Efficient synthesis of transition-metal phthalocyanines in functional ionic liquids

Article abstract of DOI:10.1055/s-2007-990879

The synthesis of transition-metal phthalocyanines by the reaction of substituted and unsubstituted phthalonitriles in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and metal salts in functional imidazolium, pyridinium and ammonium ionic liquids at 100-140°C, is reported. The best yields of metallated phthalocyanines were achieved in butyl(2-hydroxyethyl)dimethylammonium bromide ionic liquid. Metallation of free-base phthalocyanines with different metal salts in the above ionic liquid has also been achieved in good yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-990879

PAPER
3713
Efficient Synthesis of Transition-Metal Phthalocyanines in Functional Ionic
Liquids
Synthesis of
T
.
ransition-Me
M
tal
P
hthalocyanines . S. Chauhan,* Pratibha Kumari, Shweta Agarwal
Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi 110 007, India
Fax +91(11)27666845; E-mail: smschauhan@chemistry.du.ac.in
Received 26 June 2007; revised 14 August 2007
methylguanidinium trifluoroacetate20 have been used as
ionic liquids for the synthesis of metal-free and metallated
phthalocyanines. We have also highlighted the importance
of butyl(2-hydroxyethyl)dimethylammonium bromide
Abstract: The synthesis of transition-metal phthalocyanines by the
reaction of substituted and unsubstituted phthalonitriles in the pres-
ence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and metal salts
in functional imidazolium, pyridinium and ammonium ionic liquids
at 100–140 °C, is reported. The best yields of metallated phthalocy- ionic liquid for the synthesis of metal-free phthalocya-
nines under environmental benign reaction conditions.21
anines were achieved in butyl(2-hydroxyethyl)dimethylammonium
bromide ionic liquid. Metallation of free-base phthalocyanines with
In a continuation of our ongoing research into the applica-
different metal salts in the above ionic liquid has also been achieved
tion of ionic liquids as green solvents in organic synthe-
in good yields.
ses,5,14a,21,22 herein we report the reactions of
phthalonitriles in the presence of 1,8-diazabicyc-
lo[5.4.0]undec-7-ene (DBU) and metal salts in functional
Key words: phthalocyanines, ionic liquids, 1,8-diazabicyc-
lo[5.4.0]undec-7-ene, DBU, metallations, complexes
imidazolium, pyridinium and ammonium ionic liquids
(Figure 1) as well as the metallation of free-base phthalo-
Metallophthalocyanines and their derivatives are widely
cyanine in hydroxyalkylated ammonium ionic liquid to
used as dyes and pigments,1chemical sensors,2 photody-
afford various transition-metal phthalocyanines.
namic therapy agents,3 non-linear optical materials,4 cata-
lysts,5 liquid crystals6 and other newer materials7 owing to
X –
X –
R1
R1
+N
Me
their high thermal stability and distinct physiochemical
properties.8 The reactions of phthalonitriles, 1,3-diimino-
isoindolines, phthalic anhydrides or phthalimides in the
presence of metal salts in dimethylformamide, dichlo-
robenzene, pentanol, ethyleneglycol and other high-boil-
ing solvents yield metallophthalocyanines under basic or
neutral conditions.1,9 The irradiation of phthalogens10 or
metal-free phthalocyanines11 in the presence of metal
salts, affords metallophthalocyanines under microwave
conditions. Further, the metallation of free-base phthalo-
cyanines has also been achieved with different metal salts
in refluxing high boiling solvents such as pentanol and
quinoline.12 However, the above methods suffer from cer-
tain disadvantages, such as slow reaction rate, low yields,
troublesome workup procedures, tedious isolation and pu-
rification of products, drastic reaction conditions and the
formation of various linear oligomers and other side prod-
ucts.13
N
N
+
R1 = n-Bu, X = Br; [bmim][Br]
R1 = n-Bu, X = BF4; [bmim][BF4]
R1 = C2H4OH, X = Cl; [hyemim][Cl]
4
5
R1 = n-Bu, X = Br; [bpy][Br]
R1 = C2H4OH, X = Cl; [hyepy][Cl]
1
2
3
R1
X–
N+
R2
R4
R3
6
7
8
9
R1 = R2 = R3 = R4 = n-Bu, X = Br; [Bu4N][Br]
R1 = R3 = Me, R2 = C2H4OH, R4 = n-Bu, X = Br; [bhyeda][Br]
R1 = R3 = Me, R2 = C2H4OH, R4 = n-Bu, X = Cl; [bhyeda][Cl]
R1 = R2 = R3 = Et, R4 = C3H6OH, X = Cl; [thypa][Cl]
10 R1 = R2 = R3 = Et, R4 = C6H12OH, X = Cl; [thyha][Cl]
Figure 1
The reaction of phthalonitrile 11a in the presence of DBU
and Zn(OAc)2·2H2O in 1-butyl-3-methylimidazolium
bromide [bmim][Br] (1) gave phthalocyaninatozinc(II)
(12a) in 31% yield at 140 °C after one hour (Scheme 1,
Table 1, entry 1). The appearance of a characteristic Soret
band at 340 nm and an intense Q band at 671 nm in the
UV/Vis spectrum, indicated the formation of metallated
phthalocyanine 12a.1 In the IR spectrum, the absence of
CN and NH stretching bands at ~2200 cm–1 and ~3200–
3300 cm–1, respectively, suggested the complete conver-
sion of 11a into 12a. The appearance of four unsplit sig-
nals at d = 157.12, 139.58, 128.16 and 123.47 ppm in the
13C NMR spectrum and a peak at m/z 577.91, correspond-
ing to [M + H+] in the ESI-MS spectrum, further con-
firmed the formation of 12a in the reaction.
Ionic liquids (ILs) have gained wide recognition as poten-
tial environmentally benign solvents for a variety of reac-
tions.5,14 In particular, functional imidazolium-,
pyridinium- and ammonium-based ionic liquids are re-
ceiving a considerable upsurge of interest due to their ap-
plications in various reactions such as the Knoevenagel
condensation,15 the aldol condensation,16 the Heck
reaction17 and Diels–Alder reactions.18 Recently, tetrabu-
tylammonium bromide19 and 1,1,3,3-N,N,N¢,N¢-tetra-
SYNTHESIS 2007, No. 23, pp 3713–3721
x
x.
x
x
.
