Syntheses and characterization of a series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group

Article abstract of DOI:10.1142/S1088424613500673

Using aldehydes with different substituents of the aryl groups, we have synthesized a series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1- naphthyl group by one-pot reactions. Our studies suggest the steric property of substituents is the major factor to affect the reaction yields, the steric hindrance is unfavorable for such reaction. Compared with those para-substituted species, NMR studies of 2,6-substituted species show upfield shifts for their NH and ethyl protons, downfield shifts for their pyrrole protons, which is probably due to the decrease of porphyrin ring current. Three of them have been characterized by X-ray crystallography. Structures show that the ester group is hanging over the porphyrin plane, compound 3 and 4 have much different core conformations from compound 2, which is probably due to the π-π interactions in the solid state.

Full text of DOI:10.1142/S1088424613500673

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2013; 17: 392–398
DOI: 10.1142/S1088424613500673
Published at http://www.worldscinet.com/jpp/
Syntheses and characterization of a series of asymmetric
porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group
Gaohui Xua, Jiaxun Jianga and Chuanjiang Hu*a,b◊
a Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering
and Materials Science, Soochow University, Suzhou 215123, P.R. China
b State Key Lab & Coordination Chemistry Institute, Nanjing University, Nanjing 210093, P.R. China
Received 16 April 2013
Accepted 7 May 2013
ABSTRACT: Using aldehydes with different substituents of the aryl groups, we have synthesized a
series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group by one-pot reactions.
Our studies suggest the steric property of substituents is the major factor to affect the reaction yields,
the steric hindrance is unfavorable for such reaction. Compared with those para-substituted species,
NMR studies of 2,6-substituted species show upfield shifts for their NH and ethyl protons, downfield
shifts for their pyrrole protons, which is probably due to the decrease of porphyrin ring current. Three of
them have been characterized by X-ray crystallography. Structures show that the ester group is hanging
over the porphyrin plane, compound 3 and 4 have much different core conformations from compound 2,
which is probably due to the p–p interactions in the solid state.
KEYWORDS: porphyrin, naphthyl, steric, ester.
featuringnitrothiophenylandnitrooligothiophenylelectron-
accepting moieties. Their studies show that these neutral
INTRODUCTION
Asymmetric porphyrins have been widely recognized
by its applications in molecular recognition, asymmetric
dipolar molecules can express substantial b1300 values;
such conjugated, electronically asymmetric porphyrin-
catalysis and nonlinear optics [1–13]. For example, a
thiophene chromophores may thus find utility for electro
different type of binding mode was tested by Aida and
optic applications at telecom-relevant wavelengths [16].
coworkers for the enantioselective reconstitution of
In order to synthesize asymmetric porphyrins, there
cytochrome b562 with chiral porphyrins [14]. In that
are several general synthetic avenues: (i) mixing different
case, highly preferential binding of the (R)-enantiomers
(as large as by a factor of 30) not only allowed effective
optical resolution of the corresponding racemic mixture
aldehydes and pyrrole through a one-pot reaction; (ii) multi-
step total synthesis by 2 + 2 or 3 + 1 condensation; (iii) direct
introduction of functional groups into easily synthesized
but also produced essentially different CD responses in the
symmetric porphyrins to yield the desired target compounds.
Soret region. Che and coworkes have reported a series of
The first method is more straight forward, and has been
rutheniumporphyrincatalysts, includingthoseimmobilized
frequently used. Besides the short reaction path, another
onto insoluble supports and covalently attached to soluble
advantage for this method is that could lead to unexpected
supports, which can promote the oxidation of a wide variety
useful products. Such porphyrin can be used as a precusor
of organic substrates such as styrenes, cycloalkenes, a,b-
for more asymmetric or chiral porphyrins.
unsaturated ketones, steroids, benzylic hydrocarbons and
In our previous study [17], we have reported the
arenes [15]. Clays and coworkers have developed a series
synthesis of an unexpected asymmetric porphyrin,
of conjugated (porphinato)zinc(II)-based chromophores
5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl
porphyrin (H2ENTPP) with ethoxycarbonylnapthyl group
as a substituent. In that case, the 8-position substituent,
◊ SPP full member in good standing
an ester group, lies above the porphyrin plane and leads
to the axial chirality due to the steric constraints.
