A discrete π-hole•••σ-hole dimer is synthesized and X-ray characterized. It presents a perfect thumbtack geometry where the σ-hole of the linear [AuI 2 ] − anion points to the π-hole located above the central Au-atom of the [AuI 4 ] − anion. Such discrete π-hole•••σ-hole dimers are unprecedented in literature, since all mixed-valence gold(I/III) iodide compounds reported to date form infinite •••([AuI 4 ] − •••[AuI 2 ] − ) n •• chains in the solid state. If an excess of iodine is used for the synthesis, triiodide [I 3 ] − ions are partially incorporated into the [AuI 2 ] − sites, forming infinite chains. The nature of the anion•••anion interaction has been studied considering two possibilities: (i) a π-hole coinage bond or (ii) σ-hole halogen bond using high-level density functional theory calculations, the quantum theory of atoms in molecules, and the noncovalent interaction plot index.

The polymorphism and solid-state peculiarities of imidazo [1,5-a]pyridine derivatives have been investigated by a theoretical and experimental approach to shed light on the structural and energetic features of this family. Four couples of polymorphs and an ionic crystal form have been reported and analysed. Hirshfeld Surface and Energy Frameworks have been used to better understand the crystal packing features, in comparison with literature structures. The collection of all these characterizations made possible to analyse the differences between the polymorphs, the main energetic component dominating the crystal packing, and the effect of the different substitution on the central molecular skeleton on packing disposition. The assignment of vibrational spectra for the imidazo[1,5a]pyridine core has been performed for the first time. Although the discussed polymorphs are very different in their crystal packing, from the energetic point of view they present a strong similarity. In all cases, the main interactions are π‧‧‧π stacking and C-H‧‧‧π to the aromatic rings, with some tendency to the formation of C-H‧‧‧N contacts to the central imidazo [1,5a]pyridine nitrogen. The main energetic component is the dispersive one, with some contribution from the electrostatic component, and this situation is not modified by the presence of differing substituents. When hydrogen bond are present, the crystal packing is strongly modified and, energetically, the electrostatic component can overcome the dispersive on.

Shape-memory polymers and alloys are adaptable materials capable of reversing from a deformed, metastable phase to an energetically favored original phase in response to external stimuli. In the context of metal− organic frameworks, the term shape-memory is defined as the property of a switchable framework to stabilize the reopened pore phase after the first switching transition. Herein we describe a novel flexible terpyridine MOF which, upon desolvation, transforms into a nonporous structure that reopens into a shape-memory phase when exposed to CO 2 at 195 K. Based on comprehensive in situ experimental studies (SC-XRD and PXRD) and DFT energetic considerations combined with literature reports, we recommend dividing shape-memory MOFs into two categories, viz responsive and nonresponsive, depending on the transformability of the gas-free reopened pore phase into the collapsed phase. Furthermore, considering the methodological gap in discovering and understanding shape-memory porous materials, we emphasize the importance of multicycle physisorption experiments for dynamic open framework materials, including metal−organic and covalent organic frameworks.

Shape-memory polymers and alloys are adaptable materials capable of reversing from a deformed, metastable phase, to an energetically favoured original phase in response to external stimuli. In the context of metal-organic frameworks, the term shape-memory is defined as the property of a switchable framework to stabilize the reopened pore phase after the first switching transition. Herein we describe a novel flexible terpyridine MOF which, upon desolvation, transforms into a non-porous structure that reopens into a shape-memory phase when exposed to CO2 at 195 K. Based on comprehensive in situ experimental studies (SC-XRD and PXRD) and DFT energetic considerations combined with literature reports, we recommend dividing shape-memory MOFs into two categories, viz responsive and non-responsive, depending on the transformability of the gas-free reopened pore phase into the collapsed phase. Furthermore, considering the methodological gap in discovering and understanding shape-memory porous materials, we emphasize the importance of multicycle physisorption experiments for dynamic open framework materials, including metal-organic and covalent-organic frameworks.

Using the equilibrium properties of CuII in the presence of the chelating ligand and the characteristics of the dicyanoaurate anion, we were able to obtain a family of 10 bimetallic...