Project Details
Projekt
In-situ characterisable nitrosyl-iron complexes with controllable reactivity in multiphasic reaction media
Applicant
Professor Dr. Peter Klüfers
Subject Area
Inorganic Molecular Chemistry - Synthesis and Characterisation
Chemical and Thermal Process Engineering
Chemical and Thermal Process Engineering
Term
from 2014 to 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 256760414
Iron(II) salt solutions react with nitric oxide (NO) as a reactive gas under formation of nitrosyliron complexes. The formation of the nitrosylated products can be detected by optical and vibrational spectroscopy. The liquid phase is an aqueous solution of a ferrous salt. On reaction with nitric oxide, a nitrosyl-iron linkage is formed, the stability of which can be adjusted by the addition of co-ligands. Multidentate chelators such as ethylenediaminetetraacetate (edta) induce pronounced resistivity of the Fe(NO) functions towards NO loss. In the first funding period, the structural chemistry of nitrosyliron complexes was established for a series of co-ligands that belong to the class of aminecarboxylates, as does edta. As a result, structure-property relationships within the class of iron(II)/aminecarboxylate/nitrosyl complexes have become tangible, such as the consequences of coordination-number changes on NO-binding. Thus, a solid basis is available to further develop the heterogeneous reaction of an iron-containing aqueous phase and the reactive gas NO. Specifically, the chemical part of future development focuses on the construction of new ligands with further enhanced properties and includes two goals. First, we will attempt to produce an overall increase of the complexes' stability to allow for reliable NO absorption at low nitric-oxide partial pressures to include the investigation of gas mixtures with NO as the minor component. Second, we will try to achieve selective NO- over O2-binding by designing new ligands that perfectly coordinate the ferrous centres before and after NO binding. This second issue is not only of academic interest but addresses an annoying side-reaction of technically employed iron(II)/edta solutions used for the stripping of NO from flue-gas streams, namely the irreversible oxidation of the iron(II) reagent to the iron(III) oxidation state. If we succeed in repressing the irreversible oxidation by the optimisation of chemical parameters, bubble-column technology may be used to finally promote solely the desired NO absorption reaction. In the first funding period, it was demonstrated that, in methanol as the solvent, even the use of pure NO as the reactive gas could result in competing reaction sequences, namely the formation of either mononitrosyls or dinitrosyls of iron and cobalt. We plan to develop a reaction system that allows us to study the selectivity towards one of the two reactions by the variation of bubble-column parameters. In summary, besides continuing to use the intensely coloured nitrosyliron complexes for the study and modeling of the reactions in bubble columns, we aim to develop two new fields: the control of the competition between nitrosylation and oxidation on the one hand, and the control of the formation of either mononitrosyls or dinitrosyls on the other.
DFG Programme
Priority Programmes
