Synthesis, characterization, and electrochemistry of some acridine-1,8-dione dyes

Article abstract of DOI:10.1021/jo9600316

The synthesis, characterization, and electrochemical behavior of some acridinedione derivatives are reported. Cyclic voltammetric studies show that all the dyes undergo irreversible oxidation irrespective of the substitution on the nitrogen. The product formed on oxidation is the aromatic derivative in the case of N-H compounds and the acridinium salt in the case of the N-substituted compounds, which have been isolated and characterized. Formation of an intermediate carbon-centered radical is observed as evidenced by ESR spin-trapping experiments. A mechanistic scheme for the electrochemical oxidation is proposed. On carrying out reduction after oxidation, different products are formed depending on the substitution on the nitrogen. There is no reduction of the oxidized product in the case of N-H compounds, and compounds with substitution on nitrogen undergo reduction consistent with the observation in N-alkylpyridinium salts.

Full text of DOI:10.1021/jo9600316

J . Org. Chem. 1996, 61, 5083-5089
5083
Syn th esis, Ch a r a cter iza tion , a n d Electr och em istr y of Som e
Acr id in e-1,8-d ion e Dyes
†
,†
‡
,‡
N. Srividya, P. Ramamurthy,* P. Shanmugasundaram, and V. T. Ramakrishnan*
Departments of Inorganic Chemistry and Organic Chemistry, School of Chemistry, University of Madras,
Madras 600 025, India
Received J anuary 3, 1996X
The synthesis, characterization, and electrochemical behavior of some acridinedione derivatives
are reported. Cyclic voltammetric studies show that all the dyes undergo irreversible oxidation
irrespective of the substitution on the nitrogen. The product formed on oxidation is the aromatic
derivative in the case of N-H compounds and the acridinium salt in the case of the N-substituted
compounds, which have been isolated and characterized. Formation of an intermediate carbon-
centered radical is observed as evidenced by ESR spin-trapping experiments. A mechanistic scheme
for the electrochemical oxidation is proposed. On carrying out reduction after oxidation, different
products are formed depending on the substitution on the nitrogen. There is no reduction of the
oxidized product in the case of N-H compounds, and compounds with substitution on nitrogen
undergo reduction consistent with the observation in N-alkylpyridinium salts.
In tr od u ction
cally important compounds such as NADH and NADPH.
The electrochemical oxidations of dihydropyridines,
NADH, and related compounds have also received greater
Studies on the electrochemical characteristics of laser
dyes are very few. Han made a brief study of fluorescent
molecules which could be used as laser dyes. The
12
attention. Blaedel and Haas studied the electrochemi-
1
cal oxidation of some NADH and structurally similar
compounds. Other investigators have concentrated on
the electrochemical oxidation of NADH, NADPH, and
electrochemistry of some selected coumarin, rhodamine,
and oxazine types of laser dyes were studied by Bard and
Park.2 Dye lasers with an electrochemical control of
radiation parameters have been shown to have achieved
stimulated emission in a broader spectral region.3 The
spectral interval of dye laser tuning without changing
the dye solution was possible by electrochemical methods4
showing that the electrochemical phenomena could be
successfully used for improving the dye laser tuning.
Detailed investigations involving a comparison of the
redox potentials to the spectral characteristics have been
studied in cyanine and thiocyanine dyes.5 In this paper
we report the synthesis and electrochemical character-
istics of acridine-1,8-dione dyes (AD). These dyes have
been shown to have very high lasing efficiencies6 and
are also interesting in view of the electrochemical be-
havior of heterocyclic compounds. They have been used
related compounds in aqueous and nonaqueous solutions
13-15
and at different pH.
The effect of substitution on the
oxidation of 1,4-dihydropyridines was studied by Skala
16
et al. The first unambiguous evidence for the formation
of the electrolytically generated cation radical of 1,4-
dihydropyridine in acetonitrile was demonstrated by
17
Klima et al.
The mechanistic aspects of the electro-
chemical oxidation of 1,4-dihydropyridines and NADH
and its analogs have been studied in aqueous media at
glassy carbon, pyrolytic graphite, and platinum elec-
18
trodes. Different electrochemical techniques such as
DC voltammetry, cyclic voltammetry, and coulometry
,7
19
were used by Abou-Elenien et al. to investigate the
oxidation and reduction properties of different dihydro-
20
pyridine and pyridine derivatives. Pragst et al. studied
8
-10
as electron donors and electron acceptors
and in the
the anodic dehydrogenation of 1,4 dihydropyridine by
photoinitiated polymerization11 of acrylates and meth-
acrylates. They are also interesting because of the
similarity in the properties with those of 1,4-dihydropyr-
idines, which have similarities in structure to the biologi-
21
electrogenerated chemiluminescence. Ludvik et al.
studied the influence of substituents on the oxidation
potentials and proposed a suitable mechanism for the
22
oxidation of 1,4-dihydropyridines. Klima et al. used the
spin-trapping method for the identification of radical
†
Department of Inorganic Chemistry.
