Synthesis and characterization of six new carbazolyl porphyrins

Article abstract of DOI:10.1080/00397910903419811

Novel 4-(N-carbazole methyl) benzoic acid and N-carbazolacetic acid are synthesized, then six new carbazolyl porphyrins are synthesized by bonding these acids to hydroxy porphyrin or amido porphyrin via acyl chloride or N,N'-dicyclohexylcarbodiimide (DCC)

Full text of DOI:10.1080/00397910903419811

Synthetic Communications
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Synthesis and Characterization of Six New
Carbazolyl Porphyrins
Dong-Cai Guo , Ping-Liang Li , Xin Wang , Li-Ying Wang & Pan-Liang Wu
To cite this article: Dong-Cai Guo , Ping-Liang Li , Xin Wang , Li-Ying Wang & Pan-Liang
Wu (2010) Synthesis and Characterization of Six New Carbazolyl Porphyrins, Synthetic
Communications, 40:22, 3315-3321, DOI: 10.1080/00397910903419811
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Date: 17 May 2016, At: 11:27

Synthetic Communications1, 40: 3315–3321, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903419811
SYNTHESIS AND CHARACTERIZATION OF SIX NEW
CARBAZOLYL PORPHYRINS
Dong-Cai Guo, Ping-Liang Li, Xin Wang, Li-Ying Wang, and
Pan-Liang Wu
School of Chemistry and Chemical Engineering, Hunan University,
Changsha, China
Novel 4-(N-carbazole methyl) benzoic acid and N-carbazolacetic acid are synthesized,
then six new carbazolyl porphyrins are synthesized by bonding these acids to hydroxy
porphyrin or amido porphyrin via acyl chloride or N,N0-dicyclohexylcarbodiimide
(DCC)–dimethylaminopyndine methods. The formations of these title compounds, as well
as their intermediates are characterized by 1H NMR, mass spectrometry, Fourier transform–
infrared, and elemental analysis.
Keywords: Carbazole; porphyrin; synthesis
INTRODUCTION
Since tetraphenylporphine was first synthesized by Rothemund,[1] substituted
tetraphenyl porphyrins have been extensively investigated because of their increas-
ingly diverse applications in various scientific fields.[2–4] In recent years, many groups
reported the syntheses of tetra-phenylporphyrin derivatives. Guo et al.[5] synthesized
chloroalkyl piperazine and nitrogen mustard porphyrins in 2004. Guo et al.[6] synthe-
sized meso-tetrakis (4-hydroxyphenyl) porphyrin (THPP) in b-cyclodextrin and its
derivatives in 2005. Jia et al.[7] prepared meso-tetrakis(4-sulfophenyl)porphyrin in
2007. Rai et al.[8] prepared covalently linked unsymmetrical porphyrin pentads con-
taining three different porphyrin subunits in 2008. Ren et al.[9] synthesized alkyloxy
porphyrins under microwave irradiation in 2009. In the present work, 4-(N-carbazole
methyl) benzoic acid is first synthesized; then monohydroxy porphyrins and monoa-
mido porphyrins are used as a backbone, respectively, to further synthesize six kinds
of novel carbazolyl porphyrins. The synthesis route is shown in Scheme 1.
EXPERIMENTAL
Instruments and Reagents
Carbazole, ethyl bromoacetate, para-cyano benzyl bromide, N,N0-
dicyclohexylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) were
Received April 13, 2009.
Address correspondence to Dong-Cai Guo, School of Chemistry and Chemical Engineering,
Hunan University, Changsha 410082, China. E-mail: dcguo2001@163.com
3315

