Preparation, structure, and unique redox properties of mono-, bis-, and tris(diarylmethylene)-1,3,5-trithianes and related compounds

Article abstract of DOI:10.1021/jo000161l

A series of 1,3,5-trithianes 1-3 having diarylmethylene units were designed as novel electron donors giving highly colored cationic species upon oxidation. They were prepared along with the dithiane and dithiazine derivatives 4-6 by the reactions of lithiated heterocycles with diaryl ketones followed by dehydration. Voltammetric analyses indicate that a large structural change and/or transannular bonding are induced during their electrochemical oxidation. Mono(diarylmethylene) derivative 1a exhibits electrochromism with vivid change in color from faintly yellow to deep blue with concomitant rotation around the exocyclic bond. Both of the strongly colored salts obtained upon oxidation of 2,4-bis- and 2,4,6-tris(diarylmethylene)-1,3,5-trithianes (2aa and 3) consist of the dications with a 1,2,4-trithiane ring, suggesting the easy skeletal rearrangement of the transannular dications with a trithiabicylo[3.1.0]hexane ring. Upon reduction of these salts were obtained bright yellow 12 and 13, respectively, with high electron-donating properties due to the tetraarylbutadiene-type conjugation, thus giving another class of electrochromic compounds.

Full text of DOI:10.1021/jo000161l

5514
J . Org. Chem. 2000, 65, 5514-5521
P r ep a r a tion , Str u ctu r e, a n d Un iqu e Red ox P r op er ties of Mon o-,
Bis-, a n d Tr is(d ia r ylm eth ylen e)-1,3,5-tr ith ia n es
a n d Rela ted Com p ou n d s
Takanori Suzuki,* Tsuyoshi Yoshino, J un-ichi Nishida, Masakazu Ohkita, and Takashi Tsuji
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, J apan
tak@sci.hokudai.ac.jp
Received February 4, 2000
A series of 1,3,5-trithianes 1-3 having diarylmethylene units were designed as novel electron donors
giving highly colored cationic species upon oxidation. They were prepared along with the dithiane
and dithiazine derivatives 4-6 by the reactions of lithiated heterocycles with diaryl ketones followed
by dehydration. Voltammetric analyses indicate that a large structural change and/or transannular
bonding are induced during their electrochemical oxidation. Mono(diarylmethylene) derivative 1a
exhibits electrochromism with vivid change in color from faintly yellow to deep blue with concomitant
rotation around the exocyclic bond. Both of the strongly colored salts obtained upon oxidation of
2,4-bis- and 2,4,6-tris(diarylmethylene)-1,3,5-trithianes (2a a and 3) consist of the dications with a
1,2,4-trithiane ring, suggesting the easy skeletal rearrangement of the transannular dications with
a trithiabicylo[3.1.0]hexane ring. Upon reduction of these salts were obtained bright yellow 12 and
13, respectively, with high electron-donating properties due to the tetraarylbutadiene-type
conjugation, thus giving another class of electrochromic compounds.
Recently much attention has been focused on the
redox properties of novel trithiane derivatives 1-3 along
with the related heterocycles 4-6.
organic redox systems in the field of materials chemistry.
Electrochromic systems1 whose optical properties can be
controlled electrochemically are attracting special atten-
tion from the viewpoint of molecular devices or switches.2
One of the essential requirements for such systems is
vivid change in color, that could be attained when strong-
ly colored diarylmethylium units such as (p-Me2NC6H4)2C+
or (p-MeOC6H4)2C+ are formed upon electron transfer
(ET). In this connection, 9,9,10,10-tetraaryl-9,10-dihy-
drophenanthrene derivatives are of interest, which un-
dergo mesolytic C-C bond breaking to give those cat-
ionic chromophores upon oxidation.3 Large structural
changes during the interconversion are another charac-
teristic of those chromic compounds, which endow the
system with the bistability.4 On the basis of our recent
findings shown above, six-membered sulfur heterocycles
1-3 possessing diarylmethylene moieties have been
designed as novel chromic systems in the anticipation
that geometrical changes other than C-C bond fission
would be also effective in attaining the bistability.5 In
these compounds, the diarylmethylium chromophores
would be formed upon ET with concomitant transannular
bonding and/or twisting around the exo-methylene bonds.
We report here the preparation, structures, and unique
Resu lts a n d Discu ssion
P r ep a r a tion of New Don or s. Lithiation of parent
1,3,5-trithiane 7 with n-BuLi in THF followed by addition
of 4,4′-bis(dimethylamino)benzophenone gave the tertiary
alcohol 11a in nearly quantitative yield, which was
converted to olefin 1a through TsOH-catalyzed dehydra-
tion in 86% yield. By the same procedure, 1,3-dithiane
8, 5-Me-1,3,5-dihydrodithiazine 9,6 and 5-t-Bu-1,3,5-
dihydrodithiazine 107 were transformed into the corre-
sponding bis(4-(dimethylamino)phenyl)methylene deriva-
tives 4a -6a in good yields. By using 4,4′-dimethoxy-
benzophenone in place of Michler’s ketone, new donors
having p-MeOC6H4 groups, 1b and 4b-6b, were ob-
tained, respectively, from 7-10.
(1) (a) Monk, P. M. S.; Mortimer, R. J .; Rosseinsky, D. R. In
Electrochromism: Fundamentals and Applications, VHC, Weinheim,
1995. (b) Hu¨nig, S.; Kemmer, M.; Wenner, H.; Perepichka, I. F.;
Ba¨uerle, P.; Emge, A.; Gescheid, G. Chem. Eur. J . 1999, 5, 1969.
(2) Boulas, P. L.; Go´mez-Kaifer, M.; Echegoyen, L. Angew. Chem.,
Int. Ed. 1999, 37, 216.
(3) Suzuki, T.; Nishida, J .; Tsuji, T. Angew. Chem., Int. Ed. Engl.
1997, 36, 1329. Chem. Commun. 1998, 2193.
(4) Ca´rdenas, D. J .; Livoreil, A.; Sauvage, J .-P. J . Am. Chem. Soc.
1996, 118, 11980. Livoreil, A.; Dietrich-Buchecker, C. O.; Sauvage, J .-
P. J . Am. Chem. Soc. 1994, 116, 9399.
(5) Suzuki, T.; Takahashi, H.; Nishida, J .; Tsuji, T. Chem. Commun.
1998, 1331.
(6) Gunn, C.; Fevre, L.; Wood, R. J .; Fevre, L. J . Chem. Soc. 1932,
1142.
10.1021/jo000161l CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/12/2000

Mono-, Bis-, and Tris(diarylmethylene)-1,3,5-trithianes
J . Org. Chem., Vol. 65, No. 18, 2000 5515
a
Ta ble 1. Oxid a tion P oten tia ls (Eox
)
of
Mon o(d ia r ylm eth ylen e)-typ e Don or s, 1, a n d 4-6, a n d
Rela ted Heter ocycles
Y
X ) C(C6H4NMe2-p)2 X ) C(C6H4OMe-p)2
X ) H, H
S
CH2
1a +0.50 (2e), +1.17
4a +0.40 (2e), +1.16
1b +0.89 (2e)
4b +0.80 (2e)
5b +0.70b,c
7 +1.61b
8 +1.45b
NMe 5a +0.44b,c
NtBu 6a +0.32b,c
9 +1.25b,d
10 +1.20b,d
6b +0.72b,c
E/V vs SCE, 0.1 mol dm-3 Et4NClO4 in MeCN, Pt electrode,
a
scan rate 100 mV s-1
.
Irreversible waves. Values are calculated
b
as Eox ) Epa - 0.03 V. c The voltammograms show broad cathodic
d
peaks around -0.5 to -1.0 V in the return cycle. Broad anodic
waves were observed around +0.5 to +1.0 V before the distinct
peaks at +1.2 V.