2
0
0
7
Advanced online publication: 13.11.2007
DOI: 10.1055/s-2007-990879; Art ID: Z15307SS
© Georg Thieme Verlag Stuttgart · New York

3714
S. M. S. Chauhan et al.
PAPER
R1
R2
CN
CN
11
[bhyeda][Br]
DBU
IL/M2+
DBU
R2
R1
R2
R1
a) R1 = R2 = H
R1
b) R1 = H, R2 = Me
R2
R1
R2
N
N
N
c) R1 = H, R2 = OMe
d) R1 = H, R2 = OC5H11
e) R1 = H, R2 = OC8H17
f) R1 = H, R2 = OC12H25
g) R1 = R2 = OC16H33
h) R1 = R2 = OC18H37
N
N
N
N
NH
N
M2+
[bhyeda][Br]
M
N
N
N
N
HN
N
N
R2
R1
R2
R1
i) R1 = H, R2 = OCH2C6H4-4-OMe
j) R1 = H, R2 = NO2
R1
R2
R2
R1
22a
12 M = Zn 13 M = Co
14 M = Cu 15 M = Fe
16 M = Pd 17 M = Ni
Scheme 1
The reaction of 11a with Zn(OAc)2·2H2O in the presence showed a significant effect on the yield of 12a (Table 1,
of DBU in 1-butyl-3-methylimidazolium tetrafluorobo- entries 8 and 9).
rate [bmim][BF4] (2) gave 12a in 47% yield in 20 minutes
Different ionic liquids (1–10) were further compared in
(Table 1, entry 2), whereas the use of 1-(2-hydroxyethyl)-
order to synthesize lipid-soluble zinc(II) phthalocyanine
3-methylimidazolium chloride [hyemim][Cl] (3) gave
12f by the reaction of 4-dodecyloxyphthalonitrile (11f) in
the presence of DBU and Zn(OAc)2·2H2O. The results
12a in 42% yield (Table 1, entry 3). It was observed that
during the reaction of 11a in imidazolium ionic liquids 1,
with 11f were similar to those obtained with 11a
2 and 3, the reaction mixture turned red within five min-
(Table 1). Unlike 11a, the reaction of 11f in the presence
utes. The red-colored species were formed by the reaction
of DBU and Zn(OAc)2·2H2O in imidazolium ionic liquids
of 1, 2 or 3 with 11a in the presence of DBU, irrespective
(1, 2 and 3) did not yield any red-colored species in the re-
action. Although ionic liquid 6 is known to promote the
of the presence of Zn(OAc)2·2H2O.
The reaction of 11a in the presence of Zn(OAc)2·2H2O synthesis of various metallophthalocyanines,19 the reac-
and DBU in 1-butylpyridinium bromide [bpy][Br] (4) did tion of 11f in ionic liquid 6 did not give 12f under the ex-
not give 12a, even after 24 hours, whereas the same reac- perimental conditions. Further, the reaction of 11f in ionic
tion in 1-(2-hydroxyethyl)pyridinium chloride [hyepy][Cl] liquids 4, 9 and 10 also failed to yield 12f under similar re-
(5) afforded 12a in 8% yield after one hour (Table 1, entry action conditions. These differences in the course of the
4). It is worth mentioning that pyridinium ionic liquids 3 reaction could be attributed to deactivation of the cyano
and 4 decomposed in the presence of DBU even at room group by the electron-donating alkoxy group in 11f,
temperature and turned brown. The base-instability of py- which makes it less reactive towards nucleophilic attack
ridinium ionic liquids 3 and 4 could be responsible for and, therefore, needs strongly nucleophilic conditions in
their poor activity.
order to undergo the reaction. Similar to 12a, the best
yield of 12f (65%) was obtained using ionic liquid 7. The
tetrasubstituted metallophthalocyanine 12f showed broad
signals in the 1H NMR and split signals in the 13C NMR
spectra due to the formation of four constitutional isomers
(C4h, C2v, Cs and D2h).23 Further, the phthalonitrile contain-
ing two electron-donating octadecyloxy groups (11h) was
also cyclized to 12h more efficiently in ionic liquid 7 than
in 3 (Table 1, entries 18 and 19). Unlike 12f, the 1H NMR
and 13C NMR spectra of 12h showed sharp peaks (see ex-
perimental section).
The use of tetrabutylammonium bromide [Bu4N][Br] (6)
in the reaction of 11a gave 12a in 53% yield, which was
improved to 59% using butyl(2-hydroxyethyl)dimethyl-
ammonium bromide [bhyeda][Br] (7) in the reaction
(Table 1, entries 5 and 6). The same reaction in butyl(2-
hydroxyethyl)dimethylammonium chloride [bhyeda][Cl]
(8), resulted in a significant decrease in yield of 12a (39%;
Table 1, entry 7), indicating the role of anions in the reac-
tion. Introduction of long hydroxyalkylated chains on the
nitrogen of the ammonium ionic liquids (9 and 10)
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

PAPER
Synthesis of Transition-Metal Phthalocyanines
3715
Table 1 Reactions of Phthalonitriles 11a, 11f and 11h in the Presence of DBU and Zn(OAc)2·2H2O in Different Ionic Liquids (1–10) at
140 °Ca
Entry
1
Phthalonitrile
11a
11a
11a
11a
11a
11a
11a
11a
11a
11f
Phthalocyanine
12a
Ionic liquid
Time
1 h
Yield (%)b
31
1
2
2
12a
20 min
1 h
47
3
12a
3
42
4
12a
5
1 h
8
5
12a
6
1 h
53c
59
6
12a
7
10 min
30 min
2.5 h
2 h
7
12a
8
47
8
12a
9
18
9
12a
10
1
23
10
11
12
13
14
15
16
17
18
19
12f
10 min
3 h
5
11f
12f
2
28
11f
12f
3
1 h
45
11f
12f
5
3 h
20
11f
12f
7
1 h
65d
39
11f
12f
8
1 h
11f
12f
7
3 h
13e
39f
31
11f
12f
7
2 h
11h
12h
3
20 h
16 h
11h
12h
7
67
a Reaction conditions: phthalonitrile (1 mmol), DBU (2 equiv), Zn(OAc)2·2H2O (0.25 equiv), ionic liquid (1.5 g for 250 mg of phthalonitrile).
