hydrogels containing copper(II) and cobalt(II) ions. LucÃa Victoria Lombardo Lupano,. â . Juan Manuel Lázaro MartÃnez,. *,â¡. Lidia Leonor Piehl,. â«. Emilio RubÃn ...
Synthesis, characterization and catalytic properties of cationic hydrogels containing copper(II) and cobalt(II) ions. †
Lucía Victoria Lombardo Lupano, Juan Manuel Lázaro Martínez, ∫
*,‡
Lidia Leonor Piehl,
∫∫
Emilio Rubín de Celis, Rosa María Torres Sánchez, Viviana Campo Dall’ Orto
∫
*,†
†
IQUIFIB-CONICET & Departamento de Química Analítica y Fisicoquímica. Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. Junín 956 (1113), CABA, Argentina. ‡ CONICET, Av. Rivadavia 1917 (1033), CABA, Argentina & Departamento de Química Orgánica. Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. Junín 956 (1113), CABA, Argentina. ∫ Departamento de Química Analítica y Fisicoquímica. Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. Junín 956 (1113), CABA, Argentina & ∫∫ CETMIC-CONICET. Camino Centenario y 506, M. B. Gonnet (1897), Argentina.
Supporting Information
14
A
12 10
pH
8 6 4 2 0 0
2
4
6
8
10
12
14
16
Vol (mL)
1
10
pKa
9.5
9
8.5
8 -1
-0.5
0
log α/(1-α)
0.5
1
1.5
Figure S1. Forward potentiometric titration curve for Poly(EGDE–DA) in presence of HCl standard solution, using 0.09714 M NaOH standard solution. Sample amount: 0.5005 g. The end points were determined by the second derivative method (A). The representation of pKa vs log (α / (1-α)) from the data of the titration curve (B). Discussion of Figure S1: The amount of protonable –R2N groups was determined by adding an excess of standard HCl solution and forward titration with NaOH standard solution. The titration curve showed a first end point (determined by the second derivative method) corresponding to the neutralization of the excess of HCl. The second end point corresponds to the neutralization of the H+ bound to the basic groups of the polyelectrolyte.1,2 A buffer region around pH 10 was attributed to the presence of amine groups in the network following the equilibrium: -R2NH+
-R2N + H+
ruled by the corresponding apparent Ka (acid dissociation constant):
Ka
H R N R NH
2
2
The acid dissociation degree (α) for -R2NH+ was calculated from each point of the titration experiment according to the expression derived from the charge balance:
Na H OH
C
where Na+ comes from the titrant, and C = [-R2NH+ ] + [-R2N] . In order to analyze the electrostatic interaction between charged groups, the following equations can be used:3
pH pK a0 n log 1
2
pK a pK a0 (n 1) log 1
(modified Henderson–Hasselbalch equation)
The pKa is the p-value corresponding to the apparent acid dissociation constant for –R2NH+ group. It is apparent because it is sensitive to the effect of electric charges of the same sign close in the network and to some conformational changes. The pKa can be calculated from each value of pH and the corresponding α, using the Henderson-Hasselbalch equation:
pH pK a log 1 The pKa0 is the pKa value at α = 0.5. And the empirical parameter n is a measure of the electrostatic interactions magnitude in the polyelectrolytes, as well as the hydrophilicity. The parameters estimated from the modified Henderson-Hasselbalch equation were: At α < 0.5 At α > 0.5
pKa0 : 9.96 ± 0.03 pKa0 : 9.97 ± 0.02
n: 3.24 ± 0.09 n: 0.21 ± 0.02
Here, at α lower than 0.5, the repulsive electrostatic effect of –R2NH+ made these units more acidic, pKa values decreased when pH decreased, and the n parameter was significantly higher than 1. At α higher than 0.5, the electrostatic effect was less significant due to the decrease of the amount of fixed electric charges in the network, reason by which some conformational changes should account for the decrease in pKa values with increasing α. References of the Discussion of Figure S1: (1) Leal Denis, M. F.; Carballo, R. R.; Spiaggi, A. J.; Dabas, P. C.; Campo Dall’ Orto, V.; Lázaro Martínez, J. M.; Buldain; G. Y. Synthesis and sorption properties of a polyampholyte. React. Funct. Polym. 2008, 68, 169-181. (2) Lázaro Martínez, J. M.; Leal Denis, M. F.; Campo Dall’ Orto, V.; Buldain, G. Y. Synthesis, FT IR, solid state NMR and SEM studies of novel polyampholytes or polyelectrolytes obtained from EGDE, MAA and imidazoles. Eur. Polym. J. 2008, 44, 392-407. (3) Casolaro, M.; Bottari, S.; Cappelli, A.; Mendichi, R.; Ito, Y. Vinyl polymers based on lhistidine residues. Part 1. The thermodynamics of poly(ampholyte)s in the free and in the crosslinked gel form. Biomacromolecules 2004, 5, 1325-1332.