F igu r e 1. Cyclic voltammograms of 1a and 4a measured in
MeCN containing 0.1 mol dm-3 Et4NClO4 (scan rate 100 mV
s-1). The narrow peak shape in the first oxidation steps
indicates 2e-transfer. The disproportionation constant (K )
[1a +•]2/[1a 0][1a 2+] ) 0.4) was calculated by analyzing the peak
shape (Ep - Ep/2 ) 36 mV).8 Exactly the same peak width was
observed when n-Bu4NBF4 or n-Bu4NPF6 (0.1 mol dm-3) was
used as a supporting electrolyte, thus showing negligible
effects of the counteranions on the disproportionation equi-
librium.
2,4-Bis(diarylmethylene)-1,3,5-trithianes 2 could be
obtained either by applying the similar three-step se-
quence (lithiation, reaction with the diaryl ketone, and
dehydration) on mono(diarylmethylene) derivatives 1 or
by starting from the direct dilithiation of trithiane 7.
Although 2a a was obtained in 12% yield by the latter
procedure after chromatographic separation, the former
method giving 2a a in 85% yield from 1a seems more
promising by considering the higher total yield as well
as the facile isolation of the product only by recrystalli-
zation. Such a stepwise synthesis is useful in preparing
the hybrid compounds 2a b having two different diaryl-
methylene units and also applicable in obtaining the tris-
(diarylmethylene) derivative 3 from 2a a .
F igu r e 2. Changes in UV-vis spectra of 1a (3 mL; 8.28 ×
10-5 mol dm-3 in MeCN containing 0.05 mol dm-3 n-Bu4NBF4)
upon constant-current electrochemical oxidation (40 µA) at 2
min intervals.
Sch em e 1
R ed ox P r op er t ies of Mon o(d ia r ylm et h ylen e)-
tr ith ia n es 1 a n d Dith ia n e Der iva tives 4. The cyclic
voltammogram of 1a shows the two pairs of reversible
enough to account for the 2e-transfer both in the type-A
and type-B dications, by rotating the Ar2C+ moiety
around the exocyclic C-C bond in the former and by the
C-S transannular bonding in the latter. Quite similar
redox behavior of the dithiane derivatives 4 (Figure 1b)
to those of 1 indicates that the bicyclic structure of type-B
is inappropriate for 12+, thus suggesting the twisted
geometry for 12+ as in the tetraarylethylene dications.9b
Spectrophotometric monitoring of the electrochemical
oxidation of 1a showed an isosbestic point at 370 nm
(Figure 2), indicating the clean and quantitative conver-
sion from faintly yellow 1a [UV-vis (MeCN) λmax 297 nm
(log ꢀ 4.48) ] to deep blue 1a 2+ (λmax ) 646 nm). It also
suggests the negligible steady-state concentration of the
intermediary cation radical 1a •+, which is consistent with
the one-wave 2e-oxidation. Under the experimental
conditions, this dication 1a 2+ is very stable with no
ox
waves. The former (E1 ) +0.50 V) corresponds to
2e-oxidation since the electric current is nearly twice
as large as the latter (Figure 1a). The second oxida-
ox
tion potential (E2 ) +1.17 V) is similar to Eox of
(p-Me2NC6H4)2CH+BF4 (+1.02 V) but not to that of
-
trithiane 7 (Table 1), indicating that the third electron
is removed from the diarylcarbenium moiety of 1a 2+. The
ox
methoxyphenyl derivative 1b (E1 ) +0.89 V) is a
weaker donor and undergoes reversible electrochemical
oxidation at higher potential than 1a (Table 1). Its
oxidation process seems also of 2e-transfer as suggested
by the narrow peak shape (Ep - Ep/2 ) 35 mV),8 although
the direct comparisons of the peak current with the next
ox
oxidation process is impossible (E2 of 1b > +1.8 V).
Facile 2e-oxidation of the small π-system like 1 sug-
gests the drastic electronic and structural change after
1e-transfer,9,10 and dications with quite different geom-
etry from the neutral state would be produced as dipicted
in Scheme 1 (Y ) S). Coulombic repulsion seems reduced
(9) (a) Nelsen, S. F.; Kessel, C. R. J . Am. Chem. Soc. 1977, 99, 2392.
Alder, R. W.; Gill, R.; Goode, N. C. Chem. Commun. 1976, 973. Asmus,
K.-D. Acc. Chem. Res. 1979, 12, 436. (b) Baenziger, N. C.; Buckles, R.
E.; Simpson, T. D. J . Am. Chem. Soc. 1967, 89, 3405. Suzuki, T.;
Shiohara, H.; Monobe, M.; Sakimura, T.; Tanaka, S.; Yamashita, Y.;
Miyashi, T. Angew. Chem., Int. Ed. Engl. 1992, 31, 455.
(7) Angiolini, L.; Duke, R. P.; J ones, R. A. Y.; Katrizky, A. R. J .
Chem. Soc., Perkin Trans. 2 1972, 674.
(8) Ep and Ep/2 denote the peak potential and half-peak potential,
respectively. Myers, R. L.; Shain, I. Anal. Chem. 1969, 41, 980.
(10) Such a 2e-process is not surprising when these systems are
considered as new examples of the violene/cyanine hybrids (ref 1b).

5516 J . Org. Chem., Vol. 65, No. 18, 2000
Suzuki et al.
Sch em e 2
indication of decomposition, thus representing a new
addition to electrochromic systems with a vivid change
in color.
Str u ctu r e a n d Red ox P r op er ties of Mon o(d ia r yl-
m eth ylen e)d ih yd r od ith ia zin e Der iva tives 5 a n d 6.
Studies on trithianes 1 and dithianes 4 lead to the
conclusion that the sulfur atom at the 5-position in 1 does
not induce the drastic changes in the redox properties of
the diarylketene dithioacetal unit. To investigate the
effects of the heteroatom at 5 position, we next studied
the dithiazine-type donors 5 which contains N(sp3) in
place of the divalent sulfur.
According to the X-ray analysis, the heterocyclic six-
membered ring of 5a adopts the chair conformation in
the solid state (Figure S1 in Supporting Information).
One aryl group makes a large dihedral angle with the
olefinic plane (73.1°) whereas the other seems to involve
π-conjugation at least in part (dihedral angle: 40.3 °).
One noteworthy feature is the fact that the N5-Me group
occupies the axial position, which is suitable for the
through-bond interaction11 between the N5 lone pair and
the p-orbital of the exomethylene unit at 2-position
(nonbonded C‚‚‚N distance, 3.20 Å). Such geometry
suggests the possible contribution of the type-B dication
(Scheme 1, Y ) N-Me) upon 2e-oxidation of 5.
In contrast to the reversible nature observed for the
trithiane derivatives 1, the voltammograms of dithiazine-
type donors 5a and 5b showed only irreversible waves
(Ep - Ep/2 ) 50 mV in both cases) although the donating
properties are comparable to 1a and 1b, respectively
(Table 1). The corresponding cathodic peaks are ambigu-
ous but appeared in the far cathodic region, suggesting
that a certain chemical process occurs after ET. Many
attempts to obtain the dication salt of 5 were unfruitful
but giving black or green intractable mixtures. By
considering the instability of azetiniums against nucleo-
philic reagents due to the easy ring-opening polymeri-
zation of the four-membered ring,12 a t-Bu group was
substituted for the Me group on N5 in 5. The redox
properties of 6a and 6b, however, were quite similar to
those of 5a and 5b, so that the t-Bu group in 6 may not
be bulky enough for the kinetic stabilization of the labile
dications. Although the N(sp3) at the 5-position in 5 and
6 was proven to determine the properties and fate of the
oxidized species, it is still ambiguous if the dication has
the type-B structure with a bicyclo[2.2.0]hexane skeleton.
