Absorption and fluorescence properties of aryl substituted porphyrins in different media

Article abstract of DOI:10.1016/j.saa.2009.11.019

Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP), 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), and 5,10,15

Full text of DOI:10.1016/j.saa.2009.11.019

Spectrochimica Acta Part A 75 (2010) 574–577
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Absorption and fluorescence properties of aryl substituted porphyrins in
different media
Serap Seyhan Bozkurt, Melek Merdivan∗, Sevda Ayata
Dokuz Eylul University, Faculty of Sciences and Arts, Chemistry Department, Kaynaklar Campus, 35160 Izmir, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 April 2009
Received in revised form 9 November 2009
Accepted 10 November 2009
Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-
oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP),
5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl)
porphyrin
(TBHPP),
and
5,10,15,20-tetra-p-
chloromethylphenyl porphyrin (CMPP) were investigated. The UV/vis absorption, fluorescence
and excited spectra as the fluorescence quantum yields and fluorescence lifetimes for the compounds
were measured in organic solvents (chloroform (CHCl3), tetrahydrofuran (THF)) and immobilized media
(PVC film, sol–gel matrix). The fluorescence quantum yields of TAPP and TPPP were higher than the
others. The fluorescence lifetimes of all studied porphyrin derivates were found to be fifty percent lower
and their fluorescence intensities were increased fifty percent more in both of immobilized mediums,
as compared to organic solvents.
Keywords:
Porphyrin
Fluorescence
Quenching
PVC
Sol–gel
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
tophysical and photochemical properties and sensor applications
[15].
Photophysical and photochemical studies of porphyrins have
been of increasing interest in fields extending from chemistry to
biology [1,2]. Besides this the interest to study of porphyrin photo-
physical characteristics is stimulated by their medical applications,
especially due to their efficacy in photodynamic therapy (PDT) of
cancer [3,4], psoriasis, atheromatous plaque, viral and bacterial
infections including HIV [5,6] and blood substitutes [7].
The porphyrin efficacy in photonic devices and PDT depends
on its photophysical characteristics, such as lifetimes and quantum
yields of the excited (singlet and triplet) states [8–13], which in turn
depend on the environmental characteristics: pH, ionic strength,
interaction with other molecules, etc. To apply these materials in
photonics and medicine in the most effective way it is necessary to
know the behavior of all their photophysical characteristics in the
function of external conditions.
Plasticized PVC membranes are believed to be useful for sensor
applications because of their good mechanical properties, homo-
geneity, simplicity of preparation and optical transparency [16,17].
A sol–gel matrix is very attractive because of its low preparation
temperature and high chemical and mechanical stabilities [18,19].
In the sol–gel process, transparent oxide glasses are prepared by
hydrolysis and condensation of tetra alkyl orthosilicates and in one
sol–gel preparation technique molecules can become entrapped in
the growing covalent silica network.
In this study, the photophysical characteristics of aryl sub-
stituted porphyrins, TAPP, TBHPP, CMPP and TPPP, in organic
solvents (chloroform (CHCl3), tetrahydrofuran (THF)) and immo-
bilized media (PVC film, sol–gel matrix) were examined.
2. Experimental and method
In recent years, doping of organic dye molecules within polymer
matrices has gained interest. These matrices are easily prepared
and provide immobilization. Also, by this immobilization the
ground and excited state properties of single molecules can be
understandable [14]. In favourable cases, the immobilization of flu-
orescent molecules in the solid matrix may reduce intramolecular
motions and rearrangements, thus leading to enhanced photo-
stability and fluorescence capability. Entrapment of fluorescent
molecules in solid matrix allows the investigation of both pho-
2.1. Materials
PVC (high molecular weight) and the plasticizer bis-(2-
ethyl-hexyl)phalate (DOP) were supplied by Fluka (Buchs SG,
Switzerland). The polyester support (Mylar type) was provided
from Hostaphan Films, Germany. The sol–gel precursor tetraethy-
lorthosilicate (tetraethoxysilane, TEOS), the surfactant additive
Triton X-100 were obtained from Fluka (Buchs SG, Switzerland).
