THEORETICAL AND EXPERIMENTAL ANALYSIS OF PORPHYRIN DERIVATIVES WITH SUITABLE ANCHORING GROUPS
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properties for their potential exploitation as dyes in
DSSC. In order to study such molecular systems, several
theoretical methodologies using Density Functional
Theory (DFT) and semiempirical methods were applied
for prediction of their electronic and geometrical
properties aiming to find the best theoretical approach
capable to explain structural data, electronic properties
and absorption spectra. The approach is general and could
be useful for studying other similar systems containing
different functional groups in the molecular structure.
Then, 150 mg of model-porphyrin compound were
added too and the reaction was stirred for 3 h. After
this time, the reaction was cooled and re-dispersed in
water. Green crystals were filtered and washed several
times with a solution of sodium acetate. The product —
a purple solid — was purified by recrystallization with
acetone-hexane. Yield: quantitative.1H NMR (400 MHz,
CDCl3): d, ppm 9.22 (8H, s), 8.01 (8H, d, J = 8 Hz), 7.24
(8H, d, J = 8 Hz ) y -2.78 (2H, s).
Compound
4 (4-[10,15,20-tris-(3,5-di-tert-butyl-
phenyl)-porphyrin-5-yl]. The crude product was puri-
fied by flash column chromatography on silica gel, using
hexane: dichloromethane (80:20) as eluent. The product
EXPERIMENTAL
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was obtained as a purple powder. Yield 10%. H NMR
Reagents and solvents were purchased from Sigma-
Aldrich México and used without further purification.
All NMR results were obtained using Bruker Ascend
400 MHz. UV-vis spectra were recorded on a Lambda
25 Perkin Elmer Spectrometer. A4 porphyrins (1,2,4,5)
were obtained by the general Adler–Longo methodology
[26] and A3B porphyrins 9 and 10 were synthesized
via Lindsey protocol, as described elsewhere [27–29].
Attempts to synthesize compound 3 by means of Adler–
Longo and Lindsay methodologies failed, thus porphyrin
3 was obtained by the demethylation of compound 2. On
the other hand, compound 6 was hydrolyzed under KOH
alkaline conditions, however an insoluble purple powder
was obtained, thus it was not possible to determine the
absorption profile of these derivatives.
(400 MHz, CDCl3): d, ppm 8.9 (8H, s), 8.09 (8H, s), 7.79
(4H, s), 1.52 (72H, s), -2.67 (2H, s).
Compound 5 (5,10,15,20-tetrakis-(4-phenoxy-
ethyl-butyrate)-porphyrin). The crude product was
purified by flash column chromatography on silica gel,
using dichloromethane as eluent. The product was a
purple solid too.Yield 14%.1H NMR (400 MHz, CDCl3):
d, ppm 9 (d, 8H), 8.2 (d, 8H), 7.6 (t, 8H), 4.3 (m, 16H),
2.6 (d, 8H), 1.3 (m, 20H) y -2.8 (s, 2H).
General procedure for synthesis of A3B porphyrins.
To a solution of aldehyde (benzaldehyde or 3.5-di-tert-
butyl-benzaldehyde,3eq.),4-hydroxibenzaldehyde(1.0g,
4.23 mmol, 1 eq.), pyrrole (1.14 g, 16.9 mmol, 4 eq.) in
1.5 L of CHCl3 and 1.2 mL of boron trifluoride diethyl
etherate (0.7 g) were added. The reaction mixture was
stirred at room temperature under argon atmosphere for
1 h. After this period, p-chloranyl (3.12 g, 12.7 mmol,
3 eq.) were added and the mixture was heated under reflux
for 90 min.After this time, the mixture was cooled to room
temperature and concentrated under vacuum. The crude
product was purified by flash column chromatography on
silica gel, using hexane: dichloromethane as eluent. See
Scheme 2.
Synthesis
General procedure for A4 porphyrins synthesis.
Corresponding aldehyde (benzaldehyde, anysaldehyde,
3,5-di-tert-butyl-benzaldehyde, 4-oxo-ethyl-butyrate-
benzaldehyde) and pyrrole (2 g) were added to boiling
propionic acid (110 mL). After 3 h of reaction, the
mixture was cooled to room temperature and concentrated
under vacuum. The crude product was purified by flash
column chromatography on silica gel, using hexane:
dichloromethane as eluent. See Scheme 1.
Compound 9 (4-(10,15,20-triphenyl-porphyrin-5-
yl)-phenol). The crude product was purified by flash
column chromatography on silica gel, using hexane:
dichloromethane (15:85) as eluent. The product was a
Compound1(5,10,15,20-tetraphenyl-porphyrin).The
crude product was purified by flash column chromatography
on silica gel, using hexane: dichloromethane (80:20) as
eluent. The product was obtained as a purple powder. Yield
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purple solid. Yield 5%. H NMR (400 MHz, CDCl3): d,
ppm 8.88–8.84 (8H, m), 8.21 (6H, d, J = 8 Hz), 8.07–
8.12 (2H, m), 7.71–7.80 (9H, m), 7.21 (2H, d, J = 8 Hz),
-2.78 (2H, s).
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19%. H NMR (400 MHz, CDCl3): d, ppm 8.84 (8H, s),
Compound10(4-[10,15,20-tris-(3,5-di-tert-butyl-phe-
nyl)-porphyrin-5-yl]-phenol). The crude product was
purified by flash column chromatography on silica gel,
using hexane: dichloromethane (20:80) as eluent. The
product was a purple solid. Yield 7%. 1H NMR (400 MHz,
CDCl3): d, ppm 8.88–8.90 (8H, m), 8.09 (8H, s), 7.79 (3H,
s), 7.18 (2H, d, J = 8 Hz), 1.52 (56H, s), -2.71 (2H, s).
8.22 (8H, d, J = 8 Hz), 7.79–7.72 (12H, m), -2.77 (2H, s).
Compound 2 (5,10,15,20-tetrakis-(4-methoxyphe-
nyl)-porphyrin) or model-porphyrin compound. Re-
crystallized from methanol and washed several times
with ethyl acetate. The product was obtained as a purple
powder. Yield 20%. 1H NMR (400 MHz, CDCl3): d, ppm
8.87 (8H, s), 8.13 (8H, d, J = 8 Hz), 7.29 (8H, d, J =
(8 Hz), 4.10 (12H, s), -2.76 (2H, s).
Compound 3 (5,10,15,20-tetrakis-(4-hydroxyphe-
nyl)-porphyrin). In a round-bottom flask, pyridine
(5.7 mL) and concentrated HCl (6 mL) at 290°C were
added, until pyridine chloride crystals were formed.
Theoretical methodology and computational details
The free-base porphyrins were analyzed using several
methodologies in order to select the best theoretical
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 3–15