Principles Guiding the Square Bonding Motif Containing a Pair of Chalcogen Bonds between Chalcogenadiazoles

Abstract

The bonding motif adopted by a dimer of chalcogenadiazole molecules is characterized by a pair of equivalent Ch···N chalcogen bonds. Quantum calculations show that the interaction energy is substantial, varying between 4 kcal/mol for Ch = S and 17 kcal/mol for Te. The interaction is cooperative in that the total bond strength is greater than either chalcogen bond individually. Neither the addition of a phenyl ring nor the addition of a pair of cyano substituents to the diazole ring has much influence on this binding. Removal of one N from the diazole weakens the binding, and addition of two nitrogens has little effect. The largest perturbation arises with three N atoms in each ring, for which the binding energy increases by some 25%. The ring size plays a minor role in most cases, although a near doubling of bond strength occurs if there are two N atoms present on a four-membered ring.

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

“…With chalcogen bonding, the compounds under discussion in the homocrystals are often connected by [E–N] 2 square supramolecular synthons (E = S, Se, Te). 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.…”

On the reliability of atoms in molecules, noncovalent index, and natural bond orbital to identify and quantify noncovalent bonds

“…However, there have been numerous examples where the various methods conflict with one another as to which sorts of bonds might be present. [35][36][37][38] There have also been numerous cases described in the literature where AIM locates a bond path where no such bond would appear to exist, or worse, that the interaction in question is a repulsive one. 36,[39][40][41][42][43][44] Another sort of dismaying occurrence is the failure of AIM to identify a bond that is actually present.…”

“…It would indeed be comforting for analysis of noncovalent bonds if the methods indicated above provided definitive indicators of the presence of such a bond, and if the data could be treated in a quantitative manner to compare strengths of such bonds. However, there have been numerous examples where the various methods conflict with one another as to which sorts of bonds might be present 35–38 . There have also been numerous cases described in the literature where AIM locates a bond path where no such bond would appear to exist, or worse, that the interaction in question is a repulsive one 36,39–44 .…”

Chalcogen Bond as a Factor Stabilizing Ligand Conformation in the Binding Pocket of Carbonic Anhydrase IX Receptor Mimic

“…Recently, different types of these interactions including chalcogen, pnicogen, tetrel, triel, aerogen as well as halogen bonds have been extensively studied [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. In the chalcogen bond, the sulfur atom serves as an LA.…”