Phenyl-substituted planar binuclear phthalo- and naphthalocyanines: Synthesis and investigation of physicochemical properties

Article abstract of DOI:10.1016/j.dyepig.2011.10.012

Dodeca-phenyl-substituted planar binuclear phthalocyanine magnesium complexes with an extended π-conjugation system were synthesized with high yields. Two approaches to the extension of the π-system were presented: extension of an aromatic bridge or a peripheral π-system. A maximum of near-IR absorption at 972 nm was observed in the case of the planar binuclear naphthalocyanine sharing a common benzene ring. Binuclear phthalo- and naphthalocyanines were characterized by high resolution MALDI-TOF mass spectrometry, UV/Vis/NIR and ¹H NMR spectroscopy. DFT modeling of the structure and chemical shift GIAO calculations were made. The formation of nanoaggregates in a solid film was proven using AFM. The electrochemical properties of binuclear naphthalocyanine complexes were investigated for the first time.

Full text of DOI:10.1016/j.dyepig.2011.10.012

Dyes and Pigments 93 (2012) 1471e1480
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Phenyl-substituted planar binuclear phthalo- and naphthalocyanines: synthesis
and investigation of physicochemical properties
,
b
,
b,
Tatiana V. Dubinina a , Stanislav A. Trashin 1, Natalia E. Borisova a, Irina A. Boginskaya c,
*
,b,
Larisa G. Tomilova a 1, Nikolay S. Zefirov a
a Chemistry Department, M.V. Lomonosov Moscow State University, 1 Leninskie Gory, 119991 Moscow, Russian Federation
b Institute of Physiologically Active Compounds, Russian Academy of Sciences, 1 Severny proezd, 142432 Chernogolovka, Moscow Region, Russian Federation
c Institute for Theoretical and Applied Electromagnetics, Russian Academy of Sciences, 125412, 13 Izhorskaya St., Moscow, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Dodeca-phenyl-substituted planar binuclear phthalocyanine magnesium complexes with an extended
Received 30 August 2011
Received in revised form
17 October 2011
Accepted 18 October 2011
Available online 2 November 2011
p
-conjugation system were synthesized with high yields. Two approaches to the extension of the
p-
system were presented: extension of an aromatic bridge or a peripheral -system. A maximum of near-IR
p
absorption at 972 nm was observed in the case of the planar binuclear naphthalocyanine sharing
a common benzene ring. Binuclear phthalo- and naphthalocyanines were characterized by high reso-
lution MALDI-TOF mass spectrometry, UV/Vis/NIR and 1H NMR spectroscopy. DFT modeling of the
structure and chemical shift GIAO calculations were made. The formation of nanoaggregates in a solid
film was proven using AFM. The electrochemical properties of binuclear naphthalocyanine complexes
were investigated for the first time.
Keywords:
Naphthalocyanines
NIR absorption
Electrochemistry
Nanoparticles
Ó 2011 Elsevier Ltd. All rights reserved.
Pi interactions
Binuclear phthalocyanines
1. Introduction
The extension of the
nines can be performed in two ways: extension of an aromatic bridge
or a peripheral -system. Attempts at aromatic bridge extension
p-system of planar binuclear phthalocya-
Phthalocyanines with an extended
p-conjugation system are of
p
increasing importance due to the presence of absorption in the near-
IR region. This peculiarity allows for the use of planar binuclear
phthalocyanines as components of photogalvanic cells [1], optical
electronic devices for the near-IR region [2], photooxidative catalysis
[3] and laser assisted processes [4]. The phthalo- and naph-
thalocyanines possessing narrow absorption in the near-IR region
have been well-studied [5e9]. However, the absorption maximum of
these compounds is often too sharp and does not coincide well with
the wavelengths of laser light [4]. Planar binuclear phthalocyanines
have potential for this application since some electron transitions
corresponding to Q-bands occupy a wide region of wavelengths in
the near-IR region [4,10e13]. Moreover, the Q-band position can be
from benzene to naphthalene [14e16] and tetracene [17] have been
described in the literature. For these binuclear species, absorption in
the near-IR region was not found. However, in our previous work,
[11] it was shown that the extension of an aromatic bridge leads not
to the disappearance of but to the hypsochromic shift of the Q-band.
In order to expand the peripheral
p-system, an asymmetrical
binuclear compound containing phthalocyanine and naph-
thalocyanine moieties was obtained [4,18]. Synthetic approaches to
symmetrical binuclear naphthalocyanine complexes have been
recently described [12,19]. The highest value of bathochromic shift of
theQ-bandwasreachedbyusinthecaseofdodeca-substitutedplanar
binuclear naphthalocyanine sharing a common benzene ring [19].
Because of the different substituents and central ions, which
include considerable contributions to spectral properties, the
literature data on planar binuclear phthalocyanines were difficult
to systematize. Moreover, electrochemical investigations on planar
binuclear naphthalocyanines have not been carried out.
controlled using the extension of the p-system.
* Corresponding author. Chemistry Department, M.V. Lomonosov Moscow State
University, 1 Leninskie Gory, 119991 Moscow, Russian Federation. Fax: þ7 (495) 939
0290.
E-mail addresses: dubinina.t.vid@gmail.com (T.V. Dubinina), tom@org.chem.
msu.ru (L.G. Tomilova).
The main purpose of this work was to determine the correlation
between the extension of the aromatic system and the position of
1
Fax: þ7 496 524 9508.
