Synthesis and photophysical properties of 1,1′-binaphthol substituted phthalocyanines

Article abstract of DOI:10.1016/j.ica.2010.06.034

We report on the synthesis, characterization and photophysical properties of a new symmetrically tetra substituted {at non-peripheral positions with tetra(1,1′-bi-binaphtoxy)} phthalocyanines containing H₂, Mg(II), Al(III)Cl, Si(IV)Cl₂

Full text of DOI:10.1016/j.ica.2010.06.034

Inorganica Chimica Acta 363 (2010) 3384–3389
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and photophysical properties of 1,10-binaphthol
substituted phthalocyanines
Mevlude Canlica a,b, Tebello Nyokong b,
*
a Yildiz Technical University, Chemistry Department, Inorganic Chemistry Division, Davutpasa Campus, 34220 Esenler, Istanbul, Turkey
b Rhodes University, Chemistry Department, P.O. Box 6140, Grahamstown, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
We report on the synthesis, characterization and photophysical properties of a new symmetrically tetra
substituted {at non-peripheral positions with tetra(1,10-bi-binaphtoxy)} phthalocyanines containing H2,
Mg(II), Al(III)Cl, Si(IV)Cl2 in the central cavity. The synthesized compounds were characterized by the ele-
mental analyses, UV–Vis, FT-IR and 1H NMR spectroscopies. The fluorescence quantum yields, triplet
quantum yields and lifetimes of the newly synthesized H2, Mg, Al, and Si phthalocyanines were explored.
Triplet quantum yields ranged from 0.24 to 0.54. The triplet lifetime for the silicon phthalocyanine deriv-
ative was the highest ever reported for a phthalocyanine (ꢀ3.5 ms).
Received 23 March 2010
Received in revised form 8 June 2010
Accepted 16 June 2010
Available online 25 June 2010
Keywords:
Magnesium
Aluminum
Ó 2010 Elsevier B.V. All rights reserved.
Silicon phthalocyanines
Fluorescence quantum yield
Triplet quantum yield and lifetime
1. Introduction
pected to promote aggregation due to strong p–p interaction.
However, it has been reported [27] that the steric hindrance arising
from the bulky groups substituted at the non-peripheral positions
of the phthalocyanines (and linked by an atom such as oxygen) re-
sults in twisting of the substituents, hence preventing aggregation.
There are still very few complexes which contain bulky substitu-
ents at the non-peripheral position for phthalocyanines containing
the above central metals. SiPc derivatives possess covalently bound
axial substituents, which further influence the molecules’ physico-
chemical properties [28,29]. In the present paper, we describe the
synthesis and photophysical properties of the new MPc complexes
(M = H2, Mg, Al and Si) with aromatic substituents. The bulkiness of
the substituents and the location at the non-peripheral position is
aimed at preventing aggregation since aggregation is known to re-
duce photoactivity [28].
Phthalocyanines (Pcs) are remarkable macrocyclic compounds
that possess interesting physical and chemical properties. Their
bright colors, conductivity, chemical and thermal stability have
made them very desirable for many applications [1]. Pcs continu-
ally find their usefulness in contemporary and emerging technolo-
gies such as in electrocatalysis [2], non-linear optics [3], gas
sensors [4,5], thermal writing displays [5], solar cells [6] and as
photoconducting materials [7]. There is considerable interest in
metallophthalocyanines (MPcs) complexes containing non-transi-
tion metals for use as photosensitizers in the relatively new meth-
od of cancer treatment called photodynamic therapy (PDT) [8–15].
The mode of operation in PDT is based on visible light excitation of
a tumor-localized photosensitizer. After excitation, energy is trans-
ferred from the photosensitizer (in its triplet excited state) to
ground state oxygen (3O2), forming singlet state oxygen (1O2). High
triplet state quantum yields and long triplet life times are required
for efficient photosensitization, and these criteria may be fulfilled
by the incorporation of diamagnetic metals such as zinc, silicon,
aluminum into the Pc macrocycle [16]. Some studies including
synthesis, photophysics and photochemistry of Mg, Al and SiPcs
have been documented [17–26]. However aggregation is often a
problem in the molecules studied. The presence of aromatic sub-
stituents lying in the same plane as the phthalocyanine ring is ex-
2. Experimental
2.1. Materials
Chloroform, dimethyl sulfoxide (DMSO), N,N0-dimethylformam-
ide (DMF), tetrahydrofuran (THF), methanol (MeOH), acetone, gla-
cial acetic acid and n-pentanol were purchased from SAARCHEM.
