Synthesis, characterization, singlet-oxygen photogeneration, DNA photocleavage and two-photon-absorption properties of some (4-cyanophenyl) porphyrins

Article abstract of DOI:10.1002/ejic.200801047

A series of (4-cyanophenyl)porphyrins have been prepared and structurally characterized by ¹H NMR, IR and UV/Vis spectroscopy, mass spectrometry, and elemental analysis. The relative singlet-oxygen quantum yields, two-photon absorption cross-se

Full text of DOI:10.1002/ejic.200801047

FULL PAPER
DOI: 10.1002/ejic.200801047
Synthesis, Characterization, Singlet-Oxygen Photogeneration, DNA
Photocleavage and Two-Photon-Absorption Properties of Some
4-Cyanophenyl)porphyrins
(
Kai Wang,[a–c] Chun-Ting Poon, Wai-Kwok Wong,* Wai-Yeung Wong, Chun Y. Choi,
[b]
[b]
[b]
[b]
[b]
[c]
[a]
Daniel W. J. Kwong,* Heng Zhang, and Zao-Ying Li*
Keywords: Porphyrinoids / Singlet oxygen / DNA cleavage / Photochemistry / Sensitizers
A series of (4-cyanophenyl)porphyrins have been prepared
and structurally characterized by H NMR, IR and UV/Vis
spectroscopy, mass spectrometry, and elemental analysis.
The relative singlet-oxygen quantum yields, two-photon ab-
sorption cross-sections and DNA photocleavage activities of
these porphyrins were measured. The results show that (4-
cyanophenyl)porphyrins with a properly designed hydro-
phobic/hydrophilic balance for better cellular uptake have
potential application in two-photon-absorption photodyn-
amic therapy.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
1
Introduction
However, one major drawback associated with the clin-
ical application of porphyrin-based sensitizers lies in their
absorption wavelengths (the Soret band at 420–500 nm and
the weaker Q-bands at 500–600 nm), which are also ab-
sorbed significantly by vascularized tissues (e.g., skin), lead-
ing to photoallergy and therefore limiting their PDT appli-
Porphyrin-based compounds are among the most studied
photosensitizers because of their applications in photody-
namic therapy (PDT), which is an inherently selective cancer
treatment modality rendered by targeted photoirradiation
of the cancerous tissues that tend to uptake the porphyrins
[
4]
cations to mostly topical lesions. Thus, a new generation
of photosensitizers that absorb at λ Ͼ 650 nm has been de-
signed by various approaches, for example, porphyrin core-
[
1]
selectively. Although the mechanism of the selective ac-
cumulation of porphyrins in tumours remains unknown,
the damage inflicted by these photosensitizers on tumour
cells has largely been attributed to the singlet oxygen, O ,
[
4,5]
modification and expansion,
to circumvent this problem.
1
2
1
Recently, a new approach to the photogeneration of O2
generated when porphyrins are photoactivated by absorp-
by non-linear two-photon excitation of a sensitizer has been
tion at the Soret band.[ The O is produced by energy
2]
1
2
[6–8]
demonstrated.
In this process, an excited-state Sm is
transfer from the photoexcited sensitizer (in its triplet state)
to the ground-state (triplet) oxygen. This is known as the
Type II photosensitization mechanism. In contrast, when
the superoxide radical anion, O2· , is produced or a vital
biological substrate is damaged by electron transfer from
the excited photosensitizer, it occurs by the Type I mecha-
nism. Although both processes can potentially occur, the
Type II mechanism is considered to be more important in
populated as a result of the less probable simultaneous ab-
sorption of two lower-energy photons. This transition pro-
ceeds via a virtual state, S ǞS ǞS , and can follow selec-
–
0
virt
m
tion rules distinct from those corresponding to a one-pho-
[
9]
ton transition. For example, photoexcitation of a sensi-
tizer that absorbs at 400 nm in a one-photon transition can
be accomplished by laser light with λ Ͼ 800 nm by two-
photon absorption (2PA), allowing for maximum depth
[
3]
PDT.
[
10]
penetration through tissues.
Furthermore, the use of a
focused laser light, required for compensating the less prob-
[
[
[
a] College of Chemistry and Molecular Sciences, Wuhan Univer-
sity,
able two-photon absorption, affords spatial resolution to
Wuhan 430072, Hubei, P. R. China
Fax: 86-27-68754067
E-mail: zyliwuc@whu.edu.cn
1
O generation at target sites with pinpoint accuracy, which,
2
in addition to minimizing collateral photodamage to neigh-
[
10]
b] Department of Chemistry, Hong Kong Baptist University,
Kowloon Tong, Hong Kong, P. R. China
Fax: 852-3411-7348
bouring tissues,
allows one to study spatially resolved
1
[11]
cellular responses to O as well.
Successful application
2
of 2PA-PDT in vivo has recently been demonstrated.[
Moreover, if some of the two-photon excitation energy was
channelled into a radiative process of the sensitizer, such
emission from the sensitizer would inform on its localiza-
12]
E-mail: wkwong@hkbu.edu.hk
dkwong@hkbu.edu.hk
c] Key Laboratory for Green Chemical Process of the Ministry of
Education, Wuhan Institute of Technology,
Wuhan 430073, Hubei, P. R. China
922
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 922–928

Photophysical Properties of (4-Cyanophenyl)porphyrins
tion and uptake by the target tumour cells, allowing it to Figure 1). Detailed analysis of this crystal structure re-
act as both an imaging as well as a PDT agent.[
13,14]
vealed that the four pyrrole nitrogen atoms of the porphyrin
Most porphyrin-based photosensitizers used in PDT ring are not coplanar but are displaced [see Figure 1(b)], in
have distinct hydrophobic and hydrophilic ends to afford an contrast to the coplanarity commonly observed for these
optimal hydrophobic/hydrophilic balance for better cellular four nitrogen atoms in most metalloporphyrins, including
uptake and antitumour efficacy relative to those porphyrins another known example of a metallated (4-cyanophenyl)-
possessing a single hydrophobic or hydrophilic substitu- porphyrin, that is, mercury(II) tetrakis(4-cyanophenyl)por-
[
15]
[16]
II
ent. Previously, we have synthesized an amphiphilic bis- phyrinate,
porphyrin) consisting of a tetraphenylporphyrin (H TPP) porphyrin ring as a result of its large ionic radius
in which the Hg ion sits atop of the planar
(
2
and a tris(N-methyl-4-pyridyl)porphyrin linked by an –O– (Ͼ1.10 Å). This unusual structural feature is not at present
CH ) –O– spacer group, which showed a 10- and 5-fold understood. Nonetheless, the four Co–N distances,
(
2
3
increase relative to tetrakis(N-methyl-4-pyridyl)porphyrin averaged at 1.95 Å, are typically those of low-spin cobalt(II)
[
17]
(
H TMPyP) in cellular uptake and PDT efficacy towards porphyrinates.
