Selective Synthesis of Homoleptic and Heteroleptic Triarylboranes and Their Novel Colour Tunable Properties

Homoleptic BAr₃ (1) and heteroleptic Ar₂BAr’ (2) (Ar=4-OMe-2,6-Me₂-C₆H₂-, Ar′=3-Br-6-OMe-2,4-Me₂-C₆H-) have been selectively synthesized by the reaction between 4-bromo-3,5-dimethylanisole and BF₃⋅OEt₂ in the presence of n-BuLi. The selectivity of 1 and 2 was controlled by the sequential or in-situ reaction, respectively. The use of stronger base such as t-BuLi than n-BuLi gave only homoleptic 1 even in in-situ reaction. The solid state structure for 2 was confirmed by single crystal X-ray analysis. Especially, the emission of compound 2 showed a bathochromic shift of ca. 50 nm compared with that of compound 1. Both 1 and 2 exhibited significant solvatochromism of fluorescence.