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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NCHEM.1301

S1

Supplementary Information

A Molecular Ruthenium Catalyst with Water-Oxidation Activity Comparable to that of Photosystem II

Lele Duan,1 Fernando Bozoglian,2 Sukanta Mandal,2 Beverly Stewart,3 Timofei

Privalov,3,* Antoni Llobet,2,4,* Licheng Sun1,5,*

1 Department of Chemistry, School of Chemical Science and Engineering, KTH Royal

Institute of Technology, 100 44 Stockholm, Sweden

2 Institute of Chemical Research of Catalonia (ICIQ), Avinguda Països Catalans 16, E-

43007 Tarragona, Spain

3 Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University (SU),

10691 Stockholm, Sweden

4 Department of Bioinspired Science, Ewha Womens University, 120-750 Seoul, Korea

5 State Key Lab of Fine Chemicals, DUT-KTH Joint Education and Research Center on

Molecular Devices, Dalian University of Technology (DUT), 116024 Dalian, China

Table of Contents Experimental Section .................................................................................................................... 3

General. ..................................................................................................................................... 3

Supplementary Table S1. GC data ............................................................................................. 4

Supplementary Table S2. TOF and TON at various [cat.] .......................................................... 4

Synthesis of 1 ............................................................................................................................ 5

Supplementary Figure S1a ........................................................................................................ 7

Supplementary Figure S1b ........................................................................................................ 7

Supplementary Figure S1c ......................................................................................................... 8

Supplementary Figure S1d ........................................................................................................ 8



Supplementary Table S3 ......................................................................................................... 10

Supplementary Figure S3 ........................................................................................................ 12


S1

Supplementary Information

A Molecular Ruthenium Catalyst with the Water-Oxidation Activity Comparable to that of Photosystem II

Lele Duan,1 Fernando Bozoglian,2 Sukanta Mandal,2 Beverly Stewart,3 Timofei

Privalov,3,* Antoni Llobet,2,4,* Licheng Sun1,5,*

1 Department of Chemistry, School of Chemical Science and Engineering, KTH Royal

Institute of Technology, 100 44 Stockholm, Sweden

2 Institute of Chemical Research of Catalonia (ICIQ), Avinguda Països Catalans 16, E-

43007 Tarragona, Spain

3 Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University (SU),

10691 Stockholm, Sweden

4 Department of Bioinspired Science, Ewha Womens University, 120-750 Seoul, Korea

5 State Key Lab of Fine Chemicals, DUT-KTH Joint Education and Research Center on

Molecular Devices, Dalian University of Technology (DUT), 116024 Dalian, China

Table of Contents Experimental Section .................................................................................................................... 3

General. ..................................................................................................................................... 3

Supplementary Table S1. GC data ............................................................................................. 4

Supplementary Table S2. TOF and TON at various [cat.] .......................................................... 4

Synthesis of 1 ............................................................................................................................ 5



Supplementary Figure S1c ......................................................................................................... 8

Supplementary Figure S1d ........................................................................................................ 8






© 2012 Macmillan Publishers Limited. All rights reserved.



S2

Supplementary Figure S5a ...................................................................................................... 13

Supplementary Figure S5b ...................................................................................................... 13






Computational details: general considerations .......................................................................... 18

DFT-method ............................................................................................................................ 18

Basis sets ................................................................................................................................. 18

Self consistent reaction field (bulk solvent) ............................................................................ 19

The potential energy scan(s) ................................................................................................... 19

Calculated polarizability and dipole moment ......................................................................... 20

XYZ Information ....................................................................................................................... 21

Supplementary: computational, O-O bonding of isoq-ruthenium complexes ........................... 22



Supplementary Figure S10a .................................................................................................... 23

Supplementary Figure S10b .................................................................................................... 23

Supplementary Figure S11 ...................................................................................................... 24



Supplementary Scheme S1 ...................................................................................................... 26







S3

Experimental Section General. Complex 2, Ru(DMSO)4Cl2 and 2,2’-bipyridine-6,6’-dicarboxylic acid (H2bda)

were prepared according to the literature methods.1-3 All other chemicals are

commercially available. All solvents are reagent grade and predeoxygenated. The 1H

NMR spectra were recorded with 500 MHz of Bruker Avance spectrometer. Elemental

analysis was performed with a Thermoquest-Flash EA 1112 apparatus.

Electrochemistry measurements were carried out with either Autolab potentiostat with a

GPES electrochemical interface (Eco Chemie) or CH Instruments 660c potentiostat,

with pyrolytic graphite electrode (basal plane) as working electrode, Pt wire as auxiliary

and measured versus Ag/AgCl or SSCE reference electrodes. All potentials reported

herein are converted to their corresponding values versus NHE using an internal

reference of [Ru(bpy)3]2+ (E1/2(Ru2+/3+) = 1.26 V vs NHE). UV-vis data were obtained

using either a CARY 300 Bio UV/Visible spectrophotometer or a fast mixing stopped

flow module Bio-Logic SFM300 with a cryostat Huber CC3-905 VPCw and a fast JM

TIDAS UV-Vis Diode Array spectrophotometer.