*Correspondence to: Chuanjiang Hu, email: cjhu@suda.edu.
cn, tel/fax: +86 (512)-6588-0903
Copyright © 2013 World Scientific Publishing Company

SYNTHESES AND CHARACTERIZATION OF A SERIES OF ASYMMETRIC PORPHYRINS
393
Herein, we applied such one-pot synthesis to more
obtained. As shown in Table 1, their yields range from
1.4% to 10.6%. For those para-substituted species 2–7,
the yield is over 5%. For these substituents, their electronic
properties are much different. Among them, Cl, Br, F,
NO2 and 2,6-dichloro are electron withdrawing groups,
methyl, methoxy and 2,4,6-trimethyl are electron donating
groups. It seems there is no correlation between their
yields and the electronic properties of these substituents.
Considering that those substituents are on the meso
phenyl group, the corresponding electronic effect could
be too small for the entire porphyrin molecule.
As we noticed, for 2,4,6-trimethyl aldehyde, the yield
droppedto1.4%, for2,6-dichloroaldhyde, wewereunable
to even get any aimed product. Considering the structural
feature of these substituents, these 2,6-substitutions
could make the space below and above porphyrin plane
more crowded than para-substituted species. So the steric
properties must play an important role in the reaction.
For the 2,6-substituted species, the methyl group is
sterically more hindered than chlorine, while its reaction
yield is higher. It suggests the electronic properties of
substituents may have effect on the reaction yields as
well. But considering the yield differences, the steric
properties should be the major factor. Steric hindered
2,6-substitutions cause much lower reaction yield.
aldehydes with different substituents on the aryl group.
Seven new asymmetric porphyrins with an ethoxy-
carbonylnapthyl group as a substituent have been synthe-
sized and characterized.
RESULTS AND DISCUSSION
As shown in Scheme 1, this general one-pot reaction
allows for the isolation of the corresponding ester
functionalized porphyrins with different electronic and
steric groups. Besides benzaldehyde, eight aldehydes
with different substituents have been used. For seven
of them, the reaction led to the aimed porphyrins. For
2,6-dichlorobenzylaldehyde, no aimed porphyrin was
Due to the large ring current effect in the porphyrins,
chemical shifts provide a very useful probe of porphyrin
intramolecular interaction [18]. Protons above or
inside the porphyrin are in the shielding region of the
ring current effect. Then the signal at -2.4 to -2.7 ppm
region has been assigned to two NH protons, which are
typical in free base porphyrins [18]. Another feature
of NMR in these porphyrins is the resonances of ethyl
protons. For these porphyrins, resonances of two protons
(–CH2CH3) are located in the range from at 0.41 to 0.81
ppm and three protons (–CH2CH3) at -0.52 to -0.78 ppm.
Compared with naphthalene-1-carboxylic acid ethyl
ester, these resonances shift upfield [19]. It suggests that
Scheme 1. Synthetic route to the new asymmetric porphyrins
Table 1. Isolated yields and selected analytical data for compounds 1–8
No.
Substituents
Yields UV-vis
max, nm
1H NMR
l
NH, ppm CH2CH3, CH2CH3, pyrrol-H, ppm
ppm
ppm
1
2
3
4
5
6
7
8
phenyl
10.6% 421 nm
7.3% 420 nm
7.4% 421 nm
7.1% 421 nm
5.6% 426 nm
9.8% 422 nm
6.2% 424 nm
1.4% 421 nm
-2.65
-2.71
-2.69
-2.72
-2.70
-2.64
-2.64
-2.42
/
-0.73
-0.77
-0.78
-0.78
-0.76
-0.76
-0.77
-0.52
0.43,
0.42,
0.43
0.42
0.48
0.41
0.41
0.81
/
8.64, 8.78, 8.84
8.64, 8.73, 8.82
8.65, 8.73, 8.82
8.66, 8.75, 8.84
8.64, 8.71, 8.80
8.61, 8.79, 8.85
8.61, 8.78, 8.86
8.56, 8.59, 8.63
/
4-fluorophenyl
4-chlorophenyl
4-bromophenyl
4-nitrophenyl
4-methylphenyl
4-methoxyphenyl
2,4,6-trimethyl-phenyl
2,6-dichlorophenyl
/
/
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 393–398

394
G. XU ET AL.
the ethyl group is hanging over the porphyrin plane in
the shielding region, which is consistent with the crystal
structures (vide infra). Compared with meso-5,10,15,20-
tetraphenylporphyrin [20], the resonances of eight
protons at around 8.6–8.8 ppm have been assigned to b
pyrrole protons (pyrr-H).
