S1
Electrocatalytic H2 Evolution by Supramolecular Ru II‒RhIII‒RuII
Complexes: Importance of Ligands as Electron Reservoirs and
Speciation upon Reduction
Gerald F. Manbeck, Theodore Canterbury, Rongwei Zhou, Skye King, Geewoo Nam, and Karen J.
Brewer
Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061-0212, United States
Table of Contents
Figures S1 CVs of 25 mM trifluoroacetic acid with increasing concentrations of
[{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5.
S2
Figures S2 Plots of ic/ip as a function of acid concentration.
S3
Figure S3 CVs for the catalytic reduction of CF3CO2H, CF3SO3H, and CH3CO2H
using 1 mM [{(Ph2phen)2Ru(dpp)}2RhCl2](PF6)5 in DMF.
S4
Figure S4 CVs for electrocatalytic reduction of CF3CO2H or CH3CO2H using
[Rh(Cl2)(dpp)2]+ or [{(Ph2phen)2Ru(dpp)}2RhCl2](PF6)5 in DMF.
S5
Figure S5 Sequential CVs of [{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 (1mM) with 15
equiv CF3CO2H or CF3SO3H.
S6
Figure S6 CVs of [{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 before (a) and after (b) twoelectron reduction in DMF.
S7
S2
— 0.13 mM catalyst
— 0.08 mM catalyst
— 0.04 mM catalyst
— 0.0 mM catalyst
— no acid
180
160
μA
140
120
100
80
60
40
40 μA
0.00
0.0
-0.5
-1.0
V vs. Ag/AgCl
-1.5
0.04
0.08
[catalyst] mM
0.12
-2.0
Figure S1. Cyclic voltammograms of 25 mM trifluoroacetic acid with increasing concentrations
of [{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 in DMF and plot of catalytic current vs catalyst
concentration. This experiment verifies that the reaction is first order in catalyst concentration
according to the equation: 𝑖𝑐 = 𝑛𝐹𝐴[𝑐𝑎𝑡]√𝐷𝑘[𝐻 + ]2 . Scan rate = 50 mV s−1.
S3
10
8
[{(Ph2phen)2Ru(dpp)}2RhBr2]
CF3SO3H
CF3CO2H
CH3CO2H
5+
ic/ip
6
4
2
0
0
10
4
8
12
[acid], mM
16
20
16
20
5+
[{(Ph2phen)2Ru(dpp)}2RhCl2]
CF3SO3H
CF3CO2H
CH3CO2H
8
ic/ip
6
4
2
0
0
4
8
12
[acid], mM
Figure S2. Plots of ic/ip as a function of acid concentration using catalysts
[{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 (top) or [{(Ph2phen)2Ru(dpp)}2RhCl2](PF6)5 (bottom). The
current for the first ligand-based reduction was chosen as ic and the maximum current of
catalysis was used as ip. The catalyst concentration was 1.0 mM in DMF. Linear fits confirm
second order catalysis with respect to acid concentration according to the equation: 𝑖𝑐 =
𝑛𝐹𝐴[𝑐𝑎𝑡]√𝐷𝑘[𝐻 + ]2 . Scan rate = 100 mV s−1.
S4
Current / A
150x10
[{(Ph2phen)2Ru(dpp)}2RhCl2]
1 mM in DMF
0, 1, 5, 10, 25 eq. CF3CO2H
100 mV/s
-6
5+
100
50
0
0.0
Current / A
150x10
-0.5
-1.0
-1.5
E / V vs. Ag/AgCl
[{(Ph2phen)2Ru(dpp)}2RhCl2]
1 mM in DMF
0, 1, 5, 10,
15, 25 eq. CF3SO3H
100 mV/s
-6
-2.0
5+
100
50
0
0.0
Current / A
150x10
-0.5
-1.0
-1.5
E / V vs. Ag/AgCl
[{(Ph2phen)2Ru(dpp)}2RhCl2]
1 mM in DMF
0, 1, 5, 10, 25 eq. CH3CO2H
100 mV/s
-6
-2.0
5+
100
50
0
0.0
-0.5
-1.0
-1.5
E / V vs. Ag/AgCl
-2.0
Figure S3. Cyclic voltammograms for the catalytic reduction of CF3CO2H, CF3SO3H, and
CH3CO2H using 1 mM [{(Ph2phen)2Ru(dpp)}2RhCl2](PF6)5 in DMF. Scan rate = 100 mV s−1 A
CV of 22 mM of each acid in the absence of catalyst is shown as a blank.
S5
5+
[{(Ph2phen)2Ru(dpp)}2RhCl2]
or
+
[Rh(Cl2)(dpp)2]
with 0 (solid) and 10 eq. CF3CO2H (dashed)
10 μA
0.0
-0.5
-1.0
E / V vs. Ag/AgCl
5+
[{(Ph2phen)2Ru(dpp)}2RhCl2]
-1.5
-2.0
or
+
[Rh(Cl2)(dpp)2]
with 0 (solid) and 10 eq. CH3CO2H (dashed)
10 μA
0.0
-0.5
-1.0
E / V vs. Ag/AgCl
-1.5
-2.0
Figure S4. CVs for electrocatalytic reduction of CF3CO2H or CH3CO2H using [Rh(Cl2)(dpp)2]+
or [{(Ph2phen)2Ru(dpp)}2RhCl2](PF6)5 in DMF (0.1M Bu4NPF6) with 0 or 10 equivalents acid.
Scan rate = 100 mV s−1.
S6
140x10
-6
120
Current / A
100
5+
[{(Ph2phen)2Ru(dpp)}2RhBr2]
— no acid
— 15 eq. CF3CO2H, 1st scan
— 15 eq. CF3CO2H, 2nd scan (no polish)
— 15 eq. CF3CO2H, 3rd scan (polished)
80
60
40
20
0
0.0
120x10
-6
100
-0.4
-0.8
Potential / V vs. Ag/AgCl
-1.2
5+
[{(Ph2phen)2Ru(dpp)}2RhBr2]
— no acid
— 15 eq. CF3SO3H, 1st scan
— 15 eq. CF3SO3H, 2nd scan (no polish)
— 15 eq. CF3SO3H, 3rd scan (polished)
Current / A
80
60
40
20
0
0.0
-0.4
-0.8
Potential / V vs. Ag/AgCl
-1.2
Figure S5. Sequential CVs of [{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 (1mM) with 15 eq. CF3CO2H
(top) or CF3SO3H (bottom) demonstrating fowling of the electrode upon sequential scans for
CF3SO3H (blue trace). For CF3CO2H, CVs are identical regardless of polishing ruling out surface
deposition on the glassy carbon.
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2e
III/II/I
Rh
5 μA
new Rh species
a.
b.
–
2Br Br2
1.5
1.0
0.5
0.0
E / V vs. Ag/AgCl
-0.5
-1.0
Figure S6. CV’s of [{(Ph2phen)2Ru(dpp)}2RhBr2](PF6)5 before (a) and after (b) 2e reduction in
DMF. After reduction, the RhIII/II/I couple of the pristine complex is absent and bromide
oxidation is evident at +1 V. An oxidative through +1300 generates a new Rh species in the
return wave with a potential slightly cathodic of the original cis-RhCl2 reduction.