In the following sections, the trithianes having the
multiple exo-methylene units such as 2 and 3 were
investigated to test the possibility that they undergo
transannular C-C bonding upon ET13,14 to form the
cationic species having a thiiran ring.
Sch em e 3
perature. Both diarylmethylene groups are sticking out
to the opposite direction to the prow (S3) and stern (C6),
and the nonbonded distance between two quaternary
carbons (C2 and C4) is only 2.78 Å. This type of geometry
seems suitable for the π-orbital interaction to give the
bicyclic dication shown as type-C in Scheme 2.
According to the voltammetric analysis, the first oxida-
tion wave of the symmetric bis(diarylmethylene)trithiane
2a a [E1ox ) +0.43 V (2e; Ep - Ep/2 ) 35 mV), E2ox ) +1.01
V (1e), E3 ) +1.19 V (1e)] is also 2e-process as in the
case of 1a having only one diarylmethylene unit. By
comparing the redox behavior with the unsymmetric
derivative 2a b [E1 ) +0.48 V (2e; Ep - Ep/2 ) 35 mV);
E2 ) +1.15 V (1e)], however, neither the twisted form
ox
ox
ox
(type-D) nor the delocalized one (type-E) is appropriate
for the structure of the dication formed upon oxidation
of 2. Thus, 2a b possessing both p-Me2NC6H4 and
p-MeOC6H4 groups shows the 2e-oxidation wave at a
similar potential to 2a a having four p-Me2NC6H4 groups.
This fact could be accounted for by assuming the involve-
ment of the transannular cation radical having the (p-
MeOC6H4)2C• unit that undergoes much easier 1e-
oxidation than 2a b (Scheme 3), thus giving the dication
with the type-C structure. This bicyclic dication is
expected to undergo further 1e-oxidation at (p-Me2-
NC6H4)2C+ unit, and the close similarity of E2 (2a b) to
ox
the oxidation potential of (p-Me2NC6H4)2CH+ is in good
agreement with this hypothesis. Furthermore, separa-
ox
ox
tion between E2 and E3 of 2a a can be also ration-
alized by assuming the type-C dication in which two (p-
Me2NC6H4)2C+ units are arranged in a close proximity
to allow the through-space π-orbital interaction between
them.
Str u ctu r e a n d Red ox P r op er ties of Bis(d ia r yl-
m eth ylen e) Der iva tives 2. The X-ray structural analy-
sis on 2a a has revealed that the heterocycle adopts the
boat conformation (Figure S2). Even when such a con-
former is dominant in solution, ring flip of the six-mem-
bered ring must be feasible because a sharp singlet was
observed at 4.13 ppm for the CH2 group at 6-position in
the 1H NMR spectrum of 2a a measured at room tem-
Upon electrochemical oxidation of 2ab [UV-vis (MeCN)
λmax 303 (log ꢀ 4.50), 255 (4.44) nm] in MeCN, two-stage
spectroscopic changes were observed, each of which shows
the isosbestic points (Figure 3). The absorption maxima
at 524 and 662 nm in the final spectrum in Figure 3b
well correspond, respectively, to those of (p-MeOC6H4)2-
CPh+ (497 nm) and (p-Me2NC6H4)2CPh+ (619 nm) mea-
sured in MeCN, suggesting the presence of two indepen-
dent chromophores as in the type-C structure. To our
regret, the final spectrum decayed gradually upon stand-
ing, suggesting the slow decomposition of the species
under the experimental conditions.
(11) Krijnen, B.; Beverloo, H. B.; Werhoeven, J . W.; Reiss, C. A.;
Goubits, K.; Heijdenrijk, D. J . Am. Chem. Soc. 1989, 111, 4433.
(12) Gibbs, C. F.; Marvel, C. S. J . Am. Chem. Soc. 1935, 57, 1137.
(13) Horner, M.; Hu¨nig, S. J . Am. Chem. Soc. 1977, 99, 6122.
Freund, W.; Hu¨nig, S. J . Org. Chem. 1987, 52, 2154.
(14) Suzuki, T.; Kondo, M.; Nakamura, T.; Fukushima, T.; Miyashi,
T. Chem. Commun. 1997, 2325.

Mono-, Bis-, and Tris(diarylmethylene)-1,3,5-trithianes
J . Org. Chem., Vol. 65, No. 18, 2000 5517
F igu r e 4. Changes in UV-vis spectra of 12 (3 mL; 3.55 ×
10-5 mol dm-3 in MeCN containing 0.05 mol dm-3 n-Bu4NBF4)
upon constant-current electrochemical oxidation (20 µA) at 1
min intervals.
Sch em e 5
F igu r e 3. Changes in UV-vis spectra of 2a b (3 mL; 1.06 ×
10-4 mol dm-3 in MeCN containing 0.05 mol dm-3 n-Bu4NBF4)
upon constant-current electrochemical oxidation (40 µA): (a)
first stage, changes at 3 min intervals, isosbestic point at 375
nm; (b) second stage, changes at 6 min intervals, isosbestic
points at 344 and 272 nm.
of I2,16 whose structure was unambiguously determined
by X-ray analysis (Figure S3).
Although the conformation of the six-membered het-
erocycle in 122+ is not so clear due to the disorder at S2
and C3, it is evident that the C5dC6 moiety is completely
planer with the largest deviation of 0.02 Å from the least-
squares plane. With this olefinic plane, two diarylmethy-
lium units make the dihedral angles of 62.2 and 62.7°,
thus the steric repulsion among the four aryl groups is
relieved by rotation around the C+-Colefin bonds. Upon
reduction with Zn, 122+(SbCl6-)2 salt was transformed
to the neutral diene 12 in 78% yield, whose geometry is
quite different from the dicationic precursor (Scheme 5).
Based on the solid-state structure determined by X-ray
analysis (Figure S4), it is evident that neutral 12 suffers
from much severe steric hindrance. The torsion angle for
the CdC-CdC unit is as large as 51.0°, and the two
inner aryl groups are forced to stack in a face-to-face
manner (dihedral angle 16.9°; interplanar distance 3.42
Å). Due to such conformational restriction, four aryl
groups resonate at different chemical shifts in the 1H
NMR spectrum.
Sch em e 4
Because of such instability, attempts to isolate the
type-C dication salt by oxidation of 2a a did not give the
bicyclic one. Instead the monocyclic isomer 122+ having
a 1,2,4-trithiane-5-ene skeleton was obtained, whose
production is reasonably accounted for by the rearrange-
ment of the type-C dication (Scheme 4).15 Thus, the black
crystalline solid having the experimental formula equiva-
lent to the sum of 2a a and twice of SbCl6- was obtained
in 96% yield by the reaction of 2a a with 2 equiv of (p-
Upon treatment of 12 with 2 equiv of (p-BrC6H4)3N+•
-
SbCl6-, the dication salt 122+(SbCl6-)2 was isolated in
85% yield. The novel redox pair of 12 [UV-vis (MeCN)
λ
max 394 sh (log ꢀ 3.95), 310 (4.62), 276 sh (4.49) nm] and
122+ [677 (4.64), 593 sh (4.63), 561 (4.68), 434 (4.09), 303
(4.38), 265 (4.46) nm] can be also interconverted electro-
chemically with the drastic spectral change as shown in
Figure 4, and the presence of an isosbestic point at 400
1
BrC6H4)3N+•SbCl6-. In the H NMR spectrum of the salt,
all the protons are less shielded than those of neutral
2a a in accord with the presence of two positive charges
on the molecule [δ ppm (CD3CN): 6.99 (4H, AA′XX′), 6.92
(4H, AA′XX′), 6.69 (4H, AA′XX′), 6.48 (4H, AA′XX′), 4.16
(2H, s), 2.93 (12H, s), 2.86 (12H, s) for 2a a ; 7.32 (4H,
AA′XX′), 7.26 (4H, AA′XX′), 6.81 (4H, AA′XX′), 6.79 (4H,
AA′XX′), 4.90 (2H, s), 3.23 (12H, s), 3.21 (12H, s) for the
salt 122+(SbCl6-)2 ]. The salt 122+(I3-)2 showing the same
NMR was obtained by the reaction of 2a a with 3 equiv
ox
nm is in accord with the one-wave 2e-oxidation of 12 [E1
) +0.18 V (2e), E2ox ) +1.11 V (2e)]. This is another new
entry into the electrochromic system exhibiting large
structural change upon ET.
