Unsymmetrical zinc azaphthalocyanines, peripherally substituted with thiophen-2-yl and 2-functionalized phenoxy groups

Article abstract of DOI:10.1016/j.poly.2010.08.036

Four targeted octasubstituted zinc azaphthalocyanines (ZnAzaPc), substituted with thiophen-2-yl groups and ortho-substituted phenoxy groups, were obtained by cyclotetramerization of 5-aryloxy-6-(thiophen-2-yl)pyrazine-2,3- dicarbonitriles. Thiophen-2-yl s

Full text of DOI:10.1016/j.poly.2010.08.036

Polyhedron 29 (2010) 3229–3237
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Polyhedron
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Unsymmetrical zinc azaphthalocyanines, peripherally substituted with
thiophen-2-yl and 2-functionalized phenoxy groups
b
c
d
b
Eva H. Mørkved a, , Trygve Andreassen , Roland Fröhlich , Frode Mo , Per Bruheim
⇑
a Norwegian University of Science and Technology, Department of Chemistry, N-7491 Trondheim, Norway
b Norwegian University of Science and Technology, Department of Biotechnology, N-7491 Trondheim, Norway
c Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany
d Norwegian University of Science and Technology, Department of Physics, N-7491 Trondheim, Norway
a r t i c l e i n f o
a b s t r a c t
Article history:
Four targeted octasubstituted zinc azaphthalocyanines (ZnAzaPc), substituted with thiophen-2-yl groups
and ortho-substituted phenoxy groups, were obtained by cyclotetramerization of 5-aryloxy-6-(thiophen-
2-yl)pyrazine-2,3-dicarbonitriles. Thiophen-2-yl substituents are known to extend the macrocyclic con-
jugation, and thereby cause red-shifted UV–Vis Q-bands. Peripheral phenoxy groups with bulky ortho
substituents are expected to suppress aggregation and thereby improve solubility of these compounds.
The reagent Zn(quinoline)2Cl2 was used for one-step syntheses of these ZnAzaPc. Four tetrasubstituted
ZnAzaPc, with phenoxy, (2-isopropyloxy)phenoxy, (2-isopropyl)phenoxy or (2-tert-butyl)phenoxy sub-
stituents, were obtained as controls from 5-aryloxypyrazine-2,3-dicarbonitriles. The tetra- and octa-
substituted ZnAzaPc, 5 and 6, were obtained in 30–50% yields after purification by chromatography on
silica. UV–Vis Q-bands with high molar extinction coefficients (100 000–160 000), were observed at
635 nm for compounds 5, and at 660–665 nm for 6. Grass-green solutions were obtained of compounds
6 in most organic solvents, whereas the less soluble compounds 5 gave blue-green solutions. 2D NMR
methods were applied in analyses of DMSO-d6 solutions of ZnAzaPc 5 and 6. Broad and partly overlapping
1H NMR signals for some of the compounds indicate some aggregation as well as presence of two or more
structural isomers. Molecular ions of ZnAzaPc 5 and 6 were determined by mass spectrometry (MALDI-
TOF).
Received 20 July 2010
Accepted 30 August 2010
Available online 1 October 2010
Keywords:
Zinc azaphthalocyanine
Tetrapyrazinoporphyrazine
Thiophen-2-yl
Phenoxy
Pyrazine-2,3-dicarbonitrile
Crystallography
Dichlorobis(quinoline-N)zinc(II)
Structure analyses of 5-phenoxy-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (4a), and 5-(2-isopro-
pyloxyphenoxy)-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (4b), show the impact on conformation
exerted by the bulky isopropyloxy ortho-substituent of the phenoxy group in 4b, and indicates how this
substituent hinders the type of disorder found in 4a.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
properties. There is limited knowledge concerning the influence
of heteroatom substituents on both synthesis and properties of
Phthalocyanines (Pc), have served as important industrial blue-
green colourants for about 100 years, and during the last two dec-
ades both properties and numerous sophisticated applications
have been explored for this class of compounds [1]. Tetrapyrazino-
porphyrazines, here named azaphthalocyanines (AzaPc), are in
general considered less important than the parent phthalocyanines
due to different physical properties such as inferior stability, col-
our, and less resistance to oxidation. However, interest in this class
of compounds is steadily increasing, and many applications in
materials science have been reported recently [2]. Eight additional
nitrogen atoms on the periphery of AzaPc increase the polarity of
these macrocycles, and substituents may be used for tuning solu-
bility, UV–Vis absorptions i.e. shifts of Q-bands, and acid–base
AzaPc. Several years ago we synthesized some heteroatom substi-
tuted AzaPc [3,4] and found that sulfanyl-, and in particular oxo-
substituents, of pyrazine-dicarbonitriles could be replaced by
nucleophiles during cyclotetramerizations if metal alkoxides and
alcohols were used. Similar, but less pronounced problems have
been found for cyclizations of sulfanyl substituted phthalonitriles
[5].
The fragile ether bond between the macrocyclic core and oxo-
substituents of AzaPc [4], may be one reason why this class of
AzaPc has been ignored for many years. However, AzaPc which
are substituted with bulky phenoxy groups, and which are soluble
in most organic solvents, were obtained by direct synthesis as re-
ported recently by Makhseed et al. [6,7]. These compounds are of
potential interest for a variety of applications, and in particular
as fluorophores since their red fluorescence falls within the visible
spectrum.
⇑
Corresponding author. Tel.: +47 97 10 39 26; fax: +47 73 59 42 56.
E-mail address: eva.morkved@chem.ntnu.no (E.H. Mørkved).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.08.036

3230
E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
Pyridin-3-yloxy substituted Pc was studied for many years with
the purpose of obtaining sensitizers applicable in photodynamic
therapy (PDT) used in cancer treatment [8]. Recently some promis-
ing PDT sensitizers, namely cationic zinc complexes of octa(pyri-
din-3-yloxy)Pc have been reported [9]. We obtained related
octa(pyridin-3-yloxy)ZnAzaPc, and some similarly substituted
complexes [10] from reactions of substituted pyrazine-2,3-dicar-
bonitriles with Zn(quinoline)2Cl2. Due to low solubility in most or-
ganic solvents, there is limited potential for applications of those
ZnAzPc. However, complexation of the peripheral pyridin-3-yloxy
substituents with zinc(II) ions is an interesting possibility, since
peripheral complexes with other metal ions might alter solubility
and other important properties of these compounds.
We anticipate that further studies of aryloxy-substituted
ZnAzaPc will give useful knowledge about these macrocycles. Indi-
cations of potential applications, including PDT, might follow. The
Q-band, at 636 nm, of unsubstituted ZnAzaPc is considerably blue
shifted compared to that of ZnPc (674 nm). Q-bands close to
700 nm are optimal for PDT sensitizers [2]. The thiophen-2-yl
groups of octa(thiophen-2-yl)ZnAzaPc [11], induce a red shift to
673 nm in the Q-band of the UV–Vis spectrum, and also a higher
intensity of this absorption. A lowering of energy can be effected
both by a suitable extension of the delocalized electron system
brought about by a sufficient degree of coplanarity between the
thiophene substituents and the AzaPc core, and as well by polar
interactions between the electron-donating thiophene rings and
the electron-deficient macrocyclic system. Indications of the rela-
tive importance of polarity and coplanarity may be obtained from
structure studies of pyrazine-2,3-dicarbonitriles 4a–d (Scheme 1).
The purpose of our present study is to investigate how combi-
nations of the peripheral substituents thiophen-2-yl, and ortho-
substituted phenoxy groups influence the electronic properties of
ZnAzaPc. These macrocycles are synthesized from substituted pyr-
azine-2,3-dicarbonitriles. The combination of one thiophen-2-yl
group and one bulky aryloxy group on each pyrazine ring is ex-
pected to cause steric crowding, presumably favouring coplanarity
between the thiophene and pyrazine rings, the aryloxy group being
forced out of this plane. The crystal structures of monomers 4a and
4b (Scheme 1), are expected to give valuable information about
these steric assumptions.
Scheme 2. Synthesis and structure of unsymmetrical aryloxy-substituted zinc
azaphthalocyanines 5a–d and 6a–d. Only one structural isomer is shown for
compounds 5 and 6.