The oxygen evolution was recorded with a pressure transducer (Omega PX138-

030A5V) driven at 8.00 V using a power supply (TTi-PL601) plus a data acquisition

module (Omega OMB-DAQ-2416; running at 9 Hz for our measurements) and the

amount of oxygen was calibrated by GC (GC-2014 Shimadzu; equipped with a thermal

conductive detector, a 5Å Molecular sieve column and with He as carrier gas). The

pressure transducer was connected with a two-neck round flask (space = 41 mL). A

CF3SO3H aqueous solution (pH 1.0, 3 mL) was added to the flask containing 1.0 g of

Ce(NH4)2(NO3)6 under stirring. Once the CeIV was dissolved, an acetonitrile/water (1/9)

solution of catalyst (25−400 L, 2 mM) was immediately injected to the above solution

under vigorous stirring. The generated O2 was measured and recorded vs. time. After

oxygen evolution ceased, the resulting gas phase was analyzed by GC.




S4

Supplementary Table S1. GC data

catalyst [cat.] / M No. of experiment O2 area n(O2)/ mol

complex 1

2.162E-04 (1) 293427.5 433.296 (2) 293159.7 432.901 (3) 293701.8 433.701 (4) 291492.7 430.439

1.143E-04

(1) 287302.7 424.252 (2) 285460.6 421.532 (3) 285873.8 422.142

1.504E-05

(1) 280993.0 414.935 (2) 285371.7 421.400

complex 2

2.162E-04 (1) 280541.9 414.268 (2) 282215.5 416.74 (3) 292569.7 432.03 (4) 292248.5 431.555

1.143E-04 (1) 289894.6 428.079 (2) 280196.8 413.759 (3) 278554.6 411.334

5.882E-05

(1) 277367.6 409.581 (2) 266367.6 393.338

air (1) 220828.6 ------

(2) 221991.6 ------ (3) 221794.9 ------

Gas space of the reaction system: 37.7 mL. Temperature: 294.15 K. 1 mol of gas around 24.12 L at 294,15 K. Sample volume for GC analysis: 500 L. Retention time of the O2 peak: 1.57 min. Catalytic conditions: see the details in Figure 1 in the main text.

Supplementary Table S2. TOF and TON at various [cat.] Complex Concentration n(cat.)/mol TOF (per second) TON Note

1

2.16 104 M 8.00E-07 303.0 9.6a ---- (average over four reactions)

1.14 104 M 4.00E-07 236.8 8.8b ---- (average over three reactions)

1.50 105 M 5.00E-08 120.4 8.2c 8360 91 (average over two reactions)

2

2.16 104 M 8.00E-07 32.8 3.1d ---- (average over four reactions)

1.14 104 M 4.00E-07 19.0 1.8e ---- (average over three reactions)

5.88 105 M 2.00E-07 14.7 3.4f 2010 57 (average over two reactions)

a Linear fitting between −1.0 seconds. b Linear fitting between −2.0 seconds. c Linear fitting

between 0−10.0 seconds. d Linear fitting between −6.0 seconds. e Linear fitting between 0−20.0 seconds. f Linear fitting between 0−40.0 seconds.




S5

Synthesis of 1. A mixture of 2,2’-bipyridine-6,6’-dicarboxylic acid (H2bda) (24.4 mg,

0.1 mmol), Ru(DMSO)4Cl2 (48.4 mg, 0.1 mmol) and NEt3 (0.2 ml) in methanol (15 ml)

was degassed with N2 and refluxed over 2 hours. An excess of isoquinoline (129 mg, 1

mmol) was added and the reflux was continued overnight. The solvent was removed

and the residual solid was purified by column chromatography on silica gel using

dichloromethane-methanol (1:0 to 10:1, v:v) as eluents, 1 was obtained as brown solid

(43 mg, 71% yield). 1H NMR (500 MHz, methanol-d4 + CDCl3 with a small amount of

ascorbic acid): = 8.24 (s, 2H), 8.15 (d, 2H), 7.61 (d, 2H), 7.48 (t, 2H), 7.39-7.35 (m,

4H), 7.28 (t, 2H), 7.20-7.16 (m, 4 H), 7.08 (d, 2H). MS (ESI): m/z+ = 602.98 (M + H+),

calcd: 603.06. Found C 57.54, H 3.32, N 8.05. Calc. for

C30H20N4O4Ru0.25CH2Cl21.1CH3OH: C 57.22, H 3.81, N 8.51%.

1H NMR (CD3OD/CDCl3, 500 MHz) spectrum of the complex 1.




