The synthesis and characterization of nonperipherally tetra terminal alkynyl substituted phthalocyanines and glycoconjugation via the click reaction

Article abstract of DOI:10.1039/c4dt00238e

In order to obtain nonperipherally tetra terminal alkynyl substituted phthalocyanines (Pcs), new 3-pent-4-ynyloxy phthalonitrile (3) was prepared by the nucleophilic displacement reaction of 3-nitrophthalonitrile (1) and 4-pentyn-1-ol (2) and then cyclote

Full text of DOI:10.1039/c4dt00238e

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The synthesis and characterization of
nonperipherally tetra terminal alkynyl substituted
phthalocyanines and glycoconjugation via the
click reaction†
Cite this: Dalton Trans., 2014, 43,
8654
Zeliha Kanat and Hatice Dinçer*
In order to obtain nonperipherally tetra terminal alkynyl substituted phthalocyanines (Pcs), new 3-pent-4-
ynyloxy phthalonitrile (3) was prepared by the nucleophilic displacement reaction of 3-nitrophthalonitrile
(1) and 4-pentyn-1-ol (2) and then cyclotetramerization was attained in the presence of zinc acetate,
cobalt acetate, and/or DBU in n-pentanol without protection/deprotection. For the first time, the glyco-
conjugation of the nonperipherally tetra terminal alkynyl substituted zinc phthalocyanine (ZnPc) (6) can
be easily achieved via the click reaction in a high yield. The electronic absorption spectrum of the gluco-
pyranosyl substituted ZnPc (10) derivative showed a red-shifted Q band at 751 nm in dichloromethane
due to the protonation of the meso nitrogens of the Pc macrocycle. Deacylation yielded ZnPc (11)
bearing glucose substituents at nonperipheral positions with an improved water-solubility and non-aggre-
gation in DMSO. The chemical structures of the new compounds were characterized by 1H NMR, 13C
NMR, FT-IR, UV-Vis, mass spectrometry and elemental analysis. Moreover, the phthalonitrile compound
was characterized using X-ray.
Received 22nd January 2014,
Accepted 7th March 2014
DOI: 10.1039/c4dt00238e
www.rsc.org/dalton
However, studies on non-peripherally substituted Pc deriva-
tives especially tetra substituted examples are still limited.18–22
Introduction
Since the accidentally discovery of the phthalocyanines (Pcs),
Click chemistry has been applied in a wide variety of
many efforts have been devoted to the tailoring of their pro- research areas, including material science, polymer chemistry
perties to produce molecular materials and technological and pharmaceutical sciences due to its being fast, quantitative,
devices. Recently they have found use as sensors,1,2 non-linear reproducible, resistant to side reactions and highly tolerant to
optics,3,4 dye sensitized solar cells,5,6 organic light emitting reaction conditions.23 The best known click reaction is the
devices,7 molecular electronics,8,9 liquid crystals,10,11 semicon- copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition between
ductors,12 catalysts13,14 and photodynamic reagents for cancer azides and alkynes and is less used for the synthesis of substi-
therapy (PDT),15,16 among others. The properties of phthalo- tuted phthalocyanines.24–28 Recently we have shown the synth-
cyanines are closely depended on their structure that can be eses of new symmetrical and unsymmetrical Pcs with terminal
modified by metallation or substitution variations: number, alkynyl substituents starting from phthalonitrile bearing a
position, and nature. The incorporation of substituents at the terminal alkynyl moiety without the protection/deprotection
nonperipheral (np) sites as opposed to the peripheral (p) posi- concept and their click reaction with azide-end functional
tions ensures a good solubility and limited aggregation in polymers.29,30 To the best of our knowledge, there is only
most hydrophobic solvents and leads to significant batho- one example of nonperipherally terminal alkynyl substituted
chromic shifts of the Q absorption band. In addition, the phthalocyanine, that is 1,8,15,22-tetrakis(propargyloxy)phthalo-
np-substituted compounds often crystallize well enough to cyaninato-zinc(II) announced by Leznoff and coworkers in
enable X-ray crystallographic structure determinations.17 Non- 1998.65 In addition, up to now, there are no reports about non-
peripherally substituted octa- and tetra-alkyl, alkyloxy or peripherally terminal alkynyl substituted phthalocyanines
alkylthiophthalocyanines were reported in the literature. involved in the click reaction.