b Isolated yields of zinc(II) phthalocyanines 12.
c Product 12a was isolated in 4% yield when the reaction was carried out in the absence of DBU.
d Product 12f was isolated in 5% and 30% yields after 16 h and 1 h when the reaction was performed at 100 °C and 120 °C, respectively.
e Reaction was performed in the absence of DBU.
f Reaction was performed in presence of 1 equiv of DBU.
The effect of temperature and the amount of DBU on the electron-withdrawing substituents; all were synthesized in
course of the reaction of 11f was also examined (Table 1). good yields in ionic liquid 7 under mild conditions
The reaction was sluggish at 100 °C and a remarkable de- (Table 1 and Table 2). It was observed that the reaction
crease in the yield of 12f (30%) was observed when the re- time and the yields were affected by the nature and num-
action was carried out at 120 °C (Table 1, entry 14). On ber of substituents on the phthalonitriles (Table 1 and
decreasing the amount of DBU to one equivalent in the re- Table 2). The structures of all products were characterized
action of 11f in ionic liquid 7 at 140 °C, 12f was afforded by spectroscopic analyses.
in 39% yield in one hour; the same reaction performed in
the absence of DBU gave only 13% yield of 12f after three
Recyclability of ionic liquid 7 was examined for the syn-
thesis of 13a (Table 2, entry 1). The ionic liquid 7 was re-
hours (Table 1, entries 16 and 17). A similar effect of
covered from the reaction mixture by washing the crude
DBU on the yield of 12a was observed in ionic liquids 6
product with distilled water. Water was evaporated at
70 °C under reduced pressure and the resulting ionic liq-
uid was reused three times for the synthesis of 13a. In a
second run using the recovered ionic liquid 7, 13a was ob-
(Table 1, entry 5). Thus, changes to the reaction tempera-
ture and the amount of DBU in the reactions significantly
influenced both the yield and the rate of metallophthalo-
cyanine formation.
tained in 54% yield from 11a in the presence of DBU and
The present method worked well with a range of transi- cobalt(II) chloride. No substantial decrease in the yield of
tion-metal salts (M = Zn, Co, Ni, Fe, Cu, Pd) and different 13a was observed in a third run (42% yield). The ionic liq-
metallophthalocyanines with electron-donating as well as uid 7 could be used for conducting further runs.
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

3716
S. M. S. Chauhan et al.
PAPER
Table 2 Synthesis of Metallophthalocyaniones 11–17 in Ionic Liquid 7 in the Presence of Metal Salts and DBU at 140 °Ca
Entry
1
Phthalonitrile
Phthalocyanine
Metal salt
CoCl2
Time
5 min
Yield (%)b
63 (run 1)
54 (run 2)c
42 (run 3)c
11a
13a
2
3
11a
11a
11b
11b
11c
11c
11d
11e
11f
11f
11f
11g
11i
14a
15a
12b
13b
12c
13c
12d
12e
13f
14f
16f
12g
12i
Cu(OAc)2
5 min
5 min
30 min
30 min
3 h
76
58
67
69
58
59
72
74
63
32
24
62
59
40
43
FeCl3
4
Zn(OAc)2·2H2O
CoCl2
5
6
Zn(OAc)2·2H2O
CoCl2
7
3 h
8
Zn(OAc)2·2H2O
Zn(OAc)2·2H2O
Co(OAc)2
2 h
9
1 h
10
11
12
13
14
15
16
20 min
30 min
30 min
16 h
Cu(OAc)2
Pd(OAc)2
Zn(OAc)2·2H2O
Zn(OAc)2·2H2O
Zn(OAc)2·2H2O
CoCl2
2 h
11j
11j
12j
12j
10 min
10 min
a Reaction conditions: phthalonitrile (1 mmol), DBU (2 equiv), metal salt (0.25 equiv), ionic liquid 7 (1.5 g for 250 mg of phthalonitriles).
b Isolated yields.
c The same recovered ionic liquid 7 was used for each of the three runs. The reaction time for the third run was 10 min.