Except compound 8, other seven compounds have very
similar NMR resonances even they have substituents with
different electronic properties. It suggests the electronic
properties of substituents have negligible influence on
NMR. But for compound 8, the resonances of NH and
ethyl protons show obvious downfield shifts compared
withothercompounds,whilethoseofpyrroleprotonsshow
slight upfield shifts. So it is most likely that such shifts
are related to the steric properties of 2,6-disubstitutions.
In a number of studies on highly substituted porphyrins,
a decrease in the ring current effect has been invoked
to explain the chemical shift changes relative to less
substituted and thus more planar analogs [21–24]. For
example, a reduced ring current effect was suggested
to account for the downfield shift of the NH protons in
2,8,12,18-tetraethyl-3,7,13,17-tetra-methyl-5,15-bis(2,5-
dimethoxyphenyl)porphyrin (dNH = -1.80 ppm) compared
to the 5-aryl porphyrin (dNH = -2.50 ppm) and the etio-
type porphyrins without meso substituents (dNH = -3.75
ppm) [21]. Medforth et al. have also reported that the
extremely large nonplanar conformational distortions
seen for the porphyrin caused decrease in the porphyrin
ring currents [25]. In our case, the steric properties of
2,6-disubstitution could lead to large nonplanarity, which
cause the decrease of ring current effect. For the NH and
ethyl protons in the shielding region, it leads to downfield
shifts; for the pyrrole protons in the deshielding region, it
leads to upfield shifts.
Fig. 1. ORTEP view for 2 at 50% probability thermal ellipsoids.
The hydrogen atoms have been omitted for clarity
For all the compounds 1–8, UV-vis spectra exhibit a
characteristic absorption maximum in the Soret band
ranging from 420 to 426 nm. Despite the diverse nature
of aryl substituents that have been introduced into the
porphyrins, no significant correlation was observed
between the electronic and steric properties of the aryl
moiety and the absorption maximum in the Soret band.
Fig. 2. ORTEP view for 3 at 50% probability thermal ellipsoids.
The hydrogen atoms have been omitted for clarity
Crystal structures
The single crystals of compound 2, 3 and 4 were
obtained by slow evaporation of their solutions in
the mixture of methylene chloride and hexane. Their
structures are shown in Figs 1, 2 and 3, respectively. The
selected bond distances are listed in Table 2. Structures
clearly show that in all three compounds there are three
phenyl groups and one naphthyl group at meso-positions
of porphyrin. The 8-position substituent of naphthyl
group is an ester group, which is “hanging” over the
porphyrin plane. (vide supra) The O(1)-C(1)-O(2) plane
forms a dihedral angle 21.9° with porphyrin plane in
2, 18.8° in 3 and 19.6° in 4. This geometry makes the
ester group away from porphyrin core to avoid close
Fig. 3. ORTEP view for 4 at 50% probability thermal ellipsoids.
The hydrogen atoms have been omitted for clarity
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 394–398

SYNTHESES AND CHARACTERIZATION OF A SERIES OF ASYMMETRIC PORPHYRINS
395
Table 2. Selected bond lengths (Å) for compounds 2, 3 and 4
2
3
4
N(1)-C(A1) 1.382(5) N(1)-C(A1) 1.369(6) N(1)-C(A1) 1.375(6)
N(1)-C(A2) 1.353(5) N(1)-C(A2) 1.375(6) N(1)-C(A2) 1.375(5)
N(2)-C(A3) 1.355(6) N(2)-C(A3) 1.376(6) N(2)-C(A3) 1.378(6)
N(2)-C(A4) 1.380(5) N(2)-C(A4) 1.367(7) N(2)-C(A4) 1.358(6)
N(3)-C(A5) 1.368(5) N(3)-C(A5) 1.372(6) N(3)-C(A5) 1.375(6)
N(3)-C(A6) 1.379(6) N(3)-C(A6) 1.391(6) N(3)-C(A6) 1.374(5)
N(4)-C(A7) 1.360(6) N(4)-C(A7) 1.378(6) N(4)-C(A7) 1.374(5)
N(4)-C(A8) 1.385(5) N(4)-C(A8) 1.366(6) N(4)-C(A8) 1.359(6)
C(1)-O(2) 1.204(7) C(1)-O(2) 1.209(7) C(1)-O(2) 1.189(6)
C(1)-O(1) 1.320(7) C(1)-O(1) 1.335(8) C(1)-O(1) 1.349(7)
C(2)-O(1) 1.450(9) C(2)-O(1) 1.462(9) C(2)-O(1) 1.471(8)
C(24)-F(2) 1.384(6) C(24)-Cl(2) 1.746(6) C(24)-Br(2) 1.893(5)
C(34)-F(3) 1.338(6) C(34)-Cl(3) 1.744(6) C(34)-Br(3) 1.903(5)
C(44)-F(4) 1.327(4) C(44)-Cl(4) 1.729(6) C(44)-Br(4) 1.909(5)
interactions. The corresponding distances between O(1),
O(2) and porphyrin plane are 3.01 and 3.16 Å in 2, 3.09
and 3.22 Å in 3, 3.09 and 3.24 Å in 4.
