<p> Supporting Information</p><p>Modulation of quinone PCET reaction by Ca2+ ion captured by</p><p> calix[4]quinone in water</p><p>Yang-Rae Kima,‡, R. Soyoung Kima,‡, Sun Kil Kanga,§, Myung Gil Choib, Hong Yeong</p><p>Kimb, Daeheum Choc, Jin Yong Leec,*, Suk-Kyu Changb,* and Taek Dong Chunga,*</p><p> a Department of Chemistry, Seoul National University, Seoul 151-747, Korea.</p><p> b Department of Chemistry, Chung-Ang University, Seoul 156-756, Korea.</p><p> c Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea</p><p>§ Present address: Advanced Research Institute, LG Electronics Inc., Korea.</p><p>‡These authors contributed equally.</p><p>S1 Contents</p><p>Scheme S1: Synthesis of CTAQ</p><p>Figure S1: Cyclic voltammograms of CaCTAQ</p><p>Figure S2: Pourbaix diagram of CaCTAQ</p><p>Figure S3: Cyclic voltammograms of MCTAQs</p><p>Figure S4: EPR spectrum</p><p>Figure S5 – S6: Ultramicroelectrode experiments</p><p>Table S1: Details of digital simulation</p><p>Derivation of eq 10</p><p>Scheme S2, Table S2, Figure S8: DFT calculation results</p><p>References</p><p>S2 Scheme S1. Synthesis of CTAQ.1 </p><p>S3 Figure S1. Cyclic voltammograms of CTAQ in the presence of one-equivalent of Ca2+ obtained in buffered solutions at various pH values. The buffering agents were: from pH 5.7 to 6.6, MES; from pH 7.0 to 8.2, HEPES; from pH 8.2 to 9.4, CHES; from pH 10.2 to 11.4, CAPS. Concentration of</p><p>CTAQ was 1.0 mM. Scan rate was 50 mV s-1.</p><p>S4 Figure S2. E-pH diagram of CaCTAQ in Figure 2b with boundaries added to show the dominant quinone species in different areas. E and pKa values come from digital simulation. The slopes of red dash-dot lines are −59, −118, −59 mV/pH from left to right. Around the branching point (8.2 < pH <</p><p>9.0) where the points deviate from the lines, the close distance between peaks hindered accurate determination of Em.</p><p>S5 Figure S3. Cyclic voltammograms of CTAQ in the presence of one-equivalent of various alkaline earth metal ions at pH 7.4. Concentration of CTAQ was 1.0 mM. Scan rate was 50 mV s-1.</p><p>S6 Figure S4. EPR spectrum of bulk-electrolyzed CaCTAQ recorded after 18 minutes from the end of electrolysis.</p><p>S7 Ultramicroelectrode (UME) experiments. </p><p>Although the results presented in the main text strongly indicate that the two redox waves in basic pH were separate one-electron steps, we further verified this by conducting chronoamperometry experiments with a UME, considering the unusualness of this observation. At pH 10.2, step potentials that correspond to Q•−, QH− generation and Q re-generation according to cyclic voltammetry results were applied consecutively (Figure S5). Whereas electrochemical current falls to zero after sufficient time at a conventional macroelectrode, being limited by the diffusional supply of reactants, a finite steady-state current exists at a UME because of spherical diffusion and very small electrode area. At steady state, a net diffusional flux of reactant molecules is at balance with the reaction rate at the surface of the UME. The steady-state current (iss) at a disk</p><p>UME2 is simply proportional to n, the number of electrons transferred per each reactant molecule. F is Faraday’s constant (96485 C/mol), D and C* are the diffusion coefficient and the bulk concentration of the reactant, respectively, and r is the radius of the UME.