Synthesis, structure, and oxygen reduction reaction activity of 1-isopropylimidazole and 1-propylimidazole ligand-nickel borate crystals

Two imidazole-based ligand-nickel borates, [Ni(1-ipIM) 3 ·B 6 O 7 (OH) 6 ]·[H 3 BO 3 ]·2·.5H 2 O ( 1 , 1-ipIM = 1-isopropylimidazole) and [Ni(1-pIM) 6 ]·[B 5 O 6 (OH) 4 ]·2H 2 O ( 2 , 1-pIM = 1-propylimidazole) have been synthesized and structurally characterized by single-crystal X-ray diffraction, PXRD, FTIR. The oxoboron cluster structures of 1 and 2 were modulated through changing the carbon-branched structure on the N -site of the imidazole-based ligand using metallic nickel as the central atom. It is noteworthy that the structure of 1 is a hybridized skeleton formed by N -Ni-O-B bonds. The electrocatalytic oxygen reduction reaction (ORR) activity of these borate-based catalysts was investigated. The half-wave potential ( E 1/2 ) values of 1 -based and 2 -based were about 0.825 and 0.80 V, respectively.