S6

COSY (CD3OD/CDCl3, 500 MHz) spectrum of the complex 1.

(1) Duan, L.; Fischer, A.; Xu, Y.; Sun, L. J. Am. Chem. Soc. 2009, 131, 10397. (2) Dulière, E.; Devillers, M.; Marchand-Brynaert, J. Organometallics 2003, 22, 804. (3) Donnici, C. L.; Filho, D. H. M.; Moreira, L. L. C.; Reis, G. T. d.; Cordeiro, E. S.; Oliveira, I. M. F. d.; Carvalho, S.; Paniago, E. B. J. Braz. Chem. Soc. 1998, 9, 455.




S7

0 25 50 75 100 125 150 175 200 225 2500

50

100

150

200

250

300

350

400

450

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

O2 (

mol

)

time (s)

[1] = 1.50 x10-5 M

Supplementary Figure S1a. Kinetic plots of oxygen formation by 1 vs. time. Conditions: CF3SO3H aqueous solutions (3.325 mL) containing CeIV (0.538 M, 1.79 10−3 mol) and catalyst 1 (1.50 105 M, 5 10−8 mol).

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

400

450

500

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

TO

N

O2 (

mol

)

Time (s)

[2] = 5.88 x 10-5 M

Supplementary Figure S1b. Kinetic plots of oxygen formation by 2 vs. time. Conditions: CF3SO3H aqueous solutions (3.4 mL) containing CeIV (0.526 M, 1.79 10−3 mol) and catalyst 2 (5.88 105 M, 2 10−7 mol).




S8

0 10 20 300

100

200

300

400

500

O2 (

mol

)

time (s)

[1] = 2.16 x 10-4 M[2] = 2.16 x 10-4 M

Supplementary Figure S1c. Kinetic plots of oxygen formation by 1 and 2 vs. time; conditions: CF3SO3H aqueous solutions (3.7 mL) containing CeIV (0.483 M, 1.79 10−3 mol) and catalyst (2.16 104 M, 8 10−7 mol).

0 20 40 60 80 1000

100

200

300

400

500

O2 (

mol

)

time (s)

[1] = 1.14 x 10-4 M [2] = 1.14 x 10-4 M

Supplementary Figure S1d. Kinetic plots of oxygen formation by 1 and 2 vs. time. Conditions: CF3SO3H aqueous solutions (3.5 mL) containing CeIV (0.511 M, 1.79 10−3 mol) and catalyst 2 (1.14 104 M, 4 10−7 mol).




S9

E (V vs NHE)

Supplementary Figure S2a. Differential Pulse Voltammograms of 1 and 2; conditions: [catalyst] = 1 mM, solvent = mixed acetone/pH 1.0 (v:v = 1:3), scanning rate = 100 mV/s.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

RuII-OH

RuV-O or RuIV-O.

RuIV-O

RuIV-OH

RuIII-OH

RuIII-OH2

Pot

entia

l (V

vs.

NH

E)

pH

RuII-OH2

Supplementary Figure S2b. Pourbaix diagram of complex 2. The zones of stability of the different species as function of pH and E are shown and are indicated by the oxidation state of the Ru metal and the degree of protonation of the aqua group. For instance the label [RuII-H2O] is used to describe the seventh coordinate complex [Ru(bda)(pic)2(H2O)]. For RuIII/II, a diagonal line of 59 mV/pH is found from pH 5.5 to 12.9, indicating the removal of a proton coupled with the removal of an electron. The pKa values of RuIIOH2 and RuIIIOH2 were therefore 5.5 and 12.9, respectively. For RuIV/III, a one-electron-one-proton PCET process is observed over the whole pH range from 1 to 13.5, relative to [RuIVOH/RuIIIOH2] and [RuIV=O/RuIIIOH]. Further

0.4 0.8 1.2 1.60

20

40

60

80

I (A

)

E ( v vs NHE)

Complex 1 Complex 2




S10

oxidation of RuIV=O only involves electron transfer as expected while oxidation of RuIVOH is accompanied by proton transfer, forming RuV=O. The observed pH-dependent redox of complex 2 in aqueous solutions supports the coordination of a water molecule to ruthenium at a low-oxidation state.

Supplementary Table S3. Rate Constants calculated at temperature range 5.0−35.0 oC, together with their corresponding activation parameters for the reaction of complex 2 and stoichiometric amounts of and CeIV in 0.1 M CF3SO3H.