All other chemicals were obtained from Fluka and Merck. Deion-
ized water was used throughout the studies. The copper nitrate
salt used in quenching experiments was supplied by Merck and
was used without any further purification.
∗
Corresponding author. Tel.: +90 232 4128693; fax: +90 232 4534188.
E-mail address: melek.merdivan@deu.edu.tr (M. Merdivan).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.11.019

S.S. Bozkurt et al. / Spectrochimica Acta Part A 75 (2010) 574–577
575
Table 1
Absorption characteristics of porphyrins in organic solvents and immobilized media.
ꢀmax(nm) ε (L mol−1 cm−1
)
B(0–0)
Qx(1–0)
Qy(1–0)
Qx(0–0)
Qy(0–0)
TAPP
TBHPP
CMPP
TPPP
THF
CHCl3
PVC
421 (1.17 × 105)
423 (1.16 × 105)
427 (1.80 × 105)
429 (2.07 × 105)
420 (1.14 × 105)
423 (1.13 × 105)
429 (1.76 × 105)
430 (2.02 × 105)
416 (1.22 × 105)
416 (1.20 × 105)
420 (1.94 × 105)
423 (2.20 × 105)
421 (1.35 × 105)
420 (1.30 × 105)
425 (2.00 × 105)
429 (2.50 × 105)
515 (4.50 × 103)
512 (4.30 × 103)
516 (6.93 × 103)
518 (7.98 × 103)
514 (4.65 × 103)
517 (4.60 × 103)
520 (7.08 × 103)
521 (8.08 × 103)
512 (4.60 × 103)
514 (4.41 × 103)
519 (8.05 × 103)
521 (9.09 × 103)
517 (4.60 × 103)
515 (4.25 × 103)
519 (7.10 × 103)
521 (8.80 × 103)
550 (3.20 × 103)
555 (3.12 × 103)
557 (4.98 × 103)
559 (5.70 × 103)
545 (3.25 × 103)
550 (3.10 × 103)
555 (4.65 × 103)
559 (5.35 × 103)
546 (3.30 × 103)
551 (3.15 × 103)
554 (5.51 × 103)
557 (6.35 × 103)
554 (3.40 × 103)
555 (3.30 × 103)
558 (5.70 × 103)
559 (4.50 × 103)
590 (1.30 × 103)
589 (1.20 × 103)
593 (2.01 × 103)
595 (2.32 × 103)
585 (1.20 × 103)
586 (1.15 × 103)
591 (1.80 × 103)
593 (2.07 × 103)
589 (1.20 × 103)
590 (1.15 × 103)
592 (2.02 × 103)
593 (2.38 × 103)
591 (1.20 × 103)
590 (1.20 × 103)
593 (2.10 × 103)
595 (2.62 × 103)
644 (1.20 × 103)
650 (1.15 × 103)
651 (1.79 × 103)
652 (2.10 × 103)
650 (1.30 × 103)
650 (1.18 × 103)
651 (2.00 × 103)
653 (2.31 × 103)
645 (8.00 × 102)
646 (8.00 × 102)
649 (1.45 × 103)
652 (1.68 × 103)
651 (1.60 × 103)
649 (1.50 × 103)
652 (1.78 × 103)
653 (2.20 × 103)
Sol–gel
THF
CHCl3
PVC
Sol–gel
THF
CHCl3
PVC
Sol–gel
THF
CHCl3
PVC
Sol–gel
2.2. Porphyrins (Fig. 1)
cold distilled water, 2.0–3.0 mL of saturated Na2CO3 solution and
2.0–3.0 mL of distilled water. After filtration the mixture, the prod-
uct was dried under vacuum. The yield of CMPP was 71%. 1H NMR
(CDCl3, 400 MHz) ␦ (ppm): 7.28 ppm (s, 2H), 8,05–7,54 ppm (m,
34H). FTIR (KBr): 2920 cm−1 (Ar-CH2-Cl), 895 cm−1(C-Cl). Elemen-
tal analysis, expected (calculated): C-65.52 (65.97), H-4.20 (4.54),
N-5.66 (5.26).
