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 redox-active hydrazine based catecholaldimine ligand (4,6-ditert-butyl-2,3-dihydroxybenzylidene)furan-2-carbohydrazide (LH 3 ). Complex 1 was readily obtained by refluxing (LH 3 ) and Al(NO 3 ) 3 •9H 2 O in 2:1 molar ratio in the presence of triethylamine in a methanolic solution. Single-crystal X-ray diffraction analysis of complex 1shows that catecholaldimine ligands bind through octahedral coordination to Al (III) center.Complex 1 was also further characterized by various techniques such as HRMS, UV-Vis, FTIR, TGA and CHN analysis. The 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 shows 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 10 3 . The device also showed stable resistive switching behaviour for 10 2 iterations with negligible loss in 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 new diverse redox-active ligand backbone.