Reactiona t (ºC) k ΔH ╪ (kJ mol-1) ΔS ╪ (J mol-1 K-1)

kET1 (M-1 s-1) 5.0

15.0

25.0

35.0

1.2×105

1.3×105

1.8×105

2.3×105

15±1 -95±4

kD (M-1 s-1) 5.0

15.0

25.0

35.0

3.3×104

6.3×104

8.3×104

1.1×105

30±3 -51±10

kO2 (s-1) 5.0

15.0

25.0

35.0

1.9

3.0

4.5

5.8

25±2 -149±7

RuIV-OH + CeIV → RuV=O + H+ + CeIII

2RuV=O → RuIV-OO-RuIV

RuIV-OO-RuIV → 2RuIII + O2




S11

0.0032 0.0033 0.0034 0.0035 0.00365.9

6.0

6.1

6.2

6.3

6.4

6.5

6.6 Data: Datak1_lnk1TModel: EyringFittingEquation: y=(-H)*1000*x/8.314+23.76+S/8.314Weighting: y No weighting Chi^2/DoF = 0.00108R^2 = 0.99002 H 14.70073 ±1.04388S -94.97844 ±3.57054

ln(k

1/T )

T -1 (K-1)

k1

0.0032 0.0033 0.0034 0.0035 0.00364.6

4.8

5.0

5.2

5.4

5.6

5.8

6.0

6.2

ln(k

2/T )

T -1 (K-1)

Data: Datak2_CModel: EyringFittingEquation: y=(-H)*1000*x/8.314+23.76+S/8.314Weighting: y No weighting Chi^2/DoF = 0.00965R^2 = 0.97829 H 29.67611 ±3.126S -50.6378 ±10.6923

k2




S12

Supplementary Figure S3. Eyring Plots for Stoichiometric Kinetics. Note: k1 = kET1, k2 = kD and k3 = kO2.

0 2 4 6 8 10

0.000000

0.000002

0.000004

0.000006

0.000008

0.000010

0.000012

0.000014

0.000016

0.000018

0.000020

Time(sec)

Con

c

Clark

specfit

0.000000

0.000002

0.000004

0.000006

0.000008

0.000010

0.000012

0.000014

0.000016

0.000018

0.000020[Ru(III) (0.06 mM) + 2 eq Ce(IV) (0.12 mM)]

Supplementary Figure S4. Stoichiometric O2 formation by 2 recorded by Clark-type oxygen electrode (black curve) and kinetics of O-O bond formation extracted from stopped-flow UV-vis data (blue curve).

0.0032 0.0033 0.0034 0.0035 0.0036-5.2

-5.0

-4.8

-4.6

-4.4

-4.2

-4.0

-3.8

Data: Datak3_lnk3TModel: EyringFittingEquation: y=(-H)*1000*x/8.314+23.76+S/8.314Weighting: y No weighting Chi^2/DoF = 0.00417R^2 = 0.9866 H 24.95084 ±2.05644S -149.13674 ±7.03393

ln(k

3/T)

T -1 (K-1)

k3




S13

Supplementary Figure S5a. CeIV loss monitored at 360 nm by stopped-flow UV-vis spectrometer after addition of complex 1 (0.4 M) into CeIV aqueous solution (0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mM, pH 1.0). At least duplicates of each concentration of CeIV have been measured.

Applying initial rate methods (see data in the inset table of Figure S5b), plot log (vo) (vo = initial rate) versus log ([Ce]o) gives Figure S5b. From the linear fitting, a slope of 0.8 was obtained. Accordingly, CeIV loss is first order in in CeIV.

Supplementary Figure S5b. Log (vo) versus log ([Ce]o). Inset table: initial rate vo and [CeIV]o.

-3.5 -3.0 -2.5 -2.0

-2.2

-2.0

-1.8

-1.6

-1.4

log(

v o)

log([Ce]o)

Equation y = a + b*x

Weight No Weighting

Residual Sum of Squares

0.00509

Adj. R-Square 0.99391Value Standard Error

DIntercept 0.38949 0.0508Slope 0.7899 0.01863

[CeIV]o (mM)

vo (Ms-1)

0.5 0.0059 0.5 0.0061 1.0 0.011 1.0 0.0098 2.0 0.0185 2.0 0.0196 3.0 0.0237 3.0 0.0247 4.0 0.031 4.0 0.034 5.0 0.036 5.0 0.035

0 20 40 60 80 100 120 140 160-0.10.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.7

CeIV + 1 (0.4 M) 0.5 mM 1.0 mM 2.0 mM 3.0 mM 4.0 mM 5.0 mM

Abs

orba

nce

at 3

60 n

m

t (s)




S14

Supplementary Figure S6. CeIV loss as monitored at 360 nm (initial times) by a CARY 300 Bio UV/Visible spectrophotometer after addition of complex 1 (0.1 M, 0.22 M, 0.3 M and 0.4 M) into CeIV aqueous solution (1.5 mM, pH 1.0). No data was collected in the first ca. 5 seconds due to the operation for injecting catalyst and stirring solutions.

