Routes to some 3,6-disubstituted phthalonitriles and examples of phthalocyanines derived therefrom. An overview

Article abstract of DOI:10.1142/S108842461330005X

The paper reviews a selection of synthetic pathways that provide access to 3,6-disubstituted phthalonitriles, precursors for the synthesis of 1,4,8,11,15,18,22,25-octasubstituted phthalocyanine derivatives. Early routes using Diels-Alder reactions for the

Full text of DOI:10.1142/S108842461330005X

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2013; 17: 1–16
DOI: 10.1142/S108842461330005X
Published at http://www.worldscinet.com/jpp/
Routes to some 3,6-disubstituted phthalonitriles
and examples of phthalocyanines derived therefrom.
An overview
Martin J. Heeney§, Shaya A. Al-Raqaξ, Aurélien Augerж, Paul M. Burnham,
Andrew N. Cammidge, Isabelle Chambrier* and Michael J. Cook*◊
School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
Dedicated to Professor Evgeny Luk’yanets on the occasion of his 75th birthday
Received 15 February 2013
Accepted 11 April 2013
ABSTRACT: The paper reviews a selection of synthetic pathways that provide access to
3,6-disubstituted phthalonitriles, precursors for the synthesis of 1,4,8,11,15,18,22,25-octasubstituted
phthalocyanine derivatives. Early routes using Diels–Alder reactions for the synthesis of 3,6-dialkyl,
3,6-dialkoxymethyl, 3,6-dialkenyl and 3,6-diphenylphthalonitriles are appraised. However, the emphasis
of the review focuses on the scope and applications of 2,3-dicyanohydroquinone as a starting material for
obtaining 3,6-disubstituted phthalonitriles. The earliest example of the use of 2,3-dicyanohydroquinone
concerned its O-alkylation to afford 3,6-dialkoxyphthalonitriles. These are immediate precursors to
near-infrared absorbing phthalocyanine derivatives. Triflation of 2,3-dicyanohydroquinone extends the
scope of the compound for phthalocyanine synthesis; the bis-triflate derivative is susceptible to SNAr
reactions and readily reacts with thiols to provide 3,6-bis(alkylsulfanyl) and 3,6-bis(arylsulfanyl)-
phthalonitriles. 3,6-Bis(phenylselenyl)phthalonitrile has also been obtained recently from the same
precursor. Phthalocyanine derivatives obtained from them typically show a strongly bathochromically
shifted Q-band absorption that is particularly sensitive to the central metal ion. The bis-triflate of
2,3-dicyanohydroquinone is also an ideal precursor for participation in cross-coupling reactions.
Examples from the University of East Anglia group and elsewhere are presented which show the
application of the nickel-catalyzed Negishi coupling reaction using alkylzinc halide derivatives. Yields
of 3,6-dialkylphthalonitriles and 3,6-bis(substituted alkyl)phthalonitriles range from ca. 40 to 70%.
Direct comparison for one example shows that the yield from the Negishi coupling method is higher
than that using the Suzuki coupling protocol. Examples of the preparation of 3,6-diarylphthalonitriles
from 2,3-dicyanohydroquinone bis-triflate using the Suzuki coupling reaction are reported with yields
of the order of 65–70%. The review also includes a further application of 2,3-dicyanohydroquinone as a
precursor to both monobromo and dibromo derivatives of 3,6-dibutoxyphthalonitrile. These compounds
provide opportunities for cross-coupling at the brominated sites to provide more complex derivatives
with the potential to serve as precursors of highly substituted phthalocyanine derivatives.
KEYWORDS: 2,3-dicyanohydroquinone, 1,4,8,11,15,18,22,25-octakis(alkylsulfanyl)phthalocyanines,
mixed substituent phthalocyanines, near-infrared absorbing dyes, Negishi coupling, Suzuki coupling.
◊SPP full member in good standing
*Correspondence to: Isabelle Chambrier, email: I.Fernandes@uea.ac.uk; Michael J. Cook, email: m.cook@uea.ac.uk
§
Current addresses: Martin J. Heeney, Department of Chemistry, Imperial College, South Kensington Campus, Exhibition Rd,
London SW7 2AZ, United Kingdom. ξShaya A. Al-Raqa, Chemistry Department, Faculty of Science, Taibah University, P.O. Box
3002, Al-Madinah Al-Munawrah, Saudi Arabia. жAurélien Auger, CEA-Grenoble, DRT/LITEN/DTNM/LCSN, C2/459, 17 rue des
Martyrs, 38054 Grenoble Cédex 9, France
Copyright © 2013 World Scientific Publishing Company

2
M.J. HEENEY ET AL.
in this review is a small selection of published and
unpublished phthalocyanine derivatives that have been
obtained from various 3,6-disubstituted phthalonitriles
described in this paper.
INTRODUCTION
A long standing interest of the Materials Chemistry
group at the University of East Anglia (UEA) has been the
development of phthalocyanines and related derivatives.
The primary aims have aspired to develop phthalocyanine
chemistry and to exploit the properties of examples of
themacrocyclewithinanumberoffieldsofresearch[1].The
latterincludetheuseofthinfilmformulationsforgassensing
[2–6] and various other device applications [7–12], as well
as in formulations for photodynamic therapy protocols
[13–20]. The research has been “synthesis led” by which
we mean that compounds generally have been purpose
designed for individual projects. For various reasons
discussed elsewhere [1], we have favored the preparation of
single component phthalocyanine products from the classic
cyclotetramerisation reactions of phthalonitrile precursors,
rather than mixtures of regioisomers. This led us to focus
on the use of 3,6-disubstituted phthalonitriles as precursors
which provide access to 1,4,8,11,15,18,22,25-(or non-
peripheral) octasubstituted phthalocyanines [1]. In our
experiencethissubstitutionpatternhasledtophthalocyanine
derivatives with greater solubility and lower propensity
to aggregate in solution than examples of isomers where
substituents are located at the 2,3,9,10,16,17,23,24-(or
peripheral) sites.
The present review focuses on our development of
synthetic routes to various classes of 3,6-disubstituted
phthalonitriles. This includes a summary of our early
work using Diels–Alder based routes and also our
growing emphasis on the use of 2,3-dicyanohydroquinone
as a precursor. The material presented here, particularly
that which exploits the use of 2,3-dicyanohydroquinone,
draws together piecemeal reports in various refereed
journals and data included in a 2001 Patent Application
[21]. Examples of synthetic methodologies are gathered
in the Experimental section of this paper. Also included
3,6-DISUBSTITUTED
PHTHALONITRILES VIA DIELS–ALDER
PROTOCOLS
In our work undertaken during the 1980s and
1990s, we were interested in developing a route for the
synthesis of 3,6-dialkyl, 3,6-bis-functionalised alkyl, and
3,6-dialkoxymethylphthalonitriles as potential precursors
to liquid crystalline phthalocyaninesandphthalocyanines
appropriate for LB film work [1]. This substitution pattern
is not realistically available using simple electrophilic
substitution methods and at that time we turned to Diels–
Alder based approaches. Our original scheme (Fig. 1),
utilized furans as precursors [22, 23]. Apart from preparing
simple 2,5-dialkylfuran derivatives as precursors for
3,6-dialkylphthalonitriles,conditionswerefoundtoalkylate
sequentially the 2- and 5- ring positions which allowed
different groups i.e. an alkyl and a functionalised alkyl
group to be incorporated to provide access to compounds
such as 2-alkyl-5-hydroxyalkylfurans [24]. These parti-
cular furan derivatives served as precursors of 3-alkyl-
6-hydroxyalkylphthlonitriles. The latter proved useful
for cross condensation with 3,6-dialkylphthalonitriles to
form interestingly functionalized phthalocyanines that
could be linked together [25, 26]. We also used other
readily available functionalized furans such as 2,5-bis-
hydroxymethyl furan to prepare 2,5-dialkoxymethylfurans
and thence 3,6-bis(alkylmethoxy)phthalonitriles [27].
Though a large number of phthalonitrile compounds were
obtained satisfactorily the method suffers from the fact
that the Diels-Alder reaction of furans with fumaronitrile
R
O
E-NC-=-CN
E-NC-=-CN
i
R
R
CN
CN
CN
CN
v
iv
iv
R
ii
O
O
i
R
R or R'
R(R')
iii
O
R'
CH2OR
CN
CH2OH
CH2OR
O
CH2OR
CN
vi
v
E-NC-=-CN
O
O
vii
iv
CN
CH2OR
CN
CH2OR
CH2OH
CH2OR
Fig. 1. Application of Diels–Alder reactions using furan and fumaronitrile to access examples of 3,6-dialkylphthalonitriles. R and R′
refer to different alkyl or functionalised alkyl groups. i. RX/BuLi; ii. second reaction RX, BuLi; iii. BuLi/R′X where R′ ≠ R; iv. rt or
lower; v. LiN(SiMe3)2; vi. SOCl2; vii. RO-
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 2–16

ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
3
is both slow, ca. 10 days, and reversible. Entropy factors
phthalonitriles of types 1–6 shown in Fig. 4 and thence
non-peripheral octasubstituted phthalocyanines. Figure 4
also shows the generalized scheme that we and others have
used to prepare these phthalocyanine precursors; each
pathway is discussed in the sections that follow.
dictate that conversion to the adduct is enhanced at low
temperatures but then the cycloaddition reaction becomes
slower still; furthermore, a systematic study of the reaction
showed that as the length of the alkyl chain is increased the
equilibrium contains less of the adduct [28].