Photodynamic therapy (PDT) has developed over the last
century and is now becoming more widely used for the treat-
ment of cancer. It involves the delivery of a nontoxic dyes
known as photosensitizers (PS), followed by irradiation with
İstanbul Technical University, Faculty of Science and Letters, Department of
Chemistry, 34469 Maslak, İstanbul, Turkey. E-mail: dincerhat@itu.edu.tr
†CCDC number 978750. For crystallographic data in CIF or other electronic
visible light of a specific wavelength, typically in the red region
format see DOI: 10.1039/c4dt00238e
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of the spectrum (620–690 nm). Activated photosensitizers
transfer energy to molecular oxygen which results in the gen-
eration of reactive oxygen species mainly singlet oxygen (1O2)
which in turn cause the destruction of tumors.31 The develop-
ment of efficient photosensitizers in terms of the tumor-
selectivity and reactive oxygen species (ROS)-producing ability
is the main topic of many ongoing research programs.32
Phthalocyanine derivatives exhibit several optimal character-
istics for being good PSs such as a high molar absorption
coefficient in the visible region of the spectrum, a long lifetime
of the triplet excited state, and an increased oxidative stability
that allows their use as stable aqueous solutions. However, the
lack of selective accumulation of these photo actively mole-
cules within the tumor tissue, the insolubility and the aggrega-
tion in physiological fluids are major problems in PDT. The
phthalocyanines conjugated with carbohydrate moieties have
attracted considerable interest, with the aim of developing tar-
geted photosensitizers and eventually the PDT efficacy.33–37
The first carbohydrate substituted zinc(II) phthalocyanine
was reported in 1989 by Maillard et al.38 and its nonperipher-
ally substituted analogue was synthesized in 2008 by Ng and
co-workers.39 Hanack, Ziegler and co-workers40 prepared the
first example of an anomerically glycosylated zinc(II) phthalo-
cyanine in 2006 and after that several carbohydrate substituted
phthalocyanines have been reported so far.41–46 However, the
synthesis of some of the glycosylated phthalocyanines can be
rather complicated and not easy. Recently, carbohydrate conju-
gated phthalocyanines were synthesized by the click reaction
Scheme 1 The synthetic route for pent-4-ynyloxy substituted phthalo-
cyanines. (i) DMSO, K2CO3, 50 °C, 48 h. (ii) n-pentanol, DBU, Zn-
(CH3COO)2, Co(CH3COO)2, 140 °C, 24 h.
itself. Recently, we have incorporated terminal alkynyl groups
on the periphery of phthalocyanine compounds starting from
a terminal alkynyl substituted phthalonitrile precursor.29,30 In
order to vary the terminal alkynyl substituted phthalocyanines,
we designed a new phthalonitrile compound bearing an
alkyne function in the C-3 position. The classical nucleophilic
substitution of 3-nitrophthalonitrile (1) and 4-pentyn-1-ol (2)
gave the targeted 3-pent-4-ynyloxy-phthalonitrile (3) in a satis-
factory 74% yield (Scheme 1).
We recently described the successful use of the cyclotetra-
merization of terminal alkynyl substituted phthalonitrile com-
pounds without protection/deprotection.29,30 This synthetic
strategy which was adopted to prepare target 1,8(11),15(18),22-
(25)-tetra-terminal alkynyl substituted phthalocyanines (4–6)
was carried out with reasonable yields by the direct cyclotetra-
merization of an unprotected nonperipherally terminal alkynyl
substituted phthalonitrile compound in the presence of zinc
acetate, cobalt acetate, and/or DBU in pentanol (Scheme 1).
Column chromatography was used to purify the following
phthalocyanine compounds (4–6).
Phthalocyanine–carbohydrate conjugates are quite uncom-
mon especially by the click reaction. To the best of our knowl-
edge, title nonperipherally tetra glucose conjugated ZnPc (11)
will be the first example of the conjugation of a nonperipher-
ally tetra terminal alkynyl substituted phthalocyanine with
azido functional glucose via the click reaction. For this
purpose, 1,2,3,4,6-penta-O-acetyl-β-D-glucopyranose (7) was
transformed to 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide
(9) as a white solid in a 75% yield after bromination with
hydrogen bromide in acetic acid and then reaction with NaN3
in THF–water. The successful click reaction between glucopyra-
nosyl azide (9) and the nonperipherally tetra terminal alkynyl
substituted ZnPc (6) in the presence of sodium ascorbate and
copper sulfate resulted glycopyranosyl conjugated ZnPc (10)
in a satisfactory yield. Consequently, the target compound,
nonperipherally glucose conjugated ZnPc (11), was obtained
as
a novel method instead of the traditional synthesis
method.47–50
Based on the aforementioned statements, in this paper,
firstly a novel phthalonitrile compound bearing an alkyne
function in the C-3 position was designed to attain nonperiph-
erally tetra terminal alkynyl substituted phthalocyanines by its
cyclotetramerization in the presence of metal salts and/or DBU
without protection/deprotection. In addition, to prove the
viability of the click reaction concept, we have chosen the
resulting ZnPc derivative and the click reaction between non-
peripherally tetra terminal alkynyl substituted ZnPc (6) and
2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide (9) then deacyla-
tion under Zemplén conditions provided water soluble non-
peripherally tetra glucose substituted ZnPc (11) in a high yield.
The synthesis of nonperipherally tetra terminal alkynyl substi-
tuted phthalocyanines involved in the click reaction with azido
functional glucopyranosyl has never been reported so far to
the best of our knowledge.
Results and discussion
Syntheses
The terminal alkynyl substituted phthalocyanines are the
common precursors for the preparation of functionalized
analogues. This alkyne function can be introduced on the
phthalocyanine precursor (usually a phthalonitrile), but are up
to now more commonly introduced on the phthalocyanine
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Table 1 The crystal data and refinement parameters for (3)
Crystal parameters
Phthalonitrile (3)
CCDC
978750
C13H10N2O
210.23
Empirical formula
Formula weight (g mol−1
)
Temperature (K)
Wavelength (Å)
Crystal system
Space group
100(2)
0.71073
Triclinic
ˉ
P1
a (Å)
b (Å)
c (Å)
4.4256(6)
7.6883(10)
17.242(2)
α (°)
β (°)
77.679(4)
84.616(5)
γ (°)
74.348(4)
Crystal size (mm)
0.010 × 0.050 × 0.100
551.49(13)
2
1.266
0.082
V (Å3)
Z
ρcalcd (g cm−3
)
μ (mm−1
F(000)
)
220
θ Range for data collection (°)
h/k/l
2.42 to 28.36
−5/5, −10/10, −22/22
19276
2739
2739/0/145
1.086
R1 = 0.0702, wR2 = 0.1792
R1 = 0.0854, wR2 = 0.1878
0.405 and −0.330
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
Largest diff. peak and hole (e Å−3
)
Scheme 2 The synthetic route for glucose conjugated zinc phthalo-
cyanine. (i) CH2Cl2, 33% HBr–AcOH, 0 °C. (ii) THF–H2O, NaN3, 70 °C,
24 h. (iii) Cu(SO4)·5H2O, Na ascorbate, THF–H2O–MeOH, 50 °C, 48 h.
