Thioether crown complexes as templates for the assembly of extended polyiodide networks: synthesis and structures of {[M([16]aneS4)]2I}I11 (M = Pd, Pt), [Pd(cis-HO)2[14]aneS4)](I3)2, [Pd([9]aneS3)2](Ix)2 (x = 3, 5)

Anion⋯anion self-assembly under the control of σ- and π-hole bonds

The electrostatic attraction between charges of opposite signs and the repulsion between charges of the same sign are ubiquitous and influential phenomena in recognition and self-assembly processes. However, it has been recently revealed that specific attractive forces between ions with the same sign are relatively common. These forces can be strong enough to overcome the Coulomb repulsion between ions with the same sign, leading to the formation of stable anion⋯anion and cation⋯cation adducts. Hydroden bonds (HBs) are probably the best-known interaction that can effectively direct these counterintuitive assembly processes. In this review we discuss how σ-hole and π-hole bonds can break the paradigm of electrostatic repulsion between like-charges and effectively drive the self-assembly of anions into discrete as well as one-, two-, or three-dimensional adducts. σ-Hole and π-hole bonds are the attractive forces between regions of excess electron density in molecular entities (e.g., lone pairs or π bond orbitals) and regions of depleted electron density that are localized at the outer surface of bonded atoms opposite to the σ covalent bonds formed by atoms (σ-holes) and above and below the planar portions of molecular entities (π-holes). σ- and π-holes can be present on many different elements of the p and d block of the periodic table and the self-assembly processes driven by their presence can thus involve a wide diversity of mono- and di-anions. The formed homomeric and heteromeric adducts are typically stable in the solid phase and in polar solvents but metastable or unstable in the gas phase. The pivotal role of σ- and π-hole bonds in controlling anion⋯anion self-assembly is described in key biopharmacological systems and in molecular materials endowed with useful functional properties.

Words in supramolecular chemistry: the ineffable advances of polyiodide chemistry

Polyiodide chemistry has a rich history deeply intertwined with the development of supramolecular chemistry. Technological and theoretical interest in polyiodides has not diminished in the last decade, quite the contrary; yet the advances this perspective intends to cover are muddled by the involution of supramolecular vocabulary, preventing their unbiased discussion. Herein we discuss the pressing necessity of ordering the current babel of novel - and less so - supramolecular terms. Shared decisions at the community level might be required to shape the field into a harmonious body of knowledge, dominated by concepts rather than words. Secondary, σ-hole and halogen bonding schools of thought are all addressed here, together with their respective impact on the field. Then, on the basis of a shared vocabulary, a discussion of polyiodide chemistry is presented, starting with a revisited view of triiodide. The contemporary fields of supramolecular caging and polyiodide networks are then discussed, with emphasis on how the terms we choose to use deeply affect scientific progress.

A theoretical insight on the anion⋯anion interactions observed in the solid state structure of a hetero-trinuclear complex

A hetero-nuclear cobalt(iii)/potassium complex has been synthesized and characterized by several analytical techniques. DFT computations indicate the existence of anion⋯anion interactions in its solid state.

N⋯I halogen bonding supported stabilization of a discrete pseudo-linear [I12]2−polyiodide

An unprecedented discrete nearly linear dodecaiodide, [I₁₂]²⁻, can be stabilizedviaN⋯I and cation⋯I⁻interactions using a dicationic template based on the 1,4-diazabicyclo[2.2.2]octane (DABCO) diamine.