S1

SupplementaryInformation(ESI)for:

Light-activatedGenerationofNitricOxide(NO)andSulfiteAnionRadical(SO3•−)fromaRuthenium(II)NitrosylsulphitoComplex†

AntonioC.RovedaJr.*a‡,WillyG.Santosa,MaykonL.Souzaa,CharlesN.Adelsonb,FelipeS.Gonçalvesa,

EduardoE.Castellanoc,ClaudioGarinod,DouglasW.Francoa†andDanielR.Cardoso*a

aSãoCarlosInstituteofChemistry,UniversityofSãoPaulo,CEP13560-970,SãoCarlos,SP,Brazil.‡currentaddress,DepartmentofChemistry,StanfordUniverity,CA,USA.bDepartmentofChemistry,StanfordUniversity,CA,USAcSãoCarlosInstituteofPhysics,UniversityofSãoPaulo,SãoCarlosSP,BrazildDepartmentofChemistryandNISInterdepartmentalCentre,UniversityofTurin,10125Turin,Italy

†ThispaperisdedicatedinmemoriamofProf.Dr.DouglasWagnerFranco

*CorrespondenceAuthors:AntonioC.RovedaJr.(acroveda@stanford.edu/acroveda@usp.br)DanielR.Cardoso(drcardoso@usp.br)

Electronic Supplementary Material (ESI) for Dalton Transactions.This journal is © The Royal Society of Chemistry 2019

S2

Table of Contents

1.Spectroscopiccharacterizationofcomplex1................................................................................3

2.X-rayandDFTresults...............................................................................................................................5

2.1Assignmentoftheelectronictransitionsofcomplex1....................................................10

3.Stabilityofcomplex1inaqueoussolution(pH7.4)................................................................14

3.1Discussionaboutthedecompositionofcomplex1atpH7.4........................................19

4.Stabilityofcomplex1inaqueousacidicsolutions...................................................................20

5.Reactionofhydroxideions(OH−)withthecomplexes1and2...........................................21

5.1Discussionaboutthemechanismforthereactionof1withOH–................................24

6.pKaoftheN(O)SO3ligandcoordinateto1...................................................................................26

7.Photochemistryofcomplex1............................................................................................................27

7.1.Time-courseUv-visfortheirradiationof1.........................................................................27

7.2.Reactionofsulfiteradicals(SO3●–)withoxymyoglobinandcarboxy-PTIO...........28

7.3.DFTresultsonirradiationofcomplex1................................................................................30

7.4.Time-course1HNMRfortheinsituirradiationof1........................................................30

7.5.DissociationofN(O)SO3−..............................................................................................................31

7.6.X-raystructureofcomplex2......................................................................................................33

8.References..................................................................................................................................................36

S3

1.Spectroscopiccharacterizationofcomplex1

A

B

Figure S1. (A) FT-IR spectra of trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) (complex 1, red line) and of the synthetic precursor trans-[Ru(NH3)4(isn)(NO)](BF4)3 (complex 2, black line). (B) Expanded viewing of the FT-IR in Figure S1A for the complex trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) (complex 1)

4000 3500 3000 2500 2000 1500 1000 5000

10

20

30

40

50

60

70

80

Wavenumber (cm-1)

νNO

Tran

smita

nce

(%)

trans-[Ru(NH3)4isn(N(O)SO3](PF6) trans-[Ru(NH3)4isn(NO)](BF4)3

νNO

Complex2

Complex1

1750 1500 1250 1000 750 500 250

30

40

50

60

70

80

90

PF6

complex 1 - trans-[Ru(NH3)

4(isn)(N(O)SO

3)](PF

6)

νsym SO

δasynmSOνNO

Tran

smita

nce

(%)

Wavenumber (cm-1)

isonicotinamide

νasym SO

νsymSO

PF6

S4

Figure S2. 1H NMR spectrum of the complex 1 in D2O (reference TMSPd-4, δ = 0 ppm).

Figure S3. 15N NMR spectrum of the 15N-labeled complex 1 in D2O (reference, a capillary filled with 15NH4Cl (δ = –354 ppm vs. chemical shift of CH3NO2, δCH3NO2 = 0 ppm).

Isonicotinamidecoordinatedto1

TMSPd-4

RuH3N NH3

15N

NH3H3N

SO3O

N

O NH215N-labeledcomplex 1

S5

2.X-rayandDFTresultsA B

Figure S4. (A) ORTEP representation of the complex trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) (complex 1), ellipsoids at 50% probability, H omitted for clarity. (B) molecular structure of complex 1 showing Ru–N(O)SO3 bond lengths, and O–N=SO3 angle.

Table S1. Complete crystallographic data and structure refinement of the complex trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) (complex 1) ________________________________________________________________________________ Empirical formula C6 H18 F6 N7 O5 P Ru S Formula weight 1092.75 Temperature 296(2) K Wavelength 0.71073 Å Crystal system Triclinic Space group P -1 Unit cell dimensions a = 7.7298(6) Å α= 78.234(6)°. b = 9.1139(6) Å β= 82.835(6)°. c = 13.8569(10) Å γ = 69.877(7)°. Volume 895.77(12) Å3 Z 1 Density (calculated) 2.026 Mg/m3 Absorption coefficient 1.177 mm-1 F(000) 544 Crystal size 0.3 x 0.1 x 0.1 mm3 Theta range for data collection 2.616 to 25.997°. Index ranges -9 ≤ h ≤ 9, -11 ≤ k ≤ 10, -17 ≤ l ≤ 16 Reflections collected 5465 Independent reflections 3516 [R(int) = 0.0200] Completeness to theta = 25.242° 99.9 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 1.00000 and 0.98641 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3516 / 0 / 248 Goodness-of-fit on F2 1.043 Final R indices [I>2sigma(I)] R1 = 0.0369, wR2 = 0.0895 R indices (all data) R1 = 0.0475, wR2 = 0.0959 Extinction coefficient n/a Largest diff. peak and hole 0.825 and -0.541 e.Å-3 _________________________________________________________________________

RuH3NH3N NH3

NH3

N

O SO3

N

1.88 Å

1.24 Å

110.4º

124.4º

1.84Å

NH2O

2.17 Å

125.2º

complex 1

S6

Table S2. Complex 1. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (Å2x 103). U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. ________________________________________________________________________________ x y z U(eq)

