Use of novel cardanol-Porphyrin hybrids and their tio2-Based composites for the photodegradation of 4-Nitrophenol in water

Article abstract of DOI:10.3390/molecules16075769

Cardanol, a well known hazardous byproduct of the cashew industry, has been used as starting material for the synthesis of useful differently substituted "cardanol-based" porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel c

Full text of DOI:10.3390/molecules16075769

Molecules 2011, 16, 5769-5784; doi:10.3390/molecules16075769
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molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Use of Novel Cardanol-Porphyrin Hybrids and Their
TiO2-Based Composites for the Photodegradation of
4-Nitrophenol in Water
Giuseppe Vasapollo 1,*, Giuseppe Mele 1, Roberta Del Sole 1, Iolanda Pio 1, Jun Li 2 and
Selma Elaine Mazzetto 3
1
Department of Engineering for Innovation, University of Salento, Arnesano Street, Lecce 73100,
Italy
2
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education,
College of Chemistry and Materials Science, Northwest University, Xi’an, Shaanxi 710069, China;
E-Mail: junli@nwu.edu.cn (J.L.)
3
Laboratory of Products and Processes Technology (LPT), Department of Organic and Inorganic
Chemistry, Federal University of Ceará, Fortaleza 6021, Brazil; E-Mail: selma@ufc.br (S.E.M.)
* Author to whom correspondence should be addressed; E-Mail: giuseppe.vasapollo@unisalento.it;
Tel.: +39-0832-297281; Fax: +39-0832-297733.
Received: 17 May 2011; in revised form: 24 June 2011 / Accepted: 1 July 2011 /
Published: 7 July 2011
Abstract: Cardanol, a well known hazardous byproduct of the cashew industry, has been
used as starting material for the synthesis of useful differently substituted “cardanol-based”
porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel composites
prepared by impregnation of polycrystalline TiO2 powder with an opportune amount of
“cardanol-based” porphyrins, which act as sensitizers for the improvement of the
photo-catalytic activity of the bare TiO2, have been used in the photodegradation in water
of 4-nitrophenol (4-NP), which is a toxic and bio-refractory pollutant, dangerous for
ecosystems and human health.
Keywords: cardanol; porphyrins; metalloporphyrins; heterogeneous photocatalysis;
4-nitrophenol; porphyrin-TiO2 photocatalysts

Molecules 2011, 16
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1. Introduction
Cardanol is a naturally occurring phenol obtained by vacuum distillation of cashew nut shell liquid
(CNSL), a waste byproduct obtained in the cashew nut processing industry [1-5]. Despite the fact that
cardanol could really be considered a dangerous toxic waste, mainly due to the massive amounts of
CNSL produced annually, it represents a precious natural renewable resource which can be used as a
starting material for the preparation of a large variety of useful chemicals [6].
In fact, the preparation of fine chemicals from natural and renewable materials is nowadays
becoming an attractive topic of research especially for the purpose of recycling huge amounts of
agro-industrial waste.
The yellow oil obtained by vacuum distillation of CNSL, that for simplicity we call cardanol,
contains 3-n-pentadecylphenol, 3-(pentadeca-8-enyl)phenol, 3-(pentadeca-8,11-dienyl)phenol, and
3-(pentadeca-8,11,14-trienyl)phenol in approximately 8%, 80%, 8%, 6%, respectively (Figure 1) [7].
Figure 1. Main components of the cardanol mixture.
OH
R
cardanol
R=
(C H )
15 31
(C H ) ( Main compound)
15 29
(C H )
15 27
(C H )
15 25
On the other hand, the photodegradation of organic pollutants in water is a topic of growing interest
and much attention has been devoted in recent years from both academic and industrial researchers to
design new photocatalytic systems having effective application in environmentally friendly processes
like the TiO2-based photocatalysts used for the oxidative degradation of various kinds of organic
pollutants [8-10].
4-Nitrophenol (4-NP) is a harmful and bio-refractory contaminant which can cause considerable
damage to the ecosystem and human health. For this reason its efficient degradation in aqueous
effluents is important in order to minimize its deleterious effects as well as environmental
problems [11-14].
In the past, we have used 3-n-pentadecylphenol (hydrogenated cardanol), as well as cardanol, as
basic materials for the preparation of fine chemicals such as meso-tetrasubstituted cardanol-based
A4-porphyrins [15,16]; but, we noted that only a few examples concerning the use of 3-n-pentadecyl-

