A pair of highly biotolerated diamagnetic and paramagnetic iron(ii) complexes displaying electroneutrality

Abstract

A pair of structurally analogous macrocyclic iron(II) complexes with a magnetic off-on relationship is reported that exhibit electroneutrality at neutral pH and high stability in physiological media. This has been achieved by external charge compensation using nicotinate pendent arms. No contact toxicity was observed for cells up to 4 mM for the low-spin and 2 mM for the high-spin complex. These results are a necessary precursor to the future design of turn-on probes with elevated biotolerance.