloroform and
methanol. The electrochemical properties were determined by
cyclic voltammetry using Ag/AgNO3 as a reference electrode.
Compounds 5a-Mg, 5b-Mg, 5a-2H, and 5b-2H reacted with
methyl iodide to produce the corresponding methyl pyridinium
iodides. The UV/Vis and emission spectra of methylated Pcs 7a-
Mg, 7b-Mg, and 7b-2H were obtained in methanol and water.
The photobleaching of the absorbance of diphenylisobenzo-
furan (DPBF) with ambient light was examined in methanol in
the presence and in the absence of Pcs 7b-Mg and 7b-2H for
120 min. The plot of ln [DPBFAbs] vs. the reaction time showed
that 7b-2H generated singlet oxygen more effectively than 7b-
Mg.
3,6-Dioctyloxy-4,5-di(2-pyridylthio)phthalonitrile (4a). 25 %; red
brown oil; 1H NMR (400 MHz, CDCl3, 25 °C, TMS) δ = 0.87 (t, J =
6.8 Hz, 6H, CH3), 1.16–1.34 (m, ), 1.63 (quint, J = 6.8 Hz, 4H, CH2),
4.15 (t, J = 6.8 Hz, 6H, CH2), 7.03 (ddd, J = 7.7, 4.8, 0.8 Hz, 2H,
Py-H), 7.11 (7.7, 0.8 Hz, 2H, Py-H), 7.51 (ddd, J = 7.7, 7.7, 1.6 Hz, 2H,
Py-H), 8.29 (ddd, J = 4.8, 1.6, 0.8 Hz, 2H, Py-H); 13C NMR (101 MHz,
CDCl3, 25 °C, TMS) δ = 14.3, 22.9, 25.7, 29.36, 29.43, 30.1, 32.0, 76.4,
110.6, 113.4, 121.1, 122.5, 137.0, 140.8 149.9, 157.60, 159.63; HR-
FAB-MS (m/z) 603.2830 [MH+]; calcd. for C34H43N4O2S2 = 603.2827.
3,6-Dioctyloxy-4,5-di(4-pyridylthio)phthalonitrile (4b). 4 %; yel-
low oil; 1H NMR (500 MHz, CDCl3, 25 °C, TMS) δ = 0.87 (t, J = 7.0 Hz,
6H, CH3), 115–1.29 (m, 20H, CH2), 1.62 (quint, J = 6.8 Hz, 4H, CH2),
4.14 (t, J = 6.8 Hz, 4H, CH2), 6.87 (dd, J = 4.8, 1.4 Hz, 4H, Py-H), 8.40
(dd, J = 4.8, 1.4 Hz, 4H, Py-H); 13C NMR (126 MHz, CDCl3, 25 °C, TMS)
δ = 14.1, 22.6, 25.5, 29.07, 29.12, 29.8, 31.7, 76.8, 111.3, 112.5, 121.1,
138.9, 145.7, 150.0, 159.3; HR-FAB-MS (m/z) 603.2830 [MH+]; calcd.
for C34H43N4O2S2 = 603.2827.
Experimental Section
General. NMR spectra were obtained using Bruker AVANCE-500 and
DRX-400 spectrometers and a JEOL JNM-ECA 500 spectrometer.
Mass spectra were obtained using a JEOL JMS-700 mass spectrome-
ter and a Shimadzu Biotech Axima Confidence mass spectrometer.
UV/Vis spectra were recorded with a Jasco Ubest V-570 spectrome-
ter. The IR spectra were obtained using a Jasco FT/IR-4200 spec-
trometer. Emission spectra were obtained with a Jasco FP8600 spec-
trofluorometer. A Hokuto Denko Co. Model HAB-151 apparatus was
used to obtain measurements of redox potentials.
