Preparation and characterization of aluminum phthalocyanine acetate, propionate, and benzoate

Article abstract of DOI:10.1016/j.tetlet.2012.05.098

Aluminum phthalocyanine acetate, propionate and benzoate were prepared by the reaction of hydroxy aluminum phthalocyanine and the corresponding acetic, propionic, and benzoic anhydrides. The reaction products were characterized by ¹H and ¹

Full text of DOI:10.1016/j.tetlet.2012.05.098

Tetrahedron Letters 53 (2012) 4056–4058
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Preparation and characterization of aluminum phthalocyanine acetate,
propionate, and benzoate
⇑
ˇ
ˇ
ˇ
ˇ
ˇ
´
Marie Karásková , Jan Rakušan, Antonín Lycka, Jirí Cerny, Jirí Cermák
Centre for Organic Chemistry Ltd, Rybitví 296, CZ-533 54 Rybitví, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
Aluminum phthalocyanine acetate, propionate and benzoate were prepared by the reaction of hydroxy
aluminum phthalocyanine and the corresponding acetic, propionic, and benzoic anhydrides. The reaction
products were characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The thermal
behavior of the products was determined by thermal analysis of particular samples.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 16 March 2012
Revised 9 May 2012
Accepted 22 May 2012
Available online 9 June 2012
Keywords:
Aluminum phthalocyanine carboxylate
NMR
MS
Thermogravimetry
Phthalocyanine compounds, mostly those of copper, are used
both as dyestuffs and pigments. Derivatives of phthalocyanine
have attracted considerable interest due to their growing potential
as active materials in photosensitizers for photodynamic ther-
apy,1,2 catalysts,3 active layers in photovoltaic panels,4 transistors,5
various sensors6 and light-emitting diodes.7 While the utility of the
unsubstituted macrocycle of phthalocyanines is limited due to
their very poor solubility in various solvents, substitutions at
peripheral positions of the phthalocyanine macrocycle with appro-
priate functional groups improves their solubility and increases
their effectiveness in many applications.
There are 16 peripheral positions on the phthalocyanine
macrocycle which can be substituted either symmetrically or
unsymmetrically. Besides peripheral positions, substitution of
Scheme 1.
⇑
Corresponding author. Tel.: +420 466823005; fax: +420 466823900.
E-mail address: marie.karaskova@cocltd.cz (M. Karásková).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.05.098

M. Karásková et al. / Tetrahedron Letters 53 (2012) 4056–4058
4057
Table 1
1H and 13C NMR chemical shifts of compounds 1–3
1
2
3
a
a
a
dH
dH
Db
dC
dH
dH
Db
dC
dH
dH
Db
dC
1
2
3
4
COO
10
20
30
40
—
—
9.66
8.47
—
—
—
—
—
—
2.22
—
—
—
—
—
—
—
150.8
136.9
123.3
130.9
166.5
21.1
—
—
—
—
—
—
—
—
—
—
—
150.9
137.0
123.4
130.9
169.6
27.5
8.8
—
—
9.68
8.47
—
—
—
—
—
—
—
8.14
7.62
7.53
—
—
—
—
—
—
ꢀ3.10
ꢀ1.35
ꢀ0.93
150.9
136.9
123.4
131.0
161.3
133.2
126.5
126.5
129.6
9.66
8.47
—
ꢀ0.86
—1.33
—
—
—
—
ꢀ1.06
ꢀ3.28
2.49
1.18
—
ꢀ3.35
—2.51
—
—
—
—
5.04
6.27
6.60
—
—
—
—
—
—
—
—
—
—
—
The numbering of atoms is given in Scheme 1.
a
dH in corresponding anhydride.
b
D
= dH (in 1, 2 or 3)—dH (in corresponding anhydride).
Figure 1. (a) APCI(ꢀ)-MS spectra of 1–3 in the m/z range 500–700 (b) MS/MS spectra of the molecular ions.
phthalocyanines can also be realized by the presence of axial li-
gands bound to the central metallic ion, located fully or partially
in the cavity of phthalocyanine macrocycle.
Phthalocyanines with divalent metal ions are either planar sys-
tems or form structures with the central metal ion slightly above
the phthalocyanine plane. The central atom is susceptible to nucle-
ophilic axial binding.8 Such binding occurs through dative bonds.
Phthalocyanines with trivalent and tetravalent metal ions form
structures with one or two axially bound groups.
While there are several reports describing the synthesis and
properties of various axially substituted phthalocyanines of sili-
con,9 titanium,10 tin,11 gallium,12 germanium,13 hafnium,14 and zir-
conium,14 very little has been published on axially substituted
aluminum phthalocyanines. Aluminum phthalocyanine offers a
wide range of applications due to its photosensitizing properties
and usually contains a chloride or a hydroxy ligand on the central
Al atom. The reactions of anhydrides of organic acids with axial hy-
droxy ligands bound to the central ion of aluminum phthalocya-
nine, targeting esters, have not been described previously.
Herein, we report the synthesis and characterization of alumi-
num phthalocyanines substituted with esters of acetic acid, propi-
onic acid, and benzoic acid at the central aluminum ion. Aluminum
phthalocyanine acetate (1),15 propionate (2),16 and benzoate (3)17
were prepared by the reaction of hydroxy aluminum phthalocya-
nine (HOAlPc) and the corresponding acetic, propionic, and benzoic
anhydrides (Scheme 1).
The isolated reaction products were characterized by 1H and 13
C
NMR spectroscopy and by mass spectrometry. The thermal behav-
ior of the products was determined by thermal analysis of particu-
lar samples.
In the 1H NMR spectra,18 there were signals due to four equiv-
alent 1,2-disubstituted aromatic rings of the phthalocyanine and
those for the methyl, ethyl, and phenyl substituents. The relative
integral ratios of these signals were 16:3 (CH3) for compound 1,
16:2 (CH2) and 16:3 (CH3) for compound 2 and 16:2 (ortho), 16:2
(meta) and 16:1 (para) for compound 3. For proton chemical shifts,
see Table 1. The 1H chemical shifts of the carboxylate group pro-
tons were shifted considerably to lower frequencies compared to
those in the starting anhydrides. This effect is caused by the exis-
tence of diamagnetic anisotropy. Ring-current effects lead to
shielding or deshielding of the protons of the substituents depend-
ing on their mutual orientation with respect to the phthalocyanine
plane. A very convincing and clear demonstration of this effect was
Table 2
Weight losses for compounds 1–3
Compound
Weight loss for the first step (%)
Theoretical value (%)
1
2
3
10.07
12.89
18.37
8.97
11.92
18.32