2
[14]
Sarcoma 180 cells, respectively.
To evaluate their possible application in photodynamic
therapy, the singlet-oxygen quantum yields, Φ , of these (4-
∆
cyanophenyl)porphyrins were determined by measuring the
Results and Discussion
1
near-IR phosphorescence intensity of the O (at 1270 nm)
2
In this work we have synthesized a series of (4-cy- produced from these compounds upon photoexcitation.
anophenyl)porphyrins, 1–4, and investigated their photo- These spectra are shown in Figure 2. By using 5,10,15,20-
1
physical properties, particularly their O quantum yields tetraphenylporphyrin (H TPP) as a reference (Φ
=
2
2
∆
[
18]
1
and two-photon-absorption (2PA) cross-sections, and their 0.55), the relative O quantum yields of 1–8 were calcu-
2
DNA photocleavage activities. Furthermore, to modify the lated and are given in Table 1. Figure 2 shows that por-
1
cellular uptake and/or photophysical properties of the (4- phyrins 1, 2 and 5–8 show similar O quantum yields (ex-
2
cyanophenyl)porphyrin, we have also synthesized a series of perimental uncertainty ca. 20%) to that of H TPP, which
2
bis(porphyrins), 5–8, in which the hydrophilic (4-cy- indicates that (i) the introduction of a CN group into
anophenyl)porphyrin is connected to a more hydrophobic H TPP (i.e., 1 and 2) and (ii) linkage through a diether
2
(
e.g., H TPP) or hydrophilic porphyrin moiety [e.g., tris(N- group to a second porphyrin moiety, regardless of its hydro-
2
methyl-4-pyridyl)porphyrin] through a 1,3-propanediyl di- phobic (e.g., 6) or hydrophilic (e.g., 8) properties, does not
1
1
ether linker (see Scheme 1). The relative O2 quantum affect its O production capacity. For cobalt(II) (cyano-
2
1
yields, 2PA cross-sections and DNA photocleavage activi- phenyl)porphyrinate 4 no photogeneration of O was seen.
ties of the bis(porphyrins) 5–8 were measured as well.
2
1
This lack of photosensitized O production has previously
2
The (4-cyanophenyl)porphyrins and -bis(porphyrins) been observed in other paramagnetic metalloporphyrins
1
II
[19]
were structurally characterized by H NMR, IR, and UV/ with partially filled d orbitals, for example, Ag –TPP,
Vis spectroscopy, mass spectrometry, and elemental analy- presumably due to a metal-facilitated relaxation of the por-
sis. The solid-state structure of one metalloporphyrin, phyrin excited triplet state that precludes bimolecular
namely, cobalt(II) 5,10,15,20-tetrakis(4-cyanophenyl)por- quenching by oxygen. In contrast, zinc(II) (cyanophenyl)-
1
phyrinate (4) was determined by X-ray crystallography (see porphyrinate 3 showed a very high O quantum yield of
2
Scheme 1. Synthetic routes to (4-cyanophenyl)porphyrins 1–4 and -bis(porphyrins) 5–8.
Eur. J. Inorg. Chem. 2009, 922–928
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W.-K. Wong, D. W. J. Kwong, Z.-Y. Li et al.
FULL PAPER
range from 0.86 to 1.02.[20] In summary, all the (4-cyano-
II
phenyl)porphyrins, except the Co -metallated porphyrin,
1
exhibit substantial O quantum yields, which makes them
2
excellent potential PDT agents.
∆
Table 1. Relative singlet-oxygen quantum yields, Φ , and absolute
(
2)
two-photon-absorption (2PA) cross-sections,
σ , of (4-cya-
nophenyl)porphyrins 1–8.
Φ [
a]
σ(2) [GM][b]
Porphyrin
∆
1
2
3
4
5
6
7
8
0.51
0.53
0.94
nd[
0.51
0.65
0.51
0.49
37.1
39.0
57.8
33.8
180
85.4
74.7
157
c]
[
a] The singlet-oxygen quantum yields of these compounds were
measured in CHCl relative to H TPP (Φ = 0.55). The experimen-
tal uncertainty was ca. 20%. [b] 2PA cross-sections are expressed
3
2
∆
–
50
4
–1
in units of GM, where 1 GM = 10 cm sphoton . [c] nd = non-
detectable.