The tetrasubstituted ZnAzaPc 5a–d (Scheme 2), are reference
compounds, and aggregation certainly will be a problem with
some of them. The phenoxy substituents of 5a are not sufficiently
bulky to cause steric crowding, whereas the ortho-isopropyloxy-,
isopropyl- and tert-butyl-substituted phenoxy groups of respec-
tively 5b–d, may cause some steric crowding and thereby improve
solubilities.
The octasubstituted complex 6a (Scheme 2), is a reference for
6b–d (Scheme 2), which are substituted with thiophen-2-yl groups
and the same ortho-substituted phenoxy groups as in 5b–d. The
results of these investigations are expected to indicate if 6b–d
may be developed further; application as sensitizers for PDT would
be one possibility.
2. Experimental
2.1. Materials and methods
Accurate mass determination with electron spray ionisation
(ESI) was performed on an Agilent 6520 QTOF MS instrument
equipped with a dual electrospray ion source. Samples of com-
pounds 2 and 4, dissolved in acetonitrile, were injected into the
MS using an Agilent 1200 series HPLC, and analysis was performed
as a flow injection analysis without any chromatographic step.
MALDI-TOF mass spectra of compounds 5 and 6 were recorded
on a Bruker Ultraflex III MALDI-TOF–TOF mass spectrometer oper-
ated in TOF mode. Each sample was dissolved in dichloromethane
(DCM), spotted onto the target plate, airdried at ambient tempera-
ture and covered with the matrix solution which consisted of a-cy-
ano-4-hydroxycinnamic acid, acetonitrile and trifluoroacetic acid.
IR spectra were obtained on a Thermo Nicolet Nexus FT-IR spec-
trometer with a Smart Endurance reflexion cell. NMR spectra of 2
Scheme 1. Synthesis of unsymmetrically substituted pyrazine-2,3-dicarbonitriles
2a–d and 4a–d.

E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
3231
and 4 were recorded on a Bruker Avance DPX 400 NMR spectrom-
265.1086. UV–Vis (DCM): kmax, nm (
295 (sh, 9000). IR: m
1530, 1433, 1360, 1339, 1213, 1173, 1108, 1077, 992, 935, 793,
755. 1H NMR (CDCl3): d, ppm 1.20 (6H, CH3, d, J = 6.9 Hz), 2.92
(1H, CH(CH3)2, sept. J = 6.9 Hz), phenyl: 7.00 (1H, H6, dd,
e
, MÀ1 cmÀ1) 255 (18 600),
eter at 400.13 (1H) and 100.61 MHz (13C). NMR spectra of 5 and 6
were recorded on a Bruker Avance Digital 600 NMR spectrometer,
fitted with a TCI cryoprobe, at 600.18 (1H) and 150.92 MHz (13C).
Chemical shifts are given relative to internal tetramethyl silane
(TMS) when CDCl3 was used as solvent. Chemical shifts are cali-
brated relative to the DMSO signal at 2.50 ppm for 1H, and
39.51 ppm for 13C when DMSO-d6 was used as solvent. The NMR
pulse techniques COSY, ROESY, HSQC and HMBC were used to cor-
relate 1H and 13C NMR signals for all new compounds. 13C chemical
shift values of 5 and 6 were determined by indirect methods (HSQC
and HMBC) precluding the detection of 13C nuclei not coupled to
1H (usually more than three bonds away from 1H). UV–Vis spectra
were recorded on a Cary 50 UV–Vis spectrophotometer. Melting
points were obtained on a Büchi 530 melting point apparatus
and are uncorrected. Merck Kieselgel 60F 254 was used for thin
, cmÀ1 2969 (CH, w), 2240 (CN, w), 1557,
J6,5 = 8.0 Hz, J6,4 = 1.2 Hz), 7.29 (1H, H5, app. td, J = 7.9 Hz,
J5,3 = 1.6 Hz), 7.35 (1H, H4, app. td, J = 7.6 Hz, J4,6 = 1.2 Hz), 7.43
(1H, H3, dd, J3,4 = 7.7 Hz, J3,5 = 1.6 Hz), pyrazine: 8.68 (1H, H6, s).
13C NMR (CDCl3): d, ppm 23.0 (CH3), 27.5 (CH(CH3)2), 112.3 and
112.9 (CN at pyrazine C2 and C3), phenyl: 121.2 (C6), 127.4 (C5),
127.6 (C4), 127.7 (C3), 140.1 (C2), 148.6 (C1), pyrazine: 126.8
(C2), 131.4 (C3), 139.8 (C6), 160.1 (C5).
2.2.1.5. 5-(2-tert-Butylphenoxy)pyrazine-2,3-dicarbonitrile (2d). Yield
of white powder, 0.33 g (59%), m.p. 115–117 °C. ESIMS: m/z (%
rel. int.) Anal. Calc. for
278.1173. UV–Vis (DCM): kmax, nm (
IR:
, cmÀ1 2965 (CH, w), 2236 (CN, w), 1556, 1530, 1433, 1362,
C
16H14N4O (M+): 278.1168. Found:
layer chromatography (TLC) and Merck silica 63–200
lm was used
e
, MÀ1 cmÀ1) 250 (15 400).
for column chromatography. 2-Isopropyloxyphenol, 2-isopropyl-
phenol and 2-tert-butylphenol were obtained from Aldrich. 5-Chlo-
ropyrazine-2,3-dicarbonitrile (1), was prepared as in [12], and
5-chloro-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (3), was
prepared as in [13]. Compound 2a, 5-phenoxypyrazine-2,3-dicar-
bonitrile, has been reported [12], but was prepared as described
below.
m
1340, 1264, 1180, 1108, 1083, 993, 932, 791, 757. 1H NMR (CDCl3):
d, ppm 1.33 (9H, CH3, s), phenyl: 6.94 (1H, H6, dd, J6,5 = 6.0 Hz,
J6,4 = 3.5 Hz), 7.29 (1H, H4, m), 7.30 (1H, H5, m), 7.51 (1H, H3, dd,
J3,4 = 6.0 Hz, J3,5 = 3.6 Hz), pyrazine: 8.65 (1H, H6, s). 13C NMR
(CDCl3): d, ppm 30.4 (CH3), 34.7 (C(CH3)3), 112.3 and 112.9 (CN
at pyrazine C2 and C3), phenyl: 122.4 (C6), 127.0 (C4), 127.6 (C5),
128.2 (C3), pyrazine: 126.8 (C2),131.5 (C3), 140.0 (C6), 160.1 (C5).
2.2. Synthesis
2.2.1.6. 5-Phenoxy-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (4a). Yield
of lemon yellow powder 0.53 g (87%), m.p. 243–244 °C. ESIMS:
m/z (% rel. int.) Anal. Calc. for C16H9N4OS (M+H+): 305.0492. Found:
2.2.1. Compounds 2a–d and 4a–d
2.2.1.1. General procedure for the synthesis of compounds 2 and
4. Triethylamine (2.3 mmol) was added dropwise to a stirred
solution of 1 or 3 (2 mmol) and phenol, 2-isopropyloxyphenol,
2-isopropylphenol or 2-tert-butylphenol (2.2 mmol), in acetone
(20 ml). The reaction mixture was stirred at ambient temperature
for 2 h, triethylammonium chloride, which separated from the
reaction mixture, was removed by filtration. The solvent was re-
moved from the filtrate, and the crude solid was chromatographed
on silica with DCM to afford compounds 2a–d and 4a–d.
305.0501. Calc. for
322.0757. UV–Vis (DCM): kmax, nm (
IR:
, cmÀ1 3079 (CH, w), 2235 (CN, w), 1513, 1486, 1401, 1384,
C
16H12N5OS (M+NH4+): 322.0757. Found
e
, MÀ1 cmÀ1) 365 (18 500).
m
1234, 1178, 1157, 1063, 849, 806, 739, 690. 1H NMR (CDCl3): d,
ppm thiophene: 7.27 (1H, H4, dd, J4,5 = 5.0, J4,3 = 4.0) 7.78 (1H, H5,
dd, J5,4 = 5.0 Hz, J5,3 = 1.1 Hz), 8.38 (1H, H3, dd, J3,4 = 4.0 Hz,
J3,5 = 1.1 Hz), phenyl: 7.21 (2H, H2, H6, m), 7.52 (2H, H3, H5, m),
7.39 (1H, H4, m). 13C NMR (CDCl3): d, ppm 112.9 and 113.1 (CN
at pyrazine C2, C3), thiophene: 129.2 (C4), 134.2 (C3), 134.9 (C5),
136.3 (C2), phenyl: 121.4 ( C2, C6), 127.1 (C4), 130.2 ( C3, C5),
151.1 (C1), pyrazine: 126.1, 126.5 (C2, C3), 142.7 (C6), 154.9 (C5).