3316
D.-C. GUO ET AL.
Scheme 1. (a) BrCH2COOC2H5, KOH, (CH3CH2CH2CH2)4NBr; (CH3)2CO, reflux, 5.5 h; (b) NaOH
(10%H2O), reflux, 5 h; (c) p-CN(C6H4)CH2Br, KOH, (CH3CH2CH2CH2)4NBr, benzene, reflux, 18 h; (d)
m
HO(CH2CH2)OH–mH2O–mNaOH ¼ 14:6:5, 180 ꢀC, 4 h; (e) DMAP, DCC, CH2Cl2, N2, reflux, 7 h.
analytical grade. Other reagents and solvents were also analytical grade and were
obtained commercially. Reactions requiring solvents were prepared under a
nitrogen atmosphere prior to use. All reactions were performed in oven-dried
glassware.
1H NMR spectra were recorded on a 400-MHz Varian 400 NMR instrument,
and chemical shifts are reported as d values in units of parts per million relative to
Me4Si as an internal standard (CDCl3 as solvent). Elemental analyses were per-
formed through a Vario ELIII. The mass spectra (MS) were recorded with a
MAT95XP mass spectrometer. Infrared (IR) spectra were obtained in solid state
as KBr pellets on a Perkin-Elmer Spectrum One.
Synthesis of N-Carbazole Carboxylic Acid
Synthesis of N-carbazolyl ethyl acetate (1). Carbazole (0.84 g, 5 mmol),
potassium hydroxide (1 g, 17.8 mmol), and tetrabutyl ammonium bromide (0.05 g,
0.155 mmol) were dissolved in acetone (40 mL) in a 100-mL single-aperture flask,
and stirred for 20 min. Ethyl bromoacetate (1.67 g, 10 mmol) was then added to it,
and the mixture was heated and refluxed for another 5 h. The acetone was evapo-
rated under a vacuum, and the residual product was dissolved in dichloromethane
(50 mL). The organic layer was washed with water and then evaporated to obtain
a light-yellow, solid, coarse product. This product was purified over a silica-gel col-
umn with the eluent of dichloromethane=benzin (1:1, v=v). The second band was
collected, evaporated, and dried under vacuum. The product was a white solid. Yield
1
85%. H NMR (400 MHz, CDCl3) d=ppm: 1.15 (t, 3H, J ¼ 7.2 Hz), 4.13 (q, 2H,
J ¼ 7.2 Hz), 4.94 (s, 2H), 7.19 (q, 2H, J ¼ 5.1 Hz), 7.27 (d, 2H, J ¼ 8.0 Hz), 7.39 (q,
2H, J ¼ 5.1 Hz), 8.03 (d, 2H, J ¼ 7.6 Hz); MS (EI) m=z (%): 253 (M, 21), 180
(100), 152 (21), 90 (12), 76 (10).
Synthesis of N-carbazolacetic acid (2). N-Carbazolyl ethyl acetate (0.5 g,
2 mmol) and sodium hydroxide solution (10%, 40 mL) were added to the 100-mL
single-aperture flask, heated, and refluxed for 5 h with stirring. The mixture was