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.10.012

1472
T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
absorption in the near-IR region. Using a previously reported
approach [11], a series of phenyl-substituted planar binuclear
quantum chemistry program [20,21]. Thegradient-corrected
exchange-correlation Perdew, Burke and Ernzerhof (PBE) func-
tional [22,23] was used for calculations. The efficient resolution of
identity (RI) and parallel implementation of evaluating both
Coulomb and exchange-correlation integrals with optimized fitting
Gaussian basis sets in the PRIRODA code permits the performance
of calculations of the molecular systems with a large number of
basic functions [20,21]. A large integration grid (which comprises
about 800,000 points over the calculated molecules) with
a 5 ꢁ10ꢂ9 accuracy parameter of the adaptively generated grid was
used. This parameter is responsible for the precision of the
exchange-correlation energy per atom. The 10ꢂ7 threshold on the
orbital gradients at the energy calculations tag and 10ꢂ5 threshold
on the molecular gradient for the geometry optimization procedure
were employed. In all calculations, spin-restricted formalism was
chosen. For all atoms except hydrogen, SBK effective core pseudo-
potentials were used [24,25] adopted for using with the program
[26]. The valence shells were described by basis sets with the
following contraction schemes: [311/1] on H; [611111/411/11] on C,
N, and O; and [611111111/61111] on Mg atoms. All geometries were
completely optimized without any symmetry constraints. System-
atic vibrational analysis was performed to confirm whether an
optimized geometry corresponded to a minimum without an
imaginary frequency. The starting geometries were constructed
analogously to known procedures [27].
phthalo- and naphthalocyanines possessing an extended
p-system
by an aromatic bridge or peripheral -system were obtained.
p
Furthermore, planar binuclear naphthalocyanine sharing
a common naphthalene ring was synthesized for the first time.
2. Experimental
2.1. Chemicals and instruments
Column chromatography was carried out on neutral MN-
Aluminiumoxid. Preparative TLC was performed using Merck
Aluminium Oxide F254 neutral flexible plates. Gel permeation
chromatography was accomplished on the polymeric support Bio-
Beads S-X1 (BIORAD). The electrolyte [Bu4N][BF4] (SigmaeAldrich)
was recrystallized twice from ethyl acetate/hexane (9:1 V/V) and
dried under vacuum at 70 ꢀC. o-Dichlorobenzene (DCB, 99%, Sig-
maeAldrich, HPLC-grade) for voltammetric and specrtoelec-
trochemical studies was used as received. All other reagents and
solvents were obtained or distilled according to standard proce-
dures. The salt Mg(OAc)2$4H2O was dried immediately before use in
a vacuum desiccator for 10 h at 110 ꢀC. All reactions were TLC and
UV/Vis controlled until complete disappearance of the starting
reagents if not additionally specified.
Electronic absorption (UV/Vis) spectra were recorded on a Ther-
2,3,6,7-Tetracyanonaphthaline and 6,7-dibromonaphthalene-
2,3-dicarbonitrile were synthesized according to the published
procedure [11]. The pyromellitonitrile (Aldrich) and 4,5-
dichlorophthalonitrile were used without additional purification.
moSpectronic Helios-
a spectrophotometer using quartz cells
(0.5 ꢁ1 cm). UV/Vis/NIR measurements were made with a Hitachi
U-4100 spectrophotometer in quartz cells (0.5 ꢁ1 cm). MALDI-TOF
mass spectra were taken on a VISION-2000 mass spectrometer
with 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]-
malonitrile (DCTB) as the matrix. High-resolution MALDI mass
spectra were registered on a Bruker ULTRAFLEX II TOF/TOF instru-
ment with DCTB as the matrix. 1H and 13C NMR spectra were
recorded on a Bruker AVANCE 400 spectrometer (400.13 MHz) at
20 ꢀC (if not additionally specified). Chemical shifts are given in ppm
relative to SiMe4.
2.2. Synthesis and characterization
2.2.1. Preparation of 1,2-dicyano-4,5-diphenylbenzene 2
A mixture of 1 (2.00 g, 0.01 mmol), phenylboronic acid (4.36 g,
0.04 mmol), NaBr (1.06 g, 0.01 mmol) and a saturated aqueous
solution of K2CO3 (5.6 g, 0.04 mmol) were stirred in 70 mL of boiling
1,4-dioxane under argon. The dichloro-bis(triphenylphosphine)
palladium compound (0.12 g, 0.0002 mmol) was added after boiling
the solvent. The reaction was carried out for 6 h (TLC-control: Al2O3,
ethyl acetate:hexane (1:10)). The reaction mixture was cooled to
room temperature and water was added. The product was collected
by extraction with ethyl acetate. The residue was treated by flash
chromatography (ethyl acetate:hexane (1:10)) to give pale yellow
crystals of 2 (2.59 g, 92%). The target compound was additionally
purified by sublimation. Rf ¼ 0.46 (Al2O3, F254, ethyl acetate:hexane
CHN analysis was carried out using a CHNOS Elemental Analyzer
vario MICRO.