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa(2-
pyridylthio)phthalocyaninato magnesium (II) (5a-Mg). Magne-
sium (90 mg, 3.7 mmol) and iodine (30 mg, 0.12 mmol) were placed
in a glass reactor and 1-butanol (3 mL) added under Ar, then the
solution was stirred at 110 °C until the magnesium dissolved. The
solution was poured into compound 3a (235 mg, 0.52 mmol) under
Ar, and stirred at 110 °C for 18 h. After cooling, MeOH was added
to the reaction mixture and the resulting green precipitate removed
by filtration. The residue was purified by column chromatography
(Wakogel C-300HG, CHCl3 and CHCl3/MeOH = 50:1) to produce
Oxidation and reduction potential. All measurements of redox
potentials were performed by cyclic voltammetry, using Ag/AgNO3
(0.01 mol/L) as a reference electrode, glassy carbon as a working
electrode, and Pt wire as a counter electrode (scan rate: 200 mV/
s). A solution of n-Bu4NClO4 in CH2Cl2 (0.1 mol/L) was used as an
electrolyte. The oxidation potential of ferrocene was observed at
E1/2 = 0.09 V using the apparatus without any correction.
1
5a-Mg in 50 % yield (130 mg); green powder; m.p. 98–101.5 °C; H
NMR (400 MHz, CDCl3, 25 °C, TMS) δ = 0.62 (br, 24H, CH3), 1.20 (br,
16H, CH2), 1.65 (br, 16H, CH2), 4.72 (br, 16H, CH2), 6.87 (br, 8H,
Py-H), 7.21 (br, 8H, Py-H), 7.43(br, 8H, Py-H), 8.16 (br, 8H, Py-H); HR-
FAB-MS (m/z) 1984.5805 [M+]; calcd. for C104H104N16O8S824Mg =
1984.5839.
Materials. 3,6-Dibutoxy-4,5-dichlorophthalonitrile (1) and 3,6-dioct-
yloxy-4,5-dichlorophthalonitrile (2) were prepared using a method
described previously.[14]
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
3,6-Dibutoxy-4,5-di(2-pyridylthio)phthalonitrile (3a). Com-
pound 1 (685 g, 2.01 mmol), K2CO3 (835 mg, 6.04 mmol), and 2-
mercaptopyridine (493 mg, 4.43 mmol) were placed in a glass reac-
tor under Ar. The DMF (14 mL) was added to the reactor and the
solution stirred at 90 °C for 6 h, then cooled to room temperature.
Water was added to the solution and the product extracted using
ethyl acetate. The extract was washed with brine and then with
water. The organic layer was dried with MgSO4 and the solvent
evaporated. The product was purified by column chromatography
[Wakogel C-300HG, CHCl3 to CHCl3/MeOH (50:1)] and 3,6-dibutoxy-
4,5-di(2-pyridylthio)phthalonitrile (3a) was obtained in 53 % yield
(4-pyrodylthio)phthalocyaninato Magnesium (II) 5b-Mg. 60 %;
1
green solid; mp: 189–190 °C; H NMR (400 MHz, CDCl3, 25 °C, TMS)
δ = 0.54 (br, 24H, CH3), 1.14 (br, 16H, CH2), 1.67 (br, 16H, CH2), 4.76
(br, 16H, CH2), 6.94 (br, 16H, Py-H), 7.92 (br, 16H, Py-H); HR-FAB-MS
(m/z) 1984.5927 [M+]; calcd. for C104H104N16O8S824Mg = 1984.5839.
1,4,8,11,15,18,22,25-Octaoctyloxy-2,3,9,10,17,17,23,24-octa-
(2-pyrodylthio)phthalo-cyaninato Magnesium (II) 6a-Mg. 48 %;
green solid; mp: 79–80 °C; 1H NMR (400 MHz, CDCl3, 25 °C, TMS)
δ = 0.86 (t, J = 7.0 Hz, 24H, CH3),1.02–1.36 (m, 80H, CH2), 1.72–1.85
(m, 16H, CH2), 4.85 (br, 16H, CH2), 6.90 (br, 8H, Py-H), 7.22 (br, 8H,
Py-H), 7.40 (br, 8H, Py-H), 8.27 (br, 8H, Py-H); HR-FAB-MS (m/z)
2434.0935 [MH+]; calcd. for C136H169N16O8S8Mg = 2434.0926.
