Room-temperature bistability in a cobalt-octacyanidotungstate framework showing a charge-transfer phase transition with a red-blue color change?

Inorganic Chemistry Frontiers Pub Date: 2022-12-21 DOI: 10.1039/D2QI02321K

Abstract

A two-dimensional cyanido-bridged Co–W assembly, Cs+0.1(H5O2+)0.9 [Co(4-bromopyridine)2.3{W(CN)8}], was synthesized. This compound has a layer structure with H5O2+ and Cs+ ions in between the cyanido-bridged Co–W coordination sheets, and exhibits a charge transfer–induced phase transition between CoII–WV (red) and CoIII–WIV (blue) states with a drastic color change. Upon cooling, the phase transition from the CoII–WV state to the CoIII–WIV state occurs at 276 K, while the opposite transition from the CoIII–WIV state to the CoII–WV state occurs upon heating at 329 K. The present compound shows a large thermal hysteresis loop with a width of 53 K and bistability at room temperature. Analysis of the thermal phase transition using the Slichter–Drickamer model reveals the thermodynamic parameters of the transition enthalpy, transition entropy, and interaction parameter.

Graphical abstract: Room-temperature bistability in a cobalt-octacyanidotungstate framework showing a charge-transfer phase transition with a red-blue color change
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