Department of Organic Chemistry.
Abstract published in Advance ACS Abstracts, J une 15, 1996.
‡
(12) Blaedel W. J .; Haas, R. G. Anal. Chem. 1970, 42, 918.
(13) McNamara, F. T.; Nieft, J . W.; Ambrose, J . F.; Huyser, E. S. J .
Org. Chem. 1977, 42, 988.
(14) Leduc, P.; Thevnot, D. Electroanal. Chem. Interfacial Electro-
chem. 1973, 47, 543.
X
(
(
(
1) Han, M. V. Compt. Rend. 1971, 273B, 777.
2) Park, S. M.; Bard, A. J . J . Electroanal. Chem. 1977, 77, 137.
3) Tomin, V. I.; Nemkovich, N. A.; Rubinov, A. N. Kvantovaya
Elektron. 1978, 5, 986.
(15) Braun, R. D.; Santhanam, K. S. V.; Elving, P. J . J . Am. Chem.
Soc. 1975, 97, 2591.
(16) Skala, V.; Volke, J .; Ohnaka, V.; Kuthan, J . Collect. Czech.
Chem. Commun. 1977, 42, 292.
(
(
(
4) Rubinov, A. N.; Tomin.V. I. Spectrosc. Lett. 1978, 11, 951.
5) J amil, A.; Astin, K. B. Dyes Pigm. 1988, 9, 217.
6) Prabahar, K. J .; Ramakrishnan, V. T.; Sastikumar, D.; Selladu-
rai, S; Masilamani, V. Ind. J . Pure Appl. Phys. 1991, 29, 382.
7) Shanmugasuundaram, P.; Murugan, P.; Ramakrishnan, V. T.;
Srividya, N.; Ramamurthy, P. Heteroat. Chem. 1996, 7, 17.
8) Timpe, H. J .; Ulrich, S.; Ali, S. J . Photochem. Photobiol. A: Chem.
991, 61, 77.
9) Timpe, H. J .; Ulrich, S.; Fouassier, J . P. J . Photochem. Photobiol.
A: Chem. 1993, 73, 139.
10) Ulrich, S.; Timpe H. J .; Fouassier J . P.; Morlet-Savary, F. J .
Photochem. Photobiol. A: Chem. 1993, 74, 165.
11) Timpe, H. J .; Ulrich, S.; Decker, C.; Fouassier, J . P. Macro-
molecules 1993, 26, 4560.
(17) Klima, J .; Kufurst, A.; Kuthan, J .; Volke, J . Tetrahedron Lett.
1977, 31, 2725.
(18) Moiroux, J . Elving, P. J . J . Am. Chem. Soc. 1980, 102, 21.
(19) Abou-Elenien.; Reiser, J .; Ismail, N.; Wallenfalls, K. Z. Natur-
forsch. 1980, 36B, 386.
(20) Pragst, F.; Kaltofen, B.; Volke, J .; Kuthan, J . J . Electroanal.
Chem. 1981, 119, 301.
(21) Ludvik, J .; Klima, J .; Volke, J .; Kurfurst, A.; Kuthan, J . J .
Electroanal. Chem. 1982, 138, 131.
(
(
1
(
(
(
(22) Klima, J .; Ludvik, J .; Volke, J .; Krikava, M., Skala, V.; Kuthan,
J . J . Electroanal. Chem. 1984, 161, 205.
S0022-3263(96)00031-X CCC: $12.00 © 1996 American Chemical Society

5
084 J . Org. Chem., Vol. 61, No. 15, 1996
Srividya et al.
Ta ble 1. Electr och em ica l Da ta a
intermediates formed on electrochemical oxidation of 1,4-
dihydropyridines. The electrochemical study was carried
out using acridinediones because a knowledge of the
electrochemical redox potentials is important in the
process of ascertaining laser dye stability and reactivity
and could give an insight into the feasibility of other
reactions using these compounds. The products obtained
on electrolysis have been isolated and characterized. The
chemical oxidation does not yield a single desired product
in the case of N-substituted compounds, whereas the
electrochemical oxidation yields a single product of the
type III. Therefore a synthetic pathway by the electro-
chemical method to yield I, II, and III is reported.
