Investigation of synthetic pathways of carboxylic acid phthalocyanines from glycolic and lactic acids

Article abstract of DOI:10.1016/j.ica.2017.07.053

We present the study of synthetic pathways to prepare carboxylic acid substituted phthalocyanines from glycolic and lactic acids. Hydroquinone was used as an alternative catalyst for cyclotetramerization reaction of metal free and zinc phthalocyanines, which were characterized by ¹H MR spectroscopy, infrared absorption and mass analysis. The photophysical and photochemical properties in dimethyl sulfoxide (DMSO) were analyzed. We verified that the presence of the methyl radical group, that distinguish both structures, diminish the macrocycle aggregation in solution and promote higher quantum yields of fluorescence and for singlet oxygen generation.

Full text of DOI:10.1016/j.ica.2017.07.053

Accepted Manuscript
Research paper
Investigation of synthetic pathways of carboxylic acid phthalocyanines from
glycolic and lactic acids
Francisco B. do Nascimento, Anderson O. Ribeiro
PII:
S0020-1693(17)30767-3
http://dx.doi.org/10.1016/j.ica.2017.07.053
ICA 17776
DOI:
Reference:
Inorganica Chimica Acta
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Accepted Date:
15 May 2017
12 July 2017
26 July 2017
Please cite this article as: F.B. do Nascimento, A.O. Ribeiro, Investigation of synthetic pathways of carboxylic acid
phthalocyanines from glycolic and lactic acids, Inorganica Chimica Acta (2017), doi: http://dx.doi.org/10.1016/
j.ica.2017.07.053
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Investigation of synthetic pathways of carboxylic acid phthalocyanines from glycolic
and lactic acids
Francisco B. do Nascimento, Anderson O. Ribeiro*
Universidade Federal do ABC – UFABC
Avenida dos Estados, 5001, Bloco B, Santo André, SP, Brasil.
*anderson.ribeiro@ufabc.edu.br
Abstract
We present the study of synthetic pathways to prepare carboxylic acid
substituted phthalocyanines from glycolic and lactic acids. Hydroquinone was used as
an alternative catalyst for cyclotetramerization reaction of metal free and zinc
phthalocyanines, which were characterized by 1H MR spectroscopy, infrared absorption
and mass analysis. The photophysical and photochemical properties in dimethyl
sulfoxide (DMSO) were analyzed. We verified that the presence of the methyl radical
group, that distinguish both structures, diminish the macrocycle aggregation in solution
and promote higher quantum yields of fluorescence and for singlet oxygen generation.
Keywords: phthalocyanine, glycolic acid, lactic acid, photosensitizer, photodynamic
therapy
1. Introduction
Phthalocyanines (Pc’s) are aromatic macrocycles with highly conjugated π-electron
structure [1, 2]. Although they have been mainly used as blue and green dyes in the
textile and paper industries [1], their chemical, photochemical, and thermal stabilities

endorses applications as photoconduction agents in photocopying machines [3],
photoelectrochemical sensors [4-6], electrochromic display devices [7], photosensitizers
for dye sensitized solar cells [8, 9] and oxidation or reduction catalysts and
photocatalysts [10-13]. Also, these compounds are promise photosensitizers for
photodynamic therapy (PDT) [14], due to their high absorption extinction coefficient in
600 to 800 nm region and their high quantum yield of singlet oxygen generation [15-
18].
However, one problem related to biological applications of these macrocycles is their
spontaneous self-aggregation in solution, which is unfavorable to PDT because dimers
and oligomers are considered inactive or extremely inefficient to generate singlet
oxygen compared to monomers [19],[20]. To overcome this problem, synthetic
strategies have been described to introduce bulky substituents or appropriate functional
groups at the α peripheral and/or β positions [21]. Among other substituents, carboxylic
acid is very interesting due to their possible interconversion in others functional groups
and to form a covalent linkage to biological molecules that can be used as specific target
to the cells [22-25].
The mostly used method for the synthesis of tetra-carboxy phthalocyanines (TcPc’s)
and octa-carboxyphthalocyanines (OcPc’s) apply trimellitic anhydride (or pyromellitic
dianhydride), urea, a metal salt and ammonium heptamolybdate (as catalyst) grounded
together and irradiated under microwave irradiation, followed by total hydrolysis of
amide groups in KOH 50%/NaCl saturated solution [26-28]. Whereas OcPc’s are
soluble in alkaline aqueous solutions [22, 29], owing to high number of carboxyl groups
incorporated into the macrocycle, TcPc’s are poor soluble in weak alkaline conditions.
[30].

Mono-functionalized carboxyphthalocyanines were also described. Nyokong has
reported, for example, the synthesis and characterization of germanium, titanium and tin
phthalocyanine complexes with only one reactive carboxy group as an electrophile [31]
These syntheses generally apply a statistic condensation of two different
phthalonitriles, being one of them modified with a carboxylic group. Unsymmetrical
phthalocyanines modified with carboxyl and naphtol [32, 33], diethylaminoethanol [25],
cysteine [34], hexylthiol [35] 5-trifluoromethyl-2-mercaptopyridine [36] and others
were reported [37] including its attach to carbon nanotubes [38] ZnO and TiO2 films
[39], GnRH receptor [19] and gold nanoparticles [40, 41].
In our study, synthetic pathways and convenient methods to prepare carboxylic acid-
substituted phthalocyanines from glycolic and lactic acids were investigated. These two
substituents were chosen because they have very similar structure, diverging from a
methyl radical group. The photophysical and photochemical properties of all
compounds were investigated in order to evaluate their potential to be applied as
photosensitizer in PDT.
2. Experimental Section
2.1. General considerations
All reagents and starting materials were purchased from commercial sources and
used as received. When necessary, solvents were purified following standard literature
procedures. Some reactions were carried out under a nitrogen atmosphere, as specified
in experimental procedures. Britton–Robinson buffer was prepared from acetic acid,
orthophosphoric acid, boric acid, and sodium hydroxide. Melting point analysis was
performed in the Büchi Melting Point B-540 equipment. Elemental analysis was carried