</p><p>(1)</p><p>•− First, the potential was stepped to a value between E1 and E2, intended for Q generation. Then, when the potential was made sufficiently negative to allow full reduction, the steady-state current doubled. The steady-state current halved upon lowering the potential back to below E2, and fell to zero when the potential returned to its initial value. According to eq 1, such variation of iss with potential is a clear indication of distinct one-electron transfers separated in potential, assuming nearly identical diffusion coefficients for Q, Q•− and QH− forms of CaCTAQ. It is valid to assume similar diffusion coefficients as the quinone moiety undergoing reaction is only a small portion of the large calixquinone molecule.</p><p>S8 Figure S5. Multi potential step chronoamperometry at a Pt UME (25 μm dia.) in 1.0 mM CTAQ solution buffered at pH 10.2 with one-equivalent of Ca2+ added. Red line indicates applied step potentials.</p><p>Chronoamperometry with UME was also able to provide the diffusion coefficient of CaCTAQ, which was then utilized in the digital simulation of voltammograms. The transient decay of current at the first potential step of −0.2 V was analyzed according to an established methodology.3 The</p><p>-6 2 -1 diffusion coefficient (D) of CaCTAQ was estimated to be 2.4 × 10 cm s from the slope of i(t)/iss vs. t−1/2 plot, which was obtained using the following equation (Figure S6). </p><p>(2)</p><p>After determining D, the number of electrons transferred (n) could be calculated using eq 1. The diameter of UME was calibrated by an equivalent analysis of the steady-state current of 2.0 mM ferrocene in acetonitrile, 0.1 M tetrabutylammonium perchlorate solution, referring to its diffusion</p><p>S9 coefficient of 2.3 × 10−5 cm2 s-1 in the literature.4 The calculated n value was 1.1, roughly equal to 1, again confirming the extraordinary one-electron reduction behavior of CaCTAQ.</p><p>S10 Figure S6. Plot of the current ratio i(t)/iss against the inverse square root of time for the reduction of</p><p>CTAQ in the presence of one-equivalent of Ca2+ in pH 10.2 buffered solution. The chronoamperometry experiment was performed at a platinum UME (25 m dia.) by stepping the potential from a value where no current flows (0.2 V) to a value corresponding to one-electron reduction (–0.2 V) (Figure 5). y-intercept 0.7854, slope –0.337, R2=0.99.</p><p>S11 Table S1. The full mechanism employed in digital simulation of cyclic voltammograms.</p><p>Electron transfer (ET) reactionsa</p><p>0 -1 Reaction E (V vs. Ag/AgCl) ks (cm s )</p><p>Q + e− ⇌ Q•− –0.10 0.005</p><p>ET</p><p>Q•− + e− ⇌ Q2− –0.40 0.005</p><p>CPET Q•− + BH + e− ⇌ QH− + B− (depends on buffer) b 0.10</p><p>Chemical reactions (PT: proton transfer, DISP: disproportionation)</p><p>-1 -1 Reaction Keq kf (M s )</p><p>Q2− + H+ ⇌ QH− 1.2 x 1012</p><p>Q2− + BH ⇌ QH− + B− (depends on buffer) b</p><p>PT 1x1010</p><p>− + 8 QH + H ⇌ QH2 1.5 x 10</p><p>− − b QH + BH ⇌ QH2 + B (depends on buffer) </p><p>DISP Q•− + Q•− ⇌ Q + Q2− 8.5091 x 10-6 b 1x108</p><p>S12 3.02 x 107 for HEPES B− + H+ ⇌ BH 2.00 x 109 for CHES Acid- 2.51 x 1010 for CAPS base 1x1010 equilibri a + − 15 H + OH ⇌ H2O 5.5 x 10 a: All α values were assumed to be 0.5.