________________________________________________________________________________

Ru 3334(1) 8397(1) 8419(1) 32(1)

S 1814(2) 7171(1) 10667(1) 43(1)

O(2) 3255(6) 9711(4) 3112(2) 66(1)

O(1) 4002(6) 8804(5) 10253(2) 76(1)

O(12) 41(5) 7761(6) 10274(3) 96(2)

O(13) 2767(6) 5602(4) 10593(3) 90(2)

O(11) 1789(10) 7611(8) 11577(3) 137(3)

N(1) 3167(6) 8237(5) 9797(2) 45(1)

N(5) 456(5) 8996(6) 8296(3) 57(1)

N(4) 3500(7) 6008(5) 8487(3) 55(1)

N(3) 6220(5) 7805(4) 8454(3) 43(1)

N(2) 3224(5) 10775(4) 8310(2) 40(1)

N(6) 3543(4) 8647(4) 6823(2) 31(1)

N(7) 2625(6) 7454(5) 3636(3) 51(1)

C(4) 2408(6) 9894(5) 6262(3) 37(1)

C(5) 4669(5) 7485(5) 6367(3) 37(1)

C(6) 4588(6) 7453(5) 5387(3) 40(1)

C(2) 3335(5) 8699(5) 4827(3) 33(1)

C(3) 2283(6) 9974(5) 5268(3) 37(1)

C(1) 3076(6) 8664(5) 3778(3) 36(1)

P 10815(2) 5198(1) 6599(1) 38(1)

F(1) 12957(5) 4644(5) 6766(3) 96(1)

F(2) 11267(7) 5608(6) 5479(2) 104(2)

F(3) 10997(6) 3485(4) 6477(3) 102(1)

F(4) 8733(5) 5717(6) 6450(4) 124(2)

F(5) 10501(8) 4790(7) 7745(3) 132(2)

F(6) 10691(6) 6917(4) 6736(3) 93(1) ________________________________________________________________________________

S7

Table S3. Bond lengths [Å] and angles [°] of complex 1. Ru-N(1) 1.877(3) Ru-N(3) 2.111(3) Ru-N(2) 2.115(3) Ru-N(4) 2.119(4) Ru-N(5) 2.120(4) Ru-N(6) 2.167(3) S-O(13) 1.383(4) S-O(11) 1.395(4) S-O(12) 1.423(4) S-N(1) 1.844(4) O(2)-C(1) 1.217(5) O(1)-N(1) 1.244(5) N(6)-C(5) 1.335(5) N(6)-C(4) 1.338(5) N(7)-C(1) 1.322(6) C(4)-C(3) 1.378(5) C(5)-C(6) 1.373(6) C(6)-C(2) 1.379(6) C(2)-C(3) 1.379(6) C(2)-C(1) 1.500(5) P-F(4) 1.541(4) P-F(2) 1.546(3) P-F(3) 1.561(3) P-F(5) 1.563(4) P-F(6) 1.585(3) P-F(1) 1.589(4) N(1)-Ru-N(3) 88.36(16) N(1)-Ru-N(2) 87.89(14) N(3)-Ru-N(2) 86.05(14) N(1)-Ru-N(4) 93.59(15) N(3)-Ru-N(4) 93.01(16) N(2)-Ru-N(4) 178.23(15) N(1)-Ru-N(5) 94.86(16) N(3)-Ru-N(5) 176.78(14) N(2)-Ru-N(5) 94.13(17) N(4)-Ru-N(5) 86.73(18) N(1)-Ru-N(6) 178.32(14) N(3)-Ru-N(6) 91.19(13) N(2)-Ru-N(6) 90.47(12) N(4)-Ru-N(6) 88.05(13) N(5)-Ru-N(6) 85.60(13) O(13)-S-O(11) 116.7(4) O(13)-S-O(12) 113.9(3) O(11)-S-O(12) 112.5(4) O(13)-S-N(1) 102.6(2) O(11)-S-N(1) 105.7(2) O(12)-S-N(1) 103.7(2) O(1)-N(1)-S 110.4(3) O(1)-N(1)-Ru 124.4(3) S-N(1)-Ru 125.20(19)

S8

C(5)-N(6)-C(4) 116.9(3) C(5)-N(6)-Ru 121.3(2) C(4)-N(6)-Ru 121.4(3) N(6)-C(4)-C(3) 123.2(4) N(6)-C(5)-C(6) 123.2(4) C(5)-C(6)-C(2) 119.3(4) C(6)-C(2)-C(3) 117.9(3) C(6)-C(2)-C(1) 121.5(4) C(3)-C(2)-C(1) 120.5(4) C(4)-C(3)-C(2) 119.0(4) O(2)-C(1)-N(7) 123.2(4) O(2)-C(1)-C(2) 120.9(4) N(7)-C(1)-C(2) 115.9(3) F(4)-P-F(2) 91.9(3) F(4)-P-F(3) 89.1(3) F(2)-P-F(3) 89.9(2) F(4)-P-F(5) 92.2(3) F(2)-P-F(5) 175.7(3) F(3)-P-F(5) 91.6(3) F(4)-P-F(6) 92.6(2) F(2)-P-F(6) 90.5(2) F(3)-P-F(6) 178.2(2) F(5)-P-F(6) 87.9(3) F(4)-P-F(1) 179.2(3) F(2)-P-F(1) 88.8(3) F(3)-P-F(1) 90.5(2) F(5)-P-F(1) 87.1(3) F(6)-P-F(1) 87.8(2) _____________________________________________________________

S9

Figure S5. Comparison of X-ray structure and of the DFT optimized structure for complex 1 (GS = ground state ).

Table S4. Selected bond lengths and bond angles (experimental and calculated by DFT) for the GS of trans-[Ru(NH3)4(isn)(N(O)SO3)]+ (complex 1).

Distance (Å) Bond Experimental Calculated (DFT)

Ru–N(1) 1.877(3) 1.914 N(1)–O(1) 1.244(5) 1.225 N(1)–S(1) 1.844(4) 1.923 S(1)–O(11,12, 13) a 1.383–1.423 1.471–1.489 Ru–N(2, 3,4, 5) b 2.111–2.120 2.157–2.167 Ru–N(6) 2.167(3) 2.209

Angles (deg)

Bond Experimental Calculated (DFT)

Ru–N(1)–O(1) 124.4(3) 124.63 Ru–N(1)–S(1) 125.20(19) 123.90 O(1)–N(1)–S(1) 110.4(3) 111.40 N(1)–Ru–N(6) 178.32(14) 176.46 O(12)–S–O(13) 113.9(3) 114.35–115.84

a Range for the three S–O bonds; b Range for the four Ru–NH3 bonds

S10

2.1Assignmentoftheelectronictransitionsofcomplex1

Figure S6. Experimental (phosphate buffer solution pH 7.4) and theoretical UV/Vis absorption spectra of 1. Electronic transitions (tr.) are represented as vertical bars with height equal to the oscillator strength (f) values.

