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

Abstract

Our quantum chemical analyses elucidated how the replacement of O in the amide bonds of benzene-1,3-5tricarboxamides (OBTAs) with the larger chalcogens S and Se enhances the intermolecular interactions and thereby the stability of the obtained hydrogen-bonded supramolecular polymers due to two unexpected reasons: i) the SBTA and SeBTA monomers have a better geometry for self-assembly and ii) induce stronger covalent (hydrogen-bond) interactions besides enhanced dispersion interactions. In addition, it is shown that the cooperativity in benzene-1,3,5-triamide (BTA) self-assembly is caused by charge separation in the σelectronic system following the covalency in the hydrogen bonds.

Strengthened cooperativity of DNA-based cyclic hydrogen-bonded rosettes by subtle functionalization

“…The electron charge distribution has been analyzed within the Voronoi Deformation Density (VDD) analysis. 4,30…”

“…An interesting functionalization at the supramolecular level is the capability of cooperativity between hydrogen-bonded structures. 1–5…”

Chalcogen Atom Size: A Key Parameter in Modulating Carbonyl Compound Properties

“…We showed previously that the enhanced π‐electronegativity of the C=X bond explains the experimental phenomenon of enhanced hydrogen‐bond donor strengths of thio‐ and selenoamides compared to carboxamides [2,3,4] . The π‐orbital interaction that is present within amides H 2 NC(=X)H is shown in Figure 2.…”

“…We showed previously that the enhanced π-electronegativity of the C=X bond explains the experimental phenomenon of enhanced hydrogen-bond donor strengths of thio-and selenoamides compared to carboxamides. [2,3,4] The π-orbital interaction that is present within amides H 2 NC(= X)H is shown in Figure 2. This involves i) a (Pauli) repulsive orbital interaction between the nitrogen lone pair-type 2p orbital (N LP ) and the filled πbonding orbital of the C=X bond (π C=X ), and ii) a stabilizing donor-acceptor interaction of N LP into the empty antibonding π* orbital of the C=X bond (π* C=X ).…”

More Electropositive is More Electronegative: Atom Size Determines C=X Group Electronegativity

“…Rational design of new and improved catalysts and materials requires the understanding of how to tune the H‐bonding properties of amides in supramolecular assemblies. Recently, we have shown that the H‐bond donor strength of amides can be enhanced by exchanging oxygen in the C=O bond for the larger, but less electronegative Group 16 elements S and Se [3,4] . This trend may seem counterintuitive because a reduced electronegativity of X suggests, erroneously, a reduced C=X group electronegativity and, thus, a reduced H‐bond donor strength.…”