</p><p>0 0 b: Thermodynamically superfluous reactions (TSR). Their E (or Keq) values were determined by other E (or Keq) values and automatically entered by the simulation software.</p><p>From the assumption that CaCTAQ species have equal diffusion coefficient for different protonation and oxidation states, diffusion coefficients of all CaCTAQ species were set at 2.4 × 10-6 cm2 s-1, as derived from chronoamperometric transient (vide supra). Diffusion coefficients for B−,</p><p>+ − BH, H , OH , H2O were taken at reasonably assumed values as small variation in their values had little influence on the simulated voltammogram. The values were 5 x 10-6 cm2 s-1 for B− and BH, 8 x</p><p>-5 2 -1 + -5 2 -1 − 5 10 cm s for H , and 1 x 10 cm s for OH and H2O. Concentration of H2O was 55 M.</p><p>S13 Derivation of eq 10 in the manuscript.</p><p>E2 in the manuscript stands for the standard potential for the second one electron reduction.</p><p>– – Depending on pH, the product of this second reduction is distributed among QH2, QH and QH ,</p><p>0 collectively denoted as Qred. Therefore, E2, equivalent to E Q•–/Qred, changes with pH as shown below.</p><p>(In the manuscript, the superscript “0” for standard potentials was omitted.)</p><p>S14 DFT calculation.</p><p>In order to test the validity of our explanation, DFT calculation was performed on three redox states of CTAQ and MCTAQ. The fully reduced state, QH−, was singly protonated at O1 (Scheme</p><p>S2) so that the overall charge would be the same as in Q•−. Firstly, bond length change upon reduction was observed (Table S2). Taking reduction in bond length as increase in bond strength,</p><p>CTAQ and MCTAQ showed different trends that agreed well with our explanation. Specifically,</p><p>•− − •− RO2-M decreased far more in going from CTAQ to CTAQH than in going from CTAQ to CTAQ , supporting our suggestion that hydrogen bonding and protonation are more effective on the fully reduced quinone than on the semiquinone radical. Incidentally, the calculated length of semiquinone hydrogen bond agreed closely with the value obtained for the semiquinone radical anion of vitamin</p><p>6 K1 from EPR measurement (1.64 Å ). MCTAQ all showed an opposite trend in RO2-M, which is</p><p>2+ natural if the interaction between M and the quinone is primarily ionic. In addition, RC4-O2 in the fully reduced quinone was also different for CTAQ and MCTAQ. Significant elongation in the former indicated that strong bond with proton caused the carbon-oxygen bond to weaken.