1
(520 mg); brown oil; H NMR (400 MHz, CDCl3, 25 °C, TMS) δ = 0.86
(t, J = 7.6 Hz, 6H, CH3), 1.33 (sext, J = 7.6 Hz, 4H, CH2), 1.61 (quint,
J = 6.4 Hz, 4H, CH2), 4.16 (t, J = 6.4 Hz, 4H, CH2), 7.04 (ddd, J = 7.7,
4.8, 0.8Hz, 2H, Py-H), 7.12 (ddd, J = 7.7, 0.8, 0.8 Hz, 2H, Py-H), 7.52
(ddd, J = 7.7, 7.7, 1.8 Hz, 2H, Py-H), 8.29 (ddd, J = 4.8, 1.8, 0.8 Hz,
2H, Py-H); 13C NMR (101 MHz, CDCl3, 25 °C, TMS) δ = 14.1, 19.1,
1,4,8,11,15,18,22,25-Octaoctyloxy-2,3,9,10,17,17,23,24-octa-
(4-pyrodylthio)phthalocyaninato Magnesium (II) 6b-Mg. 60 %;
1
green oil; H NMR (500 MHz, CDCl3, 25 °C, TMS) δ = 0.80 (br, 24H,
32.2, 76.2, 110.7, 113.5, 121.3, 123.6, 137.2, 141.0, 150.0, 157.7, 159.7; CH3), 1.03–1.39 (s, 80H, CH2), 1.69 (br, 16H, CH2), 4.77 (br, 16H, CH2),
HR-FAB-MS (m/z) 491.1574 [MH+]; calcd. for C26H27N4O2S2
490.1497.
=
6.95 (br, 16H, Py-H), 8.28 (br, 16H, Py-H); HR-FAB-MS (m/z) 2434.0834
[MH+]; calcd. for C136H169N16O8S8Mg = 2434.0926.
Eur. J. Inorg. Chem. 2019, 4006–4013
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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
(2-pyrodylthio)phthalocyanine (5a-2H). To a solution of 5a-Mg
(50 mg, 0.025 mmol) in CHCl3 (20 mL), CF3COOH (1.0 mL) was
added slowly and the solution stirred for 15 min under reflux. The
solution was cooled to room temperature and K2CO3 was added
followed by extraction with CHCl3. After evaporation of the solvent,
the residue was purified by column chromatography (Wakogel C-
300HG, CHCl3 and CHCl3/MeOH = 50:1) to produce 5a-2H in 93 %
yield (46 mg); dark green solid; mp: 109–110 °C; 1H NMR (500 MHz,
CDCl3, 25 °C, TMS) δ = 0.75 (s, J = 7.2 Hz, 24H, CH3), 1.30 (sext, J =
7.2 Hz, 16H, CH2), 1.78 (quint, J = 6.8 Hz, 2H, CH2), 4.77 (br, 16H,
CH2), 6.94 (dd, J = 6.4, 5.2 Hz, 8H, Py-H), 7.25 (br, 8H, Py-H), 7.44
(dd, J = 7.2, 1.4 Hz, 8H, Py-H), 8.35 (d, J = 3.6 Hz, 8H, Py-H);
Keywords: Phthalocyanines · Pyridylthio groups ·
Magnesium · Photochemistry · Isobenzofuran
[1] a) A. Jana, M. Ishida, J. P. Park, S. Bähring, J. O. Jeppesen, J. L. Sessler,
Chem. Rev. 2017, 117, 2642–2710; b) S. Singh, A. Aggarwal, N. V. S. D. K.
Bhupathiraju, G. Arianna, K. Tiwari, D. M. Drain, Chem. Rev. 2015, 115,
10261–10306; c) M. Urbani, M. Grätzel, M. Nazeeruddin, T. Torres, Chem.
Rev. 2014, 114, 12330–12396.
[2] a) J. Mack, N. Kobayashi, Chem. Rev. 2011, 111, 281–321; b) F. Dumoulin,
M. Durmuş, V. Ahsen, T. Nyokong, Coord. Chem. Rev. 2010, 254, 2792–
2847.
