Synthesis, characterization and spectral properties of substituted tetraphenylporphyrin iron chloride complexes

Article abstract of DOI:10.3390/molecules16042960

A series of substituted tetraphenylporphyrin iron chloride complexes [RTPPFe(III)Cl, R=o/p-NO₂, o/p-Cl, H, o/p-CH₃, o/p-OCH₃] were synthesized by a novel universal mixed-solvent method and the spectral properties of free b

Full text of DOI:10.3390/molecules16042960

Molecules 2011, 16, 2960-2970; doi:10.3390/molecules16042960
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molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis, Characterization and Spectral Properties of
Substituted Tetraphenylporphyrin Iron Chloride Complexes
Zhi-Cheng Sun, Yuan-Bin She *, Yang Zhou, Xu-Feng Song and Kai Li
Institute of Green Chemistry and Fine Chemicals, Beijing University of Technology,
Beijing 100124, China
* Author to whom correspondence should be addressed; E-Mail: sheyb@bjut.edu.cn;
Tel.: +86-10-67392695; Fax: +86-10-67392695
Received: 22 February 2011; in revised form: 23 March 2011 / Accepted: 31 March 2011 /
Published: 6 April 2011
Abstract: A series of substituted tetraphenylporphyrin iron chloride complexes
[RTPPFe(III)Cl, R=o/p-NO2, o/p-Cl, H, o/p-CH3, o/p-OCH3] were synthesized by a novel
universal mixed-solvent method and the spectral properties of free base porphyrins and
iron porphyrin compounds were compared with each other. The experimental results
showed that the one-pot mixed solvent method was superior to the two-step method in the
yields, reaction time and workup of reaction mixtures for the synthesis of iron porphyrin
compounds. The highest yields (28.7%-40.4%) of RTPPFe(III)Cl were obtained in the
mixed solvents propionic acid, glacial acetic acid and m-nitrotoluene under reflux for 2 h.
A detailed analysis of ultraviolet-visible (UV-vis), infrared (IR) and far-infrared (FIR)
spectra suggested the transformation from free base porphyrins to iron porphyrins. The red
shift of the Soret band in ultraviolet-visible spectra due to the presence of p-nitrophenyl
substituents and the blue shift of Fe-Cl bond of TPPFeCl in far-infrared spectra were
further explained by the electron transfer and molecular planarity in the porphyrin ring.
Keywords: synthesis; porphyrin; iron porphyrin; spectra property
1. Introduction
In recent years substituted porphyrin-like complexes with conjugated macrocycles have been
essential to the study of biomimetic chemistry [1,2], iatrology [3], analytical chemistry [4] and
molecular electronic devices [5]. One of the most important applications of the porphyrin-like

Molecules 2011, 16
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complexes is as a model for the natural enzyme peroxidase, in which the dioxygen has been activated by
metalloporphyrins under mild conditions [6]. Especially, the iron porphyrin complexes are widely used as
model compounds to simulate the catalytic behavior of cytochrome P450 enzymes in life processes [7].
They can be used as biomimetic catalysts to catalyze the selective oxidation of saturated hydrocarbons,
aromatic hydrocarbons and their side chains with dioxygen [8-10]. The importance of iron porphyrin
complexes in biological systems and biomimetic catalytic reactions have prompted extensive studies
on the synthesis of iron porphyrin compounds [11]. Many new synthetic methods of metalloporphyrins
have been developed, including the tetramerization of pyrrole [12-16] and the self-condensation of
dipyrromethene [17,18]. Thereinto, the synthesis of substituted tetraphenylporphyrin compounds via
the tetramerization of benzaldehyde and pyrrole has also been improved by using different organic
oxidants [19,20], carboxylic acids [21] and solvents [22].
The tetraarylporphyrins were obtained for the first time by Rothemund [23,24]. Up to now, there
exist two simple and practical methods of synthesizing porphyrin compounds. Adler and Longo firstly
converted aromatic aldehyde and pyrrole to corresponding porphyrin complexes in a single refluxing
carboxylic acid with air oxidation [25]. The separation of products was relatively simple using the
Adler-Longo method [13], but the yields of porphyrins rarely exceeded 20%. Lindsey’s group
subsequently developed another synthetic strategy to form substituted tetraphenylporphyrin
compounds in CH2Cl2 solvent with BF3 etherate as catalyst and p-chloranil as oxidant [14]. The
Lindsey synthetic approach was more feasible for the larger scale synthesis [26] and obtained much
higher yields of substituted tetraphenylporphyrins with the addition of salts [27]. However, large
diluent agents and expensive quinones were involved in the Lindsey method, which brought about the
high cost of porphyrin synthesis and restricted their applications at present. Therefore, the Adler
method are of the advantages of simple manipulation and ease of workup with low yields, while the
Lindsey method can obviously improve the yields of porphyrins with costly and environmental
impacts. Meanwhile, the synthetic methods are different for the metalloporphyrins with various
structures in the porphyrin rings, which lead to the universal synthetic method impossible to be used in
the porphyrin complexes with various substituents. Therefore, the study on synthetic methods for
conveniently improving the yields of metalloporphyrin complexes is of great significance. In this
work, a series of substituted tetraphenylporphyrin iron chloride complexes were synthesized with two
different methods. Simultaneously, the structures of above porphyrin-like complexes were
characterized by UV-vis, IR, FIR and elemental analysis.
2. Results and Discussion
2.1. Synthesis with One-pot and Two-step Methods
Nine substituted tetraphenylporphyrin iron chloride compounds were prepared using the one-pot
mixed solvent method and the Adler two-step method. The synthetic reactions are shown in Scheme 1
and Scheme 2.