(
2)
The two-photon-absorption (2PA) cross-sections, σ , of
the (4-cyanophenyl)porphyrins 1–8 were measured at
8
00 nm by using 100 fs laser pulses with the open-aperture
[
21]
Z-scan method.
these porphyrins, from which the absolute σ values can
Figure 3 shows the Z-scan traces of
(2)
be determined (see Table 1). From Table 1 the following ob-
Figure 1. Perspective drawing of 4: (a) top view and (b) side view. servations were made. (i) The measured σ( values of the
2)
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and bond angles (°) are as follows: N(1)–Co(1) 1.948(4),
N(2)–Co(1) 1.950(4), N(3)–Co(1) 1.950(4), N(4)–Co(1) 1.955(3);
N(1)–Co(1)–N(2) 90.19(14), N(1)–Co(1)–N(3) 172.97(15), N(2)–
Co(1)–N(3) 90.17(14), N(1)–Co(1)–N(4) 90.48(14), N(2)–Co(1)– 28 GM).
monomeric (4-cyanophenyl)porphyrins 1–4, which range
from 33.8 to 57.8 GM, are consistent with those reported
(
2)
for other monomeric porphyrins such as H TPP (σ
=
2
[
22,23]
(ii) When we compare this value with those
N(4) 170.62(15), N(3)–Co(1)–N(4) 90.30(14).
of 1 (37.1 GM) and 2 (39.0 GM), the presence of a 4-cya-
nophenyl group, a charge-transfer chromophore, appears to
enhance the 2PA cross-section of the tetraphenylporphyrin.
This is consistent with a previous observation made for
0.94, which is almost twice that of the other (cyanophenyl)- other two-photon photosensitizers that more charge trans-
porphyrins studied. Such behaviour has also been observed fer in the chromophore facilitates their two-photon absorp-
II
[9]
in other Zn –TPP derivatives, with reported Φ values tion. (iii) This comparison also shows that the presence
∆
ranging from 0.68 to 0.99, and has been attributed to their of more CN groups in H TPP does not further enhance its
2
(2)
correspondingly high triplet quantum yields, Φ , which
σ
value. (iv) Comparison of the 2PA cross-sections of the
T
1
Figure 2. Near-IR phosphorescence spectra of O
2
produced from (4-cyanophenyl)porphyrins 1–8 and tetraphenylporphyrin (H
2
TPP) in
CHCl
3
under identical photoirradiation conditions [λexc = 420 nm, abs(λexc) = 0.03].
924
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Eur. J. Inorg. Chem. 2009, 922–928

Photophysical Properties of (4-Cyanophenyl)porphyrins
monomeric porphyrins 1–4 with those of the bis(porphyr-
(
2)
ins) 5–8, which range from 74.7 to 180 GM, show the σ
values of the latter were around two- to four-fold higher.
The photophysical reason behind this observation is not at
present understood. Nonetheless, the substantial 2PA cross-
sections observed in some of the (4-cyanophenyl)bis(por-
phyrins), particularly 5 and 8, together with their relatively
1
high O quantum yields, qualify them as potential 2PA-
2
PDT agents.
The DNA photocleavage activities of the water-soluble
(4-cyanophenyl)porphyrins and -bis(porphyrins), namely, 2,
3
, 5 and 8, were also measured, as well as the well-studied
[
24]
cationic porphyrin, H TMPyP.
Only the cationic por-
2
phyrins 8 and H TMPyP showed substantial photocleavage
2
activities towards the anionic DNA, with over 90% cleavage
activities observed at 13 and 2.5 µ, respectively (see Fig-
ure 4). As for porphyrins 2, 3 and 5, their insignificant
DNA photocleavage activities (data not shown) are likely
Figure 3. Open-aperture Z-scan traces of 1–8 (2 m) excited at
8
00 nm. The solvent was DMSO except for 1, 6 and 7, for which
CHCl was used instead. The average power of the laser beam used the result of a lack of a binding interaction with DNA,
3
was 0.262 mW except for 7, for which the average power was
.206 mW.
precluding a more effective oxidative attack from close
0
1
range despite their relatively high O quantum yields. This
2
result underscores the importance of a close-range interac-
tion with the target in effecting the desired outcome.
In PDT, the efficacy of a photosensitizer depends more
on its cellular uptake (i.e., lipophilic) properties than on its
1
[25]
O quantum yield. For example, even though H TMPyP
2
2
showed strong DNA-binding and photocleavage activity, its
PDT efficacy was poor due to its poor cellular uptake.
Hence, more hydrophobic porphyrins, such as 5, which are
expected to be more membrane-permeable, can be an effec-
tive PDT agent because, in addition to DNA, there are
other more hydrophobic intracellular targets for PDT ac-
[
26]
tion as well.
Conclusions
A series of (4-cyanophenyl)porphyrins and -bis(porphyr-
ins) have been synthesized, characterized and shown to pos-
sess substantial singlet-oxygen quantum yields (i.e., Φ∆
=
0
.49–0.94). Their two-photon-absorption cross-sections
(2)
σ , which range from 33.8 to 180 GM, were also measured.
Two (4-cyanophenyl)bis(porphyrins), 5 and 8, which show
substantial two-photon-absorption cross-sections as well as
1
O quantum yields, can potentially be developed as prime
2
2PA-PDT agents as they possess an additional porphyrin
that allows for various substituent modifications to achieve
an optimal hydrophobic/hydrophilic balance for cellular up-
take. The in vitro PDT activities and cellular uptake proper-
ties of these (4-cyanophenyl)bis(porphyrins) are currently
under investigation.
Figure 4. (a) Agarose gel electrophoresis images of DNA photo- Experimental Section
cleavage assays of 8 and H TMPyP as a function of their concen-
trations. The control sample contained only supercoiled DNA
Form I). Photoirradiation was conducted by using a transillumi-
nator at 455 nm for 45 min. (b) Plot of the DNA photocleavage
activities of 8 and H TMPyP as a function of their concentration.
2
Materials and Methods: DMF was distilled from calcium hydride,
and THF was distilled under nitrogen in the presence of sodium
chips by using benzophenone as indicator. 5-(4-Cyanophenyl)-
10,15,20-triphenylporphyrin (1), 5-(4-hydroxyphenyl)-10,15,20-
(
2
Eur. J. Inorg. Chem. 2009, 922–928
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W.-K. Wong, D. W. J. Kwong, Z.-Y. Li et al.