-16.2 -16.0 -15.8 -15.6 -15.4 -15.2 -15.0 -14.8 -14.6-13.5

-13.0

-12.5

-12.0

-11.5

-11.0

-10.5

-10.0

Ln(r

ate)

Ln([1])


Weight No Weightin


0.02192

Adj. R-Square 0.99356Value Standard Erro

M Intercept 21.89968 1.55025M Slope 2.17657 0.10107

Supplementary Figure S7a. Plot of Ln(rate) versus Ln([1]). The linear fitting gives a slope of 2.18 0.10, indicating second order in catalyst 1 .

4 5 6 7 8 9 10 11 12 13 14 15 160.2

0.3

0.4

0.5

0.6

0.7

0.8A

bsor

banc

e

t (s)

CeIV 1.5mM + 1 (0.1 M) CeIV 1.5mM + 1 (0.2 M) CeIV 1.5mM + 1 (0.3 M) CeIV 1.5mM + 1 (0.4 M)




S15

0 20 40 60 80 100 120 140 160

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Rat

e x

105 (M

S1

)

[1]2 x 1015 (M2)


Weight No Weighting


5.93896E-12

Adj. R-Square 0.98744Value Standard Error

K Intercept -5.20163E-7 1.43152E-6K Slope 2.38528E8 1.54975E7

Rate = 2.39 x 108 M1 s1 [1]2

R2 = 0.987

Supplementary Figure S7b. Plot of CeIV-loss rate vs. [1]2. The second order rate constant is 2.39 108 M-1s-1. For details about these calculations, please see the supporting information of Meyer’s paper (Concepcion, J. J.; Jurss, J. W.; Templeton, J. L.; Meyer, T. J. J. Am. Chem. Soc. 2008, 130, 16462-16463.)




S16

Supplementary Figure S8a. (Upper): O2 and CO2 kinetics vs time, monitored by a Pfeiffer Oministar GSD 301C mass spectrometer; conditions: complex 2 with stoichiometric CeIV. (Lower): GC spectrum showing the CO2 production (data were acquired by Agilent 3000 Micro GC). Note: (i) Under stoichiometric CeIV conditions. One equivalent of CeIV was added to the pH 1 solution of [Ru(IV)(bda)(pic)2(OH)] (generated in situ by addition of one equivalent of CeIV to the Ru(III) aqueous solution), and the gas production versus time (upper figure) was monitored by a Mass Spectrometer. A trace amount of CO2 was detected due to the contamination of air during the injection of solutions. During the steady state of oxygen production, no CO2 formation was detected. (ii) Under excess CeIV conditions. A trace amount of CO2 was detected however the amount was too little to calculate. We could not even integrate the CO2 peak using the software provided by Agilent (lower figure). Accordingly, the amount of CO2 should be at a ppm level.




S17

Supplementary Figure S8b. MS spectrum of isoquinoline isolated from the catalytic reaction. We analyzed the decomposed species after the reaction of 8000 equivalent CeIV with complex 1. The reaction solution was extracted with CH2Cl2. Then the CH2Cl2 phase was collected and evaporated. The residual was then dissolved in MeOH and used for Mass spectrometric measurements. The isoquinoline ligand was detected and interestingly no isoquinoline-N-oxide. We propose that the main decomposition pathway is the axial-ligand dissociation.




S18

Computational details: general considerations In this investigation, we performed calculations at the density functional theory (DFT) level using the so-called global hybrid meta density functional M06-2X,1 which has been shown to provide broad accuracy for main group and organometallic chemistry including good level of approximation of non-covalent interactions. For comparison, limited calculations have been also performed with the classical hybrid functional, B3LYP.2, 3 Computational workflow employed functionals as implemented in Jaguar, version 7.7, computational package, which has been employed for all calculations in this work.4 The molecular orbital visualization only has been performed with Gaussian.5

DFT-method Relatively new but already well validated, the M06-2X method have became essential tool for modeling of reactions involving organometallic complexes. The strength of the Minnesota 2006 family of density functionals, to which M06-2x belongs, is that accurate description of organic and inorganic bonding is combined with a remarkable accuracy towards noncovalent interactions.1b For example, those are well described by M06-2X in biological science systems with nucleobase packing and stacking, as well as CH...π and cation...π interactions.1 For that reason, we have relied on M06-2X functional in this work. The B3LYP functional, still one of the most popular functional in chemistry, has an estimated averaged error of 3.29 kcal/mol, while M06-2X error is only about a half of that or even better.6,1 This is fully acceptable for the general purpose where most of interactions are covalent in nature. Combined with medium size basis sets, it allows to draw conclusions based on the relative energies of intermediates and transition states.7, 8,

9 It is acknowledged that B3LYP does not allow treatment of noncovalent interactions at a sufficient level of accuracy. In the present work, that disadvantage turned out to be of an advantage since control calculations with B3LYP, compared with results provided by M06-2X method, allowed us to clearly reveal complexes and situations where noncovalent interactions between axial ligands are of central matter.