(iv) CH2Cl2, MeONa, MeOH, rt., 24 h.
by deprotection under Zémplen conditions in an 87% yield
(Scheme 2).
Structural characterizations
All new compounds (3–11) were fully characterized with
1
various spectroscopic methods such as IR, H NMR, 13C NMR,
UV-vis, mass spectroscopy, elemental analysis, and X-ray
analysis.
Fig. 1 The molecular structure of phthalonitrile (3).
The IR spectrum of phthalonitrile compound (3) presents
characteristic peaks such as the nitrile function at 2231 cm−1
and the terminal alkyne function at 3286 cm−1 and 2116 cm−1
,
.
the value observed in the related 3-(prop-2-ynyloxy)phthalo-
nitrile recently reported.56 The intermolecular C–H⋯N inter-
actions played an important role in stabilizing the packing of
the molecules in the crystal.
The disappearance of the peak at 2231 cm−1 proves the occur-
rence of cyclotetramerization to the phthalocyanine derivatives
(4–6). Furthermore, the peaks at 3286 cm−1 and 2116 cm−1
also disappeared in the case of the “clicking” of ZnPc (6).
The structure of phthalonitrile compound (3) was con-
firmed by X-ray analysis (Table 1). The single crystals of this
compound were grown by the slow evaporation of methanol.
The ORTEP representation of the compound is shown in
Fig. 1. The bond lengths and angles are all in the normal
range. The angle between the mean plane of the phenyl ring
and the plane that goes through atoms O1, C5, C4, C3, C2 and
C1 is 5.32(15)°. The C12–N1 and C13–N2 triple bond lengths
are 1.143(3) Å and 1.146(3) Å, respectively, and agree with the
corresponding distances in the literature.55,56 The value of the
C6–O1–C5–C4 torsion angle of 178.08 (18)° is consistent with
In the 1H NMR spectrum of 3, the aromatic protons
appeared as a triplet, doublet and doublet at 7.64, 7.36 and
7.28, respectively, the CH2–O protons appeared as a triplet at
4.26 ppm, the CH2 protons appeared as a multiplet at 2.48 and
2.10 ppm and the CuCH proton appeared as a triplet at
1
1.98 ppm. The H NMR spectra of the H2Pc (4) and ZnPc (6)
derivatives have almost the same chemical shifts and are
somewhat broader than the corresponding signals in the
dinitrile compound (3). The inner core –NH protons of the
metal-free phthalocyanine (4) was observed at −2.82 ppm.
The 13C NMR spectra of (3) shows typical chemical shifts
for the aliphatic carbons (14.52 and 27.21 ppm), the O–CH2
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carbon (69.36 ppm), the alkyne carbons (67.64 and the 1H NMR spectrum, the presence of the signal at
82.52 ppm), the aromatic carbons (100.40, 116.40, 117.07, 5.60–4.79 ppm was also attributed to the hydroxyl groups of
124.99, 134.56 and 161.21 ppm) and the nitrile carbons glucose. In addition, deprotection was confirmed by the
1
(114.00 and 115.12 ppm). H2Pc (4) and ZnPc (6) show the absence of signals between 2.08 and 1.81 ppm in the H NMR
typical 13C NMR shifts as indicated in the Experimental spectrum corresponding to the acetyl groups.
section.
In the mass spectra of phthalonitrile (3), the phthalo-
cyanines (4–6) and the glucoconjugated phthalocyanines
Electronic absorption spectroscopy and aggregation behavior
UV-vis absorption is one of the most important properties of
Pcs due to the fact that the spectral shape of an absorption
spectrum is closely related to the molecular structures, central
metals and substituents. The typical metallated phthalocya-
(10, 11), the molecular ion peaks were observed at m/z 210.00
[M]+ for 3, 842.78 [M]+ for 4, 899.67 [M]+ for 5, 906.82 [M]+ for
6, 2400.00 [M]+ for 10, and 1741.92 [M]+ for 11.
The conversion of 1,2,3,4,6-penta-O-acetyl-β-D-glucopyra-
nines with D4h symmetry have an unsplit lowest energy band
nose (7) to 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide (9)
(Q band) in the visible region (650–700 nm) and a less intense
1
13
was confirmed with IR, H NMR and
C NMR. The IR spec-
band (B band) in the 300–500 nm region. It is known that, the
α-substituted Pc derivatives have their Q bands at longer wave-
lengths compared to the β-substituted derivatives.57
trum of glucopyranosyl azide (9) exhibits the expected specific
peak at 2116.8 cm−1 due to the N3 stretching vibration. In the
13
1H NMR and
C NMR spectra of glucopyranosyl azide (9),
Fig. 3 shows the UV-vis spectra of the nonperipherally tetra
terminal alkynyl substituted metal free (4) cobalt (5) and zinc
phthalocyanines (6) in THF. For the nonperipherally tetra
terminal alkynyl substituted Pcs (4–6), the Q band absorptions
appear at a longer wavelength compared with the phthalocya-
nines containing the same substituents on the peripheral posi-
tions that we have recently reported29 (Table 2). The observed
red shift of the Q bands is a result of the nonperipheral substi-
tution with pent-4-ynyloxy groups.