It is interesting to note that imidazolium-based ionic liq- The influence of ionic liquids on the course of metallo-
uids promote the synthesis of metallophthalocyanines phthalocyanine formation has emerged as being associated
more efficiently than pyridinium-based ionic liquids with the Coulombic interaction between the cations and
(Table 1). This could be attributed to generation of car- anions in ionic liquids as well as the nucleophilicity of the
benes (ylides) by deprotonation at the second position of anions.28 The bulkiness of the ammonium cations renders
the imidazolium nucleus of the ionic liquids under basic their anions more nucleophilic and available to promote
condition, making it nucleophilic in nature.24 The fact that the synthesis of phthalocyanines than the planar imidazo-
better yields of metallophthalocyanines were obtained in lium and pyridinium cations. The effect of the size of the
hydroxylated imidazolium-, pyridinium- and ammonium- anion on the Coulombic interaction with the cationic nu-
based ionic liquids (3, 5, 7 and 8) than in other ionic liq- cleus of ionic liquids is also remarkable.28 Better yields of
uids, could be explained by the formation of alkoxide ions metallophthalocyanines in ionic liquid 2 compared to 1 or
in the presence of a base.25 The generation of the alkoxide in ionic liquid 7 compared to 8 could be attributed to the
1
ion 19 with DBU in ionic liquid 7 was supported by H larger size of tetrafluoroborate than bromide or bromide
NMR analysis, which indicated the presence of H+-DBU than chloride ions, which results in weaker Coulombic in-
(18) in the reaction mixture; trapping 19 with butyl bro- teractions between the cationic and anionic parts of the
mide gave butyl(2-butoxyethyl)dimethylammonium bro- ionic liquids, thereby improving the nucleophilicity of the
mide (20; Scheme 2).25,26 Thus, DBU generates alkoxide anionic partner. Based on the above observations, ionic
(in hydroxylated ionic liquids) or ylide type nucleophilic liquids with large counter anions (such as BF4 and PF6)
species (in imidazolium-based ionic liquids) which are could be promising promoters for the synthesis of phtha-
believed to attack one of the cyano groups of the phtha- locyanines; however, since generation of HF under the re-
lonitrile, leading to formation of imidoisoindoline-type action conditions limited their application,25 no further
intermediates (21), which further react with other phtha- attempts were made to prepare such ionic liquids. The
lonitriles and finally, due to a template effect of the metal high thermal and moisture stability of ionic liquid 7 offers
ion, cyclization takes place to give the metallophthalocy- an additional advantage for the synthesis of metallo-
anines 12–17 (Scheme 2).27
phthalocyanine under the experimental conditions.25,29
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

PAPER
Synthesis of Transition-Metal Phthalocyanines
3717
Me
Me
Me
Bu
n-BuBr
O
O
N
H-DBU
OH
DBU
N
+
Bu
Me
Bu
+
N
Bu
Br–
Br–
20
Br–
Me
Me
18
19
7
N
N
C
C
O
N
O
N
N
N
N
N
N
N
M
N
N
N
N
N
21
N
12–17
Scheme 2
Table 3 Metallation of Free-Base Phthalocyanine 22a with Different Metal Salts in Ionic Liquid 7
Entry
Phthalocyanine
Metal salt
Temp (°C)
140
Time
30 min
16 h
24 h
6 h
Yield (%)a
1
12a
13a
13a
14a
17a
17a
Zn(OAc)2·2H2O
Co(OAc)2
69
72
0b,c
99
95
0b,c
2
180
3
CoCl2
140
4
Cu(OAc)2
140
5
Ni(OAc)2·4H2O
NiCl2·6H2O
140
16 h
24 h
6
140
a Isolated yields.
b No metallation of 22a was observed when the reaction temperature was increased from 140 °C to 180 °C.
c No metallation of 22a was observed when the reaction was carried out in the presence of DBU (1 equiv) at 140 °C and 180 °C.
The use of ionic liquid 7 was further explored for the met- ucts, easy isolation, good to excellent yields of products,
allation of free-base phthalocyanine 22a, which was pre- tolerance of a variety of substituents and metals, and recy-
pared by cyclotetramerization of 11a in ionic liquid 7 clability of the ionic liquid.
under mild conditions (Scheme 1, Table 3).21 Quantitative
yields of metallophthalocyanines were obtained in rela-
UV/Vis spectra were recorded on a Perkin–Elmer Lambda 35 UV/
tively short reaction times, without using any base. It is
worth noting that the metallation of 22a was achieved in
good yields with acetate salts of transition metals; neither
an increase in temperature nor the addition of DBU to the
reaction mixture affected the metallation of 22a with chlo-
ride salts of transition metals.
Vis Spectrophotometer. IR spectra were recorded on a Perkin–
Elmer Spectrum 2000 infrared spectrophotometer. The 1H NMR and
13C NMR spectra were recorded on Bruker 300 MHz or 400 MHz
spectrometers using TMS as internal standard and the chemical
shifts (d) are expressed in ppm. The mass spectra (EI-MS) were re-
corded on a Jeol SX-102DA-6000 (6 kV, 10 ma) spectrometer and
ESI-MS spectra were recorded on a Micromass LCT KC 455 spec-
In conclusion, the synthesis of metallophthalocyanines by trometer (+ve mode). Phthalonitrile (11a), 4-nitrophthalonitrile
(11j) and tetrabutylammonium bromide (6) were obtained from
Spectrochem Pvt. Ltd. and 4-methylphthalonirile (11b) was ob-
tained from Aldrich. 4-methoxyphthalonitrile (11c),3 4-pentyloxy-
phthalonitrile (11d),30 4-octyloxyphthalonitrile (11e)19a 4-dodec-
the reaction of a range of phthalonitriles, in the presence
of metal salts, in hydroxylated-ammonium-based ionic
liquid 7 is simple and efficient. Moreover, hydroxylated
ammonium ionic liquids are UV/Vis transparent, biode-
gradable, cost-effective and can be easily synthesized
from bulk precursors. Furthermore, the metallation of
free-base phthalocyanines can be achieved in excellent
yields in this ionic liquid under mild conditions. The
method offers various advantages such as fewer side prod-
yloxylphthalonitrile
(11f),30
4,5-hexadecyloxylphthalonitrile
(11g),31 4,5-octadecyloxylphthalonitrile (11h)31 and ionic liquids
1,32 2,5 3,33 4,34 5,35 728 and 836 were prepared by minor modifica-
tions of literature procedure. The metal-free phthalocyanine (22a)
was prepared according to the method reported by us.21 All reac-
tions were carried out under an N2 atmosphere except where men-
tioned. All other solvents and reagents were used as received.
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

3718
S. M. S. Chauhan et al.
PAPER
Triethyl(3-hydroxypropyl)ammonium Chloride (9)
Phthalocyaninatozinc(II) (12a)37
A mixture of 3-chloro-1-propanol (4.2 mL, 5.0 mmol) and Et3N (7
mL, 5.0 mmol) was heated to reflux for 24 h under anhydrous con-
ditions. On cooling, two layers formed in the reaction mixture. The
lower layer was taken and washed repeatedly with Et2O and the re-
sulting syrup was recrystallized (EtOH–Et2O).
IR (nujol): 1646, 1602, 1459, 1318, 1195, 1116, 1089, 723 cm–1.
13C NMR (100 MHz, DMSO-d6): d = 157.12 (8 × C), 139.58
(8 × C), 128.16 (8 × C), 123.47 (8 × C).