S11

Table S5. Calculated absorption properties of 1 in water.

Tr.[a] Energy, eV (nm) f[b] Composition Character EDDM[c]

7 3.64 (341) 0.2505 H–2→LUMO (79%) H–5→LUMO (6%) H–2→L+1 (6%)

MLCT (Ru→N(O)SO3)

8 3.77 (329) 0.0342 H–5→LUMO (85%) LC (N(O)SO3)

10 3.96 (313) 0.0383 H–1→L+3 (17%)

H–1→L+5 (24%) H–4→LUMO (5%) H–2→L+1 (8%) H–1→L+4 (7%) HOMO→L+3 (6%) HOMO→L+5 (8%)

MC

26 5.00 (248) 0.0121 H–9→LUMO (75%)

H–8→LUMO (5%) H–1→L+3 (5%)

LC (N(O)SO3)

30 5.33 (233) 0.0413 H–7→L+1 (55%)

H–4→L+2 (24%) H–10→L+2 (6%) H–2→L+2 (7%)

LC (isn)

S12

31 5.37 (231) 0.1181 H–10→LUMO (68%) H–7→L+1 (6%) H–4→L+2 (9%)

LMCT (isn→Ru)

32 5.41 (229) 0.0606 H–10→LUMO (11%)

H–7→L+1 (15%) H–4→L+2 (57%)

LC (isn)

35 5.63 (220) 0.0684 H–3→L+3 (51%)

HOMO→L+6 (14%) HOMO→L+7 (21%)

MLCT (Ru→ammines)

43 5.82 (213) 0.2093 H–5→L+2 (18%)

H–3→L+4 (25%) H–3→L+5 (28%)

LMCT (N(O)SO3→Ru)

44 5.84 (212) 0.0915 H–5→L+2 (73%)

H–3→L+4 (7%) H–3→L+5 (8%)

LLCT (N(O)SO3→isn)

S13

46 5.91 (210) 0.0135 H–5→L+3 (33%) H–5→L+4 (26%) H–5→L+5 (20%) H–5→L+2 (6%)

LMCT (N(O)SO3→Ru)

53 6.16 (201) 0.0482 H–10→L+1 (75%)

H–7→L+2 (18%) mainly LC (isn)

[a] Tr. indicates transition number as obtained in the TD-DFT calculation output. [b] f = oscillator

strength (Only transitions with f > 0.01 are shown). [c] Electron-Density Difference Map (black indicates a decrease in electron density, white indicates an increase; isovalue = 0.001).

Figure S7. (A) EDDM (black indicates a decrease in electron density, white indicates an increase; isovalue = 0.001), and (B) main component’s orbitals (HOMO–2 and LUMO) of the 7th singlet-singlet transition (S7 or tr. 7) computed for complex 1.

S14

3.Stabilityofcomplex1inaqueoussolution(pH7.4)

Figure S8. Representative curves (Uv-vis) for the behavior of complex 1 in solution. Conditions: Phosphate buffer, pH 7.4, T = 40ºC. Inset: plot of Absorbance at 363 nm vs. time (s)

Figure S9. Plot of (A) ln (A) – ln (A0) vs. time in different temperatures for the stability assays of trans-[Ru(NH3)4(isn)(N(O)SO3)]+ (complex 1) in phosphate buffer (pH 7.4, C =20mM), (B) Arrhenius plot, and (C) Eyring plot.

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

0 10000 20000 30000

0,0

0,1

0,2

0,3

0,4

0,5

time (s)

Abs

orba

nce

Initial final

trans-[Ru(NH3)4(isn){N(O)SO3}](PF6)Phosphate Buffer solution, pH 7.4T = 40 ºC

Abs

orba

nce

Wavelength (nm)

0 20000 40000 60000 80000 100000 120000-2.8

-2.4

-2.0

-1.6

-1.2

-0.8

-0.4

0.0

40ºC 35ºC 30ºC 25ºC

ln (A

t) - l

n (A

0)

time (s)

20ºC

A

3.2x10-3 3.3x10-3 3.3x10-3 3.4x10-3 3.4x10-3 3.5x10-3-17.5

-17.0

-16.5

-16.0

-15.5

-15.0

-14.5

-14.0

ΔH++ = 26,46 kcal/mol

R = 8.3144 J/K mol

ln (k

/T)

Equation y = a + b*xWeight No WeightingResidual Sum of Squares

0.07154

Pearson's r -0.99329Adj. R-Square 0.98215

Value Standard ErrorK Intercept 28.3534 2.95845K Slope -13319.75738 895.67729

ln (k/t) = -ΔH++/RR = 1.98722 cal/K mol

1/T

C

3.8x10-4 3.9x10-4 4.0x10-4 4.1x10-4-11.5

-11.0

-10.5

-10.0

-9.5

-9.0

-8.5

-8.0

ln k

1/RT

Equation y = a + b*x

Weight No Weighting

Residual Sum of Squares

0.07163

Pearson's r -0.99357Adj. R-Square 0.98291

Value Standard Error

FIntercept 35.0666 2.96021Slope -113257.56936 7451.09017

B

S15

Figure S10. Thermal labilization of isonicotinamide (isn) from complex 1. (A) 1H NMR behavior of complex 1 in solution (kinetics curve is shown in Figure S11). (B) 1H NMR of commercially “free” isonicotinamide (non-coordinated to Ru). Conditions: 50% Phosphate buffer (pH 7.4, 20mM) + 50% D2O, T = 298 K. Reference TMSPd-4, (δ = 0 ppm).

“Free”isn

(A)

(B)

isncoordinatedtocomplex1

S16

Figure S11. Time evolution of the isn labilization based on the 1H NMR spectra of complex 1 in solution (Figure S10A). Table S6. Activation Parameters for labilization of isonicotinamide from trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) (complex 1) in phosphate buffer (pH 7.4 mM) at 298 K.

