S1

Electronic Supplementary Information

Photoinduced hydrogen evolution with new tetradentate

cobalt(II) complexes based on the TPMA ligand.

Mirco Natali,*a Elena Badetti,b Elisa Deponti,a Marta Gamberoni,a Francesca A. Scaramuzzo,b

Andrea Sartorel,b Cristiano Zonta *b

a. Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Ferrara, via Fossato

di Mortara 17-19, and Centro Interuniversitario per la Conversione Chimica dell'Energia Solare,

sezione di Ferrara, via L. Borsari 46, 44121 Ferrara, Italy.

E-mail: mirco.natali@unife.it

b. Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131

Padova, Italy.

E-mail: cristiano.zonta@unipd.it

Electronic Supplementary Material (ESI) for Dalton Transactions.This journal is © The Royal Society of Chemistry 2016

S2

Characterization of the ligands

L0: (6-phenyl-2-pyridylmethyl)bis(2-pyridylmethyl)-amine

The final yield was 97%. 1H-NMR, 13C-NMR and ESI-MS are according to data reported in the literature

(see C. L. Chuang, K. Lim, J. W. Canary, Supramol. Chem. 1995, 5, 39-43).

1H-NMR (300 MHz, CD3Cl,)

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.5f1 (ppm)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

FS 225_1 legante monofenile, bianco CD, prodotto finale, CDCl3

6.00

2.02

4.49

6.47

2.30

2.10

3.96

3.97

7.13

7.14

7.16

7.26

7.39

7.41

7.43

7.46

7.49

7.51

7.57

7.59

7.65

7.66

7.69

7.72

7.74

7.99

8.01

8.53

8.54

IR (KBr, cm-1)

S3

L1: [6-(3-formylphenyl)-2-pyridylmethyl]bis(2-pyridylmethyl)-amine

The compound was obtained as a brownish oil (97% yield). 1H-NMR, 13C-NMR and ESI-MS are according

to data reported in the literature (see F. A. Scaramuzzo, G. Licini, C. Zonta, Chem. Eur. J. 2013, 19, 16809-

16813).1H-NMR (300 MHz, CDCl3) (ppm): 10.03 (s, 1H, CHO), 8.47 (m, 3H, PyrH + ArH), 8.23 (d, 1H, J = 9.0

Hz, Ar H), 7.83 (d, 1H, J = 9.0 Hz, Ar H), 7.61 (m, 8H, Pyr H + Ar H), 7.08 (dd, 2H, J = 6.0 Hz Pyr H),

3.93 (s, 2H, CH2), 3.90 (s, 4H, CH2). 13C-NMR (62 MHz, CDCl3) (ppm): 191.96, 159.11, 159.04, 154.58, 148.71, 139.95, 137.05, 136.44,

136.18, 132.39, 129.39, 129.07, 127.95, 122.60, 121.73, 121.65, 118.37, 59.88, 59.73.

IR (KBr, cm-1): 3384, 2824, 1698, 1580, 1570, 1474, 1434, 1184.

ESI + MS (m/z) Calc. C25H22N4O 394.2, Found 395.4 (M+H+).

1H-NMR (300 MHz, CD3Cl,)

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.5f1 (ppm)

0

50

100

150

200

250

300

350

400

None

6.00

2.12

7.29

1.25

1.08

1.03

2.97

0.96

2.08

3.90

3.93

5.21

7.05

7.07

7.08

7.10

7.26

7.50

7.51

7.53

7.54

7.57

7.60

7.61

7.62

7.67

7.70

7.73

7.82

7.85

8.22

8.25

8.47

8.48

10.0

3

13C-NMR (62 MHz, CDCl3)

0102030405060708090100110120130140150160170180190200210220f1 (ppm)

0

50000

1E+05

2E+05

2E+05

2E+05

3E+05

4E+05

4E+05

4E+05

None

59.7

359

.88

76.4

877

.00

77.5

1

118.

3612

1.65

121.

7312

2.60

127.

9412

9.06

129.

3813

2.39

136.

1813

6.44

137.

0713

9.95

148.

71

154.

5815

9.04

159.

11

191.