Because of the steric constraint, the ester group is
rotationally hindered, which leads to axial chirality in
the single molecule (there is one axis of chirality along
the bond between the ester group and the naphthalene
system). The single porphyrin molecule is chiral as that in
H2ENTPP. However, the whole crystal is achiral because it
consists of pairs of enantiomers in the achiral space group.
In compound 2, the porphyrin core is quite planar
with the maximum deviation from the 24-atom mean
plane as 0.10 Å as shown in Fig. 4. Both compounds
3 and 4 have similar conformations which are much
different from compound 2. As shown in Figs 4b
and 4c, their conformations are typical saddling:
b pyrrole carbons of adjacent pyrrole rings are
above and below the porphyrin plane alternately
with large displacements. As shown in Figs S1
and S2 in the supporting information, for compound 3
and 4, there are p–p interactions between the chelate ring
formed by N(4), C(A7), C(A8), C(B7), C(B8) and part
of the naphthyl ring (C(15a), C(16(a), C(17(a), C(18a),
C(19a), C(20a)) of the symmetry related porphyrin
(symmetry operator a: 2-x, -1-y, -z). The corresponding
dihedral angle is 22.3° for 3 and 22.2° for 4, the
corresponding center to center distance is 3.73 Å for 3
and 3.78Å for 4. While in compound 2, the corresponding
interactions are much weaker. The dihedral angle
between two related plane as shown in Fig. S3 is 31.4°,
the corresponding center to center distance is 4.19 Å.
So it is most likely that the distorted structures of 3 and 4
are contributed by the p–p interactions in the solid state.
But in solution, there are no such p–p interactions, then
these three compounds could have similar conformation,
which is evidenced by their similar NMR spectra.
Fig. 4. Formal diagrams of the porphyrinato cores for: (a) 2;
(b) 3; (c) 4. Illustrated are the displacements of each atom from
the mean plane of the 24 atom in units of 0.01 Å
EXPERIMENTAL
General
Acenaphthenequinone (Alfa Aesar) and tetrachloro-1,4-
benzoquinone were used as received. Pyrrole and methylene
chloride were freshly distilled before use. Other solvents
were used as received. UV-vis spectra were measured on
a Shimadzu UV-3150 spectrometer. 1H NMR spectra were
carried out using a Bruker AVANCE 400 spectrometer
with tetramethylsilane (TMS) as the internal standard.
Mass spectra were taken with Agilent 6220 Accurate-Mass
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 395–398

396
G. XU ET AL.
TOF LC/MS. The IR spectra were recorded on a Nicolet-
MagNa-IR500 FT-IR spectrometer (400–4000 cm-1).
[M + H]+ 841.17, M = C51H33Cl3N4O2). Anal. calcd. for
.ꢀ
C51H33Cl3N4O2 0.2CH2Cl2: C, 71.74; H, 3.93; N, 6.54%.
Found C, 71.92; H, 4.39; N, 6.73%.