FULL PAPER
tris(4-pyridyl)porphyrin,
(
2)
5,10,15,20-tetrakis(4-cyanophenyl)por-
tion coefficient, β, the 2PA cross-section, σ , of the sample mole-
–
50
4
–1
phyrin (2) and 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin were
prepared according to literature procedures.[27] Other chemicals
were purchased from Sigma–Aldrich Company and used as re-
ceived. Silica gel 60 (0.04–0.063 mm) for column chromatography
was purchased from Merck. NMR spectra were recorded with a
Varian INOVA 400 NMR spectrometer. High-resolution matrix-
assisted laser desorption/ionization time-of-flight (MALDI-TOF)
mass spectra were recorded with a Bruker Autoflex MALDI-TOF
mass spectrometer. Low-resolution FAB mass spectra were ob-
tained with a Finnigan TSQ710 mass spectrometer. Electronic ab-
sorption spectra in the UV/Vis region were recorded with a Varian
Cary 100 UV/Vis spectrophotometer, and singlet-oxygen near-IR
cule (in units of 1 GM = 10 cm sphoton ) can be determined
by using Equation (3), where N is Avogadro’s constant, d is the
A
concentration of the sample compound in solution, h is Planck’s
constant and v is the frequency of the incident laser beam.
–
α l
0
βI (1 – e
0
)
T(z) = 1 –
(2)
(3)
)]2
0 0
2a [1 + (z/z
1
000βhv
σ(2)
=
A
N d
(
NIR) emission spectra were recorded with a Photon Technology
DNA Photocleavage Assay: The DNA photocleavage activities of
the porphyrins were measured by using the plasmid DNA relax-
ation assay. Briefly, the plasmid DNA (pBluescript), enriched with
the covalently closed circular (supercoiled) conformer, and one-
phor-all plus buffer (10 m Tris/acetate, 10 m magnesium acetate,
International (PTI) QM4 luminescence spectrometer equipped with
an InGaAs detector. The filter was LG-697-F from Corion Com-
pany. The IR spectra (KBr pellets) were recorded with a Nicolet
Magna 550 FTIR spectrometer. Elemental analyses were per-
formed by using a VarioEL III elemental analyzer at the School of
Chemical Technology & Pharmacy, Wuhan Institute of Technol-
ogy, P. R. China. All measurements were performed at ambient
temperature (20Ϯ2 °C) under atmospheric pressure. The UV/Vis
absorption and NIR emission spectra of all solution samples were
measured in a 10 mm quartz cell.
50 m potassium acetate, pH = 7.5) were vortexed. Aliquots of the
DNA were added by pipette to different Eppendorf tubes. Various
amounts of autoclaved water (control sample) or porphyrins (test
sample) were added to the Eppendorf tubes to give a final volume
of 20 µL in each sample tube. The sample mixtures were then pho-
toirradiated at 420–480 nm for 45 min by using a transilluminator
(Vilber Lourmat) containing 4ϫ15 W light tubes (Aqua Lux) with
a maximum emission at 455 nm. After photoirradiation, a 6X sam-
ple dye solution (2 µL, which contained 20% glycerol, 0.25% bro-
mophenol blue and 0.25% xylene cyanol FF) was added to each
Eppendorf tube and mixed well by centrifugation. The sample mix-
tures were loaded onto a 0.8% (v/v) agarose gel (13 cmϫ10 cm),
with Tris/borate/EDTA (TBE) buffer (89 m Tris/borate, 2.5 m
EDTA, pH = 8) used as the supporting electrolyte, and subjected
Singlet-Oxygen Measurements: Singlet oxygen was detected directly
by its phosphorescence emission at 1270 nm with an InGaAs detec-
tor. The singlet-oxygen quantum yields, Φ
porphyrins were determined in chloroform relative to the reference
compound H
where Φ is the singlet-oxygen quantum yield, AUC is the inte-
grated area under the O
at the excitation wavelength. Superscripts R and S correspond to
∆
, of the (4-cyanophenyl)-
2 ∆
TPP (Φ
= 0.55Ϯ0.11)[ by using Equation (1),
18]
∆
1
2
emission spectrum and A is absorbance
1
–1
the reference and sample, respectively. In all cases the O
2
emission
to electrophoresis at 1.3 Vcm for 3 h by using a mini gel set (CBS
spectra were measured after excitation at 420 nm with the ab-
sorbance set at 0.03 to minimize reabsorption of the emitted light.
Scientific Co., Model No. MGU-502T). After electrophoresis, the
–
1
gel was stained with 0.5 µgmL ethidium bromide solution for
0 min and then destained by using deionized water for 5 min. The
2
S
–AR
–AS
AUC (1 – 10
)
resulting gel image was viewed under 365 nm light, captured digi-
tally and analysed by using a gel documentation system (BioRad).
