Replacing the non-polarized CC bond with an isoelectronic polarized B–N unit for the design and development of smart materials

Abstract

Replacing homodiatomic CC in polyaryl systems with an isoelectronic heterodiatomic B–N unit is a powerful strategy for the rational design and construction of novel materials with versatile properties. Herein, we uncover for the first time the intriguing aggregation induced emission (AIE) properties of four tetra-arylaminoboranes (TAAB) 1–4 in which the CC fragment of the tetra-arylethene molecule is replaced by the isoelectronic B–N unit. The dipole of these compounds was fine-tuned by judiciously employing amine donor(s) on the aryl groups attached to nitrogen. The optical properties are intriguing and are greatly influenced by the number of amine donor(s) on the B–N fragment. Compounds 1–4 are weakly emissive in dilute solutions, but are strongly emissive in the aggregated/condensed state. Compounds with strong amine donor(s) on the B–N fragment exhibit reversible mechanofluorochromism. The luminescent nano-aggregates of 1–4 were explored for the detection of nitroaromatic compounds. The experimental observations are supported by detailed computational studies.