The Pcs (4–6) present typical UV-vis spectra in THF, DCM
and DMF for nonaggregated phthalocyanines showing an
intense and sharp Q band in the red visible region (Table 3)
(Fig. 4a–c). H2Pc (4) shows split Q band components at ca. 695
and 724 nm in THF, DCM and DMF (Fig. 4a). This splitting
has been interpreted as being due to the reduction of
the molecular symmetry from D4h to D2h. As can be seen in
Fig. 4b–c, CoPc (5) and ZnPc (6) show red shifted Q bands
(by 12 and 7 nm respectively) in DCM compared with their
Q bands in THF. The phthalocyanine Q band shifts to the red
visible region with an increase in the refractive index of the
signals at 4.29 ppm and 87.91 ppm indicate the CH linked to
the azido group.
The formation of glycopyranosyl conjugated ZnPc (10) was
1
13
confirmed with the IR, H NMR and
C NMR spectra. After
the click reaction between glucopyranosyl azide (9) and the
terminal alkynyl substituted ZnPc (6), in the FT-IR spectra, the
signal at 2116.8 cm−1 that was observed for the azido function
of glucopyranosyl azide (9) and the signals at 2114.15 cm−1
and 3287.34 cm−1 that were observed for the alkyne function
of ZnPc (6) have disappeared (Fig. 2). In the 1H NMR spectrum,
the peak at 4.29 ppm assigned to CH–N3 shifted to 6.99 ppm
and a new peak appeared at 8.06 ppm indicating triazole for-
mation. In the 13C NMR spectrum, the signals at 143.18 ppm
and 125.50 ppm also confirm the formation of a triazole ring.
Deprotection under Zemplén conditions afforded the title
glucose conjugated ZnPc (11) in quantitative yields. The pres-
ence of a wide band around 3251 cm−1 and an intense band at
1423 cm−1 associated to the hydroxyl groups and the disap-
pearance of the band corresponding to the carbonyl groups at
1748 cm−1 were observed in the IR spectrum of 11 (Fig. 2). In
Fig. 3 The electronic spectra of 4 (black line), 5 (red line) and 6 (blue
Fig. 2 FT-IR spectra of 9, 6, 10 and 11.
line) in THF (4 × 10−6 mol dm−3).
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Table 2 The spectral data for the nonperipherally (4–6) and peripher-
ally tetra pent-4-ynyloxy substituted Pcs29 in THF
Nonperipherally tetra
pent-4-ynyloxy
substituted Pcs (4–6)
Peripherally tetra
pent-4-ynyloxy
λmax
(nm)
λmax
(nm)
substituted Pcs29
H2Pc
315, 691,
723
H2Pc
335, 665,
702
CoPc
ZnPc
315, 682
315, 696
CoPc
ZnPc
337, 671
350, 675
Table 3 The spectral data for phthalocyanines (4–6) in different
solvents
Phthalocyanines
Solvent
Q band λmax (nm)
4
THF
723, 691
725, 697
724, 693
682
687
694
DMF
DCM
THF
DMF
DCM
THF
5
6
696
DMF
DCM
700
703
solvent,58 hence a red shifting is observed in DCM which has a
larger refractive index compared to that in THF and DMF
(Table 3).
Phthalocyanines have two types of aggregations called face-
to-face H-aggregation and side-to-side J-aggregation.59 J-type
aggregation was rarely observed for the phthalocyanine mole-
cules. The shift of the Q band to the red visible region is desir-
able for applications of phthalocyanines as photosensitizers in
photodynamic therapy (PDT). A red shifted Q band can be
attributed to the J-aggregation of the Pcs60,61 or the protona-
tion of the meso-nitrogen atoms of the Pc ring due to acidic
impurities in the solvents such as dichloromethane and
chloroform, which leads to the lowering of the symmetry and
causes splitting and a bathochromic shift of the Q band.62–64
The glycopyranosyl conjugated ZnPc (10) having a Q band
maxima at 698 nm in THF and 705 nm in DMSO did not show
any aggregation in these solvents. On the other hand, this
complex showed a Q band at 705 nm and a new band at
751 nm in DCM (Fig. 5). To find out the cause of the extra red-
shifted Q band (J-type aggregation or protonation of the Pc
ring), the addition of increasing concentrations of trifluoroace-
tic acid (TFA) to a fixed concentration of 10 in DMSO was
carried out (Fig. 6). It can be seen that in addition to the
Fig. 4 (a) The electronic spectra of 4 in THF (black line), DMF (red line)
and DCM (blue line) (4 × 10−6 mol dm−3). (b) The electronic spectra of 5
in THF (black line), DMF (red line) and DCM (blue line) (4 × 10−6 mol
dm−3). (c) The electronic spectra of 6 in THF (black line), DMF (red line)
and DCM (blue line) (1.2 × 10−5 mol dm−3).
