A Redox‐Active Dinuclear Platinum Complex Exhibiting Multicolored Electrochromism and Luminescence

Abstract

A redox series of cyclometalated platinum complexes based on a dinuclear motif linked by acetamidato (aam) bridging ligands, [Pt 2 (μ-aam) 2 (ppy) 2 ] (ppy -= 2-phenylpyridinate ion), has been synthesized. The complexes in this series are easily oxidized and reduced by both electrochemical and chemical methods, and this is accompanied by multistep changes in their optical properties, that is, multiple color changes and luminescence. Isolation of the complexes and the structural determination of three oxidation states, +2, +2.33, and +3, have been achieved. The mixed-valent complex, with an average oxidation state of +2.33, forms a trimer based on the dinuclear motif. The mixed-valent complex has a characteristic color due to intervalence transitions in the platinum chain. In contrast, the divalent complex exhibits strong red phosphorescence originating from a triplet metal-metal-to-ligand charge transfer ( 3 MMLCT) state. This study demonstrates the unique chromic behavior of a redox-active and luminescent platinum complex.

Robust Triplatinum Redox‐Chromophore for a Post‐Synthetic Color‐Tunable Electrochromic System

“…There has been growing interest in electrochromic materials that show reversible color change caused by switching between two or more redox states through an alternating applied voltage in applications such as display devices, smart windows, and optical memories . Redox chromophores for such electrochromic systems can mainly be classified into the following three categories: (i) inorganic materials such as metal oxides and metal nanoparticles, (ii) organic polymers or small organic molecules with stable radical species and charge‐transfer states, and (iii) transition‐metal complexes . Transition‐metal‐complex‐based electrochromic systems have a particular advantage by virtue of their wide range of color tunability based on multistep redox states attainable through the combination of multivalent metal ions and ligands.…”

“…Transition‐metal‐complex‐based electrochromic systems have a particular advantage by virtue of their wide range of color tunability based on multistep redox states attainable through the combination of multivalent metal ions and ligands. Therefore, transition‐metal‐based electrochromic systems have attracted much attention recently for the development of multicolored electrochromic materials …”

“…As a candidate for such a multicolor redox‐chromophore for functional electrochromic systems, we recently reported multistep color control using a double‐decker Pt complex, [Pt 2 (μ‐aam) 2 (ppy) 2 ] (Haam=acetamide, Hppy=2‐phenylpyridine) . This complex exhibits several mixed‐valence states with different colors between a luminescent divalent state and an almost colorless trivalent state.…”

“…[1] Redox chromophores for such electrochromic systemsc an mainly be classified into the followingt hree categories:( i) inorganic materials such as metal oxides andm etal nanoparticles, [2] (ii)organic polymers or small organic molecules with stable radical species and charge-transfer states, [3] and( iii)transition-metal complexes. [4,5] Transitionmetal-complex-based electrochromic systemsh ave ap articular advantage by virtue of their wide range of colort unability based on multistep redoxs tates attainable throught he combination of multivalent metal ions and ligands. Therefore, transition-metal-based electrochromic systems have attracted much attention recently for the development of multicolored electrochromic materials.…”

“…Therefore, transition-metal-based electrochromic systems have attracted much attention recently for the development of multicolored electrochromic materials. [4,5] As ac andidate for such am ulticolor redox-chromophore for functional electrochromic systems, we recently reportedm ulti-step color control using ad ouble-deckerP tc omplex, [Pt 2 (maam) 2 (ppy) 2 ]( Haam = acetamide, Hppy = 2-phenylpyridine). [5] This complex exhibits several mixed-valences tates with different colors between al uminescent divalent state and an almost colorlesst rivalent state.…”