Rationally designed Tröger's base decorated bis-carbazoles as twisted solid-state emitting materials and dead bacterial cell imaging

Abstract

This work describes the design and synthesis of three new Tröger's base appended bis-carbazole units via the oxidative coupling method aiming to achieve solid-state luminescent materials. We envisaged that the TB-appended bis-carbazolic unit will induce more twists in the molecule thereby affecting the optical properties, especially in the solid state, by preventing intermolecular π–π close stacking interactions. The careful control of the electronic attributes of these molecules by the systematic variation of the terminal rotatable groups allowed the preparation of novel luminescent materials possessing high thermal stabilities and favorable bandgaps for electron mobility indicating their potential applications as sensory materials or in optoelectronic devices. Consequently, one of the bis-TB materials demonstrated high biocompatibility against Escherichia coli and was found to effectively stain dead bacterial cells over live cells. Thus, this provides a promising strategy to assess bacterial cell death based on fluorescence on the addition of any antibacterial agent.