(16) Oxidation of 2a a with iodine formed a small amount (10-20%)
of another kind of cationic species [δ ppm (CD3CN): ca. 7.32 (8H, br
AA′XX′), 6.78 (8H, AA′XX′), 5.04 (2H, s), 3.22 (24H, s)] which is difficult
to isolate. Its proportion against 122+ varied during the dissolution
and crystallization process. Because the combustion analysis of the
(15) Under the EI-MS conditions, 2,4,6-triphenyl-1,3,5-trithiane
was reported to undergo skeletal rearrangement by S‚‚‚S bonding:
Chattopadhyaya, J . B.; Rao, A. V. R. Org. Mass Spectrom. 1974, 9,
649.
mixture gave satisfactory values for C37H42N4S3I6, it seems that this
compound is the interconvertible isomer of 122+(I3
) although its
2
-
structure is still ambiguous.

5518 J . Org. Chem., Vol. 65, No. 18, 2000
Suzuki et al.
Sch em e 6
if any, to prevent the skeletal rearrangement from
trithiabicyclo[3.1.0]hexane to 1,2,4-trithian-5-ene. Upon
reduction of the deeply colored salt was obtained the new
triene 13 (E1 ) +0.11 V), which exhibits very strong
electron-donating properties such as 12.
ox
Con clu sion
In this work, we have investigated the redox properties
of cyclic dithioacetal-type compounds substituted with the
electron-donating aryl groups. It is evident that sulfur
atoms at the vinyl positions play an important role in
stabilizing oxidized species by delocalization.19 At the
same time, however, they induce deterioration of the
charged species by skeletal rearrangement, thus prevent-
ing reversible interconversion between the neutral donors
and the transannular dications in the cases of 2 and 3.
Yet, we have successfully constructed the reversible redox
pairs (1 and 12+; 12 and 122+) that exhibit electrochro-
micity with a vivid change in color (faintly or bright
yellow to deep blue). According to their electrochemical
and crystallographic studies, large structural changes by
twisting around exocyclic bond(s) occur upon ET in these
systems. Introduction of proper substituents as well as
application of the modern technology of surface manipu-
lation to the presented motif would lead to the production
of novel materials for electrochemical sensing. Studies
in this vein are now under way.
R ed ox P r op er t ies of Tr is(d ia r ylm et h ylen e)t r i-
th ia n e 3. Electron donors having 3-fold symmetry17 like
3 have attracted considerable attention in the field of
molecular magnetism due to the possibility of triplet
dication formation. In the present case, however, oxida-
tion of 3 will not result in such an open-shell species
because transannular bonding is expected as in the case
of 2 (type-F, Scheme 6). X-ray analysis on 3 has revealed
that the nonbonded distances between quaternary car-
bons of the trithiane ring are 2.70, 2.73, and 2.75 Å,
which are slightly shorter than that in 2. Although
crystalline 3 does not adopt C3-symmetric geometry but
rather a twist conformation with pseudo-C2 symmetry
(Figure S5), all of the aryl groups are equivalent in the
1H NMR spectrum. On the basis of the conformational
flexibility of 3, there is a possibility of rapid equilibrium
between three degenerated dicationic species, so that the
two positive charges could be equally distributed over the
three diarylmethylene moieties (type-G).
Exp er im en ta l Section
P r ep a r a tion of Mon o(d ia r ylm eth ylen e)-typ e Don or s
(1, 4, 5, a n d 6). To a colorless suspension of trithiane 7 (690
mg, 5.0 mmol) in dry THF (23 mL) was added dropwise n-BuLi
(1.59 mol dm-3 in n-hexane, 3.14 mL, 5.0 mmol) at -78 °C
under Ar. After being stirred for 2.5 h at -78 °C, the mixture
was allowed to warm to -20 °C and kept at this temperature
for 2 h. Then, to the resultant solution of 2-lithio-1,3,5-trithiane
was added a suspension of 4,4′-bis(dimethylamino)benzophe-
none (1.34 g, 5.0 mmol) in 20 mL of dry THF at -78 °C and.
The whole mixture was allowed to warm to the ambient
temperature. After addition of 0.1 mL of water and evaporation
of solvent, the remaining solid was suspended in water and
extracted with CHCl3. The organic layer was washed with
brine and dried over Na2SO4. Pale tan solid of crude alcohol
11a (2.22 g) was obtained by evaporation of the solvent, which
can be directly used for the further transformation.
According to the voltammetric analysis, 3 undergoes
two-stage electrochemical oxidation [E1ox ) +0.35 V (2e;
ox
Ep - Ep/2 ) 30 mV), E2 ) +0.72 (1e, irrev) V].18 The
first 2e-oxidation process is closely related to that of 2,
indicating transannular bonding in the dication. To
investigate the possibile contribution from the type-G
structure for the dication, 3 was subjected to oxidation
1
with (p-BrC6H4)3N+•SbCl6-. In the H NMR spectrum of
the salt, peaks in the aromatic region are broadened
probably due to the restricted conformational behavior,
thus being noninformative about the structure. Reso-
nances for 12 Me groups appear around 3.2 and 3.0 ppm
in a 2:1 ratio, which are assigned to Ar2C+ moieties and
neutral Ar groups, respectively. The latter is split into
two singlets, suggesting the lower symmetry of the
species than expected for the type-F or type-G dication,
and the rearranged sturucture 132+ seems most suitable
for the isolated salt. Thus, the stabilization by charge
delocalization in the type-G structure may not be enough,
To a solution of 11a in benzene (80 mL) was added a
catalytic amount of TsOH (10 mg). After refluxing for 1 h, the
mixture was washed with water and brine and dried over
Na2SO4. Evaporation of the solvent gave 1.99 g of yellow solid
which was purified by recrystallization from benzene-EtOH.
Pure 2-[bis(4-dimethylaminophenyl)methylene]trithiane 1a
(1.68 g) was obtained as yellow crystals in 86% yield over two
1
steps from 7. Data of 1a : mp 198.5-199.5 °C; H NMR (400
MHz, CDCl3) δ/ppm 7.03 (4H, AA′XX′), 6.65 (4H, AA′XX′), 4.09
(4H, s), 2.96 (12H, s); IR (KBr) 1606, 1520, 1444 cm-1; EI-MS
m/z (relative intensity) 388 (M+, 67), 296 (100), 126 (16); UV-
vis (see text). Anal. Calcd for C20H24N2S3: C, 61.81; H, 6.22;
N, 7.21; S, 24.75. Found: C, 61.78; H, 6.25; N, 7.05; S, 24.54.
11a : colorless crystals (CHCl3); mp 184.0-184.5 °C; 1H NMR
(400 MHz, CDCl3) δ/ppm 7.35 (4H, AA′XX′), 6.66 (4H, AA′XX′),
5.08 (1H, s), 4.26 (2H, d, J ) 14.4 Hz), 4.00 (2H, d, J ) 14.4
(17) Schumaker, R. R.; Rajeswari, S.; J oshi, M. V.; Cava, M. P.;
Takassi, M. A.; Metzgar, R. M. J . Am. Chem. Soc. 1989, 111, 308.
Fourmigue´, M.; J ohannsen, I.; Boubekeur, K.; Nelson, C.; Batail, P. J .
Am. Chem. Soc. 1993, 115, 3752.