TAPP was synthesized accordance with literature given before
[20]. The synthesis procedure of others were given below.
TBHPP
A 0.170 g of tetrahydroxyphenylporphyrin was mixed with
1.2 mL concentrated H2SO4 and 150 mL of tetrahydrofuran (THF)
in a round-bottomed flask and refluxed for 3 h at 70 ◦C. The reac-
tion mixture was left to cool, and 5 mL of 0.6 M NaOH solution
and 250 ␮L of bromine were added drop by drop. The mixture was
refluxed for 1 h at 70 ◦C and left to cool, then 5 mL of 1.0 M H2SO4
was also added and mixed for 30 min. The reaction mixture was
extracted with diethyl ether and the THF in the upper phase was
evaporated by rotary evaporator. After 10 mL of distilled water was
added, the formed residue was filtered off and finally dried under
vacuum. The yield of TBHPP was 75%. 1H NMR (CDCl3, 400 MHz) ␦
(ppm): 9.88 ppm (s, 4H), 7.55 ppm (s, 2H), 7.05–6.70 ppm (m, 20H).
FTIR (KBr): 3125 cm−1 (C-OH), 897 cm−1(C-Br). Elemental analysis,
expected (calculated): C-49.55 (49.67), H-2.76 (2.82), N-5.01 (5.26).
2.3. Spectroscopic analysis
Visible spectra were obtained using Shimadzu UV-1601 spec-
trophotometer, with cuvets of 1 cm optical length. Fluorescence
emission spectra were recorded on a Varian-Cary Eclipse spec-
trofluorimeter (Mulgrave, Australia), equipped with
a Xenon
lamps source and 1.0 cm quartz, excitation and emission slit at
10 nm at medium voltage of the photomultiplier. Fluorescence
quantum yields were determined by using tetraphenylporphyrin
(TPP) in benzene (˚f = 0.13) [21] as standard. The PVC film
and sol–gel matrix were placed in diagonal position in the
quartz cell. All measurements were carried out at room temper-
ature.
TPPP
A 0.2 g of tetrahydroxyphenylporphyrin was stirred in 15 mL
dimethylformamide with 0.120 g of crushed sodium hydroxide.
0.4 g of chlorobenzene was added over 1 h using a dropping funnel.
After 30 h, 10 mL of ethanol was added to the solution, followed by
80 mL of distilled water. The product was filtered off and washed
with absolute ethanol and then dried. It was chromatographed on
alumina with chloroform. TPPP was eluted with the solvent front
and separated easily from any unreacted starting material. The yield
of TPPP was 82%. 1H NMR (CDCl3, 400 MHz) ␦ (ppm): 7.30 ppm
(s, 2H), 8,28–7,77 ppm (m, 44H). FTIR (KBr): 2100 cm−1 (Ar-O-Ar).
Elemental analysis, expected (calculated): C-77.49 (77.86), H-4.65
(4.28), N-5.16 (5.82).
Table 2
Fluorescence properties of porphyrins in organic solvents and immobilized media.
Medium
ꢀmax
ꢀmax
ꢁꢀ
(nm)
ꢂ0 (ns)
Фexp
(ex) (nm) (fl) (nm)
TAPP
THF
CHCl3
PVC
570
570
572
570
660
658
659
660
90
88
88
89
0.07 0.01 0.07 0.01
0.07 0.01 0.07 0.01
0.04 0.01 0.08 0.02
0.04 0.01 0.08 0.01
Sol–gel
TBHPP THF
CHCl3
559
559
565
550
659
657
666
660
100
0.06 0.01 0.06 0.01
0.07 0.01 0.05 0.01
0.04 0.01 0.07 0.01
0.04 0.01 0.08 0.01
98
101
110
PVC
Sol–gel
CMPP
CMPP
TPPP
THF
CHCl3
PVC
550
550
560
560
660
660
660
657
110
110
100
97
0.03 0.01 0.04 0.01
0.04 0.01 0.04 0.01
0.03 0.01 0.05 0.01
0.02 0.01 0.04 0.01
A 0.123 g of tetraphenylporphyrin was mixed with 0.002 g of
p-formaldehyde, 0.027 g of anhydrous ZnCl2 powder and 150 mL
of THF in a round-bottomed flask and refluxed for 30 min at 75 ◦C.
