Nitrite reduction by a pyridinediimine complex with a proton-responsive secondary coordination sphere

Abstract

The proton-responsive pyridinediimine ligand, (DEA)PDI (where (DEA)PDI = [(2,6-(i)PrC6H3)(N[double bond, length as m-dash]CMe)(N(Et)2C2H4)(N[double bond, length as m-dash]CMe)C5H3N]) was utilized for the reduction of NO2(-) to NO. Nitrite reduction is facilitated by the protonated secondary coordination sphere coupled with the ligand-based redox-active sites of [Fe(H(DEA)PDI)(CO)2](+) and results in the formation of the {Fe(NO)2}(9) DNIC, [Fe((DEA)PDI)(NO)2](+).

Uncoupled Redox-Inactive Lewis Acids in the Secondary Coordination Sphere Entice Ligand-Based Nitrite Reduction

“…According to the Enemark–Feltham notation, 89 4 can be characterized as a {Fe(NO) 2 } 9 complex. Other dintirosyl iron complexes (DNICs) reported on the PDI ligand scaffold 71,72,90 are also characterized as {Fe(NO) 2 } 9 complexes, and the reported bond lengths and angles are similar to those observed in 4 . The IR spectrum of 4 (Figure S16 in the SI) exhibits ν NO at 1785 and 1712 cm −1 , which shift to 1754 and 1664 cm −1 , respectively, upon isotopic substitution with 15 NO (via substitution of Na 15 NO 2 in the reaction mixture; see the SI).…”

“…These integrated (yet uncoupled) complexes are capable of storing both protons and electrons for transfer to substrate. 71,72…”

Proton-Coupled-Electron Transfer Enhances the Electrocatalytic Reduction of Nitrite to NO in a Bioinspired Copper Complex

“…5,10 The importance of nearby proton-donating residues in the mechanism of nitrite reduction by CuNIR has been highlighted by recent crystallographic 57 and site-directed mutagenesis 58 studies on the relevant enzymes. There have also been three seminal papers in recent years showcasing the importance of hydrogen bonding in the secondary coordination sphere of synthetic systems for nitrite reduction based on both iron 59,60 and copper, 61 although none of these systems were able to demonstrate catalytic turnover. However, to the best of our knowledge, there exist no examples of synthetic, small-molecule platforms for the catalytic reduction of nitrite to NO where the role of proton relays has been addressed explicitly, as it has been, for example, with synthetic platforms for catalytic proton reduction, 62−67 water oxidation, 68−70 and CO 2 reduction.…”

Nitrite Reduction in Aqueous Solution Mediated by Amavadin Homologues: N2O Formation and Water Oxidation

“…[20][21][22][23][24][25][26] Soil bacteria metabolise nitrite to NO by means of nitrite reductases, which are enzymes of the EC 1.7 group [27] with iron-, [28] copper- [29] or molybdenum-based [26] active centres. [21] Despite such great importance,t he chemical homogeneous reduction of nitrites by inorganic transition metals and internal transition-metal compounds has rarely been investigated.M ost studies focusedo ni ron [33][34][35][36][37][38][39][40][41][42][43][44][45] or copper [46][47][48][49][50][51][52] complexes that mimicked nitrite reductases.H owever,N O 2 À reduction with Ru, [53] Mo, [54][55][56] Ti,C r, [56] Co [57][58][59] andU [60] was also reported. Various fungi, including A. muscaria,a lso contribute to the nitrogen cycle with nitrite as possible metabolic substrate.…”

“…Despite such great importance, the chemical homogeneous reduction of nitrites by inorganic transition metals and internal transition‐metal compounds has rarely been investigated. Most studies focused on iron or copper complexes that mimicked nitrite reductases. However, NO 2 − reduction with Ru, Mo, Ti, Cr, Co and U was also reported.…”