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Chemiluminescence on Oxidative Formation of Triplet States of Anthrasemiquinone- and Anthraquinone-2-sulfonate.

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equivalent nuclei, which are responsible for the coupling
constant, is given in parentheses.)
The radical anions were generated either by electrolytic
reduction in N,N-dimethylformamide ((1)e and (2)e) or by
reaction with potassium in 1&dimethoxyethane ( ( 3 ) and
(41 9.
I n anticipation of a more detailed discussion of the experimental results, the following remarks can be made:
@
1. With respect to the ESR time scale and in the temperature
range investigated (+25 to -40 "C), the results are consistent
with a plane of symmetry passing through the central S
atom and vertical to the plane of the molecule.
2. The z-spin population at atom 2 is relatively large (0.2 to
0.3), whereas at atom 3 it has a smaller value (0.06 t o 0.08).
A spin distribution of this kind is in accord with the form of
the relevant orbital in the M O modelrzl.
3 . As expectedrsl, the trimethylene chain in (2)ecan occur
in two equivalent conformations which undergo rapid interconversion (frequency > l o 7 s- 1) a t room temperature.
Cooling of the solution reduces the frequency of interconversion: the spectrum recorded at -40'C
is already typical
of a "frozen" conformation. The decrease in temperature also
causes one of the two methylene protons in the 2-ethyl substituent to assume a position in which-- on time average and
relative to the freely rotating methyl group - hyperconjugation is still less favored "1 (compare data for (2) C with those
for (1)").
Received: January 7 , 1970
[Z 156 IE]
German version: Angew. Chem. H2, 294 (1970)
.
-~
~
["I
Prof. Dr. F. Gerson, Dr. R. Gleiter, and Dr. J . Heinzer
Physikalisch-Chemisches Institut der Universitiit
CH-4056 Basel, Klingelbergstrasse 80 (Switzerland)
Prof. Dr. H . Behringer
Institut f u r Organische Chemie der Universitst
8 Munchen, Karlstrasse 23 (Germany)
[ l ] Electronic Structure of Thiathiophthene, Part 2. This work
was supported by the Schweizerischer Nationalfonds (Project
No. 4651). -- Part 1: ref. 121.
[2] R . Gleiter and R . Hoffmnnn, Tetrahedron 24, 5899 (1968).
[3] See K. Maeda, Bull. chem. SOC.Japan 34, 1166 (1961), and
further literature cited therein.
141 H . Behringer, M. R u f f , and R. Wiedeinann, Chern. Ber. 97,
1732 (1964).
[ 5 ] J . Heinzer, Dissertation, ETH Zurich 1968 (No. 4255).
[6] F. Gerson, E . Heilbronner, H . A . Reddoch, D . H . Paskovich,
and N . C. Das, Helv. chim. Acta 50, 813 (1967), and further
literature cited therein.
[71 A . Carringfon and P. F. Todd, Molecular Physics 8, 299
(1 964).
Chemiluminescence on Oxidative Formation of
Triplet States of Anthrasemiquinone- and
Anthraquinone-2-sulfonate
By Joachim Stun#" and Peter Burtolmes [*I
Hydroquinones that reduce 0 2 to HzOz emit a weak light
while doing so; this light can be registered with a sensitive
photodetector. Emission of this kind is also observed when
e.g. anthraquinone-2-sulfonate is reduced to the semiquinone
under argon at a Pt cathode at pH 12.5 and is then exposed
to the action of 0 2 . Although the hydroquinone is also
present under these conditions, owing to the equilibrium
Q + HQ d 2 SQ (Q = quinone, SQ = semiquinone, HQ =
hydroquinone), the possible formation of 0; radical anions
according to SQ + 0 2 + 0; cannot be immediately ruled
out. In such a case, the chemiluminescence could be due to
singlet oxygen "1 formed by recombination of OZH radicals
which are produced by 0; and Hf. A chemiluminescence
of the same kind is also observed, however, o n oxidation of
H Q or SQ with K3[Fe(CN)6] in the complete absence of oxyAngew. Chem. internut. Edit.
