Reaction between silver trifluoroacetate and quercetin in low-polarity organic media

Article abstract of DOI:10.1134/S0036023613090210

CF₃COOAg-Qr-P systems, where Qr is quercetin and P is an organic solvent, have been studied by spectroscopic methods. The reaction between silver trifluoroacetate and quercetin has been shown to produce colloid solutions, whose destruction terminates with the precipitation of a silver phase. The kinetic characteristics of the reaction between silver trifluoroacetate and quercetin in ethyl acetate have been determined.

Full text of DOI:10.1134/S0036023613090210

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2013, Vol. 58, No. 9, pp. 1085–1089. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.P. Smagin, I.M. Fadin, 2013, published in Zhurnal Neorganicheskoi Khimii, 2013, Vol. 58, No. 9, pp. 1212–1216.
PHYSICAL METHODS
OF INVESTIGATION
Reaction between Silver Trifluoroacetate and Quercetin
in LowꢀPolarity Organic Media
V. P. Smagin and I. M. Fadin
Altai State University, pr. Lenina 61, Barnaul, 656049 Russia
Received September 20, 2012
Abstract
— CF COOAg–Qr–P systems, where Qr is quercetin and P is an organic solvent, have been studied
3
by spectroscopic methods. The reaction between silver trifluoroacetate and quercetin has been shown to proꢀ
duce colloid solutions, whose destruction terminates with the precipitation of a silver phase.The kinetic charꢀ
acteristics of the reaction between silver trifluoroacetate and quercetin in ethyl acetate have been determined.
DOI: 10.1134/S0036023613090210
Colloid solutions of metals and their compounds fluoroacetate, which was preliminary synthesized by
have unordinary physical and chemical properties. the reaction between trifluoroacetic acid and sodium
They are applied in the chemical synthesis of metal hydroxide.
powders, metallic film coatings, and functional mateꢀ
rials [1–3]. The stability, size, and size distribution of
colloid particles and the direction of their further
transformations depend to a considerable degree on
the properties of a dispersion medium. The use of disꢀ
persion media based on optical monomers and polyꢀ
mers allows one to combine the synthesis of nanosized
metal particles and metal compounds with the syntheꢀ
sis of optically transparent metalꢀcontaining polymer
materials and, among other things, to obtain quantum
dots immobilized in optically transparent polymer
matrices [4–6]. Complexation, redox, and colloidaꢀ
tion processes play an important part in these syntheꢀ
ses, but they are very poorly studied in lowꢀpolarity
organic solvents.
The quercetin C H O used in our work was of
pure grade (LACHEMA).
15
10
7
The IR spectra of compounds were recorded on an
Infralum FT 801 spectrophotometer in the region of
–1
4
000–400 cm . The electronic absorption spectra of
solutions were recorded on a Specord UV Vis spectroꢀ
photometer in the region of 200–800 nm. The absorꢀ
bance at absorption band maxima was measured on an
SFꢀ46 spectrophotometer with reference to ethyl aceꢀ
tate at a temperature of 296 K. The photometric scale
of the SFꢀ46 spectrophotometer was calibrated as
described in [11].
RESULTS AND DISCUSSION
Here our task is to perform the spectroscopic study
Solutions of silver trifluoroacetate, quercetin, and
of the reaction between silver trifluoroacetate and their mixtures were prepared in trichloromethane,
quercetin in organic media that are close to optical ethyl acetate, methylmethacrylate, and acetonitrile
–3
monomers by their polarity.
with concentrations of 1.00
×
10 mol/L and lower.
Our choice of silverꢀcontaining systems is directly
Silver trifluoroacetate solutions are colorless. The
due to the properties of silver and silverꢀcontaining longꢀwave absorption band in the spectra of solutions
functional materials [4, 6]. The use of silver trifluoroꢀ recorded with reference to the solvent is located in the
acetate is caused by its high solubility in lowꢀpolarity region of 250 nm. It is assigned to the
n
→ σ
* electron
solvents without additional components [7]. Querceꢀ transition. This band is due to the carboxyl group of
tin has a moderate reducing activity with respect to silꢀ trifluoroacetate ions. Silver trifluoroacetate solutions
ver ions in organic media [8].
are transparent in the spectral region of >270 nm.
Quercetin solutions are lightꢀyellow.In the region
of wavelengths >250 nm, the spectra contain two absorpꢀ
tion bands of quercetin at 272 and 377 nm (Fig. 1). The
apparent molar extinction coefficients at the maxima
EXPERIMENTAL
Silver trifluoroacetate was synthesized by the reacꢀ
tion between freshly precipitated Ag O H O and triꢀ
fluoroacetic acid in an aqueous medium. The crystalꢀ
line salt was separated via slow evaporation of its acidꢀ
ified solution on a water bath and subsequent drying in
air. The salt was identified by IR spectroscopy using
3
4
of these bands are
respectively. The absorption bands are related with the
electron transitions in the chromophore sysꢀ
∼
6
×
10 and ~2
×
10 L/(mol cm),
⋅
n
2
2
π
→
π
*
tems of quercetin.
After quercetin solutions were added to silver salt
literature data [9, 10] and the spectrum of sodium triꢀ solutions or vice versa, the mixtures gradually acquired
1085