CARBAZOLYL PORPHYRINS
3317
cooled down and diluted with cold water (100 mL). The solution was neutralized to
pH 5–6 with dilute HCl and formed a white deposit. The deposit was extracted with
dichloromethane and then washed with water. The solvent was evaporated and dried
1
under a vacuum. The product was a white solid. Yield 90%. H NMR (400 MHz,
CDCl3) d=ppm: 5.06 (s, 2H), 7.27 (t, 2H, J ¼ 7.0 Hz), 7.34 (d, 2H, J ¼ 8.4 Hz),
7.49ꢁ7.45 (m, 2H), 8.10 (d, 2H, J ¼ 7.6 Hz); IR (KBr) n=cmꢂ1: 3419, 2925, 1724,
1702, 1485, 1453, 1325, 750, 721; MS (EI) m=z (%): 225 (M, 33), 180 (100), 152
(23), 76 (14).
Synthesis of 4-(N-carbazole methyl) benzonitrile (3). Carbazol (1.67 g,
10 mmol), potassium hydroxide (1.5 g, 26.7 mmol), and tetrabutyl ammonium bro-
mide (0.3 g, 0.93 mmol) were dissolved in benzene (60 mL) in a 100-mL three-necked
flask, and para-cyano benzyl bromide (1.94 g, 10 mmol) was added. The mixture was
then heated, refluxed for 18 h, and then cooled to room temperature. The reaction
mixture was added to distilled water (100 mL), then extracted with benzene three
times. The organic layer was collected, washed to neutrality with water, and then
evaporated to get a coarse product. This product was purified over a silica-gel col-
umn with the eluent of dichloromethane=benzin (1:1, v=v). The second band was
collected, evaporated, and dried under a vacuum; the product was a white solid.
Yield 80%. 1H NMR (400 MHz, CDCl3) d=ppm: 7.18 (d, 2H, J ¼ 8.4 Hz),
7.25–7.30 (m, 4H), 7.42–7.45 (m, 2H), 7.53 (d, 2H, J ¼ 8.4 Hz), 8.14 (d, 2H,
J ¼ 8.4 Hz); MS (EI) m=z (%): 282 (M, 60), 180 (20), 166 (100), 140 (29), 116 (38),
89 (28).
Synthesis of 4-(N-carbazole methyl) benzoic acid (4). 4-(N-Carbazole
methyl) benzonitrile (0.3 g, 1.06 mmol), ethandiol (14 g), and distilled water (6 g)
were added to the 100-mL, three-necked flask, the mixture solution was heated
and stirred at 90 ꢀC to disperse 4-(N-carbazole methyl) benzonitrile, and then 5 g
of sodium hydroxide were added. The mixture was refluxed for 4 h, and then cooled
to room temperature. Distilled water (150 mL) was added, and the mixture was neu-
tralized to pH 5–6 with dilute HCl, which formed a white deposit. The deposit was
extracted several times with dichloromethane, washed with water, evaporated, and
dried under a vacuum. The coarse product was purified in a silica-gel column with
the eluent of acetone=benzin (1:1, v=v). The second band was collected, evaporated,
and dried under a vacuum; the product was a pale yellow solid. Yield 85%. 1H NMR
(400 MHz, CDCl3) d=ppm: 5.59 (s, 2H), 7.21 (d, 2H, J ¼ 8.0 Hz), 7.27 (t, 2H,
J ¼ 7.6 Hz), 7.32 (d, 2H, J ¼ 8.4 Hz), 7.42–7.47 (m, 2H), 7.98 (d, 2H, J ¼ 8.4 Hz),
8.15 (d, 2H, J ¼ 7.6 Hz); IR (KBr) n=cmꢂ1: 3435, 3019, 2910, 2666, 1691, 1457,
1287, 743, 721; MS (EI) m=z (%): 301 (M, 100), 180 (18), 166 (35), 135 (61), 107 (15).
Synthesis of Monohydroxy Porphyrin and Monoamido Porphyrin
Synthesis of 5-(4-hydroxy phenyl)-10,15,20-triphenyl porphyrin (5).
Benzaldehyde (10.5 g, 100 mmol), para-hydroxybenzaldehyde (4.1 g, 33.3 mmol),
and metacetonic acid (220 mL) were added to a 500-mL, three-necked flask and
heated to reflux under stirring. A solution of redistilled pyrrole (8.9 g, 133.3 mmol)
in metacetonic acid (40 mL) was then added to it. The reaction solution was refluxed
for 40 min by stirring and then distilled. Ethanol (100 mL) was added at 80 ꢀC.

