Structural, thermal, and optical properties reveal that amorphous assembling is easily attained in a series of fluoranthene-fused [3.3.3]propellanes with a rigid 3D skeleton bearing n-butoxy or longer alkoxy groups. Drop-cast films can be obtained despite the high D _3h molecular symmetry and high ratios of π-core atoms to peripheral rotatable ones.

Abstract

Solid-state assembling modes are as crucial as the chemical structures of single molecules for real applications. In this work, solid-state structures and phase-transition temperatures are investigated for a series of fluoranthene-fused [3.3.3]propellanes consisting of a rigid three-dimensional (3D) π-core and varying lengths of alkoxy groups. Compounds in this series with n-butoxy or longer alkoxy groups take an amorphous state at room temperature. In these molecules, rotatable biaryl-type bonds are not incorporated and high D _3h molecular symmetry is retained. Therefore, π-fused [3.3.3]propellanes present a unique platform for amorphous molecular materials with low ratios of flexible alkoxy atoms to rigid π-core ones.