Epa (V) vs Ag/AgCl
Epa (V) vs Ag/AgCl
compd
(air-equil)
(argon-sat)
1
2
3
4
5
6
7
8
1.16, 0.97
1.18
1.25
1.17, 0.93
1.33, 1.16
1.26
0.91
1.05
1.03, 0.93
1.16
1.19
1.24
1.17, 1.01
1.18
1.18, 1.06
1.19
a
Recorded at a scan rate of 200 mV/s.
substituent which might assume a cis geometry with the
N-methyl substituent. The 9 and 10 substituents of
9
-methyl-10-(4-methylphenyl)acridinedione have been
found to have the cis geometry as confirmed by X-ray
crystallographic studies.25 The signal due to the gem-
dimethyl group is seen as a singlet in general, which
however is distinguished as two singlets in the case of
compounds 3, 5, and 6, which must be due to a 9-phenyl
or methyl substituent. This is analogous to the effect of
2
-methylphenyl or 2-chlorophenyl substituent on the
nitrogen of the acridinedione system which makes the
2
4
C
4
(and C
The C methylene appears as a singlet at δ 3.1 in general
whereas in the case of 9-phenyl compounds 3 and 6 the
proton is seen at δ 4.85 and 5.2, respectively.
A. Electr och em ica l Stu d ies. All the dyes chosen
5
) methylene protons exhibit geminal coupling.
9
C
9
in the present study undergo irreversible oxidation. The
oxidation potentials obtained for compounds 1-8 are
given in Table 1. Solutions of the dyes in acetonitrile (1
mM) were chosen for the cyclic voltammetric studies.
Substitution in the 9 position causes the oxidation peak
to shift to a more positive potential, indicating a decrease
in the ease of oxidation. Such a behavior has been
attributed to steric factors based on the observation made
by Stradins et al.26 in the case of 1,4-dihydropyridines.
Similar arguments can be extended to the acridinediones
because the potentials for compounds 1-3 and 4-6 are
shifted to positive potential as the substituent in the 9
position is varied from H to methyl to phenyl. Substitu-
tion on the heterocyclic nitrogen by a methyl group causes
the peak to shift to less positive potentials. The electron-
releasing substituent on the heterocyclic nitrogen favors
oxidation as seen by the lower oxidation potential of 4
as compared to 1 and 7.
There is a difference in the shape of the cyclic voltam-
mograms when oxidation is carried out in air-equilibrated
and argon-saturated conditions. In the case of com-
pounds 1 and 7, two well-defined peaks are obtained in
both air-equilibrated and argon-saturated conditions.
Methyl substitution on the nitrogen or in the 9 position
(compounds 2 and 4) shows two peaks in argon-saturated
conditions but a single peak under air-equilibrated
conditions. In the case of other compounds, either two
peaks which are not very distinct or broad cyclic vol-
tammograms are obtained in an argon atmosphere, but
a sharp single peak is obtained in air-equilibrated
conditions. Also the peaks are shifted to a more positive
potential in argon-saturated conditions, thereby showing
that the oxidation is favored by the presence of oxygen.
Compounds containing two hydrogens in the 9 position
Resu lts a n d Discu ssion
Syn th esis of Acr id in ed ion es 1-8. The condensa-
tion of ethyl acetoacetate with aliphatic aldehydes and
ammonia to yield dihydropyridines was known as early
as 1882.23 The formation of the enaminone moiety by
such a condensation has led to the formation of the
acridinedione dyes. The dyes chosen for the study have
been previously reported as a class of laser dyes.6
Although their syntheses have already been reported, the
present method is able to afford considerable yields of
the product and also it does not give a mixture of products
to complicate the separation process. The condensation
of 5,5-dimethylcyclohexane-1,3-dione (dimedone) with
aldehyde furnished the tetraketone, which on reaction
with amine or ammonia under suitable conditions yields
the acridinedione. The condensation reactions, in gen-
eral, were carried out under reflux conditions in acetic
acid with or without methanol. The 10-unsubstituted
acridinediones were synthesized by the reaction of the
tetraketone with aqueous ammonia or ammonium ac-
etate in acetic acid.
,7,24
1
The H NMR spectra of the acridinediones in general
show the characteristic signals. The methyl groups
present in the 3 and 6 positions due to 12 protons appear
as a singlet around δ 0.9-1.0. The protons at the 2 and
positions and at the 4 and 5 positions appear around δ
.3-2.5 as singlets in general. The acridinediones 3 and
2 7
show the C and C methylene protons as an AB quartet
possibly due to the phenyl substituent at the 9 position.
For compound 5, an AB quartet is seen at δ 2.2-2.7
which is probably due to C /C methylene protons. This
2 7
7
2
6
splitting may be due to the effect of the 9-methyl
(
25) Sivaraman, J .; Subramanian, K.; Velmurugan, D.; Subrama-
(
23) Hantzsch, A. J ustus Liebigs Ann. Chem. 1882, 215, 1.
nian, E.; Ramakrishnan, V. T. Acta Crystallogr. 1994, C50, 2011.
(26) Stradins, Ya. P.; Dabur, G. Ya.; Bejlis, Yu. I.; Uldrikis, Ya. R.;
Krotokova, A. F. Khim. Geterosikl. Soedin 1972, 84.