3318
D.-C. GUO ET AL.
The reaction mixture was filtered after 12 h at 0 ꢀC. The filter cake was washed with
ethanol at room temperature and then dried. The coarse product was purified in the
silica-gel column with the eluent of chloroform, and the first band was collected.
Then the dichloromethane was used as eluent instead of chloroform, and the second
band was collected. The solvent was evaporated under decompression; the product
was a purple solid. Yield 3%.[10] 1H NMR (400 MHz, CDCl3) d=ppm: ꢂ2.80 (s,
2H), 7.20 (d, 2H, J ¼ 8.4 Hz), 7.73–7.79 (m, 9H), 8.09 (d, 2H, J ¼ 8.4 Hz), 8.22 (d,
6H, J ¼ 7.6 Hz), 8.62–8.67 (m, 2H), 8.94 (d, 2H, J ¼ 4.4 Hz); MS (API) m=z (%):
631 (M þ 1, 100), 632 (M þ 2, 57), 633 (M þ 3, 19); IR (KBr) tmax=cmꢂ1: 3314,
3428, 3020, 2981, 1598, 1488.
Synthesis of 5-(4-hydroxy phenyl)-10,15,20-tri-(4-methoxyphenyl)
porphyrin (6). The synthesis of compound 6 was similar to that of compound 5.
The product was a purple solid. Yield 3.5%.[11] 1H NMR (400 MHz, CDCl3) d=
ppm: ꢂ2.77 (s, 2H), 4.10 (s, 9H), 7.21 (d, 2H, J ¼ 8.4 Hz), 7.29 (d, 6H, J ¼ 8.4 Hz),
8.07 (d, 2H, J ¼ 8.8 Hz), 8.13 (d, 6H, J ¼ 8.8 Hz), 8.87 (s, 8H); MS (API) m=z (%):
721 (M þ 1, 100), 722 (M þ 2, 60), 723 (M þ 3, 18).
Synthesis of 5-(4-nitro phenyl)-10,15,20-triphenyl porphyrin (7). Tetra-
phenyl porphyrin (1.0 g, 1.63 mmol) was dissolved in chloroform (150 mL) in the
250-mL, three-necked flask at 0–5 ꢀC. Fuming nitric acid (1.25 mL, 27.5 mmol)
was then added to it for 2.5 h under a nitrogen atmosphere. The reaction solution
was stirred for another 5 h and washed with water to become neutral. The organic
layer was dried with Na2SO4. The mixture was filtered, and the filtrate was evapo-
rated and dried. The coarse product was purified over a silica-gel column with the
eluent of chloroform=petroleum benzin (1:1, v=v). The second band was collected
and then evaporated under decompression. The product was a purple solid. Yield
52%.[12] 1H NMR (400 MHz, CDCl3) d=ppm: ꢂ2.78 (s, 2H), 7.74–7.80 (m, 9H),
8.21 (d, 6H, J ¼ 7.2 Hz), 8.40 (d, 2H, J ¼ 6.8 Hz), 8.64 (d, 2H, J ¼ 6.8 Hz), 8.74 (d,
2H, J ¼ 4.8 Hz), 8.86 (s, 4H), 8.89 (d, 2H, J ¼ 4.4 Hz); MS (ESI) m=z (%): 660
(M þ 1, 100), 661 (M þ 2, 47), 662 (M þ 3, 12).
Synthesis of 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (8).
5-(4-Nitro phenyl)-10,15,20-triphenyl porphyrin (7) (0.5 g), SnCl2 ꢃ 2H2O (0.55 g),
and concentrated HCl (25 mL) were added to a 50-mL, three-necked flask. The
reaction mixture was stirred for 1.5 h at 70 ꢀC under a nitrogen atmosphere, cooled,
and put into cold H2O (50 mL). The reaction solution was neutralized to pH 8 with
concentrated ammonia water and extracted three times with chloroform. The
volume of organic layer was evaporated to ꢁ20 mL on a rotary evaporator. The
reaction solution was mixed with an appropriate amount of silica gel and then dried.
The product was then purified in a silica-gel column with the eluent of chloroform=
petroleum benzin (5:3, v=v). The last band was collected. The solvent was evaporated
under decompression to get a purple solid product. Yield 71%.[12] 1H NMR
(400 MHz, CDCl3) d=ppm: ꢂ2.76 (s, 2H), 4.01 (bs, 2H), 7.06 (d, 2H, J ¼ 8.4 Hz),
7.73–7.77 (m, 9H), 7.99 (d, 2H, J ¼ 8.4 Hz), 8.21 (d, 6H, J ¼ 7.2 Hz), 8.83 (s, 6H),
8.94 (d, 2H, J ¼ 4.4 Hz); MS (ESI) m=z (%): 630 (M þ 1, 100), 631 (M þ 2, 43),
632 (M þ 3, 10).

