Chalcogen Bond versus Halogen Bond: Changing Contributions in Determining the Crystal Packing of Dihalobenzochalcogenadiazoles

Abstract

In the crystals of 4,7-dihalobenzo[c][1,2,5]chalcogenadiazoles, the molecules are connected by two competing secondary bonding interactions: chalcogen bond (ChB) and halogen bond (HaB). Because the strengths of ChB and HaB change according to the kind of chalcogen (E: S, Se, Te) and halogen (X: Cl, Br, I), their relative contributions in determining the crystal packing can also change. Six newly determined crystal structures as well as 3 previously reported structures can be categorized into two groups: ChB-dominant and HaB-dominant structures. HaB in which X = I is strong enough to dictate the crystal packing of compounds with E = S and Se, but not where E = Te, whereas HaB in which X = Cl or Br has little effect on ChB-dominant molecular networks in crystals. The observed changing contributions of ChB and HaB may be useful for designing new supramolecular synthons for crystal engineering.

Chalcogen-bonded donor–acceptor complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4-b]pyrazine with halide ions

“…[44][45][46][47][48][49] The E-X chalcogen bondings are also observed for X atoms belonging to ring substituents and competing with the chalcogenadiazoles' N atoms for the s-holes. 50,51 Notably, the [E-N] 2 -bonded dimers may exist not only in the solid state, but in the gas phase as well. 52 as halides, 53,56 pseudohalides 57 and chalcogenolates 56,58 (for selected starting heterocycles, see Scheme 1).…”

“…44–49 The E–X chalcogen bondings are also observed for X atoms belonging to ring substituents and competing with the chalcogenadiazoles’ N atoms for the σ -holes. 50,51 Notably, the [E–N] 2 -bonded dimers may exist not only in the solid state, but in the gas phase as well. 52…”

Solid‐State Assembly by Chelating Chalcogen Bonding in Quinodimethane Tetraesters Fused with a Chalcogenadiazole

“…Comparisons of crystal packing among 2 a – 2 c show that weakened ChB involving S is overwhelmed by WHB, as in the case of TCNQ derivatives fused with a chalcogenadiazole, [8d,e,12] which is another example of the changing contribution of ChB and competing secondary bonding interactions [22] …”

“…Comparisons of crystal packing among 2 a-2 c show that weakened ChB involving S is overwhelmed by WHB, as in the case of TCNQ derivatives fused with a chalcogenadiazole, [8d,e,12] which is another example of the changing contribution of ChB and competing secondary bonding interactions. [22] The resulting 1D-rod assembly via chelating-ChB in 1 can be used to form inclusion cavities. Indeed, the hexane-solvated crystal of 1 b (1b 2 -hexane) exhibits a packing arrangement characteristic of a clathrate compound.…”

“…The presence or absence of a similar assembly in thiadiazole‐tetraesters ( 2 ) was found to depend on the kind of alkoxy groups on the ester groups (OR=OMe, OEt, and O i Pr), and only methyl ester 2 a exhibits a chelating‐ChB supramolecular synthon. Such observation can be accounted for by the changing contribution of ChB vs. weak hydrogen bond (WHB) [14] in determining the crystal packing [8d,e,12] . The details are described herein.…”