Hz), 3.10 (1H, s), 2.93 (12H, s); IR (KBr) 3456, 1614, 1522 cm-1
;
(18) The numbers of electron involved in each process are tentative.
ox
ox
Although the current ratio of E1 and E2 is nearly 2:1, there is a
possibility that four and two electrons are concerned in each process.
However, such a possibility was rejected by the measurement con-
(19) Oxidation of 4-(diarylmethylene)-2,3,5,6-tetrahydrothiopyran
gave the diarylcarbenium derivative substituted with 4-thiacyclohex-
ene ring, whose formation is reasonably accounted for by decomposition
of the resulted dication by deprotonation at C3: (the late) Tatsuo
Nakamura, Graduate Thesis at the Department of Chemistry, Faculty
of Science, Tohoku University, 1995.
red
ducted under the presence of 1 equiv of anthraquinone [E1 ) -0.93
V (1e), E2red ) -1.53 V (1e)] as an internal standard. The current ratio
for E1ox(3) and E1red(AQ) is 1.74, indicating that the 4e-oxidation of 3
in the first process is unlikely.

Mono-, Bis-, and Tris(diarylmethylene)-1,3,5-trithianes
J . Org. Chem., Vol. 65, No. 18, 2000 5519
FD-MS m/z 406 (M+). Anal. Calcd for C20H26ON2S3: C, 59.07;
H, 6.46; N, 6.89; S, 23.66. Found: C, 58.82; H, 6.41; N, 6.87;
S, 23.59.
°C; 1H NMR (400 MHz, CDCl3) δ/ppm 7.15 (4H, AA′XX′), 6.84
(4H, AA′XX′), 4.35 (4H, s), 3.80 (6H, s), 2.73 (3H, s); IR (KBr)
1606, 1510, 1244 cm-1; EI-MS m/z (relative intensity) 359 (M+,
11), 270 (100), 255 (33), 113 (7). Anal. Calcd for C19H21O2NS2:
C, 63.48; H, 5.89; N, 3.90; S, 17.84. Found: C, 63.54; H, 6.03;
N, 3.80; S, 18.00. 6b: yield 56%; pale brown crystals (acetone);
1
mp 138.8-142.2 °C; H NMR (400 MHz, CDCl3) δ/ppm 7.14
(4H, AA′XX′), 6.84 (4H, AA′XX′), 4.47 (4H, s), 3.80 (6H, s), 1.29
(9H, s); IR (KBr) 1606, 1510, 1248 cm-1; EI-MS m/z (relative
intensity) 401 (M+, 16), 270 (100), 255 (18). Anal. Calcd for
C
22H27O2NS2: C, 65.79; H, 6.78; N, 3.49; S, 15.97. Found: C,
65.83; H, 6.84; N, 3.26; S, 15.98. 11b: yield 31%; colorless
crystals (CHCl3); mp 145.5-147.1 °C; 1H NMR (400 MHz,
CDCl3) δ/ppm 7.42 (4H, AA′XX′), 6.85 (4H, AA′XX′), 5.10 (1H,
s), 4.26 (2H, d, J ) 14.7 Hz), 4.01 (2H, d, J ) 14.7 Hz), 3.78
Other 2-[bis(4-dimethylaminophenyl)methylene] derivatives
(4a , 5a , and 6a ) were prepared similarly by the two-step
procedure starting from 1,3-dithiane 8, 5-methyldihydro-1,3,5-
dithiazine 9, and 5-(2,2-dimethylpropyl)dihydro-1,3,5-dithi-
azine 10, respectively, in place of trithiane 7. Intermediary
alcohols (14a , 15a , and 16a ) were purified by recrystallization.
Data of 4a : yield 97%; yellow crystals (benzene); mp 215.5-
217.0 °C; 1H NMR (400 MHz, CDCl3) δ/ppm 7.08 (4H, AA′XX′),
6.65 (4H, AA′XX′), 2.95 (12H, s), 2.93 (4H, t, J ) 6.3 Hz), 2.12
(2H, quint, J ) 6.3 Hz); IR (KBr) 1608, 1520, 1446 cm-1; FD-
MS m/z 370 (M+). Anal. Calcd for C21H26N2S2: C, 68.06; H,
7.07; N, 7.56; S, 17.30. Found: C, 68.16; H, 7.13; N, 7.46; S,
17.46; 5a : yield 87%; pale yellow crystals (benzene); mp
(6H, s), 3.24 (1H, s); IR (KBr) 3460, 1608, 1512, 1252 cm-1
;
FD-MS m/z 380 (M+). Anal. Calcd for C18H20O3S3: C, 56.81;
H, 5.30; S, 25.28. Found: C, 56.94; H, 5.29; S, 25.14. 14b: yield
77%; colorless crystals (CHCl3); mp 169.2-171.5 °C; 1H NMR
(400 MHz, CDCl3) δ/ppm 7.46 (4H, AA′XX′), 6.84 (4H, AA′XX′),
5.05 (1H, s), 3.78 (6H, s), 3.22 (1H, s), 2.86-2.90 (4H, m), 2.05-
2.10 (1H, m), 1.78-1.90 (1H, m); IR (KBr) 3484, 1608, 1512,
1250 cm-1; FD-MS m/z 362 (M+). Anal. Calcd for C19H22O3S:
C, 62.95; H, 6.12; S, 17.69. Found: C, 63.15; H, 6.20; S, 17.73.
15b: yield 87%; colorless crystals (CHCl3); mp 142.0-142.5
°C; 1H NMR (400 MHz, CDCl3) δ/ppm 7.46 (4H, AA′XX′), 6.85
(4H, AA′XX′), 5.21 (1H, s), 4.69 (2H, d, J ) 13.2 Hz), 4.10 (2H,
d, J ) 13.2 Hz), 3.77 (6H, s), 3.18 (1H, s), 2.55 (3H, s); IR (KBr)
3500, 1610, 1512, 1250 cm-1; FD-MS m/z 377 (M+). Anal. Calcd
for C19H23O3NS2: C, 60.45; H, 6.14; N, 3.71; S, 16.99. Found:
C, 60.48; H, 6.18; N, 3.60; S, 17.16. 16b: yield 81%; colorless
crystals (CHCl3); mp 159.7-160.0 °C; 1H NMR (400 MHz,
CDCl3) δ/ppm 7.47 (4H, AA′XX′), 6.84 (4H, AA′XX′), 5.35 (1H,
s), 4.63 (2H, d, J ) 13.2 Hz), 4.51 (2H, d, J ) 13.2 Hz), 3.77
(6H, s), 3.21 (1H, s), 1.31 (9H, s); IR (KBr) 3432, 1614, 1510,
1250 cm-1; FD-MS m/z 419 (M+). Anal. Calcd for C22H29O3-
NS2: C, 62.97; H, 6.97; N, 3.34; S, 15.28. Found: C, 62.84; H,
6.94; N, 3.23; S,15.35.
P r ep a r a t ion of Bis- a n d Tr is(d ia r ylm et h ylen e)-t yp e
Don or s (2 a n d 3). To a solution of 1a (776 mg, 2.0 mmol) in
dry THF (25 mL) was added dropwise n-BuLi (1.53 mol dm-3
in n-hexane, 1.31 mL, 2.0 mmol) at -78 °C under Ar. Then,
the mixture was allowed to warm to -20 °C and kept at this
temperature for 2 h. To the resultant pale yellow suspension
was added a suspension of 4,4′-bis(dimethylamino)benzophe-
none (536 mg, 2.0 mmol) in 15 mL of dry THF at -20 °C. The
whole mixture was gradually warmed to the ambient temper-
ature during 4 h. After addition of 0.1 mL of water and
evaporation of solvent, the remaining solid was suspended in
water and extracted with CHCl3. The organic layer was
washed with brine and dried over Na2SO4. Yellow solid of the
alcohol (1.58 g) was directly used for the further transforma-
tion.