Pyridine, potassium carbonate, aluminum chloride, silicon tetra-
chloride, magnesium chloride, 1,8-diazabicyclo[5.4.0] undec-7-
ene (DBU) and lithium metal were purchased form Sigma–Aldrich.
Silica gel for column chromatography was purchased from Merck.
* Corresponding author. Tel.: +27 46 6038260; fax: +27 46 6225109.
E-mail address: t.nyokong@ru.ac.za (T. Nyokong).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.06.034

M. Canlica, T. Nyokong / Inorganica Chimica Acta 363 (2010) 3384–3389
3385
2.2. Equipment
2.3.1. 3-(1,10-Bi-binaphtoxy)phthalonitrile (3)
Compound 2 (3.31 g, 11.55 mmol) was dissolved in dry DMSO
(15 mL) and 1 (2 g, 11.55 mmol) was added under inert atmo-
sphere. To this reaction mixture finely ground anhydrous potas-
sium carbonate (3.19, 23.1 mmol) was added. After 4 h of stirring
at room temperature, further potassium carbonate (0.79 g,
5.77 mmol) was added and this same amount was added again
after 24 h of stirring. After 48 h of stirring, the reaction mixture
was poured into water (50 mL) resulting in the formation of light
brown precipitate. The crude product was centrifuged and was fur-
ther purified by chromatography over a silica gel column using a
CHCl3 as eluent. The product was recrystallized from ethanol and
then the pure product was dried using P2O5. Yield: 1.9 g (40%).
UV–Vis absorption spectra were obtained using the Varian Cary
500 UV–Vis/NIR. Fluorescence excitation and emission spectra
were recorded using a Varian Eclipse spectrophotometer. FT-IR
data (KBr pellets) were recorded using the Perkin–Elmer spectrum
2000 FTIR spectrometer. 1H NMR spectra were obtained using a
Bruker EMX 400 MHz spectrometer. Elemental analyses were done
on a Vario-Elementar Microcube EL III. Triplet absorption and de-
cay kinetics were recorded on a laser flash photolysis system, the
excitation pulses were produced by a Nd: YAG laser (Quanta-Ray,
1.5 J/9 ns) pumping dye laser (Lambda Physic FL 3002, Pyridin 1
in methanol). The analyzing beam source was from a Thermo Oriel
xenon arc lamp, and a photomultiplier tube was used as detector.
Signals were recorded with a two-channel digital real-time oscillo-
scope (Tektronix TDS 360); kinetic curves were averaged over 256
laser pulses. The triplet lifetimes were determined by exponential
fitting of the kinetic curves using the program ORIGINPRO 6.1. MALDI-
TOF mass spectra were recorded using a ABI Voyager DE-STR MAL-
DI-TOF instrument at University of Stellenbosch and using 2,
5-dihydroxy benzoic acid as matrix.
m.p.: 60 °C. IR(KBr) (m
max/cmꢁ1): 3400 (Ar–OH), 3042 (Ar–CH),
2233 (C„N), 1588 (C@C), 1268 (C–O–C). 1H NMR (DMSO-d6): d,
ppm 8.18 (2H, d, Ar–H), 8.08 (2H, d, Ar–H), 7.85 (1H, t, Ar–H),
7.55 (1H, t, Ar0–H), 7.50–7.45 (6H, t, Ar–H), 7.2(1H, s, OH),7.35
(1H, t, Ar0–H), 7.12 (2H, dd, Ar0–H). Anal. Calc. for C28H16N2O2: C,
81.54; H, 3.91; N, 6.79. Found: C, 79.37; H, 3.68; N, 8.96%. MS
m/z Calc: 412.12. Found [M]+: 411.67.
2.3.2. (3)-Tetra(1,10-bi-binaphtoxy)phthalocyaninato metal free (4a)
In 25 mL of dry pentanol, compound 3 (100 mg) was stirred un-
der reflux in an argon atmosphere at 140 °C for 10 min. Then
100 mg of lithium was added and the reaction mixture was re-
fluxed for a further 2 h. Thereafter the reaction mixture was left
to cool to room temperature. Glacial acetic acid (40 mL) was added
to the mixture resulting in unmetallated phthalocyanine. The
resulting precipitate was centrifuged and washed with water.