Compound 4. Yield 0.96 g (7.1%). UV-vis (CH2Cl2):
Synthesis
l
max, m (e, M-1.cm-1) 421 (7.5 × 105), 516 (1.5 × 105), 556
These esters were synthesized according to our
previous method [17]. The typical procedure is as the
following: The reaction was carried out under anaerobic
condition. Acenaphthenequinone (7.0 mmol), aldehyde
(21.0 mmol) and pyrrole (28.0 mmol) were dissolved
(1.2 ×105), 593 (1.3 ×105),649 (1.2 ×105). 1H NMR (CDCl3,
400 MHz): dH, ppm 8.84 (s, 4H, pyrr-H), 8.75 (d, J = 4.5 Hz,
2H, pyrr-H), 8.66 (d, J = 4.7 Hz, 2H, pyrr-H), 8.32 (d, J =
8.2 Hz, 1H, phenyl-H), 8.30–8.23 (m, 2H, phenyl-H), 8.16–
8.04 (m, 4H, phenyl-H), 8.00 (d, J = 8.1 Hz, 2H, phenyl-H),
7.95–7.84 (m, 7H, phenyl-H), 7.59 (m, 1H, phenyl-H), 7.35
(m, 1H, phenyl-H), 0.42 (s, 2H, CH3CH2), -0.78 (t, J = 7.1
Hz, 3H, CH3CH2), -2.72 (s, 2H, NH). IR (KBr): n, cm-1
3448 (m), 1720 (s), 1560 (m), 1474 (s), 1347 (m), 1274 (m),
1195 (s), 972 (s), 801 (s), 735 (s), 511 (w). Anal. calcd. for
.
in 7% solution of ethanol in chloroform (500 mL). BF3
OEt2 (7.90 mmol) was added to the above solution and
stirred for 1 h at room temperature, then tetrachloro-1,4-
benzo- quinone (27.6 mmol) was added. After 2 h under
reflux, triethylamine (8.0 mL) was added, and the mixture
was stirred for another half an hour. When it was cooled
down to room temperature, it was filtered by sintered
glass funnel. The filtrate was evaporated to dryness under
vacuum, the black solid was further purified by column
chromatography (silica, CH2Cl2/petroleum ether = 1:1
for 1, 2, 3, 4, 6, 8; CH2Cl2/petroleum ether = 4:1 for 5
and 7). The target product was collected from the second
purple band.
.
ꢀ
C51H33Br3N4O2 0.4CH2Cl2: C, 61.27; H, 3.38; N, 5.56%.
Found C, 61.68; H, 3.59; N, 5.22%.
Compound 5. Yield 0.68 g (5.6%). UV-vis (CH2Cl2):
l
max, nm (e, M-1.cm-1) 426 (6.5 × 105), 516 (1.6 × 105),
554 (1.4 × 105), 595 (1.3 × 105), 645 (1.2 × 105). 1H NMR
(CDCl3, 400 MHz): dH, ppm 8.80 (s, 4H, pyrr-H), 8.71 (s,
2H, pyrr-H), 8.64 (s, 2H, pyrr-H), 8.68 (m, 5H, phenyl-H),
8.61 (s, 1H, phenyl-H), 8.26–8.48 (m, 9H, phenyl-H),
7.91 (t, J = 7.4 Hz, 1H, phenyl-H), 7.61 (t, J = 7.7 Hz, 1H,
phenyl-H), 7.37 (d, J = 6.8 Hz, 1H, phenyl-H), 0.48 (s,
2H, CH3CH2), -0.76 (t, J = 6.9 Hz, 3H, CH3CH2), -2.70
(s, 2H, NH). IR (KBr): n, cm-1 3429 (m), 3317 (m), 2924
(w), 2852 (w), 1721 (s), 1595 (m), 1474 (m), 1346 (s),
1275 (m), 1195 (s), 973 (s), 800 (s), 730 (s), 488 (w).
Compound 1. Yield was improved to 10.6% compared
with the original report [17]. Other characterizations
were the same as reported.
Compound 2. Yield 0.80 g (7.3%). UV-vis (CH2Cl2):
l
max, nm (e, M-1.cm-1) 420 (7.4 × 105), 515 (1.5 × 105), 555
(1.3 × 105), 595 (1.3 × 105), 645 (1.25 × 105). H NMR
(CDCl3, 400 MHz): dH, ppm 8.82 (m, 4H, pyrr-H), 8.73
(d, J = 4.7 Hz, 2H, pyrr-H), 8.64 (d, J = 4.8 Hz, 2H,
pyrr-H), 8.33 (d, J = 8.3 Hz, 1H, phenyl-H), 8.26 (d, J =
7.4 Hz, 2H, phenyl-H), 8.16 (m, 4H, phenyl-H), 8.06
(d, J = 8.2 Hz, 2H, phenyl-H), 7.88 (m, 1H, phenyl-H),
7.70–7.77 (m, 6H, phenyl-H), 7.58 (m, 1H, phenyl-H),
7.34 (d, J = 7.0 Hz, 1H, phenyl-H), 0.42 (s, 2H, CH3CH2),
-0.77 (t, J = 7.1 Hz, 3H, CH3CH2), -2.71 (s, 2H, NH).
