Furan-fused TCNQ and DCNQI: Synthesis and properties

Full text of DOI:10.1021/jo991438o

J . Org. Chem. 2000, 65, 2577-2579
2577
F u r a n -F u sed TCNQ a n d DCNQI: Syn th esis
Sch em e 1
a n d P r op er ties
Kazuyuki Takahashi and Keiji Kobayashi*
Department of Chemistry, Graduate School of Arts and
Sciences, The University of Tokyo,
Komaba, Meguro-ku, Tokyo 153-8902, J apan
Received September 13, 1999
Structural modification of 7,7,8,8-tetracyanoquinodi-
methane (TCNQ) has been extensively explored to obtain
new materials with enhanced conducting properties,
principally by means of incorporation of the substituents
and of π-system extension. The extension of the π-system
has been considered to reduce intramolecular electron
repulsion and thereby lead to increased conductivities of
their radical anions. The molecular design according to
1
9 in 19% yield. Quinone 9 was converted to compound 1
in 79% yield by reaction with malononitrile in the
such guideline includes the annulation of benzene,
2
3
4
5
thiophene, thiadiazole, pyrazine, other heterocycles,
6
presence of TiCl
by Hunig.1b
4
by following the procedure described
and polyaromatic rings or multiheterocycles. Despite
these ample examples of π-expanded TCNQ derivatives,
furan-fused TCNQ, 4,8-bis(dicyanomethylene)-4,8-dihy-
drobenzo[1,2-b:4,5-b′]difuran 1, has not been reported up
to now. In this paper we describe the synthesis of furan-
fused TCNQ 1 as well as furan-fused N,N′-dicyano-p-
quinodiimine (DCNQI) 2 and their physicochemical
properties in comparison with those of thiophene ana-
logues 3, on which we have previously reported.2
The electrochemical properties of 1 were investigated
by cyclic voltammetry. The redox potentials of 1 are listed
in Table 1 together with those of several related com-
pounds measured under the same conditions. Compound
1 displays two reversible single-electron redox waves. The
1
first redox potential ( E1/2) is more anodic than those of
thiophene-fused analogue 3 and benzene-fused analogue
5
. The electron affinities of furan and thiophene have
8
been reported to be -1.76, and -1.17 eV, respectively,
implying that thiophene possesses stronger acceptor
character than furan. However, the reduction potentials
of 1 and 3 are not correlated with the electron affinity of
the fused heterocycles. A possible interpretation for this
observation would be provided on the basis of the free
energy loss which can be formulated as the π-resonance
energy difference between the neutral and radical anion
species. Upon single-electron reduction the central quinon-
oid ring gains the aromatic stability of benzene, whereas
the fused heterocyclic part loses the aromaticity of furan
or thiophene, as illustrated below. The aromatic charac-
9
ter of furan and thiophene increases in this order. Thus,
(
3) (a) Yamashita, Y.; Suzuki, T.; Mukai, T.; Saito, G. J . Chem. Soc.,
Resu lts a n d Discu ssion
Chem. Commun. 1985, 1044-1045. (b) Kabuto, C.; Suzuki, T.; Ya-
mashita, Y.; Mukai, T. Chem. Lett. 1986, 1433-1436. (c) Suzuki, T.;
Kabuto, C.; Yamashita, Y.; Mukai, T. Bull. Chem. Soc. J pn. 1987, 60,
111-2115. (d) Suzuki, T.; Fujii, H.; Yamashita, Y.; Kabuto, C.;
Tanaka, S.; Harasawa, M.; Mukai, T.; Miyashi, T. J . Am. Chem. Soc.
F u r a n -F u sed TCNQ. The synthesis of 1 was carried
out according to Scheme 1. In a procedure similar to that
used for the synthesis of thiophene-fused quinone, furan
-carboxyamide 8 was treated with 1.05 equiv of LDA in
2
7
1
992, 114, 3034-3043.
3
(4) Yamashita, Y.; Suzuki, T.; Saito, G.; Mukai, T. Chem. Lett. 1986,
15-718.
7
diethyl ether under reflux to afford furan-fused quinone
(5) (a) Martin, N.; Seoane, C.; Segura, J . L.; Marco, J . L.; Hanack,
M. Synth. Met. 1991, 41-43, 1873-1876. (b) Samsov, V. A.; Volodar-
skii, L. V.; Khisamutdinov, G. Kh. Chem. Heterocycl. Compd. (N.Y.)