Molecules 2011, 16
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phenol-based porphyrins as sensitizers to enhance the photoactivity of TiO2 in the photodegradation of
pollutants in water under UV light, have been reported [17].
Therefore, continuing our research in this area, we like to report here the synthesis and
characterization of new meso-AB3 and trans-A2B2 porphyrins, 5,10,15-triphenyl-20-mono-[4-(2-(3-
pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin (3) and 5,15-diphenyl-10,20-di-[4-(2-(3-pentadec-8-
enyl)phenoxy)ethoxy]phenylporphyrin (4), and their metal derivatives (M = Zn, Cu, Co and Fe).
We would also like to report studies concerning the photocatalytic activity of these compounds,
once deposited onto TiO2, in photodegradation of 4-nitrophenol contained in the water. The advantages
related to the use of cardanol-based porphyrins containing double bonds in the cardanol side chain has
also been noted in this work.
2. Results and Discussion
2.1. Synthesis and Characterization of Cardanol Based Porphyrins
In this work, the term cardanol is used to refer mainly to 3-(pentadeca-8-enyl)-phenol, the
monoolefinic component which can be obtained almost pure from the cardanol oil through distillation
and chromatographic separation, the purity of which, enough for our purposes, was confirmed by
GC-MS and NMR analyses. The meso-AB3 and trans-A2B2 porphyrins were obtained, using 4-[2-(3-
(pentadeca-8-enyl)phenoxy)-ethoxy]-benzaldehyde (1) which was prepared from cardanol through two
steps as shown in Scheme 1, following the procedure reported in the literature [6,18].
Scheme 1. Synthesis of 4-[2-(3-(pentadeca-8-enyl)phenoxy)-ethoxy]-benzaldehyde (1).
CHO
Br
OH
O
HO
CHO
BrCH CH Br
2
O
2
O
KOH, 70°C
C H
K CO /acetone
2
15 29
3
C H
15 29
C H
15 29
1
Thus, meso-AB3 and trans-A2B2 cardanol-based porphyrins 3 and 4, were synthesized respectively
by acid-catalyzed condensation of compound 1 by statistical reaction with pyrrole and benzaldehyde
(Method 1) or with meso-phenyldipyrrolmethane 2 (Method 2), as shown in Scheme 2 in accordance
with different reaction protocols [6,7]. The resulting porphyrins 3 and 4, brown-red sticky solids, very
1
soluble in CHCl3 or CH2Cl2, have been characterized by FT-IR, UV-Vis, H- and 13C-NMR, and
MALDI-TOF techniques. Isolated yields and UV-Vis absorption band of compounds 3 and 4 are
reported in Table 1.

Molecules 2011, 16
Scheme 2. Synthesis of meso-AB3 and trans-A2B2 cardanol-based porphyrins 3 and 4.
5772
C15H29
H
N
CHO
O
1) BF3.OEt2/CHCl3
2) Et3N 3) DDQ
(method 1)
N
NH
N
O
HN
O
O
3
H
O
C15H29
C15H29
1
NH HN
O
2
1) BF3.OEt2/CHCl3
N
NH
O
O
HN
N
2) Et3N 3) DDQ
O
(method 2)
C15H29
4
Table 1. Yields and UV-Vis absorption bands of 3, 4 and their metalloporphyrins 3a–3e, 4a–4e.
λ
Soret band
419
max, nm (CHCl3)
Q bands
Compounds
M Yields %
3
2H
Zn
Cu
Co
Fe
10
90
90
90
80
15
90
90
90
80
516 552 590 646
3a
424
554 594
539
3b
416
3c
411
530
3d
417
4
2H
Zn
Cu
Co
Fe
420
517 553 591 647
4a
425
554 596
540
4b
4c
417
412
530
4d
419
cardanol-based
A4-porphyrin
2H 14 [16]
420
518 556 593 649
For instance, the UV-Vis spectrum of 3 showed a Soret band at 419 nm and Q bands at 516, 552,
590 and 646 nm; the UV-Vis spectrum of 4 showed a 1 nm red shift, with a Soret band at 420 nm and
Q bands at 517, 553, 591 and 647 nm. A red shift in the Q bands was also observed in the previously
reported cardanol-based A4-porphyrin [16]. This suggested to us that the number of the substituents in
the porphyrin molecule influences the value of the maximum of absorption in the UV-Vis spectra,
producing a red shift when the number of substituents is increased. The MALDI-TOF analysis of the

Molecules 2011, 16
5773
metal free porphyins 3 and 4 showed a cluster of signals centered at m/z = 958 [M]+ and 1,301 [M]+,
respectively and consistent with the proposed structures.
1H-NMR and FT-IR spectra of 3 and 4 were also consistent with the proposed structures. In fact,
1H-NMR spectrum of 3 exhibited a multiplet in the 8.82–8.89 ppm range attributable to the
eight protons at the β position of the pyrrole moiety, whereas two typical doublets centered at 8.84 and
8.87 ppm for the β position of the pyrrole moiety were observed in 4, due to its higher symmetry. The
aromatic protons, found in the 8.24–6.83 ppm range and the protons of the double bond of the
side-chain in the 5.28-5.42 ppm range appear as multiplets, and were similar in both porphyrins 3 and
4. In the case of 3, two multiplets corresponding to the protons of the O–CH2CH2–O system were
found in the 5.30–5.40 and 4.59–4.64 ppm range, but in the case of 4 two triplets were found at 4.53
and 4.63 ppm. The triplets centered 2.63 and 2.64 ppm in 3 and 4, respectively, correspond to the
aliphatic protons of the Ar–CH2 system, the other aliphatic protons were in the range 0.75–2.12 ppm in
both 3 and 4. NH protons were present as a broad band centered at −2.77 and −2.76 ppm in 3 and 4,
respectively. The FT-IR spectra of porphyrins 3 and 4 showed a weak band at 3,317 cm−1, characteristic
of the NH vibration, and at 3,006 cm−1 attributed to the side-chain vinylic =C–H vibration.
Scheme 3. Preparation of the metallo-porphyrins 3a–3d and 4a–4d.
N
N
N
N
N
NH
N
MX
M
2
O
O
HN
CHCl3 or DMF
rt or reflux
O
O
3
3a-3d
O
O
N
MX
2
N
N
NH
N
N
O
O
M
O
O
CHCl3 or DMF
rt or reflux
HN
N
O
O
4
4a-4d
3a,4a: M = Zn; 3b,4b: M = Cu; 3c,4c: M = Co; 3d,4d: M=FeCl
Porphyrins 3 and 4 were next used for preparation of the corresponding metallo-derivatives 3a–3d
and 4a–4d (Scheme 3) in nearly quantitative yields, by reacting them with Zn(OAc)2, Co(OAc)2·4H2O,