out using a Analisador Elementar Flash EA 1112 CNHS instrument. UV/Vis absorption
spectra were recorded with Perkin Elmer Lambda 35 equipment in 10.00 mm quartz
cells. Fluorescence excitation and emission spectra were measured with an Agilent
Technologies Cary Eclipse Spectrofluorimeter in 10.00 mm quartz cells. Infrared
spectra were recorded with a Varian FTIR 660 spectrometer. Mass spectra were
recorded by HMRS-MALDI-TOF spectrometer (Bruker-Daltonics).
2.2. Synthesis of ethyl (3,4-dicyanophenoxy)acetate (1)
13 (4.0 g, 38.4 mmol) and 4-nitrophthalonitrile (6.65 g, 38.4 mmol) were stirred
in a three-necked flask for three days in DMF (6 mL) at room temperature in the
presence of an excess of anhydrous K2CO3 (5 g). The reaction mixture was poured into
ice water to give light yellow precipitate which was collected by filtration and washed
with water. The product was dissolved in CH2Cl2 (100 mL) and washed with distilled
water (3 x 50 mL). The organic phase was dried over with Mg2SO4, filtered and
concentrated under reduced pressure. The crude product was further purified by
chromatography on a silica gel column using hexane-ethyl acetate 2:1 v/v resulting in a
yellow solid which was finally purified by recrystallization in methanol, yielding 1 as a
white solid, (5.63 g, 63.7%). m.p. 115.35 °C m/z 230.01. 300 MHz 1H NMR (CDCl3): δ
(ppm) 7.75 (d, J=8 Hz, 1H, H-6); 7.27 (d, J=4 Hz, 1H, H-3); 7.21 (dd, J1=8 Hz, J2=4
Hz, 1H, H-1); 4.74 (s, 2H, H-10); 4.30 (q, J=8 Hz, 2H, H-14); 1.32 (t, J=8 Hz, 3H, H-
15). 100 MHz 13C NMR (CDCl3): δ (ppm) 167.11 C-11; 160.91 C-12; 135.35 C-6;
(119.90; 119.56; 117.55; 115.49; 115.12; C-Ar); 65.43 C-10; 62.14 C-14; 14.16 C-15.
FTIR (KBr) (νmax): 3118 cm-1 3081 cm-1 (Ar-H), 2996 cm-1 (C-H), 2225 cm-1 (C≡N),
,
1741 cm-1 (C=O), 1594, 1488 cm-1 (C=C) , 1382 cm-1 (C-O), 1236 cm-1 (C-O-C).

2.3. Synthesis of ethyl 2-(3,4-dicyanophenoxy)propanoate (2)
According to the procedure for 1, compound 14 (4.71 g, 39.8 mmol) was treated
with 4-nitrophthalonitrile (6.90 g, 39.8 mmol) and an excess of anhydrous K2CO3 (5 g)
in DMF (6 mL) for three days at room temperature. The compound was isolated as a
1
white solid (6.99 g, 72%). m.p. 117.75 °C m/z 244,08. 400 MHz H NMR (CDCl3): δ
(ppm) 7.72 (d, J=8 Hz, 1H, H-6); 7.23 (d, J=4 Hz, 1H, H-3); 7.15 (dd, J1=8 Hz, J2=4
Hz, 1H, H-1); 4.83 (q, J=8 Hz, 1H, H-10); 4.25 (q, J=8 Hz, 2H, H-15); 1.69 (d. J=8
Hz, 3H, H-12); 1.28 (t, J=8 Hz, 3H, H-16). 100 MHz 13C NMR (CDCl3): δ (ppm)
170.20 C-11; 160.76 C-2; 135.32 C-6; (120.21; 119.68; 117.48; 115.53; 115.15; C-Ar.);
108.05 C-7, C-8; 73.21 C-10; 62.10 C-15; 18.24 C-12; 14.15 C-16. FTIR (KBr) (νmax):
3114 cm-1 3085 cm-1 3046 cm-1(Ar-H), 2996 cm-1, 2977 cm-1, 2942 cm-1 (C-H), 2235
,
,
cm-1 (C≡N), 1743 cm-1 (C=O), 1592 cm-1 , 1496 cm-1 (C=C), 1382 cm-1 (C-O), 1236
cm-1 (C-O-C), 1024 cm-1 (C-O).
2.4. Synthesis of zinc carboxyphthalocyanines derivatives.
2.4.1. 2,9(10),16(17),23(24)-Tetra[(pentyloxycarbonyl)methyloxy]phthalocyaninato
zinc (II) (3).
o
Phthalonitrile 1 (300 mg, 1.30 mmol) was stirred in n-pentanol (5 ml) at 70 C
for 10 min, and then hydroquinone (143.61 mg, 1.30 mmol) and anhydrous zinc acetate
o
(120 mg, 0.63 mmol) were added. The resulting mixture was stirred at 150 C under
nitrogen atmosphere for 12 h. After removing the volatiles in vacuo, the residue was
purified by a silica gel column chromatography using 200 mL of DCM and then
hexane–ethyl acetate (2:1, v/v) affording 3 (126 mg, 34%). m.p. > 300 °C; HRMS-

MALDI-TOF m/z calculated for C60H64N8O12Zn [M+1]+ 1152.394, found [M+1]+
1153.384. Elemental Analysis. Calculated: C, 62.42%; H, 5.59%; N, 9.71%. Found: C,
62.47%; H, 5.41%; N, 9.80%. FTIR (KBr) (νmax): 2956 cm-1, 2927 cm-1, 2856 cm-1 (C-
H), 1760 cm-1 (C=O), 1608 cm-1, 1488 cm-1, 1398 cm-1 (C=C), 1338 cm-1 (C-O), 1201
cm-1 (C-O-C), 1091 cm-1 (C-O-C).1H NMR (CDCl3): δ (ppm) 7.81 – 7.40 (m, 4H, H-6);
7,35 – 7.26 (m, 8H, H-1 e H-3); 5.04 (s, 8H, H-8); 4.15 – 4.09 (m, 8H, H-12); 1.60 –
1.53 (m, 8H, H-15); 1.29 – 1.19 (m, 8H, H-14 e H-13); 0.85 – 0.81 (m, 8H, H-16).
2.4.2. 2,9(10),16(17),23(24)-Tetra[1-(pentyloxycarbonyl)ethyloxy]phthalocyaninato
zinc (II) (4).
According to the above procedure for 3, a suspension of 2 (300 mg, 1.23 mmol)
in n-pentanol was treated with hydroquinone (135 mg, 1.23 mmol) and anhydrous zinc
acetate (112.80 mg, 0.60 mmol) to give compound 4 (126 mg, 41%). m.p. > 300 °C;
HRMS-MALDI-TOF m/z calculated for C64H72N8O12Zn [M+1]+ 1208.456, found
[M+1]+ 1208.454. Elemental Analysis. Calculated: C, 63.49%; H, 5.99%; N, 9.26%.
Found: C, 63.57%; H, 6.65%; N, 9.18%. FTIR (KBr) (νmax): 2958 cm-1, 2927 cm-1,
2861 cm-1 (C-H), 1766 cm-1 (C=O), 1614 cm-1, 1482 cm-1, 1452 cm-1 (C=C), 1373 cm-1
(C-O), 1226 cm-1 (C-O-C), 1099 cm-1 (C-O-C).1H NMR (CDCl3): δ (ppm) 8.85 – 8.47
(m, 4H, H-6); 8.41 – 7.94 (m, 4H, H-3); 7.75 – 7.35 (m, 4H, H-1); 5.62 – 5.19 (m, 8H,
H-8); 4.50 – 4.13 (m, 8H, H-12); 2.16 – 2.04 (m, 8H, H-13); 1.89 – 1.68 (m, 8H, H-14);
1.59 – 0.91 (m, 19H, H-15 e H-22); 0.87 – 0.55 (m, 12H, H-16).