Basis sets All calculations were performed using, first, lacvp* basis for geometry optimizations and comparison of conformers, and thereafter, lacvp*+ basis sets was used for a more

1 a) Y. Zhao, D. G. Truhlar, J. Chem. Phys. 2006, 125, 194101; b) Y. Zhao, D. G. Truhlar, Chem. Phys. Lett. 2011, 502, 1-13, and references therein; c) Y. Zhao, D. G. Truhlar, Acc. chem. Res. 2008, 41, 157. 2 a) A. D. Becke, J. Chem. Phys. 1993, 98, 5648-5652; b) C. Lee, W. Yang, R. G. Parr, Phys. Rev. B: Condens. Matter 1988, 37, 785-789. 3 Lundberg, M.; Blomberg, M. R. A.; Siegbahn, P. E. M., Inorg. Chem. 2004, 43, 264, and references therein. 4 Jaguar, version 7.7, Schrodinger, LLC, New York, NY, 2010. 5 Gaussian, M. J. Frisch et al., see full reference at the end of SI. 6 Curtis, L. A:; Raghavachari, K.; Redfern, R. C.; Pople, J. A. J. Chem. Phys. 2000, 112, 7374-7383. 7 S. Ling, W. Yu, Z. Huang, Z. Lin, M. Haranczyk, M. Gutowski, J. Phys. Chem. A 2006, 110, 12282. 8 B. M. Rice, S. V. Pai, C. F. Chabalowski, J. Phys. Chem. A 1998, 102, 6950. 9 W.-R- Zheng, Y. Fu, Q.-X. Guo, J. Chem. Theory Comput. 2008, 4, 1324.




S19

accurate geometry optimizations.10, 11 Basis sets are based on the 6-31G basis set with polarization (and diffuse) functions, also including accurate electron core potential for the Ru atom. The lacvp* basis should be sufficient to describe geometries and electronic structures of cationic complexes; the lacvp*+ basis set offers a necessary improvement of the interaction monoradical Ru-complexes in the process of the radical coupling involving non covalent interactions between axial ligands. The lacvp-family of basis sets employs an effective core potential (ECP) for ruthenium atoms, thus reducing computational costs.10 Cationic and neutral species should be well represented by this basis set considering the presence of a double set of polarization functions.

Self consistent reaction field (bulk solvent) The Jaguar suite treats solvated molecular systems with a self consistent reaction field (SCRF) method based on the solution of the Poisson-Boltzmann (field) equation; the method makes possible to compute minimum- energy solvated structures of complex systems at relatively low computational cost.12 In our study, solvation calculations were carried out starting from the gas-phase phase geometries employing the dielectric constant of ε = 80.37 (water) with the use of the standard set of optimized radii as implemented in Jaguar (see Ref. 13 and references therein).

The potential energy scan(s) Taking into account activation parameters obtained with the stopped flow technique, which affirmed our earlier computational approach and results, we have concluded that the calculation of the potential (electronic) energy alone is totally sufficient at this point. We have calculated the potential energy of the analogs of the stationary encounter complex, EC(isoq) in the article, as a function of the distance between terminal oxygen atoms, x = [O1 O2], as illustrated in Scheme 2 in the article. By optimizing all degrees of freedom with the exception of the [O1-O2]-constrain we obtained accurate geometries of a sufficient number of transient complexes, those were subjected to the electronic structure and conformation analysis. At the transition state area, we have also investigated complementary possibilities of the interaction between Ru-O monomers (for example, see Figure S10a). Details of the method could be found in our earlier work.14

10 P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299-310. 11 a) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys. 1972, 56, 2257-2261; b) M. M. Francl, W. J. Pietro, W. J. Hehre, J. S. Binkley, M. S. Gordon, D. J. Defrees, J. A. Pople, J. Chem. Phys. 1982, 77, 3654-3665; c) P. C. Hariharan, J. A. Pople, Theor. Chim. Acta 1973, 28, 213-222. 12 (a) Tannor, D. J.; Marten, B.; Murphy, R.; Friesner, R. A.; Sitkoff, D.; Nicholls, A.; Ringnalda, M.; Goddard, W. A., III; Honig, B. J. Am. Chem. Soc. 1994, 116, 11875. (b) Marten, B.; Kim, K.; Cortis, C.; Friesner, R. A.; Murphy, R. B.; Ringnalda, M. N.; Sitkoff, D.; Honig, B. J. Phys. Chem. 1996, 100, 11775; ( c) Cramer, C.J.; Truhlar, D., G.; Chem .Rev., 1999, 99, 2161-2200. 13 (a) Chirlian, L. E.; Francl, M. M. J. Comput. Chem. 1987, 8, 894; (b) Woods, R. J.; Khalil, M.; Pell, W.; Moffat, S. H.; Smith, V. H., Jr. J. Comput. Chem. 1990, 11, 297; (c) Breneman, C. M.; Wiberg, K. B. J. Comput. Chem. 1990, 11, 361.