Molecules 2011, 16
5774
CuCl2, and FeCl3, respectively. FT-IR, UV-Vis, MALDI-TOF and elemental analyses of the
metalloporphyrin complexes 3a–3d and 4a–4d were consistent with the proposed structures. Yields
and UV-Vis absorption bands of 3a–3d and 4a–4d are also reported in Table 1.
From the UV-Vis absorption bands it is possible to observe that in the case of metalloporphyrins
3a–3d and 4a–4d, the Soret band is only slightly shifted compared to the corresponding metal-free
porphyins and the Q bands are reduced to two or at least one because the symmetry of porphyrin ring
increases when the hydrogen atoms were replaced by metals.
The IR spectra of 3a–3d and 4a–4d were close to those of the corresponding metal-free porphyins 3
and 4, except for the disappearance of the NH vibration at 3317 cm−1. MALDI-TOF mass spectrometry
analysis was successfully used for the determination of the molecular weight of the metalloporphyrin
1
13
complexes 3a–3cd and 4a–4d (see Experimental Section). H and C-NMR spectra were recorded
only in the case of Zn(II) complex 3a and 4a because of the paramagnetic effect of the Cu(II), Co(II)
and Fe(III) metal ions that hindered the recording of any such spectra.
2.2. Preparation of the Cardanol Based Porphyrin/TiO2 Composites and Diffuse Reflectance (DR)
Spectroscopy Characterization
TiO2 composites used as photocatalysts were prepared by impregnating of TiO2 with cardanol-based
porphyrins according with the procedure reported in the Experimental. Figure 2 shows the diffuse
reflectance spectra in air of the bare TiO2 as well as of TiO2 impregnated with 4.0 µmol of the selected
H2Pp 4 or MPps [M = Zn (II),Cu(II), Co(II), Fe(III)-Cl] porphyrins 4a–4d per gram of TiO2,
respectively, recorded in the 200–800 nm range.
Figure 2. Diffuse reflectance spectra of bare TiO2 and differently loaded samples obtained
by impregnation of TiO2 with H2Pp 4 or MPp 4a–4d.
70
60
50
40
bare TiO
30
20
10
0
2
ZnPp(4a)/TiO
2
CuPp(4b)/TiO
CoPp(4c)/TiO
2
2
FeClPp(4d)/TiO
2
H Pp(4)/TiO
2
2
200
300
400
500
600
700
800
λ
(nm)
It is worth noting that no appreciable shift of the band gap edge of TiO2 can be observed for any of
the loaded samples. This behaviour was in accord with previously studied metal free and copper
[5,10,15,20-tetra(4-tertbutylphenyl)] porphyrins [19].

Molecules 2011, 16
5775
Similar behavior was observed for the porphyrins H2Pp, 3, and MPps [M = Zn (II), Cu(II), Co(II),
Fe(III)–Cl] 3a–3d) (spectra not shown in Figure 2 for clarity). Figure 3 shows the SEM pictures of
bare TiO2 and CuPp (4b)/TiO2. Basically, the microstructures of the bare TiO2 and porphyrin
impregnated TiO2 composites show common features which are typical regarding this TiO2
polymorph. In fact, both kinds of samples seem rather similar, with spherical shaped particles.
Figure 3. SEM images of bare (a) TiO2 and (b) 4 µmol CuPp (4a)/1 g TiO2.
(a)
(b)
2.3. Photoreactivity Experiments
A few years ago, we reported that polycrystalline TiO2 samples impregnated with differently
substituted porphyrins synthesized from commercially available starting materials displayed better
photocatalytic activity, in comparison with polycrystalline bare TiO2 samples, in the photocatalytic
degradation of 4-NP in water [19,20]. In this work, novel cardanol-based composites 3/TiO2, 3a/TiO2-3d/
TiO2 and 4/TiO2, 4a/TiO2-4d/TiO2, were tested in the photocatalytic degradation of 4-NP.
The efficiency of a photodegradation catalyst has been evaluated by measuring the rate of
consumption of 4-NP in a slurry containing a finely dispersed semiconductor, under constant
illumination. It can also be noticed that the substrate was degraded using each of the photocatalysts,
following pseudo-first-order kinetics. The list of used samples is reported in Table 2, along with the initial
.
.
.
reaction rates of 4-NP disappearance as r0 × 109 (mol L−1 s−1), r0′ × 109 (mol L−1 s−1 m−2) and % conversion
of 4-NP.
Figure 4 shows the diminution of 4-NP concentration vs. irradiation time using different amounts of
CuPp (4b)/TiO2 photocatalysts. These preliminary investigations were carried out in order to establish
which among the differently impregnated photocatalysts exhibited the highest photoactivity.