Activation parameters Ea (kcal/mol) 27.06 ± 1.8 ΔH‡ (kcal/mol) 26.46 ± 1.8 ΔS‡ (cal/mol K) 9.13 ± 0.95 ΔG‡ (kcal/mol) 23.74 ± 1.52

curve 1 - isn coordinated to complex 1 curve 2 - "free" isn (non-coordinated to complex 1) Exponential Fit of Curve 1 Exponential Fit of Curve 2

0 15000 30000 45000 60000 75000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

151015.03.3 −−×±= sk

Rel

ativ

e A

mou

nt

time (s)

isn coordinatedto complex 1

"free" isn151015.03.3 −−×±= sk

S17

Figure S12. Time evolution of the 15N NMR spectra of complex 1 in solution (pH 7.4, T = 25ºC).

Each spectrum was recorded in intervals of 30 min. Conditions: Ccomplex 1 = 30 mM, solution of 50%

phosphate buffer (pH 7.4, 80 mM) + 50% D2O, T = 25ºC. Reference: 15NH4Cl (δ = –354 ppm).

Complex1δ~192.8ppm

trans-[Ru(NH3)4(OH)(NO)]2+δ~−40.3ppm

Species“A”δ~−229ppm

S18

Figure S13. Selected 15NMR spectra from Figure S12: (A) Spectrum #1; (B) Spectrum #6; (C) Spectrum #10; (D) Spectrum #15; (E) Spectrum #20; (F) Spectrum #32. Discusssions about this result is given in the next topic.

(A)

(B)

(D)

(E)

(C) (F)

Complex1 trans-[Ru(NH3)4(OH)(NO)]2+

Complex1

Complex1

trans-[Ru(NH3)4(OH)(NO)]2+Complex1

trans-[Ru(NH3)4(OH)(NO)]2+

trans-[Ru(NH3)4(OH)(NO)]2+

trans-[Ru(NH3)4(OH)(NO)]2+Complex1

Species“A”

Species“A”

Species“A”

S19

3.1Discussionaboutthedecompositionofcomplex1atpH7.4The results above and the discussions in the main text of the manuscript are summarized in

Scheme 1, and show that 1 has a significant stability at pH 7.4, slowly decomposing with a k ~ 3.1 × 10−5 s−1 for the isn labilization (Figs. S10 and S11), yielding the hydroxo nitrosyl complex trans-[Ru(NH3)4(OH)(NO)]2+ with a chemical shift of δ ~ –40 ppm (Figs. S12 and S13) in the 15N NMR spctrum.

Scheme 1. Thermal decomposition of complex 1 in aqueous buffer solutions (pH 7.4)

After formation of the hydroxo nitrosyl complex, another signal was observed in the 15N NMR spectrum at δ ~ –229 ppm (pH 7.4), labeled as species “A” (Figs. S12 and S13). Further studies are needed to settle the identity and the mechanism of formation of species “A”, but the 15N chemical shift of this species is close1 to that reported for the ammonium imidodisulfonate2 ((NH4

+)2NH(SO3)22-), at δ = –227.3 ppm (at pH 8.3)1. This compound could be a byproduct formed

in a secondary reaction between the products trans-[Ru(NH3)4(OH)(15NO)]2+ and SO32−.

S20

4.Stabilityofcomplex1inaqueousacidicsolutions

Figure S14. FT-IR of (a) complex 1 (abbreviated as RuNOSO3isn) in aqueous solution, (b) complex 1 in 1.0 M trifluoroacetic acid (HTFA) and (c) trans-[Ru(NH3)4(isn)(NO)](BF4)3 (abbreviated as RuNOisn) in 1.0 M HTFA. The NO peak at ~1930 cm-1 (ν(NO)), appears when 1 is dissolved in the acidic solution.

Figure S15. 1H NMR of complexes (A) 1 and (B) 2 in a 1.0 M DTFA (deuterated trifluoroacetic acid, in D2O; reference TMSPd-4, δ = 0 ppm). In (A) is also indicated the chemical shift (δ) of the complex 1 at neutral pH (in red ------), for comparisons. The peaks indicated at δ ~ 8.87 and 8.13 ppm are assigned to the isn ligand coordinated trans to the N(O)SO3 ligand in complex 1. These peaks are shifted to δ ~ 8.72 and 8.22 ppm when complex 1 is converted to complex 2 at acidic conditions (where the isn ligand is trans to the nitrosyl ligand, Ru–NO). This result is in agreement with the FT-IR spectra above.

(A) (B)

2040 2010 1980 1950 1920 1890 18600.000

0.001

0.002

0.003

0.004

0.005

0.006

νν (NO)

a

b

cRuNOisn + 1M HTFA

RuNOSO3isn + H2O

RuNOSO3isn + 1M HTFA

Abs

orba

nce

Wavenumber (cm-1)

νν (NO)

8.87 8.13

S21

5.Reactionofhydroxideions(OH−)withthecomplexes1and2.

Figure S16. 15N NMR spectra of the products formed after the reaction of OH− with the 15N isotope labeled complexes (A) trans-[Ru(NH3)4(isn)15NO]3+ (15N-labeled complex 2) and (B) trans-[Ru(NH3)4(isn)(15N(O)SO3)]+ (15N-labeled complex 1). Reference: a capillary containing 15NH4Cl (δ15

N = -354 ppm).

15N-labeledComplex2

15N-labeledComplex1

S22

Figure S17. Reaction between complex 2 (trans-[Ru(NH3)4(isn)(NO)]3+) and OH−: (A) Plot of absorbance at 404 nm vs. time, and (B) dependence of kobs on [OH−]. I = 1.0 M (NaCl). T = 15 ºC. n = 5 for each concentration of OH−.

0.015 0.020 0.025 0.030 0.0350.10

0.15

0.20

0.25

0.30

0.35

0.40

k obs

(s-1)

[OH-] (mol/L)

Equation y = a + b*xAdj. R-Square 0.99695

Value Standard ErrorB Intercept -0.01338 0.00708B Slope 10.5352 0.29116

trans-[Ru(NH3)4isn(NO)]3+ + OH--

T = 15 ºC

0 20 40 60 80 100 120 1400.51

0.54

0.57

0.60

0.63

Abs

orba

nce

time (s)

Experimental Fit exponential

(A)

(B)

S23

Figure S18. Reaction between complex 1 (trans-[Ru(NH3)4(isn)(N(O)SO3)]+) and OH−: (A) Plot of absorbance at 404 nm vs. time (T = 25 ºC), and dependence of kobs on [OH−] for at (B) 15 ºC and (C) 25ºC. I = 1.0 M (NaCl). n = 5 for each concentration of OH−.

