Twinning Organosuperelasticity of a Fluorinated Cyclophane Single Crystal

Abstract

Superelasticity is characterized by unique mechanical behavior, i.e., spontaneous shape recoverability by diffusionless plastic deformation and has been considered to be a property of specific alloys, so-called shape memory alloys, from its discovery in 1932. The discovery of superelasticity in an organic crystal in 2014, so-called organosuperelasticity, paved the way for functionalization of superelastic materials based on molecular design. In this context, achieving superelasiticity using various kinds of organic compounds and elucidation of its mechanism are inevitable. Here we show superelasticity in a single crystal of a derivative of sterically bulky cyclophanes: 4,5,7,8,12,13,15,16-octafluoro[2.2]paracyclophane. Crystallographic studies indicated interconversion of two centrosymmetric crystallographically independent molecules by changing molecular orientations in the crystalline state in twinning superelasticity. Our findings will contribute to propose one of the useful approaches for designing organosuperelastic materials.