The product was then purified using column chromatography
and chloroform as the eluting solvent. Yield: 0.040 g (10%). UV–
2.3. Synthesis
3-Nitrophthalonitrile (1) was synthesized as reported in litera-
ture [30,31]. 1,10-Binaphthyl-8,80-diol (2) and solvents were of re-
agent grade quality and were obtained from commercial
suppliers. All solvents were dried and purified as described by Per-
rin and Armarego [32]. The target precursor (3) was prepared by a
nucleophilic aromatic substitution reaction between 3-nitro pht-
halonitrile (1) and 1,10-binaphthyl-8,80-diol (2), Scheme 1.
Vis (DMSO) kmax/nm (log e
/dmꢁ3 molꢁ1 cmꢁ1): 720 (4.29/4.35),
CN
NO2
CN
CN
i
OH
O
+
OH
OH
CN
(1)
i : DMSO, rt, 2 days
ii : Metal salts, (b) DMF, (d) quinoline, reflux, DBU,18 h
iii: Li, n-pentanol, reflux,18 h
(2)
(3)
iii
ii
iv: Metal salts, n-pentanol, reflux, DBU, 10 h
HO
HO
HO
HO
O
O
O
N
N
N
M
N
N
N
O
N
iv
N
N
N
M
N
N
O
N
N
O
O
N
N
O
OH
OH
(4)
M = Mg (b), Al (c), Si (d)
(4)
M = H
OH
OH
2 (a)
Scheme 1. Synthetic route of non-peripherally substituted metallophthalocyanines.

3386
M. Canlica, T. Nyokong / Inorganica Chimica Acta 363 (2010) 3384–3389
716 (4.35). IR [(KBr)
m
max/cmꢁ1]: 3400 (Ar–OH), 1255 (C–O–C). 1H
2.4.2. Triplet quantum yields and lifetime
NMR (CDCl3): d, ppm 8.05–7.15 (52H, Ar–H), 9.25(s, 4H, Ar–OH),
7.1 (d, 8H, Ar–H in R group), 2.5(s, 2H). Anal. Calc. for C112H66
N8O8.H2O: C, 81.44; H, 4.03; N, 6.78. Found: C, 80.56; H, 4.10; N,
6.71%. MALDI-TOF-MS m/z Calc: 1651.77. Found [M+3H]+: 1654.5.
The solutions for triplet quantum yields and lifetimes were
introduced into a 1.0 mm pathlength UV–Vis spectrophotometric
cell, deaerated using argon. Triplet state quantum yields (UT) of
4a–d were determined by the triplet absorption method [38], using
zinc phthalocyanine (ZnPc) as a standard; Eq. (2):
2.3.3. (3)-Tetra(1,10-bi-binaphtoxy)phthalocyaninato magnesium(II)
(4b)
D
D
AT ꢂ eSTtd
UT
¼
USTtd
ð2Þ
ASTtd
ꢂ
eT
Compound 3 (0.206 g, 0.499 mmol) and MgCl2 (0.036 g) were
dissolved dry DMF (15 mL). This mixture was then refluxed for
18 h under nitrogen atmosphere and in the presence of DBU [17].
The mixture was then cooled down to room temperature and the
dark green product was precipitated by adding ethanol. The product
was chromatographed on a silica gel with chloroform as eluent.
where,
D
AT and
D
ASTtd are the changes in the triplet state absor-
bances of 4a–d and the standard, respectively. eT and eSTtd are the
triplet state molar extinction coefficients for 4a–d and the standard,
respectively. USTtd is the triplet quantum yield for the standard, ZnPc
(
USTtd = 0.65 in DMSO) [39], eT and eSTtd were determined from the
Yield: 0.030 g (4%). UV–Vis (DMSO)max/nm (log
e
/dmꢁ3 molꢁ1
m
max/cmꢁ1]: 3476 (Ar–OH), 1255 (C–O–
molar extinction coefficients of their respective ground singlet state
cmꢁ1): 694 (3.87). IR[(KBr)
(
eT and eSStd) and the changes in absorbances of the ground singlet
C). 1H NMR (DMSO): d = 8.2–7.1 (52H, Ar–H), 9.16 (s, 4H, Ar–OH),
6.95 (d, 8H, Ar–H in R group). Anal. Calc. For C112H64N8O8Mg.H2O:
C, 80.36; H, 3.85; N, 6.69. Found: C, 79.50; H, 3.93; N, 662%. MAL-
DI-TOF-MS m/z Calc: 1674.06. Found [M+4H]+: 1678.0.
states (
D
AS and
D
ASStd) according to Eq. (3):
D
AT
AS
eT
¼
eS
ꢂ
ð3Þ
D
Quantum yields of internal conversion (UIC) were obtained
2.3.4. (3)-Tetra(1,10-bi-binaphtoxy)phthalocyaninato
aluminum(III)chloride (4c)
from Eq. (4), which assumes that only three processes (fluores-
cence, intersystem crossing and internal conversion), jointly deac-
tivate the excited singlet state of the 4a–d molecules.
