Photoresponsive Molecular Memory Films Composed of Sequentially Assembled Heterolayers Containing Ruthenium Complexes

Abstract

Photoresponsive molecular memory films were fabricated by a layer-by-layer (LbL) assembling of two dinuclear Ru complexes with tetrapodal phosphonate anchors, containing either 2,3,5,6-tetra(2-pyridyl)pyrazine or 1,2,4,5-tetra(2-pyridyl)benzene as a bridging ligand (Ru-NP and Ru-CP, respectively), using zirconium phosphonate to link the layers. Various types of multilayer homo- and heterostructures were constructed. In the multilayer heterofilms such as ITO||(Ru-NP)m |(Ru-CP)n , the difference in redox potentials between Ru-NP and Ru-CP layers was approximately 0.7 V, which induced a potential gradient determined by the sequence of the layers. In the ITO||(Ru-NP)m |(Ru-CP)n multilayer heterofilms, the direct electron transfer (ET) from the outer Ru-CP layers to the ITO were observed to be blocked for m>2, and charge trapping in the outer Ru-CP layers became evident from the appearance of an intervalence charge transfer (IVCT) band at 1140 nm from the formation of the mixed-valent state of Ru-CP units, resulting from the reductive ET mediation of the inner Ru-NP layers. Therefore, the charging/discharging ("1"and "0") states in the outer Ru-CP layers could be addressed and interconverted by applying potential pulses between -0.5 and +0.7 V. The two states could be read out by the direction of the photocurrent (anodic or cathodic). The molecular heterolayer films thus represent a typical example of a photoresponsive memory device; that is, the writing process may be achieved by the applied potential (-0.5 or +0.7 V), while the readout process is achieved by measuring the direction of the photocurrent (anodic or cathodic). Sequence-sensitive multilayer heterofilms, using redox-active complexes as building blocks, thus demonstrate great potential for the design of molecular functional devices.

Multistate Redox Switching and Near-Infrared Electrochromism Based on a Star-Shaped Triruthenium Complex with a Triarylamine Core

“…Recent studies have shown that polypyridyl ruthenium complexes with a Ru-C bond, namely cyclometalated ruthenium complexes, are particularly useful for the construction of molecular switches with multiple redox processes 21 22 . The presence of the Ru-C bond significantly decreases the Ru(III/II) potential and affords diruthenium 23 or ruthenium-amine 24 25 26 conjugated complexes with three redox states.…”

Crystal structure and redox potentials of the tppz-bridged {RuCl(bpy)}+ dimer

“…Therefore, the chloro complex reported here was initially prepared and isolated as an intermediate in the synthesis of binuclear precatalysts based on the {Ru(tppz)Ru} structural framework . In addition to catalysis, the bis-tridentate tppz ligand finds relevance to the assembly of donor-acceptor metal complexes with electron/ ISSN 2056-9890 energy-transfer properties for potential applications in molecular (opto)electronic devices (Davidson et al, 2015a;Fantacci et al, 2004;Nagashima et al, 2014Nagashima et al, , 2016Wadman et al, 2009).…”

Photoinduced Charge Separation within Metallo-supramolecular Wires Built around a [Ru(bpy)3]2+–Bisterpyridine Linear Entity

“…1 The immobilization of such species on conducting surfaces has attracted great interest in the development of devices for applications dedicated to micro and nano electronics, biotechnologies, catalysis or solar energy conversion etc. [2][3][4][5] Within this context, ligands containing multiple metal-binding sites allow access to multicomponent arrays by combining different metal centers to give rich redox, optical or magnetic properties. Among the different possible chelating groups, bis (2,2':6',2"-terpyridine) derivatives are ideally suited for the construction of such well-defined metallo supramolecular assemblies on surfaces.…”