(24) Shanmugasundaram, P.; Prabahar, K. J .; Ramakrishnan, V.
T. J . Heterocycl. Chem. 1993, 30, 1003.

Acridine-1,8-dione Dyes
1, 4, and 7) show two peaks in air-equilibrated and
J . Org. Chem., Vol. 61, No. 15, 1996 5085
(
Sch em e 1
argon-saturated conditions. The first peak at the less
positive potential can be attributed to the oxidation of
the starting material. The first electron loss is followed
by the proton loss. The second peak can be assigned to
the subsequent loss of the second electron. The formation
of the second peak is influenced by the presence of the
methyl or phenyl substituents in the 9 position. The
observation of two peaks for compounds 4 and 2 in argon-
saturated conditions shows that the electron-releasing
methyl group influences the rate of the second electron
loss. In the case of compounds 1, 4, and 7, after the first
electron and proton loss, the presence of the second
hydrogen in the 9 position could facilitate the reaction
•
of the radical with oxygen to yield HO
2
. This pathway
is not favored in the case of other compounds because of
the presence of the substituents in the 9 position (refer
to Scheme 1). This may be the reason for the observation
of broad cyclic voltammograms in argon-saturated condi-
tions in those compounds which have an alkyl or aryl
substitution in the 9 position.
Cyclic voltammograms were recorded at various scan
1
/2
rates, and plots of ipa/ν vs scan rate give an indication
of the probable mechanism of oxidation. This plot shows
1
/2
that ipa/ν is independent of scan rate and there is a shift
of the peak to less positive potential with decreasing scan
rate. This gives an indication of a possible irreversible
chemical reaction following charge transfer.
In order to understand the mechanism of oxidation in
greater detail and to determine the number of electrons
involved in the oxidation process, coulometric studies
were carried out. Solutions containing accurately weighed
amount of the dyes with tetrabutylammonium perchlo-
rate (TBAP) were subjected to electrolysis at a constant
potential, slightly beyond the potential of the desired
oxidation. The working and counter platinum electrodes
were separated by a sinter in order to avoid mixing of
solutions. Coulometric studies in argon-saturated ac-
etonitrile show the involvement of two electrons in the
oxidation process.
In order to isolate the product formed on electrolysis,
both N-H and N-methyl compounds were subjected to
electrolysis for 12 h at a potential of +1.3 V vs Ag/ AgCl.
The reaction was followed by TLC from time to time. The
electrolysis was carried out in a cell similar to that used
in Coulometric studies, but the amount of substance used
was in larger quantities. Compounds 1 and 4 were
chosen as representative compounds for the product
isolation. In the case of compound 1, the acetonitrile
solution after electrolysis was evaporated under reduced
pressure in order to remove the solvent. The resulting
solid mixture was extracted with chloroform and was
chromatographed over a column of silica gel and eluted
with chloroform. Colorless crystals were filtered out. The
absorption spectrum of the isolated product I was com-
pared with the spectrum of the authentic sample ob-
tained on chemical oxidation of the starting material with
of the red product with ether and concentration of the
ether layer gave dark red crystals of compound II, which
was characterized by NMR and HRMS. The NMR
spectrum clearly reveals that the product formed is due
to a net loss of two hydrogen atoms as compared to the
starting material. Acidification of a methanolic solution
of II by perchloric acid turns the solution yellow and
precipitates the final product III. Compounds II and III
exist in an acid-base equilibrium and are reversibly
converted from one form into another by the addition of
a base or acid. In fact the product obtained after
acidification with perchloric acid is the same as the
product obtained on electrolysis, which is further con-
firmed by comparing their absorption spectra which have
a characteristic maximum at 292 nm. Figure 1 gives the
absorption spectra of compounds 4, II, and III.
MnO
2
. In the case of compound 4 the separation of the
product was not possible in a single step because the final
product obtained was a salt and separation of the desired
product from TBAP was difficult. The product obtained
on electrochemical oxidation along with the excess per-
chlorate was concentrated by rotary evaporation under
reduced pressure. To this mixture was added a concen-
trated solution of KOH, and the color of the product
changed to red from yellow. The product formed also
contained TBAP which is insoluble in ether. Extraction
The results of the UV-vis, NMR, IR, and mass spectra
obtained are tabulated in Table 2. The NMR spectrum

5
086 J . Org. Chem., Vol. 61, No. 15, 1996
Srividya et al.