2.2.1.2. 5-Phenoxypyrazine-2,3-dicarbonitrile (2a). Yield of white
powder, 0.37 g (77%), m.p. 148–152 °C, lit. [12] m.p. 150–151 °C.
UV–Vis (DCM): kmax, nm 255 (14 000). 1H NMR (CDCl3): d, ppm
phenyl: 7.16 (2H, H2, H6, m), 7.37 (1H, H4, m), 7.49 (2H, H3, H5,
m), pyrazine: 8.67 (1H, H6, s). 13C NMR (CDCl3): d, ppm 112.3 and
112.9 (CN at pyrazine C2, C3), phenyl: 120.9 (C2, C6), 127.1 (C4),
130.3 (C3, C5), 151.1 (C1), pyrazine: 126.8 (C2), 131.1 (C3), 140.2
(C6), 159.8 (C5).
2.2.1.7.
5-(2-Isopropyloxyphenoxy)-6-(thiophen-2-yl)pyrazine-2,3-
dicarbonitrile (4b). Yield 0.64 g (89%) of yellow powder, m.p.
157–158 °C. ESIMS: m/z (% rel. int.). Anal. Calc. for C19H14N4O2S
(M+): 362.0837. Found: 362.0852. UV–Vis (DCM): kmax, nm (
e,
MÀ1 cmÀ1) 370 (22 000). IR: , cmÀ1 3092 (CH, w), 2237 (CN, w),
m
1513, 1490, 1431, 1406, 1384, 1253, 1109, 937, 735. 1H NMR
(CDCl3): d, ppm 1.12 (6H, CH3, d, J = 6.1 Hz), 4.53 (1H, CH(CH3)2,
sept. J = 6.1 Hz), thiophene: 7.25 (1H, H4, dd, J4,5 = 5.0 Hz,
J4,3 = 3.9 Hz), 7.76 (1H, H5, dd, J5,4 = 5 Hz, J5,3 = 1.0 Hz), 8.38 (1H,
H3, dd, J3,4 = 3.9 Hz, J3,5 = 1.0 Hz), phenoxy: 7.03 (1H, H5, m), 7.04
(1H, H3, m), 7.22 (1H, H6, ddd, J6,5 = 8.4 Hz, J6,4 = 1.7 Hz,
J6,3 = 0.8 Hz), 7.30 (1H, H4, ddd, J = 8.3 Hz, J = 7.5 Hz, J4,6 = 1.7 Hz).
13C NMR (CDCl3): d, ppm 21.9 (CH3), 71.0 (CH(CH3)2), 113.0 and
113.2 (CN at pyrazine C2, C3), thiophene: 129.1 (C4), 134.2 (C3),
134.5 (C5), 136.6 (C2), phenoxy: 114.9 (C3), 120.9 (C5), 122.5
(C6), 127.7 (C4), 141.2 (C1), 148.8 (C2), pyrazine: 126.16 (C2 or
C3), 126.27 (C2 or C3), 142.3 (C6), 155.0 (C5).
2.2.1.3. 5-(2-Isopropyloxyphenoxy)pyrazine-2,3-dicarbonitrile (2b).
Yield of white powder, 0.48 g (86%), m.p. 93–94 °C. ESIMS: m/z (%
rel. int.) Anal. Calc. for
280.0967. UV–Vis (DCM): kmax
(8700), 255 (17 000). IR:
, cmÀ1 2983 (CH, w), 2238 (CN, w),
1494, 1431, 1358, 1333, 1281, 1252, 1187, 1105, 940, 771, 757.
1H NMR (CDCl3): d, ppm 1.16 (6H, CH3, d, J = 6.1 Hz), 4.54 (1H,
CH(CH3)2, sept., J = 6.1 Hz), phenyl: 6.99 (1H, H5, m), 7.02 (1H, H3,
m), 7.16 (1H, H6, dd, J6,5 = 7.9 Hz, J6,4 = 1.5 Hz), 7.29 (1H, H4, ddd,
J = 8.5 Hz, J = 7.6 Hz, J4,6 = 1,5 Hz), pyrazine: 8.63 (1H, H6, s). 13C
NMR (CDCl3): d, ppm 21.9 (CH3), 70.9 (CH(CH3)2), 112.4 and
113.1 (CN at pyrazine C2, C3), phenyl: 114.9 (C3), 122.2 (C6),
127.9 (C4), 140.8 (C1), 148.7 (C2), pyrazine: 126.5 (C2), 131.2
(C3), 139.5 (C6), 159.8 (C5).
C
15H12N4O2 (M+): 280.0960. Found:
,
nm (e, ) 297 (sh)
MÀ1 cmÀ1
m
2.2.1.8. 5-[2-Isopropylphenoxy)]-6-(thiophen-2-yl)pyrazine-2,3-dicar-
bonitrile (4c). Yield of yellow powder 0.63 g (91%), m.p. 209–
210 °C. EIMS: m/z (% rel. int.). Anal. Calc. for C19H14N4OS (M+):
346.0888. Found: 346.0877. UV–Vis (DCM): kmax, nm (e )
, MÀ1 cmÀ1
2.2.1.4. 5-(2-Isopropylphenoxy)pyrazine-2,3-dicarbonitrile (2c). Yield
of white powder, 0.51 g (97%), m.p. 88–90 °C. ESIMS: m/z (% rel.
int.) Anal. Calc. for
375 nm (24 000). IR: m
, cmÀ1 2956 (CH, w), 2236 (CN, w), 1518,
1406, 1383, 1336, 1234, 1165, 1077, 748, 720. 1H NMR (CDCl3):
C
15H13N4O (M+H+): 265.1084. Found:
d, ppm 1.21 (6H, CH3, d, J = 6.9 Hz), 2.92 (1H, CH(CH3)2, sept.,

3232
E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
J = 6.9 Hz), thiophene: 7.28 (1H, H4, dd, J4,5 = 5.0 Hz, J4,3 = 4.0 Hz),
7.79 (1H, H5, dd J5,4 = 5.0 Hz, J5,3 = 1.1 Hz), 8.39 (1H, H3, dd,
J3,4 = 4.0 Hz, J3,5 = 1.1 Hz), phenoxy: 7.02 (1H, H6, dd, J6,5 = 8.0 Hz,
J6,4 = 1.2 Hz), 7.30 (1H, H5, app. td, J = 8 Hz, J5,3 = 1.8 Hz), 7.37
(1H, H4, app. td, J = 7.5 Hz, J4,6 = 1.2 Hz), 7.46 (1H, H3,
J3,4 = 7.5 Hz, J3,5 = 1.8 Hz). 13C NMR (CDCl3): d, ppm 23.3 (CH3),
27.4 (CH(CH3)2), 112.9 and 113.1 (CN at pyrazine C2, C3), thio-
phene: 129.3 (C4), 134.0 (C3), 134.9 (C5), 136.4 (C2), phenoxy:
121.7 (C6), 127.4 (C5), 127.50 (C3), 127.55 (C4), 140.3 (C2), 148.6
(C1), pyrazine: 126.3 (C2 or C3), 126.4 (C2 or C3), 142.4 (C6),
155.2 (C5).
(DMSO-d6): d, ppm 0.95–1.01 (CH3, multiple d), 4.6–4.7 (CH(CH3)2,
m), phenyl: 7.2–7.3 (H5, m), 7.35–7.45 (H3, m), 7.45–7.6 (H4, m),
7.55–7.75 (H6, m), pyrazine: 9.35–9.45 (H6, 3 sharp singlets). 13C
NMR (DMSO-d6): d, ppm 21–22 (CH3), 69.5–70.5 (CH(CH3)2), phe-
nyl: 115.5–116 (C3), 120.5–121.5 (C5), 123–123.5 (C6), 126–127
(C4), 142–143.5 (C1), 148.5–150 (C2), pyrazine: 137–138 (C6),
144–145 (C2), 160.5–161.5 (C5). MS (MALDI-TOF) m/z 1185.31
[M+H+]. Anal. Calc. for C60H48N16O8Zn: 1184.313 (M), for
C
60H49N16O8Zn: 1185.317 (M+H+). The expected isotopic pattern
for zinc was found at m/z (calcd. % rel. int.) 1185.31 (65), 1186.31
(57), 1187.31 (37), 1188.31 (39), 1189.31 (25).