1086
SMAGIN, FADIN
A
A
1.4
377 nm
1.0
4
3
272 nm
1.0
0.5
3
2
1
0.5
–
0.1
250
350
λ
, nm
Fig. 1. Absorption spectra of quercetin solutions in ethyl
2
1
acetate with reference to ethyl acetate at a quercetin conꢀ
–
5
–5
centration of (
1) 1.00
×
10 , (
2) 2.00
×
10 , and (
3)
–0.1
–
5
4.00
×
10 mol/L.
400
500
600
λ
, nm
Fig. 2. Absorption spectra recorded for the CF COOAg–
3
a light pink color. With time, they became purpleꢀred.
The rate of the change in color, color intensity, and
shade depended on the concentrations and concentraꢀ
tion ratios of dissolved compounds. In the region of
Qr–Р system, where P stands for (
1
) acetonitrile, (
2)
trichloromethane, ( ) methylmethacrylate, and (
3
4
) ethyl
acetate, in 6 min beginning from the moment the solutions
were prepared.
4
50–600 nm, the spectra of solutions contained an
absorption band with a maximum at 529 nm (Fig. 2).
Its intensity grew with time (Fig. 3). The position of
the longꢀwave edge of this absorption band remained
unchanged. No shift of the absorption band maximum
was observed in the spectrum upon the replacement of
a solvent. Reasoning from the obtained results and the
literature data [8, 12–15], this band was assigned to
the absorption of colloid particles formed in the reacꢀ
tion between silver trifluoroacetate and quercetin.
This band shifted towards long wavelengths with
respect to the absorption bands of elemental silver colꢀ
loids in the spectra of aqueous solutions, lowꢀtemperꢀ
ature oxide matrices, and inverted aqueous micelles in
hydrocarbon systems [8, 12–15]. We relate this shift to
the effect of an organic medium, including a probable
interaction of silver ions with quercetin on the surface
of colloid particles. This interaction may also be one of
the factors that stabilize colloid solutions.
The kinetic of the reaction between silver trifluoroꢀ
acetate and quercetin was studied in an ethyl acetate
medium. The reaction was monitored by the change in
the absorbance of solutions. The experimental condiꢀ
tions (analytical wavelength, concentrations and conꢀ
centration ratios of reagents, and temperature) were
selected from the obtained spectral information. They
allowed us to record the absorbances of solutions with the
A
1.4
529 nm
1.0
The colloid solutions were stable during the time
period from several minutes to several days. The proꢀ
cess of their destruction terminated with the formation
of a “silver mirror” on the walls of a reaction vessel and
the settlement of a black elemental silver precipitate.
The colloid solutions in the systems prepared from
0.5
0.1
4
3
2
1
–4
equal amounts of reagents up to ~4
×
10 mol/L had
the highest stability. When the concentration of comꢀ
pounds in solutions was increased (at the same
equimolar ratios), the formation of a “silver mirror”
predominated. The excess concentration of one
reagent eventually led to the predominant settlement
of elemental silver in the form of a black precipitate on
the bottom of a reaction vessel. A considerable effect
on the rate of the formation and destruction of colloid
solutions was produced by the temperature.
–
4
00
450
550
λ
, nm
Fig. 3. Absorption spectra recorded for the CF COOAg–
Qr–ethyl acetate system with reference to ethyl acetate in
in different time intervals beginning from the moment the
solutions were (
3
–5
1–4) were prepared. cAg = 5.00 × 10
–3
mol/L, cQr = 1.00
×
10 mol/L.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