2.4.3. 2,9(10),16(17),23(24)-Tetra(carboxymethyloxy)phthalocyaninato zinc (II) (5).
In a closed reaction tube, phthalonitrile 1 (300 mg, 1.30 mmol) and zinc acetate
o
dihydrate (142.68 mg, 0.65 mmol) in DMAE (5 mL) were heated at 150 C, under
nitrogen atmosphere and constant stirring for 10 h. After cooling, the reaction mixture
was poured into a water/ethanol 10 % solution) to give dark blue precipitate, which was
collected by filtration and washed with water. The residue was solubilized in NaOH (1
mol.L-1) solution and then acidified to pH 2 with HCl (1 mol.L-1) solution, until
coagulation. The solid was centrifuged and purified by successive precipitation, using
solutions of HCl (1 mol.L-1) and NaOH (1 mol.L-1). The crude product was purified by
silica gel column chromatography using methanol-ethyl acetate 2:1 v/v to give
compound 5 (180 mg, 64%). m.p. > 300 °C; HRMS-MALDI-TOF m/z calculated for
C40H24N8O12Zn [M+1]+ 872.081, found [M+1]+ 872.067. Elemental Analysis.
Calculated: C, 54.97%; H, 2.77%; N, 12.82%. Found: C, 54.96%; H, 2.84%; N,
12.91%. FTIR (KBr) (νmax): 3500 – 2500 cm-1 (O-H), 2921 cm-1, 2827 cm-1 (C-H), 1724
cm-1 (C=O), 1604 cm-1, 1479 cm-1, 1400 cm-1 (C=C), 1334 cm-1 (C-O), 1220 cm-1 (C-O-
C), 1070 cm-1 (C-O-C).1H NMR (CDCl3): δ (ppm) 9.25 – 8.83 (m, 4H, H-6); 8.83 –
8.30 (m, 4H, H-3); 7.84 – 7.66 (m, 4H, H-1); 5.28 (s, 8H, H-8).
2.4.4. 2,9(10),16(17),23(24)-Tetra(1-carboxyethyloxy)phthalocyaninato zinc (II) (6).
Compound 6 was synthesizedtized and purified with the same conditions
adopted for 5, reacting phthalonitrile 2 (300 mg, 1.23 mmol) and zinc acetate dihydrate
(154.3 mg; 0.61 mmol) in DMAE (5 mL) to give compound 6 (208.30 mg, 73%). m.p. >
300 °C; HRMS-MALDI-TOF m/z calculated for C44H32N8O12Zn [M+1]+ 928.143,
found [M+1]+ 928.148. Elemental Analysis. Calculated: C, 56.82; H, 3.47; N, 12.05.
Found: C, 56.80; H, 3.51; N, 12.15. FTIR (KBr) (νmax): 3500 – 2500 cm-1 (O-H), 2987
cm-1, 2937 cm-1 (C-H), 1728 cm-1 (C=O), 1606 cm-1, 1479 cm-1, 1400 cm-1 (C=C), 1336

cm-1 (C-O), 1226 cm-1 (C-O-C), 1093 cm-1 (C-O-C).1H NMR (CDCl3): δ (ppm) 9.24 –
8.80 (m, 4H, H-6); 8.78 – 8.40 (m, 4H, H-3); 7.79 – 7.63 (m, 4H, H-1); 5.58 – 5.42 (m,
8H, H-8); 1.98 – 1.79 (m, 12H, H-22).
2.5. Synthesis of metal free carboxyphthalocyanines Derivatives.
2.5.1. 2,9(10),16(17),23(24)-Tetra[(pentyloxycarbonyl)methyloxy]phthalocyanine (7).
o
Phthalonitrile 1 (300 mg; 1.30 mmol) was stirred in n-pentanol at 70 C for 10 min, and
then hydroquinone (47.7 mg, 0.434 mmol) were added. The resulting mixture was
o
stirred at 150 C under nitrogen atmosphere for 12 h. After the solvent removing, the
residue was poured into ice water to give green precipitate, which was collected by
filtration, washed with the aqueous solutions of HCl (2 mol.L-1) and NaOH (1 mol.L-1),
respectively, followed by water until pH 7, and then dried in vacuo. The crude product
was purified by a silica gel column chromatography using using 200 mL of DCM and
then hexane–ethyl acetate (1:1, v/v) to give compound 7 (126 mg, 41%). m.p. > 300 °C.
FTIR (KBr) (νmax): 2956 cm-1, 2927 cm-1, 2856 cm-1 (C-H), 1760 cm-1 (C=O), 1608 cm-
1, 1488 cm-1, 1398 cm-1 (C=C), 1338 cm-1 (C-O), 1201 cm-1 (C-O-C), 1091 cm-1 (C-O-
C).1H NMR (CDCl3): δ (ppm) 7.81 – 7.40 (m, 4H, H-6); 7.35 – 7.26 (m, 8H, H-1 e H-
3); 5.42 – 5.30 (m, 8H, H-8); 4.40 – 4.34 (m, 8H, H-12); 1.80 – 1.69 (m, 8H, H-15);
1.47 – 1.35 (m, 16H, H-14 e H-13); 0.88 – 0.81 (m, 8H, H-16); -0.12 (s, 1H, NH);

2.5.2. 2,9(10),16(17),23(24)-Tetra[1-(pentyloxycarbonyl)ethyloxy]phthalocyanine (8).
According to the above procedure for 7, a suspension of 2 (300 mg; 1,23 mmol)
in n-pentanol was treated with hydroquinone (47.7 mg, 0.434 mmol) to give compound
4 45% (126 mg). m.p. > 300 °C; FTIR (KBr) (νmax): 2956 cm-1, 2927 cm-1, 2856 cm-1
(C-H), 1760 cm-1 (C=O), 1608 cm-1, 1488 cm-1, 1398 cm-1 (C=C), 1338 cm-1 (C-O),
1201 cm-1 (C-O-C), 1091 cm-1 (C-O-C).1H NMR (DMSO-d6): δ (ppm) 8.14 – 7.04 (m,
12H, H-6, H-3, H1); 5.49 – 5.10 (m, 4H, H-8); 4.81 – 3.63 (m, 8H, H-12); 2.05 – 0.58
(m, 48H, H-22, H-13, H-14, H-15, H-16); -0.12 (s, 1H, NH).
2.5.3. 2,9(10),16(17),23(24)-Tetra(carboxymethyloxy)phthalocyanine (9).
In a closed reaction tube, phthalonitrile 1 (300 mg, 1.30 mmol) was stirred in
o
DMAE (5 Ml) at 70 C for 10 min, and then an excess of metallic lithium (5 mg) was
o
added. The resulting mixture was stirred at 150 C under nitrogen atmosphere and
constant stirring for 4 h. After cooling, the reaction mixture was poured into a
water/ethanol 10 % solution to give dark blue precipitate, which was collected by
filtration and washed with water. The residue was solubilized in NaOH (1 mol.L-1)
solution and then acidified to pH 2 with HCl (1 mol.L-1) solution, until coagulation. The
solid was centrifuged and purified by successive precipitation, using solutions of HCl (1
mol.L-1) and NaOH (1 mol.L-1) The crude product was purified by silica gel column
chromatography using methanol-ethyl acetate 2:1 v/v to give the compound 9 75.00%
(216 mg). m.p. > 300 °C. FTIR (KBr) (νmax): 3448 cm-1 (O-H, N-H), 1716 cm-1 (C=O),
1616 cm-1, 1481 cm-1 (C=C), 1342 cm-1 (C-O), 1236 cm-1 (C-O-C), 1101 cm-1 (C-O-C).

2.5.4. 2,9(10),16(17),23(24)-Tetra(carboxymethyloxy)phthalocyanine (10).
Compound 10 was synthesizedtized under the same conditions adopted for 9,
reacting phthalonitrile 2 (300 mg, 1.23 mmol) and then an excess of metallic lithium (5
mg) in 5 mL of DMAE to give a dark green solid (216 mg, 82.0%). m.p. > 300° C;.
FTIR (KBr) (νmax): 3448 cm-1 (O-H, N-H), 1716 cm-1 (C=O), 1616 cm-1, 1481 cm-1
(C=C), 1342 cm-1 (C-O), 1236 cm-1 (C-O-C), 1101 cm-1 (C-O-C).1H NMR (DMSO-d6):
δ (ppm) 8.25 – 7.29 (m, 12H, H-1, H-3 e H-6); 5.66 – 4.89 (m, 4H, H-13); 2.27 – 1.61
(m, 12H, H-17).
2.6. Metallation reaction of metal free carboxyphthalocyanines derivatives
2.6.1. Metallation reaction of compound 7
A solution of 7 (0.1 g, 0.09 mmol) and anhydrous Zn(CH3COO)2 (49.5 mg, 0.27
mmol) was refluxed in 2 ml of n-pentanol with stirring for 6 h under nitrogen
atmosphere. The resulting suspension was cooled and the volatiles removed in vacuo,
the residue was purified by a silica gel column chromatography using 200 mL of DCM
and then hexane–ethyl acetate (2:1, v/v) affording the ZnPc. The structural analysis and
photofisical and photochemical properties matched with the compound 3 (section 2.4.1).
2.6.2. Metallation reaction of compound 8
According to the above procedure for 7, a solution of 8 (0.1 g, 0.087 mmol) and
anhydrous Zn(CH3COO)2 (48 mg, 0.26 mmol) was refluxed in 2 ml of n-pentanol with
stirring for 6 h under nitrogen atmosphere to give the respective zinc phthalocyanine.
The structural analysis and photophysical and photochemical properties matched with
the compound 4 (section 2.4.2).

2.6.3. Metallation reaction of compound 9
In a closed reaction tube, a solution of 9 (0.1 g, 0.09 mmol) and anhydrous
o
Zn(CH3COO)2 (49.5 mg, 0.27 mmol) was stirred in DMF (2 mL) at 90 C for 6h. The
reaction mixture was cooled and poured into a water/ethanol 10 % solution to give dark
blue precipitate, which was collected by filtration and washed with water. The residue
was solubilized in NaOH (1 mol.L-1) solution and then acidified to pH 2 with HCl (1
mol.L-1) solution, until coagulation. The solid was centrifuged and purified by
successive precipitation, using solutions of HCl (1 mol.L-1) and NaOH (1 mol.L-1), and
then washed with distilled water until the filtrate became neutral. The crude product was
purified by silica gel column chromatography using methanol-ethyl acetate 2:1 v/v. The
structural analysis and photofisical and photochemical properties matched with the
compound 5 (section 2.4.3).
2.6.4. Metallation reaction of compound 10
According to the above procedure for 9, a solution of 10 (0.1 g, 0.11 mmol) and
anhydrous Zn(CH3COO)2 (63.5 mg, 0.33 mmol) was stirred in DMF (2 mL) at 90 oC for
6h to give the respective zinc phthalocyanine. The structural analysis and photophysical
and photochemical properties matched with the compound 6 (section 2.4.4).
2.7. Photophysichal and photochemical studies
All emission, excitation and electronic absorption spectra of the phthalocyanines
were recorded in 10 mm path length fluorescence cuvettes in DMSO.
2.7.1. Fluorescence quantum yields
Fluorescence quantum yields (Φꢀ) of all compounds were determined by
comparative method using the following equation (Eq.1):

ꢊ
ꢂꢃ.ꢈ
ꢃ.ꢉ
ꢄꢅꢆꢇ
ꢁꢂ =ꢃꢁꢂ(ꢄꢅꢆꢇ)ꢃꢂ
(1)
ꢊ
ꢃ.ꢃꢃꢈꢃ.ꢃꢃꢉ
ꢄꢅꢆꢇ
ꢄꢅꢆꢇ
were ꢂ and ꢂꢄꢅꢆꢇ are the areas under the fluorescence emission curves of the
phthalocyanineslocyanines (3-12) and the standard, respectively. ꢈ and ꢈꢄꢅꢆꢇ are the
relative absorbance of the sample and standard at the excitation wavelength,
respectively. ꢉꢊꢃand ꢉꢄꢊꢅꢆꢇ are the refractive indices of the solvents for the sample and
standard, respectively. The unsubstituted ZnPc (ΦF=0.20) [42] was employed as the
standard.
2.7.2.
Phthalocyanine photooxidation
Photogeneration quantum yields of singlet oxygen (Φ∆ ) were obtained by
indirect method, using diphenylisobenzofuran (DBPF) as chemical quencher [43, 44].
Typically, a mixture of the phthalocyanine (absorption ~0.2 in 680 nm) and the DPBF
(absorption ~ 1.2 in 418 nm) was irradiated with a red LED lamp (23 mW) in 20 cycles
of 6 seconds each one. The Φ∆ values were determined using zinc phthalocyanine
(ZnPc) (Eq.2):
ꢄꢅꢆꢇ
ꢋꢃ.ꢃꢃꢌ
ꢄꢅꢆꢇ
ꢃ
ꢍꢎꢏ
ꢁ∆ =ꢃꢁ∆ꢄꢅꢆꢇ
(2)
ꢋ
ꢃ.ꢃꢃꢌ
ꢃ
ꢍꢎꢏ
where ꢁꢐꢄꢅꢆꢇ is the singlet oxygen quantum yield for the ZnPc (Φ∆= 0.67 in DMSO
[42]; ꢋ and ꢋꢄꢅꢆꢇ is the DPBF photobleaching rates in the presence of the
phthalocyanine and ZnPc, respectively (this value was obtained by the first exponential
curves using the Origin® program); ꢌꢍꢎꢏ and ꢌ
are the light absorption rates by the
ꢄꢅꢆꢇ
ꢍꢎꢏ
phthalocyanines and ZnPc, respectively.

2.7.3. Phthalocyanine photodegradation
The photodegradation quantum yield of a given substance is the ratio of the number of
oxidized molecules of this substance to the number of absorbed photons. It can be
determined by using Eq. (3) [16]:
)
ꢁꢑ =ꢃ− (
(3)
ꢒ ꢔꢒ .ꢃꢃꢖꢗ ꢃ
ꢓ
ꢕ
ꢈ
ꢌ
ꢍꢎꢏ
ꢃ.ꢃꢃꢘꢓꢃ
where C0 and Ct in mol L−1 are the concentrations before and after irradiation,
respectively; V is the reaction volume; S the irradiated cell area; t is the irradiation time;
and NA is the Avogadro’s number. The absorbed intensity Iabs is the fraction of absorbed
light times the radiation intensity Ip in photons per area per time unit:
ꢆ
ꢈ
ꢚ
ꢌꢍꢎꢏ = (ꢙ − ꢙꢕ )ꢌꢚ
(4)
was utilized for the calculation of phthalocyanine photobleaching, with no need of a
standard.
2.8. Determination of partition coefficients (PO/W
)
Five milliliters of 10 µM solution from each phthalocyanine derivative was prepared in
n-octanol. The UV-vis spectrum of solution was sampled. Then water (5 mL) was added
to solution and the container was stirred for 30 minutes. The centrifugation (5 minutes
at 5000 rpm) enabled a phase separation and the organic phase was sampled again. The
partition coefficient was obtained from the difference in the phthalocyanine absorption
intensity in both stages. At least three independent measures were performed and the
corresponding PO/W value was taken as the overall average.

3. Results and discussion
3.1. Preparation and structural characterization
Scheme 1 describe the synthetic pathways to prepare tetra-carboxylic acid and
tetra-carboxylic ester metal and metal free phthalocyanines (MTcPc’s and TcPc’s).
Scheme 1. Synthetic routes to prepare new carboxyphthalocyanine derivatives.
For the synthesis of tetra-carboxylate ZnPc’s 5 and 6 we investigated different
routes: one through to the direct metal template preparation of ZnTcPc’s and other was
the introduction of central metal into metal free phthalocyanine ring. In both cases,
subsequent hydrolysis of the ester groups was carried out to obtain the carboxylic acid
groups.

The starting compounds 13 and 14 were synthesizedtized by a selective
esterification reaction of α-hydroxycarboxylic acids using boric acid as catalyst to
convert glycolic and lactic acids to their ethyl esters [45]. Phthalonitriles precursors 1
and 2 were prepared by a nucleophilic ipso-nitro substitution reaction of 4-
nitrophthalonitrile with compounds 13 and 14 in the presence of potassium carbonate as
base. The reactions provide the ester phthalonitriles in high yields of 64 and 72%,
respectively (Scheme 2). Purity of 1 and 2 was identified by GC-MS analysis that
sowed one single pick at retention times of 18.25 and 18.10 min and their correspondent
mass, respectively.
Scheme 2. Synthesis of ethyl (3,4-dicyanophenoxy)acetate (1) and ethyl 2-(3,4-
dicyanophenoxy)propanoate (2).
Esterification reaction was a very important step. The conditions to obtain
pthalonitriles precursors from glycolic and lactic acids use heat and strong basic media,
resulting in low yields for unprotected carboxylic lactic and glycolic groups.
Afterward, the attempt in synthesize the ZnTcPc’s from these precursors fail.
ZnTcPc’s 5 and 6 were synthesized using the classical method refluxing
phthalonitriles 1 and 2 in DMAE in the presence of zinc acetate as a metal template.

The products were very soluble in water, indicating that, under these conditions, the
ester groups were totally hydrolyzed during the cyclotetramerization reaction. The same
procedure using metallic lithium as a metal template and subsequent acidification at the
end of reaction was employed to synthesize TcPc’s 9 and 10. Again, the ester groups
were totally hydrolyzed during the process. Purification of these compounds can be
accomplished by washing the precipitate with a solution of water/ethanol 10% and
dissolving the solid in aqueous hydroxide solution and re-precipitating the free acid
(TcPc or ZnTcPc) into aqueous hydrochloric acid solution. A silica chromatographic
column was applied as a final purification process to eliminate impurities.
The reaction of metal free Pc’s 9 and 10 in the presence of zinc acetate was an
alternative route employed with success to synthesize ZnPc’s complexes 5 and 6 in high
yields.
The first attempting to synthesize ester phthalocyanines 3 and 4 was the
ciclotetramerization reaction with phthalonitrile precursors 1 and 2 in the presence of
zinc acetate and organic base (1,8- diazabicyclo[5.4.0]undec-7-ene (DBU)) in n-
pentanol. These react conditions [46] led to a mixture of ZnPc’s and Pc’s esters with
both ethoxycarbonyl and pentoxycarbonyl groups, due to partial transesterification,
complicating their purification and leading to lower yields for the desired product.
In order to minimize such complications, hydroquinone was tested in the place of
DBU. Hydroquinone is a suitable organic reducing agent and used in the
cyclotetramerisation of phthalonitrile to give metal free phthalocyanines that requires
two electrons and two protons. In some cases the use of hydroquinone can greatly
increase yields of metal free and metallophthalocyanines in conventional preparations
starting from 1,2-dicyanobenzene and a metal salt [47].

One equivalent of hydroquinone and the substituted phtalonitrile were refluxed in
n-pentanol and inert atmosphere, to give the transesterificated ZnPc’s 3 and 4 and free
Pc’s 7 and 8 (when the reaction is carried out in the absence of salt metal) increasing the
formation of pentoxycarbonyl groups in more quantity. Purification of the crude
products were done by column chromatography using a binary mixture solvents of ethyl
acetate/hexane as well described in the experimental section. Another synthetic route to
obtain compounds 3 and 4 was the metalation reaction refluxing 7 and 8 in n-pentanol
and an excess of anhydrous zinc acetate.
The newly synthesized phthalonitrile compounds and their phthalocyanine
derivatives were characterized by general spectroscopic methods such as 1H NMR, FT-
IR, MALDI-TOF, UV-vis and fluorescence spectra.
In the FTIR spectra of phthalonitriles, the vibrational peaks for the nitrile groups
were observed at 2225 cm-1 for 1 and 2235 cm-1 for 2, absorptions at 2981–2994, 2952–
2931, 2900, 2875, 1745–1747, 1274, 1241–1250, and 1090–1093 cm-1 are attributed to
the asymmetric and symmetric C-H stretching vibrations, C=O stretching vibrations,
1
and the asymmetric and symmetric C-O-C stretching vibrations. The H NMR spectra
of 1 and 2 in CDCl3 showed characteristic signals for esters (CH3CH2OOC–) protons at
4.30-1.32 ppm for 1 and 4.25–1.20 ppm for 2. The singlet at 4.74 ppm for 1 and the
quartet and duplet at 4.83 and 1.69 ppm for 2 indicated, respectively, the presence of the
-CH2-, -CH- and -CH3 protons from glycolic and lactic acids substituents.
Cyclotetramerization of phthalonitriles derivatives 1 and 2 to the Pcs 3–10 were
first confirmed by the disappearance of the sharp nitrile vibration peaks about 2225 cm-
1. In this study, synthesized tetra-substituted phthalocyanine compounds were obtained
as isomer mixtures as expected. The separation of regioisomers by the preparative

chromatography was not successful. No further attempt was made to separate the
isomers of complexes.
The FTIR spectra for Pcs 3–10 were recorded and all expected vibration
frequencies of the functional groups such as CH2, CH3, benzene, ether, esters, NH and
well Pc core was assigned and presented in Table 1.
Table 1: Characteristics frequencies of phthalocyanines 3-10 KBr pellets in FTIR.
Frequency [cm-1]
H2Pc[48,
Vibration mode*
3
4
5
6
7
8
9
10
49]
759
1008
1093
744
746
742
744
744
746
740
740 C – H out-of-plane
1010 1010 1008 1012
δ (N – H)o.o.p
δ (isoindole)breath + δ (C – H)
ν (Car – O – C)as
ν(CH2, CH3,aliph,) ν(C-N)s
ν (C=Cbenzene)s
ν (C=O)
1090 1097 1090 1093 1099 1095 1101 1095
1221 1228 1222 1226 1222 1220 1232 1232
1484 1482 1479 1479 1477 1477 1479 1479
1608 1610 1604 1600 1610 1612 1612 1614
1740 1731 1724 1729 1766 1753 1730 1722
1467
1600
2860 2958
2929 2927
2960 2956
2933 2935
2921 2930
2932 2929
ν (C – H,aliph)as
2871
2871 2861
3066 3066
2855 22855
ν (C – H,aliph)s
3000
3068
3289
ν (C – Haro C – Npyrrole)s
ν (C – Haro)s
ν (N – H)s
3289 3289
*
3289
3380 3400
3448 3417
ν (COO – H)s broad signal
* Symbols ν, δ denote the stretching and bending respectively. Notations s,
as,o.o.p, breath have been used for symmetric, asymmetric, out of plane and
breathingmodes, respectively.
As showed in Table 1, C – O – C and C=O vibrations were assigned at 1220 –
1232 cm-1 and 1722 – 1766 cm-1, respectively, for all compounds. COO – H vibrations
appeared at expected frequencies as a broad signal (3380 – 3448 cm-1). Aliphatic
vibrations groups for esters Pcs 3 – 4 and 7 – 8 assigned at 2855 – 2961 cm-1 showed to
be more intense than their hydrolyzed pairs 5 – 6 and 9 – 10 due their extended carbon

chain. The important N – H vibration modes to metal free Pcs 7 – 8 and 9 – 10 were
assigned at 3289 and 1008 – 1012 cm-1.
The 1H NMR spectra of Pcs 3 – 10 can be analyzed in two groups: the esters Pcs
and acids Pcs. The characteristic chemical shifts to each group can be observed in the
1H NMR spectra of Pcs 6 and 8 (Figure 1).
Figure 1. 1H NMR (300 MHz) spectrum of 4 in CDCl3 (A) and 6 in DMSO-d6 (B) compounds.
The 1H NMR analysis of all Pcs compounds 3 – 10 were recorded in deuterated
chloroform and dimethyl sulfoxide depending on their solubility. To acid Pcs a drop of
deuterated trifluoroacetic acid was add into the solution to reduce the aggregation of the
compounds. For compound 4 and 6 the aromatic protons were observed as three broad
multiple signals with a total of twelve protons at 8.85 – 8.47 ppm, 8.41 – 7.94 ppm and
7.75 – 7.35 ppm for 4 and 9.24 – 8.80 ppm, 8.78 – 8.40 ppm and 7.79 – 7.63 ppm for 6
(Figure 1). The same patterns to all Pcs were find in the aromatic protons region with
broad multiple signals due the aggregation and the mixed isomer character of these
compounds that have two kinds of α ring protons Hα1 and Hα2. CH2 protons can be

observed 5.62 – 5.19 ppm for compound 4 and the CH at 5.58 – 5.42 ppm for 6, while
the two CH3 protons for compound 6 appeared as a multiple at 1.88 ppm and as a
multiple 1.59 – 0.91 ppm, in this case the assignment was more difficult due to
overlapping signals. The same problem was find to assign the signals protons -(CH2)4-
groups of the esters phthalocyanines 3 – 4 and 7 – 8. The hydrogens next to the
carbonyl group were observed as a broad multiple about 4.35 ppm, while the others
appeared as a multiple overlap of signals in higher field (Figure 1). The terminal proton
of the carboxyl group is often difficult to observe, as in this case which accounts for its
absence in the 1H NMR spectrum [50].
The characteristic protons from the ring cavity of free phthalocyanines were
hardly observed in CDCl3 and not appeared in the spectra because of strong
aggregation, especially in the spectra of compounds 9 – 10 [51, 52].
The mass spectra of novel compounds were taken and also confirmed the
proposed structures. The expanded MALDI spectrum for compound 4 and 6 revealed
molecular ion peaks at 1206.454 and 928.148 Da, respectively (Figure 2), indicating the
success synthesis of the ester Pcs and their hydrolyzed analogues. Another important
thing to observe is the characteristic signals of the presence of isotopes pattern peaks in
the spectra of zinc complexed into phthalocyanine ring, indicating complex formation.
A
B
Figure 2. The MALDI-TOF spectra of the 4 (a) and 6 (b) compounds.

3.2.Ground state electronic absorption spectra
Solvent studies reveal that ester phthalocyanine derivatives 3 – 4 and 7 – 8 show
good solubility in most organic solvents as ethyl acetate, acetone, CHCl3, DCM, DMF,
DMSO and THF. Complexes 5 and 6, also have good solubility in acetone, DMF and
DMSO, while 9 and 10 are hardly soluble due the absence of the central metal.
Furthermore, the ZnTcPc’s and TcPc’s are readily soluble in alkaline medium.
Spectroscopic properties of phthalocyanines 3 – 10 were measured in DMSO, a solvent
that offers convenient solubility for all of the studied phthalocyanines, and the data are
summarized in Table 2.
Table 2: photophysical and photochemical data for phthalocyanines in DMSO.
ꢣꢥ(x10-7)
ꢠꢛꢏ
ꢈꢎꢏ
Entry
ꢝꢞꢃꢟ
ꢚ
ꢃ(ꢅꢛ) ∆ꢡꢢꢃ(ꢅꢛ)
ꢝꢞꢃꢆ
ꢣꢐ
ꢣꢤ
ꢚ
ꢃ(ꢅꢛ)
ꢛꢍꢜ
ꢛꢍꢜ
3
4
690
5,01
5,12
698
699
8
0,97 0,12
0,83 0,14
0,93 0,08
0,84 0,14
0,01 0,10
0,02 0,14
0,08 0,09
0,05 0,12
0,36
5,80
4,42
7,44
2,69
6,33
3,44
4,21
0,001
0,002
1,69
1,32
-
687
12
10
11
10
7
5
680
4,36
690
691
717
718
713
713
6
680
4,53
7
707, 676
711, 679
703, 670
703, 671
3,64, 3,75
3,77, 3,83
4,83, 4,80
4,85, 4,90
8
-
9
10
10
1,60
1,57
10
The electronic absorption spectra of the novel tetra-carboxylic acid and tetra-
carboxylic ester metal and metal free phthalocyanines (3 – 10) were recorded in the
ultraviolet and visible (UV-Vis) regions of the electronic spectra. These compounds
showed strong absorptions around 240–345 nm (B band) and the other in the visible
part of the spectrum at around 670–700 nm (Q band) because of π−π∗ transitions
(Figure 3).

3
7
5
9
1,0
0,8
0,6
0,4
0,2
0,0
1,0
0,8
A
C
B
0,6
0,4
0,2
0,0
400
500
600
700
800
400
500
600
700
800
λ (nm)
λ (nm)
4
8
6
10
1,0
0,8
1,0
0,8
0,6
0,4
0,2
0,0
D
0,6
0,4
0,2
0,0
400
500
600
700
800
400
500
600
700
800
λ (nm)
λ (nm)
Figure 3. Normalized ground state electronic absorption spectra of (A) 3 and 7, (B) 5 and 9, (C)
4 and 8, and (D) 6 and 10 compounds in DMSO.
The Q band of the free TcPc’s 7–10 were observed as 2 split bands at λmax 670
and 703 nm, 674 and 704 nm, 677 and 707 nm and 679 and 711 nm, as expected due to
D2h symmetry. Figure D and B, show a slightly broadened, less intense and sharp peaks
to metal free phthalocyanines 9 and 10 when compared with 7 and 8 due their poor
solubility.
UV-Vis spectra of phthalocyanines derivatives 3–10 showed intense and sharp Q
band absorption in DMSO at λmax = 680-681 nm for complex 3 and 4, and 690-691 nm
for complex 5 and 6. The single Q bands in metallophthalocyanine derivatives are
characteristic of metalation, which maintains the planarity of the molecule and increases
the symmetry to D4h.

The substitution of the glycolic and lactic acids with esterified or non-esterified
groups to phthalocyanine ring caused red-shifted Q band absorption around 9 nm for the
first case and 19 nm for the second (the Q-band absorption of unsubstituted zinc(II)
phthalocyanine is 672 nm DMSO [38]). There is a 10 nm difference between the Q-
band positions of ester-substituted phthalocyanines and carboxylated-substituted
phthalocyanines. This implies that the electron density is higher in the carboxylated-
substituted phthalocyanine rings due to the COOH group substituents, resulting in the
lowering of the HOMO–LOMO gap of these compounds.
3.3. Aggregation studies
The aggregation behavior of 3–10 were investigated at different concentrations in
DMSO using UV-Vis spectrophotometry. For compounds 3-8, a direct correlation
between the concentration and the intensity of absorption of the Q band was find and no
new bands were observed for all complexes signifying no aggregation behavior at these
concentrations, probably due to the bulky nature of the ring substituents and the
presence of central metal. The Beer-Lambert law was obeyed for all of these
compounds at concentrations ranging from 1.2 x 10-5 to 2 x 10-6 M (Figure 4 as an
example for compound 6.

1,0
0,8
0,6
0,4
0,2
0,0
1,0
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
y = 0,0019x - 0,2022
R² = 0,9996
200
300
400
500
600
Concentration (µM)
400
500
600
700
800
λ (nm)
Figure 4. UV-Vis spectra of phthalocyanine 6 in different concentrations in DMSO.
Free TcPcs 9 and 10, on the other hand, have lower solubility in DMSO than
other compounds. It was confirmed by the broadened and diminished intensity of Q-
band, meaning that it is some aggregated in the aqueous medium. For these reason the
molar absorption coefficients for 9 and 10 were calculated at concentrations ranging
from 1.4 x 10−5 to 4 x 10−6 M.
Self-aggregation of phthalocyanines compounds in aqueous media is a common
phenomenon, which decreases their efficient generation of reactive oxygen species [5].
It can be explained by strong π−π electron interactions between the planar
phthalocyanine rings and hydrogen bonding between carboxyl groups of adjacent
molecules when the phthalocyanine ring have peripheral functional groups such as
COOH, SO3H and NH2. For compounds 5 and 6, we observed a predominance of the
monomeric species in solution until a 60% mixture of water in DMSO, which can be
verified by following the relative intensities of the Q-band in the absorption spectra