1
201.0-202.0 °C; H NMR (400 MHz, CDCl3) δ/ppm 7.11 (4H,
AA′XX′), 6.64 (4H, AA′XX′), 4.35 (4H, s), 2.95 (12H, s), 2.74
(3H, s); IR (KBr) 1608, 1520, 1352 cm-1; EI-MS m/z (relative
intensity) 385 (M+, 21), 353 (21), 296 (100), 126 (10). Anal.
Calcd for C21H27N3S2: C, 65.41; H, 7.06; N, 10.90; S, 16.63.
Found: C, 65.42; H, 7.15; N, 10.72; S, 16.61; 6a : yield 91%;
1
yellow crystals (acetone); mp 183.3-184.4 °C; H NMR (400
MHz, CDCl3) δ/ppm 7.09 (4H, AA′XX′), 6.65 (4H, AA′XX′), 4.46
(4H, s), 2.94 (12H, s), 1.29 (9H, s); IR (KBr) 1608, 1522, 1350
cm-1; EI-MS m/z (relative intensity) 427 (M+, 12), 395 (18),
296 (100), 126 (7). Anal. Calcd for C24H33N3S2: C, 67.40; H,
7.78; N, 9.83; S, 14.99. Found: C, 67.29; H, 7.75; N, 9.77; S,
15.04; 14a : yield 77%; pale greenish crystals (CHCl3); mp
1
216.0-217.2 °C; H NMR (400 MHz, CDCl3) δ/ppm 7.40 (4H,
AA′XX′), 6.66 (4H, AA′XX′), 5.03 (1H, s), 3.09 (1H, s), 2.92
(12H, s), 2.82-2.89 (4H, m), 2.04-2.09 (1H, m), 1.81-1.88 (1H,
m); IR (KBr) 3504, 1616, 1524, 1448 cm-1; FD-MS m/z 388
(M+). Anal. Calcd for C21H28ON2S2: C, 64.91; H, 7.26; N, 7.21;
S, 16.50. Found: C, 64.80; H, 7.27; N, 7.05; S, 16.61; 15a : yield
1
81%; faintly brown crystals (CHCl3); mp 183.2-184.5 °C; H
NMR (400 MHz, CDCl3) δ/ppm 7.40 (4H, AA′XX′), 6.67 (4H,
AA′XX′), 5.19 (1H, s), 4.68 (2H, d, J ) 12.9 Hz), 4.09 (2H, d, J
) 12.9 Hz), 3.06 (1H, s), 2.92 (12H, s), 2.56 (3H, s); IR (KBr)
3504, 1614, 1520, 1350 cm-1; FD-MS m/z 403 (M+). Anal. Calcd
for C21H29ON3S2: C, 62.49; H, 7.24; N, 10.41; S, 15.89. Found:
C, 62.30; H, 7.24; N, 10.22; S, 15.83. 16a : yield 78%; colorless
crystals (CHCl3); mp 174.8-175.6 °C; 1H NMR (400 MHz,
CDCl3) δ/ppm 7.40 (4H, AA′XX′), 6.65 (4H, AA′XX′), 5.32 (1H,
s), 4.61 (2H, d, J ) 13.2 Hz), 4.49 (2H, d, J ) 13.2 Hz), 3.10
(1H, s), 2.91 (12H, s), 1.30 (9H, s); IR (KBr) 3432, 1614, 1522,
To a solution of the crude alcohol in benzene (60 mL) was
added a catalytic amount of TsOH (5 mg). After refluxing for
1 h, the mixture was washed with water and brine and dried
over Na2SO4. Evaporation of the solvent gave 1.54 g of yellow
solid which was purified by recrystallization from acetone to
give yellow crystals of pure 2a a (1.08 g) in 85% yield over two
1350 cm-1; FD-MS m/z 445 (M+). Anal. Calcd for C24H35
-
ON3S2: C, 64.68; H, 7.92; N, 9.43; S, 14.41. Found: C, 64.55;
H, 7.87; N, 9.43; S, 14.55.
2-[Bis(4-methoxyphenyl)methylene] derivatives (1b, 4b, 5b,
and 6b) were also prepared by the reactions of heterocycles
7-10 with 4,4′-dimethoxybenzophenone via alcohols 11b, 14b,
15b, and 16b. Data of 1b: yield 85%; colorless crystals
(benzene); mp 154.2-155.0 °C; 1H NMR (400 MHz, CDCl3)
δ/ppm 7.08 (4H, AA′XX′), 6.86 (4H, AA′XX′), 4.09 (4H, s), 3.81
(6H, s); IR (KBr) 1604, 1510, 1250 cm-1; EI-MS m/z (relative
intensity) 362 (M+, 68), 270 (100), 255 (19), 113 (15); UV-vis
(MeCN) λmax 300 (log ꢀ 4.04), 255 (4.15) nm. Anal. Calcd for
1
steps. Data of 2a a : mp 230.0-233.0 °C; H NMR (400 MHz,
CDCl3) δ/ppm 7.13 (4H, AA′XX′), 7.02 (4H, AA′XX′), 6.67 (4H,
AA′XX′), 6.42 (4H, AA′XX′), 4.13 (2H, s), 2.96 (12H, s), 2.87
(12H, s); IR (KBr) 1608, 1520, 1356 cm-1; EI-MS m/z (relative
intensity) 638 (M+, 10), 388 (29), 296 (100), 126 (18); UV-vis
(MeCN) λmax 358 sh (log ꢀ 4.38), 309 (4.69) nm. Anal. Calcd
for C37H42N4S3: C, 69.55; H, 6.63; N, 8,77; S, 15.05. Found:
C, 69.29; H, 6.65; N, 8.51; S, 15.12.
C
18H18O2S3: C, 59.63; H, 5.00; S, 26.53. Found: C, 59.43; H,
By the reaction with 4,4′-dimethoxybenzophenone, the
similar procedure gave the unsymmetrically substituted bis-
(diarylmethylene) derivative 2a b in 65% yield from 1a . Tris-
(diarylmethylene) derivative 3 was obtained in the similar way
from 2a a and 4,4′-bis(dimethylamino)benzophenone in 54%
yield, and t-BuLi was proven more effective than n-BuLi in
the lithiation of 2a a . Data of 2a b: mp 109.2-113.5 °C
(acetone); 1H NMR (400 MHz, CDCl3) δ/ppm 7.19 (2H, AA′XX′),
4.99; S, 26.58; 4b: yield 91%; colorless crystals (benzene); mp
1
132.5-133.5 °C; H NMR (400 MHz, CDCl3) δ/ppm 7.12 (4H,
AA′XX′), 6.85 (4H, AA′XX′), 3.80 (6H, s), 2.95 (4H, t, J ) 6.3
Hz), 2.13 (2H, quint, J ) 6.3 Hz); IR (KBr) 1606, 1508, 1248
cm-1; FD-MS m/z 344 (M+). Anal. Calcd for C19H20O2S2: C,
66.24; H, 5.85; S, 18.61. Found: C, 66.17; H, 5.95; S, 18.83;
5b: yield 86%; colorless crystals (benzene); mp 159.0-160.0

5520 J . Org. Chem., Vol. 65, No. 18, 2000
Suzuki et al.
