Ground state absorption and redox properties. Extinction coefficient (ε) at peak wavelength (λ) and peak energy (E), potentials of first oxidation (E1/2 FeIII/II) and first reduction (Ep L0/−).
Complexa | λ b (nm) | E b (eV) | ε b (103 M−1 cm−1) | E 1/2 FeIII/II c (V) | E p L0/− c,d (V) |
---|---|---|---|---|---|
[Fe(pbmi)2]2+ | 456 | 2.71 | 15 | 0.31e | −2.39e |
[Fe(cpbmi)2]2+ | 515 | 2.41 | 23f | 0.45e (0.22)g | −1.71e |
[Fe(cpbmi)(dtapbmi)]2+ | 511 | 2.42 | 16 | 0.26 (0.17)g | −1.63h, −2.38 |
[Fe(cpbmi)(daapbmi)]2+ | 512 | 2.42 | 14 | 0.25 (0.19)g | −1.7h, −2.3 |
[Fe(dtapbmi)2]2+ | 459 | 2.70 | 34 | 0.06 | −2.52 |
[Fe(daapbmi)2]2+ | 454 | 2.73 | 32 | 0.05 | −2.58 |
As PF6− salt.
In acetonitrile buffered with 0.1 M TBA methanesulfonate and 0.1 M methanesulfonic acid.
Vs. Fc+/Fc in acetonitrile with 0.1 M TBAPF6.
DPV peak potential of irreversible wave.
From ref. 55.
This is a higher value than previously published,54,55 attributed to the fact that the protonated complex has higher extinction at 515 nm than the deprotonated complex.
Potential of first oxidation of the complex adsorbed on a TiO2 film (using the same procedure as for DSSC fabrication, see ESI.9) immersed in acetonitrile with 0.1 M TBAPF6.
Minor reduction peak.