Improved access to symmetrically substituted 3,6-
dialkylphthalonitriles was achieved using Diels–Alder
reactions on 2,5-dialkylthiophene-1,1-dioxide derivatives
as indicated in Fig. 2. Yields of phthalonitriles are overall
higher than when using furan compounds but the need
for an oxidation step provides limitations regarding
extension of the scheme to oxidation-sensitive substituent
groups. Nevertheless the protocol has proved to be one of
our basic tools to prepare the symmetrically substituted
3,6-dialkylphthalocyanines [23, 29]. A wide range of
compounds were prepared with alkyl groups as long
as hexadecyl [29]. These have proved important for our
research into phthalocyanine materials [1].
Elsewhere, Luk’yanets’group had been exploring Diels–
Alder protocols to give phthalonitriles from reactions
of cyclopentadienones with chloromaleonitrile [30] and
reactions of substituted dienes with dichlorofumaronitrile
(or dichloromaleonitrile/dichlorofumaronitrile mixtures)
[31]. The latter approach, using 1,4-diphenyl-1,3-butadiene,
afforded 3,6-diphenylphthalonitrile in 73% yield (Fig. 3).
3,6-Dialkoxyphthalonitriles (series 1)
Perhaps the earliest report of the use of 2,3-
dicyanohydroquinone as a precursor of useful 3,6-
disubstituted phthalonitriles for phthalocyanine synthesis
was described by Witkievic, Dabrowski and Waclawek
in 1976 [32]. The synthesis commenced with the
methylation of 2,3-dicyanohydroquinone to form 3,6-
dimethoxyphthalonitrile, see Fig. 4, left hand side.
Cyclotetramerisation of the compound generated the
non-peripheral octakis(methoxy)phthalocyanine ligand
and various metalated derivatives were obtained, see
structure 7 (Fig. 5), R = Me. The authors subsequently
undertook electrical measurements on the compounds
and investigated them as catalysts.
The UEA group’s first synthesis of novel phthalo-
cyanine compounds was directed at obtaining long chain
homologs of octakis(methoxy)phthalocyanine, i.e. further
examples of series 7. These synthetic targets were chosen in
expectationoftheirhighersolubilityinorganicsolventsand
indeed were used for Langmuir–Blodgett film deposition
studies and for doping into calamitic liquid crystal
formulations. The precursor 3,6-dialkoxyphthalonitriles
were obtained using the Williamson’s ether synthesis
employed by Witkievic et al. [32]. The substituents
investigated ranged from ethoxy through to decyloxy
as well as 4-pentenyloxy, 3-phenylpropyloxy and iso-
pentyloxy [33]. Yields of the phthalonitriles were of the
order of 35–58%. These were then converted into the
phthalocyanines, series 7, using the conventional LiOR/
ROH base catalyzed conditions. However, we found that
trans-etherification tended to occur and that, to overcome
the outcome of this process, the chainlength of the alcohol/
lithium alkoxide should be that of the alkyl
3,6-DISUBSTITUTED
PHTHALONITRILES VIA
2,3-DICYANOHYDROQUINONE
General scheme
To our knowledge, 2,3-dicyanohydroquinone is the
only readily available 1,2,3,4- tetrasubstituted benzene
derivative bearing nitrile groups at adjacent positions. It is,
therefore, a potentially useful precursor to 3,6-disubstituted
R
R
SO2
chain of the haloalkane. Apart from the
use of these phthalocyanine derivatives in
R
SO2
CN
CN
E-NC-=-CN
i
Langmuir–Blodgett (LB) film studies [34],
they also provided our first examples of
S
ii
iii
CN
CN
R
R
R
far-red/near-infrared absorbers. Thus they
exhibited the Q-band in the region lmax 738
Fig. 2. Application of Diels–Alder reactions using thiophene-1,1-dioxides
to access examples of 3,6-dialkylphthalonitriles. (i) RI/BuLi; (ii) Sodium
perborate; (iii) ca. 150 °C sealed tube
and 760 nm for the metal-free derivatives in
toluene and at 752, 748 and 742 nm for the
single Q-band of a Cu, Zn and Ni derivative
respectively in dichloromethane.
Ph
Ph
Ph
Cl
CN
CN
CN
Cl.NC-=-CN.Cl
i
3,6-Bis(alkylsulfanyl)phthalonitriles (series 2),
3,6-bis(arylsulfanyl)phthalonitriles (series 3)
and 3,6-bis(arylselenyl)phthalonitrile (compound 4)
-2HCl
CN
Cl
Ph
Ph
Ph
We first investigated the synthesis of these 3,6-
disubstituted phthalonitriles of series 2 and 3, see Fig. 4,
Fig. 3. Application of a Diels–Alder reaction using a 1,3-diene
to access 3,6-diphenylphthalonitrile. i. 180–185 °C for 2 h
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 3–16

4
M.J. HEENEY ET AL.
SO2CF3
CN
H
Ar
Ar
O
O
O
O
CN
CN
CN
CN
ArB(OH)2/ Pd cat.
(Suzuki)
triflic anhydride
or
ArZnI.Ni cat. (Negishi)
CN
(6)
CF3SO2
H
RI and base
(Williamson)
R3B /K3PO4/Pd cat.
(Suzuki)
R-S-
(SNAr)
R
Ar-S-
(SNAr)
R
CN
CN
RZnI/Ni cat.
(Negishi)
O
(Ph-Se)2
NaBH3
CN
CN
R
S
R
(5)
R
R
Ar
S
Ph
Se
CN
CN
O
CN
CN
R
CN
CN
CN
CN
(1)
S
R
(2)
(5)
S
Se
Ar
Ph
(4)
(3)
Fig. 4. Examples of classes of 3,6-disubstituted phthalonitrile derivatives available from 2,3-dicyanohydroquinone. R = alkyl; Ar =
aryl. Novel examples of compounds of series 2 and 3 reported in this paper can be found in Tables 1 and 2. Novel and known
examples of series 5 and 6 prepared by the routes shown are collected in Table 3
ArS/RS
N
SR/SAr
N
RO
N
OR
N
SR/SAr
SR/SAr
OR
OR
RO
RO
ArS/RS
ArS/RS
N
M
N
N
M
N
N
N
N
N
N
N
N
N
RO
OR
ArS/RS
SR/SAr
8
R = alkyl
9 Ar = aryl
7
R = alkyl
M = H,H or
M = H,H or
various metal ions
various metal ions
Fig. 5. Structures of series 7, 8 and 9. Novel examples of series 8 and 9 showing substituents and M ions and their characterization
data are collected in Tables 1 and 2
ca. 2000 and published a preliminary communication of
a few examples in 2003 [35]; these and other analogs are
referred to in a 2001 patent application [21] and are now
collected, with characterization data, in Tables 1 and 2.
The synthetic scheme exploits the triflate derivative of
2,3-dicyanohydroquinone (Fig. 4). The methodology
developed at UEA reacts 2,3-dicyanohydroquinone bis-
triflate with an appropriate thiol in the presence of an
excess of finely crushed potassium carbonate in DMF.
Typically, in our hands, the reaction is stirred for ca.
72 h to yield the 3,6-bis(alkylsulfanyl)phthalonitriles or
3,6-bis(arylsulfanyl)phthalonitriles (Tables 1 and 2).
These compoundswere converted into the corresponding
1,4,8,11,15,18,22,25-octakis(alkylsulfanyl or arylsulfanyl)
phthalocyanines, series 8 and 9, and examples of zinc,
magnesium, copper, lead and chloroindium metalated
derivatives, Fig. 5, and their characterization data are
collected in Tables 1 and 2 and the Experimental. Also
prepared was an example of a bis(phthalocyanine)-
cerium(IV) sandwich compound 10, Fig. 6.
