Synthesis, Spectral, and Electrochemical Properties of meso-5,10,15,20-Tetrakis(2ꢀ-chlorobenzoquinolin-3ꢀ-yl)porphyrins
5
anhydride (35.4 mL, 0.38 mol) was heated under re-
flux condition for 10 min. To this, 10 mL of water
was added and the mixture was refluxed for another
30 min. At the end of the period, the reaction mix-
ture was poured directly onto crushed ice. The re-
sulting white precipitate was filtered, washed with
water, dried in air, and was purified by recrystal-
lization from ethanol to get compound 1 as white
needle-shaped crystals. Yield of compound 1 is 24.9
g (90%), and the melting point is 158–160◦C.
of CHCl3, and zinc acetate dihydrate (19 mg, 0.08
mmol) in 5 mL of methanol was added and refluxed
for 30 min. The reaction was monitored by TLC
and electronic spectroscopy. On disappearance of
the starting material on TLC, the solvent was evap-
orated under reduced pressure. The crude solid was
dissolved in CHCl3, washed with water, and passed
over anhydrous Na2SO4. The solvent was removed
under reduced pressure, and the crude product was
purified by silica gel column chromatography using
CHCl3. Rf values of different atrop isomers in CHCl3
are 0.43 (αβαβ), 0.41 (ααββ), 0.39 (αααβ), and 0.36
(αααα). Yield is 18.2 mg (88%). 1H NMR (CDCl3, δ in
ppm): 9.50–9.52 (d, 4H, benzoquinoline 5ꢀ-H), 9.08
(s, 4H, benzoquinoline 4ꢀ-H), 8.87 (s, 8H, pyrrole β-
H), 8.05–8.07 (d, 8H, benzoquinoline 6ꢀ- and 10ꢀ-H),
7.84–7.94 (m, 12H, benzoquinoline 7ꢀ-, 8ꢀ-, and 9ꢀ-H).
Found MALDI-MS: 1219.88 (Calcd 1218.11).
Synthesis of 2-Chlorobenzoquinoline-3-carbalde-
hyde (2). To a solution of N-acetyl-1-naphthyla-
mine, 1 (2.0 g, 10.8 mmol) in dry dimethylformamide
(2.1 mL, 27 mmol) POCl3 (19 mL, 204 mmol) was
added and the mixture was stirred at 75–80◦C for
6 h. At the end of the period, the mixture was
poured onto crushed ice and the resulting mixture
was filtered, washed with water, and dried in an
oven. The compound was recrystallized from ethyl
acetate–petroleum ether to give compound 2 as yel-
low needle-shaped crystals. Yield of compound 2 is
1.8 g (69%), and the melting point is 210–212◦C.
CONCLUSIONS
A new N-heterocycle-containing porphyrin has been
synthesized, and its spectral and electrochemical
properties have been investigated. This porphyrin
showed different electronic spectral behavior com-
pared to its phenyl, 3ꢀ-pyridyl, and 3ꢀ-quinolinyl ana-
logues (phyllo vs. etio). The electron-rich benzo-
quinoline porphyrin shows unusual redox behavior
with difficulty in oxidation and ease of reduction.
The present compound will be a new material to
study the role of sterics in self-assembling behavior
of N-heterocycle-containing porphyrins.
Synthesis of meso-5,10,15,20-Tetrakis(2ꢀ-chloro-
benzoquinolin-3ꢀ-yl)porphyrin (3). In
a
500-mL
three-necked round bottom flask fitted with an argon
bubbler, 2-chlorobenzoquinoline-3-carbaldehyde
(1.1 g, 4.54 mmol) and pyrrole (0.31 mL, 4.54 mmol)
were dissolved in 250 mL of CH2Cl2. After purging
argon for 10 min, the reaction was initiated by
adding a catalytic amount of BF3 etherate (0.18
mL, 1.51 mmol). The reaction mixture was stirred
at room temperature for 45 min. At the end of the
period, DDQ (1.03 g, 4.54 mmol) was added and the
reaction mixture was stirred in air for another 1 h.
After the addition of triethylamine (0.21 mL, 1.51
mmol), the reaction mixture was stirred for 15 min.
The solvent was removed under reduced pressure,
and the crude product was purified by silica gel
column chromatography using CHCl3. Rf values
of different atrop isomers in the 1:5 CHCl3–hexane
mixture are 0.35 (αβαβ), 0.34 (ααββ), 0.32 (αααβ),
and 0.30 (αααα). Yield is 133 mg (10.2%). UV–vis
ACKNOWLEDGMENTS
RP acknowledges the senior research fellowship re-
ceived from Council of Scientific and Industrial Re-
search (CSIR), New Delhi, India.
REFERENCES
[1] Rezaeifard, A.; Jafarpour, M.; Naeimi, A. Catal Com-
mun 2011, 16, 240–244.
[2] Keinan, S.; Therien, M. J.; Beratan, D. N.; Yang, W. J
Phys Chem A 2008, 112, 12203–12207.
1
spectral data are given in Table 1. H NMR (CDCl3,
δ in ppm): 9.50 (d, 4H, benzoquinoline 5ꢀ-H), 8.99
(s, 4H, benzoquinoline 4ꢀ-H), 8.79 (s, 8H, pyrrole
β-H), 8.03–8.09 (m, 8H, benzoquinoline 6ꢀ- and
10ꢀ-H), 7.87–7.95 (m, 12H, benzoquinoline 7ꢀ-, 8ꢀ-,
and 9ꢀ-H), –2.41 (s, 2H, NH). Found MALDI-MS:
1157.62 (Calcd 1156.19).
[3] Carcel, C. M.; Laha, J. K.; Loewe, R. S.; Thamyongkit,
P.; Schweikart, K.-H.; Misra, V.; Bocian, D. F.; Lind-
sey, J. S. J Org Chem 2004, 69, 6739–6750.
[4] Ethirajan, M.; Chen, Y.; Joshi, P.; Pandey, R. K. Chem
Soc Rev 2011, 40, 340–362.
[5] Takeuchi, M.; Imada, T.; Ikeda, M.; Shinkai, S. Tetra-
hedron Lett 1998, 39, 7897–7900.
[6] Maes, W.; Vanderhaeghen, J.; Smeets, S.; Asokan,
C. V.; Renterghem, L. M. V.; Du Prez, F. E.; Smet,
M.; Dehaen, W. J Org Chem 2006, 71, 2987–2994.
[7] Drain, C. M.; Fisher, R.; Nolen, E. G.; Lehn, J. -M. J
Chem Soc, Chem Commun 1993, 243–245.
Synthesis of 5,10,15,20-Tetrakis(2,-chlorobenzo-
quinolin-3ꢀ-yl)porphyrinato zinc(II) (4). Porphyrin
3 (20 mg, 0.017 mmol) was dissolved in 20 mL
Heteroatom Chemistry DOI 10.1002/hc