Crystallographic and Theoretical Investigation on the Nature and Characteristics of Type I C═S···S═C Interactions

Abstract

Depending on the electronic environment, chalcogen atoms (mainly S, Se, Te) can act as both acceptor and donor during the formation of a noncovalent interaction. This dual behavior of chalcogens can lead to the formation of highly stabilized chalcogen-chalcogen interactions [1]. Among the chalcogen-chalcogen interactions, S…S interactions has garnered immense attention due to several applications such as in organic conductors and nanotube formations. Role of S…S interactions in molecular structures has been explored both experimentally and computationally [2]. However, a closer look at the literature reveals that most studies on S…S is centered around sp3 hybridized sulfur atom with a negligible focus to sp2 hybridized sulfur atom. A simple Cambridge Structural Database [2] search revealed that there are more than 1000 structures having sp2 hybridized organic sulfur participating in the formation of C=S…S=C interactions. However, a systematic and detailed investigation of this interaction in crystal structures has not be explored previously. In this study, we have analyzed the nature and characteristics of C═S···S═C chalcogen-chalcogen interactions by screening the Cambridge Structural Database. In addition to this, we have also performed a topological analysis and binding energy calculations on full scale dimers extracted from the Cambridge Structure Database in addition to analysing C═S···S═C interactions in (X2CS)2 model systems where X = −H, −NH2, −OH, −F, −Cl by means of the electrostatic potential maps and energy decomposition analysis [1] Bleiholder, C. et al. (2006).

Chalcogen Bonding “2S–2N Squares” versus Competing Interactions: Exploring the Recognition Properties of Sulfur

“…If they are the primary cause of dimerizations throughout the class, the preservation of highly aligned squares and contact distances for compounds like 5 a , where the sulfur σ‐hole is significantly diminished in both size and magnitude, would not be observed (Figure S5). This is in agreement with the recent comprehensive CSD X‐ray investigation of C=S ⋅⋅⋅ S=C interactions, where no meaningful correlation could be found between sulfur σ‐hole magnitude and S ⋅⋅⋅ S contact distance, binding energy, or trajectory angle . Rather, attractive binding energies and close contacts were calculated to exist even for two δ − charged S ⋅⋅⋅ S atoms in the dimers (H 2 CS) 2 and [(OH) 2 CS] 2 .…”

“…There are currently no published studies that use X‐ray analysis to systematically evaluate substituent effects on divalent S ⋅⋅⋅ S contacts in small molecules . Yet such effects are becoming increasingly relevant in the recognition of substrates, pharmaceuticals, and agrochemicals by protein receptors.…”

“…This is in agreement with the recent comprehensive CSD X-ray investigation of C=S···S=Ci nteractions, where no meaningful correlation could be found betweens ulfur s-hole magnitude and S···Sc ontact distance, binding energy,o rt rajectory angle. [101] Rather, attractive bindinge nergies and close contacts were calculated to exist even fort wo d À charged S···Sa toms in the dimers (H 2 CS) 2 and [(OH) 2 CS] 2 .F urthermore, stabilizing contributions from n!s*o rbital-orbitalo re lectrostatic interactions of the N···Sc ontacts could be evidenced by the lengthening of the accepting SÀNb ond. [39,102] However, the accepting SÀN bond length of each structured oes not follow this trend (Figure 4, in red).…”

“…There are currently no published studies that use X-ray analysis to systematically evaluate substituent effects on divalent S···Sc ontacts in small molecules. [92,98,101,117] Yets uch effectsa re becoming increasingly relevant in the recognition of substrates, pharmaceuticals, and agrochemicals by protein receptors. The sulfur atoms of methionine [118] and cysteine [43,119] are strongly involved in protein conformation and stability, [120,121] and Met frequently act as gatekeepersi nk inases,c ontrolling ATPb inding.B oeckler et al recently published the X-ray structure showing the "gatekeeper" residue Met146i nt he c-Jun Nterminal kinase 3( JNK3) interacting by CB with the neighboring sulfur of Met115 and by XB with an iodinated inhibitor (Figure 12 a).…”

Intra-/Intermolecular Bifurcated Chalcogen Bonding in Crystal Structure of Thiazole/Thiadiazole Derived Binuclear (Diaminocarbene)PdII Complexes

“…The strength of intramolecular S•••Cl CB is in the range of 2.8-2.9 kcal/mol, which is comparable with contacts in previously studied thiazole/thiadiazole derived binuclear (diaminocarbene)Pd II complexes 3a,b (3.1-3.2 kcal/mol) [58]. In the same time, the intermolecular S•••S CB is much weaker (0.9-1.3 kcal/mol) than intramolecular contact in 3c, but its energy is comparable with I type CB contacts in the X2C=S•••S=CX2 (X = H, Cl, F) systems (0.7-1.1 kcal/mol) [96]. The balance between the Lagrangian kinetic energy G(r) and potential energy density V(r) at the BCPs reveals the nature of these interactions, if the ratio −G(r)/V(r) > 1 is satisfied, than the nature of appropriate interaction is purely non-covalent, in case the −G(r)/V(r) < 1 some covalent component takes place [104].…”