Supporting Information
Effects of Competitive Active-Site Ligand Binding on Proton- and Electron-transfer Properties of the [Co4(H2O)2(PW9O34)2]10- Polyoxometalate Water Oxidation Catalyst
CCDC 1509618 for 1 contains the supplementary crystallographic data. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retreiving.html, or from the Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK.
Table S1:Crystal data and structure refinement for 1.Empirical formula / C114H248Cl4Co4N14O68P2W18
Formula weight / 6652.01
Temperature/K / 100(2)
Crystal system / monoclinic
Space group / P21/n
a/Å / 14.3539(13)
b/Å / 32.702(3)
c/Å / 20.2799(19)
α/° / 90
β/° / 109.9725(14)
γ/° / 90
Volume/Å3 / 8946.8(14)
Z / 2
ρcalcg/cm3 / 2.469
μ/mm1 / 12.034
F(000) / 6224.0
Crystal size/mm3 / 0.476 × 0.304 × 0.296
Radiation / MoKα (λ = 0.71073)
2Θ range for data collection/° / 3.046 to 54.966
Index ranges / -18 ≤ h ≤ 18, -42 ≤ k ≤ 42, -26 ≤ l ≤ 26
Reflections collected / 92049
Independent reflections / 20452 [Rint = 0.0544, Rsigma = 0.0447]
Data/restraints/parameters / 20452/985/1016
Goodness-of-fit on F2 / 1.164
Final R indexes [I>=2σ (I)] / R1 = 0.0679, wR2 = 0.1693
Additional discussion of the effect of MeCN on hydrolysis of 1.
The acid base equilibria in water for 1-H2O is described in eq I
1-H2O ⇄ 1-OH- + H+ (I)
The equilibrium constant of this reaction Ka is in eq (II)
Ka = ([1-OH-][H+])/[1-H2O] (II)
The equilibrium constant K for the equilibrium in eq III is in eq IV
1-H2O + MeCN ⇄ 1-MeCN + H2O (III)
K = ([1-MeCN][H2O])/([1-H2O][MeCN]) (IV)
For simplicity: 1-H2O = AH; 1-OH- = A-; 1-MeCN = AN; MeCN = N;
Mass balance [Atot] = [AH] + [A-] + [AN], [N] and [H2O] are in excess over 1 and therefore are constant.
From the above equations:
[Atot] = [AH] (1 + [H+]/Ka + [AN]/K) (V)
The ratio α = [A-]/[Atot] is in eq VI
α = [A-]/[Atot] = ([H+]/Ka)/(1 + [H+]/Ka + [AN]/K) (VI)
The hypothetical curves for α in the absence and in the presence of MeCN, assuming pKa = 9 and [MeCN]/K = 5 is given on Figure S3. As seen from Figure S3, acetonitrile decreases the percentage of [1-OH-] and therefore allows normal titration to higher pHs in the presence of MeCN.
Supporting Information Figures
Fig S1. (a) Changes in spectra of 0.25 mM FPIFA and 0.5 mM 1 in MeCN. (b) Dependence of absorbance at 470 nm as a function of time.
Fig S2. The spectra of intermediates (normalized per absorption at 525 nm) generated electrochemically (red) and in the reaction with FPIFA (blue).
Fig S3. The hypothetical curves for α in the absence (black) and in the presence of MeCN (red), computed at pKa = 9 and [MeCN]/K = 5