S
R
Φ
∆
= Φ
∆
(1)
R
AUC (1 – 10
)
Preparation and Characterization of the (4-Cyanophenyl)porphyrins
Two-Photon-Absorption (2PA) Measurements: The two-photon-ab-
sorption spectra (i.e., Z-scan traces) were measured at 800 nm by
the open-aperture Z-scan method using 100 fs laser pulses with a
peak power of 276 GWcm–2 from an optical parametric amplifier
operating at a repetition rate of 1 kHz generated from a Ti:sapphire
regenerative amplifier system. The laser beam was split into two
parts by a beam splitter. One was monitored by a photodiode (D1)
Zinc(II) 5,10,15,20-Tetrakis(4-cyanophenyl)porphyrinate (3): The
complex was prepared by heating 2 (100 mg, 0.14 mmol) at reflux
with an excess amount of zinc(II) acetate in CHCl
3
/methanol for
5
h; it was then purified by column chromatography on silica gel
1
with chloroform as eluent. Yield: 103 mg, 95%. H NMR
(
(
(
(
(
400 MHz, CDCl
d, J = 8.0 Hz, 8 H), 8.90 (s, 8 H) ppm. IR (KBr): ν˜ = 3320, 2228
CN), 1603, 1519, 1340, 1206, 996 (Zn , OSMB), 810 cm . HRMS
MALDI-TOF, positive mode, chloroform): m/z = 776.1421 [M]
3
): δ = 8.09–8.11 (d, J = 8.0 Hz, 8 H), 8.33–8.35
0
as the incident intensity reference, I , and the other was detected
II
–1
as the transmitted intensity by another photodiode (D2). After
passing through a lens with f = 20 cm, the laser beam was focused
and passed through a quartz cell. The position of the sample cell,
z, was moved along the direction of the laser beam (z axis) by a
computer-controlled translatable table so that the local power den-
sity within the sample cell could be changed under the constant
incident intensity laser power level. Finally, the transmitted inten-
sity from the sample cell was detected by the photodiode D2. The
photodiode D2 was interfaced to a computer for signal acquisition
and averaging. Each transmitted intensity datum represents the
+
C
0 °C):
48
H
24
N
8
Zn: calcd. 776.1409, ∆
max (log ε) 427 (5.76), 557 (4.35), 597 nm
Zn (778.15): calcd. C 74.23, H
.09, N 14.43; found C 74.11, H 3.12, N 14.34.
m 3
= 1.55 ppm). UV/Vis (CHCl ,
2
λ
3
=
–1
–1
(
24 8
3.74 dm mol cm ). C48H N
3
Cobalt(II) 5,10,15,20-Tetrakis(4-cyanophenyl)porphyrinate (4): The
complex was prepared by heating 2 (100 mg, 0.14 mmol) at reflux
3
with an excess amount of cobalt(II) acetate in CHCl /methanol for
5 h; it was then purified by column chromatography on silica gel
1
average of over 100 measurements. Assuming a Gaussian beam with chloroform as eluent. Yield: 93 mg, 94%.
H
NMR
]DMSO): δ = 8.99–9.44 (br. m, 16 H), 12.88 (br. s,
8 H) ppm. IR (KBr): ν˜ = 3312, 2227 (CN), 1605, 1500, 1350, 1002
profile, the non-linear absorption coefficient, β, can be obtained
by curve-fitting to the observed open-aperture traces, T(z), with
(400 MHz, [D
6
[
28]
II
–1
Equation (2),
the sample length (the 1 mm quartz cell) and z
length of the incident beam. After obtaining the nonlinear absorp-
where a
0
is the linear absorption coefficient, l is
(Co , OSMB), 811 cm . HRMS (MALDI-TOF, positive mode,
0
is the diffraction
chloroform): m/z = 771.1480 [M]+ (C48
24 8
H N
Co: calcd. 771.1507,
∆
m
= –3.50 ppm). UV/Vis (CHCl
3
, 20 °C): λmax (log ε) = 412 (5.91),
926
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Eur. J. Inorg. Chem. 2009, 922–928

Photophysical Properties of (4-Cyanophenyl)porphyrins
3
–1
–1
5
7
29 nm (4.59 dm mol cm ). C48
H24CoN
8
(771.69): calcd. C
cyanophenyl)porphyrin (83 mg, 0.10 mmol) and 5-(4-hy-
droxyphenyl)-10,15,20-tris(4-pyridyl)porphyrin (63 mg, 0.10 mmol)
in dry DMF (15 mL) was heated to 65 °C with stirring under nitro-
gen overnight. After cooling to room temperature, the reaction
mixture was poured into water saturated with sodium chloride
4.71, H 3.11, N 14.53; found C 74.82, H 3.03, N 14.61.
5
-[4-(3-Bromopropoxy)phenyl]-10,15,20-tris(4-cyanophenyl)porphyr-
in: In the presence of anhydrous potassium carbonate (1.0 g), a
mixture of 5-(4-hydroxyphenyl)-10,15,20-tris(4-cyanophenyl)por-
phyrin (100 mg, 0.14 mmol) and 1,3-dibromopropane (0.57 g,
.83 mmol) in dry DMF (10 mL) was heated to 65 °C with stirring
under nitrogen for 4 h. After cooling to room temperature, the reac-
tion mixture was poured into water saturated with sodium chloride
(
50 mL) and filtered. The precipitate was purified on a silica gel
column and eluted with chloroform/methanol. The second fraction
was the blue-violet title product. Yield: 77 mg, 56% after
2
1
recrystallization from chloroform/methanol. H NMR (400 MHz,
CDCl
2.84 [s, 2 H, tris(cyanophenyl), pyrrole ring NH], 2.65–2.71 (m, 2
H, CH CH CH ), 4.65–4.68 (m, 4 H, OCH ), 7.43–7.45 (m, 4 H),
3
): δ = –2.87 [s, 2 H, tris(pyridinium-4-yl), pyrrole ring NH],
(
30 mL) and filtered. The precipitate was purified on a silica gel
–
column and eluted with chloroform. The first fraction was the blue-
violet title product. Yield: 82 mg, 71%. 1H NMR (400 MHz,
2
2
2
2
8
2
5
1
.10–8.15 (m, 6 H), 8.17–8.19 (m, 6 H), 8.33–8.35 (d, J = 8.1 Hz,
H), 8.63–8.73 (m, 6 H), 8.72–8.89 (m, 16 H), 9.06–9.07 (d, J =
.8 Hz, 6 H) ppm. IR (KBr): ν˜ = 3314, 2923, 2228 (CN), 1653,
CDCl
CH CH
J = 5.6 Hz, 2 H, OCH
.31–8.33 (d, J = 7.2 Hz, 6 H), 8.73–8.76 (m, 8 H) ppm. IR (KBr):
3
): δ = –2.88 (s, 2 H, pyrrole ring NH), 2.50–2.52 (m, 2 H,
CH ), 3.77–3.80 (t, J = 6.4 Hz, 2 H, CH Br), 4.39–4.42 (t,
), 7.29–7.31 (m, 2 H), 8.06–8.10 (m, 8 H),
2
2
2
2
2
–
1
593, 1506, 1243, 799 cm . HRMS (MALDI-TOF, positive mode,
8
+
–
1
chloroform): m/z
2
= 1381.5105 [M] (C H N O : calcd.