95

0102030405060708090100110120130140150160170180190200210220f1 (ppm)

0

50000

1E+05

2E+05

2E+05

2E+05

3E+05

4E+05

4E+05

4E+05

None

59.73

59.88

76.48

77.00

77.51

118.36

121.65

121.73

122.60

127.94

129.06

129.38

132.39

136.18

136.44

137.07

139.95

148.71

154.58

159.04

159.11

191.95

IR (KBr, cm-1)

S4

L2:[6-(3-carboxyaminophenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine

The final product is a yellow solid and the yield was 87%.1H-NMR (300 MHz, CDCl3) (ppm): 8.71 (s, 1H, ArH), 8.53 (d, 2H, PyrH, J = 2.5Hz), 8.08 (d, 1H, ArH),

7.96 (d, 1H, ArH), 7.66 (m, 7H), 7.39 (d, 1H),7.15 (dd, 2H, PyrH),3.98 (s, 6H, CH2).13C-NMR (62 MHz, CDCl3) (ppm): 169.30, 159.67, 158.74, 155.70, 149.18, 139.62, 137.47, 136.65,

133.94, 129.97, 129.14, 128.54, 126.39, 123.25, 122.39, 122.24, 118.79, 60.27, 59.48.

IR (KBr, cm-1): 3359, 2821, 1667, 1591, 1570, 1433, 1381, 1121.

ESI+ MS (m/z) Calc. C25H23N5O 409.2, Found 410.1 (M+H+).

Anal. Calcd. (C25H23N5O + H2O): C, 70.24; H, 5.89; N, 16.38. Found: C, 70.92; H, 6.02; N, 16.54.

1H-NMR (300 MHz, CDCl3)

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.5f1 (ppm)

FS363

2.65

6.00

2.23

1.10

7.32

1.11

1.18

1.85

0.97

1.26

1.66

3.97

4.00

7.12

7.13

7.15

7.16

7.17

7.26

7.38

7.40

7.52

7.55

7.58

7.61

7.64

7.66

7.71

7.73

7.97

8.07

8.10

8.52

8.53

8.71

13C-NMR (62 MHz, CDCl3)

102030405060708090100110120130140150160170180190200210f1 (ppm)

FS363

59.4

860

.27

76.7

477

.16

77.5

8

118.

7912

2.24

122.

3912

3.25

126.

3912

8.54

129.

1412

9.97

133.

9413

6.65

137.

4713

9.62

149.

18

155.

7015

8.74

159.

67

169.

30

IR (KBr, cm-1)

S5

L3:[6-(3-hydroxyphenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine

The product is a brownish solid and the final yield was 80%. 1H-NMR (300 MHz, CD3CN) δ (ppm): 8.58 (d, 2H, J = 4.24 Hz, PyrH), 7.75-7.43 (m, 9H, PyrH + ArH),

7.12-7.40 (m, 3H, PyrH + ArH), 6.94(d, 1H, J = 7.1 Hz), 3.82 (s, 2H, CH2), 3.84 (s, 4H, CH2).13C-NMR (62 MHz, CD3CN) δ (ppm): 159.76, 159.33, 157.82, 156.03, 148.98, 141.02, 137.48, 136.72,

129.98, 123.17, 122.72, 122.30, 121.76, 117.52, 116.16, 113.84, 60.18.

IR (KBr, cm-1): 3393, 3055, 2918, 1569, 1449, 1436, 1308, 1245, 1151, 1121, 1083, 1048.

ESI+ MS (m/z) Calc. C24H22N4O 382.4, Found 383.5 (M+H+).

Anal. Calcd. (C24H22N4O): C, 75.70; H, 5.80; N, 14.65. Found: C, 75.32; H, 5.65; N, 14.33.

1H-NMR (300 MHz, CD3CN)

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.5f1 (ppm)

acn-Fenolo NMR

6.00

0.99

3.10

8.71

1.57

13C-NMR (62 MHz, CD3CN)

2030405060708090100110120130140150160170180f1 (ppm)

IR (KBr, cm-1)

S6

L4:[6-(3-hydroxymethylphenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine

The product is a brownish solid and the final yield was 90%. 1H-NMR (300 MHz, CDCl3) (ppm): 8.54 (d, 2H, PyrH), 8.06 (s, 1H, ArH), 7.90 (d, 1H, ArH), 7.62 (m,

6H), 7.45 (m, 3H),7.15 (dd, 2H, PyrH), 4.78 (s, 2H, CH2OH), 3.96 (s, 6H, CH2).13C-NMR (62 MHz, CDCl3) (ppm): 159.77, 159.27, 156.59, 149.22, 141.70, 137.25, 136.57, 129.02,

127.52, 126.23, 125.77, 123.06, 122.11, 121.50, 118.85, 65.46, 60.36, 60.20.