2.2.1.9. 5-[2-tert-Butylphenoxy)]-6-(thiophen-2-yl)pyrazine-2,3-dicar-
2.2.2.4. [Tetra(2-isopropylphenoxy)-(octazaphthalocyaninato)]zinc(II)
bonitrile (4d). Yield of yellow powder 0.53 g (73%), m.p. 214–
(5c). Yield of purple-black powder 0.10 g (42%). UV–Vis (DMSO):
216 °C. ESIMS: m/z (% rel. int.). Anal. Calc. for
(M+H+): 361.1118. Found: 361.1116. UV–Vis (DCM): kmax, nm (
MÀ1 cmÀ1) 375 nm (22 000). IR: , cmÀ1 2953 (CH, w), 2235 (CN,
C
20H17N4OS
kmax 635 (118 000), 575 (26 000), 355
,
nm
(
e
,
MÀ1 cmÀ1
)
e,
(85 000).). IR: m
, cmÀ1 2916, 2849 (CH, w), 1730, 1481, 1341,
m
1321, 1290, 1176, 1069, 985, 747, 618. 1H NMR (DMSO-d6): d,
ppm 1.3–1.4 (CH3, multiple d), 3.3–3.45 (CH(CH3)2, m), phenyl:
7.4–7.65 (H4 and H5, m), 7.6–7.75 (H6, m), 7.65–7.75 (H3, m), pyr-
azine: 9.25–9.45 (H6 multiplets). 13C NMR (DMSO-d6): d, ppm 22–
23 (CH3), 26.5–27.5 (CH(CH3)2), phenyl: 122–123 (C6), 126–127.5 (
C4, C5), 126.5–127.5 (C3), 139.5–142 (C2), 149.5–151 (C1), pyra-
zine: 137–138 (C6). MS (MALDI-TOF) m/z 1121.38 [M+H+]. Anal.
w), 1509, 1429, 1403, 1384, 1232, 1168, 1080, 756, 731. 1H NMR
(CDCl3): d, ppm 1.33 (9H, CH3, s), thiophene: 7.27 (1H, H4, dd,
J4,5 = 5.0 Hz, J4,3 = 4.0 Hz), 7.78 (1H, H5, dd, H5,4 = 5.0 Hz,
J5,3 = 1.1 Hz), 8.41 (1H, H3, dd, J3,4 = 4.0 Hz, J3,5 = 1.1 Hz), phenoxy:
6.87 (1H, H6, m), 7.30 (1H, H5, m), 7.31 (1H, H4, m), 7.55 (1H,
H3, m). 13C NMR (CDCl3): d, ppm 30.9 (CH3), 34.7 (C(CH3)3), 112.8
and 113.1 (CN at pyrazine C2, C3), thiophene: 129.2 (C4), 133.9
(C3), 134.8 (C5), 136.3 (C2), phenoxy: 123.2 (C6), 126.9 (C4),
127.7 (C5), 128.3 (C3), 141.6 (C2), 150.4 (C1), pyrazine: 126.46
(C2 or C3), 126.52 (C2 or C3), 142.8 (C6), 155.8 (C5).
Calc. for:
C60H48N16O4Zn 1120.33 (M), for C60H49N16O4Zn
1121.34. The expected isotopic pattern for zinc was found at m/z
(calcd. % rel. int.) 1121.4 (65), 1122.4 (57), 1123.4 (37), 1124.4
(39), 1125.4 (25), 1126.4 (8).
2.2.2. Compounds 5a–d and 6a–d
2.2.2.5.
(II) (5d). Yield of purple-black powder 0.07 g (33%). UV–Vis
(DMSO): kmax, nm (
, MÀ1 cmÀ1) 635 (135 000), 575 (30 000), 360
(94 000). IR:
, cmÀ1 2960 (CH, w), 1531, 1479, 1439, 1341, 1320,
[Tetra(2-tert-butylphenoxy)-(octazaphthalocyaninato)]zinc
2.2.2.1. General procedure for the synthesis of compounds 5 and
6. Compound 2a–d or 4a–d (0.8 mmol), Zn(quinoline)2Cl2
(0.4 mmol) and freshly distilled quinoline (0.4 ml) were trans-
ferred to a round bottom flask. The stirred reaction mixture was
flushed with nitrogen for 15 min at ambient temperature, and
heated under nitrogen at 170–175 °C for 2 h. The dark semi-solid
was sonicated with diethyl ether, and the collected dark solid
was stirred with methanol (20 ml) for 1 h at ambient temperature
in order to remove unreacted zinc salt. The crude solid was dis-
solved in a small amount of DCM and applied to a silica column.
DCM eluted a small amount of yellow impurities. Compounds 5a
and 6a were eluted with a mixture of DCM and DMF (9:1), com-
pounds 5b and 6b–d were eluted with a mixture of DCM and ace-
tone (4:1), whereas 5c and 5d were eluted with MeCN. The dark
powders were dried at 0.1 mm Hg for 5 h at ambient temperature.
e
m
1279, 1185, 1085, 1069, 984, 915, 875, 747, 718. 1H NMR
(DMSO-d6): d, ppm 1.5–1.6 (CH3, 6 partly resolved singlets), phenyl:
7.1–7.9 (H3, H4, H5, H6, m), pyrazine: 9.25–9.45 (H6, multiplets).
13C NMR (DMSO-d6): d, ppm 29.5–30.5 (CH3), phenyl: 123–128
(C4, C5, C6), 127–128 (C3), 140–142 (C2), 151–152 (C1), pyrazine:
137.5–138.5 (C6). MS (MALDI-TOF) m/z 1177.43 [M+H+]. Anal. Calc.
for C64H56N16O4Zn: 1176.40 (M), for C64H57N16O4Zn: 1177.40
(M+H+). The expected isotopic pattern for zinc was found at m/z
(calcd. % rel. int.) 1176.4 (100), 1177.4 (69), 1178.4(57), 1179.4
(40), 1180.4 (39), 1181.4 (27).
2.2.2.6. [Tetra(phenoxy)-tetra(thiophen-2-yl)-(octazaphthalocyanina-
to)]zinc(II) (6a). Yield of black powder 0.09 g (35%). UV–Vis
2.2.2.2. [Tetra(phenoxy)-(octazaphthalocyaninato)]zinc(II) (5a). Yield
(DMSO): kmax
(103 000), 600 (33 000), 385 (106 000). IR: m
,
nm
(
e
,
MÀ1 cmÀ1
)
665 (111 000), 650, sh
of dark blue powder 0.1 g (51%), UV–Vis (DMSO): kmax, nm (
MÀ1 cmÀ1) 635 (124 000), 575 (27 000), 360 (88 000). UV–Vis (pyr-
idine): kmax, nm (
, MÀ1 cmÀ1) 695 (20 000), 640 (64 000), 580
(19 000), 365 (66 160). IR:
, cmÀ1 3063 (CH, w), 1531, 1482,
e,
, cmÀ1 3071 (CH, w),
1489, 1414, 1376, 1360, 1319, 1237, 1202 (sh), 1107, 1050, 962,
918, 843, 794, 744, 906, 686. 1H NMR (DMSO-d6): d, ppm phenyl:
7.55–7.8 (H4, m), 7.65–7.85 (H3 and H5, m), 7.7–8.1 (H2 and H6
m), thiophene: 7.35–7.5 (H4, m), 8.0–8.2 (H5, m), 8.4–8.65 (H3,
m). 13C NMR (DMSO-d6): d, ppm phenyl: 121.5–122.5 ( C2, C6),
125–126 (C4), 129.5–130.5 ( C3, C5), thiophene: 128.5–129 (C4),
130.5–131.5 (C3), 131.5–132 (C5). MS (MALDI-TOF) m/z 1281.08
[M+H+]. Anal. Calc. for C64H32N16O4S4Zn: 1280.097 (M), for
e
m
1342, 1322, 1286, 1191, 1172 (sh), 1096, 1070, 985, 760, 747,
717, 688. 1H NMR (DMSO-d6): d, ppm phenyl: 7.5–7.75 (H4, broad
m), 7.65–7.85 (H3, H5, broad m), 7.7–8.0 (H2, H6, broad m), pyra-
zine: 9.1–9.45 (H6, four broad signals). 13C NMR (DMSO-d6): d,
ppm phenyl: 121.5–122 (C2, C5), 125–126 (C4), 129.5–130.5 (C3,
C5), pyrazine: 137.5–138.5 (C6). MS (MALDI-TOF) m/z 953.20
[M+H+]. Anal. Calc. for C48H24N16O4Zn: 952.146 (M), for
C
64H33N16O4S4Zn: 1281.100 (M+H+). The expected isotopic pattern
for zinc was found at m/z (calcd. % rel. int.) 1281.08 (69), 1282.08
(57), 1283.08 (40), 1284.09 (39), 1285.09 (27), 1286.09 (9),
1287.09 (5).
