Synthesis and spectral properties of dodecaphenyl-substituted planar binuclear naphthalocyanine magnesium complex sharing a common benzene ring

Article abstract of DOI:10.1016/j.mencom.2011.04.019

Dodecaphenyl-substituted planar binuclear naphthalocyanine magnesium complex possessing an intense absorption in the near IR region up to 1100 nm has been synthesized on the basis of novel 2,3-dicyano-6,7-diphenylnaphthalene.

Full text of DOI:10.1016/j.mencom.2011.04.019

Mendeleev
Communications
Mendeleev Commun., 2011, 21, 165–167
Synthesis and spectral properties of dodecaphenyl-substituted
planar binuclear naphthalocyanine magnesium complex
sharing a common benzene ring
Tatiana V. Dubinina,*a,b Natalia E. Borisova,a Kseniya V. Paramonovaa and Larisa G. Tomilovaa,b
a Department of Chemistry, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation.
Fax: +7 495 939 0290; e-mail: dubinina.t.vid@gmail.com
b Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka,
Moscow Region, Russian Federation. Fax: +7 496 524 9508; e-mail: tom@org.chem.msu.ru
DOI: 10.1016/j.mencom.2011.04.019
Dodecaphenyl-substituted planar binuclear naphthalocyanine magnesium complex possessing an intense absorption in the near IR region
up to 1100 nm has been synthesized on the basis of novel 2,3-dicyano-6,7-diphenylnaphthalene.
Absorption in the near IR region in phthalocyanines with extended
p-conjugation system allows one to use these compounds in photo-
galvanic elements,1 optical electronic devices2 and photooxidative
catalysis.3
NC
NC
B(OH)2
Br
Br
+
excess
Previously,4,5 we reported that planar binuclear phthalocyan-
ines sharing a common benzene ring exhibit intense absorption
in the near IR region and 200 nm red shift of the Q-band. Further
expansion of the p-conjugated system in planar binuclear phthalo-
cyanines can be in principle performed either in the aromatic or
in peripheral p-system. However, replacement of the benzene
bridge by a naphthalene results in a hypsochromic shift of the
Q-band by 59 nm,6 which can be explained by an increase in
the HOMO–LUMO distance7 in the resulting mutual p-system.
Further expansion of aromatic bridge to a tetracene results in
loss of absorption in the near IR region (lmax = 690 nm).8
Concerning the expansion of the peripheral p-system, until
recently there is only one report of a synthesis of a planar hetero-
dinuclear phthalo-naphthocyanine complex sharing a mutual
benzene ring.9 The absorption maximum of this compound is
hypsochromically shifted by 38 nm with respect to the analogous
binuclear phthalocyanine. However, this phenomenon was not
interpreted. In our opinion, this could be related to the asymmetry
in the structure of the complex in question. Note that synthesis
of the planar binuclear naphthalocyanine complexes was for the
first time reported recently.10,11
Extending our works on obtaining planar binuclear phthalo-
cyanines with expanded p-conjugation system,4,6,10 here we
describe synthesis and spectral properties of a planar binuclear
naphthalocyanine magnesium complex bearing twelve phenyl sub-
stituents at the periphery. Introduction of phenyl groups, we reasoned,
could also increase the solubility of the target compound.
The starting 2,3-dicyano-6,7-diphenylnaphthalene 1 was syn-
thesized by the Suzuki reaction from 6,7-dibromo-2,3-dicyano-
naphthalene (Scheme 1).6,† To provide the basicity of the reac-
tion medium, the saturated aqueous solution of K2CO3 was added.
1,4-Dioxane was used as the solvent; a small admixture of aceto-
nitrile was added to improve the solubility of 6,7-dibromo-2,3-di-
cyanonaphthalene. The use of Pd(PPh3)2Cl2 as the catalyst instead of
Pd0 salts widely employed in syntheses of similar compounds12–15
allowed us to shorten the reaction time from 13 to 6 h. This may
be due to the existence of two active sites in the catalyst molecule.
