Murschell and Sutherland
Article
coefficients are typical for molecules of this size and range from
(200 mL). After two recrystallizations from chloroform and
methanol, yellow powder tetraether was obtained in 40% yield
(0.90 g, 0.92 mmol). 1H NMR (300 MHz, CDCl3): δ 12.78 (s, 1H),
7.42 (s, 1H), 4.17 (t, J = 6.7 Hz, 2H), 4.15 (t, J = 6.6 Hz, 2H),
2.02-1.64 (m, 4H), 1.66-0.95 (m, 42H), 0.88 (t, J = 6.6 Hz, 6H).
General Procedure for Hexaether Synthesis. Compound 2
(typically 0.2 g, 0.2 mmol) was dialkylated at the 1,5-hydroxy
positions by stirring with potassium carbonate (0.20 g, 1.4 mmol),
TBAB (0.11 g, 0.33 mmol), and DMF (10 mL) at room tem-
perature (15 min) under inert conditions. The appropriate benzyl-
bromide derivative was added (approximately 3.5 mmol), and the
flask was heated to 105 °C for 20 h. The reaction mixture was
cooled to room temperature and water (10 mL) was added to
precipitate the product. The crude product was filtered from the
reaction mixture and dissolved in chloroform (50 mL), which was
extracted with water (3 ꢀ 200 mL) and brine (200 mL). After two
precipitations from mixed solvents, chloroform and ethanol,
clean yellow waxy hexaethers were obtained in 65-92% yields
(approximately 0.20 mmol).
3.5 ꢀ 10-7 to 7.3 ꢀ 10-6 cm2
s
-1. The electron transfer rate
3
constants associated with eq 2 reaction are tabulated in Table 1
and range from 0.9 to 5.2 ꢀ 10-3 cm s-1. These electron transfer
3
rates are not considered fast, but since the rates are solution-based
these compounds warrant future investigation as possible n-type
conductors.
Conclusion
This contribution shows a convenient path to the synthesis
of anthraquinone LC compounds using microwave synthesis.
UV-vis absorption profiles show that the anthraquinone is the
chromophore with little electronic perturbation derived from the
benzyl substituents and the compounds have a large HOMO-
LUMO energy gap, which is acceptable as an n-type component
in organic materials. The thermal phase properties of compounds
3a-f, X-ray diffraction data, and the cross-polarized microscopy
results indicate these AQs form discotic columnar phases that
exhibit a thermal stability window that spans 175 °C. XRD
experiments show all of the compounds synthesized display
columnar discotic structures at room temperature and are classi-
fied as either rectangular or hexagonal columnar phases. The
large, tunable LC temperature stability window is relevant to
organic photovoltaic applications. Solution electrochemical re-
sults indicate a reasonable reduction potential for n-type materials
and electron transfer kinetics that do not preclude these materials
from further device investigation. However, a lower reduction
potential and faster electron transfer rates would be beneficial,
and current efforts are directedat the synthesis of compounds that
exhibit faster charge transfer leading to better solid-state con-
ductance.
3a: 1,5-Bis(4-(t-butyl)benzyloxy)-2,3,6,7-tetradodecyloxy-
anthracene-9,10-dione. Compound 2 (0.20 g, 0.20 mmol), and
4-(tert-butyl)benzyl bromide (0.5 mL, 0.62 g, 2.2 mmol) were
reacted according to the general procedure for hexaether synth-
esis. The product was a waxy yellow solid (0.22 g, 0.17 mmol,
83%). 1H NMR (300 MHz, CDCl3): δ 7.90-7.56 (m, 3H), 7.46
(d, J = 8.2 Hz, 2H), 5.10 (s, 2H), 4.20 (t, J = 6.4 Hz, 2H), 4.10 (t,
J = 6.5 Hz, 2H), 2.17 (s, 1H), 2.03 - 1.65 (m, 4H), 1.64-1.14 (m,
45H), 0.90 (t, J=6.6 Hz, 6H). 13C NMR (75 MHz, CDCl3): δ
181.21, 157.52, 153.24, 150.98, 147.28, 134.49, 132.73, 128.76,
125.37, 120.86, 107.40, 77.36, 75.64, 74.32, 69.26, 34.67, 32.05,
31.48, 30.48, 29.85, 29.82, 29.78, 29.74, 29.65, 29.49, 29.22, 26.19,
22.81, 14.22. MS (Supporting Information) m/e calcd for
C84H132O8 (100, M þ Naþ), 1291.98; found, 1291.79. Anal. Calcd
for C84H132O8: C, 79.44; H, 10.48; N: 0. Found: C, 79.14; H,
10.37; N, 0.11.