The examples of the phthalocyanines of series 8 and 9
listedinthetablesexhibitamoresignificantbathochromic
shift of the Q-band than found in series 7, ranging from
772–848 nm. Kobayashi and coworkers account for this
in terms of the large MO coefficient of the HOMO at
the site of substitution causing the electron-donating
groups to destabilize the HOMO energy [36]. A further
feature of the data in Tables 1 and 2 is that the Q-band
lmax is sensitive to the metal ion and this, together with
bathochromic shifts of higher energy bands, leads to a set
Copyright © 2013 World Scientific Publishing Company
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ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
5
Table 1. Conversion of 2,3-dicyanohydroquinone bis-triflate into 3,6-bis(alkylsulfanyl)phthalonitriles, series 2, and their conversion
into metalated 1,4,8,11,15,18,22,25-octakis(alkylsulfanyl)phthalocyanines (series 8)
Groups
3,6-bis(alkylsulfanyl)phthalonitrile
1,4,8,11,15,18,22,25-(alkylsulfanyl)8 MPc
Series 2
Series 8
Alkyl-S
#
Yield
Formula and CHN
Found & (Required)
#
Yield, %
Formula and CHN
Found & (Required)
1H NMR (d6-benzene + 1%
d5-pyridine): d, ppm
lmax, nm
% mp
(e × 10-5)
C
H
N
C
H
N
THF
C6H13S 2a
70
C20H28N2S2
8a
8b
33
67
C80H112N8S8Zn
63.84 7.43 7.49
(63.73 7.37 7.43)
0.89 (t, 24H), 1.33 (m, 32H),
1.58 (m, 16H), 1.97 (m, 16H),
3.30 (t, 16H), 7.81(s, 8H)
781
82–83°
66.60 7.81 7.83
(1.56)
(66.62 7.72 7.77)
C80H112N8S8Mg
65.51 7.60 7.64
(65.52 7.70 7.64)
0.89 (t, 24H), 1.25–1.45
(m, 32H), 1.57–1.65 (m, 16H),
2.00 (m, 16H), 3.34 (t, 16H),
7.83 (s, 8H)
773
8c
15
20
C80H112N8S8Pb
58.29 6.65 6.65
(58.25 6.84 6.79)
0.85 (t, 24H), 1.32 (m, 32H),
1.53–1.64 (m, 16H), 1.91–2.00
(m, 16H), 3.27 (t, 16H), 7.76
(s, 8H)
818
(1.00)
8d
C80H112N8S8InCl
60.66 7.11 6.84
(60.33 7.09 7.04)
0.90 (t, 24H), 1.32–1.45
(m, 32H), 1.55–1.65 (m, 16H),
1.87–1.96 (m, 16H), 3.23
(t, 16H), 7.79 (s, 8H)
836
(2.41)
8e
8f
55
11
12
48
C80H112N8S8Cu
63.39 7.53 7.31
(63.73 7.48 7.43)
783
—
(1.56)
C7H15S 2b
C8H17S 2c
46
—
C22H32N2S2
C88H128N8S8Zn
65.25 8.03 6.78
(65.32 7.98 6.93)
0.89 (t,24H), 1.30 (m,48H),
1.60 (m,16H), 1.99 (m,16H),
3.30 (t,16H), 7.81 (s,8H)
779
67.50 8.21 7.07
(68.01 8.31 7.21)
(1.36)
27
C24H36N2S2
8g
8h
C96H144N8S8Zn
66.74 8.51 6.48
(66.63 8.39 6.48)
0.90 (t, 24H), 1.30 (m, 64H),
1.62 (m, 16H), 2.01(m, 16H),
3.34 (t, 16H), 7.84 (s, 8H)
781
91–92°
69.20 8.74 6.56
(69.19 8.72 6.73)
(1.45)
C96H144N8S8Mg
68.29 8.69 6.50
(68.18 8.58 6.63
0.91 (t, 24H), 1.25–1.52
(m, 64H), 1.57–1.68 (m, 16H),
2.03 (m, 16H), 3.37 (t, 16H),
7.86 (s, 8H)
774
782
772
781
776
781
C9H19S 2d
C10H21S 2e
C11H23S 2f
65
C26H40N2S2
70.11 8.91 6.10 (70.22
9.07 6.30)
8i
8j
15
62
65
69
33
C104H160N8S8Zn
67.69 8.71 5.91
(67.73 8.74 6.08)
0.89 (t, 24H), 1.19–1.55
(m, 80H), 1.60–1.67 (m, 16H),
2.04 (m, 16H), 3.40 (t, 16H),
7.87 (s, 8H)
86–88°
C104H160N8S8Mg
69.44 8.76 5.99
(69.27 8.94 6.21)
0.90 (t, 24H), 1.18–1.52
(m, 80H), 1.59–1.67 (m, 16H),
2.04 (m, 16H), 3.38 (t, 16H),
7.86 (s, 8H)
68
—
C28H44N2S2
8k
8l
C112H176N8S8Zn
69.01 9.05 5.71
(68.76 9.07 5.73)
0.90 (t, 24H), 1.18–1.52
(m, 96H), 1.58–1.68 (m, 16H),
2.01–2.11 (m, 16H), 3.38
(t, 16H), 7.86 (s, 8H)
71.31 9.38 5.85
(71.14 9.39 5.93)
C112H176N8S8Mg
70.36 9.38 5.77
(70.23 9.26 5.85)
0.90 (t, 24H), 1.26–1.52
(m, 96H), 1.58–1.68 (m, 16H),
2.05 (m, 16H), 3.38 (t, 16H),
7.86 (s, 8H)
63
C30H48N2S2
8m
C120H192N8S8Zn
69.64 9.33 5.39
(69.97 9.35 5.42)
0.91 (t, 24H), 1.20–1.52
(m, 112H), 1.60–1.68
92–93°
71.53 9.62 5.40
(71.94 9.66 5.59)
(m, 16H), 2.01–2.10 (m, 16H),
3.37 (t, 16H), 7.86 (s, 8H)
Copyright © 2013 World Scientific Publishing Company
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6
M.J. HEENEY ET AL.
Table 2. Conversion of 2,3-dicyanohydroquinone bis-triflate into 3,6-bis(arylsulfanyl)phthalonitriles, series 3, and thence to
1,4,8,11,15,18,22,25-octakis(arylsulfanyl)phthalocyanine derivatives series 9 and compound 10
Substituent
3,6-Bis(arylsulfanyl)phthalonitrile
1,4,8,11,15,18,22,25-(arylsulfanyl)8 MPc
Series 3
Series 9 and compound 10
Aryl-S
#
Yield %
mp
Formula and CHN
Found & (Required)
#
Yield, Formula and CHN
1H NMR(d6-benzene):
d, ppm
lmax, nm
%
Found & (Required)
(e × 10-5)
C
H
N
C
H
N
THF
PhS
3a
65
107–110°
C20H12N2S2
69.78 3.47 8.29
(69.74 3.51 8.13)
9a
9b
9c
9d
9e
9f
19
C80H48N8S8Zn
66.34 3.46 7.70
(66.57 3.35 7.76)
7.12 (s, 8H), 7.38–7.43
(m, 24H), 7.63–7.83
(m, 16H)
779
(1.62)
28
46
14
37
10
20
15
C80H48N8S8Pb
60.75 3.32 6.86
(60.62 3.52 7.07)
7.13 (s, 8H), 7.40–7.44
(m, 24H), 7.75–7.77
(m, 16H)
8.16
(0.75)
C80H48N8S8InCl
63.09 3.31 7.20
(62.88 3.17 7.33)
7.21 (s, 8H), 7.38–7.49
(m, 24H), 7.72–7.84
(m, 16H)
8.34
(1.01)
4-MePhS 3b
86
167–169°
C22H16N2S2
70.84 4.28 7.64
(70.94 4.33 7.52)
C88H64N8S8Zn
67.36 4.27 7.18
(67.96 4.15 7.20)
2.48 (s, 24H), 7.09
(s, 8H), 7.17 (d, 16H),
7.65 (d, 16H)
787
(1.58)
C80H64N8S8Pb
62.08 3.83 6.59
(62.28 3.80 6.60)
2.41 (s, 24H), 7.08
(s, 8H), 7.25 (d, 16H),
7.66 (d, 16H)
824
(1.26)
C80H64N8S8InCl
64.34 4.09 6.70
(64.44 3.93 6.83)
2.42 (s, 24H), 7.14
(s, 8H), 7.27 (d, 16H),
7.69 (d, 16H)
848
(1.29)
4-t-BuPhS 3c
94
191–192°
C28H28N2S2
73.53 6.18 6.03
(73.64 6.18 6.13)
9g
10
C112H112N8S8H2
73.53 6.28 6.15
(73.56 6.26 6.12)
C224H224N8S8Cea
70.75 5.86 5.84
(70.92 5.95 5.91)
0.36 (s, 2H), 1.24 (s, 72H),
7.24 (d, 16H), 7.50
(s, 8H), 7.91 (d, 16H)
810
754
1.37 (s, 144H), 7.15
(s, 16H), 7.47 (d, 32H),
7.72 (d, 32H)
a See Fig. 6.
ArS
SAr
N
of variously colored phthalocyanine dyes among which
the lead metalated derivative 8c, Q-band lmax 818 nm,
proved to be the first published red phthalocyanine [35].
Anumberofrecentpublicationsfromotherlaboratories
have also focused on this class of phthalocyanine
compound, extending the range of derivatives shown
in Tables 1 and 2. Thus Nyokong and coworkers
prepared the octakis(pentylsulfanyl) and (octylsulfanyl)
phthalocyanine analogues with tantalum(III) hydroxide
as the central ion for electrochemical studies [37],
the octylsulfanyl and dodecylsulfanyl analogues with
palladium as the central metal for photooxidation of
nitrobenzene on single wall carbon nanotubes [38], and
the Mn(II) acetate and Co complexes of the hexylsulfanyl
substituted ligand for electrochemical and electrocatalytic
studies [39]. Sakamoto and coworkers [40] have
extended the range of octa(arylsulfanyl) substituted
SAr
SAr
N
N
N
SAr
ArS
N
N
N
ArS
N
ArS
SAr
Ce
ArS
SAr
N
N
N
N
SAr
ArS
N
N
N
N
ArS
ArS
SAr
10 Ar = 4-t-BuPh
Fig. 6. Structure of the cerium metalated bis-phthalocyanine
complex 10. See Table 2
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 6–16

ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
7
Table 3. Conversion of 2,3-dicyanohydroquinone bis-triflate into
3,6-disubstituted phthalonitriles, series 5 and 6, using (a) Negishi
coupling or (b) Suzuki coupling. Characterization data for novel
derivatives (this work) are found in the Experimental section
phthalocyanines, where “aryl” is methoxyphenyl, tolyl
or 4-t-butylphenyl, incorporating copper, cobalt, nickel,
zinc and lead as the central metal.