C
48H25N16O4Zn: 953.15 (M+H+). The expected isotopic pattern for
zinc was found at m/z (calcd. % rel. int.) 953.20 (52), 954.20 (57),
955.19 (30), 956.19 (39), 957.19 (20), 958.19 (5).
2.2.2.7. [Tetra(2-isopropyloxyphenoxy)-tetra(thiophen-2-yl)(octazaph-
2.2.2.3. 3[Tetra(2-isopropyloxyphenoxy)-(octazaphthalocyaninato)]
thalocyaninato)]zinc(II) (6b). Yield of black powder 0.15 g (49%).
zinc(II) (5b). Yield of purple-black powder 0.13 g (53%). UV–Vis
UV–Vis (DMSO): kmax, nm (
(33 000), 385 (126 000). UV–Vis (pyridine): kmax, nm (
725 (11 000), 665 (124 000), 655, sh (119 000), 600 (32 000), 385
(126 000). IR:
, cmÀ1 2976 (CH, w), 1492, 1416, 1360, 1335,
e
, MÀ1 cmÀ1) 660 (133 000), 595
(DMSO): kmax, nm (
(85 000). IR:
, cmÀ1 2975 (CH, w), 1532, 1487, 1341, 1321,
11285, 1185, 1172, 1111, 1069, 986, 950, 740, 707. 1H NMR
e
, MÀ1 cmÀ1) 635 (121 000), 575 (28 000), 355
e )
, MÀ1 cmÀ1
m
m

E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
3233
1246, 1173, 1109, 1051, 952, 846, 792, 743, 709. 1H NMR (DMSO-
d6): d, ppm 0.91–1.01 (CH3, 14 sharp signals (0.913–1.008) which
are ascribed to doublets with J = 5.5–6.0 Hz); 4.58–4.71
2.3. X-ray crystallographic studies
7
Compounds 4a and 4b were synthesized as described in para-
graphs 2.2.1.1. (general), 2.2.1.6. (4a) and 2.2.1.7. (4b). Single crys-
tals, in both cases of light yellow colour, were obtained by slow
evaporation of solutions in acetonitrile, for 4b a small admixture
of dichloromethane proved useful. Data for both compounds were
collected with a Nonius KappaCCD diffractometer, equipped with a
rotating anode generator. Programs used for the various crystallo-
graphic operations were, for data collection: COLLECT [14], data
reduction: Denzo-SMN [15], absorption correction: Denzo [16],
structure solution by direct methods: SHELXS-97 [17], structure
refinement: SHELXL-97 [18], and graphics: ORTEP-3 [19].
A summary of crystallographic parameters, and parameters for
data collections and structure refinements is given in Table 1.
Compound 4a showed disorder in the thiophene ring compris-
ing two distinct sites, one major (A ring) and one minor (B ring)
site. The occupancies of the two rings refined to 0.748 (2), and
0.252 (2), respectively, corresponding to a ratio A:B ꢀ 3:1. For the
refinement the atomic positions C(11A) and C(11B) were con-
strained to coincide, atomic displacement parameters (ADPs) of
the other B atoms were made equal to those for the parent A atoms,
and a weak restraint was imposed on the bond lengths of the B
ring.
(CH(CH3)2, two overlapping septets; one septet centered at 4.61,
and the other centered at 4.68, J = 5.4 Hz); phenyl: 7.25–7.4 (H5,
m), 7.35–7.5 (H3, m), 7.5–7.7 (H4, m), 7.65–7.95 (H6, m), thio-
phene: 7.45–7.55 (H4, m), 8.1–8.2 (H5, m), 8.55–8.75 (H3, four d,
8.574, 8.606, 8.677, 8.706; all with J = 3.6 Hz). 13C NMR (DMSO-
d6): d, ppm 21–22 (CH3), 69.5–70.5 (CH(CH3)2), phenyl: 115.5–
116.5 (C3), 120.5–121.5 (C5), 123–124 (C6), 126–127.5 (C4), 143–
144 (C1), 148–149.5 (C2), thiophene: 128.5–129 (C4), 131–131.5
(C3), 131.5–132 (C5), 139–140.5 (C2). MS (MALDI-TOF) m/z
1513.24 [M+H+]. Anal. Calc. for C76H56N16O8S4Zn: 1512.2641 (M),
for C76H57N16O8S4Zn: 1513.2675 (M+H+). The expected isotopic
pattern for zinc was found at m/z (calcd. % rel. int.) 1513.24 (82),
1514.24 (57), 1515.24 (47), 1516.24 (39), 1517.24 (32), 1518.24
(13), 1519.25 (7).
2.2.2.8. [Tetra(2-isopropylphenoxy)-tetra(thiophen-2-yl)-(octazaph-
thalocyaninato)]zinc(II) (6c). Yield of dark green powder 0.07 g
(32%). UV–Vis (DMSO): kmax, nm (
600 (40 000), 385 (136 000). UV–Vis (pyridine): kmax, nm (
MÀ1 cmÀ1) 665 (159 000), 600 (38 000), 390 (131 000). IR:
e
, MÀ1 cmÀ1) 660 (158 000),
e,
m,
cmÀ1 2961, 2855 (CH, w), 1415, 1375, 1360, 1334, 1233, 1169,
1105, 1080, 1049, 963, 832, 793, 745, 704. 1H NMR (DMSO-d6): d,
ppm 1.3–1.5 (CH3, five doublets of approximately equal intensity:
(1.311, J = 6.6 Hz, 1.339 J = 6.78 Hz, 1.344 J = 6.8 Hz, 1.428
J = 6.8 Hz, 1.458 J = 6.8 Hz); 3.35–3.55 (CH(CH3)2, three septets:
3.362 J = 6.6 Hz, 3.479 J = 6.9 Hz, 3.526 J = 7 Hz); phenyl: 7.6–7.85
(H6, m); 7.5–7.85 (H3, H4, H5, m); thiophene: 7.5–7.6 (H4); 8.17–
8.22 (H5, m), 8.55–8.75 (H3, four doublets: 8.589 J = 3.6 Hz, 8.624
J = 3.4 Hz, 8.715 J = 3.7 Hz, 8.742 J = 3.5 Hz). ROESY shows the fol-
lowing connections between the methyl 1H signals of the isopropyl
groups and the 1H signals for thiophene-H3: 1.311/8.589; 1.339
and 1.344/8.715; 1.428/8.624; 1.458/8.742. MS (MALDI-TOF) m/ z
1449.306 [M+H+]. Anal. Calc. for C76H56N16O4S4Zn: 1448.28 (M),
for C76H57N16O4S4Zn: 1449.29 (M+H+). The expected isotopic pat-
tern for zinc was found at m/z (calcd. % rel. int.) 1449.3 (82),
1450.3 (57), 1451.3 (47), 1452.3 (39), 1453.3 (32), 1454.3 (13),
1455.3 (6).
No restraints were required in the refinement of structure 4b.
Non-H atoms were refined anisotropically in both structures.
The H atoms were calculated and refined as riding atoms using iso-
tropic ADPs. Full-matrix least-squares refinements were based on
F2 using all reflections.
Table 2 contains a selection of structure data.
