1364368-35-3Relevant academic research and scientific papers
Zn-Templated synthesis of substituted (2,6-diimine)pyridine proligands and evaluation of their iron complexes as anolytes for flow battery applications
Braun, Jason D.,Gray, Paul A.,Herbert, David E.,Nemez, Dion B.,Sidhu, Baldeep K.
, p. 16175 - 16183 (2020/12/03)
Pseudo-octahedral iron complexes supported by tridentate N^N^N-binding, redox 'non-innocent' diiminepyridine (DIP) ligands exhibit multiple reversible ligand-based reductions that suggest the potential application of these complexes as anolytes in redox flow batteries (RFBs). When bearing aryl groups at the imine nitrogens, substitution at the 4-position can be used to tune these redox potentials and impact other properties relevant to RFB applications, such as solubility and stability over extended cycling. DIP ligands bearing electron-withdrawing groups (EWGs) in this position, however, can be challenging to isolate via typical condensation routes involving para-substituted anilines and 2,6-diacetylpyridine. In this work, we demonstrate a high-yielding Zn-templated synthesis of DIP ligands bearing strong EWGs. The synthesis and electrochemical characterization of iron(ii) complexes of these ligands is also described, along with properties relevant to their potential application as RFB anolytes.
Tuning redox potentials of bis(imino)pyridine cobalt complexes: An experimental and theoretical study involving solvent and ligand effects
Moyses Araujo,Doherty, Mark D.,Konezny, Steven J.,Luca, Oana R.,Usyatinsky, Alex,Grade, Hans,Lobkovsky, Emil,Soloveichik, Grigorii L.,Crabtree, Robert H.,Batista, Victor S.
experimental part, p. 3562 - 3573 (2012/05/04)
The structure and electrochemical properties of a series of bis(imino)pyridine CoII complexes (NNN)CoX2 and [(NNN)2Co][PF6]2 (NNN = 2,6-bis[1-(4-R- phenylimino)ethyl]pyridine, with R = CN, CF3, H, CH3, OCH3, N(CH3)2; NNN = 2,6-bis[1-(2,6-(iPr) 2-phenylimino)ethyl]pyridine and X = Cl, Br) were studied using a combination of electrochemical and theoretical methods. Cyclic voltammetry measurements and DFT/B3LYP calculations suggest that in solution (NNN)CoCl 2 complexes exist in equilibrium with disproportionation products [(NNN)2Co]2+ [CoCl4]2- with the position of the equilibrium heavily influenced by both the solvent polarity and the steric and electronic properties of the bis(imino)pyridine ligands. In strong polar solvents (e.g., CH3CN or H2O) or with electron donating substituents (R = OCH3 or N(CH3) 2) the equilibrium is shifted and only oxidation of the charged products [(NNN)2Co]2+ and [CoCl4]2- is observed. Conversely, in nonpolar organic solvents such as CH 2Cl2 or with electron withdrawing substituents (R = CN or CF3), disproportionation is suppressed and oxidation of the (NNN)CoCl2 complexes leads to 18e- CoIII complexes stabilized by coordination of a solvent moiety. In addition, the [(NNN)2Co][PF6]2 complexes exhibit reversible CoII/III oxidation potentials that are strongly dependent on the electron withdrawing/donating nature of the N-aryl substituents, spanning nearly 750 mV in acetonitrile. The resulting insight on the regulation of redox properties of a series of bis(imino)pyridine cobalt(ii) complexes should be particularly valuable to tune suitable conditions for reactivity. The Royal Society of Chemistry 2012.