MS (ESI): m/z calcd for C32H16N8Zn: 577.91; found: 578.91 [M +
H+].
Yield: 5.8 g (59%); mp 155–158 °C.
UV-vis (DMF): lmax (log e) = 265 (4.01), 342 (3.37), 604 (3.19),
641 (3.15), 669 nm (3.96).
IR (neat): 3391, 2991, 2891, 2115, 1645, 1488, 1457, 1396, 1162,
1059, 936 cm–1.
1H NMR (300 MHz, CDCl3): d = 1.4–1.6 (t, J = 7.5 Hz, 9 H,
3 × CH3), 2.2–1.9 (m, 2 H, N+CH2CH2CH2OH), 3.4–3.6 (m, 6 H,
CH3CH2N+), 3.7 (m, 2 H, N+CH2CH2CH2OH), 3.8 (m, 2 H,
CH2OH), 4.2–4.3 (s, 1 H, OH).
MS (ESI): m/z calcd for C9H22ClNO: 195.73; found: 160.18 [M+ –
Cl].
Phthalocyaninatocobalt(II) (13a)37
IR (nujol): 1579, 1526, 1162, 1120, 1090, 764, 733 cm–1.
MS (ESI): m/z calcd for C32H16CoN8: 571.48; found: 572.53 [M +
H+].
UV-vis (DMF): lmax (log e) = 273 (3.99), 418 (2.82), 604 (2.63),
664 (2.73), 692 nm (2.65).
Triethyl(6-hydroxyhexyl)ammonium Chloride (10)
Starting from Et3N (6.95 mL, 5.0 mmol) and 6-chloro-1-hexanol
(6.7 mL, 5.0 mmol), the title compound 10 was synthesized as de-
scribed above.
Phthalocyaninatocopper(II) (14a)37
IR (nujol): 1648, 1578, 1525, 1289, 1119, 1092, 728, 766, 729 cm–1.
MS (ESI): m/z calcd for C32H16CuN8: 576.08; found: 577.85 [M +
H+].
Yield: 10.0 g (84%).
UV-vis (DMF): lmax (log e) = 274 (5.57), 601 (3.77), 668 (3.80),
692 nm (3.70).
IR (neat): 3368, 2936, 2861, 1647, 1461, 1395, 1309, 1159, 1055,
729 cm–1.
1H NMR (300 MHz, CDCl3): d = 1.5–1.6 (m, 17 H, CH2), 1.9 (m,
Phthalocyaninatoiron(III) Chloride (15a)38
IR (nujol): 3148, 3042, 1724, 1610, 1514, 1422, 1333, 1288, 1165,
1119, 1080, 893, 773, 753, 725 cm–1.
2 H, N+CH2CH2), 3.5–3.8 (m, 8 H, N+CH2).
MS (ESI): m/z calcd for C12H28ClNO: 237.81; found: 202.23 [M –
Cl].
MS (ESI): m/z calcd for C32H16ClFeN8: 603.82; found: 568.38 [M –
Cl].
4-[1-(4-Methoxyphenyl)methoxy]phthalonitrile (11i)
UV-vis (DMF): lmax (log e) = 300 (3.72), 600 (2.58), 662 nm (2.91).
To a mixture of 4-nitrophthalonitrile (11j; 865.65 mg, 5 mmol) and
K2CO3 (1.38 g, 10 mmol) in anhyd DMF (5 mL), 4-methoxyphenyl-
methanol (1.38 g, 10 mmol) was added and the reaction mixture was
stirred at r.t. for 48 h under a nitrogen atmosphere. The crude reac-
tion mixture was poured into distilled H2O (60 mL) and extracted
with CHCl3 (3 × 20 mL). The organic layer was washed with H2O
(3 × 20 mL) and dried over anhydrous Na2SO4. After evaporating
the solvent, the residue was purified by column chromatography on
neutral alumina (PE–CHCl3, 8:2) to give the title compound 11i.
[2(3),9(10),16(17),23(24)-Tetrakis(nitro)phthalocyani-
nato]zinc(II) (12j)39
IR (nujol): 1652, 1608, 1520, 1340, 1136, 1084, 848, 728 cm–1.
1H NMR (300 MHz, DMSO-d6): d = 8.40–7.28 (m, 12 H, PcH).
13C NMR (75 MHz, DMSO-d6): d = 161.16 (4 × C), 146.48 (8 × C),
136.0 (4 × C), 135.62 (4 × C), 125.39 (4 × C), 123.34 (4 × C),
120.33 (4 × C).
Yield: 793 mg (60%).
MS (ESI): m/z calcd for C32H12N12O8Zn: 757.38; found: 758.48 [M
+ H+].
IR (nujol): 2228, 1596, 1558, 1514, 1295, 1247, 1175, 1092, 1032,
988, 828 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.7 (d, J = 8.7 Hz, 1 H, ArH),
7.15–7.55 (m, 4 H, ArH), 7.0 (m, 2 H, ArH), 5.1 (s, 2 H, OCH2),
3.85 (s, 3 H, OCH3).
UV-vis (DMF): lmax (log e) = 345 (4.36), 648 (4.12), 684 (4.38),
703 nm (4.30).
[2(3),9(10),16(17),23(24)-Tetrakis(nitro)phthalocyaninato]co-
balt(II) (13j)40
MS (EI): m/z = 264 [M+], 173, 121, 100, 89, 77, 62.
IR (nujol): 3070, 3000, 1654, 1612, 1543, 1502, 1471, 1426, 1342,
1286, 919, 875, 777 cm–1.
Preparation of metallophthalocyanines
Reaction of Phthalonitriles 11a and 11j in Functional Ionic Liq-
uids (1–10); Procedure A
MS (ESI): m/z calcd for C32H12CoN12O8: 750.93; found: 751.94 [M
+ H+].
