Bin-Bin Cui

Three-state near-infrared electrochromism at the molecular scale.

Self-assembled monolayer films of a cyclometalated ruthenium complex with a redox-active amine substituent and three carboxylic acid groups have been prepared on ITO electrode surfaces. The obtained thin films show three-state electrochromic switching with low electrochemical potential inputs and high near-infrared absorbance outputs. Thanks to the long retention time of each oxidation states, these films have been used to demonstrate surface-confined flip-flop memory functions with high ON/OFF ratios at the molecular scale.

A Molecular Platform for Multistate Near‐Infrared Electrochromism and Flip‐Flop, Flip‐Flap‐Flop, and Ternary Memory

A diruthenium complex with a redox-active amine bridge has been designed, synthesized, and studied by single-crystal X-ray analysis and DFT and TDDFT calculations. It shows three well-separated redox processes with exclusive near-infrared (NIR) absorbance at each redox state. The electropolymerized film of a related vinyl-functionalized complex displays multistate NIR electrochromism with low operational potential, good contrast ratio, and long retention time. Flip-flop, flip-flap-flop, and ternary memories have been realized by using the obtained film (ca. 15-20 nm thick) with three electrochemical inputs and three NIR optical outputs that each displays three levels of signal intensity.

Ruthenium-Amine Conjugated Organometallic Materials for Multistate Near-IR Electrochromism and Information Storage

Monometallic and dimetallic complexes with the ruthenium-amine conjugated structural unit have been prepared. These complexes display consecutive redox waves with low potentials and rich and intense absorptions in the near-infrared region. The electrochemical and spectroscopic properties can be modulated using substituents or auxiliary ligands with different electronic natures. Through simple functionalization, electropolymerized or monolayer thin films of these complexes have been prepared. These films display multistate near-infrared electrochromism with good contrast ratios and long optical retention times. In addition, flip-flop and flip-flap-flop memories have been demonstrated on the basis of these thin films.

Resistive Memory Materials Based on Transition-Metal Complexes

A resistive memory operates as an electrical switch between high and low conductivity states (or multistates) in response to an external electric field. Due to the high capacity, high flexibility, good scalability, low cost, and low power consumption, resistive memory is promising for the next-generation high-density data storage. In addition to inorganic metal oxides, carbon nanomaterials, organic small molecular and polymeric semiconductor materials, transition-metal complexes have recently received much attention as active materials for resistive memory. In this contribution, the applications of transi- tion-metal complexes in resistive memory reported to date are summarized and discussed, mainly including group VIII (Fe(II), Ru(II), Co(III), Rh(III), Ir(III), and Pt(II) complexes), group IB and IIB (Cu(II), Au(III), and Zn(II) complexes), and lanthanide complexes (mainly Eu(III) complexes). The memory behavior and mechanism of these materials will be discussed. Transition-metal complexes often possess well-defined and reversible redox processes. The frontier energy levels and gaps can be easily modulated by changing the structures of ligands and metal species, which is beneficial for generating electrical bistates or multistates when they are used in resistive memory devices. These features make transition-metal complexes po- tentially useful as memory materials in practical applications.