2
Tetrahedron
corresponding phthalonitrile derivatives (9 or 10) and 3,6-
the carbon chain length (octyl or undecyl) on the 9 and 10
positions of the triptycene group did not affect the absorption
wavelength (Fig. 1). However, the Q-bands of A B type
didecylphthalonitrile
diazabicyclo[5.4.0]undec-7-ene (DBU) with Zn(AcO)
in
the
presence
of
1,8-
in n-
2
3
pentanol at reflux for 12 h (Scheme 1). The newly synthesized
substituted zinc(II) Pc complexes (11 and 12) were 26 nm red-
phthalocyanines (11 and 12) were fully characterized by
spectroscopic techniques; FT-IR, H-NMR, MALDI-TOF mass,
UV–vis and elemental analysis. The obtained results were in
accordance with the proposed structures.
shifted compared to the unsubstituted zinc(II) phthalocyanine
(Fig S3) in toluene (= 672 nm), implying that the HOMO-
LUMO energy gap of the phthalocyanine ring was reduced upon
introduction of the substituents, especially at the non-peripheral
positions of the phthalocyanine ring. The B bands were observed
at around 360 nm resulting from deeper π level-LUMO
transitions (Fig. 1).
1
15
In the Fourier transform infrared (FT-IR) spectra of the
starting phthalonitrile compounds, the disappearance of the OH
-
1
peaks at approximately 3412 cm and the appearance of a new
2
-
1
-1
strong peak at 2235 cm for 9 and 2237 cm for 10 belonging to
C≡N stretching vibrations indicated phthalonitrile formation.
−
1
.6
These strong −C≡N peaks disappeared after conversion of these
phthalonitriles to phthalocyanine derivatives (11 and 12).
1
1.2
0.8
The H-NMR spectra of compounds 9 and 10 showed two
1
1
2
multiplet peaks at 6.99 and 7.03 ppm for 9 and at 6.96 and 7.03
ppm for 10 which could be attributed to the four aromatic protons
and three singlet peaks at 6.88, 6.96 and 7.35 ppm for 9 and at
1
6
.88, 6.95 and 7.36 ppm for 10 which could be attributed to the
0
.4
0
six aromatic protons. The six methoxy protons appeared as a
singlet peak at 3.83 ppm for both phthalonitriles. The methylene
protons on the alkyl chains appeared as multiplets between 2.80-
3
00
400
500
600
700
800
1
.34 ppm for 9 and 2.80-1.25 ppm for 10. Additionally, another
Wavelength (nm)
triplet peak attributed to the methyl protons on the alkyl chain
Figure 1. Electronic absorption spectra of phthalocyanines 11 and 12 in
were observed at 0.93 and 0.89 ppm for 9 and 10, respectively.
-5
toluene (1.20 x 10 M).
13
The C-NMR spectra were also in agreement with the structures
1
of compounds 9 and 10. In the H NMR spectra of zinc(II)
The aggregation behavior of the unsymmetrical substituted
zinc(II) phthalocyanines (11 and 12) were investigated in various
solvents (DMF, THF, toluene and chloroform). Both
phthalocyanines did not show any aggregation in all studied
solvents (ESI, Figs. S4 and S5). Moreover, the aggregation
behavior of these phthalocyanines (11 and 12) were also
investigated at different concentrations in toluene (ESI, Figs. S6
and S7). The Beer–Lambert law was obeyed for both studied
phthalocyanines 11 and 12, some of the signals were broadened
which was likely due to chemical exchange caused by
aggregation–disaggregation equilibrium of the phthalocyanine
13
cores at the high concentration used for NMR measurements.
Nevertheless, all protons were observed within their specific
regions and the integral values were consistent with the expected
number of protons. The aromatic protons were observed as broad
peaks between 7.71-6.86 ppm for phthalocyanine 11 and 7.72-
-
5
phthalocyanines at concentrations ranging from 1.20 x 10 to
-
6
6
.84 ppm for phthalocyanine 12. The CH
3
protons of the
2.00 x 10 M. Any extra band formation that was dependent on
concentration change was not observed in toluene and only
diminution was observed in the maxima of the Q and B bands
which indicated the absence of H- or J-type aggregation.
methoxy groups were observed as singlet peaks at 3.99 ppm for
both phthalocyanines. The aliphatic protons of the octyl or
undecyl carbon chains on the triptycene group and the decyl
chains on the non-peripheral positions of the phthalocyanine ring
were observed between 3.04-1.07 and 3.06-1.09 ppm for
phthalocyanines 11 and 12, respectively. Two different aliphatic
The fluorescence behavior of the zinc(II) phthalocyanines were
studied in solutions of toluene. The electronic absorption,
fluorescence emission and excitation spectra are shown in Fig. 2
for phthalocyanine 11 and ESI, Fig. S8 for phthalocyanine 12.
Their absorption spectra were similar to the excitation spectra
and both were mirror images of the fluorescent spectra which
suggests that the nuclear configurations of the ground and excited
states were similar and not affected by excitation. The maximum
emission intensities were observed at Em= 709 nm when the
solutions were excited at Ex= 665 nm for both studied
phthalocyanines (11 and 12). The observed Stokes shifts
protons belonging to the CH
3
groups were observed at 1.00 and
0
.61 ppm for 11 and 1.00 and 0.60 ppm for 12.
The molecular ion peaks for the newly synthesized
phthalonitrile and phthalocyanine compounds were identified
using the reflectron mode by matrix-assisted laser
desorption/ionization time-of-flight mass (MALDI-TOF) mass
spectrometry. The main peaks were observed at m/z: 694.12 for
phthalonitrile 9, 779.84 for phthalonitrile 10, 1984.12 for
+
phthalocyanine 11 and 2070.83 phthalocyanine 12 as [M] (ESI,
(ΔStokes=Em-abs
)
were found to be 11 nm for both
phthalocyanines. The observed Stokes shifts of phthalocyanines
1 and 12 were found to be higher than those of unsubstituted
Fig. S1).
1
The elemental analysis results of phthalonitriles 9 and 10 and
phthalocyanine compounds 11 and 12 also confirmed their
structures.
16
zinc(II) phthalocyanine (ΔStokes= 4 nm in toluene).
The fluorescence quantum yields (Φ ) of 11 and 12 were
F
determined in toluene solutions as 0.16 for 11 and 0.14 for 12,
The ultraviolet-visible (UV-vis) spectra of the studied
unsymmetrical zinc(II) phthalocyanines (11 and 12) in toluene
showed a single (narrow) Q band due to D4h symmetry which
which were approximately two times higher than those of the
17
unsubstituted zinc(II) phthalocyanine (Φ
increase in Φ
triptycene groups on the Pc skeleton.
F
=0.07 in toluene). An
F
values could be due to the presence of the
14
were typical of metallophthalocyanines. The observed sharp
absorption bands were evidence for the formation of non-
aggregated phthalocyanine species. The Q bands were observed
at 698 nm for both studied phthalocyanines which confirmed that
Al-Sohaimi, Bandar R.