10 mL of 1.0 M HCl was added to the reaction mixture drop by drop
and refluxed for more than 15 min. Then the reaction mixture was
transferred to a separatory funnel and washed with 2.0–3.0 mL of
Sol–gel
THF
CHCl3
PVC
570
570
570
570
659
658
659
658
89
88
89
88
0.04 0.01 0.11 0.01
0.05 0.01 0.10 0.01
0.03 0.01 0.12 0.01
0.03 0.01 0.12 0.01
Sol–gel

576
S.S. Bozkurt et al. / Spectrochimica Acta Part A 75 (2010) 574–577
Fig. 1. The porphyrins determined photophysical properties.
2.4. PVC film preparation
Tables 1 and 2. Also, as an example, the fluorescence spectra of TAPP
in solution media and immobilized media were given in Fig. 2. The
absorption spectra and the molar extinction coefficients of the Soret
and Q bands of all porphyrin synthesized are quite similar under
the same conditions, indicating that the differences in substituting
groups as halogen, alkoxy or acid hydrocarbon do not affect greatly
the absorption properties. It is noted that their absorption prop-
erties are similar in THF and CHCl3, in which the molar extinction
coefficients of all studied porphyrins in CHCl3 are slightly lower
than in THF. In comparison to the solution phase, the absorption
maxima of porphyrin derivatives in PVC film and sol–gel matrix
exhibited red shifts ranging from 4 to 9 nm. This result can be
attributed to the restricted vibrational rotational motions in solid
phase. The values of molar extinction coefficients increased for all
of the porphyrin derivatives in PVC film and sol–gel matrix. The
reason can be the enhanced rigidity in immobilized medium.
Additionally the excitation and emission related data: excitation
and emission wavelengths, ꢀ (nm), Stokes shift values, ꢁꢀ (nm),
radiative life times, ꢂ0 (ns), fluorescence quantum yields, Фf of all
PVC films were prepared from a mixture of 120 mg of PVC,
240 mg of plasticizer (DOP) and 1.5 mL of 1 × 10−6 mol L−1 por-
phyrin in THF. The concentration of the porphyrins in mixture was
1 × 10−4 mol L−1. The resulting polymer cocktails were spread onto
a polyester support (Mylar type). PVC films were kept in THF con-
taining desiccator to avoid damage from the air. Each PVC film was
placed diagonally into the sample cuvette to improve the repro-
ducibility of the measurements.
2.5. Sol–gel process
Porphyrin doped sol–gel glasses were derived from a starting
composition of 4 mol of high quality acidic water (pH = 2, adjust-
ment is done by HCl) and 1 mol of TEOS. These constituents were
sonicated for 40 min in closed vials. 1.5 mL dopant was then added
in the concentration range of 1 × 10−6 mol L−1 in THF. The resulting
dopant concentration in sol was 1 × 10−4 mol L−1. The addition of
a few drops of Triton X-100, to improve the homogeneity of the
sol–gel and to give a crack-free monolith, was also performed. The
doped sol was stirred until the dye was completely dissolved before
coating a glass slide (11 × 40 × 1 mm) which had been activated by
treatment withconcentrated HNO3 for 24 h, washedwith deionized
water and then ethanol. Then the glass slides doped with porphyrin
were dried at room temperature. After evaporation of the solvent,
the coated glass slides were fixed diagonally in a quartz sample
cuvette.