To a mixture of phthalonitrile 11a or 11j (250 mg), metal salt (0.25
equiv) and functional ionic liquid 1–10 (1.5 g), DBU (304 mL, 2.0
equiv) was added and the reaction mixture was stirred at 140 °C un-
der a nitrogen atmosphere for the appropriate time (see Table 1 and
Table 2). The progress of the reaction was monitored by TLC and
UV/Vis spectroscopic analysis. After the reaction was complete, the
mixture was washed with distilled H2O (50 mL) and filtered. The
solid green product was washed thoroughly with H2O–MeOH (1:1,
100 mL) to yield the product. In the case of phthalonitrile 11a, the
product was further purified using concd H2SO4 and washed thor-
oughly with distilled H2O (150 mL). The filtrate was collected and
dried at 70 °C using a rotary evaporator to recover the ionic liquid
which was reused for the further synthesis of metallophthalocy-
anines.
UV-vis (DMF): lmax (log e) = 273 (4.50), 606 (3.74), 667 nm (3.83).
Reaction of Phthalonitriles 11b–11i in Functional Ionic Liquids
1–10; Procedure B
Procedure B was conducted as described for procedure A; the work-
up was performed as follows: The reaction mixture was quenched
with H2O (50 mL) and extracted with CHCl3 (4 × 20 mL). The or-
ganic layer was washed with H2O (3 × 30 mL), dried over anhyd
Na2SO4, concentratedand purified by column chromatography over
neutral alumina [CHCl3 to CHCl3–MeOH (98:2)] to give pure
metallophthalocyanines.
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

PAPER
Synthesis of Transition-Metal Phthalocyanines
3719
[2(3),9(10),16(17),23(24)-Tetrakis(dodecyloxy)phthalocyani-
UV-vis (CHCl3): lmax (log e) = 294 (4.61), 355 (4.66), 390 (4.30),
613 (4.16), 648 (4.18), 679 nm (4.94).
nato]zinc(II) (12f)41
IR (nujol): 1608, 1491, 1464, 1339, 1241, 1120, 1090, 1051, 744
cm–1.
[2(3),9(10),16(17),23(24)-Tetrakis(methyl)phthalocyani-
nato]zinc(II) (12b)42
1H NMR (300 MHz, CDCl3): d = 7.79– 6.76 (m, 12 H, PcH), 3.98
(br, 8 H, OCH2), 1.96 (br, 8 H, OCH2CH2), 1.59–1.27 (m, 72 H,
CH2), 0.97 (m, 12 H, CH3).
13C NMR (75 MHz, CDCl3–CS2; 3:1 v/v): d = 156.47 (4 × C),
152.94 (8 × C), 132.94 (4 × C), 125.88 (4 × C), 122.35 (4 × C),
116.47 (4 × C), 104.5 (4 × C), 68.30 (4 × C), 32.06–22.85 (40 × C),
14.21 (4 × C).
IR (nujol): 1723, 1610, 1489, 1459, 1341, 1237, 1120, 1092, 1055,
744 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.75–7.26 (m, 12 H, PcH), 2.52
(m, 12 H, CH3).
MS (ESI): m/z calcd for C36H24N8Zn: 634.02; found: 635.08 [M +
H+].
MS (ESI): m/z calcd for C80H112N8O4Zn: 1315.20; found: 1338.23
UV-vis (DMF): lmax (log e) = 348 (4.77), 609 (4.49), 674 nm (5.26).
[M + Na+].
[2(3),9(10),16(17),23(24)-Tetrakis(methyl)phthalocyani-
nato]cobalt(II) (13b)43
UV-vis (CHCl3): lmax (log e) = 284 (4.47), 350 (4.72), 350 (4.40),
615 (4.34), 683 nm (5.03).
IR (nujol): 1707, 1615, 1523, 1323, 1276, 1167, 1094, 1066, 941,
817, 749 cm–1.
[2(3),9(10),16(17),23(24)-Tetrakis(dodecyloxy)phthalocyani-
nato]cobalt(II) (13f)
MS (ESI): m/z calcd for C36H24CoN8: 627.59; found: 628.48 [M +
IR (nujol): 1580, 1526, 1288, 1163, 1120, 1092, 857, 766, 728 cm–1.
H+].
MS (ESI): m/z calcd for C80H112CoN8O4: 1308.76; found: 1331.40
UV-vis (DMF): lmax (log e) = 337 (3.57), 602 (3.09), 665 nm (3.71).
[M + Na+].
[2(3),9(10),16(17),23(24)-Tetrakis(methoxy)phthalocyani-
nato]zinc(II) (12c)3
UV-vis (CHCl3): lmax (log e) = 291 (4.45), 326 (4.38), 385 (3.95),
614 (4.19), 676 nm (4.52).
IR (nujol): 1613, 1460, 1333, 1273, 1162, 1090, 1049, 741 cm–1.
[2(3),9(10),16(17),23(24)-Tetrakis(dodecyloxy)phthalocyani-
nato]copper(II) (14f)
1H NMR (300 MHz, CDCl3): d = 8.0–7.3 (m, 12 H, PcH), 3.7 (br,
12 H, OCH3).
IR (film): 2923, 2853, 1744, 1609, 1509, 1461, 1391, 1347, 1243,
MS (ESI): m/z calcd for C36H24N8O4Zn: 698.02; found: 699.02 [M
1121, 1112, 1059, 826, 747 cm–1.
+ H+].
13C NMR (75 MHz, CDCl3–CS2; 3:1 v/v): d = 155.88 (4 × C),
153.52 (8 × C), 138.3 (4 × C), 124.7 (4 × C), 122.35 (4 × C), 117.8
(4 × C), 102.94 (4 × C), 68.73 (4 × C), 32.11–22.96 (4 × C), 14.26
(4 × C).
UV-vis (DMF): lmax (log e) = 355 (5.02), 610 (4.67), 678 nm (5.37).
[2(3),9(10),16(17),23(24)-Tetrakis(methoxy)phthalocyani-
nato]cobalt(II) (13c)44
MS (ESI): m/z calcd for C80H112CuN8O4: 1315.38; found: 1338.07
IR (nujol): 3189, 3066, 1764, 1723, 1619, 1489, 1460, 1295, 1237,
[M + Na+].