3. Results and discussion
3.1. Synthesis and characterization
3.1.1. Precursors 2a–d and 4a–d
The trisubstituted 5-(aryloxy)pyrazine-2,3-dicarbonitriles (2a–d),
i.e. 5-phenoxypyrazine-2,3-dicarbonitrile (2a), 5-(2-isopropyloxy-
phenoxy)pyrazine-2,3-dicarbonitrile (2b), 5-(2-isopropylphen-
oxy)pyrazine-2,3-dicarbonitrile (2c) and 5-(2-tert-butylphenoxy)
pyrazine-2,3-dicarbonitrile (2d), were obtained in 59–97% yields
from reactions of 5-chloropyrazine-2,3-dicarbonitrile (1) with
phenol, 2-isopropyloxyphenol, 2-isopropylphenol or 2-tert-butyl-
phenol, and triethylamine in acetone at ambient temperature
(Scheme 1). Compounds 4a–d, namely 5-phenoxy-6-(thiophen-2-yl)
pyrazine-2,3-dicarbonitrile (4a), 5-(2-isopropyloxyphenoxy)-6-
(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (4b), 5-(2-isopropyl-
phenoxy)-6-(thiophen-2-yl)-2,3-dicarbonitrile (4c) and 5-(2-tert-
butylphenoxy)-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitrile (4d),
were obtained in 73–91% yields by the same procedure (Scheme 1).
Melting points of aryloxy-substituted compounds 2 are influ-
enced by the R-substituents on the phenoxy groups (Scheme 1).
Thus, the isopropyloxy group of 2b lowers the melting point from
150 °C for 2a to 93 °C for 2b. A similar shift is observed for com-
pounds 4, i.e. 4a melts at 243 °C and 4b at 157 °C. Good solubility
in organic solvents, and absence of aggregation, are expected fea-
tures of low-melting compounds. The isopropyloxy groups of 2b
and 4b appear to be more effective than the non-polar isopropyl-
or tert-butyl groups in this respect.
2.2.2.9. [Tetra(2-tert-butylphenoxy)-tetra(thiophen-2-yl)-(octazaph-
thalocyaninato)]zinc(II) (6d). Yield of dark green powder 0.10 g
(42%). UV–Vis (DMSO): kmax, nm (
600 (30 000), 390 (100 000). UV–Vis (pyridine): kmax, nm (
MÀ1 cmÀ1) 665 (139 000), 600 (35 000), 390 (119 000)%. IR:
e
, MÀ1 cmÀ1) 660 (120 000),
e,
m,
cmÀ1 2955 (CH, w), 1519 (w), 1415, 1359, 1333, 1248, 1231,
1174, 1106, 1082, 1049, 962, 821, 793, 746, 706. 1H NMR
(DMSO-d6): d, ppm 1.46–1.58 (CH3, eight singlets of approximately
equal intensity: 1.463, 1.468, 1.506, 1.511, 1.528, 1.532, 1.572,
1.575); phenyl: 7.55–7.7 ( H4, H5, m), 7.6–7.85 (H6, m), 7.7–7.8
(H3, m), thiophene: 7.5–7.6 (H4, m), 8.15–8.25 (H5, m), 8.55–8.75
(H3, four doublets of equal intensity: (8.562 J = 3.5 Hz, 8.600
J = 3.3 Hz, 8.691 J = 3.4 Hz, 8.728 J = 3.3 Hz). ROESY showed the fol-
lowing connection between the tert-butyl 1H signals and the 1H
signals of thiophene-H3: 1.463, 1.468/8.562; 1.506, 1.511/8.691;
1.528, 1.532/8.600; 1.572, 1.575/8.728. 13C NMR (DMSO-d6): d,
ppm 30–31 (CH3, ca. 34 (C(CH3)3), phenyl: 124–125 (C6), 125–
128 ( C4, C5), 127–128 (C3), 141 (C2), 151–152 (C1), thiophene:
128.9 (C4), 130–131.1 (C3, HSQC connection between four 1H
and 13C signals: 8.728/131.1, 8.691/130.0, 8.600/131.0, 8.562/
130.9), ca. 132 (C5), ca. 140 (C2). MS (MALDI-TOF) m/z 1505.368
[M+H+]. Anal. Calc. for C80H64N16O4S4Zn: 1504.35 (M), for
The thiophen-2-yl substituents of compounds 4 are expected to
extend the conjugated system of compounds 2. UV–Vis spectra
confirm the anticipated effect; the strongest absorptions of com-
pounds 2 are found at 255 nm, whereas the corresponding absorp-
tions of 4 are observed at 365–370 nm.
C
80H65N16O4S4Zn 1505.35 (M+H+). The expected isotopic pattern
for zinc was found at m/z (calcd. % rel. int.) 1505.4 (87), 1506.4
(57), 1507.4 (50), 1508.4 (39), 1509.4 (33), 1510.4 (14), 1511.4 (6).

3234
E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
Table 1
Summary of crystallographic parameters, data acquisition and refinement data for 4a and 4b.
Compound
4a
4b
Composition
Formula weight, Mr
C
16H8N4OS
C19H14N4O2S
362.40
304.32
Mp (K)
516–517
monoclinic, P21/n
223(2)
430-431
monoclinic, P21/n
223(2)
Crystal system, space group
T (K)
Unit cell dimensions
a (Å)
b (Å)
c (Å)
b (o)
6.8886(2)
20.2377(5)
10.0773(3)
95.031(1)
1399.46(7)
1.444
5.6855(1)
20.6918(4)
14.7598(3)
98.547(1)
1717.11(6)
1.402
V (Å3)
Dcalc (Mg mÀ3
)
Molecules per unit cell, Z
k (Å)
4
4
0.71073
0.71073
Crystal size (mm)
Absorption coefficient,
0.42 Â 0.20 Â 0.08
0.30 Â 0.17 Â 0.15
l )
(mmÀ1
0.238
0.210
Transmission, minimum/maximum
0.907/0.981
0.940/0.969
Scan modes
x
0.66
96.6
and
u
x and u
0.66
97.5
Resolution, smax sinh/k (ÅÀ1
)
Completeness within smax (%)
Total no. of reflections/unique reflections
9161/3254 [Rmerge(all) = 0.059]
2573
10112/3999 [Rmerge(all) = 0.047]
3171
Unique reflections with F2 > 2 (F2) (NO)
r
No. of reflections/restraints/variables (NV)
3254/10/212
3999/0/237
Final R indices (F2 > 2 (F2))
r
R(F) = 0.0687; wR(F2) = 0.1482
R(F) = 0.0877; wR(F2) = 0.1604
0.0337/1.58
R(F) = 0.0631; wR(F2) = 0.1358
R(F) = 0.0811; wR(F2) = 0.1494
0.0342/2.16
Final R indices (all data)
Weight parameters wA and wB
Goodness-of-fit (GOF) on F2
1.091
À0.25/0.30
1.077
À0.36/0.28
Extrema in residual electron density (eÁÅÀ3
)
w = 1/[
R(F) =
wR(F2) = {
GOF = [
r
2(Fo2) + (wA Ã P)2 + wB Ã P] where P = (Max (Fo2, 0) + 2 Ã Fc2)/3.
R
||Fo| À |Fc||/
R|Fo|.
2
R
[w(Fo À Fc2)2]/
R .
[w(Fo2)2]}1/2
w(Fo À Fc2)2/(NO À NV)]1/2
.
