Ionic effect on the proton transfer mechanism in aqueous solutions

Transcription

1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is the Owner Societies 2017 Electronic Supplementary Information for Ionic effect on the proton transfer mechanism in aqueous solutions Joonyoung F. Joung, Sangin Kim, and Sungnam Park* Department of Chemistry, Korea University, Seoul, 02841, Korea * S1

2 Contents 1. Figure S1. Absorption and emission spectra of C183 in aqueous solution 2. Figure S2-5. TCSPC signals of C183 in aqueous solutions 3. Global fitting analysis 4. Figure S6. Global fitting analysis 5. Figure S7. Rate constants for the ESPT reactions 6. Figure S8. H-bond structure of C183 and local hydration structures 7. Figure S9. Results of quantum chemical calculations 8. Figure S10. Optimized reactant states for neat water and aqueous Na + and Cl solution 9. Figure S11. Intrinsic reaction coordinate (IRC) calculations. 10. Figure S12. Results of IRC calculations. 11. Table S1. Densities of aqueous ionic solutions and mole fractions of water in the first solvation shell of ions 12. Table S2. Ionic radius and hydration number of ions page 13. Table S3. Activation energies for the ESPT reactions of C183 for cations 14. References S2

3 Figure S1. Absorption and emission spectra measured with C183 in aqueous 3.0 M NaCl solution at ph=~1.7 and 25 C. In the absorption spectrum, only ROH peak is shown because ROH exists dominantly at ph=~1.7. Emission spectrum was measured by excitation at 375 nm. S3

4 Figure S2. TCSPC signals of C183 in water. S4

5 Figure S3. TCSPC signals of aqueous NaCl solutions. S5

6 Figure S4. TCSPC signals of aqueous 3.0 M alkali metal chloride solutions. S6

7 Figure S5. TCSPC signals of aqueous 1.5 M alkaline earth metal chloride solutions and 1.0 M AlCl3 solution. S7

8 Global fitting analysis The frequency- and time-resolved fluorescence signals in Figure 1b contain all dynamic information on the ESPT reaction of C183. We used the global fitting analysis to extract all the rate constants associated with the ESPT kinetics from the frequency- and time-resolved fluorescence signals. In the global fitting analysis, the frequency- and time-resolved fluorescence signals (D) can be expressed by the product of the time-dependent concentrations (C) and their corresponding spectral components (S T ), D=CS T (S1) where the columns of matrix (C, sized mk) are the time-dependent populations of the k th components at the time delay of m and the rows of matrix (S T, sized kn) are the corresponding k th spectra as a function of wavelength n. And m, k, and n represent the time delay, the number of components, and the spectra, respectively. The detailed procedure of the global fitting analysis by using Matlab codes has been reported elsewhere. 1-4 Briefly, the coupled differential equations for the time-dependent concentrations of individual species are written based on the kinetic models in Figure 1a, and the analytical solutions for the time-dependent concentrations are obtained. The frequency- and time-resolved fluorescence signals are written as the sum of the individual components with their spectra and time-dependent concentrations. For a given kinetic model, the time-dependent populations (C) are calculated with the initial rate constants. The corresponding spectral components (S T ) are obtained by the product of the pseudo-inverse matrix of C and D, T 1 S C D (S2) The fitted frequency- and time-resolved fluorescence signals (D fitted ) is constructed by the product of C and T S, S8

9 fitted T D CS (S3) The best fitted data were obtained by iteratively varying the rate constants until the difference between the experimental data (D exp ) and the fitted data (D fitted ) was minimized. An example of the global fitting analysis is presented in Figure S6. In our current experiments, all the rate constants in the kinetic model are extracted from the global fitting analysis of frequency- and time-resolved TCSPC signals measured with C183 in aqueous ionic solutions at a series of temperatures. All the rate constants determined from the global fitting analysis are shown in Figure S7. S9

10 Figure S6. Illustration of the global fitting analysis of frequency- and time-resolved fluorescence signal measured with C183 in aqueous 3.0 M NaCl solution at 25 C. S10