In an intriguing development, Kobayashi et al. recently
synthesized the octa(phenylsulfanyl)phthalocyanine
#
3/6 substituents
Coupling Yield, Ref. if not
.
containing P(OMe)2 [PF6]. This was to achieve an
method
%
this work
added shift of the Q-band to lower energy arising from
the large electronegativity of phosphorus enhanced
by the electron withdrawing effect of the +5 oxidation
state. The strategy provided a compound that exhibits
a Q-band at 1018 nm. The same group also prepared
3,6-bis(phenylselenyl)phthalonitrile, compound 4, using
the route indicated in Fig. 4, as precursor for the
corresponding octakis(phenylselenyl)phthalocyanine, a
compound exhibiting a Q-band lmax 1033 nm [41].
5a
5b
5c
5d
5e
5f
Pentyl
a
a
a
a
a
a
a
a
a
b
a
a
56
72
—
44
44
44
—
45
45
44
—
—
44
—
3-Methylbutyl
4-Methylpentyl
5-Methylhexyl
Hexyl
69
63
68
Cyclopentylmethyl
Cyclohexylmethyl
6-Methylheptyl
Decyl
45
5g
5h
5i
41
66
3,6-Dialkylphthalonitriles (series 5)
63–70
38
5i
Decyl
Alternatives to Diels–Alder based approaches to
obtainthesederivatives,describedabove,becameevident
as groups elsewhere, unconnected with macrocyclic
chemistry, were developing new methodologies for
C–C bond forming reactions catalyzed by metal
complexes [42, 43]. Some of these were evidently
applicable for accessing 3,6-dialkylphthalonitriles
and we sought to investigate this type of approach
ca. 2000 [21]. The first method we investigated was
the Ni catalysed Negishi cross-coupling reaction
between the bis-triflate of dicyanohydroquinone
and alkylzinc reagents, see right hand side of Fig. 4.
As a model, the first cross-coupling was undertaken
using decylzinc iodide as reagent. The Ni(0) catalyst
Ni(PPh3)4 was generated in situ by treatment of
NiCl2(PPh3)2 and PPh3 with n-BuLi. Substrate and
reagent were added and after 16 h a yield of 60–70% of
3,6-didecylphthalonitrile, (5i) in Table 3, was recovered.
The same conditions were then used to prepare
1,1-H-2,2-H-perfluorodecylphthalonitrile (5k) using
1,1-H-2,2-H-perfluorodecylzinc iodide as reagent and
3,6-di(4-pivaloylbutyl)phthalonitrile (5l) using
4-pivaloylbutylzinc iodide. As a further development,
the same procedure was applied using 6-chlorohexylzinc
bromide to yield 3,6-di(6′-chlorohexyl)phthalonitrile
(5m).Theyieldofthereactionwas61%.Theintroduction
of halogenated chains is not readily possible using the
furan or thiophene routes above because of the use of a
strong base in the first steps of the schemes. Of course,
the terminal chloro functionality can be displaced
with various nucleophiles to provide more complex
phthalonitrile derivatives. Further examples of the use
of the above Negishi coupling protocol, taken from
published papers [44, 45], are included in Table 3.
Attention was then given to application of the Suzuki
reaction which involves cross-coupling of an aryl
compound with an alkylboron derivative in the presence
of a Pd catalyst.As a trial we sought to prepare once again
5j
S-3,7-dimethyloctyl
68
5k
1,1-H-2,2-H-
perfluorodecyl
58
5l
4-Pivaloylbutyl
a
a
b
b
b
a
b
a
b
a
b
b
b
62
61
88
36
73
67
73
66
20
30
25
47
51
—
—
—
—
—
—
—
—
—
—
46
46
46
5m 6-Chlorohexyl
6a
6b
6c
6c
6d
6d
6e
6e
6f
Phenyl
4-t-Butylphenyl
4-Methoxyphenyl
4-Methoxyphenyl
3-Methoxyphenyl
3-Methoxyphenyl
2-Methoxyphenyl
2-Methoxyphenyl
3,5-Dimethylphenyl
Thiophen-3-yl
6g
6h
Furan-2-yl
the 3,6-didecylphthalonitrile (5i). The most successful
reaction conditions that were established utilised the
in situ formation of tridecylborane from borane and
1-decene. Base was added to form the borate complex.
To this, PdCl2(dppf) was added as catalyst along with
dicyanohydroquinone bis-triflate. After a 10 h heating
to reflux and work-up, 3,6-didecylphthalonitrile was
isolated. The yields proved to be sensitive to the added
base. Thus a yield of 38% was recovered from the
reaction using K3PO4 but was lower, 28%, when K2CO3
was used. Neither yield matched that of the Negishi
coupling reaction which has now become our method of
choice for the synthesis of 3,6-dialkylphthalonitriles, at
least for small scale preparations. Table 3 reports yields
of various coupling reactions.
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 7–16

8
M.J. HEENEY ET AL.
3,6-Diarylphthalonitriles (series 6)
arises largely because of their marked solubility in
organic solvents and a limited propensity for self-
aggregation, both features that simplify column
chromatographic separation and purification. In light
of the ready availability of series of both 3,6-dialkyl
and 3,6-diarylphthalonitriles a short program to
synthesize so-called 3:1 or AAAB type compounds,
Fig. 7, was developed to provide materials initially for
potential PDT applications. When A is used in excess
then the principal components of the product mixture
are the AAAA and AAAB type compounds of series
11; without an excess of A then other products such
as the AABB and AABB isomers, e.g. 12, can also
be formed. Examples of experimental conditions are
given in the Experimental section and characterization
data for particular AAAB products are provided in
Table 4. All reactions yield the AAAA compound, the
octakis(alkyl)phthalocyanine, as a side-product.
The application of cross-coupling approaches was then
extended to the syntheses of 3,6-diarylphthalocyanines,
Table 3. We first investigated the application of the
Suzuki reaction by reacting phenylboronic acid with
dicyanohydroquinone bis-triflate in the presence of
Pd(PPh3)4 as catalyst to provide the known 3,6-diphenyl-
phthalonitrile(6a)in79%yield.3,6-Bis(4-t-butylphenyl)-
phthalonitrile (6b) was prepared similarly. The syntheses
of3,6-bis(4-methoxyphenyl)phthalonitrile(6c),3,6-bis(3-
methoxyphenyl)phthalonitrile (6d) and 3,6-bis(2-metho-
xyphenyl)phthalonitrile (6e) were undertaken by both
Suzuki and Negishi coupling procedures for comparative
purposes.Yields recovered were broadly similar from the
twoapproaches,Table3.SeealsotheExperimentalsection.
One of the present authors, Al-Raqa, has independently
employed the Suzuki conditions satisfactorily to prepare
3,6-bis(heteroaryl)phthalonitriles [46], compounds (6g)
and (6h) in Table 3.
2,3-DICYANOHYDROQUINONE — A
PRECURSOR TO TRI- AND TETRA-
SUBSTITUTED PHTHALONITRILES
Mixed aryl and alkyl non-peripherally
octasubstituted phthalocyanines (series 11 and 12)
The UEA group has for a long time been interested
in the synthesis of non-uniformly substituted phthalo-
cyanines, such as amphiphilic materials bearing a
combination of hydrophobic and hydrophilic groups
for deposition as LB films or materials bearing a
thiol/disulfide terminated alkyl group for SAM film
studies [1]. These were synthesized through an
initial mixed cyclotetramerisation reaction of two
different 3,6-disubstituted phthalonitrile precursors,
where the groups were alkyl or functionalized alkyl.
Examples have been reviewed elsewhere [1]. A key
to the ready accessibility of these non-uniformly
substituted phthalocyanines has been the ease of
separation of the cross-condensation products. This
A further application of 2,3-dicyanohydroquinone
exploitstheconversionofthecompoundintothemono-and
di-bromo substituted derivative using N-bromosuccinimide
[47], Fig. 8. Attempts to alkylate the phenolic OH groups
using
a conventional Williamson’s ether synthesis
unexpectedly gave only the monobrominated material.
However, 4,5-dibromo-3,6-dibutoxy phthalonitrile was
obtained using the Mitsunobu reaction. Both compounds
are well-suited for further cross-coupling reactions to
replace bromide by other functionality denoted in Fig. 8 as
Z. A published example of this is illustrated in Fig. 9 [48].
Further applications of this chemistry will be published in
a forthcoming paper.