IR (KBr): n, cm-1 3444 (m), 3316 (m), 1718 (s), 1601
(m), 1560 (w), 1505 (s), 1474 (s), 1156 (s), 965 (s), 803
(s), 733 (s), 530 (m). LC-ESI-MS: m/z 791.26 (calcd. for
[M + H]+ 791.26, M = C51H33F3N4O2). Anal. calcd. for
1
.
Anal. calcd. for C51H33N7O8 ꢀ1.0C6H14: C,71.46; H, 4.94;
N, 10.23%. Found C, 71.79; H, 4.78; N, 9.96%.
Compound 6. Yield 1.06 g (9.8%). UV-vis (CH2Cl2):
l
max, nm (e, M-1.cm-1) 422 (6.7 × 105), 519 (1.5 × 105),
554 (1.3 × 105), 595 (1.4 × 105), 651 (1.3 × 105). 1H NMR
(CDCl3, 400 MHz): dH, ppm 8.85 (s, 4H, pyrr-H), 8.79 (s,
2H, pyrr-H), 8.61 (s, 2H, pyrr-H), 8.27 (m, 3H, phenyl-H),
8.14 (m, 4H, phenyl-H), 8.02 (d, J = 6.7 Hz, 2H, phenyl-H),
7.87 (s, 1H, phenyl-H), 7.61–7.47 (m, 7H, phenyl-H), 7.34
(s, J = 5.9 Hz, 1H, phenyl-H), 2.70 (d, J = 11.6 Hz, 9H,
phenylCH3), 0.41 (s, 2H, CH3CH2), -0.76 (d, J = 6.5 Hz,
3H, CH3CH2), -2.64 (s, 2H, NH). IR (KBr): n, cm-1 3455
(m), 1720 (s), 1626 (m), 1473 (m), 1347 (m), 1274 (m),
1194 (s), 965 (s), 801 (s), 735 (s), 522 (w). LC-ESI-MS:
m/z 779.33 (calcd. for [M + H]+ 779.33, M = C54H42N4O2).
.
C51H33F3N4O2 1.0C6H14: C, 78.06; H, 5.40; N, 6.39%.
Found C, 77.73; H, 4.98; N, 6.21%.
Compound 3. Yield 0.86 g (7.4%). UV-vis (CH2Cl2):
max, nm (e, M-1.cm-1) 421 (6.1 × 105), 514 (1.5 × 105),
Anal. calcd. for C54H42N4O2 2H2O: C, 79.58; H, 5.69; N,
.
l
551 (1.3 × 105), 589 (1.3 × 105), 649 (1.26 × 105). H
NMR (CDCl3, 400 MHz): dH, ppm 8.82 (s, 4H, pyrr-H),
8.73 (d, J = 4.8 Hz, pyrr-H), 8.65 d, J = 4.8 Hz, pyrr-H),
8.33 (d, J = 8.2 Hz, 1H, phenyl-H), 8.27 (d, J = 8.2 Hz,
2H, phenyl-H), 8.21 (m, 4H, phenyl-H), 8.09 (s, 2H),
7.88 (t, J = 7.6 Hz, 1H, phenyl-H), 7.58 (t, J = 7.7 Hz,
1H, phenyl-H), 7.52–7.37 (m, 6H, phenyl-H), 7.34 (d, J =
7.0 Hz, 1H, phenyl-H), 0.43 (s, 2H, CH3CH2), -0.78 (t,
J = 7.1 Hz, 3H, CH3CH2), -2.69 (s, 2H, NH). IR (KBr): n,
cm-1 3442 (m), 3310 (m), 1724 (s), 1560 (m), 1474 (m),
1396 (m), 1274 (m), 1091 (s), 965 (s), 801 (s),
734 (s), 492 (w). LC-ESI-MS: m/z 841.17 (calcd. for
6.87%. Found C, 79.86; H, 5.33; N, 6.38%.