Ta ble 2. Sp ectr a l Da ta for th e P r od u cts Sep a r a ted a fter Electr olysis
analytical data
calcd
H
found
UV-vis
(nm)
1H NMR
data (δ, ppm)
IR
mass
(m/e)
compd
(cm-1)
C
N
C
H
N
I
220
1.12 (s, 12H)
2.50 (s, 4H)
3.05 (s, 4H)
1640
1580
271
215
256
75.24
7.80
5.16
75.18
7.74
5.13
2
2
50
92
8
.76 (s, 1H)
II
520
1.10 (s, 12H)
2.25 (s, 2H)
2.35 (s, 2H)
2.50 (s, 2H)
1657
1705
285
385
75.44
56.03
8.12
6.26
4.90
3.63
69.19
56.16
7.77
4.66
3.33
3
2
2
56
44
12
3
4
7
.14 (s, 3H)
.31 (s, 1H)
.90 (s, 1H)
III
350
1.16 (s, 12H)
2.69 (s, 2H)
3.35 (s, 2H)
4.15 (s, 3H)
1710
1600
6.26
2
2
2
92
50
20
9
.17 (s, 1H)
Ta ble 3. Sp littin g Con sta n ts Obta in ed in th e ESR
Sp ectr u m of th e Sp in -Tr a p p ed Ad d u ct
splitting constants
compd
aN, G
aH, G
1
2
3
4
5
6
7
8
14.50
14.93
14.93
14.07
14.50
14.93
14.22
14.50
2.50
2.81
3.38
3.38
3.38
3.38
3.38
2.45
goes electrochemical oxidation to form a salt of type III
in the case of N-substituted compounds. The radical V
being reactive also undergoes subsequent oxidation in the
presence of oxygen to form compounds of type II. Com-
pounds of type II in the presence of TBAP, present under
electrochemical conditions, form salts of type III. In the
case of N-H compounds (1, 2, and 3), electrochemical
oxidation of radical V is followed by a subsequent proton
loss to yield a product of type I.
C. Id en tifica tion of Ra d ica l In ter m ed ia tes. In
order to gather evidence for the mechanism of electro-
chemical oxidation and to establish that the oxidation
proceeds by the formation of a radical, ESR experiments
were carried out. Electrolysis in the presence of the spin
trap N-tert-butyl-R-phenylnitrone (PBN) yielded the spin
adduct. The ESR spectra obtained after electrolysis of
the dyes are given in Figure 2. The ESR spectrum shows
the triplet due to the nitrogen and its splitting into a
doublet due to the presence of the adjacent hydrogen. aN
values around 14 G and aH splitting of 2-3 G have been
obtained in the case of dihydropyridine spin adducts.
There is no appreciable decrease in the aH splitting as
seen in the case of phenyl substitution in the 9 position
as in the case of the dihydropyridines. The splitting
constants for the spin adduct of about 14 G is consistent
with that of a carbon-centered radical as reported for
other compounds with the same spin trap.27 The ESR
data are collated in Table 3.
F igu r e 1. Absorption spectra of compound 4 (- - -) and the
products II (s) and III (- - -) formed on electrolysis.
of product I clearly indicates the presence of the aromatic
proton at δ 8.7, corresponding to the proton at position
9
, which is not present in the NMR spectrum of the
starting material. In the case of product III the peak
corresponding to the aromatic proton is shifted more
downfield because of the positive charge on the hetero-
cyclic nitrogen. The IR and mass spectral data are also
incorporated in Table 2.
B. Mech a n ism of Electr och em ica l Oxid a tion . As
there was a difference in the shape of the cyclic voltam-
mograms based on the differences in the substitution on
the heterocyclic nitrogen and the products obtained on
oxidation were different depending on the substitution
on the nitrogen, the substituent on the nitrogen is
expected to play a key role in the product formation. The
presence of at least one hydrogen atom in the 9 position
is extremely necessary for the completion of oxidation as
in the case of 1,4-dihydropyridine.20 Hence the mecha-
nism of oxidation for the N-H and N-Me substituent
follow different routes of oxidation after the initial loss
of an electron. It is evident from the ESR spectra that
the first proton loss is from the 9 position in all cases.
This may be followed by loss of a second electron in the
case of N-substituted compounds and an electron and
proton loss in the case of N-H compounds in order to yield
the final product as given in Scheme 1.
D. Red u ction a fter Oxid a tion . The cathodic be-
havior of the anodic species formed is informative. The
shapes of the cyclic voltammograms vary depending on
the substituent in the heterocyclic nitrogen (Figure 3).
A peak at about +1.0 V corresponds to oxidation in all
the dyes and is assigned as peak A or A′. No dimeric
In all the compounds studied the first step of oxidation
is the loss of an electron from the nitrogen to form the
cation radical. This is followed by a rapid proton loss to
produce a carbon-centered radical (V). Radical V under-
(27) Buettner, G. R. Free Radical Biol. Med. 1987, 3, 259.