B
Ar
Ar
N
A
R
N
R
N
A
R
R
N
CN
CN
R
A
R
R
A
R
N
M
N
N
M
N
A
A
+
N
N
N
N
N
N
R
N
R
R
N
R
CN CN
B
B
Ar
Ar
B
Ar
Ar
Ar
Ar
(12)
(11)
R = alkyl,
Ar = Ph or
substituted Ph
+ other cyclotetramerisation
products, i.e. AAAA, ABBA, etc..
Fig. 7. Scheme to prepare cross-condensation products from a 3,6-dialkylphthalonitrile and a 3,6-diarylphthalonitrile. Novel
examples of series 11 and 12 showing substituents, M, and characterization data are collected in Table 4
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 8–16

ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
9
Table 4. Characterization data for examples of novel hexakis(alkyl) diaryl substituted phthalocyanines, series 11
#
1,4,8,11,
15,18-groups groups
22,25-
M
Yield, % mp
Formula and CHN
Found & (Required)
1H NMR spectral data,
CDCl3 solvent unless stated
otherwise; d, ppm
lmax, nm
(e × 10-5)
C
H
N
THF
11a
decyl
decyl
phenyl
Zn
4a
> 250
> 250
C104H144N8Zn
79.43 9.37 6.84
(79.54 9.25 7.14)
Measured in d6-benzene:
8.20 (d, 4H, J7.5), 7.89 (s, 2H),
7.87 (s, 2H), 7.81 (m, 4H), 7.61
(t, 4H, J5.5), 7.54 (d, 2H, J7.5),
4.63 (t, 4H, J7), 4.58 (t, 4H, J7),
3.41 (t, 4H, J7), 2.37 (m, 8H),
1.11–1.77 (m, 106H)
723
(1.55)
11b
4-MeOPh Zn
9
C106H148N8O2Zn
77.87 9.12 6.59
(78.02 9.14 6.87)
7.94 (s, 2H), 7.93 (d, 4H, J8.1),
7.74 (d, 2H, J7.5), 7.62 (d, 2H,
J7.5), 7.45 (s, 2H), 7.11 (d, 4H,
J8.1), 4.35 (t, 4H, J8), 4.22
(t, 4H, J8), 3.96 (s, 6H),
3.19 (t, 4H, J8), 2.08 (m, 4H),
1.95 (m, 4H), 0.71–1.45
(m, 106H)
713
(1.40)
11c
decyl
3-MeOPh Zn
8
> 250
C106H148N8O2Zn
77.91 9.37 6.10
(78.02 9.14 6.87)
Measured in CDCl3 + 1
drop d5-pyridine: 7.88 (s, 2H),
7.77 (s, 2H), 7.68 (d, 2H, J7.6),
7.48 (dd, 4H, J8.2, 7.6),
7.14
(1.55)
7.30 (dd, 2H, J8.2, 7.6),
7.07 (brs, 2H), 6.63 (brs, 2H),
4.53 (m, 8H), 3.83 (s, 6H),
3.24 (t, 4H, J8), 2.16 (m, 8H),
0.71–1.60 (m, 106H)
11d
11e
pentyl
decyl
4-MeOPh Zn
3-MeOPh H,H
17
10
> 250
> 250
C76H88N8O2Zn
75.29 7.54 8.68
(75.38 7.32 9.25)
7.95 (s, 2H), 7.94 (d, 4H, J8.5),
7.79 (s, 2H), 7.78 (d, 2H, J7.5),
7.65 (d, 2H, J7.5), 7.16 (d, 4H,
J8.5), 4.45 (m, 8H), 4.02 (s, 6H),
3.21 (t, 4H, J8), 2.14 (m, 8H),
1.63–0.63 (m, 46H)
711
(2.33)
C106H148N8O2H2
81.17 9.61 6.83
(81.18 9.64 7.14)
7.95 (s, 2H), 7.84-7.80 (m, 4H),
7.69 (d, 2H, J7.3), 7.55 (m, 2H),
7.49 (d, 4H, J7.5), 7.15 (m, 2H),
4.39 (m, 8H), 3.84 (s, 6H), 3.16
(t, 4H, J8), 2.10 (m, 8H),
1.01–0.72 (m, 106H),
725
(1.95)
0.32 (s, 2H)
11f
pentyl
3-MeOPh H,H
4
> 250
C76H88N8O2H2
79.39 7.80 9.42
(79.54 7.90 9.76)
7.96 (s, 2H), 7.84 (d, 2H, J7.2),
7.82 (s, 2H),7.71 (d, 2H, J7.2),
7.56 (m, 2H), 7.50 (d, 4H, J6.9),
7.17 (m, 2H), 4.41 (t, 8H, J7.2),
3.85 (s, 6H), 3.17 (t, 4H, J7.2),
2.08 (q, 8H), 1.55–1.05
722
(1.73)
(m, 28H), 0.87 (m, 12H),
0.68 (t, 6H, J 6.6), 0.33 (s, 2H)
a An example of a compound of type 12 was also obtained. See the Experimental section.
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 9–16

10
M.J. HEENEY ET AL.
H
O
O
CN
CN
C4H9
C4H9
O
O
O
O
CN
CN
Z
Br
H
'cross-coupling'
i
Br
Z
CN
CN
ii
H
C4H9
C4H9
O
O
CN
CN
Br
Br
C4H9
C4H9
iii
O
O
O
H
CN
CN
'cross-coupling'
Br
Z
CN
CN
O
C4H9
C4H9
Fig. 8. Scheme showing the conversion of 2,3-dicyanohydroquinone into 4,5-dibromo-2,3-dicyanohydroquinone and products of
butylation of the latter under different conditions. (i) N-bromosuccinimide; (ii) DIAD/PPh3/butanol; (iii) K2CO3/iodobutane
C4H9
using TMS as the internal reference. Mass spectra were
OBu
O
O
N
N
obtained using the MALDI technique in Dithranol
matrix or the FAB technique in Noba matrix. UV/
vis. spectra were measured using a Hitachi U-3000
spectrophotometer. Elemental analyses for C, H and N
were undertaken by the analytical groups at either UEA
or London Metropolitan University.
CN
CN
CN
CN
Br
i
Br
OBu
C4H9
C6H13
CN
ii
Compounds
CN
C6H13
3,6-Bis(trifluoromethanesulfonyloxy)-phthalonitrile.
Trifluoromethanesulfonic anhydride (22.1 g, 0.078 mol)
in a solution of dry DCM (10 mL) was added dropwise to
a cooled solution (-20 °C) of 2,3-dicyanohydroquinone in
DCM (30 mL) and dried 2,6-lutidine (16 mL). The reaction
mixture was allowed to warm to rt with stirring over 14 h
under argon. DCM was removed under reduced pressure
and ethyl acetate (50 mL) was added. The resulting solution
was washed sequentially with 5% HCl (2 × 20 mL), 5%
aq. NaOH solution (2 × 20 mL) and brine (20 mL) and
then dried (Na2SO4) and concentrated under reduced
pressure. The crude product was recrystallized (ethyl
acetate/cyclohexane) to afford the title compound (12.71 g,
92%) as a pale yellow crystalline solid (mp 109–111 °C).
Anal. calcd. forC10H2N2O6S2F6:C, 28.31;H, 0.48;N, 6.60%.
Found C, 28.46; H, 0.29; N, 6.50%. 1H NMR (CDCl3): d,
ppm 7.87 (s, 2H). MS (EI): m/z 423.9 (5.81%, [M]+).
C6H13
C6H13
C6H13
OBu
N
N
N
N
Zn
N
N
N
N
N
OBu
C6H13
N
C6H13
C6H13
Fig. 9. Suzuki coupling. (i) pyridine boronic acid, Pd(PPh3)4,
CsF in DME; (ii) Zn(OAc)2 in Li/BuOH under reflux to form
the AAAB type cyclotetramerisation product [48]
General procedure for preparing
3,6-bis(alkylsulfanyl)phthalonitriles (series 2) and
3,6-bis(arylsulfanyl)phthalonitriles (series 3)
EXPERIMENTAL
Equipment
3,6-Bis(decylsulfanyl)phthalonitrile, 2e. In a
typical reaction,3,6-bis(trifluoromethanesulfonyloxy)-
phthalonitrile (2.0 g, 4.7 mmol) was added in portions
1H NMR spectra were measured in CDCl3 at 270 MHz
on a Jeol EX 270 or at 300 MHz on a Varian Gemini-300
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 10–16

ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
11
over 2 h to a stirred solution of decanethiol (3.30 g,
iodide) and catalyst as above, the title compound was
obtained in 68% yield (mp 41–42 °C (Lit. [8] 43–44 °C)).
3,6-Bis(1,1-H-2,2-H-perfluorodecyl)phthalonitrile,
5k. Using the same conditions and ratios of substrate,
reagent (1,1-H-2,2-H-perfluorodecylzinc iodide) and
catalyst as above the crude product was recrystallized
from a.a.a-trifluorotoluene to afford the title compound
in 58% yield. Anal. calcd. for C28H10N2F34: C, 32.96; H,
19.0 mmol) in dry DMF containing finely crushed
potassium carbonate (2.3 g). The reaction was stirred
over 72 h. The reaction mixture was poured into 5% aq.
