Table 1.
Iron binding by bipy and biheteroaryl compounds.
| Compound | Heteroaryl pKaa (ref.) | pKab | Fe(II) Complex λmaxc |
Stoichiometry (Ligand:Fe)d |
Fe20-EC50e |
|---|---|---|---|---|---|
| bipy | 5.2 (38) | 4.3 | 523 | 3:1 | 43 ± 2 |
| pypyrid | 2.3 (39) | <3 | 522 | 3:1 | 124 ± 1 |
| pypyraz | 0.8 (40) | <3 | 523 | 3:1 | 400 ± 7 |
| pyim | 7.1 (41) | 5.4 | 484 | 3:1 | 900 ± 30 |
| pypyr | 2.5 (42) | 4.1 | 441 | NDf | 2250 ± 100 |
| pythi | 2.5 (43) | <3 | 524 | 3:1 | 5100 ± 100 |
| pyox | 0.8 (44) | <3 | NOg | NOg | >18,000 |
a
pKa value of the conjugate acid of pyridine (bipy) or the non-pyridyl ring.
b
pKa value of the conjugate acid as estimated by titration of the entire compound; bipy, ref. 45.
c
Determined using spectrophotometry (see: Supporting Information).
e
Determined by titration of 20 μM FeSO4; bipy, ref. 25. Values are the mean (±SE) of 3 replicates.
f
Not determined due to prohibitive competing absorbance from iron.
g
Not observed.