Bifunctional Nanoscale Assemblies: Multistate Electrochromics Coupled with Charge Trapping and Release

Abstract

We demonstrate controlled charge trapping and release, accompanied by multiple color changes in a metallo‐organic bilayer. The dual functionality of the metallo‐organic materials provides fundamental insight into the metal‐mediated electron transport pathways. The electrochemical processes are visualized by distinct, four color‐to‐color transitions: red, transparent, orange, and brown. The bilayer is composed of two elements: 1) a nanoscale gate consisting of a layer of well‐defined polypyridyl ruthenium complexes bound to a flexible transparent electrode, and 2) a charge storage layer consisting of isostructural iron complexes attached to the surface of the gate. This gate mediates or blocks electron transport in response to an applied voltage. The charge storage and release depend on the oxidation state of the layer of ruthenium complexes (=gate). Combining electrochemistry with optical data revealed mechanistic information: the brown coloration of the bilayer directly relates to the formation of intermediate ruthenium species, providing evidence for catalytic positive charge release mediated through the gate.

Electrochromism or Water Splitting in Neutral Aqueous Solutions by a Metallo‐Organic Assembly

“…Importantly, this study shows that the performance of our MAs is comparable to that of MOFs on a surface. [24][25][26][27] Interestingly, many other metalorganic assemblies reported by us [28][29][30][31][32][33][34][35][36][37][38][39] and others [40][41][42][43][44][45][46][47] could be used for water splitting studies as well.…”

“…[25][26][27] We have developed in our laboratory a series of nanoscale metallo-organic assemblies (MAs) that are redox-active, thermally stable, and highly porous. [28][29][30][31][32][33][34][35][36][37][38][39] Coordination-based networks, comprising layers of polypyridyl complexes, and metals salts, have been generated on transparent conductive oxides (TCOs) by layerby-layer (LBL) dip-coating, automated spray-coating, or spin-coating. [29][30][31] While the polypyridyl complexes are the functional components, the metals salts (mainly palladium) function as a crosslinker by binding to the pyridyl moieties of polypyridyl complexes, generating 3D networks.…”

“…[32][33][34][35][36][37] Furthermore, these materials have excellent charge trapping and multistate electrochromic characteristics. [38,39] Higuchi, Li, Kurth, Nishihara, Zenkina, Zharnikov, and others have studied related materials and demonstrated some of these functionalities. [40][41][42][43][44][45][46][47] However, the electrocatalytic properties of these MAs have not been explored.…”

Photo-modulated wide-spectrum chromism in Eu3+ and Eu3+/Tb3+ photochromic coordination polymer gels: application in decoding secret information

“…The recent upsurge in research on coordination polymer gels (CPGs), 1–3 a new class of processable ‘soft’ materials formed by the self-assembly of suitable metal ions and a low molecular weight gelator (LMWG), 4 stems from their unique properties including responsiveness to stimuli, 5 environmental adaptation, 6 tunable degradability, 7 self-healing, 8 and dynamic nanoscale architecture. 9 The synergistic interactions between metal ions and LMWGs offer unique properties for CPGs in the optical, 10 magnetic, 11 redox, 12 and catalysis fields. 13 Lanthanide-based coordination compounds 14 with a π-chromophoric ligand show greater superiority as light-emitting materials due to their large Stokes shifted narrow visible/near infra-red (NIR) emission with a long excited-state lifetime.…”

Electrochromism or Water Splitting in Neutral Aqueous Solutions by a Metallo-Organic Assembly

“…[25][26][27] We have developed in our laboratory a series of nanoscale metallo-organic assemblies (MAs) that are redox-active, thermally stable, and highly porous. [28][29][30][31][32][33][34][35][36][37][38][39] Coordination-based networks, comprising layers of polypyridyl complexes and metals salts, have been generated on transparent conductive substrates (TCOs) by Layer-by-Layer (LBL) assembly, automated spray-coating, or spin-coating. [29][30][31] Whereas the polypyridyl complexes are the functional components, the metals salts (mainly palladium) function as a crosslinker by binding to the pyridyl moieties of polypyridyl complexes, generating 3D networks.…”