ν˜ = 3321, 2923, 2228 (CN), 1605, 1244, 1176, 967, 803 cm . MS
91 58 14
+
1381.5048, ∆m = 4.13 ppm). UV/Vis (CHCl , 20 °C): λ
(log ε) =
20 (5.62), 516 (4.28), 552 (3.83), 590 (3.69), 646 nm
(
(
(
FAB, +ve mode): m/z = 827.3 [M] . UV/Vis (CHCl
3
, 20 °C): λmax
3
max
4
log ε) = 420 (5.65), 517 (4.22), 553 (3.85), 591 (3.70), 647 nm
3
–1
–1
3
–1
–1
91 58 14 2
(3.38 dm mol cm ). C H N O (1379.53): calcd. C 79.25, H
3.66 dm mol cm ).
4.21, N 14.22; found C 79.17, H 4.27, N 14.30.
Porphyrin 5: In the presence of anhydrous potassium carbonate
1.0 g), a mixture of 5-[4-(3-bromopropoxy)phenyl]-10,15,20-tris(4-
cyanophenyl)porphyrin (100 mg, 0.12 mmol) and
81 mg, 0.12 mmol) in dry DMF (15 mL) was heated to 65 °C with
(
Porphyrin 8: Porphyrin 7 (30 mg, 0.02 mmol) was added to CH3I
(10 mL). After heating at reflux overnight, the reaction mixture was
filtered, and the precipitate was washed with CHCl /CH OH
2
H TOHPP
(
3
3
stirring under nitrogen for 6 h. After cooling to room temperature,
the reaction mixture was poured into water saturated with sodium
chloride (50 mL) and filtered. The precipitate was purified on a
silica gel column and eluted with chloroform. The second fraction
was the blue-violet title product. Yield: 43 mg, 25%. 1H NMR
(20:1). The title blue-violet product was obtained in 35 mg (91%)
yield after recrystallization from chloroform/methanol. H NMR
1
(400 MHz, [D ]DMSO): δ = –2.98 [s, 2 H, tris(cyanophenyl), pyr-
6
role ring NH], –2.96 [s, 2 H, tris(N-methyl-4-pyridyl), pyrrole ring
NH], 2.59–2.62 (m, 2 H, CH CH CH ), 4.61–4.64 (m, 4 H, OCH ),
2
2
2
2
(
400 MHz, [D
NH], –2.88 [s, 2 H, tris(cyanophenyl), pyrrole ring NH], 2.73–2.80
m, 2 H, CH CH CH ), 4.57–4.60 (m, 4 H, OCH ), 7.04–7.06 (m,
H), 7.20–7.44 (m, 6 H), 7.82–7.84 (m, 6 H), 8.00–8.02 (m, 2 H),
.05–8.12 (m, 8 H), 8.28–8.40 (m, 6 H), 8.75–8.89 (m, 16 H) ppm. (MALDI-TOF, positive mode, chloroform): m/z = 1424.5683 [M]
6
]DMSO): δ = –2.97 [s, 2 H, tris(phenyl), pyrrole ring
4.71 (s, 9 H, CH ), 7.52–7.59 (m, 4 H), 8.18–8.21 (m, 4 H), 8.26–
8.32 (m, 6 H), 8.39–8.41 (m, 6 H), 8.81–8.85 (m, 6 H), 8.97–8.99
3
(
4
8
2
2
2
2
(m, 8 H), 9.10–9.16 (m, 8 H), 9.44–9.48 (m, 6 H) ppm. IR (KBr): ν˜
–
1
= 3322, 2924, 2227 (CN), 1638, 1604, 1507, 1241, 801 cm . HRMS
+
+
IR (KBr): ν˜ = 3328, 2925, 2854, 2230 (CN), 1606, 1509, 1262, (C H N O
8
=
:
calcd. 1424.5632, ∆m
= 3.49 ppm). UV/Vis
9
4
67 14
2
–1
01 cm . HRMS (MALDI-TOF, positive mode, chloroform): m/z
(DMSO, 20 °C): λmax (log ε) = 423 (5.76), 517 (4.49), 553 (4.12),
+
3
–1
–1
1424.4905 [M] (C94
H
61
N
11
O
5
:
calcd. 1424.4883,
∆
m
=
94 67 3 14 2
590 (3.99), 646 nm (3.77 dm mol cm ). C H I N O
1
.54 ppm). UV/Vis (DMSO, 20 °C): λmax (log ε) = 422 (5.85), 517
(1804.34): calcd. C 62.53, H 3.71, N 10.86; found C 62.64, H 3.65,
N 10.78.
3
–1
–1
(
4.50), 553 (4.28), 590 (3.96), 646 nm (3.89 dm mol cm ).
(1424.56): calcd. C 79.27, H 4.29, N 10.82; found C
9.35, H 4.39, N 10.74.
Porphyrin 6: In the presence of anhydrous potassium carbonate
1.0 g), a mixture of 5-[4-(3-bromopropoxy)phenyl]-10,15,20-tris(4-
94 61 11 5
C H N O
X-ray Crystal Structure Determination of 4: Pertinent crystallo-
graphic data and other experimental details are summarized in
7
(
cyanophenyl)porphyrin (100 mg, 0.12 mmol) and 5-(4-hy-
droxyphenyl)-10,15,20-triphenylporphyrin (76 mg, 0.12 mmol) in
dry DMF (15 mL) was heated to 65 °C with stirring under nitrogen
for 5 h. After cooling to room temperature, the reaction mixture
was poured into water saturated with sodium chloride (50 mL) and
filtered. The precipitate was purified on a silica gel column and
eluted with chloroform. The second fraction was the blue-violet
Table 2. Crystallographic data for cobalt(II) 5,10,15,20-tetrakis(4-
cyanophenyl)porphyrinate–2chloroform.
