Stabilisation of Exotic Tribromide (Br3−) Anions via Supramolecular Interaction with a Tosylated Macrocyclic Pyridinophane. A Serendipitous Case

Abstract

<jats:p> Tetraaza-macrocyclic pyridinophane L-Ts, decorated with a p-toluenesulfonyl (tosyl; Ts) group, appear to be a useful tool to provide evidence on how the interplay of various supramolecular forces can help stabilise exotic anionic species such as tribromide (Br3−) anions. Indeed, crystals of (H2L-Ts)(Br3)1.5(NO3)0.5 unexpectedly grew from an acidic (HNO3) aqueous solution of L-Ts in the presence of Br− anions. The crystal structure of this compound was determined by single crystal XRD analysis. Hydrogen bonds, salt-bridges, anion-, - stacking, and van der Waals interactions contribute to stabilising the crystal lattice. The observation of two independent Br3− anions stuck over the π-electron densities of pyridine and tosyl ligand groups, one of them being sandwiched between two pyridine rings, corroborates the significance of anion-π interactions for N-containing heterocycles. We show herein the possibility of detecting anion-π contacts from fingerprint plots generated by Hirshfeld surface analysis, demonstrating the effective usage of this structural investigation technique to further dissect individual contributions of stabilising supramolecular forces.</jats:p>

Assembly of Polyiodide Networks with Cu(II) Complexes of Pyridinol-Based Tetraaza Macrocycles

“…It is known that azines may act as π-acid ligands, which can bind anions above their centers according to their positive ESPs and their molecular quadrupole moments. 28 Indeed, s -tetrazine, the most polarized molecule of this family (Q zz quadrupole moment of 11.4 Buckinghams), is prodigal in forming anion−π interactions, 89 even in solution, as recently shown by some of us. 89 , 92 − 97 Nonetheless, also pyridine, despite being the less polarized azine (Q zz quadrupole moment of 3.0 Buckinghams), forms anion−π complexes, 28 especially when they are activated by electron-withdrawing substituents 98 or by N-interaction with positive charges (H + , metal ions).…”

Crystal growth and physical properties of an antiferromagnetic molecule: trans-dibromidotetrakis(acetonitrile)chromium(III) tribromide, [CrBr2(NCCH3)4](Br3)

“…The linearity of the tribromide anion is crystallographically imposed with a symmetric bond length of 2.5461 (13) Å . This is a specific feature observed in this molecule as the symmetric tribromide anion does not commonly appear to stabilize in the solid state (Martínez-Camarena et al, 2020). This was also a characteristic of the [VBr 2 (NCCH 3 ) 4 ](Br 3 ) molecule, which is the only reported compound with a completely symmetric (Br3) À ion to the best of our knowledge (Cotton et al, 1986).…”

Interaction between Trinuclear Regium Complexes of Pyrazolate and Anions, a Computational Study

“…We will investigate the interaction of (Pz-M) 3 , M = Cu, Ag and Au, with three anions (F − , Cl − and Br − ) limiting to the lowest oxidation states (I) of the three coinage metals ( Figure 2). On a different topic, interaction between charged systems, i.e., anion-anion and cation-cation are very interesting, and were found both within the gas phase [69][70][71][72][73][74][75][76][77][78][79] and crystal structures [80,81]. This rare type of interaction, which, in principle should be repulsive, should lead to unstable complexes, i.e., they will revert into the separated ions.…”