Synthesis and spectroscopic features of iron(II) 1-aryl-5-benzothiazol-2-ylformazanates

Design of Tetrazolium Cations for the Release of Antiproliferative Formazan Chelators in Mammalian Cells

“…The cyclic voltammograms of the three complexes (recorded in DMF, Figure S5) exhibit a reversible one-electron oxidation at potentials similar to that of the ferrocene reference (Fc + /Fc, E 1/2 0.70 V vs NHE) . In fact, coordination studies with similar formazan ligands reported the formation of Fe­(II) complexes even in the presence of a Fe­(III) source (i.e., FeCl 3 ) and hypothesized the oxidation of a portion of the ligand (i.e., forming the tetrazolium cation) to produce the coordinating Fe­(II). , Because the intracellular labile iron pool consists largely of ferrous species, this type of reactivity is not a concern for our intended application.…”

“…This coordination mode was previously reported for 1a and other asymmetric formazan ligands featuring a metal-binding N-aryl group. 39,47 The presence of the hydroxyphenyl Ar 3 substituent in formazan 4a does not result in a different coordination mode: instead, in Fe(4a-H) 2 the hydroxyl group is engaged in a hydrogenbonding interaction with N4 on the formazan scaffold.…”

“…The observed Fe–N distances for the formazanate donors (i.e., N1 and N3) range from 1.864(2) to 1.946(3) Å, similar to those in other low-spin Fe­(II) complexes with tridentate formazanates (Table S4). ,, In all three complexes, the bonds to the heteroaryl N donors are slightly longer [up to 2.009(4) Å in Fe­( MTF - H ) 2 ]. The N–N and N–C distances along the formazanate backbone (i.e., N1–N2–C7–N3–N4) range narrowly between 1.311(4) and 1.371(4) Å and are consistent with charge delocalization on the conjugated anionic ligand.…”

Formazanate coordination compounds: synthesis, reactivity, and applications

“…Early work on Fe complexes with benzothiazolylformazanate ligands mirrors the results described above for Mn: treatment of Fe(III) salts with formazans leads to formation of low-spin octahedral Fe(II) complexes (16, Scheme 4), some of which were crystallographically characterized. [24][25][26] More recently, Hicks and co-workers reported an Fe(III) complex with a trianionic N 2 O 2 ligand based on the formazanate scaffold, in which the N-aryl groups have an additional phenoxide O-donor moiety. 27 The low-spin Fe(III) complex 17 was obtained by salt metathesis from in situ generated Na-salt of the tetradentate N 2 O 2 ligand with FeCl 3 (Scheme 5).…”

“…23 Scheme 4 Synthesis of homoleptic manganese(II) and iron(II) complexes with benzothiazolyl-substituted formazanate ligands (only one ligand shown in full, other abbreviated (N,N 0 ,N 00 ) for clarity). [24][25][26] Scheme 5 Synthesis of Fe(III) and Co(III) complexes with trianionic N 2 O 2 ligands based on the formazanate scaffold. 27 anionic complex 19.…”