Molecules 2011, 16
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Table 2. List of the samples used together with the initial photoreaction rates, and the
conversion (%) 4-NP after 180 min of irradiation time.
r0 × 109
r0′ × 109
4-NP
Samples a
(mol.L−1.s−1) (mol.L−1.s−1.m−2) (%) b converted at 180 min
TiO2
26.59
36.36
39.62
42.48
46.70
31.21
33.94
34.28
18.77
22.20
34.34
42.03
41.52
33.55
33.72
18.66
21.36
33.24
45.45
49.52
53.10
58.38
39.01
42.42
42.85
23.46
27.75
42.92
52.54
51.90
41.94
42.15
23.32
26.70
93.5
95.9
97.5
97.4
98.2
97.1
95.1
95.4
92.8
86.0
95.8
97.9
96.7
94.7
93.9
93.3
85.5
1.0 µmol CuPp(4b)/TiO2
2.0 µmol CuPp(4b)/TiO2
4.0 µmol CuPp(4b)/TiO2
6.0 µmol CuPp(4b)/TiO2
9.0 µmol CuPp(4b)/TiO2
6.0 µmol ZnPp(4a)/TiO2
6.0 µmol CoPp(4c)/TiO2
6.0 µmol FeClPp(4d)/TiO2
6.0 µmol H2Pp(4)/TiO2
4.0 µmol CuPp(3b)/TiO2
6.0 µmol CuPp(3b)/TiO2
6.6 µmol CuPp(3b)/TiO2
6.0 µmol ZnPp(3a)/TiO2
6.0 µmol CoPp(3c)/TiO2
6.0 µmol FeClPp(3d)/TiO2
6.0 µmol H2Pp(3)/TiO2
a
The numbers before the code used for identifying the samples indicate the mg amounts of
sensitizer [H2Pp(a), H2Pp(a), CuPp(a) or CuPp(a)] per gram of TiO2; r0: The initial photoreaction
rates per used mass; r0′: Initial photoreaction rates per used mass and per unit surface area of the
.
catalysts. The BET specific surface areas of all the samples are equal to ca. 8 m2 g−1, amount of
photocatalyst: 0.1 g/125 mL solution; b The % conversion of 4-NP was calculated by the following
formula C/C0 × 100.
Figure 4. 4-NP concentration vs. irradiation time using different amounts of CuPp
(4b)/TiO2 photocatalysts.
1.4
1.2
1.0mgCuPp(4b)/1gTiO
2.0mgCuPp(4b)/1gTiO
4.0mgCuPp(4b)/1gTiO
6.0mgCuPp(4b)/1gTiO
9.0mgCuPp(4b)/1gTiO
1.0
0.8
0.6
0.4
0.2
0.0
2
2
2
2
2
0
20
40
60
80
100
120
140
160
180
200
t/min

Molecules 2011, 16
5777
It can be seen that the samples impregnated with 6.0-CuPp (4b)/TiO2 exhibited the highest
photoactivity. These results are in accord with those observed by using the sensitizers 3a–3d as
summarized in Table 2.
As shown in the Figure 5, the Cu(II) porphyrin 4b definitely proved a more effective sensitizer in
the photodegradation of 4-NP than other MPp’s (M = Co, Zn) 4a, 4c, which have a slight beneficial
effect. Interestingly, in contrast with previous experimental evidence [19-21], there is a detrimental
effect observed for the free-base and Fe(III) porphyrin composites 4/TiO2 and 4d/TiO2 compared with
bare TiO2 which could be ascribed to the different lamp used as irradiation source.
Figure 5. 4-NP concentration vs irradiation time using 6.0 µmol of H2Pp (4) or MPps
(4a–4d) porphyrins/1 g TiO2 as photocatalysts.
1.4
1.2
ZnPp(4a)/TiO
2
CuPp(4b)/TiO
CoPp(4c)/TiO
1.0
0.8
0.6
0.4
0.2
0.0
2
2
2
FePp(4d)/TiO
H Pp(4)/TiO
2
2
bare TiO
2
0
20
40
60
80
100
120
140
160
180
200
t/min
The photocatalytic activities are also very slightly influenced by the substitutions and the spatial
positions of the substitutions of porphyrins. In particular, the composites (4, 4a–4d)/TiO2 when used as
catalysts show slightly better photocatalytic activities than (3, 3a–3d)/TiO2, but they have a similar
activity order. All the studied cases gave a conversion of 4-NP higher than 85.5%; in particular, by
using the most efficient CuPps/TiO2 photocatalysts the measured conversion was close to 98% (Table 2).
Further investigations were carried out in order to establish the photostability of the CuPp 4b
impregnated onto the TiO2 surface. Repeated recycling experiments confirmed that this porphyrin
supported onto TiO2 showed good stability under irradiation conditions and samples continued to
maintain good photocatalytic activity after several cycles. Figure 6 shows how the most active
photocatalyst, i.e., CuPp (4b) TiO2 can be recycled six times, after its first use, without significant
loss of activity.