We chose pyromellitonitrile as the starting compound for the
synthesis of the aromatic bridge; to increase the reactivity of the
Pd(PPh3)2Cl2,
K2CO3
NC
NC
1
Scheme 1
†
UV-VIS spectra were recorded with a Hitachi U-4100 spectrophoto-
meter in quartz cells (0.5×1cm) using C6H6, CHCl3 and THF as solvents.
1H and 13C NMR spectra were recorded on a Bruker Avance-400 spec-
trometer (400.13 and 100.61 MHz, respectively) using CDCl3, THF and
pyridine-d5 as solvents at 20°C. Column chromatography was performed
using neutral MN-Aluminiumoxid. Preparative TLC was performed using
Merck Aluminium Oxide F254 neutral flexible plates. Gel permeation
chromatography was performed using Bio Beads SX-1 (Bio Rad). CHN
analysis was carried out with CHNOS Elemental Analyzer Vario Micro.
Mass spectra were measured on Finnigan MAT Insoc-50 (EI, 70 eV) and
Vision-2000 (MALDI-TOF). IR spectra were recorded on Specord M-70
and Specord UR-20 spectrophotometers in liquid paraffin.
The Mg(OAc)2·4H2O salt was dried in vacuo at 100°C for 4 h just
before use.
6,7-Diphenylnaphthalene-2,3-dicarbonitrile 1. 6,7-Dibromo-2,3-dicyano-
naphthalene (1.80 g, 5.36 mmol), phenylboronic acid (2.28 g, 18.70 mmol),
dichlorobis(triphenylphosphine) palladium (0.038 g, 0.054 mmol), saturated
aqueous solution of K2CO3 (2.93 g) and 96 ml of a 1,4-dioxane–aceto-
nitrile mixture (8:3) were placed in a two-necked flask equipped with a
reflux condenser and a magnetic stirrer. The mixture was refluxed for 6 h
in a stream of argon (TLC control: Al2O3, F254, C6H6 as the eluent). The
reaction mixture was cooled, poured into water and extracted with ethyl
acetate. The organic layer was collected and evaporated; the residue was
subjected to flash chromatography. The proper fraction was additionally
purified by chromatography on a column with Al2O3 using an ethyl
acetate–hexane mixture (1:2) as the eluent. The yield of compound 1 was
1.5 g (85%), mp 230–230.3°C, Rf 0.73 [Al2O3, F254, ethyl acetate–hexane
mixture (1:2) as the eluent]. 1H NMR (CDCl3) d: 7.15–7.21 (m, 4H, o-HPh),
7.25–7.33 (m, 6H, p-HPh, m-HPh), 7.99 (s, 2H, 5,8-HAr), 8.37 (s, 1,4-HAr).
13C NMR (CDCl3) d: 110.17 (s, C2, C3), 115.97 (s, CN), 127.77 (s, p-CPh),
128.29 (s, o-CPh), 129.69 (s, m-CPh), 129.94 (s, C5, C8), 132.39 (s, C6,
C7), 135.66 (s, C1, C4), 139.45 (s, C9, C10), 144.44 (s, CPh quarternary).
Found (%): C, 87.27; H, 4.33; N, 8.68. Calc. for C24H14N2 (%): C, 87.25;
H, 4.27; N, 8.48. MS (EI), m/z: 330 (M+).
© 2011 Mendeleev Communications. All rights reserved.
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Mendeleev Commun., 2011, 21, 165–167
HN
HN
NH
NH
NH
NC
NC
Mg(OAc)2·4H2O
AmiOH, DBU
+
HN
1
2
N
N
N
N
N
N
N
N
N
N
Mg
N
N
Mg N
N
Mg
N
+
N
N
N
N
N
N
N
N
N
4
3
Scheme 2
1.0
0.8
0.6
0.4
0.2
1.8
1.2
1
1
0.6
0.0
2
2
300 400 500 600 700 800 900
400
600
800
1000
l/nm
l/nm
Figure 1 UV-VIS spectra of complex 3 in (1) THF and (2) chloroform.