Molecules 2011, 16
Scheme 1. Synthesis of iron porphyrin complexes by the one-pot mixed solvent method.
2962
R2
R1
R2
R1
N
N
N
CH3CH2COOH/CH3COOH/m-nitrotoluene
4
M
Cl
R2
4
+
+
FeCl2·4H2O
R2
N
N
reflux 2 h
R1
R1
H
CHO
R1
1: R1 = NO2, Cl, CH3, OCH3, H; R2 = H
2: R1 = H; R2 =NO2, Cl, CH3, OCH3
3: M=Fe(III)
R2
Scheme 2. Synthesis of iron porphyrin complexes with the two-step method.
R2
R1
NH N
R2
R1
CH3CH2COOH
reflux 2 h
4
4
+
R2
R2
N
HN
N
R1
R1
H
CHO
R1
R2
R2
R2
R1
R1
R1
R1
NH N
N HN
N
N
N
DMF
HCl
reflux 6-8 h
R2
R2
+
FeCl2·4H2O
M
Cl
R2
R2
N
R1
R1
R1
R1
1: R1 = NO2, Cl, CH3, OCH3, H; R2 = H
2: R1 = H; R2 =NO2, Cl, CH3, OCH3
3: M=Fe(III)
R2
R2
It was well known that the classic Adler two-step method of synthesizing metalloporphyrins is
carried out by reacting free base porphyrins with metal salts in refluxing dimethylformamide (DMF)
for a long time [28]. This method had advantages in the manipulation of synthesis and purities of
products, but the yields of synthesized free base porphyrins were much lower (< 20%) and the reaction
time for synthesizing metalloporphyrins was too long. Therefore, the prominent advantages of
synthesizing metalloporphyrins by using one-pot mixed solvent method were that much higher yields
of metalloporphyrin complexes could be obtained after shorter reaction times with simple workup of
the reaction mixtures. A comparison of yields between the one-pot and two-step synthetic methods is
given in Table 1.