Molecules 2011, 16
5778
Figure 6. Experiments carried out using recycled 6.0 µmol CuPp (4b)/TiO2 as the photocatalyst.
1.4
1.2
1.0
recycle 1
recycle 2
0.8
recycle 3
recycle 4
0.6
recycle 5
recycle 6
0.4
0.2
0.0
-20
0
20
40
60
80
100 120 140 160 180 200
t/min
Typically, 3b and 4b, being effective sensitizers, were insoluble in the water and stable under UV
irradiation, and the catalysts 3b/TiO2 and 4b/TiO2 were also reused several times without loss of
the activity.
Taking into account the r0 values reported in the Table 2 of the impregnated MPps were in the
following order: CuPp > CoPp > ZnPp > bare TiO2 > H2Pp > FePp. The results related to the
photo-degradation of 4-NP in an aqueous heterogeneous environment suggest that the Cu(II)-Cu(I)
photocatalytic redox cycle plays the main beneficial role for the occurrence of the whole process. In a
previous work [20] we demonstrated that Cu(II) could be reduced to Cu(I) [see equation (1)] by
electrons of the conduction band of TiO2 where additional electrons are injected, due to the presence of
the sensitizer:
TiO2[Cu(II)Pp] + e−CB → TiO2[Cu(I)Pp]
(1)
Despite the complex mechanism of reactions the redox process reported in equation 1 seems to be
the key step in the course of which is possible to increase the amounts of OH radicals and superoxide
anion responsible of the degradation process of 4-NP [19,20]. Moreover, in the present case, porphyrin
sensitizers containing un-saturated chains capable of being oxidized have been used for the first time.
Spectroscopic analysis (UV-Vis, FT-IR, etc.) carried out in order to check the photostability of the
porphyrins used as the sensitizers permitted us to prove the stability of the double bonds contained in
the side cardanol chains. In fact, typical spectroscopic signals of double bond of cardanol are still
present at the end of each process. This could means that the oxidizing species responsible of the photo
degradation processes by oxidative demolition of the 4-NP [19,20] act in water solution far from the
composite TiO2 surface.

Molecules 2011, 16
5779
3. Experimental
3.1. Reagents
Cardanol oil (technical grade) was kindly provided by Oltremare S.p.A. (Bologna, Italy).
TiO2 (anatase phase, specific surface area 8 m2/g), kindly provided by Tioxide Huntsman was dried
and crushed to obtain particles with a diameter smaller than 0.1 mm. All other starting materials were
purchased from Aldrich Chemical Co and used as received. Silica gel (Merck) was used in the
chromatographic separations. Solutions of 4-nitrophenol, used without further purification, were
prepared by dissolving the required quantity of 4-NP in water obtained from a New Human Power I
water purification system.
3.2. Analyses
FT-IR spectra were recorded on a JASCO FT-IR 430 spectrometer. UV-Vis spectra were recorded
1
on a Cary 100scan UV-visible spectrophotometer. H- and 13C-NMR spectra were recorded on a
Bruker Avance 400 instrument at room temperature and chemical shifts are reported relative to
tetramethylsilane.Laser desorption/ionization time of flight mass spectrometery (LDI-TOF MS) was
performed on a Reflex IV spectrometer (Bruker Daltonik, Bremen, Germany), managed by the Flex
Control 2.4 software (Bruker Daltonik, Bremen, Germany), equipped with a VSL-337ND nitrogen
laser (Laser Science Inc., Franklin, MA, USA) delivering 4 ns pulses with a repetition rate of 5 Hz and
an average power of 200 µJ. The laser attenuation setting was typically in the range 40–50. Spectra
were obtained in positive ion reflector mode, with 20–17 kV accelerating voltage and 23 kV reflection
voltage. External quadratic calibration was performed with a standard mixture ranging from 757.40 to
3147.47 kDa, giving a mass error lower than 15 ppm. One µL of sample solution of CHCl3 was spotted
on a MTP 384 massive target T (Bruker Daltonik, Bremen, Germany), both in the absence and in the
presence (Matrix Assisted LDI-TOF MS) of same volume of alpha-cyano-4-hydroxycinnamic acid
(saturated solution in water/acetonitrile/TFA 66.9/33/0.1) as ionization adjuvant, and air-dried. Each
spectrum was acquired by 100 to 200 laser shots. Diffuse reflectance (DR) spectra were obtained at room
temperature in the wavelength range 200–800 nm using a Shimadzu UV-2401PC spectrophotometer
with BaSO4 as reference material.
3.3. Synthesis
3.3.1. Synthesis of the cardanol based precursors of the porphyrins
4-[2-(3-(Pentadeca-8-enyl)phenoxy)-ethoxy]-benzaldehyde (1) was synthesized in our laboratory [6,18];
meso-phenyldipyrrolmethane (2) was synthesized with the standard procedure in the literature [7].
3.3.2. Synthesis and characterization of 5,10,15-triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl) phenoxy)
ethoxy] phenylporphyrin (3)
Compound 3 was obtained by statistical synthesis starting from a 3:1 benzaldehyde-1 mixture using
a procedure similar to that reported in reference [7]. Yield: 10%; 1H-NMR (CDCl3): δ −2.77 (br, s, 2H),