11 Figure S7. All the rate constants for the ESPT reaction of C183 in aqueous metal chloride solutions extracted from the global fitting analysis. S11

12 Figure S8. Quantum-chemically calculated H-bond structures of C183 and local hydration structures of ions in aqueous metal chloride solutions. S12

13 Figure S9. Plots of RHB, ROH, ROO, and OH frequency (OH) of C183 against the ionic charge density (). S13

14 Figure S10. The optimized structures of the reactant states in (a) neat water, and (b and c) aqueous Na + and Cl solutions. The H-bonded water channel is indicated as ball and stick representations. Na + and Cl ions, which are indicated in purple and green, respectively, interact with a water molecule in the H-bonded water channel in a different way. S14

15 Figure S11. Optimized structures of the reactant, transient state (TS), and product for the acid dissociation of C183 in neat water and aqueous Na + and Cl solutions. The proton dissociates from C183 and migrates through the H-bonded water channel. Blue, green, and orange balls are protons migrating via the Grotthuss mechanism (See the movie clips). S15

16 Figure S12. Results of IRC calculations. (a) Schematic illustration of TS configuration in neat water and aqueous Na + and Cl solution. (b) Potential energy curves for the ESPT reaction in neat water and aqueous Na + and Cl solutions. (c) The differences (i.e., δiaj = RIa RaJ) between OH lengths in two neighboring oxygen atoms (OI Ha OJ) are plotted along the IRC. Ha is equally shared by OI and OJ when δiaj = 0. (d) The OO distances (i.e., RIJ = OI OJ) along the IRC coordinate. S16

17 Table S1. Density of aqueous ionic solutions, mole fractions of waters in the first solvation shells of ions 1 Solution Density ( g ml ) n M Cl 3.0 M LiCl M NaCl M KCl M RbCl M CsCl M MgCl M CaCl M SrCl M BaCl M AlCl S17

18 Table S2. Radius and hydration number of ions. Ion Ionic radius (Å) 5 Hydration number 6-7 Li Na K Rb Cs Cl Mg Ca Sr Ba Al S18

19 Table S3. Activation energies of the ESPT reactions of C183 for cations expressed by E c me. n+ a,m a,cl c m E + a,li E + a,na E + a,k E + a,rb E + a,cs E 2+ a,mg E 2+ a,ca E 2+ a,sr E 2+ a,ba E 3+ a,al E E E E a,obs bulk a,bulk n n+ M a,m Cl a,cl E n+ a,m Ea,obs E E 1 a,bulk n Cl a,cl M Cl n M Ea,obs Ea,bulk 1 n M Cl Cl E n n M M a,cl E cme n+ a,m a,cl E c m a,obs a,bulk n M Cl Cl n M E 1 n M S19

20 References (1) van Stokkum, I. H. M.; Larsen, D. S.; van Grondelle, R. Global and Target Analysis of Time-Resolved Spectra. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2004, 1657, (2) van Wilderen, L. J.; Lincoln, C. N.; van Thor, J. J. Modelling Multi-Pulse Population Dynamics from Ultrafast Spectroscopy. PloS one 2011, 6, e (3) Ruckebusch, C.; Sliwa, M.; Pernot, P.; de Juan, A.; Tauler, R. Comprehensive Data Analysis of Femtosecond Transient Absorption Spectra: A Review. J Photoch Photobio C 2012, 13, (4) Joung, J. F.; Kim, S.; Park, S. Effect of Nacl Salts on the Activation Energy of Excited- State Proton Transfer Reaction of Coumarin 183. J. Phys. Chem. B 2015, 119, (5) Marcus, Y. Ionic-Radii in Aqueous-Solutions. Chem. Rev. 1988, 88, (6) Ohtaki, H.; Radnai, T. Structure and Dynamics of Hydrated Ions. Chem. Rev. 1993, 93, (7) Ramos, S.; Neilson, G. W.; Barnes, A. C.; Capitan, M. J. Anomalous X-Ray Diffraction Studies of Sr2+ Hydration in Aqueous Solution. J. Chem. Phys. 2003, 118, S20