Supramolecular Binding of bis‐naphthalene Cleft based Molecular Tubes

This is the authors' abstract. We don't add key points for this paper.

The endo ‐functionalized bis‐urea molecular tubes having the rigid bis‐naphthalene cleft aligned parallel or antiparallel to each other yield syn (SBU) and anti (ABU) configurational isomers which exhibit remarkable selectivity toward guest binding. In the present work the noncovalent binding from SBU and ABU receptors with heterocyclic guests viz., pyridine (py) and pyrazine (pz) is unveiled through the density functional theory. The complexation is spontaneous, thermodynamically favorable and facilitated via N−H⋅⋅⋅N hydrogen bonding, C−H⋅⋅⋅π and other non‐covalent interactions. The coexistence of multiple intermolecular interactions reflects in the infrared and 1 H NMR spectra. The ‘frequency shift’ of the characteristic vibrations accompanying the complexation is rationalized. Encapsulation of py or pz within π‐electron rich cavity of the ABU led to shielding of the guest protons while hydrogen bonded protons engender downfield signals in the calculated 1 H NMR spectra.