Table 1 The interplay between substituent groups and intramolecular hydrogen bondings in isoindigos and the corresponding impacts on redox potentials (V vs. Fc+/Fc) and CO2 binding

From: Redox-tunable isoindigos for electrochemically mediated carbon capture

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Isoindigos

1HNMR (Ha) (ppm)A

1HNMR (Hb) (ppm)A

Bond length of a (Å)B

Bond length of b (Å)B

Bond length of c (Å)B

E1/2(IId/IId●−) in N2 (V vs Fc+/Fc)

\(\log {K}_{{{{{{{\rm{CO}}}}}}}_{2}}\)

IId

9.06

10.89

1.963

1.954

1.461

−1.29

9.34

55DMIId

8.85

10.69

1.953

1.97

1.463

−1.29

9.05

5BIId

9.07

10.96

1.962

1.957

1.463

−1.19

9.05

5BIId (EWG)

9.31

11.05

1.936

1.943

1.467

−1.19

9.05

55DBIId

9.32

11.11

1.939

1.946

1.469

−1.09

9.33

6MCIId

9.07

10.94

1.960

1.954

1.954

−1.12

8.89

6MCIId (EWG)

9.15

11.08

1.956

1.944

1.476

−1.12

8.89

66DBIId

8.99

11.1

1.961

1.942

1.468

−1.14

9.59

NNDPr66DBIId

9.05

NA

1.948

NA

1.486

−1.07

4.87

  1. A 1H NMR were recorded on the neutral molecules in DMSO-d6 using solvent residual peak as the internal reference for calibration. B Bond length was obtained from DFT-optimised structures. C Results from the non-symmetric oxindole ring with the EWG-substituent.
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