Electrochemical measurements were carried out using IPC-Pro
(Econix, Moscow, Russia) and EmStat (Palm Instrument BV,
Utrecht, the Netherlands) potentiostats. Cyclic voltammetry (CVA)
and square-wave voltammetry (SWVA) were performed in
a conventional three electrode cell using Pt-disk (2.0 mm in
diameter) working and Pt-foil counter electrodes. A calomel refer-
ence electrode (SCE, 3 M NaCl) was connected to the solution
through a salt-bridge and a Luggin capillary, whose tip was placed
close to the working electrode. The junction potentials were cor-
rected by ferroceniumþ/ferrocene (Fcþ/Fc) couple each time after
(1:10)). 1H NMR (CDCl3):
(s, 2H, HAr d 3, 6). 13C NMR (CDCl3):
d
7.08e7.10, 7.25e7.33 (m, 10H, HPh); 7.84
114.38 (C1, C2); 115.37 (CN);
d
128.54 (p-CPh); 128.61 (m-CPh); 129.30 (o-CPh); 135.53 (C3, C6),
137.61 (C4, C5), 145.86 (CPh-quarternary). Anal. Calc. for C24H14N2: C
85.69; H 4.31; N 9.99%. Found: C 85.75, 85.63; H 4.35, 4.31; N 9.96,
10.03%.
a
series of measurements. Freshly distilled dichloromethane
(purium, Reachim Russia) and o-dichlorobenzene (DCB, 99% Sig-
maeAldrich, HPLC-grade) freshly passed through an Al2O3 layer
were used as solvents, and 0.15 mol/l solution of Bu4NBF4 (Sigmae
Aldrich, dried under vacuum at þ80 ꢀC) in o-dichlorobenzene
containing 2e10 ꢁ 10ꢂ4 M of sample was bubbled with argon for
20 min before measurements were taken. Blank voltammograms
were recorded in the same background solution.
AFM studies were carried out by means of a Solver-P47H (NT-
MDT) microscope. Tapping mode and a silicon probe with gold
coating for non-contact AFM were applied to obtain images.
MenzeleGlaser cover slips (18 ꢁ 18 mm) were employed as the
substrate. The rounding-off radius of the probe was 10 nm.
The calculations were performed using the resources of an MVS-
50K supercomputer of the Joint Supercomputer Center (JSC) (www.
jscc.ru). All calculations were carried out with the PRIRODA
2.2.2. Preparation of 6,7-diphenylnaphthalene-2,3-dicarbonitrile 7
2.2.2.1. Pd(0) catalysis. A mixture of 6 (1.00 g, 3.00 mmol), phe-
nylboronic acid (0.88 g, 7.20 mmol) and saturated aqueous solution
of K2CO3 (5 mL) were stirred in 55 mL of boiling mixture 1,4-
dioxane:acetonitrile (8:3 V/V) under argon. The tetracis(-
triphenylphosphine) palladium compound (0.18 g, 0.16 mmol) was
added after boiling the solvent. The reaction was carried out for 6 h
(TLC-control: Al2O3, C6H6). The reaction mixture was cooled to
room temperature and water was added. The product was collected
by extraction with ethyl acetate. The residue was treated by flash
chromatography (ethyl acetate:hexane (1:2)) in order to remove
the catalyst destruction products. The reaction product was addi-
tionally purified by chromatography on a column with Al2O3 using

T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
1473
a mixture of ethyl acetate:hexane (1:2) as the eluent to give pale
[THF, lmax/nm (I/Imax)]: 368(1), 716(0.86), 798(0.29). 1H NMR (DMF-
d7) : 7.28e7.45 (m, 60H, HPh); 7.64 (s, 12H, HPer); 9.47 (s, 4H, HAr).
The characteristics of asymmetrical substituted mono-
yellow crystals of 7 (0.61 g, 61%), m.p. 230e230,3 ꢀC, Rf ¼ 0,73
d
(Al2O3, F254
,
ethyl acetate:hexane (1:2)). 1H NMR (CDCl3):
d
7.15e7.21 (m, 4H, o-HPh); 7.25e7.33 (m, 6H, p-HPh, m-HPh); 7.99 (s,
phthalocyanine magnesium complex 4c: MS (MALDI-TOF), m/z:
1112 [M þ H]þꢃ,1094 [M-NH3]þꢃ,1067 [M-NH3-CN]þꢃ,1041 [M-NH3-
2CN]þꢃ. UVeVIS [THF, lmax/nm (I/Imax)]: 369(0.77), 647(0.19),
722(1.00), 816(0.06).
2H, HAr e 5, 8); 8.37 (s, HAr e 1, 4). 13C NMR (CDCl3):
d
110.19 (s, C2,
C3); 115.99 (s, CN); 127.79 (s, p-CPh); 128.31 (s, o-CPh); 129.71 (s, m-
CPh); 129.96 (s, C5, C8),132.41 (s, C6, C7),135.69 (s, C1, C4),139.47 (s,
C9, C10), 144.46 (s, CPh-quarternary). MS (EI) m/z: 330 (Mþ·). Anal.
Calc. for C24H14N2: C 87.25; H 4.27; N 8.48%. Found: C 87.27, 86.92;
H 4.33, 4.33; N 8.77, 8.68%.
2.2.5. Preparation of (bis(82,92,152,162,222,232-hexaphenyltrinaphth-
alo [h,o,v]-5,12,19,26-tetraazaporphyrino)-[b,e]benzene) dimagnesium
8a
2.2.2.2. Pd(II) catalysis. A mixture of 6 (1.80 g, 5.36 mmol), phe-
nylboronic acid (2.28 g, 18.70 mmol) and a saturated aqueous
solution of K2CO3 (5 mL) were stirred in 96 mL of boiling mixture
1,4-dioxane:acetonitrile (8:3 V/V) under argon. The dichloro-bis(-
triphenylphosphine) palladium compound (0.038 g, 0.054 mmol)
was added after boiling the solvent. The reaction was carried out for
6 h (TLC-control: Al2O3, C6H6). The reaction mixture was cooled to
room temperature and water was added. The product was collected
by extraction with ethyl acetate. The residue was treated by flash
chromatography (ethyl acetate:hexane (1:2)) in order to remove
the catalyst destruction products. The resulting compound was
additionally purified by chromatography on a column with Al2O3
using a mixture of ethyl acetate:hexane (1:2) as the eluent to give
pale yellow crystals of 7 (1.5 g, 85%).
