Communicating through hydrogen bonds

Chalcogen Atom Size Dictates Stability of Benzene‐1,3,5‐triamide Polymers: Overlooked Role of Geometrical Fit for Enhanced Hydrogen Bonding

“…As such, more electronic density is donated from the σ HOMOs to the σ LUMOs as is reflected by the larger Mulliken population loss and gain in Figure 3a and 3b, respectively. We have shown previously that the energetic lowering of the NH 2 ‐localised σ LUMOs for thio‐ and selenoamides is a consequence of their more positive NH 2 groups which is a result of the chalcogen steric size (see above) [3] . As the NH 2 groups are indeed more positively charged in SBTAs and SeBTAs than in OBTAs (Figure 3c), the σ LUMOs are lowered in energy down Group 16.…”

“…The orbital interaction in H‐bonds follows mainly from the covalent or charge‐transfer component [3,12] which arises for BTAs from the σ donor‐acceptor interaction between the filled chalcogen n p lone‐pair type σ HOMO orbitals on one monomer and the empty σ LUMO orbitals localized on the NH 2 groups of the other monomer. Δ E oi is more stabilizing from O to S to Se as the σ HOMOs are raised in energy while the σ LUMOs are lowered in energy upon descending Group 16 (see Figure 3a and 3b and Supporting Data S3).…”

“…it became evident that the replacement of O in the amide bond for the heavier and less electronegative chalcogens, S and Se, can produce hydrogen‐bonded polymers of benzene‐1,3,5‐triamides (BTAs) with enhanced thermal stabilities in alkane solvents than their oxygen counterparts (Figure 1). We have demonstrated recently that not the electronegativity but the steric atomic size of the chalcogen in the amide bond determines the enhanced H‐bond donor strength of thio‐ and selenoamides compared to carboxamides [3] . As the effective size of the chalcogen atom increases from O to S to Se, the amide C=X bond is elongated due to the increasing steric Pauli repulsion between the two bonded atoms for the heavier chalcogens.…”

Understanding the influence of alkali cations and halogen anions on the cooperativity of cyclic hydrogen‐bonded rosettes in supramolecular stacks

“…based on dispersion‐corrected relativistic density functional theory at the ZORA‐BLYP‐D3/TZP level for geometry optimizations and ZORA‐BLYP‐D3/TZ2P for energies. Previous works [22–24] have shown that this level of theory gives excellent understanding of bonding mechanism in hydrogen bonding and also in long range interactions within weakly‐bound complexes [11] . Furthermore, the use of the TZP basis set for large supramolecular systems has shown to furnish accurate results [16c] …”

Dynamic covalent networks with tunable dynamicity by mixing acylsemicarbazides and thioacylsemicarbazides

“…Given the differences between CO and CS bonds, 34 and isocyanates being more reactive than isothiocyanates, 35,36 we expected the chemical reactivity of the ASC and TASC motifs to be different, and thereby the kinetics of dynamic bond exchange reactions. In addition, to differences observed between ureas and thioureas, 37,38 and amides and thioamides, 39–42 we also expected the hydrogen bonding between ASC‐ASC and TASC‐TASC moieties to be different.…”