Chalcogen bond-driven self-assembly of 4-tert-butylcalix[4]arene-ebselen conjugate

Abstract

Structural and self-assembling traits of a molecular system are intricately linked to the complex interplay of weak non-covalent interactions that exist within the molecule (intramolecular) and with other molecules(intermolecular). In this work, we report the interplay of intra-and intermolecular chalcogen bond (i. e. Se•••O) on the conformational and selfassembly attributes of 4-tert-butylcalix[4]arene-ebselen conjugate (or compound 1). The compound 1 was crystallised into two distinct conformational polymorphs 1ʹ (cis, cis) and 1ʹʹ (cis, trans). The crystallographic studies have shown that both polymorphs assume 1D polymeric chains in which the repeat units are glued via Se•••O chalcogen bonding. The differential scanning calorimetry profile of amorphous solid 1 indicated a clear glass transition and a subsequent melting with an associated glass transition (Tg) and melting temperature (Tm). Powder X-Ray diffraction studies on amorphous (obtained from CHCl 3 ) and crystalline samples (obtained from CHCl 3 : MeOH) revealed that MeOH plays a structure-directing role in the self-assembly process. The computational and crystallographic studies showed that while a weak chalcogen bond between ethereal O and Se plays a conformational control, and strong chalcogen bond between amide O and Se acts as a self-assembly control.