A New Series of Cobalt and Iron Clathrochelates with Perfluorinated Ribbed Substituents

Abstract

The study tackles one of the challenges in developing platinum-free molecular electrocatalysts for hydrogen evolution, which is to seek for new possibilities to ensure large turnover numbers by stabilizing electrocatalytic intermediates. These species are often much more reactive than the initial electrocatalysts, and if not properly stabilized by a suitable choice of functionalizing substituents, they have a limited long-time activity. Here, we describe new iron and cobalt(II) cage complexes (clathrochelates) that in contrast to many previously reported complexes of this type do not act as electrocatalysts for hydrogen evolution. We argue that the most probable reason for this behavior is an excessive stabilization of the metal(I) species by perfluoroaryl ribbed groups, resulting in an unprecedented long-term stability of the metal(I) complexes even in acidic solutions.

Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

“…Complex red-ox behavior was also reported in this study, such as Co(III) hydride intermediates formed upon reduction in acidic media [168]. Zelinskii et al utilized perfluorophenyl-ribbed substituents to stabilize Co(I) in an effort to enhance the HER, but although the reduced Co(I) was successfully stabilized, the resulting Co-clathrochelate complex was not electrochemically active in the HER [169]. One of the main challenges for non-noble metal catalysts in aqueous electrolyzer cathodes is their stability in harsh acidic conditions.…”

Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

“…In this study, a more positive potential for H2 evolution correlated with a decreased activity for electrocatalysis. Complex red-ox behavior was also reported in this study, such as Co(III) hydride intermediates formed upon reduction in acidic media[170].Zelinskii et al utilized perfluorophenyl ribbed substituents to stabilize Co(I) in an effort to enhance the HER, but although the reduced Co(I) was successfully stabilized, the resulting Co-clathrochelate complex was not electrochemically active in the HER[171].One of the main challenges for non-noble metal catalysts in aqueous electrolyzer cathodes is their stability in harsh acidic conditions. The Co-clathrochelates show good stability in the reported works, exemplified by a stable overvoltage of 240 mV and a faradaic efficiency of 80 %, remaining stable for more than 7 hrs in pH = 2 and at 1 mA/cm 2 and 0.9 V[172].…”

Synthesis and Iodine Adsorption Properties of Organometallic Copolymers with Propeller-Shaped Fe(II) Clathrochelates Bridged by Different Diaryl Thioether and Their Oxidized Sulfone Derivatives

“…Iron(II) clathrochelates are robust metalorganic complexes whose intricate structural features and modular synthesis have qualified them to be utilized as potential building blocks in several applications, including as biosensors [27,28], catalysts for hydrogen generation [29,30], materials for electronic transport [31], organogels [32], supramolecular structures [33] and porous materials for the adsorption of different gases and dyes [32,[34][35][36][37]. Recently, our group has disclosed various metalorganic polymers containing Fe(II) clathrochelate derivatives, which revealed the efficient uptake of organic dyes and lithium ions from water solutions [38], as well as iodine capture [39].…”