Architecting pyrediyne nanowalls with improved inter-molecular interactions, electronic features and transport characteristics

Abstract

Synthesizing graphdiyne analogues with a well-defined structure and desirable band gap is a challenging task. Herein, we present a novel, well-defined and highly structured crystalline π-conjugated nanowall framework, called pyrediyne (pyrene + diyne = pyrediyne), with large in-plane periodicity. The bulk synthesis of the two-dimensional (2D) ultrathin polymeric framework of pyrediyne is achieved via a modified-Glaser–Hay coupling reaction using 1,3,6,8-tetraethynylpyrene. The ultrathin π-conjugated crystalline pyrediyne nanowall is well characterized by Raman, SEM, AFM, HR-TEM and XPS techniques. Electronic structure information reveals the π-conjugated framework to be completely planar with a C_s point group, where a tunable band gap of E_g ∼ 1.17 eV can be achieved depending on the number of pyrene units. The electrostatic potential maps reveal complete π-delocalization of the electron cloud throughout the framework with a high electronegative potential at the acetylenic linkages. This through-bond charge coupling via the conjugated network in conjunction with the charge delocalization via the π⋯π interactions in space accounts for the significant electrical conductivity {σ = 1.23(±0.1) × 10⁻³ S m⁻¹} of the organic material.