Q band at 705 nm, there is an extra red-shifted band observed meso-nitrogens can be deduced from the UV-vis spectra of 10
at 761 nm in DMSO by the addition of TFA. The increasing at different concentrations in DCM.
concentration of TFA diminishes the absorption at 705 nm
As shown in Fig. 7, when the solution of glycopyranosyl
while the extra peak at 761 nm increases. It is suggesting that, conjugated ZnPc (10) in DCM was diluted, the absorption of
the observed new red-shifted absorption band at 761 nm for the red shifted band at 751 nm increased.
nonperipherally tetra glycopyranosyl conjugated ZnPc (10)
The conversion of the acetyl groups to the hydroxyl groups
occurred due to the protonation of the meso-nitrogens of the has no influence on the electronic absorption spectrum. The
pc macrocycle. Another evidence for the protonation of the nonperipherally tetra glucose conjugated ZnPc (11) dissolved
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Fig. 5 The electronic spectra of 10 in THF (black line), DMSO (red line)
and DCM (blue line) (5 × 10−6 mol dm−3).
Fig. 8 The electronic absorption spectra of 11 at various concen-
trations: (i) 1.1 × 10−5, (ii) 8.6 × 10−6, (iii) 7.1 × 10−6, (iv) 6.0 × 10−6, (v)
5.2 × 10−6 and (vi) 4.6 × 10−6 mol dm−3 in DMSO.
Fig. 6 The change in the absorption spectrum of 10 (∼5
×
10−6
mol dm−3) in DMSO seen upon the addition of increasing concentrations
of TFA (0–0.050 mol dm−3).
Fig. 9 The electronic absorption spectra of 11 at various concen-
trations: (i) 1.2 × 10−5, (ii) 9.0 × 10−6, (iii) 7.2 × 10−6, (iv) 6.0 × 10−6, (v)
5.1 × 10−6, 3.5 × 10−6 mol dm−3 in water.
in DMSO exhibits a strong Q band at 705 nm, indicating that it
is practically non-aggregated.
Fig. 8 shows that the Lambert-Beer law was obeyed for 11 at
concentrations below 1.1 × 10−5 M. The solubility of the tetra
nonperipherally glucose conjugated ZnPc (11) in water was
evidenced by its UV-vis spectrum. Compound 11 is aggregated
in water and a new broader and blue shifted band at ∼655 nm
is observed. The shift to lower wavelengths is caused by H-type
aggregates. Increasing the concentration of 11 in water leads
to an increase of the blue shifted Q band demonstrating
the formation of aggregated species. Fig. 9 shows that the
Lambert-Beer law was obeyed for the non-peripherally tetra
glucose conjugated ZnPc (11) in concentrations ranging from
1.2 × 10−5 to 3.5 × 10−6 M in water.
Fig. 7 The electronic absorption spectra of 10 at various concen-
trations: (i) 1.3 × 10−5, (ii) 9 × 10−6, (iii) 6.5 × 10−6, (iv) 5.2 × 10−6 and (v)
4.3 × 10−6 mol dm−3 in DCM.
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ice water to give a yellow-brown precipitate, which was filtered
off and washed with water. After recrystallization from metha-
Conclusions
In summary, we have demonstrated the syntheses of non- nol, the title compound was obtained as a lustrous light
peripherally tetra terminal alkynyl substituted phthalocyanines bronze needle sufficiently pure for X-ray analysis. CCDC
and the corresponding new precursor having terminal alkyne number 978750 contains the supplementary crystallographic
function at the C-3 position. Cyclotetramerizations were data for this paper.
achieved in the presence of metal salts and/or DBU in n-penta-
Yield 0.90 g (74.19%), mp 127–129 °C, FT-IR γ (cm−1):
nol without the protection of the terminal alkyne function of 3286.45 (uC–H); 3099.21 (Ar–H); 2963.73–2844.82 (CH,
the phthalonitrile compound. The combination of the click aliphatic); 2231.18 (CN); 2116.37 (CuC); 1284.93 (Ar–O–C).
reaction between the nonperipherally tetra terminal alkynyl 1H NMR (500 MHz, CDCl3): δ ppm 7.64 (Ar–H, t, 1H), 7.36 (Ar–
substituted ZnPc (6) and azido functional glucopyranosyl (9) H, d, 1H), 7.28 (Ar–H, d, 1H), 4.26 (CH2–O–, t, 2H), 2.48 (CH2,
and the deacylation under Zemplén conditions yielded the m, 2H), 2.10 (CH2, m, 2H), 1.98 (CuCH, t, 1H). 13C NMR
title nonperipherally tetra glucose conjugated ZnPc (11). This (125 MHz, CDCl3): δ ppm 161.21 (Ar–C–O), 134.56 (Ar–C),
is the first example of nonperipherally tetra terminal alkynyl 124.99 (Ar–C), 117.07 (Ar–C), 116.40 (Ar–C), 115.12 (CuN),
substituted phthalocyanines involved in the click reaction with 114.00 (CuN), 100.40 (Ar–C), 82.52 (CuCH), 69.36 (CH2–O),
azido functional glucose to the best of our knowledge.
67.64 (CuCH), 27.21 (CH2), 14.52 (CH2). GC-MS: m/z
In this study, we have varied the tetra terminal alkynyl sub- (C13H10N2O) found = 210.00 (calcd for [M ]+ 210.23).
stituted phthalocyanines with the nonperipheral substitution
1,8(11),15(18),22(25)-Tetrakis(pent-4-ynoxy)phthalocyanine (4)
that are possible precursors for click chemistry. The water solu-
bility promoted by the glucose moieties provides a potential A mixture of 3-pent-4-ynyloxy-phthalonitrile (0.1 g, 0.48 mmol)
application of the ZnPc (11) derivative as a photosensitizer in and 30 µl of DBU in n-pentanol (2 mL) was heated to 140 °C
photodynamic therapy that we are currently investigating. with stirring for 24 h under N2. The dark blue mixture was
These novel nonperipherally terminal alkynyl substituted cooled to room temperature and then precipitated with
phthalocyanines are now being used for a new electrode modi- hexane. The precipitate was filtered off and washed with
fication technique, “click electrochemistry”. In addition, the hexane. The crude product was purified by column chromato-
synthesis of unsymmetrical phthalocyanine derivatives bearing graphy on silica gel using THF–hexane 100 : 70 as the eluent to
terminal alkyne function at the nonperipheral position is afford the metal free phthalocyanine as a blue solid. Yield
currently underway.