1997, 33, 471-474.
(
1) (a) Yamaguchi, S.; Tatemitsu, H.; Sakata, Y.; Misumi, S. Chem.
Lett. 1983, 1229-1230. (b) Aum u¨ ller, A.; H u¨ nig, S. Liebigs Ann. Chem.
1
4
984, 618-621. (c) Ong, B. S.; Keoshkerian, B. J . Org. Chem. 1984,
9, 5002-5003. (d) Nishizawa, Y.; Suzuki, T.; Yamashita, Y.; Miyashi,
(6) (a) Diekmann, J .; Hertler, W. R.; Benson, R. E. J . Org. Chem.
1963, 28, 2719-2724. (b) Sandman, D. J .; Garito, A. F. J . Org. Chem.
1974, 39, 1165-1166. (c) Yanagimoto, T.; Takimiya, K.; Otsubo, T.;
Ogura, F. J . Chem. Soc., Chem. Commun. 1993, 519-520. (d) Takimiya,
K.; Yanagimoto, T.; Yamashiro, T.; Ogura, F.; Otsubo, T. Bull. Chem.
Soc. J pn. 1998, 71, 1431-1435. (e) Maxfield, M.; Willi, S. M.; Cowan,
D. O.; Bloch, A. N.; Poehler, T. O. J . Chem. Soc., Chem. Commun. 1980,
947-948. (f) Acton, N.; Hou, D.; Schwarz, J .; Katz, T. J . J . Org. Chem.
1982, 47, 1011-1018. (g) Maxfield, M.; Bloch, A. N.; Cowan, D. O. J .
Org. Chem. 1985, 50, 1789-1796.
T.; Mukai, T. Nippon Kagaku Kaishi 1985, 904-909. (e) Kini, A. M.;
Cowan, D. O.; Gerson, F.; M o¨ ckel, R. J . Am. Chem. Soc. 1985, 107,
5
56-562.
(2) (a) Kobayashi, K.; Gajurel, C. L. J . Chem. Soc., Chem. Commun.
1
986, 1779-1780. (b) Kobayashi, K.; Gajurel, C. L.; Umemoto, K.;
Mazaki, Y. Bull. Chem. Soc. J pn. 1992, 65, 2168-2172. (c) Iwasaki,
F.; Toyoda, N.; Hirota, M.; Yamazaki, N.; Yasui, M.; Kobayashi, K.
Bull. Chem. Soc. J pn. 1992, 65, 2173-2179. (d) Iwasaki, F.; Hironaka,
S.; Yamazaki, N.; Kobayashi, K. Bull. Chem. Soc. J pn. 1992, 65, 2180-
(7) (a) Slocum, D. W.; Gierer, P. L. J . Org. Chem. 1976, 41, 3668-
3673. (b) Beimling, P.; Kossmehl, G. Chem. Ber. 1986, 119, 3198-3203.
(8) J . Phys. Chem. Ref. Data, Suppl. 1988, 17(1).
2
186. (e) Yasui, M.; Hirota, M.; Endo, Y.; Iwasaki, F.; Kobayashi, K.
Bull. Chem. Soc. J pn. 1992, 65, 2187-2191.
1
0.1021/jo991438o CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/18/2000

2
578 J . Org. Chem., Vol. 65, No. 8, 2000
Notes
Ta ble 1. Red ox P oten tia ls of Va r iou s Accep tor s
F igu r e 1. UV/vis spectral change upon electrochemical oxida-
tion of 1 in DMF. The arrows indicate the growth of new
absorption maxima which are characteristic of the radical
anion produced.
a
+
b
V vs Fc/Fc ; 0.1 M n-Bu4NBF4 solution in benzonitrile. ∆E
) 1
E1/2 - E1/2. Single two electron wave was observed.
2
c
furan compound 1 is more easily reduced with less
resonance energy loss than compound 3.
F igu r e 2. Projection of the columnar arrangement of 1 and
BEDTTTF molecules in the crystal structure of 1 (BEDTTTF).
