Stacking interactions of aromatic ligands in transition metal complexes

New Type of Aromatic π‐Systems for Anion Recognition: Strong Anion‐π and C−H⋅⋅⋅Anion Interactions Between Halides and Aromatic Ligands in Half‐Sandwich Compounds

“…It was shown that using quantum chemical calculations one can predict energies of noncovalent interactions. [35,36,53,54] Energy optimizations and calculations of interaction energies were performed in Gaussian 09 (version D.01) program package. [55] The geometries of selected transition metal complexes containing aromatic rings were optimized using MP2/ 6-31 + + G** level of theory.…”

“…[32,33] Transition metal coordination is known to enhance the strength of various interactions, most notably hydrogen bonding [34] and stacking interactions. [35,36] Theoretical and experimental studies have also shown that pyridine can form anion-π interactions only if its nitrogen is coordinated with silver(I), [37] while silver(I) coordination of all nitrogen atoms of pyrazine and s-tetrazine dramatically strengthens their anionπ interactions. [37,38] However, it was also shown that hexafluorobenzene coordinated to chromium in sandwich compound Cr(C 6 H 6 )(C 6 F 6 ) forms somewhat weaker anion-π interactions than uncoordinated C 6 F 6 .…”

“…We show that these ligands can form some of the strongest anion-π interactions with halides, since the electrostatic potential surfaces above their ring centres can be positive. [36,51,52] Moreover, aromatic ligands in half-sandwich compounds are capable of forming even stronger CÀ H•••X À hydrogen bonds with halide anions, as well as σ-complexes, since electrostatic potentials at hydrogen atoms of aromatic rings are even more positive.…”

Ru-containing magnetic yolk–shell structured nanocomposite: a powerful, recoverable and highly durable nanocatalyst

“…Especially in rutheniumarene complexes, an important interaction is between p-electrons of aromatic rings and the Ru cationic sites with high oxidation states. 89,90 This kind interaction leads to both immobilization and reduction of Ru species. In the present study, we used potassium perruthenate with the oxidation state of +7 for Ru.…”

Supramolecular architectures sustained by delocalised C–I⋯π(arene) interactions in molecular crystals and the propensity of their formation

“…3,4 The magnitude of parallel stacking interactions between arene rings can be moderated by substitution patterns, 5,6 the degree of offset 7,8 and whether the arene ring is involved in coordination to a metal centre. 9,10 Naturally, other entities can interact with arene rings with the most notable being hydrogen, giving rise the archetypal T-shaped or end-on C-H•••π(arene) interactions. [11][12][13] Arene rings can also interact with alkyl residues, 14 metal centres, be they neutral, 15,16 cationic [17][18][19][20] or anionic, [21][22][23] lone-pairs of electrons [24][25][26] and of the latter, prominent examples among these species are halides.…”