Rendering cross-conjugated azophenine derivatives emissive to probe the silent photophysical properties of emeraldine

Abstract

An azophenine derivative was synthesized by coupling truxene and azophenine via the copper-free Sonagashira reaction using Pd₂(dba)₃ and As(PPh)₃ as catalysts. The crystal structure of this heavy azophenine model (∼4000) was made and the identity of the structure was confirmed. By introducing truxene groups into this cross-conjugated structure, the deactivating rotations around the NH–C₆H₄ bonds were slowed down, which rendered this derivative near-IR emissive at 298 K. This species provided then the appropriate spectral and kinetic signatures for knowing where and what to look for in emeraldine, which was called non-emissive. Besides, two other compounds were also synthesized as models for this azophenine derivative for comparison and interpretation purposes.