[3] N. Kobayashi, H. Ogata, N. Nonaka, E. A. Luk'yanets, Chem. Eur. J. 2003,
9, 5123–5134; P. M. Burnham, M. J. Cook, L. A. Gerrard, M. J. Heenet, D. L.
Hughes, Chem. Commun. 2003, 2064–2065; K. Hatsusaka, M. Kimura, K.
Ohta, Bull. Chem. Soc. Jpn. 2003, 76, 781–787; M. N. Yarasir, M. Kandaz,
B. F. Senkal, A. Koca, B. Salih, Polyhedron 2007, 26, 5235–5242; T. B. Ogun-
bayo, T. Nyokong, Polyhedron 2009, 28, 2710–2718; T. Rawling, A.
McDonagh, Coord. Chem. Rev. 2007, 251, 1128–1157.
[4] T. Furuyama, T. Sato, N. Kobayashi, J. Am. Chem. Soc. 2015, 137, 13788–
13791; T. Furuyama, N. Kobayashi, Phys. Chem. Chem. Phys. 2017, 19,
15596–15612.
[5] P. Zimcik, V. Novakova, K. Kopecky, M. Miletin, R. Zeynep, U. Kobak, E.
Svandrlikova, L. Váchová, K. Lang, Inorg. Chem. 2012, 51, 4215–4223; M.
Machacek, A. Cidlina, V. Novakova, J. Svec, E. Rudolf, M. Miletin, R. Kučera,
T. Simunek, P. Zimcik, J. Med. Chem. 2015, 58, 1736–1749.
[6] A. Erdoğmuş, T. Nyokong, J. Mol. Struct. 2010, 977, 26–38; A. Sindelo,
O. L. Osifenko, T. Nyokong, Inorg. Chim. Acta 2018, 476, 68–76; S. Makh-
seed, M. Machacek, W. Alfady, A. Tuhl, M. Vinodh, T. Simunek, V. Novak-
ova, P. Kubat, E. Rudolf, P. Zimcik, Chem. Commun. 2013, 49, 11149–
11151; J. Mikkilä, E. Anaya-Plaza, V. Liljeström, J. Caston, T. Torres, A.
de la Escosura, M. A. Kostiainen, ACS Nano 2016, 10, 1565–1571.
[7] T. Ikeuchi, J. Mack, T. Nyokong, N. Kobayashi, M. Kimura, Langmuir 2016,
32, 11980–11985.
HR-FAB-MS (m/z) 1963.6171 [MH+]; calcd. for C104H107N16O8S8
1963.6224.
=
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
(4-pyridylthio)phthalocyanine (5b-2H). 38 %; dark green crystal;
1
mp: 209–210 °C; H NMR (400 MHz, CDCl3, 25 °C, TMS) δ = 0.83 (t,
J = 7.2 Hz, 24H, CH3), 1.31(sext, J = 7.2 Hz, 16H, CH2), 1.80 (quint,
J = 6.4 Hz, 16H, CH2), 4.78 (t, J = 6.4 Hz, 16H, CH2), 7.10 (dd, J = 4.8,
1.6 Hz, 16H, Py-H), 8.34 (dd, J = 4.8, 1.6 Hz, 16H, Py-H); HR-FAB-MS
(m/z) 1963.6171 [MH+]; calcd. for C104H107N16O8S8 = 1963.6224.
1,4,8,11,15,18,22,25-Octaoctyloxy-2,3,9,10,17,17,23,24-octa-
(2-pyrodylthio)phthalocyanine (6a-2H). 64 %; green solid; m.p. >
300 °C; 1H NMR (500 MHz, CDCl3, 25 °C, TMS) δ = 0.86 (t, J = 7.1 Hz,
24H, CH3), 1.05–1.33 (m, 80H, CH2), 1.80 (quint, J = 7.3 Hz, 16H,
CH2), 4.77 (br, 16H, CH2), 6.92 (ddd J = 5.1 Hz, 8H, Py-H), 7.25 (d, J =
5.1 Hz, 8H, Py-H), 7.43 (ddd, J = Hz, 8H,Py-H), 8.31 (dd, J = 4.6 Hz,
8H, Py-H); HR-FAB-MS (m/z) 2411.1214 [M+ ]; calcd. for
C136H170N16O8S8 = 2411.1153.
