Solution-processable homoleptic aluminum(iii) catecholaldimine complex as an active material for RRAM switching device

Abstract

In this paper, we report the synthesis and structural characterization of a new mononuclear aluminum complex 1, containing a redox-active hydrazine based catecholaldimine ligand (4,6-di-tert-butyl-2,3-dihydroxybenzylidene)furan-2-carbohydrazide (LH₃). Complex 1 was readily obtained by refluxing (LH₃) and Al(NO₃)₃·9H₂O in a 2 : 1 molar ratio in the presence of triethylamine in a methanolic solution. Single-crystal X-ray diffraction analysis of complex 1 shows that catecholaldimine ligands bind through octahedral coordination to the Al(III) center. Complex 1 was also further characterized by various techniques such as HRMS, UV-vis, FTIR, TGA and CHN analysis. Complex 1 was found to exhibit absorption bands at 225 and 354 nm in dichloromethane (DCM) solution assigned to ligand-based electronic transitions, which is in quite good agreement with absorption bands calculated by TD-DFT theoretically. The electrochemical characterization of complex 1 was done by cyclic voltammetry in DCM solution, which showed several quasi-reversible and irreversible oxidation–reduction peaks. The solution processable mononuclear aluminum complex 1 was further employed as an active material to fabricate a resistive switching memory device. Interestingly, the device exhibits distinct bipolar resistive switching with a maximum ON/OFF ratio of almost 10³. The device also shows stable resistive switching behaviour for 10² iterations with negligible loss of resistance ratio and stability of both resistive states (LRS and HRS) for 3300 s, demonstrating its promising potential for non-volatile memory applications. This work offers a new direction for the rational design and fabrication of high-performance resistive memory devices based on Earth-abundant aluminum metal-based molecular complexes with a new diverse redox-active ligand backbone.