2
R
3.1.2. Zinc(II) azaphthalocyanines 5a–d and 6a–d obtained from
cyclotetramerization of precursors 2a–d and 4a–d
Noncoplanarity is expected between the aryloxy groups and
the macrocyclic core. Consequently, these substituents should
provide space between stacked macrocycles, leading to less
aggregation and enhanced solubility. Due to their smaller steric
requirements the unsubstituted phenoxy groups of 5a and 6a
should have limited influence on aggregation, and these com-
pounds were synthesized as references for 5b–d and 6b–d,
respectively. The bulky, ortho-substituted phenoxy groups of
5b–d and 6b–d are expected to increase the distance between
stacked macrocycles, and to be more effective in preventing
aggregation. The absence of aggregation would become evident
One well-known method for direct synthesis of zinc(II) com-
plexes of phthalocyanines, or azaphthalocyanines, is to heat quin-
oline solutions of zinc(II) acetate and substituted phthalonitriles or
pyrazine-2,3-dicarbonitriles. However, since reactions of zinc(II)
acetate and quinoline with pyridin-3-yloxy substituted pyrazine-
2,3-dicarbonitriles resulted in extensive decomposition [10], we
decided to use the salt Zn(quinoline)2Cl2, prepared from zinc(II)
chloride and quinoline, for cyclotetramerizations of compounds 2
and 4. The synthesis and structure of ZnAzaPc 5 and 6 is shown
in Scheme 2. A moderate reaction temperature, i.e. 170–175 °C,
was considered best for these cyclotetramerizations in order to
suppress possible loss of the aryloxy substituents. However, due
to high melting points of thiophen-2-yl substituted monomers 4a
(243 °C) and 4d (214 °C), a small amount of quinoline was added
to each reaction mixture in order to keep reaction conditions con-
stant for these cyclotetramerizations. Thus, precursors 2 and 4
were heated with Zn(quinoline)2Cl2 and a small amount of quino-
line for 2 h at 170–175 °C. ZnAzaPc 5 and 6 were obtained in rea-
sonable yields after purification by chromatography on silica. In
order to compensate for the electron-donating, and expected deac-
tivating effect of thiophene, longer reaction times were tested for
reactions of 4. However, compounds 6 were not obtained in higher
yields. The immediate appearance of yellow-orange, then reddish-
brown colours for reaction solutions of 4, indicate some decompo-
sition or polymerisation. The cyclotetramerizations of 2, however,
immediately gave green-blue coloured solutions that turned dark
within a couple of minutes.
from both shape and position of the Q-bands of these 18-
p elec-
tron macrocycles.
Thiophene substituents of compounds 6 were introduced in or-
der to induce red-shifted Q-bands; i.e. thiophene and the macrocy-
cle are expected to form an extended p-electron system. Q-bands
at 660–665 nm were measured for DMSO solutions of compounds
6, and this Q-band red-shift of 25–30 nm is ascribed to the thio-
phene substituents. The shape is somewhat different for the
absorption spectra of compounds 6 and 5. A descending line is ob-
served in the 400–500 nm area for compounds 5, whereas a long
shoulder appears in the same area for compounds 6, as shown in
Fig. 1, for 5b and 6b. Consequently, solutions of 5 are blue-green,
but solutions of compounds 6 are grass-green in most organic
solvents.
A third factor, which would presumably also affect UV–Vis
absorptions of the unsymmetrically substituted macrocycles 5
and 6, is the formation of structural isomers. Broad and
unsymmetric Q-bands would be expected for this reason, as well
as from aggregation. In fact, the Q-bands for all the DMSO solutions
of 5 and 6 are slightly rounded and asymmetric, indicating the
presence of more than one structural isomer as shown for 5b and
6b (Fig. 1).
3.1.3. UV–Vis absorption of macrocycles 5 and 6
The peripheral substituents of compounds 5 and 6 will induce
shifted UV–Vis absorptions compared to unsubstituted ZnAzaPc.

E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
3235
Table 2
Selected bond lengths (Å) and bond angles (°) with esd’s in parentheses for 4a and 4b.
4a
4b
Bond lengths
C(1)–C(2)
C(2)–N(3)
N(3)–C(4)
C(4)–C(5)
C(5)–N(6)
N(6)–C(1)
C(4)–C(41)
C(41)–N(42)
C(5)–C(51)
C(51)–N(52)
1.432 (4)
1.305 (3)
1.343 (3)
1.378 (4)
1.344 (3)
1.330 (3)
1.443 (4)
1.136 (4)
1.446 (4)
1.133 (4)
1.436 (3)
1.310 (3)
1.343 (3)
1.383 (3)
1.344 (3)
1.329 (3)
1.437 (3)
1.141 (3)
1.442 (3)
1.141 (3)
C(1)–C(11)
C(11)–S(12)
S(12)–C(13)
C(13)–C(14)
C(14)–C(15)
C(15)–C(11)
1.448 (4)/1.448 (4)*
1.729 (3)/1.705 (5)*
1.721 (5)/1.729 (11)*
1.356 (5)/1.358 (9)*
1.356 (8)/1.356 (12)*
1.358 (6)/1.343 (10)*
1.451 (3)
1.719 (3)
1.698 (3)
1.350 (4)
1.417 (4)
1.388 (3)
C(2)–O(21)
O(21)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(24)–C(25)
C(25)–C(26)
C(26)–C(21)
C(22)–O(22)
O(22)–C(27)
C(27)–C(28)
C(27)–C(29)
1.336 (3)
1.416 (3)
1.360 (4)
1.416 (6)
1.357 (6)
1.348 (6)
1.376 (4)
1.361 (4)
1.342 (3)
1.410 (3)
1.387 (4)
1.396 (4)
1.375 (4)
1.376 (4)
1.383 (4)
1.374 (4)
1.366 (3)
1.455 (3)
1.497 (4)
1.502 (4)
Bond angles
C(2)–C(1)–N(6)
C(1)–C(2)–N(3)
C(2)–N(3)–C(4)
N(3)–C(4)–C(5)
C(4)–C(5)–N(6)
C(5)–N(6)–C(1)
C(4)–C(41)–N(42)
C(5)–C(51)–N(52)
118.9 (2)
123.3 (2)
116.6 (2)
121.6 (3)
121.9 (2)
117.8 (2)
178.8 (3)
178.3 (3)
119.1 (2)
123.0 (2)
116.6 (2)
121.7 (2)
121.7 (2)
117.9 (2)
177.2 (3)
177.9 (3)
N(6)–C(1)–C(11)
C(2)–C(1)–C(11)
117.3 (2)/117.3 (2)*
123.8 (2)/123.8 (2)*
118.4 (2)/123.1 (2)*
133.7 (3)/127.4 (6)*
107.9 (3)/109.4 (6)*
91.4 (2)/90.6 (7)*
116.9 (2)
124.0 (2)
117.9 (2)
131.1 (2)
111.1 (2)
92.0 (1)
112.3 (2)
113.3 (2)
111.4 (2)
Fig. 1. (a) UV–Vis absorption spectrum of compound 5b dissolved in DMSO,
concentration 0.018 mg/ml DMSO (1.5 Â 10À5 M). Blue-green solution. (b) UV–Vis
absorption spectrum of compound 6b dissolved in DMSO, concentration 0.024 mg/
ml DMSO (1.7 Â 10À5 M). Grass-green solution.
C(1)–C(11)–S(12)
C(1)–C(11)–C(15)
C(15)–C(11)–S(12)
C(11)–S(12)–C(13)
S(12)–C(13)–C(14)
C(13)–C(14)–C(15)
C(14)–C(15)–C(11)
112.2 (5)/112.2 (12)*
110.6 (6)/109.9 (13)*
117.9 (6)/117.6 (10)*
different orientations of each of the four constituents of macrocy-
cles 5 and 6, there is a total of 16 (24) possible combinations. By
drawing all combinations it is obvious that there are four possible
isomers and in total eight different sets of chemical shifts, e.g. pyr-
azine-H6 signals of 5. If the macrocycles are arbitrarily formed, the
eight different sets of NMR signals are expected to be equally
intense.
C(2)–O(21)–C(21)
C(26)–C(21)–C(22)
C(21)–C(22)–C(23)
C(22)–C(23)–C(24)
C(23)–C(24)–C(25)
C(24)–C(25)–C(26)
C(25)–C(26)–C(21)
118.7(2)
123.1 (3)
117.0 (4)
119.5 (4)
121.7 (4)
120.0 (4)
118.6 (3)
118.2 (2)
122.1 (2)
118.0 (3)
120.1 (3)
120.8 (3)
120.1 (3)
118.9 (3)
Compounds 5. The peripheral pyrazine-H6 atoms of compounds
5a–d show the following: 1H NMR signals: 5a: 9.1–9.45 ppm (two
broad and two sharp singlets), 5b: 9.35–9.45 ppm (three sharp
singlets), 5c: 9.25–9.45 ppm (four partly overlapping broad sing-
lets), 5d: 9.25–9.45 ppm (three broad singlets). We conclude from
these observations that aggregation is the origin of the broad sig-
nals of 5a, 5c and 5d, whereas there is no evidence of aggregation
for 5b. Apparently each of compounds 5a–d is formed as several
structural isomers since several 1H NMR singlets were observed
for their pyrazine-H6 atoms. 1H NMR signals of the phenoxy
ortho-substituents (R) of compounds 5b–d are informative as well.