[8] L. M. O. Lourenço, P. M. R. Pereira, E. Maciel, M. Válega, F. M. Domingues,
M. R. M. Domingues, M. G. P. M. S. Neves, J. A. S. Cavaleiro, R. Fernandes,
J. P. C. Tomé, Chem. Commun. 2014, 50, 8363–8366.
[9] E. Ranyuk, N. Cauchon, K. Klarskov, B. Guérin, J. E. van Lier, J. Med. Chem.
2013, 56, 1520–1534; H. He, P.-C. Lo, D. K. P. Ng, Chem. Eur. J. 2014, 20,
6241–6245.
[10] a) M. P. Donzello, E. Viola, X. Cai, L. Mannina, C. Rizzoli, G. Ricciardi, C.
Ercolani, K. M. Kadish, A. Rosa, Inorg. Chem. 2008, 47, 3903–3919; b) I.
Manet, F. Manoli, M. P. Donzello, C. Ercolani, D. Vittori, L. Cellai, A. Masi,
S. Monti, Inorg. Chem. 2011, 50, 7403–7411; c) I. Manet, F. Manoli, M. P.
Donzello, E. Viola, A. Masi, G. Andreano, G. Ricciardi, A. Rosa, L. Cellai,
C. Ercolani, S. Monti, Inorg. Chem. 2013, 52, 321–328; d) M. P. Donzello,
G. De Mori, E. Viola, C. Ercolani, G. Ricciardi, A. Rosa, Inorg. Chem. 2014,
53, 8009–8019.
[11] a) H. Li, J. Jensen, F. R. Fronczek, A. G. H. Vicente, J. Med. Chem. 2008,
51, 502–511; b) X. Jia, F.-F. Yang, J. Li, J.-Y. Liu, J.-P. Xue, J. Med. Chem.
2013, 56, 5797–5805; T. T. Tasso, T. Furuyama, N. Kobayashi, Inorg. Chem.
2013, 52, 9206–9215.
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
(2-methylpyridiniumthio)phthalo-cyaninato magnesium (II)
iodide (7a-Mg). Compound 7a-Mg (49 mg, 0.025 mmol) was
placed in a glass reactor and methyl iodide (6.0 mL) was added
under Ar, then the solution was stirred at 40 °C for 24 h. After
evaporation, the residue was washed with acetone and then chloro-
form. The product was dissolved in methanol and filtered. After
evaporation, the product was recrystallized from DMF and CHCl3 to
produce 7a-Mg in 69 % yield (53 mg); green crystal; m.p. > 300 °C;
1H NMR (500 MHz, CD3OD,, 25 °C, TMS) δ = 0.76 (t, J = 7.0 Hz, 24H,
CH3), 1.23–1.38 (m, 16H, CH2), 1.78–1.96 (m, 16H, CH2), 4.54 (s, 24H,
CH3), 5.16 (br, 16H, CH2), 7.74 (t, J = 6.9 Hz, 8H, Py-H), 7.96 (s, 8H,
Py-H), 8.12–8.29 (m, 8H, Py-H), 8.92 (t, J = 6.9 Hz, 8H, Py-H);
MALDI-TOF MS (m/z) 2022.4405 [M–7CH3–8I + Na]+; calcd. for
C105H107N16O8S8Na = m/z 2022.5972.
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
(4-methylpyridiniumthio)phthalo-cyaninato magnesium (II)
iodide (7b-Mg). 56 %; green solid; m.p. > 300 °C; 1H NMR (500 MHz,
CD3OD, 25 °C, TMS) δ = 0.77 (t, J = 7.4 Hz, 24H, CH3), 1.41 (sext, J =
7.4 Hz, 16H, CH2), 1.92 (br, 16H), 4.24 (brs, 24H, CH3), 5.08 (br, 16H
CH2), 8.05 (d, J = 6.9 Hz, 16H, Py-H), 8.60 (d, J = 6.9 Hz, 16HPy-
H), MALDI-TOF MS (m/z) 2022.4849 [M–7CH3–8I + Na]+; calcd. for
C105H107N16O8S8Na = 2022.5972.