A mixture of 3a (13.0 mg, 0.06 mmol), 7 (400.0 mg (1.21 mmol))
and Mg(OAc)2$4H2O (51.4 mg, 0.24 mmol) in i-AmOH (15 mL) in
the presence of DBU (0.5 mL) was heated to reflux under argon for
12 h. The reaction mixture was cooled to room temperature and
a mixture MeOH:H2O (5:1 V/V) was added. The precipitate was
filtered and washed with water and MeOH. The target compound
8a was separated using gel permeation chromatography (THF). The
solvent was evaporated, and the resulting oil was washed with n-
hexane. The precipitate was filtered off and repeatedly washed
with n-hexane and methanol to give 8a (41.0 mg, 31%). MS (MALDI-
TOF), m/z: 2285 [M ꢂ H þ Ph]þꢃ, 2209 [M]þꢃ, 2133 [M þ H ꢂ Ph]þꢃ
.
UVeVIS [THF, lmax/nm (I/Imax)]: 327(1), 772(0.33), 960(0.17). 1H
NMR (THF-d8) d: 7.23e7.24 (m, 60H, HPh); 8.20 (s,12H,1-HNPh); 8.42
(s, 12H, 2-HNph); 9.68 (s, 2H, HAr).
The characteristics were identical with those obtained by
method (a).
The 3,4,12,13,21,22,30,31 e octa-phenyl-2,3-naphthalocyanine
magnesium 9 (52.0 mg) was separated using gel permeation
chromatography. MS (MALDI-TOF), m/z:.1345 [M]þꢃ,1268 [M-Ph]þꢃ
.
2.2.3. Preparation of (bis(72,82,122,132,172,182-hexaphenyltribenzo
[g,l,q]-5,10,15,20-tetraazaporphyrino)-[b,e]benzene) dimagnesium
4a
UVeVIS [THF, lmax/nm (I/Imax)]: 340 (0.57), 689 (0.23), 734 (0.20),
772 (1.00). 1H NMR (Py-d5)
: 7.26e7.31 (m, 40H, HPh); 8.13 (s, 8H,1-
HNPh); 8.58 (s, 8H, 2-HNPh).
d
A mixture of 3a (17.0 mg, 0.08 mmol), 2 (449.0 mg, 1.60 mmol)
and Mg(OAc)2$4H2O (69.0 mg 0.32 mmol) in i-AmOH (10 mL) in the
presence of DBU (0.5 mL) was heated to reflux under argon for 19 h.
The reaction mixture was cooled to room temperature and
a mixture of MeOH:H2O (5:1 V/V) was added. The precipitate was
filtered and washed with water and MeOH. The target compound
was separated using gel permeation chromatography (C6H6:Py
(50:1 V/V)). The solvent was evaporated, and the resulting oil was
washed with n-hexane. The precipitate was filtered off and
repeatedly washed with n-hexane and methanol to give 4a
(26.0 mg, 17.0%). MS (MALDI-TOF), m/z: 1908 [M]þꢃ. UVeVIS [THF,
2.2.6. Preparation of (bis(102,112,172,182,242,252-hexaphenyltrinapht-
halo [j,q,x]-7,14,21,28-tetraazaporphyrino)-[b,g]naphthalene)
dimagnesium 8b
A
mixture of isoindolo[5,6-f]isoindole-1,3,6,8(2H,7H)-tetrai-
mine 3b (12.0 mg, 0.046 mmol), 6,7-diphenylnaphthalene-2,3-
dicarbonitrile (303.0 mg, 0.92 mmol) and Mg(OAc)2$4H2O
7
(39.4 mg, 0.18 mmol), in i-AmOH (10 mL) in the presence of DBU
(0.5 mL) was heated to reflux under argon for 13 h. The reaction
mixture was cooled to room temperature and a mixture MeOH:H2O
(5:1 V/V) was added. The precipitate was filtered and washed with
water and MeOH. The target compound 8b was separated using gel
permeation chromatography (THF). The solvent was evaporated,
and the resulting oil was washed with n-hexane. The precipitate
was filtered off and repeatedly washed with n-hexane and meth-
anol to give 8b (21.0 mg, 21%). MS (MALDI-TOF), m/z: 2259 [M]þ.
UVeVIS [Py, lmax/nm (I/Imax)]: 331(1), 785(0.65) 916(0.14). 1H NMR
lmax/nm (I/Imax)]: 372(1), 698(0.56), 846(0.66). 1H NMR (THF-d8)
d:
7.17e7.19, 7.23e7.24 (m, 60H, HPh); 7.85 (s, 12H, HPer); 10.72 (s, 2H,
HAr).
The 2,3,9,10,16,17,23,24-octa-phenyl-phthalocyanine magne-
sium 5 (100.0 mg) was separated using gel permeation chroma-
tography. MS (MALDI-TOF), m/z: 1146 [M]þꢃ. UVeVIS [THF, lmax/nm
(I/Imax)]: 364 (0.43), 622 (0.16), 658 (0.14), 688 (1.00). 1H NMR (THF-
(Py-d5, 80 ꢀC):
(br.s 4H, HAr).
d 7.36-7.41 (m, 60H, HPh), 7.69 (br, 24H, HNph), 8.58
d8) d: 7.21e7.45 (m, 40H, HPh); 8.66 (s, 8H, HPer).