1111, 1053, 1021, 897, 844, 749 cm–1.
UV-vis (CHCl3): lmax (log e) = 338 (4.74), 379 (4.35), 619 (4.57),
682 nm (4.97).
MS (ESI): m/z calcd for C36H24CoN8O4: 691.58; found: 692.65 [M
+ H+].
UV-vis (DMF): lmax (log e) = 318 (3.96), 601 (2.66), 667 nm (3.07).
[2(3),9(10),16(17),23(24)-Tetrakis(dodecyloxy)phthalocyani-
nato]palladium(II) (16f)
[2(3),9(10),16(17),23(24)-Tetrakis(pentyloxy)phthalocyani-
nato]zinc(II) (12d)45
IR (film): 2921, 2852, 1609, 1510, 1467, 1391, 1246, 1133, 1063,
821, 747 cm–1.
IR (nujol): 1607, 1489, 1464, 1338, 1293, 1230, 1117, 1090, 1054,
13C NMR (100 MHz, CDCl3–CS2; 3:1 v/v): d = 159.81 (4 × C),
153.64 (8 × C), 136.2 (4 × C), 129.55 (4 × C), 123.71 (4 × C),
117.33 (4 × C), 104.36 (4 × C), 68.36 (4 × C), 32.28–23.01
(40 × C), 14.32 (4 × C).
745 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.06– 6.03 (m, 12 H, PcH), 3.41
(br, 8 H, OCH2), 1.61–1.38 (m, 24 H, CH2), 0.99 (br, 12 H, CH3).
MS (ESI): m/z calcd for C52H56N8O4Zn: 922.45; found: 923.45 [M
MS (ESI): m/z calcd for C80H112N8O4Pd: 1356.24; found: 1379.42
+ H+].
[M + Na+].
UV-vis (CHCl3): lmax (log e) = 287 (4.57), 350 (4.92), 615 (4.57),
682 nm (5.27).
UV-vis (CHCl3): lmax (log e) = 289 (4.25), 329 (4.01), 387 (3.65),
602 (3.91), 667 nm (4.46).
[2(3),9(10),16(17),23(24)-Tetrakis(octyloxy)phthalocyani-
nato]zinc(II) (12e)46
[2,3,9,10,16,17,23,24-Octakis(octadecyloxy)phthalocyani-
nato]zinc (12h)
IR (nujol): 1608, 1490, 1464, 1339, 1283, 1226, 1119, 1091, 1052,
IR (film): 2919, 2851, 1599, 1498, 1467, 1384, 1280, 1203, 1050,
743 cm–1.
743, 720 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.03– 6.02 (m, 12 H, PcH), 3.36
(m, 8 H, OCH2), 1.65–1.35 (m, 48 H, CH2), 0.96 (br, 12 H, CH3).
13C NMR (75 MHz, CDCl3–CS2; 3:1 v/v): d = 159.29 (4 × C),
158.99 (4 × C), 158.79 (4 × C), 137.28 (4 × C), 127.98 (4 × C),
121.17 (4 × C), 116.12 (4 × C), 103.16 (4 × C), 67.71 (4 × C),
32.05–22.87 (24 × C), 14.23 (4 × C).
1H NMR (300 MHz, CDCl3): d = 7.19 (s, 8 H, PcH), 4.01–3.95 (m,
16 H, OCH2), 2.10 (s, 16 H, OCH2CH2), 1.78–0.79 [m, 264 H,
(CH2)15CH3].
13C NMR (100 MHz, CDCl3–CS2; 3:1 v/v): d = 154.01 (8 × C),
125.66 (8 × C), 115.77 (8 × C), 106.45 (8 × C), 69.58 (8 × C),
31.93–22.69 (128 × C), 14.10 (8 × C).
MS (ESI): m/z calcd for C64H80N8O4Zn: 1090.77; found: 1091.77
MS (ESI): m/z calcd for C176H304N8O8Zn: 2725.77; found: 860.70
[C40H32N8O8Zn + Na].
[M + H+].
Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

3720
S. M. S. Chauhan et al.
PAPER
(6) (a) Sleven, J.; Cardinaels, T.; Binnemans, K.; Nelis, D.;
UV-vis (CHCl3): lmax (log e) = 287 (4.48), 350 (4.86), 615 (4.64),
682 nm (5.36).
Mullens, J.; Hinz-Huebner, D.; Meyer, G. Liq. Cryst. 2003,
30, 143. (b) Maeda, F.; Hatsusaka, K.; Ohta, K.; Kimura, M.
J. Mater. Chem. 2003, 13, 243.
[2,3,9,10,16,17,23,24-Octakis(hexadecyloxy)phthalocyani-
nato]zinc (12g)47
(7) Engelkamp, H.; Middelbeek, S.; Nolte, R. J. M. Science
1999, 284, 785.
(8) Leznoff, C. C.; Lever, A. B. P.; Bonnet, R. Chem. Soc. Rev.
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(b) Uchida, H.; Reddy, P. Y.; Nakamura, S.; Toru, T. J. Org.
Chem. 2003, 68, 8736.
(10) (a) Villemin, D.; Hammadi, M.; Hachemi, M.; Bar, N.
Molecules 2001, 6, 831. (b) Ungurenasu, C. Synthesis 1999,
1729.
IR (film): 2919, 2851, 1597, 1500, 1467, 1383, 1355, 1281, 1219,
1050, 888, 743, 721 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.19 (s, 8 H, PcH), 4.01–3.99 (m,
16 H, OCH2), 1.78–0.79 [m, 248 H, (CH2)14CH3].
MS (ESI): m/z calcd for C160H272N8O8Zn: 2501.34; found: 841.79
[C40H32N8O8Zn + Na].
UV-vis (CHCl3): lmax (log e) = 295 (4.61), 354 (4.73), 612 (4.20),
650 (4.21), 678 nm (4.95).
(11) Liu, L. C.; Lee, C. C.; Hu, A. T. J. Porphyrins
Phthalocyanines 2001, 5, 806.