Acridine-1,8-dione Dyes
J . Org. Chem., Vol. 61, No. 15, 1996 5087
F igu r e 2. ESR spectrum of the spin-trapped adducts of acridinediones with PBN.
product has been isolated on oxidation which might form
from the radical V, but the possibility of the formation
of a dimer cannot be ruled out. On carrying out reduction
after oxidation the compounds with substitution on
nitrogen show two reduction peaks (B and C), one at
about -0.5 V and the second cathodic peak at about -1.0
V. Only peak B is seen in compounds with N-H sub-
stituent at about -0.5 V. At the peak B the protonated
acridinedione (IV), formed in the reaction between proton
released due to the oxidation of AD and the unoxidized
AD, gets reduced to the starting material and liberates
hydrogen. The second cathodic peak C is attributed to
reduction of the N-substituted acridinium ion (III).
The peaks obtained in cyclic voltammetry can be
assigned as
oxidation terminates at the aromatic product by loss of
the second proton. There is no peak present on direct
reduction of the starting materials in the potential range
0 to -1.5 V. This gives a clear indication that the
reduction peaks are only due to the reduction of the
oxidation products. The reduction of a compound of type
III to form V is consistent with the fact that the
2
8-31
N-alkylpyridinium ion forms a dimer on reduction.
Exp er im en ta l Section
P r ep a r a tion of 2,2′-Meth ylen ebis(5,5′-d im eth ylcyclo-
h exa n e-1,3-d ion e). A mixture of dimedone (2 mol) and the
corresponding aldehyde (1 mol) was stirred at 40-45 °C for
1
0 min in aqueous methanol until the solution became cloudy
and was allowed to stand overnight. The tetraketone (A )
formaldehyde, B ) acetaldehyde, C ) benzaldehyde) was
collected by filtration and dried. Yield: tetraketone A, 96%,
mp 186-188 °C; tetraketone B, 93%, mp 136-138 °C; tetra-
ketone C, 94%, mp 190-192 °C.
-
+
peak A:
AD (N-H) f I + 2e + 2H
-
+
peak A′:
AD (N-R) f III + 2e + H
3
,3,6,6-Tetr a m eth yl-3,4,6,7,9,10-h exa h yd r o-1,8(2H,5H)-
a cr id in ed ion e (1). To the tetraketone A (2.92 g, 10 mmol)
in methanol (10 mL) was added a 25% aqueous solution of
ammonia (2 mL), and the solution was warmed on a steam
+
H + AD f IV
-
1
peak B:
peak C:
IV + e f AD + / H
2
2
(28) Volke, J .; Naarova, M. Collect. Czech. Chem. Commun. 1972,
3
3
7, 3361.
-
III + e f V
(29) Naarova, M.; Volke, J . Collect. Czech. Chem. Commun. 1973,
8, 2671.
(
(
30) Webber, A; Osteryoung, J . J . Electrochem. Soc. 1982, 12, 2732.
31) Gaudiello, J . G.; Larkin, D.; Rawn, J . D; Sosnowski, J . J .;
Peak C, which is present for compounds 4-8, is not
present in the case of compounds 1-3 because the
Bancroft, E. E.; Blount, H. N. J . Electroanal. Chem. 1982, 131, 203.

5
088 J . Org. Chem., Vol. 61, No. 15, 1996
Srividya et al.
bath for 4 h. A bright yellow solid separated out and was
filtered, dried, and recrystallized from a chloroform-methanol
1
mixture: yield 88%; mp 317-319 °C; H NMR (CDCl
3
) δ 1.1
), 2.3 (s, 4H, C(O)-
Cd), 8.0 (s, 1H, NH).
,3,6,6,9-P en tam eth yl-3,4,6,7,9,10-h exah ydr o-1,8(2H,5H)-
(
s, 12H, gem-dimethyl), 2.2 (s, 4H, dCCH
2
CH ), 3.0 (s, 2H, dCCH
2
2
3
a cr id in ed ion e (2). The tetraketone B (1.53 g, 5 mmol) and
ammonium acetate (0.42 g, 5.5 mmol) in acetic acid (10 mL)
heated to reflux for 2 h furnished acridinedione 2: yield 92%;
-
1
mp 256-258 °C; IR (cm ) 3280 (NH), 1610 (CdO), 1595
1
(
CdC); H NMR (CDCl
3
) δ 1.0 (d, 3H, dCCHCH
), 2.4 (s, 4H, C(O)CH
.15 (q, 1H, dCCHCd), 8.45 (s, 1H, NH). Anal. Calcd for C18
3
), 1.1 (s, 12H,
gem-dimethyl), 2.3 (s, 4H, dCCH
2
2
), 3.95-
4
-
H
2
25NO : C, 75.21; H, 8.78; N, 4.87. Found: C, 75.00; H, 8.42;
N, 4.90.
