Ladder-type boron-containing π-systems with enhanced open-shell characteristics and photothermal conversion properties

Abstract

Exploration of organoborane π-radicals is of importance for organoboron chemistry and developing radical materials. However, this is a highly challenging research area because both the boron atom and radical center can induce high reactivities. In this study, we report two ladder-type boron-containing π-conjugated molecules, which feature two antiaromatic s-indacene cores embedded within the π-skeleton and two terminal triphenylborane groups. As revealed by detailed theoretical and experimental results, they possess much enhanced singlet diradical characteristic along with partial contributions of tetraradical states. As a result, they display some attractive physicochemical properties, such as magnetic activities, multi-step reversible redox activity and narrow band gaps. Notably, they have remarkable near-infrared light absorption properties, and more importantly, the as-prepared nanoparticles based on them exhibit intriguing photothermal conversion properties and excellent photostability, thus demonstrating their potential application as organic photothermal materials.