Molecules 2011, 16
5780
0.75–0.95 (m, 3H), 1.12–1.42 (m, 16H), 1.58–1.72 (m, 2H), 1.96–2.08 (m, 4H), 2.63 (t, 2H, J = 7.6 Hz),
4.49–4.54 (m, 2H), 4.59–4.64 (m, 2H), 5.30–5.40 (m, 2H), 6.83–6.93 (m, 3H), 7.24–7.27 (m, 1H), 7.33
(d, 2H, J = 8.6 Hz), 7.71–7.81 (m, 9H), 8.13 (d, 2H, J = 8.6 Hz), 8.19–8.24 (m, 6H), 8.82–8.89 (m, 8H);
13C-NMR (CDCl3): δ 14.6, 23.1, 27.6, 27.7, 29.5, 29.7, 29.7, 29.8, 29.9, 30.1, 30.2, 31.7, 31.9, 32.2,
36.3, 66.9, 67.2, 112.0, 112.9, 113.3, 115.5, 115.7, 120.4, 120.5, 120.6, 121.4, 121.8, 127.1, 128.1,
128.4, 129.7, 129.8, 130.3, 130.4, 135.0, 135.3, 136.0, 142.6, 142.6, 145.3, 155.8, 158.9, 159.1; FTIR
(neat), v/cm−1: 3317, 3006, 2923, 2852, 1598, 1583, 1508, 1470, 1441, 1350, 1244, 1175, 1157, 1109,
1072, 1032, 1001, 979, 966, 932, 909, 876, 845, 800, 731; UV-Vis (CH2Cl2) λmax, nm: 419, 516, 552,
590, 646; MALDI-TOF MS m/z: 958 [M]+; Molecular weight: 958 amu; Anal. Calc. for C67H66N4O2:
C, 83.41; H, 7.02; N, 6.91. Found: C, 83.84; H, 6.88; N, 5.84%.
3.3.3. Synthesis and characterization of 5,15-diphenyl-10, 20-di-4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]
phenyl porphyrin (4)
Aldehyde 1 (0.45g, 1 mmol) and meso-phenyldipyrrole 2 (0.22g, 1 mmol) in chloroform (150 mL)
were stirred at room temperature for 10 min, and then BF3·OEt2 (3.75 mL of 0.1 M solution in CHCl3,
0.375 mmol) was added. The reaction mixture was stirred at room temperature for 24 h, then DDQ
(0.17 g in CHCl3) was added slowly to the solution with vigorous stirring. Subsequently, the reaction
mixture was stirred at room temperature for a further 24 h and then removed the solvent under vacuum.
The reaction mixture was passed through a silica gel chromatography column (CH2Cl2/hexane 6/4 v/v).
Yield: 15%; 1H-NMR (CDCl3): δ −2.76 (br, s, 2H), 0.80–0.95 (m, 6H), 1.16–1.46 (m, 32H), 1.58–1.72
(m, 4H), 1.96–2.12 (m, 8H), 2.64 (t, 4H, J = 7.7 Hz), 4.53 (t, 4H, J = 4.5Hz), 4.63 (t, 4H, J = 4.5 Hz),
5.28–5.42 (m, 4H), 6.83–6.94 (m, 6H), 7.24–7.30 (m, 2H), 7.34 (d, 4H, J = 8.7 Hz), 7.72–7.82 (m, 6H),
8.14 (d, 4H, J = 8.7 Hz), 8.22 (d, 4H, J = 7.4 Hz), 8.84 (d, 4H, J = 4.5 Hz), 8.87 (d, 4H, J = 4.7 Hz);
13C-NMR (CDCl3): δ 14.3, 14.6, 23.1, 23.3, 26.0, 26.1, 27.7, 27.7, 29.4, 29.7, 29.7, 29.8, 29.8, 29.8,
29.8, 29.9, 30.1, 30.1, 30.1, 30.1, 30.2, 31.9, 32.0, 32.2, 36.5, 66.9, 67.3, 112.0, 113.3, 115.5, 120.2,
120.3, 120.4, 120.5, 121.8, 127.1, 128.1, 128.4, 128.6, 129.7, 130.3, 130.4, 130.4, 130.6, 135.0, 135.4,
135.4, 136.0, 142.7, 142.7, 145.2, 145.2, 158.9, 159.2; FTIR (neat), v/cm−1: 3317, 3006, 2923, 2853,
1727, 1602, 1583, 1508, 1454, 1401, 1376, 1350, 1245, 1174, 1158, 1111, 1072, 1001, 980, 966, 932,
907, 876, 844, 801, 733; UV-Vis (CH2Cl2) λmax, nm: 420, 517, 553, 591, 647; MALDI-TOF MS m/z:
1303 [M]+; Molecular weight: 1303 amu; Anal. Calc. for C90H102N4O4: C, 82.61; H, 7.74; N, 4.51.
Found: C, 82.95; H, 7.83; N, 4.30%.
3.3.4. General procedure for the synthesis of 3a–3c, 4a–4c
Porphyrin 3 (30.0 mg, 0.031 mmol) or 4 (30.0 mg, 0.023 mmol) were dissolved in CHCl3 (20 mL).
To this solution was added an excess of Zn(CH3COO)2 (34.0 mg, 0.186 mmol), CuCl2 (20.0 mg,
0.186 mmol) or Co(CH3COO)2·4H2O (46.3 mg, 0.186 mmol), and the mixture was stirred at room
temperature. The reaction was checked by TLC. After disappearance of 3 or 4, the solution was filtered
and then the solvent was removed under vacuum. The crude product was purified by silica gel
chromatography (CHCl3/Hexane, 7/3 v/v) to give 3a, 3b, 3c, 4a, 4b, 4c in nearly quantitative yields.

