Modifying silica with viologenic groups

Article abstract of DOI:10.1134/S1070363210050300

Modification of silica with viologenic groups is described. N,N'-Diallyl-γ,γ-dipyridinium dibromide obtained by the reaction of allyl bromide with γ,γ-dipyridyl was hydrosilylated with triethoxysilane followed by copolycondensation of the synthesized bis(3-triethoxysilylpropyl)-γ,γ'-dipyridinium dibromide with tetraethoxysilane. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070363210050300

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 5, pp. 1029–1033. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © L.B. Dzaraeva, A.A. Arutyuniantz, A.S. Archegova, A.N. Shpakov, 2010, published in Zhurnal Obshchei Khimii, 2010, Vol. 80,
No. 5, pp. 858–862.
Modifying Silica with Viologenic Groups
L. B. Dzaraeva, A. A. Arutyuniantz, A. S. Archegova, and A. N. Shpakov
Khetagurov North Osetian State University, ul. Vatuina 46, Vladikavkaz, 362025 Russia
e-mail: dzaraeva@mail.ru
Received July 25, 2009
Abstract―Modification of silica with viologenic groups is described. N,N'-Diallyl-γ,γ'-dipyridinium dibromide
obtained by the reaction of allyl bromide with γ,γ'-dipyridyl was hydrosilylated with triethoxysilane followed
by copolycondensation of the synthesized bis(3-triethoxysilylpropyl)-γ,γ'-dipyridinium dibromide with tetra-
ethoxysilane.
DOI: 10.1134/S1070363210050300
The polymers containing γ,γ'-dipyridinium “violo-
genic” groups attract interest as electron-ex-changing
membranes [1], the redoxites. Their study is promising
in connection with their possible semiconductor,
fotoinitiator, and electrochromic properties, as well as
their application in the systems converting solar energy
into chemical or electrical one.
dibromide (I) was hydrosilylated with triethoxysilane,
and the formed bis(3-triethoxysilylpropyl)-γ,γ'-dipyri-
dinium dibromide was involved into copoly-condensa-
tion with tetraethoxysilane (II) to form polymer (III)
(Scheme 1).
A similar polymer, but with the tosylate anion, was
obtained by hydrosilylation of allyl alcohol with 3-
hydroxypropyltriethoxysilane followed by the reaction
of the formed 3-(triethoxysilyl)propanol with tosyl
chloride and dipyridyl, and polycondensation of the
obtained bis(3-triethoxysilylpropyl)-γ,γ'-dipyridinium
ditosylate with tetraethoxysilane IV–VII (Scheme 2).
In continuation of the work [2] on the synthesis of
the polymers with viologenic groups in the main chain,
we modified silica with the viologenic groups using a
sequence of reaction. Allyl bromide was reacted with
γ,γ'-dipyridyl, the obtained N,N'-diallyl-γ,γ'-dipyridiny
Scheme 1.
N
N
+
2 CH2 CH CHBr
CH2 CH CH2
N
2
Br_
Si
O
Si
N
(EtO)4Si
(EtO)3SiH
(CH2)3
(CH2)3
(EtO)3Si
+
N
CH2CH2CH2
N
Br_
+
+
_C2H5OH
2 Br_
2
Scheme 2.
CH3C6H4OSO2Cl
(EtO)3SiH
(EtO)3Si(CH3)3OH
(EtO)3Si(CH2)3OSO2C6H4CH3
CH2 CH CH2OH
2 CH3C6H4OSO2_
Si
N
N
(EtO)4Si
Si
O
(EtO)Si(CH3)3
N
+
H3CC6H4OSO2_
+
(CH2)3
(CH2)3
N
+
N
2
1029

