Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 Supplementary Information Information on sample preparation Fluorescence studies: A micellar solution of 16.2 mM SDS in pH 7.4 phosphate buffer solution was prepared. The SDS concentration was twice the critical micelle concentration to ensure formation of micelles. A solution of 1.5 mM curcumin in methanol was used as stock. A 2 μL volume of curcumin stock was added to 3 mL of either the SDS micellar solution or methanol to achieve a final concentration of 1 μM for curcumin. In the UV-Vis absorption experiment, 40 μL of 0.15 mM CuSO4 stock in phosphate buffer was added to 3 mL of 1 μM curcumin solution to achieve a [Cu(II)]0/[Cur-H]0 = 2. The same volume of CuSO4 stock in methanol was added to 3 mL of 1 μMcurcumin to yield a [Cu(II)]0/[Cur-H]0 ratio of 2 in methanol. In the titration experiments to determine K1 and K2, 0.15 mM CuSO4 in deionized water and methanol were used as stock solutions for the studies using SDS micelles and methanol, respectively. A series of 2 μL aliquots of the CuSO4 stock were added to 3 mL of 1 μM curcumin in methanol solution in a stepwise fashion to achieve a series of Cu(II) concentrations ranging from 0.1 to 2 μM. The overall % v/v of water resulting from the addition of Cu(II) in the sample rose to approximately 2%.The values of K1, K2, Cur -H (λ) , [ Cu II-Cur] and [ Cu II-Cur ] were obtained by solving eqs 3 – 7 and was best fitted to the 2 spectroscopic data (520 nm to 590 nm for methanol and 500 nm to 570 nm for SDS micelles) simultaneously using a nonlinear least-squares method (HypSpec). UV-Vis absorption studies: In the titration experiments to determine K1 and K2, amicellar solution of 16.2 mM SDS in pH 7.4 phosphate buffer solution was prepared. A solution of 2.71 mM (1 mg/ml) curcumin in methanol was used as stock. A 11μL volume of curcumin stock was added to 3 mL of Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 either the SDS micellar solution or methanol to achieve a final concentration of 10μM for curcumin. A solution of 0.75 mM CuSO4 in deionized water and methanol were used as stock solutions for the studies using SDS micelles and methanol, respectively. A series of 2 μL aliquots of the CuSO4 stock were added to 3 mL of 1 μM curcumin in methanol solution in a stepwise fashion to achieve a series of Cu(II) concentrations ranging from 0.5 to 20 μM. The overall % v/v of water resulting from the addition of Cu(II) in the sample rose to approximately 4%. The values of K1 and K2, Cur -H (λ) , [ Cu II-Cur] and [ Cu II-Cur ] were obtained 2 by solving eqs 3 – 7 and was best fitted to the spectroscopic data (410 nm to 370 nm for methanol and 440 nm to 430 nm for SDS micelles) simultaneously using a nonlinear leastsquares method (HypSpec). In the transient absorption studies, solutions of 100 μMcurcumin in methanol and 16.2 mM SDS buffer solution were prepared using a 5.43 mMcurcumin in methanol stock solution. A solution of 8 mM CuSO4 in deionized water was used as a Cu(II) stock solution. Different volumes of this stock were added to the curcumin solution to achieve a Cu(II):curcumin mole ratios of 0:1, 1:4, 1:2, 1:1 and 2:1. Speciation expressed as proportion of [Cur-H]0 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 1 a 0.8 Cur-H Cu-Cur2 Cu-Cur 0.6 0.4 0.2 1 b 0.8 0.6 0.4 0.2 0 0.5 1 1.5 2 [Cu(II)]0/[Cur-H]0 Figure 1. Speciation plot of free curcumin and Cu(II)-curcumin complexes with [Cu(II)]0/[Cur-H]0 = 0 – 2 in (a) methanol and (b) the SDS micellar solution. In the experiment, Cu(II) was added to 1 μM curcumin in methanol or SDS micelles in a stepwise fashion to achieve Cu(II) concentrations ranging from 0.1 to 2 μM. Speciation is expressed as a proportion of [Cur-H]0. The proportion of the 1:2 Cu(II)-curcumin complex must be multiplied by 2 to obtain the proportion of Cur therein. Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 1 Normalized F 0.8 0.6 0.4 0.2 0 0.0 0.5 1.0 1.5 2.0 [Cu(II)]0/[Cur-H]0 1 Normalized F 0.8 0.6 0.4 0.2 0 0 0.5 1 [Cu(II)]0/[Cur-H]0 1.5 2 Figure 2. Normalized fluorescence intensity at 540 nm and 530 nm for curcumin in methanol (top) and SDS micelles (bottom), respectively. Normalized F is defined as F/Fmax, where Fmax is the maximum fluorescence intensity and F is the fluorescence intensity at a specific [Cu(II)]0/[Cur-H]0 value where [Cur-H]0 is 10 μM. The solid curves represent the best fits for an algorithm derived from eqs 3 – 7 over the range 500 nm – 570 nm at 0.5 nm intervals using strictly a 1:1 Cu(II)-curcumincomplexation model. Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 6 Molar Absorptivity (x104 M-1cm-1) 5 4 3 2 1 0 300 350 400 450 Wavelength (nm) 500 550 600 Figure 3. UV-vis absorption spectra ofcurcumin in methanol with addition of Cu(II) with inset showing the change in absorptivity at 410 nm and the fitting with a 1:1 and 1:2 Cu(II)curcumincomplexation model (red curve). Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 4.5 Molar absorptivity (x104 M-1cm-1) 4 3.5 3 2.5 2 1.5 1 0.5 0 300 350 400 450 Wavelength (nm) 500 550 600 Figure 4. UV-vis absorption spectra ofcurcumin in SDSwith addition of Cu(II) with inset showing the change of absorptivity at 434 nmand the fitting with a 1:1 and 1:2 Cu(II)curcumincomplexation model (red curve). Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 1.2 1.2 1 1 Normalized ∆OD 0.8 Normalized∆OD 0.8 [Cu(II)] /[Cur] = 2 0.6 0 0 [Cu(II)]0/[Cur-H] 0 =2 [Cu(II)] 0/[Cur] 0 = 3 [Cu(II)] 0/[Cur-H]0 = 3 0.6 0.4 0.2 0 -1 0.4 0 1 2 -0.2 3 4 5 Time (ps) 0.2 0 -10 -0.2 40 90 140 190 240 290 Time (ps) Figure 5. Excited state kinetics at 500 nm for [Cu(II)]0/[Cur-H]0 = 2 (blue) and 3 (red) in MeOH. Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 1.2 1.2 1 1 Normalized ∆OD 0.8 Normalized∆OD 0.8 0.6 [Cu(II)] 0/[Cur]0 = 2 0.6 0.4 0.2 [Cu(II)] 0/[Cur]0 = 3 0 0.4 -0.2 -1 0 0.2 1 2 Time (ps) 3 4 5 0 40 90 140 Time (ps) 190 240 290 Figure 6. Excited state kinetics at 500 nm for [Cu(II)]0/[Cur-H]0 = 2 (blue) and 3 (red) in SDS. Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012 Table 1. Summary of linear combination kinetic fitting. Free Cur (%) Bound Cur (%) (1 - )  0 100 0 0.25 82 ± 2 18 ± 36 0.5 21 ± 1 79 ± 15 0.75 2±1 98 ± 5 1 3±0 97 ± 11 2 0 100 [Cu(II)]0/[Cur-H]0