7.13 (2H, AA′XX′), 7.04 (2H, AA′XX′), 6.97 (2H, AA′XX′), 6.87
(2H, AA′XX′), 6.66 (2H, AA′XX′), 6.63 (2H, AA′XX′), 6.39 (2H,
AA′XX′), 4.14 (2H, s), 3.81 (3H, s), 3.72 (3H, s), 2.96 (6H, s),
2,88 (6H, s); IR (KBr) 1606, 1510, 1356, 1246 cm-1; EI-MS m/z
(relative intensity) 612 (M+, 93), 296 (100), 252 (16); UV-vis
(see text). Anal. Calcd for C35H36N2O2S3: C, 68.59; H, 5.92; N,
4.57; S, 15.70. Found: C, 68.75; H, 5.87; N, 4.52; S, 15.76; 3:
mp 295.2-298.5 °C (acetone-CH2Cl2); 1H NMR (400 MHz,
CDCl3) δ/ppm 7.09 (12H, AA′XX′), 6.53 (12H, AA′XX′), 2.92
(36H, s); IR (KBr) 1608, 1520, 1354 cm-1; FD-MS m/z 888 (M+);
UV-vis (MeCN) λmax 390 (log ꢀ 4.53), 314 (4.83), 282 sh (4.78)
nm. Anal. Calcd for C54H60N6S3: C, 72.93; H, 6.80; N, 9.45; S,
10.82. Found: C, 72.88; H, 6.90; N, 9.33; S, 10.75.
upon reduction with Zn (vide infra), yet it showed a slightly
different 1H NMR spectrum: (300 MHz, CD3CN) 7.48-7.22
(ca. 14H, m), 6.81-6.79 (ca. 10H, m), 3.23 (12H, s), 3.22 (12H,
s), 3.12 (6H, s), 3.06 (6H, s).
Red u ction of Dica tion Sa lt 132+(SbCl6-)2. To a suspen-
sion of 132+(SbCl6-)2 (59 mg, 0.038 mmol) in CH3CN (15 mL)
was added large excess of activated Zn powder (222 mg, 3.39
mmol) and stirred vigorously for 3 h. The mixture was added
water and extracted with benzene. The organic layer was
washed with brine and dried over Na2SO4. Evaporation of
solvent gave orange crystals of 13 (32 mg) in 96% yield: mp
165-200 °C (dec); 1H NMR (400 MHz, CDCl3) δ/ppm 7.06 (2H,
AA′XX′), 7.04 (2H, AA′XX′), 6.97 (2H, AA′XX′), 6.95 (2H,
AA′XX′), 6.86 (2H, AA′XX′), 6.67 (2H, AA′XX′), 6.61 (2H,
AA′XX′), 6.59 (2H, AA′XX′), 6.56 (2H, AA′XX′), 6.52 (4H,
AA′XX′), 6.42 (2H, AA′XX′), 2.97 (6H, s), 2.95 (6H, s), 2.92 (6H,
s), 2.92 (6H, s), 2.91, (6H, s), 2.84 (6H, s); IR (KBr) 1608, 1520,
1354 cm-1; FD-MS m/z 888 (M+). Anal. Calcd for C54H60N6S3:
C, 72.93; H, 6.80; N, 9.45; S, 10.82. Found: C, 72.65; H, 6.92;
N, 9.23; S, 10.63.
Oxid a tion of Bis(d ia r ylm eth ylen e)tr ith ia n e 2a a . To a
-
suspension of (p-BrC6H4)3N+•SbCl6 (571 mg, 0.700 mmol) in
dry CH2Cl2 (18 mL) was added a yellow solution of 2a a (223
mg, 0.350 mmol) in dry CH2Cl2 (10 mL) under Ar. After the
deep purple mixture containing black tarry material was
stirred for 2 d, the resulting crystalline solid of 122+(SbCl6
)
2
-
(437 mg) was filtered (yield 96%): mp > 300 °C; 1H NMR (see
text); IR (KBr) 1580, 1372,1170 cm-1; FAB-MS m/z (relative
intensity) 638 (M+, 62), 560 (51), 528 (100), 264 (35), 136 (71);
UV-vis (see text). Anal. Calcd for C37H42N4S3Sb2Cl12‚H2O: C,
33.51; H, 3.35; N, 4.23; S, 7.25; Cl, 32.09. Found: C, 33.30; H,
3.24; N, 4.24; S, 7.43; Cl, 32.04.
Red ox P oten tia ls a n d Sp ectr oelectr och em ica l Mea -
su r em en ts. Oxidation potentials (Eox) were measured by cyclic
voltammetry in dry MeCN containing 0.1 mol dm-3 Et4NClO4
as a supporting electrolyte unless otherwise noted. Ferrocene
undergoes 1e-oxidation at +0.38 V under the same conditions.
All of the values shown in the text are in E/V vs SCE. A Pt
disk electrode (diameter, 1.6 mm) and a Pt wire electrode were
used as working and counter electrodes, respectively. The
working electrode was polished using a water suspension of
Al2O3 (0.05 µm) before use. In the case of irreversible waves,
half-wave potentials were estimated from the anodic peak
potentials (Epa) as Eox ) Epa -0.03 V.
Spectroelectrochemical measurements were carried out in
a quartz cell (10 × 10 × 40 mm) equipped with a Pt mesh as
a working electrode and a salt bridge. A Pt wire was placed in
the latter as a counter electrode. Electrical current was
monitored by a microampere meter.
Similar oxidation by using iodine (3 equiv) in place of the
aminium salt gave black crystalline solid of 122+(I3
)
salt16
-
2
in 82% yield: mp > 300 °C; 1H NMR (400 MHz, CD3CN) δ/ppm
7.32 (4H, AA′XX′), 7.27 (4H, AA′XX′), 6.81 (4H, AA′XX′), 6.80
(4H, AA′XX′), 4.91 (2H, s), 3.23 (12H, s), 3.21 (12H, s); IR (KBr)
1580, 1368, 1166 cm-1; FAB-MS m/z (relative intensity) 638
(M+, 1), 358 (18), 307 (13). Anal. Calcd for C37H42N4S3I6: C,
31.73; H, 3.02; N, 4.00; S, 6.87; I, 54.37. Found: C, 31.95; H,
3.10; N, 3.93; S, 6.71; I, 54.18.
-
In ter con ver sion betw een Dica tion Sa lt 122+(SbCl6
)
2
a n d Neu tr a l Dien e 12. To a suspension of 122+(SbCl6-)2 (300
mg, 0.230 mmol) in CH3CN (40 mL) was added large excess
of activated Zn powder (625 mg, 9.56 mmol) and stirred
vigorously for 12 h. The mixture was added water and
extracted with benzene. The organic layer was washed with
brine and dried over Na2SO4. Evaporation of solvent and
recrystallization from acetone-CH2Cl2 gave red crystals of 12
(115 mg) in 78% yield: mp 163.5-167.0 °C; 1H NMR (400
MHz, CDCl3) δ/ppm 6.97 (2H, AA′XX′), 6.94 (2H, AA′XX′), 6.81
(2H, AA′XX′), 6.79 (2H, AA′XX′), 6.60 (4H, AA′XX′), 6.51 (2H,
AA′XX′), 6.47 (2H, AA′XX′), 4.30 (1H, d, J ) 11.7 Hz), 4.16
(1H, d, J ) 11.7 Hz), 2.94 (6H, s), 2.93 (6H, s), 2.91 (6H, s),
2.87 (6H, s); IR (KBr) 1606, 1520, 1354 cm-1; FD-MS m/z 638
(M+); UV-vis (see text). Anal. Calcd for C37H42N4S3: C, 69.55;
H, 6.63; N, 8.77; S, 15.05. Found: C, 69.30; H, 6.64; N, 8.58;
S, 15.30.
X-r a y An a lyses. Crystal data for 2a a :
C37H42N4S3, M
638.95, yellow prism, 0.35 × 0.35 × 0.20 mm, monoclinic P21/
a, a ) 12.919(2), b ) 16.659(2), c ) 16.376(2) Å, â ) 99.17(1)°,
V ) 3479.4(7) Å3, F (Z ) 4) ) 1.220 g cm-1. A total of 8279
unique data (2θmax ) 55°) was measured at T ) 296 K by a
four-circle diffractometer with ω-2θ scan mode (Mo-KR
radiation, λ ) 0.71069 Å). No absorption correction was applied
(µ ) 2.44 cm-1). The structure was solved by the Patterson
method (DIRDIF92 PATTY) and refined by the full-matrix
least-squares method on
F with anisotropic temperature
factors for non-hydrogen atoms. Hydrogen atoms were located
at the calculated positions. Their isotropic temperature factors
were included in the refinement. The final R and Rw values
are 0.044 and 0.036 for 5007 reflections with I > 3σI and 397
parameters.