1030
DZARAEVA et al.
Scheme 3.
N
N
HBr
Br
+
N
Br _
OH
Br H3N+
Br H3N
H2N
2
NH2
2CH2=CH_CH2Br
NaOH
+
+
N
N
N
+
+
NH2
H2N
Br _
Br _
2
(EtO)3SiH
+
+
N
NH2
Br _
Br _
(OEt)3Si
Si~
2
+
~Si
O
(EtO)4Si
(CH2)3~
NH2
+
+
N
N
+
_C2H5OH
_(CH2)3 NH2
Br_
2 Br _
Another way to fix viologenic groups on the silica
surface is as shown in Scheme 3.
nioethyl)-γ,γ'-dipyridinium tetrabromide (X). Hydro-
silylation of compound X and polycondensation of the
formed bis[2-(3-triethylsilylpropyl)ammonioethyl]-γ,γ'-
dipyridinium tetrabromide (XI) with tetraethoxysilane
led to copolymer (XII).
The β-bromethylamine hydrobromide was syn-
thesized by the known procedure [3]. Bis(2-
ammonioethyl)-γ,γ'-dipyridiny tetrabromide (VIII)
was obtained by boiling β-bromoethylamine hydro-
bromide with dipyridyl in acetonitrile. Subsequent
treatment of bis(2-ammonioethyl)-γ,γ'-dipyridinium
tetrabromide VIII with alkali and further reaction of
the formed bis(2-aminoethyl)-γ,γ'-dipyridinium dibromide
(IX) with allyl bromide led to bis(2-allylammo-
In the IR spectra of the products of hydroxylation
of allyl fragments of γ,γ'-dipyridinium groups there are
absorption bands in the regions of 820 cm–1 and 1060 cm–1
indicating the presence of Si–C bonds. The spectra of
copolymers (end products) include a band at 1010 cm–1,
which can be attributed to the Si–O–Si bonds.
Parameters of cyclic voltammograms of compounds I–IV
Reduction
Oxidation
Comp.
Compound
no.
–Еnk, V
Ink, μА
–Еna, V
Ina, μА
–Еna, V
Ina, μА
0.43
0.97
78
66
0.29
0.66
50
60
0.92
1.33
70
58
I
CH2
CH2
CH
CH2
CH2
N
+
Br _
2
0.54
0.81
1.03
40
20
30
–
–
–
–
0.80
1.36
–
76
60
–
II
CH2
N
+
Br_
0.96
20
Si(OEt)3
2
2Br _
N
O
0.38
0.82
5
1.38
88
III
IV
~Si
Si~
10
(CH2)3
N
(CH2
)
3
+
+
(EtO)3SiH
0.5
12
16
0.1
66
1.32
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

MODIFYING SILICA WITH VIOLOGENIC GROUPS
1031
R'
Scheme 4.
_
+e
_
_
+e
_
+
+
+
R
R
R'
R'
R
N
N
N
N
N
N
_e
_e
2 x _
x _
III: R = ~Si_O_Si~
_
I: R = R' = CH2=CH_CH2
x = Br
(CH2)3~
R' = _(CH2 )3
_
II: R = R' = CH2 CH_CH2
_
_
x = Br
Si(OEt)3
x = Br
The table lists the parameters of voltammograms of
compounds I–IV. Based on the data in the table, we
can conclude that the studied compounds can be both
reduced and oxidized. Electrochemical characteristics
of compounds I–III were measured from their
solutions in DMF using cyclic voltammetry on a
platinum electrode. DMF was selected as a solvent due
to the low solubility of compounds in other aprotic
solvents used commonly in organic electrochemistry.
Reduction of compounds I–III proceeds according to
Scheme 4.
transfer of one electron. In all cases anodic peaks are
observed, indicating a relatively high stability of the
species formed at the reduction. The second reduction
stage is irreversible in all cases. Thus, for compounds
II and III the secondary anodic peaks were not
observed.
All the dications (see the table, Fig. 2) are capable
of oxidation. The number of transferred electrons
determined relatively to the reference compound
ferrocene is close to unity. From the published sources
it is known that triethoxysilan is reduced at a potential
close to 0 V [4].
The obtained values of the maximum currents
(Fig. 1) which are close to those of a model compound
(2,4,6-triphenilpyrylium perchlorate) permit an
assumption that the dication is reduced with the
_
_e
_
+e
SiH
Si+
+
Si
H
+ H
I, μA
I, μA
0.97
0.43
+1.02
+1.33
–0.68
–0.29
1.6 1.2 0.8 0.4
0
E, V
E, V
Fig. 1. Reduction of dicatione.
Fig. 2. Oxidation of dicatione.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

