Hybrid organic–inorganic perovskites providing integrated functionalities for multimodal switching applications are widely sought-after materials for optoelectronics. Here, we embark on a study of a novel pyrrolidinium-based cyanide perovskite of formula (C 4 H 10 N) 2 KCr(CN) 6 , which displays thermally driven bimodal switching characteristics associated with an order–disorder phase transition. Dielectric switching combines two features important from an application standpoint: high permittivity contrast (Δε′ = 38.5) and very low dielectric losses. Third-order nonlinear optical switching takes advantage of third-harmonic generation (THG) bistability, thus far unprecedented for perovskites and coordination polymers. Structurally, (C 4 H 10 N) 2 KCr(CN) 6 stands out as the first example of a three-dimensional stable perovskite among formate-, azide-, and cyanide-based metal–organic frameworks comprising large pyrrolidinium cations. Its stability, reflected also in robust switching characteristics, has been tracked down to the Cr 3+ component, the ionic radius of which provides a large enough metal–cyanide cage for the pyrrolidinium cargo. While the presence of polar pyrrolidinium cations leads to excellent switchable dielectric properties, the presence of Cr 3+ is also responsible for efficient phosphorescence, which is remarkably shifted to the near-infrared region (770 to 880 nm). The presence of Cr 3+ was also found indispensable to the THG switching functionality. It is also found that a closely related cobalt-based analogue doped with Cr 3+ ions displays distinct near-infrared phosphorescence as well. Thus, doping with Cr 3+ ions is an effective strategy to introduce phosphorescence as an additional functional property into the family of cobalt-cyanide thermally switchable dielectrics.

In this work we report synthesis, unexpected glass-forming properties, molecular dynamics and conformational analysis of two glass-forming thiacrown ethers: 6-methyl-2,3-dihydro-1,4-benzodithiine (1) of a six-membered heterocyclic ring and macrocyclic 2,3-(4’-methylbenzo)-1,4-dithia-7-oxacyclononane (2)....

A series of five alcohols (3-methyl-2-butanol, 1-cyclopropylethanol, 1-cyclopentylethanol, 1-cyclohexylethanol, and 1-phenylethanol) was used to study the impact of the size of steric hindrance and its aromaticity on self-assembling phenomena in the liquid phase. In this Letter, we have explicitly shown that the phenyl ring exerts a much stronger effect on the self-organization of molecules via the O–H···O scheme than any other type of steric hindrance, leading to a significant decline in the size and concentration of the H-bonded clusters. Given the combination of calorimetric, dielectric, infrared, and diffraction studies, this phenomenon was ascribed to its additional proton-acceptor function for the competitive intermolecular O–H···π interactions. The consequence of this is a different packing of molecules on the short- and medium-range scale.