Fluorolog fluorimeter. Thin layer chromatography was performed
on MERCK Silica Gel 60 thick layer plates. Column chromatog-
raphy was performed on Sorbent Technologies brand silica gel (40-
63 um, Standard grade). High-resolution mass analyses were
performed at University of Illinois SCS Mass Spectrometry
Laboratory.
2,3-Dihydro-9,10-dimethoxy-1,4-anthracenedione (10). Com-
pound 10 was prepared by a modified methylation method.13
Compound 9 (2.5 g, 10.3 mmol) was added to a 500 mL oven
dried round-bottomed flask equipped with a stir bar and acetone
(200 mL) and dioxane (100 mL) were added. During stirring
dimethyl sulfate (28 mL, 169 mmol) and anhydrous potassium
carbonate (15 g, 118.2 mmol) were also added. The entire mixture
was stirred under argon at room temperature for about 30 min and
then refluxed for 12 h. The optimal formation of 10 was monitored
with GC-MS. The reaction mixture was allowed to cool and filtered.
The filtrate was concentrated and subjected to the next step without
further purification.
140.00, 139.50, 131.00, 129.75, 125.47, 124.95, 124.85, 124.76,
124.63, 123.88, 123.04, 121.49, 120.01, 115.55, 114.00, 112.00,
111.55, 80.44, 80.36, 63.71, 31.02, 29.33; HRMS m/z [M]+calcd
for C34H32O2S 504.2123, found 504.2120.
5,12-Bis(triisopropylsilylethynyl)-6,11-dimethoxytetraceno-
[2,3-b]thiophene (2). 2 was prepared by the reaction between
triisopropylsilylacetylene and 11 and purified by column, using a
mixture of hexane and dichloromethane (2:3) as the eluent. Yield
1
41%; H NMR (300 MHz, CDCl3) δ 9.53 (s, 1H), 9.47 (s, 1H),
8.32 (m, 2H), 7.54 (d, 1H), 7.45 (m, 2H), 7.38 (d, 1H), 4.10 (s,
6H), 1.33 (s, 42H); 13C NMR (300 MHz, CDCl3) δ 149.55, 140.40,
140.02, 131.68, 130.19, 125.77, 125.72, 125.16, 125.07, 124.76,
124.68, 123.68, 123.09, 121.89, 120.48, 115.62, 114.30, 107.34,
106.63, 106.33, 94.73, 63.78, 18.94, 18.44, 11.61, 11.02;
HRMS m/z [M + H]+ calcd for C44H57O2Si2S 705.3617, found
705.3621.
5,12-Bis(phenylethynyl)-6,11-dimethoxytetraceno[2,3-b]thio-
phene (3). 3 was prepared by the reaction between phenylacetylene
and 11 and purified by column, using a mixture of hexane and
dichloromethane (9:1) as the eluent. Yield 35%; 1H NMR
(300 MHz, CDCl3) δ 9.59 (s, 1H), 9.45 (s, 1H), 8.41 (m, 2H), 7.85
(m, 4H), 7.91 (d, 1H), 7.72 (d, 1H), 7.62-7.45 (m, 8H), 4.21 (s,
6H); 13C NMR (300 MHz, CDCl3) δ 149.05, 141.00, 140.05,
131.54, 131.50, 130.99, 130.88, 130.33, 128.76, 128.64, 125.98,
125.93, 125.39, 125.30, 124.78, 124.69, 124.49, 124.41, 123.88,
123.03, 121.39, 120.07, 115.32, 114.04, 103.41, 103.02, 91.48,
63.73; HRMS m/z [M]+ calcd for C38H24O2S 544.1497, found
544.1509.
6,11-Dimethoxy-5,12-tetracenequinone[2,3-b]thiophene (11).
Thiophene-2,3-carboxaldehyde (1 equiv of 10 as estimated from
the GC/MS profile) and THF (100 mL) were added to the
concentrated solution of 10 and the mixture was stirred several
minutes until all solids dissolved. Ethanolic KOH (5%, 5.75 mL)
was then added. The mixture was refluxed overnight, following
which it was cooled and poured into an ice cold water bath. The
product precipitated then was filtered and dried. The brown crude
solid product was purified by column chromatography with
dichloromethane as solvent. Evaporation of the solvent yielded pure
1
11 in the form of an orange yellow solid (yield 20%). H NMR
6,13-Bis(tert-butylethynyl)-5,14-dimethoxypentacene
(4).
(300 MHz, CDCl3) δ 8.84 (s, 1H), 8.75 (s, 1H), 8.45 (m, 2H), 7.77
(m, 3H), 7.60 (d, 1H), 4.18 (s, 6H); 13C NMR (300 MHz, CDCl3)
δ 183.06, 182.71, 156.00, 155.96, 144.53, 143.08, 132.88, 132.03,
131.45, 130.71, 129.91, 125.02, 124.83, 122.79, 122.04, 121.30,
121.27, 63.20; HRMS m/z [M]+ calcd for C22H14O4S 374.0613,
found 374.0614.