IR (KBr, cm-1): 3411, 2921, 2850, 1592, 1570, 1449, 1434, 1123, 1048.

ESI+ MS (m/z) Calc. C25H24N4O 396.2, Found 397.2 (M+H+).

Anal. Calcd. (C25H24N4O + H2O): C, 72.44; H, 6.32; N, 13.52. Found: C, 72.57; H, 6.41; N, 13.58.

1H-NMR (300 MHz, CDCl3)

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.5f1 (ppm)

FS343FS343 Legante con 3-idrossimetil in meta dopo work up

5.93

2.60

2.00

3.31

6.44

1.24

0.96

1.68

13C-NMR (62 MHz, CDCl3)

102030405060708090100110120130140150160170180190200210f1 (ppm)

FS343

60.2

060

.36

65.4

6

118.

8512

1.50

122.

1112

3.06

125.

7712

6.23

127.

5212

9.02

136.

5713

7.25

141.

70

149.

22

156.

5915

9.27

159.

77

IR (KBr, cm-1)

S7

Characterization of the complexes

CoL0: (6-phenyl-2-pyridylmethyl)bis(2-pyridylmethyl)-amine Cobalt complex

The product is a green solid and the final yield was 84%.

IR (KBr, cm-1): 3523, 3081, 1612, 1572, 1485, 1450, 1096.

ESI+ MS(m/z): Calc. C24H22N4Co 425.11, Found 212.5 (M2+/2).

Anal. Calcd. (C24H22Cl2N4O8Co): C, 46.17; H, 3.55; N, 8.97. Found: C, 45.98; H, 3.49; N, 8.12.

IR (KBr, cm-1)

CoL1: [6-(3-formylphenyl)-2-pyridylmethyl]bis(2-pyridylmethyl)-amine Cobalt complexThe product is a red-brownish solid and the final yield was 80%.

IR (KBr, cm-1): 3447, 1697, 1610, 1571, 1441, 1092.

ESI+ MS(m/z): Calc. C25H22N4OCo 453.4, Found 226.5 (M2+/2).Anal. Calcd. (C25H22Cl2N4O9Co): C, 46.03; H, 3.40; N, 8.59. Found: C, 45.88; H, 3.21; N, 8.46.

IR (KBr, cm-1)

S8

CoL2: 6-(3-carboxyaminophenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine Cobalt complex

The product is a green solid and the final yield was 85%.

IR (KBr, cm-1): 3452, 3078, 1665, 1611, 1570, 1487, 1441, 1096.

ESI+ MS(m/z): Calc. C25H23N5OCo 468.12, Found 234.0 (M2+/2).

Anal. Calcd. (C25H23Cl2N5O9Co + H2O): C, 43.81; H, 3.68; N, 10.22. Found: C, 43.94; H, 3.71; N, 10.35.

IR (KBr, cm-1)

CoL3: [6-(3-hydroxyphenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine Cobalt complex

The product is a brown solid and the final yield was 89%.

IR (KBr, cm-1): 3403, 1610, 1573, 1495, 1438, 1094.

ESI+ MS(m/z): Calc. (C24H22N4OCo + ClO4)+ 540.06, Found 540.0 (M+).

Anal. Calcd. (C24H22Cl2N4O9Co): C, 45.02; H, 3.46; N, 8.75. Found: C, 45.33; H, 2.97; N, 8.66.

IR (KBr, cm-1)

S9

CoL4:6-(3-hydroxymethylphenyl)-2-pyridylmethyl)bis(2-pyridylmethyl)-amine Cobalt complex

The product is a red-brownish solid and the final yield was 87%.

IR (KBr, cm-1): 3407, 2922, 1609, 1570, 1483, 1438, 1144, 1189, 1091.

ESI+ MS(m/z): Calc. C25H24N4OCo 455.13, Found 227.5 (M2+/2).

Anal. Calcd. (C25H24Cl2N4O9Co): C, 45.09; H, 3.63; N, 10.95. Found: C, 44.79; H, 3.48; N, 10.84.