14 J. Nyhlen, L. Duan, B. Åkermark, L. Sun, T. Privalov, Angew. Chem. Int. Ed. 2010, 49, 1773-1777;




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Calculated polarizability and dipole moment Pyridine: --------polarizability (in AU)----------- alpha(x x)= 20.556 alpha(x y)= 0.000 alpha(x z)= 0.000 alpha(y x)= 0.000 alpha(y y)= 66.434 alpha(y z)= 0.000 alpha(z x)= 0.000 alpha(z y)= 0.000 alpha(z z)= 61.140 ----first hyperpolarizability (in AU)------- beta(x,x,x)= 0.000 beta(y,y,y)= 0.000 beta(z,z,z)= 9.290 beta(x,y,y)= 0.000 beta(x,z,z)= 0.000 beta(y,x,x)= 0.000 beta(y,z,z)= 0.000 beta(z,x,x)= .739 beta(z,y,y)= 9.665 beta(x,y,z)= 0.000 sum beta(x)= 0.000 sum beta(y)= 0.000 sum beta(z)= 19.694 ----------------------- Moments from quantum mechanical wavefunction: Dipole Moments (Debye) X= 0.0000 Y= 0.0000 Z= -2.3602 Tot= 2.3602 ----------------------- Moments from Mulliken charges: Dipole Moments (Debye) X= .0000 Y= -.0001 Z= -2.8877 Tot= 2.8877 -----------------------

Picoline: --------polarizability (in AU)----------- alpha(x x)= 75.268 alpha(x y)= 2.150 alpha(x z)= 0.000 alpha(y x)= 2.150 alpha(y y)= 76.204 alpha(y z)= 0.000 alpha(z x)= 0.000 alpha(z y)= 0.000 alpha(z z)= 30.277 ----first hyperpolarizability (in AU)------- beta(x,x,x)= 15.168 beta(y,y,y)= .835 beta(z,z,z)= 0.000 beta(x,y,y)= -19.364 beta(x,z,z)= 14.164 beta(y,x,x)= 2.755 beta(y,z,z)= 6.443 beta(z,x,x)= 0.000 beta(z,y,y)= 0.000 beta(x,y,z)= 0.000 sum beta(x)= 9.968 sum beta(y)= 10.034 sum beta(z)= 0.000 ----------------------- Moments from quantum mechanical wavefunction: Dipole Moments (Debye) X= -1.4085 Y= -2.3892 Z= 0.0000 Tot= 2.7734 ----------------------- Moments from Mulliken charges: Dipole Moments (Debye) X= -1.7438 Y= -2.8733 Z= 0.0000 Tot= 3.3611 -----------------------

Isoquinoline: --------polarizability (in AU)----------- alpha(x x)= 103.447 alpha(x y)= -1.716 alpha(x z)= 0.000 alpha(y x)= -1.716 alpha(y y)= 135.616 alpha(y z)= 0.000 alpha(z x)= 0.000 alpha(z y)= 0.000 alpha(z z)= 32.191 ----first hyperpolarizability (in AU)------- beta(x,x,x)= -4.195 beta(y,y,y)= 7.283 beta(z,z,z)= 0.000 beta(x,y,y)= -15.151 beta(x,z,z)= -.874 beta(y,x,x)= 11.040 beta(y,z,z)= 1.196 beta(z,x,x)= 0.000




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beta(z,y,y)= 0.000 beta(x,y,z)= 0.000 sum beta(x)= -20.220 sum beta(y)= 19.519 sum beta(z)= 0.000 ----------------------- Moments from quantum mechanical wavefunction: Dipole Moments (Debye) X= -.9161 Y= -2.5200 Z= 0.0000 Tot= 2.6813 ----------------------- Moments from Mulliken charges: Dipole Moments (Debye) X= -1.3100 Y= -2.9284 Z= .0000 Tot= 3.2081 -----------------------

XYZ Information Due to quite a big size of complexes that we have investigated computationally, as well as large number of computed geometries, the corresponding XYZ information is available upon request from authors.

Ref. Gaussian: Gaussian 03, Revision B.02: M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 2003.




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Supplementary: computational, O-O bonding of isoq-ruthenium complexes

[O-O] = 3.22 Å

Supplementary Figure S9a. The total spin density in EC(isoq), left, and an isolated RuV=O complex. The singly occupied molecular orbitals are apparently non-interacting at the O-O distance of ca. 3.2 Å. Hydrogen atoms are removed for clarity.

Supplementary Figure S9b. A complementary point of view on the fully calculated EC(isoq). Stacking of axial isoquinolines gives EC(isoq) a moderate stability (the energy of formation is ca. -4.5kcal/mol) and is somewhat similar to π-π pairing (stacking) in proteins.