4 was prepared by the reaction between tert-butylacetylene and
12 and purified by column, using a mixture of hexane and
dichloromethane (1:1) as the eluent. Yield 40%; 1H NMR
(300 MHz, CDCl3) δ 9.40 (s, 2H), 8.26(m, 2H), 7.95 (m, 2H), 7.39
(m, 4H), 4.10 (s, 6H), 1.66 (s, 18); 13C NMR (300 MHz, CDCl3)
δ 132.19, 131.37, 128.76, 126.47, 125.73, 125.55, 124.91, 123.08,
115.11, 113.00, 80.84, 63.66, 31.34, 29.42; HRMS m/z [M]+ calcd
for C36H34O2 498.2559, found 498.2553.
5,14-Dimethoxy-6,13-pentacenequinone (12). Compound 10
was caused to react with 1,2-bezenedicarbaldehyde to obtain 12
following the same procedure employed for 11. Pure 12 was isolated
6,13-Bis(triisopropylsilylethynyl)-5,14-dimethoxypentacene (5).
5 was prepared by the reaction between triisopropylsilylacetylene
and 12 and purified by column, using a mixture of hexane and
1
as yellow solid (yield 21%). H NMR (300 MHz, CDCl3) δ 8.84
(s, 2H), 8.44 (m, 2H), 8.12 (m, 2H), 7.79 (m, 2H), 7.70 (m, 2H);
13C NMR (300 MHz, CDCl3) δ 182.98, 156.04, 135.16, 132.37,
131.42, 129.93, 129.91, 129.06, 128.74, 124.83, 121.68, 63.28;
HRMS m/z [M]+ calcd for C24H16O4 368.1048, found 368.1049.
1
dichloromethane (2:3) as the eluent. Yield 47%; H NMR (300
MHz, CDCl3) δ 9.62 (s, 2H), 8.30 (m, 2H), 7.99 (m, 2H), 7.43 (m,
4H), 4.12 (s, 6H), 1.39 (s, 42H); 13C NMR (300 MHz, CDCl3) δ
149.58, 132.49, 131.81, 128.56, 126.83, 126.11, 125.83, 125.30,
125.18, 123.15, 115.38, 107.61, 107.38, 63.73, 18.92, 12.31; HRMS
m/z [M]+ calcd for C46H58O2Si2 698.3975, found 698.3984.
General Procedure for the Synthesis of 1-6. Compounds 1-6
were synthesized starting from either 11 or 12 following a general
method. The synthesis of 1 is detailed as an example. An oven
dried 100 mL round-bottomed flask equipped with a stir bar was
clamped in a dry box. tert-Butylacetylene (0.13 mL, 1.06 mmol)
was added to the flask and dissolved in dry dichloromethane (10
mL). To this stirring solution was added n-BuLi (0.44 mL of a 2.5
M solution in hexane) dropwise. The mixture was stirred for about
30 min at room temperature. In a separate flask a solution of 11
(0.1 gm, 0.27 mmol) in dry dichloromethane (5 mL) was prepared,
and was slowly added to the lithiated tert-butylacetylene solution.
The whole mixture was allowed to stir at room temperature
overnight. Then it was taken out of the dry box and was quenched
with 10% HCl (1 mL). To this was added SnCl2 in 10% HCl (1
mL) and the mixture was stirred at room temperature under dark
and argon for 24 h. The progress of the reaction was monitored by
thin layer chromatography (TLC). After the reaction was complete,
the solution was dried with anhydrous Na2SO4 and the filtrate was
evaporated to obtain crude 1. The product was purified in the dark
by column chromatography over silica gel with a mixture of hexane
and dichloromethane (1:1) as the eluent.
6,13-Bis(phenylethynyl)-5,14-dimethoxypentacene (6).
6
was prepared by the reaction between phenylacetylene and 12 and
purified by column, using a mixture of hexane and dichloromethane
(3:7) as the eluent. Yield 38%; 1H NMR (300 MHz CDCl3) δ 9.56
(s, 2H), 8.35 (m, 2H), 8.10 (m, 2H), 7.92 (m, 4H), 7.57-7.28
(m, 10H), 4.23 (s, 6H); 13C NMR (300 MHz, CDCl3) δ 149.59,
132.52, 131.54, 131.12, 128.79, 128.68, 128.49, 126.42, 126.20,
126.03, 125.80, 125.40, 124.55, 123.07, 115.06, 104.16, 91.92,
63.67; HRMS m/z [M]+ calcd for C40H26O2 538.1933, found
538.1931.
Acknowledgment. We thank Dr T. H. Kinstle for valuable
discussions. This work has been supported by Navy (grant
number N0014-06-1-0948).
Supporting Information Available: 1H NMR and 13C NMR
of 1-6, 11, and 12, details about formation of isomeric mixture of
11 and 14, thin film absorption of 1-6, CV graphs, the ΦF values
of 1-6 recorded in different solvents. This material is available
5,12-Bis(tert-butylethynyl)-6,11-dimethoxytetraceno[2,3-b]-
thiophene (1). Yield 34%; 1H NMR (300 MHz, CDCl3) δ 9.31 (s,
1H), 9.26 (s, 1H), 8.30 (m, 2H), 7.53 (d, 1H), 7.42 (m, 3H), 4.10
(s, 6H), 1.64 (s, 18H); 13C NMR (300 MHz, CDCl3) δ 149.05,
JO0710331
J. Org. Chem, Vol. 72, No. 17, 2007 6587