1032
DZARAEVA et al.
It follows from the tabulated data that triethoxysilan
N 3.35; Si 7.12; Br 21.53. C28H50Br2N2Si2. Calculated,
%: C 46.28; H 6.88; N 3.85; Si 7.71; Br 22.03.
(compound IV) is oxidized more readily than
compounds I and II. Comparing the potentials of the
first stage of oxidation of dications I and II with IV, it
can be concluded that the ability to oxidation depends
on the presence of viologenic fragment in the
molecules of these substances.
Copolymer by polycondensation of bis(3-tri-
ethoxysilylpropyl)-γ,γ'-dipyridiny dibromide with
tetraethoxysilane (III). A mixture of 3 g (0.03 mol) of
bis(3-triethoxysilylpropyl)-γ,γ'-dipyridinium dibromide,
1 ml of tetraetoxysilane, 4 g of concentrated hydro-
chloric acid and 50 ml of ethanol was refluxed until a
precipitate separated completely, for ~24 h. The
precipitate was filtered off, washed with water and
alcohol, and dried. 2.3 g of not melting white sub-
stance was obtained. Yield 85%. Found, %: C 35.88; H
3.73; N 5.20; Si 5.25; Br 29.90. C16H20BrN2Si. Cal-
culated, %: C 44.85; H 4.67; N 6.54; Si 6.54; Br 37.38.
Based on data from elemental analysis the degree of
substitution in silica is ~80%.
The bipyridinium salts as well as respective
polymeric derivatives are known to be capable of
relatively easy forming stable cation radicals and
(poly)-cation radicals [5, 6].
Investigation of these compounds using electron
spin resonance (ESR) showed that reduction of
compounds containing viologenic groups gives rise to
radicals that are registered by ESR spectroscopy. The
hyperfine structure is similar to that of well-known
dibenzylviologen cation-radical: aN = 0.42 mT, aH =
0.14 mT (8H) and aH(CH3) = 0.28 mT (4H). De-
localization of the unpaired electron is limited by
bipyridinium fragment with the (CH2)3 group at the
nitrogen atom, and does not affect the silicon-
containing residues.
3-Tosyloxypropyltriethoxysilane (IV, V). A mix-
ture of 5.8 g (0.1 mol) of allyl alcohol, 16.4 g (0.1 mol)
of triethoxysilane, 50 ml of isopropanol, 5 ml of 0.05%
solution platinohydrochloric acid in isopropyl alcohol
was refluxed under monitoring by chromatography.
After the reaction completing, from the reaction
mixture isopropanol was distilled off, the residue was
cooled to –5°C, and to it was added 10.4 g of tosyl
chloride and 50 ml of pyridine, and the mixture was
shaken until complete dissolution of tosyl chloride and
then without removing it from the ice bath, it was left
for 3 h. Then at a temperature 5°C or below 100 ml of
water was added, initially dropwise and then poured.
The resulting tosylate was extracted with ether, the
extract was washed with cold diluted solution of
H2SO4, then with water and with a solution of NaHSO4
and then it was dried over Na2SO4. After removing
ether remained a colorless viscous liquid with a faint
smell, decomposing when heated above 100°C. Found,
%: C 50.83; H 7.07; Si 7.01; S 8.13. C16H28O6SSi.
Calculated, %: C 51.06; H 7.44; Si 7.44 ; S 8.51.
EXPERIMENTAL
N,N'-Diallyl-γ,γ'-dipyridinium dibromide (I). To
15.6 g (0.1 mol) of dipyridyl dissolved in a minimal
amount of dimethylformamide was was added while
stirring 15.6 g (0.13 mol) of allyl bromide, and the
mixture was left untill precipitate separated. The
precipitate was filtered off, washed with water and
alcohol, and then with ether. A light yellow crystalline
substance with mp 228°C (from ethanol) was obtained.
Yield quantitative. Found, %: C 46.16, H 4.48; N 6.93;
Br 3.97. C16H18Br2N2. Calculated, %: C 48.24, H 4.52;
N 7.03; Br 4.02.
Bis(3-triethoxysilylpropyl)-γ,γ'-dipyridinium di-
bromide (II). To a mixture of 16.4 g (0.1 mol) of
triethoxysilane, 38.8 g of N,N'-diallyl-γ,γ'-dipyridi-
nium dibromide in isopropanol was added 5 ml of
0.06% solution of platinumhydrochloric acid in isopro-
panol (Speier catalyst) and the mixture was stirred at
the boiling point of isopropanol at reflux. The reaction
process was monitored by chromatography. After the
reaction completion, isopropanol was distilled off and
the residue was treated with ether for separation of
catalyst. A crystalline substance of a light brown color
was obtained, softening temperature 290–300°C (from
ethanol). Yield 30 g (60%). Found, %: C 45.95; H 6.29;
Bis(3-triethoxysilylpropyl)-γ,γ'-dipyridiny ditos-
ylate (VI). To 3.12 g (0.02 mol) of dipyridyl dissolved
in a minimum amount of DMF was added 15 g
(0.04 mol) of 3-tosyloxypropyltriethoxysilane, the
mixture was left to stand until complete formation of a
precipitate which was filtered off, washed with water,
alcohol, and ether, and dried. A colorless crystalline
substance was obtained with softening temperature
250–260°C (from ethanol). Found, %: C 54.87; H
6.67; Si 5.89; N 2.97; S 5.58. C12H64O12N2S2Si2.
Calculated, %: C 55.50; H 7.04; Si 6.16; N 3.08; S
7.04.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