1
2
The E1/2 - E1/2 value (0.54 V) of 1 is larger by 0.21 V
than that of thiophene analogue 3, implying that on-site
Coulombic repulsion in the dianion of 1 is enhanced as
compared with that of thiophene derivative 3. Generation
of two negative charges over the whole molecule would
be unfavorable for the oxygen compound, because the
polarizability of oxygen is lower than that of sulfur. For
highly distorted π-conjugated acceptors such as 5, a two-
electron single wave is observed,1 since the π-conjugated
system is buckled and separated into two independent
electron pools due to steric repulsion between the fused
aromatic rings and the dicyanomethylene moieties. Thus,
the occurrence of two waves in compound 1 indicates that
crystal structure of a 1:1 charge-transfer complex of 1
with bis(ethylenedithio)tetrathiafulvalene (BEDTTTF).
The complex exhibited no electrical conductivity. The
crystal structure is shown in Figure 2. The acceptor and
donor molecules stack alternately with each other along
the c axis.10 The exocyclic CdC bond length of the
quinodimethane moiety (1.369 Å) is similar to that of the
e
11
neutral TCNQ molecule (1.374 Å), indicating that the
acceptor molecule is almost neutral. It is also the case
for the donor side: the CdC bond length connecting the
two 1,3-dithiole rings is 1.347 Å, corresponding to that
of the neutral TTF molecule (1.349 Å).12 Six atoms of the
quinonoid ring of 1 are in one plane. The dihedral angle
between the quinonoid plane and the furan ring is 2.1°.
That between the quinonoid and the dicyanomethylene
moiety is 5.6°. Thus, molecule 1 is much less distorted
than thiophene analogue 3.2
1
is not as significantly distorted as the benzene-fused
derivative 5.
The UV/vis spectra of 1 were measured during the
constant potential reduction at -0.4 V in DMF (Figure
). The absorption bands of neutral species at 414 and
40 nm gradually disappear, with concomitant occur-
c
1
4
rence of new peaks at 497, 701, and 783 nm due to the
radical ion species. Well-defined isosbestic points are
observed at 455 nm, indicating that no side reactions are
involved. With respect to the neutral species, the spectral
feature of 1 is essentially the same as that of thiophene
analogues 3.2b On the other hand, for radical anions,
there is a distinct difference in the 400-600 nm region:
the radical anion of 1 exhibits the absorption at 497 nm,
The molecular geometry of 1 was also predicted to be
planar on the basis of the PM3 semiempirical calculation
1
3
as implemented in the MOPAC-6.0 system of programs.
The optimized geometries of compounds 1 and 3 are
whereas the radical anion of 3 exhibits the absorption
at 554 nm.2b
Molecu lar Str u ctu r e in Cr ystallin e Ch ar ge-Tr an s-
fer Com p lex. Despite our intensive efforts, a single
crystal of 1 suited for an X-ray crystallographic analysis
could not be obtained. Therefore we determined the
(
10) The molecule of 1 shows an orientational disorder with respect
to an approximate molecular symmetry of mm due to the similarity of
the dimensions related with C-O-C and CdC-C moieties of the furan
ring. The structure is described for the major fraction.
(
11) Long, R. E.; Sparks, R. A.; Trueblood, K. N. Acta Crystallogr.
1
965, 18, 932.
(9) Fringuelli, F.; Marino, G.; Taticchi, A.; Grandolini, G. J . Chem.
(12) Cooper, W. F.; Kenny, N. C.; Edmonds, W. J .; Nagel. A.; Wudl,
Soc., Perkin Trans. 2 1974, 332.
F.; Coppens, P. J . Chem. Soc., Chem. Commun. 1971, 889.

Notes
J . Org. Chem., Vol. 65, No. 8, 2000 2579
was cooled before addition of ice water. The dione was extracted
three times with CH
washed with brine, dried over MgSO
crystalline residue was recrystallized from acetic acid to give 9
2
Cl
2
. The combined organic extracts were
4
, and evaporated. The
1
(
217 mg, 19%) as yellow leaflets: mp > 185 °C (sublimed); H
NMR (CDCl ) δ 7.70 (d, J ) 1.8 Hz, 2H), 6.92 (d, J ) 1.8 Hz,
H); 13C NMR (CDCl
) δ 170.6, 152.3, 148.4, 128.5, 108.6; IR
3
2
(
(
3
-
1
+
KBr) 1666 (CdO) cm ; MS m/z 188 (M ); UV/vis (CH
log ꢀ) 314 (3.8), 255 (4.0), 246 (4.0), 230 (4.3) nm. Anal. Calcd
: C, 63.84; H, 2.14. Found: C, 63.78; H, 2.38.