Molecules 2011, 16
Table 1. Comparison of metalloporphyrin yields by the one-pot and two-step methods.
2963
Optimum ratios of solvents: the volume ratios of propionic acid, glacial acetic acid and
m-nitrotoluene.
Optimum ratios of
solvents
Total yields
Total yields
No.
Compounds
(one-pot method)
(two-step method)
(one-pot method)
70:10:20
(%)
28.7
31.8
33.6
32.5
38.3
30.1
40.4
32.7
35.9
(%)
13.1
9.7
1
2
3
4
5
6
7
8
9
o-NO2TPPFeCl
o-ClTPPFeCl
o-CH3TPPFeCl
o-OCH3TPPFeCl
TPPFeCl
40:20:20
40:20:20
16.7
5.7
70:10:20
70:10:20
18.4
5.6
p-NO2TPPFeCl
p-ClTPPFeCl
p-CH3TPPFeCl
p-OCH3TPPFeCl
40:20:20
40:20:20
16.7
15.4
13.0
70:10:20
40:20:20
From Table 1, it could be found that the synthetic yields of porphyrins were improved by the one-pot
method, and the yields of substituted tetraphenylporphyrin iron chlorides were much higher (from
28.7% to 40.4%) than those (from 5.6% to 18.4%) in two-step method. For the synthesis of porphyrins
in a single carboxylic acid (e.g. propionic acid) with air oxidation, it was difficult to turn up the
appropriately corresponding conditions, especially such as polarity (dipole moment), acidity (pKa) and
reaction temperature (reflux temperature), therefore, the synthetic yields of porphyrins were relatively
low in the single carboxylic acid and this single-solvent method was not universal for the synthesis of
different substituted porphyrins. By mixing specific carboxylic acids and m-nitrotoluene in some
proportion, the polarity and acidity of the reaction system may be conveniently improved, further
promoting the deprotonation ability of α-H in pyrrole and the protonation strength of C=O in the
o
aromatic aldehyde. Simultaneously, the reflux temperature (120 C) in mixed solvents is lower than
that in the single propionic acid (141 oC) or DMF (153 oC), which decreases the side effects caused by
high reaction temperature. In addition, besides changing the polarity of the mixed solvent systems, the
m-nitrotoluene in the mixed solvents played a role of oxidant [29], since m-nitrotoluene is a weak
organic oxidant that can effectively promote the formation of free base porphyrins in contrast to
atmospheric O2 as oxidant and correspondingly increased the yields of metalloporphyrins. The ratio of
mixed solvents also had an important influence on the synthesis of substituted tetraphenylporphyrins.
By changing the ratio of mixed solvents, the polarity of mixed solvents could be better adjusted to
increase the collision frequencies of reactant molecules and accelerate the formation of porphyrins in
the one-pot mixed solvent system. Moreover, the one-pot mixed solvent method was valid for different
substituted benzaldehydes and the reaction time was shorter than that in the two-pot method. Therefore,
the one-pot mixed solvent method was an efficient one to synthesize tetraphenylporphyrin iron
compounds with different substituents.

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2.2. Spectral Analysis of RTPPFe(III)Cl
The structures of all free base porphyrins and substituted tetraphenylporphyrin iron(III) chlorides
were characterized through UV-vis and the spectral data are listed in Table 2.
Table 2. UV-vis data of free base porphyrins and substituted tetraphenylporphyrin iron
chlorides.
λmax (nm)
No.
Compounds
Soret bands
421
Q bands
516 551 593 650
511 542 587 642
512 544 589 645
512 545 589 643
514 538 585 620
516 551 594 604
514 549 589 645
516 551 592 647
518 555 593 650
510 579
1
o-NO2TPP
2
o-ClTPP
412
3
o-CH3TPP
416
4
o-OCH3TPP
TPP
417
5
417
6
p-NO2TPP
424
7
p-ClTPP
418
8
p-CH3TPP
419
9
p-OCH3TPP
o-NO2TPPFeCl
o-ClTPPFeCl
o-CH3TPPFeCl
o-OCH3TPPFeCl
TPPFeCl
421
10
11
12
13
14
15
16
17
18
422
418
505 576
416
511 585
418
513
418
507 572
p-NO2TPPFeCl
p-ClTPPFeCl
p-CH3TPPFeCl
p-OCH3TPPFeCl
421
514 584
417
509 573
418
452 511
420
509 572
By comparing the UV-vis data in Table 2, it was noticed that four absorption bands presented at the
Q band and the maximum wavelength absorption (λmax) presented at the Soret band along with the
formation of free base porphyrins. When the metal ion was inserted into the porphyrin ring and then
coordinated with four N atoms, the iron ion located in the center of the porphyrin ring to form the iron
porphyrin compounds. Then the number and intensity of the Q bands decreased and the Soret band
occurred slightly red shift (e.g. o-ClTPP to o-ClTPPFeCl, from 412 nm red shift to 418 nm), which
was the characteristics of iron porphyrin compounds formed. The reason might be that the structure
symmetry of iron porphyrin compounds with C4v point groups was improved and the energy gap
decreased comparing with free base porphyrins with D2h point groups. Therefore, the UV-vis spectra
of iron porphyrin compounds were obviously different from those of free base porphyrins.
It also could be observed that the absorption band in the UV-vis region of iron porphyrin
compounds with –NO2 group located at ~422 nm, which revealed the red shift compared with other
iron porphyrin compounds. The reason might be that the strong electron-withdrawing –NO2 group
decreased the electronic density of the porphyrin ring. Thus, the energy levels of π1 and π2 orbits were
increased and the energy gap between HOMO and LUMO of the porphyrin ring became smaller. The
π-π* electron excitation of the porphyrin ring required absorbing the light of smaller energy (longer