CARBAZOLYL PORPHYRINS
3319
Synthesis of Carbazolyl Porphyrins
Synthesis of 5-(4-(N-carbazole acetyl)phenyl)-10,15,20-triphenyl
porphyrin (9). Monohydroxy porphyrin (0.063 g, 0.1 mmol), N-carbazolacetic acid
(0.023 g, 0.1 mmol), and dimethylaminopyridine (DMAP, catalyst) were dissolved in
methylene chloride (30 mL) in a 50-mL, single-necked flask and bathed in ice water.
A solution of DCC (0.023 g, 0.1 mmol) and methylene chloride (7 mL) was then
added to the flask. The reaction mixture was stirred and refluxed for 6 h under nitro-
gen protection and then evaporated to get the coarse product under reduced pres-
sure. This product was purified over a silica-gel column with the eluent of methylene
chloride=petroleum benzin (1:1, v=v). The first band was collected. The solvent was
evaporated under decompression to get a purple solid product. Yield 80%. 1H NMR
(400 MHz, CDCl3) d=ppm: ꢂ2.83 (s, 2H), 5.45 (s, 2H), 7.36 (t, 2H, J ¼ 4.4 Hz), 7.44
(d, 2H, J ¼ 8.4 Hz), 7.60 (d, 4H, J ¼ 4.0 Hz), 7.72–7.78 (m, 9H), 8.16 ꢁ 8.21 (m, 10H),
8.77 (d, 2H, J ¼ 5.2 Hz), 8.82 (d, 6H, J ¼ 6.4 Hz); IR (KBr) n=cmꢂ1: 3443, 2924, 1453,
1627, 996, 752, 722; MS (ESI) m=z (%) 838.2 (M þ 1,100), 839.3 (M þ 2, 58), 840.4
(M þ 3, 21). Anal. Calcd. for C58H39N5O2: C, 83.13; H, 4.69; N, 8.36. Found: C,
83.59; H, 4.47; N, 8.14.
Synthesis of 5-(4-(N-carbazole acetyl)phenyl)-10,15,20-tri(4-methoxy-
phenyl) porphyrin (10). The synthetic method for compound 10 followed that
of compound 9 besides the eluent of methylene chloride=petroleum benzin (7:1,
v=v). The product was a purple solid. Yield 79%. Anal. calcd. for C61H45N5O5: C,
78.95; H, 4.89; N, 7.55. Found: C, 79.34; H, 5.12; N, 7.23.
Synthesis of 5-(4-(4-(N-carbazole methyl) benzoyl)phenyl)-10,15,20-
triphenyl porphyrin (11). The synthetic method for compound 11 followed that
of the compound 9 besides the eluent of methylene chloride=petroleum benzin
(20:1, v=v). The product was a purple solid. Yield 82%. Anal. calcd. for
C64H43N5O2: C, 84.10; H, 4.74; N, 7.66. Found: C, 84.62; H, 4.53; N, 7.71.
Synthesis of 5-(4-(4-(N-carbazole methyl)benzoyl)phenyl)-10,15,20-
tri(4-methoxy phenyl) porphyrin (12). The synthetic method for compound 12
followed that of the compound 9 besides the eluent of methylene chloride=petroleum
benzin (5:1, v=v). The product was a purple solid. Yield 79%. Anal. calcd. for
C67H49N5O5: C, 80.14; H, 4.92; N, 6.97. Found: C, 79.65; H, 5.17; N, 7.21.
Synthesis of 5-(4-(N-carbazole acetamido)phenyl)-10,15,20-triphenyl
porphyrin (13). 5-(4-Amido phenyl)-10,15,20-triphenyl porphyrin (8) (0.064 g,
0.1 mmol), N-carbazolacetic acid (0.023 g, 0.1 mmol), and DMAP (catalyst) were
together dissolved in methylene chloride (30 mL) in a 50-mL single-necked flask.
A solution of DCC (0.023 g, 0.1 mmol) and methylene chloride (7 mL) was then
added to the flask. The reaction mixture was stirred and refluxed for 6 h under nitro-
gen protection and then evaporated to get the coarse product under reduced pres-
sure. This product was purified in a silica-gel column with the eluent of methylene
chloride=petroleum benzin (5:1, v=v). The first band was collected. The solvent
was evaporated on a rotary evaporator under decompression to get a purple solid
product. Yield 65%. Anal. calcd. for C58H40N6O: C, 83.23; H, 4.82; N, 10.04. Found:
C, 83.41; H, 5.14; N, 9.59.