IR (KBr, cm-1)

S10

-0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6

0

20

40

60

80

i, A

E vs SCE, V

0 M 1.0 mM 1.5 mM 2.0 mM 2.5 mM

-0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6

0

20

40

60

80i, A

E vs SCE, V

0 M 1.0 mM 1.5 mM 2.0 mM 2.5 mM

CoL2

2

CoL3

3

CoL4

4

-0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6-10

0

10

20

30

40

50

60

i, A

E vs SCE, V

0 M 1.0 mM 1.5 mM 2.0 mM 2.5 mM

CoL1

1 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6

0

20

40

60

80

i, A

E vs SCE, V

0 M 1.0 mM 1.5 mM 2.0 mM 2.5 mM

Figure S1. Cyclic voltammetry (CV) of 1 mM CoL1 (top left panel), 1 mM CoL2 (top right panel),

1 mM CoL3 (bottom left panel), and 1 mM CoL4 (bottom left panel) in argon-purged 50/50

acetonitrile/water (0.1 M LiClO4) upon addition of 0-2.5 mM TFA. Experimental conditions: GC as

working electrode, Pt as counter electrode, SCE as reference electrode, room temperature, scan rate

v = 100 mV/s.

S11

0.5 0.0 -0.5 -1.0 -1.5

-0.001

0.000

0.001

0.002

0.003

i, A

E vs SCE, V

blank 1 mM CoL3

0 10 20 30 40 50 60

0

2

4

6

8

Char

ge, C

Time, min

blank 1 mM CoL3

0 10 20 30 40 50 60

0

10

20

30

40

n H 2,

mol

Time, min

theoretical experimental

(a)

(b)

(c)

@ −1.2 V

Figure S2. (a) Cyclic voltammetry (CV) of the blank and 1 mM CoL3 solutions (50/50

acetonitrile/water, 0.1 M LiClO4, 2.5 mM TFA) before bulk electrolysis, scan rate of v = 100 mV/s;

(b) charge build-up upon one-hour controlled potential electrolysis at −1.2 V vs. SCE; (c)

comparison of the experimental amount of hydrogen produced with the theoretical value assuming

100% Faradaic Efficiency. Experimental conditions: carbon foil (1 cm2 geometrical area, 0.5 mm

thickness) as working electrode, Pt wire as counter electrode, Ag/AgCl as reference electrode, room

temperature.

S12

0.0 0.5 1.0 1.5 2.0 2.5

0

10

20

30

40

50

60

70

80

CoL0 CoL1 CoL2 CoL3 CoL4

i C, A

[TFA], mM

Figure S3. Plot of the catalytic peak current vs. TFA concentration obtained from the

electrochemical data reported in Figure 1b (main text) and Figure S1.

S13

-0.4 -0.6 -0.8 -1.0 -1.2 -1.4

0

50

100

150

200

250

300

i, A

E vs SCE, V

0 M 0.5 mM 1.0 mM 1.5 mM 2.0 mM

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.220

30

40

50

60

70

80

90

i @ -1

.10

V,

A

[CoL0], mM

(a)

(b)

Figure S4. (a) Cyclic voltammetry (CV) of 50 mM TFA in argon-purged 50/50 acetonitrile/water

(0.1 M LiClO4) upon addition of 0-2 mM CoL0 (return scans have been omitted for clarity); (b)

plot of the catalytic current at −1.10 V vs. the CoL0 concentration. Experimental conditions: GC as

working electrode, Pt as counter electrode, SCE as reference electrode, room temperature, scan rate

v = 100 mV/s.

S14

0 60 120 180 240 300 360

05

1015202530354045

n H 2,

mol

Time, min

0 60 120 180 240 300 360

0

5

10

15

20

25

30

35

40

n H 2,

mol

Time, min

0 60 120 180 240 300 360

0

5

10

15

20

25

30

35

40

n H 2,

mol

Time, min

CoL0 CoL1

CoL2 CoL3 0 60 120 180 240 300 360

05

1015202530354045505560

n H 2,

mol

Time, min

CoL4 0 60 120 180 240 300 360

05

1015202530354045

n H 2,

mol

Time, min

Figure S5. Effect of the addition of different components after 1 h photolysis on the photocatalytic

hydrogen evolution activity by CoL0-4. Experimental conditions: 1 M acetate buffer solutions (5

mL, pH 5) containing 0.5 mM Ru(bpy)32+, 0.1 M ascorbic acid, and 75 M CoL0-4, addition of 75

M CoL0-4 (dark yellow traces), addition of 0.5 mM Ru(bpy)32+ (red traces), addition of both 75

M CoL0-4 and 0.5 mM Ru(bpy)32+ (black traces).