2 2
Cl ) λmax
for C10
4 4
H O
Tet r a cya n ob en zo[1,2-b:4,5-b]d ifu r a n -4,8-d ion ed im et h -
a n e (1). To a solution of quinone 9 (499 mg, 2.7 mmol) and
malononitrile (1.76 g, 27 mmol) in dry CH
2 2
Cl (160 mL) at 0 °C
were added successively TiCl (2.9 mL, 27 mmol) and pyridine
4
F igu r e 3. Molecular geometries of 1 and 3 optimized by PM3
calculation.
(4.3 mL, 53 mmol). The mixture was refluxed for 24 h. The
reaction mixture was cooled to room temperature and poured
onto ice. The organic layer was extracted six times with CH
2
-
illustrated in Figure 3. Compound 1 shows a planar
Cl , washed with water, and dried over MgSO , and the solvent
was evaporated. The residue was recrystallized from acetonitrile
(300 mL) to give pure 1 as violet needles (525 mg, 69%).
2
4
structure, while 3 is not planar as revealed by an X-ray
analysis.2c
Concentration of the filtrate afforded additional 1 (76 mg,
F u r a n -F u sed DCNQI. N,N′-Dicyano-p-quinodiimine
1
1
0%): mp > 260 °C (dec); H NMR (CDCl
3
) δ 7.95 (d, J ) 2.2
(
DCNQI) derivative 2 was prepared by TiCl
4
-mediated
-1
Hz, 2H), 7.77 (d, J ) 2.2 Hz, 2H); IR (KBr) 2224 (CtN) cm
MS m/z 248 (M ); UV/vis (CH
326 (4.0), 248 (4.3) nm. Anal. Calcd for C16
;
1
4
+
cyanoimination of precursor quinone 9 in 45% yield.
2
Cl
2
) λmax (log ꢀ) 436 (4.7), 416 (4.6),
Pure 2 was isolated by recrystallization of the crude
4 4 2
H N O
: C, 67.61; H,
1
1.42; N, 19.71. Found: C, 67.46; H, 1.71; N, 19.81.
N ,N ′-D ic y a n o b e n zo [1,2-b :4,5-b ]d ifu r a n -4,8-d io n e d i-
im in e (2). To a solution of quinone 9 (200 mg, 1.1 mmol) in dry
products from acetonitrile. The H NMR spectrum of 2
at room temperature occurs between 7.0 and 7.9 ppm as
broad signals and exhibited temperature dependence,
indicating that the configurational isomers due to the
dN-CN inversion are involved in fast equilibrium.1
The redox potentials of 2 as measured by cyclic
voltammetry are listed in Table 1. In the DCNQI series
CH
2 2 4
Cl (50 mL) at 0 °C were added successively TiCl (1.1 mL,
1
1 mmol) and bis(trimethylsilyl)carbodiimide (3.0 mL, 11 mmol).
4b
The mixture was refluxed for 15 h. The reaction mixture was
cooled to room temperature and poured onto ice. The organic
layer was extracted three times with CH
and dried over MgSO , and the solvent was evaporated. The
residue was recrystallized from CH CN to give pure 2 as a violet
powder (114 mg, 45%): mp > 215 °C (dec); H NMR (CDCl
2 2
Cl , washed with water,
4
2
, 4, and 6, the furan derivative exhibits again the
3
highest electron acceptability. We were interested in
determining if 2 forms a coordination polymer with CuI,
as realized in thiophene analogue 4.1 However, this type
of polymer was not obtained for 2.
1
3
+
)
-1
δ 7.0-7.9 (m); IR (KBr) 2173 (CtN) cm ; MS m/z 236 (M );
UV/vis (CH Cl ) λmax (log ꢀ) 388 (4.4), 372 (4.4), 310 (4.1), 239
4.3) nm. Anal. Calcd for C12 : C, 61.02; H, 1.71; N, 23.72.
Found: C, 60.81; H, 1.96; N, 23.46.
5
2
2
(
4 4 2
H N O
X-r a y Cr ysta llogr a p h ic Stu d y of (1) (BEDTTTF ). Inten-
sity data were collected on a Rigaku RAXIS-IV imaging plate
system using graphite-monochromated Mo KR irradiation (λ )
Exp er im en ta l Section
Gen er a l Meth od s. 1H NMR and 13C NMR spectra were
obtained at 500 and 126 MHz, respectively, with samples
0
.71069 Å). The structure was solved by a direct method using
1
6
the program SIR 88. The acceptor molecules show an orien-
tational disorder with respect to the pseudo symmetry of mm.
