High Order in a Self‐Assembled Iridium(III) Complex Gelator Towards Nanostructured IrO₂ Thin Films

Abstract

The preparation and characterization of a new metallogelator based on the Ir discrete cyclometalated complex [(ppy) Ir(bpy)](CH CH OCH CO ) are reported, where H(ppy) is 2-phenylpiridine and bpy is 2,2'-bipyridine, which is used as an ancillary ligand. The compound is able to self-assemble in water in a range of concentrations between 3 % and 6 % w/w, creating a luminescent ordered supramolecular gel. The gel and xerogel architectures were investigated through polarized optical microscopy (POM), SEM and TEM microscopies coupled with powder X-ray diffraction. The gel supramolecular organization is characterized by columnar tetragonal strands, already present at high dilution conditions, of cations surrounded by counteranions. These strands, in turn, are self-assembled in an oblique columnar cell upon gelification. The xerogel thin films obtained upon complete dehydration maintained the gel supramolecular order and can be used as a precursor for the preparation of nanostructured IrO thin films.

Nanostructured Iridium Oxide: State of the Art

“…Nanostructured IrO 2 films have also been prepared employing an ordered supramolecular gel phase generated by an organometallic Ir(III) complex, used both as templating agent and metal source. Indeed, several Ir(III) complexes can self-assemble in highly organized supramolecular phases in water, including physical gels and lyotropic liquid-crystalline gels [120][121][122]. Moreover, many metal oxide (SiO 2 , TiO 2 , ZrO 2 , ZnO and WO 3 ) nanostructures, such as nanotubes, nanoparticles, and nanowires, have been efficiently prepared taking advantage of a supramolecular gel as structural directing agent (SDA) [123].…”

“…Moreover, many metal oxide (SiO 2 , TiO 2 , ZrO 2 , ZnO and WO 3 ) nanostructures, such as nanotubes, nanoparticles, and nanowires, have been efficiently prepared taking advantage of a supramolecular gel as structural directing agent (SDA) [123]. In this context, the supramolecular gel phase of the Ir(III) compound [(ppy) 2 Ir(bpy)]EtOCH 2 CO 2 (chemical structure reported in Figure 20), where ppy is 2-phenylpiridine and bpy is 2,2bipyridine, which supramolecular architecture in water is built on a double 2D columnar system, was used as template and metal precursor for the preparation of IrO 2 films [122]. The highly ordered metallogel was deposited onto quartz substrates through spin-coating and was left to dry, obtaining the corresponding xerogel, that was calcinated at 600 • C for 4 h, obtaining a uniform IrO 2 thin film.…”

Supramolecular Gel as the Template for Catalysis, Inorganic Superstructure, and Pharmaceutical Crystallization

“…The inclusion of the halide salts in the supramolecular gel led to the formation of seed crystals and diffusion-driven base growth of nanowires [88]. A hydrogel based on the Ir(III) complex 41 reported by Godbert et al, consisted of tetragonal columnar strands formed by Ir(III) cations, which were self-assembled in a columnar oblique system [89]. Upon complete dehydration of the gel phases, the obtained xerogel thin films maintained identical supramolecular architectures.…”

Characterization of Different Metal Oxides Thin Films Deposited by Spin Coating Technique

“…Another MO is iridium oxide (IrO2), which displays exceptional thermal stability and chemical resistivity towards aggressive basic or acidic media. Moreover, its interesting electrochemical and optoelectronic properties make it the best choice for electrochromic displays, optical switching, automobile rear-view mirrors, pH monitoring, as an electrocatalyst for the oxygen evolution reaction and anodic reaction in water electrolysis, and has been used in the chloralkali industry [17][18][19][20].…”