The
3,4,12,13,21,22,30,31-octa-phenyl-2,3-naphthalocyanine
2.2.4. Preparation of (bis(92,102,142,152,192,202-hexaphenyltribenzo
[g,l,q]-7,12,17,22-tetraazaporphyrino)-[b,g]naphthalene)
magnesium 9 (269.0 mg)was separated using gel permeation
chromatography.
dimagnesium 4b
A mixture of 3b (17.0 mg, 0.065 mmol), 2 (363.0 mg, 1.30 mmol)
and Mg(OAc)2$4H2O (56.0 mg, 0.26 mmol) in i-AmOH (5 mL) in the
presence of DBU (0.5 mL) was heated to reflux under argon for 7 h.
The reaction mixture was cooled to room temperature and
a mixture MeOH:H2O (5:1 V/V) was added. The precipitate was
filtered and washed with water and MeOH. The target compound
4b (25.0 mg, 19%) was separated using gel permeation chroma-
tography (C6H6:Py (50:1 V/V)). The asymmetrical substituted
monophthalocyanine magnesium complex (39.0 mg) and mono-
phthalocyanine 5 (87.0 mg) were separated using gel permeation
chromatography (THF). MS (MALDI-TOF), m/z: 1958 [M]þꢃ. UVeVIS
3. Results and discussion
3.1. Synthesis of binuclear phthalocyanines
Planar binuclear phthalocyanine complexes were synthesized
using the statistical condensation reaction. Pyromellitonitrile and
2,3,6,7-tetracyanonaphthaline were chosen as the starting
compounds for obtaining benzene and naphthalene bridges,
respectively. These tetranitriles were converted to bis(diiminoi-
soindoline) derivatives in order to increase the reactivity in

1474
T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
3.2. Synthesis of binuclear naphthalocyanines
B(OH)2
Cl
Cl
CN
CN
CN
CN
Pd(PPh3)2Cl2
+
When using 6,7-diphenyl-2,3-dicyanonaphthaline 7 as a start-
ing compound, planar binuclear naphthalocyanine complexes were
synthesized. The nitrile 7 was obtained by SuzukieMiyaura cross-
coupling on the basis of 6,7-dibromonaphthalene-2,3-
Na Br, K2CO3
1,4-dioxane
1
2
Scheme 1. Synthesis of dinitrile 2.
CN
CN
N
N
N
N
N
N
N
N
2
Mg N
N
N
.
Mg
Mg(OAc)2 4H2O
N
+
N
N
N
N
n
HN
HN
NH
NH
NH
i-AmOH, DBU
4a,b
HN
n
3a,b
*
+
N
N
N
NH
NH
NH
N
N
N
N
N
Mg N
Mg N
N
N
N
N
N
N
n = 1 (a), 2 (b)
4c
5
Scheme 2. Synthesis of planar binuclear phthalocyanine magnesium complexes. (*) Compound 4c was isolated in the synthesis of 4b.
phthalocyanine synthesis by the analogue using a published proce-
dure [11,27].
dicarbonitrile (Scheme 3). Compared with the Pd(0) catalyst, the
use of the Pd(II) catalyst allowed the yield of the target compound
to be increased. Perhaps this phenomenon refers to the presence of
two catalytic centres in the molecule of the catalyst.
1,2-Dicyano-4,5-diphenylbenzene was chosen as the second
component of cyclization for the following reasons. First, in our
previous article [11], a bathochromic shift of the Q-band for
dodeca-alkyl-substituted planar binuclear phthalocyanines in
comparison with hexa-alkyl-substituted ones was found. This
phenomenon can be explained by the greater donor effect of twelve
butyl groups than that of six tert-butyl groups. Second, the absence
of an isomer mixture for the target phthalocyanines facilitates the
interpretation of NMR spectra.
Planar binuclear naphthalocyanine magnesium complexes 8a
and 8b were synthesized by the analogue with the synthetic
procedure for the planar binuclear phthalocyanine complexes 4a
and 4b (Scheme 4). Gel permeation chromatography was used to
separate the mixture of products. The formation of only one by-
product (octa-phenyl substituted monophthalocyanine magnesium
complex) led to increased yields of binuclear naphthalocyanine
complexes in comparison with binuclear phthalocyanine complexes.
Novel binuclear phthalo- and naphthalocyanine complexes 4
and 8 were characterized by MALDI-TOF mass spectrometry, UV/
Vis/NIR and 1H NMR spectroscopy.
Using SuzukieMiyaura cross-coupling (Scheme 1), 1,2-dicyano-
4,5-diphenylbenzene was synthesized on the basis of 4,5-
dichlorophthalonitrile
1 by the analogue using a published
method [28]. Due to the in situ substitution of chlorine to bromine,
the addition of NaBr provides an increasing of yield of the target
compound in comparison with yields of nitriles, which were ob-
tained by the literature procedure [28]. This approach, through the
cross-coupling reaction, is most preferable for 2, because the
common procedure [29], based on the DielseAlder reaction
between diphenylacetylene and pyridazine-4,5-dicarbonitrile, led
to a low yield of target compounds.
Planar binuclear phthalocyanine magnesium complexes were
obtained in boiling isoamilic alcohol under argon with the addition
of DBU as a base (Scheme 2). Using an excess of nitrile 2 relative to
bis(diiminoisoindoline) derivative 3, the yields of target complexes
can be noticeably increased [10a,11].
The MALDI-TOF mass spectra of these compounds (Fig. 1, DCTB2
used as the matrix, and Table S1 in the Supporting Information)
revealed intense molecular ion [M]þ peaks with characteristic
isotopic patterns in good accordance with simulated ones.
It is also noteworthy that in the case of 8a, two additional frag-
mentation peaks with molecular weight [M þ Ph]þ and [M ꢂ Ph]þ
ꢃ
ꢃ
which were formed during laser ionization were observed. The
displacement of the matrix from DCTB to 9-nitroanthracene did not
occur due to the disappearance of [M þ Ph]þꢃ. So, we concluded that
formation of [M þ Ph]þ occurs after the addition of the Ph group,
ꢃ
which was the fragment of the other binuclear molecule.
