Synthesis, Structure, and Characterization of Dichloro‐(1‐Benzyl‐4‐Acetato‐1,4,7‐Triazacyclononane)Iron(III)

Abstract

The synthesis, structure and aqueous solution behavior of [FeL 1 Cl 2 ] (1, L 1 ϭ 1-benzyl-4-acetato-1,4,7-triazacyclononane) is reported. The X-ray structure of 1 reveals iron(III) in distorted octahedral geometry bonded to three amine nitrogen atoms and one carboxylate oxygen atom along with two cis chloride atoms. Electrochemical measurements of 1 in acetonitrile indicate that E 1/2 ϭ Ϫ200 mV vs Ag/AgCl. The stability of the ϩ3 oxidation state is attributed to the hard N amine and carboxylate ligand donors. In acetonitrile, 1 is mononuclear and has an S ϭ 5/2 spin state. The 1087 presence of a μ-oxo bridge upon dissolution of 1 in water is supported by EPR and solution magnetic susceptibility NMR studies. pH-metric titrations and UV-vis studies indicate the presence of a total of four acidic protons. At low pH, L 1 (OH 2 )Fe-O-Fe(OH 2 )L 1 is proposed to be stabilized while at high pH, L 1 (OH)Fe-O-Fe(OH)L 1 is suggested to persist.

A Practical Route for the Preparation of 1,4,7-Triazacyclononanyl Diacetates with a Hydroxypyridinonate Pendant Arm

“…Among the polyazacycle derivatives, tetraazamacrocycles with acetate side chains have received the most attention owing to their strong chelating properties and higher selectivity toward di- or trivalent metal ions [10,11,12,13]. In contrast to tetraazamacrocycles, less attention has be paid on the triazamacrocycle derivatives [12,14,15,16,17,18,19,20,21]. The interest in the triazamacrocycle derivatives, especially 1,4,7-triazacyclononane (TACN) and TACN-based derivatives, has continued to grow in the past few years in the field of nuclear medicine for diagnosis and therapy [4,22,23,24].…”

Synthesis, Structure, and Solution Properties of [(mim-TASN)FeCl2]+ and Its μ-Oxo Derivative

“…The bridging hydroxide can be protonated or deprotonated by modulating the pH. An alternate assignment for the amphoteric complex based on a recent report by Chavez and co-workers is [L(H 2 O)Fe(μ-O)Fe(OH)L] . This is disfavored as H-bonding between the H 2 O and HO − would be expected to bend the Fe−O−Fe bond .…”

“…Most studies involving these model complexes, however, are performed in non-aqueous solvents that are also non-protic , which is in stark contrast to the aqueous environment present at the active sites of metalloenzymes. While some studies have investigated non-heme complexes under aqueous conditions, − there is a surprising paucity that utilize only a single complex under various solvent conditions. To address this we are currently evaluating the effect of solvent on ligand exchange, as well as, the influence of other donor atoms on ligand lability.…”

Oxalate Oxidase Model Studies – Substrate Reactivity

“…[22] Naphtho-Peroxyfluor-1 was synthesized according to the method of Chang et al [46] Triethylamine was distilled from CaH 2 under nitrogen. Bis-(pinacolato)diboron, potassium acetate, tetrabutylammonium hydroxide (40 wt.-%), [Pd(dppf)Cl 2 ] [dppf = bis(diphenylphosphino)ferrocene], N-phenylbis(trifluoromethanesulfonimide), N,NЈdiisopropylethylamine, and naphthofluorescein were purchased from Sigma-Aldrich.…”

“…CO 2 is then lost to afford a Mn II -superoxido-bound CO 2 radical species. [19][20][21][22] In these studies, we will present the properties and reactivity of 1 toward oxalate ions and present evidence for a proposed mechanism for the catalytic decomposition of oxalate initiated by 1. [14] There has been interest in the use of synthetic compounds to model the active site of OxOx.…”