NaOH (150 mL), filtered and the mother liquor extracted
with ethyl acetate (3 × 50 mL). The combined solution
was washed sequentially with 5% aq. NaOH solution
(50 mL), 5% HCl (50 mL) and brine (520 mL), dried
(MgSO4) and concentrated under reduced pressure. The
resulting residue was recrystallised (DCM/ethyl acetate)
to afford 3,6-bis(decylsulfanyl)phthalonitrile (1.5 g,
68%) as yellow needles. Anal. calcd. for C28H44N2S2:
C, 71.14; H, 9.39; N, 5.93%. Found C, 71.31; H, 9.38;
1
1.06; N, 2.75%. Found C, 33.01; H, 0.82; N, 2.93%. H
NMR (C6F6:C6D6, 9:1): d, ppm 7.36 (s, 2H), 3.16 (t, 4H,
J = 7.9 Hz), 2.57–2.41 (m, 4H).
3,6-Bis(4-pivaloylbutyl)phthalonitrile, 5l. Using
the same conditions and ratios of substrate, reagent
(4-pivaloylbutylzinc iodide) and catalyst as above, the
title compound was obtained in 62% yield as a colorless
oil. Anal. calcd. for C26H36N2O4: C, 70.88; H, 8.24; N,
1
N, 5.85%. H NMR (CDCl3): d, ppm 7.50 (s, 2H), 3.02
(t, 4H, J 7.5 Hz), 1.68 (m, 4H), 1.47–1.25 (m, 28H), 0.88
(t, 6H, J 6.7 Hz).
1
For characterization data and yields for homologs of
series 2 and arylsulfanyl analogs of series 3, see Tables 1
and 2 respectively.
6.36%. Found C, 70.87; H, 8.21; N, 6.28%. H NMR
(CDCl3): d, ppm 7.49 (s, 2H), 4.10 (t, 4H, J = 7.7 Hz),
2.91 (t, 4H, J = 7.2 Hz), 1.78–1.61 (m, 8H), 1.20 (s, 18H).
MS (EI): m/z 440.1 ([M]+).
3,6-Bis(6-chlorohexyl)phthalonitrile, 5m. Using
the same conditions and ratios of substrate, reagent
(6-chlorohexylzinc bromide) and catalyst as above,
the title compound was obtained in 61% yield (mp
44.5–45.5 °C).
General procedure for preparing
3,6-dialkylphthalonitriles, series 5, by Negishi
coupling
3,6-Didecylphthalonitrile, 5i. In a typical experiment,
n-BuLi (0.2 mL, 20 mol% in hexanes) was added
at rt under argon to a mixture of dry THF (5 mL),
bis(triphenylphosphine)-Ni(II)Cl2 (0.154 g, 10 mol%)
and triphenylphosphine (0.124 g, 20 mol%) to afford a
blood-red slurry. 3,6-bis(trifluoromethanesulfonyloxy)-
phthalonitrile (1.0 g, 2.36 mmol) was added under a fast
stream of argon. The resulting pale brown solution was
cooled to -78 °C. Decylzinc iodide (7.0 mmol, 5.6 mL of
a 1.24 M solution) containing LiCl (0.30 g 7.0 mmol) was
added via syringe and the solution warmed to rt over ca.
1 h. The reaction was then stirred for 16 h. 5% HCl (10
mL) was added carefully followed by ethyl acetate (20
mL). The organic layer was separated and washed with 5%
HCl (10 mL) and brine (10 mL). The aqueous waste was
extracted with ethyl acetate (10 mL). The combined organic
layers were dried (MgSO4) and evaporated to dryness. In
one work-up the crude product was stirred with acetonitrile
(10 mL) for 10 min and pure 3,6-didecylphthalonitrile
collected by filtration (0.67 g 70%). Alternatively the crude
mixture was chromatographed (silica, DCM/hexane 3:2 as
eluent) to yield the product in 63% yield (mp 70–71 °C
(Lit. [8] 70 °C)).
Use of Suzuki coupling protocol
3,6-Didecylphthalonitrile, 5i. BH3 in THF (1.2 mmol,
1.2 mL of 1 M solution) was added dropwise under argon
to a solution of 1-decene (0.51 g, 3.64 mmol) in dry THF
(5 mL) at 0 °C. The reaction mixture was stirred for
4 h at 0 °C. Dry THF (4 mL) and anhydrous potassium
phosphate (0.85 g, 4 mmol) were added and the reaction
stirred for 1 h at rt. Anhydrous LiCl (0.08 g, 1.9 mmol)
and 3,6-bis(trifluoromethanesulfonyloxy)phthalonitrile
(0.25 g, 0.59 mmol) were added followed, after 10 min, by
Pd(dppf)Cl2 {[(1,1′-bis(diphenylphosphino)ferrocene]-
dichloropalladium(II)} (21 mg, 5 mol%). The reaction
mixture was heated under reflux for 10 h, cooled, filtered
andthefiltrateevaporatedtodrynessandchromatographed
over silica (eluent: toluene) to afford the title compound
(0.09 g) in 38% yield.
General procedure for preparing
3,6-diarylphthalonitriles, series 6, by cross-coupling
reactions
The following were prepared similarly:
3,6-Dipentylphthalonitrile, 5a. Using the same
conditions and ratios of substrate, reagent (n-pentylzinc
iodide) and catalyst as above, the title compound was
3,6-Diphenylphthalonitrile, 6a(Suzukicoupling). In
a typical experiment, 3,6-bis(trifluoromethanesulfony-
loxy)-phthalonitrile (0.5 g, 1.18 mmol) and anhydrous
LiCl (0.13 g, 3 mmol) were stirred in dry toluene
under argon for 30 min. Tetrakis(triphenylphosphine)
palladium (0) (84.0 mg, 10 mol%) was added and the
mixture stirred for 10 min. Phenylboronic acid (0.43 g,
3.5 mmol) was added followed by aq. 2 M Cs2CO3
(2 mL). The reaction mixture was heated under reflux
1
obtained in 56% yield as an oil. H NMR (CDCl3): d,
ppm 7.76 (s, 2H), 2.80 (t, 4H, J = 7.7Hz), 1.61 (m, 4H),
1.30–1.22 (m, 8H), 0.89 (t, 6H, J = 6.8 Hz). IR (neat): n,
cm-1 3134, 2229 (CN).
3,6-Dihexylphthalonitrile, 5e. Using the same
conditions and ratios of substrate, reagent (hexylzinc
Copyright © 2013 World Scientific Publishing Company
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12
M.J. HEENEY ET AL.
for 14 h, cooled and diluted with ethyl acetate (15 mL).
The mixture was washed sequentially with 10% aq.
KOH solution (2 × 10 mL), 5% HCl (10 mL) and brine
(10 mL), dried (Na2SO4) and concentrated under reduced
pressure. Recrystallization of the crude product from
toluene afforded the title compound (0.26 g, 79%) (mp
221–223.5 °C (Lit. [31] 220 °C)).
conditions (see earlier) afforded the title compound,
identical to the above sample, in 30% yield.
PHTHALOCYANINE SYNTHESIS
General method for preparing zinc and
magnesium metalated 1,4,8,11,15,18,22,25-
octakis(alkylsulfanyl)phthalocyanines, series 8,
and 1,4,8,11,15,18,22,25-octakis(arylsulfanyl)-
phthalocyanines, series 9
3,6-Bis(4-t-butylphenyl)phthalonitrile, 6b (Suzuki
coupling). Application of the Suzuki coupling conditions
using 4-t-butylphenylboronic acid afforded the title
compound as a colourless crystalline solid in 36% yield
(mp 153 °C). Anal. calcd. for C28H28N2: C, 85.67; H,
1
7.19; N, 7.14%. Found C, 85.27; H, 7.05; N, 6.74%. H
1,4,8,11,15,18,22,25-Octakis(decylsulfanyl)-
phthalocyaninato zinc, 8k. In a typical reaction, a
solution of 3,6-bis(decylsulfanyl)phthalonitrile 2e (1.01
g, 2.14 mmol) was heated in dry pentanol (9 mL) under
nitrogen. DBU (0.23 g, 1.50 mmol) was added and heating
continued for 1 h. Zinc acetate dihydrate (99.999% zinc,
0.14 g, 0.64 mmol) was added and the reaction heated
for a further 20 h. The reaction mixture was cooled and
the solvent removed under reduced pressure. The residue
was chromatographed over silica (eluent: DCM/Et3N
100:1). The first reddish-brown fraction was collected,
evaporated and triturated (hot acetone) and recrystallised
from THF/methanol to afford 1,4,8,11,15,18,22,25-
octakis(decylsulfanyl)phthalocyaninato zinc (0.68 g,
65%). Anal. calcd. for C112H176N8S8Zn: C, 68.76; H,
9.07; N, 5.73%. Found C, 69.01; H, 9.05; N, 5.71%. MS
NMR (CDCl3): d, ppm 7.77 (s, 2H), 7.55 (m, 8H), 1.38
(s, 18H). MS (EI): m/z 392 ([M]+, 66%), 377 ([M+- CH3],
100%).