Empirical formula
Formula mass
Crystal size [mm]
Crystal system
Space group
a [Å]
50 6 8
C H26Cl CoN
1010.42
0.32ϫ0.25ϫ0.22
monoclinic
1
P2 /c
title product. Yield: 135 mg, 70% after recrystallization from chlo-
9.0341(5)
30.4580(16)
15.7403(8)
96.1070(10)
4306.5(4), 4
1.558
1
roform/methanol. H NMR (400 MHz, CDCl
3
): δ = –2.86 (s, 2 H,
b [Å]
c [Å]
triphenyl, pyrrole ring NH), –2.79 [s, 2 H, tris(cyanophenyl), pyr-
role ring NH], 2.63–2.66 (m, 2 H, CH CH CH ), 4.60–4.64 (m, 4
H, OCH ), 7.37–7.42 (m, 4 H), 7.64–7.77 (m, 9 H), 7.97–8.33 (m,
2 H), 8.68–8.99 (m, 16 H) ppm. IR (KBr): ν˜ = 3311, 2924, 2851,
β [°]
V [Å ], Z
2
2
2
3
2
–
3
ρ
calcd. [mgm ]
2
2
–
1
µ [mm ]
0.820
–
1
227 (CN), 1604, 1506, 1242, 966, 799 cm . MS (FAB, +ve mode):
F(000)
2044
2.39–25.00
20698
7470 (Rint = 0.0290)
0.992
+
m/z = 1376.6 [M] . UV/Vis (CHCl
3
, 20 °C): λmax (log ε) = 418
θ range for data collection [°]
Reflections collected
Independent reflections
(
(
4
5.53), 517 (4.18), 553 (3.88), 592 (3.65), 647 nm
3
–1
–1
3.62 dm mol cm ). C94
.43, N 9.59; found C 81.88, H 4.54, N 9.70.
Porphyrin 7: In the presence of anhydrous potassium carbonate
H
61
N
11
O
2
(1376.56): calcd. C 81.98, H
2
Goodness-of-fit on F
Final R indices [IϾ2σ(I)]
R indices (all data)
R
R
1
= 0.0674, wR
= 0.0876, wR
2
= 0.1854
= 0.2024
1
2
(1.0 g), a mixture of 5-[4-(3-bromopropoxy)phenyl]-10,15,20-tris(4-
Eur. J. Inorg. Chem. 2009, 922–928
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
927

W.-K. Wong, D. W. J. Kwong, Z.-Y. Li et al.
Table 2. Crystals of cobalt(II) 5,10,15,20-tetrakis(4-cyanophenyl)- [10] K. Ogawa, Y. Kobuke, Anti-Cancer Agents Med. Chem. 2008,
FULL PAPER
8
, 269–279.
11] R. W. Redmond, I. E. Kochevar, Photochem. Photobiol. 2006,
2, 1178–1186.
porphyrinate–2chloroform suitable for X-ray diffraction studies
were grown by slow concentration in air of a chloroform/methanol
solution of the complex. The crystals were wrapped in epoxy glue
to prevent them from losing solvent and mounted on a thin glass
fibre. Intensity data were collected at 293 K with a Bruker Axs
SMART 100 CCD area-detector diffractometer by using graphite-
[
[
8
12] H. A. Collins, M. Khurana, E. H. Moriyama, A. Mariampillai,
E. Dahlstedt, M. Balaz, M. K. Kuimova, M. Drobizhev,
V. X. D. Yang, D. Phillips, A. Rebane, B. C. Wilson, H. L. An-
derson, Nat. Photonics 2008, 2, 420–424.
13] Y. Chen, A. Gryshuk, S. Achilefu, T. Ohulchansky, W. Potter,
T. Zhong, J. Morgan, B. Chance, P. N. Prasad, B. W. Hender-
son, A. Oseroff, R. K. Pandey, Bioconjugate Chem. 2005, 16,
1264–1274.
14] F.-L. Jiang, C.-T. Poon, W.-K. Wong, H.-K. Koon, N.-K. Mak,
C. Y. Choi, D. W. J. Kwong, Y. Liu, ChemBioChem 2008, 9,
1034–1039.
15] Y. You, S. L. Gibson, R. Hilf, S. R. Davies, A. R. Oseroff, I.
Roy, T. Y. Ohulchansky, E. J. Bergey, M. R. Detty, J. Med.
Chem. 2003, 46, 3734–3747.
α
monochromated Mo-K radiation (λ = 0.71073 Å). The collected
[
[29]
frames were processed with the SAINT software and an absorp-
tion correction was applied (SADABS)[ to the collected reflec-
tions. The space group of the crystal was determined from the sys-
tematic absences and Laue symmetry checks and confirmed by suc-
cessful refinement of the structure. The structure was solved by
30]
[
[
[
direct methods (SHELXTL)[ and refined against F by full-ma-
trix least-squares analysis. All non-hydrogen atoms were refined an-
isotropically. Hydrogen atoms were generated in their idealized po-
sitions and allowed to ride on their respective parent carbon atoms.
CCDC-699825 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
31]
2
16] M.-C. Wang, L.-S. Sue, B.-C. Liau, B.-T. Ko, S. Elango, J.-H.
Chen, Inorg. Chem. 2001, 40, 6064–6068.
[17] W. R. Scheidt, I. Turowska-Tyrk, Inorg. Chem. 1994, 33, 1314–
1318.
[18] R. Schmidt, E. Afshari, J. Phys. Chem. 1990, 94, 4377–4378.