[12] a) M. Durmuş, H. Yaman, C. Göl, V. Ashen, T. Nyokong, Dyes Pigm. 2011,
91, 153–156; b) J. B. Pereira, E. F. A. Carvalho, M. A. F. Faustino, R. Fernan-
des, M. G. P. M. S. Neves, J. A. S. Cavaleiro, N. C. M. Gomes, Å. Cunha, A.
Almeida, J. P. C. Tomé, Photochem. Photobiol. 2012, 88, 537–547.
[13] a) T. Kimura, A. Yomogita, T. Matsutani, T. Suzuki, I. Tanaka, Y. Kawai, Y.
Takaguchi, T. Wakahara, T. J. Akasaka, Org. Chem. 2004, 69, 4716–4723;
b) T. Kimura, N. Kanota, K. Matsui, I. Tanaka, T. Tsuboi, Y. Takaguchi, A.
Yomogita, T. Wakahara, S. Kuwahara, F. Nagatsugi, T. Akasaka, Inorg.
Chem. 2008, 47, 3577–3583; c) T. Kimura, N. Murakami, E. Suzuki, T. Fu-
ruyama, T. Nakahodo, H. Fujihara, N. Kobayashi, J. Inorg. Biochem. 2016,
158, 35–44; d) T. Kimura, H. Muraoka, S. Nakajo, S. Ogawa, S. Yamamoto,
N. Kobayash, Eur. J. Org. Chem. 2018, 2018, 1255–1264.
[14] a) E. A. Safonova, A. G. Martynov, S. E. Nafedov, G. A. Kirakosyan, Y. G.
Gobunova, A. Y. Tsivadze, Inorg. Chem. 2016, 55, 2450–2459; b) M. Mat-
sutani, A. Takaki, H. Maekawa, I. Nishiguchi, Sci. Technol. Adv. Mater. 2005,
6, 172–180; c) S. Y. Al-Raqa, Dyes Pigm. 2007, 77, 259–265; d) D. S. Reddy,
Y. E. Ovchinnikov, O. V. Shichkin, Y. T. Struchkov, G. R. Desiraju, J. Am.
Chem. Soc. 1996, 118, 4085–4089.
1,4,8,11,15,18,22,25-Octabutoxy-2,3,9,10,17,17,23,24-octa-
(2-methylpyridiniumthio)phthalo-cyanine iodide (7b-2H). 30 %;
1
green solid; m.p. > 300 °C; H NMR (500 MHz, CD3OD, 25 °C, TMS)
δ = 0.68 (t, J = 7.4 Hz, 24H, CH3), 1.39 (sext, J = 7.4 Hz, 16H, CH2),
1.82 (br, 16H, CH2), 4.15 (s, 24H, CH3), 4.80–5.05 (m, 16H, CH2), 8.12
(br, 16H, Py-H), 8.64 (d, J = 7.2 Hz, 16H, Py-H); MALDI-TOF
MS (m/z) 2024.5093 [M–7CH3–8I
C105H109N16O8S8Na2 = 2023.6175.
+
2Na]+; calcd. for
Eur. J. Inorg. Chem. 2019, 4006–4013
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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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[15] D. Wöhrle, M. Eskes, K. Shigehara, A. Yamada, Synthesis 1993, 194–196.
[16] T. Nyokong, Z. Gasyna, M. J. Stillman, Inorg. Chem. 1987, 26, 548–553.
[17] S. J. Chadwick, D. Salah, P. M. Livesey, M. Brust, M. Volk, J. Phys. Chem. A
2016, 120, 10647–10657.
[19] A. Kuesner, J. Phys. E. Sci. Instrum. 1987, 20, 224–230; M. G. Levi, Gazz.
Chim. Ital. 1901, 31, 513–541.
[18] T. Furuyama, Y. Miyaji, K. Maeda, H. Maeda, M. Segi, Chem. Eur. J. 2019,
25, 1678–1682.
Received: July 11, 2019
Eur. J. Inorg. Chem. 2019, 4006–4013
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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim