Synthesis of new metal-free and metal-containing phthalocyanines with tertiary or quaternary aminoethyl substituents

Article abstract of DOI:10.1007/s007060170068

A novel phthalodinitrile derivative carrying dimethylaminoethylsulfanyl groups at positions 4 and 5 was synthesized from 2-dimethylaminoethanethiol hydrochloride and 1,2-dichloro-4,5-dicyanobenzene. Its cyclotetramerization in the presence of 2-dimethylamino-ethanol or metal salts (CoCl₂, Zn(OAc)₂) gave metal-free or metal-containing phthalocyanines (M = Co or Zn). These phthalocyanines were converted into water soluble quaternized products by reaction with methyl iodide. The new compounds were characterized by elemental analysis, IR, NMR, and electronic spectra.

Full text of DOI:10.1007/s007060170068

Monatshefte f uÈ r Chemie 132, 813±819 (2001)
Synthesis of New Metal-Free and Metal-
Containing Phthalocyanines with Tertiary
or Quaternary Aminoethyl Substituents
S uÈ leyman G uÈ rsoy, Ali Cihan, Makbule B. Ko cË ak, and Ozer Bekaro gÏ luÃ
È
Ç
Technical University of Istanbul, Department of Chemistry, TR-80626 Maslak, Istanbul, Turkey
Ç
Summary. A novel phthalodinitrile derivative carrying dimethylaminoethylsulfanyl groups at positions
and 5 was synthesized from 2-dimethylaminoethanethiol hydrochloride and 1,2-dichloro-4,5-
4
dicyanobenzene. Its cyclotetramerization in the presence of 2-dimethylamino-ethanol or metal salts
(
CoCl2, Zn(OAc)2) gave metal-free or metal-containing phthalocyanines (Mˆ Co or Zn). These
phthalocyanines were converted into water soluble quaternized products by reaction with methyl iodide.
The new compounds were characterized by elemental analysis, IR, NMR, and electronic spectra.
Keywords. Phthalodinitrile; Cyclotetramerization; Phthalocyanines; Quaternary amonium salts.
Introduction
In addition to their well-known high thermal and chemical stability, phthalocyanines
have become noted recently for their special optical and electrical properties such as
electrical conductivity, photovoltaic effects, and electrochromism [1, 2]. Also, their
use as ef®cient photosensitizers for singlet oxygen production is becoming im-
portant in photodynamic therapy [3]. However, their insolubility in common organic
solvents causes dif®culties for many applications, rendering the synthesis of soluble
derivatives an important task. Whereas peripheral substitution with bulky groups [4]
or long alkyl chains [5] leads to phthalocyanine products soluble in apolar solvents,
the introduction of sulfonyl [6], carboxyl [7], or amino [8] groups results in water
soluble derivatives, at least within certain pH ranges. Quaternized ammonium
groups are especially useful, providing solubility within a wide pH range [9±11]. In
previous contributions describing a series of phthalocyanines with oxa- and/or aza-
macrocycles or acyclic substituents, enhanced solubility of phthalocyanines with
bulky groups on the periphery has been demonstrated [12±26]. By quaternizing aza
groups or amino groups of the substituents, products soluble in water over a wide
pH range were obtained [19, 20]. In addition, a shift of the Q-band absorption to
longer wavelengths has been observed as a consequence of incorporating a sulfanyl
function on the periphery [10, 11, 27±31]. This effect is important for a number of
applications (e.g. as IR absorbers and photosensitizers).
à Corresponding author

814
S. G uÈ rsoy et al.
This paper describes the preparation of novel soluble phthalocyanine com-
pounds which carry eight 2-dimethyl- or 2-trimethylaminoethylsulfanyl substituents
on their periphery, providing extensive solubility in water over a wide pH range.
Results and Discussion
1,2-Dichloro-4,5-dicyanobenzene (1) has been used recently to prepare 4,5-disub-
stituted phthalonitrile derivatives by base-catalyzed nucleophilic aromatic displace-
ment [29±31]. The same route was applied to prepare 1,2-bis-(2-dimethyl-
aminoethylsulfanyl)-4,5-dicyanobenzene (2) from 2-dimethylaminoethanethiol and
ꢀ
1 (Scheme 1). The reaction was carried out in dry DMF at 50 C under a nitrogen
atmosphere. During the reaction, an excess of K CO was added to completely
2
3
Scheme 1. Synthetic route 2 and the corresponding metal-free and metal-containing phthalocyanines

Phthalocyanines with Aminoethyl Substituents
815
neutralize the amino group. In the IR spectrum of 2, stretching vibrations of CN,
�
1
CH , and CH groups were observed at 2238, 2723, and 2953 cm . These values
3
2
1
are in agreement with those reported for similar compounds [10]. In the H NMR
spectrum of 2 (CDCl ), the aromatic protons appear as a singlet at 7.48 ppm, the
3
aliphatic protons as triplets at 3.13 and 2.67 ppm. The CH protons of 2 are ob-
3
served as a singlet at 2.30 ppm. As a consequence of the symmetrical structure, the
1
3
C NMR spectrum of 2 shows four different signals for unsaturated carbon atoms,
one of them arising from CN (115.34 ppm). The aliphatic carbon atoms also give
three different signals at 57.34, 45.11, and 31.29 ppm for SCH , NCH , and CH ,
respectively.
2
2
3
Conversion of 2 into metal-free phthalocyanine 3 was accomplished by re¯ux-
ing it in 2-dimethylaminoethanol. The metal phthalocyaninates 4 and 5 (M ˆ Co(II),
Zn(II)) with eight tertiary aminoethylsulfanyl substituents were synthesized by
cyclotetramerization of 2 in the presence of the corresponding anhydrous metal salts
in DMF. Column chromatography on silica gel or alumina was employed to obtain
the pure products from the reaction mixture. The intensely green products are easily
soluble in various solvents such as chloroform, dichloromethane, THF, acetone,
ethanol, methanol, DMF, and DMSO.
Elemental analyses as well as IR, H NMR, 13C NMR, and UV/Vis spectra
1
con®rmed the proposed structures of 3, 4, and 5. Thus, in the IR spectrum of 3 the
�
1
NH groups in the inner core give an absorption at 3310 cm . These protons are also
1
well characterized by the H NMR spectrum, which shows a peak at � 3.05 ppm as a
result of the ring current of the 18ꢀ electron system of the phthalocyanine ring. A
distinct difference encountered in the H NMR spectra of 3 and 4 when compared
1
with previously obtained macrocycle substituted compounds are the sharp peaks,
which indicate a lower tendency to aggregate even at the concentrations used for
NMR measurements [9, 15]. The phthalocyanines 3±5 show intense Q absorption
bands above 700 nm. When compared with octakis-alkyl or -alkoxy substituted
derivatives, the shift of this intense band is typical for phthalocyanines with
peripheral thia substituents; this might be important for various near-IR appli-
cations. The characteristic Q-band absorption of metal phthalocyaninates with D4h
symmetry is observed as a single band of high intensity in the visible region. The
D symmetry of the metal-free phthalocyanine 3 is veri®ed by two absorptions in
2
h
the visible region (700±731 nm).
The addition of sulfonium or quaternary ammonium groups on the periphery led
to phthalocyanines derivatives soluble in water. When phthalocyanines 3±5 were
treated with methyl iodide in chloroform, the hygroscopic phthalocyanine products
3
a, 4a, and 5a with eight quaternary ammonium groups were obtained in high
yields (ꢁ84%). No major changes in the IR spectra were found after quaternization.
Their UV/Vis spectra in aqueous solution, however showed some differences. First,
the shift of the Q-band absorbtions to shorter wavelengths is a result of solvent
effect. Second, a single intense Q-band at 669 nm for the metal-free phthalocyanine
3
a is interesting, because commonly the D2h symmetry of these compounds is
expected to give rise to the formation of two bands in the low energy region. This
result is indicative of molecular association in polar media.
In conclusion, the results of the present work show that the dimethylamino-
ethylsulfanyl substituents enhance the solubility of phthalocyanines in common

816
S. G uÈ rsoy et al.
Fig. 1. Formula of 3a±5a
organic solvents, whereas the trimethylaminoethylsulfanyl residues enhance their
solubility in water.
Experimental
IR spectra were recorded on a Mattison 1000 FT-IR spectrometer (KBr pellets), electronic spectra on
a Unicam UV2 spectrophotometer. Elemental analyses were performed by the instrumental analysis
È
_
laboratory of the TUBITAK Marmara Research Centre; their results agree with the calculated values
1
within experimental error. H NMR spectra were recorded on a Bruker 250 MHz spectrometer using
TMS as internal standard. 1,2-Dichloro-4,5-dicyanobenzene (1) was prepared according to a reported
procedure [31].

Phthalocyanines with Aminoethyl Substituents
817
1,2-Bis-(2-dimethylaminoethylsulfanyl)-4,5-dicyanobenzene (2; C16H22N4S2)
3
2
-Dimethylaminoethanethiol hydrochloride (3.36 mmol, 0.662 g) was dissolved in 15 cm of dry
ꢀ
DMF at 50 C under N2 atmosphere, and 1 g 1 (7.05 mmol) was added. After stirring for 15 min, 2 g
®nely ground anhydrous K2CO3 (20 mmol) were added portionwise during 2 h with ef®cient stirring.
ꢀ
The reaction mixture was stirred under nitrogen at 50 C for 20 h. Then the mixture was poured into
3
200 cm of ice-water. The resulting yellow solid was collected by ®ltration and washed with H2O
until the washings were neutral. The wet solid was dissolved in CH2Cl2, and the solution was dried
over Na2SO4. The solvent was evaporated under reduced pressure, and the crude residue was
recrystallized from diethyl ether. The compound was soluble in CHCl3, CH2Cl2 EtOH, MeOH, THF,
DMSO, and DMF.
ꢀ
1
Yield: 0.500 g (45%); m.p: 102±103 C; H NMR (CDCl3, ꢁ, 250 MHz): 7.48 (s, 2H, Ar±H), 3.14
t, J ˆ 2:8 Hz, 4H, S±CH2), 2.67 (t, J ˆ 6:9 Hz, 4H, N±CH2), 2.30 (s, 12H, CH3) ppm; 13C NMR
CDCl3, ꢁ, 62.5 MHz): 144.49 (C±CN), 128.93 (CH), 115.34 (CN), 111.42 (C±S, 57.34 (CH2±S),
(
(
4
5.11 (N±CH3), 31.29 (N±CH2) ppm; IR (KBr): ꢂ ˆ 3080 (ꢂCH-arom), 2953±2851 (ꢂCH-aliph),
238 (ꢂCN), 1600, 1574, 1472, 1421, 1293, 1140, 936, 782, 553 cm
�
1
2
.
Oktakis-(2-dimethylaminoethylsulfanyl)-phthalocyanine (3; C64H90N16S8)
3
A solution of 0.2 g 2 (0.59 mmol) in 0.5 cm 2-(dimethylamino)-ethanol was re¯uxed under N2 for
12 h. After cooling, the green product was ®ltered off, washed with hot H2O, and dried in vacuo. The
product was puri®ed by column chromatography with neutral alumina (eluent: EtOH:CHCl3 ˆ 1:10).
1
Yield: 0.030 g (14.9%); H NMR (CDCl3, ꢁ, 250 MHz): 8.80 (s, 8H, ArH), 3.74 (t, J ˆ 6:7 Hz,
1
6H, SCH2), 2.98 (t, J ˆ 6:9 Hz, 16H, NCH2), 2.52 (s, CH3, 24H), � 3.05 (s, 2H, NH, exchangeable)
ppm; IR (KBr): ꢂ ˆ 3310 (ꢂNH), 3050 (ꢂCH-arom), 2953±2825 (ꢂCH-aliph), 1600, 1473, 1421, 1370,
�
1
1
7
344, 1320, 1038, 961, 757, 706, 655 cm ; UV/Vis (CHCl3): ꢃmaxꢂ"† ˆ 330 (12620), 700 (22340),
31 (23490) nm.
Octakis-(2-dimethylaminoethylsulfanyl)-phthalocyaninato cobalt(II) (4; C64H88N16S8Co)
3
A mixture of 0.25 g 2 (0.74 mmol), 0.5 cm anhydrous DMF, and 0.033 g anhydrous Zn(CH3COO)2
ꢀ
(
0.185 mmol) was heated and stirred at 140±145 C for 8 h under N2 in a round-bottomed ¯ask. The
resulting green suspension was cooled to room temperature, and the crude product was precipitated
by addition of H2O. The product was puri®ed by column chromatography on silica gel (eluent:
EtOH:CHCl3 ˆ 1:20).
Yield: 0.050 g (16%); IR (KBr): ꢂ ˆ 3046 (ꢂCH-arom), 2978±2877 (ꢂCH-aliph), 1600, 1472, 1321,
�
1
1
140, 1114, 985, 961, 808, 757, 706, 578 cm ; UV/Vis (CHCl3): ꢃmaxꢂ"† ˆ 364 (14710), 710
(
15200) nm.
Octakis-(2-dimethylaminoethylsulfanyl)-phthalocyaninato zinc(II) (5; C64H88N16S8Zn)
was prepared following the procedure described for 3, starting from 0.250 g 2 (0.74 mmol), 0.5 cm3
5
anhydrous DMF, and 0.024 g anhydrous ZnCl2 (0.190 mmol). For puri®cation by column
chromatography, neutral alumina was used as the stationary phase and EtOH:CHCl3 ˆ 1:10 as the
eluent.
1
Yield: 0.068 g (26%); H NMR (CDCl3, ꢁ, 250 MHz): 8.54 (s, 8H, ArH) 3.38 (t, J ˆ 6:4 Hz, 16H,
SCH2), 2.99 (t, J ˆ 6:7 Hz, 16H, NCH2), 1.98 (s, 24H, CH3) ppm; IR (KBr): ꢂ ˆ 3038 (ꢂCH-arom),
�
1
2
928±2825 (ꢂCH-aliph), 1625, 1497, 1472, 1421, 1293, 1191, 1140, 961, 757, 706, 578 cm ; UV/Vis
(
CHCl3): ꢃmaxꢂ"† ˆ 371 (10640), 715 (11930) nm.