0.02 0.03 0.04 0.05 0.060.05

0.10

0.15

0.20

0.25

0.30

0.35

trans-[Ru(NH3)4isn(N(O)SO3]3+ + OH--

T = 25 ºC

k obs

(s-1)

[OH-] (mol/L)

Equation y = a + b*x

Adj. R-Square 0.99473Value Standard Error

Intercept -0.03175 0.00647Slope 6.15879 0.22394

(C)

0.01 0.02 0.03 0.04 0.050.00

0.02

0.04

0.06

0.08

0.10

0.12

trans-[Ru(NH3)4isn(N(O)SO3]3+ + OH--

T = 15 ºC

k obs

(s-1)

[OH-] (mol/L)

Equation y = a + b*x

Pearson's r 0.99825Adj. R-Square 0.99533

Value Standard Error

--Intercept -0.00395 0.00209Slope 2.14839 0.07357

(B)

0 20 40 60 80 100 120 1400.5

0.6

0.7

0.8

0.9

1.0

Abs

orba

nce

time (s)

Experimental fit exponential

(A)

S24

Table S7. Rate constants (k) for the reaction of OH– with 1 and with 2.

a This work; b values calculated using the Keq, according to the procedure described on ref. 3. Keq value was obtained from the ref. 4: Keq = 2.5 x 108 M−2; c values calculated using the reduction potential of NO+/NO, according to the procedure described on ref. 3.

5.1Discussionaboutthemechanismforthereactionof1withOH–.The reaction of OH− with complex 2 or with 1 yields the respective nitro complex

trans-[Ru(NH3)4(isn)(NO2)]+ (Figure S16). The reaction of Ru(II) nitrosyl complexes with OH− was previously described for a series of nitrosyl complexes of the type trans-[Ru(NH3)4(L)(NO)]3+,3 in which the proposed mechanism is an ion pair formation between the nitrosyl ligand and the OH− ion, followed by addition of OH− to the [M–NO]n moieties, yielding [M–NO2H]n-1, and by an additional attack by a second OH− to give the nitro complex [M–NO2]n-2.3 The mechanism for the reaction of OH− with 1 is discussed below.

The complete reaction profile for complex 1 was studied by DFT calculations, to better understand the elementary steps comprising the nucleophilic addition. The initial attack of OH− to 1 leads to the formation of the trans-[Ru(NH3)4(isn)(N(O)(OH)SO3)] reaction intermediate; this associative step follows a low energy route, through transition state 1 (TS1), with no activation barrier (Figure S19). The geometries were optimized for the reaction intermediate and TS1, showing significant changes in the relevant distances upon OH– addition to the nitrogen of the N(O)SO3 moiety. In particular the Ru–N(1) (i.e. Ru–N(O)SO3) bond length increases from 1.914 to 2.148 Å with an evident trans-effect on the Ru–N(6) (isn) bond length that decreases from 2.209 to 2.098 Å (Table S8), similarly the N(1)–S(1) bond length decreases from 1.923 to 1.897 Å (Table S8).

The first reaction step is followed by an intramolecular rearrangement consisting in the proton transfer from the hydroxyl to the SO3 moiety with breaking of the N–S bond, to give the corresponding nitro complex trans-[Ru(NH3)4(isn)(NO2)]+ and bisulfite (Figure S19). This second reaction step is characterized by a very small activation barrier of 22 kJ/mol. The geometry optimized for the resulting nitro complex is in line with literature5 data for analogous {RuXnNO2}+ octahedral complexes (X = azotate ligand).

Complex k (M−1 s−1)

T = 15ºC T = 25ºC

trans-[Ru(NH3)4(isn)(N(O)SO3)]+ (complex 1) 2.15 ± 0.07 a 6.16 ± 0.22 a

trans-[Ru(NH3)4(isn)(NO)]3+ (complex 2) 10.53 ± 0.3 a 57.6b / 46.9c

S25

Figure S19. Proposed reaction mechanism and correspondingfree-energy profile for the reaction of 1 and OH–.

Table S8. Selected bond lengths calculated for 1, TS1, intermediate 1, TS2 and trans-[Ru(NH3)4(isn)(NO2)]+.

Distance (Å)

Bond Complex 1 TS1 Intermediate 1 TS2 trans-[Ru(NH3)4(isn)(NO2)]+

Ru–N(1) (NOSO3) 1.914 2.085 2.148 2.070 1.992 N(1)–S(1) 1.923 1.900 1.897 2.393 ― Ru–N(2, 3,4, 5)a 2.157–2.167 2.154–2.176 2.159–2.177 2.163–2.168 2.163 Ru–N(6) (isn)b 2.209 2.114 2.098 2.119 2.150 N(1)–O(1) 1.225 1.256 1.294 1.241 1.262 N(1)–O(OH) ― 1.800 1.576 1.491 1.262

a Range for the four Ru–NH3 bonds; b isn = N atom of the isonicotinamide ligand

S26

6.pKaoftheN(O)SO3ligandcoordinateto1.

A

B

Figure S20. (A) Titration of complex 1 and (B) the determination of the pKa by first and second derivative of the tritation curve.

0.00.20.40.60.81.01.2

Titration Curve

0.00.10.20.30.40.5A

bsor

banc

eFi

rst

Der

ivat

ive

3.0 3.6 4.2 4.8 5.4 6.0 6.6 7.2 7.8

-0.3

0.0

0.3

Sec

ond

Der

ivat

ive

pH

pKa = 5.03

pKa = 5.03

200 250 300 350 400 450 500 550 6000.0

0.5

1.0

1.5

2.0

2.5 pH 7.9 pH 3.0

Abs

orba

nce

Wavelength (nm)

Titration of complex 1

S27

A

Figure S21. Determination of the pKa of the N(O)SO3 ligand in complex 1 by the graphic resolution of the equation: pH = pKa + log (A – AM)/(AI – A) (where A = AI + AM), AM = absorbance of the molecular species, and AI = absorbance of the ionized species.