,3,6,6-Tet r a m et h yl-9-p h en yl-3,4,6,7,9,10-h exa h yd r o-
,8(2H,5H) a cr id in ed ion e (3). The compound was prepared
similar to 2 using tetraketone C 3: yield 90%; mp 250-252
3
1
-
1
1
°
C; IR (cm ) 1620 (CdO), 1575 (CdC); H NMR δ 0.90 (s, 12H,
gem-dimethyl), 1.9-2.3 (ABq, 4H, J gem ) 15 Hz), 2.4 (s, 4H),
.85 (s, 1H), 7.0-7.2 (s, 5H), 9.2 (s, NH); mass spectrum m/z
4
(
2
+
relative intensity) 349 (M ) (98), 348 (100), 332 (18), 292 (18),
73 (72), 264 (35), 220 (14), 217 (18), 180 (20). Anal. Calcd
for C23 : C, 79.04; H, 7.78; N, 4.07. Found: C, 78.81;
H, 7.81; N, 4.14.
,3,6,6,10-P e n t a m e t h yl-3,4,6,7,9,10-h e xa h yd r o-1,8-
2H,5H)-a cr id in ed ion e (4). To tetraketone A (1.46 g, 5
H
27NO
2
3
(
mmol) in acetic acid (15 mL) was added a 40% aqueous solution
of methylamine (0.41 mL, 5.2 mmol), and the solution was
heated under reflux conditions for 2 h. The reaction mixture
was concentrated and poured into cold water (200 mL), and
the solid obtained was filtered, dried, and recrystallized from
a chloroform-methanol mixture: yield 81%; mp 226-28 °C;
F igu r e 3. (Top) Cyclic voltammogram of compound 1 on
oxidation followed by reduction, showing peaks A and B due
to the formation of I and reduction of IV, respectively. (Bottom)
Cyclic voltammogram of compound 4 oxidation followed by
reduction, showing peaks A′, B, and C due to the formation of
III and reduction of IV and III, respectively.
-
1
1
IR (cm ) 1615 (CdO), 1570 (CdC); H NMR (CDCl
2H, gem-dimethyl), 2.25 (s, 4H, dCCH ), 2.45 (s, 4H, C(O)-
CH ), 3.15 (s, 2H, dCCH Cd), 3.3 (s, 3H, NCH ); mass
spectrum m/z (relative intensity) 287 (M ) (100), 286 (55), 272
22), 271 (6). Anal. Calcd for C18 : C, 75.22; H, 8.76;
N, 4.87. Found: C, 75.40; H, 8.68; N, 5.03.
,3,6,6,9,10-H e xa m e t h yl-3,4,6,7,9,10-h e xa h yd r o-1,8-
2H,5H)-a cr id in ed ion e (5). From tetraketone B (1.53 g, 5
3
) δ 1.1 (s,
1
2
2
2
3
+
(
H25NO
2
3
2 5
amounts of P O on stirring at room temperature for 12 h and
concentrating the solvent under reduced pressure furnished
the acridinedione 7.
(
mmol) and a 40% aqueous solution of methylamine (0.44 mL)
on heating to reflux with acetic acid (2 h) the acridinedione 5
(b) To tetraketone A in acetic acid was added aniline and
the solution was heated under reflux conditions for 4 h. The
formation of the product was followed by TLC. Concentration
and pouring the contents into ice-cold water yielded the
-
1
was obtained: yield 86%; mp 206-208 °C; IR (cm ) 1610
1
(
1
CdO), 1570 (CdC); H NMR (CDCl
.15 (2s, 12H, gem-dimethyl), 2.2-2.7 (dd, gem coupling, 4H,
C(O)CH ), 2.3 (s, 4H, dCCH ), 3.3 (s, 3H, NCH ), 4.05-4.25
q, 1H, dCCHCd). Anal. Calcd for C19 : C, 75.70; H,
.02; N, 4.64. Found: C, 75.52; H, 8.96; N, 4.41.
,3,6,6,10-P en tam eth yl-9-ph en yl-3,4,6,7,9,10-h exah ydr o-
,8(2H,5H)-a cr id in ed ion e (6). The compound was prepared
3
) δ 0.85 (d, 3H, dCCHCH
3
),
-
1
2
2
3
acridinedione 7: yield 86%; mp 262-264 °C; IR (cm ) 1620
(CdO), 1575 (CdC); 1H NMR (CDCl
) δ 0.90 (s, 12H, gem-
dimethyl), 1.8 (s, 4H, dCCH ), 2.25 (s, 4H, C(O)CH ), 3.3 (s,
2H, dCCH Cd), 7.3-7.7 (m, 5H, Ar H). Anal. Calcd for C23
: C, 79.05; H, 7.79; N, 4.01. Found: C, 79.03; H, 7.72;
N, 3.98.