0.023 g (23%). FT-IR γ (cm−1): 3637.93 (N–H); 3290.63 (uC–H);
3014 (Ar–H); 2954.71–2870.68 (CH, aliphatic); 2107.75 (CuC);
1267.83 (Ar–O–C). UV-Vis (THF) λmax/nm: 723, 691, 315.
1H NMR (500 MHz, DMSO d6): δ ppm 8.52 (Ar–H, m 4H), 8.29
(Ar–H, m, 4H), 7.65 (Ar–H, m, 4H), 4.27 (CH2–O–, m, 8H), 2.82
(CH2, m, 8H), 2.34 (CH2, m, 8H), 1.92 (CuCH, m, 4H), −2.82
(N–H, s, 2H). 13C NMR (125 MHz, CDCl3): δ ppm 161.23
(Ar–C–O), 136.34, 126.23, 118.99, 116.22, 115.81, 114.01 (Ar–C),
83.66 (CuCH), 72.35 (CH2–O), 68.61 (CuCH), 27.73 (CH2),
14.73 (CH2). MS: m/z (C52H40N8O4) found = 842.782 (calcd
for [M]+ 842.94). Calcd for C 74.63, H 4.73 N 13.14%; found
C 74.05, H 4.68, N 13.21.
1,8(11),15(18),22(25)-Tetrakis(pent-4-ynoxy)phthalocyaninato
cobalt(II) (5). A mixture of 3-pent-4-ynyloxy-phthalonitrile
(0.1 g, 0.48 mmol), Co(CH3COO)2 (0.028 g, 0.16 mmol) and
30 μl of DBU in n-pentanol (2 mL) was heated to 140 °C with
stirring for 24 h under N2. The dark blue mixture was cooled
to room temperature and then precipitated with hexane. The
precipitate was filtered off and washed with hexane. The crude
product was purified by column chromatography on silica gel
using THF–hexane 1 : 1 as the eluent to afford cobalt phthalo-
cyanine as a blue solid. Yield 0.026 g (18.24%), FT-IR γ (cm−1):
3293.10 (uC–H); 3040 (Ar–H); 2954.59–2870.68 (CH, aliphatic);
2112.06 (CuC); 1272.10 (Ar–O–C). UV-Vis (THF) λmax/nm: 682,
Experimental
Materials
The IR spectra were recorded on a Perkin-Elmer Spectrum One
FT-IR spectrometer with ATR capability and the electronic
spectra were recorded on a Scinco SD 1000 singlebeam ultra-
violet-visible (UV-vis) spectrophotometer using 1 cm path
length cuvettes at room temperature. The 1H NMR and 13C
NMR spectra were recorded on a Bruker 500 MHz spectrometer
using TMS as the internal reference. Elemental analyses were
performed by the Instrumental Analysis Laboratory of the
TUBITAK Marmara Research Centre. The mass spectra were
obtained using Bruker Microflex MALDI-TOF/MS and Perkin-
Elmer Clarus 500 mass spectrometers. All reagents and sol-
vents were of reagent grade quality obtained from commercial
suppliers. The homogeneity of the products was tested in each
step by TLC (SiO2). All reactions were carried out in a nitrogen
atmosphere in dried solvents. The solvents were stored over
molecular sieves.
Synthesis
3-Pent-4-ynyloxy phthalonitrile (3). 3-Nitrophthalonitrile (1) 315. MS: m/z (C52H40N8O4Co) found = 899.672 (calcd for
(1 g, 5.77 mmol), 4-pentyn-1-ol (2) (0.873 g, 10.39 mmol) and [M]+ 899.86). Calcd for C52H40N8O4Co: C 69.41, H 4.48,
anhydrous potassium carbonate (K2CO3) (2.15 g, 15.6 mmol) N 12.45, O 7.11, Co 6.55%; found C 69.33, H 4.39, N 12.451%.