Experimental Section
3b: 1,5-Bis(4-(methyl)benzyloxy)-2,3,6,7-tetradodecyloxy-
anthracene-9,10-dione. Compound 2 (0.21 g, 0.21 mmol), and
4-(methyl)benzyl bromide (0.62 g, 3.4 mmol) were reacted accord-
ing to the general procedure for hexaether synthesis. The product
Synthesis. Solvent were dried using an MBraun solvent
system. 1H- and 13C{1H}-NMR spectra were recorded on a
Bruker DMX-300 or a Bruker DRX-400 spectrometer. Elemental
analyses were performed at the University of Calgary, Depart-
ment of Chemistry. Mass spectrometry was carried out using a
Finigan SSQ700 spectrometer. Differential scanning calorimetry
was carried out using TA Instruments Q200 instrument scanning
1
was a waxy, yellow-brown solid (0.23 g, 0.19 mmol, 90%). H
NMR (300 MHz, CDCl3): δ 7.99-7.42 (m, 3H), 7.22 (m, 2H),
5.07 (s, 2H), 4.18 (t, J = 6.3 Hz, 2H), 4.06 (t, J = 6.5 Hz, 2H), 2.37
(s, 3H), 2.14-1.64 (m, 4H), 1.64-0.97 (m, 36H), 0.88 (t, J = 6.6
Hz, 6H). 13C NMR (75 MHz, CDCl3): δ 181.25, 157.54, 153.27,
147.26, 137.73, 134.53, 132.73, 129.12, 128.93, 120.82, 107.40,
77.58, 77.16, 76.74, 75.71, 74.32, 69.29, 32.05, 30.47, 29.85, 29.82,
29.78, 29.75, 29.65, 29.49, 29.22, 26.17, 22.81, 21.38, 14.23. MS-
(Supporting Information) m/e calcd for C78H120O8 (100, M þ
Naþ), 1207.89; found, 1207.63. Anal. Calcd for C78H120O8: C,
79.01; H, 10.20. Found: C, 78.48; H, 10.08.
from -50 to 200 °C at a rate of 10 °C min-1. UV-vis-NIR
3
spectra were recorded in dry THF solutions in a 1 cm quartz cell
on a Cary5000 spectrometer.
1: Rufigallol, 1,2,3,5,6,7-Hexahydroxyanthracene-9,10-dione.
The acid-mediated self-condensation of Gallic acid was facilitated
under microwave conditions using a previously reported proce-
dure and gave Rufigallol in 78-84% yield.43 Gallic acid (0.48 g,
2.8 mmol) was dissolved completely in 98% sulfuric acid (5 mL).
The vial was capped with a vented rubber septum and heated
by conventional microwave oven for 5 s, with ∼1 min breaks in
between each heating cycle for a total of 45 s. During the micro-
wave reaction, the color of the solution changed from amber to
purple. Once the reaction was complete, the sample was poured
into a beaker of ice-water, and the brick red precipitate was
filtered resulting in crude rufigallol (0.32 g, 1.1 mmol, 78%).
2: 2,3,6,7-Tetrakis(dodecyloxy)-1,5-dihydroxyanthracene-
9,10-dione. Crude rufigallol 1 (0.70 g, 2.3 mmol) was tetra-
alkylated in the 2,3,6,7-hydroxy positions by stirring with sodium
hydroxide (0.40 g, 9.9 mmol) and TBAB (3.20 g, 10.0 mmol) in
DMSO (14 mL) at room temperature (15 min) under inert
conditions. Upon addition of 1-bromododecane (2.6 mL, 2.7 g,
10.8 mmol), the sample was heated to 85 °C for 18 h. The reaction
mixture was cooled to room temperature, and water (6 mL) was
added to precipitate the product. The crude product was filtered
from the reaction mixture and dissolved in chloroform (50 mL),
which was then extracted with water (3 ꢀ 200 mL) and brine
3c: 1,5-Bis(benzyloxy)-2,3,6,7-tetradodecyloxyanthracene-
9,10-dione. Compound 2 (0.10, 0.10 mmol), and benzyl bromide
(0.3 mL, 0.43 g, 2.5 mmol) were reacted according to the general
procedure for hexaether synthesis. The product was a waxy,
1
yellow solid (0.093 g, 0.080 mmol, 78%). H NMR (300 MHz,
CDCl3) δ 7.79-7.53 (m, 3H), 7.56-7.28 (m, 3H), 5.12 (s, 2H),
4.19 (t, J = 6.4 Hz, 2H), 4.08 (t, J = 6.5 Hz, 2H), 2.04-1.81 (m,
2H), 1.81-1.63 (m, 2H), 1.63-1.10 (m, 37H), 0.88 (t, J = 6.6 Hz,
6H). 13C NMR (75 MHz, CDCl3): δ 181.26, 157.63, 153.27,
147.33, 137.58, 132.77, 128.85, 128.48, 128.10, 120.76, 107.48,
75.79, 74.38, 69.32, 32.06, 30.47, 29.83, 29.80, 29.76, 29.63, 29.50,
29.22, 26.19, 22.82, 14.24. MS (Supporting Information) m/e
calcd for C76H116O8 (100, M þ Hþ), 1157.87; found, 1157.90.
Anal. Calcd for C76H116O8: C, 78.85; H, 10.10; N, 0. Found: C,
78.16; H, 9.95; N, 0.07.
3d: 1,5-Bis(4-(bromo)benzyloxy)-2,3,6,7-tetradodecyloxy-
anthracene-9,10-dione. Compound 2 (0.09 g, 0.092 mmol), and
4-(bromo)benzyl bromide (0.30 g, 1.2 mmol) were reacted accord-
ing to the general procedure for hexaether synthesis. The product
Langmuir 2010, 26(15), 12859–12866
DOI: 10.1021/la101406s 12865