REACTION BETWEEN SILVER TRIFLUOROACETATE AND QUERCETIN
1087
A
A
0.6
0.09
35 min
0
0
0
.07
.05
.03
0
.5
30 min
5 min
5 min
2
0.4
0.3
0.2
0.1
1
0.01
0
5
10 15 20 25 30 35 40 45
, min
t
Fig. 5. Initial region of the dependence
А
/
=
f
(
t
)
for the
cQr = 2, СAg
10 mol/L.
CF3COOAg–Qr–ethyl acetate system. cAg
=
0
–4
–4
4.00
×
10 mol/L, cQr = 2.00
×
0
20
40 60
, min
80 100 120
equations of these plotd, and linearity coefficients are
*
t
given in Tables 2 and 3. The rate constant
k
=
Ag
Fig. 4.
А
=
f(t)
for the CF3COOAg–Qr–ethyl acetate sysꢀ
×
0.56
0.56
–
4
0.90 L /(mol min) and the reaction order with
respect to silver nAg = 0.56 were calculated from the
equation that describes the dependence at an excess
quercetin concentration and a variable silver trifluoroꢀ
tem. cAg
/
cQr = 2, cAg = 4.00
×
10 mol/L, cQr = 2.00
–4
10
mol/L.
lowest error and perform the reaction for 60–120 min.
The rate constants and orders of the reactions with
respect to reagents were determined by the method of
excess concentrations [16]. In this case, we assumed
that a formally simple chemical reaction proceeds in
the systems.
*
acetate concentration. The rate constant
k
= 8.2
×
Qr
2
1.44
1.44
10
L
/(mol
min) and the reaction order with
respect to quercetin nQr = 1.44 were calculated from
the equation that describes the dependence at an
excess silver trifluoroacetate concentration and a variꢀ
able quercetin concentration.
The calculation of the total reaction order n = +
nAg
Qr gives 2. The reaction rate constant was calculates as
Solutions with a constant excess quercetin concenꢀ
–3
tration (1.00
fluoroacetate concentration were prepared. Molar
ratios cQr cAg in the solutions of this series were varied
×
10 mol/L) and a decreasing silver triꢀ
n
/
*
nj
aicj
k
from 1 : 1 to 150 : 1. The second series of solutions was
prepared with a constant excess silver trifluoroacetate
i
k* =
,
where i is silver and j is quercetin for the
–
4
concentration (4.00
×
10 mol/L) and a decreasing
cQr in these
series of solutions with excess quercetin and vice versa
for the series of solutions with excess silver trifluoroacꢀ
etate, ai and aj are the stoichiometric coefficients in
the equation of the reaction between silver trifluoroacꢀ
quercetin concentration. Molar ratios cAg
/
solutions were varied from 1 : 1 to 4 : 1. The absorꢀ
bances of solutions were recorded at 529 nm.
The obtained data were used to plot А529
= f(t) plots
etate and quercetin, ai
= aj = 1. The assumption on the
that reflected the change in the absorbance of soluꢀ
tions with reaction time. Each curve may nominally be
divided into three regions: the region of the accumulaꢀ
tion of a product with a gradual increase in reaction
rate, the linear region with a constant rate, and the
region corresponding to a decrease in the reaction rate
and the termination of the reaction. The reaction rate
equality of the stoichiometric coefficients to unity folꢀ
A
y
= –0.2 + 0.0061
= 0.999
x
0.4
r
–1
(
w*, min ) was determined via graphical differentiaꢀ
0.3
tion by drawing tangent lines at different points of a
kinetic curve. The reaction rate constants and orders
with respect to reagents were determined logarithmiꢀ
cally [16]. The procedure of estimating the reaction
0
.2
.1
0
rate and plotting the dependence
w
* =
(ln plot of the logꢀ
n lnc , where is silꢀ
f(t) for one of
the solutions is illustrated in Figs. 4–8 and Table 1.
45 50 55 60 65 70 75 80 85 90 95
, min
The data for plotting a ln(
w
*) =
*
f
c)
t
arithmic function ln
w* = ln ki
+
i
i
i
Fig. 6. Middle region of the
А
=
f
(
t
)
/
plot for the
cQr = 2, cAg
10 mol/L.
ver or quercetin according to the studied series of soluꢀ
*
CF3COOAg–Qr–ethyl acetate system. cAg
=
–4
–4
tions and
k
is the rate constant found from
w*; the
4.00
×
10 mol/L, cQr = 2.00
×
i
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