/ VOI.9
(1970)
/ NO. 4
550
500
600
hlnrnl ->
Figure. ChemJluminescence spectra of the reactions: anthrasemihexacyanoferrate(ri1) (-);
anthrahydroquinone-2-sulfonate
quinone-2-sulfonate
hexacyanoferrate(lI1) (----);
and anthrahydroquinone-2-sulfonate -F 0 2 (-.-.).
+
+
gen (Ar atmosphere); the excited states that emit the photons
must therefore arise from the participating organic molecules and not from oxygen species. The quantum yield of the
reaction is about 10-10 Einstein/mole. The fact that the
reaction appears to number among the exceptional cases in
which chemiluminescence can be produced without the
participation of oxygen or peroxides 121 makes it all the more
interesting.
Since oxidation with hexacyanoferrate(rI1) can only proceed
in a series of one-electron steps, variation of the ratio q =
Fe(CN)i-/reductant should reveal which of the reactions
HQ
+ [Fe(CN)6]3-
--f
SQ*; SQ*
--t
SQ
+ hvi
(1)
and
is responsible for the emission. It was found that with H Q as
reductant the maximum intensity of luminescence occurs at
q = 2, and for SQ, on the other hand, at q = 1; moreover, the
luminescence yield in the former case was double that in the
latter. Thus light is emitted during both reaction (1) and
reaction (2). The only possible explanation is that removal
of a n electron and formation of a >C=O group each lead to
an excited state of the reaction product which releases part
of its energy in the form of light. Whereas SQ can yield only
one >C=O group, HQ can form two and thus initiate twice
as many emission processes.
This hypothesis derived further support from an approximate plot of the emission spectra recorded with the aid of
filters. The figure shows that both oxidation of HQ and SQ
with [Fe(CN)6]3- or 0 2 invariably gives rise t o two bands
that can be attributed to the emission of SQ* and Q*. Owing
to the equilibrium between HQ, Q, and SQ, both reactions
(1) and (2) must occur together; it was, however, to be expected that the relative intensity of one of the two bands,
corresponding to SQ* or Q*, would be higher than that of
the other, depending upon which starting material was used.
In fact, with HQ as starting material the band at 515 nm is
the stronger one, and the converse is true in the case of SQ.
The band a t 515nm is therefore ascribed to the excited
semiquinone and that at 568 nm to the excited quinone. This
assignment is consistent with the concept that reaction (l),
as a processes involving doubly and trebly charged anions,
must be slower than reaction (2) between singly and trebly
charged anions, and that the intensity of the quinone band
must be greater than that of the semiquinone band. More-
307
over, in the spectrum of the reaction H Q f 0 2 , the 515-nm
band is twice as strong as the 568-nm band. Since the rate of
reaction of 0 2 with HQ, having two -0- groups, must
statistically be twice as high as that of 0 2 with SQ, having
one -0- group, the same relationship is to be expected between the intensities of the emission bands.
phine sulfide are not formed, even on heating with an excess
of SO2 at 185 'C for 8 days.
Compounds ( l a ) and (16) react with SeOz in boiling benzene
to give the phosphine oxide and either selenium or the phosphine selenide, depending on the relative proportions of the
reagents.
Since the singlet states of anthraquinonesulfonate lie at 260
SQ* and Q* must be triplet
states. This means that removal of an electron from a group
2 ( l a , b)
(new*) and 320nm (n+n*),
like
>k-O:@ leaves
considerably lower energy required for its formation (49
instead of 88 kcaljmole), the antibonding state should be a
triplet state which undergoes transition into the singlet
ground state in a subsequent step, thereby emitting a very
small portion of its energy as light.
Received: January 30, 1970
[ Z 164 IE]
German version: Angew. Chem. 82, 321 (1970)
[ * ] Prof. Dr. J. Stauff and P. Bartolmes
Institut fur Physikalische Biochemie und Kolloidchemie
der Universitat
6 Frankfurt/Main 1, Robert-Mayer-Strasse 11 (Germany)
[l] 1. Stauff and F. Nimmerfall, 2. Naturforsch. 246, 852
(1969).
[2] K . D . Gundermann: Chemilumineszenz organischer Verbindungen. Springer, Berlin 1968.