Complex 4a (0.100 g, 0.060 mmol) and AlCI3 (0.036 g) were
heated in 10 mL dry n-pentanol to reflux. Then 0.2 mL DBU was
added in the solution dropwise. This mixture was kept refluxing
for 10 h under nitrogen atmosphere [22,33]. It was cooled down
to room temperature and the dark green product was precipitated
by ethanol and washed with ethanol, acetone and chloroform.
UIC ¼ 1 ꢁ ðUF
þ
UT
Þ
ð4Þ
3. Results and discussion
Yield: 0.008 g (8%). UV–Vis (pyridine) kmax/nm (log
e
/dmꢁ3 molꢁ1
m
max/cmꢁ1]: 3418 (Ar–OH), 1254
cmꢁ1): 709 (3.95). IR [(KBr)
3.1. Synthesis and characterization
(C–O–C). 1H NMR (DMSO): d = 7.8–6.85 (52H, Ar–H), 9.18 (s, 4H,
Ar–OH), 6.85 (d, 8H, Ar–H in R group). Anal. Calc. for C112H64N8O8Al-
CI.H2O: C, 78.57; H, 3.77; N, 6.54. Found: C, 77.75; H, 3.84; N, 6.48%.
MALDI-TOF-MS m/z Calc: 1712.19. Found [M+7H]+: 1719.0.
Cyclotetramerization of the phthalonitrile derivative 3 to the
metallophthalocyanines 4b, and d was accomplished in quinoline
(for 4d) and DMF (for 4b) in the presence of a metal salt (SiCl4 or
MgCl2, respectively) at reflux temperature. Cyclotetramerization
of compound 3 to 4a was achieved in n-pentanol using lithium me-
tal as a catalyst. The crude product was treated with acetic acid to
afford the metal-free phthalocyanine 4a. Complexes, 4a, 4b and 4d
were synthesized from 3, whereas 4c was synthesized from 4a,
Scheme 1. Column chromatography with silica gel using CHCI3 as
mobile phase was used to purify complexes 4a, b and d. Complex
4c was only washed in common organic solvents due to demetal-
lation after column chromatography with silica gel. The complexes
were obtained in a moderate yield (10, 4, 8 and 2% for 4a–d,
respectively). The structure and purity of the Pc derivatives was
confirmed by UV–Vis, 1H NMR and elemental analysis.
In the IR spectra of complexes 4a, b and d, the band at around
2233 cmꢁ1 corresponding to the –C„N groups in 3 disappeared
on conversion into the phthalocyanine. For all complexes there is
the broad vibrational band between 3400 and 3480 cmꢁ1 corre-
sponding to the Ar–OH, indicating the presence of OH groups.
The characteristic vibrations corresponding to ether groups
(C–O–C) were observed at around 1255 cmꢁ1 for 3 and 4a–d.
1H NMR spectra of all complexes showed complex patterns due
to the mixed isomer character of these compounds. In the 1H NMR
spectra of 3 and 4a–d, the OH protons are observed as sharp signals
around 9.2 ppm and the signal disappeared by deuterium ex-
change. In the spectrum of 3 and 4b–d, the aromatic and Pc pro-
tons appear between 8.2–6.85 ppm and for 4a between 8.05 and
7.15 ppm, integrating for a total of 66 for 4a, 64 for 4b–d complex
and 16 for 3. The 1H NMR spectra for 4c showed extensive overlap-
ping of signals. Elemental analysis results also were consistent
with the proposed structures of 3 and 4a–d as expected. The puri-
fied phthalocyanines were further characterized by mass spectra.