3
Figure S2. Transport number (t+) vs pH from the diffusion potential method used to determine the IEP of the surface of the particles. Solid line is a guide for the eye.
4
Figure S3. FTIR spectra for Poly(EGDE-DA) and for its Cu(II)- and Co(II)-complexes containing 125.0 and 12.5 mg of metal ion per gram of polymer respectively.
5
Figure S4. Adsorption isotherm of Cu(II) onto the Poly(EGDE-DA) at 24º C. Experimental data (D) fitted to the Temkin (F), Langmuir (B) and D-R (H) models.
6
Figure S5. Images of Co(II)-Poly(EGDE-DA) (brown), Poly(EGDE-DA) (white-yellowish) and Cu(II)-Poly(EGDE-DA) (green).
7
Figure S6. ESR spectra for Poly(EGDE-DA) containing 40 (black line) or 125 mg of Cu(II) per gram of polymer (red line). Discussion of Figure S6: ESR experiments were performed in order to elucidate the coordination sphere of Cu(II), however the hyperfine structures in the parallel region were not resolved at both low and high levels of Cu(II) in the hydrogel (Figure S6). These results indicate that more than one coordination mode could be coexisting together with some Cu-Cu dipolar interaction or exchange coupling as a result of a short distance (10-15 Å) between the Cu(II) complexes. With these evidences we propose that N atoms together with O atoms in the network are significant in the uptake of Cu(II). Moreover, the N atoms could be more significant than O in the formation of complexes with Cu(II), having into account some previous results in EGDE-containing polymers.1 Reference of the Discussion of Figure S6: (1) Lázaro Martínez, J. M.; Monti, G. A.; Chattah, A. K. Insights into the coordination sphere of copper ion in polymers containing carboxylic acid and azole groups. Polymer 2013, 54, 52145221.
8
Figure S7. DSC thermograms of Poly(EGDE-DA) (black line), Co(II)- Poly(EGDE-DA) (red line), Cu(II)-Poly(EGDE-DA) (blue line).
9
Figure S8. TG-DTG curves for Poly(EGDE-DA) and for its Cu(II)- and Co(II)-complexes containing 125.0 and 12.5 mg of metal ion per gram of polymer respectively.
10
A
B
C
Figure S9. EDS spectra of Poly(EGDE-DA) (A), Co(II)-Poly(EGDE-DA) (B) and Cu(II)Poly(EGDE-DA) (C).
11
Figure S10. H2O2 concentration profile in Co(II)-Poly(EGDE-DA) / H2O2 (♦) and in Cu(II)Poly(EGDE-DA) / H2O2 (●) heterogeneous system.
12
A
B
Figure S11. (A) Simulated CW ESR in band X spectra from spin trapping experiment with DMPO of Figure 3A. Heterogeneous system: Co(II)-Poly(EGDE-DA) / 63 mM H2O2. The simulation and fits of the experimental spectrum allowed establishing the presence of two species: a DMPO/OOH and a DMPO/OH adducts. The molar fractions of DMPO/OOH and DMPO/OH adducts were 0.93 and 0.07 respectively. (B) Simulated CW ESR in band X spectra from spin trapping experiment with DMPO of Figure 3B. Heterogeneous system: Cu(II)-Poly(EGDE-DA) / 63 mM H2O2. The simulation and fits of the experimental spectrum allowed establishing the presence of the DMPO/OH adduct (molar fraction: 1.00).