Reactions of Tritolylphosphines
By S. I. A . El Sheikh, B. C. Smith,and M . E. Soheir[*]
Tri-p- ( l a ) and tri-m-tolylphosphine ( I b ) resemble triphenylphosphine in their oxidation behavior, whereas tri-o-tolyphosphine ( I c ) differs in its reactions with several oxidizing
agents. Thus ( l a ) and ( I b ) react with thionyl chloride in
boiling benzene t o give the phosphine oxide and disulfur dichloride [ I ] .
The initially formed triaryldichlorophosphorane undergoes
subsequent conversion into the phosphine oxide. Under
similar conditions ( I c ) gives a mixture of the phosphine
oxide and phosphine sulfide.
( l a ) and (16) recrystallize unchanged from liquid sulfur dioxide, but undergo oxidation when the yellow solutions are
heated in sealed tubes (185 OC/2 days):
+ SO2
+ Se02
2 R3PO+ Se
--f
+ 2 R 3 P O + R3PSe
the >C=O group not in the bonding
z state but initially in the antibonding x* state. Owing to the
3 (la, 6)
3 (la, 6)
+ SeO2
+ 2 R3PO
+ R3PS
The phosphine ( I c ) does not react under these conditions.
Received: February 2, 1970
[ Z 165 IE]
German version: Angew. Cheni. 82,326 (1970)
-~
-
[*I Dr. S. I.
A. El Sheikh, Dr. B. C. Smith, and
Dr. M. E. Sobeir
Department of Chemistry
Birkbeck College (University of London)
Malet Street, London W.C. 1, (England)
111 M . E. Sobeir, B. C. Smith, A . N . Swamy, and M . Woods,
unpublished results.
Ionization Isomerism of Sulfinato Complexes of
Transition Metals
By Ekkehord Lindner and Giintev Vitzthun?1 * I
Sulfinato complexes are eminently suitable subjects for the
detection of various isomerism phenomena: alongside
stereoand valence isomers [21 we have now observed, for
the first time, ionization isomers.
Reaction of the potentially bidentate ligand ethylenediamine (en) with the sulfinato-O,O' complex ( p C H ~ C ~ H ~ S O ~ ) ~ M131
~ (inOethanol
H ~ ) Zat room temperature
affords the ionic compound [ P - C H ~ C ~ H ~ Sen21
O~M~
[p-CH3C6H4S02] ( I ) (yield about 70%). Compound ( I )
exhibits conductivity in ethanol and its cation could be
characterized in the form of [p-CH3C6H4S02Mn en2]
[B(CsH5)41 (2).
On repeated recrystallization from ethanol with tetrahydrofuran the metastable compound ( I ) is converted
irreversibly into the non-polar isomer ( J J - C H ~ C ~ H ~ S O ~ ) ~ M ~
en2 ( 3 ) , which is insoluble in all organic solvents. Composition and structure of the almost colorless sulfinato-O,O'
derivatives (1)-(3) were established by complete elemental
analysis and by the electronic and IR spectra, which indicate
a pseudo-octahedral environment of the Mn2+ ion (see
Table).
In every case, the coordinated p-CH3C6H4SO; ligand is
bonded to the central ion via both oxygen atoms ( 0 , O '
type) (41.
Table: SO2 stretching vibrations (in cm-I) of complexes ( 1 ) - ( 3 ) and
of p-CH,C&S02Na ( 4 ) .
In contrast, the isomer ( I c ) reacts with liquid SO2 to give an
orange precipitate of the complex [ ( O - C H ~ C ~ H &.PSO2]
(2), which is stabilized by specific attractions between omethyl groups and ligands. The phosphine oxide and phos970vs
IOOOvs, b
(3)
917s
1012vs
(4)
979 m
1027 m
(2)
~~
~~
The IR spectrum of ( I ) also contains the SO2 stretching
vibrations of the anion p-CH3C6H4SO; (cf. spectrum of
(4)), which are absent from that of (2). Thus ethylenediamine is bidentate in ( I ) and (2),but monodentate in ( 3 ) .
Possible stereoisomerism (cis-trans) in (3) cannot be detected
owing to the insufficient frequency splitting of va,(S02) and
Vs(SO2).
308
Angew. Chem. internat. Edit.
/ Val. 9
(1970)
1 No. 4
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sulfonated, chemiluminescence, formation, anthraquinone, oxidative, anthrasemiquinone, triple, state
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