Figure 2 UV-VIS spectra of complex 4 in (1) THF and (2) C6H6.
former in statistic condensation reaction, it was converted to
bis(diiminoisoindoline) derivative 2 by treatment with ammonia
in the presence of sodium methoxide.7,‡
The target complex 3 was obtained by the statistic condensation
method reported previously6 (Scheme 2).§ It was isolated by gel
permeation chromatography, using THF as the eluent. The product
yield amounted to 31%, which is several times higher than those
reported in the literature5,7,11,16 for binuclear phthalocyanine com-
plexes. Note that only one side product, octaphenyl-substituted
magnesium mononaphthalocyanine 4, was isolated, whereas neither
trinuclearphthalocyaninenorunsymmetricalsubstitutedcomplexes
of A3B type5,6 were found.
The absorption maximum in the UV-VIS spectra of the bi-
nuclear naphthalocyanine complex 3 is bathochromically shifted
to 960 nm (Figure 1). Such a considerable bathochromic shift for
this type of complex was attained for the first time.4–6
Complex 4 also shows a bathochromic shift of the Q-band
(Figure 2) by more than 100 nm in comparison with mono-
phthalocyanine complexes.
‡
Pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraimine 2. Methanol (40 ml)
and sodium metal (14.0 mg, 0.60 mmol) were placed in a two-necked flask
equipped with a reflux condenser and a magnetic stirrer. Once hydrogen
evolution ceased, pyromellitonitrile (500 mg, 2.8 mmol) was added. Gaseous
ammonia dried with KOH was passed for 4 h through the resulting solu-
tion with water cooling. The reaction progress was monitored by TLC
(Al2O3, C6H6 as the eluent) and by IR spectroscopy to reach the absence
of vibrations of nitrile in the 2250 cm–1 region.7 The reaction product that
formed as a brown precipitate was filtered off and washed with methanol
and Et2O, yield 588 mg (99%), Rf 0 (Al2O3, F254, C6H6 as the eluent).
IR (liquid paraffin, nmax/cm–1): 3340 (nN=H), 1740 (nC=N), 1480 (nAr(C–H)).
Intense p-stacking interactions result in aggregation effects
in the UV-VIS spectra of the naphthalocyanine complexes syn-
(THF as the eluent). The solvent was evaporated, the resulting oil was
washed with n-hexane, and the precipitate that formed was filtered off
and repeatedly washed with n-hexane and methanol. The yield of com-
§
+
·
Bis(82,92,152,162,222,232-hexaphenyltrinaphthalo[h,o,v]-5,12,19,26-
pound 3 was 41.0 mg (31%). MS (MALDI-TOF), m/z: 2285 [M+Ph] ,
+
·
+
·
tetraazaporphyrino)[b,e]benzene dimagnesium 3. Compounds 1 (400.0 mg,
1.21 mmol), 2(13.0 mg, 0.06 mmol), Mg(OAc)2·4H2O (51.4 mg, 0.24 mmol),
DBU (0.5 ml) and isoamyl alcohol (15 ml) were placed in a two-necked
flask equipped with a reflux condenser and a magnetic stirrer. The reaction
was refluxed for 12 h under argon. The reaction progress was monitored
by spectrophotometry using THF as the solvent. The mixture was cooled
and poured into a MeOH–H2O (1:1) mixture. The resulting blue preci-
pitate was filtered off and washed with water and then with methanol.
The target compound was isolated by gel permeation chromatography
2209 [M] , 2133 [M–Ph] . UV-VIS [THF, lmax/nm (I/Imax)]: 734 (0.94),
772 (1.00), 960 (0.213). 1H NMR (THF-d6) d: 7.23–7.24 (m, 60H, HPh),
8.20 (s, 12H, 1-HNPh), 8.42 (s, 12H, 2-HNPh), 9.68 (s, 3-HAr).