7.Photochemistryofcomplex17.1.Time-courseUv-visfortheirradiationof1

Figure S22. Electronic spectra recorded during the irradiation (λirrad = 355 nm) of 1. Each spectrum was recorded at intervals of 30 s. Conditions: Ccomplex 1 = 1.4 × 10−4 M, phosphate buffer pH 7.4 (20 mM), T = 25ºC.

250 300 350 400 450 500 550 600 650 7000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Abs

orba

nce

Wavelength (nm)

Irradiation Period initial 30s 60s 90s 120s 150s 180s 210s 240s 270 s

Irradiation of Complex 1 with 355 nm light

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.03.03.54.04.55.05.56.06.57.07.5

pKa = 5.12pH

log [(A-Am)/(Ai-A)]

R2 = 0.9963

S28

7.2.Reactionofsulfiteradicals(SO3●–)withoxymyoglobinandcarboxy-PTIO

Two widely used methodologies for nitric oxide (NO) detection6 are i) oxymyoglobin

(oxyMb), using Uv-vis spectroscopy, and ii) carboxy-PTIO (2-(4-Carboxyphenyl)-4,4,5,5-

tetramethylimidazoline-1-oxyl-3-oxide potassium salt) or PTIO (2-Phenyl-4,4,5,5-

tetramethylimidazoline-1-oxyl 3-oxide), using EPR spectroscopy:

i) Reaction of oxyMb with NO yields metmyoglobin (metMb):

oxyMB + NO → metMb + NO3−

ii) the reaction of PTIO (or carboxy-PTIO) with NO yield PTI (or caboxy-PTI):

Unfortunately, these two methodologies failed for detection of NO produced in the case of

irradiation of complex 1, since we realized that these procedures are not specific only for nitric

oxide, and the same spectral changes were observed when nitric oxide or sulfite radicals (SO3●–)

reacted with oxyMB and carboxy-PTO. In the Figures S23 and S24 are shown the reaction of SO3●–

with oxyMb and carboxy-PTIO, respectively. The results observed in these figures are the same as

those observed when NO reacts with oxyMb6b, c or, carboxy-PTIO or PTIO 6a, 7.

Figure S23. UV-vis spectral changes during irradiation of a solution containing oxymyoglobin (oxyMb) and sodium sulfite (Na2SO3). (a) oxyMb + Na2SO3 before irradiation (blue line), and (b) formation of metmyoglobin (red line) due to formation of SO3

●– during irradiation of Na2SO3. Conditions: oxyMb (~5.0 µM) + Na2SO3 (2.0 × 10−4 M) in phosphate buffer (pH 7.4, 20 mM); T = 2 ºC, each spectrum was recorded after irradiation intervals of 2 min.

S29

Figure S24. EPR spectra for the irradiation of solutions containing carboxy-PTIO and (a) phosphate buffer pH 7.4, (b) complex 2 (abbreviated as RuNOisn), which is a well-described NO donor triggered by irradiation, (c) sodium sulfite (Na2SO3), and (d) complex 1 (trans-[Ru(NH3)4(isn)(N(O)SO3)]+). Solutions (b), (c) and (d) are also in phosphate buffer pH 7.4.

We overcame difficulties about distinghishing the production of NO during irradiation

of 1 using the enzyme catalase (CatIII) for NO detection8. This method enabled us to

distinguish among the release of NO or SO3●–. Catalase contains a heme group with a Fe(III)

center, which reacts8 with NO with a kf = 3.0 × 107 M−1s−1, forming two characteristic bands

in the Uv-vis spectra:

CatIII + NO (NO)CatIII

3435 3450 3465 3480 3495 3510 3525

(d)

(c)

(b)

H (Gauss)

C-PTIO + complex 1irrad. 2 min

carboxy PTIO + Na2SO3

irrad. 6min

carboxy PTIO + RuNOisn(a NO donor)irrad. 15 min

carboxy-PTIO + phosphate bufferirrad. 20 min(a)

S30

7.3.DFTresultsonirradiationofcomplex1.

Figure S25. Comparison of X-ray structure, ground state (GS) structure and 7th singlet electronic excited state (S7) structure for complex 1. 7.4.Time-course1HNMRfortheinsituirradiationof1

Figure S26. 1H NMR spectra recorded at different intervals during the in situ irradiation of trans-[Ru(NH3)4(isn)(N(O)SO3)]+. The first five spectra were recorded at intervals of 1 min, and the next ones, after intervals of 10 min. Conditions: (CRu = 20 mM) in 50% phosphate buffer pH 7.4 (50 mM) + 50% D2O, T = 25ºC. Reference TMSPd-4 (δ = 0 ppm).

photolabilizedisn

isncoordinatedtocomplex1

S31

Figure S27. Time course of the 1H NMR spectra recorded shown in Figure S26 at different intervals during the in situ irradiation (410 nm) of 1.

Same results as those shown in Figure S26 for the in situ irradiation (λirrad = 410 nm) of 1,

were obtained for ex situ photolysis of 1 with λirrad = 355 nm.

7.5.DissociationofN(O)SO3−

Figure S28. Normal mode corresponding to the imaginary frequency in the N(O)SO3

− homolysis pathway (Transition State). The arrows indicate the displacement vectors. Oxygen atoms are depicted as red, nitrogen as blue, and sulfur as yellow.

0 2000 4000 6000 8000 10000 12000 14000 16000

0.0

0.2

0.4

0.6

0.8

1.0

Curve B - free isn

Exponential Fit of curve A Exponential Fit of curve B

Rel

ativ

e In

tens

ity

time (s)

Model Exponential

Equationy = y0 + A*exp(R0*x)

Reduced Chi-Sqr

6.51856E-5

Adj. R-Square 0.99308Value Standard Error

I y0 0.27488 0.15258I A 0.69993 0.15102I R0 -4.55056E-5 1.23685E-5

Model Exponential

Equationy = y0 + A*exp(R0*x)

Reduced Chi-Sqr

6.51856E-5

Adj. R-Square 0.99308Value Standard Error

J y0 0.72512 0.15258J A -0.69993 0.15102J R0 -4.55056E-5 1.23685E-5

Curve Aisn coordinated to 1

S32

Table S9. Calculated absorption properties of N(O)SO3– in water solution.