in DMSO (15 mL) were stirred for two days at 50 °C. The reac-
1,8(11),15(18),22(25)-Tetrakis(pent-4-ynoxy)phthalocyanina-
tion mixture was cooled to room temperature and poured into tozinc(II) (6). A mixture of 3-pent-4-ynyloxy-phthalonitrile
8660 | Dalton Trans., 2014, 43, 8654–8663
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(0.1 g, 0.48 mmol), Zn(CH3COO)2 (0.029 g, 0.16 mmol) and tozinc(II) (10). To a solution of terminal alkynyl substituted
30 µl of DBU in n-pentanol (2 mL) was heated to 140 °C with ZnPc (6) (0.030 g, 0.033 mmol) and 2,3,4,6-tetra-O-acetyl-β-D-
stirring for 24 h under N2. The dark blue mixture was cooled glucopyranosyl azide (9) (0.061 g, 0.165 mmol) in THF–H2O–
to room temperature and then precipitated with hexane. The MeOH 3 : 1 : 1 (10 mL), CuSO4·5H2O (0.021 g, 0.132 mmol) and
precipitate was filtered off and washed with hexane. The crude sodium ascorbate (0.078 g, 0.396 mmol) were added consecu-
product was purified by column chromatography on silica gel tively. The mixture was stirred vigorously at 50 °C for 48 h
using THF as the eluent to afford zinc phthalocyanine as under nitrogen. The solvent was removed under reduced
a blue solid. Yield 0.077 g (53.84%), FT-IR γ (cm−1): 3287.34 pressure, and the residue was taken-up in dichloromethane,
(uC–H); 3034.48 (Ar–H); 2921.42–2870.68 (CH, aliphatic); washed with water and dried over MgSO4. After the filtration
2114.15 (CuC); 1262.90 (Ar–O–C). UV-Vis (THF) λmax/nm: 696, and evaporation of the solvent, the crude product was purified
1
315. H NMR (500 MHz, DMSO d6): δ ppm 8.88 (Ar–H, m 4H), by column chromatography with silica gel using first THF–
8.10 (Ar–H, m, 4H), 7.40 (Ar–H, m, 4H), 4.56 (CH2–O–, m, 8H), hexane (1 : 1) then THF as the eluent. Yield: (0.042.g), 52%.
2.82 (CH2, m, 8H), 2.37 (CH2, m, 8H), 1.90 (CuCH, m, 4H). FT-IR γ (cm−1): 2952.58–2866.63 (CH, aliphatic); 1748.84
13C NMR (125 MHz, CDCl3): δ ppm 156.37, 152.94, 152.82, (CvO); 1587.23, 1431.96 (CvC phenyl); 1216.05 (Ar–O–C).
152.68 (Ar–C–O), 141.48, 130.86, 126.49, 125.36, 116.08 (Ar–C), UV-Vis (THF) λmax/nm: 698, 317. 1H NMR (500 MHz, CDCl3)
84.59 (CuCH), 72.03 (CH2–O), 69.67 (CuCH), 28.65 (CH2), δ ppm: 9.15 (12H, br, Ar–H), 8.06 (4H, br, CH–N3), 6.99 (4H, br,
15.19 (CH2). MS: m/z (C52H40N8O4Zn) found = 906.818 (calcd H-1), 5.38–5.02 (24H, br, aliphatic protons of glucopyranosyl),
for [M]+ 906.32). Calcd for C52H40N8O4Zn: C 68.91, H 4.45, 4.11 (8H, br, OCH2CH2CH2), 2.28 (8H, d, OCH2CH2CH2), 2.18
N 12.36%; found C 68.80, H 4.39 N 12.39%.
(8H, d, –OCH2CH2CH2), 2.08, 2.02, 1.89, 1.81 (4 × 12H, s,
2,3,4,6-Tetra-O-acetyl-β-D-glucopyranosyl azide (9). To a vigo- –OC(O)CH3). 13C NMR (125 MHz, CDCl3) δ ppm: 170.52,
rously stirred solution of 1,2,3,4,6-penta-O-acetyl-β-D-glucopyr- 169.90 (–OC(O)CH3), 156.27, 135.77, 132.58, 128.07 (Ar–C),
anose (7) (2.4 g, 6.1 mmol) in CHCI2 (20 mL) a solution of 143.18 (CCHN3), 125.50 (CCHN3), 85.68 (C-1), 74.87 (O–CH2),
33% hydrobromic acid in glacial acetic acid (10 mL) at 0 °C 72.74 (C-5), 70.47 (C-3), 68.62 (C-2), 67.66 (C-4), 61.59 (C-6),
was added carefully. The resulting solution was stirred for 7 h. 34.96 (OCH2CH2), 24.39 (OCH2CH2CH2), 21.17, 20.68, 20.50,
The orange solution was poured in ice-water. The combined 20.07 (4 × –OC(O)CH3). MS: m/z (C108H116N20O40Zn) found =
organic phases were consecutively washed with sat. aq. 2400 (calcd for [M]+ 2399.58). Calcd for C108H116N20O40Zn:
NaHCO3 (2 × 600 mL), dist. water (300 mL), and brine (2 × C 54.06, H 4.87, N 11.67%; found C 53.93, H 4.81, N 11.72%.