Binuclearcomplexes 4a and 4b were isolated using gel permeation
chromatography. Octa-phenyl-substituted monophthalocyanine 5
was the by-product of the statistical condensation reaction. Besides
this, in the synthesis of 4b, the asymmetrical substituted A3B-type
monophthalocyanine 4c with diiminoisoindoline group was isolated
and characterized by UV/Vis spectroscopy and MALDI-TOF mass-
spectrometry.
3.3. Electronic absorption spectra
In the UV/Vis/NIR spectra of binuclear phthalo- and naph-
thalocyanine magnesium complexes, there are two peculiarities
2
DCTB e 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]-malonitrile.

T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
1475
the Q1 and Q2 bands, which was larger than hypsochromic shift
induced by the extension of aromatic bridge. So, the Q2-band of
planar binuclear naphthalocyanine sharing a common benzene
ring 8a was the most red-shifted up to 972 nm.
B(OH)2
CN
CN
CN
CN
Br
Br
Pd cat.
+
K2CO3
1,4-dioxane - CH3CN
6
7
It was found for the first time that in the case of binuclear
phthalo- and naphthalocyanines with the same aromatic bridge,
Scheme 3. Synthesis of dinitrile 7.
CN
CN
N
N
N
N
N
N
N
N
Mg N
.
Mg N
Mg(OAc)2 4H2O
7
N
N
N
N
N
N
n
i-AmOH, DBU
+
HN
HN
HN
NH
NH
NH
8a,b
n
3a,b
+
N
N
N
N
Mg N
N
N
N
n = 1 (a), 2 (b)
9
Scheme 4. Synthesis of planar binuclear naphthalocyanine magnesium complexes.
referring to the Q-band region: Q1(blue shifted) and Q2(red shifted).
This fact could be interpreted by the split of the frontier orbitals,
which has been previously calculated [12,27].
The hypsochromic shift of Q2-band and the decrease in the
Q1eQ2 distance going from benzene to naphthalene ring was
observed (Table 1). These results correlate with LUMO destabili-
zation for binuclear phthalocyanines sharing a common naphtha-
lene ring in comparison with those sharing a common benzene ring
[27, 30].
the “100 nm” rule takes place: about 100 nm bathochromic shifts
are observed going from 4a to 8a and from 4b to 8b (Table 1). This
regularity was earlier noticed for monophthalocyanines [31] and
sandwich-type [32] phthalocyanines. According to this rule,
a bathochromic shift of the Q-band for naphthalocyanine 9 in
comparison with phthalocyanine 5 was also observed.
The extension of the
phthalo- and naphthalocyanines leads to strong
p
-conjugation system for planar binuclear
stacking
pep
intermolecular interactions [11]. This phenomenon results in the
influence of the solvent to the character of the absorption bands
(Fig. 2A).
The extension of the peripheral
p-system from binuclear
phthalo- to naphthalocyanines resulted in a bathochromic shift of
Fig. 1. MALDI-TOF mass spectrum of 8b, isotopic patterns for the molecular ion (inset A) and simulated MS patterns of the molecular ion (inset B).

1476
T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
Table 1
UV/Vis/NIR of planar binuclear complexes.
Compound
l
(I/Imax), nm in pyridine
l (I/Imax), nm in THF
4a
4b
5
858(0.70), 696(0.57), 374(1)
817(0.30), 725(0.89), 371(1)
698(1.00), 668(0.17), 628(0.19), 688(1.00), 658(0.14), 622(0.16),
369(0.54) 364(0.43)
846(0.66), 700(0.56), 372(1)
798(0.29), 716(0.86), 368(1)
8a
972(0.10), 786(0.37), 744(0.48), 960(0.17), 772(0.33), 327(1)
342(1)
8b
9
916(0.14), 785(0.65), 331(1)
783(1.00), 744(0.15), 697(0.17), 772(1.00), 733(0.15), 689(0.16),
349(0.44) 361(0.34)
905(0.18), 776(0.34), 331(1)
In Fig. 2A, the UV/Vis/NIR spectra of 4a in different solvents were
shown. In non-coordinating solvents (e.g. C6H6), a noticeable
broadening of the Q-bands and B-band and a reduction in Q2-band
intensity were observed. Similar effect was observed in the case of
binuclear naphthalocyanine complexes (Fig. 3). In comparison with
binuclear phthalocyanine complexes, the largest extension of the
Fig. 3. UV/Vis/NIR of planar binuclear naphthalocyanine 8b.
p
-conjugation system for planar binuclear naphthalocyanine
complexes resulted in strong aggregation effects, even in coordi-
nating solvents. This phenomenon led to the low intensity of the
Q2-band compared to the Q1-band and broadening of the absorp-
tion bands.
one, which was observed going from pyromellitonitrile (9.95 ppm)
[27] to 2,3,6,7-tetracyanonaphthaline (9.01 ppm) [11]. This
depends on the aromatic ring current which decreased with an
increase in ring size.
The UV/Vis/NIR spectrum of a 4a thin film which was deposited
from a THF solution onto a cover slip is shown in Fig. 2B. The
broadening of all absorption bands, especially in the case of Q2, was
more distinct than for non-coordinating solvents. This effect could
be explained by the formation of band-type structures with strong
intermolecular interactions [33]. According to the Ref [34], part of
the material forms H-aggregates, which leads to hypsochromic
shifted broadening of the Q-band. Another part forms J-aggregates
which results in bathochromic shifted broadening of the Q-band.