Tr.[a] Energy, eV (nm) f[b] Composition EDDM[c]

1 1.40 (885) 0.000 HOMO→LUMO (100%)

2 3.22 (385) 0.0009 H–1→LUMO (100%)

3 4.30 (288) 0.0012 H–2→LUMO (100%)

4 4.50 (276) 0.0096 H–3→LUMO (94%)

HOMO→L+1 (6%)

5 5.31 (234) 0.0011 H–4→LUMO (100%)

6 5.31 (234) 0.0025 H–5→LUMO (96%)

HOMO→L+1 (4%)

7 5.64 (220) 0.1899 HOMO→L+3 (77%)

HOMO→L+2 (16%) H–5→LUMO (3%) H–3→LUMO (3%)

8 6.09 (204) 0.0001 H–1→L+1 (96%)

H–2→L+1 (4%)

[a] Tr. indicates transition number as obtained in the TD-DFT calculation output. [b] f = oscillator strength. [c] Electron-Density Difference Map (black indicates a decrease in electron density, white indicates an increase; isovalue = 0.001).

S33

Figure. S29 (A) Geometry optimized structure of S1 state of N(O)SO3

–, showing the dissociative nature of the S–N bond (2.20 Å).

7.6.X-raystructureofcomplex2

Figure S30. (A) ORTEP representation of complex 2, H omitted for clarity.

S34

Table S10. Complete crystallographic data and structure refinement of complex 2.

Empirical formula C6 H18 B3 F12 N7 O2 Ru

Formula weight 581.77

Temperature 293(2) K

Wavelength 0.71073 Å

Crystal system Orthorhombic

Space group P n m a

Unit cell dimensions a = 24.6469(14) Å α= 90°.

b = 8.6875(5) Å β= 90°.

c = 9.7514(5) Å γ = 90°.

Volume 2088.0(2) Å3

Z 4

Density (calculated) 1.851 Mg/m3

Absorption coefficient 0.874 mm-1

F(000) 1144

Crystal size 0.11 x 0.03 x 0.02 mm3

Theta range for data collection 2.664 to 34.533°.

Index ranges -37<=h<=37, -13<=k<=12, -14<=l<=15

Reflections collected 19332

Independent reflections 4454 [R(int) = 0.0429]

Completeness to theta = 25.242° 99.9 %

Absorption correction Semi-empirical from equivalents

Max. and min. transmission 1.00000 and 0.99119

Refinement method Full-matrix least-squares on F2

Data / restraints / parameters 4454 / 0 / 166

Goodness-of-fit on F2 1.049

Final R indices [I>2sigma(I)] R1 = 0.0416, wR2 = 0.0983

R indices (all data) R1 = 0.0656, wR2 = 0.1085

Extinction coefficient n/a

Largest diff. peak and hole 2.190 and -1.140 e.Å-3

S35

Table S11. Complex 2: Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (Å2x 103)

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

________________________________________________________________________________

x y z U(eq)

________________________________________________________________________________

Ru 1597(1) 7500 -121(1) 22(1)

O(1) 2007(1) 7500 -2874(3) 61(1)

O(2) 807(1) 7500 6796(3) 50(1)

N(1) 1868(1) 7500 -1781(3) 33(1)

N(2) 1025(1) 9166(2) -692(2) 30(1)

N(4) 2144(1) 5823(2) 616(2) 31(1)

N(6) 1238(1) 7500 1830(3) 24(1)

N(7) -22(1) 7500 5860(4) 61(1)

C(1) 1113(1) 6177(3) 2468(2) 33(1)

C(2) 877(1) 6142(3) 3745(3) 39(1)

C(3) 750(1) 7500 4387(3) 30(1)

C(6) 508(2) 7500 5804(3) 37(1)

F(11) 1219(1) 2500 3186(4) 75(1)

F(12) 2012(1) 1210(2) 3263(3) 71(1)

F(13) 1737(2) 2500 5057(3) 103(2)

B(1) 1731(2) 2500 3651(5) 41(1)

F(21) 3149(1) 6193(2) 3009(2) 62(1)

F(22) 2973(2) 7500 4928(2) 59(1)

F(23) 2376(1) 7500 3177(3) 67(1)

B(2) 2912(2) 7500 3528(5) 38(1)

F(31) 809(1) 2500 -332(4) 67(1)

F(32) 269(1) 1203(2) 1128(2) 52(1)

F(33) -87(1) 2500 -646(3) 62(1)

B(3) 314(2) 2500 313(4) 34(1)

________________________________________________________________________________

S36

Table S13. Complex 2: Bond lengths [Å] and angles [°].

Ru-N(1) 1.750(3)

Ru-N(2)#1 2.0964(19)

Ru-N(2) 2.0964(19)

Ru-N(6) 2.099(3)

Ru-N(4) 2.1097(19)

Ru-N(4)#1 2.1097(19)

O(1)-N(1) 1.119(4)

O(2)-C(6) 1.216(4)

N(2)-H(2A) 0.8900

N(2)-H(2B) 0.8901

N(2)-H(2C) 0.8900

N(4)-H(4A) 0.8900

N(4)-H(4B) 0.8900

N(4)-H(4C) 0.8901

N(6)-C(1) 1.343(3)

N(6)-C(1)#1 1.343(3)

N(7)-C(6) 1.307(5)

N(7)-H(7A) 0.8600

N(7)-H(7B) 0.8600

C(1)-C(2) 1.374(3)

C(1)-H(1) 0.9300

C(2)-C(3) 1.372(3)

C(2)-H(2) 0.9300

C(3)-C(2)#1 1.372(3)

C(3)-C(6) 1.505(5)

F(11)-B(1) 1.340(5)

F(12)-B(1) 1.370(3)

F(13)-B(1) 1.371(6)

B(1)-F(12)#2 1.370(3)

F(21)-B(2) 1.373(3)

F(22)-B(2) 1.373(5)

F(23)-B(2) 1.367(5)

B(2)-F(21)#1 1.373(3)

F(31)-B(3) 1.372(5)

F(32)-B(3) 1.383(3)

F(33)-B(3) 1.360(5)

B(3)-F(32)#2 1.383(3)

N(1)-Ru-N(2)#1 90.62(9)

S37

N(1)-Ru-N(2) 90.62(9)

N(2)#1-Ru-N(2) 87.33(11)

N(1)-Ru-N(6) 177.39(12)

N(2)#1-Ru-N(6) 87.50(8)

N(2)-Ru-N(6) 87.50(8)

N(1)-Ru-N(4) 94.12(9)