3,6-Bis(4-methoxydiphenyl)phthalonitrile, 6c
(Suzuki coupling). Under the conditions used above
4-methoxyphenylboronic acid (0.45 g, 3.5 mmol) was
crossed-coupledto3,6-bis(trifluoromethanesulfonyloxy)-
phthalonitrile to afford the title compound as a white
crystalline solid (0.29 g, 73%) (mp 213–215 °C). Anal.
calcd. for C22H16N2O2: C, 77.6; H, 4.74; N, 8.23%. Found
1
C, 77.38; H, 4.68; N, 8.21%. H NMR (CDCl3): d, ppm
7.74 (s, 2H), 7.55 (d, 4H, J = 8.5 Hz), 7.06 (d, 4H, J =
8.5), 3.89 (s, 6H). MS (EI): m/z 340 ([M]+, 21%).
3,6-Bis(4-methoxyphenyl)phthalonitrile, 6c
(Negishi coupling). Application of the Negishi coupling
conditions (see earlier) afforded the title compound,
identical to the above sample, in 67% yield.
1
(MALDI): isotopic cluster at m/z 1956 ([M]+). H NMR
(C6D6 with 1% d5-pyridine): d, ppm 7.86 (s, 8H), 3.38
(t, 16H, J = 7.25 Hz), 2.11–2.01 (m, 16H), 1.68–1.58
(m, 16H), 1.52–1.18 (m, 96H), 0.90 (t, 24H, J = 6.6 Hz).
UV-vis (THF): l, nm 781.
Yields and selected characterization data for zinc
metalated homologs 8a, 8f, 8g, 8i and 8m and for
9a and 9d are shown in Tables 1 and 2 respectively.
Magnesium metalated compounds, 8b, 8h, 8j and 8l,
were prepared similarly using MgCl2 in place of zinc
acetate. Selected characterization data and yields are
also shown in Table 1.
3,6-Bis(3-methoxyphenyl)phthalonitrile, 6d
(Suzuki coupling). Under the conditions used above
3-methoxyphenylboronic acid (0.45 g, 3.5 mmol) was
crossed-coupledto3,6-bis(trifluoromethanesulfonyloxy)-
phthalonitrile to afford the title compound as a white
crystalline solid (0.28 g, 70%) (mp 236–239 °C). Anal.
calcd. for C22H16N2O2: C, 77.63; H, 4.74; N, 8.23%.
1
Found C, 77.54; H, 4.64; N, 8.24%. H NMR (CDCl3):
d, ppm 7.79 (s, 2H), 7.45 (t, 2H, J = 8 Hz), 7.16 (ddd,
2H), 7.11 (t, 2H, J = 2.5 and 1.6 Hz), 7.06 (ddd, 2H), 3.89
(s, 6H). MS (EI): m/z 340 ([M]+, 100%).
3,6-Bis(3-methoxyphenyl)phthalonitrile, 6d
(Negishi coupling). Application of the Negishi coupling
conditions (see earlier) afforded the title compound,
identical to the above sample, in 67% yield.
General method for preparing lead, chloroindium
and copper metalated 1,4,8,11,15,18,22,25-octakis-
(alkylsulfanyl or arylsulfanyl)phthalocyanines of
series 8 and 9
3,6-Bis(2-methoxyphenyl)phthalonitrile, 6e
(Suzuki coupling). Under the conditions used above
2-methoxyphenylboronic acid was crossed-coupled to
3,6-bis(trifluoromethanesulfonyloxy)phthalonitrile to
afford the title compound as a pale yellow crystalline
solid in 20% yield (mp 196–199 °C). Anal. calcd. for
C22H16N2O2: C, 77.63; H, 4.74; N, 8.23%. Found C, 77.27;
H, 4.68; N, 8.25%. 1H NMR (CDCl3): d, ppm 7.54 (s, 2H),
7.30 (d, 2H, J = 8 Hz), 7.16 (t, 2H, J = 7.5 Hz), 6.96 (m,
4H), 3.71 (s, 6H). MS (EI): m/z 340 ([M]+, 100%).
3,6-Bis(2-methoxyphenyl)phthalonitrile, 6e
(Negishi coupling). Application of the Negishi coupling
1,4,8,11,15,18,22,25-Octakis(hexylsulfanyl)-
phthalocyaninato lead, 8c. By adapting the general
method above, the title compound was prepared from
3,6-bis(hexylsulfanyl)phthalonitrile (0.5 g, 1.39 mmol)
in pentanol (7 mL), in the presence of DBU (0.14 mL,
0.097 mmol) and lead acetate (0.15 g, 0.42 mmol). The
compound was purified by chromatography over silica,
pre-treated with DCM:Et3N 99:1, using DCM as eluent,
and recrystallized from THF/acetone to give the title
compound (87 mg, 15%) as dark red crystals (mp 145–
148 °C). MS (MALDI): isotopic cluster at m/z 1650 ([M
Copyright © 2013 World Scientific Publishing Company
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ROUTES TO SOME 3,6-DISUBSTITUTED PHTHALONITRILES AND EXAMPLES OF PHTHALOCYANINES
13
1
+ 1]+). CHN analysis results, H NMR data and Q-band
bis[1,4,8,11,15,18,22,25-octakis(4-t-butylphenylsulfanyl)-
phthalocyaninato cerium(IV) as a purple solid (mp 196–
197 °C). MS (MALDI): isotopic cluster at m/z 3792.3
l
max are given in Table 1.
1,4,8,11,15,18,22,25-Octakis(phenylsulfanyl)-
1
phthalocyaninato lead, 9b, and 1,4,8,11,15,18,22,25-
octakis(4-methylphenylsulfanyl)phthalocyaninato
lead, 9e, were prepared similarly, see Table 2.
([M]+). CHN analysis results, H NMR data and Q-band
lmax are given in Table 2.
1,4,8,11,15,18,22,25-Octakis(hexylsulfanyl)-
phthalocyaninato chloroindium, 8d. Application of
the method above gave the title compound from 3,6-
bis(hexylsulfanyl)phthalonitrile (0.5 g, 1.39 mmol) in
pentanol (7 mL), in the presence of DBU (0.14 mL,
0.097mmol)andindium(III)chloride(93mg,0.42mmol).
The compound was purified by chromatography over
silica, pre-treated as above with DCM:Et3N 99:1. A first
(yellow) fraction was eluted with DCM and discarded.
Change of eluent to THF gave a dark second fraction.
This was re-chromatographed using first DCM and
then DCM:THF (95:5) collecting the first deep blue
fraction. The recrystallized (THF/acetone) sample of
the title compound (17 mg, 3%) was obtained as a
deep blue/black solid (mp 202–204 °C). CHN analysis
General method for preparing
1,4,8,11,15,18-hexakis(alkyl)-22,25-bis(aryl)-
phthalocyaninato zinc derivatives
1,4,8,11,15,18-Hexakis(decyl)-22,25-bis(phenyl)-
phthalocyaninato zinc, 11a, (and compound 12).
DBU (106 mg) was added to a refluxing solution of
3,6-diphenylphthalonitrile (0.28 g, 1.00 mmol) and
3,6-didecylphthalonitrile (0.82 g, 2.00 mmol) in pentanol
(10 mL). Heating under reflux was continued for 1 h,
zinc acetate dihydrate (0.07 g, 0.3 eq.) was added, and
the solution was heated under reflux for a further 24
h. Removal of solvent and trituration of the resultant
slurry with methanol afforded a green solid that was
chromatographed over silica. The first fraction collected
(eluent petrol/DCM 9:1) was 1,4,8,11,15,18,22,25-octak-
is(decyl)phthalocyaninato zinc (105 mg, 7%), identical
with an authentic sample [49]. Further elution (petrol/
DCM 9:1) afforded 1,4,8,11,15,18-hexakis(decyl)-22,25-
bis(phenyl)phthalocyaninato zinc 11a (60 mg, 4%) after
recrystallization from THF/MeOH (mp > 250 °C). MS
(MALDI): isotopic cluster at m/z 1571 ([M]+). Further
characterization data are collected in Table 3. Changing
the eluent (petrol/DCM 1:3) afforded a third fraction
1,4,15,18-tetrakis(decyl)-8,11,22,25-tetrakis(phenyl)
phthalocyaninato zinc 12 (30 mg, 2%) as a green solid
(mp > 250 °C). MS (MALDI): isotopic cluster at m/z
1443 ([M]+). 1H NMR (C6D6): d, ppm 7.76 (s, 4H), 7.73
(d, 4H, J = 7.7 Hz), 7.70 (s, 4H), 7.67 (d, 8H, J = 7.7 Hz),
7.42 (t, 8H, J = 7.7 Hz), 3.49 (t, 8H, J = 7.5 Hz), 1.76
(m, 8H), 1.36–1.05 (m, 56H), 0.81 (t, 12H, J = 7.5 Hz).
UV-vis (THF): l, nm 723 (e 1.55 × 105).