For binuclear complexes 4a and 8a in contrast to 4b and 8b, the
down-field shift of HPer protons was found. This in turn further
suggests that the ring current can be explained by a five-orbital
model, taking the central TAP core and the surrounding four
aromatic moieties into account, rather than a single-orbital model
considering a whole molecule as a single loop [35]. The strongest
aggregation effect was observed for binuclear naphthalocyanine
8b, possessing an extended
p-system by an aromatic bridge and
a peripheral -system. An equimolar amount of ethylene glycol was
p
added to decrease the aggregation by coordination of extra ligands
to the metal ion [11]. The nature of the solvent had a strong
influence on the chemical shifts of phthalocyanine metal
complexes, not only by their specific solvation effects, but also by
the chemical interactions of the solvent with the metal ion in the
phthalocyanine cavity. Such interactions could lead to significant
differences between experimental and calculated chemical shift
values [36] and, on the other hand, lead to strong dependencies of
the chemical shifts on the nature of the solvent. Due to the low
solubility of the phthalocyanine systems under the investigation,
we performed NMR experiments in a wide range of polar solvents.
Only two compounds, 4a and 8a, had enough solubility in one
solvent, THF-d8, to make the NMR spectra comparable to each
other. The spectra clearly show the great contribution of the nature
3.4. 1H NMR spectroscopy of planar binuclear complexes
1H NMR study of planar binuclear phthalocyanines is associated
with difficulties due to the strong aggregation at concentrations
above 10ꢂ4 mol/l [4,14]. Broadening of signals in the aromatic area
is observed and the width of signals reaches 3.7 ppm [4].
In the present study, in order to reach more distinct resolution of
signals in the 1H NMR spectra, polar coordinating solvents were
used (e.g. THF-d8, Py-d5 and DMF-d7). Besides this, 1H NMR spectra
were recorded under high temperature to destroy aggregates.
The following regularities were found. Additional shielding of
aromatic bridge protons HAr was found (Table 2), going from
common benzene to the naphthalene ring by the analogue with
A
B
Fig. 2. UV/Vis/NIR of planar binuclear phthalocyanine 4a.

T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
1477
Table 2
observed in THF-d8 and further chemical shifts were compared
with GIAO calculated shifts. The calculated chemical shifts support
the assignments of all of the protons; moreover, the calculations
agreed with the relative shielding of the aromatic protons (HAr) and
protons of peripheral rings (HPer) for naphthalene-bridged mole-
cules contrary to benzene-bridged ones. The strongest effect on the
chemical shift of protons of the aromatic bridge (HAr) factor is the
number of shared aromatic rings: the naphthalene-bridged mole-
cules possess 1 ppm more shielded protons than benzene-bridged
ones. This is in coincidence with the general behavior of phthalo-
cyanines, which show a diminished ring current with the expan-
sion of the phthalocyanine macrocycle. The number of shared
aromatic rings also had an effect on the chemical shifts of the
peripheral aromatics of binuclear phthalocyanine which are the
most sensitive to changes from a phthalocyanine to a naph-
thalocyanine system. As we expected, the chemical shift of the
phenyl-substituents were affected mostly by the naphthalo- or
phthalocyanine macrocycle.
1H NMR data for planar binuclear complexes.
Compound HAr
HPer
HPh
Solvent
4a
10.72 (s)
12.0
7.85 (s)
10.2
9.9
7.64 (br.s)
10.1
9.9
7.17e7.19, 7.23e7.24 (m) THF-d8
4aa
7.5e8.7 HPh-o
7.5e8.3 HPh-m
7.28e7.45 (m)
7.4e8.5 HPh-o
7.4e7.9 HPh-m
7.6 HPh-p
e
4b
9.47 (s)
11.1
DMF-d7
e
4ba
8a
9.68 (s)
12.1
8.20 (s), 8.42 (s) 7.23e7.24 (br.m)
THF-d8
e
8a[19] a
10.5 2-HNph
10.5 2-HNph
10.8 2-HNph
9.1 1-HNph
9.3 1-HNph
9.1 1-HNph
7.5e8.5 HPh-o
7.6e8.1 HPh-m
7.8 HPh-p
8b
8.58 (br.s) 7.69 (br)
11.1 10.3 2-HNph
7.36e7.41 (m)
7.3e8.2 HPh-o
7.4e8.0 HPh-m
7.6 HPh-p
Py-d5
e
8ba
10.5 2-HNph
10.3 2-HNph
8.9 1-HNph
9.1 1-HNph
9.0 1-HNph
3.6. AFM study of thin films
a
DFT calculations.
An investigation of the particles which were obtained during the
formation of the thin film on the cover slip was provided using AFM
for binuclear complex 4a. The concentration of the solution for
deposition was about 10ꢂ6 M.
During deposition from a methanol suspension, which was
preliminary held in an ultrasonic bath, the obtained films possessed
an “island-type” [38], large-grain structure. The size of the grains
was 4 nm in height and 250 nm in width (Fig. 4).
When depositing from a THF solution, the size of aggregates
became smaller and reached 2 nm in height and 50 nm in width
(Fig. 5). This fact can be explained by the coordination of solvent
molecules to the magnesium ion and blocking of the formation
large-scale particles by steric factors.
of the phthalocyanine moiety to the shifts of not only the peripheral
aromatic rings of the phthalo- or naphthalocyanine macrocycle but
also to the shared aromatic ring. The HAr protons of the phthalo-
cyanine 4a are 1 ppm less shielded than that for naphthalocyanine
8a. Contrary to the deshielding of HAr, the HPer protons are 1 ppm
shielded for phthalocyanine 4a. The protons of the phenyl
substituents are less affected by the expansion of the aromatic
system. To elucidate the 1H NMR spectra of the most aggregated
naphthalocyanine 8b, we performed DFT modeling of the structure
of the phthalocyanines under study as well as their chemical shifts.