S15

500 550 600 650 700 750 800 850

Inte

nsity

, a.u

.

wavelength, nm

0 M 0.05 M 0.10 M 0.15 M 0.20 M 0.25 M

0.00 0.05 0.10 0.15 0.20 0.25

1.0

1.5

2.0

2.5

3.0

3.5

kSV = 8.4 M-1

kQ = 2.1 x 107 M-1s-1

I 0 / I

[ascorbic acid], M

a)

b)

Figure S6. (a) Photoluminescence spectra (excitation at 450 nm) of a 50 M Ru(bpy)32+ solution in

1 M acetate buffer (pH 5) in the presence of 0-0.25 M ascorbic acid; (b) Stern-Volmer analysis.

S16

0.0 0.1 0.2 0.3 0.4 0.5

1.00

1.02

1.04

1.06

1.08

1.10

1.12

1.14

kSV = 250 M-1

kQ = 6.3 x 108 M-1s-1

I 0 / I

[CoL0], mM0.0 0.1 0.2 0.3 0.4 0.5

1.00

1.05

1.10

1.15

1.20

kSV = 396 M-1

kQ = 9.9 x 108 M-1s-1

I 0 / I

[CoL1], mM

0.0 0.1 0.2 0.3 0.4 0.5

1.00

1.04

1.08

1.12

1.16

1.20

kSV = 428 M-1

kQ = 1.1 x 109 M-1s-1

I 0 / I

[CoL2], mM0.0 0.1 0.2 0.3 0.4 0.5

0.981.001.021.041.061.081.101.121.141.161.18

kSV = 339 M-1

kQ = 8.5 x 108 M-1s-1

I 0 / I

[CoL3], mM

0.0 0.1 0.2 0.3 0.4 0.50.98

1.00

1.02

1.04

1.06

1.08

1.10

1.12

1.14

1.16

I 0 / I

[CoL4], mM

kSV = 264 M-1

kQ = 6.6 x 108 M-1s-1

Figure S7. Stern-Volmer analyses of the quenching of the Ru(bpy)32+ emission by CoL0-4 obtained

from photoluminescence spectra of 50 M Ru(bpy)32+ solutions in 1 M acetate buffer (pH 5)

(excitation at 450 nm) at different CoL0-4 concentration.

S17

0 5 10 15 20 25 30 35 40 450.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

OD

(510

nm

)

time, s

0 M 0.1 mM 0.2 mM

0 5 10 15 20 25 30 35 40 450.00

0.01

0.02

0.03

0.04

0.05

OD

(510

nm

)

time, s

0 M 0.1 mM 0.2 mM

CoL1

0 5 10 15 20 25 30 35 40 450.00

0.01

0.02

0.03

0.04

0.05

0.06

OD

(510

nm

)

time, s

0 M 0.1 mM 0.2 mM

0.00 0.05 0.10 0.15 0.20

0

5

10

15

20

25

k ET, 1

04 s-1

[CoL2], mM

k = 1.1 x 109 M-1s-1

CoL2

CoL3

CoL4

0.00 0.05 0.10 0.15 0.20

0

10

20

30

40

50

k ET, x

104 s

-1

[CoL1], mM

k = 2.1 x 109 M-1s-1

0.00 0.05 0.10 0.15 0.20

0

5

10

15

20

k ET, x

104 s

-1

[CoL3], mM

k = 1.0 x 109 M-1s-1

0.00 0.05 0.10 0.15 0.20-5

0

5

10

15

20

25

30

35

40

k ET, 1

04 s-1

[CoL4], mM

k = 1.8 x 109 M-1s-1

0 5 10 15 20 25 30 35 40 450.00

0.01

0.02

0.03

0.04

0.05O

D (5

10 n

m)

time, s

0 M 0.1 mM 0.2 mM

Figure S8. Kinetic traces at 510 nm with related single-exponential fitting (left panels) obtained by

laser flash photolysis (excitation at 355 nm) on 0.1 mM Ru(bpy)32+ solutions in 1 M acetate buffer

(pH 5) in the presence of 0.1 M ascorbic acid and 0-0.2 mM CoL1-4 and plot of the pseudo-first

order rate vs. the CoL1-4 catalyst concentration (right panels) for the estimation of the bimolecular

rate constant.

S18

450 500 550 600 650 700 750

0.00

0.01

0.02

0.03

0.04

0.05

1 s 5 s 40 s

OD

wavelength, nm

Figure S9. Transient absorption spectra obtained by laser flash photolysis (excitation at 355 nm) of

a 1 M acetate buffer (pH 5) solution containing 100 M Ru(bpy)32+, 0.1 M ascorbic acid and 0.1

mM CoL0 at 1, 5, and 40 s time delays.