13
A B
3470
3480
3490
3500
3510
3520
3530
3540
3550
Magnetic Field (G)
Figure S12. Experimental (A) and simulated (B) CW ESR in band X spectra from spin trapping experiments with DMPO. Heterogeneous system: Co(II)-Poly(EGDE-DA) / 63 mM H2O2 in the presence of 200 U mL-1 SOD. The simulation and fits of the experimental spectrum allowed establishing the presence of the DMPO/OH adduct (molar fraction: 1.00).
14
A
2.4
Absorbance
1.9
1.4
0.9
0.4
-0.1 200
300
400
500
600
700
Wavelength (nm)
B
1.9
Absorbance
1.4
0.9
0.4
I III -0.1 200
300
II 400
500
600
700
Wavelength (nm)
Figure S13. UV- visible spectra at different times of reaction of 42 μM MO with Co(II)Poly(EGDE-DA) / 63 mM H2O2 (A) and with Cu(II)-Poly(EGDE-DA) / 63 mM H2O2 (B).
15
Discussion of Figure S13: Our evidence about the degradation products is based on the UV-visible spectra of MO in aqueous solutions treated with H2O2 in presence of Co(II)-Poly(EGDE-DA) and of Cu(II)Poly(EGDE-DA). In the Figure S13A, the black-line curve represents the spectrum of MO in aqueous solution. The addition of H2O2 produced a broad band below 300 nm (dark-blue curve). The degradation reaction started when Co(II)-Poly(EGDE-DA) was added: the band with a maximum at 464 nm decreased during 100 minutes and the intensity of the orange color of the MO solution was also affected (blue-line spectra), at the time that a new band centered at 310 nm was increasing in absorbance. Here, we can conclude that the first step of this oxidative degradation is to damage the conjugated structure of MO, at the time that a predominant degradation product is forming. 1-3 The maximum of absorbance at 310 nm is consistent with the presence of a p-benzenediaminetype derivative. Other possible degradation products related to p-amino benzenesulfonate have a small absorption band close to 300 nm. In the Figure S13B, the curve I represents the spectrum of MO in aqueous solution. The addition of H2O2 produced a broad band below 300 nm. The degradation reaction started when Cu(II)-Poly(EGDE-DA) was added: the band with a maximum at 464 nm rapidly decreased during the first 10 minutes and the intensity of the orange color of the MO solution was also significantly affected (blue-line spectra). Beyond the first ten minutes, an opalescence of the solution was observed, together with an increase of absorbance in the range below 400 nm (brown-line spectra). Then, beyond 300 min, the solution went from pale-yellowish and translucent to colorless, and the absorbance kept low at wavelengths higher than 300 nm (curves II and III, dark grey-line spectra). Analyzing these results, we can conclude that the first step of this oxidative degradation is to damage the conjugated structure of MO, correspondingly occurs the bleaching reaction. During the second step, the oxidized intermediates with benzene-related structures open the ring and generate the oxidized aliphatic chain compounds. Eventually, aliphatic chain compounds would take on a further degradation into CO2 and H2O.1-3 References of Discussion of Figure S13: (1) Dai, K.; Chen, H.; Peng, T.; Ke, D.; Yi, H. Photocatalytic degradation of methyl orange in aqueous suspension of mesoporous titania nanoparticles. Chemosphere 2007, 69, 1361-1367. (2) Baiocchi, C.; Brussino, M. C.; Pramauro, E.; Bianco Prevot, A.; Palmisano, L; Marcí, G. Characterization of methyl orange and its photocatalytic degradation products by HPLC/UV– VIS diode array and atmospheric pressure ionization quadrupole ion trap mass spectrometry. Int. J. Mass Spectrom. 2002, 214, 247–256. (3) He, Y.; Grieser, F.; Ashokkumar, M. The mechanism of sonophotocatalytic degradation of methyl orange and its products in aqueous solutions. Ultrason. Sonochem. 2011, 18, 974–980.
