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.

Comprehensive investigations revealed a pressure–temperature phase diagram for 2D hybrid perovskite MHy₂PbI₄, demonstrating its high structural elasticity and ability to generate polar phases mimicking its ferroelectric analogue MHy₂PbBr₄.

The rich dielectric properties of hybrid formate frameworks are tightly related to the dipolar dynamics and phase transitions of these compounds. A complete understanding of such phenomena requires experiments performed under non-standard conditions. Herein, we report high-pressure dielectric properties of anisotropic single crystals of a 1,4-diaminobutane zinc-formate framework [NH₃(CH₂)₄NH₃][Zn₂(HCOO)₆]. Experiments performed over wide temperature and pressure ranges allowed us to determine the equation of state of this compound. We reveal that a reversible structural phase transition, associated with a change of the crystal symmetry and partial ordering of the 1,4-diaminobutane cations, is characterized by a linear increase of the transition temperature with increasing pressure (dT₀/dp = 5.8(2) K GPa⁻¹). The X-ray diffraction and high-pressure dielectric experiments show that zinc cations together with formate anions form a rigid cage with crystal axis-dependent response to pressure, which affects the dynamics of 1,4-diaminobutane cations. We also demonstrate that the structural phase transition of this compound occurs at a constant value of the dielectric relaxation time (isochronic conditions) further revealing a tight relation between the framework and molecular cations. Our experimental results are supported by the molecular dynamics simulations.

In the past decades, para-terphenyls have been attracting tremendous attention due to their polymorphism and conformational diversity. In this work we report the synthesis, crystal structure, polymorphism and dielectric properties of two 2,2′′-bis-substituted para-terphenyls: 2,2′′-bis(hydroxymethyl)-para-terphenyl and 2,2′′-bis(acetyloxymethyl)-para-terphenyl. On the basis of calorimetric and X-ray studies, we showed that the latter compound occurs in at least four polymorphic forms with melting points equal to 364, 345, 341 and 326 K, differentiated also in terms of thermodynamic stability and crystal symmetry. The most stable polymorph I is characterized by the P2₁/n space group. 2,2′′-Bis(hydroxymethyl)-para-terphenyl crystallizes in the monoclinic P2₁/c space group. Both 2,2′′-bis-substituted para-terphenyls can undergo vitrification, which is a highly exceptional feature for this class of chemical compounds and has not been reported before. Consequently, the molecular dynamics and conformational changes in the glassy and supercooled liquid states were analyzed by means of IR and broadband dielectric spectroscopy. Two relaxation processes were observed for both compounds: structural α-relaxation, connected with reorientational motions of molecules in supercooled liquid, and intermolecular γ-relaxation, ascribed to rotational motions of substituents of the para-terphenyl skeleton. Taking into account the ongoing discussion about the conformational diversity of the para-terphenyl skeleton, we showed that although free rotation of benzene rings is suppressed, the molecules in the glassy and liquid states can adopt both twisted and helical conformations, which results in diversity of the polymorphic forms.