[
19] H. Kunkely, A. Vogler, Inorg. Chem. Commun. 2007, 10, 479–
4
81.
Acknowledgments
[20] M. Pineiro, A. L. Carvalho, M. M. Pereira, A. M. d’A. Ro-
cha Gonsalves, L. G. Arnaut, S. J. Formosinho, Chem. Eur. J.
1998, 4, 2299–2307.
The authors are grateful for the financial support of the Hong
Kong Research Grants Council (grant nos. HKBU 2023/04P and
HKBU 202308) and the National Natural Science Foundation of
China (grant no. 20672082).
[
21] M. Sheik-Bahae, A. A. Said, T.-H. Wei, D. J. Hagan, E. W.
Van Stryland, IEEE J. Quantum Electron. 1990, 26, 760–769.
22] F.-L. Jiang, W.-K. Wong, X.-J. Zhu, G.-J. Zhou, W.-Y. Wong,
P.-L. Wu, H.-L. Tam, K.-W. Cheah, C. Ye, Y. Liu, Eur. J. Inorg.
Chem. 2007, 3365–3374.
[
[
1] a) T. Hasan, B. Ortel, A. C. E. Moor, B. W. Pogue in Holland-
Frei Cancer Medicine 6 (Eds.: D. W. Kufe, R. E. Pollock, R. R.
Weichselbaum, R. C. Bast Jr, T. S. Gansler, J. F. Holland, E.
Frei III), B. C. Decker, Hamilton, Ontario, 2003, pp. 605–622;
b) E. D. Sternberg, D. Dolphin, Tetrahedron 1998, 54, 4151–
[23] G. S. He, L.-S. Tan, Q. Zheng, P. N. Prasad, Chem. Rev. 2008,
108, 1245–1330.
[24] a) R. J. Fiel, J. Biomol. Struct. Dyn. 1989, 6, 1259–1274; b)
R. F. Pasternack, E. J. Gibbs, J. Villafranca, Biochemistry 1983,
22, 2406–2414; c) P. Lugo-Ponce, D. R. McMillan, Coord.
Chem. Rev. 2000, 208, 169–191.
[25] S. Ben-Dror, I. Bronshtein, A. Wiehe, B. Roder, M. O. Senge,
B. Ehrenberg, Photochem. Photobiol. 2006, 82, 695–701.
[26] a) R. Hilf, J. Bioenerg. Biomembr. 2007, 39, 85–89; b) R. Chen,
Z. Huang, G. Chen, Y. Li, X. Chen, J. Chen, H. Zeng, Int. J.
Oncol. 2008, 32, 861–867; c) A. Villaneuva, E. N. Durantini,
J. C. Stockert, S. Rello, R. Vidania, M. Canete, A. Juarranz,
R. Arranz, V. Rivalora, Anti-Cancer Drug Des. 2001, 16, 279–
290.
[27] a) X.-J. Zhu, W.-K. Wong, F.-L. Jiang, C.-T. Poon, W.-Y.
Wong, Tetrahedron Lett. 2008, 49, 2114–2118; b) C. Casas, B.
Saint-Jalmes, C. Loup, C. J. Lacey, B. Munier, J. Org. Chem.
1993, 58, 2913–2917; c) L. R. Milgrom, J. Chem. Soc. Perkin
Trans. 1 1983, 2535–2539.
[28] K. S. Kim, J. M. Lim, A. Osuka, D. Kim, J. Photochem. Pho-
tobiol. C: Photochem. Rev. 2008, 9, 13–28.
4202.
[
2] D. E. J. G. Dolmans, J. D. Fukumura, R. K. Jain, Nature Rev.
Cancer 2003, 3, 380–387.
[3] a) A. Juzeniene, J. Moan, Photodiagn. Photodyn. Ther. 2007,
4, 3–11; b) A. P. Castano, T. N. Demidova, M. R. Hamblin,
Photodiagn. Photodyn. Ther. 2005, 2, 91–106.
[
4] M. R. Detty, S. L. Gibson, S. J. Wagner, J. Med. Chem. 2004,
47, 3897–3915.
[
5] a) D. G. Hilmey, M. Abe, M. I. Nelen, C. E. Stilts, G. A. Baker,
S. N. Baker, F. V. Bright, S. R. Davies, S. O. Gollnick, A. R.
Oseroff, S. L. Gibson, R. Hilf, M. R. Detty, J. Med. Chem.
2
002, 45, 449–461; b) J. L. Sessler, R. A. Miller, Biochem. Phar-
macol. 2000, 59, 733–739.
[
6] P. K. Frederiksen, M. Jorgensen, P. R. Ogilby, J. Am. Chem.
Soc. 2001, 123, 1215–1221.
[
7] T. D. Poulsen, P. K. Frederiksen, M. Jorgensen, K. V.
Mikkelsen, P. R. Ogilby, J. Phys. Chem. A 2001, 105, 11488–
[29] SAINT, Reference Manual, Siemens Energy and Automation,
Madison, WI, 1994–1996.
11495.
[
8] A. Karotki, M. Drobizhev, M. Kruk, C. Spangler, E. Nickel,
[30] G. M. Sheldrick, SADABS, Empirical Absorption Correction
Program, University of Göttingen, 1997.
N. Mamar-Dashvili, A. Rebane, J. Opt. Soc. Am. B 2003, 20,
TM
321–332.
[31] G. M. Sheldrick, SHELXTL , Reference Manual, version 5.1,
[
9] P. K. Frederiksen, S. P. McIlroy, C. B. Nielsen, L. Nikolajsen,
E. Skovsen, M. Jorgensen, K. V. Mikkelsen, P. R. Ogilby, J.
Am. Chem. Soc. 2005, 127, 255–269.
Siemens, Madison, WI, 1997.
Received: October 25, 2008
Published Online: January 29, 2009
928
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 922–928