4058
M. Karásková et al. / Tetrahedron Letters 53 (2012) 4056–4058
Figure 2. TGA analysis of compound 3.
provided by Fernández and Fernándes-Sánchez19 for 1:2 com-
plexes of iron(II) phthalocyanine with decylamine or benzylamine.
The largest difference between proton chemical shifts in com-
plexed and free amines (except for the concentration-dependent
resonance position of the free amino group) was observed for
protons of the first methylene group (about ꢀ5.7 ppm),19 while
we observed a maximum difference of ꢀ3.35 ppm (Table 1). 2D
gradient-selected (gs)-HMQC and gs-HMBC spectra18 were used
for the assignment of 13C NMR resonances (Table 1).
Atmospheric pressure chemical ionization (APCI) mass spectra
were recorded using an Agilent LC/MSD Trap XCT Plus mass spec-
trometer. Direct infusion of the sample solution in acetoni-
trile:dimethyl sulfoxide (5:1) into the APCI ion source was used.
The AlPc derivatives were detected by APCI(ꢀ) MS (Fig. 1a). The
radical molecular ions MꢀÅ were observed in particular cases at
m/z 598, 612 and 660. The MS/MS experiment on these ions
(Fig. 1b) clearly gave fragment ions of AlOHPc at m/z 557. Com-
pound 3 also produced a fragment ion [Mꢀ44]ꢀ (loss of CO2) as
the base peak. The fragment ions observed in the MS/MS spectra
corresponded to the suggested structures.
the compounds were fully characterized by 1H and 13C NMR spec-
troscopy, mass spectrometry, and thermogravimetry. The products
exhibit higher solubility in polar solvents and may be useful for
several applications such as photodynamic therapy.
Reference and notes
1. Ben-Hur, E.; Chan, W.-Sh. In The Porphyrin Handbook; Kadish, K. M.; Smith, K.
M.; Guilard, R. Eds.; Academic Press: Amsterdam, 2003; Vol. 19, pp 1–35.
2. Tedesco, A. C.; Rotta, J. C. G.; Lunardi, C. N. Curr. Org. Chem. 2003, 7, 187–196.
3. Borisenkova, S. A.; Girenko, E. G.; Mikhalenko, S. A.; Negrimovskii, V. M.; Soloveva,
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L. I.; Kaliya, O. L.; Lukyanets, E. A. Vestn. Mosk. U. Khim. 2002, 43, 192–193.
4. Pannemann, C.; Dyakonov, V.; Parisi, J.; Hild, O.; Wöhrle, D. Synth. Met. 2001,
121, 1585–1586.
5. Ye, R.; Baba, M.; Suzuki, K.; Mori, K. Thin Solid Films 2009, 517, 3001–3004.
6. Singh, S.; Saini, G. S. S.; Tripathi, S. K. J. Optoelectron Adv. Mater. 2008, 10, 185–
189.
7. Rosenow, T. C.; Walzer, K.; Leo, K. J. Appl. Phys. 2008, 103, 043105/1-043105/4.
8. Yang, Y. J. Phys. Chem. A 2011, 115, 9043–9054.
9. Brewis, M.; Clarkson, G. J.; Goddard, V.; Helliwell, M.; Holder, A. M.; McKeown,
N. B. Angew. Chem., Int. Ed. 1998, 37, 1092–1094.
10. Maree, S. E. Porphyrins Phthalocyanines 2005, 9, 880–883.
11. Ding, X.-X.; Zheng, S.-N.; Peng, Y.-R.; Weng, J.-B.; Lin, P.-P.; Zhang, H. Hecheng
Huaxue 2008, 16, 12–14.
12. Chen, Y.; Hanack, M.; Araki, Y.; Ito, O. Chem. Soc. Rev. 2005, 34, 517–529.