Molecules 2011, 16
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wavelength), accordingly the absorption band (Soret band) occurred red shift and located in the long
wavelength region. Infrared and far-infrared spectra data of above porphyrin compounds were listed in
Table 3.
Table 3. IR/FIR data of free base porphyrins and iron porphyrin compounds.
IR (cm-1)
No.
Compounds
νN-H
ν=C-H
3060
3056
3016
3070
3051
3055
3024
3024
2925
νC=C
1606
1626
1599
1580
1594
1595
1627
1561
1596
νC=N
1349
1346
1348
1349
1352
1347
1349
1349
1346
γ=C-H
722
750
739
753
732
800
796
798
805
νFe-N
—
—
—
—
—
—
—
—
—
νFe-Cl
—
—
—
—
—
—
—
—
—
(δN-H
)
3321
(968)
3325
(967)
3315
(965)
3322
(966)
3309
(966)
3322
(967)
3315
(965)
3317
(967)
3320
(967)
—
1
2
3
4
5
6
7
8
9
o-NO2TPP
o-ClTPP
o-CH3TPP
o-OCH3TPP
TPP
p-NO2TPP
p-ClTPP
p-CH3TPP
p-OCH3TPP
10
11
12
13
14
15
16
17
18
o-NO2TPPFeCl
o-ClTPPFeCl
o-CH3TPPFeCl
o-OCH3TPPFeCl
TPPFeCl
2925
2923
3014
2934
2923
2925
3133
3022
2923
1607
1673
1598
1596
1597
1595
1682
1494
1605
1345
1334
1332
1334
1340
1346
1338
1338
1334
740
754
753
756
750
802
805
799
810
999
999
998
998
991
999
999
999
998
367
370
361
360
379
368
359
360
359
—
—
—
—
p-NO2TPPFeCl
p-ClTPPFeCl
p-CH3TPPFeCl
p-OCH3TPPFeCl
—
—
—
—
As shown in Table 3, the IR absorption frequencies were different for free base porphyrins and iron
porphyrin complexes with different functional groups. It was found that the N-H bond stretching and
bending frequencies of free base porphyrins located at ~3,300 cm-1 and ~960 cm-1. When the iron ion was
inserted into the porphyrin ring, the N-H bond vibration frequency of free base porphyrins disappeared and
the characteristic functional groups of Fe-N bond formed at ~1,000 cm-1, which indicated the formation of
iron porphyrin compounds [30]. The bands at 2,923~3,133 cm-1 were assigned to the C-H bond of the
benzene ring and pyrrole ring. The bands at 1,494~1,682 cm-1 and 1,334~1,352 cm-1 were assigned to the
C=C stretching mode and the C=N stretching vibration respectively. The bands at ~800 cm-1 and ~750
cm-1 were respectively assigned to the C-H bond bending vibration of para-substituted and