300 mL) and dried over Na2SO4. Filtration and evaporation
1,8(11),15(18),22(25)-Tetrakis[((1-N-(β-D-glucopyranosyl)-1H-
gave the crude glycosyl bromide (8) as a yellow oil. The recrys- 1,2,3-triazol-4-yl)propoxy)] phthalocyaninatozinc(II)(11). Com-
tallization from ethanol yielded the pure bromide as white pound 10 (0.030 g, 0.012 mmol) was dissolved in DCM
solid (1.34 g, 53%). Sodium azide (1.49 g, 23 mmol) and (2.5 mL) containing 2.5 mL of MeONa solution in methanol
2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl bromide (8) (0.95 g, and stirred at room temperature for 24 h. After the evaporation
2.31 mmol) were suspended in a mixture of THF–water 10/1 of the solvent, the solid product was washed with THF, DCM
(22 mL) and stirred at 70 °C for 24 h. Evaporation to dryness and methanol, respectively. The product was chromatographi-
afforded a yellow-white residue that was dissolved in chloro- cally pure. Yield: (0.019 g) 87%. FT-IR γ (cm−1): 3251.61 (O–H,
form (500 mL) and water (200 mL). The phases were separated glucopyranosyl); 2923.39–2864.02 (CH, aliphatic); 1423.34
and the organic layer was washed consecutively with dist. (C–O–H). UV-Vis (DMSO) λmax/nm: 705, 319 1H NMR
water (300 mL), sat. aq. NaHCO3 (400 mL) and brine (200 mL) (500 MHz, CDCl3) δ ppm: 9.03, 8.34–8.14 (12H, br, Ar–H), 7.77
and dried over Na2SO4. The crude yellowish product obtained (4H, br, C2HN3), 5.74 (4H, br, H-1), 5.60–4.79 (16H, br, –OH),
after filtration and evaporation, was washed with cold ethanol. 4.11 (8 H, br, –O–CH2), 3.58–3.16 (24H, br, aliphatic protons
After recrystallization from ethanol, the title compound of glucopyranosyl), 2.63 (8H, m, O–CH2–CH2–), 2.36 (8H, m,
2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl azide (9) was obtained O–CH2–CH2–CH2) .MS: m/z (C77H87N20O24Zn) found = 1741.92
as a white solid. Yield: (0.64 g), 74.53%. FT-IR γ (cm−1): (calcd for [M]+ 1742.02). Calcd for C77H87N20O24Zn: C 53.09,
2968.60–2906.60 (CH, aliphatic); 2116.8 (N3), 1748.2 (CvO); H 5.03, N 16.08%; found C 52.99, H 4.93, N 16.15.
1
1206 (C–O–C). H-NMR (500 MHz, CDCl3): δ ppm 5.23 (1H, t,
X-ray crystallographic details of 3-Pent-4-ynyloxy phthalo-
H-3), 5.11 (1H, t, H-4), 4.97 (1H, t, H-2), 4.66 (1H, d, H-6a), 4.29 nitrile (3). The crystal data and details of the data collection
(1H, dd, H-1), 4.19 (1H, dd, H-6b) 3.82–3.79 (1H, m, H-5), 2.11 and structure refinement are given in Table 1. The unit cell
(3H, s, –OC(O)CH3), 2.09 (3H, s, –OC(O)CH3), 2.04 (3H, s, –OC measurements and intensity data collection were performed
(O)CH3), 2.02 (3H, s, –OC(O)CH3). 13C-NMR (125 MHz, CDCl3): on an Bruker D 8 Venture three-circle diffractometer using
δ ppm 170.58, 170.10, 169.29, 169.18 (4 × –OC(O)CH3), 87.91 monochromatized Mo Kα X-radiation (k = 0.71073 Å). The data
(C-1), 74.03 (C-5), 72.60 (C-3), 70.64 (C-2), 67.88 (C-4), 61.65 reduction included a correction for Lorentz and polarization
(C-6), 20.69, 20.55, 20.53, 20.53 (4 × –OC(O)CH3). Calcd for effects, with an applied multiscan absorption correction
C14H19N3O9: C 45.04, H 5.13, N 11.26%; found C 44.97, H 5.03, (SADABS).51 The space groups were determined using XPREP
N 11.33%.
implemented in APEX.52 The structure was solved using the
1,8(11),15(18),22(25)-Tetrakis[((1-N-(2,3,4,6-tetra-O-acetyl-β-D- direct methods procedure in SHELXS-9753 and then refined
glucopyranosyl)-1H-1,2,3-triazol-4-yl)propoxy)] phthalocyanina- by full matrix least-squares refinements on F2 using the
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Dalton Transactions
SHELXL-2013. All non-hydrogen atoms were refined anisotro- 18 Y. Gao, Y. Chen, R. Li, Y. Bian, X. Li and J. Jiang, Chem. -
pically using all reflections with I > 2σ(I). The C-bound Eur. J., 2009, 15, 13241–13252.
H atoms were positioned geometrically and refined using a 19 K. Sanusi, E. Antunes and T. Nyokong, Dalton Trans., 2014,
riding mode. The final geometrical calculations and the mole-
43, 999–1010.
cular drawings were carried out with the MERCURY54 program. 20 M. van Leeuwen, A. Beeby and S. H. Ashworth, Photochem.
Photobiol. Sci., 2010, 9, 370–375.
21 S. E. Korkut, U. Avciata and M. K. Şener, J. Coord. Chem.,
2011, 64, 2936–2944.
22 M. Canlica and T. Nyokong, Dalton Trans., 2011, 40, 1497–1502.
Acknowledgements
The authors thank ‘The Scientific & Technological Research 23 V. D. Bock, H. Hiemstra and J. H. van Maarseveen,
Council of Turkey (TUBITAK)’, for financial support of this
Eur. J. Org. Chem., 2006, 1, 51–68.
work (Project no. 113Z030). They are also thankful to Dr Yunus 24 Y. Zorlu, F. Dumoulin, D. Bouchu, V. Ahsen and D. Lafont,
Zorlu (Gebze Institute of Technology) and Mr Kerem Kaya
(Istanbul Technical University) for performing X-ray analysis.
Tetrahedron Lett., 2010, 51, 6615–6618.
25 F. Dumoulin and V. Ahsen, J. Porphyrins Phthalocyanines,
2011, 15, 481–504.
26 D. Quinton, E. Antunes, S. Griveau, T. Nyokong and
F. Bedioui, Inorg. Chem. Commun., 2011, 14, 330–332.
27 Y. Yilmaz, M. K. Şener, I. Erden and U. Avciata, Polyhedron,
2009, 28, 3419–3424.
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