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Supplementary Figure S10a. An illustration of two equivalent pathways of O-O bonding from EC(isoq). In our calculations, both pathways lead to nearly identical transition states TSOO'(isoq) and TSOO(isoq). A difference between them is that the forming O-O bond is positioned one one or the other side with respect to the Ru1-Ru2 line.

Supplementary Figure S10b. The calculated transition state of the radical O-O

bonding, TSOO(isoq). For an alternative TSOO'(isoq), calculated geometrical parameters

are nearly same. All distances are in Å. For clarity, the point of view is perpendicular to

the bda-ligands.




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σ*p-p

occupation: 1 σ*p-p

occupation: 0

σp-p

occupation: 1 σp-p

occupation: 2 Triplet electronic state Singlet electronic state

Supplementary Figure S11. At the transition state of the radical O-O bonding,

TSOO(isoq), the low energy singlet electronic state has doubly occupied O-O bonding

σp-p orbital and the unoccupied σ*p-p; the higher energy triplet electronic state has two

singly occupied molecular orbitals, σp-p and σ*p-p. Hydrogen atoms are removed for

clarity.

We have checked that the "relaxation" of the TSoo(isoq) directly leads to the peroxo

RuIV dimer, Dp(isoq),while at larger O-O distances TSoo(isoq) gradually converts back

into EC(isoq).




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Supplementary Figure S12. The optimized geometry of the peroxo dimer Ru(IV)-OO-Ru(IV), Dp(isoq). All distances are in Å. For clarity, the point of view is perpendicular to the bda-ligands.

Dsuperoxo(isoq) Calculated result of a "spontaneous"

dissociation of Dsuperoxo(isoq) into two Ru(III) monomers and O2

Supplementary Figure S13. The superoxo Ru(III)/Ru(IV) dimer which readily evolves into two non-covalently bonded Ru(III) monomers with the O2 in the ground electronic state (triplet). All distances are in Å.




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Supplementary Scheme S1. Calculated the potential energy profile for the O-O bonding directly from Figure 5; blue line represent the triplet electronic state (not shown in Figure 5 for reasons of clarity); red represents the lower energy singlet electronic state. The lower energy barrier belongs to the singlet electronic state profile.

Supplementary Table S4. Selected electronic energies for Scheme S1. *)Relative energies account for solvent effects which turned out to be quite small due to similarities between structures along the whole reaction pathway.

The O-O distance (Å)

Reference electronic energies (hartree)

Triplet, relative energies*

Singlet, relative energies*

3,25 -3686,50177582 0,0000 0,0000 2,8 -3686,50014493 1,0 0,85

2,625 -3686,49826722 2,2 1,8 2,575 -3686,49755581 2,7 2,1

2,4 -3686,49420723 4,8 3,7 2,255 -3686,48841928 8,4 6,3

2,1775 -3686,48516653 10,4 7,8 2,1 -3686,48438018 10,9 8,4

2,0375 -3686,48432883 10,95 8,4 1,975 -3686,48467693 10,7 8,4 1,925 -3686,48619475 9,8 7,6

1,9 -3686,48795300 8,7 6,5 ... ... ... ...

Minima: Ru(IV)-O-O-Ru(IV) peroxo-dimer

0

2

4

6

8

10

12

1,852,052,252,452,652,853,053,25




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ΔE > 0

Supplementary Figure S14. Left: steric collision of axial ligands, Me-groups of picolines hinder the formation of an encounter complex between RuV=O complexes with axial picolines. Right: a high-energy reacting complex with nearly perpendicular bda-ligands which although lowers steric collision of axial ligands, at the same time inhibits radical molecular orbital overlap which is central for the radical O-O bond formation between two RuV=O species.

Peroxo Superoxo

Formal electronic structures of the peroxo- and superoxo dimers which is based on the molecular orbital analysis. The electronic structure assignment of the molecular orbitals is independent on the level of theory, i.e. M06-2X or B3LYP, which give very similar results.




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Supplementary: computational, excess CeIV conditions.

Supplementary Figure S15. The optimized geometry of the proposed the [RuIV-O●O-RuIV]3+

dimer with axial 4-picoline ligands. All distances are in Å.

In water, the calculated potential for the [RuIV-OO-RuIV]2+ → [RuIV-O ̇O-RuIV]3+ process, which involves the oxidation of the O2

2- cationic bridge towards the superoxide (O2-) while

each of the two ruthenium centers remains in the RuIV state, is 1.03 V vs NHE at pH 1, based on the Born – Haber cycle for the theoretical prediction of the standard redox potentials in solution:

where

Within the Born-Harber cycle, the calculated redox potentials are defined as the free energy change of the half reaction represented in the insert. This consists of the free energy change in the gas phase and the solvation free energies of the reduced and the oxidized species, the




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second and the third terms in the equation above, respectively. The standard Nernst equation connects the overall reaction-energy change with the standard one-electron redox potential.


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