Thus, on the basis of AFM experiments, we showed that in the
solid film the nanoparticles were formed and the size of these ones
depends on the nature of the solvent.
3.5. DFT modeling of the binuclear naphthalocyanines
DFT optimizations were made for structures 4 and 8 using the
PBE functional and TZV basis set [19]. All of the structures were
found to possess almost flat phthalocyanine moieties, contrary to
the further investigated phenyl-substituted deformed phthalocya-
nines [37]. The optimized geometries are represented in the Sup-
porting Information. The calculations of chemical shifts were made
using the gauge-independent atomic orbital (GIAO) method. The
calculated chemical shifts are in good agreement with the experi-
mental data, but keep in mind that the spectra were recorded in
different solvents. Strong solvent dependence was found for
magnesium porphirinates [36], for which the 1H NMR spectra were
3.7. Electrochemistry
The redox properties of the phthalo- and naphthalocyanines
were studied using cyclic voltammetry (CVA) and square-wave
voltammetry (SWVA). Fig. 6 represents the SWVA voltammo-
grams of phthalocyanine complexes 4a, b and 5. The voltammo-
grams of 8a, b and 9 were similar and provided in the Supporting
Information.
The redox potentials and the difference of potentials between
first reduction and oxidation (DE0x1-Red1) for all studied complexes
Fig. 4. AFM image of 4a thin film a (full image) and b (fragment). (For interpretation of color referred in this figure legend the reader is referred to web version of the article.)

1478
T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
Fig. 5. AFM image of 4a thin film deposited from a methanol suspension (a) and from a THF solution (b). (For interpretation of color referred in this figure legend the reader is
referred to web version of the article.)
Fig. 6. SWVA of phthalocyanine complexes 5 (A), 4a (B) and 4b (C). Cathodic currents are shown by red dashed line, arrows gave the scan directions. The blue dashed line in (A) and
(C) shows the scanning in the restricted interval. (For interpretation of color referred in this figure legend the reader is referred to web version of the article.)

T.V. Dubinina et al. / Dyes and Pigments 93 (2012) 1471e1480
1479
Table 3
deshielded protons due a diminished aromatic ring current. DFT
modeling of the structure and the chemical shifts of the molecules
also support this observation. The calculated chemical shifts
support the assignments of all of the protons; moreover, the
calculations agreed with the relative shielding of the aromatic
protons (HAr) and the protons of the peripheral rings (HPer) for
naphthalene-bridged molecules contrary to benzene-bridged ones.
Using the AFM technique, we showed that in the solid film an
“island-type”, large-grain structure, composed of nanoaggregates,
was formed. The size of these particles depends on the nature of the
solvent.
Half-wave potentials in o-DCB.
Reduction
Oxidation
Ox1
Red3
Red2
Red1
Ox2
Ox3
5
e
e
e
ꢂ1.310
ꢂ1.426
ꢂ1.332
ꢂ0.926
0.636
e
1.258
e
e
4a
4b
9
ꢂ0.961, ꢂ0.841
ꢂ0.934
1.483
0.637
0.304
e
1.362, 1.559 1.807
1.044
ꢂ1.718 ꢂ1.394
ꢂ1.028
1.524
1.539
8a ꢂ1.754 ꢂ1.477, ꢂ1.258 ꢂ1.043, ꢂ0.885
e
8b ꢂ1.797 ꢂ1.396
E1/2(FeFc2) ¼ 0.592 V.
ꢂ1.163, ꢂ1.011 0.46, 0.838 1.116, 1.316 1.541
Acknowledgement
are listed in Table 3. The decrease in
DE0x1‑Red1 from 1.562 V for
phthalocyanine 5 to 1.332 V for naphthalocyanine 9 is in accor-
dance with the bathochromic shift of the corresponding Q-band
The research was supported by the Russian Foundation for Basic
Research (Grant No. 08-03-00753), Sinosteel Anshan Research
Institute of Thermo-Energy (RDTE) and the program of the
Presidium of the Russian Academy of Science ‘‘Development of
a strategy of organic synthesis and creation of compounds with
valuable and applied proprieties”. We thank Institute of Biomedical
Chemistry of Russian Academy of Medical Sciences for high-reso-
lution MALDI mass spectra and Joint Supercomputer Center (JSC)
for computing time on MVS-50K.
which is due to straight correlation between
DE0x1-Red1 and the
HOMOeLUMO gap.
Unfortunately, CVAs for the binuclear complexes were not well
resolved (data not shown), probably because of strong aggregation
of the complexes and some irreversibility of the redox processes.
However, SWVA was sensitive enough to reveal the positions of the
redox processes.
Binuclear 4a, 8a and 8b gave the split of Red1 with
D
Esplit ¼ 0.15 V. The redox process Red2 was split only for 8a
(D
Esplit ¼ 0.15 V) but not for 8b or 4a,b. The benzene bridge and
Appendix. Supplementary information
naphthalene periphery probably resulted in a stronger interaction
between the two subunits of the binuclear complexes compared to
the naphthalene bridge and benzene periphery. This is also sup-
ported by the split values of Q-bands for the complexes (Table 1).
The maximal split of the Q-band was demonstrated for 8a, while 4b
gave the minimal split.
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.dyepig.2011.10.012.
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SWVA scans in the oxidation direction showed only slightly
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