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Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand.

ABSTRACT: Complexes [M(n)MST(NH3)](n-3) (M(n) = Fe(II), Fe(III), Ga(III)) were prepared and each contains an intramolecular hydrogen bonding network involving the ammonia ligand. Deprotonation of the Fe(III)-NH3 complex afforded a putative [Fe(III)MST(NH2)](-) species whose reactivity has been explored.

SUBMITTER: Sickerman NS

PROVIDER: S-EPMC3954711 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand.

Sickerman Nathaniel S NS Peterson Sonja M SM Ziller Joseph W JW Borovik A S AS

Chemical communications (Cambridge, England) 20140124 19

Complexes [M(n)MST(NH3)](n-3) (M(n) = Fe(II), Fe(III), Ga(III)) were prepared and each contains an intramolecular hydrogen bonding network involving the ammonia ligand. Deprotonation of the Fe(III)-NH3 complex afforded a putative [Fe(III)MST(NH2)](-) species whose reactivity has been explored. ...[more]

PMID: 24457593

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Project description:The Fe coordination chemistry of several tripodal aminopyridyl hexadentate chelators is reported along with cytotoxicity toward cultured Hela cells. The chelators are based on cis, cis-1,3,5-triaminocyclohexane (tach) with three pendant -CH2-2-pyridyl groups where 2-pyridyl is R-substituted thus are named tach-x-Rpyr where x=3, R=Me; x=3, R=MeO; x=6; R=Me. The structures of [Fe(tach-3-Mepyr)]Cl2 and [Fe(tach-3-MeOpyr)](FeCl4) are reported and their metric parameters indicate strongly bound, low-spin Fe(II). The structure of [Fe(tach-6-Mepyr)](ClO4)2 implies steric effects of 6-Me groups push donor Npy's away so one Fe-Npy bond is substantially longer at 2.380(3)A vs. 2.228(3)A for the others, and Fe(II) in the high-spin-state. Accordingly, anions X(-)=Cl or SCN afford [Fe(tach-6-Mepyr)(X)]+ from [Fe(tach-6-Mepyr)]2+ (UV-vis spectroscopy). Consistent with a biological cytotoxicity involving Fe chelation, chelators of low-spin Fe(II) have greater toxicity in the order [IC50(72 h) is in parentheses then the spin-state SS=H (high) or L (low)]: tachpyr=tach-3-Mepyr (6 microM, SS=L) greater, similar tach-3-MeOpyr (12microM, SS=L)>>tach-6-Mepyr (>200 microM, SS=H). Iron-mediated oxidative dehydrogenation with O2 oxidant removes hydrogens from coordinated nitrogen and the adjacent CH2, converting aqueous [Fe(tach-3-Rpyr)]2+ (R=H, Me and MeO) into a mix of low-spin imino- and aminopyridyl-armed complexes, but [Fe(tach-6-Mepyr)]2+ does not react (NMR and ESI-MS spectroscopies). The difference of IC(50) for chelators at different time points (delta IC50=[IC50(24h)-IC50(72 h)]) is used to compare rate of cytotoxic action to qualitative rate of oxidation in the Fe-bound chelator, giving the order, from rapid to slow oxidation and cell killing of: [Fe(tach-3-Mepyr)]2+ (delta IC50=5 microM)>[Fe(tachpyr)]2+ (delta IC50=16 microM)>[Fe(tach-3-MeOpyr)]2+ (delta IC50=118 microM). Thus, those chelators whose Fe(II) complexes undergo rapid oxidation kill cells faster, and those that bind Fe(II) as low-spin are far more cytotoxic.

Dataset Information

Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand.

Publications

Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand.

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