In addition, gel permeation chromatography gave 52.0 mg (32%) of
complex 3,4,12,13,21,22,30,31-octaphenyl-2,3-naphthalocyanine mag-
+
·
+
·
nesium 4. MS (MALDI-TOF), m/z: 1345 [M] , 1268 [M – Ph] . UV-VIS
[THF, lmax/nm (I/Imax)]: 340 (0.57), 689 (0.23), 734 (0.20), 772 (1.00).
1H NMR (pyridine-d5) d: 7.26–7.31 (m, 40H, HPh), 8.13 (s, 8H, 1-HNPh),
8.58 (s, 8H, 2-HNPh).
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Mendeleev Commun., 2011, 21, 165–167
According to quantum chemical computations, complex 3 is
an almost planar molecule with nearly Cs symmetry (Figure 3).
The deviation from the plane of the naphthalocyanine macro-
cycles does not exceed 0.1 Å for any of the atoms. Magnesium
ions are coordinated in two cavities of the naphthalocyanine ligand
(ion deviation from the naphthalocyanine ligand plane does not
exceed 0.1 Å). Computation data confirm the conclusions made
by comparing proton shielding that the signals are shifted down-
field in the sequence HPh (~7.5 ppm) < 1-HNPh (~9.1 ppm) <
< 2-HNPh (~10.5 ppm) < 3-HAr (12.1 ppm). The observed and
calculated chemical shifts differ because the solvation effect and
bonding of THF molecules with magnesium ions are not taken
into account.18
2.488 Å
4.031 Å
4.049 Å
12.1
10.5 9.1
10.5
9.1
10.8
9.3
In conclusion, 2,3-dicyano-6,7-diphenylnaphthalene has been
synthesized in high yield. Starting from this compound, dodeca-
phenyl-substituted planar binuclear naphthalocyanine magnesium
complex has been prepared. A considerable bathochromic shift
of absorption up to 1100 nm has been detected for the first time
for this type of complexes.
Figure 3 Structure of complex 3 according to DFT calculations.
thesized, namely, an increase in the intensity of the Soret band
with respect to the Q-band (Figure 2) and broadening of the
Q-band (Figures 1 and 2).
These interactions have the most significant effect in the case
of a binuclear naphthalocyanine complex, which is due to an
expansion of the p-electron conjugation system. Absorption in
the near IR region is not observed in a non-coordinating solvent
(Figure 1). The use of a coordinating solvent (THF) results in
partial or complete disaggregation owing to coordination to the
central metal ion, as we reported previously.6
The authors are grateful to the Joint Supercomputer Center
(JSC) for computing time on MVS-50K.
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2011.04.019.
The naphthalocyanine complexes 3 and 4 were characterised
by MALDI-TOF mass spectrometry. To assist the ionization
of the complexes, trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-
propenylidene]malononitrile (DCTB) was used as the matrix. In
this case the mass spectrum of complex 3¶ contained a molecular
ion peak along with a peak corresponding to the interaction of
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¶
For MALDI-TOF (Figure 1S) and 1H NMR (Figure 2S) spectra of com-
plex 3, see Online Supplementary Materials.
†† DFT calculations details. All calculations were performed using the
resources of an MVS-50K supercomputer of the Joint Supercomputer
Center (JSC) (www.jscc.ru), at the DFT level of theory. Geometry opti-
mizations were carried out using the PBE generalized gradient functional.19
Geometries were optimized using the TZ2P20 valence basis set and SBKJC
effective core potentials for Mg, C, and N atoms.21–23 Chemical shifts
were calculated using the cc-pCVTZ basis set.24 The shielding of TMS
protons was calculated to be 31.3915 ppm for H. Vibration frequencies
were used to characterize stationary point as minima. All calculations
were performed using the PRIRODA program.25,26
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Received: 9th November 2010; Com. 10/3626
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