</p><p>Secondly, reasoning that larger delocalization of electrons likely brings more stability,7 the sum of atomic mulliken charge densities on the quinone moiety, denoted as the quinone group charge density (Q), was obtained.8 The change in Q upon reduction (ΔQ) was used as a measure of the degree of delocalization and stability. For instance, for the first reduction, ΔQ without any delocalization would be −1. Its relatively positive value for CaCTAQ implies there is a strong delocalization of the additional electron density over the entire molecule,9 which may account for the stabilizing effect of Ca2+ on Q•−. The ΔQ value was more positive for smaller metal ions having higher Lewis acidity, and it was the most negative for CTAQ. Upon second reduction to QH−, however, free CTAQ showed more positive ΔQ, indicating that the added electron is more delocalized in CTAQH− than in MCTAQH−. Considering the bond length results, this may be ascribed to bond formation between O2 and a proton from carboxylic acid. There was no perceptible trend in the value of ΔQ for second reduction among different metal ions, but it is S15 evident that the metal ion is not as effective as proton in stabilizing the fully reduced quinone.</p><p>Therefore, our argument regarding the different stabilities of quinone species was supported by computational results.</p><p>We also provide figures of the calculated structures and matrix coordinates for CTAQ and</p><p>CaCTAQ (Figure S8).</p><p>Scheme S2. Labeling scheme used for DFT calculation of the quinone moiety in CTAQ and</p><p>MCTAQ. The lines do not indicate bond order. For CTAQ, M is a hydrogen atom from one of the carboxylic substituents that approached the quinone upon geometry optimization.</p><p>Table S2. Calculation results of the three redox states of CTAQ and MCTAQ.a</p><p>MCTAQ Parameters CTAQ Ca2+ Sr2+ Ba2+ Mg2+ Q 1.22116 1.21989 1.22040 1.22059 1.21993 •− RC1-O1 Q 1.25415 1.25367 1.25418 1.25444 1.25274 QH− 1.37385 1.38213 1.38269 1.38317 1.37997 Q 1.22198 1.22824 1.22853 1.22836 1.23075 •− RC4-O2 Q 1.28521 1.27991 1.27850 1.27753 1.28820 QH− 1.34570 1.29704 1.29496 1.29420 1.30628 Q 1.91245 2.33670 2.49719 2.66881 2.09816 •− RO2-M Q 1.61126 2.22434 2.38417 2.53352 1.91172 QH− 1.00503 2.19272 2.34873 2.49712 1.88486 Q→Q•− −0.412 −0.172 −0.287 −0.307 −0.062 ΔQb Q•−→QH− 0.321 −0.009 −0.123 −0.084 −0.032 a R is bond length in Å . Atom labels in the subscript follow Scheme S2.</p><p>S16 bQ is the sum of Mulliken charges of atoms labeled with a number in Scheme S2 (six carbon, two oxygen, two hydrogen atoms in total).</p><p>Figure S8. First row: CTAQ, second row: CaCTAQ. The columns represent Q, Q•− and QH− from left to right. Their coordinates follow next page. </p><p>S17 Cartesian coordinates (in Å ) of species in Figure S8.</p><p>CTAQ O -0.27197800 -0.03505400 2.41025500 Electronic energy: -2138.7542457 Hartrees O 0.42102300 2.63367300 3.42495400 ------•− O -0.00659100 4.80809900 3.61613200 CTAQ O -0.42787700 2.57346200 0.90031300 Electronic energy: -2138.8669431 Hartrees O -0.07622100 -2.61023000 0.89184800 ------O 0.68589800 -4.77891000 3.58802800 O 5.12963200 -3.58760100 1.41087000 O 1.41466100 0.08173000 0.36490000 O 2.81402000 -1.23879000 0.13765700 C -0.00798200 3.80112200 2.95504700 O -1.98706000 1.33632900 1.52259100 C -0.48160400 3.84949600 1.51563200 O -3.24586800 0.61165100 4.71791600 C -0.29732700 2.61685500 -0.47596800 O -0.97398800 -1.19815600 0.79750900 C 0.98458100 2.70693500 -1.03561200 C 4.16976600 -2.85512900 1.32597900 C 1.10190100 2.76988000 -2.42293000 C 