The expected mass values corresponded with the found values
2.3.5. (3)-Tetra(1,10-bi-binaphtoxy)phthalocyaninato
silicon(IV)dichloride (4d)
A mixture of compound 3 (0.452 g, 1.096 mmol), SiCI4 (0.2 mL)
and dry quinoline (2 mL) was refluxed for 120 min under nitrogen
atmosphere and allowed to cool. The precipitate was filtered
[33,34] and Soxhlet extraction with methanol and acetone yielded
the pure compound 4d. Yield: 0.040 g (2%). UV–Vis (DMSO) kmax
/
nm (log
e
/dmꢁ3 molꢁ1 cmꢁ1): 697 (4.32). IR [(KBr) max/cmꢁ1]:
m
3465 (Ar–OH), 1254 (C–O–C). 1H NMR (DMSO): d = 8.2–7.1 (52H,
Ar–H), 9.16 (s, 4H, Ar–OH), 6.95 (d, 8H, Ar–H in R group). Anal. Calc.
For C112H64 CI2N8O8Si.H2O: C, 76.92; H, 3.69; N, 6.41. Found: C,
76.14; H, 3.77; N, 6.34%. MALDI-TOF-MS m/z Calc: 1748.75. Found
[Mꢁ2Cl]ꢁ: 1677.68.
2.4. Photophysical studies
2.4.1. Fluorescence quantum yields
Fluorescence quantum yields (UF) were determined by the
comparative method [35,36], (Eq. (1)):
F ꢂ AStd ꢂ n2
UF
¼
UFðStdÞ
;
ð1Þ
FStd ꢂ A ꢂ n2Std
where, F and FStd are the areas under the fluorescence curves of 4a–
d and the standard, respectively. A and AStd are the respective absor-
bances (which was ꢀ0.05 in all solvents used) of the sample and
standard at the excitation wavelengths, and n and nStd are the
refractive indices of solvents used for the sample and standard,
respectively. ZnPc (UF = 0.20 in DMSO) was employed as the stan-
dard [37].

M. Canlica, T. Nyokong / Inorganica Chimica Acta 363 (2010) 3384–3389
3387
Table 1
1
Spectral data for the complexes in DMSO.
0.8
0.6
0.4
0.2
0
Compound
kmax (nm) (log e )
/dmꢁ3 molꢁ1 cmꢁ1
Absorption
Emission
721
Excitation
690/722
Stoke’s shift
1
A
4a
688 (4.29)
719 (4.35)
694 (3.87)
695 (3.95)
697 (4.32)
4b
4c
4d
705
702
706
694
695
694
11
7
12
E
350
450
550
650
750
for all complexes. MPc complexes have been observed to degrade
with molecular ion peaks [M]+, [M+nH]+ or [MꢁnH]+ (n = 1–3)
[40]. The matrix employed in this work is 2,5-dyhydroxybenzoic
acid, which is known [40] to intensify the fragmentation process,
hence the observed mass spectral data.
Wavelength / nm
1.8
y = 4118.1x- 0.0182
2
R
= 0.9999
1.4
1.2
1
0.8
0.6
0.4
0.2
0
A
1.3
0.8
0.3
The UV–Vis spectral data in DMSO given in Table 1 (and Fig. 1)
are also in accord with the expected structure. The phthalocya-
nines show typical electronic spectra with two strong absorption
regions, one of them in the UV region at about 300–350 nm (B
bands) and the other in the visible portion at 600–700 nm (Q
band). The characteristic Q band transition of metallophthalocya-
nines with D4h symmetry is observed as a single band of high
intensity in the visible region. Aggregation behavior of the Pc is de-
picted as a coplanar association of rings progressing from mono-
mer to dimer and higher order complexes and it is dependent on
concentration, nature of solvent, substituents, metal ions and tem-
perature [41]. In this study, the aggregation behavior of the Pcs
derivatives were investigated in DMSO (for complexes 4a and b
as representative) at different concentrations. The ground state
electronic absorption spectra of all the complexes showed mono-
meric behavior in DMSO as evidenced by single Q-band, typical
of metalled Pcs, Fig. 2a and b, the spectra is split for unmetalated
(4a) as expected. As the concentration was increased, the intensity
of absorption of the Q-band also increased and there were no new
bands due to the aggregated species [42]. Lambert–Beer law was
obeyed for the complexes in the concentration ranging from 10ꢁ4
1
3
Concentration / M (x10-4
)
E
350
450
550
650
750
Wavelength / nm
Fig. 2. Absorption spectra of 4a and 4b at different concentrations and in DMSO.
Concentration ranges: 4a = (A) 2 ꢃ 10ꢁ5 to (E) 6 ꢃ 10ꢁ6 mol dmꢁ3 and 4b = (A)
3 ꢃ 10ꢁ4 to (E) 1 ꢃ 10ꢁ4 mol dmꢁ3. Inset: Lambert–Beer law plot.
symmetry. The observation of one Q band in the emission spectra,
is typical of unmetallated Pcs [44]. For complex 4b, the absorption
and excitation spectra show the same Q band maxima, however,
the excitation spectrum is broadened compared to the absorption
spectrum, suggesting some change in symmetry on excitation.