13. Soncin, M.; Polo, L.; Reddi, E.; Jori, G.; Kenney, M. E.; Cheng, G.; Rodgers, M. A. J.
Brit. J. Cancer 1995, 71, 727–732.
Thermogravimetric analyses were performed using a Mettler
Toledo TGA/DSC 1 STARe System in a 70
ll alumina crucible. A
14. Gerasymchuk, Y. S.; Volkov, S. V.; Chernii, V. Ya.; Tomachynski, L. A.; Radzki, St.
J. Alloy Compd. 2004, 380, 186–190.
small amount of the test compound (ꢁ5 mg) was weighed into
the measuring crucible and heated using a controlled temperature
program between 25 °C and 700 °C using a gradient of 10 °C/min. A
flow of nitrogen (about 20 mL/min) was used as a protective gas.
During the heating process weight-curves were recorded over the
complete temperature range. All three compounds demonstrated
the same behavior during the heating process. Cleavage of an acyl
group occurred as the first step and aluminum phthalocyanine was
formed. For compound 1, only the first step was elimination of
crystal water from the molecule with subsequent cleavage of an
acyl group. Table 2 shows the weight losses during the heating of
the studied samples. From the results it is apparent that the found
values are in very good agreement with the theoretical values.
Figure 2 shows the weight-curve of compound 3. The first loss of
weight (18.37%) was observed between 190 °C and 480 °C. The sec-
ond loss of weight (22.33%) was observed between 480 °C and 700 °C.
In conclusion, three axially substituted aluminum phthalocya-
nines containing acyl groups were prepared for the first time. All
15. Preparation of aluminum phthalocyanine acetate (1): 1 g of hydroxy aluminum
phthalocyanine (HOAlPc) was dispersed in 50 mL of Ac2O and the dispersion
refluxed for 4 h. After cooling, the precipitated product was filtered, washed
thoroughly with H2O and dried in vacuo at 100 °C. Yield: 771 mg (72%).
16. Preparation of aluminum phthalocyanine propionate (2): 1 g of hydroxy
aluminum phthalocyanine (HOAlPc) was dispersed in 50 mL of propionic
anhydride and the dispersion refluxed for 4 h. After cooling, the precipitated
product was filtered, washed thoroughly with acetone and dried in vacuo at
70 °C. Yield: 841 mg (76%).
17. Preparation of aluminum phthalocyanine benzoate (3): 1 g of hydroxy
aluminum phthalocyanine (HOAlPc) was mixed with 25 g of benzoic
anhydride and the mixture stirred and heated for 12 h at 200 °C. After
cooling, the precipitated product was filtered, washed thoroughly with acetone
and dried in vacuo at 70 °C. Yield: 609 mg (51%).
18. NMR spectra were recorded on a Bruker Avance II spectrometer (400.13 MHz
for 1H and 100.62 MHz for 13C) in DMSO-d6. The 1H and 13C chemical shifts
were referenced to the central signal of the solvent [d = 2.55 (1H) and 39.6
(
13C)]. 2D NMR experiments [gradient-selected (gs)-HMQC, gs-HMBC] were
performed using TOPSPIN 2.1.
19. Fernández, I.; Fernándes-Sánchez, J. F. J. Chem. Educ. 2010, 87, 320. and
Supplementary data.