[2(3),9(10),16(17),23(24)-Tetrakis{1-(4-methoxyphenyl)meth-
oxy}phthalocyaninato]zinc(II) (12i)
(12) (a) Swarts, J. C.; Langner, E. H. G.; Krokeide-Hove, N.;
Cook, M. J. J. Mater. Chem. 2001, 11, 434. (b) Nolte, R. J.
M.; van der Pol, J. F.; Neeleman, E.; Zwikker, J. W.; Nolte,
R. J. M.; Drenth, W.; Aerts, J.; Visser, R.; Picken, S. J. Liq.
Cryst. 2006, 33, 1373. (c) Kantekin, H.; Rakap, M.; Gok,
Y.; Sahinbas, H. Z. Dyes Pigm. 2007, 74, 21.
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1995, 68, 1001. (b) Janczak, J.; Kubiak, R. Acta Chem.
Scand. 1999, 53, 602. (c) Kim, I.-B.; Rixman, M. A.; Tsai,
Z.-H.; Wu, D.; Njus, J. M.; Stark, J. C.; Hankins, J.;
Sandman, D. J. Macromolecules 2001, 34, 7576.
(14) (a) Jain, N.; Kumar, A.; Chauhan, S.; Chauhan, S. M. S.
Tetrahedron 2005, 61, 1015. (b) Olivier-Bourbigou, H.;
Magna, L. J. Mol. Catal. A: Chem. 2002, 182-183, 419.
(c) Welton, T. Chem. Rev. 1999, 99, 2071. (d) Chowdhury,
S.; Mohan, R. S.; Scott, J. L. Tetrahedron 2007, 63, 2363.
(15) Xu, X. M.; Li, Y. Q.; Zhou, M. Y. Youji Huaxue 2004, 24,
1253.
IR (nujol): 3168, 1769, 1706, 1612, 1514, 1317, 1280, 1245, 1173,
1086, 1050, 818, 747 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.99–6.94 (m, 28 H, ArH), 5.10
(s, 8 H, OCH2), 3.82 (s, 12 H, CH3).
MS (ESI): m/z calcd for C64H48N8O8Zn: 1125.92; found: 1126.29
[M + H+].
UV-vis (DMF): lmax (log e) = 354 (4.82), 613 (4.42), 681 nm (5.08).
Metallation of Free-Base Phthalocyanine 22a in Ionic Liquid 7
A mixture of metal-free phthalocyanine 22a (1 mmol) and metal
salt (1.5 mmol) in ionic liquid 7 (550 mg) was heated with stirring
at 140–180 °C for the appropriate time (Table 3). The progress of
the reaction was monitored by UV/Vis spectroscopic analysis of the
reaction mixture. After the reaction was complete, the mixture was
washed with distilled H2O (50 mL) and filtered. The solid product
was washed thoroughly with distilled H2O.
(16) Abello, S.; Medina, F.; Rodriguez, X.; Cesteros, Y.; Salagre,
P.; Sueiras, J. E.; Tichit, D.; Coq, B. Chem. Commun. 2004,
9, 1096.
(17) Zhou, L.; Wang, L. Synthesis 2006, 2653.
(18) Abbott, A. P.; Capper, G.; Davies, D. L.; Rasheed, R. K.;
Tambyrajah, V. Green Chem. 2002, 4, 24.
Phthalocyaninatonickel(II) (17a)37
IR (nujol): 1523, 1336, 1159, 1118, 1093, 1006, 764, 732 cm–1.
MS (ESI): m/z calcd for C32H16NiN8: 571.23; found: 572.04 [M +
H+].
(19) (a) Lo, P. C.; Cheng, D. Y. Y.; Ng, D. K. P. Synthesis 2005,
1141. (b) Safari, N.; Jamaat, P. R.; Shirvan, S. A.;
Shoghpour, S.; Ebadi, A.; Darvishi, M.; Shaabani, A. J.
Porphyrins Phthalocyanines 2005, 9, 256.
UV-vis (DMF): lmax (log e) = 272 (3.10), 612 (2.42), 668 nm (2.53).
Acknowledgment
(20) (a) Shaabani, A.; Rezayan, A. H. J. Porphyrins
Phthalocyanines 2005, 9, 617. (b) Shaabani, A.; Maleki, A.
J. Porphyrins Phthalocyanines 2006, 10, 1253.
(21) Chauhan, S. M. S.; Agarwal, S.; Kumari, P. Synth. Commun.
2007, 37, 2917.
Pratibha Kumari and Shweta Agarwal acknowledge the Council of
Scientific and Industrial Research (CSIR), New Delhi for award of
Senior Research Fellowship. S.M.S. Chauhan acknowledges CSIR
and DST for financial support.
(22) (a) Jain, N.; Kumar, A.; Chauhan, S. M. S. Tetrahedron Lett.
2005, 46, 2599. (b) Kumar, A.; Jain, N.; Chauhan, S. M. S.
Synlett 2007, 411.
(23) (a) Hanack, M.; Meng, D.; Beck, A.; Sommerauer, M.;
Subramanian, L. R. J. Chem. Soc., Chem. Commun. 1993,
58. (b) Leznoff, C. C.; Hu, M.; McArthur, C. R.; Qin, Y.
Can. J. Chem. 1994, 72, 1990.
(24) (a) Xu, L.-W.; Gao, Y.; Yin, J.-J.; Li, L.; Xia, C.-G.
Tetrahedron Lett. 2005, 46, 5317. (b) Aggarwal, V. K.;
Emme, I.; Mereu, A. Chem. Commun. 2002, 1612.
(25) Earle, M. J.; Frohlich, U.; Huq, S.; Katdare, S.; Lukasik, R.
M.; Bogel, E.; Plechkova, N. V.; Seddon, K. R. WO
2006072785 A2 20060713, 2006; Chem. Abstr. 2006, 145,
145001.
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Synthesis 2007, No. 23, 3713–3721 © Thieme Stuttgart · New York

PAPER
indicating the presence of protonated NH in H+-DBU(18)
Synthesis of Transition-Metal Phthalocyanines
3721
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