Molecules 2011, 16
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ortho-substituted phenyl ring. The FIR characterization of Fe-Cl bond vibration located at 359~379 cm-1. The
above results were in good agreement with the substituted tetraphenylporphyriniron chlorides as
expected. Moreover, it could be well observed that the Fe-Cl bond vibration frequency (379 cm-1) of
TPPFeCl was obviously higher than that in other substituted tetraphenylporphyrin iron chlorides.
Generally, the vibration frequency shifted to the higher frequency region (blue shift) as the bond
energy increased. Owing to the fact TPPFeCl has a MOOP structure [30] it was roughly planar and this
led to better resonance effects than RTPPFeCl with a ruffling structure. Accordingly, the bond energy
of Fe-Cl bond in TPPFeCl increased and the vibrational frequency greatly shifted to the higher region.
3. Experimental
3.1. Materials and Instruments
All chemicals were obtained commercially and used as received unless otherwise noted. Pyrrole
was redistilled before use. CH2Cl2 was dehydrated. Neutral Al2O3 was baked at 100 °C for 5 h.
Chromatography was performed on neutral Al2O3. UV-Vis spectra were recorded in CH2Cl2 with a
HITACHI U-3010 spectrophotometer. IR spectra were recorded as KBr pellets via a Nicolet
AVATAR-360 spectrophotometer. FIR spectra were recorded on a Brucker FT-IR VERTEX 70
spectrometer. The data of elemental analysis were obtained with an EURO EA3000 elemental
analyzer.
3.2. Synthesis of RTPPFe(III)Cl
3.2.1. Synthesis–Adler Two-step Method
RTPPH2 (R=o/p-NO2, o/p-Cl, H, o/p-CH3, o/p-OCH3) were synthesized by the direct condensation of
pyrrole with substituted benzaldehydes according to the documented procedure [13]. The free base
porphyrins were purified through a column of Al2O3 (grade III) and eluted with CH2Cl2. The solvent
was then removed under vacuum and the purified porphyrin complexes were obtained in yields of less
than 20%.
o-NO2TPPFeCl. o-NO2TPPH2 (0.2 g, 0.25 mmol) was dissolved in DMF (100 mL). The solution was
heated to reflux with magnetic stirring. Upon dissolution of the o-NO2TPPH2, FeCl2·4H2O (0.3 g, 1.5
mmol) was added into the solution in three portions over 30 min, thin-layer chromatography (alumina,
using CH2Cl2 as eluant) indicated no free base porphyrins at this point. After that, DMF (50 mL) was
removed from the solution. The solution was cooled to 50-60 °C and 6 M HCl (40 mL) was added into
it. The solid appeared from the solution and then was filtrated and washed with 3 M HCl until the filter
cake no longer appeared green. The resulting solid was vacuum-dried to afford over 91.9% yield of o-
NO2TPPFeCl. Mp > 300 °C; Anal. Calcd. for C44H24N8O8ClFe: C 59.78; H 2.74; N 12.68; Found: C
59.35, H 2.64, N 12.52; UV-vis (CH2Cl2) λmax: 422 nm (Soret band), 510 nm, 579 nm (Q band); IR
(KBr) νmax: 999 cm-1 (νFe-N), 367 cm-1 (νFe-Cl).

Molecules 2011, 16
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o-ClTPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl and the final
solid was recrystallized from CH2Cl2 to yield 94.7% of the title compound. Mp > 300 °C; Anal. Calcd.
for C44H24N4Cl5Fe: C 62.78, H 2.87, N 6.66; Found: C 62.44, H 3.16, N 7.01; UV-vis (CH2Cl2) λmax
418 nm (Soret band), 505 nm, 576 nm (Q-band); IR (KBr) νmax: 999 cm-1 (νFe-N), 367 cm-1 (νFe-Cl).
:
o-CH3TPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl and the final
solid was recrystallized from CH2Cl2 in 91.5% yield. Mp > 300 °C; Anal. Calcd. for C48H36N4ClFe: C
59.78, H 2.64, N 12.61; Found: C 59.35, H 2.74, N 12.68; UV-vis (CH2Cl2) λmax: 416 nm (Soret band),
511 nm, 585 nm (Q-band); IR (KBr) νmax: 998 cm-1 (νFe-N), 361 cm-1 (νFe-Cl).
o-OCH3TPPFeCl was prepared in 91.5% yield using the same procedure as described for o-
NO2TPPFeCl and the final solid was recrystallized from CH2Cl2. Mp > 300 °C; Anal. Calcd. for:
C48H36N4ClFeO4: C 69.96, H 4.40, N 6.80; Found: C 69.36, H 4.73, N 6.78; UV-vis (CH2Cl2) λmax
418 nm (Soret band), 513 nm (Q-band); IR (KBr) νmax: 998 cm-1 (νFe-N), 360 cm-1 (νFe-Cl).
:
TPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl and recrystallized
from CH2Cl2/CH3OH to yield up to 97.4% of the target compound. Mp > 300 °C; Anal. Calcd. for
C44H28N4ClFe: C 75.07, H 4.01, N 7.96; Found: C 74.29, H 4.07, N 7.92; UV-vis (CH2Cl2) λmax: 418
nm (Soret band), 507 nm, 572 nm (Q-band); IR (KBr) νmax: 991 cm-1 (νFe-N), 379 cm-1 (νFe-Cl).
p-NO2TPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl and the final
solid was vacuum-dried and afforded above 92.0% yield of product. Mp > 300 °C; Anal. Calcd. for
C44H24N8O8ClFe: C 59.78; H 2.74; N 12.68; Found: C 59.35, H 2.74, N 12.68; UV-vis (CH2Cl2) λmax
421 nm (Soret band), 514 nm, 584 nm (Q-band); IR (KBr) νmax: 999 cm-1 (νFe-N), 368 cm-1 (νFe-Cl).
:
p-ClTPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl and
recrystallized from CH2Cl2/CH3OH to yield up to 99.4% of product. Mp > 300 °C; Anal. Calcd. for
C44H24N4Cl5Fe: C 62.78, H 2.87, N 7.04; Found: C 62.32, H 3.31, N 6.66; UV-vis (CH2Cl2) λmax: 417
nm (Soret band), 509 nm, 573 nm (Q-band); IR (KBr) νmax: 999 cm-1 (νFe-N), 359 cm-1 (νFe-Cl).
p-CH3TPPFeCl was prepared in up to 90.4% yield using the same procedure as described for o-
NO2TPPFeCl and the final solid was recrystallized from CH2Cl2. Mp > 300 °C; Anal. Calcd. for
C48H36N4ClFe: C 59.78, H 2.64, N 12.61; Found: C 59.43, H 2.89, N 12.96; UV-vis (CH2Cl2) λmax: 418
nm (Soret band), 452 nm, 511 nm (Q-band); IR (KBr) νmax: 999 cm-1 (νFe-N), 360 cm-1 (νFe-Cl).
p-OCH3TPPFeCl was prepared using the same procedure as described for o-NO2TPPFeCl. The
resulting solid was washed twice with water (50 mL) and recrystallized from CH2Cl2/CH3OH to yield
up to 95.2% of product. Mp > 300 °C; Anal. Calcd. for C48H36N4ClFeO4: C 69.96, H 4.40, N 6.80;
Found: C 69.30, H 4.68, N 6.86; UV-vis (CH2Cl2): λmax: 420 nm (Soret band), 509 nm, 572 nm (Q-
band); IR (KBr) νmax: 998 cm-1 (νFe-N), 359 cm-1 (νFe-Cl).