N(2)#1-Ru-N(4) 92.45(8)

N(2)-Ru-N(4) 175.27(8)

N(6)-Ru-N(4) 87.77(8)

N(1)-Ru-N(4)#1 94.12(9)

N(2)#1-Ru-N(4)#1 175.27(8)

N(2)-Ru-N(4)#1 92.45(8)

N(6)-Ru-N(4)#1 87.77(8)

N(4)-Ru-N(4)#1 87.37(11)

O(1)-N(1)-Ru 175.4(3)

Ru-N(2)-H(2A) 109.5

Ru-N(2)-H(2B) 109.5

H(2A)-N(2)-H(2B) 109.5

Ru-N(2)-H(2C) 109.5

H(2A)-N(2)-H(2C) 109.5

H(2B)-N(2)-H(2C) 109.5

Ru-N(4)-H(4A) 109.5

Ru-N(4)-H(4B) 109.5

H(4A)-N(4)-H(4B) 109.5

Ru-N(4)-H(4C) 109.5

H(4A)-N(4)-H(4C) 109.5

H(4B)-N(4)-H(4C) 109.5

C(1)-N(6)-C(1)#1 117.8(3)

C(1)-N(6)-Ru 121.10(14)

C(1)#1-N(6)-Ru 121.10(14)

C(6)-N(7)-H(7A) 120.0

C(6)-N(7)-H(7B) 120.0

H(7A)-N(7)-H(7B) 120.0

N(6)-C(1)-C(2) 122.3(2)

N(6)-C(1)-H(1) 118.8

C(2)-C(1)-H(1) 118.8

C(3)-C(2)-C(1) 119.4(2)

C(3)-C(2)-H(2) 120.3

C(1)-C(2)-H(2) 120.3

C(2)-C(3)-C(2)#1 118.6(3)

S38

C(2)-C(3)-C(6) 120.64(15)

C(2)#1-C(3)-C(6) 120.64(15)

O(2)-C(6)-N(7) 124.9(3)

O(2)-C(6)-C(3) 119.2(3)

N(7)-C(6)-C(3) 115.8(3)

F(11)-B(1)-F(12) 112.4(3)

F(11)-B(1)-F(12)#2 112.5(3)

F(12)-B(1)-F(12)#2 109.8(4)

F(11)-B(1)-F(13) 110.4(5)

F(12)-B(1)-F(13) 105.7(3)

F(12)#2-B(1)-F(13) 105.7(3)

F(23)-B(2)-F(21) 108.5(2)

F(23)-B(2)-F(21)#1 108.5(2)

F(21)-B(2)-F(21)#1 111.6(4)

F(23)-B(2)-F(22) 110.8(4)

F(21)-B(2)-F(22) 108.7(2)

F(21)#1-B(2)-F(22) 108.7(2)

F(33)-B(3)-F(31) 109.2(4)

F(33)-B(3)-F(32)#2 109.7(2)

F(31)-B(3)-F(32)#2 109.6(2)

F(33)-B(3)-F(32) 109.7(2)

F(31)-B(3)-F(32) 109.6(2)

F(32)#2-B(3)-F(32) 109.1(3)

_____________________________________________________________

Symmetry transformations used to generate equivalent atoms:

#1 x,-y+3/2,z #2 x,-y+1/2,z

8.References

1(a) G. J. Martin, M. L. Martin and J.-P. Gouesnard, NMR Basic Principles and Progress, Vol. 18, Springer-Verlag, Berlin, Heidelberg, New York, 1981; (b) M. Witanowski and L. Stefaniak, Annual Reports on NMR Spectroscopy Academic Press, New York, 1986.

2 W. Spillane, Chem. Rev., 2014, 114, 2507-2586.

3 F. Roncaroli, M. E. Ruggiero, D. W. Franco, G. L. Estiu and J. A. Olabe, Inorg. Chem., 2002, 41, 5760-5769.

4 M. G. Gomes, C. U. Davanzo, S. C. Silva, L. G. F. Lopes, P. S. Santos and D. W. Franco, J. Chem. Soc., Dalton Trans, 1998, 601-607.

S39

5(a) N. Chanda, S. M. Mobin, V. G. Puranik, A. Datta, M. Niemeyer and G. K. Lahiri, Inorg. Chem., 2004, 43, 1056-1064; (b) N. Chanda, D. Paul, S. Kar, S. M. Mobin, A. Datta, V. G. Puranik, K. K. Rao and G. K. Lahiri, Inorg. Chem., 2005, 44, 3499-3511; (c) P. De, T. K. Mondal, S. M. Mobin, B. Sarkar and G. K. Lahiri, Inorg. Chim. Acta., 2010, Volume 363, 2945–2954; (d) P. De, B. Sarkar, S. Maji, A. K. Das, E. Bulak, S. M. Mobin, W. Kaim and G. K. Lahiri, Eur. J. Inorg. Chem., 2009, 2009, 2702-2710; (e) K. Hansongnern, U. Saeteaw, J. Cheng, F.-L. Liao and T.-H. Lu, Acta Crystallographica Section C, 2001, 57, 895-896; (f) K. Karidi, A. Garoufis, N. Hadjiliadis, M. Lutz, A. L. Spek and J. Reedijk, Inorg. Chem., 2006, 45, 10282-10292; (g) S. Sarkar, B. Sarkar, N. Chanda, S. Kar, S. M. Mobin, J. Fiedler, W. Kaim and G. K. Lahiri, Inorg. Chem., 2005, 44, 6092-6099.

6(a) A. C. Roveda Jr., T. B. R. Papa, E. E. Castellano and D. W. Franco, Inorg. Chim. Acta., 2014, 409 part A, 147-155; (b) A. C. Merkle, A. B. McQuarters and N. Lehnert, Dalton Trans., 2012, 41, 8047-8059; (c) A. C. Roveda Jr., H. D. Aguiar, K. M. Miranda, C. C. Tadini and D. W. Franco, J. Mater. Chem. B, 2014, 2, 7232-7242.

7 T. Akaike, M. Yoshida, Y. Miyamoto, K. Sato, M. Kohno, K. Sasamoto, K. Miyazaki, S. Ueda and H. Maeda, Biochemistry, 1993, 32, 827-832.

8 M. Hoshino, K. Ozawa, H. Seki and P. C. Ford, J. Am. Chem. Soc., 1993, 115, 9568-9575.