MODIFYING SILICA WITH VIOLOGENIC GROUPS
1033
Copolymer by polycondensation of bis(3-tri-
ethoxysilylpropyl)-γ,γ'-dipyridinium ditosylate (VII)
was obtained as the previous copolymer. A mixture of
9.3 g (0.01 mol) of bis(3-triethoxysilylpropyl)-γ,γ'-
dipyridinium tosylate, 2 ml of tetraethoxysilane, 4 g of
concentrated hydrochloric acid and 50 ml of ethanol
was refluxed for 24 h. The precipitate was filtered off,
washed with water and alcohol, and dried. Infusible
white substance, 8 g, was obtained. Found, %: C
42.83; H 4.59; N 3.35; Si 3.56; S 8.5. C28H36N2O6S2Si.
Calculated, %: C 57.14; H 6.12; N 4.76; Si 10.88. The
degree of substitution is ~75%.
49.01; C20H30Br4N4. Calculated, %: C 37.15; H 4.64; N
8.66; Br 49.53.
Bis-2-(3-triethylsilylpropyl)ammonioethyl-γ,γ'-
dipyridiny dibromide (XI). 6.74 g (0.01 mol) of bis-
2-(3-triethylsilylpropyl)ammonioethyl-γ,γ'-dipyridi-
nium dibromide was dissolved in 50 ml of isopropanol
and to the solution was added 3.28 g (0.02 mol) of
triethoxysilane, 0.001 g of H2PtCl3 in 5 ml of
isopropanol (catalyst Speier). The mixture was boiled
for 5 min, then cooled, the precipitate was filtered off,
washed with ethanol and dried, mp 300°C (from
acetonitrile). Found, %: C 39.02; H 5.97; N 6.03; Si
6.10; Br 32.57. C32H62 Br4N4O6Si2. Calculated, %: C
39.42; H 6.36; N 6.36; Br 32.85.
Bis(ammonioethyl)-γ,γ'-dipyridinium tetrabro-
mide (VIII). A mixture of 3 g (0.02 mol) of dipyridyl,
8 g (0.04 mol) of β-bromethylamine hydrobromide,
and 30 ml of dry acetonitrile (distilled over P2O5) was
refluxed with stirring. Within 20 minutes after the
reaction started oil separated. The contents of the flask
was cooled, the precipitate was filtered off, washed
with acetonitrile, and dried. Yield 8.3 g (73%). A
crystalline solid of dark orange color was obtained, mp
145°C. Found, %: C 29.36; H 3.72; N 9.36; Br 53.53;
C14H22Br4N4. Calculated, %: C 29.68; H 3.88; N 9.42;
Br 53.87.
Copolymer by polycondensation of bis-2-(3-
triethoxysilylpropyl)ammonioethyl-γ,γ'-dipyridinium
tetrobromide with tetraethoxysilane (XII) was
obtained similarly to previous copolymers. Solid non-
melting white material. Found, %: C 26.25; H 3.54; Si
3.10; N 6.21; Br 35.49. (C20H32Br4 N4Si)n. Calculated,
%: C 35.50; H 4.73; Si 4.14; N 8.28; Br 47.33. From
the data of elemental analysis follows the degree of
substitution equal to ~75%.
REFERENCES
Bis(ammonioethyl)-γ,γ'-dipyridinium dibromide
(IX). Bis(ammonioethyl)-γ,γ'-dipyridinium tetrabromide
was dissolved in 2 M aqueous NaOH and left for
12 h. Colorless needle-shaped crystals precipitated,
which were filtered off, washed with water and
alcohol, and dried, mp 120°C (from ethanol). Yield
quantitative. Found, %: C 41.23; H 4.71; N 9.62; Br
56.47. C14H20Br2N4. Calculated, %: C 41.58; H 4.95; N
9.89; Br 56.59.
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polimernykh donorno-aktseptornykh kompleksov (Photo-
chemistry of Polymeric Donor–Acceptor Complexes),
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cheskoi khimii (Experimental Methods in Organic
Chemistry), Moscow: Mir, 1969
Bis(2-allyammonioethyl)-γ,γ'-dipyridinium tetra-
bromide (X). 8 g (0.02 mol) of bis(ammonioethyl)-
γ,γ'-dipyridinium dibromide and 5 g (0.04 mol) of allyl
bromide was dissolved in 30 ml of DMF and the
mixture was refluxed for 3 h with stirring. The mixture
was then cooled, the precipitate formed was filtered
off, washed with water, alcohol, and ether, and dried.
The obtained crystals are yellow-orange, mp 175°C
(from ethanol). Found, %: C 36.81; H 4.31; N 8.13; Br
4. Berberova, N.T., Doctorate Sci. (Chem.) Dissertation,
Rostov-on-Don, 1991.
5. Krainov, I.P., Kramarenko, S.F., Dotsenko, E.I., Bum-
ber, A.A., et al., Khim. Geterotsikl. Soedin., 1986, no. 5,
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010