1
Compound 7. Yield 0.71 g (6.2%). UV-vis
(CH2Cl2): lmax, nm (e, M-1.cm-1) 424 (6.8 × 105),
517 (1.5 × 105), 557 (1.3 × 105), 591 (1.3 × 105),
1
651 (1.3 × 105). H NMR (CDCl3, 400 MHz): dH,
ppm 8.86 (m, 4H, pyrr-H), 8.78 (s, 2H, pyrr-H),
8.61 (s, 2H, pyrr-H), 8.24–8.33 (m, 3H, phenyl-H),
8.10–8.20 (m, 4H, phenyl-H), 8.05 (d, J = 7.6 Hz,
2H, phenyl-H), 7.87 (t, J = 7.5 Hz, 1H, phenyl-H), 7.57 (s,
J = 7.5 Hz, 1H, phenyl-H), 7.26–7.35 (m, 7H, phenyl-H),
4.09(d,J=10.8Hz,9H,phenylOCH3),0.41(d,J=1.0Hz,
2H, CH3CH2), -0.77 (t, J = 7.1 Hz, 3H, CH3CH2), -2.64
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 396–398

SYNTHESES AND CHARACTERIZATION OF A SERIES OF ASYMMETRIC PORPHYRINS
397
(m, 2H, NH). IR (KBr): n, cm-1 3443 (m), 3318 (m), 2917
file (CCDC number: 928739–928741). For both 3 and 4,
one asymmetric unit contains one independent porphyrin
molecule and one methylene chloride molecule. For 2,
one asymmetric unit contains one independent porphyrin
molecule and disordered solvent. Due to an extensive
solvent disorder, contributions of solvent molecules were
removed from the diffraction data with SQUEEZE [27].
Thirty electrons were found in one void of 479 Å3, which
corresponds to roughly to 0.3 molecules of C6H14 per
asymmetric unit. Brief crystal data for these structures
are listed in Table 3.
(w), 1719 (s), 1606 (m), 1466 (m), 1347 (m), 1288 (m),
1175 (s), 971 (s), 802 (s), 739 (s), 484 (w). LC-ESI-MS:
m/z 827.32 (calcd. for [M + H]+ 827.32 M = C54H42N4O5).
.
Anal. calcd. for C54H42N4O5 ꢀ0.1CH2Cl2: C, 77.78; H, 5.09;
N, 6.71%. Found C, 77.37; H, 5.39; N, 6.77%.
Compound 8. Yield 0.17 g (1.4%). UV-vis (CH2Cl2):
l
max, nm (e, M-1.cm-1) 421 (7.2 × 105), 517(1.5 × 105), 555
1
(1.2 × 105), 591 (1.3 × 105), 648 (1.2 × 105). H NMR
(CDCl3, 400 MHz): dH, ppm 8.63 (s, 4H, pyrr-H), 8.59 (d,
J = 4.7 Hz, 2H, pyrr-H), 8.56 (s, 2H, pyrr-H), 8.28 (t, J =
9.4 Hz, 2H, phenyl-H), 8.10 (d, J = 5.3 Hz, 1H,
phenyl-H), 7.82 (t, J = 6.3 Hz, 1H, phenyl-H),
7.60 (t, J = 5.6 Hz, 1H, phenyl-H), 7.45 (d, J =
Table 3. Crystallographic data for 2, 3 and 4a
6.3 Hz,, 1H, phenyl-H), 7.33 (s, 1H, phenyl-H),
7.27 (s, 5H, phenyl-H), 2.62 (d, J = 8.4 Hz, 9H,
mesityl CH3), 2.12 (s, 3H, mesityl CH3), 1.94 (s,
6H, mesityl CH3), 1.81 (s, 6H, mesityl CH3), 1.68
(s, 3H, mesityl CH3), 0.81 (s, 2H, CH3CH2), -0.52
(t, J = 5.7 Hz, 3H, CH3CH2), -2.42 (s, 2H, NH).
IR (KBr): n, cm-1 3448 (m), 3316 (m), 3055 (m),
2917 (w), 1725(s), 1610 (m), 1471 (m), 1344 (m),
1273 (m), 1194 (s), 970 (s), 802 (s), 738 (s), 555
(w). LC-ESI-MS: m/z 863.43 (calcd. for [M +
H]+ 863.43, M = C60H54N4O2). Anal. calcd. for
Complex
2
3
4
Empirical formula
C51H33F3N4O2
790.81
C52H35Cl5N4O2
925.09
C52H35Br3Cl2N4O2
1058.47
Formula weight,
g.mol-1
Temperature
Wavelength
Crystal system
Space group
293(2) K
0.71073
Monoclinic
Pc
223(2) K
0.71073
293(2) K
0.71073
Monoclinic
P2(1)/c
Monoclinic
P2(1)/c
Unit cell dimensions a = 10.828(2) Å
b = 12.139(2) Å
c = 18.120(4) Å
a = 90°
a = 7.6792(15) Å a = 7.7475(15) Å
.