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3.3.5. General procedure for synthesis of 3d and 4d
Porphyrin 3 (30.0 mg, 0.031 mmol) or 4 (30.0 mg, 0.023 mmol) were dissolved in DMF (15 mL).
To this solution, an excess of FeCl3 (30.2 mg, 0.186 mmol) was added. The reaction was heated to
reflux and monitored by UV/Vis spectroscopy. The metal insertion was completed in 4 h. Then the
solvent was removed under vacuum and the residue was purified by silica gel chromatography
(CHCl3/hexane, 7/3 v/v) to give 3d and 4d respectively.
Representative data for compounds 3a–3d, 4a–4d
Zn(II)5,10,15-Triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin
(3a).
Purplish red solid. Yield 95%; 1H-NMR (CDCl3): δ 0.86–0.90 (m, 3H), 1.26–1.39 (m, 16H), 1.62–1.68
(m, 2H), 1.96–2.01 (m, 4H), 2.63 (t, 2H, J = 7.4 Hz), 4.48–4.50 (m, 2H), 4.58–4.61 (m, 2H), 5.33–5.39
(m, 2H), 6.83–6.90 (m, 3H), 7.23–7.27 (m, 1H), 7.32 (d, 2H, J = 8.6 Hz), 7.73–7.78 (m, 9H), 8.13 (d,
13
2H, J = 8.6 Hz), 8.22–8.24 (m, 6H,), 8.95–8.99 (m, 8H); C-NMR (400 MHz, CDCl3): δ 14.6, 23.1,
27.6, 27.7, 29.6, 29.7, 29.7, 29.7, 29.8, 30.1, 30.1, 30.2, 31.8, 32.2, 36.4, 68.2, 112.0, 113.2, 115.5,
122.0, 126.9, 127.2, 127.9, 128.0, 128.4, 128.6, 129.7, 130.3, 130.4, 130.4, 130.5, 130.8, 132.3, 132.4,
132.4, 134.9, 135.8, 143.3, 145.2, 145.2, 150.6, 158.5; FTIR (neat), v/cm−1: 3007, 2924, 2853, 1600,
1584, 1485, 1446, 1378, 1339, 1255, 1157, 1071, 1024, 997, 912, 873, 797, 774, 720, 695; UV-Vis
(CHCl3) λmax, nm: 424, 554, 594; MALDI-TOF MS: an isotopic cluster peaking at m/z: 1021 [M]+;
Molecular weight: 1021 amu; Anal. Calc. for C67H64N4O2Zn: C, 78.61; H, 6.14; N, 5.54. Found: C,
78.82; H, 6.27; N, 5.49%.
Cu(II)5,10,15-triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin
(3b).
Red solid. Yield: 95%; FTIR (neat), v/cm−1: 3007, 2924, 2849, 1599, 1583, 1509, 1491, 1442, 1377,
1346, 1245, 1216, 1175, 1158, 1072, 1003, 799, 753, 717; UV-Vis (CHCl3) λmax, nm: 416, 539;
MALDI-TOF MS: An isotopic cluster peaking at m/z: 1021 [M]+; Molecular weight: 1021 amu; Anal.
Calc. for C67H64N4O2Cu: C, 78.61; H, 6.14; N, 5.54. Found: C, 78.82; H, 6.27; N, 5.49%.
Co(II)5,10,15-Triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin
(3c).
Peach-red solid. Yield: 85%; FTIR (neat), v/cm−1: 3006, 2924, 2853, 1600, 1583, 1510, 1491, 1448,
1475, 1350, 1283, 1244, 1175, 1158, 1072, 1004, 796, 752, 716, 701; UV-Vis (CHCl3) λmax, nm: 411,
530; MALDI-TOF MS: An isotopic cluster peaking at m/z: 1017 [M]+; Molecular weight: 1017 amu;
Anal. Calc. for C67H64N4O2Co: C, 79.05; H, 6.29; N, 5.51. Found: C, 78.89; H, 6.16; N, 5.64%.
Fe(III)5,10,15-Triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin
chloride
(3d). Brown red solid. Yield: 85%; FTIR (neat), v/cm−1: 3008, 2924, 2853, 1599, 1588, 1485, 1455,
1377, 1340, 1247, 1156, 1072, 1004, 875, 802, 750, 719, 699; UV-Vis (CHCl3) λmax, nm: 417;
MALDI-TOF MS: An isotopic cluster peaking at m/z: 1013 [M−Cl−H]+; Molecular weight: 1049.5
amu; Anal. Calc. for C67H64N4O2FeCl: C, 76.61; H, 6.10; N, 5.33. Found: C, 76.72; H, 6.23; N, 5.54%.
Zn(II)5,15-Diphenyl-10,20-di-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin (4a). Purplish
1
red solid. Yield: 95%; H-NMR (CDCl3): δ 0.82–0.94 (m, 6H), 1.18–1.44 (m, 32H), 1.60–1.72 (m,
4H), 1.93–2.09 (m, 8H), 2.64 (t, 4H, J = 7.5 Hz), 4.48–4.55 (m, 4H), 4.59–4.66 (m, 4H), 5.25–5.45 (m,