Molecules 2011, 16
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3.2.2. Synthesis–One-pot Mixed Solvent Method
o-NO2TPPFeCl: Propionic acid (50 mL), glacial acetic acid (10 mL) and m-nitrotoluene (10 mL) were
added into a 250 mL three-neck round-bottom flask equipped with stirrer, reflux condenser and
dropping funnel. The mixture was stirred under reflux for 30 min. After that, o-nitrobenzaldehyde
(1.51 g, 10 mmol) dissolved in propionic acid (20 mL) and freshly distilled pyrrole (0.7 mL, 10 mmol)
dissolved in m-nitrotoluene (10 mL) were simultaneously added into the flask through two dropping
funnels in 15 min. After 10 min, the mixture was stopped heating and cooled to 90-100 °C,
FeCl2·4H2O (2 g, 10 mmol) was added into the reaction solution and was again heated to reflux with
magnetic stirring for about 50 min. When the thin-layer chromatography (alumina) indicated no free
base porphyrins at this point, the reaction was stopped. The crude mixture was filtered and washed
with methanol three times. The further purification by column chromatography on alumina using
100% CH2Cl2 removed the porphyrin isomers and use of acetone/ethyl acetate (1:1) as eluent gave the
final products. The iron porphyrin was eluted as the second band, leading to the pure compound
obtained after solvent elimination (yield up to 28.7%). Other iron porphyrin complexes (RTPPFeCl)
were prepared with the same procedure as o-NO2TPPFeCl. The ratios of mixed solvents and the yields
of porphyrins were listed in Table1. The spectra data of iron porphyrins were in accordance with the
results of two-step method.
4. Conclusions
Two different methods were applied to synthesize substituted tetraphenylporphyrin iron chloride
complexes and the structures of above porphyrin compounds were characterized by UV-vis, IR, FIR
and elemental analysis. Compared with the two-step method, the one-pot mixed solvent method
offered the advantages of higher yields, shorter reaction time and convenient workup of reaction
mixtures. The yields of iron porphyrins may be improved effectively by mixing different carboxylic
acids and m-nitrotoluene in some proportion. The highest yields (28.7%-40.4%) of RTPPFe(III)Cl
were obtained by using the one-pot mixed solvent method. Additionally, the characteristics of
electronic spectra and molecular vibration spectra of above porphyrin compounds were analyzed
respectively. Meanwhile, the red shift of the Soret band due to the presence of p-nitrophenyl
substituents and the blue shift of Fe-Cl bond of TPPFeCl in the vibration frequency were explained by
the electron transfer and molecular planarity in the porphyrin ring.
Acknowledgements
This work was supported by the Project of the National Natural Science Foundation of China (Grant
No. 20776003, 21036009 and 1076004) and the Funding Project for Academic Human Resources
Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality (Grant
No. PHR201107104).

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Sample Availability: Samples of the compounds are available from the authors.
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