Redox‐Active Bis‐Catecholaldimine Cu(II)‐Salen Complex with Hydroxyl Functionality as Cathode Material in Li‐Ion Battery

In this paper, we report the synthesis, structure, and application of bis‐catecholaldimine‐based Cu II ‐Salen complex as a cathode material in lithium‐ion battery. [Cu(LH 2 )] ( 1 ) complex was prepared using the ligand 6,6′‐{[Ethane‐1,2‐diylbis(azanylidene)]bis(methanylidene)}‐bis(3,5‐di‐ tert ‐butyl‐1,2‐dihydroxybenzene) (LH 4 ). The complex 1 was characterized structurally by single‐crystal X‐ray diffraction technique. It was also further characterized by various techniques such as high‐resolution mass spectrometry, Fourier Transform Infrared, thermogravimetric analysis, and elemental carbon, hydrogen, nitrogen (CHN) analysis. Complex 1 is a mononuclear complex that crystallizes in the triclinic P‐1 Space group with a Cu +2 ion present in a slightly distorted square planar geometry. Complex 1 [Cu(LH 2 )] was further employed as a cathode material for a secondary lithium‐ion battery, which shows superior cyclic and rate capability performance. The [Cu(LH 2 )] ( 1 ) electrode shows an average capacity of 73.5 mAh/g at 50 mA/g after rate capability test, as compared to the 21.8 mAh/g specific capacity for the LH 4 electrode. To understand the redox chemistry of the Cu‐complex, a series of Density functional theory (DFT) computations were carried out for the complex 1 and its corresponding one‐ and two‐electron reduced species.