Synthesis, Characterization, and HER Activity of Pendant Diamine Derivatives of NiATSM

• Published in: European journal of inorganic chemistry 2019-08, Vol.2019 (33)
• Main Authors: Calvary, Caleb A., Hietsoi, Oleksandr, Strain, Jacob M., Mashuta, Mark S., Spurgeon, Joshua M., Buchanan, Robert M., Grapperhaus, Craig A.
• Format: Article
• Language: English
• Subjects: Chemistry; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 1434-1948; 1099-0682

A pair of bis-thiosemicarbazonato-Ni(II) complexes with pendant polyamines, (N,N'-(dimethylethylenediaminothiosemi-carbazonato)-4-(methylthiosemi-carbazonato)butane-2,3-diimine)-nickel(II) (1) and (N,N'-bis(dimethylethyl-enediaminothiosemi-carbazonato)butane-2,3-diimine)-nickel(II) (3), have been synthesized. Methylation at the terminal amines yields the cationic derivatives 2 and 4. All complexes are fully characterized by spectroscopic, electrochemical, and single-crystal X-ray diffraction methods. Single crystal X-ray diffraction studies on all four Ni(II) complexes confirm a square planar Ni(II) framework with no significant changes in the coordination environment as a function of the pendant groups. Spectroscopic studies are consistent with a similar electronic structure in all complexes. However, electrochemical investigations reveal significant cathodic shifts in the Ni(II)L/Ni(II)L·– and Ni(II)L·–/Ni(I)L·2– reduction potentials of the methylated vs. non-methylated species. The HER activity of all four nickel complexes were evaluated in acetonitrile with glacial acetic acid. The 3 complex was shown to have the highest activity with a TOF of 6.3 × 103 s-1, an overpotential of 0.56 V, and faradaic efficiency of 100%.