3. Results and discussion
3.1. Spectral characterization studies
The absorption and emission based spectral data of all four por-
phyrin derivatives in different host matrices are summarized in
Fig. 2. The emission spectra of 1 × 10−6 mol L−1 TAPP in all of media.

S.S. Bozkurt et al. / Spectrochimica Acta Part A 75 (2010) 574–577
577
The data were acquired at the maximum emission wavelength of
porphyrin derivatives in all of media. As an example, only the data
collected for TAPP after 1 h monitoring is shown in Fig. 3. The exper-
imental results revealed that the porphyrin derivatives exhibited
excellent photostability in all of the employed solvents and PVC
film and sol–gel matrix.
4. Conclusion
The aim of this work was to investigate the photophysical prop-
erties of aryl substituted porphyrins including halogen, alkoxy
or acid hydrocarbon groups in organic solvents and immobilized
media. Thus, UV/vis absorption and fluorescence spectra, fluores-
cence quantum yield, lifetimes and photostabilities of porphyrins
were measured in organic solvents and immobilized media. The
absorption maxima of porphyrin derivatives in PVC film and sol–gel
matrix exhibited red shifts ranging from 4 to 9 nm. Radiative life-
time values, ꢂ0, in PVC film and sol–gel matrix were obtained as the
lower for all the porphyrin derivatives. The quantum yield values
in PVC film and sol–gel matrix was higher than solution media for
the all porphyrin derivatives.
Fig. 3. Photostability test results of 1 × 10−6 mol L−1 TAPP in (a) sol–gel matrix, (b)
PVC film, (c) THF, (d) CHCl3 after 1 h of monitoring.
porphyrins in all studied media were summarized in Table 2. In
all of the employed solvents and immobilized media, the excita-
tion wavelength was chosen at between 550 and 572 nm and the
emission spectra were recorded.
Two fluorescence bands around 657–666 and 720–728 nm, cor-
responding to Q transitions, were observed in the all studied
porphyrins. The studied porphyrins derivatives exhibited Stokes
shift ranging from 88 to 101 nm in all of the employed media.
In halogen derivated porphyrins, TBHPP and CMPP, the degree of
Stokes shift was seen higher.
Acknowledgement
The authors acknowledge the Scientific Research Funds of Dokuz
Eylul University (Project No: 2007 KB FEN 022).
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2009.11.019.
Fluorescence quantum yield (Фexp) was calculated from
F{1 − exp(−Aref ln 10)}n2
References
˚
= ˚
exp
ref
F
{1 − exp(−A ln 10)}n2
ref
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where F denotes the integral of the corrected fluorescence spec-
trum, A is the absorbance at the excitation wavelength, and n is the
refractive index of the medium. The reference system used were
tetraphenylporphyrin (ꢀex = 560 nm, Фf = 0.13 in benzene).
The radiative lifetime (ꢂ0, in ns) was calculated from the modi-
fied Strickler–Berg equation [22]:
ꢀ
ꢁ
f1.specF(v˜)dv˜
f1.specF(v˜)v˜−3dv˜
1
ꢂ0
= 2.88 × 10−9n2 ꢀ
ε(v˜)v˜−1dv˜
abs.spec
where F(ꢃ),ꢃ and ε(ꢃ) denote the corrected fluorescence spectrum,
the wavenumber of the light (cm−1), and the molar absorptivity,
respectively.
The radiative lifetimes values, ꢂ0, for all the porphyrin deriva-
tives in immobilized media were highly low with respect to
solution media. This decrease in the solid phase arises from lowered
difference of equilibrium geometries between ground and excited
states in immobilized media with respect to solutions and can be
attributed to the same reason of restricted vibrational rotational
motions. In addition, the lowest radiative lifetime value, ꢂ0, in all
host matrices was seen in CMPP.
The quantum yield values calculated were shown in Table 2. The
TPPP exhibited high quantum yield. Moreover, the quantum yield
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media for the all porphyrin derivatives.
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