-
To a suspension of (p-BrC6H4)3N+•SbCl6 (77 mg, 0.094
mmol) in dry CH2Cl2 (3 mL) was added a degassed solution of
12 (30 mg, 0.047 mmol) in dry CH2Cl2 (5 mL). After stirring
overnight under Ar, the deeply colored solution was concen-
trated, and the black precipitates formed upon addition of
ether were collected by suction to give 122+(SbCl6-)2 (52 mg,
yield 85%).
Crystal data for 3‚(CH2Cl2)2: C56H64N6S3Cl4, M 1059.15,
very fluorescent yellow cube, 0.30 × 0.30 × 0.15 mm, triclinic
P1 bar, a ) 11.7697(6), b ) 15.766(3), c ) 16.000(1) Å, R )
87.257(4)°, â ) 77.318(5)°, γ ) 73.061(5)°, V ) 2770.5(5) Å3, F
(Z ) 2) ) 1.270 g cm-1. A total of 11784 unique data (2θmax
)
55°) was measured at T ) 203 K by a CCD camera apparatus
(Mo-KR radiation, λ ) 0.71069 Å). Numerical absorption
correction was applied (µ ) 3.68 cm-1). The structure was
solved by the direct method (SIR92) and refined by the full-
matrix least-squares method on F with anisotropic tempera-
ture factors for non-hydrogen atoms. Hydrogen atoms except
those of solvents were located at the calculated positions. The
final R and Rw values are 0.106 and 0.129 for 7775 reflections
with I > 3σI and 632 parameters. Relatively high R values
are due to the rapid deterioration of the crystal due to the
solvent loss as well as the disorder of the solvent position in
the crystal.
Crystal data for 5a : C21H27N3S2, M 385.58, colorless rod,
0.40 × 0.20 × 0.20 mm, orthorhombic P212121, a ) 17.952(4),
b ) 19.219(3), c ) 6.026(4) Å, V ) 2079(1) Å3, F (Z ) 4) )
1.232 g cm-1. A total of 2770 unique data (2θmax ) 55°) was
measured at T ) 296 K by a four-circle diffractometer with ω
-2θ scan mode (Mo-KR radiation, λ ) 0.71069 Å). No
Oxid a tion of Tr is(d ia r ylm eth ylen e)tr ith ia n e 3. To a
degassed yellow solution of 3 (20 mg, 0.023 mmol) in dry CH2-
Cl2 (7 mL) was added (p-BrC6H4)3N+•SbCl6 (37 mg, 0.045
-
mmol). After stirring for 2 d under Ar, an insoluble black solid
was removed, and the mother liquor was concentrated into a
half of the volume. Black precipitates were formed upon
addition of ether, which was collected by suction and dried in
vacuo to give 132+(SbCl6-)2 (20 mg, yield 57%): mp 230-250
°C (dec); 1H NMR (300 MHz, CD3CN) 7.22-7.63 (ca. 14H, m),
6.75-6.82 (ca. 10H, m), 3.24 (12H, s), 3.22 (12H, s), 3.09 (6H,
s), 3.04 (6H, s); IR (KBr) 1580, 1374, 1170 cm-1; MS spectrum
could not be obtained under the FAB technique. Anal. Calcd
for C54H60N6S3Sb2Cl12‚C4H10O: C, 42.67; H, 4.32; N, 5.15; S,
5.89. Found: C, 42.92; H, 4.04; N, 5.62; S, 6.35. Analytically
pure sample could not be obtained due to the difficulty in its
purification. The initially formed insoluble solid (11 mg) seems
also to be the salt of 132+, as suggested by the formation of 13

Mono-, Bis-, and Tris(diarylmethylene)-1,3,5-trithianes
J . Org. Chem., Vol. 65, No. 18, 2000 5521
absorption correction was applied (µ ) 2.66 cm-1). The
structure was solved by the direct method (SIR92) and refined
by the full-matrix least-squares method on F with anisotropic
temperature factors for non-hydrogen atoms. Hydrogen atoms
were located at the calculated positions. Their isotropic tem-
perature factors were included in the refinement. The final R
and Rw values are 0.042 and 0.025 for 2095 reflections with I
> 3σI and 235 parameters.
radiation, λ ) 0.71069 Å). Numerical absorption correction was
applied (µ ) 41.98 cm-1). The structure was solved by the
direct method (SIR92) and refined by the full-matrix least-
squares method on F with anisotropic temperature factors for
non-hydrogen atoms. Hydrogen atoms were not included in
the refinement. The final R and Rw values are 0.057 and 0.054
for 8000 reflections with I > 3σI and 437 parameters.
Crystal data for 12: C37H42N4S3, M 638.95, red prism, 0.45
× 0.25 × 0.25 mm, monoclinic P2/c, a ) 10.821(2), b ) 11.311-
(2), c ) 15.349(1) Å, â ) 94.640(8)°, V ) 1872.5(4) Å3, F (Z )
2) ) 1.134 g cm-1. A total of 4539 unique data (2θmax ) 55°)
was measured at T ) 296 K by a four-circle diffractometer
with ω -2θ scan mode (Mo-KR radiation, λ ) 0.71069 Å). No
absorption correction was applied (µ ) 2.28 cm-1). The
structure was solved by the direct method (SAPI91) and
refined by the full-matrix least-squares method on F with
anisotropic temperature factors for non-hydrogen atoms. Hy-
drogen atoms were located at the calculated positions. Their
isotropic temperature factors were included in the refinement.
The final R and Rw values are 0.059 and 0.053 for 2829
reflections with I > 3σI and 208 parameters. Refinement by
supposing a lower symmetric space group (Pc) did not give
more fruitful results. Even in this case, S2 and C3 atoms still
suffer from positional disorder.
Ack n ow led gm en t. This work was supported by the
Ministry of Education, Science and Culture, J apan (No.
10146101). Financial support from the Izumi Science
and Technology Foundation and a Research Grant from
the Iwatani Naoji Foundation is gratefully acknowl-
edged. We thank Prof. Tamotsu Inabe (Hokkaido Uni-
versity) for use of the X-ray structure analysis system.
Elemental analyses were carried out by Ms. Akiko
Maeda and Ms. Hiroko Matsumoto at the Center for
Instrumental Analysis (Hokkaido University). MS spec-
tra were measured by Mr. Kenji Watanabe and Dr. Eri
Fukushi at the GC-MS & NMR Laboratory (Faculty of
Agriculture, Hokkaido University).
Su p p or tin g In for m a tion Ava ila ble: Ortep drawings
(Figure S1-S5) and structural data for the X-ray analyses
(positional and thermal parameters; bond distances and
angles) of 2a a , 3, 5a , 12, and 122+(I3-)2. This material is
available free of charge via the Internet at http://pubs.acs.org.
Crystal data for 122+(I3-)2: C37H42I6N4S3, M 1400.37, black
plate, 0.20 × 0.30 × 0.10 mm, triclinic P1 bar, a ) 14.266(1),
b ) 15.722(1), c ) 12.0915(9) Å, R ) 97.424(3)°, â ) 110.926-
(3)°, γ ) 108.438(2)°, V ) 2311.6(3) Å3, F (Z ) 2) ) 2.012 g
cm-1. A total of 10114 unique data (2θmax ) 55°) was measured
at T ) 296 K by an imaging plate apparatus (Mo-KR
J O000161L