The emission spectra are mirror images of the excitation spectra,
with maxima shown in Table 1. For 4c, the excitation spectrum
is the same as the absorption spectrum and both are mirror images
of the emission spectrum. Stoke’s shifts ranged from 1 to 12 nm.
The fluorescence quantum yield (UF) values are not too different
and are typical of MPc complexes [28], Table 2. The large value
of UF for MgPc derivative (4b), could be due to the small size of
the central metal, which would result in less intersystem crossing
to the triplet state compared to complexes 4c and 4d. A high value
would have then been expected for 4a, but this is not the case in
Table 2.
to 10ꢁ6 mol dmꢁ3
.
The spectra of the complexes in CHCl3, Fig. 1, showed mono-
meric behavior. However, complex 4b in CHCl3 (Fig. 1) showed
an extra band near 730 nm, which could be associated with loss
of symmetry or partial demetalation often observed in chlorinated
solvents [43].
3.2. Fluorescence spectra and quantum yields
The absorption and fluorescence excitation spectra of 4a–d in
DMSO are shown in Fig. 3. The excitation, absorption and emission
spectral data are listed in Table 1. For complex 4a, the low energy
component of the Q band is red shifted in the excitation spectrum
compared to absorption spectrum, suggesting some change in
3.3. Triplet quantum yields (UT) and lifetimes (sT
)
The triplet quantum yields and lifetimes of the complexes are
listed Table 2 and Fig. 4 shows a representative triplet decay curve
for the complexes. Triplet quantum yield UT represents the fraction
of absorbing molecules that undergo intersystem crossing to the
metastable triplet excited state. Therefore, factors which induce
spin–orbit coupling will certainly populate the triplet excited state.
High UT values and correspondingly low UF values suggest more
efficient intersystem crossing (ISC) in the presence of the aromatic
substituents. The UT values for 4a–d are 0.54, 0.24, 0.34 and 0.35,
respectively. The low UT value for the MgPc derivative corresponds
to the high value of UF
All complexes showed reasonably large triplet lifetimes with sT
ranging from 310 to 3460 s. The latter value is larger than has
.
l
ever been reported for an MPc complex [28], showing that the
combination of naphthol and silicon central metal results in a very
good photosensitizer. The high triplet lifetime for the silicon
phthalocyanine derivative could be a result of the presence of both
the bulky substituents at non-peripheral positions and two axial
Fig. 1. Absorption spectra of 4a–d in CHCl3.

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M. Canlica, T. Nyokong / Inorganica Chimica Acta 363 (2010) 3384–3389
Fig. 3. Absorption (a), emission (b) and excitation (c) spectra of 4a, 4b, 4c and 4d in DMSO at excitation wavelength = 621, 620, 630, 630 nm, respectively.
tal analyses, IR, UV/VIS, 1H NMR and mass spectra confirm the pro-
Table 2
Photophysical parameters of 4a–d in DMSO.
posed structure of the compounds. The complexes contain bulky
aromatic substituents at the non-peripheral positions, aggregation
was not observed due to the twisting of the organic substituents
around the C–O–C bond preventing stacking of the phthalocyanine
units. The triplet lifetime also increased for all complexes in the
presence of an aromatic group and axial group due to the heavy
atom effect. The triplet lifetime for the silicon phthalocyanine
derivative was the highest ever reported for a phthalocyanine
(ꢀ3.5 ms) showing that the combination of naphthol and silicon
central metal results in a very good photosensitizer.
Compound
UF 0.01
UT 0.02
UIC
sT (ls)
4a
4b
4c
4d
0.10
0.57
0.11
0.17
0.54
0.24
0.34
0.35
0.36
0.19
0.55
0.48
310
570
610
3460
Acknowledgements
This work was supported by the Department of Science and
Technology (DST) and National Research Foundation (NRF), South
Africa through DST/NRF South African Research Chairs Initiative
for Professor of Medicinal Chemistry and Nanotechnology as well
as Rhodes University.
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4. Conclusions
This work has described the synthesis, spectral, photophysical
properties of new substituted phthalocyanine complexes. Elemen-

M. Canlica, T. Nyokong / Inorganica Chimica Acta 363 (2010) 3384–3389
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