Molecules 2011, 16
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4H), 6.83–6.94 (m, 6H), 7.24–7.30 (m, 2H), 7.33 (d, 4H, J = 7.5Hz), 7.72–7.82 (m, 6H), 8.14 (d, 4H,
13
J = 8.3 Hz), 8.23 (d, 4H, J = 6.5 Hz), 8.94 (d, 4H, J = 4.8 Hz), 8.98 (d, 4H, J = 5.1 Hz); C-NMR
(CDCl3): δ 14.5, 23.1, 23.2, 26.0, 26.1, 27.6, 27.6, 29.4, 29.7, 29.7, 29.8, 29.8, 29.9, 30.1, 30.1, 30.1,
30.2, 30.2, 31.4, 31.8, 31.8, 32.2, 36.5, 66.9, 67.3, 112.1, 113.2, 115.5, 121.4, 121.8, 126.9, 127.9,
128.4, 129.7, 130.2, 130.3, 130.4, 130.5, 132.3, 132.3, 132.4, 134.8, 135.8, 136.0, 143.3, 145.2, 145.2,
150.6, 150.9, 150.9, 158.8, 159.2; FTIR (neat), v/cm−1: 3007, 2923, 2852, 1602, 1523, 1509, 1485,
1447, 1373, 1338, 1243, 1174, 1108, 1069, 997, 931, 879, 846, 797, 753, 720, 700; UV-Vis (CHCl3)
λ
max, nm: 425, 554, 596; MALDI-TOF MS: An isotopic cluster peaking at m/z: 1365 [M]+; Molecular
weight: 1365 amu; Anal. Calc. for C90H100N4O4Zn: C, 79.01; H, 7.54; N, 4.21. Found: C, 79.12; H,
7.33; N, 4.10%.
Cu(II)5,15-Diphenyl-10,20-di-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin (4b). Red
solid. Yield: 95%; FTIR (neat), v/cm−1: 3008, 2925, 2852, 1601, 1583, 1504, 1446, 1377, 1345, 1244,
1215, 1174, 1158, 1072, 1000, 800, 749,701; UV-Vis (CHCl3) λmax, nm: 417, 540; MALDI-TOF MS:
An isotopic cluster peaking at m/z: 1365 [M]+; Molecular weight: 1365 amu; Anal. Calc. for
C90H100N4O4Cu: C, 79.12; H, 7.33; N, 4.10. Found: C, 78.92; H, 7.26; N, 4.24%.
Co(II)5,15-Diphenyl-10,20-di-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin (4c). Peach-red
solid. Yield: 95%; FTIR (neat), v/cm−1: 3006, 2924, 2853, 1602, 1583, 1463, 1377, 1351, 1261, 1215,
1175, 1158, 1074, 1005, 799, 755, 701; UV-Vis (CHCl3) λmax, nm: 412, 530; MALDI-TOF MS: An
isotopic cluster peaking at m/z: 1361 [M]+; Molecular weight: 1361 amu; Anal. Calc. for
C90H100N4O4Co: C, 79.35; H, 7.35; N, 4.11. Found: C, 79.22; H, 7.31; N, 4.27%.
Fe(III)5,15-Diphenyl-10,20-di-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenylporphyrin chloride (4d).
Brown red solid. Yield: 85%; FTIR (neat), v/cm−1: 3005, 2924, 2853, 1600, 1582, 1509, 1485, 1449,
1376, 1338, 1246, 1158, 1071, 998, 875, 801, 751, 722, 697; UV-Vis (CHCl3) λmax, nm: 419; MALDI-TOF
MS: An isotopic cluster peaking at m/z: 1358 [M-Cl]+; Molecular weight: 1393.5 amu; Anal. Calc. for
C90H100N4O4FeCl: C, 77.50; H, 7.18; N, 4.02. Found: C, 77.65; H, 7.23; N, 4.12%.
3.4. Preparation of the Cardanol-Based Porphyrin/TiO2 Composites
The loaded samples used as photocatalysts for the photoreactivity experiments were prepared by
impregnating TiO2 with cardanol-based porphyrins. The procedure is as follows: An opportune amount
of sensitizer 3a–3d and 4a–4d was dissolved in CH2Cl2 (20 mL) and finely ground TiO2 (1 g) was
added into this solution. The mixture was stirred for 3–4 h and the solvent removed under vacuum. The
resulting composites were marked as 3a/TiO2-3d/TiO2 and as 4a/TiO2-4d/TiO2, respectively.
3.5. Photo-Reactivity Experiments
Photoreactivity experimenta were carried out in a set-up equipped with a UV lamp (250 W Hg
200 ULTRA lamp), the distance between lamp and the surface of solution is 40 cm with an intensity of
30 W/m2. The temperature inside the reactor was maintained at ca. 300 K. The reacting aqueous
suspension of 4-nitrophenol (4-NP, 20 mg/L, 125 mL) and catalyst (100 mg) was stirred with a
magnetic bar. The initial pH of the suspension was adjusted to 4.0 by the addition of H2SO4. Air was

Molecules 2011, 16
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bubbled into the suspension when switching on the lamp. Samples (3 mL) were withdrawn from the
suspension every 30 min during the irradiation. The photocatalysts were separated from the solution by
centrifugation and successively filtered through 0.45-µm celluloseacetate membranes (HA, Millipore)
before to perform the quantitative determination of 4-NP by measuring its absorption at 316 nm with
UV-Vis spectrophotometer. Bare TiO2 was also tested for the sake of comparison under the same
experimental conditions.
4. Conclusions
In this paper we have described the synthesis and characterization of some new cardanol-based
porphyrins, 5,10,15-triphenyl-20-mono-[4-(2-(3-pentadec-8-enyl) phenoxy) ethoxy] phenyl porphyrin,
(3), and 5,15-diphenyl-10,20-di-[4-(2-(3-pentadec-8-enyl)phenoxy)ethoxy]phenyl porphyrin, (4), as
well as their zinc(II), copper(II) and cobalt(II) metal derivatives, 3a, 3b, 3c, 4a, 4b and 4c. Selected
Cu(II) porphyrins used as sensitizers onto TiO2 samples showed the best photo-catalytic activity for
the photo-degradation of 4-NP in water, compared with the other MPp/TiO2 composites.
Acknowledgments
The authors are grateful the University of Salento for financial support.
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Sample Availability: Not available.
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