3320
D.-C. GUO ET AL.
Synthesis of 5-(4-(4-(N-carbazole methyl)benzamido)phenyl)-10,15,20-
triphenyl porphyrin (14). The synthetic method for compound 14 was similar to
that of compound 13 besides the eluent of methylene chloride=petroleum benzin
(10:1, v=v). The product was a purple solid. Yield 71%. Anal. calcd. for
C64H44N6O: C, 84.19; H, 4.86; N, 9.20. Found: C, 84.43; H, 5.14; N, 8.89.
RESULTS AND DISCUSSION
The acyl chloride method and the DCC–DMAP method are two common
methods for the synthesis of ester and amide. In this report, the six kinds of porphyr-
ins synthesized were ester group–coupled or amide group–coupled carbazolyl por-
phyrins. The reaction conditions of carbazolyl porphyrin are explored using both
methods.
For the synthesis of these compounds, the acyl chloride method needs two
steps; however, the DCC–DMAP method needs only a one-step reaction, thus sim-
plifying the reaction process. Experimental results show that the products prepared
by the acyl chloride method are very complicated and difficult to separate and purify;
the yield is also poor (about 50%). The reason is that the acyl chloride is very
unstable and easily decomposes to produce by-products. The DCC–DMAP method
has overcome these defects of the acyl chloride method; the ester and amide products
can be synthesized under mild conditions, and the reaction possesses advantages
such as high reaction selectivity, excellent high yield (80%), easy separation, and easy
purification. The DCC–DMAP method is widely applied to the synthesis of esters
and amides, which can also be prepared by the carboxylic acid reacting with various
types of alcohol, phenols, primary amines, and secondary amines. When the carba-
zolyl porphyrins are synthesized with using DCC–DMAP methods, the reaction time
are prolonged at room temperature and yields are only 50%, but as heating and
refluxing are performed, the reaction time as monitored via thin-layer chromato-
graphy (TLC) decreases to 5 h and yields increase up to 80%. A possible reason is
the influence of porphyrins’ structure.
It has been determined by the reaction mechanism[13] that the DCC–DMAP
method has these advantages because the carboxylic acid can be anhydrated in the
presence of DCC to form the acid anhydride, which has much stronger esterification
ability; this reaction can proceed under more mild conditions and has better yields.
In the reaction process, DCC can be transferred to the by-product carbamide that is
not dissolved in CH2Cl2 or most organic solvents and easily separated by filtration.
DMAP is a very efficient catalyst for esterification reactions; its catalytic activation
rate is mainly due to a 4-dimethylin functional group possessing a strong
electron-donating capacity, which causes the active intermediate N-acylate pyridine
to be more stable.[14]
ACKNOWLEDGMENTS
The authors are grateful for the financial support of the National Natural
Science Talent Foundation of China (No. J0830415), the Natural Science Foun-
dation of Hunan Province (No. 05JJ30020), and the Development Foundation of

CARBAZOLYL PORPHYRINS
3321
the Scientific and Technological Bureau of Hunan Province (No. 04GK3035). We
thank Dr. William Hickey for English editing.
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