1,4,8,11,15,18-Hexakis(decyl)-22,25-bis(4-
methoxyphenyl)phthalocyaninato zinc, 11b. Applying
the method described above, 3,6-bis(4-methoxyphenyl)-
phthalonitrile (0.13 g, 0.38 mmol), 3,6-didecylphthalo-
nitrile (0.94 g, 2.29 mmol), DBU (30 mg, 0.7 eq.) and zinc
acetate dihydrate (0.18 g, 0.3 eq.) in pentanol (10 mL)
afforded 1,4,8,11,15,18-hexakis(decyl)-22,25-bis(4-
methoxyphenyl)phthalocyaninato zinc (50 mg, 8%) as
the second fraction during separation over silica (petrol/
DCM) (mp >250°C). MS (MALDI): isotopic cluster at
m/z 1631 ([M]+). CHN analysis results, 1H NMR data and
Q-band lmax are given in Table 4.
1
results, H NMR data and Q-band lmax are given in
Table 1.
1,4,8,11,15,18,22,25-Octakis(4-methylphenyl-
sulfanyl)phthalocyaninato chloroindium, 9c, and 1,4,
8,11,15,18,22,25-octakis(4-methylphenylsulfanyl)-
phthalocyaninato chloroindium, 9f, were prepared
similarly, see Table 2.
1,4,8,11,15,18,22,25-Octakis(hexylsulfanyl)-
phthalocyaninato copper, 9e. Adapting the general
method above, the title compound was obtained from
3,6-bis(hexylsulfanyl)phthalonitrile (0.5 g, 1.39 mmol)
in pentanol (7 mL), in the presence of DBU (0.14 mL,
0.097 mmol) and copper acetate (84 mg, 0.42 mmol).
The product was chromatographed over silica, eluent
DCM:Et3N 99:1, and the title compound collected
as the first colored fraction and recrystallized from
THF/acetone (289 mg, 55%) (mp 135–140 °C). MS
(MALDI): isotopic cluster at m/z 1607 ([M]+). CHN
analysis results, 1H NMR data and Q-band lmax are given
in Table 1.
Bis[1,4,8,11,15,18,22,25-octakis(4-t-butylphenyl-
sulfanyl)phthalocyaninato] cerium(IV), 10, and 1,4,8,-
11,15,18,22,25-octakis(4-t-butylphenylsulfanyl)-
phthalocyanine, 9g. Application of the method above gave
bothtitlecompoundsfrom3,6-bis(4-t-butylphenylsulfanyl)-
phthalonitrile (1.00 g, 2.20 mmol) in pentanol (20 mL) in
the presence of DBU (1.33 g, 8.77 mmol) and cerium(III)
chloride (32 mg, 0.13 mmol) and after heating under
reflux for 5 h. The compound mixture was separated
by chromatography over silica, eluent DCM, to give
1,4,8,11,15,18,22,25-octakis(4-t-butylphenylsulfanyl)-
phthalocyanine as the first fraction (100 mg, 10%) as a
dark red crystalline solid (mp 155–156 °C). MS (MALDI):
isotopic cluster at m/z 1827.5 ([M]+). CHN analysis results,
1H NMR data and Q-band lmax are given in Table 2. The
second fraction eluted with DCM/THF (9:1) afforded
1,4,8,11,15,18-Hexakis(decyl)-22,25-bis(3-
methoxyphenyl)phthalocyaninato zinc, 11c. Applying
the method described above, 3,6-bis(3-methoxyphenyl)-
phthalonitrile(0.13g,0.38mmol),3,6-didecylphthalonitrile
(0.94 g, 2.29 mmol), DBU (30 mg, 0.7 eq.) and zinc acetate
dihydrate (0.18 g, 0.3 eq.) in pentanol (10 mL) afforded
Copyright © 2013 World Scientific Publishing Company
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14
M.J. HEENEY ET AL.
1,4,8,11,15,18-hexakis(decyl)-22,25-bis(3-methoxy-
phenyl)phthalocyaninato zinc (50 mg, 8%) as the second
fraction during separation over silica (petrol/DCM) (mp
>250 °C). MS (MALDI): isotopic cluster at m/z 1631
substituents are alkoxy, alkylsulfanyl, the recently
described phenylselenyl, alkyl, functionalized-alkyl and
aryl groups. Such compounds are immediate precursors
to a wide range of 1,4,8,11,15,18,22,25-(non-peripheral)
octasubstituted phthalocyanine derivatives. Early
routes for the preparation of 3,6-dialkylphthalonitriles,
3,6-functionalized dialkylphthalonitriles and 3,6-diph-
enylphthalonitrile employed Diels–Alder chemistry
within convenient but multistep sequences. However,
an attractive alternative access to these and other
classes of 3,6-disubstituted phthalonitriles is the use of
2,3-dicyanohydroquinone, a precursor that has the two
adjacent cyano groups already in place together with
two phenolic OH groups. Alkylation of the OH groups
provided early access to 3,6-dialkoxyphthalonitriles
and thence non-peripherally octaalkoxy substituted
phthalocyanine derivatives. However, conversion of
2,3-dicyanohydroquinone to the bis-triflate derivative
offers the prospect of cleaving the ring-to-oxygen bond
to enable alternative functionality to be introduced. This
has been illustrated through the use of SNAr reactions to
introduce alkylsulfanyl, arylsulfanyl and phenylselenyl
groups at the 3,6-positions of the phthalonitrile unit.
In addition the advent of organometallic catalyzed
cross-coupling reactions to create new carbon-carbon
bonds adds a further dimension that allows direct
incorporation of alkyl and aryl substituents at the 3-
and 6-positions of phthalonitrile. Finally, bromination
of 2,3-dicyanohydroquinone to form 5,6-dibromo-
2,3-dicyanohydroquinone is shown to provide access
to both monobromo and dibromo derivatives of
3,6-dibutoxyphthalonitrile. These compounds provide
opportunities for cross-coupling reactions at the
brominated sites to provide more complex derivatives
with the potential to serve as precursors of highly
substituted phthalocyanine derivatives. Examples of a
range of phthalocyanine compounds derived from the
phthalonitrile precursors described above are included in
the review.
1
([M]+). CHN analysis results, H NMR data and Q-band
l
max are given in Table 4.
1,4,8,11,15,18-Hexakis(pentyl)-22,25-bis(4-
methoxyphenyl)phthalocyaninato zinc, 11d. Applying
theproceduredescribedabove, 3,6-bis(3-methoxyphenyl)-
phthalonitrile (0.41 g), 3,6-dipentylphthalonitrile (1.60 g),
DBU(265mg)andzincacetatedihydrate(175mg)inpentanol
(15 mL) afforded 1,4,8,11,15,18-hexakis(pentyl)-22,25-
bis(3-methoxyphenyl)phthalocyaninato zinc (210 mg,
17%) as the second fraction during separation over silica
(petrol/DCM) (mp > 250 °C). MS (MALDI): isotopic
cluster at m/z 1211 ([M]+). CHN analysis results, 1H NMR
data and Q-band lmax are given in Table 4.
General method for preparing
1,4,8,11,15,18-hexakis(alkyl)-22,25-bis(aryl)-
phthalocyanines
1,4,8,11,15,18-Hexakis(decyl)-22,25-bis(3-
methoxyphenyl)phthalocyanine, 11e. Lithium metal
(0.40 g) was added portionwise to a solution of 3,6-bis(3-
methoxyphenyl)phthalonitrile (0.33 g, 0.97 mmol) and
3,6-didecylphthalonitrile (3.57 g, 8.73 mmol) in pentanol
(30 mL) heated under reflux for 6 h. Glacial acetic acid
(40 mL) was added to the cooled solution and the mixture
stirred for 1 h. The solvents were removed under reduced
pressure and the resultant slurry triturated with methanol.
The green solid was collected and chromatographed
over silica. The first fraction (eluent: petrol/DCM 9:1)
was collected and shown to be 1,4,8,11,15,18,22,25-oct-
akis(decyl)phthalocyanine (0.98 g, 28%), identical to
an authentic sample. The second fraction eluted with
petrol/DCM 7:3, 1,4,8,11,15,18-hexakis(decyl)-22,25-
bis(3-methoxyphenyl)phthalocyanine (152 mg, 10%)
was recrystallized from THF/MeOH. MS (MALDI):
isotopic cluster at m/z 1568 ([M]+). CHN analysis results,
1H NMR data and Q-band lmax are given in Table 4.
1,4,8,11,15,18-Hexakis(pentyl)-22,25-bis(3-
methoxyphenyl)phthalocyanine, 11f. Using the same
procedure as above, the title compound (40 mg, 4%)
was obtained as the second fraction from the reaction
of 3,6-bis(3-methoxyphenyl)phthalonitrile (0.33 g,
0.97 mmol) and 3,6-dipentylphthalonitrile (2.34 g, 8.73
mmol) in pentanol (30 mL) into which lithium metal had
been added. MS (MALDI): isotopic cluster at m/z 1147
([M]+). CHN analysis results, 1H NMR data and Q-band
Acknowledgements
We thank Gentian A/S for primary funding of this
work and the EPSRC for studentships. MJC thanks the
Leverhulme Foundation for the award of a Leverhulme
Emeritus Fellowship.
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