Electrochemistry and Stability of 1,1′-Ferrocene-Bisphosphonates

Abstract

Here, we investigate the electrochemical properties and stability of 1,1′-ferrocene-bisphosphonates in aqueous solutions. 31 P NMR spectroscopy enables to track decomposition at extreme pH conditions revealing partial disintegration of the ferrocene core in air and under an argon atmosphere. ESI-MS indicates the decomposition pathways to be different in aqueous H 3 PO 4 , phosphate buffer, or NaOH solutions. Cyclovoltammetry exhibits completely reversible redox chemistry of the evaluated bisphosphonates, sodium 1,1′-ferrocene-bis(phosphonate) (3) and sodium 1,1′-ferrocene-bis(methylphosphonate) (8), from pH 1.2 to pH 13. Both the compounds feature freely diffusing species as determined using the Randles-Sevcik analysis. The activation barriers determined by rotating disk electrode measurements revealed asymmetry for oxidation and reduction. The compounds are tested in a hybrid flow battery using anthraquinone-2-sulfonate as the counterside, yielding only moderate performance.

Reduction Behavior of Anisyl‐substituted P‐Ferrocenyl Phospholes

“…Ferrocene is known to be oxidized reversibly at comparably low potentials (e. g., +0.31 V half wave potential versus SCE in 90 % ethanol) [14] . While for P(V)‐substituted ferrocenes the redox activity is limited to the ferrocene site which has been employed in flow‐cell battery systems, [15] for P(III)‐substituted ferrocenylphosphanes oxidation of the phosphorus atom needs to be considered as well. In order to receive information about the redox behavior of our 1‐ferrocenylphospholes we performed CV‐measurements of 1 a and 2 a .…”

“…Elemental analysis (%): calculated: C 68.97, H 5.98, found: C 69.25, H 6. 15. HRMS (APCI) m/z: 523.1304 [M + H] + , calculated: 523.1309.…”

Influence of the Substituent’s Size in the Phosphinate Group on the Conformational Possibilities of Ferrocenylbisphosphinic Acids in the Design of Coordination Polymers and Metal–Organic Frameworks

“…By studying these factors, researchers can gain insights into how to design coordination polymers with specific structural and functional properties for various applications [42,43]. This possibility of tuning electronic and steric properties with two aryl/alkyl substituents directly attached to phosphorus atom of phosphinic acids translates into unique properties of materials that cannot be replicated by the utilization of analogous phosphonates or carboxylates [29][30][31]. The properties of phosphinates fall in many ways between the properties of carboxylates and phosphonates, combining somewhat stronger binding to hard metal ions compared to carboxylates with less damaging effect on surfaces and more predictable coordination modes than phosphonates.…”