How molecular spacers enhance the bonding strength of trimeric Janus-like rosettes through secondary interactions

Abstract

Modulation of hydrogen bond strengths remains a challenging topic in non-covalent synthesis. In this work, the tunability of the binding energy of trimeric rosettes has been investigated by changing the molecular spacer between the sides of a Janus monomer derived from pyridone molecules. Density functional theory computations were used to analyze five Janus molecules (ASB) with three molecular spacers (S): benzene, dihydropyridine, and 1,4-cyclohexadiene. Energy decomposition analyses combined with electron charge density analyses revealed that secondary interactions between distant neighboring atoms can significantly increase the binding energy of the dimer and trimer while leaving the hydrogen bonds almost unchanged. The bonding energy increases by 22 kcal mol⁻¹ from AB₃ to ASB₃ (S = dihydropyridine). The Janus monomer could also be enlarged by adding benzene rings to the spacer without affecting the bonding energy of the dimer and trimer.