Waves of Halogen–Halogen Bond Formation in the Cocrystallization of Hexabromobenzene and 1,2,4,5-Tetrabromobenzene with C₇₀

Abstract

The single crystal X-ray structures of three well-ordered cocrystals of C 70 with brominated benzenes are examined. The crystals are those of C 70 • C 6 Br 6 •C 7 H 8 , C 70 •C 6 Br 6 •C 6 H 6 , and C 70 •2(1,2,4,5-tetrabromobenzene)•CS 2 . While all three structures exhibit extensive van der Waals interactions, the presence of a wavelike C−Br---Br structural motif is a distinctive part of the cocrystal assembly.In these three crystal structures, it is observed that the Br---Br interactions are a cross between type I and II halogen−halogen bonds. In our hands, this structural motif does not occur in structures with C 60 .

Unusual Magneto‐Structural Features of the Halo‐Substituted Materials [FeIII(5‐X‐salMeen)2]Y: a Cooperative [HS‐HS]↔[HS‐LS] Spin Transition

“…Crystalp acking reveals dimers of complexc ations, [19] formed by CÀ H imine ···O phenolate interactions (Figures 2-5 and Figure S2), promoting cooperativity betweent he paramagnetic centres. Further cooperativity between thec omplex cations [Fe III (5-X-salMeen) 2 ] + derives from type-II halogenhalogen bonding interactions, [36][37][38][39][40][41] previously not reportedf or any member of the [Fe III (X-salRen) 2 ] + family (Figure 4a nd Figure S4). These are most dominant in [Fe III (5-I-salMeen) 2 ]ClO 4 ,b ut non-existent in [Fe III (5-F-sal-Meen) 2 ]ClO 4, as expected.…”

“…Furthermore, in the compounds [Fe III (5‐X‐salMeen) 2 ]ClO 4 (X=Cl, Br, I) we have encountered halogen‐halogen bonding, which is a dominant feature of the structures. To the best of our knowledge, hitherto there has been no crystallographic documentation of the occurrence of halogen‐halogen bonding within the [Fe III (X‐salRen) 2 ]Y spin‐crossover family. Halogen‐halogen bonds (C 1 −X 1 ⋅⋅⋅X 2 −C 2 , X=halogen) are categorized as types I and II.…”

“…Halogen‐halogen bonds (C 1 −X 1 ⋅⋅⋅X 2 −C 2 , X=halogen) are categorized as types I and II. Geometrically, these types are readily distinguishable by their characteristic angles θ 1 and θ 2 : whereas for type‐I interactions, θ 1 and θ 2 are obtuse and nearly equivalent; for type‐II contacts, θ 1 and θ 2 are comparable with the idealized linear and right angles, respectively. Chemically, the type‐II halogen‐halogen bond differs from that of type‐I in that it is electrostatic in nature (C−X δ+ ⋅⋅⋅X δ− −C), that is, electrophilic (positive “σ‐hole”)/nucleophilic interaction, and the order of prevalence is Cl<Br<I in accordance with the polarizability of the halogen atom …”

“…To the best of our knowledge,h itherto there has been no crystallographic documentation of the occurrence of halogen-halogen bonding [36][37][38][39][40][41] within the [Fe III (X-salRen) 2 ]Y spin-crossover family.H alogen-halogen bonds( C 1 ÀX 1 ···X 2 ÀC 2 ,X = halogen)a re categorized as types Ia nd II. Geometrically,t hese types are readily distinguishable by their characteristic angles q 1 and q 2 : [36,37,[39][40][41] whereas for type-I interactions, q 1 and q 2 are obtuse and nearly equivalent;f or type-II contacts, q 1 and q 2 are comparable with the idealized linear and right angles, respectively.C hemically,t he type-II halogen-halogen bond differs from that of type-I in that it is electrostatic in nature (CÀX d + ···X dÀ ÀC), that is, electrophilic (positive "s-hole")/nucleophilic interaction, and the order of prevalence is Cl < Br < Ii na ccordance with the polarizability of the halogen atom. [37,41] Ac omparison of the structural analyses of the compounds [Fe III (5-Cl-salMeen) 2 ]ClO 4 (2)a nd [Fe III (5-Cl-sal-Meen) 2 ]BPh 4 ·2MeOH (5·2MeOH)i llustrates the combinedi nfluence of intermolecular forces and crystal packing on the magneto-structural properties of SCO materials.…”

A 2:1 Receptor/C60 Complex as a Nanosized Universal Joint

“…C 60 @ 6 2 represents a rather uncommon packing pattern, with the fullerene completely encapsulated by two receptor molecules with no intimate contact with other carbon cages 17. 18 In contrast to the several reported structures of fullerene cocrystals, which demonstrate the critical nature of solvent molecules in the crystal packing of such assemblies,19 no solvent molecules are incorporated into the crystal of C 60 @ 6 2 . The topology of buckycatcher II results in the unprecedented crystal arrangement of four corannulene subunits interacting in a concave–convex fashion with a single fullerene cage in a trimeric C 60 @ 6 2 assembly.…”