16
Figure S14. MO concentration profile in the heterogeneous system, which consisted on 100 mL of 42 μM MO solution in contact with: 0.1000 g of the Poly(EGDE-DA) and 63 mM H2O2 (▲); and 0.1000 g of the Poly(EGDE-DA) (∆).
17
Figure S15. MO concentration profile in the heterogeneous system, which consisted on 0.0644 mmol of sites in 100 mL of 42 μM MO solution. The amounts of complexes were: 0.2500 g of the Co(II)-Poly(EGDE-DA) in presence of 63 mM H2O2 solution (♦); 0.2500 g of the Co(II)Poly(EGDE-DA) (◊); 0.0241 g of the Cu(II)-Poly(EGDE-DA) in presence of 63 mM H2O2 solution (●); and 0.0241 g of the Cu(II)-Poly(EGDE-DA) (○).
18
Figure S16. MO concentration profile in 100 mL of 42 μM MO solution in contact with: 0.1000 g of the Co(II)-Poly(EGDE-DA) and 63 mM H2O2 (♦); 0.1000 g of the Co(II)-Poly(EGDE-DA) (◊); 63 mM H2O2 previously activated with 0.1000 g of the Co(II)-Poly(EGDE-DA) (+); and 0.1000 g of the Co(II)-Poly(EGDE-DA) previously activated with 63 mM H2O2 (X). The homogeneous system was also tested with 42 μM MO, 0.35 mM Co(II) and 63 mM H2O2 (∆).
19
Figure S17. MO concentration profile in 100 mL of 42 μM MO solution in contact with: 0.1000 g of the Cu(II)-Poly(EGDE-DA) and 63 mM H2O2 (●); 0.1000 g of the Cu(II)-Poly(EGDE-DA) (○); 63 mM H2O2 previously activated with 0.1000 g of the Cu(II)-Poly(EGDE-DA) (+); and 0.1000 g of the Cu(II)-Poly(EGDE-DA) previously activated with 63 mM H2O2 (X). The sum of the effects of activated supernatant and activated solid on MO concentration was also represented (●).
20
Table S1. Dependence of the Poly(EGDE-DA) equilibrium swelling and water content on pH and I.
pH
I
Swelling degree
Water content %
g g-1 3.0
< 0.001
4.79 ± 0.08
82.7 ± 0.2
3.0
0.50
2.97 ± 0.05
74.8 ± 0.3
9.8
0.50
3.1 ± 0.2
75.8 ± 0.9
Table S2. BET surface area and adsorption average pore width of the particles of Poly(EGDEDA) and its complexes with Co(II) and Cu(II). Sample
BET surface Adsorption average area (m2 g-1)
pore width (Å)
Poly(EGDE-DA)
0.2145
24.9151
Co(II)-Poly(EGDE-DA)
0.4525
49.5847
Cu(II)-Poly(EGDE-DA)
2.7870
285.9206
21
Table S3. Increase of O2 partial pressure in distilled water and in H2O2 solution, at 10 min of the addition of the polyelectrolyte or a complex.
Average O2 partial
H2O20
pressure increase (%)*
(mM)
Poly(EGDE-DA)
3.9
-
Poly(EGDE-DA)
9.3
63
Co(II)-Poly(EGDE-DA)
0.4
-
Co(II)-Poly(EGDE-DA)
54.1
63
Cu(II)-Poly(EGDE-DA)
0.5
-
Cu(II)-Poly(EGDE-DA)
52.6
63
Polymer
* The R.S.D.% was below 1 % in the presence of H2O2.
Scheme S1. Chemical structures of Methyl Orange, epinephrine and adrenochrome.
22