818
S. G uÈ rsoy et al.
Oktakis-((2-trimethylaminoethylsulfanyl)-phthalocyanine) octaiodide (3a; C72H114N16S8I8)
3
3
3
(0.050 g, 0.035 mmol) was dissolved in 2 cm CHCl31 and 0.052 g CH3I (23 mm , 0.373 mmol)
were added. After re¯uxing for 3 h, the mixture was cooled to room temperature, and resulting green
precipitate was ®ltered off, washed with CHCl3, and dried in vacuo.
Yield: 0.073 g (84%); IR (KBr): ꢂ ˆ 3260 (ꢂNH), 3030 (ꢂCH-arom), 2953±2872 (ꢂCH-aliph†, 1625,
�
1
1
497, 1421, 1395, 1293, 1217, 1089, 1038, 910, 757, 680 cm ; UV/Vis (H2O): ꢃmaxꢂ"† ˆ 321
(
15820), 669 (20300) nm.
Octakis-((2-trimethylaminoethylsulfanyl)-phthalocyaninato-cobalt(II)) octaiodide
(
4a; C72H112N16S8I8Co)
4
a was prepared following the procedure described for 3a, starting from 0.05 g 4 (0.035 mmol) in
3
3
2
cm CHCl3 and, 0.044 g CH3I (22 mm , 0.315 mmol).
Yield: 0.075 g (84%); IR (KBr): ꢂ ˆ 3030 (ꢂCH-arom), 2910±2850 (ꢂCH-aliph), 1600, 1460, 1300,
�
1
1
120, 920, 740 cm ; UV/Vis (H2O): ꢃmaxꢂ"† ˆ 370 (7970), 678 (15340) nm.
Octakis-((2-trimethylaminoethylsulfanyl)-phthalocyaninato zinc(II)) octaiodide
(
5a; C72H112N16S8I8Zn)
5
a was prepared following the procedure described for 3a, starting from 0.05 g 5 (0.035 mmol) in
3
3
2
cm CHCl3 and 0.044 g CH3I (22 mm , 0.315 mmol).
Yield: 0.076 g (84.8%); IR (KBr): ꢂ ˆ 3030 (ꢂCH-arom), 2928±2825 (ꢂCH-aliph), 1676, 1625, 1497,
�
1
1
421, 1293, 1191, 961, 757, 706 cm ; UV/Vis (H2O): ꢃmaxꢂ"† ˆ 365 (14500), 668 (11100) nm.
Acknowledgements
This work was supported by the Research Fund of the Technical University of Istanbul.
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Received December 5, 2000. Accepted (revised) January 5, 2001