(Figure 5). This is an important result because the water solubility of this kind of
compounds is very important for many different applications.
1,0
0,8
0,6
1,0
0,8
0,6
% H O
% H O
2
2
A
B
0%
0%
20%
40%
60%
80%
20%
40%
60%
80%
0,4
0,2
0,0
0,4
0,2
0,0
450
500
550
600
650
700
750
800
450
500
550
600
650
700
750
800
λ (nm)
λ (nm)
Figure 5: UV-Vis spectra of phthalocyanines 5 (A) and 6 (B) in different proportions of H2O
and DMSO with respectively concentration of 0.18 and 0.22 µM.
3.4. Fluorescence spectra and quantum yields studies
Fluorescence spectra of studied phthalocyanine compounds 3-10 were carried
out in DMSO at room temperature and the data are summarized in Table 2. The
fluorescence excitation and emission spectra of 3, 4, 5 and 6 are typical of metal
phthalocyanine complexes in DMSO with maximum intensities in the region between
699 and 690 nm, where the excitation spectra are similar to absorption and both of them
were mirror images of the fluorescent spectra, suggesting that the nuclear configurations
of the ground and excited states are similar and not affected by excitation [50, 53].
Fluorescence spectra for free TcPc’s 7, 8, 9 and 10 showed a single band of emission
with maximum intensities in the region between 718 and 713 nm. The observed Stokes
shifts of the phthalocyanines analogues 3-10 were within the region observed for typical
phthalocyanine complexes, with similar values than those of the unsubstituted ZnPc
(∆ꢡꢢꢃ(ꢅꢛ)= 10 nm) [25] in DMSO. Figure 6 showed fluorescence emission excitation
spectra for complex 6 in DMSO as an example.

1,0
0,8
0,6
0,4
0,2
0,0
400
500
600
700
800
900
λ (nm)
Figure 6. Absorption and emission spectra of compound 6 in DMSO. Excitation
wavelength = 612 nm.
The fluorescence quantum yields of Pcs 3-10 in DMSO are given in Table 2.
The ratio of excited photons to relaxed photons via fluorescence is called fluorescence
quantum yield (ꢦꢧ) and can be measured observing the process when an electron absorbs
a photon of light, is excited to higher quantum state in the phthalocyanine and then
deactivation processes (fluorescence, internal conversion, vibrational relaxation and
intersystem crossing) occur. The fluorescence quantum yields of the compounds 3-10
were lower as compared to unsubstituted zinc(II) phthalocyanine complex in DMSO
(ꢦꢧꢃ= 0,08 [42, 51]), especially in cases of 5 (ꢦꢧꢃ= 0,08) and 9 (ꢦꢧꢃ= 0,09).

3.5. Singlet oxygen generation studies
Singlet oxygen production is an important parameter to be observed in PDT. It
results of the energy transfer between the triplet state of photosensitizers and ground
state molecular oxygen. The amount of singlet oxygen generates depend on the
efficiency of this process. The efficiency of singlet-oxygen production was evaluated
using the absorbance of DPBF. This compound is a widely utilized singlet-oxygen
trapping agent, which strongly absorbs light around 410–420 nm and emits blue-colored
1
fluorescence. DPBF quantitatively reacts with O2 to form o-dibenzoylbenzene, which
does not absorb visible light. Therefore, the decrease in DPBF absorbance reflects the
1
amount of generated O2 (Figure 7)[54, 55]. The data were collected for studied
phthalocyanine compounds 3-10 in DMSO and their observed ꢣꢐ values were given in
Table 2.
1,0
(A)
1,0
0,8
0,8
0,6
0,4
0,6
0,2
0,0
0
20
40
60
80
100
120
0,4
0,2
0,0
time (s)
400
500
600
700
800
λ (nm)

(B)
1,0
0,8
0,6
0,4
0,2
0,0
1,0
0,8
0,6
0,4
0,2
0
20
40
60
80
100
120
λ (nm)
400
500
600
700
800
λ (nm)
Figure 7. Typical spectral changes for the determination of singlet oxygen quantum
yield of 6 (A) and 10 (B) in DMSO. (Inset: plots of DPBF absorbance versus time).
Comparing the exponential absorption decay of compound 6 and 10 (Figure 7)
and the ꢣꢐ values observed during the singlet oxygen quantum yield determination, it
can be said that zinc atom effect into the phthalocyanine ring play an important role in
the high efficiency of singlet oxygen formation. There was no change in the Q-band
intensities of compounds during the light irradiation for ꢣꢐ determinations. This
supported that the compounds were not degraded by used light irradiation during singlet
oxygen measurements.
3.6.Photodegradation studies
Photostabilities of all compounds were determined in DMSO by measuring the
absorption spectral changes over time by irradiation with red light and listed in Table 2.
The decrease in the intensity of Q-bands for the ZnPcs is shown in Figure 7 (giving 3 as
an example). It is obvious that photodegradation occurred along with irradiation. The
time decay of the absorbance maxima of Q-bands for all the compounds basically
followed the first-order kinetics as shown in Figure 8 (insert). It can be seen that the
photostabilities of these compounds follow the trend 3 > 7 > 9 > 10 ≈ 5 > 4 > 8 > 6. The

phthalocyanines 3 present higher photostabilitie in DMSO than the others analogues.
The ZnTcPc’s 6 shows the lowest photostability.
1.2
0s
1,0
0,8
0,6
0,4
0,2
0,0
1.0
0.8
0.6
0.4
0.2
0.0
300s
600s
900s
1200s
1500s
1800s
y = -2E-05x + 0,9981
R² = 0,9188
0
400
800
1200
1600
2000
time (s)
300
400
500
600
700
800
λ (nm)
Figure 8. Typical spectral changes for the determination of photodegradation quantum yields of
compound 3 in DMSO. (Inset: plot of Q band absorbance versus time).
4. Conclusion
In our study, the synthesis of tetra-carboxylic acid-substituted phthalocyanines
derivatives from glycolic and lactic acids were described. After investigation of some
possible synthetic routes, we concluded that the cyclotetramerization reaction in the
presence of hydroquinone increased the yields and the selectivity of the esters metal free
and metallophthalocyanines substituted with pentoxycarbonyl groups. Metal free
phthalocyanines were synthesized in good yields with lithium and hydroquinone as
catalyst. The metalation reactions with zinc salt were carried out with relative facility
and no need of complicated purification process. The fluorescence properties of these
phthalocyanines were affected significantly by the absence of the central metal. Metal
freelated phthalocyanines (7-8) showed a low capacity to generate singlet oxygen while