(
9
H
27NO
2
3
2
2
3
2
-
1
H27NO
2
similar to 4 using tetraketone C. 6: yield 80%; mp 200-202
-
1
1
°
1
2
C; IR (cm ) 1615 (CdO), 1570 (CdC); H NMR (CDCl
3
) δ
), 2.4-
3
), 5.2 (s, 1H,
3,3,6,6,9-P en tam eth yl-10-ph en yl-3,4,6,7,9,10-h exah ydr o-
1,8(2H,5H)-a cr id in ed ion e (8). The compound was prepared
similar to 7 using tetraketone B. 8: yield 80%; mp 264-265
.07-1.13 (s, 12H, gem-dimethyl), 2.3 (s, 4H, dCCH
.85 (ABq, 4H, C(O)CH ), 3.2 (s, 3H, NCH
2
2
-
1
1
dCCHCd), 7.3-7.6 (m, 5H, Ar H); mass spectrum m/z (relative
°C; IR (cm ) 1615 (CdO), 1570 (CdC); H NMR (CDCl
(d, 3H, dCCHCH ), 1.1 (s, 12H, gem-dimethyl), 2.3 (s, 4H,
dCCH d), 2.4 (s, 4H, dC(O)CH d), 3.9-4.1 (q, 1H, dCCHCd),
3
) δ1.0
+
intensity) 363 (26) (M ), 286 (100), 273 (100), 217 (65). Anal.
3
Calcd for C24
7
3
H
29NO
2
: C, 79.3; H, 8.04; N, 3.85. Found: C,
8.0; H, 7.67; N, 3.85.
,3,6,6,-Tetr a m eth yl-10-p h en yl-3,4,6,7,9,10-h exa h yd r o-
2
2
7.3-7.7 (m, 5H, Ar H); mass spectrum m/z (relative intensity)
363 (16.5) (M ), 286 (71), 273 (100), 217 (38), 203 (16.5). Anal.
+
1
,8(2H,5H)-a cr id in ed ion e (7). (a ) Tetraketone A (2.92 g,
Calcd for C24
2
H29NO : C, 79.3; H, 8.04; N, 3.85. Found: C,
1
0 mmol) and aniline (1.0 g, 11 mmol) in ethanol with catalytic
78.8; H, 7.81; N, 4.04.

Acridine-1,8-dione Dyes
J . Org. Chem., Vol. 61, No. 15, 1996 5089
The preparations of some of the dyes chosen for the study
have been reported previously by different methods.
carried out at room temperature, and the solutions were
purged with argon when necessary. The electrochemical cell
has four necks for the working, counter, and reference elec-
trodes and inlet and outlet for the gas, respectively. The
absorption spectra were recorded using Hitachi-320 or HP-
8452A diode array spectrophotometers. IR spectra were
3
2,33
Acetonitrile used for the study was HPLC grade obtained
from Qualigens Fine Chemicals Ltd., India. Tetrabutylam-
monium bromide from Fluka was converted into its perchlorate
with perchloric acid. The excess acid was washed with water,
and the TBAP obtained was recrystallized twice from a 1:1
methanol-water mixture. The purity of the sample was
ascertained by running a cyclic voltammogram with TBAP in
acetonitrile. The spin trap N-tert-butyl-R-phenylnitrone ob-
tained from Sigma Chemical Co. was used as received.
Cyclic voltammograms were recorded on a Princeton Applied
Research (PAR) model 173 potentiostat/galvanostat. A cyclic
triangular wave of potential was produced by a PAR model
1
recorded on a Perkin-Elmer 258 spectrophotometer. H NMR
spectra were recorded on a Varian EM-390 spectrometer.
Mass spectra were recorded on a HP 5985 GC/MS. Melting
point measurements are uncorrected. ESR experiments were
performed on a Bruker ER-200-D ESR spectrometer with a
TE102 cavity. The electrochemical oxidations were performed
with the spin trap added to the solution in a cell in which all
three electrode compartments were kept separated using a
sinter. The oxidized solution containing the spin trap was
taken into the ESR cavity to record the ESR spectrum of the
spin adduct formed.
1
75 universal programmer and applied to the system through
the potentiostat/galvanostat. The current output was moni-
tored using a PAR model 176 current follower. The voltam-
mograms were recorded using a Perkin Elmer Hitachi model
0
57 x-y recorder. Platinum was used as both the working
and counter electrodes and Ag/AgCl was used as the reference
electrode. The electrodes were cleaned after each experiment
to remove the adsorbed impurities. All the experiments were
Ack n ow led gm en t. N.S is thankful to CSIR for
providing a fellowship. The authors are also thankful
to the University Grants Commission for its sustained
support through the COSIST program.
(32) Bakibaev, A. A.; Filimonov, V. D. Zh. Org. Khim. 1989, 25, 1579.
33) Greenhill, J . V. J . Chem. Soc. (C) 1971, 2699.
(
J O9600316