The carbon and oxygen atoms at the peri-positions of the
benzoquinonoid framework were treated to be disordered. The
atomic positions and isotropic temperature factors of the disor-
dered atoms were fixed. The hydrogen atoms were located from
calculations. All the atoms except for the disordered atoms and
hydrogen atoms were refined anisotropically. The occupancy
factors for disordered structures were refined to be 0.58:0.42.
dissolved in CDCl
impact at 70 eV. All solvents (benzene, diethyl ether, DMF, and
CH Cl ) were purified by using normal methods. Reactions were
carried out under a dry, N atmosphere.
-Dieth ylca r ba m oylfu r a n (8). A mixture of 3-furoic acid 7
25.1 g, 0.224 mol) and thionyl chloride (65.3 mL, 0.90 mol) was
refluxed for 4 h. To the reaction mixture was added dry benzene
60 mL), and the solution was distilled to remove an excess of
3
. Mass spectra were measured under electron
2
2
2
3
(
(
thionyl chloride: the treatment with benzene was repeated
twice. The resulting mixture was added dropwise to a solution
Crystal data for (C10
H
8
S
8
)(C16
H
4
N
4
O
2
): MW ) 668.89, P2
1
/n
(
9
No. 14), a ) 13.215(3) Å, b ) 13.079(3) Å, c ) 7.828(1) Å, â )
of diethylamine (92.6 mL) in dry CH
the solution was stirred at room temperature and poured into
ice water. The furan was extracted three times with CH Cl
The combined organic extracts were washed with dilute HCl and
water, successively, dried over MgSO , and evaporated. Purifica-
tion was achieved by chromatography on silica gel (elution with
:1 ethyl acetate-hexane). 8 was isolated (32.9 g, 88%) as a
2 2
Cl (100 mL) at 0 °C, and
3
-3
2.77(3)°, V ) 1351.4(4) Å , Z ) 2, D ) 1.644 g cm , crystal
c
dimensions ) 0.50 × 0.20 × 0.20 mm, 2θmax ) 55.3°, Nobs ) 4193,
2
2
.
N
R
ref[/I
o
/ > 3σ(/I
o
/)] ) 2956, no. of variables ) 172, R ) 0.080,
w
) 0.091, GOF ) 8.68.
4
Ack n ow led gm en t. This research was supported by
a Grant-in-Aid for Scientific Research on Priority Areas
No. 10146101) from the Ministry of Education, Science,
2
1
colorless oil: H NMR (CDCl
3
) δ 7.70 (dd, J ) 0.9, 1.5 Hz, 1H),
(
7
3
.41 (dd, J ) 1.5, 1.8 Hz, 1H), 6.59 (dd, J ) 0.9, 1.8 Hz, 1H),
Sports and Culture, J apan.
.48 (q, J ) 7.0 Hz, 4H), 1.22 (t, J ) 7.0 Hz, 6H).
Ben zo[1,2-b:4,5-b′]d ifu r a n -4,8-d ion e (9). To a stirred solu-
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
details, bond lengths, bond angles, positional parameters,
isotropic thermal parameters, and calculated positional
parameters for the hydrogen atoms of (1) (BEDTTTF). This
material is available free of charge via the Internet at
http://pubs.acs.org.
tion of diisopropylamine (1.76 mL, 12.6 mmol) in diethyl ether
30 mL) at 0 °C was added via syringe a solution of butyllithium
1.6 M, 7.7 mL, 12.6 mmol), and the resulting solution was
stirred for 10 min. To this generated LDA solution was added a
solution of 8 (2.00 g, 12.0 mmol) in dry diethyl ether (20 mL).
The resulting mixture was refluxed for 4 h. Then the solution
(
(
J O991438O
(
13) Stewart, J . J . P. MOPAC: A General Molecular Orbital Package
version 6.0). QCPE 1990, 10, 455.
14) (a) Aum u¨ ller, A.; H u¨ nig, S. Angew. Chem., Int. Ed. Engl. 1984,
2
1
(
(15) Takahashi, K.; Mazaki, Y.; Kobayashi, K. J . Chem. Soc., Chem.
Commun. 1996, 2275-2276.
(16) Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.;
Polidori, G.; Spagna, R.; Viterbo, D. J . Appl. Crystallogr. 1989, 22, 389.
(
3, 447-448. (b) Aum u¨ ller, A.; H u¨ nig, S. Liebigs Ann. Chem. 1986,
42-164.