3.92052500 -2.10299600 0.03343100 C -0.02418300 2.73269300 -3.23788500 C 2.19020500 -0.96035300 -1.06256500 C -1.28090800 2.60588800 -2.66334900 C 1.21818700 -1.84215000 -1.54531700 C -1.44026700 2.54395900 -1.27702600 C 0.66210700 -1.57014100 -2.79724000 C -2.82192100 2.33485800 -0.69700100 C 1.03563000 -0.44217200 -3.51856400 C -3.38457800 1.01031800 -1.14838300 C 1.91872000 0.47453700 -2.96062900 C -4.35236100 0.92507800 -2.15019400 C 2.49657900 0.23715300 -1.71367700 C -4.76965200 -0.31062500 -2.63440900 C 3.29390300 1.31993000 -1.02071800 C -4.19355000 -1.47909100 -2.14621700 C 2.47839000 2.58692300 -0.96617700 C -3.22228200 -1.43359500 -1.14500300 C 2.84864500 3.71677600 -1.69590400 C -2.86488600 -0.18172700 -0.63904500 C 2.03336000 4.84313300 -1.73705400 C -2.48859200 -2.67194900 -0.69397800 C 0.81330300 4.83262100 -1.07056200 C -1.09421500 -2.69969700 -1.28081500 C 0.40336700 3.71905600 -0.33370500 C -0.93503100 -2.73176200 -2.66827600 C 1.26532300 2.61779200 -0.26308000 C 0.32449100 -2.69135800 -3.24904500 C -0.96757400 3.67678800 0.29424500 C 1.45025900 -2.59028400 -2.43900900 C -1.89236200 2.70980600 -0.41233000 C 1.33291000 -2.55497000 -1.05084500 C -2.24309800 2.92995300 -1.74397500 C 0.05261000 -2.63167800 -0.48492200 C -3.06644200 2.03644700 -2.41898900 C 2.57593100 -2.37716400 -0.20707600 C -3.53177500 0.90060900 -1.76682100 C 3.25905300 -1.07963300 -0.51848900 C -3.19824800 0.63750200 -0.43697600 C 4.48075800 -0.97378400 -1.06624700 C -2.38819000 1.56796700 0.22674000 C 5.09010300 0.33735000 -1.37217300 C -3.67366700 -0.65470300 0.19133300 C 4.31024100 1.55227400 -1.05575600 C -2.93640500 -1.85160300 -0.35502500 C 3.08564000 1.48926000 -0.50781200 C -3.57395200 -2.76309100 -1.15506200 C 2.50226000 0.15813500 -0.18694700 C -2.89009100 -3.88516100 -1.75914700 C 2.23664100 2.68252800 -0.18675500 C -1.46277500 -3.93204800 -1.52878300 C 0.04695500 -3.88217000 1.50530000 C -0.80114000 -3.02078900 -0.74782200 C 0.52873300 -3.77600200 2.93916400 C -1.53146000 -1.98605700 -0.05114500 H 0.30424200 1.89931100 2.79120900 C 0.70203000 -2.99355800 -0.70370500 H 0.55570700 -1.84289000 2.80268400 C -2.90714700 1.53900600 2.56401600 H -1.50416900 4.25649000 1.50093400 C -2.73444800 0.46907800 3.62991300 H 0.16249400 4.56928500 0.98873300 H 2.60514100 -2.03131800 2.12609900 H 2.09518800 2.83945900 -2.86644900 H -1.71497000 -0.60851100 2.35089200 H -2.16479600 2.54063900 -3.29697700 H 4.83742400 -1.54999500 -0.22641800 H -2.77620800 2.39006100 0.39577600 H 3.75997900 -2.85990100 -0.75044200 H -3.49004900 3.13812800 -1.03500100 H -0.10363500 -2.23834200 -3.18820900 H -4.77902700 1.84266200 -2.55410500 H 2.13665400 1.41004000 -3.47625900 H -4.49565300 -2.44602700 -2.54738100 H 3.56599700 0.98256200 -0.01262600 H -3.04727300 -3.55657000 -1.02758800 H 4.23034000 1.52617600 -1.55811600 H -2.42977700 -2.71963300 0.39841200 H 3.78973100 3.70147000 -2.24544300 H -1.82298700 -2.77676900 -3.29790500 H 0.15226900 5.69772400 -1.12572400 H 2.44200900 -2.52781900 -2.88703600 H -1.39685000 4.68730500 0.24316400 H 2.31401800 -2.38830700 0.85752800 H -0.90457600 3.41493500 1.35627500 H 3.28043400 -3.19998700 -0.38545700 H -1.85026800 3.80969200 -2.25446100 H 5.08368900 -1.84630800 -1.31565300 H -4.14640800 0.17505000 -2.29982600 H 4.79076100 2.49976500 -1.29752700 H -3.58247300 -0.62653800 1.28067000 H 1.97037900 2.64831300 0.87619600 H -4.74249300 -0.77909600 -0.02953800 H 2.82843700 3.59225200 -0.35240100 H -4.63891600 -2.66717200 -1.37237600 H 0.77330800 -4.51048900 0.96868700 H -0.91314600 -4.72126900 -2.04443500 H -0.91324200 -4.42038800 1.50205400 H 1.06188500 -2.88146900 0.32581200 O -1.94928800 -0.11857900 0.39714200 H 1.09071100 -3.95103600 -1.08065700 C -2.57592200 -0.16240100 1.66300700 H -3.94709600 1.50216900 2.20488200 C -1.56277700 -0.11334500 2.77886400 H -2.75847800 2.52073600 3.04110700 H -3.16742800 -1.08269700 1.78991700 O 0.90548500 1.51030700 0.46755300 H -3.26649200 0.68421600 1.80204600 C 1.09324700 1.62832200 1.87272300 O -1.89494400 -0.14288900 3.93201900 C 1.74765000 0.38238300 2.43786600 H -0.16683700 -0.02817300 1.43460200 H 0.11682200 1.76802200 2.36592600 H 0.08067500 2.78812300 -4.31830300 H 1.75174900 2.47334700 2.10781000 H 0.43005000 -2.72437100 -4.33031900 O 2.75227700 0.45473600 3.11177900 H -5.53313900 -0.36238500 -3.40653000 H 0.40356900 -0.82095600 1.54331100 O 6.19775500 0.41439400 -1.88049700 H 0.59064900 -0.24887200 -4.49213400 O 0.78950000 -2.56422800 3.41925500 H -3.33310500 2.21620800 -3.45809500 S18 H 2.33870100 5.71929900 -2.30484800 O 5.51848900 1.94082800 -2.46158000 O -3.48523000 -4.72975100 -2.47003700 O 2.09492900 -1.36431300 3.31371300 O -2.03067200 -0.59808800 3.29662000 O -0.43099300 1.36851300 2.12125300 O 1.15573700 -0.77996800 2.21373900 O -0.51451100 4.01295700 2.41618800 O 3.29664600 -2.70757200 2.30705600 H 6.16072300 1.23586500 -2.59362300 CTAQH− Electronic energy: -2139.4850594 Hartrees CaCTAQ ------Electronic energy: -2815.26253140 Hartrees O -0.87575900 6.04924100 1.60586000 ------O -1.66710900 2.88098800 0.21516000 O 0.06226300 -4.60522200 2.02155100 O 0.81522600 -2.51931000 1.37102400 O 0.90726000 -2.15134400 0.20956500 O 2.57173700 -3.29896800 4.30948700 O -0.29563900 2.19170100 1.36368800 O 1.45693700 0.14942700 0.81169600 O -0.53620200 2.91084700 4.84088700 C -0.94574900 4.83960600 1.49663800 O -1.50357700 -0.51958800 0.80383900 C -1.54332400 4.28092100 0.21430100 C 0.88750800 -3.72441200 1.97863700 C -1.28272900 2.18913200 -0.90083500 C 1.58469400 -3.34356700 0.67986700 C 0.04937700 2.20075100 -1.33971900 C 0.49495600 -2.20551400 -1.11834100 C 0.35486000 1.51468900 -2.51893100 C -0.80920400 -2.63196600 -1.41602300 C -0.61532100 0.79578800 -3.20607600 C -1.19197000 -2.70085100 -2.75581200 C -1.89160300 0.68317700 -2.66863000 C -0.30762100 -2.37409000 -3.77461700 C -2.23571600 1.35241800 -1.49530800 C 0.97153100 -1.94446300 -3.45415900 C -3.53173700 1.02766600 -0.78083800 C 1.39737300 -1.84236100 -2.12770800 C -3.71543000 -0.46736100 -0.74241300 C 2.78484600 -1.29606500 -1.85154300 C -4.78112600 -1.09533200 -1.38680500 C 2.80921900 0.19093900 -2.12561900 C -4.85710600 -2.48357000 -1.46656000 C 3.11853400 0.66831400 -3.39925200 C -3.83234500 -3.25984500 -0.93489800 C 3.01431800 2.02105600 -3.70197400 C -2.74926600 -2.66545200 -0.28454700 C 2.53474400 2.90368900 -2.74392900 C -2.72719400 -1.27143700 -0.15382000 C 2.21212400 2.46953300 -1.45512000 C -1.56862900 -3.47893100 0.17964800 C 2.42790500 1.12194100 -1.15045900 C -0.31903300 -3.16329200 -0.61471000 C 1.52555500 3.40808700 -0.49103000 C -0.32267500 -3.27933000 -2.00447000 C 0.02627700 3.33546300 -0.71319600 C 0.80479700 -2.95417900 -2.74999100 C -0.53630600 3.85504200 -1.88108800 C 1.94647200 -2.48865000 -2.10821300 C -1.88936500 3.71011900 -2.15626100 C 1.98998000 -2.34852800 -0.72023700 C -2.70319900 3.01892300 -1.26622000 C 0.84833500 -2.70778100 0.00715600 C -2.18737900 2.49706600 -0.08117000 C 3.22320800 -1.74038200 -0.08221400 C -0.82195300 2.68265400 0.18812500 C 3.37163800 -0.28382000 -0.44506100 C -3.11190400 1.75187700 0.86237000 C 4.42013700 0.14527800 -1.25894500 C -3.57779200 0.44395100 0.28885200 C 4.48767500 1.46598600 -1.68736900 C -4.81375000 0.21153200 -0.18511100 C 3.45473800 2.33780600 -1.36824800 C -5.20357300 -1.10045600 -0.74821000 C 2.38461600 1.92835000 -0.57298900 C -4.18782000 -2.17543500 -0.77952800 C 2.38718200 0.62855800 -0.03446900 C -2.93992300 -1.98541600 -0.31815800 C 1.15565500 2.79033900 -0.47678200 C -2.60342200 -0.67242100 0.27889300 C 1.48653100 -3.42789300 2.20187100 C -1.83761400 -3.00380500 -0.36638700 C 2.09618800 -2.68796400 3.38049000 C -0.45382200 3.06058200 2.51471700 H -0.62650800 3.02239900 2.24563800 C -0.34332200 2.25811800 3.82313600 H 1.69260900 -1.02612100 2.47881000 H 1.94439500 -2.34601500 2.87201600 H -2.53273600 4.74522400 0.09296500 H 2.65498500 -3.12765100 0.81320600 H -0.91652800 4.63345000 -0.61759600 H 1.44230500 -4.15220100 -0.04343500 H 1.38473500 1.50250700 -2.87362900 H -2.20235800 -3.03081800 -2.99680800 H -2.62303500 0.02125100 -3.13347100 H 1.66455600 -1.67553500 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-4.29615000 2.59206200 H -1.60126700 2.25133700 4.61284300 H 2.52542400 -2.13309000 5.16931200 H -2.62602700 -4.28923500 2.61239900 O -6.64660400 0.88071800 0.22610300 H 2.57819500 -2.15194400 5.13721100 O 1.31389900 -1.21581900 -3.44557000 O -6.59710700 0.82197500 0.29247700 O 2.85282800 1.23646500 -1.73942500 O 1.19996800 -1.16647500 -3.48219400 O 1.64686600 3.29570800 -2.71438800 O 2.82315700 1.23524500 -1.76606700 Ca 0.76536900 0.15138000 -1.66854300 S20 H -7.10327500 0.05548300 0.03468600</p><p>References</p><p>(1) Chung, T. D.; Kang, S.-K.; Kim, H.-S.; Kim, J. R.; Oh, W. S.; Chang, S.-K. Chem. Lett. 1998, 1225. (2) Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications; 2nd ed.; Wiley: United States, 2001. (3) Shoup, D.; Szabo, A. J. Electroanal. Chem. Interfacial Electrochem. 1982, 140, 237–245. (4) Ji, X.; Banks, C. E.; Silvester, D. S.; Wain, A. J.; Compton, R. G. J. Phys. Chem. C 2007, 111, 1496–1504. (5) Lee, S. H.; Rasaiah, J. C. J. Chem. Phys. 2011, 135, 124505. (6) Niklas, J.; Epel, B.; Antonkine, M. L.; Sinnecker, S.; Pandelia, M.-E.; Lubitz, W. J. Phys. Chem. B 2009, 113, 10367–10379. (7) Oh, J.-W.; Lee, Y. O.; Kim, T. H.; Ko, K. C.; Lee, J. Y.; Kim, H.; Kim, J. S. Angew. Chem. Int. Ed. 2009, 48, 2522–2524. (8) Zhang, C. J. Hazard. Mater. 2009, 161, 21–28. (9) Wheeler, D. E.; Rodriguez, J. H.; McCusker, J. K. J. Phys. Chem. A 1999, 103, 4101–4112.</p><p>S21</p>