About seven doublets at 0.95–1.0 ppm are observed for the isopro-
pyloxy-methyl groups of 5b, and a multiplet at 4.6–4.7 ppm for the
isopropyloxy-methine hydrogens. The 1H signals from the isopro-
pyl groups of 5c are several apparent doublets at 1.3–1.4 ppm for
the methyl hydrogens, and a multiplet at 3.3–3.45 ppm for the
methine hydrogens. The methyl hydrogens of the tert-butyl groups
of 5d appear as six, partly unresolved, singlets at 1.5–1.6 ppm.
*
First value applies for A ring (major), second value for B ring (minor). C(11A) and
C(11B) are constrained to superpose.
3.1.4. NMR analysis of macrocycles 5 and 6
Whereas dilute solutions were used for UV–Vis spectroscopy,
the NMR solutions had to be far more concentrated (approximately
10À3 M), and therefore aggregation became a problem. Compounds
5 and 6 are soluble in chloroform, dichloromethane and DMSO, but
only DMSO-d6 was used for the NMR analyses of 5 and 6 in order to
minimise aggregation. Identifications of the 1H NMR and corre-
sponding 13C NMR signals were made by using the pulse tech-
niques COSY, ROESY, HSQC and HMBC. Multiple 1H NMR signals
may occur for several of the hydrogen atoms of compounds 5
and 6 due to the possibility of structural isomerism. With two

3236
E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
Compounds 6. 1H NMR signals similar to those of 5b are ob-
showed close spatial connection between the phenoxy-tert-butyl
groups and the thiophene-H3 hydrogens, analogous to the connec-
tion between the isopropyl group and the thiophene-H3 hydrogens
of 6c.
served for the isopropyloxy groups of 6b. Seven doublets at 0.91–
1.01 ppm (J = 5.5–6.0 Hz), are observed for the respective methyl
groups, and two overlapping septets are observed at 4.58–
4.71 ppm (J = 5.4 Hz), for the methine hydrogens of 6b. The
thiophene-H3 signals of 6b are observed as four doublets at
8.55–8.75 ppm (J = 3.6 Hz). Similar observations are made for 6c
where the methyl signals of the isopropyl groups are five doublets
at 1.3–1.5 ppm (J = 6.6–6.8 Hz). The methine signals of the isopro-
pyl groups are three septets at 3.35–3.55 ppm (J = 6.6–7 Hz). The
thiophene-H3 signals are four doublets of about equal intensities
at 8.55–8.75 ppm (J = 3.4–3.7 Hz). The ROESY experiment showed
NOE transfer between the isopropyl-methyl protons and the H3
protons of thiophene, linking together chemical shifts belonging
to the same isomer. Eight sharp 1H NMR singlets are observed at
1.46–1.58 ppm for the tert-butyl-methyl hydrogens of 6d, and thi-
ophene-H3 signals appear as four doublets of about equal intensity
at 8.55–8.75 ppm, (J = 3.3–3.5 Hz). The ROESY pulse technique
3.1.5. Mass spectrometry of macrocycles 5 and 6
Mass spectrometry (MALDI-TOF) of compounds 5 and 6 show
the calculated molecular ions with the expected isotopic clusters
characteristic of zinc. The compounds were dissolved in dichloro-
methane, spotted onto the target plate and dried at ambient tem-
perature before being covered with matrix and injected into the
spectrometer.
3.1.6. Crystal structures of compounds 4a and 4b
Similar projections of the two molecules with the atomic num-
bering are shown in Fig. 2(a) and (b). Common to both are three
rings, pyrazine, thiophene and a phenoxy ring, denoted in the fol-
lowing as rings I, II and III, respectively. The disorder of the thio-
phene rings of 4a can be described as
a 180° rotational
isomerism defined by rings A and B that occur in the ratio 3:1.
The juxtaposed rings are nearly coplanar. For the calculations of
conformation involving ring II in 4a we have used the more precise
atomic coordinates of the major A ring. Rings I and II are almost ex-
actly coplanar in 4a, the interplanar angle being ꢀ3°. Ring III makes
an angle of about 83° with ring II, thus there is a nearly orthogonal
arrangement of the rings in this structure. In 4b ring II is rotated
slightly clockwise about the C(1)–C(11) bond vector making the
interplanar angle between I and II about 12°. Ring III is rotated
more away from orthogonality with ring II than in 4a, the interpla-
nar angle between III and II being ꢀ69°. The combined effect of
these rotations is to relieve close contacts between ring II and
the isopropyloxy group of ring III. Fig. 3(a) and (b) illustrate the
Fig. 2. Molecular conformation of compounds 4a in (a) and 4b in (b) with atomic
numbering. Disorder in 4a corresponds to a 180° rotational isomerism in the
thiophene ring. The ratio of rings A to B is 3:1. ADP ellipsoids represent a 50%
probability.
Fig. 3. Comparison of the orientation of the three rings I, II and III, in 4a in (a) and
4b in (b). The planes of the thiophene (II) and the phenoxy (III) rings are both very
nearly parallel to the line of projection in the figures.

E.H. Mørkved et al. / Polyhedron 29 (2010) 3229–3237
3237
differences in conformation between structures 4a and 4b. In these
figures the planes of both rings II and III are very nearly parallel to
the line of projection.
of the 1H NMR signals from the thiophene-H3 atoms of these com-
pounds. The lower tendency for aggregation of compound 5b com-
pared to 5c and 5d, points to the isopropyloxy group as the
preferred phenoxy substituent. The thiophen-2-yl peripheral sub-
stituents of compounds 6a–d induce red-shifted Q-bands to 660–
665 nm for compounds 6, from 635 nm for compounds 5.
The structure study of 4a and 4b shows that the presence of a
bulky isopropyloxy ortho-substituent in the phenoxy group in 4b
has induced a small rotation of the thiophene ring from coplanarity
with the pyrazine ring as found in 4a, and a further rotation of the
phenoxy ring away from orthogonality compared with the confor-
mation in 4a. Both changes serve to accommodate the isopropyl-
oxy group which appears to prevent the 180° rotational
isomerism of the thiophene ring that was found in 4a.
Atoms O(21) and H(15) are nearly eclipsed in both structures,
the distance between these atoms is 2.26 Å in 4a and 2.30 Å in
4b. In the disordered 4a structure O(21) also makes a very short
contact, 2.68 Å, with S(12B) of the minor thiophene ring. It appears
that both the oxygen atom O(22) and the C(29) methyl of the iso-
propyloxy group in 4b would make short contacts with a S atom
vicinal to the phenoxy oxygen O(21) and therefore hinder 180°
rotational isomerism, i.e. disorder.
Contacts involving H have been calculated with C(sp2)–H bonds
normalised at 1.09 Å, C(sp3)–H bonds at 1.10 Å.
A selection of bonding parameters for the two structures is
listed in Table 2. The geometry of the two I rings is very similar.
With one exception the deviations between corresponding bond
lengths and bond angles are 62 esd. The differences in rings II
are larger, average and maximum values for bond lengths are
0.026 and 0.061 Å, respectively, parent differences in the bond an-
gles are 2.6° and 6.5°. The increased disparity may be ascribed lar-
gely to difficulties in modelling and refining disorder in ring II of
4a. The magnitudes of the discrepancies are largest for parameters
involving C(14A/B), C(15A/B) and C(11). The bond lengths in 4b are
in overall better agreement with average values given for unsubsti-
tuted thiophene rings, C(sp2)–S bonds: 1.712 Å, C(sp2)–C(sp2) dou-
ble bonds: 1.362 Å, and the C(sp2)–C(sp2) single bond: 1.424 Å [20].
Comparing bonding parameters of rings III (note opposite number-
ing of C atoms in 4a and 4b) one finds for the average and maxi-
mum deviations in bond lengths 0.023 and 0.033 Å, respectively,
parent values for the bond angles are 0.85° and 1.9°.
5. Supplementary data
CCDC 783407 and 783406 contain the supplementary crystallo-
graphic data for (4a) and (4b). These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgement
Mr. Lars Hagen is thanked for technical assistance with the
MALDI-TOF analyses.
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The targeted octa-substituted compounds 6b–d are quite solu-
ble in organic solvents, and resist aggregation to a large degree,
presumably due to the close vicinity of bulky ortho-substituted
phenoxy groups and thiophen-2-yl substituents. 1H NMR analysis
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groups of 6c and 6d do. The same conclusion is made by analysis