C60H54N4O2 ꢀ2H2O: C, 80.15; H, 6.50; N, 6.23%.
Found C, 80.28; H, 6.81 N, 6.42%.
b = 26.522(5) Å
c = 21.898(4) Å
a =ꢀ90°
b = 26.825(5) Å
c = 22.067(4) Å
a = 90°
b = 102.98(3)°
b = 96.12(3)°
g = 90°
b = 95.43(3)°
g = 90°
X-ray data collection and structure
determination
g = 90°
Volume, Å3
Z
2320.7(8)
2
4434.5(15)
4
4565.5(15)
4
The single crystals of 2, 3 and 4 were
obtained through the diffusion of their methy-
lene chloride/hexane solutions. All X-ray data
collection were made on a Rigaku Mercury
CCD X-ray diffractometer by using graphite
monochromated Mo Ka (l = 0.071073 nm).
Their structures were all solved by direct
methods and refined on F2 using full matrix
least-squares methods with SHELXTL version
97 [26]. For compound 2, in the corresponding
checkCIF report, a “level B” alert suggests
a higher pseudo symmetry “P21/c”. But the
refinement based on such symmetry can not
give satisfied result, so the final structure was
solved in “Pc.” All non-hydrogen atoms were
refined anisotropically. In the three structures,
all the N–H hydrogen atoms were found in
difference Fourier maps, and their coordinates
and isotropic temperature factors were refined,
other hydrogen atoms were theoretically
added and riding on their parent atoms.
Crystallographic details, atomic coordinates,
anisotropic thermal parameters, and fixed
hydrogen atom coordinates are given in the CIF
r, g.cm-3
F(000)
1.132
820
1.386
1.540
1904
2120
Crystal size, mm3
0.50 × 0.40 × 0.30 0.40 × 0.30 × 0.30 0.50 × 0.40 × 0.30
Theta range for data 3.14 to 25.00
collection
3.02 to 25.00
3.04 to 25.00°
Limiting indices
-12 ≤ h ≤ 12
-14 ≤ k ≤ 14
-21 ≤ l ≤ 21
17644/7005
-8 ≤ h ≤ 9
-9 ≤ h ≤ 8
-31 ≤ k ≤ 30
-25 ≤ l ≤ 25
35531/7793
-31 ≤ k ≤ 31
-26 ≤ l ≤ 22
36283/8020
Reflections
collected/unique
Data/restraints/
parameters
7005/1542/537
7793/2/575
8020/2/575
GOF
1.002
1.187
1.112
R1,wR2[I > 2s(I)]
R1 = 0.0796
wR2 = 0.2220
R1 = 0.0931
wR2 = 0.2384
R1 = 0.1048
wR2 = 0.2631
R1 = 0.1543
wR2 = 0.2980
R1 = 0.0663
wR2 = 0.1671
R1 = 0.0999
wR2 = 0.1869
R1,wR2 (all data)
Largest diff. peak
and hole, e.Å-3
0.323 and -0.235 0.320 and -0.393 0.669 and -0.698
aw = 1/[s2 (Fo2) + (aP)2 + bP] where P = (Fo2 + 2Fc2)/3.
Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 397–398

398
G. XU ET AL.
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CONCLUSION
In conclusion, a series of new asymmetric porphyrin
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one-pot reactions. Results suggest the steric properties
are the dominant factors to affect the yields. Steric
effect is also the reason to cause NMR shift. Such one-
pot reaction is especially effective for para-substituted
aldehydes. These esters can be further used as precusors
for more asymmetric porphyrins.
Acknowledgements
This work was supported by the Natural Science
Foundation of China (Nos. 20971093 and 21271133) and
the Priority Academic Program Development of Jiangsu
Higher Education Institutions.
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Supporting information
Figures S1–S3 display the packing diagrams showing
p–p interactions and are given in the supplementary
material. This material is available free of charge via the
Internet at http://www.worldscinet.com/jpp/jpp.shtml.
Crystallographic data have been deposited at the
Cambridge Crystallographic Data Centre (CCDC) under
numbers CCDC-928739, 928740 and 928741. Copies
can be obtained on request, free of charge, via www.
ccdc.cam.ac.uk/data_request/cif or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK (fax: +44 1223-336-033 or email: deposit@
ccdc.cam.ac.uk).
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Copyright © 2013 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2013; 17: 398–398