1088
SMAGIN, FADIN
3
–1
A
w* × 10 , min
1
10 min
1
05 min
0
.50
.45
6
5
4
3
2
1
1
00 min
115 min
0
0.40
1
0 20 30 40 50 60 70 80 90 100 110 120
t
94 96 100 104 108 112 116 120
t, min
, min
Fig. 7. End region of the
А
=
f
(
t
)
plot for the CF3COOAg–Qr–
Fig. 8.
w
* =
cQr = 2, cAg = 4.00
10 mol/L.
f(t) for the CF3COOAg–Qr–ethyl acetate sysꢀ
–
4
–4
ethyl acetate system. cAg
/
cQr = 2, cAg = 4.00
×
10 mol/L,
tem. cAg
/
× 10 mol/L, cQr = 2.00 ×
–4
–4
cQr = 2.00
×
10 mol/L.
lows from the singleꢀelectron exchange in the redox ical wavelength in the absorption band of colloid parꢀ
reaction between silver ions and quercetin and is based
on the character of the interaction of metals with querꢀ
cetin [9]. As a result, the average reaction rate constant
w*
εl
k*
εl
ticles as
w
=
and
k
=
,
where w* and k* are the
–1
reaction rate (min ) and the reaction rate constant
4
2
2
amounted ~4
×
10 L /(mol min). Noninteger reacꢀ
which are determined from
extinction coefficient, L/(mol cm), and
ness of an analytical cell, cm. The estimation of
similar systems is a very complicated problem. For
example, it variates from
for colloid elemental silver particles [8]. The average
molar extinction coefficient calculated for colloid parꢀ
А
=
f(t),
ε
is the molar
is the thickꢀ
tion orders with respect to compounds and partial
reaction rate constant ratios indicate a complex charꢀ
acter of the process and its high sensitivity to the
changing quercetin concentration in solution.
l
ε
in
3
4
7
×
10 to
1 10 L/(mol cm)
×
The conversion to the reaction rate (
min)), the partial reaction rate constants (kAg
w, mol/(L
,
0
.44
0.44
0.44
0.44
mol /(L min); kQr, L /(mol
total reaction rate constant (
, L/(mol min)) can be its termination, and the concentrations of a reagent on
min)), and the ticles from the rates of the reaction w*, the time until
k
performed using the Bouguer–Lambert–Beer law and the basis of the data for the entire series of studied
knowing the molar extinction coefficient at an analytꢀ solutions both with excess silver trifluoroacetate and
Table 1. Data for plotting
w
* =
f
(
t
) for the CF COOAg–Qr–ethyl acetate system. cAg
/
cQr = 2, cAg = 4.00
×
10–4 mol/L,
3
–
4
and cQr = 2.00
×
10 mol/L
t
, min
15
25
1.60
30
35
45
95
100
5.33
105
110
2.67
115
3
–1
w
*
×10 , min
0.18
2.67
4.13
6.10
6.10
4.00
0.54
Table 2. Data for plotting a ln
w
* =
f(lnc) plot for the CF COOAg–Qr–ethyl acetate system at a constant excess quercetin
3
–
3
concentration of 1.00
× 10 mol/L
cAg, mol/L
lncAg [mol/L]
w*, min–1
6.00
10–5
×
5.00
×
10–5
4.00
×
10–5
2.00
×
10–5
0.68 ×
10–5
–9.72
0.0040
–5.52
–9.90
0.0038
–5.57
–10.1
0.0036
–5.63
–10.8
0.0019
–6.27
–11.9
0.0013
–6.65
–1
lnw* [min ]
Equation, linearity coefficient
* = (lnc) plot for the CF COOAg–Qr–ethyl acetate system at a constant excess silver triꢀ
3
ln
w
* = –0.102 + 0.556ln cAg, r = 0.980
Table 3. Data for plotting a ln
w
f
×
–4
fluoroacetate concentration of 4.00
10 mol/L
4.00
10–4
cQr, mol/L
lnCQr [mol/L]
w*, min–1
×
3.00
–8.11
0.0099
–4.62
ln
×
10–4
2.00
–8.52
0.0061
×
10–4
1.00
–9.21
0.0010
–6.91
×
10–4
–7.82
0.0060
–5.12
–
1
ln
w
* [min ]
–5.10
Equation, linearity coefficient
w
* = 6.71 + 1.44ln cQr, r = 0.863
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

REACTION BETWEEN SILVER TRIFLUOROACETATE AND QUERCETIN
1089
×
103 L/(mol cm) that is close to the
7
8
9
. V. P. Smagin, R. A. Maier, G. M. Mokrousov, and
R. A. Chupakhina, Patent RU 1806152, Byull. Izobret.,
No. 12 (1993).
. E. M. Egorova, Extended Abstract of Doctoral Disserꢀ
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. K. Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds, New York: WileyꢀInterꢀ
science, 1986; Mir, Moscow, 1991).
quercetin is ~6
data [8].
Hence, as a result of our study, we have detected the
formation of colloid silver particles in the reaction
between silver trifluoroacetate and quercetin in
organic media that are close to optical monomers in
their polarity. The kinetic characteristics of the reacꢀ
tion of the components in an ethyl acetate medium
have been determined.
10. E. V. Karpova, Candidate’s Dissertation in Chemistry
Moscow, 2000).
(
1
1. A. J. Gordon and R. A. Ford, The Chemist’s Companion:
A Handbook of Practical Data, Techniques and Referꢀ
ences (Wiley, New York, 1972; Mir, Moscow, 1976).
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Translated by E. Glushachenkova
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013